Philips 7603 series, Руководство по обслуживанию

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Standby
The set goes to Standby in the following cases:
•
After pressing the 'standby' key on the remote control.
•
When the set is in protection mode.
In Standby, the power supply works in 'burst mode'. Burst mode can be used to reduce the power consumption below 1 W at
stand-by. During this mode, the controller is active (generating gate pulses) for only a short time and for a longer time
inactive waiting for the next burst cycle.
In the active period the energy is transferred to the secondary and stored in the buffer capacitor CSTAB in front of the linear
stabilizer (see Figure below). During the inactive period, the load (e.g. microprocessor) discharges this capacitor. In this
mode, the controller makes use of the Safe-Restart mode.
Basic Burst mode configuration
The system enters burst mode standby when the microprocessor activates the 'Stdby_con' line. When this line is pulled high,
the base of Q7541 is allowed to go high. This is triggered by the current from collector Q7542. When Q7541 turns 'on', the
opto-coupler (7515) is activated, sending a large current signal to pin 3 (Ctrl). In response to this signal, the IC stops
switching and enters a 'hiccup' mode.
This burst activation signal should be present for longer than the 'burst blank' period (typically 30 ?s): the blanking time
prevents false burst triggering due to spikes.
Burst mode standby operation continues until the microcontroller pulls the 'Stdby_con' signal low again. The base of Q7541
is unable to go high, thus cannot turn 'on'.
This will disable the burst mode. The system then enters the start-up sequence and begins normal switching behavior.