Power Supply Protection Circuits (OPP/OCP/OVP/UVP/SCP/OTP/NLO/SIP) for Custom-Built PCs

The protection circuits in a power supply unit are important features that protect the power supply itself and other computer parts.

These circuits help improve the overall safety and lifespan of a computer, so it is recommended to choose a power supply unit with protection circuits whenever possible.

If there are no protection circuits, there is a risk of parts malfunctioning or being damaged, or even a fire, when abnormal situations like overcurrent, overvoltage, short circuits, or overheating occur.

This article explains in detail the importance and types of protection circuits in power supply units.

Key Points of This Article

Protects against various abnormalities such as overload, overcurrent, overvoltage, short circuit, overtemperature, and surges.
Without protection functions, parts may fail or be damaged, and in the worst case, a fire may occur.
For those unfamiliar with electrical systems, protection circuits are recommended for peace of mind.
Protection circuits rarely activate, but they provide safety as a form of insurance!

This article also explains the basics of power supply unit standards and cables, as well as how to choose one from the perspectives of performance and compatibility.

Select PC parts and online stores to instantly generate an estimate, check compatibility, and calculate power requirements. You can save up to five different builds, making it easy to try out multiple configurations.

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About Power Supply Unit Protection Circuits

First, let’s review the basic knowledge about protection circuits in power supply units.

About Power Supply Unit Protection Circuits

The Need for Protection Circuits
Peace of Mind for Users
Long-Term Cost Savings
Check for Protection Circuits on the Product Specification Page

The Need for Protection Circuits

Protection circuits are essential for ensuring the safety and reliability of a power supply unit.

A power supply unit can experience abnormal conditions such as overcurrent, overvoltage, short circuits, or overheating.

If these abnormalities occur, the power supply unit itself or connected parts may malfunction or be damaged.

In the worst case, a fire could start from a part and lead to a serious accident.

Protection circuits detect these abnormalities and respond quickly to protect the power supply unit and other parts.

For example, an overcurrent protection circuit will cut off power if the current exceeds a set value, and an overtemperature protection circuit will stop operation if the temperature goes beyond a safe range.

This greatly reduces the risk of damage or fire to the power supply unit and parts.

Therefore, protection circuits are essential for improving the safety and reliability of a power supply unit and for using a computer for as long as possible.

That said, while it is definitely better to have protection circuits as a form of insurance, in reality, they rarely activate.

Having built several custom PCs and used computers for at least 8 hours a day for over 20 years, there has never been a time when the protection circuit was triggered.

If an abnormality is detected, the power supply unit will stop working and the computer will shut down, so it should be noticeable.

Therefore, protection circuits are there just in case, and the chances of them activating are quite low.

However, the losses can be significant if something does happen, so it is better to eliminate risks as much as possible by having protection circuits.

Peace of Mind for Users

Personally, electrical systems can be scary, and not only the power supply unit but also the connected parts can fail or be damaged.

In the worst case, a fire could break out and lead to a serious accident.

Working on a computer while worrying about these risks is not good for mental health, so to reduce such risks, a power supply unit with protection circuits is recommended.

Long-Term Cost Savings

Protection circuits in a power supply unit help prevent failures or damage when abnormalities like overload, overcurrent, or overheating occur.

Because of this, the frequency of repairs or replacements can be reduced, so even if a power supply unit with protection circuits costs a bit more, it leads to long-term cost savings.

Also, when protection circuits work properly, unexpected downtime for repairs can be reduced, helping maintain work efficiency.

Ken

It would be terrible if the computer broke while making documents or reports and repairs took two weeks!

Furthermore, having protection circuits increases the reliability of the power supply unit itself, allowing for stable power supply over a long period.

This extends the replacement cycle of the power supply unit and leads to long-term cost savings.

Check for Protection Circuits on the Product Specification Page

Building a custom PC can cost between 150,000 and 300,000 yen, so it is important to reduce the risks of failure or fire as much as possible.

For this reason, be sure to check the product specification page to see if protection circuits are included when choosing a power supply unit.

Protection circuits are especially reassuring when using expensive parts or handling important data.

