WO2019019814A1 - Secondary side feedback control circuit and switching power supply using the same - Google Patents

Secondary side feedback control circuit and switching power supply using the same Download PDF

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Publication number
WO2019019814A1
WO2019019814A1 PCT/CN2018/090364 CN2018090364W WO2019019814A1 WO 2019019814 A1 WO2019019814 A1 WO 2019019814A1 CN 2018090364 W CN2018090364 W CN 2018090364W WO 2019019814 A1 WO2019019814 A1 WO 2019019814A1
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Prior art keywords
port
voltage
output voltage
feedback
feedback switch
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PCT/CN2018/090364
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French (fr)
Chinese (zh)
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肖华
唐盛斌
於昌虎
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广州金升阳科技有限公司
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Publication of WO2019019814A1 publication Critical patent/WO2019019814A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection

Definitions

  • the invention relates to a switching power supply controller, in particular to a magnetically isolated high output voltage secondary side feedback control circuit and a switching power supply using the same.
  • FIG. 1 shows the commonly used secondary side feedback control technique.
  • the task of isolated feedback is carried out by an isolation amplifier consisting of device TL431, optocoupler and auxiliary device.
  • the basic principle is that the transconductance amplifier composed of TL431 and sampling resistors R1 and R2 amplifies the error voltage signal of the output voltage and the reference voltage into a current signal.
  • the output voltage When the output voltage is high, the current flowing through the TL431 becomes larger, that is, the current.
  • the voltage of the controller FB port becomes smaller, so that the controller output duty ratio becomes smaller, so that the transformer transmits less energy to the secondary side output terminal, and the output voltage starts to decrease; otherwise, if the output voltage is biased Low, increase the output voltage by increasing the transmission energy of the transformer by feeding the error signal back to the primary side to control the increase of the duty cycle. Repeatedly adjusting the control so that the output voltage is stabilized at the set value.
  • This kind of feedback technology is called the secondary side feedback because its detection and comparison link is on the secondary side of the switching power supply, that is, the load side.
  • the invention patent application with the publication number CN 105610306 A and the invention name "secondary feedback control method and its control circuit” proposes a novel secondary side feedback circuit, which is suitable for having An isolated switching power supply of a secondary circuit formed by a primary winding formed by a primary winding of the transformer and a secondary winding of the transformer.
  • 2 is a diagram showing the operation state of the feedback switch of the circuit of FIG. 2 and the voltage waveform diagram of 124, and the secondary side feedback switch switching power supply shown in FIG.
  • the secondary side modulator is composed of an output voltage coding control module and a detection and determination module.
  • a secondary degaussing circuit comprising two ports of a first port 110 and a second port 111; an output capacitor comprising two ports of a first port 131 and a second port 132; a feedback switch comprising a drain port 133, a source terminal Port 135 and gate port 134 are three ports.
  • An output voltage encoding control module comprising three ports of a first port 112, a second port 113, and a third port 114; a detection judging module, comprising a first port 115, a second port 116, a third port 117, and a fourth port 118, fifth port 119 five ports; auxiliary winding voltage detection upper resistance, which includes a first port 120 and a second port 121; auxiliary winding voltage detection lower resistance, which includes a first port 122 and a second port 123; a feedback switch a state detecting module comprising two ports of a first port 124 and a second port 125; an output voltage decoding feedback module comprising two ports of a first port 126 and a second port 127; a duty cycle modulation circuit comprising the first The port 128, the second port 129, and the third port 130 have three ports.
  • port 102 is connected to the positive terminal 101 of the input power source, port 103 is connected to the port 130; port 104, port 131, port 119 are connected together, the connection point forms the positive port 108 of the switching power supply output voltage; port 105, The port 110, the drain port 133 of the feedback switch, and the port 115 are connected together; the port 111, the port 118, the source port 135 of the feedback switch, and the port 132 are connected together, and the connection point forms the negative port 109 of the switching power supply output voltage; the feedback switch
  • the gate port 134 is connected to the port 112; the port 113 is connected to the port 116; the port 114 is connected to the port 117; the port 120 is connected to the port 106; the port 121, the port 122, and the port 124 are connected together; the port 125 is connected to the port 126; Port 127 is connected to port 128; port 129, port 123, and port 107 are connected together, and the connection point forms the negative terminal of the
  • the excitation process of the flyback power switching power supply is the same as that of the conventional flyback switching power supply.
  • the difference is how to feed back the change of the output voltage from the secondary side to the primary side during the degaussing phase.
  • the specific working principle is detailed in paragraphs 0086-0090 of the relevant manual.
  • the feedback switch state detecting module is difficult to detect whether the conduction state of the feedback switch changes, and the decoding and the duty cycle modulation module cannot complete the decoding of the feedback switch conduction state and the duty ratio adjustment, and further The power system is not working properly.
  • the feedback switch cannot be turned on after the excitation phase and degaussing of the transformer. Otherwise, the charge of the output capacitor may be reversed, which may cause a power system failure.
  • the timing diagram of the feedback switch operation is shown in FIG. 3, where H represents the output voltage encoding control module 112.
  • the port outputs a high level, the drive feedback switch is turned on, and the feedback switch is in a low resistance region; L indicates that the output voltage code control module 112 port outputs a low level, the drive feedback switch is turned off, and the source port 135 of the feedback switch is connected to the switching power supply.
  • the negative terminal 109 of the output voltage is in the high resistance region when the feedback switch is turned off.
  • the excitation phase of the transformer is 0 ⁇ t1, t4 ⁇ t5. If the feedback switch needs to be turned on during the degaussing phase of the transformer t1 ⁇ t3, t5 ⁇ t6, the detection and judgment module needs to detect the voltage at 133 through port 115, and the voltage at port 133.
  • the feedback switch When the threshold value is reached, the feedback switch is turned off, that is, the feedback switch is turned off at t2, so that the feedback switch of the output capacitor is not backed up in the time period from t3 to t4 and t6 to t7 after the degaussing of the transformer is completed.
  • Feedback switch control is relatively complicated. Since the feedback switch is connected in parallel with the degaussing circuit, the feedback switch needs to use a high voltage resistant device to increase the power system cost.
  • the technical problem to be solved by the present invention is to propose a secondary side feedback control circuit suitable for a high output voltage, a switching power supply.
  • a secondary side feedback control circuit is applicable to an isolated switching power supply having a secondary side circuit formed by a primary side winding formed by a primary winding of a transformer and a secondary winding formed by a secondary winding of the transformer, comprising: a secondary side degaussing circuit, a detection judging module, and an output Voltage coding control module, feedback switch, auxiliary winding voltage detection upper resistance, auxiliary winding voltage detection lower resistance, feedback switch state detection module, output voltage decoding feedback module and duty cycle modulation circuit;
  • the secondary degaussing circuit is in a conducting state during the degaussing stage of the transformer, providing a path for the storage of the transformer to charge the output capacitor; in the non-degaussing stage of the transformer, the high resistance state is prevented, and the charge of the output capacitor is prevented from being reversed;
  • the detection judging module detects the output voltage of the isolating switching power supply, compares the voltage with the internal reference voltage, outputs the voltage change information, and sends the voltage to the output voltage encoding control module;
  • the output voltage coding control module performs coding according to the received communication change protocol according to the agreed communication protocol, and controls the working state of the feedback switch according to the coding;
  • the feedback switch state detecting module samples the voltage of the auxiliary winding by the auxiliary winding voltage detecting upper resistor and the auxiliary winding voltage detecting the partial pressure of the resistor at the appointed time of the degaussing phase of each switching cycle, and detects the current detected voltage with the previous detected voltage. The voltage is compared, the magnitude of the change of the voltage and the direction of the change of the voltage are obtained, and the change information of the working state of the feedback switch is output and sent to the output voltage decoding feedback module;
  • the output voltage decoding feedback module receives the feedback state change state information of the feedback switch, decodes according to the agreed communication protocol, determines whether the output voltage is high or low, outputs the modulation voltage, and sends it to the duty cycle to adjust to the circuit;
  • the duty cycle modulation circuit receives the modulation voltage, and modulates the duty ratio of the excitation of the main side winding of the transformer according to the magnitude of the voltage, and increases the duty ratio when the modulation voltage increases, and vice versa;
  • the utility model is characterized in that: the control end of the feedback switch is connected to the output voltage coding control module, the conduction current outflow end of the feedback switch is connected to the secondary side degaussing circuit, and the conduction current inflow end of the feedback switch is connected to the negative port of the output voltage of the switching power supply.
  • the feedback switch operating state change information is that the increased amplitude exceeds the set value, it is considered that the working state of the feedback switch jumps from the linear region to the saturation region; otherwise, the feedback switch operating state change information is the reduced amplitude exceeds the set value.
  • the value is considered to be the transition from the saturation region to the linear region.
  • the output voltage decoding feedback module outputs the result of the period is “output voltage is high”, and then gradually reduces the modulation voltage until “output voltage is low”; otherwise, if the result of the current decoding is “output voltage” If it is low, the modulation voltage is gradually increased until the "switching power supply output voltage is high”.
  • the feedback switch is a MOS tube.
