### Overview of the VIPER17H The **VIPER17H** is a high-performance offline converter belonging to the VIPerPlus family by STMicroelectronics. It integrates an 800V avalanche-rugged power MOSFET with PWM current mode control. It is specifically designed for high-efficiency SMPS (Switched-Mode Power Supplies). --- ### Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Integrated MOSFET V(BR)DSS** | 800 V | | **Switching Frequency** | 115 kHz (Fixed) | | **Drain Peak Current (IDlim)** | 0.8 A | | **RDS(on)** | 20 $\Omega$ (Typical) | | **Supply Voltage (VCC)** | 8.5 V to 23.5 V | | **Package Options** | DIP-7, SO-16 | --- ### Internal Functional Blocks The VIPER17H is composed of several critical electronic sub-circuits that allow it to function with minimal external components: 1. **High Voltage Startup:** An internal high-voltage current source charges the VCC capacitor during power-up, eliminating the need for external bleed resistors. 2. **PWM Controller:** Operates in current mode to regulate the output voltage based on feedback from the optocoupler. 3. **Jittering Circuit:** The switching frequency is modulated (jittered) to spread the Energy Spectrum, which significantly reduces EMI (Electromagnetic Interference). 4. **SenseFET:** Instead of a traditional sense resistor, it uses an integrated SenseFET to monitor the current flowing through the power switch with high efficiency. --- ### Pin Configuration (DIP-7 Package) | Pin Name | Description | | :--- | :--- | | **GND** | Ground and Source of the internal MOSFET. | | **VCC** | Supply voltage for the internal control logic. | | **CONT** | Control pin for compensating the control loop or connecting external components for protection. | | **FB** | Feedback input. Connected to an optocoupler for secondary regulation. | | **BR** | Brown-out protection. Monitors the input mains voltage level. | | **DRAIN** | Connection to the internal MOSFET drain and the transformer primary. | --- ### Integrated Protections The device is "fully protected," meaning it includes circuitry to prevent failure under fault conditions: * **Hysteretic Thermal Shutdown:** Turns off the device if the junction temperature exceeds 150°C. * **Overload Protection (OLP):** Limits power if the output is shorted or heavily loaded. * **Open Loop Protection:** Safely shuts down if the feedback signal is lost. * **Brown-out:** Detects if the AC input voltage is too low to prevent overheating at high currents. --- ### Typical Application Diagram ```mermaid graph LR AC_In --> Rectifier Rectifier --> Transformer_Primary Transformer_Primary --> VIPER17H_Drain VIPER17H_FB --> Optocoupler Transformer_Secondary --> DC_Out ```