Lighting science: to teach you a classic analysis of the LED drive mode

LED drive power supply will convert the power supply to specific voltage current to drive the LED voltage converter, typically LED drive power supply input includes high voltage ac power frequency ( The mains) Dc, high-voltage direct current, low voltage, low voltage high frequency ac ( Such as electronic transformer output) And so on. And the output of the LED driver power supply are mostly can change with LED positive pressure drop values and change the voltage of the constant current source.

LED core components including power switch controller, the inductor, switch components ( MOSfet) , the feedback resistance, input filter, output filter parts, etc. In accordance with the requirements of different occasions, also have input over-voltage protection circuit, input under-voltage protection circuit, LED open circuit protection, over current protection circuit, etc. Drive mode classification

press ( 1) Constant flow

constant current drive circuit of the output current is constant, and the output dc voltage is different with the size of the load resistance within a certain range, 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 it is forbidden to load completely open;

LED constant current drive circuit drive is ideal, but relatively high prices;

should be paid attention to by using maximum current and voltage, it limits the number of using leds.

　　( 2) Voltage type

when regulating circuit, to determine the various parameters of the output voltage is fixed, and the output current is as the load increase and decrease and change;

regulating circuit is not afraid of open load, but it is forbidden to load completely short circuit;

with voltage driving circuit to drive the LED, each string need to add the appropriate resistance can make average a string of LED display brightness;

brightness will be affected by rectification of voltage change.

the characteristics of the LED drive power supply

( 1) High reliability,

special like LED street lamp driver power supply, in a high altitude, maintenance is not convenient, the cost of maintenance is also big.

　　( 2)

the LED is energy saving products with high efficiency, the efficiency of the driving power supply. For the power supply installed in the lamps and lanterns and heat dissipation is very important. Power supply of high efficiency, its power consumption is small, in the lamps and lanterns of calorific value is small, also lower the temperature of lamps and lanterns. Good for delaying the LED light failure.

　　( 3) High power factor

power factor is the requirement of load of power grid. Generally below 70 watts of household electrical appliances, there is no mandatory indicators. Though the power of a single use lower electric power factor, the impact on the grid is not big, but the use of large amount of lighting at night, the same load is too concentrated, can produce serious pollution to grid. For 30 ~ 40 watts of the LED drive power supply, it is said that in the near future, may be the index of power factors have certain requirements.

　　( 4) Drive way

now there are two general one is a constant voltage source for multiple constant current source, each constant-current source separately for each LED power supply. This way, flexible combination, LED failure all the way, don't affect the work of other leds, but the cost would be slightly higher. The other is a constant current power supply directly, leds in series or parallel operation. It has the advantage of low cost, but poor flexibility, but also solve a LED failure, does not affect other LED running problem. These two forms, for a period of time. Multi-channel constant current output power supply way, in terms of cost and performance will be better. Maybe the mainstream direction of the future.

　　( 5) Surge protection

LED the ability of anti surge is relatively poor, especially the reverse voltage resistance. Strengthening the protection is also very important. Some LED lights installed outdoors, such as the LED street light. As a result of the power grid load and sling and lightning induction, into the various surge from the grid system and some surge can cause the damage of the LED. As for the power supply and frequent replacement of lamps and lanterns, LED drive power to suppress surge intrusion, ability to protect the LED was damaged.

　　( 6) Protection function

power supply in addition to the conventional protection function, the best in the constant current output increase LED temperature feedback, prevent LED temperature is too high; To conform to the requirements of safety and electromagnetic compatibility.

the constant current and constant current by road works

the advantages and disadvantages compared with integral constant current, constant current by road though drawback is more, the cost is high. But it can really protect leds and prolong the life of the LED, so by constant current is the trend of the future.

Bober

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