The **VIPER22ADIP-E** is a popular off-line primary switcher IC manufactured by STMicroelectronics. It combines a dedicated current mode PWM controller with a high-voltage Power MOSFET on the same silicon chip. It is widely used in low-power AC/DC switch-mode power supplies (SMPS). --- ## 1. Key Specifications The following table summarizes the primary electrical characteristics of the VIPER22ADIP-E: | Parameter | Value / Description | | :--- | :--- | | **Package** | DIP-8 (Dual In-line Package) | | **Drain-Source Voltage ($V_{DSS}$)** | 730V (Integrated Power MOSFET) | | **Switching Frequency** | Fixed 60 kHz | | **Supply Voltage ($V_{DD}$)** | 9V to 38V | | **Max Output Power** | 12W (Wide range 85-265 VAC) / 20W (Single 230 VAC) | | **Feedback Control** | Current Mode | --- ## 2. Pin Configuration (DIP-8) The DIP-8 package uses a specific layout to handle heat dissipation and high voltage: | Pin Number | Name | Function | | :--- | :--- | :--- | | **1 - 2** | SOURCE | Ground reference and source of the internal MOSFET. | | **3** | FB | Feedback input; controls the PWM duty cycle based on output voltage. | | **4** | VDD | Power supply for the control logic; usually fed by an auxiliary winding. | | **5 - 8** | DRAIN | High voltage drain of the MOSFET; also used for heat sinking. | --- ## 3. Core Functional Parts The internal architecture of the VIPER22ADIP-E consists of several critical sub-circuits: ### A. High Voltage Start-up Unlike standard PWM controllers, the VIPER22ADIP-E has an internal high-voltage current source. When power is applied, it draws current directly from the Drain pin to charge the $V_{DD}$ capacitor, eliminating the need for external start-up resistors. ### B. Current Mode Controller It uses current mode control for regulation, which provides: * Excellent line and load regulation. * Inherent pulse-by-pulse current limiting. * Protection against transformer saturation. ### C. Protection Circuits The IC is "ruggedized" with several built-in safety features: 1. **Hysteretic Over-Temperature Protection:** Shuts down the IC if it exceeds 170°C. 2. **Under-Voltage Lockout (UVLO):** Ensures the IC only operates when $V_{DD}$ is stable. 3. **Over-Voltage Protection:** Prevents damage if the feedback loop fails. --- ## 4. Typical Application Diagram In a standard Flyback converter, the VIPER22ADIP-E is the "brain" and the "muscle": ```text AC Input -> Bridge Rectifier -> Bulk Capacitor -> [VIPER22A] -> Transformer -> DC Output ^ | | | Optocoupler <---/ ``` ---