Purpose in syncronizing electronic signals

[stuart smith]

Can anyone explain to me the purpose in syncronizing electronic signals?
Is this purely to keep noise low? if so, how does this help with noise?

Example i can this is with a power supply. Why would it be better to use an external sync signal with an assembly like this.

Any info would be obliged.
SS

 

[shrtrnd]

That's kind of an open-ended question.
If you want an accurate explanation, we need to know your application.
What power supply, and what external sync signal are we talking about?
A little more information please.

 

[stuart smith]

That's kind of an open-ended question.
If you want an accurate explanation, we need to know your application.
What power supply, and what external sync signal are we talking about?
A little more information please.

Thanks for the reply.
Forget the power supply part then.
what about the purpose in syncronizing electronic signals?

thanks again

 

[Martaine2005]

what about the purpose in syncronizing electronic signals?

Synchronizing "anything" is to get them to perform / function the same.
Or have I completely misunderstood you?

Martin

 

[AnalogKid]

"forget the power supply" makes your question even harder to understand. There are hundreds of different general reasons for a system to require that some or all of the internal or external signals be synchronized, and millions of specific reasons. If you are talking about a power supply with multiple independent switching regulator circuits, synchronizing the switching frequencies can be a general purpose noise control technique, or the switching frequencies can be synchronized to a critical signal within the system so that measurements are made in between the switching discontinuities to reduce captured interference. Or or or or or or or ...

ak

 

[duke37]

Transmitters can be synchronised so that a beat signal is not generated in the area where both signals are received.
Phase sensitive detectors can be used to increase sensitivity and reduce noise. A transmitter and detector can be synchronised from a satellite and radio signals of no more than a few milliwatts can then be decoded at the other side oif the world. They trade sensitivity for speed.

 

[shrtrnd]

Now I'm beginning to wonder if you're talking about some kind of digital command signal sync?
If it's not for a power supply, what type of circuit are you wondering about for a sync signal?

 

[cjdelphi]

You're describing a PLL or Phase Locked Loop...

Basically a PLL will decrease or increase it's frequency until it's locked or synced with the main clock...

Useful for cpus where hardware shares the same bus to pass data, out of sync could lead to corrupted data / crashing, for example it's it acts on a high rising edge but it's out of sync so the wrong bit is set at the wrong time..

 

[Harald Kapp]

You're describing a PLL or Phase Locked Loop...

Not necessarily. There are many reasons why one would want or need to scnchronize signals. There are also many ways of doing this.

Synchronizing also is not limited to the world of electronics but happens in real life quite as often. Generally speaking synchronizing two (or more) events means to establish a well know relationshift (typically with respect to their timing: Greek syn=equal, chronos=time) to ensure reliable and repeatable operation. Take for example traffic lights: they synchronize the stop and go of crossing traffic to ensure a steady flow of traffic without accidents.

In a similar way synchronizing electrical signals ensures that they are available at the right place at the same time. An example is the synchronous operation of the address bus signal, data bus signals and control signals of a processor bus. Only the right timing ensures that the right data from the right address isread or written at the right time.

Strictly speaking synchronous means "happening at the same time". However, in pratcice the term doesn't always imply simultaneity. Events can be synchronous but happen at different times. Synchronicity means that the event have a well known (and typically fixed) tempral relationship, e.g. event_2 happens always 10 milliseconds after event_1.

 

[Merlin3189]

Can anyone explain to me the purpose in syncronizing electronic signals?
Is this purely to keep noise low? if so, how does this help with noise?
Example i can this is with a power supply

I can think of some examples of synchronising signals is used:
In a synchronous counter (as compared with a ripple counter) the outputs change all at the same time, because if the bits change at different times, in between the first and last bit changing, the output will be a random number.
When receiving digital signals, you need to know when each bit starts/ends. So the receiver needs to have a clock synchronised with the transmitter clock. Even in asynchronous communications the receiver restarts its clock when it detects a start bit, so as to try to be in synch with the transmitter. The uncertainty in the synchronisation of the clocks limits the length of the block of bits that can be sent between each start bit.
As for noise reduction, I think maybe if a receiver has a synchronised clock, it can sample the bits in the middle of each pulse where the logic level is most likely to be stable. Or maybe it can simply avoid the transitions where noise, distortion, ringing etc will be most noticeable. One UART I used had an internal clock at 16x the bit rate, which it zeroed at the start of the first transition, then sampled the signal on the count of 8, 24, 40 etc so as to be near the centre of each pulse.
A bit out of date (as all my examples!) but synchronisation was a big issue for analogue TV receivers. The oscillator that scans the CRT has to stay in synch with the oscillator that scanned the camera, otherwise the picture slid about, tore, rolled and was generally unuseable. Originally scanning synch was achieved by triggering each cycle of the oscillator and interference could break up the picture quite easily. When phase locked loops (or flywheel synch as it was known in TV's) came in, pictures became much steadier. And of course now you have digital TV, the pictures are always perfect (or so they tell me!)

On a more facetious note I like my power supplies to be synchronised so that they come on when I switch on and go off when I switch off. It would be a pain if the output were not synchronised with the switch.

 

[shrtrnd]

stuart smith where are you?