AL1791/1792/1793/1794

Document number:37957 Rev. 3 - 2

13 of 18

www.diodes.com

September 2015

© Diodes Incorporated

AL1791/1792/1793/1794

Application Information

Examples of Smart Light Bulb and LED Panel Light System Configurations

Emerging smart LED light bulbs, including Tunable White and Tunable Color products used in either wired or wireless control applications,

address human needs for energy saving, light quality scene setting and entertainment light management. A typical block diagram of a smart light

bulb consists of four major functional blocks: AC to DC Power Conversion, Wireless/Color Management MCU, an LED driver and an emitter

module. The AL179X family fits well with emerging Smart Connected Light bulbs illustrated as below:



1-Channel Dimmable White (Figure 2)

Brightness adjustment with Fixed Correlated Color Temperature (CCT) White



2-Channel Tunable White (Figure 3)

CCT Tuning with range from 2,700K to 6,500K



3-Channel Tunable Color (Figure 4)

Color Mixing for CCT White Generation and Tunable RGB



4-Channel White with Tunable Color (Figure 5)

Main White Light with Tunable RGB

For wireless-enabled Smart Connected LED Panel Lights, Troffers, and Ceiling Lights, AL1791/2 can be used to drive emitter string(s) for either 1-

channel Dimmable White or 2-channel Tunable White applications as shown in Figure 2 and Figure 3.

Interface with AC to DC Power Conversion and AL179x

The AC to DC Power Conversion provides necessary output constant voltages (CVs) to power the MCU, and the LED Driver blocks of the entire

smart light bulbs. Typical applications for smart light bulbs might require 3.3V for MCU and 12/24V for LED emitter strings of mainstream smart

light bulbs. Anodes of top LED emitter strings are connected to a 12/24V power supply, and cathodes of bottom LED emitter strings are connected

to LEDx pins of AL179x.

Interface with Wireless/Color Management MCU and AL179x

The main physical interfaces between MCU and AL179x include EN, PWMx pins, and FAULTB. MCU activates the EN (asserted high) to turn on

AL179x in active state for normal LED lighting operation. When EN pin is asserted low, the entire AL1794 enters into shutdown state with

minimum power consumption. For typical light dimming or mixing operations, MCU generates proper PWM signal output through PWMx pins. In

case of any general fault occurring in AL179x, FAULTB pin is asserted LOW to interrupt MCU for proper actions.

LED Driver Design Topology and Implementation

AL179x-powered LED Driver/Emitter block adopts a multi-channel LED driver structure with either analog or PWM dimming control for each

channel. The parallel LED driver channel structure covers mainstream applications for Smart Connected Lighting products. Given the maximum

allowable input voltage of 30V, AL179x can support an LED string up to 8 emitters of W, B, G (assuming LED Emitter Forward Voltage Drop,

As an example of a 2-channel Tunable White light bulb design (Figure 3), an AL1792 drives two emitter strings, namely, CCTcold (6,500K) and

The associated MCU could generate suitable PWM patterns to meet the required CCT tuning to target light output.

In the case of 3-channel Tunable Color light bulb, AL1794 (Figure 4) drives three separate channels attached to different color emitters (Green -

Channel 1, Red - Channel 2, and Blue - Channel 3). The additional channel (Channel 4 in the example) could be connected to Channel 1 to

enhance green light output. Any given CIE coordinates within the Color Triangle formed by CIE coordinates of three color emitters can be

generated by proper PWM signal pattern generated by the MCU. Therefore, CCT white light tuning tracing the CIE Planckian Locus could be

achieved.

In the case of 4-channel White RGB light bulb (Figure 5), combination of AL1791 and AL1793 ICs are used to drive four separate emitter strings,

White, Green, Red, and Blue emitters. This system configuration provides more flexibility in channel current settings and higher white light output.