Contactor drive circuit, drive method, and energy storage capacitor state adaptive method

Abstract

This invention relates to the field of drive circuit technology, specifically to a contactor drive circuit, drive method, and energy storage capacitor state adaptive method, applied to high-power AC contactors; it includes: a main power supply, a reference ground and enable control circuit, a contactor coil (KM), an energy storage capacitor (C1), a first switching transistor (Q1), a second switching transistor (Q2), a gate pull-up branch, a gate drive branch, and a constant current charging circuit. This invention aims to solve the technical problems in existing high-power AC contactor drive schemes, such as high power capacity requirements, bus voltage drops, strong electromagnetic interference, and slow engagement response due to the peak starting power being entirely borne by the front-end power supply; severe heat generation in series resistor voltage reduction schemes; and the lack of precise charging management in energy storage capacitor-assisted starting schemes.

Description

Technical Field

[0001] This invention relates to the field of drive circuit technology, specifically to a contactor drive circuit, a drive method, and an adaptive method for the state of an energy storage capacitor. Background Technology

[0002] High-power AC contactors need to overcome the reaction force of the return spring and the inertia of the armature at the moment of engagement, and their coils must have sufficient ampere-turns. Therefore, a very large peak power is required at the moment of startup. However, after the armature is engaged and the air gap is closed, the power required to maintain engagement drops significantly. The power difference between startup and maintenance can be tens of times. This characteristic determines that the contactor drive circuit must strike a balance between instantaneous strong excitation and long-term low power consumption.

[0003] Currently, the control circuits of high-power AC contactors generally adopt the following two types of schemes:

[0004] Option 1: Direct DC or AC drive. Use the rated voltage directly, such as 48V DC or 220V AC, to trigger the contactor coil via a relay or optocoupler. To ensure reliable engagement, the power supply voltage must be high enough to overcome the reaction force of the large spring.

[0005] Option 2: Voltage-reduced sustaining drive. Addressing the significant difference in power consumption between startup and sustaining, a dual-coil structure is employed, or a high-power resistor is connected in series in the control circuit for voltage reduction: a full-voltage, high-current circuit is provided at startup; after the contactor engages, the voltage is reduced by resistor division or switching to the sustaining coil, thereby lowering sustaining power consumption.

[0006] The aforementioned prior art has the following drawbacks:

[0007] High power supply and circuit losses: Conventional high-power contactors require extremely high peak power at startup, such as 2000W. If directly supplied by a 48V power supply, the instantaneous current can reach over 40A, placing extremely high demands on the load-carrying capacity of the front-end power supply, which can easily lead to voltage drops and even damage to the preceding circuitry. If a series resistor is used for current limiting, the resistor will overheat significantly, resulting in extremely low overall system efficiency.

[0008] Slow drive response speed: Due to the limited current output capability of the pre-amplifier, the rise rate of the coil current is limited, the contactor's engagement time is relatively long, and the response delay is obvious.

[0009] Severe electromagnetic interference: The huge surge current at startup generates strong electromagnetic interference, affecting sensitive electronic equipment in the vicinity.

[0010] Lack of energy storage capacitor charging and discharging management: Although some solutions use energy storage capacitors to assist in starting, they often lack precise charging control: uncontrolled charging current can lead to excessive power supply load and bus voltage drop; and under multiple continuous operations, insufficient capacitor charging can easily cause the contactor to fail to engage properly. Summary of the Invention

[0011] This invention aims to solve the technical problems in existing high-power AC contactor drive schemes, such as high power capacity requirements, bus voltage drop, strong electromagnetic interference, and slow engagement response caused by the front-end power supply bearing all the peak starting power, as well as the serious heat generation of the series resistor voltage reduction scheme and the lack of precise charging management in the energy storage capacitor assisted starting scheme.

[0012] To achieve the above-mentioned objectives, the present invention provides a contactor drive circuit for use in high-power AC contactors; comprising:

[0013] Main power supply, reference ground and enable control circuitry;

[0014] A contactor coil (KM), one end of which forms a first node (P) and the other end forms a second node (M); the first node (P) is connected to the main power supply.

[0015] An energy storage capacitor (C1) is connected in series in the drive circuit of the contactor coil (KM). The positive terminal of the energy storage capacitor (C1) is connected to the first node (P), and the negative terminal of the energy storage capacitor (C1) forms the third node (N).

[0016] The first switching transistor (Q1) has its source connected to the main power supply, its drain connected to the third node (N), and its gate forming the fourth node (S).

[0017] The second switch (Q2) has its drain connected to the reference ground, its source connected to the second node (M), and its gate connected to the output of the enable control circuit.

[0018] The gate pull-up branch includes a pull-up resistor group connected between the main power supply and the fourth node (S);

[0019] The gate drive branch includes a Zener diode (ZD1) and a first resistor (R1), which are connected between the second node (M) and the fourth node (S). The anode of the Zener diode (ZD1) is connected to the second node (M), and the cathode is connected to the fourth node (S) via the first resistor (R1), which is used to clamp the potential of the fourth node (S) relative to the second node (M) when the second switch (Q2) is turned on.

[0020] The constant current charging circuit includes a transistor (Q3), an emitter resistor (R2), and a base bias resistor; the collector of the transistor (Q3) is connected to the third node (N), the emitter is connected to the reference ground via the emitter resistor (R2), and the base is connected to the first node (P) via the base bias resistor to obtain a bias potential;

[0021] The first diode (D1) has its anode connected to the base of the transistor (Q3) and its cathode connected to the second node (M).

[0022] A pull-down resistor (R3) is connected between the third node (N) and the reference ground;

[0023] in,

[0024] When the output signal of the enable control circuit is invalid, the second switch (Q2) is turned off, the second node (M) is floated at the potential of the first node (P) through the contactor coil (KM) so that the voltage across the contactor coil (KM) is zero, the first switch (Q1) is turned off because its gate is pulled up to the potential of the main power supply by the gate pull-up branch, and the transistor (Q3) operates in the amplification region and charges the energy storage capacitor (C1) with a constant current;

[0025] When the output signal of the enable control circuit is valid, the second switch (Q2) is turned on, pulling the second node (M) low to the potential of the reference ground, causing the fourth node (S) to be pulled low through the gate drive branch, thus turning on the first switch (Q1), raising the third node (N) to the potential of the main power supply, and simultaneously raising the potential of the first node (P) to the sum of the voltage across the energy storage capacitor (C1) and the main power supply voltage to form the pump-up start-up voltage; the first diode (D1) is forward-biased and turned on, clamping the base of the transistor (Q3) at a low level to stop the constant current charging circuit from working;

[0026] After the contactor coil (KM) enters the holding phase, the first switch (Q1) remains on to maintain the third node (N) at the potential of the main power supply, thereby keeping the energy storage capacitor (C1) fully discharged and preventing the energy storage capacitor (C1) from being recharged before the next start-up, which would cause pump failure.

