Control circuit for controlling output current at the primary side of a power converter
First Claim
1. A control circuit for controlling an output current at a primary side of a power converter, comprising:
- a waveform detector, generating a current-waveform signal by sampling a primary side switching current of a transformer through a current-sense device;
a discharge-time detector, coupled to said transformer for detecting a discharging time of a secondary side switching current;
an integrator, for generating an integrated signal in response to said discharging time and said current-waveform signal; and
a switching control circuit, including a reference voltage, wherein said switching control circuit generates a switching signal in response to said integrated signal and said reference voltage;
wherein said switching signal switches said transformer and regulating the output current of said power converter in accordance with said reference voltage.
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Abstract
A control circuit controlling output current at the primary side of a power converter is provided. A waveform detector generates a current-waveform signal. A discharge-time detector detects a discharge-time of a secondary side switching current. An oscillator generates an oscillation signal for determining the switching frequency of the switching signal. An integrator generates an integrated signal by integrating an average current signal with the discharge-time. The average current signal is generated in response to the current-waveform signal. The time constant of the integrator is correlated with the switching period of the switching signal, therefore the integrated signal is proportional to the output current. An error amplifier amplifies the integrated signal and provides a loop gain for output current control. A comparator controls the pulse width of the switching signal in reference to the output of the error amplifier. Therefore, the output current of the power converter can be regulated.
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Citations
15 Claims
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1. A control circuit for controlling an output current at a primary side of a power converter, comprising:
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a waveform detector, generating a current-waveform signal by sampling a primary side switching current of a transformer through a current-sense device; a discharge-time detector, coupled to said transformer for detecting a discharging time of a secondary side switching current; an integrator, for generating an integrated signal in response to said discharging time and said current-waveform signal; and a switching control circuit, including a reference voltage, wherein said switching control circuit generates a switching signal in response to said integrated signal and said reference voltage;
wherein said switching signal switches said transformer and regulating the output current of said power converter in accordance with said reference voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A control circuit for controlling an output current at a primary-side of a power converter, comprising:
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a waveform detector, for generating a current-waveform signal by sampling a primary side switching current signal, wherein said primary side switching current signal is generated from a primary side switching current of a transformer; a discharge-time detector for detecting a discharging time of a secondary side switching current via an auxiliary winding of said transformer, wherein said secondary side switching current is generated from the secondary side of said transformer; an oscillator, for generating an oscillation signal for determining a switching frequency of a switching signal, wherein said switching signal is used for switching said transformer and regulating the output of said power converter; an integrator, for generating an integrated signal by integrating an average current signal with said discharging time, wherein said average current signal is generated in response to said current-waveform signal; an error amplifier, having an operational amplifier and a reference voltage for amplifying said integrated signal and providing a loop gain for controlling the output current of said power converter; and a comparator, for controlling a pulse width of said switching signal in reference to an output of said error amplifier, wherein the output current of said power converter is regulated in response to said reference voltage. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification