LED switching power supply capable of suppressing output surge current

Abstract

The utility model discloses an LED switching power supply capable of suppressing output surge current. The LED switching power supply comprises a main switching power supply circuit, an independent switching circuit power supply, a voltage feedback circuit, an MCU control circuit, a power supply control circuit and an MOS tube Q1. After being powered on, the power supply of the independent switching circuit supplies power to the MCU control circuit, the MCU control circuit closes the power supply of the main switching power supply circuit, the MCU control circuit conducts the MOS tube Q1, and the MCU control circuit opens the power supply of the main switching power supply circuit; the circuit can reduce the surge current generated due to the fact that the output load is provided with the electrolytic capacitor, prevents the power supply from being damaged or protected due to the overlarge surge current, and has very good practicability.

Description

Technical Field

[0001] The utility model relates to the technical field of switching power supplies, and particularly relates to an LED switching power supply capable of suppressing output surge current. Background Art

[0002] With the development of technology, the load connected to the output end of the LED power supply is no longer an LED lamp bead, but some control circuits or controllers. Since these circuits or controllers often have many electrolytic capacitors, when the LED power supply directly outputs voltage at the output end, a very large surge current will be generated, which often triggers short-circuit detection and causes the LED power supply to enter a protection state. How to reduce and suppress the output surge current has become an urgent problem to be solved for the current LED power supply. Content of the Utility Model

[0003] The utility model aims to solve at least one of the technical problems existing in the prior art. For this purpose, the utility model provides an LED switching power supply capable of suppressing output surge current.

[0004] An embodiment of the utility model adopts the following technical solution to solve its technical problems: an LED switching power supply capable of suppressing output surge current, including a main switching power supply circuit, an independent switching circuit power supply, a voltage feedback circuit, an MCU control circuit, a power supply control circuit, and a MOS transistor Q1;

[0005] The input end of the main switching power supply circuit is connected to an external power supply, the first output end is connected to one end of a load, the second output end is connected to the source electrode of the MOS transistor Q1, and the other end of the load is connected to the drain electrode of the MOS transistor Q1;

[0006] The independent switching circuit power supply is connected between the external power supply and the MCU control circuit;

[0007] The voltage feedback circuit is connected between the first output end of the main switching power supply circuit, the feedback end of the main switching power supply circuit, and the MCU control circuit, and is used for detecting the output voltage and feeding it back to the MCU control circuit;

[0008] The MCU control circuit is connected between the power supply terminal of the main switching power supply circuit, the power supply control circuit, and the gate electrode of the MOS transistor Q1;

[0009] After power-on, it operates according to the timing sequence that the independent switching circuit power supply supplies power to the MCU control circuit, the MCU control circuit shuts off the power supply of the main switching power supply circuit, the MCU control circuit turns on the MOS transistor Q1, and the MCU control circuit turns on the power supply of the main switching power supply circuit.

[0010] As one of the preferred embodiments of the present utility model, the main switch power supply circuit includes a DC-DC chip U3, a capacitor C2, a diode D2, an electrolytic capacitor EC6, and a transformer T1. The input pin of the DC-DC chip U3 is connected to an external power supply, the output pin of the DC-DC chip U3 is connected to the first winding of the transformer T1. One end of the auxiliary winding of the transformer T1 is connected to the anode of the diode D2, and the cathode of the diode D2 is respectively connected to the power supply control circuit and the positive electrode of the electrolytic capacitor EC6. The other end of the auxiliary winding of the transformer T1 and the negative electrode of the electrolytic capacitor EC6 are connected to the ground terminal. The power supply pin of the DC-DC chip U3 is respectively connected to the power supply control circuit and one end of the capacitor C2, and the other end of the capacitor C2 and the ground pin of the DC-DC chip U3 are connected to the ground terminal.

