TWI674492B - Linear constant current circuit - Google Patents
Linear constant current circuit Download PDFInfo
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- TWI674492B TWI674492B TW107129144A TW107129144A TWI674492B TW I674492 B TWI674492 B TW I674492B TW 107129144 A TW107129144 A TW 107129144A TW 107129144 A TW107129144 A TW 107129144A TW I674492 B TWI674492 B TW I674492B
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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
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
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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
- 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
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/14—Arrangements for reducing ripples from dc input or output
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0006—Arrangements for supplying an adequate voltage to the control circuit of converters
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/0045—Converters combining the concepts of switch-mode regulation and linear regulation, e.g. linear pre-regulator to switching converter, linear and switching converter in parallel, same converter or same transistor operating either in linear or switching mode
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Continuous-Control Power Sources That Use Transistors (AREA)
Abstract
公開了一種線性恒流電路，包括第一和第二功率開關、輸出電容、電流取樣電阻、運算放大器、及第二功率開關的控制電路，其中：輸出電容的正端與電路負載的正電壓端連接，第一功率開關的汲極與電路負載的負電壓端連接，第一功率開關的源極經由電流取樣電阻連接到系統大地，第一功率開關的閘極與運算放大器的輸出端連接，第二功率開關的汲級與第一功率開關的汲級連接，第二功率開關的源極與輸出電容的負端連接並作為控制電路的參考地，第二功率開關的閘極與控制電路的輸出端連接，控制電路基於表徵電路負載或輸出電容兩端的輸出電壓的輸出表徵電壓、第二和第三參考電壓，生成用於控制第二功率開關的導通與關斷的第二開關控制信號。 A linear constant current circuit is disclosed, which includes a first and second power switch, an output capacitor, a current sampling resistor, an operational amplifier, and a control circuit for a second power switch, wherein: the positive terminal of the output capacitor and the positive voltage terminal of the circuit load Connection, the drain of the first power switch is connected to the negative voltage terminal of the circuit load, the source of the first power switch is connected to the system ground via a current sampling resistor, the gate of the first power switch is connected to the output terminal of the operational amplifier, the The drain stage of the two power switches is connected to the drain stage of the first power switch. The source of the second power switch is connected to the negative terminal of the output capacitor and serves as a reference ground for the control circuit. The gate of the second power switch is connected to the output of the control circuit. The terminal is connected, and the control circuit generates a second switch control signal for controlling the on and off of the second power switch based on the output characterization voltage, the second and third reference voltages that characterize the output voltage across the load or output capacitor of the circuit.
Description
本發明涉及電路領域，更具體地涉及一種線性恒流電路。 The invention relates to the field of circuits, and more particularly to a linear constant current circuit.
第1圖示出了傳統的線性恒流電路的工作原理圖。在第1圖所示的線性恒流電路中，輸出電容Co的正端和負端分別與負載的兩端連接；功率開關S1的汲極與輸出電容Co的負端連接；功率開關S1的源極經由電流取樣電阻Rcs連接到系統大地；功率開關S1的閘極與運算放大器(EA)的輸出端連接，其中：電流取樣電阻Rcs對流過負載的輸出電流Io進行取樣，生成電流取樣電壓Vcs；運算放大器(EA)基於電流取樣電壓Vcs和參考電壓Vref，生成用於控制功率開關S1的導通與關斷的開關控制信號Out1，以在輸出電壓Vin波動時通過對功率開關S1的控制來實現對輸出電流Io的恒流控制。 Figure 1 shows the working principle of a conventional linear constant current circuit. In the linear constant current circuit shown in Figure 1, the positive and negative terminals of the output capacitor Co are connected to both ends of the load, respectively; the drain of the power switch S1 is connected to the negative terminal of the output capacitor Co; the source of the power switch S1 The electrode is connected to the system ground through a current sampling resistor Rcs; the gate of the power switch S1 is connected to the output of the operational amplifier (EA), wherein: the current sampling resistor Rcs samples the output current Io flowing through the load to generate a current sampling voltage Vcs; The operational amplifier (EA) generates a switching control signal Out1 for controlling the on and off of the power switch S1 based on the current sampling voltage Vcs and the reference voltage Vref, so as to control the power switch S1 when the output voltage Vin fluctuates. Constant current control of output current Io.
