Auxiliary power supply and overcurrent protection method

Abstract

The application provides an auxiliary power supply and an overcurrent protection method. The auxiliary power supply comprises a main power circuit, a current detection unit, an overload protection circuit, a short-circuit protection circuit and a logic control unit, and the main power circuit comprises a first dual-tube forward unit and a second dual-tube forward unit. The current detection unit detects a first current and a second current and outputs a detection signal, the overload protection circuit delays output of an overload protection signal when the voltage of the detection signal is greater than or equal to a first voltage threshold, the short-circuit protection circuit outputs a short-circuit protection signal when the voltage of the detection signal is greater than or equal to a second voltage threshold, and the logic control unit outputs a control signal when the overload protection signal or the short-circuit protection signal is received, and the control signal is used for blocking a pulse width modulation signal input to the main power circuit. The auxiliary power supply provided by the application can adapt to the power supply use demand of a direct-current fan.

Description

Technical Field

[0001] This invention relates to the field of photovoltaics, and in particular to an auxiliary power supply and an overcurrent protection method. Background Technology

[0002] The auxiliary power supply is a core component that ensures the stable operation of the photovoltaic inverter. It mainly supplies power to the AC fan inside the inverter under traditional operating conditions.

[0003] With the continuous development of the photovoltaic industry, the industry's requirements for equipment energy efficiency, operational reliability and overall integration are constantly increasing. Due to defects such as strong electromagnetic interference, low speed regulation accuracy and high maintenance costs, AC fans are gradually being replaced by DC fans.

[0004] However, the current auxiliary power supply performance cannot meet the power supply requirements of DC fans. Summary of the Invention

[0005] This application provides an auxiliary power supply and overcurrent protection method to adapt to the power supply requirements of DC fans.

[0006] In a first aspect, this application provides an auxiliary power supply, including a main power circuit, a current detection unit, an overload protection circuit, a short-circuit protection circuit, and a logic control unit. The main power circuit includes a first two-transistor forward converter and a second two-transistor forward converter. The current detection unit is electrically connected to the first two-transistor forward converter, the second two-transistor forward converter, the overload protection circuit, and the short-circuit protection circuit, respectively. The overload protection circuit and the short-circuit protection circuit are also electrically connected to the logic control unit. The input sides of the first two-transistor forward converter and the second two-transistor forward converter are connected in series, and the output sides of the first two-transistor forward converter and the second two-transistor forward converter are connected in parallel. The current detection unit is used to detect a first current and a second current, and output a detection signal based on the first current and the second current, wherein the first current is the input side of the first two-transistor forward converter. The current, the second current being the input-side current of the second dual-transistor forward converter; the overload protection circuit, used to receive the detection signal and output an overload protection signal after a delay when the voltage of the detection signal is greater than or equal to a first voltage threshold; the short-circuit protection circuit, used to receive the detection signal and output a short-circuit protection signal when the voltage of the detection signal is greater than or equal to a second voltage threshold, wherein the time interval between the start output time of the short-circuit protection signal and a first time is less than or equal to a first preset value, the first time being the start time when the voltage of the detection signal is greater than or equal to the second voltage threshold, and the second voltage threshold being greater than the first voltage threshold; the logic control unit, used to output a control signal when receiving the overload protection signal or the short-circuit protection signal, the control signal being used to block the pulse width modulation signal input to the main power circuit.

[0007] In conjunction with the first aspect, in one possible implementation, the overload protection circuit includes: a first comparison unit and a delay unit; a first input terminal of the first comparison unit is electrically connected to the current detection unit, an output terminal of the first comparison unit is electrically connected to the input terminal of the delay unit, and an output terminal of the delay unit is electrically connected to the input terminal of the logic control unit; the first comparison unit is configured to receive the detection signal through a first input terminal, receive the first voltage threshold through a second input terminal, and output an overload trigger signal when the voltage of the detection signal is greater than or equal to the first voltage threshold; the delay unit is configured to output the overload protection signal with a delay based on the overload trigger signal.

[0008] In conjunction with the first aspect, in one possible implementation, the delay unit includes: an integrator circuit and a hysteresis comparator; the input terminal of the integrator circuit is electrically connected to the output terminal of the first comparison unit, the output terminal of the integrator circuit is electrically connected to the input terminal of the hysteresis comparator, and the output terminal of the hysteresis comparator is electrically connected to the input terminal of the logic control unit; the integrator circuit is used to integrate the overload trigger signal and output an integrated voltage; the hysteresis comparator is used to set the overload protection signal to an active state and output it when the integrated voltage rises to an upper threshold voltage during the integration processing period, and to set the overload protection signal to an inactive state and output it when the integrated voltage falls from the upper threshold voltage to a lower threshold voltage; the logic control unit is used to output the control signal when the overload protection signal is active.

[0009] In conjunction with the first aspect, in one possible implementation, the integrating circuit includes an integrating capacitor, and the integrating voltage is the voltage across the integrating capacitor; during the charging and discharging cycle of the integrating capacitor, the time required for the integrating voltage to rise from zero to the upper threshold voltage is the same as the delay time, the delay time being the time interval between a second moment and the start output moment of the overload protection signal in an active state, the second moment being the start moment when the voltage of the detection signal is greater than or equal to the first voltage threshold; the time required for the integrating voltage to fall from the upper threshold voltage to the lower threshold voltage is equal to the duration for which the overload protection signal is in an active state, and the duration for which the overload protection signal is in an active state is greater than or equal to a second preset value.

[0010] In conjunction with the first aspect, in one possible implementation, the delay unit further includes: a first voltage holding unit; the input terminal of the first voltage holding unit is electrically connected to the output terminal of the first comparison unit, and the output terminal of the first voltage holding unit is electrically connected to the input terminal of the integrating circuit; the first voltage holding unit is configured to output a broadened pulse signal of a preset level based on the overload trigger signal, wherein the effective duration of the broadened pulse signal is greater than the effective duration of the overload trigger signal; the integrating circuit is configured to integrate the broadened pulse signal and output the integrated voltage.

[0011] In conjunction with the first aspect, in one possible implementation, the short-circuit protection circuit includes: a second comparison unit and a second voltage holding unit; a first input terminal of the second comparison unit is electrically connected to the current detection unit, an output terminal of the second comparison unit is electrically connected to the input terminal of the second voltage holding unit, and an output terminal of the second voltage holding unit is electrically connected to the input terminal of the logic control unit; the second comparison unit is configured to receive the detection signal through the first input terminal, receive the second voltage threshold through the second input terminal, and output a short-circuit trigger signal when the voltage of the detection signal is greater than or equal to the second voltage threshold; the second voltage holding unit is configured to output the short-circuit protection signal based on the short-circuit trigger signal, wherein the effective duration of the short-circuit protection signal is greater than the effective duration of the short-circuit trigger signal, and the effective duration of the short-circuit protection signal is greater than or equal to a third preset value.

[0012] In conjunction with the first aspect, in one possible implementation, the current detection unit includes: a first current detection circuit, a second current detection circuit, and a signal conditioning circuit; the first current detection circuit is connected to the first dual-transistor forward converter, the second current detection circuit is connected to the second dual-transistor forward converter, and the signal conditioning circuit is connected to the first current detection circuit, the second current detection circuit, the overload protection circuit, and the short-circuit protection circuit, respectively; the first current detection circuit is used to detect the first current; the second current detection circuit is used to detect the second current; and the signal conditioning circuit is used to sum the first current and the second current and convert them into a voltage signal to generate the detection signal.

