Nip In The Bud :Some Common Protection Circuits

Since there are some unstable factors in the power supply circuit, the circuit designed to prevent such unstable factors from affecting the circuit is called the protection circuit. The protection circuits are common in all kinds of electronic products, such as: overcurrent protection, overvoltage protection, overheat protection, no-load protection, short circuit protection and so on. This paper has sorted out some common protection circuit.

Motor Overheating Protection Circuit

In the production of automatic lathe, electric heating oven, ball mill and other continuous operation of the mechanical and electrical equipments , as well as other unattended equipments, because accidents happen from time to timethe because of motor overheating or temperature controller failure , it’s necessary to take appropriate security measures. PTC thermistor overheat protection circuit can conveniently and effectively prevent the above accidents.

The following figure is an example of motor overheating protection, composed of PTC thermistor and Schmitt circuit control circuit. In the figure, RT1, RT2 and RT3 are three step PTC thermistors with the same characteristics, which are embedded in the windings of the motor stator respectively. Under normal circumstances, PTC thermistor is in normal state, the total resistance is less than 1 k Ω. At this time, V1 is cut off, V2 is conducted, relay K gets the normally open contact of electric absorption, and the motor is operated by the power supply of the municipal electric power.

When motor faultdue to local overheating , as long as there is a PTC thermistor heat exceeds the preset temperature, the resistance will be more than 10 k Ω. So V1 conduction, V2 cut-off, VD2 display red alarm, K loss of power release, motor stop running, to achieve the purpose of protection.

The selection of PTC thermistor depends on the insulation level of the motor. The Curie temperature of PTC thermistor is usually selected in a range about 40℃ lower than the limit temperature corresponding to the insulation grade of the motor. For example, for the B1 insulation of the motor, its limit temperature is 130℃, Curie temperature 90℃ PTC thermistor should be selected .

Protection Circuit In Inverter Power Supply

Inverters often need to carry out current conversion, if the current in the circuit exceeds the limited range, it will cause great damage to the circuit and key devices, so the protection circuit in the inverter power supply is particularly important.

Anti - Reverse Protection Circuit

If the inverter has no anti-reverse circuit, in the case of input battery anti-reverse will often cause disastrous consequences, light to burn fuse, heavy to burn most of the circuit. There are three kinds of anti-reverse connection protection circuits in the inverter: anti-reverse connection protection circuit composed of anti-parallel Schottky diode, as shown in the figure below.

From the figure, when the battery is reversed, the Schottky diode D is conducted but F is burned. If the back is Lord of the push-pull structure transform circuit, the two push-pull switches MOS tube parasitic diodes are equivalent and D in parallel, but the pressure drop is much bigger than Schottky, instantaneous current impact resistance ability and lower than the Schottky diode D, thus avoiding the large current through the parasitic diodes MOS tube, thereby protecting the two push-pull switches MOS tube.

This anti-reverse connection protection circuit structure is simple, it will not affect the efficiency, but after protection the fuse F will be burnt out, and it needs to be replaced to restore normal work.

Anti-reverse connection protection circuit of relay is adopted. The basic circuit is as follows:

As can be seen from the figure, if the battery is connected inversely and D inversely deflected, no current passes through the coil of relay K, the contact cannot be closed, and the power supply of the inverter will be cut off. This anti-reverse connection protection circuit has a better effect and will not burn out fuse F, but the volume of it is relatively large and the contact life of the relay is limited.

The anti-reverse connection protection circuit using MOS tube, the basic circuit is as follows:

In the figure, D is a parasitic diode with anti-reverse MOS connection, which is easy to draw the principle of analysis. When the battery polarity is not inversely connected, D is positively and partially conductive, and GS electrode of Q is positively and partially conductive by going through F, R1 and D to the negative electrode of the battery. The voltage drop after Q conduction is much smaller than that of D, so after Q conduction, D will not get enough forward voltage and stop.

When the polarity of the battery is reversed, D will end due to reverse bias, Q will also end due to reverse bias of GS, and the inverter cannot start. Due to the absence of mechanical contact switch, this anti-reverse connection protection circuit has a relatively long service life, and will not burn fuses like the anti-reverse connection protection circuit composed of anti-reverse Schottky diode. Therefore, it is widely used, but the disadvantage is that MOS has a certain loss when conducting.

LVD-Low Voltage Disconnect

In order to prevent the battery from being damaged by excessive discharge, we need to make the inverter stop working when the battery voltage is discharged to a certain voltage. It should be pointed out that the battery undervoltage protection is too sensitive to protect when the impact load is started. This makes it difficult for the inverter to start such loads, especially when the battery power is not very sufficient. See the battery undervoltage protection circuit below.

