"ARRANGEMENT OF A CIRCUIT"
BACKGROUND OF THE INVENTION The invention relates to an arrangement of a circuit for operating a discharge lamp with a high frequency current comprising: - input terminals for connection to a low frequency supply voltage, - a mechanism rectifier coupled to said input terminals to rectify said low frequency supply voltage, - a first circuit consisting of a series arrangement of a first unidirectional mechanism, - a second unidirectional mechanism and a first capacitive mechanism coupled to said first terminal N3 for outputting said rectifier mechanism and to a second terminal N5 for outputting said rectifier mechanism, - an inverter mechanism deriving said first capacitive mechanism for generating the high frequency current, - a charging circuit consisting of an array in series of an inductive mechanism, a second capacitive mechanism and a mechanism to apply a voltage to the discharge lamp; said serial array connects a terminal NI of said inverting mechanism to a terminal N2 between the first unidirectional mechanism and the second unidirectional mechanism, and - a second circuit consisting of a third capacitive mechanism and connecting terminal N2 to terminal N5 . Said circuit arrangement is known from the US document. UU No. 5,404,082. The known circuit arrangement is very suitable to be operated from a regular supply of the main conductor which generates, for example, a supply voltage having a r.m. (Regular supply voltage of main conductor) 230 Volt and a frequency of 50 Hz. The known circuit arrangement has a relatively high power factor that can be achieved with comparatively simple mechanisms. A drawback of the known circuit arrangement is, however, that the total harmonic distortion of the current drawn from the low frequency supply voltage source is greatly increased if the mechanism for applying a voltage to the discharge lamp is not it comprises a transformer and the voltage of the lamp is relatively high. In case, for example, the supply voltage has a r.m. of 230 Volt, the harmonic distortion increases greatly for a lamp voltage greater than approximately 70 Volts. It may be mentioned that there is a similar problem even for discharge lamps that have much lower lamp voltage values in nations such as the United States of America, where the supply voltage has a r.m. of only 120 Volt. This harmonic distortion can be reduced by incorporating a transformer in the mechanisms to apply a voltage to the discharge lamp. In the case, however, that the lamp voltage is relatively high and the mechanism for applying a voltage to the discharge lamp comprises a transformer equipped with a primary winding and a secondary winding provided with terminals for the connection of the lamp both the primary winding and the other components comprising the charging circuit and the inverter have to conduct a relatively large current. This relatively large current can shorten the tare of the circuit arrangement or make it necessary to size the circuit array according to this relatively large current, which is expansive. Another drawback of the known circuit arrangement is that, often, it is necessary to include a frequency modulator in the circuit array to modulate the frequency of the high frequency current generated by the inverter mechanism to correct the amplitude modulations in this circuit. high frequency current and to co-factor the crest factor of the lamp current to a value less than about 1.7. It is an object of the present invention to provide a circuit arrangement that causes a relatively small harmonic distortion of the low frequency supply current., while the circuit arrangement can also operate discharge lamps having a relatively high lamp voltage without the drawback of components comprised in the charging circuit and the inverter having to conduct a relatively large current during the Operation of the Lamp. DESCRIPTION OF THE INVENTION A circuit arrangement according to the invention is characterized, for this purpose, in that the first output terminal N3 of the rectifier mechanism is connected to a terminal N4 between the second unidirectional mechanism and the first capacitive mechanism by means of a third circuit consisting of a serial arrangement of a third unidirectional mechanism and a fourth unidirectional mechanism; and a terminal N7, between said third unidirectional mechanism and between said fourth unidirectional mechanism, is connected to a terminal N6 that is part of the charging circuit by means of a fourth circuit and in which neither the first circuit nor the third circuit consists of mechanisms inductive During the operation of the circuit arrangement, the fourth circuit couples the power from terminal N6 to terminal N7. It has been found that this energy feedback that is carried out with relatively simple mechanisms causes a substantial decrease in harmonic distortion when compared to the harmonic distortion caused by the known circuit arrangement. Correspondingly, the energy factor increases substantially with respect to the energy factor of the known circuit arrangement. Surprisingly, in spite of the feedback carried out by means of the fourth circuit, in a circuit arrangement according to the present invention, the current conducted by the components which are comprised in the charging circuit and the inverter is relatively small, yet