JP4040518B2 - Discharge lamp lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a discharge lamp lighting device, and more particularly to a discharge lamp lighting device in which an inverter circuit is configured by using a low breakdown voltage transistor.
[0002]
[Prior art]
Demand for projectors using metal halide lamps as a light source has been increasing, and there has been a demand for smaller, lighter, and lower-priced devices. In order to meet such a demand, improvement of the power supply circuit is inevitable.
[0003]
By the way, in order to light a high-intensity lamp such as a metal halide lamp, for example, a DC voltage of 350 V is applied to the lamp to cause glow discharge, and then a high-voltage trigger pulse of tens of kV is applied to cause arc discharge. When the lamp is turned on, the lamp is controlled at a constant power. At that time, the lamp voltage drops to about 140 V or less.
[0004]
Since a voltage of 350 V for causing glow discharge is applied from the buck converter circuit to the lamp via the inverter circuit, a transistor having a withstand voltage of about 600 V is usually used as the transistor constituting the inverter circuit. On the other hand, since the voltage applied to the inverter circuit is at most about 140 V after the lamp is lit, in this state, it is sufficient that the transistors constituting the inverter circuit have a withstand voltage of about 250 V to 300 V. In general, a transistor having a lower withstand voltage has a merit that the outer dimension is smaller, the on-resistance is lower, and the price is lower.
[0005]
Focusing on the above points, a circuit configuration for using a transistor having a lower withstand voltage than that of a conventional one in a bridge circuit has been proposed (for example, Patent Document 1). In the circuit described in Patent Document 1, a low voltage transistor is used to form a full bridge inverter, and a switching element is connected to the low voltage transistor so that a high voltage is not temporarily applied.
[0006]
[Patent Document 1]
JP 2000-215991 (page 3)
[0007]
[Problems to be solved by the invention]
However, in the circuit described in Patent Document 1, a timer, a delay circuit, and the like are required to control the switching element connected to the low breakdown voltage transistor, and the circuit configuration is complicated.
[0008]
An object of this invention is to implement | achieve the discharge lamp lighting device containing the inverter circuit comprised with the low voltage | pressure-resistant transistor with a simple circuit structure.
[0009]
[Means for Solving the Problems]
  The discharge lamp lighting device according to claim 1, which has been made to achieve the above object, performs glow discharge when a predetermined voltage is applied and applies a high-pressure trigger pulse.From glow dischargeArc dischargeMoved toA discharge lamp lighting device used for a discharge lamp that is lit in the first stage, wherein a first voltage lower than the predetermined voltage is output before the discharge lamp is lit, and constant power control is performed on the discharge lamp after the discharge lamp is lit. A back converter circuit; an inverter circuit that converts a DC voltage output from the buck converter circuit into an AC voltage and applies the AC voltage to the discharge lamp during constant power control of the buck converter circuit; and the high-pressure trigger pulse in the discharge lamp A high voltage trigger pulse generation circuit that outputsA boost-up circuit having a coil and a capacitor connected between the electrodes of the discharge lamp, and generating the predetermined voltage by charging the capacitor; and between the coil and the capacitorSemiconductor electrical device connected toSwitching means for switching enable / disable of the boost-up circuit,The first voltage is output from the buck converter circuit to the inverter circuit to cause the discharge lamp to glow discharge,The switching means enables the boost up circuit to charge the capacitor with a voltage generated by applying a voltage to the boost up circuit, and when the discharge lamp starts glow discharge, the switching means disables the boost up circuit. Able,The semiconductor electrical element carries a second voltage corresponding to a difference between the predetermined voltage and the first voltage.
[0010]
  In the discharge lamp lighting device configured as described above, the first voltage is generated and output from the buck converter circuit before the discharge lamp is turned on. At this time, the inverter circuit is driven so as to output the first voltage as an input voltage from the buck converter circuit as it is. on the other hand,The boost-up circuit enabled by the switching means isA predetermined voltage required for glow discharge of the discharge lamp is applied to the output side of the inverter circuit. As a result, the output voltage from the buck converter circuit is the first voltage lower than the predetermined voltage, but the discharge lampBoost-up circuitTherefore, it is possible to receive a voltage necessary for performing glow discharge.
[0011]
  However, in this case, the first voltage is applied to the input side of the inverter circuit, and a voltage higher than the first voltage is applied to the output side. Therefore, inverter circuitOutput sideA semiconductor electrical element is inserted into the inverter circuit to maintain the voltage balance between the input and output of the inverter circuit.
[0012]
The discharge lamp lighting device according to claim 2 is the discharge lamp lighting device according to claim 1, wherein the inverter circuit is configured by a switching element, and the switching element is the first input / output voltage. It is characterized by taking a value not less than the voltage and not more than the predetermined voltage.
