Switching power supply with adjustable output voltage

Abstract

The application relates to the technical field of switching power supplies, in particular to a switching power supply with adjustable output voltage, which comprises a transformer T1 and a power management module coupled to the primary side of the transformer T1, wherein the power management module is integrated with a power management chip; the switching power supply further comprises a master control chip, a photoelectric coupler U1 and an adjustable voltage reference module; the light receiver of the photoelectric coupler U1 is coupled to the feedback end of the power management chip, and the master control chip is coupled to the light source of the photoelectric coupler U1 through the adjustable voltage reference module; the master control chip is used for controlling the voltage size transmitted by the adjustable voltage reference module to the light source of the photoelectric coupler U1; the problems that the adjustable range of the output voltage of the switching power supply is small and the adjustment stability cannot be guaranteed are solved.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, and in particular to a switching power supply with adjustable output voltage. Background Technology

[0002] The output of the switching power supply is sampled by a voltage divider circuit, and the actual output voltage is fed back to the power management chip on the primary side of the transformer. The power management chip judges the voltage deviation and adjusts the switching quantity of the switching transistor on the primary side of the transformer, thereby achieving dynamic balance, stabilizing the output voltage of the switching power supply, and enhancing its resistance to load changes or signal disturbances. The output voltage of the switching power supply is regulated by setting a BUCK circuit (or chopper circuit) on the secondary side of the transformer, and the output voltage of the switching power supply is changed by chopping.

[0003] The current output voltage regulation method of switching power supplies limits the adjustment of the output voltage to a step-down adjustment based on the secondary voltage of the transformer, resulting in a limited adjustable range. Furthermore, regulation at the output of the switching power supply (i.e., the secondary side of the transformer) is susceptible to fluctuations on the primary side of the transformer, sudden load changes, or signal disturbances, leading to voltage fluctuations (such as ringing). Even with feedback mechanisms, the inherent hysteresis of feedback means that these fluctuations cannot be completely eliminated. Summary of the Invention

[0004] To address the aforementioned shortcomings, the present invention aims to provide a switching power supply with adjustable output voltage, which solves the problems of small adjustable range of output voltage and inability to guarantee adjustment stability in switching power supplies.

[0005] To achieve this objective, the present invention adopts the following technical solution: An adjustable output voltage switching power supply includes a transformer T1 and a power management module coupled to the primary side of the transformer T1, wherein the power management module integrates a power management chip; it also includes a main control chip, an optocoupler U1, and an adjustable voltage reference module; the photodetector of the optocoupler U1 is coupled to the feedback terminal of the power management chip, and the main control chip is coupled to the light source of the optocoupler U1 via the adjustable voltage reference module; The main control chip is used to control the voltage transmitted from the adjustable voltage reference module to the light source of the optocoupler U1.

[0006] Furthermore, the adjustable voltage reference module includes a controllable voltage regulator K1; the output terminal of the main control chip is electrically connected to the reference electrode of the controllable voltage regulator K1, the anode of the controllable voltage regulator K1 is grounded, the cathode of the controllable voltage regulator K1 is electrically connected to the cathode of the light source of the optocoupler U1, and the anode of the light source of the optocoupler U1 is connected to the light source voltage.

[0007] Furthermore, the adjustable voltage reference module also includes a diode D4, a resistor R3, and a resistor R4; the cathode of the diode D4 is electrically connected to the positive terminal of the secondary side of the transformer T1; the anode of the diode D4 is connected in series with the resistors R3 and R4 and then electrically connected to the negative terminal of the secondary side of the transformer T1; the anode of the light source of the optocoupler U1 is electrically connected to the connection point of the resistors R3 and R4.

[0008] Furthermore, the controllable voltage regulator K1 is encapsulated within the optocoupler U1.

