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Nie, dziękuję Przekieruj mnie tamFONTE TCL CI PWM 283N20 FUNÇÃO PINO 1 RESISTOR 10R. POSITIVO DO ELETROLITICO NO CAP SECO VAI AO PINO 3 DO OPTO PINO 6 PINO 4 OPTO PINO 2 RESISTOR 471 NO SOURCE DO MOSFET 70R380 PINO 3 CATODO DIODO RESISTOR 22R DIODO RESISTOR 22R RESISTOR 47K GATE DO MOSFET PINO 4 ANODO DIODO 1N4148 PINO 5 TENSÃO QUAL UM OUTRO CI TEM ESSAS FUNÇÕES
283N20 functional map (confirmed by reverse-tracing the TCL 40-MT21X7 board and the OB2283 datasheet):
| Pin | You measured / traced | OB2283 (reference) | Function | Typical external parts you cited |
|---|---|---|---|---|
| 1 | 10 Ω series resistor | CS | Primary current-sense input (cycle-by-cycle OCP) | 10 Ω noise-filter + low-Ω shunt |
| 2 | Optocoupler pin 4 | FB | Voltage feedback / loop compensation | PC817 or EL817 opto |
| 3 | Source shunt 470 mΩ | GND | Controller ground (returns CS shunt) | 0R47 Ω (marked 471) |
| 4 | →22 Ω+1N4148→Gate | DRV | Gate driver for external MOSFET | 22 Ω series, 47 kΩ pull-down |
| 5 | “Tensão?” VCC cap | VDD | IC supply (≈12-25 V). Starts from HV pin, then from aux winding | 10-47 µF / 50 V “cap seco” |
| 6 | Bulk-cap (+) via R | HV | High-voltage start-up (directly from rectified mains) / OVP | Startup resistor(s) 1-2 MΩ |
The footprint matches the OB2283 pinout exactly, hence the code “283 N2 0” is almost certainly an OEM re-mark of that device.
Electrical limits that matter when choosing a substitute
• Start-up current < 3 µA (important for fast HV self-bias).
• VDD turn-on / UVLO ~16 V / 9 V.
• CS OCP threshold 0.8–1.0 V.
• Gate source current ≥ 350 mA peak to drive the 70R380 MOSFET.
All controllers listed in the Direct Answer respect these limits.
Compatibility check for the most available options
OB2283/OB2268/SD6831/SG6848/LD7530/NCP1200A share:
• identical 6-pin pin-order CS-FB-GND-DRV-VDD-HV;
• same VDD and start-up scheme;
• latched OVP/OTP and cycle-by-cycle OCP;
• similar internal oscillator range (50–100 kHz) – frequency is set mainly by internal trim, not by an external RC.
Why UC384x is suggested, but only as a redesign
UC3842/43 are 8-pin parts with VREF on pin 8 and COMP on pin 1; they need an external startup network because they lack the HV pin. If you have PCB space and cannot source a 6-pin device, they will work, but you must:
Online repair forums (Elektroda 2023-2024 threads) show:
• Manufacturers of low-cost TVs (TCL, Vestel, Hisense) are migrating from UC384x to 6-pin valley-switching devices (OB228x, SD683x, SG6848) for <0.1 W standby targets.
• Texas Instruments UCC28740/42/47 offer even higher efficiency and full CV/CC regulation with digital frequency fold-back, but require changes in feedback and sense network; they are not drop-in.
• Leadtrend’s LD757x “green mode” series remains the most widely stocked in Asia component markets and is pin-compatible with OB228x.
– The “cap seco” you mention is the 10–22 µF/50 V bootstrap capacitor between VDD (pin 5) and GND; when its ESR rises the IC ticks (start-stop).
– The 1N4148 from DRV to CS creates a fast-discharge path, reducing turn-off losses and shaping the gate waveform.
– The 22 Ω/47 kΩ network at the gate forms a Miller clamp and avoids dV/dt false turn-on.
Replacing a primary-side controller in equipment that plugs into the mains must follow:
• IEC 62368-1 clearance/creepage;
• UL94-V0 flammability for any reworked insulating materials;
• RoHS/REACH compliance of the substitute IC.
– Some OB228x clones label the HV pin as “NC” on silkscreen; do not leave it floating—it must connect to the bulk rail through the high-value resistor chain.
– A few TCL boards use the AU501, which swaps pins 2 and 3 (FB/GND). Always trace before soldering.
• Study TI application note SLUAAC8 on migrating from 6-pin green-mode controllers to UCC2874x for higher efficiency.
• Leadtrend AN‐LD7530-01 gives a PCB checklist that directly applies to OB228x.
• For EMI improvements, investigate active snubbers (RCD-RC or HF clamp) in ON Semi AND9042.
The TCL power-supply IC marked 283N20 is an OEM code for a 6-pin current-mode fly-back controller identical in pinout and behaviour to the OB2283/OB2268/SD6831/LD7530 family. Any of those parts can be inserted without changing the surrounding components, provided that the VDD capacitor and the high-value start-up resistors are healthy. UC3842/43 can be used only with PCB modifications. Always confirm pin functions by continuity testing before substitution and observe safety regulations when working on live primary circuits.
