[ARC5] Cool New DC-DC Converter

[Peter Gottlieb]

It’s a bit different with switchers, a lot depends on the design.  The input section has a power limitation and each output section has limitations. In a very simple design the output section limitations may be the components, such as diodes, acting like fuses. A lack of load on one section could well allow a lot more output on another section before the input section reaches its limit. However, in this case, filaments may take long enough when cold to cause a diode failure. You may need to replace the low voltage section diode with a beefier version to handle the warm-up overload. 

A more sophisticated power supply would have overload protection on each output and may limit current or even shut down the supply trying to light filaments. 


Peter

> On Mar 16, 2018, at 12:19 PM, Dennis Monticelli <dennis.monticelli at gmail.com> wrote:
> 
> Brian,
> 
> I think there is a misunderstanding.  I think Scott was only trying to point out that the primary winding and mag core are shared by all secondary loads.  You can only get so many VA out of a transformer before hitting the limitations of primary winding resistance and/or core saturation.
> 
> Dennis AE6C
> 
>> On Fri, Mar 16, 2018 at 2:42 AM, Brian <brianclarke01 at optusnet.com.au> wrote:
>> Hello Scott,
>> 
>> Where did you get this idea that power supplies share their output loads?
>> Doesn't apply to any SMPSU I know, nor to any rotary supplies either.
>> 
>> 73 de Brian, VK2GCE.
>> 
>> On Friday, March 16, 2018 1:35 AM, Scott claimed: 
>> Folks,
>> 
>> Cold heaters take about twice as much as when warm. But, there's no B+ drain then, so the supply can direct all its primary power capability to the heater circuit. Most of these are power limited at about 1.3 times the rating so:12V 3A is 36W + 60 mA x 520V = 25W makes a total power limit of 61W. If all that is directed to a 12V heater circuit, you could get 5A, or 10A for 6V. I'm not sure the 10A would actually work bu the 12V 5A ought to.
>> 
>> Someone needs to buy one and see what it actually does.
>> 
>> Happy glowing,
>> 
>> Scott  Robinson
>> 
>> 
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