What Is a Power Supply?

A power source is a device that converts other forms of energy into electrical energy.

A good power supply typically has

There are many types of power ICs, and their common characteristics are:

Low working voltage : The general working voltage is 3.0 3.6V. Some have lower operating voltages, such as 2.0, 2.5, 2.7V, etc .; some have 5V operating voltages, and a few special-purpose voltage sources of 12V or 28V.

Small working current: from a few milliamps to a few amps, but since the operating current of most embedded electronic products is less than 300mA, power ICs of 30 to 300mA account for a large proportion in variety and quantity.

Small package size: Portable products developed in recent years have used SMD devices, and power ICs are no exception. They mainly include SO packages, SOT-23 packages, MAX packages, the smallest SC-70 packages, and the latest SMD packages. Make the space occupied by the power supply smaller and smaller.

Complete protection measures: The new power IC has comprehensive protection measures, which include: output overcurrent limit, overheat protection, short circuit protection, and reverse polarity protection of the battery, so that the power supply works safely and reliably, and is not easily damaged.

Low power consumption and power-off function: The quiescent current of new power ICs is small, generally tens of A to hundreds of A. Individual micropower linear regulators have a quiescent current of only 1.1 A. In addition, many power supply ICs have a function to turn off the power control terminal (using level control). When the power supply is turned off, the IC itself consumes about 1 A. Because it can make a part of the circuit inoperable, it can save a lot of power. For example, on a wireless communication device, the receiving circuit may be turned off when in a transmitting state; the display circuit may be turned off when a signal is not received.

There is a power supply status signal output: Many portable electronic products have a single-chip microcomputer. When the output voltage drops by a certain percentage due to overheating or low battery voltage, the power supply IC has a power supply status signal to the single-chip microcomputer to reset the single-chip microcomputer. This signal can also be used to indicate the working status of the power supply (LED display when the battery is low).

High output voltage accuracy: The accuracy of the general output voltage is between ± 2 and 4%, and there are many new power supply ICs with accuracy of ± 0.5 to ± 1%; and the temperature coefficient of the output voltage is small, generally ± 0.3 to ± 0.5mV / , and some can reach the level of ± 0.1mV / . The linear adjustment rate is generally 0.05% to 0.1% / V, and some can reach 0.01% / V; the load adjustment rate is generally 0.3 to 0.5% / mA, and some can reach 0.01% / mA.

New combined power IC: step-up DC / DC converter with high efficiency but high ripple and noise voltage, low dropout linear regulator with low efficiency but minimum noise. The dual output power IC combined by the two can be better To solve the problem of efficiency and noise. For example, the digital circuit section uses a step-up DC / DC converter power supply and the noise-sensitive circuit uses an LDO power supply. Such power ICs include MAX710 / 711, MAX1705 / 1706, and so on. Another example is a charge pump + LDO composed of a charge pump power supply IC with output voltage regulation, such as MAX868, which can output a stable voltage adjustable from 0 to -2VIN and can provide 30mA current; MAX1673 regulated charge pump power supply IC The output has the same negative voltage as VIN, and the output current can reach 125mA.

ACPI: is a power management specification jointly launched by Intel, Microsoft, etc. It integrates power management into hardware, operating system and applications, and realizes comprehensive management of power by the operating system. ACPI-capable computers are in a very low-power suspend state when not in use, and modems can automatically turn on when they receive a signal, and can implement software shutdown to meet growing network application requirements.

Power supply efficiency: Power supply efficiency is closely related to the power supply design circuit. A high-efficiency power supply can improve the efficiency of power use, and can reduce the power consumption and heat generation of the power supply to a certain extent.

Breakdown voltage (Uaw, Ua): The highest instantaneous voltage value that can be continuously applied to the specified end of the protector before breakdown. The overvoltage protection is broken in the following cases: a) If the peak value of the current flowing through the resistance element exceeds 1mA; b) If the peak value of the current flowing through the protector exceeds 1mA due to overvoltage.

