A circuit to prevent unidirectional IO port power backflow

Abstract

A circuit for preventing unidirectional IO port power backflow belongs to the field of circuit protection technology. The present invention includes an anti-backflow protection circuit arranged between two circuits. When the voltage of the IO port power supply of one circuit is greater than or equal to the voltage of the IO port power supply of the other circuit, the output end of one circuit is electrically connected to the input end of the other circuit through the anti-backflow protection circuit, and the output end of the other circuit is electrically connected to the input end of one circuit through the anti-backflow protection circuit. In the present invention, the anti-backflow protection circuit is arranged between the two circuits and can play a role in level conversion during normal operation, so that the relevant circuits can work normally. When the IO port power supply of a circuit is powered off, it can also ensure that the circuit cannot obtain the high-level voltage of the other circuit, thereby avoiding the phenomenon of power backflow.

Description

Technical Field

[0001] The present invention belongs to the technical field of circuit protection, and in particular relates to a circuit for preventing unidirectional IO port power backflow. Background Art

[0002] In some existing low-power circuits, the power supply of a part of the circuit is usually cut off directly to maximize energy saving. However, the current IC ports are all designed with anti-static protection circuits (such as Figure 1 As shown, this is similar to the internal protection circuits of other bipolar transistors, MOS tubes, SCRs, etc. When the voltage of the chip pin is greater than the input voltage VDD, a conductive path will be formed from the chip pin through the protection device to VDD). Since the power consumption of the chip is often relatively low, as long as the chip pin (IO port) is connected to the high level of the powered circuit, it is possible to input a high level from the IO port, and then through the pull-up diode to the power supply, causing the chip to work intermittently or continuously, resulting in abnormal operation of the entire circuit or complete failure of the corresponding function. Summary of the Invention

[0003] The present invention mainly solves the technical problems existing in the above-mentioned prior art and provides a circuit for preventing unidirectional IO port power backflow.

[0004] The above-mentioned technical problem of the present invention is mainly solved by the following technical solution: a circuit for preventing unidirectional IO port power backflow, comprising an anti-backflow protection circuit arranged between two circuits, wherein when the voltage of the IO port power supply of one of the circuits is greater than or equal to the voltage of the IO port power supply of the other circuit, the output end of one of the circuits is electrically connected to the input end of the other circuit through the anti-backflow protection circuit, and the output end of the other circuit is electrically connected to the input end of one of the circuits through the anti-backflow protection circuit.

[0005] Preferably, the IO port power supply of one of the circuits is turned on, and the IO port power supply of the other circuit is turned on or off. The anti-backflow protection circuit includes a diode D1, a resistor R1, a resistor R3, a resistor R5 and a transistor Q1. The cathode of the diode D1 is connected to the output end of one of the circuits, the anode of the diode D1 is respectively connected to one end of the resistor R1 and the input end of the other circuit, the other end of the resistor R1 is connected to the IO port power supply of the other circuit, one end of the resistor R3 is connected to the IO port power supply of the other circuit, the other end of the resistor R3 is connected to the base of the transistor Q1, the emitter of the transistor Q1 is connected to the output end of the other circuit, the collector of the transistor Q1 is respectively connected to one end of the resistor R5 and the input end of one of the circuits, and the other end of the resistor R5 is connected to the IO port power supply of one of the circuits.

[0006] Preferably, the anti-backflow protection circuit further includes a resistor R2, and the cathode of the diode D1 is electrically connected to the output end of one of the circuits through the resistor R2, or the anode of the diode D1 is electrically connected to the input end of another circuit through the resistor R2.

[0007] Preferably, the anti-backflow protection circuit further includes a resistor R6, and the emitter of the transistor Q1 is electrically connected to the output end of another circuit through the resistor R6, or the collector of the transistor Q1 is electrically connected to the input end of one of the circuits through the resistor R6.

[0008] Preferably, the anti-backflow protection circuit further includes a resistor R4, one end of the resistor R4 is respectively connected to the other end of the resistor R3 and the base of the transistor Q1, and the other end of the resistor R4 is grounded.