  • a specific implementation of the isolated switching power supply applying the technical solution includes: a three-winding transformer, which is composed of three windings of a primary winding NP, a secondary winding NS, and an auxiliary winding NA, which respectively include a first port and a first a two-port; a secondary degaussing circuit comprising two ports of a first port and a second port; an output capacitor comprising two ports of a first port and a second port; and a feedback switch comprising a drain port, a source port, and Three ports of the gate port; an output voltage code control module, which includes a first port and a second port; a detection and determination module, which includes a first port and a second port; and an auxiliary winding voltage detecting upper resistor, which includes the first port and a second port; an auxiliary winding voltage detecting resistor, comprising a first port and a second port; a feedback switch state detecting module comprising a first port and a second port; an output voltage decoding feedback module comprising
  • connection relationship is: the first port of the primary winding NP is connected to the positive pole of the input power supply, the second port is connected to the third port of the duty cycle modulation circuit; the first port of the secondary winding NS, the first port of the output capacitor, The first ports of the detection and determination module are connected together, the connection point forms a positive port of the switching power supply output voltage; the second port of the secondary winding NS and the first port of the secondary degaussing circuit are connected together; the second port of the secondary degaussing circuit, The source port of the feedback switch is connected; the second port of the output voltage code control module is connected to the second port of the detection and judgment module; the drain port of the feedback switch and the second port of the output capacitor are connected together, and the connection point forms a switching power supply output voltage a negative port; the gate port of the feedback switch is connected to the first port of the output voltage encoding control module; the first port of the auxiliary winding voltage detecting upper resistor is connected to the first port of the auxiliary winding NA; the
  • the feedback switch is a MOS tube.
  • the agreed communication protocol means that the output voltage of the sampled switching power supply is numbered according to a predetermined rule, and the encoding rule is defaulted in the decoding process of the primary side, and the purpose is to determine whether the output voltage is high or low.
  • the specific encoding and decoding process can be understood by the detailed explanation of the embodiments.
  • the appointment time of the degaussing phase means that the secondary side feedback switch is scheduled to operate at a certain time or time in the degaussing phase, and the detection module of the primary side senses the action to be valid during the predetermined time period.
  • the control terminal of the feedback switch the port that controls the conduction switch to be turned on and off.
  • the MOS transistor it refers to the gate of the MOS transistor; for the triode, it refers to the base of the triode.
  • the current flowing into the port refers to the drain of the MOS transistor, regardless of N-channel, P-channel, enhanced or depleted MOS
  • the tube When the tube is turned on, the current flows from the drain with a high voltage to the source with a low voltage.
  • the triode it refers to the collector of the triode.
  • the current flows from the collector with a high voltage to a low voltage. The emitter.
  • the conduction current flowing out of the feedback switch after the feedback switch is turned on, the port through which the current flows, such as the MOS tube, refers to the source of the MOS tube; for the triode, it refers to the emitter of the triode.
  • Feedback switch operating state refers to the appropriate driving voltage to the feedback switch to operate in the saturation zone or linear zone, the saturation zone and the linear zone are relative rather than set absolute limits, they differ only in the feedback switch Whether the control voltage can be detected on the primary side and correctly judge the change of its working state.
  • the logic relationship in the encoding process in the embodiment is expressed in a specific form, for example, the message "the output voltage is high” is saturated with the "feedback switch".
  • “Representation”, in the actual product implementation, the "output voltage is too high” information can also be carried by “feedback switch in the linear region”, only to better illustrate the invention, and is not intended to limit the invention.
  • the present invention has the following beneficial effects:
  • the feedback switch is connected in series with the degaussing path, and the degaussing circuit will automatically cut off after the excitation phase and the degaussing to prevent the charge of the output capacitor from being reversed.
  • the timing of the working state diagram of the feedback switch is as shown in FIG. 5, wherein H indicates that the output voltage encoding control module 112 port outputs a high level, the driving feedback switch is turned on, the feedback switch operates in a linear region; L indicates that the output voltage encoding control module 112 port outputs a low level, and the drain of the feedback switch in the present invention 135 is connected to the negative port 109 of the switching power supply output voltage. When the port 112 is low, the feedback switch operates in the saturation region.
  • the transformer excitation phase is 0 to t1, t3 to t4, and the degaussing end phase is t2 to t3 and t5 to t6.
  • the detection and judgment module does not need to detect whether the transformer is in the degaussing phase t1 ⁇ t2, t4 ⁇ t5 by sampling the voltage at the first port of the degaussing circuit of the secondary side, and only needs to detect the output voltage of the switching power supply through the positive port of the output voltage of the switching power supply. And compare the voltage with the internal reference voltage. The result of the comparison determines the working state of the feedback switch and reduces the difficulty of controlling the feedback switch. This is its outstanding advantage.
  • the feedback switch of the present invention only needs to use a low voltage device to reduce the power system cost.
  • Figure 1 is a typical circuit diagram of a switching power supply using a conventional secondary side feedback controller
  • FIG. 2 is a typical circuit diagram of a switching power supply of a novel application secondary side feedback control circuit
  • Figure 3 is a diagram showing the working state of the feedback switch of the circuit of Figure 2 and the voltage waveform at 124;
  • FIG. 4 is a block diagram showing the principle of a switching power supply to which a secondary side feedback control circuit according to a first embodiment of the present invention is applied;
  • FIG. 5 is a diagram showing the working state of the feedback switch and the voltage waveform at 124 in the present invention.
  • the switching power supply includes a three-winding transformer including three windings of a primary winding NP, a secondary winding NS, and an auxiliary winding NA.
  • the winding NP comprises a first port 102 and a second port 103
  • the winding NS comprises a first port 104 and a second port 105
  • the winding NA comprises a first port 106 and a second port 107
  • a secondary side degaussing circuit which comprises Two ports of one port 110 and second port 111; an output capacitor comprising two ports of a first port 131 and a second port 132; a feedback switch comprising a drain port 135, a source port 133 and a gate port 134 a port; an output voltage encoding control module, comprising a first port 112, a second port 114; a detection judging module comprising a first port 119, a second port 117; an auxiliary winding voltage detecting upper resistor R FA1 , which includes the first port 120 and second port 121; the auxiliary winding voltage detection resistor R FA2, which comprises a first port 122 and second port 123; feedback switch state detection module, comprising a first and second port
  • port 102 is connected to the positive terminal 101 of the input power source, port 103 is connected to the port 130; port 104, port 131, port 119 are connected together, the connection point forms the positive port 108 of the switching power supply output voltage; port 105, The ports 110 are connected together; the port 111 and the source port 133 of the feedback switch are connected together; the drain port 135 and the port 132 of the feedback switch are connected together, the connection point forms the negative port 109 of the switching power supply output voltage; and the gate port 134 of the feedback switch Ports 112 are connected together; port 114 is connected to port 117; port 120 is connected to port 106; port 121, port 122, port 124 are connected together; port 125 is connected with port 126; port 127 is connected with port 128; port 129, Port 123 and port 107 are connected together, and the connection point forms the negative terminal of the input power.
  • the function of the detection and judgment module is: detecting the output voltage of the switching power supply through the port 119, and comparing the voltage with the internal reference voltage, the result of the comparison can determine whether the feedback switch changes the working state, and passes the information through its port port. 117 is passed to the output voltage encoding control module.
  • the output voltage coding control module includes two functions: one is the coding function, and the coding rule is set.
  • the feedback switch operation state needs to change from a saturation region to a linear region, and vice versa.
  • the feedback switch operating state needs to change from a linear region to a saturated region.
  • the control function controls the feedback switch gate to be at the corresponding encoding level, that is, the port 112 outputs a low level when the output voltage is high, and the port 112 outputs a high level when the output voltage is low.
  • the minimum voltage difference between the winding NS port 104 and the port 105 is (V OUT +V BE +V dson ), where V Dson is the voltage difference between the drain and the source when the feedback switch operates in the linear region; when the feedback switch operates in the saturation region during the degaussing phase, the voltage difference between the winding NS port 104 and the port 105 is (V OUT +V BE + V DS ), where V DS is the voltage difference between the drain and the source when the feedback switch operates in the saturation region.
  • the feedback MOS switch in the degaussing stage operates in the linear region or the saturation region, so that the voltage difference across the winding has undergone a large abrupt change.
  • the voltage variation at the port 124 of the feedback switch state detecting module is:
  • n A / n S is the ratio of the winding NA to the number of turns of the winding NS.
  • the decoding rule should be set to decode the corresponding result when receiving the judgment result of “the feedback switch operating state changes from the saturation region to the linear region”.
  • the output voltage changes from a high state to a low state.
  • the output voltage is correspondingly decoded from the low state to the high state. status. If the decoding result is "the output voltage changes from the high state to the low state", it indicates that the output voltage is too high before the change, and the current output voltage is low until the state change in the opposite direction is received again; otherwise, it can be obtained Know that the current output voltage is too high.
  • the output voltage of the secondary side of the isolation transformer can be fed back to its primary side.
  • the modulation voltage Vcrl is gradually decreased, which controls the duty ratio to gradually decrease, thereby causing the output voltage to decrease; conversely, when the output voltage is low, the duty ratio is gradually increased to rise again. Repeat this way to stabilize the output voltage at the set value.
  • the detection switch module and the output voltage code control module enable the feedback switch tube to operate in the linear region or the saturation region, thereby increasing the amplitude of the voltage change at the port 124, so that the feedback switch state detection module can be reliable when the power system is at a high output voltage.