CCEE safety certification: The CCEE safety certification mark is also known as the Great Wall mark, which is a special certification mark for electrical products. The China Electrotechnical Product Certification Commission (CCEE) is the only legal agency authorized by the State Technical Supervision Bureau to represent China in the International Electrotechnical Commission's Electrotechnical Product Safety Certification Organization (IECEE), and implements safety certification (Great Wall logo certification) of electrical products on behalf of national organizations.

Port throughput: Port throughput refers to the port packet forwarding capability. It is usually measured using pps: packets per second. It is the packet forwarding capability of the router on a port. Two identical rate interface tests are usually used. But the test interface may be related to the interface position and relationship. For example, the throughput measured between ports on the same card may be different from the throughput value between ports on different cards.

Breakdown time: mainly reflects the characteristics of the protective element. The higher the protection level, the longer the breakdown time. The breakdown time can vary within a certain range, depending on the slope of du / dt or di / dt.

Short circuit protection: When the protected line tends to be short-circuited and generates more than 5 times the rated current, the protector cuts off the line. ^[1]

Power products are widely used in industrial automation control, military equipment, scientific research equipment, industrial control equipment, computers and computers, communications equipment, power equipment, instruments, medical equipment, semiconductor cooling and heating and other fields.

Asia-Pacific

Name Power Outlet Condition

Japan 100V double hole flat type

Korea 220V double hole round type

Hong Kong, China 220V three-hole flat power supply is normal

Macau, China 220V three hole type

220V double-hole round and flat power supply in Vietnam is still stable, with intermittent power outages

Thailand 220V double hole round and flat power supply is still good

Malaysia 220-240V three-hole power supply is still normal

Singapore 220V three-hole flat head power supply is stable

Philippines 220V double-hole flat and three-hole power supply is still stable, with occasional power outages

220V double hole round power supply in Indonesia is still stable, occasional power outages

India's 240V three-hole plug-in (two types of 5 and 15 amps) power supply is unstable, often power failure, all appliances need to be equipped with voltage regulator

Australia 240V 60HZ Eight-shaped three-hole voltage stability, no power outages, TV, video recorder is PAL system

New Zealand 220V figure-shaped power supply is stable

West Asia

Name Power Outlet Condition

Russia 220V50-60hz double-hole circular power supply is still good, but the voltage is unstable

Saudi Arabia, Arabia 110 and 220V double-hole flat and round power supply stable, three-hole flat socket of air conditioner or direct power wiring

Jordan 220V double-hole flat and round power supply still says stable use of socket converter

Kuwait 220-240V three-hole type (including ground) power supply is still stable

Israel 220-240V 50Mhz double-hole round power supply is still stable, with intermittent short-term power outages

Bahrain 220V three-hole power supply is still stable

Oman 220V three-hole power supply with stable power supply

Turkish 220V round power supply is good (capital region)

East Canada 220-240V figure three three-hole power supply is normal

North America

Name Power Outlet Condition

American 120V AC grounded three-wire power supply is good

Hawaii 120V AC grounded three-wire power supply is good

Guam 120V AC grounded three-wire power supply is good

Canada 110V double hole flat type power supply is good ^[2]

1. What is the basic working principle of industrial power supply?

Answer: By running the high-frequency switching technology, the higher input AC voltage (AC) is converted into the lower DC voltage (DC) required for the PC computer to work.

2. What is the working process of industrial power supply?

Answer: When the mains power enters the power source, high frequency noise and interference signals are removed by choke coils and capacitor filtering, and then high voltage direct current is obtained after rectification and filtering. Then, the direct current is converted into high-frequency pulsating direct current through the switching circuit, and then sent to the high-frequency switching transformer to step down. Then filter out the high-frequency AC part, so that the final output for the computer to use relatively pure low-voltage DC power.

3. What is the main role of EMI circuits?

Answer: The role of the EMI circuit is to filter out various interference signals coming from the power grid and prevent high-frequency disturbances formed by the power switch circuit from penetrating the power grid. EMI is an important part of CCC certification.

