Direct current contactor coil back electromotive force suppression circuit and control method thereof

Abstract

The embodiment of the invention discloses a DC contactor coil reverse electromotive force suppression circuit and a control method thereof. The method comprises a power supply circuit; the starting coil control circuit is used for controlling starting or power loss of the starting coil; the holding coil control circuit is used for controlling starting or power loss of the holding coil; the detection circuit is used for detecting voltage and current in the direct-current contactor coil reverse electromotive force suppression circuit and the contact state of the direct-current contactor; the single-chip microcomputer is used for controlling the starting coil control circuit and the holding coil control circuit to work according to the detection result of the detection circuit, and controlling the starting coil to start reversely when the holding coil loses power so as to suppress the reverse electromotive force of the holding coil until the contact of the direct current contactor is released successfully. Through the above mode, the embodiment of the invention can counteract the electromagnetic force generated by the holding coil when the fly-wheel diode conducts the residual current by multiplexing the starting coil to add the reverse voltage at the moment of opening, so that the opening is more reliable, and the opening time is shortened.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of electromagnetic control technology, and in particular to a DC contactor coil reverse electromotive force suppression circuit and a control method thereof. Background Art

[0002] When the coil drive signal of the DC contactor and relay double coil in the traction converter control system of electric locomotive is disconnected, a reverse electromotive force opposite to the drive voltage will be generated at both ends of the coil. Generally, a freewheeling diode or a varistor is used to prevent this, but the disconnection delay is increased, and the arcing time of the contact is increased, which affects the life of the relay or contactor contacts.

[0003] In addition, in order to keep the coil power constant under different input voltage conditions, it is necessary to adjust the coil power supply duty cycle. This process will also generate reverse electromotive force, which can easily break down surrounding electronic devices. Summary of the invention

[0004] In view of the above problems, an embodiment of the present invention provides a DC contactor coil reverse electromotive force suppression circuit and a control system thereof, which overcomes the above problems or at least partially solves the above problems.

[0005] According to one aspect of an embodiment of the present invention, a DC contactor coil reverse electromotive force suppression circuit is provided, comprising: a power supply circuit, used for processing an input DC power supply, and outputting an input power supply voltage, a first reference power supply voltage, and a second reference power supply voltage; a starting coil control circuit, connected to the power supply circuit, and used for controlling the starting or power failure of a starting coil in a DC contactor; a holding coil control circuit, connected to the power supply circuit, and used for controlling the starting or power failure of a holding coil in a DC contactor; a detection circuit, connected to the power supply circuit, and used for detecting the voltage, current, and contact state of the DC contactor coil reverse electromotive force suppression circuit; a single-chip microcomputer, connected to the power supply circuit, the starting coil control circuit, and the holding coil control circuit, and used for controlling the starting coil control circuit and the holding coil control circuit to work according to the detection result of the detection circuit, and controlling the starting coil to start in reverse when the holding coil loses power to suppress the reverse electromotive force of the holding coil until the contacts of the DC contactor are successfully released.

[0006] Optionally, the power supply circuit includes: a lightning surge suppression circuit, a filtering circuit, a chopping circuit and a DC / DC voltage stabilizing circuit connected in sequence; the lightning surge suppression circuit and the filtering circuit are respectively used to protect the input DC power supply from lightning surge impact and filter, and output the input power supply voltage, the chopping circuit is used to chop the DC power supply voltage into the first reference power supply voltage, and the DC / DC voltage stabilizing circuit is used to convert the first reference power supply voltage into the second reference power supply voltage.

[0007] Optionally, the starting coil control circuit includes: a bridge MOS forward and reverse switching circuit and a reverse electromotive force absorption circuit connected to the single-chip microcomputer, the bridge MOS forward and reverse switching circuit is used to receive the control signal of the single-chip microcomputer, and control the starting coil to be forward powered, reverse powered, or powered off according to the control signal, and the reverse electromotive force absorption circuit is used to be turned on when the starting coil is powered off, so as to suppress the reverse electromotive force generated by the coil.

[0008] Optionally, the bridge MOS forward and reverse switching circuit includes: a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor and an eighth resistor; the first end of the first switch tube and the first end of the second switch tube are connected to the power supply circuit through the first resistor, the first end of the third switch tube and the first end of the fourth switch tube are connected to the power supply circuit through the second resistor, one end of the starting coil is connected to the second end of the second switch tube and the second end of the first switch tube, the other end of the starting coil is connected to the second end of the third switch tube and the second end of the fourth switch tube, the third end of the first switch tube and the third end of the fourth switch tube are grounded, and the second switch tube The third end of the fifth switch tube and the third end of the third switch tube are connected to the power supply circuit; the first end of the fifth switch tube is connected to the single-chip microcomputer through the third resistor, the second end of the fifth switch tube is connected to the first end of the sixth switch tube, and is connected to the first reference power supply voltage through the fourth resistor, the second end of the sixth switch tube is connected to the first end of the second switch tube through the fifth resistor, and the third end of the fifth switch tube and the third end of the sixth switch tube are grounded; the first end of the seventh switch tube is connected to the single-chip microcomputer through the sixth resistor, the second end of the seventh switch tube is connected to the first end of the eighth switch tube, and is connected to the first reference power supply voltage through the seventh resistor, the second end of the eighth switch tube is connected to the first end of the third switch tube through the eighth resistor, and the third end of the seventh switch tube and the third end of the eighth switch tube are grounded.

[0009] Optionally, the reverse electromotive force absorption circuit includes: a ninth switch tube, a tenth switch tube, a first diode, a second diode, a ninth resistor and a tenth resistor; the first end of the ninth switch tube is connected to the single-chip microcomputer through the ninth resistor, the first end of the tenth switch tube is connected to the single-chip microcomputer through the tenth resistor, the cathode of the first diode and the second end of the tenth switch tube are connected to one end of the starting coil, the third end of the tenth switch tube is connected to the anode of the second diode, the cathode of the second diode and the second end of the ninth switch tube are connected to the other end of the starting coil, and the third end of the ninth switch tube is connected to the anode of the first diode.

[0010] Optionally, the holding coil control circuit includes: an eleventh switch tube, an eleventh resistor, a twelfth resistor, a first relay, a third diode and a voltage divider control circuit; the first end of the first relay is connected to the second reference power supply voltage through the eleventh resistor, the second end of the first relay is connected to the single-chip microcomputer, the third end of the first relay is connected to the first end of the eleventh switch tube, the fourth end of the first relay is connected to the first reference power supply voltage through the twelfth resistor, the second end of the eleventh switch tube is connected to the power supply circuit, the third end of the eleventh switch tube is connected to the voltage divider control circuit and the cathode of the third diode, the anode of the third diode is grounded, and the voltage divider control circuit is connected between the single-chip microcomputer and the holding coil.

[0011] Optionally, the detection circuit includes: a current monitoring circuit, a voltage monitoring circuit and a first magnetic isolation coupling circuit connected to the single-chip microcomputer; one end of the first magnetic isolation coupling circuit is connected to the contacts of the DC contactor, and the other end is connected to the single-chip microcomputer, for detecting the state of the contacts of the DC contactor; the current monitoring circuit includes a thirteenth resistor, and the voltage monitoring circuit includes a fourteenth resistor and a fifteenth resistor, one end of the thirteenth resistor is connected to the single-chip microcomputer and the holding coil, and the other end of the thirteenth resistor is grounded; one end of the fourteenth resistor is connected to the input power supply voltage, and the other end is connected to the single-chip microcomputer, and is grounded through the fifteenth resistor.

[0012] Optionally, the DC contactor coil reverse electromotive force suppression circuit also includes: an overvoltage and overcurrent protection circuit connected to the power supply circuit, the holding coil control circuit and the single-chip microcomputer; the overvoltage and overcurrent protection circuit is used to receive the overcurrent or overvoltage protection drive signal output by the single-chip microcomputer, and disconnect the path between the power supply circuit and the holding coil control circuit according to the protection drive signal.

