PTC heating device

Abstract

The embodiment of the invention provides a PTC heating device. The system comprises a PTC heater used for drawing electric energy from a low-voltage input end and / or a high-voltage input end; the first end of the impact current suppression circuit is connected to the high-voltage input end, and the second end of the impact current suppression circuit is connected with the enable signal output end of the PTC heater; and the high-voltage detection circuit is used for generating a high-voltage detection signal and providing the high-voltage detection signal to the PTC heater when the high-voltage power supply supplies power to the PTC device. The impulse current suppression circuit comprises a current discharge unit which forms a first end, and the current discharge unit works in a discharge state or a filtering state; the discharge control unit is connected with the current discharge unit and used for controlling the working state of the current discharge unit; the discharge control unit is powered by a low-voltage power supply, and the discharge control unit further forms a second end.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicles, and in particular to a PTC heating device. Background Art

[0002] With the rapid development of the new energy vehicle industry, changes in thermal management systems have created a huge demand for PTC heaters. Since electric vehicles cannot use engine waste heat for heating, efficient electric heating technology has become a necessity.

[0003] PTC heaters, with their economical and safe advantages, have become a core solution for thermal management in new energy vehicles. Typically, a PTC heater's power supply system consists of a high-voltage power supply and a low-voltage power supply system, allowing it to be powered by either a high-voltage or low-voltage power supply.

[0004] When powered by a high-voltage power supply, the high-voltage distribution box in a new energy vehicle controls the energization of a relay on the high-voltage busbar, allowing the power battery pack to power the PTC heater. At the moment the relay energizes the PTC heater, the capacitor on the high-voltage busbar merely serves as a power filter. At this point, the capacitor acts as a short circuit to ground, generating a large inrush current in the circuit.

[0005] Since PTC heaters are capacitive loads and lack surge current protection, this surge current can easily damage components in the PTC heater's high-voltage circuit, leading to high failure rates and increased repair costs. Summary of the Invention

[0006] The present invention provides a PTC heating device, aiming to solve the problem of high failure rate of PTC heating devices in the prior art.

[0007] In a first aspect, an embodiment of the present invention provides a PTC heating device, wherein a low-voltage input terminal of the PTC heating device is connected to a low-voltage power supply, and a high-voltage input terminal of the PTC heating device is connected to a high-voltage power supply. The PTC heating device includes: a PTC heater, which is respectively connected to the low-voltage input terminal and the high-voltage input terminal, and is used to draw electrical energy from the low-voltage input terminal and / or the high-voltage input terminal; an inrush current suppression circuit, a first end of the inrush current suppression circuit is connected to the high-voltage input terminal, and a second end of the inrush current suppression circuit is connected to the enable signal output terminal of the PTC heater; a high-voltage detection circuit, a detection end of the high-voltage detection circuit is connected to the high-voltage input terminal, and is used to generate a high-voltage detection signal and provide it to the PTC heater when the high-voltage power supply supplies power to the PTC device; wherein the inrush current suppression circuit includes: a current discharge unit, which forms the first end and operates in a discharge state or a filtering state; a discharge control unit, which is connected to the current discharge unit and is used to control the working state of the current discharge unit; the discharge control unit is powered by the low voltage, and the discharge control unit also forms the second end.

[0008] Optionally, the control end of the current discharge unit is connected to the discharge control unit; wherein, the current discharge unit is used to: switch to the filtering state when the control end receives a switching signal; and keep working in the discharge state when the control end does not receive a switching signal; the discharge control unit is used to: provide the switching signal to the control end of the current discharge unit when the second end receives a first control signal; and not provide the switching signal when the second end does not receive the first control signal; the PTC heater is used to: output the first control signal to the second end after receiving the high-voltage detection signal and after a preset time interval.

[0009] Optionally, the current discharge unit includes: a first capacitor, a third resistor and a first switching tube; wherein, one end of the first capacitor is connected to the high-voltage input end to form the first end, and the other end of the first capacitor is connected to the reference ground through the third resistor to form a current discharge path; the first end of the first switching tube is connected between the first capacitor and the third resistor, the second end of the first switching tube is connected to the reference ground, and the control end of the first switching tube forms the control end of the current discharge unit; when the first switching tube is disconnected, the current discharge unit operates in the discharge state; when the first switching tube is turned on, the current discharge unit operates in the filtering state.

