Close-loop PWM controller for primary-side controlled power converters
First Claim
1. A close-loop PWM controller for a primary-side controlled power converter, comprising:
- a voltage-waveform detector, coupled to a transformer, for generating a voltage-feedback signal and a discharge-time signal by measuring a reflected voltage from said transformer, wherein said discharge-time signal represents a discharge time of a secondary-side switching current of said transformer;
a current-waveform detector and an integrator, for producing a current-feedback signal by integrating a current-waveform signal with said discharge-time signal, wherein said current-waveform signal is generated by measuring a primary-side switching current of said transformer through a current-sense device;
a voltage-loop error amplifier and a current-loop error amplifier, for amplifying said voltage-feedback signal and said current-feedback signal respectively; and
a switching control circuit, for generating a switching signal in response to an output of said voltage-loop error amplifier and an output of said current-loop error amplifier, wherein said switching signal is used for switching said transformer and regulating an output of the power converter.
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Abstract
A close-loop PWM controller for a primary-side controlled power converter is provided. A voltage-waveform detector produces a voltage-feedback signal and a discharge-time signal. A current-waveform detector generates a current-waveform signal by measuring a primary-side switching current. An integrator generates a current-feedback signal by integrating the current-waveform signal with the discharge-time signal. A time constant of the integrator is correlated with a switching period of the switching signal, therefore the current-feedback signal is proportional to the output current of the power converter. The close-loop PWM controller further including a voltage-loop error amplifier and a current-loop error amplifier. A PWM circuit and comparators control the pulse width of the switching signal in response to the outputs of the voltage-loop error amplifier and the current-loop error amplifier. The output voltage and the maximum output current of the power converter are therefore regulated.
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Citations
18 Claims
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1. A close-loop PWM controller for a primary-side controlled power converter, comprising:
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a voltage-waveform detector, coupled to a transformer, for generating a voltage-feedback signal and a discharge-time signal by measuring a reflected voltage from said transformer, wherein said discharge-time signal represents a discharge time of a secondary-side switching current of said transformer; a current-waveform detector and an integrator, for producing a current-feedback signal by integrating a current-waveform signal with said discharge-time signal, wherein said current-waveform signal is generated by measuring a primary-side switching current of said transformer through a current-sense device; a voltage-loop error amplifier and a current-loop error amplifier, for amplifying said voltage-feedback signal and said current-feedback signal respectively; and a switching control circuit, for generating a switching signal in response to an output of said voltage-loop error amplifier and an output of said current-loop error amplifier, wherein said switching signal is used for switching said transformer and regulating an output of the power converter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A close-loop PWM controller for a primary-side controlled power converter, comprising:
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a voltage-waveform detector, for producing a voltage-feedback signal and a discharge-time signal by multi-sampling a reflected voltage from an auxiliary winding of a transformer, wherein said discharge-time signal represents a discharge time of a secondary-side switching current; a current-waveform detector, for generating a current-waveform signal by measuring a primary-side switching current signal, wherein said primary-side switching current signal is converted from a primary-side switching current; an oscillator, for generating an oscillation signal to determine a switching frequency of a switching signal, wherein said switching signal is used for switching said transformer and regulating an output of the power converter; an integrator, for producing a current-feedback signal by integrating said current-waveform signal with said discharge-time signal; a voltage-loop error amplifier, including a first operational amplifier and a first reference voltage for amplifying said voltage-feedback signal and providing a loop gain for output voltage control; a current-loop error amplifier, including a second operational amplifier and a second reference voltage for amplifying said current-feedback signal and providing a loop gain for output current control; a PWM circuit, associated with a first comparator and a second comparator to control the pulse width of said switching signal in response to an output of said voltage-loop error amplifier and an output of said current-loop error amplifier; and a programmable current source, for connecting to an input of said voltage-waveform detector for temperature compensation, wherein said programmable current source produces a programmable current in response to a junction temperature of said close-loop PWM controller. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification