Switch control method, circuit and switch power supply system

Abstract

The invention relates to a switch control method and circuit and a switch power supply system, the switch control circuit comprises a voltage monitoring module and a control module, the voltage monitoring module is coupled with the control module and a power device in the switch power supply circuit, and the control module is also coupled with the power device; when the power device is in the conducting state, the voltage monitoring module monitors the conducting voltage drop of the power device; when the conduction voltage drop is greater than a voltage threshold value, the control module generates a first control signal to control the power device to be in a turn-off state; the voltage monitoring module comprises a first switching device and a second switching device, the first end of the first switching device is coupled with the power device, the first end of the second switching device is coupled with the second end of the first switching device, and the second end of the second switching device is coupled with the grounding end; when the power device is in a turn-off state, the control module pulls down the voltage of the first end of the second switching device. By adopting the method, the switching power supply circuit is protected by turning off the power device.

Description

Technical Field

[0001] The present application relates to the technical field of switching power supplies, and in particular to a switching control method, circuit and switching power supply system. Background Art

[0002] With the long-term use and aging of the switching power supply circuit, the dynamic resistance of the power device will gradually increase due to electron migration, degradation or defects of semiconductor materials, and the dynamic resistance of the power device is closely related to the performance of the switching power supply circuit. When the dynamic resistance of the power device increases, the performance of the switching power supply circuit deteriorates, such as the increase of switching loss and conduction loss of the switching power supply circuit, the decrease of efficiency, the slow response speed, and the increase of voltage spikes during switching. More seriously, it may cause the power device to overheat and be damaged, causing explosion and serious losses. Therefore, it is very important to protect the switching power supply circuit. Summary of the invention

[0003] Based on this, it is necessary to provide a switch control method, circuit and switch power supply system for protecting the switch power supply circuit by shutting down the power device to address the above technical problems.

[0004] In a first aspect, the present application provides a switch control circuit, including a voltage monitoring module and a control module, wherein the voltage monitoring module is used to electrically connect the control module and a power device in a switch power supply circuit respectively, and the control module is also used to electrically connect the power device;

[0005] The voltage monitoring module is used to monitor the conduction voltage drop of the power device when the power device is in the on state;

[0006] The control module is used to generate a first control signal to control the power device to be in an off state when the on-state voltage drop is greater than a voltage threshold;

[0007] The voltage monitoring module includes a first switch device and a second switch device, wherein the first end of the first switch device is used to couple the power device, the first end of the second switch device is respectively coupled to the second end of the first switch device and the control module, and the second end of the second switch device is coupled to the ground;

[0008] The control module is further configured to lower the voltage of the first end of the second switch device when the power device is in the off state.

[0009] In some embodiments, the control module is further configured to control the working state of the power device according to the control logic of the switch control circuit when the on-state voltage drop is less than the voltage threshold.

[0010] In some embodiments, the control module includes a comparator, a logic unit and a driving unit, the non-inverting input terminal of the comparator is electrically connected to the second terminal of the first switching device, the inverting input terminal of the comparator is electrically connected to the voltage threshold, the logic unit is electrically connected to the output terminal of the comparator, the third terminal of the first switching device, the third terminal of the second switching device and the driving unit respectively, and the driving unit is also used to electrically connect the power device;

[0011] The logic unit is used to generate the first control signal when the output of the comparator is at a high level;

[0012] The driving unit is used to control the power device to be in an off state according to the first control signal.

[0013] In some embodiments, the logic unit is further configured to generate a second control signal according to the control logic of the switch control circuit when the on-state voltage drop is less than the voltage threshold;

[0014] The driving unit is further used to control the working state of the power device according to the second control signal;

[0015] The voltage monitoring module is used to monitor the on-state voltage drop of the power device when the second control signal is at a target level.

[0016] In some embodiments, the voltage monitoring module further includes a NOT gate; two ends of the NOT gate are electrically connected to the logic unit and the third end of the second switch device, respectively.

