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WO2024031994A1 - Current backflow preventing circuit structure - Google Patents

Current backflow preventing circuit structure Download PDF

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Publication number
WO2024031994A1
WO2024031994A1 PCT/CN2023/083232 CN2023083232W WO2024031994A1 WO 2024031994 A1 WO2024031994 A1 WO 2024031994A1 CN 2023083232 W CN2023083232 W CN 2023083232W WO 2024031994 A1 WO2024031994 A1 WO 2024031994A1
Authority
WO
WIPO (PCT)
Prior art keywords
power switch
voltage
terminal
operational amplifier
comparator
Prior art date
Application number
PCT/CN2023/083232
Other languages
French (fr)
Chinese (zh)
Inventor
杨镇
徐伟
王蕾
张凤菊
Original Assignee
无锡力芯微电子股份有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 无锡力芯微电子股份有限公司 filed Critical 无锡力芯微电子股份有限公司
Priority to KR1020237014344A priority Critical patent/KR20240022436A/en
Publication of WO2024031994A1 publication Critical patent/WO2024031994A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/18—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to reversal of direct current
    • 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
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
    • 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
    • H02M1/0012—Control circuits using digital or numerical techniques
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

Definitions

  • the invention relates to a protection circuit between a power conversion output terminal and a lithium battery charging input terminal, specifically a circuit structure to prevent current backflow.
  • the first type is achieved by adding a natural anti-backfeed power device between the power conversion output end and the lithium battery charging end.
  • a typical representative of this type of device is the power level Schottky diode.
  • the first type of anti-backfeed protection structure is shown in Figure 1.
  • the power switch tube M1 can control its switching state through the pre-drive structure.
  • the power diode D1 is turned on when it needs to be turned on in the forward direction (IN is higher than the OUT voltage). It needs to be prevented. Turns off when backfeed occurs (OUT is higher than IN voltage).
  • This structure takes advantage of the natural forward conduction characteristics of the diode and has a simple structure.
  • the second category is to build a control system consisting of a drive module, a power switch module, and a voltage sampling and comparison module to ensure that when the battery terminal voltage is higher than the power conversion output terminal voltage, the power switch module is cut off in time to achieve anti-backfeed protection.
  • the second type of anti-backfeed protection structure is shown in Figure 2. It consists of a comparator circuit CMP, a pre-drive circuit Driver, and a power switch tube M1.
  • the power switch tube M1 is composed of two identical MOS tubes connected back to back in series. When M1 is in the cut-off state, it can ensure that the bidirectional current is cut off.
  • the second type of anti-backflow structure chooses back-to-back MOS tubes to replace the MOS tube + diode structure in the first type. It has a smaller conduction voltage drop and lower conduction during forward conduction. loss.
  • the comparator circuit detects that the OUT terminal voltage is higher than the IN terminal voltage, it outputs a signal to the pre-drive circuit Driver and turns off the power switch to achieve the anti-backfeed function.
  • the specific working process is: if the OUT voltage is slightly higher than the IN voltage, it is determined that the anti-backfeed is triggered.
  • the comparator outputs a control signal to the pre-drive circuit Driver to turn off the power switch.
  • the comparator determination threshold is adjusted to a slightly lower OUT voltage.
  • the comparator in order to prevent false triggering of the anti-backfeed function (for example, when external signal interference causes the OUT terminal voltage value collected by the comparator circuit to be higher than the IN terminal voltage at a certain moment), a comparison is generally designed. toggle threshold hysteresis.
  • the comparator flip threshold hysteresis results in a certain delay from the anti-backfeed function triggering until the power switch state changes. During the delay time, if If the power switch tube fails to be turned off in time, the IN voltage will follow the rise of the OUT voltage through the turned-on power tube, thereby invalidating the anti-backfeed function.
  • the technical problem to be solved by the present invention is to provide a circuit structure that prevents current backflow.
  • This circuit structure consumes little power during normal operation and does not cause the problem of backflow prevention failure.
  • the circuit structure for preventing current backflow of the present invention includes a power switch M1, a comparator and a pre-drive circuit.
  • the IN terminal of the power switch M1 is connected to the non-inverting input terminal of the comparator
  • the OUT terminal of the power switch M1 is connected to the inverting input terminal of the comparator
  • the output terminal of the comparator is connected to the pre-drive circuit.
  • the pre-drive circuit is adaptively connected to the power switch tube M1, and is used to drive the power switch tube M1 to conduct. Its characteristic is that it also includes an operational amplifier S1.
  • the feedback terminal B of the operational amplifier S1 is connected to the OUT terminal of the power switch M1.
  • the voltage input terminal A of the operational amplifier S1 is connected to the input voltage.
  • the value of the input voltage is lower than that of the power switch M1.
  • IN terminal voltage value the output terminal of operational amplifier S1 is adapted to the pre-drive circuit.
  • the closed-loop negative feedback characteristic of the operational amplifier is used to make the voltage of the feedback terminal B of the operational amplifier S1 follow the voltage of the voltage input terminal A, thus ensuring that the voltage of the IN terminal of the power switch M1 is always greater than the voltage of the OUT terminal of the power switch M1.
  • the power switch tube M1 is composed of two identical MOS tubes connected back to back in series.
  • the substrate levels of the two MOS tubes are parasitic with diodes.
  • a set of source and drain electrodes of the two MOS tubes are connected to each other.
  • the other source and drain of one MOS tube is the IN terminal of the power switch M1, and the other one is the IN terminal of the power switch M1.
