Abstract: A transformer simulating circuit includes a primary side, a secondary side, a first coupling capacitor, and a second coupling capacitor. The primary side includes a primary core-loss resistor, a primary intra-winding capacitor, and a magnetizing inductor connected in parallel, and includes a primary leakage inductor module connected between a primary winding and the primary intra-winding capacitor, and a primary winding resistor connected to the primary leakage inductor module. The secondary side includes a secondary leakage inductor module connected between a secondary winding and a secondary intra-winding capacitor, and a secondary winding resistor connected to the secondary leakage inductor module. The first coupling capacitor and the second coupling capacitor are connected between the primary side and the secondary side. Therefore, a simulated frequency response of the transformer simulating circuit is closer to a measured frequency response of a real transformer.

Abstract: A method for sensing an output current Iout of the fly-back converter has steps of sensing a voltage US of the switching node to obtain a time period TSW of a switching cycle of the fly-back converter and a time period TOFF of a OFF stage of the switching cycle; and then calculating the output current Iout according to a formula I out = k ? T OFF 2 T SW , wherein k is a predictable constant. By the method, a user just need to sense the voltage US of the switching node of the fly-back converter, and then the output current Iout of the fly-back converter is obtained by the formula without using a sensing resistor to sense any current in the fly-back converter.

Abstract: A surge current suppressing circuit is applied between an AC power and an electronic device that receives the AC power via a first AC power line and a second AC power line. The surge current suppressing circuit has a first input fuse connected to the first AC power line, and a first air-core inductor connected in series with the first input fuse on the first AC power line to suppress a surge current. Depending upon the practical applications, the surge current suppressing circuit can further have a second air-core inductor connected to the second AC power line, a capacitor connected between the two AC power lines or both.

Abstract: A lamp housing capable of serving as a bobbin for a light emitting diode (LED) lamp has a containing portion for receiving a converter module, and a winding portion for mounting a cap. Windings of inductor unit of the converter module are wound on the winding portion and form large inductance that is able to replace multiple inductors and a surge protector that are originally mounted on a circuit board of the converter module. The LED lamp with the lamp housing has reduced emissions and enhanced effect of protecting against electrical surge and spikes, and meets safety regulations. Since electrical elements mounted on the circuit board are reduced and the metal cap also dissipates heat generated by the windings of the inductor unit, the converter module operates properly under suitable temperatures.

Abstract: A surge current suppressing circuit is applied between an AC power and an electronic device that receives the AC power via a first AC power line and a second AC power line. The surge current suppressing circuit has a first input fuse connected to the first AC power line, and a first air-core inductor connected in series with the first input fuse on the first AC power line to suppress a surge current. Depending upon the practical applications, the surge current suppressing circuit can further have a second air-core inductor connected to the second AC power line, a capacitor connected between the two AC power lines or both.

Abstract: A push-pull type self-oscillating power converter uses a main power transformer connected to a current transformer in series in such a way that a secondary current flowing through secondary sides of the two transformers is feedback to the primary side of the current drive transformer to generate a drive current for driving two switches. The drive current is proportional to the secondary current in the secondary side of the main power transformer.

Abstract: A push-pull type self-oscillating power converter uses a main power transformer connected to a current transformer in series in such a way that a secondary current flowing through secondary sides of the two transformers is feedback to the primary side of the current drive transformer to generate a drive current for driving two switches. The drive current is proportional to the secondary current in the secondary side of the main power transformer.

Abstract: The present invention relates to a device (10) for converting an AC voltage from the mains electricity supply into a DC voltage of predetermined level (and waveform), comprising:—a rectifier circuit (16, 17, 18, 19) for connecting to the mains electricity supply;—a switching circuit connected to the rectifier circuit;—a main transformer (26) connected to the switching circuit and—an auxiliary transformer (28) which is connected to the switching circuit and the secondary winding of which is coupled to the secondary winding of the main transformer such that the current through the switching circuit and the main transformer is limited to a predetermined value.