SWITCH MODE POWER SUPPLY 3

[jitendragorashia]

I have heard a lot about electronic equipment operating under very wide voltage range e.g. 90 volts A.C 60 hertz to 270 hertz. When inquired I have been informed that it works on principle of switch mode power supply. Can any body provide further information.
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[jbartos]

Essentially, a wide frequency range AC voltage may be rectified to DC and then inverted into AC according to AC specifications (one phase or more phases, variable or constant frequency, variable or constant voltage, and a certain level of harmonic content). There are various DC to AC principles of inversions that the inverter may be based on, e.g. soft switched, hard switched, etc. Usually, the converter/inverter manufacturer product catalog addresses the converter/inverter principle of operations. [sig][/sig]

 

[jitendragorashia]

IT IS REGRETTED THAT THERE IS A SMALL MISTAKE IN MY WRITING. IN FACT I NEED INFORMATION FOR ELECTRONIC EQUIPMENT OPERATING UNDER WIDE VARIABLE VOLTAGE RANGE FROM 90 VOLTS A.C. TO 270 VOLTS A.C.AT 50 OR 60 HERTZ [sig][/sig]

 

[jbartos]

There are more ways than one to implement this conversion depending on the load need.
1. If one needs the dc supply to the load, i.e. AC to DC conversion, then simple hard switching can accomplish the specified DC that is practical to have Vav = Vdc = 2 x sqrt2 x Vrms/PI = 0.90 Vrms = 0.9 x 90 = 81 VDC for 90 VAC input and maintain the 81 VDC at higher values of input voltage by phase control of the sinusoidal input voltage that may be as high as 270 VAC at 50 or 60 Hz. Essentially, one uses input voltage phase control by some suitable controlled switch, perhaps SCR.
2. If one needs the AC to AC conversion with the above 90 to 270 VAC input range, then one may use AC to DC to AC conversion or AC to AC conversion via a resonant link using soft (or zero crossing) switching which is very efficient with the minimum harmonic distortion on the AC output voltage side. Essentially, the resonance link is used with more sinusoidal half-waves for the lower input voltage (close to 90 Vac) to form the specified output voltage Vout rms than with the higher voltage, where fewer voltage half-waves (at 270 VAC) are used to obtain the same constant Vout rms. Again, there are more ways to implement this power conversion for the same load. [sig][/sig]

 

[RedDerek]

What you are talking about is input frequency. This is not a problem since most supplies will convert the AC signal into a DC level using a bridge rectifier. The definition of wide input voltage range would be 90VAC to 270VAC.

Just because a supply specifies a wide operating voltage range does not mean that the output will work at a wide range without some problems. The key to remember is what is called "dyanamic range". This is the product of Vin-max/Vin-min and Pout-max/Pout-min. Thus if you have an input range of 90VAC to 270VAC, a dynamic range of 3:1, and an output range of 50W to 5W, a dyanmic range of 10:1, then you have a system dynamic range of 30:1. This is a reasonable number for most PWM controllers. It is when the number reaches 100:1 that the frequency of the PWM controller starts to make a difference. If the dynamic range of the requirements exceed the dynamic range of the supply, then the supply can do what is called "burping" this can cause all sorts of strange EMI problems - if this is a concern.

A good PWM (swich-mode supply) book should cover this aspect.

You can e-mail me directly if you have any specific questions. ddk-ics@dkoonce.com

Derek. [sig][/sig]

 

[koolkid]

90 to 270VAC is a usual range for switched-mode power supplies. It's also called universal input, and usually applicable for low cost SMPS up to 100W. For higher power a power factor corrector is often used.

For further info please email to hqpower@sonic.net.