An integrated intelligent closed-loop control method for electromagnetic contactor

Abstract

The present invention proposes an integrated intelligent closed-loop control method for an electromagnetic contactor, including an integrated drive circuit and an embedded control system, wherein the electromagnetic contactor is driven and controlled by an integrated drive circuit including an integrated power chip; the integrated power chip replaces the external current detection circuit with a SenseFET sensor that can accurately and real-timely provide lower tube source-drain current information; the embedded control system includes a system MCU, which collects coil voltage through an ADC module u coil , Current i coil And through the integral operation, it is converted into magnetic flux, which is used for the closed-loop control of constant flux in the starting stage; and the process control of the electromagnetic contactor is carried out through the timer module for the timing disconnection of the contactor, and the integrated half-bridge chip of the integrated power chip is controlled through the PWM output module. U 1. U 2 internal switch tube, thereby controlling the exciting voltage state at both ends of the contactor coil; the present invention can improve the integration of the control circuit, thereby improving the overall reliability of the intelligent contactor and reducing the hardware cost.

Description

Technical Field

[0001] The invention relates to the technical field of intelligent control of switch electrical appliances, in particular to an integrated intelligent closed-loop control method of an electromagnetic contactor. Background Art

[0002] A contactor is a control device suitable for frequently connecting and disconnecting AC and DC main circuits and large-capacity control circuits over long distances. Traditional electromagnetic contactors are widely used in low-voltage electrical systems, and their manufacturing technology and application market are very mature. However, they usually generate a lot of noise during operation, and the coil needs to be energized for a long time to maintain the holding state, which will cause the coil temperature to rise, and the energy consumption is high when working for a long time.

[0003] At present, most intelligent control schemes of electromagnetic contactors are implemented by discrete components. The hardware topology of the driving circuit is mainly composed of asymmetric half-bridge circuits composed of MOS tubes, and the switch tube needs multiple auxiliary power supplies to drive. The control method of coil excitation is mostly based on PWM current closed loop. Although direct closed-loop control of coil current has the advantages of natural current limiting, safety and reliability. However, the electromagnetic mechanism under current closed-loop control belongs to a constant magnetic potential system, and it is impossible to automatically adjust the starting current according to the change of magnetic circuit inductance (air gap between dynamic and static iron cores) to complete the optimization control; it is difficult to minimize the starting energy and make a natural transition from starting to holding; the holding process will produce harsh audio noise due to the closed-loop adjustment of the duty cycle of the high-frequency excitation square wave; in addition, the coil voltage and current need to be equipped with sensors for signal detection, which are used as feedback signals to be sent to the embedded chip to complete the closed-loop control. The circuit structure of the whole scheme is complex, with many components, high hardware cost and low reliability, which restricts the intelligent development of electromagnetic contactors.

[0004] The present invention proposes an integrated control circuit solution for electromagnetic contactors, which solves the defect of a large number of discrete components in traditional circuits and improves the operating reliability of intelligent contactors. On this basis, a magnetic linkage closed loop is used to optimize the starting process of the contactor, suppress the closing bounce, and make a natural transition from the starting to the holding process. The holding process adopts a noise adaptive suppression strategy to make the spectrum distribution of the holding noise relatively stable, which is convenient for suppressing the audible noise of the human ear. Summary of the invention

[0005] The present invention proposes an integrated intelligent closed-loop control method for electromagnetic contactors. Aiming at the defects of poor operating reliability and high cost of intelligent control modules of electromagnetic contactors, an integrated intelligent control solution is proposed. The integrated power chip is applied to the drive control of the electromagnetic contactor to improve the integration of the control circuit, thereby improving the overall reliability of the intelligent contactor and reducing the hardware cost. The FREDFET switch tube inside the integrated chip is driven by a dynamic self-powered mode, overcoming the defect that the traditional drive solution requires an auxiliary power supply; at the same time, the chip integrates SenseFET sensing, which can provide accurate and real-time lower tube source and drain current information, without the need to build an external current detection circuit, further simplifying the hardware circuit. On this basis, a magnetic flux closed-loop control strategy is designed, and a constant magnetic flux closed-loop control is adopted during the contactor starting process to minimize the starting operation work and suppress bounce; a noise adaptive suppression strategy is adopted during the holding process to effectively move the holding noise spectrum out of the audible range of the human ear; negative pressure rapid demagnetization is adopted during the opening process to increase the opening speed, thereby optimizing the performance of the electromagnetic contactor.

[0006] The present invention adopts the following technical solutions.

[0007] An integrated intelligent closed-loop control method for an electromagnetic contactor, the method comprising an integrated drive circuit and an embedded control system, wherein the electromagnetic contactor is driven and controlled by an integrated drive circuit including an integrated power chip; the FREDFET switch tube inside the integrated power chip is driven in a dynamic self-powered manner, and the integrated power chip replaces an external current detection circuit with a SenseFET sensor that can accurately and real-timely provide lower tube source-drain current information;

[0008] The embedded control system includes the system MCU, which collects the coil voltage u through the ADC module coil 、Current i coil And it is converted into magnetic flux through integral operation, which is used for constant flux closed-loop control in the starting stage; and the process control of the electromagnetic contactor is carried out through the timer module for contactor timing disconnection, and the internal switch tubes of the integrated half-bridge chip U1 and U2 of the integrated power chip are controlled through the PWM output module, thereby controlling the excitation voltage state at both ends of the contactor coil.

[0009] In the integrated drive circuit, the circuit for rectifying the AC input voltage into DC includes a rectifier bridge B1 and a filter capacitor C1, HV+ and HV- are respectively the positive polarity end and the negative polarity end of the DC input voltage after rectification and filtering, which are respectively connected to the HD and LS pins of the integrated half-bridge chips U1 and U2, and are used to drive the integrated drive circuit;

[0010] The integrated drive circuit converts the voltage at both ends of HV+ and HV- into 3.3V through a step-down module for powering the embedded control system.

