Control circuit and method for high-reliability dc-dc power supply charge-discharge high-speed switching

Abstract

This invention discloses a highly reliable control circuit and method for high-speed switching of charging and discharging of a DC-DC power supply. The circuit includes: an output positive and negative current sampling circuit, employing a sampling resistor and a dual-transistor differential amplifier circuit to detect the output current direction in real time; an output current detection and comparison circuit, converting the differential voltage signal into high and low level signals; an output voltage detection circuit; and a main control unit digital control processor. The main control unit prioritizes responding to the level transition signal output by the current comparator, completing the high-speed switching of charging and discharging states within microseconds; simultaneously, it monitors the output voltage as a backup switching condition to prevent switching failure when the output current is extremely low. This invention solves the problems of slow switching speed, low reliability, high cost, or reliance on external commands in existing technologies. It has the advantages of fast response speed, high reliability, low cost, and wide applicability, and is particularly suitable for scenarios with rapidly changing load currents, such as electric vehicles, where there is no communication connection.

Description

Technical Field

[0001] This invention belongs to the field of bidirectional energy storage power technology, and particularly relates to a control circuit and method for high-speed switching of charging and discharging of a DC-DC power supply with high reliability. Background Technology

[0002] Currently, the industry typically uses communication to transmit charging or discharging commands for switching in bidirectional DC-DC power supply technology, or it uses hardware buttons or similar function switches to achieve charging or discharging switching. Some methods use current sensors to detect positive or negative output current, but this requires additional current sensors and positive and negative power supplies. Furthermore, conventional current sensors have significant current delays, and high-current sensors are inherently expensive. Voltage loops are also used for charging or discharging switching, but these have significant hysteresis and are prone to malfunctions during dynamic switching. In applications where low-voltage lithium iron phosphate batteries combined with a bidirectional DC-DC power supply with a BMS replace lead-acid batteries used in various small electric vehicles, the lack of communication between the battery and the vehicle's motor control necessitates a higher requirement for the switching response speed of the bidirectional DC-DC power supply. Figure 1 As shown, there are three main reasons for this: first, the motor requires a large instantaneous current to start; second, the acceleration, deceleration, and braking states of the trolley during operation are quite unpredictable; and third, the maximum current fed back by the motor varies between different trolleys, and the specific current magnitude under different conditions is also unclear. For example, during operation, acceleration or climbing may require increased output from the bidirectional DC-DC converter, followed by deceleration or braking requiring immediate feedback of energy from the bidirectional DC-DC converter. Then, acceleration or further climbing may be needed, requiring the bidirectional power supply to provide sufficient power to the trolley motor. In these situations, the bidirectional DC-DC converter needs to be able to quickly switch between discharging (powering the motor from the lithium battery via a boost voltage boost) and charging (charging the lithium battery via a step-down voltage boost) states. Otherwise, it may lead to loss of control during operation, or, during high-current feedback from the motor, a long switching delay may cause the bidirectional DC-DC converter output voltage to be charged too high, leading to reliability issues or abnormal input or feedback voltage of the trolley motor. Summary of the Invention

[0003] The purpose of this invention is to provide a highly reliable control circuit and method for high-speed switching of DC-DC power charging and discharging, aiming to solve the technical problems of slow response speed, low reliability, high cost or dependence on external commands in existing bidirectional DC-DC power charging and discharging switching technologies.

[0004] The present invention is implemented as follows: a high-reliability control circuit for high-speed switching of charging and discharging of a DC-DC power supply, the control circuit including an output positive and negative current sampling circuit, an output current detection and comparison circuit, an output voltage detection circuit, and a main control unit digital control processor DSC1;

[0005] The output positive and negative current sampling circuit is used to detect the current direction of the positive and negative currents during charging and discharging at the output terminal of the bidirectional DC-DC power supply in real time, and output two differential voltage signals VO_ISE_2 and VO_ISE_1.

[0006] The output current detection and comparison circuit has its input terminal connected to the output terminal of the output positive and negative current sampling circuit. It is used to receive the differential voltage signals VO_ISE_2 and VO_ISE_1 output by the output positive and negative current sampling circuit and convert them into high and low level signals Vout_CP_D2C that characterize the current direction.