[0010] Optionally, the discharge control unit includes: a first resistor, a second resistor, a fourth resistor, a fifth resistor, a sixth resistor, a second capacitor, and a second switching transistor; wherein one end of the first resistor is connected to the power supply terminal of the discharge control unit, and the other end of the first resistor is connected to the reference ground through the sixth resistor; one end of the fourth resistor is connected between the first resistor and the sixth resistor, and a common connection node of the fourth resistor, the first resistor, and the sixth resistor forms the second end; the other end of the fourth resistor is connected to the control terminal of the second switching transistor, and the first end of the second switching transistor is connected to the power supply terminal through the second resistor; the second end of the second switching transistor is connected to the reference ground; one end of the second capacitor is connected to the first end of the second switching transistor, and the other end of the second capacitor is connected to the reference ground; one end of the fifth resistor is also connected to the first end of the second switching transistor, and the other end of the fifth resistor is connected to the reference ground.

[0011] Optionally, when the low-voltage power supply supplies power to the PTC heating device, the PTC heater is used to: output the second control signal to the second end; and the discharge control unit is used to: control the current discharge unit to operate in the discharge state when the second end receives the second control signal.

[0012] Optionally, the first control signal is a low-level signal, the second control signal is a high-level signal, and the switching signal is a high-level signal.

[0013] The beneficial effect of the PTC heating device of the embodiment of the present invention is that: through the additional inrush current suppression circuit composed of a current discharge unit and a discharge control unit, it can effectively cope with the inrush current generated by the high-voltage power supply in a variety of different power supply scenarios, and avoid damage to the internal components of the PTC heater caused by the inrush current. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of a PTC heating device according to an embodiment of the present invention.

[0015] Figure 2 2 is a circuit diagram of a PTC heating device according to an embodiment of the present invention.

[0016] Figure 3 This is a schematic diagram of a scenario in which the PTC heating device according to an embodiment of the present invention is applied to a new energy vehicle. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0019] Furthermore, 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 the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means more than two, unless otherwise specifically defined.

[0020] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0021] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0022] In the description of this specification, the reference terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0023] Figure 1 Schematic diagram of the PTC heating device provided in the embodiment of the present application. Figure 1 As shown, the PTC heating device has a low-voltage input terminal LV connected to a low-voltage power supply and a high-voltage input terminal HV connected to a high-voltage power supply. It can be powered by a high-voltage power supply or a low-voltage power supply, or by both high-voltage and low-voltage power supplies.

[0024] Please continue reading Figure 1 The PTC heating device includes: a PTC heater 10, an inrush current suppression circuit 20 and a high voltage detection circuit 30 The PTC heater 10 is the core functional unit of the PTC heating device. It is connected to the low-voltage input terminal LV and the high-voltage input terminal HV, respectively, drawing electrical energy from these terminals and converting it into heat. The PTC heater 10 also includes control circuits and other related peripheral circuits to ensure its proper operation.

[0025] The inrush current suppression circuit 20 is a functional circuit for dissipating inrush current to protect the PTC heater. It has two terminals, referred to as a first terminal and a second terminal. The first terminal of the inrush current suppression circuit 20 is connected to the high-voltage input terminal HV, and the second terminal of the inrush current suppression circuit 20 is connected to the enable signal output terminal of the PTC heater.

[0026] In this embodiment, the inrush current suppression circuit 20 includes a current discharge unit 21 and a discharge control unit 22 .

[0027] The current discharge unit 21 forms a first end connected to the high-voltage input terminal HV. It can switch between two different operating states: a discharge state and a filtering state. When operating in the discharge state, the current discharge unit 21 forms a current discharge path, consuming and suppressing the inrush current generated by the high-voltage input terminal HV. When operating in the filtering state, the current discharge unit 21 is used to filter the voltage inputted by the high-voltage input terminal HV, improving voltage stability.