第2圖示出了第1圖所示的線性恒流電路中的一些關鍵點的電壓和電流的波形圖，其中：Vin表示通過對交流電壓進行整流得到的輸入電壓，Vo表示負載或輸出電容Co兩端的輸出電壓，Vcs表示電流取樣電阻Rcs上的電流取樣電壓，Vref表示參考電壓，Io表示流過負載的輸出電流。 Figure 2 shows the voltage and current waveforms of some key points in the linear constant current circuit shown in Figure 1, where Vin represents the input voltage obtained by rectifying the AC voltage, and Vo represents the load or output capacitance. The output voltage across Co, Vcs represents the current sampling voltage on the current sampling resistor Rcs, Vref represents the reference voltage, and Io represents the output current flowing through the load.
如第2圖所示，當輸入電壓Vin大於輸出電壓Vo時，功率開關S1工作于放大區，以控制電流取樣電阻Rcs上的電流取樣電壓Vcs與參考電壓Vref相等，輸入電壓Vin在給負載提供輸出電流Io的同時對輸出電容Co充電；當輸入電壓Vin小於輸出電壓Vo時，功率開關S1處於導通狀態，但是輸入電壓Vin無法給負載提供輸出電流Io，電流取樣電 阻Rcs上的電流採樣電壓Vcs為零，流過負載的輸出電流Io由輸出電容Co提供(即，輸出電容Co對負載放電)。 As shown in Figure 2, when the input voltage Vin is greater than the output voltage Vo, the power switch S1 works in the amplification region to control the current sampling voltage Vcs on the current sampling resistor Rcs to be equal to the reference voltage Vref. The input voltage Vin is provided to the load. The output capacitor Co is charged while outputting the current Io; when the input voltage Vin is less than the output voltage Vo, the power switch S1 is on, but the input voltage Vin cannot provide the output current Io to the load. The current sampling voltage Vcs on the resistance Rcs is zero, and the output current Io flowing through the load is provided by the output capacitor Co (that is, the output capacitor Co discharges to the load).
因此，在第1圖所示的線性恒流電路中，當輸入電壓Vin低頻波動時，輸出電流Io也隨之低頻波動。具體地，在每個低頻週期內，輸入電壓Vin小於輸出電壓Vo的時間為Tdis，輸出電容Co兩端的電壓的波紋大小(即，輸出電壓Vo的波紋大小)為△V=Io*Tdis/Co；輸出電容Co的容量越小，輸出電壓Vo的紋波越大，輸出電流Io的紋波也越大；輸出電容Co的容量越大，輸出電壓Vo的紋波越小，輸出電流Io的紋波也越小。 Therefore, in the linear constant current circuit shown in FIG. 1, when the input voltage Vin fluctuates at a low frequency, the output current Io also fluctuates at a low frequency. Specifically, in each low-frequency period, the time when the input voltage Vin is less than the output voltage Vo is Tdis, and the ripple of the voltage across the output capacitor Co (that is, the ripple of the output voltage Vo) is △ V = Io * Tdis / Co ; The smaller the capacity of the output capacitor Co, the larger the ripple of the output voltage Vo, and the larger the ripple of the output current Io; the larger the capacity of the output capacitor Co, the smaller the ripple of the output voltage Vo, and the ripple of the output current Io. The smaller the wave is.
在某些應用場景中，要求輸出電流Io的低頻紋波盡可能小，這就需要輸出電容Co的容量較大，但是輸出電容Co一般都是電解電容，容量越大，體積也會大很多，這樣就無法實現電源體積的小型化。 In some application scenarios, the low-frequency ripple of the output current Io is required to be as small as possible, which requires a large capacity of the output capacitor Co, but the output capacitor Co is generally an electrolytic capacitor. The larger the capacity, the larger the volume. This makes it impossible to reduce the size of the power supply.
鑒於以上所述的一個或多個問題，本發明提供了一種新穎的線性恒流電路。 In view of one or more of the problems described above, the present invention provides a novel linear constant current circuit.
