Switching power supply circuit and electronic equipment

Abstract

The utility model discloses a switching power supply circuit and electronic equipment, the switching power supply circuit comprises a rectification module, a power supply module, a voltage transformation module, a first driving switch, a control module and a pull-down module, the power supply end of the control module is connected with the output end of the power supply module, and the output end of the control module is connected with the control end of the first driving switch. The pull-down module is connected with the input end of the rectification module and the power supply end of the control module, and the pull-down module is configured to pull down the potential of the power supply end of the control module when the input end of the rectification module does not receive the first voltage signal so as to discharge the power supply end of the switching power supply control chip. In this way, the switching power supply circuit can be prevented from being restarted.

Description

Technical Field

[0001] The present application relates to the field of electronic circuits, and in particular to a switching power supply circuit and an electronic device. Background Art

[0002] Switching power supply is a kind of power supply widely used in various electronic devices.

[0003] To ensure the reliability and safety of the product, there will be an anti-restart circuit in the switching power supply circuit. When the input AC power of the switching power supply is cut off, since the output rectification is a synchronous rectification scheme, it is very easy for the output current to be reversed, causing the switching power supply control chip to restart and the output voltage to restart briefly, causing program confusion and crashes in the back-end MCU, DSP and other programmable chips. If the back-end load is a buzzer, LED light or other device, the second restart will cause the buzzer to sound abnormally or the LED light to flash abnormally, which greatly affects the user experience. Utility Model Content

[0004] In order to solve the above problems, the present application provides a switching power supply circuit and an electronic device, which can prevent the switching power supply circuit from restarting.

[0005] A technical solution adopted in the present application is: to provide a switching power supply circuit, which includes: a rectifier module, the input end of the rectifier module is configured to receive a first voltage signal; a power supply module, the input end of the power supply module is connected to the output end of the rectifier module to receive a second voltage signal output by the rectifier module; a transformer module, the transformer module includes a primary winding and a secondary winding, the same-name end of the primary winding is connected to the input end of the power supply module, and the non-same-name end of the secondary winding is configured to output a third voltage signal; a first drive switch, the first end of the first drive switch is connected to the non-same-name end of the primary winding, and the second end of the first drive switch is grounded; a control module, the power supply end of the control module is connected to the output end of the power supply module, and the output end of the control module is connected to the control end of the first drive switch; a pull-down module, the pull-down module is connected to the input end of the rectifier module and the power supply end of the control module, and the pull-down module is configured to pull down the potential of the power supply end of the control module when the input end of the rectifier module does not receive the first voltage signal, so as to discharge the power supply end of the switching power supply control chip.

[0006] In one embodiment, the power supply module includes: a voltage divider unit, a first end of the voltage divider unit is configured to receive a second voltage signal, and a voltage divider node of the voltage divider unit is connected to the pull-down module; a first capacitor, a first end of the first capacitor is connected to the second end of the voltage divider unit, and the second end of the first capacitor is grounded.

[0007] In one embodiment, the pull-down module includes: a charge and discharge unit, the charge and discharge unit is connected to the voltage dividing node of the voltage dividing unit, the input end of the rectifier module and the common node, the charge and discharge unit is configured to charge the common node using the voltage of the voltage dividing node of the voltage dividing unit when the input end of the rectifier module does not receive the first voltage signal, and discharge the common node when the input end of the rectifier module receives the first voltage signal; a first voltage regulator tube, the cathode of the first voltage regulator tube is connected to the common node; a pull-down switch unit, the first end of the pull-down switch unit is connected to the power supply end of the control module, the second end of the pull-down switch unit is grounded, and the control end of the pull-down switch unit is connected to the anode of the first voltage regulator tube.

[0008] In one embodiment, the charge and discharge unit includes: a second capacitor, a first end of the second capacitor is connected to the voltage dividing node of the voltage dividing unit, and a second end of the second capacitor is grounded; a first resistor, a first end of the first resistor is connected to the first end of the second capacitor; a third capacitor, a first end of the third capacitor is connected to the second end of the first resistor, and a second end of the third capacitor is grounded; a first optocoupler, an anode of the primary diode of the first optocoupler is connected to the first input end of the rectifier module, a cathode of the primary diode of the first optocoupler is connected to the second input end of the rectifier module, a first end of the secondary side of the first optocoupler is connected to a common node, and a second end of the secondary side of the first optocoupler is grounded; a second optocoupler, an anode of the primary diode of the second optocoupler is connected to the second input end of the rectifier module, a cathode of the primary diode of the first optocoupler is connected to the first input end of the rectifier module, a first end of the secondary side of the second optocoupler is connected to the common node, and a second end of the secondary side of the second optocoupler is grounded.

