阅读说明：本技术 开关电源的电压调整系统、调整方法及电源系统 (Voltage adjusting system and method of switching power supply and power supply system ) 是由 白东培 蔡希桐 周宏明 于 2020-12-31 设计创作，主要内容包括：本申请公开了一种开关电源的电压调整系统、调整方法及电源系统。所述开关电源具有一路稳压输出端和至少一路非稳压输出端,所述电压调整系统包括：电压检测电路,用于检测所述非稳压输出端的输出电压；驱动控制器,连接所述电压检测电路,用于基于所述非稳压输出端的输出电压生成驱动信号；电流负载调整电路,连接于所述非稳压输出端与接地端之间,用于在所述驱动信号的驱动下导通或者断开,以调整所述非稳压输出端的输出电压。本申请实施例可以基于检测的非稳压输出端的输出电压来进行稳压控制,避免了通过设定假负载的负载电流导致的稳压设计与待机功耗之间的矛盾,利于降低开关电源的待机功耗并实现开关电源的非稳压输出端的稳压控制。(The application discloses a voltage adjusting system and method of a switching power supply and a power supply system. The switching power supply has a voltage-stabilizing output terminal and at least one non-voltage-stabilizing output terminal, and the voltage adjusting system includes: the voltage detection circuit is used for detecting the output voltage of the non-stabilized output end; the driving controller is connected with the voltage detection circuit and used for generating a driving signal based on the output voltage of the non-stabilized voltage output end; and the current load adjusting circuit is connected between the non-voltage-stabilizing output end and a grounding end and is used for being switched on or off under the driving of the driving signal so as to adjust the output voltage of the non-voltage-stabilizing output end. The embodiment of the application can perform voltage stabilization control based on the detected output voltage of the non-voltage stabilization output end, avoids contradiction between voltage stabilization design and standby power consumption caused by setting the load current of the dummy load, and is favorable for reducing the standby power consumption of the switching power supply and realizing the voltage stabilization control of the non-voltage stabilization output end of the switching power supply.)

1. A voltage regulation system of a switching power supply, the switching power supply having a regulated output and at least one unregulated output, the voltage regulation system comprising:

the voltage detection circuit is used for detecting the output voltage of the non-stabilized output end;

the driving controller is connected with the voltage detection circuit and used for generating a driving signal based on the output voltage of the non-stabilized voltage output end;

and the current load adjusting circuit is connected between the non-voltage-stabilizing output end and a grounding end and is used for being switched on or off under the driving of the driving signal so as to adjust the output voltage of the non-voltage-stabilizing output end.

2. The voltage regulation system of claim 1, wherein the current load regulation circuit comprises: the dummy load and the switching tube are used for controlling the dummy load to be connected or disconnected based on the driving signal.

3. The voltage regulation system of claim 2 wherein a first terminal of the dummy load is coupled to the unregulated output terminal, a second terminal of the dummy load is coupled to a collector of the switching transistor, and an emitter of the switching transistor is coupled to the ground terminal.

4. The voltage regulation system of claim 2, wherein a collector of the switching tube is connected to the unregulated output terminal, an emitter of the switching tube is connected to a first terminal of the dummy load, and a second terminal of the dummy load is connected to the ground terminal.

5. The voltage regulation system of claim 1, wherein the drive controller is configured to obtain the output voltage of the unregulated output terminal detected by the voltage detection circuit, and output the PWM drive signal based on the output voltage of the unregulated output terminal.

6. The voltage regulation system of claim 5, wherein the drive controller determines that the output voltage of the unregulated output is greater than or equal to a protection threshold and outputs the PWM drive signal.

7. The voltage regulation system of claim 6, wherein after the driving controller outputs the PWM driving signal, the driving controller is further configured to adjust a duty cycle of the PWM driving signal based on the detected output voltage of the unregulated output terminal to stabilize the output voltage of the unregulated output terminal.

8. A power supply system, comprising: comprising a switching power supply and a voltage regulation system as claimed in any one of claims 1 to 7.

9. A voltage regulation method of a switching power supply, applied to the voltage regulation system according to any one of claims 1 to 7, the voltage regulation method comprising:

the driving controller determines that the output voltage of the unstable voltage output end detected by the voltage detection circuit is greater than or equal to a protection threshold value, and outputs an initial PWM driving signal to the current load adjusting circuit.

