X-bit labs

3 Zalman Power Supply Units Roundup (page 2)

Category: Other

by Oleg Artamonov

[ 03/12/2004 | 02:09 AM ]

The PSU deviates somewhat from the industry-accepted standard as it uses the relatively rare single-cycle circuit. Accordingly, the high-voltage rectifier at the input has one 180uF, which corresponds to two 360uF capacitors in the ordinary two-cycle circuit. The capacitance is rather low for a 300W PSU, but this model uses active power factor correction and has demands less from the capacitance of the rectifying capacitor.

The manufacturer also took care of the heatsinks, which have exactly the necessary thickness, about 4mm. It is a fact that the thinner the heatsink is, the wider the temperature gradient along this heatsink is. That is, the insufficient heat conductivity of the thin aluminum sheet results in the temperature on top of the heatsink being much lower than that at the bottom (where the heat-producing transistors and diodes are fastened). So the top of the heatsink doesn’t play any role in cooling. Practice shows that the 4mm thickness is the most reasonable choice for a small heatsink – without spending extra material, but providing enough cooling. Larger heatsinks may require to be around 6-7mm thick, but they are not for standard computer PSUs then.

Among other pleasant trifles we may notice the diode assemblages and transistors placed into liquid paste for better heat conductivity (besides the standard heat-conductive isolators) and equipped with ferrite pipes on their pins for filtering high-frequency noise. Regrettably, such care about small things is rare nowadays…

I was most curious to see the cooling of the PSU. Zalman promotes actively its Computer Noise Prevention System brand claiming that equipment under this brand contributes to making your computer less noisy. Meanwhile, we have an ordinary 80mm fan (Protechnic Electric MGA8012HB) here, which is also installed into other PSU models from FSP. The fan is connected via an automatic rotation speed controller (you can see its sensor on top of the heatsink with the output diode assemblages). As our measurements showed, the fan speed is increasing steadily from 1370 to 1900rpm as the load grows from 50 to 280W. There is no activation threshold as in other models from Fortron/Source (for example, in FSP300-60BTV) – the speed increases smoothly. The fan produces some noise, of average loudness, not annoying. However, this PSU can’t be called perfectly noiseless.