A PTC control system

Abstract

The utility model discloses a kind of PTC control systems, including high voltage input unit and PTC control branch, the high voltage input unit includes high voltage bus positive pole and high voltage bus negative pole, one end of the PTC control branch is connected with high voltage bus positive pole, the other end of PTC control branch is connected with high voltage bus negative pole, the high voltage input unit further includes abnormal peak absorption circuit, the abnormal peak absorption circuit includes first inductor, second inductor and capacitor, the first inductor is connected in series on high voltage bus positive pole, the second inductor is connected in series on high voltage bus negative pole, the capacitor is connected across between high voltage bus positive pole and high voltage bus negative pole.The PTC control system of the utility model increases abnormal peak absorption circuit in the input end front stage of traditional PTC, abnormal peak absorption circuit can absorb the abnormal peak generated in the operation process of PTC, can prevent the PTC anomaly caused by peak current voltage, to protect PTC product.

Description

Technical Field

[0001] This utility model belongs to the field of automotive air conditioning heating technology, specifically relating to a PTC control system. Background Technology

[0002] Because ceramic PTC materials exhibit the NTC effect, current overshoot occurs during startup and PWM control, resulting in a large du / dt during startup. This leads to startup spikes, which can easily cause the vehicle's fuses to blow or the PTC to burn out. Utility Model Content

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art, and proposes a PTC control system.

[0004] The technical solution of this utility model is implemented as follows: This utility model provides a PTC control system, including a high-voltage input unit and a PTC control branch. The high-voltage input unit includes a positive terminal and a negative terminal of the high-voltage bus. One end of the PTC control branch is connected to the positive terminal of the high-voltage bus, and the other end of the PTC control branch is connected to the negative terminal of the high-voltage bus. The high-voltage input unit also includes an abnormal spike absorption circuit, which includes a first inductor, a second inductor, and a capacitor. The first inductor is connected in series with the positive terminal of the high-voltage bus, the second inductor is connected in series with the negative terminal of the high-voltage bus, and the capacitor is connected across the positive and negative terminals of the high-voltage bus.

[0005] In some embodiments, one end of the positive terminal of the high-voltage bus is the high-voltage positive input terminal, and the other end of the positive terminal of the high-voltage bus is the high-voltage positive output terminal; one end of the negative terminal of the high-voltage bus is the high-voltage negative input terminal, and the other end of the negative terminal of the high-voltage bus is the high-voltage negative output terminal; one end of the first inductor is connected to the high-voltage positive input terminal, and the other end of the first inductor is connected to the high-voltage positive output terminal; one end of the second inductor is connected to the high-voltage negative input terminal, and the other end of the second inductor is connected to the high-voltage negative output terminal; one end of the capacitor is connected to the high-voltage positive output terminal, and the other end of the capacitor is connected to the high-voltage negative output terminal.

[0006] And / or,

[0007] The first and second inductors are differential-mode inductors;

[0008] And / or,

[0009] The capacitor is a thin-film capacitor.

[0010] In some embodiments, the high-voltage input unit further includes an overvoltage protection circuit, which includes an overvoltage detection circuit for detecting overvoltage of the high-voltage bus and an input control switch connected in series with the positive or negative terminal of the high-voltage bus. The output terminal of the overvoltage detection circuit is connected to the input control switch.

[0011] In some embodiments, the output of the overvoltage detection circuit is also connected to the input of the main control circuit.

[0012] In some embodiments, the overvoltage detection circuit includes a high-voltage bus voltage acquisition circuit and an overvoltage triggering circuit. The output terminal of the high-voltage bus voltage acquisition circuit is connected to the input terminal of the overvoltage triggering circuit, and the output terminal of the overvoltage triggering circuit is connected to an input control switch.

