Introduction IGBTs are widely used in power electronic devices, such as frequency converters and various power supplies. IGBTs combine the advantages of bipolar power transistors and power MOSFETs, offering benefits such as voltage control, high input impedance, low drive power, simple control circuitry, low switching losses, fast switching speed, and high operating frequency. However, like other power electronic devices, the application of IGBTs depends on circuit conditions and the switching environment. Therefore, the drive and protection circuits of IGBTs are both challenging and crucial in circuit design, forming a critical link in the operation of the entire device. To address the reliable drive problem of IGBTs, various IGBT manufacturers and companies specializing in IGBT applications have developed numerous IGBT driver integrated circuits or modules, such as the commonly used EXB8 series from Fuji Electric Corporation (Japan), the M579 series from Mitsubishi Electric Corporation (M579), and the IR21 series from IR Systems (USA). However, the EXB8 series, M579 series, and IR21 series lack soft-shutdown and undervoltage protection, while HP's HCLP-316J offers overcurrent protection, undervoltage protection, and IGBT soft-shutdown, and is relatively inexpensive. Therefore, this paper will study it and provide a drive and protection circuit for 1700V, 200-300A IGBTs. 1. IGBT Operating Characteristics An IGBT is a voltage-controlled device that requires very little drive current and power, allowing direct connection to analog or digital function blocks without any additional interface circuitry. The IGBT's turn-on and turn-off are controlled by the gate voltage UGE. When UGE is greater than the turn-on voltage UGE(th), the IGBT turns on; when a reverse signal is applied between the gate and emitter, or no signal is applied, the IGBT turns off. Like ordinary transistors, IGBTs can operate in the linear amplification region, saturation region, and cutoff region, and are primarily used as switching devices. In the driving circuit, the main focus is on the two states of IGBT: saturation conduction and cutoff, ensuring that both the rising edge of turn-on and the falling edge of turn-off are relatively steep. 2. IGBT Driving Circuit Requirements The following points must be considered when designing an IGBT driver: 1) The magnitude of the gate forward drive voltage will significantly affect circuit performance and must be correctly selected. When the forward drive voltage increases, the IGBT's on-resistance decreases, reducing turn-on losses; however, if the forward drive voltage is too large, the short-circuit current IC increases with UGE when the load is short-circuited, potentially causing a latch-up effect in the IGBT, leading to gate failure and damage. If the forward drive voltage is too small, the IGBT will exit the saturation conduction region and enter the linear amplification region, causing overheating and damage. A voltage of 12V ≤ UGE ≤ 18V is preferable. A gate negative bias voltage can prevent the IGBT from mistakenly turning on due to excessive surge current during turn-off; generally, a negative bias voltage of -5V is suitable. In addition, after the IGBT is turned on, the drive circuit should provide sufficient voltage and current amplitude to prevent the IGBT from exiting the saturation conduction region and being damaged under normal operation and overload conditions. 2) Fast IGBT turn-on and turn-off are beneficial for increasing the operating frequency and reducing switching losses. However, the switching frequency of the IGBT should not be too high under large inductive loads, because high-speed turn-on and turn-off will generate very high peak voltages, which may cause the IGBT or other components to break down. 3) Selecting appropriate gate series resistor RG and gate emitter capacitor CG is very important for driving the IGBT. If RG is small, the charging and discharging time constant between the gate and emitter is relatively small, which will result in a large instantaneous current during turn-on, thus damaging the IGBT; if RG is large, it is beneficial for suppressing dvce/dt, but it will increase the switching time and switching losses of the IGBT. Appropriate CG is beneficial for suppressing dic/dt. If CG is too large, the turn-on time will be delayed, and if CG is too small, the effect of suppressing dic/dt is not obvious. 4) When the IGBT is turned off, the gate-emitter voltage is easily affected by the parasitic parameters of the IGBT and the circuit, causing the gate-emitter voltage to cause the device to mis-turn on. To prevent this phenomenon, a resistor can be connected in parallel between the gate and emitter. In addition, in practical applications, to prevent high voltage spikes in the gate drive circuit, it is best to connect two reverse-connected series Zener diodes in parallel between the gate and emitter. Their Zener voltage should be the same as the positive and negative gate voltages. 3. HCPL-316J Drive Circuit 3.1 HCPL-316J Internal Structure and Working Principle The internal structure of HCPL-316J is shown in Figure 1, and its external pins are shown in Figure 2. [align=center] [/align] As can be seen from Figure 1, HCPL-316J can be divided into two parts: the input IC (left) and the output IC (right). The input and output can fully meet the requirements of high-voltage, high-power IGBT drive. The functions of each pin are as follows: Pin 1 (VIN+) Positive signal input; Pin 2 (VIN-) Reverse signal input; Pin 3 (VCG1) Input power supply; Pin 4 (GND) Ground of the input terminal; Pin 5 (RESERT) Chip reset input; Pin 6 (FAULT) Fault output, outputting a fault signal through the optocoupler when a fault occurs (undervoltage output or IGBT short circuit); Pin 7 (VLED1+) Optocoupler test pin, suspended; Pin 8 (VLED1-) Ground; Pins 9 and 10 (VEE) Provide reverse bias voltage to the IGBT; Pin 11 (VOUT) Output drive signal to drive the IGBT; Pin 12 (VC) Collector power supply of the three-stage Darlington transistor; Pin 13 (VCC2) Drive voltage source; Pin 14 (DESAT) IGBT short-circuit current detection; Pin 15 (VLED2+) Optocoupler test pin, suspended; Pin 16 (VE) Output reference ground. Its