Digital power controllers offer simple configuration, ease of use

May 19, 2015 //By Graham Prophet
STMicroelectronics' STNRG ICs build on ST’s high-resolution State Machine Event Driven technology; the digital-controller family helps designers maximise the advantages of digital power conversion, including high efficiency under all load conditions, enhanced safety, diagnostics, and network connectivity.

Rugged enough for high-end industrial applications as well as outdoor equipment such as solar-power converters, EV charging stations, and industrial switched-mode power supplies (SMPS), the STNRG ICs contain ST’s State Machine Event Driven (SMED) high-resolution pulse-width modulation (PWM) generator, in combination with an STM8-based supervisory core. The devices integrate 32 kB EEPROM, 6 kB RAM, an ADC, op-amp, I²C port, and GPIOs.

Configuring the SMED requires no specialist software competencies, unlike a DSP or microcontroller-based approach, ST asserts. The SMED can be triggered from the internal timer or an external event such as peak current, over current, or zero crossing. This allows a peak-current detecting buck converter, with constant off time set by the timer, to operate without intervention by the core processor. A simple P-I (proportional-integral) loop executed in the core sets the peak-current value for output regulation.

The STNRG family comprises the STNRG288A with four SMED-controlled outputs, the STNRG328A with five SMEDs, and the STNRG388A with six SMEDs. Designers have the option to connect two SMED cells together to generate dual gate-drive signals with inserted dead time for half-bridge configurations. ST’s SMED is already in use as a high-performing solution for digital control in STLUX ICs for LED lighting.

All devices are in production now, priced from $2.20 (1000) for the STNRG388A in TSSOP38 package.