[0009] In one embodiment, the charge and discharge unit also includes: a second voltage regulator tube, the cathode of the second voltage regulator tube is connected to the first end of the second capacitor, and the anode of the second voltage regulator tube is grounded; a second resistor, the first end of the second resistor is connected to the anode of the first voltage regulator tube, and the second end of the second resistor is connected to the control end of the pull-down switch unit; a third resistor, the first end of the third resistor is connected to the control end of the pull-down switch unit, and the second end of the third resistor is grounded.

[0010] In one embodiment, the pull-down switch unit includes: an NPN transistor, the base of the NPN transistor is connected to the second end of the second resistor, and the emitter of the NPN transistor is grounded; a fourth resistor, the first end of the fourth resistor is connected to the power supply end of the control module, and the second end of the fourth resistor is connected to the collector of the NPN transistor.

[0011] In one embodiment, the charge and discharge unit also includes: a fifth resistor, a first end of the fifth resistor is connected to the cathode of the primary diode of the first optocoupler; a first diode, an anode of the first diode is connected to the second end of the fifth resistor, and a cathode of the first diode is connected to the second input end of the rectifier module; a sixth resistor, a first end of the sixth resistor is connected to the cathode of the primary diode of the second optocoupler; a second diode, an anode of the second diode is connected to the second end of the sixth resistor, and a cathode of the second diode is connected to the first input end of the rectifier module.

[0012] In one embodiment, the transformer module also includes: an auxiliary winding, the same-name end of the auxiliary winding is grounded; a third diode, the anode of the third diode is connected to the non-same-name end of the auxiliary winding; a seventh resistor, the first end of the seventh resistor is connected to the cathode of the third diode, and the second end of the seventh resistor is connected to the power supply end of the control module.

[0013] In one embodiment, the transformer module also includes: a second drive switch, a first end of the second drive switch is connected to the same-name end of the secondary winding, and a second end of the second drive switch is grounded; a synchronous drive module, connected to the control end of the second drive switch; a fourth capacitor, a first end of the fourth capacitor is connected to the non-same-name end of the secondary winding, and a second end of the fourth capacitor is grounded.

[0014] In one embodiment, the switching power supply circuit further includes: a sampling module, a first end of the sampling module is connected to the second end of the first driving switch and the first feedback end of the control module, and a second end of the sampling module is grounded; a feedback module, a first end of the feedback module is connected to the non-same-name end of the secondary winding, and a second end of the feedback module is connected to the second feedback end of the control module.

[0015] Another technical solution adopted by the present application is to provide an electronic device, which includes the above-mentioned switching power supply circuit.

[0016] The switching power supply circuit provided by the present application includes: a rectifier module, wherein the input end of the rectifier module is configured to receive a first voltage signal; a power supply module, wherein the input end of the power supply module is connected to the output end of the rectifier module to receive a second voltage signal output by the rectifier module; a transformer module, wherein the transformer module includes a primary winding and a secondary winding, wherein the same-name end of the primary winding is connected to the input end of the power supply module, and the non-same-name end of the secondary winding is configured to output a third voltage signal; a first drive switch, wherein the first end of the first drive switch is connected to the non-same-name end of the primary winding, and the second end of the first drive switch is grounded; a control module, wherein the power supply end of the control module is connected to the output end of the power supply module, and the output end of the control module is connected to the control end of the first drive switch; a pull-down module, wherein the pull-down module is connected to the input end of the rectifier module and the power supply end of the control module, and wherein the pull-down module is configured to pull down the potential of the power supply end of the control module when the input end of the rectifier module does not receive the first voltage signal, so as to discharge the power supply end of the control module.

[0017] Through the above method, after the input AC power of the switching power supply is cut off, the voltage at the power supply end of the control module is pulled down by the pull-down module, so that the voltage at the power supply end of the control module drops to the undervoltage point, the control module stops working, and the switching power supply circuit no longer works, thereby preventing the switching power supply circuit from restarting due to the restart of the control module. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] in:

[0020] Figure 1 is a structural schematic diagram of a first embodiment of a switching power supply circuit provided by the present application;

[0021] Figure 2 is a structural schematic diagram of a second embodiment of a switching power supply circuit provided by the present application;

[0022] Figure 3 is a structural schematic diagram of a third embodiment of a switching power supply circuit provided by the present application;

[0023] Figure 4 is a structural schematic diagram of a fourth embodiment of a switching power supply circuit provided by the present application;

[0024] Figure 5 is a structural schematic diagram of a fifth embodiment of a switching power supply circuit provided by the present application;

[0025] Figure 6 It is a structural schematic diagram of an embodiment of an electronic device provided by the present application. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It will be appreciated that the specific embodiments described herein are only used to explain the present application, rather than to limit the present application. It should also be noted that, for ease of description, only some but not all structures related to the present application are shown in the drawings. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the art without making creative work are within the scope of protection of the present application.

