Switch control method, switch control circuit and switch power supply system

Abstract

The invention relates to a switch control method, a switch control 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 a 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 supply, in particular to a switching control method, a switching control circuit and a switching power supply system. BACKGROUND

[0002] With the long-term use and aging of the switching power supply circuit, the dynamic resistance of the power device gradually increases due to electron migration, semiconductor material degradation or defects, and the dynamic resistance of the power device is closely related to the performance of the switching power supply circuit. In the case of increasing dynamic resistance of the power device, the performance of the switching power supply circuit is deteriorated, such as increasing switching loss and conduction loss of the switching power supply circuit, reducing efficiency, slowing response speed, increasing voltage peak during switching, etc. More seriously, it may cause the power device to overheat and damage, causing a machine explosion and causing serious losses. Therefore, how to protect the switching power supply circuit is very important.

[0003] In addition, in terms of switching power supply circuit protection, peak current control is a commonly used overcurrent protection control strategy. By detecting the inductor current peak value in real time to adjust the duty cycle, this direct current control method has faster response speed and can effectively prevent inductor saturation and power device overcurrent, achieving fast dynamic response and internal overcurrent protection. In order to realize peak current control, it is necessary to detect the current flowing through the power device in real time, and the commonly used method is to detect it through a sampling resistor Rcs or a current sensor Sense MOS. The sampling resistor Rcs sampling method has high precision, but an additional high-precision sampling resistor needs to be coupled with the power device, which also increases the loss, and the sampling resistor often needs a larger package to ensure heat dissipation, which will affect the integration of the entire circuit. In addition, the Layout design of the circuit board also needs special attention to avoid interference affecting the detection accuracy. Another commonly used way is to detect the current through the Sense MOS, which is conducive to improving the system integration and has no additional loss, and is suitable for high-current and integrated design. However, this sampling method is greatly affected by the process, and the precision is poor, and the cost of integrated Sense MOS is much higher than that of ordinary MOS.

[0004] Therefore, it is necessary to provide a new structure or control method to solve at least part of the above problems. SUMMARY

[0005] Therefore, it is necessary to provide a new structure or control method to solve at least part of the above problems.

[0006] In a first aspect, the application provides a switching control circuit, comprising a voltage monitoring module and a control module, the voltage monitoring module being configured to be electrically connected to the control module and a power device in a switching power supply circuit respectively, and the control module being further configured to be electrically connected to the power device;

[0007] The voltage monitoring module is configured to monitor a conduction voltage drop of the power device when the power device is in a conduction state.

[0008] The control module is configured to generate a first control signal to control the power device to be in an off state when the conduction voltage drop is greater than a voltage threshold.

[0009] The voltage monitoring module comprises a first switch device and a second switch device, a first end of the first switch device being configured to be coupled to the power device, a first end of the second switch device being configured to be coupled to a second end of the first switch device and the control module respectively, and a second end of the second switch device being configured to be coupled to a ground terminal.

[0010] The control module is further configured to pull down a voltage of the first end of the second switch device when the power device is in the off state.

[0011] In some embodiments, the control module is further configured to control a working state of the power device according to a control logic of the switching control circuit when the conduction voltage drop is less than the voltage threshold.

[0012] In some embodiments, the control module comprises a comparator, a logic unit and a driving unit, a non-inverting input terminal of the comparator being electrically connected to the second end of the first switch device, an inverting input terminal of the comparator being electrically connected to the voltage threshold, the logic unit being electrically connected to an output terminal of the comparator, a third end of the first switch device, a third end of the second switch device and the driving unit respectively, and the driving unit being further configured to be electrically connected to the power device.

[0013] The logic unit is configured to generate the first control signal when an output of the comparator is a high level.

[0014] The driving unit is configured to control the power device to be in the off state according to the first control signal.

[0015] In some embodiments, the logic unit is further configured to generate a second control signal according to the control logic of the switching control circuit when the conduction voltage drop is less than the voltage threshold.

[0016] The driving unit is further configured to control the working state of the power device according to the second control signal.

[0017] The voltage monitoring module is configured to monitor a conduction voltage drop of the power device when the second control signal is a target level.

[0018] In some embodiments, the voltage monitoring module further comprises a first NOT gate, and two ends of the first NOT gate are electrically connected to the logic unit and a third end of the second switch device, respectively.

[0019] In some embodiments, the voltage monitoring module further comprises a first resistor and a second resistor, and two ends of the first resistor are electrically connected to a first end of the first switch device and the power device, respectively, and two ends of the second resistor are electrically connected to a second end of the first switch device and a ground terminal, respectively.

[0020] In some embodiments, the switch control circuit further comprises a junction field effect transistor, a gate of the junction field effect transistor is electrically connected to a ground terminal, a source of the junction field effect transistor is electrically connected to a first end of the first switch device, and a drain of the junction field effect transistor is electrically connected to the power device.

[0021] In a second aspect, the application further provides a switching power supply circuit and the switch control circuit as described in the first aspect, and the switching power supply circuit comprises a power device.

[0022] In a third aspect, the application further provides a switch control method, which is applied to the switch control circuit as described in the first aspect, and the method comprises:

[0023] monitoring a conduction voltage drop of the power device when the power device is in a conduction state;

[0024] generating a first control signal to control the power device to be in an off state when the conduction voltage drop is greater than a voltage threshold value;

[0025] pulling down a voltage of a first end of the second switch device when the power device is in the off state.

