TCL 283N20 PWM IC Equivalent: OB2268, AU501, NCP1200A, FAN7602, Pinout and Replacement Guide

User question

FONTE 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

Artificial Intelligence Response

Direct answer to the question

• “283N20” is a TCL house-code for a 6-pin, current-mode, fly-back PWM controller that is function-by-function compatible with the On-Bright OB2268/OB2269 (and the later AU501 used on the same MT21X7 platform).
• Any controller whose pinout is
1-VCC (through 10 Ω), 2-CS, 3-DRV (to MOSFET gate), 4-GND, 5-HV or VDD, 6-FB/COMP (from opto)
will reproduce the behaviour you described.
• Commonly stocked near-drop-in choices:
– OB2268 / OB2269
– AU501 (MediaTek/TCL)
– ON-Semi NCP1200A/NCP1203
– FAN7602 / FAN6754
– Power-Integrations TinySwitch-V (TNY276-TNY280) or LinkSwitch-TN2 (LNK362-LNK364)
– Richtek RT7730/31
– ST VIPer06 / VIPer22A
Check start-up VCC, current-sense threshold and gate-drive current before final substitution.

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Detailed problem analysis (core technical content)

1. Pin function mapping derived from your trace
   • Pin 1 → 10 Ω resistor from bulk-VCC: start-up/bias – therefore VCC.
   • Pin 2 → 471 Ω in MOSFET source: peak-current sense (CS).
   • Pin 3 → 22 Ω/diode/47 k gate network of MOSFET 70R380: driver output (DRV).
   • Pin 4 → common return, anode of 1N4148 fast-discharge diode: GND.
   • Pin 5 → labelled “tensão” (voltage) with no external network except local decoupling: internal HV or regulated VDD pin that feeds Vref block.
   • Pin 6 → optocoupler transistor collector (pin 4 of opto): feedback/compensation (FB or COMP).
    This sequence exactly matches most 6-pin primary-side regulators (PSR) aimed at low-power fly-back supplies (≤40 W).

2. Electrical requirements you must meet
   • Start-up: ~90 kΩ/10 Ω path normally charges VCC to 14–18 V; UVLO off ≈8 V.
   • CS threshold: 0.8–1.0 V for the 471 Ω ⇒ ≈1.7–2.0 A peak in primary.
   • Gate drive: 500 mA source/800 mA sink minimum for 70 R 380 N-MOSFET.
   • Protection: OVP, OLP, and brown-out preferred for TV stand-by supplies.

3. Why OB2268/69 or AU501 is the closest match
   • They are delivered only in SOT-23-6, SOP-8 or DIP-6 with the pin order above.
   • Start-up and UVLO thresholds, gate-drive current (±800 mA), and CS levels align with the behaviour measured on MT21X7 boards published in repair forums in 2023-2024.
   • TCL’s newer boards silkscreen the same position as “AU501”, confirming corporate migration from the 283N20 code.

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Current information and trends

• Service data for TCL 40-MT21X7 boards is still restricted; community forums (Elektroda, Electronica-PT) agree that AU501/OB2269 are the current production substitutes.
• Market trend: TV OEMs move from 8-pin UC3842-style parts to 6-pin PSR devices to cut BOM and standby power (< 75 mW EU ErP).
• Future devices (PI LinkSwitch-TN3, MPS MPX200x) integrate synchronous-rectifier drivers and brown-in/out detection; footprints, however, remain 6-pin.

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Supporting explanations and details

1. Gate-drive network 47 k//22 Ω/1N4148 = Miller and soft-turn-off damping – keep identical when changing IC.
2. Optocoupler connection (open-collector to FB pin) shows secondary-side TL431; any replacement must have internal pull-up on FB or be externally pulled-up (OB226x has 5 kΩ).
3. If you choose an 8-pin controller (UC3842, NCP120X) you will have to reroute pins and add an external Vref decoupling cap – feasible but not plug-and-play.

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Ethical and legal aspects

• Work on primary (mains) side only with isolation transformer and discharge bleeder; lethal voltages present even when set is off.
• Respect regional safety approvals (IEC 60065/62368-1); altering controller must not void creepage/clearance or energy-hazard tests.
• Firmware-locked “house-codes” are not copyrighted, but re-marking ICs for sale as originals is illegal.

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Practical guidelines

1. Confirm pin functions with oscilloscope before desoldering (startup VCC, gate waveform, CS pulses).
2. Pick candidate IC; print pinout table; verify:
    • UVLO start/stop matches original
    • CS threshold <1.0 V
    • Drive ≥1 A pk, VDS ≤ 650 V for internal HV devices
3. Replace, clean flux, power through incandescent lamp limiter first, check standby consumption.
4. If unsure, replace complete power board (≈ US$14–20 for MT21X7 on marketplaces).

Potential challenges & fixes
• No start-up → VCC too low → use 1 MΩ from HV bus to pin 5 (for devices without internal HV).
• Burst/no-load instability → adjust opto LED resistor to keep FB within 1.5–2.5 V.

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Possible disclaimers or additional notes

• Exact proprietary parameters (brown-out, OLP delay) of 283N20 are undocumented; minor functional differences may exist.
• Power-Integrations parts integrate MOSFET; external MOSFET must be removed or left un-driven.

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Suggestions for further research

• Request the “40-MT21X7-MPA2HG Power/Back-light board” service manual in TCL’s Self-Repair portal.
• Compare waveforms of OB2269 and AU501 on working boards to build a cross-reference sheet.
• Examine emerging GaN-based primary controllers (NCP51820 + GaN FET) for next-generation replacements.

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Brief summary

The TCL-marked 283N20 is not an industry number but a 6-pin primary-side current-mode PWM very similar to the OB2268/OB2269 (later branded AU501).
Choose any controller with pins 1-VCC, 2-CS, 3-DRV, 4-GND, 5-HV/VDD, 6-FB, matching start-up, CS, and gate-drive specs.
The most reliable drop-ins are OB2268/9, AU501, NCP1200A, FAN7602, or PI TinySwitch-V devices.
Verify thresholds, keep the original gate-snubber network, and follow safety practices when working on mains-connected circuitry.

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.