Fonctionnement détaillé de la carte Vestel 17IPS72 : alimentation et circuits

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pourrais-je avoir une description détaillée du fonctionnement de la carte 17ips72 de Vestel
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Initial assessment of available information
- Vestel’s 17IPS72 power board is used across many TV models and exists in several hardware revisions (R2/R3/R4). Public schematics for R3/R4 show a three-block architecture: an always‑on standby flyback (generates 5V_STBY and often 12V_STBY), an active PFC pre‑regulator, and a main half‑bridge LLC resonant converter with synchronous rectification; an LED boost driver (OB33xx family) is integrated on the same PCB. The PFC controller is shown as FAN7529 in the R3 print; the LED driver appears as OB3363; synchronous rectifier drivers are TEA1792. These details are visible on the R3/R4 schematic scans. (scribd.com)
- Field repair notes and forum syntheses identify a recurring “no start/no 5V_STBY” fault tied to the standby PWM controller (commonly Infineon ICE3BR1765J or an MPS MP150GJ variant) and its small VCC electrolytic (often C313/C316). (elektroda.com)

Direct answer to the question (startup of the 17IPS72)
Below is the clean, theory-first startup sequence (then how to diagnose and repair):

1) AC input and rectification (always)
- AC passes EMI filter, NTC inrush limiter, and fuse, then a bridge rectifier charges the primary bulk capacitor.
- Expected bulk voltage with AC applied but the set still in standby:
- ~160–170 VDC on 120 VAC mains (USA).
- ~320–340 VDC on 230 VAC mains (EU). PFC is idle at this point. (elektroda.com)

2) Standby flyback self‑starts (always-on section)
- A high-value startup resistor chain biases the standby PWM IC from the bulk rail. When its VCC reaches the IC’s start threshold (typ. around the high‑teens for the ICE3BR family), the IC begins switching the small flyback transformer.
- The auxiliary (bias) winding then takes over powering the IC VCC; the secondary provides regulated +5V_STBY (and often +12V_STBY) via TL431 + optocoupler feedback. (infineon.com)

3) Mainboard wakes and asserts PS_ON (transition out of standby)
- The TV’s mainboard, now powered by 5V_STBY, pulls the PS_ON line active (typically to >2.5–3.3 V, board‑dependent). That command enables the high‑power stages on 17IPS72. (elektroda.com)

4) Active PFC ramp (enabled by PS_ON)
- The PFC stage (FAN7529 in R3) boosts the bulk rail from ~160/325 VDC up to ~390–410 VDC to meet efficiency/EMC requirements. (scribd.com)

5) LLC resonant converter soft‑starts (enabled after/with PFC)
- The half‑bridge resonant controller drives the two primary MOSFETs; energy transfers via the main transformer. Synchronous rectifier drivers (TEA1792) on the secondary reduce losses and deliver the main 12 V / 24 V rails. (scribd.com)

6) LED boost driver enables on BL_ON/PWM_DIM
- The LED driver (e.g., OB3363) generates the high V_LED rail and regulates LED string current. It turns on only when BL_ON (and often a dimming pin) is asserted by the mainboard. (scribd.com)

7) Regulation and “power good”
- Once rails are within tolerance, the mainboard proceeds with panel/init; protections (OCP/OVP/OTP) remain armed in all blocks.

Detailed problem analysis (focus: “won’t start” or “stuck in standby”)
Work methodically and observe isolation/safety on the primary side.

A) Identify your reference points
- “Hot ground” (primary negative of the bulk capacitor) is for primary/PFC/standby‑IC VCC measurements.
- “Cold ground” (secondary ground on output connector) is for 5V_STBY/12 V/24 V/LED measurements. Do not mix grounds across the isolation barrier.

B) Minimal toolset
- Isolation transformer, series incandescent limiter (60–100 W), DMM with diode/ESR capability; oscilloscope strongly recommended.

C) Start here: three quick checks
1. Bulk DC on the big capacitor (power applied):
- ~160–170 V (120 VAC) or ~320–340 V (230 VAC). If low/zero: suspect fuse, bridge, NTC, cracked traces. (elektroda.com)
2. 5V_STBY at the mainboard connector (cold ground reference):
- 4.9–5.2 V is normal. If missing, stay in the standby section (Step D).
3. PS_ON level (cold ground):
- Standby: near 0 V. Run: typically >2.5 V. If 5V_STBY is OK but PS_ON never asserts, the issue is on the mainboard, not the PSU. (elektroda.com)

D) If 5V_STBY is missing or pulsing (the key “no start” cluster)
- Measure the standby IC VCC (hot ground). Typical behavior with an ICE3BR1765J‑type device:
- VCC ramps up toward its start threshold; if the small VCC electrolytic (often C313/C316, 22–47 µF/50 V) is dried out or the startup resistors have gone open, VCC never reaches start or collapses back into UVLO. Replace the VCC cap first; check/replace the startup chain next. (infineon.com)
- Check the 5V_STBY Schottky and its filter capacitors for shorts (common). A short on the 5 V rail forces hiccup or immediate shutdown. (elektroda.com)
- If VCC is healthy and there’s still no switching, suspect the standby controller IC (ICE3BR1765J/MP150GJ). Confirm no shorts in the snubber or bias network before replacing. (infineon.com)

E) If 5V_STBY is present but main rails never come up
- Confirm PS_ON goes active. If it does, check the PFC boost level: it should climb to roughly 390–410 VDC. If it stays at rectified level (~160/325 V), troubleshoot the PFC (FAN7529 controller, PFC MOSFET/diode/boost coil). (scribd.com)
- If PFC is OK but no 12/24 V rails, move to the resonant section: check the two primary MOSFETs, resonance capacitors, and the resonant controller bias. On the secondary, verify synchronous rectifier driver supply and gate paths (TEA1792 area). (scribd.com)
- Backlight off with sound present: LED driver/strings fault; check BL_ON/PWM, LED driver OB3363 supply and sense network, and for open LED strings (V_LED quickly rises then trips OVP). (scribd.com)

