Signal isolation conversion circuit, bidirectional equalization control circuit and power converter

Abstract

The application provides a signal isolation conversion circuit, a bidirectional balance control circuit and a power converter, wherein the isolation conversion circuit comprises an isolation device and a signal conversion circuit; the isolation device receives a control signal and transmits the control signal to the signal conversion circuit; the signal conversion circuit converts the control signal into an enable signal and a reference voltage; and the signal conversion circuit outputs the enable signal and the reference voltage to a constant current control circuit at the rear end from an output port of the signal conversion circuit; the reference voltage value and the level of the enable signal are controlled by adjusting the control signal; the reference voltage controls the size of the charging current of the primary side of the power converter and the size of the discharging current of the secondary side; the enable signal controls the forward working or reverse working of the power converter; the application only uses one isolation device, and the switching between the two different working states of the forward charging and the reverse discharging can be realized; the charging current or the discharging current value can be adjusted by adjusting the control signal, and the charging / discharging current is maintained constant; the product size is reduced, and the product cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of voltage equalization technology, and in particular to a signal isolation conversion circuit, a bidirectional equalization control circuit, and a power converter. Background Technology

[0002] The battery energy storage industry is developing rapidly and its applications are becoming increasingly widespread. Due to factors such as battery materials and manufacturing processes, the voltage of individual cells within a battery pack can become inconsistent after charging or discharging. This leads to reduced battery pack lifespan and safety issues caused by overcharging and discharging. Since batteries account for over 80% of the total cost, improving battery lifespan is equivalent to significantly reducing costs; therefore, battery balancing technology has become a necessary means to improve battery lifespan. Simply put, bidirectional balancing technology charges cells with lower voltage and discharges cells with higher voltage, ultimately bringing the voltage of each cell closer to the same level and achieving consistent operating conditions. To facilitate adaptation to different application scenarios, the industry has proposed online current adjustment functionality for the bidirectional balancing module, hoping to allow real-time adjustment of the constant current values ​​during charging and discharging via a host computer.

[0003] Constant current control is currently a mature technology. During charging, the primary-side control circuit typically employs a primary-side feedback constant current control scheme, which enables constant current output control of the secondary side from the primary side. The secondary-side control circuit does not need to participate in the operation. Figure 1 As shown. During discharge, the secondary-side control circuit and the discharge current share a common ground. This can be easily achieved using conventional current sampling and error amplifier feedback on the secondary side; the primary-side control circuit does not need to participate. For example... Figure 2 As shown.

[0004] In existing solutions, the host computer sends enable and current control signals to the primary and secondary control circuits. Typically, the host computer and the primary control circuit share a common ground. Taking a flyback topology as an example, when the equalization module is charging, the host computer enables the primary control circuit to operate, while the secondary control circuit remains inactive without the enable signal, forming a flyback topology with left input and right output. The host computer can also input a forward current control signal to control the charging current value, known as forward charging. When the equalization module is discharging, due to the isolation between the host computer and the secondary control circuit, the host computer enables the secondary control circuit to operate through isolation device 1, while the primary control circuit remains inactive without the enable signal, forming a flyback topology with right input and left output. Simultaneously, the host computer also needs to output a reverse current control signal through isolation device 2 to control the discharge current value, known as reverse discharging. Existing bidirectional equalization schemes require two isolation devices: one to control whether the secondary control circuit operates, and the other to control the magnitude of the secondary battery discharge current. As the requirements for isolation withstand voltage and creepage distance increase, the size of isolation devices will become larger and the cost will increase significantly.

[0005] It should be noted that the information disclosed in the background section is intended only to enhance the understanding of the overall background of this application and should not be construed as an admission or implication in any way that the information is prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a signal isolation conversion circuit, a bidirectional equalization control circuit, and a power converter, which solves the problems of large product size and high cost caused by the need for two isolation devices to achieve bidirectional equalization control in the prior art.

[0007] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a signal isolation conversion circuit, including an isolation device and a signal conversion circuit. The isolation device receives a control signal sent by a front-end host computer and transmits it to the signal conversion circuit. The signal conversion circuit converts the control signal into an enable signal and a reference voltage, which are output from two output ports of the signal conversion circuit to a back-end constant current control circuit. The output reference voltage value and the level of the enable signal are controlled by adjusting the control signal.