  • the other source and drain of the MOS tube is the OUT terminal of the power switch tube M1.
  • the IN terminal of the power switch M1 is connected to one end of the resistor R, and the other end of the resistor R is connected to the voltage input terminal A of the operational amplifier S1 to form the input voltage.
  • One end of the resistor R connected to the voltage input terminal A of the operational amplifier S1 is connected in series with the current source I and then connected to ground.
  • the feedback terminal B of the operational amplifier S1 of the circuit structure for preventing current backflow of the present invention is connected to the OUT terminal of the power switch M1
  • the voltage input terminal A of the operational amplifier S1 is connected to the input voltage, and the value of the input voltage is lower than that of the power switch M1.
  • the voltage value of the IN terminal of the tube M1 is connected to the output terminal of the operational amplifier S1 and the pre-drive circuit.
  • the closed-loop negative feedback characteristic of the operational amplifier is adopted so that the voltage of the feedback terminal B of the operational amplifier S1 follows the voltage of the voltage input terminal A, thus Ensure that the voltage at the IN terminal of the power switch M1 is always greater than the voltage at the OUT terminal of the power switch M1.
  • This circuit structure to prevent current backflow adds an operational amplifier circuit to the second type of structure in the background technology, and the normal conduction The power consumption during communication is small.
  • the voltage of the feedback terminal B of the operational amplifier S1 follows the voltage of the voltage input terminal A, that is, the voltage of the OUT terminal of the power switch M1 is approximately equal to the input voltage.
  • the voltage of the OUT terminal of the power switch M1 also changes. There will be no fluctuation, that is, the OUT terminal voltage of the power switch M1 is always lower than the IN terminal voltage. Therefore, there is no need to set the comparator flip threshold hysteresis.
  • the comparator can instantly shut down the pre-drive circuit to ensure that the power switch M1 is in the cut-off state and avoid the comparator failure.
  • the flip threshold hysteresis causes the problem of anti-backfeed failure.
  • Figure 1 is a circuit schematic diagram of the first type of anti-backfeed structure in the background technology
  • Figure 2 is a circuit schematic diagram of the second type of anti-backflow structure in the background technology
  • Figure 3 is a circuit schematic diagram of the circuit structure for preventing current backflow according to the present invention.
  • Figure 4 is a schematic diagram of the formation of input voltage.
  • the circuit structure for preventing current backflow of the present invention includes a power switch M1, a comparator 2, a pre-drive circuit 1 and an operational amplifier S1.
  • the IN terminal of the power switch M1 is connected to the non-inverting input terminal of the comparator 2
  • the OUT terminal of the power switch M1 is connected to the inverting input terminal of the comparator 2
  • the output terminal of the comparator 2 is connected to the pre-drive circuit. 1 is adapted for connection.
  • the pre-drive circuit 1 is adapted for connection with the power switch tube M1, and is used to drive the power switch tube M1 to conduct.
  • the feedback terminal B of the operational amplifier S1 is connected to the OUT terminal of the power switch M1.
  • the voltage input terminal A of the operational amplifier S1 is connected to an input voltage. The value of the input voltage is lower than the IN terminal voltage value of the power switch M1.
  • the operational amplifier The output end of S1 is adaptively connected to the pre-drive circuit 1.
  • the closed-loop negative feedback characteristics of the operational amplifier are used to make the voltage of the feedback terminal B of the operational amplifier S1 follow the voltage of the voltage input terminal A, that is, the voltage of the feedback terminal B is approximately equal to the voltage of the voltage input terminal A, and since the value of the input voltage is lower than The voltage value of the IN terminal of the power switch M1. Therefore, it is ensured that the IN terminal voltage of the power switch M1 is always greater than the OUT terminal voltage of the power switch M1.
  • the power switch tube M1 is composed of two identical MOS tubes connected back to back in series.
  • the substrate levels of the two MOS tubes are parasitic with diodes.
  • a set of source and drain electrodes of the two MOS tubes are connected to each other.
  • the other source and drain of one MOS tube is the IN terminal of the power switch M1, and the other one is the IN terminal of the power switch M1.
  • the other source and drain of the MOS tube is the OUT terminal of the power switch tube M1.
  • Back-to-back MOS tubes have small conduction voltage drop and small conduction loss when conducting forward.
  • the IN terminal of the power switch M1 is connected to one end of the resistor R, and the other end of the resistor R is connected to the voltage input terminal A of the operational amplifier S1 to form the input voltage.
  • the resistor R is used to create a voltage drop, thus ensuring that the output The input voltage is less than the IN terminal voltage, and the specific value of the input voltage is related to the resistance of the resistor R.
  • One end of the resistor R connected to the voltage input terminal A of the operational amplifier S1 is connected in series with the current source I and then connected to ground.
  • the purpose of using current source I is that when the current source is turned on, the current in the branch is the current output by the current source, thereby ensuring the stability of the input voltage.
  • the voltage at point A is 50mV lower than the IN terminal voltage
  • the power switch conduction resistance is 25m ⁇
  • the backfeed flip threshold of comparator 2 is designed so that the OUT terminal is 10mV lower than the IN terminal.
  • the op amp uses the closed-loop feedback of the OUT terminal to make the power switch tube work in the saturation zone, and the OUT terminal remains 50mV lower than the IN terminal.
  • Io is the load current at the OUT terminal.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)
  • Continuous-Control Power Sources That Use Transistors (AREA)
  • Direct Current Feeding And Distribution (AREA)

