Want to improve test efficiency LED power supply, the most efficient and easy way is to choose the right electronic load. If knowledge is not familiar with the electronic load, or insufficient proficiency can not grasp it, and even cause a decline in confidence in the test results, which affects the quality of the product, but also lead to serious accidents. This article focuses on the principle of electronic load CV, and some errors LED power tests are introduced.
CV mode electronic load with load, is the basis for LED power supply tests. CV, is a constant voltage, the load current only tensile load device itself can not provide a constant voltage, the so-called CV, only by a voltage negative feedback circuit to output changes of the servo power supply LED current, the LED output capacitor charge balance, thus achieving a constant voltage. Therefore, the decision CV accuracy has two core elements:
Load Bandwidth
LED power output capacitor size
When high power LED output current ripple frequency, if the load insufficient bandwidth, you can not change current servo, caused concussion, concussion occurs when the load input voltage rapid change, LED output capacitance will be frequent high-current charge and discharge the detected current ripple at this time, will be much larger than the actual current ripple LED power supply during steady state operation.
When bandwidth is insufficient load, if the LED power supply output capacitance is large enough, volatility can be controlled within an acceptable range, but unfortunately, the power LED price competition is fierce, generally inadequate output capacitance, therefore, LED power supply for testing, load the bandwidth requirements are very demanding.
Bandwidth load indicators, manufacturers are not directly labeled only with reference to another indicator: full-scale current rise time, it is clear that the full-scale current rise time is smaller, the higher the bandwidth load. The higher the bandwidth load, the lower the power output of the LED capacitance requirements, in general, 10uS full-scale load current rise time, to meet the power needs of most LED test, but in theory, any load in CV mode next, there is the possibility of shock, in this case, when the LED output capacitor constant, the higher the bandwidth load, the smaller the volatility, the higher the confidence level test results, so users in the use of electronic load when testing, you must pay close attention to changes in load input voltage ripple Vpp, once it is out of range, the entire test results will no longer be credible, this point is very important, we must remember.
In CV mode, constant voltage, and current ripple are usually very large, and the load in order to improve test efficiency, data refresh rate is often high, so beating big data, many users in order to determine whether the load is suitable for LED test, in fact, this is a very serious misunderstanding, stable data or not, is actually very easy, you only need to increase the measurement time data filtering can be achieved, a short low-end electronic load, because of the low accuracy, so had large time scale filter, but instead a blessing in disguise, so that the data appears to be more stable, in fact, this is an illusion. To achieve accurate measurements, the fundamental approach is to increase the sampling rate can not increase the sampling rate, the measurement result is such confidence is very low, it may lead to serious quality accident.
Based on the above analysis, LED power supply testing, loaded with stringent requirements, mainly in the following points:
Full-scale current rise time is to ensure accurate load fundamental value as low as possible;
Data sampling rate, is the fundamental guarantee accurate measurement, the higher the value, the better;
Vpp real-time display of measurement data is to determine whether credible fundamental;
Filtering speed adjustment function, was able to get a small steady current data means;
Finally, drew attention to the market there are some load, known as LED power supply test dedicated electronic load, in fact, is a face-lift from General Electric load, but generally do not meet the bandwidth and sampling rate electronic load test requirements modified from its and did not improve their bandwidth because the bandwidth load technology is the core technology, and the cost is also closely related, it is difficult to improve, they tend to be improved through three ways in which the current data more stable, but also more credible.
The easiest way to increase filter strength, forcing the data is stable. So that this method is simple, easily lead to miscarriage of justice, causing mass accident.
Adjust the voltage feedback loop, voltage feedback signal strong filtering to reduce the current volatility. This method is just the opposite, to further reduce the bandwidth load, the situation is not very sharp shocks with shock, it has become smaller amplitude of oscillation.
Increase in internal load capacitance, this method can be suppressed flapping or amplitude, but the measurement of current ripple, ripple serious than the actual small, but helpful for testing the DC operating point. But the load rated voltage is generally higher, so the price and size of the high voltage capacitor is a very serious problem, and therefore it is difficult to ideal conditions, and often integrated with the first two methods. Another problem is that, in this situation, they tend to use a relatively inexpensive high-voltage capacitor solutions, it will bring a lot of parasitic problems.
