EP1315406A2 - Electronic circuit for supplying high-frequency power for fluorescent lamps - Google Patents
Electronic circuit for supplying high-frequency power for fluorescent lamps Download PDFInfo
- Publication number
- EP1315406A2 EP1315406A2 EP02079806A EP02079806A EP1315406A2 EP 1315406 A2 EP1315406 A2 EP 1315406A2 EP 02079806 A EP02079806 A EP 02079806A EP 02079806 A EP02079806 A EP 02079806A EP 1315406 A2 EP1315406 A2 EP 1315406A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- power
- lamp
- circuit
- power supply
- supply 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.)
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Classifications
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- 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
-
- 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
- H05B41/26—Circuit arrangements in which the lamp is fed by power derived from DC by means of a converter, e.g. by high-voltage DC
- H05B41/28—Circuit arrangements in which the lamp is fed by power derived from DC by means of a converter, e.g. by high-voltage DC using static converters
- H05B41/282—Circuit arrangements in which the lamp is fed by power derived from DC by means of a converter, e.g. by high-voltage DC using static converters with semiconductor devices
- H05B41/2825—Circuit arrangements in which the lamp is fed by power derived from DC by means of a converter, e.g. by high-voltage DC using static converters with semiconductor devices by means of a bridge converter in the final stage
Definitions
- the present invention refers to an electronic circuit for supplying high-frequency power to fluorescent lamps of different types and powers.
- Electronic ballasts are apparatuses which allow high-frequency power supply (in the order of tens of kHz) to fluorescent lamps with undoubted advantages in terms of efficiency and performance, such as protection against working anomalies, no flickering, etc.
- the purpose of the present invention is therefore that of avoiding the aforementioned drawbacks and, in particular, that of realising an electronic circuit for supplying high-frequency power for fluorescent lamps which is capable of supplying fluorescent lamps of different types and powers, overcoming the limitations of apparatuses available up to now.
- Another purpose of the present invention is that of realising an electronic circuit for supplying high-frequency power for fluorescent lamps which is particularly reliable and which is capable of recognising the type of lamp connected to it, then supplying it in the correct manner.
- a further purpose of the present invention is that of indicating an electronic circuit for supplying high-frequency power for fluorescent lamps which is also simple to realise, safe and relatively economic, also concerning the low management and maintenance costs, with respect to the electronic "ballasts" of the conventional type.
- the topology of the power stage of the power supply circuit for fluorescent lamps object of the invention is a half-bridge with series resonant load, consisting of the capacitor CRES and of the inductor LRES, and has the fluorescent lamp LF connected in parallel to the resonance capacitor CRES.
- Two power MOSFETs are connected to the series resonant load and are supplied with power by a supply line or high voltage bus HVB (about 400 Volts) .
- the power MOFSETs QHIGH and QLOW are driven by a suitable integrated command circuit ("half-bridge driver") - indicated with HBD in figure 1.
- the power supply circuit or "ballast" starts to oscillate at a frequency value far from the value of the resonance frequency of the mains comprising the capacitor CRES and the inductor LRES, allowing the cathodes or filaments of the lamp to be preheated, without switching it on.
- the voltage at the ends of the lamp LF is, indeed, kept below a predetermined value which is shown on the specific lamp. Such a value is the lowest from all of the lamps which can be supplied.
- the frequency of oscillation of the supply circuit gradually decreases moving closer to the resonance value of the mains L-C formed by the capacitor CRES and by the inductor LRES.
- the voltage at the ends of the lamp LF increases allowing it to be switched on.
- the supply circuit or "ballast" functions at the minimum frequency of oscillation corresponding to the maximum power.
- the procedure with which the electronic power supply recognises the lamp LF consists of measuring the average power absorbed by it and of varying the frequency of oscillation of the half-bridge circuit to adapt the current and voltage values to that which is requested by the lamp LF.
- the measurement of the power absorbed by the lamp LF is carried out through a resistance, indicated with RS in figure 2 connected in series to the "SOURCE" of the MOSFET with power QLOW.
