The customer should change a new piece of the battery of green laserpointer

green laser pointer includes the projection screen, lecture screen and so on
Plus capacitor leakage current, long time to charge, but will make the output voltage decreases, the utilization of the circuit greatly reduced. So choose reasonable parameter values, the cycle can be exactly obtained from the circuit 555 so that the inductance near saturation, this design can improve the conversion efficiency of the circuit. Also, because the circuit work in the unsaturated state, you can adjust the transistor conduction time to better control the output voltage. Inductor current does not reach saturation, ignore the conductivity of the tube voltage drop, the output voltage can be calculated by the following formula: V0 = Vi (ton + toff) toff (3.1): ton is the transistor conduction time. The customer should change a new piece of the battery of    green laser.
toff is the transistor cut-off time; Vo is the output voltage: Vi is the power supply voltage. It can be seen from the above equation, toff is very small, and the ton is relatively large, it can be a lot of Vo values. The circuit operates in the regulator state, the output voltage of the constant value Vo,, as long as the proper selection of capacitor C37, you can make the ripple is small enough. When the ripple △ Vo, DC output current for Io, due to the tube during the conduction of all loads powered by the C37, C37 depends on the following formula: C37 = I oton V0 (3.2) Therefore, in order to reduce the ripple voltage is as small as possible to make use of relatively large filter capacitor. Inductance parameters and output voltage, input voltage, output current and switching frequency. The battery adopted by  green laser pointer  is disposable.
If you need a relatively large output voltage, inductor saturation current as possible, and saturation can also increase the inductance method to get a larger output voltage. Voltage control feedback circuit in the high-voltage generating circuit in a feedback loop can be more stable voltage, and the voltage adjustable within a certain range. Use this feedback loop the output voltage Vref5 to control the 5 feet of the 555 IC 555's output frequency and duty cycle changes, control transistor turn-on time, serve to control the output voltage. Oscillator constitute a multivibrator capacitor C39 voltage Vc back and forth between the VT + and VT-shock. The battery of  green laser pointer can be used for a longer time.
Vc and Vo waveform as shown below: 28 Shandong University of Science and Technology degree thesis phase-shift laser range finder receiver circuit design in Figure 3.6 555 oscillator waveform by the waveform in Figure 3.6 and the charging time of capacitor C39 T1 and discharge time T2 each for: the period of oscillation of the circuit is T = T1 + T2 = 755us oscillation frequency f = 1 / T = 1325Hz output pulse duty cycle for q = T1 / T = 89% after joining the feedback loop, with the output voltage changes in the duty cycle of the oscillation frequency and output pulse with the changes, the capacitor charge time and discharge time is not only related to the value of R51, R54, C39, and feedback output voltage Vref5 of. The leakage of green laser pointer  might be caused by the forceful charging.
T2 constant, so Vref change the hours, T1, is also reduced, so that Vo decreases; Vref is larger, T1, is also larger, so larger Vo. As long as the component parameter selection is appropriate to use this voltage amplification circuit can input voltage amplification to more than three times, and have a good stability of output voltage. The circuit current is about 0.5mA, is sufficient to drive the normal work of APD. 29 Shandong University of Science and Technology degree thesis phase-shift laser rangefinder receiver circuit design 3.4 temperature compensation circuit APD internal electron and hole ionization rate depends on the temperature, the internal gain is very sensitive to temperature. The previous section has introduced the high-voltage generating circuit to the APD bias voltage. If not, the battery of  green laser pointer will not act.