[0013]
Thus, a switching element with a low withstand voltage can be used as a switching element used in an inverter circuit. If MOSFETs are used as switching elements and semiconductor electrical elements, the invention according to claim 2 similarly uses MOSFETs in the inverter circuit as compared with the conventional circuit that uses four MOSFETs with high withstand voltage in the inverter circuit. If this is used, an inverter circuit is configured using a total of five MOSFETs, one more in total. However, MOSFETs constituting the inverter circuit can use low breakdown voltage, and MOSFETs as semiconductor electric elements can similarly use low breakdown voltage, so the number of MOSFETs is increased but the cost is reduced. be able to.
[0015]
  Claim3The discharge lamp lighting device according to claim1The high-pressure trigger pulse generation circuit includes a transformer for generating the high-pressure trigger pulse.HaveIt is characterized by that.
[0016]
  Claim4The discharge lamp lighting device according to claim1The discharge lamp lighting device according to claim 1, whereinBoost-up circuitIs characterized in that the capacitor is charged by a voltage generated by applying a step voltage to a resonance circuit composed of a coil and a capacitor.
[0017]
  Claim5The discharge lamp lighting device according to claim1The discharge lamp lighting device according to claim,in frontA voltage detector that detects the voltage across the capacitorStepPossess,in frontWhen the voltage across the capacitor detected by the voltage detecting means is less than or equal to the predetermined voltage, the switching means enables the resonance circuit, and when the voltage reaches the predetermined voltage, the switching means It is characterized by disabling the circuit.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a discharge lamp lighting device according to an embodiment of the present invention will be described with reference to the accompanying drawings. 1 to 6 are diagrams showing circuit configurations of ballast power supplies of discharge lamp lighting devices according to first to sixth embodiments of the present invention, respectively. FIG. 7 is a diagram showing a circuit configuration of a ballast power source that is the basis of these six embodiments.
[0019]
A high-intensity discharge lamp such as a metal halide lamp is in an insulated state between the electrodes before lighting. In order to light the lamp, first, a glow discharge is applied by applying a bias voltage of about 350 V, and then a high voltage trigger pulse voltage of several tens of kV is superimposed on the bias voltage to cause dielectric breakdown between the electrodes of the lamp. This shifts from glow discharge to arc discharge, and the lamp starts to light.
[0020]
Immediately after the transition to arc discharge, the arc is not stable and is emitting light but still weak. When the output current from the ballast power source is lower than the arc discharge holding current, the arc discharge cannot be held and the lamp is extinguished. For this reason, in order to maintain the arc holding current or more, the lamp is subjected to constant current control immediately after lighting. When the arc discharge stabilizes, strong light begins to be emitted. Thereafter, the control is shifted to the constant power control and the lamp is turned on by alternating current.
[0021]
Before describing the embodiment of the present invention, the configuration of a ballast power source common to the first to sixth embodiments will be described with reference to FIG.
[0022]
The ballast power supply 10 shown in FIG. 7 includes a buck converter circuit (down chopper circuit) 20, an inverter circuit 30, a high voltage trigger pulse generation circuit 40, and a control unit 50. A DC power supply circuit (not shown) is connected to the input side of the buck converter circuit 20, and an inverter circuit 30 and a high-voltage trigger pulse generation circuit 40 are connected to the output side.
[0023]
The buck converter circuit 20 has a + side input terminal a and a − side input terminal b, and a DC power supply circuit (not shown) is connected between the input terminals a and b. The buck converter circuit 20 includes a MOSFET (hereinafter simply referred to as “transistor”) Q1, a driver 21 that controls on / off of the transistor Q1, a diode D1, a smoothing capacitor C1, and a coil L1. A controller 50 is connected to the driver 21 via a photocoupler.
[0024]
The inverter circuit 30 includes a full bridge circuit composed of transistors Q2 to Q5 and a driver 31 for driving the full bridge circuit. A controller 50 is connected to the driver 31. The output of the inverter circuit 30 is connected to the lamp L.
[0025]
The high-voltage trigger pulse generation circuit 40 has transformers T1 and T2, a resistance R1, a capacitor C2, and a bidirectional characteristic element D2 are provided on the primary side of the transformer T1, and a diode D4, an arrester D3, a trigger transformer are provided on the secondary side. T2 and capacitor C3 are connected. The secondary winding of the transformer T2 is connected between the inverter circuit 30 and the lamp L. A capacitor C4 is connected between the output terminals of the inverter circuit 30.
[0026]
Next, the operation of the ballast power supply 10 configured as described above will be described. Hereinafter, for ease of understanding, the operation will be described while showing specific voltage values. However, the numerical values described below are merely examples, and the present invention is not limited to these numerical values.
[0027]
A DC voltage of 350 V is applied to input terminals a and b of the buck converter circuit 20 from a DC power source (not shown). In order to cause glow discharge, the control unit 50 sends a control signal to the driver 21 of the buck converter circuit 20 to continuously turn on the transistor Q1. As a result, the voltage (350 V) applied between the input terminal terminals a and b of the buck converter circuit 20 appears as it is between the terminals c and d of the inverter circuit 30, and a DC voltage of 350 V is generated between the inverter circuit 30 and the high voltage trigger pulse. Applied to the generation circuit 40. When the voltage applied from the DC power source to the buck converter circuit 20 is 350 V or higher, the output voltage from the buck converter circuit 20 is controlled to 350 V by adjusting the switching frequency and duty of the transistor Q1.
[0028]
At this time, a control signal is sent from the control unit 50 to the driver 31 of the inverter circuit 30, and the driver 31 sends a drive signal to turn on the transistors Q2 and Q5 and turn off the transistors Q3 and Q4 that constitute the full bridge circuit. Output. As a result, the capacitor C4 connected between the output terminals e and f of the inverter circuit 30 is charged with the input voltage of the inverter circuit 30 as it is. When the capacitor C4 is charged to a bias voltage of 350V, glow discharge is performed.
[0029]
The high voltage trigger pulse generation circuit 40 is a circuit for generating a high voltage trigger pulse with the output voltage of the buck converter circuit 20 as an input. Since the output voltage (350 V) of the buck converter circuit 20 is applied to the series circuit of the resistor R1 and the capacitor C2, the voltage of the capacitor C2 gradually increases. When the voltage of the capacitor C2 is applied to the bidirectional characteristic element D2, and the voltage of the capacitor C2 reaches a predetermined value, the bidirectional characteristic element D2 breaks down. The voltage causing the dielectric breakdown of the bidirectional characteristic element D2 is set to 150V or more and 180V or less.
[0030]
When the bidirectional characteristic element D2 breaks down, the energy stored in the capacitor C2 is transmitted to the capacitor C3 through the transformer T1 and the diode D4. When the electric charge stored in the capacitor C2 is transmitted to the capacitor C3, the capacitor C2 is charged again through the resistor R1, and the same operation as described above is repeated. This repetition frequency is determined by the constants of the resistor R1 and the capacitor C2.
[0031]
Each time the bidirectional characteristic element D2 repeats dielectric breakdown, and the electric charge stored in the capacitor C2 is transmitted to the capacitor C3, the voltage of the capacitor C3 increases. When the voltage of the capacitor C3 reaches 1 kV, the arrester D3 breaks down and turns on. When the arrester D3 is turned on, the discharge current of the capacitor C3 flows to the primary winding of the trigger transformer T2 via the arrester D3, and a trigger pulse voltage of tens of kV is generated on the secondary side. This trigger pulse voltage of several tens of kV is applied to the lamp L superimposed on the bias voltage of 350V. Then, the lamp L proceeds from glow discharge to arc discharge, and the lamp L is lit.
[0032]
Immediately after the lamp L is lit, the mercury in the lamp L has not completely evaporated, so the lamp voltage becomes a low value. The value is about 10 to 20 V, which is about a fraction of the rated voltage. Therefore, in order to quickly move the lamp L to the stable state, the current value is increased to increase the input power. When a certain amount of time elapses from lighting and the mercury vapor pressure inside the lamp L starts to rise, the lamp voltage becomes a value almost close to the rated voltage. The ballast power supply 10 performs constant current control while observing the lamp voltage until the lamp voltage becomes a value close to the rated voltage after the lamp L is turned on.
[0033]
When the lamp L is lit, the voltage of the capacitor C1 of the buck converter circuit 20 is reduced to about 100 V, which is the lamp voltage. The voltage does not rise to a voltage, and a high voltage trigger pulse is not generated from the trigger transformer T2.
In addition, it has been described that the voltage causing the dielectric breakdown of the bidirectional characteristic element D2 is set to 150 V or more and 180 V or less. However, since the maximum value of the lamp voltage is 150 V, the trigger pulse is generated when the lamp L is lit. This is to prevent this from occurring.
[0034]
When the lamp L enters a stable lighting state, the constant current control is shifted to the constant power control. At this time, the pair of transistors Q2 and Q5 and the pair of transistors Q3 and Q4 of the inverter circuit 30 are alternately switched on and off at several hundred Hz. As a result, a low-frequency rectangular wave voltage is supplied to the lamp L. In order to perform constant power control, the voltage between the output terminals c and d of the buck converter circuit 20 and the current flowing through the coil L1 are detected by a detection circuit (not shown).
[0035]
Embodiments of the present invention will be described below. In each embodiment described below, the following modifications are made to the configuration shown in FIG. First, before the lamp L is turned on, a voltage lower than 350 V, for example, 200 V is output from the buck converter circuit 20. On the other hand, a voltage generator for generating a voltage of 350 V is provided, and the voltage on the output side of the inverter circuit 30 is set to 350 V, and 350 V is applied to the lamp L. However, if this is done, the input side voltage of the inverter circuit 30 is 200 V, whereas the output side voltage is 350 V, and a differential voltage of 150 V is applied to the transistors in the inverter circuit 30 that is turned on. Therefore, a semiconductor electrical element that can have a voltage between input and output of 150 V is incorporated in the inverter circuit 30.
[0036]
First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 11 is a timing chart for explaining the operation of the ballast power supply 10A shown in FIG.
[0037]
The ballast power supply 10A shown in FIG. 1 includes a buck converter circuit 20A, an inverter circuit 30A, a high-voltage trigger pulse generation circuit 40A, and a control circuit 50A, similar to the basic configuration shown in FIG. This corresponds to the buck converter circuit 20, the inverter circuit 30, the high-voltage trigger pulse generation circuit 40, and the control circuit 50 shown. This is the same for the ballast power source shown in FIGS.
[0038]
The inverter circuit 30A has a configuration in which a diode D7 and a transistor Q7 are newly connected in the inverter circuit 30 shown in FIG. Further, a charging circuit for a capacitor C4 using a transformer T1 is added to the high voltage trigger pulse generation circuit 40A. The transistor Q7 is connected to the arm side of the transistors Q2 and Q4 constituting the full bridge of the inverter circuit 30, that is, between the connection point of the transistors Q2 and Q4 and the terminal e. The diode D7 is connected between the drain and source of the transistor Q7 so as to serve as a bypass for the transistor Q7.
[0039]
The transformer T1 in the high-voltage trigger pulse generating circuit 40A has a secondary winding divided into three parts, an N2 winding, an N3 winding, and an N4 winding, and the turn ratio of the N2 winding and the N3 winding is N2. : N3 = 3: 1 is set. The N2 winding corresponds to the secondary winding of the transformer T1 shown in FIG. 7, and is used to generate a high voltage trigger pulse.
[0040]
The secondary side N3 winding of the transformer T1, the diode D6, and the transistor Q6 constitute a charging circuit for the capacitor C4, and the capacitor C4 is charged to 350V. A drive resistor R2 is connected between the gate and source of the transistor Q6 constituting the charging circuit. Further, the N4 winding of the secondary winding of the transformer T1 divided into three has its plus side connected to the gate of the transistor Q6 via the diode D5.
[0041]
Next, the operation of the ballast power supply 10A shown in FIG. 1 will be described with reference to FIG. The constant current control after the lamp L is turned on and the subsequent constant power control are not different from the explanation given for the circuit shown in FIG. 7, so the explanation is omitted and only the operation of the ballast power supply 10A before the lamp L is turned on. explain.
[0042]
The circuit configuration of the buck converter circuit 20A is not different from the configuration shown in FIG. 7, but the operation is different. A DC voltage of 350 V is applied from a DC power source (not shown) to the input terminals a and b of the buck converter circuit 20A shown in FIG. This is the same as the buck converter circuit 20 of FIG. However, in the present embodiment, control unit 50A sends a control signal to driver 21 of buck converter circuit 20A via photocoupler P1, adjusts the switching frequency or duty of transistor Q1, and outputs voltage from buck converter circuit 20A. Is controlled to 200V. That is, the buck converter circuit 20A does not output a 350V voltage necessary for causing the lamp L to cause a glow discharge, but outputs a 200V DC voltage lower than that.
[0043]
The DC voltage of 200V is output to the inverter circuit 30A and the high voltage trigger pulse generation circuit 40A. At this time, the driver 31 of the inverter circuit 30A outputs drive signals to the transistors Q2 and Q5 constituting the full bridge, but does not output drive signals to the transistors Q3, Q4, and Q7. That is, the transistors Q2 and Q5 are on and the transistors Q3 and Q4 are off. Therefore, the input voltage 200V from the buck converter circuit 20A appears as it is in the output of the full bridge, the capacitor C4 starts to be charged, and the voltage at both ends thereof rises to 200V.
[0044]
On the other hand, a DC voltage of 200 V is also applied to the series circuit of the resistor R1 and the capacitor C2 of the high voltage trigger pulse generating circuit 40, and the voltage of the capacitor C2 also rises. Since the voltage causing the dielectric breakdown of the bidirectional characteristic element D2 is set to 150 V or more and 180 V or less, when the voltage of the capacitor C2 reaches 150 V, the bidirectional characteristic element D2 breaks down. Then, the energy of the capacitor C2 is transmitted to the capacitor C3 via the transformer T1 and the diode D4. Each time the bidirectional characteristic element D2 repeats dielectric breakdown, the voltage of the capacitor C3 increases, and the capacitor C3 is charged to a voltage of 1 kV at which the arrester D3 breaks down. Since the turns ratio of the transformer T1 is set to N2: N3 = 3: 1, the capacitor C4 is charged to about 350V by the forward operation.
