Re: Voltage Converter?

w_tom <w_tom1@xxxxxxx> writes:
On Mar 29, 9:10 am, "BillW50" <Bill...@xxxxxxx> wrote:
Wow! I must be living in a parallel universe here! I just checked my
Toshibas (some dating back to '99), Gateways, LCD external monitors,
etc. And they all say an input voltage of 100V to 240V.

It was called a universal power supply. Standard throughout the
world especially on portable equipment (cell phones, digital cameras,
cam corders, electric razors, etc). Also found on many if not most
video monitors. Some other equpment have a switch labled 110/220.
But one IC could replace that switch so that power supply
automatically switches to correct voltages. The technology is decades
old.

You're actually talking about two different power supply designs.

Many desk/tower computers have a power supply with a 120/240 V switch on
them. The switch changes the configuration of the input circuitry to
either be a normal full-wave rectifier (when set to 240) or a voltage
doubler (when set to 120). When set correctly for the voltage applied,
the input capacitors have about 300 V across them and this powers the
rest of the power supply. It's basically a circuit designed for a
single supply voltage, with a switchable voltage doubler in the input.

This design will *not* work properly if you set the switch wrong, and
it only operates correctly for an input voltage that is near (e.g.
+-15%) the marked voltage. Using one of these designed for 120/240 V
on the 100 V in Japan might be iffy.

This is not the sort of design normally used by laptop power supplies.
Instead, they generally have a wide-range power supply that works from
(for example) 90-250 V in without switching. *Any* voltage in the
listed range should operate the unit properly. The circuitry is simply
designed to operate OK over the entire range of voltage, automatically
adjusting itself without any external switches.

Dave
.

Relevant Pages

  • boost regulator with LDO mode when Vin > Vout ?
    ... I am trying to design a power supply for a 5V/50mA circuit, ... switch, or from another switch-mode power supply giving ... sometimes lower than the input voltage. ... What other chips should I look at? ...
    (sci.electronics.design)
  • Re: Simple 555 PWM - disappointing performance
    ... Further since you are now switching voltage across the motor, ... The diode is placed to ensure the motor current has somewhere to commutate to when the switch turns off. ... for a pnp switch, the pnp collector goes to the motor and the cathode of the ... Connecting the emitter to the motor places the pnp transistor in a ...
    (sci.electronics.design)
  • Re: Voltage Gain Switch (Design Help)
    ... Their capacitances are in the 100-pF range at low voltage, ... switch gains through the MOSFETs. ... the overall gain of the two stages being at least 2. ... It`s unlikely that I will use this design, but I am interested in how ...
    (sci.electronics.design)
  • Analysis of KVM Switch Problems
    ... The mouse and keyboard each send digital messages to the ... sent by changing the voltage on the wires back and forth between ... the KVM switch must maintain the ... In this case, the clock signals would ...
    (alt.os.linux.suse)
  • Re: CFL flickers - when switch is off. . .
    ... circuit in my stairway that pulses very weak light, from near the base of the discharge tube, about every second, when the switch is in the "off" position. ... And that probably uses a very small neon bulb. ... voltage across the empty socket would give the full 110 volts. ... The likely cause was a "plug and wire change" last year which was shortly followed by the engine running very rough rough because the stationary electrode fell right off the plug in that same cylinder. ...
    (alt.home.repair)