Protection Features
Desktop power supply units (PSUs) include several protection features to safeguard both the PSU itself and the connected PC components (motherboard, CPU, GPU, drives, etc.). These protections prevent damage from electrical faults, overloads, or abnormal conditions.
| OCP (Normal @ 28.9°C) | 12V: 124.20A (124.20%), 11.938V 5V: 31.8A (127.20%), 4.99V 3.3V: 33.9A (135.60%), 3.284V 5VSB: 5.4A (180.00%), 4.943V |
| OCP (Hot @ 46.2°C) | 12V: 120.40A (120.40%), 11.941V 5V: 31.7A (126.80%), 4.992V 3.3V: 33.7A (134.80%), 3.288V 5VSB: 5.2A (173.33%), 4.948V |
| OPP (Normal @ 28.7°C) | 1452.41W (121.03%) |
| OPP (Hot @ 45.3°C) | 1412.40W (117.70%) |
| OTP | ✓ (107°C @ Heat Sink) |
| SCP | 12V to Earth: ✓ 5V to Earth: ✓ 3.3V to Earth: ✓ 5VSB to Earth: ✓ -12V to Earth: ✓ |
| PWR_OK | Proper Operation |
| UVP (Full Load @ 90V) | ✓ |
| UVP (No Damage @ 80V) | ✓ |
| Conducted Emissions EN55032 & CISPR 32 | ✓ |
| NLO | ✓ |
| Fan Failure Protection | ✗ |
| SIP | Surge: MOV Inrush: NTC & Bypass Relay |
The OCP triggering points are conservative at 12V under normal and hot conditions, and the difference between them is satisfactory. The 5V rail’s OCP triggering points remain below 130%, but due to the high nominal values, it reaches 32A under both normal and hot conditions. The 3.3V rail is also allowed for even higher amperage, which is not correct since no modern system requires so much power from this rail. Lastly, the minor rails have closely set OCP triggering points under normal and hot conditions, which is not ideal.
The over power triggering points are conservative, but I would like to see a larger difference between normal and hot conditions. The rest of the essential protection features are present and function well, except for fan failure protection, which is not implemented. Manufacturers have to quickly realize that fan failure protection is crucial and start implementing it in their designs.
EMC Pre-Compliance at a Glance
Every electronic device, including PSUs, can be an EMI source, which, depending on the amount of EMI emitted, can affect the proper operation of nearby devices. EMI can, in some extreme cases, even render them unusable. Some standards have been established to minimize electromagnetic interference (EMI) noise. The corresponding standards for IT (Information Technology) products are CISPR 32 and its derivative, EN 55032, which applies to products sold in the EU. In the EU, every product bearing the “CE” marking must comply with the EN 55032 standard. CISPR 32 and EN 55032 standards categorize devices into two classes: A and B. Class B equipment is intended for domestic environments. Hence, its permitted EMI emissions are significantly lower than those of A-class devices.
Our equipment for EMI readings:
- Rohde & Schwarz FPC1500 (loaded with all options)
- Tekbox TBLC08 LISN
- Tekbox TBFL1 transient limiter
- Tekbox EMCview software
| CISPR 32 / EN55032 Limits | ||
| CISRP 32 / EN 55032 Class A Conducted EMI Limit | ||
| Frequency of Emission (MHz) | Conducted Limit (dBuV) | |
| Quasi-peak | Average | |
| 0.15 – 0.50 | 79 | 66 |
| 0.50 – 30.0 | 73 | 60 |
| CISPR 32 / EN 55032 Class B Conducted EMI Limit | ||
| Frequency of Emission (MHz) | Conducted Limit (dBuV) | |
| Quasi-peak | Average | |
| 0.15 – 0.50 | 66 – 56 | 56 – 46 |
| 0.50 – 5.00 | 56 | 46 |
| 5.00 – 30.00 | 60 | 50 |
| CISRP 32 / EN 55032 Class A 10-Meter Radiated EMI Limit | ||
| Frequency of Emission (MHz) | Field Strength Limit (dBuV/m) | |
| 30 – 88 | 39 | |
| 88 – 216 | 43.5 | |
| 216 – 960 | 46.5 | |
| > 960 | 49.5 | |
| CISRP 32 / EN 55032 Class B 3-Meter Radiated EMI Limit | ||
| Frequency of Emission (MHz) | Field Strength Limit (dBuV/m) | |
| 30 – 88 | 40 | |
| 88 – 216 | 43.5 | |
| 216 – 960 | 46.0 | |
| > 960 | 54.0 | |
Please note that the ATX spec allows a 4 dB margin for conducted and radiated emissions. This means that if a PSU exceeds the limits but stays within the 4 dB margin, it meets the corresponding ATX spec requirement (8.1 Emissions).
EMI Results
The PSU’s EMI emissions are under control.