根據本發明實施例的線性恒流電路，包括第一功率開關、第二功率開關、輸出電容、電流取樣電阻、運算放大器、以及第二功率開關的控制電路，其中：輸出電容的正端與電路負載的正電壓端連接，第一功率開關的汲極與電路負載的負電壓端連接，第一功率開關的源極經由電流取樣電阻連接到系統大地，第一功率開關的閘極與運算放大器的輸出端連接，第二功率開關的汲級與第一功率開關的汲級連接，第二功率開關的源極與輸出電容的負端連接並作為控制電路的參考地，第二功率開關的閘極與控制電路的輸出端連接，電流取樣電阻對流過電路負載的輸出電流進行取樣以生成電流取樣電壓，運算放大器基於電流取樣電壓和第一參考電壓生成用於控制第一功率開關的導通與關斷的第一開關控制信號，控制電路基於表徵電路負載或所述輸出電容兩端的輸出電壓的輸出表徵電壓、第二參考電壓、以及第三參考電壓，生成用於控制第二功率開關的導通與關斷的第二開關控制信號。 The linear constant current circuit according to the embodiment of the present invention includes a first power switch, a second power switch, an output capacitor, a current sampling resistor, an operational amplifier, and a control circuit for the second power switch, wherein the positive terminal of the output capacitor and the circuit The positive voltage end of the load is connected, the drain of the first power switch is connected to the negative voltage end of the circuit load, the source of the first power switch is connected to the system ground via a current sampling resistor, and the gate of the first power switch is connected to the op amp. The output terminal is connected. The drain stage of the second power switch is connected to the drain stage of the first power switch. The source of the second power switch is connected to the negative terminal of the output capacitor and serves as the reference ground of the control circuit. The gate of the second power switch Connected to the output of the control circuit, the current sampling resistor samples the output current flowing through the circuit load to generate a current sampling voltage, and the operational amplifier generates the first power switch to control the on and off of the first power switch based on the current sampling voltage and the first reference voltage. Control signal of the first switch, the control circuit is based on characterizing the circuit load or the output across the output capacitor. Characterization of the output voltage of the voltage, the second reference voltage, and a third reference voltage, generating a second power switch for controlling the ON and OFF the second switch control signal.
在一些實施例中，上述線性恒流電路還包括分壓網路， 該分壓網路的一端與輸出電容的負端連接、另一端與第一功率開關的源極連接，輸出表徵電壓是由分壓網路對控制電路的參考地與系統大地之間的電壓進行分壓得到的。 In some embodiments, the linear constant current circuit further includes a voltage dividing network, One end of the voltage division network is connected to the negative terminal of the output capacitor, and the other end is connected to the source of the first power switch. The output characteristic voltage is determined by the voltage between the reference ground of the control circuit and the system ground. Partial pressure is obtained.
在一些實施例中，當線性恒流電路的輸入電壓大於輸出電壓時，第一功率開關工作於放大區，第二功率開關處於導通狀態，輸入電壓在對電路負載提供輸出電流的同時對輸出電容充電。 In some embodiments, when the input voltage of the linear constant current circuit is greater than the output voltage, the first power switch operates in the amplification region, and the second power switch is in an on state. The input voltage provides output current to the circuit load and simultaneously provides output capacitance. Charging.
在一些實施例中，當線性恒流電路的輸入電壓下降至無法給輸出電容充電但是仍然大於輸出電壓時，控制電路基於輸出表徵電壓和第二參考電壓控制第二功率開關從導通狀態變為關斷狀態，以切斷輸出電容對電路負載放電的通路。 In some embodiments, when the input voltage of the linear constant current circuit drops to the point where the output capacitor cannot be charged but is still greater than the output voltage, the control circuit controls the second power switch from being turned on to off based on the output characterization voltage and the second reference voltage. Off state to cut off the path for the output capacitor to discharge the circuit load.
在一些實施例中，當線性恒流電路的輸入電壓下降到小於輸出電壓從而無法給電路負載提供輸出電流時，第一功率開關處於導通狀態，控制電路基於輸出表徵電壓和第三參考電壓控制第二功率開關從關斷狀態變為導通狀態，以使輸出電容給電路負載提供輸出電流。 In some embodiments, when the input voltage of the linear constant current circuit drops below the output voltage and is unable to provide output current to the circuit load, the first power switch is in an on state, and the control circuit controls the first The two power switches change from the off state to the on state, so that the output capacitor provides output current to the circuit load.
