20A Regulated Supply
The LM723 is considered obsolete. But the uA723 from TI is still in production.
Design
Not a very complicated power supply. The Application Note in the Datasheet has a
rough schematic of the design used.
Concept of Operations
How the 723 and 2N3055 (pass transistor) go together:
(However, the 2N3055 at the time of this writing is no longer available. A replacement is MJ15003)
uA723 / LM723
- Provides precision reference voltage
- Has an error amplifier
- Has a small internal pass transistor that can sink/source modest current
- Includes current limit sense circuitry
2N3055
- Used as the external series pass transistor
- Handles the heavy load current and power dissipation
- Typical linear regulator topology:
- 723 powered from the input rail (within its limits, usually < 40 V).
- 723 output pin drives the base of the 2N3055 through a resistor.
- The emitter of the 2N3055 is the regulated output.
-
The 723 senses that output via a feedback divider (error amp pins).
Optional: a small value resistor in the 2N3055 emitter (or collector, depending on configuration) goes to the 723's current-sense pins for current limiting.
Implementation Summary
This supply is a 10-15V regulated (LM723 - Datasheet) power supply with 2N3055 pass transistors and computer-grade filter caps. The interface provides APP and Banana
plug access to the supply. A front-panel mounted fuse for over-current,
and a on PCB 15A fuse for over-voltage protection (SCR + Zener).
Features
Amp meter fullscale at 15A, voltmeter fullscale at 15V.
Front panel - clockwise from left:
- Voltage control pot (10-15V)
- Amp meter
- Voltage meter
- LED power light
- Anderson Power Pole jacks (2x)
- Fuse for over-current
- Banana plug (0.75" spacing).
PCB's were hand etched. Stand-offs and aluminum work were
hand machined. Panels were hand-made.
Pictures
Front Panel (hi-res) |
Front Panel (lo-res)
Front Panel 2 (hi-res)|
Front Panel 2 (lo-res)
Side (hi-res)|
Side (lo-res)
Side 2 (hi-res)|
Side 2 (lo-res)
Top (hi-res)|
Top (lo-res)
Top 2 (hi-res)|
Top 2 (lo-res)
Sources
A lot of the parts are free/flea-market sourced. The most expensive part
is the transformer (18 VCT @20A), the rest of the parts are simple
components found at flea-markets, mouser.com, or local
retail (except: AVOID VETCO - they sell over-priced junk and they fired
their most experienced sales staff).
Plan ahead and get parts from Mouser or Digi-Key.