[0026] In some embodiments, the method further comprises:

[0027] controlling a working state of the power device according to a control logic of the switch control circuit when the conduction voltage drop is less than the voltage threshold value.

[0028] In some embodiments, the generating a first control signal to control the power device to be in an off state comprises:

[0029] generating a first control signal;

[0030] controlling the power device to be in an off state according to the first control signal;

[0031] controlling, according to a control logic of the switch control circuit, an operating state of the power device includes:

[0032] generating a second control signal according to the control logic of the switch control circuit;

[0033] controlling, according to the second control signal, the operating state of the power device;

[0034] the monitoring of the on-state voltage drop of the power device in the case that the power device is in the on state includes:

[0035] the monitoring of the on-state voltage drop of the power device in the case that the second control signal is the target level.

[0036] An embodiment of the present application discloses a switch control circuit, which comprises a control module and a monitoring module, the control module being coupled to the monitoring module; the monitoring module comprises a current monitoring module, the current monitoring module comprising:

[0037] a high-voltage switch tube, a first end of which is coupled to the power device;

[0038] a fifth switch device, a first end of which is coupled to a second end of the high-voltage switch tube; and

[0039] a third resistor, a first end of which is coupled to a second end of the fifth switch device, and a second end of which is coupled to the ground;

[0040] wherein the control module comprises a comparison circuit, a first input end of the comparison circuit being coupled to the fifth switch device to obtain a sampling signal representing a current flowing through the power device, a second input end of the comparison circuit being coupled to a current reference signal, and an output end of the comparison circuit outputting a comparison result signal, the control module being configured to control an operating state of the power device according to the comparison result signal.

[0041] In an embodiment, the control module further comprises a logic unit and a driving unit, an input end of the logic unit being coupled to the output end of the comparison circuit, an output end of the logic unit being coupled to an input end of the driving unit, and the driving unit being configured to drive the power device.

[0042] In an embodiment, the current monitoring module further comprises a sixth switch device, a first end of the sixth switch device being coupled to the first input end of the comparison circuit, a second end of the sixth switch device being coupled to the ground, and a control end of the sixth switch device being coupled to the output end of the logic unit.

[0043] In an embodiment, when the sampling signal is less than the current reference signal, the control module controls the fifth switch device to be turned on and the sixth switch device to be turned off; and when the sampling signal is greater than the current reference signal, the control module controls the fifth switch device to be turned off and the sixth switch device to be turned on.

[0044] In an embodiment, the switch control circuit further comprises a high voltage supply module, the switch control circuit is provided with a drain pin, and the high voltage supply module is coupled to the drain pin.

[0045] In an embodiment, the monitoring module further comprises a voltage monitoring module configured to monitor a turn-on voltage drop of the power device when the power device is in the turn-on state, the voltage monitoring module comprises a first switch device and a second switch device, a first end of the first switch device is configured to be coupled to the power device, a first end of the second switch device is configured to be coupled to a second end of the first switch device and the control module respectively, and a second end of the second switch device is configured to be coupled to a ground terminal; and the control module is further configured to generate the first control signal to control the power device to be in the turn-off state when the turn-on voltage drop is greater than a voltage threshold.

[0046] Another embodiment of the present application further discloses a switch control method for the switch control circuit according to any one of the above, the switch control method comprises:

[0047] obtaining a sampling signal representing a current flowing through the power device, comparing the sampling signal with a current reference signal and generating a comparison result signal; and

[0048] controlling an operating state of the power device according to the comparison result signal.

[0049] In an embodiment, the current monitoring module further comprises a sixth switch device, a first end of the sixth switch device is coupled to the first input end of the comparison circuit, a second end of the sixth switch device is coupled to the ground, and a control end of the sixth switch device is coupled to the logic unit; and the switch control method further comprises: when the sampling signal is less than the current reference signal, the control module controls the fifth switch device to be turned on and the sixth switch device to be turned off; and when the sampling signal is greater than the current reference signal, the control module controls the fifth switch device to be turned off and the sixth switch device to be turned on.

[0050] In this embodiment, the switch control circuit includes 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 switching 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 a voltage threshold. The voltage monitoring module includes a first switching device and a second switching device. The first terminal of the first switching device is used to couple to the power device, and the first terminal of the second switching device is coupled to the second terminal of the first switching device and the control module, respectively. The second terminal of the second switching device is coupled to the ground terminal. The control module is also used to pull down the voltage of the first terminal of the second switching device when the power device is in the off state. With a fixed power supply circuit for the power device, the on-state voltage drop of the power device is positively correlated with its dynamic resistance (i.e., on-resistance). The larger the dynamic resistance, the larger the on-state voltage drop. When the on-state voltage drop exceeds the voltage threshold, it indicates a large dynamic resistance. Therefore, the control module can keep the power device in a turned-off state, preventing it from continuing to operate and causing a power failure, thus protecting the switching power supply circuit. Furthermore, the first terminal of the second switching device is a high-impedance point, while the second terminal is grounded. When the power device is in a turned-off state, pulling the voltage at the first terminal of the second switching device to ground can achieve false trigger protection, improving the reliability of the switching power supply circuit.