  • the ground switch detects the change of the working state of the feedback switch, and then adjusts the duty ratio after decoding to stabilize the output voltage at the set value.

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  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

Disclosed in the present invention is a secondary side feedback control circuit, which is suitable for a isolating switching power supply having a primary circuit formed by a primary winding of a transformer and a secondary circuit formed by a secondary winding of the transformer. The secondary side feedback control circuit comprises: a secondary side degaussing circuit, a detection and decision module, an output voltage coding control module, a feedback switch, an auxiliary winding voltage detection upper resistance, an auxiliary winding voltage detection lower resistance, a feedback switch state detection module, an output voltage decoding feedback module and a duty cycle modulation circuit. Since the feedback switch is connected in series with the secondary side degaussing circuit, the power supply system of the present invention can work stably at a high output voltage. Moreover, charge backflow of the output capacitor can be prevented, the difficulty of controlling the feedback switch can be reduced. At the same time, the feedback switch only needs to use low-voltage devices, reducing the cost of the power supply system.

Description

副边反馈控制电路及应用该电路的开关电源Secondary side feedback control circuit and switching power supply using the same 技术领域Technical field
本发明涉及开关电源控制器，特别涉及磁隔离的高输出电压副边反馈控制电路及应用该电路的开关电源。The invention relates to a switching power supply controller, in particular to a magnetically isolated high output voltage secondary side feedback control circuit and a switching power supply using the same.
背景技术Background technique
为了避免负载对供电输入端的干扰和破坏，隔离型开关电源已成为各种供电***中不可或缺的部分。既要实现输出电压和输入电压之间的隔离又要把输出电压稳定在设定值，必然需要采用隔离器件把输出电压的大小反馈到输入一侧进行调节控制。图1是常用的副边反馈控制技术，隔离反馈的任务由器件TL431、光耦及辅助器件组成的隔离放大器来承担。基本原理是：TL431与采样电阻R1、R2等元件组成的跨导放大器把输出电压与基准电压的误差电压信号放大为电流信号，当输出电压偏高时流过TL431的电流变大，也就是流过光耦的电流变大，控制器FB端口的电压变小，从而控制器输出占空比变小使得变压器传递更小的能量到副边输出端，输出电压开始降低；反之，若输出电压偏低，通过把误差信号反馈到原边控制占空比的增加来增加变压器的传输能量，从而提高输出电压。如此反复不断地调节控制把输出电压稳定在设定值。这种反馈技术因其检测和比较环节在开关电源的副边，即负载一侧，所以称其为副边反馈。这种直接检测输出电压的方式具有精度高的特点，但是由于这些检测、放大器、隔离反馈器件的存在增加了电源***板的空间，显然在成本和体积上没有优势。特别是光耦不能在高温下工作，且易于老化，使得这种电源的高温寿命短，无法满足一些高温应用。In order to avoid the interference and damage of the load to the power input, the isolated switching power supply has become an indispensable part of various power supply systems. In order to achieve the isolation between the output voltage and the input voltage and to stabilize the output voltage at the set value, it is necessary to use an isolation device to feed back the magnitude of the output voltage to the input side for adjustment control. Figure 1 shows the commonly used secondary side feedback control technique. The task of isolated feedback is carried out by an isolation amplifier consisting of device TL431, optocoupler and auxiliary device. The basic principle is that the transconductance amplifier composed of TL431 and sampling resistors R1 and R2 amplifies the error voltage signal of the output voltage and the reference voltage into a current signal. When the output voltage is high, the current flowing through the TL431 becomes larger, that is, the current. When the current of the optocoupler becomes larger, the voltage of the controller FB port becomes smaller, so that the controller output duty ratio becomes smaller, so that the transformer transmits less energy to the secondary side output terminal, and the output voltage starts to decrease; otherwise, if the output voltage is biased Low, increase the output voltage by increasing the transmission energy of the transformer by feeding the error signal back to the primary side to control the increase of the duty cycle. Repeatedly adjusting the control so that the output voltage is stabilized at the set value. This kind of feedback technology is called the secondary side feedback because its detection and comparison link is on the secondary side of the switching power supply, that is, the load side. This way of directly detecting the output voltage has the characteristics of high precision, but since the presence of these detection, amplifier, and isolation feedback devices increases the space of the power system board, there is obviously no advantage in cost and size. In particular, optocouplers cannot operate at high temperatures and are prone to aging, making the power supply's high temperature life short and unable to meet some high temperature applications.
为了解决上述所遇到的技术问题，公开号为CN 105610306 A，发明名称为《副边反馈控制方法及其控制电路》的发明专利申请提出了一种新型的副边反馈电路，它适用于具有由变压器的原边绕组形成的原边电路和变压器的副边绕组形成的副边电路的隔离开关电源。图2来自上述发明申请实施例四的图6，图3为图2电路反馈开关的工作状态及124处电压波形图，图2所示的副边反馈开关开关电源，它包括：三绕组变压器，它由主边绕组NP、副边绕组NS、辅助绕组NA这三个绕组组成，其中绕组NP包含第一端口102和第二端口103，绕组NS包含第一端口104和第二端口105，绕组NA包含第一端口106和第二端口107。副边调制器由输出电压编码控制模块、检测判断模块构成。副边消磁电路，它包含第一端口110和第二端口111两个端口；输出电容，它包含第一端口131和第二端口132两个端口；反馈开关，它包含漏极端口133、源极端口135和栅极端口134三个端口。输出电压编码控制模块，它包含第一端口112、第二端口113、第三端口114三个端口；检测判断模块，它包含第一端口115、 第二端口116、第三端口117、第四端口118、第五端口119五个端口；辅助绕组电压检测上电阻，它包含第一端口120和第二端口121；辅助绕组电压检测下电阻，它包含第一端口122和第二端口123；反馈开关状态检测模块，它包含第一端口124和第二端口125两个端口；输出电压解码反馈模块，它包含第一端口126和第二端口127两个端口；占空比调制电路，它包含第一端口128、第二端口129、第三端口130三个端口。In order to solve the above-mentioned technical problems, the invention patent application with the publication number CN 105610306 A and the invention name "secondary feedback control method and its control circuit" proposes a novel secondary side feedback circuit, which is suitable for having An isolated switching power supply of a secondary circuit formed by a primary winding formed by a primary winding of the transformer and a secondary winding of the transformer. 2 is a diagram showing the operation state of the feedback switch of the circuit of FIG. 2 and the voltage waveform diagram of 124, and the secondary side feedback switch switching power supply shown in FIG. 2, which includes: a three-winding transformer, It consists of three windings, a primary winding NP, a secondary winding NS, and an auxiliary winding NA, wherein the winding NP comprises a first port 102 and a second port 103, the winding NS comprising a first port 104 and a second port 105, winding NA A first port 106 and a second port 107 are included. The secondary side modulator is composed of an output voltage coding control module and a detection and determination module. a secondary degaussing circuit comprising two ports of a first port 110 and a second port 111; an output capacitor comprising two ports of a first port 131 and a second port 132; a feedback switch comprising a drain port 133, a source terminal Port 135 and gate port 134 are three ports. An output voltage encoding control module, comprising three ports of a first port 112, a second port 113, and a third port 114; a detection judging module, comprising a first port 115, a second port 116, a third port 117, and a fourth port 118, fifth port 119 five ports; auxiliary winding voltage detection upper resistance, which includes a first port 120 and a second port 121; auxiliary winding voltage detection lower resistance, which includes a first port 122 and a second port 123; a feedback switch a state detecting module comprising two ports of a first port 124 and a second port 125; an output voltage decoding feedback module comprising two ports of a first port 126 and a second port 127; a duty cycle modulation circuit comprising the first The port 128, the second port 129, and the third port 130 have three ports.
它们的连接关系为：端口102与输入电源的正极端101相连，端口103与端口130相连；端口104、端口131、端口119一起相连，连接点形成开关电源输出电压的正极端口108；端口105、端口110、反馈开关的漏极端口133、端口115一起相连；端口111、端口118、反馈开关的源极端口135、端口132一起相连，连接点形成开关电源输出电压的负极端口109；反馈开关的栅极端口134与端口112一起相连；端口113与端口116相连；端口114与端口117相连；端口120与端口106相连；端口121、端口122、端口124一起相连；端口125与端口126一起相连；端口127与端口128一起相连；端口129、端口123、端口107一起相连，连接点形成输入电源的负极端。该反激电源开关电源的励磁过程与传统反激开关电源是一样的，它的不同之处在于如何在消磁阶段从副边把输出电压的变化信息反馈到原边。其具体的工作原理详见相关说明书的0086-0090段。Their connection relationship is: port 102 is connected to the positive terminal 101 of the input power source, port 103 is connected to the port 130; port 104, port 131, port 119 are connected together, the connection point forms the positive port 108 of the switching power supply output voltage; port 105, The port 110, the drain port 133 of the feedback switch, and the port 115 are connected together; the port 111, the port 118, the source port 135 of the feedback switch, and the port 132 are connected together, and the connection point forms the negative port 109 of the switching power supply output voltage; the feedback switch The gate port 134 is connected to the port 112; the port 113 is connected to the port 116; the port 114 is connected to the port 117; the port 120 is connected to the port 106; the port 121, the port 122, and the port 124 are connected together; the port 125 is connected to the port 126; Port 127 is connected to port 128; port 129, port 123, and port 107 are connected together, and the connection point forms the negative terminal of the input power. The excitation process of the flyback power switching power supply is the same as that of the conventional flyback switching power supply. The difference is how to feed back the change of the output voltage from the secondary side to the primary side during the degaussing phase. The specific working principle is detailed in paragraphs 0086-0090 of the relevant manual.
