Power supply circuit and electronic equipment

Abstract

The present application discloses a power supply circuit and an electronic device, including a first input terminal, a second input terminal, a rectifier circuit, an isolation converter, a relay, a first resistor, a zero-crossing detection circuit and a control circuit. The present application sets a zero-crossing detection circuit at the first input terminal and the second input terminal, which is used to detect the zero-crossing point of the mains power and generate a zero-crossing detection signal; and also adds a control circuit for receiving the zero-crossing detection signal, thereby controlling the relay to be disconnected or turned on. Through the cooperation of the zero-crossing detection circuit and the control circuit, when the power supply circuit is powered on, the control circuit controls the relay to be turned on according to the zero-crossing detection signal, that is, the two contacts of the relay are connected; when the power supply circuit is powered off, the relay is controlled to be disconnected in a relatively short time, that is, the two contacts of the relay are disconnected, and when the power supply circuit is powered on again, the generation of surge current is effectively limited, the probability of device damage is reduced, and the risk is reduced.

Description

Technical Field

[0001] The present application relates to the field of power supply technology, and in particular to a power supply circuit and electronic equipment. Background Art

[0002] As the demand for miniaturization and cost-effectiveness of electronic devices increases, the design of simple power modules has received more and more attention. Among them, simple power modules are low-cost power conversion devices used to convert input power into the voltage and current required by electronic devices. When designing low-cost power modules, the self-starting method is favored because it does not require additional auxiliary power.

[0003] The simple power module outputs bus voltage from AC voltage of mains through rectification circuit, and then outputs isolation voltage through DC / DC isolation converter, which is directly used to drive surge relay at input end. The existing control method of relay cannot disconnect the contacts of relay in a short time during power-off stage, resulting in high surge current when powering on again, thus causing damage to the device and posing a great risk. Summary of the invention

[0004] The main technical problem solved by the present application is to provide a power supply circuit and an electronic device to solve the problem that the relay cannot be disconnected in a short time when the power is off.

[0005] The present application provides a power supply circuit, comprising:

[0006] a first input terminal and a second input terminal;

[0007] A rectifier circuit, wherein the rectifier circuit receives AC power through the first input terminal and the second input terminal;

[0008] An isolation converter, the isolation converter is connected to the output end of the rectifier circuit, and the isolation converter is used to output an isolation voltage;

[0009] A bus capacitor, wherein a positive electrode of the bus capacitor is connected between the rectifier circuit and the isolation converter, and a negative electrode of the bus capacitor is grounded;

[0010] A relay and a first resistor, wherein two contacts of the relay are connected between the second input terminal and the rectifier circuit, and the first resistor is connected in parallel with the relay;

[0011] A zero-crossing detection circuit, wherein a first end of the zero-crossing detection circuit is connected between the first input end and the rectifier circuit, and a second end of the zero-crossing detection circuit is connected between the relay and the rectifier circuit;

[0012] a control circuit, connected to the zero-crossing detection circuit and the relay, respectively, receiving the isolation voltage and receiving a zero-crossing detection signal from the zero-crossing detection circuit, wherein the control circuit is used to control the relay to be disconnected or turned on based on the zero-crossing detection signal;

[0013] Wherein, the control circuit includes a first switch tube, a second switch tube, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, a second capacitor and a first diode, the anode of the first diode is connected to the first end of the first switch tube, the cathode of the first diode receives the isolation voltage and is connected to the first end of the second switch tube, one end of the second resistor and one end of the first capacitor, the first end of the relay is connected to the anode of the first diode, and the second end of the relay is connected to the cathode of the first diode;

[0014] The second end of the first switch tube is grounded, the third end of the first switch tube is connected to the second end of the second switch tube through the third resistor, the third end of the second switch tube is respectively connected to the other end of the second resistor, the other end of the first capacitor and one end of the fourth resistor, and the other end of the fourth resistor is connected to the zero-crossing detection circuit;

[0015] One end of the fifth resistor and one end of the second capacitor are connected to the third end of the first switch tube, and the other end of the fifth resistor and the other end of the second capacitor are grounded.

[0016] Wherein, the resistance value of the fifth resistor is greater than the resistance value of the third resistor.

[0017] Among them, when the power supply circuit is powered off, the second switch tube is turned off, the second capacitor is discharged through the fifth resistor, the first switch tube is turned off when the voltage of the second capacitor is less than the turn-on voltage of the first switch tube, and the two contacts of the relay are disconnected.

[0018] Among them, when the power supply circuit is powered on, the zero-crossing detection circuit detects the AC power, the second switch tube is alternately turned on or off, the charging rate of the second capacitor is greater than the discharging rate, the first switch tube is turned on when the voltage of the second capacitor is greater than or equal to the turn-on voltage of the first switch tube, and the two contacts of the relay are turned on.

[0019] In which, the control circuit also includes a second diode, one end of the second diode is connected to the third end of the first switch tube, and the other end of the second diode is grounded; the second diode includes a voltage regulator diode or a transient voltage suppression diode, which is used for voltage clamping of the first switch tube.

[0020] Wherein, the zero-crossing detection circuit includes a third diode, a fourth diode, a fifth diode, a sixth diode, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor and a photoelectric coupler, one end of the sixth resistor is connected between the first input end and the rectifier circuit, the other end of the sixth resistor is connected to the positive electrode of the third diode through the seventh resistor, and the negative electrode of the third diode is connected to the first end of the photoelectric coupler; one end of the eighth resistor is connected between the second input end and the rectifier circuit, the other end of the eighth resistor is connected to the positive electrode of the fourth diode through the ninth resistor, and the negative electrode of the fourth diode is connected to the negative electrode of the third diode and the first end of the photoelectric coupler; the positive electrode of the fifth diode is connected to the second end of the photoelectric coupler, and the negative electrode of the fifth diode is connected to the positive electrode of the seventh resistor and the third diode; the positive electrode of the sixth diode is connected between the positive electrode of the fifth diode and the second end of the photoelectric coupler, and the negative electrode of the sixth diode is connected between the ninth resistor and the positive electrode of the fourth diode; the third end of the photoelectric coupler is connected to the fourth resistor, and the fourth end of the photoelectric coupler is grounded.

[0021] Wherein, when the power circuit is powered off, the third terminal and the fourth terminal of the photoelectric coupler are disconnected, and the first switch tube is turned off.

[0022] Wherein, when the power supply circuit is powered on, the zero-crossing detection circuit detects the mains power, the third end and the fourth end of the photoelectric coupler are alternately connected or disconnected, and the first switch tube is turned on.

[0023] The present application also provides an electronic device, comprising the above-mentioned power supply circuit.

[0024] The beneficial effects of the present application are as follows: the present application sets a zero-crossing detection circuit at the first input terminal and the second input terminal for detecting the zero-crossing point of the mains power and generating a zero-crossing detection signal; a control circuit is also added for receiving the zero-crossing detection signal, thereby controlling the relay to be disconnected or turned on. Through the cooperation of the zero-crossing detection circuit and the control circuit, when the power circuit is powered on, the control circuit controls the relay to be turned on according to the zero-crossing detection signal, that is, the two contacts of the relay are connected; when the power circuit is powered off, the relay is controlled to be disconnected in a relatively short time, that is, the two contacts of the relay are disconnected, and when the power circuit is powered on again, the generation of surge current is effectively limited, the probability of device damage is reduced, and the risk is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0026] Figure 1 is a circuit diagram of an embodiment of a power supply circuit provided by the present application;

[0027] Figure 2 is a circuit diagram of another embodiment of the power supply circuit provided by the present application. DETAILED DESCRIPTION

[0028] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0030] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0031] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0032] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be connected between, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0033] The existing control method for relays cannot disconnect the contacts of the relays in a short time during the power-off stage, resulting in a high surge current when powering on again, thereby causing damage to the device and posing a great risk.

[0034] See also Figure 1 As shown, Figure 1 The power supply circuit 10 of the present application includes a first input terminal 11, a second input terminal 12, a rectifier circuit 13, an isolation converter 14, a relay 15, a first resistor R1, a zero-crossing detection circuit 16 and a control circuit 17.

[0035] The first input terminal 11 and the second input terminal 12 receive mains power, for example, the first input terminal 11 and the second input terminal 12 receive single-phase mains power. Mains power refers to industrial frequency alternating current, for example, the mains power in this embodiment is single-phase mains power with a voltage of 220V and a frequency of 50Hz.

[0036] Two contacts of the relay 15 are connected between the second input terminal 12 and the rectifier circuit 13 , that is, one contact of the relay 15 is connected to the second input terminal 12 , and the other contact of the relay 15 is connected to the rectifier circuit 13 .

