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

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 highvoltage 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 m BCD 1P4M process. The total chip area is 2.50 x 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.