[0028] The discharge control unit 22 is connected to the current discharge unit 21 and is a functional circuit for controlling the operating state of the current discharge unit 21. The discharge control unit is powered by a low-voltage power supply and has a second terminal connected to the enable signal output terminal of the PTC heater 10. The discharge control unit controls the operating state of the current discharge unit 21 according to the control signal output by the enable signal output terminal.

[0029] The high-voltage detection circuit 30 is a detection unit used to detect whether the high-voltage power supply is on. Its detection terminal is connected to the high-voltage input terminal HV. Upon detecting a high voltage at the high-voltage input terminal HV (i.e., the high-voltage power supply is on), the high-voltage detection circuit 30 generates a high-voltage detection signal and provides it to the PTC heater 10.

[0030] Specifically, the current discharge unit 21 has a control terminal. Its current operating state is determined by the electrical signal received by the control terminal. When the control terminal of the current discharge unit 21 receives a switching signal, it switches to the filtering state. When the control terminal of the current discharge unit 21 does not receive a switching signal, it remains in the discharge state. In other words, the default operating state of the current discharge unit 21 is the discharge state, and it only switches to the filtering state when the control terminal receives a switching signal. As long as the control terminal does not receive a switching signal, it switches to the discharge state.

[0031] Accordingly, the discharge control unit 22 is connected to the control end of the current discharge unit 21 and determines whether to provide a switching signal to the current discharge unit 21 based on whether there is a low-voltage power supply and a control signal provided by the PTC heater through the second end.

[0032] Specifically, when the second terminal of the discharge control unit 22 receives the first control signal provided by the PTC heater, a switching signal is provided to the control terminal of the current discharge unit 21. When the second terminal of the discharge control unit 22 does not receive the first control signal, no switching signal is provided. In other words, the discharge control unit 22 provides a switching signal only when it receives the first control signal, and does not provide a switching signal in other circumstances (for example, when it receives the second control signal).

[0033] The first control signal is provided by the PTC heater 10. The PTC heater 10 outputs the first control signal to the second terminal only after receiving the high-voltage detection signal and after a preset time interval. Otherwise, the PTC heater 10 outputs the second control signal by default. The preset time interval can be set based on actual needs and is not specifically limited here.

[0034] In some embodiments, as Figure 2 As shown, the current discharge unit 21 includes: a first capacitor C1, a third resistor R3 and a first switch tube Q1.

[0035] One end of the first capacitor C1 is connected to the high voltage input terminal HV to form a first end. The other end of the first capacitor C1 is connected to the reference ground GND via a third resistor R3 to form a current discharge path. A first end of the first switch tube Q1 is connected between the first capacitor C1 and the third resistor R3 , a second end of the first switch tube Q2 is connected to the reference ground GND, and a control end of the first switch tube Q1 serves as a control end of the current discharge unit.

[0036] Therefore, when the first switch Q1 is off, the current discharge unit operates in a discharge mode. The inrush current is discharged to the reference ground GND through the first capacitor C1 and the third resistor R3 in sequence, where it is suppressed and consumed by the third resistor R3. When the first switch Q1 is on, the current discharge unit operates in a filtering mode. In this state, the third resistor R3 is short-circuited by the first switch Q1 (the internal resistance of the first switch Q1 is significantly lower than that of the third resistor R3 when it is on). The first capacitor C1 acts as a filter capacitor, filtering the input voltage at the high-voltage input terminal HV.

[0037] For details, please refer to Figure 2 The discharge control unit 22 includes: a first resistor R1, a second resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a second capacitor C2 and a second switch tube Q2.

[0038] One end of the first resistor R1 is connected to the power supply terminal VCC of the discharge control unit, and the other end of the first resistor R1 is connected to the reference ground GND through the sixth resistor R6. One end of the fourth resistor R4 is connected between the first resistor R1 and the sixth resistor R6, and a common connection node of the fourth resistor R4, the first resistor R1, and the sixth resistor R6 forms the second end.

