FR2465372A1 - SEMICONDUCTOR SWITCHING SYSTEM FOR COUPLING A DIRECT CURRENT SUPPLY CIRCUIT TO A LOAD - Google Patents

Abstract

THE DC POWER SUPPLY CIRCUIT IS CONNECTED TO A LOAD VIA A POWER TRANSISTOR 10 TAKEN TO SATURATION BY PERIODIC RECURRENCE PULSES HAVING A SEPARATION TIME BETWEEN SUCCESSIVE PULSES LESS THAN THE STORAGE TIME OF THE TRANSISTOR. AS A RESULT OF ITS STORAGE TIME, THE TRANSISTOR 10 REMAINS SATURATED IN THE ABSENCE OF BASIC CURRENT BETWEEN PULSES AND MAINTAINS A CONTINUOUS COUPLING OF THE DC POWER SUPPLY CIRCUIT 12 AT THE LOAD 14. WITH INTERMITTENT BASE CURRENT, A SIGNIFICANT POWER IS SAVED NOT ONLY IN THE BASE CONTROL CIRCUIT, BUT AGAIN IN THE TRANSISTOR ITSELF.

Description

The present invention relates to a semi-switching arrangement

conductor for controlling the supply of direct current energy to a load. A

well-known arrangement of the prior art consists in connecting

  ter the emitter-collector path of a power transistor in series with the load and the power source in

  direct current. When you want to pass the tran-

  sistor in the conductive state to apply the energy in flow

dant continuous to the load, a direct current is permanently supplied to the base-emitter junction so as to bring the transistor to its saturation mode and to maintain it there. In fact, the transistor operates as a relay. A basic current

of relatively small amplitude controls the flow of the col-

  high value reader or charging current. However, this switching arrangement of the prior art consumes a fairly large power, it wastes energy and

is ineffective.

  The present invention provides a significant improvement to the switching arrangements of the prior art

  for the connection of power supply circuits

  continuous to charge circuits, since the arrangement of the present invention not only has a construction

simple and inexpensive, skinny consumes very little power

and is highly effective.

2. The semiconductor switching system of the present invention makes it possible to control the application to a

load of a DC voltage produced by a supply circuit

DC statement. The system includes a transis-

  power tor comprising a base, a transmitter and a collector and having a predetermined storage time. A means is provided for coupling the supply circuit in

  direct current and the load in series with the con-

  emitter-collector duction of the transistor. A source of impulse

sions periodically produces recurrence pulses

  having a separation time between successive pulses in-

  lower than the storage time of the transistor.

mutation also includes a way to apply the impulses

  between the base and the emitter and bring the transistor to

  saturation, which has the effect of coupling the supply circuit

tation in direct current to the load and to apply the voltage

continuous voltage transistor remaining saturated between successive pulses so as to maintain a continuous application of

the DC voltage at the load.

  The present invention will be well understood during the

following description made in conjunction with the attached drawing,

  which represents the diagram of the device of the present invention

  tion. A transistor 10 is an NPN power transistor

  classic capable of withstanding very high intensities.

  A DC power supply circuit 12 (represented schematically by a simple battery) can comprise a DC voltage source of fixed value,

be variable. For example, in one of the app-

of the present invention, circuit 12 can

  be a source with a voltage of approximately 300 volts. At ti-

In another example, the device of the present invention can be incorporated in an inverter where four switching transistors, such as transistor 10, pass to the state

conductive and non-conductive in pairs and in a sequence

this predetermined so as to alternate the polarity of the voltage

  continuous load applied to a load, thereby delivering effective

3.

tive single-phase alternating power to the load.

In this type of application incorporating an inverter, the ampli

Study of the DC voltage supplied by the supply circuit 12 can be adjustable so as to vary the amplitude of the AC voltage produced by the inverter.

Depending on the practical application. from the pre-

  invention 14, the charge 14 can take different forms

  and include resistors, inductors and / or conden-

  sators. For example, when transistor 10, and three au-

  very similar transistors, operate as switches

in an inverter, the output of this inverter can be

  fitted with a single-phase alternating induction motor to control rotation. In this case, charge 14 would be a

inductive load.

  The load 14 and the DC power supply circuit 12 are connected in series with the collector 16 and the emitter 17 of the transistor 10. Like the transistor

  is normally non-conductive, it acts as a normal switch

  improperly opened to maintain the disconnection between the circuit

power supply 12 and load 14. The switch is closed, to apply the DC voltage from the

source 12 to load 14, providing base 18 with a

  rant of sufficient amplitude to bring the transistor to saturation, moment o an impedance of very low value

  will be present between the collector 16 and the emitter 17.

