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Analysis of constant current control technology of AC drive-free LED
by：Demo
2021-07-09
AC drive-free LED fails to avoid the indispensable constant current control technology analysis
1. AC drive-free LED is not a fundamental change of the device.
In other words, there is actually no LED chip with an AC electric field working mechanism. The AC drive-free LED that comes out now is a device with a special arrangement of internal chipsets. It is only a change in the internal structure of the LED device, of course It is not easy to reach this level of craftsmanship.
The introduction of AC drive-free LEDs now mostly quote the information published by Seoul Semiconductor. It can be seen from this that the traditional rectifier bridge circuit is used to solve the problem of AC power supply to the so-called DC LED. It seems that the benefit is the omission of the rectifier diode, but the reverse withstand voltage of the LED is limited. If it is damaged when the power grid surge peak is large, it is not necessarily a benefit.
Because it is an imitated rectifier bridge circuit, only half of the current flows through the four bridge arms, while the entire current flows through the DC load end, which causes the current distribution on each group of LEDs to be quite unbalanced, such as undercurrent will affect Luminous lumens and luminous efficiency, such as overcurrent, will cause LED Light module decay and affect life.
The solution is simple, just remove the LED on the DC side and short-circuit it directly, and the current on the remaining four bridge arms can be the same. Take a closer look at the circuit, now that each group of forward and reverse LEDs are connected in parallel. In fact, it didn't have to be too complicated at the beginning, as long as the forward and reverse are connected in parallel, the positive and negative half cycles of the exchange can be passed.
2. AC drive-free LED fails to circumvent the indispensable constant current control technology.
From the introduction, the luminous efficiency of AC LEDs is not high enough compared with ordinary LEDs. It is said that it is in the development stage and will be higher in the future. The author believes that the light-emitting basis of similar LED chips is the same, and the main factor that restricts the amount of light emitted per watt is the type of rectifier bridge circuit. Imagine that only one of the five groups of LEDs can work normally and give full play to the luminous efficiency. The remaining four groups, which account for 80%, are working in an undercurrent state with very poor luminous efficiency. No matter how it develops together, the luminous efficiency is inherently lower than that of ordinary LEDs. The improvement method is to abandon the impractical rectifier bridge circuit, and directly connect the forward and reverse parallel connections and all work in a state of good luminous efficiency.
AC drive-free LED has no constant current protection function. When using, an external current limiting resistor must be connected, but when the current is limited to the upper limit of the power supply voltage, it will work under normal or low voltage with low LED Light module efficiency under current status. Resistor current limiting is a poor protection method. Not only does it have defects, but it also depends on energy consumption to reduce power utilization, that is, energy efficiency.
I want to add a PTC to solve the LED constant current problem, because the performance of the component is not fully understood. PTC is mainly used in overcurrent protection and thermal protection. When the current in the circuit is too large and the PTC reaches the Curie point temperature after heating, the resistance value rises sharply and approaches the open circuit. The degaussing circuit in the color TV uses it to generate large current attenuation amplitude. Degauss.
When the PTC resistor body is affected by the surrounding heat and the temperature exceeds the Curie point, it will be in an open-circuit state, which can play a switch-type thermal protection function.
If you want to rely on the positive temperature coefficient characteristic of the PTC resistor to protect the LED from constant current, you should also think of:
One is that the PTC resistor passes current, and there is a heating time process to heat up. When the resistance has not increased enough, the excess current may have already damaged the LED.
Secondly, if the self-heating temperature of the PTC resistor can really control the constant current, the influence of high or low ambient temperature that may change by tens of degrees will also make this 'constant current value' change meaningless.
Can it be generalized, isn't it possible that ordinary LED devices can be so simple and constant current? Unfortunately, it can't be done. And usually AC constant current is more troublesome than DC constant current.
In fact, there can be commercial LED adaptive constant current drivers such as simplified circuits, low energy consumption control, accurate constant current, surge resistance, high reliability, small size, and low cost, as well as many AC driver-free LED driver manufacturers. Support of all kinds of high-quality products. Instead of focusing on non-professional circuit technology, LED manufacturers should focus on the development of low-cost, high-efficiency LED lighting products that can better meet market demands.
However, with the increased prevalence of About Us, it has become far more affordable.
With comprehensive knowledge on About Us,why not visit the highly recommended site Demo Led Module to get a full appreciation of the best ?
