PTC heater over-temperature protection system and method

Abstract

The invention provides a PTC heater over-temperature protection system and method.The PTC heater over-temperature protection system comprises a PTC heater, a switch control module, a current sampling module, a PTC control module, a communication module and a DCDC module, the switch control module is used for controlling on-off of a working circuit of the PTC heater, the current sampling module is used for sampling the current value of the PTC heater in real time, and the PTC control module is used for controlling on-off of a working circuit of the PTC heater; the PTC control module is used for triggering an over-temperature protection action of the PTC core body when a triggering condition reaches a preset threshold value, the DCDC module is used for providing working voltage for the PTC control module, the communication module and the switch control module, and the communication module is used for communication between the PTC control module and a whole vehicle system; triggering conditions of over-temperature protection in the PTC control module comprise a voltage threshold value, a PWM value, a current threshold value and a delay time threshold value, and over-temperature protection of the PTC core is triggered only when the triggering conditions are met at the same time. According to the invention, low-cost and high-reliability over-temperature protection of the PTC heater is realized; and meanwhile, the automatic recovery time after PTC over-temperature protection is set, so that the PTC heater can work more efficiently.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy PTC heaters, and in particular to a PTC heater over-temperature protection system and method. Background Art

[0002] With the continuous development of the automobile industry and technological progress, the application scope of PTC heaters in new energy electric vehicles is also expanding, and it has gradually become the mainstream heating element for automobile air conditioning and heating.

[0003] At present, most of the PTC heater core over-temperature protection on the market uses core temperature sensors to collect temperature to achieve over-temperature protection. Its disadvantages are:

[0004] (1) Overall cost: Currently, for PTC products with multiple temperature zones, a sensor needs to be placed in each temperature zone, which will increase the overall cost;

[0005] (2) Sealing: The core temperature sensor usually needs to be placed on the side of the heating core, which affects the sealing of the core structure;

[0006] (3) After-sales cost: If the core temperature sensor is damaged or fails, the entire PTC assembly may need to be replaced, which is difficult and costly to repair;

[0007] (4) EMC performance: The core temperature sensor is arranged on the side of the core, and external radiation interference will be coupled into the PTC controller along the sensor wiring harness.

[0008] Therefore, it is necessary to propose a new PTC heater over-temperature protection technology. Summary of the invention

[0009] The purpose of the present invention is to provide a PTC heater over-temperature protection system and method to solve the current problem of over-temperature protection of the PTC heater core. The present invention can judge the core over-temperature according to the working characteristics of the PTC core by the collected current value, so the core temperature sensor can be directly removed, and the PTC can also perform VAVE cost reduction. The specific technical solution is as follows:

[0010] A PTC heater over-temperature protection system comprises a PTC heater, a switch control module, a current sampling module and a PTC control module, wherein the PTC heater, the switch control module and the current sampling module are sequentially connected between the positive and negative electrodes of a high-voltage power supply, and the PTC heater, the switch control module and the current sampling module are all connected to the PTC control module;

[0011] The switch control module is used to control the on and off of the working circuit of the PTC heater, the current sampling module is used to sample the working current value of the PTC heater in real time, and the PTC control module is used to trigger the PTC core over-temperature protection when all trigger conditions are met.

[0012] Furthermore, the PTC heater is provided with thermocouples, the thermocouples are evenly arranged on the PTC core heating tube and the heat dissipation strip, and the temperature of the thermocouples can be monitored and displayed by a temperature detector.

[0013] Furthermore, the switch control module includes an IGBT driver chip and an IGBT switch, the collector of the IGBT switch is connected to the PTC heater, the emitter of the IGBT switch is connected to the current sampling module, and the gate of the IGBT switch is connected to the PTC control module through the IGBT driver chip.

[0014] Furthermore, the current sampling module may adopt a current sensor or a sampling resistor and a current sampling circuit, one end of the sampling resistor is connected to the emitter of the IGBT switch, and the other end is connected to the negative electrode of the high voltage power supply. The sampling resistor is also connected to the current sampling circuit, and the current sampling circuit samples the current value of the PTC heater in real time through the sampling resistor.

[0015] Furthermore, the over-temperature protection triggering conditions in the PTC control module must be met simultaneously to trigger the PTC core over-temperature protection action, and the over-temperature protection triggering conditions include a preset current threshold and delay time threshold, a voltage threshold and a PWM value of the IGBT.

[0016] Furthermore, the current threshold is the current value when the PTC core is dry-burned at 140°C, the delay time refers to the duration of the current threshold, the voltage threshold can be preset according to the vehicle voltage, the voltage threshold is greater than the minimum operating voltage of the vehicle, and the PWM value of the IGBT is 100%.

