## VIPER319: High-Voltage Off-Line Converter The **VIPER319** belongs to the VIPerPlus family of high-voltage converters produced by STMicroelectronics. It is specifically designed for smart power supplies, combining a high-performance PWM controller with an 800 V avalanche-rugged Power MOSFET in a single package. --- ### 1. Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Drain-Source Voltage ($V_{DSS}$)** | 800 V (Internal MOSFET) | | **Max Output Power** | Up to 18W (Wide range) / 30W (European range) | | **Operating Frequency** | 30 kHz / 60 kHz / 132 kHz (depending on variant) | | **Supply Voltage ($V_{CC}$)** | 8.5 V to 23.5 V | | **Standby Power** | < 10 mW at 230 $V_{AC}$ | --- ### 2. Core Internal Components The VIPER319 integrates several electronic subsystems to reduce external component count: 1. **800 V Power MOSFET:** The "muscle" of the chip. Its high breakdown voltage allows the design of robust power supplies that can handle surges without bulky snubber circuits. 2. **PWM Controller:** Manages the switching frequency and duty cycle based on the feedback loop. 3. **High-Voltage Startup:** An internal high-voltage current source allows the chip to start up directly from the rectified mains, eliminating the need for external startup resistors. 4. **Frequency Jittering:** The internal oscillator varies the switching frequency slightly to spread the energy of the EMI (Electromagnetic Interference), simplifying filter design. 5. **SenseFET:** Integrated current sensing technology that eliminates the need for an external sense resistor in the source path. --- ### 3. Integrated Protection Features The device includes a comprehensive suite of protections to prevent circuit failure: * **Pulse-by-Pulse Current Limiting:** Limits the peak current in the MOSFET to prevent saturation of the transformer. * **Hysteretic Over-Temperature Protection (OTP):** Shuts down the device if the internal junction temperature exceeds a safe threshold. * **Overvoltage Protection (OVP):** Protects the load if the feedback loop fails. * **Short-Circuit Protection:** Enters "hiccup mode" during a short circuit, significantly reducing power consumption until the fault is cleared. --- ### 4. Typical Application Circuit In a standard **Flyback Converter** configuration, the VIPER319 requires very few external parts: * **Input Stage:** Bridge rectifier and bulk capacitor. * **Transformer:** Primary connected to the Drain pin; auxiliary winding provides $V_{CC}$. * **Feedback:** Typically an optocoupler and a TL431 voltage reference connected to the **FB** pin. * **Compensation:** A small capacitor on the **COMP** pin to stabilize the control loop.