What the general rules of Protecting the DC Switching Power Supply

[Kynix]

I want to know about the general rules about the protection of DC switching power supply to teach my students who is a newcomer in the electronic field. I hope to use the easy words to let he know the key points, so I browse among websites to look for the material arranging my idea.

And recently I read an article about the protection of DC switching power supply, including overvoltage protection (OVP), overthermal protection (OTP), overload protection (OLP). This article is using the specific examples to describe something about series of protections, but I think it is not enough and something is not suitble, maybe wrong...

So is there anyone can give me some advice or the direct concise info about the protection of DC switching power supply is ok?

Thanks a lot.

enclosing the article URL: https://www.kynix.com/Blog/469.html, is there any problems with this article? hoping the valueble reply.

 

[d123]

Hi,

The article in the link is correct.

A good way of checking what to teach your students about typical protecion blocks is to look at actual smps ICs by manufacturers such as TI, Analog Devices, Maxim, Intersil/Renesas, ST, etc. and look at the schematics and block diagrams in the datasheets. Datasheets are great learning tools, as are application notes.

Typical is as in the article: OVP, UVP, over temperature/thermal shutdown, over current protection, maybe reverse polarity protection.

 

[andre_luis]

The article do not mentions anything about keeping the switching device operation under the safe operating area (SOA), which in other words means limiting instantaneous power dissipation at a rate that can be handled by the heatsink.

 

[BradtheRad]

As a general rule, decide which components you wish to protect.

Here are factors to consider:
* Is the component expensive?
* Is component irreplaceable?
* Is component easy to access and remove?
* Is downtime expensive?
* Is the unit needed to avoid an emergency?
* Will component failure endanger other equipment?
Etc.

A fuse is commonly installed as an easy solution for a large number of faults. However we need to choose a threshold point where the fuse activates, and that requires knowledge of normal operation of the project, as well as knowledge what can go wrong with the operation.

 

[Kynix]

Hello,
Thanks a lot firstly. I have searched some websites to find some switching mode power supply schematic diagrams to tell the different protections to my student, and I also check in some datasheets to get the acurate comentary to let my student well understand the protection of DC switching power supply.

- - - Updated - - -

Hi,
The specific stuff is the switch tube is controlled by high frequency PWM (Pulse width Modulation) signal, the DC is added to the primary level of the switch transformer, the switch transformer induces the high frequency voltage, and the load is supplied by rectifying and filtering. The output part feedback to the control circuit through a certain circuit to control the duty cycle of PWM to achieve the purpose of stable output. When AC power is input, it usually goes through EUB to filter out the interference on the power grid, meanwhile, it also filters out the interference of the power supply to the power grid.
When the power is the same, the higher the switching frequency, the smaller the volume of the switch transformer. But the higher the demand on the switch tube, the secondary of the switch transformer can contain more windings or windings have more than one tap to get the desired output. Protection circuits such as no-load, short circuit protection should also be added, otherwise the switching power supply may be destroyed.
I haven't arranged all the specific thing that I collect yet...