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Application Note : DCDC Converters (Switching Regulators)

Overcurrent Protection

There are three types of overcurrent protections that are used in Ricoh’s DCDC converters: Latch type protection, Reset type protection, or Hiccup type protection, and Foldback type protection.

Overcurrent Protection

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 CE 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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