Shutdown control circuit and switching power supply

Abstract

The application provides a shutdown control circuit and a switching power supply. The shutdown control circuit comprises a first switching module, a voltage detection module, a comparison module and a second switching module. The first switching module is electrically connected with the drain, the source and the substrate of a synchronous tube respectively. The comparison module is electrically connected with the voltage detection module and the second switching module respectively. The second switching module is electrically connected with a driving module. When the boost converter is shut down, the first switching module turns on the substrate of the synchronous tube and the source of the synchronous tube according to the gate driving voltage and the drain voltage of the synchronous tube. The voltage detection module outputs a first enable signal when the difference between the output voltage and the input voltage is greater than a preset value. The comparison module outputs a comparison signal to the second switching module according to the input voltage, the output voltage and the first enable signal. The second switching module switches to the first state according to the comparison signal, so that the power supply voltage is equal to the output voltage. The application can solve the problem of the output end backflowing current to the input end when the boost converter is shut down.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of switching power supply, and particularly relates to a shutdown control circuit and a switching power supply. BACKGROUND

[0002] In the field of power management of electronic devices, a boost converter (Boost circuit) as a core DC-DC conversion structure is widely used in display systems, portable terminals, industrial control and other scenarios. Its core function is to raise a lower input voltage to a higher output voltage to provide stable power supply for the subsequent load. With the improvement of circuit integration and energy efficiency requirements, the synchronous Boost circuit has gradually replaced the traditional asynchronous structure. Compared with the diode used in the non-synchronous circuit to realize the freewheeling, the synchronous Boost circuit replaces the freewheeling diode with a MOS tube, which can significantly reduce the conduction loss and improve the energy conversion efficiency. However, the synchronous Boost circuit lacking the output discharge function will store a large amount of electrical energy in the output end filter capacitor during shutdown, resulting in that the output voltage is maintained at a high level for a long time, which is prone to cause the problem of reverse current from the output end to the input end. SUMMARY

[0003] The application embodiment provides a shutdown control circuit and a switching power supply, which can solve the problem that the output voltage is maintained at a high level for a long time during shutdown of the boost converter, which is prone to cause the problem of reverse current from the output end to the input end.

[0004] In a first aspect, the application embodiment provides a shutdown control circuit, comprising a first switching module, a voltage detection module, a comparison module and a second switching module, the first switching module is electrically connected with the drain of a synchronous tube in a boost converter, the source of the synchronous tube and the substrate of the synchronous tube respectively, the comparison module is electrically connected with the voltage detection module and the second switching module respectively, and the second switching module is electrically connected with a driving module.

[0005] When the boost converter is shut down, the first switching module is used to turn on the substrate of the synchronous tube and the source of the synchronous tube according to the gate drive voltage and the drain voltage of the synchronous tube; the voltage detection module is used to output a first enable signal to the comparison module when the difference between the output voltage and the input voltage is greater than a preset value; the comparison module is used to output a comparison signal to the second switching module according to the input voltage, the output voltage and the first enable signal; and the second switching module is used to switch to a first state according to the comparison signal, so that the power supply voltage output by the second switching module to the driving module is equal to the output voltage.

[0006] In one possible implementation of the first aspect, the first switching module includes a first switching transistor and a second switching transistor. The gate of the first switching transistor is used to receive the gate drive voltage. The source of the first switching transistor and the gate of the second switching transistor are both used to be electrically connected to the drain of the synchronous transistor. The drain of the first switching transistor is electrically connected to the drain of the second switching transistor and the substrate of the synchronous transistor, respectively. The source of the second switching transistor is used to be electrically connected to the source of the synchronous transistor.

[0007] In one possible implementation of the first aspect, the voltage detection module includes a voltage detection unit and an enable output unit, wherein the enable output unit is electrically connected to the voltage detection unit and the comparison module, respectively.

[0008] The voltage detection unit is used to output a detection signal to the enable output unit when the difference between the output voltage and the input voltage is greater than a preset value; the enable output unit is used to output the first enable signal to the comparison module according to the detection signal.

[0009] In one possible implementation of the first aspect, the voltage detection unit includes a third switch, a fourth switch, a fifth switch, a sixth switch, a first resistor, and a second resistor. The gate of the third switch is used to receive a control signal. The source of the third switch is electrically connected to the second terminal of the second resistor. The drain of the third switch is electrically connected to the gate of the fourth switch, the drain of the fourth switch, the gate of the fifth switch, and the gate of the sixth switch. The sources of the fourth, fifth, and sixth switches are all grounded. The drain of the fifth switch is used to output a first current. The drain of the sixth switch is electrically connected to the second terminal of the first resistor and the enable output unit. The first terminal of the first resistor is used to receive the input voltage, and the first terminal of the second resistor is used to receive the output voltage.

[0010] In one possible implementation of the first aspect, the enable output unit includes a trigger, the input of which is electrically connected to the voltage detection unit, and the output of which is electrically connected to the comparison module.

[0011] In one possible implementation of the first aspect, the comparison module includes a comparator and a level conversion unit. The first input terminal of the comparator is used to receive the input voltage, the second input terminal of the comparator is used to receive the output voltage, the output terminal of the comparator is electrically connected to the level conversion unit, and the level conversion unit is electrically connected to the voltage detection module and the second switching module respectively. The level conversion unit is used to output the comparison signal to the second switching module according to the first enable signal.

