WO2022033239A1 - Current detection circuit, converter, and current detection method for converter - Google Patents

Current detection circuit, converter, and current detection method for converter Download PDF

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Publication number
WO2022033239A1
WO2022033239A1 PCT/CN2021/104747 CN2021104747W WO2022033239A1 WO 2022033239 A1 WO2022033239 A1 WO 2022033239A1 CN 2021104747 W CN2021104747 W CN 2021104747W WO 2022033239 A1 WO2022033239 A1 WO 2022033239A1
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Prior art keywords
switch
capacitor
resonant
current detection
circuit
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PCT/CN2021/104747
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French (fr)
Chinese (zh)
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杜鹃
吴辉
李斌华
李永昌
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广州金升阳科技有限公司
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Publication of WO2022033239A1 publication Critical patent/WO2022033239A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
    • 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
    • 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
    • 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
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0009—Devices or circuits for detecting current in a converter
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Definitions

  • the present invention relates to the technical field of switching converters, in particular to a current detection circuit, a converter including the current detection circuit, and a current detection method in the converter.
  • switching converters have been widely used. People put more demands on switching converters: high power density, high reliability and small size. Among them, LLC resonant converters have been widely used due to their advantages such as soft switching, low noise, and low stress.
  • the existing current detection scheme uses current detection resistors or current transformers to realize current detection, as shown in Figure 1 and Figure 2 respectively, in which the primary coil of the transformer includes the actual excitation inductance. The cavity is described, and the transformer magnetizing inductance Lm is marked in the drawing.
  • the current-sense resistor Rcr is directly connected in series in the loop that needs current detection, and the detected current is reflected by the terminal voltage of the current-sense resistor Rcr; although the circuit structure of this scheme is simple, the loss caused by the current-sense resistor cannot be ignored.
  • the current detection range and sampling accuracy are limited and affect system performance.
  • the resonant current is coupled to the secondary circuit through a current transformer, converted into a voltage signal after being rectified by a diode, and sent to the control circuit;
  • the components of this detection scheme are complex, requiring a current transformer, four rectifier diodes D3, D4, D5, D6 and a sampling resistor Rcr have high manufacturing cost; and the primary side of the current transformer is connected in series in the resonant cavity, and the primary side current is the current of the resonant cavity.
  • the working current of the resonant converter is relatively large. For the detection accuracy, the more turns of the secondary winding of the sampling circuit, the better, which will lead to a larger volume of the current transformer, and the detection accuracy is affected by the accuracy of the transformer.
  • Figure 3 provides a peak current detection scheme applied to asymmetric half-bridge flyback and other similar resonant topologies.
  • the current detection scheme of Fig. 3 can only convert the current flowing through the resonance capacitor Cr into a voltage signal proportionally through the resistor Rs when the current direction of the resonance capacitor Cr is from right to left for the control circuit to use; the detection scheme uses a diode D1 filters out the sampled negative current signal, and can only be used in the case where the resonant capacitor of the switching converter has a stable reference ground, and cannot meet the resonant current detection requirements of the full-bridge structure.
  • the present invention proposes a technical solution to solve the defects of the existing current detection circuit.
  • the technical problem to be solved by the present invention is to provide a practical current detection scheme for the floating device in the switching converter, so as to solve the problems of complicated circuit, high cost and high loss in the existing current detection technology.
  • the present invention provides a current detection circuit, which includes: a shunt resistor Rcr, a shunt capacitor Cc, a switching diode Dcr and a detection switch Q5; the cathode of the switching diode Dcr is connected to the shunt resistor Rcr and the shunt capacitor At the series node of Ccr, the anode of the switching diode Dcr is powered by a voltage source through a resistor Rv or directly powered by a constant current source; one end of the detection switch Q5 is connected to the anode of the switching diode Dcr.
  • the shunt resistor Rcr and the shunt capacitor Ccr form a shunt branch and are connected in parallel to both ends of the resonant capacitor Cr of the resonant circuit.
  • the detection switch Q5 is a controlled switch. When the voltage of one end of the resonant capacitor Cr is floating, the detection switch Q5 is controlled to be turned on, and the switch diode Dcr is reversely turned off; when the voltage of one end of the resonant capacitor Cr is in common ground , the detection switch Q5 is controlled to be turned off, the switch diode Dcr is turned on, and the voltage generated by the anode of the switch diode Dcr reflects the size of the current flowing through the resonant capacitor Cr.
  • the detection switch Q5 is a controlled switch, which is a triode, a MOSFET or an IGBT.
  • the present invention also provides a converter, which includes the above-mentioned current detection circuit, an inverter circuit, a resonance circuit, a transformer and a rectifier network, the resonance circuit has a resonance inductance Lr and a resonance capacitor Cr, and a shunt resistance in the current detection circuit Rcr and the shunt capacitor Ccr form a shunt branch, and the shunt branch is connected in parallel with both ends of the resonant capacitor Cr.
  • the inverter circuit is a full-bridge topology structure composed of four switch tubes or a half-bridge topology structure composed of two switch tubes, and the inverter circuit has a first output end and a second output end;
  • the resonant capacitor Cr and the resonant inductor Lr are connected in series between the first output end of the inverter circuit and the first end of the primary coil of the transformer, and the connection of the resonant capacitor Cr is a floating connection;
  • the second end of the primary coil of the transformer is connected to the second output end of the inverter circuit, and the secondary side of the transformer is connected to the rectifier network.
  • the resonant circuit is further provided with a resonant capacitor Cr1, the resonant capacitor Cr1 is connected between the second end of the primary coil of the transformer and the second output end of the inverter circuit, and the connection of the resonant capacitor Cr1 is a floating connection , the two ends of the resonance capacitor Cr1 are connected in parallel with a second current detection circuit, and the second current detection circuit has a shunt resistor R1, a shunt capacitor C1, a switching diode D3, a voltage source Vc, a resistor R2 and a detection switch Q6;
  • the cathode of the switching diode D3 is connected to the series node of the shunt resistor R1 and the shunt capacitor C1, the anode of the switching diode D3 is powered by the voltage source through the resistor R2 or directly powered by the constant current source; one end of the detection switch Q6 is connected to the anode of the switching diode D3.
  • the present invention also provides a current detection method, comprising the following steps:
  • the switch tube is controlled so that one end of the floating capacitor Cr is grounded;
  • the detection switch Q5 is controlled so that the switch diode Dcr is turned on, and when the switch diode Dcr is turned on, the current data flowing through the capacitor Cr is obtained by collecting the voltage data of the anode of the switch diode Dcr.
  • the switch tube includes a switch tube Q1, a switch tube Q2, a switch tube Q3 and a switch tube Q4, and the switch tube Q1, the switch tube Q2, the switch tube Q3 and the switch tube Q4 form a full-bridge topology structure ;
  • the present invention has the following beneficial effects:
  • the structure of the present invention adopts a shunt branch in parallel with both ends of the resonant capacitor Cr, the current flowing through the shunt branch is very small, and the shunt resistance value Rcr is very small, which is equivalent to non-destructive testing, and can ensure the normal working efficiency of the circuit;
  • the current detection scheme proposed by the present invention only needs to use patch devices such as resistors, capacitors, and diodes to realize the detection of the resonant cavity current, the circuit structure is simple, and the cost is low; and it is verified by the sampling results of the preferred embodiment of the present invention. , the sampling accuracy of the detection circuit is high;
  • the current detection scheme proposed by the present invention can provide a beneficial current detection idea for floating devices in switching converters, and is widely used.
  • FIG. 1 is a schematic diagram of a circuit for implementing current detection using a current-sensing resistor in the prior art
  • Fig. 2 is the circuit schematic diagram of adopting current transformer to realize current detection in the prior art
  • FIG. 3 is a schematic diagram of a peak current detection circuit applied to a resonant topology such as an asymmetric half-bridge flyback in the prior art;
  • FIG. 4 is a schematic diagram of the LLC resonant converter according to the first embodiment of the present invention.
  • Fig. 5 is the current detection result of the first embodiment of the present invention.
  • FIG. 6 is a schematic diagram of an LLC resonant converter according to a second embodiment of the present invention.
