Abstract: The present invention provides a power supply circuit without current transformers. A voltage increasing chopping is is applied to an alternating current input between a common line and another input terminal under control of a control circuit and a voltage increasing chopper circuit and filter, to obtain voltage-increased direct-current voltage at the positive and negative charge sides relative the common line, and to improve the power factor, the stabilized direct-current voltage is converted to alternating current voltage by a subsequent half bridge type DC-AC inverter. High-Frequency components are are removed by an output filter comprising a reactor and condenser. An input current detecting resistance is placed in the common line and an output current detecting resistance is placed at the output filter produce input and output current information for the control circuit.

Abstract: An object of the present invention is to obtain a portable product capable of switching to a plurality of kinds of voltage, supporting any type of battery, and informing a user of an output voltage abnormality, service interruption and an end of discharge. It is an AC adapter power supply apparatus comprising a line for supplying a DC voltage of an AC-DC conversion circuit 11 directly to a DC output circuit 23, and a line for supplying the same from a battery 14, wherein an output side of a DC output detection circuit 17 connected to the AC-DC conversion circuit 11 is connected to an apparatus status output circuit 22 for outputting a status monitoring signal to the outside and to a battery switch circuit 15, and a changeover switch 19 for switching a set-up output voltage is connected to the AC-DC conversion circuit 11 and the DC-DC conversion circuit 16.

Abstract: A switching power supply apparatus which effectively utilizes energy accumulated in a leak inductance of a circuit to enhance the efficiency. The switching power supply apparatus having a switch element on/off controlled by a driving signal generated from a driver circuit, wherein a first capacitor and a first diode are inserted in series between both terminals of the switch , and a second capacitor and a second diode are further connected in series between a connecting point of the first capacitor and the first diode and a grounding terminal of the switch element to use charges accumulated on the second capacitor as a voltage source.

Abstract: An inverter for DC/AC conversion includes an inverter bridge controlled by a PWM controller. The inverter has a first control loop for performing PWM control in accordance with the difference between the instantaneous AC value of an inverter output and an amplitude of waveform data read out from an AC waveform memory. The inverter also has a second control loop for multiplying the amplitude value of the waveform data by a coefficient adjusted on the basis of the error between the means AC current or voltage value of the inverter outputs and a target control value, and performing PWM control in accordance with waveform data having the adjusted amplitude. By using a delta scheme of finely increasing/decreasing at a time the coefficient by which waveform data is multiplied, an inverter with a high control precision and high stability can be obtained.

Abstract: A DC constant voltage circuit comprises a rectifier and a boosting chopper circuit controlled by a general purpose PWM control IC. The general purpose PWM control IC receives a reference voltage Vref which regulates the output voltage by pulse width modulation and produces a voltage having the same waveform and phase as the input current to improve the power factor of the output voltage. An AC constant voltage circuit comprises a common line connecting an AC input terminal and an output terminal, positive and negative boosting chopper circuits for boosting and chopping a half-wave rectified respectively in both positive and negative sides into a DC voltage and a DC-AC inverter for inverting the DC voltage into the AC output voltage. The positive and negative boosting chopper circuits are used as a filter for improving the power factor and adjusting the waveform and phase of the output voltage to be the same as the sine full waveform of the input voltage.

Abstract: The present invention relates to a switching power supply a microwave oven in which DC power is changed to a pulse form by means of a switching element coupled to a primary winding of an inverter transformer to supply the power to a high frequency oscillator (hereinafter referred to as a magnetron) coupled to a secondary winding. A reference voltage is set lower than an ordinary state from the time of turning on until the oscillation of the magnetron starts. Accordingly, power supplied from the secondary winding of the inverter transformer to the magnetron is set to a low level. The reference voltage increases when oscillation of the magnetron starts, and returns to the ordinary state when the oscillation returns to the ordinary state.

Abstract: A DC-DC convertor includes a transformer having a primary winding adapted to be connected in series with a DC power source and a secondary winding, a rectifier and smoothing circuit, a main switching device, adapted to be connected in series with the DC power source, for connecting the rectifier and smoothing circuit to the secondary winding of the transformer when the main switching device is in an on-state, an auxiliary switching circuit connected in parallel with the main switching device, and a signal generating circuit for providing a first control signal to the main switching device and a second control signal to the auxiliary switching circuit. The auxiliary switching circuit includes a first capacitor connected in parallel with a second capacitor that is connected in series with an auxiliary switching device.

Abstract: A DC-DC converter includes a transformer and a switching element. The primary winding of the transformer and the switching element are connecting in series with a DC power source. A DC output is extracted via a rectifier circuit connected to a secondary winding of the transformer. A capacitor is connected in parallel to the switching element, and a saturable reactor is connected between the secondary winding of the transformer and the rectifier.

Abstract: The present invention relates to a switching power supply for a microwave oven in which a DC power is changed to a pulse by means of a switching element coupled to a primary winding of an inverter transformer to supply the power to a high frequency oscillator (hereinafter referred to as the magnetron) coupled to a secondary winding. The inverter transformer has a supplementary winding which is coupled to control side of the switching element to form a self-excited voltate resonance type. As to the self-excited type, a switching frequency is changed by itself relative to the change of the input voltage and output power for stabilizing the output, thereby realizing same level of operation as a power switching circuit compulsory excited from outside control circuit (hereinafter referred to as The Outside-excited type).

Abstract: A self-excited inverter circuit primarily includes a main transformer two switching elements e.g. the first and second (FET) switching elements, wherein capacitors at both ends of said first FET are charged during a time T.sub.1 -T.sub.2 when said first FET is turned off, and the voltage V.sub.g1 across said first FET is clamped by a charge voltage V.sub.c1 and then, a voltage V.sub.gs is applied across the gate and the source of said second FET for electrical continuity to cause the voltage to be clamped. The clamped state is maintained from T.sub.1 to T.sub.2, the saturation reactor is saturated at time T.sub.3, and V.sub.gs, which has been negative, starts to change toward O, thereby causing the first FET to change to ON; V.sub.q falls towards VPi at TP3 and further towards zero point. Thus, the voltage V.sub.q2 changes to zero to cause V.sub.gs of the second FET to become zero and the second FET to be shut off. When said voltage V.sub.q2 is clamped to a fixed value, a high -V.sub.

Abstract: When the power source voltage is charged to a capacitor between the source side of a MOSFET and a saturation reactor at the time of starting, the gate voltage of the MOSFET is caused to rise. When this charging voltage or the gate voltage exceeds the threshold voltage, the MOSFET is energized. The energization of this MOSFET induces a voltage in the tertiary self-excited oscillation winding through the primary winding, and a part of the induced voltage is applied to the gate of the MOSFET while some other part is applied to the reactor. This causes the magnetic flux of the saturation reactor to be set to the direction opposite that which had been set before. When the product of the voltages applied to the saturation reactor has reached the level for the allowable saturation magnetic flux density the saturation reactor is saturated and the gate voltage is discharged to turn off the MOSFET.

Abstract: A stabilized power supply unit designed to supply the power from the commercial power source as far as the commercial power source is normal but supply the power from a battery that can be made available by an automatic switching device when the commercial power source has failed, wherein the AC voltage from the commercial power source is rectified by a rectification circuit to obtain almost equal DC currents on both the positive and negative sides of the common line while the commercial power source is normal. Said DC voltage is chopped by the boosting chopper circuit to boost the voltage on both the positive and negative sides. The boosted voltage is converted into the AC voltage through the DC-AC inverter, and the high-frequency component of the AC voltage is compressed through the filter in order to be outputted as an AC voltage of specified frequency.