## Overview of the VIPER50ASP The **VIPER50ASP** is a high-performance SMPS (Switched Mode Power Supply) primary switcher IC developed by STMicroelectronics. It integrates a dedicated current mode PWM controller with a high-voltage Power MOSFET on the same silicon chip. This component is widely used in off-line power supplies, providing a compact solution for AC-DC conversion. --- ### 1. Key Internal Components The VIPER50ASP is an "all-in-one" solution that contains several critical electronic sub-systems: | Component | Function | | :--- | :--- | | **Power MOSFET** | Handles high voltage (typically up to 700V) and switching currents. | | **PWM Controller** | Regulates the output voltage by adjusting the pulse width of the switching frequency. | | **Start-up Circuit** | High voltage current source that charges the VDD capacitor during initial power-up. | | **Error Amplifier** | Compares feedback voltage to an internal reference to maintain stability. | | **Protection Logic** | Manages Over-Temperature (OTP) and Over-Current (OCP) scenarios. | --- ### 2. Pin Configuration (PowerSO-10 Package) The VIPER50ASP is typically found in the **PowerSO-10** surface-mount package. Below are the functional pin descriptions: 1. **DRAIN**: Connected to the internal MOSFET drain; typically connected to the primary winding of the transformer. 2. **SOURCE**: Ground reference for the device and the MOSFET source. 3. **VDD**: Supply voltage for the internal control circuits (usually 9V to 15V). 4. **COMP**: Input for the feedback loop (compensation pin). 5. **OSC**: Connection for an external RC network to set the switching frequency. --- ### 3. Technical Specifications | Parameter | Typical Value | | :--- | :--- | | **Drain-Source Voltage ($V_{DSS}$)** | 700 V | | **Switching Frequency** | Up to 200 kHz (adjustable) | | **Maximum Drain Current ($I_d$)** | 1.5 A | | **Supply Voltage Range ($V_{DD}$)** | 8 V to 15 V | | **Thermal Shutdown** | 170 °C | --- ### 4. Distinctive Features * **Adjustable Frequency**: Unlike fixed-frequency switchers, the VIPER50ASP allows the designer to tune the frequency using an external resistor and capacitor on the OSC pin. * **Current Mode Control**: Provides better transient response and simplified loop compensation compared to voltage mode control. * **Burst Mode Operation**: In low-load conditions, the device enters a "burst mode" to reduce power consumption and improve efficiency (Green Mode). * **Robust Protection**: Includes built-in thermal shutdown with hysteresis and current limiting to prevent component failure during a short circuit. --- ### 5. Application Example (Typical Circuit) ```mermaid graph LR AC_Input --> Bridge_Rectifier Bridge_Rectifier --> Bulk_Capacitor Bulk_Capacitor --> Transformer_Primary Transformer_Primary --> VIPER50_Drain VIPER50_Source --> Ground Optocoupler --> VIPER50_Comp ```