  • the current detection circuit of the present invention can be applied to an LLC resonant converter composed of an inverter circuit, a resonant circuit, a transformer and a rectifier network, and is used for current detection of a floating type device of the LLC resonant converter.
  • the primary coil of the transformer includes the actual excitation inductance.
  • the excitation inductance Lm of the transformer is marked in FIG. 4 .
  • the LLC resonant converter is taken as the preferred implementation topology, and the specific current detection implementation process is introduced.
  • the LLC resonant converter includes a current detection circuit, an inverter circuit, a resonant circuit, a transformer, and a rectifier network.
  • the inverter circuit can be a full-bridge structure composed of a switch tube Q1, a switch tube Q2, a switch tube Q3, and a switch tube Q4, and the inverter circuit can also be a half-bridge structure composed of a switch tube Q1 and a switch tube Q3, wherein the switch tube Q1-Q4 are used to control the working state of the power circuit, which can be controlled components such as MOSFET and IGBT;
  • the resonant circuit includes a resonant inductor Lr, a transformer excitation inductance Lm and a resonant capacitor Cr;
  • the rectifier network can be composed of two diodes D1-D2
  • the full-wave rectification network is composed of parallel output filter capacitor C 0 , or it can also be composed of a full-bridge rectifier network composed of four diodes D1-D4 and output filter capacitor C 0 in parallel.
  • the drain of the switch Q1 is connected to the drain of the switch Q2 and the positive terminal of the input power supply Vin, and the source of the switch Q1 is connected to the drain of the switch Q3 and the first terminal of the resonant capacitor Cr.
  • VC1 the second end of the resonant capacitor Cr is defined as VC2
  • VC2 is connected to one end of the resonant inductance Lr
  • the other end of the resonant inductance Lr is connected to one end of the excitation inductance Lm and the first end of the primary winding of the transformer T
  • the second end of the primary winding of the transformer T is connected to the other end of the excitation inductance Lm
  • the source of the switch Q2, the drain of the switch Q4, and the source of the switch Q4 is connected to the source of the switch Q3 and the input The negative pole of the power supply Vin. It can be known from the connection state of the circuit that the terminal voltages VC1 and VC2 of the resonant capacitor Cr are always in a floating state.
  • the current detection circuit has a shunt resistor Rcr, a shunt capacitor Ccr connected in series with the shunt resistor Rcr, a switch diode Dcr, a voltage source Vc, a resistor Rv and a detection switch Q5.
  • One end of the shunt resistor Rcr of the current detection circuit is connected to the VC1 end of the resonant capacitor, the other end of the shunt resistor Rcr is connected to one end of the shunt capacitor Ccr, and the other end of the shunt capacitor Ccr is connected to the VC2 end of the resonant capacitor Cr;
  • the cathode is connected to the series node of the shunt resistor Rcr and the shunt capacitor Ccr, the anode of the switch diode Dcr is connected to one end of the resistor Rv, and the other end of the resistor Rv is connected to the voltage source Vc; the anode of the switch diode Dcr is connected to the detection switch Q5 at the same time.
  • the anode of the Dcr of the switching diode is powered by the voltage source Vc through Rv.
  • the anode of the Dcr of the switching diode can be directly powered by a constant current source without any resistance.
  • the above-mentioned current detection circuit can realize current sampling by controlling the on-off of the detection switch Q5, wherein the control signal of the detection switch Q5 can be determined by the working state of the circuit. disconnected, at this time, the anode voltage Vcr of the switch diode Dcr can reflect the current size of the resonant cavity; when the left terminal voltage VC1 of the resonant capacitor Cr is floating, the control detection switch Q5 is turned on, and the detection circuit is in a rest state at this time, and no current detection is performed. .
  • the above current detection circuit is applied in the full-bridge LLC resonant converter.
  • the switching tubes Q1-Q4 keep the duty ratio of 0.5 and are fixed, and the switching tubes Q1 and Q2 Complementary conduction, the switch Q1 and the switch Q4 are turned on and off at the same time, the switch Q2 and the switch Q3 are turned on and off at the same time, and the output voltage V 0 is achieved by adjusting the switching frequency of the switches Q1-Q4.
  • the specific working principle of realizing resonant current detection is as follows:
  • the left terminal voltage VC1 of the resonant capacitor Cr is grounded, and the control detection switch Q5 is turned off, then the switch diode Dcr is turned on, and the anode voltage Vcr of the switch diode Dcr can reflect the current i cr flowing through the resonant capacitor Cr:
  • Vcr icr1 ⁇ Rcr+V Dcr (2)
  • V Dcr represents the conduction voltage drop of the switching diode Dcr.
  • the half-cycle resonant tank current can be reflected by sampling the anode voltage Vcr of the switching diode Dcr.
  • the resonant capacitor Cr current flowing through the resonant circuit can be calculated. That is to say, when the external current acquisition module needs to acquire the current flowing through the resonant capacitor Cr, the anode voltage Vcr of the switching diode Dcr can be acquired, and the current of the resonant capacitor Cr flowing through the resonant circuit can be obtained by calculation.
  • Figure 5 shows the current detection results of the first embodiment of the present invention.
  • the square wave in the figure is the Q2 driving waveform
  • the middle is the actual resonant current waveform
  • the bottom waveform is the resonant current waveform measured by the detection method of the present invention. It can be seen from FIG. 5 that, compared with the actual resonant current signal, the resonant current signal obtained by the current detection circuit proposed by the present invention has the same waveform in the half cycle when Q2 is turned on, and the sampling accuracy is high.
  • FIG. 6 is a schematic diagram of the LLC resonant converter according to the second embodiment of the present invention.
  • this embodiment has an additional set of current detection circuits, that is, in this embodiment, the LLC resonant converter
  • the device includes a first current detection circuit and a second current detection circuit.
  • the first current detection circuit is the same as the current detection circuit in the first embodiment.
  • the LLC resonant converter is also used as the preferred implementation topology, and the specific current detection implementation process is introduced.
  • the resonant capacitor is divided into Cr and Cr1 in series, and the connection method of the resonant capacitor Cr is the same as that of the first embodiment.
  • the first end of the resonant capacitor Cr1 is connected between the source of the switch Q2 and the drain of the switch Q4, the first end is defined as VC3, and the second end of the resonant capacitor Cr1 is connected to the second end of the transformer T and the other end of the excitation inductance Lm, the second end is defined as VC4; similarly, the terminal voltages VC3 and VC4 of the resonance capacitor Cr1 are often in a floating state.
  • the second current detection circuit is connected in parallel with both ends of the resonant capacitor Cr1, that is, one end of the shunt resistor R1 is connected to the VC3 end of the resonant capacitor Cr1, and the other end of the shunt capacitor C1 is connected to the VC4 end of the resonant capacitor Cr1.
  • the connection relationship of the second current detection circuit is the same as that of the current detection circuit in the first embodiment.
  • the second current detection circuit includes a shunt resistor R1, a shunt capacitor C1, a switching diode D3, a voltage source Vc, a resistor R2 and a detection switch Q6.
  • the shunt resistor R1, the shunt capacitor C1, the switching diode D3, the voltage source Vc, the resistor R2, and the detection switch Q6 correspond to the shunt resistor Rcr, the shunt capacitor Ccr, the switching diode Dcr, the voltage source Vc, the resistor in the first embodiment, respectively.
  • Fig. 6 current sampling is realized by detecting the on-off of switches Q5 and Q6, wherein the control signals of the detection switches Q5 and Q6 can be determined by the working state of the circuit.
  • the detection switches Q5 and Q6 are disconnected, the anode voltages Vcr and Vcr1 of the switching diodes Dcr and D3 can reflect the current of the resonant cavity; when the left terminal voltages VC1 and VC3 of the resonance capacitor are floating, the control detection switches Q5 and Q6 are turned on. , the detection circuit is in a resting state at this time.
  • This embodiment is applied to the full-bridge LLC resonant converter.
  • the switching transistors Q1-Q4 maintain a fixed duty ratio of 0.5, and the switching transistors Q1 and Q2 are complementary.