[0013] In conjunction with the first aspect, in one possible implementation, the logic control unit is further configured to receive an external blocking signal; the logic control unit is configured to output the control signal upon receiving any one of the overload protection signal, the short-circuit protection signal, and the external blocking signal; the auxiliary power supply further includes: a pulse width modulation signal control chip, a voltage feedback circuit, and a drive circuit; the pulse width modulation signal control chip is connected to the logic control unit, the voltage feedback circuit, and the drive circuit respectively; the pulse width modulation signal control chip is configured to receive the control signal output by the logic control unit and block the pulse width modulation signal based on the control signal; the voltage feedback circuit is configured to sample the output voltage of the main power circuit and output a feedback signal to the pulse width modulation signal control chip based on the output voltage, the feedback signal being used to adjust the duty cycle of the pulse width modulation signal; the drive circuit is configured to enhance the driving capability of the pulse width modulation signal.

[0014] Secondly, this application provides an overcurrent protection method applied to an auxiliary power supply as described in the first aspect or any possible implementation thereof. The method includes: generating a detection signal based on a first current and a second current, wherein the first current is the input-side current of a first dual-transistor forward converter in the auxiliary power supply, and the second current is the input-side current of a second dual-transistor forward converter in the auxiliary power supply; triggering an overload protection function when the voltage of the detection signal is greater than or equal to a first voltage threshold, the overload protection function including: delaying the blocking of a pulse width modulation signal from a second moment, the second moment being the start moment when the voltage of the detection signal is greater than or equal to the first voltage threshold; triggering a short-circuit protection function when the voltage of the detection signal is greater than or equal to a second voltage threshold, the short-circuit protection function including: blocking the pulse width modulation signal, and the time interval between the start moment of blocking the pulse width modulation signal and the first moment is less than or equal to a first preset value, the first moment being the start moment when the voltage of the detection signal is greater than or equal to the second voltage threshold, the second voltage threshold being greater than the first voltage threshold.

[0015] In conjunction with the second aspect, in one possible implementation, the overload protection function further includes: the blocking duration of the pulse width modulation signal is greater than or equal to a second preset value; the short circuit protection function further includes: the blocking duration of the pulse width modulation signal is greater than or equal to a third preset value.

[0016] The technical solution provided in this application connects the input sides of the first and second two-transistor forward converters in series to handle a wide range of DC bus inputs; and connects the output sides of the first and second two-transistor forward converters in parallel to increase the output power of the auxiliary power supply, enabling it to support power output at the kilowatt level, thereby meeting the power supply requirements of the DC fan. This application sets a first voltage threshold and a second voltage threshold. When the detected signal exceeds the first voltage threshold, an overload protection signal is output with a delay, thereby delaying the blocking of the PWM signal. This avoids false overload protection operation caused by normal short-term inrush current, while allowing the auxiliary power supply to safely complete the overload process using its own thermal inertia. When the detected signal exceeds the second voltage threshold, a short-circuit protection signal is output quickly, thereby quickly blocking the PWM signal, achieving rapid protection against short-circuit faults and improving the power supply reliability of the auxiliary power supply. Attached Figure Description

[0017] Figure 1 A schematic structural diagram of an auxiliary power supply provided in this application;

[0018] Figure 2 A schematic structural diagram of another auxiliary power supply provided in this application; Figure 3 A schematic topology diagram of the main power circuit in the auxiliary power supply provided in this application; Figure 4 A schematic structural diagram of the current detection unit, overload protection circuit and short circuit protection circuit in the auxiliary power supply provided in this application; Figure 5 A signal timing diagram of the overload protection circuit in the auxiliary power supply provided in this application; Figure 6 A signal timing diagram of the short-circuit protection circuit in the auxiliary power supply provided in this application; Figure 7 A schematic structural diagram of the logic control unit and PWM control chip in the auxiliary power supply provided in this application; Figure 8 A schematic structural diagram of the voltage feedback circuit in the auxiliary power supply provided in this application; Figure 9 A schematic flowchart illustrating the overcurrent protection method provided in this application. Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Auxiliary power supplies are core components ensuring the stable operation of photovoltaic inverters, primarily used to power the AC fans within the inverter. As the photovoltaic industry continues to develop, the industry's requirements for equipment energy efficiency, operational reliability, and overall integration are constantly increasing. AC fans, due to their drawbacks such as strong electromagnetic interference, low speed regulation accuracy, and high maintenance costs, are gradually being replaced by DC fans.

[0021] However, the current auxiliary power supply performance cannot meet the actual power supply requirements of DC fans.

[0022] From the perspective of power and operational adaptability, the power supply capacity of a single high-power DC wind turbine can reach hundreds of watts. If a multi-fan coordinated cooling solution is adopted, the overall output power requirement of the auxiliary power supply will reach the kilowatt level, while the output power of traditional auxiliary power supplies is limited to tens to hundreds of watts, resulting in a serious lack of power margin. At the same time, the output voltage stability of traditional auxiliary power supplies is poor and the dynamic response speed is slow, making it difficult to match the operating characteristics of DC wind turbines. This can easily lead to problems such as DC wind turbine speed fluctuations and reduced heat dissipation efficiency, ultimately affecting the power generation efficiency and equipment lifespan of the photovoltaic power generation system.

[0023] From the perspective of safety protection and power supply reliability, traditional auxiliary power supply overcurrent protection schemes detect peak current through a primary-side current sampling resistor and employ a single threshold trigger logic. When the detected current exceeds a preset threshold, the pulse width modulation (PWM) signal output is delayed and the system enters a periodic restart mode. This overcurrent protection scheme can achieve fault recovery under overload scenarios, but when faced with short-circuit faults, the inability to promptly shut down the PWM output leads to a surge in instantaneous current that breaks down the switching transistors inside the auxiliary power supply, causing the auxiliary power supply to fail. Consequently, the overall power supply reliability is insufficient, making it difficult to achieve a highly stable power supply guarantee for DC fans.

[0024] Therefore, how to improve the output power, output voltage stability, dynamic response speed, and overall power supply reliability of the auxiliary power supply to meet the power supply requirements of DC fans has become the technical problem to be solved in this application.

[0025] In view of this, this application provides an auxiliary power supply and an overcurrent protection method. The technical solution provided in this application employs a main power circuit with a two-transistor forward converter architecture. The high-voltage side of the main power circuit is connected in series to handle a wide range of DC bus inputs, while the low-voltage side is connected in parallel to improve the power output level of the auxiliary power supply, thereby adapting to the power supply requirements of the DC unit. Furthermore, the auxiliary power supply uses dual-threshold overcurrent protection to achieve independent protection against overload and short-circuit faults. This allows for rapid limitation of the short-circuit current to a safe and controllable range in the event of a short-circuit fault, greatly reducing the risk of excessive stress on the switching transistors in the auxiliary power supply and improving the reliability of the auxiliary power supply.

[0026] The following is combined with Figures 1 to 9 This application provides a detailed description of the technical solution provided.

[0027] Figure 1 This is a schematic structural diagram of an auxiliary power supply provided in this application. Figure 1 As shown, the auxiliary power supply 100 includes: a main power circuit 110, a current detection unit 120, an overload protection circuit 130, a short-circuit protection circuit 140, and a logic control unit 150. The main power circuit 110 includes a first power conversion unit and a second power conversion unit. In this application, the first power conversion unit is a first dual-transistor forward converter 111, and the second power conversion unit is a second dual-transistor forward converter 112, as an example for explanation.

[0028] like Figure 1 As shown, the current detection unit 120 is electrically connected to the first dual-transistor forward converter 111, the second dual-transistor forward converter 112, the overload protection circuit 130, and the short-circuit protection circuit 140, respectively. The overload protection circuit 130 and the short-circuit protection circuit 140 are also electrically connected to the logic control unit 150, respectively. The input sides of the first dual-transistor forward converter 111 and the second dual-transistor forward converter 112 are connected in series, and the output sides are connected in parallel.

[0029] In some embodiments, the input sides of the first dual-transistor forward converter 111 and the second dual-transistor forward converter 112 can be understood as high-voltage sides or primary sides, used for connection to the DC bus; the output sides of the first dual-transistor forward converter 111 and the second dual-transistor forward converter 112 can be understood as low-voltage sides or secondary sides, used for connection to the load.

[0030] The current detection unit 120 is used to detect a first current and a second current, and output a detection signal based on the first current and the second current. The first current is the input current of the first dual-transistor forward converter 111, and the second current is the input current of the second dual-transistor forward converter 112.

[0031] It should be noted that when an overload fault or short-circuit fault occurs, it will directly cause a change in the output load current of the main power circuit 110, which in turn causes a change in the output load current of the first dual-transistor forward converter 111 and the second dual-transistor forward converter 112. However, since there is an approximately linear proportional relationship between the input current and the output load current of the dual-transistor forward converter, and the detection of the output load current is difficult, this application detects the input current of the first dual-transistor forward converter 111 and the second dual-transistor forward converter 112, namely the first current and the second current, and determines whether a short-circuit fault or overload fault has occurred based on the detection signal generated by the first current and the second current. This has the advantages of low implementation cost, low implementation complexity, and high reliability.

[0032] The overload protection circuit 130 receives a detection signal and outputs an overload protection signal after a delay when the voltage of the detection signal is greater than or equal to a first voltage threshold. For example, when the voltage of the detection signal is continuously greater than or equal to the first voltage threshold for a target duration, an overload protection signal is output. The first voltage threshold can be set according to actual needs and is not specifically limited here. Optionally, the first voltage threshold can be pre-stored in the overload protection circuit 130.

[0033] It should be noted that overload faults are characterized by a slow increase in load current. That is, when an overload fault occurs, the load current does not experience a sudden change, but rather rises continuously and gradually until it exceeds the rated value. This characteristic ensures that the stress on the switching transistors within the auxiliary power supply accumulates smoothly and is controllable. Based on this, the solution in this application allows for the introduction of a configurable overload protection trigger delay within the rated capacity range of the switching transistors. This effectively filters out false protection actions caused by instantaneous current spikes, power fluctuations, or transient load disturbances, significantly improving the operational stability and power supply reliability of the auxiliary power supply.

[0034] The short-circuit protection circuit 140 receives a detection signal and outputs a short-circuit protection signal when the voltage of the detection signal is greater than or equal to a second voltage threshold. The time interval between the initial output time of the short-circuit protection signal and a first time point is less than or equal to a first preset value to achieve rapid output of the short-circuit protection signal. The first time point is the initial time when the voltage of the detection signal is greater than or equal to the second voltage threshold. The first preset value and the second voltage threshold can be set according to actual needs and are not limited here.

[0035] It should be noted that short-circuit faults and overload faults have fundamentally different current characteristics. Specifically, when a short-circuit fault occurs, the load current rapidly rises to 5-20 times its rated value within microseconds. This characteristic causes the stress on the switching transistors inside the auxiliary power supply to instantaneously exceed the device's withstand voltage. If the circuit is not immediately disconnected, the switching transistors will suffer permanent breakdown and damage within a short time. Based on this, this application employs a no-delay triggering mechanism for short-circuit faults: when the voltage of the detection signal is greater than or equal to the second voltage threshold, a short-circuit protection signal is rapidly output, thereby achieving a rapid response to short-circuit faults and improving the power supply reliability of the auxiliary power supply.

[0036] In this application, the second voltage threshold is greater than the first voltage threshold.

[0037] Optionally, the second voltage threshold can be pre-stored in the short-circuit protection circuit 140.

[0038] The logic control unit 150 outputs a control signal upon receiving an overload protection signal or a short-circuit protection signal. This control signal blocks the PWM signal input to the main power circuit 110, thereby providing overcurrent protection against overload and short-circuit faults. Blocking the PWM signal can be understood as forcing the PWM signal output to an invalid state, thus shutting down the power switching transistors in the main power circuit 110 and protecting them, thereby improving the operational reliability of the auxiliary power supply 100.

[0039] Optionally, the logic control unit 150 is also used to receive an external blocking signal. The external blocking signal can be a signal input by the user to enable manual control on the user side. The external blocking signal can also be a signal issued by the main control system to enable linkage between the auxiliary power supply 100 and the main control system. Therefore, the logic control unit 150 is used to output a control signal when it receives any one of the overload protection signal, short-circuit protection signal, and external blocking signal.

[0040] The technical solution provided in this application connects the input sides of the first and second two-transistor forward converters in series to handle a wide range of DC bus inputs; and connects the output sides of the first and second two-transistor forward converters in parallel to increase the output power of the auxiliary power supply, enabling it to support power output at the kilowatt level, thereby meeting the power supply requirements of the DC fan. This application sets a first voltage threshold and a second voltage threshold. When the detected signal exceeds the first voltage threshold, an overload protection signal is output with a delay, thereby delaying the blocking of the PWM signal. This avoids false overload protection operation caused by normal short-term inrush current, while allowing the auxiliary power supply to safely complete the overload process using its own thermal inertia. When the detected signal exceeds the second voltage threshold, a short-circuit protection signal is output quickly, thereby quickly blocking the PWM signal, achieving rapid protection against short-circuit faults and improving the power supply reliability of the auxiliary power supply.

[0041] In one possible implementation, the overload protection circuit 130 includes: a first comparison unit 131 and a delay unit 132, such as... Figure 2 As shown.

[0042] The first input terminal of the first comparison unit 131 is electrically connected to the current detection unit 120, the output terminal of the first comparison unit 131 is electrically connected to the input terminal of the delay unit 132, and the output terminal of the delay unit 132 is electrically connected to the input terminal of the logic control unit 150.

[0043] The first comparison unit 131 is used to receive a detection signal through a first input terminal, receive a first voltage threshold through a second input terminal, and output an overload trigger signal when the voltage of the detection signal is greater than or equal to the first voltage threshold.

[0044] The delay unit 132 is used to delay the output of the overload protection signal based on the overload trigger signal.

[0045] like Figure 2 As shown, the delay unit 132 includes an integrator circuit and a hysteresis comparator. The input terminal of the integrator circuit is electrically connected to the output terminal of the first comparison unit 131, the output terminal of the integrator circuit is electrically connected to the input terminal of the hysteresis comparator, and the output terminal of the hysteresis comparator is electrically connected to the input terminal of the logic control unit 150.

[0046] An integrating circuit is used to integrate the overload trigger signal and output an integrated voltage.

[0047] The hysteresis comparator is used to set the overload protection signal to an active state and output it when the integrated voltage rises to the upper threshold voltage during the integration process, and to set the overload protection signal to an inactive state when the integrated voltage drops from the upper threshold voltage to the lower threshold voltage.

[0048] It should be understood that the logic control unit 150 is used to output a control signal when the overload protection signal is in an active state, thereby blocking the PWM signal.

[0049] Optionally, the integrating circuit includes an integrating capacitor, and the integrating voltage is the voltage across the integrating capacitor. During the charging and discharging cycle of the integrating capacitor, the time required for the integrating voltage to rise from zero to the upper threshold voltage is the same as the delay time. The delay time is the time interval between the second moment and the initial output moment of the overload protection signal in an effective state. The second moment is the starting moment when the voltage of the detected signal is greater than or equal to the first voltage threshold. In some embodiments, the second moment can be understood as the starting moment of the target duration when the voltage of the detected signal is continuously greater than or equal to the first voltage threshold.