[0017] In some embodiments, the voltage monitoring module also includes a first resistor and a second resistor; the two ends of the first resistor are respectively electrically connected to the first end of the first switching device and the power device, and the two ends of the second resistor are respectively electrically connected to the second end of the first switching device and the ground.

[0018] In some embodiments, the switch control circuit also includes a junction field effect transistor, a gate of the junction field effect transistor is electrically connected to the ground, a source of the junction field effect transistor is electrically connected to the first end of the first switching device, and a drain of the junction field effect transistor is electrically connected to the power device.

[0019] In a second aspect, the present application further provides a switching power supply circuit and a switching control circuit as described in the first aspect, wherein the switching power supply circuit includes a power device.

[0020] In a third aspect, the present application further provides a switch control method, which is applied to the switch control circuit as described in the first aspect, and the method includes:

[0021] When the power device is in an on state, monitoring a conduction voltage drop of the power device;

[0022] When the on-state voltage drop is greater than a voltage threshold, generating a first control signal to control the power device to be in an off state;

[0023] When the power device is in the off state, the voltage of the first end of the second switch device is pulled down.

[0024] In some embodiments, the method further comprises:

[0025] When the on-state voltage drop is less than the voltage threshold, the working state of the power device is controlled according to the control logic of the switch control circuit.

[0026] In some embodiments, generating a first control signal to control the power device to be in an off state includes:

[0027] generating a first control signal;

[0028] Controlling the power device to be in an off state according to the first control signal;

[0029] The controlling the working state of the power device according to the control logic of the switch control circuit comprises:

[0030] generating a second control signal according to the control logic of the switch control circuit;

[0031] controlling the working state of the power device according to the second control signal;

[0032] When the power device is in the on state, monitoring the on-state voltage drop of the power device includes:

[0033] When the second control signal is at a target level, the on-state voltage drop of the power device is monitored.

[0034] In an embodiment of the present application, the switch control circuit includes a voltage monitoring module and a control module, the voltage monitoring module is respectively used to electrically connect the control module and the power device in the switch power supply circuit, and the control module is also used to electrically connect the power device; the voltage monitoring module is used to monitor the on-state voltage drop of the power device when the power device is in the on-state; the control module is used to generate a first control signal to control the power device to be in the off-state when the on-state voltage drop is greater than the voltage threshold; the voltage monitoring module includes a first switch device and a second switch device, the first end of the first switch device is used to couple the power device, the first end of the second switch device is respectively coupled to the second end of the first switch device and the control module, and the second end of the second switch device is coupled to the ground; the control module is also used to lower the voltage of the first end of the second switch device when the power device is in the off-state. When the power supply circuit of the power device is fixed, the on-state voltage drop of the power device is positively correlated with the dynamic resistance (i.e., on-state resistance) of the power device. The larger the dynamic resistance of the power device, the larger the on-state voltage drop of the power device. When the on-state voltage drop of the power device is greater than the voltage threshold, it indicates that the dynamic resistance of the power device is large. Therefore, the control module can control the power device to be in the off state, which can prevent the power device from continuing to work and causing the machine to explode, thereby protecting the switching power supply circuit. In addition, the first end of the second switching device is a high impedance point, and the second end of the second switching device is coupled to the ground. When the power device is in the off state, the voltage of the first end of the second switching device is pulled down to the ground, which can achieve false triggering protection and improve the reliability of the switching power supply circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the drawings required for use in the embodiments of the present application or related technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 is a structural schematic diagram of a switch control circuit provided in an embodiment of the present application;

[0037] Figure 2 is a structural schematic diagram of another switch control circuit provided in an embodiment of the present application;

[0038] Figure 3 is a structural schematic diagram of another switch control circuit provided in an embodiment of the present application;

[0039] Figure 4 is a structural schematic diagram of another switch control circuit provided in an embodiment of the present application;

[0040] Figure 5 is a structural schematic diagram of another switch control circuit provided in an embodiment of the present application;

[0041] Figure 6 is a structural schematic diagram of a switching power supply system provided in an embodiment of the present application;

[0042] Figure 7 It is a flow chart of a switch control method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0044] Figure 1 Schematic diagram of a switch control circuit provided in an embodiment of the present application. Figure 1 As shown, the switch control circuit may include a voltage monitoring module and a control module. The voltage monitoring module is used to electrically connect the control module and the power device in the switch power supply circuit, and the control module is also used to electrically connect the power device.

