Linearized controller for switching power converter

A controller for a power conversion circuit which includes an inductor having its first terminal coupled to a first power voltage V1 and its second terminal switched so that it alternately connects to a second, higher, power voltage V2 or to a common terminal of the two power voltages, said controller comprising:

• a sawtooth voltage generator which produces a ramp voltage Vramp 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 Vramp 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 t1 during which said second terminal is connected to said common terminal and a second interval t2 during which said second terminal is connected to V2;
• such that when said Vy is maintained in a fixed proportion to V1, V2 will be driven so as to be in the same proportion to Vx, independently of changes in V1, and alternatively when Vx is maintained in a fixed proportion to V2, V1 will be driven to be in the same proportion to Vy, independently of changes in V2.