4. 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 role is to convert 220V AC mains to 300V DC.

5. What kinds of high-voltage electrolytic capacitors generally have?

Answer: There are usually two large-capacity electrolytic capacitors, which are very large because of their high withstand voltage. In terms of capacity, high-voltage electrolytic capacitors generally have 330uf, 470uf, 680uf, 820uf, 1000uf, 1200uf, etc. The withstand voltage is generally 200V and the temperature is 85 degrees.

6. What is the principle of the switching circuit?

Answer: The principle of the switching circuit is to form an oscillating circuit by a switching tube and a PWM (Pulse Width Modulation) control chip to generate high-frequency pulses. The high-voltage DC power generated by the high-voltage rectification filter circuit is converted into high-frequency pulsed DC power and sent to the main transformer for voltage reduction to become low-frequency pulsed DC power.

7. What is the principle of the low-voltage rectification filter circuit?

Answer: The low-frequency pulsed direct current is rectified by a diode and then filtered by an electrolytic capacitor. In this way, a stable current of different voltage is output. Because the voltage here is already very low, although the capacitor capacity is very large, usually 1000uf, 2200uf, etc., but because it does not need a high withstand voltage value, the capacitor volume is very small.

8. What is the role of the auxiliary circuit?

Answer: 300V DC power becomes pulse current through the auxiliary power switch tube. Two sets of AC voltage are output through the auxiliary power transformer. One is regulated by a rectifier and a three-terminal regulator. The output is + 5VSB, which is added to the motherboard as the standby voltage. Rectifier filtering, output auxiliary 20V power supply, for PWM and other chip work. With the auxiliary circuit, the computer can realize software startup and shutdown.

9. What is PFC?

Answer: PFC (Power Factor Correction) stands for "Power Factor Correction", which is mainly used to characterize the efficiency of electrical products using electrical energy. The higher the power factor, the higher the utilization efficiency of electrical energy. Computer power supplies that have passed CCC certification must add a PFC circuit. The position is after the second layer of filtering and before the full-bridge rectifier circuit. There are two types of PFC, one is passive PFC (also called passive PFC), and the other is active PFC (also called active PFC).

10. What are the characteristics of active PFC?

Answer: The active PFC input voltage 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 an auxiliary power source without the need for an auxiliary power transformer; the output DC voltage ripple is small Therefore, the power supply using active PFC does not need to use a large-capacity filter capacitor. ^[3]

DC power supply

DC power has two positive and negative electrodes. The potential of the positive electrode is high and the potential of the negative electrode is low. When the two electrodes communicate with the circuit, it can maintain a constant potential difference between the two ends of the circuit. A current flows from the positive electrode to the negative electrode. The difference in water level alone cannot maintain a stable water flow, and the constant water level can be maintained by forming a stable water flow with the help of a pump that continuously sends water from a low place to a high place. Similarly, the electrostatic field generated by the charge alone cannot maintain a stable current. With the help of a DC power supply, non-static action (referred to as "non-static force") can be used to make the positive charge from the negative electrode with a lower potential. The power source returns to the positive electrode with a higher potential to maintain the potential difference between the two electrodes, thereby forming a stable current. Therefore, a DC power supply is an energy conversion device that converts other forms of energy into electrical energy supply circuits to maintain a steady flow of current.

AC power

An AC power supply capable of providing a stable voltage and frequency is called an AC stabilized power supply. At present, the work done by most domestic manufacturers is stable AC voltage. The following summarizes the classification characteristics of some AC stabilized power supplies in the market. Parameter adjustment (resonant) type of stabilized voltage power supply, the basic principle of voltage stabilization is LC series resonance, the magnetic saturation type regulator that appeared earlier belongs to this category. Its advantages are: simple structure, no many components The reliability is quite high, the voltage regulation range is quite wide, and the anti-interference and anti-overload capabilities are strong. The disadvantages are: high energy consumption, high noise, bulky and high cost.