Control of lighting devices with a central AC/DC cascaded converter

0001The present invention relates to the control of a plurality of illuminant operating devices starting from a central unit.

0002The invention goes from one in <figref idref="f0002">Fig. 2</figref> schematically represented system. In this example, the illuminant is a gas discharge lamp 5, which is controlled by an electrical ballast (EVG) 1 as an operating device. In a conventional manner, this electronic ballast 1 has a rectifier 2 with a power factor correction circuit (PFC, Power Factor Correction), an electrolyte storage capacitor 4 and an HF inverter 3, which in turn controls the gas discharge lamp 5 via its output circuit 6. The DC voltage (bus voltage) is therefore only available within the ECG.

0003In addition, an emergency lighting control 7 can be provided.

0004The rectifier 2 in the electronic ballast 1 is usually supplied with alternating voltage 9, for example mains voltage.

0005At the same time, it is known to control the electronic ballast 1 via a digital or analog bus control 8 in order to thus start, dim or switch off the lamp 5. It should be noted that with this prior art, each lamp operating device (ECG 1) has its own rectifier 2 with a PFC circuit. Such a PFC circuit is known to reduce disturbing harmonics in the input current. On the other hand, these inverters with PFC 2, which are provided locally in each ECG 1, represent a considerable cost factor that severely limits the trend towards extremely cost-effectively manufactured ECGs.

0006In the scientific publication "Analysis and Design of a Modular, High Power Converter with High Efficiency for Electrical Power Distribution Systems" published by the IEEE Institute in 2002, L. Heinemann describes a modular high-performance converter, which consists of three common converter modules, whereby each module is made up of a high-frequency transformer with high insulation capacity. The converter allows redundant operation in the event of a module failure. Furthermore, the modular structure of the converter guarantees simple and quick adaptation to different voltages with different power / frequency values.

0007The documents <patcit id="pcit0001" dnum="WO03102890A2"><text>WO03 / 102890 A2</text></patcit>, <patcit id="pcit0002" dnum="US20030142060A1"><text>US2003 / 0142060 A1</text></patcit>, <patcit id="pcit0003" dnum="WO0230828A"><text>WO02 / 30828</text></patcit>, and <patcit id="pcit0004" dnum="US20020171379A1"><text>US2002 / 0171379 A1</text></patcit> each describe methods for controlling illuminant operating devices with PFC units which supply at least one illuminant operating device by means of a DC output circuit.

0008Accordingly, the starting point for the present invention is to propose a control for illuminant operating devices, which enables cheaper manufacturing of operating devices.

0009The central point of the invention is that the rectifier / PFC unit is no longer provided locally in each operating device, but rather centrally for several operating devices. According to the invention, the connection between this central unit and the individual operating devices takes place via a DC output circuit.

0010In particular, the present invention is concerned with the aspect of using a central cascaded AC / DC converter in a central unit. This converter can provide a variety of output voltages for operating lamps in a flexible manner.

0011More specifically, the above object is solved by the features of the independent claims. The dependent claims further develop the central idea of ​​the invention in a particularly advantageous manner.

0012According to a first aspect of the present invention, a method for controlling illuminant operating devices by means of a central rectifier / PFC unit is provided. This central unit supplies at least one illuminant operating device by means of at least one DC output circuit. The DC output circuit enables unidirectional or bidirectional communication between the central unit and the lamp control gear. According to the invention, the central unit for load adaptation of the DC output circuit has a central AC / DC converter which is constructed from a plurality of PFC modules connected in parallel, to which a rectifier is connected upstream.

0013For this purpose, the PFC modules can feed at least one cascaded DC / DC converter which consists of converter modules which can be interconnected in different ways and which can provide different output voltages.

0014At least one cascaded DC / DC converter can be used for the central dimming of the lamp control gear.

0015At least two converter modules can be connected in parallel.

0016The individual converter modules can have different input voltages.

0017In addition, the individual converter modules can be activated and deactivated.