开关电源开关电源上述方案的反馈控制简化过程为：副边采样输出电压→编码→控制反馈开关阻态变化→原边检测阻态变化→解码→产生电压调制占空比。该方案既不需要光耦器件也不需要其它额外的隔离传输器件，从而不仅避免这些器件本身所带来的一些固有缺陷，也不会有为辅助这些器件工作而添加的器件，能减小体积和成本，使体积、成本、性能到达最优化，适用范围更广。同时也不会有原边反馈技术的输出电压精度低和不能在副边通过控制进行改变输出电压的问题。Switching Power Supply Switching Power Supply The feedback control simplification process of the above scheme is as follows: secondary side sampling output voltage → coding → control feedback switch resistance state change → primary side detection resistance state change → decoding → generating voltage modulation duty ratio. This solution requires neither optocoupler devices nor other additional isolated transfer devices, thereby avoiding some inherent defects caused by these devices themselves, and there are no devices added to assist the operation of these devices, which can reduce the volume. And cost, to optimize the size, cost, performance, and a wider range of applications. At the same time, there is no problem that the output voltage of the primary feedback technique is low and the output voltage cannot be changed by the secondary side.
但上述方案需保证ΔVref﹤ΔV 124，也就是检测模块能够判断出这种电压突变。若电源***输出电压V OUT＝12V，V 124＝3V，V BE＝3V，ΔV ref＝0.1V，反馈开关导通压降V sdon＝0.06V。 However, the above scheme needs to ensure that ΔVref < ΔV 124 , that is, the detection module can determine such a sudden change in voltage. If the power system output voltage is V OUT =12V, V 124 =3V, V BE =3V, ΔV ref =0.1V, and the feedback switch turns on voltage drop V sdon =0.06V.
由公式：By the formula:
Figure PCTCN2018090364-appb-000001
Figure PCTCN2018090364-appb-000001
可得出：Can be derived:
Figure PCTCN2018090364-appb-000002
Figure PCTCN2018090364-appb-000002
Figure PCTCN2018090364-appb-000003
Figure PCTCN2018090364-appb-000003
导致ΔV ref＞ΔV 124。因此，在高输出电压时，反馈开关状态检测模块难以检测到反馈开关的导通状态是否发生改变，解码与占空比调制模块无法完成反馈开关导通状态的解码及占空比的调整，进而导致电源***无法正常工作。此外，反馈开关在变压器励磁阶段和消磁结束后不能开通，否则会出现输出电容的电荷倒灌，可能导致电源***故障，反馈开关工作时序图如图3所示，其中H表示输出电压编码控制模块112端口输出高电平，驱动反馈开关导通，反馈开关处于低阻区；L表示输出电压编码控制模块112端口输出低电平，驱动反馈开关关闭，由于反馈开关的源极端口135连接至开关电源输出电压的负极端口109，反馈开关关闭时处于高阻区。变压器励磁阶段为0～t1、t4～t5，若在变压器消磁阶段t1～t3、t5～t6时间段内需要开通反馈开关，检测判断模块还需通过端口115检测133处电压，在端口133处电压达到阈值时关闭反馈开关，即t2处关闭反馈开关，避免变压器消磁结束后t3～t4、t6～t7时间段内反馈开关没有及时关闭而出现输出电容的电荷现倒灌。反馈开关控制相对复杂。由于反馈开关与消磁电路并联，反馈开关需采用耐高压器件，增加电源***成本。 Resulting in ΔV ref >ΔV 124 . Therefore, at a high output voltage, the feedback switch state detecting module is difficult to detect whether the conduction state of the feedback switch changes, and the decoding and the duty cycle modulation module cannot complete the decoding of the feedback switch conduction state and the duty ratio adjustment, and further The power system is not working properly. In addition, the feedback switch cannot be turned on after the excitation phase and degaussing of the transformer. Otherwise, the charge of the output capacitor may be reversed, which may cause a power system failure. The timing diagram of the feedback switch operation is shown in FIG. 3, where H represents the output voltage encoding control module 112. The port outputs a high level, the drive feedback switch is turned on, and the feedback switch is in a low resistance region; L indicates that the output voltage code control module 112 port outputs a low level, the drive feedback switch is turned off, and the source port 135 of the feedback switch is connected to the switching power supply. The negative terminal 109 of the output voltage is in the high resistance region when the feedback switch is turned off. The excitation phase of the transformer is 0~t1, t4~t5. If the feedback switch needs to be turned on during the degaussing phase of the transformer t1~t3, t5~t6, the detection and judgment module needs to detect the voltage at 133 through port 115, and the voltage at port 133. When the threshold value is reached, the feedback switch is turned off, that is, the feedback switch is turned off at t2, so that the feedback switch of the output capacitor is not backed up in the time period from t3 to t4 and t6 to t7 after the degaussing of the transformer is completed. Feedback switch control is relatively complicated. Since the feedback switch is connected in parallel with the degaussing circuit, the feedback switch needs to use a high voltage resistant device to increase the power system cost.
发明内容Summary of the invention
本发明要解决的技术问题是提出一种适用于高输出电压的副边反馈控制电路，开关电源。The technical problem to be solved by the present invention is to propose a secondary side feedback control circuit suitable for a high output voltage, a switching power supply.
本发明解决上述技术问题的技术方案如下：The technical solution of the present invention to solve the above technical problems is as follows:
一种副边反馈控制电路，适用于具有由变压器的原边绕组形成的原边电路和变压器的副边绕组形成的副边电路的隔离开关电源，包括：副边消磁电路、检测判断模块、输出电压编码控制模块、反馈开关、辅助绕组电压检测上电阻、辅助绕组电压检测下电阻、反馈开关状态检测模块、输出电压解码反馈模块及占空比调制电路；A secondary side feedback control circuit is applicable to an isolated switching power supply having a secondary side circuit formed by a primary side winding formed by a primary winding of a transformer and a secondary winding formed by a secondary winding of the transformer, comprising: a secondary side degaussing circuit, a detection judging module, and an output Voltage coding control module, feedback switch, auxiliary winding voltage detection upper resistance, auxiliary winding voltage detection lower resistance, feedback switch state detection module, output voltage decoding feedback module and duty cycle modulation circuit;
副边消磁电路在变压器消磁阶段处于导通状态，为变压器的储能给输出电容充电提供路径；在变压器非消磁阶段处于高阻状态，防止输出电容的电荷倒灌；The secondary degaussing circuit is in a conducting state during the degaussing stage of the transformer, providing a path for the storage of the transformer to charge the output capacitor; in the non-degaussing stage of the transformer, the high resistance state is prevented, and the charge of the output capacitor is prevented from being reversed;
检测判断模块检测隔离开关电源的输出电压，并把该电压与内部的基准电压进行比较，输出电压变化信息，并将其发送给输出电压编码控制模块；The detection judging module detects the output voltage of the isolating switching power supply, compares the voltage with the internal reference voltage, outputs the voltage change information, and sends the voltage to the output voltage encoding control module;
输出电压编码控制模块根据接收到的电压变化信息，按照约定的通信协议进行编码，并根据该编码控制反馈开关的工作状态；The output voltage coding control module performs coding according to the received communication change protocol according to the agreed communication protocol, and controls the working state of the feedback switch according to the coding;
反馈开关状态检测模块在每个开关周期的消磁阶段的约定时间通过辅助绕组电压检测上电阻、辅助绕组电压检测下电阻的分压来采样辅助绕组的电压，并且把当前检测的电压与之前检测到的电压进行比较，获得电压的变化幅度和电压的变化方向，输出反馈开关工 作状态变化信息，并将其发送给输出电压解码反馈模块；The feedback switch state detecting module samples the voltage of the auxiliary winding by the auxiliary winding voltage detecting upper resistor and the auxiliary winding voltage detecting the partial pressure of the resistor at the appointed time of the degaussing phase of each switching cycle, and detects the current detected voltage with the previous detected voltage. The voltage is compared, the magnitude of the change of the voltage and the direction of the change of the voltage are obtained, and the change information of the working state of the feedback switch is output and sent to the output voltage decoding feedback module;
输出电压解码反馈模块接收反馈开关工作状态变化信息，根据约定的通信协议进行解码，判断出输出电压偏高还是偏低，输出调制电压，并将其发送给占空比调至电路；The output voltage decoding feedback module receives the feedback state change state information of the feedback switch, decodes according to the agreed communication protocol, determines whether the output voltage is high or low, outputs the modulation voltage, and sends it to the duty cycle to adjust to the circuit;
占空比调制电路接收调制电压，并根据此电压的大小调制变压器主边绕组励磁的占空比，调制电压增加则增加占空比，反之则减小占空比；The duty cycle modulation circuit receives the modulation voltage, and modulates the duty ratio of the excitation of the main side winding of the transformer according to the magnitude of the voltage, and increases the duty ratio when the modulation voltage increases, and vice versa;
其特征在于：反馈开关的控制端连接输出电压编码控制模块、反馈开关的导通电流流出端连接副边消磁电路、反馈开关的导通电流流入端连接开关电源输出电压的负极端口。The utility model is characterized in that: the control end of the feedback switch is connected to the output voltage coding control module, the conduction current outflow end of the feedback switch is connected to the secondary side degaussing circuit, and the conduction current inflow end of the feedback switch is connected to the negative port of the output voltage of the switching power supply.
