A 95.2% Efficiency DC–DC Boost Converter Using Peak Current Fast Feedback Control (PFFC) for Improved Load Transient Response

The load transient response and unity gain bandwidth of DC-DC boost converters are primarily restricted by the presence of a right half plane zero (RHPZ). In this paper, a control scheme termed peak current fast feedback control (PFFC) is proposed to improve the load transient response without the need for additional power switches or passive components. In the proposed PFFC method, the closed loop output impedance (<inline-formula> <tex-math notation="LaTeX">$Z_{OCL})$</tex-math> </inline-formula> is improved by reducing the DC value and by increasing the bandwidth of <inline-formula> <tex-math notation="LaTeX">$Z_{OCL}$</tex-math> </inline-formula> as compared to conventional peak current mode control (CPCM), thus improving the steady state and transient performance. The fast feedback (FFB) path is implemented within the error amplifier (EA) with an increase of only 2% in the active area as compared to CPCM. The boost converter is designed for <inline-formula> <tex-math notation="LaTeX">$V_{OUT}$</tex-math> </inline-formula> <inline-formula> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 5V, <inline-formula> <tex-math notation="LaTeX">$V_{IN}$</tex-math> </inline-formula> <inline-formula> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 2.5V-4.4V and <inline-formula> <tex-math notation="LaTeX">$I_{LOAD}$</tex-math> </inline-formula> <inline-formula> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 10mA-1A operating at a fixed frequency of 2MHz. Measurement results show that with PFFC enabled, the settling time reduces by <inline-formula> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula>2.6<inline-formula> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> and the undershoot reduces by 62% to 12<inline-formula> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula>s and 41mV respectively when compared to CPCM for 10mA to 1A load step at 2A/<inline-formula> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula>s. The converter achieves a peak efficiency of 95.2% at 0.5W output power with <inline-formula> <tex-math notation="LaTeX">$V_{IN}$</tex-math> </inline-formula> <inline-formula> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 4.4V and load regulation of 9mV/A at <inline-formula> <tex-math notation="LaTeX">$V_{IN}$</tex-math> </inline-formula> <inline-formula> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 2.5V.