Modulating DC Signal From Standard Power Supply - Page 1
Forum section: electronics / beginners

author: tarun172
author_rank: Regular Contributor
timestamp: February 03, 2017, 09:56:52 pm
content: I need to modulate DC Signal from Standard Bench Power Supply with a 1Vpp 1KHz sinusoidal signal. Modulation by definition is multiplication of two signals. So, if I connect a signal generator and a standard bench power supply in series it should work right? or it shouldn't? When I do that I get is sinusoidal signal with DC offset. I did not see anything in the manual on this topic. Do I need a special type of power supply with this feature?

author: tautech
author_rank: Super Contributor
timestamp: February 03, 2017, 10:05:35 pm
content: Current requirements ?This is standard fare for most AWG's or do you only have a Sig gen ?

author: danadak
author_rank: Super Contributor
timestamp: February 03, 2017, 10:29:52 pm
content: There are many ways to do this. If yiou need the power levels thata signal generator cannot supply here are some approaches to theproblem -1) If you power supply has remote sensing capability you could modulateon the sense leads. This of course depends on how much modulation youwant, common mode range of sense inputs.....2) You could use a three terminal adjustable regulator, and modulate itsreference leg. Trial and error type of experiment.What is -1) Power level you need ?2) Range of power supply Vout and/or Iout ?3) Modulation frequency ?4) Modulation waveform, type, sine, square, ramp....?Regards, Dana.

author: Seekonk
author_rank: Super Contributor
timestamp: February 03, 2017, 10:39:20 pm
content: Or put a transformer in series. Not sure that modulating the feedback on a power supply will respond well at 1K. Modulating a regulator chip does seem a possibility if a sufficient load, a pull down resistor may be needed on the output. DC power amp module maybe.

author: tarun172
author_rank: Regular Contributor
timestamp: February 03, 2017, 10:55:50 pm
content: @ tautech : I need about 20-30 VDC with 30 mA max.@ danadak: 1) Power level you need ? 30 VDC @ 30 mA Max2) Range of power supply Vout and/or Iout ? 24-30 VDC3) Modulation frequency ? 100 Hz - 10 KHz4) Modulation waveform, type, sine, square, ramp....? SineI like modulating reference voltage idea. I am try that now. Connecting signal generator in parallel with power supply does not work. It goes in voltage overload mode.

author: james_s
author_rank: Super Contributor
timestamp: February 03, 2017, 11:37:24 pm
content: Trying to modulate the output of the power supply directly at such high frequencies is not likely to work, often there is significant capacitance in the output and the regulator is damped so that it doesn't glitch all over the place if there's a little dirt in the pot. I think what you want is an audio amplifier that you can drive with the signal generator. There are single ICs that should do what you want with just a handful of external parts.

author: tautech
author_rank: Super Contributor
timestamp: February 04, 2017, 07:56:35 am
content: Quote from: tarun172 on February 03, 2017, 10:55:50 pmMany AWG's can supply those kind of currents but the voltages are at the top end of most units these days.A Siglent AWG accessory might be worth looking at, it's a 10W amp for use with any of the Siglent AWG's and is listed as able to supply a sinewave @ 25.4 Vpp.A basic description of it is here:https://store.siglentamerica.com/product/spa1010-10-watt-amplifier/Manual link:http://www.siglent.com/2014EnglishWebsite/Documents/UserManual/SPA1000_UserManual_UM60010-E01A.pdf4.1 Mb

author: tarun172
author_rank: Regular Contributor
timestamp: February 08, 2017, 01:50:10 pm
content: Does anybody has any experience with Kepco Power Supply BOP Series? See link here:http://www.kepcopower.com/catalog/050-054-bop.pdf

author: tarun172
author_rank: Regular Contributor
timestamp: February 14, 2017, 07:41:27 pm
content: All,Thank you all for the help. After playing for a while, I found two ways of doing it:1. Limit the current coming of power supply by adding a resistor in series.2. You can use batteries in series which are usually current limited.Both seems to work for me.