优选地，反馈开关工作状态变化信息为增加的幅度超过设定值，则认为反馈开关的工作状态由线性区跳变到了饱和区；反之，反馈开关工作状态变化信息为减小的幅度超过设定值，则认为反馈开关的工作状态由饱和区跳变到了线性区。Preferably, if the feedback switch operating state change information is that the increased amplitude exceeds the set value, it is considered that the working state of the feedback switch jumps from the linear region to the saturation region; otherwise, the feedback switch operating state change information is the reduced amplitude exceeds the set value. The value is considered to be the transition from the saturation region to the linear region.
优选地，输出电压解码反馈模块本周期解码的结果是“输出电压偏高”，则逐渐减小调制电压，直到出现“输出电压偏低”为止；反之，若本周期解码的结果是“输出电压偏低”，则逐渐增加调制电压，直到出现“开关电源输出电压偏高”为止。Preferably, the output voltage decoding feedback module outputs the result of the period is “output voltage is high”, and then gradually reduces the modulation voltage until “output voltage is low”; otherwise, if the result of the current decoding is “output voltage” If it is low, the modulation voltage is gradually increased until the "switching power supply output voltage is high".
优选地，所述的反馈开关为MOS管。Preferably, the feedback switch is a MOS tube.
作为应用本技术方案的隔离开关电源的具体的实施方式，包括：三绕组变压器，它由主边绕组NP、副边绕组NS、辅助绕组NA这三个绕组组成，它们分别包含第一端口和第二端口；副边消磁电路，它包含第一端口和第二端口两个端口；输出电容，它包含第一端口和第二端口两个端口；反馈开关，它包含漏极端口、源极端口和栅极端口三个端口；输出电压编码控制模块，它包含第一端口、第二端口；检测判断模块，它包含第一端口、第二端口；辅助绕组电压检测上电阻，它包含第一端口和第二端口；辅助绕组电压检测下电阻，它包含第一端口和第二端口；反馈开关状态检测模块，它包含第一端口和第二端口；输出电压解码反馈模块，它包含第一端口和第二端口两个端口；占空比调制电路，它包含第一端口、第二端口、第三端口三个端口；A specific implementation of the isolated switching power supply applying the technical solution includes: a three-winding transformer, which is composed of three windings of a primary winding NP, a secondary winding NS, and an auxiliary winding NA, which respectively include a first port and a first a two-port; a secondary degaussing circuit comprising two ports of a first port and a second port; an output capacitor comprising two ports of a first port and a second port; and a feedback switch comprising a drain port, a source port, and Three ports of the gate port; an output voltage code control module, which includes a first port and a second port; a detection and determination module, which includes a first port and a second port; and an auxiliary winding voltage detecting upper resistor, which includes the first port and a second port; an auxiliary winding voltage detecting resistor, comprising a first port and a second port; a feedback switch state detecting module comprising a first port and a second port; an output voltage decoding feedback module comprising the first port and the Two ports and two ports; a duty cycle modulation circuit, which includes three ports of a first port, a second port, and a third port;
其连接关系为：主边绕组NP的第一端口与输入电源正极相连，第二端口与占空比调制电路的第三端口相连；副边绕组NS的第一端口、输出电容的第一端口、检测判断模块的第一端口一起相连，连接点形成开关电源输出电压的正极端口；副边绕组NS的第二端口、副边消磁电路的第一端口一起相连；副边消磁电路的第二端口、反馈开关的源极端口相连；输出电压编码控制模块的第二端口与检测判断模块的第二端口相连；反馈开关的漏极端口、输出电容的第二端口一起相连，连接点形成开关电源输出电压的负极端口；反馈开关的栅极端口与输出电压编码控制模块的第一端口项连接；辅助绕组电压检测上电阻的第一端口 与辅助绕组NA的第一端口相连；辅助绕组电压检测上电阻的第二端口、辅助绕组电压检测下电阻的第一端口、反馈开关状态检测模块的第一端口一起相连；反馈开关状态检测模块的第二端口与输出电压解码反馈模块的第一端口一起相连；输出电压解码反馈模块的第二端口与占空比调制电路的第一端口一起相连；占空比调制电路的第二端口、辅助绕组电压检测下电阻的第二端口、辅助绕组NA的第二端口一起相连，连接点形成输入电源的负极端。The connection relationship is: the first port of the primary winding NP is connected to the positive pole of the input power supply, the second port is connected to the third port of the duty cycle modulation circuit; the first port of the secondary winding NS, the first port of the output capacitor, The first ports of the detection and determination module are connected together, the connection point forms a positive port of the switching power supply output voltage; the second port of the secondary winding NS and the first port of the secondary degaussing circuit are connected together; the second port of the secondary degaussing circuit, The source port of the feedback switch is connected; the second port of the output voltage code control module is connected to the second port of the detection and judgment module; the drain port of the feedback switch and the second port of the output capacitor are connected together, and the connection point forms a switching power supply output voltage a negative port; the gate port of the feedback switch is connected to the first port of the output voltage encoding control module; the first port of the auxiliary winding voltage detecting upper resistor is connected to the first port of the auxiliary winding NA; the auxiliary winding voltage is detected by the upper resistor a second port, a first port of the auxiliary winding voltage detecting resistor, and a first end of the feedback switch state detecting module Connected together; the second port of the feedback switch state detection module is connected with the first port of the output voltage decoding feedback module; the second port of the output voltage decoding feedback module is connected with the first port of the duty cycle modulation circuit; The second port of the modulation circuit, the second port of the auxiliary winding voltage detecting lower resistor, and the second port of the auxiliary winding NA are connected together, and the connection point forms a negative terminal of the input power source.
优选地，所述的反馈开关为MOS管。Preferably, the feedback switch is a MOS tube.
上述相关术语解释如下：The above related terms are explained as follows:
约定的通信协议：是指对采样到的开关电源输出电压按照预定的规则进行编号，在原边的解码过程中又默认此编码规则，目的是可以判断出输出电压是否偏高或偏低。具体的编码和解码过程可通过实施例的详细讲解来理解。The agreed communication protocol means that the output voltage of the sampled switching power supply is numbered according to a predetermined rule, and the encoding rule is defaulted in the decoding process of the primary side, and the purpose is to determine whether the output voltage is high or low. The specific encoding and decoding process can be understood by the detailed explanation of the embodiments.
消磁阶段的约定时间：是指副边反馈开关约定在消磁阶段的某时刻或时段动作，原边的检测模块在此预定的时间段感应到此动作才认为有效。The appointment time of the degaussing phase means that the secondary side feedback switch is scheduled to operate at a certain time or time in the degaussing phase, and the detection module of the primary side senses the action to be valid during the predetermined time period.
反馈开关的控制端：控制反馈开关导通与截止的端口，如对于MOS管，指的是MOS管的栅极；对于三极管，指的是三极管的基极。The control terminal of the feedback switch: the port that controls the conduction switch to be turned on and off. For example, for the MOS transistor, it refers to the gate of the MOS transistor; for the triode, it refers to the base of the triode.
反馈开关的导通电流流入端：反馈开关导通后，电流流入的端口，如对于MOS管，指的是MOS管的漏极，无论N沟道、P沟道、增强型还是耗尽型MOS管，在导通时，电流都是由电压高的漏极流向电压低的源极；对于三极管，指的是三极管的集电极，在导通时，电流是由电压高的集电极流向电压低的发射极。On-in current of the feedback switch: When the feedback switch is turned on, the current flowing into the port, such as the MOS transistor, refers to the drain of the MOS transistor, regardless of N-channel, P-channel, enhanced or depleted MOS When the tube is turned on, the current flows from the drain with a high voltage to the source with a low voltage. For the triode, it refers to the collector of the triode. When turned on, the current flows from the collector with a high voltage to a low voltage. The emitter.
反馈开关的导通电流流出端：反馈开关导通后，电流流出的端口，如对于MOS管，指的是MOS管的源极；对于三极管，指的是三极管的发射极。The conduction current flowing out of the feedback switch: after the feedback switch is turned on, the port through which the current flows, such as the MOS tube, refers to the source of the MOS tube; for the triode, it refers to the emitter of the triode.
反馈开关工作状态：是指给反馈开关适当的驱动电压使其工作在饱和区或线性区，饱和区和线性区是相对的而不是设定绝对的界限，它们的区别仅在于反馈开关所产生的控制电压能否在原边检测并正确判断出其工作状态的变化。Feedback switch operating state: refers to the appropriate driving voltage to the feedback switch to operate in the saturation zone or linear zone, the saturation zone and the linear zone are relative rather than set absolute limits, they differ only in the feedback switch Whether the control voltage can be detected on the primary side and correctly judge the change of its working state.
