MXPA97007847A - Electronic supply switch for two alamb energy - Google Patents

Abstract

The present invention relates to a two-wire power supply switch, connected in series are a load between two poles of electrical power supply of alternating current main conductors, conventionally includes a main triac between two terminals of the switch that is turned on the conduction of an optotriac with a time delay relative to the zero crossing of the voltage between the switch terminals determined by the disruptive voltage of a series of Zener diodes. The switch includes a power supply unit with a rectifier bridge connected to one terminal directly and connected to the other terminal through a capacitor. An auxiliary triac that drifts to the capacitor is turned on by the optotriac on each zero crossing of the voltage between the terminals of the switch. This optimizes conditions when the switch is opened and when the switch closes separately

Description

ELECTRONIC SUPPLY SWITCH FOR TWO ALAM BRES ENERGY BACKGROUND OF THE I NVENTION FIELD OF THE I NVENTION The invention relates to a switch that is to be connected in series with a load between two poles of an electric power supply of main alternating current conductors, which has two terminals to be connected to a pole of the supply of main conductors and to the load, respectively, the load is connected to the other pole of the supply of the main conductors and includes a tripled bidirectional driving main switch connected between two terminals of the switch and an adapted controller, in response to an active state of a control signal, for turning on the main switch with a particular time delay relative to the zero crossing of the voltage between the two terminals of the switch, the controller includes a power supply unit of the rectifier type having a first input directly connected to the first of the two terminals of the switch and a second input connected to the second terminal of the i switch through a capacitor adapted to limit the current in the power supply unit.

DESCRITION OF THE PREVIOUS TECHNIQUE Switches of this type are usually called two-wire power supply switches, because the circuit requires only two wires. Given this, in a circuit of this type, when the main switch is turned on, the instantaneous voltage between the two terminals of the switch, and consequently the instantaneous voltage at the input of the power supply unit, is practically zero, no longer power would be supplied to the controller if the switch was turned on at the time of the zero crossing of the voltage between the two terminals. Consequently, it is turned on with a particular time delay relative to the zero crossing, in such a way that an approximately triangular voltage appears between the terminals of the switch, the peak of which corresponds to the elongation of the voltage between the terminals of the switch in the time that it precedes the triggering of the main switch. The impedance of the load is usually negligible compared to that of the power supply unit of the controller, while the main switch does not turn on the voltage between the terminals of the switch is the supply voltage of the main conductors, which gives As a result, the delay of ignition time and the peak voltage between the terminals of the circuit breaker are closely related. It goes without saying that the controller's power supply unit must provide the latter with a relatively stable DC voltage, despite variations in voltage between the inputs of the power supply unit, depending on whether the switch is open or closed; In addition to the voltage stabilizing components downstream of the rectifier (the seat of the dissipating losses increasing in direct proportion to the suppressed variations), this requires an impedance in series with the input of the power supply unit, advantageously a reactive impedance of so that the energy does not dissipate. In practice, this impedance is obtained with a capacitor, the one referred to above adapting to limit the current in the power supply unit. The current limitation is mainly beneficial when the switch is open, when the voltage between the inputs of the power supply unit is practically the same as the voltage between the poles of the supply of the main conductors, whereas when the switch is closed, the applied voltage between the inputs of the power supply unit is reduced to that of the supply of the main conductors between each zero crossing of the latter and the consecutive ignition of the main switch, that is, during the time delay. During this short period of time, the capacitor must allow enough power to pass to the power supply unit (the more since the controller often consumes more power when the switch is closed). This leads to the use of a relatively bulky and expensive capacitor, unless the ignition time delay is excessively increased. An object of the invention is to reduce the total size of the switch by reducing that of the current limiting capacitor and by reducing the power dissipation in the switch components.

