Switching power supply circuit and switching power supply

Abstract

The invention provides a switching power supply circuit and a switching power supply. The switching power supply circuit comprises a switching power supply chip and a starting circuit, the starting circuit comprises an input end used for receiving the input voltage of the switching power supply; the first capacitor is connected with the power supply end of the switching power supply chip; the first charging module is connected with the input end and the first capacitor and is used for charging the first capacitor during power-on so as to increase the voltage at the power supply end of the switching power supply chip until the voltage reaches the working voltage, so that the switching power supply chip is started to work; and the starting control module is connected with the first charging module and is used for controlling the first charging module to disconnect with the first capacitor after the switching power supply chip is started to work. According to the scheme, the starting working time of the switching power supply is shortened, and the working efficiency of the switching power supply is improved.

Description

Technical Field

[0001] This application relates to the field of switching power supply technology, and in particular to a switching power supply circuit and a switching power supply. Background Technology

[0002] A flyback power supply is a power conversion device based on a flyback switching power supply topology. It is mainly used to convert input voltage (such as AC or DC) into the required stable DC output voltage. It is widely used because of its simple structure, low cost and ability to achieve isolation.

[0003] Currently, some application scenarios have high requirements for the start-up time of flyback power supplies; in some solutions, shortening the start-up time of switching power supplies will increase the power loss of switching power supplies, resulting in low working efficiency of switching power supplies. Summary of the Invention

[0004] The switching power supply circuit and switching power supply provided in this application are used to reduce the startup time of the switching power supply and improve its working efficiency.

[0005] In a first aspect, embodiments of this application provide a switching power supply circuit, including: a switching power supply chip and a startup circuit; the startup circuit includes: an input terminal for receiving an input voltage from the switching power supply; a first capacitor connected to the power supply terminal of the switching power supply chip; a first charging module connected to the input terminal and the first capacitor, used to charge the first capacitor when powered on, thereby increasing the voltage at the power supply terminal of the switching power supply chip until it reaches the operating voltage, so that the switching power supply chip starts working; and a startup control module connected to the first charging module, used to control the first charging module to disconnect from the first capacitor after the switching power supply chip starts working.

[0006] In one possible implementation, the first charging module includes: a first resistor and a first switching transistor; a first end of the first resistor is connected to the input terminal, and a second end of the first resistor is connected to the first end of the first switching transistor; the control terminal of the first switching transistor is connected to a startup control module, which is specifically used to control the first switching transistor to turn off after the switching power supply chip starts working.

[0007] In one possible implementation, the first charging module includes: a first diode; the positive terminal of the first diode is connected to the second terminal of the first switching transistor, and the negative terminal of the first diode is connected to the first terminal of the first capacitor; the second terminal of the first capacitor is grounded.

[0008] In one possible implementation, the circuit further includes: an auxiliary winding; the auxiliary winding is connected to the first end of the first capacitor, and is used to charge the first capacitor after the switching power supply chip starts working, so as to maintain the operating voltage at the power supply terminal of the switching power supply chip and enable the switching power supply chip to start working.

[0009] In one possible implementation, the circuit further includes: a second diode and a second resistor;

[0010] The positive terminal of the second diode is connected to the auxiliary winding, and the negative terminal of the second diode is connected to the first terminal of the second resistor; the second terminal of the second resistor is connected to the first terminal of the first capacitor, so that the auxiliary winding charges the first capacitor through the second diode and the second resistor.

[0011] In one possible implementation, the startup control module includes: a detection module and a control module; the detection module is connected to the switching power supply chip and is used to send a shutdown voltage signal to the control module when the switching power supply chip is detected to start working; the control module is connected to the detection module and the control terminal of the first switching transistor and is used to control the first switching transistor to turn off in response to the shutdown voltage signal, so as to disconnect the connection between the first charging module and the first capacitor.

[0012] In one possible implementation, the circuit further includes: a second charging module; a first terminal of the second charging module is connected to the input terminal, and a second terminal of the second charging module is connected to the first capacitor, used to charge the first capacitor when an output short circuit occurs after the switching power supply chip starts working, until the voltage at the power supply terminal of the switching power supply chip reaches the operating voltage, so that the switching power supply chip resumes startup; the equivalent impedance of the second charging module is greater than the equivalent impedance of the first charging module.

[0013] In one possible implementation, the second charging module includes: at least one third resistor connected in series; the first end of the at least one third resistor connected in series is connected to the input terminal, and the second end of the at least one third resistor connected in series is connected to the first capacitor.

[0014] In one possible implementation, the detection module is further configured to send a shutdown voltage signal to the control module after the switching power supply resumes startup, so as to maintain the shutdown state of the first switching transistor controlled by the control module, thereby maintaining the disconnection between the first charging module and the first capacitor.

[0015] In one possible implementation, the detection module includes: a fourth resistor, a second switching transistor, and a second capacitor;

[0016] The first end of the fourth resistor is connected to the first capacitor, and the second end of the fourth resistor is connected to the first end of the second switching transistor. The second end of the second switching transistor is connected to the first end of the second capacitor and the control module. The second end of the second capacitor is grounded. The control terminal of the second switching transistor is connected to the reference voltage output terminal of the switching power supply chip. When the second switching transistor receives the reference voltage from the switching power supply chip, it turns on to charge the second capacitor from the first capacitor, generating a turn-off voltage signal, which is then sent to the control module.

[0017] In one possible implementation, the detection module further includes: a third switch and a fifth resistor; the first end of the third switch is connected to the control terminal of the second switch, and the second end of the third switch is grounded; the control terminal of the third switch is connected to the reference voltage output terminal of the switching power supply chip; the third switch turns on after receiving the reference voltage from the switching power supply chip to control the second switch to turn on; the first end of the third resistor is connected to the first end of the second switch, and the second end of the fifth resistor is connected to the control terminal of the second switch.

[0018] In one possible implementation, the first terminal of the second capacitor is connected to the second terminal of the second resistor and the first terminal of the first capacitor, and the first terminal of the second capacitor is connected to the control module; the auxiliary winding is used to charge the second capacitor after the switching power supply chip starts working, generate a turn-off voltage signal, and send it to the control module.

[0019] In one possible implementation, the detection module includes: a sixth resistor and a fourth switch; the first end of the sixth resistor is connected to the first end of the first capacitor, and the second end of the sixth resistor is connected to the first end of the fourth switch; the second end of the fourth switch is connected to the first end of the second capacitor and the control module; the control terminal of the fourth switch is connected to the reference voltage output terminal of the switching power supply chip; the fourth switch is turned on when it receives the reference voltage from the switching power supply chip, so that the first capacitor charges the second capacitor, generating a turn-off voltage signal, which is then sent to the control module.

[0020] In one possible implementation, the detection module includes: a fifth switch and a seventh resistor; the first terminal of the fifth switch is connected to the control terminal of the fourth switch, and the second terminal of the fifth switch is grounded; the control terminal of the fifth switch is connected to the reference voltage output terminal of the switching power supply chip; the fifth switch turns on after receiving the reference voltage from the switching power supply chip to control the fourth switch to turn on; the first terminal of the seventh resistor is connected to the first terminal of the fourth switch; the second terminal of the seventh resistor is connected to the control terminal of the fourth switch.

