Introduction
The LM3404/04HV is a buck-regulator designed for driving high powered LEDs at forward currents of up to 1.0A, At 1.0A, a single-die white LED can dissipate more than 3W, heatsink should be design such a way that it should dissipate the heat faster.
The test circuit uses the LM3404HV to drive five series-connected 3W white LEDs from an input voltage of 24V. The total forward current, IF, is 1A, Switching frequency is 550 kHz and the circuit is surge protected up to 60V
When driven at 350 mA, the total power delivered to the five LEDs will be approximately
5 W. At 700 mA drive, the load power will be approximately 10W. At 1000 mA drive, the load power will be approximately 15W.Care must be taken not to operate the LEDs beyond the maximum junction temperature specified in the data sheet.It is recommended that you mount the metal PCB to a heat-sink to allow continuous operation.
Setup Procedure
To operate the evaluation board, you need to complete the following steps:
1. Configure the board for the desired current output level.
2. Attach a LED load to the output terminals.
3. Connect a power supply to the input.
Detailed instructions are provided below for each step.
Use jumper settings shown in table 1 for setting the output current to desired value.
Output | Jumper setting |
| 0.35 | Install J1 |
| 0.7 | Install J2 |
| 1 | Install J3 |
Table -1
Connect the assembled 5 LED to the evaluation board output terminals (VO/LED+ and VO/LED -) using test clips .The anode of the LEDs should be connected to the VO/LED+ terminal on the evaluation board. The cathode of the LEDs should be connected to the VO/LED - output terminal on the evaluation board.
Connect a power supply to VIN & GND to power up the LED Lighting Eval Board, The input voltage source should be 6V to +75V range. Ensure that the chosen power supply can provide enough current at the selected voltage to properly power the LEDs.
An external PWM options are available on evaluation board.
The best way to evaluate the LED Lighting Eval Board is to dig into the circuit and measure voltages and currents with a multi-meter and probe the board with an oscilloscope to measure switching frequency. You can use the following procedure to verify the LED input power:
- To measure the output voltage (VO/LED), connect the multi-meter across VO/LED+ and VO/LED
- To measure the output current ( ILED), connect the multi-meter in series with VO/LED+ and LED load and second probe to VO/LED
- The output power can be calculated as PLED = ILED * VO/LED.
Reading taken at 350mA | ||||||
| Vin(v) | Iin(mA) | Vo(v) | Io(mA) | Pin(w) | Po(w) | Efficency (%) |
| 20 | 0.28 | 15.17 | 0.347 | 5.6 | 5.26 | 94.00 |
25 | 0.23 | 15.19 | 0.354 | 5.75 | 5.38 | 93.52 |
30 | 0.2 | 15.21 | 0.354 | 6 | 5.38 | 89.74 |
40 | 0.15 | 15.26 | 0.356 | 6 | 5.43 | 90.54 |
50 | 0.12 | 15.26 | 0.359 | 6 | 5.48 | 91.31 |
60 | 0.1 | 15.26 | 0.361 | 6 | 5.51 | 91.81 |
Reading taken at 700mA | ||||||
Vin(v) | Iin(mA) | Vo(v) | Io(mA) | Pin(w) | Po(w) | Efficency (%) |
20 | 0.52 | 15.71 | 0.617 | 10.4 | 9.69 | 93.20 |
25 | 0.46 | 15.76 | 0.672 | 11.5 | 10.59 | 92.09 |
30 | 0.41 | 15.79 | 0.709 | 12.3 | 11.20 | 91.02 |
40 | 0.31 | 15.76 | 0.715 | 12.4 | 11.27 | 90.87 |
50 | 0.25 | 15.76 | 0.718 | 12.5 | 11.32 | 90.53 |
60 | 0.21 | 15.76 | 0.72 | 12.6 | 11.35 | 90.06 |
Reading taken at 1000mA | ||||||
Vin(v) | Iin(mA) | Vo(v) | Io(mA) | Pin(w) | Po(w) | Efficency (%) |
20 | 0.87 | 15.76 | 0.955 | 17.4 | 15.05 | 86.50 |
25 | 0.75 | 15.84 | 1.016 | 18.75 | 16.09 | 85.83 |
30 | 0.64 | 15.89 | 1.06 | 19.2 | 16.84 | 87.73 |
40 | 0.5 | 15.95 | 1.11 | 20 | 17.70 | 88.52 |
50 | 0.42 | 16 | 1.138 | 21 | 18.21 | 86.70 |
60 | 0.35 | 16.04 | 1.156 | 21 | 18.54 | 88.30 |
Lux reading taken at 1mtr & 2 mtr.
- Good Uniformity 194lux @ 1mtr and 510lux @ 0.5mtr