[0051] In another embodiment of the present invention, the switch control circuit includes a control module and a monitoring module, with the control module coupled to the monitoring module. The monitoring module includes a current monitoring module, which comprises a high-voltage switching transistor, a fifth switching device, and a third resistor. A first terminal of the high-voltage switching transistor is coupled to a power device. A first terminal of the fifth switching device is coupled to a second terminal of the high-voltage switching transistor. A first terminal of the third resistor is coupled to a second terminal of the fifth switching device, and a second terminal of the third resistor is grounded. The control module includes a comparator circuit, with a first input terminal coupled to the fifth switching device to obtain a sampling signal characterizing the current flowing through the power device, a second input terminal coupled to a current reference signal, and an output terminal outputting a comparison result signal. The control module is used to control the operating state of the power device based on the comparison result signal. The switch control circuit, switch control method, and switch power supply system proposed in this invention eliminate the need for an external sampling resistor coupled to the power device when implementing current protection, which is beneficial for improving chip integration, optimizing efficiency, and reducing costs. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a schematic diagram of a switch control circuit provided in an embodiment of this application;

[0054] Figure 2 This is a schematic diagram of another switch control circuit provided in an embodiment of this application;

[0055] Figure 3 This is a schematic diagram of another switch control circuit provided in the embodiments of this application;

[0056] Figure 4 This is a schematic diagram of another switch control circuit provided in the embodiments of this application;

[0057] Figure 5 This is a schematic diagram of another switch control circuit provided in the embodiments of this application;

[0058] Figure 6 This is a schematic diagram of the structure of a switching power supply system provided in an embodiment of this application;

[0059] Figure 7 This is a schematic diagram of a switch control circuit provided in an embodiment of this application;

[0060] Figure 8 This is a schematic diagram of another switch control circuit provided in an embodiment of this application;

[0061] Figure 9 This is a schematic diagram of the structure of a switching power supply system provided in an embodiment of this application;

[0062] Figure 10 This is a schematic flowchart of a switch control method provided in an embodiment of this application. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0064] Figure 1 This is a schematic diagram of a switch control circuit provided in an embodiment of this application. Figure 1As shown, the switching 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 devices in the switching power supply circuit, and the control module is also used to electrically connect the power devices.

[0065] Power devices can be metal-oxide-semiconductor field-effect transistors (MOSFETs), transistors, insulated-gate bipolar transistors (IGBTs), gallium nitride field-effect transistors (GaNFETs), or other types of power devices.

[0066] When the power device is in the on state, that is, during the power device's conduction period, 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.

[0067] The control module can determine whether the on-state voltage drop of the power device is greater than the voltage threshold. If 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. The first control signal can be generated to control the power device to be in the off state. That is, the first control signal is generated to immediately or immediately control the power device to be in the off state, and then the power device is kept in the off state until the switching power supply circuit is powered off or de-energized.

[0068] The on-state voltage drop of a power device may vary depending on its type. For example, when the power device is a MOSFET, the on-state voltage drop is the voltage drop between the source and drain terminals of the MOSFET. Similarly, when the power device is a transistor, the on-state voltage drop is the voltage drop between the emitter and collector terminals of the transistor.

[0069] Different application scenarios for switching power supply circuits may have different requirements for efficiency, switching losses, conduction losses, response speed, and maximum voltage. Therefore, voltage thresholds can be set to meet the specific application scenario, meaning that different application scenarios can lead to different voltage thresholds, which can improve the flexibility and versatility of switching power supply circuit applications.

[0070] The voltage monitoring module may include a first switching device Q1 and a second switching device Q2. The first terminal of the first switching device Q1 is used to couple to a power device. The first terminal of the second switching device Q2 is coupled to the second terminal of the first switching device Q1 and the control module, respectively. The second terminal of the second switching device Q2 is coupled to the ground terminal.

[0071] The control module is also used to pull down the voltage at the first terminal of the second switching device Q2 when the power device is in the off state.

[0072] The switching device can be a MOSFET, an IGBT, or other types of switching devices. The diagram below illustrates this using a MOSFET as an example.

[0073] When the power device is in the off state, the control module can control the first switching device Q1 to turn off and the second switching device Q2 to turn on, so that the voltage at the first terminal of the second switching device Q2 can be pulled down to ground.

[0074] When the power device is in the on state, the control module can control the first switching device Q1 to turn on and the second switching device Q2 to turn off, so that the on-state voltage drop of the power device can be monitored through the first switching device Q1.

[0075] With a fixed power supply circuit for the power device, the on-state voltage drop of the power device is positively correlated with its dynamic resistance. The larger the dynamic resistance, the larger the on-state voltage drop. When the on-state voltage drop exceeds the voltage threshold, it indicates a large dynamic resistance. Therefore, the control module can keep the power device in a turned-off state, preventing it from continuing to operate and causing a power failure. This protects the switching power supply circuit and improves its reliability. Furthermore, the first terminal of the second switching device Q2 is a high-impedance point, while its second terminal is grounded. When the power device is turned off, pulling the voltage at the first terminal of Q2 to ground provides false trigger protection, further enhancing the reliability of the switching power supply circuit.

[0076] In some embodiments, when the on-state voltage drop of the power device is less than the voltage threshold, the control module can control the operating state of the power device according to the control logic of the switch control circuit.

[0077] The control logic of the switch control circuit is the logic that controls the operating state of the power device under normal conditions.

[0078] When the switching power supply circuit is powered on, the control module can control the operating state of the power devices normally according to the control logic of the switching control circuit. After the switching power supply circuit is powered on, with the power devices in the on-state, the voltage monitoring module can monitor the on-state voltage drop of the power devices in real time. The control module can determine whether the on-state voltage drop monitored by the voltage monitoring module is greater than a voltage threshold. If 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. If 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 operating state of the power devices can continue to be controlled according to the control logic of the switching control circuit.

