EP0852453A1 - Electronic ballast for a discharge lamp, provided with a lamp power measurement by means of a DC-signal - Google Patents
Electronic ballast for a discharge lamp, provided with a lamp power measurement by means of a DC-signal Download PDFInfo
- Publication number
- EP0852453A1 EP0852453A1 EP97660149A EP97660149A EP0852453A1 EP 0852453 A1 EP0852453 A1 EP 0852453A1 EP 97660149 A EP97660149 A EP 97660149A EP 97660149 A EP97660149 A EP 97660149A EP 0852453 A1 EP0852453 A1 EP 0852453A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- lamp
- regulation
- ballast
- power
- load circuit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/36—Controlling
- H05B41/38—Controlling the intensity of light
- H05B41/39—Controlling the intensity of light continuously
- H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
- H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
- H05B41/3925—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations by frequency variation
Definitions
- the present invention relates to a dimmable or controllable electronic ballast for a low-pressure discharge lamp, especially a fluorescent lamp, whose operation is based on regulating the light output of a lamp by varying the frequency of a voltage supplied to the lamp.
- the invention relates to a circuit system for accurately measuring a power delivered by such a ballast to a lamp load so as to find out the proportion of power required for sustaining discharge of the lamp.
- the structure of electronic ballasts for low-pressure discharge lamps is prior known from the Applicant's patent No. FI 64487 as well as the theoretical principles from the Applicant's patent No. FI 63314.
- the Applicant's patent No. FI 63146 in turn discloses the structure and operation of a low-voltage controlled electronic ballast for gaining a light output proportional to an external control signal.
- the ballast depicted in fig. 1 includes a rectifier V1 connected to a supply voltage UV, a smoothing capacitor C1, a high-frequency oscillator A1, as well as transistors TR1 and TR2 constituting a halfbridge circuit.
- a lamp LL is coupled as part of a resonance circuit, constituted by a capacitor C2 and an inductance L2 and supplied by the pushpull transistors TR1 and TR2.
- a filament pre-heating current for the cathodes of the lamp LL during a switch-on sequence of the lamp is conducted by way of a capacitor C3.
- the oscillator A1 is provided with a control circuit CO1 - CO2, wherethrough a control signal influences the oscillating frequency of the oscillator.
- the electronic ballast must generally be provided with a separate safety feature in anticipation of certain special circumstances, such as over- or undervoltage in an electrical network supplying the ballast, overheating of the device, a lamp missing, or breaking of the lamp cathodes, as described e.g. in the Applicant's patent application FI 955695.
- a power supplied to the lamp LL be measured at a sufficient accuracy.
- This measurement information is utilized in the operation of a control block Al in such a manner that the lamp LL can be supplied in a stable fashion with a power proportional to the voltage between control lines CO1 and CO2 for regulating the light output of the lamp.
- the power supplied to the lamp load LL by the halfbridge-connected transistor circuit TR1 and TR2 consists of two components: an actual lamp power, which sustains a light-generating discharge in the lamp, and a filament power, which is used for heating the lamp cathodes.
- Other components of the load circuit experience power losses as well. Especially at lower regulation levels, the power consumed by a lamp discharge being low, the power of cathode incandescence constitutes a considerable portion of the power of the entire circuit.
- a problem with the ballast shown in fig. 1 is the measurement of a load power in such a manner that the actual lamp power can be measured at a sufficient accuracy without the power required by incandescence having a significant effect on the measuring result.
- An object of the invention is to resolve this problem involving measuring technology and to provide a ballast of the type defined in the preamble of claim 1, wherein the inaccuracy factors associated with the measurement of a lamp power can be sufficiently eliminated.
- the effective energy consumed by the halfbridge TR1 - TR2 transfers primarily to a load circuit C2, L2, LL, and C3.
- the current through either supply of the halfbridge is proportional to the energy consumed by the load circuit, if the supply voltage of the halfbridge is maintained constant.
- the load circuit is constituted by an inductance or coil L2, a lamp LL, and capacitors C2, C3.
- the lamp LL is the only one to consume effective power.
- the energy consumed by the lamp LL is divided into an energy input required by the lamp discharge and an energy consumed by filaments. In terms of the output of light, the energy of a lamp current is interesting.
