What is Holding Current?
Holding current in a Silicon Controlled Rectifier (SCR), also known as a thyristor, is an important parameter that determines the lowest current necessary to keep the device conducting.
Below this threshold, the SCR will switch off and stop conducting.
This is the minimum anode current required for the SCR to remain in the ON state. If the current goes below this threshold, the SCR will stop conducting & enter the OFF state.
Ex: If the holding current is set to 5 mA, the anode current must fall below that number for the SCR to switch off.
Relationship to Latching Current
The holding current differs from another important metric known as the Latching Current (IL)
What is Latching Current?
This is the minimum current needed to turn on the SCR. When the SCR is turned on and surpasses this current, it will continue to conduct even after the gate current is removed.
Differences Between Holding and Latching Current
Holding Current vs Latching Current
| Parameters | Holding Current | Latching Current |
|---|---|---|
| Definition | Minimum current required to sustain the ON state. | Minimum current to Turn ON. |
| Relation | Always less than the latching current. | Always greater than holding current. |
| Function | Related to turn-off process. | Related to the turn-on process. |
| Typical Values | Generally lower than Latching Current. | Typically two to three times Holding Current. |
Operational Significance
Understanding holding current is essential when constructing circuits with SCRs. If an application requires the SCR to be shut off at particular periods, the anode current must be able to drop below the holding current. This property enables fine control over power supply in a variety of applications, including motor control, light dimming, & power regulation systems.
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