[0013] In some embodiments, the high-voltage bus voltage acquisition circuit includes a resistor voltage divider network, which includes a plurality of voltage divider resistors connected in series between the positive and negative terminals of the high-voltage bus. The resistor voltage divider network has a voltage dividing point, which serves as the output terminal of the high-voltage bus voltage acquisition circuit and is connected to the input terminal of the overvoltage triggering circuit.

[0014] And / or,

[0015] The overvoltage triggering circuit includes an optocoupler. The positive terminal of the light-emitting diode of the optocoupler is directly or via a first resistor connected to the output terminal of the high-voltage bus voltage acquisition circuit. The negative terminal of the light-emitting diode of the optocoupler is directly or via a second resistor grounded. The emitter of the phototransistor of the optocoupler is grounded. The collector of the phototransistor of the optocoupler is directly or via a third resistor connected to a first voltage. The collector of the phototransistor of the optocoupler serves as the output terminal of the overvoltage triggering circuit and is connected to the input control switch.

[0016] In some embodiments, the input control switch is a relay, the contacts of which are connected in series with the positive or negative terminal of the high-voltage busbar, one end of the relay coil is connected to a first voltage, and the other end of the relay coil is connected to the output terminal of the overvoltage detection circuit.

[0017] In some embodiments, the PTC control branch includes a load control switch and a PTC load connected in series. The load control switch is electrically connected to the output terminal of the load control switch drive circuit, and the input terminal of the load control switch drive circuit is electrically connected to the main control circuit.

[0018] In some embodiments, the load control switch is a transistor, and the load control switch driving circuit is a transistor driving circuit.

[0019] In some embodiments, the transistor driving circuit includes an input and preamplifier circuit and a push-pull driving circuit. The input terminal of the input and preamplifier circuit is electrically connected to the output terminal of the main control circuit, the output terminal of the input and preamplifier circuit is electrically connected to the input terminal of the push-pull driving circuit, and the output terminal of the push-pull driving circuit is electrically connected to the gate of the transistor.

[0020] This utility model has at least the following beneficial effects:

[0021] The PTC control system of this invention adds an abnormal spike absorption circuit to the front stage of the input terminal of the traditional PTC. When a high voltage is input, the abnormal spike absorption circuit, composed of a differential mode inductor and a thin film capacitor, can absorb the abnormal spikes generated during the operation of the PTC, which can prevent PTC abnormalities caused by spike current and voltage, and thus protect the PTC product.

[0022] The PTC control system of this invention also includes a high-voltage sampling circuit and a hardware overvoltage protection circuit. The high-voltage input, after passing through the abnormal spike absorption circuit and the input control switch, supplies power to the PTC load. When the hardware system detects that the voltage is too high, the system will automatically cut off the input control switch (that is, cut off the high-voltage input power supply circuit), thereby protecting the downstream circuits.

[0023] Meanwhile, the system's overvoltage detection uses a purely hardware-based circuit design, eliminating the misjudgments common in traditional PTC software, ensuring system stability and reliability. Simultaneously, when an overvoltage is detected, the MCU controls the transistor drive circuit to shut down the transistor, ensuring the high-voltage power is cut off and protecting product and personnel safety. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic block diagram of a PTC control system provided in one embodiment of the present invention;

[0026] Figure 2 A circuit diagram of a high-voltage input unit provided in one embodiment of this utility model;

[0027] Figure 3 A circuit diagram of the abnormal spike absorption circuit provided in an embodiment of this utility model;

[0028] Figure 4 A circuit diagram of a transistor driving circuit provided for an embodiment of this utility model;

[0029] Figure 5 PTC ceramic core characteristic curves;

[0030] Figure 6 This is a schematic diagram of the AC component of the bus voltage (blue) and the bus current (yellow) in the traditional scheme (i.e., without abnormal spike absorption circuit);

[0031] Figure 7 This is a schematic diagram of the AC component of the bus voltage (blue) and the bus current (yellow) of this utility model (i.e., the abnormal spike absorption circuit). Detailed Implementation

[0032] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.