[0007] The output voltage detection circuit is used to detect the voltage at the output terminal of the bidirectional DC-DC power supply in real time and generate an output voltage detection signal Vout_SE.

[0008] The main control unit digital control processor DSC1 has its input terminals connected to the output terminals of the output current detection and comparison circuit and the output terminals of the output voltage detection circuit, respectively. It is used to receive high and low level signals Vout_CP_D2C and output voltage detection signals Vout_SE, and control the switching of the bidirectional DC-DC power supply charging and discharging states based on the signal judgment results.

[0009] Specifically, when the output current detection and comparison circuit outputs a level signal that changes abruptly, the main control unit digital control processor DSC1 controls the bidirectional DC-DC power supply to switch between charging and discharging states; and,

[0010] When the output voltage value detected by the output voltage detection circuit has a preset deviation from the preset threshold, the main control unit digital control processor DSC1 controls the bidirectional DC-DC power supply to switch between charging and discharging states.

[0011] A further technical solution of the present invention is: the output positive and negative current sampling circuit includes a sampling resistor R3, which is connected in series between the negative terminal Vout_N of the bidirectional DC-DC power supply output and the working ground GND1;

[0012] A differential amplifier circuit consisting of a dual transistor pair VT1, resistor R1, and resistor R2;

[0013] The two bases of the dual transistor pair VT1 are respectively connected to the two ends of the sampling resistor R3 to collect the voltage difference across the sampling resistor R3; the resistors R1 and R2 are respectively connected between the two collectors of the dual transistor pair VT1 and the power supply VCC+3.3VA to convert the current signal into differential voltage signals VO_ISE_1 and VO_ISE_2 and output them to the output current detection and comparison circuit.

[0014] A further technical solution of the present invention is: the output current detection and comparison circuit includes a differential comparator D2;

[0015] The differential voltage signals VO_ISE_1 and VO_ISE_2 are respectively passed through an RC filter network and then input to the inverting input and non-inverting input of the differential comparator D2.

[0016] The output of the differential comparator D2 outputs the high / low level signal Vout_CP_D2C to the main control unit digital control processor DSC1.

[0017] A further technical solution of the present invention is: the output voltage detection circuit includes a voltage divider network composed of resistors R7 and R8, which is connected between the positive terminal Vout_P of the bidirectional DC-DC power supply output terminal and the working ground GND1.

[0018] The midpoint of the voltage divider network outputs the output voltage detection signal Vout_SE to the main control unit digital control processor DSC1.

[0019] A further technical solution of the present invention is: the main control unit digital control processor DSC1 is configured as follows:

[0020] When the high-low level signal Vout_CP_D2C changes from high level to low level, it is determined that the output current changes from positive to negative, and the bidirectional DC-DC power supply is controlled to switch from the discharging state to the charging state.

[0021] When the high / low level signal Vout_CP_D2C changes from low to high, it is determined that the output current changes from negative to positive, and the bidirectional DC-DC power supply is controlled to switch from charging state to discharging state.

[0022] Another objective of this invention is to provide a highly reliable control method for high-speed switching of charging and discharging of DC-DC power supplies, the control method comprising the following steps:

[0023] S1: Real-time detection of the current at the output terminal of the bidirectional DC-DC power supply through the positive and negative current sampling circuit, and generation of a differential voltage signal characterizing the current direction;

[0024] S2: The differential voltage signal is converted into a high / low level signal Vout_CP_D2C by the output current detection and comparison circuit;

[0025] S3: The high and low level signals Vout_CP_D2C are monitored in real time by the main control unit digital control processor DSC1;

[0026] S4: When a transition is detected in the high / low level signal Vout_CP_D2C, the main control unit digital control processor DSC1 immediately controls the bidirectional DC-DC power supply to switch between charging and discharging states.

[0027] A further technical solution of the present invention is that the control method further includes a switching step based on the output voltage:

[0028] S5: Real-time detection of the voltage at the output terminal of the bidirectional DC-DC power supply via the output voltage detection circuit, generating the output voltage detection signal Vout_SE;

[0029] S6: The main control unit digital control processor DSC1 compares the output voltage detection signal Vout_SE with a preset voltage threshold;

[0030] S7: When the bidirectional DC-DC power supply is in a discharging state and the output voltage detection signal Vout_SE is higher than the first preset threshold, it immediately switches to the charging state;

[0031] When the bidirectional DC-DC power supply is in a charging state and the output voltage detection signal Vout_SE is lower than the second preset threshold, it immediately switches to a discharging state.