10. The voltage adjustment method according to claim 9, further comprising:

the drive controller adjusts the duty ratio of the PWM drive signal based on the detected output voltage of the unregulated output terminal, so that the output voltage of the unregulated output terminal is stabilized at the protection threshold.

Technical Field

The present disclosure relates to the field of switching power supplies, and in particular, to a voltage regulation system, a voltage regulation method, and a power supply system of a switching power supply.

Background

With the development of electronic technology, the conventional linear power supply is gradually replaced by a switching power supply having a switching characteristic. With the evolution of application environment, the switching power supply with single output is often difficult to meet the application requirements, so that the switching power supply with multiple outputs is developed.

In the related art, the multi-output switching power supply usually performs voltage stabilization control based on one output voltage, that is, the feedback loop only samples one output voltage as feedback to realize voltage stabilization output of the sampling output path (also called as a voltage stabilization output end), and the other non-sampling output paths (also called as non-voltage stabilization output ends) are realized through a transformer. Because other non-sampling output circuits do not participate in closed-loop feedback, the voltage cannot be stabilized. Generally, when the regulated output terminal is fully loaded and the unregulated output terminal is lightly loaded, the unregulated output terminal voltage will rise due to the influence of the cross regulation rate. In order to avoid the voltage at the unregulated output terminal from fluctuating greatly due to the change of the load size, a dummy load is usually added at the unregulated output terminal, and the dummy load design usually needs to set a reasonable load current, which may result in the unregulated output terminal failing to stabilize the voltage if the load current is designed to be too small, and may result in the standby power consumption being large if the load current is designed to be too large.

Disclosure of Invention

In view of this, embodiments of the present application provide a voltage adjustment system, an adjustment method, and a power supply system for a switching power supply, which aim to effectively improve a contradiction between a voltage stabilization design and standby power consumption of an unregulated output terminal of the switching power supply.

The technical scheme of the embodiment of the application is realized as follows:

the embodiment of the application provides a switching power supply's voltage regulation system, switching power supply has voltage-stabilizing output and at least one kind of non-voltage-stabilizing output all the way, voltage regulation system includes:

the voltage detection circuit is used for detecting the output voltage of the non-stabilized output end;

the driving controller is connected with the voltage detection circuit and used for generating a driving signal based on the output voltage of the non-stabilized voltage output end;

and the current load adjusting circuit is connected between the non-voltage-stabilizing output end and a grounding end and is used for being switched on or off under the driving of the driving signal so as to adjust the output voltage of the non-voltage-stabilizing output end.

In some embodiments, the current load regulation circuit comprises: the dummy load and the switching tube are used for controlling the dummy load to be connected or disconnected based on the driving signal.

In some embodiments, a first terminal of the dummy load is connected to the unregulated output terminal, a second terminal of the dummy load is connected to a collector of the switching tube, and an emitter of the switching tube is connected to the ground terminal.

In some embodiments, the collector of the switching tube is connected to the non-regulated output terminal, the emitter of the switching tube is connected to the first terminal of the dummy load, and the second terminal of the dummy load is connected to the ground terminal.

In some embodiments, the driving controller is configured to obtain the output voltage of the unregulated output terminal detected by the voltage detecting circuit, and output a PWM (Pulse Width Modulation) driving signal based on the output voltage of the unregulated output terminal.

In some embodiments, the drive controller determines that the output voltage of the unregulated output terminal is greater than or equal to a protection threshold, and outputs the PWM drive signal.

In some embodiments, after the driving controller outputs the PWM driving signal, the driving controller is further configured to adjust a duty ratio of the PWM driving signal based on the detected output voltage of the unregulated output terminal to stabilize the output voltage of the unregulated output terminal.

An embodiment of the present application further provides a power supply system, including: the voltage regulation system comprises a switching power supply and the voltage regulation system.

The embodiment of the present application further provides a voltage adjustment method of a switching power supply, which is applied to the voltage adjustment system in the embodiment of the present application, and the voltage adjustment method includes:

the driving controller determines that the output voltage of the unstable voltage output end detected by the voltage detection circuit is greater than or equal to a protection threshold value, and outputs an initial PWM driving signal to the current load adjusting circuit.

