JPH04322169A - Discharge lamp lighting apparatus - Google Patents

Abstract

PURPOSE:To quickly detect a lamp voltage of a discharge lamp. CONSTITUTION:One end of a discharge lamp DL is connected to a connecting point of switching elements Q1, Q2 via an inductor L1, the other end of the discharge lamp DL is connected to a connecting point of switching elements Q3, Q4 via an inductor L2 having an inductance value almost equal to that of the inductor L1, and a capacitor C0 is connected in parallel with the discharge lamp DL. Moreover, a voltage detecting means (not illustrated) for detecting voltages VA, VB across the discharge lamp DL is also provided. Thereby, the voltage across the discharge lamp DL is not varied due to high frequency switching operation of the switching elements Q1 to Q4. Accordingly, an integration circuit for controlling voltage variation is no longer required and delay of detection by integration can be eliminated. As a result, a lamp voltage of the discharge lamp DL can be detected quickly and ON-OFF states of the first to fourth switching elements Q1 to Q4 can be controlled depending on the condition change of the discharge lamp DL.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for lighting, for example, a high-pressure discharge lamp in a rectangular wave using a full-bridge inverter.

0002

2. Description of the Related Art FIG. 14 shows a circuit diagram of a conventional discharge lamp lighting device of this type. As shown in FIG. 14, this discharge lamp lighting device has first and second switching elements Q1 and Q2 connected in series in this order between the positive and negative electrodes of the DC power source VDC, and the positive and negative electrodes of the DC power source VDC. Third and fourth switching elements Q3 and Q4 are connected between the negative electrode and the negative electrode.
are connected in series in this order, and the first, second, third and fourth diodes D1, D2 are connected to the first, second, third and fourth switching elements Q1, Q2, Q3, Q4.
, D3, and D4 are connected in antiparallel.

Then, one end of the discharge lamp DL is connected to the connection point of the first and second switching elements Q1 and Q2, and the third and fourth switching elements Q3 and Q4 are connected to each other.
The discharge lamp DL is connected via the inductor L0 to the connection point of
The other end is connected, and a capacitor C0 is connected in parallel to the discharge lamp DL. Further, a potential detection means (not shown) is provided for detecting the potentials VA and VB (the difference voltage becomes the lamp voltage) at both ends of the discharge lamp DL, and the first, second, third and fourth switching Element Q1,
A control means (not shown) is provided to control on/off of Q2, Q3, and Q4.

[0004] In the discharge lamp lighting device configured as described above, the control means specifically causes the first and fourth switching elements Q1 and Q4 to be repeatedly turned on and off at a high frequency, and the second and third switching elements Switching element Q
2 and Q3 are kept off, and a second state where the second and third switching elements Q2 and Q3 are repeatedly turned on and off at a high frequency and the first and fourth switching elements Q1 and Q4 are kept off. State 2 is alternately repeated at a low frequency.

Furthermore, based on the detection result of the potential detection means, the first, second, third and fourth switching elements Q1
, Q2, Q3, and Q4, the lamp voltage or lamp current is controlled by controlling the length of the on period and off period of Q2, Q3, and Q4. The above discharge lamp lighting device is a discharge lamp DL
The potentials VA and VB at both ends of are shown in FIG. 15(a) and
The result is as shown in (b). In FIG. 15, SW1 is a period of the first state in which the first and fourth switching elements Q1 and Q4 are repeatedly turned on and off at a high frequency, and the second and third switching elements Q2 and Q3 are kept off. , SW2 is the second and third
This is a second state period in which the switching elements Q2 and Q3 are repeatedly turned on and off at a high frequency, and the first and fourth switching elements Q1 and Q4 are kept off.

VDL is a lamp voltage, and the lamp voltage VDL is superimposed on the potential VB with a negative polarity during a period SW1, and the lamp voltage VDL is superimposed with a positive polarity during a period SW2. In the above, as a potential detection means for detecting the potential at both ends of the discharge lamp DL, for example, a differential amplifier DA3 as shown in FIG.
By inputting the potentials VA and VB at both ends of the DC power supply VDC with the negative pole side of the DC power supply VDC as the ground, the differential amplifier DA3
A lamp voltage VDL as shown in FIG. 17 can be detected as the output voltage VO1. In addition, in FIG. 17,
In the period SW1, the lamp voltage VDL has a positive polarity, and in the period SW2, it has a negative polarity.

