Buck switching regulator with tow control loops

Claim 1

A voltage regulation apparatus wherein changes in load current are not rapidly reflected in the input current comprising, a power source for providing an input current, means having a controllable duty cycle for pulse width modulating the input current at a preselected frequency, filter means connected to the output of the means for pulse width modulating, which removes the preselected frequency, a load connected to the output of the filter means, a load voltage appearing thereacross, first feedback means responsive to the load voltage for controlling the duty cycle of the pulse width modulator so as to regulate the load voltage, said first feedback means having a relatively long time constant so that changes in the load current are not rapidly reflected in the input current, and second feedback means responsive to the load voltage rising above a predetermined level for providing an analog control signal to the pulse width modulator for varying the pulse width of the signal outputted thereby, said second feedback means having a relatively short time constant for more tightly regulating the load voltage in those instances where such voltage rises above said predetermined level.