# How can I design the circuit that will convert the variable voltage range from 0-200 Vac to 3 volts Vdc?

#### hrn9lia

Joined Aug 21, 2020
6
Hello,I want to design a circuit like topic title.The amount of current I want to get from the circuit is between 25-30 ma.I will use this current to run the microcontroller and to turn on some LEDs.the voltage range is quite wide, but the amount of current I want to get from the circuit is not that much.The voltage range is quite wide, but the amount of current I want to get from the circuit is not that much.How to design this circuit in a simple and professional way or how can I find a ready-made circuit?

#### ronsimpson

Joined Oct 7, 2019
1,459
0-200 Vac to 3 volts Vdc?
You can not convert 0 to 3 volts. There is no energy at 0V.
Almost any "cell phone charger-USB wall wort" will do the 110/220 vac to 5V. Which is probably 100V to 250vac.
Do you need isolation?
If you must drop below 100V there is no ready-made circuit.

This link will take you to a 60V to 500Vac power supply IC. It is not isolated!

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#### Dodgydave

Joined Jun 22, 2012
10,050
An ordinary phone charger will power the LEDs it will give out 5V..

Joined Feb 20, 2016
3,909
What is the input power source?
And if you need the 5V output at 0V input as you title states, then a battery sounds like it could be a good idea.
Another good idea is to explain your project to us in some detail so we can help you better.

#### hrn9lia

Joined Aug 21, 2020
6
You can not convert 0 to 3 volts. There is no energy at 0V.
Almost any "cell phone charger-USB wall wort" will do the 110/220 vac to 5V. Which is probably 100V to 250vac.
Do you need isolation?
If you must drop below 100V there is no ready-made circuit.

This link will take you to a 60V to 500Vac power supply IC. It is not isolated!
you can think as follows: 3-200 Vac to around 3 Vdc

#### MrChips

Joined Oct 2, 2009
24,175
To your advantage, the current draw is relatively low, 30mA.

Let us assume for the moment that this is some kind of piezoelectric generator which can produce 200V at low current for a very short period of time.

What you are seeking is a piezoelectric energy harvester.

The first thing I would do is to provide a high impedance load to the generator using a series resistor (e.g. 100kΩ). Rectify the current through a series Schottky diode (e.g. 1N5817) and dump the charge into a storage capacitor.

Depending on your energy source and pulse duty cycle select the value of the storage capacitor to give you a suitable output voltage.

Then use an energy harvester chip, or buck-boost switching converter to give the desired output voltage.

Do the energy calculation to make sure you can supply the desired amount of energy taking losses and efficiency into consideration.
For example, 30mA @ 3.3V = 100mW
Can your energy source supply 150-200mW?

#### hrn9lia

Joined Aug 21, 2020
6
What is the input power source?
And if you need the 5V output at 0V input as you title states, then a battery sounds like it could be a good idea.
Another good idea is to explain your project to us in some detail so we can help you better.
power supply has variable voltage range.between 0-200 Vac.
power supply not always active.If there is voltage from the power source, I should be able to use that voltage as a supply.The problem is that the power supply can generate voltage at 5Vac,35Vac,150Vac,200Vac ... (0-200Vac)

#### Alec_t

Joined Sep 17, 2013
12,199
the power supply can generate voltage at 5Vac,35Vac,150Vac,200Vac ... (0-200Vac)
What sort of power supply do you have that can generate those voltages? It might be controllable.

#### hrn9lia

Joined Aug 21, 2020
6
To your advantage, the current draw is relatively low, 30mA.

Let us assume for the moment that this is some kind of piezoelectric generator which can produce 200V at low current for a very short period of time.

What you are seeking is a piezoelectric energy harvester.

The first thing I would do is to provide a high impedance load to the generator using a series resistor (e.g. 100kΩ). Rectify the current through a series Schottky diode (e.g. 1N5817) and dump the charge into a storage capacitor.

Depending on your energy source and pulse duty cycle select the value of the storage capacitor to give you a suitable output voltage.

Then use an energy harvester chip, or buck-boost switching converter to give the desired output voltage.

Do the energy calculation to make sure you can supply the desired amount of energy taking losses and efficiency into consideration.
For example, 30mA @ 3.3V = 100mW
Can your energy source supply 150-200mW?
"Then use an energy harvester chip, or buck-boost switching converter to give the desired output voltage. "
yes it makes sense.

but I guess there is no ready chip for this wide voltage range. Do you know a chip for solution or buck-boost switching converter?

#### hrn9lia

Joined Aug 21, 2020
6
What sort of power supply do you have that can generate those voltages? It might be controllable.
Actually these voltages are a result. But you can think of it as a voltage source. I have to use this voltage as a supply.

