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LED driver power supply introduction and characteristics缩略图

LED driver power supply introduction and characteristics

LED driver power supply is the power supply is converted to a specific voltage and current to drive the LED light-emitting voltage converter, usually: LED driver power supply inputs include high-voltage frequency AC (i.e., utility), low-voltage DC, high-voltage DC, low-voltage high-frequency AC (e.g., the output of the electronic transformer) and so on. The output of the LED driver power supply is mostly a constant current source that can change the voltage with the LED forward voltage drop value. The following for the first time in the industry to provide some knowledge of the LED driver power supply.

LED driver power supply introduction and characteristics插图

1, what is the LED driver power supply

  LED drive power supply to convert the power supply to a specific voltage and current to drive the LED light-emitting voltage converter, usually: LED drive power supply inputs include high-voltage frequency AC (i.e., utility), low-voltage DC, high-voltage DC, low-voltage high-frequency AC (e.g., the output of the electronic transformer) and so on. The output of the LED driver power supply is mostly a constant current source that can change the voltage with the change of LED forward voltage drop value.The core components of the LED power supply include switching controllers, inductors, switching components (MOSfet), feedback resistors, input filters, output filters, etc. According to the requirements of different occasions, there should also be input filters, output filters, and so on. According to the requirements of different occasions, but also the input over-voltage protection circuit, input under-voltage protection circuit, LED open-circuit protection, over-current protection and other circuits.

2, LED drive power supply features

  (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 lamps and lanterns within the junction 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 beneficial 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 indicator. Although the power factor of the individual appliances with low power factor is not much of an impact on the power grid, but the use of lighting at night, the same kind of load is too concentrated, will produce more serious pollution of the power grid. For 30 watts ~ 40 watts of LED driver power supply, it is said that in the near future, may be on the power factor aspects of the requirements of certain indicators.

  (4) drive mode

  Now there are two kinds of pass: one is a constant voltage source for more than one constant current source, each constant current source individually 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 a direct constant current power supply drive, LED series or parallel operation. Its advantage is that the cost is a little lower, but poor flexibility, but also to solve the problem of a LED failure, does not affect the operation of other LEDs. These two forms, in a period of time co-exist. Multiple constant current output power supply method, in terms of cost and performance will be better. Perhaps the mainstream direction in the future.

LED driver power supply introduction and characteristics插图2

  (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 are installed outdoors, 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 LED damage.

  (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; to meet the requirements of safety regulations and electromagnetic compatibility.

 3、Categorized by driving mode

  (1) constant current

  Constant-current drive circuit output current is constant, while the output DC voltage is different with the size of the load resistance changes within a certain range, the load resistance is small, the output voltage is low, the greater the load resistance, the higher the output voltage;

  Constant-current circuit is not afraid of load short-circuit, but the load is strictly prohibited completely open circuit;

  Constant-current drive circuit to drive the LED is more ideal, but relatively high prices;

  Should pay attention to the use of the maximum withstand current and voltage values, which limits the number of LEDs used.

  (2) voltage regulator

  When the parameters of the voltage regulator circuit to determine the output voltage is fixed, while the output current with the increase or decrease of the load and change;

  The voltage regulator circuit is not afraid of load open-circuit, but the load is strictly prohibited from being completely short-circuited;

  Regulated drive circuit to drive the LED, each string needs to add a suitable resistance to make each string of LED display brightness average;

  Brightness will be affected by the voltage change from the rectifier.

 4, the overall constant current and circuit-by-circuit constant current mode of operation advantages and disadvantages

  Compared with the overall constant current, although the circuit by circuit constant current has more disadvantages, the cost is also higher. But it can really play a role in protecting the LED and extend the life of the LED, so the circuit-by-circuit constant current is the future trend.

LED driver power supply introduction and characteristics插图4

 5, LED power supply shortage

  LED driver power supply currently exists for insufficient reasons:

  Production of LED lighting and related products, the company's technical staff do not know enough about the switching power supply, to make the power supply can work properly, but some critical evaluation and electromagnetic compatibility is not enough to consider, there are still some hidden dangers;

  Most of the LED power supply manufacturers are transformed from ordinary switching power supply to do the LED power supply, the characteristics of the LED and the use of knowledge is not enough;

  At present, there is almost no standard on LED, most of them refer to the standard of switching power supply and electronic rectifier;

  Now most of the LED power supply is not unified, so most of the volume is relatively small. Purchasing a small amount, the price is high, and component suppliers are not very cooperative;

  Stability of LED power supply: wide voltage input, high and low temperature operation, over-temperature, over-voltage protection and other issues have not been solved one by one;

  First of all, the overall life of the drive circuit, especially the key devices such as: capacitors at high temperatures directly affect the life of the power supply;

  Is the LED driver should be challenged to higher conversion efficiency, especially in driving high-power LED is more so, because all the power not as light output as heat dissipation, power conversion efficiency is too low, affecting the LED energy-saving effect of play;

  At present, in the smaller power (1-5W) applications, constant current drive power supply costs accounted for the proportion has been close to 1/3, has been close to the cost of the light source, to a certain extent, affecting the market promotion.

LED drive power supply of the two major classifications

  LED driver power supply is the power supply is converted to a specific voltage and current to drive the LED light-emitting voltage converter, usually: LED driver power supply inputs include high-voltage industrial frequency AC (i.e., utility), low-voltage DC, high-voltage DC, low-voltage high-frequency AC (e.g., the output of the electronic transformer) and so on. The output of the LED driver power supply is mostly a constant current source that can change the voltage with the LED forward voltage drop value.

  Due to a variety of specifications of different LED power supply performance and conversion efficiency varies, so choose the appropriate, efficient LED special power supply, in order to truly reveal the characteristics of high-performance LED light source. Because the low efficiency of the LED power supply itself needs to consume a lot of electricity, so in the process of power supply to the LED will not be able to highlight the energy-saving characteristics of the LED. In short, the LED power supply in the LED work in the stability, energy saving, life expectancy, with an important role.

What is the classification 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, the power supply structure should be waterproof, moisture-proof, the shell should be resistant to sunlight.

  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, the two sources of heat how to reasonably emit out of the lamp design engineers must consider the question of the