[0050] Furthermore, during the charging and discharging cycle of the integrating capacitor, the time required for the integrated voltage to drop from the upper threshold voltage to the lower threshold voltage is the duration for which the overload protection signal is active. It should be noted that if the upper threshold voltage is less than the saturation voltage of the integrating capacitor, the integrated voltage will reach the upper threshold voltage twice during the charging and discharging cycle: once during charging and once during discharging. Therefore, the duration for which the overload protection signal is active can be understood as the time required for the integrated voltage to drop from the first reached upper threshold voltage to the lower threshold voltage.

[0051] In this application, the effective duration of the overload protection signal can be greater than or equal to a second preset value to improve the stress relief of the switching transistors in the auxiliary power supply and avoid false triggering of the overload protection function. The second preset value can be set according to actual needs and is not limited here. The effective duration of the overload protection signal is the duration for which the overload protection signal is in an effective state.

[0052] like Figure 2 As shown, the delay unit 132 may further include a first voltage holding unit. The input terminal of the first voltage holding unit is electrically connected to the output terminal of the first comparison unit 131, and the output terminal of the first voltage holding unit is electrically connected to the input terminal of the integrating circuit.

[0053] The first voltage holding unit is used to output a widened pulse signal with a preset level based on the overload trigger signal. The effective duration of the widened pulse signal is longer than the effective duration of the overload trigger signal.

[0054] An integrating circuit is used to integrate a broadened pulse signal and output an integrated voltage.

[0055] In this application, by adding a first voltage holding unit, the overload trigger signal is held and broadened to control the charging and discharging process of the integrating capacitor, thereby achieving flexible control of the overload protection trigger delay time.

[0056] In one possible implementation, the short-circuit protection circuit 140 includes: a second comparison unit 141 and a second voltage holding unit 142, such as... Figure 2 As shown.

[0057] The first input terminal of the second comparison unit 141 is electrically connected to the current detection unit 120, the output terminal of the second comparison unit 141 is electrically connected to the input terminal of the second voltage holding unit 142, and the output terminal of the second voltage holding unit 142 is electrically connected to the input terminal of the logic control unit 150.

[0058] The second comparison unit 141 is used to receive a detection signal through a first input terminal, receive a second voltage threshold through a second input terminal, and output a short-circuit trigger signal when the voltage of the detection signal is greater than or equal to the second voltage threshold.

[0059] The second voltage holding unit 142 is used to output a short-circuit protection signal based on the short-circuit trigger signal. The effective duration of the short-circuit protection signal is longer than the effective duration of the short-circuit trigger signal, and the effective duration of the short-circuit protection signal is greater than or equal to a third preset value. The third preset value can be set according to actual needs and is not limited here.

[0060] In this application, the short-circuit trigger signal is held and extended by the second voltage holding unit to prolong the effective duration of the short-circuit protection signal, thereby allowing the short-circuit current to be fully discharged, avoiding the residual energy from repeatedly impacting the switching transistor, and improving the operational reliability of the auxiliary power supply.

[0061] Optionally, an OR logic circuit can be added between the overload protection circuit 130 and the short-circuit protection circuit 140 to activate the logic control unit 150 based on the overload protection signal or the short-circuit protection signal. The first input terminal of the OR logic circuit is electrically connected to the output terminal of the overload protection circuit 130 to receive the overload protection signal, and the second input terminal of the OR logic circuit is electrically connected to the output terminal of the short-circuit protection circuit 140 to receive the short-circuit protection signal. The output terminal of the OR logic circuit is electrically connected to the logic control unit 150.

[0062] In one possible implementation, the current detection unit 120 includes: a first current detection circuit 121, a second current detection circuit 122, and a signal conditioning circuit 123, such as... Figure 2 As shown.

[0063] The first current detection circuit 121 is connected to the first dual-transistor forward converter 111, the second current detection circuit 122 is connected to the second dual-transistor forward converter 112, and the signal conditioning circuit 123 is connected to the first current detection circuit 121, the second current detection circuit 122, the overload protection circuit 130, and the short-circuit protection circuit 140, respectively.

[0064] The first current detection circuit 121 is used to detect the first current.

[0065] The second current detection circuit 122 is used to detect the second current.

[0066] The signal conditioning circuit 123 is used to superimpose the first current and the second current to convert them into a voltage signal, and then perform voltage division on the voltage signal to generate a detection signal. The superposition process is, for example, a summation process.

[0067] like Figure 2 As shown, the auxiliary power supply 100 also includes a PWM control chip 160, a voltage feedback circuit 170, and a drive circuit 180. It can be seen that the PWM control chip 160 is connected to the logic control unit 150, the voltage feedback circuit 170, and the drive circuit 180, respectively.

[0068] The PWM control chip 160 receives the control signal output by the logic control unit 150 and blocks the PWM signal based on the control signal. It should be noted that even if the logic control unit 150 does not output a control signal, or if the PWM control chip 160 does not receive a control signal, the PWM control chip 160 will still output a PWM signal normally, thereby restarting the auxiliary power supply 100.

[0069] The voltage feedback circuit 170 is used to sample the output voltage of the main power circuit 110 and output a feedback signal to the PWM control chip 160 based on the sampled output voltage. The feedback signal is used to adjust the duty cycle of the PWM signal, thereby adjusting the output voltage of the main power circuit 110.

[0070] The drive circuit 180 is used to enhance the driving capability of the PWM signal.

[0071] In this application, the current detection unit 120 is used to detect the current of the main power circuit 110 and generate a detection signal based on the detected current; the overload protection circuit 130 outputs an overload protection signal based on the detection signal and a first voltage threshold, and the short-circuit protection circuit 140 outputs an overcurrent protection signal based on the detection signal and a second voltage threshold; when the logic control unit 150 receives any one of the overload protection signal, the overcurrent protection signal, and the external blocking signal, it outputs a control signal to the PWM control chip 160 to control the PWM control chip 160 to block the PWM signal. During normal operation of the auxiliary power supply 100, the PWM control chip 160 adjusts the duty cycle of the PWM signal based on the feedback signal output by the voltage feedback circuit 170, thereby adjusting the output voltage of the main power circuit 110 and improving the voltage stability of the auxiliary power supply 100. When the driving capability of the PWM signal is insufficient to drive the switching transistor in the main power circuit 110, the driving capability of the PWM signal can be amplified by the drive circuit 180.

[0072] The following is combined with Figures 3 to 8 This application provides a detailed description of the auxiliary power supply provided.

[0073] Figure 3 A schematic topology diagram of a main power circuit is shown. (For example...) Figure 3 As shown, the topology of the main power circuit 110 is a two-transistor forward converter.

[0074] See Figure 3 As can be seen, the main power circuit 110 includes a first two-transistor forward converter 111 and a second two-transistor forward converter 112. The high-voltage sides of the first two-transistor forward converter 111 and the second two-transistor forward converter 112 are connected in series to handle a wide range of DC bus input; the low-voltage sides of the first two-transistor forward converter 111 and the second two-transistor forward converter 112 are connected in parallel to improve the output capability of the main power circuit 110, enabling it to support output power in the kilowatt range, thus ensuring that the auxiliary power supply's output power meets the power supply requirements of the DC fan. The positive bus voltage is as follows: Figure 3 In VBUS+, the negative bus voltage is as follows Figure 3 In VBUS-, the DC bus midpoint voltage is as follows: Figure 3 BUS_M in the context.

[0075] like Figure 3 As shown, the first two-transistor forward converter 111 includes a transformer T3 and its primary and secondary circuits. The second two-transistor forward converter 112 includes a transformer T4 and its primary and secondary circuits.

