The first step to understanding POWER SUPPLIES ICs! | ④ Protection functions to protect POWER SUPPLIES ICs from failure | NEXTY Electronics, an electronic components and semiconductor trading company

Most POWER SUPPLIES ICs have built-in protection circuits to ensure safe use and to prevent damage.
Here we will explain the protection circuits that are often included in POWER SUPPLIES ICs.

Thermal Shutdown

Thermal shutdown is a function that prevents IC destruction, characteristic degradation, and malfunction when the IC's Tj (junction temperature) rises to around the maximum rated value.
When Tj rises to around the maximum rated value, the thermal shutdown function operates, stopping SWITCHES operation and turning the output off.
In addition to thermal shutdown, there are two types of protection functions: latch type and reset (automatic recovery) type, and these differ in how they behave after shutdown.

Reset Type

After shutdown, when the temperature drops to the set value, the IC automatically resumes operation and starts SWITCHES.
If the overload state continues after restart, Tj will rise again, causing thermal shutdown and automatic recovery to occur repeatedly.

Latch Type

After shutdown, the IC will remain shut down even if the temperature drops.
To operate the IC again, you must turn POWER SUPPLIES off and on again.

UVLO (Under Voltage Lock Out)

This refers to a function to prevent undervoltage lockout, commonly known as UVLO.
This function turns off the IC to prevent malfunction when the input voltage is outside the IC's input voltage range.
An input voltage outside the operating range may cause the circuit to behave in an unexpected manner, and this function prevents such failures in advance.

OCP (Over Current Protection)

OCP is also known as overcurrent protection.
If the output current becomes larger than expected, it may cause malfunction or degradation, or damage the IC itself or other connected circuits.
When the OCP is activated, it limits the current to a certain value and protects the device from further current flow.
The type of OCP varies depending on the device, and there are characteristics such as drooping and foldback.

droop protection

The output current Iout maintains the limit value and the output voltage drops.

Folding protection

After the output current Iout reaches the limit value, both the output voltage and output current decrease.

Combined droop and foldback protection

The OCP characteristic transitions from a drooping characteristic to a fold-back characteristic.

Power Good function (PGOOD)

The power good function is a function that indicates (outputs a flag) that the output voltage of POWER SUPPLIES IC is at the specified value.
It can monitor whether POWER SUPPLIES supply to the downstream system has started up without any problems and whether the output voltage is at an abnormal value even after stable operation.
This function is also used when you want to create a sequence that starts up POWER SUPPLIES ICs in a specific order.