Apparatus and methods for generating an AC power signal for cable tv distribution systems

DETAILED DESCRIPTION In copending U.
S.
patent application Ser.
No.
07/967,773, the Applicant recognized that the steeply rising AC power signal generated by prior art power supplies in standby or inverter mode can cause the interference problem discussed above.
Specifically, the RF coupling capacitor 88 and transformer winding 92 form an integrator circuit that generates a voltage spike for each leading and trailing edge of each half-cycle of the AC power signal.
These brief voltage spikes saturate the taps and prevent passage of the cable TV signal twice during each cycle of the AC power signal.
In the '773 application, the Applicant thus proposed that these leading and trailing edges must be shaped in a manner that eliminates this saturation of the taps.
Specifically, the Applicant disclosed generating an AC power signal having at least a positive half-cycle, where the positive half-cycle comprises a rising portion, a falling portion, and a central portion.
The slew rate of the AC power signal within the rising portion should be limited in the environment of the cable TV distribution system to a range of 30 V/ms to 50 V/ms inclusive.
Preferably, the slew rate of the AC power signal within the falling portion is limited to the range of -30 V/ms and -50 V/ms inclusive.
This method results in a waveform that does not cause saturation of the taps under normal circumstances.
The AC power signal disclosed in the '773 application may alternatively be defined as an AC power signal having at least a positive half-cycle, where the positive half-cycle comprises a rising portion, a falling portion, and a central portion that is relatively flat in comparison to the rising portion.
Within the rising portion, the AC power signal is so limited that the AC power signal remains within a range inclusively defined by (a) a first line segment extending between a first point at the beginning of the rising portion and a second point at the end of the rising portion, and (b) a first curve segment of a first sinusoidal curve having the same period as the AC power signal, the first curve segment extending between the first and second points