Transient Response
These tests monitor the response of the power supply in two different scenarios. First, a transient load (15 A at +12V, 6 A at +5V, 6 A at +3.3V, and 0.5 A at 5VSB) is applied to the power supply for 20 ms while it is operating at 20% load. In the second scenario, the power supply, while operating at 50% load, is hit by the same transient load. In both tests, our oscilloscope measures the voltage drops caused by the transient load. All voltages should remain within the control limits defined by the ATX specification.
In real-world operation, a power supply always operates under varying loads, depending on whether the CPU or the graphics card is busy. It is of immense importance that the power supply is able to keep its rails within the limits defined by the ATX specification. Smaller deviations reduce the load on the system components. Note that the ATX specification requires capacitive loading during transient testing, but in our methodology we chose to apply the worst-case scenario with no additional capacitance on the rails. Although the ATX specification mandates this capacity, a system at the end user – the motherboard and its other parts – may not provide it, and this must also be taken into account.
| Advanced Transient Response 20% – 50 Hz | ||||
|---|---|---|---|---|
| Voltage | Before | After | Change | Pass/Fail |
| 12 V | 12.035V | 11.854V | 1.50% | Passport |
| 5 V | 5.026V | 4.962V | 1.27% | Passport |
| 3.3 V | 3.280V | 3.199V | 2.47% | Passport |
| 5VSB | 5.011V | 4.967V | 0.88% | Passport |
| Advanced Transient Response 50% – 50 Hz | ||||
|---|---|---|---|---|
| Voltage | Before | After | Change | Pass/Fail |
| 12 V | 11.984V | 11.887V | 0.81% | Passport |
| 5 V | 5.019V | 4.954V | 1.30% | Passport |
| 3.3 V | 3.277V | 3.192V | 2.59% | Passport |
| 5VSB | 4.997V | 4.943V | 1.08% | Passport |
Switch-on load peaks
In the next test series, we measure the behavior of the power supply in simpler scenarios with transient load – during the power-on phase of the power supply. In the first test, we turn off the power supply, select the maximum current the 5VSB can output, and then turn on the power supply. In the second test, we select the maximum load that can handle +12V and turn on the power supply while the power supply is in standby mode. In the final test, we select the maximum load the +12V rail can handle while the PSU is completely off (we disconnect the power or turn off the PSU by flipping its on/off switch) before turning on the PSU via the loader and restoring power. The ATX specification states that the recorded voltage peaks on all rails should not exceed 10% of their nominal values (e.g. +10% for +12 V is 13.2 V and 5.5 V for +5 V).
Inrush current (Inrush)
Inrush current or inrush current surge refers to the maximum instantaneous input current drawn by an electrical device when it is first switched on. A sufficiently large inrush current can cause circuit breakers and fuses to trip and can also damage switches, relays and bridge rectifiers. Therefore, the lower the inrush current of a power supply directly at switch-on, the better. The inrush current of 52.6 A is low for a 230 V input, and the same applies to 115 V.
Leakage Current
We use a GW Instek GPT-9904 as an electrical safety tester to measure the so-called leakage current. According to the IEC-60950-1 regulation, no power supply should exceed a leakage current of 3.5 mA, which is low enough not to harm anyone touching the enclosure. This test is performed at 110% of the rated input voltage. The leakage current is pleasingly low at 1.05 mA.
- 1 - Unboxing, Vorstellung und technische Daten
- 2 - Anschluss-Kabel und Kabel-Management
- 3 - Innerer Aufbau und Komponenten
- 4 - Spannungsregulation und Restwelligkeit (Ripple)
- 5 - Effizienz
- 6 - Geräuschemission und Lüfterdrehzahlen
- 7 - Crossload im Detail
- 8 - Timing Tests
- 9 - Erweiterte Transienten-Tests
- 10 - Schutzfunktionen, Power Sequencing, EMV
- 11 - Zusammenfassung und Fazit
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