A tool has been developed that allows users to estimate, check compatibility, and calculate power requirements just by selecting PC parts. It also lets users check the protection circuit specifications of power supply units, so be sure to use it.

Links to official product specification pages are also provided for quick checking.

Types and List of Power Supply Unit Protection Circuits

Power supply units are equipped with various types of protection circuits.

Let’s look at what each one protects against and how they work.

First, here is a table summarizing the overview and role of each protection circuit, followed by detailed explanations.

Protection Circuit	Overview	Role
Over Power Protection (OPP)	Stops operation if the power supply exceeds its maximum output.	Prevents overheating or failure of the power supply or parts.
Over Current Protection (OCP)	Cuts off the circuit if excessive current flows.	Protects parts from short circuits or overload risks.
Over Voltage Protection (OVP)	Cuts off power if the voltage exceeds the set limit.	Prevents damage to parts from overvoltage.
Under Voltage Protection (UVP)	Stops operation if voltage falls below a certain standard.	Prevents data loss or part failure from low voltage.
Short Circuit Protection (SCP)	Immediately cuts off power if a short circuit occurs.	Protects parts from sudden current increases due to shorts.
Over Temperature Protection (OTP)	Automatically stops operation if the power supply overheats.	Prevents damage to internal components and ensures safety.
No Load Operation Protection (NLO)	Operates safely even when no load is connected.	Prevents abnormal voltage/current and extends power supply life.
Surge/Inrush Current Protection (SIP)	Protects against sudden current changes or surge voltage.	Protects internal circuits and parts from inrush current or lightning surges.

Overload Protection (OPP)

Overload Protection (OPP: Over Power Protection) is a function that automatically cuts off power when the load exceeds the rated output of the power supply unit.

This protection circuit is usually monitored by circuits inside the power supply unit, and when overload is detected, it instantly cuts off power.

This prevents overheating or damage to the power supply unit and connected parts.

An overload state means that the load exceeds the maximum power the power supply unit can supply.

For example, if a power supply unit has a 500W capacity, a load exceeding 500W is considered overload.

When overload protection activates, the power supply unit automatically stops supplying power and will not restart until the overload is resolved.

Therefore, when choosing parts, it is important to check if the power supply unit’s capacity is appropriate for the configuration.

How to Calculate Power Supply Capacity and a tool that calculates power supply capacity just by selecting parts are also available, so please use them.

Overcurrent Protection (OCP)

Overcurrent Protection (OCP: Over Current Protection) is a function that automatically cuts off the circuit when the output current of the power supply unit exceeds the allowable current.

Overcurrent can occur due to short circuits or overload, and if left unchecked, the risk of equipment failure or fire increases.

For example, in the following cases:

When internal wiring or circuit boards are shorted
When parts like the motherboard or graphics card fail and demand abnormal current
Incorrect wiring or poor connector contact during part installation
When a faulty external device is connected
When a system abnormality causes higher than normal current demand
Incorrect overclocking settings

If a circuit board is shorted, resistance becomes almost zero, causing abnormally high current to flow.

There are many causes, but most occur when abnormal current is demanded due to failure or incorrect settings.

OCP is an important protection function to prevent these risks in advance.

Overvoltage Protection (OVP)

Overvoltage Protection (OVP: Over Voltage Protection) is a function that automatically cuts off power when the voltage supplied by the power supply unit exceeds a set upper limit.

This prevents connected parts and circuits from being damaged by overvoltage.

For example, in the following cases:

Internal failure of the power supply unit
Voltage fluctuations or unstable power supply from outside
Improper overclocking
Cheap power supply units

Cheap or poorly designed power supply units may have unstable voltage regulation or rapidly rising output voltage with load changes.

Therefore, unless there is a special sale, it is better to avoid power supply units that are unusually cheap compared to the market price.

OVP plays an important role in protecting custom PCs from these risks.

Undervoltage Protection (UVP)

Undervoltage Protection (UVP: Under Voltage Protection) is a function that automatically cuts off power when the voltage supplied by the power supply unit falls below a certain standard.

This protection circuit is designed to prevent unstable voltage from negatively affecting computer operation.

If low voltage continues, electronic components may not work properly, leading to data loss or hardware failure.

