Starting control circuit for contactor

Abstract

The utility model belongs to the field of contactor control, and discloses a starting control circuit of a contactor, which is characterized in that a starting reference voltage curve is designed through the starting control circuit, voltage values converted from current of an electromagnetic coil of the contactor are sampled and compared, and under a wide-voltage input condition, the starting reference voltage curve is calculated; and controlling the coil current of the contactor to linearly transform according to the starting reference voltage curve, so that the current rising slope of the electromagnetic coil of the contactor in a wide voltage input range is consistent.

Description

Technical Field

[0001] The utility model belongs to the field of contactor control, and in particular relates to a start-up control circuit for a contactor. Background Art

[0002] As the scope of use of contactors continues to expand, the use scenarios of wide-voltage input are also gradually increasing. For conventional contactors, they are usually powered directly by 220V AC, and there are few control methods for wide-voltage input conditions. During the contactor's pull-in rising stage, wide-voltage input will cause inconsistent changes in the rising slope of the contact line electromagnetic coil current, which is manifested as a large speed difference in the pull-in rising stage under high and low voltages, the pull-in time cannot be accurately determined, and there is no linear correlation between the electromagnetic coil current and time. Utility Model Content

[0003] The utility model aims to overcome at least one defect (shortcoming) in the above-mentioned prior art and provide a constant current starting method and control circuit based on a contactor to solve the problem that the rising slope of the current of the contact line electromagnetic coil is inconsistent under a wide voltage input range, resulting in a large speed difference in the rising stage of the attraction under high and low voltages, and the attraction time cannot be accurately determined.

[0004] In order to solve the above problems, the utility model adopts the following technical solutions:

[0005] Provided is a control circuit of a contactor, a start-up control circuit for a contactor, the contactor comprising: a first power tube, a second power tube and an electromagnetic coil, one end of the electromagnetic coil is connected to one end of the first power tube, and the other end of the electromagnetic coil is connected to one end of the second power tube, the start-up control circuit comprising:

[0006] The coil current sampling circuit collects the current of the electromagnetic coil of the contactor and converts the current into a sampling voltage;

[0007] A reference voltage generating circuit, wherein the reference voltage generating circuit generates a starting reference voltage which increases linearly with time when the contactor is started;

[0008] A comparator is connected to the coil current sampling circuit and the reference voltage generating circuit respectively. The comparator receives the sampling voltage and the starting reference voltage, and outputs a shutdown control signal for controlling the shutdown of the second power tube when the sampling voltage and the starting reference voltage are equal.

[0009] Preferably, the control circuit also includes a clock, a rising edge extraction unit and a D flip-flop, the ground end of the clock is connected to the ground, the positive pole of the clock is connected to one end of the rising edge extraction unit, the other end of the rising edge extraction unit is connected to the enable end of the D flip-flop, the reset end of the D flip-flop is connected to the output end of the comparator, and the output end of the D flip-flop is connected to the control end connected to the second power tube.

[0010] Preferably, the reference voltage generating circuit includes a constant current source, a capacitor and an adjustable voltage-controlled voltage source, the ground terminal of the constant current source is connected to the ground, the other end of the constant current source is respectively connected to one end of the capacitor and the input end of the adjustable voltage-controlled voltage source, the ground terminal of the capacitor and the ground end of the adjustable voltage-controlled voltage source are commonly connected to the ground, the output end of the adjustable voltage-controlled voltage source is connected to the input anode of the comparator, and the input cathode of the comparator is connected to the sampling voltage.

[0011] The utility model also provides a start-up control circuit for a contactor, the contactor comprising: a first power tube, a second power tube and an electromagnetic coil, one end of the electromagnetic coil is connected to one end of the first power tube, and the other end of the electromagnetic coil is connected to one end of the second power tube, the start-up control circuit comprises: a clock, a rising edge extraction unit, a D trigger, a reference voltage generation circuit and a coil current sampling circuit; the reference voltage generation circuit is used to generate a start-up reference voltage that increases linearly with time when the contactor is started, and the reference voltage generation circuit comprises a constant current source, a capacitor and an adjustable voltage-controlled voltage source;