To control the operation of transistor 10, a source of controlled pulses 20 produces periodically

positive direction recurrence pulses, with a frequency

relatively high repeat rate. Preferably, the

  frequency will be at least 100 kilohertz. The amplitude of each

  that positive direction pulse will be high enough to bring the transistor to saturation. Therefore, each

  once you want to connect load 14 to the supply circuit

  ment 12, the source 20 can be appropriately controlled so that a series or train of periodic recurrent pulses is applied between the base 18 4. and the emitter 17 to bring the transistor to saturation and the

  make it conductive. When the device of the present in-

  vention is found in the environment of an inverter, the

  pulse source 20 will be controlled by the logic circuits

conventional, so as to bring the four transistors (identical to the transistor) to the conductive and non-conductive state

) at the correct times.

  A particular characteristic of the present invention lies in maintaining the transistor in its state

  saturated during the application of a series of pulses dis-

aunts of each other, although the base current is

deleted between pulses. This is accomplished by uti-

  reading of the load storage characteristic of the tran

sistor. When a transistor is brought to saturation by the current of its base, the minority carriers accumulate in the regions of the base and of the collector and these carriers

must be scanned, for example by recombination or ab-

sorption, after the termination of the basic current before the transistor leaves its state of saturation and becomes nonconductive. This process of removing minority carriers requires a finite time interval which is called "storage time". While in many transistor applications, the storage time has a significant drawback, this property is advantageously used in the present invention. The specific duration of the storage time for a given transistor is determined by

  several factors on which it depends, for example by the ty-

eg of transistor, the amplitude of the emitter-collector current

or charging current, the junction temperature and the impe

  external dance coupled between the base and the transmitter.

  Whatever the storage time of the particular power transistor used, the pulse source 20 must be designed so that the pulses emitted have a separation time (i.e. the time interval between the edge back of one pulse and the front edge of the next pulse) less than this storage time. The

  waveforms, frequencies, and duty cycle of pulses

2 / i65372 5. sions can be various, and the switching system can still operate according to the present invention as long

  that the separation time between successive pulses ap-

  plicated at the base-emitter junction is less than the storage time of the transistor. Under these conditions, the minority carriers will maintain the transistor 10 in its saturated state, between pulses, when the base current

is absent. Therefore, whenever the source 20 ap-

  apply a series of pulses between base 18 and the transmitter

  17, the transistor 10 remains saturated between successive pulses

ves and maintains the continuous application of a DC voltage supplied by the supply circuit 12,

chargeable 14.

  Thanks to the use of an inter-

mittent in order to keep the transistor in its

conductive state, significant energy savings are obtained

  held both in the control circuit of the base and in the transistor itself. When the base current is zero between pulses, the power consumed in the base-emitter junction will also be zero. In addition, no basic current flowing in the junction, the voltage

  base-transmitter will be lower than it would be in present

this of a basic current. As a result, the voltage emits-

  collector falls during the time intervals between

be impulses and this has the effect of reducing dissipation

  of power in the transistor in the conduction path

  emitter-collector. In addition, using a command

  by train of pulses instead of continuous control, savings are made in the construction of the control circuit. For example, the size of the supply circuit for controlling the base can be reduced since less power is dissipated in the base-transmitter junction.

  The present invention is not limited to the examples

ples of realization which have just been described, it is on the contrary susceptible of variants and modifications which

will appear to those skilled in the art.

6.

Claims (1)

  1 - Semiconductor switching system for applying a DC voltage supplied by a DC power supply circuit to a load, characterized in that it comprises: - a power transistor ( 10) with a   base (18), a transmitter (17) and a collector (16) and present both a predetermined storage time; - a means for coupling the DC power supply circuit (12) and the load (14) in series with the emitter-collector conduction path of the transistor; - a pulse source (20) for periodically producing recurrence pulses having a separation time between successive pulses less than the storage time of the transistor; - and a means for applying the pulses between   the base and the emitter in order to bring the transistor to saturation   tion, which has the effect of coupling the DC power supply circuit to the load and applying the   direct current voltage, the transistor remaining saturated in-   be successive pulses so as to maintain an application permanent cation of the DC voltage at the load.