  • the switch Q1 and the switch Q4 are turned on and off at the same time, the switch Q2 and the switch Q3 are turned on and off at the same time, and the output voltage V 0 control;
  • the specific working principle of realizing resonant current detection is as follows:
  • Vcr1 icr2 ⁇ R1+V D3 (3)
  • icr2 represents the current flowing through the shunt capacitor C1.
  • Vcr icr1 ⁇ Rcr+V Dcr (4)
  • V D3 and V Dcr represent the conduction voltage drop of the switching diodes D3 and Dcr, respectively.
  • the current of the entire resonant tank can be reflected by controlling the on-off of the detection switches Q5 and Q6 and sampling the anode voltages Vcr and Vcr1 of the switching diodes.
  • the currents flowing through the resonant capacitor Cr and the resonant capacitor Cr1 are respectively detected, so that full-cycle sampling of the resonant current can be realized, so that the detection results are comprehensive and accurate.
  • the structure of the present invention adopts the shunt branch to be connected in parallel at both ends of the resonant capacitor, the current flowing through the shunt branch is very small, and the shunt resistance value is very small, which is equivalent to non-destructive testing, and can ensure the normal working efficiency of the circuit;
  • the current detection scheme proposed by the present invention only needs to use resistors, capacitors, diodes and other devices to realize the current detection of the resonant cavity, and provides signals for load identification, overload protection or short circuit protection, the circuit structure is simple, and the cost is low;
  • the current detection scheme proposed by the present invention can provide a beneficial current detection idea for floating type devices in switching converters, including but not limited to resonant converters, and has wide applications.

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Abstract

A current detection circuit, comprising a shunt resistor Rcr, a shunt capacitor Ccr, a switching diode Dcr, a voltage source Vc, a resistor Rv and a detection switch Q5. The current detection circuit can be applied to the current detection of a device which is composed of an inverter circuit, a resonant circuit, a transformer and a rectifier network and is similar to a floating-ground type device in an LLC resonant converter; and according to an operating state of the LLC resonant converter, when common grounding occurs in a terminal voltage of a resonant capacitor Cr, the detection switch Q5 is switched off, and a resonant cavity current can be reflected by means of sampling a terminal voltage Vcr of the shunt resistor Rcr.

Description

一种电流检测电路、变换器及该变换器中的电流检测方法A current detection circuit, a converter and a current detection method in the converter 技术领域technical field
本发明涉及开关变换器技术领域，具体地说涉及一种电流检测电路、包含有该电流检测电路的变换器、以及该变换器中的电流检测方法。The present invention relates to the technical field of switching converters, in particular to a current detection circuit, a converter including the current detection circuit, and a current detection method in the converter.
背景技术Background technique
随着电力电子技术的迅猛发展，开关变换器得到了广泛的应用。人们对开关变换器提出更多要求：高功率密度、高可靠性和小体积。其中，LLC谐振变换器凭借其软开关、低噪声、低应力等诸多优势得到了广泛的应用。With the rapid development of power electronics technology, switching converters have been widely used. People put more demands on switching converters: high power density, high reliability and small size. Among them, LLC resonant converters have been widely used due to their advantages such as soft switching, low noise, and low stress.
在开关变换器的设计实现过程中，电流检测是保证变换器实现电流控制和电流异常保护的关键。对于LLC谐振变换器，现有电流检测方案采用检流电阻或电流互感器来实现电流检测，分别如图1和图2所示，其中变压器原边线圈即包括实际的励磁电感，为了便于对谐振腔进行描述，将变压器励磁电感Lm在附图中标出。图1中，直接将检流电阻Rcr串联在需要进行电流检测的回路中，通过检流电阻Rcr端电压来反映被检测电流；该方案虽然电路结构简单，但检流电阻产生的损耗不容忽视，检流范围及采样精度受限，且会影响到***性能。In the design and implementation process of switching converters, current detection is the key to ensure that the converter can realize current control and current abnormal protection. For LLC resonant converters, the existing current detection scheme uses current detection resistors or current transformers to realize current detection, as shown in Figure 1 and Figure 2 respectively, in which the primary coil of the transformer includes the actual excitation inductance. The cavity is described, and the transformer magnetizing inductance Lm is marked in the drawing. In Figure 1, the current-sense resistor Rcr is directly connected in series in the loop that needs current detection, and the detected current is reflected by the terminal voltage of the current-sense resistor Rcr; although the circuit structure of this scheme is simple, the loss caused by the current-sense resistor cannot be ignored. The current detection range and sampling accuracy are limited and affect system performance.
图2中，通过电流互感器将谐振电流耦合至次级电路，经二极管整流后转化为电压信号并送至控制电路；此检测方案元器件复杂，需要一个电流互感器、四个整流二极管D3、D4、D5、D6和一个采样电阻Rcr，其制造成本较高；且电流互感器原边串联在谐振腔内，原边电流即为谐振腔电流，通常谐振变换器的工作电流较大，为了保证检测精度，采样电路副边绕组匝数就越多越好，由此会导致电流互感器的体积较大，且检测精度受互感器精度的影响。In Figure 2, the resonant current is coupled to the secondary circuit through a current transformer, converted into a voltage signal after being rectified by a diode, and sent to the control circuit; the components of this detection scheme are complex, requiring a current transformer, four rectifier diodes D3, D4, D5, D6 and a sampling resistor Rcr have high manufacturing cost; and the primary side of the current transformer is connected in series in the resonant cavity, and the primary side current is the current of the resonant cavity. Usually, the working current of the resonant converter is relatively large. For the detection accuracy, the more turns of the secondary winding of the sampling circuit, the better, which will lead to a larger volume of the current transformer, and the detection accuracy is affected by the accuracy of the transformer.
考虑到常规电流检测方式的损耗较大，图3提供了一种应用于不对称半桥反激等类似谐振拓扑的峰值电流检测方案。图3的电流检测方案仅在谐振电容Cr的电流方向从右至左时，可通过电阻Rs将流过谐振电容Cr上的电流成比例的转换成电压信号供控制电路使用；该检测方案利用二极管D1滤除采样的负值电流信号，仅能应用在开关变换器的谐振电容有一个稳定的参考地场合，不能满足全桥结构的谐振电流检测要求。Considering the large loss of conventional current detection methods, Figure 3 provides a peak current detection scheme applied to asymmetric half-bridge flyback and other similar resonant topologies. The current detection scheme of Fig. 3 can only convert the current flowing through the resonance capacitor Cr into a voltage signal proportionally through the resistor Rs when the current direction of the resonance capacitor Cr is from right to left for the control circuit to use; the detection scheme uses a diode D1 filters out the sampled negative current signal, and can only be used in the case where the resonant capacitor of the switching converter has a stable reference ground, and cannot meet the resonant current detection requirements of the full-bridge structure.
针对现有电流检测电路较为复杂、检测精度受限、成本较高等问题，本发明提出一种技术方案以解决现有电流检测电路存在的缺陷。Aiming at the problems that the existing current detection circuit is complicated, the detection accuracy is limited, and the cost is high, the present invention proposes a technical solution to solve the defects of the existing current detection circuit.
发明内容SUMMARY OF THE INVENTION
本发明所要解决的技术问题是，为开关变换器中的浮地型器件提供一种实用的电流检测方案，以解决现有电流检测技术中电路过于复杂、成本高、损耗高等问题。The technical problem to be solved by the present invention is to provide a practical current detection scheme for the floating device in the switching converter, so as to solve the problems of complicated circuit, high cost and high loss in the existing current detection technology.
为解决现有技术存在的问题，本发明提供一种电流检测电路，其包括；分流电阻Rcr、分流电容Cc、开关二极管Dcr以及检测开关Q5；开关二极管Dcr的阴极连接于分流电阻Rcr与分流电容Ccr的串联节点，开关二极管Dcr的阳极由电压源经电阻Rv供电或者由恒流源直接供电；检测开关Q5的一端连接所述开关二极管Dcr的阳极。In order to solve the problems existing in the prior art, the present invention provides a current detection circuit, which includes: a shunt resistor Rcr, a shunt capacitor Cc, a switching diode Dcr and a detection switch Q5; the cathode of the switching diode Dcr is connected to the shunt resistor Rcr and the shunt capacitor At the series node of Ccr, the anode of the switching diode Dcr is powered by a voltage source through a resistor Rv or directly powered by a constant current source; one end of the detection switch Q5 is connected to the anode of the switching diode Dcr.