[0079] The operating states of power devices can include on and off states. Controlling the operating states of power devices can be understood as controlling the power devices to switch between on and off states according to a certain pattern.

[0080] As can be seen, 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, thus protecting 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 operate normally. Therefore, when the dynamic resistance of the power device is low, normal operation of the power device can be guaranteed, and when the dynamic resistance of the power device is high, protection of the switching power supply circuit can be achieved.

[0081] Figure 2 This is a schematic diagram of another switch control circuit provided in an embodiment of this 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 drive unit. The non-inverting input of the comparator C is electrically connected to the second terminal of the first switching device Q1, and the inverting input of the comparator C is electrically connected to the voltage threshold. The logic unit is electrically connected to the output of the comparator C, the third terminal of the first switching device Q1, the third terminal of the second switching device Q2, and the drive unit, respectively. The drive unit is also used to electrically connect to the power device.

[0082] A logic unit is used to generate a first control signal when the output of comparator C is high. A drive unit is used to control the power device to be in the off state according to the first control signal.

[0083] When the power device is in the on state, comparator C can compare the on-state voltage drop of the power device at the non-inverting input terminal with the voltage threshold at the inverting input terminal. If the on-state voltage drop of the power device is greater than the voltage threshold, the comparator outputs a high level; if the on-state voltage drop of the power device is less than the voltage threshold, the comparator outputs a low level.

[0084] The logic unit can detect the output of comparator C. When the output of comparator C is high, 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. This first control signal can then be sent to the drive unit. After receiving the first control signal, the drive unit can control the power device to be in a turned-off state according to the first control signal. For example, the first control signal can be a low-level signal.

[0085] The logic unit can also output a first control signal to the first switching device Q1 to turn off the first switching device Q1, thereby stopping the monitoring of the on-state voltage drop of the power device and avoiding unnecessary voltage monitoring, thus reducing the power consumption of the switching control circuit.

[0086] The logic unit can also control the second switching device Q2 to turn on according to the first control signal, so as to pull down the voltage at the first terminal of the second switching device Q2.

[0087] 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 a voltage threshold. The drive unit is further configured to control the operating state of the power device according to the second control signal. The voltage monitoring module is configured to monitor the on-state voltage drop of the power device when the second control signal is at a target level.

[0088] When the logic unit detects that the switching power supply circuit is powered on, it can generate a second control signal according to the control logic of the switching control circuit, and then send the second control signal to the voltage monitoring module and the drive unit respectively. When the power device is in the ON state and the output of comparator C is low (i.e., the on-state voltage drop of the power device is less than the voltage threshold), the logic unit can continue to generate a second control signal according to the control logic of the switching control circuit, and then send the second control signal to the voltage monitoring module and the drive unit respectively. After receiving the second control signal, the drive unit can control the operating state of the power device 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. For example, during the period when the second control signal is high (i.e., the target level is high), the voltage monitoring module can monitor the on-state voltage drop of the power device.

[0089] For example, 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 switching control circuit, and then control the operating 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 high, and control the power device to be in the off state when the PWM signal is low. The voltage monitoring module can monitor the on-state voltage drop of the power device when the PWM signal is high. The control logic of the switching control circuit can include information such as the period and duty cycle of the PWM signal.

[0090] For example, when the PWM signal is high, the first switching device Q1 is turned on and the second switching device Q2 is turned off. The voltage monitoring module can monitor the on-state voltage drop of the power device through the first switching device Q1. When the PWM signal is low, the first switching device Q1 is turned off and the second switching device Q2 is turned on. The voltage monitoring module can pull down the voltage at the first terminal of the second switching device Q2 to avoid false triggering.

[0091] It is evident that the operating states of the first switching device Q1 and the second switching device Q2 are opposite; that is, when the first switching device Q1 is on, the second switching device Q2 is off, and when the first switching device Q1 is off, the second switching device Q2 is on. Therefore, the control signals at the third terminal of the first switching device Q1 and the third terminal of the second switching device Q2 are opposite.

[0092] In one scenario, the logic unit outputs two signals to the voltage monitoring module. These two signals are opposite, allowing one signal to be output to the third terminal of the first switching device Q1 and the other signal to be output to the third terminal of the second switching device Q2, thus ensuring that the operating states of the first switching device Q1 and the second switching device Q2 are opposite.

[0093] In another scenario, the signal output by the logic unit to the voltage monitoring module is a single signal. The voltage monitoring module can directly send this signal to the third terminal of the first switching device Q1, or it can process this signal to obtain an inverse signal, which is then sent to the third terminal of the second switching device Q2, ensuring that the operating states of the first switching device Q1 and the second switching device Q2 are opposite.

[0094] For example, Figure 3 This is a schematic diagram of another switch control circuit provided in an embodiment of this application. Wherein, 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 first NOT gate N. The two ends of the first NOT gate N are electrically connected to the logic unit and the third terminal of the second switching device Q2, respectively.

