Stabilized power supply means that its output voltage is relatively stable, which is closely related to people's daily life. Also called regulated power supply and voltage regulator. With the development of electronic technology, the application field of electronic system is more and more extensive, and the types of electronic equipment are more and more, and the requirements for regulated power supply are more flexible and diverse. The miniaturization and low cost of electronic equipment make the regulated power supply develop in the direction of light, thin, small and high efficiency. In design, the regulated power supply has also developed rapidly from the traditional transistor series regulated power supply to the switching regulated power supply with high efficiency, small volume and light weight.
In daily work, electronic engineers usually divide the voltage regulator into DC voltage regulator and AC voltage regulator according to the stable objects. The output voltage of DC voltage regulator is DC, and the output voltage of AC voltage regulator is AC, both of which are generally supplied by commercial power. Therefore, we can divide the regulated power supply into DC regulated power supply and AC regulated power supply according to the types of voltage regulators. Let's briefly introduce these two types of regulated power supplies (see table 1).
A, the classification of regulated power supply
Second, the classification and characteristics of AC regulated power supply
The power supply that can provide stable AC voltage and frequency is called AC regulated power supply, and the AC regulated power supply in the market can be roughly divided into the following categories:
2. 1. Parameter adjustment (resonance) type
The basic principle of this kind of regulated power supply is LC series resonance, and the early regulated power supply with magnetic saturation regulator belongs to this kind. Its advantages are simple structure, few required components, wide voltage stabilizing range, high reliability and strong anti-interference and anti-overload ability. Disadvantages are high energy consumption, high noise, large volume and high cost.
2.2. Automatic coupling (variable ratio) adjustment type
2.2. 1. Mechanical pressure regulating type
The servo motor drives the carbon brush to move on the winding sliding surface of the autotransformer, and changes the ratio of output voltage (vo) to input voltage (Vi), thus realizing the adjustment and stability of the output voltage of the regulated power supply. It has the characteristics of simple structure, low cost and small output waveform distortion. However, due to the sliding of the carbon brush, the contact is easy to generate sparks, which leads to the damage or even burning of the brush and the slow speed of voltage regulation.
2.2.2. Change the tap type
The autotransformer is made into a plurality of fixed taps, and relays or thyristors (solid-state relays) are used as switches to automatically change the tap positions, thus realizing the stability of the output voltage. This regulated power supply has the advantages of simple circuit, wide regulation range (130V-280V), high efficiency (≥95%) and low price. The disadvantages are low voltage stabilization accuracy (8 ~ 10%) and short working life. Suitable for supplying power to air conditioners at home.
2.2.3. High-power compensation type purification regulator (including precision regulator)
This kind of regulated power supply uses compensation link to stabilize the output voltage, which is easy to realize microcomputer control. Its advantages are good anti-interference performance, high voltage stabilization accuracy (≤ 1%), fast response (40 ~ 60 ms), simple circuit and reliable operation. The disadvantage is that it has low-frequency oscillation to nonlinear loads such as computers and program-controlled switches; Large input current distortion and low source power factor; The output voltage is phase shifted from the input voltage. Because of its advantages of stable voltage, anti-interference, fast response and moderate price, it has been widely used.
2.3. Switching AC regulated power supply
The difference between high frequency pulse width modulation technology and general switching power supply is that its output must be AC voltage with the same frequency and phase as the input. Its output voltage waveform has quasi-square wave, step wave, sine wave and so on. Uninterruptible Power Supply (UPS) in the market is a switching AC regulated power supply by removing storage power supply and charger. Switching AC regulated power supply has good voltage stability, strong control function and easy realization of intelligence, and is a promising AC regulated power supply. However, due to its complicated circuit, high price and slow popularization.
Classification and characteristics of DC regulated power supply
According to custom, DC regulated power supply can be divided into chemical power supply, linear regulated power supply and switching regulated power supply. We will introduce these types of power supplies in detail below.
3. 1. Chemical power supply
The dry batteries, lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries and lithium-ion batteries we usually use are all chemical power sources, each with its own advantages and disadvantages. With the development of science and technology, smart batteries came into being. In terms of rechargeable battery materials, American researchers have found an iodide of manganese, which can be used to manufacture cheap, compact, long-term discharge batteries and maintain good performance after repeated charging.
3.2. Linear DC regulated power supply (LPS)
Linear DC regulated power supply refers to the DC regulated power supply in which the regulator tube works in a linear state. Linear DC regulated power supply mainly includes power frequency transformer, output rectifier filter, control circuit and protection circuit.
