Never!
7812 or other voltage regulators are low output impedance voltage source. Even very tiny output voltage difference between two 7812 chips would lead to a large amount of current flowing between them.
Take a look at the 78XX application note and there are simple methods to increase its current capability. One suggestion would be using bypass transistor.
7812 or other voltage regulators are low output impedance voltage source. Even very tiny output voltage difference between two 7812 chips would lead to a large amount of current flowing between them.
Take a look at the 78XX application note and there are simple methods to increase its current capability. One suggestion would be using bypass transistor.
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I realise that the regulator will do this, but I was wondering if anyone had any circuits out there already that I could use to bypass the voltage regulator (to allow MUCH bigger currents to flow)whilst still maintaining this ability for the regulator to limit the current. As, with most of thee things I have come up with so far either dissapet a lot of heat or have no limit on the current which can flow in the bypass transistors.
However, having a look around, I'm not too sure I should do this, as I'm not to sure the voltage regultor would be fast enough to keep up with the varying demands of a class AB power amplifier. So I was thinking I might try and build my own design using a fast op-amp as an error amplifier driving an output stage in relation to a regulated reference (using a zenner and constant current scource). The only problem with this is I will pretty much need to build two power amp style output stages which could get expensive and would need even bigger heatsinks.
I guess I should ask arround to see if there is anyone out there who has built anything with a large power output (+/- 55V at up to 25A possibly bridged if I ever find big enough speekers) which has a regulated supply, as to date I have only heard roumers about one Krell product which uses a regulated supply for it's power stages (I should go an have a look for it I guess).
anyway, enough for now, but please let me know if you think it would be possible/worthwile improvement to a power amp project.
However, having a look around, I'm not too sure I should do this, as I'm not to sure the voltage regultor would be fast enough to keep up with the varying demands of a class AB power amplifier. So I was thinking I might try and build my own design using a fast op-amp as an error amplifier driving an output stage in relation to a regulated reference (using a zenner and constant current scource). The only problem with this is I will pretty much need to build two power amp style output stages which could get expensive and would need even bigger heatsinks.
I guess I should ask arround to see if there is anyone out there who has built anything with a large power output (+/- 55V at up to 25A possibly bridged if I ever find big enough speekers) which has a regulated supply, as to date I have only heard roumers about one Krell product which uses a regulated supply for it's power stages (I should go an have a look for it I guess).
anyway, enough for now, but please let me know if you think it would be possible/worthwile improvement to a power amp project.
parallel regulators
Actually you will probably wind with an oscillating circuit since a voltage regulator is an amplifier with a large DC offset voltage and no input signal. If you had very closely matched voltages you could probably add a 0.1 ohm resistor to the output of each regulator and run the circuit from the junction. You would need to have an output cap at the output of each regulator before the summing resistors. You can also add a bypass cap to ground the junction of the two resistors. I have seen this done to increase to current capacity of the regulator circuit. Trimming the DC current for each is not that hard. AC stability is a bigger issue.
Actually you will probably wind with an oscillating circuit since a voltage regulator is an amplifier with a large DC offset voltage and no input signal. If you had very closely matched voltages you could probably add a 0.1 ohm resistor to the output of each regulator and run the circuit from the junction. You would need to have an output cap at the output of each regulator before the summing resistors. You can also add a bypass cap to ground the junction of the two resistors. I have seen this done to increase to current capacity of the regulator circuit. Trimming the DC current for each is not that hard. AC stability is a bigger issue.
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