DE4330114A1 - Control circuitry for several discharge lamps - has central control unit with bus connector to ballasts with Zener diode overvoltage protection for transmit/receive branches - Google Patents

Abstract

A central control circuit (5) for several ballast units (3) for discharge lamps (4) has a bus connector (1). Each ballast or coupling unit has a receiving branch to convey information from the central unit to the lamp and a transmitting branch to convey information back to the central unit. The information is in the form of a modulated alternating or pulse voltage. An overvoltage protection device is provided in one or both of these branches. This device consists of a Zener diode with a transistor pair which decouples the branch from the bus in the event of overvoltage. There is a another rapid- acting zener diode for overvoltages of very short duration. ADVANTAGE - Minimal power consumption with overvoltage protection.

Description

The invention relates to a circuit arrangement for controlling a plurality by consumers such as lamps. Especially when using Gas discharge lamps require each of these lamps to have its own ballast Gas discharge lamp to supply the necessary ignition or operating voltage. When using a large number of such lamps, it is advisable to use the respective Ballasts from a central control unit via a central data line head for.

From GB 2,072,467 A, on the basis of the preamble of claim 1 is known, a circuit arrangement in which a central control unit via a data bus is connected to several peripheral units, their functions can be controlled via the data bus. Each peripheral unit has one Coupling unit, which is divided into a receiving branch and a transmitting branch is. The receiving branch is used to transmit information from the central Control unit to the peripheral unit, the central control unit information in the form of a modulated AC or pulse voltage to the data bus. Of the Transmitter branch is used to transmit information from the peripheral unit the central control unit. The information is obtained by varying the Output resistance of the transmission branch from the peripheral unit to the data bus.

Furthermore, EP 0 490 329 A1 describes a circuit arrangement for controlling the Brightness and the operating behavior of gas discharge lamps known. Here a central control unit controls a large number of data buses Ballasts for gas discharge lamps. Each ballast is over one Coupling unit connected to the data line. In doing so, the data line Data via a capacitor circuit or by means of a transmitter to the respective Ballast transmitted. Should feedback signals from the ballast to the Central control unit are transmitted when there is no data on the Data line are present, a coupling of these signals from the ballast in the Data line possible via the same coupling unit.

Both known circuit arrangements have the possibility of using appropriate control signals to bring the peripheral unit into an idle state, in which it has only a reduced current, but the receiving branch remains the  Coupling unit fully activated even in the idle state, which means the data bus is charged even if there are no signals. This leads especially if a large number of peripheral devices are used, one at a time considerable power consumption in the central unit.

Furthermore, it is disadvantageous in both circuit arrangements that the coupling unit can easily be damaged by overvoltage on the data bus. This can for example, happen when the circuit arrangement is more common House installations, such as lamp systems, is installed. An accidental Connect the data bus with a mains voltage line - 220 volts or 380 volts - would damage the coupling unit of the circuit arrangement immediately, thereby the whole arrangement would be out of order.

The invention is therefore based on the object of a circuit arrangement for Controlling a plurality of consumers of the type described in the introduction to train that always with minimal power consumption, a safe operation is guaranteed.

This object is achieved with those specified in claim 1 Means solved.

Accordingly, the coupling unit has a receiving branch for the transmission of Control information from the central control unit to that of the coupling unit assigned consumers and a transmission branch for the transmission of Feedback information from the consumer to the central control unit. It is also provided that both the receive branch and the transmit branch in the coupling unit has protection against overvoltages. So there is always a ensures safe operation of the circuit arrangement.

According to claims 2 to 6 are easy to set up advantageous embodiments of the Surge protection described in the transmission branch, wherein according to claims 3 and 4 an additional protective device against overvoltages at the output of the transmission branch is described, which is provided in the event that the provided according to claim 2 Switch does not disconnect the transmission branch sufficiently quickly from the bus.

According to claims 7 and 8, a further development of the surge protection is Receiving branch described.  

According to claims 9 to 11, an advantageous development is that the Consumers and the central control unit on a common data line are connected, which means the circuitry for connecting the consumer to the central control unit is minimized. Since the consumers of the data line in the respective coupling units are galvanically isolated is an undesirable Avoidance of equalizing currents avoided, using an optocoupler enables the transmission of rectangular signals without the need for a transformer have to use, which are significantly more expensive to buy.

