Contents
- 1Introduction
- 1.1Packaging and accessories
- 2Connectors & cabling
- 2.1Casing & cooling
- 3Input filtering
- 4Primary side
- 4.1+5 V stand-by rail
- 5Secondary side
- 5.1Build quality
- 6Load testing
- 6.1Loading +5 V SB
- 6.2Combined loading
- 6.3Combined loading ripple
- 6.4Crossloading, overloading
- 6.5Crossloading, overloading ripple
- 7Conclusion and evaluation
- 7.1Thanks
Input filtering
The first part of the input filtering inside the Strider Gold S 550 W starts, as usually, directly on the AC inlet with two ceramic Y and one film X capacitor in a heatshrink sleeve. The receptacle is also partially shielded. The wires from the power switch to the main board go through a ferrite core for extra filtration.
The X capacitor itself carries a small daughterboard with Champion Micro CMD02X IC used to discharge the film X caps only after power is lost, not continuously while wasting power. It is a very clever way of saving space and it is also good the board is here as it can also discharge capacitors on the main board if the fuse is intact and the switch is turned on (and if not, the charge stays there and cannot harm anybody touching the plug pins).
The second part of the filtration is on the main power board itself, consisting of two common-mode chokes, two extra Y capacitors and one X capacitor. There is also a metal-oxide varistor (MOV) right next to the input bridge rectifier, not visible on this picture and without any heatshrink. However, thermistor is not present at all so there is no inrush current suppression (beyond the circuit resistance)! Shame on Sirtec.
X capacitors (between phase and neutral) and Y (between phase and ground/neutral and ground, often also between one side of the high-voltage DC and ground) are used to filter out high-frequency ripple from power grid (often from devices which lack filtration because of cost cutting, but also from devices where filtration is very difficult to implement) and also keeps ripple from this unit from entering the grid. Chokes are used for the same reason, together they form an input filter. These components may also (partially) help to filter smaller voltages spikes in the power grid while the MOV is used to suppress more serious spikes (for example from lightning hitting the power grid at a distance). These days, more Y capacitors are used even between rectified ground (ground after an input rectifier) and earth ground to suppress internal interference and keep it from getting to secondary side, because really high-frequency ripple goes everywhere it can to some extent (including coupling through the insulation, metal casing etc.). That is also why the AC wires themselves are often inserted through the ferrite core.
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