TCL Power Supply Schematic - 01-L14TH4-PWB

Circuit Overview

The schematic details a power supply unit, likely for a television or similar electronic device, incorporating a Power Factor Correction (PFC) stage, a main power conversion stage, and a dedicated LED driver section. The design is divided into "HOT" (primary) and "COLD" (secondary) sides, separated by isolation barriers.

Input and Protection Stage (HOT Side)

This section handles the AC input power. It includes:

• AC Input: Connection points for mains power.
• Surge Protection: Components like varistors (RV1), fuses (F1, F6, F7, F8), and rectifier diodes (RD1-RD8, BD1, BD2) protect against voltage spikes and overcurrent.
• EMI Filtering: Inductors (LF1, LF2, LF3) and capacitors (CY1-CY4, CX1-CX2) are used to suppress electromagnetic interference.
• Input Rectification: Bridge rectifiers (BD1, BD2) convert AC to DC.

Power Factor Correction (PFC) Stage

This stage aims to improve the power factor of the input current. Key components include:

• PFC Controller IC: U301 (likely a dedicated PFC controller).
• Switching Transistors: Q301, Q302, QW1, QW1A.
• PFC Inductor: L301 (LP1).
• Capacitors: C301-C315 for filtering and energy storage.
• Diodes: D303-D306, D309, D310 for rectification and switching.
• Resistors: R301-R338 for biasing and current sensing.
• Voltage Levels: Indicates expected voltage ranges like Vcc MAX (20-24V), Vcc ON (11-13V), Vcc OFF (7.5-9.5V).

Main Power Conversion Stage (COLD Side)

This section converts the high voltage DC from the PFC stage into various output voltages. It utilizes:

• Secondary Side Controller IC: U401 (e.g., LNK6768V, a highly integrated power conversion IC).
• Switching Elements: Transistors Q403-Q406.
• Output Inductors: L401, L402.
• Output Rectifiers/Diodes: D401-D405, D410, D414, D417, D418.
• Filtering Capacitors: C401-C450.
• Resistors: R401-R474 for feedback, current sensing, and biasing.
• Output Signals: Includes VBUS, DR-VCC, P_DIM, BL_ON, 3D_EN, and test points (TS1, TS2, TS3).

LED Driver Stage (COLD Side)

This dedicated section drives LED backlighting, supporting both 2-channel and 4-channel configurations. It features:

• LED Driver IC: U601.
• Switching Transistors: Q601-Q603.
• LED Driver Inductors: L601, L602.
• LED Driver Diodes: D611, D612, D615-D618, D630.
• Filtering Capacitors: C601-C634.
• Resistors: R601-R699, including specific configurations for current limiting and channel selection (e.g., R617, R695/R696, R698/R699).
• LED Outputs: Connections for LED strings (L1+, L1-, L2+, L2-, L3+, L3-, L4+, L4-).
• Configuration Notes: Specific resistor values are noted for 2-channel vs. 4-channel operation.

Component Designators and Symbols

The schematic uses standard electronic component designators. Common symbols and their representations include:

Configuration Notes and Special Instructions

The schematic includes specific notes for different operating modes or configurations:

• AC Input Condition: For AC input >= 150V, specific components like H1 and H2 are noted as 'NC' (Not Connected).
• R617 Configuration: For "HAS BOOST", R617 is 4k7. For "NO BOOST", R617 is 0R.
• LED Driver Channel Configuration:
  • Capacitors C617/C618/C619: 0.47uF for 2CH, 0.22uF for 4CH.
  • Diodes D615/D616: Short for 2CH, ER206 for 4CH.
  • Resistors R680/R681: NC for 2CH, 0R for 4CH.
  • Resistors R695/R696: 0R for 2CH, 560K for 4CH.
  • Resistors R698/R699: NC for 2CH, 0R for 4CH.
• Current Limiting Resistors: Specific resistor values are provided for different current/channel configurations (e.g., 130mA/4CH: 33R*4+220R*2, 300mA/2CH: 15R*4+56R*2).
• VAL? / Z?: Indicates components where the value or type is not specified on the diagram or may vary.