According to claims 12 to 15 is a further advantageous embodiment of the Invention given that the central post unit when it does not Data signals on the data line outputs a signal whose voltage level is different from the voltage level of the data signals. This will Coupling device signals that the central post device is not in the Send but is in the receive state, which makes it possible in a simple manner is, by means of a switching device, for example with a Zener diode, in the To switch the coupling unit to inactive.

According to claims 16 to 18, an advantageous further development is given by that the power consumption in the coupling device, for example, with a a constant current source formed by a MOS field effect transistor is monitored so that in the case of incorrect wiring or a defective component, another Employment of the circuit arrangement is avoided.

Finally, there is an advantageous development of the invention according to claims 19 and 20 in that the coupling unit has reverse polarity protection, which is formed, for example, with a rectifier bridge circuit. In this way the connection of the coupling unit to the data line is simplified and at the same time damage to the coupling unit or the consumer Incorrect connection protected. The rectifier bridge circuit brings in particular Connection with the optocouplers has the advantage that the coupling unit Square wave signals can be transmitted largely without distortion.

The invention will be described in more detail below with reference to the drawings explained.  

It shows:

Fig. 1 is a block diagram of the circuit arrangement,

Fig. 2 is a circuit diagram of an embodiment of the circuit arrangement,

Fig. 3 (a) and (b) variations to the exemplary embodiment of FIG. 2.

In Fig. 1 a block diagram is shown in which a central unit or central control unit 5 is connected to a data bus or a data line 1. Furthermore, several coupling units 3 are connected to the data line 1 , which couple the data line to the consumers 4 . The signals output by the central control unit ( 5 ) on the data line are thus also present at the inputs of all consumers 4 . It is therefore necessary, if individual consumers are to be controlled, to code the data signals in a consumer-specific manner. For data transmission from the data line to the consumer, the coupling unit has a receiving branch for a connection directed to the consumer. Analogously to the data transmission from the consumer to the data line, there is a connection directed from the consumer to the coupling unit, which forms a transmission branch.

In FIG. 2 a circuit diagram is shown for one embodiment of the circuit arrangement, wherein two connection points between components is referred to as the node with the reference numerals of the components. The central control unit 5 is connected to the data line 1 formed from a two-wire line, the central control unit 5 having a signal generator which generates rectangular data signals, which in this case have a peak level of 12 V. Furthermore, a DC voltage generator DC with an internal resistance Ri is provided, which emits a DC voltage of 4 V. Both generators generate their signals against a common ground potential, to which one of the two connections of the data line is also connected. A control switch S is connected with its movable working contact to the second connection of the data line and is connected with its fixed selection contacts to one output of each of the two generators.

At the other end of the data line 1 , an electronic ballast EVG for, for example, a gas discharge lamp is coupled with its coupling unit 3 . At the interface between the data line 1 and the electronic ballast, there is first a rectifier bridge circuit BR on the device side, ie in the coupling unit 3 . The AC voltage connections of the bridge circuit are connected to the interface, while the connections +/- are connected to the subsequent components of the coupling unit 3 . A self-conducting MOS field-effect transistor T3 is connected to its drain connection to the plus connection of the bridge circuit BR. A resistor R3 is connected in parallel between the gate connection and the source connection. At the same time, a series circuit consisting of a PTC thermistor RK, a Zener diode ZD1, a resistor RV and an optocoupler V2 is connected between the resistor R3 and the minus connection of the rectifier BR, the anode connection of the Zener diode ZD1 via the resistor RV is connected to the anode connection of the transmitter diode of the optocoupler V2. For the sake of simplicity, the minus connection of the bridge rectifier BR is referred to below as the minus line. Furthermore, a series circuit is connected between the node R3 / RK and the negative line, which consequently consists of a transistor T1, resistors R1 and R5 and the output of an optocoupler V1. Here, the transistor T1 is connected with its collector to the positive connection of the bridge rectifier BR and with its emitter connection to the resistor R1. At the base terminal of transistor T1 is the collector of a transistor T2, the emitter of which is connected to the negative line. At the same time, one terminal of a resistor R4 is connected to the collector of transistor T2, while the other terminal is connected to node RK / ZD1. A Zener diode ZD3 is connected to its cathode at the same node, while a resistor R6 is connected in series with its anode to the minus connection of the bridge rectifier. A resistor R2 is connected between the base connection of the transistor T2 and the node ZD3 / R6. Furthermore, a parallel circuit comprising a Zener diode ZD4 and a transistor T4 is connected between the node R1 / R5 and the negative line, the Zener diode with its cathode contact and the transistor T4 with its collector being connected to this node. The emitter of transistor T4 is connected to the minus line and the base connection at node R5 / V1. Finally, a Zener diode ZD2 is connected with its anode to the negative lead and with its cathode to the node RK / ZD1. On the receiving side of the optocoupler V2, the connections of the receiving transistor are connected to the data input lines DS and Gnd of a control unit 4 of the electronic ballast, while on the transmitting side of the optocoupler V1 the connections of the transmitting diode are connected with connections of error feedback lines RS and Gnd of the control unit 4 of the electronic ballast are. According to the exemplary embodiment shown in FIG. 2, the respective ground lines Gnd of the data line and the error feedback lines can be combined and implemented as a common ground line Gnd.

