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IRF6645 Fiches technique(PDF) 8 Page - International Rectifier |
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IRF6645 Fiches technique(HTML) 8 Page - International Rectifier |
8 / 44 page www.irf.com 7 RD-0617 Performance” section, only limited data for the stand-alone Class D power stage is given. For example, results for THD+N vs. Output Power are provided, utilizing a range of different inductors. By changing the inductor and repeating this test, a designer can quickly evaluate a particular inductor. Figure 4. Results of THD+N vs. Output Power with Different Output Inductors Self-Oscillating PWM Modulator The IRAUDAMP4 Class D audio power amplifier features a self-oscillating type PWM modulator for the lowest component count and robust design. This topology represents an analog version of a second-order sigma-delta modulation having a Class D switching stage inside the loop. The benefit of the sigma-delta modulation, in comparison to the carrier-signal based modulation, is that all the error in the audible frequency range is shifted to the inaudible upper-frequency range by nature of its operation. Also, sigma- delta modulation allows a designer to apply a sufficient amount of correction. The self-oscillating frequency is determined by the total delay time inside the control loop of the system. The delay of the logic circuits, the IRS20955 gate-driver propagation delay, the IRF6645 switching speed, the time-constant of front-end integrator (e.g. R25 + R29P, C11 and C13 for CH1) and variations in the supply voltages are critical factors of the self-oscillating frequency. Under nominal conditions, the switching-frequency is around 400 kHz with no audio input signal and a +/-35 V supply. Adjustments of Self-Oscillating Frequency The PWM switching frequency in this type of self-oscillating switching scheme greatly impacts the audio performance, both in absolute frequency and frequency relative to the other channels. In absolute terms, at higher frequencies, distortion due to switching-time becomes significant, while at lower frequencies, the bandwidth of the amplifier suffers. In relative terms, interference between channels is most significant if the relative frequency difference is within the audible range. Normally when adjusting the self-oscillating frequency of the different channels, it is best to either match the frequencies accurately, 0.0001 100 0.001 0.01 0.1 1 10 % 100m 200m 500m 1 2 5 10 20 50 100 200 W TT TTTTTTT |
Numéro de pièce similaire - IRF6645 |
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Description similaire - IRF6645 |
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