A planar 4.5-GHz DC-DC power converter

Abstract

In this paper, we present two dc-dc converters that operate at a microwave frequency. The first converter consists of a Class-E switched-mode microwave amplifier, which performs the dc-ac conversion, and two half-wave diode rectifier outputs. The Class-E MESFET amplifier has a maximum power-added efficiency of 86%, corresponding drain efficiency of 95%, and 120 mW of output power at 4.5 GHz. The diode rectifier has a maximum conversion efficiency of 98% and an overall efficiency of 83%. The second converter consists of a high-efficiency Class-E oscillator and a diode rectifier. The Class-E oscillator has a maximum efficiency of 57% and maximum output power of 725 mW. The dc-dc converter is planar and compact, with no magnetic components, and with a maximum overall dc-dc conversion efficiency of 64% for a dc input of 3 V, and the output voltage across a 87-load of 2.15 V.

High-Efficiency Harmonically Terminated Diode and Transistor Rectifiers

“…The applications of such power rectifiers include wireless power beaming [7], recycling power in highpower circuits [18], and ultra-fast switching integrated dc-dc converters with no magnetics [19].…”

“…The values of at which the transition between the conducting and nonconducting regions occurs are found to be (18) The dc and fundamental frequency values of the voltage and current waveforms can be found through a Fourier analysis using the transition points in (18). The first Fourier coefficient of gives the dc component of the voltage, which can be derived as (19) The fundamental frequency voltage is found from , where (20) and can be reduced to (21) Similarly, the dc component of the current waveform is found to be (22) The fundamental frequency current has and the coefficient can be shown to be equal to (23) The input power at the fundamental frequency is found from (24) Substituting (21) and (23) into the above results in (25) where is defined as (26) Solving for as a function of when is nonzero after some arithmetic results in two solutions, one of which is negative. The positive solution for the maximal current is (27) with .…”

“…Next, the dc voltage and current are evaluated using (19) and (22), respectively, to give V and mA. The fundamental frequency voltage and current Fourier coefficients are then calculated to be V and mA, respectively.…”

“…Additional applications where rectifier efficiency is important include microwave power recycling [18], and dc-dc converters with extremely high-frequency switching [19], [20]. In many of the reported microwave rectifiers, filtering of the harmonics at both the input and output has been investigated, e.g., [21] and [22], mainly to reduce re-radiated harmonic power.…”

Class-E rectifiers and power converters

“…Implementations at HF and VHF bands have become common, where solutions based on the class-Φ 2 inverter may be highlighted [5] for their high-efficiency and low-voltage stress performance. At microwave frequencies, a low-power 64% efficient 4.6-GHz planar converter combining a GaAs MESFET class-E PA and a Schottky diode rectifier was demonstrated as early as 1999 [6].…”