Patent ID: 7612544

Claim:
A controller for a power conversion circuit which includes an inductor having its first terminal coupled to a first power voltage V 1 and its second terminal switched so that it alternately connects to a second, higher, power voltage V 2 or to a common terminal of the two power voltages, said controller comprising: a sawtooth voltage generator which produces a ramp voltage V ramp having a period T and an amplitude which may be varied in response to a first control voltage Vx; and a voltage comparator arranged to compare V ramp to a second control voltage Vy, the output of the comparator arranged to control the switching of said second inductor terminal so as to divide period T into a first interval t 1 during which said second terminal is connected to said common terminal and a second interval t 2 during which said second terminal is connected to V 2 ; such that when said Vy is maintained in a fixed proportion to V 1 , V 2 will be driven so as to be in the same proportion to Vx, independently of changes in V 1 , and alternatively when Vx is maintained in a fixed proportion to V 2 , V 1 will be driven to be in the same proportion to Vy, independently of changes in V 2 .