US 5,856,739 AGranted

Wide input range step-down DC to DC converter

AssigneeSpartec International Corp.

InventorAlexander Trica

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Abstract

A DC to DC converter power supply for converting a varying unregulated DC voltage into a lower voltage regulated output. The DC to DC converter has a buck topology and includes a high frequency switch with a variable duty cycle, a regulating filter, a current inner control loop, a voltage outer control loop, a latching switch that provides a load bypass during startup, a logic circuit oscillator that controls the high frequency switch frequency duty cycle as a function of both the inner control loop current and the outer control loop voltage, and a circuit that taps the source voltage for a power input to the logic circuit oscillator during startup. The DC to DC converter admits a source voltage range of approximately 4:1 and provides a regulated fixed output voltage that ranges from approximately 30% of the source voltage at the lowest accommodated source voltage to approximately 5% of the source voltage at the highest accommodated source voltage.

Claims20

Dependent claims

A DC to DC converter for generating a regulated DC output voltage from an unregulated DC input voltage comprising:

input means for connecting to a source of unregulated DC voltage;
output means for connecting to a DC load;
first switch means for switching said unregulated DC voltage defining an output pulse train;
filtering means for smoothing the output of the first switch means, defining a smoothed output;
an oscillator and drive circuit means for controlling the switching activity of said first switch means;
feedback means, responsive to a voltage feedback signal that varies in accordance with the voltage across said load and to a current feedback signal that varies in accordance with the current through said output for controlling the operation of said oscillator and drive circuit means and thereby regulating the voltage at said output;
second switch means for switching said smoothed output, connected to said filtering means and to said output, said second switch means having a first, starting state in which current through said output is limited to a relatively low value and a second, running state in which current through said output is not limited to said relatively low value;
and
first means connected to said input means for supplying operating power to said oscillator and drive circuit means when said second switch is in its starting state, and second means connected to said output for supplying operating power to said oscillator and drive circuit means when said second switch means is in its running state.

6 more elements

Dependencies are inferred from the claim text.