Contactor control circuit and contactor coil voltage control method

Abstract

The contactor control circuit and contactor coil voltage control method of the present invention are as follows: the voltage acquisition circuit of the contactor control circuit is connected with the power supply circuit to acquire the current power supply voltage of the power supply circuit; the input end of the control circuit is connected with the output end of the voltage acquisition circuit; the control circuit adjusts the duty cycle to output a control signal according to the current power supply voltage; the input end of the drive circuit is connected with the output end of the control circuit; the output end of the drive circuit is connected with the switch element; the drive circuit receives the control signal sent by the control circuit to control the on and off of the switch element; the switch element is connected with the coil, and the on and off of the switch element controls the presence or absence of voltage at both ends of the coil. The contactor coil voltage control method adjusts the duty cycle to output a control signal according to the current power supply voltage and the current temperature of the coil to control the voltage at both ends of the control coil; the contactor control circuit of the present invention has safe and stable performance, simple and compact structure, and low cost.

Description

Technical Field

[0001] The invention relates to the field of low-voltage electrical appliances, and in particular to a contactor control circuit and a coil voltage control method. Background Art

[0002] After the traditional contactor is energized by the coil, the lower iron core generates magnetic force to make the upper iron core overcome the elastic force of the reset spring to operate, and the upper iron core drives the moving contact to move and contact the static contact. AC contactor is a low-voltage electrical appliance that is frequently operated and has a wide range of uses. There are many control coil voltage specifications, including both AC control and DC control.

[0003] At present, different coils need to be configured for the same shell product, and they need to be matched with the corresponding voltage when used. The on-site use is cumbersome, and the coil maintenance power consumption is relatively high. With the development of automation technology, some current-type control methods for AC contactor coils have emerged, but most of them are modified from power chips, the coil working voltage range is not wide enough, and the circuit design is complicated. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a contactor control circuit and a contactor coil voltage control method which have safe and stable performance, simple and compact structure and low cost.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A contactor control circuit comprises a power supply circuit, a voltage acquisition circuit, a control circuit, a drive circuit, a switch element and a coil;

[0007] The input end of the power supply circuit is connected to an external power supply for obtaining power, and the output end of the power supply circuit is connected to a voltage collection circuit, a control circuit, a switch element and a coil to supply power to the voltage collection circuit, the control circuit, the switch element and the coil;

[0008] The input end of the voltage acquisition circuit is connected to the power supply circuit to acquire the current power supply voltage of the power supply circuit, and the input end of the control circuit is connected to the output end of the voltage acquisition circuit.

[0009] The control circuit adjusts the duty cycle according to the current power supply voltage to output a control signal, the input end of the drive circuit is connected to the output end of the control circuit, the output end of the drive circuit is connected to the switch element, and the drive circuit receives the control signal from the control circuit to control the on and off of the switch element;

[0010] The switch element is connected to the coil, and the on-off of the switch element controls the presence or absence of voltage at both ends of the coil.

[0011] Preferably, it also includes a temperature acquisition circuit, the input end of the temperature acquisition circuit is connected to the coil to obtain the temperature of the coil, the output end of the temperature acquisition circuit is connected to the control circuit to send the acquired temperature signal of the coil to the control circuit; the control circuit adjusts the duty cycle to output a control signal according to the current power supply voltage and the current temperature of the coil.

[0012] Preferably, it also includes an EMI circuit, which is connected in parallel to one side of the input end of the power supply circuit; the EMI circuit includes an inductor L1, a varistor RV1, a capacitor C2 and a capacitor C1, and the capacitor C1 and the capacitor C2 are connected in parallel at both ends of the inductor L1, the capacitor C1 is close to one side of the power supply circuit, the capacitor C2 is close to one side of the external power supply, and the varistor RV1 is connected in parallel to one side of the capacitor C2 close to the external power supply.

[0013] Preferably, the power supply circuit includes a rectifier circuit and a step-down voltage stabilizing circuit; the input end of the rectifier circuit is connected to an external power supply, and the output end of the rectifier circuit is connected to the step-down voltage stabilizing circuit; the rectifier circuit is a full-wave rectifier bridge BR1; the step-down voltage stabilizing circuit includes a resistor R1, a resistor R2, a transistor Q1, a resistor R7, a resistor R8, a transistor Q2, a resistor R11, a resistor R14, a transistor Q3, a voltage stabilizing tube D1, a capacitor C3, a capacitor C8, a transient suppression diode TVS2, a capacitor C9, a capacitor C14, a voltage stabilizing chip VOT1, and a capacitor C15; the capacitor C3 is connected in parallel to the output end of the rectifier circuit, one end of the resistor R1 and the resistor R2 are connected to the negative electrode of the output end of the rectifier circuit, the resistor R1, the resistor R7, the resistor R11 and the voltage stabilizing tube D1 are connected in series in sequence, and one end of the voltage stabilizing tube D1 is connected to the positive electrode of the output end of the rectifier circuit. After the resistor R2, transistor Q1, resistor R8, transistor Q2, resistor R14, transistor Q3 and capacitor C8 are connected in series in sequence, one end of the capacitor C8 is connected to the positive electrode of the output end of the rectifier circuit, the base of the transistor Q1 is connected to the middle node of the resistor R1 and the resistor R7, the base of the transistor Q2 is connected to the middle node of the resistor R7 and the resistor R11, the base of the transistor Q3 is connected to the middle node of the resistor R11 and the voltage regulator D1, the transient suppression diode TVS2 and the capacitor C9 are connected in parallel to one end of the capacitor C8 in sequence; one end of the capacitor C9 is grounded, and the other end is connected to the capacitor C14 and the voltage regulator chip VOT1, the output pin of the voltage regulator chip is connected to the capacitor C15, and the other pins of the capacitor C14, the voltage regulator chip VOT1 and the capacitor C15 are grounded; wherein the capacitor C9 also provides power to the drive circuit; the voltage regulator chip VOT1 supplies power to the control circuit.

