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In Reply to: Save your money and go with dedicated power... posted by mark on January 28, 2001 at 06:23:04:
I feel that the regeneration of power like the PS approach is not an optimum solution as a unit like this causes additional distortion of the line voltage (on the power line side). As it is well less than 100% efficient, more distortion is generated than the original equipment that is being powered generates. A solution like the PS could offer overall system performance improvement when it is used on low-power equipment in the system such as preamps and music-source equipment because it will reduce or eliminate power line harmonics from entering those equipments. In general though, the correct solution to power line voltage distortion is power line harmonic filters. This is the accepted solution in industry for reducing line-frequency harmonics, which are responsible for all sorts of problems. Most modern harmonic filters are actually PWM (switching) power amplifiers that sample the line voltage and inject distortion-bucking current back into the line to reduce the harmonics (distortion).Almost all amplifiers made today generate harmonic distortion on the power line. Harmonic distortion is generated by anything that does not behave like a pure-resistive load. Reactive loads like transformers, inductors, and capacitors tend to generate lead and lag currents, and loads with rectifiers charging capacitors generate 3rd and higher-order harmonics, assuming full wave rectifiers, (half-wave generate even-order harmonics too). Rectifier loads on the secondary of a power transformer are reflected back through the transformer to the line. All of this is why the PS approach makes so little sense for a power amplifier, that is, the amplifier's power supply itself is the major source of the line voltage harmonic distortion.
There are two ways to make an amplifier so that it generates minimal harmonic distortion on the power line. One approach is to have a choke input to the filter (continous conduction mode), that is, no capacitor directly after the rectifier. Any filiments should be ac heated, and a capacitor will probably have to be put across the line to correct any transformer and choke phase lag distortion that will appear as harmonic distortion in current draw. The other way to do it is active power-factor correction, as in integral part of a switching power supply.
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Follow Ups
- Re: Save your money and go with dedicated power... - DBerning 05:32:44 01/30/01 (0)
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