[0045] The power device may be a Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) (i.e., MOS tube), a triode, an Insulate-Gate Bipolar Transistor (IGBT), a Gallium Nitride Field-Effect Transistor (GaNFET) (i.e., GaN tube), or other types of power devices.

[0046] When the power device is in the on state, that is, during the on period of the power device, the voltage monitoring module can monitor the on-state voltage drop of the power device in real time, and then send the on-state voltage drop of the power device to the control module.

[0047] The control module can determine whether the on-state voltage drop of the power device is greater than the voltage threshold. When the on-state voltage drop of the power device is greater than the voltage threshold, it indicates that the dynamic resistance of the power device is large. A first control signal can be generated to control the power device to be in an off state, that is, a first control signal is generated to immediately or immediately control the power device to be in an off state, and then the power device is kept in the off state until the switching power supply circuit is powered off or loses power.

[0048] The on-state voltage drop of a power device may be different for different types of power devices. For example, when the power device is a MOS tube, the on-state voltage drop of the power device is the voltage drop between the source and drain of the MOS tube. For example, when the power device is a triode, the on-state voltage drop of the power device is the voltage drop between the emitter and collector of the triode.

[0049] The application scenarios of the switching power supply circuit are different, and the requirements for the efficiency, switching loss, conduction loss, response speed, maximum voltage, etc. of the switching power supply circuit may be different. Therefore, according to different application scenarios, a voltage threshold that meets the application scenario can be set, that is, the application scenarios of the switching power supply circuit are different, and the voltage threshold can be different, which can improve the flexibility and universality of the application of the switching power supply circuit.

[0050] The voltage monitoring module may include a first switching device Q1 and a second switching device Q2, wherein the first end of the first switching device Q1 is used to couple the power device, the first end of the second switching device Q2 is respectively coupled to the second end of the first switching device Q1 and the control module, and the second end of the second switching device Q2 is coupled to the ground.

[0051] The control module is further used to lower the voltage of the first end of the second switch device Q2 when the power device is in the off state.

[0052] The switch device may be a MOS tube, an IGBT, or other types of switch devices. The following figure takes the MOS tube as an example for explanation.

[0053] When the power device is in the off state, the control module can control the first switch device Q1 to be turned off and the second switch device Q2 to be turned on, so that the voltage at the first end of the second switch device Q2 can be pulled down to the ground voltage.

[0054] When the power device is in the on state, the control module can control the first switch device Q1 to be on and the second switch device Q2 to be off, so that the on-state voltage drop of the power device can be monitored through the first switch device Q1.

[0055] When the power supply circuit of the power device is fixed, the on-state voltage drop of the power device is positively correlated with the dynamic resistance of the power device. The larger the dynamic resistance of the power device, the larger the on-state voltage drop of the power device. When the on-state voltage drop of the power device is greater than the voltage threshold, it indicates that the dynamic resistance of the power device is large. Therefore, the control module can control the power device to be in the off state, which can prevent the power device from continuing to work and causing the machine to explode, thereby protecting the switching power supply circuit and improving the reliability of the switching power supply circuit. In addition, the first end of the second switching device Q2 is a high impedance point, and the second end of the second switching device Q2 is coupled to the ground. When the power device is in the off state, the voltage of the first end of the second switching device Q2 is pulled down to the ground, which can achieve false triggering protection and improve the reliability of the switching power supply circuit.

[0056] In some embodiments, when the on-state voltage drop of the power device is less than the voltage threshold, the control module may control the working state of the power device according to the control logic of the switch control circuit.

[0057] The control logic of the switch control circuit is the logic for controlling the working state of the power device under normal circumstances.

