[Dreamslacker]

As above.

I have no formal education in electronics, so I need to check with you guys here. Is the following circuit possible for a high current shunt using a TL431? If not, would it be that the emitter must point to the output?

I'm trying to make a dual-voltage shunt regulated psu.

Thanks.

 

[Dreamslacker]

 

[jasonhanjk]

Very funny design you got there... Have not seen it before but this circuits seems like acting a switch between Vss and ground. May not work.

 

[zzz]

you're missing a series resistor (that's a shunt after all) + tl431 won't be able to control an npn transistor like this as its cathode doesn't like to swing below the reference voltage (your circuit has ~2.5v vref and ~0.6-0.7v cathode).

what you want is fig. 21 in http://focus.ti.com/lit/ds/symlink/tl431.pdf .

 

[Dreamslacker]

Quote:

Originally posted by zzz you're missing a series resistor (that's a shunt after all) + tl431 won't be able to control an npn transistor like this as its cathode doesn't like to swing below the reference voltage (your circuit has ~2.5v vref and ~0.6-0.7v cathode). what you want is fig. 21 in http://focus.ti.com/lit/ds/symlink/tl431.pdf .

Hrmm.. I see.... I always thought the cathode voltage was at Vref.. Lol.. Looks like I made a mistake there.

In this case, if I want to build a dual-voltage psu, would the circuit be as follows?

 

[alsq]

Application question:

When is it a good idea to use a shunt regulator
instead of a linear regulator or some other
flavor of regulator?

 

[Dreamslacker]

Realised that I made a mistake in the 2nd picture.

So if I want a postive + negative high current shunt regulator, do i stack the datasheet's circuit one on top of another?

Like this:

 

[rickcr42]

Quote:

Application question:

mostly for bandwidth and transient response.i use shunt regs for my dacs and my class A followers

since there is nothing in series with the DC voltage the bandwidth is high and the tranmsient response good.

the shunt reg works like it sounds-it shunts exess voltage to ground so what happens when it has a low input voltage (something that happens more than we would like) it just stops regulating and passes the DC voltage from the rectifiers straight through-this CAN be a disaster depending on the circuit and the unregulated /regulated voltage ratio

also not the lowest noise that can be had so i would steer clear for mic or phono preamp applications

 

[Dreamslacker]

Quote:

Originally posted by rickcr42 also not the lowest noise that can be had so i would steer clear for mic or phono preamp applications

I intend to add a cap. multiplier after the shunt. =)