## Overview of the VIPER22-LED-EV The **VIPER22-LED-EV** is an evaluation board designed to demonstrate a low-cost, high-efficiency power supply solution for LED applications. It is built around the **VIPer22A-E**, a monolithic smart power switch that integrates a dedicated current mode PWM controller with a high-voltage Power MOSFET. --- ### Key Electronic Components The board consists of several functional sections. Below is a breakdown of the primary electronic parts: | Component Category | Key Parts | Function | | :--- | :--- | :--- | | **Power Controller** | VIPer22A-E | Combines the PWM controller and a 730V Power MOSFET in one 8-pin package. | | **Input Protection** | Fuse / NTC Resistor | Protects against overcurrent and limits inrush current during startup. | | **Rectification** | Bridge Rectifier (e.g., 1N4007 series) | Converts AC input voltage to a high-voltage DC bus. | | **Filtering** | Electrolytic Capacitors & Inductors | Smooths the rectified DC voltage and reduces Electromagnetic Interference (EMI). | | **Transformer** | High-Frequency Flyback Transformer | Provides galvanic isolation and steps down the voltage to the level required by LEDs. | | **Feedback Loop** | Optocoupler (e.g., PC817) & TL431 | Monitors output voltage/current and sends a signal to the VIPer22A to regulate power. | | **Output Rectifier** | Schottky Diode | Rectifies the high-frequency AC from the transformer secondary into DC for the LEDs. | --- ### Functional Block Details #### 1. The VIPer22A-E IC This is the "brain" of the board. It operates at a fixed frequency of **60 kHz**. * **Drain Pin:** Connected to the primary winding of the transformer. * **Source Pin:** Connected to the ground. * **Feedback (FB) Pin:** Receives the signal from the optocoupler to adjust the duty cycle. * **VDD Pin:** Supplies power to the internal control circuits. #### 2. The Feedback Mechanism To drive LEDs safely, constant current is required. The evaluation board uses a secondary-side sensing circuit: * **Sensing Resistor:** Converts the output current into a voltage. * **Error Amplifier:** Usually a **TL431**, which compares the sensed voltage against a reference. * **Optocoupler:** Provides isolation while passing the error signal back to the primary side VIPer22A IC. #### 3. Snubber Circuit Typically consisting of a diode, capacitor, and resistor (RCD snubber), this part protects the internal MOSFET of the VIPer22A from high-voltage spikes caused by transformer leakage inductance during switching. --- ### Technical Specifications Summary | Feature | Value | | :--- | :--- | | **Input Voltage Range** | 85 VAC to 265 VAC (Universal) | | **Switching Frequency** | 60 kHz | | **Max Power Output** | ~10W to 12W (depending on thermal design) | | **Standby Power** | < 100 mW | ---