The working process of the main circuit of the linear power supply is as follows: the input power is first initially regulated by the pre-regulator circuit, then converted into DC power by the main working transformer for isolation and rectification. Finally, under the intelligent control of the control circuit and the single-chip microprocessor controller, the linear adjustment element is finely adjusted to output a high-precision DC voltage source. 1. Power transformer and rectification: Converts 380V AC power into the required DC power; 2. Pre-regulator circuit: Uses relay elements or thyristor elements to pre-adjust and initially regulate the input AC or DC voltage, thereby reducing the power consumption of the linear adjustment element, improving working efficiency, and ensuring high precision and stability of the output voltage source; 3. Linear adjustment element: Finely adjusts the filtered DC voltage to achieve the required value and precision; 4. Filter circuit: Maximum suppression and absorption of DC power supply ripple, interference, and noise, thereby ensuring low ripple, low noise, and low interference in the DC power supply output voltage; 5. Single-chip microprocessor. Control system: The single-chip microprocessor controller compares, judges, calculates and analyzes the various signals detected, and then issues corresponding control commands to make the overall voltage regulation system of the DC regulated power supply work normally, reliably and in coordination; 6. Auxiliary power supply and reference voltage source: provides a high-precision reference voltage source and power supply required for the operation of electronic circuits for the DC regulated power supply; 7. Voltage sampling and voltage regulation: detects the output voltage value of the DC regulated power supply and sets and adjusts the output voltage value of the DC regulated power supply; 8. Comparison amplifier circuit: compares the output voltage value of the DC regulated power supply with the voltage of the reference source to obtain the error voltage signal, and then amplifies and feedbacks it and controls the linear adjustment element to ensure the stability of the output voltage; 9. Current detection circuit: obtains the output current value of the DC regulated power supply and provides information for current limiting or protection control; 10. Drive circuit: a power amplifier circuit set up to drive the executable element; 11. Display: displays the output voltage value and output current value of the DC regulated power supply [1].
A good power supply system ensures a more stable circuit and prevents disruption to normal use. Currently, the most popular power supply systems are linear power supplies and switching power supplies. So, what are the advantages and disadvantages of linear power supplies and switching power supplies? Let's take a look together.
What are the advantages and disadvantages of linear power supplies and switching power supplies?
(I) Linear Power Supply
1. Advantages
(1) Although linear power supplies may seem bulky, their power is generally determined by the transformer and regulating tube. Although the power of linear power supplies is relatively low, they do not introduce additional interference, so the electromagnetic interference of linear power supplies is relatively small, and the ripple factor is also very low, almost negligible.
(2) Linear power supplies generally have a higher voltage regulation rate and a simpler internal design. If a problem occurs and needs to be repaired, it is very convenient. Any technician with a basic understanding of electronics can usually know how to repair it. Therefore, the repair cost of linear power supplies is generally much lower than that of switching power supplies.
(3) Linear power supplies have relatively good lightning protection performance because the transformer inside a linear power supply is generally composed of two coils and an iron core. The voltage applied across the coils generally does not change abruptly, so it generally has strong suppression of instantaneous high voltage. If accidentally struck by lightning, a linear power supply can generally survive, while a switching power supply will generally be burned out.
2. Missing
(1) The working efficiency of linear power supplies is generally low because a linear power supply is a conversion process of electricity to magnetism and then back to electricity. During operation, the iron or copper inside will inevitably wear out, so the working efficiency will be reduced.
(2) The input range of a linear power supply is relatively narrow, generally between 200 volts and 240 volts. If it is below this range, the output voltage of the linear power supply will be insufficient. If it is above this range, the linear power supply may be burned out.
(3) Linear power supplies are generally larger than switching power supplies and are very bulky.
(II) Switching Power Supply
1. Advantages
(1) Switching power supplies generally have high operating efficiency and small size. Because switching power supplies generally do not experience iron or copper losses during operation, and the internal component losses are generally negligible, their operating efficiency is generally higher than that of linear power supplies. The internal components of a switching power supply generally only contain components and circuit boards, so the size and weight of a switching power supply are generally small.
