Isolated half-bridge gate driver with integrated high-side supply

Abstract

Half-bridge gate drivers have been widely used in a variety of applications, such as motor drives, power supplies, and plasma display panels. However, they are difficult to use because of the need for isolation and the need to provide isolated power supply for high-side gate drive. Here I will describe an isolated half-bridge gate driver with an integrated DC/DC converter providing an isolated high-side supply at 15V, all in a 16L SOIC package. Coreless micro-transformers are not only used for transmitting gate drive signals from input to isolated outputs, but also used for delivering power to the isolated high-side supply. The gate drive signals are encoded before they are sent to the signal transformers, and then decoded to reproduce the gate drive output signals. The power transformers are switched resonantly at 160MHz to achieve efficient energy transfer. Both the transformer switches and Schottky diodes used for high frequency rectification are implemented on chip. As much as 5kV isolation is achieved through 20μm thick polyimide layers sandwiched in between the primary coils and the secondary coils. Both gate drive outputs can provide 0.3A sinking and 0.1A sourcing up to 10Mbps. The converter for the high side supply is measured to deliver 15mA at 15V with 25% efficiency. An example application of the half-bridge gate drivers in an isolated AC-DC power supply will be discussed.