With the rapid development of China's industry, switching power supplies have gradually embarked on the world stage, and the volume of power supplies has gradually become more modular and miniaturized, and the power supply's immunity is also becoming stronger. How does the switching power supply achieve voltage control? What is the internal structure? Let's take a quick look at it.
First, what is the switching power supply
Switching power supply is the abbreviation of switching power supply, generally refers to the AC-DC converter whose input is AC voltage and the output is DC voltage. The power switch inside the switching power supply works in the high-frequency switching state, and the energy consumed by itself is very low. The power efficiency can reach 75%~90%, which is double that of the ordinary linear regulated power supply (linear power supply).
Speaking of linear power (as shown in Figure 1), what is the difference between it and switching power supply? The popular point is that the voltage regulation of the linear power supply can be regarded as the adjustment of the resistance value, which is equivalent to adjusting the sliding rheostat to change the voltage. The switching power supply can be seen as changing the voltage by adjusting the frequency of the switch.
Figure 1 Linear power supply
Second, switching power supply classification
No power frequency transformer type switching power supply
The power-free transformer-type switching power supply replaces the bulky power frequency transformer with a small-sized high-frequency transformer, and the experiment is isolated from the power grid. Since the internal components of the switching power supply operate in the high frequency switching state, the energy consumed by the switching power supply is low, and the power supply efficiency is doubled compared with the ordinary linear power supply.
Figure 2 Block diagram of the switching power supply
Switching regulator
Switching regulator is a switch-type integrated voltage regulator. It integrates PWM controller, power output stage and protection circuit into one chip. The efficiency of the regulator can reach over 90%, and some can continuously adjust the output. Voltage, suitable for manufacturing switching power supplies from tens of watts to hundreds of watts.
Monolithic switching power supply
The monolithic switching power supply integrates the main circuits of the switching power supply into the chip, which can realize output isolation, pulse width modulation and various protection functions, and has the highest integration degree. The monolithic switching power supply is adapted to AC power of 85~265V and 47~400HZ through the input rectification filter. Moreover, it has the advantages of high integration, high cost performance, simplest peripheral circuits, best performance indicators, etc. It has become a preferred integrated circuit for developing medium and small power switching power supplies, precision switching power supplies and switching power supplies of 600W or less.
Figure 3 Single-chip switching power supply module
Third, the switching power supply works
Switching power supplies are classified according to the control principle and can be classified into the following four categories:
1) Pulse width modulation (referred to as PWM, ie pulse width modulation) type: simply speaking, the voltage regulation is achieved by adjusting the pulse width, and the core is the PWM controller. In this way, the application of the switching power supply is the most common, and the duty cycle adjustment range is large, and the PWM can also be synchronized with the clock of the main system.
2) Pulse frequency modulation (referred to as PFM, ie pulse frequency modulation): Similar to pulse width debugging, it adjusts the switching frequency to achieve voltage regulation. The core is PFM controller. This approach is suitable for portable devices that reduce the quiescent current of the control chip at low duty cycle, low frequency conditions.
3) Pulse density modulation (referred to as PDM, ie pulse-tight modulation): It is characterized by a constant pulse width and the purpose of voltage regulation by adjusting the number of pulses. It uses zero voltage technology to significantly reduce power switch losses.
4) Hybrid Modulation: It is a combination of PWM and PFM. Switch cycle switching cycle and pulse width are adjustable
It should be noted that the PWM controller can be used as a stand-alone integrated circuit, integrated switch regulator, or integrated in a switching power supply. Among them, the switching regulator belongs to the DC-DC converter, and the switching power supply is generally an AC-DC converter. As shown in Figure 4:
Figure 4 monolithic switching power supply
From the figure, we can see that the front-end rectification filtering part can be regarded as a DC-DC converter, and the front-end rectification filtering part is an AC-DC converter.
Fourth, the basic principle of switching power supply
The basic principle of the switching power supply is shown in Figure 5. Mainly composed of the following seven parts:
1) input rectifier filter, including rectifier bridge and input filter capacitor;
2) Single-chip switching power supply, including power switch tube and controller (including oscillator, voltage reference, error amplifier and PWM comparator), MOSFET;
3) Drain clamp protection circuit;
4) high frequency transformer;
5) output rectifier filter;
6) optocoupler feedback circuit;
7) A bias circuit that biases the phototransistor's phototransistor.
Figure 5 Basic principle of single-chip switching power supply
Fifth, the principle analysis
The principle of voltage regulation is analyzed as follows:
When V rises for some reason, the current on the LED increases, and the emitter current of the receiving tube rises through the optocoupler, so that the current at the control terminal of the TOPSWITCH becomes larger, and the duty ratio becomes smaller, resulting in a decrease in V. To achieve the effect of voltage regulation.
Summary
From the above we can see that the switching power supply is the pamper of the power supply industry today, it has a long life cycle, and the advantages are obvious. From the operating principle, many factors will affect the quality of the switching power supply, and the increase of other protection circuits will also ensure the safety of the switching power supply. The selection of isolation will also affect the response of the power supply. ZLG Zhiyuan Electronics' power module takes into account the power requirements of the vast enterprise industry, whether it is the power supply volume or power supply security, to ensure the stable output of the power supply circuit of major enterprises, provide power supply design support, and realize real customers and manufacturers. of interaction.
iDealTek-Electronics has accumulated rich application experience and design technical knowledge in the field of High-voltage power supplies, from Linear High Voltage Power Supplies based on power frequency transformers to Switching High Voltage power supplies based on IGBT components, from 60KV, 1KW High Voltage Power Module, to 5KV ~ 40KV, 1KW 2U Laboratory High-voltage power supplies, and to 5KV ~ 60KV, 2KW 4U and 5KV ~ 100KV, 6U rack-mounted capacitor charging high-voltage power supplies, and then to floor-standing cabinet-type high-current high-power high-voltage power supplies, all our high voltage power supplies are featured for high reliability, excellent high-voltage output stability and low-ripple electronic characteristics.
Through the reliable and durable operation panel on the front panel of the high-voltage power supply, the output voltage and current can be easily set and controlled. The high-precision LED or LCD ensures intuitive and high-precision high-voltage output measurement functions. Our high-voltage power supplies can be equipped with a wealth of remote-control interfaces, such as RS232 / RS485 /DB15 / DB25 / DB50 analog signal interface, etc. for remote high-voltage enable and inhibit, high-voltage output control programming and data monitoring.
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At present, our high voltage power supplies are widely used in high-voltage laboratories, capacitor charging, electron beam, ion implantation, FUSION power generation and other industries.
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