According to the working state of the regulator, we often divide the regulated power supply into two types: linear regulated power supply and switching regulated power supply.
Linear regulated power supply refers to the regulated power supply in which the regulator works in a linear state. In the switching power supply, the switch tube (in the switching power supply, we generally call the adjusting tube switch tube) works in the on and off states: On - resistance is very small; on - resistance is very small; on - resistance is very small; Off - high resistance.
Switching power supply is a new type of power supply. It has the advantages of high efficiency, light weight, high output power, etc. But because the circuit works in the switch state, so the noise is relatively large. Let's talk about the working principle of buck switching power supply. When the switch is closed, the inductor stores energy; When the switch is off, the inductor releases energy, so the inductor L is called energy storage inductor. Diode D is responsible for providing current path to inductor L when the switch is off, so diode D is called freewheeling diode.
In practical switching power supply, switch K is replaced by transistor or FET. When the switch is off, the current is very small; When the switch is closed, the voltage is very small, so the heating power is u × I will be very small. This is the reason of high efficiency of switching power supply.
The application of module power supply is analyzed as follows
1、 Choice
1. When choosing the module power supply, we should first select the type of power supply reasonably according to the requirements of the application environment, such as the accuracy of voltage, the type of load, the variation range of current, the use environment, etc. to make clear the product use environment and requirements is the premise and condition for the reasonable selection and customization of power supply.
2. Module power supply can be divided into single circuit and double circuit.
The performance and index of single power supply is higher than that of dual power supply, especially the load regulation rate. When the dual power supply is under the equal proportion load, the output voltage accuracy is less affected by the load. If the load is skewed, the output voltage accuracy will be greatly affected. Therefore, if the dual output voltage accuracy is required to be higher or the output voltage symmetry is good, two groups of the same single power supply can be used, or special power supply can be selected to improve the output voltage accuracy. In the power supply controlled by main and auxiliary circuits, in order to make each auxiliary circuit have corresponding voltage accuracy, the main circuit should have a certain load range (such as ≥ 10 [%] rated load), which should be paid attention to when selecting.
2、 Testing
At present, there are some differences in the names of power technical indexes and test methods given by various manufacturers or power technical data, but the principles are the same. The regulations and measurement methods are as follows:
1. Test environment conditions
In the absence of special requirements, the tests are carried out under the following environmental conditions: temperature: 15 ~ 35 ℃, relative humidity: 20% ～ 80%], atmospheric pressure: 86 ~ 106 kPa, no strong electromagnetic interference
2. Detailed requirements (under one normal test environment): output voltage accuracy and voltage regulation rate (voltage stability)
3、 Application
1. The input and output terminals of the module power supply are equipped with filtering measures, which can effectively suppress the EMI clutter and surge current from the input side. If the power supply quality is poor or there are more requirements for the power system, the filtering network can be added before and after the DC module power supply.
2. The polarity of DC input voltage can not be reversed, nor can it be used beyond the range, otherwise the DC module power supply will be permanently invalid.
3. When using the module power supply, the rated power of 20 [%] to 80 [%] is generally selected as the best. It can not be used beyond the rated power in the later period, so as not to affect the service life of the power supply.
4. When the output current is large, the wire diameter of transmission current should not be too long or too thin to avoid large interference and error.
5. For the module power supply with natural heat dissipation, the ambient temperature should not exceed the given temperature range, so as to avoid overheating damage.