[0013] Optionally, the overvoltage and overcurrent protection circuit includes a second relay, a fourth diode, a sixteenth resistor, a seventeenth resistor and a twelfth switch tube; the first end of the twelfth switch tube is connected to the single-chip microcomputer through the sixteenth resistor, and is also connected to the second reference power supply voltage through the seventeenth resistor, the second end of the twelfth switch tube is connected to the anode of the fourth diode and the first end of the second relay, and the third end of the twelfth switch tube is grounded; the second end of the second relay is connected to the cathode of the fourth diode and is connected to the second reference power supply voltage, the third end of the second relay is connected to the power supply circuit, and the fourth end of the second relay is connected to the holding coil control circuit.

[0014] Based on the same inventive concept, an embodiment of the present invention further proposes a control method for the reverse electromotive force suppression circuit of the DC contactor coil, comprising: when the DC contactor is closed, the single chip microcomputer controls the starting coil of the DC contactor to be energized through the starting coil control circuit, controls the contact of the DC contactor to be closed, and when the contact closure is detected by the detection circuit, the single chip microcomputer controls the holding coil of the DC contactor to be energized through the holding coil control circuit, and controls the starting coil to be de-energized through the starting coil control circuit, and the DC contactor completes the closing; when the DC contactor is working normally, the single chip microcomputer controls the power of the holding coil to be constant through the holding coil control circuit according to the detected input power supply voltage and coil current; when the DC contactor is opened, the single chip microcomputer controls the holding coil to be de-energized through the holding coil control circuit, and controls the starting coil to start in reverse through the starting coil control circuit, and the electromagnetic force generated by the starting coil is greater than the electromagnetic force of the holding coil and in the opposite direction, until the detection circuit detects that the contact of the DC contactor is successfully released.

[0015] The embodiment of the present invention processes the input DC power supply through the power supply circuit, and outputs the input power supply voltage, the first reference power supply voltage and the second reference power supply voltage; the starting coil control circuit is used to control the starting or power failure of the starting coil in the DC contactor; the holding coil control circuit is used to control the starting or power failure of the holding coil in the DC contactor; the detection circuit is used to detect the voltage, current and contact state of the DC contactor in the reverse electromotive force suppression circuit of the DC contactor coil; the single-chip microcomputer is used to control the operation of the starting coil control circuit and the holding coil control circuit according to the detection result of the detection circuit, and controls the starting coil to start in reverse when the holding coil loses power to suppress the reverse electromotive force of the holding coil until the contacts of the DC contactor are successfully released, and can offset the electromagnetic force generated by the residual current of the holding coil when the freewheeling diode is turned on by reusing the starting coil at the moment of opening, so as to make the opening more reliable and shorten the opening time.

[0016] The above description is only an overview of the technical solution of the embodiment of the present invention. In order to more clearly understand the technical means of the embodiment of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the embodiment of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0018] Figure 1 A schematic diagram of the structure of a DC contactor coil reverse electromotive force suppression circuit provided by an embodiment of the present invention is shown;

[0019] Figure 2 A schematic diagram of the structure of a lightning surge suppression circuit according to an embodiment of the present invention is shown;

[0020] Figure 3 A schematic diagram showing the structure of a filter circuit according to an embodiment of the present invention is shown;

[0021] Figure 4 A schematic diagram showing the structure of a chopper circuit according to an embodiment of the present invention is shown;

[0022] Figure 5 A schematic diagram showing the structure of a DC / DC voltage stabilizing circuit according to an embodiment of the present invention is shown;

[0023] Figure 6 A schematic structural diagram of a second magnetic isolation coupling circuit according to an embodiment of the present invention is shown;

[0024] Figure 7 A schematic diagram showing the structure of a start coil control circuit according to an embodiment of the present invention is shown;

[0025] Figure 8 A schematic diagram showing the structure of a holding coil control circuit according to an embodiment of the present invention is shown;

[0026] Fig. 9 A schematic diagram showing the structure of a detection circuit according to an embodiment of the present invention is shown;

[0027] Fig.10 A schematic structural diagram of a first magnetic isolation coupling circuit according to an embodiment of the present invention is shown;

[0028] Fig.11 A schematic flow chart of a control method of a DC contactor coil reverse electromotive force suppression circuit provided by an embodiment of the present invention is shown;

[0029] Fig.12 A schematic diagram of a closing process of a DC contactor according to an embodiment of the present invention is shown;

[0030] Fig.13 A schematic diagram of a process of controlling and maintaining a constant coil power according to an embodiment of the present invention is shown;

[0031] Fig.14 A schematic diagram of a flow chart of opening a DC contactor according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0032] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0033] Figure 1 FIG. 1 shows a schematic diagram of a DC contactor coil reverse electromotive force suppression circuit according to an embodiment of the present invention. Figure 1 As shown, the DC contactor coil reverse electromotive force suppression circuit includes: a power supply circuit 1, which is used to process the input DC power supply and output the input power supply voltage VCC, the first reference power supply voltage VDC and the second reference power supply voltage VDD. A starting coil control circuit 2, which is connected to the power supply circuit 1, is used to control the starting or de-energizing of the starting coil L1 in the DC contactor. A holding coil control circuit 3, which is connected to the power supply circuit 1, is used to control the starting or de-energizing of the holding coil L2 in the DC contactor. A detection circuit 4, which is connected to the power supply circuit 1, is used to detect the voltage, current and contact state of the DC contactor in the DC contactor coil reverse electromotive force suppression circuit. A single-chip computer U1, which is connected to the power supply circuit 1, the starting coil control circuit 2 and the holding coil control circuit 3, is used to control the starting coil control circuit 2 and the holding coil control circuit 3 to work according to the detection result of the detection circuit 1, and control the starting coil L1 to start in reverse when the holding coil L2 loses power to suppress the reverse electromotive force of the holding coil L2 until the contact S1 of the DC contactor is released successfully.

[0034] In an embodiment of the present invention, the power supply circuit 1 includes: a lightning surge protection circuit 11, a filter circuit 12, a chopper circuit 13 and a DC / DC voltage regulator circuit 14 connected in sequence; the lightning surge protection circuit 11 and the filter circuit 12 are respectively used to protect the input DC power supply from lightning surge impact and filter, and output the input power supply voltage VCC, the chopper circuit 13 is used to chop the DC power supply voltage to the first reference power supply voltage VDC, and the DC / DC voltage regulator circuit 14 is used to convert the first reference power supply voltage into the second reference power supply voltage VDD. The input DC power supply is an external DC power supply that provides a DC voltage to the coil loop, preferably DC110V. The input power supply voltage VCC is a 110V DC power supply voltage after lightning surge protection and filtering, the first reference power supply voltage VDC is preferably 12V-15V, and the second reference power supply voltage VDD is preferably 3.3V. The external DC voltage 110V first passes through the lightning surge suppression circuit 11 and the filter circuit 12; then passes through the chopper circuit 13 to reduce the 110V to 12V, and the 12V voltage is converted to 3.3V through the DC / DC voltage regulator circuit 14. The power supply circuit 1 provides the required 110V, 12V, and 3.3V voltages for the dual coil circuit, the MOS tube drive circuit, the optical coupler, and the single-chip microcomputer U1 in sequence.

[0035] The lightning surge suppression circuit 11 is connected in parallel with the coil and the two ends of the DC power supply, which can effectively absorb spikes and overvoltages. Figure 2 As shown, the lightning surge suppression circuit 11 includes an interface J1, a first gas discharge tube GDT1, an eighteenth resistor R18, and a first transient voltage suppression diode TVS1. The first gas discharge tube GDT1, the eighteenth resistor R18, and the first transient voltage suppression diode TVS1 are connected in parallel with each other, one end of which is connected to a DC power supply DC110 through the interface J1, and the other end is grounded GND. The eighteenth resistor R18 is a varistor.

