Heating driving circuit capable of measuring resistance of heater in real time and driving method

Abstract

The invention belongs to the field of heating circuit design, and particularly relates to a heating driving circuit capable of measuring resistance of a heater in real time and a driving method. A traditional heating control circuit is difficult to measure the resistance of a heater, a current detection loop is generally needed to be added, the resistance of the heater is calculated according to the heating voltage, and high-precision control over the heating voltage cannot be achieved. The heating control circuit is mainly composed of two heating control circuits, one heating control circuit is used for heating resistor voltage feedback of a rear-end heater, the other heating control circuit is used for heating voltage output of the rear-end heater, and each heating control circuit is composed of a photoelectric coupler, a grid driver, a field effect transistor, a resistor, a capacitor and a switching diode. The resistance of the heater can be measured in real time in the working process of the heater, the heating voltage is fed back and adjusted according to the resistance condition of the heater, and high-precision control over the heating power is achieved.

Description

Technical Field

[0001] The invention belongs to the field of heating circuit design, and in particular relates to a heating drive circuit and a drive method capable of measuring the resistance of a heater in real time. Background Art

[0002] At present, when using MOS tubes or other power devices to make the back-end heater during the heating process, it is impossible to monitor the working status of the heater. Most of them are to add a current sensor to detect the heating current status to confirm whether the heater in the circuit is working normally, and judge whether the heater resistance has parameter drift, short circuit, or open circuit during use based on the heater current.

[0003] However, when a momentary short circuit occurs in the heater, the current detection method often has a certain delay and cannot cut off the heating voltage immediately, which may cause the risk of damaging the heater and the supporting heating drive circuit. Summary of the invention

[0004] The purpose of the present invention is to meet the requirements of the sensitivity of the heating circuit to the change of the heater resistance. The present invention uses two heating control circuits and a time-sequential output to achieve real-time measurement of the heater resistance during the heating process. Within a heating cycle, the heating is started only after the heater resistance is normal, thereby achieving real-time protection of the heater and the heating drive circuit under abnormal working conditions.

[0005] The technical solution of the present invention is: a heating drive circuit capable of measuring the resistance of a heater in real time, the heating drive circuit comprising a first heating control circuit and a second heating control circuit, the first heating control circuit receiving a first heating control signal and outputting a first heating voltage signal via a photocoupler N1, a gate driver N3, a field effect transistor V1 and parallel resistors R5 and R6, the first heating voltage signal also outputting a heater resistance measurement signal V via a resistor R8 电阻测量 , the resistance of resistor R8 is much greater than the resistance of heater R, the output end of resistor R8 is also connected in parallel with switch diode V7, and the other two ports of switch diode V7 are respectively connected to the power supply VCCD and GND of acquisition circuit; the second heating control circuit receives the second heating control signal and outputs the second heating voltage signal through photocoupler N2, gate driver N4 and field effect transistor V2; field effect transistor V1 and field effect transistor V2 have heating power supply U; the first heating control signal and the second heating control signal are outputted in time sequence through the acquisition circuit, the heater resistance R is detected through the first heating control signal, and the heating voltage signal is outputted through the second heating control signal; wherein the calculation of the heater resistance R is as follows:

[0006] R=(R5×R6) / (R5+R6)×V 电阻测量 / (UV 电阻测量).

[0007] Advantageously, the floating power supply VB of the gate driver N3 and the gate driver N4 is provided by VCC through the switching diode V3 and the switching diode V4 respectively, and the floating power supply VB is connected to the floating power supply ground VS through the capacitor C3 and the capacitor C4 respectively, and the floating power supply ground VS is also grounded through the switching diode V5 and the switching diode V6 respectively.

[0008] Advantageously, in the second heating control circuit, one end of the resistor R7 is grounded and the other end is divided into two paths, one path is connected to the floating power ground VS of the gate driver N4, and the other path is connected to the floating power ground VS of the gate driver N3 via parallel voltage divider resistors R5 and R6.

[0009] Advantageously, the acquisition circuit uses a single chip microcomputer to acquire the resistance measurement signal V of the heater through an AD sampling circuit. 电阻测量 , the single chip microcomputer also controls the first heating control signal and the second heating control signal at the same time.

[0010] Advantageously, the signal periods of the first heating control signal and the second heating control signal are adjustable to cope with different heating usage environments.

[0011] Advantageously, the signal pulse width of the first heating control signal is 1 / 20 of the heating period T.

