Number calculated by known high power led flashlight

Example: rated output power of 10W power supply, rated forward current 20mA Power Dissipation 70mW conditions can configure the number of LEDs? According to the above formula (take data from integer)

1: For constant voltage drive:

Known output power voltage is calculated each series LED quantity and the number of parallel branches

(1) Calculate the number of each branch of the LED

(2) Calculate the number of parallel branches

Note: VLED value is different according to the different light color, drive the LED with a regulated power supply, in order to control the current, usually require a series resistor.

Example: a rated output voltage of DC 24V, power is 10W power supply, the rated forward current 20mA, power dissipation of 70mW rated forward voltage to 1.8V. Configurable number of LED? (Take data from an integer)

With 10 branches, each 14 LED series circuit consisting of a total of 140 LEDs.

2: For constant current drive mode

Known power supply output current and LED current value calculated number of the number of parallel branches and each branch

(1) the number of branches of computing in parallel

(2) Calculate the number of branch in series LED:

Example: a rated output current for DC 0.35A, rated power is 10W power supply, drive power dissipation to 70mW, the LED forward current of 0.02A, how to configure?

Parallel count road:

(Data obtained was an integer)

Each branch connected in series: the number

That with 17 groups, each group of eight LEDs in series, a total of 136 LEDs.

Line losses and line drop calculation

P wire = I R V wire = IR

R wire = sigma (Note: L is the length of the cord; S is the cross-sectional area of the wire; the sigma for wire and electrical conductivity) can also check electrician Manual.

Example: length 10 meters (positive and negative wires of the 5 m), 24AWG copper wire, through the current of 2A, loss of power and line drop?

Check the electrical manual shows: R wire = 0.737W

V wire = 2 × 0.737 = 1.474V

Wire P = 2 × 0.737 = 2.948W

As can be seen from the above calculation, the line current is larger, should pay attention to select appropriate wire cross-section, or line losses and line drop is quite large.

We only fully understand the basic characteristics of the LED and LED power supply in order to properly design and use of the led torch light source.