[0027] Preferably, it further includes a second diode (D2) with its anode connected to the main power supply and its cathode connected to the first node (P); after the energy storage capacitor (C1) has discharged, the second diode (D2) is forward biased and conducts to bypass the energy storage capacitor (C1), and clamps the potential of the first node (P) at the level of the main power supply voltage minus the forward voltage drop of the first diode, so that the contactor coil (KM) is kept engaged by the main power supply, while preventing the energy storage capacitor (C1) from being reverse charged.

[0028] Preferably, the pull-up resistor group includes a second resistor (R4) and a third resistor (R5) connected in parallel.

[0029] Preferably, it also includes an accelerating capacitor (C2) connected between the fourth node (S) and the main power supply, used to make the potential of the fourth node (S) change rapidly with the second node (M) when the second switch (Q2) is turned on or off, so as to accelerate the turn-on and turn-off of the first switch (Q1).

[0030] Preferably, a freewheeling diode (D3) is included; the freewheeling diode (D3) is connected in reverse parallel across the two ends of the contactor coil (KM), the cathode of the freewheeling diode (D3) is connected to the first node (P), and the anode of the freewheeling diode (D3) is connected to the second node (M).

[0031] Preferably, a bus support capacitor (C3) is included, which is connected between the main power supply and the reference ground, to supplement the main power supply with instantaneous current at the moment the pump-up start-up voltage is formed, so as to suppress the voltage drop of the main power supply.

[0032] Preferably, the enable control circuit includes an optocoupler (U) and a current-limiting resistor (R6); the input terminal of the optocoupler (U) receives an external enable signal through the current-limiting resistor (R6), and the output terminal is connected to the gate of the second switching transistor (Q2).

[0033] Preferably, the constant current charging circuit is implemented by a constant current diode, or by a programmable precision reference source combined with a transistor, or by a step-down constant current DC-DC converter.

[0034] Based on the above-described contactor driving circuit, the present invention also provides a contactor driving method, comprising the following steps:

[0035] S100. During the period when the output signal of the enable control circuit is invalid, the second switch (Q2) is turned off, causing the second node (M) to float at the potential of the first node (P) through the contactor coil (KM) so that the voltage across the contactor coil (KM) is zero. At the same time, the fourth node (S) is pulled up to the potential of the main power supply by the gate pull-up branch so that the first switch (Q1) is turned off, and the energy storage capacitor (C1) is charged by the transistor (Q3) with a constant current.

[0036] S200: When the output signal of the enable control circuit is valid, the second switch (Q2) is turned on to pull the second node (M) low to the potential of the reference ground. At the same time, the fourth node (S) is pulled low through the gate drive branch, causing the first switch (Q1) to turn on, and the third node (N) is raised to the potential of the main power supply. Based on the characteristic that the voltage across the capacitor cannot change abruptly, the potential of the first node (P) is synchronously raised to the sum of the voltage across the energy storage capacitor (C1) and the main power supply voltage, forming a pump-up start-up voltage. Simultaneously, the first diode (D1) is forward-biased and turned on, clamping the base of the transistor (Q3) at a low level, causing the constant current charging circuit to stop working.

[0037] S300, the energy storage capacitor (C1) is discharged through the contactor coil (KM), and the voltage across its terminals decays exponentially, and the potential of the first node (P) is smoothly reduced from the pump-up starting voltage to the main power supply voltage.

[0038] S400: After the energy storage capacitor (C1) has finished discharging, the second diode (D2) is forward-biased and conducts to bypass the energy storage capacitor (C1), and the potential of the first node (P) is clamped at the level of the main power supply voltage minus the forward voltage drop of the first diode, so that the contactor coil (KM) is kept engaged by the main power supply; and during this stage, the first switch (Q1) is kept on, so that the third node (N) is maintained at the potential of the main power supply and the energy storage capacitor (C1) remains in the state of being fully discharged;

[0039] S500: After the output signal of the enable control circuit is removed, the second switch (Q2) is turned off, so that the current of the contactor coil (KM) is discharged to zero through the circuit formed by the freewheeling diode (D3);

[0040] S600, the first diode (D1) is reverse biased again, the transistor (Q3) re-enters the amplification region, and the main power supply recharges the energy storage capacitor (C1) with a constant current through the second diode (D2).

[0041] Preferably, in step S100, the transistor (Q3) charges the energy storage capacitor (C1) with a constant current, the constant current I being determined by the base bias potential V of the transistor (Q3). B Collector potential V BE Together with the emitter resistor (R2), it satisfies = Furthermore, the constant charging current is less than the pull-in threshold current of the contactor coil (KM); when the energy storage capacitor (C1) is nearly fully charged, the amplification process automatically terminates because the collector voltage of the transistor (Q3) is depleted and it exits the amplification region.

[0042] Preferably, the value of the pull-down resistor (R3) is selected to satisfy the following conditions: when the third node (N) is maintained at the voltage of the main power supply in step S400, the leakage current flowing through the pull-down resistor (R3) and its power consumption do not exceed a preset value; and the pull-down resistor (R3) provides a defined low potential to the third node (N) when the first switch (Q1) is turned off.

[0043] Preferably, the discharge time constant is determined by the product of the capacitance C of the energy storage capacitor (C1) and the equivalent resistance R of the contactor coil (KM). = The duration of the pump-up starting voltage is on the same order of magnitude as the engagement time of the contactor coil (KM), so that the full duration of the pump-up starting voltage covers the entire engagement process of the contactor.

[0044] Based on the above contactor driving method, a third aspect of the present invention also provides an adaptive method for the state of an energy storage capacitor, comprising the following steps:

[0045] T100. During each startup step S300, the discharge voltage curve across the energy storage capacitor (C1) is collected.

[0046] T200. Measure the time taken for the discharge voltage curve to drop from the initial discharge value to 36.8% of the initial value, and obtain the discharge time constant;

[0047] T300, In step S400, after the energy storage capacitor (C1) has finished discharging, the steady-state holding voltage and steady-state holding current of the contactor coil (KM) are obtained, and the equivalent resistance of the contactor coil (KM) is calculated.

[0048] T400. Divide the discharge time constant by the equivalent resistance to obtain the actual capacitance value of the energy storage capacitor (C1);

[0049] T500 compares the actual capacitance value with the nominal capacitance value to obtain the aging coefficient, and outputs an alarm signal when the aging coefficient is lower than a preset threshold, prompting the replacement of the energy storage capacitor (C1), or prohibiting the next enabling action.