- the average value of the voltage signal at the ends of the resistance RS is directly proportional to the average power absorbed by the lamp LF.
- a low power filter R-C is used, generically indicated with LPF in figure 3.
- a discriminator circuit of the power absorbed is foreseen which, in preferred example embodiments of the present invention, consists of a comparator CMP with output DO, of the open-drain type (see, in particular, figure 3).
- the signal coming from RS, mediated by the low power filter LPF, is compared with a low voltage reference LVR.
- a second comparator circuit PI ("preheat inhibit") is used to inhibit the recognition of the fluorescent lamp LF during the preheating step of the filaments.
- the output OUT of the comparator PI is low and forces to ground the low voltage reference LVR of the comparator CMP.
- the output DO (open-drain output) of the comparator CMP relative to the power signal is connected to the pin 6 (capacitor CT) of an integrated circuit which functions as a half-bridge driver circuit.
- the integrated circuit IR2156 is used as a half-bridge driver HBD.
- the output DO of the comparator CMP is also connected to the pin 4 (resistance RT) of the integrated driver circuit HBD, respectively, through a signal diode DS (usually a 1N4148 diode is used) and a resistance RSH.
- the output DO of the comparator CMP is high (circuit open), i.e. in minimum power conditions, the resistance RSH is connected in parallel to the resistance RT, unless there is a drop in potential on the diode DS. In such conditions, the capacitor CT is charged faster and the frequency of oscillation of the half-bridge is higher.
- the value of the resistance RT together with the value of CT, set the minimum value of the frequency of oscillation (and a corresponding maximum power value), whereas the value of the resistance RSH sets the frequency of oscillation relative to the minimum operating power condition.
- CMOS with output DO (open-drain) is used, indicated with CDO in figure 5.
- the comparator TS393 was used, in which the two voltage thresholds LVR (threshold of the power comparator CMP of figure 3) and HVR (threshold of "inhibit” of Figure 3) are obtained by a partition, formed by the resistances RDV1, RDV2, RDV3 of figure 5, of the supply voltage VCC of all of the integrated circuits, the typical value of which is 15.6 Volts.
- LVR and HVR are respectively connected to the non-inverting input of the power comparator CMP (pin 3 of the comparator CDO) and to the inverting input of the inhibit comparator PI (pin 6 of the comparator CDO).
- the inverting input of the power comparator CMP (pin 2 of the comparator CDO) is connected to the signal S coming from the resistance RS, mediated by the low-power filter R-C, whereas the inverting input of the inhibit comparator PI (pin 5 of the comparator CDO) is connected to the capacitor CPH (pin 7 of the driver circuit HBD of figure 5), with which the preheating time of the fluorescent lamp LF is set.
- figure 6 schematically illustrates the overall circuit of the power supply device or "ballast" object of the invention.
- said circuit has been divided into five blocks and, in particular, it is possible to identify an interference filter F ("EMI filter”), a stage S1 for the active control of the power factor (“PFC section”), a half-bridge driver circuit HBD, a discriminator circuit CDO of the power absorbed (“power comparator”) and a resonant load LR.
- EMI filter interference filter
- PFC section stage S1 for the active control of the power factor
- HBD half-bridge driver circuit
- CDO of the power absorbed power comparator
- LR resonant load
- the interference filter F is not essential for the operation of the supply circuit, but is obviously necessary to contain the interference within the limits set by the current norms in the field.
- the stage S1 allows the values of the power factor near to the unit to be obtained and allows the harmonic content of the current absorbed by the mains to be limited within the limits dictated by the norms.
- the stage S1 also allows a virtually constant continuous regulated voltage (with a low residual "ripple” at 100 Hz) to be obtained with which the half-bridge is to be supplied.
