Electric heater, air conditioner warm air system and new energy automobile

Abstract

The utility model discloses an electric heater, an air conditioner warm air system and a new energy automobile, the electric heater comprises a heating circuit, the first end of the heating circuit is connected with the positive electrode of a power supply circuit, the second end of the heating circuit is connected with the negative electrode of the power supply circuit, and the heating circuit is used for generating heat; the protection circuit comprises a protection switch and a protective tube, the protection switch is connected with the heating circuit in parallel, and the protective tube is connected with the heating circuit in series; the control circuit is connected with the control end of the protection switch and can output a protection control signal to the control end of the protection switch when it is determined that the heating circuit is abnormal so as to control the protection switch to be switched on, and then the protective tube is fused under the action of the short-circuit current. According to the electric heater, the protective tube can be quickly fused when the heating circuit is abnormal, so that short-circuit fault protection is realized, the response time is short, and the product is safer and more reliable.

Description

Technical Field

[0001] The present application relates to the technical field of new energy vehicles, and more specifically, to an electric heater, an air conditioning heating system and a new energy vehicle. Background Art

[0002] New energy vehicles usually use electric heaters for heating. Electric heaters are generally resistive loads, and use insulated gate bipolar transistors (IGBTs) as power switches to adjust the output power of the heater. As a power device, IGBTs are easily broken down when used improperly, usually showing a short circuit. If the heater does not handle this fault in time and protect it, it will cause thermal runaway of the heater, causing overheating damage. Utility Model Content

[0003] In view of this, the present application provides an electric heater, an air conditioning heating system and a new energy vehicle to solve the problem of being unable to effectively and quickly protect switching devices such as IGBTs from short-circuit faults.

[0004] In a first aspect, the present application provides an electric heater, comprising: a heating circuit, a first end of the heating circuit being connected to a positive pole of a power supply circuit, a second end of the heating circuit being connected to a negative pole of the power supply circuit, and the heating circuit being used to generate heat; a protection circuit, comprising a protection switch and a fuse, the protection switch being connected in parallel with the heating circuit, and the fuse being connected in series with the heating circuit; a control circuit, connected to a control end of the protection switch, and capable of outputting a protection control signal to the control end of the protection switch when determining that the heating circuit is abnormal, so as to control the protection switch to be turned on, thereby causing the fuse to melt under the action of a short-circuit current.

[0005] Preferably, the electric heater also includes: a detection circuit connected to the heating circuit and used to detect circuit parameters in the heating circuit; the control circuit is connected to the detection circuit and used to determine whether the heating circuit is abnormal based on the circuit parameters detected by the detection circuit.

[0006] Preferably, the control circuit includes a hardware protection circuit and a protection drive circuit, the protection drive circuit is connected to the hardware protection circuit and the control end of the protection switch, and the detection circuit includes: a first detection circuit, connected to the hardware protection circuit and used to detect the temperature of the electric heater, and the circuit parameters include the temperature of the electric heater; the hardware protection circuit is used to determine that the heating circuit is abnormal when the temperature detected by the first detection circuit is greater than a preset temperature threshold, and control the protection drive circuit to output the protection control signal.

[0007] Preferably, the heating circuit includes at least one group of heating components, each group of the heating components includes a resistor and a switching device connected in series between the first end and the second end of the heating circuit; the control circuit includes a controller, the controller has at least one first output end, the first output end is connected to the switching device in a one-to-one correspondence, and the control circuit sends a PWM control signal to the corresponding switching device through the at least one first output end to control the conduction or disconnection of the corresponding switching device, thereby realizing power regulation.

[0008] Preferably, the control circuit also includes a protection drive circuit, the controller has a second output terminal, the protection drive circuit is connected to the second output terminal and the control terminal of the protection switch, and the detection circuit includes: a second detection circuit, connected to the controller and the heating circuit, and used to detect the voltage between the first terminal and the second terminal of the heating circuit and the current passing through the first terminal or the second terminal of the heating circuit, and the circuit parameters include the voltage and the current; the controller is used to determine that the heating circuit is abnormal when the voltage and the current detected by the second detection circuit and the PWM control signal meet a preset relationship, and control the protection drive circuit to output the protection control signal.

[0009] Preferably, the electric heater comprises: a low-side driving circuit having at least one first connection terminal and at least one second connection terminal, the first connection terminal being connected to the first output terminal in a one-to-one correspondence, and the second connection terminal being connected to the control terminal of the switching device in a one-to-one correspondence.