[0027] The terms "first", "second", etc. in this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0028] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0029] See also Figure 1 , Figure 1 1 is a schematic diagram of the structure of the first embodiment of the switching power supply circuit provided by the present application. The switching power supply circuit 100 includes a rectifier module 10, a power supply module 20, a transformer module 30, a first drive switch 40, a control module 50 and a pull-down module 60.

[0030] Among them, the input end of the rectifier module 10 is configured to receive a first voltage signal S1; the input end of the power supply module 20 is connected to the output end of the rectifier module 10 to receive a second voltage signal S2 output by the rectifier module 10; the transformer module 30 includes a primary winding and a secondary winding, the same-name end of the primary winding is connected to the input end of the power supply module 20, and the non-same-name end of the secondary winding is configured to output a third voltage signal S3; the first end of the first drive switch 40 is connected to the non-same-name end of the primary winding, and the second end of the first drive switch 40 is grounded; the power supply end Vcc of the control module 50 is connected to the output end of the power supply module 20, and the output end Out of the control module 50 is connected to the control end of the first drive switch 40; the pull-down module 60 is connected to the input end of the rectifier module 10 and the power supply end Vcc of the control module 50, and the pull-down module 60 is configured to pull down the potential of the power supply end Vcc of the control module 50 when the input end of the rectifier module 10 does not receive the first voltage signal S1, so as to discharge the power supply end Vcc of the control module 50.

[0031] Optionally, the input end of the rectifier module 10 is configured to receive a first voltage signal S1 and output a second voltage signal S2 after rectifying the first voltage signal S1 .

[0032] Optionally, the input end of the power supply module 20 is connected to the output end of the rectifier module 10 to receive the second voltage signal S2 output by the rectifier module 10 and store the energy transmitted by the second voltage signal S2 to provide a start-up voltage for the control module 50 .

[0033] Optionally, the transformer module 30 includes a primary winding and a secondary winding, the same-name end of the primary winding is connected to the input end of the power supply module 20, and the non-same-name end of the secondary winding is configured to output a third voltage signal S3. The primary winding stores the energy transmitted by the received second voltage signal S2, and the secondary winding provides energy to the load and provides a feedback signal to the control module 50.

[0034] Optionally, the first end of the first drive switch 40 is connected to the non-same-name end of the primary winding, and the second end of the first drive switch 40 is grounded, providing a loop for releasing energy for the primary winding and switching the switch state of the first drive switch 40 according to the high and low level drive signals received from the control module 50. For example, the first drive switch 40 can be a MOS transistor, specifically an NMOS transistor, and the drive signal is a gate voltage signal of the NMOS transistor. When the drive signal is at a high level, the NMOS transistor is in an on state, and when the drive signal is at a low level, the NMOS transistor is in an off state. In other embodiments, the first drive switch 40 can also be a PMOS tube, a triode or other semiconductor devices with a switch function, which are not listed here one by one.

[0035] Optionally, the power supply terminal Vcc of the control module 50 is connected to the output terminal of the power supply module 20, and the output terminal Out of the control module 50 is connected to the control terminal of the first drive switch 40. The control module 50 is used to perform internal logic processing according to the feedback signal, thereby adjusting the duty cycle and frequency of the drive signal output by the first drive switch 40 to achieve stability of the output voltage of the switching power supply circuit 100.

[0036] Optionally, the pull-down module 60 is connected to the input end of the rectifier module 10 and the power supply end Vcc of the control module 50. The pull-down module 60 is configured to pull down the potential of the power supply end Vcc of the control module 50 when the input end of the rectifier module 10 does not receive the first voltage signal S1, so as to discharge the power supply end Vcc of the control module 50, so that when the input of the switching power supply circuit 100 is disconnected, the power supply end Vcc of the control module 50 is in an undervoltage state, thereby disconnecting the output of the switching power supply circuit 100 and preventing the output of the switching power supply circuit 100 from restarting.

[0037] It can be understood that, through the above method, the pull-down module 60 is used as the key hub of the switching power supply circuit 100. When the input of the switching power supply circuit 100 is disconnected, the voltage of the power supply terminal Vcc of the control module 50 is pulled down by the pull-down module 60, so that the voltage of the power supply terminal Vcc of the control module 50 drops to the undervoltage point, the control module 50 stops working, and the switching power supply circuit 100 also stops working, thereby preventing the switching power supply circuit 100 from restarting due to the restart of the control module 50.

[0038] See also Figure 2 , Figure 2 1 is a schematic diagram of the structure of the second embodiment of the switching power supply circuit provided by the present application. The switching power supply circuit 100 includes a rectifier module 10, a power supply module 20, a transformer module 30, a first drive switch 40, a control module 50 and a pull-down module 60.

