Relay driving circuit and bus capacitor pre-charging circuit

Abstract

The utility model discloses a relay drive circuit and a bus capacitor pre-charging circuit, the relay drive circuit acts on a relay, and the relay drive circuit comprises a control signal source, a power supply VCC, a filter circuit, an operational amplifier follower circuit and a triode; the operational amplifier follower circuit comprises an operational amplifier, the positive input end of the operational amplifier is connected to a control signal source through a filter circuit, the negative input end and the output end of the operational amplifier are connected, and the positive power supply end of the operational amplifier is connected to a power supply VCC; a collector of the triode is connected to a power supply VCC through a coil of the relay, a base is connected to the output end of the operational amplifier, and an emitter is grounded; the bus capacitor pre-charging circuit acts on a bus capacitor and comprises a power supply Vin, a resistor RT1, the bus capacitor and a relay which are sequentially connected in series to form a closed loop; a contact of the relay is connected with the resistor RT1 in parallel, and a coil of the relay is driven by the relay driving circuit. The utility model has the characteristics of low power consumption and heat emission, and good EMI performance.

Description

Technical Field

[0001] The utility model relates to the technical field of power electronics, in particular to a relay drive circuit and a bus capacitor pre-charging circuit. Background Art

[0002] like Figure 1 As shown in the figure, the traditional relay drive circuit is widely used in power supply systems. It is usually composed of a transistor or MOSFET and a current limiting resistor, which is directly connected to the relay coil to control the contact and release of the relay to achieve automatic switching and protection functions of the circuit. The principle is to control the relay by controlling the switching state of the transistor or MOSFET.

[0003] The disadvantages of traditional relay drive circuits are:

[0004] Power consumption problem: Constant current is provided during the relay closure and holding phase, resulting in high power consumption throughout the process, especially when the relay is held for a long time. Temperature rise problem: Due to high power consumption, the relay is prone to heat up, and long-term operation may cause temperature rise problems, affecting the stability and life of the equipment. EMI problem: Compared with the drive circuit that uses PWM control to reduce power consumption, although it is effective, it will generate high electromagnetic interference, affecting the normal operation of other electronic equipment. Summary of the invention

[0005] The purpose of the utility model is to overcome the deficiencies in the prior art, provide a relay drive circuit and a bus capacitor pre-charging circuit, and solve the technical problems of power consumption, temperature rise, EMI, etc. existing in the traditional relay drive circuit.

[0006] In order to achieve the above purpose, the utility model is implemented by adopting the following technical solutions:

[0007] In a first aspect, the utility model provides a relay driving circuit, which acts on a relay and includes a control signal source, a power supply VCC, a filter circuit, an operational amplifier follower circuit and a transistor;

[0008] The operational amplifier follower circuit comprises an operational amplifier, the positive input terminal of the operational amplifier is connected to the control signal source through the filter circuit, the negative input terminal and the output terminal of the operational amplifier are connected, the positive power supply terminal of the operational amplifier is connected to the power supply VCC, and the negative power supply terminal of the operational amplifier is grounded;

[0009] The collector of the transistor is connected to the power supply VCC through the coil of the relay, the base of the transistor is connected to the output end of the operational amplifier, and the emitter of the transistor is grounded.

[0010] Optionally, a resistor R3 is also connected between the operational amplifier and the filter circuit; the filter circuit adopts an RC filter circuit, and the RC filter circuit includes a resistor R2 and a capacitor C1, the resistor R2 and the resistor R3 are connected in series with the control signal source and the positive input terminal of the operational amplifier in sequence, and the common end of the resistor R2 and the resistor R3 is grounded through the capacitor C1.

[0011] Optionally, the operational amplifier follower circuit further includes a capacitor C2, and the capacitor C2 is connected between the positive power supply terminal and the negative power supply terminal of the operational amplifier.

[0012] Optionally, the operational amplifier follower circuit further includes a resistor R4, wherein the resistor R4 is connected to the output end of the operational amplifier, and the output end of the operational amplifier is connected to the base of the transistor through the resistor R4.

[0013] Optionally, a resistor R1 is further connected between the power supply VCC and the coil of the relay.

[0014] Optionally, a diode is connected in parallel to the coil of the relay, and the anode of the diode is connected to the collector of the transistor.

