FET voltage and current stress

AN3256

14/23

Doc ID 17790 Rev 1

5

FET voltage and current stress

The images below were taken at the peak of the line voltage waveform, where stress on the

parts is greatest.

●

Yellow = FET voltage, 100 V/div

●

Blue = FET current, appx. 0.24 A/div

The FET sees only the peak line voltage. The diode (D8) has turned off well before the FET

turns on - there is no reverse recovery problem. The leading edge spike is small, and is due

only to the FET discharging D8's and L2's capacitance, and includes the gate drive leading

edge current.

Figure 18.

132 V input, 4 LED load

Figure 19.

132 V input, 4 LED load, single

pulse

Figure 20.

132 V input, 12 LEDs

Figure 21.

132 V input, 12 LEDs, single pulse