EP0239420A1 - Ballast à haute fréquence pour tubes à décharge en atmosphère gazeuse - Google Patents

Ballast à haute fréquence pour tubes à décharge en atmosphère gazeuse Download PDF

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Publication number
EP0239420A1
EP0239420A1 EP87302692A EP87302692A EP0239420A1 EP 0239420 A1 EP0239420 A1 EP 0239420A1 EP 87302692 A EP87302692 A EP 87302692A EP 87302692 A EP87302692 A EP 87302692A EP 0239420 A1 EP0239420 A1 EP 0239420A1
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EP
European Patent Office
Prior art keywords
circuit
voltage
frequency
power
current
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
Application number
EP87302692A
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German (de)
English (en)
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EP0239420B1 (fr
Inventor
Thomas E. Dean
William H. Henrich
David M. Fischer
Lawrence J. Stratton
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Advance Transformer Co
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Thomas Industries Inc
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Priority to AT87302692T priority Critical patent/ATE71244T1/de
Publication of EP0239420A1 publication Critical patent/EP0239420A1/fr
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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
    • H05B41/26—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
    • H05B41/285—Arrangements for protecting lamps or circuits against abnormal operating conditions
    • H05B41/2851—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions
    • H05B41/2856—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions against internal abnormal circuit conditions
    • 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
    • H05B41/285—Arrangements for protecting lamps or circuits against abnormal operating conditions
    • H05B41/2858—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the lamp against abnormal operating conditions

