Matsui 1410R, Руководство по обслуживанию

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8
Power Supply
Mains isolated switched mode power supply (SMPS), control IC7514 (TDA4605) gives oscillation, variable frequency, variable duty
cycle, switching FET, no opto coupler, no thrystor switching windings on the secondary side, slow start circuitry and no standby
mode of the power supply. Via sense windings 4-2 frequency and duty cycle control on the primary side.
Duty cycle and frequency of the power depends on T-on of FET TS7525 which is controlled by IC7514. This IC detects variations
of the +100 (at the secondary side of 5525 at winding 5-7) via sensing windings 4-2 at the primary side of 5525. The switching
period of TS7525 is divided in three main areas T-on, T-off and T-dead:
During T-on energy is extracted from the mains into the primary winding 8-12 of transformer 5525 with a linear increasing primary
current (slope depends on voltage across C2505). Via T-on regulation the duty cycle and the frequency of the SMPS and so the
+100 can be controlled.
During T-off energy "inside" transformer is supplied to the load via secondary windings of 5525. Current through secondary side of
the transformer decreases linear with firm slope.
During T-dead no energy is extracted or supplied. During T-dead the L-prim is demagnetised (polarity L-prim and C2524 is switched).
PRIMARY SIDE
Degaussing; R3501 is a dual PTC (2 PTC's in one housing). After switch on set, PTC is cold so low-ohmic and so degaussing
current is very high. After degaussing, PTC is heated so high-ohmic, so in normal operation degaussing current very low.
Mains voltage is filtered by L5500, full wave rectified by diodes 6502-6505 and smoothed by C2505 to VIN (300 V DC for 220V AC
mains).
Start up; Via start up circuitry via R3507 the DC voltage VIN
is used to start up IC7514. As soon as the supply voltage Vpin6 12V
the IC7514 starts; the internal oscillator of IC7514 drives TS7525 into conduction at the lowest frequency (during start up C2523
determines the frequency; as C2523 is uncharged at start up this gives a low start). The power supply automatically starts up.
Take over IC7514; During start up a voltage across winding 4-2 is built up. At the moment the voltage across winding 4-2 reaches
approx. +15V, D6521 starts conducting and takes over the +15 supply voltage at pin 6 IC7514.
CONTROL CIRCUITRY
+100 feedback for frequency and duty cycle control; Sense windings 4-2 has same polarity as winding 5-7. During T-off winding 5-
7 and so winding 4-2 are positive. D6515 conducts and so charges C2515; the DC level across C2515 is a reference for the +100.
Via R3518, R3517 and R3508 this DC-voltage is brought to the required level for input pin 1 IC7514; this voltage is used for
frequency and duty cycle control of IC7514.
R3518 is a potentiometer and so +100 can be adjusted.
IC7514 co100 by controlling T-on and so the frequency and the duty cycle; IC7514 compares voltage at pin 1 with an internal
reference voltage.
* In a stable situation the voltage at pin 1 is the same as the internal reference voltage, so frequency and duty cycle remains the
same.
* If +100 increases the voltage at pin 1 increases, and so the frequency and duty cycle and so the +100 will be decreased (new
balance of voltage at pin 1 and the reference voltage and so new lower stable frequency and duty cycle).
* If +100 decreases, the voltage at pin 1 decreases. The frequency and duty cycle and so the +100 will be increased.
The voltage at pin 1 is in a stable situation typical 400 mV.
Undervoltage protection; If Vpin6 supply voltage drops under 7V25, the logic in IC7514 will shut the output at pin 5. The power
supply will stop running.
Overvoltage protection; The power at pin 3 IC7515 is a measure for the mains voltage and so the DC Vin across C2505. As soon
as the voltage Vpin3 6V6, the logic in IC7514 will shut the output at pin 5. The power supply will stop running.
Overload protection; If the secondary load becomes too high, the T-on becomes too long. The internal sawtooth used for oscillation
is measured over C2509 at pin 2 IC7514. If Vpin2
3V (foldback point) the IC will switch into overload mode giving protection (hick-
up or burst mode): IC7514 switches TS7525 and so power supply "off" as long as I-prim is too high, starts up again, if I-prim still
too high switches "off" again, etc.
SECONDARY SIDE
±100 for the line output stage ±100A for the tunning (V VARI), +11 for sound output amplifier, +11A for start up of the line circuitry,
±5 for pull up and +5A for µC and EEPROM. No secondary protections are available.