WO2002087067A1

WO2002087067A1 - Electronic supply device for electronic-switching motors

Info

Publication number: WO2002087067A1
Application number: PCT/EP2002/004448
Authority: WO
Inventors: Fernando Lina
Original assignee: Bitron S.P.A.
Priority date: 2001-04-24
Filing date: 2002-04-23
Publication date: 2002-10-31
Also published as: ITTO20010393A0; ITTO20010393A1

Abstract

An electronic supply device for small motors (M) of a brushless type used, in particular, for ventilation of refrigerators and freezers, basically comprises an electronic drive circuit, in which there is provided an ac-to-dc converter through a phase-variation conduction; in this way, the performance features of the circuit are independent of the mains voltage (V), and hence the device enables production of a motor (M) which has high efficiency, is self-regulating, and provides a number of performance features, which are obtained simply by varying a reference voltage (Vx).

Description

ELECTRONIC SUPPLY DEVICE FOR ELECTRONIC-SWITCHING

MOTORS

The present invention relates to the production of an electronic circuit

designed for small brushless motors of the sort used, in particular, for the

ventilation of refrigerators and freezers.

There currently exist numerous solutions, present on the market, for

electronic supply circuits for brushless motors.

However, all these circuits present a number of substantial drawbacks, which limit their convenience of use, such as, in particular, a high influence of the supply voltage on the performance, the need to diversify the models according

to the supply voltage itself and to the performance features, as well as a low

static torque.

A purpose of the present invention is therefore to provide an electronic supply device for electronic-switching motors which will overcome the drawbacks referred to above, and, in particular, to provide an electronic supply

device for electronic-switching motors which will enable a substantial

insensitivity to the variation of the supply voltage to be obtained, thus guaranteeing, at the same time, good overall efficiency.

A further purpose of the present invention is to provide an electronic supply

device for electronic-switching motors, which will enable a self-regulating

operation to be obtained, so reducing, at the same time, the number of variants

of the models that may be used, according to the performance features and to the type of mains-power supply (for example, 120 Vac for the US market and 230 Vac for the European market). Yet a further purpose of the invention is to provide an electronic supply

device for small brushless motors of the sort used, in particular, for the

ventilation of refrigerators and freezers.

Not the least important purpose of the present invention is to provide an

electronic supply device for electronic-switching motors at relatively contained

costs, on account of the advantages achieved, at the same time guaranteeing a substantial reliability of operation.

The above purposes are ensured by an electronic supply device for

electronic-switching motors according to Claim 1, to which the reader is referred for reasons of brevity.

Advantageously, the purpose of the solution according to the present invention is to obtain an electronic supply circuit for small brushless motors

which affords high efficiency and which is substantially insensitive to any variation in the power-supply voltage. In addition, a self-regulating operation is provided, as well as a reduction in the number of variants of models that can be built according to the use for which they are designed.

Further purposes and advantages of the present invention will emerge clearly

from the ensuing description and from the attached drawings, which are

provided purely by way of explanatory, non-limiting example of embodiment, in which:

- Figure 1 represents a preferred, but non-limiting, example of an electronic

circuit used for an electronic supply device for electronic-switching motors according to the present invention; - Figures 2 and 3 are schematic representations, in cartesian form, of the

qualitative plots in time of important electrical quantities measured in the

electronic circuit illustrated in Figure 1, according to the present invention.

With reference to the figures mentioned above, the electronic supply circuit,

represented in detail in Figure 1, according to a preferred, but non-limiting,

example of embodiment, consists essentially of an ac-to-dc converter, obtained through a phase-variation conduction.

In particular, the a.c. supply voltage V is brought to the negative input of the comparator A through the voltage divider formed by the resistors Rl and R2,

whilst, to the positive output of the comparator A is brought the voltage V_x

which falls on the resistor R3 via the voltage divider R3, R4. This combination of signals leads to excitation of the MOS transistor, designated by Ml, only for an interval of time, for each mains-voltage half-period, in which the gate voltage V_G of the MOS Ml assumes a pulse-like pattern.

The voltage pulse VG occurs in a time interval Tl (see, in this connection, Figure 2), corresponding to the intersections M, N between the waveform of the voltage V_x and the waveform of the voltage Vo (designated by Vo is a voltage equal to the mains voltage V reduced by the voltage divider Rl, R2; namely V₀

= V-R1/(R1+R2)).

The circuit of Figure 1 further comprises a diode D3 used for blocking the

negative portion of the waveform of the mains voltage V, as well as a diode D4, which is inserted for preventing excitation of the MOS transistor Ml during the trailing edge of the waveform of the mains voltage V. Finally, a capacitor Cl is connected to the circuit, through one terminal, by

means of the diode Dl and, trough the other terminal, by means of the MOS

transistor Ml.