[0010] Preferably, the protection switch includes an insulated gate bipolar transistor IGBT, the gate of the IGBT serves as the control end of the protection switch, the collector of the IGBT is connected to the first end of the heating circuit, and the emitter of the IGBT is connected to the second end of the heating circuit; or, the protection switch includes a metal oxide semiconductor MOS tube, the gate of the MOS tube serves as the control end of the protection switch, the first connection end of the MOS tube is connected to the first end of the heating circuit, and the second connection end of the MOS tube is connected to the second end of the heating circuit.

[0011] Preferably, one end of the fuse is connected to the positive pole of the power supply circuit, and the other end is connected to the first end of the heating circuit; or, one end of the fuse is connected to the negative pole of the power supply circuit, and the other end is connected to the second end of the heating circuit.

[0012] In a second aspect, the present application provides an air conditioning and heating system, which includes the above-mentioned electric heater.

[0013] In a third aspect, the present application provides a new energy vehicle, which includes the above-mentioned air conditioning and heating system.

[0014] According to the technical solution of the present application, by connecting the protection switch in parallel with the heating circuit and connecting the fuse in series with the heating circuit, when the heating circuit is abnormal, the control circuit can output a protection control signal to the control end of the protection switch to control the protection switch to be turned on, so that the fuse is blown under the action of the short-circuit current, thereby realizing short-circuit fault protection. In addition, since the current passing through the fuse is relatively high, the fuse can be blown quickly, thereby improving the response capability and making the product safer and more reliable.

[0015] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings constituting a part of the present application are used to provide a further understanding of the present application, and the schematic implementation modes and descriptions of the present application are used to explain the present application. In the accompanying drawings:

[0017] Figure 1 A graph showing an exemplary fusing characteristic of a fuse;

[0018] Figure 2 A schematic diagram of the circuit structure of an electric heater provided in an embodiment of the present application. DETAILED DESCRIPTION

[0019] The technical solution of the present application will be described in detail below with reference to the accompanying drawings and in combination with specific embodiments.

[0020] In order to prevent thermal runaway caused by the breakdown of switching devices such as IGBT in the electric heater and short circuit failure, the following solutions are mainly used to prevent thermal runaway of the electric heater in the related art:

[0021] 1) Place a group of IGBTs on the high side and low side of the heating resistor, where the high side IGBT is used as redundant protection and the low side IGBT is used as power drive. When a short circuit occurs on one of the high side and the low side, the protection purpose is achieved by turning off the IGBT on the other side. However, this solution cannot achieve complete protection, because in some cases both the high side and the low side IGBT may be broken down and short-circuited. At this time, effective protection cannot be performed and the heater will still be in a thermal runaway state.

[0022] 2) Use the temperature characteristics of the positive temperature coefficient (PTC) for protection. Since the resistance value of the PTC heater increases rapidly when it reaches a certain temperature (Curie point), it has the characteristic of instantaneous resistance jump. Therefore, it can be used for overcurrent and overtemperature protection during thermal runaway. However, this solution cannot be used for other types of heaters.

[0023] 3) Use a temperature fuse to protect the heater. For example, the temperature fuse is connected in series to the power supply end of the high-voltage bus. When the temperature of the heater cavity or the environment reaches the set value, the temperature fuse will directly melt, thereby cutting off the high-voltage power supply to achieve the purpose of protection. However, the temperature fuse usually has a long melting time. When the temperature of the heater is out of control, the melting time is usually more than 1 minute, which cannot achieve the purpose of rapid protection.

[0024] 4) Use relays to protect the heater. Specifically, the vehicle supplies power to the heater through a relay. When the temperature of the heater is out of control, the electronic control unit (ECU) is notified through the communication bus to turn off the relay and cut off the high-voltage power supply. This solution requires the cooperation of the vehicle ECU, and the response time and initiative are poor.

[0025] In view of this, the present application provides an electric heater, an air conditioning heating system and a new energy vehicle, which can effectively and quickly protect the short circuit fault of a switching device such as an IGBT. Among them, the air conditioning heating system includes the above-mentioned electric heater. The new energy vehicle includes the above-mentioned air conditioning heating system. The electric heater of the embodiment of the present application can quickly blow the fuse when the heating circuit is abnormal, thereby effectively realizing short circuit fault protection, and the reaction time is short, making the product safer and more reliable.

[0026] In order to ensure that the heater does not experience thermal runaway, when a short circuit failure of the switching device occurs, the fusing characteristics of the fuse can be used to disconnect the high voltage power supply. Figure 1 FIG. 1 is a graph showing an exemplary fusing characteristic of a fuse. Figure 1 As shown, taking a 25A fuse as an example, at 2 times the current (50A), it usually takes 20s to 200s to blow; at 3 times the current (75A), it usually takes about 1s to blow; at 5 times the current (125A), it only takes less than 0.1s to blow instantly.

