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What are the requirements of LED explosion-proof lamp power supply to ensure the normal operation of the lamp?
Since the LED explosion-proof lamp has many advantages such as environmental protection, long lifespan, high photoelectric efficiency (the current luminous efficiency has reached 100LM/W), and earthquake resistance, it has been rapidly applied in various industries in recent years. In theory, the service life of the LED is 100,000 hours. Around, but in the actual application process, some LED explosion-proof lamp designers lack of understanding of the LED driver power supply or improper use or blind pursuit of low-cost, resulting in LED lamp product life is greatly reduced, so that the advantages of LED explosion-proof lamp is not very good The play. The LED driving power supply is a voltage converter that converts the power supply into a specific voltage and current to drive the LED to emit light. Under normal circumstances, the input of the LED driving power includes high-voltage power frequency AC, low-voltage DC, high-voltage DC, and low-voltage high-frequency AC (such as electronic Transformer output) etc.
The output of the LED driver is mostly a constant current source that changes the voltage as the LED forward voltage drop changes. The LED power core components include switch controllers, inductors, switching elements (MOSfets), feedback resistors, input filter components, output filter components, and the like. According to different occasion requirements, there must be input over-voltage protection circuit, input under-voltage protection circuit, LED open circuit protection, over-current protection circuit.
Do a good job of a LED explosion-proof light products, the key lies in heat dissipation, drive power, light source, and heat dissipation is particularly important, heat dissipation effects directly affect the quality of life of lighting products, and drive power supply itself, the life and output current, voltage stability of the product The overall life quality also has a great influence, and the light source is the core part of the entire product. The following provides some knowledge of LED driver power supply.
Constant Current Drive: Because of the special nature of LED processing and manufacturing, the current and voltage characteristics of LEDs produced by different manufacturers and even the same manufacturer in the same batch of products have large individual differences. Now take the typical example of high-power 1W white LED as an example, according to the LED current, voltage change rules to do a brief description, the general 1W white light application forward voltage is about 3.0-3.6V, that is, when the nominal 1W LED In the 350mA current flow, the voltage across it may be 3.1V, may also be 3.2V or 3.5V may also be other values, in order to ensure the lifetime of the 1WLED, the general LED manufacturer recommends the lamp factory to use the 350mA current Driving, when the forward current through the LED reaches 350 mA, the positive voltage at both ends of the LED increases very little, which will cause the LED forward current to rise substantially, causing the LED temperature to rise linearly, thereby accelerating the LED light decay. This shortens the life of the LED and even burns the LED in severe cases. Due to the particularity of the voltage and current changes of the LED, strict requirements are imposed on the power supply that drives the LED.
Constant current source driving is the best LED driving method. It adopts constant current source driver and does not require current limiting resistor in series in the output circuit. Current flowing on LED is also not affected by external power supply voltage change, ambient temperature change, and discreteness of LED parameters. Influence, can keep the electric current constant, give full play to various excellent characteristic of LED. LED constant current power supply is used to power the LED explosion-proof lamp. Since the current flowing through the LED will be automatically detected and controlled during power supply operation, there is no need to worry about high current flowing through the LED at the instant of power-on, and there is no need to worry about load short circuit. Burn out the power.
Electrolytic Capacitors: Some manufacturers are concerned that the use of electrolytic capacitors in the power driver board will affect the life of the power supply. This is actually a misunderstanding. For example, if 105 degrees are selected and the life time is 8000 hours, the electrolytic capacitor will be used. According to the prevailing electrolytic capacitor life estimation method, “Each 10 degrees lower, life expectancy doubled, then it works for 16000 hours at 95 degrees, 32,000 hours at 85 degrees, and 64,000 hours at 75 degrees, if the actual operating temperature Lower, then life will be longer! From this point of view, as long as the use of high-quality electrolytic capacitors has no effect on the life of the drive power supply.
