Отправлено IVX 25 ноября 2003 г. 22:31 В ответ на: Виноват, неправильно выразился, совсем другое имел в виду отправлено -=Shura=- 25 ноября 2003 г. 12:20

Tripath appnote:
"Low-frequency Power Supply Pumping
A potentially troublesome phenomenon in single-ended switching amplifiers is power supply pumping.
This is caused by current from the output filter inductor flowing into the power supply output filter
capacitors in the opposite direction as a DC load would drain current from them. Under certain
conditions (usually low-frequency input signals), this current can cause the supply voltage to “pump”
(increase) and eventually cause over-voltage/under-voltage shut down. Moreover, since over/undervoltage
are not “latched” shutdowns, the effect would be an amplifier that oscillates between on and
off states. If a DC offset on the order of 0.3V is allowed to develop on the output of the amplifier (see
“DC Offset Adjust”), the supplies can be boosted to the point where the amplifier’s over-voltage
protection triggers.
One solution to the pumping issue is to use large power supply capacitors to absorb the pumped
supply current without significant voltage boost. The low frequency pole used at the input to the
driver determines the value of the supply capacitor required.
Another solution to the supply pumping problem uses the fact that music has low frequency
information that is correlated in both channels (it is in phase). This information can be used to
eliminate boost by putting the two channels of a TA0104A amplifier out of phase with each other.
This works because each channel is pumping out of phase with the other, and the net effect is a
cancellation of pumping currents. The phase of the audio signals needs to be corrected by
connecting one of the speakers in the opposite polarity as the other channel."