This article introduces the principle of a comprehensive electronic load, especially in LED electronic load measurement errors exist in the process were highlighted. Moreover, in this paper, which also made a number of possible solutions, in order to obtain a more stable current data. I hope you can gain something after reading this article after.
CV mode electronic load with load, is the basis for LED power supply tests. CV, is a constant voltage, the load current only tensile load device itself can not provide a constant voltage, the so-called CV, only by a voltage negative feedback circuit to output changes of the servo power supply LED current, the LED output capacitor charge balance, thus achieving a constant voltage. Therefore, the decision CV accuracy has two core elements:
Load Bandwidth
LED power output capacitor size
When high power LED output current ripple frequency, if the load insufficient bandwidth, you can not change current servo, caused concussion, concussion occurs when the load input voltage rapid change, LED output capacitance will be frequent high-current charge and discharge the detected current ripple at this time, will be much larger than the actual current ripple LED power supply during steady state operation.
When bandwidth is insufficient load, if the LED power supply output capacitance is large enough, volatility can be controlled within an acceptable range, but unfortunately, the power LED price competition is fierce, generally inadequate output capacitance, therefore, LED power supply for testing, load the bandwidth requirements are very demanding.
Bandwidth load indicators, manufacturers are not directly labeled only with reference to another indicator: full-scale current rise time, it is clear that the full-scale current rise time is smaller, the higher the bandwidth load. The higher the bandwidth load, the lower the power output of the LED capacitance requirements, in general, 10uS full-scale load current rise time, to meet the power needs of most LED test, but in theory, any load in CV mode next, there is the possibility of shock, in this case, when the LED output capacitor constant, the higher the bandwidth load, the smaller the volatility, the higher the confidence level test results, so users in the use of electronic load when testing, you must pay close attention to changes in load input voltage ripple Vpp, once it is out of range, the entire test results will no longer be credible, this point is very important, we must remember.
In CV mode, constant voltage, and current ripple are usually very large, and the load in order to improve test efficiency, data refresh rate is often high, so beating big data, many users in order to determine whether the load is suitable for LED test, in fact, this is a very serious misunderstanding, stable data or not, is actually very easy, you only need to increase the measurement time data filtering can be achieved, a short low-end electronic load, because of the low accuracy, so had large time scale filter, but instead a blessing in disguise, so that the data appears to be more stable, in fact, this is an illusion. To achieve accurate measurements, the fundamental approach is to increase the sampling rate can not increase the sampling rate, the measurement result is such confidence is very low, it may lead to serious quality accident.
Based on the above analysis, LED power supply testing, loaded with stringent requirements, mainly in the following points:
Full-scale current rise time is to ensure accurate load fundamental value as low as possible;
Data sampling rate, is the fundamental guarantee accurate measurement, the higher the value, the better;
Vpp real-time display of measurement data is to determine whether credible fundamental;
Filtering speed adjustment function, was able to get a small steady current data means;
Finally, drew attention to the market there are some load, known as LED power supply test dedicated electronic load, in fact, is a face-lift from General Electric load, but generally do not meet the bandwidth and sampling rate electronic load test requirements modified from its and did not improve their bandwidth because the bandwidth load technology is the core technology, and the cost is also closely related, it is difficult to improve, they tend to be improved through three ways in which the current data more stable, but also more credible.
The easiest way to increase filter strength, forcing the data is stable. So that this method is simple, easily lead to miscarriage of justice, causing mass accident.
Adjust the voltage feedback loop, voltage feedback signal strong filtering to reduce the current volatility. This method is just the opposite, to further reduce the bandwidth load, the situation is not very sharp shocks with shock, it has become smaller amplitude of oscillation.
Increase in internal load capacitance, this method can be suppressed flapping or amplitude, but the measurement of current ripple, ripple serious than the actual small, but helpful for testing the DC operating point. But the load rated voltage is generally higher, so the price and size of the high voltage capacitor is a very serious problem, and therefore it is difficult to ideal conditions, and often integrated with the first two methods. Another problem is that, in this situation, they tend to use a relatively inexpensive high-voltage capacitor solutions, it will bring a lot of parasitic problems.
This article introduces the principle of a comprehensive electronic load, especially in LED electronic load measurement errors exist in the process were highlighted. Moreover, in this paper, which also made a number of possible solutions, in order to obtain a more stable current data. I hope you can gain something after reading this article after.
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