[0008] Furthermore, the isolation device is a first transformer T1; one end of the primary winding of the first transformer T1 is input to the control signal, and the other end is connected to ground through the first MOS transistor Q1; a first resistor R1 is also connected between the two ends of the primary winding of the first transformer T1; the other end of the primary winding of the first transformer T1 is connected to the drain of the first MOS transistor Q1; the source of the first MOS transistor Q1 is connected to the primary ground, and a square wave signal with a fixed frequency and duty cycle is input to the gate; a signal conversion circuit is connected between the two ends of the secondary winding of the first transformer T1.

[0009] Furthermore, the signal conversion circuit includes a diode D1, a first capacitor C1, a second resistor R2, and a first comparator COMP1; the anode of diode D1 is connected to one end of the secondary winding, and the cathode of diode D1 is connected to one end of the first capacitor C1, one end of the second resistor R2, and the positive input terminal of the first comparator COMP1, and serves as the first output terminal of the signal isolation conversion circuit to output a reference voltage; the other end of the secondary winding, the other end of the first capacitor C1, and the other end of the second resistor R2 are connected to the secondary ground; the negative input terminal of the first comparator COMP1 receives the threshold voltage signal EN_TH, and the output terminal of the first comparator COMP1 serves as the second output terminal of the signal isolation conversion circuit to output an enable signal.

[0010] Furthermore, the isolation device is a first transformer T1; one end of the primary winding of the first transformer T1 is input with the supply voltage VDD, and the other end is connected to ground through a first MOSFET Q1; a first resistor R1 is also connected between the two ends of the primary winding of the first transformer T1; the other end of the primary winding of the first transformer T1 is connected to the drain of the first MOSFET Q1; the source of the first MOSFET Q1 is connected to the primary ground, and the gate is input with a control signal; the two ends of the secondary winding of the first transformer T1 are connected to a signal conversion circuit.

[0011] Furthermore, the signal conversion circuit includes a diode D1, a first capacitor C1, a second resistor R2, a third resistor R3, and a first comparator COMP1. The anode of diode D1 is connected to one end of the secondary winding, and the cathode of diode D1 is connected to one end of the first capacitor C1, one end of the second resistor R2, and the positive input terminal of the first comparator COMP1, and serves as the first output terminal of the signal isolation conversion circuit to output a reference voltage. The other end of the secondary winding, the other end of the first capacitor C1, and the other end of the second resistor R2 are connected to the secondary ground. The negative input terminal of the first comparator COMP1 receives the threshold voltage signal EN_TH, and the output terminal of the first comparator COMP1 serves as the second output terminal of the signal isolation conversion circuit to output an enable signal. The third resistor R3 is connected between the cathode of diode D1 and the positive input terminal of the first comparator COMP1.

[0012] Furthermore, the isolation device includes an optocoupler OPT1. The anode of the optocoupler OPT1 receives the control signal sent by the host computer through the fourth resistor R4, the collector is supplied with the power supply voltage, and the emitter is connected to the signal conversion circuit.

[0013] Furthermore, the signal conversion circuit includes a fifth resistor R5, a sixth resistor R6, a second capacitor C2, and a second comparator COMP2; one end of the fifth resistor R5 is connected to the emitter of the optocoupler OPT1; the other end of the fifth resistor R5 is connected to one end of the sixth resistor R6, one end of the second capacitor C2, and the positive input terminal of the second comparator COMP2, and serves as the first output terminal of the signal isolation conversion circuit to output a reference voltage; the negative input terminal of the second comparator COMP2 receives the threshold voltage signal EN_TH, and the output terminal of the second comparator COMP2 serves as the second output terminal of the signal isolation conversion circuit to output an enable signal.

[0014] Secondly, the present invention provides a bidirectional equalization control circuit, including an isolation device, a forward signal conversion circuit, a reverse signal conversion circuit, a forward constant current control circuit, and a reverse constant current control circuit; the isolation device and the reverse signal conversion circuit are the aforementioned signal isolation conversion circuits; the forward signal conversion circuit is the aforementioned signal conversion circuit; the input terminal of the forward signal conversion circuit and the isolation device respectively receive control signals sent by a host computer; the forward signal conversion circuit converts the control signals into an enable signal and a reference voltage and transmits them to the forward constant current control circuit; the reverse signal conversion circuit converts the control signals into an enable signal and a reference voltage and transmits them to the reverse constant current control circuit; the forward constant current control circuit controls the primary power circuit of the power converter to turn on and off, and samples the primary charging current of the power converter when it is on; the reverse constant current control circuit controls the secondary power circuit of the power converter to turn on and off, and samples the secondary discharge current of the power converter when it is on; the bidirectional equalization control circuit is controlled to operate in the forward or reverse direction by the control signal; and the reference voltage value is adjusted by the control signal, thereby controlling the forward charging current to be constant or the reverse discharge current to be constant.