[0011] The four FREDFET switch tubes S1, S2, S3, and S4 inside the two chips U1 and U2 form a full-bridge drive circuit to drive the electromagnetic contactor coil; C2, C4 and C3, C5 are the self-bias capacitors of the internal integrated switch tubes of U1 and U2, respectively, and provide dynamic self-power supply voltage for the internal upper and lower tubes through the BPH and BPL pins; R2 and R3 are the lower tube current limiting resistors of the integrated chips of U1 and U2, respectively, and provide hardware-adjustable self-locking current limiting thresholds for the U1 and U2 chips through the XL pin; R1 and R4 are current detection resistors, and the output current flowing through the source and drain channels of the lower tubes of U1 and U2 is respectively detected through the IPH pin; R5 and R6 form a resistor voltage divider circuit, and the voltage across the capacitor C1 is converted into the voltage across the contactor coil Coil1 through the voltage calculation module; INH and INL are the gate logic control input pins of the integrated half-bridge chips U1 and U2, respectively, and are connected to PWM1~PWM4 of the embedded control system, which are used to control the state of the internal integrated switch tube, where INH is effective at a low level and INL is effective at a high level;

[0012] The specific connection method of PWM1~PWM4 and the internal switch tubes of the integrated half-bridge chip is as follows: PWM1 and PWM2 are connected to the internal switch tubes S1 and S2 of U1 respectively, and PWM3 and PWM4 are connected to the internal switch tubes S3 and S4 of U2 respectively. Among them, the upper tubes S1 and S3 are turned on by the low level of PWM signal and turned off by the high level; the lower tubes S2 and S4 are turned on by the high level of PWM signal and turned off by the low level.

[0013] In the control method, the following three circuit states are defined according to the voltage polarity applied to both ends of the electromagnetic contactor coil;

[0014] When S1 and S4 are turned on at the same time and S2 and S3 are turned off complementarily, a forward voltage is applied to both ends of the coil, causing the coil current to rise rapidly. This circuit state is defined as the +1 state.

[0015] When only S4 is turned on and the positive coil current continues to flow through D2 and S4, the coil terminal voltage is close to 0V, causing the coil current to slowly decrease. The circuit state at this time is defined as 0 state;

[0016] When S1, S2, S3, and S4 are turned off at the same time and the coil current continues to flow through diodes D2 and D3, a negative coil voltage is applied to both ends of the coil, causing the coil current to drop rapidly. This circuit state is defined as -1 state.

[0017] The relationship between the circuit state and the change of coil current and flux linkage is shown in the circuit state selection table in Table 1 below.

[0018] Table 1 Circuit state selection table

[0019] Circuit Status A <![CDATA[Switching transistor states (S1~S4)]]> Flux and current changes +1 status +1 (1，0，0，1) ↑↑ 0 state 0 (0，0，0，1) ↓ -1 state -1 (0，0，0，0) ↓↓ .

[0020] The integrated half-bridge chips U1 and U2 are BRD1267C integrated half-bridge chips or other BridgeSwitch series chips.

[0021] When the integrated half-bridge chips U1 and U2 use the BRD1267C integrated half-bridge chip, the functions of their pins are as follows:

[0022] HD pin: electrically connected to the drain of the upper FREDFET integrated inside the chip, and also the input end of the internal upper and lower FREDFET self-powered circuit, connected to the rectified and filtered DC input voltage HV+ end;

[0023] BPH pin: This pin is connected to the bypass capacitors C2 and C4 of the upper tube FREDFET gate driver of U1 and U2 to provide self-powered voltage for the upper tube operation;

[0024] BPL pin: This pin is connected to the bypass capacitors C3 and C5 of the FREDFET gate driver of the lower tube of U1 and U2 to provide self-powered voltage for the lower tube operation;

[0025] INH pin: This pin is the gate drive control input terminal of the upper tube FREDFET and is connected to the system MCU PWM1 (U1) and PWM3 (U2) output pins;

[0026] INL pin: This pin is the gate drive control input terminal of the lower tube FREDFET and is connected to the system MCU PWM2 (U1) and PWM4 (U2) output pins;

[0027] IPH pin: This pin is grounded through small signal resistors R1 and R4, providing the source and drain channel current information of the FREDFET under U1 and U2 respectively;

[0028] XL pin: This pin is grounded through resistors R2 and R3 and is used to set the hardware self-locking current limiting threshold of the FREDFET under U1 and U2;

[0029] LS pin: This pin is electrically connected to the source of the lower FREDFET integrated inside the chip;

[0030] HB pin: This pin connects the source of the upper tube FREDFET and the drain of the lower tube FREDFET, and connects the two ends of the contactor coil.

[0031] In the starting stage of the electromagnetic contactor, a constant magnetic flux linkage method is adopted to construct a coil voltage calculation module according to the following formula 1: the voltage u across the filter capacitor C1 is C1 Converted to contactor coil terminal voltage u coil :

[0032] Where: u coil is the coil terminal voltage, A represents the coil terminal voltage polarity, R5 and R6 are the voltage divider resistances, ΔT is the PWM period, T on is the switch on time;

[0033] According to the following formula 2, a current calculation module is constructed to calculate the output current i of the IPH pin of U2. sense Converted into contactor coil current i coil :

[0034] i coil =i sense *g Formula 2;

[0035] Where: i coil is the coil current value, i sense is the output current of the IPH pin of U2. g is the gain factor, which is related to the resistance value of R4;

[0036] Then, the flux integral calculation module is constructed according to the following formula 3 to convert the coil voltage, current and resistance into magnetic flux for starting constant flux closed-loop control:

[0037] ψ coil =∫(u coil -i coil R coil )dt Formula 3;

[0038] Where: coil is the magnetic flux, R coil is the coil resistance;

[0039] The control of the electromagnetic contactor coil adopts the flux linkage / current hysteresis controller, f s is the hysteresis frequency, ε is the hysteresis width, and the magnetic flux of the corresponding comparison coil ψ coil Or coil current i coil With reference flux ψ ref Or reference current i ref Get the flux error Δψ or current error Δi,

[0040] That is: Δψ=ψ coil -ψ ref / Δi=i coil -i ref ;

[0041] The system MCU automatically selects the appropriate circuit state according to Δψ / Δi and ε and converts it into the driving state of the corresponding switch tube according to Table 1. Specifically, when Δψ / Δi<0, select the +1 state circuit, turn on S1 and S4, turn off S2 and S3, and quickly excite the coil; when 0≤Δψ / Δi≤ε, select the 0 state circuit, turn on only S4, turn off S1, S2, and S3, and slowly demagnetize the coil. When Δψ / Δi>ε, select the -1 state circuit, turn off S1, S2, S3, and S4, so that a negative voltage is applied to both ends of the coil, and the coil is quickly demagnetized.

[0042] The embedded control system uses a magnetic flux closed-loop control strategy to enable the electromagnetic contactor to adopt a constant magnetic flux closed-loop control during the starting process to minimize the starting operation work and suppress bounce. The embedded control system enables the electromagnetic contactor to adopt a noise adaptive suppression strategy during the holding process to effectively move the holding noise spectrum out of the audible range of the human ear; the embedded control system enables the electromagnetic contactor to use negative pressure rapid demagnetization during the opening process to increase the opening speed, thereby optimizing the performance of the electromagnetic contactor.

[0043] The electromagnetic contactor uses the three-position hysteresis controller shown in the starting stage, and the control variable selects the coil flux ψ coil , specifically: Calculate the coil flux ψ according to formula 3 coil , and with the reference flux ψ ref By comparison, the three-position hysteresis controller selects the appropriate circuit state, which is then converted into the switch states of S1 to S4 through the circuit state selection table to form a flux closed-loop control, so that the starting flux tracks the reference flux;

[0044] The electromagnetic contactor adopts a noise adaptive suppression strategy in the holding stage, which is also based on the hysteresis controller. It automatically captures the current value at the holding moment during the start-up flux closed-loop control process as the holding current reference value. After that, the control variable is changed from coil flux to coil current to perform current closed-loop control, that is, compare the coil current i coil and holding current reference value i ref Get Δi, according to Δi and ε, automatically select the appropriate circuit state and convert it into the driving state of the corresponding switch tube according to Table 1. When Δi<0, select the +1 state circuit, open S1 and S4, PWM output duty cycle D1 is 100%, and the coil current rises rapidly; when 0<Δi<ε, select the 0 state circuit, only open S4, PWM output duty cycle D2 is 0%, and the coil current decreases slowly; when Δi>ε, select the -1 state circuit, close S1~S4, PWM output duty cycle D3 is 0%, and the coil current decreases rapidly. Through the three-position hysteresis control, the coil current is kept dynamically constant at the reference value; after the current is kept stable, N PWM cycles are executed cyclically, and the average duty cycle of N cycles is calculated according to the following formula 4 Then switch to PWM control mode. When -ε≤Δi≤ε, switch to pseudo open-loop control mode to update the duty cycle D. Given D, the contactor is kept stable and silent under the constant duty cycle to achieve noise suppression. When Δi exceeds the hysteresis width ε, reselect the current hysteresis control mode, and recalculate after the current stabilizes again (when -ε≤Δi≤ε) And update to D, so that the coil current quickly tracks the reference value and maintains it silently; so as to achieve fast dynamic closed-loop regulation of the coil current and effectively suppress the noise;

[0045]

[0046] Where: is the average duty cycle of N cycles, a is the number of cycles of the +1 state circuit in N cycles, and D1 is the duty cycle of the +1 state circuit; b is the number of cycles of the 0 state circuit in N cycles, and D2 is the duty cycle of the 0 state circuit; c is the number of cycles of the -1 state circuit in N cycles, and D3 is the duty cycle of the -1 state circuit.

[0047] Under the above hysteresis control, the electromagnetic contactor action process is optimized and controlled, specifically: during the starting process, the flux reference value is set to a constant value, and as the air gap between the moving and static cores decreases, the excitation current is automatically adjusted to make the flux dynamically stable at the reference value, and the contactor starts with constant flux;

[0048] In the holding stage, the coil current at the holding moment is automatically captured as the current reference value of the holding stage to perform energy-saving holding. At the same time, a noise adaptive suppression strategy is adopted to reasonably switch the PWM control mode, taking into account the fast closed-loop regulation of the coil current and the suppression of high-frequency noise;

[0049] During the disconnection process, all switch tubes are closed, full negative pressure disconnection is performed, the coil current drops rapidly, and the disconnection operation is completed quickly, thereby achieving optimized control of the electromagnetic contactor's starting, holding and disconnection processes.

[0050] During the constant magnetic chain starting process of the electromagnetic contactor, if the coil current exceeds the current limiting threshold set by resistors R2 and R3, the integrated chip performs hardware self-locking current limiting on the switch tube to protect the drive circuit from damage, which is used as the final coil overcurrent or short circuit protection;

[0051] When the coil current needs to be limited cycle by cycle during the closed-loop control of the electromagnetic contactor flux linkage, the specific control method is as follows: the programmable DAC outputs the current limiting threshold i max , coil current i coil and current limiting threshold i max The MCU internal hardware comparator is connected to the MCU internal PWM output module. coil Greater than imax When the comparator outputs a complementary shutdown signal to the PWM module, the switch tube is turned off for one PWM cycle until the coil current i coil Less than the current limiting threshold i max When the PWM cycle is reopened, the flux closed-loop control is performed according to the above hysteresis control method. On the basis of the flux closed-loop control, software-programmable cycle-by-cycle current limiting is performed to control the maximum value of the coil current and ensure the reliable operation of the contactor.

