A latching current is the minimal current required to keep a component conducting or latched in power electronics.
This perspective is frequently connected with semiconductor devices such as thyristors, notably silicon-controlled rectifiers (SCRs), or other related devices.
Thyristors are semiconductor devices that may regulate the flow of electricity.
They continue in the conducting condition after being triggered into conduction until the current across them falls below a specified threshold or an external signal is utilized to turn them off.
The latching current is important since it represents the minimal current required to keep the thyristor conducting once it has been triggered.
If the current goes below that level, the thyristor will switch off and will require an external trigger (or) pulse to turn back on.
- The latching current is the least amount of anode current required to keep the thyristor in the ON state instantly.
- When a thyristor is turned ON, the gate signal is disconnected.
- This current is associated with the ON process.
- The value of this current is approximately two to three times that of holding current. The value of holding current and latching current is steady.
- As a result, it is not affected by the amplitude of the gate current.
- Considering the latching current is important in the design & analysis of thyristor circuits, as it helps assure the circuit’s stability and reliability.
- Engineers must take latching current requirements into account when designing control circuits that can reliably keep the thyristor in the conducting state across a wide range of operating conditions.
- The minimum current is the SCR Latching current in forwarding bias that anode current must achieve in order to remain in forwarding conduction mode even after gate current is detached.
- If the anode current is less than this number, the SCR will not continue to operate in the forward direction if the gate current is disconnected.
- When the anode current exceeds the latching current, the gate terminal loses power and may become detached. Subsequently the SCR will proceed with its work.
Triggering: A gate current is fed to the gate terminal to turn on an SCR. This gate current allows the SCR to flip from the off to the ON state, enabling current to flow from anode to cathode.
Latching: When the SCR has been activated and entered ON state, it remains in the conducting state even after gate current is removed. This is referred to as latching. The latching current is the minimal current that has to continue to flowing through the device to maintain it latched in the on state.
Holding Current: Along with the latching current, another significant component is the holding current. The holding current is the minimal current that’s necessary to maintain the latched state. If the current across the SCR drops under the holding current, it will turn OFF & return to the OFF state.
It’s like turning on a non-stop tap. This property enables thyristors to be employed in latching circuits, in which a high voltage signals on the Gate is utilized to latch on the supply of current through the device.