Hi Guys,
i would like to know what the best resistor for a power supply with CRC circuit? thank you! Maxpou
i would like to know what the best resistor for a power supply with CRC circuit? thank you! Maxpou
It's important to properly size the power rating of the R in the CRC filter.
The voltage ripple on the first C is mostly dissipated in the R,
in addition to the dissipation due to the DC voltage drop across the R.
You can approximate the equivalent DC voltage due to the ripple by
measuring the peak to peak ripple voltage, and dividing that by 2.
Or measure it with a true RMS DVM across the R, instead.
For example, if the R is 0.47R, and if the ripple on the first C is 0.5Vpp,
and the DC voltage drop across the R is 1V, then the total dissipation in the 0.47R is:
( 0.5V/2 )^2 / 0.47R + ( 1V )^2 / 0.47R = 2.7W, so use a 5W part.
Often several lower rated parts are used, in parallel, to make up the total R.
The voltage ripple on the first C is mostly dissipated in the R,
in addition to the dissipation due to the DC voltage drop across the R.
You can approximate the equivalent DC voltage due to the ripple by
measuring the peak to peak ripple voltage, and dividing that by 2.
Or measure it with a true RMS DVM across the R, instead.
For example, if the R is 0.47R, and if the ripple on the first C is 0.5Vpp,
and the DC voltage drop across the R is 1V, then the total dissipation in the 0.47R is:
( 0.5V/2 )^2 / 0.47R + ( 1V )^2 / 0.47R = 2.7W, so use a 5W part.
Often several lower rated parts are used, in parallel, to make up the total R.
^i will use a 10 watt resistor for a part that will dissipate 2.7 watts...
Me too, but many will balk at so much derating.
Maybe use 3 to 5 parallel, inexpensive metal oxide 3W resistors for R.
Maybe use 3 to 5 parallel, inexpensive metal oxide 3W resistors for R.
It also has to survive start up, preferably even start up when the second (presumably electrolytic) capacitor's dielectric has degraded due to long inactivity.
During start-up, an energy C2 V2/2 where C2 is the second capacitor's capacitance gets dissipated in the resistor. If I don't have the resistor's pulse ratings, I usually assume that its thermal time constant is likely to be more than a second, so a 5 W resistor should be able to survive an energy of 5 J.
During start-up, an energy C2 V2/2 where C2 is the second capacitor's capacitance gets dissipated in the resistor. If I don't have the resistor's pulse ratings, I usually assume that its thermal time constant is likely to be more than a second, so a 5 W resistor should be able to survive an energy of 5 J.
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Technically or sonicly?. As described above work out the dissapation. As for how they sound in your crc i have found the mundorf 10watt m resist classic sound lovely/gee is that a hifi world. And they dont cost an arm or a leg.
Do you seriously claim that different resistors in a PSU CRC arrangement do sound differently? Well, my claim is, due to the 2nd C the resistor's impact on sound will be shorted - if a resistor »sounds« at all. Hence, any WW resistor of proper wattage and value will do.
Bst regards!
Bst regards!
Speaking of resistors for CRC, what kind of resistor is more suited: inductive or non inductive and why?
I like WW although i always wonder if they’re ahead of the choke they can act as an antenna for any mains noise?
Basically, a WW resistor's inductance adds to the filtering properties, as it is in series with the ohmic part. But we're talking about µH's, or, at it's best, mH's here, so what?
Best regards!
Best regards!
Ah, I finally understand Kay meant wirewound. I was wondering why he prefers resistors manufactured during a world war...
Same as some prefer Russian miltary grade PIO capacitors 😛😛😛...
No, you're right, of course, WW stands for wire wound.
Best regards!
No, you're right, of course, WW stands for wire wound.
Best regards!