Control circuit and method for rapid charging and discharging switching of bidirectional DCDC power supply

Abstract

The invention is suitable for the field of bidirectional energy storage power supply technology improvement, and provides a control circuit and method for rapid charging and discharging switching of a bidirectional DCDC power supply, and the method is used for carrying out parallel and real-time dual detection and judgment on output voltage and output current. When the power supply is in a discharging state, if the output voltage is higher than a set value V, or it is detected that the output current is changed from positive to negative, switching to a charging state is triggered immediately; in the charging state, if the output voltage is lower than a set value V1 or it is detected that the output current is changed from negative to positive, switching to the discharging state is triggered immediately; the switching is performed on the basis of the voltage or current signal which firstly meets the condition. According to the invention, through a dual rapid detection mechanism of voltage and current, rapid and reliable state switching of tens of microseconds is realized, the problem of system out-of-control or voltage abnormity caused by switching delay in a traditional method is effectively solved, and the method has the advantages of high reliability, rapid response and low cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical improvement field of bidirectional energy storage power supply, in particular to a control circuit and method for fast switching of bidirectional DCDC power supply charging and discharging. BACKGROUND

[0002] Currently, in the industry, the charging and discharging switching technology of bidirectional DCDC power supply is usually switched by communication to transfer charging or discharging instructions, or by hardware buttons or similar function switches to realize the switching of charging and discharging. There is also a way to realize switching by detecting the positive and negative currents of the output through a current sensor. This method needs to increase the current sensor, and the detection of positive and negative currents also needs positive and negative power supplies. In addition, the current delay of the conventional current sensor is large, and the cost of the high-current sensor itself is also high. There is also a way to realize switching by using a voltage loop, but the hysteresis of the voltage loop is large, and the dynamic nature can easily lead to misoperation of the charging and discharging switching. In the battery pack composed of low-voltage lithium iron phosphate battery and bidirectional DCDC power supply with BMS, it is used to replace the lead-acid battery in the application of various small electric vehicles. Because there is no communication connection between the battery and the motor control on the electric vehicle, the response speed of the bidirectional DCDC switching is required to be higher. As shown in the figure, first, the motor needs a large current instantaneously, second, the acceleration, deceleration or braking state of the electric vehicle during driving is relatively random, third, the maximum current of the motor feedback power is different on different electric vehicles, and the specific current size under different states is also unknown. For example, during driving, it may be required to accelerate or climb, which requires the bidirectional DCDC to increase the output, and then instantaneously requires deceleration or braking to immediately feedback power to the bidirectional DCDC, and then it may be required to accelerate or continue to climb, which requires the bidirectional DCDC power supply to provide sufficient power to the motor of the electric vehicle. In the above states, the bidirectional DCDC power supply needs to quickly switch between discharging (referring to the lithium battery through the bidirectional DCDC to provide power to the motor) and charging (referring to the lithium battery through the bidirectional DCDC to charge the lithium battery) states, otherwise it is easy to cause the driving state to lose control, or when the motor feedback current is large, the switching delay is too long, which causes the bidirectional DCDC output voltage to be too high, resulting in reliability problems or causing the input supply voltage or feedback voltage of the electric vehicle motor to be abnormal. Figure 1 SUMMARY

[0003] ​In view of the above problems, the application provides a control circuit and method for fast switching of bidirectional DCDC power supply charging and discharging.

[0004] The application aims to provide a control circuit and method for fast switching of bidirectional DCDC power supply charging and discharging, and aims to solve the above technical problems.

[0005] The application is implemented as follows: a control circuit for fast switching of bidirectional DCDC power supply charging and discharging, the control circuit comprising an output positive and negative current sampling circuit, an output positive and negative current detection circuit, an output voltage detection and comparison circuit, and a main control unit digital controller DSC1. The output positive and negative current sampling circuit is used for collecting positive current of bidirectional DCDC power supply to a motor car motor and negative current of motor car motor feedback power, and outputting sampling current signals ISE_S1_GND1 and ISE_S1. The output positive and negative current detection circuit is used for receiving the sampling current signals ISE_S1_GND1 and ISE_S1, outputting a unipolar positive voltage signal of positive and negative current signal ISE4_DSC to the main control unit digital controller DSC1 after operational amplification processing. The output voltage detection and comparison circuit is used for receiving a voltage signal of bidirectional DCDC power supply output positive terminal Vout_P, comparing the reference voltage formed by filtering of PWM signal PWM_VREF output by the main control unit digital controller DSC1, and outputting switching trigger signals Vout_CP_D2C and Vout_CP_C2D to the main control unit digital controller DSC1. The master unit digital controller DSC1 is used for receiving the output positive and negative current signals ISE4_DSC, the switching trigger signals Vout_CP_D2C and Vout_CP_C2D, outputting the PWM signal PWM_VREF, and controlling the bidirectional DCDC power supply to quickly switch between the charging state and the discharging state based on the received signals.

[0006] A further technical solution of the application is that the output positive and negative current sampling circuit comprises an electrolytic capacitor C1, a sampling resistor R3, a resistor R6 and a resistor R7, one end of the output filter electrolytic capacitor C1 is connected with the output positive terminal Vout_P, the other end of the electrolytic capacitor C1 is connected with the working ground GND1, one end of the sampling resistor R3 is connected with the working ground GND1, the other end of the sampling resistor R3 is respectively connected with one end of the resistor R7 and the output negative terminal Vout_N, the other end of the resistor R7 outputs a sampling current signal ISE_S1, one end of the resistor R6 is connected with the working ground GND1, and the other end of the resistor R6 outputs a sampling current signal ISE_S1_GND1.

