Vehicle-mounted high-voltage PTC control circuit

Abstract

The invention provides a vehicle-mounted high-voltage PTC control circuit. The vehicle-mounted high-voltage PTC control circuit comprises a switching tube Q, an inductor L, a diode D and a capacitor C, the first end of the switching tube Q is connected with an input power supply; one end of the inductor L is connected with the second end of the switching tube Q, and the other end of the inductor L is used for connecting one end of the vehicle-mounted high-voltage PTC and one end of the capacitor C; the negative electrode of the diode D is connected with the second end of the switching tube Q and one end of the inductor L. The positive electrode of the diode D is connected with the grounding end, the other end of the capacitor C and the other end of the vehicle-mounted high-voltage PTC. The PTC is controlled by the control circuit, stable voltage can be effectively output, the change rate of voltage and current is more controllable, after the voltage is stabilized by the control circuit, the change of the voltage and the current becomes smooth, and generation of electromagnetic radiation is effectively reduced. After the voltage is stabilized, the current in the grounding loop is more stable, and the stable grounding current can reduce the generation of noise voltage, thereby reducing the influence of electromagnetic radiation on the system.

Description

Technical Field

[0001] The invention relates to the technical field of thermistor heating control, and in particular to a vehicle-mounted high-voltage PTC control circuit and a vehicle-mounted heating device and a vehicle having the same. Background Art

[0002] PTC is a special type of thermistor whose resistance value increases with temperature and can convert electrical energy into heat energy.

[0003] In traditional high-voltage PTC control, the switch tube is directly used for control. The switch tube controls the on and off of the circuit by simply turning on and off. When the switch tube is turned on, the circuit is connected and the voltage is applied to the PTC; when the switch tube is turned off, the circuit is disconnected and the voltage on the PTC is zero. This method of voltage control is relatively direct and simple. It is an "on" or "off" control mode, that is, high voltage (close to the input voltage) and low voltage (close to zero voltage). When the switching frequency increases, the number of switches per unit time increases, and the voltage and current will change rapidly when the switch is turned on and off. For example, at the moment of switch on and off, the rate of change of voltage and current (dv / dt, di / dt) increases significantly. In addition, since the switch tube directly controls the on and off, the stability of the output voltage is relatively poor and is easily affected by factors such as input voltage fluctuations and load changes. When the input voltage changes suddenly increase, the output voltage may fluctuate greatly.

[0004] These rapidly changing voltages and currents will generate strong electromagnetic radiation through the parasitic inductance and capacitance in the circuit, resulting in increased electromagnetic interference. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a vehicle-mounted high-voltage PTC control circuit, which uses a step-down conversion circuit as a control circuit for the thermistor to obtain a stable voltage value at the output end and avoid large fluctuations in voltage and current.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A vehicle-mounted high-voltage PTC control circuit, comprising: A switch tube Q, wherein a first end of the switch tube Q is used to connect an input power supply; An inductor L, one end of which is connected to the second end of the switch tube Q, and the other end of which is used to connect to one end of the PTC; A diode D, wherein a cathode of the diode D is connected to the second end of the switch tube Q and one end of the inductor L, and an anode of the diode D is connected to a ground terminal and the other end of the PTC.

[0007] Preferably, it further comprises a capacitor C, and the capacitor C is connected in parallel with the PTC.

[0008] Preferably, the third end of the switch tube Q is connected to a microcontroller MCU.

[0009] Preferably, the microcontroller MCU is used to generate a pulse width modulation signal.

[0010] Preferably, it also includes: A current sampling device is connected to the PTC.

[0011] Preferably, the current sampling device is connected to the microcontroller MCU.

[0012] The present invention also provides a vehicle-mounted heating device, comprising the above-mentioned vehicle-mounted high-voltage PTC control circuit and a PTC connected to the control circuit.

[0013] The present invention also provides a car, comprising the above-mentioned vehicle-mounted heating device.

[0014] The above technical solution of the present invention has at least one of the following beneficial effects: The control circuit in this embodiment can ensure that the voltage and current in the circuit will not change rapidly through the coordination of various components, thereby ensuring that the voltage and current at the output end can be output stably.

[0015] Controlling the PTC through the control circuit of this embodiment can effectively output a stable voltage, especially under high voltage conditions, the rate of change of voltage and current is more controllable. After the control circuit stabilizes the voltage, the changes in voltage and current become smooth, effectively reducing the generation of electromagnetic radiation.

[0016] After the control circuit of this embodiment stabilizes the voltage, the current in the ground loop will also be more stable. The stable ground current can reduce the generation of such noise voltage, thereby reducing the impact of electromagnetic radiation on the entire system.

