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LED drives need a fittest design which besed on th Changes of the voltage current rate, so understanding their characteristics and based on the specific application of choosing appropriate drive circuit is very important. This driving circuit for the LED to provide voltage and current ratings, to create a good condition for their normal work.

To achieve the purpose of light, LED needs a positive voltage to current flow. So the led drivers to provide a positive bias in order to make the light LED. LED light levels or brightness is usually associated with positive current is proportional to the size of. In addition, the current through the LED should not exceed the specified rated current equipment, otherwise it may cause permanent damage. The constant current drive circuit is the current control in the ideal scheme correct driving LED. In. In other words, a power LED driver circuit is a constant current instead of constant voltage conversion circuit. LED drive circuit at least comprises a voltage detection circuit and a current switching circuit.

When the different voltage level voltage detection circuit detects the power, will send a signal to the current switch circuit, and a current switching circuit is started automatically, to re adjust the settings of LED using electrical current predetermined value, thus effectively brighten as much LED.

Linear actuator

Linear regulator with a current connection between the regulator output terminal and a ground node sampling resistance, can provide a simple method for generating a constant current. Constant output voltage of the regulator through the feedback resistor to generate a constant current. The sampling resistor LED is determined by the current supply reference voltage and current. Linear regulator is often used to drive low power LED backlight, such as such as PDA portable equipment. Typical current these LED values at 15 mA to 25 mA, Vf at 3 V to 3.4V. If the linear drive for a plurality of LED power supply, then the LED should be connected in series, to ensure that all the same current through LED, thereby the luminous quantity approximately equal.

Switch driver

 

For high current applications of wide input range, quantity of heat, simple drive solutions such as mentioned above will produce higher and lower efficiency. While the switch driver with constant current output is driven high power LED preferred. The driver is usually used for the switch control of the power supply voltage inductor and LED series load or parallel capacitor and LED. The inductance or capacitance is used when the switch is opened to save electric energy; and then close is to provide current for LED switch. Unlike the linear driver, switch driver can be configured to achieve voltage decline (Buck), (boost) or increasing coexist function. So it is obvious the switch drive allows the led driver module to operate in a wide input voltage range. Besides the current adjustment function constant amounts of light, and they can be reduced to the minimum power loss. There is no doubt that the switching regulator is more efficient than the linear regulator. However, compared with the linear regulators, switching drive higher cost and the need for careful design to solve the EMI problem. In order to pass the appropriate way to drive the LED, you need to find a most satisfactory performance price ratio.