[0007] A further technical solution of the application is that the output voltage detection comparison circuit comprises a comparator D1 and a comparator D2, the comparator D2 receives the output positive terminal Vout_P through a first voltage division network at the non-inverting input end and receives a reference voltage VREF at the inverting input end, and is used for outputting a high-level output signal Vout_CP_D2C when the output voltage is higher than the reference voltage AV; the comparator D1 receives the output positive terminal Vout_P through a second voltage division network at the inverting input end and receives the reference voltage VREF at the non-inverting input end, and is used for outputting a high-level output signal Vout_CP_C2D when the output voltage is lower than the reference voltage AV1.

[0008] A further technical solution of the application is that the master unit digital controller DSC1 receives the switching trigger signals Vout_CP_D2C and Vout_CP_C2D through a common I / O port, a capture I / O or an internal comparator, detects the signal level change in real time through the above interface, and receives the output positive and negative current signals ISE4_DSC through an analog quantity input interface and detects the numerical value change.

[0009] A further technical solution of the application is that the sampling resistor R3 in the output positive and negative current sampling circuit is arranged on the right side of the output filter electrolytic capacitor C1, and the arrangement of the sampling resistor R3 at this position ensures that when the bidirectional DCDC power supply is in the discharging state, if a charging negative current fed back by a trolley motor appears at the output terminal, the sampling resistor R3 can collect the negative current in real time, so as to avoid the switching delay caused by the deviation of the sampling position.

[0010] The further technical scheme of the present application is: the output positive and negative current detection circuit comprises a capacitor C9, a resistor R18, a resistor R19, a capacitor C8, a resistor R17, a diode VD1, a capacitor C7, a resistor R16, a capacitor C6, a diode VD2, an operational amplifier D3, a diode VD3, a resistor R20, a resistor R22, a capacitor C11, a resistor R21 and a capacitor C10, the sampling current signal ISE_S1_GND1 is connected to one end of the capacitor C9 and one end of the resistor R18 respectively, the other end of the capacitor C9 is connected to the working ground GND1, the other end of the resistor R8 is connected to one end of the resistor R19, one end of the capacitor C8, one end of the resistor R17, the second pin of the diode VD1 and the fourth pin of the reverse input pin of the operational amplifier D3 respectively, the other end of the resistor R19 is connected to the working ground GND1, the other end of the capacitor C8 is connected to the other end of the resistor R17, one end of the resistor R16 and the first pin of the output pin of the operational amplifier D3, the second pin of the diode VD1 is connected to the power supply positive +5VA_DC, the fifth pin of the operational amplifier D3 and one end of the capacitor C7, the other end of the capacitor C7 is connected to the working ground GND1, the first pin of the diode VD1 is connected to the working ground GND1, the second pin of the operational amplifier D3 is connected to the working ground GND1, the sampling current signal ISE_S1 is connected to one end of the capacitor C10 and one end of the resistor R21, the other end of the capacitor C10 is connected to the working ground GND1, the other end of the resistor R21 is connected to one end of the resistor R22, one end of the capacitor C11, one end of the resistor R20, the third pin of the diode VD3 and the third pin of the same input pin of the operational amplifier D3 respectively, the other end of the resistor R22, the other end of the capacitor C11 and the first pin of the diode VD3 are connected to the working ground GND1, the third pin of the diode VD3 is connected to the power supply positive +5VA_DC, the other end of the resistor R16 is connected to the third pin of the diode VD2 and one end of the capacitor C6 to form a current detection signal ISE4_DSC, the current detection signal ISE4_DSC is sent to the master control unit digital controller DSC1, the other end of the capacitor C6 and the first pin of the diode VD2 are connected to the working ground GND1, and the second pin of the diode VD2 is connected to the power supply VCC+3.3VA.