[0027] Since the heater product is a resistive load, when a short circuit occurs in the switch device, its maximum operating current generally does not exceed 2 times the current, so it cannot ensure that the high-voltage power supply is quickly cut off, and thermal runaway problems will still occur. In order to avoid thermal runaway problems, it is necessary to give the fuse connected in series in the high-voltage power supply line a larger fuse current.

[0028] Figure 2 This is a schematic diagram of the circuit structure of an electric heater provided in an embodiment of the present application. Figure 2 As shown, the electric heater includes a heating circuit, a protection circuit and a control circuit. The heating circuit may include at least one set of heating components, each set of heating components includes a resistor and a switch device connected in series between a first end and a second end of the heating circuit. Figure 2 In the embodiment, the heating circuit includes two groups of heating components, the first group of heating components includes a first resistor R1 and a first switch device Q1, and the second group of heating components includes a second resistor R2 and a second switch device Q2. The first end of the heating circuit is connected to the positive electrode HV+ of the power supply line, and the second end of the heating circuit is connected to the negative electrode HV- of the power supply line. The heating circuit is used to generate heat.

[0029] The protection circuit includes a protection switch Q and a fuse F1. The protection switch Q is connected in parallel with the heating circuit, and the fuse F1 is connected in series with the heating circuit. Figure 1 In the embodiment, one end of the fuse F1 is connected to the positive electrode HV+ of the power supply circuit, and the other end is connected to the first end of the heating circuit. In other embodiments, one end of the fuse F1 is connected to the negative electrode HV- of the power supply circuit, and the other end is connected to the second end of the heating circuit.

[0030] Furthermore, in some embodiments, the protection switch Q includes an insulated gate bipolar transistor IGBT, the gate of the IGBT serves as the control terminal of the protection switch Q, the collector of the IGBT is connected to the first terminal of the heating circuit, and the emitter of the IGBT is connected to the second terminal of the heating circuit. In other embodiments, the protection switch Q includes a metal oxide semiconductor MOS tube, the gate of the MOS tube serves as the control terminal of the protection switch Q, the first connection terminal of the MOS tube is connected to the first terminal of the heating circuit, and the second connection terminal of the MOS tube is connected to the second terminal of the heating circuit. In other embodiments, the protection switch Q may also be other devices, such as a thyristor.

[0031] The control circuit is connected to the control end of the protection switch Q, and can output a protection control signal to the control end of the protection switch Q when determining that the heating circuit is abnormal, so as to control the protection switch Q to be turned on, thereby causing the fuse F1 to fuse under the action of the short-circuit current.

[0032] According to the technical solution of the present application, by connecting the protection switch Q in parallel with the heating circuit and connecting the fuse F1 in series with the heating circuit, when the heating circuit is abnormal, the control circuit can output a protection control signal to the control end of the protection switch Q to control the protection switch Q to be turned on, thereby causing the fuse F1 to melt under the action of the short-circuit current, thereby realizing short-circuit fault protection. In addition, the current passing through the fuse is relatively high, which can cause the fuse to melt quickly, thereby improving the response capability and making the product safer and more reliable.

[0033] In addition, if a protective switch such as an IGBT is connected in series in the heating circuit, the overload current is generally less than 1.5 times the rated value, so it takes a long time for the fuse F1 to melt, usually more than 2 minutes. For electric heaters, when an IGBT failure causes thermal runaway, the temperature may rise to more than 250°C within 30 seconds, which may cause thermal damage. From the perspective of thermal safety, it is hoped that the high-voltage power supply can be cut off within a few seconds. Therefore, the present application adopts a bypass IGBT method, which is connected in parallel with the heating circuit. When the IGBT is turned on, the high-voltage power supply will be directly short-circuited to the ground, so that more than 3 to 5 times the rated current will flow through the fuse. According to the working characteristics of the fuse, when the current is less than 1.5 times, it takes more than 2 minutes to melt, and when the current is more than 3 to 5 times, it only takes 1 to 2 seconds to melt. Therefore, the use of the IGBT bypass method can instantly cut off the high-voltage power supply to achieve the purpose of preventing thermal runaway.