Abstract

The present invention relates to a protection circuit between a power supply conversion output end and a lithium battery charging input end, in particular to a current backflow preventing circuit structure. The circuit structure comprises a power switch transistor M1, a comparator and a pre-driver circuit, an IN end of the power switch transistor M1 being connected to a non-inverting input end of the comparator, an OUT end of the power switch transistor M1 being connected with an inverting input end of the comparator, an output end of the comparator being in adaptation connection with the pre-driver circuit, and the pre-driver circuit being in adaptation connection with the power switch transistor M1 and being used for driving the power switch transistor M1 to be turned on. The circuit structure is characterized by further comprising an operational amplifier S1, a feedback end B of the operational amplifier S1 being connected to the OUT end of the power switch transistor M1, a voltage input end A of the operational amplifier S1 being connected to an input voltage, the value of the input voltage being lower than the voltage value of the IN end of the power switch transistor M1, and an output end of the operational amplifier S1 being in adaptation connection with the pre-driver circuit. The circuit structure has low power consumption during normal operation, and avoids the problem of backflow prevention failures.

Description

一种防电流反灌的电路结构A circuit structure to prevent current backflow 技术领域Technical field

本发明涉及一种电源转换输出端和锂电池充电的输入端之间的保护电路，具体说是防止电流反灌的电路结构。The invention relates to a protection circuit between a power conversion output terminal and a lithium battery charging input terminal, specifically a circuit structure to prevent current backflow.

背景技术Background technique

随着科技的发展，大至新能源汽车，小至无线耳机，都内置了锂电池作为其内部电能的来源。在如此广泛的应用场景下，面对各种复杂的充电环境，需要在电源转换输出端和锂电池充电的输入端之间设置各类保护电路。防止电流反灌也是其中一个关键的保护功能。With the development of technology, everything from new energy vehicles to wireless headphones have built-in lithium batteries as their internal source of electrical energy. In such a wide range of application scenarios and in the face of various complex charging environments, various protection circuits need to be installed between the power conversion output end and the lithium battery charging input end. Preventing current backflow is also one of the key protection functions.

