It is often heard that people in the industry have complained that every time a LED lamp breaks down, the power supply is broken, so the most unreliable thing in a LED lamp is the power supply. Perhaps he is talking about the fact. However, it also requires in-depth analysis of the reasons for the LED power supply damage.
Recently, my home's LED lamps have also been broken. When I took a look at it, it turned out that the power supply was bad, but even though the phenomenon is like this, it should be analyzed carefully.
1. Use of inexpensive low quality components <br> <br> we can see, it is a bridge rectifier composed of four rectifier diodes, rather than an integrated bridge rectifier. We know that the cost of the four diodes is much lower than that of an integrated rectifier bridge because there are many companies that can produce diodes because diodes can be produced using only some of the simplest semiconductor production equipment that has been eliminated in the past, and that can produce There are not many companies that integrate rectifier bridges, because they must have high-quality integrated circuit production equipment and raw materials, and some large companies can only produce them, and their prices are certainly much more expensive than the four diodes. In fact, high-back-pressure diodes are not easy to do, and the average manufacturer may not necessarily be able to produce highly reliable high-voltage diodes. Later, I measured it with a multimeter, and I realized that there was a rectifier diode breakdown and the electrolytic capacitor was still good.
Is there no problem with the integrated rectifier bridge? This is not the case, and there are many times when the electrolytic capacitor is broken because it is not protected. In addition, when selecting components such as pressure resistance, power consumption, etc., we must try to leave room, such as the pressure resistance of electrolytic capacitors, although at the rated voltage of 220V, the peak voltage is only 220Vx1.4=308V. The electrolytic capacitor voltage on the power board is 400V, which should be enough, but we usually use 450V electrolytic capacitors, so the insurance factor can be larger.
2. Did not use any protection components
As can be seen from the photos, this power supply is not equipped with any protection device. However, as a power source connected to the mains, it is necessary to add protection components. This is because there are often various surge voltages on the mains. It may be a lightning strike at a long distance or a high-power device on the power grid. High voltage pulse caused by switching. If the high voltage pulse is not protected, it can easily break through the electrolytic capacitor.
LED lamp power supply protection device LED power supply protection device has two main functions, one is to protect the power supply itself, to prevent external damage and damage. On the other hand, the external circuit environment is protected from external circuits due to the operation or damage of the LED lamp.
The most important protection devices are the following:
Varistor
The varistor is used to protect the LED luminaire itself. It can be said that regardless of the power supply used by the LED luminaire, switching power supply, linear power supply, such protection is required. It is used to protect the surge voltage that often occurs on the mains network. The so-called surge voltage is mainly due to short-time high-voltage pulses caused by lightning or high-power electrical equipment starting and stopping. Lightning strikes are the main reason. Lightning strikes can be divided into direct lightning strikes and indirect lightning strikes. Direct lightning strikes are lightning strikes that directly hit the power supply network. This possibility is rare, and most large-scale power supply network systems have lightning protection measures. Indirect lightning strikes are surges induced by lightning and transmitted on electricity networks. Such surges are very likely to occur because there are 1,800 thunderstorms and 600 lightning strikes per second every moment of the world. Each lightning stroke induces a surge voltage on the nearby electrical network. The width of the surge pulse is usually only a few microseconds or even shorter, and the amplitude of the pulse may be as high as several thousand volts. Mainly because of its high amplitude, it has the greatest impact on the damage of electronic devices. Without protection, various electronic devices can easily be damaged. Fortunately, surge protection is simple, just add an anti-surge varistor, usually it is connected in parallel before the rectifier.
The principle of this type of varistor is that it has a non-linear resistor whose resistance is close to an open circuit within a specified threshold, and once the applied voltage exceeds the threshold, its resistance immediately approaches zero. This will easily absorb this surge. Moreover, varistors are a type of recoverable device. After the surge is absorbed, it can be used for protection.
Its main indicators are: 1) The maximum continuous operating voltage (divided into two kinds of AC and DC, such as 415V DC), 2) The varistor voltage (threshold, such as 510V) refers to the starting voltage when the current is greater than 0.1mA. 3) The maximum limit voltage is the maximum peak voltage Vp above the varistor that can withstand a peak current Ip (for example, 200A), for example, 845V; in fact, the surge is usually only a small width (a few microseconds). The narrow pulse, its voltage and current relationship is not already described by the resistor, because it is actually a nonlinear device.
