Bench Power Supply
Test Instrument
Adjustable voltage with an adjustable current limit — the current limit is the whole point. Set it just above what the circuit should draw, and your prototype's mistakes cost a red light instead of smoke.
What it looks like
Bench Power Supply
A typical test instrument — exact shape, colour and markings vary between manufacturers.
Types & variants
Key specs
Voltage range
V0–30 V covers most electronics; dual ±15 V channels serve op-amp analog work.
Current limit range
A0–5 A typical. CC mode turns the supply into a current source — also how you safely test LEDs and charge experiments.
CV/CC operation
—Constant-voltage until the load hits the set current, then it folds into constant-current at reduced voltage. Front-panel LEDs show which mode rules.
Ripple & noise
mVppLinear: <1–5 mV (best for RF/audio/ADC work); switchers: tens of mV unless well filtered.
Resolution
mV / mA10 mV/1 mA setting resolution helps micro-power and battery-simulation work.
Markings
Panel: V/A displays per channel, coarse/fine or encoder knobs, CV/CC indicators, output enable button (use it — set first, then enable). Terminals: +, −, and earth (chassis) — note − is floating, not earthed, unless you strap it.
Standard values
Single 30 V/5 A (RD6006/DPS5005 module class, or Korad KA3005 bench class), 30 V/10 A for motors, triple-output (2×30 V + 5 V) for analog labs.
How to choose
1) 30 V/5 A single channel is the sweet spot first supply. 2) Linear (or well-reviewed switcher) for sensitive analog. 3) An output ENABLE button and accurate current limiting are the features you'll bless daily. 4) Programmable output helps automated tests and battery-profile simulation. 5) For MCU work, verify no overshoot on enable — some cheap units spike.
Pinout & package
Banana jacks (4 mm) front panel; use decent leads with croc/hook ends. Floating output allows series-stacking two channels for ± rails or higher voltage (mind ratings).
Example circuits
- Powering a new prototype at 5 V with the limit set to 100 mA — a solder bridge now just lights the CC lamp
- CC mode driving a power LED at exactly 700 mA regardless of its Vf
- Two floating channels in series giving ±12 V for an op-amp circuit
- Slowly raising voltage on a repaired vintage board while watching current for trouble
Common failures
Blown output stage from back-fed voltage (motors, charged capacitor banks, batteries connected reverse), crunchy potentiometers, fan failure then heat death, and cheap units' displays reading optimistically — verify with a DMM.
How to test
Check setpoints against a trusted DMM at several voltages; short the output deliberately with a low current limit set — it must fold to CC gracefully, not bang. Scope the output for ripple and for enable-overshoot before trusting it with a 3.3 V MCU.
Substitutes
USB-PD trigger boards (fixed 5/9/12/15/20 V), a DPS module on a laptop brick, an ATX supply broken out (fixed rails, no CC), or battery + regulator. None replace a real adjustable current limit — that's the feature that saves prototypes.