In previous articles, we discussed passive electronic components like resistors, capacitors, inductors, and transformers. Passive components are particularly useful in designing various analog circuits.
The real fun of modern electronics starts with semiconductors and digital electronics. Electronics deals with signals (in the form of voltage or current) and the processing of signals by components and circuits. Semiconductor electronics is made possible by processing electronic signals as binary values (0 and 1, or Low and High). This application of semiconductor electronics to process signals as binary values leads to the implementation of Boolean logic in the form of digital electronics. Thus began the use of electronics for 'computing'. Soon, engineers and researchers developed ways to measure various physical quantities, converting them into analog electrical signals and digitizing these analog signals into digital values. They also developed ways to convert digital signals into equivalent analog electrical signals. Now, computers can also interact and respond to the physical world.
Most modern electronics deals with “electronic computing” and its real-world applications. Electronic computing, combined with display technologies and electronic input/output devices, leads to the development of general-purpose computers. Electronic computing, combined with various communication technologies, leads to the development of telecommunications, television and internet technologies. Electronic computing combined with wireless communication and sensors leads to the development of mobile electronics and wearables. Electronic computing combined with sensors and actuators leads to the development of applications such as embedded systems, robotics and automation.
But, before we begin the never-ending journey of semiconductors and digital electronics, it will be better to have some basic knowledge about power supplies. It is the power supply that gives life to any circuit or electronic device. Every electronic circuit or device essentially needs to have a power supply section or may need to be connected as a load to an external power supply circuit.
The source of electrical energy can be electrical transmission lines (electrical grid), electromechanical systems (alternators and generators), solar energy or storage devices such as cells and batteries. Power supplies are power converters that convert electrical energy from a source into voltage, current, and frequency suitable for a load circuit. The electrical energy source can be AC or DC. Just like generators and the electrical grid, electricity provides AC power, while batteries and solar devices provide DC power. A power supply circuit can receive power from an AC or DC source and generate AC or DC power converted to suit a load. Therefore, power supply circuits can be classified as AC to AC, AC to DC, DC to DC, and DC to AC sources.
Various AC to AC power supplies include variable AC supplies, isolation transformers, and frequency changers. AC to DC power supplies are the most common. Some of the AC to DC power supplies include linear unregulated DC power supply, linearly regulated DC power supply (bench power supply), switching regulated power supplies, and ripple regulated power supply. Battery-based power supplies, solar power supplies, and DC-to-DC converters are examples of DC-to-DC power supplies. Battery-based power supplies and solar power sources are used to directly power electronic circuits, while DC to DC converters are generally used to convert input DC at different levels to power different circuits in the same device, rather than using different AC-to-DC sources to obtain different voltage/current levels. Inverters, generators, and UPS are commonly used DC to AC power sources.
Variable AC power supply
Variable AC power supplies are designed using adjustable transformers or autotransformers. They are used to convert AC to AC voltage levels. A transformer with multiple windings or taps can be used to design such a power supply, otherwise an adjustable autotransformer can be used. These supplies convert AC voltage and current levels while the power supply frequency remains unchanged.
Frequency changers
Frequency changers are used to convert the frequency of AC power. These can be designed using electromechanical devices like a motor-generator set or with the help of a rectifier-inverter set. The rectifier first converts AC to DC and then the inverter converts DC back to AC of different frequencies.
Isolation Transformers
Isolation transformers are used for AC to AC power where impedance matching is required between the power supply and the load circuit. Isolation transformers generally do not convert the voltage levels or frequency of the power supply. They are useful in connecting balanced and unbalanced circuits.
These isolation transformers are used to step up or step down voltage while keeping mains and output circuits isolated through CE certified reinforced insulation. (Image: Signal Transformer)
Unregulated linear power supply
Unregulated linear power supplies are simple AC to DC power supplies. They are designed using a step-down transformer, rectifier, filter capacitor and bleeder resistor. First, a transformer converts the line voltage to the required AC voltage level. The reduced AC voltage is then converted to DC voltage using a half-wave or full-wave rectifier. The rectifier is designed with diodes. The pulsating DC from the rectifier is smoothed using filter capacitors. A bleed resistor can be connected in parallel to the filter capacitor for protection.
