Epson LQ-2550 Technical Manual page 142

REV.-A
Each block in the PF
1. Phase Drivers (A to D)
These drivers are turned on and off upon receiving the drive pulses A02 to D02 from the MCU (4 B).
When the input signal is HIGH, the corresponding phase driver turns on.
2. PF Motor Power Switches (A/C phase and B/D phase)
This switch is turned on and off upon receiving the output from CMP 1 (CMP2). When the output from
the CMP1 (CMP2) is HIGH, +35 V is applied to
3. Current Detection Resistors (R95 end R94)
Voltage is induced across the current detection resistors in proportion to the current that flows to the
PF motor coil. The voltage is input to the minus terminal of CMP1 (CMP2).
4. Reference Voltage Circuit
The current applied to the PF motor coil is determined by the reference voltage applied to the plus
terminal of CMP1 or CMP2.
5. CMP1 and CMP2
terminal, which is from the current detection resistor (R95 or R94). When the reference voltage is lower
than the voltage across the current detection resistor, the output goes LOW.
6. Surge Voltage Absorbing Circuit
When a phase driver changes from on to off, a surge voltage is induced due to reactance in the motor
coil. This voltage is absorbed by ZD5 via flywheel diode DA or DC (DB or DD).
7. Driving/holding Control
Driving and holding of the PF motor is controlled by the POT3 terminal of the MCU (4 B). When the output
at the terminal is HIGH, the motor is held, and when it is LOW, the motor is driven. When the motor
is held, the PF motor power switch turns off, and + 5 V is applied to
motor drive circuit is described below.
2-96
via D 16 and R99