[0011] The further technical scheme of the present application is: the output voltage detection comparison circuit comprises resistance R1, resistance R12, resistance R4, resistance R11, capacitor C3, capacitor C4, capacitor C5, capacitor C2, resistance R2, resistance R5, resistance R8, resistance R9, resistance R10, resistance R13, resistance R14, resistance R15, NMOS tube VT1, comparator D1 and comparator D2, the output positive terminal Vout_P is connected with one end of the resistance R1 and one end of the resistance R4 respectively, the other end of the resistance R1 is connected with the reverse input pin No.4 of the comparator D1, one end of the resistance R12 and one end of the capacitor C5 respectively, the other end of the resistance R12, the other end of the capacitor C5 and the No.2 pin of the comparator D1 are connected with the working ground GND1 respectively, the other end of the resistance R4 is connected with the same input pin No.3 of the comparator D2, one end of the resistance R11 and one end of the capacitor C4 respectively, the other end of the resistance R11, the other end of the capacitor C4 and the No.2 pin of the comparator D2 are connected with the working ground GND1 respectively, the No.5 pin of the comparator D1 and the No.5 pin of the comparator D2 are connected with the positive supply power +5VA_DC respectively, the same input pin No.3 of the comparator D1, the reverse input pin No.4 of the comparator D2, one end of the resistance R10 and one end of the capacitor C3 are connected to form the reference voltage VREF of the comparator, the other end of the capacitor C3 is connected with the working ground GND1, the other end of the resistance R10 is connected with one end of the resistance R9 and one end of the capacitor C2 respectively, the other end of the capacitor C2 is connected with the working ground GND1, the other end of the resistance R9 is connected with one end of the resistance R8, one end of the resistance R13 and the drain of the NMOS tube VT1 respectively, the other end of the resistance R8 is connected with the positive supply power VCC+3.3VA, the other end of the resistance R13 and the source of the NMOS tube VT1 are connected with the working ground GND1, the gate of the NMOS tube VT1 is connected with one end of the resistance R15 and one end of the resistance R14 respectively, the other end of the resistance R15 is connected with the working ground GND1, the other end of the resistance R14 is connected with the PWM signal PWM_VREF output by the master control unit digital processor DSC1, the output pin No.1 of the comparator D1 is connected with one end of the resistance R2 and the output signal Vout_CP_C2D, the other end of the resistance R2 is connected with the positive supply power VCC+3.3VA, and the output signal Vout_CP_C2D is sent to the master control unit digital processor DSC1, the output pin No.1 of the comparator D2 is connected with one end of the resistance R5 and the output signal Vout_CP_D2C respectively, the other end of the resistance R5 is connected with the positive supply power VCC+3.3VA, and the output signal Vout_CP_D2C is sent to the master control unit digital processor DSC1.

[0012] Another object of the present application is to provide a control method for fast switching of bidirectional DCDC power supply charging and discharging, which is applied to the scene of replacing the original lead-acid battery of a small trolley with a battery pack composed of a low-voltage lithium iron phosphate battery and a bidirectional DCDC power supply with BMS. Real-time detection of the output positive terminal Vout_P of the bidirectional DCDC power supply and the current flowing through the output loop; When the bidirectional DCDC power supply is in the discharging state, if it is detected that the output positive terminal Vout_P is higher than the current set reference voltage by a first voltage threshold AV, a first switching signal is triggered; When the bidirectional DCDC power supply is in the charging state, if it is detected that the output positive terminal Vout_P is lower than the current set reference voltage by a second voltage threshold AV1, a second switching signal is triggered; Real-time determination of the direction of the output current; When the bidirectional DCDC power supply is in the discharging state, if it is detected that the output current changes from positive current to negative current, a third switching signal is triggered; When the bidirectional DCDC power supply is in the charging state, if it is detected that the output current changes from negative current to positive current, a fourth switching signal is triggered; In response to the first switching signal or the third switching signal that is triggered first, the working state of the bidirectional DCDC power supply is immediately switched from discharging to charging; In response to the second switching signal or the fourth switching signal that is triggered first, the working state of the bidirectional DCDC power supply is immediately switched from charging to discharging.

[0013] A further technical solution of the present application is that the current set reference voltage is generated after the pulse width modulation signal PWM_VREF output by the master control unit is filtered and divided.

[0014] A further technical solution of the present application is that the setting of the first voltage threshold AV and the second voltage threshold AV1 is related to at least the capacitance value of the output filter capacitor C1, the size of the discharging current ID_0 and the charging current IC_0.

[0015] The present application has the following beneficial effects: In the switching process, the output positive terminal Vout_P is detected in real time, AV and AV1 are set, which ensures that the output positive terminal Vout_P will not trigger overvoltage protection and ensures that the output positive terminal Vout_P will not affect normal power supply and feedback; In the switching process, the output positive and negative current values are detected in real time, which is beneficial to the smoother and more stable charging and discharging switching state; Through real-time detection of the output voltage and the output current, the real-time detection and reliability of the charging and discharging state switching are ensured; The switching speed is fast, and the switching is under the condition that the charging and discharging currents are large; the switching response time of the detection output positive terminal Vout_P is generally about tens of microseconds, and the switching response time is 300 microseconds under the condition of small current switching through the detection output current; The switching control strategy of the bidirectional DCDC power supply is applicable to the scene without communication with the load end, and is also applicable to the scene with communication function, and can ensure stable and reliable operation of the bidirectional DCDC power supply even in the case of communication disturbance and communication interruption; the circuit is simple and easy to realize. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the background art diagram of the present application.

[0017] Figure 2 is the principle diagram of the control circuit for fast switching of bidirectional DCDC power supply charging and discharging provided by the embodiment of the present application.