[0012] In one possible implementation of the first aspect, the second switching module includes a seventh switch and an eighth switch, the gate of the seventh switch and the gate of the eighth switch are both electrically connected to the comparison module, the drain of the seventh switch is used to receive the input voltage, the source of the seventh switch is electrically connected to the source of the eighth switch and the driving module, and the drain of the eighth switch is used to receive the output voltage.

[0013] In one possible implementation of the first aspect, the power-off control circuit further includes a power consumption control module, which is electrically connected to the voltage detection module and the drive module respectively;

[0014] The power consumption control module is used to pull down the node voltage according to the first enable signal, the second enable signal, the power supply voltage, the output voltage and the first current output by the voltage detection module, wherein the node voltage is the voltage of the common terminal of the driving module and the power consumption control module.

[0015] In one possible implementation of the first aspect, the power consumption control module includes a first control unit, a first switching unit, and a second switching unit, wherein the first switching unit is electrically connected to the first control unit, the second switching unit, and the drive module, respectively.

[0016] The first control unit is configured to output a first control signal to the first switching unit based on the first current and the power supply voltage when the first enable signal is a high-level signal and the second enable signal is a low-level signal; the first switching unit is configured to turn on according to the first control signal and pull the node voltage low; the second switching unit is configured to turn on when both the first enable signal and the second enable signal are low-level signals and pull the node voltage low.

[0017] Secondly, embodiments of this application provide a switching power supply, including the shutdown control circuit described in any one of the first aspects.

[0018] The beneficial effects of the embodiments in this application compared with the prior art are:

[0019] The power-off control circuit provided in this application includes a first switching module, a voltage detection module, a comparison module, and a second switching module. When the boost converter is powered off, the first switching module switches to a first state based on the gate drive voltage and the drain voltage of the synchronous transistor, connecting the substrate and source of the synchronous transistor to isolate the output and input terminals. The voltage detection module receives the input and output voltages and outputs a first enable signal to the comparison module when the difference between the output and input voltages is greater than a preset value (the output voltage is still relatively large). The comparison module outputs a comparison signal to the second switching module based on the input voltage, output voltage, and the first enable signal. The second switching module switches to the first state based on the comparison signal, ensuring that the power supply voltage output by the second switching module to the drive module equals the output voltage, thus preventing the synchronous transistor from immediately turning off when the boost converter is powered off. Therefore, the shutdown control circuit provided in this application embodiment monitors the voltage difference between the output and input voltages in real time through a voltage detection module. Combined with the logic judgment of the comparison module, it can control the second switching module to switch to the first state when the boost converter is shut down but the output voltage remains at a high level (posing a risk of backflow). The output voltage then powers the drive module, preventing the synchronous transistor from immediately turning off when the output voltage is high. Simultaneously, the first switching module connects the substrate and source of the synchronous transistor, isolating the output and input terminals. Ultimately, this circuit blocks the potential current path from the output to the input during the shutdown phase when the output voltage is high, achieving reliable control without backflow during the boost converter shutdown process. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a circuit diagram of an existing boost converter that uses diode freewheeling;

[0022] Figure 2 This is a circuit diagram of an existing boost converter that uses two back-to-back MOSFETs;

[0023] Figure 3 This is a schematic diagram of an existing boost converter that achieves output and input isolation;

[0024] Figure 4 This is a schematic block diagram of a shutdown control circuit provided in one embodiment of this application;

[0025] Figure 5This is a circuit connection diagram of the first switching module provided in an embodiment of this application;

[0026] Figure 6 This is a circuit connection diagram of a voltage detection module provided in an embodiment of this application;

[0027] Figure 7 This is a circuit connection diagram of the comparison module and the second switching module provided in an embodiment of this application;

[0028] Figure 8 This is a circuit connection diagram of a power consumption control module provided in an embodiment of this application.

[0029] In the figure, 101 is the first switching module; 102 is the voltage detection module; 1021 is the voltage detection unit; 1022 is the enable output unit; 103 is the comparison module; 104 is the second switching module; 105 is the power consumption control module; 1051 is the first control unit; 1052 is the first switching unit; 1053 is the second switching unit; and 200 is the drive module. Detailed Implementation

[0030] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0031] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0032] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0033] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if [the described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [the described condition or event] is detected," or "in response to detection of [the described condition or event]."

[0034] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0035] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0036] In the field of power management for electronic devices, boost converters, as a core DC-DC conversion structure, are widely used in display systems, portable terminals, industrial control, and other scenarios. Their core function is to boost a lower input voltage to a higher output voltage, providing a stable power supply to downstream loads. For example... Figure 1 As shown, when the asynchronous Boost circuit is powered off, only the main switch M0 needs to be directly turned off. The energy stored in the inductor L can be discharged to zero naturally through the freewheeling diode D1. The output voltage VOUT gradually decreases with load consumption, and there is no risk of reverse current flowing from the output to the input. With the increasing demands for circuit integration and energy efficiency, synchronous Boost circuits have gradually replaced traditional asynchronous structures. Compared to asynchronous circuits that use diodes for freewheeling, synchronous Boost circuits use MOSFETs instead of freewheeling diodes, which can significantly reduce conduction losses and improve energy conversion efficiency. However, if a synchronous transistor rectification structure is used, attention needs to be paid to the power-down sequence. One existing design is as follows: Figure 2 As shown, two back-to-back MOSFETs are used, and complete input and output isolation can be achieved by controlling the turn-off of the isolation transistor M02. However, using two MOSFETs significantly increases the chip area. Another design is as follows... Figure 3 As shown, complete isolation between input and output can be achieved by controlling the Bulk terminal (substrate) of the synchronous transistor M01. When the voltage at the LX terminal is higher than VOUT, the Bulk terminal is connected to LX; when the main switch M0 is turned on and the voltage at LX is lower than VOUT, the Bulk terminal is connected to VOUT.

