The switching power supply is generally composed of the pulse width modulation (PWM) control IC and MOSFET. It uses modern power electronic technology to control the time ratio of the switching tube to open and turn off, and maintain a stable output voltage.The essence of the switching power supply is an oscillating circuit. The main work content is boosting and pressure. This method of conversion power is not only applied to power circuits, but also commonly used in other circuits, such as the backlight circuit of LCD monitors, solar lights, etc.EssenceToday, lets take a look at the purchase and switching power supply and the attention of the switching power supply.
Switch power supply
1. Select the appropriate input voltage range.Taking AC input as an example, the commonly used input voltage specifications are 110V and 220V, so there are three specifications: 110V, 220V AC switching, and general input voltage (AC: 85V-264V).The input voltage specifications should be selected according to the area in use.
2. Select the right power.The switching power supply consumes part of the power while working, and is released in the form of heat.In order to increase the life of the power supply, it is recommended to use 30%output power rated models.
3. Consider the load characteristics.In order to improve the reliability of the system, it is recommended that the switching power supply work at 50%-80%of the load, that is, assuming that the power is used at 20W, the output power should be selected with an output power of 25W-40W.
4. If the load is a motor, a light bulb or a capacitive load, the current is large when the current is turned on, and the appropriate power supply should be used to avoid overload.If the load is a motor, consider the overwhelming of the electricity when the stop is stopped.
5. In addition, it is necessary to consider the working environment temperature of the power supply and whether there is an additional auxiliary heat dissipation equipment.Refer to the amount of reduction of the output power of the circular temperature.
6. Select various functions according to the application: protection function: overvoltage protection (OVP), over -temperature protection (OTP), overload protection (OLP), etc.Application function: signal function (normal power supply, power supply failure), remote control function, remote test function, parallel function, etc.Special functions: Correction (PFC), continuous electricity (UPS)
7. Select the required security and electromagnetic compatibility (EMC) certification.According to the usage, set the required output voltage and current; the size, installation method and installation of the power supply; there are several outputs, whether the output of each output requires electrical isolation;The degree of amount, power power; whether it is required to certify and security standards; cooling methods of power supply: natural cooling or forced air cooling; electromagnetic compatibility standards.
8. Try to choose the standard power supply of the manufacturer, including standard size and output voltage.In this way, the delivery period is relatively fast; on the contrary, special size and output voltage will extend the delivery period and increase costs.
9. Select the brand.The switching power supply as the heart of the electronic device plays a vital role in the safe and reliable operation of electronic equipment.Therefore, it is also important to choose the brands switching power supply.
Pay attention to switching power supply
1. Before using the power supply, first determine whether the input and output voltage specifications are consistent with the nominal value of the power supply.
2. Before power -on, check whether the lead in the input and output is connected correctly to avoid damage to the user equipment.
3. Check whether the installation is firm, the installation screw is in contact with the power board device, and measure the insulation resistance of the shell to the input and output to avoid electric shock.
4. In order to ensure the safety of use and reduce interference, ensure that the ground end is reliable.
5. The power supply of multi -road output is generally divided into the main and auxiliary output. The main output characteristics are better than the auxiliary output. Generally, the main output with large output current is the main output.In order to ensure indicators such as output load adjustment and output dynamics, it is generally required to bring at least 10%of the load per road.If you use auxiliary road without the main road, the main road will definitely add appropriate fake loads.See the specifications of the corresponding model.
6. Please note: Frequent power switches will affect its life.The working environment and the degree of load will also affect its life.
Switch power maintenance
1. In the case of power off, "see, smell, ask, quantitative" look: turn on the shell of the power supply, check whether the fuse is melted, and then observe the internal conditions of the power supply.The components and related circuit components should be checked here.Hearing: I heard whether there is a smell inside the power and check whether there is a burnt component.Question: Ask if the power of the power is damaged and whether the power is illegally operated.Quantity: Before power -on, measure the voltage at both ends of the high -voltage capacitor with a multimeter.If it is caused by the failure of the switching power supply or the opening of the switching tube, in most cases, the voltage at both ends of the high -voltage filter capacitors has not been discharged, and the positive and reverse resistance and capacitors charging of both ends of the AC power cord is measured.The value should not be too low, otherwise there may be short circuits inside the power supply.The capacitor should be able to charge and discharge.Take off the load and measure the ground resistance of the output end of each group respectively. Normally, the table should have a capacitor charging and discharge swing. The resistance value of the leakage resistance of the road should be finally indicated.
2. After power -on detection, observe whether the power supply has burned insurance and some component smoke.There are 300 volt outputs at both ends of the high -voltage filter capacitor.Measure whether there are outputs in the secondary coils of high -frequency transformers, and if there is no focus on checking whether the switch tube is damaged, whether it is vibrated, whether the protection circuit is moving, etc. If so, check the rectifier diode, filter capacitor, and stable three links of each output side.Pressure pipes, etc.If the power supply is stopped, the power supply can directly measure the voltage of the input foot of the PWM chip to protect the input foot. If the voltage exceeds the specified value, it means that the power supply should be checked when the power supply is in a protected state.

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