Epson LQ-510 - Page 66

PRINCIPLES OF OPERATION
REV.-A
Pulse Width Modulation (PWM) Circuit
Figure 2-30 shows the internal circuit of the TL494lC. The output control (pin 13) is fixed at “L,” and SO the
IC’s internal push-pull circuit is never used.
The wired OR of the EA1 and EA2 outputs is input to the negative terminal of the PWM, a sawtooth waveform
from the oscillator is input to the positive terminal, and the PWM modulated waveform is output as shown
in Figure 2-31.
GND
cl
RT
Et
a
CT
El
Dead Time
Control
Non Inv.
Input
PWM COMPARATOR
Figure 2-30. lC494 Internal Circuit
Figure 2-31. PWM Output
This circuit does not perform dead time control.
2-24
LQ-510