Short answer: No. In precision applications, switching noise is often cited as a concern. But at high power levels (>1kW), noise (typically 5-50mVrms) is acceptable because high-power loads are less sensitive, and recovery time matters more than noise floor[1].
01.The Scale of the Problem
When moving from lab bench (30V/3A) to industrial rack (600V/20A), the physics changes.
A 1kW Linear supply is size of a mini-fridge and weighs 50kg. A 1kW Switching supply is a 1U rack unit weighing 5kg.
The trade-off is switching noise. But does it matter?
02.Reality Check: Your Load
| Application | Sensitivity | Verdict |
|---|---|---|
| Resistive Heating | Nil | NOISE IRRELEVANT |
| Electroplating | Low | NOISE IRRELEVANT |
| Inverter Testing | Moderate | CHECK SPECS |
| Accelerator Magnets | High (Stability) | STABILITY MATTERS |
For 90% of high-power applications, Line Regulation (stability against input changes) and Load Regulation (stability against load changes) are 100x more important than PARD.
03.The "Clean Switching" Era
Early switching supplies were notoriously noisy (500mVpp+). Modern industrial units utilize ZVS (Zero Voltage Switching) topology.
By switching only when the voltage across the transistor is zero, switching losses and EMI are drastically reduced. Furthermore, switching noise occurs at high frequencies (>50kHz), which is easier to filter out than the 50/60Hz "hum" of linear transformers.
[ KEY INSIGHT ]
A modern 3kW Switching Supply often has less effective ripple energy than a budget Linear Supply because the noise is pushed into frequencies that your load (e.g., a heater's thermal mass) simply cannot see.
04.Sourcing Strategy
If you are building an industrial test rack, do not repurpose IT server power supplies. They lack the adjustable CV/CC control loops required for engineering loads.
Always verify the Recovery Time spec (typically <2ms) rather than obsessing over an extra millivolt of noise floor.
Frequently Asked Questions
Is 50mV of noise acceptable for high-power applications?
Yes, for most industrial loads >1kW. Resistive heaters, electroplating baths, and motor controllers are insensitive to 50mV ripple. The load's impedance is typically low enough that voltage variations of this magnitude have negligible impact.
What is recovery time and why does it matter?
Recovery time is how fast the supply returns to the set voltage after a load transient. For high-power applications, a <2ms recovery time is critical to prevent voltage sag during motor startup or pulsed loads.
This matters more than noise floor because a slow recovery can cause:
- Brownouts during load steps
- False fault triggers in control systems
- Unstable operation of DC motors
Can I use a server power supply for lab testing?
No. Server PSUs are designed for fixed-voltage IT loads and lack:
- Adjustable voltage/current control
- CV/CC crossover modes
- Front-panel metering
- SCPI programmability
Use a dedicated lab power supply with proper CV/CC control loops.
References
[1] Wikipedia: Switched-mode Power Supply - Technical overview of SMPS topologies