| 摘要 |
The invention relates to a circuit for controlling the conducting phase of switching transistors in switched-mode power supplies, and refers to the field of supplying power to electronic apparatuses. The aim and object are to develop a circuit which allows base-current control of the switching transistor proportional to the collector current at a small additional cost, and which considerably reduces the negative influence of the storage time of the switching transistor on the control characteristics of the switched-mode power supply. This is achieved according to the invention in that a transistor is used as the control transistor which has a complementary conductivity to the switching transistor, with its collector connected to the foot of the control winding in the base circuit of the switching transistor, with its emitter connected via a resistor to the emitter of the switching transistor, with its base connected to the connection of the emitter resistor of the switching transistor remote from the emitter of the switching transistor, and a further resistor being arranged between the collector and base of the control transistor. In a development, a diode is arranged between the base of the control transistor and the connection of the emitter resistor of the switching transistor remote from the emitter, and is shunted-out by a capacitor.
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