Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Utility Patent
1999-07-12
2001-01-02
Wong, Peter S. (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S273000, C363S089000
Utility Patent
active
06169391
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the conversion of high voltage alternating current (AC) to low voltage direct current (DC). Specifically the present invention relates to an apparatus and a method for converting high voltage AC to low voltage DC without the use of transformers, large capacitive coupling circuits or high voltage linear regulators.
2. Description of the Related Art
There are devices such as consumer appliances and electronics, i.e. refrigerators, washing machines, dishwashers, microwave ovens, televisions, video cassette recorders, audio components, etc., which require high voltage AC power and low voltage DC power. The low voltage DC requirement is for powering analog and digital control circuitry, display indicators such as Light Emitting Diodes and other low power devices.
The prior art identifies attempts to provide AC to DC conversion in three principal categories: the transformer approach, the high voltage linear regulator approach and the high voltage capacitive coupling approach. Each of these three approaches has limitations which are discussed below.
Referring to
FIG. 1
, the transformer approach with full wave rectifier is illustrated. The step down transformer will drop the input voltage, which is typically 110-120 VAC for devices operating in the U.S. and Canada and typically 220-240 VAC for devices operating in Europe and elsewhere in the world, to a low voltage in the range of 5-24 VAC, depending on the application. After step down, the sinusoidal AC input is then rectified by a full wave rectifier, i.e. diodes D
1
, D
2
, D
3
and D
4
. The capacitors C
1
and C
2
combine with the linear regulator to provide a stable DC output voltage.
The disadvantage to this approach, and to all transformer approaches, is the prohibitive cost, size, weight and power consumption of step down transforms. Furthermore, the approach of
FIG. 1
also requires a four diode bridge rectifier.
Referring to
FIG. 2
, a step down transformer is used in conjunction with a half wave rectifier. The transformer provides a low voltage AC component as in FIG.
1
. However, in the case of
FIG. 2
, a single diode D
1
is used to form the half wave rectifier. The capacitors C
1
and C
2
with the linear regulator provide a stable DC output voltage. Although this approach uses only one diode, as compared to four diodes in
FIG. 1
, the capacitor C
1
must be significantly larger than its counterpart in the full wave rectifier configuration to compensate for the half wave rectification. Thus, the disadvantage to this approach, in addition to the step down transformer, is the size of the capacitor C
1
.
Referring to
FIG. 3
, another configuration of the transformer approach is illustrated using a center tap transformer and a full wave rectifier comprised of diodes D
1
and D
2
. The center tapped transformer, while permitting a two diode full wave rectifier, adds complexity and therefore cost to the configuration.
Referring to
FIG. 4
, the high voltage linear regulator approach is illustrated. In this approach, the bulky and costly step down transformer is eliminated from the circuit. The high voltage AC input is rectified by the full wave rectifier, diodes D
1
, D
2
, D
3
and D
4
and stored by capacitor C
1
. The high voltage linear regulator reduces the high DC voltage to a low DC output voltage, typically in a range of 5-24 VDC. Capacitor C
2
provides a filter for the DC output voltage. The disadvantage of the high voltage linear regulator approach is excessive power dissipation caused by the storage of high voltages on capacitor C
1
.
Referring to FIG.
5
,, the high voltage capacitive coupling approach is illustrated. Once again the step down transformer is eliminated. Capacitor C
1
couples the AC component to the full wave rectifier, i.e. diodes D
1
, D
2
, D
3
and D
4
, across resistor R
1
. The zener diode Z
1
limits the output of the full wave rectifier to the desired low voltage DC output. Capacitor C
2
provides a filter for the DC output voltage. Although this approach reduces the power consumption over the approach shown in
FIG. 4
, the size of capacitor C
1
is prohibitively large.
Therefore, a solution to the complexity, cost and size limitations imposed by the transformer approach, the high voltage linear regulator approach and the high voltage capacitive coupling approach of the prior art was needed for converting high voltage alternating current to low voltage direct current.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to convert high voltage alternating current to low voltage direct current without the use of one or more transformers.
It is an object of the present invention to convert high voltage alternating current to low voltage direct current without the use of large capacitive coupling circuits.
It is an object of the present invention to convert high voltage alternating current to low voltage direct current without the use of high voltage linear regulators.
It is another object of the present invention to provide a rectifier, which may be either a full wave rectifier or a half wave rectifier, for converting high voltage alternating current to high voltage direct current.
It is another object of the present invention to provide a control circuit for detecting the voltage level of the high voltage DC input power signal and for switching on and off the connection between the high voltage DC input power signal and the low voltage direct current output signal. The control circuit also limits the voltage as seen by the linear regulator and the storage capacitor.
It is still another object of the present invention to provide a linear regulator for limiting the DC voltage output as seen by the load and for removing voltage anomalies induced by the charging and discharging of the storage capacitor.
It is still another object of the present invention to provide a storage capacitor which charges when the switch within the control circuit is on and which discharges when the switch within the control circuit is off.
In accordance with one embodiment of the present invention, a device for converting high voltage alternating current to low voltage direct current comprises an alternating current (AC) input voltage; a rectifier coupled to the AC input voltage; a control circuit coupled to the rectifier; a linear regulator coupled to the control circuit; and a storage capacitor coupled to the control circuit and further coupled to the linear regulator.
In accordance with another embodiment of the present invention, the invention further comprises a filtering capacitor coupled to the linear regulator.
In accordance with still another embodiment of the present invention, the control circuit comprises a voltage sensing circuit and a switch.
The foregoing and other objects, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiments of the invention, as illustrated in the accompanying drawings.
REFERENCES:
patent: 3777253 (1973-12-01), Callan
patent: 4010401 (1977-03-01), Yasumatsuya et al.
patent: 4568877 (1986-02-01), Tinsley
patent: 5132893 (1992-07-01), Klein et al.
patent: 5258701 (1993-11-01), Pizzi et al.
patent: 5357418 (1994-10-01), Clavel
patent: 5414340 (1995-05-01), Gannon
patent: 5528485 (1996-06-01), Devilbliss et al.
patent: 5894243 (1999-04-01), Hwang
patent: 5929663 (1999-07-01), Dougherty
Davis Paul W.
Harry M. Weiss & Associates, P.C.
Laxton Gary L.
Supertex Inc.
Wong Peter S.
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