[0014] Preferably, the voltage acquisition circuit includes resistor R3, resistor R4, resistor R5, resistor R9, resistor R12, capacitor C4, and transient suppression diode TVS1; in the voltage acquisition circuit, resistor R3 is connected to the power supply circuit, and the other end is connected in series with resistor R4, resistor R4 is connected in series with resistor R5, resistor R5 is connected in series with resistor R9, resistor R9 is connected in series with resistor R12, resistor R12 and capacitor C4, transient suppression diode TVS1 are connected in parallel, resistor R12 and capacitor C4, transient suppression diode TVS1 are grounded at the other end; the node between resistor R9 and resistor R12 provides a signal to the control circuit.

[0015] Preferably, the control circuit includes a control chip U1, capacitors C6 and C7, resistors R15 and capacitors C10; the third pin of the control chip U1 is connected to the output end of the voltage acquisition circuit, the eighth pin of the control chip U1 and the nineteenth pin of the control chip U1 are grounded, one end of the capacitors C6 and C7 connected in parallel is connected to the twentieth pin of the control chip U1, the other end is grounded, and the middle node of the resistor R15 and capacitor C10 is connected to the first pin of the control chip U1. Preferably, the control circuit includes a control chip U1, capacitors C6 and C7; the third pin of the control chip U1 is connected to the output end of the voltage acquisition circuit, the eighth pin of the control chip U1 and the nineteenth pin of the control chip U1 are grounded, one end of the capacitors C6 and C7 connected in parallel is connected to the twentieth pin of the control chip U1, the other end is grounded, the seventh pin of the control chip U1 is connected to the output end of the temperature acquisition circuit, and the middle node of the resistor R15 and capacitor C10 is connected to the first pin of the control chip U1.

[0016] Preferably, the temperature acquisition circuit includes a thermistor R6, a resistor R10, a resistor R13 and a capacitor C5, one end of the thermistor R6, the resistor R10 and the resistor R13 being connected in series is connected to a constant power supply, and the other end is grounded, the capacitor C5 is connected in parallel to both ends of the resistor R13, the thermistor R6 is installed close to the coil, and the connecting line between the resistor R10 and the resistor R13 is connected to the control circuit.

[0017] Preferably, the driving circuit includes a driving chip U2, a capacitor C12, a capacitor C11, a resistor R17, a resistor R18, a capacitor C13, a resistor R16 and a diode D2; the input end of the driving chip U2 is connected to the control circuit, the power supply end of the driving chip U2 is connected to one end of the capacitor C12 and the capacitor C11 in parallel, the other end of the capacitor C12 and the capacitor C11 in parallel is grounded, the ground end of the driving chip U2 is grounded, the output end of the driving chip U2 is connected to one end of the resistor R17, the other end of the resistor R17 is connected to the switching element and one end of the resistor R18, the other end of the resistor R18 is connected to the positive electrode of the diode D2 after passing through the capacitor C13 and the resistor R16, the coil is connected in parallel to the two ends of the diode D2, and the positive electrode of the diode D2 is connected to the switching element.

[0018] The present invention also provides a contactor coil voltage control method, the method comprising:

[0019] Get the current input power supply voltage;

[0020] Obtain the current coil temperature, and according to the corresponding relationship between the coil temperature and the coil resistance, obtain the current coil resistance based on the current coil temperature;

[0021] When holding, the coil holding voltage is obtained based on the coil resistance * the coil current during holding, and the current holding duty cycle is obtained based on the current power supply voltage and the coil holding voltage. According to the holding duty cycle, the voltage across the coil of the contactor is adjusted to keep the contactor in a reliable holding state.

[0022] Preferably, during startup, the coil starting voltage is obtained based on the coil resistance * the coil current during startup, and the current starting duty cycle is obtained based on the current power supply voltage and the coil starting voltage. According to the starting duty cycle, the voltage across the coil of the contactor is adjusted to activate the contactor.