目前，常用的防反灌保护结构主要有两类，第一类是在电源转换输出端和锂电池充电端之间增加天然防反灌的功率器件来实现，这类器件的典型代表即为功率级肖特基二极管。第一类防反灌保护结构如图1所示，功率开关管M1可通过前置驱动结构控制其开关状态，功率二极管D1在需要正向开启(IN高于OUT电压)时导通，需要防反灌(OUT高于IN电压)时关闭。该结构利用了二极管天然正向导通的特性，结构简单。但是二极管正向导通压降较大，正常工作过程中功耗太高。第二类则是搭建一个由驱动模块、功率开关模块、电压采样比较模块组成的控制系统，确保当电池端电压高于电源转换输出端电压时，及时切断功率开关模块，实现防反灌保护。第二类防反灌保护结构如图2所示，它具有比较器电路CMP、前置驱动电路Driver，功率开关管M1组成。其中功率开关管M1由两个相同的MOS管背靠背串联组成，在M1截至状态时，可确保双向电流截至。第二类防反灌结构相比第一类结构，选择背靠背MOS管替代第一类中的MOS管+二极管的结构，在正向导通时具有更小的导通压降，更低的导通损耗。当比较器电路检测到OUT端电压高于IN端电压时，输出信号给前置驱动电路Driver，关闭功率开关管，以实现防反灌的功能。具体工作过过程是：如果OUT电压略高于IN电压，判定触发防反灌，比较器输出控制信号给前置驱动电路Driver将功率开关管关闭，同时将比较器判定阈值调整为OUT电压略低于IN电压；当OUT电压略低于IN电压时，比较器输出控制信号给前置驱动电路Driver再次将功率开关管打开。然而，第二类结构在实际应用中，为了防止误触发防反灌功能(如外界信号干扰导致比较器电路采集的某个瞬间的OUT端电压值高于IN端电压时)，一般会设计比较器翻转阈值迟滞。但是，比较器翻转阈值迟滞导致从防反灌功能触发直至功率开关管状态的改变存在一定的延时。延时时间内如 果功率开关管未能及时关闭，IN电压会通过导通的功率管跟随OUT电压的升高，从而使防反灌功能失效。At present, there are two main types of commonly used anti-backfeed protection structures. The first type is achieved by adding a natural anti-backfeed power device between the power conversion output end and the lithium battery charging end. A typical representative of this type of device is the power level Schottky diode. The first type of anti-backfeed protection structure is shown in Figure 1. The power switch tube M1 can control its switching state through the pre-drive structure. The power diode D1 is turned on when it needs to be turned on in the forward direction (IN is higher than the OUT voltage). It needs to be prevented. Turns off when backfeed occurs (OUT is higher than IN voltage). This structure takes advantage of the natural forward conduction characteristics of the diode and has a simple structure. However, the forward voltage drop of the diode is large, and the power consumption during normal operation is too high. The second category is to build a control system consisting of a drive module, a power switch module, and a voltage sampling and comparison module to ensure that when the battery terminal voltage is higher than the power conversion output terminal voltage, the power switch module is cut off in time to achieve anti-backfeed protection. The second type of anti-backfeed protection structure is shown in Figure 2. It consists of a comparator circuit CMP, a pre-drive circuit Driver, and a power switch tube M1. The power switch tube M1 is composed of two identical MOS tubes connected back to back in series. When M1 is in the cut-off state, it can ensure that the bidirectional current is cut off. Compared with the first type of structure, the second type of anti-backflow structure chooses back-to-back MOS tubes to replace the MOS tube + diode structure in the first type. It has a smaller conduction voltage drop and lower conduction during forward conduction. loss. When the comparator circuit detects that the OUT terminal voltage is higher than the IN terminal voltage, it outputs a signal to the pre-drive circuit Driver and turns off the power switch to achieve the anti-backfeed function. The specific working process is: if the OUT voltage is slightly higher than the IN voltage, it is determined that the anti-backfeed is triggered. The comparator outputs a control signal to the pre-drive circuit Driver to turn off the power switch. At the same time, the comparator determination threshold is adjusted to a slightly lower OUT voltage. to the IN voltage; when the OUT voltage is slightly lower than the IN voltage, the comparator outputs a control signal to the pre-drive circuit Driver to turn on the power switch again. However, in practical applications of the second type of structure, in order to prevent false triggering of the anti-backfeed function (for example, when external signal interference causes the OUT terminal voltage value collected by the comparator circuit to be higher than the IN terminal voltage at a certain moment), a comparison is generally designed. toggle threshold hysteresis. However, the comparator flip threshold hysteresis results in a certain delay from the anti-backfeed function triggering until the power switch state changes. During the delay time, if If the power switch tube fails to be turned off in time, the IN voltage will follow the rise of the OUT voltage through the turned-on power tube, thereby invalidating the anti-backfeed function.