[0039] The other end of the fourth resistor R4 is connected to the control end of the second switching tube Q2, and the first end of the second switching tube Q2 is connected to the power supply terminal VCC through the second resistor R2; the second end of the second switching tube Q2 is connected to the reference ground GND; one end of the second capacitor C2 is connected to the first end of the second switching tube Q2, and the other end of the second capacitor C2 is connected to the reference ground GND; one end of the fifth resistor R5 is also connected to the first end of the second switching tube Q2, and the other end of the fifth resistor R5 is connected to the reference ground GND.

[0040] Therefore, when the power supply terminal VCC has a DC supply voltage (e.g., 12V) from a low-voltage power supply, and the second terminal receives the first control signal, the second switch Q2 is turned off. At this point, the common connection node of the second resistor R2, the fifth resistor R5, and the second switch Q2 is at a high level, generating a switching signal. When the second terminal receives the second control signal, the second switch Q2 is turned on. At this point, the voltage level of the common connection node of the second resistor R2, the fifth resistor R5, and the second switch Q2 is pulled low, and no longer generates a switching signal.

[0041] Figure 3 The following is a schematic diagram of a scenario in which the PTC heating device according to an embodiment of the present invention is applied to a new energy vehicle. Figure 3 , describes in detail the specific process of the PTC heating device suppressing and consuming inrush current in different power supply scenarios.

[0042] like Figure 3 As shown, the high-voltage power supply is primarily provided by the new energy vehicle's power battery pack 2. The high-voltage input of the PTC heater 1 is connected to the high-voltage busbar via relay K1. The high-voltage distribution box 3 controls the activation and deactivation of relay K1. The low-voltage power supply 4 is connected to the low-voltage input of the PTC heater 1.

[0043] 1) The power system of a new energy vehicle first uses a high-voltage power supply to power the PTC heater, and then uses a low-voltage power supply to power the PTC heater: First, the high-voltage distribution box 3 controls relay K1 to close, connecting the high-voltage input terminal to the high-voltage bus. At this point, the low-voltage power supply is disconnected, the power supply terminal of the discharge control unit 22 in the inrush current circuit unit is de-energized, and the enable signal output terminal of the PTC heater 10 is also de-energized.

[0044] In this state, the second switch Q2 is in the off state, the common connection node of the second resistor R2, the fifth resistor R5 and the second switch Q2 is in the low level state. The first switch Q1 does not receive the switching signal and remains off.

[0045] The first capacitor C1 is equivalent to a short circuit at the power-on moment when the relay K1 is energized. The inrush current generated on the high-voltage bus is discharged to the reference ground GND after passing through the first capacitor C1 and the third resistor R3. The third resistor R3 suppresses and consumes the inrush current generated at the power-on moment, thereby protecting the PTC heater.

[0046] Then, the low-voltage power supply starts to supply power to the PTC heater, the power supply terminal VCC of the discharge control unit 22 in the inrush current circuit unit is provided with a 12V DC voltage, and the enable signal output terminal of the PTC heater outputs a second control signal (high level signal).

[0047] In this state, the second switch Q2 is turned on, causing the voltage level of the common connection node of the second resistor R2, the fifth resistor R5, and the second switch Q2 to be pulled down to a low level. The first switch Q1 does not receive a switching signal and remains off. The current discharge unit 21 remains in the discharge state.

[0048] Finally, the high voltage detection signal generated by the high voltage detection circuit 30 is provided to the PTC heater 10. After detecting the high voltage detection signal and after a preset delay time, the PTC heater 10 outputs a first control signal (low level signal) at the enable signal output terminal.

[0049] In this state, the second switch Q2 is turned off, causing the common connection node of the second resistor R2, the fifth resistor R5, and the second switch Q2 to be in a high-level state, forming a switching signal. The first switch Q1 is correspondingly turned on. The current discharge unit 21 remains in the filtering state. The current input from the high-voltage input terminal flows sequentially through the first capacitor C1 and the first switch Q1 to the reference ground, and the first capacitor C1 acts as a filter.