[0058] When the switching power supply circuit is powered on, the control module can normally control the working state of the power device according to the control logic of the switching control circuit. After the switching power supply circuit is powered on, when the power device is in the on state, the voltage monitoring module can monitor the on-state voltage drop of the power device in real time. The control module can determine whether the on-state voltage drop of the power device monitored by the voltage monitoring module is greater than the voltage threshold. When the on-state voltage drop of the power device is greater than the voltage threshold, it indicates that the dynamic resistance of the power device is large, and the power device can be controlled to be in the off state. When the on-state voltage drop of the power device is less than the voltage threshold, it indicates that the dynamic resistance of the power device is small, and the working state of the power device can continue to be controlled according to the control logic of the switching control circuit.

[0059] The working state of the power device may include an on state and an off state. Controlling the working state of the power device may be understood as controlling the power device to switch between the on state and the off state according to a certain rule.

[0060] It can be seen that when the on-state voltage drop of the power device is greater than the voltage threshold, the control module can control the power device to be in the off state, which can achieve protection of the switching power supply circuit. When the on-state voltage drop of the power device is less than the voltage threshold, the power device can work normally. Therefore, when the dynamic resistance of the power device is small, the normal operation of the power device can be guaranteed, and when the dynamic resistance of the power device is large, the switching power supply circuit can be protected.

[0061] Figure 2is a schematic diagram of another switch control circuit provided in an embodiment of the present application. Figure 2 The switch control circuit shown is composed of Figure 1 The switch control circuit shown is optimized. Figure 2 As shown, the control module may include a comparator C, a logic unit and a driving unit, wherein the non-inverting input terminal of the comparator C is electrically connected to the second terminal of the first switching device Q1, the inverting input terminal of the comparator C is electrically connected to the voltage threshold, the logic unit is electrically connected to the output terminal of the comparator C, the third terminal of the first switching device Q1, the third terminal of the second switching device Q2 and the driving unit, respectively, and the driving unit is also used to electrically connect the power device.

[0062] The logic unit is used to generate a first control signal when the output of the comparator C is at a high level. The driving unit is used to control the power device to be in an off state according to the first control signal.

[0063] When the power device is in the on state, comparator C can compare the on-state voltage drop of the power device input at the non-inverting input terminal with the voltage threshold input at the inverting input terminal. When the on-state voltage drop of the power device is greater than the voltage threshold, the comparator outputs a high level. When the on-state voltage drop of the power device is less than the voltage threshold, the comparator outputs a low level.

[0064] The logic unit can detect the output of the comparator C. When the output of the comparator C is at a high level, it indicates that the on-state voltage drop of the power device is greater than the voltage threshold, and a first control signal can be generated, and then the first control signal can be sent to the driving unit. After the driving unit receives the first control signal, the power device can be controlled to be in an off state according to the first control signal. Exemplarily, the first control signal can be a low-level signal.

[0065] The logic unit may also output a first control signal to the first switch device Q1 to turn off the first switch device Q1, thereby stopping monitoring the conduction voltage drop of the power device and avoiding unnecessary voltage monitoring, thereby reducing the power consumption of the switch control circuit.

[0066] The logic unit may also control the second switch device Q2 to be turned on according to the first control signal to pull down the voltage of the first end of the second switch device Q2.

[0067] In some embodiments, the logic unit is further used to generate a second control signal according to the control logic of the switch control circuit when the on-state voltage drop is less than the voltage threshold. The drive unit is further used to control the working state of the power device according to the second control signal. The voltage monitoring module is used to monitor the on-state voltage drop of the power device when the second control signal is at a target level.