[0021] In one possible implementation, the circuit further includes a third diode; the positive terminal of the third diode is connected to the first terminal of the second capacitor, and the negative terminal of the third diode is connected to the first terminal of the first capacitor.

[0022] In one possible implementation, the control module includes: an eighth resistor, a sixth switch, and a ninth resistor; the first terminal of the eighth resistor is used to receive a turn-off voltage signal; the second terminal of the eighth resistor, the first terminal of the ninth resistor, and the control terminal of the sixth switch are connected; the first terminal of the sixth switch is connected to the control terminal of the first switch, and the second terminal of the sixth switch is grounded; the second terminal of the ninth resistor is connected to the second terminal of the sixth switch; the sixth switch is used to turn on in response to the turn-off voltage signal to control the first switch to turn off.

[0023] In one possible implementation, the circuit further includes: a tenth resistor, a first Zener diode, and a second Zener diode; the first end of the tenth resistor is connected to the input terminal, and the second end of the tenth resistor is connected to the first end of the first Zener diode; the second end of the first Zener diode is connected to the first end of the second Zener diode and the control terminal of the first switching transistor; the second end of the second Zener diode is connected to the second end of the first switching transistor.

[0024] In one possible implementation, the circuit further includes: a primary winding, a secondary winding, and a seventh switching transistor; the first end of the primary winding is connected to the input terminal, and the second end of the primary winding is connected to the first end of the seventh switching transistor; the second end of the seventh switching transistor is grounded, and the control terminal of the seventh switching transistor is connected to the switching power supply chip, and the seventh switching transistor is used to turn on or off in response to the pulse signal output by the switching power supply chip in the startup working state; the first end of the secondary winding is used to connect to the load, and the second end of the secondary winding is grounded, so as to output a power signal to the load when the switching power supply chip is in the startup working state.

[0025] In one possible implementation, the circuit further includes: an eleventh resistor; the first end of the eleventh resistor is connected to the second end of the seventh switching transistor and the sampling current input terminal of the switching power supply chip, and the second end of the eleventh resistor is grounded; the switching power supply chip is also used to adjust the pulse signal based on the signal at the sampling current input terminal to adjust the magnitude of the power supply signal when it is in the startup working state.

[0026] In one possible implementation, the circuit further includes: a fourth diode, a third capacitor, and a twelfth resistor; the positive terminal of the fourth diode is connected to the first end of the secondary winding, and the negative terminal of the fourth diode is connected to the first end of the third capacitor and the first end of the twelfth resistor; the second end of the third capacitor is connected to the second end of the secondary winding and the second end of the twelfth resistor.

[0027] Secondly, embodiments of this application provide a switching power supply, including the switching power supply circuit as described above.

[0028] The switching power supply circuit and switching power supply provided in this application include a switching power supply chip and a startup circuit. The startup circuit includes an input terminal and a first charging module connected to the input terminal, enabling rapid charging of a first capacitor upon power-on. The first capacitor is connected to the switching power supply chip and serves as its startup capacitor. Rapid startup of the switching power supply chip allows the switching power supply to start operating quickly. A startup control module connected to the first charging module controls the first charging module to disconnect after the first capacitor has been charged to the startup voltage of the switching power supply chip for normal operation. This disconnects the first charging module from the first capacitor, reducing the power loss of the first switching module in the switching power supply circuit. The solution in this application, through the design of the first charging module and startup control module, achieves rapid startup of the switching power supply chip, thereby enabling rapid operation of the switching power supply. Simultaneously, after the switching power supply chip starts operating, disconnecting the first switching module from the circuit reduces power loss and improves the operating efficiency of the switching power supply. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0030] Figure 1 A schematic diagram of a flyback power supply for example;

[0031] Figure 2 A diagram illustrating the protective mechanism against hiccups;

[0032] Figure 3 This is a schematic diagram of the structure of a switching power supply circuit as an example of this application;

[0033] Figure 4 This is a schematic diagram of a switching power supply circuit, which is another example of this application.

[0034] The accompanying drawings have illustrated specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0035] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0036] It should be noted that the brief descriptions of terms in this application are only for the convenience of understanding the embodiments described below, and are not intended to limit the embodiments of this application. Unless otherwise stated, these terms should be understood in their ordinary and common meaning. The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar or related objects or entities, and do not necessarily mean to limit a specific order or sequence, unless otherwise indicated. It should be understood that such terms can be used interchangeably where appropriate, for example, to be implemented in an order other than those given in the illustrations or descriptions of the embodiments of this application. The terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this application, are intended to be omnipresent but not exclusive. For example, a product or device that comprises a series of components is not necessarily limited to those components that are explicitly listed, but may include other components that are not explicitly listed or are inherent to such products or devices. The term "module" as used in this application refers to any known or subsequently developed hardware, software, firmware, artificial intelligence, fuzzy logic, or combination of hardware and / or software code capable of performing the functions associated with that element.

[0037] Figure 1 A schematic diagram of a flyback power supply is shown as an example; Figure 1As shown, when the input power supply is activated, the input voltage Vin supplies power to capacitor C4 through high-voltage start-up resistors R8 and R9. This process is a typical RC (resistor-capacitor) charging circuit. When the chip's operating voltage (VCC) reaches the power chip's start-up voltage threshold VTH, the power chip starts working, VREF (the power chip's reference voltage) is stably established, and the power chip outputs a pulse wave (PWM wave) to generate the gate-source voltage VGS of the MOSFET, controlling the MOSFET's on / off state. When the MOSFET is on, the input DC voltage is applied to the primary winding of the transformer, storing magnetic field energy in the transformer core. However, the current at the same terminal of the secondary winding is hindered by the diode, so the magnetic field energy stored in the transformer core cannot be released, and the load can only be powered by the output capacitor. When the MOSFET is off, the primary current decreases, and according to Lenz's law, the secondary current flows out through the same terminal and powers the load through the diode. During this process, the magnetic field energy stored in the core is released. The auxiliary winding works on the same principle as the secondary winding. Its output is rectified by diode (D2) and stored in capacitor C4 to achieve self-sustaining power supply for the power chip. When the transformer output is short-circuited, the feedback signal (COMP) becomes smaller, and the current signal received at the chip's sampling current (ISENSE) terminal becomes too large, causing the duty cycle of the PWM signal to decrease and thus reducing the output voltage. At this time, the voltage at which the secondary winding charges capacitor C4 also decreases, thus causing the VCC supply voltage to also decrease. When the VCC supply voltage is lower than the minimum operating voltage VCC(MIN) after the power chip starts up, the power chip stops working, causing a waveform interruption. Afterward, the startup process of supplying power to capacitor C4 through high-voltage startup resistors R8 and R9 (usually high-resistance resistors) is repeated. This process is also called "hiccup" protection. Figure 2 A diagram illustrating the working process of the "hiccup" protection; such as Figure 2 As shown, under normal circumstances, hiccups consist of two processes: wave generation and recovery startup. The wave generation process only lasts for a few switching cycles (T2 is in the millisecond range), while the recovery startup time is relatively long (T3 is several seconds). Although the instantaneous current during the wave generation process is large, the average power during the hiccup process is effectively reduced due to the long recovery startup process T3. Even with a prolonged short circuit, the switching power supply (especially the transformer and secondary diodes) will not overheat and be damaged.