[0009] Preferably, the IO port power supply of another circuit is turned on, and the IO port power supply of one of the circuits is turned on or off, and the anti-backflow protection circuit includes a diode D11, a resistor R11, a resistor R12, a resistor R13, a resistor R15 and a transistor Q11, the positive electrode of the diode D11 is connected to the output end of one of the circuits, the negative electrode of the diode D11 is connected to one end of the resistor R12, the other end of the resistor R12 is respectively connected to one end of the resistor R11 and the input end of the other circuit, the other end of the resistor R11 is grounded, one end of the resistor R13 is connected to the IO port power supply of the other circuit, the other end of the resistor R13 is connected to the base of the transistor Q11, the emitter of the transistor Q11 is connected to the output end of the other circuit, the collector of the transistor Q11 is respectively connected to one end of the resistor R15 and the input end of one of the circuits, and the other end of the resistor R15 is connected to the IO port power supply of one of the circuits.

[0010] Preferably, the anti-backflow protection circuit further includes a resistor R16, and the emitter of the transistor Q11 is electrically connected to the output end of another circuit through the resistor R16, or the collector of the transistor Q11 is electrically connected to the input end of one of the circuits through the resistor R16.

[0011] Preferably, the anti-backflow protection circuit further includes a resistor R14, one end of the resistor R14 is respectively connected to the other end of the resistor R13 and the base of the transistor Q11, and the other end of the resistor R14 is grounded.

[0012] Preferably, when the voltage of the IO port power supply of one of the circuits is equal to the voltage of the IO port power supply of the other circuit, or is greater than the voltage of the IO port power supply of the other circuit by within 0.2V, the resistor R12 is an optional device with adjustable position, and the anode of the diode D11 is electrically connected to the output end of one of the circuits through the resistor R12, or the cathode of the diode D11 is electrically connected to the input end of the other circuit through the resistor R12, or the cathode of the diode D11 is connected to the input end of the other circuit, and the anode of the diode D11 is connected to the output end of one of the circuits.

[0013] Preferably, the diode D1 is a low voltage drop type high frequency small current Schottky diode, or when the input low level of the circuit is raised by 0.4V and can work stably when using a low voltage drop type high frequency small current Schottky diode, the diode D1 is a switching diode.

[0014] Preferably, the transistor Q1 is a switching transistor or a high-frequency transistor.

[0015] Preferably, the diode D11 is a low-voltage-drop, high-frequency, low-current Schottky diode, or when the voltage of the IO port power supply of one of the circuits is greater than the voltage of the IO port power supply of the other circuit by more than 0.5V, the diode D11 can also be a switching diode.

[0016] Preferably, the transistor Q11 is a switching transistor or a high-frequency transistor.

[0017] The present invention has the beneficial effects as follows: in the present invention, the anti-backflow protection circuit is arranged between two circuits, and can play the role of level conversion during normal operation, so that the relevant circuits can work normally. When the power supply of the IO port of a circuit is cut off, it can also ensure that the circuit cannot obtain the high-level voltage of the other circuit, thereby avoiding the power backflow phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a circuit diagram of an anti-static protection circuit inside a chip in the prior art;

[0019] Figure 2 It is a structural schematic diagram of the present invention;

[0020] Figure 3 is a circuit diagram of embodiment 1 of the present invention;

[0021] Figure 4 It is a variation of the anti-backflow protection circuit in embodiment 1 of the present invention;

[0022] Figure 5It is a variation of the anti-backflow protection circuit in embodiment 1 of the present invention;

[0023] Figure 6 It is a variation of the anti-backflow protection circuit in embodiment 1 of the present invention;

[0024] Figure 7 is a circuit diagram of embodiment 2 of the present invention;

[0025] Figure 8 It is a variation of the anti-backflow protection circuit in embodiment 2 of the present invention;

[0026] Figure 9 It is a variation of the anti-backflow protection circuit in embodiment 2 of the present invention;

[0027] Figure 10 It is a variation of the anti-backflow protection circuit in embodiment 2 of the present invention.

[0028] In the figure: 1. Circuit; 2. Anti-backflow protection circuit; 3. IO port power supply; 4. Output end; 5. Input end. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0030] A circuit for preventing unidirectional IO port power backflow includes an anti-backflow protection circuit 2 arranged between circuit A and circuit B. When the voltage of the IO port power supply VDDA of circuit A is greater than or equal to the voltage of the IO port power supply VDDB of circuit B, the output end OutA of circuit A is electrically connected to the input end InB of circuit B through the anti-backflow protection circuit 2, and the output end OutB of circuit B is electrically connected to the input end InA of circuit A through the anti-backflow protection circuit 2.