0018The switch-on time or the switch-on frequency of the individual converter modules can vary.

0019The PFC modules or the converter modules can be identical and can be designed as plug-in modules.

0020At least one converter module connected in parallel and / or at least one PFC module connected in parallel can serve as a redundant module.

0021A redundant module can replace a failed module. The replacement for changing the output voltage of the DC output circuit can be carried out and done automatically or manually.

0022A PFC module and a fuse module can be provided in the central unit for each line.

0023According to a further aspect of the present invention, a control system for illuminant operating devices is provided. The control system has a central rectifier / PFC unit which supplies at least one illuminant operating device by means of at least one DC output circuit. The DC output circuit enables unidirectional or bidirectional communication between the central unit and the lamp control gear. According to the invention, a central AC / DC converter comprising a plurality of PFC modules connected in parallel is used to adapt the load of the DC output circuit in the central unit, which is preceded by a rectifier.

0024Further features, advantages and properties of the present invention will now be explained in more detail with reference to the figures of the accompanying drawings and the following detailed description of exemplary embodiments of the invention.<dl id="dl0001"><dt>Fig. 1</dt><dd>1 shows a schematic view of a control system according to the invention for illuminant operating devices with a central rectifier / PFC unit and DC output circuit,</dd><dt>Fig. 2</dt><dd>1 shows an operating medium configuration for gas discharge lamps known from the prior art,</dd><dt>Fig. 3</dt><dd>1 shows a central unit having a central cascaded AC / DC converter formed from PFC modules and a plurality of DC output circuits according to an embodiment of the present invention,</dd><dt>Fig. 4</dt><dd>shows a central unit having a central cascaded AC / DC converter, wherein parallel PFC modules feed a cascaded DC / DC converter,</dd><dt>Fig. 5</dt><dd>shows a detailed cascaded DC / DC converter with one output,</dd><dt>Fig. 6</dt><dd>shows a time diagram of the output voltage of the central processing unit according to the invention, comprising the cascaded DC / DC converter,</dd><dt>Fig. 7</dt><dd>shows a time diagram of the input voltages of the cascaded DC / DC converter,</dd><dt>Fig. 8</dt><dd>shows a timing diagram of the control voltages of the cascaded DC / DC converter,</dd></dl>

0025As in <figref idref="f0001">Fig. 1</figref> is shown, a central unit 18 is provided, having a rectifier 2 and a power factor correction circuit (PFC) 10 for a plurality of illuminant operating devices 1, 1 ', 1 ". The central unit 18 is supplied with AC voltage 9. The central unit 18 is also otherwise spatially separated from the control gear and can be arranged, for example, centrally for a room, a floor or even a building in a control cabinet etc.

0026As in <figref idref="f0001">Fig. 1</figref> indicated schematically, the various illuminant operating devices 1, 1 ', 1' 'can control a wide variety of illuminants, such as a gas discharge lamp 5, light emitting diodes 5', etc. The lamps can thus be operated with DC or AC voltage, in the latter case an inverter being provided in the associated operating device.

0027Furthermore, other (for example passive) lighting or building technology devices, such as a light sensor 5 ″ or a motion detector (not shown) can also be connected to the output circuit 11 of the central unit 18.

0028Depending on the nature of the connected illuminants 5, 5 'or sensors 5' ', the operating devices 1, 1', 1 '' are designed differently. In the event that the gas discharge lamp 5 is to be actuated, the corresponding operating device 3 is designed, for example, as a ballast with an inverter. In this case, the operating devices can also be referred to as "output converters".

0029The power supply for the operating devices and lamps as well as the unidirectional or bidirectional communication between the central unit and the local operating devices 1, 1 ', 1' 'takes place via at least one DC output circuit 11, 12. As in <figref idref="f0001">Fig. 1</figref> schematically shown, an output circuit 11 can be configured like a bus, so that starting from this central common bus 11, the various operating devices 1, 1 ', 1' 'are supplied via stub lines 13, 13', 13 ''. Alternatively or additionally, individual output circuits 12 can be provided for individual operating devices or groups of operating devices that are jointly supplied.