[0045]
The N4 winding of the transformer T1 and the diode D5 are for applying a gate voltage to the transistor Q6, and the drive resistor R2 provides a discharge path when the transistor Q6 is turned off. The transistor Q6 inserted in the charging path is for preventing current from flowing through the N3 winding of the transformer T1 when the lamp L is lit. When the lamp L is lit, the bidirectional characteristic element D2 does not break down, so that no voltage is induced on the secondary side of the transformer T1, and the transistor Q6 is off. For this reason, no current flows through the N3 winding of the transformer T1, and therefore the charging operation of the capacitor C4 is not performed. However, if the transistor Q6 is not provided, the diode D6 conducts due to the AC voltage generated in the capacitor C4 during lighting, and a current flows through the N3 winding.
[0046]
When the voltage of the capacitor C4 rises above 200V, the drain-source voltage of the transistor Q7 also rises, and the voltage between the input and output of the inverter circuit 30 maintains a balance. When the voltage of the capacitor C4 rises to 350V, the lamp L performs glow discharge.
[0047]
As described above, the output voltage of the buck converter circuit 20A is stepped down to 200V. However, in order to stably turn on the lamp L, it is necessary to apply a voltage of 350V to the lamp L. Therefore, the high-voltage trigger pulse generation circuit 40A. The secondary winding of the transformer T1 is divided and the divided winding is used to charge the capacitor C4 to 350V.
[0048]
Further, before the lamp L is lit, the voltage on the input side of the inverter circuit 30A is 200V and the voltage on the output side is 350V, so that the transistor Q7 bears the difference of 150V. Without the transistor Q7, 150V of the voltage difference between the input side and the output side of the inverter circuit 30A is applied to the transistor Q2, and if the transistor Q2 is a MOSFET, the built-in diode of the MOSFET is turned on and the capacitor C4 is charged to 350V. You can't do that. Moreover, if an IGBT is used as a switch of the bridge circuit, the breakdown voltage exceeds the reverse breakdown voltage between the collector and the emitter, resulting in destruction.
[0049]
Next, a second embodiment of the present invention will be described with reference to FIG.
[0050]
The inverter circuit 30B of the ballast power supply 10B shown in FIG. 2 has a configuration in which a diode D7 and a transistor Q7 are connected to the inverter circuit 30 having the basic configuration shown in FIG. 7, and this point is the inverter circuit 30A shown in FIG. Is the same. In the high voltage trigger pulse generation circuit 40B, a charging circuit for the capacitor C4 using the transformer T1 is provided.
[0051]
The transformer T1 in the high voltage trigger pulse generation circuit 40 has a primary winding divided into an N1 winding and an N2 winding. The primary N2 winding, the diode D6, and the transistor Q5 form a charging circuit for the capacitor C4. The capacitor C4 is charged to 350 V by the charging circuit.
[0052]
Next, the operation of the ballast power supply 10B shown in FIG. 2 will be described with reference to FIG.
[0053]
Similarly to the ballast power source 10A shown in FIG. 1, the buck converter circuit 20B according to the present embodiment is also applied with a DC voltage of 350V from a DC power source (not shown) to the input terminals a and b, and 200V from the output terminals c and d. DC voltage is output. The DC voltage of 200V is output to the inverter circuit 30B and the high voltage trigger pulse generation circuit 40B. At this time, the transistors Q2 and Q5 of the inverter circuit 30B are controlled to be on, and the transistors Q3 and Q4 are controlled to be off. Therefore, the input voltage 200V from the buck converter circuit 20B appears as it is in the output of the full bridge, the capacitor C4 starts to be charged, and the voltage at both ends thereof rises to 200V.
[0054]
On the other hand, a DC voltage of 200 V is also applied to the series circuit of the resistor R1 and the capacitor C2 of the high voltage trigger pulse generating circuit 40B, and the voltage of the capacitor C2 also rises. When the voltage of the capacitor C2 reaches 150V, the bidirectional characteristic element D2 breaks down. Then, the electric charge stored in the capacitor C2 is transmitted to the capacitor C3 via the transformer T1 and the diode D4. At the same time, a current flows from the primary winding N2 of the transformer T1 to the loop returning to the winding N2 through the diode D6, the terminal e, the capacitor C4, the terminal f, and the transistor Q5, and the capacitor C4 is charged. Each time the bidirectional characteristic element D2 repeats dielectric breakdown, the voltages of the capacitors C3 and C4 rise.
[0055]
When the voltage of the capacitor C4 rises above 200V, the drain-source voltage of the transistor Q7 also rises, and the voltage between the input and output of the inverter circuit 30B maintains a balance. When the voltage of the capacitor C4 rises to 350V, the lamp L performs glow discharge. Glow discharge Subsequently, a high pressure trigger pulse is output from the high pressure trigger pulse generation circuit 40B, causing arc discharge, and the lamp L is turned on. The constant current control after the lamp L is turned on and the subsequent constant power control are as described in the circuit shown in FIG.
[0056]
In this way, the primary winding of the transformer T1 of the high-voltage trigger pulse generation circuit 40B is divided, and the capacitor C4 is charged to 350 V using the divided winding. Further, the transistor Q7 takes charge of the voltage difference between the input side and the output side of the inverter circuit 30B before the lamp L is turned on.
