Epson DFX-8500 service manual Printhead Drive Circuit Block Diagram

OPERATING PRINCIPLES

2.3.9 Printhead Drive Circuit

Figure 2-27 shows a printhead drive circuit block diagram.

‰￿General :

The print data lines from IC1 are active when they are HIGH. When ports HDR1 (HDL1) to HDR9 (HDL9) of IC1 go HIGH, the FET gates are biased, and the FETs are turned on to apply the current to the printhead coil. At the same time, ports HDRS1 (HDLS1) to HDRS9 (HDLS9) of IC1 go HIGH, the FET gates are biased, and the FETs are turned on because the each printhead coil is driven by bipolar drive method. When the HD port of IC1 goes LOW, the FET is turned off and the printhead coil current is cut.

Two +37 VDC lines (VP1-GP1 on the C204 DRV-B board and VP2-GP2 on the C204 MAIN board) assign the common voltage for the printhead coil. Pins #1, #2, #7, #9, #10, #11, #12, #16, and #17 are supplied by the VP2-GP2 line (CN1 on the C204 MAIN board). Pins #3, #4, #5, #6 #8, #13, #14, #15, and #18 are supplied by the VP1-GP1 line (CN1 on the C204 DRV-B board).

The CPU monitors the printhead temperature and head fan (HF) temperature. When the temperature rises abnormally, printing stops at once until the temperature cools.

The CPU also monitors the printhead driver status, P-channel and N-channel FET respectively. If the printhead driver FET shorts, CPU (IC2) port PDRERR (P-channel) / NDRERR (N-channel) detects HIGH level and the E05B36 (IC1) sends the DRERR (Driver Error) signal to the C204 PSB/PSE board. When the C204 PSB/PSE board receives this signal, it stops the output voltage and the printer beeps.

MAIN Board FTMP

HF Motor Thermistor

FTMP

TMP95C061A

(IC2)

HTMP PDRERR NDRERR

		HFANA
FANA	Q10
E05B36 (IC1)		HFANB
FANAX	Q11
HDR1-HDR9 HDRS1-HDRS9 HDL1-HDL9 HDLS1-HDLS9

VX VP1 GP1 VX VP2 GP2

HF Motor

			Printhead Driver Circuit
		DRV-B Board		1/2
		Printhead Driver
		Circuit	2/2
	VP2	HNSENS	HPSENS	HTMP
	R100		Monitoring NPNs
			Short Circuit
		R101	Monitoring PNPs
			Short Circuit
ZD4
5.1V		ZD1	24V
	GP2
			R98

Printhead Coils 1/2

Printhead Coils 2/2

Printhead Thermistor

R99

GP2

Figure 2-27. Printhead Drive Circuit Block Diagram

Rev. B 2-33