[0039] Among them, the input end of the rectifier module 10 is configured to receive a first voltage signal S1; the input end of the power supply module 20 is connected to the output end of the rectifier module 10 to receive a second voltage signal S2 output by the rectifier module 10; the transformer module 30 includes a primary winding and a secondary winding, the same-name end of the primary winding is connected to the input end of the power supply module 20, and the non-same-name end of the secondary winding is configured to output a third voltage signal S3; the first end of the first drive switch 40 is connected to the non-same-name end of the primary winding, and the second end of the first drive switch 40 is grounded; the power supply end Vcc of the control module 50 is connected to the output end of the power supply module 20, and the output end Out of the control module 50 is connected to the control end of the first drive switch 40; the pull-down module 60 is connected to the input end of the rectifier module 10 and the power supply end Vcc of the control module 50, and the pull-down module 60 is configured to pull down the potential of the power supply end Vcc of the control module 50 when the input end of the rectifier module 10 does not receive the first voltage signal S1, so as to discharge the power supply end Vcc of the control module 50.

[0040] Optionally, the power supply module 20 includes a voltage divider unit 21 and a first capacitor C1. The first end of the voltage divider unit 21 is configured to receive the second voltage signal S2, and the voltage divider node of the voltage divider unit 21 is connected to the pull-down module 60; the first end of the first capacitor C1 is connected to the second end of the voltage divider unit 21, and the second end of the first capacitor C1 is grounded. In one embodiment, the first voltage divider unit 21 may include a plurality of resistors connected in series, such as an eleventh resistor R11, a twelfth resistor R12, and a thirteenth resistor R13.

[0041] Optionally, the pull-down module 60 includes a charge-discharge unit 61, a first voltage regulator tube Z1 and a pull-down switch unit 62. The charge-discharge unit 61 is connected to the voltage dividing node of the voltage dividing unit 21 (for example, the common end of the twelfth resistor R12 and the thirteenth resistor R13), the input end of the rectifier module 10 and the common node (for example, the common end of the charge-discharge unit 61 and the first voltage regulator tube Z1); the cathode of the first voltage regulator tube Z1 is connected to the common node; the first end of the pull-down switch unit 62 is connected to the power supply terminal Vcc of the control module 50, the second end of the pull-down switch unit 62 is grounded, and the control end of the pull-down switch unit 62 is connected to the anode of the first voltage regulator tube Z1.

[0042] Specifically, the power supply module 20 receives the second voltage signal S2 output by the rectifier module 10, and provides a charging voltage to the first capacitor C1, a starting voltage to the control module 50, and a charging voltage to the charge and discharge unit 61. The charge and discharge unit 61 is configured to charge the common node using the voltage of the voltage dividing node of the voltage dividing unit 21 when the input end of the rectifier module 10 does not receive the first voltage signal S1, and to discharge the common node when the input end of the rectifier module 10 receives the first voltage signal S1.

[0043] See also Figure 3 , Figure 3 1 is a schematic diagram of the structure of the third embodiment of the switching power supply circuit provided in the present application. The switching power supply circuit 100 includes a rectifier module 10, a power supply module 20, a transformer module 30, a first drive switch 40, a control module 50 and a pull-down module 60.

[0044] Among them, the input end of the rectifier module 10 is configured to receive a first voltage signal S1; the input end of the power supply module 20 is connected to the output end of the rectifier module 10 to receive a second voltage signal S2 output by the rectifier module 10; the transformer module 30 includes a primary winding and a secondary winding, the same-name end of the primary winding is connected to the input end of the power supply module 20, and the non-same-name end of the secondary winding is configured to output a third voltage signal S3; the first end of the first drive switch 40 is connected to the non-same-name end of the primary winding, and the second end of the first drive switch 40 is grounded; the power supply end Vcc of the control module 50 is connected to the output end of the power supply module 20, and the output end Out of the control module 50 is connected to the control end of the first drive switch 40; the pull-down module 60 is connected to the input end of the rectifier module 10 and the power supply end Vcc of the control module 50, and the pull-down module 60 is configured to pull down the potential of the power supply end Vcc of the control module 50 when the input end of the rectifier module 10 does not receive the first voltage signal S1, so as to discharge the power supply end Vcc of the control module 50.

[0045] Figure 3 The switching power supply circuit 100 shown in FIG. Figure 2The main difference between the switching power supply circuit 100 shown in FIG. 1 is that the relevant description of the charging and discharging unit 61 is added. Therefore, the following mainly describes the charging and discharging unit 61. For other components in the switching power supply circuit 100, please refer to FIG. Figure 2 The relevant description of the embodiment shown, for example Figure 3 The power supply module 20 can be seen in Figure 2 The description of the power supply module 20 in FIG. 2 is omitted here.

[0046] Optionally, the charge and discharge unit 61 includes a second capacitor C2, a first resistor R1, a third capacitor C3, a first optical coupler OC1 and a second optical coupler OC2.

