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PWM controllers... shopping

ut really only need one PWM signal and

If there's anything EMI sensitive on the cold plate, you'll want to filter better than that--the end plates of the TEC are made of alumina, which has an epsilon around 10. You can couple an astounding amount of hash through t hat. That's why I generally use a Class H drive with a buck switcher and low-sat BJT drive--almost as efficient and much much quieter. If you really sit on the SMPS supervision, you can keep V_CE down below 200 mV, so you c an put a few amps through a SOT23 transistor.

The other thing to watch out for is ripple current heating. Dissipation goe s like I_RMS but cooling goes like I_avg.

Cheers

Phil Hobbs

Reply to
pcdhobbs
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but really only need one PWM signal and

r better than that--the end plates of the TEC are made of alumina, which ha s an epsilon around 10. You can couple an astounding amount of hash through that. That's why I generally use a Class H drive with a buck switcher an d low-sat BJT drive--almost as efficient and much much quieter. If you real ly sit on the SMPS supervision, you can keep V_CE down below 200 mV, so you can put a few amps through a SOT23 transistor.

If you use an inductor-capacitor filter, you can do a lot better, and if yo u mess around with PWM waveform you can do even better.

Sloman A.W., Buggs P., Molloy J., and Stewart D. ?A microcontroller

-based driver to stabilise the temperature of an optical stage to 1mK in th e range 4C to 38C, using a Peltier heat pump and a thermistor sensor? ? Measurement Science and Technology, 7 1653-64 (1996)

oes like I_RMS but cooling goes like I_avg.

That's not entirely correct. Ohmic heating goes up as I^2 (as it always doe s) while Peltier heating and cooling is directly proportional to the curren t. I went into the issue in more detail in the paper above.

Email me if you need a reprint at snipped-for-privacy@ieee.org

--
Bill Sloman, Sydney
Reply to
Bill Sloman

r better than that--the end plates of the TEC are made of alumina, which ha s an epsilon around 10. You can couple an astounding amount of hash through that. That's why I generally use a Class H drive with a buck switcher an d low-sat BJT drive--almost as efficient and much much quieter. If you real ly sit on the SMPS supervision, you can keep V_CE down below 200 mV, so you can put a few amps through a SOT23 transistor.

oes like I_RMS but cooling goes like I_avg.

Thanks for sharing this. Yes, there is potentially EMI-sensitive stuff on the cold plate. I am now throwing the original H-bridge idea in the garbag e. Cheers.

Reply to
sea moss

er-based driver to stabilise the temperature of an optical stage to 1mK in the range 4C to 38C, using a Peltier heat pump and a thermistor sensor? ?? Measurement Science and Technology, 7 1653-64 (1996)

ent of the PWM waveform down by playing around a small programmable logic d evice. The device is long obsolete, but there are plenty of more modern equ ivalents around.

I found this paper online, but to read it I have to let academia.edu have a ccess to my google contacts.. WTF?! I will email you for a copy. Thanks

Reply to
sea moss

ller-based driver to stabilise the temperature of an optical stage to 1mK i n the range 4C to 38C, using a Peltier heat pump and a thermistor sensor? ?? Measurement Science and Technology, 7 1653-64 (1996)

ntent of the PWM waveform down by playing around a small programmable logic device. The device is long obsolete, but there are plenty of more modern e quivalents around.

access to my google contacts.. WTF?! I will email you for a copy. Thanks

I tried snipped-for-privacy@ieee.org, but it bounced back, what's the full address?

Reply to
sea moss

Klaus, what was the advantage of using a microcontroller? Software-adjustable dead time?

Reply to
sea moss

roller-based driver to stabilise the temperature of an optical stage to 1mK in the range 4C to 38C, using a Peltier heat pump and a thermistor sensor ? Measurement Science and Technology, 7 1653-64 (1996)

content of the PWM waveform down by playing around a small programmable log ic device. The device is long obsolete, but there are plenty of more modern equivalents around.

ve access to my google contacts.. WTF?! I will email you for a copy. Than ks

s?