Definitions

  • the present invention relates to circuits for energizing gaseous discharge lamps such as fluorescent lamps or high intensity discharge lamps. More particularly, it relates to a ballast using solid state switches and adapted to energize the lamps with high frequency current. Ballast circuits of this type are normally designed to receive energy from a conventional 60 Hz. cycle as is commonly available, and by means of frequency inversion, generate a higher frequency signal (in the range of 25-100 KHz.) to energize the lamps.
  • ballast manufacturers have, in the last few years, given increased attention to high frequency excitation. Lamp manufacturers have concluded that lamp life may seriously be diminished if the crest factor of the excitation current is not maintained within certain limits.
  • the crest factor for lamp current (which is defined as the ratio of peak current to RMS current) was approximately 1.41 because 60 Hz. voltage is sinusoidal.
  • a desired crest factor can be obtained simply by using large inductors and capacitors to filter the line voltage, but the power requirements of these components make them expensive and somewhat bulky, despite operation at higher frequencies.
  • the preferred embodiment of the present invention is directed to a high frequency inverter ballast for gaseous discharge lamps which achieves a desired crest factor for lamp current with a relatively simple and inexpensive circuit which does not require magnetic components for sensing the lamp current, yet which has many of the desirable characteristics of other solid state ballast circuits.
  • the present invention uses first and second power switches which are operated sequentially and mutually exclusively to cause current to flow in the primary winding of a power transformer when conducting.
  • the lamp circuit is connected in the secondary of the power transformer.
  • Current is regulated in the primary by sensing the current through the power switches and turning off the conducting switch when the sensed current reaches a predetermined value, thereafter turning on the complementary power switch, causing current to flow in the opposite polarity in the secondary of the power transformer.
  • current mode operation or regulation.
  • current mode regulation may be employed in various circuit configurations, but the principal advantage is that it maintains the peak amplitude of transformer primary current (and consequently secondary current as well) substantially constant.
  • the B+ voltage for the inverter circuit is derived from a conventional 60 Hz. source which is full-wave rectified and from a make-up source which supplied a minimum voltage during periods when the full-wave rectified voltage would otherwise reduce to zero.
  • Make-up power is supplied from a capacitor which is charged during voltage peaks.
  • the power switches are connected in a push-pull circuit arrangement and operated in current mode regulation.
  • the frequency of operation of the power switches (and thus, the frequency of the lamp circuit) is also increased.
  • the frequency of operation decreases.
  • the maximum current flowing in the switches remains constant.
  • the load circuit is designed such that its inpedance increases with frequency.
  • the frequency of operation is also higher, and the impedance of the load is greater at the higher frequency.
  • the source voltage is at a lower value the inverter operating frequency is lower and the load impedance is lower. This has the effect of equalizing lamp current and maintaining the peak value of load current at a substantially constant value even though the B+ voltage varies considerably from its peak value to the value of the make-up voltage (which is one-half the peak voltage). A desirable crest factor for lamp current is thereby achieved.
  • Another feature of the present invention is a circuit provision wherein as power is drawn from the B+ source to be stored in the make-up voltage supply, a signal is generated which increases the current flowing in the power switches so as not to diminish the actual lamp current during periods when energy is being tapped from the primary source and stored in the make-up voltage source.
  • a minimum frequency oscillator is also incorporated in the circuit so that in the case normal operation is interrupted for any reason, the minimum frequency oscillator becomes actuated and drives the power switches at a minimum frequency (which, advantageously, is a function of the magnitude of the B+ voltage also).
  • the minimum frequency oscillator is reset and re-synchronized with the operation of the inverter switches during each half cycle of normal operation so it does not drive the inverter switches during normal operation.
  • Input electrical power is received from a conventional source, such as 60 Hz, 115 v. or 220 v. power line and coupled to input terminals 10.
  • the input power is fed to a full-wave rectifier bridge circuit generally designated 12, the output of which is fed to an input terminal 13 of a power transformer generally designated 15.
  • Terminal 13 may be a center tap of first and second primary windings designated 16, 17 respectively, as illustrated.
  • a make-up voltage supply generally designated by reference numeral 20 stores power during peaks of the B voltage and couples it along a line 21 to the terminal 13 of the power transformer 15 during periods when the voltage falls below a predetermined value of the B+ source. These periods are sometimes referred to as inter-cusp periods.