[0037] The first resistor R1 is connected in parallel with the relay 15, that is, one end of the first resistor R1 is connected to the second input end 12, and the other end of the first resistor R1 is connected to the rectifier circuit 13. The second input end 12 is connected to the rectifier circuit 13, so that the rectifier circuit 13 receives the mains power through the first input end 11 and the second input end 12.

[0038] When the power circuit 10 is powered on, that is, the rectifier circuit 13 receives AC power through the first input terminal 11 and the second input terminal 12, the two contacts of the relay 15 are disconnected, and the AC current passes through the first resistor R1, which can limit the surge current, reduce the probability of damage to the relay 15, and increase the life of the relay 15.

[0039] The rectifier circuit 13 refers to a circuit for converting AC power into DC, that is, the rectifier circuit 13 is used to convert AC power into DC voltage.

[0040] The isolation converter 14 is connected to the output end of the rectifier circuit 13 and is used to output an isolation voltage U1, wherein the isolation voltage U1 includes at least one voltage. For example, the isolation converter outputs two voltages, and the two voltages are not equal, for example, one voltage is 24V and the other voltage is 48V.

[0041] The isolation converter 14 is also called an isolation converter, which is an electronic device for converting voltage or current. It isolates the input and output ends by physical isolation to achieve electrical isolation and safety. The isolation converter 14 includes but is not limited to a DC / DC isolation converter, an AC / DC isolation converter, and a DC / AC isolation converter. The isolation converter 14 of this embodiment is a DC / DC isolation converter.

[0042] A first end of the zero-crossing detection circuit 16 is connected between the first input terminal 11 and the rectifier circuit 13 , and a second end of the zero-crossing detection circuit 16 is connected between the relay 15 and the rectifier circuit 13 .

[0043] Zero-crossing detection refers to the detection made by the zero-crossing detection circuit 16 when the waveform switches from the positive half cycle to the negative half cycle and passes through the zero position in the AC system.

[0044] The zero-crossing detection circuit 16 samples and detects the AC power input from the first input terminal 11 and the second input terminal 12 , and outputs a zero-crossing detection signal.

[0045] The control circuit 17 is connected to the zero-crossing detection circuit 16 and the relay 15 respectively, receives the isolation voltage U1, and receives the zero-crossing detection signal from the zero-crossing detection circuit 16. The control circuit 17 is used to control the relay 15 to be disconnected or turned on based on the zero-crossing detection signal.

[0046] The control circuit 17 refers to a circuit used for controlling mechanical and electrical equipment. For example, in this embodiment, the control circuit 17 is used to control the relay 15 to be disconnected or connected.

[0047] The control circuit 17 controls the two contacts of the relay 15 to be disconnected, or the control circuit 17 controls the two contacts of the relay 15 to be connected. The isolation voltage U1 is used to provide power for the control circuit 17 to drive the relay 15.

[0048] When the isolation converter 14 outputs more than one voltage, the control circuit 17 receives one of the voltages to provide power for the control circuit 17 to drive the relay 15 .

[0049] When the power circuit 10 is powered on, the control circuit 17 receives the zero-crossing detection signal output by the zero-crossing detection circuit 16 and controls the relay 15 to be turned on; when the power circuit 10 is powered off, the control circuit 17 controls the relay 15 to be turned off in a shorter time based on the zero-crossing detection signal. When the power circuit 10 is powered on again, the surge current can be limited, the probability of damage to the relay 15 can be reduced, and the risk can be reduced.

[0050] According to some embodiments of the present application, the power supply circuit 10 of this embodiment further includes a bus capacitor C3, the positive electrode of the bus capacitor C3 is connected between the rectifier circuit 13 and the isolation converter 14, and the negative electrode of the bus capacitor C3 is grounded.

[0051] The power supply circuit 10 is powered on, and the bus capacitor C3 is charged by the DC voltage output by the rectifier circuit 13 .

[0052] When the power supply circuit 10 is powered off and the voltage of the bus capacitor C3 is high, the control circuit 17 controls the relay 15 to disconnect in a shorter time based on the zero-crossing detection signal. In this case, no matter when the power supply circuit 10 is powered on, the surge current can be limited, the probability of damage to the relay 15 is reduced, and the risk is reduced.

[0053] According to some embodiments of the present application, the control circuit 17 of this embodiment includes a first switch tube Q1, a second switch tube Q2, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first capacitor C1, a second capacitor C2 and a first diode D1.

[0054] Among them, the anode of the first diode D1 is connected to the first end of the first switch tube Q1, the cathode of the first diode D1 receives the isolation voltage U1 and is connected to the first end of the second switch tube Q2, one end of the second resistor R2 and one end of the first capacitor C1, the first end of the relay 15 is connected to the anode of the first diode D1, and the second end of the relay 15 is connected to the cathode of the first diode D1.

[0055] The second end of the first switch tube Q1 is grounded, the third end of the first switch tube Q1 is connected to the second end of the second switch tube Q2 through the third resistor R3, the third end of the second switch tube Q2 is respectively connected to the other end of the second resistor R2, the other end of the first capacitor C1 and one end of the fourth resistor R4, and the other end of the fourth resistor R4 is connected to the zero-crossing detection circuit 16.

[0056] One end of the fifth resistor R5 and one end of the second capacitor C2 are connected to the third end of the first switch tube Q1 , and the other end of the fifth resistor R5 and the other end of the second capacitor C2 are grounded.

[0057] The resistance of the fifth resistor R5 is greater than the resistance of the third resistor R3.

[0058] The isolation voltage U1 output by the isolation converter 14 is connected to the relay 15 through the second switch tube Q2 , the third resistor R3 and the first switch tube Q1 , so as to drive the relay 15 .

[0059] Optionally, the first end of the relay 15 is one end of the coil of the relay 15 , and the second end of the relay 15 is the other end of the coil of the relay 15 .

[0060] The control circuit 17 of this embodiment is simple in circuit, easy to implement, and reduces costs.

[0061] According to some embodiments of the present application, when the power supply circuit 10 is powered on, the zero-crossing detection circuit 16 detects the AC power, the second switch tube Q2 is alternately turned on or off, the charging rate of the second capacitor C2 is greater than the discharging rate, the first switch tube Q1 is turned on when the voltage of the second capacitor C2 is greater than or equal to the turn-on voltage of the first switch tube Q1, and the two contacts of the relay 15 are turned on.

[0062] The power supply circuit 10 is powered on, and the zero-crossing detection circuit 16 samples and detects the mains power input from the first input terminal 11 and the second input terminal 12, and the bus capacitor C3 is charged. The control circuit 17 receives the zero-crossing detection signal and controls the second switch tube Q2 to be turned on or off, wherein the zero-crossing detection signal is a high level or a low level; since the mains power is an AC voltage, the mains power will pass through the zero crossing point within the power frequency cycle, for example, the power frequency cycle is 10ms. When the mains power is at the zero crossing point, the second switch tube Q2 is turned off, for example, 2ms is turned off; when the mains power is at the peak value, the second switch tube Q2 is turned on, for example, 8ms is turned on. That is, the control circuit 17 receives the zero-crossing detection signal and controls the second switch tube Q2 to be alternately turned on or off.

[0063] When the second switch tube Q2 is turned on, the second capacitor C2 is charged, and when the second switch tube Q2 is turned off, the second capacitor C2 is discharged; and the resistance value of the fifth resistor R5 is greater than the resistance value of the third resistor R3, at this time, the charging rate of the second capacitor C2 is greater than the discharging rate. When the voltage of the second capacitor C2 is greater than or equal to the turn-on voltage of the first switch tube Q1, the first switch tube Q1 is turned on, the isolation voltage U1 supplies power to the coil of the relay 15, and the two contacts of the relay 15 are connected, that is, the relay 15 is turned on.

[0064] In this embodiment, the control circuit 17 controls the relay 15 to be turned on after the bus capacitor C3 is fully charged through the zero-crossing detection signal, which can limit the surge current, reduce the probability of damage to the relay 15, and increase the life of the relay 15.

[0065] According to some embodiments of the present application, when the power supply circuit 10 is powered off, the second switch tube Q2 is turned off, the second capacitor C2 is discharged through the fifth resistor R5, the first switch tube Q1 is turned off when the voltage of the second capacitor C2 is less than the turn-on voltage of the first switch tube Q1, and the two contacts of the relay 15 are disconnected.

[0066] When the power supply circuit 10 is powered off, the control circuit 17 receives a zero-crossing detection signal, wherein the zero-crossing detection signal is at a low level. At this time, the second switch tube Q2 is turned off, and the second capacitor C2 is discharged through the fifth resistor R5; when the voltage of the second capacitor C2 is less than the turn-on voltage of the first switch tube Q1, the first switch tube Q1 is turned off, the coil of the relay 15 is de-energized, and the two contacts of the relay 15 are disconnected, that is, the relay 15 is disconnected.