[0009] Furthermore, the optocoupler U1 includes an electrical component with pin 1, an electrical component with pin 2, an electrical component with pin 3, an electrical component with pin 4, an electrical component with pin 5, a light source chip, a light receiver chip, and a plastic encapsulation shell; the light receiver chip is placed inside the electrical component with pin 1, and the collector of the light receiver chip is electrically connected to the inside of the electrical component with pin 1; the emitter of the light receiver chip is electrically connected to the inside of the electrical component with pin 2 via a flying wire; The outer sides of the electrical component at pin 1 and the outer sides of the electrical component at pin 2 serve as the collector and emitter of the photodetector of the optocoupler U1, respectively. The light source chip and the controllable voltage regulator K1 are both placed inside the electrical component at pin 4. The reference electrode of the controllable voltage regulator K1 is electrically connected to the inside of the electrical component at pin 4. The cathode of the controllable voltage regulator K1 is electrically connected to the cathode of the light source chip via a flying wire. The anode of the light source chip is electrically connected to the inside of the electrical component at pin 3 via a flying wire. The anode of the controllable voltage regulator K1 is electrically connected to the inside of the electrical component at pin 5 via a flying wire. The outer side of the electrical component at pin 3 is used as the anode of the light source of the optocoupler U1, the outer side of the electrical component at pin 4 is electrically connected to the output terminal of the main control chip, and the outer side of the electrical component at pin 5 is grounded. The plastic encapsulation shell encapsulates the inner sides of the electrical components with pin 1, pin 2, pin 3, pin 4, and pin 5, as well as the light source chip, the light receiver chip, and the controllable voltage regulator K1.

[0010] Furthermore, the adjustable voltage reference module includes resistors R5 and R6 and at least two voltage value units; the tail end of the previous voltage value unit and the head end of the next voltage value unit are electrically connected. The positive terminal of the secondary side of the transformer T1 is electrically connected to the first end of the first voltage value unit, and the tail end of the last voltage value unit is electrically connected to one end of the resistor R5. The other end of the resistor R5 and one end of the resistor R6 are both electrically connected to the anode of the light source of the optocoupler U1, and the other end of the resistor R6 and the cathode of the light source of the optocoupler U1 are both grounded. The output terminal of the main control chip is electrically connected to the control terminal of the voltage value unit. The voltage value unit is used to generate a constant voltage, and the main control chip is used to control whether the voltage value unit generates a constant voltage.

[0011] Furthermore, the voltage value unit includes a Zener diode ZD1 and a MOSFET M1; the gate of the MOSFET M1 serves as the control terminal of the voltage value unit, the cathode of the Zener diode ZD1 serves as the first terminal of the voltage value unit, and the anode of the Zener diode ZD1 serves as the last terminal of the voltage value unit. The drain and source of the MOS transistor M1 are electrically connected to the cathode and anode of the Zener diode ZD1, respectively.

[0012] Furthermore, it also includes a resistor R2. The collector of the photodetector of the optocoupler U1 is connected to the power supply voltage, and the emitter of the photodetector of the optocoupler U1 is electrically connected to the feedback terminal of the power management chip via the resistor R2.

[0013] The technical solution provided by this invention can include the following beneficial effects: the voltage regulation control is changed from the traditional secondary side BUCK step-down to the main control chip directly controlling the feedback reference fed back to the primary side power management chip, breaking through the limitation of only step-down regulation. The power management chip actively adjusts the voltage output from the primary side of transformer T1 to the secondary side, thereby greatly expanding the adjustable range of the output voltage at the output terminal of the switching power supply.

[0014] In addition, the voltage regulation stage is moved forward to the primary side feedback loop, changing from the traditional passive reception of the output voltage to active voltage regulation by the power management chip. This avoids the direct impact of load changes, primary side fluctuations, and signal disturbances on voltage regulation, and eliminates the need for a feedback mechanism to ensure the accuracy of voltage regulation, significantly reducing voltage jitter and ringing phenomena. Attached Figure Description

[0015] Figure 1 This is a circuit diagram of a switching power supply with adjustable output voltage according to Embodiment 1 of the present invention.

[0016] Figure 2 Is it like this? Figure 1 The diagram shows the internal structure of the optocoupler U1.

[0017] Figure 3This is a circuit diagram of a switching power supply with adjustable output voltage according to Embodiment 2 of the present invention.