[0031] Example 1, as Figure 2-Figure 6 As shown, when the IO port power supply VDDA of circuit A is turned on and the IO port power supply VDDB of circuit B is turned on or off, the anti-backflow protection circuit 2 includes a diode D1, a resistor R1, a resistor R3, a resistor R5 and a transistor Q1. The cathode of the diode D1 is connected to the output end OutA of circuit A, the anode of the diode D1 is respectively connected to one end of the resistor R1 and the input end InB of circuit B, the other end of the resistor R1 is connected to the IO port power supply VDDB of circuit B, one end of the resistor R3 is connected to the IO port power supply VDDB of circuit B, the other end of the resistor R3 is connected to the base of the transistor Q1, the emitter of the transistor Q1 is connected to the output end OutB of circuit B, the collector of the transistor Q1 is respectively connected to one end of the resistor R5 and the input end InA of circuit A, and the other end of the resistor R5 is connected to the IO port power supply VDDA of circuit A.

[0032] The diode D1 is a low-voltage-drop, high-frequency, low-current Schottky diode. Alternatively, when the circuit's input low level is raised by 0.4V and stable operation is achieved using a low-voltage-drop, high-frequency, low-current Schottky diode, the diode D1 is a switching diode. The transistor Q1 is a switching transistor or a high-frequency transistor.

[0033] In order to increase the stability of the anti-backflow protection circuit 2, resistors R2, R4 and R6 can be added to the anti-backflow protection circuit 2. The resistors R2 and R6 can be connected at any series position of their respective signal main paths, and the small voltage drop caused in the circuit will vary slightly with the change of position. The cathode of the diode D1 is electrically connected to the output end OutA of the A circuit through the resistor R2, or the anode of the diode D1 is electrically connected to the input end InB of the B circuit through the resistor R2. The emitter of the transistor Q1 is electrically connected to the output end OutB of the B circuit through the resistor R6, or the collector of the transistor Q1 is electrically connected to the input end InA of the A circuit through the resistor R6. The resistors R2 and R6 both have a current limiting function, which is used to prevent the circuit from burning out due to the two outputs being connected together and the output polarity being opposite when the port configuration is incorrect or the wiring is wrong. The values ​​of the resistors R2 and R6 are generally tens of ohms to thousands of ohms.

[0034] One end of resistor R4 is connected to the other end of resistor R3 and the base of transistor Q1, respectively, and the other end of resistor R4 is grounded. Resistor R4 and resistor R3 work together to act as a voltage divider, raising the maximum effective low level of the output terminal OutB of circuit B and increasing the circuit's noise tolerance. For example, a typical small-signal transistor may turn on when Vbe reaches 0.5V, and the voltage on the emitter reaches (VDDB-0.5)V to turn on CE. This means that transistor Q1 outputs a low level when the input is below (VDDB-0.5)V, and outputs a high level when it is above (VDDB-0.5)V. After adding resistor R4, this high and low level limit can be lowered. For example, if resistor R4 divides the voltage to 2V, then the voltage on the emitter must be 1.5V or below for BE to turn on, thereby also turning on CE. In this way, the threshold level can be adjusted to around half VDDB, ensuring that the output terminal OutB of circuit B must sense a higher interference signal before the circuit can be mistakenly flipped.

[0035] During normal operation, if circuit A outputs to circuit B: when the output terminal OutA of circuit A outputs a high level, diode D1 is reversely blocked, and the voltage at the input terminal InB of circuit B is the pull-up voltage of the IO port power supply VDDB of circuit B through resistor R1, thus obtaining a high level; when the output terminal OutA of circuit A outputs a low level, diode D1 is turned on, and the low level obtained at the input terminal InB of circuit B is the low level output by circuit A plus the conduction voltage of diode D1; when the IO port power supply VDDB of circuit B is turned off, the voltage of the IO port power supply VDDB of circuit B is 0. Regardless of whether the output terminal OutA of circuit A outputs a high level or a low level, diode D1 is turned off, and the input terminal InB of circuit B does not obtain a high level, thereby ensuring that the IO port power supply VDDB of circuit B is not reversely fed.