[0047] Optionally, the first end of the second capacitor C2 is connected to the voltage dividing node of the voltage dividing unit 21, and the second end of the second capacitor C2 is grounded; the first end of the first resistor R1 is connected to the first end of the second capacitor C2; the first end of the third capacitor C3 is connected to the second end of the first resistor R1, and the second end of the third capacitor C3 is grounded; the anode of the primary diode OC1A of the first optocoupler OC1 is connected to the first input end of the rectifier module 10, the cathode of the primary diode OC1A of the first optocoupler OC1 is connected to the second input end of the rectifier module 10, the first end of the secondary side OC1B of the first optocoupler OC1 is connected to the common node, and the second end of the secondary side OC1B of the first optocoupler OC1 is grounded; the anode of the primary diode OC2A of the second optocoupler OC2 is connected to the second input end of the rectifier module 10, the cathode of the primary diode OC2A of the second optocoupler OC2 is connected to the first input end of the rectifier module 10, the first end of the secondary side OC2B of the second optocoupler OC2 is connected to the common node, and the second end of the secondary side OC2B of the second optocoupler is grounded.

[0048] Optionally, the charge and discharge unit 61 further includes: a second voltage regulator tube Z2, a second resistor R2 and a third resistor R3. The cathode of the second voltage regulator tube Z2 is connected to the first end of the second capacitor C2, and the anode of the second voltage regulator tube Z2 is grounded; the first end of the second resistor R2 is connected to the anode of the first voltage regulator tube Z1, and the second end of the second resistor R2 is connected to the control end of the pull-down switch unit 62; the first end of the third resistor R3 is connected to the control end of the pull-down switch unit 62, and the second end of the third resistor R3 is grounded.

[0049] Specifically, when the first voltage signal S1 is normal, the second voltage signal S2 charges the second capacitor C2, the capacitor voltage of the second capacitor C2 is stabilized at a fixed value by the second voltage regulator Z2, and the second capacitor C2 charges the third capacitor C3 through the first resistor R1; at this time, the primary diode OC1A of the first optocoupler OC1 and the primary diode OC2A of the second optocoupler OC2 are both in the on state, and the secondary side OC1B of the first optocoupler OC1 and the secondary side OC2B of the second optocoupler OC2 are also in the on state; at this time, the voltage of the third capacitor C3 is released and cannot reach the breakdown voltage of the first voltage regulator Z1, so the pull-down switch unit 62 is also disconnected. When the first voltage signal S1 is disconnected, the first optical coupler OC1A and OC2A cannot be turned on, and C3 will not be discharged through the secondary side OC1B of the first optical coupler OC1 or the secondary side OC2B of the second optical coupler OC2. Therefore, the capacitor voltage of the second capacitor C2 can quickly charge the voltage of the third capacitor C3 to a higher value to break down the first voltage regulator Z1. At this time, the pull-down switch unit 62 is turned on, and the power supply voltage Vcc of the control module 50 is released through the pull-down switch unit 62. The Vcc voltage drops to the undervoltage point, then the control module 50 stops working, and the switching power supply circuit 100 no longer works. Since the capacitance of the second capacitor C2 is large, the pull-down switch unit 62 can be kept turned on for a long time to continuously pull down the Vcc voltage. Even if the current backflow phenomenon occurs after the first voltage signal S1 is disconnected, it will not be able to restart due to the undervoltage of Vcc, thereby avoiding the problem of secondary restart of the switching power supply circuit.

[0050] See also Figure 4 , Figure 4 1 is a schematic diagram of the structure of the third embodiment of the switching power supply circuit provided in the present application. The switching power supply circuit 100 includes a rectifier module 10, a power supply module 20, a transformer module 30, a first drive switch 40, a control module 50 and a pull-down module 60.

[0051] Among them, the input end of the rectifier module 10 is configured to receive a first voltage signal S1; the input end of the power supply module 20 is connected to the output end of the rectifier module 10 to receive a second voltage signal S2 output by the rectifier module 10; the transformer module 30 includes a primary winding and a secondary winding, the same-name end of the primary winding is connected to the input end of the power supply module 20, and the non-same-name end of the secondary winding is configured to output a third voltage signal S3; the first end of the first drive switch 40 is connected to the non-same-name end of the primary winding, and the second end of the first drive switch 40 is grounded; the power supply end Vcc of the control module 50 is connected to the output end of the power supply module 20, and the output end Out of the control module 50 is connected to the control end of the first drive switch 40; the pull-down module 60 is connected to the input end of the rectifier module 10 and the power supply end Vcc of the control module 50, and the pull-down module 60 is configured to pull down the potential of the power supply end Vcc of the control module 50 when the input end of the rectifier module 10 does not receive the first voltage signal S1, so as to discharge the power supply end Vcc of the control module 50.

