As we mentioned on other articles, the first place we like to take a look when opening a power supply to have a hint about its quality is its filtering stage. The recommend components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor) and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components than that, usually removing the MOV, which is essential for cutting spikes coming from the power grid, and the first coil.

This power supply uses more components than the minimum recommended: three ferrite coils, four Y capacitors, two X capacitors and one MOV (see Figure 17). As the MOV was hidden between the rectifying bridges, the PFC electrolytic capacitor and one of the ferrite coils, we took another picture from this component after we removed the electrolytic capacitors and the rectifying bridges, see Figure 18. Before the standard transient filtering stage there are two ceramic capacitors connected in series with the main AC power wires, which is unusual, as they are not using “X” or “Y” configurations (on these two configuration the capacitors are connected in parallel with the main AC power wires, not in series).

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Figure 16: Transient filtering stage (part 1).

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Figure 17: Transient filtering stage (part 2).

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Figure 18: Detail of the MOV used in this power supply.

Now let’s have a more detailed discussion regarding the components and design used on Tagan TurboJet TG1100-U95.