For example, this can happen if the power supply unit can no longer supply normal voltage due to aging, or if the output capacity does not meet the system’s requirements.

UVP reduces these risks and ensures system stability and reliability.

Short Circuit Protection (SCP)

Short Circuit Protection (SCP: Short Circuit Protection) is a function that protects the power supply unit when a short circuit is detected.

When a short circuit occurs, current increases rapidly, increasing the risk of damage or fire, but the protection function protects the power supply unit and connected parts from these dangers.

Short circuits can occur in the following situations:

Wiring mistakes or poor contact during assembly
Failure of internal components such as capacitors, transistors, or IC chips
Foreign objects like metal pieces or screws falling onto the circuit board
Moisture or liquid getting on the circuit board
Insulation deteriorating due to aging

Wiring mistakes, poor contact, or spilling drinks are all possibilities.

SCP detects such situations and instantly cuts off power to prevent damage.

Overtemperature Protection (OTP)

Overtemperature Protection (OTP: Over Temperature Protection) is a function that automatically stops operation when the internal temperature of the power supply unit becomes abnormally high.

This reduces the risk of internal electronic components deteriorating, failing, or catching fire.

Overtemperature protection activates when a temperature sensor inside the power supply unit detects that a certain temperature has been exceeded.

When the temperature returns to a safe range, the power supply unit resumes normal operation.

This function is especially important in high-load environments or situations with insufficient cooling.

For example, in the following cases:

Temperature rises due to cooling fan failure, poor airflow, or dust buildup
High-load environments such as gaming or video editing for long periods
Using the computer in high room temperatures during summer or in direct sunlight

Overtemperature protection is one of the most important protection circuits for improving the reliability of the power supply unit and preventing failures in advance.

No Load Operation Protection (NLO)

No Load Operation Protection (NLO: No Load Operation Protection) is a function that protects the power supply unit when it detects operation without a load.

This prevents unstable operation or damage to the power supply unit in a no-load state.

Power supply units are usually designed to be connected to parts that require power, but for some reason, if the load is removed, operation in a no-load state may be necessary.

For example, this can happen if the power supply unit is operated without connecting any cables or parts during assembly, or if all cable connectors become loose or disconnected by accident.

Without no load operation protection, the power supply unit may enter abnormal states such as overvoltage or overcurrent in a no-load situation.

Surge & Inrush Current Protection (SIP)

Surge & Inrush Current Protection (SIP: Surge & Inrush Current Protection) is a function that protects the power supply unit from sudden current changes.

A surge means a sudden voltage increase due to lightning, and inrush current means a sudden large current when power is turned on.

If high voltage from turning on the power or from external factors like lightning flows into the power supply unit, it can damage internal circuits and connected parts.

SIP detects such sudden current increases and protects the power supply unit and parts.

Specifically, SIP uses components like thermistors to limit inrush current when turning on the power.

This prevents excessive current from flowing before the power supply unit starts normal operation.

Also, when high voltage from external sources like lightning surges occurs, a varistor absorbs the overvoltage to protect internal circuits.

In this way, surge and inrush current protection is an essential function for improving the reliability and longevity of the power supply unit.

Summary: Electrical Accidents Are Scary, So Make Sure to Have Protection Circuits!

This article explained the basic knowledge and detailed roles of each protection circuit in a power supply unit.

Here are the key points again.

Key Points of This Article

Protects against various abnormalities such as overload, overcurrent, overvoltage, short circuit, overtemperature, and surges.
Without protection functions, parts may fail or be damaged, and in the worst case, a fire may occur.
For those unfamiliar with electrical systems, protection circuits are recommended for peace of mind.
Protection circuits rarely activate, but they provide safety as a form of insurance!

Protection functions are there to protect the power supply unit and other parts when abnormal conditions like overcurrent, overvoltage, short circuits, or overheating occur.

Such situations do not happen often, but if an expensive part fails or is damaged, or in the worst case, a fire occurs, the consequences can be serious.

Therefore, it is recommended to choose a power supply unit with protection functions, even as a form of insurance.

This article also explains the basics of power supply unit standards and cables, as well as how to choose one from the perspectives of performance and compatibility.