Abstract: A controller applied to a power converter is installed in a primary side of the power converter. The controller includes a capacitor, an adjustment signal generation circuit, and a discharge circuit. The capacitor is used for generating a tracking voltage. The adjustment signal generation circuit is used for generating an adjustment signal according to a feedback voltage and the tracking voltage. The discharge circuit is used for discharging the capacitor according to the feedback voltage and the adjustment signal. The tracking voltage is used for tracking a state of a magnetizing current of a magnetizing inductor of the primary side of the power converter, and when the tracking voltage consists with the state of the magnetizing current, the tracking voltage is applied to at least one of zero-voltage switching (ZVS) control and quasi-resonant (QR) control of the power converter.

Abstract: A primary-side controller applied to a power converter is used for controlling a frequency of a gate control signal according to a grouping mode. The primary-side controller includes a first counter, a second counter, an adjuster, a gate control signal generation circuit, and a logic circuit. The first counter generates a first signal according to the gate control signal and a predetermined number. The second counter generates a second signal according to a clock signal and the predetermined number. The adjuster determines whether to adjust the predetermined number according to the second signal, the predetermined number, and a frequency of the clock signal. The logic circuit generates a reset signal to the first counter and the second counter and an enable signal to the gate control signal generation circuit according to the first signal, the second signal, and the gate control signal.

Abstract: A controller applied to a power converter is installed in a primary side of the power converter. The controller includes a capacitor, an adjustment signal generation circuit, and a discharge circuit. The capacitor is used for generating a tracking voltage. The adjustment signal generation circuit is used for generating an adjustment signal according to a feedback voltage and the tracking voltage. The discharge circuit is used for discharging the capacitor according to the feedback voltage and the adjustment signal. The tracking voltage is used for tracking a state of a magnetizing current of a magnetizing inductor of the primary side of the power converter, and when the tracking voltage consists with the state of the magnetizing current, the tracking voltage is applied to at least one of zero-voltage switching (ZVS) control and quasi-resonant (QR) control of the power converter.

Abstract: A power converter provides a dummy load to lower an output voltage under a light-load or no-load condition. The power converter has a primary winding and a secondary winding isolated from each other. The secondary winding can de-energize to provide the output voltage at an output node for powering a load. The winding voltage at across the secondary winding is sensed to provide a non-switching time, which is checked if it exceeds a predetermined reference time. The output voltage is compared with a predetermined voltage. A discharge current is provided as the dummy load to drain from the output node and to lower the output voltage if the on-switching time exceeds the predetermined reference time and the output voltage exceeds the predetermined voltage.

Abstract: Methods and apparatuses for providing a dummy load in a power converter are disclosed. The power converter has a primary winding and a secondary winding isolated from each other. The secondary winding can de-energize to provide an output voltage at an output node for powering a load. The winding voltage at across the secondary winding is sensed to provide a non-switching time, which is checked if it exceeds a predetermined reference time. The output voltage is compared with a predetermined safe voltage. A discharge current is provided as a dummy load to drain from the output node and to lower the output voltage if the on-switching time exceeds the predetermined reference time and the output voltage exceeds the predetermined safe voltage.

Abstract: The present invention provides a control circuit having a multi-function terminal. The control circuit comprises a switching circuit, a sample-and-hold circuit, a detection circuit, and a comparator. The sample-and-hold circuit is coupled to the multi-function terminal for generating a sample voltage by sampling the feedback signal during a first period. The detection circuit is coupled to the multi-function terminal during a second period for generating a detection voltage. The comparator compares the detection voltage and the sample voltage for generating an over-temperature signal, wherein the over-temperature signal is couple to disable the switching signal.

Abstract: The present invention proposes a switching controller of a flyback power converter. The switching controller includes a switching circuit, a sample-and-hold circuit, a voltage detection circuit, an oscillation circuit, and a comparator. The voltage detection circuit generates a holding signal when a level of an input voltage of the flyback power converter is lower than a low-threshold. The oscillation circuit limits the maximum frequency of switching signal. The maximum frequency is increased in response to a decrement of a modulation signal. The modulation signal correlated with a level of the input voltage is used to generate a control signal when the level of the input voltage is lower than an ultra-low-threshold. The control signal is enabled to operate the flyback power converter in continuous current mode operation. Therefore, an input capacitor can be eliminated and manufacturing cost is saved.

Abstract: A dual switches Flyback power converter with a wide input voltage range according to the present invention comprises an input diode and an energy-storage 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-storage capacitor will store the reflected voltage and the energy of the leakage inductor of the power transformer. The energy stored in the energy-storage 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.

