2 drive circuit design
The circuit into three parts: a. Switching power supply, to achieve low-voltage electricity to meet the current constant current LED conversion; b. PWM modulation circuit, the efficiency of the LED light out of control; c. Control circuit, and PWM of the switching power supply connection and control to achieve mixed after a light gray light control.
2.1 Based on MAXl6801/16802 of AC / DC switching power supply
High-brightness (HB) LED driver control IC MAXl680l/16802 basically meet the actual LED driver circuit of the key requirements for high-intensity lighting and display applications, can be 85 ~ 265V AC rectified voltage input of the need to adjust the LED current accuracy , available on-chip error amplifier and a 1% accurate reference. Through on-chip PWM dimming can be achieved wide dimming range.
2.2 single LED chip PWM control circuit
2. 3 Three-color real-time control circuit
In NCPl200 control, using ATmega8515 microcontroller. ATmega8515 input for the user to set the light intensity and temperature feedback and the feedback, the output is a pulse width modulation PWM in NCPl200 control information.
In the ATmega8515 I / O port via the keyboard, multi-dial switch control signal settings. Can also be computed in accordance with the proportion of three-color mixing table with three-chip PWM pulse width ratio of full-color single programming input for fast color.
2.4 Overall framework
In order to ensure the LED light intensity due to fever caused by attenuation compensation, the output with the temperature feedback and the light intensity feedback is used to correct heat caused by light attenuation.
3 Conclusion
In order to achieve high-power, full-color LED lighting, designed to MAXl6801/16802 the opening of the core power supply, respectively, through the PWM regulator chip for red, green and blue color of the RG-BLED lighting power driver design. This design takes into account the work LEDI chip temperature rise resulting light attenuation, the output wavelength shift, lumen depreciation and other practical problems, and make appropriate compensation. To achieve a certain degree of gray scale adjustment. In the ATmega8515 microcontroller as the core control system, the use of temperature sensors and optical sensors as a feedback source to achieve adaptive control. Experiments show that this driver circuit works well, can achieve a certain degree of multi-color lighting, used in outdoor lighting and landscape lighting.