[0015] Thirdly, the present invention provides a power converter, including the aforementioned bidirectional equalization control circuit, and further including a second transformer T2, a primary-side MOSFET Q2, a secondary-side MOSFET Q3, and a battery; the drain of the primary-side MOSFET Q2 is connected to one end of the primary winding of the second transformer T2, and the source of the primary-side MOSFET Q2 is connected to the negative terminal of the power supply; the other end of the primary winding of the second transformer T2 is connected to the positive terminal of the power supply; the gate of the primary-side MOSFET Q2 is connected to the output terminal of the forward constant current control circuit; the sampling terminal of the forward constant current control circuit is connected to the source of the primary-side MOSFET Q2 to sample the primary-side charging current value; the drain of the secondary-side MOSFET Q3 is connected to one end of the secondary winding of the second transformer T2, and the source of the secondary-side MOSFET Q3 is connected to the negative terminal of the battery; the other end of the secondary winding of the second transformer T2 is connected to the positive terminal of the battery; the gate of the secondary-side MOSFET Q3 is connected to the output terminal of the reverse constant current control circuit; the sampling terminal of the reverse constant current control circuit is connected to the source of the secondary-side MOSFET Q3 to sample the secondary-side discharging current value.

[0016] This invention uses only one isolation device to achieve switching between two different operating states: forward charging and reverse discharging. Furthermore, the charging or discharging current value can be adjusted simply by changing the control signal sent by the host computer, maintaining a constant charging / discharging current. This reduces product size and lowers product cost. Attached Figure Description

[0017] Figure 1 This is a block diagram of an application of equalization control circuit for charging a single battery cell in the prior art.

[0018] Figure 2 This is a block diagram of an application of a balancing control circuit for discharging a single battery cell in existing technology.

[0019] Figure 3 This is a block diagram of the equalization control circuit and its application according to the present invention.

[0020] Figure 4 This is one of the circuit schematics of the signal isolation conversion circuit of the present invention.

[0021] Figure 5 This is the second circuit schematic diagram of the signal isolation and conversion circuit of the present invention.

[0022] Figure 6 This is the third circuit diagram of the signal isolation and conversion circuit of the present invention.

[0023] Figure 7 This is a circuit diagram of the reverse constant current control circuit of the present invention. Detailed Implementation

[0024] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0025] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0026] This application provides a signal isolation and conversion circuit, including an isolation device and a signal conversion circuit. The isolation device receives a control signal sent by a host computer and transmits it to the signal conversion circuit. The signal conversion circuit converts the control signal into an enable signal and a reference voltage, which are output from two output ports of the signal conversion circuit to a downstream constant current control circuit. The output reference voltage value and the level of the enable signal are controlled by adjusting the control signal.

[0027] Furthermore, as a first embodiment of the signal isolation conversion circuit, such as Figure 4 As shown, the isolation device includes a first transformer T1. The primary winding of the first transformer T1 receives a control signal sent by the host computer. This control signal is an analog signal, and its voltage amplitude is denoted as V. SIGA control signal is input to one end of the primary winding of the first transformer T1, and the other end is connected to ground through the first MOSFET Q1. A first resistor R1 is also connected between the two ends of the primary winding of the first transformer T1. The other end of the primary winding of the first transformer T1 is connected to the drain of the first MOSFET Q1. The source of the first MOSFET Q1 is connected to the primary ground, and a square wave signal with a fixed frequency and duty cycle is input to its gate. A signal conversion circuit is connected to the two ends of the secondary winding of the first transformer T1. The signal conversion circuit includes a diode D1, a first capacitor C1, a second resistor R2, and a first comparator COMP1. The anode of diode D1 is connected to one end of the secondary winding. The cathode of diode D1 is connected to one end of the first capacitor C1, one end of the second resistor R2, and the positive input terminal of the first comparator COMP1, and serves as the first output terminal of the signal isolation conversion circuit to output a reference voltage. The other end of the secondary winding, the other end of the first capacitor C1, and the other end of the second resistor R2 are connected to the secondary ground. The negative input terminal of the first comparator COMP1 receives the threshold voltage signal EN_TH, and the output terminal of the first comparator COMP1 serves as the second output terminal of the signal isolation conversion circuit, outputting the enable signal. The first capacitor C1 and the second resistor R2 are used for filtering.