[0017] Through the parallel capacitor C, after the switch tube Q is disconnected, the capacitor C immediately discharges to power the PTC, ensuring the stability of the current and voltage of the PTC, thereby effectively suppressing the power ripple.

[0018] The output voltage of the control circuit is a relatively smooth DC voltage, which is lower than the input voltage, and the output current is a relatively smooth DC current, which is conducive to current sampling. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of a vehicle-mounted high-voltage PTC control circuit in an embodiment of the present invention is shown; Figure 2 A schematic diagram showing the principle of the vehicle-mounted high-voltage PTC control circuit when it is turned on in an embodiment of the present invention is shown; Figure 3 A schematic diagram showing the principle of the vehicle-mounted high-voltage PTC control circuit when it is turned off in an embodiment of the present invention is shown; Figure 4 The voltage output waveform diagram of the switch tube directly controlling the on and off is shown. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are 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 a limitation on the present invention.

[0022] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be a component centered. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may also be a component centered. When a component is considered to be "set on" another component, it may be directly set on the other component or there may also be a component centered. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0023] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0024] In the existing PTC control, the switch tube is directly used for control. The switch tube controls the on and off of the circuit by simply turning on and off. When the switch tube is turned on, the circuit is connected and the voltage is applied to the PTC; when the switch tube is turned off, the circuit is disconnected and the voltage on the PTC is zero. This method of voltage control is relatively direct and simple. It is an "on" or "off" control mode, that is, high voltage (close to the input voltage) and low voltage (close to zero voltage). When the switching frequency increases, the number of switches per unit time increases, and the voltage and current will change rapidly when the switch is turned on and off. For example, at the moment of switch on and off, the rate of change of voltage and current (dv / dt, di / dt) increases significantly. Moreover, since the switch tube directly controls the on and off, the stability of the output voltage is relatively poor and is easily affected by factors such as input voltage fluctuations and load changes. When the input voltage changes suddenly, the output voltage may fluctuate greatly. These rapidly changing voltages and currents will generate strong electromagnetic radiation through the parasitic inductance and capacitance in the circuit, thereby increasing EMI (electromagnetic interference).

[0025] like Figure 1 As shown, in order to solve the problem of large voltage and current fluctuations, an embodiment of the present invention provides a vehicle-mounted high-voltage PTC control circuit, including a switch tube Q, an inductor L, and a diode D. The first end of the switch tube Q is used to connect to the input power supply; one end of the inductor L is connected to the second end of the switch tube Q, and the other end of the inductor L is used to connect to one end of the PTC; the cathode of the diode D is connected to the second end of the switch tube Q and one end of the inductor L, and the anode of the diode D is connected to the ground terminal and the other end of the PTC.

[0026] The control circuit in this embodiment can ensure that the voltage and current in the circuit will not change rapidly through the coordination of various components, thereby ensuring that the voltage and current at the output end can be output stably. The specific working principle is as follows: When the switch tube Q is turned on, Figure 2 In the current loop shown, the current cannot pass through the negative pole of the freewheeling diode D, and continues to flow through the inductor L. The inductor L converts the electrical energy into magnetic energy for storage. The current continues to flow through the PTC and returns to the negative pole of the power supply. The entire circuit is unobstructed, and the PTC at the output end works normally. In this cycle, the inductance is positive on the left and negative on the right. Since the relationship between the induced electromotive force E and the current i is: E=-L*di / dt, where L is the inductance and di / dt is the rate of change of the current, it can be seen from this formula that the induced electromotive force E is proportional to the rate of change of the current di / dt, and the direction is opposite. When the switching frequency is very high, that is, di / dt is very large, the reverse induced electromotive force is also very large, so the current cannot complete the mutation instantly, and the current of the PTC gradually increases.

[0027] When the switch tube Q is turned off, Figure 3As shown in the figure, the input power is disconnected, and the magnetic energy stored in the inductor L is converted into electrical energy and released. At this time, the positive and negative poles of the inductor L are reversed, becoming negative on the left and positive on the right, and the inductor L becomes the power supply in the circuit. Since the current flows from the positive pole to the negative pole, a current loop is formed as shown in the figure, and the freewheeling diode D is forward-conducting at this time.

[0028] Controlling the PTC through the control circuit of this embodiment can effectively output a stable voltage, especially in the case of high voltage, the rate of change of voltage and current is more controllable. After the control circuit stabilizes the voltage, the changes of voltage and current become smooth, effectively reducing the generation of electromagnetic radiation. In addition, the jittering voltage may cause the current in the ground loop to be unstable, and the unstable ground current will generate noise voltage on the ground plane, which is also a potential source of EMI. After the control circuit of this embodiment stabilizes the voltage, the current in the ground loop will also be more stable. The stable ground current can reduce the generation of such noise voltage, thereby reducing the impact of electromagnetic radiation on the entire system.

