Abstract: An improved electric circuit structure for short circuit protection is applicable to examining a device under test, comprising a circuit breaking element, a thermistor, a filtering and rectifying module and a capacitor. A first end of the circuit breaking element is electrically connected to a power source. A first end of the thermistor is electrically connected to a ground. The filtering and rectifying module is connected between the second end of the circuit breaking element and the second end of the thermistor. The capacitor is connected to the filtering and rectifying module and in parallel with the device under test. The circuit breaking element disclosed in the present invention is a multi-protector fuse and forms an open circuit when the device under test forms a short circuit. Meanwhile, the multi-protector fuse is able to withstand voltage between its first and second end without generating any physical damage.

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 power adapter with a combinational plug has a plug assembly and a converter assembly. The converter assembly has two guide walls formed on a bottom surface thereof for a base of the plug assembly to be inserted therein, and at least one fixing member and a positioning boss formed on the base to engage at least one engagement slot and a positioning slot formed in the base. The base is mounted within the guide walls, the at least one fixing member engages the at least one engagement slot, and the positioning boss engages the positioning slot for the plug assembly and the converter assembly to be firmly combined. The locations of the positioning boss and the positioning slot are unique for each power adapter. Accordingly, a power adapter with low production cost and misuse protection can be provided.

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 power adapter with a combinational plug has a plug assembly and a converter assembly. The converter assembly has two guide walls formed on a bottom surface thereof for a base of the plug assembly to be inserted therein, and at least one fixing member and a positioning boss formed on the base to engage at least one engagement slot and a positioning slot formed in the base. The base is mounted within the guide walls, the at least one fixing member engages the at least one engagement slot, and the positioning boss engages the positioning slot for the plug assembly and the converter assembly to be firmly combined. The locations of the positioning boss and the positioning slot are unique for each power adapter. Accordingly, a power adapter with low production cost and misuse protection can be provided.

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 charging base has a bottom case, a printed circuit board (PCB) and a top case. The bottom case includes at least one drainage hole. The PCB is mounted in the bottom case and includes a mounting hole, a positioning block and charging terminals. The positioning block is attached to the PCB and has through holes. The charging terminals are secured to the positioning block and have apertures. The top case covers the bottom case and includes terminal holes and a top enclosed wall. The top enclosed wall is secured around the positioning block. Therefore, when water accidentally enters the charging base via the terminal holes, the water will sequentially flow through the apertures of the charging terminals, the through holes of the positioning block and the mounting hole of the PCB and subsequently drain out of the drainage hole of the bottom case.

Abstract: A power adapter with a rotatable plug module has a body, a circuit module and a plug module. The body has multiple fasteners and multiple clasps. The fasteners are arranged in a ring shape. Each of the clasps is formed on one side of each fastener and extends from the fasteners in the same orientation. The circuit module has a circuit board mounted in the body. The plus module has multiple conducting blades and multiple holes. The holes are engaged with the fasteners of the substrate when the plug module is rotated to correspond to the fasteners. The conducting blades are electrically connected to the circuit board. Because the plug module is rotatable and can be removed from the body, the power adapter with suitable conducting pins is available to various sockets.

Abstract: A power adapter having a replaceable and rotatable plug has a body having an annular chamber, two conducting elements inside the annular chamber, four channels recessed on a top thereof to communicate with the annular chamber, and an engagement slot abutting each of the four channels; and a hollow plug having two intermediate conducting elements, a cylinder protruding beyond a bottom of the plug and received in the annular chamber, four arced holes communicating with an inner portion of the plug, four engagement blocks protruding from a cylindrical periphery to respectively correspond to the four channels and four engagement slots, and at least two prongs mounted on a top thereof, one end of each of the two prongs penetrating through the plug to electrically connect with corresponding intermediate conducting elements. Given the aforementioned structure, the plug can be replaced and selectively oriented with respect to the body.

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 transformer has a pair of cores, a winding assembly, a primary coil and a secondary coil. Each core has a center and an elliptical central core formed at the center. The winding assembly has a body and two mounting brackets. The body is a hollow elliptical column with two ends and has an outer surface and an elliptical mounting hole. The two mounting brackets are attached respectively to the two ends of the body, and each mounting bracket has a slot with a rounded edge and multiple pins. Since the central cores are elliptic, each central core may have a larger volume, such that the transformer may have a greater heat-absorbing capability, so transformer temperature rises slower. Furthermore, the winding assembly mounted on the central core is more stable, and even if the pins detach, the winding assembly will remain in position.

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.

Abstract: An adjustable right angle electrical plug with an interchangeable plug assembly has a casing, an interchangeable plug assembly and an electric cord. The casing is hollow and has a base, a cover and two resilient contacts. The cover is mounted on the base and has a plug recess. The plug recess is symmetric. The resilient contacts protrude into the plug recess. The interchangeable plug assembly is mounted detachably in the plug recess has a body, two prongs and a bottom cover. The body is hollow, corresponds to the plug recess and has an open bottom. The prongs are mounted through and protrude from the body and may be flat blades or cylindrical prongs. The bottom cover has two curved contacts. Each curved contact extends through the bottom cover at two places separated by 90°, makes contact with one of the resilient contacts and is connected to one of the prongs.

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.

Abstract: A battery charger having a detachable plug has a charger body and a changeable plug provided with a first plate and second plate. The second plate has at least two conductor blades extending out therefrom. The plug is detachably connected to the charger body by the first retaining device on the first plate and the second retaining device on the second plates. Therefore, the battery charger is securely and electrically insertable in an outlet of a power supply.