Abstract: An indicating circuit for a switching power supply is provided. An LED and a resistor are connected in series, and then are connected in parallel with a capacitor, and the parallel-connected circuit and a diode are connected in series in the same direction, and then are connected in parallel with an inductor to form the indicating circuit. The cathode of the indicating circuit is a terminal 1, and the anode of the indicating circuit is a terminal 2.

Abstract: A switch power supply having active power factor correction is provided, including a power factor correction (PFC) circuit, a filter circuit, a main power stage, a first capacitor (C1) and an indicating circuit. An alternating-current input (IN) is connected to the first capacitor through the PFC circuit and is connected to the filter circuit through the indicating circuit. The indicating circuit consists of a light emitting diode (LED) having unidirectional conductivity and an inductor (L); and the current direction of power supplied from the PFC circuit to the main power stage through the inductor is opposite to the conduction direction of the LED. The LED may also be a light emitter of a photocoupler. The filter circuit at least comprises an electrolytic capacitor (C2). When the electrolytic capacitor is normal, an exciting current of the main power stage basically does not appear in the inductor and the LED does not emit light.

Abstract: A direct filtering type switching power supply is provided, for an occasion including pulsating direct current, including a filter circuit, a main power stage and an indicating circuit. A direct current input is connected to the filter circuit through the indicating circuit. The filter circuit and the main power stage are connected in parallel. The indicating circuit is formed by connecting a light emitting unit with an inductor in parallel, and make sure that the direction of the direct current input passing through the inductor is opposite to the conducting direction of the light emitting unit. The filter circuit at least includes an electrolytic capacitor. When the electrolytic capacitor is normal, an excitation current of a switching transistor in the main power stage basically does not appear in the inductor, and an LED in the light emitting unit does not emit light.

Abstract: A self-excitation push-pull type converter with a transformer having a closed magnetic core or iron core, which formed of a main part (52) and a local part (53). The local part reaches magnetic saturation earlier than the main part under the same increasing magnetic field excitation. When the self-excitation push-pull type converter is in a light load state, the efficiency is significantly improved, and further improved in a rated load state. As the number of turns of the coil on the magnetic saturation transformer is reduced, the working frequency of the converter increases while still keeping the loss low. The probability of generating a current peak at the moments of switching on or off is reduced, thereby further improving the efficiency and reducing output ripples.

Abstract: A magnetic core for a transformer, which includes a closed ring with a thick part and a thin part. The thin part is magnetically saturated before the thick part when excited by the same increasing magnetic fields. The thin part only operates briefly at or near first quadrant saturation point or a third quadrant saturation point and, for the rest of the time, it operates in a state between the first quadrant saturation point and the third quadrant saturation point. The present invention overcomes the drawbacks of the conventional magnetic core for a self-excitation push-pull type converter, and significantly improves the efficiency of the converter when it is under a light load, and further improves its efficiency while under a rated load. As the number of turns of the coil on the magnetic saturation transformer is reduced, the working frequency of the converter is improved while still keeping the loss low.

Abstract: A self-excited push-pull converter, where between the bases of the push-pull converter's transistors (TR1, TR2) and the effective power suppler there is provided a constant current source (II), which provides a constant current to the bases of the transistors. With the working voltage increases, the circuit enters into an operating mode not based on the core-saturation working mode, because the transistors' base current is limited by the constant current source and consequently the transistors' collector current cannot increase.

Abstract: An AC to DC circuit includes a rectifier circuit, a voltage detecting circuit, the current source and the output circuit. The rectifier circuit converts the AC power to pulsating DC. The constant current source provides current to the voltage detection circuit and to the control port of the output circuit. The current passing throughout the constant current source is the sum of the current flowing to the voltage detection circuit and to the output circuit. The voltage detection circuit increases with the instantaneous value of the output voltage of the rectifier circuit, it absorbs more current from the current provided by the constant current source and less current flows from the constant current source to the control port of the output circuit. The output circuit amplifies the current of the control port and outputs it to power the load.

Abstract: A self-excited push-pull converter, where between the bases of the push-pull converter's transistors (TR1, TR2) and the effective power suppler there is provided a constant current source (II), which provides a constant current to the bases of the transistors. With the working voltage increases, the circuit enters into an operating mode not based on the core-saturation working mode, because the transistors' base current is limited by the constant current source and consequently the transistors' collector current cannot increase.

Abstract: An AC to DC circuit includes a rectifier circuit, a voltage detecting circuit, the current source and the output circuit. The rectifier circuit converts the AC power to pulsating DC. The constant current source provides current to the voltage detection circuit and to the control port of the output circuit. The current passing throughout the constant current source is the sum of the current flowing to the voltage detection circuit and to the output circuit. The voltage detection circuit increases with the instantaneous value of the output voltage of the rectifier circuit, it absorbs more current from the current provided by the constant current source and less current flows from the constant current source to the control port of the output circuit. The output circuit amplifies the current of the control port and outputs it to power the load.

Abstract: A magnetic core for a transformer, which includes a closed ring with a thick part and a thin part. The thin part is magnetically saturated before the thick part when excited by the same increasing magnetic fields. The thin part only operates briefly at or near first quadrant saturation point or a third quadrant saturation point and, for the rest of the time, it operates in a state between the first quadrant saturation point and the third quadrant saturation point. The present invention overcomes the drawbacks of the conventional magnetic core for a self-excitation push-pull type converter, and significantly improves the efficiency of the converter when it is under a light load, and further improves its efficiency while under a rated load. As the number of turns of the coil on the magnetic saturation transformer is reduced, the working frequency of the converter is improved while still keeping the loss low.

Abstract: A self-excitation push-pull type converter with a transformer having a closed magnetic core or iron core, which formed of a main part (52) and a local part (53). The local part reaches magnetic saturation earlier than the main part under the same increasing magnetic field excitation. When the self-excitation push-pull type converter is in a light load state, the efficiency is significantly improved, and further improved in a rated load state. As the number of turns of the coil on the magnetic saturation transformer is reduced, the working frequency of the converter increases while still keeping the loss low. The probability of generating a current peak at the moments of switching on or off is reduced, thereby further improving the efficiency and reducing output ripples.

Abstract: A self-excited push-pull converter, which comprises a Royer circuit, wherein an inductor is further connected between a supply terminal of said Royer circuit and a center tap of primary windings of a transformer in said Royer circuit, an inductance amount of said inductor is less than 1/10 of the inductance amount of one of the primary windings of the transformer, and the center tap of said primary windings is a connection point between the two primary windings of said transformer. The self-excited push-pull converter of the present invention show high consistency, easy adjustment, low requirements on the manufacturing process and good short circuit protection performance.

Abstract: A self-excited push-pull converter, comprising a Jensen circuit, characterized in that a two-terminal network with an electrical property of passing high frequencies and blocking low frequencies exists between a terminal of a magnetic saturation transformer primary winding and a terminal of a main transformer primary winding in said Jensen circuit, i.e. said magnetic saturation transformer primary winding is connected in parallel with said main transformer primary winding through said two-terminal network. The self-excited push-pull converter of the present invention has a good self-protection capability and can be restored by itself to normal operation after overcurrent and short circuit disappear.