What is an over-current protection (OCP) for DC/DC converters?

DC/DC Switching RegulatorsProtection

There are four types of overcurrent protections that are used in Nisshinbo Micro Devices’ DC/DC converters: Pulse-by-pulse type, Latch type protection, Reset type protection, or Hiccup type protection, and Foldback type protection.

Pulse-by-pulse Type Protection

When the peak value of the switching current exceeds a certain value, the switching current is reduced by turning off the power MOSFET for one cycle (pulse). It operates in the same way in the next cycle (pulse) and limits the peak value of the switching current for each pulse.

Latch Type Protection

Latch type latches the power MOSFET to the OFF state during an excessive high load in case it persists for a specified time (the protection delay time). The circuit can be released by changing the IC into the standby mode and back to the active mode by the EN (CE, CONTROL) pin, or by turning the power off and back on. There are some products which an adjustable protection delay time by a capacitor connected to the DLY pin (DELAY pin).

• Reset Type Protection, or Hiccup Type Protection

  Reset type or Hiccup type controls the power MOSFET to the OFF state during an excessive high load in case it persists for a specified time (the protection delay time). The circuit is automatically released after removal of the excessive load and by triggering the soft start operation. The protection delay time is fixed within the IC.

  Foldback Type Protection

  Foldback type decreases the oscillator frequency when the output voltage decreases below the preset value. Therefore the minimum ON duty decreases and the inductor ripple current increases. As a result the output current decreases. The protection is automatically released after the excessive load is removed.

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