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AssigneeInternational Business Machines Corporation
InventorsRobert J. Huljak, Stephen F. Newton, Kenneth A. Wallace
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A DC to DC power converter having reduced switching loss for operation at high frequencies. As disclosed, a buck, or forward, converter includes a first FET as the switching device in series with an inductor and a second FET as the flywheel device. At the common node to which the two FET's and the inductor are connected, there is sufficient capacitance that the FET's may be turned off without appreciable voltage change across the FET's. The value of the inductor is chosen, with respect to the input and output voltages and frequencies of operation involved, to insure that the inductor current polarity reverses each cycle, raising the node voltage to the level of the input voltage, substantially eliminating turn-on losses of the first FET. Control circuitry is provided for regulation of the power converter to control the peak-to-peak current in the inductor and to insure that at least a selected minimum value of the inductor current is present for each cycle of operation of the converter. An over-voltage protection circuit for the output of the converter is also provided.
A method for converting a DC voltage at a source to a DC voltage of a different value at an output, comprising the steps of:
A power converter comprising an input couplable to a DC voltage source, an output couplable to a DC voltage load, a first FET and an inductor connected in series between the input and the output and connected at a node, the first FET being operable to be gated on to conduct current in a forward direction from the input through the first FET to the node and having an internal diode permitting current flow in a reverse direction from the node through the FET to the input, a second FET connected between circuit common and the node and being operable to be gated on to conduct current in a forward direction from the node to circuit comon and having an internal diode permitting the flow of current from circuit common to the node, means for gating on the first FET, means for gating off the first FET after a selected peak-to-peak current change in the current through the first FET, means for gating on the second FET after the first FET has been gated off while current is flowing through the internal diode of the second FET and the inductor to the output and before the current in the inductor has reversed, means for gating off the second FET after the current in the inductor has reversed and is flowing from the output through the inductor and the second FET to circuit common, the means for gating on the first FET being operable to gate on the first FET after reverse current through the inductor has raised the voltage at the node substantially to the level of the input voltage after the second FET has been gated off.
A power converter comprising an input couplable to a DC voltage source, an output couplable to a DC voltage load, an inductor coupled to the input and to the output, a first semiconductor switch coupled in series with the inductor having (a) a conductive condition in which current flows from the input through the inductor and the first semiconductor switch and (b) a non-conductive condition, a second semiconductor switch coupled in series with the inductor having (a) a conductive condition in which current flows through the inductor and the second semiconductor switch to the output and (b) a non-conductive condition, and means for alternately placing the first and the second semiconductor switches in a conductive condition for times which are proportional to the value of the inductance of the inductor and inversely proportional to the voltage across the inductor when each switch is in its conductive condition.
The power converter of claim 6 which further comprises means for establishing a limit value for a peak of the inductor current.
A method for converting a DC voltage at a source to a DC voltage of a lesser value at an output, comprising the steps of:
A method for converting a DC voltage at a source to a DC voltage of a lesser value at an output, comprising the steps of:
A power converter comprising an input couplable to a DC voltage source, an output couplable to a DC voltage load, a first semiconductor switch connected to the input having (a) a conductive condition in which current can flow from the input through the first semiconductor, an inductor connected at a first end to the first semiconductor switch at a node and having a second end connected to the output, a second semiconductor switch connected between circuit common and the node having (a) a conductive condition in which current can flow through the second semiconductor switch and (b) a non-conductive condition, and means for alternately placing the first and second semiconductor switches in a conductive condition, the first semiconductor switch being in a conductive condition for a time proportional to the inductance of the inductor and inversely proportional to the difference between the voltage at the DC voltage source and the voltage at the DC voltage load, and the second semiconductor switch being in a conductive condition for a time proportional to the inductance of the inductor and inversely proportional to the voltage at the DC voltage load.
A method for converting a DC voltage at a source to a DC voltage of a greater value at an output, comprising the steps of:
A power converter comprising an input couplable to a DC voltage source, an output couplable to a DC voltage load, an inductor and a first FET connected in series between the input and circuit common and connected at a node, the first FET being operable to be gated on to conduct current in a forward direction from the node through the first FET to circuit common and having an internal diode permitting current flow in a reverse direction from circuit common through the first FET to the node, a second FET connected between the node and the output and being operable to be gated on to conduct current in a forward direction from the output to the node and having an internal diode permitting the flow of current from the node to the output, means for gating on the first FET, means for gating off the first FET after a selected peak-to-peak current change in the current through the first FET, means for gating on the second FET after the first FET has been gated off while current is flowing through the internal diode of the second FET to the output and before the current in the second FET has reversed, means for gating off the second FET after the current in the second FET has reversed and is flowing from the output through the second FET to the node, after raising the voltage at the node and reversing the direction of current flow through the inductor, the voltage at the node falling to circuit common after the second FET is gated off, the means for gating on the first FET being operable to gate on the first FET after reverse current through the inductor has lowered the voltage at the node substantially to the level of circuit common.
A method for converting a DC voltage at a source to a DC voltage of a different value at an output, comprising the steps of:
A power converter comprising an input couplable to a DC voltage source, an output couplable to a DC voltage load, a first FET and an inductor connected in series between the input and circuit common and connected at a node, the first FET being operable to be gated on to conduct current in a forward direction from the input through the first FET to the node and having an internal diode permitting current flow in a reverse direction from the node through the FET to the input, a second FET connected between the output and the node and being operable to be gated on to conduct current in a forward direction from the node to the output and having an internal diode permitting the flow of current from the output to the node, means for gating on the first FET, means for gating off the first FET after a selected peak-to-peak current change in the current through the first FET, means for gating on the second FET after the first FET has been gated off while current is flowing through the internal diode of the second FET and the inductor from the output to circuit common and before the current in the inductor has reversed, means for gating off the second FET after current in the inductor has reversed and is flowing from circuit common through the inductor in the second FET to the output, the means for gating on the first FET being operable to gate on the first FET after reverse current through the inductor has raised the voltage at the node substantially at the level of the input voltage after the second FET has been gated off.
Dependencies are inferred from the claim text.