[0036] During normal operation, if circuit B outputs to circuit A: when circuit B's output terminal OutB outputs a high level, transistor Q1's BE is disconnected and its CE is forward-biased. The voltage at circuit A's input terminal InA is the pull-up voltage of circuit A's IO port power supply VDDA through resistor R5. Because circuit A's IO port power supply VDDA is greater than circuit B's IO port power supply VDDB, transistor Q1's BC is disconnected and its CE is reverse-biased, outputting a high level to circuit A. When circuit B's output terminal OutB outputs a low level, transistor Q1's BE and CE are connected. The low level at circuit A's input terminal InA is the low level of circuit B's output plus the forward voltage drop across transistor Q1's CE. When circuit B's IO port power supply VDDB is off, transistor Q1's BE is free of voltage and its BC is reverse-biased. Transistor Q1 remains off, preventing backflow of circuit B's IO port power supply VDDB.

[0037] Example 2, as Figure 7-10As shown, when the IO port power supply VDDB of circuit B is turned on and the IO port power supply VDDA of circuit A is turned on or off, the anti-backflow protection circuit 2 includes a diode D11, a resistor R11, a resistor R12, a resistor R13, a resistor R15 and a transistor Q11, the positive electrode of the diode D11 is connected to the output terminal OutA of circuit A, the negative electrode of the diode D11 is connected to one end of the resistor R12, the other end of the resistor R12 is respectively connected to one end of the resistor R11 and the input terminal InB of circuit B, the other end of the resistor R11 is grounded, one end of the resistor R13 is connected to the IO port power supply VDDB of circuit B, the other end of the resistor R13 is connected to the base of the transistor Q11, the emitter of the transistor Q11 is connected to the output terminal OutB of circuit B, the collector of the transistor Q11 is respectively connected to one end of the resistor R15 and the input terminal InA of circuit A, and the other end of the resistor R15 is connected to the IO port power supply VDDA of circuit A.

[0038] The diode D11 is a low-voltage-drop, high-frequency, low-current Schottky diode. Alternatively, when the voltage of the IO port power supply VDDA of circuit A is greater than the voltage of the IO port power supply VDDB of circuit B by more than 0.5V, the diode D11 can also be a switching diode. The transistor Q11 is a switching transistor or a high-frequency transistor.

[0039] In order to increase the stability of the anti-backflow protection circuit 2, a resistor R12, a resistor R14 and a resistor R16 can be added to the anti-backflow protection circuit 2. The resistor R16 can be connected to any series position of the main signal path, and the small voltage drop caused in the circuit will vary slightly with the change of position. The emitter of the transistor Q11 is electrically connected to the output end OutB of the B circuit through the resistor R16, or the collector of the transistor Q11 is electrically connected to the input end InA of the A circuit through the resistor R16. The resistor R16 plays a current limiting role and is used to avoid the situation where two outputs are connected together and the output polarity is opposite when the port configuration is wrong or the line is connected incorrectly, causing the circuit to burn out. The value of the resistor R16 is generally tens of ohms to thousands of ohms.

[0040] One end of resistor R14 is connected to the other end of resistor R13 and the base of transistor Q11, respectively. The other end of resistor R14 is grounded. Resistor R14 and resistor R13 work together to divide the voltage, thereby raising the most effective low level of the output terminal OutB of circuit B and increasing the noise tolerance of the circuit.

[0041] When the voltage of the IO port power supply VDDA of circuit A is equal to the voltage of the IO port power supply VDDB of circuit B, or is within 0.2V greater than the voltage of the IO port power supply VDDB of circuit B, the resistor R12 is used as an optional component to increase the stability of the anti-backflow protection circuit 2. If the anti-backflow protection circuit 2 does not include resistor R12, the positive electrode of the diode D11 is connected to the output terminal OutA of circuit A, and the negative electrode of the diode D11 is connected to one end of the resistor R11 and the input terminal InB of circuit B respectively; if the anti-backflow protection circuit 2 includes resistor R12, the resistor R12 can be connected to any series position in the main signal path, and the small voltage drop caused in the circuit will vary slightly with the position. For example, the anode of diode D11 is electrically connected to the output terminal OutA of circuit A through resistor R12, and the cathode of diode D11 is connected to one end of resistor R11 and the input terminal InB of circuit B. Alternatively, the anode of diode D11 is connected to the output terminal OutA of circuit A, the cathode of diode D11 is connected to one end of resistor R12, and the other end of resistor R12 is connected to one end of resistor R11 and the input terminal InB of circuit B. Alternatively, the anode of diode D11 is connected to the output terminal OutA of circuit A, the cathode of diode D11 is connected to one end of resistor R11 and one end of resistor R12, and the other end of resistor R12 is connected to the input terminal InB of circuit B. In this case, the function and value of resistor R12 are the same as those of resistor R16.

