High Power Rgb Led Driver Supports Color Lighting Design - Electronics Industry

High Power Rgb Led Driver Supports Color Lighting Design - Electronics Industry

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Architectural and decorative lighting on the appropriate mix of the next generation through the red, green and blue LED output colors can be more comprehensive. In such a high-brightness, multi-LED series applications, the typical on-the decline may reach 22V to 36V, 1A to absorb the current 2A. Figure 1 shows the LED driver can provide a number of modules in series LED drive current, forward voltage up to 36V. The circuit driver RGBLED only one color, three colors of the driver needs three times this drive. Since LED brightness conduction current, and their non-linear relationship, the PWM selection (rather than the current range of LED) production control the brightness level of control by a fixed pulse current intensity modulation for each LED. Using average current mode controller IC to provide LED drive requires minimal external components.

Projects to provide current drive efficiency, LED and continuous conduction mode (CCM) boost topology with average current mode control boost converter input voltage, load LED constant current driver, driver. Single chip (MAX16821B) work in the 300kHz to control the work of the boost converter. Since the input and output converter boost converter topology provides a direct channel to ensure that the minimum input voltage is greater than turning the power LED series the maximum voltage. Through the MOSFET (Q1) and the sense resistor (Regulation 13) LED load cross-connected to the boost converter's output, in the first quarter of the LED PWMON rotor current, PWMOFF disconnecting the current channel. Detection of the regulatory 13 (by the name of the existing LED) when, IC can suppress common mode noise and DIFF pin for 6V / V output signal of the vibration amplifier output gain and the internal 0.6V reference voltage error amplifier reference voltage to provide In contrast, the differential amplifier galvanometer 6V / V gain for the current detection range is 0.6V to 0.1V reference point down, the rated load current, R13 0.1V only difference between the type of pressure will help improve efficiency. With average current control mode boost converter two, LED current control feedback loop. Outer ring road test LED current and the reference voltage EAOUT (17 pin), produced amplified error signal. Detected in the loop error amplifier output voltage, the corresponding control, through the inductor (L1) of the current. Error amplifier output also decided to set the LED drive current R13 required inductor current, LED's rated current in the R13 type of voltage drop to 0.1V's.


The second sense resistor (R15) for setting the inductor current return channel. U2, the internal differential current sense amplifier provides 34.5V / V gain. Current error amplifier output voltage error amplifier output voltage and comparing the error signal to generate the average current control loop. The amplified error signal and the internal oscillator ramp comparison, the resulting PWM signal (DL, 3-pin) to drive MOSFETQ2. Current error amplifier's high gain, so that the requirements of the circuit of the voltage circuit to produce an inductor current (in the allowable limits), a very low error. Specified input voltage and LED forward voltage (ignoring switch, diode, sense resistor and other components of the pressure), the boost converter's PWM CCM switching pattern determines the duty cycle, fixed duty cycle, which requires that the corresponding LED current to determine the required inductor current. Current loop closed-loop control voltage generated by the average inductor current, thus providing the required LED current. Two separate control loop compensation should be provided to ensure stability.



The converter parameters required are as follows:

Input voltage range: 9V to 15V,

LED maximum forward voltage: 33V The LED current: 2A Switching Frequency: 300kHz (for low-frequency filters will increase the cost of a higher frequency of these factors reduce the efficiency and EMI, in the 300kHz switching frequency optimized basis.).



Calculated using the ON duty cycle of Q2:

Type VLEDMAX biggest turn-on voltage of the LED (should include MOSFETQ1 pressure drop across the sense resistor R13 voltage drop), VD is the voltage across the diode D1, VINMIN is the minimum input voltage, vertical channel field-effect transistor ON, the average voltage In MOSFETQ2. Circuit: The dMAX = 0.74.

Choose inductor (L1), we must consider the inductance and peak current rating, the use of calculating the maximum average inductor current (ILAVG) the following formula:



Determine the peak inductor current (ILPEAK), they should pay attention to flow through the inductor ripple current, the inductor value, switching frequency. Assuming the maximum peak inductor current ripple is 20% (ILPP). Since the average inductor current ILAVG ILPP 20%, then:



Replace the known parameters of the type: ILAVG = 7.7A, ILPEAK = 9.24A.



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