The protect function Test of FP series power amplifier

A few days ago, a new customer was very curious about the protection function of FP series amplifiers. He said that he hoped that we could take some videos to prove it. (This customer has bought products with unqualified protection functions before, so I am very concerned about it) These videos are organized in this article, I hope it will help you.

Everyone knows that the protection function of electrical appliances not only protects the electrical appliances themselves, but also protects the users. A qualified electrical appliance must have real protection functions, such as soft-start protection, DC protection, short-circuit protection, and over-current protection. , Overheating protection and so on. Today, I will focus on short-circuit protection and overheating protection.

When the output terminal of the power amplifier is short-circuited due to some reasons, the current output by the power amplifier will circulate in its own circuit and become infinite. This situation is very dangerous, so there must be an accurate and fast short-circuit protection circuit to protect the power amplifier equipment. [Each power amplifier must have the function of short-circuit protection, safe issue cannot be ignored. 】

Under normal circumstances, when a short circuit occurs in the power amplifier, first it will control the input signal to reduce its amplitude or even to zero. If the situation does not improve (the current flowing through the power amplifier still exceeds a safe value), it will suppress the output current and let The current flowing inside the power amplifier is always lower than the safe value of the output stage transistor. Once the short circuit is removed, it can work normally, and can automatically adjust the voltage according to the electrical load, and can save electricity.

It can be seen from the video that when the engineer made a fault to the output terminal, the power amplifier quickly activated the short-circuit protection, and after the fault was removed, it quickly resumed normal operation.

A well-designed amplifier will not trigger overheat protection under normal use. It will only act when the external use environment is bad or the internal failure occurs. The hottest part of the entire power amplifier is the C pole (collector) of the output stage transistor, so the temperature sensor for overheat protection is generally installed in the closest place to the C pole of the transistor or the hottest place on the radiator. That is, the power amplifier board of the FP series.

In the video, the fault is simulated by directly heating the transistor externally. The maximum temperature of the transistor we use is greater than 200 degrees Celsius. The heat gun makes the temperature of the transistor rise to 200 degrees Celsius, and the A channel of the power amplifier activates the overheating protection (the separate channel protection of the FP series , Which means that if only a single channel fails, it will not affect the work of other channels.)  When the temperature drops, the amplifier can operate normally (the video has been accelerated, and it actually took nearly a minute to cool down. )