[0032] A further technical solution of the present invention is that the total response time of the state switching triggered by the high / low level signal Vout_CP_D2C transition in step S4 is less than 2 microseconds.

[0033] A further technical solution of the present invention is: the response time Δt of the output voltage detection trigger state switching in step S7 is related to the capacitance value C1_0 of the output filter capacitor C1, the voltage change threshold ΔV or ΔV1, and the current change ID_0-IC_0. The estimation formula is: Δt≈(C1_0*ΔV) / (ID_0-IC_0) or Δt≈(C1_0*ΔV1) / (ID_0-IC_0).

[0034] A further technical solution of the present invention is: the output voltage detection trigger state switching is for scenarios where a very small current flows through the sampling resistor R3, and the response time is adjusted according to the current magnitude.

[0035] The beneficial effects of this invention are: high reliability: the differential sampling circuit using a dual transistor pair provides strong anti-interference capability; the dual current + voltage detection logic covers both large and small current switching scenarios, ensuring comprehensive detection. Fast switching speed: the current detection switching response time is as short as 900 nanoseconds, meeting the dynamic switching requirements of electric vehicles. Wide applicability: suitable for scenarios without communication, maintaining stable switching even when communication is disrupted or interrupted; only the transistor pair and comparator are added, allowing for a significant reduction in the capacitance of the electrolytic capacitor, eliminating the need for additional voltage detection costs. Easy to implement: the circuit structure is simple, capable of detecting ±200A rated current, with a sampling resistor of only 0.1 milliohms. Attached Figure Description

[0036] Figure 1 It is a structural block diagram of the technical solution in the prior art.

[0037] Figure 2 This is a block diagram of the principle of the control circuit for high-reliability DC-DC power supply charging and discharging high-speed switching provided in the embodiment of the present invention.

[0038] Figure 3 This is an electrical schematic diagram of the control circuit for high-reliability DC-DC power supply charging and discharging high-speed switching provided in the embodiments of the present invention. Detailed Implementation

[0039] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0040] To address the aforementioned problems, this invention proposes a highly reliable control circuit and method for high-speed switching between charging and discharging of a bidirectional DC-DC power supply. A differential amplifier circuit continuously monitors the output current of the bidirectional power supply to the motor. When the motor is in a discharging state and the detected current is positive, the differential amplifier circuit outputs a positive differential voltage signal, which is sent to the output current detection and comparison circuit, resulting in a high-level output signal. When the motor is in a charging state and the detected current is negative, the differential amplifier circuit outputs a negative differential voltage signal, which is also sent to the output current detection and comparison circuit, resulting in a low-level output signal. The output signal from the output current detection and comparison circuit is then sent to the main control unit's digital control processor (DSC1) for judgment and processing. When a change between positive and negative current is detected in the bidirectional DC-DC output current, the DSC1 correspondingly switches the output signal from the output current detection and comparison circuit between high and low levels, and the DSC1 immediately performs the corresponding discharging and charging switch.

[0041] The output voltage is monitored in real time. When the battery is supplying power to the motor, if the output voltage is detected to be higher than the set output voltage by ΔV, the system immediately switches from the discharge state to the battery charging and energy feedback state. When the output voltage is detected to be lower than the set output voltage by ΔV1, the system immediately switches to the discharge state, that is, switches to the motor supply state.

[0042] To better achieve the above objectives, the schematic diagram of the technical solution of this invention is as follows: Figure 2 As shown, 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 elaborated here. The technical solution will be specifically explained as follows:

[0043] like Figure 2 , Figure 3 As shown, the high-reliability DC-DC power supply charging and discharging high-speed switching control circuit provided by the present invention includes an output positive and negative current sampling circuit, an output current detection and comparison circuit, an output voltage detection circuit, and a main control unit digital control processor DSC1.