Abstract: The present invention provides a controller for a power converter. The controller comprises a PWM circuit, a detection circuit, a signal generator, an oscillation circuit, a valley-lock circuit, a timing circuit and a burst circuit. The PWM circuit generates a switching signal coupled to switch a transformer of the power converter. A feedback signal is coupled to control and disable the switching signal. The detection circuit is coupled to the transformer via a resistor for generating a valley signal in response to a waveform obtained from the transformer. The signal generator is coupled to receive the feedback signal and the valley signal for generating an enabling signal. The oscillation circuit generates a maximum frequency signal. The maximum frequency signal associates with the enabling signal to generate a turning-on signal. The turning-on signal is coupled to enable the switching signal. A maximum frequency of the turning-on signal is limited.

Abstract: Disclosure includes an exemplified power controller for controlling a power switch in a power supply. The power supply converts an input power source into an output power source. The exemplified power controller comprises a maximum frequency maker, a voltage detector, and a logic circuit. Based on dependence of a maximum switching frequency upon a compensation signal, the maximum frequency maker provides a control signal with a minimum switching cycle. The compensation signal correlates to an output power from the output power source, and the minimum switching cycle is the reciprocal of the maximum switching frequency. The voltage detector detects a line voltage of the input power source. The logic circuit controls the power switch in response to the control signal, and makes a switching cycle of the power switch not less than the minimum switching cycle. The line voltage determines the dependence.

Abstract: A control circuit with protection circuit for power supply according to the present invention comprises a peak-detection circuit and a protection circuit. The peak-detection circuit detects an AC input voltage and generates a peak-detection signal. The protection circuit generates a reset signal to reduce the output of the power supply in response to the peak-detection signal. The present invention can protect the power supply in response to the AC input voltage effectively through the peak-detection circuit.

Abstract: A switching control circuit for a switching power converter is provided. The switching control circuit is coupled to a switching device and an auxiliary winding of a transformer. The switching control circuit includes a valley detecting circuit, a valley lock circuit, and a PWM circuit. The valley detecting circuit is coupled to receive a reflected voltage signal from the auxiliary winding of the transformer for outputting a control signal in response to the reflected voltage signal. The valley lock circuit is coupled to receive the control signal for outputting a judging signal in response to the control signal during a first period and a second period following the first period. The PWM circuit outputs a switching signal in response to the judging signal.

Abstract: The present invention proposes a switching controller of a flyback power converter. The switching controller includes a switching circuit, a sample-and-hold circuit, a voltage detection circuit, an oscillation circuit, and a comparator. The voltage detection circuit generates a holding signal when a level of an input voltage of the flyback power converter is lower than a low-threshold. The oscillation circuit limits the maximum frequency of switching signal. The maximum frequency is increased in response to a decrement of a modulation signal. The modulation signal correlated with a level of the input voltage is used to generate a control signal when the level of the input voltage is lower than an ultra-low-threshold. The control signal is enabled to operate the flyback power converter in continuous current mode operation. Therefore, an input capacitor can be eliminated and manufacturing cost is saved.

Abstract: The present invention provides a controller for a power converter. The controller comprises a PWM circuit, a detection circuit, a signal generator, an oscillation circuit, a valley-lock circuit, a timing circuit and a burst circuit. The PWM circuit generates a switching signal coupled to switch a transformer of the power converter. A feedback signal is coupled to control and disable the switching signal. The detection circuit is coupled to the transformer via a resistor for generating a valley signal in response to a waveform obtained from the transformer. The signal generator is coupled to receive the feedback signal and the valley signal for generating an enabling signal. The oscillation circuit generates a maximum frequency signal. The maximum frequency signal associates with the enabling signal to generate a turning-on signal. The turning-on signal is coupled to enable the switching signal. A maximum frequency of the turning-on signal is limited.

Abstract: The present invention provides a control circuit having a multi-function terminal. The control circuit comprises a switching circuit, a sample-and-hold circuit, a detection circuit, and a comparator. The sample-and-hold circuit is coupled to the multi-function terminal for generating a sample voltage by sampling the feedback signal during a first period. The detection circuit is coupled to the multi-function terminal during a second period for generating a detection voltage. The comparator compares the detection voltage and the sample voltage for generating an over-temperature signal, wherein the over-temperature signal is couple to disable the switching signal.

Abstract: 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.

Abstract: 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.

Abstract: A switching control circuit for a switching power converter is provided. The switching control circuit is coupled to a switching device and an auxiliary winding of a transformer. The switching control circuit includes a valley detecting circuit, a valley lock circuit, and a PWM circuit. The valley detecting circuit is coupled to receive a reflected voltage signal from the auxiliary winding of the transformer for outputting a control signal in response to the reflected voltage signal. The valley lock circuit is coupled to receive the control signal for outputting a judging signal in response to the control signal during a first period and a second period following the first period. The PWM circuit outputs a switching signal in response to the judging signal.