BRIEF DESCRIPTION OF THE INVENTION The above object is achieved with a switch adapted to be connected in series with a load between two poles of a power supply of main conductors of alternating current, which has two terminals adapted to be connected to a pole of such supply of main conductors , and at such a load, respectively, the load is connected to the other pole of such main conductor supply and includes a tripled bidirectional conducting main switch connected between the two terminals and an adapted controller, in response to an active state of a command signal , to turn on such a master switch with a particular time delay relative to the zero crossing of the voltage between such two terminals, the controller includes a rectifier power supply unit having a first input directly connected to the first terminal and a second connected input. to the second terminal through a capacitor adapts In order to limit the current in such power supply unit, where the controller includes an auxiliary two-way fired trip switch that derives such capacitor, the auxiliary switch is turned on at the time of zero crossing of the voltage between such two terminals with such signal of command in an active state. Consequently, when the switch is closed, the capacitor short-circuits the auxiliary switch and does not limit the energy absorbed by the power supply unit; the latter is then in proportion to the energy supplied to the controller, at a DC voltage substantially corresponding to the voltage elongation at the input of the power supply unit at the time the main switch is turned on. The value of the capacitor can therefore be chosen to maintain the voltage rectified by the power supply unit, when the switch is opened, when the voltage between the terminals of the latter is substantially the same as (full wave) voltage between the poles of the supply of main drivers, and no more than this one. Accordingly, both when the switch is closed and when it is open, the power supply unit receives a measured amount of energy to maintain an appropriate value of the rectified voltage it discharges. This reduces the value of the current limiting capacitor, and therefore its overall size, and minimizes the dissipation of energy caused by stabilizing the rectified voltage, which reduces the overall size and cost of the dissipating components. The main and auxiliary switches are preferably triacs with a trigger that triggers conduction in both directions, to minimize the number of switch components. The main switch is preferably turned on by a voltage derived from the voltage between the inputs of the power supply unit that crosses a predetermined level. However, as mentioned previously, the ignition timing delay and the peak voltage at the ignition timing are closely related, the ignition when the voltage crosses a technically preset level is simpler and reduces voltage fluctuations at the input of the power supply unit.

The secondary aspects and advantages of the invention will emerge from the following description given by way of example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic view of a two wire power supply switch of the prior art. Figure 2 is a diagram of the voltages between the poles of the main conductor supply, between the terminals of a two-wire power supply switch, and in the load. Figure 3 is a schematic view of a switch according to the invention.