[0038] In some current applications, the startup time of the switching power supply is critical (e.g., startup within 2 seconds). In such cases, the initial power-on startup time T1 can be shortened by reducing the resistance values ​​of the high-voltage startup resistors R8 and R9. However, this results in resistors R8 and R9 (with smaller resistance values) remaining connected to the high-voltage input terminal after the power chip starts operating, leading to higher power consumption and impacting the output efficiency of the switching power supply. Furthermore, due to the small startup resistors, there is a risk of rapid and repeated restarts during output short circuits, potentially causing thermal failure of components.

[0039] The switching power supply circuit and switching power supply provided in this application include a switching power supply chip and a startup circuit. The startup circuit includes an input terminal and a first charging module connected to the input terminal, enabling rapid charging of a first capacitor upon power-on. The first capacitor is connected to the switching power supply chip and serves as its startup capacitor. Rapid startup of the switching power supply chip allows the switching power supply to start operating quickly. A startup control module connected to the first charging module controls the first charging module to disconnect after the first capacitor has been charged to the startup voltage of the switching power supply chip for normal operation. This disconnects the first charging module from the first capacitor, reducing power loss to the switching power supply circuit. The solution in this application, through the design of the first charging module and startup control module, achieves rapid startup of the switching power supply chip, thus enabling rapid operation of the switching power supply. Simultaneously, after the switching power supply chip starts operating, disconnecting the first charging module from the circuit reduces power loss and improves the operating efficiency of the switching power supply.

[0040] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0041] Example 1

[0042] Figure 3 This is a schematic diagram of the structure of a switching power supply circuit as an example of this application; Figure 4 This is a schematic diagram of a switching power supply circuit, which is another example of this application.

[0043] Please refer to the following: Figure 3 and Figure 4 The switching power supply circuit of this application includes: a switching power supply chip 10 and a startup circuit; wherein the startup circuit includes:

[0044] Input terminal 20 is used to receive the input voltage of the switching power supply; the first capacitor is connected to the power supply terminal of the switching power supply chip.

[0045] The first charging module 30 is connected to the input terminal and the first capacitor. It is used to charge the first capacitor when the power is on to increase the voltage at the power supply terminal of the switching power supply chip until it reaches the working voltage, so that the switching power supply chip can start working.

[0046] The start control module 40 is connected to the first charging module and is used to control the first charging module to disconnect from the first capacitor after the switching power supply chip starts working.

[0047] Specifically, the switching power supply circuit in this example includes a switching power supply chip 10 and a startup circuit for starting the switching power supply chip. The startup circuit includes: an input terminal 20 for receiving the input voltage Vin of the switching power supply; a first capacitor C4 connected to the power supply terminal of the switching power supply chip 10; for example, the switching power supply chip can be a DC-DC chip; the first capacitor C4 is connected to the input terminal of the startup voltage of the switching power supply chip 10, serving as the startup capacitor of the switching power supply chip; when the first capacitor C4 is charged to the startup voltage VCC of the switching power supply chip 10, the switching power supply chip 10 can start working, and at this time the switching power supply chip 10 establishes a stable reference voltage VREF. The first charging module 30, connected to the input terminal 20 and the first capacitor C4, charges the first capacitor C4 upon power-up to increase the voltage at the power supply terminal of the switching power supply chip 10 until it reaches the operating voltage VCC, thus enabling the switching power supply chip 10 to start working. For example, powering on the switching power supply refers to the initial startup of the switching power supply, where the input voltage Vin is charged through the first charging module 30 to the first capacitor C4 until it reaches the operating voltage VCC of the switching power supply chip 10. The startup control module 40, connected to the first charging module 30, controls the first charging module 30 to disconnect from the first capacitor C4 after the switching power supply chip 10 has started working. For example, disconnecting the first charging module 30 from the first capacitor C4 after the switching power supply chip 10 has started working reduces the power consumption of the switching power supply. In this example, by setting the first charging module to charge the first capacitor, the switching power supply chip starts working quickly; after the switching power supply has started working, the startup control module disconnects the first charging module from the first capacitor to reduce the loss of the first charging module to the switching power supply circuit and improve the working efficiency of the switching power supply.

[0048] Optionally, the first charging module 30 includes: a first resistor and a first switching transistor;

[0049] The first end of the first resistor is connected to the input terminal, and the second end of the first resistor is connected to the first end of the first switching transistor.

[0050] The control terminal of the first switching transistor is connected to the startup control module, which is specifically used to control the first switching transistor to turn off after the switching power supply chip starts working.

[0051] Specifically, the first charging module 30 includes a first resistor R10 and a first switching transistor Q5N. For example, the first end of the first resistor R10 is connected to the input terminal 20, and the second end of the first resistor R10 is connected to the first end of the first switching transistor Q5N. The control terminal of the first switching transistor Q5N is connected to the startup control module 40. The startup control module 40 is specifically used to control the first switching transistor Q5N to turn off after the switching power supply chip 10 starts working. For example, the first resistor R10 is a low-resistance resistor, and the first switching transistor is a high-voltage NMOS transistor. The first switching transistor can also be a PMOS transistor; this application does not specifically limit the type of the first switching transistor. When it is a PMOS transistor, to prevent the first switching transistor from being overvoltage-damaged, a voltage limiting device needs to be configured to limit the voltage before connecting to the first charging module. In this example, the first resistor of the first charging module has a low resistance value, which can enable rapid charging of the first capacitor when the switching power supply is first started, so that the switching power supply chip can start working quickly, reducing the startup time of the switching power supply and improving the working efficiency of the switching power supply.

[0052] Optionally, the first charging module 30 includes: a first diode;

[0053] The positive terminal of the first diode is connected to the second terminal of the first switching transistor, and the negative terminal of the first diode is connected to the first terminal of the first capacitor.

[0054] The second terminal of the first capacitor is grounded.

[0055] Specifically, the first charging module 30 also includes a first diode D3; the anode of the first diode D3 is connected to the second terminal of the first switching transistor Q5N, and the cathode of the first diode D3 is connected to the first terminal of the first capacitor C4; the second terminal of the first capacitor C4 is grounded; when the first charging module 30 charges the first capacitor C4, the first capacitor C4 is charged through the first resistor R10, the first switching transistor Q5N, and the first diode D3; the first diode D3 is used to ensure that the circuit is only turned on when the first switching module 30 is charging the first capacitor C4, and that the first capacitor C4 will not discharge in reverse to the first charging module 30 after charging is complete. In this example, the first diode is set to ensure unidirectional conduction when the first charging module charges the first capacitor, preventing the first capacitor C4 from discharging through the second Zener diode Z2 and the sixth switching transistor Q4N.

[0056] Optionally, the circuit may also include: an auxiliary winding;

[0057] The auxiliary winding is connected to the first end of the first capacitor and is used to charge the first capacitor after the switching power supply chip 10 starts working, so as to maintain the working voltage at the power supply terminal of the switching power supply chip and enable the switching power supply chip 10 to start working.

[0058] Specifically, the switching power supply circuit also includes an auxiliary winding, which is connected to the first terminal of the first capacitor C4. In practical applications, when the switching power supply starts to power on, the auxiliary winding receives the input voltage and begins to store energy. After the switching power supply chip 10 starts working, the auxiliary winding charges the first capacitor C4 to maintain the voltage of the first capacitor C4 so as to maintain the working voltage at the power supply terminal of the switching power supply chip 10, thereby enabling the switching power supply chip 10 to maintain its working state and achieve self-sustaining power supply of the switching power supply chip.

