LED Lighting Solutions Summer 2010 Adding Intelligence to Lighting Applications LED Lighting Design Guide www.microchip.
LED Lighting Solutions Table of Contents LED Lighting ................................................................ 3 LED Applications ......................................................... 3 Efficient LED Control .................................................... 3 Driving LEDs with a Charge Pump ................................. 4 MCP1252 Charge Pump Backlight Demonstration Board (MCP1252DM-BKLT) ................. 4 Driving LEDs with a Boost Regulator .............................
LED Lighting Solutions LED Lighting Efficient LED Control LEDs are no longer used just for providing the pretty red and green indicator lights on electronic equipment. Advances in technology have allowed LEDs to be used as practical sources of illumination. The primary benefits of LEDs are long life, durability and efficiency. When driven properly, a power LED can last tens of thousands of hours without a degradation of light output.
LED Lighting Solutions Driving LEDs with a Charge Pump Driving LEDs with a Boost Regulator A charge pump power supply does not have inductors that are required in other SMPS topologies. This provides a more compact and less expensive circuit. The downside is that charge pumps cannot supply large amounts of current compared to the other topologies. Charge pump circuits are most useful for backlighting applications. Common applications include PCs, LCD displays and automotive instrumentation.
LED Lighting Solutions MCP1650 Multiple White LED Demonstration Board Driving LEDs with a SEPIC Regulator (MCP1650DM-LED2) The MCP1650 Multiple White LED Demo Board uses the MCP1650 IC to power the nine white LEDs which are connected in series. A PIC10F202 microcontroller in a SOT-23 6-pin package is used to provide the PWM signal to the MCP1650. It also accepts a push button input that allows the user to adjust the white LEDs to three different intensities of 100%, 50% and 25%.
LED Lighting Solutions High Efficiency LED Smart Driver 9-13 volt systems easily adapt to a Smart Driver Circuit to drive High Power LEDs using the MCP1702, MCP1652 and a PIC10F202. The MCP1702 directly connected to the 12 volt source creates a 5 volt bias supply capable of delivering 250 mA to the intelligent boost control circuit. The LEDs are powered by the source voltage boosted by the MCP1652, minimizing the current requirements for the 5V power system.
LED Lighting Solutions Adding Intelligence – PIC10F Solutions Package Comparison SOT-23 vs. MSOP and SOIC 8-TDFN (MC/MNY) 2 x 3 mm 6-SOT (OT) 3 x 3 mm PIC10F2XX 8-MSOP (MS) 3 x 5 mm 8-SOIC (SN) 5 x 6 mm Shown approximate size. Provide Simple Dimming Control LED lighting applications can benefit from the intelligence of a MCU. The MCU can be used for a variety of tasks, including the user interface, communication, battery status monitoring and temperature measurement.
LED Lighting Solutions Integrate Multiple Tasks – PIC12 and PIC16 Mixed Signal Solutions Easy Migration The 8, 14 and 20-pin devices in the PIC12F and PIC16F families have compatible pin-outs for upward and downward migration. Common connections such as power and ground are located in the same positions on the package footprint so that an 8-pin design can easily be expanded to a 14 or 20-pin design. The LED current drive function can be integrated with other tasks on the same MCU.
LED Lighting Solutions Generating PWM Control Signals ■ An external PWM peripheral IC may be used. This option There are multiple ways to generate PWM control signals to control power circuits. ■ Devices with the Capture-Compare-PWM (CCP) module can generate PWM signals to control power circuits using an on-chip digital timebase. The signal pulse width is controlled by the MCU clock and a duty cycle register.
LED Lighting Solutions Mixed-Signal LED Drivers Some devices, such as the PIC16F616, have a SR latch module that can be used in many different ways along with the comparators and other digital signal events. Events such as clock pulses or comparator signals can be programmed to set or reset the SR latch. These programming options allow almost any kind of control signal to be generated.
LED Lighting Solutions MCP1630 and MCP1631 High-Speed PWM Controllers MCP1630 Boost Mode LED Driver Demonstration Board (MCP1630DM-LED2) The MCP1630 and MCP1631 offer another method that can be used to generate high speed PWM signals for high power LED drivers. The MCP1630 is an 8-pin device that contains the components needed to generate an analog PWM control loop, including an error amplifier, comparator and a high current output pin to drive a power transistor.
LED Lighting Solutions Digital Control vs. Analog Control Low Cost Digital Control LEDs can be driven with a fully digital control loop. Instead of measuring the LED current with an op amp or comparator circuit, the LED current is sampled using an ADC. Some type of digital algorithm replaces the analog control loop. A proportional-integral-derivative (PID) control algorithm is commonly used because it has software coefficients that can readily be adjusted to affect the controller behavior.
LED Lighting Solutions High Performance Digital Control Devices in the PIC18F, PIC24 and dsPIC33F families offer 8-bit and 16-bit solutions for fast calculation of digital control loops. In addition, these families have device variants with fast ADC peripherals and specialized PWM modules that are optimized for power control applications. A selection of devices for digital power control is shown in the table below.
LED Lighting Solutions Wired Communication Solutions for Lighting DMX512 Many lighting applications require some form of communication for remote control but also for diagnostic purposes. Some of the most common interfaces used in lighting are: ■ 0-10V ■ DMX512 ■ Digitally Addressable Lighting Interface (DALI) The DMX512 interface (ANSI E1.11) has gained great popularity in theatrical/entertainment lighting applications because of its simplicity and low cost.
LED Lighting Solutions Advanced Communication Solutions for Lighting Development Tools Several advanced wired and wireless communication interfaces are being evaluated for use in a multitude of innovative lighting applications including: ■ ZigBee® and MiWi™ wireless protocols based on the IEEE 802.15.4 standard ■ Wi-Fi™, IEEE 802.11 ■ Ethernet, IEEE 802.3 ■ USB ■ CAN, LIN MRF24J10 – a fully integrated 2.4 GHz IEEE 802.15.4 compatible transceiver DM163027-4 – PICDEM Z 2.
LED Lighting Solutions USB Interface With the demise of the serial port, any application that requires a connection with a personal computer has now to be routed to the USB port. Some innovative lighting applications occasionally require such a connection to be established. Several models of PIC18F microcontrollers incorporate a complete USB interface.
LED Lighting Solutions Temperature Sensing Solutions for Power LED Applications Every light source has a specific energy efficiency. A certain portion of the energy supplied to it is wasted in the form of heat. One of the fundamental differences between Power LED technology and other traditional sources of light is in the way this heat is transferred.
LED Lighting Solutions Using TC6501 Open Drain Output for Current Set-Point Control Fan Controller Application Using TC6502 If a cooling device (fan) is available, a TC6502 device (with the HYST pin connected to VCC to obtain a 10°C hysteresis threshold) can directly control a cooling fan to improve the heat transfer. There are different ways that the TC6501 and TC6502 temperature sensors can be used in an application.
LED Lighting Solutions Voltage Output Temperature Sensors The most basic technique employed to protect the device from damaging over-temperature conditions is to provide a shutdown signal to the driver circuit when a pre-defined threshold is reached. However, this behavior can be unacceptable in applications where continuous lighting is required for safety or regulatory conditions.
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