Portable projector 6A RGB LED driver reference design - Power Circuit - Circuit Diagram

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Abstract: This article describes a reference design for a 6A step-down LED driver based on the MAX16821. This circuit can drive an LED. Reference designs include circuit specifications, schematics, circuit descriptions, and performance introductions.

Overview

This reference design is for a 6A step-down LED driver for portable projectors. The reference design is based on the PWM HB LED driver MAX16821, which drives one LED; three LEDs are required to drive RGB tri-color LEDs.

LED driver specifications

Input voltage range (VIN): 10V to 15V

Output voltage (VLED): 4.5V to 6V

Output current (ILED): 1.5A to 6A, analog control

Analog control voltage: 1.1V to 2.8V, corresponding to 1.5A to 6A

Maximum LED turn-on duty: 50%

Maximum LED current rise/fall time: < 1μs

Maximum LED current ripple: <15% at 6A

enter

VIN (J1 and J2 are connected to VIN+, J3 and J4 are connected to GND): 10V to 15V input power supply.

On/Off Control (J8): Floating or connected to +5V to enable the driver; J8 disables the board when shorted.

PWM input (J7): PWM dimming input, connected to a PWM signal with an amplitude of 3V to 5V. In order to ensure that the PWM input can drive Q1 and Q7, the signal source should drive the 300pF load with a rise/fall time of less than 500ns. Since the rise/fall time of the output signal is controlled within 1 μs, any 3 to 4 times PWM signal with a period of 1 μs can be used.

LED current control (J6): ​​LED current regulation input. Load 1.1V to 2.8V and adjust the LED current from 1.5A to 5A.

Output

LED+ (J9, J10): Connected to the LED anode.

LED- (J11, J12): Connect to the LED cathode.

Inductor Current Output (J5): Provides a signal proportional to the LED current. The OUTV voltage is 135 times the R9 voltage.