AN2383 datasheet(13/39 Pages) STMICROELECTRONICS

13 / 39 page

AN2383

Schematic

Doc ID 12433 Rev 3

13/39

ALARM has to be sent to the MCU as fast as possible, therefore this input has been

configured as an external interrupt. As soon as an alarm occurs, the MCU immediately

starts the alarm management routine so it can rapidly take the necessary actions.

DATA, SCLK and /LE are used to drive the 8-bit constant current LED sink driver present in

the user interface board. In this way, the MCU can address a 7-segment display using only 3

pins.

PWM0 generates a PWM signal with a 50% duty cycle. It is sent directly to the IGBT driver.

Depending on the working level (and therefore on the power required), the frequency of the

square waveform varies in a range between 19 and 60 kHz.

RELAY and FAN drive the safety relay in the mains circuitry and the fan, respectively. The

fan is used to cool the heatsink next to the IGBTs and the power diode bridge.

The last pin, 50 Hz, is configured as an external interrupt. It is synchronized with the voltage

mains and, every 10 ms, it captures the moment when the AC voltage crosses zero.

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