Power-supply and communication

Details Power-supply and communication Power-supply and communication

1996-10-16

1998-08-25

Nguyen, Matthew V.

Electric power conversion systems

Current conversion

Including d.c.-a.c.-d.c. converter

H02M 3335

Patent

active

057989133

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to a power-supply and communication circuit for an electrical apparatus, comprising: a first electrical unit, a second electrical unit which receives electric power from the first electrical unit via a transformer having a primary and a secondary winding, the secondary winding supplying a secondary alternating voltage, and means for transmitting data signals between the first electrical unit and the second electrical unit via the transformer.
The invention also relates to an electrical apparatus comprising such a power-supply and communication circuit. The invention further relates to a handle for a vacuum cleaner, the handle comprising the second electrical unit, and to a suction part for a vacuum cleaner, the suction part comprising the second electrical unit.
2. Description of the Related Art
Such a power-supply and communication circuit and electrical apparatus are known from U.S. Pat. No. 5,081,738, which discloses a vacuum cleaner with motor power control having control switches on a handle. The control switches form part of a second electrical unit in the handle, which is powered from a first electrical unit in the canister via a transformer. The primary winding of the transformer forms part of an LC resonant circuit which is driven by an oscillator. The voltage across the secondary winding is rectified and powers the second electrical unit. In the second electrical unit a capacitor is connected in parallel with the secondary winding and the value of this capacitor can be influenced in response to the control switches on the second electrical unit. A change in the capacitor value causes the resonant frequency of the LC circuit to change, as a result of which the amplitude of the voltage across the LC circuit at the primary side of the transformer changes likewise. This amplitude variation is detected and further processed. In this way the second electrical unit receives power from the first electrical unit and data communication is possible from the second electrical unit in the handle to the first electrical unit in the canister.
When the prior art power-supply and communication circuit is used in a vacuum cleaner, the impedance of the connecting wires in the hose between the secondary winding of the transformer and the second electrical unit in the handle is included in the LC resonant circuit. This hose impedance is subject to spread. The impedance of the transformer itself also exhibits a substantial spread. The influence of the spreads complicates the design and may lead to inaccurate results. Moreover, the prior art power-supply and communication circuit is only suitable for data communication from the second unit to the first unit.


SUMMARY OF THE INVENTION

It is an object of the invention to provide an accurate power-supply and communication circuit.
A first aspect of the invention is characterized in that the power supply further comprises a switching element in series with the primary winding, which switching element has a control terminal for receiving control pulses for periodically turning on and turning off the primary winding, and in that the power-supply and communication circuit further comprises at least one combination from a first combination of first means for obtaining a suppression of said periodically turning on and off of the primary winding in response to a first data signal generated in the first electrical unit and second means in the second electrical unit for detecting of fluctuations in the secondary alternating voltage as a result of the suppression, and a second combination of third means for actively modulating the secondary alternating voltage in response to a second data signal generated in the second electrical unit, and fourth means in the first electrical unit for detecting fluctuations in a primary alternating voltage across the primary winding as a result of the modulation of the secondary alternating voltage.
It is a second aspect of the invention to provide an electrical apparat

REFERENCES:
patent: 5081738 (1992-01-01), Schiller et al.
patent: 5708572 (1998-01-01), Bergk

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