Patent ID: 8754590
Filing Date: 2014-06-17
Classification: H02M,H05B,Y02B

Abstract:
1. A power supply device comprising: a rectifying circuit which rectifies ac power and supplies power to a first node on the basis of a second node; a switch element provided between the first node and a third node; a current detection resistor provided between the third node and a fourth node; an inductor provided between the fourth node and a fifth node; a diode provided between the second node and the third node with the second node side as an anode; an output capacitor provided between the fifth node and the second node; a control circuit which operates with the fourth node as a ground power supply voltage and controls on/off of the switch element, based on a first voltage developed at the third node; and a resistance dividing circuit which performs voltage division between the first node and the fourth node to generate a second voltage, wherein the control circuit includes: a multiplication circuit which multiplies a feedback signal from a load circuit supplied with a power supply voltage by the output capacitor and the second voltage by each other, a square circuit which performs a square arithmetic operation on an output voltage of the multiplication circuit, a first comparator circuit which detects that the first voltage has reached an output voltage of the square circuit, and a second comparator circuit which detects that the first voltage has reached a zero level, wherein the switch element is driven on in response to a detection signal outputted from the second comparator circuit, and the switch element is driven off in response to a detection signal outputted from the first comparator circuit.