[0018] The components include: transformer T1, power management module 2, power management chip 21, main control chip 1, optocoupler U1, adjustable voltage reference module 3, controllable voltage regulator K1, electrical component 10 (pin 1), electrical component 20 (pin 2), electrical component 30 (pin 3), electrical component 40 (pin 4), electrical component 50 (pin 5), light source chip 60, light receiver chip 70, and plastic casing 80. The adjustable voltage reference module 3 includes resistor R5, resistor R6, voltage value unit 31, Zener diode ZD1, MOSFET M1, and resistor R2. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0020] In the description of embodiments of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0021] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention according to the specific circumstances.

[0022] The following is combined Figures 1 to 3 This describes a switching power supply with adjustable output voltage according to an embodiment of the present invention.

[0023] An adjustable output voltage switching power supply includes a transformer T1 and a power management module 2 coupled to the primary side of the transformer T1. The power management module 2 integrates a power management chip 21. It also includes a main control chip 1, an optocoupler U1, and an adjustable voltage reference module 3. The photodetector of the optocoupler U1 is coupled to the feedback terminal of the power management chip 21. The main control chip 1 is coupled to the light source of the optocoupler U1 via the adjustable voltage reference module 3. The main control chip 1 is used to control the voltage transmitted from the adjustable voltage reference module 3 to the light source of the optocoupler U1.

[0024] In a preferred embodiment of the present invention, an adjustable output voltage switching power supply is provided, such as... Figure 1 As shown, the voltage regulation control has been changed from the traditional secondary-side BUCK step-down to the main control chip 1 directly controlling the feedback reference fed back to the primary-side power management chip 21. This breaks through the limitation of only step-down regulation. The power management chip 21 actively adjusts the voltage output from the primary side of transformer T1 to the secondary side, thereby greatly expanding the adjustable range of the output voltage at the output terminal of the switching power supply.

[0025] In addition, the voltage regulation stage is moved forward to the primary side feedback loop, changing from the traditional passive receiving of the output voltage to active voltage regulation by the power management chip 21. This avoids the direct impact of load changes, primary side fluctuations, and signal disturbances on voltage regulation, and eliminates the need for a feedback mechanism to ensure the accuracy of voltage regulation, significantly reducing voltage jitter and ringing phenomena.

[0026] It should be noted that the power management module 2 integrates the power management chip 21 and switching transistors, etc., for the control of the primary side (i.e., the primary side of transformer T1) of the switching power supply.

[0027] Example 1 Furthermore, the adjustable voltage reference module 3 includes a controllable voltage regulator K1; the output terminal of the main control chip 1 is electrically connected to the reference electrode of the controllable voltage regulator K1, the anode of the controllable voltage regulator K1 is grounded, the cathode of the controllable voltage regulator K1 is electrically connected to the cathode of the light source of the optocoupler U1, and the anode of the light source of the optocoupler U1 is connected to the light source voltage.

[0028] In this embodiment, the controllable voltage regulator K1, such as TL431, has a precise voltage adjustment capability of 2.5~36V. Using it as the adjustable voltage reference module 3, the main control chip 1 can precisely adjust the voltage transmitted to the light source of the optocoupler U1 by controlling the adjustable voltage reference module 3, thereby feeding back to the power management chip 21 to adjust the output voltage of the switching power supply.

[0029] Furthermore, the adjustable voltage reference module 3 also includes a diode D4, a resistor R3, and a resistor R4; the cathode of the diode D4 is electrically connected to the positive terminal of the secondary side of the transformer T1; the anode of the diode D4 is connected to the negative terminal of the secondary side of the transformer T1 after being connected in series with resistors R3 and R4; the anode of the light source of the optocoupler U1 is electrically connected to the connection point of resistors R3 and R4.