[0095] When the switching power supply circuit is powered on, the logic unit generates a PWM signal according to the control logic of the switching control circuit. The drive unit can control the power device to conduct during the high-level period of the PWM signal, i.e., control the power device to be in the on state. During the high-level period of the PWM signal, i.e., when the power device is in the on state, the voltage monitoring module controls the first switching device Q1 to conduct and the second switching device Q2 to turn off. The on-state voltage drop of the first switching device Q1 is small and negligible; therefore, the on-state voltage drop of the power device can be determined as the voltage at the second terminal of the first switching device Q1. Comparator C compares the on-state voltage drop of the power device with the voltage threshold Vth. If the on-state voltage drop of the power device is less than the voltage threshold Vth, comparator C outputs a low-level signal, and the logic unit continues to output the PWM signal. If the on-state voltage drop of the power device is greater than the voltage threshold Vth, comparator C outputs a high-level signal, and the logic unit can continuously output a low-level signal. The drive unit can control the power device to remain in the off state based on this low-level signal. At the same time, the first switching device Q1 is turned off, the second switching device Q2 is turned on, the positive input of comparator C is 0, the output of comparator C is 0, and the logic unit can continue to output a low-level signal.

[0096] When the voltage monitoring module is in the low-level period of the PWM signal, that is, when the power device is in the off state, the first switching device Q1 is off, the second switching device Q2 is on, the positive input of comparator C is 0, the output of comparator C is 0, and the logic unit can continue to output the PWM signal.

[0097] As can be seen, during the period when the comparator output is low, the working logic of the logic unit remains unchanged. That is, the first control signal is generated first, and the second control signal is generated according to the control logic of the switch control circuit.

[0098] When the PWM signal is high, the first switching device Q1 can monitor the on-state voltage drop of the power device. When the PWM signal is low, or when the on-state voltage drop of the power device exceeds the voltage threshold, the second switching device Q2 can pull the positive input of the comparator C to 0. This can prevent the positive input of the comparator C from exceeding the voltage threshold in the presence of interference or coupling, thus achieving false trigger protection and improving the reliability of the switching control circuit.

[0099] Figure 4 This is a schematic diagram of another switch control circuit provided in an embodiment of this application. Wherein, 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 two ends of the first resistor R1 are electrically connected to the first terminal of the first switching device Q1 and the power device, respectively, and the two ends of the second resistor R2 are electrically connected to the second terminal of the first switching device Q1 and the ground terminal, respectively.

[0100] When the switching power supply circuit is powered on, the logic unit generates a PWM signal according to the control logic of the switching control circuit. The drive unit can control the power device to conduct during the high level of the PWM signal. During the high level of the PWM signal, the voltage monitoring module turns on the first switching device Q1 and turns off the second switching device Q2. The on-state voltage drop of the first switching 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. If 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. If 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 continuously outputs a low level signal, and the drive unit controls the power device to remain off according to this low level signal. At the same time, the first switching device Q1 is turned off, the second switching device Q2 is turned on, the positive input of comparator C is 0, the output of comparator C is 0, and the logic unit can continue to output a low-level signal.

[0101] When the PWM signal is low, the voltage monitoring module turns off the first switching device Q1 and turns on the second switching device Q2. The positive input of comparator C is 0, the output of comparator C is 0, and the logic unit can continue to output the PWM signal.

[0102] For further detailed descriptions, please refer to the relevant descriptions above.

[0103] It can be seen that when the on-state voltage drop of a power device is greater than the voltage threshold, it can be understood as the total on-state voltage drop of the power device being greater than the voltage threshold, or it can be understood as a portion of the on-state voltage drop of the power device being greater than the voltage threshold.

[0104] For different application scenarios, the resistance values ​​of the first resistor R1 and the second resistor R2 can be different to ensure that the voltage threshold is different for different application scenarios.

[0105] Figure 5 This is a schematic diagram of another switch control circuit provided in an embodiment of this application. Wherein, 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 (JFET) Q3, the gate of the JFET Q3 is electrically connected to ground, the source of the JFET Q3 is electrically connected to the first terminal of the first switching device Q1, and the drain of the JFET Q3 is electrically connected to the power device.

[0106] When the power device is a MOSFET, the drain of the JFET 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 power supply voltage, which is generally high. Based on the operating characteristics of the JFET Q3, the voltage applied to the first switching device Q1 can be limited to a certain range, preventing the power supply of the power device from being directly applied to the first switching device Q1, thus achieving high-voltage isolation.

[0107] 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.

[0108] Since the junction field-effect transistor Q3 has the function of isolating high voltage, the voltage monitoring module does not need to use high voltage devices, but low voltage devices can be used instead. No additional external devices are required, which can simplify the circuit and facilitate integration. It can also improve the reliability of the switching control circuit and reduce the cost of the switching control circuit.

[0109] Figure 6 This is a schematic diagram of a switching power supply system provided in an embodiment of this application. For example... 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.

[0110] For a detailed description of the switch control circuit, please refer to the relevant description above.

[0111] A switching power supply circuit can convert a first electrical signal into a second electrical signal. The first electrical signal and the second electrical signal are different.

[0112] The first electrical signal can be either a direct current (DC) or alternating current (AC) signal. The second electrical signal can also be either a DC or AC signal. The switching power supply circuit can convert DC signals to AC signals, and it can also convert AC signals to DC.

[0113] The first electrical signal can be a voltage signal or a direct current signal. The second electrical signal can be a voltage signal or a current signal. The switching power supply circuit can perform voltage conversion, current conversion, and conversion between voltage and current.

[0114] The first electrical signal is different from the second electrical signal. This can be because the first electrical signal and the second electrical signal are different in signal type, different in value, or both different in signal type and value.

[0115] For example, the first electrical signal can be a DC voltage signal, and the second electrical signal can be a DC current signal.

[0116] For example, the first electrical signal can be a current signal, and the second electrical signal can be an alternating current signal.