发明内容Contents of the invention

本发明要解决的技术问题是提供一种防止电流反灌的电路结构，该电路结构在正常工作时功耗小，不会出现防反灌失效的问题。The technical problem to be solved by the present invention is to provide a circuit structure that prevents current backflow. This circuit structure consumes little power during normal operation and does not cause the problem of backflow prevention failure.

为解决上述问题，提供以下技术方案：To solve the above problems, the following technical solutions are provided:

本发明的防电流反灌的电路结构包括功率开关管M1、比较器和前置驱动电路。所述功率开关管M1的IN端与比较器的同相输入端相连，所述功率开关管M1的OUT端与比较器的反相输入端相连，比较器的输出端与前置驱动电路适配连接，前置驱动电路与功率开关管M1适配连接，用于驱动功率开关管M1导通。其特点是还包括运算放大器S1，运算放大器S1的反馈端B与功率开关管M1的OUT端相连，运算放大器S1的电压输入端A接输入电压，该输入电压的值低于功率开关管M1的IN端电压值，运算放大器S1的输出端与前置驱动电路适配连接。采用运算放大器闭环负反馈特性，使运算放大器S1的反馈端B的电压跟随电压输入端A的电压，从而确保功率开关管M1的IN端电压始终大于功率开关管M1的OUT端电压。The circuit structure for preventing current backflow of the present invention includes a power switch M1, a comparator and a pre-drive circuit. The IN terminal of the power switch M1 is connected to the non-inverting input terminal of the comparator, the OUT terminal of the power switch M1 is connected to the inverting input terminal of the comparator, and the output terminal of the comparator is connected to the pre-drive circuit. , the pre-drive circuit is adaptively connected to the power switch tube M1, and is used to drive the power switch tube M1 to conduct. Its characteristic is that it also includes an operational amplifier S1. The feedback terminal B of the operational amplifier S1 is connected to the OUT terminal of the power switch M1. The voltage input terminal A of the operational amplifier S1 is connected to the input voltage. The value of the input voltage is lower than that of the power switch M1. IN terminal voltage value, the output terminal of operational amplifier S1 is adapted to the pre-drive circuit. The closed-loop negative feedback characteristic of the operational amplifier is used to make the voltage of the feedback terminal B of the operational amplifier S1 follow the voltage of the voltage input terminal A, thus ensuring that the voltage of the IN terminal of the power switch M1 is always greater than the voltage of the OUT terminal of the power switch M1.

其中，所述功率开关管M1由两个同样的MOS管背靠背串联而成。Among them, the power switch tube M1 is composed of two identical MOS tubes connected back to back in series.

两个所述MOS管的衬底级均寄生有二级管，两个MOS管的一组源漏极互相连接，其中一个MOS管的另外一个源漏极为功率开关管M1的IN端，另一个MOS管的另外一个源漏极为功率开关管M1的OUT端。The substrate levels of the two MOS tubes are parasitic with diodes. A set of source and drain electrodes of the two MOS tubes are connected to each other. The other source and drain of one MOS tube is the IN terminal of the power switch M1, and the other one is the IN terminal of the power switch M1. The other source and drain of the MOS tube is the OUT terminal of the power switch tube M1.

所述功率开关管M1的IN端与电阻R的一端相连，电阻R的另一端与运算放大器S1的电压输入端A相连，形成所述输入电压。The IN terminal of the power switch M1 is connected to one end of the resistor R, and the other end of the resistor R is connected to the voltage input terminal A of the operational amplifier S1 to form the input voltage.

与运算放大器S1的电压输入端A相连的电阻R一端串联电流源I后接地。One end of the resistor R connected to the voltage input terminal A of the operational amplifier S1 is connected in series with the current source I and then connected to ground.

采取以上方案，具有以下优点：Adopting the above solution has the following advantages:

由于本发明的防止电流反灌的电路结构的运算放大器S1的反馈端B与功率开关管M1的OUT端相连，运算放大器S1的电压输入端A接输入电压，该输入电压的值低于功率开关管M1的IN端的电压值，运算放大器S1的输出端与前置驱动电路适配连接，采用运算放大器闭环负反馈特性，使运算放大器S1的反馈端B的电压跟随电压输入端A的电压，从而确保功率开关管M1的IN端电压始终大于功率开关管M1的OUT端电压。这种防止电流反灌的电路结构在背景技术中第二类结构上增加运算放大器电路，正常导 通时功耗较小。另外，由于运算放大器S1的反馈端B的电压跟随电压输入端A的电压，即功率开关管M1的OUT端电压与输入电压近似相等，在外界出现干扰时，功率开关管M1的OUT端电压也不会有波动，即功率开关管M1的OUT端电压始终低于IN端电压。因而，无需设置比较器翻转阈值迟滞，一旦出现功率开关管M1的0UT电压高于IN端电压，比较器即可瞬时关闭前置驱动电路，确保功率开关管M1处于截止状态，避免了因比较器翻转阈值迟滞导致防反灌失效的问题。Since the feedback terminal B of the operational amplifier S1 of the circuit structure for preventing current backflow of the present invention is connected to the OUT terminal of the power switch M1, the voltage input terminal A of the operational amplifier S1 is connected to the input voltage, and the value of the input voltage is lower than that of the power switch M1. The voltage value of the IN terminal of the tube M1 is connected to the output terminal of the operational amplifier S1 and the pre-drive circuit. The closed-loop negative feedback characteristic of the operational amplifier is adopted so that the voltage of the feedback terminal B of the operational amplifier S1 follows the voltage of the voltage input terminal A, thus Ensure that the voltage at the IN terminal of the power switch M1 is always greater than the voltage at the OUT terminal of the power switch M1. This circuit structure to prevent current backflow adds an operational amplifier circuit to the second type of structure in the background technology, and the normal conduction The power consumption during communication is small. In addition, since the voltage of the feedback terminal B of the operational amplifier S1 follows the voltage of the voltage input terminal A, that is, the voltage of the OUT terminal of the power switch M1 is approximately equal to the input voltage. When interference occurs from the outside, the voltage of the OUT terminal of the power switch M1 also changes. There will be no fluctuation, that is, the OUT terminal voltage of the power switch M1 is always lower than the IN terminal voltage. Therefore, there is no need to set the comparator flip threshold hysteresis. Once the OUT voltage of the power switch M1 is higher than the IN terminal voltage, the comparator can instantly shut down the pre-drive circuit to ensure that the power switch M1 is in the cut-off state and avoid the comparator failure. The flip threshold hysteresis causes the problem of anti-backfeed failure.

附图说明Description of drawings

图1是背景技术中第一类防反灌结构的电路示意图；Figure 1 is a circuit schematic diagram of the first type of anti-backfeed structure in the background technology;

图2是背景技术中第二类防反灌结构的电路示意图；Figure 2 is a circuit schematic diagram of the second type of anti-backflow structure in the background technology;

图3是本发明的防止电流反灌的电路结构的电路示意图；Figure 3 is a circuit schematic diagram of the circuit structure for preventing current backflow according to the present invention;

图4是输入电压的形成示意图。Figure 4 is a schematic diagram of the formation of input voltage.

具体实施方式Detailed ways

如图3和图4所示，本发明的防电流反灌的电路结构包括功率开关管M1、比较器2、前置驱动电路1和运算放大器S1。所述功率开关管M1的IN端与比较器2的同相输入端相连，所述功率开关管M1的OUT端与比较器2的反相输入端相连，比较器2的输出端与前置驱动电路1适配连接，前置驱动电路1与功率开关管M1适配连接，用于驱动功率开关管M1导通。所述算放大器S1的反馈端B与功率开关管M1的OUT端相连，运算放大器S1的电压输入端A接输入电压，该输入电压的值低于功率开关管M1的IN端电压值，运算放大器S1的输出端与前置驱动电路1适配连接。As shown in Figures 3 and 4, the circuit structure for preventing current backflow of the present invention includes a power switch M1, a comparator 2, a pre-drive circuit 1 and an operational amplifier S1. The IN terminal of the power switch M1 is connected to the non-inverting input terminal of the comparator 2, the OUT terminal of the power switch M1 is connected to the inverting input terminal of the comparator 2, and the output terminal of the comparator 2 is connected to the pre-drive circuit. 1 is adapted for connection. The pre-drive circuit 1 is adapted for connection with the power switch tube M1, and is used to drive the power switch tube M1 to conduct. The feedback terminal B of the operational amplifier S1 is connected to the OUT terminal of the power switch M1. The voltage input terminal A of the operational amplifier S1 is connected to an input voltage. The value of the input voltage is lower than the IN terminal voltage value of the power switch M1. The operational amplifier The output end of S1 is adaptively connected to the pre-drive circuit 1.