[0036] The filter circuit 12 is connected in parallel at both ends of the power supply to suppress common-mode interference, differential-mode interference, and absorb peak voltage. Figure 3As shown, the filter circuit 12 includes: a first capacitor C1, a common mode inductor T1, a second capacitor C2, a differential mode inductor T2, a third capacitor C3, a second gas discharge tube GDT2, a fourth capacitor C4 and a fifth capacitor C5. The first end of the common mode inductor T1 is connected to the output end of the lightning surge suppression circuit 11, and the second end is grounded GND. The first capacitor C1 is connected in parallel between the first end and the second end of the common mode inductor T1, the third end of the common mode inductor T1 is connected to the first end of the differential mode inductor T2, and the fourth end of the common mode inductor T1 is connected to the second end of the differential mode inductor T2. The second capacitor C2 is connected in parallel between the third end and the fourth end of the common mode inductor T1. The third capacitor C3, the second gas discharge tube GDT2, the fourth capacitor C4 and the fifth capacitor C5 are all connected in parallel between the third end and the fourth end of the differential mode inductor T2, and the fourth end of the differential mode inductor T2 is grounded. The third end of the differential mode inductor T2 outputs the input power supply voltage VCC after the lightning surge impact and filtering process.

[0037] like Figure 4 As shown, the chopper circuit 13 includes: a thirteenth switch tube Q13, a fourteenth switch tube Q14, a nineteenth resistor R19, a fifteenth switch tube Q15, a twentieth resistor R20, a twenty-first resistor R21, a sixteenth switch tube Q16, a twenty-second resistor R22, a twenty-third resistor R23, a sixth capacitor C6, a fifth diode D5, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9 and a tenth capacitor C10. The first end of the thirteenth switch tube Q13 is connected to the single-chip microcomputer U1, specifically connected to the P2B0A8 pin of the single-chip microcomputer U1. The second end of the thirteenth switch tube Q13 is connected to the first end of the fourteenth switch tube Q14, the first end of the fourteenth switch tube is also grounded through the nineteenth resistor R19, the second end of the fourteenth switch tube Q14 is connected to the first end of the fifteenth switch tube Q15, and the third end of the fourteenth switch tube Q14 and the third end of the thirteenth switch tube Q13 are grounded. The second end of the fifteenth switch tube Q15 is connected to the first end of the fifteenth switch tube Q15 through the twentieth resistor R20, and is connected to the first end of the sixteenth switch tube Q16 through the twenty-first resistor R21. The third end of the fifteenth switch tube Q15 is connected to the second end of the sixteenth switch tube Q16 and is connected to the input power supply voltage VCC.

[0038] The first end of the sixteenth switch tube Q16 is also connected to the ground GND through the sixth capacitor C6 and the fifth diode D5 connected in parallel. The third end of the sixteenth switch tube Q16 is connected to the ground GND through the twenty-third resistor R23, the seventh capacitor C7, the eighth capacitor C8, the ninth capacitor C9 and the tenth capacitor C10 connected in parallel. The third end of the sixteenth switch tube Q16 is an output end, which outputs the first reference power supply voltage VDC. Among them, the sixteenth switch tube Q16 is a composite triode, and the fifth diode D5 is a voltage regulator diode. The thirteenth switch tube Q13, the fourteenth switch tube Q14 and the fifteenth switch tube Q15 are MOS tubes, the first end is the gate, the second end is the drain, and the third end is the source.

[0039] like Figure 5 As shown, the DC / DC voltage stabilizing circuit 14 includes: a voltage stabilizing chip U2, an eleventh capacitor C11 and a twelfth capacitor C12. The input end of the voltage stabilizing chip U2 is connected to the output end of the chopper circuit 13, and the first reference power supply voltage VDC is input. The ground end of the voltage stabilizing chip U2 is grounded GND. The output end of the voltage stabilizing chip U2 outputs the second reference power supply voltage VDD, and is grounded GND through the eleventh capacitor C11 and the twelfth capacitor C12 connected in parallel. The DC / DC voltage stabilizing circuit 14 converts the first reference power supply voltage VDC into the second reference power supply voltage VDD through the voltage stabilizing chip U2, which is used as the power supply voltage VDD of the single-chip computer U2 to ensure the voltage stability of the single-chip computer U1.

[0040] In the embodiment of the present invention, the thirteenth switch tube Q13 is driven to be turned on and off by the single-chip microcomputer U1, so that the input power supply voltage VCC is chopped by the fifteenth switch tube Q and the sixteenth switch tube Q16, the fifth diode D5 and the auxiliary circuit form a series adjustment voltage stabilizing circuit. The fifth diode D5 stabilizes the voltage across the twenty-third resistor R23 to 12V. The voltage stabilizing diode D5 can prevent the voltage across the voltage stabilizing chip U2 from being too high and burning the voltage stabilizing chip U2.

[0041] The power supply circuit 1 also includes a second magnetic isolation coupling circuit 15 connected to the single-chip microcomputer U1, which is used to transmit an external input enable signal to the single-chip microcomputer U1. At the same time, through the second magnetic isolation coupling circuit 15, the interference signal on the line can be isolated to prevent the single-chip microcomputer U1 from being interfered. Figure 6As shown, the second magnetic isolation coupling circuit 15 includes: a switch S2, a second transient voltage suppression diode TVS2, a seventeenth switch tube Q17, a twenty-fourth resistor R24, a sixth diode D6, a twenty-fifth resistor R25, a thirteenth capacitor C13, a seventh diode D7, a first magnetic isolation coupler T3, an eighth diode D8, a ninth diode D9, an eighteenth switch tube Q18, a twenty-sixth resistor R26, a nineteenth switch tube Q19, a fourteenth capacitor C14 and a twenty-seventh resistor R27. One end of the switch S2 is connected to the second reference power supply voltage VDD, and the other end is connected to the first end of the first magnetic isolation coupler T3 and the cathode of the sixth diode D6, and the anode of the sixth diode D6 is connected to the first end of the seventeenth switch tube Q17. The other end of the switch S2 is also connected to the first end of the seventeenth switch tube Q17 through the twenty-fourth resistor R24, connected to the cathode of the seventh diode D7 through the twenty-fifth resistor R25 and the thirteenth capacitor C13 connected in parallel, and grounded GND through the second transient voltage suppression diode TVS2. The second end of the seventeenth switch tube Q17 is connected to the anode of the seventh diode D7 and the second end of the first magnetic isolation coupler T3. The third end of the first magnetic isolation coupler T3 is connected to the anode of the eighth diode D8 and the anode of the ninth diode D9, and is connected to the first end of the nineteenth switch tube Q19 through the twenty-sixth resistor R26, and the second end of the nineteenth switch tube Q19 is grounded GND. The cathode of the ninth diode D9 is connected to the first end of the eighteenth switch tube Q18, the cathode of the eighth diode D8 is connected to the second end of the eighteenth switch tube Q18, the third end of the eighteenth switch tube Q18 is connected to the third end of the nineteenth switch tube Q19, and is grounded GND through the fourteenth capacitor C14 and the twenty-seventh resistor R27 connected in series. The third end of the eighteenth switch tube Q18 is the output end connected to the single-chip computer U1, specifically connected to the P2B0A8 pin of the single-chip computer U1. Among them, the first magnetic isolation coupler T3 can also be replaced by an optical coupler, but the magnetic isolation coupler has a stronger anti-interference ability than the optical coupler. The seventeenth switch tube Q17 is a MOS tube, with a first end as a gate, a second end as a drain, and a third end as a source. The eighteenth switch tube Q18 and the nineteenth switch tube Q19 are bipolar transistors, with a first end as a base, a second end as a collector, and a third end as an emitter.