Furthermore, instead of the differential amplifier DA3 in FIG. 16, a diode D11 and a resistor R17 as shown in FIG.
By using a detection circuit DW consisting of a capacitor C4 and a capacitor C4, the lamp voltage VDL can be easily detected. In other words, this detection circuit DW has a configuration in which the potential VB is half-wave rectified and integrated with the negative electrode side of the DC power supply VDC as the ground, and the resistor R17 and capacitor C4
The time constant of is set sufficiently larger than the switching period of period SW1 and period SW2, and the output voltage VO
2, the voltage shown in FIG. 19 is obtained. Note that the peak value of this voltage VO2 is VDC+VDL. however,
It is assumed that the DC power supply voltage VDC is constant.

[0008]

[Problem to be solved by the invention] The circuit shown in FIG.
In the first conventional example combining the differential amplifier DA3,
The difference between the potential VA and the potential VB becomes the lamp voltage VDL, and a power supply voltage chopped at the switching frequency is superimposed on each of the potentials VA and VB as an in-phase component. A differential amplifier DA3 is used to calculate such a difference in signal potential. However, the differential amplifier DA3 has a property that its ability to remove the common mode component decreases as the frequency of the common mode component increases. Therefore, the differential amplifier DA
The in-phase component is superimposed on the output of 3, and it becomes necessary to add an integrating circuit to remove it.

Furthermore, the detection circuit D of FIG. 18 is added to the circuit of FIG.
In the second conventional example in which W is combined, a half-cycle voltage is generated by an integrating circuit, so it must have a sufficiently long time constant with respect to the switching cycle. in this way,
It becomes necessary to insert an integrating circuit into the lamp voltage VDL detection circuit. However, when the time constant of the integrating circuit is long, there is a time delay in detection with respect to the actual state of the discharge lamp DL, so there is a problem that control according to the state of the discharge lamp DL cannot be performed.

[0010] Accordingly, an object of the present invention is to provide a discharge lamp lighting device that can detect the lamp voltage of a discharge lamp at high speed.

[0011]

[Means for Solving the Problems] As shown in FIG. 1, the discharge lamp lighting device of the present invention includes first and second switching elements Q1 and Q between the positive and negative electrodes of a DC power supply VDC.
2 are connected in series in this order, and the DC power supply VDC
Third and fourth switching elements Q3 and Q4 are connected in series in this order between the positive and negative electrodes of the transistor. The discharge lamp D is connected to the connection point between the first and second switching elements Q1 and Q2 via the first inductor L1.
The other end of the discharge lamp DL is connected to the connection point between the third and fourth switching elements Q3 and Q4 via a second inductor L2 whose inductance value is approximately equal to that of the first inductor L1. , a capacitor C0 is connected in parallel to the discharge lamp DL.

Furthermore, the potential VA across the discharge lamp DL
, VB is provided,
A first state in which the first and fourth switching elements Q1 and Q4 are repeatedly turned on and off and the second and third switching elements Q2 and Q3 are held off; and a second state in which the second and third switching elements Q2 and Q3 are kept off.
and a second state in which the first and fourth switching elements Q1 and Q4 are kept off are alternately repeated, and the first, second, and third switching elements are Further, a control means is provided for controlling the lengths of the on period and off period of the fourth switching elements Q1, Q2, Q3, and Q4.

D1 to D4 are switching elements Q1
This is a diode connected in antiparallel to Q4. Note that the first and second inductors L1 and L2 may have a common core or may have independent cores.

[0014]

[Operation] According to the structure of the present invention, since the first and second inductors L1 and L2 having substantially equal inductance values are provided on both sides of the discharge lamp DL, the high frequency of the first to fourth switching elements Q1 to Q4 is Fluctuations in the potential across the discharge lamp DL due to switching are eliminated. Therefore, there is no need for an integrating circuit for suppressing voltage fluctuations, and there is no detection delay due to integration. As a result, the lamp voltage of the discharge lamp DL can be detected at high speed, and the on/off of the first to fourth switching elements Q1 to Q4 can be controlled in accordance with changes in the state of the discharge lamp DL.

[0015]

【Example】

(First Embodiment) A first embodiment of the present invention will be explained based on FIGS. 2 to 4. This discharge lamp lighting device is shown in Figure 2.
As shown in FIG.
The other end of the discharge lamp DL is connected to the connection point between the third and fourth switching elements Q3 and Q4 through the first inductor L1, and the other end of the discharge lamp DL is connected to the connection point between the third and fourth switching elements Q3 and Q4 through the second inductor L2. connected. The first and second inductors L1 and L2 are set to have substantially equal inductance values, and their series combined inductance value is set to be the same as that of the conventional inductor L0.