[0044] The output positive and negative current sampling circuit includes an output filter electrolytic capacitor C1. One end of the output filter electrolytic capacitor C1 is connected to the output positive terminal Vout_P, and the other end 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 sampling resistor R3 is connected to pin 3 of the dual transistor pair VT1 and the output negative terminal Vout_N. Pin 4 of the dual transistor pair VT1 is connected to the working ground GND1. Pin 1 of the dual transistor pair VT1 is connected to one end of the resistor R1 to form VO_ISE_1, which is sent to the output current detection and comparison circuit. Pin 2 of the dual transistor pair VT1 is connected to one end of the resistor R2 to form VO_ISE_1, which is sent to the output current detection and comparison circuit. The other ends of resistor R1 and resistor R2 are connected to the power supply positive VCC+3.3VA. One end of capacitor C2 is connected to the working ground GND1, and the other end of capacitor C2 is connected to the power supply positive VCC+3.3VA.

[0045] The output current detection and comparison circuit compares the voltage magnitudes of input signals VO_ISE_2 and VO_ISE_1. When VO_ISE_2 is greater than or equal to VO_ISE_1, it outputs a high-level signal Vout_CP_D2C; when VO_ISE_2 is less than VO_ISE_1, it outputs a low-level signal Vout_CP_D2C. The Vout_CP_D2C signal is sent to the main control unit's digital control processor DSC1. Signal VO_ISE_2 is connected to one end of resistor R4, and the other end of resistor R4 is connected to one end of capacitor C4 and pin 3 (non-inverting input) of comparator D2. The other end of capacitor C4 is connected to ground GND1. Signal VO_ISE_1 is connected to one end of resistor R5, and the other end of resistor R5 is connected to one end of capacitor C5 and pin 4 (inverting input) of comparator D2. The other end of capacitor C5 is connected to ground GND1. Pin 2 of comparator D2 is also connected to ground GND1. Pin 5 of comparator D2 and one end of capacitor C6 are connected to the power supply positive VCC+3.3VA, and the other end of capacitor C6 is connected to the working ground GND1. Pin 1 of the push-pull output pin of comparator D2 is connected to one end of resistor R6, and the other end of resistor R6 is connected to one end of capacitor C3 to form the output high and low level signal Vout_CP_D2C. The signal Vout_CP_D2C is sent to the main control unit digital control processor DSC1, and the other end of capacitor C3 is connected to the working ground GND1.

[0046] The main control unit, digital control processor DSC1, judges the input high and low level signals Vout_CP_D2C. When the signal Vout_CP_D2C is high, the output current is positive; when the signal Vout_CP_D2C is low, the output current is negative; when the signal Vout_CP_D2C changes from high to low, the bidirectional DC-DC power supply immediately switches from the discharging state to the charging state, and when the signal Vout_CP_D2C changes from low to high, the bidirectional DC-DC power supply immediately switches from the charging state to the discharging state.

[0047] One end of resistor R7 is connected to the output positive signal Vout_P, and the other end of resistor R7 is connected to one end of resistor R8, one end of capacitor C7, and pin 3 of diode VD1 to generate the output voltage detection signal Vout_SE. The signal Vout_SE is sent to the main control unit digital control processor DSC1.

[0048] The output voltage detection circuit detects the output voltage in real time and generates an output voltage detection signal Vout_SE, which is then sent to the main control unit digital control processor DSC1.

[0049] The main control unit digital control processor DSC1 compares the value of the signal Vout_SE with the preset high or low switching value and then immediately controls the switching of the bidirectional DC-DC power supply charging and discharging states.

[0050] The working principle and control method of the technical solution of the present invention are described in detail 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.

[0051] In the positive and negative current sampling circuit, sampling resistor R3 samples the positive current during charging and the negative current during discharge. This sampling resistor R3 should be placed to the right of electrolytic capacitor C1 to immediately detect the negative charging current when there is one at the output during discharge. A differential circuit consisting of dual transistors VT1, resistors R1 and R2 detects the current flowing through sampling resistor R3. The red arrow indicates positive current (discharge current is positive, charging current is negative). When a positive current is detected during discharge, two voltage signals VO_ISE_2 and VO_ISE_1 are output, with VO_ISE_2 being greater than VO_ISE_1. When a negative current is detected during charging... When the switching current is large, such as several hundred amperes, the value of the sampling resistor R3 will be smaller, and the peak values ​​of the positive and negative voltages on the sampling resistor R3 are generally much less than 1V. If the peak voltage exceeds the allowable reverse voltage of the two BE junctions of the dual transistor pair VT1, it is necessary to consider connecting a forward diode (two independent diodes packaged together) in series in the forward voltage drop direction of the two BE junctions of the dual transistor pair VT1 to improve the ability to resist reverse voltage stress. Signals VO_ISE_2 and VO_ISE_1 are sent to the output current detection and comparison circuit.