0030This DC output circuit 11, 12 has the advantage that it is less susceptible to parasitic effects compared to corresponding AC circuits.

0031Emergency light control units 7 or further control units 8 can be connected to the DC output circuit 11 or 12, these devices also being able to read signals from the connected operating devices from the DC bus if they have a powerline demodulator.

0032It should therefore be noted that, according to the present invention, the central unit 18 is provided jointly for a plurality of operating devices, the central unit being connected to the operating devices by means of at least one DC output circuit 11, 12. The voltage on the output circuit 11 can be, for example, 400 volts DC.

0033In <figref idref="f0003">Fig. 3</figref> A central supply unit 18 according to an embodiment of the present invention is shown. The central power supply unit 18 consists of a rectifier 2 and a central cascaded AC / DC converter 19 having several PFCs.

0034In the <figref idref="f0003">Fig. 3a</figref> The central supply unit 18 shown is composed of three PFC units 14, 14 ', 14' 'and three fuse units 15, 15', 15 ''. Furthermore, the power factor correction circuits 14 14 '14' 'are arranged in parallel. The central unit 18 has as many PFC units as strands 16, 16 ', 16' ', so that each individual strand has a PFC unit 14, 14', 14 '' and then a fuse unit 15, 15 ', 15' 'contains.

0035The electronic output fuses 15, 15 ', 15' 'serve to ensure electrical isolation between the supply unit 18 and the respective outputs 17, 17', 17 '' which feed the DC output circuits 11, 12. The central cascaded AC / DC converter 19 is thus also decoupled from the current flowing in the DC output circuits 11, 12.

0036According to the invention, a PFC module 14 ″ serves as a redundant circuit, so that another PFC module can be replaced if necessary. The redundant PFC module 14 ″ then takes over the output supply if a module 14, 14 ′ of the central cascaded converter 19 fails. The transfer can take place either automatically or manually.

0037In <figref idref="f0003">Fig. 3b</figref> it is shown that, according to one embodiment of the present invention, a supply unit 18 offers a plurality of output stages. The individual output stages can feed different output circuits. The outputs 17, 17 ', 17' 'can therefore have different output voltages, such as 400V, 12V and 120V.

0038According to the invention, the modules of the central unit 18 - including the one or more redundant modules - which perform the same function are identical and, for example, are designed as plug-in modules. For example, the PFC circuits 14, 14 ', 14' 'of the central cascaded AC / DC converter 19 are designed as identical plug-in modules. In this way, these modules can be replaced. The size of the central supply unit 18 depends on the requirements per fire compartment or the space required per subdistributor and appropriate wiring of the installation.

0039The <figref idref="f0004">Fig. 4</figref> shows a further embodiment of the invention. The central unit 18 is constructed from a rectifier 2 and a central cascaded AC / DC converter 19. There are three strands 16, 16 ', 16' 'within the central cascaded converter 19. A PFC module 14, 14 ', 14' 'is connected to each line. In addition, as in<figref idref="f0003">Fig. 3</figref> already explained, the central unit 18 can also occupy one fuse module 15, 15 ', 15' 'per line.

0040The PFC modules are connected to inputs of a cascaded DC / DC converter 20 which has at least one output 17. The cascaded DC / DC converter 20 contains several converter modules and can react to different load conditions by different switch-on cycles and switching converter modules on or off.

0041According to the present invention, the <figref idref="f0005">Fig. 5</figref> an embodiment of the cascaded DC / DC converter 20 with three converter modules 35, 35 ', 35' '. According to the invention, the three converters are connected in parallel and can be implemented, for example, with half-bridge flow converters 35, 35 ', 35' '.

0042The following description of the functional principle of a converter module 35 also applies to the other converter modules 35 ', 35' '.

0043Both switches 23 and 24 are switched on and off simultaneously with a pulse width modulated voltage.