[0057]
Next, a third embodiment of the present invention will be described with reference to FIG.
[0058]
The inverter circuit 30C of the ballast power source 10C shown in FIG. 3 has a configuration in which a diode D7 and a transistor Q7 are connected to the inverter circuit 30 having the basic configuration shown in FIG. 7, and a transformer T1 is included in the high-voltage trigger pulse generation circuit 40C. A charging circuit for the capacitor C4 utilizing the above is added.
[0059]
Unlike the ballast power supplies 10A and 10B shown in FIGS. 1 and 2, in the ballast power supply 10C shown in FIG. 3, the transistor Q7 has the other arm constituting the full bridge of the inverter circuit 30C, that is, the transistors Q3 and Q5. It is connected on the arm side, specifically, between the connection point of the transistors Q3 and Q5 and the terminal f. The diode D7 is connected between the drain and source of the transistor Q7.
[0060]
Similar to the ballast power supply 10B shown in FIG. 2, the transformer T1 in the high voltage trigger pulse generating circuit 40C has its primary winding divided into N1 winding and N2 winding. The primary N2 winding, the transistor Q2 and the diode D6 constitute a charging circuit for the capacitor C4, which charges the capacitor C4 to 350V.
[0061]
Next, the operation of the ballast power supply 10C shown in FIG. 3 will be described with reference to FIG.
[0062]
The operation of the ballast power source 10C according to the present embodiment is basically the same as the operation of the ballast power source 10B shown in FIG. 2, but the charging path for charging the capacitor C4 is different. When the voltage of the capacitor C2 reaches 150V and the bidirectional characteristic element D2 breaks down, the energy stored in the capacitor C2 is transmitted to the capacitor C3 via the transformer T1 and the diode D4. At the same time, a current flows from the primary winding N2 of the transformer T1 to the loop returning to the winding N2 through the transistor Q2, the terminal e, the capacitor C4, the terminal f, and the diode D6, and the capacitor C4 is charged. Each time the bidirectional characteristic element D2 repeats dielectric breakdown, the voltages of the capacitors C3 and C4 rise.
[0063]
When the voltage of the capacitor C4 exceeds 200V, the drain-source voltage of the transistor Q7 also increases. As a result, the potential of the terminal f transitions in the negative direction with respect to the potential of the terminal b, and the voltage between the input and output of the inverter circuit 30C maintains a balance. When the voltage of the capacitor C4 rises to 350V, the lamp L performs glow discharge. Glow discharge Subsequently, a high pressure trigger pulse is output from the high pressure trigger pulse generation circuit 40C, causing arc discharge, and the lamp L is turned on. The constant current control after the lamp L is turned on and the subsequent constant power control are as described in the circuit shown in FIG.
[0064]
Next, a fourth embodiment of the present invention will be described with reference to FIG.
[0065]
Also in the ballast power source 10D shown in FIG. 4, the inverter circuit 30 has a configuration in which a diode D7 and a transistor Q7 are connected in the inverter circuit 30D having the basic configuration shown in FIG. A charging circuit for a capacitor C4 using a transformer T1 is added in the high voltage trigger pulse generating circuit 40D.
[0066]
Similar to FIGS. 1 and 2, also in the ballast power supply 10D shown in FIG. 4, the transistor Q7 is connected to the arm side of the transistors Q2 and Q4 constituting the full bridge of the inverter circuit 30D. In addition, a series circuit of a Zener diode ZD1, a capacitor C4, and a diode D6 is connected to both ends of the capacitor C3 on the secondary side of the transformer T1 in the high-voltage trigger pulse generation circuit 40D to form a charging circuit for the capacitor C4. ing. Zener diode ZD1 breaks down at 650V.
[0067]
Next, the operation of the ballast power supply 10D shown in FIG. 4 will be described with reference to FIG.
[0068]
The operation of the ballast power supply 10D according to the present embodiment is basically the same as that of the ballast power supplies 10A, 10B, and 10C shown in FIGS. 1 to 3, but the operation of charging the capacitor C4 is different. When the voltage of the capacitor C2 reaches 150V and the bidirectional characteristic element D2 breaks down, the energy stored in the capacitor C2 is transmitted to the capacitor C3 via the transformer T1 and the diode D4. Each time the bidirectional characteristic element D2 repeats dielectric breakdown, the voltage of the capacitor C3 increases. However, when the voltage of the capacitor C3 is 650 V or less, the Zener diode ZD1 does not break down, and the capacitor C3, Zener diode ZD1, terminal e, capacitor No current flows through the charging loop returning to the capacitor C3 via C4, the terminal f, and the diode D6. Therefore, the capacitor C4 is not charged to 200V or more.