Heat dissipation: As the LED emits a lot of heat during the work process, the junction temperature of the die rises rapidly. The higher the LED power, the greater the heating effect. LED chip temperature will lead to changes in the performance of light-emitting devices and the decline in the efficiency of electro-optic conversion, even in the event of serious failure, according to experimental tests show that: LED itself temperature rises by 5 degrees Celsius, luminous flux decreased by 3%, so the explosion-proof LED lights must pay attention The heat dissipation of the LED light source itself should, where possible, increase the heat dissipation area of ​​the LED light source as much as possible to reduce the operating temperature of the LED itself. If the conditions permit, it is better to separate the power source from the light source.
Reliability: Especially like the driving power source of LED explosion-proof street lamps, it is installed at a high altitude, so it is inconvenient to maintain and the maintenance cost is also large.
Efficiency: LED is an energy-saving product, and the efficiency of driving power is high. It is very important for the heat dissipation of the power supply installed in the lamp. The efficiency of the power supply is high, its power consumption is small, and the heat generated in the lamp is small, which also reduces the temperature rise of the lamp. It is beneficial to delay the decay of the LED.
Power factor: The power factor is the grid's load requirements. Electrical appliances below 70 watts are generally not mandatory. Although the single power device with low power has a low power factor, it has little impact on the power grid. However, the large amount of lighting used at night and the similar load is too concentrated can cause serious pollution to the power grid. For a 30-watt to 40-watt LED driver, it is said that in the near future, there may be certain indicators of power factor requirements.
Surge protection: The ability of the LED to withstand surges is relatively poor, especially against reverse voltage capability. It is also important to strengthen this protection. Some LED lights are installed outdoors, such as LED street lights. Due to the start of the grid load and the induction of lightning strikes, various surges can be invaded from the grid system, and some surges can lead to LED damage. Therefore, the analysis of the "China Branch Hui Bao" drive power in the surge protection should have certain shortcomings, and as for frequent replacement of power supplies and lamps, LED drive power to inhibit the intrusion of surges to protect the LED is not damaged.
Over-temperature protection: In addition to the conventional protection function, it is better to increase the LED temperature negative feedback in the constant current output to prevent the LED temperature from being too high; it must meet the requirements of safety regulations and electromagnetic compatibility. Because the LED will emit a lot of heat at work, the brightness will decrease with the increase of heat. If the heat treatment is bad, it will burn the LED lamp and cause fire. At the same time, changes in the LED junction temperature will also bring about changes in the voltage, causing instability in the driver's work. Therefore, it is necessary to consider over-temperature protection when designing the LED driver. If necessary, turn off the output to prevent danger.
Input voltage: Since the voltage standards of the mains in different countries are different, the LED driving voltage also has many specifications. The rated input voltage refers to the specific input voltage of the driver under the specified operating conditions. The value and conditions are specified in this specification or specified by the manufacturer or seller. The commonly used LED driver input voltage is AC85-265V, some manufacturers do AC277V.
Output power: The specific output power of the driver under the specified operating conditions, which is specified in this specification or specified by the manufacturer or seller. LED drivers are generally constant current output, allowing the output voltage to fluctuate within a certain range. So the output power is a range.
Start-up time: The time period during which the AC power supply is connected to the constant current output rated current (or constant voltage output rated voltage) is established by 90%.
Overshoot amplitude: The phenomenon that the output DC voltage or current exceeds a stable value due to transients of a certain amount of influence is overshoot. The overshoot amplitude is the maximum transient amplitude of the output current or deviation from the stable value.
Load Regulation: The relative change in the output current (or constant voltage driver output voltage) of a constant current driver due to changes in the load when all other influences remain constant.
Input voltage regulation rate: The relative change in the output current of a constant current driver (or constant voltage driver output voltage) due to changes in the input voltage when all other influences remain constant.
Output voltage ripple and noise: peaks and peaks of the AC component included in the output DC voltage.
Input inrush current: The maximum instantaneous current value of the AC input circuit when the power is turned on.
LED explosion-proof lamp creepage distance: The shortest path between two conductive parts measured along the insulating surface or between the conductive parts and the protective interface of the equipment.