High-precision IGBT temperature sampling circuit with isolation

Abstract

The invention provides a high-precision IGBT temperature sampling circuit with isolation. The high-precision IGBT temperature sampling circuit comprises a threshold signal generation unit, an NTC sampling circuit, a comparison circuit and an isolation circuit. Wherein the threshold signal generation unit outputs a threshold signal; the NTC sampling circuit outputs different partial voltage values according to different temperatures; the comparison circuit is used for comparing a threshold signal output by the threshold signal generation unit with a voltage division value output by the NTC sampling circuit and then outputting a certain duty ratio in an overturning manner; the isolation circuit isolates the duty ratio input by the comparison circuit through an optical coupler and then sends the duty ratio to the MCU for sampling, thereby avoiding jitter interference caused by direct input of NTC sampling to the MCU. Compared with a traditional IGBT temperature sampling circuit, the IGBT temperature sampling circuit has the advantages that the problems of insufficient sampling precision and incapability of isolating strong current and weak current are solved, the IGBT temperature sampling is more accurate and reliable, the IGBT is prevented from being damaged under extreme working conditions, and a new energy automobile is safer and more reliable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy motor controller, and particularly relates to a high-precision IGBT temperature sampling circuit with isolation. BACKGROUND

[0002] In a new energy automobile electric drive system, normal operation of the motor controller is extremely important, and once the motor control fails, the system will be abnormal, and the car and people will be destroyed. As the core component of the motor controller, the normal monitoring of the IGBT temperature is inevitable. The common way is to pass through the resistance voltage division, and then sample through the high-voltage side of the drive chip, and output on the low-voltage side, and then send to the MCU for sampling. This sampling method can realize the monitoring of the temperature, but the sampling jitter error is large, the precision is low, the drive chip resources are occupied, the internal temperature of the IGBT cannot be well monitored, and the IGBT has the risk of damage or false protection. SUMMARY

[0003] In view of the above problems in the prior art, the purpose of the present application is to provide a high-precision IGBT temperature sampling circuit with isolation, how to monitor the internal temperature of the IGBT, avoid the damage of the IGBT, and improve the precision of the sampling circuit.

[0004] To achieve the purpose, the technical scheme adopted by the present application is as follows:

[0005] A high-precision IGBT temperature sampling circuit with isolation, characterized in that it comprises a threshold signal generating unit, an NTC sampling circuit, a comparison circuit and an isolation circuit, wherein,

[0006] The threshold signal generating unit outputs a threshold signal;

[0007] The NTC sampling circuit outputs different voltage division values according to different temperatures;

[0008] The comparison circuit compares the threshold signal output by the threshold signal generating unit with the voltage division value output by the NTC sampling circuit, and then inverts and outputs a certain proportion of duty cycle;

[0009] The isolation circuit inputs the duty cycle from the comparison circuit through optical coupling isolation, and then sends it to the MCU for sampling, thereby avoiding the jitter interference of the NTC sampling directly input to the MCU.

[0010] Further, the NTC sampling circuit comprises a sixth resistor (R6), a seventh resistor (R7), an eighth resistor (R8), a ninth resistor (R9), a third filter capacitor (C3), a fourth filter capacitor (C4), and a fifth filter capacitor (C5); two ends of the seventh resistor (R7) of the NTC sampling circuit are connected to two ends of the NTC resistor respectively, and the sixth resistor (R6) and the eighth resistor (R8) form a bridge voltage dividing circuit; two ends of the third filter capacitor (C3) of the NTC sampling circuit are connected to two ends of the seventh resistor (R7) respectively; two ends of the fourth filter capacitor (C4) of the NTC sampling circuit are connected to two ends of the eighth resistor (R8) respectively; the ninth resistor (R9) and the fifth capacitor (C5) of the NTC sampling circuit form an RC filter circuit, one end of the ninth resistor (R9) is connected to the connection end of the sixth resistor (R6) and the seventh resistor (R7), and the other end of the ninth resistor (R9) is connected to the connection end of the fifth capacitor (C5) and the sixth pin of the second comparator (U1B).

[0011] Further, the comparison circuit comprises a second comparator (U1B), the fifth pin of the positive input end of the second comparator (U1B) is connected to the output pin of the first comparator (U1A) through the fourth resistor (R4), the sixth pin of the negative input end of the second comparator (U1B) is connected to the NTC sampling circuit through the ninth resistor (R9), and the output pin seventh pin of the second comparator (U1B) is connected to the optical coupling isolation circuit through the fifth resistor (R5).

[0012] Further, the isolation circuit comprises a first optical coupling, the seventh pin of the high-voltage side input pin of the first optical coupling is connected to the output of the second comparator (U1B) through the fifth resistor (R5), the eighth pin of the first optical coupling is a high-voltage side power supply positive pin, is connected to the power supply 5V_HV after being filtered through the seventh capacitor (C7), the fifth pin of the first optical coupling is a high-voltage side power supply negative pin, and is connected to GND_VH, the sixth pin of the first optical coupling is an NC pin, the first pin of the first optical coupling is a low-voltage side power supply positive pin, is connected to the power supply VDD_GM after being filtered through the eighth capacitor (C8), the fourth pin of the first optical coupling is a low-voltage side power supply negative pin, and is connected to GND, the third pin of the first optical coupling is an NC pin, and the second pin of the first optical coupling is an output pin, is connected to the MCU after being filtered through the tenth resistor (R10) and the ninth capacitor (C9).

[0013] Compared with the prior art, the present application has the following beneficial effects:

[0014] 1. In the circuit of this invention, the threshold signal circuit includes a comparator and peripheral circuitry. Through capacitor charging and discharging, the comparator achieves high-low switching and outputs a threshold signal. The NTC sampling circuit uses a bridge voltage divider to divide the voltage according to the different resistance values ​​exhibited by the NTC at different temperatures, and sends different voltages to the comparator. The comparator circuit has its positive input terminal connected to the output of the threshold signal generation unit and its negative input terminal connected to the NTC sampling circuit. When the threshold signal voltage is higher than the NTC sampling voltage, it outputs a high level; when the threshold signal voltage is lower than the NTC sampling voltage, it outputs a low level. The isolation circuit includes an optocoupler and peripheral circuitry. After isolating the PWM level input to the comparator circuit, it outputs it to the MCU for sampling, achieving strong and weak current isolation.

[0015] 2. Compared with traditional IGBT temperature sampling circuits, the IGBT temperature sampling circuit of this invention avoids the problems of insufficient sampling accuracy and inability to isolate strong and weak currents, making IGBT temperature sampling more accurate and reliable, preventing IGBT damage under extreme operating conditions, and making new energy vehicles safer and more reliable. Attached Figure Description

[0016] Figure 1 This is a circuit diagram of the high-precision IGBT temperature sampling circuit with isolation according to the present invention. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0018] like Figure 1 As shown, this invention provides a high-precision IGBT temperature sampling circuit with isolation, including a threshold signal generation unit, an NTC sampling circuit, a comparator circuit, and an isolation circuit. The threshold signal generation unit outputs a threshold signal; the NTC sampling circuit outputs different voltage division values ​​according to different temperatures; the comparator circuit compares the threshold signal output by the threshold signal generation unit with the voltage division value output by the NTC sampling circuit and then flips the output to show a certain duty cycle; the isolation circuit sends the duty cycle input to the comparator circuit to the MCU for sampling after optocoupler isolation, avoiding jitter interference from direct NTC sampling input to the MCU.

[0019] The threshold signal generation unit includes a first comparator U1A and peripheral circuitry. By charging and discharging a capacitor, the comparator can switch between high and low values ​​to output a threshold signal.

[0020] The NTC sampling circuit comprises a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a third filter capacitor C3, a fourth filter capacitor C4, and a fifth filter capacitor C5; two ends of the seventh resistor R7 of the NTC sampling circuit are respectively connected to two ends of an NTC resistor, and the seventh resistor R7 and the eighth resistor R8 form a bridge voltage dividing circuit with the sixth resistor R6; two ends of the third filter capacitor C3 of the NTC sampling circuit are respectively connected to two ends of the seventh resistor R7; two ends of the fourth filter capacitor C4 of the NTC sampling circuit are respectively connected to two ends of the eighth resistor R8; the ninth resistor R9 and the fifth capacitor C5 of the NTC sampling circuit are connected in series to form an RC filter circuit, one end of the ninth resistor R9 is connected to a connection end of the sixth resistor R6 and the seventh resistor R7, and the other end of the ninth resistor R9 is connected to a connection end of the fifth capacitor C5 and a sixth pin of a second comparator U1B.

[0021] The comparison circuit comprises a second comparator U1B, a fifth pin of a positive input end of the second comparator U1B is connected to an output pin of a first comparator U1A through a fourth resistor R4, a sixth pin of a negative input end of the second comparator U1B is connected to the NTC sampling circuit through a ninth resistor R9, and a seventh pin of an output end of the second comparator U1B is connected to an optical coupling isolation circuit through a fifth resistor R5.

[0022] The isolation circuit comprises a first optical coupling, a seventh pin of a strong current side input pin of the first optical coupling is connected to an output of the second comparator U1B through the fifth resistor R5, an eighth pin of the first optical coupling is a high voltage side power supply positive pin and is connected to a power supply 5V_HV after being filtered by a seventh capacitor C7, a fifth pin of the first optical coupling is a high voltage side power supply negative pin and is connected to GND_VH, a sixth pin of the first optical coupling is an NC pin, a first pin of the first optical coupling is a low voltage side power supply positive pin and is connected to a power supply VDD_GM after being filtered by an eighth capacitor C8, a fourth pin of the first optical coupling is a low voltage side power supply negative pin and is connected to GND, a third pin of the first optical coupling is an NC pin, and a second pin of the first optical coupling is an output pin and is connected to an MCU after being filtered by an RC filter formed by a tenth resistor R10 and a ninth capacitor C9.

[0023] The embodiment (attached Figure 1In the first comparator U1A, the second comparator U1B, the first optocoupler, the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, the eighth resistor R8, the tenth resistor R, the first capacitor C1, the second capacitor C2, the seventh capacitor C7, the eighth capacitor C8, the third capacitor C3, the fourth capacitor C4, the sixth capacitor C6, and the ninth capacitor C9 are all TPA5572Q-SO1R-S.

[0024] The working principle of the IGBT temperature sampling circuit is as follows:

[0025] The threshold signal generating unit includes a first comparator U1A, the third input pin of the first comparator U1A is input after being divided by the first resistor R1 and the second resistor R2, the second input pin of the first comparator U1A is connected with the fourth resistor R4 and the first capacitor C1, the eighth pin of the first comparator U1A is a positive power supply pin connected with the second capacitor C2 and the power supply 5V_HV, the fourth pin of the first comparator U1A is a negative power supply pin connected with GND, and the first pin of the first comparator U1A is an output pin connected with the fourth resistor R4. When the first pin of the first comparator U1A outputs a high level, the first capacitor C1 is charged through the fourth resistor R4, the third resistor R3 and the first resistor R1 are in parallel, at this time, the third pin of the first comparator U1A inputs a voltage of 5XR2 / (R2+R1 / / R3)=4.286V, when the capacitor charging voltage is greater than 4.28V, the comparator flips, the third resistor R3 and the second resistor R2 are in parallel, at this time, the third pin of the comparator U1A inputs a voltage of 5XR2 / / R3 / (R1+R2 / / R3)=0.714V, and the first capacitor C1 starts to discharge, when the first capacitor C1 discharges to a voltage lower than 0.714V, the first comparator U1A flips to output a high level, and the threshold signal is output in this way.

[0026] In the NTC sampling circuit, the NTC and the resistor R7 are in parallel, and form a bridge voltage divider with the sixth resistor R6 and the eighth resistor R8; the NTC shows different resistance values at different temperatures, and the voltage division value also changes accordingly, the ninth resistor R9 and the fifth capacitor C5 form an RC filter circuit, and the voltage division value is filtered and input to the negative input end of the second comparator U1B.

[0027] The comparison circuit includes a second comparator U1B, the positive input end of the second comparator U1B is connected to the output of the first comparator U1A, and the negative input end of the second comparator U1B is connected to the NTC sampling circuit through an RC filter circuit (R9, C5); the first comparator U1A outputs a threshold signal with a low level of 0.714V and a high level of 4.286V, 0.714V is less than the NTC voltage, and the first comparator U1A outputs a threshold signal level; when 0.714V is less than the threshold signal level and the NTC voltage is less than 4.286V, the second comparator U1B outputs a low level; and when the threshold signal level is greater than the NTC voltage, the second comparator U1B outputs a high level. Because the first comparator U1A outputs a repeated threshold signal, the second comparator U1B outputs a high or low level with a certain duty ratio.

[0028] The isolation circuit includes a first optocoupler U2, which isolates the PWM level input by the second comparator U1B and sends it to the MCU for sampling. The seventh pin of the strong electric side input pin of the first optocoupler U2 is connected to the output of the second comparator U1B through the fifth resistor R5. Taking the NTC temperature of 0℃ as an example, the specific calculation is as follows:

[0029] According to the NTC temperature characteristic table, the resistance value of 0℃ is R NTC = 13.72KΩ, and in actual use, the corresponding resistance value at different temperatures is taken according to the NTC temperature characteristic table;

[0030] Wherein R6=3KΩ, R7=20KΩ, R8=510Ω, R1=10KΩ, R2=10KΩ, and R3=2KΩ.