[0052] Figure 4 The switching power supply circuit 100 shown in FIG. Figure 3 The main difference of the switching power supply circuit 100 shown in FIG. 1 is that the components added to the charging and discharging unit 61 and the pull-down switch unit 62 are added. Therefore, the components added to the charging and discharging unit 61 and the pull-down switch unit 62 are mainly described below. For other components in the switching power supply circuit 100, please refer to FIG. Figure 3 The relevant description of the embodiment shown, for example Figure 4 The power supply module 20 can be seen in Figure 3 The description of the power supply module 20 in FIG. 2 is omitted here.

[0053] Optionally, the pull-down switch unit 62 includes an NPN transistor Q3 and a fourth resistor R4. The base of the NPN transistor Q3 is connected to the second end of the second resistor R2, and the emitter of the NPN transistor Q3 is grounded; the first end of the fourth resistor R4 is connected to the power supply terminal Vcc of the control module 50, and the second end of the fourth resistor R4 is connected to the collector of the NPN transistor Q3.

[0054] Optionally, the charge and discharge unit 61 further includes: a fifth resistor R5, a first diode D1, a sixth resistor R6 and a second diode D2. The first end of the fifth resistor R5 is connected to the cathode of the primary diode of the first optical coupler OC1; the anode of the first diode D1 is connected to the second end of the fifth resistor R5, and the cathode of the first diode D1 is connected to the second input end of the rectifier module 10; the first end of the sixth resistor R6 is connected to the cathode of the primary diode of the second optical coupler OC2; the anode of the second diode D2 is connected to the second end of the sixth resistor R6, and the cathode of the second diode D2 is connected to the first input end of the rectifier module 10.

[0055] Specifically, the base of the NPN transistor Q3 is connected to the second end of the second resistor R2. When the first voltage signal S1 is disconnected, the first optocoupler OC1 and the second optocoupler OC2 are both in a cut-off state, and the capacitor voltage of the second capacitor C2 charges the voltage of the third capacitor C3 to a higher value to break down the first voltage regulator Z1, thereby turning on the NPN transistor Q3. The power supply Vcc of the power supply terminal of the control module 50 is discharged through the NPN transistor Q3, so that the control module 50 is in an undervoltage state and cannot work.

[0056] See also Figure 5 , Figure 5 1 is a schematic diagram of the structure of the fifth embodiment of the switching power supply circuit provided in the present application. The switching power supply circuit 100 includes a rectifier module 10, a power supply module 20, a transformer module 30, a first drive switch 40, a control module 50 and a pull-down module 60.

[0057] Among them, the input end of the rectifier module 10 is configured to receive a first voltage signal S1; the input end of the power supply module 20 is connected to the output end of the rectifier module 10 to receive a second voltage signal S2 output by the rectifier module 10; the transformer module 30 includes a primary winding and a secondary winding, the same-name end of the primary winding is connected to the input end of the power supply module 20, and the non-same-name end of the secondary winding is configured to output a third voltage signal S3; the first end of the first drive switch 40 is connected to the non-same-name end of the primary winding, and the second end of the first drive switch 40 is grounded; the power supply end Vcc of the control module 50 is connected to the output end of the power supply module 20, and the output end Out of the control module 50 is connected to the control end of the first drive switch 40; the pull-down module 60 is connected to the input end of the rectifier module 10 and the power supply end Vcc of the control module 50, and the pull-down module 60 is configured to pull down the potential of the power supply end Vcc of the control module 50 when the input end of the rectifier module 10 does not receive the first voltage signal S1, so as to discharge the power supply end Vcc of the control module 50.

[0058] Figure 5 The switching power supply circuit 100 shown in FIG. Figure 4 The main difference of the switching power supply circuit 100 shown in FIG. 1 is that the voltage conversion module 30, the sampling module 70, the feedback module 80 and the components added to the switching power supply circuit 100 are added. Therefore, the following mainly describes the voltage conversion module 30, the sampling module 70, the feedback module 80 and the components added to the switching power supply circuit 100. For other components in the switching power supply circuit 100, please refer to FIG. Figure 4 The relevant description of the embodiment shown, for example Figure 5 The pull-down switch unit 62 in FIG. Figure 4 The description of the pull-down switch unit 62 in FIG. 6 is not repeated here.

[0059] Optionally, the transformer module 30 further includes an auxiliary winding, a third diode D3 and a seventh resistor R7. The same-name end of the auxiliary winding is grounded; the anode of the third diode D3 is connected to the non-same-name end of the auxiliary winding; the first end of the seventh resistor R7 is connected to the cathode of the third diode D3, and the second end of the seventh resistor R7 is connected to the power supply terminal Vcc of the control module 50.