[0059] Optionally, the circuit may also include: a second diode and a second resistor;

[0060] The positive terminal of the second diode is connected to the auxiliary winding, and the negative terminal of the second diode is connected to the first terminal of the second resistor.

[0061] The second end of the second resistor is connected to the first end of the first capacitor, so that the auxiliary winding charges the first capacitor through the second diode and the second resistor.

[0062] Specifically, the switching power supply circuit also includes a second diode D2 and a second resistor R7. The positive terminal of the second diode D2 is connected to the auxiliary winding, and the negative terminal of the second diode D2 is connected to the first terminal of the second resistor R7. The second terminal of the second resistor R7 is connected to the first terminal of the first capacitor C4. For example, the second diode D2 and the second resistor R7 form the path for the auxiliary winding to charge the first capacitor C4 after the switching power supply chip has started working normally, allowing the auxiliary winding to charge the first capacitor C4 through the second diode D2 and the second resistor R7. The second diode D2 also ensures unidirectional conduction of the circuit when the auxiliary winding is charging the first capacitor C4, preventing the first capacitor C4 from discharging into the auxiliary winding when the auxiliary winding is not charging it. The second resistor R7 limits the current transmitted from the auxiliary winding before transmitting it to the first capacitor C4, thus acting as a power supply protection circuit. In this example, controlling the unidirectional conduction of the auxiliary winding to charge the first capacitor through the second diode and rectifying the output current of the auxiliary winding before transmitting it to the first capacitor through the second resistor improves the operating efficiency and safety of the switching power supply.

[0063] Optionally, the start control module 40 includes: a detection module 41 and a control module 42;

[0064] The detection module 41 is connected to the switching power supply chip 10 and is used to send a shutdown voltage signal to the control module 42 when the switching power supply chip 10 is detected to start working.

[0065] The control module 42 is connected to the control terminal of the detection module 41 and the first switching transistor, and is used to respond to the turn-off voltage signal to control the first switching transistor to turn off, so as to disconnect the first charging module 30 from the first capacitor.

[0066] Specifically, the startup control module 40 includes a detection module 41 and a control module 42. The detection module 41 is connected to the switching power supply chip 10 and is used to send a shutdown voltage signal VOFF to the control module when the switching power supply chip 10 is detected to be starting up. For example, after the switching power supply chip 10 starts up, it generates a stable reference voltage signal VREF. When the detection module 41 detects the reference voltage signal VREF, it generates the shutdown voltage signal VOFF based on the received reference voltage signal VREF and sends it to the control module 42. The control module 42 is connected to the detection module 41 and the control terminal of the first switching transistor Q5N and is used to control the first switching transistor Q5N to turn off in response to the shutdown voltage signal VOFF, thereby disconnecting the first charging module 30 and the first capacitor C4. For example, the startup control module 40 is connected to the first switching transistor Q5N of the first charging module 30. After the switching power supply chip 10 starts working, when the reference voltage VREF signal for the startup of the switching power supply chip 10 is detected, the shutdown voltage signal VOFF is sent to the control module 42. The control module 42 is connected to the first switching transistor Q5N and controls the first switching transistor Q5N to turn off, thereby disconnecting the first charging module 30. This reduces the losses generated by the first charging module 30 on the switching power supply circuit and improves the working efficiency of the switching power supply.

[0067] Optionally, the circuit may also include: a second charging module 50;

[0068] The first end of the second charging module 50 is connected to the input terminal 20, and the second end of the second charging module 50 is connected to the first capacitor. It is used to charge the first capacitor when an output short circuit occurs after the switching power supply chip 10 starts working, until the voltage at the power supply terminal of the switching power supply chip 10 reaches the working voltage, so that the switching power supply chip 10 resumes startup. The equivalent impedance of the second charging module 50 is greater than the equivalent impedance of the first charging module 30.

[0069] Specifically, the switching power supply circuit also includes a second charging module 50; the first end of the second charging module 50 is also connected to the input terminal 20, and the second end of the second charging module 50 is connected to the first capacitor C4; it is used to charge the first capacitor C4 to the operating voltage of the switching power supply chip 10 when an output short circuit occurs after the switching power supply chip 10 starts working, so that the switching power supply needs to resume startup; the equivalent impedance of the second charging module 50 is greater than the equivalent impedance of the first charging module 30. For example, when the switching power supply chip 10 starts working and an output short circuit occurs, it needs to be restarted. In practical applications, when an output short circuit occurs, the switching power supply chip stops working, and the reference voltage VREF drops to 0. At this time, because the turn-off voltage signal VOFF will slowly decrease and remain for a period of time, the first switching transistor Q5N remains off, and the first charging module remains disconnected. To protect the switching power supply from damage, the first capacitor C4 is slowly charged through the second charging module 50 with a large equivalent impedance, so that it reaches the operating voltage of the switching power supply chip 10 again, restarting the switching power supply chip. When an output short circuit occurs and the switching power supply needs to be restarted, the second charging module charges the first capacitor, which ensures a longer recovery startup time and lower average power during the restart process, preventing damage to the switching power supply. During output short circuit protection and restart, the first charging module remains off, avoiding repeated restarts that could lead to component thermal failure.

[0070] Optionally, the second charging module 50 includes at least one third resistor connected in series;

[0071] The first end of at least one third resistor connected in series is connected to the input terminal 20, and the second end of at least one third resistor connected in series is connected to the first capacitor.

[0072] Specifically, the second charging module 50 includes at least one third resistor connected in series; wherein, the first end of the at least one resistor is connected to the input terminal 20, and the second end of the at least one third resistor is connected to the first capacitor C4. Figure 3 and Figure 4 Taking two third resistors R8 and R9 as an example; the first end of resistor R8 is connected to the input terminal 20, the second end of resistor R8 is connected to the first end of resistor R9, and the second end of resistor R9 is connected to the first capacitor C4.

[0073] Optionally, the detection module 41 is also used to send a shutdown voltage signal to the control module 42 after the switching power supply chip 10 resumes startup, so as to maintain the shutdown state of the first switching transistor controlled by the control module 42, as well as the shutdown state of the first charging module 30 and the first capacitor.

[0074] In conjunction with the foregoing example, the detection module 41 is further configured to, after the switching power supply chip 10 starts working, experiences an output short circuit, and then resumes operation, send a shutdown voltage signal VOFF to the control module 42, so that the control module 42 controls the first switching transistor Q5N to turn off, thereby disconnecting the first charging module 30 from the first capacitor C4; that is, after the output short circuit occurs and the switching power supply chip 10 resumes operation, the detection module 41 still sends the shutdown voltage signal VOFF to the control module 42, so that the control module 42 controls the first switching transistor Q5N to turn off; for example, when the switching power supply experiences an output short circuit, the switching power supply chip 10 stops working, but the shutdown voltage signal VOFF from the detection module will be maintained for a period of time, so the first switching transistor Q5N can remain off. When the switching power supply chip 10 resumes operation, the detection module 41 receives the reference voltage VREF of the switching power supply chip 10 again, generates the shutdown voltage signal VOFF, and the control module 42 then responds to the VOFF signal to disconnect the first switching transistor Q5N, so the first switching transistor Q5N can remain off indefinitely.

