Panasonic TC-2588 TV at the end of the switch power supply secondary various voltage output is provided with perfect over-current protection circuit, when fault occurs when the output circuit, protection circuit to start, through the optocoupler will switch power oscillation circuit to enter the shutdown state protection.
The machine is provided with a switch power supply output B voltage over-voltage protection, combined load over current protection, combined load short-circuit protection, +46V voltage load short-circuit protection and 16V voltage load short circuit protection and other protection circuit. The protection circuit as shown in figure.
The protection circuit of the actuating element is q805, when various detection circuit voltage protection was sent to him, Q805b extremely high levels of saturated conduction, cut-off D825, Optocoupler D811 cut-off, oscillation circuit for switching power supply stop vibration. The protection detection circuit is as follows:
1, +B voltage over-voltage protection circuit. Divided into press tube D831 switch power supply B voltage over-voltage protection of circuit caliber r850, R851 and regulator, when the switch power supply output B voltage is too high, partial pressure of the midpoint voltage of the circuit exceeds 10V, voltage regulator tubes D831 breakdown conduction, high level added protection execution element Q805b.
2, +B load overcurrent protection circuit. Peripheral components Q831 and the sampling resistance R834/R835 such as composition B load overcurrent protection circuit, when the combined load flow, increases the voltage R834/R835 drop, when higher than 0.7 V, Q831 conduction, the C is extremely high level, through the R831 d832 enable protection execution circuit q805 conduction.
3, +B load short-circuit protection circuit. When the combined load short-circuit and d830 negative short-circuit grounding and d830 conduction, will stop D825, Optocoupler D811 cut-off into state protection.
4, +46V voltage load short-circuit protection circuit. D837 voltage +46V load short-circuit protection circuit, when the +46V voltage load short circuit, the D837 negative electrode short circuit grounding, D837 conduction, cut-off D825, Optocoupler D811 cut-off, into the state protection.
5, 16V voltage load short-circuit protection. When the 16V voltage load is short, the 16V voltage disappears, and the D811 voltage of the protection circuit 16V is lost or very low, the D811 is off, and enters the protection state.
6, field overcurrent protection circuit. Q454 and the sampling resistance R476 and over-current protection circuit composed of field spot output circuit failure caused by excessive current, the voltage on the R476 drop increases, when higher than 0.7 V, Q454 conduction, the C is extremely high level, through the R554 enable q805 conduction.