[0050] T600: Calculate the charging time required to fully charge the energy storage capacitor (C1) based on the actual capacitance value, and set the minimum action interval between two enabling actions accordingly, so that the energy storage capacitor (C1) is fully charged before each start-up.

[0051] Preferably, the method further includes: calculating the equivalent series resistance of the energy storage capacitor (C1) based on the ratio of the voltage drop value of the energy storage capacitor (C1) at the moment of discharge initiation to the discharge current; and outputting an alarm signal when the equivalent series resistance exceeds a preset upper limit.

[0052] The technical solution provided by this invention achieves the following beneficial effects: Through the energy transport mechanism of charging, pumping, and discharging the energy storage capacitor, the instantaneous high-power portion that originally required direct power supply is converted into instantaneous energy provided by the capacitor, significantly reducing the peak current pressure and capacity requirements of the front-end power supply, greatly reducing the burden on the front-end power supply, and lowering the system power supply cost; utilizing a pump-up voltage of approximately twice the rated voltage for high-voltage start-up, the coil current rise rate is multiplied, significantly shortening the response time of the pull-in action; after start-up, it quickly drops back to low-voltage maintenance, and the transition between high-voltage start-up and low-voltage maintenance does not pass through any energy-consuming components, avoiding the serious heat generation problem caused by the series resistor scheme and extending circuit life; the constant current charging design makes the capacitor charging process stable and controllable, avoiding voltage drops caused by excessive charging current in the front-end power supply, and ensuring that the capacitor can be stably charged throughout the continuous operating cycle, improving system reliability; the start-up energy mainly comes from the stable discharge of the energy storage capacitor rather than the surge output of the power supply, significantly reducing the current change rate on the main power supply side, thereby suppressing conducted and radiated interference and electromagnetic interference. Significantly reduced; the single conduction action of the second switch simultaneously completes three functions: connecting the coil circuit, turning on the first switch to realize pumping, and turning off the constant current charging circuit. The charging mode and the pumping mode are naturally mutually exclusive, eliminating the need for additional interlocking logic circuits; the first diode serves a triple function: charging path, preventing reverse current injection during pumping up, and bypassing the energy storage capacitor after discharge. The freewheeling diode absorbs the reverse electromotive force when the coil is turned off and clamps the switch. The Zener diode clamps the gate-source voltage of the first switch, ensuring long-term stable operation under strong electromagnetic interference environments and realizing multiple protection mechanisms; without adding any sensors or excitation injection circuits, the actual capacitance value and equivalent series resistance of the energy storage capacitor can be identified online using the discharge curve itself, timely detecting capacitor aging and issuing alarms or prohibiting action before it affects the driving performance, improving the reliability of long-term operation; by collecting the discharge curve of each start-up action to deduce the actual capacitance value of the capacitor, and then setting the minimum action interval or prohibiting action when the capacitor deteriorates, the driving circuit can obtain consistent and predictable pull-in performance throughout the entire life cycle of the capacitor. Attached Figure Description

[0053] Figure 1 This is a contactor drive circuit diagram according to an embodiment of the present invention;

[0054] Figure 2 This is a flowchart of the contactor driving method according to an embodiment of the present invention;

[0055] Figure 3 This is a flowchart of the energy storage capacitor state adaptive method according to an embodiment of the present invention.

[0056] In the diagram: +48V_ISO, main power supply; GND48_ISO, reference ground; KM, contactor coil; P, first node; M, second node; N, third node; S, fourth node; C1, energy storage capacitor; C2, accelerating capacitor; C3, bus support capacitor; Q1, first switching transistor; Q2, second switching transistor; Q3, transistor; ZD1, Zener diode; D1, first diode; D2, second diode; D3, freewheeling diode; R1, first resistor; R2, emitter resistor; R3, pull-down resistor; R4, second resistor; R5, third resistor; R6, current limiting resistor. Detailed Implementation

[0057] The technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described invention is only a part of the invention, not all of the invention. All other inventions obtained by those skilled in the art based on the invention without creative effort are within the scope of protection of this invention.

[0058] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0059] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0060] In existing high-power AC contactor drive solutions, the peak starting power is entirely borne by the front-end power supply, resulting in high power capacity requirements, bus voltage drop, strong electromagnetic interference, slow engagement response, severe heat generation in series resistor voltage reduction schemes, and a lack of precise charging management in energy storage capacitor-assisted starting schemes.

[0061] like Figure 1 As shown, in order to solve the above-mentioned technical problems, this embodiment provides a contactor drive circuit that is applied to a high-power AC contactor.

[0062] The following is the overall structure of the contactor drive circuit:

[0063] The contactor drive circuit of this embodiment includes a contactor coil KM, a main power supply +48V_ISO, a reference ground GND48_ISO, an enable control circuit, a constant current charging circuit, an energy storage and voltage pumping branch, a gate drive and clamping branch, a release and protection circuit, and a bus support circuit.

[0064] One end of the contactor coil KM forms the first node P, and the other end forms the second node M. The first node P is connected to the main power supply +48V_ISO through the second diode D2. The anode of the second diode D2 is connected to the main power supply +48V_ISO, and the cathode is connected to the first node P.

[0065] In the enable control circuit, the input terminal of optocoupler U receives the external enable signal RLYAC via current-limiting resistor R6, and its output terminal is connected to the gate of the second switch Q2. The function of optocoupler U is to electrically isolate the signal side from the main power supply +48V_ISO power side. The drain of the second switch Q2 is connected to reference ground GND48_ISO, its source is connected to the second node M, and its gate is connected to the output terminal of the enable control circuit.

[0066] The energy storage and voltage boosting branch includes an energy storage capacitor C1 and a first switching transistor Q1. The energy storage capacitor C1 is connected in series in the drive circuit of the contactor coil KM. The positive terminal of the energy storage capacitor C1 is connected to the first node P, and the negative terminal of the energy storage capacitor C1 forms the third node N. The source of the first switching transistor Q1 is connected to the main power supply +48V_ISO, the drain is connected to the third node N, and the gate forms the fourth node S.

[0067] The constant current charging circuit consists of transistor Q3, first diode D1, and base bias resistors, including fourth resistor R7 and fifth resistor R8. The collector of transistor Q3 is connected to the third node N, the emitter is connected to reference ground GND48_ISO via emitter resistor R2, and the base is connected to the first node P via the base bias resistor. The bias potential is obtained by voltage division using fourth resistor R7 and fifth resistor R8. The constant charging current satisfies... = The anode of the first diode D1 is connected to the base of the transistor Q3, and the cathode is connected to the second node M. The pull-down resistor R3 is connected between the third node N and the reference ground GND48_ISO to provide a defined low potential to the third node N when the first switch Q1 is turned off, preventing it from floating.