[0060] Optionally, the transformer module 30 further includes a second drive switch Q2, a synchronous drive module 31 and a fourth capacitor C4. The first end of the second drive switch Q2 is connected to the same-name end of the secondary winding, and the second end of the second drive switch Q2 is grounded; the synchronous drive module is connected to the control end of the second drive switch Q2; the first end of the fourth capacitor C4 is connected to the non-same-name end of the secondary winding, and the second end of the fourth capacitor is grounded.

[0061] Specifically, the auxiliary winding is used to provide a working voltage to the power supply terminal Vcc of the control module 50. The synchronous drive module 31 includes a synchronous drive chip. After the synchronous drive chip detects that the polarity of the transformer module 30 is reversed, it sends a drive signal to drive the second drive switch Q2 to turn on, so that the fourth capacitor C4 outputs the output voltage of the switching power supply circuit 100. The output voltage adjusts the duty cycle and frequency of the drive signal at the output terminal Out of the control module 50 through the feedback voltage output by the feedback module 80, so that the output voltage reaches a steady state.

[0062] Optionally, the switching power supply circuit 100 further includes a sampling module 70 and a feedback module 80. A first end of the sampling module 70 is connected to a second end of the first drive switch 40 and a first feedback end Cs of the control module 50, and a second end of the sampling module 70 is grounded; a first end of the feedback module 80 is connected to a non-same-name end of the secondary winding, and a second end of the feedback module 80 is connected to a second feedback end Comp of the control module 50.

[0063] Specifically, the sampling module 70 includes a filtering circuit and a sampling resistor Rs, the first end of the filtering circuit is connected to the first feedback end Cs of the control module 50, the second end of the filtering circuit is connected to the first end of the sampling resistor Rs, and the second end of the sampling resistor Rs is grounded; the sampling module 70 is used to transmit the sampled voltage signal to the control module 50 and provide a logic processing signal inside the control module 50.

[0064] Optionally, the switching power supply circuit 100 also includes a driving circuit, a first end of the driving circuit is connected to the output end Out of the control module 50, and a second end of the driving circuit is connected to the control end of the first driving switch 40. Specifically, the driving circuit is used to drive the first driving switch 40 to open or close, thereby adjusting the output voltage of the switching power supply circuit 100.

[0065] Optionally, the switching power supply circuit 100 further includes an eighth resistor R8 and a fourth diode D4. A first end of the eighth resistor R8 is connected to a voltage dividing node of the first voltage dividing unit 21, a second end of the eighth resistor R8 is connected to an anode of the fourth diode D4, and a cathode of the fourth diode D4 is connected to a first end of the fourth resistor. Specifically, the eighth resistor R8 is mainly used to divide the voltage of the voltage dividing node of the first voltage dividing unit 21 to limit the charging voltage of the second capacitor C2.

[0066] See also Figure 6 , Figure 6 1 is a schematic diagram of the structure of an electronic device according to an embodiment of the present application. The electronic device comprises a switching power supply circuit 100, and the switching power supply circuit 100 is as described in the above embodiment, and will not be described in detail here.

[0067] When the switching power supply circuit of this embodiment is applied to electronic equipment, the pull-down module is used as the key hub. After the input AC power of the switching power supply is cut off, the voltage at the power supply end of the control module is pulled down by the pull-down module, so that the voltage at the power supply end of the control module drops to the undervoltage point, the control module stops working, and the switching power supply circuit no longer works, thereby preventing the switching power supply circuit from restarting due to the restart of the control module, and improving the safety and reliability of the circuit.

[0068] The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A switching power supply circuit, characterized in that: include: A rectifier module, wherein an input end of the rectifier module is configured to receive a first voltage signal; A power supply module, wherein an input end of the power supply module is connected to an output end of the rectifier module to receive a second voltage signal output by the rectifier module; A transformer module, the transformer module comprising a primary winding and a secondary winding, the same-name end of the primary winding is connected to the input end of the power supply module, and the non-same-name end of the secondary winding is configured to output a third voltage signal; A first drive switch, wherein a first end of the first drive switch is connected to a non-same-name end of the primary winding, and a second end of the first drive switch is grounded; A control module, wherein a power supply end of the control module is connected to an output end of the power supply module, and an output end of the control module is connected to a control end of the first drive switch; A pull-down module, wherein the pull-down module is connected to the input end of the rectifier module and the power supply end of the control module, and the pull-down module is configured to pull down the potential of the power supply end of the control module to discharge the power supply end of the control module when the input end of the rectifier module does not receive the first voltage signal.

2. The switching power supply circuit according to claim 1, characterized in that: The power supply module comprises: A voltage dividing unit, wherein a first end of the voltage dividing unit is configured to receive the second voltage signal, and a voltage dividing node of the voltage dividing unit is connected to the pull-down module; A first capacitor, wherein a first end of the first capacitor is connected to a second end of the voltage dividing unit, and a second end of the first capacitor is grounded.