在一个实施例中，电流检测电路用于检测谐振电路的电流时，所述分流电阻Rcr和所述分流电容Ccr组成分流支路并联在谐振电路的谐振电容Cr的两端。In one embodiment, when the current detection circuit is used to detect the current of the resonant circuit, the shunt resistor Rcr and the shunt capacitor Ccr form a shunt branch and are connected in parallel to both ends of the resonant capacitor Cr of the resonant circuit.
在一个实施例中，检测开关Q5为受控开关，当谐振电容Cr的一端电压浮地时，检测开关Q5受控导通，开关二极管Dcr反向截止；当谐振电容Cr的一端电压共地时，检测开关Q5受控断开，开关二极管Dcr导通，开关二极管Dcr阳极产生电压大小反映流过谐振电容Cr电流的大小。In one embodiment, the detection switch Q5 is a controlled switch. When the voltage of one end of the resonant capacitor Cr is floating, the detection switch Q5 is controlled to be turned on, and the switch diode Dcr is reversely turned off; when the voltage of one end of the resonant capacitor Cr is in common ground , the detection switch Q5 is controlled to be turned off, the switch diode Dcr is turned on, and the voltage generated by the anode of the switch diode Dcr reflects the size of the current flowing through the resonant capacitor Cr.
在一个实施例中，检测开关Q5为受控开关，其为三极管、MOSFET或IGBT。In one embodiment, the detection switch Q5 is a controlled switch, which is a triode, a MOSFET or an IGBT.
本发明还提供一种变换器，其包括上述电流检测电路、逆变电路、谐振电路、变压器以及整流网络，所述谐振电路具有谐振电感Lr和谐振电容Cr，所述电流检测电路中的分流电阻Rcr与分流电容Ccr组成分流支路，分流支路并联在谐振电容Cr的两端。The present invention also provides a converter, which includes the above-mentioned current detection circuit, an inverter circuit, a resonance circuit, a transformer and a rectifier network, the resonance circuit has a resonance inductance Lr and a resonance capacitor Cr, and a shunt resistance in the current detection circuit Rcr and the shunt capacitor Ccr form a shunt branch, and the shunt branch is connected in parallel with both ends of the resonant capacitor Cr.
在一个实施例中，逆变电路为由四个开关管组成的全桥拓扑结构或由两个开关管组成的半桥拓扑结构，逆变电路具有第一输出端以及第二输出端；In one embodiment, the inverter circuit is a full-bridge topology structure composed of four switch tubes or a half-bridge topology structure composed of two switch tubes, and the inverter circuit has a first output end and a second output end;
谐振电容Cr和谐振电感Lr串联后连接在逆变电路的第一输出端与变压器的原边线圈的第一端之间，谐振电容Cr的连接为浮地连接；The resonant capacitor Cr and the resonant inductor Lr are connected in series between the first output end of the inverter circuit and the first end of the primary coil of the transformer, and the connection of the resonant capacitor Cr is a floating connection;
变压器原边线圈的第二端与逆变电路的第二输出端连接，所述变压器的副边与所述整流网络连接。The second end of the primary coil of the transformer is connected to the second output end of the inverter circuit, and the secondary side of the transformer is connected to the rectifier network.
在一个实施例中，谐振电路还设有谐振电容Cr1，谐振电容Cr1连接在变压器原边线圈的第二端与逆变电路的第二输出端之间，且谐振电容Cr1的连接为浮地连接，谐振电容Cr1的两端并联有第二电流检测电路，第二电流检测电路具有分流电阻R1、分流电容C1、开关二极管D3、电压源Vc、电阻R2以及检测开关Q6；In one embodiment, the resonant circuit is further provided with a resonant capacitor Cr1, the resonant capacitor Cr1 is connected between the second end of the primary coil of the transformer and the second output end of the inverter circuit, and the connection of the resonant capacitor Cr1 is a floating connection , the two ends of the resonance capacitor Cr1 are connected in parallel with a second current detection circuit, and the second current detection circuit has a shunt resistor R1, a shunt capacitor C1, a switching diode D3, a voltage source Vc, a resistor R2 and a detection switch Q6;
开关二极管D3的阴极连接于分流电阻R1与分流电容C1的串联节点，开关二极管D3的阳极由电压源经电阻R2供电或者由恒流源直接供电；检测开关Q6的一端连接开关二极管D3的阳极。The cathode of the switching diode D3 is connected to the series node of the shunt resistor R1 and the shunt capacitor C1, the anode of the switching diode D3 is powered by the voltage source through the resistor R2 or directly powered by the constant current source; one end of the detection switch Q6 is connected to the anode of the switching diode D3.
本发明还提供一种电流检测方法，包括如下步骤：The present invention also provides a current detection method, comprising the following steps:
根据变换器的工作状态，控制开关管，使得浮地连接的电容Cr的一端接地；According to the working state of the converter, the switch tube is controlled so that one end of the floating capacitor Cr is grounded;
控制检测开关Q5，使得开关二极管Dcr导通，并且在所述开关二极管Dcr导通时，通过采集所述开关二极管Dcr的阳极的电压数据以获得流经所述电容Cr的电流数据。The detection switch Q5 is controlled so that the switch diode Dcr is turned on, and when the switch diode Dcr is turned on, the current data flowing through the capacitor Cr is obtained by collecting the voltage data of the anode of the switch diode Dcr.
在一个实施例中，所述开关管包括开关管Q1、开关管Q2、开关管Q3以及开关管Q4，所述开关管Q1、开关管Q2、开关管Q3以及开关管Q4组成的全桥拓扑结构；In one embodiment, the switch tube includes a switch tube Q1, a switch tube Q2, a switch tube Q3 and a switch tube Q4, and the switch tube Q1, the switch tube Q2, the switch tube Q3 and the switch tube Q4 form a full-bridge topology structure ;
通过控制所述开关管Q1和所述开关管Q4同时断开，且所述开关管Q2和所述开关管Q3同时导通，使得所述电容Cr的一端接地。By controlling the switch tube Q1 and the switch tube Q4 to be turned off at the same time, and the switch tube Q2 and the switch tube Q3 to be turned on at the same time, one end of the capacitor Cr is grounded.
与现有技术相比，本发明具有如下有益效果：Compared with the prior art, the present invention has the following beneficial effects:
1)本发明结构采用分流支路并联在谐振电容Cr两端，流过分流支路的电流很小，且分流电阻值Rcr很小，相当于无损检测，可以确保电路正常的工作效率；1) The structure of the present invention adopts a shunt branch in parallel with both ends of the resonant capacitor Cr, the current flowing through the shunt branch is very small, and the shunt resistance value Rcr is very small, which is equivalent to non-destructive testing, and can ensure the normal working efficiency of the circuit;
2)本发明提出的电流检测方案仅需要使用电阻、电容、二极管等贴片器件即可实现谐振腔电流的检测，电路结构简单，成本较低；且经本发明较佳实施例的采样结果验证，该检测电路的采样精度高；2) The current detection scheme proposed by the present invention only needs to use patch devices such as resistors, capacitors, and diodes to realize the detection of the resonant cavity current, the circuit structure is simple, and the cost is low; and it is verified by the sampling results of the preferred embodiment of the present invention. , the sampling accuracy of the detection circuit is high;
3)本发明提出的电流检测方案可为开关变换器中的浮地型器件提供一种有益的电流检测思路，应用场合广泛。3) The current detection scheme proposed by the present invention can provide a beneficial current detection idea for floating devices in switching converters, and is widely used.