[0067] From the above, it can be seen that the delay time for the relay 15 to disconnect is the time for the second capacitor C2 to discharge through the fifth resistor R5, that is, the time for the relay 15 to disconnect can be configured by the values ​​of the second capacitor C2 and the fifth resistor R5, which can further shorten the time for controlling the relay 15 to disconnect.

[0068] When the power supply circuit 10 is powered off, the control circuit 17 can control the relay 15 to disconnect in a short time and when the voltage of the bus capacitor C3 is high through the zero-crossing detection signal. When the power supply circuit 10 is powered on again, the surge current is effectively limited, the probability of device damage is reduced, the risk is reduced, and the reliability is improved.

[0069] like Figure 1 As shown, since the first capacitor C1 and the second resistor R2 are connected in parallel to the first end and the third end of the second switch tube Q2, as a bypass device of the second switch tube Q2, the anti-interference ability of the second switch tube Q2 can be enhanced, and the second switch tube Q2 can be prevented from being turned on due to external interference, thereby improving the anti-interference ability.

[0070] The first diode D1 is used as a freewheeling channel for the coil of the relay 15 when the first switch tube Q1 is turned off. The first diode D1 can protect the first switch tube Q1 from being broken down by overvoltage.

[0071] According to some embodiments of the present application, the control circuit 17 further includes a second diode D2 , one end of the second diode D2 is connected to the third end of the first switch tube Q1 , and the other end of the second diode D2 is grounded.

[0072] The second diode D2 includes a voltage regulator diode or a transient voltage suppression diode, and is used for voltage clamping of the first switch tube Q1. In this embodiment, the second diode D2 can protect the first switch tube Q1 from being broken down by overvoltage.

[0073] The present application realizes the control circuit 17 to control the relay 15 to be disconnected or turned on by the zero-crossing detection signal. When the power circuit 10 is powered on, the bus capacitor C3 is fully charged, and the control relay 15 is turned on; when the power circuit 10 is powered off, the control relay 15 can be disconnected in a short time and when the bus capacitor C3 voltage is high. When the power circuit 10 is powered on again, the generation of surge current is effectively limited, the probability of device damage is reduced, the risk is reduced, and the reliability is improved.

[0074] See also Figure 2 As shown, Figure 2 1 is a circuit diagram of another embodiment of the power supply circuit provided by the present application. The power supply circuit 10 of this embodiment is Figure 1 The power supply circuit 10 is different in that the zero-crossing detection circuit 16 includes a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9 and a photocoupler OC.

[0075] One end of the sixth resistor R6 is connected between the first input terminal 11 and the rectifier circuit 13, the other end of the sixth resistor R6 is connected to the anode of the third diode D3 through the seventh resistor R7, and the cathode of the third diode D3 is connected to the first end of the photocoupler OC; one end of the eighth resistor R8 is connected between the second input terminal 12 and the rectifier circuit 13, the other end of the eighth resistor R8 is connected to the anode of the fourth diode D4 through the ninth resistor R9, and the cathode of the fourth diode D4 is connected between the cathode of the third diode D3 and the first end of the photocoupler OC; the anode of the fifth diode D5 is connected to the second end of the photocoupler OC, and the cathode of the fifth diode D5 is connected between the seventh resistor R7 and the anode of the third diode D3; the anode of the sixth diode D6 is connected between the anode of the fifth diode D5 and the second end of the photocoupler OC, and the cathode of the sixth diode D6 is connected between the ninth resistor R9 and the anode of the fourth diode D4; the third end of the photocoupler OC is connected to the fourth resistor R4, and the fourth end of the photocoupler OC is grounded.

[0076] Among them, the photocoupler OC is also called the photoelectric isolator, or optocoupler for short. It is an electric-light-electric conversion device that uses light as the medium to transmit electrical signals. The optocoupler consists of two parts: a light source and a light receiver. The light source and the light receiver are assembled in the same closed housing and isolated from each other by a transparent insulator. The pin of the light source is the input end, and the pin of the light receiver is the output end. The common light source is a light-emitting diode, and the light receiver is a photosensitive diode, a photosensitive transistor, and so on.

