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Introduction to Design Process of Isolated Switching Power Supply Module
Release time:
2022-07-01 14:49
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IsolationSwitching power supply moduleThere are various types of circuits, and power supplies that can support different applications can be designed according to their characteristics. Then, let's learn about isolation together.Switching power supply moduleDesign process introduction!
Isolate first.Switching power supply module：
Select the appropriate topology based on specific requirements, such as isolationSwitching power supply module, Select the flyback method to basically meet the requirements.
Select appropriate PWMIC and MOS for preliminary circuit design:
IsolationSwitching power supply moduleAfter determining the flyback topology design, it is necessary to select the appropriate PWMIC and MOS for the initial circuit diagram design. You can select split or integrated. Tower PWMIC and MOS are separated, with the advantages of power free combination, and the disadvantages of long design and debugging cycles. The integrated PWMIC and MOS are integrated in one package, which can save designers many calculation and debugging steps, and is very suitable for engineers who are just starting out or developing rapidly.
Drawing schematics:
After determining the selected chip, start drawing the circuit diagram. Before designing, look at the corresponding datasheet and see the simple parameters. When selecting individual designs such as PI Integration, 384x, and OBLD, you need to refer to the data sheet. The general datasheet is accompanied by a simple circuit diagram. These diagrams are the basis of our design.
Determine the appropriate parameters:
After completing the circuit diagram, the corresponding parameters need to be determined to enter the next PCB Layout. Of course, different companies have different processes. We need to follow proper processes and develop good design habits. This step may have a preliminary evaluation, schematic confirmation, can be calculated after signing.
Determine the switching frequency, select the core to determine the transformer:
IsolationSwitching power supply moduleThe frequency of the chip can be set by an external RC. The operating frequency is the same as the switching frequency. The function of this peripheral device helps to better design the switching power supply and adopts the external synchronization function. Typical ACDC power modules do not want to set the operating frequency to 100kHz or higher. Mainly switching power supply frequency is too high will not be conducive to the stability of the system and EMC through. If the frequency is too high, di/dtdv/dt will increase accordingly. The choice of magnetic core is very important on the basis of switching frequency and power, and there are many empirical choices. Of course, to calculate, we need to get more core parameters, such as magnetic body, Curie temperature, frequency characteristics and so on.
Design and calculation of transformers:
If the parameters such as efficiency, duty cycle and magnetic induction intensity are set at the same time according to the input and output, switching frequency and selected core parameters, the next calculation is entered to find out the power, average and peak voltage and current, the number of turns and inductance. After confirming the number of turns, the wire diameter has a certain value as the ordinary resistance. You only need to remember a few commonly used constant wire diameters. Next, it is necessary to determine the size of the input and output capacitors, so the layout and layout can be carried out. input and output electrolytic capacitor calculation:
Here, the specification of the electrolytic capacitor is determined based on the input power and the output current calculated in the previous step. The frequency and impedance are selected according to the use environment. The larger the theoretical selection value of the capacitor Cin, the more suitable for the latter stage, but from the viewpoint of cost, a large capacity is not unlimitedly selected. At this point, the PCB needs to determine the shape of the device has been completed. That is, the PCB package is completed. Next, you can define the device package in the schematic.
PCB Layout :
IsolationSwitching power supply moduleConfirmed the transformer, schematic diagram, electrolytic capacitor. Next is the standard. You can create a network table in sch, define the edge of the board in the PCB file, load the corresponding package library, and directly import the network table for layout. The ring area formed by the RCD absorption part of the layout and the transformer is as small as possible, so that the corresponding radiation and conduction can be reduced. The ground wire should be as short and wide as possible to ensure that the corresponding zero level is conducive to the stability of the benchmark. Where di/dtdv/dt varies greatly, minimize the loop, widen the line, and reduce unwanted inductance characteristics.
Specific parameters:
After PCB Layout is completed, the same name end of the transformer can be determined, the transformer can be completely defined, samples can be made and wound by itself.
IsolationSwitching power supply moduleDebugging process:
Complete the above part, basically an isolationSwitching power supply moduleThe design is completed, followed by the debugging process of the welded plate. The simple equipment required for debugging is voltage regulator, oscilloscope, multimeter, etc., and the auxiliary equipment is power meter, LCR bridge, electronic load, etc. Static inspection shall be carried out after the plate is welded. If there is LCR bridge, the parameters such as the same name end and inductance of the transformer can be measured before welding. Static detection mainly depends on whether there is virtual welding, even tin, etc. After static detection, a multimeter can be used to measure whether the input and output are in short-circuit state and carry out current measurement test.