[0037] If the DC-DC converter has a discharge function, that is, it discharges VOUT when the power is off, so VOUT will drop quickly. However, if the DC-DC converter lacks an output discharge function, the output filter capacitor will store a large amount of energy when the power is off, causing the output voltage VOUT to remain at a high level for a long time, which can easily cause the problem of reverse current flowing from the output to the input.

[0038] To address the aforementioned issues, the power-off control circuit provided in this application includes a first switching module, a voltage detection module, a comparison module, and a second switching module. When the boost converter is powered off, the first switching module switches to a first state based on the gate drive voltage and the drain voltage of the synchronous transistor, connecting the substrate and source of the synchronous transistor to isolate the output and input terminals. The voltage detection module receives the input and output voltages and outputs a first enable signal to the comparison module when the difference between the output and input voltages is greater than a preset value (the output voltage is still relatively large). The comparison module outputs a comparison signal to the second switching module based on the input voltage, output voltage, and the first enable signal. The second switching module switches to the first state based on the comparison signal, ensuring that the power supply voltage output by the second switching module to the drive module equals the output voltage, thus preventing the synchronous transistor from immediately turning off when the boost converter is powered off. Therefore, the shutdown control circuit provided in this application embodiment monitors the voltage difference between the output and input voltages in real time through a voltage detection module. Combined with the logic judgment of the comparison module, it can control the second switching module to switch to the first state when the boost converter is shut down but the output voltage remains at a high level (posing a risk of backflow). The output voltage then powers the drive module, preventing the synchronous transistor from immediately turning off when the output voltage is high. Simultaneously, the first switching module connects the substrate and source of the synchronous transistor, isolating the output and input terminals. Ultimately, this circuit blocks the potential current path from the output to the input during the shutdown phase when the output voltage is high, achieving reliable control without backflow during the boost converter shutdown process.

[0039] To illustrate the technical solution described in this application, specific embodiments are provided below.

[0040] Figure 4 A schematic block diagram of a shutdown control circuit according to an embodiment of this application is shown. See also... Figure 4 As shown, the power-off control circuit includes a first switching module 101, a voltage detection module 102, a comparison module 103, and a second switching module 104. The first switching module 101 is electrically connected to the drain, source, and substrate Bulk of the synchronous transistor M01 in the boost converter, respectively. The comparison module 103 is electrically connected to the voltage detection module 102 and the second switching module 104, respectively. The second switching module 104 is electrically connected to the drive module 200, and the drive module 200 is electrically connected to the gate of the synchronous transistor M01.

[0041] Specifically, when the boost converter is powered off, the first switching module 101 switches to a first state based on the gate drive voltage PGATE and the drain voltage of the synchronous transistor M01, connecting the substrate Bulk of the synchronous transistor M01 and its source, thereby isolating the output and input terminals. The voltage detection module 102 receives the input voltage VIN and the output voltage VOUT, and outputs a first enable signal EN1 to the comparison module 103 when the difference between the output voltage VOUT and the input voltage VIN is greater than a preset value (the output voltage VOUT is still relatively large). The comparison module 103 outputs a comparison signal to the second switching module 104 based on the input voltage VIN, the output voltage VOUT, and the first enable signal EN1. The second switching module 104 switches to the first state based on the comparison signal, making the power supply voltage VSWP output by the second switching module 104 to the drive module 200 equal to the output voltage VOUT, thus preventing the synchronous transistor M01 from immediately turning off when the boost converter is powered off. Therefore, the shutdown control circuit provided in this application embodiment monitors the voltage difference between the output voltage VOUT and the input voltage VIN in real time through the voltage detection module 102, and combines this with the logic judgment of the comparison module 103. When the boost converter is shut down and the output voltage VOUT remains at a high level (posing a risk of backflow), the second switching module 104 is controlled to switch to the first state, i.e., the output voltage VOUT supplies power to the drive module 200, thus preventing the synchronous transistor M01 from immediately turning off when the output voltage VOUT is high. Simultaneously, the first switching module 101 connects the substrate Bulk of the synchronous transistor M01 to its source, isolating the output and input terminals. Ultimately, this circuit blocks the potential current path from the output terminal to the input terminal during the shutdown phase when the output voltage VOUT is high, achieving reliable control without backflow during the boost converter shutdown process.