[0011] As one of the preferred embodiments of the present utility model, the independent switch circuit power supply includes a DC-DC chip U6, a voltage regulator chip U7, a transformer T2, a diode D5, an electrolytic capacitor EC7, and a capacitor C5. The input pin of the DC-DC chip U6 and one end of the primary winding of the transformer T2 are connected to an external power supply, the output pin of the DC-DC chip U6 is connected to the other end of the primary winding of the transformer T2. One end of the secondary winding of the transformer T2 is respectively connected to the positive electrode of the electrolytic capacitor EC7 and the input pin of the voltage regulator chip U7 through the diode D5. The output pin of the voltage regulator chip U7 is respectively connected to the MCU control circuit and one end of the capacitor C5. The other end of the secondary winding of the transformer T2, the negative electrode of the electrolytic capacitor EC7, the ground pin of the voltage regulator chip U7, and the other end of the capacitor C5 are connected to the ground terminal.

[0012] As one of the preferred embodiments of the present utility model, the voltage feedback circuit includes a control chip U4, an optocoupler U2, resistors R9-12, capacitors C3-4, and a diode D4. The pin 8 of the control chip U4 is connected to the VCC terminal. The pin 2 of the control chip U4 is respectively connected to the cathode of the diode D4, one end of the resistor R11, and one end of the capacitor C4. The other end of the resistor R11 is respectively connected to the pin 2 of the control chip U4, the other end of the capacitor C4, one end of the resistor R9, and one end of the resistor R12 through the capacitor C3. The other end of the resistor R9 is connected to the first output terminal of the main switch power supply circuit. The anode of the diode D4 is respectively connected to one end of the light-emitting device of the optocoupler U2 and one end of the resistor R10. The other end of the resistor R10 is connected to the VCC terminal. One end of the light-receiving device of the optocoupler U2 is connected to the feedback terminal of the main switch power supply circuit through the resistor R8. The other end of the light-emitting device of the optocoupler U2, the other end of the light-receiving device of the optocoupler U2, and the other end of the resistor R12 are connected to the ground terminal.

[0013] As one of the preferred embodiments of the present utility model, the MCU control circuit includes an MCU control chip U5, resistors R3-4, resistor R7, and capacitor C1. One end of pin 17 of the MCU control chip U5 is connected to one end of resistor R4 and one end of capacitor C1 respectively. Pin 19 of the MCU control chip U5 is connected to the gate of MOS transistor Q1. The other end of resistor R4 is connected to one end of resistor R3, one end of resistor R7, and a voltage feedback circuit respectively. The other end of resistor R3 is connected to the independent switch circuit power supply. The other end of resistor R7 and the other end of capacitor C1 are connected to the ground terminal.

[0014] As one of the preferred embodiments of the present utility model, the power supply control circuit includes an optocoupler U1, resistors R2, R6, R13-14, and a triode Q3. One end of the light emitter of the optocoupler U1 is connected to one end of resistor R13 and the base of the triode Q3 respectively through resistor R4. The other end of resistor R13 is connected to the main switch power supply circuit and the emitter of the triode Q3 respectively. The collector of the triode Q3 is connected to the main switch power supply circuit. One end of the light receiver of the optocoupler U1 is connected to one end of resistor R2 and one end of resistor R6 respectively. The other end of resistor R2 is connected to the MCU control circuit. The other end of the light emitter of the optocoupler U1, the other end of the light receiver of the optocoupler U1, and the other end of resistor R6 are connected to the ground terminal.

[0015] The beneficial effects of the present utility model: An LED switching power supply capable of suppressing output surge current includes a main switch power supply circuit, an independent switch circuit power supply, a voltage feedback circuit, an MCU control circuit, a power supply control circuit, and a MOS transistor Q1. The input end of the main switch power supply circuit is connected to an external power supply, the first output end is connected to one end of a load, the second output end is connected to the source of the MOS transistor Q1, and the other end of the load is connected to the drain of the MOS transistor Q1. The independent switch circuit power supply is connected between the external power supply and the MCU control circuit. The voltage feedback circuit is connected between the first output end of the main switch power supply circuit, the feedback end of the main switch power supply circuit, and the MCU control circuit, and is used to detect the output voltage and feedback it to the MCU control circuit. The MCU control circuit is connected between the power supply terminal of the main switch power supply circuit, the power supply control circuit, and the gate of the MOS transistor Q1. After power-on, it operates according to the timing sequence of the independent switch circuit power supply supplying power to the MCU control circuit, the MCU control circuit turning off the power supply of the main switch power supply circuit, the MCU control circuit turning on the MOS transistor Q1, and the MCU control circuit turning on the power supply of the main switch power supply circuit. Through the above circuit, the surge current generated due to the electrolytic capacitor in the output load can be reduced, and the damage or protection of the power supply caused by excessive surge current can be avoided, which has very good practicability. Description of the Drawings