DESCRI PCIÓ N DETAILED OF THE MODALI DAD PREFERI DA The two-wire power supply switch of the prior art shown in Figure 1 is connected in series with a load 1 between two poles P (phase) and N (neutral) of a power supply of main conductors of alternating current. It has two terminals 2a and 2b, the terminal 2a is connected to the pole P and the terminal 2b to the load 1, the latter is connected to the pole N. A triac 20 constituting the main switch is connected between the terminals 2a and 2b, its trigger 20a is connected to the terminal 2b through two Zener diodes 22a and 22b connected in series and in opposite conduction directions and an optotriac 21. The switch further includes a rectifier 3 comprising a bridge 31 with a first input connected to the terminal 2b directly and a second input connected to the terminal 2b through a capacitor 30 to limit the flow of current through the rectifier point 31. The latter powers a power supply unit 4 which includes a Zener diode 40 whose peak limits the rectified voltage and a filter capacitor 44 on the output side of a diode 43 without return so that the capacitor 44 is charged substantially at the disruptive voltage of the Zener diode 40 (24 volts). The power supply unit 4 has two output terminals, namely a negative terminal 47 and a positive terminal 48, from which the power is supplied to the auxiliary circuits of the switch, constituting with the power supply unit 4 a controller adapted to generate a control signal from the representative data of the chosen conditions under which, in combination, the switch is closed and opened. The power supply unit further includes a ce that controls the closing of the switch that includes a light emitting diode 42 with its anode connected to the positive output of the bridge 32 and its cathode connected through the resistor to the collector of a transistor 41, the emitter of which is connected to the negative output of the bridge 31. The light emitting diode 42 is optically coupled to the optotriac 21 in such a way that the optotriac 21 is turned on by emitting light from the diode 42. The base of the transistor 41 receives a closing command signal from a control terminal 49, the active signal seta is a voltage at terminal 49 that is positive with respect to negative terminal 47. The active state of the command signal in the terminal 49 turns on the transistor 41 and causes the diode 42 to emit light. The optotriac 21 is then turned on by the voltage between its terminals. The optotriac 21 receives the voltage between the terminals 2a and 2b through the Zener diodes 22a and 22b, and the resistor 22c. Accordingly, the optotriac 21, illuminated by the light emitting diode, is turned on when the instantaneous voltage between the terminals 2a and 2b reaches the disruptive voltage of one of the Zener diodes 22a and 22b, in accordance with the direction of the instantaneous voltage between the two terminals 2a and 2b; it will be remembered that Zener diodes conduct voltages in the opposite direction to their disruptive voltages. The conduction of the combination of the optotriac 21, the diodes 22a and 22b of Zener and the resistor 22c injects charges in the trigger of the triac 20 (main switch) that turns it on. This is delayed with respect to the zero crossing of the voltage between the terminals 2a and 2b for a period long enough for the AC line voltage to reach the disruptive voltage of the diodes 22a and 22b. This is clear with reference to Figure 2, in which curve 50 represents the evolution of the voltage between the poles P and N of the main conductor supply, the curve 51 the voltage between the terminals 2a and 2b of the switch and the curve 52 of the voltage at the terminals of load 1. It is not necessary to say that the voltage which is the sum of the curves 51 and 52 is equal to the voltage of curve 50. It is assumed that load 1 has an impedance with practically no reactive component. In consecuense, when triac 20 is not on, the impedance between terminals 2a and 2b is very high compared to that of load 1 and the instantaneous voltage between terminals 2a and 2b is practically equal to the AC line voltage, between terminals P and N, which corresponds to the switch being open. On the contrary, when the triac 20 is on, the voltage between the terminals 2a and 2b is substantially zero and the voltage of the load 1 is practically the AC line voltage between the poles P and N, which corresponds above all to the switch being closed. On the substantially sinusoidal curve 50 the dotted lines 54, 54 ', parallel to the axis of the abscissa, represent the disruptive voltages of the diodes 22a and 22b, respectively. To simplify the figure, the relationship between the disruptive voltages and the amplitude of the AC line voltage is exaggerated. In practice, the disruptive voltages are of the order of 30 volts, while the amplitude of the AC line voltage of 220 volts is approximately 310 volts. The zero crossings of AC line voltage 50, for a complete wave, are points 50a, 50c, 50e. The crossing of level 54 is point 50b and the crossing of level 54 'is point 50d. In curves 51 and 52 the indices are the same for synchronous points. Considering voltage 51, between terminals 2a and 2b of the switch, it can be seen that it increases from zero at point 51 a and separates sharply at point 51 b, because triac 20 is turned on, and remains at zero as far as point 51 c, then decreasing as far as the point 51 d where it reaches level 54 'and goes to zero as far as point 51 e. The voltage 52 is the complement of the voltage 52 for the line voltage AC 50, between the terminals 2a, 2b, that is, zero from the point 52a to the point 52b, where, suddenly increases to the level 54 to reproduce the rest of the half wave up to point 52c at which it falls to zero; it remains at zero as far as point 52d where it goes to level 54 * to reproduce the rest of the second half wave as far as point 52e. Taking into account the ratio indicated in the above between the level of the voltage that turns on the triac 20 and the amplitude of the AC line voltage, the ignition time delay is about 0.73 ms for a supply of 50 Hertz main conductors. The voltage 51 between the terminals 2a and 2b is similar to a series of triangular pulses of alternating signal and short duration, while the voltage 52 at the terminals of the load 1 is practically sinusoidal. However, when the command signal input terminal 49 is at the same potential as the negative terminal 47 of the power supply unit 4 (inactive command signal), the voltage between the terminals 2a and 2b is at all times the line voltage of AC. Accordingly, the rectifier 3 at the input of the power supply unit 4 receives through the capacitor 30, either a full-wave AC voltage 50 or a series of alternating-sign triangular pulses with a low peak voltage and a short duration compared to the period of supply 51 of main conductors, depending on whether the switch is open or closed, respectively. The value of the capacitor 30 must be such that: In the open condition, the voltage between the inputs of the rectifier bridge 31 is limited to avoid overloading the power supply unit, in particular to limit the current in the Zener diode 40 . In the closed condition, the energy injected into the bridge 31 and the power supply unit 4, through the capacitor 30 through the series of triangular pulses 51, must be sufficient to keep the capacitor 34 charged despite the consumption of the controller. In practice, the capacitor 30 must have a value that leads to significant losses in open condition if the controller is to be supplied with power correctly in the closed condition; these losses make it necessary to overestimate the components in question, while the energy dispatched to the controller in the closed condition is limited, which limits the functions of the controller. It may be important to increase the available power in the closed condition by increasing the time delay when the main switch is turned on by increasing the disruptive voltage of the Zener diodes 22a, 22b. This possibility is also limited, however, because the nominal voltage delivered by the power supply unit 4 must be compatible with the estimated voltages of the components used in the controller; the triangular voltage peak (curve 51) is certainly higher than the nominal voltage of the power supply unit, but it must be of the same order of magnitude in such a way that when increasing the voltage at the input of the power supply unit , do not only increase the losses. In the selected embodiment of the invention, shown in Figure 3, a triac 130 derives the capacitor 30 and its trigger is connected to the optotriac 21, the triac 130 constitutes an auxiliary switch. The power supply unit 4 includes, in addition to the transistor 41, which receives on its base the command signal applied to the terminal 49, a second transistor 140d the emitter of which is connected to the negative output of the bridge 31 and the collector of the which is connected to the negative output of this bridge through two Zener diodes in series with the same driving direction, namely, a diode 140a connected to the positive output of the bridge 31 and a diode 140b connected to the collector of the transistor 140d. The common point of the diodes 140a and 140b is connected to a third Zener diode 140c conducting in the same direction as the diode 140a. This Zener diode 140c is connected to a resistor 140g which is connected to the positive output of the bridge 31. The common point of the Zener diode 140c and the resistor 140g are connected to two diodes 140e and 140f respectively leading to the base of the transistor 140d and to the collector of the transistor 41. The operation is as follows: When the command signal is inactive, the triac is turned off and the rectifier 3 receives the full wave from the main conductor supply through the load 1 and the capacitor 30, the latter is estimated only by the rectifier 31 to maintain the load on the capacitor 44.t.

