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What causes the increasingly high-pitched sound emitted by a capacitor charging circuit, such as that found in a camera flash?
I think that it's like that smelly smoke that Faust mentioned the factories installing in components to show when they aren't working properly. The manufactures of capacitors build noise into them so you can tell when they are working.brewnog said:What causes the increasingly high-pitched sound emitted by a capacitor charging circuit
It's the electronic circuit. The high voltage is generated with a switching power supply, I believe.brewnog said:What causes the increasingly high-pitched sound emitted by a capacitor charging circuit, such as that found in a camera flash?
dlgoff said:It's the electronic circuit. The high voltage is generated with a switching power supply, I believe.
Best guess(s) is the ransformer, choke, and just maybe an electrolytic capacitor. These things are designed with the switching frequency above the audio range, but somehow a sub-harmonic may be generated.brewnog said:...What's vibrating? Just anything metallic within the circuit which is being influenced by a changing magnetic field?
Are you sure it is a change in pitch? The sound volume may increase with load, but I would think the frequency would not.brewnog said:Why does the pitch increase? Is this due to any change in switching frequency?
Any one that I've experienced definitely got higher in frequency as well as volume. Some of them are downright painful just short of full charge.GENIERE said:Are you sure it is a change in pitch? The sound volume may increase with load, but I would think the frequency would not.
GENIERE said:Are you sure it is a change in pitch? The sound volume may increase with load, but I would think the frequency would not.
It's magnetostriction in the inductor that is the main energy storage elelment in the "boost" DC-DC converter. Magnetostriction is a mechanical vibration caused by the AC magnetic flux in the magnetic material. That's why most DC-DC converters are run above the range of human hearing. I don't know why camera flash chargers are run in the audible range -- kind of obnoxious. Even the 15,750 flyback transformers in TV sets can be bad sometimes, and the design of flybacks and their mechanical mounting methods usually take into account the need to avoid mechanical resonances at their swithching frequency.brewnog said:But what's actually happening?
What's vibrating? Just anything metallic within the circuit which is being influenced by a changing magnetic field? Why does the pitch increase? Is this due to any change in switching frequency?
Excuse any ignorance, I've only taken a few EE modules.
There are different ways that DC-DC converters regulate their output voltage. Some do it with strict PWM and a constant frequency, and others change frequency as their pulse width narrows. This second type of DC-DC is usually frowned on by folks that have to worry about power supply noise in their circuits (like low-level analog circuits, or RF circuits, etc.), because the fundamental and harmonics walk all over the place as the power supply output loading changes.dlgoff said:I was thinking the change in pitch might actually be because of less loading on the circuit when the capacitor get closer to full charge. Does that sound right berkeman?
Regards
Don
berkeman said:…But allowing the frequency to change as the pulse width changes can sometimes let you save a little money in the design of the DC-DC converter circuit, so if the rest of the circuitry in the device can tolerate it…
The high-pitched sound in camera flash circuits is caused by the vibration of the flash capacitor. When the capacitor is charging, it creates a high-pitched whine as the electric current flows through it. This sound is amplified by the camera's body and can be heard when the flash is activated.
Yes, the high-pitched sound is a normal and common occurrence in camera flash circuits. It is a byproduct of the charging and discharging of the flash capacitor and does not indicate any malfunction or defect in the camera.
No, the high-pitched sound is not harmful to the camera or the user. It is simply a noise generated by the electrical components of the camera and does not pose any danger or risk.
The high-pitched sound in camera flash circuits cannot be stopped or reduced without altering the circuit design. However, some cameras have a silent mode or a "whisper charge" feature that can minimize the sound produced by the flash capacitor.
No, the high-pitched sound has no impact on the quality of the photos. It is simply a noise produced by the camera's internal components and does not affect the camera's ability to capture images.