The **VIPER28LD** is a high-voltage converter from STMicroelectronics. It belongs to the *VIPerPlus* family, specifically designed for high-performance off-line Power Supplies (SMPS). It integrates an 800V avalanche-rugged power MOSFET with a PWM controller in a single package (SO-16 narrow). --- ### 1. Key Technical Specifications | Parameter | Value / Description | | :--- | :--- | | **Drain-Source Voltage ($V_{DSS}$)** | 800 V | | **$R_{DS(on)}$ (Typical)** | 7 Ω | | **PWM Frequency** | 60 kHz (Fixed) | | **Max Output Power** | ~18W (Wide range) / ~28W (European range) | | **Package** | SO-16 (Surface Mount) | | **Protections** | OLP, OVP, OTP, SCP | --- ### 2. Core Internal Components The VIPER28LD is an "all-in-one" solution that combines several electronic functions: * **Power MOSFET:** An 800V rated transistor that handles the switching of the high-voltage DC bus. * **PWM Controller:** Manages the switching frequency and duty cycle to maintain a stable output voltage. * **High Voltage Startup:** It contains an internal high-voltage current source. This allows the chip to start up directly from the rectified mains voltage, eliminating the need for external "bleeder" resistors. * **SenseFET:** Instead of using a lossy external resistor to sense current, it uses an integrated SenseFET to monitor the drain current with high efficiency. --- ### 3. Key Features and Functions #### A. Frequency Jittering The device features built-in frequency jittering. By slightly shifting the switching frequency, it spreads the energy of electromagnetic interference (EMI) over a wider band, reducing the cost of input filters. #### B. Standby Performance The VIPER28LD is designed for "Green" requirements. It enters **Burst Mode** during light loads or no-load conditions, significantly reducing power consumption (less than 30mW at 230VAC). #### C. Protection Circuits The chip is highly robust due to integrated protection logic: * **Over-Voltage Protection (OVP):** Shuts down the IC if the output voltage exceeds a safe threshold. * **Over-Load Protection (OLP):** Limits the power if the output is shorted or heavily loaded. * **Thermal Shutdown:** Turns off the device if the internal temperature exceeds ~150°C. --- ### 4. Typical Application Diagram The VIPER28LD is most commonly used in **Flyback Converters**. ```mermaid graph LR AC_Input --> Bridge_Rectifier Bridge_Rectifier --> Transformer_Primary Transformer_Primary --> VIPER28LD_Drain VIPER28LD_Source --> Ground Feedback_Opto --> VIPER28LD_FB_Pin ``` --- ### 5. Common Use Cases 1. **Home Appliances:** Control boards for washing machines, dishwashers, and refrigerators. 2. **Adapters:** High-efficiency wall chargers and power bricks. 3. **Industrial:** Auxiliary power supplies for PLCs and industrial automation. 4. **LED Lighting:** Drivers for small to medium LED arrays.