特别地，为了让人更容易理解本发明中的工作原理，在实施例中的编码过程中逻辑关系使用了特定的形式来表示，例如“输出电压偏高”这一信息用“反馈开关处于饱和区”来代表，在实际的产品实现中“输出电压偏高”这一信息也可用“反馈开关处于线性区”来承载，仅是为了更好地阐述本发明，而不是用于限定本发明。In particular, in order to make it easier to understand the working principle in the present invention, the logic relationship in the encoding process in the embodiment is expressed in a specific form, for example, the message "the output voltage is high" is saturated with the "feedback switch". "Representation", in the actual product implementation, the "output voltage is too high" information can also be carried by "feedback switch in the linear region", only to better illustrate the invention, and is not intended to limit the invention.
与现有技术相比，本发明具有以下有益效果：Compared with the prior art, the present invention has the following beneficial effects:
(1)不需要光耦器件也不需要其它额外的隔离传输器件，从而不仅避免这些器件本身所 带来的一些固有缺陷，也不会有为辅助这些器件工作而添加的器件，减小体积和成本，使体积、成本、性能到达最优化，适用范围更广。(1) No optocoupler devices are required and no additional isolation transfer devices are required, thereby avoiding not only some of the inherent defects inherent in these devices, but also devices added to assist in the operation of these devices, reducing the size and The cost is optimized for volume, cost and performance, and the scope of application is wider.
(2)同时也不会有原边反馈技术的输出电压精度低和不能在副边通过控制进行改变输出电压的问题。(2) At the same time, there is no problem that the output voltage of the primary feedback technique is low and the output voltage cannot be changed by the secondary side.
(3)在高输出电压时可确保ΔV ref﹤ΔV 124，使电源***稳定工作，相关原理分析在实施例部分以具体的开关电源设计及计算进行展示。 (3) At high output voltage, ΔV ref <ΔV 124 can be ensured to make the power supply system work stably. The relevant principle analysis is shown in the embodiment part with specific switching power supply design and calculation.
(4)此外，该发明中反馈开关与消磁通路串联，在变压器励磁阶段和消磁结束后消磁电路会自行截止以防止输出电容的电荷倒灌，反馈开关的工作状态图时序如图5所示，其中H表示输出电压编码控制模块112端口输出高电平，驱动反馈开关导通，反馈开关工作于线性区；L表示输出电压编码控制模块112端口输出低电平，本发明中由于反馈开关的漏极135连接至开关电源输出电压的负极端口109，112端口为低电平时反馈开关工作于饱和区。变压器励磁阶段为0～t1、t3～t4，消磁结束阶段为t2～t3、t5～t6。(4) In addition, in the invention, the feedback switch is connected in series with the degaussing path, and the degaussing circuit will automatically cut off after the excitation phase and the degaussing to prevent the charge of the output capacitor from being reversed. The timing of the working state diagram of the feedback switch is as shown in FIG. 5, wherein H indicates that the output voltage encoding control module 112 port outputs a high level, the driving feedback switch is turned on, the feedback switch operates in a linear region; L indicates that the output voltage encoding control module 112 port outputs a low level, and the drain of the feedback switch in the present invention 135 is connected to the negative port 109 of the switching power supply output voltage. When the port 112 is low, the feedback switch operates in the saturation region. The transformer excitation phase is 0 to t1, t3 to t4, and the degaussing end phase is t2 to t3 and t5 to t6.
(5)检测判断模块无需通过采样副边消磁电路第一端口处的电压来判断变压器是否处于消磁阶段t1～t2、t4～t5，只需通过开关电源输出电压的正极端口检测开关电源的输出电压，并把该电压与内部的基准电压进行比较，比较的结果决定反馈开关工作状态，降低反馈开关控制难度，这是它的突出优点。(5) The detection and judgment module does not need to detect whether the transformer is in the degaussing phase t1~t2, t4~t5 by sampling the voltage at the first port of the degaussing circuit of the secondary side, and only needs to detect the output voltage of the switching power supply through the positive port of the output voltage of the switching power supply. And compare the voltage with the internal reference voltage. The result of the comparison determines the working state of the feedback switch and reduces the difficulty of controlling the feedback switch. This is its outstanding advantage.
(6)本发明中的反馈开关只需采用低压器件，降低电源***成本。(6) The feedback switch of the present invention only needs to use a low voltage device to reduce the power system cost.
附图说明DRAWINGS
图1为应用传统副边反馈控制器的开关电源典型电路图；Figure 1 is a typical circuit diagram of a switching power supply using a conventional secondary side feedback controller;
图2为新型应用副边反馈控制电路的开关电源典型电路图；2 is a typical circuit diagram of a switching power supply of a novel application secondary side feedback control circuit;
图3为图2电路反馈开关的工作状态及124处电压波形图；Figure 3 is a diagram showing the working state of the feedback switch of the circuit of Figure 2 and the voltage waveform at 124;
图4为应用本发明第一实施例的副边反馈控制电路的开关电源原理框图；4 is a block diagram showing the principle of a switching power supply to which a secondary side feedback control circuit according to a first embodiment of the present invention is applied;
图5为本发明反馈开关的工作状态及124处电压波形图。FIG. 5 is a diagram showing the working state of the feedback switch and the voltage waveform at 124 in the present invention.
具体实施方式Detailed ways
为了使本发明更加清楚明白，以下结合附图及实施例，对本发明进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。In order to make the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
实施例一Embodiment 1
图4为应用本发明第一实施例的副边反馈控制电路的开关电源原理框图，该开关电源包括：三绕组变压器，它由主边绕组NP、副边绕组NS、辅助绕组NA这三个绕组组成，其中绕组NP包含第一端口102和第二端口103，绕组NS包含第一端口104和第二端口105， 绕组NA包含第一端口106和第二端口107；副边消磁电路，它包含第一端口110和第二端口111两个端口；输出电容，它包含第一端口131和第二端口132两个端口；反馈开关，它包含漏极端口135、源极端口133和栅极端口134三个端口；输出电压编码控制模块，它包含第一端口112、第二端口114；检测判断模块，它包含第一端口119、第二端口117；辅助绕组电压检测上电阻R FA1，它包含第一端口120和第二端口121；辅助绕组电压检测下电阻R FA2，它包含第一端口122和第二端口123；反馈开关状态检测模块，它包含第一端口124和第二端口125两个端口；输出电压解码反馈模块，它包含第一端口126和第二端口127两个端口；占空比调制电路，它包含第一端口128、第二端口129、第三端口130三个端口。 4 is a block diagram showing a principle of a switching power supply to which a secondary side feedback control circuit according to a first embodiment of the present invention is applied. The switching power supply includes a three-winding transformer including three windings of a primary winding NP, a secondary winding NS, and an auxiliary winding NA. Composition, wherein the winding NP comprises a first port 102 and a second port 103, the winding NS comprises a first port 104 and a second port 105, the winding NA comprises a first port 106 and a second port 107; a secondary side degaussing circuit, which comprises Two ports of one port 110 and second port 111; an output capacitor comprising two ports of a first port 131 and a second port 132; a feedback switch comprising a drain port 135, a source port 133 and a gate port 134 a port; an output voltage encoding control module, comprising a first port 112, a second port 114; a detection judging module comprising a first port 119, a second port 117; an auxiliary winding voltage detecting upper resistor R FA1 , which includes the first port 120 and second port 121; the auxiliary winding voltage detection resistor R FA2, which comprises a first port 122 and second port 123; feedback switch state detection module, comprising a first and second port 124 Port 125 two ports; an output voltage decoding feedback module, which includes two ports, a first port 126 and a second port 127; a duty cycle modulation circuit, which includes a first port 128, a second port 129, and a third port 130 Ports.
它们的连接关系为：端口102与输入电源的正极端101相连，端口103与端口130相连；端口104、端口131、端口119一起相连，连接点形成开关电源输出电压的正极端口108；端口105、端口110一起相连；端口111、反馈开关的源极端口133一起相连；反馈开关的漏极端口135、端口132一起相连，连接点形成开关电源输出电压的负极端口109；反馈开关的栅极端口134、端口112一起相连；端口114与端口117相连；端口120与端口106相连；端口121、端口122、端口124一起相连；端口125与端口126一起相连；端口127与端口128一起相连；端口129、端口123、端口107一起相连，连接点形成输入电源的负极端。Their connection relationship is: port 102 is connected to the positive terminal 101 of the input power source, port 103 is connected to the port 130; port 104, port 131, port 119 are connected together, the connection point forms the positive port 108 of the switching power supply output voltage; port 105, The ports 110 are connected together; the port 111 and the source port 133 of the feedback switch are connected together; the drain port 135 and the port 132 of the feedback switch are connected together, the connection point forms the negative port 109 of the switching power supply output voltage; and the gate port 134 of the feedback switch Ports 112 are connected together; port 114 is connected to port 117; port 120 is connected to port 106; port 121, port 122, port 124 are connected together; port 125 is connected with port 126; port 127 is connected with port 128; port 129, Port 123 and port 107 are connected together, and the connection point forms the negative terminal of the input power.
具体的工作原理是：The specific working principle is:
检测判断模块的作用为：通过端口119检测开关电源的输出电压，并把该电压与内部的基准电压进行比较，比较的结果可决定反馈开关是否改变工作状态，并把此信息通过它的端口端口117传递给输出电压编码控制模块。The function of the detection and judgment module is: detecting the output voltage of the switching power supply through the port 119, and comparing the voltage with the internal reference voltage, the result of the comparison can determine whether the feedback switch changes the working state, and passes the information through its port port. 117 is passed to the output voltage encoding control module.
