Electronics > Projects, Designs, and Technical Stuff
How do make a current limiting knob using LM723 for Linear Reg power supplies?
Kleinstein:
The Phillips instructions include a view slightly different versions: one for 0-7 V and higher current and also one that is for 20 V and likely about 2 A. But it is relatively straight forward to change that.
For a high power at least transformer tap switching should be used - but high power should only be version 2 or 3.
oldway:
Many engineers have been working on the project of a 0-30V 0-5A linear lab power supply and the result of their work is what is found on the market ....
Are they all fools or stupids ?
Do you think you can do simpler, cheaper, more reliable ?
Ian.M:
The Fig. 1000 circuit (page 20 of Philips PSU manual, Oldway's Reply #7 link) is about as simple as it gets fror a real PSU that wont let the holy smoke out the first time you connect it to a difficult load.
The specs on page 5 say: PE 1535-00 0V - 40V 0A - 0.5A.
Beefing it up to a 5A supply would be possible with a better pair of pass transistors and a preregulator feeding the pass transistors. However that increases the complexity again . . . . .
oldway:
These Philips power supplies were highly appreciated for their robustness and ease of use.
However, this kind of circuit only applies to limited output power.
For larger power (400W and 1000W), Philips used a thyristors pre-regulator, but their schematics had major design shortcomings and errors, so I do not recomend to use their circuits.
https://elektrotanya.com/philips_pe-1642_1644_1646_1648_0-20-40-75-150v%2C0-20-10-6-3a_400w_bench_psu_1987_sm.pdf/download.html
Kleinstein:
The circuit diagram for the HY3002 has one obvious mistake in the drawing: the emitter of V26A should be at ground level.
To make it cheaper one could use an LM324 for all the OPs and maybe leave out the extra TL431 reference and use the 78xx instead. Chances are one could eliminate the -6V or -12 V internal supply. Still this would be only marginal savings.
The voltage regulation looks a little odd. The way of adjusting the feedback divider usually means the loop gain depends on the voltage setting and thus a compromise type performance. It might lead to instability for the combination of low voltage setting and highly capacitive load.
The phillips circuit for the 7 V/3 A version with two transistors in parallel could be a problem as show - just add emitter resistors and it should be fine. A slightly higher power version (like 30 V 2 A) should be OK -it just needs a lot of heat sink.
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