Abstract: A switching power supply includes a power converter which includes a transformer and a switch, a current sensor, a switch controller and a compensation resistor. The current sensor is operable for generating a current monitoring signal indicating a current through a primary winding of the transformer. The switch controller is operable for receiving a feedback signal indicating an output voltage of the power converter, generating a driving signal based on the feedback signal to control an input power and an output power of the transformer, receiving a line voltage signal indicating an input voltage of the power converter, and generating a compensation current corresponding to a peak value of the line voltage signal. The compensation resistor is coupled between the current sensor and the switch controller. A voltage of the current monitoring signal is inversely proportional to the input voltage under control of the compensation current and the compensation resistor.

Abstract: A switching power supply includes a power converter which includes a transformer and a switch, a current sensor, a switch controller and a compensation resistor. The current sensor is operable for generating a current monitoring signal indicating a current through a primary winding of the transformer. The switch controller is operable for receiving a feedback signal indicating an output voltage of the power converter, generating a driving signal based on the feedback signal to control an input power and an output power of the transformer, receiving a line voltage signal indicating an input voltage of the power converter, and generating a compensation current corresponding to a peak value of the line voltage signal. The compensation resistor is coupled between the current sensor and the switch controller. A voltage of the current monitoring signal is inversely proportional to the input voltage under control of the compensation current and the compensation resistor.

Abstract: A flyback converter includes a transformer and a controller operable for controlling a switch coupled in series with a primary winding of the transformer. The controller is configured to operate in multiple modes including a burst mode and a standby mode. In the burst mode, the controller generates a first plurality of discrete pulse groups to turn on the switch and a duration of each pulse in the first plurality of discrete pulse groups is determined by a first reference signal having a first predetermined voltage. In the standby mode, the controller generates a second plurality of discrete pulse groups to turn on the switch and a duration of each pulse in the second plurality of discrete pulse groups is determined by a second reference signal having a second predetermined voltage which is greater than the first predetermined voltage of the first reference signal.

Abstract: A controller for controlling a power converter includes a signal generator and a driver. The power converter receives an input voltage and provides an output voltage to power a load. The signal generator receives a sense signal indicating a current flowing through the power converter, receives a detection signal indicating whether the power converter operates in a predetermined state, and generates a square wave signal according to the sense signal and the detection signal. The square wave signal has a first voltage level proportional to a peak level of the current when the power converter operates in the predetermined state; otherwise, the square wave signal has a second voltage level. The driver generates a driving signal based on the square wave signal to control a current flowing through the load.

Abstract: A circuit includes a transformer and a controller. The transformer includes a primary winding and a secondary winding, and operates in multiple switching cycles. A switching cycle includes a charging period and a discharging period. During the charging period, the transformer is powered by the input voltage and a current flowing through the primary winding increases. During the discharging period the transformer discharges to power the load and a current flowing through the secondary winding decreases. The controller includes a pin that receives a first feedback signal indicating the input voltage during the charging period and receives a second feedback signal indicating an electrical condition of the secondary winding during the discharging period. The controller generates a first control signal and a second control signal to regulate the input voltage and an output current flowing through the load, respectively.

Abstract: A flyback converter includes a transformer and a controller operable for controlling a switch coupled in series with a primary winding of the transformer. The controller is configured to operate in multiple modes including a burst mode and a standby mode. In the burst mode, the controller generates a first plurality of discrete pulse groups to turn on the switch and a duration of each pulse in the first plurality of discrete pulse groups is determined by a first reference signal having a first predetermined voltage. In the standby mode, the controller generates a second plurality of discrete pulse groups to turn on the switch and a duration of each pulse in the second plurality of discrete pulse groups is determined by a second reference signal having a second predetermined voltage which is greater than the first predetermined voltage of the first reference signal.

Abstract: Embodiments of the invention provided a driving circuit for powering a light-emitting diode (LED) light source. The driving circuit includes a rectifier, a filter capacitor, and a control circuit. The rectifier converts an AC voltage from an AC power source to a rectified AC voltage. The filter capacitor coupled to the rectifier filters the rectified AC voltage to provide a DC voltage. The control circuit controls power supplied to the LED light source. The control circuit enables a discharging current periodically to discharge the filter capacitor if a switch coupled between an AC power source and a rectifier is turned off and disables the discharging current if the control circuit determines that the switch is turned on.