[0023] Preferably, the coil temperature is obtained through a thermistor in close contact with the coil.

[0024] The contactor control circuit of the present invention comprises a power supply circuit, a voltage acquisition circuit, a control circuit, a drive circuit, a switch element and a coil; the control circuit receives the current power supply voltage acquired by the voltage acquisition circuit, and adjusts the duty cycle according to the current voltage signal to output a control signal; the control circuit calculates the value of the duty cycle by acquiring the current voltage, and drives the switch element to change the voltage of the coil of the contactor, so as to realize the start and maintenance of the coil, so as to achieve that the voltage at both ends of the coil is basically constant under different voltages, thereby making the average value of the voltage at both ends of the coil stable, the working voltage range of the coil is relatively wide, the circuit structure is simple and compact, the power consumption of the coil is low, and the cost is low.

[0025] Furthermore, the contactor control circuit of the present invention also includes a temperature acquisition circuit for acquiring the temperature of the coil. The control circuit receives the current power supply voltage acquired by the voltage acquisition circuit and the current temperature of the coil acquired by the temperature acquisition circuit. The control circuit adjusts the duty cycle to output a control signal based on the current power supply voltage signal and the current temperature of the coil, drives the switching element to change the voltage of the coil of the contactor, realizes the start and maintenance of the coil, and achieves a basically constant voltage at both ends of the coil, thereby stabilizing the average voltage at both ends of the coil. The control circuit adjusts the duty cycle to output a control signal based on the current power supply voltage signal and the current temperature of the coil. The performance of the contactor control circuit is more stable and reliable, the coil operating voltage range is wider, the circuit structure is simple and compact, the coil power consumption is low, and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural block diagram of an embodiment of the contactor control circuit of the present invention;

[0027] Figure 2 is a structural block diagram of another embodiment of the contactor control circuit of the present invention;

[0028] Figure 3 It is a partial circuit diagram of the power supply circuit of the present invention;

[0029] Figure 4 It is a specific circuit diagram of the voltage acquisition circuit of the present invention;

[0030] Figure 5 is a circuit diagram of a control circuit of an embodiment of the present invention;

[0031] Figure 6 is a circuit diagram of a control circuit of another embodiment of the present invention;

[0032] Figure 7 is a circuit diagram of a driving circuit of the present invention;

[0033] Figure 8 It is a partial circuit diagram of the voltage step-down and voltage stabilizing circuit of the present invention;

[0034] Fig. 9 It is a partial circuit diagram of the voltage step-down and voltage stabilizing circuit of the present invention. DETAILED DESCRIPTION

[0035] The following is combined with Figures 1 to 9 The given embodiments further illustrate the specific implementation of the contactor control circuit and the contactor coil voltage control method of the present invention. The contactor control circuit and the contactor coil voltage control method of the present invention are not limited to the description of the following embodiments.

[0036] like Figure 1As shown, the contactor control circuit of the present invention includes a power supply circuit, a voltage collection circuit, a control circuit, a drive circuit, a switch element and a coil; the input end of the power supply circuit is connected to an external power supply for obtaining power, and the output end of the power supply circuit is connected to the voltage collection circuit, the control circuit, the switch element and the coil to supply power to the voltage collection circuit, the control circuit, the switch element and the coil; the input end of the voltage collection circuit is connected to the power supply circuit for collecting the current power supply voltage signal of the power supply circuit, the input end of the control circuit is connected to the output end of the voltage collection circuit, and the control circuit receives the current power supply voltage signal collected by the voltage collection circuit; the control circuit adjusts the duty cycle according to the current voltage signal to output a control signal, the input end of the drive circuit is connected to the output end of the control circuit, the output end of the drive circuit is connected to the switch element, the drive circuit receives the control signal sent by the control circuit, and controls the conduction and closing of the switch element; the switch element is connected to the coil, and the on-off control of the switch element controls the presence or absence of voltage at both ends of the coil.

[0037] The contactor control circuit of the present invention comprises a power supply circuit, a voltage acquisition circuit, a control circuit, a drive circuit, a switch element and a coil; the control circuit receives the current power supply voltage acquired by the voltage acquisition circuit, and adjusts the duty cycle according to the current power supply voltage to output a control signal, drives the switch element to change the voltage of the coil of the contactor, realizes the start and maintenance of the coil, and achieves that the voltage at both ends of the coil is basically constant under different power supply voltages, thereby making the average value of the voltage at both ends of the coil stable, the working voltage range of the coil is wide, the circuit structure is simple and compact, the coil power consumption is low, and the cost is low.

