DSC-F1 (serv.man2) - Sony Digital Camera Service Manual (repair manual). Page 11

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When the UNREG voltage is lower than the output voltage, only the latter-stage step-up SWR operates. This step-up SWR

is composed of the voltage setting circuit (IC004, Q007 to Q022), comparison and PWM output circuit (IC005, IC006), and
sync rectifying circuit (IC008, IC009, and IC010).

• Level shifting the error output voltage

First, 1.5V is output from the VREF terminal (Pin 2) of the PWM controller (IC004) as a reference voltage.
This voltage is resistance-divided, and input to the Q010, Q013, Q017, and Q020 bases to control the respective emitter

voltages. (When the emitter voltage increases, the transistor turns ON.)

As a result, when the difference amplitude output of each regulator output from the PWM controller is higher than the

regulated voltage, it will be clamped (level-shifted).

The error difference amplitude output of the output voltage of each regulator is input to the operation amplifier (IC005,

IC006).

• PWM waveform output

The triangular wave output from the CT terminal (Pin @™ of IC004) of the PWM controller is input to Pin 5 of IC006,

etc. The output obtained by comparing this triangular wave and 5V difference amplitude output becomes the PWM
waveform, and inverted by the inverter (IC007) to turn ON/OFF the step-up transistor.

The 2.8V and 3.1V voltages are input to Pin !¡ of IC004 due to the need to invert the phase of the triangular wave

output from the CT terminal of the PWM controller (Pin @™ of IC004), and the phase-inverted triangular wave is output
from Pin !™. This is then input to Pin 5 of IC005.

This triangular wave and 2.8V/3.1V difference amplitude output are compared to generate the PWM waveform, and this

is inverted by the inverter (IC007) to turn ON/OFF the step-up transistor.

• Diode cancel output

During step-down operations, the cancel output of IC005 or IC006 (Refer to Table -2) becomes L, the buffer output of

the sync rectification circuit (IC8, IC9) becomes L, and the step-up diode is short-circuited.

During step-up operations, only when the PWM waveform input of the step-up SWR is H will the diode be short-

circuited.

Comparison output

IC006

Pin !£

IC005

Pin !£

IC006

Pin !¢

IC005

Pin !¢

Cancel output

IC006

Pin 2

IC005

Pin 2

IC006

Pin 1

IC005

Pin 1

SWR

Q035

Q038

Q037

Q036

Difference amplitude output

(IC004)

Pin !¶

Pin @º

Pin #∞

Pin #•

5V REG

2.8V REG

DIGITAL

5V REG

3.1V REG

The power supply voltage (5V) for IC005, IC006, IC007, etc. is output from the 5V REG composed of Q023, etc. When

the UNREG voltage is lower than 5V, these circuits operate on this UNREG voltage.

The power supply voltage (8V) for IC008, IC009, IC010, etc. is output from the 8V REG composed of IC012, etc. This

circuit outputs 8V which is created by adding 3V whose sawtooth wave has been rectified to the 5V output.

When the reset switch (S001) of the DD board is pressed, the HI microprocessor is reset, and the reset signal (XHRST) is

output. The main microprocessor (IC602), address decoder (IC607), and ROM (IC606) are reset by this reset signal.