Add the extra full stop - you need two, not one.

--
Bill Sloman, Sydney (where it is bed-time)
Reply to
Bill Sloman

I am really puzzled why I am the only one on the planet doing it but the perfect chip for that exists and I have been using it in countless designs for decades now.It is the 74HC123, earlier the 74LS123 and even earlier the 74123. You have to provide an oscillator but you get two PWMs using a 123 part (using half of it as oscillator is doable but very unreliable, sometimes it just won't start). I typically use a 555 to get something like

500 kHz and it clocks all the 123-s. A *significant* benefit over using the 123 instead of an MCU with timers/pwm is that there is no clock granularity.

Dimiter

====================================================== Dimiter Popoff, TGI

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Reply to
Dimiter_Popoff

Plus all that phase noise smooths out the spectrum. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com
Reply to
Phil Hobbs

Not much phase noise if done right (it is sensitive to power supply noise, especially via the feedback network), our (up to) 5kV HV bias for HPGe detectors has really minimal noise, a few mV (this is just noise, no ripple to speak of, the current load is what goes into the

1G feedback resistor). But it can get noisy, many years ago I learned the "quiet power" lesson the hard way :-).

Dimiter

Reply to
Dimiter_Popoff

So you replace Rext with a variable current source or something like that?

I'd be okay using something like that closed-loop, but I don't see any specified min/max pulse width specs, so I wouldn't be super confident using it open loop. AFAICT it could be as bad as the HC4046, i.e. 3:1 or worse.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com
Reply to
Phil Hobbs

Sort of. If I can power the error opamp off something like 10-12 volts its output drives directly Rext (instead of having Rext to +5V). I usually use 1/2 LMC6482 for that purpose, last 25+ years at least. But if all I have is the (quiet) 5V supply the output of the 6482 drives the gate of a say 2N176 (SST176 really), source to +5V, drain into some Rext (last time it was a 2k).

Oh I use it closed loop only of course. One can get 0 to say 80+% duty (you can keep the 123 constantly on by pulling the RC pin to GND, handy for protections, gating etc., obviously the power switch is off while the 123 is on). That said 123 parts are remarkably similar, even between vendors, have been over the years. The RC is specified for time and probably they all use the same currents/thresholds or sort of. Or it is just the same design they all use, no idea.

Dimiter

====================================================== Dimiter Popoff, TGI

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Reply to
Dimiter_Popoff

Good to know, thanks!

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com
Reply to
Phil Hobbs

ller-based driver to stabilise the temperature of an optical stage to 1mK i n the range 4C to 38C, using a Peltier heat pump and a thermistor sensor? ?? Measurement Science and Technology, 7 1653-64 (1996)

ntent of the PWM waveform down by playing around a small programmable logic device. The device is long obsolete, but there are plenty of more modern e quivalents around.

access to my google contacts.. WTF?! I will email you for a copy. Thanks

What you don't have a crap google account for stuff like this?

--

  Rick C. 

  --- Get 1,000 miles of free Supercharging 
  --- Tesla referral code - https://ts.la/richard11209
Reply to
Ricky C

I do for youtube, but on SED I drive without a seatbelt.

Reply to
sea moss

The attiny25 allows use of the comparator and a pwm timer/counter at the same time. A few pennies more, though.

Hul

bitrex wrote:

Reply to
Hul Tytus

What does SED have to do with academia.edu?

--

  Rick C. 

  --+ Get 1,000 miles of free Supercharging 
  --+ Tesla referral code - https://ts.la/richard11209
Reply to
Ricky C

Never mind, I misunderstood what you were saying. Yeah I can use a throwaway for that.

Reply to
sea moss

We had a microcontroller there already, so it was just to save cost. Digital control is normally slower than analog, but can remove component tolerances and cut cost

In that design it controlled a half bridge converter, a boost converter, a maximum power point tracker and a backlight LED. Oh, and then also the main purpose of the product, a Modbus controller

Cheers

Klaus

Cheers

Klaus

Reply to
Klaus Kragelund

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