Power supply circuitry

Claim 1

In a power supply connectable to a battery undergoing substantial negative transients and voltage slumps, said power supply including a DC to DC up converter and a DC to DC series regulator coupled to the DC to DC up converter for supplying at least a minimum predetermined DC output voltage to volatile circuitry, said DC to DC up converter including a forward path having an oscillator, a Schmitt trigger and a converting circuitry having a transistor switch, inductor, diode and capacitor, the transistor switch turned on in response to pulses from the Schmitt trigger being applied thereto, the transistor switch connected to a first terminal of the inductor and the anode of the diode, a second terminal of the inductor connected to the battery, the cathode of the diode connected to the capacitor across which is provided a DC to DC up converter output voltage, and said DC to DC up converter including a feedback path having a voltage divider connected to the DC to DC up converter output voltage, a reference voltage and a comparator responsive to the voltage divider output and the reference voltage for controlling the Schmitt trigger, said power supply including improvement which comprises: means coupled to the DC to DC up converter output voltage for providing said reference voltage therefrom, said reference voltage powering the oscillator and Schmitt trigger; at least one input sighal; switching means responsive to said input signal for switching the voltage divider from a first ratio corresponding to a DC to DC up converter output voltage of a standby predetermined magnitude to a second ratio corresponding to a DC to DC up converter output voltage of a normal predetermined magnitude, the normal predetermined magnitude being greater than the standby predetermined magnitude; and said comparator responsive to the reference voltage and the voltage sensed by the voltage divider for automatically disabling the Schmitt trigger when the magnitude of the battery voltage, as indicated by the DC to DC up converter output voltage, is greater than the standby predetermined magnitude, and greater than the normal predetermined magnitude when the input signal is present, the battery voltage being coupled to the DC to DC up converter output voltage by the converting circuitry when the Schmitt trigger is disabled.