- the regulation functions well as long as the lamp power is higher than the filament power.
- the regulation becomes inaccurate. Depending on the type of lamp, this occurs between 10...20 % light level.
- the effect of the filament power must be eliminated from a measuring signal. This can be done by measuring e.g. a voltage existing across one of the cathodes of the lamp LL, as set forth in the Applicant's patent application "Measurement of a lamp power in a regulable electronic ballast".
- a problem is how to achieve a sufficient accuracy, since there are losses also in other circuit elements, such as ignition capacitors, lamp inductances, and switching transistors.
- An object of this invention is to introduce a circuit connection for a ballast, whereby the power of a low-pressure discharge lamp, especially a fluorescent lamp, can be measured in such a way that said inaccuracy factors in the measurement can be eliminated.
- This is performed by feeding through a lamp a separate direct-current signal, which is used for producing a direct-voltage signal proportional to the effective resistance of the lamp.
- Said direct current through a lamp brings about a further advantage that the dark stripes visible on the surface of the lamp bulb, or a so-called striation effect, at lower regulation levels and especially at lower operating temperatures, can be avoided.
- Fig. 2 of the drawing illustrates one embodiment of the above-described measuring principle.
- the total power of a load circuit is measured by using a resistance R2, the voltage produced thereby and proportional to the current of a halfbridge TR1 - TR2 being filtered with elements R3 and C4 as well as being conducted to an oscillator block A1.
- the operation of the oscillator block A1 is here divided in two sections, whereof a sub-block II handles the processing of measuring signals and a sub-block I the control of the halfbridge transistors TR1 and TR2.
- a resistance R4 is used for developing a direct-current component in an alternating current passing through the lamp LL.
- the lamp has a substitution resistance of about 275 ohms, at a 50 % light level about 600 ohms, and at a 5 % light level about 14 kilo-ohms.
- the direct current component supplied to a lamp is 1,5 mA, the result will be a direct voltage of about 20 V across the lamp.
- the direct voltage measurement has a wide dynamic range and the measuring signal can be readily utilized in the control block of a ballast.
- the regulation of a light level at low light levels can be made considerably more accurate than by using conventional power measurement.
- the Applicant's patent FI 65524 describes how said direct current component through a low-pressure discharge lamp can be used for avoiding a so-called striation effect, which is a serious problem in controllable and dimmable ballasts.
- this patent discloses a variety of ways of producing a direct current component.
- the undeniable strength of this invention lies in the fact that one and the same direct current signal can be used to gain two major benefits in terms of the operation of regulable ballasts, namely an accurate regulation and an unstreaked output of light from the lamp.
- the invention is not limited solely to the described embodiments but is equally well adaptable to numerous other frequency-regulation based ballast circuits, e.g. multiple-lamp ballast versions.
- the technology applied in switching transistors used in the halfbridge has no significance regarding the usefulness of the described circuit, i.e. in this context, useful components include a.o. a bipolar transistor and various designs of field effect transistors.
- the control signal of the oscillator A1 in the circuit CO1 - CO2 can be digital as well, the sub-block II including necessary circuit elements for processing digital information, e.g. by means of a programmable micro-controller.
Abstract
The invention relates to a controllable
or dimmable electronic ballast for a
low pressure discharge lamp, especially
a fluorescent lamp. A halfbridge
inverter (TR1, TR2; V2, V3) supplies
power to a load circuit (L2, C2, C3,
LL). A regulation or control block
(A1/I, II) regulates the frequency of
the halfbridge inverter for regulating
the light output of a lamp. One branch
of the halfbridge inverter is provided
with current measuring elements (R2,
R3, C4), from which is obtained current
measurement information proportional to
the load circuit power for the regulation
or control block, which is further
supplied separately with measurement
information about a direct current
that has passed through the lamp and is
proportional to the internal resistance
of the lamp. The latter measurement
information is used for controlling
regulation of the lamp at low regula
tion levels of the light output.
Description
The present invention relates to a dimmable or controllable
electronic ballast for a low-pressure discharge lamp,
especially a fluorescent lamp, whose operation is based on
regulating the light output of a lamp by varying the frequency
of a voltage supplied to the lamp. The invention
relates to a circuit system for accurately measuring a
power delivered by such a ballast to a lamp load so as to
find out the proportion of power required for sustaining
discharge of the lamp.