[0068] When the logic unit detects that the switching power supply circuit is powered on, a second control signal can be generated according to the control logic of the switch control circuit, and then the second control signal can be sent to the voltage monitoring module and the driving unit respectively. When the power device is in the on state and the output of the comparator C is low, that is, the on-state voltage drop of the power device is less than the voltage threshold, the logic unit can continue to generate the second control signal according to the control logic of the switch control circuit, and then the second control signal can be sent to the voltage monitoring module and the driving unit respectively. After the driving unit receives the second control signal, the working state of the power device can be controlled according to the second control signal. After receiving the second control signal, the voltage monitoring module can identify the level of the second control signal. When the second control signal is at the target level, it indicates that the power device is in the on state, and the on-state voltage drop of the power device can be monitored. When the second control signal is not at the target level, the monitoring of the on-state voltage drop of the power device can be stopped. Exemplarily, during the period when the second control signal is at a high level (that is, the target level is at a high level), the voltage monitoring module can monitor the on-state voltage drop of the power device.

[0069] Exemplarily, when the switching power supply circuit is powered on, the logic unit can generate a (Pulse Width Modulation, PWM) signal according to the control logic of the switch control circuit, and then control the working state of the power device according to the PWM signal. The drive unit can control the power device to be in the on state when the PWM signal is at a high level, and can control the power device to be in the off state when the PWM signal is at a low level. The voltage monitoring module can monitor the on-state voltage drop of the power device when the PWM signal is at a high level. The control logic of the switch control circuit may include information such as the period and duty cycle of the PWM signal.

[0070] Exemplarily, when the PWM signal is at a high level, the first switch device Q1 is turned on, the second switch device Q2 is turned off, and the voltage monitoring module can monitor the conduction voltage drop of the power device through the first switch device Q1. When the PWM signal is at a low level, the first switch device Q1 is turned off, the second switch device Q2 is turned on, and the voltage monitoring module can pull down the voltage of the first end of the second switch device Q2 to avoid false triggering.

[0071] It can be seen that the working states of the first switch device Q1 and the second switch device Q2 are opposite, that is, when the first switch device Q1 is turned on, the second switch device Q2 is turned off, and when the first switch device Q1 is turned off, the second switch device Q2 is turned on. Therefore, the control signals of the third terminal of the first switch device Q1 and the third terminal of the second switch device Q2 are opposite.

[0072] In one case, the logic unit outputs two signals to the voltage monitoring module, and the two signals are opposite. One signal can be output to the third end of the first switching device Q1, and the other signal can be output to the third end of the second switching device Q2, so as to ensure that the working states of the first switching device Q1 and the second switching device Q2 are opposite.

[0073] In another case, the signal output by the logic unit to the voltage monitoring module is a signal. The voltage monitoring module can directly send this signal to the third terminal of the first switch device Q1, and can also process this signal to obtain a signal opposite to this signal, and then send it to the third terminal of the second switch device Q2, so as to ensure that the working states of the first switch device Q1 and the second switch device Q2 are opposite.

[0074] For example, Figure 3 is a structural diagram of another switch control circuit provided in an embodiment of the present application. Figure 3 The switch control circuit shown is composed of Figure 2 The switch control circuit shown is optimized. Figure 3 As shown, the voltage monitoring module may further include a NOT gate N. Two ends of the NOT gate N are electrically connected to the logic unit and the third end of the second switch device Q2 respectively.

[0075] When the switching power supply circuit is powered on, the logic unit can generate a PWM signal according to the control logic of the switch control circuit. The driving unit can control the power device to turn on during the period when the PWM signal is at a high level, that is, the power device is in a conducting state. The voltage monitoring module is in a period when the PWM signal is at a high level, that is, the power device is in a conducting state, the first switch device Q1 is turned on, and the second switch device Q2 is turned off. The on-state voltage drop of the first switch device Q1 is small and can be ignored. Therefore, the on-state voltage drop of the power device can be determined as the voltage at the second end of the first switch device Q1. The comparator C compares the on-state voltage drop of the power device with the voltage threshold Vth. When the on-state voltage drop of the power device is less than the voltage threshold Vth, the comparator C outputs a low-level signal, and the logic unit continues to output the PWM signal. When the on-state voltage drop of the power device is greater than the voltage threshold Vth, the comparator C outputs a high level, the logic unit can continue to output a low-level signal, and the driving unit can control the power device to be continuously in the off state according to the low-level signal. At the same time, the first switch device Q1 is turned off, the second switch device Q2 is turned on, the positive input terminal of the comparator C is 0, the output of the comparator C is 0, and the logic unit can continue to output a low level signal.

