| 摘要 |
A DC/DC converter for supplying a plurality of direct-current output voltages using a single pulse-width-modulator. A voltage regulator in the DC/DC converter comprises first and second switch elements, a pulse width modulator for generating a switching signal to control the switching of the first switch element, an inductor the generation and the collapse of the magnetic field thereof being controlled by selective conduction of the first switch element, and a capacitor charged with current supplied in response to the collapse of the magnetic field of the inductor as conducted thereto by selective conduction of the second switch element. The level of output voltage from the voltage regulator means is sensed to generate a control voltage, applied through output feedback circuitry for cutting off the generation and the collapse of the magnetic field of said inductor responsive to the control signal indicating that the level of the output voltage exceeds a prescribed value, thus to regulate the amount of charge supplied to the capacitor in response to the switching signal generated by the pulse width modulator. The output feedback circuitry includes first and second transistors that are connected by Darlington method with a base electrode of the first transistor having an emitter electrode of the second transistor connected thereto, with a base electrode of the second transistor connected to receive the control voltage, with an emitter electrode of the first transistor connected to receive the switching signal generated by the pulse width modulator, and with an interconnection of the collector electrodes of the first and second transistors connected to the first switch element for controlling the selective conduction thereof.
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