The structure of electronic ballasts for low-pressure
discharge lamps is prior known from the Applicant's patent
No. FI 64487 as well as the theoretical principles from the
Applicant's patent No. FI 63314. The Applicant's patent No.
FI 63146 in turn discloses the structure and operation of a
low-voltage controlled electronic ballast for gaining a
light output proportional to an external control signal.
The structure and operation of a controllable or dimmable
ballast set forth in the Applicant's patent No. FI 63146
will be described in more detail with reference made to
fig. 1 of the appended drawings, which depicts one preferred
embodiment of such a ballast. In order to simplify
the representation, fig. 1 only depicts structural components
that are most essential in terms of understanding the
operation.
The ballast depicted in fig. 1 includes a rectifier V1
connected to a supply voltage UV, a smoothing capacitor C1,
a high-frequency oscillator A1, as well as transistors TR1
and TR2 constituting a halfbridge circuit. A lamp LL is
coupled as part of a resonance circuit, constituted by a
capacitor C2 and an inductance L2 and supplied by the pushpull
transistors TR1 and TR2. A filament pre-heating current
for the cathodes of the lamp LL during a switch-on
sequence of the lamp is conducted by way of a capacitor C3.
The oscillator A1 is provided with a control circuit CO1 -
CO2, wherethrough a control signal influences the oscillating
frequency of the oscillator. The electronic ballast
must generally be provided with a separate safety feature
in anticipation of certain special circumstances, such as
over- or undervoltage in an electrical network supplying
the ballast, overheating of the device, a lamp missing, or
breaking of the lamp cathodes, as described e.g. in the
Applicant's patent application FI 955695.
It is general knowledge that heating the cathodes of low-pressure
discharge lamps during the switch-on or ignition
sequence of a lamp contributes positively to the service
life and operating characteristics of the lamp. An appropriately
dimensioned filament power can be attributed to
prolong the service life of a lamp by reducing a stress
applied to the lamp cathodes and particularly to the emission
material layer serving as a coating therefor. At the
same time, this enables the ignition of a lamp without
flicker at a lower voltage across the lamp than what is
required whenever the pre-heating is not employed. The
requirements set for electronic ballasts regarding incandescence
of the cathodes upon switching on a lamp are set
forth in the International standard IEC 929. The purpose of
these requirements is to make sure that fluorescent lamps
according to standards IEC 81 abd IEC 901 reach the service
life specified therefor. Diversion from the requirements
set forth in said standards may cause also other adverse
effects, such as blackening of the glass bulb of a lamp in
areas next to the cathodes, some fo the material emitting
from the cathodes accumulating on the internal surface of
the glass bulb.
It is also prior known that said incandescence of the lamp
cathodes is unavoidable whenever it is desirable to regulate
the light output of a lamp. The purpose of sufficient
cathode heating is to make sure that a sufficient number of
charge carriers are emitted from the cathodes for sustaining
discharge in a lamp as the current passing therethrough
is diminishing. A sufficient heating level is also
necessary for maintaining the service life of a lamp at an
acceptable level.
In terms of the operation of a controllable ballast as
described above, it is essential that a power supplied to
the lamp LL be measured at a sufficient accuracy. This
measurement information is utilized in the operation of a
control block Al in such a manner that the lamp LL can be
supplied in a stable fashion with a power proportional to
the voltage between control lines CO1 and CO2 for regulating
the light output of the lamp. The power supplied to the
lamp load LL by the halfbridge-connected transistor circuit
TR1 and TR2 consists of two components: an actual lamp
power, which sustains a light-generating discharge in the
lamp, and a filament power, which is used for heating the
lamp cathodes. Other components of the load circuit experience
power losses as well. Especially at lower regulation
levels, the power consumed by a lamp discharge being low,
the power of cathode incandescence constitutes a considerable
portion of the power of the entire circuit.
A problem with the ballast shown in fig. 1 is the measurement
of a load power in such a manner that the actual lamp
power can be measured at a sufficient accuracy without the
power required by incandescence having a significant effect
on the measuring result.