It can be seen that this circuit can quickly establish the sampling voltage of the battery and delay protection by adding D1 and C1.

Lithium Battery Charging Protection Circuit

Lithium battery over both charge and discharge will affect the battery life. In the design, we should pay attention to the lithium battery charging voltage, charging current. Then selecting the appropriate charging chip. Taking attention to prevent lithium battery overcharge, overdischarge, short circuit protection and other problems. At the same time, the design has to go through a lot of testing.

Design of Lithium Battery Charging Circuit

The chip TP4056 is selected as an example. The maximum charging current can be controlled according to different resistances. You can design the charging indicator and the charging temperature that the range of degrees which need charging.

Charging Protection Circuit

The combination of DW01 and GTT8205 can protect short circuit and over charge and discharge.

Overcurrent Protection Circuit In Switching Power Supply

There are various forms of overcurrent protection, including resistance primary current-limiting circuit, base drive current-limiting circuit, power-free current-limiting circuit and 555 current-limiting circuit. The following diagram shows the comparison of these kinds of over-current protection circuits:

Chip Competition: 5G Chip Manufacturers Infighting And the Establishment of A New Pattern

In the early hours of July 26, 2019, Apple announced that it had agreed to buy Intel's smartphone baseband business for $1 billion. Under the deal, Apple will receive 2,200 Intel employees, patents and IP related to 5G modems, and specialized equipment after the deal closes. After the acquisition, Apple will own 17,000 wireless technology patents, which will help it take greater initiative in the coming 5G era. It can also provide support for the industry to build differentiated products in the future.

Since the beginning of 2019, the global 5G baseband chip manufacturers have been surging, the 5G market structure is unpredictable, and the infighting among major chip manufacturers has become increasingly fierce.

April 2019 is a month of earth-shaking pattern of 5G baseband chips. In mid-April, several big things happened in 5G chips. First, the patent licensing dispute between Qualcomm and Apple has finally been settled. Second, Apple and Qualcomm re-signed a patent licensing agreement. Third, Intel pulled out of its 5G smartphone modem business, citing a lack of clear revenue lines.

Why is Intel pulling out of 5G at this point? For one thing, Intel's baseband chips have always been Apple's only customer, but to win orders from Apple, Intel is essentially offering "zero margin" services. On the other hand, the dispute between Apple and Qualcomm is also a guarantee for Intel to obtain Apple orders. At the same time of Apple and Qualcomm's settlement, this guarantee is weak. After all, the baseband chip quality of Intel and Qualcomm is obvious to all. Therefore, Intel officially announced the withdrawal of 5G mobile phone baseband chip field. Obviously, the combination of Apple and Qualcomm makes Intel's huge investment in 5G mobile phone baseband chip "waste". From this point of view, in contact with unisplink 5G baseband chip research and development agreement, Intel seems to have planned to exit 5G mobile baseband chip field.

Robert Swan, Intel's chief executive, said: "we are very excited about the opportunities for 5G and the cloud of networks, but in the smartphone modem business there is clearly no clear monetisation opportunity and good returns. 5G remains a strategic focus for Intel, and our team has developed a range of valuable wireless products and intellectual property. "We are evaluating options to realize the value we create, including opportunities for a variety of data-centric platforms and devices in the 5G world."

After Intel withdrew from the 5G baseband chip competition, there are only three foreign players of 5G phone baseband chip: Qualcomm of the United States, samsung of South Korea and Apple. So, so far, the three major foreign players 5G baseband chip situation?

Qualcomm's first 5G baseband chip, the Snapdragon X50, is now commercially available, and on February 20 this year launched its second generation 5G baseband chip, the Snapdragon X55 (Snapdragon X55). Commercial supplies of the snapdragon X55 are expected to start as soon as the end of this year. The main feature of the 5G baseband chip X55 launched this time is to cover all the main frequency bands from 5G to 2G multi-mode, supporting independent (SA) and non-independent (NSA) network deployment. In addition, the X55 is the world's first 5G baseband chip capable of 7Gbps, which means Qualcomm has the fastest 5G baseband chip in the world. Previously, the first generation X50 only supported a maximum download rate of 5Gbps. Currently, the X55 has no mobile terminal products for sale, and Qualcomm expects to launch its first X55 baseband 5G smartphone in 2020.

Samsung released its first 5G baseband chip, the Exynos Modem 5100, last year. Exynos Modem 5100 chip is manufactured by 10nm LPP process, supports Sub 6GHz low frequency and millimeter wave high frequency, and is compatible with 2G/3G/4G communication modes downward.

