Overview
  Next-generation cell phones will have a high quality camera. With the improvement of the image sensor and optical components to be put on the market, people will gradually invest in high-quality attention to "flash" lighting. Access to quality photographic flash lighting is a key factor in performance, it requires focus and careful consideration.
  Flash lighting solutions
  Currently, there are two main flash lighting solutions - LED (light emitting diode) and flash. LED has the advantage of the continued support of working capacity and low-density circuits. The important feature of the flash is to achieve high-quality photography. It is a linear source of light output brightness LED point source output hundreds of times, in a wide range of regions and easily spread the light intensity. In addition, the flash color temperature between the 5500oK to 6000oK, very close to natural light, without having to peak output white LED's blue color correction necessary for the process.
  Flash based
  Cylindrical glass tube filled with flash xenon, direct contact with the anode and cathode gas; and distribution of the outer surface of the flash trigger electrode does not touch the gas. Gas breakdown potential range of several thousand volts, in the event of breakdown, flash impedance down to = 1O. Gas breakdown when the high current will produce a strong visible light. In fact, the large current requirements needed before the light flash in low-impedance state. Trigger electrode is responsible for achieving this function, which is transmitted in the tube high voltage pulse, the ionization in the xenon lamp. Breakdown of the gas ionization process, so that a low impedance state. Low impedance so that a large number of current can be passed between the anode and cathode, and a strong light. Contains high energy, so that current and output light to limit the operating range of the pulse. Continuous operation quickly generate extreme temperatures, or even destroy the flash. When the current pulse decay, the flash voltage drops to a low point and flash back to its high impedance state, which needs another trigger to start transmission.
  Support circuitry

Figure 1, the flash circuit including the charging circuit, storage capacitors, triggers, and lights. Trigger command ionized gas inside the lamp, the capacitor discharges through the flash. Capacitor must be recharged, triggers the flash to make flash again.
  Figure 1 is a flash operation to support the work of the circuit diagram. Flash generated by a trigger circuit and the high transient current to operate the storage capacitor. Flash capacitor voltage is typical of the work of 300V. Initially, the capacitor can not discharge, since the flash is in a high impedance state. Instruction to the flash trigger circuit to generate a few kV trigger pulse. Flash is the breakdown, the capacitor can discharge 1. Capacitors, cables and lights are usually a total of only a few ohms impedance, resulting in the instantaneous current within the range of 100A. Powerful current pulse will have a strong flash. The flash repetition rate of the most important limitation is that flash can safely release heat, followed by the flash capacitor charging circuit to the time required to fully charge. Charging a large capacitor with high voltage charging circuit with limited output impedance, to limit the charging speed. According to available input power, capacitance and charging circuit characteristics of the charge time limit of 1 to 5 seconds.

Figure 2, in Figure 1, based on the addition of the drive / power switch, allowing the capacitor part of the discharge to control light emission. Allowed before the main flash of light pulses of low intensity can be reduced as much as possible, "Red Eye" phenomenon.
  The figure shows the command received by the trigger capacitor discharge process. Sometimes asked to select the part of the discharge, resulting in very strong flash. This operation can reduce the "red eye", which weakened the strength of one or more of the flash immediately ahead of the main flash 2. Figure 2 is that this mode of operation. It is based on Figure 1 to add a drive and a high current switch. These components through open pathways to stop flashing the flash capacitors discharge. This layout so that the "trigger / flash command" line of control pulse width to set the current flow time and the flash energy. Low energy, the capacitor part of the discharge that would allow rapid recharge and can not damage the case of the flash immediately before the main flash several times in rapid succession to low light flash.

Figure 3, the flash capacitor charger circuit including the IC regulator, step-up transformer, rectifier and capacitors. Controller T1 flyback pulse by monitoring the control of the capacitor voltage feedback resistor divider to eliminate the traditional path loss. Control pins, including charging orders, and charge completion ("DONE") display.
Consideration of the flash capacitor charging circuit
Flash capacitor charger (Figure 3) is basically a transformer with special features coupled boost converter. When the "charge" control line goes high, the regulator the power switch on time, so that step-up transformer T1 to produce high voltage pulses. These pulses are rectified and filtered to produce a 300V DC output voltage. Conversion efficiency is about 80%. When you reach the required voltage, the circuit will stop the drive power switch through regulation. It can also pull down "DONE" line to show the full scale charge the capacitor. All capacitor leakage losses through the cycle intervals to compensate for the power switch. Typically, the output voltage through the resistor divider to provide feedback. Since this method requires additional switching cycle to offset the constant feedback resistor power leakage, are generally not used. This approach can maintain regulation, and it will leak from the main power supply extra power (which can be assumed to be a battery.) Instead, by monitoring the T1 flyback pulse characteristics to achieve the adjustment, which reflects the amplitude of T1's secondary. Output voltage by the turns ratio of T1 set. This feature allows access to accurate capacitor voltage regulation, which is no more than light energy or the case of rated voltage of the capacitor to ensure the necessary conditions for the flash intensity. Similarly, without changing other circuit, as long as the capacitor value can be easily set by the flash of energy.
Details of the circuit
Before the in-depth study, the reader must realize that in the construction, testing and using this circuit to be very careful. High voltage potential risk factors and fatal in this circuit. Therefore, the use and connection circuits should be particularly careful. Again: The circuit includes risk and high risk, must be more careful.

Figure 4, the complete circuit including the capacitor charging flash components (Figure left), the flash capacitor C1, the trigger (R1, C2, T2), Q1 - Q2 drives, Q3 power switch and flash. TRIGGER command also bias Q3, T2 ionized by the flash. C1 discharges through the lamp light.
  Figure 4 is based on the earlier discussion of the full flash circuit. Displayed in the upper left corner of the capacitor charging circuit similar to Figure 3. Add a D2, secure clamping transient voltage T1 inversion generated. Q1 and Q2 drive high current switch Q3. Generated by the step-up transformer T 2 high-voltage trigger pulse. Suppose C1 is fully charged, when the Q1-Q2 turns on Q3, C2 accumulation of current to the primary side of T2, then T2 secondary-side high-voltage trigger pulse to the flash pass, ionization to the conduction. C1 discharge within the lamp and the formation of flash.