A different idea from A More Efficient Bridge Rectifier?
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From: Joerg on 14 Feb 2010 17:46 Jim Thompson wrote: > On Sun, 14 Feb 2010 14:18:51 -0800, Joerg <invalid(a)invalid.invalid> > wrote: > >> Paul E. Schoen wrote: >>> "MooseFET" <kensmith(a)rahul.net> wrote in message >>> news:50cfb635-5888-428a-be43-efdc1cd3318d(a)x10g2000prk.googlegroups.com... >>> On Feb 13, 3:51 pm, Joerg <inva...(a)invalid.invalid> wrote: >>>> D from BC wrote: >>>>> In article <aabc57bc-4faf-4067-8ed2-df32f921f214 >>>>> @b9g2000pri.googlegroups.com>, kensm...(a)rahul.net says... >>>>>> On Feb 9, 5:06 pm, D from BC <myrealaddr...(a)comic.com> wrote: >>>>>>> My offline smps design has 3 parts making the most heat. >>>>>>> A power diode, a mosfet and a bridge rectifier. >>>>>>> I'm interested in any cookbook designs that replaces a bridge >>>>>>> rectifier. >>>>>>> Any pointers? >>>>>> Imagine the no input ripple version of the transformer coupled SEPIC >>>>>> circuit. >>>>>> ie: there are 3 windings the third being the isolated output. >>>>>> Now take the power MOSFET and replace it with a pair in series source >>>>>> to source. >>>>>> This circuit can be connected directly to the unrectified maines. It >>>>>> makes >>>>>> an isolated squarewavish wave form. This can then be run into a >>>>>> sychronous >>>>>> rectifier to make a DC output. >>>>>> All this involves no diode drops from the mains to the DC output. >>>>> Neato :) >>>> Except then you still have to replace the Schottky diode in the SEPIC >>>> with a synchronously controlled FET circuit ;-) >>> Yes, it requires some good timing control on the fets and a pair of >>> perhaps 600V MOSFETs. This is two less of the costly parts than the >>> MOSFET bridge idea. >>> >>> It can be a PFC replacement for the transformer, bridge and capacitor >>> style power supply. The SEPIC doesn't put all that high of demands on >>> the core. It only has to hold the energy of one cycle plus a little >>> to make the current continuous to keep the ripple at zero. >>> >>> ------------------------------------------------------------------------- >>> >>> I still say that the bridge rectifier, or perhaps a doubler circuit, will >>> be the most efficient solution if one takes into account cost, complexity, >>> and reliability. One or two volts drop on 120 or 240 VAC mains is at most >>> 2% loss. >>> >>> Even better overall efficiency may be obtained by converting our electrical >>> distribution system to DC. There will be less losses due to EMF effects. >>> Most appliances can be made to use DC directly. Anything with a switching >>> power supply can bypass the input rectifiers, and induction motors can be >>> driven by PWM bridge controllers. And of course lighting and heating work >>> as well on DC as AC. >>> >> ... and then it gets cold, uncle Leroy plugs in the old space heater, >> the one that didn't have a safety thermodisk yet ... phsss ... *PHUT* >> ... li'l meltdown on the carpet but uncle Leroy has dozed off by now ... >> smoke alarms blare ... sirens start wailing at the engine company 17 ... > > There Joerg goes again *PHUT* *PHUT* *PHUT* *PHUT* *PHUT* *PHUT* > > Whew! Sure glad I don't live next door ;-) > Well, the good news is that the next fire hydrant is across from our driveway :-) -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jim Thompson on 14 Feb 2010 17:56 On Sun, 14 Feb 2010 14:46:09 -0800, Joerg <invalid(a)invalid.invalid> wrote: >Jim Thompson wrote: >> On Sun, 14 Feb 2010 14:18:51 -0800, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> Paul E. Schoen wrote: >>>> "MooseFET" <kensmith(a)rahul.net> wrote in message >>>> news:50cfb635-5888-428a-be43-efdc1cd3318d(a)x10g2000prk.googlegroups.com... >>>> On Feb 13, 3:51 pm, Joerg <inva...(a)invalid.invalid> wrote: >>>>> D from BC wrote: >>>>>> In article <aabc57bc-4faf-4067-8ed2-df32f921f214 >>>>>> @b9g2000pri.googlegroups.com>, kensm...(a)rahul.net says... >>>>>>> On Feb 9, 5:06 pm, D from BC <myrealaddr...(a)comic.com> wrote: >>>>>>>> My offline smps design has 3 parts making the most heat. >>>>>>>> A power diode, a mosfet and a bridge rectifier. >>>>>>>> I'm interested in any cookbook designs that replaces a bridge >>>>>>>> rectifier. >>>>>>>> Any pointers? >>>>>>> Imagine the no input ripple version of the transformer coupled SEPIC >>>>>>> circuit. >>>>>>> ie: there are 3 windings the third being the isolated output. >>>>>>> Now take the power MOSFET and replace it with a pair in series source >>>>>>> to source. >>>>>>> This circuit can be connected directly to the unrectified maines. It >>>>>>> makes >>>>>>> an isolated squarewavish wave form. This can then be run into a >>>>>>> sychronous >>>>>>> rectifier to make a DC output. >>>>>>> All this involves no diode drops from the mains to the DC output. >>>>>> Neato :) >>>>> Except then you still have to replace the Schottky diode in the SEPIC >>>>> with a synchronously controlled FET circuit ;-) >>>> Yes, it requires some good timing control on the fets and a pair of >>>> perhaps 600V MOSFETs. This is two less of the costly parts than the >>>> MOSFET bridge idea. >>>> >>>> It can be a PFC replacement for the transformer, bridge and capacitor >>>> style power supply. The SEPIC doesn't put all that high of demands on >>>> the core. It only has to hold the energy of one cycle plus a little >>>> to make the current continuous to keep the ripple at zero. >>>> >>>> ------------------------------------------------------------------------- >>>> >>>> I still say that the bridge rectifier, or perhaps a doubler circuit, will >>>> be the most efficient solution if one takes into account cost, complexity, >>>> and reliability. One or two volts drop on 120 or 240 VAC mains is at most >>>> 2% loss. >>>> >>>> Even better overall efficiency may be obtained by converting our electrical >>>> distribution system to DC. There will be less losses due to EMF effects. >>>> Most appliances can be made to use DC directly. Anything with a switching >>>> power supply can bypass the input rectifiers, and induction motors can be >>>> driven by PWM bridge controllers. And of course lighting and heating work >>>> as well on DC as AC. >>>> >>> ... and then it gets cold, uncle Leroy plugs in the old space heater, >>> the one that didn't have a safety thermodisk yet ... phsss ... *PHUT* >>> ... li'l meltdown on the carpet but uncle Leroy has dozed off by now ... >>> smoke alarms blare ... sirens start wailing at the engine company 17 ... >> >> There Joerg goes again *PHUT* *PHUT* *PHUT* *PHUT* *PHUT* *PHUT* >> >> Whew! Sure glad I don't live next door ;-) >> > >Well, the good news is that the next fire hydrant is across from our >driveway :-) Same here, actually, straight across the street. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Tim Williams on 14 Feb 2010 18:30 "Hammy" <spam(a)spam.com> wrote in message news:sstgn5p9ib16pu4mibl3u72n7vctn3326h(a)4ax.com... > The reason DC transmission is seldom used is because of DC > transmission losses. For example how would you get 300Vdc to every > residence say at +/- 20%? The DC losses in the transmission line make > that difficult and costly to implement on a wide scale. Not too bad. The technology exists today to replace our infrastructure with DC -- same voltages for transmission efficiency reasons, just use DC transformers (i.e. converters). Nice part is each 'transformer' can be regulating and current protected, electronically. The advantage over the current system would be slight, while retooling the world as we know it (putting a VFD in front of every motor) would cost trillions, which is why nobody's doing it, of course. Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: Paul E. Schoen on 14 Feb 2010 18:29 "Joerg" <invalid(a)invalid.invalid> wrote in message news:7trb6dF308U2(a)mid.individual.net... > Paul E. Schoen wrote: >> >> Even better overall efficiency may be obtained by converting our >> electrical distribution system to DC. There will be less losses due to >> EMF effects. Most appliances can be made to use DC directly. Anything >> with a switching power supply can bypass the input rectifiers, and >> induction motors can be driven by PWM bridge controllers. And of course >> lighting and heating work as well on DC as AC. >> > > ... and then it gets cold, uncle Leroy plugs in the old space heater, the > one that didn't have a safety thermodisk yet ... phsss ... *PHUT* ... > li'l meltdown on the carpet but uncle Leroy has dozed off by now ... > smoke alarms blare ... sirens start wailing at the engine company 17 ... Of course, DC mains will have their own unique standards for plugs and sockets, and devices made for 300VDC will have their own safety requirements. Even if someone splices a pigtail on an old 120 VAC heater and plugs it into 300 VDC, it will likely pop the main breaker before it melts down. A greater danger would be that the squirrel cage fan would burn up, and anyone with half a nose or an eye would smell it and see smoke and pull the plug within seconds. If uncle Leroy ignores the obvious signs of the heater self-destructing, and dozes off within the few seconds that it would take to become obvious, then poor drugged up and drunken uncle Leroy has just been eliminated from the gene pool by Darwinian selection. Paul
From: Paul E. Schoen on 14 Feb 2010 19:07
"Tim Williams" <tmoranwms(a)charter.net> wrote in message news:hla13a$fci$1(a)news.eternal-september.org... > "Hammy" <spam(a)spam.com> wrote in message > news:sstgn5p9ib16pu4mibl3u72n7vctn3326h(a)4ax.com... >> The reason DC transmission is seldom used is because of DC >> transmission losses. For example how would you get 300Vdc to every >> residence say at +/- 20%? The DC losses in the transmission line make >> that difficult and costly to implement on a wide scale. > > Not too bad. The technology exists today to replace our infrastructure > with DC -- same voltages for transmission efficiency reasons, just use DC > transformers (i.e. converters). Nice part is each 'transformer' can be > regulating and current protected, electronically. > > The advantage over the current system would be slight, while retooling > the world as we know it (putting a VFD in front of every motor) would > cost trillions, which is why nobody's doing it, of course. If electric power becomes much more expensive, then the efficiency advantages are magnified to the point where they may become worthwhile. Much of the infrastructure is in need of upgrade anyway, and conversion can be done on a gradual and piecemeal basis. When 300VDC is brought into a residence, it would not be too costly to install a PWM VF motor controller that could provide 3 phase power at 60 Hz for the entire house. 220 VAC appliances usually run fine on 208 VAC. The electrical power for a typical house is about 20 kW or 15 HP, which is a moderate size controller. Ideally, the house would be rewired for 300 VDC, which could be done using the same wiring and different sockets. One or two circuits could be left as 60 Hz AC and connected to a small motor controller or inverter. It would also have the advantage of a fairly simple battery backup system for power outages. A bank of 25 automotive type batteries could supply 50*300 = 15000 W-H of power, which would last 24 hours at an emergency level of 625 watts. That's plenty for lighting, small appliances, and a computer or TV set. The inception of a changeover such as this would provide thousands of skilled and semi-skilled jobs and also provide an impetus for technological innovation. Eventually it may cost trillions, but that is money that stays in the country and fosters improvement of local economies. Any downsides? Paul |