The mode of operation of the circuit arrangement described above with reference to FIG. 2 is explained below. If the central control unit 5 is in the transmission mode, data signals are generated by the square-wave signal generator in accordance with the desired transmission data. These have a signal level of 12 V and are routed to data line 1 via the setting switch S. Because the bridge circuit BR is located at the input of the coupling unit 3 , the polarity of the signal generator or the connection arrangement of the data line 1 with the central control unit or with the electronic ballast is of no importance. Thus, the signals picked up by the coupling unit 3 are always conducted with the correct polarity to the transmission diode of the optocoupler V2. Here, by converting the electrical signals into light signals and converting the light signals into electrical signals at the receiving end, there is a galvanic separation between the control unit 4 of the electronic ballast and the data line 1 . The data signals forwarded in this way are led to the processing devices of the control unit 4 and processed there in the usual way.

If the central control unit 5 does not send any data signals to the data line 1 , the setting switch S switches over to the DC voltage generator DC. A DC voltage of, for example, 4 V is now present on the data line 1 , which signals the readiness for reception of the central control unit 5 to the electronic ballast, the polarity of the DC voltage generator DC also being of no importance as a result of the bridge rectifier BR in the input of the control unit. Characterized in that the Zener diode ZD1 has a Zener voltage, the value of which is lower than the signal level of the data signal generator and greater than the level of the DC voltage generator DC, for example 4.7 V, the receiving unit of the central control unit 5, the optocoupler V2 by means of the Zener Diode ZD1 switched off. The transmission diode of the optocoupler V2 thus does not consume any electrical energy that has to be supplied via the data line 1 when the central control unit is in the receiving mode.

If the 4 V DC voltage emitted by the DC voltage generator DC is present on the data line 1 , this is determined by the Zener diode ZD3 as an allowable voltage if the Zener voltage of this Zener diode is between 15 V and 20 V. The transistor T1 is now controlled via the resistor R4, as a result of which the voltage forwarded by the rectifier BR is present on the data line between the collector and emitter of the initially blocking transistor T4 via the resistor R1. Because the collector / base section of the receiving transistor of the optocoupler V1 is in reverse polarity, only the reverse current of the receiving transistor is conducted on this circuit branch, so that as long as no data are to be output from the electronic ballast into the data line, also from the optocoupler V1 does not consume any significant current to be supplied via the data line. As soon as a signal from the control unit of the electronic ballast via the feedback signal line RS, such as an error feedback, is to be transmitted to the central control unit, these signals are sent out via the transmission diode of the optocoupler V1. In analogy to the data transmission in the optocoupler V1, these signals are also first converted into optical signals and then recovered as electrical signals, as a result of which the connection between the control unit 4 of the electronic ballast and the data line 1 is also galvanically isolated. The conductivity of the receiving transistor is modulated by the reception of the optical signal emitted by the transmission diode of the optocoupler V1, which switches the transistor T4 to conductive via the voltage drop across the resistor R5, which places a load on the DC voltage generator DC in the central control unit 5 . This load is determined and evaluated in the central control unit 5 at the resistor Ri.

The maximum current consumption of the coupling unit 3 is limited by the self-conducting MOS field effect transistor V3. This is inherently conductive without a signal between the gate connection and the source connection. Due to a current flowing through the drain-source path and thus also through the resistor R3, a voltage drop occurs at a resistor R3, which at the same time causes a voltage signal between the gate connection and the source connection. In accordance with this signal, the conductivity of the transistor T3 is reduced, as a result of which the current consumption of the coupling unit 3 is restricted. This current limitation essentially serves as a safety device which is intended to prevent damage to the components in the coupling unit if an incorrectly dimensioned signal source is connected to the interface of the coupling unit 3 . The current flow through the optocoupler V2 is limited by the resistor RV. Since a current limiting device is already provided with the MOS field effector T3, this resistance RV itself can be omitted. However, since the MOS field-effect transistor T3 serves to limit the current of the receiving transistor of the optocoupler V1 and the transmitting diode of the optocoupler V2, the use of the resistor RV is recommended on the one hand because of the differences in components and because of the strong temperature dependency of the MOS field-effect transistor T3. The same applies analogously to the resistor R1.