[0012] Advantageously, a current limiting resistor R3 is provided between the output terminal of the gate driver N3 and the field effect transistor V1 , and a current limiting resistor R4 is provided between the output terminal of the gate driver N4 and the field effect transistor V2 .

[0013] Advantageously, the power input terminals of the gate driver N3 and the gate driver N4 are also grounded through capacitors C1 and C2 respectively, which play the role of filter capacitors.

[0014] The present invention also provides a heating driving method capable of measuring the resistance of a heater in real time, which adopts the above-mentioned heating driving circuit and comprises the following steps:

[0015] S1, the acquisition circuit sends a first heating control signal in a time sequence;

[0016] S2: After the first heating control circuit is turned on, it outputs the first heating voltage signal and the heater resistance measurement signal V 电阻测量 ;

[0017] S3. The heater resistance R is calculated by the acquisition circuit using the following formula:

[0018] R=(R5×R6) / (R5+R6)×V 电阻测量 / (UV 电阻测量 );

[0019] S4. If the heater resistance R is normal, send a second heating control signal to achieve heating voltage output within the heating cycle; if the heater resistance R is abnormal, return to step S1.

[0020] Beneficial effects of the present invention:

[0021] 1) When outputting the heating voltage, the heater resistance can be detected in real time;

[0022] 2) When the heater is momentarily short-circuited, the sensitivity requirements of the heating circuit to the change of the heater resistance can be met;

[0023] 3) According to the change of heater resistance, the pulse width of the heating voltage PMW can be fed back to ensure constant power output to the rear-end heater and constant power operation of the heater;

[0024] 4) The working state of the heater can be detected without adding a current sensor in the circuit, which increases the economy of the circuit;

[0025] 5) In a heating cycle, ensure that the heater resistance is normal before starting heating, which can realize real-time protection of the heater and heating drive circuit under abnormal working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The schematic diagram of the heating drive circuit of the present invention capable of measuring the resistance of the heater in real time;

[0027] Figure 2 This is a timing diagram of input and output signals of the heating drive circuit of the present invention. DETAILED DESCRIPTION

[0028] like Figure 1 The embodiment of the heating driving circuit that can measure the resistance of the heater in real time mainly includes a first heating control circuit and a second heating control circuit. The first heating control circuit mainly includes a photocoupler N1, a gate driver N3, a field effect transistor V1, a switching diode V3, a switching diode V5, and a plurality of resistors and capacitors. The second heating control circuit mainly includes a photocoupler N2, a gate driver N4, a field effect transistor V2, a switching diode V4, a switching diode V6, and a plurality of resistors and capacitors.

[0029] Taking the first heating control circuit as an example, the photocoupler N1 receives the first heating control signal and transmits it to the gate driver N3 at the back end. The gate driver N3 sends a start signal to the gate G of the field effect transistor V1 according to the received heating control signal, so that the drain D and the source S are turned on, and the drain D of the field effect transistor V1 is connected to the heating power supply U, thereby realizing the output of the heating power supply signal. The floating power supply VB of the gate driver N3 is provided by VCC through the switching diode V3. The floating power supply VB of the gate driver N3 is connected to the floating power supply ground VS through the capacitor C3. When the gate driver N3 drives the field effect transistor V1 to turn on, the amplitude of the floating power supply VB becomes VCC+VS. In order to ensure that the VCC voltage is not affected by the fluctuation of the floating power supply side, the switching diode V3 is used to play the role of anti-reverse protection. The floating power supply ground VS of the gate driver N3 is also grounded through the switching diode V5. When a negative voltage appears, the negative voltage energy is conducted to the ground loop to prevent the negative voltage generated when the field effect transistor V1 is turned on and off from damaging the floating power supply ground VS of the gate driver N3. C3 acts as a bootstrap capacitor. Since the source S of the field effect transistor V1 is connected to the floating power ground VS of the gate driver N3, when the field effect transistor V1 is turned on, the amplitude of the floating power ground VS of the gate driver N3 is the heating power supply U. Since the voltage across the capacitor C3 cannot suddenly change, the amplitude of the floating power supply VB of the gate driver N3 is raised to VCC+VS to realize the driving function of the gate.

