# Bridge Rectifier and control circuit

#### MisterFisk

Joined Jun 8, 2020
18
Good day,

I was hoping someone could help me understand this circuit.

As far as I understand the circuit its a Bridge rectifier, where C1 acts as a smoothing capacitor. X2 and X3 are OP amps and they serve to raise the Max voltage of the circuit of which the load is R5.

I am uncertain what the circuit around X1 is used for.

Any help would be appreciated.

#### Attachments

• 120.7 KB Views: 130

#### wayneh

Joined Sep 9, 2010
17,153
... C1 acts as a smoothing capacitor.
Agreed. Steady power for the op-amps.
X2 and X3 are OP amps and they serve to raise the Max voltage of the circuit of which the load is R5.
No voltage increase. X3 is configured as a comparator to switch the MOSFET full on or full off.
I am uncertain what the circuit around X1 is used for.
Me too. I suspect it oscillates and then the frequency (or duty cycle?) at the MOSFET is controlled by that. You could look over a list of standard op-amp circuits and identify how X1 is configured. I've seen it before but don't recall the purpose.

An LTspice simulation would be interesting.

#### LesJones

Joined Jan 8, 2017
3,476
I think I understand what the circuit does but as this is homework you would learn nothing if I told you. Instead I will ask you what you expect the waveform to be on the output of X2 and to draw this below the incoming sine wave. I think this should make you realise the function of X1 and Q2.
Thinking about the purpose of diode D1 should help.
Les.

#### MisterFisk

Joined Jun 8, 2020
18
Agreed. Steady power for the op-amps.
No voltage increase. X3 is configured as a comparator to switch the MOSFET full on or full off.

Me too. I suspect it oscillates and then the frequency (or duty cycle?) at the MOSFET is controlled by that. You could look over a list of standard op-amp circuits and identify how X1 is configured. I've seen it before but don't recall the purpose.

An LTspice simulation would be interesting.
You wouldn't happen have a link to a list where I can research this?

#### Ian0

Joined Aug 7, 2020
3,186
I hope X2 is the type of op-amp that will withstand its negative input being taken to a voltage higher than its positive supply.

#### MrAl

Joined Jun 17, 2014
8,473
Good day,

I was hoping someone could help me understand this circuit.

As far as I understand the circuit its a Bridge rectifier, where C1 acts as a smoothing capacitor. X2 and X3 are OP amps and they serve to raise the Max voltage of the circuit of which the load is R5.

I am uncertain what the circuit around X1 is used for.

Any help would be appreciated.
Hi,

Here is a hint in case you did not realize this yet.
One or more of those op amps is being used as a voltage comparator rather than an actual linear op amp. That tells you something about their output too. Ask the question why would the designer want to do that.

#### jean_neau

Joined Apr 7, 2020
2