recent years LEDs and LED lighting has emerged as the leading
candidates for next-generation lighting due to their low energy
consumption, high efficiency, and long life.
The following are 25 topics and keywords covering the comparatively complex field of LEDs.
Topic : Switching power supplies
Power supplies are used in virtually all electronic devices
A switching power supply outputs a stable DC voltage based on rectification and control via a semiconductor switch that performs ON/OFF operation at high frequency. It is the preferred choice in a variety of devices due to its relatively small size, light weight, and high efficiency. Additional features are often included, such as noise filters, activation/rectifier circuits, and protection functions for better performance.
Topic : AC/DC and DC/DC converters
Essential for voltage rectification
• An AC/DC converter is a switching power supply that converts AC voltage to DC.
A DC/DC converter is a switching regulator that converts one DC voltage
(i.e. from a battery) to another. Normally features excellent switching
Topic : Fixed voltage drive
Simple, cost-effective LED lighting method
This type of driving method provides the required current by supplying constant voltage to the LED(s). This is the simplest method to implement and is cost-effective. However, one major drawback is that the current will vary based on the different Vf of each LED and the heat generated by the chip itself. This will result in fluctuating brightness. Heat loss at the limiting resistor must also be considered.
Topic : Fixed current drive
Efficient lighting method
This type of drive provides constant current, improving efficiency while reducing heat generation. Although more complex and costly than constant voltage circuits, brightness fluctuations are minimized.
Topic : Duty control method
Required for adjusting the brightness without changing the color
method controls the brightness by switching the LEDs ON and OFF at high
speeds with constant forward current. The duty ratio is expressed as
the fraction of the ON/OFF cycle the LED is lit up (or ON).
Brightness is determined based on the value of the forward current (If). This type of circuit is used in circuits where the brightness fluctuates greatly with just a small change in current or applications where the color tone varies with brightness.
Topic : PWM control
Brightness based on duty factor
The PWM (Pulse Width Modulation) method controls LED brightness by varying the pulse width. The ratio the LED is ON is called the duty cycle. LEDs are turned ON and OFF at high speed and the brightness is adjusted by varying the ON time. If switching is early, residual imaging may occur.
Topic : Phase control
Brightness changes based on the amount of power
control involves controlling the power supplied to the load using power
control elements such as thyristors. Current flows only when a signal
is supplied to the Gate terminal of the thyristor, even if voltage is
provided. Current (and therefore brightness) is adjusted by controlling
the conduction time.
Advantages include continuous adjustment due to the wide output range, a small, low-cost control circuit, and reduced power loss.
Topic : Wireless communication
Signal transmission via electromagnetic waves
This method transmits information without wires. Various standards are used, such as infrared, Bluetooth, Zigbee, wireless LAN, and radio broadcast. Differentiating factors include transmission rate, communication distance, and power consumption.