| 摘要 |
A control circuit is disclosed for use in a switching-type regulator which includes a source of unregulated DC voltage, a switching circuit for interrupting the unregulated DC voltage to produce an AC voltage having a duty cycle which is a function of the operation of the switching circuit, a converter for converting the AC voltage to a regulated DC voltage, a controllable pulse generator for supplying pulses of controllable duration to the switching circuit so as to determine the duty cycle of the AC voltage, a feedback circuit responsive to variations in the regulated DC voltage for controlling the duration of the generated pulses to maintain the regulated DC voltage at a desired level, and disabling circuit for selectively limiting the operation of the pulse generator. The control circuit is used to reset the disabling circuit to an initial state and to change gradually the duration of the pulses which are generated by the pulse generator when the regulator first is turned ON. By resetting the disabling circuit, there is no limitation on the operation of the pulse generator at the outset. By gradually increasing the duration of the pulses generated by the pulse generator, the so-called "soft start" operation is performed, whereby the regulated DC voltage gradually is increased from a zero level to its desired level. The control circuit includes a voltage generator for generating a control voltage which increases rapidly during an initial interval and then increases at a significantly slower rate after it attains a first level. The disabling circuit is reset when the control voltage reaches its first level; and when the control voltage thereafter increases at a much slower rate, the slowly-increasing control voltage is used to correspondingly increase the duration of the generated pulses, whereby the level of the regulated DC voltage likewise increases. |