Unregulated power supplies are simple and durable. However, its output voltage may vary due to variation in input voltage or load current. So these are not very reliable. Furthermore, they can only be designed to produce fixed voltage and current.
Linear Regulated Power Supply
Linear regulated power supplies are AC to DC power supplies. They are the same as unregulated (brute force) power supplies, except that they use a transistor circuit operating in an active or linear region in place of the bleeder resistor. This active transistor stage allows output to different precise levels of DC voltage. There are several voltage regulator ICs available that have an active transistor circuit integrated into them. Linear regulated power supplies are stable, safe, reliable and noise-free. There are voltage regulator ICs available for a wide range of input and output voltages and they produce fixed DC voltages. The main disadvantages of these supplies are their cost, size, and energy efficiency. These sources lose a lot of power due to power dissipation and may require the use of a heatsink with regulator ICs.
The Acopian power supplies' linear power supply (top) is ten times larger and heavier than a comparable switching supply (bottom) that is also from Acopian, but the linear unit has beneficial attributes than the switcher supply. cannot match.
Changing Regulated Power Supply
Regulated switching power supplies are complex AC to DC power supplies that tend to combine the advantages of both regulated and unregulated power supplies. In SMPS, the line voltage is rectified to DC and then converted back to AC square wave with the help of switching transistors. This high frequency square wave is then reduced or intensified and then rectified again. Rectified DC voltage is filtered before being supplied to a load.
Ripple Regulated Power Supply
Ripple regulated power supply is an improved variation of unregulated AC to DC power supply. It is designed by combining an unregulated power supply with a transistor circuit operating in the saturation region. The transistor circuit transfers DC power to a capacitor to maintain voltage levels. The main advantage of ripple-regulated supply is its energy efficiency.
Adjustable regulated power supplies
Linearly regulated power supplies can be modified to provide a range of adjustable voltages using a variable resistor in the final stage. The variable resistor can reduce the output voltage to adjustable values. Such an adjustable power supply can then supply voltages in the range from zero to the maximum voltage regulated by the supply. Symmetrical linearly regulated power supplies can also be modified to supply voltages in negative polarity.
Battery and solar energy sources
Batteries, cells and solar panels provide DC power. Energy from storage devices or solar panels must first be filtered to remove pulsating ripples. It can then be regulated to desired DC voltage levels using voltage regulator ICs. If the supply voltage of a battery or solar panel needs to be increased, this can be done using transistors as amplifiers.
DC to DC Converters
DC-DC converters are used to increase or decrease DC voltages. DC to DC converters can be semiconductor, electromechanical or electrochemical types. DC to DC SMPS such as push-pull converter, buck converter, boost converter, buck-boost converter are some examples of semiconductor type DC to DC converters. These sources are generally used to convert DC (rectified from the mains or other AC source) to provide different levels of DC, rather than using many AC to DC sources in one device.
An example of a 2 W dc-dc power supply in SMD (Image: Recom).
DC to AC power supplies
These types of power supplies are generally used for power backup. Inverters, UPS and generators are examples of such power supply systems.
Hobbyists and electronics engineers often use linearly regulated power supplies and battery power supplies. Other types of power supplies are generally designed and produced for specific applications or circuits. Some circuits may require designing a power supply using solar panel(s).
For beginners, it is always convenient to start with a linearly regulated power supply providing commonly used DC voltages such as 12V, 9V, 5V, and 3V. For portable circuits, the same voltages can be achieved using battery-based regulated supplies. Battery-based regulated supplies may require battery replacement at regular intervals. Therefore, a linearly regulated power supply that provides commonly used DC voltage levels is best for prototyping and testing electronic circuits. The production circuits can then be powered by battery or solar panel-based circuits if necessary.
In the next article we will discuss cells and batteries.