The constant current source with the MOS field effect transistor T3, as shown in FIG. 3, can also be replaced by other circuit arrangements which represent constant current sources or current limiting devices. For this purpose, temperature-stable circuit arrangements should preferably be selected. Should be able to dispense completely with the protective effect of this current-limiting device, so the constant current source may, as in Fig. 2 and Fig. 3 is indicated by dashed lines, can be omitted, whereby also easy to replace the constant current source would be conceivable by a resistor.

As soon as an impermissibly high voltage is present at the input of the coupling unit 3 , this is short-circuited by the Zener diode ZD2, which has a Zener voltage of, for example, 20 volts. In this way, the impermissibly high voltage in the receiving branch of the coupling unit 3 is derived in front of the optocoupler V2. In the exemplary embodiment specified, voltages which are above 20 volts are therefore defined as an impermissibly high voltage. However, this definition depends entirely on the permissible limit values of the optocoupler V2, so that the Zener diode ZD2 must also be dimensioned accordingly in a differently selected optocoupler.

In the transmission branch of the coupling unit 3 , the Zener diode ZD3 first recognizes that an inadmissibly high voltage is present, as a result of which it becomes conductive, so that a voltage drops across the resistor R6 and is supplied to the base of the transistor T2 via the resistor R2. This becomes conductive and short-circuits the base-emitter voltage of the transistor T1, so that it switches off and changes into a non-conductive state. In this way, impermissibly high voltages are kept away from the transistor T4 and the optocoupler V1 in the transmission branch of the coupling unit 3 . Since the previously described switching off of the transmission branch does not take place sufficiently quickly in some cases, the Zener diode ZD4 is additionally provided for the brief occurrence of an overvoltage.

When using Zener diodes as overvoltage protection, care must be taken that the Zener diode must simultaneously carry a high current when discharging an overvoltage, as a result of which a large amount of electrical energy is converted into thermal energy in the Zener diode. This can easily damage the Zener diode, which would then open the connection if it melted, which would lead to the elimination of the proposed overvoltage protection. For this reason, the PTC thermistor RK was provided in the receiving branch of the coupling unit 3 , which initially has a very low resistance, but with a permanently high current flow, its resistance value increases along with its heating. In this way, if there is a permanent overvoltage, it is taken over by the PTC thermistor RK and the current flow through the Zener diode ZD2 is limited. Analog protection of the Zener diode ZD4 is not necessary, since at the latest when the circuit arrangement with the transistors T1 and T2 is switched off, the Zener diode ZD4 no longer dissipates overvoltage. Furthermore, it should be pointed out that for the transmission branch of the coupling unit 3 , overvoltage protection only from a Zener diode with a PTC thermistor does not work satisfactorily. The PTC thermistor would interfere too much with the transmission of signals to the data bus, since a flow of high currents is provided for the function of the transmission branch, which is determined by the resistance modulation by means of the transistor T4. A PTC thermistor in the transmission branch of the coupling unit would, in the event that the resistance of the transistor T4 is varied with, for example, a rectangular curve, lead to a smoothing of this curve. When monitoring the load on the DC voltage source DC at the resistor R1 in the central control unit 5 , such loops could lead to the reception in the central control unit 5 being disturbed.

As shown by the dashed line in FIG. 2, any number of similar electronic ballasts can be connected to the data line 1 via respective coupling units 3 . The result is an arrangement as shown in FIG. 1. The advantage of the circuit arrangement described is particularly evident when using a large number of such electronic ballasts. Without switching off the transmission diode of the optocoupler V2, the DC voltage generator DC would be constantly loaded with a DC signal, which would make an unnecessarily high dimensioning with regard to the load capacity of the DC voltage generator DC in the central control unit 5 necessary when using many devices. In the circuit arrangement described above, on the other hand, when the central control unit 5 is in the receiving mode, the DC voltage generator is only loaded in the event of a feedback coming from one of the electronic ballasts. The outlay for the DC voltage wave DC in the central control unit 5 can thus be minimized, which considerably reduces the manufacturing costs for such an arrangement.