采用运算放大器闭环负反馈特性，使运算放大器S1的反馈端B的电压跟随电压输入端A的电压，即反馈端B的电压与电压输入端A的电压近似相等，且由于输入电压的值低于功率开关管M1的IN端电压值。因而，确保功率开关管M1的IN端电压始终大于功率开关管M1的0UT端电压。The closed-loop negative feedback characteristics of the operational amplifier are used to make the voltage of the feedback terminal B of the operational amplifier S1 follow the voltage of the voltage input terminal A, that is, the voltage of the feedback terminal B is approximately equal to the voltage of the voltage input terminal A, and since the value of the input voltage is lower than The voltage value of the IN terminal of the power switch M1. Therefore, it is ensured that the IN terminal voltage of the power switch M1 is always greater than the OUT terminal voltage of the power switch M1.

所述功率开关管M1由两个同样的MOS管背靠背串联而成。两个所述MOS管的衬底级均寄生有二级管，两个MOS管的一组源漏极互相连接，其中一个MOS管的另外一个源漏极为功率开关管M1的IN端，另一个MOS管的另外一个源漏极为功率开关管M1的0UT端。背靠背MOS管在正向导通时导通压降小，导通损耗小。The power switch tube M1 is composed of two identical MOS tubes connected back to back in series. The substrate levels of the two MOS tubes are parasitic with diodes. A set of source and drain electrodes of the two MOS tubes are connected to each other. The other source and drain of one MOS tube is the IN terminal of the power switch M1, and the other one is the IN terminal of the power switch M1. The other source and drain of the MOS tube is the OUT terminal of the power switch tube M1. Back-to-back MOS tubes have small conduction voltage drop and small conduction loss when conducting forward.

所述功率开关管M1的IN端与电阻R的一端相连，电阻R的另一端与运算放大器S1的电压输入端A相连，形成所述输入电压。利用电阻R形成压降，从而确保形成所述输 入电压小于IN端电压，具体输入电压的具体数值与电阻R的阻值相关。The IN terminal of the power switch M1 is connected to one end of the resistor R, and the other end of the resistor R is connected to the voltage input terminal A of the operational amplifier S1 to form the input voltage. The resistor R is used to create a voltage drop, thus ensuring that the output The input voltage is less than the IN terminal voltage, and the specific value of the input voltage is related to the resistance of the resistor R.

与运算放大器S1的电压输入端A相连的电阻R一端串联电流源I后接地。采用电流源I的作用是当电流源导通后，所在支路的电流就是电流源输出的电流，从而确保输入电压的稳定。One end of the resistor R connected to the voltage input terminal A of the operational amplifier S1 is connected in series with the current source I and then connected to ground. The purpose of using current source I is that when the current source is turned on, the current in the branch is the current output by the current source, thereby ensuring the stability of the input voltage.

具体原理分3种情况来说明。为了方便叙述，举例A点电压低于IN端电压50mV，功率开关管导通阻抗25mΩ，比较器2反灌翻转阈值设计为OUT端低于IN端10mV。The specific principle is explained in three situations. For the convenience of description, for example, the voltage at point A is 50mV lower than the IN terminal voltage, the power switch conduction resistance is 25mΩ, and the backfeed flip threshold of comparator 2 is designed so that the OUT terminal is 10mV lower than the IN terminal.

一、空载或者轻载状态。此时运放通过OUT端的闭环反馈，使功率开关管工作于饱和区，OUT端保持低于IN端50mV的状态。空载和轻载时，虽然功率管处于饱和区，但是功率开关管的功率耗散很小，为：
P＝Io×50mV1. No-load or light-load state. At this time, the op amp uses the closed-loop feedback of the OUT terminal to make the power switch tube work in the saturation zone, and the OUT terminal remains 50mV lower than the IN terminal. At no-load and light load, although the power tube is in the saturation zone, the power dissipation of the power switch tube is very small, as:
P＝Io×50mV

其中，Io为OUT端负载电流。Among them, Io is the load current at the OUT terminal.

二、重载状态。当OUT端负载电流大于2A时，运放超过最大输出幅度，功率开关管工作于线性区，OUT端电压将随负载的增大而持续减小，此时功率开关管的功率耗散为：
2. Overload state. When the load current at the OUT terminal is greater than 2A, the operational amplifier exceeds the maximum output amplitude, the power switch tube operates in the linear region, and the voltage at the OUT terminal will continue to decrease as the load increases. At this time, the power dissipation of the power switch tube is:

三、防反灌状态。当外部电源使OUT电压从低于IN端电压50mV的点开始升高使，运放超出最小输出幅度，功率开关管工作于截止区。当OUT电压升高至低于IN端电压10mV时，比较器2CMP同时强制关闭功率开关管前置驱动电路1，确保功率开关管保持截止状态。 3. Anti-backfeed status. When the external power supply causes the OUT voltage to rise from a point 50mV lower than the IN terminal voltage, the op amp exceeds the minimum output amplitude and the power switch tube works in the cut-off area. When the OUT voltage rises to 10mV lower than the IN terminal voltage, the comparator 2CMP also forcibly turns off the power switch pre-drive circuit 1 to ensure that the power switch tube remains in the off state.