[0042] It should be noted that when the boost converter is first powered on, the LX voltage is higher than the output voltage VOUT. The first switching module 101 switches to the second state based on the gate drive voltage PGATE and the drain voltage of the synchronous transistor M01, connecting the substrate Bulk of the synchronous transistor M01 and the drain of the synchronous transistor M01. After the boost converter is powered off, the output voltage VOUT is higher than the LX voltage, and the first switching module 101 switches to the first state, connecting the substrate Bulk of the synchronous transistor M01 and the source of the synchronous transistor M01.

[0043] It should be noted that the voltage detection module 102 is also used to output a level signal that is logically mutually exclusive with the first enable signal EN1 to the comparison module 103 when the difference between the output voltage VOUT and the input voltage VIN is less than a preset value (i.e., the output voltage VOUT has dropped to a safe threshold and the risk of backflow has been basically eliminated). This allows the comparison module 103 to control the second switching module 104 to switch to the second state. At this time, the power supply voltage VSWP of the drive module 200 switches from the output voltage VOUT to the input voltage VIN. After the power supply switching is completed, the drive module 200 uses the input voltage VIN as the power supply to drive the synchronous transistor M01 to turn off. In short, the second switching module 104 will only switch its state and synchronously switch the power supply of the drive module 200 when the output voltage VOUT drops to a safe threshold and the risk of backflow is basically eliminated, thereby driving the synchronous transistor M01 to complete the turn-off action. This avoids backflow caused by improper power supply switching or improper turn-off of the synchronous transistor M01 when the output voltage VOUT is high.

[0044] In one embodiment of this application, such as Figure 5 As shown, the first switching module 101 includes a first switching transistor M1 and a second switching transistor M2. The gate of the first switching transistor M1 is used to receive the gate drive voltage PGATE. The source of the first switching transistor M1 and the gate of the second switching transistor M2 are both used to be electrically connected to the drain of the synchronous transistor M01. The drain of the first switching transistor M1 is electrically connected to the drain of the second switching transistor M2 and the substrate Bulk of the synchronous transistor M01, respectively. The source of the second switching transistor M2 is used to be electrically connected to the source of the synchronous transistor M01.

[0045] Specifically, in the first switching module 101, the first switch M1 and the second switch M2 work together to achieve precise conduction control of the substrate Bulk of the synchronous transistor M01 and its source / drain, providing crucial support for power-off reverse current prevention. Specifically, the first switch M1 turns on or off based on the gate drive voltage PGATE, connecting the substrate Bulk of the synchronous transistor M01 to its drain. The second switch M2 turns on or off based on the drain voltage (i.e., LX voltage) of the synchronous transistor M01, connecting the substrate Bulk of the synchronous transistor M01 to its source. When the boost converter is powered off, the LX node voltage is lower than the output voltage VOUT, causing the first switching module 101 to switch to the first state, i.e., the first switch M1 is off and the second switch M2 is on. At this time, the substrate Bulk of the synchronous transistor M01 is electrically connected to its source, isolating the output and input terminals.

[0046] For example, designers can select the types of the first switch M1 and the second switch M2 according to the actual situation; that is, both can be fully controlled power devices such as metal-oxide-semiconductor field-effect transistors or insulated-gate bipolar transistors. For instance, both the first switch M1 and the second switch M2 can be selected as PMOS transistors.

[0047] It should be noted that the embodiments provided in this application only show one circuit structure as the first switching module 101, and do not mean that only this one circuit structure can realize the function of the first switching module 101. Other circuit structures that can realize this function can also be substituted, and are not limited to this.

[0048] Since the output voltage VOUT may be high, in order to correctly turn the synchronous transistor M01 on and off, a floating output voltage VOUT minus 5V needs to be generated based on the output voltage VOUT to drive the synchronous transistor M01 to turn on and off. However, at the beginning of power-on, since the input voltage VIN is greater than the output voltage VOUT, the driver module 200 of the synchronous transistor M01 needs to select the input voltage VIN as the power supply; when the output voltage VOUT rises to a certain value, it switches to the output voltage VOUT as the power supply for the driver module 200 of the synchronous transistor M01.

[0049] Based on the dynamic power supply adaptation requirements of the aforementioned drive module 200, the shutdown control circuit also includes a voltage detection module 102, a comparison module 103, and a second switching module 104, such as... Figure 6 As shown, the voltage detection module 102 includes a voltage detection unit 1021 and an enable output unit 1022, which is electrically connected to the voltage detection unit 1021 and the comparison module 103 respectively.

[0050] Specifically, the voltage detection unit 1021 can receive the output voltage VOUT and the input voltage VIN, and output a detection signal to the enable output unit 1022 when the difference between the output voltage VOUT and the input voltage VIN is greater than a preset value (indicating that the output voltage VOUT is high and there is a risk of backflow). The enable output unit 1022 outputs a first enable signal EN1 to the comparison module 103 according to the detection signal, so that the comparison module 103 can operate according to the first enable signal EN1 and control the second switching module 104 to switch to the first state.

[0051] It should be noted that if the output voltage VOUT has dropped to the safety threshold, the enable output unit 1022 will output a level signal that is logically mutually exclusive with the first enable signal EN1 to the comparison module 103, so that the comparison module 103 controls the second switching module 104 to switch to the second state according to the level signal that is logically mutually exclusive with the first enable signal EN1.

