Communications: electrical – Systems – Selsyn type
Reexamination Certificate
1999-04-20
2001-09-11
Trieu, Van T. (Department: 2632)
Communications: electrical
Systems
Selsyn type
C340S315000, C315S194000, C315SDIG004
Reexamination Certificate
active
06288630
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the transmission of an information over an A.C. supply line of a load with a capacitive input impedance. The present invention relates, more specifically, to the transmission of an operating control signal for a circuit meant to supply a load from an approximately D.C. voltage obtained by rectifying an A.C. voltage.
BACKGROUND OF THE INVENTION
FIG. 1
very schematically shows the electric connection of a system
1
of supply of a load
2
(Q) from an A.C. voltage Vin, provided with a bridge
5
for rectifying voltage Vin and with a circuit
4
of supply of load
2
from an approximately D.C. voltage Vout. Voltage Vout is taken across a capacitor C receiving a rectified A.C. output voltage of bridge
5
.
Input voltage Vin of system
1
is an A.C. voltage coming, for example, from a variator
3
of an A.C. supply voltage Vac, for example, the mains voltage.
When it is desired to vary the supply power of a load having a resistive input impedance, a phase angle or phase angle switching variator is generally used to modulate the power transmitted to load
2
.
Although such a phase angle variator is well adapted to applications for which load
2
is of resistive type and does not require a supply from a recovery of a D.C. voltage, conversely to what is shown in
FIG. 1
, such a phase angle variator raises several problems in the case of a capacitive input impedance load.
A first problem is that, for the phase angle variation to translate as a power variation of load
2
, the approximately D.C. voltage Vout has to follow the power variations linked to the phase angle variation. As a result, circuit
4
used to supply load
2
sees its own supply vary, which can cause malfunctions due to the supply needs of the components of circuit
4
. For example, if circuit
4
forms a switched-mode converter used to supply a load
2
formed of a fluorescent lamp, a variation of voltage Vout adversely affects the proper operation of the switched-mode converter.
Further, a switching in the charge area of a capacitor constitutive of the input impedance results in a significant effective current, which is not desirable.
Accordingly, for loads having a capacitive input impedance, other means than the phase angle variation are conventionally used to act upon the operation of system
1
.
In a conventional circuit
4
such as shown in
FIG. 1
, the power variation function is generally performed from an analog low voltage input E of circuit
4
. The signal applied to terminal E is used, for example in an application to a fluorescent lamp, to modify the frequency of the alternating current provided by the switched-mode converter to vary the light intensity. Terminal E of light intensity dimming control is meant to be controlled by an external variator
3
setting a control voltage generally included between 0 and 5 volts and proportional to the desired light intensity.
A major disadvantage of this variation solution is the need for a low voltage link between system
1
of control of load
2
(here, a fluorescent lamp) and a generally remote mechanical potentiometer-switch (variator
3
). As illustrated in
FIG. 1
, in addition to the two conductors
8
,
9
(phase and neutral) of A.C. supply Vin, two low voltage conductors (dotted lines
7
) indeed have to be provided between a switch
3
including a dimmer and electronic system
1
of control of load
2
.
Another conventional solution to transmit a light intensity order to a load supply control circuit
4
consists of performing a modulation of the carrier current, that is, modulating the alternating supply current with a high frequency signal transmitting the light intensity order. Such a solution requires, on the side of dimmer
3
, a carrier current modulation system (not shown) to transmit the order and, on the side of system
1
, a demodulator (not shown) for extracting the power order from the A.C. supply.
Such a solution has the advantage of avoiding the need for an additional link
7
. However, it has the disadvantage of being particularly complex and expensive to implement.
SUMMARY OF THE INVENTION
The present invention aims at providing a novel solution to transmit an order to a load supply circuit.
The present invention aims, in particular, at providing a simple solution which requires no additional link between the control element and the load supply circuit.
The present invention aims, in particular, at providing a system of acquisition of an order, coming from a variation by phase angle switching of an A.C. supply voltage, within a circuit of load supply from an approximately D.C. voltage obtained by rectifying this A.C. voltage.
More generally, the present invention aims at providing a transmission system which enables transmitting any analog order by using the A.C. supply voltage as a transmission support and without requiring to use a high frequency modulation transmission-reception system.
To achieve these objects, the present invention provides a circuit for supplying a load from an approximately D.C. voltage obtained by rectifying an A.C. voltage, including means for extracting from the rectified A.C. voltage information depending on a phase angle variation of the A.C. voltage, and means for making the approximately D.C. load supply voltage independent from the phase angle variation of the A.C. voltage.
According to an embodiment of the present invention, the rectified A.C. voltage is provided between two respectively positive and negative terminals, the circuit including, between the positive terminal and a first terminal of a capacitor across which the approximately D.C. supply voltage of the load is taken, a one-way conduction element, and between the positive and negative terminals, a voltage dividing bridge providing a low voltage proportional to the rectified voltage.
According to an embodiment of the present invention, the circuit includes a means of integration of the rectified low voltage to provide an analog low voltage depending on the phase angle of the A.C. voltage.
According to an embodiment of the present invention, the phase angle variation of the A.C. voltage is performed over at most one half-halfwave and outside charge periods of the capacitor.
According to an embodiment of the present invention, the information is an operating order for an energy converter means to control the load.
According to an embodiment of the present invention, the phase angle variation of the A.C. voltage is performed between 50 and 100% by means of a variator by phase angle cut-off.
According to an embodiment of the present invention, the load is a fluorescent lamp.
The present invention further provides a method of transmission of information over an A.C. supply line of a supply circuit of a load having a capacitive input impedance including a capacitor adapted to providing an approximately D.C. voltage, this method consisting, on the transmitter side, of varying the phase angle of the A.C. voltage over at most one half-halfwave and outside charge periods of the capacitor, and on the receiver side, of isolating the information relative to the phase angle upstream of the capacitor.
The foregoing objects, features and advantages of the present invention, will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings.
REFERENCES:
patent: 4328482 (1982-05-01), Belcher et al.
patent: 4644320 (1987-02-01), Carr et al.
patent: 4868539 (1989-09-01), Foord
patent: 5691605 (1997-11-01), Xia et al.
patent: 5872429 (1999-02-01), Xia et al.
patent: 5999849 (1999-12-01), Cord et al.
Carlson David V.
Galanthay Theodore E.
Seed Intellectual Property Law Group PLLC
STMicroelectronics S.A.
Trieu Van T.
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