working principle is shown in Figure 1. If VIN+ is input normally, there is no overcurrent signal at pin 14, and VCC2-VE=12V, meaning the output positive drive voltage is normal, the drive signal outputs a high level, and the fault signal and undervoltage signal output a low level. First, all three signals are input to JP3. Point D is low, and point B is also low, so the 50×DMOS is off. At this time, the four states of the input to JP1 are low, high, low, low from top to bottom, with point A at a high level, driving the three-stage Darlington transistor to conduct, and the IGBT is also turned on. If an overcurrent signal occurs in the IGBT (pin 14 detects a voltage of 7V on the IGBT collector), and the input drive signal continues to be applied to pin 1, the undervoltage signal is low, point B outputs a low level, the three-stage Darlington transistor is turned off, the 1×DMOS conducts, and the voltage between the IGBT gate and emitter is slowly discharged, achieving a slow drop in gate voltage. When VOUT=2V, that is, VOUT outputs a low level, point C becomes low level, point B is high level, the 50×DMOS turns on, and the IGBT gate emitter discharges rapidly. The signal on the fault line passes through the optocoupler, and then through the RS flip-flop, Q outputs a high level, thus blocking the input optocoupler. Similarly, the cases of undervoltage only and both undervoltage and overcurrent can be analyzed. 3.2 Drive Circuit Design The drive circuit and parameters are shown in Figure 3. VIN+, FAULT, and RESET on the left side of HCPL-316J are connected to the microcomputer. R7, R8, R9, D5, D6, and C12 serve as input protection to prevent excessively high input voltage from damaging the IGBT. However, the protection circuit will produce a delay of about 1µs, which is not suitable for use when the switching frequency exceeds 100kHz. Q3 mainly serves an interlocking function. When both PWM signals (on the same bridge arm) are high level, Q3 turns on, pulling the input level low, making the output also low level. In Figure 3, the interlock signals Interlock and Interlock2 are connected to another 316J Interlock2 and Interlock1, respectively. R1 and C2 amplify and filter the fault signal, ensuring the microcomputer can correctly receive information when interference is present. At the output, R5 and C7 affect the IGBT turn-on speed and switching losses; increasing C7 significantly reduces dic/dt. First, calculate the gate resistance: where ION is the gate current injected into the IGBT during turn-on. To ensure rapid IGBT turn-on, the design sets IONMAX to 20A. The output low level VOL = 2V. C3 is a crucial parameter, primarily serving a charging delay function. When the system starts and the chip begins operation, the collector voltage of the IGBT is still much higher than 7V. Without C3, an incorrect short-circuit fault signal would be issued, causing the output to turn off directly. After the chip is operating normally, if the collector voltage spikes momentarily and then immediately returns to normal, without C3, an incorrect fault signal would also be issued, causing the IGBT to turn off incorrectly. However, an excessively high value for C3 will slow down the system response, and under saturation conditions, it may cause the IGBT to burn out within the delay time, failing to provide proper protection. A value of 100pF for C3, with its delay time determined by two diodes connected in series in the collector detection circuit, can improve the overall reverse withstand voltage, thereby increasing the drive voltage level. However, the reverse recovery time of the diodes must be very small, and each reverse withstand voltage level must be 1000V. Generally, BYV261E is selected, with a reverse recovery time of 75 ns. R4 and C5 retain the soft-turn-off characteristic of the HCLP-316J after an overcurrent signal. The principle is that C5 achieves soft turn-off through the discharge of the internal MOSFET. In Figure 3, the output voltage VOUT is output through a push-pull output of two fast transistors, allowing the maximum drive current to reach 20A, enabling rapid driving of 1700V, 200-300A IGBTs. 3.3 Drive Power Supply Design In drive design, a stable power supply is essential for the normal operation of the IGBT. As shown in Figure 4. The power supply uses a forward converter, which has strong anti-interference capability. The secondary side does not have a filter inductor, resulting in low input impedance and a relatively stable output voltage even under heavy load. When switch S is on, +12V (a relatively stable and highly accurate power supply) is applied to the winding connected to switch S on the primary side of the transformer. Energy coupling causes the secondary side to be rectified and output. When switch S is off, the energy of the magnetic core is fed back to the power supply through the primary diode and its connected winding, resetting the transformer core. A 555 timer is configured as a multivibrator. By charging and discharging capacitor C1, the potential between pins 2 and 6 changes between 4 and 8V, causing pin 3 to output a square wave signal, which is used to control the switching on and off of switch S. +12V charges capacitor C1 through resistors R1 and diode D2. The charging time t1 ≈ R1C2ln2; the discharging time t2 = R2C1ln2. The output is high during charging and low during discharging. Therefore, the duty cycle = t1 / (t1 + t2). The transformer is designed with the following parameters: primary side +12V, frequency 60kHz, working magnetic flux density Bw 0.15T, secondary side +15V output 2A, -5V output 1A, efficiency n=80%, window fill factor Km 0.5, core fill factor Kc 1, coil wire current density d 3 A/mm². Therefore, the output power is: PT = (15 + 0.6) × 2 × 2 + (5 + 0.6) × 1 × 2 = 64W. Since the output voltage of the drive power supply will decrease under load, in practical applications, increasing the frequency and duty cycle is considered to stabilize the output voltage. 4. Conclusion This paper designs a drive circuit capable of driving 1700V, 200-300A IGBTs. The hardware implements interlocking of two IGBTs (on the same bridge arm) and designs a drive power supply that can directly power the two IGBTs.