输出电压编码控制模块包括两个作用：一是，编码作用，设定编码规则——输出电压从偏高状态变化到偏低状态时反馈开关工作状态需从饱和区变化到线性区，反之，输出电压从偏低状态变化到偏高状态时反馈开关工作状态需从线性区变化到饱和区。那么，输出电压偏高时反馈开关工作状态应处于饱和区，反馈开关驱动电平为低电平；输出电压偏低时反馈开关应处于线性区，反馈开关驱动电平为高电平。二是，控制作用，控制反馈开关栅极处于相应的编码电平，即输出电压偏高时端口112输出低电平，输出电压偏低时端口112输出高电平。The output voltage coding control module includes two functions: one is the coding function, and the coding rule is set. When the output voltage changes from a high state to a low state, the feedback switch operation state needs to change from a saturation region to a linear region, and vice versa. When the voltage changes from a low state to a high state, the feedback switch operating state needs to change from a linear region to a saturated region. Then, when the output voltage is high, the feedback switch should be in the saturation region, and the feedback switch drive level should be low; when the output voltage is low, the feedback switch should be in the linear region, and the feedback switch drive level is high. Second, the control function controls the feedback switch gate to be at the corresponding encoding level, that is, the port 112 outputs a low level when the output voltage is high, and the port 112 outputs a high level when the output voltage is low.
变压器的传输过程：因为有输出电容C OUT储能作用的存在，开关电源在一个甚至几个周期内输出电压是不会发生较大的突变，所以在短时间内可以忽略电容C OUT电压V OUT的变化。 根据本发明内容可知，现在需要在V OUT上叠加一个控制电压，为此我们采用整流二级管作为副边消磁通路，如图4所示，这是最简单也是最常用的方式。因为二级管的结压降V BE的存在，反馈开关在消磁阶段工作于线性区时，绕组NS端口104与端口105的压差最小值为(V OUT+V BE+V dson)，其中V dson是反馈开关工作于线性区时漏极与源极之间的压差；反馈开关在消磁阶段工作于饱和区时，绕组NS端口104与端口105的压差值为(V OUT+V BE+V DS)，其中V DS是反馈开关工作于饱和区时漏极与源极之间的压差。可见，消磁阶段反馈MOS开关工作于线性区或饱和区可使得绕组两端的压差发生了较大的突变，通过折算，在反馈开关状态检测模块的端口124处电压变化大小为： Transformer transmission process: Because there is the storage capacity of the output capacitor C OUT , the output voltage of the switching power supply will not change greatly in one or even several cycles, so the capacitor C OUT voltage V OUT can be ignored in a short time. The change. According to the present invention, it is now necessary to superimpose a control voltage on V OUT . For this purpose, we use a rectifying diode as the secondary side degaussing path, as shown in Figure 4, which is the simplest and most common way. Because of the junction voltage drop V BE of the diode, when the feedback switch operates in the linear region during the degaussing phase, the minimum voltage difference between the winding NS port 104 and the port 105 is (V OUT +V BE +V dson ), where V Dson is the voltage difference between the drain and the source when the feedback switch operates in the linear region; when the feedback switch operates in the saturation region during the degaussing phase, the voltage difference between the winding NS port 104 and the port 105 is (V OUT +V BE + V DS ), where V DS is the voltage difference between the drain and the source when the feedback switch operates in the saturation region. It can be seen that the feedback MOS switch in the degaussing stage operates in the linear region or the saturation region, so that the voltage difference across the winding has undergone a large abrupt change. By conversion, the voltage variation at the port 124 of the feedback switch state detecting module is:
Figure PCTCN2018090364-appb-000004
Figure PCTCN2018090364-appb-000004
其中n A/n S是绕组NA与绕组NS匝数之比。 Where n A / n S is the ratio of the winding NA to the number of turns of the winding NS.
反馈开关状态检测模块的检测判断过程：为了让人更加直观地理解此传输过程，下面具体地设计一个电源开关电源来阐述。选择V OUT＝12V，V 124＝3V，ΔV ref＝0.1V，V BE＝0.4V，反馈开关管工作于饱和区的导通压降V DS＝3V，反馈开关管工作于线性区的导通压降V dson＝0.06V。 The detection and determination process of the feedback switch state detecting module: In order to make the transmission process more intuitive, a power switching power supply is specifically designed to be explained below. Select V OUT =12V, V 124 =3V, ΔV ref =0.1V, V BE =0.4V, the feedback switch operates in the saturation region with a turn-on voltage drop of V DS =3V, and the feedback switch operates in the linear region. The pressure drop V dson = 0.06V.
由公式：By the formula:
Figure PCTCN2018090364-appb-000005
Figure PCTCN2018090364-appb-000005
可得出：Can be derived:
Figure PCTCN2018090364-appb-000006
Figure PCTCN2018090364-appb-000006
Figure PCTCN2018090364-appb-000007
Figure PCTCN2018090364-appb-000007
ΔV ref＜ΔV 124，可以判断出反馈开关工作状态从线性区变化到了饱和区；反之，则可以判断出反馈开关工作状态从饱和区变化到了线性区。 ΔV ref <ΔV 124 , it can be judged that the working state of the feedback switch changes from the linear region to the saturation region; conversely, it can be judged that the working state of the feedback switch changes from the saturation region to the linear region.
解码与占空比调制过程：按照编码过程中设定的编码规则，应该设定解码规则为，当接收到“反馈开关工作状态从饱和区变化到线性区”的判断结果时相应地解码出“输出电压从偏高状态变化到偏低状态”，反之，当接收到“反馈开关工作状态从线性区变化到饱和区”的判断结果时相应地解码出“输出电压从偏低状态变化到偏高状态”。若解码结果是“输出电压从偏高状态变化到偏低状态”，表明变化之前输出电压是偏高的，当前输出电压是偏 低的，直到再次接收到相反方向的状态变化；反之，可以得知当前输出电压是偏高的。可见，只要按照这两个设定而构成的通信协议进行控制和传输，便可把隔离变压器副边输出电压的大小反馈到它的原边。当输出电压偏高时逐渐减小调制电压V crl，它控制占空比逐渐减小，从而致使输出电压降低；反之，输出电压偏低时逐渐增加占空比使其再次升高。如此反复，把输出电压稳定在设定值。 Decoding and duty cycle modulation process: According to the coding rules set in the encoding process, the decoding rule should be set to decode the corresponding result when receiving the judgment result of “the feedback switch operating state changes from the saturation region to the linear region”. The output voltage changes from a high state to a low state. On the contrary, when the judgment result of the "feedback switch operating state changes from the linear region to the saturation region" is received, the output voltage is correspondingly decoded from the low state to the high state. status". If the decoding result is "the output voltage changes from the high state to the low state", it indicates that the output voltage is too high before the change, and the current output voltage is low until the state change in the opposite direction is received again; otherwise, it can be obtained Know that the current output voltage is too high. It can be seen that as long as the communication protocol formed by the two settings is controlled and transmitted, the output voltage of the secondary side of the isolation transformer can be fed back to its primary side. When the output voltage is high, the modulation voltage Vcrl is gradually decreased, which controls the duty ratio to gradually decrease, thereby causing the output voltage to decrease; conversely, when the output voltage is low, the duty ratio is gradually increased to rise again. Repeat this way to stabilize the output voltage at the set value.
通过检测判断模块和输出电压编码控制模块使得反馈开关管工作于线性区或饱和区，增大了端口124处电压的变化幅值，使得电源***在高输出电压时，反馈开关状态检测模块能可靠地检测到反馈开关工作状态的变化，进而解码后调节占空比，把输出电压稳定在设定值。The detection switch module and the output voltage code control module enable the feedback switch tube to operate in the linear region or the saturation region, thereby increasing the amplitude of the voltage change at the port 124, so that the feedback switch state detection module can be reliable when the power system is at a high output voltage. The ground switch detects the change of the working state of the feedback switch, and then adjusts the duty ratio after decoding to stabilize the output voltage at the set value.
以上仅是本发明的优选实施方式，应当指出的是，上述优选实施方式不应视为对本发明的限制，本发明的保护范围应当以权利要求所限定的范围为准。对于本技术领域的普通技术人员来说，在不脱离本发明的精神和范围内，还可以做出若干改进和润饰，这些改进和润饰也应视为本发明的保护范围。The above is only a preferred embodiment of the present invention, and it should be noted that the above-described preferred embodiments are not to be construed as limiting the scope of the invention, and the scope of the invention should be determined by the scope defined by the claims. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and scope of the invention.