[0038] like Figure 3 As shown, the contactor control circuit of the present invention also includes an EMI circuit. The EMI circuit is connected in parallel to one side of the input end of the power supply circuit; the EMI circuit includes an inductor L1, a varistor RV1, a capacitor C2 and a capacitor C1, and the capacitor C1 and the capacitor C2 are connected in parallel at both ends of the inductor L1, the capacitor C1 is close to one side of the power supply circuit, the capacitor C2 is close to one side of the external power supply, and the varistor RV1 is connected in parallel to one side of the capacitor C2 close to the external power supply. The EMI circuit can filter out the interference of high-frequency pulses of the external power grid on the power supply, and at the same time reduce the electromagnetic interference of the switching power supply itself to the outside world.

[0039] like Figure 3 , 8As shown in Figures 9 and 10, the power supply circuit of the present invention includes a rectifier circuit and a step-down voltage stabilizing circuit; the input end of the rectifier circuit is connected to an external power supply, and the output end of the rectifier circuit is connected to the step-down voltage stabilizing circuit; the rectifier circuit is a full-wave rectifier bridge BR1; the step-down voltage stabilizing circuit includes a resistor R1, a resistor R2, a transistor Q1, a resistor R7, a resistor R9, a transistor Q2, a resistor R11, a resistor R14, a transistor Q3, a voltage stabilizing tube D1, a capacitor C3, a capacitor C8, a transient suppression diode TVS2, a capacitor C9, a capacitor C14, a voltage stabilizing chip VOT1, and a capacitor C15; the capacitor C3 is connected in parallel to the output end of the rectifier circuit, one end of the resistor R1 and the resistor R2 are connected to the negative electrode of the output end of the rectifier circuit, the resistor R1, the resistor R7, the resistor R11 and the voltage stabilizing tube D1 are connected in series in sequence, one end of the voltage stabilizing tube D1 is connected to the positive electrode of the output end of the rectifier circuit, the resistor R2 After Q1, transistor Q1, resistor R8, transistor Q2, resistor R14, transistor Q3, and capacitor C8 are connected in series in sequence, one end of capacitor C8 is connected to the positive electrode of the output end of the rectifier circuit, the base of transistor Q1 is connected to the middle node of resistor R1 and resistor R7, the base of transistor Q2 is connected to the middle node of resistor R7 and resistor R11, the base of transistor Q3 is connected to the middle node of resistor R11 and voltage regulator D1, transient suppression diode TVS2 and capacitor C9 are connected in parallel to one end of capacitor C8 in sequence; one end of capacitor C9 is grounded, and the other end is connected to capacitor C14 and voltage regulator chip VOT1, the output pin of the voltage regulator chip is connected to capacitor C15, and the other pins of capacitor C14, voltage regulator chip VOT1 and capacitor C15 are grounded; capacitor C9 also provides power to the drive circuit; voltage regulator chip VOT1 provides power to the control circuit. The power supply circuit adopts a step-down voltage stabilizing circuit composed of a resistor, a triode and a diode, and can also be a DC-DC step-down circuit or an LDO step-down circuit.

[0040] like Figure 4 As shown, the voltage acquisition circuit of the present invention includes a resistor R3 in the voltage acquisition circuit connected to the power supply circuit, the other end of which is connected in series with a resistor R4, the resistor R4 is connected in series with a resistor R5, the resistor R5 is connected in series with a resistor R9, the resistor R9 is connected in series with a resistor R12, the resistor R12 is connected in parallel with a capacitor C4, and a transient suppression diode TVS1, the resistor R12 is connected in parallel with the capacitor C4, and the other end of the transient suppression diode TVS1 is grounded; the node of the resistor R9 and the resistor R12 provides a signal to the control circuit. The voltage acquisition circuit is used to collect the current power supply voltage signal output by the power supply circuit.

[0041] like Figure 6As shown, the control circuit of the present invention includes a control chip U1, a capacitor C6 and a capacitor C7; the third pin of the control chip U1 is connected to the output end of the voltage acquisition circuit, the eighth pin of the control chip U1 and the nineteenth pin of the control chip U1 are grounded, one end of the capacitor C6 and the capacitor C7 connected in parallel is connected to the twentieth pin of the control chip U1, and the other end is grounded, and the middle node of the resistor R15 and the capacitor C10 is connected to the first pin of the control chip U1. The control circuit of the present invention adopts a single-chip microcomputer or a dedicated driver chip.

[0042] like Figure 7 As shown, the driving circuit includes a driving chip U2, a capacitor C12, a capacitor C11, a resistor R17, a resistor R18, a capacitor C13, a resistor R16 and a diode D2; the input end of the driving chip U2 is connected to the control circuit, the power supply end of the driving chip U2 is connected to one end of the capacitor C12 and the capacitor C11 in parallel, the other end of the capacitor C12 and the capacitor C11 in parallel is grounded, the ground end of the driving chip U2 is grounded, the output end of the driving chip U2 is connected to one end of the resistor R17, the other end of the resistor R17 is connected to the switch element and one end of the resistor R18, the other end of the resistor R18 is connected to the positive electrode of the diode D2 after passing through the capacitor C13 and the resistor R16, the coil is connected in parallel to the two ends of the diode D2, and the positive electrode of the diode D2 is connected to the switch element. The driving chip U2 can use a driving chip of model FAN3111E, and the driving circuit of the present invention uses a dedicated driver, or it can be composed of discrete devices.