[0018] Figure 3 is the topological diagram of the control circuit for fast switching of bidirectional DCDC power supply charging and discharging provided by the embodiment of the present application. DETAILED DESCRIPTION

[0019] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0020] As Figure 2 , Figure 3 shown, in order to better achieve the above object, for the bidirectional DCDC power supply itself having internal auxiliary power supply, bidirectional DCDC power conversion circuit, other protection and control circuit and other basic function circuits and corresponding control, further elaboration is not made here, and the technical solutions provided by the present application are mainly described as follows: The control circuit for fast switching of bidirectional DCDC power supply charging and discharging provided by the present application comprises an output positive and negative current sampling circuit, an output positive and negative current detection circuit, an output voltage detection comparison circuit and a main control unit digital controller DSC1. In the output positive and negative current sampling circuit, one end of the output filter electrolytic capacitor C1 is connected to the output positive terminal Vout_P, and the other end of the output filter electrolytic capacitor C1 is connected to the working ground GND1; one end of the output positive and negative current sampling resistor R3 is connected to the working ground GND1, and the other end of the output positive and negative current sampling resistor R3 is connected to one end of resistor R7 and the output negative terminal Vout_N respectively, and the other end of resistor R7 is connected to the signal ISE_S1; one end of resistor R6 is connected to the working ground GND1, and the other end of resistor R6 is connected to the signal ISE_S1-_GND1; The output positive and negative current detection circuit detects the output positive and negative current sampling signals ISE_S1-_GND1 and ISE_S1, and after internal operational amplification, generates the output positive and negative current signal ISE4_DSC. This output positive and negative current signal ISE4_DSC is itself a unipolar positive voltage signal, which is sent to the main control unit digital controller DSC1; for example... Figure 3 As shown, in the topology of the output positive and negative current detection circuit, the signals ISE_S1-_GND1 are connected to one end of capacitor C9 and one end of resistor R18, respectively. The other end of capacitor C9 is connected to the working ground GND1. The other end of resistor R18 is connected to one end of resistor R19, one end of capacitor C8, one end of resistor R17, pin 3 of diode VD1, and pin 4 of the inverting input pin of operational amplifier D3. The other end of resistor R19 is connected to the working ground GND1. The other end of capacitor C8 is connected to the other end of resistor R17, one end of resistor R16, and pin 1 of the output pin of operational amplifier D3, respectively. Pin 2 of diode VD1 is connected to the positive +5VA_DC power supply, pin 5 of operational amplifier D3, and one end of capacitor C7. Pin 1 of diode VD1, the other end of capacitor C7, and pin 2 of operational amplifier D3 are connected to the working ground GND1. Signal ISE_S1 is connected to one end of capacitor C10 and one end of resistor R21. The other end of capacitor C10 is connected to ground GND1. The other end of resistor R21 is connected to one end of resistor R22, one end of capacitor C11, one end of resistor R20, pin 3 of diode VD3, and pin 3 of the non-inverting input of operational amplifier D3. The other end of resistor R22, the other end of capacitor C11, and pin 1 of diode VD3 are connected to ground GND1. Pin 2 of diode VD3 is connected to the +5VA DC power supply. The other end of resistor R16 is connected to pin 3 of diode VD2 and one end of capacitor C6 to form current detection signal ISE4_DSC. Signal ISE4_DSC is sent to the main control unit digital controller DSC1. The other end of capacitor C6 and pin 1 of diode VD2 are connected to ground GND1. Pin 2 of diode VD2 and the other end of resistor R20 are connected to the +3.3VA power supply.

[0021] The output voltage detection comparison circuit compares the voltage between the output positive terminal Vout_P and the ground with a given reference voltage, which is formed by filtering the average value of the PWM signal PWM_VREF given by the master unit digital controller DSC1, and when the detected output voltage is higher than the set output voltage by△V in the case of the battery supplying power to the motor, i.e. discharging, the output signal Vout_CP_D2C changes from low to high immediately; and when the detected output voltage is lower than the set output voltage by△V1 in the case of the battery charging feedback power, i.e. charging, the output signal Vout_CP_C2D changes from low to high immediately. The output signals Vout_CP_D2C and Vout_CP_C2D of the output voltage detection comparison circuit are sent to the master unit digital controller DSC1; for example Figure 3As shown in the topology of the output voltage detection comparison circuit, the output positive terminal Vout_P is connected to one end of resistor R1 and one end of resistor R4, the other end of resistor R1 is connected to the fourth pin of the inverting input pin of comparator D1, one end of resistor R12 and one end of capacitor C5, the other end of resistor R12, the other end of capacitor C5 and the second pin of comparator D1 are connected to the working ground GND1, the other end of resistor R4 is connected to the third pin of the non-inverting input pin of comparator D2, one end of resistor R11 and one end of capacitor C4, the other end of resistor R11, the other end of capacitor C4 and the second pin of comparator D2 are connected to the working ground GND1, the fifth pin of comparator D1 and the fifth pin of comparator D2 are connected to the positive supply power +5VA_DC, the third pin of the non-inverting input pin of comparator D1, the fourth pin of the inverting input pin of comparator D2, one end of resistor R10 and one end of capacitor C3 are connected to form the reference voltage VREF of the comparator, the other end of capacitor C3 is connected to the working ground GND1, the other end of resistor R10 is connected to one end of resistor R9 and one end of capacitor C2, the other end of capacitor C2 is connected to the working ground GND1, one end of resistor R9 is connected to one end of resistor R8, one end of resistor R13 and the drain of NMOS transistor VT1, the other end of resistor R8 is connected to the positive supply power VCC+3.3VA, the other end of resistor R13 and the source of NMOS transistor VT1 are connected to the working ground GND1, the gate of NMOS transistor VT1 is connected to one end of resistor R15 and one end of resistor R14, the other end of resistor R15 is connected to the working ground GND1, the other end of resistor R14 is connected to the output PWM signal PWM_VREF of the master control unit digital processor DSC1, the first pin of the output pin of comparator D1 is connected to one end of resistor R2 and the output signal Vout_CP_C2D, the other end of resistor R2 is connected to the positive supply power VCC+3.3VA, the signal Vout_CP_C2D is sent to the master control unit digital processor DSC1, the first pin of the output pin of comparator D2 is connected to one end of resistor R5 and the output signal Vout_CP_D2C, the other end of resistor R5 is connected to the positive supply power VCC+3.3VA, the signal Vout_CP_D2C is sent to the master control unit digital processor DSC1.