[0075] Optional, please refer to details. Figure 3 The detection module 41 includes: a fourth resistor, a second switching transistor, and a second capacitor;

[0076] The first end of the fourth resistor is connected to the first capacitor, and the second end of the fourth resistor is connected to the first end of the second switching transistor.

[0077] The second terminal of the second switching transistor is connected to the first terminal of the second capacitor and the control module 42; the second terminal of the second capacitor is grounded.

[0078] The control terminal of the second switching transistor is connected to the reference voltage output terminal of the switching power supply chip 10; when the second switching transistor receives the reference voltage from the switching power supply chip, it turns on to charge the first capacitor to the second capacitor, generating a turn-off voltage signal, which is then sent to the control module 42.

[0079] Specifically, the detection module 41 includes: a fourth resistor R15, a second switch Q3N ( Figure 3 Not shown in the image. Figure 3 Taking a PMOS transistor as an example, the second capacitor is C5; the first terminal of the fourth resistor R15 is connected to the first capacitor C4, and the second terminal of the fourth resistor R15 is connected to the first terminal of the second transistor Q3N; the second terminal of the second transistor Q3N is connected to the first terminal of the second capacitor C5 and the control module 42; the second terminal of the second capacitor C5 is grounded; for example, when Figure 3When the second switching transistor is an NMOS transistor Q3N, the control terminal of the second switching transistor Q3N is connected to the reference voltage output terminal of the switching power supply chip 10. When the second switching transistor Q3N receives the reference voltage from the switching power supply chip 10, it conducts, causing the first capacitor C4 to charge the second capacitor C5, generating a turn-off voltage signal VOFF, which is then sent to the control module 42. When the second switching transistor is an NMOS transistor, to prevent overvoltage breakdown, a voltage limiting device needs to be connected and the peripheral circuit redesigned before connecting it to the second switching transistor to enable it to conduct. Figure 3 (Not shown in the image). For example, the control terminal of the second switch is connected to the pin of the reference voltage output terminal of the switching power supply chip 10. When the switching power supply chip 10 is working normally, a stable reference voltage VREF is established. When the control terminal of the second switch receives the reference voltage VREF, it is turned on. At this time, the first capacitor C4 charges the second capacitor C5 through the fourth resistor R15 and the second switch Q3N. After the second capacitor C5 is charged, it sends a turn-off voltage signal VOFF to the control module 42. At this time, the control module 42 is turned on. Subsequently, the control module 42 transmits the turn-off voltage signal to control the first switch Q5N to turn off, thereby disconnecting the first charging module 30. In this example, charging the second capacitor through the first capacitor causes the detection module to generate a turn-off voltage signal, controlling the turn-off of the first switch, thus improving the working efficiency of the switching power supply.

[0080] Optionally, the detection module 41 may also include: a third switching transistor and a fifth resistor;

[0081] The first terminal of the third switch is connected to the control terminal of the second switch, and the second terminal of the third switch is grounded.

[0082] The control terminal of the third switch is connected to the reference voltage output terminal of the switching power supply chip 10; the third switch turns on after receiving the reference voltage from the switching power supply chip 10, thereby controlling the second switch to turn on.

[0083] The first end of the fifth resistor is connected to the first end of the second switching transistor, and the second end of the fifth resistor is connected to the control terminal of the second switching transistor.

[0084] Specifically, the detection module 41 also includes a third switch Q2N and a fifth resistor R14; the first terminal of the third switch Q2N is connected to the control terminal of the second switch Q3P, and the second terminal of the third switch Q2N is grounded; the control terminal of the third switch Q2N is connected to the reference voltage output terminal of the switching power supply chip 10; the third switch Q2N turns on after receiving the reference voltage VREF from the switching power supply chip 10, thereby controlling the second switch Q3P to turn on; the first terminal of the fifth resistor R14 is connected to the first terminal of the second switch Q3P; the second terminal of the fifth resistor R14 is connected to the control terminal of the second switch Q3P; for example, the control terminal of the third switch Q2N is connected to the pin of the reference voltage output terminal of the switching power supply chip 10. When the control terminal of the third switch Q2N receives the reference voltage VREF from the switching power supply chip 10, the third switch Q2N will be turned on. For example, the third switch is an NMOS transistor and the second switch is a PMOS transistor. The second switch Q3P is also turned on by the third switch Q2N and the fifth resistor R14. The fifth resistor R14 serves as the driving resistor for the second switch Q3P. When the third switch Q2N is turned on, the second switch Q3P is driven to turn on through the fifth resistor R14, so that the first capacitor C4 charges the second capacitor C5 through the fourth resistor R15 and the second switch Q3P to generate a turn-off voltage signal VOFF, which is sent to the control module 42, thereby improving the efficiency of the switching power supply circuit.

[0085] Please refer to the following for details. Figure 4 ;

[0086] Optionally, the first end of the second capacitor is connected to the second end of the second resistor and the first end of the first capacitor, and the first end of the second capacitor is connected to the control module 42; the auxiliary winding is used to charge the second capacitor after the switching power supply chip 10 starts working, generate a turn-off voltage signal, and send it to the control module 42.

[0087] Specifically, the first terminal of the second capacitor C5 is connected to the second terminal of the second resistor R7 and the first terminal of the first capacitor C4, and the first terminal of the second capacitor C5 is connected to the control module 42. At this time, the auxiliary winding is used to charge the second capacitor C5 after the switching power supply chip 10 starts working, generating a turn-off voltage signal VOFF, and sending the turn-off voltage signal VOFF to the control module 42. At the same time, the first capacitor C4 is charged through the third diode D4 to maintain the operation of the switching power supply chip.

[0088] Optionally, the detection module 41 includes: a sixth resistor and a fourth switching transistor;

[0089] The first end of the sixth resistor is connected to the first end of the first capacitor, and the second end of the sixth resistor is connected to the first end of the fourth switching transistor.

[0090] The second terminal of the fourth switching transistor is connected to the first terminal of the second capacitor and the control module;

[0091] The control terminal of the fourth switching transistor is connected to the reference voltage output terminal of the switching power supply chip 10; when the fourth switching transistor receives the reference voltage from the switching power supply chip, it turns on to charge the second capacitor from the first capacitor, generating a turn-off voltage signal, which is then sent to the control module 42.