An object of the invention is to resolve this problem
involving measuring technology and to provide a ballast of
the type defined in the preamble of claim 1, wherein the
inaccuracy factors associated with the measurement of a
lamp power can be sufficiently eliminated.
This object is achieved by means of the invention, the
characterizing features of which are set forth in the
appended claim 1. The non-independent claims disclose
preferred embodiments of the invention.
The operation of the invention will now be described in
more detail with reference made to the accompanying drawings,
in which
- fig. 1
- shows a prior art as described above and
- fig. 2
- shows a ballast according to one embodiment of the invention, most of whose functions have already been described in reference to fig. 1. As an addition to the former, there are so-called free-wheel diodes V2 and V3, which allow forward passage for the current of the oscillating circuit whenever either transistor TR1 or TR2 in parallel therewith has cut off the circuit current in the opposite direction.
The effective energy consumed by the halfbridge TR1 - TR2
transfers primarily to a load circuit C2, L2, LL, and C3.
As a result of the symmetrical operation of the circuit,
the current through either supply of the halfbridge is
proportional to the energy consumed by the load circuit, if
the supply voltage of the halfbridge is maintained constant.
Pload ~Ihalfbridge,supply
Pload ~Ihalfbridge,supply
Thus, the load circuit is constituted by an inductance or
coil L2, a lamp LL, and capacitors C2, C3. As for these,
the lamp LL is the only one to consume effective power. The
energy consumed by the lamp LL is divided into an energy
input required by the lamp discharge and an energy consumed
by filaments. In terms of the output of light, the energy
of a lamp current is interesting.
When the effective power of a load circuit or the light
output produced by the lamp LL is regulated by using the
halfbridge supply current as a reference value, the regulation
functions well as long as the lamp power is higher
than the filament power. When said powers are equal or the
lamp power is lower than the filament power, the regulation
becomes inaccurate. Depending on the type of lamp, this
occurs between 10...20 % light level. When it is desirable
to adjust to a lightlevel lower than this, the effect of
the filament power must be eliminated from a measuring
signal. This can be done by measuring e.g. a voltage existing
across one of the cathodes of the lamp LL, as set forth
in the Applicant's patent application "Measurement of a
lamp power in a regulable electronic ballast". As for these
measuring methods, a problem is how to achieve a sufficient
accuracy, since there are losses also in other circuit
elements, such as ignition capacitors, lamp inductances,
and switching transistors.
An object of this invention is to introduce a circuit
connection for a ballast, whereby the power of a low-pressure
discharge lamp, especially a fluorescent lamp, can be
measured in such a way that said inaccuracy factors in the
measurement can be eliminated. This is performed by feeding
through a lamp a separate direct-current signal, which is
used for producing a direct-voltage signal proportional to
the effective resistance of the lamp. Said direct current
through a lamp brings about a further advantage that the
dark stripes visible on the surface of the lamp bulb, or a
so-called striation effect, at lower regulation levels and
especially at lower operating temperatures, can be avoided.
A lamp power measurement by means of a DC-signal according
to the invention will now be described in even more detail.
Fig. 2 of the drawing illustrates one embodiment of the
above-described measuring principle. In this case, the
total power of a load circuit is measured by using a resistance
R2, the voltage produced thereby and proportional to
the current of a halfbridge TR1 - TR2 being filtered with
elements R3 and C4 as well as being conducted to an oscillator
block A1. For the sake of clarity, the operation of
the oscillator block A1 is here divided in two sections,
whereof a sub-block II handles the processing of measuring
signals and a sub-block I the control of the halfbridge
transistors TR1 and TR2. A resistance R4 is used for developing
a direct-current component in an alternating current
passing through the lamp LL. Thus, across the lamp develops
also a direct-voltage component, which is proportional to
the effective resistance of the lamp. The direct voltage is
measured by means of circuit elements R5, R6 and C5 and
this measuring signal is likewise conducted to the sub-block
II of the oscillator circuit A1. Here is formed a
difference between said measuring signals, whereby the
control block has at its disposal a real measuring signal
proportional to the lamp power. By means of this and a
control signal fed into the lines CO1 - CO2 the control
block II is able to perform its control function in such a
manner that the control of the halfbridge TR1 - TR2 through
the sub-block I guarantees a stable lighting regulation
function for the ballast, as planned.
