EN 简体中文 English


Common LED Drive Power Supply
2020-01-06 17:11:53
 I. Common LED drive power supply
There are many types of LED power supply, and the quality and price of various types of power supply vary greatly, which is also one of the important factors affecting product quality and price. LED drive power supply can usually be divided into three categories, one is the switch constant current source, two is the linear IC power supply, three is the resistance capacity step-down power supply.
Switch constant current source
The transformer is used to change the high voltage into low voltage, and the filter is rectified to output stable low voltage dc. Switch constant current source is divided into isolated power supply and non-isolated power supply, isolation refers to the output high and low voltage isolation, very high security, so the insulation of the shell requirements are not high. Non-isolated safety is a little bit worse, but the cost is also relatively low, the traditional energy-saving lamp is the use of non-isolated power supply, the use of insulating plastic shell protection.
Switching power supply is relatively high security (generally output low voltage), stable performance, the disadvantages are complex circuit, high price. The switch power supply technology is mature, the performance is stable, is the current LED lighting mainstream power supply.
Detail explanation of LED drive power supply commonly used for dry goods |

Linear IC power supply
The use of one IC or more IC to distribute voltage, electronic components, power factor, power efficiency is very high, do not need electrolytic capacitor, long life, low cost. The disadvantage is that the output high voltage is not isolated, there is stroboscopic, the shell is required to do a good job of anti-shock isolation protection.
The market claims no (to) electrolytic capacitor, super long life, are linear IC power supply. IC drive power supply has the advantages of high reliability, high efficiency and low cost. It is the ideal LED drive power supply in the future.
Detail explanation of LED drive power supply commonly used for dry goods |Resistance capacity step-down power supply
A capacitor is used to provide the driving current through its charge and discharge. The circuit is simple, low in cost, but poor in performance and stability. It is extremely easy to burn the LED when the grid voltage fluctuates. Low power factor, short life, generally only suitable for economic small power products (within 5W).
High power products, large output current, capacitance can not provide large current, otherwise easy to burn out. In addition, the country has requirements on the power factor of high-power lamps, that is, the power factor requirements of more than 7W are greater than 0.7, but the resistance and capacitance step-down power supply is far from (generally between 0.2-0.3), so high-power products should not be used resistance and capacitance step-down power supply. On the market, the low end of the product, almost all is the use of resistance capacity buck power supply, there are some high power cheap low-end products, is also the use of resistance capacity buck power supply.
Detail explanation of LED drive power supply commonly used for dry goods |

Ii. Differences between LED switching power supply and drive power supply
Generally speaking, LED drive is also a kind of switching power supply, but it has a few characteristics, but also the general nature of this kind of switching power supply, so it is traditionally classified as LED drive.

The particularity of these points is:
Its voltage output is a multiple of 3.2, that is, the voltage output in the form of 3.2v, 6.4v, 9.6v, 12.8v, but generally not more than 25.6v. Because after exceeding this number, when the LED is turned on, the possibility of burning the last LED instantly will occur due to the poor consistency of the product. Moreover, the voltage is not constant, but varies with the load to achieve the purpose of constant current.

Its output current is constant, and the ideal circuit is to keep the current of the power supply constant no matter how the LED's characteristic curve changes. However, limited to the component precision, there will still be a small number of changes, and this change is also an important parameter to judge whether the driver circuit is excellent. The LED conduction and voltage function is a nonlinear "three-section" relationship, so it is very important to maintain a constant current.

It starts with a soft boot. Since the consistency of LED is very poor, and the activity of internal PN junction changes instantaneously during conduction, the drive of LED is generally designed as soft start to avoid this defect.

Its circuit requirements are the simplest, because most of the time, the circuit is required to be installed in a small space, to match the convenience of LED lighting, so the circuit should be as simple as possible, so as to save costs and reduce energy consumption.

It generally does not require isolation, because many products are similar to the general floodlight structure, safety can be similar to the floodlight is. But this first is an "optional reading", we do not have a misunderstanding when understanding, because some drivers or need to be isolated, this characteristic only applies to our current popular circuit, not necessarily suitable for the future circuit development needs.

To sum up, it can be considered that: soft start, constant current, step voltage, circuit simplicity is its characteristics.

One more point here:
Many people one-sided emphasis on the constant current, but do not mention the voltage, is wrong. Because the constant current concept has nothing to do with voltage, for example, a power supply, if it's just a constant current of 30V output, then when you open the circuit, its voltage is 30V; If you attach an LED, the component that works directly with the PN junction will burn up before the most accurate circuit response.
Because any circuit needs reaction time, and the device in the circuit is the semiconductor. The PN junction can only react after the power supply gives the sampling signal, while the LED PN junction directly starts to work, so its "reaction" is faster than the "numerous PN junction coordination" in the circuit, burning out in advance! Of course, there are special occasions to use this kind of drive, but this kind of LED drive does not allow the output side open. It is not allowed to open the output terminal and then connect the LED