Using Choke in LCRC filter in power supply

vangogh-hk · 21st November 2005, 05:16 PM

In my power supply for a ground grid pre-amp; I use bridge diode rectifier and LCRCRC filter.
Could any one told me if I using a choke of 10H - 200mA in a LCRCRC filter supplying a load requiring only 10mA. Will there be any problem.

i.e. What is the drawback of using a choke with much higher current rating than required?

Thanks

amperex · 21st November 2005, 05:48 PM

The choke will not act as a choke input unless Icret is met. Icret is when enough current is drawn in that the capacitor following that choke does not charge up to 1.4 x the choke input voltage. To meet Icrit, you will need more load (current) thru the choke with a large bleeder resistor. How about a new Hammond HC154G for $8.50 You could probally sell the large choke for more than that.

vangogh-hk · 22nd November 2005, 04:31 PM

Thanks

How about if I change the choke input to capacitor input. Could the choke work in this case.

How could I determine the value of the Icrit if the rectifier output volatage is about 230V and the working current is about 8mA?

Johan Potgieter · 22nd November 2005, 10:31 PM

It was mentioned in another thread some time ago (which I cannot trace now), that choke-input filters are not really used for pre-amps.

Firstly the choke needs to be of a minimum inductance inversely proportional to the current drawn as said, and secondly the normally low current needed and available B+ voltage make the use of CRC filters so much more convenient. And even if the designer is a perfectionist, high voltage semi-conductors for series elements are available at a fraction of the cost of a suitable choke, that can really reduce ripple to academic proportions.

There might even be high voltage IC regulators on the market, although I do not know of any. Are there?

hagtech · 23rd November 2005, 05:22 AM

I use choke supplies for preamp. Many have done this. Size of choke is not prohibitive. For an easy way to calculate the choke you need, try this:

www.hagtech.com/theory.html#choke

jh

aletheian · 24th November 2005, 06:21 PM

Quote:

Originally posted by hagtech
I use choke supplies for preamp. Many have done this. Size of choke is not prohibitive. For an easy way to calculate the choke you need, try this:

www.hagtech.com/theory.html#choke

jh

WOW! Those are incredibly helpful calculators! Thatnx for the link.

21st November 2005, 05:16 PM	#1
vangogh-hk diyAudio Member Join Date: Mar 2005 Location: hong kong	Using Choke in LCRC filter in power supply In my power supply for a ground grid pre-amp; I use bridge diode rectifier and LCRCRC filter. Could any one told me if I using a choke of 10H - 200mA in a LCRCRC filter supplying a load requiring only 10mA. Will there be any problem. i.e. What is the drawback of using a choke with much higher current rating than required? Thanks

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21st November 2005, 05:48 PM	#2
amperex diyAudio Member Join Date: Feb 2005 Location: MI	The choke will not act as a choke input unless Icret is met. Icret is when enough current is drawn in that the capacitor following that choke does not charge up to 1.4 x the choke input voltage. To meet Icrit, you will need more load (current) thru the choke with a large bleeder resistor. How about a new Hammond HC154G for $8.50 You could probally sell the large choke for more than that.

22nd November 2005, 04:31 PM	#3
vangogh-hk diyAudio Member Join Date: Mar 2005 Location: hong kong	Thanks How about if I change the choke input to capacitor input. Could the choke work in this case. How could I determine the value of the Icrit if the rectifier output volatage is about 230V and the working current is about 8mA?

22nd November 2005, 10:31 PM	#4
Johan Potgieter diyAudio Member Join Date: May 2005 Location: Pretoria, South Africa	It was mentioned in another thread some time ago (which I cannot trace now), that choke-input filters are not really used for pre-amps. Firstly the choke needs to be of a minimum inductance inversely proportional to the current drawn as said, and secondly the normally low current needed and available B+ voltage make the use of CRC filters so much more convenient. And even if the designer is a perfectionist, high voltage semi-conductors for series elements are available at a fraction of the cost of a suitable choke, that can really reduce ripple to academic proportions. There might even be high voltage IC regulators on the market, although I do not know of any. Are there?

23rd November 2005, 05:22 AM	#5
hagtech diyAudio Member Join Date: Mar 2002 Location: Hawaii	I use choke supplies for preamp. Many have done this. Size of choke is not prohibitive. For an easy way to calculate the choke you need, try this: www.hagtech.com/theory.html#choke jh

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