0044In the switch-on phase of the switches 23, 24, the voltage of an inductor 27 is equal to the input voltage V_in of the converter module 35. The inductance 27 is the primary winding (N₁) of a transformer 27, 28 and is in the same direction with the secondary winding 28 (N₂) of the transformer, so that the voltage V₂₈= V_in* N₂/ N₁ is present. This voltage V₂₈ charges an output capacitor 33 via a choke 32.

0045During the switch-off phase of the switches 23, 24, no current flows through the inductor 27 and therefore also not through the inductor 28. The storage inductor 32 draws its current via the freewheeling diode 31. During this switch-off phase, the magnetic flux in the transformer 27, 28 must also be reduced . This is done via the primary winding of the transformer 27, 28: namely, the inductor 27 and the primary-side diode 21, 22 against the input voltage V_in demagnetized.

0046Demagnetization essentially takes as much time as magnetization. Therefore, this switch-off phase of the switches 23, 24 must last at least as long as the switch-on phase. The maximum duty cycle t₁/ T of the converter module must therefore not be higher than 50%, where t₁ and T represent the duration of a switch-on phase or an entire period, ie two successive switch-on and switch-off phases.

0047If the converter module 35 is cyclically switched on and off and the converters 35 'and 35 "remain switched off, the voltage V is₃₁ the diode 31 a pulse width modulated voltage, which lies between the values ​​zero and V₂₈= V_in* N₂/ N₁ jumps. The subsequent low pass, formed from a choke 32 and an output capacitor 33, forms with the voltage V._out the mean value of this voltage V₃₁.

0048According to the invention <figref idref="f0005">Fig. 5</figref> three converter modules 35, 35 ', 35' 'connected in parallel, which form a cascaded DC / DC converter 20. The converter modules are switched on and off by the control of the respective diodes 23/24, 23 '/ 24' and 23 '' / 24 ''.

0049In one embodiment of the invention, at most one converter module is switched on at any time. To ensure this, each converter module 35, 35 ', 35' 'is periodically assigned a time slot in which it may be switched on.

0050For this purpose, the three converter modules can alternatively be switched on and off in the same order. According to the invention, the three converter modules are switched on and off cyclically in succession, so that each time slot T_p is assigned in which the respective module may be switched on. The maximum switch-on time of a converter module is therefore at most time T_p. After that 2 * T_p only the two other modules can be switched on. Therefore, the duty cycle cannot be higher than 33%, which ensures the demagnetization of the respective transformers 27-28, 27'-28 ', 27' '- 28' '.

0051If the converter modules 35, 35 ', 35' 'are switched on and off in succession, the voltage V₃₁ of diode 31 jump between the following values ​​depending on the time slot: zero and V₂₈= V_in* N₂/ N₁, Zero and V₂₈'= V_in'* N₂'/ N₁', or zero and V₂₈'' = V_in'' * N₂'' / N₁''. Since the output voltage V_out the mean value of the voltage V₃₁ forms, it can be adapted to different load conditions by changing the switch-on time and by deactivating the respective converter modules. This adjustable output voltage also enables central dimming of the connected light sources.

0052Incidentally, a converter module 35 ″ can be used to provide redundancy and take over the supply of the output stage if a converter module 35, 35 ′ fails

0053<figref idref="f0006">Fig. 6</figref> is a timing diagram of the output voltage V_out of the cascaded DC / DC converter 20 and the output 17 of the central unit 18. In the different phases shown, different converter modules 35, 35 ', 35' 'are activated and different duty cycles are used. According to one embodiment of the invention, the modules 35, 35 ', 35' 'are switched on and off with the same duty cycle.

0054In phase 1, only one module 35 is activated. This means that only this one is switched on and off and the other modules remain switched off. In phases 2 and 3, two modules 35, 35 'and three modules 35, 35', 35 '' are activated. As can be seen, the central processing unit 18 is able to compensate for different load conditions by activating and deactivating individual modules.

