Variable DC-DC converter and no-load clamp
AssigneeMurata Manufacturing Co., Ltd.
InventorFrank Warnes
Life of this patent
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Abstract
A variable DC-DC converter includes a no-load voltage clamp in which a rectified, filtered, and loaded control signal drives a switch. The switch switches in a load resistance across the output terminals of the converter when the output terminals are unloaded or lightly loaded. Due to a combined rectification, smoothing, and filtering operation of the control signal circuit, the control signal provides a steady voltage of the output voltage selected by a user of the converter based on predetermined output requirements. The control signal is therefore not subject to the voltage spikes that the main output is subject to. The circuit compares the control signal to the output voltage, and switches in the load resistance when the voltage at the output rises above the control signal.
Claims16
A variable DC-DC converter, comprising:
- an input circuit connected to a primary winding, the input circuit including an input switch to switch a voltage across the primary winding and a controller to supply a driving frequency to the input switch to output a predetermined voltage;
- an output circuit connected to a secondary winding, the secondary winding including a pair of winding terminals;
- the output circuit including:
- a first rectifier;
- a pair of output terminals coupled respectively to each of the pair of winding terminals;
- a smoothing circuit connected between the pair of output terminals;
- and
- a voltage clamp connected between the pair of winding terminals, the voltage clamp including:
- an output switch, connected between the pair of winding terminals, to connect or disconnect a shunt load between the pair of output terminals;
- a low-pass filter connected between the pair of winding terminals and including a filter output, wherein the filter output outputs a control signal to the output switch;
- a second rectifier connected in series with the low-pass filter;
- and
- a load resistance connected to the filter output to load the low-pass filter, wherein
- the low-pass filter provides the control signal output to the output switch to connect the shunt load across the pair of winding terminals when an actual voltage across the pair of output terminals becomes higher than the predetermined voltage and to disconnect the shunt load across the pair of winding terminals at other times.
Dependencies are inferred from the claim text.