4A isolated half-bridge gate driver with 4.5V to 18V output drive voltage

Isolated half-bridge gate drivers are used in a variety of applications that range from motor drives to isolated power supplies. However, providing isolated, adequate and well-timed half-bridge gate drive signals in these applications presents its own set of challenges. This paper presents an isolated half-bridge gate driver which supports 4.5V to 18V gate drive voltages. The gate drive outputs can switch capacitive loads up to 2nF in 12ns with 4A peak currents, at frequencies up to 1MHz, with no constraints on duty-cycle variation. Coreless micro-transformers are used for transmitting gate drive signals from input to isolated outputs. The gate drive signals are encoded before they are sent to the transformers, and then decoded to reproduce the gate drive output signals. The optimized encoding/decoding scheme enables sub 40ns propagation delay and less than 1ns delay matching, which are designed to improve the performance and efficiency of AC-to-DC and DC-to-DC power supplies, solar-power inverters and motor-control designs. Up to 5kV isolation is achieved through 20μm polyimide layers sandwiched in between the primary coils and the secondary coils. Also with two independent isolation channels, the half-bridge gate driver provide 800V galvanic isolation between the drivers´ high-side and low-side outputs, which minimizes the potential for cross conduction and makes it ideal for providing reliable control over a wide range of bus voltages. An example application of the half-bridge gate drivers in a motor driver will also be discussed.