[0030] In this embodiment, the light source voltage connected to the anode of the light source of the optocoupler U1 can be obtained from the positive terminal of the secondary side of the transformer T1 (i.e. the output terminal of the switching power supply) through a stable voltage divider circuit composed of diode D4, resistor R3 and resistor R4. This allows the light source of the optocoupler U1 to obtain the light source voltage while simultaneously monitoring the output voltage stability of the switching power supply output terminal, and feeds it back to the power management chip 21 for stability adjustment through the optocoupler U1.

[0031] It should be noted that stability adjustment and output voltage adjustment of the main control chip 1 can coexist. For example, when the output voltage is unstable and needs to be adjusted, the two are superimposed and fed back. The power management chip 21 directly adjusts the voltage based on the superimposed voltage difference, thus solving the two adjustment needs at the same time.

[0032] Furthermore, the controllable voltage regulator K1 is packaged within the optocoupler U1.

[0033] In this embodiment, considering the complexity of microwave interference in the circuit board and the irregular layout and routing of discrete components in the circuit board, when the controllable voltage regulator K1 and the light source of the optocoupler U1 are far apart, the signal transmission will be affected by the unknown electromagnetic influence caused by the trace length and space, and the signal stability may not be guaranteed. Therefore, it is preferable to directly encapsulate the controllable voltage regulator K1 in the optocoupler U1, which can ensure signal stability and reduce the possibility of poor soldering of discrete components on the circuit board (integrated chips have higher reliability of electrical connection due to their packaging environment, micro-automatic soldering technology and chip testing process).

[0034] The specific structure of the controllable voltage regulator K1 integrated within the optocoupler U1 is as follows: Figure 2 As shown, the specific structural relationship is as follows: The optocoupler U1 includes an electrical component 10 (pin 1), an electrical component 20 (pin 2), an electrical component 30 (pin 3), an electrical component 40 (pin 4), an electrical component 50 (pin 5), a light source chip 60, a light receiver chip 70, and a plastic casing 80. The light receiver chip 70 is placed inside the electrical component 10 (pin 1), and the collector of the light receiver chip 70 is electrically connected to the inside of the electrical component 10 (pin 1). The emitter of the light receiver chip 70 is electrically connected to the inside of the electrical component 20 (pin 2) via a flying wire. The outer side of the electrical component 10 at pin 1 and the outer side of the electrical component 20 at pin 2 are used as the collector and emitter of the photodetector of the optocoupler U1, respectively. The light source chip 60 and the controllable voltage regulator K1 are both placed inside the electrical component 40 with pin 4. The reference electrode of the controllable voltage regulator K1 is electrically connected to the inside of the electrical component 40 with pin 4. The cathode of the controllable voltage regulator K1 is electrically connected to the cathode of the light source chip 60 through a flying wire. The anode of the light source chip 60 is electrically connected to the inside of the electrical component 30 with pin 3 through a flying wire. The anode of the controllable voltage regulator K1 is electrically connected to the inside of the electrical component 50 with pin 5 through a flying wire. The outer side of the electrical component 30 at pin 3 is used as the anode of the light source of the optocoupler U1, the outer side of the electrical component 40 at pin 4 is electrically connected to the output terminal of the main control chip 1, and the outer side of the electrical component 50 at pin 5 is grounded. The plastic casing 80 encapsulates the inner side of the electrical component 10 with pin 1, the inner side of the electrical component 20 with pin 2, the inner side of the electrical component 30 with pin 3, the inner side of the electrical component 40 with pin 4, the inner side of the electrical component 50 with pin 5, the light source chip 60, the light receiver chip 70, and the controllable voltage regulator K1.

[0035] In this embodiment, the light source chip 60, the light receiver chip 70, and the controllable voltage regulator K1 are placed through the pin electrical components. This serves two purposes: first, to support the chip (support frame), and second, to minimize the traces between the chip and the pin electrical components.