[0015] Optionally, the control signal source adopts a single-chip microcomputer, and the single-chip microcomputer is used to output a PWM control signal.

[0016] In a second aspect, the utility model provides a bus capacitor pre-charging circuit, which acts on the bus capacitor, and includes a power supply Vin, a resistor RT1, a relay, a power supply voltage sampling module, and a capacitor voltage sampling module;

[0017] The positive end of the power source Vin, the resistor RT1, the bus capacitor and the negative end of the power source Vin are sequentially connected in series to form a closed loop;

[0018] The contact of the relay is connected in parallel with the resistor RT1, and the coil of the relay is driven by the relay driving circuit as described above;

[0019] The power supply voltage sampling module is connected in parallel with the power supply Vin, and the capacitor voltage sampling module is connected in parallel with the bus capacitor.

[0020] Optionally, the power supply voltage sampling module includes a resistor R5, a resistor R7 and a resistor R9 connected in series in sequence, and the voltage at the common end of the resistor R5 and the resistor R7 is taken as the output voltage of the power supply voltage sampling module; the capacitor voltage sampling module includes a resistor R6, a resistor R8 and a resistor R10 connected in series in sequence, and the voltage at the common end of the resistor R6 and the resistor R8 is taken as the output voltage of the capacitor voltage sampling module.

[0021] Optionally, output ends of the power supply voltage sampling module and the capacitor voltage sampling module are both connected to the control signal source.

[0022] Compared with the prior art, the utility model has the following beneficial effects:

[0023] The utility model provides a relay drive circuit and a bus capacitor pre-charging circuit. The relay drive circuit adopts a filter circuit and an op amp follower circuit to effectively control the current supply of the relay coil, thereby reducing the power consumption and heat generation during the relay closure and holding stages. Compared with the PWM duty cycle control drive, the utility model avoids the high electromagnetic interference problem caused by fast switching and ensures the EMC performance of the circuit. The bus capacitor pre-charging circuit inherits the advantages of the relay drive circuit while ensuring the safety of the bus capacitor. The circuit designs of the relay drive circuit and the bus capacitor pre-charging circuit are both simple, without the need for additional power supply and complex control logic, and are easy to integrate and maintain. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a circuit schematic diagram of a traditional relay drive circuit provided in the background technology of the utility model;

[0025] Figure 2 1 is a circuit schematic diagram of a relay drive circuit provided in Embodiment 1 of the present utility model;

[0026] Figure 3 It is a circuit schematic diagram of the bus capacitor pre-charging circuit provided in the second embodiment of the utility model. DETAILED DESCRIPTION

[0027] The utility model is further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the utility model, and cannot be used to limit the protection scope of the utility model.

[0028] Embodiment 1:

[0029] like Figure 2 As shown, an embodiment of the utility model provides a relay driving circuit, which acts on relay K1, including a control signal source, a power supply VCC, a filtering circuit, an operational amplifier follower circuit and a transistor Q1; the operational amplifier follower circuit includes an operational amplifier U1, the positive input terminal NI+ of the operational amplifier U1 is connected to the control signal source through the filtering circuit, the negative input terminal NI- of the operational amplifier is connected to the output terminal, the positive power supply terminal V+ of the operational amplifier is connected to the power supply VCC, and the negative power supply terminal V- of the operational amplifier is grounded GND; the collector of the transistor Q1 is connected to the power supply VCC through the coil K1B of the relay K1, the base of the transistor is connected to the output terminal of the operational amplifier U1, and the emitter of the transistor is grounded GND.

[0030] Specifically, an RC filter circuit and a resistor R3 are also connected between the operational amplifier and the filter circuit; the filter circuit adopts an RC filter circuit, and the RC filter circuit includes a resistor R2 and a capacitor C1. The resistor R2 and the resistor R3 are connected in series with the control signal source and the positive input terminal NI+ of the operational amplifier U1 in sequence, and the common end of the resistor R2 and the resistor R3 is grounded GND through the capacitor C1.

[0031] Specifically, the operational amplifier follower circuit also includes a capacitor C2 and a resistor R4. The capacitor C2 is connected between the positive power supply terminal V+ and the negative power supply terminal V- of the operational amplifier U1. The resistor R4 is connected to the output terminal of the operational amplifier U1, and the output terminal of the operational amplifier U1 is connected to the base of the transistor Q1 through the resistor R4.

[0032] Specifically, a resistor R1 is connected between the power source VCC and the coil K1B of the relay K1. A diode D1 is also connected in parallel to the coil K1B of the relay K1, and the anode of the diode D1 is connected to the collector of the transistor Q1.

[0033] Specifically, the control signal source adopts a single-chip microcomputer, and the single-chip microcomputer is used to output a PWM control signal PWM_Io.

[0034] Component selection for the above relay drive circuit:

[0035] a) Relay K1: A normally open 12V relay used as a switch in the power circuit, with an operating voltage of 9.6V, a release voltage of 1.0V, and a coil resistance of 185Ω.

[0036] b) Power supply Vin: set to 300V to provide the required high voltage for the entire circuit.

[0037] c) Power supply VCC: set to 12V to provide stable power for the control components in the circuit.

[0038] d) Resistors R1, R2, R3, and R4, where resistor R1 is 15Ω, resistor R2 is 100KΩ, and resistors R3 and R4 are 1KΩ, are used to set the current and voltage levels in the circuit.

[0039] e) Capacitors C1 and C2, where capacitor C1 is 10nF and capacitor C2 is 100nF, are used for filtering and energy storage to stabilize the control signal of the circuit.

[0040] f) Diode D1: Model 4148 is used for rectification and protection circuit.

[0041] g) Transistor Q1: 8050 model is used as a switching element to control the closing and releasing of the relay.

[0042] h) Operational amplifier U1: LMV321 model is used to form an operational amplifier follower circuit to stabilize and amplify the control signal.

[0043] i) Control signal source (PWM_Io): Provided by a 5V microcontroller, used to control the contact and low power consumption of the relay.

[0044] The working principle of the above relay drive circuit is:

[0045] The existing program is burned into the MCU in advance, PWM_Io outputs a high-level signal and delays for a preset time, and PWM_Io outputs a PWM signal.

[0046] When PWM_Io outputs a high-level signal, it is followed by the op amp follower circuit and reaches the base of the transistor, causing the transistor to conduct, the coil of the relay to be energized, and the contacts of the driving relay to be closed;

[0047] The delay preset time is to ensure that the relay contacts are completely closed;

[0048] When PWM_Io outputs PWM signal, it generates a stable low voltage through RC filter circuit, which is less than or equal to the duty cycle of PWM signal multiplied by power supply VCC voltage. The op amp follower circuit amplifies and stabilizes this low voltage to control the current of relay coil, maintain the holding voltage of relay, and keep the relay at low power consumption. At this time, the relay can still stably attract, but the power consumption and heat generation are small.

[0049] The above working principle needs to be implemented based on a single-chip microcomputer. In another optional implementation, it can be simplified, for example, through a crystal oscillator and a single-pole double-throw switch, the power supply VCC and the crystal oscillator are respectively connected to the two fixed ends of the single-pole double-throw switch. At the beginning, the moving end of the single-pole double-throw switch is connected to the fixed end on the power supply VCC side, and then switched to the fixed end on the crystal oscillator side.

[0050] Embodiment 2:

[0051] like Figure 3 As shown, an embodiment of the utility model provides a bus capacitor pre-charging circuit, which acts on the bus capacitor CJ1, including a power supply Vin, a resistor RT1, a relay K1, a power supply voltage sampling module and a capacitor voltage sampling module; the positive end Vin+ of the power supply Vin, the resistor RT1, the bus capacitor CJ1 and the negative end Vin- of the power supply Vin are connected in series in sequence to form a closed loop; the contact K1A of the relay K1 is connected in parallel with the resistor RT1, and the coil K1B of the relay K1 is driven by the relay driving circuit provided in Example 1; the power supply voltage sampling module is connected in parallel with the power supply Vin, and the capacitor voltage sampling module is connected in parallel with the bus capacitor.

[0052] Specifically, the power supply voltage sampling module includes resistors R5, R7 and R9 connected in series, and the voltage at the common end of resistors R5 and R7 is taken as the output voltage of the power supply voltage sampling module; the capacitor voltage sampling module includes resistors R6, R8 and R10 connected in series, and the voltage at the common end of resistors R6 and R8 is taken as the output voltage of the capacitor voltage sampling module. The output ends of the power supply voltage sampling module and the capacitor voltage sampling module are both connected to the control signal source.

[0053] The power supply voltage sampling module and the capacitor voltage sampling module are used to detect the voltage of the power supply Vin and the bus capacitor CJ1 respectively. Only when the voltage difference between the two is less than the preset voltage threshold can the contact K1A of the relay K1 be driven to close, thereby protecting the bus capacitor CJ1 from being damaged by the direct impact of the power supply Vin when the voltage is too low, thereby ensuring its working safety. At the same time, it inherits the advantages of low power consumption and heat generation of the relay drive circuit of Example 1.

[0054] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A relay driving circuit, acting on a relay, characterized in that: Including control signal source, power supply VCC, filter circuit, operational amplifier follower circuit and triode; The operational amplifier follower circuit comprises an operational amplifier, the positive input terminal of the operational amplifier is connected to the control signal source through the filter circuit, the negative input terminal and the output terminal of the operational amplifier are connected, the positive power supply terminal of the operational amplifier is connected to the power supply VCC, and the negative power supply terminal of the operational amplifier is grounded; The collector of the transistor is connected to the power supply VCC through the coil of the relay, the base of the transistor is connected to the output end of the operational amplifier, and the emitter of the transistor is grounded.

2. The relay drive circuit according to claim 1, characterized in that: A resistor R3 is also connected between the operational amplifier and the filter circuit; the filter circuit adopts an RC filter circuit, and the RC filter circuit includes a resistor R2 and a capacitor C1. The resistor R2 and the resistor R3 are connected in series to the control signal source and the positive input terminal of the operational amplifier in sequence, and the common end of the resistor R2 and the resistor R3 is grounded through the capacitor C1.

3. The relay drive circuit according to claim 1, characterized in that: The operational amplifier follower circuit further includes a capacitor C2, and the capacitor C2 is connected between the positive power supply terminal and the negative power supply terminal of the operational amplifier.

4. The relay drive circuit according to claim 1, characterized in that: The operational amplifier follower circuit further includes a resistor R4, wherein the resistor R4 is connected to the output end of the operational amplifier, and the output end of the operational amplifier is connected to the base of the transistor through the resistor R4.

5. The relay drive circuit according to claim 1, characterized in that: A resistor R1 is also connected between the power source VCC and the coil of the relay.

6. The relay drive circuit according to claim 1, characterized in that: A diode is also connected in parallel to the coil of the relay, and the anode of the diode is connected to the collector of the transistor.

7. The relay drive circuit according to claim 1, characterized in that: The control signal source adopts a single chip microcomputer, and the single chip microcomputer is used to output a PWM control signal.

8. A bus capacitor pre-charging circuit, acting on a bus capacitor, characterized in that: It includes a power supply Vin, a resistor RT1, a relay, a power supply voltage sampling module and a capacitor voltage sampling module; The positive end of the power source Vin, the resistor RT1, the bus capacitor and the negative end of the power source Vin are sequentially connected in series to form a closed loop; The contact of the relay is connected in parallel with the resistor RT1, and the coil of the relay is driven by the relay driving circuit according to any one of claims 1 to 7; The power supply voltage sampling module is connected in parallel with the power supply Vin, and the capacitor voltage sampling module is connected in parallel with the bus capacitor.

9. The busbar capacitor pre-charging circuit according to claim 8, characterized in that: The power supply voltage sampling module includes a resistor R5, a resistor R7 and a resistor R9 connected in series in sequence, and the voltage at the common end of the resistor R5 and the resistor R7 is taken as the output voltage of the power supply voltage sampling module; the capacitor voltage sampling module includes a resistor R6, a resistor R8 and a resistor R10 connected in series in sequence, and the voltage at the common end of the resistor R6 and the resistor R8 is taken as the output voltage of the capacitor voltage sampling module.

10. The bus capacitor pre-charging circuit according to claim 8, characterized in that: The output ends of the power supply voltage sampling module and the capacitor voltage sampling module are both connected to the control signal source.

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