## Overview of the VIPER26HD The **VIPER26HD** is a high-performance, high-voltage converter belonging to the VIPerPlus family by STMicroelectronics. It is designed for use in offline Power Supplies (SMPS) and integrates an 800 V avalanche-rugged power MOSFET with PWM current-mode control. --- ### Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Drain-Source Voltage ($V_{DSS}$)** | 800 V | | **Switching Frequency** | 115 kHz (Fixed) | | **RDS(on)** | 7 $\Omega$ (Typical) | | **Maximum Drain Current** | 800 mA | | **Input Voltage Range** | 85 VAC to 265 VAC (Universal) | | **Package Options** | SO16 narrow, DIP-7 | --- ### Internal Electronic Components & Architecture The VIPER26HD is a "monolithic" device, meaning several critical electronic sub-systems are integrated into a single chip: 1. **Power MOSFET:** An 800 V rugged MOSFET that handles high-voltage switching, reducing the need for external high-voltage transistors. 2. **PWM Controller:** A Pulse Width Modulation controller that regulates the output voltage by adjusting the duty cycle. 3. **High-Voltage Startup:** It includes an internal high-voltage current source that charges the $V_{CC}$ capacitor during startup, eliminating the need for bulky external startup resistors. 4. **Frequency Jittering:** The internal oscillator incorporates jittering to spread the energy of the switching frequency, significantly reducing EMI (Electromagnetic Interference) emissions. 5. **Current Sensing:** Integrated sense-FET technology allows for precise current limiting without an external sense resistor, improving efficiency. --- ### Protection Features The device includes a robust suite of protection mechanisms to ensure circuit safety: * **Hiccup Mode:** Automatically restarts the device during a short circuit or overload. * **Thermal Shutdown:** Shuts the device down if the junction temperature exceeds $150^\circ C$. * **Overvoltage Protection (OVP):** Protects the load if the feedback loop fails. * **Open Loop Protection:** Detects if the optocoupler or feedback path is broken. --- ### Typical Application Circuit Parts When designing with the VIPER26HD, you will typically use these external components: ```markdown 1. Input Bridge Rectifier (Converts AC to DC) 2. Bulk Capacitor (Filters DC ripple) 3. Transformer (Flyback topology) 4. Snubber Circuit (RCD network to protect the MOSFET from spikes) 5. Optocoupler (Isolation and feedback) 6. Output Diode (Schottky or Ultra-fast recovery) ```