Ilpi354 Va Schematic Upd ❲UHD❳

| Pin | Name | Function Description | |------|---------------|----------------------------------------------------------------------------------| | 1 | COMP | Compensation pin – connects to an RC network for loop stability. | | 2 | VFB | Voltage feedback input – from optocoupler (TL431). Inverts output voltage sense. | | 3 | ISENSE | Current sense input – monitors MOSFET source current via a resistor (0.22–0.47Ω).| | 4 | RT/CT | Oscillator timing – resistor to GND, capacitor to Vref sets switching frequency. | | 5 | GND | Ground – return for both power and control signals. | | 6 | OUT | Gate driver output – connects to MOSFET gate (series resistor ~10–22Ω). | | 7 | VCC | Power supply – filtered DC voltage (typically 12–18V). | | 8 | VREF | 5V reference output – for external circuits (max 20mA). |

AC Input → [EMI Filter] → [Bridge Rectifier] → +320V DC │ ├───[R1+R2]───┐ │ │ [T1 primary] └───► Pin7 (VCC) │ │ +───► [Drain of Q1] ├───[C4 47µF/35V]─GND │ │ [Source of Q1]──[R10]─GND │ Pin3 (ISENSE) ← via RC filter (R9, C7) │ ├───────────────┐ │ │ Pin6 (OUT)──[R7]───┘ (to Q1 Gate) On the secondary side: ilpi354 va schematic upd

T1 secondary (12V) → [D5] → +12V out → [C8, C9] → load │ └─[R12, R13 divider]─→ TL431 Ref │ PC817 LED ←── TL431 Cathode PC817 transistor → Pin2 (VFB) | Old Schematic (Pre-2020) | Updated (UPD) Version | |--------------------------|------------------------| | No soft-start circuit | Added C5 (1µF) from COMP to GND for soft-start | | Direct feedback from optocoupler | Series resistor + diode (R14, D7) for better transient response | | Single current sense filter | Dual RC filter (R9-C7 + internal leading-edge blanking) | | 50kHz oscillator | Increased to 65kHz to reduce transformer size | Part 4: Step-by-Step Troubleshooting Using the ILPI354 VA Schematic UPD If your power supply is dead or cycling, use this guided procedure. Symptom 1: No output, VCC (pin 7) oscillates between 9V and 15V Likely cause: Startup circuit functional, but UVLO cycling due to short or overload. | Pin | Name | Function Description |