0055Phase 4 differs from phases 1 to 3, in which the time period d₂ a switch-on phase of a module is changed. An adaptation to the load status can also be made by changing the module switch-on time.

0056In <figref idref="f0006">Fig. 7</figref> the input voltages of the cascaded DC / DC converter 20 are shown, depending on the activation and deactivation state of the individual converter modules 35, 35 ', 35' '. The various modules have different DC input voltages, e.g. 700V, 600V and 500V. A module is deactivated when its input voltage is set to zero.

0057In phases 1, 2 and 3 the duty cycle remains constant so that the influence of the number of activated modules can be analyzed. In the first phase 1, a module 35 is activated. As a result, the voltage V₃₁ the diode 31 a pulse width modulated voltage, which lies between the values ​​zero and V₂₈= V_in* N₂/ N₁ jumps. The output voltage V_out then forms the average of this voltage V₃₁. For continuous operation, in which the current through the choke 32 never becomes zero, the following therefore applies:<maths id="math0001" num="(Eq. 1)"><math display="block"><mrow><msub><mi>V</mi><mrow><mmultiscripts><mrow><msub><mrow><mo>/</mo></mrow><mrow><mi mathvariant="italic">phase</mi><mn>1</mn></mrow></msub></mrow><mprescripts /><none /><mi mathvariant="italic">out</mi></mmultiscripts></mrow></msub><mo>=</mo><msub><mi>V</mi><mi mathvariant="italic">in</mi></msub><mo>⋅</mo><mfrac><mrow><msub><mi>N</mi><mn>2</mn></msub></mrow><mrow><msub><mi>N</mi><mn>1</mn></msub></mrow></mfrac><mo>⋅</mo><mfrac><mrow><msub><mi>d</mi><mn>1</mn></msub></mrow><mrow><msub><mi>T</mi><mi>P</mi></msub></mrow></mfrac></mrow></math><img file="EP1583402B1_D0001.tif" /></maths> where d₁/ T_p determines the duty cycle of switching a module on and off.

0058In phase 2, module 35 'is activated in addition to module 35. Since the modules are not switched on at the same time, the voltage V jumps this time₃₁ between the values ​​zero, V₂₈= V_in* N₂/ N₁ and V₂₈'= V_in'* N₂'/ N₁'. The output voltage then forms its mean value:<maths id="math0002" num="(Eq. 2)"><math display="block"><mrow><msub><mi>V</mi><mrow><mmultiscripts><mrow><msub><mrow><mo>/</mo></mrow><mrow><mi mathvariant="italic">phase</mi><mn>2</mn></mrow></msub></mrow><mprescripts /><none /><mi mathvariant="italic">out</mi></mmultiscripts></mrow></msub><mo>=</mo><mfenced separators=""><msub><mi>V</mi><mi mathvariant="italic">in</mi></msub><mo>⋅</mo><mfrac><mrow><msub><mi>N</mi><mn>2</mn></msub></mrow><mrow><msub><mi>N</mi><mn>1</mn></msub></mrow></mfrac><mo>+</mo><msub><mi>V</mi><mi mathvariant="italic">in</mi></msub><mo>′</mo><mo>⋅</mo><mfrac><mrow><msub><mi>N</mi><mn>2</mn></msub><mo>′</mo></mrow><mrow><msub><mi>N</mi><mn>1</mn></msub><mo>′</mo></mrow></mfrac></mfenced><mo>⋅</mo><mfrac><mrow><msub><mi>d</mi><mn>1</mn></msub></mrow><mrow><msub><mi>T</mi><mi>P</mi></msub></mrow></mfrac></mrow></math><img file="EP1583402B1_D0002.tif" /></maths>

0059When activating more or fewer converter modules that can be supplied with different input voltages, the cascaded DC / DC converter 20 can consequently have several different output voltages V_out to offer. The central supply unit 18 can thus adapt to the load of the connected lamps.

