60-V Non-Inverting Four-Mode Buck-Boost Converter with Bootstrap Sharing for Non-Switching Power Transistors

Abstract

This paper presents a non-inverting buck-boost converter for high-voltage automotive applications. The converter includes a newly proposed controller chip and four off-chip NMOS power transistors with two bootstrap capacitors. Conventional non-inverting buck-boost converters have two operation modes: the buck and boost modes. This study implements four operation modes for smooth transition between these modes. In converters with four operation modes, non-switching high-side power transistors require continuous high gate-driving voltages without the bootstrapping operation. The designed non-inverting buck-boost converter drives non-switching high-side NMOS transistors through the proposed bootstrap-sharing technique. A new current sensing technique is also proposed that works reliably under high-voltage operating conditions. This current sensing enables the converter's modulation scheme of the current programmed control. The proposed converter was fabricated using a 0.18~\mu \text{m} BCD 1P4M process. The total chip area is 2.50\times 2.50\,\,mm^{2} , including the bonding pads. The output voltage range is from 1.05 to 60 V, with a typical input automotive battery voltage of 14 V. Because the automotive battery exhibit a wide voltage fluctuation, the input voltage range is designed from 7 to 60 V. Its switching frequency range is from 600 to 1000 kHz and the maximum power efficiency is 96.1% at a load current of 1.5 A.