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- Circuit Arrangements For Discharge Lamps (AREA)
Abstract
An electronic circuit for supplying high-frequency power for fluorescent lamps (LF) of different types and powers, according to which the lamp (LF) is recognised by measuring the active power absorbed and, therefore, it is supplied with suitable current and voltage values; the power supply circuit thus adapts to each individual lamp, ensuring high performance, high efficiency and long useful life. <IMAGE>
Description
The present invention refers to an electronic circuit
for supplying high-frequency power to fluorescent lamps
of different types and powers.
Electronic ballasts are apparatuses which allow high-frequency
power supply (in the order of tens of kHz) to
fluorescent lamps with undoubted advantages in terms of
efficiency and performance, such as protection against
working anomalies, no flickering, etc.
Nevertheless, all of the types of electronic "ballast"
currently on the market can only supply a single type
of lamp, of a certain power, or groups of lamps having
electrical characteristics (lamp current and voltage)
which are similar between the individual lamps, with
the consequent drawbacks given by low performance
which, in many cases, is not congruous with the type of
lamp supplied, by low efficiency and by the relatively
short useful life.
The purpose of the present invention is therefore that
of avoiding the aforementioned drawbacks and, in
particular, that of realising an electronic circuit for
supplying high-frequency power for fluorescent lamps
which is capable of supplying fluorescent lamps of
different types and powers, overcoming the limitations
of apparatuses available up to now.
Another purpose of the present invention is that of
realising an electronic circuit for supplying high-frequency
power for fluorescent lamps which is
particularly reliable and which is capable of
recognising the type of lamp connected to it, then
supplying it in the correct manner.
A further purpose of the present invention is that of
indicating an electronic circuit for supplying high-frequency
power for fluorescent lamps which is also
simple to realise, safe and relatively economic, also
concerning the low management and maintenance costs,
with respect to the electronic "ballasts" of the
conventional type.
These and other purposes are achieved, in the
invention, by realising an electronic circuit for
supplying high-frequency power for fluorescent lamps
according to claim 1, to which we refer for the sake of
brevity.
Further characteristics and advantages of an electronic
circuit for supplying high-frequency power for
fluorescent lamps, according to the invention, shall
become clearer from the following description, given as
an example and not limiting purposes, referring to the
attached drawings, in which:
- figure 1 shows a circuit diagram relative to the topology of the power stage of the power supply device, according to the present invention;
- figure 2 shows a circuit for measuring the power absorbed by each lamp, which is used in the power supply device, according to the present invention;
- figures 3 and 4 show a block diagram of a discriminator circuit of the power absorbed and a circuit for changing the frequency of oscillation, which are present in a power supply device, according to the present invention;
- figure 5 represents a circuit for comparing and varying the frequency used in the power supply device, according to the present invention;
- figure 6 shows an example overall embodiment of the electronic circuit for supplying high-frequency power for fluorescent lamps, according to the present invention.
As can be seen clearly in the aforementioned figure 1,
the topology of the power stage of the power supply
circuit for fluorescent lamps object of the invention
is a half-bridge with series resonant load, consisting
of the capacitor CRES and of the inductor LRES, and has
the fluorescent lamp LF connected in parallel to the
resonance capacitor CRES.
Two power MOSFETs, indicated with QHIGH and QLOW in
figure 1, are connected to the series resonant load and
are supplied with power by a supply line or high
voltage bus HVB (about 400 Volts) . Moreover, the power
MOFSETs QHIGH and QLOW are driven by a suitable
integrated command circuit ("half-bridge driver") -
indicated with HBD in figure 1.
Connecting to the mains, the power supply circuit or
"ballast" starts to oscillate at a frequency value far
from the value of the resonance frequency of the mains
comprising the capacitor CRES and the inductor LRES,
allowing the cathodes or filaments of the lamp to be
preheated, without switching it on.
The voltage at the ends of the lamp LF is, indeed, kept
below a predetermined value which is shown on the
specific lamp. Such a value is the lowest from all of
the lamps which can be supplied.
Moreover, during the preheating step, recognition of
the lamp LF is stopped and the power supply circuit
oscillates at the same frequency independently of the
lamp LF connected.
