Epson SEIJ98006 manual EPSON Stylus Color, Revision C, Smoothing circuit, Operating Principles

EPSON Stylus Color 900 Revision C

Once the Q1 is off, the energy charged in the primary side flows into the secondary side all at once. This occurs because the energy transfers in the same direction as the reverse diode characteristics with the Q1 off.

The secondary side of the transformer (T1), which has the specified numbers of coiling lines for 42 VDC production, creates the 42 VDC out of the energy led to the secondary side by the electromagnetic induction.

The secondary side has numbers of stabilizing circuits to output stabilized￿voltages, as listed below:

Smoothing circuit:

Since the energy led from the transformer (T1) to the secondary side by the electromagnetic induction is alternating current, it must be smoothed by the electrolysis condensers C51 and C52

￿to be direct current.

+42 V line constant voltage control circuit:

7 zener diodes (ZD51, ZD81 - ZD86) connected in series monitors +42 V status used to drive various mechanisms. To keep the output voltage at a constant levelI, the circuit controls the on/off timing of the Q1 slightly according to the signals fed

￿back from the photocoupler (PC1).

+42 V line overvoltage protection circuit:

This circuit includes 2 zener diodes (ZD52, ZD87) connected in series. It monitors the +42 V line used to drive various mechanisms to detect abnormal rise in the voltage level caused by a defect in the circuit. If the output voltage rises to +48 V, the signal is input to a port of one of the 2 channels in the photocoupler (PC1) to completely cut off the Q1 operation. Once this circuit is active, a normal flow does not recover unless the

￿printer is turned off and back on.

+5 VDC production circuit:

L4960 (IC51) produces +5 VDC out of +42 VDC. Since the IC internally operates PWM control, it can always produce constant

+5 VDC by changing output pulses in spite of diverse input voltage levels. This operation serves as a constant voltage

￿control circuit.

+5 V line overvoltage protection circuit:

ZD53 in the circuit monitors the +5 V line for overcurrent. In case the voltage rises to 7 V for reasons such as a defective board, the circuit shuts the Q1 gate in the same process as the +42 V

￿line overvoltage protection circuit follows.

Voltage drop delay circuit at power off

The C265 PSB/PSE board uses the secondary switch that includes the delay circuit. The delay circuit allows the printer to complete the power off operation properly even though the printer is turned off while it is printing.

A normal power off operation by the user is monitored by the C265 main board. When it detects a power off, the program immediately starts the power-off sequence, capping the printheads, and drops the power.

The electrolysis condenser (C84) continues to operate to allow the printer to execute this proper power off sequence.

See the following page for the electrical circuit diagram.

Operating Principles Electrical Circuit Operation Principles 57