  • the B+ voltage at terminal 13 is a full-wave rectified sinusoidal voltage which does not diminish below a predetermined, fixed minimum level. That minimum level preferably is approximately one-half the peak voltage, is seen in idealized form in FIG. 2, line L1 and generally designated by reference numeral 25.
  • a power inverter circuit generally designated 28 includes first and second semi-­conductor switches 30, 31 which, as illustrated, may be N-channel, enhancement mode MOSFET's such as are commercially available under the designation IRF 730 from General Electric Co. or RCA, Inc.
  • the power switches 30, 31 are turned “on” (i.e., switched to a conducting state) when a positive level voltage is fed to the gate input lead. When that level is removed, the associated power switch is turned “off” (i.e., non-conducting).
  • Power switches 30, 31 (sometimes referred to as “inverter switches") are connected in series with series-connected primary windings 16, 17.
  • the junction between power switches 30, 31 is designated 32 and connected to ground through a current-sensing resistor 33.
  • the power transformer includes a secondary winding generally designated 34 which is coupled to a lamp circuit generally designated 35 and including at least one gaseous discharge lamp such as a fluorescent lamp, seen at 36. In this case, a second lamp 37 is included in the lamp circuit.
  • a gaseous discharge lamp such as a fluorescent lamp, seen at 36.
  • a second lamp 37 is included in the lamp circuit.
  • the illustrated circuit once it is understood, may be employed to energize and operate other lamp circuit configurations or different gaseous discharge lamps, such as so-called High Intensity Discharge (HID) lamps.
  • HID High Intensity Discharge
  • an inductor 38 (which may be the leakage inductance of the power transformer) is illustrated schematically as connected in series with the lamps and transformer secondary so that any current flowing in the lamps 36, 37 also flows in the inductor 38.
  • Logic circuitry generally designated by reference numeral 40 controls the state of power switches 30, 31 in current mode control, and it also provides a suitable turn-off voltage and timing sequence for applying the control voltages for the power switches.
  • a first comparator circuit 42 senses the voltage at junction 32 which is a signal representative of the current flowing in whichever of the power switches 30, 31 is conducting at any given time. Comparator 42 senses the signal on its negative or inverting input lead and compares it with a fixed reference voltage V ST.PT. (standing for a "set point” voltage) and generates an output signal when the sensed "current" signal (actually a voltage representation of current) reaches a predetermined value determined by the set point voltage.
  • the logic circuit 40 includes a flip-flop circuit 43 which changes its output state each time a positive-going signal appears at its clock input, C.
  • the output signals of the flip-flop 43 are coupled through gating circuitry to be described for turning the inverter power switches 30, 31 on and off in mutually exclusive time periods so that they operate in "push-pull" fashion with only one semiconductor switch conducting at any given time.
  • the low frequency supply voltage is derived from the input line voltage connected to the source lines 10 and rectified by bridge circuit 12. It is fed to the input terminal 13 of the primary winding 15 of the power transformer.
  • the voltage appearing at the junction 13 from output of the bridge rectifier circuit 12 would be a full-wave rectified voltage, but it is modified by power fed from the make-up power source 20 coupled from the winding 19 of the transformer 15 and storing energy in a capacitor to be described which is then coupled back to the junction 13 of the power transformer during periods when the output voltage of the bridge circuit 12 is reduced below a predetermined level.
  • the solid line generally designated 25 represents the B+ voltage appearing at the junction 13.
  • Each cycle of the B+ voltage includes a portion of a sinusoidal wave form such as is designated 44a which increases to a peak and then reduces, and a fixed DC minimum level represented by the horizontal line 44b.
  • the make-up voltage source 20 supplies a DC level to sustain inverter operation.
  • power switch 31 is non-conducting, and a voltage will appear at the secondary winding 34 of the power transformer to energize the lamp load circuit.
  • the current I1 builds up generally linearly because of the inductive reactance in the circuit, so the voltage at the junction 32 increases in accordance with, and is representative of, the current flowing in the power switch 30. It is also representative of the currentflowing in the lap circuit, as persons skilled in the art will appreciate.
  • the voltage at junction 32 is coupled to the negative (or inverting) input of comparator 42.
  • the comparator 42 When that signal exceeds the set point voltage V ST.PT. which is fed to the positive (or non-inverting) input of comparator 42, the comparator 42 will switch states.
  • the output signal is fed to the logic circuitry 40 and causes the flip-flop circuit 43 to change its output state, thereby turning off the power switch 30, and very shortly thereafter, turning on power switch 31, causing a similar current to flow in the primary winding 16 of the power transformer as indicated by the arrow I2 in FIG. 1.
  • FIG. 3 Since the current increases in the sensing resistor 33 at the initial portion of an exponential increase, it can be considered to be substantially linear. If the voltage (or current) is rising to one level (for example, the level V1 in FIG. 3), the voltage will be a line as seen at 46 in FIG. 3. If, however, the voltage is rising toward a second, higher level, such as that designated at V2 in FIG. 3, then the voltage will increase as represented by line 47.
