Philpis PE1535 power supply

[maher471]

Hello,
just a little question about the Philips power supply PE1535, why the negative power supply realized with VZ113, V114 and V115 that produce -10v are connected to the positive output X2

[AndersJ]

Perhaps to help reaching 0V output.
Disconnect the -10V and see what happens.

[coromonadalix]

hum

I think it could be an error or its okay  in the schematic ??  but the surrent sense resistor is in the negative rail, could be okay

Yes  it help to negate the regulator minimal output voltage around 1.2 - 1.5 volts,   the lm723 by design  doesn't go down to zero volts

One of my old design use this scheme ... i have a perfect zero volt ...


Normally the negative voltage is added in the voltage feedback potentiometer circuit,  some google search on some projects will show you that

[maher471]

link to original manual :
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Philips/PE1535%20-%20PE1545.pdf

[blackdog]

Hi  maher471, 

The negative power suply is primarily intended as a sort of a "current source" to improve the dynamic behavior and to compensate for the current required for the power section to operate properly to achieve "0V" output voltage.

Kind regards,
Bram

[maher471]

So if I understand correctly :
1- This negative power supply acts as a load at the output of the power supply, but what is the limit of this method?
2- What are the advantages and disadvantages of this method

[coromonadalix]

Its to get an ov output as  explained earlier, the lm723  can't go down to zero volts  unless you use this kind of trick,

the limit is this application, for the rest you calculate the voltage  potentiometer and the voltage feedback parts values to suit your needs