The key to About Us is understanding where there is a problem or need in certain markets and knowing how to solve it.
1. AC drive-free LED is not a fundamental change of the device.
In other words, there is actually no LED chip with an AC electric field working mechanism. The AC drive-free LED that comes out now is a device with a special arrangement of internal chipsets. It is only a change in the internal structure of the LED device, of course It is not easy to reach this level of craftsmanship.
The introduction of AC drive-free LEDs now mostly quote the information published by Seoul Semiconductor. It can be seen from this that the traditional rectifier bridge circuit is used to solve the problem of AC power supply to the so-called DC LED. It seems that the benefit is the omission of the rectifier diode, but the reverse withstand voltage of the LED is limited. If it is damaged when the power grid surge peak is large, it is not necessarily a benefit.
Because it is an imitated rectifier bridge circuit, only half of the current flows through the four bridge arms, while the entire current flows through the DC load end, which causes the current distribution on each group of LEDs to be quite unbalanced, such as undercurrent will affect Luminous lumens and luminous efficiency, such as overcurrent, will cause LED Light module decay and affect life.
The solution is simple, just remove the LED on the DC side and short-circuit it directly, and the current on the remaining four bridge arms can be the same. Take a closer look at the circuit, now that each group of forward and reverse LEDs are connected in parallel. In fact, it didn't have to be too complicated at the beginning, as long as the forward and reverse are connected in parallel, the positive and negative half cycles of the exchange can be passed.
2. AC drive-free LED fails to circumvent the indispensable constant current control technology.
From the introduction, the luminous efficiency of AC LEDs is not high enough compared with ordinary LEDs. It is said that it is in the development stage and will be higher in the future. The author believes that the light-emitting basis of similar LED chips is the same, and the main factor that restricts the amount of light emitted per watt is the type of rectifier bridge circuit. Imagine that only one of the five groups of LEDs can work normally and give full play to the luminous efficiency. The remaining four groups, which account for 80%, are working in an undercurrent state with very poor luminous efficiency. No matter how it develops together, the luminous efficiency is inherently lower than that of ordinary LEDs. The improvement method is to abandon the impractical rectifier bridge circuit, and directly connect the forward and reverse parallel connections and all work in a state of good luminous efficiency.
AC drive-free LED has no constant current protection function. When using, an external current limiting resistor must be connected, but when the current is limited to the upper limit of the power supply voltage, it will work under normal or low voltage with low LED Light module efficiency under current status. Resistor current limiting is a poor protection method. Not only does it have defects, but it also depends on energy consumption to reduce power utilization, that is, energy efficiency.
I want to add a PTC to solve the LED constant current problem, because the performance of the component is not fully understood. PTC is mainly used in overcurrent protection and thermal protection. When the current in the circuit is too large and the PTC reaches the Curie point temperature after heating, the resistance value rises sharply and approaches the open circuit. The degaussing circuit in the color TV uses it to generate large current attenuation amplitude. Degauss.
When the PTC resistor body is affected by the surrounding heat and the temperature exceeds the Curie point, it will be in an open-circuit state, which can play a switch-type thermal protection function.
If you want to rely on the positive temperature coefficient characteristic of the PTC resistor to protect the LED from constant current, you should also think of:
One is that the PTC resistor passes current, and there is a heating time process to heat up. When the resistance has not increased enough, the excess current may have already damaged the LED.
Secondly, if the self-heating temperature of the PTC resistor can really control the constant current, the influence of high or low ambient temperature that may change by tens of degrees will also make this 'constant current value' change meaningless.
Can it be generalized, isn't it possible that ordinary LED devices can be so simple and constant current? Unfortunately, it can't be done. And usually AC constant current is more troublesome than DC constant current.
In fact, there can be commercial LED adaptive constant current drivers such as simplified circuits, low energy consumption control, accurate constant current, surge resistance, high reliability, small size, and low cost, as well as many AC driver-free LED driver manufacturers. Support of all kinds of high-quality products. Instead of focusing on non-professional circuit technology, LED manufacturers should focus on the development of low-cost, high-efficiency LED lighting products that can better meet market demands.
However, with the increased prevalence of About Us, it has become far more affordable.
With comprehensive knowledge on About Us,why not visit the highly recommended site Demo Led Module to get a full appreciation of the best ?
The key to About Us is understanding where there is a problem or need in certain markets and knowing how to solve it.
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