[0022] The master control unit digital controller DSC1 detects and processes the input signal ISE4_DSC, the signal Vout_CP_D2C and the signal Vout_CP_C2D, and outputs the PWM signal PWM_VREF.

[0023] The working principle and control method of the technical scheme of the application are specifically described as follows: The sampling resistor R3 in the output positive and negative current sampling circuit samples the positive current discharged by the charger and the negative current charged, and the sampling resistor R3 should be placed on the right side of the electrolytic capacitor C1, so as to immediately detect the negative current charged when the output terminal has the negative current charged in the discharging state. The output positive and negative current sampling signals ISE_S1_GND1 and ISE_S1 are amplified by the output positive and negative current detection circuit to form a unipolar output positive and negative current signal ISE4_DSC, and the ISE4_DSC positive voltage signal is a unipolar power supply for the operational amplifier. The signal ISE4_DSC is sent to the main control unit digital controller DSC1 for detection and judgment. When the output current is zero, the signal ISE4_DSC value is ISE4_DSC_0. When the real-time detection signal ISE4_DSC value is greater than ISE4_DSC_0, the output is positive current, that is, the discharging state. When the real-time detection signal ISE4_DSC value is less than ISE4_DSC_0, the output is negative current, that is, the charging state. When the real-time detection signal ISE4_DSC value corresponding to the current value changes from positive to negative, the control of the bidirectional DCDC power supply is immediately switched from discharging to charging. When the real-time detection signal ISE4_DSC value corresponding to the current value changes from negative to positive, the control of the bidirectional DCDC power supply is immediately switched from charging to discharging. The detection signal ISE4_DSC has a large delay after filtering processing, and the normal delay is about 300uS. The signal ISE4_DSC can also be used as the input current value of the output current limiting loop and the output power limiting loop in the discharging state. When the small current discharging state is switched to the small current charging state, the signal ISE4_DSC corresponding to the current value changes from positive to negative with a long delay, but the output voltage changes relatively slowly, and the delay of triggering state switching is longer. Therefore, the switching between the discharging and charging states is realized by detecting and judging the conversion of the positive and negative values of the signal ISE4_DSC corresponding to the current. The output voltage detection comparison circuit compares the voltage between the output positive terminal Vout_P and the ground with a given reference voltage, which is formed by filtering the average value of the PWM signal PWM_VREF given by the master unit digital controller DSC1. The output signals Vout_CP_D2C and Vout_CP_C2D of the output voltage detection comparison circuit are sent to the master unit digital controller DSC1. In the case of battery power supply to the motor, i.e. discharging, when the detected output voltage is higher than the set output voltage by △V, the output signal Vout_CP_D2C changes from low to high immediately, and the master unit digital controller DSC1 switches the control from discharging to charging immediately. In the case of feedback power supply to the battery, i.e. charging, when the detected output voltage is lower than the set output voltage by △V1, the output signal Vout_CP_C2D changes from low to high immediately, and the master unit digital controller DSC1 switches the control from charging to discharging immediately. Taking the power supply to the motor drive as an example, in the discharging state, the larger the current ID_0 is, the larger the motor feedback current IC_0 will be. In this state, the discharging current of the bidirectional power supply DCDC and the charging current of the motor feedback charge the output electrolytic capacitor C1 at the same time. The change of the output positive terminal Vout_P on the output electrolytic capacitor C1 is rapid, and the fast trigger signal Vout_CP_D2C changes to high level, and the master control power supply digital control processor DSC1 switches the control from discharging to charging immediately. If a high-speed comparator is selected, the comparator transmission delay is from several nanoseconds to several tens of nanoseconds, and the delay of the ordinary comparator is about 1μS, which is relatively negligible. When the bidirectional DCDC power supply works in the discharging state, the discharging current is ID_0, and the delay △t (unit: μS) from the moment when the negative current IC_0 starts to flow from the output sampling resistor R3 to the moment when the comparator output signal Vout_CP_D2C in the output voltage comparison circuit changes from low to high can be estimated as follows, where C1_0 is the capacitance of the output electrolytic capacitor C1 (unit: μF): △t≈(C1_0*△V) / ( ID_0-IC_0) For example, when the output positive terminal Vout_P is 60VDC, C1 is 2000μF, ID_0 is 50A, IC_0 is -50A, and △V is 2V, then △t is about 40μS. When the bidirectional DCDC power supply works in the charging state, the charging current is IC_0, and the delay △t1 (unit: μS) from the moment when the positive current ID_0 starts to flow from the output sampling resistor R3 to the moment when the comparator output signal Vout_CP_C2D in the output voltage comparison circuit changes from low to high can be estimated as follows: △t1≈(C1_0*△V1) / ( ID_0-IC_0) The main control power supply digital control processor DSC1 detects the high and low level signals Vout_CP_D2C and Vout_CP_C2D, as well as the analog signal ISE4_DSC, in real time. It realizes the rapid switching of the bidirectional DC-DC power supply charging and discharging states by switching the low to high levels of signals Vout_CP_D2C and Vout_CP_C2D, and the positive and negative current corresponding to the value of signal ISE4_DSC. The rapid switching of the bidirectional DC-DC power supply charging and discharging states is executed by using the state that is switched first.

