Patent ID: 7468896
Filing Date: 2008-12-23
Classification: H02M,Y02B

Abstract:
1. A drive circuit for providing a drive signal to a switch in a switching converter, the switching converter having output terminals for providing an output voltage, and in which a feedback signal that corresponds to the output voltage is available, the drive circuit comprising: a capacitive storage circuit; a charging/discharging circuit connected to a first terminal of the capacitive storage circuit, the charging/discharging circuit configured to receive as inputs at least one load signal, the at least one load signal adopting at least a first and second state, the charging/discharging circuit further configured to charge and discharge the capacitive storage circuit cyclically in the first state between a first limit value and a second limit value, and to only charge the capacitive storage circuit in the second state; a load signal generation circuit configured to generate the at least one load signal responsive to the feedback signal, wherein the at least one load signal indicates a normal load condition or an overload/open feedback loop condition of the switching converter; at least a first operating mode circuit coupled to receive a charge state signal that corresponds to a charge state of the capacitive storage circuit, and to receive the at least one load signal, the first operating mode circuit configured to set a normal operating state or an exceptional operating state of the drive circuit in accordance with the at least one load signal and the charge state signal, wherein the operating mode circuit sets the exceptional state only if the charge state signal reaches a reference value that is higher than the first limit value, and if the at least one load signal indicates the overload/open feedback loop condition; an oscillator circuit operably coupled to receive the charge state signal, and configured to provide an oscillating signal having a frequency that varies according to the charge state signal; and a drive signal generation circuit configured to generate the drive signal based at least in part on the oscillating signal and the feedback signal.