LIGHT CONTROL CIRCUIT FOR INCANDESCENT LAMPS AND NETWORK CONNECTION BLOCKS, INCLUDING A PROTECTIVE AND LIMITING CIRCUIT BREAKER INTENDED FOR ACHIEVING ELECTRONIC SAFETY

Abstract

Brightness control circuit for incandescent lamps and mains connection blocks, incorporating a protective and limiting circuit breaker for electronic safety. In addition to the circuit described in the main patent, the circuit includes an electronic circuit breaker M, C2, which eliminates the need to replace a blown fuse, as would be required with conventional dimmers. Application: Dampening voltage surges in a household circuit.

Description

The main patent application relates to a circuit brightness control for incandescent lamps- cence and to constituent parts of a switching network tion of network connection blocks, this circuit does not include the interference suppression components necessary in triac-type light intensity dimmers. This The control circuit makes it possible to forgo anti- interference used in control devices rants proceeding by phase cutting, which are linked to triacs, and yet obtaining a sufficiently low level of parasitic voltages with in mfe time for noise elimination in the control circuit. It can be applied to a domestic installation. The distinctive feature of the main patent application lies in the fact that a self-locking field-effect transistor, placed diagonally in a bridge-type rectifier, is controlled by a control circuit of a in such a way that the field-effect transistor is conductive the conductor at the zero crossing of the alternating voltage and remains in the conducting state, for an adjustable time, in the control circuit for a desired part of the half- network wave, and then cuts with an appropriately adjusted cutoff curve flank, before occurring the new reset. The invention contained in this application for certificate of addition (hereinafter referred to as "the invention") a no- particularly with the aim of developing the demand proposal of the main patent in such a way that the com- circuit brightness control should be complemented by a type of security electronic circuit breaker. This avoids the need for replacement. The melted fuse, necessary in common light intensity dimmers, for example in the event of a short circuit caused by the combustion of the filament of an incandescent lamp. As the adaptation of disturbance and peak limiting devices, as well as a protective device, are necessary, additional measures concerning the circuit are indispensable, compared to the circuit implementation form according to the main patent application. To solve this problem, the present application specifies that, using an additional Miller capacitor and its corresponding pre-resistor, as well as another capacitor located between a portion of this pre-resistor and ground, the source-to-ground cutoff voltage will follow an S-shaped path with a predetermined slope between the two curved sections of the S. Furthermore, between the source of the metal-oxide-semiconductor field-effect transistor and ground, two resistors will be arranged in series. The resistor in these resistors will be located in parallel with the base emitter region of the transistor and will directly determine the maximum current flowing through it. the transistor by controlling the gate voltage of the transistor field-effect metal-oxide tor, has a resistance value This is lower than the resistance on which the base emitter region of the transistor rests, which causes the monostable flip-flop ("monoflop") to switch off and thus interrupts the current flow in the metal-oxide transistor. field effect; and that the Miller capacitor serves as an element- function doubling to put the metal-oxide field-effect transistor in case of overvoltage- injuries caused by sharp points. The circuit arrangement according to the invention offers the advantage of current limitation in the metal-oxide field-effect transistor connected in the circuit, in the event of a short circuit in the load or discharge due to an overvoltage coupled in the circuit. (points). The additional Miller capacitor can also be formed by other components, such as resistors these automatically varying, transil diodes or similar organs. The pre-resistor corresponding to the Miller capacitor, or the other capacitor mentioned above, can be switched mechanically or automatically between operation with incandescent lamps and operation with a mains connection block, such that, in the case of operation with incandescent lamps, the other capacitor or the pre-resistor corresponding to the Miller capacitor has a lower value, thus resulting in a lower switching time constant. The following, with reference to the attached drawing, describes this by way of illustration and not limitation. an example of the implementation of the protection and limitation circuit tation according to the invention. We show: in Figure 1, the known connection diagram, intended born to the brightness control circuit of incandescent lamps descent and network connection blocks, In Figure 2, the protection and limitation circuit- In the embodiment according to the invention, Figure 3 shows a graphical representation of how the voltage interruption occurs; and Figure 4 shows an automatic switching mechanism designed to reduce power loss while maintaining voltage. parasite at a low level. The block diagram in Figure 1 shows a detailed overview of the brightness control circuit, as described in the main patent application. According to this application, block 1 contains the rectifier GL, the automatically varying resistor (or varistor) V for peak limiting, and the pre-inductor L with a lower inductance than the pre- resistance in the case of fast spikes for resistance- This automatically variable Vs. Block 2 includes the trans- T1 metal-oxide field-effect transistor and the protection and limiting circuit, not shown, as well as: the circuit intended for the formation of the cut flank. Block 3 already includes the power supply known from the monostable flip-flop M, the detection of the half- network wave and, from this, the excitation of the monostable flip-flop at the zero crossing of the network half-wave, as well as the monostable flip-flop itself, whose operating time can be adjusted by means of a potentiometer. Furthermore, N designates neutral, L the line of network, Z a Zener diode, ZC a load diode. An example of an embodiment of the circuit device according to the invention is explained below with reference to Figure 2, the elements for determining the slope of the flank and the necessary interference suppression being shown in detail. This is achieved in particular by means of the elements R1 (pre-resistor), C1 (another capacitor), R2 (pre-resistor) and C2 (Miller capacitor addition- nel), as well as by the Miller capacitance of the metal-oxide field-effect transistor Tl and to a small extent by a resistor R3. If the monostable flip-flop is triggered during the passing through zero does not create parasitic voltage. If there were a break within the half-wave—output A, voltage jump, from H to L—it would occur, in case the absence of the elements mentioned above, a strong tendency parasitic sion. In the case of incandescent lamps, the rise of the drain voltage follows proportionally the va- Current variation of the metal-oxide-semiconductor field-effect transistor T1, after discharge of the high-capacitance Miller capacitor, and the steepest slope of this rise The tension is reached