What are the classifications of the power supply of LED?
A. LED power supply can be divided into two main categories according to the driving method:
A. Voltage regulator type:
1, the voltage regulator circuit to determine the parameters, the output is a fixed voltage, the output current but with the increase or decrease of the load and changes
2, although the voltage regulator circuit is not afraid of load open-circuit, but the load is strictly prohibited completely short-circuit
3, the rectified voltage changes will affect the brightness of the LEDs
4, in order to make each string of regulator circuit to drive the LED display brightness uniformity, you need to add the appropriate resistance to be able to
B. Constant current type:
1, constant current drive circuit to drive LED is ideal, the disadvantage is that the price is high
2, constant current circuit is not afraid of the load short circuit, but the load is strictly prohibited completely open circuit
3, constant-current drive circuit output current is constant, while the output DC voltage is different with the size of the load resistance within a certain range of change
4, to limit the use of the number of LED, because it has the maximum withstand current and voltage values
Second, LED power supply according to the circuit structure can be divided into six categories:
1, conventional transformer step-down:
This power supply has the advantage of small size, the shortcomings are heavy weight, power supply efficiency is also very low, generally in 45% ~ 60%, because the reliability is not high, so generally rarely used.
2, capacitor buck:
This way of LED power supply is susceptible to grid voltage fluctuations, power supply efficiency is low, not suitable for LED in the flashing use, because the circuit through the capacitor step-down, in the flashing use, due to the role of charging and discharging, through the LED of the instantaneous current is very great, easy to damage the chip.
3, electronic transformer step-down:
The shortcomings of this power structure is low conversion efficiency, narrow voltage range, generally 180 ~ 240V, ripple interference.
4, resistance buck:
This power supply method power supply efficiency is very low, and the reliability of the system is also lower. Because the circuit through the resistor buck, by the grid voltage changes in the interference is large, not easy to make a regulated power supply, and the buck resistor itself to consume a large part of the energy.
5, RCC buck switching power supply:
This way of LED power supply advantage is the regulator range is wider, power supply efficiency is higher, generally can be in 70% ~ 80%, more widely used. Disadvantages are mainly switching frequency is not easy to control, load voltage ripple coefficient is large, abnormal load adaptability is poor.
6, PWM control type switching power supply:
At present, PWM control mode design of LED power supply is more ideal, because the output voltage or current of this switching power supply is very stable. Power conversion efficiency is very high, generally can be as high as 80% ~ 90%, and the output voltage and current are very stable. This way of LED power supply is mainly composed of four parts they are: input rectifier filter part, output rectifier filter part, PWM voltage regulator control part, switching energy conversion part. And this circuit has perfect protection measures, belongs to the high reliability power supply.
LED driver power supply nine performance characteristics required
According to the rules of the power grid and the characteristics of the LED drive power requirements, in the selection and design of LED drive power supply should take into account the following nine major performance characteristics requirements:
1. high reliability, especially like the LED street lamp drive power, installed in the high altitude, maintenance is not convenient, maintenance costs are also large.
2. High efficiency LED is an energy-saving products, drive power supply efficiency should be high. For the power supply installed in the structure of the lamp, especially important. Because the luminous efficiency of the LED with the LED temperature increases and decreases, so the LED heat dissipation is very important. High efficiency of the power supply, its power loss is small, in the lamps and lanterns within the heat is small, also reduces the temperature rise of the lamps and lanterns. It is favorable to slow down the light decay of LED.
3. High power factor Power factor is the power grid requirements for the load. Generally 70 watts or less of electrical appliances, there is no mandatory indicators. Although the power factor of the individual appliances is not very low power factor is not much impact on the grid, but at night we light, similar loads are too concentrated, will produce more serious pollution of the grid. For 30 watts ~ 40 watts of LED driver power supply, it is said that in the near future, maybe there will be a certain indicator of power factor requirements.
4. drive mode There are two kinds of pass now: one is a constant voltage source for more than one constant current source, each constant current source alone to each road LED power supply. This way, the combination of flexible, all the way LED failure, does not affect the work of other LED, but the cost will be slightly higher. Another is direct constant current power supply, LED series or parallel operation. Its advantage is that the cost is a little lower, but the flexibility is poor, but also to solve the problem of a LED failure, does not affect the operation of other LEDs. These two forms, coexist in a period of time. Multiple constant current output power supply method, in terms of cost and performance will be better. Perhaps the mainstream direction in the future.
5. Surge protection LED surge resistance is relatively poor, especially the ability to resist reverse voltage. Strengthen this aspect of protection is also very important. Some LED lights installed in outdoor, such as LED street lights. Due to the grid load start dumping and lightning induction, from the grid system will invade a variety of surges, some surges will lead to damage to the LED. Therefore, the LED driver power supply should have the ability to inhibit the intrusion of surges, to protect the LED from being damaged.
6. protection function power supply in addition to the conventional protection function, it is best to increase the LED temperature negative feedback in the constant current output, to prevent the LED temperature is too high.
7. Protection Lamps outside the installation type, power supply structure should be waterproof, moisture-proof, the shell should be sunlight-resistant.
8. Drive the life of the power supply to match the life of the LED.
9. To meet the safety regulations and electromagnetic compatibility requirements.
With the increasing application of LED, LED driver power supply performance will be more and more suitable for the requirements of LED.
Determine the quality of the LED driver power supply seven principles
1, give up more than 4-way output, the development of single or two-way output, give up high current and ultra-high current, the development of small current.
The more the number of output channels the more complex, the current interference between different out of the way to solve the high cost, such as not solving the failure rate is high. In addition, the more the number of output routes, the total output current is also the greater the current is the main reason for the heat, the voltage itself does not directly lead to heat, simply put, the heat is proportional to the square of the current, that is to say, the current increased to the original 2 times, then, the heat will be increased to the original 4 times, the current increased to the original 3 times, the heat will be increased to the original 9 times. In summary, single or two-way output LED lamp power supply failure rate will be much lower.
2, intelligent control is one of the advantages of LED lamps and lanterns, and the power supply is the key to intelligent control.
Intelligent control in the LED street lights and LED tunnel lights lighting applications on the most mature conditions, the most obvious effect, intelligent control can be in different time periods, according to the density of road traffic to realize the power of the lamps and lanterns stepless control, not only to meet the requirements of the application, but also to achieve a huge energy-saving effect, you can save a lot of money for the highway authority. The application of tunnel lighting can not only save energy, but also in accordance with the brightness of the tunnel outside the tunnel automatically adjusts the tunnel entrance and exit brightness, to provide drivers with a visual overstage to ensure driving safety.
3, give up high-power, ultra-high-power, choose a higher stability of small and medium-power power supply.
Because the higher the power, the greater the heat, the more compact parts inside, not conducive to heat dissipation, and the temperature is the main culprit of power failure. Moreover, the development of small power supply is relatively more mature, stability and cost advantages. In fact, many high-power power supply program has not been verified by time and practice, are hastily launched the project, are experimental products, so the failure of numerous. In contrast, small and medium-power power supply due to the development of earlier, more mature technology programs.
4, heat dissipation and protection is the main external factors of power failure.
Not only will the power supply itself will heat up, the lamps will also heat up, these two heat sources how to reasonably emit out of the lamps and lanterns design engineers must consider the problem, must prevent excessive concentration of heat, the formation of heat island effect, affecting the life of the power supply. Separate power supply program is a good choice.
5, the feasibility of maintenance.
Power supply failure problems can not be completely avoided, Chengdu Chaoyue photoelectric proposed the principle of maintenance simplicity. Only the replacement of the power supply to do with the replacement of conventional lighting light source so simple, in order to be a happy user, even if the power supply is bad, the mood will not be too bad, and the user's mood determines the fate of the LED light manufacturers.
6, protection performance.
Protection is also very important, the penetration of moisture may cause power short circuit, the shell of the sand and dust will affect the power of the heat dissipation, sun exposure is easy to cause high temperature and wire and other components of the aging, from the actual use of experience, the rotary plug failure rate is higher, most of the leakage caused by the failure.
7, modular design.
Modular design has become today's trend, we must think of ways to integrate the module power supply, if the power supply can be plugged to solve the maintenance problem, will be welcomed by the user, but also need to establish the interface standardization, so that different manufacturers of LED lights power supply can be common.
Summarize: LED lamp power supply is best to use the split design, while focusing on the reliability and life of the power supply, even if it increases the cost a little bit, only stand in the customer's point of view to design the product, the enterprise can get a long time to develop.For more LED industrial lighting issues, please contact recolux.