Joined Feb 20, 2016
3,909
It REALLY would help if you were not so vague.
That sort of question makes it very hard for you to get a good answer.
What is the power source, actually?
Can you post a circuit digram of it?

#### ronsimpson

Joined Oct 7, 2019
1,459
Isolated?

To get 10:1 input range is hard. 40:1 is real hard to do. Then if you say "isolated" then the power must go through a transformer.
Part of the problem: a 3V to 3V supply is very different than a 220V to 3V. Many of the ICs that work at power line voltages will not operate below 15 volts. And the low voltage ICs that work at 3V will not go above 15V. And the medium voltage power supply ICs will not work at 3V or 100V.

#### MrChips

Joined Oct 2, 2009
24,175
We still cannot help until you tell us the power source.
Is it a wind turbine?

#### sparky 1

Joined Nov 3, 2018
576
Arduino AC converter depending if it plugs into the wall or power comes from something else.
( wall wort ) 220 AC converter to 9V DC The DC plug uses a 5.5x2.1 mm male barrel jack center positive
Not much to it, possibly could use a little more filtering.

#### hrn9lia

Joined Aug 21, 2020
6
We still cannot help until you tell us the power source.
Is it a wind turbine?
Okay,Power supply is a special smps.It only generates voltage at certain times.When a voltage is generated by smps, I have to use this voltage as a supply source for my circuit.Yes, the voltage range is wide, but I don't need to take a lot of current.
30mA is enough for the circuit I will run.You can look the picture.simply this way.All I need is the regulated voltage portion.

There is a chip called Ncp785a.I can get the voltage output I want from this chip..But input voltage range of this chip is 85Vac-260Vac.So,I can't use this chip.Also,the regulated voltage need not be exactly 3 volts.The regulated voltage can rise to 5-6 volts depending on the input voltage.For example If input voltage is 50Vac ,output voltage 3V,else if input voltage is 90Vac ,output voltage 4V.

#### ronsimpson

Joined Oct 7, 2019
1,459
1) remove D1. It is not necessary. BR1 does that job. D1 looses 0.7V and that is a big piece of 3 volts.
2) C2 must have higher voltage rating. 200vac has peak voltage of 280V. (1.414x) Use 400 volt capacitor.
3) I have asked many time but you do not understand my question. In this schematic I show the regulator and the logic using the same "ground" as C2 and BR1. This is "not isolated". It puts the logic circuits on the power line. This is not safe. It is done with small products. Please ask the person why made the logic if the logic connects to another product. Ask if it is safe to have the logic ground connected to the power line. Or tell me what you are making.

4)C2 must have the voltage rating for high voltage and the current holding capacity for low line. Example: At 200vac you have about 280vdc on C2 and the current is very low. (300uA) But at 3vac the current is 40mA and the capacitor must be sized for 40mA. The larger the capacitor the smaller the ripple on the DC at C2. It the cap is too small the DC voltage might be 3V but the ripple might allow the voltage to drop to 1V.
5)Ncp785a : Nice part. It will not work below 25V input! Data sheet: dc input voltage 25 to 450V.
6)Ncp785a : It is probably hot. At high voltage, 300Vdc and 30mA = 9 watts. This part will burn up.
7)Ncp785a : Max output current 10.5mA. Will not work at 30mA.
8)Ncp785a : I do not know why it is not working for you. It works for me. It must have capacitors from input to ground and output to ground as shown in the data sheet.

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#### MrChips

Joined Oct 2, 2009
24,175
Instead of diode D4, replace it with a high-side transistor switch.
You control the switch with a PWM signal to bring the storage capacitor to a desired voltage.
You don't need a 400V capacitor if your target voltage at the storage capacitor is going to be 6V, for example.

#### ronsimpson

Joined Oct 7, 2019
1,459
Use a PWM to reduce power loss at high voltage. At 200vac it is 80% efficient.
This part has a 700 volt transistor inside. I think it will do the 30V to 200Vac well.
It will not start up below 30V and that I think I can fix.
It is designed for 300mA and does not regulate well below 30mA. I think that can be fixed.
UCC28881

#### ronsimpson

Joined Oct 7, 2019
1,459
I like this part. 150Vdc max input which is only about 100vac.
LTC3639

Joined Feb 20, 2016
3,909
Okay,Power supply is a special smps.It only generates voltage at certain times.
That is like saying "This engine is a special motor".
What is the source of the energy? Wind, Solar, Zero Point......?
How much power can it supply at the various voltages?
How often and for what length of time is sufficient power available?
Is it capable of rapidly charging a battery when there is power? If so, just make a battery charger and step down regulator.
Why is it so often hard to get real info from some folk?
You want help, but are not willing to answer questions of real relevance. Very frustrating!