In some embodiments, the voltage adjustment method further comprises:

and the drive controller adjusts the duty ratio of the PWM drive signal based on the detected output voltage of the non-voltage-stabilizing output end, so that the output voltage of the non-voltage-stabilizing output end is stabilized at the protection threshold value.

According to the technical scheme provided by the embodiment of the application, the voltage detection circuit detects the output voltage of the non-voltage-stabilizing output end, and the driving controller is connected with the voltage detection circuit and used for generating a driving signal based on the output voltage of the non-voltage-stabilizing output end; the current load adjusting circuit is connected between the non-voltage-stabilizing output end and the grounding end and used for being switched on or switched off under the driving of the driving signal so as to adjust the output voltage of the non-voltage-stabilizing output end, voltage stabilization control can be carried out based on the detected output voltage of the non-voltage-stabilizing output end, the contradiction between voltage stabilization design and standby power consumption caused by setting the load current of the dummy load is avoided, the standby power consumption of the switching power supply is favorably reduced, and the voltage stabilization control of the non-voltage-stabilizing output end of the switching power supply is realized.

Drawings

Fig. 1 is a schematic structural diagram of a voltage regulation system of a switching power supply according to an embodiment of the present application;

fig. 2 is a schematic circuit diagram of a power supply system according to an application example of the present application;

fig. 3 is a schematic diagram of an operation curve of a power supply system in an application example of the present application.

Description of reference numerals:

1. a switching power supply; 11. a voltage stabilization output end; 12. an unregulated output;

2. a voltage regulation system; 21. a voltage detection circuit;

22. a drive controller; 23. a current load regulation circuit.

Detailed Description

The present application will be described in further detail with reference to the following drawings and examples.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

Where in the description of the present application reference has been made to the terms "first", "second", etc. merely to distinguish between similar items and not to indicate a particular ordering for the items, it is to be understood that "first", "second", etc. may be interchanged with respect to a particular order or sequence of events to enable embodiments of the application described herein to be performed in an order other than that illustrated or described herein. Unless otherwise indicated, "plurality" means at least two.

In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the term "connected" is to be interpreted broadly, for example, as either a mechanical or electrical connection; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

The embodiment of the present application provides a voltage adjustment system of a switching power supply, as shown in fig. 1, the switching power supply 1 has a voltage-stabilizing output terminal 11 and at least one non-voltage-stabilizing output terminal 12, and the voltage adjustment system 2 includes: a voltage detection circuit 21, a drive controller 22, and a current load adjustment circuit 23. The voltage detection circuit 21 is configured to detect an output voltage of the unregulated output terminal 12; the driving controller 22 is connected with the voltage detection circuit 21 and used for generating a driving signal based on the output voltage of the non-stabilized output end 12; the current load adjusting circuit 23 is connected between the unregulated output terminal 12 and the ground terminal, and is turned on or off by the driving signal to adjust the output voltage of the unregulated output terminal 12.

Here, the drive controller 22 can perform the voltage stabilization control based on the output voltage of the unregulated output terminal detected by the voltage detection circuit 21, avoid a contradiction between the voltage stabilization design and the standby power consumption caused by setting the load current of the dummy load, and contribute to reducing the standby power consumption of the switching power supply and realizing the voltage stabilization control of the unregulated output terminal of the switching power supply.

For example, the driving controller 22 may control the current load adjusting circuit 23 to be turned on when it is determined that the output voltage of the unregulated output terminal 12 reaches or exceeds the protection threshold, and by introducing a dummy load in the current load adjusting circuit 23, the load of the unregulated output terminal 12 may be increased, thereby reducing the output voltage of the unregulated output terminal 12, and thus implementing the regulated control of the unregulated output terminal 12. In addition, when the switching power supply 1 is in standby, the output voltage of the non-regulated output terminal 12 is smaller than the protection threshold, and the current load adjusting circuit 23 is switched off, so that the problem of standby power consumption increase caused by the conventional dummy load can be effectively solved.

It is understood that when the switching power supply 1 has multiple unregulated outputs 12, a voltage detecting circuit 21 and a current load adjusting circuit 23 may be respectively disposed at each unregulated output 12, and the driving controller 22 may control the conducting state of the corresponding current load adjusting circuit 23 based on the output voltage of the unregulated output 12, thereby implementing the regulated control of the corresponding unregulated output 12. Namely, the voltage detection circuit 21 and the current load adjustment circuit 23 are provided in one-to-one correspondence with the respective unregulated output terminals 12. The driver controller 22 may be shared by multiple unregulated outputs 12 to save control cost.

