Just a quick query,
Balancing resistors for 2x 220uf electrolytics (in series) on the output of a lm317 regulator. Circuit states 100uf but I have only 220uf hence the serial connection. The caps are rated at 100v(!) Regulator output will be 11v (can be 9-15v but will be 11v, not 12, not 15 but 11, I have reasons)
I dont think balancing resistors are necessary but would like to install them for good practice and completeness.
Using a couple of online calculators, I'm getting values between 1k to 4.5k (2 seperate calcs on illinois Capacitor Inc), and 450k or so using the Rbalance = NVrate-Vbus over 0.0015CVbus.
Obviously three separate methods of calc getting three separate answers means they're all wrong.
Thanks in advance.
Balancing resistors for 2x 220uf electrolytics (in series) on the output of a lm317 regulator. Circuit states 100uf but I have only 220uf hence the serial connection. The caps are rated at 100v(!) Regulator output will be 11v (can be 9-15v but will be 11v, not 12, not 15 but 11, I have reasons)
I dont think balancing resistors are necessary but would like to install them for good practice and completeness.
Using a couple of online calculators, I'm getting values between 1k to 4.5k (2 seperate calcs on illinois Capacitor Inc), and 450k or so using the Rbalance = NVrate-Vbus over 0.0015CVbus.
Obviously three separate methods of calc getting three separate answers means they're all wrong.
Thanks in advance.
Very noncritical (not even needed) in this case.
If you draw 1mA through the resistors to swamp the capacitor leakage,
the resistors would each be 0.5 x ( 11V / 1mA ) = 5.5k so use 5.6k each.
Wattage dissipated in each resistor is 5.5V x 1mA = 0.0055W, so use anything you have.
If you draw 1mA through the resistors to swamp the capacitor leakage,
the resistors would each be 0.5 x ( 11V / 1mA ) = 5.5k so use 5.6k each.
Wattage dissipated in each resistor is 5.5V x 1mA = 0.0055W, so use anything you have.
Yes, the 220uF may prematurely degrade if operated at such low voltages.
If you only have 220uF 100V capacitors, I'd just use one of them.
It will do no harm to use the larger value instead of 100uF.
OK thanks again. Double checking I do actually have 50v ones too, again at 220uf, so I'll use one of those, only one!
No Osvaldo, just 220uf's, at either 100v or 50v. That's all I have so I'll just use one of the 50v caps.