25 Khz oscillato

[zjaakco]

Hi, all
I search for a schematic of a 25 Khz oscillator. The type or brand
is not importend, I look for an oscillator as stabel by frequentcy as possible. I will use it in a smps.
Is there anybody out there who will help me? Thanks.
Regards
Zjaakco

[nigelwright7557]

You can use am op-amp oscillator.
Or a comparator oscillator.

Or use a crystal controlled microcontroller if it has to be very accurate.

There are logic gates that have oscillators. 4060 if I remember right.

[dchisholm]

You need to give a better description than " as stabel by frequentcy as possible ". Standards laboratories have spent millions of dollars to create frequency sources that are as accurate and stable as possible. I don't know what the present state-of-the-art is, but I suspect it's in the parts-per-billion range.

For most of us, accuracy and stability of a few parts-per-million is acceptable. I would start with a 100 KHz quartz crystal resonator such as the Citizen CFS type < http://cfm.citizen.co.jp/english/pro...df/CFS-CFV.pdf >, in a Pierce oscillator circuit created from logic gates. Be careful to avoid overdriving the crystal. Then I would use a pair of flip-flops to divide the frequency down to 25 KHz.

This arrangement can be initially trimmed to an accuracy of 1 ppm or better if you have a standard to compare it with. The long-term drift over a month's time, as well as short-term variation due to temperature, should be a few ppm.

Dale

[zjaakco]

Hi, nigelwright7557. hi Dale
I will try to be more clear. First, I have no experience with smps.
I ever read that a smps have a cleaner power than a lineair one.I will a smps use in a dac. This means a power consumption of a few VA. From this I think a complex smps is not necessary. I think a sinus signal amplified to a power mosfet, swiched in source follower and than with a transformer, to, for example 12 Vac,.and then rectified, This mean, if I start with 25Khz, a dc voltage with a ripple of 50 Khz.
So an oscillator with a reasonable quality and price is what I mean. The reason why I choose for 25 Khz is that the higher the
frequency there wil be more noise, that must be filtered off.
In my experience a lineair supply is not easy to clean up.
Next, it is diy, its become try and error, and time consumption.
But this is the only way to lurn.
So, every respons is wellcome.
Regards
Zjaakco

[Mooly]

I think what you are describing is little more than an amplifier feeding a transformer with a sine wave... which you then rectify as normal. Only difference over 50/60 hz is that the ripple component is higher frequency.

If that is what mean then it's not really an SMPS.

An SMPS would drive the switching transistor cleanly either full on or fully off (no sine waves) and storing the energy in a coil/transformer in such a way that it can be recovered and rectified. There are low voltage SMPS designs but imo a linear is definitely the way to go for DIY and certainly for such low currents.

[zjaakco]

Hi Mooly
That my thought isn't a smps. ok, I will name it a high
frequency power supply. My thought keep on of what I says in my last post.
I start with an oscillator of 25Khz, because from this choice. one can calculate a main filter, and after rectifying the frequency is high enough above the audio range and 44,1/48 sample freq.
You says keep on by a lineair supply, but I still belief that a lineair supply is unsatisfactory for a good sound. I think, just its not usual it become easyer for shooting off. Almost no diy have tryed or have experience with a smps or high freq. supply.
Is there anybody who can help me for an oscillator diagram?
And any respons is wellcome.
Regards
Zjaakco

[zjaakco]

Hi dchisholm
Thank you for the citizen link, 32Khz is certain a possibility
for a start of a high freq. power supply.
Is there a Pierce oscillator with an op-amp?
I gues I need some amplification after the oscillator.
Regards
Zjaakco

[Mooly]

Look at some application notes for opamps (LM4562 for example) as these give sine wave oscillator circuits. The 4562 circuit uses a small filament bulb for amplitude stabiliisation (used as a thermistor) or there are this type using zeners and FET,

http://www.simplecircuitdiagram.com/...ve-oscillator/

One thing you definiely do not need is crystal stability

[TechGuy]

Here you go, just plug in 25Khz: (assuming you want a squarewave output)

555 Timer Oscillator Frequency Calculator

[geraldfryjr]

I just finished building a variable Hv supply that uses a 555 timer running at 100Khz.
it works okay with the timer chip but a sine drive would be much better as you can't get a perfect 50% duty cycle from the 555 by itself,Close but not perfect.
This can cause a few problems in the output stage.

Jer