shortly before reaching the ten- maximum sion. The capacitance of capacitor C2, when in circuit, delays the drop in gate voltage through feedback coupling caused by the variation of the / dt of the drain voltage. This is therefore a Miller circuit with, as a pre-resistor, resistor R1 in series with resistor R, and with capacitor C2 as the Miller capacitor. As, due to energy loss in the metal-oxide-semiconductor transistor T1, field, one cannot flatten the flank of the cut at will- re, a supplementary circuit arrangement is necessary- re. The capacitance of the Miller capacitor, located inside- front of the metal-oxide field-effect transistor, deter- The flank is reduced at the beginning of the drain voltage rise, while the capacitance of Miller capacitor C2, along with resistors R1 and R2, determines most of the flank. In this case, C2 is sized so as not to exceed the maximum permissible energy loss for T1. Capacitor C1, along with resistor R1 and its discharge time constant of t - 3T, exerts an influence. on the control voltage in low values, that is- that is, shortly before the metal-oxide-semiconductor transistor The field does not cut off completely. If we measure the voltage source- ce-masse (or source-drain), depending on how the circuit is constructed, we obtain a voltage trace of cut corresponding to the graphical representation appa- rising to figure 3. Figure 3 shows the different tracings in detail. of cutoff voltage appearing under different conditions tions (ordinate U: voltage; abscissa t: time). Curve "a" shows the shape of the cutoff voltage if there is no intervention on the circuit, curve "b" shows this shape when elements C2, R1, and R2 are switched on; while, in curve "c", we takes into account elements C1, C2 as well as R1 and R2. Thanks to the S-shaped curve, which forms during the variation represented by "'c", the harmonic waves are largely reduced, resulting in a 49 dB improvement. In the case of incandescent lamps, the voltage the load decreases immediately with the decrease in neck rant during the interruption, which is equivalent to an increase in the source-to-ground voltage. It thus occurs, on the Miller's C2 capacitor, a back-coupling which is of au- all the greater as the increase in source voltage- mass is large. The ratio, which is established between the variable- The decrease in source-to-ground voltage and the drop in source-gate voltage result in a certain drain current, which decreases over time. In the case of a block for network connection, there are wire- capacities significant factors determine the voltage. When the gate voltage is switched off, the source-to-ground voltage changes only slowly and is far from reaching its maximum value, while the drain current is already completely cut off. The small variation in source-to-ground voltage acts as if there were no Miller capacitor. in the circuit. The current drop is significant- faster than in the case of a load consisting of an incandescent lamp. If, in the case of operation- ment on the network connection block, the side is de- Depending on the parasitic voltage conditions, it becomes flatter with a load consisting of an incandescent lamp. Thus, the parasitic voltage decreases, but the loss increases in the metal-oxide transistor T1. field effect. To avoid this, R1 or C1 can be manually reduced in the case of incandescent lamp operation, so that the parasitic voltage remains within permissible limits, and the power loss corresponds to that of the operating current. with network connection blocks. Figure 4 mon- An automatic switching system is used to reduce losses while maintaining parasitic voltage within permissible limits. When, in the case of operation with a mains connection block, the drain current becomes zero, the source-to-ground voltage rising to the highest point of the mains half-wave is 5150 V in the event of a break. Therefore, if transistor T4 is connected to 2150 V by means of its base control via resistors R11 and R12 on the collector-emitter path, the time constant R11.C1 is reduced to R1 x R13 x C1 R1 + R13 That is to say, in the case of switching in the incandescent lamp range, the voltage variation accelerates when the source-to-ground voltage begins to exceed 150 V. This reduces power loss. In the case of switching in the mains connection block, the switching behavior remains unchanged as long as current flows through transistor T. Field-effect metal-oxide. The voltage slope during current flow and the current characteristic are exactly the same as what occurs without an automatic device. switching. In the circuit layout shown in Figure 2, the The known arrangement R6C3 serves to dampen the peaks of ten- sion which occur, for example in the case of a char- inductive loop. The elements or components R4, R5, T2, T3, R7, and, in addition, the reactions of the monostable flip-flop serve to limit the current when the metal-oxide field-effect transistor T1 is conducting (connected), in the case of a short circuit in the load or discharge. due to peak demand. In a known manner, a source resistor (R4 + R5) is introduced in the current-carrying region of the transistor to allow the voltage across this resistor to be used as a criterion for adjustment. According to the invention, this resistance is represented by R4 and R5, with the value of R4 being greater than that of R5. Since each resistor provides the control voltage for the base emitter region of transistors T2 and T3, it follows that, as the current increases over time, the monostable flip-flop circuit is initially "monoflop" is kept out of the circuit at point "A" by step- sant from "H" to "L" via T3 and this is not that it then ensures the limitation of the direct current- ment on the T1 metal-oxide field-effect transistor, by gate voltage reduction via T2. The current regulated via the U-gate is higher than the normal operating current, and, moreover, this current results directly from the height of the U-gate control voltage, the resistance value RDSoN* of the metal-oxide field-effect transistor will go fast- The current will increase, and despite the fact that the current is kept constant, the power loss on T1 will increase. Thanks to resistor R4, and its higher value than that of R5, we are assured that, in each case, after a short time, the U-shaped gate of the single-position rocker- ble will be switched to zero and, thus, an increase Loss will be prohibited. In addition to this, a voltage limitation is in- This is unnecessary when the metal-oxide-semiconductor field-effect transistor T1 is blocked. The varistor Vs of block 1 in Figure 1 and the RC organ formed by R6 and C3, according to Figure 2, will- wind to this in a known way. But, in the case of impulses rapid es due to poies s containing considerable energy- These measures are insufficient. Capacitor C2 is therefore used here to connect T1 to the circuit. The function of Zener diode D1 is to prevent the gate voltage U from to exceed the Zener voltage. The measure itself, known to eliminate the overvoltage using the T1 switch, is executed. in the case of the circuit of the invention, by means of the condenser- sator C2 which, as mentioned previously, is also essential for determining the slope of the flank. * It can be noted that RDSON designates the resistance inte- higher, on the source-drain path, of the metal- transistor field-effect oxide, when this transistor is conducting teur, however, in figure 1, CO designates in the block III the control circuit.

