Abstract: A switching circuit for a switched power supply, and the like, which includes a field effect transistor as a power switch. The switching circuit includes a simple circuit for providing gate drive bias for the field effect transistor which forces it to share turn-off voltage with other field effect transistors connected in series with it. The switching circuit also includes a network for generating a negative gate bias for the field effect transistor to speed up switch-off of the transistor.

Abstract: A keep-alive circuit for a regulated switched-type power supply for forcing the power supply to generate power pulses under conditions where the apparent output voltage level is such as to cause the regulator circuit normally to reduce the power pulses effectively to zero. The keep-alive circuitry responds to the absence of the power pulses over a predetermined time interval to modify the regulating circuit so that the regulating circuit responds to a different output voltage level to force the power supply to generate a power pulse under the aforesaid conditions. The action is made cyclic and the power supply is thereby caused to generate a series of low frequency power pulses indicating that it is still alive.

Abstract: A unity power factor power supply which includes a boost converter connected to the alternating current line which is controlled to draw sinusoidal current from the line by operating as a current regulator having a current reference control signal which tracks the line voltage waveform, thereby to minimize the required input current for a given power output.

Abstract: A transformer isolated switched power supply of the forward converter type in which a small bias winding is provided on the transformer so that both sides of the operating area of the B/H curve of the transformer core may be used for increased efficiency.

Abstract: An over-current sensing circuit for use with a switching-type power supply for achieving fold-back, which senses not only the load current drawn from the power supply, but also the voltage at the load and the voltage across the power supply potentiometer which is used to set the output voltage. The sensing circuit thereby serves to maintain the current limit point at which fold-back occurs virtually constant in the presence of adjustments of the output voltage of the power supply and regardless of the resistance of the bus which connects the power supply to the load.