LIDL

Overview This technical teardown deconstructs a LIDL LED light fitting to analyze its internal power delivery system. While the chassis is functionally unserviceable—earning it the label of "landfill tech"—the internal driver presents a surprisingly robust implementation of an isolated constant current supply. Understanding this circuit matters for hardware enthusiasts who want to repurpose high-quality power components from otherwise disposable consumer electronics. Prerequisites To follow this logic, you should understand: * **AC/DC Rectification**: How bridge rectifiers convert mains voltage. * **Isolated vs. Non-Isolated**: The safety implications of transformer-based separation. * **Constant Current Regulation**: Why LEDs require specific amperage (260mA) rather than fixed voltage. Key Components & Tools * KP11191: The primary switching controller chip managing the power conversion. * **Transformer**: Provides galvanic isolation with triple-insulated windings. * **ES2G Diode**: A high-speed rectifier used on the secondary output side. * **Fusible Resistor**: Acts as a sacrificial safety component (15 ohm) during catastrophic failure. * **Low ESR Capacitor**: High-frequency electrolytic capacitor (47µF, 50V) critical for stability. Code Walkthrough: The Schematic Logic We can represent the driver's power logic through this functional pseudocode flow: ```cpp void driveLEDs() { // Input Stage: Safety and Rectification apply_mains_power(230V_AC); pass_through(fusible_resistor_15ohm); bridge_rectify(); // Convert to DC // Filtering Stage filter_noise(inductor_4_7mH, filter_capacitor_220nF); // Controller Loop (KP11191) while (power_on) { float current = sense_current(resistor_1_5ohm); if (current < target_260mA) { switch_mosfet(ON); // Energize transformer } else { switch_mosfet(OFF); // Collapse field to secondary } monitor_ovp(pin_10k_resistor); // Check for open circuit } } ``` The KP11191 monitors the secondary side via the collapsing magnetic field in the transformer. It uses a **1.5 ohm** current sense network to maintain a steady **260mA** output, even as the forward voltage of the LED string fluctuates between **25V and 40V**. Syntax Notes * **Current Sensing**: The controller uses two 3-ohm resistors in parallel to achieve 1.5 ohms. This distributes heat and allows for fine-tuning the output current. * **Snubber Network**: A diode-resistor-capacitor (RCD) snubber protects the internal MOSFET from voltage spikes during high-speed switching. Practical Examples * **Driver Salvage**: Remove the driver from the "landfill" housing to power 9-13 one-watt LEDs in a custom enclosure. * **Repair**: If the light flickers, replace the output **low ESR capacitor**, as this is the most common point of failure due to thermal stress. Tips & Gotchas * **Heat Transfer**: The manufacturer glues the driver to the metal case. When repurposing, ensure adequate airflow since the driver is rated for **10W**. * **ID Identification**: To read faint markings on the KP11191 chip, rub a small amount of thermal paste (zinc oxide) over the surface and wipe it clean to highlight the etched text.