[0076] When the PWM signal of the voltage monitoring module is at a low level, that is, the power device is in the off state, the first switch device Q1 is turned off, the second switch device Q2 is turned on, the positive input terminal of the comparator C is 0, the output of the comparator C is 0, and the logic unit can continue to output the PWM signal.

[0077] It can be seen that during the period when the output of the comparator is at a low level, the working logic of the logic unit maintains the previous working logic unchanged, that is, the first control signal originally generated continues to be generated, and the second control signal originally generated according to the control logic of the switch control circuit continues to be generated according to the control logic of the switch control circuit.

[0078] When the PWM signal is at a high level, the first switching device Q1 can monitor the on-state voltage drop of the power device. When the PWM signal is at a low level, or after the on-state voltage drop of the power device is greater than the voltage threshold, the second switching device Q2 can pull the positive input terminal of the comparator C to 0, thereby avoiding the situation where the positive input terminal of the comparator C is greater than the voltage threshold in the presence of interference or coupling, thereby achieving false triggering protection and improving the reliability of the switch control circuit.

[0079] Figure 4 is a structural diagram of another switch control circuit provided in an embodiment of the present application. Figure 4 The switch control circuit shown is composed of Figure 2 The switch control circuit shown is optimized. Figure 4 As shown, the voltage monitoring module may further include a first resistor R1 and a second resistor R2. The first resistor R1 has two ends electrically connected to the first end of the first switch device Q1 and the power device, and the second resistor R2 has two ends electrically connected to the second end of the first switch device Q1 and the ground.

[0080] When the switching power supply circuit is powered on, the logic unit can generate a PWM signal according to the control logic of the switch control circuit. The driving unit can control the power device to turn on during the period when the PWM signal is at a high level. During the period when the PWM signal is at a high level, the first switch device Q1 of the voltage monitoring module is turned on and the second switch device Q2 is turned off. The on-state voltage drop of the first switch device Q1 is small and can be ignored. Therefore, the on-state voltage drop of the power device can be determined as the voltage drop of the first resistor R1 and the second resistor R2. After the first resistor R1 and the second resistor R2 divide the on-state voltage drop of the power device, the voltage drop of the second resistor R2 is input to the positive input terminal of the comparator C. The comparator C compares the voltage drop of the second resistor R2 with the voltage threshold Vth. When the voltage drop of the second resistor R2 is less than the voltage threshold Vth, the comparator C outputs a low level, and the logic unit continues to output the PWM signal. When the voltage drop of the second resistor R2 is greater than the voltage threshold Vth, the comparator C outputs a high level, the logic unit continues to output a low level signal, and the driving unit controls the power device to be continuously turned off according to the low level signal. At the same time, the first switch device Q1 is turned off, the second switch device Q2 is turned on, the positive input terminal of the comparator C is 0, the output of the comparator C is 0, and the logic unit can continue to output a low level signal.

[0081] When the PWM signal of the voltage monitoring module is at a low level, the first switch device Q1 is turned off, the second switch device Q2 is turned on, the positive input terminal of the comparator C is 0, the output of the comparator C is 0, and the logic unit can continue to output the PWM signal.

[0082] For other detailed descriptions, please refer to the above related descriptions.

[0083] It can be seen that the on-state voltage drop of the power device is greater than the voltage threshold, which can be understood as the entire on-state voltage drop of the power device is greater than the voltage threshold, or can be understood as the partial on-state voltage drop of the power device is greater than the voltage threshold.

[0084] For different application scenarios, the resistance values ​​of the first resistor R1 and the second resistor R2 may be different, which can ensure that the voltage thresholds of different application scenarios are different.

[0085] Figure 5 is a structural diagram of another switch control circuit provided in an embodiment of the present application. Figure 5 The switch control circuit shown is composed of Figure 1 The switch control circuit shown is optimized. Figure 5 As shown, the switch control circuit may further include a junction field effect transistor Q3, the gate of the junction field effect transistor Q3 being electrically connected to the ground, the source of the junction field effect transistor Q3 being electrically connected to the first end of the first switch device Q1, and the drain of the junction field effect transistor being electrically connected to the power device.