在一些實施例中，當輸出表徵電壓大於第二參考電壓時，控制電路輸出低電平的第二開關控制信號，以控制第二功率開關從導通狀態變為關斷狀態。 In some embodiments, when the output characteristic voltage is greater than the second reference voltage, the control circuit outputs a low-level second switch control signal to control the second power switch from the on state to the off state.
在一些實施例中，當輸出表徵電壓大於第三參考電壓時，控制電路輸出高電平的第二開關控制信號，以控制第二功率開關從關斷狀態變為導通狀態，第三參考電壓大於第二參考電壓。 In some embodiments, when the output characteristic voltage is greater than the third reference voltage, the control circuit outputs a high-level second switch control signal to control the second power switch from the off state to the on state, and the third reference voltage is greater than Second reference voltage.
根據本發明實施例的線性恒流電路可以降低每個工頻週期中輸出電流的峰值附近的電流平均值，從而減小輸出電流的低頻紋波。 The linear constant current circuit according to the embodiment of the present invention can reduce the current average value near the peak of the output current in each power frequency cycle, thereby reducing the low-frequency ripple of the output current.
Co‧‧‧輸出電容 Co‧‧‧ output capacitor
Out1、Out2‧‧‧開關控制信號 Out1, Out2‧‧‧ switch control signal
S1、S2‧‧‧功率開關 S1, S2‧‧‧ Power Switch
Vin、Vo‧‧‧電壓 Vin, Vo‧‧‧Voltage
Rcs‧‧‧電流取樣電阻 Rcs‧‧‧Current Sampling Resistor
R1、R2‧‧‧電阻 R1, R2‧‧‧ resistance
Io‧‧‧輸出電流 Io‧‧‧Output current
FB‧‧‧輸出表徵電壓 FB‧‧‧Output Characteristic Voltage
Vcs‧‧‧取樣電壓 Vcs‧‧‧Sampling voltage
1、2‧‧‧比較器 1, 2‧‧‧ comparator
off、on‧‧‧控制信號 off, on‧‧‧control signal
EA‧‧‧運算放大器 EA‧‧‧ Operational Amplifier
Vref、ref1、ref2‧‧‧參考電壓 Vref, ref1, ref2‧‧‧ reference voltage
從下面結合附圖對本發明的具體實施方式的描述中可以更好地理解本發明，其中：第1圖示出了傳統的線性恒流電路的工作原理圖；第2圖示出了第1圖所示的線性恒流電路中的一些關鍵點的電壓和電流的波形圖；第3圖示出了根據本發明實施例的線性恒流電路的工作原理圖；第4圖示出了第2圖所示的線性恒流電路中的一些關鍵點的電壓和電流的波形圖。 The present invention can be better understood from the following description of specific embodiments of the present invention with reference to the accompanying drawings, wherein: FIG. 1 shows the working principle diagram of a conventional linear constant current circuit; and FIG. 2 shows the first diagram Waveform diagrams of voltage and current at some key points in the linear constant current circuit shown in FIG. 3; FIG. 3 shows a working principle diagram of a linear constant current circuit according to an embodiment of the present invention; Shown are voltage and current waveform diagrams of some key points in a linear constant current circuit.
下面將詳細描述本發明的各個方面的特徵和示例性實施例。在下面的詳細描述中，提出了許多具體細節，以便提供對本發明的全面理解。但是，對於本領域技術人員來說很明顯的是，本發明可以在不需要這些具體細節中的一些細節的情況下實施。下面對實施例的描述僅僅是為了通過示出本發明的示例來提供對本發明的更好的理解。本發明決不限於下面所提出的任何具體配置，而是在不脫離本發明的精神的前提下覆蓋了元素、部件和演算法的任何修改、替換和改進。在附圖和下面的描述中，沒有示出公知的結構和技術，以便避免對本發明造成不必要的模糊。 Features and exemplary embodiments of various aspects of the invention will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to a person skilled in the art that the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is merely for providing a better understanding of the present invention by showing examples of the present invention. The present invention is by no means limited to any specific configuration proposed below, but covers any modification, replacement, and improvement of elements, components, and algorithms without departing from the spirit of the present invention. In the drawings and the following description, well-known structures and techniques are not shown in order to avoid unnecessarily obscuring the present invention.