[0052] N is an integer not less than 100.

[0053] The advantages of the present invention are:

[0054] (1) The power chip is cleverly applied to the integrated control of the electromagnetic contactor, and the control module has high integration, reliable circuit, small size and low cost;

[0055] (2) The internally integrated FREDFET switch tube adopts dynamic self-powered operation, which overcomes the defect that the traditional electromagnetic contactor drive solution requires auxiliary power supply, further reducing the size and cost;

[0056] (3) The chip integrates SenseFET current sensing, eliminating the need for external active current and voltage sensors, further simplifying the hardware control solution;

[0057] (4) The system has both software and hardware current limiting functions, using hardware self-locking current limiting and PWM cycle-by-cycle current limiting to ensure operational reliability;

[0058] (5) The starting process adopts constant magnetic flux closed-loop control to minimize the operating work while suppressing contact bounce. The holding process adopts a noise adaptive suppression control strategy to take into account the fast closed-loop regulation of the coil current and the effective suppression of audio noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0060] Attached Figure 1 It is a schematic diagram of the principle of the present invention;

[0061] Attached Figure 2 1 is a comparative schematic diagram of three states of the circuit of the present invention;

[0062] Attached Figure 3 It is the principle diagram of the flux / current three-position hysteresis controller;

[0063] Attached Figure 4 It is a control strategy flow chart of the present invention. DETAILED DESCRIPTION

[0064] As shown in the figure, an integrated intelligent closed-loop control method for an electromagnetic contactor includes an integrated drive circuit and an embedded control system, wherein the electromagnetic contactor is driven and controlled by an integrated drive circuit including an integrated power chip; the FREDFET switch tube inside the integrated power chip is driven in a dynamic self-powered manner, and the integrated power chip replaces the external current detection circuit with a SenseFET sensor that can accurately and real-timely provide the source-drain current information of the lower tube;

[0065] like Figure 1 As shown, the embedded control system includes a system MCU, which collects the coil voltage u through the ADC module coil 、Current i coil And it is converted into magnetic flux through integral operation, which is used for constant flux closed-loop control in the starting stage; and the process control of the electromagnetic contactor is carried out through the timer module for contactor timing disconnection, and the internal switch tubes of the integrated half-bridge chip U1 and U2 of the integrated power chip are controlled through the PWM output module, thereby controlling the excitation voltage state at both ends of the contactor coil.

[0066] In the integrated drive circuit, the circuit for rectifying the AC input voltage into DC includes a rectifier bridge B1 and a filter capacitor C1, HV+ and HV- are respectively the positive polarity end and the negative polarity end of the DC input voltage after rectification and filtering, which are respectively connected to the HD and LS pins of the integrated half-bridge chips U1 and U2, and are used to drive the integrated drive circuit;

[0067] The integrated drive circuit converts the voltage at both ends of HV+ and HV- into 3.3V through a step-down module for powering the embedded control system.

[0068] like Figure 2As shown in the figure, the dashed boxes are schematic diagrams of the main internal structures of the integrated half-bridge chips U1 and U2. The four FREDFET switch tubes S1, S2, S3, and S4 inside the two chips U1 and U2 form a full-bridge drive circuit to drive the electromagnetic contactor coil; C2, C4 and C3, C5 are the self-bias capacitors of the integrated switch tubes inside U1 and U2, respectively, and provide dynamic self-power supply voltage for the internal upper and lower tubes through the BPH and BPL pins; R2 and R3 are the lower tube current limiting resistors of the U1 and U2 integrated chips, respectively, and provide hardware-adjustable voltage for the U1 and U2 chips through the XL pin. The self-locking current limiting threshold of the section; R1 and R4 are current detection resistors, which detect the current flowing through the source and drain channels of the lower tubes of U1 and U2 through the IPH pin respectively; R5 and R6 form a resistor voltage divider circuit, which converts the voltage across the capacitor C1 into the voltage across the contactor coil Coil1 through the voltage calculation module; INH and INL are the gate logic control input pins of the integrated half-bridge chips U1 and U2 respectively, which are connected to PWM1~PWM4 of the embedded control system respectively, and are used to control the state of the internal integrated switch tube, where INH low level is valid and INL high level is valid;

[0069] The specific connection method of PWM1~PWM4 and the internal switch tubes of the integrated half-bridge chip is as follows: PWM1 and PWM2 are connected to the internal switch tubes S1 and S2 of U1 respectively, and PWM3 and PWM4 are connected to the internal switch tubes S3 and S4 of U2 respectively. Among them, the upper tubes S1 and S3 are turned on by the low level of PWM signal and turned off by the high level; the lower tubes S2 and S4 are turned on by the high level of PWM signal and turned off by the low level.

[0070] In the control method, the following three circuit states are defined according to the voltage polarity applied to both ends of the electromagnetic contactor coil;

[0071] When S1 and S4 are turned on at the same time and S2 and S3 are turned off complementarily, a forward voltage is applied to both ends of the coil, causing the coil current to rise rapidly. This circuit state is defined as the +1 state.

[0072] When only S4 is turned on and the positive coil current continues to flow through D2 and S4, the coil terminal voltage is close to 0V, causing the coil current to slowly decrease. The circuit state at this time is defined as 0 state;

[0073] When S1, S2, S3, and S4 are turned off at the same time and the coil current continues to flow through diodes D2 and D3, a negative coil voltage is applied to both ends of the coil, causing the coil current to drop rapidly. This circuit state is defined as -1 state.

[0074] The relationship between the circuit state and the change of coil current and flux linkage is shown in the circuit state selection table in Table 1 below.

[0075] Table 1 Circuit state selection table

[0076] Circuit Status A <![CDATA[Switching transistor states (S1~S4)]]> Flux and current changes +1 status +1 (1，0，0，1) ↑↑ 0 state 0 (0，0，0，1) ↓ -1 state -1 (0，0，0，0) ↓↓ .

[0077] The integrated half-bridge chips U1 and U2 are BRD1267C integrated half-bridge chips or other BridgeSwitch series chips.

[0078] When the integrated half-bridge chips U1 and U2 use the BRD1267C integrated half-bridge chip, the functions of their pins are as follows:

[0079] HD pin: electrically connected to the drain of the upper FREDFET integrated inside the chip, and also the input end of the internal upper and lower FREDFET self-powered circuit, connected to the rectified and filtered DC input voltage HV+ end;

[0080] BPH pin: This pin is connected to the bypass capacitors C2 and C4 of the upper tube FREDFET gate driver of U1 and U2 to provide self-powered voltage for the upper tube operation;

[0081] BPL pin: This pin is connected to the bypass capacitors C3 and C5 of the FREDFET gate driver of the lower tube of U1 and U2 to provide self-powered voltage for the lower tube operation;

[0082] INH pin: This pin is the gate drive control input terminal of the upper tube FREDFET and is connected to the system MCU PWM1 (U1) and PWM3 (U2) output pins;

[0083] INL pin: This pin is the gate drive control input terminal of the lower tube FREDFET and is connected to the system MCU PWM2 (U1) and PWM4 (U2) output pins;

[0084] IPH pin: This pin is grounded through small signal resistors R1 and R4, providing the source and drain channel current information of the FREDFET under U1 and U2 respectively;

[0085] XL pin: This pin is grounded through resistors R2 and R3 and is used to set the hardware self-locking current limiting threshold of the FREDFET under U1 and U2;

[0086] LS pin: This pin is electrically connected to the source of the lower FREDFET integrated inside the chip;

[0087] HB pin: This pin connects the source of the upper tube FREDFET and the drain of the lower tube FREDFET, and connects the two ends of the contactor coil.

[0088] In the starting stage of the electromagnetic contactor, a constant magnetic flux linkage method is adopted to construct a coil voltage calculation module according to the following formula 1: the voltage u across the filter capacitor C1 is C1 Converted to contactor coil terminal voltage u coil :

[0089]

[0090] Where: u coil is the coil terminal voltage, A represents the coil terminal voltage polarity, R5 and R6 are the voltage divider resistances, ΔT is the PWM period, T on is the switch on time;

[0091] According to the following formula 2, a current calculation module is constructed to calculate the output current i of the IPH pin of U2. sense Converted into contactor coil current i coil :

[0092] i coil =i sense *g Formula 2;

[0093] Where: i coil is the coil current value, i sense is the output current of the IPH pin of U2. g is the gain factor, which is related to the resistance value of R4;

[0094] Then, the flux integral calculation module is constructed according to the following formula 3 to convert the coil voltage, current and resistance into magnetic flux for starting constant flux closed-loop control:

[0095] ψ coil =∫(u coil -i coil R coil )dt Formula 3;

[0096] Where: coil is the magnetic flux, R coil is the coil resistance;

[0097] The control of the electromagnetic contactor coil adopts a flux / current hysteresis controller, such as Figure 3 As shown, f s is the hysteresis frequency, ε is the hysteresis width, and the magnetic flux of the corresponding comparison coil ψ coil Or coil current i coil With reference flux ψ ref Or reference current i ref Get the flux error Δψ or current error Δi,

[0098] That is: Δψ=ψ coil -ψ ref / Δi=i coil -i ref ;

[0099] The system MCU automatically selects the appropriate circuit state according to Δψ / Δi and ε and converts it into the driving state of the corresponding switch tube according to Table 1. Specifically, when Δψ / Δi<0, select the +1 state circuit, turn on S1 and S4, turn off S2 and S3, and quickly excite the coil; when 0≤Δψ / Δi≤ε, select the 0 state circuit, turn on only S4, turn off S1, S2, and S3, and slowly demagnetize the coil. When Δψ / Δi>ε, select the -1 state circuit, turn off S1, S2, S3, and S4, so that a negative voltage is applied to both ends of the coil, and the coil is quickly demagnetized.

[0100] The embedded control system uses a magnetic flux closed-loop control strategy to enable the electromagnetic contactor to adopt a constant magnetic flux closed-loop control during the starting process to minimize the starting operation work and suppress bounce. The embedded control system enables the electromagnetic contactor to adopt a noise adaptive suppression strategy during the holding process to effectively move the holding noise spectrum out of the audible range of the human ear; the embedded control system enables the electromagnetic contactor to use negative pressure rapid demagnetization during the opening process to increase the opening speed, thereby optimizing the performance of the electromagnetic contactor.

