### Overview of VIPER15HD The **VIPER15HD** is a high-performance, high-voltage converter belonging to the **VIPerPlus** family from STMicroelectronics. It integrates an 800 V avalanche-rugged power MOSFET with a Pulse Width Modulation (PWM) controller. It is specifically designed for SMPS (Switched Mode Power Supplies) applications. --- ### Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Drain-Source Voltage ($V_{DSS}$)** | 800 V (Minimum) | | **Switching Frequency ($F_{OSC}$)** | 115 kHz (Fixed) | | **Integrated MOSFET $R_{DS(on)}$** | 20 $\Omega$ (Typical) | | **Drain Current ($I_{Dlim}$)** | 350 mA (Minimum) | | **Supply Voltage Range ($V_{DD}$)** | 8.5 V to 23.5 V | | **Package Options** | SO16 (Narrow) / DIP-7 | --- ### Internal Architecture & Pin Functions The device reduces component count by integrating several protective and functional blocks: #### 1. Pin Configuration (Typical DIP-7/SO16) * **DRAIN:** Connected to the internal power MOSFET drain and high-voltage startup current source. * **SOURCE:** Ground reference for the control circuits and MOSFET source. * **VDD:** Supply voltage for the internal control logic. * **FB (Feedback):** Input for the control loop; it regulates the output voltage by adjusting the MOSFET duty cycle. * **BR (Brown-out):** Detects undervoltage conditions on the AC mains to protect the system. * **CONT (Control):** Used to set the current limit or for compensation. #### 2. Functional Blocks * **High-Voltage Startup:** It pulls current directly from the DRAIN pin to charge the VDD capacitor, eliminating the need for an external startup resistor. * **Jittered Frequency:** The 115 kHz switching frequency is slightly modulated (jittered) to reduce EMI (Electromagnetic Interference) emissions. * **Burst Mode Operation:** Under light loads, the device enters a "burst mode" to keep power consumption extremely low (less than 30 mW at 265 VAC). --- ### Embedded Protection Features The VIPER15HD is designed for high reliability with several built-in safety mechanisms: 1. **Hysteretic Thermal Shutdown:** Shuts down the IC if the junction temperature exceeds 170°C. 2. **Overload Protection (OLP):** Limits power if the output is shorted or heavily loaded. 3. **Brown-out Protection:** Monitors the input mains voltage; if the voltage is too low, the device stops switching to prevent overheating. 4. **Auto-Restart:** After a fault occurs, the device attempts to restart periodically until the fault is cleared. --- ### Common Application Diagram In a standard Flyback converter topology, the VIPER15HD is connected as follows: ```text AC Input -> Bridge Rectifier -> Bulk Cap -> Transformer Primary -> VIPER15HD (Drain) | (FB Pin) <- Optocoupler <- Output Voltage Sense ``` ---