[0052] The output current detection and comparison circuit performs a differential comparison on signals VO_ISE_2 and VO_ISE_1. For example, if signals VO_ISE_2 and VO_ISE_1 are used as the non-inverting and inverting input signals of the differential comparator D2 in the output current detection and comparison circuit, respectively, the output level signal Vout_CP_D2C will be high when the current flowing through the sampling resistor R3 is positive or zero, and low when the current flowing through the sampling resistor R3 is negative.

[0053] The signal Vout_CP_D2C is sent to the main control unit digital control processor DSC1. When the main control unit digital control processor DSC1 detects that the signal Vout_CP_D2C changes from high level to low level, the bidirectional DC-DC power supply immediately switches its working state from the discharging state to the charging state. When the main control unit digital control processor DSC1 detects that the signal Vout_CP_D2C changes from low level to high level, the bidirectional DC-DC power supply immediately switches its working state from the charging state to the discharging state.

[0054] In practical products, the differential amplification factor is limited, and the differential comparator also has certain requirements for the differential voltage at the input terminal. Theoretically, even when the differential voltage at the input terminal of the differential comparator is very small and close to zero, it cannot achieve a valid high or low level output. Therefore, theoretically, when the maximum charging and discharging current of the bidirectional DC-DC power supply reaches hundreds of amperes, a sampling resistor R3 of less than 1 milliohm is generally preferred for low loss. However, when the minimum charging and discharging current is only tens of milliamperes, a few milliamperes, or even smaller, the sampling signal is too small to achieve a valid high or low level output. Therefore, when the bidirectional DC-DC power supply switches between positive and negative currents with such a small current in the sampling resistor, the signal Vout_CP_D2C cannot form a valid high level, thus failing to perform the corresponding charging and discharging switch. In practical applications, since the starting and feedback currents of electric vehicle motors cannot be very small, the high-speed switching in the above solution already meets the requirements. However, theoretically, to ensure that the bidirectional DC-DC power supply can promptly and effectively detect and switch between charging and discharging states when extremely small positive and negative currents flow through the sampling resistor R3,

[0055] When the battery powers the motor, i.e., the bidirectional DC-DC power supply is in the discharge state, when the main control unit digital control processor DSC1 detects that the output voltage Vout_P is higher than the set output voltage by △V, it immediately switches from the discharge state to the battery charging and energy feedback state. When the battery is charging and energy feedback state, i.e., the bidirectional DC-DC power supply is in the lithium battery charging state, when the main control unit digital control processor DSC1 detects that the output voltage is lower than the set output voltage by △V1, it immediately switches to the discharge state, i.e., switches to the motor power supply state.

[0056] Since the output voltage detection and control are mainly for the special case where the current flowing through the sampling resistor R3 is very small, the output voltage changes very slowly. Therefore, it is only necessary to send the output voltage detection signal Vout_SE to the main control unit digital control processor DSC1 for judgment and processing, and the output voltage detection speed requirement is not high.

[0057] exist Figure 3The sampling resistor R3 has a resistance of 1mΩ. The switching current flowing through the sampling resistor R3 is +0.1A and -0.1A. The comparator is a high-speed comparator. The response delay of the signal Vout_CP_D2C with the switching current is as follows: when the current flowing through the sampling resistor R3 switches from +0.1A to -0.1A, the response time of Vout_CP_D2C from high level to low level is delayed by about 800ns. When the current flowing through the sampling resistor R3 switches from -0.1A to +0.1A, the response time of Vout_CP_D2C from low level to high level is delayed by about 200ns. It can be seen that the detection switching speed is very fast.

