Power Supply Circuit - Epson DFX-9000 Service Manual

Epson DFX-9000

2.3.3 Power supply circuit

The power supply circuit consists of the following sections.
Input noise filter
Inrush control / rectifier smoothing circuit
PFC smoothing
+5 V RCC converter
+42 V FCC converter
+37 V step-down chopper
AC
presence/absence
detection circuit
Inrush
control/
rectifier
Input
AC input
smoothing
noise
connector
circuit
filter
section
Inrush
control/
rectifier
smoothing
circuit
Figure 2-38. Power Supply Circuit Block Diagram
The PFC, +5 V, +42 V, and +37 V circuit sections are described below.
PFC smoothing
This section is a power-factor improvement circuit that controls
high-frequency current.
Operating Principles
.
5 V output
Rectifier
RCC
ON/OFF
smooth
converter
switch
section
section
+42V/+37V
ON/OFF
control
PFC Rectifier
FCC
smooth
smooth
converter
section
section
+37 V
step-down
chopper section
+5V converter section
This section consists of a ringing choke converter and has the
following functions.
Overcurrent control
If the +5 V load somehow becomes shorted, the +5 V output is
drooped automatically to prevent the power supply from being
damaged.
Overvoltage control
If an overvoltage occurs on the +5 V output due to a malfunction
of the converter, the status is detected in the overvoltage
detection section and the +5 V output is shut off.
+5 V ON/OFF switch section
This section executes the sequence that cuts off the 5 V first
during power-down (at AC OFF) by detecting a signal from the
AC presence/absence detection circuit.
+5V
+42V converter section
This section consists of a forward choke converter (FCC) that uses a
switching control IC and has the following functions.
*42VST
+42 V/ +37 V ON/OFF control
The +42/+37 V circuit ON/OFF is controlled using the *42VST
signal. The +42/+37 V is ON when *42VST is low, and shuts off
+42V
when *42VST is high.
Overcurrent control
+37V If the +42 V load somehow becomes shorted, the +42 V output is
drooped to prevent the power supply from being damaged.
Overvoltage control
If an overvoltage occurs on the +42 V output due to a
malfunction of the converter, the status is detected in the
overvoltage detection section, and the +42 V output is shut off.
+37 V step-down chopper section
This section consists of a step-down chopper circuit based on the
+42 V output and has the following functions.
Circuit operation
Revision B
90