In the previous articles, we discussed passive electronic components likeresistors,capacitors,inductors， 和Transformers. The passive components are particularly useful in designing various analog circuits.

现代电子产品的真正乐趣始于半导体和数字电子产品。电子设备全都是关于信号（电压或电流的形式）以及组件和电路的处理信号。通过将电子信号作为二元值（0和1，或低和高）处理，使半导体电子设备成为可能。作为二进制值，该半导体电子在处理信号中的应用导致以数字电子形式实施布尔逻辑。因此，开始将电子设备用于“计算”。很快，工程师和研究人员通过将它们转换为模拟电信号并将这些模拟信号数字化到数字值来设计方法来测量各种物理量。他们还设计了将数字信号转换为同等模拟电信号的方法。现在，计算机还可以互动并响应物理世界。

Most of the modern electronics is about ‘electronic computing’ and its applications to the real world. Electronic computing, combined with display technologies and input/output electronic devices leads to the development of general-purpose computers. Electronic computing, combined with various communication technologies, leads to the development of telecommunication, 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 like embedded systems, robotics, and automation.

But, before we begin the never-ending journey of semiconductor and digital electronics, it will be better to have some basic understanding of power supplies. It is the power supply that gives life to any electronic circuit or device. Every electronic circuit or device essentially needs to have a power supply section or may need to connect as a load with an external power supply circuit.

The source of electrical power can be electrical transmission lines (mains electricity), electromechanical systems (alternators and generators), solar power, or storage devices like cells and batteries. Power supplies are power converters that convert electrical power from a source to voltage, current, and frequency suitable to a load circuit. The source of electrical power can be AC or DC. Like generators and mains, electricity provides AC power while batteries and solar devices source DC power. A power supply circuit may input power from an AC or DC source, and output AC or DC power converted to suit a load. So, power supply circuits can be classified as AC-to-AC, AC-to-DC, DC-to-DC, and DC-to-AC supplies.

各种AC-to-AC电源包括变量C supplies, isolation transformers, and frequency changers. AC-to-DC power supplies are the most common. Some of the AC-to-DC power supplies include unregulated linear DC supply, linear 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 supplies are used to directly power electronic circuits, while DC-to-DC converters are generally used for converting input DC to different levels to feed different circuits in the same device rather than using different AC-to-DC supplies for getting a different voltage/current levels. Inverters, generators, and UPS are commonly used DC-to-AC power supplies.

Variable AC power supply
Variable AC power supplies are designed using transformers or adjustable autotransformers. These are used to convert AC-to-AC voltage levels. A transformer with multiple windings or taps may be used to design such power supply otherwise adjustable autotransformer can be used. These supplies convert AC voltage and current levels while the frequency of the source power remains unchanged.

频率更换器
频率更换器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 supply, where impedance matching is required between the power source and the load circuit. Isolation transformers usually do not convert voltage levels or frequency of the source power. These are useful in connecting balanced and unbalanced circuits.

Unregulated linear power supply
不受管制的线性电源是简单的AC-DC电源。这些是使用降低变压器，整流器，滤波器电容器和出血电阻设计的。首先，变压器将线路电压转换为AC中所需的电压水平。然后使用半波或全波整流器将降低的交流电压转换为直流电压。整流器是使用二极管设计的。使用过滤器电容器使整流器的脉动直流平滑。Ableeding resistor可以并行连接到过滤器电容器以进行保护。

不受管制的电源简单耐用。但是，由于输入电压或负载电流的变化，它们的输出电压可能会有所不同。因此，这些并不可靠。同样，这些产品仅能为输出固定电压和电流而设计。

Linear regulated power supply
Linear regulated power supplies are AC-to-DC power supplies. These 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 bleeding resistor. This active transistor stage enables output to different accurate DC voltage levels. There are several voltage-regulator ICs available that have an active transistor circuit integrated within 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 output fixed DC voltages. The major disadvantages of these supplies is their cost, size, and energy efficiency. These supplies lose a lot of energy due to power dissipation and may need the use of heat sink with regulator ICs.

切换管制的电源
Switching regulated power supplies are complex AC-to-DC power supplies that tend to combine the advantages of unregulated and regulated power supplies. In SMPS, the line voltage is rectified to DC, and then it is again converted to square wave AC with the help of switching transistors. This high-frequency square wave is then stepped down or stepped up and then again rectified. The rectified DC voltage is filtered before supplying it to a load.

波纹管制电源
波纹管制的电源是不受管制的AC-DC电源的改进变化。它的设计是将不受管制的电源与在饱和区域中运行的晶体管电路相结合。晶体管电路将直流电源传输到电容器以维持电压水平。波纹管制供应的主要优点是其能源效率。

可调regulated power supplies
可以修改线性调节电源，以通过在末端使用可变电阻器来提供一系列可调电压。可变电阻可以将输出电压降低到可调值。这样的adjustable power supply然后，可以提供从供应的调节的从零到最大电压的范围内的电压。Symmetrical linear regulated power suppliescan be modified to supply voltages in negative polarity as well.

电池和太阳能电源
电池，电池和太阳能电池板提供直流电源。需要首先过滤存储设备或太阳能电池板的电源以删除脉动纹波。然后可以通过使用电压调节器IC将其调节为所需的直流电压水平。如果需要加强电池或太阳能电池板的电源电压，则可以使用晶体管作为放大器来完成。

DC到DC转换器
DC到DC转换器用于上升或降低直流电压。DC到DC转换器可以是半导体，机电或电化学类型。DC-to-DC SMPlikepush-pull converter,buck converter,boost converter,buck-boost converter是半导体型DC到DC转换器的一些示例。这些耗材通常用于转换直流（从电源或其他AC来源纠正）以提供不同的直流水平，而不是在设备中使用许多AC-DC供应。

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.

电子业余爱好者和工程师最常使用线性调节的电源和电池电源。其他类型的电源通常是为特定应用或电路设计和生产的。有些电路可能需要使用太阳能电池板设计电源。

For beginners, it is always convenient to start with a linear regulated power supply providing commonly used DC voltages like 12V, 9V, 5V, and 3V. For portable circuits, the same voltages can be achieved using regulated supplies based on batteries. The battery-based regulated supplies may require battery replaced at regular intervals. So, a linear regulated power supply providing commonly used DC voltage levels is best for prototyping and testing electronic circuits. The production circuits can then be supplied power by battery or solar panel-based circuits if required.

In the next article, we will discuss cells and batteries.

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