[0052] In one embodiment of this application, such as Figure 6As shown, the voltage detection unit 1021 includes a third switch M3, a fourth switch M4, a fifth switch M5, a sixth switch M6, a first resistor R1, and a second resistor R2. The gate of the third switch M3 is used to receive control signals. The source of the third switch M3 is electrically connected to the second terminal of the second resistor R2. The drain of the third switch M3 is electrically connected to the gates of the fourth switch M4, the drain of the fourth switch M4, the gate of the fifth switch M5, and the gate of the sixth switch M6, respectively. The sources of the fourth switch M4, the fifth switch M5, and the sixth switch M6 are all grounded. The drain of the fifth switch M5 is used to output a first current IBIAS. The drain of the sixth switch M6 is electrically connected to the second terminal of the first resistor R1 and the enable output unit 1022, respectively. The first terminal of the first resistor R1 is used to receive the input voltage VIN, and the first terminal of the second resistor R2 is used to receive the output voltage VOUT.

[0053] Specifically, when the boost converter is powered off, the control signal PBIAS is pulled up to the input voltage VIN. If the output voltage VOUT is higher than a threshold voltage of the control signal, i.e., the difference between the output voltage VOUT and the input voltage VIN is greater than a preset value, then the third switch M3 is turned on. When the third switch M3 is turned on, current flows through the second resistor R2 and the third switch M3. The current is equal to (VOUT - Vgsm0 - VIN) / R2, where Vgsm0 is the difference between the gate and source voltages of the third switch M3, and the second resistor R2 is used for voltage-to-current conversion. Since the fourth switch M4 is connected in series with the third switch M3, the above current also flows through the fourth switch M4. Since the fourth switch M4, the fifth switch M5, and the sixth switch M6 form a current mirror, the current flowing through the sixth switch M6 is proportional to the above current. After passing through the first resistor R1 for current-to-voltage level conversion, a detection signal is output to the enable output unit 1022. These devices work together to convert the voltage relationship between the output voltage VOUT and the input voltage VIN into a detection signal, providing a reliable original detection basis for the subsequent enable output unit 1022 to generate the first enable signal EN1.

[0054] It should be noted that when the output voltage VOUT is lower than the turn-on voltage of the third switch M3, the fourth switch M4, the fifth switch M5, and the sixth switch M6 will not draw current and will not generate additional current consumption.

[0055] For example, designers can select the types of the third switch M3, the fourth switch M4, the fifth switch M5, and the sixth switch M6 according to the actual situation; that is, they can all be fully controllable power devices such as metal-oxide-semiconductor field-effect transistors or insulated-gate bipolar transistors. For example, the third switch M3 can be selected as a PMOS transistor, and the fourth switch M4, the fifth switch M5, and the sixth switch M6 can all be selected as NMOS transistors.

[0056] In one embodiment of this application, such as Figure 6 As shown, the enable output unit 1022 includes a trigger, the input terminal of which is electrically connected to the voltage detection unit 1021, and the output terminal of which is electrically connected to the comparison module 103.

[0057] Specifically, the trigger, as a key signal latching and buffering component, plays a crucial role in timing shaping and state locking of the detection signal output by the voltage detection unit 1021. When the input of the trigger receives the detection signal (reflecting the voltage difference between the output voltage VOUT and the input voltage VIN) from the voltage detection unit 1021, it performs synchronization processing on the signal based on its own triggering logic (such as edge triggering or level triggering), filtering out signal jitter caused by high-frequency noise or transient interference. This ensures that the first enable signal EN1 (or its mutual exclusion signal) output to the comparison module 103 has a stable level and clear timing boundaries, providing a reliable signal reference for the comparison module 103 to execute subsequent power switching logic, and ensuring precise synchronization between the power supply switching action and voltage state changes. The first enable signal EN1 can be set to a high-level signal, and its mutual exclusion signal can be a low-level signal.

[0058] For example, a Schmitt trigger can be selected, which has unique hysteresis characteristics (i.e., the trigger thresholds are different when the input signal rises and falls). This allows the Schmitt trigger to effectively filter out small fluctuations or noise interference in the signal when receiving the detection signal output by the voltage detection unit 1021. That is, when the input signal fluctuates slightly near the threshold, the output signal will not change frequently, but will remain stable. Since the voltage difference between the output voltage VOUT and the input voltage VIN may fluctuate momentarily near the switching threshold due to load fluctuations or load noise interference, the hysteresis characteristic of the Schmitt trigger can prevent the enable signal from being falsely triggered by these non-substantial changes. This ensures that the output state of the first enable signal EN1 (or its mutual exclusion signal) only switches when the voltage difference actually crosses the stable threshold, thereby providing a more stable and reliable control basis for the comparison module 103 and further improving the anti-interference capability and operational accuracy of the entire shutdown control circuit under complex operating conditions.

[0059] It should be noted that the embodiments provided in this application only show one circuit structure as the voltage detection module 102, and do not represent that only this one circuit structure can realize the function of the voltage detection module 102. Other circuit structures that can realize this function can also be substituted, and are not limited to this.