[0076] Optionally, the switching transistors S1 to S4 in the main power circuit 110 can be silicon carbide (SiC) power transistors, thereby increasing the power conversion efficiency of the main power circuit 110 to over 94%.

[0077] Each switching transistor is equipped with a gate drive circuit and a clamping diode. The gate drive circuit provides a reliable isolated drive signal for the corresponding switching transistor. The clamping diode absorbs the spike energy of the transformer primary leakage inductance when the switching transistor is turned off and clamps the drain-source voltage of the switching transistor to prevent overvoltage breakdown. For example, the gate drive circuit of switching transistor S1 includes: power supply DRV_G1, power supply DRV_E1, resistors R28, R29, and R30, and the clamping diode is D9. The gate drive circuit of switching transistor S2 includes: power supply DRV_G2, power supply DRV_E2, resistors R31, R32, and R33, and the clamping diode is D8. The gate drive circuit of switching transistor S3 includes: power supply DRV_G3, power supply DRV_E3, resistors R34, R35, and R36, and the clamping diode is D11. The gate drive circuit of the switching transistor S2 includes: power supply DRV_G4, power supply DRV_E4, resistor R37, resistor R38 and resistor R39, and clamping diode D10.

[0078] like Figure 3 As shown, capacitors C14 and C15 are the input bus capacitors of the main power circuit 110. Diode D12 is the secondary rectifier diode of transformer T3. Diode D13 is the secondary rectifier diode of transformer T4. Diode D14 provides a freewheeling path for the output inductor L1 and suppresses output voltage spikes. Capacitors C16, C17, and C18 form a filter capacitor bank, which, together with the output inductor L1, forms a low-pass filter to convert the output current of the main power circuit 110 into a stable DC voltage.

[0079] like Figure 3 As shown, the first current detection circuit 121 includes a current transformer, CT1 is the primary input terminal of the current transformer and is electrically connected to the switching transistor S2, used to detect the first current; the second current detection circuit 122 includes a current transformer, CT2 is the primary input terminal of the current transformer and is electrically connected to the switching transistor S3, used to detect the second current.

[0080] It should be noted that the first current detection circuit 121 can also detect the current on the switching transistor S1, and the second current detection circuit 122 can also detect the current on the switching transistor S4.

[0081] Figure 4 A schematic structural diagram of a current detection unit, an overload protection circuit, and a short-circuit protection circuit is shown. Figure 5 This is a signal timing diagram for an overload protection circuit. Figure 6 This is a signal timing diagram of a short-circuit protection circuit.

[0082] like Figure 4 As shown, the first current detection circuit 121 includes a current transformer T1, diode D1 is a protection diode for current transformer T1, and diode D3 is a rectifier diode for current transformer T1; the second current detection circuit 122 includes a current transformer T2, diode D2 is a protection diode for current transformer T2, and diode D4 is a rectifier diode for current transformer T2. The signal conditioning circuit 123 includes resistors R1 and R2. Current transformers T1 and T2 can be DC pulse transformers.

[0083] It can be seen that the first current and the second current detected are added together and converted into voltage signals through resistors R1 and R2. After voltage division, a detection signal is generated. The detection signal is input to the first comparison unit 131 of the overload protection circuit 130 and the second comparison unit 141 of the short circuit protection circuit 140, respectively.

[0084] First comparison unit 131, as shown Figure 4 Comparator U1 in the middle, the second comparison unit is as follows Figure 4 Comparator U4 in the middle. The first voltage holding unit is as follows: Figure 4 The repeatable monostable multivibrator U2 and the integrator circuit are as follows: Figure 4 The resistor R10 and capacitor C4 are included. The hysteresis comparator includes comparator U3, resistors R12, R13, R11, and R14. The second voltage holding unit 142 is as follows: Figure 4 The repeatable monostable trigger U5 in the middle.

[0085] The working principle of the overload protection circuit 130 is as follows: like Figure 4As shown, the detection signal is filtered by a filter unit composed of resistor R5 and capacitor C1 and then input to the non-inverting input of comparator U1. The first voltage threshold is input to the inverting input of comparator U1. The first voltage threshold is generated by a reference voltage generation circuit composed of a 5V power supply, resistors R3 and R4, and is the voltage across resistor R4. Optionally, the resistance values ​​of resistors R3 and R4 can be 2 kΩ, then the first voltage threshold is 2.5V, corresponding to the first current threshold Iref1.

[0086] like Figure 5 As shown, the voltage of the detected signal is 2.5734V, which is greater than the first voltage threshold. The overload trigger signal output by comparator U1 is high, as shown by the 4.9929V voltage in the figure. Since the first current and the second current are the switching transistor currents, the voltage of the detected signal will change with the switching frequency of the switching transistor, thus the overload trigger signal is a pulse signal. The first voltage holding unit is used to hold and broaden the overload trigger signal to output a broadened pulse signal at a preset level. The holding time is determined by resistor R8 and capacitor C3. For example, when the switching period of the switching transistor is 10 microseconds, the holding time can be 200ms. It can be seen that the preset level is 4.5V, and the effective duration of the broadened pulse signal is greater than the effective duration of the overload trigger signal. When the broadened pulse signal is high, capacitor C4 starts charging through resistor R10, and the integrated voltage across capacitor C4 slowly rises and is input to the non-inverting input of comparator U3. The saturation voltage of the integrating capacitor is 3.5173V.

[0087] When the integral voltage rises to the upper threshold voltage of the hysteresis comparator, comparator U3 will output a high-level overload protection signal, as shown in the figure at 4.8393V, indicating that the hysteresis comparator output is in an active overload protection state. When the integral voltage drops from the upper threshold voltage to the lower threshold voltage, comparator U3 will output a low-level overload protection signal, indicating that the hysteresis comparator output is in an inactive overload protection state.

[0088] like Figure 4 As shown, the upper threshold voltage and the lower threshold voltage satisfy the following relationships: ;

[0089] Among them, V H V is the upper threshold voltage. L V is the lower threshold voltage. u3- The voltage at the inverting input of comparator U3 is generated by a reference voltage generation circuit consisting of a 5V power supply, resistors R12 and R13, with VCC being 5V.

[0090] like Figure 4As shown, the charging time and discharging time of capacitor C4 satisfy the following relationships: ;

[0091] Among them, t c The charging time t is for capacitor C4. f This is the discharge time of capacitor C4.

[0092] In this application, the upper threshold voltage can be 3.33V, and the lower threshold voltage can be 1.67V. This means that during the charge / discharge cycle, after capacitor C4 charges to 3.33V, the hysteresis comparator will set the overload protection signal to an active state and output it to block the PWM signal, thereby stopping the main power circuit 110. After the main power circuit 110 stops, no current flows through the switching transistor, so the voltage of the detection signal drops to a low level, meaning the input of comparator U1 switches to a low level, causing the overload trigger signal output by comparator U1 to switch to a low level. Correspondingly, the first voltage holding unit will switch to a low level after a delay, and capacitor C4 discharges through resistors R10 and R9. When the integrated voltage across capacitor C4 drops to 1.67V, the hysteresis comparator will set the overload protection signal to an inactive state and output it, the PWM signal blocking will be released, and the main power circuit 110 will restart. This process repeats to create the overload protection hiccup phenomenon.

[0093] It should be understood that the time required for the integrated voltage across capacitor C4 to charge to the upper threshold voltage can characterize the duration of allowable continuous overload, that is, the duration of the allowed delay to block the PWM signal under overload conditions. The time required for the integrated voltage across capacitor C4 to drop from the upper threshold voltage to the lower threshold voltage can characterize the effective duration of the overload protection signal, or the blocking duration of the PWM signal. In this application, the allowable delay to block the PWM signal is approximately 500 milliseconds (ms), and the blocking duration of the PWM signal is approximately 1.5 seconds.