[0042] The external enable signal controls the switch S2 to close, introducing a level signal, namely, the second reference power supply voltage VDD, driving the seventeenth switch tube Q17 to turn on, and passing through the first magnetic isolation coupler T3 to couple the input signal 1:1, and then through the eighteenth switch tube Q18 and the nineteenth switch tube Q19, the input signal is converted into high and low level signals that can be obtained by the microcontroller U1, thereby obtaining the enable signal.

[0043] In an embodiment of the present invention, the starting coil control circuit 2 includes: a bridge MOS forward and reverse switching circuit 21 and a reverse electromotive force absorption circuit 22 connected to the single-chip computer U1, the bridge MOS forward and reverse switching circuit 21 is used to receive the control signal of the single-chip computer U1, and control the starting coil L1 to be forward powered, reverse powered, or powered off according to the control signal, and the reverse electromotive force absorption circuit 22 is used to be turned on when the starting coil L1 is powered off, so as to suppress the reverse electromotive force generated by the coil.

[0044] like Figure 7As shown, the bridge MOS forward and reverse switching circuit 21 includes: a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, a fourth switch tube Q4, a fifth switch tube Q5, a sixth switch tube Q6, a seventh switch tube Q7, an eighth switch tube Q8, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7 and an eighth resistor R8. The first end of the first switch tube Q1 and the first end of the second switch tube Q2 are connected to the power supply circuit 1 through the first resistor R1, the first end of the third switch tube Q3 and the first end of the fourth switch tube Q4 are connected to the power supply circuit 1 through the second resistor R2, one end of the start coil L1 is connected to the second end of the second switch tube Q2 and the second end of the first switch tube Q2, the other end of the start coil L1 is connected to the second end of the third switch tube Q3 and the second end of the fourth switch tube Q4, the third end of the first switch tube Q1 and the third end of the fourth switch tube Q4 are grounded GND, the third end of the second switch tube Q2 and the third end of the third switch tube Q3 are connected to the power supply circuit 1. The first end of the fifth switch tube Q5 is connected to the single-chip computer U1 through the third resistor R3, specifically connected to the P2B6A14 pin of the single-chip computer U1. The second end of the fifth switch tube Q5 is connected to the first end of the sixth switch tube Q6, and is connected to the first reference power supply voltage VDC through the fourth resistor R4. The second end of the sixth switch tube Q6 is connected to the first end of the second switch tube Q2 through the fifth resistor R5. The third end of the fifth switch tube Q5 and the third end of the sixth switch tube Q6 are grounded GND. The first end of the seventh switch tube Q7 is connected to the single-chip computer U1 through the sixth resistor R6, specifically connected to the P2B6A15 pin of the single-chip computer U1. The second end of the seventh switch tube Q7 is connected to the first end of the eighth switch tube Q8, and is connected to the first reference power supply voltage VDC through the seventh resistor R7. The second end of the eighth switch tube Q8 is connected to the first end of the third switch tube Q3 through the eighth resistor R8. The third end of the seventh switch tube Q7 and the third end of the eighth switch tube Q8 are grounded GND. Among them, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3 and the fourth switch tube Q4 are MOS tubes, the first end is the gate, the second end is the drain, and the third end is the source. The fifth switch tube Q5, the sixth switch tube Q6, the seventh switch tube Q7 and the eighth switch tube Q8 are bipolar transistors, the first end is the base, the second end is the collector, and the third end is the emitter. The source of the second switch tube Q2 and the third switch tube Q3 in the bridge MOS forward and reverse switching circuit 21 is specifically connected to the output end of the filter circuit 12.

[0045] The bridge MOS forward and reverse switching circuit 21 can provide forward and reverse coil voltages for the dual-coil starting coil L1 in the DC contactor, and the state of the bridge MOS forward and reverse switching circuit 21 is controlled by the single-chip microcomputer U1. When it is necessary to apply a current from left to right to the starting coil l1, the single-chip microcomputer U1 is required to control the second switch tube Q2 and the fourth switch tube Q4 to be turned on, and the first switch tube Q1 and the third switch tube Q3 are controlled to be turned off. When it is necessary to apply a current from right to left to the starting coil L1, the single-chip microcomputer U1 is required to control the first switch tube Q1 and the third switch tube Q3 to be turned on, and the second switch tube Q2 and the fourth switch tube Q4 are controlled to be turned off. The single-chip microcomputer U1 can realize that the starting coil L1 generates electromagnetic forces in two different opposite directions by controlling the output signals of the first switch tube Q1, the second switch tube Q2, the third switch tube Q3 and the fourth switch tube Q4.

[0046] Continue to see Figure 7 The reverse electromotive force absorption circuit 22 includes: a ninth switch tube Q9, a tenth switch tube Q10, a first diode D1, a second diode D2, a ninth resistor R9 and a tenth resistor R10. The first end of the ninth switch tube Q9 is connected to the single-chip computer U1 through the ninth resistor R9, and is specifically connected to the P2B6A12 pin of the single-chip computer U1. The first end of the tenth switch tube Q10 is connected to the single-chip computer U1 through the tenth resistor R10, and is specifically connected to the P2B6A13 pin of the single-chip computer U1. The cathode of the first diode D1 and the second end of the tenth switch tube Q10 are connected to one end of the starting coil L1, the third end of the tenth switch tube Q10 is connected to the anode of the second diode D2, the cathode of the second diode D2 and the second end of the ninth switch tube Q9 are connected to the other end of the starting coil L1, and the third end of the ninth switch tube Q9 is connected to the anode of the first diode D1. The ninth switch tube Q9 and the tenth switch tube Q10 are bipolar transistors, with a first end being a base, a second end being a collector, and a third end being an emitter.

[0047] The single-chip computer U1 drives the transistor to control the reverse electromotive force absorption circuit 22 to be connected in parallel at both ends of the starting coil L1, so as to achieve the effect of suppressing the reverse electromotive force generated by the power failure of the starting coil L1. Specifically, when the reverse electromotive force is generated by the power failure of the starting coil L1, the single-chip computer U1 selects to connect the first diode D1 or the second diode D2 by controlling the ninth switch tube Q9 or the tenth switch tube Q10 before the power failure of the starting coil L1 according to the direction of opening of each MOS tube in the bridge MOS forward and reverse switching circuit 21, and connects the first gas discharge tube GDT1, the varistor R18, and the first transient voltage suppression diode TVS1 in the lightning protection surge suppression circuit 11 in parallel at both ends of the starting coil L1 to suppress the reverse electromotive force generated by the starting coil L1.

[0048] In the embodiment of the present invention, Figure 8 As shown, the holding coil control circuit 3 includes: an eleventh switch tube Q11, an eleventh resistor R11, a twelfth resistor R12, a first relay X1, a third diode D3 and a voltage division control circuit 31. The first end of the first relay X1 is connected to the second reference power supply voltage VDC through the eleventh resistor R11, the second end of the first relay X1 is connected to the single-chip computer U1, the third end of the first relay X1 is connected to the first end of the eleventh switch tube Q11, the fourth end of the first relay X1 is connected to the first reference power supply voltage VDC through the twelfth resistor R12, the second end of the eleventh switch tube Q11 is connected to the power supply circuit 1, the third end of the eleventh switch tube Q11 is connected to the voltage division control circuit 31 and the cathode of the third diode D3, the anode of the third diode D3 is grounded GND, and the voltage division control circuit 31 is connected between the single-chip computer U1 and the holding coil L2.