in the event that the mechanism for applying a voltage to the discharge lamp consists of a transformer. For this reason, it is not necessary to dimension the inverter and the charging circuit for a relatively large current, and the charging circuit and the inverter circuit can, therefore, be made with relatively inexpensive components. Furthermore, it has been found that it is possible to omit the use of a transformer in the charging circuit of a circuit arrangement according to the invention and to keep the harmonic distortion at a relatively low level, at the same time, even in the case that The voltage of the discharge lamp operated with the circuit arrangement is relatively high. In case the charging circuit does not consist of a transformer, the amplitude of the current flowing through the components of the inverter mechanism and the charging circuit during the operation decreases further with respect to the circuit arrangements according to the other invention comprising a transformer in the charging circuit. Another important advantage of a circuit arrangement according to the invention is that a frequency modulator for modulating the frequency of the high frequency current can also be omitted, since it was found that the amplitude of the high frequency current generated by a The circuit arrangement according to the invention is not strongly modulated and, therefore, the crest factor of the lamp current is relatively low. Both the modulator and, more particularly, the transformer are relatively expensive components so that the possibility of avoiding the use of both in a circuit arrangement according to the invention is another reason why the circuit arrangement according to the invention it has a relatively simple configuration and is, therefore, relatively cheap. It can be mentioned that a circuit arrangement consisting of a double feedback of energy similar to the double energy feedback in a circuit arrangement according to the present invention has been discovered in EP 679046-A1. In the circuit arrangement discovered in this document EP 679046- ^ 1, the improvement of the energy factor is carried out, mainly, by making use of a storage coil. Bliss, storage coil is a rather expensive component. In a circuit arrangement according to the present invention a high energy factor is achieved without making use of a storage coil. For this reason, the operation of a circuit arrangement according to the present invention differs from that found in EP 679046-Al. Further, a circuit arrangement as discovered in the present invention offers a substantial advantage over the discovery of EP 679046-A1 because in the circuit arrangement according to the invention, the storage coil face can be omitted . It has been found that a uniform operation of the circuit arrangement could be carried out in the event that the second circuit also consists of a first capacitive mechanism. A uniform operation of the circuit arrangement was also found for configurations of the circuit arrangement where the fourth circuit consists of a fourth capacitive mechanism. The unidirectional mechanism preferably consists of diode mechanisms. A) Yes, the unidirectional mechanisms are carried out in a very simple way. In a preferred embodiment of the circuit arrangement according to the invention, the reversing mechanism consists of a series arrangement of a first switching element, the Ni terminal and a second switching element, and a coupled DC transmission circuit. to the switching elements to generate a transmission signal to make the switching elements alternately conductive and non-conducting. Therefore, the inverter is made in a simple and reliable way. It has been found that the circuitry according to the invention is very suitable for operating two parallel discharge lamps. In a preferred embodiment of a circuit arrangement according to the invention for operating two discharge lamps, the charging circuit consists of another series arrangement of an inductive mechanism, a capacitive mechanism and a mechanism for applying a voltage to a discharge lamp, and a terminal N8, which is part of the other array in series, is connected to terminal N7 by means of a third circuit. The third circuit, preferably, consists of a fifth capacitive mechanism. In another preferred embodiment of a circuit arrangement according to the invention, the terminal N4 is connected to the terminal N7 by means of a circuit consisting of a switch element S and a control circuit coupled to a control electrode of the element S switch to make the element S conductive and non-conductive switch. The control circuit makes the element S conductive switch when the lamp current is zero, for example, during the pre-heating of the lamp electrodes or during the firing of the discharge lamp. In accordance with the foregoing, an overvoltage on the first layer-cytive mechanism is avoided. After the discharge lamp has been turned on, the control circuit makes the S element non-conductive switch. The control circuit could, for example, comprise a mechanism for detecting a current from the lamp. It has been found, however, that a very simple and reliable way of constructing the control circuit is to equip said control circuit with a mechanism to make the element S conductive and non-conductive switch depending on the voltage on said first capacitive