[0033] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this utility model, unless otherwise stated, "a plurality of" or "several" means two or more.

[0034] See Figure 5 The graph shows the characteristic curves of the PTC ceramic core. Because the ceramic PTC material itself has an NTC effect that causes current overshoot during startup, the PTC resistive load will gradually stabilize only after the NTC characteristic segment of the ceramic core is passed. This is because under the current ambient temperature and given voltage, the heat generation and heat dissipation of the ceramic PTC heating unit reach a balance, and the system enters a steady state.

[0035] During PWM closed-loop startup, a current spike occurs when the transistor (i.e., IGBT) turns on, and this spike current is significantly higher than the steady-state current. This phenomenon arises because the ceramic PTC heating elements are arranged in parallel, resulting in weak capacitance within the heating devices themselves. During startup, the abnormal spike absorption circuit's du / dt ratio is large, leading to a startup spike. When multiple IGBTs turn on simultaneously, the multiple spike currents overlap, exacerbating the problem.

[0036] In order to effectively improve or even completely solve the above-mentioned problems in the related technologies, this disclosure provides corresponding solutions.

[0037] See Figures 1 to 3 This utility model provides a PTC control system, including a high-voltage input unit and a PTC control branch. The high-voltage input unit includes a positive terminal and a negative terminal of a high-voltage bus. One end of the PTC control branch is connected to the positive terminal of the high-voltage bus, and the other end of the PTC control branch is connected to the negative terminal of the high-voltage bus. The high-voltage input unit also includes an abnormal spike absorption circuit, which includes a first inductor L1, a second inductor L2, and a capacitor C1. The first inductor is connected in series with the positive terminal of the high-voltage bus, the second inductor is connected in series with the negative terminal of the high-voltage bus, and the capacitor is connected across the positive and negative terminals of the high-voltage bus.

[0038] The first inductor L1 and the second inductor L2 are differential-mode inductors. Capacitor C1 is a film capacitor. The function of differential-mode inductor L1 is to suppress differential-mode interference and stabilize the circuit current. The function of differential-mode inductor L2 is to suppress differential-mode interference and stabilize the circuit current. The function of film capacitor C1 is to filter and absorb voltage spikes. This invention's abnormal spike absorption circuit has low cost, high reliability, and is easy to use and maintain.

[0039] Due to the characteristics of the PTC ceramic core, abnormal spikes may occur on the busbar during PTC operation. Furthermore, since the operating frequency of PTCs is low (typically less than 100Hz), adding an abnormal spike absorption circuit before the PTC input can effectively suppress these spikes. The differential-mode inductor in the abnormal spike absorption circuit suppresses differential-mode interference; a larger inductance value results in better suppression. The film capacitor in the abnormal spike absorption circuit should be a high-voltage capacitor with high ripple current withstand capability.

[0040] In some embodiments, the abnormal spike absorption circuit is disposed on a PCB board, which is located inside the housing 1. The housing 1 is provided with a high-voltage positive input terminal 2, a high-voltage negative input terminal 3, a high-voltage positive output terminal 4, and a high-voltage negative output terminal 5.

[0041] The outer casing is used to secure the PCB board.

[0042] In some embodiments, the housing is a metal housing.

[0043] In some embodiments, one end of the positive terminal of the high-voltage bus is a high-voltage positive input terminal, which is connected to the high-voltage positive input terminal 2; the other end of the positive terminal of the high-voltage bus is a high-voltage positive output terminal, which is connected to the high-voltage positive output terminal 4; one end of the negative terminal of the high-voltage bus is a high-voltage negative input terminal, which is connected to the high-voltage negative input terminal 3; the other end of the negative terminal of the high-voltage bus is a high-voltage negative output terminal, which is connected to the high-voltage negative output terminal 5; one end of the first inductor is connected to the high-voltage positive input terminal; the other end of the first inductor is connected to the high-voltage positive output terminal; one end of the second inductor is connected to the high-voltage negative input terminal; the other end of the second inductor is connected to the high-voltage negative output terminal; one end of the capacitor is connected to the high-voltage positive output terminal; and the other end of the capacitor is connected to the high-voltage negative output terminal.