[0101] The electromagnetic contactor uses the three-position hysteresis controller shown in the starting stage, and the control variable selects the coil flux ψ coil , specifically: Calculate the coil flux ψ according to formula 3 coil , and with the reference flux ψ ref By comparison, the three-position hysteresis controller selects the appropriate circuit state, which is then converted into the switch states of S1 to S4 through the circuit state selection table to form a flux closed-loop control, so that the starting flux tracks the reference flux;

[0102] like Figure 4 As shown in the figure, the electromagnetic contactor adopts a noise adaptive suppression strategy in the holding stage, and also takes the hysteresis controller as the core, automatically capturing the current value at the holding moment during the start-up flux closed-loop control process as the holding current reference value. After that, the control variable is changed from coil flux to coil current, and current closed-loop control is performed, that is, comparing the coil current i coil and holding current reference value i ref Get Δi, according to Δi and ε, automatically select the appropriate circuit state and convert it into the driving state of the corresponding switch tube according to Table 1. When Δi<0, select the +1 state circuit, open S1 and S4, PWM output duty cycle D1 is 100%, and the coil current rises rapidly; when 0<Δi<ε, select the 0 state circuit, only open S4, PWM output duty cycle D2 is 0%, and the coil current decreases slowly; when Δi>ε, select the -1 state circuit, close S1~S4, PWM output duty cycle D3 is 0%, and the coil current decreases rapidly. Through the three-position hysteresis control, the coil current is kept dynamically constant at the reference value; after the current is kept stable, N PWM cycles are executed cyclically, and the average duty cycle of N cycles is calculated according to the following formula 4 Then switch to PWM control mode. When -ε≤Δi≤ε, switch to pseudo open-loop control mode to update the duty cycle D. Given D, the contactor is kept stable and silent under the constant duty cycle to achieve noise suppression. When Δi exceeds the hysteresis width ε, reselect the current hysteresis control mode, and recalculate after the current stabilizes again (when -ε≤Δi≤ε) And update to D, so that the coil current quickly tracks the reference value and maintains it silently; so as to achieve fast dynamic closed-loop regulation of the coil current and effectively suppress the noise;

[0103]

[0104] Where: is the average duty cycle of N cycles, a is the number of cycles of the +1 state circuit in N cycles, and D1 is the duty cycle of the +1 state circuit; b is the number of cycles of the 0 state circuit in N cycles, and D2 is the duty cycle of the 0 state circuit; c is the number of cycles of the -1 state circuit in N cycles, and D3 is the duty cycle of the -1 state circuit.

[0105] Under the above hysteresis control, the electromagnetic contactor action process is optimized and controlled, specifically: during the starting process, the flux reference value is set to a constant value, and as the air gap between the moving and static cores decreases, the excitation current is automatically adjusted to make the flux dynamically stable at the reference value, and the contactor starts with constant flux;

[0106] In the holding stage, the coil current at the holding moment is automatically captured as the current reference value of the holding stage to perform energy-saving holding. At the same time, a noise adaptive suppression strategy is adopted to reasonably switch the PWM control mode, taking into account the fast closed-loop regulation of the coil current and the suppression of high-frequency noise;

[0107] During the disconnection process, all switch tubes are closed, full negative pressure disconnection is performed, the coil current drops rapidly, and the disconnection operation is completed quickly, thereby achieving optimized control of the electromagnetic contactor's starting, holding and disconnection processes.

[0108] During the constant magnetic chain starting process of the electromagnetic contactor, if the coil current exceeds the current limiting threshold set by resistors R2 and R3, the integrated chip performs hardware self-locking current limiting on the switch tube to protect the drive circuit from damage, which is used as the final coil overcurrent or short circuit protection;

[0109] When the coil current needs to be limited cycle by cycle during the closed-loop control of the electromagnetic contactor flux linkage, the specific control method is as follows: the programmable DAC outputs the current limiting threshold i max , coil current i coil and current limiting threshold i max The MCU internal hardware comparator is connected to the MCU internal PWM output module. coil Greater than imax When the comparator outputs a complementary shutdown signal to the PWM module, the switch tube is turned off for one PWM cycle until the coil current i coil Less than the current limiting threshold i max When the PWM cycle is reopened, the flux closed-loop control is performed according to the above hysteresis control method. On the basis of the flux closed-loop control, software-programmable cycle-by-cycle current limiting is performed to control the maximum value of the coil current and ensure the reliable operation of the contactor.

[0110] N is an integer not less than 100. In this example, N=100.

Claims

1. An integrated intelligent closed-loop control method for an electromagnetic contactor, characterized in that: The method includes an integrated drive circuit and an embedded control system, wherein the electromagnetic contactor is driven and controlled by an integrated drive circuit including an integrated power chip; the FREDFET switch tube inside the integrated power chip is driven in a dynamic self-powered manner, and the integrated power chip replaces the external current detection circuit with a SenseFET sensor that can accurately and real-timely provide the source and drain current information of the lower tube; The embedded control system includes the system MCU, which collects the coil voltage u through the ADC module coil 、Current i coil And it is converted into magnetic flux through integral operation, which is used for constant flux closed-loop control in the starting stage; and the process control of the electromagnetic contactor is carried out through the timer module for contactor timing disconnection, and the internal switch tubes of the integrated half-bridge chip U1 and U2 of the integrated power chip are controlled through the PWM output module, thereby controlling the excitation voltage state at both ends of the contactor coil.