[0012] The ground end of the clock is connected to the ground, the positive pole of the clock is connected to one end of the rising edge extraction unit, the other end of the rising edge extraction unit is connected to the enable end of the D flip-flop, the signal input end (D) of the D flip-flop is connected to the power supply port, the output end of the D flip-flop is connected to the control end of the second power tube, the reset end of the D flip-flop is connected to the output end of the comparator, the ground end of the constant current source is connected to the ground, the other end of the constant current source is respectively connected to one end of the capacitor and the input end of the adjustable voltage-controlled voltage source, the ground end of the capacitor and the ground end of the adjustable voltage-controlled voltage source are connected to the ground together, the output end of the adjustable voltage-controlled voltage source is connected to the input anode of the comparator, the input cathode of the comparator is connected to the sampling voltage, and the coil current sampling circuit is used to collect the excitation current of the electromagnetic coil of the contactor and convert the excitation current into a sampling voltage.

[0013] The utility model further provides a start-up control circuit for a contactor, the contactor comprising: a first power tube, a second power tube and an electromagnetic coil, one end of the electromagnetic coil is connected to one end of the first power tube, and the other end of the electromagnetic coil is connected to one end of the second power tube, the start-up control circuit comprises:

[0014] The coil current sampling circuit is used to collect the current of the electromagnetic coil of the contactor to obtain a sampling voltage;

[0015] A reference voltage generating circuit, used for generating a starting reference voltage which increases linearly with time when the contactor is started;

[0016] The comparator is connected to the coil current sampling circuit and the reference voltage generating circuit respectively, and is used to compare the sampling voltage with the startup reference voltage and output a shutdown control signal for controlling the shutdown of the second power tube according to the comparison result.

[0017] The beneficial effects of the utility model are as follows: by starting the control circuit, a period of pull-in rise time is set, and the starting reference voltage increases linearly with the passage of time, and at the same time, the voltage value converted from the current flowing through the electromagnetic coil of the contactor when the second power tube is turned on is sampled and compared with the above-mentioned starting reference voltage to shut down the second power tube; by controlling the contactor coil current to rise according to the involved starting reference voltage curve, it is ensured that the rising slope of the contactor electromagnetic coil current is consistent under a wide voltage input range, thereby ensuring that when the input voltage changes from low to high, the pull-in rise time also changes from long to short, and vice versa; the stability and reliability of the contactor operation are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a control system structure diagram of the contactor of the utility model.

[0019] Figure 2 The utility model is a start-up control circuit diagram of the contactor.

[0020] Figure 3 This is a working timing diagram of the startup control circuit of the contactor of the utility model. DETAILED DESCRIPTION

[0021] The present utility model / utility model and its beneficial effects will be further described in detail below in conjunction with specific implementation methods and drawings of the specification, but the specific implementation methods of the present utility model are not limited thereto.

[0022] like Figure 1 As shown in the figure, it is a control system structure diagram of the contactor. The control system mainly consists of four parts: a dual-tube forward topology circuit, the electromagnetic coil L2 of the contactor, a high-voltage starting unit, and a main control unit. Among them, the main control unit contains a starting control circuit for realizing constant current starting of the contactor. The starting control circuit is a constant current starting control circuit.

[0023] The operation of the contactor mainly includes four parts: the attraction rising stage, the attraction stabilization stage, the holding stage and the disconnection stage. The attraction rising stage and the attraction stabilization stage are described in detail in this application. The other stages are the same as the existing working mode and will not be repeated later.

[0024] like Figure 1As shown, the dual-tube forward topology circuit includes a rectifier bridge D1, a capacitor C2, a diode D2, a diode D3, a power tube Q1 (a first power tube), a power tube Q2 (a second power tube) and a coil current sampling circuit, and the coil current sampling circuit consists of a resistor R1, a resistor R2 and a capacitor C1.

[0025] The L port is connected to one end of the rectifier bridge D1, the other end of the rectifier bridge D1 is connected to the N port, the negative electrode of the rectifier bridge D1 is connected to the ground, the positive electrode of the rectifier bridge D1 is connected to one end of the capacitor C2, the other end of the capacitor C2 is connected to the ground, the drain of the power tube Q1 and the cathode of the diode D2 are commonly connected to the positive electrode of the rectifier bridge D1, the source of the power tube Q1 is respectively connected to one end of the electromagnetic coil L2 and the cathode of the diode D3, the other end of the electromagnetic coil L2 is respectively connected to the drain of the power tube Q2 and the anode of the diode D2, the source of the power tube Q2 is respectively connected to one end of the resistors R1 and R2, the other end of the resistor R2 and the anode of the diode D3 are commonly connected to the ground, the other end of the resistor R1 is connected to one end of the capacitor C1, and the other end of the capacitor C1 is connected to the ground. Among them, the coil current sampling circuit composed of resistors R1, R2 and capacitor C1 mainly samples the excitation current IL2 of the electromagnetic coil L2 when the power tube Q2 is turned on, and inputs the sampling voltage converted from the excitation current IL2 into the electromagnetic coil current sampling port VS (hereinafter referred to as the VS port) of the main control unit for real-time comparison with the starting reference voltage output by the adjustable voltage-controlled voltage source U74 to control the shutdown moment of the power tube Q2, so that the contactor can maintain working in a constant current state in the rising stage of attraction when a wide voltage input is applied.