[0028] The oscillator outputs a square wave signal with a fixed frequency and duty cycle to control the switching of MOSFET Q3. The host computer sends an analog signal to the primary winding of the transformer, causing the primary winding to generate a periodic analog signal. The turns ratio of the primary and secondary windings of transformer T1 is denoted as N. SIG The voltage at point A is approximately: Formula (1) The voltage at point A is used as the reference voltage V for the downstream constant current control circuit. REF From formula (1), it can be seen that the reference voltage V REF The voltage amplitude V of the analog signal SIG Linear correlation.

[0029] At the same time, when V A < Threshold voltage V at the negative input of the first comparator COMP1 EN_TH When V is low, the enable signal output by the first comparator COMP1 is low; when V A > Threshold voltage V at the negative input of the first comparator COMP1 EN_TH At this time, the enable signal output by the first comparator COMP1 is high. The threshold voltage V should be set appropriately. EN_TH It can control whether the back-end constant current control circuit works.

[0030] Therefore, it is only necessary to adjust the voltage amplitude V of the analog signal sent by the host computer. SIGThe signal isolation and conversion circuit can be used to determine whether the constant current control circuit is working during reverse discharge, and to control the battery discharge current value through the constant current control circuit, thereby achieving constant current control during discharge.

[0031] Furthermore, as a second embodiment of the signal isolation conversion circuit, such as Figure 5 As shown, unlike the first embodiment of the signal isolation conversion circuit, there is no need for an oscillator to generate a square wave signal with a fixed frequency and duty cycle. Instead, the host computer sends the square wave signal to the gate of the first MOSFET Q1 to control the turn-on or turn-off of the first MOSFET Q1. One end of the primary winding of the first transformer T1 receives the supply voltage VDD. The signal conversion circuit also includes a third resistor R3, which is connected between the cathode of diode D1 and the positive input terminal of the first comparator COMP1.

[0032] When the host computer does not send a square wave signal or the duty cycle D of the square wave signal is less than the threshold voltage V EN_TH When the enable signal output by the first comparator COMP1 is low ( / VDD), the reverse constant current control circuit does not operate. When the square wave signal D>V from the host computer... EN_TH / VDD, the enable signal output of the first comparator COMP1 is high, enabling the reverse constant current control circuit to operate. Similarly, the reference voltage is: Formula (2) Using the methods described above, and combining them with the principle of the reverse constant current control circuit mentioned earlier, it can be seen that the host computer only needs to adjust the duty cycle to achieve the functions of enabling / disabling reverse control and controlling the reverse discharge constant current value.

[0033] Furthermore, as a third embodiment of the signal isolation conversion circuit, such as Figure 6 As shown, the isolation device uses optocoupler OPT1. The anode of optocoupler OPT1 receives a square wave signal sent by the host computer through the fourth resistor R4, and the collector is supplied with the power supply voltage VDD. The signal conversion circuit includes a fifth resistor R5, a sixth resistor R6, a second capacitor C2, and a second comparator COMP2. One end of the fifth resistor R5 is connected to the emitter of optocoupler OPT1; the other end of the fifth resistor R5 is connected to one end of the sixth resistor R6, one end of the second capacitor C2, and the positive input terminal of the second comparator COMP2, serving as the first output terminal of the signal isolation conversion circuit to output a reference voltage. The negative input terminal of the second comparator COMP2 receives the threshold voltage signal EN_TH, and the output terminal of the second comparator COMP2 serves as the second output terminal of the signal isolation conversion circuit to output an enable signal.

[0034] The signal sent by the host computer is a square wave signal, and the voltage at point A is: Formula (3) Where D is the duty cycle of the square wave signal sent by the host computer.

[0035] When the host computer does not send a square wave signal or the duty cycle D < threshold voltage V EN_TH When / VDD, the enable signal is low, and the reverse constant current control circuit at the back end does not work. When the square wave signal D>V from the host computer... EN_TH When the / VDD enable signal is high, the reverse constant current control circuit at the back end is enabled to work.

[0036] And the reference voltage V REF =V A Therefore, by simply adjusting the duty cycle of the square wave signal sent by the host computer, the signal isolation and conversion circuit can be used to determine whether the constant current control circuit works during reverse discharge, and to control the battery discharge current value through the constant current control circuit, thus achieving constant current control during discharge.