附图说明Description of drawings
图1为现有技术中采用检流电阻实现电流检测的电路原理图；1 is a schematic diagram of a circuit for implementing current detection using a current-sensing resistor in the prior art;
图2为现有技术中采用电流互感器实现电流检测的电路原理图；Fig. 2 is the circuit schematic diagram of adopting current transformer to realize current detection in the prior art;
图3为现有技术中应用于不对称半桥反激等类似谐振拓扑的峰值电流检测电路原理图；3 is a schematic diagram of a peak current detection circuit applied to a resonant topology such as an asymmetric half-bridge flyback in the prior art;
图4为本发明第一实施例的LLC谐振变换器原理图；4 is a schematic diagram of the LLC resonant converter according to the first embodiment of the present invention;
图5为本发明第一实施例的电流检测结果；Fig. 5 is the current detection result of the first embodiment of the present invention;
图6为本发明第二实施例的LLC谐振变换器原理图。FIG. 6 is a schematic diagram of an LLC resonant converter according to a second embodiment of the present invention.
具体实施方式detailed description
为了保证本发明的技术方案更加清晰，以下结合附图及实施例对本发明的技术方案进行详细的说明。In order to ensure that the technical solutions of the present invention are clearer, the technical solutions of the present invention are described in detail below with reference to the accompanying drawings and embodiments.
第一实施例first embodiment
本发明电流检测电路可应用于由逆变电路、谐振电路、变压器和整流网络组成的LLC谐振变换器中，用于LLC谐振变换器的浮地型器件的电流检测。需要说明的是，变压器原边线圈即包括实际的励磁电感，为了便于对谐振电路进行描述，将变压器励磁电感Lm在附图4中标出。The current detection circuit of the present invention can be applied to an LLC resonant converter composed of an inverter circuit, a resonant circuit, a transformer and a rectifier network, and is used for current detection of a floating type device of the LLC resonant converter. It should be noted that the primary coil of the transformer includes the actual excitation inductance. In order to facilitate the description of the resonant circuit, the excitation inductance Lm of the transformer is marked in FIG. 4 .
本实施例中，以LLC谐振变换器作为较佳实施拓扑，对具体的电流检测实现过程进行介绍。LLC谐振变换器包括电流检测电路、逆变电路、谐振电路、变压器以及整流网络。In this embodiment, the LLC resonant converter is taken as the preferred implementation topology, and the specific current detection implementation process is introduced. The LLC resonant converter includes a current detection circuit, an inverter circuit, a resonant circuit, a transformer, and a rectifier network.
逆变电路可以为由开关管Q1、开关管Q2、开关管Q3、开关管Q4组成的全桥结构，逆变电路也可以为由开关管Q1、开关管Q3组成的半桥结构，其中开关管Q1-Q4用来控制功率电路的工作状态，可以为MOSFET、IGBT等受控元件；谐振电路包括谐振电感Lr、变压器励磁电感Lm和谐振电容Cr；整流网络可以为由2个二极管D1-D2构成的全波整流网络并联输出滤波电容C 0构成，也可以为由4个二极管D1-D4构成的全桥整流网络并联输出滤波电容C 0构成。 The inverter circuit can be a full-bridge structure composed of a switch tube Q1, a switch tube Q2, a switch tube Q3, and a switch tube Q4, and the inverter circuit can also be a half-bridge structure composed of a switch tube Q1 and a switch tube Q3, wherein the switch tube Q1-Q4 are used to control the working state of the power circuit, which can be controlled components such as MOSFET and IGBT; the resonant circuit includes a resonant inductor Lr, a transformer excitation inductance Lm and a resonant capacitor Cr; the rectifier network can be composed of two diodes D1-D2 The full-wave rectification network is composed of parallel output filter capacitor C 0 , or it can also be composed of a full-bridge rectifier network composed of four diodes D1-D4 and output filter capacitor C 0 in parallel.
具体的针对全桥结构，开关管Q1的漏极连于开关管Q2的漏极和输入电源Vin的正端，开关管Q1的源极连于开关管Q3的漏极和谐振电容Cr的第一端，该端定义为VC1，谐振电容Cr的第二端定义为VC2，VC2连于谐振电感Lr的一端，谐振电感Lr的另一端连于励磁电感Lm的一端和变压器T原边绕组的第一端，变压器T原边绕组的第二端连于励磁电感Lm的另一端、开关管Q2的源极、 开关管Q4的漏极，开关管Q4的源极连于开关管Q3的源极和输入电源Vin的负极。由电路的连接状态可知，谐振电容Cr的端电压VC1与VC2常处于浮地状态。Specifically for the full-bridge structure, the drain of the switch Q1 is connected to the drain of the switch Q2 and the positive terminal of the input power supply Vin, and the source of the switch Q1 is connected to the drain of the switch Q3 and the first terminal of the resonant capacitor Cr. This end is defined as VC1, the second end of the resonant capacitor Cr is defined as VC2, VC2 is connected to one end of the resonant inductance Lr, the other end of the resonant inductance Lr is connected to one end of the excitation inductance Lm and the first end of the primary winding of the transformer T The second end of the primary winding of the transformer T is connected to the other end of the excitation inductance Lm, the source of the switch Q2, the drain of the switch Q4, and the source of the switch Q4 is connected to the source of the switch Q3 and the input The negative pole of the power supply Vin. It can be known from the connection state of the circuit that the terminal voltages VC1 and VC2 of the resonant capacitor Cr are always in a floating state.
所述电流检测电路具有分流电阻Rcr、与分流电阻Rcr串联连接的分流电容Ccr、开关二极管Dcr、电压源Vc、电阻Rv以及检测开关Q5。The current detection circuit has a shunt resistor Rcr, a shunt capacitor Ccr connected in series with the shunt resistor Rcr, a switch diode Dcr, a voltage source Vc, a resistor Rv and a detection switch Q5.
电流检测电路的分流电阻Rcr的一端与谐振电容的VC1端相连，分流电阻Rcr的另一端与分流电容Ccr的一端相连，分流电容Ccr的另一端与谐振电容Cr的VC2端连接；开关二极管Dcr的阴极连接分流电阻Rcr与分流电容Ccr的串联节点，开关二极管的Dcr的阳极连接电阻Rv的一端，电阻Rv的另一端与电压源Vc相连；开关二极管的Dcr的阳极同时与检测开关Q5相连。本实施例中，所述开关二极管的Dcr的阳极由电压源Vc经Rv供电，在其它实施例中，所述开关二极管的Dcr的阳极可直接由恒流源供电，而不经过任何电阻。One end of the shunt resistor Rcr of the current detection circuit is connected to the VC1 end of the resonant capacitor, the other end of the shunt resistor Rcr is connected to one end of the shunt capacitor Ccr, and the other end of the shunt capacitor Ccr is connected to the VC2 end of the resonant capacitor Cr; The cathode is connected to the series node of the shunt resistor Rcr and the shunt capacitor Ccr, the anode of the switch diode Dcr is connected to one end of the resistor Rv, and the other end of the resistor Rv is connected to the voltage source Vc; the anode of the switch diode Dcr is connected to the detection switch Q5 at the same time. In this embodiment, the anode of the Dcr of the switching diode is powered by the voltage source Vc through Rv. In other embodiments, the anode of the Dcr of the switching diode can be directly powered by a constant current source without any resistance.
上述电流检测电路可通过控制检测开关Q5的通断实现电流采样，其中检测开关Q5的控制信号可由电路的工作状态决定，具体的：当谐振电容Cr的左端电压VC1共地时，控制检测开关Q5断开，此时开关二极管Dcr阳极电压Vcr即可反映谐振腔电流大小；当谐振电容Cr的左端电压VC1浮地时，控制检测开关Q5导通，此时检测电路处于休息状态，不进行电流检测。The above-mentioned current detection circuit can realize current sampling by controlling the on-off of the detection switch Q5, wherein the control signal of the detection switch Q5 can be determined by the working state of the circuit. disconnected, at this time, the anode voltage Vcr of the switch diode Dcr can reflect the current size of the resonant cavity; when the left terminal voltage VC1 of the resonant capacitor Cr is floating, the control detection switch Q5 is turned on, and the detection circuit is in a rest state at this time, and no current detection is performed. .
