SONY LDU-1540L
Service Manual

3-3. G Board (power system)
3-3-1. Filter & AC Rectifier Block
After AC inlet, a discharge resistor R101 and a normal mode lightning surge protect varistor VDR101 are arranged. After that, the 2-stage filter is composed of C101/LF101 and LF102/C102, and rectification is done with D101.

3-3-5. Output Voltages
5.8 V Output After output from the T101 secondary winding terminal, the power is rectified at D204 and D205, and a ripple component is reduced by a p type filter, then the voltage is output from the output terminal CN201 a8 to ![ pins. The output voltage is detected by the operation amplifier of IC202 5, 6, 7 pins, then it is returned to the IC103 != pin via PH101 so as to be stabilized through the frequency control system. Both 5.8 V and 4.1 V are adjusted with RV201. Also, by detecting the voltage at both ends of L204 with IC202 1, 2, 3 pins, if the current in 5.8 V line is taken about 12 A or more, Q202 turns on via D215 and D214, PH102 operates, IC103 OVP terminal (6 pin) becomes �H�, IC101 is latched, and the switching of power supply block stops. To reset, turn off the AC and allow time for about one minute so as to lower the IC103 VIN terminal (4 pin) to 12V or less. 5.0 V Output As for the 5 V output, the power is branched prior to L204 for 5.8 V output, and it is controlled to 5 V by 4-pin regulator IC201 having low saturation, then output from the output terminal CN201 a!] to !\ pins. 4.1 V Output After output from the T101 secondary winding terminal, the 4.1 V power is supplied from D206 and magnetic amplifier consisting of L201 and L202. A ripple component is reduced by a p type filter, then the voltage is output from the output terminal CN201 a3 to 7 pins. The output voltage is detected by the operation amplifier of IC202 8, 9, 0 pins, then it is returned to the magnetic amplifier via Q201 so as to be stabilized. Also, by detecting the voltage at both ends of L206 with IC202 !=, ![, !] pins, if the current in 4.1 V line is taken about 14 A or more, Q202 turns on via D215 and D214, PH102 operates, IC103 OVP terminal (6 pin) becomes �H�, IC101 is latched, and the switching of power supply block stops. To reset, turn off the AC and allow time for about one minute so as to lower the IC103 Vin terminal (4 pin) to 12 V or less. 12 V Output After output from the T101 secondary winding terminal, the 12 V is output from the double voltage circuit composing of C201, C202, and D202, D203, D209, D210 using the 5.8 V line. After that, it is branched into two lines; in one line, a ripple component is reduced by a p type filter, then it becomes Vcc for the circuit system on the secondary side, and in another line, the voltage is output from the output terminal CN201 a1 to 2 pins through the TH201 for current restriction.

3-3-2. PFC Block
After rectification, a boost up converter is composed of Q101, D102, and C110, and the output voltage is maintained to about 380 V (adjusted with RV101) under control of IC101. The IC101 detects the input current waveform to make the input current similar to the input voltage of the same phase so as to improve the power factor. When the power is turned on, the power is supplied from R153, R154, then after the power supply block started to operate, the power is supplied from D105 and R117 of the T101 tertiary winding. As for the overvoltage, etc. caused by alarms in the PFC control system, the double protection circuit of restriction by IC102 (5, 6, 7 pins) and latch through detection by IC103 is provided. The PFC output voltage is set to about 380 V with RV101. Also for the overvoltage or overcurrent caused by alarms in the PFC control system, the protection circuit operates through monitoring by the IC103.

3-3-3. Power Supply Block
Basic circuit composition is the 2-crystal current resonance circuit consisting of Q104 and Q105. Using C117 and T101 primary winding leakage inductance, the resonance system is made up to perform zero current switching. By the switching, the output of IC103 OUT 1, 2 pins is transmitted to the respective drive circuits for Q104 and Q105 via T102 drive transformer. The control system is a frequency control system, where the output voltage is controlled to constant level by varying the RT2 terminal via PH101.

3-3-4. OTP (Temperature Protection) Circuit
This circuit consists of THP101 and Q106 attached to the heat sink, and when the heat sink temperature rises over 100dC, THP101 opens, IC103 OVP terminal (6 pin) becomes �H�, IC101 is latched, and the switching of power supply block stops. To reset, turn off the AC and allow time for about one minute so as to lower the IC103 Vin terminal (4 pin) to 12 V or less. 3-4 (E)

3-3-6. OVP Circuit
The 5.8 V and 4.1 V output voltages are monitored by Zener diode D212 and D211, and if overvoltage occurs, Q202 turns on via D215 and 214, PH102 operates, IC103 OVP terminal (6 pin) becomes �H�, IC101 is latched, and the switching of power supply block stops. To reset, turn off the AC and allow time for about one minute so as to lower the IC103 Vin terminal (4 pin) to 12 V or less.
LDU-1530/1540/1515