home-garden-light-led
Currently, white LEDs are available that emit a significant amount of light. Their brightness is such that direct eye contact should be avoided. Although they are still relatively expensive, this is expected to change in the future. A highly effective solid-state pocket torch can be constructed using several of these white LEDs. The most straightforward method involves using a separate series resistor for each LED, which operates at approximately 3.5 V and 20 mA. Depending on the supply voltage, considerable power may be dissipated in the resistors. The converter described here generates a voltage sufficient to connect ten LEDs in series. Additionally, this converter provides a constant current rather than a constant voltage. A resistor in series with the LEDs creates a voltage drop that is dependent on the current flowing through the LEDs. This voltage is compared within the integrated circuit (IC) to a 1.25 V reference value, maintaining the current at a constant 18.4 mA (1.25 V / 68). The IC utilized is part of a series of simple switchers from National Semiconductor. The inductor value is not critical and can vary by plus or minus 50 percent. The black Newport coil rated at 220 µH and 3.5 A (1422435) is a suitable option. Any Schottky diode capable of handling at least 1 A at 50 V can be employed. Although zener diodes are not strictly necessary, they are included for additional protection of the IC. If the LED string is interrupted during testing, the voltage may rise to levels that could damage the IC.
The described circuit employs a switching regulator topology to efficiently power multiple white LEDs in series. The design ensures that the LEDs receive a consistent current, which is crucial for maintaining their brightness and longevity. The converter operates by stepping up the input voltage to a level that allows for the desired number of LEDs to be connected in series. The use of a constant current source is particularly advantageous in LED applications, as it mitigates the risk of thermal runaway, a condition where increased temperature leads to increased current, potentially damaging the LEDs.
In this schematic, the main components include the switching regulator IC, an inductor, a Schottky diode, and a series resistor. The inductor plays a pivotal role in energy storage and transfer, allowing the circuit to maintain a stable output current. The Schottky diode is essential for preventing reverse current flow, which could otherwise disrupt the operation of the LEDs. The series resistor, while necessary for current regulation, should be selected carefully to minimize power loss and heat generation.
The feedback mechanism within the IC continuously monitors the current flowing through the LEDs. When the current exceeds the set point, the IC reduces the duty cycle of the switching signal, thereby lowering the energy supplied to the inductor and maintaining the current at the desired level. Conversely, if the current drops below the set point, the IC increases the duty cycle to restore the current to the target value.
In summary, this LED driver circuit is designed for efficiency and reliability, allowing for the creation of a powerful pocket torch with white LEDs. The inclusion of protective components, such as zener diodes, enhances the robustness of the design, ensuring that the circuit can withstand variations in operating conditions without compromising performance.Nowadays you can buy white LEDs, which emit quite a bit of light. They are so bright that you shouldn`t look directly at them. They are still expensive, but that is bound to change. You can make a very good solid-state pocket torch using a few of these white LEDs. The simplest approach is naturally to use a separate series resistor for each LED, w hich has an operating voltage of around 3. 5 V at 20 mA. Depending on the value of the supply voltage, quite a bit of power will be lost in the resistors. The converter shown here generates a voltage that is high enough to allow ten LEDs to be connected in series. In addition, this converter supplies a constant current instead of a constant voltage. A resistor in series with the LEDs produces a voltage drop that depends on the current through the LEDs.
This voltage is compared inside the IC to a 1. 25-V reference value, and the current is held constant at 18. 4 mA (1. 25 V G· 68 ). The IC used here is one of a series of National Semiconductor simple switchers`. The value of the inductor is not critical; it can vary by plus or minus 50 percent. The black Newport coil, 220 µH at 3. 5 A (1422435), is a good choice. Almost any type of Schottky diode can also be used, as long as it can handle at least 1A at 50V. The zener diodes are not actually necessary, but they are added to protect the IC. If the LED chain is opened during experiments, the voltage can rise to a value that the IC will not appreciate. 🔗 External reference
The described circuit employs a switching regulator topology to efficiently power multiple white LEDs in series. The design ensures that the LEDs receive a consistent current, which is crucial for maintaining their brightness and longevity. The converter operates by stepping up the input voltage to a level that allows for the desired number of LEDs to be connected in series. The use of a constant current source is particularly advantageous in LED applications, as it mitigates the risk of thermal runaway, a condition where increased temperature leads to increased current, potentially damaging the LEDs.
In this schematic, the main components include the switching regulator IC, an inductor, a Schottky diode, and a series resistor. The inductor plays a pivotal role in energy storage and transfer, allowing the circuit to maintain a stable output current. The Schottky diode is essential for preventing reverse current flow, which could otherwise disrupt the operation of the LEDs. The series resistor, while necessary for current regulation, should be selected carefully to minimize power loss and heat generation.
The feedback mechanism within the IC continuously monitors the current flowing through the LEDs. When the current exceeds the set point, the IC reduces the duty cycle of the switching signal, thereby lowering the energy supplied to the inductor and maintaining the current at the desired level. Conversely, if the current drops below the set point, the IC increases the duty cycle to restore the current to the target value.
In summary, this LED driver circuit is designed for efficiency and reliability, allowing for the creation of a powerful pocket torch with white LEDs. The inclusion of protective components, such as zener diodes, enhances the robustness of the design, ensuring that the circuit can withstand variations in operating conditions without compromising performance.Nowadays you can buy white LEDs, which emit quite a bit of light. They are so bright that you shouldn`t look directly at them. They are still expensive, but that is bound to change. You can make a very good solid-state pocket torch using a few of these white LEDs. The simplest approach is naturally to use a separate series resistor for each LED, w hich has an operating voltage of around 3. 5 V at 20 mA. Depending on the value of the supply voltage, quite a bit of power will be lost in the resistors. The converter shown here generates a voltage that is high enough to allow ten LEDs to be connected in series. In addition, this converter supplies a constant current instead of a constant voltage. A resistor in series with the LEDs produces a voltage drop that depends on the current through the LEDs.
This voltage is compared inside the IC to a 1. 25-V reference value, and the current is held constant at 18. 4 mA (1. 25 V G· 68 ). The IC used here is one of a series of National Semiconductor simple switchers`. The value of the inductor is not critical; it can vary by plus or minus 50 percent. The black Newport coil, 220 µH at 3. 5 A (1422435), is a good choice. Almost any type of Schottky diode can also be used, as long as it can handle at least 1A at 50V. The zener diodes are not actually necessary, but they are added to protect the IC. If the LED chain is opened during experiments, the voltage can rise to a value that the IC will not appreciate. 🔗 External reference