In some embodiments, the current load adjusting circuit 23 includes: the dummy load and the switching tube are used for controlling the dummy load to be connected or disconnected based on the driving signal.

Here, the switching transistor may be a MOS transistor (metal-oxide semiconductor field effect transistor) or an IGBT transistor (insulated gate bipolar transistor), and the present application is not particularly limited thereto.

In some embodiments, the first terminal of the dummy load is connected to the non-regulated output terminal 12, the second terminal of the dummy load is connected to the collector of the switch tube, and the emitter of the switch tube is connected to the ground terminal. The control electrode of the switching tube is connected to the driving controller 22 for controlling the conducting state based on the driving signal.

In some embodiments, the collector of the switch tube is connected to the non-regulated output terminal 12, the emitter of the switch tube is connected to the first terminal of the dummy load, and the second terminal of the dummy load is connected to the ground terminal. The control electrode of the switching tube is connected to the driving controller 22 for controlling the conducting state based on the driving signal.

In some embodiments, the driving controller 22 is configured to obtain the output voltage of the unregulated output 12 detected by the voltage detecting circuit 21, and output the PWM driving signal based on the output voltage of the unregulated output 12.

Here, since the drive signal output by the drive controller 22 is a PWM drive signal, the adjustment of the magnitude of the load current of the current load adjusting circuit 23 can be realized based on the PWM drive signal, so that the load current of the current load adjusting circuit 23 can be increased as the output voltage of the unregulated output terminal 12 is higher, thereby realizing the regulated control of the unregulated output terminal 12.

Illustratively, the driving controller 22 determines that the output voltage of the unregulated output terminal 12 is greater than or equal to the protection threshold, and outputs a PWM driving signal to control the current load adjusting circuit 23 to be connected to shunt and regulate the unregulated output terminal 12.

Illustratively, after the driving controller 22 outputs the PWM driving signal, it is further configured to adjust the duty ratio of the PWM driving signal based on the detected output voltage of the unregulated output terminal 12 to stabilize the output voltage of the unregulated output terminal. For example, when the driving controller 22 determines that the detected output voltage of the unregulated output terminal 12 continues to increase, the duty ratio of the PWM driving signal is increased, so that the load current of the current load adjusting circuit 23 can be increased, that is, the load current of the current load adjusting circuit 23 is dynamically adjusted, and the load of the unregulated output terminal 12 is further adjusted, thereby implementing the regulated control of the unregulated output terminal 12.

It can be understood that the voltage detection circuit 21 adopts a voltage dividing resistor structure to collect the output voltage of the unregulated output terminal 12.

Illustratively, the drive Controller 22 may be implemented using an Application Specific Integrated Circuit (ASIC), a DSP, a Programmable Logic Device (PLD), a Complex Programmable Logic Device (CPLD), an FPGA, a general-purpose processor, a Microcontroller (MCU), a Microprocessor (Microprocessor), or other electronic components.

An embodiment of the present application further provides a power supply system, including: the voltage regulation system comprises a switching power supply 1 and a voltage regulation system 2 of the embodiment of the application.

The present application is described in further detail below with reference to application examples.

As shown in fig. 2, the present application example discloses a power supply system of an air conditioner electric control main control, the power supply system includes a switching power supply 1, the switching power supply 1 has two voltage output terminals V1, V2, wherein the voltage output terminal V1 is a regulated voltage output terminal, and the voltage output terminal V2 is an unregulated voltage output terminal. The voltage detection circuit 21, the drive controller 22, and the current load adjustment circuit 23 are provided on the voltage output terminal V2 side.

