Patent ID: 7064966

Claim:
A switching dc power supply capable of operation in either normal load mode or light load mode depending upon the power requirement of a load, the dc power supply comprising: (a) dc input means for providing a dc input voltage; (b) inductance means connected to the dc input means; (c) a voltage regulator switch connected to the dc input means via the inductance means and adapted to be turned on and off for controlled application of the dc input voltage to the inductance means; (d) dc output means to be connected to a load; (e) a rectifying and smoothing circuit connected between the inductance means and the dc output means for providing a dc output voltage to be applied to the load; (f) feedback circuit means for providing a feedback signal indicative of the dc output voltage of the rectifying and smoothing circuit; (g) a switch control pulse generator circuit connected to the voltage regulator switch for applying switch control pulses thereto in order to controllably drive the voltage regulator switch; (h) a mode selector circuit connected to the feedback circuit means for generating a mode select signal, the mode select signal having a first state for permitting the switch control pulse generator circuit to drive the voltage regulator switch, and a second state for preventing the switch control pulse generator circuit from driving the voltage regulator switch; (i) a conduction terminator circuit connected between the feedback circuit means and the switch control pulse generator circuit for applying conduction terminator pulses to the latter in order to cause the switch control pulse generator circuit to terminate conduction through the voltage regulator switch as dictated by the feedback signal; and (j) a conduction initiator circuit connected to the switch control pulse generator circuit for applying conduction initiator pulses thereto in order to cause the switch control pulse generator circuit to initiate conduction through the voltage regulator switch upon lapse of a preassigned length of time following the termination of each conducting period of the voltage regulator switch, the conduction initiator circuit being connected to the mode selector circuit in order to be thereby prevented from applying the conduction initiator pulses to the switch control pulse generator circuit when the mode select signal is in the second state, and to resume application of the conduction initiator pulses to the switch control pulse generator circuit upon lapse of the preassigned length of time following the end of the second state of the mode select signal.