[0086] In the case where the power device is a MOS tube, the drain of the junction field effect tube is electrically connected to the drain of the power device. The drain of the power device is electrically connected to the power supply. When the power device is in the off state, the drain voltage of the power device is the voltage of the power supply, which is generally high. According to the working characteristics of the junction field effect transistor (JFET) Q3, the voltage applied to the first switch device Q1 can be limited to a certain range, the power supply of the power device can be avoided from being directly applied to the first switch device Q1, and high-voltage isolation can be achieved.

[0087] When the power device is in the on state, the junction field effect transistor Q3 is turned on. The on-state voltage drop of the junction field effect transistor Q3 is small and can be ignored, so it does not affect the monitoring of the on-state voltage drop of the power device.

[0088] Since the junction field effect transistor Q3 has the function of isolating high voltage, the devices in the voltage monitoring module do not need to use high-voltage devices, but can use low-voltage devices. There is no need to add additional peripheral devices, which can simplify the circuit and be easy to integrate, improve the reliability of the switch control circuit, and reduce the cost of the switch control circuit.

[0089] Figure 6 Schematic diagram of a switching power supply system provided in an embodiment of the present application. Figure 6 As shown, the switching power supply system may include a switching power supply circuit and a switching control circuit. The switching power supply circuit may include a power device Q4.

[0090] For a detailed description of the switch control circuit, please refer to the above related description.

[0091] The switching power supply circuit can convert a first electrical signal into a second electrical signal. The first electrical signal is different from the second electrical signal.

[0092] The first electrical signal may be a direct current signal or an alternating current signal. The second electrical signal may be a direct current signal or an alternating current signal. The switching power supply circuit may perform direct current signal conversion or alternating current signal conversion, and may also perform alternating current to direct current conversion.

[0093] The first electrical signal may be a voltage electrical signal or a direct current electrical signal. The second electrical signal may be a voltage electrical signal or a current electrical signal. The switching power supply circuit may perform voltage conversion, current conversion, or conversion between voltage and current.

[0094] The first electrical signal is different from the second electrical signal. This may be that the signal types of the first electrical signal and the second electrical signal are different, or the values ​​of the first electrical signal and the second electrical signal are different, or both the signal types and values ​​of the first electrical signal and the second electrical signal are different.

[0095] Exemplarily, the first electrical signal may be a direct current voltage signal, and the second electrical signal may be a direct current signal.

[0096] Exemplarily, the first electrical signal may be a current electrical signal, and the second electrical signal may be an alternating current electrical signal.

[0097] Figure 7 is a flow chart of a switch control method provided in an embodiment of the present application. The switch control method can be applied to the above switch control circuit. Figure 7 As shown, the switch control method may include the following steps.

[0098] 701. When the power device is in an on state, monitor the on-state voltage drop of the power device.

[0099] 702. When the on-state voltage drop is greater than the voltage threshold, generate a first control signal to control the power device to be in an off state;

[0100] When the power device is in the off state, the voltage of the first terminal of the second switch device is pulled down.

[0101] In some embodiments, the switch control method may further include the following steps:

[0102] When the switching power supply circuit is powered on, or when the on-state voltage drop of the power device is less than the voltage threshold, the working state of the power device is controlled according to the control logic of the switch control circuit.

[0103] In some embodiments, a first control signal may be generated first, and then the power device may be controlled to be in an off state according to the first control signal.

[0104] In some embodiments, the second control signal may be generated first according to the control logic of the switch control circuit, and then the working state of the power device may be controlled according to the second control signal.

[0105] In some embodiments, when the second control signal is at a target level, the on-state voltage drop of the power device may be monitored.

