| 摘要 |
PURPOSE:To reduce the loss of a bias circuit by feeding back part of an emitter current to a base current for use. CONSTITUTION:An ON-OFF type self-excited switching regulator has a switching transistor (Tr) Q1, control Tr Q2-Q3, a starting resistor R1, rectifying diodes D1-D8, a converter transformer T1, and a current transformer CT, etc. When the Tr Q1 is turned ON, an emitter current flows to the primary winding N6 of the current transformer CT to induce a voltage at its secondary winding N7, and a current IB'' flows to the base of the Tr Q1 at the moment that the Tr Q1 is turned ON through a capacitor C5. The base current IB becomes IB'+BB'', and the base current IB adapted for a collector current Ic is supplied in the ON state of the Tr Q1. Thus, since part of the emitter current is fed back to the base current Ib, the turning OFF time can be reduced.
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