Judging from the current market pattern of 5G baseband chips in foreign countries, other 5G manufacturers will share the blue ocean of 5G baseband chips, excluding samsung which only does internal supply. And with Intel's exit, the United States is currently only Qualcomm in the lead. However, with Qualcomm's original market advantages and technical advantages, and the advantages of American manufacturers in the field of 5G rf devices, the United States will occupy half of the 5G field in the future.

Generally speaking, 5G is a qualitative change of the current new generation of information technology and a key point of scientific and technological competition among countries. It is of great significance to the country's scientific, technological and economic development.

Tunguska Explosion and Nikola Tesla

Tunguska Explosion

Have you ever heard of the Tunguska Explosion?Speculation about the Tunguska explosion is that it was just an alternating current test run by the legendary Nikola Tesla.Based on the carbonization of the trees and the magnetization of the ground, this is not the usual linear lightning, but more like the huge energy released by spherical lightning. In the night before the explosion, extremely bright lightning was seen over cities such as Moscow, which may be Tesla's experiment in transmitting energy wirelessly over long distances. Accurate calculations (to within one degree) focused the powerful alternating current on the uninhabited Tunguska. What is certain is that when the explosion occurred, Tesla is in Russian Ilkuzk, one of the places to able to see the big bang. Tesla once said something similar: "I can split the world, but I won't do it." At the same time, the evidence continues to suggest that only he could have released the energy equivalent of a Hiroshima bomb 1,000 times. Another detail is that before the tunguska explosion, the great scientist made several trips to the library to consult maps of Siberia.

So, is Tesla really as great as it sounds? I don't think so. I think it's just a myth, and it must be an exaggeration. Still I admire Tesla.

Nikola Tesla

Tesla famously said, "I'm just an ordinary person, and I don't have special abilities. Every little part of the universe contains all the information of the whole universe, and there is some mysterious database in it that contains all the information of the universe. I am just lucky to have access to this database."

Nikola Tesla is a "science superman", a prodigy of science. Tesla was the man who opened the doors to electricity and magnetism, the pioneer of modern electrical engineering and the second industrial revolution. Despite his achievements in electromagnetism and engineering, Tesla is also considered to have contributed to various fields such as robotics, ballistics, information science, nuclear physics and theoretical physics. Including the Internet, which we use.

In 1889 he invented the method of transmitting electricity wirelessly. And a laboratory was built in Colorado Spring, USA to develop and study the wireless transmission technology, which converts the current low frequency (5060Hz) high voltage current into high frequency current, and then transmits the electricity through the air as the transmission medium. This wireless transmission technology not only saves the cost of transmission cables, but also eliminates the loss caused by resistance during transmission. After eight months of research, Tesla decided to build the first power transmission tower, called Tesla Coil, on Long Island.

Tesla Coil can produce high voltage alternating current at both high frequency and low current. This high-frequency current can be transmitted wirelessly through the air to another receiver over a long distance without any adverse effects on the human body. Tesla discovered that high-voltage current could be converted into high-frequency high-voltage current, which could carry electricity indefinitely. Tesla Coil is the invention of this wireless transmission technology, and it is even a kind of free energy that human beings have been dreaming of.

The current status of Tesla

Unfortunately, the tesla coil is not in great use at present. Common radio applications in life are: no contact radio frequency card (bus card), wireless charger, artificial lightning, etc.

Bus card

 Wireless charger

Artificial lighting

Tesla coil sounds great and wireless transmission is such a great idea, so why isn't it so cool to actually use it?

Why tesla coils are not widely used

There are two sayings about the reasom.One is that instead of generating electricity, tesla coils consume it. For the principle of the tesla coil, it needs to input a certain amount of electric energy in the working process.

The high voltage generated by it is only the energy storage characteristics of inductors and capacitors that store the low-voltage high-current form of electric energy and release it in the form of high-voltage and low-current in a very short moment. The whole process is only the transformation of electric energy form, but no energy is generated. On the contrary, there will be some losses in the conversion process.

So tesla coils don't generate electricity, they consume it, and there's no such thing as "the ubiquity of free electricity."

Another saying is that Tesla's main energy is to study the essence of the world and the application of principles. His time of research is estimated to be 60 or 70 years, and no one in the world can reach his basic knowledge and research ability. Moreover, with the loss of some research materials in the later stage and the difficulty in understanding technical abstruse, the research on wireless transmission becomes difficult.

Disccusion

So what do you think? I admire Tesla and I approve his opinion.Because if that's the case, tesla coils consume electricity, Tesla would have figured it out before, and would not have thought of free energy later. Or Tesla might have imagined changing it. If tesla were alive, I believe he would be able to realize his vision.