| 摘要 |
<p>A lamp power measurement circuit (73) measures average power delivered to a gas discharge lamp (14). The circuit (73) includes a voltage sensor (62) having a first measurement output (72) representative of AC voltage across the lamp (14) and a current sensor (60) having a- second measurement output (70) representative of AC current through the lamp (14). A first absolute value circuit (80) is coupled in series with the first measurement output (72) and has a first absolute value output (102). A second absolute value circuit (78) is coupled in series with the second measurement output (70) and has a second absolute value output (100). A pulse width modulator (82) modulates one of the first and second absolute value outputs (78, 80) with the other of the first and second absolute value outputs (78, 80) and has a pulse width modulated output (104). A low-pass filter (84) is coupled in series with the pulse width modulated output (104) and has a DC voltage output (88, 90) representative of average power dissipated through the lamp (14).</p> |
