Patent ID: 8957655
Filing Date: 2015-02-17
Classification: G05F,H02J,H02M

Abstract:
1. A hold-up circuit coupled to a first node to receive an input voltage and to provide a hold-up voltage, the hold-up circuit comprising: an inductor coupled between the first node and a second node, the input voltage being provided to the first node; a constant on-time buck-boost control circuit configured to drive a high-side power switch and a low-side power switch to operate in a buck mode and a boost mode of operation, the low-side switch having a first current handling terminal coupled to the second node and a second current handling terminal coupled to a ground potential, the high-side switch having a first current handling terminal coupled to the second node and a second current handling terminal; and an energy storage capacitor coupled between the second current handling terminal of the high-side switch and the ground potential, wherein in response to the input voltage being greater than a predetermined threshold, the buck-boost control circuit is configured in the boost mode to drive the low-side power switch with constant on-time pulses and to charge the energy storage capacitor through the high-side power switch; and in response to the input voltage being less than the predetermined threshold, the buck-boost control circuit is configured in the buck mode to drive the high-side power switch with constant on-time pulses and to drive the low-side power switch under synchronous operation to supply the energy stored on the energy storage capacitor to the inductor to provide the hold-up voltage to the first node.