  • the frequency of the inverter current will increase and as the B+ voltage decreases, the frequency of the inverter current will decrease.
  • the inverter switches are operated in current mode control, the peak value of the inverter current will be constant and thus regulated, even though its frequency varies monotonically with the magnitude of the B+ voltage.
  • FIG. 2 there are shown three sets or ramp waveforms designated respectively 48, 49 and 50 and depicting, in idealized form, the voltage at junction 32 at times t1, t2 and t3 on line L-1 of FIG. 2.
  • the first ramp of each of the sets of ramps 48, 49 and 50 represents the voltage at junction 32 during the time when power switch 30 is conducting, and the subsequent ramp of each set indicates the corresponding voltage at the time when power switch 31 is conducting.
  • the resulting voltage waveform on the secondary of the power transformer is seen on line L-2 of FIG. 2.
  • This waveform has also been drawn in idealized form to illustrate the principle involved rather than to try to depict accurately the exact frequencies or voltages, as is customary.
  • the frequency of the current in the primary winding (and thus the secondary winding), of the power transformer 15 is at a relative high frequency; and when the input source voltage is relatively low, the frequency of the load current is relatively low.
  • the impedance of inductor 38 is proportionately greater; and when the frequency of the lamp current is relatively low, the impedance offered by the inductor 38 is correspondingly low.
  • the resulting load current as seen in line L-4 of FIG. 2, has a peak amplitude which is substantially constant, although the frequency of the load current varies from a minimum frequency during time t3, to approximately twice the minimum frequency at time t1, when the B+ voltage is at a maximum.
  • the excitation frequency of the lamp is in the range of 30 KHz-75 KHz, thereby achieving the benefits of high frequency excitation, but the crest factor of the lamp current is maintained in a desired range, as discussed more fully below.
  • current regulation and improved crest factor are achieved without sensing lamp current in the secondary of the transformer 15 (which requires inductive sensors such as current transformers) thereby minimizing bulk, cost and quality assurance restrictions.
  • the input section includes a fuse 52 in one of the lines 10 for system protection, a metal oxide varistor (MOV) over-voltage protection device 53 for protection against transient excursions of the input voltage, as electromagnetic interference filter circuit generally designated 54 and including series inductors L1 and L2 and shunt capacitors C1 and C2 in each input line, and the previously identified bridge rectifier circuit 12.
  • the filter circuit not only prevents electromagnetic interference generated in the circuit from being coupled to the power lines, but it isolates the inverter switches from any high frequency transients on the input power lines.
  • a high frequency bypass capacitor 55 is also coupled between the output of the bridge circuit 12 and ground.
  • Low voltage for the logic circuitry is derived from the output of the bridge circuit 12 through a resistor 56 to a zener diode 57.
  • a filter capacitor 58 and a high frequency bypass capacitor 59 are connected across the diode 57, the low voltage source being designated V cc. .
  • the voltage V cc for the logic supply is less than the output voltage of the bridge circuit 12. This voltage difference can be achieved economically by a voltage drop across a series resistor (i.e., resistor 56) in the illustrated embodiment without substantially reducing operating efficiency and without more costly components because arranging the power switches in a current mode control, push-pull configuration requires less logic circuitry and, therefore, less power than many alternative designs.
  • each of the power switches 30, 31 has a "snubber" circuit 60 connected across its power terminals for protecting the devices against high frequency transient signals.
  • winding 19 of transformer 15 couples power fed from the source lines 10 to a second bridge rectifier circuit 61, the output of which is connected to a storage capacitor 62.
  • the other output terminal of the bridge circuit 61 is connected through a resistor 63 to ground; and a high frequency by-pass capacitor 64 is connected across the storage capacitor 62.
  • a diode 65 couples the make-up voltage source to the input terminal 13 of the power transformer.
  • the previously described input signal to comparator 42 from the junction 32 is coupled through a resistor 67; and a capacitor 68 is connected between the negative input terminal of comparator 42 and ground and serves as a high frequency shunt. Additional signals are coupled to the negative input terminal of comparator 42 from the source voltage at junction 13 through resistor 69 and from the signal developed across resistor 63 through a resistor 70. The functions of these two signals will be described below.
  • the flip-flop 43 is a "D" type flip-flop, having a data input designated D and a clock input designated C.
  • the output of flip-flop 43 is coupled through a NAND gate 72 and an inverter 73 to the gate lead of power switch 30.
  • the Q output of flip-flop 43 is coupled through a NAND gate 74 and an inverter 75 to the gate input of power switch 31.
