The **VIPER17** is a high-performance, high-voltage offline converter produced by STMicroelectronics. It belongs to the VIPerPlus family and is specifically designed for Switch Mode Power Supplies (SMPS). --- ### 1. Key Internal Components The VIPER17 integrates several electronic parts into a single monolithic chip (usually in a DIP-7 or SO-16 package): | Component | Description | | :--- | :--- | | **Power MOSFET** | An 800V breakdown voltage rugged power MOSFET that handles high-voltage switching. | | **PWM Controller** | A Pulse Width Modulation controller that regulates output voltage by varying the duty cycle. | | **Start-up Cell** | A high-voltage current source that allows the chip to start up without an external resistor, improving efficiency. | | **SenseFET** | A specialized transistor used for accurate current sensing without significant power loss. | --- ### 2. Technical Specifications Below are the critical electrical parameters for the VIPER17: | Parameter | Value / Range | | :--- | :--- | | **Drain-Source Voltage ($V_{DSS}$)** | 800 V (Minimum) | | **Switching Frequency** | 60 kHz (VIPER17L) or 115 kHz (VIPER17H) | | **Max Output Power** | ~7W (Wide range) to 12W (European range) | | **Supply Voltage ($V_{DD}$)** | 8.5 V to 23.5 V | | **Standby Power** | < 30 mW at 265 $V_{AC}$ | --- ### 3. Key Features and Protection Circuits The electronic design of the VIPER17 includes several "smart" features to protect the power supply: * **Jittered Frequency:** The switching frequency varies slightly (frequency jittering) to reduce EMI (Electromagnetic Interference) emissions. * **Adjustable Current Limit:** Users can limit the peak primary current by connecting a resistor to the `CONT` pin. * **Overload Protection (OLP):** Automatically detects if the output is drawing too much power and shuts down to prevent damage. * **Hysteretic Thermal Shutdown:** If the silicon temperature exceeds 150°C, the device stops switching until it cools down. * **Soft-Start:** Gradually increases the current limit during power-up to reduce stress on electronic components. --- ### 4. Typical Application Circuit The VIPER17 is commonly used in **Flyback Converter** topologies. Its pinout simplifies the PCB layout: ```text DRAIN (Pins 7, 8): Connected to the Transformer primary winding. GND (Pin 4): Common ground reference. VDD (Pin 2): Supply voltage for the internal control circuits. FB (Pin 3): Feedback input (usually from an Optocoupler) to regulate voltage. CONT (Pin 1): Used to set the current limit or connect a decoupling capacitor. ```