[0049] Continue to see Figure 8 , the voltage division control circuit 31 includes: the 20th switch tube Q20-26th switch tube Q26, the 28th resistor R28-56th resistor R56, and the third relay X3-9th relay X9. The 20th switch tube Q20-26th switch tube Q2 is a bipolar transistor, the input end of the third relay X3-9th relay X9 is connected to the single chip U1, and the output end is respectively connected to the base of the 20th switch tube Q20-26th switch tube Q26. The 49th resistor R49-56th resistor R56 are connected in series in sequence and are respectively connected between the collector and emitter of the 20th switch tube Q20-26th switch tube Q26. The end of the 49th resistor R49 away from the 50th resistor R50 is connected to the source of the 11th switch tube Q11, and the end of the 56th resistor R56 away from the 55th resistor R55 is grounded GND. Among the 20th switch tube Q20-26th switch tube Q26, the emitter of the previous switch tube is connected to the collector of the next switch tube.

[0050] When the voltage divider control circuit 31 keeps the coil L2 in the double coil working, it can reduce the power consumption of the coil; by detecting the voltage and current of the loop where the coil is located, after AD sampling and calculation processing by the single chip U1, the voltage divider control circuit 31 is controlled to dynamically adjust the holding voltage of the holding coil L1, so that the holding coil L1 is in a low power consumption state. The specific principle is:

[0051] First, the MOS tube Q11 controls whether to connect to the holding coil L2. Under the premise of ignoring the internal resistance of Q20~Q26, it is assumed that R49 is 10Ω, and R50~R56 are 1Ω, 2Ω, 3Ω, 5Ω, 10Ω, 30Ω, and 50Ω respectively. If Q20~Q26 are all turned off, the voltage division ratio is about 101Ω / 111Ω=91%; if Q20~Q26 are all turned on, the voltage division ratio is about 0 / 10Ω=0%. The single-chip computer U1 controls the number of transistors Q20~Q26 that are turned on and off, realizes the resistance value of R50~R56, realizes the adjustment of the 0-91% voltage division of the holding coil L2, and can realize the low-power operation of the holding coil L2. When the MOS tube Q11 is turned off, the third diode D3 acts as a freewheeling diode to conduct the reverse electromotive force. Because the driving voltage of the single-chip microcomputer U1 is relatively low, the driving of the MOS tube Q11 and the transistors Q20-Q26 is performed by the optocoupler X1, X3-X9 driving circuit, and the driving control signal is given by the single-chip microcomputer U1. The single-chip microcomputer U1 provides the voltage and current detected by the detection circuit 4, and adjusts the voltage across the holding coil 2 by controlling the on / off state of the transistors Q20-Q26, so that the holding coil L2 works in a low power consumption state.

[0052] Continue to see Figure 1 The detection circuit 4 includes: a current monitoring circuit 41, a voltage monitoring circuit 42 and a first magnetic isolation coupling circuit 43 connected to the single chip microcomputer U1. One end of the first magnetic isolation coupling circuit 43 is connected to the contact S1 of the DC contactor, and the other end is connected to the single chip microcomputer U1, and is used to detect the state of the contact S1 of the DC contactor. Fig. 9 As shown, the current monitoring circuit 41 includes a thirteenth resistor R13, and the voltage monitoring circuit 42 includes a fourteenth resistor R14 and a fifteenth resistor R15. One end of the thirteenth resistor R13 is connected to the single-chip microcomputer U1 and the holding coil L2, and the other end of the thirteenth resistor R13 is grounded GND; one end of the fourteenth resistor R14 is connected to the input power supply voltage VCC, and the other end is connected to the single-chip microcomputer U1, and is grounded GND through the fifteenth resistor R15. The thirteenth resistor R13 is a current sampling resistor, and the fifteenth resistor R15 is a voltage sampling resistor. The current detection circuit 41 samples the current through the current sampling resistor R13, and the sampled current is transmitted to the port of the single-chip microcomputer U1. The single-chip microcomputer U1 monitors the voltage of the sampling circuit R13, calculates the current in the holding coil L2, and determines whether it exceeds the overcurrent threshold. The voltage monitoring circuit 42 samples the voltage through the voltage sampling resistor, and monitors the fluctuation of the input power supply voltage VCC according to the sampled voltage. The input power supply voltage VCC is calculated according to the resistance value of the voltage divider of the fourteenth resistor R14 and the fifteenth resistor R15, and it is determined that the input power supply voltage VCC exceeds the overvoltage threshold.

[0053] The first magnetic isolation coupling circuit 43 is used to transmit the state feedback signal of the contact S1 to the single-chip microcomputer U1. At the same time, through the first magnetic isolation coupling circuit 43, the interference signal on the line can be isolated to prevent the single-chip microcomputer U1 from being interfered. Fig.10 As shown, the first magnetic isolation coupling circuit 43 includes: a contact S1, a third transient voltage suppression diode TVS3, a twenty-seventh switch tube Q27, a fifty-seventh resistor R57, a tenth diode D10, a fifty-eighth resistor R58, a fifteenth capacitor C15, an eleventh diode D11, a second magnetic isolation coupler T4, a twelfth diode D12, a thirteenth diode D13, a twenty-eighth switch tube Q28, a fifty-ninth resistor R59, a twenty-ninth switch tube Q29, a sixteenth capacitor C16 and a sixtieth resistor R60. One end of the contact S1 is connected to the second reference power supply voltage VDD, and the other end is connected to the first end of the second magnetic isolation coupler T4 and the cathode of the tenth diode D10, and the anode of the tenth diode D10 is connected to the first end of the twenty-seventh switch tube Q27. The other end of the contact S1 is also connected to the first end of the twenty-seventh switch tube Q27 through the fifty-seventh resistor R57, connected to the cathode of the eleventh diode D11 through the fifty-eighth resistor R58 and the fifteenth capacitor C15 connected in parallel, and grounded to GND through the third transient voltage suppression diode TVS3. The second end of the twenty-seventh switch tube Q27 is connected to the anode of the eleventh diode D11 and the second end of the second magnetic isolation coupler T4. The third end of the second magnetic isolation coupler T4 is connected to the anode of the twelfth diode D12 and the anode of the thirteenth diode D13, and connected to the first end of the twenty-ninth switch tube Q29 through the fifty-ninth resistor R59, and the second end of the twenty-ninth switch tube Q29 is grounded to GND. The cathode of the thirteenth diode D13 is connected to the first end of the twenty-eighth switch tube Q28, the cathode of the twelfth diode D12 is connected to the second end of the twenty-eighth switch tube Q28, the third end of the twenty-eighth switch tube Q28 is connected to the third end of the twenty-ninth switch tube Q29, and grounded to GND through the sixteenth capacitor C16 and the sixtieth resistor R60 connected in series. The third end of the twenty-eighth switch tube Q28 is the output end connected to the single-chip computer U1, specifically connected to the P2B1A9 pin of the single-chip computer U1. Among them, the second magnetic isolation coupler T4 can also be replaced by an optical coupler, but the magnetic isolation coupler has a stronger anti-interference ability than the optical coupler. The twenty-seventh switch tube Q27 is a MOS tube, the first end is the gate, the second end is the drain, and the third end is the source. The twenty-eighth switch tube Q28 and the twenty-ninth switch tube Q29 are bipolar transistors, the first end is the base, the second end is the collector, and the third end is the emitter.

[0054] When the contact S1 of the DC contactor is closed, the state feedback signal of the contact S1 drives the twenty-seventh switch tube Q27 to conduct, and the input signal is coupled 1:1 through the second magnetic isolation coupler T4, and then the input signal is converted into high and low level signals that can be obtained by the single-chip computer U1 through the twenty-eighth switch tube Q28 and the twenty-ninth switch tube Q29, so as to obtain the auxiliary contact feedback signal. The second magnetic isolation coupler T4 can also be replaced by an optical coupler, but the magnetic isolation couple has a stronger anti-interference ability than the optical coupler.

