Abstract: A power amplifier for use in a PWM signal includes a pulse width modulation signal generating circuit proportional to an amplitude of an input signal, an amplitude modulating circuit for amplitude-modulating the pulse width modulating signal in accordance with the level of the input signal and a power amplifying stage driven by the pulse width modulation signal which was amplitude-modulated. The amplitude modulating circuit or modulator is comprised of, by way of example, a pair of level shifting circuits (21) and (22), each being supplied with the input signal, a pair of switching circuits (23) and (24) for switching the respective outputs of these level shifting circuits by the pulse width modulation signal and an adder (25) for adding the outputs from these switching circuits, wherein this adder can produce at its output a pulse width modulation signal which is amplitude-modulated and the power amplifying stage utilizing bipolar transistors can efficiently be driven by this pulse width modulation signal.

Abstract: A transformer includes a magnetic core; an input or primary winding structure wound on a bobbin secured to the magnetic core and including first and second primary winding portions; an output or secondary winding structure wound on the bobbin and including first and second secondary winding portions; and a control or tertiary winding structure wound on the bobbin and including first and second tertiary winding portions with the first tertiary winding portion being comprised of first and second windings connected in series, the primary, secondary and tertiary winding structures being wound on the bobbin in the order of the first primary winding portion, the first winding of the first tertiary winding portion, the first secondary winding portion, the second secondary winding portion, the second winding of the first tertiary winding portion, the second primary winding portion, and the second tertiary winding portion, so as to provide a high degree of magnetic coupling between the first primary and secondary wind

Abstract: DC to DC converter having DC input and DC output, a first switching element to repetitively connect and disconnect the DC input to an inductance winding connected through the first switching element. A source of pulse width modulated signal provides a control signal based on the detected output voltage of the converter. A second detector which detects a variation in the output load. A second switching element which controls the inductance of the winding is actuated based on the second detected signal.

Abstract: A switching regulator includes a switching transformer and a switching transistor connected in series between a DC voltage source through the primary winding of the switching transformer. A pulse width modulator and a control pulse signal generator are provided so as to produce a pair of ON- and OFF-pulse signals which are supplied to the control electrode of the switching transistor so as to increase the switching speed thereof.

Abstract: A switching regulator includes an inrush current protective resistor and a starter circuit for a pulse width modulator consisting of a starting resistor and a capacitor. At initial starting mode, the inrush current protective resistor is connected to the starter circuit, and after starting both of the inrush current protective resistor and starting resistor are disconnected so as to reduce power dissipation or consumption thereby. At the same time, a DC voltage source for the pulse width modulator is derived from a rectified secondary voltage through the starting capacitor.

Abstract: A switching regulator includes a DC voltage source having a pair of DC output terminals, a switching transformer having first and second primary windings connected in series, a magnetic core and a secondary winding, a first switching transistor connected in series between the pair of DC output terminals through the first primary winding, a second switching transistor connected in series between the pair of DC output terminals through the first and second primary windings, a rectifier circuit connected across the secondary winding. A pulse width modulator is provided to produce a PWM (pulse width modulated) control signal the duty of which is proportional to the voltage of the rectifier circuit and the PWM control signal is selectively supplied to one of the first and second switching transistors in accordance with the low or high circumstance of the load.

Abstract: A protective circuit for a switching regulator includes a DC voltage source having a pair of terminals, a transformer having primary, secondary windings and a magnetic core, a switching transistor having first, second and third electrodes, a circuit for connecting the second and third electrodes between the pair of terminals through the primary winding, a DC output circuit connected across the secondary winding to produce a DC signal in response to the ON/OFF operation of the switching transistor, a control circuit connected to the first electrode of the switching transistor so as to ON/OFF-control the switching transistor in response to the DC signal, a detecting circuit for detecting an over-current flowing through the primary winding of the transformer and for producing a control signal in accordance with a change of the saturated magnetic flux density of the magnetic core when the temperature thereof is increased to a predetermined value, and a protective circuit for stopping the ON/OFF operation of the s

Abstract: A control circuit is disclosed for use in a switching-type regulator which includes a source of unregulated DC voltage, a switching circuit for interrupting the unregulated DC voltage to produce an AC voltage having a duty cycle which is a function of the operation of the switching circuit, a converter for converting the AC voltage to a regulated DC voltage, a controllable pulse generator for supplying pulses of controllable duration to the switching circuit so as to determine the duty cycle of the AC voltage, a feedback circuit responsive to variations in the regulated DC voltage for controlling the duration of the generated pulses to maintain the regulated DC voltage at a desired level, and disabling circuit for selectively limiting the operation of the pulse generator. The control circuit is used to reset the disabling circuit to an initial state and to change gradually the duration of the pulses which are generated by the pulse generator when the regulator first is turned ON.

Abstract: In a power supply circuit having a circuit for supplying an input DC voltage through a switching element to a winding, a circuit for producing a desired DC voltage by switching the switching element with a pulse and a circuit for detecting the level of the DC output voltage, and changing the duty ratio of the pulse with the detected output so as to stabilize the DC output voltage at a constant value. There is provided a circuit which limits the maximum value of the duty ratio of the pulse.