AL1771/1772

Document number: DS41314 Rev. 1 - 2

16 of 24

www.diodes.com

August 2018

© Diodes Incorporated

AL1771/1772

Application Information

6.

Examples of Smart Light Bulb and LED Panel Light

(1)

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. Typical block diagram of a smart light

bulb, consisting of four major functional blocks - PFC Power Conversion, Wireless/Color Management MCU, LED driver and an emitter module.

AL1771/1772 fits well with emerging Smart Connected Light bulbs illustrating as below:

1-Channel Dimmable White (Figure 1)

Brightness adjustment with Fixed Correlated Color Temperature (CCT) White

2-Channel Tunable White (Figure 2)

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

4-Channel White+RGB (Figure 3)

White +RGB color mixing

For wireless-enabled Smart Connected LED Panel Lights, Troffers and Ceiling Lights, AL1771/1772 can be used to drive emitter string(s) for

either 1-channel Dimmable White or 2-channel Tunable White applications as shown in Figure 1 and Figure 2. The AL1771/1772 can also be used

to drive White+RBG 4-channel LEDs combined with AL1782 for color mixing application as shown in Figure 3.

(2)

Interface with Emitter Strings and AL1771/1772

The AL1771/1772 PFC Power Conversion circuitry provides necessary output constant voltages (CVs) to power the MCU and the Linear 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 12/24V power supply. And cathodes of bottom LED

emitter strings are connected to LEDx pins of AL1771/1772.

(3)

Interface with Wireless/Color Management MCU and AL1771/1772

The main physical interfaces between MCU and AL1771/1772 are PWMx pins and FAULTB. MCU activates the PWMx (asserted high) to turn on

AL1771/1772 in active state for normal LED lighting operation. When PWMx pins are asserted low for 4ms, the entire AL1771/1772 enters Low-

Power mode with minimum power consumption. For typical light dimming or mixing operations, MCU generates proper PWM signals output

through PWMx pins. In case of any general fault occurs in AL1771/1772, FAULTB pin is asserted LOW to interrupt MCU for proper actions.

(4)

LED Driver Design Topology and Implementation

For AL1771/1772-powered LED Driver/Emitter block adopts a multi-channel LED driver structure with 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

AVCC/DVDD as long as AVCC and DVCC are below 30V.

Ω as

As an example of a 2-channel Tunable White light bulb design (Figure 2), an AL1772 drives two emitter strings, namely, CCTcold (6,500k) and

Ω, the maximum current for Channel 1 and Channel 2 will be 365mA if each PWM signal is

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

values to obtain different channel current if desired. However, the total channel current is advised not to exceed a total of 1,500mA with hard-limit

to 750mA maximum for each channel.

Figure 3 describes how designer can use AL1772+AL1782 to drive more than two channel LEDs, specially in this case, to drive White+RGB LEDs

for color mixing application. The AL1772 PFC CV stage produces three voltage outputs for white and RGB LED connections. 25V is used to

connect with White LED Anode, 12V is for Green and Blue LEDs, and 8V is for Red LED. The White LED and Red LED cathodes are connected

with AL1772 channel 1 and channel 2 respectively, and the Green and Blue LED cathodes are connected with AL1782 channels. In Figure 3,

AL17050 high voltage BUCK converter is used to produce MCU power supply voltage 3.3V for high efficiency and low standby power

considerations.