[0117] like Figure 7As shown, an embodiment of the present invention discloses a switch control circuit. The switch control circuit includes a control module and a monitoring module, with the control module coupled to the monitoring module. The monitoring module includes a current monitoring module, which includes a high-voltage switching transistor, a fifth switching device Q5, and a third resistor R3. In one embodiment, the high-voltage switching transistor is a junction field-effect transistor (JFET) Q3. The first terminal of the JFET Q3 is coupled to a power device Q4 (not shown in the figure). The control terminal of the JFET Q3 is coupled to ground or coupled to a preset voltage. The first terminal of the fifth switching device Q5 is coupled to the second terminal of the JFET Q3. The first terminal of the third resistor R3 is coupled to the second terminal of the fifth switching device Q5, and the second terminal of the third resistor R3 is coupled to ground. The control module includes a comparator circuit (not shown in the figure). The first input terminal of the comparator circuit is coupled to the fifth switching device Q5 to obtain a sampling signal characterizing the current flowing through the power device Q4. The second input terminal of the comparator circuit is coupled to a current reference signal, and the output terminal of the comparator circuit outputs a comparison result signal. The control module is used to control the operating state of the power device according to the comparison result signal. The operating state of the power device may include an on state and an off state. In one embodiment, when the sampled signal is less than the current reference signal, the control module allows the power device to continue conducting until the sampled signal reaches the current reference signal. When the sampled signal is greater than the current reference signal, the control module controls the power device to perform overcurrent protection. In one embodiment, when the sampled signal reaches the current reference signal, the control module can control the power device to turn off to achieve overcurrent protection. In one embodiment, when overcurrent protection is triggered, the control module controls the power device to be in the off state. In another embodiment, the control module is also used to control the operating state of the fifth switching device according to the comparison result signal. The first input terminal of the comparator circuit is coupled to the first terminal of the fifth switching device Q5, and the second input terminal of the comparator circuit is coupled to the current reference signal. The output terminal of the control module is coupled to the control terminal of the fifth switching device. When the sampled signal is less than the current reference signal, the control module controls the fifth switching device to be in the conducting state. When the sampled signal is greater than the current reference signal, the control module controls the fifth switching device to be in the off state. In one embodiment, the high-voltage switching transistor is one of a junction field-effect transistor (JFET), a high-voltage depletion-type metal-oxide-semiconductor (MODS) field-effect transistor (MODS), etc. In one embodiment, the high-voltage switching transistor is a switching transistor with a withstand voltage of 500V or higher.

[0118] In another embodiment, such as Figure 8As shown, the switch control circuit includes a control module and a monitoring module, with the control module coupled to the monitoring module. The monitoring module includes a current monitoring module, which comprises a junction field-effect transistor Q3, a fifth switching device Q5, and a third resistor R3. The control module includes a comparator circuit, a logic unit, and a drive unit. The first input terminal of the comparator circuit is coupled to the first terminal of the fifth switching device Q5, and the second input terminal of the comparator circuit is coupled to a current reference signal Vcs_ref. The output terminal of the comparator circuit outputs a comparison result signal. The input terminal of the logic unit is coupled to the output terminal of the comparator circuit, and the output terminal of the logic unit is coupled to the control terminal of the fifth switching device and the input terminal of the drive unit, respectively. The drive unit is used to drive the power device. The drive unit is used to control the operating state of the power device according to the comparison result signal. In another embodiment, the first input terminal of the comparator circuit is coupled to the second terminal of the fifth switching device Q5.

[0119] In one embodiment, such as Figure 9 As shown, the switch control circuit includes a control module and a monitoring module, with the control module coupled to the monitoring module. The monitoring module includes a current monitoring module, which comprises a junction field-effect transistor (JFET) Q3, a fifth switching device Q5, a third resistor R3, and a sixth switching device Q6. The first terminal of the sixth switching device Q6 is coupled to the first input terminal of the comparator circuit, the second terminal of the sixth switching device Q6 is coupled to ground, and the control terminal of the sixth switching device Q6 is coupled to a logic unit. The control module includes a comparator circuit, a logic unit, a driver unit, and a second NOT gate. The first input terminal of the comparator circuit is coupled to the first terminal of the fifth switching device Q5, the second input terminal of the comparator circuit is coupled to the current reference signal Vcs_ref, and the output terminal of the comparator circuit outputs the comparison result signal. The input terminal of the logic unit is coupled to the output terminal of the comparator circuit, and the output terminal of the logic unit is coupled to the control terminal of the fifth switching device, the input terminal of the second NOT gate, and the input terminal of the driver unit, respectively. The output terminal of the second NOT gate is coupled to the control terminal of the sixth switching device Q6. The driver unit is used to drive the power device; specifically, the driver unit controls the operating state of the power device based on the comparison result signal. In one embodiment, when the sampled signal is less than the current reference signal Vcs_ref, the control module controls the fifth switching device to turn on and the sixth switching device to turn off. The control module can acquire the sampled signal in real time. When the sampled signal is greater than the current reference signal Vcs_ref, the control module controls the fifth switching device to turn off and the sixth switching device to turn on. When the power device is in the off state, the voltage at the sampling signal terminal is cleared to zero to prevent false triggering of overcurrent protection.

[0120] In one embodiment, the switch control circuit further includes a high-voltage power supply module. The switch control circuit has a drain pin, and the high-voltage power supply module is coupled to the drain pin. In another embodiment, the switch control circuit is a chip. The switch control circuit has a drain pin, a drive pin, and a ground pin. The drain pin is used to couple to the drain of the power device, the drive pin is used to couple to the gate of the power device, and the ground pin is used to couple to ground. The power device is externally mounted on the chip. The high-voltage power supply module is used to charge the power supply terminal of the chip. When the supply voltage VDD of the power supply terminal reaches a certain value, the chip starts to work. When the chip requires high-voltage power, the switch control circuit can reuse a junction field-effect transistor Q3.