  • the output of flip-flop 43 is also connected to the data input D.
  • the output of comparator 42 is connected through an inverter 76 to the clock input C of the flip-flop 43.
  • an initialization (or start-up) circuit senses input voltage and inhibits operation of the logic circuit 40 until the input voltage level has reached a predetermined threshold, as during start up.
  • the circuit includes a comparator 81 having its positive (non-inverting) input connected to a voltage divider circuit comprising resistors 82, 83 connected between the low voltage source V cc and ground.
  • the output of comparator 81 is connected through a diode 84 to a junction designated 85 which is the input to the inverter 76 described above.
  • a resistor 86 is connected between the source V cc and the junction 85.
  • a resistor 87 is connected between the low voltage source and the output of comparator 81, and a resistor 88 is connected between the positive input and the output of comparator 81.
  • the resistors 87, 88 provide positive feedback to the input of comparator 81 so that once it is switched it will remain switched unless the input voltage diminishes appreciably as will be understood. This hysteresis effect of the start-up circuit prevents undesired switching of the logic enable circuit when the source voltage is passing through the threshold for operation.
  • a resistor 90 is connected between the low voltage source and a zener diode 91.
  • the voltage developed across the diode 91 is coupled directly to the negative input of comparator 81.
  • the function of the initialization circuit 80 is to inhibit operation of the power switches until the low voltage source has stabilized when the circuit is initially energized.
  • Resistors 82 and 83 form a voltage divider network which is designed such that the voltage fed to the non-inverting input of comparator 81 is less than the reference voltage across diode 91 until the diode conducts and clamps the voltage at the non-inverting input of comparator 81 which by design does not occur until V cc has nearly reached its desired value.
  • the output of the comparator 81 is clamped to ground, thereby holding the voltage at junction 85 at a low level through diode 84.
  • the junction 85 is also connected to inputs of the NAND gates 72, 74, and serves as an "enable" signal.
  • the output of the comparator 81 is relatively low, the gates 72, 74 are disabled, so that the power switches cannot conduct.
  • a positive or relatively high signal is required on the gate lead of a power switch to cause it to conduct.
  • a minimum frequency oscillator generally designated 95 is set at a frequency below the normal operating range and does not affect the operation of the circuit unless the operating frequency of the push-pull inverter falls below the design range or stops operating altogether. In such a case, the minimum frequency oscillator serves to operate the inverter at a minimum frequency which preferrably varies with the magnitude of the input supply voltage B+.
  • the minimum frequency oscillator 95 includes a capacitor 96 having one terminal grounded and the other terminal connected to the low voltage power source through a diode designated 99 of a reverse polarity, and it is also connected to the B+ voltage through a resistor 100.
  • the positive terminal of capacitor 96 is also connected through a resistor 101 to the output of a comparator circuit 102.
  • a comparator circuit 103 has its positive input connected to the previously described reference voltage generated across the diode 91 (as is the negative input of the comparator 102).
  • the negative input of comparator 103 is connected to the positive terminal of the capacitor 96.
  • the positive input of the comparator 102 is connected through an inverter 105 to the output of the previously described inverter 76.
  • the set point voltage, V ST.PT. is generated across a capacitor 108, the positive terminal of which is connected to the movable arm of a potentiometer generally designated 109.
  • a fixed resistor 110 is connected in series with the fixed resistor of the potentiometer 109 to the reference voltage developed across zener diode 91. As previously mentioned, the set point voltage is fed to the positive input of the comparator 42.
  • the minimum frequency oscillator 95 serves to establish a minimum switching frequency for the inverter (i.e., the power switches 30, 31) so that in the event comparator 42 does not trigger the flip-flop 43, the minimum frequency oscillator 45 will perform that function. Otherwise, it would be possible to have one of the power switches 30, 31 be left on indefinitely, thereby saturating the power transformer and preventing normal operation of the circuit.
  • the normal operation of the circuit proceeds as follows. Assuming the power switch 30 has just been switched to a conducting state, the voltage at the junction 32 increases as current flows through resistor 33. That voltage signal is fed through resistor 67 to the negative input of comparator 42, the positive input of which is at the fixed set point voltage.
  • comparator 42 When the increasing voltage appearing on the negative input of comparator 42 exceeds the set point voltage, the output of comparator 42 switches to a relatively low voltage which is fed directly to the gates 72, 74 to disable them for a short period of time to permit the flip-flop 43 to switch its state and to permit current flowing through power switch 30 to return to zero (which does not happen intantaneously).
  • the voltage on the negative (inverting) input of comparator 42 is represented by the ramp voltage 107.
