1. What is a high voltage rectifier filter circuit?
Answer:The high voltage rectifier filter circuit consists of a rectifier bridge and two high voltage electrolytic capacitors. The function is to convert 220V AC power into 300V DC power.
2. What is conduction interference?
Answer: Conducted interference is a concept used to measure the size of electronic interference signals sent to the whole power grid by electronic products during operation. When all electronic products use electricity, they will send out interference signals to the power grid. If the interference signal is too large, it will affect the power quality of the whole power grid, thereby interfering with the normal operation of other electrical appliances. Therefore, most countries have a rigid regulation on conductive interference indicators of electronic products, prohibiting the production and sale of products with excessive conductive interference.
3. What is the principle of switching circuit?
Answer: The principle of switching circuit is composed of switching tube and PWM (Pulse Width Modulation) control chip to generate high frequency pulse. The high-voltage DC generated by the high-voltage rectifier filter circuit is transformed into high-frequency pulsed DC, which is sent to the main transformer to step down and become low-frequency pulsed DC.
4. What is conversion efficiency?
Answer: Because the Power Adapter is working, part of the energy is converted into heat loss. Therefore, the power adapter must minimize the loss of heat. Conversion efficiency is the percentage of output power divided by input power. Version 1.3 requires a minimum conversion efficiency of 70% at full load. Version 2.0 also improves the recommendation conversion efficiency to 80%.
5. What is the principle of low voltage rectifier filter circuit?
Answer: Low-frequency pulsed DC is filtered by electrolytic capacitor after diode rectification, so that the stable current of different voltage is output. Because the voltage here is already very low, although the capacitance capacity is very large, usually 1000uf, 2200uf, etc., but because it does not need a high withstand voltage value, the capacitance volume is very small.
6．What is the workflow of power supply?
Answer: When the municipal electricity enters the power supply, the high-frequency clutter and interference signals are removed by choke coil and capacitance filter, and then the high-voltage direct current is obtained by rectification and filtering. Then the DC current is converted into high frequency pulsating DC through switching circuit, and then sent to high frequency switching transformer to reduce voltage. Then filter out the high-frequency AC part, so that the final output of the computer using relatively pure low-voltage DC.
7. What are the characteristics of active PFC?
Answer: The input voltage of active PFC can be from 90V to 270V; the power factor is higher than 0.99, and it has the advantages of low loss and high reliability; it can be used as auxiliary power supply without auxiliary power transformer; the output DC voltage ripple is very small, so the active PFC power supply does not need to use a large capacity filter capacitor.
8. What is PFC?
Answer: PFC (Power Factor Correction), or “Power Factor Correction”, is mainly used to characterize the efficiency of electronic products in the use of energy. The higher the power factor is, the higher the utilization efficiency of electric energy is. The PFC circuit must be added to the computer power supply certified by CCC. The position is after the second filter and before the full bridge rectifier circuit. There are two kinds of PFC, one is passive PFC (also known as passive PFC), the other is active PFC (also known as active PFC).
9. What is surge current?
Answer: Surge current refers to the peak current flowing into the power supply equipment at the moment of power connection. Because the input filter capacitor charges rapidly, the peak current is much larger than the steady-state input current. The power supply should limit the surge level that AC switches, rectifier bridges, fuses and EMI filters can withstand. The AC input voltage should not damage the power supply or cause the fuse to burn out.
10. What kinds of high voltage electrolytic capacitors are there generally?
Answer: High voltage electrolytic capacitors, which we usually call large capacitors, usually have two capacitors. Because of their high voltage withstanding value, they are very large. According to the capacity, the high voltage electrolytic capacitors are generally 330 uf, 470 uf, 680 uf, 820 uf, 1000 uf, 1200 uf, etc. The voltage withstanding value is generally 200 V, and the temperature withstanding is 85 degrees.
