STEVAL-L6986IV1 38 V, 5 W synchronous iso-buck converter evaluation board with dual isolated output based on the L6986I

The STEVAL-L6986IV1 evaluation board is based on L6986I 38 V, 5 W synchronous step-down switching regulator designed for isolated buck topology.

The primary output voltage can be accurately adjusted, whereas the isolated secondary output is generated by using a transformer. No optocoupler is required.

The primary sink capability (typ. 1.9 A) allows proper energy transfer to the secondary side as well as a tracked soft-start of the secondary output. The control loop is based on a peak current mode architecture and the device operates in forced PWM.

The 300 ns blanking time filters oscillations generated by the transformer leakage inductance, making the solution more robust. Pulse by pulse current sensing on both power elements implements an effective constant current protection on the primary side. Thanks to the primary reverse current limit, the secondary output is protected against short-circuit.

The secondary voltage is stabilized over current by using a power transistor and a shunt voltage reference (TL431AIL3T).

The STEVAL-L6986IV1 evaluation board generates two isolated voltages (positive around 18 V and negative between 4 and 5 V), particularly suitable for supplying the IGBT/SiC MOSFET gate driver for multiple applications. A simple by-pass enables the supply of a single isolated voltage.