  • the output of comparator 42 goes relatively low, thereby disabling the switches 72, 74 and turning off the power switch 30 at time t6 in FIG. 4.
  • the current flowing through the switch takes some finite time to reduce to zero as indicated by the portion 108, although the lines 107 and 108 are not necessarily drawn to the same time scale.
  • the same output signal of comparator 42 which disables the gates 72, 74 is inverted by inverter 76 and fed to the clock input C of the flip-flop 43 to cause its outputs to change state because the output is connected to the data input D of the flip-flop.
  • the gates 72, 74 are disabled before flip-flop 43 changes its state so that the switching signals on the output leads of the flip-flop are not fed directly to the power switches.
  • the output signal of the inverter 76 is coupled through inverter 105, the output signal of which is a negative pulse which causes comparator 102 to switch to a low output level and thereby create a low impedance path for quickly discharging capacitor 96. This resets the timing of the minimum frequency oscillator and synchronizes it with the switching of the inverter switches under normal operating conditions.
  • the minimum frequency oscillator will nevertheless sustain operating at a minimum frequency as follows.
  • comparator 102 changes state from a relatively low voltage output to a relatively high voltage output, the output of the comparator is floating so that it becomes a comparatively high impedance and is not a substantial factor in charging capacitor 96. Rather, capacitor 96 is charged as a function of the magnitude of voltage of the B+ supply (through resistor 100).
  • comparator 103 when the voltage on capacitor 96 exceeds the reference voltage across zener diode 91, comparator 103 will switch its output from a relatively high voltage level to a low voltage level, thereby disabling gates 72, 74, triggering the clock input of the flip-flop 43 via inverter 76, and causing the output of comparator 102 to go low. This discharges capacitor 96 which, in turn, causes comparator 103 to change states once more so that its output goes to a relatively high voltage level. As described above, when the signal at junction 85 goes positive, gates 72, 74 are enabled once more, but since the state of flip-flop 43 has changed, the complementary power switch (30, 31) will conduct this half cycle.
  • the timing of the charging of capacitor 96 depends primarily on the value of the capacitor and the value of resistor 100, and the magnitude of the B+ voltage.
  • the minimum operating frequency of the minimum frequency oscillator (which is not a fixed frequency oscillator, it will be observed, because of the influence on the charging timer capacitor 96 caused by the value of the B+ voltage), is designed to be lower than the minimum operating frequency of the inverter during normal operation. This insures that the inverter will be operating as designed for normal operation and not under the minimum frequency oscillator.
  • the gates 72, 74 are disabled, as described, and the flip-flop 43 is clocked, but also, the same signal is fed through inverter 105 to cause the comparator 102 to change states and have its output grounded, thereby discharging capacitor 96 and resetting the time base for the minimum frequency oscillator.
  • the minimum frequency oscillator is synchronized automatically each half cycle, with the switching on of the power switches.
  • the minimum frequency oscillator comes into play only after the current in current sensing resistor 33 and the voltage at junction 32 do not exceed the set point voltage during a period of time longer than the time it takes capacitor 96 to charge to the reference voltage on the positive input of comparator 103.
  • the time for the voltage at junction 32 to reach the set point voltage will be correspondingly less.
  • the period of the minimum frequency oscillator 95 will be correspondingly less and the operating frequency will be higher because, with the B+ voltage comparatively high, charging current through resistor 100 to charge the timing capacitor 96 will be correspondingly greater, thereby reducing the time for the capacitor to charge to the reference voltage on the positive input of comparator 103.
  • the base or set frequency of the minimum frequency oscillator increases and decreases as the B+ voltage increases and decreases.
  • Persons skilled in the art will appreciate that having the base frequency of the minimum frequency oscillator 95 vary with the value of B+ voltage reduces the requirements and thus the size of the power transformer. Reduced size, in turn, reduces its cost.
  • resistor 69 is connected between the B+ voltage terminal 13 and the inverting input of comparator 42. As the B+ voltage becomes greater, more current is fed through resistor 69, causing comparator 42 to change states earlier than otherwise would occur, and thereby compensating for the overshooting current mentioned above.
  • Resistor 70 and its associated circuitry compensates for yet another effect.
  • the storage capacitor 62 which stores power for the make-up voltage during the inter-cusp period is charged by the bridge circuit 61 only when the B+ voltage is near a peak, and during that time, energy drawn from the source reduces the energy available to the lamp circuit. Since a constant load current is desired, and some input power is diverted to the make-up power source as just indicated, a signal is generated across resistor 63 during the time when capacitor 62 is being charged. This signal is a negative signal which draws a slight current through resistor 70 and causes the current through resistor 33 to rise to a slightly higher value before the input signal to the inverting input of comparator 42 will switch.