3. The switching power supply circuit according to claim 2, characterized in that: The pull-down module comprises: a charge-discharge unit, the charge-discharge unit being connected to the voltage dividing node of the voltage dividing unit, the input end of the rectifier module and a common node, the charge-discharge unit being configured to charge the common node using the voltage of the voltage dividing node of the voltage dividing unit when the input end of the rectifier module does not receive the first voltage signal, and to discharge the common node when the input end of the rectifier module receives the first voltage signal; A first voltage regulator tube, wherein a cathode of the first voltage regulator tube is connected to the common node; A pull-down switch unit, wherein a first end of the pull-down switch unit is connected to a power supply end of the control module, a second end of the pull-down switch unit is grounded, and a control end of the pull-down switch unit is connected to an anode of the first voltage regulator tube.

4. The switching power supply circuit according to claim 3, characterized in that: The charging and discharging unit comprises: a second capacitor, wherein a first end of the second capacitor is connected to the voltage dividing node of the voltage dividing unit, and a second end of the second capacitor is grounded; a first resistor, wherein a first end of the first resistor is connected to a first end of the second capacitor; a third capacitor, wherein a first end of the third capacitor is connected to the second end of the first resistor, and a second end of the third capacitor is grounded; a first optocoupler, wherein an anode of a primary diode of the first optocoupler is connected to a first input terminal of the rectifier module, a cathode of a primary diode of the first optocoupler is connected to a second input terminal of the rectifier module, a first terminal of a secondary side of the first optocoupler is connected to the common node, and a second terminal of a secondary side of the first optocoupler is grounded; A second optocoupler, wherein the anode of the primary diode of the second optocoupler is connected to the second input terminal of the rectifier module, the cathode of the primary diode of the first optocoupler is connected to the first input terminal of the rectifier module, the first end of the secondary side of the second optocoupler is connected to the common node, and the second end of the secondary side of the second optocoupler is grounded.

5. The switching power supply circuit according to claim 4, characterized in that: The charging and discharging unit further includes: A second voltage-stabilizing tube, wherein a cathode of the second voltage-stabilizing tube is connected to a first end of the second capacitor, and an anode of the second voltage-stabilizing tube is grounded; a second resistor, wherein a first end of the second resistor is connected to an anode of the first voltage regulator tube, and a second end of the second resistor is connected to a control end of the pull-down switch unit; A third resistor, a first end of the third resistor is connected to the control end of the pull-down switch unit, and a second end of the third resistor is grounded.

6. The switching power supply circuit according to claim 5, characterized in that: The pull-down switch unit comprises: An NPN transistor, wherein the base of the NPN transistor is connected to the second end of the second resistor, and the emitter of the NPN transistor is grounded; A fourth resistor, wherein a first end of the fourth resistor is connected to a power supply end of the control module, and a second end of the fourth resistor is connected to a collector of the NPN transistor.

7. The switching power supply circuit according to claim 4, characterized in that: The charging and discharging unit further includes: a fifth resistor, wherein a first end of the fifth resistor is connected to a cathode of a primary diode of the first optical coupler; a first diode, wherein an anode of the first diode is connected to the second end of the fifth resistor, and a cathode of the first diode is connected to the second input end of the rectifier module; a sixth resistor, wherein a first end of the sixth resistor is connected to a cathode of a primary diode of the second optical coupler; A second diode, wherein an anode of the second diode is connected to the second end of the sixth resistor, and a cathode of the second diode is connected to the first input end of the rectifier module.

8. The switching power supply circuit according to claim 1, characterized in that: The voltage transformation module also includes: An auxiliary winding, wherein the same-name end of the auxiliary winding is grounded; a third diode, wherein an anode of the third diode is connected to a non-identical end of the auxiliary winding; A seventh resistor, wherein a first end of the seventh resistor is connected to the cathode of the third diode, and a second end of the seventh resistor is connected to the power supply end of the control module.

9. The switching power supply circuit according to claim 1, characterized in that: The voltage transformation module also includes: A second drive switch, wherein a first end of the second drive switch is connected to the same end of the secondary winding, and a second end of the second drive switch is grounded; A synchronous driving module connected to the control end of the second driving switch; A fourth capacitor, wherein a first end of the fourth capacitor is connected to a non-same-name end of the secondary winding, and a second end of the fourth capacitor is grounded.

10. The switching power supply circuit according to claim 1, characterized in that: The switching power supply circuit also includes: A sampling module, wherein a first end of the sampling module is connected to the second end of the first driving switch and the first feedback end of the control module, and a second end of the sampling module is grounded; A feedback module, wherein a first end of the feedback module is connected to a non-same-name end of the secondary winding, and a second end of the feedback module is connected to a second feedback end of the control module.

11. An electronic device, characterized in that: The electronic device comprises the switching power supply circuit as described in any one of claims 1-10.

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