2. Negative temperature coefficient resistor NTC
Many LED power supplies are equipped with electrolytic capacitors behind the rectifiers. The charging current of the electrolytic capacitors when they are just connected to the power supply is usually very large, often measured in several amps. If a room has many such power supplies connected at the same time, then The added charge current will cause the grid of this room to generate a very large instantaneous current enough to make the fuse switch trip. Therefore, in order to avoid such a situation, in the LED power supply, it is necessary to install a negative temperature coefficient resistor (NTC) in front of the electrolytic capacitor. Its characteristic is that the resistance is usually very small, and when it encounters a momentary high current, its resistance Because the heat suddenly becomes extremely large, it also limits the instantaneous high current. When the large current is passed, it quickly returns to the usual small resistance, thus avoiding the external impact of the LED power supply.
3. Fuse <br> <br> its role is similar to ordinary fuses, mainly in the LED load when a short circuit occurs due to various reasons, which itself brought this short circuit fuse will immediately disconnect the load, so as not to affect Trip to outside circuit.
The position of the above three protection devices in the LED power supply circuit is shown in the following figure:
The varistor is actually a surge-proof varistor. And these three kinds of protection devices are the most basic, are a kind of standard protection circuit, also all LED lamp power supplies should use! Unfortunately, most of the LED power supplies on the market are not equipped with such protection circuits. Only a few high-end LED lamp power supplies use this protection circuit. For example, many non-electrolytic capacitor light engines, or AC LED light engines that claim to be powerless, do not use this protection circuit. Because the height of the previous varistor is very large and high, its height is about 4-5mm, so the naked eye can immediately see whether or not a surge-proof varistor is installed.
Some of the so-called “powerless†“AC LED†light engine products are open to internal construction and it is clear that no protective components have been added, and only high-end scintillation-free light engines with electrolytic capacitors have added all protection circuits, such as Philae's light engine:
Effele's high-efficiency (99%) flicker-free light engine, with the fuse in the middle, the varistor with the largest volume below, and the negative temperature coefficient resistor NTC on the left (electrolytic capacitor on the back of the board).
4.Lightning Protection of LED Street Lights There are two kinds of street lights, one is a solar street light and the other is an AC circuit light. Solar street lights do not need to be connected to the power grid, so there is no surge problem. However, because they are often set up in open areas, there is a high possibility of direct lightning strikes. Therefore, most solar street lights require the installation of lightning rods to directly introduce lightning strikes underground.
In addition to occasionally installing lightning rods, power grid lights are the most important issue, and because the power supply circuit may be set up in the wild for a long time, the possibility of direct lightning strikes is also increased. At this time, the surge becomes Widely destructive wide pulses require more effective anti-surge measures.
In this case, a small varistor is not enough, but must be changed to a gas detonator, which is a gas discharge tube with a gas discharge gap space sealed by the metal electrode and the porcelain tube, using ceramic insulators and electrodes The welded shell ensures the tightness of the discharge gap.
When a high-voltage pulse is applied to it, the gas is punctured, the high voltage of the pulse is cut off, and the subsequent circuit is protected.
Conclusion
In summary, in fact, it is not difficult to be a highly reliable LED driving power, as long as the following points are followed:
1. Use high quality components. In fact, people with a little common sense know why some components are cheap and some are expensive. The difference lies in reliability. Therefore, do not sacrifice reliability in pursuit of low prices, and finally destroy the reputation of your company.
2. Make allowances when choosing device parameters. For example, withstanding voltage, you cannot assume that the mains voltage is 220V. Generally, we all require that the voltage should be as high as 265V or even higher. So any engineering design must leave room.
3. The circuit design must use the protection device, the circuit that does not protect the device is equal to your home door does not have the lock, does not have the lock home you dare to live?
4. The better circuit board should also be coated with three anti-paints. The so-called three anti-paints are moisture-proof, anti-salt spray, anti-mildew, plus dust, leak-proof, and better waterproof (IP67). The long life of this circuit board is more assured.
5. Some export circuit boards also require CE, UL certification, and some also ROHS certification (that is, lead-free certification) in order to avoid lead poisoning incidents in the recycling of these boards.
To achieve the above points, the life of the power supply can also be as high as tens of thousands of hours. Before many home appliances, such as televisions, took more than ten years to be not bad, it means that high reliability is achievable.
Unfortunately, almost 80% of the LED power supply on the market today is designed to reduce costs without using any protection devices. This method of using self-inflicted advantage to benefit others should indeed be condemned by the public.
