Epson LQ-2550 Technical Manual page 122

2.3.5.2 Printhead Drive Circuit
The printhead drive circuit converts the print signals output from the E05A02LA into printhead coil drive
voltages. The major drive circuits are incorporated in hybrid IC STK66082E ( 1 A). Figure 2-72 shows
the equivalent circuit.
Refer to Appendix A.1.l.l 4 for the details of the STK66082E.
c o o
SUB CPU
(7B)
PC7
*1: +35 V Switching Transistor
*2: +35 V Power Transistor
*3: Printhead Coil Switching Transistor
The functions of each section are as follows.
+35 V Switching Transistor
This transistor turns on when both printhead drive pulse HPW from the sub CPU and chopper type drive
signal PNPON are LOW.
+35 V Power Transistor
This transistor outputs +35 V to common lines P 1 through P8 when the 35 V switching transistor is
on.
Coil Switching Transistor
This transistor corresponds to outputs H 1 through H24 of the E05A02 LA. The E05A02LA transmits
the print signal to this transistor when HPW is LOW. When the print signal is active, this transistor turns
on. When the transistor turns on, ~ through N24 are shorted by GH, current flows to the printhead
coil from the +35 V line, and printing is executed.
Figure 2-73 shows the printhead drive circuit signal timing.
DNP1
- t - - - J
Figure 2-72. Printhead Drive Equivalent Circuit
* 3
2
2-76
+35 ~ ,
I
2 4
Coil