Switch mode power stage
First Claim
1. A power conversion device operable in a discontinuous conduction mode under the control of a switching means and wherein during operation in the discontinuous conduction mode, an oscillating voltage exists across the switching means prior to a turn-on of the switching means, the device comprising:
- switch control means arranged to cause turn-on of the switching means to occur at a minimum of the oscillating voltage; and
timing means arranged to provide a controlled time period following a first turn-on of the switching means, during which a second turn-on of the switching means can not occur.
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Accused Products
Abstract
The invention provides a power conversion device operable in a discontinuous conduction mode under the control of a switch. During operation in the discontinuous conduction mode, an oscillating voltage exists across the switch means prior to a turn-on of the switch means. The power conversion the device comprises a switching controller arranged to ensure that turn-on of the switch occurs at a minimum of the oscillating voltage. The power conversion device also comprises a timer arranged to provide a controlled time period following a first turn-on of the switching means, during which a second turn-on of the switching means can not occur. Such an arrangement is advantageous in that a low power level of operation of the device and a short conduction time of the switch means does not lead to an undesirable increase in switching frequency. Consequently, a reduction in a parasitic capacitance of the switch will be rewarded by an increase in efficiency.
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Citations
48 Claims
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1. A power conversion device operable in a discontinuous conduction mode under the control of a switching means and wherein during operation in the discontinuous conduction mode, an oscillating voltage exists across the switching means prior to a turn-on of the switching means, the device comprising:
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switch control means arranged to cause turn-on of the switching means to occur at a minimum of the oscillating voltage; and
timing means arranged to provide a controlled time period following a first turn-on of the switching means, during which a second turn-on of the switching means can not occur. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47)
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17. A method of operating a power conversion device in a discontinuous conduction mode, the method comprising the steps of:
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controlling operation of the device in the discontinuous conduction mode with a switching means;
causing turn-on of the switching means to occur when an oscillating voltage across the switching means is at a minimum; and
providing a controlled time period following a first turn-on of the switching means, during which a second turn-on of the switching means can not occur.
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23. A power conversion device comprising:
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an inductor and a switch connected in series across a power supply;
a rectifier and a load connected in series across the switch;
a one-shot arranged to provide a pulse of controlled duration to the input of the switch;
a comparator and a delay means arranged to detect a voltage polarity reversal across the inductor and to produce a delayed logic signal corresponding to the voltage polarity across the inductor; and
means for providing a controlled time period following a first pulse of the one-shot during which the comparator can not trigger the one-shot.
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48. In a power conversion circuit operating in a discontinuous conduction mode under the control of a switching means, a voltage waveform across the switching means comprising:
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a first voltage waveform portion during which the switching means is on, allowing a current to build in an inductive element;
a second voltage waveform portion after the first voltage waveform portion, during which the switching means is off, voltage across the switching means is non-zero and the current in the inductive element falls; and
a third voltage waveform portion after the second voltage waveform portion during which the switching means remains off and the voltage waveform is oscillatory;
wherein a subsequent turn-on of the switching means occurs proximal to a minimum of the oscillatory voltage waveform, and wherein the subsequent turn-on of the switching means occurs only after a controlled time period has passed since the start of the first voltage waveform portion.
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Specification