On the other hand, LED luminaires that use this kind of power cuts are usually cheaper. We also have to advise consumers that the Chinese are saying: One price, one price, and no good goods! If you want to buy long-life LED lamps or you should buy expensive, better high-end products!
Recently, my home's LED lamps have also been broken. When I took a look at it, it turned out that the power supply was bad, but even though the phenomenon is like this, it should be analyzed carefully.
1. Use of inexpensive low quality components <br> <br> we can see, it is a bridge rectifier composed of four rectifier diodes, rather than an integrated bridge rectifier. We know that the cost of the four diodes is much lower than that of an integrated rectifier bridge because there are many companies that can produce diodes because diodes can be produced using only some of the simplest semiconductor production equipment that has been eliminated in the past, and that can produce There are not many companies that integrate rectifier bridges, because they must have high-quality integrated circuit production equipment and raw materials, and some large companies can only produce them, and their prices are certainly much more expensive than the four diodes. In fact, high-back-pressure diodes are not easy to do, and the average manufacturer may not necessarily be able to produce highly reliable high-voltage diodes. Later, I measured it with a multimeter, and I realized that there was a rectifier diode breakdown and the electrolytic capacitor was still good.
Is there no problem with the integrated rectifier bridge? This is not the case, and there are many times when the electrolytic capacitor is broken because it is not protected. In addition, when selecting components such as pressure resistance, power consumption, etc., we must try to leave room, such as the pressure resistance of electrolytic capacitors, although at the rated voltage of 220V, the peak voltage is only 220Vx1.4=308V. The electrolytic capacitor voltage on the power board is 400V, which should be enough, but we usually use 450V electrolytic capacitors, so the insurance factor can be larger.
2. Did not use any protection components
As can be seen from the photos, this power supply is not equipped with any protection device. However, as a power source connected to the mains, it is necessary to add protection components. This is because there are often various surge voltages on the mains. It may be a lightning strike at a long distance or a high-power device on the power grid. High voltage pulse caused by switching. If the high voltage pulse is not protected, it can easily break through the electrolytic capacitor.
LED lamp power supply protection device LED power supply protection device has two main functions, one is to protect the power supply itself, to prevent external damage and damage. On the other hand, the external circuit environment is protected from external circuits due to the operation or damage of the LED lamp.
The most important protection devices are the following:
Varistor
The varistor is used to protect the LED luminaire itself. It can be said that regardless of the power supply used by the LED luminaire, switching power supply, linear power supply, such protection is required. It is used to protect the surge voltage that often occurs on the mains network. The so-called surge voltage is mainly due to short-time high-voltage pulses caused by lightning or high-power electrical equipment starting and stopping. Lightning strikes are the main reason. Lightning strikes can be divided into direct lightning strikes and indirect lightning strikes. Direct lightning strikes are lightning strikes that directly hit the power supply network. This possibility is rare, and most large-scale power supply network systems have lightning protection measures. Indirect lightning strikes are surges induced by lightning and transmitted on electricity networks. Such surges are very likely to occur because there are 1,800 thunderstorms and 600 lightning strikes per second every moment of the world. Each lightning stroke induces a surge voltage on the nearby electrical network. The width of the surge pulse is usually only a few microseconds or even shorter, and the amplitude of the pulse may be as high as several thousand volts. Mainly because of its high amplitude, it has the greatest impact on the damage of electronic devices. Without protection, various electronic devices can easily be damaged. Fortunately, surge protection is simple, just add an anti-surge varistor, usually it is connected in parallel before the rectifier.
The principle of this type of varistor is that it has a non-linear resistor whose resistance is close to an open circuit within a specified threshold, and once the applied voltage exceeds the threshold, its resistance immediately approaches zero. This will easily absorb this surge. Moreover, varistors are a type of recoverable device. After the surge is absorbed, it can be used for protection.
Its main indicators are: 1) The maximum continuous operating voltage (divided into two kinds of AC and DC, such as 415V DC), 2) The varistor voltage (threshold, such as 510V) refers to the starting voltage when the current is greater than 0.1mA. 3) The maximum limit voltage is the maximum peak voltage Vp above the varistor that can withstand a peak current Ip (for example, 200A), for example, 845V; in fact, the surge is usually only a small width (a few microseconds). The narrow pulse, its voltage and current relationship is not already described by the resistor, because it is actually a nonlinear device.
