regulators

[Kevin Weddle]

I am concerned with linear regulators and switching regulators. It occured to me that the switching regulator has a filtered output. I believe that a regulator should regulate and not filter. Does anybody have experience with power supply regulators?

 

[ante1]

I believe the filtered output is a necessity because the way switchers work. They shop the current at 40 to 100 kHz (sometimes more) and create spikes and some interference that must be restrained.

Ante :

 

[Kevin Weddle]

What is nice is that since the control is already digital, a digital device can be used to help regulate logically. Maybe there can be compensation for voltage drift. The problem is the regulator can't regulate the output of a filter capacitor. So I guess that a power supply filter might have a filter regulator filter combination.

 

[Kevin Weddle]

It also occured to me that the regulator is regulating against the changing signal. Is it safe to say the regulator is a junction of two signals?

 

[MP1]

You would not refer to a regulator as a junction of two signals since the voltage at both sides of the regulator are from the same source. A junction would also imply the source comes from different directions, and the regulator is working with DC, which means direction of both sides of the regulator are the same. The output voltage of the regulator is the input voltage with a change made to it. I hope this explanation is helpful.

MP

 

[Kevin Weddle]

Do you notice that the control element is sometimes an opamp. Iwould tend to use a base transistor with an exterior, digitally controlled analog IC that feeds it. I am sure the IC would probably have an opamp.

 

[Kevin Weddle]

I am perplexed at the use of large capacitors on the output of the regulator. I have seen small ones used in their place and I think this is correct. The regulator would have trouble trying to change the voltage with a large capacitor. And remember that the DC voltage is always determined by the load, not the capacitor.

 

[MP1]

The regulator is not changing the voltage at this end. It is already regulated. Larger caps on the output of the regulator will help curb fluctuations in voltage caused by the circuit that is being powered much better than small ones. In many circuits, I see both a small and a large cap in parallel. This is because of inherent noise that might be generated by the circuit being powered.
A fluctuating DC voltage is in a sense an AC voltage. Remember, DC does not pass through the capacitor. It is only the AC signal that will go through it. The size of the capacitor is determined with a formula for frequency.

MP

 

[Kevin Weddle]

I believe the output capacitor is tagged on to some power supplies mistakenly. If you were to take the most simple circuit and want a supply that will maintain a voltage, then I doubt it would include a large capacitor. A constant voltage with a change in current is merely a simple task. Most of the finished products in use today use simple voltage regulation. That is the voltage that occurs on the output is fed back, inverted, and applied to the output. This is a simple voltage loop, for lack of a better description.

 

[MP1]

It really depends upon what the circuit is doing after it receives the regulated voltage. Try this, make a simple regulator circuit on a breadboard to power something on your workbench. Try this with and without a capacitor on the output of the regulator and watch the voltage fluctuations as the device is working and as it is needing the current.

MP

 

[Kevin Weddle]

I am bewildered by all the different types of regulators on the market. Regulators are simple to construct if you are dealing with one small signal application. What are some examples of the different types of loads one might see in electronics?

 

[Guest]

Capacitors are required to improve the transient response of the regulator,well as we were told while being taught.However it is not required if input to the regulator is 6 inchs away at the input and similarly if the load is at a distance then a capacitor is required at the output of regulator.