[0069]
When the voltage of the capacitor C3 exceeds 650V, the Zener diode ZD1 breaks down, a current flows through the charging loop, and the capacitor C4 is charged to 200V or more through the charging loop. At this time, the drain-source voltage of the transistor Q7 also increases as the voltage of the capacitor C4 increases. When the voltage of the capacitor C3 reaches 1 kV, the voltage of the capacitor C4 is 350 V and the glow discharge of the lamp L is performed. Glow discharge Subsequently, a high pressure trigger pulse is output from the high pressure trigger pulse generation circuit 40D, causing arc discharge, and the lamp L is turned on. The constant current control after the lamp L is turned on and the subsequent constant power control are as described in the circuit shown in FIG.
[0070]
Next, a fifth embodiment of the present invention will be described with reference to FIG.
[0071]
  The inverter circuit 30E of the ballast power source 10E shown in FIG. 5 includes a charging voltage generator for connecting the diode D7 and the transistor Q7 in the inverter circuit 30E having the basic configuration shown in FIG. 7 and charging the capacitor C4 to 350V. Is provided. Similar to the ballast power source shown in the other figures except FIG. 3, in this embodiment, the transistor Q7 is connected to the arm side of the transistors Q2 and Q4 constituting the full bridge of the inverter circuit 30 via the coil L2. Yes. In addition, a boost-up circuit composed of the coil L2, the capacitor C4, and the transistor Q8 functions as a charging voltage generator. Further, a voltage detection circuit 60E for detecting the voltage across the capacitor C4 is provided. The voltage detection circuit 60E includes resistors R2 and R3.The transistor Q7 corresponds to switching means described in the claims.
[0072]
In the embodiment described with reference to FIGS. 1 to 4, the charging voltage generator for charging the capacitor C4 up to 350V is provided in the high voltage trigger pulse generating circuit 40. However, in the present embodiment, the charging circuit is provided in the inverter circuit 30. It differs from the first to fourth embodiments in that it is provided.
[0073]
Next, the operation of the ballast power source 10E shown in FIG. 5 will be described with reference to FIG.
[0074]
  The operation of the ballast power supply 10E according to the present embodiment is basically the same as that of the ballast power supplies 10A, 10B, and 10C shown in FIGS. 1 to 3, but the operation of charging the capacitor C4 is different. In order to charge the voltage of the capacitor C4 to 350V, the transistor Q8 is switched and boosted by the coil L2 while the voltage detection circuit 60E detects the voltage of the capacitor C4. Coil L2 is a capacitor C4Therefore, the inductance value is set to several tens of μH or less. In this case, the transistors Q7 and Q8 need a withstand voltage of 400V or more. When the voltage detection circuit 60E detects that the voltage across the capacitor C4 has reached 350V, the transistor Q8 is turned off and the charging operation is stopped.
[0075]
As the voltage of the capacitor C4 increases, the drain-source voltage of the transistor Q7 also increases. When the capacitor C4 is charged to 350 V, the glow discharge of the lamp L is performed. Glow discharge Subsequently, a high pressure trigger pulse is output from the high pressure trigger pulse generation circuit 40E, causing arc discharge, and the lamp L is turned on. The constant current control after the lamp L is turned on and the subsequent constant power control are as described in the circuit shown in FIG.
[0076]
Finally, a sixth embodiment of the present invention will be described with reference to FIG.
[0077]
The ballast power supply 10F shown in FIG. 6 has a configuration in which the voltage detection circuit 60E and the transistor Q8 are removed from the configuration of the ballast power supply 10E shown in FIG. 5, and a resonance circuit is configured by the coil L2 and the capacitor C4. . By applying on / off control of the transistors Q2 and Q5 and applying a step voltage, the capacitor C4 is charged to a voltage twice as high as the voltage on the input side of the resonance circuit. In order to charge the capacitor C4 to 350V, the switching operation of the transistor Q1 is performed so that the voltage on the input side, that is, the voltage between the terminals c and d becomes 175V.
[0078]
In the basic configuration shown in FIG. 7, since a voltage of about 350 V is applied to the transistors Q2 to Q5, it is necessary to use a transistor having a breakdown voltage of about 600 V. However, in the above-described embodiment of the present invention, the buck converter The output voltage from the circuit 20 (A to F) is stepped down to 200 V or less, and a transistor having a low withstand voltage is used for the inverter circuit 30 (A to F) in the next stage. On the other hand, a circuit for compensating for a decrease in the output voltage from the buck converter circuit 20 (A to F) is added.
[0079]
The discharge lamp lighting device of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, the transistor Q7 in the first embodiment shown in FIG. 1 may be replaced with diodes D9 and D10 as shown in FIG. The diode D9 is connected between the terminal c and the drain of the transistor Q2, and the diode D8 is connected between the terminal f and the transistor Q5 in the forward direction.