[0092] like Figure 4 As shown, the detection module 41 includes a sixth resistor R17 and a fourth switch Q7N ( Figure 4 Not shown in the image. Figure 4 (Taking a PMOS as an example of the fourth switching transistor); when an output short-circuit protection occurs, during the restart process of the switching power supply chip 10, the voltage of the second capacitor C5 is sufficient to generate a turn-off voltage signal VOFF, which is sent to the control module 42 to disconnect the first charging module 30. The first terminal of the sixth resistor R17 is connected to the first terminal of the first capacitor C4, and the second terminal of the sixth resistor R17 is connected to the first terminal of the fourth switching transistor Q7N; the second terminal of the fourth switching transistor Q7N is connected to the first terminal of the second capacitor C5 and the control module 42. For example, when... Figure 4 When the fourth switching transistor is an NMOS transistor Q7N, its control terminal is connected to the reference voltage output terminal of the switching power supply chip 10. When the fourth switching transistor Q7N receives the reference voltage from the switching power supply chip 10, it conducts, causing the first capacitor C4 to charge the second capacitor C5, generating a turn-off voltage signal VOFF, which is then sent to the control module 42. When the fourth switching transistor is an NMOS transistor, to prevent the second switching transistor from overvoltage breakdown, a voltage limiter needs to be connected and the peripheral circuitry redesigned before connecting to the fourth switching transistor to enable it to conduct. Figure 4 (Not shown in the diagram). For example, the control terminal of the fourth switch is connected to the pin of the reference voltage output terminal of the switching power supply chip 10. When the switching power supply chip 10 is working normally, a stable reference voltage VREF will be established. When the control terminal of the fourth switch receives the reference voltage VREF, it will be turned on. At this time, the first capacitor C4 will charge the second capacitor C5 through the sixth resistor R17 and the fourth switch Q7N. The second capacitor C5 will send a turn-off voltage signal VOFF to the control module 42. At this time, the control module 42 will be turned on. The subsequently turned-on control module 42 will transmit a turn-off voltage signal to control the first switch Q5N to turn off, thereby disconnecting the first charging module 30.

[0093] Please continue reading. Figure 4 The detection module 41 includes: a fifth switching transistor and a seventh resistor;

[0094] The first terminal of the fifth switch is connected to the control terminal of the fourth switch, and the second terminal of the fifth switch is grounded.

[0095] The control terminal of the fifth switching transistor is connected to the reference voltage output terminal of the switching power supply chip 10; the fifth switching transistor turns on after receiving the reference voltage from the switching power supply chip 10, thereby controlling the fourth switching transistor to turn on.

[0096] The first end of the seventh resistor is connected to the first end of the fourth switching transistor; the second end of the seventh resistor is connected to the control terminal of the fourth switching transistor.

[0097] Specifically, the detection module 41 also includes a fifth switch Q6N and a seventh resistor R16; the first terminal of the fifth switch Q6N is connected to the control terminal of the fourth switch Q7P, and the second terminal of the fifth switch Q6N is grounded; the control terminal of the fifth switch Q6N is connected to the reference voltage output terminal of the switching power supply chip 10; the fifth switch Q6N turns on after receiving the reference voltage VREF from the switching power supply chip 10, thereby controlling the fourth switch Q7N to turn on; the first terminal of the seventh resistor R16 is connected to the first terminal of the fourth switch Q7N; the second terminal of the seventh resistor R16 is connected to the control terminal of the fourth switch Q7N; for example, the control terminal of the fifth switch Q6N is connected to the switching power supply chip 10. The pin connection of the reference voltage output terminal is such that when the control terminal of the fifth switch Q6N receives the reference voltage VREF from the switching power supply chip 10, the fifth switch Q6N will be turned on. The fifth switch Q6N and the seventh resistor R16 control the fourth switch Q7P to also be turned on. The fifth resistor R16 serves as the driving resistor for the fourth switch Q7P to start. When the fifth switch Q6N is turned on, the fourth switch Q7P is turned on through the seventh resistor R16, so that the first capacitor C4 charges the second capacitor C5 through the sixth resistor R17 and the fourth switch Q7P to generate the turn-off voltage signal VOFF, which is sent to the control module 42, thereby improving the efficiency of the switching power supply circuit.

[0098] Please continue reading. Figure 4 The circuit also includes a third diode;

[0099] The positive terminal of the third diode is connected to the first terminal of the second capacitor, and the negative terminal of the third diode is connected to the first terminal of the first capacitor.

[0100] Specifically, in conjunction with the aforementioned example, the switching power supply circuit also includes a third diode D4. The positive terminal of the third diode D4 is connected to the first terminal of the second capacitor C5, and the negative terminal of the third diode D4 is connected to the first terminal of the first capacitor C4. The auxiliary winding charges the first capacitor C4 through the second diode D2, the second resistor R7, and the third diode D4, maintaining the voltage of the first capacitor C4 at the operating voltage of the switching power supply chip 10, and maintaining the normal operation of the first power chip 10.

[0101] Figure 4In the switching power supply circuit shown, after the switching power supply starts working, the auxiliary winding charges the second capacitor C5 through the second diode D2 and the second resistor R7 to generate the turn-off voltage signal VOFF. Simultaneously, the auxiliary winding charges the first capacitor C4 through the second diode D2, the second resistor R7, and the third diode D4 to maintain the normal operation of the switching power supply chip. To reduce the power supply loss from the auxiliary winding to the first capacitor C4 and the second capacitor C5, diodes with low on-state voltage drop and low leakage current are selected for the second diode D2 and the third diode D4. Furthermore, in the event of an output short circuit and subsequent restart, the third diode D4 also prevents the first capacitor C4 from directly charging the second capacitor C5 without passing through the current-limiting resistor, thus improving the safety of the switching power supply.

[0102] Please continue reading below. Figure 3 and Figure 4 The control module 42 includes: an eighth resistor, a sixth switching transistor, and a ninth resistor;

[0103] The first terminal of the eighth resistor is used to receive the turn-off voltage signal; the second terminal of the eighth resistor is connected to the first terminal of the ninth resistor and the control terminal of the sixth switch.

[0104] The first terminal of the sixth switch is connected to the control terminal of the first switch, and the second terminal of the sixth switch is grounded; the second terminal of the ninth resistor is connected to the second terminal of the sixth switch; the sixth switch is used to turn on in response to the turn-off voltage signal to control the first switch to turn off.

[0105] Specifically, the control module 42 includes an eighth resistor R12, a sixth switch Q4N, and a ninth resistor R13. The first end of the eighth resistor R12 is used to receive the turn-off voltage signal VOFF. The second end of the eighth resistor R12, the first end of the ninth resistor R13, and the control terminal of the sixth switch Q4N are connected. The first end of the sixth switch Q4N is connected to the control terminal of the first switch Q5N, and the second end of the sixth switch Q4N is grounded. The second end of the ninth resistor R13 is connected to the second end of the sixth switch Q4N. The eighth resistor R12 receives the turn-off voltage signal VOFF sent by the detection module 41. After being divided by the eighth resistor R12 and the ninth resistor R13, the signal is transmitted to the sixth switch Q4N. The sixth switch Q4N is turned on in response to the turn-off voltage signal VOFF. After the sixth switch Q4N is turned on, it controls the first switch Q5N to turn off, thereby disconnecting the first charging module 30 and improving the efficiency of the switching power supply.

[0106] Optionally, the circuit may also include: a tenth resistor, a first Zener diode, and a second Zener diode;

[0107] The first end of the tenth resistor is connected to the input terminal 20, and the second end of the tenth resistor is connected to the first end of the first Zener diode; the second end of the first Zener diode is connected to the first end of the second Zener diode 36 and the control terminal of the first switching transistor.

[0108] The second terminal of the second Zener diode is connected to the second terminal of the first switching transistor 32.