[0058] The signal Vout_CP_D2C is sent to the main control unit digital control processor DSC1. When the main control unit digital control processor DSC1 detects that the signal Vout_CP_D2C changes from high level to low level, the bidirectional DC-DC power supply immediately switches its working state from the discharging state to the charging state. When the main control unit digital control processor DSC1 detects that the signal Vout_CP_D2C changes from low level to high level, the bidirectional DC-DC power supply immediately switches its working state from the charging state to the discharging state.

[0059] For the theoretically possible extremely small current change in the sampling resistor, switching is achieved by detecting the output voltage. The detection signal Vout_SE and the output voltage Vout_P have the following relationship:

[0060] Vout_SE = R8 * Vout_P / (R8 + R7)

[0061] When the bidirectional DC-DC power supply is operating in discharge mode, if the detected output voltage Vout_P increases by ΔV based on the current given output voltage Vout_P_REF, that is...

[0062] Vout_P = Vout_P_REF + △V

[0063] Thus, the main control unit of the bidirectional DC-DC power supply, the digital control processor DSC1, immediately switches the working state of the bidirectional DC-DC power supply from the original discharging state to the charging state.

[0064] When the bidirectional DC-DC power supply is operating in discharge mode, the discharge current is ID_0. The time delay Δt (in μs) from the start of a negative current IC_0 in the sampling resistor R3 to the trigger increase of the output voltage ΔV can be estimated as follows. The capacitance of the output electrolytic capacitor C1 is C1_0 (in Mf):

[0065] △t≈(C1_0*△V) / (ID_0-IC_0)

[0066] If Vout_P is 60VDC, C1 has a capacitance of 2000μF, ID_0 is 50mA, IC_0 is -50mA, and ΔV is 2V, then Δt is approximately 40S;

[0067] If Vout_P is 60VDC, C1 has a capacity of 2000μF, and the discharge current ID_0 is a large current of 50A, but the motor feedback current is -50mA and ΔV is 2V, then Δt is approximately 80μS.

[0068] When a bidirectional DC-DC power supply is charging, if the detected output voltage Vout_P decreases by ΔV1 from the current given output voltage Vout_P_REF, that is...

[0069] Vout_P = Vout_P_REF - △V1

[0070] Thus, the main control unit of the bidirectional DC-DC power supply, the digital control processor DSC1, immediately switches the working state of the bidirectional DC-DC power supply from the original charging state to the discharging state.

[0071] When the bidirectional DC-DC power supply is operating in charging mode, the charging current is IC_0. The delay Δt (in μs) from the positive current ID_0 in the sampling resistor R3 to the trigger output voltage drop ΔV1 can be estimated as follows. The capacitance of the output electrolytic capacitor C1 is C1_0 (in Mf):

[0072] △t≈(C1_0*△V1) / (ID_0-IC_0)

[0073] If Vout_P is 60VDC, C1 has a capacitance of 2000μF, IC_0 is -50mA, ID_0 is 50mA, and ΔV1 is 2V, then Δt is approximately 40S. The reason is that when the absolute value of the negative current flowing through the sampling resistor is very small, the output signal Vout_CP_D2C is still at a high level.

[0074] If Vout_P is 60VDC, C1 has a capacity of 2000μF, and the charging current ID_0 is 150mA, but the motor requires 50mA to start and ΔV is 2V, then since the current detection comparison method can detect the switching between low and high levels of the output signal Vout_CP_D2C, only about 800ns of delay is needed to switch from charging to discharging.

[0075] Compared with existing technologies, this invention has high reliability. During the switching process, it detects the positive and negative current values ​​in real time and outputs the corresponding differential voltage positive and negative values. It does not require linear accuracy; it only needs these differential voltage positive and negative values ​​as input signals of the comparator to form corresponding high and low level signals. The output positive and negative current sampling circuit is composed of a pair of bipolar transistors with their bases connected, providing current-mode amplification and strong anti-interference capability. For situations that are almost impossible to occur in actual scenarios, that is, when theoretically a very small positive and negative current flows through the sampling resistor R3, it can also effectively detect changes in positive and negative current in real time by detecting the output voltage Vout_P of the bidirectional DC-DC power supply and immediately switch between charging and discharging states. This makes the detection more comprehensive and complete, and the reliability higher.

