RFUnderstanding SCR Holding Current: Maintaining Conduction
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The holding current in a Silicon Controlled Rectifier (SCR) is a critical parameter that dictates its behavior. It’s the minimum amount of current that must flow through the SCR to keep it in the “ON” state after it’s been triggered into conduction. Think of it as the lifeline that keeps the SCR working once it’s started.
How Holding Current Works
Once an SCR is turned on – usually by applying a pulse to its gate terminal – it latches into the conductive state. It will continue to conduct electricity as long as the forward current (the current flowing from anode to cathode) remains above a specific level. This level is the holding current.
If the forward current dips below this holding current value, the SCR will automatically turn off. And once it turns off, a new gate trigger pulse will be needed to switch it back on again.
Why Holding Current Matters
The holding current is a very important factor in designing circuits that use SCRs. SCR datasheets always specify the holding current, usually in amperes. You absolutely need to take this into account when designing your circuit.
The load current in your circuit must remain above the SCR’s holding current to ensure it remains in the conducting state. If the current drops below the holding current the SCR will stop working until it gets another pulse.
This is especially relevant in applications like motor control, where continuous conduction through the SCR is vital for the system’s proper operation. Imagine a motor suddenly stopping because the SCR momentarily turned off; that’s exactly what you want to avoid by understanding and managing the holding current.
