Patent ID: 8564260

Claim:
A circuit that converts an input voltage to an output voltage, the circuit comprising: a first stage voltage converter that receives the input voltage and converts the input voltage, the first stage voltage converter comprising a first rail at a high intermediate voltage and a second rail at a low intermediate voltage; the low intermediate voltage above ground; the first stage voltage converter comprising a first inductor; a first capacitor at the high intermediate voltage; a second capacitor at the low intermediate voltage; a first transistor to couple the first inductor to the first capacitor when switched on; a second transistor to couple the first inductor to the second capacitor when switched on; a switch controller to control the duty cycles of the first and second transistors to control a voltage difference between the high intermediate voltage and the low intermediate voltage; and a second stage voltage converter that receives the high intermediate voltage and the low intermediate voltage and produces the output voltage; the second stage voltage converter comprising a second inductor; a third transistor to provide the high intermediate voltage to the second inductor when switched on; a fourth transistor to provide the low intermediate voltage to the second inductor when switched on; and a control circuit to control the duty cycles of the third and fourth transistors to hold the output voltage within a desired range.