A charging circuit includes an oscillation transformer and an oscillation transistor.
The oscillation transistor oscillates at a secondary current returned from a secondary
coil in the charging circuit. The oscillation transistor increases/decreases a
primary current, which flows from a battery to a primary coil, and flows the secondary
current through the secondary coil to charge a main capacitor. The oscillation
transistor, which satisfies the following conditions, is used: a DC current gain
hFE1 is 50010 when a collector-emitter voltage VCE is
2V and a collector current IC is 0.5 A, and a DC current gain hFE2
is 29010 when the collector-emitter voltage VCE is 2V and
the collector current IC is 5 A.