0060<figref idref="f0007">Fig. 8</figref> shows a timing diagram of the control voltages V_s, V_s' and V_s'' of the respective modules 35, 35 ', 35' 'of the cascaded DC / DC converter 20. According to the invention, the converter modules are cyclically switched on and off one after the other, with a maximum of only one being switched on at any time. From phase 3 to phase 4 only the switch-on time of the converter modules from d₁ to d₂ changed. This period can be halved, for example, so that d₂= d₁/ 2nd This has an effect on the output voltage V_out of the cascaded DC / DC converter 20 by the value <maths id="math0003" num="(Eq. 3)"><math display="block"><mrow><msub><mi>V</mi><mrow><mmultiscripts><mrow><msub><mrow><mo>/</mo></mrow><mrow><mi mathvariant="italic">phase</mi><mn>3</mn></mrow></msub></mrow><mprescripts /><none /><mi mathvariant="italic">out</mi></mmultiscripts></mrow></msub><mo>=</mo><mfenced separators=""><msub><mi>V</mi><mi mathvariant="italic">in</mi></msub><mo>⋅</mo><mfrac><mrow><msub><mi>N</mi><mn>2</mn></msub></mrow><mrow><msub><mi>N</mi><mn>1</mn></msub></mrow></mfrac><mo>+</mo><msub><mi>V</mi><mi mathvariant="italic">in</mi></msub><mo>′</mo><mo>⋅</mo><mfrac><mrow><msub><mi>N</mi><mn>2</mn></msub><mo>′</mo></mrow><mrow><msub><mi>N</mi><mn>1</mn></msub><mo>′</mo></mrow></mfrac><mo>+</mo><msub><mi>V</mi><mi mathvariant="italic">in</mi></msub><mo>"</mo><mo>⋅</mo><mfrac><mrow><msub><mi>N</mi><mn>2</mn></msub><mo>"</mo></mrow><mrow><msub><mi>N</mi><mn>1</mn></msub><mo>"</mo></mrow></mfrac></mfenced><mo>⋅</mo><mfrac><mrow><msub><mi>d</mi><mn>1</mn></msub></mrow><mrow><msub><mi>T</mi><mi>P</mi></msub></mrow></mfrac></mrow></math><img file="EP1583402B1_D0003.tif" /></maths> in phase 3 to the value <maths id="math0004" num="(Eq. 4)"><math display="block"><mrow><msub><mi>V</mi><mrow><mmultiscripts><mrow><msub><mrow><mo>/</mo></mrow><mrow><mi mathvariant="italic">phase</mi><mn>4</mn></mrow></msub></mrow><mprescripts /><none /><mi mathvariant="italic">out</mi></mmultiscripts></mrow></msub><mo>=</mo><mfenced separators=""><msub><mi>V</mi><mi mathvariant="italic">in</mi></msub><mo>⋅</mo><mfrac><mrow><msub><mi>N</mi><mn>2</mn></msub></mrow><mrow><msub><mi>N</mi><mn>1</mn></msub></mrow></mfrac><mo>+</mo><msub><mi>V</mi><mi mathvariant="italic">in</mi></msub><mo>′</mo><mo>⋅</mo><mfrac><mrow><msub><mi>N</mi><mn>2</mn></msub><mo>′</mo></mrow><mrow><msub><mi>N</mi><mn>1</mn></msub><mo>′</mo></mrow></mfrac><mo>+</mo><msub><mi>V</mi><mi mathvariant="italic">in</mi></msub><mo>"</mo><mo>⋅</mo><mfrac><mrow><msub><mi>N</mi><mn>2</mn></msub><mo>"</mo></mrow><mrow><msub><mi>N</mi><mn>1</mn></msub><mo>"</mo></mrow></mfrac></mfenced><mo>⋅</mo><mfrac><mrow><msub><mi>d</mi><mn>2</mn></msub></mrow><mrow><msub><mi>T</mi><mi>P</mi></msub></mrow></mfrac><mo>=</mo><msub><mi>V</mi><mrow><mmultiscripts><mrow><msub><mrow><mo>/</mo></mrow><mrow><mi mathvariant="italic">phase</mi><mn>3</mn></mrow></msub></mrow><mprescripts /><none /><mi mathvariant="italic">out</mi></mmultiscripts></mrow></msub><mo>⋅</mo><mfrac><mrow><msub><mi>d</mi><mn>2</mn></msub></mrow><mrow><msub><mi>d</mi><mn>1</mn></msub></mrow></mfrac><mo>=</mo><msub><mi>V</mi><mrow><mmultiscripts><mrow><msub><mrow><mo>/</mo></mrow><mrow><mi mathvariant="italic">phase</mi><mn>3</mn></mrow></msub></mrow><mprescripts /><none /><mi mathvariant="italic">out</mi></mmultiscripts></mrow></msub><mo>⋅</mo><mfrac><mn>1</mn><mn>2</mn></mfrac></mrow></math><img file="EP1583402B1_D0004.tif" /></maths> varies in phase 4 (<figref idref="f0005">Fig. 5</figref>). The variation of the output voltage between phases 3 and 4 is halved in this case and is in<figref idref="f0006">Fig. 6</figref> clear to see.