[0043] As shown in the figure, the switching element is a MOS tube Q4, and a power transistor or IGBT may also be used.

[0044] Combine the following Figure 1 , 3 , 6, 7, 8, 9 illustrate the working principle of the contactor control circuit of the present invention:

[0045] After the contactor control circuit is turned on, the control circuit detects the rectified power supply voltage value and compares the minimum starting voltage value required by the coil with the current sampled power supply voltage value.

[0046] When the rectified power supply voltage value is greater than the minimum starting voltage value of the coil, the ratio of the minimum starting voltage of the coil to the rectified power supply voltage is used as the starting duty cycle. According to the starting duty cycle, the voltage at both ends of the coil of the contactor is adjusted. After passing through the driving circuit, the power tube is driven to conduct for a certain period of time to make the contactor operate; then it is converted into a smaller holding duty cycle to make the average voltage at both ends of the coil lower, provide a small holding voltage and satisfy the contactor in a reliable holding state, and the ratio of the coil holding voltage to the rectified power supply voltage is used as the holding duty cycle. According to the holding duty cycle, the voltage at both ends of the coil of the contactor is adjusted, and the smaller maintenance coil duty cycle is adjusted with the change of the rectified voltage, so as to achieve the stability of the average voltage at both ends of the coil. The minimum starting voltage value of the coil and the coil holding voltage are known values. Of course, in addition to the method of using the ratio of the minimum starting voltage of the coil and the coil holding voltage to the rectified voltage respectively, the starting duty cycle and the holding duty cycle can also be calculated in other ways.

[0047] When the rectified voltage value is lower than the preset shutdown value, the control circuit turns off the duty cycle output, the power tube is in the cut-off state, the coil has no maintenance voltage, and the contactor is in the disconnected state.

[0048] Figure 2 A schematic structural diagram of another contactor control circuit provided by the present invention.

[0049] like Figure 2 As shown, the contactor control circuit of the present invention includes a power supply circuit, a voltage acquisition circuit, a control circuit, a drive circuit, a switch element, a temperature acquisition circuit and a coil; the input end of the power supply circuit is connected to an external power supply for obtaining power, and the output end of the power supply circuit is connected to the voltage acquisition circuit, the control circuit, the switch element and the coil to supply power to the voltage acquisition circuit, the control circuit, the switch element and the coil; the input end of the voltage acquisition circuit is connected to the power supply circuit for acquiring the current power supply voltage signal of the power supply circuit, and the input end of the control circuit is connected to the output end of the voltage acquisition circuit to receive the current power supply voltage acquired by the voltage acquisition circuit; the temperature acquisition circuit is connected to the coil for acquiring the temperature of the coil, and the output end of the temperature acquisition circuit is connected to the control circuit for sending the acquired temperature signal of the coil to the control circuit; the control circuit adjusts the duty cycle to output a control signal according to the current power supply voltage and the current temperature of the coil, the input end of the drive circuit is connected to the output end of the control circuit, the output end of the drive circuit is connected to the switch element, the drive circuit receives the control signal sent by the control circuit, and controls the conduction and closing of the switch element; the switch element is connected to the coil, and the on-off control of the switch element controls the presence or absence of voltage at both ends of the coil.

[0050] The contactor control circuit of the present invention comprises a power supply circuit, a voltage acquisition circuit, a control circuit, a drive circuit, a switch element, a temperature acquisition circuit and a coil; the control circuit receives the current power supply voltage acquired by the voltage acquisition circuit and the current temperature of the coil acquired by the temperature acquisition circuit; the control circuit adjusts the duty cycle to output a control signal according to the current power supply voltage and the current temperature of the coil; drives the switch element to change the voltage of the coil of the contactor, realizes the start and maintenance of the coil, and achieves that the voltage at both ends of the coil is basically constant, thereby stabilizing the average value of the voltage at both ends of the coil; the control circuit adjusts the duty cycle to output the control signal according to the current power supply voltage and the current temperature of the coil; the performance of the contactor control circuit is more stable and reliable, the working voltage range of the coil is wider, the circuit structure is simple and compact, the coil power consumption is low, and the cost is low.

[0051] like Figure 2 As shown, the temperature acquisition circuit is connected to the coil to acquire the temperature of the coil, and the output end of the temperature acquisition circuit is connected to the control circuit to send the acquired temperature signal of the coil to the control circuit.

[0052] like Figure 5 As shown, the control circuit of the present invention includes a control chip U1, a capacitor C6 and a capacitor C7; the third pin of the control chip U1 is connected to the output end of the voltage acquisition circuit, the eighth pin of the control chip U1 and the nineteenth pin of the control chip U1 are grounded, one end of the capacitor C6 and the capacitor C7 connected in parallel is connected to the twentieth pin of the control chip U1, and the other end is grounded, the seventh pin of the control chip U1 is connected to the output end of the temperature acquisition circuit, and the middle node of the resistor R15 and the capacitor C10 is connected to the first pin of the control chip U1. The control chip U1 adopts a single-chip microcomputer.