  • the additional power is coupled to store energy in storage capacitor 62 for use during the inter-cusp period of source voltage and thereby partly compensate for the effect of draining power during voltage peaks of the primary source voltage to charge the make-up capacitor 62 by extending the "on" time of the power switches as a function of the magnitude of the B+ voltage.
  • Inductor 38 is illustrated in FIG. 1 as a separate component. Preferably, however, it is incorporated into the magnetic design of the power transformer 15. In either case, whether a separate component is included or the transformer 15 is designed to have the desired higher impedance at higher frequency, the overall effect is that as the inverter operating frequency increases, the impedance seen by the power switches also increases and the lamp load current remains substantially constant.
  • the inductor 38 may be approximately 4 mhy (millihenry).
  • the operating frequency of the power inverter under normal conditions varies from 30 KHz to 75 KHz; and a crest factor of approximately 1.6 has been obtained.
  • the minimum frequency oscillator operates in a frequency range from approximately 23 KHz to 40 KHz.
  • measuring inverter current in the circuit connected to the primary winding of the power transformer, as distinguished from the load circuit in the secondary of the transformer further reduces cost because it eliminates any need for a current transformer in the secondary or load circuit.
  • FIG. 5 there is shown an alternative embodiment of the invention which uses current mode regulation as described above, but which includes the switches and power transformer in a half-bridge circuit configuration, as distinguished from the push-pull arrangement shown in FIG. 1 and described above.
  • the half-bridge circuit has isolating transformers for sensing current in, and for driving the power switches and these components will increase cost.
  • the half-bridge configuration also requires increased capacity in the low voltage (i.e., logic) power supply.
  • the half-bridge circuit arrangement permits the use of power MOSFET switches with lower voltage and higher current ratings which currently are less expensive.
  • the half-bridge circuit may be used, for example, with a 277 v. line voltage.
  • the B+ voltage is derived with a full-wave rectifier and a make-up source as described in connection with the embodiment of FIG. 1
  • Corresponding elements in FIG. 5 are given the same reference numeral as in FIG. 1 followed by an "A".
  • the MOSFET power switches are designated 30A and 31A and are connected in series across the B+ supply.
  • Capacitors 220 and 221 are also connected in series across the B+ supply voltage; and the primary winding 222 of power transformer 223 forms the diagonal branch of the bridge circuit.
  • the lamp load circuit 35A is connected to the secondary winding 224 of the power transformer.
  • power transformer 223 has a leakage inductance similar to that designated 38 in FIG. 1 and performs a similar function.
  • current flowing in the conducting power switch is sensed by a current transformer 226 having its primary coil connected in series with primary winding 222.
  • the current transformer could be in the secondary of the power transformer.
  • the output signal of current transformer 226 is coupled to the input of logic circuit 140 which may be substantially the same as the previously described logic circuit 40, except that it is responsive to the absolute value of the output of current transformer 226 (i.e., not polarity sensitive).
  • the output of the current transformer 226 may be coupled through a diode bridge (which gives a signal representative of the absolute value of the input signal and is not sensitive to the polarity of the input signal) to the junction of resistor 70 and capacitor 68 of FIG.
  • the inverter drive signals of inverter circuits 73, 75 are, in this case, coupled to the primary winding 228 of a drive transformer 229 having two secondary windings 230 and 231 which are connected in the gate circuits respectively of the power switches 30A, 30B. Resistor 67 of the FIG. 1 embodiment is eliminated.
  • the drive transformer 229 has its secondary windings arranged in a polarity to cause only one of the switches to conduct at any given time.
  • switch 30A When switch 30A conducts, for example, current flows from the positive terminal of the B+ voltage through MOSFET 30A, the primary of current transformer, the primary winding 222 of the power transformer (from the plus to the minus terminal) and capacitor 221 to the negative terminal of the B+ supply.
  • the bistable circuit of the logic circuit switches states; and after switch 30A becomes non-conducting, switch 30B is turned on and current flows through capacitor 220, primary winding 222 (this time in the opposite direction), the current transformer and switch 30B.
  • an alternating current is generated in the power transformer to energize the lamp load circuit 35A.
  • the frequency of operation of the inverter increases and decreases, but the peak value of current flowing in the primary (and secondary) of the power transformer 223 is substantially constant.
  • the leakage reactance of the power transformer is such as to present an increased impedance so that the peak value of load current also remains substantially constant and the crest factor of load current remains below a desired value.

