The simple and innovative AC/DC front end circuit limits inrush current

     STMicroelectronics' STEVAL-SCR002V1 introduces a simple and innovative AC/DC front-end circuit that limits inrush current in any converter with an input rectifier bridge topology. This discrete control circuit consisting of a Z0110MN SMD bidirectional SCR and two STTH110A diodes provides a compact and non-insulated high voltage driver for the mains SCR.

     The driver circuit synchronizes the SCR gate signal with the AC line polarity and feeds the SCR gate directly from the mains. This operation does not generate reverse losses in the SCR. Compared to electromechanical solutions, this STEVAL-SCR002V1 solid-state solution has high reliability, long service life, reduced electromagnetic interference and faster response.

     The solution is compatible with inrush current limits performed in NTC/PTC bypass mode or MCU phase control mode. The enable control pin of the SCR driver is referenced by GND_DC, so it can use a non-insulated power supply or be directly controlled by the MCU. STEVAL-SCR002V1 provides five cables and is designed for easy plug and play testing on existing AC-DC converters. It is suitable for applications with a maximum RMS current of 4.3A (ambient temperature +60°C).