TopSwitch vs. TinySwitch.

Larry,


The primary difference between the two device families is in the feedback control scheme used. TopSwitch-HX utilizes a PWM controller, whereby the on-time of the MOSFET is adjusted to control the amount of power transferred to the output stage. TinySwitch-III uses a control scheme we refer to as "on/off" control. This is a very binary control scheme, where entire switching cycles are enabled or disabled to control the flow of power. Designing with either one of these products is largely preferential. If you are very familiar with PWM driven supplies, you might find designing with TopSwich-HX designs. That being said, the on/off control scheme offers many advantages over PWM designs.

TinySwitch-III offers:


-Very Low component count
Because the on/off system control loop is very stable, no elaborate loop compensation is necessary. This greatly reduces the component count as compared with a PWM supply.


-No Bias Winding Necessary
TinySwitch does not rely on the bias winding to provide a feedback signal to the device. A bias winding can be used to power the chip and reduce no-load consumption, but is not necessary for operation.


TinySwitch designs do tend to be simpler than TopSwitch based supplies because of the simple feedback systems which can be used with an on/off control scheme.


Cheers!

Larry.......well for 5 or 6 Watts who needs PWM?....a simple on/off TNY sounds like you.

You cannot use ON/OFF control at high powers as you get bursts of pulses....and the frequency of the envelope of these bursts can be low and can get thru' your input EMI filter.

ON/OFF control can also sometimes give you a buzzing smps transformer...due again to the audio frequency of the bursts

Of course, if you learn how to do gain/phase analysis of any design using a gainphase analyzer ..................if it says your stable then who cares what design yuo did?.....ridley has articles on use in switchingpowermagazine.com

Basso in his book talks specifically of how to do gainphase on powerint chips.

Because of the current limit state-machine implemented in the TNY-III families, we are able to prevent "pulse-bunching" at low frequencies. Thus, our chips do not have the issues common to other "burst" mode switching devices and we do not have issues with EMI performance at higher powers.


Audible noise can be an issue with SMPS transformers, however dip varnishing the completed assembly drastically reduces this noise. Long core transformers sometimes have more issues with audible noise due to the increased surface area of the ferromagnetic material, so we suggest avoiding these if possible.


Overall, our customers have had great success designing TNY-III at relatively high powers. TinySwitch-III is commonly used by computer manufacturers for PC Standby applications at power levels between 20 - 30 Watts.


Cheers!

I agree the TNY chips are an excellent part.....but this on/off control...even with your algorithm to stop pulse-bunching cannot be perfect....because surely everyone would use TNY chips if they could?....after all, why bother with feedback compensation if you've no need.......so the TNY on/off controllers must have some limitations?.....as otherwise everyone would use them for everything............and i would put it that even though the powerint algorithm limits the effects of pulse bunching....it cannot get pulse bunching down to the low level of occurrence of it that you get with PWM chips.........Am i right to say that on/off control certainly cannot be used above 50 Watts.........it certainly has an upper power limit?

hi........surely nobody would design with PWM for preferential reasons?.....after all, if you can get away with simple on/off control then surely you are going to use it......why burden oneself unneccessarily?...................The thing is that TNY chips must have some limitations but may i request what these are?