Abstract: A circuit for discharging an X capacitor includes an AC detection unit, a reset unit, a counter, and a discharging unit. The AC detection unit is coupled to two terminals of the X capacitor through a pin. The AC detection unit has a plurality of reference levels for detecting a DC voltage level according to the plurality of reference levels, and outputting a detection signal. The reset unit is coupled to the AC detection unit for generating a reset signal according to the detection signal. The counter is coupled to the reset unit for being reset according to the reset signal. When the counter does not receive the reset signal within a first predetermined time, the counter generates a turning-on signal. The discharging unit is coupled to the counter for discharging the X capacitor according to the turning-on signal.

Abstract: A controller is applied with a protection circuit and a protection method. A controller detects an input signal generated by a current flowing through a detection resistor, thereby turning on or off a switch, for controlling the current. A shielding time generator provides a shielding time. When the switch is turned on and when a current timing without the shielding time, a short-circuit detector compares the input signal with a first reference voltage, thereby asserting a short-circuit detection signal. When the switch is turned off or when the current timing is during the shielding time, the short-circuit detection signal is not asserted. Each time the short-circuit detection signal is asserted, a logic controller turns off the switch, thereby reducing the current.

Abstract: Power supplies together with related over voltage protection methods and apparatuses. A power supply has a transformer including a primary winding and an auxiliary winding. A power switch is coupled to the primary winding and a sensing resistor coupled between the power switch and a grounding line. A multi-function terminal of a controller is coupled to the sensing resistor. A diode and a first resistor is coupled between the auxiliary winding and the multi-function terminal.

Abstract: The present invention is to provide a flyback converter by utilizing harmonic effect generated by a transformer thereof, after transferring electric energy in the transformer in a boundary mode, through cooperating with a simple control circuit to draw the charges stored in a main switch thereof out and enable the main switch to perform a zero voltage switch under a variety of loads in the boundary mode, which not only greatly reduces switch loss thereof, but also effectively limits an operating frequency of the main switch in a predetermined range to greatly decrease peak value of voltage caused by inductance leakage and have the advantages of high efficiency, high switching frequency and low noise without increasing the manufacturing cost.

Abstract: The present invention is to provide a flyback converter by utilizing harmonic effect generated by a transformer thereof, after transferring electric energy in the transformer in a boundary mode, through cooperating with a simple control circuit to draw the charges stored in a main switch thereof out and enable the main switch to perform a zero voltage switch under a variety of loads in the boundary mode, which not only greatly reduces switch loss thereof, but also effectively limits an operating frequency of the main switch in a predetermined range to greatly decrease peak value of voltage caused by inductance leakage and have the advantages of high efficiency, high switching frequency and low noise without increasing the manufacturing cost.

Abstract: The present invention relates to an electronic ballast of fluorescent lamp, which comprises an resonant element being parallelly connected to a lamp at a distal side from a power source for participating in starting the lamp or preheating electrodes thereof to achieve the purposes of providing an appropriate current for preheating electrodes in starting and substantially reducing or eliminating the current of electrodes after the lamp being turned on, so that an undesirable power consumption in electrodes is avoided.