[0068] It's acceptable. The constant current charging circuit can be implemented using a constant current diode, a programmable precision reference source with a transistor, or a step-down constant current DC-DC converter. When using a constant current DC-DC converter instead of a linear constant current source, the transistor power consumption and temperature rise in the initial stage of charging can be further reduced.

[0069] It's important to note here that the pull-down resistor R3 and the constant current charging circuit have different functions. If only the pull-down resistor R3 forms the charging path, the charging time constant will be... = Given R3 = 22kΩ, C1 = 15000μF, and the charging time constant... =22kΩ×15000μF≈330s, fully charging takes about 27.5 minutes, which cannot meet the requirements of industrial applications; if the resistance value of the pull-down resistor R3 is reduced to speed up charging, then during the maintenance phase when the third node N is clamped at 48V of the main power supply +48V_ISO, a current of 48V / R3 will continuously flow through the pull-down resistor R3. For example, take... When the resistance is 100Ω, the power consumption will reach 23W, which exceeds the holding power consumption of the contactor coil KM itself.

[0070] The function of a constant current charging circuit is to provide a controllable path that is equivalent to low resistance during charging and automatically exits without generating additional power consumption after charging is completed, thereby simultaneously satisfying the two contradictory requirements of fast charging and low leakage during the maintenance phase.

[0071] After the energy storage capacitor C1 has finished discharging, the second diode D2 is forward biased and conducts to bypass the energy storage capacitor C1, and clamps the potential of the first node P at the level of the main power supply +48V_ISO voltage minus the forward voltage drop of the first diode D1, so that the contactor coil KM is kept engaged by the main power supply +48V_ISO, while preventing the energy storage capacitor C1 from being reverse charged.

[0072] The gate drive and clamping branch includes the gate pull-up branch and the gate drive branch.

[0073] The gate pull-up branch includes a pull-up resistor group connected between the main power supply +48V_ISO and the fourth node S. The pull-up resistor group includes a second resistor R4 and a third resistor R5 connected in parallel.

[0074] The gate drive branch includes a Zener diode ZD1 and a first resistor R1, connected between the second node M and the fourth node S. The anode of the Zener diode ZD1 is connected to the second node M, and the cathode is connected to the fourth node S via the first resistor R1. This is used to clamp the potential of the fourth node S relative to the second node M when the second switch Q2 is turned on.

[0075] In the gate drive and clamping branch, if the following technical parameters are used: R4=R5=7.5kΩ, ZD1 voltage regulation value=12V, R1=510Ω, when the second switch Q2 is turned on, the third node M is 0V. The reverse breakdown of the Zener diode ZD1 causes the potential of the fourth node S to be determined by the regulated voltage of 12V and the voltage drop across the first resistor R1. The first switch Q1 then obtains the gate-source voltage required for conduction. In practical applications, the values ​​of the above parameters should be checked in conjunction with the rated maximum value of the gate-source voltage of the selected first switch Q1. If necessary, the resistance value of the first resistor R1 or the voltage regulation value of the Zener diode ZD1 should be adjusted to ensure that the gate-source voltage falls within the allowable range of the device.

[0076] It also includes an accelerating capacitor C2 connected between the fourth node S and the main power supply +48V_ISO. Utilizing the characteristic that the voltage across the capacitor cannot change abruptly, the potential of the fourth node S changes rapidly with the second node M when the second switch Q2 is turned on or off, thereby accelerating the turn-on and turn-off of the first switch Q1.

[0077] In the release and protection circuit, the freewheeling diode D3 is connected in reverse parallel across the two ends of the contactor coil KM, with its cathode connected to the first node P and its anode connected to the third node M. It is used to absorb the reverse electromotive force generated when the contactor coil KM is turned off and to clamp the drain of the second switching transistor Q2 at a safe potential.

[0078] In the bus support circuit, the bus support capacitor C3 is connected between the main power supply +48V_ISO and the reference ground GND48_ISO. It is used to supplement the instantaneous current to the main power supply +48V_ISO at the moment the pump-up start voltage is formed, and to suppress the voltage drop of the main power supply +48V_ISO.

[0079] In the above circuit structure, the selection of each component must ensure that the circuit structure can operate normally.

[0080] When selecting the first switching transistor Q1, the drain-source withstand voltage of the first switching transistor Q1 should not be lower than the pump-up start voltage and should have sufficient margin; when selecting the second switching transistor Q2, the drain-source voltage it withstands during the turn-off freewheeling period is approximately the first node P potential plus the forward voltage drop of the freewheeling diode D3, and its withstand voltage should be selected accordingly.

[0081] When selecting the second diode D2, it is necessary to withstand the high voltage after pumping, and its reverse withstand voltage should be selected according to the pumping voltage; when selecting the freewheeling diode D3, a fast recovery or Schottky diode should be used, and its forward current rating should not be less than the peak current of the coil.

[0082] When selecting the value of the energy storage capacitor C1, it should be combined with the selection of the equivalent resistance R of the contactor coil KM to ensure the discharge time constant. = The engagement time is on the same order of magnitude as that of a contactor. If the voltage is too low, the pump will not be able to maintain the high pressure for long enough, and the voltage will drop before the engagement is complete. If the value is too large, the capacitor discharges extremely slowly, the pumped energy is not fully released, and the minimum interval required between the two actions is extended.

[0083] When selecting the value of the pull-down resistor R3, two constraints should be considered: Firstly, its resistance should be large enough to ensure that the leakage current and power consumption generated when the third node N is clamped to the main power supply voltage during the holding phase are negligible. For example, a 22kΩ resistor would have a leakage current of approximately 2.2mA and a power consumption of approximately 0.1W. Secondly, its resistance should be small enough to provide a definite low potential for the third node N when the first switch Q1 is turned off, preventing it from floating and causing malfunctions. Simultaneously, the selection of the constant current charging current I also needs to consider two constraints: Firstly, it should be much smaller than the pull-in threshold current of the contactor coil KM to avoid malfunctions caused by the charging current or excessive power supply load. Secondly, the minimum interval between two actions should not be less than the capacitor charging time. = This ensures that the capacitor is fully charged before each startup.

[0084] During operation, the output signal of the enable control circuit is divided into two states: invalid and valid. The complete operation process is further divided into five stages:

[0085] Phase 1: Constant current charging and energy storage phase.

