Variable timing switching system and method

Abstract

A low-EMI switched circuit comprises two or more switches, wherein impedance transitions of the switches are overlapped and the overlap is varied using variable switch timing based on an output power level of the switched circuit. The variable timing results in a variable impedance overlap between the switches. In one example, when one switch turns off (begins a low to high impedance transition) and a second switch turns on (begins a high to low impedance transition), a greater timing delay in beginning the second switch's transition results in a higher switch impedance overlap than a shorter delay does. If the variable timing is based on output power of the switched circuit, the variable delay can operate to reduce fly-back voltages at high power output levels and reduce shoot-through current at lower power levels, reducing EMI and quiescent current of the switched circuit.