[0055] The DC contactor coil reverse electromotive force suppression circuit also includes: an overvoltage and overcurrent protection circuit 5 connected to the power supply circuit 1, the holding coil control circuit 3 and the single-chip computer U1. The overvoltage and overcurrent protection circuit 5 is used to receive the overcurrent or overvoltage protection drive signal output by the single-chip computer U1, and disconnect the path between the power supply circuit 1 and the holding coil control circuit 3 according to the protection drive signal.

[0056] Continue to see Fig. 9 The overvoltage and overcurrent protection circuit 5 includes a second relay X2, a fourth diode D4, a sixteenth resistor R16, a seventeenth resistor R17 and a twelfth switch tube Q12. The first end of the twelfth switch tube Q12 is connected to the single-chip computer U1 through the sixteenth resistor R16, and is also connected to the second reference power supply voltage VDD through the seventeenth resistor R17. The second end of the twelfth switch tube Q12 is connected to the anode of the fourth diode D4 and the first end of the second relay X2. The third end of the twelfth switch tube Q12 is grounded GND; the second end of the second relay X2 is connected to the cathode of the fourth diode D4 and is connected to the second reference power supply voltage VDD. The third end of the second relay X2 is connected to the power supply circuit 1, specifically to the output end of the filter circuit 12 in the power supply circuit 1. The fourth end of the second relay X2 is connected to the holding coil control circuit 3, specifically to the drain of the switch tube Q11 in the holding coil control circuit 3.

[0057] The overvoltage and overcurrent protection circuit drives the normally closed relay X2 through the transistor Q12 according to the overcurrent or overvoltage protection drive signal output by the microcontroller U1. When abnormal conditions such as overvoltage or overcurrent are detected in the circuit, the circuit where the holding coil L2 is located is disconnected in time, and the power supply is cut off to prevent the holding coil L2 from burning out.

[0058] In the embodiment of the present invention, when the DC contactor is closed, the winding of the start coil L1 is energized first, and after the DC relay contacts are energized and connected, the winding of the holding coil L2 is energized, and at the same time, the winding of the start coil L1 is de-energized, and the reverse electromotive force of the start coil L1 is suppressed by the TVS1 tube, the diode D1, the transistor Q9 or the TVS1, the diode D2, and the transistor Q10. When the DC contactor is working normally, the winding of the holding coil L2 is continuously energized, and the real-time power and the set holding power are calculated by monitoring the change of the power supply voltage and the current of the holding coil L2. The single-chip computer U1 adjusts the voltage at both ends of the holding coil L2 by driving the on-off state of the transistors Q20~Q26 through the optical coupler, and realizes the constant power of the holding coil L2 by driving the pulse width duty cycle of Q11. When the DC contactor is opened, the winding of the holding coil L2 is de-energized and the reverse electromotive force is conducted through the freewheeling diode D3, and the current and electromagnetic force change process of the holding coil L2 is measured. At this time, the winding of the starting coil L1 is driven in reverse to control the coil current process so that its electromagnetic force is equal to the winding of the holding coil L2 in magnitude and opposite in direction until the DC contactor is opened.

[0059] In summary, the embodiment of the present invention processes the input DC power supply through the power supply circuit, and outputs the input power supply voltage, the first reference power supply voltage and the second reference power supply voltage; the starting coil control circuit is used to control the starting or power failure of the starting coil in the DC contactor; the holding coil control circuit is used to control the starting or power failure of the holding coil in the DC contactor; the detection circuit is used to detect the voltage, current and contact state of the DC contactor in the reverse electromotive force suppression circuit of the DC contactor coil; the single-chip microcomputer is used to control the operation of the starting coil control circuit and the holding coil control circuit according to the detection result of the detection circuit, and controls the starting coil to start in reverse when the holding coil loses power to suppress the reverse electromotive force of the holding coil until the contacts of the DC contactor are successfully released, and can offset the electromagnetic force generated by the residual current of the holding coil when the freewheeling diode is turned on by reusing the starting coil at the moment of opening, so as to make the opening more reliable and shorten the opening time.

[0060] The above specific embodiments of the present invention are described. In some cases, the actions or steps recorded in the embodiments of the present invention can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the process depicted in the accompanying drawings does not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0061] Based on the same concept, an embodiment of the present invention also provides a control method for a DC contactor coil reverse electromotive force suppression circuit. Fig.11 As shown, the control method of the DC contactor coil reverse electromotive force suppression circuit includes:

[0062] Step S11: When the DC contactor is closed, the single-chip microcomputer controls the starting coil of the DC contactor to be energized through the starting coil control circuit, controls the closing of the contacts of the DC contactor, and when the contact closure is detected by the detection circuit, the single-chip microcomputer controls the holding coil of the DC contactor to be energized through the holding coil control circuit, and at the same time controls the starting coil to be de-energized through the starting coil control circuit, and the DC contactor completes the closing.

[0063] Specifically, Fig.12 As shown, including:

[0064] Step 100: Power on and initialize.

[0065] Power on and initialize the DC contactor coil reverse electromotive force suppression circuit.

[0066] Step 101: Enable signal input.

[0067] The external enable switch S2 is closed, and the external input enable signal is transmitted to the single chip microcomputer U1 through the second magnetic isolation coupling circuit 15 .

[0068] Step 102: Monitor the external input voltage.

[0069] The single chip microcomputer U1 monitors the external input voltage through a voltage detection circuit. The external input voltage is the input power supply voltage VCC provided by the DC power supply after being protected from lightning surges and filtered.

[0070] Step 103: Determine whether the voltage is within the working range. If yes, go to step 105, otherwise go to step 104.

[0071] The single chip microcomputer U1 determines whether the input power supply voltage VCC is within the operating range.

[0072] Step 104: Perform overvoltage and undervoltage protection.

[0073] If the input power supply voltage VCC is detected to be overvoltage or undervoltage, the single chip microcomputer U1 controls and starts the overvoltage and overcurrent protection circuit 5 to perform overvoltage and undervoltage protection.

[0074] Step 105: Control the start coil to power on.

[0075] If the input power supply voltage VCC is detected to be within the working range, the single chip microcomputer U1 controls the bridge MOS forward and reverse switching circuit 21 to be turned on, the starting coil L1 is powered on, and the contact S1 of the DC contactor is closed.

[0076] Step 106: Determine whether the contact signal has feedback. If yes, execute step 110, otherwise execute step 107.

[0077] The single chip computer U1 determines whether a state feedback signal indicating that the contact S1 is closed is detected by the first magnetic isolation coupling circuit 43 .

[0078] Step 107: Delay waiting.

[0079] If no status feedback signal indicating that contact S1 is closed is received, the delay waiting continues.

[0080] Step 108: Determine whether the delay is exceeded. If yes, go to step 109, otherwise return to step 106.

[0081] If the delay time is exceeded, go to step 109 , otherwise return to step 106 .

[0082] Step 109: Closing failed.

[0083] If the status feedback signal indicating that the contact S1 is closed is not received within the delay time, it indicates that the closing has failed, and the starting process ends.

[0084] Step 110: Control the coil to be powered on.

[0085] If a state feedback signal indicating that the contact S1 is closed is received, the single chip computer U1 controls the holding coil to be powered on through the holding coil control circuit 3. Specifically, the first relay X1 and the eleventh switch tube Q11 are controlled to be turned on, and the input power supply voltage output by the filter circuit 12 is transmitted to the holding coil L2 to complete the power-on.

[0086] Step 111: Control the starting coil to stop.

[0087] Then, the single chip microcomputer U1 controls the start coil L1 to lose power through the bridge MOS forward and reverse switching circuit 21 .

[0088] Step 112: Perform reverse electromotive force suppression.

[0089] When the starting coil L1 loses power, the single chip microcomputer U1 also controls the reverse electromotive force absorption circuit 22 to be turned on, so as to suppress the reverse electromotive force generated when the starting coil L1 loses power.

[0090] Step 113: Closing is successful.

