STMicroelectronics has implemented a simple and innovative ac-dc front-end circuit which enables the designer to perform inrush current limitation in any converter that has an input rectifier bridge topology.
The STEVAL-SCR002V1 is based on a control circuit made of one Z0110MN surface-mount triac and two STTH110A diodes. Two 800 V TN1605H-8T silicon-controlled rectifiers (SCRs) are used to bypass an inrush resistor.
The evaluation board provides a compact and non-insulated high-voltage driver for a mains SCR. The drive circuit synchronizes the SCR gate signals with the ac line polarity, and powers the SCR gate directly from the mains. This operation does not generate reverse losses in the SCR.
Compared to electromechanical alternatives, this solid-state solution provides higher reliability, longer service lifetime, lower EMI, and faster response. This ST circuit is also compatible with inrush current limitation performed either in the NTC/PTC bypass mode or in microcontroller phase-control mode.
The STEVAL-SCR002V1 may be powered by an uninsulated power supply, or directly controlled by an MCU. It is suitable for applications with an rms current up to 4.3 A at 60°C, and is compatible with ac-dc converters with or without PFC operating in continuous conduction, critical conduction or discontinuous conduction modes.