Linear DC stabilized power supply is to transform alternating current through transformer, and then rectify and filter through rectifier circuit to get unstable DC voltage. In order to achieve high-precision DC voltage, the output voltage must be adjusted by voltage feedback, which can reach a very high level. Stable, ripple is also very small, and there is no interference and noise with switching regulated power supply. But its disadvantage is that it needs a huge and bulky transformer, and the volume and weight of the filter capacitor are also quite large. Moreover, the voltage feedback circuit works in a linear state, and there is a certain voltage drop on the regulating tube. When outputting large working current, the power consumption of the regulating tube is too large, the conversion efficiency is low, and a large heat sink is installed.
3.3. Switching DC regulated power supply
Switching DC regulated power supply is a kind of power supply which uses modern power electronics technology to control the time ratio of switching transistor on and off and maintain stable output voltage. Its circuit forms mainly include single-ended flyback, single-ended flyback, half bridge, push-pull and full bridge. The basic switching DC regulated power supply mainly includes input power grid filter, input rectifier filter, inverter, output rectifier filter, control circuit and protection circuit. The advantages of switching DC regulated power supply are small size, light weight, stability and reliability. Disadvantages: Compared with linear DC regulated power supply, the ripple is larger (generally ≤ 1%VP-P). The following categories introduce several switching DC regulated power supplies:
3.3. 1. AC /DC power supply
This kind of power supply, also known as primary power supply, obtains energy from the power grid, and obtains a DC high voltage through high voltage rectification and filtering, so that the DC/DC converter can obtain one or several stable DC voltages at the output end. Power varies from several watts to several kilowatts and is used in different occasions.
3.3.2.DC/DC power supply
Also known as secondary power supply in communication system, it is a DC input voltage provided by primary power supply or DC battery pack, and after DC/DC conversion, one or several DC voltages are obtained at the output end.
3.3.3. Communication power supply
Communication power supply is essentially a DC/DC converter power supply, but it is usually powered by DC-48V or-24V, and the standby battery is used as a DC power supply to convert the DC power supply voltage into the circuit working voltage. Generally, it is divided into three types: central power supply, layered power supply and single board power supply, and single board power supply has the highest reliability.
3.3.4. Radio power supply
The power input of the radio station is AC220V/ 1 10V, and the output is DC13.8V. The power depends on the power of the power supply station. In order to prevent the power failure of AC power grid from affecting the radio station, the battery pack is needed as a backup, so this power supply not only outputs DC voltage of 13.8V, but also has the function of automatic conversion of battery charging.
3.3.5. Module power supply
With the rapid development of science and technology, the requirements of reliability, capacity and volume ratio of power supply are getting higher and higher, and modular power supply is showing its advantages more and more. It has high working frequency, small volume, high reliability and easy installation and expansion, so it is widely used.
3.3.6. Special power supply
High voltage low current power supply, high current power supply, 400Hz input AC /DC power supply, etc. Can be classified into this category, can be selected according to special needs.
Fourth, choose the right power supply.
The classification of regulated power supply has no clear meaning and boundary, and we can also classify power supply according to other characteristics of power supply regulators. Facing a wide variety of power products, how to choose a suitable regulated power supply is very important. When choosing a regulated power supply, we should not only determine the model and type of the power supply, but also consider whether the electrical characteristics of the selected regulated power supply can meet the work needs. For an ideal regulated power supply, besides the power and output voltage of the power supply meet the working needs, for AC regulated power supply, we also need to determine the phase number, regulated range and regulated accuracy of the regulated power supply, and also need to meet the working needs. For DC regulated power supply, the power regulation rate, output power, load regulation rate and ripple of regulated power supply need to be considered.
Verb (abbreviation of verb) noun explanation
1. Power supply regulation rate: the voltage stabilization accuracy of the output when the input changes.
2. Load regulation rate: the voltage stabilization accuracy of the output terminal when the load changes.
3. Filter: A device for eliminating interference and noise, which filters the input or output to obtain pure alternating current.
4. Maximum ripple voltage: the absolute value of output voltage ripple (including noise) under rated output voltage and load current. Usually expressed by peak-to-peak value or effective value.
5. Commercial power: alternating current (AC). The components of alternating current include voltage, current and frequency. The frequency can be divided into 50HZ and 60HZ. The voltage range is100 v ~ 240 v; The waveform of normal alternating current is sine wave.
6. Series/parallel connection of batteries: a plurality of batteries with the same performance and capacity are connected in series according to a certain polarity to form a battery pack; A plurality of batteries or battery packs with the same voltage are connected at their ends with the same polarity to form a parallel output.
7. Common abbreviations: CC- constant current CV- constant voltage Cr- constant resistance