[0053] like Figure 5 As shown, the temperature acquisition circuit includes a thermistor R6, a resistor R10, a resistor R13 and a capacitor C5. The single chip collects the voltage drop generated by the resistor R13. One end of the thermistor R6, the resistor R10 and the resistor R13 connected in series is connected to a 5V constant power supply, and the other end is grounded. The capacitor C5 is connected in parallel to both ends of the resistor R13. The thermistor R6 is installed close to the coil. The connecting line between the resistor R10 and the resistor R13 is connected to the control circuit. The resistor R10 and the resistor R13 are voltage divider resistors. The single chip collects the voltage drop generated by the resistor R13. Obviously, the temperature acquisition circuit can also be implemented using other temperature sensors, and the coil temperature is collected by the temperature sensor.

[0054] exist Figure 2 In the embodiment shown, the power supply circuit, the voltage acquisition circuit, and the drive circuit can be the same as those described above. Figure 1 The same circuit is used in the illustrated embodiment, but different circuits may also be used.

[0055] Combine the following Figure 2 , 3 , 4, 5, 6, 7, 8, 9 illustrate the working principle of the contactor control circuit of the present invention:

[0056] After the contactor control circuit is turned on, the control circuit obtains the rectified power supply voltage value through the voltage acquisition circuit, and compares the minimum starting voltage value required by the coil with the sampled current power supply voltage value.

[0057] When the current power supply voltage value is greater than the minimum starting voltage value of the coil, the ratio of the minimum starting voltage of the coil to the power supply voltage is used as the starting duty cycle. After passing through the driving circuit, the power tube is driven to conduct for a certain period of time, and then converted into a smaller holding duty cycle to make the average value at both ends of the coil lower and meet the reliable holding state of the contactor. The holding duty cycle of the smaller maintenance coil is adjusted with the change of the rectified voltage and the change of the coil temperature, so as to achieve the stability of the average voltage at both ends of the coil. When the coil temperature changes, the control circuit reads the coil temperature through the temperature acquisition circuit and calculates the coil resistance at this time, and calculates the duty cycle in combination with the input power supply voltage value at this time. The thermistor is tightly attached to the coil, and the coil temperature is transmitted to the thermistor to change the resistance of the thermistor. The circuit composed of the thermistor and the voltage divider resistor has an unchanged input power supply voltage. When the resistance of the thermistor changes with temperature, the voltage drop of the voltage divider resistor has a corresponding relationship with the temperature, thereby obtaining the temperature of the coil. The corresponding relationship between the coil temperature and the coil resistance is proportional. When the temperature rises, the resistance increases. After many tests, the corresponding relationship between the coil temperature and the coil resistance is obtained. The coil resistance is written into the single-chip microcomputer at room temperature. The single-chip microcomputer of the circuit connection control circuit reads the input voltage of the power circuit. When the starting voltage threshold is reached, the starting current is calculated according to I=U / R, where the voltage at both ends of the coil can be adjusted to obtain the ideal value by adjusting the duty cycle; after starting, a smaller holding duty cycle is used to make the average value at both ends of the coil lower, provide a small holding voltage and meet the contactor in a reliable holding state. When the coil temperature rises during holding, the coil resistance increases. The coil holding voltage is obtained based on the coil resistance * the coil current during holding. The ratio of the coil holding voltage to the input power supply voltage is used as the holding duty cycle. By increasing the duty cycle, the voltage at both ends of the coil increases, ensuring the constant coil current. On the contrary, when the coil temperature decreases, the coil resistance decreases, and the coil resistance * the coil current during holding obtains the coil holding voltage. The coil holding voltage decreases. By reducing the duty cycle, the voltage at both ends of the coil is reduced, ensuring the constant coil current, and ensuring the stable starting power and stable holding power of the contactor coil at different temperatures.

[0058] When the rectified voltage value is lower than the preset shutdown value, the control circuit turns off the duty cycle output, the power tube is in the cut-off state, the coil has no maintenance voltage, and the contactor is in the disconnected state.

[0059] Embodiment 1 After the power supply voltage is detected by the voltage acquisition circuit, the PWM duty cycle is changed according to the power supply voltage to achieve voltage control of the coil and complete the contactor's action characteristics. Its disadvantage is that the coil resistance will increase with the ambient temperature or the product itself heating up, while under the same input voltage, the duty cycle in the PWM of the previous technology does not change, resulting in a smaller coil current and a smaller contactor pull-in force, which causes the contactor's action characteristics to change. The present invention acquires the temperature of the coil through a temperature acquisition circuit to achieve temperature compensation control. When the temperature rises, the coil resistance increases and the PWM duty cycle also changes, thereby increasing the voltage across the coil, so that the current in the coil is close to that before the temperature rises, thereby ensuring that the contactor pull-in force is close to the pull-in force at the same voltage and different temperatures to maintain consistent action characteristics. (The minimum starting voltage of the coil refers to the voltage that just causes the contactor to act. Voltages greater than this minimum starting voltage can cause it to act and are also called starting voltages. The starting voltage marked on the product is generally higher than the minimum starting voltage.)

