Infineon BCR533: A Comprehensive Technical Overview and Application Note
The Infineon BCR533 is a highly integrated, linear constant current regulator (CCR) designed to provide a simple and cost-effective solution for driving LEDs. It represents a significant advancement in solid-state lighting control, offering enhanced reliability and simplifying circuit design by eliminating the need for external components typically required by traditional driving schemes.
Technical Overview
At its core, the BCR533 is a three-terminal device (Anode, Cathode, Reference) that functions as a self-contained current source. Its key electrical characteristics define its application range:
Output Current: The device regulates a fixed, constant output current of 70 mA (±15%), making it ideal for a wide array of medium-power LEDs.
Operating Voltage Range: It can operate with a forward voltage (V_F) ranging from 6 V to a maximum of 42 V, providing significant flexibility in string length and supply voltage selection.
Low Drop-Out Voltage: With a typical drop-out voltage (V_KL) of only 0.5 V at 70 mA, it minimizes power dissipation and improves overall system efficiency.
High-Side Current Sensing: The integrated high-side sensing allows for easy implementation in various circuit configurations, particularly where the cathode of the LED string is grounded.
A standout feature of the BCR533 is its built-in over-temperature protection. The IC actively reduces the output current if the junction temperature exceeds a critical threshold, thereby safeguarding both itself and the connected LEDs from thermal damage. This intrinsic protection enhances the long-term reliability and robustness of the lighting application.
Application Notes
The primary application for the BCR533 is in AC/DC and DC/DC constant current LED drivers. Its simplicity makes it exceptionally suitable for:
Retrofit LED Lamps and Bulbs: Replacing incandescent and halogen bulbs with LED technology often requires a compact driver circuit. The BCR533's minimal external component count is a major advantage here.
Signage and Decorative Lighting: Driving strings of LEDs in architectural and decorative applications where stable, uniform illumination is critical.
Industrial and Commercial Lighting: For auxiliary lighting, indicator bars, and simple downlights.
A typical application circuit is remarkably straightforward. The BCR533 is placed in series with the LED string. The Anode is connected to the positive supply rail, the Cathode to the LED anode, and the Reference pin must be connected directly to the Cathode pin. No external resistors or other components are needed to set the current, which is fixed internally. For operation close to its maximum voltage rating or in environments with significant voltage transients, additional protective components like a transient voltage suppression (TVS) diode may be considered for enhanced robustness.
When designing with the BCR533, thermal management is the most critical consideration. The power dissipated by the device is calculated as P_Diss = (V_AK - V_F_LED) I_F. This power loss must be managed effectively through adequate PCB copper area or a heatsink to ensure the junction temperature remains within safe operating limits, allowing the internal protection circuit to function only under abnormal conditions.
The Infineon BCR533 is a paradigm of elegant simplification in LED driver design. It offers designers a highly reliable, thermally protected, and exceptionally easy-to-use solution that reduces both component count and design complexity. For applications requiring a stable, medium-current driver up to 42 V, the BCR533 presents an outstanding balance of performance, protection, and cost-effectiveness.
Keywords:
1. Constant Current Regulator (CCR)
2. LED Driver
3. Over-Temperature Protection
4. Thermal Management
5. High-Side Sensing