11. What are the most important items in power supply testing?
Answer: There are mainly cross load, surge, input voltage, ripple noise, output short circuit, over power, conversion efficiency, power factor, response time, sequence, noise, conductive radiation, leakage current, high and low temperature test, etc
12. What is the main function of EMI circuit?
Answer: The function of EMI circuit is to filter out all kinds of interference signals coming from power grid and prevent high frequency interference from power switch circuit. EMI is an important part of CCC certification.
13. What is the realization of the software power-on function of power supply?
Answer: Software power-on function of power supply is realized by PW-OK circuit. When standby, PW-OK outputs zero-level power supply self-test signal to the host, and the host stops working in a standby state. After the controlled start-up, the PW-OK will delay several hundred milliseconds after the output voltage of the switching power supply is stabilized, jumping from 0 level to +5V, and output high-level signals to the host. This signal is equivalent to the PG signal of AT power supply. The host starts the system after detecting the signal of PW-OK power supply intact. In case of power failure or shutdown, the output signal of PW-OK disappears hundreds of milliseconds earlier than the output voltage of ATX switching power supply+5V. The trigger system of the main engine is notified to shut down automatically before power failure, so as to prevent the hard disk head from moving to the landing area and scratching the hard disk when power failure occurs suddenly.
14. What role does the auxiliary circuit play?
Answer: 300V DC current is transformed into pulse current by auxiliary power supply switch, and two sets of AC voltage are output through auxiliary power transformer. One way is regulated by rectifier and three-terminal regulator, and the output is + 5VSB, which is added to the motherboard as standby voltage. The other way is filtered by rectifier and output auxiliary 20V power supply to work on chips such as PWM. With the auxiliary circuit, the computer can turn on and off the software.
15. What is the difference between power factor and conversion efficiency?
Answer: Although power factor and conversion efficiency refer to the utilization rate of power supply, they differ greatly. Simply put, the loss caused by power factor is the burden of the power sector, and the loss of conversion efficiency is the burden of users themselves. It can be seen that power factor, EMI and so on are the protection of the state grid.
16. What is overpower protection?
Answer:In addition to the rated power, there is another data called “overload protection” and “OPP” in English. Overload protection means that the load of the power supply keeps rising, and when it reaches a certain point, the power supply will automatically be cut off so as not to damage the power supply or other parts of the computer due to over current. OPP value is usually about 1.3 times the rated power. Some manufacturers set OPP too high, which is actually unsafe. There will be an interval between the rated power and OPP. For example, the rated power of the new cold drill is 300W and the OPP is 370W. Then, the area between 300 and 370W is a “blind area”. If you stay in this area for too long (usually lasting tens of seconds), it is likely to cause the power supply or other parts of the computer to burn down.
17. What are the characteristics of passive PFC?
Answer: Passive PFC generally adopts inductance compensation method to improve power factor by reducing the phase difference between fundamental current and voltage of AC input. The power factor of passive PFC is not very high, it can only reach 0.7-0.8, and the calorific value is relatively large.
18. What is rated power?
Answer: Rated power refers to the maximum load of a power supply under stable and continuous operation. Rated power represents the real load capacity of a power supply. For example, the rated power of a power supply is 300W, which means that the sum of all loads can not exceed 300W 24 hours a day and 365 days a year. But in fact, the power supply has certain redundancy, such as 300 W rated power supply, it can work stably at 310W, but try not to exceed the rated power, otherwise it may cause the power supply or other computer components to burn down due to over current.
19. What is the basic principle of power supply?
Answer: By running high-frequency switching technology, the higher AC input voltage will be converted to the lower DC required for PC operation.
20. What is the principle of temperature-controlled power supply?
Answer:The temperature control circuit is mainly realized by thermistor. When the power supply starts to work, the supply voltage of the fan is 7V. When the temperature in the power supply increases, the resistance value of the thermistor decreases, the voltage gradually increases, and the speed of the fan also increases. In this way, the temperature in the case can be maintained at a lower level. In the case of very light load, the silence effect can be achieved. When the load is large, it can ensure heat dissipation.
Post time: Oct-20-2022