[Milsurplus] 12 to 24 volt conversion, the issue of cost
Tom Dawson
wb3akd at earthlink.net
Fri Oct 9 08:56:37 EDT 2009
Mike,
here's a link to the of the National Semi app notes.
www.national.com/appinfo/power/files/f5.pdf
73
Tom
WB3AKD
----- Original Message -----
From: "Tom Dawson" <wb3akd at earthlink.net>
To: "Jim Whartenby" <antqradio at sbcglobal.net>; <milsurplus at mailman.qth.net>
Sent: Friday, October 09, 2009 12:43 PM
Subject: Re: [Milsurplus] 12 to 24 volt conversion, the issue of cost
> Jim,
>
> Only drawback to the 555 is the duty cycle limitation in astable mode
> which won;t exceed 50 %. Given probably losses in the switch transistor
> and inductor, a 12 to 24 boost converter would need more that 50% DC.
>
> Still it is a great place to start and I've used it with a Ford ignition
> coil and TV voltage tripler to power surplus image converter tubes.
>
> 73
>
> Tom
> WB3AKD
>
>
> ----- Original Message -----
> From: "Jim Whartenby" <antqradio at sbcglobal.net>
> To: <milsurplus at mailman.qth.net>
> Sent: Friday, October 09, 2009 1:31 AM
> Subject: Re: [Milsurplus] 12 to 24 volt conversion, the issue of cost
>
>
> You PWM a NE555 using pin 5 which connects to the top junction of the
> three 5k ohm resistors used to set the limits of the voltage comparators.
>
> The 555 should make a usable PWM for the step up converter.
> Jim
>
> --- On Thu, 10/8/09, Tom Dawson <wb3akd at earthlink.net> wrote:
>
>> On your DC-DC converter project, I might recommend that you
>> investigate boost converters as the inductors are a single
>> winding. I've made
>> experimental converters with just a 555 driving the switch transistor.
>> Regulation is achieved via adjusting the duty cycle
>> (something other than a
>> 555 is needed if you want to regulate this way, but the 555
>> is a good place
>> to start). National semiconductor has application
>> which greatly notes on
>> their controller chips and boost supplies in
>> general.
>>
>
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