First, ledThe working principle of the flashlight
There are many energy levels in atomic electrons. When electrons transition from high energy levels to low energy levels, the The energy is reduced, and the reduced energy is converted into photons and emitted. A large number of these photons are lasers.
The LED lighting principle is similar. However, the difference is that the LED does not emit light through electronic jumps inside the atoms, but by applying a voltage across the PN junction of the LED, so that the PN junction itself forms an energy level (actually, a series of energy level), then electrons jump at this energy level and produce photons to emit light.
two, led flashlight circuit diagram
strong light flashlight circuit diagram
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This circuit can be roughly divided into three parts: 1. The rectifier and step-down part; 2. The battery; 3. The light-emitting circuit part
1. The rectifier and step-down part consists of AC1, AC2, R1, C1, D1-D4, R and AC indicator light. The 220V AC power supply is connected to AC1 and AC2. After dividing by R1 and C1, an AC voltage of about 6V is obtained. After bridge rectification, a DC voltage of about 4.2V is obtained between the negative electrode and the positive electrode of the battery.
2. There are three working states of the battery part: charging, discharging, and neither charging nor discharging.
(1) If the AC power is plugged in, and the reverse polarity voltage is connected to both ends of the battery and is greater than the battery discharge voltage, the battery is in a charging state (regardless of whether the switch is closed or not).
(2) Do not plug in the AC power, close the switch, the light-emitting circuit is connected, the light is on, and the battery is discharged.
(3) If the AC power is not plugged in and the switch is turned off, the battery will neither be charged nor discharged.
3. The light-emitting circuit is composed of a switch, a white light-emitting diode, its current limiting resistor and the battery. The light comes on as long as the switch is closed. Plugged in AC powered by AC, otherwise battery powered.
This is simple, C1 is the current limiting capacitor, R1 is the bleeder resistor of C1 (to prevent the residual voltage of C1 from passing through the plug after the plug is unplugged), D1~D4 constitute a bridge rectifier, Change the AC after C1 current limit into DC, and then send it to the battery for charging. Because of the existence of the battery, the voltage after the current limit will not be lower than the battery voltage (equivalent to voltage regulation). Considering the step-down effect of the diode, Therefore, there is a reason for the 6V voltage at the D1 end.
LED10 and 330 ohm resistor are charging indicator. As for the part behind the lamp, it is a lighting circuit composed of 5 groups of LEDs and a current-limiting resistor, nothing special.
In fact, strictly speaking, the capacitor is not a step-down capacitor, but only a current limiter. The step-down needs to be matched with the zener diode behind it. However, people usually like to call this circuit a “capacitor buck” circuit.
If AC2 voltage is high, current flows through D4, battery, D2 and then to AC1. If AC1 voltage is high, current flows through D1, battery, D3 and then to AC2. Therefore, no matter how high the AC is, the voltage on the top is always high, and it becomes the upper positive and the lower negative, that is, rectification is realized.
If there is no D2, then when the AC1 voltage is high, it will be directly short-circuited to AC2 through D3.
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