As shown in fig. 2, the switching power supply 1 includes: the transformer T1, resistance R1, electric capacity C1, diode D1, power chip U1, wherein, insert DC power supply between transformer T1's primary winding terminal 1, 3, resistance R1, electric capacity C1, diode D1 constitute the RCD absorption circuit of primary winding side, be used for absorbing the unnecessary energy of secondary reflection back. Pin 4 of the power chip U1 is connected to the primary winding terminal 3, and can control the voltage of the transformer T1. A winding terminal 4 of the transformer T1 is connected to a negative electrode of a dc power supply, a winding terminal 5 is used for supplying power to a power chip U1, the winding terminal 5 is connected to an anode of a diode D2, a cathode of a diode D2 is connected to a first end of a resistor R2, a second end of a resistor R2 is connected to a pin 2 of the power chip U1, a second end of the resistor R2 is further connected to the negative electrode of the dc power supply through a capacitor C2, a first end of the resistor R2 is connected to a power supply terminal (shown as +17V in fig. 2), and a first end of the resistor R2 is further connected to the negative electrode of the dc power supply through an electrolytic capacitor E1 and a.

The secondary winding terminal 7 of the transformer T1 is connected to the anode of the diode D4, the cathode of the diode D4 is connected to the voltage output terminal V1, the secondary winding terminal 6 of the transformer T1 is grounded, and the cathode of the diode D4 is grounded via the electrolytic capacitor E3. The output voltage of the voltage output terminal V1 is 12V. The voltage output terminal V1 is further provided with an output feedback circuit for voltage stabilization control, the output feedback circuit including: the voltage regulator circuit comprises an optical coupler U2, a controllable voltage regulator U3, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11 and a capacitor C4, wherein a first end of the resistor R9 is connected with a voltage output end V1, a second end of the resistor R9 is connected with a first end of a resistor R11, a second end of the resistor R11 is grounded, a first end of a resistor R7 is connected with a voltage output end V1, a second end of the resistor R7 is connected with a first end of a resistor R8, a common end of the resistor R2 is connected with a pin A of the optical coupler U2, a second end of the resistor R8 is connected with a cathode of the controllable voltage regulator U8, a common end of the optical coupler U8 is connected with a pin K, an anode of the controllable voltage regulator U8 is grounded, a reference electrode of the resistor R8 is connected with a first end of the resistor R8. The on-state voltage of the controllable voltage-stabilizing source U3 can be set through the resistance values of the resistor R9 and the resistor R11, and when the controllable voltage-stabilizing source U3 detects that the output of the voltage output end V1 reaches 12V, the controllable voltage-stabilizing source U3 is turned on, so that the optical coupler U2 is turned off. Pin 1 of the power chip U1 is connected with pin C of the optocoupler U2, the common end of the power chip U1 is connected with the negative electrode of the direct-current power supply through a resistor R3, and pin E of the optocoupler U2 is connected with the negative electrode of the direct-current power supply. When the optocoupler U2 cuts off, the switch tube of the power supply chip U1 cuts off, so that the power supply chip U1 can perform voltage stabilization control based on the output voltage of the voltage output end V1. It is to be understood that the output feedback circuit may also be in other forms, which is not limited in this application.

The secondary winding terminal 10 of the transformer T1 is connected to the anode of the diode D3, the cathode of the diode D3 is connected to the voltage output terminal V2, the secondary winding terminal 9 of the transformer T1 is grounded, and the cathode of the diode D3 is grounded via the electrolytic capacitor E2. The voltage output terminal V2 outputs 26V, which is unregulated voltage.

In the present application example, the current load adjustment circuit 23 includes: triode Q1 and resistance R13, resistance R13 are as the dummy load, and the first end of resistance R13 is connected voltage output end V2, and the second end of resistance R13 is connected the collector of triode Q1, and the base of triode Q1 is connected drive controller 22, and the emitter of triode Q1 is ground. The driving controller 22 is connected to the voltage detection circuit 21 for detecting the output voltage of the voltage output terminal V2, and outputs a PWM driving signal to the base of the transistor Q1 based on the voltage detected by the voltage detection circuit 21.

Illustratively, the operation of the drive controller 22 is as follows:

the drive controller 22 sets a maximum voltage value Vd (i.e., a protection threshold) to the voltage output terminal V2, for example, set Vd equal to 28V; in normal operation of the air conditioner electric control main control, when the voltage output end V1 is connected with a load, the voltage output end V2 is lightly loaded, and along with the increase of the load of the voltage output end V1, the output voltage of the voltage output end V2 can rise; when the output voltage of the voltage output end V2 rises and exceeds the Vd value, the driving controller 22 outputs a PWM driving signal with a set duty ratio to control the conduction of the transistor Q1, and at the same time, the current flowing through the resistor R13 is controlled by adjusting the duty ratio D of the PWM driving signal, and when the working current on the voltage output end V1 side is larger, the voltage rising trend of the voltage output end V2 is larger, the load current of the adjusting resistor R13 is larger, and until the voltage of the voltage output end V2 does not rise any more, the balance is achieved.