[0016] The above and / or additional aspects and advantages of the present utility model will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0017] Figure 1 It is a principle block diagram of an LED switching power supply that can suppress output surge current;

[0018] Figure 2 It is a partial circuit diagram of an LED switching power supply that can suppress output surge current;

[0019] Figure 3 It is a circuit diagram of an independent switching power supply circuit;

[0020] Figure 4 It is a circuit diagram of a voltage feedback circuit;

[0021] Figure 5 It is a circuit diagram of an MCU control circuit;

[0022] Figure 6 It is a circuit diagram of a power supply control circuit. Specific embodiments

[0023] This part will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the drawings. The function of the drawings is to supplement the description of the text part of the specification, enabling people to intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it should not be construed as a limitation on the protection scope of the present invention.

[0024] In the description of the present invention, the meaning of "plurality" is more than two. Understandings such as "greater than", "less than", "exceeding", etc. do not include the present number, and understandings such as "above", "below", "within", etc. include the present number. If there is a description of "first" and "second", it is only for the purpose of distinguishing technical features and cannot be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0025] In the description of the present invention, it should be understood that when it comes to orientation descriptions, such as up, down, front, back, left, right, etc., the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on the present invention.

[0026] In the present utility model, unless otherwise clearly defined, terms such as "arranged", "installed", "connected", etc. shall be understood in a broad sense. For example, they can be directly connected, or indirectly connected through an intermediate medium; they can be fixedly connected, or detachably connected, or integrally formed; they can be mechanically connected; they can be the communication inside two components or the interaction relationship between two components. Those skilled in the art can reasonably determine the specific meanings of the above terms in the present utility model in combination with the specific content of the technical solution.

[0027] Referring to Figures 1 to 6 , a LED switching power supply capable of suppressing output surge current includes a main switching power supply circuit 10, an independent switching circuit power supply 20, a voltage feedback circuit 30, an MCU control circuit 40, a power supply control circuit 50, and a MOS transistor Q1;

[0028] The input end of the main switching power supply circuit 10 is connected to an external power supply, the first output end is connected to one end of a load, the second output end is connected to the source electrode of the MOS transistor Q1, and the other end of the load is connected to the drain electrode of the MOS transistor Q1;

[0029] The independent switching circuit power supply 20 is connected between the external power supply and the MCU control circuit 40;

[0030] The voltage feedback circuit 30 is connected between the first output end of the main switching power supply circuit 10, the feedback end of the main switching power supply circuit 10, and the MCU control circuit 40, and is used for detecting the output voltage and feeding it back to the MCU control circuit 40;

[0031] The MCU control circuit 40 is connected between the power supply terminal of the main switching power supply circuit 10, the power supply control circuit 50, and the gate electrode of the MOS transistor Q1;

[0032] After power-on, it operates according to the timing sequence that the independent switching circuit power supply 20 supplies power to the MCU control circuit 40, the MCU control circuit 40 shuts off the power supply of the main switching power supply circuit 10, the MCU control circuit 40 turns on the MOS transistor Q1, and the MCU control circuit 40 turns on the power supply of the main switching power supply circuit 10.

[0033] In the present utility model, the working principle is as follows:

[0034] As Figure 1 shown, in this embodiment, alternating current is input to the switching power supply circuit 101 through the input terminal L and the input terminal N, and the switching power supply circuit 101 outputs direct current. 201 is the output load, and there is an electrolytic capacitor in this load. 301 is the control module of the MCU; 401 is the switching power supply voltage regulation feedback circuit. 501 is the independent switching power supply circuit.