[0044] In some embodiments, the high-voltage input unit further includes an overvoltage protection circuit, which includes an overvoltage detection circuit for detecting overvoltage of the high-voltage bus and an input control switch connected in series with the positive or negative terminal of the high-voltage bus. The output terminal of the overvoltage detection circuit is connected to the input control switch.

[0045] When the overvoltage detection circuit detects an overvoltage on the high-voltage bus, the input control switch is disconnected, cutting off the power supply to the high-voltage bus.

[0046] In some embodiments, the output of the overvoltage detection circuit is also connected to the input of the main control circuit.

[0047] When the overvoltage detection circuit detects an overvoltage on the high-voltage bus, the main control circuit controls the load control switch, i.e., the IGBT, to turn off, thus cutting off the PTC control branch.

[0048] In some embodiments, the overvoltage detection circuit includes a high-voltage bus voltage acquisition circuit and an overvoltage triggering circuit. The output terminal of the high-voltage bus voltage acquisition circuit is connected to the input terminal of the overvoltage triggering circuit, and the output terminal of the overvoltage triggering circuit is connected to an input control switch.

[0049] In some embodiments, the high-voltage bus voltage acquisition circuit includes a resistor voltage divider network. The resistor voltage divider network includes multiple voltage divider resistors connected in series between the positive and negative terminals of the high-voltage bus. The resistor voltage divider network has a voltage dividing point, which serves as the output terminal of the high-voltage bus voltage acquisition circuit and is connected to the input terminal of the overvoltage triggering circuit. The number of voltage divider resistors connected in series between the positive and negative terminals of the high-voltage bus is set as needed.

[0050] In a preferred embodiment, the overvoltage trigger circuit includes an optocoupler IC1. The positive terminal of the light-emitting diode of the optocoupler IC1 is directly or via resistor R7 connected to the output terminal of the high-voltage bus voltage acquisition circuit. The negative terminal of the light-emitting diode of the optocoupler IC1 is directly or via resistor R8 grounded. The emitter of the phototransistor of the optocoupler is grounded. The collector of the phototransistor of the optocoupler is directly or via resistor R5 connected to a first voltage. The collector of the phototransistor of the optocoupler serves as the output terminal of the overvoltage trigger circuit and is connected to the input control switch.

[0051] The overvoltage triggering circuit of this invention can use optocoupler IC1, but it is not limited to optocoupler IC1; other alternative solutions can also be used.

[0052] In some embodiments, the input control switch is a relay RL1. The contacts of relay RL1 are connected in series with the positive or negative terminal of the high-voltage bus. One end of the coil of relay RL1 is connected to a first voltage, and the other end of the coil of relay RL1 is connected to the output terminal of the overvoltage detection circuit. The contacts connected in series with the positive or negative terminal of the high-voltage bus are normally closed contacts.

[0053] In some embodiments, a diode D1 is connected in parallel across the relay coil. The diode D1, connected in parallel across the coil of the high-voltage relay, provides a discharge path for the reverse electromotive force generated when power is off, protecting other components in the circuit from damage.

[0054] In some embodiments, the relay is a high-voltage relay.

[0055] In some embodiments, the power supply coil of the high-voltage relay is supplied with low-voltage 12V.

[0056] In some embodiments, the PTC control branch includes a load control switch and a PTC load connected in series. The load control switch is electrically connected to the output terminal of the load control switch drive circuit, and the input terminal of the load control switch drive circuit is electrically connected to the main control circuit.

[0057] In some embodiments, the load control switch is a transistor, and the load control switch driving circuit is a transistor driving circuit. The transistor driving circuit of this invention can employ existing transistor driving circuits. See also... Figure 4 This is a circuit diagram of a transistor driving circuit provided in one embodiment of the present invention. The transistor driving circuit is used to amplify the PWM (Pulse Width Modulation) control signal and drive the transistor to achieve rapid turn-on and turn-off.