[0060] In one embodiment of this application, such as Figure 7 As shown, the comparison module 103 includes a comparator and a level conversion unit. The first input terminal of the comparator is used to receive the input voltage VIN, and the second input terminal of the comparator is used to receive the output voltage VOUT. The output terminal of the comparator is electrically connected to the level conversion unit. The level conversion unit is electrically connected to the voltage detection module 102 and the second switching module 104 respectively. The level conversion unit is used to output a comparison signal to the second switching module 104 according to the first enable signal EN1.

[0061] Specifically, the comparator, as the core judgment component, receives the input voltage VIN through the first input terminal (positive input terminal) and the output voltage VOUT through the second input terminal (negative input terminal). It compares the voltage amplitudes of the two in real time and outputs a voltage comparison signal (e.g., if VIN > VOUT, the comparator outputs a high level; otherwise, it outputs a low level), directly reflecting the voltage relationship between the input and output. When the boost converter is first powered on, the input voltage VIN is greater than the output voltage VOUT, the comparator outputs a high level, and the voltage detection module 102 outputs a low level signal. The level conversion module controls the second switching module 104 to switch to the second state based on the high-level signal output by the comparator, so that the input voltage VIN supplies power to the drive module 200. When the boost converter is powered off, since the enable signal has disappeared, the comparator cannot output a correct voltage comparison signal. At this time, the level conversion unit outputs a comparison signal that meets the interface level requirements of the second switching module 104 based on the first enable signal EN1 (high-level signal) received from the voltage detection module 102, ensuring that the second switching module 104 switches to the first state, so that the output voltage VOUT supplies power to the drive module 200.

[0062] For example, the level conversion unit may include an inverter, enabling it to logically invert the voltage comparison signal output by the comparator, while adapting to the level standards between different modules. When the comparator outputs a high level, the inverter converts it to a low level; when the comparator outputs a low level, it converts it to a high level. This logical inversion achieves matching with the control logic of the second switching module 104.

[0063] It should be noted that the embodiments provided in this application only show one circuit structure as the comparison module 103, and do not mean that only this one circuit structure can realize the function of the comparison module 103. Other circuit structures that can realize this function can also be substituted, and are not limited to this.

[0064] In one embodiment of this application, such as Figure 7 As shown, the second switching module 104 includes a seventh switch M7 and an eighth switch M8. The gates of the seventh switch M7 and the eighth switch M8 are both electrically connected to the comparator module 103. The drain of the seventh switch M7 is used to receive the input voltage VIN. The source of the seventh switch M7 is electrically connected to the source of the eighth switch M8 and the drive module 200, respectively. The drain of the eighth switch M8 is used to receive the output voltage VOUT.

[0065] Specifically, both the seventh switch M7 and the eighth switch M8 function as switching devices, selectively switching the power supply to the drive module 200 through complementary conduction logic, providing a drive reference for the synchronous transistor M01 to adapt to different operating conditions. The seventh switch M7 controls the input voltage VIN path; when triggered by a comparison signal, it connects the input voltage VIN to the drive module 200, adapting to the low-voltage drive requirements during initial power-on or after the output voltage VOUT drops to a safe threshold. The eighth switch M8 controls the output voltage VOUT path; when triggered by a comparison signal, it connects the output voltage VOUT to the drive module 200, adapting to the high-voltage drive requirements when the output voltage VOUT is higher during power-off. The gates of the two switches share the comparison signal, forming a complementary operating mode, meaning only one switch is active at any given time. This allows for rapid switching of the power supply to the drive module 200 based on the comparison signal, precisely matching the drive requirements of the synchronous transistor M01 at different voltage stages, and providing hardware support for backflow prevention control and reliable shutdown.

[0066] It should be noted that the comparison signal output by the comparison module 103 includes a first signal and a second signal, wherein the first signal serves as the gate signal of the seventh switch M7, and the second signal serves as the gate signal of the eighth switch M8. When the boost converter is powered off, the first signal output by the comparison module 103 is a high-level signal, and the second signal is a low-level signal, causing the seventh switch M7 to turn off and the eighth switch M8 to turn on, so that the output voltage VOUT is connected to the drive module 200.

[0067] For example, designers can select the types of the seventh switch M7 and the eighth switch M8 according to the actual situation; that is, both can be fully controlled power devices such as metal-oxide-semiconductor field-effect transistors or insulated-gate bipolar transistors. For instance, both the seventh switch M7 and the eighth switch M8 can be selected as PMOS transistors.

[0068] It should be noted that the embodiments provided in this application only show one circuit structure as the second switching module 104, and do not mean that only this one circuit structure can realize the function of the second switching module 104. Other circuit structures that can realize this function can also be substituted, and are not limited to this.

[0069] In one embodiment of this application, such as Figure 8 As shown, the shutdown control circuit also includes a power consumption control module 105, which is electrically connected to the voltage detection module 102 and the drive module 200.

[0070] Specifically, the power consumption control module 105 pulls the node voltage low (pulls FGND to ground) based on the first enable signal EN1, the second enable signal EN, the power supply voltage VSWP, the output voltage VOUT, and the first current IBIAS output by the voltage detection module 102. This prevents the drive module 200 from operating normally even with a low input voltage VIN. The node voltage is the voltage at the common terminal of the drive module 200 and the power consumption control module 105, and the second enable signal EN is the signal that controls the power-on and power-off of the boost converter.

