This article is about electronics industry. For personal-use electronic devices, see consumer electronics. For scientific magazine, see Electronics (magazine).
Surface mount electronic components
Electronics is the branch of science and technology which makes use of the controlled motion of electrons through different media and vacuum. The ability to control electron flow is usually applied to information handling or device control. Electronics is distinct from electrical science and technology, which deals with the generation, distribution, control and application of electrical power. This distinction started around 1906 with the invention by Lee De Forest of the triode, which made electrical amplification possible with a non-mechanical device. Until 1950 this field was called "radio technology" because its principal application was the design and theory of radio transmitters, receivers and vacuum tubes.
Most electronic devices today use semiconductor components to perform electron control. The study of semiconductor devices and related technology is considered a branch of physics, whereas the design and construction of electronic circuits to solve practical problems come under electronics engineering. This article focuses on engineering aspects of electronics.
Electronic devices and components:
An electronic component is any physical entity in an electronic system used to affect the electrons or their associated fields in a desired manner consistent with the intended function of the electronic system. Components are generally intended to be connected together, usually by being soldered to a printed circuit board (PCB), to create an electronic circuit with a particular function (for example anamplifier, radio receiver, or oscillator). Components may be packaged singly or in more complex groups as integrated circuits. Some common electronic components are capacitors, resistors, diodes,transistors, etc. Components are often categorized as active (e.g. transistors and thyristors) or passive (e.g. resistors and capacitors).
Types Of Circuits:
Circuits and components can be divided into two groups:
analog and digital. A particular device may consist of circuitry that has one or the other or a mix of the two types.
Analog circuits:
Most analog electronic appliances, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a continuous range of voltage as opposed to discrete levels as in digital circuits.
The number of different analog circuits so far devised is huge, especially because a 'circuit' can be defined as anything from a single component, to systems containing thousands of components.
Analog circuits are sometimes called linear circuits although many non-linear effects are used in analog circuits such as mixers, modulators, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, operational amplifiers and oscillators.
One rarely finds modern circuits that are entirely analog. These days analog circuitry may use digital or even microprocessor techniques to improve performance. This type of circuit is usually called "mixed signal" rather than analog or digital.
Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear operation. An example is the comparator which takes in a continuous range of voltage but only outputs one of two levels as in a digital circuit. Similarly, an overdriven transistor amplifier can take on the characteristics of a controlled switch having essentially two levels of output.
Digital circuits:
Digital circuits are electric circuits based on a number of discrete voltage levels. Digital circuits are the most common physical representation of Boolean algebra and are the basis of all digital computers. To most engineers, the terms "digital circuit", "digital system" and "logic" are interchangeable in the context of digital circuits. Most digital circuits use two voltage levels labeled "Low"(0) and "High"(1). Often "Low" will be near zero volts and "High" will be at a higher level depending on the supply voltage in use. Ternary (with three states) logic has been studied, and some prototype computers made.
Computers, electronic clocks, and programmable logic controllers (used to control industrial processes) are constructed of digital circuits. Digital Signal Processors are another example.
Building-blocks:
- Logic gates
- Adders
- Binary Multipliers
- Flip-Flops
- Counters
- Registers
- Multiplexers
- Schmitt triggers
Highly integrated devices:
- Microprocessors
- Microcontrollers
- Application-specific integrated circuit (ASIC)
- Digital signal processor (DSP)
- Field-programmable gate array (FPGA)
Mukund Krishna
Light Emitting Diodes have come a long way from simply being cheap and inexpensive indicator lights on a myriad of electronic appliances. Today they are powerful source of illumination for a wide range of room, signage, displays and decorative lighting applications.
LEDs have been gaining importance over incandescent and fluorescent lamps for their capability to provide an equivalent amount of light for a significantly reduced intake of energy. Energy is one of the biggest debates of this century and is soon expected to become one of the most important issues concerning designers across the planet.
There are many potential benefits for lamp manufacturers to use LEDs. However, there are also many vendors trying to get in early on the LED action, so there is a pressing need for product differentiation. Also, with energy conservation and human labor costs being the prime design concerns, large lighting installations are almost expected to be ‘intelligent’.
The ability of a lamp to be able to communicate with a ‘parent’ controller, to monitor its own condition, modify its mode of operation based on this monitoring, and even ensure movement to a safe state during faults are all examples of what the next generation LED lamp is expected to be. This article will explore a few of these ‘intelligent’ options suited for LED lamps and the steps involved in achieving them.
Figure 1. Input Under-Voltage Lockout
The input voltage to an LED drive system is usually DC. The supply is either produced by an AC-DC converter working off the line or from a bus. Apart from providing the power for the LED drive, this supply will also be used to power the controller in the system (after converting to 5V or 3.3V as suited to the controller).
As shown in Figure 1, above, this controller power supply will usually be designed such that it will start operating when the input supply is a little above the required output voltage. For instance, a 5V regulator will start operating when the input reaches 6-7 volts. However, the steady state level of such a supply could be 24V supplying a string of 5-6 LEDs with 1A per string.
Once the controller powers up, it assumes that power is available and turns the LED drive system on (assuming it is configured as such), which will then try to draw the full power. If the input has reached only 10V by this time, the amount of current required from the input supply would be much higher than under steady state conditions, and it could collapse due to the sudden draw. The excess current draw could also surpass the ratings of the cable, connectors, and any other components on the power supply input, potentially causing permanent damage to the system.
In order to avoid this situation, the system should implement an ‘under-voltage lockout’ feature. The hardware for this involves a resistor divider setup that steps down the input voltage to a range that is tolerable by the controller’s inputs. The input is connected to a comparator internally.
The behavior inside the controller (firmware) should be designed such that the power section is turned on only when the input voltage has crossed the threshold that is deemed reasonable for operation.
Moreover, rather than turn on the power system as soon as the comparator switches, the firmware must poll the output of the comparator to check that the condition is consistent (since the comparator is a piece of combinational logic) and then turn the power system on. Figure 2 below shows the hardware schematic (simplified) that implements this feature.
Figure 2: Load (LED) monitoring
The load here has a constant current that is regulated through the LEDs. While it is true that the current regulation system is inherently monitoring the load, the purpose is to ensure that the correct load current is flowing. LEDs are prone to damage, which often shows up as open circuits or short circuits.
These kinds of faults can also be caused by loose wires, connectors, assembly issues on PCBs, and so forth. A short circuit on the channel could also be caused due to damage to the MOSFET (which plays the role of the switch).