[0017] Furthermore, the over-temperature protection action of the PTC control module will not lock the heating function of the PTC heater. After the set over-temperature protection time ends, the PTC heater will return to a normal heating state.

[0018] Furthermore, it also includes a communication module, which is used for the PTC control module to communicate with the entire vehicle system, and the communication module is connected to the PTC control module through a digital isolator.

[0019] Furthermore, it also includes a DCDC module, which is used to provide working voltage to the PTC control module, the communication module, and the switch control module. The DCDC module is connected to the communication module and the PTC control module through a low-voltage linear regulator.

[0020] The present invention also provides a PTC heater over-temperature protection method, using the above-mentioned PTC heater over-temperature protection system, the method comprises the following steps:

[0021] S1, PTC heater is turned on to enable PTC heating;

[0022] S2, the current sampling module samples the current value of the PTC heater in real time and transmits it to the PTC control module;

[0023] S3, when all the triggering conditions of the PTC core over-temperature protection are met, the PTC control module triggers the PTC core over-temperature protection;

[0024] S4, the switch control module is disconnected and the PTC heater stops working;

[0025] S5. After the over-temperature protection time ends, the PTC heater resumes working and continues heating.

[0026] The present invention provides a PTC heater over-temperature protection system and method, which has the following beneficial effects compared with the prior art:

[0027] The present invention provides a PTC heater over-temperature protection system and method, which eliminates the core temperature sensor, determines whether the PTC core is over-temperature by collecting real-time current values ​​according to the working characteristics of the PTC core, and combines the voltage threshold, time threshold and PWM to trigger the PTC core over-temperature protection, thereby realizing low-cost and high-reliability PTC heater over-temperature protection; at the same time, the automatic recovery time of the PTC heater is set, so that the PTC heater can work more efficiently. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of a framework of a PTC heater over-temperature protection system provided by the present invention;

[0029] Figure 2 It is a schematic diagram of the working characteristics of the PTC core provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the accompanying drawings provided by the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. According to the following description, the advantages and features of the present invention will be more clear. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0031] In the description of the present invention, unless otherwise clearly stipulated and limited, the terms "connection" and "connected" should be interpreted in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] In the description of the present invention, terms such as "up", "down", "left", "right", "front", "back", "center", "horizontal", "vertical", "top", "bottom", "inside" and "outside" and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of description and simplification of operation, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0033] The existing PTC core has a temperature sampling circuit, which is connected through the temperature sensor socket. When the temperature value collected by the temperature sensor is transmitted to the MCU through the temperature sampling circuit, the software will report the temperature collected at that time in real time. When the temperature reaches the preset value, the core will be protected from overheating. However, if the core temperature sensor is flooded, temperature collection fails, the wiring harness is damaged, or the wire is clamped, the PTC will fail and will not be able to heat, which will affect the entire vehicle.

[0034] The present invention eliminates the PTC core temperature sensor and studies the over-temperature protection strategy through the working characteristics of the PTC ceramic sheet. It can be seen from the working characteristics of the PTC ceramic sheet that after crossing TRmin (temperature at minimum resistance), the PTC resistance value will also increase synchronously with the increase of temperature. At this time, the PTC working amplitude current will also gradually decrease. By collecting the PTC working amplitude current and temperature data for calibration, the software amplitude current protection threshold and judgment time are formulated to realize the PTC core over-temperature protection, and realize low-cost and high-reliability core temperature over-temperature protection.

[0035] Example 1

[0036] This embodiment provides a PTC heater over-temperature protection system. Figure 1As shown, the system includes a PTC heater, a switch control module, a current sampling module, a PTC control module, a communication module and a DCDC module. The PTC heater, the switch control module and the current sampling module are sequentially connected between the positive electrode HV+ and the negative electrode HV- of the high-voltage power supply, the switch control module, the PTC heater and the current sampling module are all connected to the PTC control module, the DCDC module is connected to the communication module and the PTC control module through a low-voltage linear regulator, and the communication module is connected to the PTC control module through a digital isolator.

[0037] The system is described in detail below.

[0038] As an implementation method of the PTC heater, a temperature sensor is not arranged on the core of the PTC heater, but thermocouples are arranged evenly on the heating tube and the heat dissipation strip of the PTC core. The temperature of the thermocouples on the heating tube and the heat dissipation strip of the PTC core can be detected and displayed in real time by a temperature tester.

[0039] As an implementation mode of the switch control module, the switch control module is used to control the on and off of the PTC heating circuit, including an IGBT driver chip and an IGBTR switch, wherein the collector of the IGBT switch is connected to the PTC heater, the emitter of the IGBT switch is connected to the current sampling module, the gate of the IGBT switch is connected to the over-temperature protection module through the IGBT driver, and the IGBT driver is connected to the DCDC module and the PTC control module.

[0040] As an implementation of the current sampling module, the current sampling module is used to sample the working current of the PTC heater in real time and transmit it to the over-temperature protection module. The current sampling module can use a current sensor. In other implementations, the current sampling module can also use a sampling resistor and a current sampling circuit. The sampling resistor is connected in the PTC heating circuit, one end is connected to the emitter of the IGBT switch, and the other end is connected to the high-voltage negative electrode HV-. The sampling resistor is also connected to the current sampling circuit. The current sampling circuit samples the current value in the PTC heating circuit in real time through the sampling resistor, and transmits it to the PTC control module after the integrated operational amplifier.

[0041] As an implementation of the PTC control module, the PTC control module is used to control the PTC heater and perform overcurrent, overvoltage, short circuit and overtemperature protection, and an MCU chip can be used. The overtemperature protection is triggered when all the triggering conditions are met.

[0042] See also Figure 2As shown, it is a schematic diagram of the working characteristics of the PTC heater core, in which Rn represents the rated temperature zero-power resistance, Rmin represents the minimum zero-power resistance, TRmin represents the temperature at the minimum resistance, Tc represents the switching temperature or Curie temperature, Rc represents the switching resistance, Rmax represents the maximum resistance, and TRmax represents the temperature at the maximum resistance.

[0043] As can be seen from the figure, the resistance value of the PTC core is affected by temperature. The temperature of the startup process is below 25°C. As the temperature rises, the resistance value of the PTC core gradually decreases, and the PTC heater enters the surge current (impact current), also known as TRmin (temperature at the minimum resistance value). As the temperature continues to rise, it exceeds the working area and enters the safe low-power consumption area. At this time, the heat generation and heat dissipation of the PTC core reach a balance state. If it continues to dry burn, the PTC core will enter the failure area and the PTC core will be damaged. Due to different chip resistance arrangement methods, the heating power of the PTC heater is different. Therefore, it is necessary to test the dry burning of the same core under different voltages and different air volumes to find out the appropriate current value of the core under dry burning. This current value can be determined according to the temperature of the thermocouple. When the PTC heater is dry burning, the temperature will become higher and higher. The temperature of the PTC core can be observed through the temperature detector, and the PTC working current value can be obtained through the current sampling module. When the temperature of the thermocouple is about 140°C, the current value at this time is the condition value for judging the dry burning of the core. This current value is preset as the current threshold as one of the triggering conditions for the PTC core overtemperature protection. In order to prevent false alarms, after defining the current value, it is necessary to add the judgment condition of the delay time. After reaching the set current threshold, it is judged as a core overtemperature fault after a delay of a few seconds. The delay time can be set to 10-15s. At the same time, the PTC air heater is PWM closed-loop control. When one PTC is dry-burned, as the temperature rises, the IGBT duty cycle will gradually rise to 100%. Therefore, the overtemperature protection can also be calibrated as IGBT PWM = 100%. With the limitations of PWM value, current value and delay time, in order to prevent normal voltage fluctuations and false triggering of PTC core overtemperature protection, it is also necessary to add the judgment of the voltage value. The voltage value can be preset according to the voltage range of the whole vehicle, which is generally greater than the minimum operating voltage of the whole vehicle.

[0044] In summary, the triggering conditions of the PTC core over-temperature protection in the PTC control module include: current threshold and delay time, voltage threshold, and PWM value. The above four triggering conditions must be met at the same time to trigger the PTC core over-temperature protection action. After the PTC core over-temperature protection, the core over-temperature recovery condition can be determined according to the actual situation. It can generally be defined as that after the PTC core over-temperature protection, the duration is greater than a certain time and it will automatically recover. The PTC will work normally again for heating, so the PTC heating function will not be locked.

[0045] As an implementation method of the DCDC module, the DCDC module is used to provide operating voltage for the PTC control module, the communication module and the IGBT driver.

[0046] As an implementation mode of the communication module, the communication module is used for the PTC control module to communicate with the whole vehicle system.

[0047] Example 2

[0048] This embodiment provides a PTC heater over-temperature protection method, which uses the PTC heater over-temperature protection system in Embodiment 1. The method specifically includes the following steps:

[0049] S1, PTC heater is turned on to enable PTC heating;

[0050] Specifically, the PTC heater is turned on and enabled, and the current passes through the PTC heater, the switch control module, the current sampling module, and finally to the high-voltage negative electrode HV- from the high-voltage positive electrode HV+, and the PTC heater performs heating work.