[0106] When the power supply circuit of the power device is fixed, the on-state voltage drop of the power device is positively correlated with the dynamic resistance of the power device. The larger the dynamic resistance of the power device, the larger the on-state voltage drop of the power device. When the on-state voltage drop of the power device is greater than the voltage threshold, it indicates that the dynamic resistance of the power device is large. Therefore, the switch control circuit can control the power device to be in the off state, which can avoid serious losses caused by the continued operation of the power device, thereby protecting the switching power supply circuit.

[0107] For a detailed description of the above switch control method, reference may be made to the corresponding description of the above switch control circuit, which will not be repeated here.

[0108] It should be understood that the same, similar or corresponding contents in different embodiments may be referenced to each other.

[0109] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0110] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0111] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A switch control circuit, characterized in that: It includes a voltage monitoring module and a control module, wherein the voltage monitoring module is used to electrically connect the control module and the power device in the switch power supply circuit respectively, and the control module is also used to electrically connect the power device; The voltage monitoring module is used to monitor the conduction voltage drop of the power device when the power device is in the on state; The control module is used to generate a first control signal to control the power device to be in an off state when the on-state voltage drop is greater than a voltage threshold; The voltage monitoring module includes a first switch device and a second switch device, wherein the first end of the first switch device is used to couple the power device, the first end of the second switch device is respectively coupled to the second end of the first switch device and the control module, and the second end of the second switch device is coupled to the ground; The control module is further configured to lower the voltage of the first end of the second switch device when the power device is in the off state.

2. The switch control circuit according to claim 1, characterized in that: The control module is further configured to control the working state of the power device according to the control logic of the switch control circuit when the on-state voltage drop is less than the voltage threshold.

3. The switch control circuit according to claim 1 or 2, characterized in that: The control module comprises a comparator, a logic unit and a driving unit, wherein the non-inverting input terminal of the comparator is electrically connected to the second terminal of the first switch device, the inverting input terminal of the comparator is electrically connected to the voltage threshold, the logic unit is electrically connected to the output terminal of the comparator, the third terminal of the first switch device, the third terminal of the second switch device and the driving unit respectively, and the driving unit is also used to electrically connect the power device; The logic unit is used to generate the first control signal when the output of the comparator is at a high level; The driving unit is used to control the power device to be in an off state according to the first control signal.

4. The switch control circuit according to claim 3, characterized in that: The logic unit is further configured to generate a second control signal according to the control logic of the switch control circuit when the on-state voltage drop is less than the voltage threshold; The driving unit is further used to control the working state of the power device according to the second control signal; The voltage monitoring module is used to monitor the on-state voltage drop of the power device when the second control signal is at a target level.

5. The switch control circuit according to claim 3, characterized in that: The voltage monitoring module further includes a NOT gate; two ends of the NOT gate are electrically connected to the logic unit and the third end of the second switch device respectively.

6. The switch control circuit according to claim 3, characterized in that: The voltage monitoring module also includes a first resistor and a second resistor; two ends of the first resistor are electrically connected to the first end of the first switching device and the power device respectively, and two ends of the second resistor are electrically connected to the second end of the first switching device and the ground respectively.

7. The switch control circuit according to claim 1 or 2, characterized in that: The switch control circuit also includes a junction field effect transistor, a gate of the junction field effect transistor is electrically connected to the ground, a source of the junction field effect transistor is electrically connected to the first end of the first switch device, and a drain of the junction field effect transistor is electrically connected to the power device.

8. A switching power supply system, characterized in that: It comprises a switching power supply circuit and a switching control circuit as claimed in any one of claims 1 to 7, wherein the switching power supply circuit comprises a power device.

9. A switch control method, characterized in that: The method is applied to the switch control circuit according to any one of claims 1 to 7, and the method comprises: When the power device is in an on state, monitoring a conduction voltage drop of the power device; When the on-state voltage drop is greater than a voltage threshold, generating a first control signal to control the power device to be in an off state; When the power device is in the off state, the voltage of the first end of the second switch device is pulled down.

10. The method according to claim 9, characterized in that The method further comprises: When the on-state voltage drop is less than the voltage threshold, the working state of the power device is controlled according to the control logic of the switch control circuit.

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