Claims (5)

一种防电流反灌的电路结构，包括功率开关管M1、比较器(2)和前置驱动电路(1)；所述功率开关管M1的IN端与比较器(2)的同相输入端相连，所述功率开关管M1的OUT端与比较器(2)的反相输入端相连，比较器(2)的输出端与前置驱动电路(1)适配连接，前置驱动电路(1)与功率开关管M1适配连接，用于驱动功率开关管M1导通；其特征在于还包括运算放大器S1，运算放大器S1的反馈端B与功率开关管M1的OUT端相连，运算放大器S1的电压输入端A接输入电压，该输入电压的值低于功率开关管M1的IN端电压值，运算放大器S1的输出端与前置驱动电路(1)适配连接；采用运算放大器闭环负反馈特性，使运算放大器S1的反馈端B的电压跟随电压输入端A的电压，从而确保功率开关管M1的IN端电压始终大于功率开关管M1的OUT端电压。A circuit structure to prevent current backflow, including a power switch tube M1, a comparator (2) and a pre-drive circuit (1); the IN terminal of the power switch tube M1 is connected to the non-inverting input terminal of the comparator (2) , the OUT terminal of the power switch M1 is connected to the inverting input terminal of the comparator (2), the output terminal of the comparator (2) is adaptively connected to the pre-drive circuit (1), and the pre-drive circuit (1) It is adaptively connected to the power switch M1 to drive the power switch M1 to conduct; it is characterized in that it also includes an operational amplifier S1, the feedback terminal B of the operational amplifier S1 is connected to the OUT terminal of the power switch M1, and the voltage of the operational amplifier S1 The input terminal A is connected to the input voltage, and the value of the input voltage is lower than the IN terminal voltage value of the power switch M1. The output terminal of the operational amplifier S1 is adaptively connected to the pre-drive circuit (1); using the closed-loop negative feedback characteristics of the operational amplifier, Make the voltage of the feedback terminal B of the operational amplifier S1 follow the voltage of the voltage input terminal A, thereby ensuring that the voltage of the IN terminal of the power switch M1 is always greater than the voltage of the OUT terminal of the power switch M1. 如权利要求1所述的防电流反灌的电路结构，其特征在于所述功率开关管M1由两个同样的MOS管背靠背串联而成。The circuit structure for preventing current backflow according to claim 1, characterized in that the power switch tube M1 is composed of two identical MOS tubes connected back to back in series. 如权利要求2所述的防电流反灌的电路结构，其特征在于两个所述MOS管的衬底级均寄生有二级管，两个MOS管的一组源漏极互相连接，其中一个MOS管的另外一个源漏极为功率开关管M1的IN端，另一个MOS管的另外一个源漏极为功率开关管M1的OUT端。The circuit structure for preventing current backflow according to claim 2, characterized in that the substrate levels of the two MOS tubes are both parasitic with diode tubes, and a set of source and drain electrodes of the two MOS tubes are connected to each other, one of which is parasitic. The other source and drain of the MOS tube is the IN terminal of the power switch M1, and the other source and drain of the other MOS tube is the OUT terminal of the power switch M1. 如权利要求1-3中任一项所述的防电流反灌的电路结构，其特征在于所述功率开关管M1的IN端与电阻R的一端相连，电阻R的另一端与运算放大器S1的电压输入端A相连，形成所述输入电压。The circuit structure for preventing current backflow according to any one of claims 1 to 3, characterized in that the IN end of the power switch M1 is connected to one end of the resistor R, and the other end of the resistor R is connected to the operational amplifier S1. The voltage input terminal A is connected to form the input voltage. 如权利要求4所述的防电流反灌的电路结构，其特征在于与运算放大器S1的电压输入端A相连的电阻R一端串联电流源I后接地。 The circuit structure for preventing current backflow according to claim 4, characterized in that one end of the resistor R connected to the voltage input terminal A of the operational amplifier S1 is connected in series with the current source I and then connected to the ground.
PCT/CN2023/083232 2022-08-09 2023-03-23 Current backflow preventing circuit structure WO2024031994A1 (en)

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