[0086] When the output signal of the enable control circuit is invalid, the second switch Q2 is turned off. At this time, the lower end of the contactor coil KM is suspended through the second node M. Since there is no current or voltage drop in the contactor coil KM, the second node M is floated at the potential of the first node P through the contactor coil KM. Therefore, the voltage across the contactor coil KM is zero, and there will be no malfunction due to energization. The fourth node S is pulled up to a potential close to the main power supply +48V_ISO by the gate pull-up branch. The gate-source voltage of the first switch Q1 is approximately -0.06V, far below the conduction threshold, so the first switch Q1 is turned off. The anode potential of the first diode D1 is lower than its cathode potential and is reverse-biased, thus not interfering with the base bias of the transistor Q3. The transistor Q3 operates in the amplification region, charging the energy storage capacitor C1 with a constant current through the second diode D2. Charging current = The charging current is determined solely by the base bias potential and emitter resistance, and is independent of the collector potential. During charging, the first node P is clamped by the first diode D1 at the level of the main power supply +48V_ISO voltage minus its forward voltage drop. The potential of the third node N gradually decreases from this value to zero as the voltage of the energy storage capacitor C1 rises. When the energy storage capacitor C1 is nearly fully charged, the transistor Q3 exits the amplification region due to the depletion of its collector voltage, and the charging current naturally tends to zero, achieving self-consistent termination without the need for an additional charging completion detection circuit.

[0087] Phase Two: Voltage Pump Start-up Phase.

[0088] The key to enabling the output signal of the control circuit in this embodiment lies in the linkage effect of the second node M. The optocoupler U output turns on the second switch Q2, pulling the second node M low to the reference ground GND48_ISO potential. This single action triggers three results simultaneously: First, the lower end of the contactor coil KM is grounded, connecting the drive circuit; second, the fourth node S is pulled low via the gate drive branch, causing the gate-source voltage of the first switch Q1 to become negative and turn on, raising the third node N to the main power supply +48V_ISO potential. Based on the characteristic that the voltage across a capacitor cannot change abruptly, the potential of the first node P is synchronously raised to the energy storage capacitor C. 1. The sum of the voltage across the terminals and the main power supply +48V_ISO voltage forms a pump-up starting voltage across the contactor coil KM. The current in the contactor coil KM rises at a rate much higher than that under the rated voltage, and the armature starts quickly. 2. The first diode D1 is forward biased and conducts because the anode potential is higher than the cathode potential. This clamps the base of transistor Q3 to a low level, causing transistor Q3 to exit the amplification region and stop charging, thus preventing the main power supply +48V_ISO from forming a DC path through the first switching transistor Q1, transistor Q3, and emitter resistor R2.

[0089] Phase 3: Energy release and voltage drop phase.

[0090] The energy storage capacitor C1 continuously discharges through the contactor coil KM, and the voltage across its terminals decays exponentially. Consequently, the potential at the first node P smoothly drops from the pump-up voltage back to the main power supply +48V_ISO voltage. Discharge time constant. = The pump's boost pressure is on the same order of magnitude as the contactor's engagement time, ensuring the entire engagement process is fully covered. During this stage, the energy provided by the discharge of the storage capacitor C1 and the energy provided by the main power supply +48V_ISO are superimposed on the contactor coil KM, jointly overcoming the spring reaction force to complete the engagement.

[0091] Phase 4: Low-pressure steady-state maintenance phase.

[0092] After the energy storage capacitor C1 finishes discharging, its voltage approaches zero and attempts to reverse. At this time, the second diode D2 is forward-biased and conducts, bypassing the energy storage capacitor C1 and clamping the potential of the first node P at the level of the main power supply +48V_ISO voltage minus the forward voltage drop of the second diode D2. The contactor coil KM is maintained engaged by the main power supply +48V_ISO. The transition from high-voltage startup to low-voltage maintenance is accomplished by the discharge characteristics of the energy storage capacitor C1 itself and the bypassing effect of the second diode D2, without the need for a timing switching circuit, PWM converter, or dual-coil structure. After the contactor coil KM enters the maintenance engagement stage, the first switch Q1 remains on to maintain the third node N at the potential of the main power supply +48V_ISO, thus keeping the energy storage capacitor C1 in a fully discharged state and preventing it from being recharged before the next startup, which could lead to pump failure.

[0093] If the first switch Q1 is turned off at this time, the second node N will drop to zero potential through the pull-down resistor R3, and the first node P will be clamped to the main power supply +48V_ISO potential by the second diode D2. The energy storage capacitor C1 will reappear with a positive voltage of approximately the main power supply potential and be recharged, resulting in a lack of discharge process and pump failure during the next startup.

[0094] Phase 5: Shutdown and Reset Phase.

[0095] When the output signal of the enable control circuit is removed, the second switch Q2 is turned off. The current in the contactor coil KM cannot change abruptly. The current is discharged through the loop formed by the freewheeling diode D3, generating a reverse electromotive force at the second node M. The freewheeling diode D3 conducts and clamps the second node M at the level of the first node P potential plus the forward voltage drop of the diode, providing a discharge loop for the current in the contactor coil KM. The coil current follows... = The voltage decays to zero, simultaneously clamping the drain of the second switch Q2 to a safe potential. Then, the second diode D2 returns to reverse bias, and transistor Q3 re-enters the amplification region. The main power supply recharges the energy storage capacitor C1 with a constant current through the second diode D2, and the circuit resets, awaiting the next operation.

[0096] The core concept of the contactor drive circuit provided in this embodiment is to connect an energy storage capacitor in series in the drive circuit of the contactor coil. Utilizing the characteristic that the voltage across the capacitor cannot change abruptly, the voltage pre-stored in the energy storage capacitor is injected into the drive circuit at the moment of startup, causing the voltage across the contactor coil to be pumped up from the main power supply voltage to approximately twice the main power supply voltage. After the startup process ends, the energy storage capacitor is fully discharged and naturally becomes equivalent to a wire. The voltage of the contactor coil automatically drops back to the main power supply voltage and enters the low-voltage maintenance stage. At the same time, a constant current charging circuit is connected in series in the negative terminal circuit of the energy storage capacitor, making the charging process of the capacitor stable and controllable, and the charging current does not flow through the contactor coil.

[0097] like Figure 2 As shown, based on the above-described contactor drive circuit, the second aspect of this embodiment also provides a contactor drive method, including the following steps:

[0098] S100. During the period when the output signal of the enable control circuit is invalid, the second switch Q2 is turned off, causing the second node M to float at the potential of the first node P through the contactor coil KM, thus making the voltage across the contactor coil KM zero. At the same time, the fourth node S is pulled up to the potential of the main power supply +48V_ISO by the gate pull-up branch, causing the first switch Q1 to turn off, and the energy storage capacitor C1 is charged by the transistor Q3 with a constant current.

[0099] In step S100, the constant charging current I is determined by the base bias potential V of transistor Q3. B Collector potential V BE Together with the emitter resistor R2, it is determined to satisfy the following conditions. = Furthermore, the constant charging current is less than the pull-in threshold current of the contactor coil KM; when the energy storage capacitor C1 is nearly fully charged, the amplification process automatically terminates because the collector voltage of the transistor Q3 is depleted and it exits the amplification region.

