App note: A logic-level transient-voltage protected AC switch

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STMicroelectronics’ AC switch directly controlled by microcontroller. Link here (PDF)

Home appliances such as washing machines, refrigerators and dishwashers employ a lot of low power loads such as valves, door lock systems, dispensers or drain pumps. Since these loads are powered by the mains in ON / OFF mode, they were initially controlled by relays. Recently, relays have been replaced by triacs, due to their smaller size and lower driving energy. Nevertheless triacs don’t fulfill alone the new requirements that users now need and are used with others components.

Power switches must now be directly driven by a microcontroller unit (MCU) and must be robust to withstand the A.C. line transients so that systems may fall into line with electromagnetic compatibility (EMC) standards. ACSs (for Alternating Current Switches) have been designed with this goal mind, i.e. to offer logic level and more robust semiconductor devices.

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1 Comment

  1. It might not be an option when you’re designing a product down to the last $0.0001, but under normal circumstances I’d just toss in the first optotriac within reach then call it a day and head to the pub.

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