[0051] S2, the current sampling module samples the current value of the PTC heater in real time and transmits it to the PTC control module;

[0052] S3, when the triggering conditions of the PTC core over-temperature protection all reach the preset threshold, the PTC control module triggers the PTC core over-temperature protection;

[0053] Specifically, when the current sampling value reaches the preset current threshold, the PTC core is judged to be dry-burned. At the same time, the duration of the current threshold reaches the preset delay time, and the PWM of the IGBT is 100%, and the voltage reaches the preset voltage threshold, the PTC core over-temperature protection action is triggered in the PTC control module.

[0054] S4, the switch control module is disconnected and the PTC heater stops working;

[0055] Specifically, the PTC control module controls the IGBT drive to disconnect the IGBT switch, and the PTC heater stops heating.

[0056] S5. After the over-temperature protection time ends, the PTC heater resumes working and continues heating.

[0057] Specifically, the over-temperature protection of the PTC core will not lock the PTC heater. After a period of over-temperature protection, such as the over-temperature protection time is set to 10s, the PTC control module controls the IGBT drive to turn on the IGBT switch, and the PTC heater resumes heating.

[0058] Those skilled in the art should understand that the present invention can be implemented in many other specific forms without departing from the spirit and scope of the present invention. Based on the embodiments of the present invention, any changes and modifications made by ordinary technicians in the field of the present invention according to the above disclosure are within the scope of protection of the claims.

Claims

1. A PTC heater over-temperature protection system, characterized in that: It includes a PTC heater, a switch control module, a current sampling module, and a PTC control module, wherein the PTC heater, the switch control module, and the current sampling module are sequentially connected between the positive and negative electrodes of a high-voltage power supply, and the PTC heater, the switch control module, and the current sampling module are all connected to the PTC control module; The switch control module is used to control the on and off of the working circuit of the PTC heater, the current sampling module is used to sample the working current value of the PTC heater in real time, and the PTC control module is used to trigger the PTC core over-temperature protection when all trigger conditions are met.

2. The PTC heater over-temperature protection system according to claim 1, characterized in that: The PTC heater is provided with thermocouples, and the thermocouples are evenly arranged on the PTC core heating tube and the heat dissipation strip. The temperature of the thermocouples can be monitored and displayed by a temperature detector.

3. The PTC heater over-temperature protection system according to claim 2, characterized in that: The switch control module includes an IGBT drive chip and an IGBT switch, the collector of the IGBT switch is connected to the PTC heater, the emitter of the IGBT switch is connected to the current sampling module, and the gate of the IGBT switch is connected to the PTC control module through the IGBT drive chip.

4. The PTC heater over-temperature protection system according to claim 3, characterized in that: The current sampling module can use a current sensor or a sampling resistor and a current sampling circuit. One end of the sampling resistor is connected to the emitter of the IGBT switch, and the other end is connected to the negative electrode of the high-voltage power supply. The sampling resistor is also connected to the current sampling circuit. The current sampling circuit samples the current value of the PTC heater in real time through the sampling resistor.

5. The PTC heater over-temperature protection system according to claim 4, characterized in that: The over-temperature protection triggering conditions in the PTC control module must be met simultaneously to trigger the over-temperature protection action of the PTC core, and the over-temperature protection triggering conditions include a preset current threshold and delay time threshold, a voltage threshold and a PWM value of the IGBT.

6. The PTC heater over-temperature protection system according to claim 5, characterized in that: The current threshold is the current value when the PTC core is dry-burned at 140°C. The delay time refers to the duration of the current threshold. The voltage threshold can be preset according to the vehicle voltage. The voltage threshold is greater than the minimum operating voltage of the vehicle. The PWM value of the IGBT is 100%.

7. The PTC heater over-temperature protection system according to claim 5, characterized in that: The over-temperature protection action of the PTC control module will not lock the heating function of the PTC heater. After the set over-temperature protection time ends, the PTC heater will return to the normal heating state.

8. The PTC heater over-temperature protection system according to claim 1, characterized in that: It also includes a communication module, which is used for the PTC control module to communicate with the entire vehicle system, and the communication module is connected to the PTC control module through a digital isolator.

9. The PTC heater over-temperature protection system according to claim 8, characterized in that: It also includes a DCDC module, which is used to provide working voltage to the PTC control module, the communication module and the switch control module. The DCDC module is connected to the communication module and the PTC control module through a low-voltage linear regulator.

10. A PTC heater over-temperature protection method, using the PTC heater over-temperature protection system according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: S1, PTC heater is turned on to enable PTC heating; S2, the current sampling module samples the current value of the PTC heater in real time and transmits it to the PTC control module; S3, when all the triggering conditions of the PTC core over-temperature protection are met, the PTC control module triggers the PTC core over-temperature protection; S4, the switch control module is disconnected and the PTC heater stops working; S5. After the over-temperature protection time ends, the PTC heater resumes working and continues heating.

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