## Overview of the VIPER100B The **VIPER100B** is a high-performance SMPS (Switched Mode Power Supply) IC that combines a dedicated current mode PWM controller with a high-voltage Power MOSFET on the same silicon chip. It is widely used in offline power supplies for applications like battery chargers, TV power supplies, and industrial adapters. --- ### 1. Internal Architecture The device integrates several critical electronic components into a single TO-220 or PowerSO-10 package: | Component | Function | | :--- | :--- | | **Power MOSFET** | Handles high voltage (up to 700V) and switching currents. | | **PWM Controller** | Regulates the duty cycle based on feedback. | | **Error Amplifier** | Compares feedback voltage to an internal reference. | | **Startup Circuit** | High voltage current source for initial power-up. | | **Protection Logic** | Manages thermal shutdown and overcurrent limits. | --- ### 2. Key Technical Specifications Understanding these parameters is essential for circuit design: * **Drain-Source Voltage ($V_{DSS}$):** 700V (High ruggedness against voltage spikes). * **Switching Frequency:** Programmable up to 200 kHz via external RC components. * **Current Limit:** Adjustable current limiting to protect the transformer and output diodes. * **Standby Consumption:** Low power consumption in no-load conditions. --- ### 3. Pinout Description (TO-220 / PowerSO-10) | Pin Name | Function | Description | | :--- | :--- | :--- | | **Drain** | Power Output | Connected to the primary winding of the transformer. | | **Source** | Ground/Return | Common ground for the power and control circuits. | | **VCC** | Supply Voltage | Power supply for the internal control logic (typically 9V to 18V). | | **COMP** | Compensation | Input for the feedback loop to regulate output voltage. | | **OSC** | Oscillator | External RC network connected here sets the switching frequency. | --- ### 4. Circuit Protection Features The VIPER100B includes "smart" electronic parts that prevent catastrophic failure: 1. **Thermal Shutdown:** If the junction temperature exceeds ~170°C, the device shuts down to prevent melting. 2. **Overcurrent Protection (OCP):** The internal MOSFET current is sensed cycle-by-cycle; if it exceeds a threshold, the pulse is terminated. 3. **Hiccup Mode:** In case of a short circuit, the device enters a low-duty cycle "hiccup" mode to reduce heat and power consumption until the fault is removed. --- ### 5. Application Example: Flyback Converter In a standard Flyback configuration: * The **VIPER100B** acts as the primary switch. * An **Optocoupler** (like PC817) sends feedback to the **COMP** pin. * An **Auxiliary Winding** on the transformer provides the $V_{CC}$ voltage once the chip starts up.