Tag: Power Device IGBT
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Power devices, such as IGBTs, Power MOSFETs, and Bipolar Power Transistors, need to be adequately protected from damage caused by conditions such as undervoltage, missing saturation, Miller effect, overload, and short circuit. This webinar explains why optocoupler gate drivers are widely accepted and used, not only because of their high output current drive capability, but also because of their fast switching speed. More importantly, it also has Protect the required functionality of the power device. Protection features for these power devices include undervoltage lockout (UVLO), DESAT detection, and active Miller clamps. All of these protection functions are important in systems such as power converters, motor drives, solar and wind power systems, as they ensure safe and stable operation of these systems. In addition, it is an indispensable skill for system design engineers to design and use these optocoupler gate drivers to effectively use/control these functions to make the whole system simpler, more efficient and more reliable.
The following is a wonderful interactive selection of engineers and experts (2) from this online seminar. To learn more about Avago IGBT gate drive products, please click on the link.
1. Excuse me: What are the fault protection functions? Are they integrated in the isolated drive? Thank you!
Three fault protection features are integrated into Avago's highly integrated gate driver ACPL-33xJ - UVLO (to avoid turning on the IGBT when VCC2 is not high enough), DESAT (to protect the IGBT from overcurrent or short circuit), and Miller clamp (to prevent false triggering of IGBT caused by parasitic Miller capacitance)
2. Excuse me: How to avoid the Miller effect? ​​Thank you!
One of the problems faced by IGBT operation is the parasitic capacitance of the Miller effect. This effect is evident in the 0 to 15 V type of gate driver (single power driver). The gate set-electrode coupling is due to the high dV / dt transients that can induce parasitic IGBT pass (gate voltage spikes) during IGBT turn-off, which is a potential hazard.
When the IGBT of the upper half bridge is turned on, the dVCE/dt voltage change occurs across the IGBT of the lower half bridge. Current will flow through Miller's parasitic capacitance, gate resistance and internal gate drive resistance. This will fall to the generation of the gate resistance voltage. If this voltage exceeds the IGBT gate threshold voltage, it may cause parasitic IGBT pass.
There are two traditional solutions. The first is to add the capacitance between the gate and emitter. The second solution is to use a negative gate drive. The first solution will result in a loss of efficiency. The extra cost required for the second solution is the negative supply voltage.
Our solution is to shorten the gate-emitter path by using an additional transistor between the gate-emitter. After reaching a certain threshold, the transistor will short the gate-emitter region. This technology is called Active Miller Clamp and is available in our door for the ACPL-3xxJ product. You can refer to the Avago application note AN5314
3. I would like to ask: For 30-75A and 1200V IGBTs operating on 600V DC bus, can the ACPL-33x and ACPL-H342 5 gate drive optocouplers with miller clamp protection be powered by a single power supply? Achieve high reliability drive, compared to the traditional positive and negative power supply, reliability is higher, or is it insufficient? Thank you!
The gate drive optocouplers of the Avago ACPL-332J, ACPL-333J and ACPL-H342 can output 2.5A. These products are suitable for driving 1200V, 100A type IGBTs.
1) When using a negative power supply, you do not need to use Miller clamps, but at an additional cost on the negative power supply.
2) If only a single power supply is available, the designer can use the built-in active Miller clamp.
Both solutions are just as reliable. The Miller clamp pin needs to be connected to VEE when not in use.
4. I would like to ask: In which applications need to consider the impact of the Miller effect? ​​Thank you!
One of the problems faced by IGBT operation is the parasitic capacitance of the Miller effect. This effect is evident in the 0 to 15 V type of gate driver (single power driver). The gate set-electrode coupling is due to the high dV / dt transients that can induce parasitic IGBT pass (gate voltage spikes) during IGBT turn-off, which is a potential hazard.
When the IGBT of the upper half bridge is turned on, the dVCE/dt voltage change occurs across the IGBT of the lower half bridge. Current will flow through Miller's parasitic capacitance, gate resistance and internal gate drive resistance. This will fall to the generation of the gate resistance voltage. If this voltage exceeds the IGBT gate threshold voltage, it may cause parasitic IGBT pass.
There are two traditional solutions. The first is to add the capacitance between the gate and emitter. The second solution is to use a negative gate drive. The first solution will result in a loss of efficiency. The extra cost required for the second solution is the negative supply voltage.
Our solution is to shorten the gate-emitter path by using an additional transistor between the gate-emitter. After reaching a certain threshold, the transistor will short the gate-emitter region. This technology is called Active Miller Clamp and is available in our door for the ACPL-3xxJ product. You can refer to the Avago application note AN5314
5. I would like to ask: Our PV inverter is installed in the power plant, the ambient temperature is quite bad. What is the working temperature range of your company's optocoupler? Thank you!
Our products are designed to operate in a temperature range of -40°C to 105°C. It is sufficient in industrial applications. If the customer needs a higher operating temperature, our R2Coupler optocoupler can operate at an extended temperature of 125 °C.
6, I would like to ask: How high is the optocoupler insulation voltage of your company? Thank you!
Our gate drive optocouplers are available in different packages. Each package has its own characteristics - such as different creepage distances and gaps to suit different applications. Different creepage distances and gaps correspond to different working insulation voltages, Viorm. The maximum Viorm is between 566V and 2262V. You can refer to the isolation product selection guide.
7, I would like to ask: Under pressure, how to avoid saturation is better to avoid? Thank you!
AVAGO gate drive optocouplers feature undervoltage lockout (UVLO) protection. When the IGBT fails, the voltage supplied by the gate drive optocoupler may be below the threshold. This latching protection ensures that the IGBT continues to be in a low resistance state.
Our smart gate drive optocouplers, HCPL-316J and ACPL-33xJ, come with DESAT detection. When the voltage on the DESAT pin exceeds the internal reference voltage of approximately 7V while the IGBT is still running, approximately 5μs afterwards, the Fault pin changes to a logic low state to inform the MCU/DSP.
At the same time, the 1X small transistor will turn on and discharge the gate level of the IGBT through the RG resistor. Since this transistor is about 50 times smaller than the actual turn-off transistor, the IGBT gate voltage will be gradually discharged resulting in a so-called soft shutdown. Avago's application note AN5324 provides a more detailed description of the soft shutdown.
8. What is the highest output current of the optocoupler gate driver? Thank you!
Depending on the part number you choose, Avago's optocoupler gate drivers can achieve maximum output currents of 0.4A, 0.6A, 1.0A, 1.5A, 2.5A, 3.0A, 4.0A and 5.0A. You can refer to the isolation product selection guide.
9. I would like to ask: How many amps can the maximum output current reach? Thank you!
Depending on the part number you choose, Avago's optocoupler gate drivers can achieve maximum output currents of 0.4A, 0.6A, 1.0A, 1.5A, 2.5A, 3.0A, 4.0A and 5.0A.
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