Application circuit description

AN2252

16/21

full negative current that flows during the storage time. Only part of it can be seen. The

storage time estimated from Figure 13. is of about 800ns.

Figure 13.

Primary switch collector voltage, gate voltage and base current at full

load and minimum input voltage

Note:

Channel 1 shows the switch collector voltage (dark blue), channel 2 shows the gate voltage

(light blue) and channel 4 shows the base current (green).

Figure 14. shows the same waveforms as Figure 13. but under maximum input voltage

conditions. Since the flyback voltage is lower than the input voltage, the switch turn-on does

not occur at zero voltage as can be seen from the collector voltage. The storage time

remains the same.

Figure 14.

Primary switch collector voltage, gate voltage and base current at full

load and maximum input voltage

Note:

Channel 1 shows the switch collector voltage (dark blue), channel 2 shows the gate voltage

(light blue) and channel 4 shows the base current (green).