Technical Requirements for Glue Filling of Switching Power Supply Module
Release time:
2019-04-20 14:15
Source:
Switching power supply module manufacturers
The potting of the AC-DC power module is very important. This process not only involves the protection of the AC-DC power module (waterproof, moisture-proof, dust-proof, anti-corrosion, etc.) but also involves the thermal design of the AC-DC power module.
Power potting is a two-component, thermally conductive, additive potting silicone rubber. The rubber material is stored for a long time after mixing at room temperature, but it can be cured quickly under heating conditions, which is especially beneficial to the use of automatic production lines. No corrosion to metal, temperature resistance, high temperature aging resistance. After curing in a wide temperature range (-60~280 ℃) to maintain rubber elasticity, excellent insulation performance. It does not shrink during curing, and has good waterproof, moisture-proof and anti-aging properties. It can seal and bond electronic components and does not pollute the surrounding environment, fully complying with the requirements of the EU ROHS directive.
Power module potting materials are commonly divided into three categories: epoxy resin, polyurethane and silicone rubber
Epoxy resin cannot be used for stress-sensitive and module potting containing chip components due to hardness, and is basically eliminated in the module power supply. However, due to its low cost, this epoxy resin is also used in micro-power supplies with high cost requirements. Some bad power supply manufacturers in China also use this epoxy resin for AC-DC power supply modules, but due to stress problems, the failure rate of this power supply is very high, and buyers are miserable.
At present, the most commonly used power module potting is to use addition type silica gel. This silica gel is generally 1:1 ratio, which is convenient for operation. Attention should be paid to its thermal conductivity when designing AC-DC power module potting. But the bonding ability is not too strong, can use the primer to improve.
Polyurethane has been used in China for a period of time, but its high hardness, inconvenient maintenance, and the price reduction factor of silicone rubber, the cost performance of polyurethane is not high. Domestic basically do not see its application.
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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.
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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.
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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.
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Can switching power supply and module power supply be universal?
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The difference between switching power supply and module power supply
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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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