[0100] S200: When the output signal of the enable control circuit is valid, the second switch Q2 is turned on to pull the second node M down to the reference ground GND48_ISO potential. This single action simultaneously performs three functions: connecting the contactor coil KM circuit, turning on the first switch Q1 to raise the third node N to the main power supply +48V_ISO voltage to achieve voltage boosting, and turning on the first diode D1 to turn off the constant current charging circuit.

[0101] Specifically, the fourth node S is pulled low via the gate drive branch, causing the first switch Q1 to conduct, raising the third node N to the potential of the main power supply +48V_ISO. Based on the characteristic that the voltage across the capacitor cannot change abruptly, the potential of the first node P is synchronously raised to the sum of the voltage across the energy storage capacitor C1 and the voltage of the main power supply +48V_ISO, forming the pump-up start-up voltage. At the same time, the first diode D1 is forward biased and conducts, clamping the base of the transistor Q3 at a low level, causing the constant current charging circuit to stop working.

[0102] S300 causes the energy storage capacitor C1 to discharge through the contactor coil KM, and the voltage across its terminals decays exponentially. Consequently, the potential of the first node P smoothly drops from the pump-up starting voltage back to the main power supply +48V_ISO voltage.

[0103] In this step, the energy provided by the discharge of the energy storage capacitor C1 is superimposed on the contactor coil KM along with the energy provided by the main power supply +48V_ISO.

[0104] S400. After the energy storage capacitor C1 has finished discharging, the second diode D2 is forward-biased and conducts to bypass the energy storage capacitor C1, and the potential of the first node P is clamped at the level of the main power supply +48V_ISO voltage minus the forward voltage drop of the second diode D2, so that the contactor coil KM is kept engaged by the main power supply +48V_ISO; and during this stage, the first switch Q1 is kept on, so that the third node N is maintained at the potential of the main power supply +48V_ISO, thus keeping the energy storage capacitor C1 in the state of being fully discharged.

[0105] In this step, the value of the pull-down resistor R3 should be selected to meet the following requirements: when the third node N is maintained at the main power supply voltage of +48V_ISO, the leakage current flowing through the pull-down resistor R3 and its power consumption do not exceed the preset value; and the pull-down resistor R3 provides a certain low potential for the third node N when the first switch Q1 is turned off.

[0106] The discharge time constant is determined by the product of the capacitance C of the energy storage capacitor C1 and the equivalent resistance R of the contactor coil KM. = The engagement time of the contactor coil KM is on the same order of magnitude, ensuring that the full duration of the pump-up starting voltage covers the entire engagement process of the contactor.

[0107] The transition between step S300 and step S400 is accomplished by the discharge characteristics of the energy storage capacitor C1 itself and the bypassing effect of the second diode D2. No timing switching circuit, pulse width modulation converter or dual coil structure is required, so the control logic is simple, the number of components is small and the reliability is high.

[0108] S500: After the output signal of the enable control circuit is removed, the second switch Q2 is turned off, so that the current of the contactor coil KM is discharged to zero through the circuit formed by the freewheeling diode D3.

[0109] S600 restores the first diode D1 to reverse bias, and the transistor Q3 re-enters the amplification region. The main power supply +48V_ISO is used to recharge the energy storage capacitor C1 with a constant current through the second diode D2.

[0110] Based on the contactor driving method described above, the third aspect of this embodiment also provides an adaptive method for the state of the energy storage capacitor, which reuses the discharge and maintenance processes of the driving circuit itself without adding any additional sensors or excitation injection circuits, such as... Figure 3 As shown, it includes the following steps:

[0111] T100. During each startup step S300, the discharge voltage curve across the energy storage capacitor C1 is collected.

[0112] T200: Measure the time taken for the discharge voltage curve to drop from the initial discharge value to 36.8% of that initial value, and obtain the discharge time constant.

[0113] During the discharge phase, the voltage across the energy storage capacitor C1 follows the formula... = The voltage decreases according to a regular pattern. The time it takes for the voltage to drop from the initial discharge value V0 to 0.368V0 is measured; this time is the discharge time constant. .

[0114] Where the constant Defined as the time it takes for the voltage to decay to 1 / e of its initial value. Its acquisition process is as follows: The expression for RC discharge: = , = . Put t= Substitute in: = =0.367879≈36.8

[0115] Therefore, 36.8% is 1 / e, not the selected measurement point, but the definition of the time constant τ itself.

[0116] T300, In step S400, after the energy storage capacitor C1 has finished discharging, the steady-state holding voltage and steady-state holding current of the contactor coil KM are obtained, and the equivalent resistance of the contactor coil KM is calculated.

[0117] The steady-state sustaining voltage is determined by the topology and is a known quantity. After entering the sustaining phase, the energy storage capacitor C1 is fully discharged, and the second diode D2 is forward-biased and conducts, bypassing the energy storage capacitor C1. The voltage drop across the second diode D2 is set to 0.5V, and point P at the first node is clamped by the second diode D2. = =48V - 0.5V = 47.5V. The second node M at the lower end of the contactor coil KM is pulled to ground (0V) by the second switching transistor Q2, so the voltage across the contactor coil KM is 47.5V. This value is a known constant determined by the topology and diode voltage drop.

[0118] The steady-state holding current needs to be measured after stabilization. When initially entering the holding phase, the current in the contactor coil KM still carries a pump-up margin. The inductor current is calculated according to... = Attenuation, approximately 5 The stable current value I was obtained after 50ms. hold .

[0119] The equivalent resistance of the contactor coil KM is obtained as follows: .

[0120] T400, divide the discharge time constant by the equivalent resistance to obtain the actual capacitance value of the energy storage capacitor C1.

[0121] T500 compares the actual capacitance value with the nominal capacitance value to obtain the aging coefficient, and outputs an alarm signal when the aging coefficient is lower than the preset threshold, prompting the replacement of the energy storage capacitor C1, or prohibiting the next enabling action.

[0122] T600 calculates the charging time required to fully charge the energy storage capacitor C1 based on the actual capacitance value, and sets the minimum action interval between two enable actions accordingly, so that the energy storage capacitor C1 is fully charged before each start-up.

[0123] It also includes: calculating the equivalent series resistance of the energy storage capacitor C1 based on the ratio of the voltage drop value of the energy storage capacitor C1 at the moment of discharge initiation to the discharge current; and outputting an alarm signal when the equivalent series resistance exceeds a preset upper limit.