[0024] like Figure 2 , 3 As shown, the working principle of the embodiment of the technical solution of the present invention is explained below. The basic functional circuits and corresponding controls of the bidirectional DC-DC power supply itself, such as the internal auxiliary power supply, bidirectional DC-DC power conversion circuit, and other protection and control circuits, will not be further described here.

[0025] Bidirectional DC-DC power supplies are used in, for example Figure 1 In the scenario shown, an integrated battery pack replaces the original lead-acid battery, such as a 64V 100AH. To allow the electric vehicle to display the current battery capacity in segments based on the battery voltage, the positive output terminal Vout_P is set in steps based on the voltage value of a 64V 100AH ​​lead-acid battery with the same capacity as the current lithium battery. In other applications, the required voltage can be output as needed.

[0026] The main control unit digital processor DSC1 outputs the signal PWM_VREF, with a duty cycle of 'a'. By adjusting the duty cycle 'a', the required reference voltage VREF can be obtained. The voltage of the reference signal REF in the input pins of comparators D1 and D2 is VREF. The relationship between VREF and the duty cycle 'a' is as follows: VREF = (1-a)*3.3*R13 / (R13+R8) When the bidirectional DC-DC power supply is discharging, the detection signal Vout_CP_D2C of the main control unit digital processor DSC1 should be low. This can be detected through the capture I / O, general I / O, or internal comparator of the main control unit digital processor DSC1. When the output voltage increases by ΔV based on the positive output terminal Vout_P, the output signal Vout_CP_D2C of comparator D2 is triggered to switch from low to high. That is, when the following relationship holds, the output of comparator D2 is triggered to switch from low to high. VREF=(Vout_P+△V)*R11 / (R11+R4) Thus, the main controller of the bidirectional DC-DC power supply, the digital processor DSC1, immediately switches the working state of the bidirectional DC-DC power supply from the original discharging state to the charging state. When the bidirectional DC-DC power supply is charging, the main control unit's digital processor DSC1 detects the transition of the signal Vout_CP_C2D from low to high. This transition can be achieved through the capture I / O, general I / O, or internal comparator of the main control unit's digital processor DSC1. When the output voltage drops by ΔV1 from the positive output terminal Vout_P, it triggers the comparator D1 to switch its output signal from low to high. That is, the following relationship is true when the output of comparator D1 switches from low to high. VREF=(Vout_P-△V1)*R12 / (R12+R1) Thus, the main control unit digital processor DSC1 of the bidirectional DC-DC power supply immediately switches the working state of the bidirectional DC-DC power supply from the original charging state to the discharging state. The main control unit of the bidirectional DC-DC power supply, the digital processor DSC1, also detects the voltage of the output current signal ISE4_DSC of the positive and negative current detection circuit in real time. When the output current is zero, the voltage value of the signal ISE4_DSC is ISE4_DSC_0. If ISE4_DSC - ISE4_DSC_0 > 0, it is a positive current; If SE4_DSC - ISE4_DSC_0 < 0, it indicates a negative current. When the bidirectional DC-DC power supply is in the discharge state, the real-time detection signal ISE4_DSC value of the main control unit digital processor DSC1 should be greater than ISE4_DSC_0, that is, it should be a positive current; when the detected ISE4_DSC value should be less than ISE4_DSC_0, that is, the output current of the bidirectional DC-DC power supply is a negative current, the bidirectional DC-DC power supply immediately switches from the original discharge state to the charging state. When the bidirectional DC-DC power supply is in the charging state, the real-time detection signal ISE4_DSC value of the main control unit digital processor DSC1 should be less than ISE4_DSC_0, that is, it should be a negative current; when the detected ISE4_DSC value should be greater than ISE4_DSC_0, that is, the output current of the bidirectional DC-DC power supply is a positive current, the bidirectional DC-DC power supply immediately switches from the original charging state to the discharging state. When the bidirectional DC-DC power supply is in the discharge state, the main control unit digital processor DSC1 detects the signal ISE4_DSC and the comparator D2 output signal Vout_CP_D2C in real time. The switch from the discharge state to the charging state is immediately executed based on whichever occurs first: the output current changes from positive to negative or the comparator D2 output signal Vout_CP_D2C changes from low to high.

[0027] When the bidirectional DC-DC power supply is in charging mode, the main control unit digital processor DSC1 detects the signal ISE4_DSC and the comparator D1 output signal Vout_CP_C2D in real time. It immediately executes the switch from charging mode to discharging mode based on whichever occurs first: the output current changes from negative to positive or the comparator D1 output signal Vout_CP_C2D changes from low to high.