第3圖示出了根據本發明實施例的線性恒流電路的工作原理圖。如第3圖所示，根據本發明實施例的線性恒流電路除了包括與第1圖所示的線性恒流電路完全相同的電路部分以外，還包括功率開關S2及其控制電路。 FIG. 3 shows a working principle diagram of a linear constant current circuit according to an embodiment of the present invention. As shown in FIG. 3, the linear constant current circuit according to the embodiment of the present invention includes a power switch S2 and a control circuit thereof, in addition to the circuit portion exactly the same as the linear constant current circuit shown in FIG.
在第3圖所示的線性恒流電路中，功率開關S2的汲級與功率開關S1的漏級連接；功率開關S2的源極與輸出電容Co的負端連接，並作為功率開關S2的控制電路的參考地；功率開關S2的閘極與其控制電路的輸出端連接；電阻R1和R2組成的分壓網路對功率開關S2的控制電路的參考地與系統大地之間的電壓進行分壓，生成表徵輸出電壓Vo的輸出表徵電壓FB；功率開關S2的控制電路基於輸出表徵電壓FB、參考電壓ref1、以及參考電壓ref2生成用於控制功率開關S2的導通與關斷的開關控制信號Out2，以減小在輸入電壓Vin低頻波動時輸出電流Io的紋波的大小。 In the linear constant current circuit shown in FIG. 3, the drain stage of the power switch S2 is connected to the drain stage of the power switch S1; the source of the power switch S2 is connected to the negative terminal of the output capacitor Co, and is used as the control of the power switch S2. The reference ground of the circuit; the gate of the power switch S2 is connected to the output of its control circuit; the voltage dividing network composed of resistors R1 and R2 divides the voltage between the reference ground of the control circuit of the power switch S2 and the system ground, Generate an output characterization voltage FB characterizing the output voltage Vo; the control circuit of the power switch S2 generates a switching control signal Out2 for controlling the on and off of the power switch S2 based on the output characterization voltage FB, the reference voltage ref1, and the reference voltage ref2, Reduce the ripple of the output current Io when the input voltage Vin fluctuates at a low frequency.
在第3圖所示的線性恒流電路中，當輸入電壓Vin大於輸出電壓Vo時，功率開關S1工作於放大區，以控制流過電流取樣電阻Rcs的電流取樣電壓Vcs恒定；當輸入電壓Vin小於輸出電壓Vo時，功率開關S1處於導通狀態，輸入電壓Vin無法給負載提供輸出電流Io，電流 取樣電阻Rcs上的電流取樣電壓Vcs為零，流過負載的輸出電流Io由輸出電容Co提供(即，輸出電容Co對負載放電)。 In the linear constant current circuit shown in FIG. 3, when the input voltage Vin is greater than the output voltage Vo, the power switch S1 works in the amplification region to control the current sampling voltage Vcs flowing through the current sampling resistor Rcs to be constant; when the input voltage Vin When the output voltage Vo is smaller than the power switch S1, the input voltage Vin cannot provide the output current Io to the load. The current sampling voltage Vcs on the sampling resistor Rcs is zero, and the output current Io flowing through the load is provided by the output capacitor Co (that is, the output capacitor Co discharges to the load).
第4圖示出了第2圖所示的線性恒流電路中的一些關鍵點的電壓和電流的波形圖，其中：Vin表示通過對交流電壓進行整流得到的輸入電壓，Vo表示負載兩端的輸出電壓，Vcs表示電流取樣電阻Rcs上的電流採樣電壓，ref1和ref2分別表示用於功率開關S2的控制電路中的兩個參考電壓，Io表示流過負載的輸出電流，Out2表示功率開關S2的控制電路生成的、用於控制功率開關S2的導通與關斷的開關控制信號。 Figure 4 shows the voltage and current waveforms of some key points in the linear constant current circuit shown in Figure 2, where Vin represents the input voltage obtained by rectifying the AC voltage, and Vo represents the output across the load. Voltage, Vcs represents the current sampling voltage on the current sampling resistor Rcs, ref1 and ref2 represent the two reference voltages in the control circuit for power switch S2, Io represents the output current flowing through the load, and Out2 represents the control of power switch S2 A switch control signal generated by the circuit for controlling the on and off of the power switch S2.