[0094] It should be noted that because the detected signal is less than the second voltage threshold, the second comparison unit 141 and the second voltage holding unit 142 are not activated, meaning the short-circuit protection function will not be triggered. Figure 5 As shown.

[0095] The working principle of the short-circuit protection circuit 140 is as follows: like Figure 4As shown, the detection signal is filtered by a filter unit composed of resistor R17 and capacitor C5 and then input to the non-inverting input of comparator U4. The second voltage threshold is input to the inverting input of comparator U4. The second voltage threshold is generated by a reference voltage generation circuit composed of a 5V power supply, resistors R15 and R16, and is the voltage across resistor R16. Optionally, the resistance of resistor R15 can be 2kΩ and the resistance of resistor R16 can be 4.7kΩ, then the second voltage threshold is 3.5V, corresponding to the second current threshold Iref2.

[0096] like Figure 6 As shown, the voltage of the detection signal is 3.5899V, which is greater than the second voltage threshold, and the short-circuit trigger signal output by comparator U4 is high. Since the first current and the second current are the switching currents of the transistors, the voltage of the detection signal will change with the switching frequency of the transistors. Therefore, the short-circuit trigger signal is a pulse signal, and its voltage is 4.7612V. Because the short-circuit current is an instantaneous inrush current, the detection signal will also increase instantaneously, resulting in a small duty cycle for the short-circuit trigger signal output by comparator U4. The second voltage holding unit 142 is used to hold and broaden the short-circuit trigger signal to output a short-circuit protection signal, the voltage of which is 4.5V. The holding time is determined by resistor R20 and capacitor C7. For example, the holding time can be 1 second.

[0097] It can be seen that the effective duration of the short-circuit protection signal is longer than that of the short-circuit trigger signal, thus extending the blocking time of the PWM signal and allowing the short-circuit current to be fully discharged. When the short-circuit protection signal switches to a low level, the PWM signal blocking is released, and the main power circuit 110 restarts. If the short-circuit fault continues to occur, a hiccuping phenomenon will also occur. Compared with overload protection, once the short-circuit protection is triggered, it will quickly block the PWM signal to prevent the short-circuit current from increasing further, thereby protecting the stress on the switching transistor within a controllable range.

[0098] It should be noted that when a short-circuit fault occurs, the voltage of the detection signal will exceed the first voltage threshold, causing the comparator U1 to output a high-level overload trigger signal, such as... Figure 6 The voltage is 4.9929V. Correspondingly, the first voltage holding unit will hold and widen the overload trigger signal to output a widened pulse signal with a preset level of 4.5V. However, since the effective duration of the widened pulse signal is short, the capacitor C4 will not be fully charged, so the overload protection signal is in an invalid state and the overload protection function will not be triggered.

[0099] Among them, overload protection signals such as Figure 4 The OL_Delay_off signal and short-circuit protection signal are as follows: Figure 4The SC_Delay_off signal in the middle.

[0100] Figure 7 A schematic structural diagram of the logic control unit and PWM control chip is shown. Figure 7 As shown. The logic control unit 150 includes: diode D7, switching transistor Q3, resistor R23, resistor R25, and capacitor C13. Diode D7 performs an OR operation between the external blocking signal and the overload protection signal. When either the external blocking signal or the overload protection signal is active, switching transistor Q3 is turned on, pulling the voltage of the comp pin of the PWM control chip 160 to a low potential, thereby blocking the PWM signal. Resistors R23, R25, and capacitor C13 form a voltage conversion circuit for switching transistor Q3, converting the levels of the external blocking signal, overload protection signal, or short-circuit protection signal received by the logic control unit 150 into reliable operating signals suitable for the operation of switching transistor Q3, and improving the circuit's anti-interference capability. The external blocking signal is as follows: Figure 7 EN_L in the PWM control chip 160, such as Figure 7 U6 in the middle.

[0101] It should be noted that, Figure 4 The functions of diodes D5 and D6 are the same as those of diode D7, and will not be elaborated here.

[0102] like Figure 7 As shown, when any one of the external blocking signal, overload protection signal, and short-circuit protection signal is active (e.g., high level), the switching transistor Q3 is turned on, pulling the voltage of the comp pin of the PWM control chip 160 to a low level, thereby blocking the PWM signal. When all three signals are inactive (e.g., low level), the switching transistor Q3 is turned off, and the COMP pin of the PWM control chip 160 normally receives the feedback signal, the PWM signal is re-output, and the main power circuit 110 restarts. The voltage of the COMP pin determines the output of the PWM signal, thus controlling the on-time of the switching transistor in the main power circuit 110. The feedback signal output by the voltage feedback circuit 170 is as follows: Figure 7 The COMP signal in [the system / system].

[0103] like Figure 7As shown, resistor R24, capacitor C9, and switching transistors Q2 and Q1 constitute the soft-start circuit of the PWM control chip 160. The PWM control chip 160 starts operating after the VCC pin voltage reaches the startup threshold, causing capacitor C9 to charge through resistor R24, thus gradually increasing the voltage on the COMP pin. As the voltage on capacitor C9 gradually increases, the voltage on the COMP pin also increases, and the PWM signal duty cycle slowly increases from 0%. This process limits the charging current and output voltage rise rate of the power devices when the main power circuit 110 starts up, until capacitor C9 is fully charged, at which point the main power circuit 110 enters the normal operating state controlled by the voltage feedback circuit 170. The soft-start time is determined by the time constants of capacitor C9 and resistor R24. It should be noted that in the event of overload protection or short-circuit protection, switching transistor Q1 will also conduct, and capacitor C9 will begin to discharge, thus ensuring that each overload startup of the main power circuit 110 is a soft start. The switching frequency of the PWM control chip 160 is determined by resistor R26 and capacitor C11.

[0104] like Figure 7 As shown, resistors R21 and R22 and capacitor C8 form a voltage conversion circuit for the switching transistor Q1, which converts the levels of external blocking signals, overload protection signals or short-circuit protection signals received by the logic control unit 150 into reliable operating signals suitable for the operation of the switching transistor Q1, and improves the circuit's anti-interference capability.

[0105] Combination Figure 4 and Figure 7 It can be seen that the voltage CS signal across resistor R2 in the current detection unit 120 is filtered by the filter unit composed of resistor R27 and capacitor C12 before being input to the ISNS pin of the PWM control chip 160. The PWM control chip 160 compares the voltage on the ISNS pin with a fixed threshold voltage (e.g., 1V). When the CS voltage is greater than the fixed threshold voltage, the PWM control chip 160 resets the PWM latch to quickly force the output of the PWM signal to be turned off, thereby further improving the reliability of the auxiliary power supply.

[0106] Figure 8 A schematic diagram of a voltage feedback circuit is shown. (For example...) Figure 8 As shown, the voltage feedback circuit 170 includes: a sampling voltage divider network composed of resistors R46, R47, and R48, a Zener diode D15, a reference voltage source U8, and an isolation optocoupler U7. The Zener diode D15 can be a 24V Zener diode. The reference voltage source U8 can be a TL431.

[0107] The sampling voltage divider network is used to sample the output voltage of the main power circuit 110, and the sampled voltage is then divided and input to terminal 1 of the reference voltage source U8. The output voltage is as follows: Figure 8The voltage is 50V.