2. The integrated intelligent closed-loop control method for an electromagnetic contactor according to claim 1, characterized in that: In the integrated drive circuit, the circuit for rectifying the AC input voltage into DC includes a rectifier bridge B1 and a filter capacitor C1, HV+ and HV- are respectively the positive polarity end and the negative polarity end of the DC input voltage after rectification and filtering, which are respectively connected to the HD and LS pins of the integrated half-bridge chips U1 and U2, and are used to drive the integrated drive circuit; The integrated drive circuit converts the voltage at both ends of HV+ and HV- into 3.3V through a step-down module for powering the embedded control system. The four FREDFET switch tubes S1, S2, S3, and S4 inside the two chips U1 and U2 form a full-bridge drive circuit to drive the electromagnetic contactor coil; C2, C4 and C3, C5 are the self-bias capacitors of the internal integrated switch tubes of U1 and U2, respectively, and provide dynamic self-power supply voltage for the internal upper and lower tubes through the BPH and BPL pins; R2 and R3 are the lower tube current limiting resistors of the U1 and U2 integrated chips, respectively, and provide hardware-adjustable self-locking current limiting thresholds for the U1 and U2 chips through the XL pin; R1 and R4 are current detection resistors, and the output current flowing through the source and drain channels of the lower tubes of U1 and U2 is respectively detected through the IPH pin; R5 and R6 form a resistor voltage divider circuit, and the voltage across the capacitor C1 is converted into the voltage across the contactor coil Coil1 through the voltage calculation module; INH and INL are the gate logic control input pins of the integrated half-bridge chips U1 and U2, respectively, and are connected to PWM1~PWM4 of the embedded control system, which are used to control the state of the internal integrated switch tube, where INH is effective at a low level and INL is effective at a high level; The specific connection method between PWM1~PWM4 and the internal switch tubes of the integrated half-bridge chip is as follows: PWM1 and PWM2 are respectively connected to the internal switch tubes S1 and S2 of U1, and PWM3 and PWM4 are respectively connected to the internal switch tubes S3 and S4 of U2; among them, the upper tubes S1 and S3 are turned on by the low level of PWM signal and turned off by the high level; the lower tubes S2 and S4 are turned on by the high level of PWM signal and turned off by the low level.

3. The integrated intelligent closed-loop control method for an electromagnetic contactor according to claim 2, characterized in that: In the control method, the following three circuit states are defined according to the voltage polarity applied to both ends of the electromagnetic contactor coil; When S1 and S4 are turned on at the same time and S2 and S3 are turned off complementarily, a forward voltage is applied to both ends of the coil, causing the coil current to rise rapidly and the magnetic flux to increase. This circuit state is defined as the +1 state. When only S4 is turned on and the positive coil current continues to flow through D2 and S4, the coil terminal voltage is close to 0V, causing the coil current to slowly decrease and the magnetic flux to weaken. The circuit state at this time is defined as 0 state; When S1, S2, S3, and S4 are turned off at the same time and the coil current continues to flow through diodes D2 and D3, a negative coil voltage is applied to both ends of the coil, causing the coil current to drop rapidly and the magnetic flux to weaken. This circuit state is defined as the -1 state.

4. The integrated intelligent closed-loop control method for an electromagnetic contactor according to claim 3, characterized in that: The integrated half-bridge chips U1 and U2 are BRD1267C integrated half-bridge chips or other BridgeSwitch series chips.

5. The integrated intelligent closed-loop control method for an electromagnetic contactor according to claim 3, characterized in that: When the integrated half-bridge chips U1 and U2 use the BRD1267C integrated half-bridge chip, the functions of their pins are as follows: HD pin: electrically connected to the drain of the upper FREDFET integrated inside the chip, and also the input end of the internal upper and lower FREDFET self-powered circuit, connected to the rectified and filtered DC input voltage HV+ end; BPH pin: This pin is connected to the bypass capacitors C2 and C4 of the upper tube FREDFET gate driver of U1 and U2 to provide self-powered voltage for the upper tube operation; BPL pin: This pin is connected to the bypass capacitors C3 and C5 of the FREDFET gate driver of the lower tube of U1 and U2 to provide self-powered voltage for the lower tube operation; INH pin: This pin is the gate drive control input terminal of the upper tube FREDFET and is connected to the system MCU PWM1 (U1) and PWM3 (U2) output pins; INL pin: This pin is the gate drive control input terminal of the lower tube FREDFET and is connected to the system MCU PWM2 (U1) and PWM4 (U2) output pins; IPH pin: This pin is grounded through small signal resistors R1 and R4, providing the source and drain channel current information of the FREDFET under U1 and U2 respectively; XL pin: This pin is grounded through resistors R2 and R3 and is used to set the hardware self-locking current limiting threshold of the FREDFET under U1 and U2; LS pin: This pin is electrically connected to the source of the lower FREDFET integrated inside the chip; HB pin: This pin connects the source of the upper tube FREDFET and the drain of the lower tube FREDFET, and connects the two ends of the contactor coil.

6. The integrated intelligent closed-loop control method for an electromagnetic contactor according to claim 5, characterized in that: In the starting stage of the electromagnetic contactor, a constant magnetic flux linkage method is adopted to construct a coil voltage calculation module according to the following formula 1: the voltage u across the filter capacitor C1 is C1 Converted to contactor coil terminal voltage u coil : Where: u coil is the coil terminal voltage, A represents the coil terminal voltage polarity, R5 and R6 are the voltage divider resistances, ΔT is the PWM period, T on is the switch on time; According to the following formula 2, a current calculation module is constructed to calculate the output current i of the IPH pin of U2. sense Converted into contactor coil current i coil : i coil =i sense *gFormula 2; Where: i coil is the coil current value, i sense is the output current of the IPH pin of U2; g is the gain coefficient, which is related to the resistance value of R4; Then, the flux integral calculation module is constructed according to the following formula 3 to convert the coil voltage, current and resistance into magnetic flux for starting constant flux closed-loop control: ψ coil =∫(u coil -i coil R coil )dt formula 3; Where: coil is the magnetic flux, R coil is the coil resistance; The control of the electromagnetic contactor coil adopts the flux linkage / current hysteresis controller, f s is the hysteresis frequency, ε is the hysteresis width, and the magnetic flux of the corresponding comparison coil ψ coil Or coil current i coil With reference flux ψ ref Or reference current i ref Get the flux error Δψ or current error Δi, That is: Δψ=ψ coil -ψ ref / Δi=i coil -i ref ; The system MCU automatically selects the appropriate circuit state according to Δψ / Δi and ε and converts it into the driving state of the corresponding switch tube. The specific conversion is: when Δψ / Δi<0, select the +1 state circuit, turn on S1 and S4, and turn off S2 and S3 to quickly excite the coil; when 0≤Δψ / Δi≤ε, select the 0 state circuit, only turn on S4, turn off S1, S2, S3, so that the coil is slowly demagnetized; when Δψ / Δi>ε, select the -1 state circuit, turn off S1, S2, S3, S4, so that a negative voltage is applied to both ends of the coil, so that the coil is quickly demagnetized.