mechanism . DESCRIPTION OF THE DRAWINGS The embodiments of the invention will be explained in more detail with reference to the drawings, in which: Figure 1 is a simplified schematic diagram of a first embodiment of a circuit arrangement according to the present invention with a lamp The discharge connected to the circuit arrangement; Figure 2 is a simplified schematic diagram of a second embodiment of a circuit array according to the invention with two discharge lamps, LA1 and LA2 connected to the circuit array, and Figure 3 is a simplified schematic diagram of a third embodiment. of a circuit arrangement according to the present invention, with a discharge LA lamp connected to the circuit arrangement. DETAILED DESCRIPTION OF THE INVENTION In Figure 1, Kl and K2 are the input terminals for connection to a low frequency supply voltage source. L2 and L2 'are inductors that form an input filter together with capacitor C3. The diodes D1-D4 are rectifying mechanisms for rectifying said low frequency supply voltage. In this embodiment, diodes D5 and D6 form the first and second unidirectional mechanism, respectively. Capacitor C4 is a first capacitive mechanism and forms, together with diodes D5 and D6, a first circuit. The elements Ql and Q2 switches, together with the DC transmission circuit form the inverting mechanism. The transmission circuit DCO is a part of the circuit for generating transmission signals to make the Ql and Q2 elements conductive and non-conductive switches. The inductor Ll, capacitor C2 and terminals K3 and K4 for connecting a discharge lamp together form a charging circuit. In the embodiment shown in Figure 1, the inductor Ll forms the inductive mechanism, the capacitor 2 forms the second capacitive mechanism and the terminals K3 and K4 to connect to a discharge lamp form the mechanism to apply a voltage to the discharge lamp . The capacitor Cl forms the third capacitive mechanism. Capacitor Cl and capacitor C4 together form a second circuit. The diodes D7 and D8 form, respectively, the third and fourth unidirectional mechanisms. The series arrangement of diodes D7 and D8 forms a third circuit. The capacitor C5 forms the fourth capacitive mechanism and also a fourth circuit. The input terminals Kl and K2 are connected by means of a series arrangement of the inductor L2, the capacitor C3 and the inductor L2 ', respectively. A first side of the capacitor C3 is connected to a first input terminal of the bridge rectifier and a second side of the capacitor C3 is connected to a second input terminal of the bridge rectifier. A first output terminal N3 of the rectifier bridge is connected to a second output terminal N5 of the rectifier bridge by means of a series arrangement of diode D5, diode D6 and capacitor C4. N2 is a common terminal of diode D5 and diode D6. N4 is a common terminal of diode D6 and capacitor C4. Terminal N2 is connected to terminal N4 by means of capacitor Cl. The series arrangement of diodes D5 and D6 is derived by a series arrangement of diodes D7 and D8. N7 is a common terminal of diodes D7 and D8. The capacitor C4 is derived by a series arrangement of the elements Ql and Q2 switches. A control electrode of the switch element Ql is connected to a first output terminal of the transmission DC circuit. A control electrode of the switch element Q2 is connected to a second output terminal of the transmission DC circuit. NI is a common terminal of the element Ql switch and element Q2 switch. The terminal NI is connected to the terminal N2 by means of a series array of, respectively, the inductor Ll, the capacitor C2, the terminal K3, the discharge lamp LA, and the terminal K4. N6 is a common terminal of capacitor C2 and terminal K3. Terminal N6 is connected to terminal N7 via capacitor C5. The operation of the circuit arrangement shown in Figure 1 is as follows: When the input terminals Kl and K2 are connected to the poles of a low frequency supply voltage source, the rectifier bridge rectifies the supply voltage of the rectifier. low frequency supplied by this source so that a DC voltage is present on capacitor C4 that serves as a buffer capacitor. The DC transmission circuit makes the Ql and Q2 elements switches, alternatively conductors and non-conductors, and as a result a substantially square wave voltage having an amplitude approximately equivalent to the amplitude of the DC voltage on the capacitor C4 at the terminal NI is presented. The substantially square wave voltage present at terminal NI causes an alternating current to flow through inductor Ll and capacitor C2. A first part of this alternating current flows through terminals K3 and K4, discharge lamp LA and terminal N2. The remaining part of this alternating current flows through capacitor C5 and terminal N7. As a result, both. In the terminal N2 as in the terminal N7, voltages are presented that have the same frequency as the substantially square wave voltage. These voltages present at terminal N2 and at terminal N7 cause a pulsing current to be drawn from the supply voltage source also when the voltage on capacitor C4 is higher than the current amplitude of the rectified low supply voltage. frequency. For this reason, the energy factor of the circuit arrangement has a relatively high value and the total harmonic distortion of the supply current is relatively low. It can be mentioned that