General Converter Considerations for Utility Applications It is often practical to design a power conversion system utilizing two converter stages based on the following considerations: 1.Conversion from a utility source (60 hz AC) to DC by means of rectifiers is inexpensive and well understood. 2.Many efficient approaches have been developed for generating common output power formats from a DC source: DC output (DC/DC converter) Low frequency AC < 100 kHz (Inverters) High Frequency AC > 100 Khz (HF Oscillators) Utility LoadAC - DCDC - ? Control Linked by DC voltage: “Voltage Link”

+ V IN - L I + v A (t) - Switching Power Pole Switching Function: q(t) = 1 for NT < t < (N + d A )T 0 otherwise 0 < d A <1 (“Duty cycle”) dATdAT 3T2TT V IN Switching Frequency: f = 1/T v A (t) Switch UP when q(t) = 1 Switch DOWN when q(t) = 0 t V A = d A V IN q(t) 1

+ V IN - L I OUT + v A (t) - + V OUT = V A - i L (t) i IN (t) “Buck” Converter Illustration of Power Pole Incorporation 3T2TT V IN t V OUT = V A = d A V IN dATdAT I OUT i IN (t) i L (t) v A (t) I IN = d A I OUT I IN V IN = I OUT V OUT

+ V IN - L I OUT i L (t) Practical Power Pole Implementation Transistor “ON” Transistor “OFF”