Landscapes

  • Circuit Arrangements For Discharge Lamps (AREA)
  • Inverter Devices (AREA)
EP87302692A 1986-03-28 1987-03-27 Ballast à haute fréquence pour tubes à décharge en atmosphère gazeuse Expired - Lifetime EP0239420B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT87302692T ATE71244T1 (de) 1986-03-28 1987-03-27 Hochfrequenz-vorschaltgeraet fuer gasentladungslampen.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US84585386A 1986-03-28 1986-03-28
US845853 1986-03-28

Publications (2)

Publication Number Publication Date
EP0239420A1 true EP0239420A1 (fr) 1987-09-30
EP0239420B1 EP0239420B1 (fr) 1992-01-02

Family

ID=25296241

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87302692A Expired - Lifetime EP0239420B1 (fr) 1986-03-28 1987-03-27 Ballast à haute fréquence pour tubes à décharge en atmosphère gazeuse

Country Status (6)

Country Link
EP (1) EP0239420B1 (fr)
JP (1) JPS63999A (fr)
AT (1) ATE71244T1 (fr)
AU (1) AU609388B2 (fr)
CA (1) CA1327991C (fr)
DE (1) DE3775588D1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0311424A2 (fr) * 1987-10-08 1989-04-12 ADVANCE TRANSFORMER CO. (a Division of Philips Electronics North America Corporation) Circuit ballast haute fréquence pour lampe à décharge gazeuse
EP0320944A1 (fr) * 1987-12-17 1989-06-21 Pintsch Bamag Antriebs- und Verkehrstechnik GmbH Convertisseur pour une lampe à décharge
EP0392834A1 (fr) * 1989-04-14 1990-10-17 TLG plc Circuits ballast pour lampes à décharge
EP0622888A1 (fr) * 1993-04-27 1994-11-02 Electronic Lighting, Inc. Alimentation en courant continu avec un facteur de puissance amélioré
EP0677982A1 (fr) * 1994-04-15 1995-10-18 Knobel Ag Lichttechnische Komponenten Procédé pour commander un ballast de lampes à décharge

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07118394B2 (ja) * 1987-06-15 1995-12-18 松下電工株式会社 放電灯点灯装置
JPH01186790A (ja) * 1988-01-18 1989-07-26 Mitsubishi Electric Corp 放電ランプの点灯装置
US6172468B1 (en) 1997-01-14 2001-01-09 Metrolight Ltd. Method and apparatus for igniting a gas discharge lamp

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0013866A1 (fr) * 1978-12-22 1980-08-06 Contrinex S.A. Alimentation en énergie de charges ohmiques-inductives
DE3142613A1 (de) * 1981-10-28 1983-05-05 Philips Patentverwaltung Gmbh, 2000 Hamburg Schaltungsanordnung zum zuenden und betrieb einer niederdruckquecksilberdampfentladungslampe
EP0081884A2 (fr) * 1981-12-14 1983-06-22 Philips Patentverwaltung GmbH Dispositif de circuit pour le fonctionnement de lampes de décharge à gaz et à haute pression
US4525648A (en) * 1982-04-20 1985-06-25 U.S. Philips Corporation DC/AC Converter with voltage dependent timing circuit for discharge lamps

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4560908A (en) * 1982-05-27 1985-12-24 North American Philips Corporation High-frequency oscillator-inverter ballast circuit for discharge lamps
US4873471A (en) * 1986-03-28 1989-10-10 Thomas Industries Inc. High frequency ballast for gaseous discharge lamps

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0013866A1 (fr) * 1978-12-22 1980-08-06 Contrinex S.A. Alimentation en énergie de charges ohmiques-inductives
DE3142613A1 (de) * 1981-10-28 1983-05-05 Philips Patentverwaltung Gmbh, 2000 Hamburg Schaltungsanordnung zum zuenden und betrieb einer niederdruckquecksilberdampfentladungslampe
EP0081884A2 (fr) * 1981-12-14 1983-06-22 Philips Patentverwaltung GmbH Dispositif de circuit pour le fonctionnement de lampes de décharge à gaz et à haute pression
US4525648A (en) * 1982-04-20 1985-06-25 U.S. Philips Corporation DC/AC Converter with voltage dependent timing circuit for discharge lamps

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0311424A2 (fr) * 1987-10-08 1989-04-12 ADVANCE TRANSFORMER CO. (a Division of Philips Electronics North America Corporation) Circuit ballast haute fréquence pour lampe à décharge gazeuse
EP0311424A3 (en) * 1987-10-08 1989-10-18 Thomas Industries Inc. High frequency ballast for gaseous discharge lamps
EP0320944A1 (fr) * 1987-12-17 1989-06-21 Pintsch Bamag Antriebs- und Verkehrstechnik GmbH Convertisseur pour une lampe à décharge
EP0392834A1 (fr) * 1989-04-14 1990-10-17 TLG plc Circuits ballast pour lampes à décharge
EP0622888A1 (fr) * 1993-04-27 1994-11-02 Electronic Lighting, Inc. Alimentation en courant continu avec un facteur de puissance amélioré
EP0677982A1 (fr) * 1994-04-15 1995-10-18 Knobel Ag Lichttechnische Komponenten Procédé pour commander un ballast de lampes à décharge
US5563477A (en) * 1994-04-15 1996-10-08 Knobel Ag Lichttechnische Komponenten Method for operating a ballast for discharge lamps

Also Published As

Publication number Publication date
AU7067187A (en) 1987-10-01
EP0239420B1 (fr) 1992-01-02
CA1327991C (fr) 1994-03-22
AU609388B2 (en) 1991-05-02
JPS63999A (ja) 1988-01-05
ATE71244T1 (de) 1992-01-15
DE3775588D1 (de) 1992-02-13

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