F) Waveform and threshold cues (useful numbers)
- ICE3BR1765J family: fixed‑frequency flyback controller with integrated HV MOSFET; operates once VCC has reached its start threshold; UVLO and burst/auto‑restart behaviors are typical of this CoolSET series. Expect VCC operating range roughly 10.5–25 V with turn‑on near the high‑teens. (infineon.com)
- PS_ON threshold: service docs for sets using 17IPS72 show “run” above ~2.5 V on the PS_ON pin; check your exact PDF for pin mapping. (elektroda.com)
- PFC output in run: approximately 390–410 VDC. (scribd.com)

Current information and trends
- Across 2024–2025 forum reports, the dominant startup failures remain: dried‑out standby VCC electrolytic (C313/C316), open HV startup resistors feeding the standby IC, and shorted 5 V Schottky. Many “dead” 17IPS72 boards revive by replacing the VCC cap and (if needed) the ICE3BR1765J/MP150GJ. (elektroda.com)
- Multiple sub‑revisions exist; controllers may be substituted by supply chain, but the functional blocks and startup sequence are the same. Always match to the silkscreened revision (e.g., 17IPS72‑R3). (scribd.com)

Supporting explanations and details
- Why PFC is quiet in standby: Without PS_ON, only the small standby flyback is running. Once PS_ON asserts, PFC boosts the bus so the LLC can operate efficiently and within EMI limits. (scribd.com)
- Why the tiny VCC cap is critical: Startup current through mega‑ohm resistors is minuscule. Any ESR rise or capacitance loss prevents VCC from reaching the controller’s turn‑on threshold; the IC hiccups or stays off. (elektroda.com)
- LED driver sequencing: BL_ON/PWM_DIM come from the mainboard; the OB3363‑class driver sets LED current via ISET/CS network and will trip OVP on open strings. (scribd.com)

Interdisciplinary connections
- The active PFC stage is there to comply with efficiency and power‑quality standards (reduced harmonics, higher power factor), and it lowers conducted EMI before the resonant converter. (scribd.com)

Ethical and legal aspects
- Safety: this is an off‑line SMPS with lethal potentials. Follow EN 62368‑1 practices, use an isolation transformer and a series bulb for first power‑up after repair. Do not defeat fuses/MOVs/NTCs. Dispose of e‑waste responsibly.

Practical guidelines (diagnosis to repair)
- Fast isolation test plan:
- Visual and ESR inspection; reflow cracked joints at transformer pins/connectors/power resistors.
- Bulk DC present but no 5V_STBY → replace the VCC electrolytic (C313/C316), measure/replace HV startup resistors (often 1–5 MΩ total), test 5 V Schottky for short; only then suspect the standby IC. (elektroda.com)
- 5V_STBY OK, PS_ON high, but no main rails → verify PFC boost (~390–410 V). If absent, repair PFC (controller, MOSFET, boost diode, inductor). If present, move to LLC (MOSFETs, resonance caps, controller bias). (scribd.com)
- Backlight complaints → verify BL_ON/PWM and LED driver OB3363 supply/sense; check for open strips. (scribd.com)
- Parts/replacement notes:
- Use 105 °C low‑ESR caps; replace the standby VCC cap proactively.
- Match Schottky voltage/current ratings; ensure proper heatsinking.
- When replacing controllers, inspect the snubber network and auxiliary winding path to avoid repeat failures. (elektroda.com)
- Test aids:
- Dummy load for 5V_STBY: 100–120 Ω, 2–3 W.
- Confirm cold/hot ground separation; never clip the scope ground to hot ground without isolation.

Corrections to common misconceptions
- Some summaries call the entire 17IPS72 a “flyback PSU.” In reality (see R3/R4 schematics), only the standby is flyback; the main supply is an active‑PFC‑fed half‑bridge LLC with synchronous rectification, and the LED boost is a separate converter. (scribd.com)

Possible disclaimers or additional notes
- Component designators can shift between R2/R3/R4. Always match to your PCB silkscreen and the exact schematic PDF for that revision. (scribd.com)

Suggestions for further research (documents to keep at hand)
- 17IPS72 R3/R4 schematics (Scribd/ElektroTanya mirrors). (scribd.com)
- Consolidated fault/repair notes and schematic links for 17IPS72. (scribd.com)
- Standby controller background (ICE3BR1765J CoolSET page for family behaviors/limits). (infineon.com)

Brief summary
- Startup path: rectified bulk → standby flyback produces 5V_STBY → mainboard asserts PS_ON → PFC boosts to ~390–410 V → LLC resonant converter generates 12/24 V → LED driver enables on BL_ON. (scribd.com)
- Most “dead” boards: fix the standby section first (VCC cap, startup resistors, 5 V Schottky; sometimes the standby IC). With 5V_STBY present, PS_ON and PFC/LLC sequencing determine the rest. (elektroda.com)

Questions for you (to tailor diagnostics)
- Which exact board revision is printed on your PCB (e.g., 17IPS72‑R3 or R4)?
- What mains are you using (120 VAC in the US or 230 VAC)?
- With the set plugged in (no attempt to turn on), what are:
- Bulk DC across the primary capacitor?
- 5V_STBY at the connector (cold ground)?
- When you try to turn the TV on, what is the PS_ON voltage?
- If PS_ON is high, does the bulk rail boost above 360–400 V (PFC active)?
Provide these four numbers and I’ll map you to the next checks component‑by‑component.