Active Off Mode; Light Mode - Sony CPD-G400 Training Manual

Active off Mode

The monitor can also operate in an Active Off mode. When the computer
is turned OFF, there is no video sync input the monitor. Within the moni-
tor, this loss is detected by the CPU (not shown). The CPU turns ON
SCR D616, which increases the error voltage. This increase to 6.5V is
detected by IC603/pin 14 via D608 and the oscillator stops to lower the
output voltage. Since it takes a longer time for the voltage to return to
normal, the oscillator resumes in the low output Active Off or Burst mode.
In the Active Off mode IC603 turns ON the power supply's oscillator in
bursts, every 163msec (6 times/second). The bursts last 18.5msec.
,
c h 1 : d T = 1 6 3 m s d V = 4 . 0 0 V
T
1
2
C H 1 1 0 0 V =
CH2 10.0 V=
Active Off Power Supply Burst Intervals
Name
Channel 1 Amplified OSC
Channel 2 Oscillator Output
Time base
Each burst consists of oscillator pulses at 18.2kHz. These pulses change
in width to regulate the power supply output voltages in the Active Off
mode.
ch2: pkpk= 9.57 V
ch2: freq= 20.8kHz
T
1
2
CH1 100 V= STOP
CH2 10.0 V= MTB 200us- 1.36dv ch1-
MTB50.0ms- 1.36dv ch1-
Location
Q605/D 180Vp-p
IC603/pin 4 11Vp-p
50msec/div
23
Channel 1
Channel 2
Time base
These bursts provide sufficient voltage at T602/pin 14 to only regulator
IC609. IC609 powers the CPU, IC1001. The SCR is reset because there
is insufficient current to keep it latched.

Light Mode

From the Active Off mode, the monitor can return to the ON mode when
input video sync is detected or if a front panel input has been selected.
Both inputs are monitored by the CPU. The CPU discontinues the SCR
(Heater) signal and turns ON both regulators. The regulators immedi-
ately load the power supply stage.
The decrease in peak to peak feedback voltage from T602/pin 2 causes
IC603 to power up. IC603 first eliminates the bursts and provides a con-
tinuous oscillator signal from pin 4 (Light Operating Mode). If the Light
Operating Mode does not bring the secondary voltage up fast enough,
Voltage
IC603 increases the frequency and pulse width to meet the power de-
mand (normal mode).
When the power demand is minimal, such as in screen saver or a front
panel input in triggered with no video input, the power supply may choose
the Light-operating mode. The monitor current is measured at IC603/pin
5. In this light mode, the power supply does not have to work as hard to
maintain the secondary voltages that are used to drive the monitor. As a
result, the oscillator frequency is only 26KHz in the light mode, instead of
the normal 63kHz.
Active Off Power Supply Burst
Name Location
Amplified Osc Q605/D
Oscillator Output IC603/pin 4
200usec/div
Voltage
180Vp-p
11Vp-p