Claims (20)

1. Circuit arrangement, comprising a central unit, for example a central control unit ( 5 ), and a plurality of peripheral units ( 3 , 4 ) connected to it via a bus ( 1 ), for example control units ( 4 ) for lamps, each are connected to the bus ( 1 ) via a coupling unit ( 3 ), each coupling unit ( 3 ) having a receiving branch for transmitting information from the central unit ( 5 ) to the peripheral unit and a transmitting branch for transmitting information from the peripheral -Unit to the central unit ( 5 ), the central unit ( 5 ) providing information in the form of a modulated AC or pulse voltage to the bus ( 1 ) and the transmitting branch thereby providing information to the bus ( 1 ), that the output resistance of the transmission branch is varied, characterized by an overvoltage protection circuit for the reception and / or transmission branch. 2. Circuit arrangement according to claim 1, characterized in that a switch (T1) controlled by an overvoltage detector (ZD3, T2) is arranged in series with the transmission branch, which opens in the event of overvoltage and decouples the transmission branch from the bus ( 1 ). 3. Circuit arrangement according to claim 2, characterized thereby that between the switch (T1) and the transmission branch a fast circuit breaker (ZD4) is provided, which derives a brief overvoltage. 4. Circuit arrangement according to claim 3, characterized, that the fast circuit breaker is a Zener diode connected in parallel to the transmission branch (ZD4) whose Zener voltage is below a permissible for the transmission branch There is tension. 5. Circuit arrangement according to one of claims 2 to 4, characterized, that the overvoltage detector has a Zener diode which is used for the Transmitter permissible voltage switches the switch (T1) and when detected  an overvoltage activates a first transistor (T2) which switches (T1) switches non-conductive. 6. Circuit arrangement according to one of claims 2 to 5, characterized, that the switch arranged in series with the transmission branch has a second transistor (T1) is. 7. Circuit arrangement according to one of the preceding claims, characterized, that a Zener equipped with an overload protection Is connected diode that derives overvoltages occurring at the receiving branch. 8. Circuit arrangement according to claim 7, characterized, that the overload protection is a PTC thermistor, which leads to parallel connection Receiving branch and Zener diode (ZD2) is connected in series. 9. Circuit arrangement according to one of the preceding claims, characterized in that the central control unit ( 5 ) is either switched into a transmission mode or into a reception mode and has an output device which has at least one signal indicating the transmission mode of the control unit ( 5 ) or a reception mode the control unit ( 5 ) outputs signal. 10. Circuit arrangement according to one of the preceding claims, characterized in that when the control unit ( 5 ) is not in operation, the transmitting branch of the coupling units ( 3 ) is constantly active and the receiving branch of the coupling units ( 3 ) is inactive and consumes no or only a very small quiescent current. 11. Circuit arrangement according to one of the preceding claims, characterized in that each coupling unit ( 3 ) both in the receiving branch and in the transmitting branch each have a transmission device which galvanically separate the data line from the consumer. 12. Circuit arrangement according to claim 11 characterized, that the respective transmission device is formed with an optocoupler (V1, V2) is. 13. Circuit arrangement according to claim 12, characterized in that each coupling unit ( 3 ) has a switching device which puts the receiving branch of the coupling unit ( 3 ) in the inactive state when the central control unit ( 5 ) does not output the signal indicating the transmission mode. 14. Circuit arrangement according to claim 13, characterized, that the switching device has a switch, the switching state of Voltage level of the signals coming from the data line depends. 15. Circuit arrangement according to claim 14, characterized, that the switch is formed with a Zener diode (ZD1). 16. Circuit arrangement according to one of the preceding claims, characterized, that a current limiting circuit is provided in the coupling unit, which maximum current consumption of the coupling unit determined. 17. Circuit arrangement according to claim 16, characterized, that the current limiting circuit is formed by means of a constant current source. 18. Circuit arrangement according to claim 17, characterized, that the constant current source contains a MOS field effect transistor (T3). 19. Circuit arrangement according to one of the preceding claims, characterized in that the coupling unit ( 3 ) for connection to the data line ( 1 ) has reverse polarity protection. 20. Circuit arrangement according to claim 19, characterized, that the reverse polarity protection is formed with a rectifier bridge circuit (BR).