[0109] Specifically, the switching power supply circuit also includes a tenth resistor R11, a first Zener diode Z1, and a second Zener diode Z2. The first end of the tenth resistor R11 is connected to the input terminal 20, and the second end of the tenth resistor R11 is connected to the first end of the first Zener diode Z1. The second end of the first Zener diode Z1 is connected to the first end of the second Zener diode Z2 and the control terminal of the first switching transistor Q5N. The second end of the second Zener diode Z2 is connected to the second end of the first switching transistor Q5N. Specifically, when the switching power supply is first started, the first charging module 30 needs to be turned on. At this time, the tenth resistor R11, the first Zener diode Z1, and the second Zener diode Z2 need to regulate the input voltage, pull up the first switching transistor Q5N to turn it on, thus charging the first capacitor C4. In this example, the pull-up resistor and the two Zener diodes work together to turn on the first switching transistor Q5N of the first charging module 30, reducing the startup time of the switching power supply circuit, improving the operating efficiency of the switching power supply, and preventing overvoltage breakdown of the first switching transistor through the Zener diodes, thereby improving the safety of the switching power supply voltage.

[0110] Optionally, the circuit may also include: a primary winding, a secondary winding, and a seventh switching transistor;

[0111] The first end of the primary winding is connected to the input terminal, and the second end of the primary winding is connected to the first end of the seventh switching transistor. The second end of the seventh switching transistor is grounded, and the control terminal of the seventh switching transistor is connected to the switching power supply chip 10. The seventh switching transistor is used to turn on or off in response to the pulse signal output by the switching power supply chip 10 in the startup working state.

[0112] The first end of the secondary winding is used to connect to the load, and the second end of the secondary winding is grounded to output a power signal to the load when the switching power supply chip 10 is in the startup state.

[0113] Specifically, the switching power supply circuit also includes a primary winding, a secondary winding, and a seventh switching transistor Q1N. The first end of the primary winding is connected to the input terminal 20, and the second end of the primary winding is connected to the first end of the seventh switching transistor Q1N. The second end of the seventh switching transistor Q1N is grounded, and the control terminal of the seventh switching transistor Q1N is connected to the switching power supply chip 10. The seventh switching transistor Q1N is used to turn on or off in response to a pulse signal output by the switching power supply chip 10 during startup. For example, when the seventh switching transistor Q1N is turned on, the input DC voltage is applied to the primary winding of the transformer, storing magnetic field energy in the transformer core. When the seventh switching transistor Q1N is turned off, the current in the secondary winding flows out through the diode to supply power to the load, releasing the magnetic field energy stored in the core. The first end of the secondary winding is used to connect to the load, and the second end of the secondary winding is grounded. The secondary winding outputs a power signal to the load when the switching power supply chip 10 is in startup mode. For example, the secondary winding terminal serves as the output terminal of the switching power supply circuit, connected to the load, and acts as the power supply terminal for supplying power to the load.

[0114] The circuit also includes: the eleventh resistor;

[0115] The first end of the eleventh resistor is connected to the second end of the seventh switching transistor and the sampling current input terminal of the switching power supply chip 10, and the second end of the eleventh resistor is grounded.

[0116] The switching power supply chip 10 is also used to adjust the pulse signal based on the signal at the sampling current input terminal when it is in the startup working state, so as to adjust the magnitude of the power supply signal.

[0117] Specifically, the first terminal of the eleventh resistor R6 is connected to the second terminal of the seventh switch Q1N and the sampling current input terminal of the switching power supply chip 10, and the second terminal of the eleventh resistor R6 is grounded; furthermore, the second terminal of the aforementioned seventh switch Q1N is connected to the eleventh resistor R6, and grounded through the second terminal of the eleventh resistor R6. The switching power supply chip 10 is also used to, when the switching power supply chip 10 is in the startup operating state, receive the signal at the sampling current input terminal based on the sampling current transmitted by the eleventh resistor R6, thereby adjusting the pulse signal PMW signal output by the switching power supply chip, thereby adjusting the magnitude of the power supply signal.

[0118] Optionally, the circuit may also include: a fourth diode, a third capacitor, and a twelfth resistor;

[0119] The positive terminal of the fourth diode is connected to the first terminal of the secondary winding, and the negative terminal of the fourth diode is connected to the first terminal of the third capacitor and the first terminal of the twelfth resistor.

[0120] The second terminal of the third capacitor is connected to the second terminal of the secondary winding and the second terminal of the twelfth resistor.

[0121] Specifically, the switching power supply circuit also includes a fourth diode D1, a third capacitor C2, and a twelfth resistor RL. The anode of the fourth diode D1 is connected to the first terminal of the secondary winding, and the cathode of the fourth diode D1 is connected to the first terminal of the third capacitor C2 and the second terminal of the twelfth resistor RL. The second terminal of the third capacitor C2 is connected to the second terminal of the secondary winding, serving as the energy storage capacitor at the output of the switching power supply circuit. The second terminal of the twelfth resistor RL is connected to the second terminal of the third capacitor RL, used to filter the output voltage and transmit it to the load to supply power.

[0122] The switching power supply circuit provided in this embodiment includes a switching power supply chip and a startup circuit. The startup circuit includes an input terminal and a first charging module connected to the input terminal to achieve rapid charging of a first capacitor upon power-on. The first capacitor is connected to the switching power supply chip and serves as its startup capacitor. Rapid startup of the switching power supply chip enables the switching power supply to start operating quickly. A startup control module connected to the first charging module controls the first charging module to disconnect after the first capacitor has been charged to the startup voltage of the switching power supply chip and is operating normally. This disconnects the first charging module from the first capacitor, reducing the power loss of the first switching module to the switching power supply circuit. The solution in this application, through the design of the first charging module and the startup control module, achieves rapid startup of the switching power supply chip, thereby enabling rapid operation of the switching power supply. Simultaneously, after the switching power supply chip starts operating, disconnecting the first switching module from the circuit reduces power loss and improves the efficiency of the switching power supply. During the restart process after output short-circuit protection, the first charging module remains off, preventing repeated restarts that could lead to component thermal failure.

[0123] Example 2

[0124] This application provides a switching power supply, which includes the switching power supply circuit in any of the above embodiments. The switching power supply circuit has been described in detail in the above embodiments and will not be repeated here.

[0125] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A switching power supply circuit, characterized in that, include: Switching power supply chip and startup circuit; The startup circuit includes: The input terminal is used to receive the input voltage of the switching power supply; the first capacitor is connected to the power supply terminal of the switching power supply chip. The first charging module is connected to the input terminal and the first capacitor. When powered on, it charges the first capacitor to increase the voltage at the power supply terminal of the switching power supply chip until it reaches the operating voltage, so that the switching power supply chip can start working. A startup control module, connected to the first charging module, is used to control the first charging module to disconnect from the first capacitor after the switching power supply chip starts working.

2. The circuit according to claim 1, characterized in that, The first charging module includes: a first resistor and a first switching transistor; The first end of the first resistor is connected to the input terminal, and the second end of the first resistor is connected to the first end of the first switching transistor. The control terminal of the first switching transistor is connected to the startup control module, which is specifically used to control the first switching transistor to turn off after the switching power supply chip starts working.

3. The circuit according to claim 2, characterized in that, The first charging module includes: a first diode; The positive terminal of the first diode is connected to the second terminal of the first switching transistor, and the negative terminal of the first diode is connected to the first terminal of the first capacitor. The second terminal of the first capacitor is grounded.

4. The circuit according to claim 3, characterized in that, The circuit also includes: an auxiliary winding; The auxiliary winding is connected to the first end of the first capacitor and is used to charge the first capacitor after the switching power supply chip starts working, so as to maintain the working voltage at the power supply terminal of the switching power supply chip and enable the switching power supply chip to start working.

