## VIPER27H: Offline High Voltage Converter The **VIPER27H** is a high-performance offline converter belonging to the *ViperPlus* family by STMicroelectronics. It integrates an 800V avalanche-rugged power MOSFET with a Pulse Width Modulation (PWM) controller. It is specifically designed for high-efficiency SMPS (Switched-Mode Power Supplies). --- ### 1. Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Drain-Source Voltage ($V_{DSS}$)** | 800 V | | **Switching Frequency** | 115 kHz (Fixed) | | **RDS(on)** | 7 $\Omega$ (Typical) | | **Max Drain Current ($I_D$)** | 0.8 A | | **Supply Voltage ($V_{CC}$)** | 8.5 V to 23.5 V | | **Package Options** | DIP-7 or SO-16 | --- ### 2. Main Internal Components The VIPER27H is an "all-in-one" chip that simplifies power supply design by including: 1. **800V Power MOSFET:** This eliminates the need for an external transistor and provides a high safety margin against voltage spikes from the AC mains. 2. **PWM Controller:** Manages the switching cycle based on feedback to maintain a constant output voltage. 3. **High Voltage Startup:** An internal high-voltage current source charges the $V_{CC}$ capacitor during startup, removing the need for external bleed resistors. 4. **Frequency Jittering:** The device slightly fluctuates the switching frequency to spread Energy across a wider spectrum, significantly reducing **EMI (Electromagnetic Interference)**. --- ### 3. Protection Features The device is highly integrated with "Smart" protection mechanisms to prevent circuit failure: * **Hiccup Mode OCP:** Overcurrent protection that shuts down and restarts the device during a short circuit. * **Thermal Shutdown:** Shuts down the IC if the junction temperature exceeds ~150°C. * **Overvoltage Protection (OVP):** Protects the load if the feedback loop fails. * **Brown-out Protection:** Monitors the input mains voltage and disables the device if the voltage is too low to prevent overheating. --- ### 4. Typical Application Circuit Pinout (DIP-7) ```markdown Pin 1: GND (Ground) Pin 2: VCC (Supply voltage for the control logic) Pin 3: CONT (Control pin for compensated feedback) Pin 4: FB (Feedback input) Pin 5: BR (Brown-out protection) Pin 7/8: DRAIN (High voltage MOSFET drain connection) ``` --- ### 5. Common Applications * **Power Adapters:** For laptops, tablets, and smartphones. * **Home Appliances:** Control boards for washing machines, refrigerators, and ovens. * **LED Lighting:** Low to medium power LED drivers. * **Industrial:** Auxiliary power supplies for factory automation.