FR2458941A1 - POWER SUPPLY CIRCUIT - Google Patents

Abstract

POWER SUPPLY CIRCUIT IN WHICH THE PRIMARY CURRENT OF A TRANSFORMER IS SWITCHED AND TURNED OFF IN ORDER TO KEEP THE OUTPUT LEVEL AT A DESIRED VALUE. WHEN THE SUPPLY CURRENT IS TURNED OFF, AN ADDITIONAL CURRENT IS SENT TO TRANSFORMER 11 IN ORDER TO KEEP CORE 14 AT A MAGNET LEVEL SUCH AS THE ENTIRE HYSTERESIS STROKE OF THE TRANSFORMER IS USED DURING THE FOLLOWING ALTERNATION . APPLICATION TO POWER SUPPLY CIRCUITS WITH TRANSFORMATION OF ALTERNATIVE CURRENT INTO CONTINUOUS VOLTAGE.

Description

The invention relates generally to power supplies

  and more particularly to a power supply of the type in which the primary current of a transformer is turned on and off in order to regulate the output voltage. Many circuits and electronic systems

  require a supply of continuous voltages which are

  stable even when the source voltage and / or the load imposed on the system are likely to vary. The

  source of energy is often a source of alternating

  native, either single-phase or three-phase. A simple DC power supply for use with a

  single-phase AC voltage includes a redundant diode

  which is combined with a capacitive filter. The redevelopment

  may be alternating or double alternating or may be in bridge and is usually connected to the source of

  direct current through a transformer.

  Unfortunately, this simple DC power supply is sensitive to variations on the one hand of the voltage of the alternating current source and on the other hand of the

load connected to it.

  Voltage regulators are often used to reduce the effect of variations of the input AC voltage on the DC output voltage. A "switching regulator", for example, detects the output voltage and

  switches on and off the input current with a coeffi-

  cient of use that maintains the output voltage at

  desired level. While these regulators are bringing about an improvement

  the effect of the transformer of the energy source with poor efficiency, since only a small part of the hysteresis curve of the transformer is

  used during each alternation of the input current.

  So you need a transformer with a larger core than

  the one that would otherwise be needed.

  The subject of the invention is a source of food

  a new and improved method and a process using a larger part of the hysteresis curve so that

  the transformer can operate more efficiently

  ciency. According to the invention, an additional current of

  magnetization is applied to the transformer in order to maintain

  Nit the core to a predetermined level of magnetization when the primary current is cut. This transformer can therefore be smaller than those of the power sources of the prior art. Therefore, according to an essential feature of the invention, the transformer comprises a core of material

  magnetizable and a regulator varies the coefficient of use

  the feeding current applied to the processing

  by connecting and cutting the current periodically so that this current does not arrive in the transformer for a limited part of each alternation. An additional current is applied to the transformer in order to

  maintain the kernel at a predetermined state of magnetization

  the interval between successive applications of the feed stream so that the hysteresis curve

  be used on a larger part.

  The invention will be described in more detail with reference to the accompanying drawings by way of non-limiting example and in which - Figure 1 is a block diagram of a mode

  of a power supply according to the invention.

  -vention; FIG. 2 is a graph representing two alternations of the input voltage and illustrating the mode of

  operation of the voltage regulator of the form of

  tion of Figure 1; and - Figure 3 is a graph showing the

  transformer hysteresis curve of the exemplary embodiment

of Figure 1.

  FIG. 1 represents a power source comprising a transformer 11 comprising a winding of the primary 12, a winding 13 of the secondary and a core 14

  of magnetizable material, for example iron.

  An AC source applies power to the transformer via an induction coil 16 and a triac 17 connected in series on the primary. The induction coil is intended to limit the instantaneous amplitude of the current in the primary circuit and the triac is a switch which switches on and off the primary current so as to regulate the output voltage of a current. way that will be

  explained in more detail later.

  The secondary of the transformer comprises a central plug 19 which is connected to ground and diodes 21 and 22 are connected between the terminals of the secondary and an output terminal 23 so as to form a full-wave rectifier. It must be obvious, however, that it is possible to use any other suitable rectifier, for example a half-wave rectifier or a bridge rectifier. A filter capacitor 24 is connected between the

output terminal and ground.

  A voltage regulator 26 detects the voltage at which the output terminal is located and sends a control signal to the triac control electrode 17 to maintain the voltage applied to the output terminal at the desired level. The regulator 26 and the triac 17 form what is sometimes called a "switching regulator" and the operating mode of this circuit will be well understood from Figure 2. The regulator makes the triac passing during the second and fourth quadrants of each cycle of the feed stream, as represented by the

  shaded areas 28 and 29 of Figure 2. Where the

  The emitter detects that the output voltage is too low, the triac is turned on earlier in the cycle, and when the output voltage is too high, the triac is turned on later. Thus, the regulator and the triac regulate the utilization coefficient of the primary current of

  to maintain the output voltage at the desired level.