[0058] In some embodiments, the transistor is an IGBT.

[0059] In some embodiments, the transistor driving circuit includes an input and preamplifier circuit and a push-pull driving circuit. The input terminal of the input and preamplifier circuit is electrically connected to the output terminal of the main control circuit, the output terminal of the input and preamplifier circuit is electrically connected to the input terminal of the push-pull driving circuit, and the output terminal of the push-pull driving circuit is electrically connected to the gate of the transistor.

[0060] In some embodiments, the input and preamplifier circuit includes transistors Q1 and Q2. The base of transistor Q1 is connected to the output terminal of the main control circuit, the emitter of transistor Q1 is grounded, the collector of transistor Q1 is connected to the base of transistor Q12 via resistor R15, the collector of transistor Q1 is connected to a first positive voltage (such as, but not limited to, +15V) via resistor R17, the base of transistor Q2 is grounded via capacitor C10, the emitter of transistor Q2 is grounded, the collector of transistor Q2 is electrically connected to the input terminal of the push-pull drive circuit via resistor R16, and the collector of transistor Q2 is connected to the first positive voltage (such as, but not limited to, +15V) via resistor R18.

[0061] In some embodiments, a PWM input and filtering circuit is provided between the base of transistor Q1 and the output terminal of the main control circuit. The PWM input and filtering circuit includes a resistor R14 and a capacitor C9. One end of resistor R14 is connected to the output terminal of the main control circuit, and the other end of resistor R14 is connected to one end of capacitor C9 and the base of transistor Q1. The other end of capacitor C9 is grounded. The PWM signal is input through resistor R14, and capacitor C9 acts as a filter / decoupling capacitor to stabilize the input voltage and suppress high-frequency interference.

[0062] The push-pull drive circuit includes transistors Q3 and Q4. The base of transistor Q3 is connected to the base of transistor Q4, serving as the input terminal of the push-pull drive circuit. It is also connected to the collector of transistor Q2 via resistor R16. The collector of transistor Q3 is connected to a first positive voltage. The emitter of transistor Q3 is connected to the emitter of transistor Q4, serving as the output terminal of the push-pull drive circuit. It is also connected to the gate of a transistor (such as an IGBT) via resistor R20. One end of resistor R20 is connected to one end of resistor R19 and the output terminal of the push-pull drive circuit. The other end of resistor R19 is connected to the cathode of diode D2. The anode of diode D2 is connected to the other end of resistor R20 and the gate of the transistor (such as an IGBT). The gate of the transistor (such as an IGBT) is connected to a first negative voltage via capacitor C11. The gate of the transistor (such as an IGBT) is also connected to a first negative voltage via resistor R21. Q3 (NPN type) and Q4 (PNP type) form a push-pull circuit, whose core function is to provide high current drive capability and accelerate the turn-on / turn-off speed of IGBT.

[0063] In some embodiments, capacitors C12 and C13 are connected in series between the collector and emitter of a transistor (such as an IGBT).

[0064] Diode D2 is a freewheeling diode, used to provide a path for the reverse discharge current of the gate when the IGBT is turned off, thereby accelerating the turn-off process.

[0065] Capacitor C11 is an accelerating capacitor that assists in the rapid charging and discharging of the gate, further improving the switching speed of the IGBT.

[0066] In some embodiments, the main control circuit uses an MCU.

[0067] In some embodiments, the PTC control system further includes a high-voltage connector through which high-voltage power is input to the high-voltage bus. In some embodiments, the PTC control system further includes a low-voltage connector through which low-voltage power is input.

