# How can I use a 5v pwm signal to control a high voltage?

#### aydinguy

Joined Nov 25, 2020
3
Noob question: I have a pwm signal which goes up to 5 volts. I need to make some driver which will take it as input and output 0-18 volts proportional to the signal (where 0v-0v, 2.5v-9v, 5v-18v, etc.). I have an 18v power supply, I just need the pwm signal to regulate it. I'm using it to drive power to a transformer. I have only a very vague idea of how I might do this, and would greatly appreciate help.

#### Ian0

Joined Aug 7, 2020
8,425
Have you a vague idea about what you want to achieve?
Do you need PWM output from the 18V or DC output?
Obviously you need AC to drive the transformer. . . .

#### aydinguy

Joined Nov 25, 2020
3
Have you a vague idea about what you want to achieve?
Do you need PWM output from the 18V or DC output?
Obviously you need AC to drive the transformer. . . .
The power supply is powering a mazilli circuit, which drives the transformer, so no AC. DC or pwm output doesn't matter, whatever is easiest.

#### BobTPH

Joined Jun 5, 2013
7,563
I have a pwm signal which goes up to 5 volts.
No you don’t. A PWM signal varies in duty cycle, not voltage. So which is it, a variable voltage analog signal or a PWM signal.

Bob

#### aydinguy

Joined Nov 25, 2020
3
No you don’t. A PWM signal varies in duty cycle, not voltage. So which is it, a variable voltage analog signal or a PWM signal.

Bob
oh, I had though PWM was used only as a means of changing average voltage by altering duty cycle. But yes, it's a PWM signal.

#### Ian0

Joined Aug 7, 2020
8,425
You can easily get a 0-18V PWM (I mean 0V in the low state and 18V in the high state) by connecting a MCP1401 to your PWM output. You could get about 100mA out if it (but you haven’t said how much current you need).
But how do you intend to connect it to your self-oscillating push-pull circuit, which I suspect would prefer a steady DC supply.

#### crutschow

Joined Mar 14, 2008
32,933
For a steady DC from the PWM you could low-pass filter the PWM signal and feed it to an amp with a gain of 18/5 = 3.6.

What's the PWM frequency, and how much current does your circuit require?
Is here a response time requirement for a change in the PWM duty-cycle to the change in output voltage?

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