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EEVblog #273 – Power Factor Correction with the MC34262
Posted on May 4th, 2012 14 comments
http://www.onsemi.com/pub/Collateral/MC34262-D.PDF
http://www.youtube.com/watch?v=bX8IIjf15qYThis was supposed to be a small side piece in the Manson PSU Teardown, but it was almost 10 minutes, so I decided to separate it out to keep the teardown as short as possible. You should watch the PSU teardown to get the context of this where the chip is used.
14 responses to “EEVblog #273 – Power Factor Correction with the MC34262”
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Hi Dave,
Thanks for the teardown video. As you were saying we didn’t bother with PFC even in the eighties when the 800 W power supply / charger that I worked on took abot 18 A peak from the 240 V mains despite being close to 90 % efficient.
The input and output Electroltyics in the Manson power supply don’t look very big. I wonder how long they would last at the full rated power?-
Niklas Jansson May 5th, 2012 at 03:07
With the PFC circuit you can actually decrease the amount of output capacitance compared to a rectifier only-solution. The boost converter refills the output capacitor more often, actually several thousands of times per second. We had 3*470 uF before PFC and just 1*470 uF after we introduced PFC in a 1kW rated frequency inverter. The EMC filters was not so small though, adding a lot of BOM cost for an additional differential mode choke and extra filter capacitors.
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Thanks for this. I didn’t know what power factor correction was, this explained it nicely.
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tchicago May 5th, 2012 at 05:46
This should also carry some efficiency loss. It makes the whole thing a double-conversion PSU.
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Luciano May 5th, 2012 at 18:17
The chip is (was) also used as preconverter in the electronic ballast of fluorescent lamps.
Electronic Lamp Ballast Design:
http://www.onsemi.com/pub_link/Collateral/AN1543-D.PDFMotorola, Inc. 1996 Rev 1:
http://www.datasheetcatalog.org/datasheet/motorola/MC34262P.pdf -
allan May 6th, 2012 at 00:34
I hadn’t heard of PFC until now. I gather that this device’s purpose is similar to that of an antenna tuner used with an amateur radio transmitter. The function of the antenna tuner is to zero-out the antenna’s imaginary reactances (capacitive and/or inductive) so that the antenna appears to be a purely resistive load.
Applying this analogy, I infer that this device is helpful in minimizing electrical energy consumption in driving a load with either capacitive and/or inductive reactances. -
Leslie Green May 6th, 2012 at 04:25
Did you spot the dumb ass circuit diagram in the data sheet where on a MAINS circuit they EARTH the output of the bridge rectifier? These circuit diagrams need to come with a public health warning:
“WARNING: Whoever drew this circuit diagram doesn’t realise that the safety Earth symbol should NOT be used for a 0V reference that clearly is not anywhere near Earth potential. If you connect your scope earth to that point you will get a big BANG!” -
Luciano May 6th, 2012 at 05:19
@Leslie Green:
Grounding: Terms and Symbols
http://digital.ni.com/public.nsf/allkb/11BE00780D41622686256BE5006F04CFThree diagonal lines from a horizontal bar represents earth or chassis ground.
Three decreasing-length parallel lines represents analog or circuit ground.
The hollow triangle usually means digital ground, but is often used as a reference ground.
* * *
See also the schematic of the Manson 9400 power supply: (EEVblog #272).
http://eevblog.com/files/SPS9400_ServiceManual.pdfBest regards,
Luciano
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Indeed, this device is helpful in minimizing electrical energy consumption
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I’ve often wondered if it’s worth it to do PFC on an automotive alternator/generator or some other power source that has variable frequency. It seems to me that the windings would run a bit cooler. Automotive alternators feed a battery so the PF is quite high. Apparantly the chip makers don’t think it’s worth the bother. The PFC chips I’ve found all work at a fixed frequency.
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PeterK May 15th, 2012 at 14:16
PFC can indeed be used (and there is active research being done) for variable frequency applications (most often wind) where you want to decrease the harmonic losses in the windings. In a car it is less of an issue. These applications often have other control logic involved (MPPT, etc) which lend them to custom microcontroller control rather than ICs
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c srinivas January 2nd, 2013 at 19:04
plz send the i used input180v-265V PFC CIRCUIT WITH IC MC34262 BUT I USED 220V SO I DONT HAVE RATING AND TURNS RATIO OF TRANSFORMER,URGENTLY I HAVE PROJECT SIR.
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PChi May 4th, 2012 at 21:48