[0035] When the machine is powered on, at the moment when the Q1 NMOS transistor is turned on, due to the existence of an electrolytic capacitor at the output terminal, and the characteristic of a capacitor is that the voltage cannot change suddenly. This means that at the moment of power-on, the voltage across the capacitor remains zero. The capacitor needs time to accumulate charge, and this process causes the capacitor to act as a short circuit directly connecting the two ends of the power supply at the moment of power-on. At this time, a very large inrush current will be generated, which is more than 100 A or even larger, resulting in overcurrent protection, or damage to the Q1 NMOS transistor, or protection of the switching power supply, etc. The present utility model can suppress the control method of the output inrush current. The specific implementation method is as follows: When the machine is powered on, the 501 independent switching power supply circuit supplies power to the 301 MCU control circuit. The 301 MCU control circuit has the function of turning off and turning on the 101 switching power supply circuit. When the 301 MCU control circuit is powered on, it first turns off the 101 switching power supply circuit, making the voltage on EC1 zero; then the 301 MCU control circuit turns on the Q1 NMOS transistor. At this time, because the voltage on EC1 is zero, no inrush current will be generated; then the 301 MCU control circuit turns on the power supply of the 101 switching power supply circuit, and through the 401 switching power supply voltage regulation feedback circuit, the voltage on EC1 rises from a low voltage to the specified target. Since the Q1 NMOS transistor has been turned on, when the 101 switching power supply works, the voltage on EC1 will gradually establish a basic voltage from small to large. This gradually established basic voltage from small to large makes the voltage of the electrolytic capacitor at the output load also a process of establishing from small to large. Because this voltage gradually increases from small to large, the electrolytic capacitor at the output terminal has sufficient charging time from this basic voltage. This time is very short, so it can be fully charged in a short time, thereby suppressing the output inrush current. The 301 MCU control circuit makes EC1 rise to the specified target voltage through the 401 switching power supply voltage regulation feedback circuit. The above embodiments are only the best implementation schemes of the present utility model, not the only ones, and are not limited to the above embodiments. As long as the same or similar means are used to achieve the technical effects of the present utility model, they should fall within the protection scope of the present utility model.

[0036] The advantages of the present utility model are as follows: Through the above circuit, the inrush current generated due to the electrolytic capacitor at the output load can be reduced, avoiding damage or protection of the power supply caused by excessive inrush current, and having very good practicability.

[0037] In one embodiment, the main switch power supply circuit 10 includes a DC-DC chip U3, a capacitor C2, a diode D2, an electrolytic capacitor EC6, and a transformer T1. The input pin of the DC-DC chip U3 is connected to an external power supply. The output pin of the DC-DC chip U3 is connected to the first winding of the transformer T1. One end of the auxiliary winding of the transformer T1 is connected to the anode of the diode D2. The cathode of the diode D2 is respectively connected to the power supply control circuit 50 and the positive electrode of the electrolytic capacitor EC6. The other end of the auxiliary winding of the transformer T1 and the negative electrode of the electrolytic capacitor EC6 are connected to the ground terminal. The power supply pin of the DC-DC chip U3 is respectively connected to the power supply control circuit 50 and one end of the capacitor C2. The other end of the capacitor C2 and the ground pin of the DC-DC chip U3 are connected to the ground terminal.

[0038] In one embodiment, the independent switch circuit power supply 20 includes a DC-DC chip U6, a voltage regulator chip U7, a transformer T2, a diode D5, an electrolytic capacitor EC7, and a capacitor C5. The input pin of the DC-DC chip U6 and one end of the primary winding of the transformer T2 are connected to an external power supply. The output pin of the DC-DC chip U6 is connected to the other end of the primary winding of the transformer T2. One end of the secondary winding of the transformer T2 is respectively connected to the positive electrode of the electrolytic capacitor EC7 and the input pin of the voltage regulator chip U7 through the diode D5. The output pin of the voltage regulator chip U7 is respectively connected to the MCU control circuit 40 and one end of the capacitor C5. The other end of the secondary winding of the transformer T2, the negative electrode of the electrolytic capacitor EC7, the ground pin of the voltage regulator chip U7, and the other end of the capacitor C5 are connected to the ground terminal.

