Panasonic LX600 Technical Information

Also see for Lx-600: Tuner firmware installation instructions Operating instructions

Contents

Panasonic LX600 Technical Information Manual pdf 12 page image

12Main 5V SupplyThe Main 5V, Main 9V, Sound 20V, and Panel 12V supplies are very similarin their design and operation. Panasonic utilizes several Buck regulatorcircuits to generate these voltages. The primary difference is that theinput voltage to the Main 5V regulator is 10V whereas the 9V, 20V, and12V supplies use 24V.1. Operation begins when the Main_On signal, derived from theTV_Main_On (active low) signal turns off Q7303, providing the “Enable”for operation of IC7205 on pin 5.2. The 10V input voltage is switched between pins 1 and 2 at a frequency of125Khz through the use of an internal oscillator and PWM circuit.3. When the switch is closed, current flows through coil L7203 causing afield buildup.4. When the switch opens, current generated by the field collapses in L7203and charges the capacitor C7255; D7231 acts as a ground return.5. Voltage feedback and regulation is accomplished through the use of avoltage divider, which consists of R7292 and R7293.6. D7230 prevents peaks generated by L7203 from exceeding 10V anddestroying the IC.7. Zener diode D7301 monitors the Main 5V output for over voltage and goesinto conduction if the output voltage becomes excessive. Diode D7302which is reversed biased during normal operation goes into conductionand trips the AC shutoff circuit.