Patent ID: 6191959
Filing Date: 2001-02-20
Classification: H02M

Abstract:
A switched-mode power supply comprising:a series arrangement of an inductor (Lp) and a main current path of a switching element (S), the series arrangement being coupled to receive a DC input voltage (Vin),a rectifier element (D2) coupled to the inductor (Lp; Ls) for generating a DC output voltage (Vout),a feedback circuit (Fb) comprising an output for indicating whether a value of the DC output voltage (Vout) exceeds a predetermined value (Vp),a control circuit (Cc) having an output coupled to a control input of the switching element (S) for periodically switching said main current path on and off when the value of the DC output voltage (Vout) is below said predetermined value (Vp), and for keeping said main current path in a non-conductive state when the value of the DC output voltage (Vout) exceeds said predetermined value (Vp) to obtain a burst mode,a capacitor (C1), and a supply circuit (Sc) for generating a capacitor voltage (Vc) across the capacitor (C1) for supplying power to the control circuit (Cc), characterized in that the output of the feedback circuit (Fb) is coupled to the capacitor (C1) for influencing the capacitor voltage (Vc) in dependence on the value of the DC output voltage (Vout), the control circuit (Cc) further receiving the capacitor voltage (Vc) for periodically switching said main current path on and off when the capacitor voltage (Vc) is in a first range indicating that the DC output voltage (Vout) is lower than the predetermined value (Vp), and for keeping said main current path in a non-conductive state when said capacitor voltage (Vc) is in a second range indicating that the DC output voltage (Vout) exceeds the predetermined value (Vp), said first and second range being non-overlapping.