How to design a super bright LED lamp with a nickel metal hydride battery

, a voltage circuit design a Ni MH battery is only 1.2V, and ultra bright LED needs to work to ensure the voltage above 3.3V enough brightness. Therefore. It is necessary to try to raise the voltage, there are generally two types of boost circuit, that is, high-frequency oscillation circuit and electromagnetic induction boost circuit. For the boost circuit, there are two circuits to choose from. As shown in Figure 1 and figure 2.

The circuit figure 1 using a small pulse transformer, power tube VT3 high frequency oscillation signal amplification, and through direct boost transformer T in L1. Figure 2 is to enhance the utilization of high voltage self inductance. When the oscillation signal is input to the base of the VT3, the VT3 is periodically saturated and closed.

When saturated, inductance L electricity, electrical energy into magnetic energy stored in L, when the diode cutoff, C3 rely on stored energy to the load power supply; when the VT3 is off. The inductance will produce a positive and negative electromotive force. The self induction electromotive force of the diode is superposed with the electric potential of the power supply to charge the capacitor C3 and load the power supply. Can be higher than the power supply voltage, the specific size of the main load and VT3 saturation inductance L through the current ratio determined.

Two circuits can be 1.2V higher than 3.3V, the first circuit in transformer winding and if positive feedback coil. Oscillating circuit. Make the circuit more concise. But the use of this circuit is more complex. The output power is difficult to adjust, the transformer winding is also some trouble. Second only a small inductance. The inductance is not large, and the output voltage can be adjusted conveniently by adjusting the driving current of the inductor. Second circuits are adopted in this paper.

Oscillation circuit adopts the circuit shown in Figure 3, although there are a lot of oscillating circuit can work normally under the voltage of 1.2V, but the practice proved that the 3 circuit made easy, simple calculation. High success rate. Oscillation frequency is also easy to determine. And By adjusting the size of the R4, the amplitude of the signal can be adjusted without affecting the frequency of the signal, so that a high frequency square wave pulse is used to prepare the boost circuit. In this way, the circuit design is completed, together with figure 2 and figure 3.

, two parameters on the circuit parameter calculation, the key lies in the power. After the inductor is energized, the stored electric energy is E=LI2/2, and the frequency of the square wave is f, and the switch tube in the 1A will conduct f times. The inductance per second stored energy is W=f * E, set to load these energy conversion efficiency for ETA, then the output power is P=, * W+Po, Po power supply directly to the power supply load (because the power and self pressure superposition. This must be taken into account. Estimate now. Drive a led about 100mW. The power of the Po is about 20mW. In order to ensure supply, press P=100mW. Take the =80%, and then casually looking for a few hundred uH inductors, such as 500 uH. On the other hand, according to the energy conservation. 3.3V is about 3 times of 1.2V. Because of the efficiency problem. The driving current of the inductor is about 3-4 times the operating current of LED, which is 120mA. Can calculate the oscillation frequency is about 34kHz, so, take R=2k, C=0.01 uF can meet the requirements. When determining parameters. High frequency can not be low, not too small inductance, so as to ensure that the output power is large enough to have enough room for adjustment.

Element table

Three, making because of a simple circuit. Components on 2 x 2cm board. As long as the operation is correct, turn on the power supply circuit can work. Do not connect to the LED, measured with a multimeter output voltage, this time, adjust the size of the R4, the greater the R4, the smaller the output voltage. Vice versa, when the output voltage is about 3.2V, can be connected to the LED, and then adjust the size of the R4, so that it is bright enough to pay attention, not to let the voltage at both ends of the LED more than 3.6V, otherwise it is possible to burn LED. As a result, the circuit will be completed debugging.