[0121] This invention proposes a switch control circuit that eliminates the need for an external sampling resistor and an integrated current sensor. When the power device is in the ON state, overcurrent protection is achieved by replicating the current iL flowing through the power device at a certain ratio. Combined with... Figure 8 and 9 The formula can be obtained as follows:

[0122] isense=iL*Rds_on / (Rsense+Rjfet)

[0123] Where isense is the current flowing through the third resistor, Rds_on is the on-resistance of the power device, Rsense is the resistance of the third resistor, and Rjfet is the on-resistance of the junction field-effect transistor. Based on the above formula, the sampling voltage Vsense can be obtained:

[0124] Vsense=iL*Rds_on*Rsense / (Rsense+Rjfet)

[0125] The sampling signal can correspond to the sampling voltage Vsense. In one embodiment, the sampling signal is equal to the sampling voltage. In another embodiment, the sampling signal is proportional to or positively correlated with the sampling voltage. In one embodiment of the present invention, the switch control circuit can compare the sampling signal and the current sampling signal to obtain a comparison result signal, and control the operating state of the power device according to the comparison result signal, thereby realizing the overcurrent protection control of the power device. The external circuit does not require a sampling resistor, which is beneficial to improving circuit integration and optimizing efficiency; at the same time, it also eliminates the need for an integrated current sensor, greatly reducing chip cost. The present invention effectively solves the problems existing in the prior art through circuit design such as internal integration of a third resistor chip.

[0126] In another embodiment, the switch control circuit includes a control module and a monitoring module, with the control module coupled to the monitoring module. The monitoring module includes a current monitoring module and a voltage monitoring module. The current monitoring module includes a junction field-effect transistor (JFET), a fifth switching device, and a third resistor. The voltage monitoring module is used to monitor the on-state voltage drop of the power device when it is in the on-state. The voltage monitoring module includes a first switching device and a second switching device. The first terminal of the first switching device is coupled to the power device, and the first terminal of the second switching device is coupled to the second terminal of the first switching device and the control module. The second terminal of the second switching device is coupled to ground. The control module is also 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 a voltage threshold. The switch control circuit in this embodiment can realize overcurrent protection of the power device and real-time monitoring and protection of the on-resistance of the power device, improving the reliability of the system. To further optimize the implementation scheme, in one embodiment, the voltage monitoring module may also include one or more technical features as described in any of the above embodiments to obtain better technical effects. In another embodiment, the monitoring module includes a current monitoring module and a voltage monitoring module. The current monitoring module and the voltage monitoring module can share a junction field-effect transistor Q3 to achieve their respective circuit functions.

[0127] Figure 10 This is a schematic flowchart of a switch control method provided in an embodiment of this application. This switch control method can be applied to the aforementioned switch control circuit. Figure 10 As shown, the switch control method may include the following steps.

[0128] 1001. Monitor the on-state voltage drop of the power device when it is in the on state.

[0129] 1002. When the on-state voltage drop is greater than the voltage threshold, a first control signal is generated to control the power device to be in the off state.

[0130] When the power device is in the off state, the voltage at the first terminal of the second switching device is lowered.

[0131] In some embodiments, the switch control method may further include the following steps:

[0132] 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 operating state of the power device is controlled according to the control logic of the switching control circuit.

[0133] In some embodiments, a first control signal may be generated first, and then the power device may be controlled to be in a shutdown state according to the first control signal.

[0134] In some embodiments, a second control signal can be generated first according to the control logic of the switch control circuit, and then the operating state of the power device can be controlled according to the second control signal.

[0135] In some embodiments, when the second control signal is at the target level, the on-state voltage drop of the power device can be monitored.

[0136] With the power supply circuit of the power device 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. 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 switching control circuit can control the power device to be in the off state, which can prevent the power device from continuing to work and causing serious damage, thereby protecting the switching power supply circuit.

[0137] An embodiment of the present invention also provides a switching control method for a switching control circuit as described in any of the preceding claims, the switching control method comprising:

[0138] Step S01: Acquire a sampled signal characterizing the current flowing through the power device, compare the sampled signal with the current reference signal, and generate a comparison result signal; and

[0139] Step S02: Control the operating state of the power device based on the comparison result signal.

[0140] In one embodiment, the switching control circuit includes a control module and a monitoring module, with the control module coupled to the monitoring module. The monitoring module includes a current monitoring module. The monitoring module acquires a sampled signal characterizing the current flowing through the power device. The control module compares the sampled signal with a current reference signal and generates a comparison result signal. The control module also controls the operating state of the power device based on the comparison result signal.

[0141] In another embodiment, the current monitoring module further includes a sixth switching device. The first terminal of the sixth switching device is coupled to the first input terminal of the comparator circuit, the second terminal of the sixth switching device is coupled to ground, and the control terminal of the sixth switching device is coupled to a logic unit. The switching control method further includes: when the sampled signal is less than the current reference signal, the control module controls the fifth switching device to turn on and the sixth switching device to turn off; and when the sampled signal is greater than the current reference signal, the control module controls the fifth switching device to turn off and the sixth switching device to turn on.

[0142] For a detailed description of the above switch control method, please refer to the corresponding description in the switch control circuit above, which will not be repeated here.