Claims

DEMANDS 1. A brightness control circuit for incandescent lamps and for network switching components of mains connection blocks, this circuit not comprising the interference suppression elements necessary in triac-type light intensity dimmers, but comprising a self-locking field-effect transistor which, located in the diagonal of a bridge rectifier (GL), is controlled by a control circuit (CO) such that the field-effect transistor (T1) is conductive at the zero crossing of the alternating voltage and remains in the conductive state in the control circuit for an adjustable time on the desired half-wave portion of the mains and then breaks the circuit with a cutoff curve slope set appropriately before the next zero crossing occurs according to claim 1 of the main patent,circuit characterized in that, with the aid of an additional Miller capacitor (C2) and the corresponding pre-resistor (R1 + R2), as well as another capacitor (C1), which is located between a part of this pre-resistor and ground, the voltage, The source-to-ground cutoff adopts a pre- S-shaped path sensing a predetermined slope between the two curved parts of the S, and in that between the source of the tran- siistor (T1) metal-oxide field effect and ground, are arranged in series, two resistors (R4 and R5), the resist- tance (R5) which is located in parallel with the emitting zone base trice of the transistor (T2) and which directly determines- The maximum current flowing through the transistor (T1) is controlled by the transistor's gate voltage -(T1) metal-oxide effect of field, having a lower resistance value than that of the re- resistance (R4), on which the basic emitting zone of the transmission is based sister (T3), which switches off the monostable flip-flop (M) and thereby interrupts the current flow in the metal-oxide-semiconductor field-effect transistor (T1); and in that the capacitor Miller's serves as a function dubbing element for met- to put in circuit the metal-oxide effect transistor (T1) field in case of overvoltages caused by spikes.

2. Brightness control circuit according to the resv- dication 1, characterized in that the condensa- teur (C2) can also be formed by other components healthy, such as automatically varying resistors ("varistor"), transil diodes or similar components.

3. Brightness control circuit according to one of the claims 1 and 2, characterized in that the pre-resist- The resistance (R1) or the capacitor (C1) can be switched mechanically or automatically between operation with incandescent lamps and operation with a mains connection block, such that, in the case of operation with incandescent lamps, the capacitor (C1) or the pre-resistor (R1) has a lower value, thus obtaining a constant of shorter downtime.