In the power supply unit 4, the transistor 41 is turned off. The base of transistor 140d is connected through diode 140e and resistor 140g to the positive output of bridge rectifier 31, and this transistor is therefore turned on. Serially connected Zener dodos 140a and 140b, each of which has a disruptive voltage of approximately 12 volts, are replaced by the Zener diode 40 of Figure 1, with a 24 volt spark voltage. If an active command signal appears at this time in terminal 49, transistor 41 is turned on and light emitting diode 42 emits light. Optotriac 21 is turned on at the next zero crossing of the voltage between terminals 2a and 2b, optotriac 21 is connected to terminal 2b directly and also through a transistor and rectifier bridge 31 to terminal 2a. The triac 130 is turned on and short circuits the capacitor 30, thus applying the full voltage between the terminals 2a and 2b to the inputs of the bridge rectifier. In parallel to this, the fact that the transistor 41 is turned on, turns off the transistor 140d. The voltage at the output of the rectifier bridge 31 is then limited by diodes 140a (12 volts) and 140c (20 volts) of Zener, connected to series at approximately 32 volts. Insofar as the disruptive voltage of the Zener diodes 22a and 22b is 30 volts, that is, slightly less than the sum of the disruptive voltages of Zener diodes 140a and 140c, the triac 20 (main switch) is turned on just before the Zener diodes 140a and 140c limit the voltage on the bridge rectifier. The operation of the triac 20 is not changed in comparison to the prior art circuit shown in Figure 1. The triac 20 then short-circuits the terminals 2a and 2b of the switch. The voltage on the triac 130 (auxiliary interlocker) is also removed and turned off. The same process occurs in each half wave. Accordingly, the value of the capacitor 30 can be determined exclusively to maintain the voltage provided by the power supply unit 4 between the output terminals 47 and 48 when the switch is open with the control signal in the idle terminal 49. The energy that the controller can absorb when the switch is closed becomes essentially dependent on the time delay for turning on the triac 20 and the value of the filter capacitor 44. Although the description only mentions triacs as the main and auxiliary switches (20 and 130), in particular because the trigger can command after driving in both directions, it is obvious that any semiconductor circuit of fired conduction that allows bidirectional conduction, such As an antiparallel combination of the ti-risistors, it can be used to implement the invention. Furthermore, the invention is of course not limited to the described examples but includes all variant executions thereof within the scope of the claims.

Claims (6)

1K CLAIMS

1 . A switch adapted to be connected in series with a load between two poles of a power supply of main alternating current conductors, having two terminals adapted to be connected to a pole of such supply of main conductors and to such load, respectively, the load is connected to the other pole of such supply of main conductors, and includes a tripled bidirectional driving main switch connected between the two terminals and an adapted controller, in response to an active state of a command signal, to turn on such an interrupter With a particular time delay relative to the zero crossing the voltage between the two terminals, the controller includes a rectifier power supply unit having a first input directly connected to a first terminal and a second input connected to the second terminal to through a capacitor adapted to limit the current in t to the power supply unit, characterized in that the controller includes a bidirectional auxiliary trip switch tripped that derives such a capacitor, the auxiliary switch is turned on at the time of each zero crossing of the voltage between the two terminals with the command signal in a state active.

2. The switch according to claim 1, characterized in that said main and auxiliary switches are triacs with a trigger that triggers conduction in both directions.

3. The switch according to claim 1, characterized in that the main switch is turned on by a voltage derived from the voltage between the inputs of such a power supply unit that crosses a predetermined level.

4. The switch according to claim 3, characterized in that the main switch has a trigger that receives such voltage derived from the voltage at the input of the power supply unit through two Zener diodes connected in series with opposite conduction directions .

5. The switch according to claim 3, characterized in that the power supply includes a rectifier bridge that charges a filter capacitor through a non-return diode and a transistor connected to at least one Zener diode forming a rectified voltage limiter.

6. The switch according to claim 5, characterized in that the controller further includes a transistor adapted to be turned on by the active state of the command signal and connected in series with a light emitting diode connected to the rectifier output upstream of the diode without return and optically coupled to an adapted phototriac, when driving, to turn on the auxiliary switch.