LED rechargeable flashlight circuit diagram

LED rechargeable flashlight circuit diagram (I)

    These flashlights are very useful in night vision or dark environments. It uses HLMP8150T4LED with a wavelength of 637nm. The figure shows the flashlight module circuit. When the battery pack consisting of four NiCad cells is fully charged (J1 has no voltage), a 4.8 volt DC current flows through the trimmer potentiometer R2, the normally closed contact relay RY1 and the power switch Al.

LED rechargeable flashlight circuit diagram (II)

    As shown in the figure above, the 5 white LEDs of the flashlight are connected in parallel and are mainly used for lighting. The other red LED is the charging indicator.

    Let's look at the main circuit. There are three main parts to pay attention to.

    1. Voltage reduction. Capacitor voltage reduction is mainly used here. It is usually used to obtain non-isolated low-current power supply at low cost. Its output voltage can usually range from a few volts to more than 30 volts, depending on the Zener voltage regulator used. The current that can be provided is proportional to the capacity of the current limiting capacitor. However, be careful when using this circuit, because it is not isolated from the 220V AC high voltage, please pay attention to safety and prevent electric shock!

    2. Rectification. The rectifier circuit here is a bridge rectifier circuit. Why use a bridge rectifier circuit?

    3. Charging indicator circuit. As shown in the blue box in the figure above. Since the LED must be lit by direct current, the current first flows through the rectifier bridge. The current direction is shown in the figure above. When the battery is fully charged, that is, the Vb potential is equal to Va, the indicator light will go out.