[0039] In one embodiment, the voltage feedback circuit 30 includes a control chip U4, an optocoupler U2, resistors R9-12, capacitors C3-4, and a diode D4. The pin 8 of the control chip U4 is connected to the VCC terminal. The pin 2 of the control chip U4 is respectively connected to the cathode of the diode D4, one end of the resistor R11, and one end of the capacitor C4. The other end of the resistor R11 is respectively connected to the pin 2 of the control chip U4, the other end of the capacitor C4, one end of the resistor R9, and one end of the resistor R12 through the capacitor C3. The other end of the resistor R9 is connected to the first output terminal of the main switch power supply circuit 10. The anode of the diode D4 is respectively connected to one end of the emitter of the optocoupler U2 and one end of the resistor R10. The other end of the resistor R10 is connected to the VCC terminal. One end of the receiver of the optocoupler U2 is connected to the feedback terminal of the main switch power supply circuit 10 through the resistor R8. The other end of the emitter of the optocoupler U2, the other end of the receiver of the optocoupler U2, and the other end of the resistor R12 are connected to the ground terminal.

[0040] In one embodiment, the MCU control circuit 40 includes an MCU control chip U5, a resistor R3-4, a resistor R7, and a capacitor C1. One end of pin 17 of the MCU control chip U5 is connected to one end of the resistor R4 and one end of the capacitor C1 respectively. Pin 19 of the MCU control chip U5 is connected to the gate of the MOS transistor Q1. The other end of the resistor R4 is connected to one end of the resistor R3, one end of the resistor R7, and the voltage feedback circuit 30 respectively. The other end of the resistor R3 is connected to the independent switch circuit power supply 20. The other end of the resistor R7 and the other end of the capacitor C1 are connected to the ground terminal.

[0041] In one embodiment, the power supply control circuit 50 includes an optocoupler U1, a resistor R2, a resistor R6, resistors R13-14, and a triode Q3. One end of the light emitter of the optocoupler U1 is connected to one end of the resistor R13 and the base of the triode Q3 respectively through the resistor R4. The other end of the resistor R13 is connected to the main switch power supply circuit 10 and the emitter of the triode Q3 respectively. The collector of the triode Q3 is connected to the main switch power supply circuit 10. One end of the light receiver of the optocoupler U1 is connected to one end of the resistor R2 and one end of the resistor R6 respectively. The other end of the resistor R2 is connected to the MCU control circuit 40. The other end of the light emitter of the optocoupler U1, the other end of the light receiver of the optocoupler U1, and the other end of the resistor R6 are connected to the ground terminal.

[0042] Of course, the present invention is not limited to the above embodiments. Those skilled in the art can make equivalent deformations or substitutions without departing from the spirit of the present invention. These equivalent deformations and substitutions are all included within the scope defined by the claims of this application.

Claims

1. An LED switching power supply capable of suppressing output inrush current, characterized in that: It includes a main switch power supply circuit (10), an independent switch circuit power supply (20), a voltage feedback circuit (30), an MCU control circuit (40), a power supply control circuit (50), and a MOS transistor Q1; The input end of the main switch power supply circuit (10) is connected to an external power supply, the first output end is connected to one end of a load, the second output end is connected to the source electrode of the MOS transistor Q1, and the other end of the load is connected to the drain electrode of the MOS transistor Q1; The independent switch circuit power supply (20) is connected between the external power supply and the MCU control circuit (40); The voltage feedback circuit (30) is connected between the first output end of the main switch power supply circuit (10), the feedback end of the main switch power supply circuit (10), and the MCU control circuit (40) for detecting the output voltage and feeding it back to the MCU control circuit (40); The MCU control circuit (40) is connected between the power supply end of the main switch power supply circuit (10), the power supply control circuit (50), and the gate electrode of the MOS transistor Q1; After power-on, it operates according to the timing sequence that the independent switch circuit power supply (20) supplies power to the MCU control circuit (40), the MCU control circuit (40) shuts off the power supply of the main switch power supply circuit (10), the MCU control circuit (40) turns on the MOS transistor Q1, and the MCU control circuit (40) turns on the power supply of the main switch power supply circuit (10).

2. The LED switching power supply capable of suppressing output inrush current according to claim 1, wherein: The main switch power supply circuit (10) includes a DC-DC chip U3, a capacitor C2, a diode D2, an electrolytic capacitor EC6, and a transformer T1. The input pin of the DC-DC chip U3 is connected to an external power supply, the output pin of the DC-DC chip U3 is connected to the first winding of the transformer T1, one end of the auxiliary winding of the transformer T1 is connected to the anode of the diode D2, the cathode of the diode D2 is respectively connected to the power supply control circuit (50) and the positive electrode of the electrolytic capacitor EC6, the other end of the auxiliary winding of the transformer T1 and the negative electrode of the electrolytic capacitor EC6 are connected to the ground terminal, the power supply pin of the DC-DC chip U3 is respectively connected to the power supply control circuit (50) and one end of the capacitor C2, and the other end of the capacitor C2 and the ground pin of the DC-DC chip U3 are connected to the ground terminal.

3. The LED switching power supply capable of suppressing output surge current according to claim 1, wherein: The independent switch circuit power supply (20) includes a DC-DC chip U6, a voltage regulator chip U7, a transformer T2, a diode D5, an electrolytic capacitor EC7, and a capacitor C5. The input pin of the DC-DC chip U6 and one end of the primary winding of the transformer T2 are connected to an external power supply, the output pin of the DC-DC chip U6 is connected to the other end of the primary winding of the transformer T2, one end of the secondary winding of the transformer T2 is respectively connected to the positive electrode of the electrolytic capacitor EC7 and the input pin of the voltage regulator chip U7 through the diode D5, the output pin of the voltage regulator chip U7 is respectively connected to the MCU control circuit (40) and one end of the capacitor C5, and the other end of the secondary winding of the transformer T2, the negative electrode of the electrolytic capacitor EC7, the ground pin of the voltage regulator chip U7, and the other end of the capacitor C5 are connected to the ground terminal.

4. The LED switching power supply capable of suppressing output surge current according to claim 1, wherein: The voltage feedback circuit (30) includes a control chip U4, an optocoupler U2, resistors R9 - 12, capacitors C3 - 4, and a diode D4. The pin 8 of the control chip U4 is connected to the VCC terminal. The pin 2 of the control chip U4 is respectively connected to the cathode of the diode D4, one end of the resistor R11, and one end of the capacitor C4. The other end of the resistor R11 is respectively connected to the pin 2 of the control chip U4, the other end of the capacitor C4, one end of the resistor R9, and one end of the resistor R12 through the capacitor C3. The other end of the resistor R9 is connected to the first output terminal of the main switch power supply circuit (10). The anode of the diode D4 is respectively connected to one end of the light-emitting device of the optocoupler U2 and one end of the resistor R10. The other end of the resistor R10 is connected to the VCC terminal. One end of the light-receiving device of the optocoupler U2 is connected to the feedback terminal of the main switch power supply circuit (10) through the resistor R8. The other end of the light-emitting device of the optocoupler U2, the other end of the light-receiving device of the optocoupler U2, and the other end of the resistor R12 are connected to the ground terminal.

5. A LED switching power supply capable of suppressing output surge current according to claim 1, characterized in that: The MCU control circuit (40) includes an MCU control chip U5, resistors R3 - 4, a resistor R7, and a capacitor C1. The pin 17 of the MCU control chip U5 is respectively connected to one end of the resistor R4 and one end of the capacitor C1. The pin 19 of the MCU control chip U5 is connected to the gate of the MOS transistor Q1. The other end of the resistor R4 is respectively connected to one end of the resistor R3, one end of the resistor R7, and the voltage feedback circuit (30). The other end of the resistor R3 is connected to the independent switch circuit power supply (20). The other end of the resistor R7 and the other end of the capacitor C1 are connected to the ground terminal.

6. The LED switching power supply capable of suppressing output surge current according to claim 1, wherein: The power supply control circuit (50) includes an optocoupler U1, resistors R2, R6, R13 - 14, and a triode Q3. One end of the light-emitting device of the optocoupler U1 is respectively connected to one end of the resistor R13 and the base of the triode Q3 through the resistor R4. The other end of the resistor R13 is respectively connected to the main switch power supply circuit (10) and the emitter of the triode Q3. The collector of the triode Q3 is connected to the main switch power supply circuit (10). One end of the light-receiving device of the optocoupler U1 is respectively connected to one end of the resistor R2 and one end of the resistor R6. The other end of the resistor R2 is connected to the MCU control circuit (40). The other end of the light-emitting device of the optocoupler U1, the other end of the light-receiving device of the optocoupler U1, and the other end of the resistor R6 are connected to the ground terminal.

Images