[0108] Because the sampling voltage exceeds the maximum allowable voltage difference Vka between the cathode and anode of the TL431 (37V), the TL431 needs to be powered through a Zener diode D15. Figure 8 As shown, Zener diode D15 is connected in parallel between the cathode of TL431 and ground, thus clamping the cathode voltage of TL431 to a maximum of 24V, lower than the maximum Vka value of TL431. Resistor R45 is the total current-limiting resistor for both Zener diode D15 and TL431, providing the current required for normal operation of Zener diode D15. Resistor R42 is the cathode current-limiting resistor for TL431, used to limit the maximum current flowing into TL431. Resistor R43 is the load resistor for TL431, thus providing the minimum operating current to ensure its regulated operation.

[0109] like Figure 8 As shown, TL431 compares the voltage across resistor R48 with a preset value and outputs a current signal to the isolation optocoupler U7 based on the comparison result. The isolation optocoupler U7 generates a feedback signal based on the current signal and outputs it through the calector pin to the COMP pin of the PWM control chip 160 to provide feedback on the output voltage of the main power circuit 110. For example, when the output voltage of the main power circuit 110 is stable, the voltage across resistor R48 is equal to the preset value. Therefore, TL431 outputs a stable current signal to the isolation optocoupler U7, and the feedback signal output by the isolation optocoupler U7 remains stable. This stabilizes the voltage at the COMP pin of the PWM control chip 160, keeps the duty cycle of the PWM signal stable, and consequently keeps the output voltage of the main power circuit 110 constant. For example, when the output voltage of the main power circuit 110 increases, the voltage across resistor R48 exceeds a preset value. This causes the current signal output from TL431 to the isolation optocoupler U7 to increase, and the feedback signal output from the isolation optocoupler U7 to increase accordingly. This, in turn, increases the voltage at the COMP pin of the PWM control chip 160. The PWM control chip 160 then reduces the duty cycle of the PWM signal, thereby decreasing the output voltage of the main power circuit 110. Conversely, when the output voltage of the main power circuit 110 decreases, the voltage across resistor R48 falls below a preset value. This causes the current signal output from TL431 to the isolation optocoupler U7 to decrease, and the feedback signal output from the isolation optocoupler U7 to decrease accordingly. This, in turn, decreases the voltage at the COMP pin of the PWM control chip 160, and the PWM control chip 160 increases the duty cycle of the PWM signal, thereby increasing the output voltage of the main power circuit 110.

[0110] Resistor R40 can be connected in parallel with the LED of the isolation optocoupler U7, thereby splitting the LED and improving the sensitivity of the optocoupler adjustment. Resistor R41 acts as a current-limiting resistor for the LED in the isolation optocoupler U7 to limit the maximum current flowing into the LED. Capacitor C19 and resistor R44 are used for proportional-integral (PI) regulation of the voltage feedback circuit 170 to optimize the frequency characteristics of the voltage feedback circuit 170 and balance its response speed and output voltage stability.

[0111] The auxiliary power supply provided in this application can be integrated with the main control system and has soft start, external control, and overcurrent hiccup functions, thereby improving the power supply reliability of the auxiliary power supply.

[0112] This application also provides an overcurrent protection method that can be applied to the auxiliary power supply as described in the foregoing embodiments. Figure 9 As shown, the overcurrent protection method may include S910 to S930.

[0113] It should be noted that this overcurrent protection method can be implemented by hardware and / or software modules within the auxiliary power supply, and this application does not impose any specific restrictions on it.

[0114] S910 generates a detection signal based on a first current and a second current. The first current is the input current of the first dual-transistor forward converter in the auxiliary power supply, and the second current is the input current of the second dual-transistor forward converter in the auxiliary power supply.

[0115] In this application, after the auxiliary power supply is powered on and soft-started, the first current and the second current can be detected, and the first current and the second current are superimposed and converted into a voltage signal to generate a detection signal. For details, please refer to the relevant content in the foregoing embodiments, which will not be repeated here.

[0116] S920 triggers an overload protection function when the voltage of the detected signal is greater than or equal to a first voltage threshold. The overload protection function includes: delaying and blocking the PWM signal from a second moment, where the second moment is the starting moment when the voltage of the detected signal is greater than or equal to the first voltage threshold.

[0117] In this application, after generating the detection signal, it can be determined whether the voltage of the detection signal is greater than or equal to a first voltage threshold. If the voltage of the detection signal is less than the first voltage threshold, it indicates that there is no overload fault; if the voltage of the detection signal is greater than or equal to the first voltage threshold, it indicates that there is an overload fault, thereby triggering the overload protection function, i.e., delaying and blocking the PWM signal. For details, please refer to the relevant operations in the foregoing embodiments, which will not be repeated here. The first voltage threshold can be set according to actual needs and is not limited here.

[0118] Optionally, the delay duration can be 500ms. The delay duration can be understood as the time interval from the second moment to the start moment of blocking the PWM signal.

[0119] Optionally, the overload protection function also includes: the blocking duration of the PWM signal is greater than or equal to a second preset value to ensure sufficient discharge of overload current. The second preset value can be set according to actual needs and is not limited here. For example, the blocking duration of the PWM signal is 1.5s.

[0120] S930, when the voltage of the detected signal is greater than or equal to the second voltage threshold, triggers the short-circuit protection function. The short-circuit protection function includes: blocking the PWM signal, and the time interval between the start time of blocking the PWM signal and the first time is less than or equal to the first preset value, where the first time is the start time when the voltage of the detected signal is greater than or equal to the second voltage threshold.

[0121] In one possible implementation, after generating the detection signal, it can be further determined whether the voltage of the detection signal is greater than or equal to a second voltage threshold. If the voltage of the detection signal is greater than or equal to the second voltage threshold, it indicates the presence of a short-circuit fault, thereby triggering the short-circuit protection function, i.e., quickly blocking the PWM signal. For details, please refer to the relevant operations in the aforementioned embodiments, which will not be elaborated further here. The second voltage threshold can be set according to actual needs, and will not be described in detail here.

[0122] In this implementation, S930 and S920 can operate in parallel, thus enabling a faster response to short-circuit faults.

[0123] In one possible implementation, if a detection signal is generated and its voltage is greater than or equal to a first voltage threshold, it can be further determined whether the voltage of the detection signal is greater than or equal to a second voltage threshold. If the voltage of the detection signal is greater than or equal to the second voltage threshold, a short-circuit protection function is triggered. If the voltage of the detection signal is less than the second voltage threshold, it indicates that only an overload fault exists, thereby triggering an overload protection function.

[0124] In this implementation, S920 is executed first, followed by S930.

[0125] In some embodiments, S930 can be executed first, followed by S920, to enable a rapid response to short-circuit faults. For example, after generating the detection signal, it can be further determined whether the voltage of the detection signal is greater than or equal to a second voltage threshold. If the detection signal is greater than or equal to the second voltage threshold, the short-circuit protection function is triggered; if the detection signal is less than the second voltage threshold, it can be further determined whether the voltage of the detection signal is greater than or equal to a first voltage threshold. If the detection signal is greater than or equal to the first voltage threshold, the overload protection function is triggered.

[0126] Optionally, the short-circuit protection function also includes: the blocking duration of the PWM signal is greater than or equal to a third preset value to ensure sufficient discharge of the short-circuit current. The third preset value can be set according to actual needs and is not limited here. For example, the blocking duration of the PWM signal is 1 second.

[0127] The term "multiple" in this document refers to two or more. It should be understood that in the description of this application, words such as "first" and "second" are used only for the purpose of distinguishing descriptions and should not be construed as indicating or implying relative importance or order.