[0124] It is important to note that the adaptive state method for the energy storage capacitor in this embodiment is based on a constraint determined by the topology itself: the energy storage capacitor C1 is charged by the main power supply +48V_ISO via the second diode D2, and its final charging value is clamped at the level of the main power supply +48V_ISO voltage minus the forward voltage drop of the diode, approximately 47.5V, and cannot be increased further. Therefore, when capacitance decay causes a pump-up energy gap, it cannot be compensated by increasing the charging voltage. Calculated according to the aforementioned example parameters, the available pump-up energy of the energy storage capacitor C1 changes with capacitance decay as follows: approximately 16.9J of energy storage at a new 15000μF; approximately 13.5J of energy storage at 20% decay at 12000μF, with an energy gap of approximately 3.4J; and approximately 10.2J of energy storage at 40% decay at 9000μF, with an energy gap of approximately 6.8J. Therefore, the only way to deal with this is to promptly detect aging and take measures such as replacement or limiting the operating frequency. The adaptive control measures adopted in this embodiment are to reduce the operating frequency to extend the charging time, output a replacement prompt, or disable the enable operation when the capacitor is severely degraded, so as to ensure the reliability of the drive circuit even when the energy gap cannot be compensated.

[0125] In the following example parameters, the main power supply +48V_ISO is 48V, C1 is 15000μF, the contactor coil KM has an equivalent resistance of 5Ω and an equivalent inductance of 50mH, and the forward voltage drop of the second diode D2 is 0.5V. The simulation results are as follows: charging time is approximately 7.1s; pump-up starting voltage is approximately 95.5V; the peak current of the contactor coil KM is approximately 15.4A, occurring approximately 24ms after startup; the holding current is approximately 9.5A; after the energy storage capacitor C1 finishes discharging, it experiences a reverse voltage of approximately −0.5V, clamped by the second diode D2; the turn-off freewheeling time constant is... = =10ms, decays to zero in about 50ms, and releases about 2.3J of energy.

[0126] A comparison was made between this embodiment and the 48V direct drive method during startup, with the following results: At startup, this embodiment causes the voltage across the contactor coil KM to jump from 48V to approximately 95.5V, with the peak coil current reaching approximately 15.4A. In contrast, the steady-state current under the 48V direct drive method is only 9.6A, representing a peak current increase of over 50%. In the peak instantaneous power, the portion borne by the energy storage capacitor C1 is roughly equivalent to that borne by the main power supply +48V_ISO, meaning that the energy storage capacitor C1 shares approximately half of the instantaneous power with the front-end power supply, thus significantly reducing the peak current pressure on the front-end power supply. Using 8A as the pull-in threshold current for the contactor coil KM, the pull-in response time in this embodiment is approximately 5.5ms, while the 48V direct drive method is approximately 17.9ms, resulting in a response time advancement of approximately 12.4ms. Furthermore, when the pull-in threshold current exceeds 9.6A, the 48V direct drive method cannot engage the contactor at all, while this embodiment can still reliably engage it.

[0127] The above comparison shows that the technical solution provided in this embodiment can not only shorten the pull-in response time, but more importantly, it makes it feasible to use a higher impedance coil to reduce the holding power consumption, which is a technical effect that cannot be covered by simply improving the quantity.

[0128] It should be noted that the above embodiment takes a 48V DC power supply system as an example, but the core architecture of the present invention is also applicable to DC power supply systems of other voltage levels, such as 24V, 12V or higher 110V systems. It is only necessary to change the withstand voltage of the energy storage capacitor, the withstand voltage parameters of each switching transistor, the voltage regulation value of the Zener diode and the resistance value of the gate resistor according to the voltage level.

[0129] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A contactor drive circuit, characterized in that: Applications in high-power AC contactors; including: Main power supply, reference ground, and enable control circuitry; A contactor coil (KM), one end of which forms a first node (P) and the other end forms a second node (M); the first node (P) is connected to the main power supply. An energy storage capacitor (C1) is connected in series in the drive circuit of the contactor coil (KM). The positive terminal of the energy storage capacitor (C1) is connected to the first node (P), and the negative terminal of the energy storage capacitor (C1) forms the third node (N). The first switching transistor (Q1) has its source connected to the main power supply, its drain connected to the third node (N), and its gate forming the fourth node (S). The second switch (Q2) has its drain connected to the reference ground, its source connected to the second node (M), and its gate connected to the output of the enable control circuit. The gate pull-up branch includes a pull-up resistor group connected between the main power supply and the fourth node (S); The gate drive branch includes a Zener diode (ZD1) and a first resistor (R1), which are connected between the second node (M) and the fourth node (S). The anode of the Zener diode (ZD1) is connected to the second node (M), and the cathode is connected to the fourth node (S) via the first resistor (R1), which is used to clamp the potential of the fourth node (S) relative to the second node (M) when the second switch (Q2) is turned on. The constant current charging circuit includes a transistor (Q3), an emitter resistor (R2), and a base bias resistor; the collector of the transistor (Q3) is connected to the third node (N), the emitter is connected to the reference ground via the emitter resistor (R2), and the base is connected to the first node (P) via the base bias resistor to obtain a bias potential; The first diode (D1) has its anode connected to the base of the transistor (Q3) and its cathode connected to the second node (M). A pull-down resistor (R3) is connected between the third node (N) and the reference ground; in, When the output signal of the enable control circuit is invalid, the second switch (Q2) is turned off, the second node (M) is floated at the potential of the first node (P) through the contactor coil (KM) so that the voltage across the contactor coil (KM) is zero, the first switch (Q1) is turned off because its gate is pulled up to the potential of the main power supply by the gate pull-up branch, and the transistor (Q3) operates in the amplification region and charges the energy storage capacitor (C1) with a constant current; When the output signal of the enable control circuit is valid, the second switch (Q2) is turned on, pulling the second node (M) low to the potential of the reference ground, causing the fourth node (S) to be pulled low through the gate drive branch, thus turning on the first switch (Q1), raising the third node (N) to the potential of the main power supply, and simultaneously raising the potential of the first node (P) to the sum of the voltage across the energy storage capacitor (C1) and the main power supply voltage to form the pump-up start-up voltage; the first diode (D1) is forward-biased and turned on, clamping the base of the transistor (Q3) at a low level to stop the constant current charging circuit from working; After the contactor coil (KM) enters the holding phase, the first switch (Q1) remains on to maintain the third node (N) at the potential of the main power supply, thereby keeping the energy storage capacitor (C1) fully discharged and preventing the energy storage capacitor (C1) from being recharged before the next start-up, which would cause pump failure.

2. The contactor drive circuit according to claim 1, characterized in that: It also includes a second diode (D2) with its anode connected to the main power supply and its cathode connected to the first node (P); after the energy storage capacitor (C1) has discharged, the second diode (D2) is forward biased and conducts to bypass the energy storage capacitor (C1), and clamps the potential of the first node (P) to the level of the main power supply voltage minus the forward voltage drop of the first diode, so that the contactor coil (KM) is kept engaged by the main power supply, while preventing the energy storage capacitor (C1) from being reverse charged.