如第4圖所示，當輸入電壓Vin大於輸出電壓Vo時，輸入電壓Vin在對負載提供輸出電流Io的同時對輸出電容Co充電，功率開關S2處於導通狀態。 As shown in FIG. 4, when the input voltage Vin is greater than the output voltage Vo, the input voltage Vin charges the output capacitor Co while supplying the output current Io to the load, and the power switch S2 is in an on state.
如第4圖所示，當輸入電壓Vin下降至輸出電壓Vo附近時，輸入電壓Vin無法給輸出電容Co充電但是仍然可以對負載提供輸出電流Io；此時，輸出表徵電壓FB大於參考電壓ref2，比較器2輸出高位準的控制信號off；功率開關S2的控制電路輸出低位準的開關控制信號Out2，以控制功率開關S2從導通狀態變為關斷狀態，從而切斷輸出電容Co對負載放電的通路。 As shown in Figure 4, when the input voltage Vin drops to the vicinity of the output voltage Vo, the input voltage Vin cannot charge the output capacitor Co but can still provide the output current Io to the load; at this time, the output characteristic voltage FB is greater than the reference voltage ref2, The comparator 2 outputs a high-level control signal off; the control circuit of the power switch S2 outputs a low-level control signal Out2 to control the power switch S2 from the on state to the off state, thereby cutting off the output capacitor Co from discharging the load. path.
如第4圖所示，當輸入電壓Vin下降到小於輸出電壓Vo時，輸入電壓Vin既無法給輸出電容Co充電也無法給負載提供輸出電流Io；此時，輸出表徵電壓FB大於參考電壓ref1，比較器1輸出高位準的控制信號on；功率開關S2的控制電路輸出高位準的開關控制信號Out2，以控制功率開關S2從關斷狀態變為到導通狀態，從而使得輸出電容Co給負載提供輸出電流Io。 As shown in Figure 4, when the input voltage Vin drops below the output voltage Vo, the input voltage Vin can neither charge the output capacitor Co nor provide the output current Io to the load; at this time, the output characteristic voltage FB is greater than the reference voltage ref1, The comparator 1 outputs a high-level control signal on; the control circuit of the power switch S2 outputs a high-level switch control signal Out2 to control the power switch S2 from the off state to the on state, so that the output capacitor Co provides output to the load. Current Io.
這裡，需要說明的是，控制信號on和off是上升沿有效的控制信號，即它們在從低位準變成高位準的瞬間有效。 Here, it should be noted that the control signals on and off are valid control signals with rising edges, that is, they are effective at the moment when they change from a low level to a high level.
第3圖所示的線性恒流電路可以降低每個工頻週期中輸出電流Io的峰值附近的電流平均值，從而減小輸出電流Io的低頻紋波。 The linear constant current circuit shown in FIG. 3 can reduce the current average value near the peak of the output current Io in each power frequency cycle, thereby reducing the low-frequency ripple of the output current Io.
本發明可以以其他的具體形式實現，而不脫離其精神和本質特徵。例如，特定實施例中所描述的演算法可以被修改，而系統體系 結構並不脫離本發明的基本精神。因此，當前的實施例在所有方面都被看作是示例性的而非限定性的，本發明的範圍由所附權利要求而非上述描述定義，並且，落入權利要求的含義和等同物的範圍內的全部改變從而都被包括在本發明的範圍之中。 The present invention may be implemented in other specific forms without departing from the spirit and essential characteristics thereof. For example, the algorithm described in a particular embodiment can be modified and the system architecture The structure does not depart from the basic spirit of the present invention. Therefore, the present embodiments are to be considered in all respects as illustrative and not restrictive, the scope of the present invention is defined by the appended claims rather than the above description, and falls within the meaning and equivalent of the claims All changes within the scope are thus included in the scope of the present invention.
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| CN113992161B (en) * | 2021-10-27 | 2022-05-20 | 陕西亚成微电子股份有限公司 | Dynamic current supply circuit and method for reducing ripples |
| CN115932380A (en) * | 2023-02-23 | 2023-04-07 | 杰华特微电子股份有限公司 | Power detection circuit and detection method of switching circuit and switching circuit |
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| CN108880252A (en) | 2018-11-23 |
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