[0091] After the start coil L1 is de-energized, the DC contactor closes successfully, ending the closing process of the DC contactor.

[0092] The closing of the DC contactor is now completed.

[0093] Step S12: When the DC contactor works normally, the single chip microcomputer controls the power of the holding coil to be constant through the holding coil control circuit according to the detected input power voltage and coil current.

[0094] Specifically, Fig.13 As shown, including:

[0095] Step 200: Start.

[0096] Step 201: Setting to maintain constant power of the coil.

[0097] The single chip microcomputer U1 is provided with a constant power to keep the coil L2 working normally.

[0098] Step 202: Keep the coil powered on.

[0099] The single chip microcomputer U1 controls the holding coil L2 to be powered on through the holding coil control circuit 3.

[0100] Step 203: Monitor the input power supply voltage.

[0101] The microcontroller U1 monitors the input power supply voltage through a voltage detection circuit.

[0102] Step 204: Monitor the coil current.

[0103] The microcontroller U1 monitors the current of the holding coil L2 through a current detection circuit.

[0104] Step 205: Determine whether the holding coil is at constant power. If yes, go to step 206, otherwise go to step 207.

[0105] The single chip microcomputer U1 calculates the power of the holding coil L2 by detecting the voltage and current of the holding coil L2 through the detection circuit 4, and determines whether the power is the set constant power.

[0106] Step 206: No adjustment.

[0107] If the single chip computer U1 determines that the holding coil L2 operates at a constant power, the power of the holding coil L2 is not adjusted.

[0108] Step 207: Adjust the voltage across the coil to maintain constant power.

[0109] If the single-chip computer U1 determines that the holding coil L2 is not working at a constant power, the voltage at both ends of the holding coil is adjusted to maintain the constant power. The specific adjustment process is: the single-chip computer U1 provides the voltage and current detected by the detection circuit 4, and controls the number of transistors Q20-Q26 that are turned on and off to achieve the resistance value of R50-R56, and achieves the adjustment of the 0-91% voltage division of the holding coil L2, thereby controlling the holding coil L2 to work in a low power consumption state with a constant power.

[0110] Step 208: End.

[0111] Step S13: When the DC contactor is opened, the single-chip microcomputer controls the holding coil to lose power through the holding coil control circuit, and controls the starting coil to start in reverse through the starting coil control circuit. The electromagnetic force generated by the starting coil is greater than the electromagnetic force of the holding coil and in the opposite direction, until the detection circuit detects that the contacts of the DC contactor are successfully released.

[0112] Specifically, Fig.14 As shown, including:

[0113] Step 300: Start.

[0114] Step 301: Calculate the electromagnetic force of the holding coil.

[0115] The electromagnetic force of the holding coil is calculated based on the coil current and coil parameters.

[0116] Step 302: Control the holding coil to be de-energized.

[0117] The single chip microcomputer U1 controls the holding coil to lose power through the holding coil control circuit 3. Specifically, the first relay X1 and the eleventh switch tube Q11 are turned off, and the input power supply voltage output by the filter circuit 12 cannot be transmitted to the holding coil L2, and the holding coil L2 loses power.

[0118] The starting coil winding and the holding coil winding are concentrically wound on the same coil frame, and the influence of the leakage flux is ignored, and the magnetic flux passing through the two is assumed to be the same. The holding coil winding is powered off and the reverse electromotive force is conducted through the freewheeling diode D3, and the change process of the coil current and electromagnetic force is measured. Since the reverse electromotive force is conducted by the freewheeling diode, the reverse electromotive force can be ignored during the release process, and the following formula is obtained:

[0119]

[0120] Among them, i1 and i2 are the actual currents of the starting coil and the holding coil respectively, R1 and R2 are the coil resistances, N1 and N2 are the number of coil turns, and Φ is the coil magnetic flux.

[0121] During the release process, the excitation current is 0 and the induced current i i The resulting magnetic potential is:

[0122]

[0123] For electromagnetic systems, the three-dimensional finite element analysis method is used to analyze the magnetic field distribution in the solution domain. The formula is:

[0124]

[0125] Among them, μ r is the relative magnetic permeability of the medium, μ0 is the vacuum magnetic permeability; φ is the scalar magnetic potential, Hj The magnetic field strength provided for the motional electromotive force of the coil and armature movement.

[0126] The corresponding electromagnetic force is:

[0127]

[0128] Among them, B is the magnetic induction intensity, and dx is the virtual displacement of the armature.

[0129] Step 303: Control the starting coil to start in reverse direction to generate an electromagnetic force opposite to the holding coil.

[0130] The single chip microcomputer U1 controls the bridge MOS forward and reverse switching circuit 21 to conduct, and reversely energizes the starting coil L1 to generate an electromagnetic force opposite to the holding coil.

[0131] Step 304: Determine whether the reverse electromagnetic force of the start coil is greater than the electromagnetic force of the hold coil. If yes, go to step 306, otherwise go to step 305.

[0132] Step 305: Adjust the reverse starting power of the starting coil.

[0133] The reverse starting power of the starting coil L1 is adjusted by adjusting the duty cycle of the driving signal pulse width.

[0134] Reverse drive the starting coil winding and control the coil current process so that its electromagnetic force is equal to the holding coil winding in magnitude and opposite in direction. The following formula is established:

[0135]

[0136] Where u is the starting voltage of the coil winding.

[0137]

[0138] Step 306: Monitor the auxiliary feedback status.

[0139] The single chip computer U1 determines whether a state feedback signal indicating that the contact S1 is disconnected is detected by the first magnetic isolation coupling circuit 43 .

[0140] Step 307: Determine whether the feedback contact is released. If yes, go to step 312, otherwise go to step 308.

[0141] The single chip computer U1 detects whether the contact S1 is disconnected through the first magnetic isolation coupling circuit 43, that is, the feedback contact is released.

[0142] Step 308: Delay waiting.

[0143] If the feedback contact is not released, wait for a while.

[0144] Step 309: Determine whether the release has timed out. If yes, go to step 310, otherwise return to step 306.

[0145] Determine whether the contact has timed out and not been released.

[0146] Step 310: Opening failure.

[0147] If the contact does not release after the timeout, it means that the DC contactor has failed to open.

[0148] Step 311: The release is successful and the MCU status is reset.

[0149] If the feedback contact is released, it means that the DC contactor is released successfully and the microcontroller status is reset.

[0150] Step 312: End.

[0151] The embodiment of the present invention monitors the external input voltage through a single-chip microcomputer, can understand the external power supply environment state externally, can make adjustments and execute protection internally through an algorithm, the process is programmable and controlled, and the same hardware can adapt to different contactors, relays and working scenarios; by driving resistors with different proportional resistance values ​​and transistors in series cascade circuits, the graduation value of 1Ω is continuously adjustable, and the voltage of the holding coil is adjusted; by reusing the starting winding to add a reverse voltage at the moment of opening the gate, the reverse electromagnetic force is generated in conjunction with the magnetized armature to offset the electromagnetic force generated by the residual current of the holding coil when the freewheeling diode is turned on, making the opening more reliable.

[0152] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present disclosure is limited to these examples. Based on the concept of the present disclosure, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0153] This application is intended to cover all such substitutions, modifications and variations that fall within the broad scope of all embodiments. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the scope of protection of this disclosure.

Claims

1. A DC contactor coil reverse electromotive force suppression circuit, characterized in that: The DC contactor coil reverse electromotive force suppression circuit comprises: A power supply circuit, used for processing an input DC power supply and outputting an input power supply voltage, a first reference power supply voltage, and a second reference power supply voltage; A starting coil control circuit, connected to the power supply circuit, for controlling the starting or de-energizing of the starting coil in the DC contactor; A holding coil control circuit, connected to the power supply circuit, for controlling the start-up or de-energization of the holding coil in the DC contactor; A detection circuit, connected to the power supply circuit, for detecting the voltage and current in the reverse electromotive force suppression circuit of the DC contactor coil and the contact state of the DC contactor; A single chip microcomputer is connected to the power supply circuit, the starting coil control circuit and the holding coil control circuit, and is used to control the operation of the starting coil control circuit and the holding coil control circuit according to the detection result of the detection circuit, and to control the starting coil to start in reverse when the holding coil loses power to suppress the reverse electromotive force of the holding coil until the contacts of the DC contactor are successfully released.

