How does this shunt regulator work?

[zhi_yi]

hi there, please help me, please tell me how do this shunt regulator circuit works? and please tell me what is the advantages and the disadvantages of this circuits?

thank you

 

[IanP]

Re: Shunt Regulator 1

As it is it will not work at all ..
You will need to reverse the transistor so its emitter is connected to the zener diode and collector to Rs ..
After this "modofocation" transistor will be "open" if its base voltage is higher than Vz+0.7V = Vload *R1/(R1+R2) .. so Vload=(Vz+0.7V)*(R1+R2)/R1
The disadvantage of this circuit is that the control current has to be conducted by zener diode ..
Reards,
IanP

 

[echo47]

Shunt Regulator 1

It will work if Vin is negative, but rather poorly because it uses Vbe as the reference.
Yes, it's probably misdrawn.

 

[zhi_yi]

Re: Shunt Regulator 1

thank you very much


the circuit would not work at all if the Vin is positive, is it the reason is because if the Vin is positive, then the emitter and the collector would be reverse biased, and the base voltage that need to overcome the Vbe in emitter is negative, so the emitter base diode would be reverse biased, so the transistor would be off, is it?

and if i reverse the transistor, the collector would be in reverse biased, and base would be forward biased if the base voltage is higher thank Vz + Vbe, right? and if the base voltage is higher than Vz + Vbe, the transistor would be active, is it? and Vb = Vout * R1/(R1+R2) (if we ignored the current flow into the base), and then Vout = (Vz+Vbe) * (R1+R2)/R1, so, if i want the circuit become more efficient, i need to use higher resistance of R1 and R2, so the current would flow to the load, is it true?? please correct me..

thank you..

 

[jawadasheikh]

Re: Shunt Regulator 1

use the transistor its emitter is connected to the zener diode and collector to Rs