Patent application number | Description | Published |
20100097104 | CONTROL CIRCUIT HAVING OFF-TIME MODULATION TO OPERATE POWER CONVERTER AT QUASI-RESONANCE AND IN CONTINUOUS CURRENT MODE - A control circuit is developed to adaptively operate a power converter at quasi-resonance (QR) and in a continuous current mode (CCM) to achieve high efficiency. The control circuit includes a PWM circuit generating a switching signal coupled to switch a transformer. A signal generation circuit generates a ramp signal and a pulse signal. The pulse signal is generated in response to the ramp signal for switching on the switching signal. A feedback circuit produces a feedback signal according to an output load of the power converter. The feedback signal is coupled to switch off the switching signal. A detection circuit is coupled to the transformer for generating a valley signal in response to the waveform of the transformer. The valley signal is further coupled to generate the pulse signal when the ramp signal is lower than a threshold. The level of the threshold is correlated to the feedback signal. | 04-22-2010 |
20100124079 | OFFLINE SYNCHRONOUS RECTIFIER WITH CAUSAL CIRCUIT FOR RESONANT SWITCHING POWER CONVERTER - A synchronous rectifier of a resonant switching power converter is provided to improve efficiency. The synchronous rectifier includes a power transistor and a diode connected to a transformer and an output of the resonant switching power converter for ratifications. A controller generates a drive signal to control the power transistor in response to an on signal and an off signal. A causal circuit is developed to generate the off signal in accordance with the on signal. The on signal is enabled once the diode is forward biased. The on signal is coupled to enable the drive signal for switching on the power transistor. The off signal is coupled to disable the drive signal for switching off the power transistor. The off signal is enabled before the on signal is disabled. | 05-20-2010 |
20100202162 | ASYMMETRICAL RESONANT POWER CONVERTERS - A resonant power converter is provided and includes a capacitor, an inductive device, a first transistor, a second transistor, and a control circuit. The capacitor and the inductive device develop a resonant tank. The first transistor and the second transistor are coupled to switch the resonant tank. The control circuit generates a first signal and a second signal to control the first transistor and the second transistor respectively. Frequencies of the first signal and the second signal are changed for regulating output of the resonant power converter. The control circuit is further coupled to detect an input voltage of the resonant power converter. A pulse width of the second signal is modulated in response to change of the input voltage. | 08-12-2010 |
20100232182 | DUAL-SWITCHES FLYBACK POWER CONVERTER WITH SELF-EXCITED SUPPLY TO POWER THE HIGH-SIDE DRIVER - An exemplary embodiment of a flyback power converter includes a transformer for power transfer, a high-side transistor, a low-side transistor, two diodes, a control circuit, and a high-side drive circuit. The high-side transistor and the low-side transistor are coupled to switch the transformer. The two diodes are coupled to said transformer to circulate energy of leakage inductance of the transformer to an input power rail of the power converter. The control circuit generates a switching signal coupled to control the high-side transistor and the low-side transistor. The high-side drive circuit is coupled to receive the switching signal for driving the high-side transistor. The transformer has an auxiliary winding generating a floating power to provide power supply for said high-side drive circuit. | 09-16-2010 |
20110292702 | METHOD AND APPARATUS TO IMPROVE DYNAMIC RESPONSE OF THE SYNCHRONOUS RECTIFYING FOR RESONANT POWER CONVERTERS - A synchronous rectifying circuit for a switching power converter is provided. The synchronous rectifying circuit includes a power transistor, a diode, and a control circuit. The power transistor and the diode are coupled to a transformer and an output of the power converter for rectification. The control circuit generates a drive signal to switch on the power transistor once the diode is forward biased. The control circuit includes a monitor circuit. The monitor circuit generates a monitor signal an off signal to switch off the power transistor in response to a pulse width of the drive signal for generating an off signal to switch off the power transistor. The monitor circuit further reduces the pulse width of the drive signal in response to a change of a feedback signal. The feedback signal is correlated to an output load of the power converter. | 12-01-2011 |
20110305048 | ACTIVE-CLAMP CIRCUIT FOR QUASI-RESONANT FLYBACK POWER CONVERTER - An active clamp circuit for a QR flyback power converter according to the present invention comprises an active-clamper connected to a primary winding of a power transformer of the QR flyback power converter in parallel. A high-side transistor driver is coupled to drive the active-damper. A charge-pump circuit is coupled to the high-side transistor driver to provide a power supply to the high-side transistor driver in accordance with a voltage source. A control circuit generates a control signal coupled to control the high-side transistor driver. The control signal is generated in response to a PWM signal and an input voltage of the QR flyback power converter. | 12-15-2011 |
20110305055 | ADAPTIVE SYNCHRONOUS RECTIFICATION CONTROL METHOD AND APPARATUS - An adaptive synchronous rectification control circuit and a control method are developed. The control circuit comprises an adaptive circuit that generates a reference signal in response to a detection signal of a power converter. A clamped circuit clamps the reference signal at a threshold voltage if the reference signal equals or is greater than the threshold voltage. A switching circuit generates a control signal to control a synchronous switch of the power converter in response to the detection signal and the reference signal. The control method generates the reference signal in response to the detection signal. The reference signal is clamped at the threshold voltage if the reference signal equals or is greater than the threshold voltage. The method further generates the control signal to control the synchronous switch of the power converter in response to the detection signal and the reference signal. | 12-15-2011 |
20110317454 | DUAL SWITCHES FLYBACK POWER CONVERTER WITH WIDE INPUT VOLTAGE RANGE - A dual switches Flyback power converter with a wide input voltage range according to the present invention comprises an input diode and an energy-store capacitor. The input diode can prevent the reflected voltage from the power transformer of the power converter to charge the electrolytic capacitor of the power converter. The energy-store capacitor will store the reflected voltage and the energy of the leakage inductor of the power transformer. The energy stored in the energy-store capacitor will be recycled to the output voltage of the power converter. Further, the input diode can be replaced by an input transistor to prevent the reflected voltage from the power transformer to charge the electrolytic capacitor. | 12-29-2011 |