[0031] NTC sampling output value:

[0032]

[0033] Threshold signal high level:

[0034]

[0035] Threshold signal low circuit:

[0036]

[0037] According to the formula for calculating the charging and discharging time of the capacitor:

[0038]

[0039] V0 is the initial voltage value of the capacitor, V1 is the full voltage value of the capacitor, and VT is the voltage value at any time;

[0040] NTC sampling output value charging to threshold signal high level time:

[0041] R=3.9KΩ, C=33nF, V1=5V, VT=3.711V, V0=4.286V;

[0042]

[0043] Threshold signal high level discharge to NTC sampling output value time:

[0044] R=3.9KΩ, C=33nF, V1=0V, VT=3.711V, V0=4.286V;

[0045]

[0046] Threshold signal low level charging to threshold signal high level time:

[0047] R=3.9KΩ, C=33nF, V1=5V, VT=4.286V, V0=0.714V;

[0048]

[0049] Threshold signal high level discharge to threshold signal low level time:

[0050] R=3.9KΩ, C=33nF, V1=0V, VT=0.714, V0=4.286V;

[0051]

[0052] Output duty cycle:

[0053]

[0054] In summary, the application forms a high-precision IGBT temperature sampling circuit with isolation by two comparators, a photo-coupler, and a plurality of resistors and capacitors. The threshold signal generation unit outputs a threshold signal, which is input to the comparator together with the NTC sampling circuit voltage (different temperatures show different voltage division values). After the comparator flips, a certain proportion of the duty cycle is output, and then the light coupling is isolated, and sent to the MCU for sampling, avoiding the jitter interference of the NTC sampling directly input to the MCU, and having high precision and high safety function.

[0055] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit the technical solutions. Those of ordinary skill in the art should understand that those who modify or equivalently replace the technical solutions of the present application without departing from the spirit and scope of the technical solutions should be covered in the scope of the claims of the present application.

Claims

1. A high-precision IGBT temperature sampling circuit with isolation, characterized in that, The threshold signal generating unit, the NTC sampling circuit, the comparison circuit and the isolation circuit are included. The threshold signal generating unit outputs a threshold signal. The NTC sampling circuit outputs different voltage division values according to different temperatures. The comparison circuit compares the threshold signal output by the threshold signal generating unit with the voltage division value output by the NTC sampling circuit, and then inverts and outputs a certain duty ratio. The isolation circuit inputs the duty ratio output by the comparison circuit through optical coupling isolation, and then sends the duty ratio to the MCU for sampling, thereby avoiding the jitter interference caused by the direct input of the NTC sampling to the MCU.

2. The high-precision IGBT temperature sampling circuit with isolation according to claim 1, characterized in that, The NTC sampling circuit includes a sixth resistor (R6), a seventh resistor (R7), an eighth resistor (R8), a ninth resistor (R9), a third filter capacitor (C3), a fourth filter capacitor (C4) and a fifth filter capacitor (C5). The two ends of the seventh resistor (R7) of the NTC sampling circuit are respectively connected to the two ends of the NTC resistor, and the sixth resistor (R6) and the eighth resistor (R8) form a bridge voltage division circuit. The two ends of the third filter capacitor (C3) of the NTC sampling circuit are respectively connected to the two ends of the seventh resistor (R7). The two ends of the fourth filter capacitor (C4) of the NTC sampling circuit are respectively connected to the two ends of the eighth resistor (R8). The ninth resistor (R9) and the fifth capacitor (C5) of the NTC sampling circuit are connected in series to form an RC filter circuit. One end of the ninth resistor (R9) is connected to the connection end of the sixth resistor (R6) and the seventh resistor (R7), and the other end of the ninth resistor (R9) is connected to the connection end of the fifth capacitor (C5) and the sixth pin of the second comparator (U1B).

3. The high-precision IGBT temperature sampling circuit with isolation according to claim 1, characterized in that, The comparison circuit includes a second comparator (U1B). The fifth pin of the positive input end of the second comparator (U1B) is connected to the output pin of the first comparator (U1A) through the fourth resistor (R4). The sixth pin of the negative input end of the second comparator (U1B) is connected to the NTC sampling circuit through the ninth resistor (R9). The output pin seventh pin of the second comparator (U1B) is connected to the optical coupling isolation circuit through the fifth resistor (R5).

4. The high-precision IGBT temperature sampling circuit with isolation according to claim 1, characterized in that, The isolation circuit includes a first optocoupler. The seventh pin of the high-voltage side input pin of the first optocoupler is connected to the output of the second comparator (U1B) through the fifth resistor (R5). The eighth pin of the first optocoupler is the high-voltage side power supply positive pin, which is connected to the power supply 5V_HV after being filtered by the seventh capacitor (C7). The fifth pin of the first optocoupler is the high-voltage side power supply negative pin, which is connected to GND_VH. The sixth pin of the first optocoupler is the NC pin. The first pin of the first optocoupler is the low-voltage side power supply positive pin, which is connected to the power supply VDD_GM after being filtered by the eighth capacitor (C8). The fourth pin of the first optocoupler is the low-voltage side power supply negative pin, which is connected to GND. The third pin of the first optocoupler is the NC pin. The second pin of the first optocoupler is the output pin, which is connected to the MCU after being filtered by the tenth resistor (R10) and the ninth capacitor (C9).

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