A High Voltage Level Shifter for Automotive Buck Converter with a Fast Transient Response

This paper proposes a high voltage level shifter circuit for a buck converter suitable for an automotive application operating with an input supply range of 4-36 V. There is an underlying trade-off between the speed and the power in such level shifter circuits. The conventional high voltage level shifter circuit has a limited speed of operation, large asymmetric propagation delays and a high switching power loss due to a large crowbar current. In the proposed circuit, these limitations are eliminated by strengthening the pull up path during transients. Combining the cross-coupled latching inverters with the assisting pull up transistors, the high voltage stress during transients is also avoided at the internal nodes. The proposed level shifter circuit shows a very fast response with a typical delay of 2 ns making it suitable for a high voltage, high switching frequency application. With a difference of < 2 ns between the rising edge and the falling edge delays, the proposed level shifter minimizes the asymmetry in the responses to a greater extent. Additionally, it consumes nearly zero static power. The dynamic power consumption varies from $122.7 ~\mu \mathrm{W} /$MHz to 1.1 mW/MHz over an input supply range of 4 to 36 V. The circuit is designed in a $0.18~ \mu \mathrm{m}$ high voltage BCD process.