With the preheating of the filaments of the lamp LF
completed, the frequency of oscillation of the supply
circuit gradually decreases moving closer to the
resonance value of the mains L-C formed by the
capacitor CRES and by the inductor LRES. The voltage at
the ends of the lamp LF increases allowing it to be
switched on.
With the lamp LF switched on, the supply circuit or
"ballast" functions at the minimum frequency of
oscillation corresponding to the maximum power.
The procedure with which the electronic power supply
recognises the lamp LF consists of measuring the
average power absorbed by it and of varying the
frequency of oscillation of the half-bridge circuit to
adapt the current and voltage values to that which is
requested by the lamp LF.
If an average power value greater than a certain
threshold is measured this means that the lamp LF with
the highest power is connected and the "ballast"
continues to function at the lowest frequency
corresponding to the maximum power.
If, on the other hand, an absorbed power value lower
than the aforementioned threshold is detected, this
means that a lamp LF with the lowest power is connected
and, in this case, the "ballast" increases the
frequency of oscillation reducing the power supplied to
the lamp LF.
The measurement of the power absorbed by the lamp LF is
carried out through a resistance, indicated with RS in
figure 2 connected in series to the "SOURCE" of the
MOSFET with power QLOW. The average value of the
voltage signal at the ends of the resistance RS is
directly proportional to the average power absorbed by
the lamp LF.
To obtain the average value of the voltage drop at the
ends of RS, according to the present invention, a low
power filter R-C is used, generically indicated with
LPF in figure 3. Following on from such a low power
filter LPF, a discriminator circuit of the power
absorbed is foreseen which, in preferred example
embodiments of the present invention, consists of a
comparator CMP with output DO, of the open-drain type
(see, in particular, figure 3).
The signal coming from RS, mediated by the low power
filter LPF, is compared with a low voltage reference
LVR.
When the signal S coming from the sensing circuit and,
therefore, coming from the resistance RS is greater
than the reference LVR the output DO of the comparator
circuit CMP is forced to ground. Vice-versa, when the
signal S is lower than the reference LVR the output DO
of the comparator CMP is an open circuit.
A second comparator circuit PI ("preheat inhibit") is
used to inhibit the recognition of the fluorescent lamp
LF during the preheating step of the filaments. In
practice, until the voltage VCPH is less than a high
voltage reference HVR, the output OUT of the comparator
PI is low and forces to ground the low voltage
reference LVR of the comparator CMP.
As can be seen in figure 4, the output DO ("open-drain
output") of the comparator CMP relative to the power
signal is connected to the pin 6 (capacitor CT) of an
integrated circuit which functions as a half-bridge
driver circuit. In particular, in preferred but not
limiting embodiments of the present invention, the
integrated circuit IR2156 is used as a half-bridge
driver HBD.
The output DO of the comparator CMP is also connected
to the pin 4 (resistance RT) of the integrated driver
circuit HBD, respectively, through a signal diode DS
(usually a 1N4148 diode is used) and a resistance RSH.
When the output DO of the comparator CMP is low
(practically at ground level), i.e. in maximum power
conditions, the resistance RSH is disconnected from the
pin 6 (capacitor CT) of the driver circuit HBD, since
the diode DS is inversely polarised, the voltage at the
pin 6 (and therefore the voltage taken at the ends of
the capacitor CT) always being greater than 4.8 Volts.
If, on the other hand, the output DO of the comparator
CMP is high (circuit open), i.e. in minimum power
conditions, the resistance RSH is connected in parallel
to the resistance RT, unless there is a drop in
potential on the diode DS. In such conditions, the
capacitor CT is charged faster and the frequency of
oscillation of the half-bridge is higher.
The value of the resistance RT, together with the value
of CT, set the minimum value of the frequency of
oscillation (and a corresponding maximum power value),
whereas the value of the resistance RSH sets the
frequency of oscillation relative to the minimum
operating power condition.