2. Negative temperature coefficient resistor NTC
Many LED power supplies are equipped with electrolytic capacitors behind the rectifiers. The charging current of the electrolytic capacitors when they are just connected to the power supply is usually very large, often measured in several amps. If a room has many such power supplies connected at the same time, then The added charge current will cause the grid of this room to generate a very large instantaneous current enough to make the fuse switch trip. Therefore, in order to avoid such a situation, in the LED power supply, it is necessary to install a negative temperature coefficient resistor (NTC) in front of the electrolytic capacitor. Its characteristic is that the resistance is usually very small, and when it encounters a momentary high current, its resistance Because the heat suddenly becomes extremely large, it also limits the instantaneous high current. When the large current is passed, it quickly returns to the usual small resistance, thus avoiding the external impact of the LED power supply.
3. Fuse <br> <br> its role is similar to ordinary fuses, mainly in the LED load when a short circuit occurs due to various reasons, which itself brought this short circuit fuse will immediately disconnect the load, so as not to affect Trip to outside circuit.
The position of the above three protection devices in the LED power supply circuit is shown in the following figure:
The varistor is actually a surge-proof varistor. And these three kinds of protection devices are the most basic, are a kind of standard protection circuit, also all LED lamp power supplies should use! Unfortunately, most of the LED power supplies on the market are not equipped with such protection circuits. Only a few high-end LED lamp power supplies use this protection circuit. For example, many non-electrolytic capacitor light engines, or AC LED light engines that claim to be powerless, do not use this protection circuit. Because the height of the previous varistor is very large and high, its height is about 4-5mm, so the naked eye can immediately see whether or not a surge-proof varistor is installed.
Some of the so-called “powerless†“AC LED†light engine products are open to internal construction and it is clear that no protective components have been added, and only high-end scintillation-free light engines with electrolytic capacitors have added all protection circuits, such as Philae's light engine:
Effele's high-efficiency (99%) flicker-free light engine, with the fuse in the middle, the varistor with the largest volume below, and the negative temperature coefficient resistor NTC on the left (electrolytic capacitor on the back of the board).
4.Lightning Protection of LED Street Lights There are two kinds of street lights, one is a solar street light and the other is an AC circuit light. Solar street lights do not need to be connected to the power grid, so there is no surge problem. However, because they are often set up in open areas, there is a high possibility of direct lightning strikes. Therefore, most solar street lights require the installation of lightning rods to directly introduce lightning strikes underground.
In addition to occasionally installing lightning rods, power grid lights are the most important issue, and because the power supply circuit may be set up in the wild for a long time, the possibility of direct lightning strikes is also increased. At this time, the surge becomes Widely destructive wide pulses require more effective anti-surge measures.
In this case, a small varistor is not enough, but must be changed to a gas detonator, which is a gas discharge tube with a gas discharge gap space sealed by the metal electrode and the porcelain tube, using ceramic insulators and electrodes The welded shell ensures the tightness of the discharge gap.
When a high-voltage pulse is applied to it, the gas is punctured, the high voltage of the pulse is cut off, and the subsequent circuit is protected.
Conclusion
In summary, in fact, it is not difficult to be a highly reliable LED driving power, as long as the following points are followed:
1. Use high quality components. In fact, people with a little common sense know why some components are cheap and some are expensive. The difference lies in reliability. Therefore, do not sacrifice reliability in pursuit of low prices, and finally destroy the reputation of your company.
2. Make allowances when choosing device parameters. For example, withstanding voltage, you cannot assume that the mains voltage is 220V. Generally, we all require that the voltage should be as high as 265V or even higher. So any engineering design must leave room.
3. The circuit design must use the protection device, the circuit that does not protect the device is equal to your home door does not have the lock, does not have the lock home you dare to live?
4. The better circuit board should also be coated with three anti-paints. The so-called three anti-paints are moisture-proof, anti-salt spray, anti-mildew, plus dust, leak-proof, and better waterproof (IP67). The long life of this circuit board is more assured.
5. Some export circuit boards also require CE, UL certification, and some also ROHS certification (that is, lead-free certification) in order to avoid lead poisoning incidents in the recycling of these boards.
To achieve the above points, the life of the power supply can also be as high as tens of thousands of hours. Before many home appliances, such as televisions, took more than ten years to be not bad, it means that high reliability is achievable.
Unfortunately, almost 80% of the LED power supply on the market today is designed to reduce costs without using any protection devices. This method of using self-inflicted advantage to benefit others should indeed be condemned by the public.
On the other hand, LED luminaires that use this kind of power cuts are usually cheaper. We also have to advise consumers that the Chinese are saying: One price, one price, and no good goods! If you want to buy long-life LED lamps or you should buy expensive, better high-end products!
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