Types And Selection Of DC Stabilized Power Supplies

An electronic device that can provide a stable DC power supply for a load. Most of the power sources for DC stabilized power supplies are AC power sources. When the voltage or load resistance of the AC power supply changes, the DC output voltage of the regulator will remain stable. With the development of electronic devices towards high precision, high stability, and high reliability, DC stabilized power supplies have put forward higher requirements for the power supply of electronic devices.

 

Types and selection of DC stabilized power supplies:

 

1, Linear DC stabilized power supply

1) Transistor series DC stable power supply: The transistor series DC stable power supply operates in a linear amplification state, with fast response speed, high voltage stability and load stability, low output ripple voltage, and low noise. In terms of circuit technology, its control circuit uses fewer components. There are no special requirements for the switching characteristics of the regulating tube and the high-frequency performance of the filter, resulting in high reliability.

 

A serious drawback of a series regulated power supply is its low efficiency. To improve efficiency, it is necessary to reduce the pressure drop on the regulating tube and minimize losses on the regulating tube. Solution: 1. PNP and NPN transistors are complementary: when the output power current of a series regulated power supply is high, the adjustment transistor is usually connected to a Darlington combination transistor with a common collector electrode. Due to the same electrical parameters of the transistor, maintaining the same current amplification factor reduces the collector emitter voltage drop of the complementary connected combination regulator, thereby improving the efficiency of the power supply. 2. Bias method: The voltage drop between the collector and emitter of a common collector combination tube generally depends to some extent on the bias current. By using bias connection method, the power efficiency can be effectively improved when the output current is constant. 3. Switching voltage regulator as a pre adjustment: When the input and output voltage difference is large and the output current is large, using a switching voltage regulator as a pre adjustment for a series voltage regulator is also effective in improving power efficiency. Method to implement. The pre adjustment of the switch can also be set on the primary side of the power transformer.

 

2) The development of integrated linear regulators: In the early market, there were many manufacturers of integrated regulators with large output and wide application areas. It is mainly divided into two categories: semiconductor single-chip integrated voltage regulators and hybrid integrated voltage regulators. Their circuit forms, packaging, voltage and current specifications are diverse. Integrated voltage regulators can be divided into constant voltage, adjustable, tracking, and floating. However, regardless of the form, they typically consist of a reference voltage source, a comparative amplifier, a regulating element i.e. power transistor, and some form of current limiting circuit. Some integrated voltage regulators also have internal logic shutdown circuits and thermal cutoff circuits. Compared with voltage regulators composed of discrete components, integrated voltage regulators have significant advantages, including low cost, small size, convenient use, good performance, and high reliability.

 

3) Constant current source network stabilized power supply technology: The use of constant current network stabilized power is a characteristic of current series stabilized power supplies. The use of a constant current network can effectively improve the stability of the power supply. Constant current networks are commonly used for integrating voltage regulators. Series voltage regulators composed of discrete components are increasingly adopting constant current technology. Constant current can be achieved by using components such as transistors, field-effect transistors, and constant current diodes. It is more convenient to use constant current diodes in series voltage regulators with discrete components.

 

2, Switching DC stabilized power supply

A switch type DC regulated power supply refers to a DC regulated power supply whose power regulation components operate in an "on" and "off" manner. Early magnetic amplifier switching DC stabilized power supplies used the "saturated" and "unsaturated" states of the iron core to perform "on" and "off" control. That is a low-frequency magnetic amplifier. The thyristor phase controlled rectifier power supply that appears during this process is also a type of switching DC power supply. Subsequently, the high-frequency switching power supply conversion technology has developed rapidly, mainly referring to high-frequency switching DC stabilized power supplies in the form of converters. In the 1990s, power electronics technology, PWM and other technologies became increasingly mature, and DC switching power supplies and AC switching power supplies became the dominant players in the market. Power electronics technology is a discipline that utilizes power electronics technology to control and convert electrical energy. It includes three parts: power electronic devices, converter circuits, and control circuits. It is an interdisciplinary field between the three major electrical engineering technologies of power, electronics, and control. With the development of science and technology, power electronics technology has gradually developed into a comprehensive technical discipline with interdisciplinary infiltration due to its close connection with modern control theory, materials science, electrical engineering, microelectronics technology and many other fields.

 

1) No power frequency transformer: Eliminating power frequency power transformers and adopting rectification input directly from the power grid is an important measure to reduce the volume and weight of switching power supplies. The absence of power frequency transformers has become a characteristic of contemporary advanced switching power supplies. Compared with various DC stabilized power supplies with power frequency transformers, the outstanding advantages of switch mode power supplies without power frequency transformers are small size, light weight, and high efficiency. The circuit forms of switch mode power supplies are diverse. In terms of modulation technology, there are pulse width modulation, frequency modulation, hybrid modulation, etc., among which pulse width modulation accounts for the vast majority. At present, there are completely transformer free switching power supplies that do not even require high-frequency converters. The biggest feature of this power supply is that its volume is much smaller than that of current switch mode power supplies without power frequency transformers, and there are no components such as wound transformers. It can be manufactured using integrated circuit technology.

 

2) High frequency switching power supply: A significant feature of modern switching power supplies is the continuous increase in switching frequency. Transistor switching power supply, thyristor switching power supply, or field-effect transistor switching power supply are all developing towards high frequency. With the emergence of power IGBTs and MOSFETs, the operating frequency of switching power supplies has gradually increased from the early typical 20KHz to the megahertz range or even the gigahertz range.

 

3) Integration of control circuits: The control circuits of early switching power supplies were composed of discrete components. In this way, the circuit design is complex, debugging and maintenance are troublesome, which affects the promotion and application of switch mode power supplies. In order to adapt to the rapid development of switch mode power supplies, integrated switch mode power supply control circuits have been successfully developed, and their functions are becoming increasingly complete. The integration of switch mode power supply control circuit greatly simplifies the design of switch mode power supply, improves the electrical performance and reliability of switch mode power supply, and has a small volume, reducing costs.

 

4) High frequency of main components: In order to adapt to the rapid development of switching power supplies, the main components used in switching power supplies are also rapidly developing, and their main goal is to achieve high frequency. The switching components in switching power supplies - power transistors, thyristors, and field-effect transistors - have all made progress in increasing operating frequency. However, the most eye-catching are the emergence of power transistor IGBT composite transistors and MOSFET field-effect transistors, which not only increase the switching frequency to 1 MHz -1 GHz, but also have special advantages such as good switching characteristics, low required driving power, no secondary wear, and the ability to prevent thermal runaway. In addition, the emergence of high current Schottky barriers has greatly improved the rectification efficiency of low-voltage high current switching power supplies. It has the advantages of fast switching speed, short reverse recovery time, and small forward voltage drop. During the filtering process, capacitors and other devices must also be developed in terms of materials, structure, and technology to meet the high-frequency requirements of switching power supplies.

 

5) Fully digital control: The control of switching power supplies has gone through analog control and mixed analog and digital control, and has now entered the stage of fully digital control. Full digital control is a new development trend that has been applied in many power conversion devices. However, in the past, the application of digital control was relatively limited in DC/DC converters. Over the years, high-performance fully digital control chips for switching power supplies have been developed, and the cost has also been reduced to a relatively reasonable level. Many companies in Europe and the United States have developed and manufactured digital control chips and software for switch converters. The advantage of fully digital control is that digital signals can be calibrated to smaller quantities than mixed analog digital signals, and the chip price is also cheaper. The current sensing error can be accurately digitally corrected, making voltage sensing more accurate. Can achieve fast and flexible control design.