I have put together a pcb that is controlled by a 14M2 and has all of the extra circuitry that I want in my kit-built vacuum tube preamp -- relay-switched in/out, delay, muting, etc. It all works well except it draws rather more current than I would like due to the Rube-Goldberg dual LM317 setup I'm using.
Part of what I want is 12V 25mA power to be the "trigger" to turn on my downstream power amp. Presently I use two LM317s (U3 and U4 in the photo) to first regulate current and then regulate voltage to achieve the 12V 25mA output. It works, but between the two ICs I waste quite a bit of current and I wish I had a better method. I stumbled across the "battery charger" circuit which uses one 317 and three resistors and I understand the general idea but I do not understand what happens when the load asks for more than 12V or 25mA. The brief explanations I have found always say the circuit "protects the battery" but nowhere can I find where it says how it protects the battery, and it claims to provide a low current float charge when the battery is fully charged.
Has anyone used this battery charger circuit? How does it work and is it appropriate for my application? Will it deliver the 12V and 25mA in normal operation and then what happens when the demand exceeds the specification? Voltage drop? Current drop?
Part of what I want is 12V 25mA power to be the "trigger" to turn on my downstream power amp. Presently I use two LM317s (U3 and U4 in the photo) to first regulate current and then regulate voltage to achieve the 12V 25mA output. It works, but between the two ICs I waste quite a bit of current and I wish I had a better method. I stumbled across the "battery charger" circuit which uses one 317 and three resistors and I understand the general idea but I do not understand what happens when the load asks for more than 12V or 25mA. The brief explanations I have found always say the circuit "protects the battery" but nowhere can I find where it says how it protects the battery, and it claims to provide a low current float charge when the battery is fully charged.
Has anyone used this battery charger circuit? How does it work and is it appropriate for my application? Will it deliver the 12V and 25mA in normal operation and then what happens when the demand exceeds the specification? Voltage drop? Current drop?
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