[0034] Furthermore, in order to facilitate the control circuit to determine whether the heating circuit is abnormal, in some embodiments, the electric heater further includes a detection circuit. The detection circuit is connected to the heating circuit and is used to detect circuit parameters in the heating circuit. The control circuit is connected to the detection circuit and is used to determine whether the heating circuit is abnormal based on the circuit parameters detected by the detection circuit. Exemplarily, the control circuit may have but is not limited to the following two schemes:

[0035] The first solution: the control circuit includes a hardware protection circuit and a protection drive circuit, and the protection drive circuit is connected to the hardware protection circuit and the control end of the protection switch Q. The detection circuit includes a first detection circuit, which is connected to the hardware protection circuit and is used to detect the temperature of the electric heater, and the circuit parameters include the temperature of the electric heater. The hardware protection circuit is used to determine that the heating circuit is abnormal when the temperature detected by the first detection circuit is greater than a preset temperature threshold, and control the protection drive circuit to output a protection control signal.

[0036] The second solution - the control circuit includes a controller such as an MCU, the controller has at least one first output terminal, the first output terminal is connected to the switching devices (such as the first switching device Q1 and the second switching device Q2) in a one-to-one correspondence, and the control circuit sends a PWM control signal (such as PWM1 and PWM2) to the corresponding switching device through the at least one first output terminal to control the conduction or disconnection of the corresponding switching device, thereby realizing power regulation.

[0037] In addition, the electric heater may further include a low-side drive circuit. The low-side drive circuit has at least one first connection terminal and at least one second connection terminal, the first connection terminal is connected to the first output terminal in a one-to-one correspondence, and the second connection terminal is connected to the control terminal of the switch device (such as the first switch device Q1 and the second switch device Q2) in a one-to-one correspondence.

[0038] Furthermore, the control circuit may also include a protection drive circuit, the controller has a second output terminal, and the protection drive circuit is connected to the second output terminal and the control terminal of the protection switch Q. The detection circuit includes a second detection circuit. The second detection circuit is connected to the controller and the heating circuit, and is used to detect the voltage between the first terminal and the second terminal of the heating circuit and the current passing through the first terminal or the second terminal of the heating circuit, and the circuit parameters include voltage and current. The controller is used to determine that the heating circuit is abnormal when the voltage and current detected by the second detection circuit and the PWM control signal meet a preset relationship, and control the protection drive circuit to output a protection control signal. Exemplarily, the value of the product of the voltage and the current multiplied by the duty cycle can be compared with a preset power threshold. If the value is greater than the preset power threshold, it is determined that the heating circuit is abnormal; if the value is less than the preset power threshold, it is determined that the heating circuit is normal.

[0039] The electric heater in the embodiment of the present application, when the electric heater is operating normally, receives a heating command, calculates the duty cycle of the PWM control according to the power demand and the current voltage, and can send a PWM1 signal to control the conduction or disconnection of the first switching device Q1, and send a PWM2 signal to control the conduction or disconnection of the second switching device Q2, thereby achieving the purpose of power regulation. At this time, the protection switch Q remains in the disconnected state.

[0040] When one or both of the first switch device Q1 and the second switch device Q2 for power control have a short-circuit fault, the software can diagnose the corresponding short-circuit fault through voltage and current detection. At this time, the software sends a protection control signal to force the protection switch Q to enter the on state, thereby causing a short-circuit current to appear on the fuse F1. The short-circuit current is much larger than the rated working current of the fuse, such as 3 to 5 times or more. The fuse F1 will melt in a very short time (such as 0.1 to 1.5s) under 3 to 5 times the current, thereby cutting off the high-voltage power supply and achieving the purpose of protecting the heater from thermal runaway.

[0041] In worse cases, the software also goes out of control. At this time, the temperature of the heater continues to rise. When the temperature detected by the temperature detection circuit exceeds the set value (i.e., the hardware temperature protection threshold), the hardware protection circuit forces the protection switch Q to enter the on state, causing the fuse F1 to melt in a very short time, thereby achieving the purpose of avoiding thermal runaway.

[0042] That is to say, there can be two temperature protection points, and the lower temperature protection point triggers the software to perform protection driving first (that is, the software sends a protection control signal to force the protection switch Q to enter the on state). If the software protection fails, the temperature will continue to rise to a higher hardware temperature protection point. At this time, the hardware protection circuit will act (that is, force the protection switch Q to enter the on state) to perform protection driving.

[0043] To sum up, in order to solve the problem that the electric heaters of existing new energy vehicles cannot effectively and quickly protect switching devices such as IGBT short-circuit faults, the present application proposes a solution of using a high-voltage fuse in conjunction with a power switch (i.e., a protection switch) so that the high-voltage fuse can be quickly blown, thereby achieving short-circuit fault protection.

[0044] Specifically, when a short circuit fault is detected in at least one switch device for power control, such as the first switch device or the second switch device, the software or hardware circuit forces the protection switch to be turned on, and the instantaneous large current can cause the fuse to melt in a very short time, thereby cutting off the high-voltage power supply and preventing the heater from overheating and running away. In addition, the circuit structure is simple and easy to implement, and the cost is lower than that of the high-low side redundancy solution or the temperature insurance solution, and the protection is faster and more reliable.