[0030] In the first heating control circuit, the source S of the field effect transistor V1 is also connected to the voltage-dividing resistors R5 and R6 in parallel. The other end of the voltage-dividing resistors R5 and R6 in parallel is divided into two paths, one of which outputs the heater resistance measurement signal V through the resistor R8. 电阻测量 , and the other is connected to the heater voltage terminal to output the first heating voltage signal. Because the resistance of resistor R8 is much larger than the resistance of the heater, when the field effect transistor V1 is turned on, the parallel resistors R5 and R6 act as a voltage divider for the heater. Resistor R8 is the current limiting resistor of the rear heater resistance measurement circuit. When the first heating voltage signal is output, it ensures that the heating voltage signal will not affect the heater resistance measurement signal V 电阻测量 The output end of resistor R8 can also be connected in parallel with a switching diode V7, which is a protection diode. The other two ports are connected to the power supply VCCD and GND of the acquisition circuit respectively to ensure that the amplitude of the heater resistance measurement signal is between the power supply VCCD and GND of the acquisition circuit. When the heating voltage signal is output, prevent the heater resistance measurement signal V 电阻测量 Exceeds the voltage range of the back-end acquisition circuit.

[0031] In this embodiment, the back-end acquisition circuit uses a single chip microcomputer to collect the resistance measurement signal V of the heater through the AD sampling circuit.电阻测量 , further confirm the heater resistance.

[0032] The second heating control circuit has the same heating control structure as the first heating control circuit. The photocoupler N2 receives the second heating control signal and transmits it to the gate driver N4 at the back end. The gate driver N4 sends a start signal to the gate G of the field effect transistor V2 according to the received heating control signal, so that the drain D and the source S are turned on, and the drain D of the field effect transistor V2 is connected to the heating power supply U, thereby realizing the output of the heating power supply signal. The source S of the field effect transistor V2 is connected to the heating voltage terminal of the heater to output the second heating voltage signal. In the second heating control loop, one end of the resistor R7 is grounded, and the other end is divided into two paths, one is connected to the floating power supply ground VS of the gate driver N4, and the other is connected to the floating power supply ground VS of the gate driver N3 through the parallel voltage divider resistors R5 and R6. Its function is to provide a ground level reference voltage for the floating power supply ground VS when the gate drivers N3 and N4 are not turned on. When the start signal comes, it ensures rapid start-up under the stable voltage difference between the floating power supply VB and the floating power supply ground VS.

[0033] In the design of this solution, the switch diodes V3 and V4 play an anti-reverse role to prevent the field effect transistors V1 and V2 from causing reverse voltage to the power input terminal when they are turned on. The drive signal is isolated by using parallel voltage divider resistors R5 and R6.

[0034] The first heating control circuit receives the first heating control signal and outputs a first heating voltage signal and a heater resistance measurement signal V 电阻测量 The second heating control circuit receives the second heating control signal and outputs a second heating voltage signal. The first heating control signal and the second heating control signal of the present solution have a timing relationship during use. The first heating control signal is first input to measure the heater resistance, and then the second heating control signal is output to output the heating voltage signal. The periods of the first heating control signal and the second heating control signal are adjustable to cope with different heating usage environments.

[0035] In this embodiment, the signal pulse width of the first heating control signal is 1 / 20 cycle, which ensures that the heater resistance measurement signal is easy to collect while causing little impact on the heating voltage. 电阻测量 When the heating voltage is turned on, its signal amplitude is the power supply VCCD of the back-end acquisition circuit, ensuring that the heater resistance measurement signal V 电阻测量 The amplitude is between the power supply VCCD and GND of the acquisition circuit, and when the heating voltage signal is output, the heater resistance measurement signal V 电阻测量 It exceeds the voltage range of the back-end acquisition circuit, thereby affecting the back-end acquisition circuit.

[0036] The calculation of the heater resistance R is realized by the voltage division relationship between the parallel resistors R5 and R6 and the heater resistance R to the heating power supply U. The calculation formula is as follows:

[0037] R=(R5×R6) / (R5+R6)×V 电阻测量 / (UV 电阻测量 )

[0038] The implementation process of this embodiment includes the following steps:

[0039] S1, the acquisition circuit (a single chip microcomputer in this embodiment) sends a first heating control signal in a time sequence;

[0040] S2, the first heating control circuit turns on the field effect transistor V1 through the photocoupler N1 and the gate driver N3, and transmits the first heating voltage signal and the heater resistance measurement signal V 电阻测量 ;

[0041] S3. The heater resistance R is calculated by the acquisition circuit using the following formula:

[0042] R=(R5×R6) / (R5+R6)×V 电阻测量 / (UV 电阻测量 )

[0043] S4. If the heater resistance R is normal, send a second heating control signal. The second heating control circuit turns on the field effect transistor V2 through the photocoupler N2 and the gate driver N4, and transmits the heating voltage signal to realize the output of the second heating voltage signal within the heating cycle. If the heater resistance R is abnormal, return to step S1.

