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Capacitors are lossless with 0 ESR and rise in temperature and become less reliable by 50% for every 10’C rise due to I^2ESR=Pd losses. However the current spectrum must be known with the ESR frequ...
Answer
#2: Post edited
by
TonyStewart
·
2021-06-06T08:00:58Z (almost 3 years ago)
- Capacitors are lossless with 0 ESR and rise in temperature and become less reliable by 50% for every 10’C rise due to I^2ESR=Pd losses. However the current spectrum must be known with the ESR frequency graph in order to estimate losses.
- The ultimate goal is to attenuate ripple voltage by the impedance ratio so impedance is the primary concern for a given current spectrum. Even if the current is a step or impulse, then you can compute or measure the spectrum and do the same. The secondary importance is self heating from ESR losses. Both are important.
Ideally you want to attenuate as much as possible with the least power dissipation factor because dielectrics are also poor thermal conductors and it is better to use a resistive series loss to dampen a response with a heat sink as it is hard to put a heatsink on dielectrics other than SMT on a large copper area of 1W/sqin which is not cost effective for large powers.
- Capacitors are lossless with 0 ESR and rise in temperature and become less reliable by 50% for every 10’C rise due to I^2ESR=Pd losses. However the current spectrum must be known with the ESR frequency graph in order to estimate losses.
- The ultimate goal is to attenuate ripple voltage by the impedance ratio so impedance is the primary concern for a given current spectrum. Even if the current is a step or impulse, then you can compute or measure the spectrum and do the same. The secondary importance is self heating from ESR losses. Both are important.
- Ideally you want to attenuate as much as possible with the least power dissipation factor because dielectrics are also poor thermal conductors and it is better to use a resistive series loss to dampen a response with a heat sink as it is hard to put a heatsink on dielectrics other than SMT on a large copper area of 1W/sqin which is not cost effective for large powers.
- By having a power loss budget for each component and a max temperature rise, a designer must also insider the undamped Q of a closed loop and mitigate control instabilities from an extremely low ESR and high Q circuit by using low duty cycles to start up and prevent overshoot with Kd compensation to improve phase margin un a wide range of step loads.
#1: Initial revision
by
TonyStewart
·
2021-06-06T07:57:20Z (almost 3 years ago)
Capacitors are lossless with 0 ESR and rise in temperature and become less reliable by 50% for every 10’C rise due to I^2ESR=Pd losses. However the current spectrum must be known with the ESR frequency graph in order to estimate losses. The ultimate goal is to attenuate ripple voltage by the impedance ratio so impedance is the primary concern for a given current spectrum. Even if the current is a step or impulse, then you can compute or measure the spectrum and do the same. The secondary importance is self heating from ESR losses. Both are important. Ideally you want to attenuate as much as possible with the least power dissipation factor because dielectrics are also poor thermal conductors and it is better to use a resistive series loss to dampen a response with a heat sink as it is hard to put a heatsink on dielectrics other than SMT on a large copper area of 1W/sqin which is not cost effective for large powers.