SMPS Regulation Query.

Thread Starter

beatsal

Joined Jan 21, 2018
218
Switched Mode PS: Is it regulated on the primary side of transformer? I don't think a good idea on the secondary side. Also, are they regulated by transistors in PWM mode?
 

Papabravo

Joined Feb 24, 2006
16,116
Switched Mode PS: Is it regulated on the primary side of transformer? I don't think a good idea on the secondary side. Also, are they regulated by transistors in PWM mode?
They don't necessarily involve a transformer. How about you pony up a schematic and we can use that as a basis of discussion. The usual regulation device is a field effect transistor. These are preferred for many applications because of their low ON-resistance. BJTs can be used in boost converters when there is no convenient voltage source to turn on a FET.
 

Thread Starter

beatsal

Joined Jan 21, 2018
218
They don't necessarily involve a transformer. How about you pony up a schematic and we can use that as a basis of discussion. The usual regulation device is a field effect transistor. These are preferred for many applications because of their low ON-resistance. BJTs can be used in boost converters when there is no convenient voltage source to turn on a FET.
I tried to get a schematic but maybe my search skills? It is a Craftsman P/N700994 120 vac in 18vdc, 2.2 A out
 

Thread Starter

beatsal

Joined Jan 21, 2018
218
Yes and on the secondary side if they have a transformer.
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Thanks. It looks like the transistors are on the primary i.e. 120 V side. Also there is a 100uF 400v CAPACITOR which seems to confirm this. I can post a pic if it helps.
 

Papabravo

Joined Feb 24, 2006
16,116
I tried to get a schematic but maybe my search skills? It is a Craftsman P/N700994 120 vac in 18vdc, 2.2 A out
If that is the case there is no apriori reason why this should be an SMPS (Switched Mode Power Supply). More likely it is a transformer,rectifier, and capacitor and it might or might not have any subsequent regulation. Motors don't necessarily care about regulated voltage, they run on just about any form of current
 
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