Auxiliary power supply apparatus and method for isolated power converters
First Claim
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1. An apparatus comprising:
- a pulse-width modulation (PWM) generator configured to generate a PWM signal for controlling a power switch of a power converter;
a bias switch and a bias capacitor connected in series and coupled to a magnetic winding of the power converter, wherein the bias capacitor is configured to provide bias power for the PWM generator; and
a comparator having a first input connected to the bias capacitor, a second input connected to a predetermined reference and an output configured to generate a comparison signal, wherein based on the comparison signal and the PWM signal, a signal is generated for controlling the bias switch to allow a magnetizing current from the magnetic winding to charge the bias capacitor when a voltage across the bias capacitor is less than the predetermined reference and prevent the magnetizing current from charging the bias capacitor when the voltage across the bias capacitor is greater than the predetermined reference.
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Abstract
An apparatus includes a pulse-width modulation (PWM) generator configured to generate a PWM signal for controlling a power switch of a power converter, a bias switch and a bias capacitor connected in series and coupled to a magnetic winding of the power converter and a comparator having a first input connected to the bias capacitor, a second input connected to a predetermined reference and an output configured to generate a signal for controlling the bias switch to allow a magnetizing current from the magnetic winding to charge the bias capacitor when a voltage across the bias capacitor is less than the predetermined reference.
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Citations
20 Claims
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1. An apparatus comprising:
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a pulse-width modulation (PWM) generator configured to generate a PWM signal for controlling a power switch of a power converter; a bias switch and a bias capacitor connected in series and coupled to a magnetic winding of the power converter, wherein the bias capacitor is configured to provide bias power for the PWM generator; and a comparator having a first input connected to the bias capacitor, a second input connected to a predetermined reference and an output configured to generate a comparison signal, wherein based on the comparison signal and the PWM signal, a signal is generated for controlling the bias switch to allow a magnetizing current from the magnetic winding to charge the bias capacitor when a voltage across the bias capacitor is less than the predetermined reference and prevent the magnetizing current from charging the bias capacitor when the voltage across the bias capacitor is greater than the predetermined reference. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method comprising:
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detecting a voltage across a bias capacitor of a power converter, wherein the bias capacitor is configured to provide bias power for a controller of the power converter; comparing the voltage across the bias capacitor with a first predetermined threshold to generate a comparison result; generating a PWM signal for controlling a power switch of the power converter; based on the comparison result and the PWM signal, generating a control signal for controlling a bias switch connected in series with the bias capacitor; turning on the bias switch connected in series with the bias capacitor and using a magnetizing current to charge the bias capacitor when the voltage across the bias capacitor drops below the first predetermined threshold; and turning off the bias switch after the voltage across the bias capacitor is above a second predetermined threshold greater than the first predetermined threshold. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A device comprising:
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a controller configured to generate a gate drive signal for controlling a power switch of a power converter; a sense switch and the power switch connected in series between a magnetic winding and ground; a bias switch and a bias capacitor connected in series between a common node of the power switch and the sense switch, and ground; and a comparator having a first input connected to the bias capacitor, a second input connected to a reference and an output configured to generate a control signal, wherein based on the control signal and the gate drive signal, a signal is generated for controlling the bias switch to allow a magnetizing current from the magnetic winding to charge the bias capacitor when a voltage across the bias capacitor is less than the reference. - View Dependent Claims (18, 19, 20)
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Specification