What's the difference between MOSFET high side and low side switching?

[joelyoung]

Hello my friend please remember to send me the schematic with the tl494 as pwm for dc to dc 170v with feed backloop. Thank you I await your reply

 

[joelyoung]

Re: MOSFET switching.

Hello my friend such a long time you have not replied to my message. Anyway I reach a little further with the inverter now but the problem I am having is the 170v is falling off with a load as little as 9 watts please give me sugestions as how to check the feed baack loop on the sg3525 circuit. Thank you. Waiting your reply

 

[datapersada]

Thamid, please see my Sony schematic and my question are:
1. Which mosfet is on low and on high (PQ7 & PQ11, PQ8 & PQ12)?
2. From which mosfet allways on 5v and allways on 3.3v?

 

[Tahmid]

Thamid, please see my Sony schematic and my question are:
1. Which mosfet is on low and on high (PQ7 & PQ11, PQ8 & PQ12)?
2. From which mosfet allways on 5v and allways on 3.3v?

View attachment 76670

I don't get your question clearly.

Since the MOSFETs are N-channel, they'll all be switched on with a logic high to the gate.

Hello my friend such a long time you have not replied to my message. Anyway I reach a little further with the inverter now but the problem I am having is the 170v is falling off with a load as little as 9 watts please give me sugestions as how to check the feed baack loop on the sg3525 circuit. Thank you. Waiting your reply

Posting a schematic would make it easier to spot where the mistake may lie.

 

[joelyoung]

hello Tahamid I have been trying so hard to get you but I cant get your attention. I really have a problem with floating frequency in my inverter I need you to help me with

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hello Tahamid I have been trying so hard to get you but I cant get your attention. I really have a problem with floating frequency in my inverter I need you to help me with

 

[Tahmid]

What exactly do you mean by "floating frequency"? Also, as I said above, you should also post the schematic.

 

[ismu]

Re: MOSFET switching.

Hi,
High side switching is required when your MOSFET is in high side configuration. This is when the drain is connected to +ve and load is taken through source to ground. As a result source has no direct connection to ground. Here when +ve is 200v, your VGS has to be 200+10 = 210V because source is not directly connected to ground, and when on has a potential of 200v.
Low side is where load is taken from drain and source is connected to ground. Here, VGS is always eg 10v as source is connected directly to ground.

In bridge circuits you need both high and low side switching.


Hope this helps.
Tahmid.

Which one is best [leave it about expense ] .means more efficency , heat conseption , etc...