[0037] This application provides a bidirectional equalization control circuit, such as Figure 3 As shown, the circuit includes an isolation device, a forward signal conversion circuit, a reverse signal conversion circuit, a forward constant current control circuit, and a reverse constant current control circuit. The isolation device and the reverse signal conversion circuit constitute the aforementioned signal isolation conversion circuit. The forward signal conversion circuit is implemented using the signal conversion circuit within the aforementioned signal isolation conversion circuit. The input terminal of the forward signal conversion circuit and the isolation device respectively receive control signals sent from the host computer. The forward signal conversion circuit converts the control signal into an enable signal and a reference voltage and transmits them to the forward constant current control circuit. The reverse signal conversion circuit converts the control signal into an enable signal and a reference voltage and transmits them to the reverse constant current control circuit. The forward constant current control circuit controls the primary-side power circuit of the power converter to turn on and off, and samples the primary-side charging current of the power converter when it is on. The reverse constant current control circuit controls the secondary-side power circuit of the power converter to turn on and off, and samples the secondary-side discharging current of the power converter when it is on.

[0038] The circuit structure and working principle of the signal isolation conversion circuit, which consists of isolation devices and inverting signal conversion circuits, have been described above and will not be repeated here.

[0039] The difference between a forward signal conversion circuit and a signal isolation conversion circuit is that the primary side does not require isolation, so there is no isolation device. The host computer directly sends the control signal to the signal conversion circuit. Figure 4 Taking the host computer and the forward signal conversion circuit as an example, the host computer inputs an analog signal to the anode of diode D1, and the voltage amplitude of the analog signal is V. SIG If the forward voltage drop of diode D1 is ignored, then the reference voltage V REF =V A =V SIG Similarly, when V A< Threshold voltage V at the negative input of the first comparator COMP1 EN_TH When V is low, the enable signal output by the first comparator COMP1 is low; when V A > Threshold voltage V at the negative input of the first comparator COMP1 EN_TH At this time, the enable signal output by the first comparator COMP1 is high. The threshold voltage V should be set appropriately. EN_TH This allows control over whether the back-end constant current control circuit operates. Therefore, it is only necessary to adjust the voltage amplitude V of the analog signal sent by the host computer. SIG This allows the forward constant current control circuit to be activated during charging via a forward signal conversion circuit, and also controls the voltage amplitude V. SIG Control the magnitude of the reference voltage.

[0040] Forward signal conversion circuit is Figure 5 In the signal conversion circuit shown, the host computer sends a square wave signal to the anode of diode D1. The duty cycle of the square wave signal is D, and the positive voltage is V. DD Similarly, if we ignore the forward voltage drop of diode D1, the reference voltage is: Formula (4) Here, VDD refers to the high-level voltage of the square wave signal sent by the host computer. Since the host computer is generally powered by VDD, the high-level value of the square wave signal sent by the host computer is also VDD.

[0041] Forward signal conversion circuit is Figure 6 In the signal conversion circuit shown, the host computer sends a square wave signal to one end of the fifth resistor R5. The duty cycle of the square wave signal is D, and the positive voltage is V. DD Reference voltage Formula (5) In this application, the forward constant current control circuit can be implemented using existing technology, such as a flyback primary-side feedback control chip, combined with... Figure 3 Using a power converter as an example, the function of the flyback primary-side feedback control chip is to ensure that the ratio of the complete demagnetization time of transformer T2 to the switching cycle of primary-side MOSFET Q2 is a constant, expressed by the formula: T DS / T=k.

[0042] in: k is a constant, generally taken as 0.4~0.6 in engineering. T DS The time for transformer T2 to be completely demagnetized, where T is the switching cycle of MOSFET Q2.

[0043] The constant charging current value of the power converter during forward operation is I充 for: Formula (6) in: N PS This refers to the primary and secondary turns ratio of transformer T2. I PK The peak current of the primary side of transformer T2 is obtained by detecting the drain current of the primary-side MOSFET Q2 when it is turned on through a forward constant current control circuit. The peak current I... PK The charging constant current value I is linearly related to the reference voltage of the input positive constant current control circuit. According to formula (4), the charging constant current value I can be obtained. 充 It is linearly related to the reference voltage. Therefore, by sending an adjustable control signal through the host computer, the reference voltage can be adjusted, thereby regulating the charging current in real time to keep the charging current constant.

[0044] In this application, the reverse constant current control circuit can be implemented using current-mode PWM control or voltage-mode PWM control. Its purpose is to sample the discharge current I when the power converter discharges in reverse. 放 If the discharge current is too large, a reverse control signal is output to control the on-state of MOSFET Q3 on the secondary side of the transformer, reducing the discharge current to a constant value. If the discharge current is too small, a reverse control signal is output to control the on-state of MOSFET Q3 on the secondary side of the transformer, increasing the discharge current to a constant value. This ensures a constant discharge current.

[0045] Combination Figure 7 This article provides a detailed explanation of the working principle of the reverse constant current control circuit, but it does not limit the reverse constant current control circuit to only this one embodiment. Other constant current control circuits in the prior art, as long as they can achieve the same function, can be used as specific implementation circuits of the reverse constant current control circuit of this application.