[0076] The switching speed is very fast. When switching between charging and discharging current, the response time of the output positive and negative current sampling circuit to detect the switching signal is about 100 nanoseconds. If the comparator in the output current detection and comparison circuit is selected as a high-speed push-pull output or an OC gate output, the response time is generally a few nanoseconds to tens of nanoseconds. Because RC filtering delay is required to filter out the power frequency, the total response time from the switching of the charging and discharging current to the signal Vout_CP_D2C to form the corresponding low and high level is about 900 nanoseconds. If a normal comparator is selected, the total response time from the switching of the charging and discharging current to the signal Vout_CP_D2C to form the corresponding low and high level is generally about 2 microseconds. The switching speed for a theoretically possible very small current change of 50mA in the sampling resistor through output voltage detection is relatively slow, with a response time of about 40 seconds. If the absolute value of the switching positive and negative current is smaller, the delay will be longer. However, in this case, delaying the switching is more suitable for normal application scenarios, avoiding unnecessary and too frequent switching between charging and discharging working states.

[0077] Wide range of applications: The switching control strategy of this bidirectional DC-DC power supply is suitable for scenarios where there is no communication with the load to transmit charging and discharging switching commands, as well as scenarios where there is communication function. Even in the case of communication interference and interruption, it can ensure that the bidirectional DC-DC power supply can follow the dynamic switching of charging current at high speed to make corresponding charging and discharging switching, ensuring the stable operation of the bidirectional DC-DC power supply and associated equipment.

[0078] Low cost: Compared to conventional bidirectional DC-DC power supplies, the main hardware cost increases are the addition of a transistor pair and a comparator. Since the output voltage detection speed is not critical, the output voltage closed-loop control itself performs this detection; only the appropriate voltage value for the charging / discharging switching of the bidirectional DC-DC power supply, comparison judgment, and control are needed, without any additional cost. Due to the high response speed, the capacitance of the electrolytic capacitor at the output end to delay output voltage changes can be significantly reduced, thus appropriately lowering costs.

[0079] The detection switching current is relatively large and easy to implement: the circuit is simple, the detection is easy to implement, and the detection switching current is large. For example, if the rated current is ±200A, the sampling resistor is 0.1 milliohm.

[0080] 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 highly reliable control circuit for high-speed switching of charging and discharging of a DC-DC power supply, characterized in that, The control circuit includes an output positive and negative current sampling circuit, an output current detection and comparison circuit, an output voltage detection circuit, and a main control unit digital control processor (DSC1). The output positive and negative current sampling circuit is used to detect the current direction of the positive and negative currents during charging and discharging at the output terminal of the bidirectional DC-DC power supply in real time, and output two differential voltage signals VO_ISE_2 and VO_ISE_1. The output current detection and comparison circuit has its input terminal connected to the output terminal of the output positive and negative current sampling circuit. It is used to receive the differential voltage signals VO_ISE_2 and VO_ISE_1 output by the output positive and negative current sampling circuit and convert them into high and low level signals Vout_CP_D2C that characterize the current direction. The output voltage detection circuit is used to detect the voltage at the output terminal of the bidirectional DC-DC power supply in real time and generate an output voltage detection signal Vout_SE. The main control unit digital control processor DSC1 has its input terminals connected to the output terminals of the output current detection and comparison circuit and the output terminals of the output voltage detection circuit, respectively. It is used to receive high and low level signals Vout_CP_D2C and output voltage detection signals Vout_SE, and control the switching of the bidirectional DC-DC power supply charging and discharging states based on the signal judgment results. Specifically, when the output current detection and comparison circuit outputs a level signal that changes abruptly, the main control unit digital control processor DSC1 controls the bidirectional DC-DC power supply to switch between charging and discharging states; and When the output voltage value detected by the output voltage detection circuit has a preset deviation from the preset threshold, the main control unit digital control processor DSC1 controls the bidirectional DC-DC power supply to switch between charging and discharging states. The output positive and negative current sampling circuit includes a sampling resistor R3, which is connected in series between the negative terminal Vout_N of the bidirectional DC-DC power supply output and the working ground GND1. A differential amplifier circuit consisting of a dual transistor pair VT1, resistor R1, and resistor R2; The two bases of the dual transistor pair VT1 are respectively connected to the two ends of the sampling resistor R3 to collect the voltage difference across the sampling resistor R3; the resistors R1 and R2 are respectively connected between the two collectors of the dual transistor pair VT1 and the power supply VCC+3.3VA to convert the current signal into differential voltage signals VO_ISE_1 and VO_ISE_2 and output them to the output current detection and comparison circuit.