[0042] During normal operation, if circuit A outputs to circuit B: when the output terminal OutA of circuit A outputs a high level, diode D11 conducts forward, and the voltage at the input terminal InB of circuit B is the voltage obtained by subtracting the forward voltage drop of diode D11 from the high level output of circuit A, and then dividing the voltage across resistor R11 through the voltage divider circuit formed by resistors R12 and R11, resulting in a high level. When the output terminal OutA of circuit A outputs a low level, diode D11 is turned off, and the voltage at the input terminal InB of circuit B is the low level obtained by pulling down the IO port power supply VDDB of circuit B through resistor R11. When the IO port power supply VDDA of circuit A is turned off, diode D11 is turned off regardless of the voltage at the input terminal InB of circuit B, thereby preventing the IO port power supply VDDA of circuit A from flowing back.

[0043] During normal operation, if circuit B outputs to circuit A: when the output terminal OutB of circuit B outputs a high level, the BE terminals of transistor Q11 are disconnected, and the CE terminals are forward-cut off. The voltage on the input terminal InA of circuit A is the pull-up voltage of the IO port power supply VDDA of circuit A through resistor R15. Because the voltage of the IO port power supply VDDA of circuit A is greater than or equal to the voltage of the IO port power supply VDDB of circuit B, the BC terminals of transistor Q11 are disconnected, and the CE terminals are reverse-cut off, thereby outputting a high level to circuit A; when the output terminal OutB of circuit B outputs a low level, the BE terminals and CE terminals of transistor Q11 are connected, and the low level of the input terminal InA of circuit A is the low level output by circuit B plus the voltage of transistor Q11. When the IO port power supply VDDA of circuit A is turned off and the output terminal OutB of circuit B outputs a high level, the BE voltage of transistor Q11 is disconnected, but the BC voltage is forward-conducting, causing the CE voltage to be in a reverse amplification state. However, the reverse amplification factor of a transistor is generally only a few tenths of a factor, meaning that the Ice voltage it can provide is even smaller than Ibe. Therefore, the current that can flow from circuit B to circuit A is very small, and the voltage that can be divided across the equivalent resistance of circuit A is also very low. Simulations show that when the equivalent resistance of circuit A ranges from a few kilohertz to several hundred kilohertz, the IO port power supply VDDA of circuit A is always less than 1V, far below the voltage at which circuit A can begin to operate (whether in normal or abnormal operation). Therefore, the IO port power supply VDDA of circuit A is also protected from reverse flow.

[0044] To sum up, in the present invention, the anti-backflow protection circuit is arranged between the two circuits, and can play the role of level conversion during normal operation, so that the relevant circuits can work normally. When the IO port power supply of a circuit is cut off, it can also ensure that the circuit cannot obtain the high-level voltage of the other circuit, thereby avoiding the power backflow phenomenon.

[0045] Finally, it should be noted that the above embodiments are merely representative examples of the present invention. Obviously, the present invention is not limited to the above embodiments and is susceptible to numerous variations. Any simple modifications, equivalent variations, and modifications to the above embodiments based on the technical essence of the present invention are deemed to fall within the scope of protection of the present invention.

