Toko, Inc.

Tetushi Otake

Noriyuki Yoshizawa

A switching power supply, eliminating effect of a potential difference generated in a driving circuit, in which a rapid operation speed of a switching transistor Q,and a high efficiency are obtained. An auxiliary bias circuit forming a polarity inversion circuit together with the switching transistor Q,is constructed by connecting a capacitor C,and a diode D,in series between a collector of the switching transistor Q,and a ground, and by connecting a diode D,and a capacitor C,in series between a connection point of the capacitor C,and the diode D,and a ground. One end of a main current path of the transistor Q,which conducts when the switching transistor Q,is in an OFF state, is connected to a connection point of the diode D,and the capacitor C,in the auxiliary bias circuit,, thereby supplying a voltage obtained in the auxiliary bias circuit,to the switching transistor Q,via the transistor Q,. This voltage is applied as a reverse bias to the switching transistor Q,and eliminates a voltage between a base and an emitter of the transistor Q

Switching power supply for speeding up turn-off operation of a switching element

A self-oscillation-resonance type power supply circuit having a stabilizer for output voltages or output currents. A transformer and two transistors (a first transistor and a second transistor) are used to form a push-pull type self-oscillation-resonance type power supply circuit. Feedback signals that change according to resonant voltages are inputted to individual gates of the first transistor and the second transistor, a controller for generating error signals corresponding to the difference between a voltage signal and a reference signal is included in the circuit, and the error signals are fed to the individual gates of the first transistor and the second transistor, whereby conduction timing of the individual transistors is changed to vary the self-oscillation frequency. When the self-oscillation frequency changes,, the amount of energy to be transferred form a resonant circuit formed by a resonance capacitor circuit and a first finding of the transformer to a second winding of the transformer so as to control output voltages.

Self-oscillation-resonance type power supply circuit

A power supply control device, by which a plurality of switching power supply circuits of different properties are operated under switching conditions respectively fitted therefor simultaneously with the prevention of an occurrence of what is called a low-frequency switching beat phenomenon, thereby achieving the miniaturization and the increasing of the efficiency of a power supply unit. To synchronize the timing of switching operations among control systems or units of the power supply control device, the control device of the multi-channel type or the control device having a master-slave function is used. Further, a frequency divider circuit or a frequency multiplier circuit is connected to a comparator of such a control device. Thereby, although synchronizing the timing among the switching operations, a plurality of pulse output signals of different frequencies are outputted from the control systems or the control units. Incidentally, a frequency divider circuit or a frequency multiplier circuit may be added to an oscillation circuit of the control device, instead of connecting the frequency divider circuit or the frequency multiplier circuit to the comparator.

Power supply control device

A switching power supply is provided in which the efficiency is improved and the regulation and cross-regulation of an output voltage is also improved. Terminals (A) and (B) of a primary winding N1 and secondary winding N2 at which the same polarity is set are interconnected via a first capacitor C4. A tap provided at a given winding position (C) of the primary winding N1 and the other terminal (D) of the secondary winding N2 are interconnected via a second capacitor. Herein, assuming that areas of the primary winding N1 divided by the tap are N.sub.11 and N.sub.12, the number of turns in the area N.sub.11 between the terminal (A) and winding position (C) is nearly the same with the number of turns existing between the one terminal (B) of the secondary winding N2 and the other terminal (C) thereof. Owing to the configuration, an equivalent coupling coefficient observed between the primary winding N1 and secondary winding N2 approaches 1.0. Consequently, the efficiency of a power supply can be improved, and regulation and cross-regulation can be improved.

Switching power supply

A low-cost and highly reliable flyback isolation-type switching power supply comprises a main transformer and an auxiliary transformer. A secondary winding of the main transformer is connected in parallel with an input winding of the auxiliary transformer. A series network of a diode and a capacitor is connected between the terminals of an output winding of the auxiliary transformer, and a voltage corresponding to the output voltage of the power supply is obtained across the capacitor. The main transformer and the auxiliary transformer preferably share a core having a plurality of bobbin sections, with the windings of each transformer wound around respective different bobbin sections. The equivalent degree of coupling between the secondary winding and the output winding is thus sufficiently larger than the degree of coupling between the primary winding and the output winding.

Isolation-type switching power supply

A self-excited oscillation type power supply device comprises an auxiliary transistor Q4. When the device is started, a voltage signal providing forward biasis applied to the base of the auxiliary transistor; and when the device is operated, besides the forward bias, at least one of a voltage signal derived from alternate voltage which occurs at a choke coil L1 and a voltage signal corresponding to output voltage, is applied thereto. More specifically, the voltage signal providing forward bias is provided by a resistor R9 connected between the base of the auxiliary transistor Q4 and input terminal 1; the voltage signal derived from the alternate voltage is provided by a capacitor C4 connected between the base of the auxiliary transistor Q4 and one end of a choke coil L1; and the voltage signal corresponding to output voltage is provided by a constant-voltage diode DZ2 connected between the base of the auxiliary transistor Q4 and output terminal 2.

Self-excited oscillation type power supply device

A switching power supply in which high efficiency is obtained by further reducing a loss occurring in a PNP type transistor as a rectifying element, particularly in case of making a switching frequency higher. Further, the switching power supply is a boost/buck converter in which an application range of an input voltage is broadened by causing a circuit not to perform intermittent operation when the voltage V.sub.IN is higher than an output voltage V.sub.o. One end of a choke coil L1 is connected to an input terminal 1 and another end thereof is connected to an emitter of a PNP type transistor Q2 as a rectifying element. A base of transistor Q2 is connected to a collector of a driving transistor Q3 via a resistor R4. The base of the driving transistor Q3 is connected to another end of the choke coil L1 via a series circuit of a capacitor C3 and a resistor R3. Further, the base of the transistor Q2 is connected to one end of the input terminal side of the choke coil via an auxiliary bias circuit 4 or an impedance circuit 5.

An object of the present invention is to reduce a cost and a power consumption, eliminating a voltage source for generating a reference voltage in an isolated switching power source achieving a feedback from an output side of the power source to a control circuit in an input side of the power source through a photo-coupler. A voltage V.sub.1 obtained by dividing an output voltage V.sub.0 by a voltage dividing resistors 8, 9 is applied to a base of a transistor 11-1 for an error amplifier, and a photo-coupler light emitting element 10-1 is connected between an emitter of the transistor 11-1 and a negative side of an power source output. A forward dropping voltage of the photo-coupler light emitting element becomes approximately constant (approximately 1.1 v) over a variation range of a current flowing to the photo-coupler light emitting element at actually using time. Utilizing such a characteristic, it is possible to cause the photo-coupler 10-1 to have a function generating the reference voltage to be compared with the output voltage V.sub.0 as well as a function achieving a feedback to the control circuit 5 in the input side of the power source.

Isolated switching power source

In a non-insulated, self-oscillation type DC-DC converter, a first PNP switching transistor (Q1) has the emitter thereof connected to the emitter of a second switching transistor (Q2) of the same conductivity type as the first switching transistor. The base of the first switching transistor (Q1) is connected to the collector of the second switching transistor (Q2). The base of the first switching transistor (Q1) is connected to the base of the second switching transistor (Q2) through a resistor R2. A feedback circuit (4) is connected between the collector of the first switching transistor (Q1) and the base of the second switching transistor (Q2).

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Tokyo, Japan

Tetushi Otake