2. The DC contactor coil reverse electromotive force suppression circuit according to claim 1, characterized in that: The power supply circuit includes: a lightning surge suppression circuit, a filtering circuit, a chopping circuit and a DC / DC voltage stabilizing circuit connected in sequence; the lightning surge suppression circuit and the filtering circuit are respectively used to protect the input DC power supply from lightning surge impact and filter, and output the input power supply voltage, the chopping circuit is used to chop the DC power supply voltage into the first reference power supply voltage, and the DC / DC voltage stabilizing circuit is used to convert the first reference power supply voltage into the second reference power supply voltage.

3. The DC contactor coil reverse electromotive force suppression circuit according to claim 1, characterized in that: The starting coil control circuit includes: a bridge MOS forward and reverse switching circuit and a reverse electromotive force absorption circuit connected to the single-chip microcomputer. The bridge MOS forward and reverse switching circuit is used to receive the control signal of the single-chip microcomputer, and control the starting coil to be powered on forward, powered on reversely, or powered off according to the control signal. The reverse electromotive force absorption circuit is used to be turned on when the starting coil is powered off, so as to suppress the reverse electromotive force generated by the coil.

4. The DC contactor coil reverse electromotive force suppression circuit according to claim 3, characterized in that: The bridge MOS forward and reverse switching circuit includes: a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor and an eighth resistor; a first end of the first switch tube and a first end of the second switch tube are connected to the power supply circuit through the first resistor, a first end of the third switch tube and a first end of the fourth switch tube are connected to the power supply circuit through the second resistor, one end of the starting coil is connected to the second end of the second switch tube and the second end of the first switch tube, the other end of the starting coil is connected to the second end of the third switch tube and the second end of the fourth switch tube, the third end of the first switch tube and the third end of the fourth switch tube are grounded, and the first end of the second switch tube is connected to the first end of the third switch tube. The three ends of the first switching tube and the third end of the third switching tube are connected to the power supply circuit; the first end of the fifth switching tube is connected to the single-chip microcomputer through the third resistor, the second end of the fifth switching tube is connected to the first end of the sixth switching tube, and is connected to the first reference power supply voltage through the fourth resistor, the second end of the sixth switching tube is connected to the first end of the second switching tube through the fifth resistor, and the third end of the fifth switching tube and the third end of the sixth switching tube are grounded; the first end of the seventh switching tube is connected to the single-chip microcomputer through the sixth resistor, the second end of the seventh switching tube is connected to the first end of the eighth switching tube, and is connected to the first reference power supply voltage through the seventh resistor, the second end of the eighth switching tube is connected to the first end of the third switching tube through the eighth resistor, and the third end of the seventh switching tube and the third end of the eighth switching tube are grounded.

5. The DC contactor coil reverse electromotive force suppression circuit according to claim 4, characterized in that: The reverse electromotive force absorption circuit includes: a ninth switch tube, a tenth switch tube, a first diode, a second diode, a ninth resistor and a tenth resistor; the first end of the ninth switch tube is connected to the single-chip microcomputer through the ninth resistor, the first end of the tenth switch tube is connected to the single-chip microcomputer through the tenth resistor, the cathode of the first diode and the second end of the tenth switch tube are connected to one end of the starting coil, the third end of the tenth switch tube is connected to the anode of the second diode, the cathode of the second diode and the second end of the ninth switch tube are connected to the other end of the starting coil, and the third end of the ninth switch tube is connected to the anode of the first diode.

6. The DC contactor coil reverse electromotive force suppression circuit according to claim 1, characterized in that: The holding coil control circuit includes: an eleventh switch tube, an eleventh resistor, a twelfth resistor, a first relay, a third diode and a voltage divider control circuit; the first end of the first relay is connected to the second reference power supply voltage through the eleventh resistor, the second end of the first relay is connected to the single-chip microcomputer, the third end of the first relay is connected to the first end of the eleventh switch tube, the fourth end of the first relay is connected to the first reference power supply voltage through the twelfth resistor, the second end of the eleventh switch tube is connected to the power supply circuit, the third end of the eleventh switch tube is connected to the voltage divider control circuit and the cathode of the third diode, the anode of the third diode is grounded, and the voltage divider control circuit is connected between the single-chip microcomputer and the holding coil.

7. The DC contactor coil reverse electromotive force suppression circuit according to claim 1, characterized in that: The detection circuit includes: a current monitoring circuit, a voltage monitoring circuit and a first magnetic isolation coupling circuit connected to the single-chip microcomputer; one end of the first magnetic isolation coupling circuit is connected to the contacts of the DC contactor, and the other end is connected to the single-chip microcomputer, for detecting the state of the contacts of the DC contactor; the current monitoring circuit includes a thirteenth resistor, and the voltage monitoring circuit includes a fourteenth resistor and a fifteenth resistor, one end of the thirteenth resistor is connected to the single-chip microcomputer and the holding coil, and the other end of the thirteenth resistor is grounded; one end of the fourteenth resistor is connected to the input power supply voltage, and the other end is connected to the single-chip microcomputer, and is grounded through the fifteenth resistor.

8. The DC contactor coil reverse electromotive force suppression circuit according to claim 1, characterized in that: The DC contactor coil reverse electromotive force suppression circuit also includes: an overvoltage and overcurrent protection circuit connected to the power supply circuit, the holding coil control circuit and the single-chip microcomputer; the overvoltage and overcurrent protection circuit is used to receive the overcurrent or overvoltage protection drive signal output by the single-chip microcomputer, and disconnect the path between the power supply circuit and the holding coil control circuit according to the protection drive signal.

9. The DC contactor coil reverse electromotive force suppression circuit according to claim 8, characterized in that: The overvoltage and overcurrent protection circuit includes a second relay, a fourth diode, a sixteenth resistor, a seventeenth resistor and a twelfth switch tube; the first end of the twelfth switch tube is connected to the single-chip microcomputer through the sixteenth resistor, and is also connected to the second reference power supply voltage through the seventeenth resistor, the second end of the twelfth switch tube is connected to the anode of the fourth diode and the first end of the second relay, and the third end of the twelfth switch tube is grounded; the second end of the second relay is connected to the cathode of the fourth diode and is connected to the second reference power supply voltage, the third end of the second relay is connected to the power supply circuit, and the fourth end of the second relay is connected to the holding coil control circuit.

10. A control method for a DC contactor coil reverse electromotive force suppression circuit according to any one of claims 1 to 9, characterized in that: The method comprises: When the DC contactor is closed, the single-chip microcomputer controls the starting coil of the DC contactor to be energized through the starting coil control circuit, controls the contact of the DC contactor to be closed, and when the contact closure is detected by the detection circuit, the single-chip microcomputer controls the holding coil of the DC contactor to be energized through the holding coil control circuit, and controls the starting coil to be de-energized through the starting coil control circuit, and the DC contactor completes the closing; When the DC contactor works normally, the single chip microcomputer controls the power of the holding coil to be constant through the holding coil control circuit according to the detected input power supply voltage and coil current; When the DC contactor is opened, the single chip microcomputer controls the holding coil to lose power through the holding coil control circuit, and controls the starting coil to start in reverse through the starting coil control circuit. The electromagnetic force generated by the starting coil is greater than the electromagnetic force of the holding coil and in the opposite direction, until the detection circuit detects that the contacts of the DC contactor are successfully released.

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