For the discriminator stage of the power absorbed
schematised in figure 3, according to the invention, a
double comparator CMOS with output DO ("open-drain") is
used, indicated with CDO in figure 5.
In particular, in the case of the present invention,
the comparator TS393 was used, in which the two voltage
thresholds LVR (threshold of the power comparator CMP
of figure 3) and HVR (threshold of "inhibit" of Figure
3) are obtained by a partition, formed by the
resistances RDV1, RDV2, RDV3 of figure 5, of the supply
voltage VCC of all of the integrated circuits, the
typical value of which is 15.6 Volts.
These two references LVR and HVR are respectively
connected to the non-inverting input of the power
comparator CMP (pin 3 of the comparator CDO) and to the
inverting input of the inhibit comparator PI (pin 6 of
the comparator CDO).
The inverting input of the power comparator CMP (pin 2
of the comparator CDO) is connected to the signal S
coming from the resistance RS, mediated by the low-power
filter R-C, whereas the inverting input of the
inhibit comparator PI (pin 5 of the comparator CDO) is
connected to the capacitor CPH (pin 7 of the driver
circuit HBD of figure 5), with which the preheating
time of the fluorescent lamp LF is set.
Finally, figure 6 schematically illustrates the overall
circuit of the power supply device or "ballast" object
of the invention. For the sake of clarity, said circuit
has been divided into five blocks and, in particular,
it is possible to identify an interference filter F
("EMI filter"), a stage S1 for the active control of
the power factor ("PFC section"), a half-bridge driver
circuit HBD, a discriminator circuit CDO of the power
absorbed ("power comparator") and a resonant load LR.
The interference filter F is not essential for the
operation of the supply circuit, but is obviously
necessary to contain the interference within the limits
set by the current norms in the field.
The stage S1 allows the values of the power factor near
to the unit to be obtained and allows the harmonic
content of the current absorbed by the mains to be
limited within the limits dictated by the norms.
The stage S1 also allows a virtually constant
continuous regulated voltage (with a low residual
"ripple" at 100 Hz) to be obtained with which the half-bridge
is to be supplied.
From the description which has been made, the
characteristics of the electronic circuit for supplying
high-frequency power for fluorescent lamps object of
the present invention are clear, just as the advantages
are also clear.
Finally, it is clear that numerous other variants can
be brought to the supply circuit in question, without
for this reason leaving the novelty principles inherent
to the inventive idea, just as it is clear that, in the
practical embodiment of the invention, the materials,
the shapes and the sizes of the illustrated details can
be whatever according to requirements and they can be
replaced with others which are technically equivalent.
Claims (9)
- Electronic circuit for supplying high-frequency power for fluorescent lamps (LF), characterised in that it comprises a command circuit (HBD) of a power stage, a resonant load circuit (LR) and a discriminator circuit (CDO) of the active power absorbed by each lamp (LF), which measures the power absorbed by each type of fluorescent lamp (LF), so that said lamp (LF) is correctly supplied with consequent determined values of current and voltage.
- Electronic power supply circuit according to claim 1, characterised in that it also comprises at least one interference filter (F) and at least one circuit stage (S1) for actively controlling the power factor, in order to obtain power factor values near to the unit and to limit the harmonic content of the current absorbed by the mains, said circuit control stage (S1) also allowing a substantially constant continuous regulated voltage to be obtained with which said power stage is to be supplied.
- Electronic power supply circuit according to claim 1, characterised in that said power stage is of the half-bridge type and comprises a resonant load of the series type with resonance capacitor (CRES) and inductor (LRES), said fluorescent lamp (LF) being connected in parallel to said resonance capacitor (CRES).
- Electronic power supply circuit according to claim 1, characterised in that power transistor devices (QHIGH, QLOW), which are supplied with power by a high voltage ballast (HVB), are connected to said series resonant load, said transistor devices (QHIGH, QLOW) being driven by said driver circuit (HBD) and said connection to the supply line being used to operate a preheating step of the filaments of said lamp (LF) during which said supply circuit oscillates at a predetermined frequency value, independently from the type of fluorescent lamp (LF) connected.