5. The circuit according to claim 4, characterized in that, The circuit also includes: a second diode and a second resistor; The positive terminal of the second diode is connected to the auxiliary winding, and the negative terminal of the second diode is connected to the first terminal of the second resistor; The second end of the second resistor is connected to the first end of the first capacitor, so that the auxiliary winding charges the first capacitor through the second diode and the second resistor.

6. The circuit according to claim 5, characterized in that, The startup control module includes: a detection module and a control module; The detection module is connected to the switching power supply chip and is used to send a shutdown voltage signal to the control module when the switching power supply chip is detected to start working. The control module is connected to the control terminal of the detection module and the first switching transistor, and is used to respond to the shutdown voltage signal to control the first switching transistor to turn off, thereby disconnecting the first charging module from the first capacitor.

7. The circuit according to claim 6, characterized in that, The circuit also includes: a second charging module; The first end of the second charging module is connected to the input end, and the second end of the second charging module is connected to the first capacitor. It is used to charge the first capacitor when an output short circuit occurs after the switching power supply chip starts working, until the voltage at the power supply end of the switching power supply chip reaches the working voltage, so that the switching power supply chip resumes startup; the equivalent impedance of the second charging module is greater than the equivalent impedance of the first charging module.

8. The circuit according to claim 7, characterized in that, The second charging module includes: at least one third resistor connected in series; The first end of the at least one series-connected third resistor is connected to the input terminal, and the second end of the at least one series-connected third resistor is connected to the first capacitor.

9. The circuit according to claim 8, characterized in that, The detection module is further configured to send a shutdown voltage signal to the control module after the switching power supply chip resumes startup, so as to maintain the shutdown state of the first switching transistor and the shutdown state of the first charging module and the first capacitor controlled by the control module.

10. The circuit according to claim 9, characterized in that, The detection module includes: a fourth resistor, a second switching transistor, and a second capacitor; The first end of the fourth resistor is connected to the first capacitor, and the second end of the fourth resistor is connected to the first end of the second switching transistor. The second terminal of the second switching transistor is connected to the first terminal of the second capacitor and the control module; the second terminal of the second capacitor is grounded. The control terminal of the second switching transistor is connected to the reference voltage output terminal of the switching power supply chip; when the second switching transistor receives the reference voltage from the switching power supply chip, it turns on to charge the first capacitor to the second capacitor, generating a turn-off voltage signal, which is then sent to the control module.

11. The circuit according to claim 10, characterized in that, The detection module also includes: a third switching transistor and a fifth resistor; The first terminal of the third switch is connected to the control terminal of the second switch, and the second terminal of the third switch is grounded. The control terminal of the third switch is connected to the reference voltage output terminal of the switching power supply chip; the third switch turns on after receiving the reference voltage from the switching power supply chip to control the second switch to turn on. The first end of the fifth resistor is connected to the first end of the second switching transistor, and the second end of the fifth resistor is connected to the control terminal of the second switching transistor.

12. The circuit according to claim 6, characterized in that, The first terminal of the second capacitor is connected to the second terminal of the second resistor and the first terminal of the first capacitor, and the second terminal of the second capacitor is connected to the control module; the auxiliary winding is used to charge the second capacitor after the switching power supply chip starts working, generate the shutdown voltage signal, and send it to the control module.

13. The circuit according to claim 12, characterized in that, The detection module includes: a sixth resistor and a fourth switching transistor; The first end of the sixth resistor is connected to the first end of the first capacitor, and the second end of the sixth resistor is connected to the first end of the fourth switch. The second terminal of the fourth switching transistor is connected to the first terminal of the second capacitor and the control module; The control terminal of the fourth switching transistor is connected to the reference voltage output terminal of the switching power supply chip; when the fourth switching transistor receives the reference voltage of the switching power supply chip, it turns on to charge the second capacitor from the first capacitor, generating the shutdown voltage signal, and sending it to the control module.

14. The circuit according to claim 13, characterized in that, The detection module includes: a fifth switching transistor and a seventh resistor; The first terminal of the fifth switch is connected to the control terminal of the fourth switch, and the second terminal of the fifth switch is grounded. The control terminal of the fifth switch is connected to the reference voltage output terminal of the switching power supply chip; the fifth switch turns on after receiving the reference voltage from the switching power supply chip, thereby controlling the fourth switch to turn on. The first end of the seventh resistor is connected to the first end of the fourth switch transistor; the second end of the seventh resistor is connected to the control terminal of the fourth switch transistor.

15. The circuit according to claim 14, characterized in that, The circuit also includes a third diode; The positive terminal of the third diode is connected to the first terminal of the second capacitor, and the negative terminal of the third diode is connected to the first terminal of the first capacitor.

16. The circuit according to any one of claims 2-15, characterized in that, The control module includes: an eighth resistor, a sixth switching transistor, and a ninth resistor; The first end of the eighth resistor is used to receive the turn-off voltage signal; the second end of the eighth resistor and the first end of the ninth resistor are connected to the control terminal of the sixth switch. The first terminal of the sixth switch is connected to the control terminal of the first switch, and the second terminal of the sixth switch is grounded; the second terminal of the ninth resistor is connected to the second terminal of the sixth switch; the sixth switch is used to turn on in response to the turn-off voltage signal to control the first switch to turn off.

17. The circuit according to claim 16, characterized in that, The circuit also includes: a tenth resistor, a first Zener diode, and a second Zener diode; The first end of the tenth resistor is connected to the input terminal, and the second end of the tenth resistor is connected to the first end of the first Zener diode; the second end of the first Zener diode is connected to the first end of the second Zener diode and the control terminal of the first switching transistor. The second terminal of the second Zener diode is connected to the second terminal of the first switching transistor.

18. The circuit according to any one of claims 4-15, characterized in that, The circuit also includes: a primary winding, a secondary winding, and a seventh switching transistor; The first end of the primary winding is connected to the input terminal, and the second end of the primary winding is connected to the first end of the seventh switching transistor. The second end of the seventh switching transistor is grounded, and the control terminal of the seventh switching transistor is connected to the switching power supply chip. The seventh switching transistor is used to turn on or off in response to the pulse signal output by the switching power supply chip in the startup working state. The first end of the secondary winding is used to connect to the load, and the second end of the secondary winding is grounded, so as to output a power signal to the load when the switching power supply chip is in the startup state.

19. The circuit according to claim 18, characterized in that, The circuit also includes: an eleventh resistor; The first end of the eleventh resistor is connected to the second end of the seventh switch and the sampling current input terminal of the switching power supply chip, and the second end of the eleventh resistor is grounded. The switching power supply chip is also used to adjust the pulse signal based on the signal at the sampling current input terminal when it is in the startup working state, so as to adjust the magnitude of the power supply signal.

20. The circuit according to claim 19, characterized in that, The circuit also includes: a fourth diode, a third capacitor, and a twelfth resistor; The positive terminal of the fourth diode is connected to the first terminal of the secondary winding, and the negative terminal of the fourth diode is connected to the first terminal of the third capacitor and the first terminal of the twelfth resistor. The second terminal of the third capacitor is connected to the second terminal of the secondary winding and the second terminal of the twelfth resistor.

21. A switching power supply, characterized in that, include: The switching power supply circuit as described in any one of claims 1-20.

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