[0046] One specific circuit structure of the reverse constant current control circuit of this application includes a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a first operational amplifier OP1, a second operational amplifier OP2, a third capacitor C3, a third comparator COMP3, and an RS flip-flop U2. One end of the seventh resistor R7 and the negative terminal of the battery are connected to the secondary ground. The other end of the seventh resistor R7 is connected to the source of the MOSFET Q3, the non-inverting input of the first operational amplifier OP1, and the positive input of the third comparator COMP3. The inverting input of the first operational amplifier OP1 is connected to one end of the eighth resistor R8 and one end of the ninth resistor R9. The other end of the eighth resistor R8 is grounded, and the other end of the ninth resistor R9 and the output of the first operational amplifier OP1 are connected to the inverting input of the second operational amplifier OP2. The third capacitor C3 is connected between the inverting input and the output of the second operational amplifier OP2. The non-inverting input of the second operational amplifier OP2 receives a reference voltage. The output of the second operational amplifier OP2 is connected to the negative input of the third comparator COMP3. The output of the third comparator COMP3 is connected to the R terminal of the RS flip-flop U2. The S-terminal of the RS flip-flop U2 receives a clock signal, generated by the clock generator U1, or other components. The Q-terminal of the RS flip-flop U2 outputs a square wave signal to the MOSFET Q2, controlling the on / off state of MOSFET Q3, further controlling the battery discharge current. An enable signal can be given to any component in the reverse constant current control circuit to control its operation, thus controlling whether the reverse constant current control circuit operates, such as whether to supply power to it. The same applies to the control of the forward constant current control circuit using the enable signal.

[0047] Resistor R7 is used to sample the peak current when MOSFET Q3 is turned on, and the average value of the current sampled by R7 is also the average value of the battery discharge current. Therefore, the first operational amplifier OP1 and the third comparator COMP3 are used to sample the average value of the battery discharge current. The first operational amplifier OP1, the eighth resistor R8, the ninth resistor R9, and the fourth capacitor C4 form a proportional amplifier and low-pass filter to amplify and filter the peak value of the sampled current. The voltage output by the first operational amplifier OP1 is the sampled voltage of the discharge current. After comparing the sampled voltage of the discharge current with the reference voltage, it is amplified by the error amplifier composed of the second operational amplifier OP2 and the third capacitor C3. The third capacitor C1 is used for loop compensation. The third comparator COMP3, the clock signal generator U1, and the RS flip-flop U2 constitute a current-type PWM control circuit, which is a well-known technology in the switching power supply industry and its principle will not be further described. The above circuit forms a negative feedback circuit. When the discharge current increases, the voltage at the negative input terminal of the second operational amplifier OP2 also increases, the output voltage of the second operational amplifier OP2 decreases, and the duty cycle of the current-type PWM control circuit also decreases, thereby controlling the discharge current to decrease. Figure 7Under the reverse constant current control circuit shown, the error amplifier will control the voltage at its positive input terminal and the negative input terminal to be equal, so the constant current value for battery discharge is obtained as follows: Formula (7) In the formula, V 基准电压 R7 is the reference voltage value output by the inverting signal conversion circuit, R8 is the resistance value of the seventh resistor, R9 is the resistance value of the eighth resistor, and R9 is the resistance value of the ninth resistor.

[0048] As can be seen from formula (7), by adjusting the reference voltage value, the constant current value of battery discharge can be adjusted in real time to stabilize it at a constant value. Since the reference voltage is linearly related to the control signal sent by the host computer, the battery discharge current can be adjusted simply by adjusting the control signal sent by the host computer.

[0049] This application also provides a power converter, including the aforementioned bidirectional equalization control circuit, and further including a second transformer T2, a primary-side MOSFET Q2, a secondary-side MOSFET Q3, and a battery. The drain of the primary-side MOSFET Q2 is connected to one end of the primary winding of the second transformer T2, and the source of the primary-side MOSFET Q2 is connected to the negative terminal of the power supply. The other end of the primary winding of the second transformer T2 is connected to the positive terminal of the power supply. The gate of the primary-side MOSFET Q2 is connected to the output terminal of the forward constant current control circuit. The sampling terminal of the forward constant current control circuit is connected to the source of the primary-side MOSFET Q2 to sample the primary-side charging current value. The drain of the secondary-side MOSFET Q3 is connected to one end of the secondary winding of the second transformer T2, and the source of the secondary-side MOSFET Q3 is connected to the negative terminal of the battery. The other end of the secondary winding of the second transformer T2 is connected to the positive terminal of the battery. The gate of the secondary-side MOSFET Q3 is connected to the output terminal of the reverse constant current control circuit. The sampling terminal of the reverse constant current control circuit is connected to the source of the secondary-side MOSFET Q3 to sample the secondary-side discharging current value.

