Abstract: In a power supply having transformer coupling for regulation of voltage by a pulsing of primary current, a control circuit integrates the output voltage to obtain a measure of flux and primary current. A comparator monitors the integrated voltage to terminate a pulse of primary current prior to saturation of a core of the transformer. This insures linear operation and efficient transfer of energy from the primary to the secondary windings of the transformer. A sensor of secondary current initiates a new pulse of primary current when the secondary current has decayed to a fractional value of the peak secondary current.

Abstract: A transformerless drive circuit for operation of a switch mode regulator includes a turn-on circuit and a turn-off circuit coupled to a control terminal of the switch, respectively, for inducing a state of conduction in the switch and for terminating the state of conduction. The switch is, in the preferred embodiment, a P-channel DMOS field-effect transistor (FET) with a source electrode connected to the positive voltage terminal of a power supply, and with the drain terminal connected to load circuitry of the regulator. The gate electrode serves as the control terminal. The regulator includes a sensor of output voltage and circuitry for providing a pulse-width modulated control signal for designating the average amount of current to be passed by the switch. The turn-on circuit and the turn-off circuit share a common diode which operates alternately for conduction or turn-off.

Abstract: The invention includes a first switching transistor which is actuated by a logic signal. This switching transistor is disposed in a current path from the base of the power transistor. When this switch is actuated, the invention provides a large steady state base drive current superimposed with a base current peaking pulse from a current generator. The invention also includes a second switch which applies a reverse potential to the base of the switching transistor for fast turnoff. The specific embodiments disclose circuitry for regulating forward base drive current to minimize line voltage variations and component tolerances. An improved bipolar power transistor base drive circuit for switching regulator and DC to DC converter power supplies is disclosed.

Abstract: A circuit is disclosed which provides overcurrent protection for switching regulator power supplies with soft start and soft turn OFF features. The invention includes first means for sensing the current through the switching transistor of the regulator and second means for providing a voltage signal to the switching transistor deactivation circuitry whenever the current through the switching transistor exceeds a predetermined threshold. In a specific embodiment, the current generator is provided by a transistor biased for nominal operation in its active mode. The means for sensing the current through the switching transistor is provided by a resistor the voltage drop across which provides the input voltage threshold to the bipolar transistor current generator. The current generated by the transistor causes a voltage to quickly develop across an RC network referenced to ground potential.