Prevent power supply oscillation

[Jony130]

Prevent power supply from oscillation

Hi,
I build in LTspice some old power supply using LM723.
But this circuit start oscillate when entering constant current mode.
Someone has any idea how prevent this oscillation?

 

[Sceadwian]

You're not using an input or output supply bypass caps... That'd be a good place to start!

 

[RCinFLA]

Your separate current limiting circuit is operating too fast for its loop gain. Slow it down with an RC somewhere in the feedback path or reduce its gain. The LM358 on output should not be operated at open loop gain. If you are trying to get an overcurrent latched shutdown then you need to add a latch with a manual reset Otherwise the circuit must operate in linear mode where the regulator output voltage is reduced until an equilibrium is reached at the desired maximum output current.

 

[Boncuk]

The LM723 starts oscillating if its output current is abruptly reduced to zero.

In 99% of all those cases it will fry instantaneously.

Depending on the output voltage take care of a steady current flow of 10mA. (still 90mA to play with).

Boncuk

 

[RCinFLA]

Used them many times, never had problem. You should be using the 100 pF comp cap to -inv input.

The only thing all the extra current limit circuitry will buy you is tighter current control over temp and maybe less voltage drop then the 0.6v for internal cutback NPN Vbe.

 

[Jony130]

The op amps circuit add constant current mode. So power supply should act just like a constant current source.
CC mode triggers when the load current reach

[LATEX] I = \frac{V6}{ 1 + \frac{R17}{R10} * R6} = \frac{V6}{2.3} [/LATEX]

Where V6 is a voltage set by P6 potentiometer.

But this circuit when entering CC mode start to oscillate

 

[Sceadwian]

..... There are no buffering capacitors....
What magic can an IC create the overcome that?