Furthermore, the potential VA across the discharge lamp DL
, VB are diodes D5, D6 and resistor R1
It is detected by the maximum value detection circuit MX1 consisting of the potential VA
, VB is output as the output voltage VO3. In this case, first and second inductors L1 and L2 having substantially equal inductance values are provided on both sides of the discharge lamp DL.
, the first to fourth switching elements Q1
Discharge lamp D by high frequency switching ~Q4
There is no fluctuation in the potentials VA and VB at both ends of L. Therefore, there is no need for an integrating circuit for suppressing voltage fluctuations, and there is no detection delay due to integration. As a result, discharge lamp DL
lamp voltage can be detected with high precision and high speed,
It is possible to control on/off of the first to fourth switching elements Q1, Q2, Q3, Q4 in accordance with state changes of the discharge lamp DL, and for example, fluctuations in lamp voltage, lamp current, etc. can be suppressed.

Moreover, the circuit configuration includes diodes D5,
Maximum value detection circuit MX1 consisting of D6 and resistor R1
Voltage detection can be performed with an extremely simple circuit. Further, as shown in FIG. 13, inverter IV (first to fourth switching elements Q1 to Q4
Even if a ground fault occurs in the two cables leading from (consisting of the
~Q4 will not be destroyed.

FIG. 3 shows the input and output voltages of the maximum value detection circuit MX1 in the discharge lamp lighting device of FIG. 2, and (a)
(b) shows the potential VB, and (c) shows the voltage VO3. As is clear from FIG. 3, the potential VA is (VDC+VDL) during period SW1.
/2, and in period SW2 (VDC-VDL)/2
becomes. Further, the potential VB is (VD
C-VDL)/2, and in period SW2, (VDC+
VDL)/2. Therefore, maximum value detection circuit MX
1 outputs the maximum value of potentials VA and VB, so
It is always (VDC+VDL)/2.

FIG. 4 is a characteristic diagram showing changes in voltage VO3 with changes in lamp voltage VDL, where VDL0 is the no-load lamp voltage. (Second Embodiment) A second embodiment of the present invention will be described based on FIGS. 5 and 6. This discharge lamp lighting device is shown in Figure 2.
In place of the maximum value detection circuit MX1 in , a minimum value detection circuit MI1 consisting of diodes D7 and D8 and a resistor R2 is used, and the other configurations are the same as the discharge lamp lighting device of FIG.

In this embodiment, as in the first embodiment, the lamp voltage can be detected with high precision and at high speed without requiring an integrating circuit for suppressing voltage fluctuations. therefore,
It is possible to control on/off of the first to fourth switching elements Q1, Q2, Q3, Q4 in accordance with state changes of the discharge lamp DL, and for example, fluctuations in lamp voltage, lamp current, etc. can be suppressed.

Moreover, the circuit configuration includes diodes D7,
Minimum value detection circuit MI1 consisting of D8 and resistor R2
Voltage detection can be performed extremely easily by simply using the . Minimum value detection circuit M in this embodiment
Since the output voltage VO4 of I1 outputs the minimum value of the potentials VA and VB, it is always (VDC-VDL)/2.

FIG. 6 is a characteristic diagram showing changes in voltage VO4 with changes in lamp voltage VDL. (Third Embodiment) A third embodiment of the present invention will be described based on FIGS. 7 and 8. This discharge lamp lighting device is shown in Figure 2.
In place of the maximum value detection circuit MX1, a differential amplifier DA1
The other configuration is the same as that of the discharge lamp lighting device shown in FIG.

In this embodiment as well, since the first and second inductors L1 and L2 having substantially equal inductance values are provided on both sides of the discharge lamp DL, the high frequency of the first to fourth switching elements Q1, Q2, Q3, and Q4 is The potential VA across the discharge lamp DL due to the switching of
, VB fluctuation disappears. Therefore, voltage detection can be performed with high accuracy and high speed without requiring a differential amplifier with a high common-mode component removal function or an integrating circuit as in the first conventional example.

