In SX Microcontrollers, SX/B Compiler and SX-Key Tool, g_daubach wrote:

Please find attached the schematic of how I use a photo coupler (OK1) for shifting the IGBT gate drive level. Using the photo coupler also allows to completely isolate the SX side from the power parts (including ground). Right now, I do not make use of the Sense line to detect over-current. This line could be fed into a comparator, powered from the +24_Regulated supply, driving another photo coupler to still keep the SX and power grounds separated.

The schematic also shows two parallel IGBTs for increased output current. Each gate should be driven through a separate resistor (R11, R12), and the common resistor R13 is used to quickly discharge the gates when the photo coupler turns off. R7 and D8 provide the required gate voltage for the IGBTs.

As the IGBTs are used as low-end drivers in this circuit with the motor connected to +24V_Unregulated (MOT_A), and to the IGBT's collectors (MOT_B), their internal flyback diodes do not potect the IGBTs against the motor's reverse voltage when the IGBTs turn off. Therefore a fast switching power diode pair (D7), with both diodes wired in parallel is used to kill such spikes.

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