At a maximum regulation level the lamp has a substitution
resistance of about 275 ohms, at a 50 % light level about
600 ohms, and at a 5 % light level about 14 kilo-ohms. When
the direct current component supplied to a lamp is 1,5 mA,
the result will be a direct voltage of about 20 V across
the lamp. Thus, the direct voltage measurement has a wide
dynamic range and the measuring signal can be readily
utilized in the control block of a ballast.
By means of a circuit system of the invention, the regulation
of a light level at low light levels can be made
considerably more accurate than by using conventional power
measurement. The Applicant's patent FI 65524 describes how
said direct current component through a low-pressure discharge
lamp can be used for avoiding a so-called striation
effect, which is a serious problem in controllable and
dimmable ballasts. In addition, this patent discloses a
variety of ways of producing a direct current component.
The undeniable strength of this invention lies in the fact
that one and the same direct current signal can be used to
gain two major benefits in terms of the operation of
regulable ballasts, namely an accurate regulation and an
unstreaked output of light from the lamp.
It is evident for a skilled person that the invention is
not limited solely to the described embodiments but is
equally well adaptable to numerous other frequency-regulation
based ballast circuits, e.g. multiple-lamp ballast
versions. In particular, the technology applied in switching
transistors used in the halfbridge has no significance
regarding the usefulness of the described circuit, i.e. in
this context, useful components include a.o. a bipolar
transistor and various designs of field effect transistors.
It is also obvious that the control signal of the oscillator
A1 in the circuit CO1 - CO2 can be digital as well, the
sub-block II including necessary circuit elements for
processing digital information, e.g. by means of a programmable
micro-controller.
Claims (4)
- A controllable or dimmable electronic ballast for a low-pressure discharge lamp, especially a fluorescent lamp, comprisingcharacterized in that the device further includes elements (R5, C5, R6) for measuring the direct current passing through the lamp and for feeding the measurement information to the regulation or control block (A1/I, II) for using the same in controlling the regulation of the light output of the lamp.at least one halfbridge inverter (TR1, TR2, V2, V3) or a corresponding AC-source, which supplies power to a load circuit,a load circuit, including a current limiting inductance (L2) and a filament current supplying capacitance (C3) as well as a discharge lamp (LL) connectable to the ballast,a regulation or control block (A1/I, II) for adjusting the frequency of the inverter or a corresponding AC-source for regulating the light output of the lamp,elements (R2, R3, C4) for measuring a current proportional to the load circuit power and for conducting the measurement information (Umeas.) to the regulation or control block; andelements (R4) for producing a direct current passing through the lamp,
- A ballast as set forth in claim 1, characterized in that a measuring signal proportional to the lamp power is produced as difference between said pieces of measurement information.
- A ballast as set forth in claim 1 or 2, characterized in that each of said current measuring elements includes at least one resistance (R2; R6) and at least one capacitor (C4; C5) connected in parallel with the resistance.
- A ballast as set forth in any of claims 1-3, characterized in that the element producing the direct current passing through the lamp is a resistance (R4), which is connected in parallel with a capacitor (C2) included in the load circuit, and that the direct current measuring elements (R5, R6, C5) are connected between said resistance (R4) and the lamp (LL).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI970018A FI101188B (en) | 1997-01-03 | 1997-01-03 | Electronic connector for discharge lamp equipped with lamp power measurement by means of DC signal |
| FI970018 | 1997-01-03 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0852453A1 true EP0852453A1 (en) | 1998-07-08 |