[0028] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control circuit for rapid switching of bidirectional DC-DC power supply charging and discharging, characterized in that, The control circuit includes an output positive and negative current sampling circuit, an output positive and negative current detection circuit, an output voltage detection and comparison circuit, and a main control unit digital controller DSC1; The output positive and negative current sampling circuit is used to collect the positive current supplied by the bidirectional DC-DC power supply to the tram motor and the negative current of the tram motor feeding back electrical energy, and outputs the sampling current signals ISE_S1-_GND1 and ISE_S1; The output positive and negative current detection circuit is used to receive the sampled current signals ISE_S1-_GND1 and ISE_S1, and after operational amplification, output a unipolar positive voltage signal of positive and negative current signal ISE4_DSC to the main control unit digital controller DSC1. The output voltage detection and comparison circuit is used to receive the voltage signal of the positive terminal Vout_P of the bidirectional DC-DC power supply, compare it with the reference voltage formed by filtering the PWM signal PWM_VREF output by the main control unit digital controller DSC1, and output switching trigger signals Vout_CP_D2C and Vout_CP_C2D to the main control unit digital controller DSC1. The main control unit digital controller DSC1 is used to receive the output positive and negative current signals ISE4_DSC, the switching trigger signals Vout_CP_D2C and Vout_CP_C2D, output the PWM signal PWM_VREF, and control the bidirectional DC-DC power supply to quickly switch between charging and discharging states based on the received signals.

2. The control circuit for rapid switching of bidirectional DC-DC power supply charging and discharging according to claim 1, characterized in that, The output positive and negative current sampling circuit includes an electrolytic capacitor C1, sampling resistors R3, R6, and R7. One end of the output filtering electrolytic capacitor C1 is connected to the output positive terminal Vout_P, and the other end of the electrolytic capacitor C1 is connected to the working ground GND1. One end of the sampling resistor R3 is connected to the working ground GND1, and the other end of the sampling resistor R3 is connected to one end of the resistor R7 and the output negative terminal Vout_N. The other end of the resistor R7 outputs the sampling current signal ISE_S1. One end of the resistor R6 is connected to the working ground GND1, and the other end of the resistor R6 outputs the sampling current signal ISE_S1-_GND1.

3. The control circuit for rapid switching of bidirectional DC-DC power supply charging and discharging according to claim 1 or 2, characterized in that, The output voltage detection and comparison circuit includes comparator D1 and comparator D2. The non-inverting input of comparator D2 receives the positive output terminal Vout_P through a first voltage divider network, and the inverting input receives the reference voltage VREF. It is used to output a high-level output signal Vout_CP_D2C when the output voltage is higher than the reference voltage ΔV. The inverting input of comparator D1 receives the positive output terminal Vout_P through a second voltage divider network, and the non-inverting input receives the reference voltage VREF. It is used to output a high-level output signal Vout_CP_C2D when the output voltage is lower than the reference voltage ΔV1.

4. The control circuit for rapid switching of bidirectional DC-DC power supply charging and discharging according to claim 3, characterized in that, The main control unit digital controller DSC1 receives the switching trigger signals Vout_CP_D2C and Vout_CP_C2D through ordinary I / O ports, capture I / O, or internal comparators, and detects the signal level changes in real time through the above interfaces. At the same time, it receives the positive and negative current signals ISE4_DSC through the analog input interface and detects the changes in their values.

5. The control circuit for rapid switching of bidirectional DC-DC power supply charging and discharging according to claim 4, characterized in that, The sampling resistor R3 in the output positive and negative current sampling circuit is located to the right of the output filter electrolytic capacitor C1. This position ensures that when the bidirectional DC-DC power supply is in the discharge state, if a negative charging current fed back by the tram motor appears at the output terminal, the sampling resistor R3 can collect the negative current in real time, avoiding switching delay caused by sampling position deviation.