[0068] In some embodiments, the PTC control system further includes a low-voltage power supply circuit, which includes a low-voltage input circuit and an LDO circuit. The input terminal of the low-voltage input circuit is connected to a low-voltage power supply, and the output terminal of the low-voltage input circuit is connected to the input terminal of the LDO circuit. The output terminal of the LDO circuit is used to output a second voltage to power the main control circuit. The low-voltage input circuit outputs a first voltage to power the relay.

[0069] In some embodiments, the first voltage is a low voltage of 12V.

[0070] In some embodiments, the low-voltage input circuit includes a low-voltage filter circuit, the input terminal of which is connected to a low-voltage power supply, and the output terminal of which is connected to the input terminal of a power management circuit.

[0071] The working principle of this utility model is as follows: L1 and L2 are differential mode inductors used to suppress differential mode interference and stabilize circuit current; C1 is a thin film capacitor used to filter and absorb peak voltage; RL1 is a high-voltage relay located at the high-voltage bus input terminal to control the on / off state of high-voltage electricity; resistors R1, R2, R3, R4, R6, and R9 are used for high-voltage voltage division to realize the conversion from high voltage to low voltage; resistors R7 and R8 are current-limiting resistors used to drive the IC1 optocoupler; IC1 is an optocoupler used to realize signal isolation conversion; resistor R5 is a pull-up resistor used to realize the high / low level conversion of the hardware overvoltage flag bit A.

[0072] When a voltage is input, the overvoltage flag is pulled high by resistor R5, causing the high-voltage relay coil to de-energize and remain normally closed. When high voltage is input to the system, due to the voltage divider design of resistors R1, R2, R3, R4, R6, and R9, the voltage at the voltage divider point increases with the input voltage until the optocoupler IC1 activates (i.e., this is the hardware overvoltage state). With the activation of optocoupler IC1, the hardware overvoltage flag changes from high to low, energizing the high-voltage relay coil and turning it normally open, thus disconnecting the bus voltage input.

[0073] The high-voltage input unit of this invention can prevent PTC malfunctions caused by peak current and voltage, thereby protecting PTC products. The PTC control system of this invention is applicable to various PTC products such as wind, water, and heat pumps, meeting the needs of different application scenarios and greatly improving system reliability.

[0074] This invention adds an input protection circuit (i.e., an abnormal spike absorption circuit) to the pre-stage of the input section of a traditional PTC. This input protection circuit (i.e., an abnormal spike absorption circuit) can absorb abnormal spikes generated during the operation of the PTC. Figure 6 The waveform diagram shows the AC component of the bus voltage (blue) and the bus current (yellow) in the traditional scheme (i.e., without abnormal spike absorption circuit). The waveform shows obvious transient fluctuations such as voltage spikes. Figure 7 This is a schematic diagram of the AC component of the bus voltage (blue) and the bus current (yellow) of this utility model (i.e., the one with the abnormal spike absorption circuit). Figure 7 It can be seen that the addition of the abnormal spike absorption circuit significantly suppresses the "transient spikes and oscillations" of the AC component of the bus voltage, resulting in a significant improvement in waveform stability. The "transient impacts and sharp pulses" of the bus current are also essentially eliminated, greatly improving the transient characteristics and reliability of the overall circuit. According to actual measurement data, adding the input protection circuit (i.e., the abnormal spike absorption circuit) can effectively reduce the peak value by 40%, improving the reliability and lifespan of the PTC, making it particularly suitable for current new energy vehicles.

[0075] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A PTC control system, comprising a high-voltage input unit and a PTC control branch, wherein the high-voltage input unit includes a positive terminal and a negative terminal of a high-voltage bus, one end of the PTC control branch is connected to the positive terminal of the high-voltage bus, and the other end of the PTC control branch is connected to the negative terminal of the high-voltage bus, characterized in that: The high-voltage input unit also includes an abnormal spike absorption circuit, which includes a first inductor, a second inductor, and a capacitor. The first inductor is connected in series with the positive terminal of the high-voltage bus, the second inductor is connected in series with the negative terminal of the high-voltage bus, and the capacitor is connected across the positive and negative terminals of the high-voltage bus.

