DC Voltage regulators compatible with AC Voltage.

Thread Starter

James 26

Joined Mar 26, 2020
10
Hello,

I want to regulate the output of a transformer to be exactly 9v regardless of load current. Will a standarad 9v DC regulator do this or is their some other way it needs to bed done?
 

dl324

Joined Mar 30, 2015
16,943
I want to regulate the output of a transformer to be exactly 9v regardless of load current.
It depends on what you mean by exactly. Voltage regulators have line and load regulation specifications. Output voltage on fixed regulators have a tolerance.
 

BobTPH

Joined Jun 5, 2013
8,998
Hello,

I want to regulate the output of a transformer to be exactly 9v regardless of load current. Will a standarad 9v DC regulator do this or is their some other way it needs to bed done?
The output of the transformer is AC, a DC regulator will not regulate that. If you want regulated DC output, then you need a rectifier and smoothing capacitor before going to a D C regulator.
 

LowQCab

Joined Nov 6, 2012
4,075
How High is "UP" ???
1)
How much space do You have to work with ?

2)
Describe the Load that You intend to Supply with ~9-Volts.

3)
What will be the maximum Current demanded by the Load ?

4)
Do You want to limit the maximum-Current at a fixed Value ?

5)
Do You intend to use an existing Transformer that You already have ?,
or are You willing to purchase a Transformer that will be adequate for the job ?

6)
How tight must the regulation be ?,
plus-or-minus 0.5-Volts ?, or,
plus-or-minus 0.005-Volts ?

7)
Why do You need Voltage Regulation in the first place ?
.
.
.
 

Reloadron

Joined Jan 15, 2015
7,523
Hello,

I want to regulate the output of a transformer to be exactly 9v regardless of load current. Will a standarad 9v DC regulator do this or is their some other way it needs to bed done?
No it needs done another way. Load current needs to be supplied by Supply current capability. The load cannot exceed the supply's capacity. If the load exceeds supply the supply voltage will begin to drop (fold over) and your transformer will begin getting hot and unfused will burn up.

There are AC voltage regulators depending on your exact application. No, a DC regulator will not work.

Ron
 

MisterBill2

Joined Jan 23, 2018
18,584
If you need exactly 9.00 volts AC at the load , you need an adjustable transformer such as a "Variac" or a "Powerstat". Both are available in whatever current ratings you may require. But you will also need an accurate voltmeter with adequate resolution.
 

DickCappels

Joined Aug 21, 2008
10,187
…You can change the transformer’s output to DC and use that to provide power to a stable amplitude sine wave oscillator, after that you can scale the gain of an amplifier to get whatever voltage you choose.
 

DickCappels

Joined Aug 21, 2008
10,187
Do you need sine waves out or would something that outputs alternating positive and negative trapezoids be ok? There is an application for an LM317 and an LM337 in a National Semiconductor application note.
 

MisterBill2

Joined Jan 23, 2018
18,584
Post#8 is certainly ON POINT!!!
Please give a detailed description of just exactly what it is required. That will include both the anticipated current, minimum and maximum, and how closely the voltage must be regulated, and if you are really seeking a regulated sine wave voltage peak to peak value, or whatever. And certainly we need to know if the regulated output must be isolated from the mains supply source. So we need a lot of answer details before any useful suggestions can be made.
 

MisterBill2

Joined Jan 23, 2018
18,584
Certainly that is what is requested. But there is no hint as to the anticipated current required, nor any mention of the possible range of the source, and both of those have a large effect on the regulation system.
Given the number of different schemes available, the choice depends a lot on information not provided.
In addition, often, without any hint of the application, the reality is that the actual requirement is different from what is requested. Thus most of the responses have asked for the needed additional information.
so rather than guess at the actual requirement, responders have asked for more details.
And the original post was made several days ago, no further messages from the TS. So no further guesses.
 
I want to regulate the output of a transformer to be exactly 9v regardless of load current. Will a standarad 9v DC regulator do this or is their some other way it needs to bed done?
May I ask why? I'm struggling to think of a real world application where the AC voltage of a transformer secondary needs to be controlled to provide a constant AC voltage regardless of load. If you are looking for a controlled 9V DC voltage, start with 9 V AC from a transformer secondary, full wave recitify and you will still have enough headroom to use a Linear regulator like an LM317 to get 9V DC with a wide variation in load up to about 1.5A
 

MisterBill2

Joined Jan 23, 2018
18,584
The solution is simple but far from cheap: Get a constant voltage transformer with a custom secondary from the SOLA ELECTRIC company. As long as the mains frequency is held constant the transformers do a decent job of holding a steady output voltage. At least they used to be able to do that back in the auto plants.
 
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