How to realize the optimal design of IR2110 driving circuit

　　There are many integrated drive modules with protection and isolation functions for driving IGBT voltage-type power devices. These modules have advantages such as multiple protection functions, isolated drive, good circuit parameter consistency, stable and reliable operation, etc., but they are relatively expensive and can only drive a single power tube. The IR2110 is a dual-channel high-voltage, high-speed voltage-type power switch device gate driver with a bootstrap floating power supply. The drive circuit is simple, and only one power supply is needed to drive the upper and lower bridge arms at the same time, but there are defects such as the inability to generate negative bias and weak anti-interference. Here, the module is optimized in terms of protection and anti-interference, making its advantages more prominent and thus having a wider range of uses.

　　2 IR2110 Functional Modules

　　Figure 1 is a block diagram of the internal structure of IR2110. IR2110 is made of CMOS technology, with a logic power supply voltage range of 5-20 V, suitable for TTL or CMOS logic signal input, and has two independent high-end and low-end output channels. Since the logic signals are connected to their respective channels through level coupling circuits, an offset of -5 to +5 V is allowed between the logic circuit reference ground (Vss) and the power circuit reference ground (COM), and pulses less than 50 ns can be shielded. CMOS Schmitt trigger input is used to improve the anti-interference ability of the circuit. IR2110 consists of logic input, level shifting and output protection. The logic input circuit is compatible with TTL/CMOS levels; an offset of ±5 V is allowed between the logic power supply ground (Vss) and the power ground (COM); the operating frequency is high, up to 500 kHz; the turn-on and turn-off delays are small, 120 ns and 94 ns respectively: the output peak current can reach 2 A, and the upper bridge arm channel can withstand a voltage of 500 V. The bootstrap floating drive power supply can drive the upper and lower switching devices of the same bridge arm at the same time, which greatly simplifies the drive power supply design.

　　3 Optimal design of drive circuit

　　3.1 Input and output signal processing

　　The drive circuit converts the signal processing from the optical fiber input into a drive signal output, and when the signal overcurrent occurs, it outputs a blocking signal to the control part of the system, and the control part stops the output of the PWM signal and turns off the IGBT tube, as shown in Figure 2.

　　In high and medium power applications, the du/dt and di/dt of the switch tube are very high, which can easily interfere with weak current signals such as the control circuit, seriously threatening the safe operation of the power inverter. Therefore, optical fiber connectors are used to isolate the main circuit and the control circuit. Optical fiber connectors can realize long-distance transmission of PWM control signals, with low delay and can eliminate interference from power switch devices.

　　As shown in Figure 2, when the optical receiver receives a signal (i.e., a PWM signal arrives), it is at a low level, and the other end of the NAND gate U1 is connected to +15 V as a high level. After passing through the NAND gate U1, it is at a high level, and then receives a signal through the XOR gate U2 and the AND gate U3. The signal is connected to the low channel input terminal LIN of IR2110 to drive the IGBT at one end of IR2110. The XOR gate U6, the NAND gate U5, the resistor R1 and the capacitor C3 form a confirmation pulse generation circuit. Whenever the input signal jumps, the XOR gate U6 outputs a positive pulse, the width of which is determined by the capacitor C3 and the resistor R1, and is sent through the optical fiber transmitter. When the IGBT is overcurrent, OVC is at a low level, and its low potential is fed back to the input terminal of U3, so that DRG is forced to be high, thereby turning off the IGBT. At this time, the SO terminal will also appear at a low level, and the output optical fiber will transmit the status to the system control part. The system sends a signal to turn off the IGBT tube uniformly.

　　3.2 Protection circuit

　　IR2110 has its own protection function. The input terminal SD can realize the overcurrent protection control function, but it should be used with caution when driving large and medium power IGBT tubes, because the turn-off di/dt is very large under large current. If the control and drive circuits are not well shielded, a large interference signal will be generated, which is easy to cause SD end protection malfunction. Turning off the drive under strong inductive and large current will cause high-voltage burrs on the DC bus. The maximum voltage allowed by IR2110 is only 500 V, which is likely to make the drive module fail and burn out the IGBT module. Therefore, the protection circuit is redesigned here to better protect the blocking signal, as shown in Figure 3.

　　The protection circuit processes overcurrent and undervoltage detection signals to complete overcurrent protection and undervoltage protection. The core of the entire protection circuit is LM555.

　　(1) In the overcurrent protection circuit diagram 3, the diode VD3, the resistors R14, R16, R15, the capacitor C6, and the MOS tube VQ4 form an overcurrent feedback circuit, which is compared with the reference voltage formed by R11, R12 and the voltage regulator tube VD2; R8, R9, R10, C4 and the MOS tube VQ3 form a blocking time circuit. When there is a signal input (IGBT is turned on), the MSURE signal is low, VQ4 is turned off, and the voltage of the C pole is fed back to the pin 6 of the LM555; when there is no signal input (IGBT is turned off), VQ4 is turned on, and the voltage of the LM555 pin 6 is 0 V. During the conduction period of the IGBT, when VCE (the voltage of the C pole relative to the E pole) exceeds a certain value, V6E (the voltage of the pin 6 of the LM555 relative to the E pole) is greater than V5E (the voltage of the pin 5 of the LM555 relative to the E pole), the output of the LM555 pin 7 is low, that is, OVC is low, and the overcurrent protection is started, and it returns to normal after the blocking time; otherwise, pin 7 is a gate open circuit and the circuit works normally.

　　(2) Undervoltage protection circuit This circuit consists of resistors R5, R6, R7, transistor VQ2 and voltage regulator VD1 in Figure 3. Under normal conditions, transistor VQ2 is turned on and the RESET signal (pin 4) of LM555 does not work; when the given voltage is lower than a certain value, pin 4 of LM555 is 0 V, the RESET signal works, and the LM555 is in a reset state. Pin 7, i.e., OVC, is at a low level, and the protection circuit is activated.

　　3.3 Negative bias circuit

　　Another shortcoming of IR2110 is that it cannot generate negative bias voltage. In high-power IGBT driving applications, each drive power supply is independent, and the integrated driver can generally generate negative voltage, -5 V. It is used to enhance the reliability of IGBT shutdown and prevent misleading conduction due to the Miller effect. Although the IR2110 device cannot generate negative voltage internally, it can generate negative voltage through external passive devices, as shown in Figure 4.

　　A negative voltage circuit consisting of a capacitor and a 5 V voltage regulator is added to the upper and lower tube driving circuits. Its working principle is: the power supply voltage Vcc is 20 V. During power-on, the power supply charges C11 through R10, and C11 maintains a 5 V voltage. When LIN is high, LO outputs a high level of 20 V relative to COM. At this time, the voltage applied to the lower tube VG1 is 15 V, and the IGBT is turned on normally. When the LIN input is low, LO outputs OV, and the voltage of VG1 is -5 V, achieving negative voltage when turned off. Similarly, for the upper tube VG2, when HIN input is high, HO outputs 20 V, and the voltage applied to VG2 is 15 V. When HIN is low, HO outputs 0 V, and the voltage of VG2 is -5 V. The selected C11 and C12 must be larger than the IGBT gate input parasitic capacitance Ciss. The diode VD4 in the bootstrap capacitor charging circuit must be a fast recovery diode to ensure fast conduction within a limited time.

　　4 Conclusion

　　Through the analysis and research of the driver module IR2110, based on its simple driving circuit and independent high-end and low-end output driving channels, this paper designs a practical optimized driving circuit to enable the module to drive, control and overcurrent protect the IGBT more effectively during use.