Switching control circuit with variable switching frequency for primary-side-controlled power converters
First Claim
1. A switching control circuit for a primary-side-controlled power converter, comprising:
- a switch for switching a transformer;
wherein said transformer is coupled to an input voltage of the power converter;
a sense device, which is coupled to said transformer for sensing current or/and voltage of said transformer;
a switching signal, coupled to said switch for regulating an output voltage and a maximum output current of the power converter; and
a controller, coupled to said transformer to generate a first feedback signal and a discharge-time signal by multi-sampling a voltage signal and a discharge time of said transformer during an off-time of said switching signal, said controller further coupled to said sense device to generate a second feedback signal in response to said discharge-time signal and a current signal of said transformer, wherein said controller generates said switching signal in response to said first feedback signal, said controller controlling a switching frequency of said switching signal in response to said second feedback signal.
9 Assignments
0 Petitions
Accused Products
Abstract
The invention presents a switching control circuit for a primary-side-controlled power converter. A pattern generator produces a digital pattern to control a programmable capacitor that is connected to an oscillator, which produces frequency hopping to reduce the EMI. A voltage-waveform detector produces a voltage-feedback signal and a discharge-time signal by multi-sampling a voltage signal of a transformer. A current-waveform detector and an integrator generate a feedback signal. The integration of a current-waveform signal with a timing signal generates the average-current signal. Time constant of the integrator is correlated to the switching frequency. The oscillator generates the timing signal and a pulse signal in response to the output of a current-loop error amplifier. A PWM circuit generates the switching signal in response to the pulse signal and the output of a voltage-loop error amplifier for switching the switching device and regulating the output of the power converter.
125 Citations
15 Claims
-
1. A switching control circuit for a primary-side-controlled power converter, comprising:
-
a switch for switching a transformer;
wherein said transformer is coupled to an input voltage of the power converter;
a sense device, which is coupled to said transformer for sensing current or/and voltage of said transformer;
a switching signal, coupled to said switch for regulating an output voltage and a maximum output current of the power converter; and
a controller, coupled to said transformer to generate a first feedback signal and a discharge-time signal by multi-sampling a voltage signal and a discharge time of said transformer during an off-time of said switching signal, said controller further coupled to said sense device to generate a second feedback signal in response to said discharge-time signal and a current signal of said transformer, wherein said controller generates said switching signal in response to said first feedback signal, said controller controlling a switching frequency of said switching signal in response to said second feedback signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
-
-
13. A switching control circuit for a primary-side-controlled power converter, comprising:
-
a switch for switching a transformer;
in which said transformer is coupled to an input voltage of the power converter;
a switching signal coupled to said switch for regulating said output voltage; and
a controller coupled to said transformer to generate a first feedback signal by multi-sampling a voltage signal and a discharge time of said transformer during an off-time of said switching signal, wherein said controller generates said switching signal in response to said first feedback signal, wherein said controller comprises a first waveform detector. - View Dependent Claims (14, 15)
-
Specification