[0026] The working principle of the dual-tube forward topology circuit is as follows: when there is an input voltage Vin, it is directly used as the input voltage of the high-voltage starting unit after passing through the rectifier bridge D1. The output voltage of the high-voltage starting unit is connected to the power supply port VCC of the main control unit to power the main control unit; when the contactor starts working, the power tube Q1 remains on, and the power tube Q2 is triggered to turn on by the internal clock V4 of the main control unit, and the sampling voltage of the excitation current IL2 of the electromagnetic coil L2 is compared with the starting reference voltage that increases linearly with time through the current sampling port VS to control the power tube Q2 to turn off, so that the contactor completes the working process of the pull-in rising stage (i.e. the starting stage). When the power tubes Q1 and Q2 are both turned on, the electromagnetic coil L2 begins to be excited. When the power tube Q2 is turned off, the current in the electromagnetic coil continues to flow through the conduction circuit of the power tube Q1. The contactor completes the work in the attraction and holding stages through the above control method. When the power tubes Q1 and Q2 are both turned off, the current in the electromagnetic coil L2 flows back to the capacitor C2 through the diodes D2 and D3, and the contactor is disconnected at this time.

[0027] The high voltage startup unit includes three ports: input port IN, output port OUT, and ground GND. Its main function is to supply power to the main control unit. The input port IN of the high voltage startup unit is connected to one end of the capacitor C2, the ground port GND is connected to the ground, and the output port OUT is connected to the power supply port VCC of the main control unit.

[0028] The main control unit includes a power supply port VCC, a drive signal port G1, a drive signal port G2, an electromagnetic coil current sampling port VS (hereinafter referred to as the VS port) and a ground port GND. Its important function is to sample the excitation current IL2 of the contactor electromagnetic coil L2 through the VS port to maintain the voltage signal on the capacitor C1, and to generate a shutdown control signal of the power tube Q2 of the contactor in the rising stage of the pull-in by comparing with the start-up reference voltage of the internal start-up control circuit, and to control the power tube Q1 to maintain a long-on state when the contactor is working. The drive signal port G1 of the main control unit is connected to the gate of the power tube Q1, the drive signal port G1 is connected to the gate of the power tube Q2, the VS port is connected to one end of the capacitor C1, and the ground port GND is connected to the ground.

[0029] like Figure 2 As shown, the start control circuit is located inside the main control unit, and the start control circuit includes a reference voltage generating circuit, a clock V4, a rising edge extraction unit, a D trigger U8 and a coil current sampling circuit; wherein, the reference voltage generating circuit is used to generate a start reference voltage U74_OUT that increases linearly with time when the contactor is started, and the reference voltage generating circuit includes a constant current source I4, a capacitor C12 and an adjustable voltage-controlled voltage source U74 with adjustable upper and lower limits.

[0030] The ground terminal of the clock V4 is connected to the ground, the positive electrode of the clock V4 is connected to one end of the rising edge extraction unit, the other end of the rising edge extraction unit is connected to the enable end of the D flip-flop U8, the signal input end (D) of the D flip-flop U8 is connected to the power supply port VCC, and the output end Q of the D flip-flop U8 is connected to the control end of the power tube Q2 through the drive signal port G2. The reset end RST of the D flip-flop U8 is connected to the output end of the comparator U7. The ground terminal of the constant current source I4 is connected to the ground, and the other end of the constant current source is respectively connected to one end of the capacitor C12 and the input end of the adjustable voltage-controlled voltage source U74, the ground terminal of the capacitor C12 and the ground terminal of the adjustable voltage-controlled voltage source U74 are connected to the ground together, and the output end of the adjustable voltage-controlled voltage source U74 is connected to the input anode of the comparator U7, and the input cathode of the comparator U7 is connected to the VS port, and the VS port is connected to the coil current sampling circuit.

[0031] The following combination Figure 2 , Figure 3 , the working principle of the startup control circuit is explained. Figure 3In the figure, VCC represents the voltage of the power supply port VCC, VIN represents the input voltage, U74_OUT represents the start reference voltage, VS represents the voltage of the VS port (i.e., the sampling voltage), G2 represents the drive signal output by the drive signal port G2, and IL2 represents the excitation current in the electromagnetic coil L2. In the rising stage of the pull-in, on the one hand, by extracting the rising edge of the clock V4, the D trigger U8 is enabled to turn on the power tube Q2; on the other hand, the upper and lower limits of its output voltage are set by the adjustable voltage-controlled voltage source U74, the lower limit is 0V, and the upper limit is the maximum voltage value of the start reference voltage U74_OUT in the rising stage of the pull-in. Within this range, the capacitor C12 is charged by the constant current source I4, so that the voltage on the capacitor C12 gradually increases with time until the voltage on the capacitor C12 reaches the maximum voltage value of the start reference voltage U74_OUT. In other words, in the rising stage of the pull-in of the contactor, the start reference voltage U74_OUT is expressed as a linearly increasing voltage curve, such as Figure 3 As shown; synchronously, the voltage signal (ie, the sampling voltage) maintained on the capacitor C1 by sampling the excitation current IL2 of the electromagnetic coil L2 through the VS port, and compares it with the start reference voltage U74_OUT output of the adjustable voltage-controlled voltage source U74, as shown Figure 3 The voltage waveform of the VS port (i.e., the sampling voltage) is shown in Figure 1. When the voltage of the VS port hits the rising curve of the starting reference voltage U74_OUT (i.e., when the sampling voltage is equal to the starting reference voltage U74_OUT), the comparator U7 flips from a high level to a low level (i.e., outputs a shutdown control signal for controlling the shutdown of the power tube Q2), and pulls down the level of the output terminal Q through the reset port of the D trigger U8, thereby shutting down the power tube Q2 and completing a cycle of work. In this way, the excitation current IL2 in the electromagnetic coil L2 can be made to rise at a fixed slope regardless of whether the input voltage of the contactor is high or low at this time, thereby ensuring the consistency of the excitation current IL2 in the electromagnetic coil L2 under a wide voltage input, so that the contactor works in a stable state.

Claims

1. A start-up control circuit for a contactor, the contactor comprising: A first power tube (Q1), a second power tube (Q2) and an electromagnetic coil (L2), one end of the electromagnetic coil (L2) is connected to one end of the first power tube (Q1), and the other end of the electromagnetic coil (L2) is connected to one end of the second power tube (Q2), characterized in that: the start control circuit comprises: A coil current sampling circuit, wherein the coil current sampling circuit collects the excitation current of the electromagnetic coil (L2) of the contactor and converts the excitation current into a sampling voltage; A reference voltage generating circuit, wherein the reference voltage generating circuit generates a starting reference voltage (U74_OUT) that increases linearly with time when the contactor is started; A comparator (U7), the comparator (U7) being connected to the coil current sampling circuit and the reference voltage generating circuit respectively, the comparator receiving the sampling voltage and the start-up reference voltage (U74_OUT), and outputting a shutdown control signal for controlling the shutdown of the second power tube (Q2) when the sampling voltage and the start-up reference voltage (U74_OUT) are equal.

2. The starting control circuit for a contactor according to claim 1, characterized in that: It also includes a clock (V4), a rising edge extraction unit and a D flip-flop (U8), wherein the ground end of the clock (V4) is connected to the ground, the positive electrode of the clock (V4) is connected to one end of the rising edge extraction unit, the other end of the rising edge extraction unit is connected to the enable end of the D flip-flop (U8), the reset end (RST) of the D flip-flop (U8) is connected to the output end of the comparator (U7), and the output end (Q) of the D flip-flop (U8) is connected to the control end connected to the second power tube (Q2).