[0060] Based on the above embodiment of the contactor control circuit, the present invention further provides a contactor coil voltage control method, the method comprising:

[0061] Get the current input power supply voltage;

[0062] Obtain the current coil temperature, and according to the corresponding relationship between the coil temperature and the coil resistance, obtain the current coil resistance based on the current coil temperature;

[0063] At startup, the coil starting voltage is obtained based on the coil resistance * the coil current at startup, and the current starting duty cycle is obtained based on the current power supply voltage and the coil starting voltage. According to the starting duty cycle, the voltage at both ends of the coil of the contactor is adjusted to make the contactor operate;

[0064] When holding, the coil holding voltage is obtained based on the coil resistance * the coil current during holding, and the current holding duty cycle is obtained based on the current power supply voltage and the coil holding voltage. According to the holding duty cycle, the voltage across the coil of the contactor is adjusted to keep the contactor in a reliable holding state.

[0065] The power supply voltage can be obtained based on the voltage acquisition circuit of the present invention, that is, the rectified voltage. The coil temperature can be obtained based on the temperature sampling circuit of the present invention. The temperature sampling circuit can be a temperature sensor, or it can be obtained based on a thermistor. The coil current at startup and the coil current at maintenance are both known values. The maintenance duty cycle can be obtained based on the ratio of the coil maintenance voltage to the power supply voltage, or other calculation methods can be used. The corresponding relationship between the coil temperature and the coil resistance is a known value, which can be obtained from the supplier during procurement, or obtained through experiments. The coil temperature can be ignored during startup, and startup can be performed in the manner of Example 1. During maintenance, the current power supply voltage and coil temperature are considered to output the maintenance duty cycle.

[0066] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A contactor control circuit, characterized in that: Including power supply circuit, voltage acquisition circuit, control circuit, drive circuit, switch element and coil; The input end of the power supply circuit is connected to an external power supply for obtaining power, and the output end of the power supply circuit is connected to a voltage collection circuit, a control circuit, a switch element and a coil to supply power to the voltage collection circuit, the control circuit, the switch element and the coil; The input end of the voltage acquisition circuit is connected to the power supply circuit to acquire the current power supply voltage of the power supply circuit, and the input end of the control circuit is connected to the output end of the voltage acquisition circuit. It also includes a temperature acquisition circuit, the input end of the temperature acquisition circuit is connected to the coil to acquire the temperature of the coil, and the output end of the temperature acquisition circuit is connected to the control circuit to send the acquired temperature signal of the coil to the control circuit; The control circuit adjusts the duty cycle according to the current power supply voltage and the current temperature of the coil to output a control signal. The input end of the drive circuit is connected to the output end of the control circuit. The output end of the drive circuit is connected to the switch element. The drive circuit receives the control signal sent by the control circuit to control the on and off of the switch element. The switch element is connected to the coil, and the on-off of the switch element controls the presence or absence of voltage at both ends of the coil; The voltage acquisition circuit includes a resistor R3, a resistor R4, a resistor R5, a resistor R9, a resistor R12, a capacitor C4, and a transient suppression diode TVS1; In the voltage acquisition circuit, the resistor R3 is connected to the power supply circuit, and the other end is connected in series with the resistor R4, the resistor R4 is connected in series with the resistor R5, the resistor R5 is connected in series with the resistor R9, the resistor R9 is connected in series with the resistor R12, the resistor R12 is connected in parallel with the capacitor C4, and the transient suppression diode TVS1, the resistor R12 is connected in parallel with the capacitor C4, and the other end of the transient suppression diode TVS1 is grounded; the node between the resistor R9 and the resistor R12 provides a signal to the control circuit; The power supply circuit includes a rectifier circuit and a buck stabilizing circuit; the input end of the rectifier circuit is connected to an external power supply, and the output end of the rectifier circuit is connected to the buck stabilizing circuit; The rectifier circuit is a full-wave rectifier bridge BR1; The step-down voltage stabilizing circuit includes a resistor R1, a resistor R2, a transistor Q1, a resistor R7, a resistor R8, a transistor Q2, a resistor R11, a resistor R14, a transistor Q3, a voltage stabilizing tube D1, a capacitor C3, a capacitor C8, a transient suppression diode TVS2, a capacitor C9, a capacitor C14, a voltage stabilizing chip VOT1, and a capacitor C15; The capacitor C3 is connected in parallel to the output end of the rectifier circuit, one end of the resistor R1 and the resistor R2 are connected to the negative electrode of the output end of the rectifier circuit, the resistor R1, the resistor R7, the resistor R11 and the voltage regulator D1 are connected in series in sequence, one end of the voltage regulator D1 is connected to the positive electrode of the output end of the rectifier circuit, the resistor R2, the transistor Q1, the resistor R8, the transistor Q2, the resistor R14, the transistor Q3, and the capacitor C8 are connected in series in sequence, one end of the capacitor C8 is connected to the positive electrode of the output end of the rectifier circuit, the base of the transistor Q1 is connected to the middle node of the resistor R1 and the resistor R7, and the transistor The base of Q2 is connected to the middle node of the resistor R7 and the resistor R11, the base of the transistor Q3 is connected to the middle node of the resistor R11 and the voltage regulator D1, the transient suppression diode TVS2 and the capacitor C9 are sequentially connected in parallel to one end of the capacitor C8; one end of the capacitor C9 is grounded, and the other end is connected to the capacitor C14 and the voltage regulator chip VOT1, the output pin of the voltage regulator chip is connected to the capacitor C15, and the other pins of the capacitor C14, the voltage regulator chip VOT1 and the capacitor C15 are grounded; the capacitor C9 also provides power to the drive circuit; the voltage regulator chip VOT1 provides power to the control circuit; The control circuit includes a control chip U1, the control chip U1 is connected to the output end of the voltage acquisition circuit, and the control chip U1 is connected to the output end of the temperature acquisition circuit; The driving circuit includes a driving chip U2 , an input end of the driving chip U2 is connected to the control circuit, and an output end of the driving chip U2 is connected to the switch element.