3. The contactor drive circuit according to claim 2, characterized in that: The pull-up resistor group includes a second resistor (R4) and a third resistor (R5) connected in parallel.

4. The contactor drive circuit according to claim 3, characterized in that: It also includes an accelerating capacitor (C2) connected between the fourth node (S) and the main power supply, which is used to make the potential of the fourth node (S) follow the rapid change of the second node (M) when the second switch (Q2) is turned on or off, so as to accelerate the turn-on and turn-off of the first switch (Q1).

5. The contactor drive circuit according to claim 4, characterized in that: Includes a freewheeling diode (D3); the freewheeling diode (D3) is connected in reverse parallel across the two ends of the contactor coil (KM), the cathode of the freewheeling diode (D3) is connected to the first node (P), and the anode of the freewheeling diode (D3) is connected to the second node (M).

6. The contactor drive circuit according to claim 4, characterized in that: It includes a bus support capacitor (C3) connected between the main power supply and the reference ground, used to supplement the main power supply with instantaneous current at the moment the pump-up start-up voltage is formed, so as to suppress the voltage drop of the main power supply.

7. The contactor drive circuit according to claim 4, characterized in that: The enable control circuit includes an optocoupler (U) and a current-limiting resistor (R6); the input terminal of the optocoupler (U) receives an external enable signal through the current-limiting resistor (R6), and the output terminal is connected to the gate of the second switching transistor (Q2).

8. The contactor drive circuit according to any one of claims 1-7, characterized in that: The constant current charging circuit is implemented by a constant current diode, or by a programmable precision reference source combined with a transistor, or by a step-down constant current DC-DC converter.

9. A driving method based on the contactor driving circuit of claim 5, characterized in that: Includes the following steps: S100. During the period when the output signal of the enable control circuit is invalid, the second switch (Q2) is turned off, causing the second node (M) to float at the potential of the first node (P) through the contactor coil (KM) so that the voltage across the contactor coil (KM) is zero. At the same time, the fourth node (S) is pulled up to the potential of the main power supply by the gate pull-up branch so that the first switch (Q1) is turned off, and the energy storage capacitor (C1) is charged by the transistor (Q3) with a constant current. S200: When the output signal of the enable control circuit is valid, the second switch (Q2) is turned on to pull the second node (M) low to the potential of the reference ground. At the same time, the fourth node (S) is pulled low through the gate drive branch, causing the first switch (Q1) to turn on, and the third node (N) is raised to the potential of the main power supply. Based on the characteristic that the voltage across the capacitor cannot change abruptly, the potential of the first node (P) is synchronously raised to the sum of the voltage across the energy storage capacitor (C1) and the main power supply voltage, forming a pump-up start-up voltage. Simultaneously, the first diode (D1) is forward-biased and turned on, clamping the base of the transistor (Q3) at a low level, causing the constant current charging circuit to stop working. S300, the energy storage capacitor (C1) is discharged through the contactor coil (KM), and the voltage across its terminals decays exponentially, and the potential of the first node (P) is smoothly reduced from the pump-up starting voltage to the main power supply voltage. S400: After the energy storage capacitor (C1) has finished discharging, the second diode (D2) is forward-biased and conducts to bypass the energy storage capacitor (C1), and the potential of the first node (P) is clamped at the level of the main power supply voltage minus the forward voltage drop of the first diode, so that the contactor coil (KM) is kept engaged by the main power supply; and during this stage, the first switch (Q1) is kept on, so that the third node (N) is maintained at the potential of the main power supply and the energy storage capacitor (C1) remains in the state of being fully discharged; S500: After the output signal of the enable control circuit is removed, the second switch (Q2) is turned off, so that the current of the contactor coil (KM) is discharged to zero through the circuit formed by the freewheeling diode (D3); S600, the first diode (D1) is reverse biased again, the transistor (Q3) re-enters the amplification region, and the main power supply recharges the energy storage capacitor (C1) with a constant current through the second diode (D2).

10. The driving method according to claim 9, characterized in that: In step S100, the transistor (Q3) charges the energy storage capacitor (C1) with a constant current, the current I of which is determined by the base bias potential V of the transistor (Q3). B Collector potential V BE Together with the emitter resistor (R2), it is determined to satisfy... = Furthermore, the constant charging current is less than the pull-in threshold current of the contactor coil (KM); when the energy storage capacitor (C1) is nearly fully charged, the amplification process automatically terminates because the collector voltage of the transistor (Q3) is depleted and it exits the amplification region.

11. The driving method according to claim 10, characterized in that: The value of the pull-down resistor (R3) is selected to satisfy the following conditions: when the third node (N) is maintained at the voltage of the main power supply in step S400, the leakage current flowing through the pull-down resistor (R3) and its power consumption do not exceed a preset value; and the pull-down resistor (R3) provides a defined low potential to the third node (N) when the first switch (Q1) is turned off.

12. The driving method according to claim 10, characterized in that: The discharge time constant is determined by the product of the capacitance C of the energy storage capacitor (C1) and the equivalent resistance R of the contactor coil (KM). = The duration of the pump-up starting voltage is on the same order of magnitude as the engagement time of the contactor coil (KM), so that the full duration of the pump-up starting voltage covers the entire engagement process of the contactor.

13. An adaptive method for the state of an energy storage capacitor, applied to the driving method according to any one of claims 9-12, characterized in that: Includes the following steps: T100. During each startup step S300, the discharge voltage curve across the energy storage capacitor (C1) is collected. T200. Measure the time taken for the discharge voltage curve to drop from the initial discharge value to 36.8% of the initial value, and obtain the discharge time constant; T300, In step S400, after the energy storage capacitor (C1) has finished discharging, the steady-state holding voltage and steady-state holding current of the contactor coil (KM) are obtained, and the equivalent resistance of the contactor coil (KM) is calculated. T400. Divide the discharge time constant by the equivalent resistance to obtain the actual capacitance value of the energy storage capacitor (C1); T500 compares the actual capacitance value with the nominal capacitance value to obtain the aging coefficient, and outputs an alarm signal when the aging coefficient is lower than a preset threshold, prompting the replacement of the energy storage capacitor (C1), or prohibiting the next enabling action. T600: Calculate the charging time required to fully charge the energy storage capacitor (C1) based on the actual capacitance value, and set the minimum action interval between two enabling actions accordingly, so that the energy storage capacitor (C1) is fully charged before each start-up.

14. The energy storage capacitor state adaptive method according to claim 13, characterized in that: Also includes: The equivalent series resistance of the energy storage capacitor (C1) is calculated based on the ratio of the voltage drop value of the energy storage capacitor (C1) at the moment of discharge initiation to the discharge current; and an alarm signal is output when the equivalent series resistance exceeds a preset upper limit.

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