This LED driver circuit, using the LT1932 chip, is like a special power supply for your LEDs.
LEDs are a bit fussy about how much electricity they get, and this circuit makes sure they get exactly the right amount to shine brightly and last a long time.
The LT1932 chip acts like a traffic cop keeping the electricity flowing smoothly so your LEDs can light up perfectly.
Circuit Working:
Parts List:
| Category | Component | Quantity | Notes |
|---|---|---|---|
| Resistor | 1.5k | 1 | |
| Capacitors | Electrolytic 1µF 25V | 2 | |
| Semiconductors | IC LT1932 | 1 | |
| Schottky diode MBR0540 | 1 | ||
| LEDs | White 5mm 20mA | 3 | |
| Coil Inductor | 4.7uH | 1 | |
| Miscellaneous | ON/OFF Switch | 1 |
Presenting an intriguing circuit for a truly portable and charming solid state bright light built with the LT1932.
This light operates on two AA size dry rechargeable pen light cells.
The circuit does not include a housing allowing you to unleash your creativity in deciding its use.
Whether as a searchlight, cupboard light, pathway light or an inspection headlight the possibilities are endless!
The LED Bright Light circuit utilizes the small 6 pin integrated circuit in SMD package LT1932 IC1 from linear technologies.
The LT1932 is a fixed frequency step up DC to DC converter designed to function as a constant current source.
Due to its ability to directly regulate output current, the LT1932 is ideal for driving light emitting diodes LEDs, where the light intensity is determined by the current passing through them rather than the voltage across their terminals.
The LT1932 ensures precise regulation of LED current even when the input voltage exceeds the LED voltage simplifying battery powered designs.
A single external resistor sets the LED current between 5mA and 40mA.
In this configuration, the LED current is set to 15mA with R1=1.5kilo ohm.
Here, IC1 is set up as a two cell driver for three white LEDs D2 to D4.
This design strictly adheres to the LT application data of LT1932.
A small SMD prototyping board can be used for constructing the entire circuit.
As with all switching regulators, careful attention must be paid to PCB board layout and SMD component placement to avoid radiation and high frequency resonance issues.
Proper layout of the high frequency switching path is crucial.
Minimize the length and area of all traces connected to pin 1 and always use a ground plane under the switching regulator to minimize interplane coupling.
The signal path, including pin 1 output diode D1 and output capacitor C2 has nanosecond rise and fall times and should be kept as short as possible.
Additionally, the ground connection for resistor R1 should be directly tied to pin 2 and not shared with any other component to ensure a clean noise free connection.
To minimize output ripple voltage, use a low ESR equivalent series resistance capacitor for C2.
Similarly, D1 must be a schottky diode with low forward voltage drop and fast switching speed ensuring it has a voltage rating greater than the output voltage.
MBR0540 500mA 40V is a good choice for D1.
The value and type of power inductor L1 also play a critical role in overall system efficiency.
Since core losses at 1.2MHz are much lower for ferrite cores than for cheaper powdered iron ones, a ferrite core inductor should be used for optimal efficiency.
Choose a 4.7 micro henry inductor capable of handling at least 500mA.
Note: If you wish to use only one LED at the output simply connect its anode to the cathode terminal of D1 and its cathode terminal to pin 3 of IC1.
Electrical Characteristic of IC LT1932
| PARAMETER | CONDITIONS | MIN | TYP | MAX | UNITS |
|---|---|---|---|---|---|
| Minimum Input Voltage | 1 | 1 | V | ||
| Quiescent Current | (V_{RSET}=0.2V) | 1.2 | 1.6 | mA | |
| (V_{\overline{SHDN}}=0V) | 0.1 | 1.0 | μΑ | ||
| RSET Pin Voltage | (R_{SET}=1.50k) | 100 | mV | ||
| LED Pin Voltage | (R_{SET}=1.50k, V_{IN}<V_{OUT}) Figure 1) | 120 | 180 | mV | |
| LED Pin Current | (R_{SET}=562\Omega, V_{IN}=1.5V) | 33 | 38 | 45 | mA |
| (R_{SET}=750\Omega, V_{IN}=1.2V) | 25 | 30 | 36 | mA | |
| (R_{SET}=1.50k, V_{IN}=1.2V) | 12.5 | 15 | 17.5 | mA | |
| (R_{SET}=4.53k, V_{IN}=1.2V) | 5 | mA | |||
| LED Pin Current Temperature Coefficient | (I_{LED}=15mA) | -0.02 | [mA/^{\circ}C] | ||
| Switching Frequency | (V_{IN}=1V) | 0.8 | 1.2 | 1.6 | MHz |
| Maximum Switch Duty Cycle | 90 | 95 | % | ||
| Switch Current Limit | 400 | 550 | 780 | mA | |
| Switch (V_{CESAT}) | (I_{SW}=300mA) | 150 | 200 | mV | |
| SHDN Pin Current | (V_{\overline{SHDN}}=0V) | 0 | 0.1 | μΑ | |
| (V_{SHDN}=2V) | 15 | 30 | μΑ | ||
| Start-Up Threshold (SHDN Pin) | 0.85 | V | |||
| Shutdown Threshold (SHDN Pin) | 0.25 | V | |||
| Switch Leakage Current | Switch Off, (V_{SW}=5V) | 0.01 | 5 | μΑ |
How to Build:
To build a below mentioned Simple Led Driver Circuit using IC LT1932 follow these steps:
Prepare the Components:
- Gather all the components required for the circuit.
- Ensure they are in good condition and match the specifications mentioned in the circuit description.
Layout the Circuit:
- Use the SMD prototyping board to layout the circuit according to the schematic.
- Place the LT1932 IC and other components in their respective positions on the board.
Solder Components:
- Carefully solder each component onto the board making sure to follow the correct polarity and orientation for each component.
- Use a soldering iron with a fine tip for precision soldering.
Connect the Power Source:
- Connect the two AA size dry rechargeable pen light cells to the circuit.
- Ensure the polarity is correct to avoid damaging the components.
Test the Circuit:
- Once the circuit is fully assembled test it to ensure it is working correctly.
- Check that the LEDs light up and the circuit is drawing the correct amount of current.
Final Testing:
- After enclosing the circuit, perform a final test to ensure everything is working correctly.
- Make any necessary adjustments or repairs before using the light.
Note:
- This is a basic overview of the building process.
- It’s essential to refer to the datasheets of the components used and follow proper safety practices when working with electronics.
Conclusion:
The LT1932 IC offers an efficient and reliable solution for driving LEDs in various applications.
Its ability to function as a constant current source makes it ideal for maintaining consistent LED brightness even when input voltage varies.
By following proper circuit design practices and using quality components a LED driver circuit using the LT1932 can provide a stable and bright light output for portable and other low power applications.