Parallel-type switching power supplies are highly efficient power conversion devices. Their core function is to use a high-frequency switching regulator to convert the input DC voltage into the desired output voltage. This power supply design is widely used in computers, telecommunications equipment, industrial control systems, and other electronic devices because it provides a stable output voltage and features high efficiency, small size, and light weight.
Basic principles
The 220V AC power, after rectification and filtering by capacitor C1, forms a 300V DC voltage across capacitor C1. When a high-level pulse signal is applied to the base of the switching transistor VT, VT enters saturation conduction. At this time, the 300V DC voltage flows to ground through the loop formed by VT and L1. The inductor L1 generates a reverse electromotive force (positive at the top, negative at the bottom) due to the current flowing through it, and energy is stored in L1. Subsequently, when a low-level pulse signal is sent to the base of VT, VT is turned off, and no current flows through L1, immediately generating a reverse electromotive force (negative at the top, positive at the bottom). This causes the freewheeling diode VD1 to conduct. At this point, the energy stored in L1 begins to be released and charges capacitor C2 through VD1, forming a voltage U0 (negative at the top, positive at the bottom) across C2. This voltage provides power to the load RL.
The voltage regulation process of a parallel switching power supply is achieved through a negative feedback mechanism. The main steps are as follows:
Sampling and Comparison: First, the output voltage is monitored in real time through a sampling circuit. Then, the sampled voltage is compared with an internal reference voltage. The reference voltage is very stable and serves as the standard that the output voltage should meet.
Error Amplification: The comparison result generates an error signal, which reflects the deviation between the output voltage and the ideal value. This error signal is sent to an error amplifier for amplification, generating a control signal for adjusting the duty cycle of the switching transistor.
Modulation and Control: After receiving the amplified error signal, the control circuit adjusts the duty cycle of the switching transistor, that is, it adjusts the ratio of the switching transistor's on and off times. If the output voltage is lower than the set value, the duty cycle is increased to prolong the switching transistor's on time, allowing more energy to be transferred to the secondary coil; conversely, if the output voltage is higher than the set value, the duty cycle is decreased to shorten the switching transistor's on time, reducing the energy transferred.
Feedback and Stabilization: The adjusted pulse signal drives the switching transistor, and after passing through the transformer and rectification/filtering stages, the output voltage is corrected and tends to stabilize. Throughout the process, negative feedback ensures that the output voltage fluctuates slightly around the set value, achieving the purpose of voltage regulation.
Multi-output voltage regulation: In parallel-type switching power supplies, if there are multiple output voltages, each output has its own independent control loop. This ensures that even if the load at one output changes, it will not affect the stability of the other outputs.
What are the differences between high-frequency switching power supplies and AC switching power supplies? High-frequency switching power supplies and AC switching power supplies are two different types of power supplies, and they differ in their working principles, application areas, advantages, and disadvantages. The differences between these two types of power supplies will be explained in detail below.
First, the working principle of a high-frequency switching power supply is to use high-frequency switching transistors to perform switching actions to achieve power supply operation, while an AC switching power supply converts AC power to DC power. High-frequency switching power supplies generally use solid-state switching elements (such as...
MOSFET
IGBT
A switching power supply (such as an AC power supply) performs switching actions to achieve high-frequency switching operations and output a stable DC voltage. An AC switching power supply, on the other hand, takes an AC voltage input and, through processes such as rectification, filtering, and adjustment, obtains the required DC voltage output.
Secondly, high-frequency switching power supplies are mainly used in electronic products, such as computers, mobile phones, televisions, and other household appliances and communication equipment, where their primary function is to provide a stable DC power supply. AC switching power supplies, on the other hand, are widely used in industrial fields, such as frequency converters, industrial control computers, UPS power supplies, and power adapters for household appliances. AC switching power supplies are mainly used to convert AC mains power to DC, and can be used for various load requirements.
Furthermore, high-frequency switching power supplies and AC switching power supplies also differ in efficiency. High-frequency switching power supplies operate at higher frequencies and are therefore more efficient than AC switching power supplies. This is because high-frequency switching power supplies have faster switching speeds, enabling quicker power conversion and reducing energy loss. AC switching power supplies, on the other hand, operate at lower frequencies, resulting in relatively higher energy losses.
Furthermore, high-frequency switching power supplies differ from AC switching power supplies in size and weight. High-frequency switching power supplies typically employ a miniaturized design, resulting in a smaller size and lighter weight, making them easy to carry and install. AC switching power supplies, on the other hand, require more component connections and circuit design, resulting in a larger size and heavier weight. This makes AC switching power supplies less suitable for applications with limited space and stringent weight requirements.
Finally, high-frequency switching power supplies and AC switching power supplies also differ in reliability and cost. High-frequency switching power supplies, due to their use of advanced solid-state switching components and control technology, offer higher reliability and are easier to implement with automatic control and protection functions. AC switching power supplies, on the other hand, are relatively simpler, easier to implement and maintain, but their reliability is relatively lower. Furthermore, high-frequency switching power supplies have higher manufacturing and process requirements, thus their cost is typically higher, while AC switching power supplies are relatively lower.
In summary, high-frequency switching power supplies and AC switching power supplies differ in their operating principles, application areas, efficiency, size and weight, reliability, and cost. Understanding these differences helps us choose the appropriate power supply type and apply it reasonably in different scenarios to meet power supply requirements.