[0080]
Further, as shown in FIG. 9, the first embodiment shown in FIG. 1 may be modified. In FIG. 9, in order to connect the input of the high voltage trigger pulse generation circuit 40A to the input side of the buck converter circuit 20A and prevent the high voltage trigger pulse generation circuit 40A from operating after the lamp L is turned on, the switch Q8 is connected to the transformer T1. Is inserted on the primary winding side. The switch Q8 is kept on until the lamp L is lit, and is turned off after lighting.
[0081]
The configuration shown in FIG. 10 is obtained by adding the same change to the fourth embodiment shown in FIG. Also in the modification of FIG. 10, the input of the high-voltage trigger pulse generation circuit 40D is connected to the input side of the buck converter circuit 20D, and the switch Q8 is inserted on the primary winding side of the transformer T1.
[0082]
【The invention's effect】
According to the present invention, a switch having a low withstand voltage can be used as the switch constituting the inverter circuit. A MOSFET having a lower drain-source voltage rating has a lower on-resistance, and can be obtained at a small size and at a low price. Therefore, if an inverter circuit is configured using a MOSFET, a small, inexpensive and highly efficient discharge lamp can be obtained. A lighting device can be provided.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a discharge lamp lighting device according to a first embodiment of the present invention.
FIG. 2 is a circuit diagram of a discharge lamp lighting device according to a second embodiment of the present invention.
FIG. 3 is a circuit diagram of a discharge lamp lighting device according to a third embodiment of the present invention.
FIG. 4 is a circuit diagram of a discharge lamp lighting device according to a fourth embodiment of the present invention.
FIG. 5 is a circuit diagram of a discharge lamp lighting device according to a fifth embodiment of the present invention.
FIG. 6 is a circuit diagram of a discharge lamp lighting device according to a sixth embodiment of the present invention.
FIG. 7 is a circuit diagram of a discharge lamp lighting device comprising portions common to the respective embodiments of the present invention.
8 is a circuit diagram showing a modification of the inverter circuit included in the discharge lamp lighting device shown in FIG.
9 is a circuit diagram showing a modification of the discharge lamp lighting device shown in FIG.
10 is a circuit showing a modification of the discharge lamp lighting device shown in FIG. 4;
11 is a timing chart for explaining the operation of the discharge lamp lighting device shown in FIGS. 1, 2 and 3. FIG.
12 is a timing chart for explaining the operation of the discharge lamp lighting device shown in FIG. 4;
13 is a timing chart for explaining the operation of the discharge lamp lighting device shown in FIG.
14 is a timing chart for explaining the operation of the discharge lamp lighting device shown in FIG.
[Explanation of symbols]
10 (A to E): Discharge lamp lighting device, 20 (A to E): Inverter circuit, 30 (A to E): Inverter circuit, 40 (A to E): High pressure trigger pulse generation circuit, L: Lamp

Claims (5)

A discharge lamp lighting device for use in a discharge lamp that performs glow discharge when a predetermined voltage is applied , and transitions from glow discharge to arc discharge when a high-pressure trigger pulse is applied,
A back converter circuit that outputs a first voltage lower than the predetermined voltage before lighting the discharge lamp, and that controls the discharge lamp at a constant power after the discharge lamp is lit;
At the time of constant power control of the buck converter circuit, an inverter circuit that converts a DC voltage output from the buck converter circuit into an AC voltage and applies it to the discharge lamp;
A high pressure trigger pulse generating circuit for outputting the high pressure trigger pulse to the discharge lamp;
A boost-up circuit having a coil and a capacitor connected between the electrodes of the discharge lamp, and generating the predetermined voltage by charging the capacitor;
A switching means for switching the enable / disable of the boost-up circuit, comprising a semiconductor electrical element connected between the coil and the capacitor ;
Have
In order to cause the discharge lamp to glow discharge, the first voltage is output from the buck converter circuit to the inverter circuit, and the switching means is generated by enabling the boost-up circuit and applying a voltage to the boost-up circuit. Charging the capacitor with a voltage to
When the discharge lamp starts glow discharge, the switching means disables the boost-up circuit,
The discharge lamp lighting device, wherein the semiconductor electric element carries a second voltage corresponding to a difference between the predetermined voltage and the first voltage.   2. The discharge lamp lighting according to claim 1, wherein the inverter circuit includes a switching element, and the switching element takes a value not lower than the first voltage and not higher than the predetermined voltage as a voltage between input and output. apparatus. It said high trigger pulse generating circuit discharge lamp lighting device according to claim 1, wherein the benzalkonium that having a transformer for generating the high voltage trigger pulse. The boost-up circuit, a discharge lamp lighting device according to claim 1, characterized by charging the capacitor by the voltage generated by applying a step voltage to the resonant circuit composed by the said and the coil condenser. Has a voltage detecting means for detecting the voltage across the previous SL capacitor, when the voltage across said capacitor prior SL voltage detecting means has detected is equal to or less than the predetermined voltage, the switching means and enabling the boost-up circuit, said if it reaches a predetermined voltage, said switching means discharge lamp lighting device according to claim 1, characterized in that the disabling said boost-up circuit.

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