Electrical power source

Details Electrical power source Electrical power source

1987-01-15

1987-12-08

Wong, Peter S.

Electric power conversion systems

Current conversion

With means to connect the input to diverse power sources

323303, 363 89, H02M 110

Patent

active

047121718

DESCRIPTION:

BRIEF SUMMARY
This invention relates to electrical power sources.
Many pieces of domestic electrical equipment need to be capable of working with different mains supply voltages, the most common which are the 110 volts supply existing, for example, in the United States of America and the 220 volts supply existing, for example, in Europe. In some countries the standard voltage is slightly different from these standard voltages whilst in other countries the supply itself may have a rather erratic and variable value.
To meet the differences between a 110 volts and a 220 volts supply, equipment such as electric shavers may use a simple resistor which can be manually switched into and out of circuit to dissipate the excess of the larger voltage. Alternatively a transformer can be used where a large power supply is concerned but it is still necessary to adjust the tap position manually to match the supply and in many cases adjustment for the relatively small changes from the two standard voltages is not provided for. Also no account is taken of erratic changes in voltage.
It is therefore an object of this invention to provide a simple power source which can accept a wide range of AC power input voltages yet which will automatically provide a relatively constant DC output.
According to the invention there is provided an electrical power source capable of accepting an input within a range of AC input voltages and providing a substantially constant DC output supply, comprising converter means for providing from the AC input supply a number of outputs of differing voltages each proportional to the input voltage, each of these outputs being connected respectively to one of a number of parallel circuit lines each of which includs a rectifier, a maximum voltage regulator and non-return current device, the outputs of these lines being connected to a common output intended to provide the substantially constant DC voltage supply, each voltage regulator having a set regulating voltage which is one of a discrete range of voltage steps close to the required substantially constant DC voltage, the lowest of the steps being no greater than the voltage reached for the line connected to the highest output from the converter means when the input supply is at the low end of the range of AC voltages, the next of the steps being greater than the lowest and being reached for the line connected to the next highest output from the converter means, and, if there are more than two parallel circuit lines, the next step being greater and being reached for the line connected to the next highest output from the converter means and so on, so as to cover the range of possible input AC voltages.
Such a power supply can be very simple to make and in addition can occupy a relatively small space. It can, therefore, fit easily within many domestic electrical appliances. Also the supply automatically accepts any AC voltage within the designed range of AC input voltage and gives a substantially constant DC output. Further the power source accepts automatically any erratic and fluctuating changes in the input voltage substantially within affecting the output DC voltage.
Typically there will be four parallel circuit lines to cover an input AC voltage range from 80 to 260 volts.
In order to improve the stability of the output DC voltage the common output can be fed through another maximum voltage regulator having a set output voltage which is lower than any of the set values of those in the parallel circuit lines. In this way even though there will be small voltage changes as a result of current being drawn from one or other of the parallel circuit lines depending on the input voltage, the final output voltage can be very stable. In some cases, however, this further step may not be necessary because the relatively small differences in output from the various parallel circuit lines may insignificant to the piece of equipment receiving the DC output.
An important advantage of the invention is that the power source has low high-frequency noise and so a low risk of radio

REFERENCES:
patent: 3414802 (1968-12-01), Harrigan
patent: 4052660 (1977-10-01), Shuey
patent: 4415964 (1983-11-01), Scharfe

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