[0071] In one embodiment of this application, such as Figure 8 As shown, the power consumption control module 105 includes a first control unit 1051, a first switch unit 1052, and a second switch unit 1053. The first switch unit 1052 is electrically connected to the first control unit 1051, the second switch unit 1053, and the drive module 200, respectively.

[0072] Specifically, the first control unit 1051 outputs a first control signal to the first switching unit 1052 based on the first current IBIAS and the power supply voltage VSWP when the first enable signal EN1 is high (indicating that the output voltage VOUT is higher than the input voltage VIN by a threshold) and the second enable signal EN is low (indicating that the boost converter is off). The first switching unit 1052 is turned on according to the first control signal to pull down the node voltage, ensuring that the drive module 200 maintains the necessary functions while reducing redundant power consumption under this condition. When both the first enable signal EN1 and the second enable signal EN are low, indicating that the output voltage VOUT has dropped to a safe threshold and the boost converter is off, the second switching unit 1053 is turned on to pull down the node voltage. Since the power supply voltage VSWP is not connected to the output voltage VOUT, when the second switching unit 1053 is turned on, there is no path for the power supply voltage VSWP to ground through the second switching unit 1053, and therefore no additional current consumption is generated.

[0073] In one embodiment of this application, such as Figure 8As shown, the first control unit 1051 includes a third resistor R3, a first capacitor C1, a first Zener diode Z0, a first logic unit, and a ninth switch M9. The first terminal of the third resistor R3, the first terminal of the first capacitor C1, and the cathode of the first Zener diode Z0 are all used to receive the power supply voltage VSWP. The second terminal of the third resistor R3 is electrically connected to the second terminal of the first capacitor C1, the anode of the first Zener diode Z0, the drain of the ninth switch M9, and the first switch unit 1052, respectively. The gate of the ninth switch M9 is electrically connected to the output terminal of the first logic unit, and the source of the ninth switch M9 is electrically connected to the voltage detection module 102. The input terminal of the first logic unit is used to receive the first enable signal EN1 and the second enable signal EN.

[0074] Specifically, the first logic unit outputs a first logic signal based on the first enable signal EN1 and the second enable signal EN. The ninth switch M9 is turned on or off according to the first logic signal, thereby providing a first control signal to the first switching unit 1052. When the first enable signal EN1 is high and the second enable signal EN is low, the first logic signal output by the first logic unit is high, causing the ninth switch M9 to turn on, thereby providing a first control signal to the first switching unit 1052. The third resistor R3 and the first capacitor C1 form an RC filter network, which, together with the first Zener diode Z0, ensures the stability of the power supply voltage VSWP.

[0075] For example, designers can select the type of the ninth switch M9 according to the actual situation, that is, it can be a fully controllable power device such as a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor. For example, the ninth switch M9 can be selected as an NMOS transistor.

[0076] In one embodiment of this application, such as Figure 8 As shown, the first switching unit 1052 includes a tenth switching transistor M10, a fourth resistor R4, a second capacitor C2, and a second Zener diode Z1. The gate of the tenth switching transistor M10 is electrically connected to the first control unit 1051. The source of the tenth switching transistor M10 is electrically connected to the second terminal of the fourth resistor R4, the second terminal of the second capacitor C2, the anode of the second Zener diode Z1, the second switching unit 1053, and the drive module 200, respectively. The drain of the tenth switching transistor M10 is grounded. The first terminal of the fourth resistor R4, the first terminal of the second capacitor C2, and the cathode of the second Zener diode Z1 are all used to receive the output voltage VOUT.

[0077] Specifically, the tenth switching transistor M10 acts as a switching device, turning on according to the first control signal output by the first control unit 1051, thus pulling down the node voltage. The fourth resistor R4 and the second capacitor C2 form an RC filter network, which, together with the second Zener diode Z1, ensures the stability of the output voltage VOUT.

[0078] For example, designers can select the type of the tenth switch M10 according to the actual situation, that is, it can be a fully controllable power device such as a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor. For example, the tenth switch M10 can be selected as a PMOS transistor.

[0079] In one embodiment of this application, such as Figure 8 As shown, the second switching unit 1053 includes an eleventh switching transistor M11 and a second logic unit. The input terminal of the second logic unit is used to receive the first enable signal EN1 and the second enable signal EN. The output terminal of the second logic unit is electrically connected to the gate of the eleventh switching transistor M11. The drain of the eleventh switching transistor M11 is electrically connected to the first switching unit 1052 and the driving module 200, respectively. The source of the eleventh switching transistor M11 is grounded.

[0080] Specifically, the second logic unit outputs a second logic signal based on the first enable signal EN1 and the second enable signal EN, and the eleventh switch M11 is turned on or off according to the second logic signal. When both the first enable signal EN1 and the second enable signal EN are low-level signals, the second logic signal output by the second logic unit is a high-level signal, which turns on the eleventh switch M11, thereby pulling down the node voltage.

[0081] It should be noted that traditional solutions typically connect VSWP to VOUT. After the eleventh switch M11 is turned on, there will be a path from VSWP to ground through the eleventh switch M11, resulting in additional current consumption. However, this application isolates VSWP from VOUT, eliminating the path from VSWP to ground through the eleventh switch M11 and thus avoiding additional current consumption.

[0082] It should be noted that the embodiments provided in this application only show one circuit structure as the power consumption control module 105, and do not mean that only this one circuit structure can realize the function of the power consumption control module 105. Other circuit structures that can realize this function can also be substituted, and are not limited to this.

[0083] This application also discloses a switching power supply, including a boost converter and the aforementioned shutdown control circuit. By employing the shutdown control circuit, the switching power supply can prevent reverse current from flowing from the output to the input during the shutdown process, thereby improving the overall energy efficiency ratio and giving it a significant advantage in fields with stringent reliability and energy efficiency requirements, such as consumer electronics and industrial control.

[0084] Since the processing and functions implemented by the voltage converter in this embodiment are basically the same as the embodiments, principles and examples of the aforementioned shutdown control circuit, any details not covered in this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0085] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A power-off control circuit, characterized in that, The device includes a first switching module, a voltage detection module, a comparison module, and a second switching module. The first switching module includes a first switching transistor and a second switching transistor. The gate of the first switching transistor is used to receive a gate drive voltage. The source of the first switching transistor and the gate of the second switching transistor are both electrically connected to the drain of the synchronous transistor in the boost converter. The drain of the first switching transistor is electrically connected to the drain of the second switching transistor and the substrate of the synchronous transistor, respectively. The source of the second switching transistor is electrically connected to the source of the synchronous transistor. The comparison module is electrically connected to the voltage detection module and the second switching module, respectively. The second switching module is electrically connected to the drive module. When the boost converter is powered off, the first switching module is used to turn on the substrate and source of the synchronous transistor according to the gate drive voltage and the drain voltage of the synchronous transistor; the voltage detection module is used to output a first enable signal to the comparison module when the difference between the output voltage and the input voltage is greater than a preset value; the comparison module is used to output a comparison signal to the second switching module according to the input voltage, the output voltage and the first enable signal; the second switching module is used to switch to a first state according to the comparison signal, so that the power supply voltage output by the second switching module to the drive module is equal to the output voltage.

2. The shutdown control circuit according to claim 1, characterized in that, The voltage detection module includes a voltage detection unit and an enable output unit, and the enable output unit is electrically connected to the voltage detection unit and the comparison module respectively; The voltage detection unit is used to output a detection signal to the enable output unit when the difference between the output voltage and the input voltage is greater than a preset value; the enable output unit is used to output the first enable signal to the comparison module according to the detection signal.

3. The shutdown control circuit according to claim 2, characterized in that, The voltage detection unit includes a third switch, a fourth switch, a fifth switch, a sixth switch, a first resistor, and a second resistor. The gate of the third switch is used to receive a control signal. The source of the third switch is electrically connected to the second terminal of the second resistor. The drain of the third switch is electrically connected to the gates of the fourth switch, the drain of the fourth switch, the gates of the fifth switch, and the gates of the sixth switch. The sources of the fourth, fifth, and sixth switches are all grounded. The drain of the fifth switch is used to output a first current. The drain of the sixth switch is electrically connected to the second terminal of the first resistor and the enable output unit. The first terminal of the first resistor is used to receive the input voltage, and the first terminal of the second resistor is used to receive the output voltage.

4. The shutdown control circuit according to claim 2, characterized in that, The enable output unit includes a trigger, the input of which is electrically connected to the voltage detection unit, and the output of which is electrically connected to the comparison module.

5. The shutdown control circuit according to claim 1, characterized in that, The comparison module includes a comparator and a level conversion unit. The first input terminal of the comparator is used to receive the input voltage, the second input terminal of the comparator is used to receive the output voltage, and the output terminal of the comparator is electrically connected to the level conversion unit. The level conversion unit is electrically connected to the voltage detection module and the second switching module respectively. The level conversion unit is used to output the comparison signal to the second switching module according to the first enable signal.

6. The shutdown control circuit according to claim 1, characterized in that, The second switching module includes a seventh switch and an eighth switch. The gates of the seventh switch and the eighth switch are both electrically connected to the comparison module. The drain of the seventh switch is used to receive the input voltage. The source of the seventh switch is electrically connected to the source of the eighth switch and the driving module, respectively. The drain of the eighth switch is used to receive the output voltage.

7. The shutdown control circuit according to any one of claims 1-6, characterized in that, The power-off control circuit also includes a power consumption control module, which is electrically connected to the voltage detection module and the drive module respectively. The power consumption control module is used to pull down the node voltage according to the first enable signal, the second enable signal, the power supply voltage, the output voltage and the first current output by the voltage detection module, wherein the node voltage is the voltage of the common terminal of the driving module and the power consumption control module.

8. The shutdown control circuit according to claim 7, characterized in that, The power consumption control module includes a first control unit, a first switching unit, and a second switching unit. The first switching unit is electrically connected to the first control unit, the second switching unit, and the drive module, respectively. The first control unit is configured to output a first control signal to the first switching unit based on the first current and the power supply voltage when the first enable signal is a high-level signal and the second enable signal is a low-level signal; the first switching unit is configured to turn on according to the first control signal and pull the node voltage low; The second switching unit is used to turn on when both the first enable signal and the second enable signal are low-level signals, thereby pulling the node voltage low.

9. A switching power supply, characterized in that, Includes the shutdown control circuit as described in any one of claims 1-8.

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