similar results were obtained for a configuration of a circuit array slightly different from the configuration shown in Figure 1, in which capacitor Cl connects terminal N2 with terminal N5 instead of terminal N. In this slightly different configuration, capacitor Cl forms the third capacitive mechanism and a second circuit. In a practiced embodiment of the invention as shown in Figure 1, the dimensions were as follows: Ll = 905 μH, C5 = 5.6 nF, Cl = 38 nF, C4 = 11 μF, C3 = 220 nF and C2 = 180 nF, L2 = 1 mH and L2 '= 1 mH, With this incorporation a low pressure mercury discharge lamp was operated with a nominal power of 58 Watt. The lamp voltage of this lamp was 110 Volt. The frequency of the substantially square wave voltage was about 50 kHz and the energy consumed from the low frequency supply voltage source was 52.3 Watt. The low frequency supply voltage source was a European main conductor supply that supplied 230 Volts of r.m. with a frequency of 50 IIz. The current of the lamp was 452 mA r.m.s .. The crest factor of the current of the lamp was 1.43. The current through the switching elements is 591 mA r.m.s .. The total harmonic distortion was less than 10%. It was found that when the same low pressure mercury discharge lamp was operated by means of a circuit arrangement known as described in the US document. UU No. 5,404,082, and was equipped with a substantially identical input filter, a transformer was needed in the charging circuit to maintain the total harmonic distortion level of less than 10%. When the value of r.m.s. of the current through the low pressure mercury discharge lamp operated by means of the known circuit arrangement was approximately equivalent to 452 mA, the current through the switching elements was approximately 798 mA r.m.s .. The value r.m.s. The current through the switch elements was therefore 35% higher than when a circuit arrangement according to the invention was used. The embodiment shown in Figure 2 is largely similar to the embodiment shown in Figure 1. Similar components and circuit parts with the same reference numbers are indicated in both figures. The charging circuit of the embodiment of Figure 2 consists of another series arrangement of the inductive mechanism, the capacitive mechanism and the mechanism for applying a voltage to a discharge lamp, formed respectively by the inductor L3, layer-citor C3, and terminal K5 and terminal K6. A discharge lamp LA2 is connected to terminals K5 and K6. In order to achieve clarity, the discharge lamp connected to terminals K3 and K4 is indicated by LA1 in Figure 2. Terminal K6 is connected to terminal K4. An N8 terminal between the capacitor C6 and the terminal K5 is connected to a first side of the capacitor C7. Another side of capacitor C7 is connected to N7. The capacitor C7 forms in this embodiment both a fifth circuit and a fifth capacitive mechanism. The operation of the embodiment shown in Figure 2 is similar to that of the embodiment shown in Figure 1 and will not be described separately. The embodiment shown in Figure 3 differs from the embodiment shown in Figure 1 in that a switch element S connects terminal N4 with terminal N7. A control electrode of the switch element S is coupled to an output terminal of the circuit part ST. In Figure 3 this is indicated by a dotted line. Capacitor C4 is derived by a series arrangement of resistor Rl and resistor R2. A common terminal of the resistor R1 and the re-sistor R2 is connected to an input terminal of the circuit part ST. The embodiment shown in Figure 3 is also equipped with a bale mechanism to preheat the electrodes of the discharge lamp before ignition. These mechanisms consist of the secondary windings L2 and L3 of coil Ll and capacitors C6 and C7. Each of the electrodes of the lamp is derived by a series arrangement of a secondary winding and one of the capacitors C6 and C7. The operation of the embodiment shown in Figure 3 is as follows. Before the discharge lamp is turned on, the electrodes of the lamp are pre-heated for a predetermined period of time by making the switching elements conductive and non-conductive at a frequency at which the impedance of the capacitors C6 and C7 It is relatively low. Both during this pre-heating and during the ignition phase, the amplitude of the voltage on the capacitor C4 is increased to a value that is higher than the value during the stationary operation of the discharge lamp. This higher amplitude is caused by the fact that the lamp current is zero while the energy is fed back by capacitor C5. The voltage to the input terminal of the ST part of the circuit is proportional to the voltage over capacitor C4. When the voltage on the capacitor C4 reaches a first predetermined value, the circuit part ST makes the switch element S conductive so that the diode D8 is shorted, so that another voltage increase on the capacitor C4 is avoided. When after the firing of the discharge lamp, the amplitude of the voltage on the capacitor C4 drops below a second previously determined value (lower than the first predetermined value), the circuit part ST makes the element S non-conductive. switch so that the energy feedback is activated by capacitor C5. The operation of the embodiment shown in Figure 3 during the stationary operation is identical to that of the embodiment shown in Figure 1 and will not be described again.