[0077] For example, in this embodiment, the photocoupler OC is composed of a light emitting diode and a phototransistor, the light emitting diode is located at the input end, also called the primary side; the phototransistor is the output end, also called the secondary side.

[0078] According to some embodiments of the present application, when the power supply circuit 10 is powered on, the zero-crossing detection circuit 16 detects the AC power, the third terminal and the fourth terminal of the photocoupler OC are alternately connected or disconnected, and the first switch tube Q1 is turned on.

[0079] When the power supply circuit 10 is powered on, the zero-crossing detection circuit 16 detects the mains power. When the mains power is at the peak value, the primary current of the photocoupler OC is large, and the secondary side is turned on, that is, the third and fourth ends of the photocoupler OC are connected, at this time, one end of the fourth resistor R4 is grounded, and the second switch tube Q2 is turned on; when the mains power is at the zero crossing point, the primary current of the photocoupler OC is small, and the secondary side is cut off, that is, the third and fourth ends of the photocoupler OC are disconnected, and at this time, the second switch tube Q2 is cut off. That is, the control circuit 17 receives the zero-crossing detection signal, the second switch tube Q2 is alternately turned on or off, the first switch tube Q1 is turned on when the voltage of the second capacitor C2 is greater than or equal to the turn-on voltage of the first switch tube Q1, and the two contacts of the relay 15 are turned on.

[0080] According to some embodiments of the present application, when the power circuit 10 is powered off, the third terminal and the fourth terminal of the photocoupler OC are disconnected, and the first switch tube Q1 is turned off.

[0081] When the power supply circuit 10 is powered off, the primary current of the photocoupler OC is small and the secondary current is cut off, that is, the third and fourth terminals of the photocoupler OC are disconnected. At this time, the second switch tube Q2 is cut off, and the first switch tube Q1 is cut off when the voltage of the second capacitor C2 is less than the turn-on voltage of the first switch tube Q1, and the two contacts of the relay 15 are disconnected.

[0082] Referring to the above, it can be known that when the power supply circuit 10 is powered on, that is, the first input terminal 11 and the second input terminal 12 input 50Hz mains power, the zero-crossing detection circuit 16 detects that the mains power is at zero crossing, the primary current of the photoelectric coupler OC is small, and the secondary side is cut off; when the mains power is detected at the peak, the primary current of the photoelectric coupler OC is large, and the secondary side is turned on, and at this time the secondary side can obtain a 100Hz square wave signal; when the power supply circuit 10 is powered off, the primary current of the photoelectric coupler OC is small, and the secondary side is cut off, and at this time the secondary side is at a high level. The zero-crossing detection circuit 16 is used to determine whether the power supply circuit 10 is powered off, and the control circuit 17 controls the time when the relay 15 is disconnected according to the zero-crossing detection signal.

[0083] After the power circuit 10 is powered on, the photocoupler OC in the zero-crossing detection circuit 16 is alternately turned on at 100 Hz. When the cutoff frequency of the second capacitor C2 and the fifth resistor R5 is less than 50 Hz, frequent switching of the first switch tube Q1 can be reduced.

[0084] It should be noted that the implementation methods of the zero-crossing detection circuit 16 in this embodiment include but are not limited to those shown above.

[0085] Optionally, the first switch tube Q1 of the present application is an N-type MOS tube, and the second switch tube Q2 is a PNP-type triode. In other embodiments, the types of the first switch tube Q1 and the second switch tube Q2 are set according to actual conditions.

[0086] The present application also provides an electronic device, including the power supply circuit 10 of the above embodiment, which will not be described in detail here.

[0087] In summary, the present application realizes the disconnection or conduction of the relay 15 by the zero-crossing detection signal through the control circuit 17. When the power supply circuit 10 is powered on, the bus capacitor C3 is fully charged, and the control relay 15 is turned on; when the power supply circuit 10 is powered off, the control relay 15 can be disconnected in a short time and when the voltage of the bus capacitor C3 is high. When the power supply circuit 10 is powered on again, the generation of surge current is effectively limited, the probability of device damage is reduced, the risk is reduced, and the reliability is improved.

