Two supplies can both be called 400 W and still cover very different jobs. One gives you its full current only up to a fixed voltage. The other trades voltage for current along its power limit, so the same box runs a 36 V motor driver in the morning and a 5 V FPGA board in the afternoon.
Shaded blue: everything the UDP5000 model can deliver. Yellow and pink outlines: two fixed-range supplies with the same power rating. The dot is your test point.
A rectangle or a curve
A fixed-range supply has a maximum voltage and a maximum current, and its rated power is their product. A 400 W fixed-range supply might be 40 V and 10 A. Every point inside that rectangle works. A 5 V load that needs 30 A does not, even though it only asks for 150 W.
A wide-range supply has a larger voltage limit and a larger current limit, and its output is held under the rated power by the control loop. The operating area is bounded by the power curve, V × I = P, between the two limits. The UDP5040-40 reaches 40 V or 40 A, at up to 400 W in any combination.
A fixed-range supply has a power ratio of 1. Every UDP5000 model has a ratio of 4: 40 V × 40 A ÷ 400 W on the UDP5040-40, and 800 V × 2 A ÷ 400 W on the UDP5800-2. To cover the same corners with fixed-range supplies you would need a 1,600 W unit, or two smaller supplies on the bench.
What you give up
You cannot have full voltage and full current at the same time. At 40 V the UDP5040-40 delivers 10 A, the same as the fixed-range unit. The gain is everywhere else on the curve. If your work really is one fixed point at full voltage and full current, size the supply for that point.
The front binding posts carry up to 10 A. Above that, wire the load to the rear output terminals.
Try this
- On the UDP5040-40, press Middle: 12 V at 30 A, a 12 V automotive module on the bench. The UDP5000 covers it at 360 W. The 40 V / 10 A fixed-range supply runs out of current, and the 10 V / 40 A one runs out of voltage.
- Press High voltage, then High current. The first point fits only the full-voltage rectangle and the second only the full-current one. The shaded area covers both.
- Switch the model to the UDP5250-6 and press Middle. The curve has the same shape at a higher voltage: 250 V or 6 A, up to 400 W.
Power ratio 4 on all 20 models. 40 V to 800 V, 400 W to 2000 W.
See the UDP5000 seriesRelated: Constant voltage vs. constant current · Linear vs. switching supplies. UNI-T. Design. Debug. Deploy.™