[0036] Example 2 Furthermore, the adjustable voltage reference module 3 includes resistors R5 and R6 and at least two voltage value units 31; the tail end of the previous voltage value unit 31 and the head end of the next voltage value unit 31 are electrically connected. The positive terminal of the secondary side of transformer T1 is electrically connected to the first end of the first voltage value unit 31, and the tail end of the last voltage value unit 31 is electrically connected to one end of resistor R5. The other end of resistor R5 and one end of resistor R6 are both electrically connected to the anode of the light source of optocoupler U1, and the other end of resistor R6 and the cathode of the light source of optocoupler U1 are both grounded. The output terminal of the main control chip 1 is electrically connected to the control terminal of the voltage value unit 31. The voltage value unit 31 is used to generate a constant voltage, and the main control chip 1 is used to control whether the voltage value unit 31 generates a constant voltage.

[0037] In this embodiment, as Figure 3As shown, without considering fine adjustment and integrating the adjustable voltage reference module 3 into the optocoupler U1, the adjustable voltage reference module 3 can also be composed of resistors R5 and R6 and at least two voltage value units 31. The main control chip 1 controls which voltage value unit 31 generates a constant voltage, thereby determining the superposition value of the constant voltage in the series circuit (addition; for each additional voltage value unit 31 that generates a constant voltage, an additional constant voltage value is added), forming a clear gradient voltage regulation; suitable for situations where the switching power supply has a large load, and the load requires sufficient output voltage to drive it, and the output voltage adjustment range will be larger than that of the scheme in Example 1.

[0038] Furthermore, the voltage value unit 31 includes a Zener diode ZD1 and a MOSFET M1; the gate of the MOSFET M1 is used as the control terminal of the voltage value unit 31, the cathode of the Zener diode ZD1 is used as the first terminal of the voltage value unit 31, and the anode of the Zener diode ZD1 is used as the last terminal of the voltage value unit 31. The drain and source of MOSFET M1 are electrically connected to the cathode and anode of Zener diode ZD1, respectively.

[0039] In this embodiment, the voltage value unit 31 is preferably composed of a Zener diode ZD1 and a MOSFET M1. The MOSFET M1 has better voltage withstand and overcurrent capabilities, while the Zener diode ZD1 can provide a constant voltage value. Furthermore, the magnitude of the constant voltage can be selected by choosing the Zener diode ZD1. When the MOSFET M1 is turned on, the Zener diode ZD1 is short-circuited and does not generate a constant voltage; when the MOSFET M1 is turned off, the Zener diode ZD1 is connected in series in the circuit, generating a constant voltage.

[0040] In addition, the circuit for coupling the photodetector of optocoupler U1 to the feedback terminal of power management chip 21 is typically as follows (both Embodiment 1 and Embodiment 2 can be used): It also includes resistor R2. The collector of the photoreceiver of optocoupler U1 is connected to the power supply voltage (the source of the power supply voltage is not limited, for example, it can be coupled from the auxiliary winding of transformer T1). The emitter of the photoreceiver of optocoupler U1 is electrically connected to the feedback terminal of power management chip 21 through resistor R2 (used for current limiting and chip pin protection). Thus, the photoreceiver of optocoupler U1 can be powered on to sense the transmission voltage of the light source and feed it back to power management chip 21.

[0041] Other configurations and operations of a switching power supply with adjustable output voltage according to embodiments of the present invention are known to those skilled in the art and will not be described in detail here.

[0042] In the description of this specification, references to terms such as "embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0043] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A switching power supply with adjustable output voltage, comprising a transformer T1 and a power management module coupled to the primary side of the transformer T1, wherein the power management module integrates a power management chip; characterized in that: It also includes a main control chip, an optocoupler U1, and an adjustable voltage reference module; the photodetector of the optocoupler U1 is coupled to the feedback terminal of the power management chip, and the main control chip is coupled to the light source of the optocoupler U1 via the adjustable voltage reference module; The main control chip is used to control the voltage transmitted from the adjustable voltage reference module to the light source of the optocoupler U1.

2. The switching power supply with adjustable output voltage according to claim 1, characterized in that: The adjustable voltage reference module includes a controllable voltage regulator K1; the output terminal of the main control chip is electrically connected to the reference electrode of the controllable voltage regulator K1, the anode of the controllable voltage regulator K1 is grounded, the cathode of the controllable voltage regulator K1 is electrically connected to the cathode of the light source of the optocoupler U1, and the anode of the light source of the optocoupler U1 is connected to the light source voltage.

