Patent ID: 8305065
Filing Date: 2012-11-06
Classification: H02M,Y02B

Abstract:
1. In a power supply apparatus of a back type direct current to direct current (DC-to-DC) converter driven by a first-order feedback control system, said power supply apparatus comprising: a power system output filter, including an inductor (L) and a capacitor (C); first and second capacitor-resistor (CR) smoothing filters provided at both ends of the inductor (L) of said power system output filter in a parallel manner to each other; a pair of power semiconductor switching elements configured to supply output power to said power system output filter; a driving unit configured to drive said pair of power semiconductor switching elements; a pulse-width modulation (PWM) oscillator configured to perform a pulse-width modulation so as to supply a drive signal to said driving unit; an error amplifier configured to supply an error signal between an output from said first CR smoothing filter and a new reference voltage to said PWM oscillator; a new reference voltage generating circuit arranged by a differential amplifier configured to produce said new reference voltage, an adder, and a reference voltage; a transient variation detecting circuit configured to judge a small/large relationship among an output of said second CR smoothing filter, an upper limit threshold, and a lower limit threshold; a selector configured to output a PWM pulse having a desirable duty ratio to said driving unit in response to a load condition based upon the output information of said transient variation detecting circuit; an output voltage detection circuit configured to detect information which is later employed in order to judge a soft-start operation period and a steady operation period; a light load processing unit configured to be operated in such a manner that reduces power consumption and improves power efficiency of the power supply apparatus at a light load, as follows: a comparator configured to compare an output voltage of said differential amplifier with a light load setting voltage; a D-type flip-flop configured to produce an output signal which defines an output state of said comparator, based upon an output pulse newly provided in said output voltage detection circuit and falling edge timing of an output pulse from said PWM oscillator, so as to turn both OFF said pair of power semiconductor switching elements and said PWM oscillator; and an RS-type flip-flop configured to generate a pulse obtained by that said RS-type flip-flop is set by a PWM pulse having a duty ratio of 100% generated when said transient variation detecting circuit detects an abrupt load change, and also, said RS-type flip-flop is configured to reset in response to rising edge timing of an output pulse which is newly provided in said output voltage detection circuit so as to turn ON only said upper-sided power semiconductor switching element within said pair of power semiconductor switching elements.