上述电流检测电路应用在全桥结构LLC谐振变换器中，当逆变电路工作在全桥LLC变频模态时，开关管Q1～Q4保持占空比为0.5且固定，开关管Q1和开关管Q2互补导通，开关管Q1和开关管Q4同时导通、同时关断，开关管Q2和开关管Q3同时导通、同时关断，通过调节开关管Q1～Q4的开关频率大小实现输出电压V 0的控制；其中实现谐振电流检测的具体工作原理为： The above current detection circuit is applied in the full-bridge LLC resonant converter. When the inverter circuit works in the full-bridge LLC frequency conversion mode, the switching tubes Q1-Q4 keep the duty ratio of 0.5 and are fixed, and the switching tubes Q1 and Q2 Complementary conduction, the switch Q1 and the switch Q4 are turned on and off at the same time, the switch Q2 and the switch Q3 are turned on and off at the same time, and the output voltage V 0 is achieved by adjusting the switching frequency of the switches Q1-Q4. The specific working principle of realizing resonant current detection is as follows:
(1)当开关管Q1和Q4同时导通且开关管Q2和开关管Q3同时关断时，谐振电容Cr的左端电压VC1浮地，谐振电容Cr左端电压VC1即等于输入电压，同时控制检测开关Q5导通，则开关二极管Dcr反向截止，此时不进行电流检测；(1) When the switches Q1 and Q4 are turned on at the same time and the switches Q2 and Q3 are turned off at the same time, the left terminal voltage VC1 of the resonant capacitor Cr floats, and the left terminal voltage VC1 of the resonant capacitor Cr is equal to the input voltage, and the detection switch is controlled at the same time. When Q5 is turned on, the switching diode Dcr is turned off in the reverse direction, and no current detection is performed at this time;
(2)当开关管Q2和Q3导通且开关管Q1和Q4同时关断时，流过谐振电容Cr的电流记为i cr，流过分流支路的电流记为i cr1，根据并联分流原理，可得： (2) When the switches Q2 and Q3 are turned on and the switches Q1 and Q4 are turned off at the same time, the current flowing through the resonant capacitor Cr is recorded as i cr , and the current flowing through the shunt branch is recorded as i cr1 , according to the principle of parallel shunt ,Available:
Figure PCTCN2021104747-appb-000001
Figure PCTCN2021104747-appb-000001
此时，谐振电容Cr的左端电压VC1共地，控制检测开关Q5断开，则开关二极管Dcr导通，开关二极管Dcr阳极电压Vcr即可反映流过谐振电容Cr的电流i cr大小： At this time, the left terminal voltage VC1 of the resonant capacitor Cr is grounded, and the control detection switch Q5 is turned off, then the switch diode Dcr is turned on, and the anode voltage Vcr of the switch diode Dcr can reflect the current i cr flowing through the resonant capacitor Cr:
Vcr＝icr1·Rcr+V Dcr     (2) Vcr=icr1·Rcr+V Dcr (2)
式(2)中V Dcr表示开关二极管Dcr的导通压降。 In the formula (2), V Dcr represents the conduction voltage drop of the switching diode Dcr.
基于以上原理，可以通过采样开关二极管Dcr的阳极电压Vcr来反映半个周期的谐振回路电流，也即，通过上述公式(1)和公式(2)，将采样开关二极管Dcr的阳极电压VCr，即可计算获得流经谐振电路的谐振电容Cr电流。也就说，当外部电流采集模块需要采集流过谐振电容Cr电流时，可通过采集开关二极管Dcr的阳极电压Vcr，并通过计算获得流经谐振电路的谐振电容Cr电流。Based on the above principles, the half-cycle resonant tank current can be reflected by sampling the anode voltage Vcr of the switching diode Dcr. The resonant capacitor Cr current flowing through the resonant circuit can be calculated. That is to say, when the external current acquisition module needs to acquire the current flowing through the resonant capacitor Cr, the anode voltage Vcr of the switching diode Dcr can be acquired, and the current of the resonant capacitor Cr flowing through the resonant circuit can be obtained by calculation.
如图5为本发明第一实施例的电流检测结果展示，图中的方波为Q2驱动波形，中间为实际谐振电流波形，下方的波形为本发明检测方法所测得的谐振电流波形。由图5可看出，本发明提出的电流检测电路得到的谐振电流信号与实际的谐振电流信号相比，在Q2导通的半个周期内波形一致，采样精度高。Figure 5 shows the current detection results of the first embodiment of the present invention. The square wave in the figure is the Q2 driving waveform, the middle is the actual resonant current waveform, and the bottom waveform is the resonant current waveform measured by the detection method of the present invention. It can be seen from FIG. 5 that, compared with the actual resonant current signal, the resonant current signal obtained by the current detection circuit proposed by the present invention has the same waveform in the half cycle when Q2 is turned on, and the sampling accuracy is high.
第二实施例Second Embodiment
图6为本发明第二实施例的LLC谐振变换器原理图，与第一实施例不同的是，该实施例多了一套电流检测电路，也即，本实施例中，所述LLC谐振变换器包含第一电流检测电路和第二电流检测电路。其中，第一电流检测电路与第一实施例中的电流检测电路相同。6 is a schematic diagram of the LLC resonant converter according to the second embodiment of the present invention. The difference from the first embodiment is that this embodiment has an additional set of current detection circuits, that is, in this embodiment, the LLC resonant converter The device includes a first current detection circuit and a second current detection circuit. The first current detection circuit is the same as the current detection circuit in the first embodiment.
同样以LLC谐振变换器作为较佳实施拓扑，对具体的电流检测实现过程进行介绍，如图6所示，谐振电容分为Cr与Cr1串联组成，其中谐振电容Cr的连接方式与第一实施例相同，谐振电容Cr1的第一端连接至开关管Q2的源极与开关管Q4的漏极之间，该第一端定义为VC3，谐振电容Cr1的第二端连接至变压器T的第二端以及励磁电感Lm的另一端，该第二端定义为VC4；同样的，谐振电容Cr1的端电压VC3与VC4也常处于浮地状态。The LLC resonant converter is also used as the preferred implementation topology, and the specific current detection implementation process is introduced. As shown in Figure 6, the resonant capacitor is divided into Cr and Cr1 in series, and the connection method of the resonant capacitor Cr is the same as that of the first embodiment. Similarly, the first end of the resonant capacitor Cr1 is connected between the source of the switch Q2 and the drain of the switch Q4, the first end is defined as VC3, and the second end of the resonant capacitor Cr1 is connected to the second end of the transformer T and the other end of the excitation inductance Lm, the second end is defined as VC4; similarly, the terminal voltages VC3 and VC4 of the resonance capacitor Cr1 are often in a floating state.
第二电流检测电路并联在谐振电容Cr1的两端，即分流电阻R1的一端与谐振电容Cr1的VC3端相连，分流电容C1的另一端连与谐振电容Cr1的VC4端。The second current detection circuit is connected in parallel with both ends of the resonant capacitor Cr1, that is, one end of the shunt resistor R1 is connected to the VC3 end of the resonant capacitor Cr1, and the other end of the shunt capacitor C1 is connected to the VC4 end of the resonant capacitor Cr1.
第二电流检测电路的连接关系与第一实施例中的电流检测电路的连接方式相同，第二电流检测电路包括分流电阻R1、分流电容C1、开关二极管D3、电 压源Vc、电阻R2以及检测开关Q6。其中分流电阻R1、分流电容C1、开关二极管D3、电压源Vc、电阻R2以及检测开关Q6，分别对应于第一实施例中的分流电阻Rcr、分流电容Ccr、开关二极管Dcr、电压源Vc、电阻Rv以及检测开关Q5。The connection relationship of the second current detection circuit is the same as that of the current detection circuit in the first embodiment. The second current detection circuit includes a shunt resistor R1, a shunt capacitor C1, a switching diode D3, a voltage source Vc, a resistor R2 and a detection switch Q6. The shunt resistor R1, the shunt capacitor C1, the switching diode D3, the voltage source Vc, the resistor R2, and the detection switch Q6 correspond to the shunt resistor Rcr, the shunt capacitor Ccr, the switching diode Dcr, the voltage source Vc, the resistor in the first embodiment, respectively. Rv and detection switch Q5.
