Printhead Drive Pulse Width Control Circuit - Epson LX-HOO Technical Manual

2.4.7.2 Printhead Drive Pulse Width Control Circuit

In order to keep the value of the printhead drive pulse width constant, the CpU monitors the +24 VDC
line, the printhead common voltage, and uses the voltage level to adjust the width of the FIRE signal.
The printhead drive pulse width is controlled to be within the area shown by the oblique lines in Figure
The CPU monitors the +24 V line at AN5 of the 8-bit analog to digital converter, computes the result,
and controls the drive pulse width of the signal (FIRE) output from the event timer. 4.7 V is applied to
reference voltage input VAref by ZD3, and the voltage obtained by dividing +24 V by R37 and R35
(approximately 4.08 V at +24.OV) is input to AN5.
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Fig. 2-30. Printhead Drive Pulse Width Range
+ 5
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Fig. 2-31. +24 VDC Monitor Circuit
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2 . 2 K l/2W
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26.4