- Electronic power supply circuit according to claim 4, characterised in that following said preheating step of the filaments of the lamp (LF) there is a step in which said frequency of oscillation gradually reduces moving closer to the resonant frequency value of said resonant circuit (CRES, LRES), so that the voltage at the ends of said lamp (LF), increasing, allows it to be switched on.
- Electronic power supply circuit according to claim 5, characterised in that said frequency of oscillation of the half-bridge circuit is regulated so as to adapt the voltage and current values applied to said fluorescent lamp (LF), according to the average power values absorbed by the lamp (LF) with respect to a determined threshold value.
- Electronic power supply circuit according to claim 6, characterised in that one of the terminals of at least one of said power transistor devices (QLOW) is connected to at least one resistive element (RS), suitable for measuring the power absorbed by said lamp (LF), said resistive element (RS) being connected to a low-power filter (LPF) which is, in turn, connected in cascade to said discriminator circuit (CDO) of the power absorbed.
- Electronic power supply circuit according to claim 7, characterised in that said discriminator circuit (CDO) comprises at least one first comparator device (CMP) with output (DO) of the open-drain type, said first comparator (CMP) taking care of comparing a signal (S) coming from said resistive element (RS) and mediated by said low-power filter (LPF) with a low voltage reference (LVR), so as to force said output (DO) to ground or to make it an open circuit, according to the value of said signal (S) compared to said low voltage reference (LVR).
- Electronic power supply circuit according to claim 8, characterised in that a second comparator device (PI) is used to inhibit the recognition of said fluorescent lamp (LF) during the preheating step of the filaments, the output (OUT) of said second comparator (PI) being connected to said low voltage reference (LVR).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ITMI20012453 | 2001-11-21 | ||
| ITMI20012453 ITMI20012453A1 (en) | 2001-11-21 | 2001-11-21 | HIGH FREQUENCY ELECTRONIC POWER CIRCUIT FOR LAMPS |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP1315406A2 true EP1315406A2 (en) | 2003-05-28 |
| EP1315406A3 EP1315406A3 (en) | 2004-05-12 |
Family
ID=11448622
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP02079806A Withdrawn EP1315406A3 (en) | 2001-11-21 | 2002-11-18 | Electronic circuit for supplying high-frequency power for fluorescent lamps |
Country Status (2)
| Country | Link |
|---|---|
| EP (1) | EP1315406A3 (en) |
| IT (1) | ITMI20012453A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010031535A1 (en) | 2008-09-16 | 2010-03-25 | Tridonicatco Gmbh & Co. Kg | Determination of the type of a lamp or the topology of a plurality of lamps |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1980001839A1 (en) * | 1979-02-27 | 1980-09-04 | New Nippon Electric Co | Gas concentration detector |
| US4356432A (en) * | 1981-02-25 | 1982-10-26 | Exxon Research And Engineering Co. | Solid state power switch for gas discharge lamps |
| JPH0658830B2 (en) * | 1987-11-30 | 1994-08-03 | 池田電機株式会社 | Discharge lamp lighting device |
| JP3273161B2 (en) * | 1996-06-11 | 2002-04-08 | シャープ株式会社 | Load drive circuit |
| JP3694146B2 (en) * | 1997-06-10 | 2005-09-14 | 三菱電機株式会社 | Discharge lamp lighting device |
-
2001
- 2001-11-21 IT ITMI20012453 patent/ITMI20012453A1/en unknown
-
2002
- 2002-11-18 EP EP02079806A patent/EP1315406A3/en not_active Withdrawn
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010031535A1 (en) | 2008-09-16 | 2010-03-25 | Tridonicatco Gmbh & Co. Kg | Determination of the type of a lamp or the topology of a plurality of lamps |
Also Published As
| Publication number | Publication date |
|---|---|
| EP1315406A3 (en) | 2004-05-12 |
| ITMI20012453A1 (en) | 2003-05-21 |
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