# how can i reduce the ripple?

#### tuto

Joined May 2, 2021
15
hi everyone.

i got a question. i was doing this circuit, in which i want to make a voltage source, connected to the line and that returns approximately 30V, but the problem is that it has a lot of ripple, I put the inductor to lower the ripple and fix it a bit, the problem is that I do not have inductors with values so large, otherwise the ripple would be completely reduced with an inductor of for example 1h, but i can't get an electronic component of such value.
.i can't get an electronic component of such apacitor value either, so those are the values I can't change. the 60ohm resistor I can't change it either because it represent an equivalent circuit connected to this source.(the voltage of the line is 220*sqrt(2) here, and 50hz) (the for diodes are Schottky type, )

What else can I do to decrease the ripple?

here is the .asc (voltagesource.asc (below))and a .png of the circuit

Another thing I try is adding a zener diode to it as seen in the picture, and that solves the problem, but it gives me gigantic currents in the inductor and all the diodes. currents much greater than their maximum values (the TFZ12B is a zener diode)

(voltagesource0.asc)(below)

thanks!

#### Attachments

• 2.5 KB Views: 5
• 2.7 KB Views: 1

#### ronsimpson

Joined Oct 7, 2019
2,878
Thankyou for attaching your .ASC files.
The inductance for the transformer is very small. You have 1500 amps in the primary and R1. I changed by 1000:1. Now there is more voltage on the secondary. (there was voltage loss in R1 and the primary if the transformer) Now there is only about 2A in the primary.

#### Attachments

• 2.8 KB Views: 3

#### neonstrobe

Joined May 15, 2009
190
You are much more likely to have inductances in the region of 10H or more on a mains transformer. Try setting L1=10 and L2=625m. That should give you more realistic currents.
I would also suggest a simple transistor regulator to reduce ripple. You might find some companies offering custom wound coils but a 1H choke will probably cost as much as the mains transformer if not more. They are effective though.
Do you need voltage regulation as well as ripple filtering or just ripple filtering?

#### LowQCab

Joined Nov 6, 2012
3,929
What is the AC-Voltage Output-Rating of the Secondary of your Transformer ?,
and what Filtered DC-Voltage and Current do you want at the Output ?,
( I see that you have a 60-Ohm Load ),
maybe ~14VAC at the Secondary,
and you want Filtered ~12VDC with a 60-Ohm Load,
( 12 / 60 = 0.200, = 200ma X 12V = 2.4-Watts) ?
.
.
.

#### tuto

Joined May 2, 2021
15
Thankyou for attaching your .ASC files.
The inductance for the transformer is very small. You have 1500 amps in the primary and R1. I changed by 1000:1. Now there is more voltage on the secondary. (there was voltage loss in R1 and the primary if the transformer) Now there is only about 2A in the primary.
View attachment 241596
thanks for the reply!. the ripple decreases
but I think there are some problems with your circuit: first: when I assemble the circuit, I cannot get an inductor of value greater than 10mh. so those 400mh and 25mh are not components that are going to be able to be obtained. If instead of those values I put 10mh in the primary and 1 mh in the secondary, I get that: the ripple also drops but the current in the primary inductor is very large, is that a problem for the inductor? In addition, the current is huge for R1. It means that if I put that resistance with the voltage of 311V it would burn me. i don´t know how to fix these problems. here is the modified circuit
i change the diodes because more current passes than the maximum of the diodes and the same with the voltage).
Someone else upstairs suggests I put a linear voltage regulator out on the vout. is that available in ltspice? I did not find it.
thnks!

#### Attachments

• 2.8 KB Views: 4

#### MrChips

Joined Oct 2, 2009
30,435
How much ripple are you measuring?
What are the low and high voltages at the output?
What output voltage and max current do you require?

#### ronsimpson

Joined Oct 7, 2019
2,878
I cannot get an inductor of value greater than 10mh. so those 400mh and 25mh are not components that are going to be able to be obtained.
What you are looking for is pictured below. You can not go out and get two inductors and make a transformer. The 400:25mH is only to tell SPICE how the transformer is make. We really don't care that the inductance is but we do care the turn ratio. 110:24V in the case of the picture. (110+110:12+12)

The ripple problem is not a function of inductance of the transformer. It is a function of RC. R=load and C= all the caps across the load. Also frequency. (50 or 60hz)

#### crutschow

Joined Mar 14, 2008
33,983
You are much more likely to have inductances in the region of 10H or more on a mains transformer.
Just to be clear, that inductance is not seen by the secondary output current, it only determines the primary magnetizing current.

