I'm going to make a flash, and I'm going to ask for a schematic diagram and a principle explanation.

I. Basic working circuit of ordinary flash lamp

Ordinary flash lamp refers to a flash lamp whose flash output energy is not adjustable, that is, the nominal flash number GN of the flash lamp is a constant value.

The circuit consists of four parts: the oscillating boosting part, the rectifying charging part, the voltage indicating part and the pulse triggering

flashing part.

when the power supply is turned on, an intermittent oscillation is formed by using the switching characteristics of transistor V1, so that the primary of T1 gets an alternating voltage

, and the secondary gets an alternating voltage greater than 3V after being boosted by T1. The alternating voltage is converted into DC voltage after half-wave rectification by diode D1, which charges and stores the main capacitor C2 and trigger capacitor C3. When the voltage is charged to about 7% of the fixed voltage, the neon lamp (Ne) in the indicating circuit lights up, indicating that the flash lamp is in a standby state such as normal flashing. When the button AN is pressed, the trigger circuit (composed of R3, C3, T2 and Xe) generates a pulse voltage, and an instantaneous high voltage (about 1kV) pulse is induced in the secondary of T2

, and the nitrogen in the Xe flash tube is ionized and turned on through the trigger electrode of the Xe flash tube, and the electric energy stored in the capacitor C2 is instantly discharged through the flash tube and converted into light energy, thus completing a flash < P > light.

the working principle of the built-in flash in the camera is the same as above. When the brightness of the external scene is insufficient, the camera's

photometric system will send out a low light message, and at this time, the camera will charge and flash

manually or automatically by turning on the flash circuit. Some cameras also have a system to automatically control the amount of flash (automatic dimming flash) to get more accurate exposure.

second, the working principle of automatic dimming flash

after the flash is fully charged, the flash synchronous contact on the camera is connected to the flash circuit. During the flashing period,

light is emitted from the flashing light to irradiate the object to be photographed, reflected from the object to enter the camera (for exposure)

and the flashing light metering element. The light measuring element quickly converts the light energy into an electric signal and inputs it into the integrating circuit, and then the product

sub-circuit outputs an electric signal proportional to the flash light value; When the value of flash light reaches the requirement of appropriate exposure, the output electric signal of the integrating circuit causes the control circuit to trigger the flash stop circuit, thus turning off the flash.

Because the continuous flash time of the flash lamp is very short, the flash metering element

used for dimming it must be a photosensitive element with quick response ability.

according to the different circuit structures, the control methods of automatic dimming flash can be divided into parallel connection and series connection.

a drain tube v is connected in parallel at both ends of the main flash tube Xe. The ignition circuit of the main < P > flash tube is the same as that of the ordinary type. When the luminous quantity of the main flash lamp reaches a certain reference value < P >, it is received by the photometric element, and the integrating circuit and the control circuit touch the discharge tube to immediately discharge the energy that has not been discharged < P > in the main control mode, so that the main flash tube is extinguished.

The parallel automatic dimming flash has simple circuit structure, low price and many applications. However, because it discharges all the remaining energy of the

main capacitor every time, it takes a long time to recharge and consumes a lot of battery.

The series control mode is to connect the thyristor rectifier SCR, a semiconductor switching element, with the main flash lamp in series.

When the light output from the main flash lamp tube meets the requirements of appropriate exposure, the thyristor rectifier SCR

automatically cuts off the discharge circuit, so that the main flash lamp tube is immediately extinguished, and automatic dimming control is realized.

the advantage of series control mode is that the remaining energy in the main capacitor is still preserved, so the recharging time can be shortened

, and the battery consumption is also reduced accordingly, which is beneficial to rapid flashing and recycling. The disadvantage is that the circuit is complicated and the cost is high.

schematic diagram: