Dimmable Linear LED Controller

This 48V, 200mA dimmable linear LED driver is a highly reliable solution for various LED applications. The project features the BCR602 chip, which supports LED engines, LED modules, and LED strips. The driver utilizes a MOSFET (Q1) and the BCR602 chip to provide constant current control, and it can also be equipped with a Bipolar Junction Transistor (BJT).

The BCR602 chip regulates the LED current using the power Q1 transistor, allowing for precise control over the current level. The LED current is fully scalable by adjusting the external Current Sense (CS) resistor (R6), providing flexibility in design. Additionally, the BCR602 chip suppresses voltage ripple from the power supply, ensuring a constant LED current that results in better light quality.

The LED current can be dimmed using a resistor (R_set R7) or by applying an analog PWM signal to the Multi-Function Input Output (MFIO) pin. The embedded hot plug protection feature enables safe plug-in and plug-out of any LED load during operation, without compromising the driver’s performance.

The LED current level is configured to 200mA and has been thoroughly tested. The shunt resistors define the maximum LED current, which can be adjusted down to an effective resistor R6. The voltage drop at the V_SENSE pin, caused by the shunt resistors, is 400mV, or less in case of dimming, resulting in improved overall system efficiency and providing extra voltage headroom to compensate for tolerances in LED forward voltage or supply voltage.

Furthermore, the driver features a smart Over-Temperature Protection (OTP) function, which reduces the LED current when the junction temperature of the BCR602 chip exceeds a certain threshold, ensuring safe and reliable operation.

Features

• Supply 8V to 48V (Supports Up to 60V -> Read Note)
• Load Current 200mA (Supports Higher Current -> Read Note)
• Project can drive 20 Series LEDs (With 60V Power Supply)
• LED current precision ±3%
• BCR602 Supports MOSFET and BJT (DPAK or SOT-223
• 100 Hz/120 Hz supply ripple suppression
• 3 percent analog dimming or 1 percent PWM dimming of LED current at the MFIO pin
• Board suitable for assembly with transistor packages of types SOT-223, DPAK
• Rset functionality at the MFIO pin (R7)
• Hot-plug protection to minimize LED inrush current
• OTP function vs junction temperature
• Screw Terminals for LED and Power Input
• Header Connector for Dimmer Voltage Input 0 to 3.3V or PWM Input
• PCB Dimensions 31.75 x 20.96 mm

Hot-plug

Hot-plug protection allows plug-in and plug-out of any LED load during operation without damaging the LEDs caused by surge currents. Hot-plug condition is detected a VSENSE threshold of 8 mV. Its purpose is the controlled power-up of the system to stable operation.

Overtemperature protection OTP

The OTP circuit protects the IC by reducing the target LED current to one-third. With respect to dimming OTP is independent from the type of MFIO dimming used, i.e. the target current is also reduced the same way in case of PWM dimming. OTP protects the device from damage in case of high ambient temperature. Activation temperature is higher than deactivation temperature, hence there is a hysteresis of greater than 20°C. OTP is independent of the grade and type of MFIO dimming.

External driver transistors Q1: BCR602 is able to drive NPN transistors as well as NMOSFETs. NPN transistors can be used for LED currents up to several 100 mA while NMOSFETs are preferable for high LED currents. The smaller current using BJTs is caused by the DC current gain value hFE value of the used BJT. E.g. a typical hFE of 75 limits the application to a maximum below 750 mA.

Pure PWM dimming:  The PWM duty cycle at pin MFIO defines the dimming level. The PWM voltage amplitude corresponding to LED on must be in the voltage range specified by VMFIO, 100% and PWM voltage amplitude corresponding to LED off must be in the voltage range specified by VMFIO, off. The LED current is PWM modulated according to the PWM input signal. CN3 Pin 1 and 2 can be used for PWM signal input, frequency range up to 3.5Khz.

BCR602 is a linear LED controller IC regulating the LED current by means of an external driver transistor. BCR602 supports use of NPN bipolar transistors and NMOSFETs to cover a wide LED current and power range up to several hundred mA. The LED current is fully scalable by dimensioning an external current sense resistor. BCR602 suppresses the voltage ripple of the power supply driving a constant LED current for better light quality. The LED current can be dimmed by resistors as well as analog or digital PWM voltages connected to the Multi-Function Input Output (MFIO) pin. The embedded hot plug protection allows plug in and plug out of any LED load during operation. The overtemperature protection will dim the LED current if the BCR602 junction temperature threshold is exceeded. In this case the LED current will be reduced to 30% of the nominal current. Once the junction temperature drops below the temperature hysteresis nominal LED current is resumed. The BCR602 is a perfect fit for LED applications by combining small form factor with low cost. Through its higher integration, BOM savings and ensuring long lifetime of LEDs, this controller has many advantages compared to discrete solutions.

Connections

• CN1 Power Input: Pin 1 + 48V DC, Pin 2 GND
• CN2 LED: Pin 1 + LED, Pin 2 -LED (Supports up to 20 Series LEDs with 60V Power Input)
• CN3 Dimmer Control Voltage Input: Pin 1,2= Dimmer Voltage Input 0 to 3.3V, Pin 3 = GND
• Resistor R7: Default Load Current is set to 200mA, Choose 10K ohms to 470K for Current Change (Fixed Dimmer)

Schematic

Parts List

Connections

Dimming Diagram

Gerber View

Photos

BCR602 Datasheet

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