[0050] When forward charging is required, the host computer sends a control signal to the forward signal conversion circuit, which then operates. The reverse signal conversion circuit, however, does not operate because it does not receive a control signal. The forward signal conversion circuit converts the control signal into an enable signal and a reference voltage. The enable signal controls the forward constant current control circuit, which outputs a high level to turn on the primary-side MOSFET Q2. The forward constant current control circuit samples the charging current. If the charging current is too large, it adjusts the amplitude of the control signal sent by the host computer, thereby adjusting the reference voltage and reducing the charging current. The relationship between the reference voltage and the charging current is explained in formula (6) and will not be repeated here.

[0051] When reverse discharge is required, the host computer sends a control signal to the isolation device, which then transmits it to the reverse signal conversion circuit after isolation. The reverse signal conversion circuit operates, while the forward signal conversion circuit does not operate because it does not receive a control signal. The reverse signal conversion circuit converts the control signal into an enable signal and a reference voltage. The enable signal controls the reverse constant current control circuit to operate, and the reverse constant current control circuit outputs a high level to control the secondary MOSFET Q3 to conduct. The reverse constant current control circuit samples the discharge current. If the discharge current is too large, it adjusts the amplitude of the control signal sent by the host computer, adjusts the reference voltage, and thus adjusts the discharge current to decrease. The relationship between the reference voltage and the discharge current has been explained in formula (7) and will not be repeated here.

[0052] This invention requires only one isolation device to switch between two different operating states: forward charging and reverse discharging. Furthermore, the charging or discharging current value can be adjusted by simply changing the control signal sent by the host computer, maintaining a constant charging / discharging current.

[0053] The above description is merely illustrative of the embodiments of the present invention and is not intended to limit the present invention. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made without creative effort within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A signal isolation and conversion circuit, characterized in that, It includes a signal conversion circuit and an isolation device. The isolation device receives the control signal sent by the front-end host computer and transmits it to the signal conversion circuit. The signal conversion circuit converts the control signal into an enable signal and a reference voltage, which are output from the two output ports of the signal conversion circuit to the back-end constant current control circuit. The output reference voltage value and the level of the enable signal are controlled by adjusting the control signal.

2. The signal isolation and conversion circuit according to claim 1, characterized in that, The isolation device is a first transformer (T1); one end of the primary winding of the first transformer (T1) is input with a control signal, and the other end is connected to ground through a first MOS transistor (Q1); a first resistor (R1) is also connected between the two ends of the primary winding of the first transformer (T1); the other end of the primary winding of the first transformer (T1) is connected to the drain of the first MOS transistor (Q1); the source of the first MOS transistor (Q1) is connected to the primary ground, and a square wave signal with a fixed frequency and duty cycle is input to the gate; a signal conversion circuit is connected between the two ends of the secondary winding of the first transformer (T1).

3. The signal isolation and conversion circuit according to claim 2, characterized in that, The signal conversion circuit includes a diode (D1), a first capacitor (C1), a second resistor (R2), and a first comparator (COMP1). The anode of the diode (D1) is connected to one end of the secondary winding, and the cathode of the diode (D1) is connected to one end of the first capacitor (C1), one end of the second resistor (R2), and the positive input terminal of the first comparator (COMP1), and serves as the first output terminal of the signal isolation conversion circuit to output a reference voltage. The other end of the secondary winding, the other end of the first capacitor (C1), and the other end of the second resistor (R2) are connected to the secondary ground. The negative input terminal of the first comparator (COMP1) receives a threshold voltage (EN_TH), and the output terminal of the first comparator (COMP1) serves as the second output terminal of the signal isolation conversion circuit to output an enable signal.

4. The signal isolation and conversion circuit according to claim 1, characterized in that, The isolation device is a first transformer (T1); one end of the primary winding of the first transformer (T1) is input with the supply voltage (VDD), and the other end is connected to ground through a first MOSFET (Q1); a first resistor (R1) is also connected between the two ends of the primary winding of the first transformer (T1); the other end of the primary winding of the first transformer (T1) is connected to the drain of the first MOSFET (Q1); the source of the first MOSFET (Q1) is connected to the primary ground, and the gate is input with a control signal; the two ends of the secondary winding of the first transformer (T1) are connected to a signal conversion circuit.