3. The starting control circuit for a contactor according to claim 1, characterized in that: The reference voltage generating circuit comprises a constant current source (I4), a capacitor (C12) and an adjustable voltage-controlled voltage source (U74); the grounding end of the constant current source (I4) is connected to the ground; the other end of the constant current source (I4) is respectively connected to one end of the capacitor (C12) and the input end of the adjustable voltage-controlled voltage source (U74); the grounding end of the capacitor (C12) and the grounding end of the adjustable voltage-controlled voltage source (U74) are commonly connected to the ground; the output end (Q) of the adjustable voltage-controlled voltage source (U74) is connected to the input anode of the comparator (U7); and the input cathode of the comparator (U7) is connected to the sampling voltage.

4. A start-up control circuit for a contactor, the contactor comprising: A first power tube (Q1), a second power tube (Q2) and an electromagnetic coil (L2), one end of the electromagnetic coil (L2) is connected to one end of the first power tube (Q1), and the other end of the electromagnetic coil (L2) is connected to one end of the second power tube (Q2), characterized in that the startup control circuit comprises: a reference voltage generating circuit, a clock (V4), a rising edge extraction unit, a D trigger (U8) and a coil current sampling circuit; the reference voltage generating circuit is used to generate a startup reference voltage (U74_OUT) that increases linearly with time when the contactor is started, and the reference voltage generating circuit comprises a constant current source (I4), a capacitor (C12) and an adjustable voltage-controlled voltage source (U74), The grounding terminal of the clock (V4) is connected to the ground, the positive electrode of the clock (V4) is connected to one end of the rising edge extraction unit, the other end of the rising edge extraction unit is connected to the enable end of the D flip-flop (U8), the signal input end (D) of the D flip-flop (U8) is connected to the power supply port, the output end (Q) of the D flip-flop (U8) is connected to the control end of the second power tube (Q2), the reset end (RST) of the D flip-flop (U8) is connected to the output end of the comparator (U7), the grounding terminal of the constant current source (I4) is connected to the ground, and the constant current source The other end is respectively connected to one end of the capacitor (C12) and the input end of the adjustable voltage-controlled voltage source (U74); the grounding end of the capacitor (C12) and the grounding end of the adjustable voltage-controlled voltage source (U74) are commonly connected to the ground; the output end of the adjustable voltage-controlled voltage source (U74) is connected to the input anode of the comparator (U7); the input cathode of the comparator (U7) is connected to the coil current sampling circuit; the coil current sampling circuit is used to collect the excitation current of the electromagnetic coil (L2) of the contactor and convert the excitation current into a sampling voltage.

5. A startup control circuit for a contactor, the contactor comprising: A first power tube (Q1), a second power tube (Q2) and an electromagnetic coil (L2), one end of the electromagnetic coil (L2) is connected to one end of the first power tube (Q1), and the other end of the electromagnetic coil (L2) is connected to one end of the second power tube (Q2), characterized in that: the start control circuit comprises: A coil current sampling circuit, used for collecting the excitation current of the electromagnetic coil (L2) of the contactor to obtain a sampling voltage; A reference voltage generating circuit, used for generating a starting reference voltage (U74_OUT) which increases linearly with time when the contactor is started; A comparator is connected to the coil current sampling circuit and the reference voltage generating circuit respectively, and is used to compare the sampling voltage with the start-up reference voltage (U74_OUT) and output a shutdown control signal for controlling the shutdown of the second power tube (Q2) according to the comparison result.

6. The starting control circuit for a contactor according to claim 5, characterized in that: It also includes a clock (V4), a rising edge extraction unit and a D flip-flop (U8), wherein the ground end of the clock (V4) is connected to the ground, the positive electrode of the clock (V4) is connected to one end of the rising edge extraction unit, the other end of the rising edge extraction unit is connected to the enable end of the D flip-flop (U8), the reset end (RST) of the D flip-flop (U8) is connected to the output end of the comparator, and the output end of the D flip-flop (U8) is connected to the control end connected to the second power tube (Q2).

7. The starting control circuit for a contactor according to claim 5, characterized in that: The reference voltage generating circuit comprises a constant current source (I4), a capacitor (C12) and an adjustable voltage-controlled voltage source (U74); the grounding end of the constant current source (I4) is connected to the ground, the other end of the constant current source is respectively connected to one end of the capacitor (C12) and the input end of the adjustable voltage-controlled voltage source (U74); the grounding end of the capacitor (C12) and the grounding end of the adjustable voltage-controlled voltage source (U74) are commonly connected to the ground; the output end of the adjustable voltage-controlled voltage source (U74) is connected to the input anode of the comparator (U7); and the input cathode of the comparator (U7) is connected to the sampling voltage.

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