In this way, the voltage V_c at which the capacitor Cl is charged and which

supplies the brushless motor M is given by the equation:

where No = V R1/(R1+R2),

from which we obtain:

Figure 3 represents, in the form of a graph, the waveforms for the gate voltage V_G of the MOS transistor Ml (conduction period of Ml) and for the voltage Vc taken across the capacitor Cl and the motor M.

In this way, it is possible to obtain a supply voltage for the brushless motor M, given by the product of a reference voltage (in the case in point, Vx) and a constant (in the case of the circuit illustrated in Figure 1, equal to (R1+R2)/R1). This solution enables the performance features of the brushless motor M to be

obtained, these performance features being independent of the mains supply (in

effect, the voltage Vc is independent of V), as well as enabling a number of performance features to be obtained from one and the same brushless motor M.

In particular, a high conversion efficiency is achieved, owing to the fact that

the only dissipative element (namely the MOS transistor Ml) always operates in

conditions of saturation.

Furthermore, a self-regulating operation and a high static torque (higher than

the steady torque) are achieved, these advantages being typical of a motor of the type of the brushless motor M, which is supplied at a constant voltage that is

independent of the mains-supply voltage.

The electronic circuit described thus enables a supply of the windings of

small brushless motors to be obtained, given by the product of a reference

voltage and a constant, in such a way that the performance features of the motor will be independent of the mains voltage.

The above fact makes it possible to propose the same motor, without any

variant, both for the European market (where there is a mains voltage of 230 Vac) and for the US market (where there is a mains voltage of 120 Vac), and

finally enables a brushless motor having a number of performance features, obtained simply by varying a reference voltage, to be provided.

From the foregoing description the characteristics of the electronic supply device for electronic-switching motors, which forms the subject of the present invention emerge clearly, as likewise are clear the advantages afforded.

In particular, the aforesaid advantages are represented by:

- high efficiency

- insensitivity to any variation of the power supply voltage;

- self-regulating operation; and

- reduction in the number of variants.

Finally, it is evident that numerous other variations can be made to the electronic supply device in question, without thereby departing from the

principles of novelty inherent in the inventive idea, just as it is clear that, in the practical embodiment of the invention, the materials, the shapes and the

dimensions of the items illustrated may be any whatsoever according to the requirements, and the said items may be replaced with other technically

equivalent ones.

Claims

1. An electronic supply device for electronic-switching motors (M) of the type

comprising an electronic drive circuit, in which there is provided an ac-to-dc

converter through a phase-variation conduction; in this way, the performance

features of the circuit are independent of the mains voltage (V) and depend uniquely on the reference voltage (Vx).

2. The electronic device according to Claim 1, characterized in that said mains

voltage (V) is brought to the negative input of a comparator (A) through at

least a first voltage divider (Rl, R2), whilst, at least one portion of the said reference voltage (Vx) is brought to the positive output of said comparator (A) via a second voltage divider (R3, R4) in such a way as to enable excitation of a dissipative element (Ml), at least for a predetermined time interval, for each mains-voltage half-period, in which a voltage signal (V_G) at input to said dissipative element (Ml) assumes a pulse-like pattern.

3. The electronic device according to Claim 2, characterized in that the voltage pulse (V_G ) occurs in a time interval (Tl) corresponding to the intersections (M, N) between the waveform of said reference voltage (V_x) and the waveform of

at least one portion (Vo) of said mains voltage (V).

4. The electronic device according to Claim 2, characterized in that said circuit

comprises at least one first component (D3) used for blocking the negative portion of the waveform of the mains voltage (V), as well as at least one second

component (D4), which is inserted for preventing excitation of said dissipative

element (Ml) during the trailing edge of the waveform of the mains voltage (V),

and at least one capacitor (Cl), connected to said dissipative element (Ml) and connected in parallel to the motor (M), in such a way that the supply voltage of

said motor (M) is given by the product of said reference voltage (Vx) and a

constant, in order to obtain performance features of said motor (M) that are

independent of the mains voltage and a number of performance features from one and the same motor (M).

5. The electronic device according to Claim 4, characterized in that said

dissipative element (Ml) consists of at least one MOS transistor (Ml), which always operates in conditions of saturation.

6. The electronic device according to Claim 4, characterized in that said motor (M) is supplied at a constant voltage that is independent of the mains voltage

(V), in such a way that a single model can be proposed both for the European market and for the US market.

7. The electronic device according to Claim 1, characterized in that said drive circuit supplies small brushless motors that are used, in particular, for ventilation of refrigerators and freezers.

8. An electronic device for supplying electronic-switching motors, as described

and illustrated in the attached drawings and for the purposes herein specified.