Claims

1. A circuit for preventing unidirectional IO port power backflow, characterized in that: It includes an anti-backflow protection circuit provided between two circuits. When the voltage of the IO port power supply of one circuit is greater than or equal to the voltage of the IO port power supply of the other circuit, the output end of one circuit is electrically connected to the input end of the other circuit through the anti-backflow protection circuit, and the output end of the other circuit is electrically connected to the input end of one circuit through the anti-backflow protection circuit. The IO port power supply of one of the circuits is turned on, and the IO port power supply of the other circuit is turned on or off. The anti-backflow protection circuit includes a diode D1, a resistor R1, a resistor R3, a resistor R5 and a transistor Q1. The cathode of the diode D1 is connected to the output end of one of the circuits, the anode of the diode D1 is respectively connected to one end of the resistor R1 and the input end of the other circuit, the other end of the resistor R1 is connected to the IO port power supply of the other circuit, one end of the resistor R3 is connected to the IO port power supply of the other circuit, the other end of the resistor R3 is connected to the base of the transistor Q1, the emitter of the transistor Q1 is connected to the output end of the other circuit, the collector of the transistor Q1 is respectively connected to one end of the resistor R5 and the input end of one of the circuits, and the other end of the resistor R5 is connected to the IO port power supply of one of the circuits.

2. The circuit for preventing unidirectional IO port power backflow according to claim 1, characterized in that: The anti-backflow protection circuit further includes a resistor R2, and the cathode of the diode D1 is electrically connected to the output end of one of the circuits through the resistor R2, or the anode of the diode D1 is electrically connected to the input end of another circuit through the resistor R2.

3. The circuit for preventing unidirectional IO port power backflow according to claim 1, characterized in that: The anti-backflow protection circuit further includes a resistor R6, and the emitter of the transistor Q1 is electrically connected to the output end of another circuit through the resistor R6, or the collector of the transistor Q1 is electrically connected to the input end of one of the circuits through the resistor R6.

4. The circuit for preventing unidirectional IO port power backflow according to claim 1, characterized in that: The anti-backflow protection circuit further includes a resistor R4 , one end of which is connected to the other end of the resistor R3 and the base of the transistor Q1 , respectively, and the other end of the resistor R4 is grounded.

5. A circuit for preventing unidirectional IO port power backflow, characterized in that: It includes an anti-backflow protection circuit provided between two circuits. When the voltage of the IO port power supply of one circuit is greater than or equal to the voltage of the IO port power supply of the other circuit, the output end of one circuit is electrically connected to the input end of the other circuit through the anti-backflow protection circuit, and the output end of the other circuit is electrically connected to the input end of one circuit through the anti-backflow protection circuit. The IO port power supply of another circuit is turned on, and the IO port power supply of one of the circuits is turned on or off. The anti-backflow protection circuit includes a diode D11, a resistor R11, a resistor R12, a resistor R13, a resistor R15 and a transistor Q11. The positive electrode of the diode D11 is connected to the output end of one of the circuits, the negative electrode of the diode D11 is connected to one end of the resistor R12, the other end of the resistor R12 is respectively connected to one end of the resistor R11 and the input end of the other circuit, the other end of the resistor R11 is grounded, one end of the resistor R13 is connected to the IO port power supply of the other circuit, the other end of the resistor R13 is connected to the base of the transistor Q11, the emitter of the transistor Q11 is connected to the output end of the other circuit, the collector of the transistor Q11 is respectively connected to one end of the resistor R15 and the input end of one of the circuits, and the other end of the resistor R15 is connected to the IO port power supply of one of the circuits.

6. The circuit for preventing unidirectional IO port power backflow according to claim 5, characterized in that: The anti-backflow protection circuit further includes a resistor R16, and the emitter of the transistor Q11 is electrically connected to the output end of another circuit through the resistor R16, or the collector of the transistor Q11 is electrically connected to the input end of one of the circuits through the resistor R16.

7. The circuit for preventing unidirectional IO port power backflow according to claim 5, characterized in that: The anti-backflow protection circuit further includes a resistor R14 , one end of which is connected to the other end of the resistor R13 and the base of the transistor Q11 , respectively, and the other end of the resistor R14 is grounded.

8. The circuit for preventing unidirectional IO port power backflow according to claim 5, characterized in that: When the voltage of the IO port power supply of one of the circuits is equal to the voltage of the IO port power supply of the other circuit, or is greater than the voltage of the IO port power supply of the other circuit by within 0.2V, the resistor R12 is an optional component with adjustable position, and the anode of the diode D11 is electrically connected to the output end of one of the circuits through the resistor R12, or the cathode of the diode D11 is electrically connected to the input end of the other circuit through the resistor R12, or the cathode of the diode D11 is connected to the input end of the other circuit, and the anode of the diode D11 is connected to the output end of one of the circuits.

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