  A circuit applies additional current to the transformer during the time intervals during which the primary current is cut in order to keep the core in a magnetization state such as the transformer

  works on a larger part of his hys-

  teresis he would not do in the absence of this circuit. This circuit comprises a capacitor 31 and a resistor 32 connected in series on a part of the secondary winding of the transformer. When the primary current is in circuit, the capacitor is charged by the secondary current.

  when the primary current is interrupted, the conden-

  sateur returns the current to the winding. The resistor connected in series with the capacitor prevents it from discharging too quickly and ensures that the current delivered in this capacitor remains during the time interval during which the current of the primary is cut. In an example of a power supply in which the secondary voltage is 350 volts, the capacitor 31 may have a value of 4 microfarads and the resistor 32 may have a value of

  350 ohms. In the embodiment shown, the condensation

  The teacher understands at the secondary level a single spire and

  The magnetizer is connected to terminals of half of this turn. The invention can be used, of course, for transformers that can have any number of turns and the capacitor can be connected to the terminals of the

  all or part of any of the turns.

  It is however preferable to connect the capacitor to a relatively low voltage winding in order to reduce the dimensions of the necessary capacitor. Thus, for example, when the primary of the transformer is under 220 volts and the secondary is under 3500 volts and two turns of the

  are at 350 volts, the capacitor is

  neatly connected to one of the turns under 350 volts.

  The mode of operation and implementation of the power source and the corresponding method of the invention will be described with reference to FIG. 3. This figure shows the relationship between the magnetization force H which is a function of the current of the primary and the magnetization or density of the B-stream of the nucleus. The current induced in the

  secondary is of course a function of the density of the flow.

  In the absence of the capacitor 31 and the resistor 32, each cycle would begin in the vicinity of the center of the hysteresis curve, either at the point a, or at the point b, according to the polarity of the supply current during the previous alternation. For a positive alternation, for example, the magnetization level would begin at point a and rise to point c at the moment the triac is turned on. When the sinusoidal supply current reaches the zero value and the triac ceases to pass at the end of the positive half cycle, the magnetization of the core should fall to the level of

  point b. During the next alternation, the magnet level

  should arrive at point b when the triac is passed and returned to point a when the triac ceases

  to be initiated. With this mode of operation, the transformation

  only one part of the hysteresis curve and the

  Transformer response is limited accordingly.

  The capacitor 31 and the resistor 32 being connected to the secondary, the capacitor 31 charges during the active part of each alternation, that is to say when the triac is turned on. When the triac stops

  to be passing, the capacitor delivers current to the second

  to maintain the core at a level of

  mantation that is superior to that which is possible without additional current. During a positive alternation, the magnetization level of the nucleus starts at point a ', then reaches point c and falls back to point b'. During a negative alternation, the magnetization level begins at point b ', then reaches point d and falls back to point a'. The points a 'and b' are placed further away from the origin or center of the hysteresis curve than points a and b and the transformer operates over a larger part of the curve at each half-cycle. alternately. Increasing the oscillation or the use of the hysteresis allows

  to get a desired answer with a smaller kernel.

  For a given power supply in which the principle of the invention is implemented, the transformer must contain for example only about two-thirds of the

  iron that would be needed without the capacitor.

  The foregoing description shows that the invention

  The invention provides an improvement to the device and the method of power supply. It is also understood that the invention has only been described by way of example and that various modifications can be made to the circuit

  described and represented without leaving his domain.

Claims (3)

  1. A power supply circuit, characterized in that it comprises a transformer (11) comprising a core (14) of magnetizable material, a regulating device (17) for varying the coefficient   using the feed current applied to the trans-   trainer by plugging and cutting this periodic current-   in such a way that the current is sent to the transformer only during a limited portion of each alternation of the current and a device (31) for applying an additional current to the transformer in order to maintain the core in a predetermined state of magnetization during the time interval between applications   successive stages of the feed stream.   2. Power supply circuit according to   claim 1, characterized in that the application device   cation of an additional current consists of a condensation   tor (31) connected in parallel with a winding (13) of the trans-   former. Power supply circuit according to Claim 2, characterized in that a resistor (32) is connected in series with the capacitor (31), the resistor and capacitor being connected in parallel to each other. the winding (13) of the transformer.