## Overview of the VIPER26K The **VIPER26K** is a high-voltage converter belonging to the VIPerPlus family from STMicroelectronics. It is specifically designed for smart meters and ultra-wide input voltage power supplies, integrating an **800V avalanche-rugged power MOSFET** with PWM current mode control. --- ### Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Drain-Source Voltage ($V_{DSS}$)** | 1050 V | | **Max Output Power** | 7 W (Wide range) / 10 W (European range) | | **Switching Frequency** | 60 kHz (Fixed) | | **Supply Voltage ($V_{CC}$)** | 7 V to 38 V | | **Typical $R_{DS(on)}$** | 7 $\Omega$ | --- ### Internal Electronic Blocks The VIPER26K is an "all-in-one" solution that reduces the Bill of Materials (BOM). Its internal architecture consists of several critical stages: 1. **High-Voltage Start-up:** An internal high-voltage current source allows the device to start up without an external resistor connected to the bulk capacitor, improving efficiency and reducing standby power. 2. **Pulse Width Modulator (PWM):** Uses current-mode control to regulate the output voltage. It includes a jittering feature to reduce EMI (Electro-Magnetic Interference). 3. **Power MOSFET:** The 1050V rated MOSFET provides a high safety margin against voltage spikes, making it ideal for 3-phase systems or unstable grids. 4. **Error Amplifier:** Features an embedded error amplifier with a 1.2V reference, allowing for direct feedback sensing. --- ### Protection Features The device includes a comprehensive set of protection mechanisms to ensure system reliability: * **Hiccup Mode:** Triggered during overload or short-circuits to prevent overheating. * **Thermal Shutdown:** Shuts the device down if the internal junction temperature exceeds safety limits (typically 150°C). * **Overvoltage Protection (OVP):** Monitors the $V_{CC}$ pin to protect against regulation failure. * **Soft Start:** Gradually increases the current limit during power-up to reduce stress on components. --- ### Typical Application Circuit In a standard Flyback configuration, the VIPER26K requires very few external parts: ```mermaid graph LR Input[AC/DC Input] --> Filter[EMI Filter] Filter --> Bridge[Bridge Rectifier] Bridge --> VIPER[VIPER26K IC] VIPER --> Transformer[Flyback Transformer] Transformer --> Output[DC Output] Output --> Feedback[Optocoupler/TL431] Feedback --> VIPER ``` ---