3. The switching power supply with adjustable output voltage according to claim 2, characterized in that: The adjustable voltage reference module also includes a diode D4, a resistor R3, and a resistor R4; the cathode of the diode D4 is electrically connected to the positive terminal of the secondary side of the transformer T1; the anode of the diode D4 is connected in series with the resistors R3 and R4 and then electrically connected to the negative terminal of the secondary side of the transformer T1; the anode of the light source of the optocoupler U1 is electrically connected to the connection point of the resistors R3 and R4.

4. The switching power supply with adjustable output voltage according to claim 2, characterized in that: The controllable voltage regulator K1 is encapsulated within the optocoupler U1.

5. A switching power supply with adjustable output voltage according to claim 4, characterized in that: The optocoupler U1 includes an electrical component with pin 1, pin 2, pin 3, pin 4, and pin 5, a light source chip, a light receiver chip, and a plastic encapsulation shell. The light receiver chip is placed inside the electrical component with pin 1, and the collector of the light receiver chip is electrically connected to the inside of the electrical component with pin 1. The emitter of the light receiver chip is electrically connected to the inside of the electrical component with pin 2 via a flying wire. The outer sides of the electrical component at pin 1 and the outer sides of the electrical component at pin 2 serve as the collector and emitter of the photodetector of the optocoupler U1, respectively. The light source chip and the controllable voltage regulator K1 are both placed inside the electrical component at pin 4. The reference electrode of the controllable voltage regulator K1 is electrically connected to the inside of the electrical component at pin 4. The cathode of the controllable voltage regulator K1 is electrically connected to the cathode of the light source chip via a flying wire. The anode of the light source chip is electrically connected to the inside of the electrical component at pin 3 via a flying wire. The anode of the controllable voltage regulator K1 is electrically connected to the inside of the electrical component at pin 5 via a flying wire. The outer side of the electrical component at pin 3 is used as the anode of the light source of the optocoupler U1, the outer side of the electrical component at pin 4 is electrically connected to the output terminal of the main control chip, and the outer side of the electrical component at pin 5 is grounded. The plastic encapsulation shell encapsulates the inner sides of the electrical components with pin 1, pin 2, pin 3, pin 4, and pin 5, as well as the light source chip, the light receiver chip, and the controllable voltage regulator K1.

6. The switching power supply with adjustable output voltage according to claim 1, characterized in that: The adjustable voltage reference module includes resistors R5 and R6 and at least two voltage value units; the tail end of the previous voltage value unit and the head end of the next voltage value unit are electrically connected. The positive terminal of the secondary side of the transformer T1 is electrically connected to the first end of the first voltage value unit, and the tail end of the last voltage value unit is electrically connected to one end of the resistor R5. The other end of the resistor R5 and one end of the resistor R6 are both electrically connected to the anode of the light source of the optocoupler U1, and the other end of the resistor R6 and the cathode of the light source of the optocoupler U1 are both grounded. The output terminal of the main control chip is electrically connected to the control terminal of the voltage value unit. The voltage value unit is used to generate a constant voltage, and the main control chip is used to control whether the voltage value unit generates a constant voltage.

7. A switching power supply with adjustable output voltage according to claim 6, characterized in that: The voltage value unit includes a Zener diode ZD1 and a MOSFET M1; the gate of the MOSFET M1 is used as the control terminal of the voltage value unit, the cathode of the Zener diode ZD1 is used as the first terminal of the voltage value unit, and the anode of the Zener diode ZD1 is used as the last terminal of the voltage value unit. The drain and source of the MOS transistor M1 are electrically connected to the cathode and anode of the Zener diode ZD1, respectively.

8. The switching power supply with adjustable output voltage according to claim 1, characterized in that: It also includes a resistor R2. The collector of the photoreceiver of the optocoupler U1 is connected to the power supply voltage, and the emitter of the photoreceiver of the optocoupler U1 is electrically connected to the feedback terminal of the power management chip through the resistor R2.

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