Patent ID: 6088251
Filing Date: 2000-07-11
Classification: H02M

Abstract:
A switching circuit, comprising:an input node, an output node, and a control node;a switch coupled to said input node and said output node, said switch having an on state in which it couples said input node to said output node and an off state in which it decouples said input node from said output node;means in the form of a control circuit for cycling said switch between the on state and the off state in a periodic series of cycles of variable switch duty ratio in order to produce a chopped signal at said output node from an input signal coupled to said input node;said control circuit including means for producing a feedback signal that has a level that is substantially linearly related to the time-integrated value of the switch duty ratio, wherein said switch duty ratio is integrated over more than one cycle;said control circuit including means for generating a ramp signal responsive to said feedback signal, the amplitude of said ramp signal varies as a function of time, such that the instantaneous absolute value of said ramp signal is increasing in time and the instantaneous absolute value of slope of said ramp signal is decreasing in time;said control circuit including means responsive to said ramp signal and a control signal coupled to said control node for resetting said ramp signal and for varying the switch duty ratio in order to maintain the average value of the switch duty ratio approximately linearly related to the average value of said control signal;whereby said switching circuit can be used as an element in a switching power supply or switching amplifier to provide substantially linear control of switch duty ratio at any average level of said chopped signal.