Further, even if the wiring leading to the discharge lamp DL is drawn out from the inverter IV, less common mode noise is generated. Other effects are the same as in each of the above embodiments. (Fourth Embodiment) A fourth embodiment of the present invention will be described based on FIG. 9. This discharge lamp lighting device is a discharge lamp DL
Rather than applying the potentials VA and VB across the terminals directly to the differential amplifier DA1 as shown in FIG.
and an average value circuit consisting of capacitor C1 and resistor R
4 and an average value circuit consisting of capacitor C2,
After the average values VA' and VB' of the potentials VA and VB are determined, they are input to the differential amplifier DA2. In this case, the time constants of resistor R3 and capacitor C1 and the time constants of resistor R4 and capacitor C2 are set sufficiently larger than the switching cycles of periods SW1 and SW2, respectively. Others are the same as in FIG. 2.

In the above configuration, since the average value VA' of the potential VA and the average value VB' of the potential VB are both VDC/2, normally the differential amplifier DA2
The output voltage VO6 is zero. However, as shown in FIG. 13, if one of the power lines from the inverter IV to the discharge lamp DL has a ground fault, VA'=VB'=VDC
/2, so some voltage is output as the voltage VO6. Thereby, an abnormality in the inverter IV can be detected.

Other structural effects are the same as in the prior art example. (Fifth Embodiment) A fifth embodiment of the present invention will be described based on FIGS. 10 and 11. This discharge lamp lighting device is
In place of the maximum value circuit MX1 of FIG. 2, a maximum value circuit MX2 including a resistance attenuation circuit is used, and the other configurations are the same as those of FIG.

This maximum value circuit MX2 has a voltage dividing resistor R5.
, R6, R7, R8 and transistors Q5, Q
6, Q7 and load resistances R9, R10,
The voltage dividing resistors R5 and R7 have the same resistance value, and the voltage dividing resistors R5 and R7 have the same resistance value.
6 and R8 have the same resistance value. This maximum value circuit MX2
divides the potential VA by voltage dividing resistors R5 and R6,
Potential VB is divided by voltage dividing resistors R7 and R8, and the maximum value of both divided voltages is selected by NPN type transistors Q5 and Q6, which also serve as current amplification, and transistors Q5 and Q6
The output voltage VO7 is taken out through the emitter follower of a PNP transistor Q7, which is of the opposite conductivity type. Note that VCC is a control power supply voltage, and VO7≦VCC.

The reason for the above configuration is as follows. In general, control circuits that use detected voltages use much lower voltages than inverter circuits, so it is common to attenuate the potentials VA and VB instead of detecting them as they are. As shown in FIG. 11, if an attenuator is inserted to output the maximum value, simply add a voltage dividing resistor R5 to the maximum value circuit MX1 in FIG.
, R6, R7, and R8 can be considered, but in this circuit, the load resistance R9
Due to this influence, the attenuation rate R2/(R1 +R2) cannot be maintained accurately.

Therefore, as in the circuit shown in FIG. 10, instead of the diodes D9 and D10, N
Constructed using PN type transistors Q5 and Q6,
In addition to accurately maintaining the attenuation rate without being affected by the load resistor R9, an emitter follower circuit consisting of a PNP transistor Q7 of the conductivity type opposite to that of the transistors Q5 and Q6 and a load resistor R10 is provided.
, Q6 are compensated for.

In this embodiment, the maximum value can be detected while the potentials VA and VB at both ends of the discharge lamp DL are attenuated, and the attenuation rate can be accurately maintained, and fluctuations due to temperature changes can be detected. can also be eliminated. Other effects are similar to those of the first embodiment. (Sixth Embodiment) A sixth embodiment of the present invention will be described based on FIG. 12. This discharge lamp lighting device uses a maximum value circuit MI2 including a resistive attenuation circuit in place of the minimum value circuit MI1 shown in FIG. 5, and the other configuration is the same as that shown in FIG.

This minimum value circuit MI2 has a voltage dividing resistor R1
1, R12, R13, R14 and transistors Q8, Q
9, Q10, and load resistors R15, R16,
The voltage dividing resistors R11 and R13 have the same resistance value, and the voltage dividing resistor R
12 and R14 have the same resistance value. This minimum value circuit MI2
divides the potential VA by voltage dividing resistors R11 and R12,
Potential VB is divided by voltage dividing resistors R13 and R14, and the minimum value of both divided voltages is selected by PNP type transistors Q8 and Q9 which also serve as current amplification, and transistors Q8 and Q9
The output voltage VO8 is taken out through the emitter follower of an NPN transistor Q10, which is of the opposite conductivity type. Note that VCC is a control power supply voltage, and VO8≦VCC.

