The **VIPer22A** (often referred to simply as **VIPer22**) is a popular "Off-line Primary Switcher" integrated circuit. It combines a dedicated PWM controller with a high-voltage Power MOSFET on a single silicon chip. Below is an explanation of its electronic components, internal architecture, and pin configuration. --- ### 1. Key Internal Components The VIPer22A integrates several discrete stages into one 8-pin package: | Component | Function | | :--- | :--- | | **Power MOSFET** | Handles high voltage (typically up to 730V) to switch the primary transformer winding. | | **PWM Controller** | Regulates the duty cycle based on feedback to maintain a constant output voltage. | | **SenseFET** | A specialized part of the MOSFET that measures current without needing an external shunt resistor. | | **H.V. Start-up Source** | Allows the chip to power itself directly from the high-voltage DC bus during initial power-on. | | **Protection Logic** | Includes Thermal Shutdown, Overvoltage Protection (OVP), and Overcurrent Protection. | --- ### 2. Pinout Configuration (DIP-8 / SO-8) The device is designed for simplicity, requiring very few external components. | Pin Number | Name | Description | | :--- | :--- | :--- | | **1 - 2** | **SOURCE** | Internal MOSFET Source and circuit ground. | | **3** | **FB (Feedback)** | Input for the feedback loop (usually connected to an optocoupler). | | **4** | **VDD** | Supply voltage for the internal control logic (9V to 38V range). | | **5 - 8** | **DRAIN** | Internal MOSFET Drain; connects to the primary winding of the transformer. | --- ### 3. Technical Specifications Typical operating parameters for the VIPer22A: * **Fixed Switching Frequency:** 60 kHz. * **Voltage Range:** 9V to 38V (VDD). * **Drain-Source Voltage ($V_{ds}$):** 730V maximum. * **Output Power:** * **85-265 VAC (Wide range):** ~12W * **230 VAC (European range):** ~20W --- ### 4. Basic Application Circuit A typical circuit using the VIPer22A follows the **Flyback Topology**: 1. **Input:** AC mains are rectified by a diode bridge and smoothed by a high-voltage capacitor. 2. **Switching:** The VIPer22A Drain (Pins 5-8) switches the transformer primary at 60 kHz. 3. **Feedback:** An optocoupler (like the PC817) and a TL431 voltage reference monitor the secondary output and send a signal to the **FB pin** to adjust the pulse width. 4. **Auxiliary Winding:** A small winding on the transformer provides the running voltage to the **VDD pin** once the chip has started up. ---