图6中，通过检测开关Q5、Q6的通断实现电流采样，其中检测开关Q5、Q6的控制信号可由电路的工作状态决定，具体的：当谐振电容的左端电压VC1、VC3共地时，控制检测开关Q5、Q6断开，此时开关二极管Dcr、D3的阳极电压Vcr、Vcr1即可反映谐振腔电流大小；当谐振电容的左端电压VC1、VC3浮地时，控制检测开关Q5、Q6导通，此时检测电路处于休息状态。In Fig. 6, current sampling is realized by detecting the on-off of switches Q5 and Q6, wherein the control signals of the detection switches Q5 and Q6 can be determined by the working state of the circuit. When the detection switches Q5 and Q6 are disconnected, the anode voltages Vcr and Vcr1 of the switching diodes Dcr and D3 can reflect the current of the resonant cavity; when the left terminal voltages VC1 and VC3 of the resonance capacitor are floating, the control detection switches Q5 and Q6 are turned on. , the detection circuit is in a resting state at this time.
该实施例应用在全桥结构LLC谐振变换器中，当逆变电路工作在全桥LLC变频模态时，开关管Q1～Q4保持占空比为0.5且固定，开关管Q1和开关管Q2互补导通，开关管Q1和开关管Q4同时导通、同时关断，开关管Q2和开关管Q3同时导通、同时关断，通过调节开关管Q1～Q4的开关频率大小实现输出电压V 0的控制；其中实现谐振电流检测的具体工作原理为： This embodiment is applied to the full-bridge LLC resonant converter. When the inverter circuit works in the full-bridge LLC frequency conversion mode, the switching transistors Q1-Q4 maintain a fixed duty ratio of 0.5, and the switching transistors Q1 and Q2 are complementary. On, the switch Q1 and the switch Q4 are turned on and off at the same time, the switch Q2 and the switch Q3 are turned on and off at the same time, and the output voltage V 0 control; the specific working principle of realizing resonant current detection is as follows:
(1)当开关管Q1和Q4同时导通且开关管Q2和开关管Q3同时关断时，谐振电容Cr的左端电压VC1浮地，因此控制检测开关Q5导通，则开关二极管Dcr反向截止，此时第一电流检测电路不进行电流采样；而谐振电容Cr1的左端电压VC3共地，因此控制检测开关Q6断开，则开关二极管D3导通，D3的阳极电压Vcr1即可反映谐振电容Cr1的电流i cr大小： (1) When the switch tubes Q1 and Q4 are turned on at the same time and the switch tube Q2 and the switch tube Q3 are turned off at the same time, the left terminal voltage VC1 of the resonant capacitor Cr floats, so the control detection switch Q5 is turned on, and the switch diode Dcr is reversely turned off , at this time, the first current detection circuit does not conduct current sampling; and the left terminal voltage VC3 of the resonant capacitor Cr1 is in common ground, so the control detection switch Q6 is turned off, then the switch diode D3 is turned on, and the anode voltage Vcr1 of D3 can reflect the resonant capacitor Cr1. The current i cr size:
Vcr1＝icr2·R1+V D3     (3) Vcr1＝icr2·R1+V D3 (3)
其中，
Figure PCTCN2021104747-appb-000002
icr2代表流过分流电容C1的电流。 in,
Figure PCTCN2021104747-appb-000002
icr2 represents the current flowing through the shunt capacitor C1.
(2)当开关管Q2和Q3导通且开关管Q1和Q4同时关断时，谐振电容Cr1的左端电压VC3浮地，因此控制检测开关Q6导通，则开关二极管D3反向截止，此时第二检测电路不进行电流采样；而谐振电容Cr的左端电压VC1共地，因此控制检测开关Q5断开，则开关二极管Dcr导通，Dcr的阳极电压Vcr即可反映谐振电容电流i cr大小： (2) When the switches Q2 and Q3 are turned on and the switches Q1 and Q4 are turned off at the same time, the left terminal voltage VC3 of the resonant capacitor Cr1 is floating, so the control detection switch Q6 is turned on, and the switch diode D3 is turned off in the reverse direction. The second detection circuit does not perform current sampling; and the left terminal voltage VC1 of the resonant capacitor Cr is in common ground, so the control detection switch Q5 is turned off, then the switch diode Dcr is turned on, and the anode voltage Vcr of Dcr can reflect the resonant capacitor current i cr size:
Vcr＝icr1·Rcr+V Dcr      (4) Vcr=icr1·Rcr+V Dcr (4)
其中，
Figure PCTCN2021104747-appb-000003
式(3)、(4)中V D3、V Dcr分别表示开关二极管D3、Dcr的导通压降。 in,
Figure PCTCN2021104747-appb-000003
In formulas (3) and (4), V D3 and V Dcr represent the conduction voltage drop of the switching diodes D3 and Dcr, respectively.
基于以上原理，可以通过控制检测开关Q5、Q6的通断，采样开关二极管的阳极电压Vcr、Vcr1来反映整个谐振回路电流。Based on the above principles, the current of the entire resonant tank can be reflected by controlling the on-off of the detection switches Q5 and Q6 and sampling the anode voltages Vcr and Vcr1 of the switching diodes.
本实施例中，通过设置第一电流检测电路和第二电流检测电路，来分别对流过谐振电容Cr和谐振电容Cr1的电流进行检测，从而能够实现谐振电流的全周期采样，使得检测结果全面准确。In this embodiment, by setting the first current detection circuit and the second current detection circuit, the currents flowing through the resonant capacitor Cr and the resonant capacitor Cr1 are respectively detected, so that full-cycle sampling of the resonant current can be realized, so that the detection results are comprehensive and accurate. .
与现有技术相比，本发明的有益效果在于：Compared with the prior art, the beneficial effects of the present invention are:
(1)本发明结构采用分流支路并联在谐振电容两端，流过分流支路的电流很小，且分流电阻值很小，相当于无损检测，可以确保电路正常的工作效率；(1) The structure of the present invention adopts the shunt branch to be connected in parallel at both ends of the resonant capacitor, the current flowing through the shunt branch is very small, and the shunt resistance value is very small, which is equivalent to non-destructive testing, and can ensure the normal working efficiency of the circuit;
(2)本发明提出的电流检测方案仅需要使用电阻、电容、二极管等器件即可实现谐振腔电流的检测，为负载识别，过载保护或短路保护提供信号，电路结构简单，成本较低；(2) The current detection scheme proposed by the present invention only needs to use resistors, capacitors, diodes and other devices to realize the current detection of the resonant cavity, and provides signals for load identification, overload protection or short circuit protection, the circuit structure is simple, and the cost is low;
(3)经本发明较佳实施例的采样结果验证，本发明提出的检测电路采样精度高；(3) It is verified by the sampling results of the preferred embodiment of the present invention that the detection circuit proposed by the present invention has high sampling accuracy;
(4)本发明提出的电流检测方案可为开关变换器中的浮地型器件提供一种有益的电流检测思路，包括但不仅限于谐振变换器，应用场合广泛。(4) The current detection scheme proposed by the present invention can provide a beneficial current detection idea for floating type devices in switching converters, including but not limited to resonant converters, and has wide applications.
以上实施例的说明只是用于帮助理解本申请的发明构思，并不用以限制本发明，对于本技术领域的普通技术人员来说，凡在不脱离本发明原理的前提下，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。The descriptions of the above embodiments are only used to help understand the inventive concept of the present application, and are not intended to limit the present invention. For those of ordinary skill in the art, any modifications, Equivalent replacements, improvements, etc., should all be included within the protection scope of the present invention.

Claims (10)

  1. 一种电流检测电路，其特征在于，包括：分流电阻Rcr、分流电容Cc、开关二极管Dcr以及检测开关Q5；所述开关二极管Dcr的阴极连接于分流电阻Rcr与分流电容Ccr的串联节点，所述开关二极管Dcr的阳极由电压源经电阻Rv供电或者由恒流源直接供电；所述检测开关Q5的一端连接所述开关二极管Dcr的阳极。A current detection circuit is characterized in that it comprises: a shunt resistor Rcr, a shunt capacitor Cc, a switching diode Dcr and a detection switch Q5; the cathode of the switching diode Dcr is connected to the series node of the shunt resistor Rcr and the shunt capacitor Ccr, the The anode of the switching diode Dcr is powered by a voltage source through a resistor Rv or directly powered by a constant current source; one end of the detection switch Q5 is connected to the anode of the switching diode Dcr.
