The simplistic Salas low voltage shunt regulator - Page 389

canvas · 02:36 AM

Salas,

The load current varies in OCXO. At power-on, it needs 500ma to warm up for approx 3 minutes. After that, it consumes 250ma constantly. Coincidently, the TC of R1 helps the load current. While R1 is hot, its resistance increases which lowers the CCS current from 630ma to 550ma. So, the temperature of IRF9610 drops a bit.

By the way, can I parallel 2 2N5458 to increase its Idss? I found several 2N5458s, but their Idss is only 4.5ma.

Salas · 10th April 2011, 03:15 AM

Using way too much current for those sinks I am afraid. 1R you put for R1? Theoretically you can parallel 2N5458s if they will not oscillate there. Try with the smaller Ref resistor, maybe you can narrow the drift. OCXO's PSU voltage margin? Can work between say 4.8V to 5.5V?

*Is that 0.1uF MKP necessary? Better not be there if not. At least to test if it plays a role creating instability.

canvas · 10th April 2011, 03:37 AM

1. R1 is 4.7R as you suggest in post #3881. The circuit draws 630ma in total.
2. Well, I don't know my OCXO's voltage margin, but some manufacturers list +-5%. So, I guess 5.25V is probably the absolute maximum. It's custom made and not cheap, I really don't want to lose it.
3. In my previous PS, this 0.1uf MKP helps the sound a bit, so I decided to leave it there. I do check for oscillation, couldn't find any. Do you still think I should remove it?

Salas · 10th April 2011, 03:47 AM

If it does not oscillate, its not our right now concern. The 1.0 circuit with the Leds should draw as much with a 4R7. This one draws Vbe/R1. Would need 1R to draw around 0.6A. Something's fishy. Is the BC560 near the 9610 showing Vbe around 0.6V? If you got 2 green LEDS 2-2.2V Vf you can use them instead of the Ref resistor 27K etc. Those will resist drift. Crank the trimmer to 0 Ohm if with LEDs.

canvas · 10th April 2011, 03:52 AM

Salas,

Sorry, my mistake. You are right. R1 is 1.2R.(lowest I have in hand, 4.7R is for 25ma TCXO) And the post you suggest me is at #3720 not #3881.

I will try the leds, will report back again. Thanks.

Salas · 10th April 2011, 03:55 AM

Make a string of 2 selected LEDS for 4.4V total. That plus Vbe will give 5V. Cathode faces down south circuit.

merlin el mago · 10th April 2011, 04:57 PM

Nick V1.0 RS how much headroom does that shunt require?

Salas · 10th April 2011, 05:10 PM

Will work from 3V headroom upwards. BUT if aiming low near 5Vo the Vin must allow for CCS LEDS drop+3V. I.e around 9V input min.

merlin el mago · 10th April 2011, 05:19 PM

Thanks Nick, the information is for the Hypno with remote sense is powering the Legato +-15V

canvas · 11th April 2011, 03:32 PM

Salas,

Last night I tried to measure the vout of the 1.2R for TCXO, and it shows severe oscillation! I thought it was the oscons, so I replace them with Panasonic FM and removed the 0.1uf MKP. But, it still oscillates... I found the oscillation was due to the TCXO or OCXO. If I power my reclock circuit with the same 1.2R board, it does not oscillate. I even tried the IRF9530, but no help at all. Is there anything I should pay attention if 1.2R was fed into an XO?

10th April 2011, 02:32 AM	#3881
canvas diyAudio Member Join Date: Nov 2003 Location: Taiwan	Salas, The load current varies in OCXO. At power-on, it needs 500ma to warm up for approx 3 minutes. After that, it consumes 250ma constantly. Coincidently, the TC of R1 helps the load current. While R1 is hot, its resistance increases which lowers the CCS current from 630ma to 550ma. So, the temperature of IRF9610 drops a bit. By the way, can I parallel 2 2N5458 to increase its Idss? I found several 2N5458s, but their Idss is only 4.5ma. Last edited by canvas; 10th April 2011 at 02:36 AM.

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10th April 2011, 03:15 AM	#3882
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Using way too much current for those sinks I am afraid. 1R you put for R1? Theoretically you can parallel 2N5458s if they will not oscillate there. Try with the smaller Ref resistor, maybe you can narrow the drift. OCXO's PSU voltage margin? Can work between say 4.8V to 5.5V? *Is that 0.1uF MKP necessary? Better not be there if not. At least to test if it plays a role creating instability.

10th April 2011, 03:37 AM	#3883
canvas diyAudio Member Join Date: Nov 2003 Location: Taiwan	1. R1 is 4.7R as you suggest in post #3881. The circuit draws 630ma in total. 2. Well, I don't know my OCXO's voltage margin, but some manufacturers list +-5%. So, I guess 5.25V is probably the absolute maximum. It's custom made and not cheap, I really don't want to lose it. 3. In my previous PS, this 0.1uf MKP helps the sound a bit, so I decided to leave it there. I do check for oscillation, couldn't find any. Do you still think I should remove it?

10th April 2011, 03:47 AM	#3884
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	If it does not oscillate, its not our right now concern. The 1.0 circuit with the Leds should draw as much with a 4R7. This one draws Vbe/R1. Would need 1R to draw around 0.6A. Something's fishy. Is the BC560 near the 9610 showing Vbe around 0.6V? If you got 2 green LEDS 2-2.2V Vf you can use them instead of the Ref resistor 27K etc. Those will resist drift. Crank the trimmer to 0 Ohm if with LEDs.

10th April 2011, 03:52 AM	#3885
canvas diyAudio Member Join Date: Nov 2003 Location: Taiwan	Salas, Sorry, my mistake. You are right. R1 is 1.2R.(lowest I have in hand, 4.7R is for 25ma TCXO) And the post you suggest me is at #3720 not #3881. I will try the leds, will report back again. Thanks.

10th April 2011, 03:55 AM	#3886
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Make a string of 2 selected LEDS for 4.4V total. That plus Vbe will give 5V. Cathode faces down south circuit.

10th April 2011, 04:57 PM	#3887
merlin el mago diyAudio Member Join Date: Sep 2009 Location: Catalonia new Europe state	Nick V1.0 RS how much headroom does that shunt require?

10th April 2011, 05:10 PM	#3888
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Will work from 3V headroom upwards. BUT if aiming low near 5Vo the Vin must allow for CCS LEDS drop+3V. I.e around 9V input min.

10th April 2011, 05:19 PM	#3889
merlin el mago diyAudio Member Join Date: Sep 2009 Location: Catalonia new Europe state	Thanks Nick, the information is for the Hypno with remote sense is powering the Legato +-15V

11th April 2011, 03:32 PM	#3890
canvas diyAudio Member Join Date: Nov 2003 Location: Taiwan	Salas, Last night I tried to measure the vout of the 1.2R for TCXO, and it shows severe oscillation! I thought it was the oscons, so I replace them with Panasonic FM and removed the 0.1uf MKP. But, it still oscillates... I found the oscillation was due to the TCXO or OCXO. If I power my reclock circuit with the same 1.2R board, it does not oscillate. I even tried the IRF9530, but no help at all. Is there anything I should pay attention if 1.2R was fed into an XO?