| EP0852453B1 EP0852453B1 (en) | 2000-08-16 |
Family
ID=8547419
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP19970660149 Revoked EP0852453B1 (en) | 1997-01-03 | 1997-12-19 | Electronic ballast for a discharge lamp, provided with a lamp power measurement by means of a DC-signal |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0852453B1 (en) |
| DE (1) | DE69702829T2 (en) |
| FI (1) | FI101188B (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000059273A1 (en) * | 1999-03-30 | 2000-10-05 | Innoware Oy | Supply coupling of a fluorescent lamp |
| US7679293B2 (en) | 2007-12-20 | 2010-03-16 | General Electric Company | Anti-striation circuit for current-fed ballast |
| WO2011055158A1 (en) * | 2009-11-03 | 2011-05-12 | City University Of Hong Kong | A passive lc ballast and method of manufacturing a passive lc ballast |
| US7982452B2 (en) | 2009-07-30 | 2011-07-19 | Infineon Technologies Austria Ag | Detection of a load state of a half-bridge |
| WO2013034386A1 (en) * | 2011-09-07 | 2013-03-14 | Osram Ag | Electronic ballast and method for operating a discharge lamp |
| WO2013034387A1 (en) * | 2011-09-07 | 2013-03-14 | Osram Ag | Electronic ballast and method for operating a discharge lamp |
| US8638048B2 (en) | 2011-04-12 | 2014-01-28 | Infineon Technologies Ag | Circuit for determining an average value |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0422255A1 (en) * | 1989-10-09 | 1991-04-17 | Siemens Aktiengesellschaft | Electronic ballast |
| GB2246034A (en) * | 1990-07-13 | 1992-01-15 | Lutron Electronics Co | Circuit and method for improved dimming of gas discharge lamps |
| EP0589081A1 (en) * | 1992-09-24 | 1994-03-30 | Knobel Ag Lichttechnische Komponenten | Circuit for operating a fluorescent lamp with a current measuring circuit |
| WO1997001945A1 (en) * | 1995-06-29 | 1997-01-16 | Philips Electronics N.V. | Circuit arrangement |
-
1997
- 1997-01-03 FI FI970018A patent/FI101188B/en active IP Right Grant
- 1997-12-19 DE DE1997602829 patent/DE69702829T2/en not_active Revoked
- 1997-12-19 EP EP19970660149 patent/EP0852453B1/en not_active Revoked
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0422255A1 (en) * | 1989-10-09 | 1991-04-17 | Siemens Aktiengesellschaft | Electronic ballast |
| GB2246034A (en) * | 1990-07-13 | 1992-01-15 | Lutron Electronics Co | Circuit and method for improved dimming of gas discharge lamps |
| EP0589081A1 (en) * | 1992-09-24 | 1994-03-30 | Knobel Ag Lichttechnische Komponenten | Circuit for operating a fluorescent lamp with a current measuring circuit |
| WO1997001945A1 (en) * | 1995-06-29 | 1997-01-16 | Philips Electronics N.V. | Circuit arrangement |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2000059273A1 (en) * | 1999-03-30 | 2000-10-05 | Innoware Oy | Supply coupling of a fluorescent lamp |
| US6504318B1 (en) | 1999-03-30 | 2003-01-07 | Innoware Oy | Supply coupling of a fluorescent lamp |
| AU764223B2 (en) * | 1999-03-30 | 2003-08-14 | Innoware Oy | Supply coupling of a fluorescent lamp |
| US7679293B2 (en) | 2007-12-20 | 2010-03-16 | General Electric Company | Anti-striation circuit for current-fed ballast |
| US7982452B2 (en) | 2009-07-30 | 2011-07-19 | Infineon Technologies Austria Ag | Detection of a load state of a half-bridge |
| WO2011055158A1 (en) * | 2009-11-03 | 2011-05-12 | City University Of Hong Kong | A passive lc ballast and method of manufacturing a passive lc ballast |
| US8952617B2 (en) | 2009-11-03 | 2015-02-10 | City University Of Hong Kong | Passive LC ballast and method of manufacturing a passive LC ballast |
| US8638048B2 (en) | 2011-04-12 | 2014-01-28 | Infineon Technologies Ag | Circuit for determining an average value |
| WO2013034386A1 (en) * | 2011-09-07 | 2013-03-14 | Osram Ag | Electronic ballast and method for operating a discharge lamp |
| WO2013034387A1 (en) * | 2011-09-07 | 2013-03-14 | Osram Ag | Electronic ballast and method for operating a discharge lamp |
Also Published As
| Publication number | Publication date |
|---|---|
| FI101188B1 (en) | 1998-04-30 |
| DE69702829T2 (en) | 2000-12-07 |
| DE69702829D1 (en) | 2000-09-21 |
| FI970018A0 (en) | 1997-01-03 |
| FI101188B (en) | 1998-04-30 |
| EP0852453B1 (en) | 2000-08-16 |
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