  2. 根据权利要求1所述的电流检测电路，其特征在于，所述电流检测电路用于检测谐振电路的电流时，所述分流电阻Rcr和所述分流电容Ccr组成分流支路并联在所述谐振电路的谐振电容Cr的两端。The current detection circuit according to claim 1, wherein when the current detection circuit is used to detect the current of the resonant circuit, the shunt resistor Rcr and the shunt capacitor Ccr form a shunt branch and are connected in parallel to the resonant circuit Both ends of the resonant capacitor Cr.
  3. 根据权利要求2所述的电流检测电路，其特征在于，所述检测开关Q5为受控开关，当谐振电容Cr的一端电压浮地时，所述检测开关Q5受控导通，所述开关二极管Dcr反向截止；当所述谐振电容Cr的一端电压共地时，所述检测开关Q5受控断开，所述开关二极管Dcr导通，所述开关二极管Dcr阳极产生电压大小反映流过所述谐振电容Cr电流的大小。The current detection circuit according to claim 2, wherein the detection switch Q5 is a controlled switch, when the voltage of one end of the resonance capacitor Cr is floating, the detection switch Q5 is controlled to be turned on, and the switching diode Dcr is reversely turned off; when the voltage at one end of the resonant capacitor Cr is in common ground, the detection switch Q5 is controlled to be turned off, the switching diode Dcr is turned on, and the voltage generated by the anode of the switching diode Dcr reflects the voltage flowing through the The size of the resonant capacitor Cr current.
  4. 根据权利要求1所述的电流检测电路，其特征在于：所述检测开关Q5为受控开关，其为三极管、MOSFET或IGBT。The current detection circuit according to claim 1, wherein the detection switch Q5 is a controlled switch, which is a triode, a MOSFET or an IGBT.
  5. 一种变换器，包括电流检测电路、逆变电路、谐振电路、变压器以及整流网络，其特征在于：所述电流检测电路为如权利要求1所述的电流检测电路，所述谐振电路具有谐振电感Lr和谐振电容Cr，所述电流检测电路中的所述分流电阻Rcr与所述分流电容Ccr组成分流支路，所述分流支路并联在所述谐振电容Cr的两端。A converter, comprising a current detection circuit, an inverter circuit, a resonance circuit, a transformer and a rectifier network, wherein the current detection circuit is the current detection circuit as claimed in claim 1, and the resonance circuit has a resonance inductance Lr and the resonant capacitor Cr, the shunt resistor Rcr and the shunt capacitor Ccr in the current detection circuit form a shunt branch, and the shunt branch is connected in parallel to both ends of the resonant capacitor Cr.
  6. 根据权利要求5所述的变换器，其特征在于：所述逆变电路为由四个开关管组成的全桥拓扑结构或由两个开关管组成的半桥拓扑结构，所述逆变电路具有第一输出端以及第二输出端；The converter according to claim 5, wherein the inverter circuit is a full-bridge topology composed of four switch tubes or a half-bridge topology composed of two switch tubes, and the inverter circuit has a first output end and a second output end;
    所述谐振电容Cr和谐振电感Lr串联后连接在所述逆变电路的第一输出端与所述变压器的原边线圈的第一端之间，所述谐振电容Cr的连接为浮地连接；The resonant capacitor Cr and the resonant inductor Lr are connected in series between the first output end of the inverter circuit and the first end of the primary coil of the transformer, and the resonant capacitor Cr is connected in a floating connection;
    所述变压器原边线圈的第二端与所述逆变电路的第二输出端连接，所述变压器的副边与所述整流网络连接。The second end of the primary coil of the transformer is connected to the second output end of the inverter circuit, and the secondary side of the transformer is connected to the rectifier network.
  7. 根据权利要求6所述的变换器，其特征在于：所述谐振电路还设有谐振电容Cr1，所述谐振电容Cr1连接在所述变压器原边线圈的第二端与所述逆变电路的第二输出端之间，且所述谐振电容Cr1的连接为浮地连接，所述谐振电容Cr1的两端并联有第二电流检测电路，所述第二电流检测电路具有分流电阻R1、分流电容C1、开关二极管D3、电压源Vc、电阻R2以及检测开关Q6；The converter according to claim 6, wherein the resonant circuit is further provided with a resonant capacitor Cr1, and the resonant capacitor Cr1 is connected between the second end of the primary coil of the transformer and the first end of the inverter circuit. Between the two output terminals, and the connection of the resonant capacitor Cr1 is a floating connection, two ends of the resonant capacitor Cr1 are connected in parallel with a second current detection circuit, and the second current detection circuit has a shunt resistor R1 and a shunt capacitor C1 , switch diode D3, voltage source Vc, resistor R2 and detection switch Q6;
    所述开关二极管D3的阴极连接于分流电阻R1与分流电容C1的串联节点，所述开关二极管D3的阳极由电压源经电阻R2供电或者由恒流源直接供电；所述检测开关Q6的一端连接所述开关二极管D3的阳极。The cathode of the switching diode D3 is connected to the series node of the shunt resistor R1 and the shunt capacitor C1, and the anode of the switching diode D3 is powered by the voltage source through the resistor R2 or directly powered by the constant current source; one end of the detection switch Q6 is connected to the anode of the switching diode D3.
  8. 根据权利要求5所述的变换器，其特征在于：所述检测开关Q5为受控开关，当谐振电容Cr的一端电压浮地时，所述检测开关Q5受控导通，所述开关二极管Dcr反向截止；当所述谐振电容Cr的一端电压共地时，所述检测开关Q5受控断开，所述开关二极管Dcr导通，所述开关二极管Dcr阳极产生电压大小反映流过所述谐振电容Cr电流的大小。The converter according to claim 5, wherein the detection switch Q5 is a controlled switch, when the voltage of one end of the resonant capacitor Cr is floating, the detection switch Q5 is controlled to be turned on, and the switching diode Dcr Reverse cut-off; when the voltage of one end of the resonant capacitor Cr is common to the ground, the detection switch Q5 is controlled to be turned off, the switch diode Dcr is turned on, and the voltage generated by the anode of the switch diode Dcr reflects the flow through the resonance The size of the capacitor Cr current.
  9. 一种权利要求5-8任一项所述变换器中的电流检测方法，其特征在于：包括如下步骤：A current detection method in the converter according to any one of claims 5-8, characterized in that: comprising the steps of:
    根据变换器的工作状态，控制开关管，使得浮地连接的电容Cr的一端接地；According to the working state of the converter, the switch tube is controlled so that one end of the floating capacitor Cr is grounded;
    控制检测开关Q5，使得开关二极管Dcr导通，并且在所述开关二极管Dcr导通时，通过采集所述开关二极管Dcr的阳极的电压数据以获得流经所述电容Cr的电流数据。The detection switch Q5 is controlled so that the switch diode Dcr is turned on, and when the switch diode Dcr is turned on, the current data flowing through the capacitor Cr is obtained by collecting the voltage data of the anode of the switch diode Dcr.
  10. 根据权利要求9所述的电流检测方法，其特征在于：所述开关管包括开关管Q1、开关管Q2、开关管Q3以及开关管Q4，所述开关管Q1、开关管Q2、开关管Q3以及开关管Q4组成的全桥拓扑结构；The current detection method according to claim 9, wherein the switch tube comprises a switch tube Q1, a switch tube Q2, a switch tube Q3 and a switch tube Q4, the switch tube Q1, the switch tube Q2, the switch tube Q3 and The full-bridge topology composed of the switch tube Q4;
    通过控制所述开关管Q1和所述开关管Q4同时断开，且所述开关管Q2和所述开关管Q3同时导通，使得所述电容Cr的一端接地。By controlling the switch tube Q1 and the switch tube Q4 to be turned off at the same time, and the switch tube Q2 and the switch tube Q3 to be turned on at the same time, one end of the capacitor Cr is grounded.
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