[0045] The preferred embodiments of the present application are described in detail above; however, the present application is not limited to the specific details in the above embodiments. Within the technical concept of the present application, a variety of simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the protection scope of the present application.

[0046] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present application will not further describe various possible combinations. In addition, the various different embodiments of the present application can also be combined arbitrarily, as long as they do not violate the idea of ​​the present application, they should also be regarded as the contents disclosed in the present application.

Claims

1. An electric heater, characterized in that: include: A heating circuit, wherein a first end of the heating circuit is connected to a positive electrode of a power supply circuit, a second end of the heating circuit is connected to a negative electrode of the power supply circuit, and the heating circuit is used to generate heat; A protection circuit, comprising a protection switch and a fuse, wherein the protection switch is connected in parallel with the heating circuit, and the fuse is connected in series with the heating circuit; The control circuit is connected to the control end of the protection switch and can output a protection control signal to the control end of the protection switch when it is determined that the heating circuit is abnormal, so as to control the protection switch to be turned on, thereby causing the fuse to melt under the action of the short-circuit current.

2. The electric heater according to claim 1, characterized in that: Also includes: A detection circuit, connected to the heating circuit and used to detect circuit parameters in the heating circuit; The control circuit is connected to the detection circuit and is used to determine whether the heating circuit is abnormal according to the circuit parameters detected by the detection circuit.

3. The electric heater according to claim 2, characterized in that: The control circuit includes a hardware protection circuit and a protection drive circuit, the protection drive circuit is connected to the hardware protection circuit and the control end of the protection switch, and the detection circuit includes: a first detection circuit connected to the hardware protection circuit and used to detect the temperature of the electric heater, wherein the circuit parameters include the temperature of the electric heater; The hardware protection circuit is used to determine that the heating circuit is abnormal when the temperature detected by the first detection circuit is greater than a preset temperature threshold, and control the protection drive circuit to output the protection control signal.

4. The electric heater according to claim 2, characterized in that: The heating circuit comprises at least one set of heating components, each set of the heating components comprises a resistor and a switch device connected in series between a first end and a second end of the heating circuit; The control circuit includes a controller having at least one first output terminal, wherein the first output terminal is connected to the switching device in a one-to-one correspondence, and the control circuit sends a PWM control signal to the corresponding switching device through the at least one first output terminal to control the conduction or disconnection of the corresponding switching device, thereby realizing power regulation.

5. The electric heater according to claim 4, characterized in that: The control circuit further includes a protection drive circuit, the controller has a second output terminal, the protection drive circuit is connected to the second output terminal and the control terminal of the protection switch, and the detection circuit includes: a second detection circuit connected to the controller and the heating circuit and used to detect a voltage between the first end and the second end of the heating circuit and a current passing through the first end or the second end of the heating circuit, wherein the circuit parameters include the voltage and the current; The controller is used for determining that the heating circuit is abnormal when the voltage and the current detected by the second detection circuit and the PWM control signal satisfy a preset relationship, and controlling the protection drive circuit to output the protection control signal.

6. The electric heater according to claim 4, characterized in that: include: The low-side driving circuit has at least one first connection terminal and at least one second connection terminal, wherein the first connection terminal is connected to the first output terminal in a one-to-one correspondence, and the second connection terminal is connected to the control terminal of the switching device in a one-to-one correspondence.

7. The electric heater according to claim 1, characterized in that: The protection switch comprises an insulated gate bipolar transistor IGBT, the gate of the IGBT serves as the control terminal of the protection switch, the collector of the IGBT is connected to the first terminal of the heating circuit, and the emitter of the IGBT is connected to the second terminal of the heating circuit; or, The protection switch includes a metal oxide semiconductor (MOS) tube, a gate of which serves as a control end of the protection switch, a first connection end of the MOS tube connected to a first end of the heating circuit, and a second connection end of the MOS tube connected to a second end of the heating circuit.

8. The electric heater according to any one of claims 1 to 7, characterized in that: One end of the fuse is connected to the positive electrode of the power supply circuit, and the other end is connected to the first end of the heating circuit; or, One end of the fuse is connected to the negative pole of the power supply circuit, and the other end is connected to the second end of the heating circuit.

9. An air conditioning and heating system, characterized in that: Comprising an electric heater according to any one of claims 1-8.

10. A new energy vehicle, characterized in that: It comprises the air conditioning and heating system according to claim 9.

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