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AN-CM-301 LED Lamp Driver

1 Terms and Definitions

CCMP Current Comparator
CMP Comparator
DC Direct Current
GPO General Purpose Output
HV High Voltage
LED Light Emitting Diode
MCU Microcontroller Unit
PWM Pulse-Width Modulation

2 References

For related documents and software, please visit:

https://www.dialog-semiconductor.com/products/greenpak.

Download our free GreenPAK™ Designer software [1] to open the .gp files [2] and view the proposed circuit design. Use the GreenPAK development tools [3] to freeze the design into your own customized IC in a matter of minutes. Dialog Semiconductor provides a complete library of application notes [4] featuring design examples as well as explanations of features and blocks within the Dialog IC.

  1. GreenPAK Designer Software , Software Download and User Guide, Dialog Semiconductor
  2. AN-CM-301, LED Lamp Driver.gp , GreenPAK Design File, Dialog Semiconductor
  3. GreenPAK Development Tools, GreenPAK Development Tools Webpage, Dialog Semiconductor
  4. GreenPAK Application Notes, GreenPAK Application Notes Webpage, Dialog Semiconductor
  5. SLG47105 , Datasheet, Dialog Semiconductor

Author: Serhii Prykhodko

3 Introduction

This application note describes the HV PAK configuration for LED control. Since LEDs have high efficiency and brightness, this makes them leaders in many lighting applications.

In this case, the SLG47105 [5] is configured as the LED driver with four buttons to control LED brightness and color temperature. These features are useful for LED table lamps (see Figure 1) or other lighting devices.

Figure 1: Example LED Table Lamp

4 Construction and Control

Figure 2: Typical Application Circuit

The design has four inputs for the LED driver control, as shown on Figure 2:

  • PIN#3 – increase lamp brightness
  • PIN#17 – decrease lamp brightness
  • PIN#14 – shift color temperature to the warm range
  • PIN#2 – shift color temperature to the cold range

The general block diagram can be found in Figure 3.

Figure 3: Block Diagram

Table 1: LEDs used in this example

Name

Current, mA

Voltage, V

Power, W

Emitted Color

Peak Wavelength, nm

GNL-5630UWC-Y50

150

3.2

0.5

Warm While

2800K-3200K

GNL-5630UWC-C50

150

3.2

0.5

Cold White

5500K-7000K

In this design example, LEDs were used without a PCB. Because of the resulting thermal limitations, the LED current was limited to 100 mA.

Current CMP disables HV OUTs when LED current is higher than 100 mA.

Current Comparator Vref calculation:

The power supply voltage for three LEDs connected in series should be higher than 9.6 V (3.2 V x 3). Maximum voltage is 13.2 V for the SLG47105.

Figure 4 and Figure 5 show LEDs connected to an Evaluation board with warm and cold LEDs each alternately turned fully on. Buttons SW1, SW4 allow setting color temperature anywhere in between.

Figure 4: Warm LEDs On, Cold LEDs Off

Figure 5: Cold LEDs On, Warm LEDs Off

5 HV PAK Design

Figure 6: Design View

5.1 Design Operation

There are two PWM blocks, as shown in Figure 6.

The PWM0 block generates 49 kHz frequency and controls the general LEDs brightness (for cold and warm LED strings together) using the PWM duty cycle. The duty cycle can be changed by PIN3 (increase) and PIN17 (decrease) in a range from 0 % to 100 %. The HIGH level on PIN3 or PIN17 disables the PWM0 KEEP signal through NXOR 2-L2, and CNT2 starts to clock the duty cycle. KEEP signal is active when PIN3 and PIN17 are LOW or HIGH together.

The PWM1 block generates a PWM signal with 120 Hz frequency to control LEDs color temperature. When PWM1 OUT is HIGH, then only warm LEDs are turned on, and when OUT is LOW – only cold LEDs are turned on. The PWM1 duty cycle can be changed by PIN14 (increase) and PIN2 (decrease). The buttons for PWM1 work similarly to PWM0 control buttons.

Figure 7: PWM1 OUT Signal

PWM1 signal is modulated by PWM0 signal, as shown on Figure 8. As a result, the general brightness depends on the PWM0 duty cycle and the color temperature depends on the PWM1 duty cycle.

Figure 8: Modulated PWM1 Signal

5.2 Current Limitation

The CCMP turns off HV OUTs when current is higher than 100 mA, see Figure 9.

Figure 9: Current Limitation

6 Waveforms

Figure 10: Warm LEDs On Max Brightness

Figure 11: Cold LEDs On Max Brightness

Figure 12: Cold LEDs 50 % and Warm LEDs 50 % Brightness

7 Conclusion

The application note describes how to configure the HV PAK for advanced LED control. The driver has a flexible configurable control logic, PWM frequency, and current limit. The HV PAK can control loads with current up to 2 A per one output, so it is possible to create powerful solutions using a single small GreenPAK IC, all with minimum external components.