6. The control circuit for rapid switching of bidirectional DC-DC power supply charging and discharging according to claim 5, characterized in that, The output positive and negative current detection circuit includes capacitor C9, resistors R18 and R19, capacitor C8, resistor R17, diode VD1, capacitor C7, resistor R16, capacitor C6, diode VD2, operational amplifier D3, diode VD3, resistor R20, resistor R22, capacitor C11, resistor R21, and capacitor C10. The sampling current signal ISE_S1-_GND1 is connected to one end of capacitor C9 and one end of resistor R18, respectively. The other end of capacitor C9 is connected to ground GND1, and the other end of resistor R8 is connected to resistor R19. One end of the capacitor is connected to one end of the capacitor C8, one end of the resistor R17, pin 2 of the diode VD1, and pin 4 of the inverting input pin of the operational amplifier D3. The other end of the resistor R19 is connected to ground GND1. The other end of the capacitor C8 is connected to the other end of the resistor R17, one end of the resistor R16, and pin 1 of the output pin of the operational amplifier D3. Pin 2 of the diode VD1 is connected to the +5VA_DC power supply, pin 5 of the operational amplifier D3, and one end of the capacitor C7. The other end of the capacitor C7 is connected to ground GND1. Pin 1 of the diode VD1 is connected to ground GND1. Pin 2 of operational amplifier D3 is connected to ground GND1. The sampling current signal ISE_S1 is connected to one end of capacitor C10 and one end of resistor R21. The other end of capacitor C10 is connected to ground GND1. The other end of resistor R21 is connected to one end of resistor R22, one end of capacitor C11, one end of resistor R20, pin 3 of diode VD3, and pin 3 of the non-inverting input pin of operational amplifier D3. The other end of resistor R22, the other end of capacitor C11, and pin 1 of diode VD3 are connected to ground GND1. Pin 3 of diode VD3 is connected to the positive +5VA_DC power supply. The other end of resistor R16 is connected to pin 3 of diode VD2 and one end of capacitor C6 to form the current detection signal ISE4_DSC. The current detection signal ISE4_DSC is sent to the main control unit digital controller DSC1. The other end of the capacitor C6 and the first pin of the diode VD2 are connected to the working ground GND1. The second pin of the diode VD2 is connected to the power supply VCC+3.3VA. The output voltage detection and comparison circuit includes resistors R1, R12, R4, and R11; capacitors C3, C4, C5, and C2; resistors R2, R5, R8, R9, R10, R13, R14, and R15; an NMOS transistor VT1; comparators D1 and D2. The positive output terminal Vout_P is connected to one end of resistor R1 and one end of resistor R4. The other end of resistor R1 is connected to pin 4 of the inverting input of comparator D1, one end of resistor R12, and one end of capacitor C5. The other ends of resistor R12, capacitor C5, and pin 2 of comparator D1 are connected to ground GND1. The other end of resistor R4 is connected to pin 3 of the non-inverting input of comparator D2, one end of resistor R11, and one end of capacitor C4. The other ends of resistor R11, capacitor C4, and pin 2 of comparator D2 are connected to ground GND1. Pins 5 of comparator D1 and comparator D2 are connected to the positive +5VA_DC power supply. Pin 3 of the non-inverting input of comparator D1, pin 4 of the inverting input of comparator D2, one end of resistor R10, and one end of capacitor C3 are connected to form the comparator's reference voltage VREF. The other end of capacitor C3 is connected to ground GND1. The other end of resistor R10 is connected to one end of resistor R9 and one end of capacitor C2. The other end of capacitor C2 is connected to ground GND1. The other end of resistor R9 is connected to one end of resistor R8, one end of resistor R13, and the drain of NMOS transistor VT1. The other end of resistor R8 is connected to the positive VCC +3.3VA power supply. The other end of resistor R13 and the source of NMOS transistor VT1 are connected to the working ground GND1. The gate of NMOS transistor VT1 is connected to one end of resistor R15 and one end of resistor R14. The other end of resistor R15 is connected to the working ground GND1. The other end of resistor R14 is connected to the PWM signal PWM_VREF output by the main control unit digital processor DSC1. Pin 1 of the output of comparator D1 is connected to one end of resistor R2 and the output signal Vout_CP_C2D. The other end of resistor R2 is connected to the power supply positive VCC+3.3VA, and the output signal Vout_CP_C2D is sent to the main control unit digital processor DSC1. Pin 1 of the output of comparator D2 is connected to one end of resistor R5 and the output signal Vout_CP_D2C. The other end of resistor R5 is connected to the power supply positive VCC+3.3VA, and the output signal Vout_CP_D2C is sent to the main control unit digital processor DSC1.

7. A control method for rapid switching of bidirectional DC-DC power supply charging and discharging, applied to scenarios where a low-voltage lithium iron phosphate battery is combined with a bidirectional DC-DC power supply with a BMS to form a battery pack, replacing the original lead-acid battery in a small electric vehicle, characterized in that... The control method includes the following steps: Real-time monitoring of the positive output terminal Vout_P of the bidirectional DC-DC power supply and the current flowing through the output circuit; When the bidirectional DC-DC power supply is in a discharging state, if the output positive terminal Vout_P is detected to be higher than the current set reference voltage by a first voltage threshold △V, then the first switching signal is triggered. When the bidirectional DC-DC power supply is in a charging state, if the output positive terminal Vout_P is detected to be lower than the current set reference voltage by a second voltage threshold △V1, then the second switching signal is triggered. The direction of the output current is determined in real time; When the bidirectional DC-DC power supply is in a discharging state, if the output current is detected to change from positive to negative, a third switching signal is triggered. When the bidirectional DC-DC power supply is in a charging state, if the output current is detected to change from negative current to positive current, the fourth switching signal is triggered. In response to the first switching signal or the third switching signal that is triggered first, the operating state of the bidirectional DC-DC power supply is immediately switched from discharging to charging; In response to the first triggered second switching signal or the fourth switching signal, the operating state of the bidirectional DC-DC power supply is immediately switched from charging to discharging.

8. The control method for rapid switching of bidirectional DC-DC power supply charging and discharging according to claim 7, characterized in that, The real-time determination of the direction of the output current includes: The voltage flowing through the output sampling resistor R3 is sampled to obtain a differential signal containing current direction information; The differential signal is converted into a unipolar voltage signal ISE4_DSC that is proportional to the current magnitude; The output current is determined to be positive or negative by comparing the unipolar voltage signal ISE4_DSC with a reference voltage value ISE4_DSC_0 corresponding to zero current.

9. The control method for rapid switching of bidirectional DC-DC power supply charging and discharging according to claim 8, characterized in that, The current reference voltage is generated by filtering and voltage division of the pulse width modulation signal PWM_VREF output by the main control unit.

10. The control circuit and method for rapid switching of bidirectional DC-DC power supply charging and discharging according to claim 9, characterized in that, The setting of the first voltage threshold ΔV and the second voltage threshold ΔV1 is at least related to the capacitance value of the output filter capacitor C1, the discharge current ID_0, and the charging current IC_0.

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