2. The PTC control system as described in claim 1, characterized in that: One end of the positive terminal of the high-voltage bus is the high-voltage positive input terminal, and the other end of the positive terminal of the high-voltage bus is the high-voltage positive output terminal. One end of the negative terminal of the high-voltage bus is the high-voltage negative input terminal, and the other end of the negative terminal of the high-voltage bus is the high-voltage negative output terminal. One end of the first inductor is connected to the high-voltage positive input terminal, and the other end of the first inductor is connected to the high-voltage positive output terminal. One end of the second inductor is connected to the high-voltage negative input terminal, and the other end of the second inductor is connected to the high-voltage negative output terminal. One end of the capacitor is connected to the high-voltage positive output terminal, and the other end of the capacitor is connected to the high-voltage negative output terminal. And / or, The first and second inductors are differential-mode inductors; And / or, The capacitor is a thin-film capacitor.

3. The PTC control system as described in claim 1, characterized in that: The high-voltage input unit also includes an overvoltage protection circuit, which includes an overvoltage detection circuit for detecting overvoltage of the high-voltage bus and an input control switch connected in series with the positive or negative terminal of the high-voltage bus. The output terminal of the overvoltage detection circuit is connected to the input control switch.

4. The PTC control system as described in claim 3, characterized in that: The output of the overvoltage detection circuit is also connected to the input of the main control circuit.

5. The PTC control system as described in claim 3, characterized in that: The overvoltage detection circuit includes a high-voltage bus voltage acquisition circuit and an overvoltage triggering circuit. The output terminal of the high-voltage bus voltage acquisition circuit is connected to the input terminal of the overvoltage triggering circuit, and the output terminal of the overvoltage triggering circuit is connected to the input control switch.

6. The PTC control system as described in claim 5, characterized in that: The high-voltage bus voltage acquisition circuit includes a resistor voltage divider network, which includes multiple voltage divider resistors connected in series between the positive and negative terminals of the high-voltage bus. The resistor voltage divider network has a voltage dividing point, which serves as the output terminal of the high-voltage bus voltage acquisition circuit and is connected to the input terminal of the overvoltage triggering circuit. And / or, The overvoltage triggering circuit includes an optocoupler. The positive terminal of the light-emitting diode of the optocoupler is directly or via a first resistor connected to the output terminal of the high-voltage bus voltage acquisition circuit. The negative terminal of the light-emitting diode of the optocoupler is directly or via a second resistor grounded. The emitter of the phototransistor of the optocoupler is grounded. The collector of the phototransistor of the optocoupler is directly or via a third resistor connected to a first voltage. The collector of the phototransistor of the optocoupler serves as the output terminal of the overvoltage triggering circuit and is connected to the input control switch.

7. The PTC control system according to any one of claims 3 to 6, characterized in that: The input control switch is a relay. The relay contacts are connected in series to the positive or negative terminal of the high-voltage bus. One end of the relay coil is connected to the first voltage, and the other end of the relay coil is connected to the output terminal of the overvoltage detection circuit.

8. The PTC control system as described in claim 1, characterized in that: The PTC control branch includes a load control switch and a PTC load connected in series. The load control switch is electrically connected to the output terminal of the load control switch drive circuit, and the input terminal of the load control switch drive circuit is electrically connected to the main control circuit.

9. The PTC control system as described in claim 8, characterized in that: The load control switch is a transistor, and the load control switch driving circuit is a transistor driving circuit.

10. The PTC control system as described in claim 9, characterized in that: The transistor driving circuit It includes an input and preamplifier circuit and a push-pull drive circuit. The input terminal of the input and preamplifier circuit is electrically connected to the output terminal of the main control circuit, the output terminal of the input and preamplifier circuit is electrically connected to the input terminal of the push-pull drive circuit, and the output terminal of the push-pull drive circuit is electrically connected to the gate of the transistor.

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