Abstract: A controller for controlling a power converter includes a signal generator and a driver. The power converter receives an input voltage and provides an output voltage to power a load. The signal generator receives a sense signal indicating a current flowing through the power converter, receives a detection signal indicating whether the power converter operates in a predetermined state, and generates a square wave signal according to the sense signal and the detection signal. The square wave signal has a first voltage level proportional to a peak level of the current when the power converter operates in the predetermined state; otherwise, the square wave signal has a second voltage level. The driver generates a driving signal based on the square wave signal to control a current flowing through the load.

Abstract: A power converter includes a transformer operated in multiple switching cycles. At least one switching cycle includes a charging period, a discharging period, and an adjusting period. The transformer has a primary winding coupled to a power source and a secondary winding coupled to a load. During the charging period the transformer is powered by the power source and a current flowing through the primary winding increases. During the discharging period the transformer discharges to power the load and a current flowing through the secondary winding decreases. A ratio of a duration of the discharging period to a total duration of the charging period, the discharging period and the adjusting period is constant.

Abstract: A circuit includes a transformer and a controller. The transformer includes a primary winding and a secondary winding, and operates in multiple switching cycles. A switching cycle includes a charging period and a discharging period. During the charging period, the transformer is powered by the input voltage and a current flowing through the primary winding increases. During the discharging period the transformer discharges to power the load and a current flowing through the secondary winding decreases. The controller includes a pin that receives a first feedback signal indicating the input voltage during the charging period and receives a second feedback signal indicating an electrical condition of the secondary winding during the discharging period. The controller generates a first control signal and a second control signal to regulate the input voltage and an output current flowing through the load, respectively.

Abstract: A controller for controlling power to an LED light source includes a control terminal and control circuitry coupled to the control terminal. The control terminal provides a control signal to control a transformer. A cycle of the control signal includes a charging period, a discharging period, and an adjusting period. The control circuitry controls a primary winding of the transformer to receive power during the charging period and controls a secondary winding of the transformer to discharge power to the LED light source during the discharging period. The control circuitry further varies a frequency of the control signal periodically by controlling the adjusting period.

Abstract: Embodiments of the invention provided a driving circuit for powering a light-emitting diode (LED) light source. The driving circuit includes a rectifier, a s filter capacitor, and a control circuit. The rectifier converts an AC voltage from an AC power source to a rectified AC voltage. The filter capacitor coupled to the rectifier filters the rectified AC voltage to provide a DC voltage. The control circuit controls power supplied to the LED light source. The control circuit enables a discharging current periodically to discharge the filter capacitor if a switch coupled between an AC power source and a rectifier is turned off and disables the discharging current if the control circuit determines that the switch is turned on.

Abstract: A power supply system includes a power converter, a switch, and a controller. The power converter is operable for providing power to a load. The switch is coupled to the power converter and is operable for adjusting the power to the load. The switch has a gate, a source and a drain. The controller is coupled to the switch and is operable for controlling a state of the switch. The controller has a first control terminal for providing a gate voltage to the gate of the switch, a second control terminal for providing a source voltage to the source of the switch, and an input terminal for receiving a supply voltage via the source of the switch. The controller is also operable for limiting the supply voltage within a predetermined maximum level by regulating the gate voltage to a preset level.

Abstract: A controller for controlling power to an LED light source includes a control terminal and control circuitry coupled to the control terminal. The control terminal provides a control signal to control a transformer. A cycle of the control signal includes a charging period, a discharging period, and an adjusting period. The control circuitry controls a primary winding of the transformer to receive power during the charging period and controls a secondary winding of the transformer to discharge power to the LED light source during the discharging period. The control circuitry further varies a frequency of the control signal periodically by controlling the adjusting period.

Abstract: A power converter includes a transformer operated in multiple switching cycles. At least one switching cycle includes a charging period, a discharging period, and an adjusting period. The transformer has a primary winding coupled to a power source and a secondary winding coupled to a load. During the charging period the transformer is powered by the power source and a current flowing through the primary winding increases. During the discharging period the transformer discharges to power the load and a current flowing through the secondary winding decreases. A ratio of a duration of the discharging period to a total duration of the charging period, the discharging period and the adjusting period is constant.

Abstract: A power supply system includes a power converter, a switch, and a controller. The power converter is operable for providing power to a load. The switch is coupled to the power converter and is operable for adjusting the power to the load. The switch has a gate, a source and a drain. The controller is coupled to the switch and is operable for controlling a state of the switch. The controller has a first control terminal for providing a gate voltage to the gate of the switch, a second control terminal for providing a source voltage to the source of the switch, and an input terminal for receiving a supply voltage via the source of the switch. The controller is also operable for limiting the supply voltage within a predetermined maximum level by regulating the gate voltage to a preset level.