[0029] During the PTC operation, the output voltage controlled by the circuit of this embodiment is a relatively smooth DC voltage, which is lower than the input voltage. The output voltage can be adjusted by controlling the ratio of the on time to the off time (i.e., the duty cycle) of the switch tube in the circuit.

[0030] In a preferred solution of this embodiment, the control circuit further includes a capacitor C, and the capacitor C is connected in parallel with the PTC.

[0031] When the switch tube Q is turned off, the freewheeling diode D is forward-conducted, and the inductor L releases current. However, as the current released by the inductor L gradually decreases, the voltage and current on the PTC gradually decrease before the next switch tube Q is turned on. When the switch tube Q is turned on again, the voltage and current begin to increase again, resulting in the appearance of power supply ripples. This embodiment can effectively suppress power supply ripples by connecting a parallel capacitor C. The working principle is as follows: When the switch tube Q is turned on, the capacitor C is charged. After the switch tube Q is turned off, since the voltage across the capacitor C cannot change suddenly, the capacitor C discharges to power the PTC, ensuring the stability of the PTC current and voltage, thereby effectively suppressing the power ripple.

[0032] In a preferred solution of this embodiment, the third end of the switch tube Q is connected to the microcontroller MCU. The microcontroller MCU controls the on and off of the switch tube by sending a high-frequency pulse signal.

[0033] In a preferred solution of this embodiment, the microcontroller MCU is capable of generating a pulse width modulation (PWM) signal.

[0034] In a preferred solution of this embodiment, the control circuit further includes a current sampling device, and the current sampling device is connected to the PTC.

[0035] In PTC control, current sampling is also important, and real-time current feedback is conducive to the stable operation of the system. However, if the switch tube Q is used directly to control the on-off, the effective sampling window Ton is small under the high-frequency on-off of the switch tube Q (such as Figure 4 The output current of the control circuit of this embodiment is a relatively smooth DC current, so intuitive and accurate current sampling can be performed.

[0036] In a preferred solution of this embodiment, the current sampling device is connected to a microcontroller MCU. The microcontroller MCU can adjust its output according to the current data collected by the current sampling device.

[0037] An embodiment of the present invention further provides a vehicle-mounted heating device, comprising the above-mentioned vehicle-mounted high-voltage PTC control circuit and a PTC connected to the control circuit.

[0038] The present invention also provides a car, comprising the above-mentioned vehicle-mounted heating device.

[0039] Since the vehicle heating device and the vehicle include the above control circuit, the vehicle heating device and the vehicle can effectively output a stable voltage, and the change rate of the voltage and current is more controllable. After the control circuit stabilizes the voltage, the change of the voltage and current becomes smooth, which effectively reduces the generation of electromagnetic radiation. After the voltage is stabilized, the current in the ground loop will also be more stable. The stable ground current can reduce the generation of noise voltage, thereby further reducing the impact of electromagnetic radiation.

[0040] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A vehicle-mounted high-voltage PTC control circuit, characterized in that: include: A switch tube Q, wherein a first end of the switch tube Q is used to connect an input power supply; An inductor L, one end of which is connected to the second end of the switch tube Q, and the other end of which is used to connect to one end of the PTC; A diode D, wherein a cathode of the diode D is connected to the second end of the switch tube Q and one end of the inductor L, and an anode of the diode D is connected to a ground terminal and the other end of the PTC.

2. The vehicle-mounted high-voltage PTC control circuit according to claim 1, characterized in that: It also includes a capacitor C, which is connected in parallel with the PTC.

3. The vehicle-mounted high-voltage PTC control circuit according to claim 1 or 2, characterized in that: The third end of the switch tube Q is connected to the microcontroller MCU.

4. The vehicle-mounted high-voltage PTC control circuit according to claim 3, characterized in that: The microcontroller MCU is used to generate a pulse width modulation signal.

5. The vehicle-mounted high-voltage PTC control circuit according to claim 4, characterized in that: Also includes: A current sampling device is connected to the PTC.

6. The vehicle-mounted high-voltage PTC control circuit according to claim 5, characterized in that: The current sampling device is connected to the microcontroller MCU.

7. A vehicle-mounted heating device, characterized in that: It comprises the vehicle-mounted high-voltage PTC control circuit as claimed in any one of claims 1 to 6 and a PTC connected to the control circuit.

8. A car, characterized in that: It includes the vehicle-mounted heating device as claimed in claim 7.

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