Variable-frequency converter with constant programmed delay
First Claim
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1. A power converter circuit, comprising:
- a transformer having primary and secondary windings;
a first controllable switch connected to vary current, from an input voltage connection, through said primary winding;
wherein said input voltage varies substantially continuously;
a power output connection operatively connected to draw power from said secondary winding of said transformer; and
control logic operatively connected to control switching of said switch, with a variable switching frequency, in a control relationship which includes a delay which is independent of the switching frequency, and is not dependent on direct sensing of the current across said switch nor of the current across said primary winding, and is determined by the LC time constant of the inductance of said primary winding in combination with the net capacitance across terminals of said switch.
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Abstract
A variable-frequency variable-input-voltage switched-mode power converter, in which a voltage minimum on the primary switching transistor IS estimated as a fixed value which is determined by the time constant of the reactances on the primary side of the converter, and does not vary with the switching frequency. In the presently preferred embodiment, this fixed time-constant-determined delay is used by a secondary-side control subsystem to estimate zero-crossings of the current on the primary side, without using any dissipative current sensing techniques.
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Citations
40 Claims
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1. A power converter circuit, comprising:
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a transformer having primary and secondary windings; a first controllable switch connected to vary current, from an input voltage connection, through said primary winding;
wherein said input voltage varies substantially continuously;a power output connection operatively connected to draw power from said secondary winding of said transformer; and control logic operatively connected to control switching of said switch, with a variable switching frequency, in a control relationship which includes a delay which is independent of the switching frequency, and is not dependent on direct sensing of the current across said switch nor of the current across said primary winding, and is determined by the LC time constant of the inductance of said primary winding in combination with the net capacitance across terminals of said switch. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A power conversion method, comprising the steps of:
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(a.) repeatedly switching a transistor to switch an input voltage, which varies over a voltage range of at least 3;
1, onto a primary winding of a transformer, whilekeeping the frequency of said switching step substantially fixed whenever said input voltage falls within a first range of magnitudes, and varying the frequency of said switching step in dependence on said input voltage, whenever said input voltage falls within a second range of magnitudes;
wherein said magnitudes of said second range are all greater than said magnitudes of said first range, andunder at least some circumstances, delaying said switching step by a duration which is determined by the LC time constant of the inductance of said primary winding in combination with the net capacitance across terminals of said transistor; and (b.) coupling power out from said inductance to provide an output of converted power. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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19. A power converter circuit, comprising:
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a transformer having primary and secondary windings; a first controllable switch connected to vary current, from an input voltage connection, through said primary winding;
wherein said input voltage varies substantially continuously;a power output connection operatively connected to draw power from said secondary winding of said transformer; and secondary-side control logic operatively connected to draw power from said secondary winding of said transformer, and configured to control switching of said switch in a control relationship which, under at least some circumstances, includes a delay which is proportional to the LC time constant of the inductance of said primary winding in combination with the net capacitance across terminals of said switch. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A power conversion method, comprising the steps of repeatedly:
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(a.) turning on a switch, which is connected in series with a primary winding of a transformer which also includes a secondary winding inductively coupled to said primary winding, and ramping up current through said switch; and (b.) turning off said switch, to initiate a current in said secondary winding; and wherein under at least some circumstances, said turning on step is delayed by a duration which is determined by the LC time constant of the inductance of said primary winding in combination with the net capacitance across terminals of said switch. - View Dependent Claims (30, 31, 32)
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33. A computer system, comprising:
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memory, and a microprocessor operatively connected to read and write said memory; a graphics controller connected to said microprocessor; a video display connected to said graphics controller; and
a transformer having primary and secondary windings;a first controllable switch connected to vary current, from an input voltage connection, through said primary winding;
wherein said input voltage varies substantially continuously;a power output connection operatively connected to draw power from said secondary winding of said transformer; and secondary-side control logic operatively connected to draw power from said secondary winding of said transformer, and configured to control switching of said switch in a control relationship which, under at least some circumstances, includes a delay which is proportional to the LC time constant of the inductance of said primary winding in combination with the net capacitance across terminals of said switch. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40)
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Specification