[0143] It should be understood that identical, similar, or corresponding content in different embodiments may be referenced to each other.

[0144] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0145] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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.

[0146] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A switch control circuit, characterized in that, It includes a voltage monitoring module and a control module. The voltage monitoring module is used to electrically connect the control module and the power devices in the switching power supply circuit, respectively. The control module is also used to electrically connect the power devices. 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 a turn-off state when the on-state voltage drop is greater than a voltage threshold. The voltage monitoring module includes a first switching device and a second switching device. The first end of the first switching device is used to couple to the power device. The first end of the second switching device is coupled to the second end of the first switching device and the control module, respectively. The second end of the second switching device is coupled to the ground terminal. The control module is also configured to lower the voltage at the first terminal of the second switching 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 operating 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 includes a comparator, a logic unit, and a drive unit. The non-inverting input of the comparator is electrically connected to the second terminal of the first switching device, and the inverting input of the comparator is electrically connected to the voltage threshold. The logic unit is electrically connected to the output of the comparator, the third terminal of the first switching device, the third terminal of the second switching device, and the drive unit. The drive unit is also used to electrically connect to the power device. The logic unit is configured to generate the first control signal when the output of the comparator is high. The driving unit is used to control the power device to be in a shutdown 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 configured to control the operating 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 the target level.

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

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

7. The switch control circuit according to claim 1 or 2, characterized in that, The switching control circuit further includes a junction field-effect transistor (JFET), the gate of which is electrically connected to ground, the source of which is electrically connected to the first terminal of the first switching device, and the drain of which is electrically connected to the power device.

8. A switch control circuit, characterized in that, The switch control circuit includes a control module and a monitoring module, with the control module coupled to the monitoring module; the monitoring module includes a current monitoring module, which further includes: A high-voltage switching transistor, the first terminal of which is used to couple to a power device; The fifth switching device, whose first terminal is coupled to the second terminal of the high-voltage switching transistor; and The third resistor has its first end coupled to the second end of the fifth switching device, and its second end coupled to ground. The control module includes a comparator circuit. The first input terminal of the comparator circuit is coupled to a fifth switching device to obtain a sampling signal characterizing the current flowing through the power device. The second input terminal of the comparator circuit is coupled to a current reference signal. The output terminal of the comparator circuit outputs a comparison result signal. The control module is used to control the operating state of the power device according to the comparison result signal.

9. The switch control circuit according to claim 8, characterized in that, The control module also includes a logic unit and a drive unit. The input of the logic unit is coupled to the output of the comparator circuit, and the output of the logic unit is coupled to the input of the drive unit. The drive unit is used to drive the power devices.

10. The switch control circuit according to claim 8, characterized in that, The current monitoring module also includes a sixth switching device. The first terminal of the sixth switching device is coupled to the first input terminal of the comparator circuit, the second terminal of the sixth switching device is coupled to ground, and the control terminal of the sixth switching device is coupled to the output terminal of the logic unit.

11. The switch control circuit according to claim 10, characterized in that, When the sampled signal is less than the current reference signal, the control module controls the fifth switching device to turn on and the sixth switching device to turn off; and when the sampled signal is greater than the current reference signal, the control module controls the fifth switching device to turn off and the sixth switching device to turn on.

12. The switch control circuit according to claim 8, characterized in that, The switch control circuit also includes a high-voltage power supply module. The switch control circuit has a drain pin, and the high-voltage power supply module is coupled to the drain pin.

13. The switch control circuit according to claim 8, characterized in that, The monitoring module also includes a voltage monitoring module, which is used to monitor the on-state voltage drop of the power device when the power device is in the on state. The voltage monitoring module includes a first switching device and a second switching device. The first terminal of the first switching device is used to couple to the power device, and the first terminal of the second switching device is coupled to the second terminal of the first switching device and the control module. The second terminal of the second switching device is coupled to the ground terminal. The control module is also 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 a voltage threshold.

14. A switching power supply system, characterized in that, It includes a switching power supply circuit and a switching control circuit as described in any one of claims 1-13, wherein the switching power supply circuit includes power devices.

15. A switching control method, characterized in that, The method is applied to the switch control circuit as described in any one of claims 1-7, and the method includes: When the power device is in the on state, monitor the on-state voltage drop of the power device; When the on-state voltage drop is greater than the voltage threshold, a first control signal is generated to control the power device to be in the off state; When the power device is in the off state, the voltage at the first terminal of the second switching device is pulled down.

16. The method according to claim 15, characterized in that, The method further includes: When the on-state voltage drop is less than the voltage threshold, the operating state of the power device is controlled according to the control logic of the switch control circuit.

17. A switching control method for a switching control circuit as described in any one of claims 8-13, characterized in that, The switch control method includes: Acquire a sampled signal characterizing the current flowing through the power device, compare the sampled signal with a current reference signal, and generate a comparison result signal; and The operating state of the power device is controlled based on the comparison result signal.

18. The switching control method according to claim 17, characterized in that, The current monitoring module also includes a sixth switching device. The first terminal of the sixth switching device is coupled to the first input terminal of the comparator circuit, the second terminal of the sixth switching device is coupled to ground, and the control terminal of the sixth switching device is coupled to a logic unit. The switching control method further includes: when the sampled signal is less than the current reference signal, the control module controls the fifth switching device to turn on and the sixth switching device to turn off; and when the sampled signal is greater than the current reference signal, the control module controls the fifth switching device to turn off and the sixth switching device to turn on.

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