Compared with linear power supplies, the core advantages of switching power supplies are reflected in efficiency, volume, voltage adaptability, and functional scalability, especially in the miniaturization and high-power demand scenarios of modern electronic devices. So why is the efficiency of switching power supplies so much higher than that of linear regulated power supplies?
The main reason why the efficiency of switching power supplies is higher than that of linear regulated power supplies is that their working principles are different.
1. Comparison of working principles
1.1 Linear regulated power supply: The linear regulated power supply reduces the input voltage to the required output voltage through the adjustment tube. The adjustment tube is always in an amplified state, resulting in a large voltage drop and power loss. When the current is large, the loss will also increase, resulting in lower efficiency.
1.2 Switching power supply: The switching power supply adjusts the voltage by switching the switch tube between on and off. The switch tube is close to zero power consumption when it is on (the resistance in the saturation zone is extremely small), and no current passes when it is off. There is only a short power consumption at the switching moment. Due to the high switching frequency and controllable duty cycle, the overall average power consumption is significantly reduced, so the efficiency is higher.
Specific reasons for efficiency differences
1.3Loss mechanism: The adjustment tube in the linear regulated power supply continuously works in the amplification state, resulting in a large voltage drop and power loss. The switch tube of the switching power supply is close to zero power consumption when turned on, and no current passes when turned off, and the overall average power consumption is significantly reduced
1.4Working state: The adjustment tube of the linear regulated power supply is always in the amplification state, while the switch tube of the switching power supply switches between on and off. This working mode makes the switching power supply more efficient.
2. For example
Each child needs half a cookie. Now there are N children. How many cookies do they need? How to distribute?
Switching power supply: Give one cookie to every two children, and they divide it by themselves, and a total of N/2 cookies are needed
Linear power supply: Give one cookie to each child, and use a ruler to measure it before giving it to them, break it in half and throw it away, and a total of N cookies are needed
Switching power supply: If the two children are not friendly, it is easy to argue--------The output of the switching power supply has ripple
Linear power supply: It can be divided very accurately, but the waste is a bit large--------Linear power supply has low efficiency
3. Where does the power consumption of the linear regulated power supply go?
The loss problem of linear regulated power supply
The loss of linear regulated power supply is not small. Part of the input power is converted into heat energy and dissipated, which will have a certain impact on the performance of the circuit.
3.1 Working principle of linear regulated power supply
Linear regulated power supply is a power supply that reduces a large voltage to a small voltage through a power transistor, and then maintains the voltage unchanged through a voltage regulator. Its working principle is simpler than that of the switching regulated power supply, and it also has the advantages of high precision and low noise.
3.2 Loss problem of linear regulated power supply
During the conversion process, part of the electrical energy will be converted into heat energy and dissipated, which is the loss problem of linear regulated power supply. Compared with switching regulated power supply, linear regulated power supply has lower efficiency and greater loss. Under normal circumstances, the efficiency of linear regulated power supply is only 60% to 70%, and the other 30% to 40% of the power is converted into heat energy and dissipated.
3.3 The impact of linear regulated power supply loss on circuit performance
1. Temperature increase
Due to the large amount of heat energy dissipation, the temperature of the linear regulated power supply will rise accordingly. Excessive temperature will cause the power supply stability to decrease and even damage the power supply. At the same time, temperature will also affect the working performance of capacitors and resistors and affect the stability of the circuit.
2. Increased noise
Increased temperature will also cause increased power supply noise, which will in turn affect the circuit signal-to-noise ratio.
3. Shortened equipment life
The loss caused by excessive temperature will also shorten the life of the equipment.
3.4 How to reduce the loss of linear regulated power supply
1. Use step-down circuit to reduce voltage drop
Adding a step-down circuit after the voltage regulator to reduce the working point of the voltage regulator to a lower voltage can reduce the loss to a certain extent.
2. Use high conversion efficiency module
Using high conversion efficiency module can reduce loss and improve power supply efficiency and performance.
3. Use clamping voltage regulator module
Using clamping voltage regulator module can achieve high efficiency and low noise voltage regulation effect, reducing the loss problem of linear regulated power supply.
4.How does the switching power supply overcome the disadvantage of loss problem?
The main methods for switching power supply to overcome the loss problem include optimizing power device selection, designing magnetic components, improving control strategy, reducing circuit parasitic parameters, using soft switching technology and improving power factor.
Optimizing power device selection: Selecting power devices with low on-resistance and low switching loss, such as silicon carbide (SiC) and gallium nitride (GaN) devices, can significantly reduce switching loss.
Design magnetic components: Select high-performance core materials, such as ferrite cores or nanocrystalline cores, reasonably design winding structures, reduce winding resistance and leakage inductance, and thus reduce the loss of magnetic components.
Improve control strategy: Adopt adaptive control algorithms to dynamically adjust switching frequency and duty cycle according to load changes to optimize efficiency.
Reduce circuit parasitic parameters: Optimize PCB layout and wiring, reduce the influence of parasitic inductance and capacitance, and use multi-layer PCB boards and reasonable grounding methods to help improve circuit performance.
Use soft switching technology: Such as zero voltage switching (ZVS) and zero current switching (ZCS) technology to reduce energy loss during switching.
Improve power factor: Reduce reactive power and improve the effective use of input power through power factor correction (PFC) circuits.
Advantages and disadvantages in practical applications Advantages: The switching power supply has high efficiency, small size, and light weight, and is suitable for high-power occasions. Since the switching power supply has low loss and low heat generation, it does not require high heat dissipation.
Disadvantages: The switching power supply has high noise, while the linear regulated power supply has low noise and is suitable for noise-sensitive application scenarios.
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