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
- 6.2Voltage hold-up time
- 6.3Combined loading
- 6.4Combined loading ripple
- 6.5Crossloading, overloading
- 6.6Crossloading, overloading ripple
- 6.7Fan speed and temperatures
- 7Conclusion and evaluation
- 7.1Thanks
- 8Addendum - working on the unit
- 8.1Discussion
Input filtering
Familiar? Yes. Sirtec spent the money where it needed to be spent here… Not only did they cleverly integrate the Champion Micro CMD02X discharge IC directly on the film X capacitor, but they’ve used the same receptacle and filtering capacitors that they use on most of their units. So they can buy milions of the same components and use them in almost all of their units. Besides the X cap, we have two ceramic Y capacitors. The receptacle is partially shielded, and the AC wires that connect the double-pole switch to the mainboard go through a ferrite toroid inductor.
Next we have here two more Y caps on the main board (and there’s a fifth one by the input capacitor, between the earth ground and the primary common) as well as one flying X film cap, and two common-mode chokes, and both are wrapped in heatshrink. The varistor sits right next to the input rectifier, and there’s also a thermistor in front of the input capacitor. Seems that the Zalman ZM500-GVM isn’t missing anything in this department.
The X capacitors (between the live and neutral) and Y capacitors (between live and ground/neutral and ground) are used to filter out high-frequency ripple that emanate from the power grid. That is the noise of which manifests in the form of feedback from electronic devices which lack adequate filtering due to cost cutting. But also from devices where filtering was very difficult to implement (powerfull devices, i. e. microvawe ovens). It also prevents ripple from this unit itself from feeding back into the grid.
Chokes are used for the same reason, and together with the X/Y capacitors they form an input filter. Such filters are often made as one component, they may also be integrated together with AC receptacle. These components may also (partially) help to filter smaller voltage spikes in the power grid. To suppress more serious spikes (for example from distant lightning strikes hitting the power grid), the MOV (metal-oxide varistor) is used. Thermistor is than used to suppress current spikes when first connecting the unit to power (i. e. flipping the power switch).
The Y capacitors are also often situated between the high-voltage primary and the low-voltage secondary sides. These days, more Y capacitors are used even between primary common (ground after an input rectifier) and earth ground to suppress internal interference and keep it from getting to the secondary side. It is 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 toroid inductor (to suppress such coupling).
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