(2) Switching power supplies have a wider input range, generally between 160 volts and 270 volts.
2. Disadvantages
(1) Although switching power supplies look small, they are more susceptible to electromagnetic interference and have a larger ripple coefficient. Especially in the audio and video fields, switching power supplies are more susceptible to electromagnetic interference, which usually results in an impure tone or a hissing sound.
(2) The internal design of switching power supplies is generally more complex, so it is usually more troublesome to repair. If a switching power supply has a problem, it is usually necessary to find a professional repairman to help repair it, and the repair cost is usually higher. Non-professionals usually cannot repair it, so it is more appropriate to just discard it.
(3) Switching power supplies are generally small in size, and many components are squeezed together, so the internal heat dissipation is generally not good. Over time, the casing may deform.
(4) Switching power supplies generally have weak lightning protection capabilities. If they are accidentally struck by high voltage, they are prone to burnout.
Because the regulating transistor of a linear power supply operates in amplification mode, it requires a good heat sink to dissipate a large amount of heat, and also necessitates a large power inverter. When producing multiple voltage outputs, the transformer becomes very large.
Because the control transistors in switching power supplies operate in saturation and cutoff states, they generate less heat, are highly efficient (75% or higher), and eliminate the need for large-capacity transformers. However, a significant ripple (typically 50mV at 5V output) overlaps with the DC output of the switching power supply. This ripple can be mitigated by connecting a Zener diode in parallel on the output side. Additionally, the switching transistors exhibit significant spike interference, necessitating their connection in the circuit and the use of a ferrite bead in series to improve this. In contrast, linear power supplies do not suffer from these drawbacks, and their ripple can be very small (less than 5mV).
When power efficiency and installed capacity are required, switching power supplies are recommended. Similarly, when electromagnetic interference and power purity (e.g., capacitor leakage detection) are required, linear power supplies are typically used. Furthermore, when isolation circuitry is needed, DC-DC converters are now primarily used to power the isolated sections (DC-DC converters are considered switching power supplies due to their operating principle). Additionally, the high-frequency transformers used in switching power supplies are cumbersome to wind up.
Switching power supplies and linear power supplies have completely different internal structures. As their names suggest, they involve switching operations and achieve different voltages through variable duty cycles and frequency conversion methods. Implementation is complex. Their biggest advantage is high efficiency. The disadvantages, exceeding 90%, are high ripple and switching noise. They are suitable when ripple and noise requirements are not high. Linear power supplies do not involve switching operations and belong to continuous analog control, but their internal structure is relatively simple, and the chip area is small. Their advantages are low cost and low ripple noise; their biggest disadvantage is low efficiency. They have their own disadvantages and complement each other in applications!
Advantages of linear power supplies:
1. While linear power supplies are inefficient, they do not cause additional interference, meaning they have low electromagnetic interference and a very low ripple factor, which is negligible. In surveillance, there is little advantage over this. Image quality is highly dependent on power consumption. Due to high power requirements, especially for small-amplitude analog signals (such as audio and video sources), some audiophiles use transformers instead of switching power supplies.
2. It has a high voltage regulation rate, simple design, and is very convenient to maintain. In case of failure, it can be repaired by technicians who are very knowledgeable about electronic equipment, and the maintenance cost is much lower than that of switching power supplies.
3. Excellent lightning protection. Because the transformer consists of two coils and an iron core, the voltage applied to the coils cannot change suddenly, and instantaneous high voltage is strongly suppressed. Therefore, in the event of a lightning strike, the transformer power supply is spared, while switching power supplies are invariably burned out.
Disadvantages of linear power supplies:
1. Low efficiency. Because transformers are "electromagnetic-to-electromagnetic" conversion processes, losses of iron and copper are unavoidable and the process is inefficient.
2. Narrow input range. Typically, it's around 200V to 240V, but if it's below this range, the output voltage will be insufficient, and if it's above, the transformer may burn out. In most cases, this voltage range is sufficient and shouldn't be a major concern. Additionally, the transformer is larger and more bulky than a switching power supply.