2. The contactor control circuit according to claim 1, characterized in that: It also includes an EMI circuit, which is connected in parallel to one side of the input end of the power supply circuit; the EMI circuit includes an inductor L1, a varistor RV1, a capacitor C2 and a capacitor C1, and the capacitor C1 and the capacitor C2 are connected in parallel at both ends of the inductor L1, the capacitor C1 is close to one side of the power supply circuit, the capacitor C2 is close to one side of the external power supply, and the varistor RV1 is connected in parallel to one side of the capacitor C2 close to the external power supply.

3. The contactor control circuit according to claim 1, characterized in that: The control circuit includes capacitor C6 and capacitor C7; the eighth pin of the control chip U1 and the nineteenth pin of the control chip U1 are grounded, one end of the capacitor C6 and the capacitor C7 connected in parallel is connected to the twentieth pin of the control chip U1, and the other end is grounded, and the middle node of the resistor R15 and the capacitor C10 is connected to the first pin of the control chip U1.

4. The contactor control circuit according to claim 1, characterized in that: The temperature acquisition circuit includes a thermistor R6, a resistor R10, a resistor R13 and a capacitor C5. One end of the thermistor R6, the resistor R10 and the resistor R13 connected in series is connected to a constant power supply, and the other end is grounded. The capacitor C5 is connected in parallel to both ends of the resistor R13. The thermistor R6 is installed closely to the coil, and the connecting line between the resistor R10 and the resistor R13 is connected to the control circuit.

5. The contactor control circuit according to claim 1, characterized in that: The driving circuit includes a capacitor C12, a capacitor C11, a resistor R17, a resistor R18, a capacitor C13, a resistor R16 and a diode D2; The power supply end of the driving chip U2 is connected to one end of the capacitor C12 and the capacitor C11 in parallel, the other end of the capacitor C12 and the capacitor C11 in parallel is grounded, the ground end of the driving chip U2 is grounded, the output end of the driving chip U2 is connected to one end of the resistor R17, the other end of the resistor R17 is connected to the switching element and one end of the resistor R18, the other end of the resistor R18 is connected to the positive electrode of the diode D2 after passing through the capacitor C13 and the resistor R16, the coil is connected in parallel to the two ends of the diode D2, and the positive electrode of the diode D2 is connected to the switching element.

6. A contactor coil voltage control method based on the contactor control circuit of any one of claims 1 to 5, characterized in that: The method comprises: Get the current input power supply voltage; Obtain the current coil temperature, and according to the corresponding relationship between the coil temperature and the coil resistance, obtain the current coil resistance based on the current coil temperature; When holding, the coil holding voltage is obtained based on the coil resistance * the coil current during holding, and the current holding duty cycle is obtained based on the current power supply voltage and the coil holding voltage. According to the holding duty cycle, the voltage across the coil of the contactor is adjusted to keep the contactor in a reliable holding state.

7. The contactor coil voltage control method according to claim 6, characterized in that: At startup, the coil starting voltage is obtained based on the coil resistance * the coil current at startup, and the current starting duty cycle is obtained based on the current power supply voltage and the coil starting voltage. According to the starting duty cycle, the voltage across the coil of the contactor is adjusted to make the contactor operate.

8. The contactor coil voltage control method according to claim 6, characterized in that: The coil temperature is obtained through a thermistor that is in close contact with the coil.

Images