OC5A2B00

The OC5A2B00 is a high-voltage step-down constant-current LED driver IC from OCX Semiconductor (欧创芯半导体), designed specifically for high-power LED lighting applications. Operating from a wide 6V to 60V input voltage range, this device integrates a high-voltage power MOSFET and operates as a buck topology constant-current regulator, eliminating the need for external switching transistors and reducing overall solution size and cost. The OC5A2B00 provides accurate constant-current regulation for LED strings, ensuring consistent brightness and long LED lifespan. The output current is programmed via an external current sense resistor, with a low sense voltage to minimize power loss and improve efficiency. The device supports both PWM dimming (via the DIM pin) and analog dimming, providing flexibility for different lighting control requirements. PWM dimming allows for very wide dimming ranges with no color shift, while analog dimming offers smooth, flicker-free brightness control. With efficiency levels up to 95%, the OC5A2B00 minimizes heat generation and reduces thermal management requirements. Comprehensive protection features include over-current protection, output short-circuit protection, over-voltage protection, and thermal shutdown, ensuring reliable operation under fault conditions. The compact ESOP-8 package with exposed thermal pad provides excellent thermal performance for high-power operation.

The OC5A2B00 operates as a buck (step-down) constant-current LED driver using a peak current-mode control approach: 1) Power Stage: The integrated high-side power MOSFET switches the input voltage across the LED load and inductor. A low-side Schottky diode (external, for non-synchronous versions) or low-side MOSFET provides the freewheeling path when the high-side switch is off. 2) Current Regulation: The LED current is regulated by sensing the current through a low-side sense resistor (RS) in series with the LED string. The CS pin monitors the voltage across this resistor. The device operates in continuous conduction mode with a fixed switching frequency. Each cycle, the high-side switch turns on at the beginning of the cycle, causing the inductor and LED current to ramp up. When the current reaches the programmed peak level, the switch turns off and the current flows through the freewheeling path, ramping down until the next cycle begins. 3) Dimming Control: – PWM Dimming: When a PWM signal is applied to the DIM pin, the LED current is switched on and off at the PWM frequency. The brightness is proportional to the PWM duty cycle. This provides very accurate dimming with no color shift. – Analog Dimming: Adjusting the DC voltage on the DIM pin changes the current reference level, allowing continuous brightness adjustment. 4) Soft-Start: At power-up, an internal soft-start circuit gradually increases the LED current to prevent inrush current and protect the LEDs from current overshoot. 5) Protection Mechanisms: – Over-Current Protection (OCP): If the current sense voltage exceeds the OCP threshold, the switch cycle is terminated immediately. – Over-Voltage Protection (OVP): If the output voltage exceeds the OVP threshold (e.g., LED open circuit), the device shuts down. – Thermal Shutdown (TSD): When the junction temperature exceeds the safe limit, the device stops switching to prevent damage. It auto-restarts after cooling. – UVLO: Ensures proper startup only when the input voltage is above the minimum threshold.

• Automotive LED headlights and daytime running lights (DRL)
• High-bay and low-bay industrial LED warehouse lighting
• Outdoor street lighting and area lighting
• Architectural and decorative LED lighting systems
• Automotive interior ambient lighting
• Constant-current LED power supply modules
• Stage lighting and studio LED fixtures
• LED grow lights for horticulture