The **VIPer22A** is a popular low-power offline switched-mode power supply (SMPS) controller produced by STMicroelectronics. It integrates a dedicated current mode PWM controller with a high-voltage Power MOSFET on a single chip. --- ### 1. Key Technical Specifications The device is commonly used in battery chargers, adapters, and auxiliary power supplies for appliances. | Feature | Specification | | :--- | :--- | | **Drain-Source Voltage ($V_{dss}$)** | 730V | | **Switching Frequency** | Fixed at 60 kHz | | **Supply Voltage ($V_{DD}$)** | 9V to 38V | | **Feedback Control** | Current Mode | | **Package Types** | DIP-8 or SO-8 | | **Max Output Power** | 12W (Wide range 85-265VAC) / 20W (European range) | --- ### 2. Pin Configuration (DIP-8) The VIPer22A is designed to be simple to implement, requiring very few external components. | Pin Number | Name | Description | | :--- | :--- | :--- | | 1 - 2 | **SOURCE** | Ground connection for the internal MOSFET and circuit reference. | | 3 | **FB** | Feedback input. Controls the burst mode and regulation. | | 4 | **VDD** | Supply voltage for the control logic; also used for startup. | | 5 - 8 | **DRAIN** | High voltage drain pins connected to the primary transformer winding. | --- ### 3. Core Functional Parts #### A. Internal High-Voltage Startup The VIPer22A contains a high-voltage current source. When power is applied, it draws current directly from the **Drain** pin to charge the capacitor connected to the **VDD** pin. This eliminates the need for an external startup resistor, reducing "standby" power consumption. #### B. PWM Controller It uses **Current Mode Control**. This means it monitors the current passing through the MOSFET and compares it to the feedback signal to determine when to turn the switch off. This provides: * Excellent line regulation. * Inherent pulse-by-pulse current limiting. #### C. Protection Circuitry The chip is "rugged" because it includes built-in safety mechanisms: * **Hysteretic Over-Temperature Protection:** Shuts down the chip if it gets too hot ($170^\circ C$). * **Undervoltage Lockout (UVLO):** Ensures the chip only operates when $V_{DD}$ is within a stable range. * **Overvoltage Protection:** Protects the internal logic from voltage spikes. --- ### 4. Basic Application Circuit In a typical Flyback converter setup, the VIPer22A acts as the primary switch. ```mermaid graph LR AC_In --> Rectifier Rectifier --> Transformer_Primary Transformer_Primary --> VIPer22A_Drain VIPer22A_Source --> Ground Optocoupler --> VIPer22A_FB ``` 1. **Rectification:** AC mains are rectified to high-voltage DC. 2. **Switching:** The VIPer22A switches the DC through the transformer at 60kHz. 3. **Regulation:** An optocoupler sends a signal from the output side back to the **FB** pin to maintain a constant output voltage. ---