Claims

1. A heating drive circuit capable of measuring the resistance of a heater in real time, characterized in that: The heating drive circuit includes a first heating control circuit and a second heating control circuit. The first heating control circuit receives a first heating control signal and outputs a first heating voltage signal via a photocoupler N1, a gate driver N3, a field effect transistor V1 and parallel resistors R5 and R6. The first heating voltage signal also outputs a heater resistance measurement signal V via a resistor R8. 电阻测量 , the resistance of resistor R8 is much greater than the resistance of heater R, the output end of resistor R8 is also connected in parallel with switch diode V7, and the other two ports of switch diode V7 are respectively connected to the power supply VCCD and GND of acquisition circuit; the second heating control circuit receives the second heating control signal and outputs the second heating voltage signal through photoelectric coupler N2, gate driver N4 and field effect transistor V2; field effect transistor V1 and field effect transistor V2 have heating power supply U; the first heating control signal and the second heating control signal are outputted in time sequence through the acquisition circuit, the heater resistance R is detected through the first heating control signal, and the heating voltage signal is outputted through the second heating control signal; wherein the calculation of the heater resistance R is as follows: R=(R5×R6) / (R5+R6)×V 电阻测量 / (U-V 电阻测量 )。 2. The heating drive circuit capable of measuring the resistance of a heater in real time according to claim 1, characterized in that: The floating power supply VB of the gate driver N3 and the gate driver N4 is provided by VCC through the switching diode V3 and the switching diode V4 respectively. The floating power supply VB is connected to the floating power supply ground VS through the capacitor C3 and the capacitor C4 respectively. The floating power supply ground VS is also grounded through the switching diode V5 and the switching diode V6 respectively.

3. The heating drive circuit capable of measuring the resistance of a heater in real time according to claim 1, characterized in that: In the second heating control circuit, one end of the resistor R7 is grounded, and the other end is divided into two paths, one is connected to the floating power ground VS of the gate driver N4, and the other is connected to the floating power ground VS of the gate driver N3 through parallel voltage-dividing resistors R5 and R6.

4. The heating drive circuit capable of measuring the heater resistance in real time according to claim 1, characterized in that: The acquisition circuit uses a single-chip microcomputer to collect the resistance measurement signal V of the heater through the AD sampling circuit. 电阻测量 , the single chip microcomputer also controls the first heating control signal and the second heating control signal at the same time.

5. The heating drive circuit capable of measuring the resistance of a heater in real time according to claim 1, characterized in that: The signal periods of the first heating control signal and the second heating control signal are adjustable to cope with different heating usage environments.

6. The heating drive circuit capable of measuring the resistance of a heater in real time according to claim 5, characterized in that: The signal pulse width of the first heating control signal is 1 / 20 of the heating period T.

7. The heating drive circuit capable of measuring the resistance of a heater in real time according to claim 1, characterized in that: A current limiting resistor R3 is provided between the output end of the gate driver N3 and the field effect transistor V1 , and a current limiting resistor R4 is provided between the output end of the gate driver N4 and the field effect transistor V2 .

8. The heating drive circuit capable of measuring heater resistance in real time according to claim 1, characterized in that: The power input terminals of the gate driver N3 and the gate driver N4 are grounded through capacitors C1 and C2 respectively, which play the role of filter capacitors.

9. A heating driving method capable of measuring the resistance of a heater in real time, characterized in that: The method adopts the heating drive circuit according to any one of claims 1 to 8, comprising the following steps: S1, the acquisition circuit sends a first heating control signal in a time sequence; S2: After the first heating control circuit is turned on, it outputs the first heating voltage signal and the heater resistance measurement signal V 电阻测量 ; S3. The heater resistance R is calculated by the acquisition circuit using the following formula: R=(R5×R6) / (R5+R6)×V 电阻测量 / (U-V 电阻测量 ); S4. If the heater resistance R is normal, send a second heating control signal to achieve heating voltage output within the heating cycle; if the heater resistance R is abnormal, return to step S1.

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