IGBT is widely used in high-power conversion system because of its high switching frequency, low power consumption and convenient gate control. In the application of IGBT, apart from its own technical level, another important factor to be considered is whether its driver design is reasonable and reliable. As the interface circuit between the power circuit and the controller, IGBT driver has great relation to the power consumption and reliability of the system, and an optimized driver is indispensable in the power conversion system.
The driver mainly accomplishes three functions:
First, drive function. Provide enough driving current for IGBT switch to ensure IGBT can be reliably opened and closed under control of driver;
Second, protection function. When IGBT occurs short circuit or overcurrent, the driver can turn off IGBT in the shortest time to protect the power device;
Third, electrical isolation. In high-voltage, high-power applications, the driver as the bridge between the control circuit and the power circuit, must ensure that the control circuit will not be affected by the interference of the power circuit.
Due to the difference current capacity and voltage level of IGBT, the technical requirements for its drivers are also different. In low-power applications, most integrated drivers are used because the driving current is relatively small. In high-power and high-voltage applications, such as the high-power UPS (Uninterruptible Power Supply) and high-voltage frequency converter, drivers are required to provide higher driving current, higher isolation voltage and better protection function. EXSENSE Electronics first from the high-power IGBT perfect signal processing function of the technical characteristics to analyze.
In high-voltage high-power applications, it is very important to ensure the reliability of IGBT drive signal considering the strong interference caused by switches and the high cost of IGBT. Therefore, high-power IGBT usually has a perfect drive pulse signal pre-processing function, its purpose is to ensure the reliability of pulse signal of IGBT gate. The common driving signal processing functions are as follows:
First, double-path pulse interlocking function
When the drive module outputs two pulse signals to control the upper and lower IGBTs on the same bridge arm, if the drive signal controls the two IGBTs at the same time, the phenomenon of straight short circuit will occur, which may cause damage to IGBTs or other devices. In order to prevent the above situation, the signal interlocking circuit is designed inside the drive module to ensure that when the input two pulse signals are high at the same time, the two output signals are low at the same time to prevent the phenomenon of straight-through. When independent control of dual drive signals is required, the interlocking function can also be shielded through external terminals.
Second, IGBT inhibits narrow pulse function
Narrow pulse signal caused by control circuit or interference, etc., through the driver added to the gate of IGBT, may cause IGBT in a short time to complete a switching process, too short pulse signal so that IGBT is not fully turned on then turned off, the output of the converter has adverse effects, and increase the switching loss of IGBT, reduces the efficiency of the system. A filter circuit is designed in the driver to remove narrow pulse signal, which is beneficial to improve the reliability of IGBT.
Third, IGBT dead time setting function
In the half-bridge mode, two IGBTs must be turned on in turn. In order to prevent two IGBTs from being switched on at the same time, a certain dead time must be added when the two IGBTs are switched on alternately. According to IGBT of different characteristics, the dead time is different. In the double-path high-power drive module, the internal design of the dead zone control circuit can adjust the size of the dead zone through the different connection of the external terminal, such as through the external connection of different capacitance or high, low level.
NTC thermistor chip for IGBT produced by EXSENSE Electronics Technology Co., Ltd. has the characteristics of high stability, great thermal cycle and high precision, which can effectively assist high-power IGBT to operate more steadily in the course of work.
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