This minimum value circuit MI2 is constructed using NPN type transistors Q5 and Q6 which also serve as current amplification, and maintains the attenuation rate accurately without being affected by the load resistance R9. An emitter follower circuit consisting of a PNP transistor Q7 of the conductivity type opposite to Q6 and a load resistor R10 is provided to compensate for the temperature characteristics of the transistors Q5 and Q6.

In this embodiment, the minimum value can be detected while the potentials VA and VB at both ends of the discharge lamp DL are attenuated, and the attenuation rate can be maintained accurately, and fluctuations due to temperature changes can be detected. can also be eliminated. Note that the inductors L1 and L2 of each of the above embodiments
The wires may be wound on the same core or on separate cores.

[0034]

According to the discharge lamp lighting device of the present invention, since the first and second inductors having substantially equal inductance values are provided on both sides of the discharge lamp, high-frequency switching of the first to fourth switching elements can be performed. Fluctuations in potential across both ends of the discharge lamp can be eliminated. Therefore, there is no need for an integrating circuit for suppressing voltage fluctuations, and there is no detection delay due to integration. As a result, the lamp voltage of the discharge lamp can be detected at high speed, and the first to fourth switching elements can be turned on and off in accordance with changes in the state of the discharge lamp.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of a discharge lamp lighting device of the present invention.

FIG. 2 is a circuit diagram of a discharge lamp lighting device according to a first embodiment of the present invention.

FIG. 3 is a time chart of each part in FIG. 2;

4 is a characteristic diagram showing changes in voltage VO3 with respect to changes in lamp voltage VDL in the circuit of FIG. 2; FIG.

FIG. 5 is a circuit diagram showing the configuration of main parts of a discharge lamp lighting device according to a second embodiment of the present invention.

6 is a characteristic diagram showing changes in voltage VO3 with respect to changes in lamp voltage VDL in the circuit of FIG. 5; FIG.

FIG. 7 is a circuit diagram showing the configuration of main parts of a discharge lamp lighting device according to a third embodiment of the present invention.

FIG. 8 is a time chart of the output voltage of the circuit in FIG. 7;

FIG. 9 is a circuit diagram showing the configuration of main parts of a discharge lamp lighting device according to a fourth embodiment of the present invention.

FIG. 10 is a circuit diagram showing the configuration of main parts of a discharge lamp lighting device according to a fifth embodiment of the present invention.

FIG. 11 is a circuit diagram of a maximum value circuit for reference.

FIG. 12 is a circuit diagram showing the configuration of main parts of a discharge lamp lighting device according to a sixth embodiment of the present invention.

FIG. 13 is a schematic diagram showing a state of a ground fault in the discharge lamp lighting device.

FIG. 14 is a circuit diagram showing a conventional example of a discharge lamp lighting device.

FIG. 15 is a time chart of each part of the circuit in FIG. 14;

FIG. 16 is a circuit diagram of a portion that detects the voltage across the discharge lamp.

FIG. 17 is a time chart of the output voltage of the circuit in FIG. 16;

FIG. 18 is a circuit diagram of a portion that detects the voltage across the discharge lamp.

FIG. 19 is a time chart of the output voltage of the circuit of FIG. 18;

[Explanation of symbols]

VDC DC power supply Q1 First switching element Q2 Second switching element Q3 Third switching element Q4 Fourth switching element DL discharge lamp C0 Capacitor L1 First inductor L2 Second inductor

Claims (1)

[Claims] 1. First and second switching elements are connected in series in this order between the positive and negative electrodes of a DC power source, and third and fourth switching elements are connected between the positive and negative electrodes of the DC power source. The first and second switching elements are connected in series in this order, one end of the discharge lamp is connected to the connection point of the first and second switching elements via a first inductor, and the first end of the discharge lamp is connected to the connection point of the third and fourth switching elements. The other end of the discharge lamp is connected through a second inductor having an inductance value substantially equal to that of the inductor, a capacitor is connected in parallel to the discharge lamp, and potential detection means is provided for detecting the potential at both ends of the discharge lamp. a first state in which the first and fourth switching elements are repeatedly turned on and off and the second and third switching elements are held off; a first state in which the second and third switching elements are repeatedly turned on and off; A second state in which the first and fourth switching elements are held off is alternately repeated, and the first, second, third and fourth switching elements are turned on based on the detection result of the potential detection means. A discharge lamp lighting device provided with a control means for controlling the length of a period and an off period.