[0128] It is understood that, in the embodiments of this application, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0129] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. An auxiliary power supply, characterized in that, It includes a main power circuit, a current detection unit, an overload protection circuit, a short circuit protection circuit, and a logic control unit. The main power circuit includes a first dual-transistor forward converter and a second dual-transistor forward converter. The current detection unit is electrically connected to the first dual-transistor forward converter, the second dual-transistor forward converter, the overload protection circuit, and the short-circuit protection circuit, respectively. The overload protection circuit and the short-circuit protection circuit are also electrically connected to the logic control unit, respectively. The input sides of the first dual-transistor forward converter and the second dual-transistor forward converter are connected in series, and the output sides of the first dual-transistor forward converter and the second dual-transistor forward converter are connected in parallel. The current detection unit is used to detect a first current and a second current, and output a detection signal based on the first current and the second current. The first current is the input current of the first dual-transistor forward converter, and the second current is the input current of the second dual-transistor forward converter. The overload protection circuit is used to receive the detection signal and output an overload protection signal after a delay when the voltage of the detection signal is greater than or equal to a first voltage threshold. The short-circuit protection circuit is used to receive the detection signal and output a short-circuit protection signal when the voltage of the detection signal is greater than or equal to a second voltage threshold. The time interval between the start output time of the short-circuit protection signal and a first time is less than or equal to a first preset value. The first time is the start time when the voltage of the detection signal is greater than or equal to the second voltage threshold, and the second voltage threshold is greater than the first voltage threshold. The logic control unit is used to output a control signal when it receives the overload protection signal or the short circuit protection signal. The control signal is used to block the pulse width modulation signal input to the main power circuit.

2. The auxiliary power supply according to claim 1, characterized in that, The overload protection circuit includes: a first comparison unit and a delay unit; The first input terminal of the first comparison unit is electrically connected to the current detection unit, the output terminal of the first comparison unit is electrically connected to the input terminal of the delay unit, and the output terminal of the delay unit is electrically connected to the input terminal of the logic control unit. The first comparison unit is configured to receive the detection signal through a first input terminal, receive the first voltage threshold through a second input terminal, and output an overload trigger signal when the voltage of the detection signal is greater than or equal to the first voltage threshold. The delay unit is used to output the overload protection signal after a delay based on the overload trigger signal.

3. The auxiliary power supply according to claim 2, characterized in that, The delay unit includes: an integrator circuit and a hysteresis comparator; The input terminal of the integrator circuit is electrically connected to the output terminal of the first comparison unit, the output terminal of the integrator circuit is electrically connected to the input terminal of the hysteresis comparator, and the output terminal of the hysteresis comparator is electrically connected to the input terminal of the logic control unit. The integrating circuit is used to integrate the overload trigger signal and output an integrated voltage. The hysteresis comparator is used to set the overload protection signal to an active state and output it when the integrated voltage rises to the upper threshold voltage during the integration processing period, and to set the overload protection signal to an inactive state and output it when the integrated voltage drops from the upper threshold voltage to the lower threshold voltage. The logic control unit is used to output the control signal when the overload protection signal is in an active state.

4. The auxiliary power supply according to claim 3, characterized in that, The integrating circuit includes an integrating capacitor, and the integrating voltage is the voltage across the integrating capacitor. During the charging and discharging cycle of the integrating capacitor, the time required for the integrated voltage to rise from zero voltage to the upper threshold voltage is the same as the delay time. The delay time is the time interval between the second moment and the start output moment of the overload protection signal in the effective state. The second moment is the start moment when the voltage of the detection signal is greater than or equal to the first voltage threshold. The time required for the integral voltage to drop from the upper threshold voltage to the lower threshold voltage is equal to the duration for which the overload protection signal is in an active state, and the duration for which the overload protection signal is in an active state is greater than or equal to a second preset value.

5. The auxiliary power supply according to claim 4, characterized in that, The delay unit further includes: a first voltage holding unit; The input terminal of the first voltage holding unit is electrically connected to the output terminal of the first comparison unit, and the output terminal of the first voltage holding unit is electrically connected to the input terminal of the integrating circuit. The first voltage holding unit is used to output a widened pulse signal with a preset level based on the overload trigger signal, wherein the effective duration of the widened pulse signal is longer than the effective duration of the overload trigger signal; The integrating circuit is used to integrate the broadened pulse signal and output the integrated voltage.

6. The auxiliary power supply according to claim 1, characterized in that, The short-circuit protection circuit includes: a second comparison unit and a second voltage holding unit; The first input terminal of the second comparison unit is electrically connected to the current detection unit, the output terminal of the second comparison unit is electrically connected to the input terminal of the second voltage holding unit, and the output terminal of the second voltage holding unit is electrically connected to the input terminal of the logic control unit. The second comparison unit is configured to receive the detection signal through a first input terminal, receive the second voltage threshold through a second input terminal, and output a short-circuit trigger signal when the voltage of the detection signal is greater than or equal to the second voltage threshold. The second voltage holding unit is used to output the short-circuit protection signal based on the short-circuit trigger signal. The effective duration of the short-circuit protection signal is greater than the effective duration of the short-circuit trigger signal, and the effective duration of the short-circuit protection signal is greater than or equal to a third preset value.

7. The auxiliary power supply according to claim 1, characterized in that, The current detection unit includes: a first current detection circuit, a second current detection circuit, and a signal conditioning circuit; The first current detection circuit is connected to the first dual-transistor forward converter, the second current detection circuit is connected to the second dual-transistor forward converter, and the signal conditioning circuit is connected to the first current detection circuit, the second current detection circuit, the overload protection circuit, and the short-circuit protection circuit, respectively. The first current detection circuit is used to detect the first current; The second current detection circuit is used to detect the second current; The signal conditioning circuit is used to sum the first current and the second current and convert them into a voltage signal to generate the detection signal.

8. The auxiliary power supply according to claim 1, characterized in that, The logic control unit is also used to receive external blocking signals; The logic control unit is configured to output the control signal when it receives any one of the overload protection signal, the short circuit protection signal, and the external blocking signal; The auxiliary power supply also includes: a pulse width modulation signal control chip, a voltage feedback circuit, and a drive circuit; The pulse width modulation signal control chip is connected to the logic control unit, the voltage feedback circuit, and the drive circuit, respectively. The pulse width modulation signal control chip is used to receive the control signal output by the logic control unit and block the pulse width modulation signal based on the control signal; The voltage feedback circuit is used to sample the output voltage of the main power circuit and output a feedback signal to the pulse width modulation signal control chip based on the output voltage. The feedback signal is used to adjust the duty cycle of the pulse width modulation signal. The driving circuit is used to enhance the driving capability of the pulse width modulation signal.

9. An overcurrent protection method, applied in an auxiliary power supply as described in any one of claims 1 to 8, characterized in that, The method includes: A detection signal is generated based on a first current and a second current, wherein the first current is the input current of the first dual-transistor forward converter in the auxiliary power supply, and the second current is the input current of the second dual-transistor forward converter in the auxiliary power supply. When the voltage of the detected signal is greater than or equal to a first voltage threshold, an overload protection function is triggered. The overload protection function includes: delaying and blocking the pulse width modulation signal from a second moment, where the second moment is the starting moment when the voltage of the detected signal is greater than or equal to the first voltage threshold. When the voltage of the detected signal is greater than or equal to a second voltage threshold, a short-circuit protection function is triggered. The short-circuit protection function includes: blocking the pulse width modulation signal, and the time interval between the start time of blocking the pulse width modulation signal and a first time is less than or equal to a first preset value, wherein the first time is the start time when the voltage of the detected signal is greater than or equal to the second voltage threshold, and the second voltage threshold is greater than the first voltage threshold.

10. The overcurrent protection method according to claim 9, characterized in that, The overload protection function further includes: the blocking duration of the pulse width modulation signal is greater than or equal to a second preset value; The short-circuit protection function also includes: the blocking duration of the pulse width modulation signal is greater than or equal to a third preset value.

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