The operating current flowing through the resistor R13 can be calculated by the following formula:

Id＝U2/r13*D

wherein, U2 is the output voltage value of the voltage output terminal V2, D is the duty ratio of the PWM driving signal, and R13 is the resistance value of the resistor R13.

Fig. 3 shows an operation curve diagram of the power supply system, wherein I is the operation current on the side of the voltage output terminal V1, curve a is the output voltage of the voltage output terminal V2, and curve B is the duty ratio of the PWM driving signal. As can be seen from fig. 3, as the operating current on the side of the voltage output terminal V1 increases, the output voltage of the voltage output terminal V2 gradually increases, but after the operating current increases to the maximum voltage value Vd, the output voltage is stabilized at Vd by the current load adjusting circuit 23 driven by the PWM driving signal, so that the voltage stabilization control of the voltage output terminal V2 can be realized.

It can be understood that, when the voltage output terminal V2 is heavily loaded, since the voltage of the voltage output terminal V2 does not exceed 27V, the driving controller 22 does not output the PWM driving signal, and controls the transistor Q1 to be turned off, and no current flows through the current load adjusting circuit 23, so that power consumption can be reduced, and an energy saving effect can be achieved.

Through the control, the two-path output flyback switching power supply circuit of the air conditioner electric control master control is realized, the output voltage of the voltage output end V2 cannot be higher than the designed voltage value under different loads of the voltage output end V1 and the voltage output end V2, and the low-power-consumption standby can be realized under the standby condition.

It can be understood that the power supply system of the embodiment of the present application can be applied to the field of household electrical appliances such as air conditioners and washing machines, wherein the number of the non-voltage-stabilized output terminals of the switching power supply can be one or more, for a plurality of non-voltage-stabilized output terminals, the corresponding voltage detection circuit 21 and the current load adjustment circuit 23 can be respectively provided, and the driving control is performed by an independent or shared driving controller based on the detected voltage of each non-voltage-stabilized output terminal, so as to realize the voltage-stabilized control of each non-voltage-stabilized output terminal.

The embodiment of the present application further provides a voltage adjustment method of a switching power supply, which is applied to the voltage adjustment system of the embodiment of the present application, and the voltage adjustment method includes:

the driving controller determines that the output voltage of the unstable voltage output end detected by the voltage detection circuit is greater than or equal to a protection threshold value, and outputs an initial PWM driving signal to the current load adjusting circuit.

Here, the protection threshold may be set appropriately according to the voltage stabilization requirement of the non-stabilized output terminal. The driving controller obtains the voltage detected by the voltage detection circuit, compares the detected voltage with a protection threshold value, outputs an initial PWM driving signal if the detected output voltage of the unstable voltage output is determined to be greater than or equal to the protection threshold value, and does not output the PWM driving signal if the detected output voltage of the unstable voltage output is determined to be less than the protection threshold value, so that unnecessary power consumption is avoided.

In some embodiments, the voltage adjustment method further comprises:

and the drive controller adjusts the duty ratio of the PWM drive signal based on the detected output voltage of the non-voltage-stabilizing output end, so that the output voltage of the non-voltage-stabilizing output end is stabilized at a protection threshold value.

It can be understood that the driving controller may adjust the duty ratio of the PWM driving signal based on the detected output voltage of the unregulated output terminal, for example, if it is determined that the output voltage of the unregulated output terminal is increasing based on the two adjacent detected output voltages, the duty ratio of the PWM driving signal is increased, that is, the load current of the dummy load in the current load adjusting circuit 23 is increased until the output voltage of the unregulated output terminal is stabilized at the protection threshold, or the output voltage of the unregulated output terminal is smaller than the protection threshold, and the PWM driving signal is stopped being output, so that the voltage of the unregulated output terminal is stabilized at the protection threshold based on the feedback control.

It should be noted that: "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.

The technical means described in the embodiments of the present application may be arbitrarily combined without conflict.

The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.