[0050] 2) The power system of a new energy vehicle first uses a low-voltage power supply to power the PTC heater, and then uses a high-voltage power supply to power the PTC heater: First, the low-voltage power supply supplies power to the PTC heater 10 , the power supply terminal VCC of the discharge control unit 22 in the inrush current circuit unit provides a 12V DC voltage, and the enable signal output terminal of the PTC heater outputs a second control signal (high level signal).

[0051] In this state, the second switch Q2 is turned on, so that the voltage level of the common connection node of the second resistor R2, the fifth resistor R5 and the second switch Q2 is pulled down to a low level state. The first switch Q1 is turned off, and the current discharge unit 21 works in the discharge state.

[0052] The high-voltage distribution box 3 then controls relay K1 to close, connecting the high-voltage input terminal to the high-voltage busbar. At this point, the high-voltage detection circuit 30 generates a high-voltage detection signal and provides it to the PTC heater 10. During the preset delay period, the enable signal output terminal of the PTC heater 10 continues to output the second control signal, keeping the current discharge unit 21 in the discharge state.

[0053] In this state, the surge current generated on the high-voltage bus is discharged to the reference ground GND after passing through the first capacitor C1 and the third resistor R3. The third resistor R3 suppresses and consumes the surge current generated at the moment of power-on, thereby protecting the PTC heater.

[0054] Finally, after a preset delay time, the enable signal output terminal of the PTC heater 10 switches to outputting the first control signal.

[0055] In this state, the second switch Q2 is turned off, causing the common connection node of the second resistor R2, the fifth resistor R5, and the second switch Q2 to be in a high-level state, forming a switching signal. The first switch Q1 is correspondingly turned on, and the current discharge unit 21 remains in a filtering state. The current input from the high-voltage input terminal flows sequentially through the first capacitor C1 and the first switch Q1 to the reference ground, with the first capacitor C1 acting as a filter.

[0056] 3) Scenario where the power system of a new energy vehicle uses both low-voltage and high-voltage power supplies to power the PTC heater: On the one hand, the low-voltage power supply starts to supply power to the PTC heater, so that the power supply terminal VCC of the discharge control unit 22 in the inrush current circuit unit is provided with a 12V DC voltage.

[0057] During the power-on process, the RC circuit formed by the second resistor R2 and the second capacitor C2 ensures that the common connection node of the second resistor R2, the fifth resistor R5 and the second switch tube Q2 is stably in a low level state.

[0058] After power-on, the voltage divider circuit formed by the first resistor R1 and the sixth resistor R6 turns on the second switch Q2, and the level of the common connection node of the second resistor R2, the fifth resistor R5 and the second switch Q2 is pulled down to a low level state.

[0059] Accordingly, the first switch tube Q1 remains turned off during the entire power-on process, and the current discharge unit 21 remains in the discharge state.

[0060] On the other hand, the high-voltage distribution box 3 also controls the relay K1 to be energized, so that the high-voltage input terminal is connected to the high-voltage bus, and the high-voltage power supply simultaneously supplies power to the PTC heater.

[0061] At this time, the current discharge unit 21 remains in the discharge state. The inrush current generated on the high-voltage bus is discharged to the reference ground GND after passing through the first capacitor C1 and the third resistor R3. The third resistor R3 suppresses and dissipates the inrush current generated at power-on, thus protecting the PTC heater.

[0062] When the high voltage detection signal generated by the high voltage detection circuit 30 is provided to the PTC heater 10 and a preset delay time has passed, the PTC heater 10 outputs a first control signal (low level signal) at the enable signal output terminal.

[0063] In this state, the second switch Q2 is turned off, causing the common connection node of the second resistor R2, the fifth resistor R5, and the second switch Q2 to be in a high-level state, forming a switching signal. The first switch Q1 is correspondingly turned on. The current discharge unit 21 remains in the filtering state. The current input from the high-voltage input terminal flows sequentially through the first capacitor C1 and the first switch Q1 to the reference ground, and the first capacitor C1 acts as a filter.