5. The signal isolation and conversion circuit according to claim 4, characterized in that, The signal conversion circuit includes a diode (D1), a first capacitor (C1), a second resistor (R2), a third resistor (R3), and a first comparator (COMP1). The anode of the diode (D1) is connected to one end of the secondary winding, and the cathode of the diode (D1) is connected to one end of the first capacitor (C1), one end of the second resistor (R2), and the positive input terminal of the first comparator (COMP1), serving as the first output terminal of the signal isolation conversion circuit to output a reference voltage. The other end of the secondary winding, the other end of the first capacitor (C1), and the other end of the second resistor (R2) are connected to the secondary ground. The negative input terminal of the first comparator (COMP1) receives the threshold voltage signal EN_TH, and the output terminal of the first comparator (COMP1) serves as the second output terminal of the signal isolation conversion circuit to output an enable signal. The third resistor (R3) is connected between the cathode of the diode (D1) and the positive input terminal of the first comparator (COMP1).

6. The signal isolation and conversion circuit according to claim 1, characterized in that, The isolation device includes an optocoupler (OPT1). The anode of the optocoupler (OPT1) receives the control signal sent by the host computer through the fourth resistor (R4), the collector is supplied with the power supply voltage, and the emitter is connected to the signal conversion circuit.

7. The signal isolation and conversion circuit according to claim 6, characterized in that, The signal conversion circuit includes a fifth resistor (R5), a sixth resistor (R6), a second capacitor C2, and a second comparator (COMP2). One end of the fifth resistor (R5) is connected to the emitter of the optocoupler (OPT1). The other end of the fifth resistor (R5) is connected to one end of the sixth resistor (R6), one end of the second capacitor C2, and the positive input terminal of the second comparator (COMP2), and serves as the first output terminal of the signal isolation conversion circuit to output a reference voltage. The negative input terminal of the second comparator (COMP2) receives a threshold voltage (EN_TH), and the output terminal of the second comparator (COMP2) serves as the second output terminal of the signal isolation conversion circuit to output an enable signal.

8. A bidirectional equalization control circuit, characterized in that, The system includes an isolation device, a forward signal conversion circuit, a reverse signal conversion circuit, a forward constant current control circuit, and a reverse constant current control circuit; the isolation device and the reverse signal conversion circuit are signal isolation conversion circuits as described in any one of claims 1 to 7; the forward signal conversion circuit is the signal conversion circuit as described in any one of claims 3, 5, and 7; the input terminal of the forward signal conversion circuit and the isolation device respectively receive control signals sent by the host computer; the forward signal conversion circuit converts the control signals into an enable signal and a reference voltage and transmits them to the forward constant current control circuit; the reverse signal conversion circuit converts the control signals into an enable signal and a reference voltage and transmits them to the reverse constant current control circuit; the forward constant current control circuit controls the primary power circuit of the power converter to turn on and off, and samples the primary charging current of the power converter when it is on; the reverse constant current control circuit controls the secondary power circuit of the power converter to turn on and off, and samples the secondary discharge current of the power converter when it is on; the bidirectional equalization control circuit is controlled to work in the forward or reverse direction by the control signal; and the reference voltage value is adjusted by the control signal, thereby controlling the forward charging current to be constant or the reverse discharge current to be constant.

9. A power converter, characterized in that, The bidirectional equalization control circuit, as described in claim 8, further includes a second transformer (T2), a primary-side MOSFET (Q2), a secondary-side MOSFET (Q3), and a battery; the drain of the primary-side MOSFET (Q2) is connected to one end of the primary winding of the second transformer (T2), and the source of the primary-side MOSFET (Q2) is connected to the negative terminal of the power supply; the other end of the primary winding of the second transformer (T2) is connected to the positive terminal of the power supply; the gate of the primary-side MOSFET (Q2) is connected to the output terminal of the forward constant current control circuit; the forward constant current control circuit... The sampling terminal is connected to the source of the primary-side MOSFET (Q2) to sample the primary-side charging current value; the drain of the secondary-side MOSFET (Q3) is connected to one end of the secondary winding of the second transformer (T2), and the source of the secondary-side MOSFET (Q3) is connected to the negative terminal of the battery; the other end of the secondary winding of the second transformer (T2) is connected to the positive terminal of the battery; the gate of the secondary-side MOSFET (Q3) is connected to the output terminal of the reverse constant current control circuit; the sampling terminal of the reverse constant current control circuit is connected to the source of the secondary-side MOSFET (Q3) to sample the secondary-side discharge current value.

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