[0088] The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A power supply circuit, characterized in that: include: a first input terminal and a second input terminal; A rectifier circuit, wherein the rectifier circuit receives AC power through the first input terminal and the second input terminal; An isolation converter, the isolation converter is connected to the output end of the rectifier circuit, and the isolation converter is used to output an isolation voltage; A bus capacitor, wherein a positive electrode of the bus capacitor is connected between the rectifier circuit and the isolation converter, and a negative electrode of the bus capacitor is grounded; A relay and a first resistor, wherein two contacts of the relay are connected between the second input terminal and the rectifier circuit, and the first resistor is connected in parallel with the relay; A zero-crossing detection circuit, wherein a first end of the zero-crossing detection circuit is connected between the first input end and the rectifier circuit, and a second end of the zero-crossing detection circuit is connected between the relay and the rectifier circuit; a control circuit, connected to the zero-crossing detection circuit and the relay, respectively, receiving the isolation voltage and receiving a zero-crossing detection signal from the zero-crossing detection circuit, wherein the control circuit is used to control the relay to be disconnected or turned on based on the zero-crossing detection signal; Wherein, the control circuit includes a first switch tube, a second switch tube, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, a second capacitor and a first diode, the anode of the first diode is connected to the first end of the first switch tube, the cathode of the first diode receives the isolation voltage and is connected to the first end of the second switch tube, one end of the second resistor and one end of the first capacitor, the first end of the relay is connected to the anode of the first diode, and the second end of the relay is connected to the cathode of the first diode; The second end of the first switch tube is grounded, the third end of the first switch tube is connected to the second end of the second switch tube through the third resistor, the third end of the second switch tube is respectively connected to the other end of the second resistor, the other end of the first capacitor and one end of the fourth resistor, and the other end of the fourth resistor is connected to the zero-crossing detection circuit; One end of the fifth resistor and one end of the second capacitor are connected to the third end of the first switch tube, and the other end of the fifth resistor and the other end of the second capacitor are grounded.

2. The power supply circuit according to claim 1, characterized in that: The resistance value of the fifth resistor is greater than the resistance value of the third resistor.

3. The power supply circuit according to claim 1, characterized in that: When the power circuit is powered off, the second switch tube is turned off, the second capacitor is discharged through the fifth resistor, the first switch tube is turned off when the voltage of the second capacitor is less than the turn-on voltage of the first switch tube, and the two contacts of the relay are disconnected.

4. The power supply circuit according to claim 1, characterized in that: When the power supply circuit is powered on, the zero-crossing detection circuit detects the AC power, the second switch tube is alternately turned on or off, the charging rate of the second capacitor is greater than the discharging rate, the first switch tube is turned on when the voltage of the second capacitor is greater than or equal to the turn-on voltage of the first switch tube, and the two contacts of the relay are turned on.

5. The power supply circuit according to claim 1, characterized in that: The control circuit also includes a second diode, one end of which is connected to the third end of the first switch tube, and the other end of the second diode is grounded; the second diode includes a voltage regulator diode or a transient voltage suppression diode, which is used for voltage clamping of the first switch tube.

6. The power supply circuit according to claim 1, characterized in that: The zero-crossing detection circuit includes a third diode, a fourth diode, a fifth diode, a sixth diode, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor and a photoelectric coupler, one end of the sixth resistor is connected between the first input terminal and the rectifier circuit, the other end of the sixth resistor is connected to the anode of the third diode through the seventh resistor, and the cathode of the third diode is connected to the first end of the photoelectric coupler; one end of the eighth resistor is connected between the second input terminal and the rectifier circuit, the other end of the eighth resistor is connected to the anode of the fourth diode through the ninth resistor, and the cathode of the fourth diode is connected to the cathode of the third diode and the first end of the photoelectric coupler; the anode of the fifth diode is connected to the second end of the photoelectric coupler, and the cathode of the fifth diode is connected to the anode of the seventh resistor and the third diode; the anode of the sixth diode is connected between the anode of the fifth diode and the second end of the photoelectric coupler, and the cathode of the sixth diode is connected between the ninth resistor and the anode of the fourth diode; the third end of the photoelectric coupler is connected to the fourth resistor, and the fourth end of the photoelectric coupler is grounded.

7. The power supply circuit according to claim 6, characterized in that: When the power circuit is powered off, the third terminal and the fourth terminal of the photoelectric coupler are disconnected, and the first switch tube is turned off.

8. The power supply circuit according to claim 6, characterized in that: When the power supply circuit is powered on, the zero-crossing detection circuit detects the mains power, the third end and the fourth end of the photoelectric coupler are alternately connected or disconnected, and the first switch tube is turned on.

9. An electronic device, characterized in that: Comprising a power supply circuit as claimed in any one of claims 1 to 8.

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