Claims (6)

  1. 一种副边反馈控制电路，适用于具有由变压器的原边绕组形成的原边电路和变压器的副边绕组形成的副边电路的隔离开关电源，包括：副边消磁电路、检测判断模块、输出电压编码控制模块、反馈开关、辅助绕组电压检测上电阻、辅助绕组电压检测下电阻、反馈开关状态检测模块、输出电压解码反馈模块及占空比调制电路；A secondary side feedback control circuit is applicable to an isolated switching power supply having a secondary side circuit formed by a primary side winding formed by a primary winding of a transformer and a secondary winding formed by a secondary winding of the transformer, comprising: a secondary side degaussing circuit, a detection judging module, and an output Voltage coding control module, feedback switch, auxiliary winding voltage detection upper resistance, auxiliary winding voltage detection lower resistance, feedback switch state detection module, output voltage decoding feedback module and duty cycle modulation circuit;
    副边消磁电路在变压器消磁阶段处于导通状态，为变压器的储能给输出电容充电提供路径；在变压器非消磁阶段处于高阻状态，防止输出电容的电荷倒灌；The secondary degaussing circuit is in a conducting state during the degaussing stage of the transformer, providing a path for the storage of the transformer to charge the output capacitor; in the non-degaussing stage of the transformer, the high resistance state is prevented, and the charge of the output capacitor is prevented from being reversed;
    检测判断模块检测隔离开关电源的输出电压，并把该电压与内部的基准电压进行比较，输出电压变化信息，并将其发送给输出电压编码控制模块；The detection judging module detects the output voltage of the isolating switching power supply, compares the voltage with the internal reference voltage, outputs the voltage change information, and sends the voltage to the output voltage encoding control module;
    输出电压编码控制模块根据接收到的电压变化信息，按照约定的通信协议进行编码，并根据该编码控制反馈开关的工作状态；The output voltage coding control module performs coding according to the received communication change protocol according to the agreed communication protocol, and controls the working state of the feedback switch according to the coding;
    反馈开关状态检测模块在每个开关周期的消磁阶段的约定时间通过辅助绕组电压检测上电阻、辅助绕组电压检测下电阻的分压来采样辅助绕组的电压，并且把当前检测的电压与之前检测的电压进行比较，获得电压的变化幅度和电压的变化方向，输出反馈开关工作状态变化信息，并将其发送给输出电压解码反馈模块；The feedback switch state detecting module samples the voltage of the auxiliary winding through the auxiliary winding voltage detecting upper resistor and the auxiliary winding voltage detecting the partial pressure of the resistor at the appointed time of the degaussing phase of each switching cycle, and the current detected voltage is compared with the previously detected voltage. The voltage is compared, the magnitude of the change of the voltage and the direction of the change of the voltage are obtained, and the change information of the working state of the feedback switch is output and sent to the output voltage decoding feedback module;
    输出电压解码反馈模块接收反馈开关工作状态变化信息，根据约定的通信协议进行解码，判断出输出电压偏高还是偏低，输出调制电压，并将其发送给占空比调至电路；The output voltage decoding feedback module receives the feedback state change state information of the feedback switch, decodes according to the agreed communication protocol, determines whether the output voltage is high or low, outputs the modulation voltage, and sends it to the duty cycle to adjust to the circuit;
    占空比调制电路接收调制电压，并根据此电压的大小调制变压器主边绕组励磁的占空比，调制电压增加则增加占空比，反之则减小占空比；The duty cycle modulation circuit receives the modulation voltage, and modulates the duty ratio of the excitation of the main side winding of the transformer according to the magnitude of the voltage, and increases the duty ratio when the modulation voltage increases, and vice versa;
    其特征在于：反馈开关的控制端连接输出电压编码控制模块、反馈开关的导通电流流出端连接副边消磁电路、反馈开关的导通电流流入端连接开关电源输出电压的负极端口。The utility model is characterized in that: the control end of the feedback switch is connected to the output voltage coding control module, the conduction current outflow end of the feedback switch is connected to the secondary side degaussing circuit, and the conduction current inflow end of the feedback switch is connected to the negative port of the output voltage of the switching power supply.
  2. 根据权利要求1所述的副边反馈控制电路，其特征在于：反馈开关工作状态变化信息为增加的幅度超过设定值，则认为反馈开关的工作状态由线性区跳变到了饱和区；反之，反馈开关工作状态变化信息为减小的幅度超过设定值，则认为反馈开关的工作状态由饱和区跳变到了线性区。The secondary side feedback control circuit according to claim 1, wherein the feedback switch operating state change information is that the increased amplitude exceeds the set value, and then the operating state of the feedback switch is changed from a linear region to a saturated region; If the feedback switch operating state change information is that the reduced amplitude exceeds the set value, it is considered that the working state of the feedback switch jumps from the saturation region to the linear region.
  3. 根据权利要求1所述的副边反馈控制电路，其特征在于：输出电压解码反馈模块本周期解码的结果是“输出电压偏高”，则逐渐减小调制电压，直到出现“输出电压偏低”为止；反之，若本周期解码的结果是“输出电压偏低”，则逐渐增加调制电压，直到出现“开关电源输出电压偏高”为止。The secondary side feedback control circuit according to claim 1, wherein the output voltage decoding feedback module outputs "the output voltage is too high", and the modulation voltage is gradually decreased until the "output voltage is low" occurs. On the other hand, if the result of the decoding of this period is "the output voltage is low", the modulation voltage is gradually increased until the "switching power supply output voltage is high" appears.
  4. 根据权利要求1所述的副边反馈控制电路，其特征在于：反馈开关为MOS管。The secondary side feedback control circuit according to claim 1, wherein the feedback switch is a MOS transistor.
  5. 应用权利要求1所述副边反馈控制电路的开关电源，其特征在于：包括：三绕组变压器，它由主边绕组NP、副边绕组NS、辅助绕组NA这三个绕组组成，它们分别包含第一端口和第二端口；副边消磁电路，它包含第一端口和第二端口两个端口；输出电容，它包含第一端口和第二端口两个端口；反馈开关，它包含漏极端口、源极端口和栅极端口三个端口；输出电压编码控制模块，它包含第一端口、第二端口；检测判断模块，它包含第一端口、第二端口；辅助绕组电压检测上电阻，它包含第一端口和第二端口；辅助绕组电压检测下电阻，它包含第一端口和第二端口；反馈开关状态检测模块，它包含第一端口和第二端口；输出电压解码反馈模块，它包含第一端口和第二端口两个端口；占空比调制电路，它包含第一端口、第二端口、第三端口三个端口。A switching power supply applying the secondary side feedback control circuit according to claim 1, comprising: a three-winding transformer comprising three windings of a primary winding NP, a secondary winding NS, and an auxiliary winding NA, respectively a port and a second port; a secondary degaussing circuit comprising two ports of a first port and a second port; an output capacitor comprising two ports of a first port and a second port; a feedback switch comprising a drain port, Three ports of source port and gate port; output voltage coding control module, which includes a first port and a second port; a detection and determination module, which includes a first port and a second port; and an auxiliary winding voltage detection upper resistor, which includes a first port and a second port; an auxiliary winding voltage detecting lower resistor, comprising a first port and a second port; a feedback switch state detecting module comprising a first port and a second port; and an output voltage decoding feedback module comprising Two ports of one port and two ports; a duty cycle modulation circuit, which includes three ports of a first port, a second port, and a third port.
    其连接关系为：主边绕组NP的第一端口与输入电源正极相连，第二端口与占空比调制电路的第三端口相连；副边绕组NS的第一端口、输出电容的第一端口、检测判断模块的第一端口一起相连，连接点形成开关电源输出电压的正极端口；副边绕组NS的第二端口、副边消磁电路的第一端口一起相连；副边消磁电路的第二端口、反馈开关的源极端口相连；输出电压编码控制模块的第二端口与检测判断模块的第二端口相连；反馈开关的漏极端口、输出电容的第二端口一起相连，连接点形成开关电源输出电压的负极端口；反馈开关的栅极端口与输出电压编码控制模块的第一端口相连；辅助绕组电压检测上电阻的第一端口与辅助绕组NA的第一端口相连；辅助绕组电压检测上电阻的第二端口、辅助绕组电压检测下电阻的第一端口、反馈开关状态检测模块的第一端口一起相连；反馈开关状态检测模块的第二端口与输出电压解码反馈模块的第一端口一起相连；输出电压解码反馈模块的第二端口与占空比调制电路的第一端口一起相连；占空比调制电路的第二端口、辅助绕组电压检测下电阻的第二端口、辅助绕组NA的第二端口一起相连，连接点形成输入电源的负极端。The connection relationship is: the first port of the primary winding NP is connected to the positive pole of the input power supply, the second port is connected to the third port of the duty cycle modulation circuit; the first port of the secondary winding NS, the first port of the output capacitor, The first ports of the detection and determination module are connected together, the connection point forms a positive port of the switching power supply output voltage; the second port of the secondary winding NS and the first port of the secondary degaussing circuit are connected together; the second port of the secondary degaussing circuit, The source port of the feedback switch is connected; the second port of the output voltage code control module is connected to the second port of the detection and judgment module; the drain port of the feedback switch and the second port of the output capacitor are connected together, and the connection point forms a switching power supply output voltage a negative port; a gate port of the feedback switch is connected to the first port of the output voltage encoding control module; a first port of the auxiliary winding voltage detecting upper resistor is connected to the first port of the auxiliary winding NA; and an auxiliary winding voltage detecting upper resistor The first port of the two-port, auxiliary winding voltage detection resistor, and the first port of the feedback switch state detection module Connected; the second port of the feedback switch state detection module is connected with the first port of the output voltage decoding feedback module; the second port of the output voltage decoding feedback module is connected with the first port of the duty cycle modulation circuit; The second port of the modulation circuit, the second port of the auxiliary winding voltage detecting lower resistor, and the second port of the auxiliary winding NA are connected together, and the connection point forms a negative terminal of the input power source.
  6. 根据权利要求5所述的开关电源，其特征在于：反馈开关为MOS管。A switching power supply according to claim 5, wherein the feedback switch is a MOS transistor.
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