0061The output voltages V_out can thus also by changing the switch-on time d₁ of the modules can be adjusted.

0062According to a further aspect of the invention, the output voltages V_out by changing the clock frequency f_P= 1 / T_P customized.

0063The following table summarizes the reference numerals of the figures:<tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="20mm" /><colspec colnum="2" colname="col2" colwidth="118mm" /><tbody><row><entry>1,1',1''</entry><entry>Illuminant control gear</entry></row><row><entry>2</entry><entry>a rectifier</entry></row><row><entry>3</entry><entry>an operating device</entry></row><row><entry>4</entry><entry>an electrolyte storage capacitor</entry></row><row><entry>5,5',5''</entry><entry>Illuminant, or a gas discharge lamp, a light emitting diode, a light sensor</entry></row><row><entry>6</entry><entry>an RF inverter output circuit</entry></row><row><entry>7</entry><entry>an emergency light control unit</entry></row><row><entry>8</entry><entry>Control units</entry></row><row><entry>9</entry><entry>an AC voltage</entry></row><row><entry>10</entry><entry>a PFC</entry></row><row><entry>11,12</entry><entry>DC output circuits</entry></row><row><entry>13,13',13''</entry><entry>Stub lines</entry></row><row><entry>14,14',14''</entry><entry>PFC modules</entry></row><row><entry>15,15',15''</entry><entry>Security modules</entry></row><row><entry>16,16',16''</entry><entry>Central unit strands</entry></row><row><entry>17,17',17''</entry><entry>Central unit DC outputs</entry></row><row><entry>18</entry><entry>a central unit</entry></row><row><entry>19</entry><entry>a central cascaded AC / DC converter</entry></row><row><entry>20</entry><entry>a cascaded DC / DC converter</entry></row><row><entry>21,21',21''</entry><entry>diode</entry></row><row><entry>22,22',22''</entry><entry>diode</entry></row><row><entry>23,23',23''</entry><entry>counter</entry></row><row><entry>24,24',24''</entry><entry>counter</entry></row><row><entry>26,26',26''</entry><entry>Input of a converter module</entry></row><row><entry>27,27',27''</entry><entry>Inductance, primary winding of a transformer</entry></row><row><entry>28,28',28''</entry><entry>Inductance, secondary winding of a transformer</entry></row><row><entry>29</entry><entry>a resistance</entry></row><row><entry>30,30',30''</entry><entry>diode</entry></row><row><entry>31</entry><entry>a free-wheeling diode</entry></row><row><entry>32</entry><entry>a choke</entry></row><row><entry>33</entry><entry>an output capacitor</entry></row><row><entry>34</entry><entry>a burden</entry></row><row><entry>35,35',35''</entry><entry>Converter modules</entry></row></tbody></tgroup></table></tables>