Lighting circuit solution
AT310 typical application 2 ---- 1W LED lighting circuit solution
Figure 1. Schematic
Unit | Name / value | Encapsulation | Factory |
U0 | AT310 | SOT23-5 | |
Q1 | irf7807 | SOP8 | N-channel MOS tube for IRF DC-DC |
D1 | zhcs1000 | SOT23-1 | Zetex, 1A Schottky Diode |
C1 | 4.7UF | 1210 | |
L0 | 65UH | SMD-L | |
DLED1～DLED7 | 3.4V/350mA | 1206 | CREE |
This circuit removes the current sampling resistor to make the AT310 work at full load. When using a 7-bead 1W high-power LED in series, if the LED can reach the nominal brightness, the input power must be 8V / 2A. But at the same time, the efficiency of this working mode will be reduced (about 30%, 3 beads can reach 79.22% efficiency). According to different applications, the number of LEDs in series can also be relatively reduced, so that the input voltage is also reduced. The user can choose the number of LEDs as appropriate.
Obviously, this mode can be applied to DC power environment that can provide low voltage and large current, such as automotive lighting, medical lighting and other fields.
1W LED has a nominal working current of 350MA and a working voltage of 4-3.4V. A single pearl luminous flux can reach 80-120LM (lumens). The following is the efficiency curve 2 under the test conditions shown in Figure 1 (when the number of LEDs is 1), and the load current curve is shown in Figure 3. When the system uses 2.8V power supply, the efficiency can reach 72.9%, and the current is 350mA.
Figure 2. Efficiency graph of a 1W LED
Figure 3. Load Current of a 1W LED
The following is the efficiency curve 4 under the test conditions shown in Figure 1 (when the number of LEDs is 3) and the load current curve is shown in Figure 5. When the system uses 8.4V power supply, the efficiency can reach 81.2%, and the current is 350mA.
Figure 4. Efficiency graph of 3 1W LEDs
Figure 5. Three 1W LED load current graphs
The following is the efficiency curve of the test conditions shown in Figure 1 (when the number of LEDs is 4) Figure 6, the load current curve is shown in Figure 7. When the system uses 11V power supply, the efficiency can reach 84.8%, and the current is 350mA.
Figure 6. Efficiency graph of 4 1W LEDs
Figure 7. Three 1W LED load current graphs
The following is the efficiency curve of the test conditions shown in Figure 1 (when the number of LEDs is 5). When the system uses 10.7V power supply, the efficiency can reach 82.2%, and the current is 350mA.
Figure 8. Efficiency graph of 5 1W LEDs. Figure 8. Load current graph of 3 1W LEDs.
