The difference between switch mode power supply and linear power supply
What is a switching power supply
Switching power supply is the abbreviation for switching voltage regulator power supply, generally referring to an AC (alternating current) - DC (direct current) converter that inputs AC voltage and outputs DC voltage. The power switch tube inside the switching power supply operates in a high-frequency switching state, consuming very low energy. The power efficiency can reach 75% to 90%, which is twice as high as that of ordinary linear stabilized power supplies.
Working principle of switch mode power supply
Switching power supply is a type of power supply that utilizes modern power technology to control the time ratio of switching transistors on and off, maintaining a stable output voltage. The switching power supply is composed of pulse width modulation (PWM) control (metal oxide semiconductor field-effect transistors).
Switching power supply consists of four main parts: main circuit, control circuit, detection circuit, and auxiliary circuit. Switching power supply, as the name suggests, is equivalent to having a door here, one door allowing current to pass through and the other door stopping current from passing through. So what is a door?
Some switching power supplies use thyristors, while others use switching transistors, which rely on the base and control electrode (thyristor) plus pulse signals to complete conduction and cutoff, allowing the electronic switch to continuously 'turn on' and 'turn off', and enabling the electronic switch device to pulse modulate the input voltage, thereby achieving DC/AC, DC/DC voltage conversion, as well as adjustable and automatic voltage regulation of the output voltage.
The difference between switch mode power supply and linear power supply
Simply put, the voltage regulation of a linear power supply can be seen as a resistance value regulation, which is equivalent to changing the voltage by adjusting the sliding resistor, while a switching power supply changes the voltage by adjusting the frequency of the switch. Meanwhile, compared with linear power supplies, the cost of both switching power supplies increases with the increase of output power, but the growth rates of the two are different.
1. The cost of a linear power supply is actually higher than that of a switching power supply at a certain output power point.
Therefore, with the development and innovation of power electronics technology, switch mode power supply technology continues to break through and innovate. This cost issue has instead shifted switch mode power supply technology towards the low output power end, providing a wide range of development space for switch mode power supply.
2. The relationship between power electronic devices and people's work and life is becoming increasingly close, and electronic devices cannot do without reliable power sources. After entering the 1980s, computers fully realized switch mode power supply, and in the 1990s, switch mode power supplies successively entered various electronic and electrical fields.
In just ten years, switch mode power supply technology has rapidly occupied the core position of power electronic devices. Is this just because switch mode power supplies are small in size?
3. In fact, from the schematic diagram of the switching power supply, it can be understood that it does not use bulky power frequency transformers, and because the dissipated power on the adjustment tube is greatly reduced, it eliminates the need for large heat sinks. This reduces the size and weight of the switching power supply. However, the biggest advantage of switch mode power supplies is low power consumption and high efficiency. In the switching power supply circuit, the transistor repeatedly switches between 'on' and 'off' states under the excitation signal, with a very fast conversion speed and a frequency of only 50Hz, greatly improving the power efficiency.
4. The switching power supply has a wide voltage regulation range. The output voltage of the switching power supply is regulated by the duty cycle of the excitation signal, and the variation of the input signal voltage can be compensated by frequency modulation or width modulation. In this way, even when the voltage of the power grid varies greatly, it can still ensure a relatively stable output voltage.
5. The operating frequency of switch mode power supplies is currently basically 50kHz, which is 1000 times higher than that of linear regulated power supplies. This also increases the filtering efficiency of rectified power supplies by almost 1000 times; Even with half wave rectification and capacitor filtering, the efficiency has been increased by 500 times. At the same ripple output voltage, when using a switching power supply, the capacity of the filtering capacitor is only 1/500~1/1000 of that in a linear regulator power supply.
