# [EVDL] Basic Boost Converter circuit



## EVDL List (Jul 27, 2007)

I would like to find a basic DC - DC boost converter
circuit thet I can build. The goal is to input
anywhere between 6 and 120 V (various combination of
batteries) and output a constant 118 V (fully charged
voltage of 18 golf cart batts) current limited to 10 A
max. I may want to adjust the 118 +/- 2%. I'm really
thinking about standard voltages available from Li Ion
packs (i.e. power tool batteries that I could put in
series or parallel). The purpose is a slow recharge
while sitting when no outlet is available - a dual
pack system.

I have already done this using a 12 V source (various
12 V lead acid batts in parallel), off the shelf 700
Watt continuous power inverter and battery charger. I
use it to charge while sitting in the parking lot. 
But, I'd like the flexibility to charge off different
voltage inputs (i.e. a small NiMH pack isn't 12 V. It
may be closer to 48 V - that's about 40 D cells in
series.). Anyway, I don't have a 12 V source in NiMH
or Li Ion. So, I need to do something different. 
Also, the inverter / charger system is pretty
inefficient.

I want at least 75% efficiency of the system, and I'l
like it to be able to be built for a parts cost of <
$200.

Any ideas?

Thanks,

Steve


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## EVDL List (Jul 27, 2007)

> Steve Powers wrote:
> > I would like to find a basic DC - DC boost converter
> > circuit that I can build... input 6 to 120 V...
> > output a constant 118 V +/- 2%... Any ideas?
> ...


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## EVDL List (Jul 27, 2007)

As long as your input is always lower than the output
(you indicated up to 120V with 116V-120V output - can
you live with input no higher than 100V, such that the
18 GC batteries will always be higher than the input?

The standard config for boost is to have an inductor
connected to the input + and short the inductor to
ground with an (electronic) switch, builing up current
to whatever your current limit says is allowed, then
producing the high voltage when the switch is opened,
flowing through a diode to the output.
http://en.wikipedia.org/wiki/Boost_converter

Current limit can be done in the connection from
switch to ground or in the supply to the load.
The way to control output current is to vary PWM
of the switch.
The way to control output voltage is to use a capacitor
is the load does not represent a capacitive element or
can be disconnected.
Voltage is regulated by allowing PWM switching control to
go to the switch or disable it on a cycle by cycle basis.
See the description of the discontinuous mode in the
Wikipedia article.

Cor van de Water
Systems Architect
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925
Fax: +1 408 731 3675 eFAX: +31-87-784-1130
Second Life: www.secondlife.com/?u=3b42cb3f4ae249319edb487991c30acb

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Steve Powers
Sent: Monday, December 03, 2007 8:49 AM
To: ev
Subject: [EVDL] Basic Boost Converter circuit

I would like to find a basic DC - DC boost converter circuit thet I can build. The goal is to input anywhere between 6 and 120 V (various combination of
batteries) and output a constant 118 V (fully charged voltage of 18 golf cart batts) current limited to 10 A max. I may want to adjust the 118 +/- 2%. I'm really thinking about standard voltages available from Li Ion packs (i.e. power tool batteries that I could put in series or parallel). The purpose is a slow recharge while sitting when no outlet is available - a dual pack system.

I have already done this using a 12 V source (various
12 V lead acid batts in parallel), off the shelf 700 Watt continuous power inverter and battery charger. I use it to charge while sitting in the parking lot. 
But, I'd like the flexibility to charge off different voltage inputs (i.e. a small NiMH pack isn't 12 V. It may be closer to 48 V - that's about 40 D cells in series.). Anyway, I don't have a 12 V source in NiMH or Li Ion. So, I need to do something different. 
Also, the inverter / charger system is pretty inefficient.

I want at least 75% efficiency of the system, and I'l like it to be able to be built for a parts cost of < $200.

Any ideas?

Thanks,

Steve


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## EVDL List (Jul 27, 2007)

You will have no trouble meeting the efficiency requirement but the parts
cost is tough to meet if you want it in a robust mechanical configuration to
work in an automotive environment.

I would use:
1. a universal input 15 volt power supply running off the output to run the
switching logic,
2. a UC3842 type PWM controller,
3. a MOSFET switching element,
4. a toroidal inductor running in discontinuous conduction mode, and
5. appropriate thermal shutdown features.

You can find some reference designs on the TI website.
I would start with the 3842 data sheet and application report slva061.pdf.

Joe Smalley
Rural Kitsap County WA
Former owner of 48 Volt Fiesta
NEDRA 48 volt street conversion record holder
[email protected]


----- Original Message ----- 
From: "Steve Powers" <[email protected]>
To: "ev" <[email protected]>
Sent: Monday, December 03, 2007 8:49 AM
Subject: [EVDL] Basic Boost Converter circuit


> I would like to find a basic DC - DC boost converter
> circuit thet I can build. The goal is to input
> anywhere between 6 and 120 V (various combination of
> batteries) and output a constant 118 V (fully charged
> voltage of 18 golf cart batts) current limited to 10 A
> max. I may want to adjust the 118 +/- 2%. I'm really
> thinking about standard voltages available from Li Ion
> packs (i.e. power tool batteries that I could put in
> series or parallel). The purpose is a slow recharge
> while sitting when no outlet is available - a dual
> pack system.
>
> I have already done this using a 12 V source (various
> 12 V lead acid batts in parallel), off the shelf 700
> Watt continuous power inverter and battery charger. I
> use it to charge while sitting in the parking lot.
> But, I'd like the flexibility to charge off different
> voltage inputs (i.e. a small NiMH pack isn't 12 V. It
> may be closer to 48 V - that's about 40 D cells in
> series.). Anyway, I don't have a 12 V source in NiMH
> or Li Ion. So, I need to do something different.
> Also, the inverter / charger system is pretty
> inefficient.
>
> I want at least 75% efficiency of the system, and I'l
> like it to be able to be built for a parts cost of <
> $200.
>
> Any ideas?
>
> Thanks,
>
> Steve
>
>
>
____________________________________________________________________________
________
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> with Yahoo Mobile. Try it now.
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>
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> http://lists.sjsu.edu/mailman/listinfo/ev

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## EVDL List (Jul 27, 2007)

Steve, You can get the efficiency you want with 
the boost circuit I sketched providing you use enough low channel resistance 
FET's 
in parallel. Remember, that at 1200watts and 6 volts input, you are at an 
average of 200amps plus efficiency losses, which is also a peak current of 
maybe 300amps that the FET's see. You need the equivalent of a Zilla 1k 
controller to switch that current. However, losses can be made low by 
component selection and you can be over 90% efficiency even 
at 20:1 boost. I use SG3526 IC's for this application. Let me know what 
you think. The key to efficiency is the use of a relay on the input for 
reverse polarity protection rather than a diode which would have a very 
large loss, percentage wise, at 6 volts. Another option is to scale down 
your power requirement at low voltage, for example, 1200w at 12v input 
derated to 600w at 6v input. Another refinement would be to use additional 
FET's in synchronous rectification across the output diode. Probably not 
necessary since the losses at this diode are low due to the low average 
10amp output current. I sent the schematic privately because I can't attach 
the schematic to the EVDL list













On Mon, 3 Dec 2007 08:49:13 -0800 (PST), Steve Powers wrote
> I would like to find a basic DC - DC boost converter
> circuit thet I can build. The goal is to input
> anywhere between 6 and 120 V (various combination of
> batteries) and output a constant 118 V (fully charged
> voltage of 18 golf cart batts) current limited to 10 A
> max. I may want to adjust the 118 /- 2%. I'm really
> thinking about standard voltages available from Li Ion
> packs (i.e. power tool batteries that I could put in
> series or parallel). The purpose is a slow recharge
> while sitting when no outlet is available - a dual
> pack system.
> 
> I have already done this using a 12 V source (various
> 12 V lead acid batts in parallel), off the shelf 700
> Watt continuous power inverter and battery charger. I
> use it to charge while sitting in the parking lot. 
> But, I'd like the flexibility to charge off different
> voltage inputs (i.e. a small NiMH pack isn't 12 V. It
> may be closer to 48 V - that's about 40 D cells in
> series.). Anyway, I don't have a 12 V source in NiMH
> or Li Ion. So, I need to do something different. 
> Also, the inverter / charger system is pretty
> inefficient.
> 
> I want at least 75% efficiency of the system, and I'l
> like it to be able to be built for a parts cost of <
> $200.
> 
> Any ideas?
> 
> Thanks,
> 
> Steve
> 
> 
_____________________________________________________________________________
_______
> Be a better sports nut! Let your teams follow you 
> with Yahoo Mobile. Try it now. 
http://mobile.yahoo.com/sports;_ylt=At9_qDKvtAbMuh1G1SQtBI7ntAcJ
> 
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

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## EVDL List (Jul 27, 2007)

> George Swartz wrote:
> > Steve, you can get the efficiency you want with the boost circuit I
> > sketched providing you use enough low channel resistance FET's in
> > parallel. Remember, that at 1200 watts and 6 volts input, you are at
> ...


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## EVDL List (Jul 27, 2007)

Lee, I had recommended using iron cut core or laminations and copper strip 
winding at lower (audio) frequencies in a single phase unit to meet Steve's 
cost goal of $200 assuming some iron cores in the junk box. N phase also 
reduces rms current on input and output electrolytics. 20 phase is ideal for 
a 20 to 1 boost. Depending on the I squared R losses and FET junction 
resistance, the efficiency should be in the high 90% range for most of the 
6v to 118v input voltage range. 

This could have applicability to use as a boost motor control which has been 
discussed before, where only a few larger cells are needed for a low voltage 
battery, and any higher voltage motor can be used. Of course, I would use 
ferrite for such an application for low weight.




On Tue, 04 Dec 2007 12:18:51 -0600, Lee Hart wrote


> > George Swartz wrote:
> > > Steve, you can get the efficiency you want with the boost circuit I
> > > sketched providing you use enough low channel resistance FET's in
> > > parallel. Remember, that at 1200 watts and 6 volts input, you are at
> ...


----------



## EVDL List (Jul 27, 2007)

> George Swartz wrote:
> > Lee, I had recommended using iron cut core or laminations and copper
> > strip winding at lower (audio) frequencies in a single phase unit to
> > meet Steve's cost goal of $200 assuming some iron cores in the junk
> ...


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