[SI-LIST] Re: DC Power supplies Connected in parallel
- From: Paul Levin <levinpa@xxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Sat, 11 Aug 2012 16:00:17 -0700
On the other hand, if the 5V supply has working over-voltage protection,
that 5V OVP circuit may save the 5V supply by simply blowing the fuse
of the 12V supply.
I say *working* because I just experienced a +/-15V power supply "with
over-voltage protection" run its positive output up to +22V, just a tad
past where I would have expected the OVP level to be set (and also a tad
past what most of my parts could tolerate.)
Paul Levin
Director of Engineering
InnoSense LLC
Torrance, CA
________________
On 8/11/2012 11:49 AM, O. Laney wrote:
> Power supplies can't be treated as theoretical sources of the pspice
> kind plus output impedance. Your typical positive supply can only
> source current and can't sink it. If the outputs of a 5V and 12V supply
> are tied together, the 12V supply will pull the 5V supply above its set
> point and the regulation loop in the 5V supply will turn off the pass
> transistor. Whether the 5V output can pull clear to 12V without
> something breaking down is a matter of supply design. For instance, the
> output caps in the 5V supply will likely be rated for less than 12V and
> might not survive the overvoltage for very long. The pass transistor
> might break down from the inverted voltage (...or not. The raw voltage
> is probably 9 to 12V.)
>
> Orin
>
> ------ Original Message ------
> From: "Erfan" <erfan@xxxxxxxxxxxxxxx>
> To: si-list@xxxxxxxxxxxxx
> Sent: 8/11/2012 2:13:59 AM
> Subject: [SI-LIST] DC Power supplies Connected in parallel
>> Hai Everyone,
>>
>>
>> I have few questions regarding the DC power supplies.
>>
>>
>>
>> What happens when 2 DC-power supplies are connected in parallel which has 2
>> different voltages let say one has 12V and other has 5V. What happens to
>> their voltage and current, current has to get added up to my knowledge does
>> it really happen in this case? What happens to voltage do I see 12V or 5V?
>> what happens in case of grounds are isolated and not isolated? If I have to
>> generate more current using 2 DC supplies in parallel then what care or
>> configuration I should use. Wanted to know the practical limitations of
>> using them.
>>
>>
>>
>> Kindly through some light in this regard.
>>
>>
>>
>> Regards,
>>
>> Erfan
>>
>>
>>
>>
>>
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