2. The high-reliability DC-DC power supply charging and discharging high-speed switching control circuit according to claim 1, characterized in that, The output current detection and comparison circuit includes a differential comparator D2; The differential voltage signals VO_ISE_1 and VO_ISE_2 are respectively passed through an RC filter network and then input to the inverting input and non-inverting input of the differential comparator D2. The output of the differential comparator D2 outputs the high / low level signal Vout_CP_D2C to the main control unit digital control processor DSC1.

3. The high-reliability DC-DC power supply charging and discharging high-speed switching control circuit according to claim 2, characterized in that, The output voltage detection circuit includes a voltage divider network consisting of resistors R7 and R8, connected between the positive output terminal Vout_P of the bidirectional DC-DC power supply and the working ground GND1. The midpoint of the voltage divider network outputs the output voltage detection signal Vout_SE to the main control unit digital control processor DSC1.

4. The high-reliability DC-DC power supply charging and discharging high-speed switching control circuit according to claim 3, characterized in that, The main control unit digital control processor DSC1 is configured as follows: When the high-low level signal Vout_CP_D2C changes from high level to low level, it is determined that the output current changes from positive to negative, and the bidirectional DC-DC power supply is controlled to switch from the discharging state to the charging state. When the high / low level signal Vout_CP_D2C changes from low to high, it is determined that the output current changes from negative to positive, and the bidirectional DC-DC power supply is controlled to switch from charging state to discharging state.

5. A highly reliable control method for high-speed switching of charging and discharging of a DC-DC power supply, characterized in that, The control method includes the following steps: S1: Real-time detection of the current at the output terminal of the bidirectional DC-DC power supply through the positive and negative current sampling circuit, and generation of a differential voltage signal characterizing the current direction; S2: The differential voltage signal is converted into a high / low level signal Vout_CP_D2C by the output current detection and comparison circuit; S3: The high and low level signals Vout_CP_D2C are monitored in real time by the main control unit digital control processor DSC1; S4: When a transition is detected in the high / low level signal Vout_CP_D2C, the main control unit digital control processor DSC1 immediately controls the bidirectional DC-DC power supply to switch between charging and discharging states.

6. The high-reliability DC-DC power supply charging and discharging high-speed switching control method according to claim 5, characterized in that, The control method further includes a switching step based on the output voltage: S5: Real-time detection of the voltage at the output terminal of the bidirectional DC-DC power supply via the output voltage detection circuit, generating the output voltage detection signal Vout_SE; S6: The main control unit digital control processor DSC1 compares the output voltage detection signal Vout_SE with a preset voltage threshold; S7: When the bidirectional DC-DC power supply is in a discharging state and the output voltage detection signal Vout_SE is higher than the first preset threshold, it immediately switches to the charging state; When the bidirectional DC-DC power supply is in a charging state and the output voltage detection signal Vout_SE is lower than the second preset threshold, it immediately switches to a discharging state.

7. The high-reliability DC-DC power supply charging and discharging high-speed switching control method according to claim 6, characterized in that, The total response time for the state switching triggered by the high / low level signal Vout_CP_D2C transition in step S4 is less than 2 microseconds.

8. The high-reliability DC-DC power supply charging and discharging high-speed switching control method according to claim 7, characterized in that, In step S7, the response time Δt of the output voltage detection trigger state switching is related to the capacitance value C1_0 of the output filter capacitor C1, the voltage change threshold ΔV or ΔV1, and the current change ID_0-IC_0. The estimation formula is: Δt≈(C1_0*ΔV) / (ID_0-IC_0) or Δt≈(C1_0*ΔV1) / (ID_0-IC_0).

9. The high-reliability DC-DC power supply charging and discharging high-speed switching control method according to claim 8, characterized in that, The output voltage detection trigger state switching is for scenarios where a very small current flows through the sampling resistor R3, and the response time is adjusted according to the current magnitude.

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