akgfan
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I found this schematic and it looks interesting like Sigma11 by AMB. But it doesn't need that hard to find current regulator diodes. What's more, it can be simplified and you can leave out short-circuit protection if you wish.
Here's a link, but I don't know who the author was: http://www.extremecircuits.net/2010/06/ultra-low-drop-linear-voltage-regulator_14.html .
I copy it here just in case.
Here's the original text:
This circuit is a Mosfet-based linear voltage regulator with a voltage drop of as low as 60mV at 1A. The circuit uses a 15V-0-15V transformer and employs an IRF540 N-channel Mosfet (Q1) to deliver the regulated 12V output. The gate drive voltage required for the Mosfet is generated using a voltage doubler circuit consisting of diodes D1 & D2 and capacitors C1 & C2. To turn the Mosfet fully on, the gate terminal should be around 10V above the source terminal which is connected to the DC output. The voltage doubler feeds this voltage to the gate via resistor R3. IC2, a TL431 adjustable shunt regulator, is used as the error amplifier. It dynamically adjusts the gate voltage to maintain the regulation at the output. With an adequate heatsink for the Mosfet, the circuit can provide up to 3A output at slightly elevated minimum voltage drop.
Trimpot VR1 is used for fine adjustment of the output voltage. The RC network consisting of R5 and C6 provides error-amplifier compensation. The circuit is provided with short-circuit crowbar protection to guard against an accidental short at the output. This crowbar protection works as follows: under normal working conditions, the voltage across capacitor C5 will be 6.3V and diode D5 will be reverse-biased by the output voltage of 12V. However, during output short-circuit conditions, the output will momentarily drop, causing D5 to conduct. This triggers the MOC3021 Triac optocoupler (IC1) which in turn pulls the gate voltage to ground. This limits the output current. The circuit will remain latched in this state and the input voltage has to be switched off to reset the circuit.
I tested this circuit today and it works but I didn't have irf540 but irf520. So i needed to tweak resistors r6, r7 and r8. And I left out short-circuit protection: r1, r2, zd1, c5, ic1, d5 and r4. And off cource you can use diode bridge rectifier, transformer with single secondary winding and I would use c3 and c4 low esr with higher value.
Hope I will have irf3205, irfz44n, irfz48n or irf540 yesterday and be testing more. They have less Rds(on) like irlz24n in Sigma11.
I don't know how good is this voltage regulator in comparison with Sigma11. I tested it with my mosfet amp and I noticed a bit strange colored sound. But I guess that is because that high Rds(on) off irf520. Or maybe it is how it should sound. I had 78s12 regulator and now I'm using lm317t which is a bit better and I believe with a bit more bass.
Edit: I'm currently using this regulator with 12V transformer and works great. Vin drops to 15,9V, Vout is set to 15V (!) and Iout is 0,5A. So no need for huge Vin-Vout voltage as with 7812, LM317T or other regulators.
Here's a link, but I don't know who the author was: http://www.extremecircuits.net/2010/06/ultra-low-drop-linear-voltage-regulator_14.html .
I copy it here just in case.
Here's the original text:
This circuit is a Mosfet-based linear voltage regulator with a voltage drop of as low as 60mV at 1A. The circuit uses a 15V-0-15V transformer and employs an IRF540 N-channel Mosfet (Q1) to deliver the regulated 12V output. The gate drive voltage required for the Mosfet is generated using a voltage doubler circuit consisting of diodes D1 & D2 and capacitors C1 & C2. To turn the Mosfet fully on, the gate terminal should be around 10V above the source terminal which is connected to the DC output. The voltage doubler feeds this voltage to the gate via resistor R3. IC2, a TL431 adjustable shunt regulator, is used as the error amplifier. It dynamically adjusts the gate voltage to maintain the regulation at the output. With an adequate heatsink for the Mosfet, the circuit can provide up to 3A output at slightly elevated minimum voltage drop.
Trimpot VR1 is used for fine adjustment of the output voltage. The RC network consisting of R5 and C6 provides error-amplifier compensation. The circuit is provided with short-circuit crowbar protection to guard against an accidental short at the output. This crowbar protection works as follows: under normal working conditions, the voltage across capacitor C5 will be 6.3V and diode D5 will be reverse-biased by the output voltage of 12V. However, during output short-circuit conditions, the output will momentarily drop, causing D5 to conduct. This triggers the MOC3021 Triac optocoupler (IC1) which in turn pulls the gate voltage to ground. This limits the output current. The circuit will remain latched in this state and the input voltage has to be switched off to reset the circuit.
I tested this circuit today and it works but I didn't have irf540 but irf520. So i needed to tweak resistors r6, r7 and r8. And I left out short-circuit protection: r1, r2, zd1, c5, ic1, d5 and r4. And off cource you can use diode bridge rectifier, transformer with single secondary winding and I would use c3 and c4 low esr with higher value.
Hope I will have irf3205, irfz44n, irfz48n or irf540 yesterday and be testing more. They have less Rds(on) like irlz24n in Sigma11.
I don't know how good is this voltage regulator in comparison with Sigma11. I tested it with my mosfet amp and I noticed a bit strange colored sound. But I guess that is because that high Rds(on) off irf520. Or maybe it is how it should sound. I had 78s12 regulator and now I'm using lm317t which is a bit better and I believe with a bit more bass.
Edit: I'm currently using this regulator with 12V transformer and works great. Vin drops to 15,9V, Vout is set to 15V (!) and Iout is 0,5A. So no need for huge Vin-Vout voltage as with 7812, LM317T or other regulators.