[0064] In summary, the inrush current suppression circuit 20 provided in the embodiment of the present invention can ensure that the PTC heater can effectively suppress the inrush current generated when the high voltage is powered on under a variety of different power supply conditions, thereby protecting the PTC heater and ensuring that the components in the high-voltage circuit are not damaged by the inrush current, thereby effectively reducing the failure rate and maintenance cost of the PTC heater.

[0065] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solutions and concepts of the present invention, and all these changes or substitutions should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A PTC heating device, wherein the low-voltage input terminal of the PTC heating device is connected to a low-voltage power supply, and the high-voltage input terminal of the PTC heating device is connected to a high-voltage power supply, characterized in that: The PTC heating device comprises: A PTC heater, the PTC heater being connected to the low-voltage input end and the high-voltage input end respectively, and being used to draw electrical energy from the low-voltage input end and / or the high-voltage input end; an inrush current suppression circuit, wherein a first end of the inrush current suppression circuit is connected to the high voltage input end, and a second end of the inrush current suppression circuit is connected to the enable signal output end of the PTC heater; a high-voltage detection circuit, wherein a detection terminal of the high-voltage detection circuit is connected to the high-voltage input terminal, and is configured to generate a high-voltage detection signal and provide the signal to the PTC heater when the high-voltage power supply supplies power to the PTC device; Wherein, the inrush current suppression circuit includes: a current discharge unit, the current discharge unit forming the first end, the current discharge unit operating in a discharge state or a filtering state; A discharge control unit is connected to the current discharge unit and is used to control the working state of the current discharge unit; the discharge control unit is powered by the low-voltage power supply, and the discharge control unit also forms the second end.

2. The PTC heating device according to claim 1, characterized in that: The control end of the current discharge unit is connected to the discharge control unit; The current discharge unit is configured to: switch to the filtering state when the control end receives a switching signal; and maintain operation in the discharge state when the control end does not receive a switching signal; The discharge control unit is configured to: provide the switching signal to the control terminal of the current discharge unit when the second terminal receives the first control signal; and not provide the switching signal when the second terminal does not receive the first control signal; The PTC heater is configured to output the first control signal to the second end after receiving the high-voltage detection signal and after a preset time interval.

3. The PTC heating device according to claim 2, characterized in that: The current discharge unit includes: a first capacitor, a third resistor and a first switch tube; One end of the first capacitor is connected to the high voltage input end to form the first end, and the other end of the first capacitor is connected to the reference ground through the third resistor to form a current discharge path; A first end of the first switch tube is connected between the first capacitor and the third resistor, a second end of the first switch tube is connected to the reference ground, and a control end of the first switch tube forms a control end of the current discharge unit; When the first switch tube is disconnected, the current discharge unit operates in the discharge state; When the first switch tube is turned on, the current discharge unit operates in the filtering state.

4. The PTC heating device according to claim 2, characterized in that: The discharge control unit includes: a first resistor, a second resistor, a fourth resistor, a fifth resistor, a sixth resistor, a second capacitor and a second switch tube; One end of the first resistor is connected to the power supply end of the discharge control unit, and the other end of the first resistor is connected to the reference ground through the sixth resistor; One end of the fourth resistor is connected between the first resistor and the sixth resistor, and a common connection node of the fourth resistor, the first resistor and the sixth resistor forms the second end; The other end of the fourth resistor is connected to the control end of the second switch tube, the first end of the second switch tube is connected to the power supply end through the second resistor; the second end of the second switch tube is connected to the reference ground; One end of the second capacitor is connected to the first end of the second switch tube, and the other end of the second capacitor is connected to the reference ground; one end of the fifth resistor is also connected to the first end of the second switch tube, and the other end of the fifth resistor is connected to the reference ground.

5. The PTC heating device according to claim 3 or 4, characterized in that: When the low-voltage power supply supplies power to the PTC heating device, the PTC heater is configured to: output the second control signal to the second end; The discharge control unit is configured to control the current discharge unit to operate in the discharge state when the second end receives the second control signal.

6. The PTC heating device according to claim 5, characterized in that: The first control signal is a low-level signal, the second control signal is a high-level signal; and the switching signal is a high-level signal.

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