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2019-08-06
Product selection and application considerations
The design power of each product of our company will have a certain amount of redundant power, which can run for a long time under full load or even over the rated load. However, for the sake of high reliability and prolonging the service life of the power supply, please do not let the load reach the rated value. It is generally recommended to use 60%-80% of the rated load, and the ambient temperature is recommended to be about 30 ℃, which can be fully loaded at an ambient temperature of 55 ℃, but this will undoubtedly greatly reduce the reliability and service life of the product. In actual use, please pay attention to the two factors of controlling load and temperature. If the ambient temperature is relatively high, it is necessary to reduce the load as much as possible (that is, to increase the load margin and select products with greater output power). On the contrary, if a large load current is required, then try to do a good job of ventilation and heat dissipation, such as placing the power supply module in an open space and increasing cooling fans. The specific value is not absolutely fixed. Generally, it is recommended that the load should not exceed 20% of the rated load when the ambient temperature is 55 ℃, which can keep the product very high reliability. Tip: Please use temperature measuring equipment to evaluate the temperature, and do not rely on skin feeling. Short time and a small proportion of full load, high temperature operation, the reliability and life has little effect. For example: each full load lasts less than 1 minute or half a minute, and the interval is more than 10 minutes, while the load during the interval is less than 15% of the rated load, then even if the operation at 55 ℃ is also possible. Safe Use Warning: Since the bare board series does not have a shell, the input is 220V AC at the same time. The input pins and corresponding terminals of the module are directly connected to 220V. Please pay great attention to prevent short circuit between electric shock and metal objects and ensure that the power supply is disconnected before any touch. Load Requirements for 2. Use of Multiple Output Power Supplies Generally, the voltage accuracy of the output of the multi-output power supply is: the nominal value of the main output is plus or minus 1%, and the nominal value of the secondary output is plus or minus 5%-10%. The first output of the multi-output power supply is the main circuit, and the other output is the secondary circuit. The voltage accuracy and carrying capacity of the main circuit are higher than those of the secondary circuit. Therefore, the main circuit with large current and high voltage accuracy requirements should be generally selected, it is appropriate that the ratio of each current is 50-100%, and the secondary circuit must not be loaded separately under the condition of no load on the main circuit, otherwise the secondary circuit voltage is too low to be used normally. In addition, if the main circuit load is full load and the secondary circuit load is light load, the secondary circuit voltage may increase, otherwise the secondary circuit voltage will decrease, and the reliability and service life will have little effect. For example, if each full load lasts less than 1 minute or half a minute, and the interval is more than 10 minutes, while the load during the interval is less than 15% of the rated load, then even operation at 55°C is possible.
2018-08-29
Application field of switching power supply module
Switching power supply module is applied in several major aspects 1. Electric power, mainly including integrator and electric meter and intelligent electric meter 2. Industrial control, industrial control field 3. Medical treatment, medical equipment, mainly including tire protection instrument, monitor and so on 4. Military industry, military industry is a very widely used aspect. in military equipment. Switching power supply module applications in several major areas.
2018-08-29
Precautions for the use of switching power supply modules
The high-frequency transformer of switching power supply is generally shielded for the first time, which is not described above. Switching power supply is a high-frequency product, PCB component layout for EMI, please pay close attention to this point. If the switching power supply has a mechanical shell, the structure of the shell has a great influence on the radiation, please pay close attention to this point. The parameters of different manufacturers of the main switch tube and the main diode have certain differences, which have certain influence on EMC. Please pay close attention to this point.
2018-08-29
Can switching power supply and module power supply be universal?
A module power supply is a power supply that can be mounted directly on a printed circuit board and is characterized by providing power to application-specific integrated circuits (ASICs), digital signal processors (DSPs), microprocessors, memory, field programmable gate arrays (FPGAs), and other digital or analog loads. In general, such modules are called point-of-load (POL) power supply systems or point-of-use power supply systems (PUPS).
2018-08-29
The difference between switching power supply and module power supply
(1) The difference in use: module power supply, output voltage, remote control switch circuit, input protection circuit. Switching power supply, control the switch tube on and off time ratio, maintain a stable output voltage of a power supply. (2) The difference in composition: Switching power supply: Generally composed of pulse width modulation (PWM) control IC and MOSFET. Module power supply: it is composed of power supply module with a small amount of discrete components.
2018-10-19
Loss of switching power module
The loss of high-power module switching power supply mainly includes high-frequency switching loss, high-frequency transformer loss, rectifier loss and line conduction loss. In the application of low voltage and high current output, the rectifier loss and line conduction loss occupy a larger proportion, the lower the output voltage, the greater the output current, the rectifier loss and line conduction loss accounted for the proportion of the total loss of the module switching power supply.
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