#### sparky 1

Joined Nov 3, 2018
755
Last edited:

#### Sensacell

Joined Jun 19, 2012
3,396
Using the LC style filter is a textbook exercise, in the practical world it's not used for mains frequency power supplies because the required inductors are huge, expensive, and impractical.

#### tuto

Joined May 2, 2021
15
I've been doing a few things that you guys suggested and I can lower the ripple with an LM317 linear voltage regulator. the problem is that I need 30V, and I have only 16V. I was trying to change some values of the circuit components but the voltage did not turn up. doesn´t matter if i change R1, is still 16V on Vout .
what can i do? any ideas? Here is the asc and the LM317 file.
thnks!

#### Attachments

• 3.7 KB Views: 0
• 1.4 KB Views: 0
• 443 bytes Views: 0

#### tuto

Joined May 2, 2021
15
What you are looking for is pictured below. You can not go out and get two inductors and make a transformer. The 400:25mH is only to tell SPICE how the transformer is make. We really don't care that the inductance is but we do care the turn ratio. 110:24V in the case of the picture. (110+110:12+12)
View attachment 241628
The ripple problem is not a function of inductance of the transformer. It is a function of RC. R=load and C= all the caps across the load. Also frequency. (50 or 60hz)
I've been doing a few things that you guys suggested and I can lower the ripple with an LM317 linear voltage regulator. the problem is that I need 30V, and I have only 16V. I was trying to change some values of the circuit components but the voltage did not turn up. doesn´t matter if i change R1, is still 16V on Vout .
what can i do? any ideas? Here is the asc and the LM317 file.
thnks!

#### Attachments

• 443 bytes Views: 0
• 1.4 KB Views: 0
• 3.7 KB Views: 0

#### ronsimpson

Joined Oct 7, 2019
2,878
Added Q1 to handle high current, and D5 to make a stable voltage.

#### Attachments

• 3.3 KB Views: 2

#### tuto

Joined May 2, 2021
15

#### tuto

Joined May 2, 2021
15
Added Q1 to handle high current, and D5 to make a stable voltage.
View attachment 241706
i´m sorry, i got one more question: the emitter-base voltage of the transistor 2N3055 has a maxvoltage of 7V. but in the circuit it´s 50V passing through the emitter-base leg. am i right? i mean that transistor can´t take that voltage right? is there a solution of that problem?
thnk!

#### ronsimpson

Joined Oct 7, 2019
2,878
The transistor does not care or know what the voltage is from Base to Ground. It cares about B-E, E-C, C-B voltage.
Base to Emitter is about 0.7 volts. It will not go over 0.8 and should not go below -5 volts. (maybe -7V on some parts)
The Collector to Emitter voltage is about 20 volts.

This circuit is fine and works. The B to E voltage is good.

#### tuto

Joined May 2, 2021
15
The transistor does not care or know what the voltage is from Base to Ground. It cares about B-E, E-C, C-B voltage.
Base to Emitter is about 0.7 volts. It will not go over 0.8 and should not go below -5 volts. (maybe -7V on some parts)
The Collector to Emitter voltage is about 20 volts.

This circuit is fine and works. The B to E voltage is good.
View attachment 241919
ok cool.if lastly, I wanted to change Vout to 30V instead of 50V I need to change R1 from 0.2 ohms to 200 ohms. And that's how it works, the only problem is that it would have 0W to 300W in R1 when with 0.2 ohms it would have -14W to 8W.
maybe there are resistors that can have a power as big as 14W, but surely there are none that can have 300W. Is there any way for Vout to be 30V without putting a 200ohms R1 ?, since it would have too much power and probably burn it.

#### Sensacell

Joined Jun 19, 2012
3,396
Here is an example of a simple all-transistor regulated power supply that doesn't need monster power resistors and has an adjustable output voltage.
The circuit uses a capacitance multiplier concept for high ripple rejection.

#### Attachments

• 11.8 KB Views: 8