What are the definitions of linear power supply, switching power supply, and thyristor power supply? What are their differences? What are their applications? What are their advantages and disadvantages?

okhxyyo

What are the definitions of linear power supply, switching power supply, and thyristor power supply? What are their differences? What are their applications? What are their advantages and disadvantages? [Copy link]

 

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Today in the switching power supply study group, someone asked: What is a linear power supply? What is a switching power supply?

Well, let's talk about it in this post. What are the linear power supply, switching power supply and thyristor power supply in your knowledge?

What is the difference between them?

What are the application scenarios?

What are the advantages and disadvantages of each?

It may be a bit confusing to ask so many questions at once. But it doesn’t matter, let’s learn together~

Everyone is welcome to follow the thread for discussion. The administrator will sort out the relevant information and knowledge points and follow up in this post later.

okhxyyo

The difference between linear regulated power supply (LDO) and switching power supply

Tips on switching power supply design

The essence of linear regulated power supply

Analysis on the current status and development trend of linear and switching power supplies in China

Comparison of linear power supply and switching power supply in access control application

Linear Power Supply VS Switching Power Supply

Comparison between switching power supply and linear power supply

Differences and applications between switching power supply and linear power supply

maychang

Let me talk about thyristors (also known as "silicon controlled rectifiers") first.

An ordinary thyristor is a three-terminal device with three electrodes: cathode, anode and gate. When the cathode is positive to the anode, just like a reverse voltage is applied to an ordinary diode, there is only a small leakage current between the cathode and the anode, regardless of whether a voltage is applied between the gate and the cathode. When the anode is positive to the cathode, if there is no voltage between the gate and the cathode, there is still only a small leakage current between the anode and the cathode. However, if a not-so-large positive voltage is applied to the cathode by the gate (the gate is positive, the voltage generally only needs 1 to 2V, and the current ranges from a few milliamperes to hundreds of milliamperes), the anode and the cathode will be in a conducting state, and the current direction is from the anode to the cathode, with a voltage drop of only 1V to 2V. After the thyristor is turned on, even if the gate voltage is removed, the thyristor will remain on until the current between the anode and the cathode drops to near zero. The time for applying the gate voltage can be very short, as short as microseconds to "trigger" the thyristor to make it "conducting".

maychang

Thyristors are often called "half-controlled" devices because applying a voltage to the gate can turn the thyristor on, but not off - once the thyristor is on, the gate has no effect. In contrast, the control terminal of a bipolar transistor, field effect transistor, or IGBT can either turn the tube on or off.

maychang

Because of the "half-controlled" characteristic of thyristors, the use of thyristors is relatively narrow. However, thyristors have high withstand voltage and large current (thyristors with a current capacity of hundreds of A are common), so thyristors are mainly used in the power sector for controlled rectification. They are rarely used in electronic equipment.

There is another type of bidirectional thyristor, which is also a three-terminal device with three electrodes, A1, A2, and G (gate). The characteristic of this thyristor is that A1 and A2 can be bidirectionally conductive, that is, after the gate applies a trigger voltage to A1, A1 can be conductive when A2 is positive or negative. Moreover, whether the gate is positive or negative to A1, A1 and A2 can be conductive. Of course, the trigger sensitivity of the four quadrants is different.

Bidirectional thyristors are often used in industrial frequency AC control circuits, such as controlling heating power, controlling the luminous intensity of incandescent lamps, etc.

maychang

Thyristor controlled rectification, or used to control the luminous intensity of incandescent lamps, etc., is also considered a switching power supply. However, unlike the switching power supply we usually talk about, thyristors are usually only used at industrial frequency and at higher power, while the switching power supply we are talking about usually works at tens of kHz or even higher.

maychang

There are many kinds of thyristors, such as turn-off thyristors, etc. However, because their characteristics cannot meet the requirements of switching power supplies, they have not been widely used in electronic technology.

振动试验仪器

The MOSFET tube has a small current, and one advantage is that it has good parallel characteristics. It becomes even more powerful when it evolves into IGBT.

111wgr

Linear power supplies use the principle of voltage division to achieve voltage stabilization, and excess energy is consumed in resistors. Therefore, extremely efficient switching power supplies are used to replace linear power supplies.