7. The integrated intelligent closed-loop control method for an electromagnetic contactor according to claim 6, characterized in that: The embedded control system uses a magnetic flux closed-loop control strategy to enable the electromagnetic contactor to adopt a constant magnetic flux closed-loop control during the starting process to minimize the starting operation work and suppress bounce. The embedded control system enables the electromagnetic contactor to adopt a noise adaptive suppression strategy during the holding process to effectively move the holding noise spectrum out of the audible range of the human ear; the embedded control system enables the electromagnetic contactor to use negative pressure rapid demagnetization during the opening process to increase the opening speed, thereby optimizing the performance of the electromagnetic contactor.

8. The integrated intelligent closed-loop control method for an electromagnetic contactor according to claim 7, characterized in that: The electromagnetic contactor uses the hysteresis controller described in claim 6 during the starting phase, and the control variable selects the coil flux ψ coil , specifically: Calculate the coil flux ψ according to formula 3 coil , and with the reference flux ψ ref By comparison, the hysteresis controller selects the appropriate circuit state, transforms the switch states of S1 to S4, and forms a flux closed-loop control, so that the starting flux tracks the reference flux; The electromagnetic contactor adopts a noise adaptive suppression strategy in the holding stage, which is also based on the hysteresis controller. It automatically captures the current value at the holding moment during the start-up flux closed-loop control process as the holding current reference value. After that, the control variable is changed from coil flux to coil current to perform current closed-loop control, that is, compare the coil current i coil and holding current reference value i ref Get Δi, and automatically select the appropriate circuit state according to Δi and ε and convert it into the driving state of the corresponding switch tube. When Δi<0, select the +1 state circuit, turn on S1 and S4, the PWM output duty cycle D1 is 100%, and the coil current rises rapidly; when 0<Δi<ε, select the 0 state circuit, only turn on S4, the PWM output duty cycle D2 is 0%, and the coil current decreases slowly; when Δi>ε, select the -1 state circuit, turn off S1~S4, the PWM output duty cycle D3 is 0%, and the coil current decreases rapidly; The coil current is kept dynamically constant at the reference value through the hysteresis controller; After the current is kept stable, N PWM cycles are executed in a loop, and the average duty cycle of N cycles is calculated according to the following formula 4: Then switch to PWM control mode. When -ε≤Δi≤ε, switch to pseudo open-loop control mode to update the duty cycle D. Assign D, the contactor is kept stable and silent under the constant duty cycle to achieve noise suppression; when Δi exceeds the hysteresis width ε, reselect the current hysteresis control mode, and recalculate when the current stabilizes again and -ε≤Δi≤ε And update to D, so that the coil current quickly tracks the reference value and maintains it silently; so as to achieve fast dynamic closed-loop regulation of the coil current and effectively suppress the noise; Where: is the average duty cycle of N cycles, a is the number of cycles of the +1 state circuit in N cycles, and D1 is the duty cycle of the +1 state circuit; b is the number of cycles of the 0 state circuit in N cycles, and D2 is the duty cycle of the 0 state circuit; c is the number of cycles of the -1 state circuit in N cycles, and D3 is the duty cycle of the -1 state circuit.

9. The integrated intelligent closed-loop control method for an electromagnetic contactor according to claim 8, characterized in that: Under the above hysteresis control, the electromagnetic contactor action process is optimized and controlled, specifically: during the starting process, the flux reference value is set to a constant value, and as the air gap between the moving and static cores decreases, the excitation current is automatically adjusted to make the flux dynamically stable at the reference value, and the contactor starts with constant flux; In the holding stage, the coil current at the holding moment is automatically captured as the current reference value of the holding stage to perform energy-saving holding. At the same time, a noise adaptive suppression strategy is adopted to reasonably switch the PWM control mode, taking into account the fast closed-loop regulation of the coil current and the suppression of high-frequency noise; During the disconnection process, all switch tubes are closed, full negative pressure disconnection is performed, the coil current drops rapidly, and the disconnection operation is completed quickly; thereby achieving optimized control of the starting, holding and disconnection processes of the electromagnetic contactor.

10. The integrated intelligent closed-loop control method for an electromagnetic contactor according to claim 9, characterized in that: During the constant magnetic chain starting process of the electromagnetic contactor, if the coil current exceeds the current limiting threshold set by resistors R2 and R3, the integrated chip performs hardware self-locking current limiting on the switch tube to protect the drive circuit from damage, which is used as the final coil overcurrent or short circuit protection; When the coil current needs to be limited cycle by cycle during the closed-loop control of the electromagnetic contactor flux linkage, the specific control method is as follows: the programmable DAC outputs the current limiting threshold i max , coil current i coil and current limiting threshold i max The MCU internal hardware comparator is connected to the MCU internal PWM output module. coil Greater than i max When the comparator outputs a complementary shutdown signal to the PWM module, the switch tube is turned off for one PWM cycle until the coil current i coil Less than the current limiting threshold i max When the PWM cycle is reopened, the flux closed-loop control is performed according to the above hysteresis control method. On the basis of the flux closed-loop control, software-programmable cycle-by-cycle current limiting is performed to control the maximum value of the coil current and ensure the reliable operation of the contactor. N is an integer not less than 100.

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