JP3898406B2 - Discharge lamp lighting method and discharge lamp lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a discharge lamp lighting method and apparatus, and more particularly, to a discharge lamp lighting method and apparatus for reducing winding noise of a winding transformer.
[0002]
[Prior art]
Conventionally, in a discharge lamp lighting device (also called a backlight inverter device) for lighting a discharge lamp (for example, a cold cathode fluorescent tube or a fluorescent tube), the dimming of the luminance of the fluorescent tube changes the current flowing through the fluorescent tube, that is, the tube current. Let me go.
[0003]
FIG. 1 is a block diagram showing a conventional discharge lamp lighting device. In the figure, 11 is a DC power source such as a battery, 12 is a DC-DC converter circuit, 13 is a self-excited inverter circuit (hereinafter referred to as an inverter circuit), 14 is a current detection circuit, and 15 is a cold cathode fluorescent tube.
[0004]
In the above configuration, the fluorescent tube current flowing through the cold cathode fluorescent tube (hereinafter referred to as a fluorescent tube) 15 is detected by the current detection circuit 14, and the detection result is fed back to the DC-DC converter circuit 12.
[0005]
The DC-DC converter circuit 12 converts the voltage level supplied from the DC power supply 11 into another voltage level based on the feedback signal from the current detection circuit 14 and outputs the voltage level to the inverter circuit 13.
[0006]
The inverter circuit 13 converts the DC voltage input from the DC-DC converter circuit 12 into an AC voltage having a predetermined frequency and applies it to the fluorescent tube 15.
[0007]
As described above, the tube current detected by the current detection circuit 14 is fed back to the DC-DC converter circuit 12 and the supply voltage of the inverter circuit 13 is changed, so that the tube current is subjected to constant current control.
[0008]
The tube current flowing through the fluorescent tube 15 is a continuous current, and is controlled to be a predetermined level set in advance. Further, the light can be dimmed in the range of luminance MAX 100% to 50%, and this dimming method is generally called a current dimming method.
[0009]
In order to widen the low luminance side range in order to widen the dimming range, it is necessary to operate with a reduced tube current. However, since the discharge becomes unstable due to the nature of the fluorescent tube 15 as the tube current is reduced, in the continuous constant current control method as described above, the lower limit on the low luminance side is about 50% of the luminance MAX. It is a limit.
[0010]
FIG. 2 is a configuration diagram showing a discharge lamp lighting device using a conventional current dimming method. In the figure, 31 is a DC power source such as a battery, 32 is a DC-DC converter circuit, 33 is a self-excited inverter circuit, 34 is a cold cathode fluorescent tube (hereinafter simply referred to as a fluorescent tube), and 35 is a detection / feedback circuit. It is.
[0011]
The DC-DC converter circuit 32 includes an error amplifier 321, a dead time adjustment voltage generation circuit 322, a comparator 323, a triangular wave generation circuit 324, a PNP transistor 325, and a diode 326.
[0012]
The error amplifier 321 receives the feedback voltage output from the detection / feedback circuit 35, and outputs an error voltage ER corresponding to the difference voltage so that the feedback voltage is substantially the same as the reference voltage Vref.
[0013]
The dead time adjustment voltage generation circuit 322 generates a dead time adjustment voltage DT by dividing the reference voltage by a resistor and outputs the dead time adjustment voltage DT.
[0014]
The comparator 323 compares the triangular wave voltage TR output from the triangular wave generating circuit 324 with the error voltage ER and the dead time adjustment voltage DT, and when the triangular wave voltage TR is larger than the error voltage ER and the dead time adjustment voltage DT. When the error voltage ER or the dead time adjustment voltage DT is higher than the triangular wave voltage TR, a low level voltage is output. This output voltage is input to the base of the transistor 325, and the transistor 325 performs a switching operation.
[0015]
As a result, when the transistor 325 is on, power is supplied to the inverter circuit 33. In the off state, the diode 326 is conducted by the back electromotive force of the choke coil 332 of the inverter circuit 33, and the input power to the inverter circuit 33 is averaged.
[0016]
The inverter circuit 33 includes a winding transformer 331, a choke coil 332, NPN transistors 333 and 334, a resistor 335, and capacitors 336 and 337, and has a well-known Royer circuit.
[0017]
The output voltage of the DC-DC converter circuit 32 is applied to the intermediate tap of the primary winding of the transformer 331 via a choke coil 332 and a fuse (may be omitted), and the tertiary winding via the choke coil 332 and the resistor 335. Applied to one end of the line and the base of transistor 333. The other end of the tertiary winding of the transformer 331 is connected to the base of the transistor 334, the collectors of the transistors 333 and 334 are connected to both ends of the primary winding of the transformer 331, and the emitter is grounded. A capacitor 336 is connected between both ends of the primary winding. One end of the secondary winding of the transformer 331 is connected to one end of the fluorescent tube 34 via the capacitor 337, and the other end of the secondary winding is grounded.
[0018]
The detection / feedback circuit 35 includes resistors R1 to R3, a diode D1, a capacitor C1, and a variable resistor VR1, and the other end of the fluorescent tube 34 is grounded via the resistor R1 and the anode of the diode D1. It is connected to the.
[0019]
The cathode of the diode D1 is connected to one end of the resistor R2 and grounded via the capacitor C1, and the other end of the resistor R2 is grounded via the resistor R3 and the variable resistor VR1 connected in series. Yes.
[0020]
As a result, the tube current flowing through the fluorescent tube 34 is converted into a voltage by the resistor R1, and this detection voltage is rectified by the diode D1, and then divided by the resistors R2 and R3 and the variable resistor VR1 to obtain a feedback voltage. Is output as The level of the feedback voltage can be changed by the variable resistor VR1.
[0021]
That is, the inverter frequency AC signal (detection voltage) rectified by the diode D1 is smoothed by the capacitor C1 to become a DC voltage. The voltage of the capacitor C1 is divided by the resistors R2 and R3 and the variable resistor VR1, and added to the feedback input of the DC-DC converter circuit 32 as a feedback voltage.
[0022]
Adjustment of the tube current flowing through the fluorescent tube 34 is performed by adjusting the level of the feedback voltage applied to the feedback input of the DC-DC converter circuit 32 by changing the variable resistor VR1. Thereby, when the value of the variable resistor VR1 is small, the tube current increases to increase the brightness, and when the value is large, the tube current is decreased to decrease the brightness.
[0023]
On the other hand, recently, a method of operating a fluorescent tube with high power consumption with low luminance has been used in order to extend the operating time of battery drive in a notebook personal computer or the like. In this case, a luminance MAX of about 100% to 10% is required as the luminance dimming range.
[0024]
As a method for expanding the dimming range, there is a limit in constant current control using a continuous current. For example, as disclosed in Japanese Patent Laid-Open No. 5-198384, a burst in which tube current is interrupted and its ratio is changed is disclosed. A dimming method is used. This dimming method is also called duty dimming or frequency dimming.
[0025]
FIG. 3 is a diagram illustrating an example of a discharge lamp lighting device using a conventional burst dimming method. The discharge lamp lighting device shown in FIG. 3 is obtained by changing the conventional discharge lamp lighting device shown in FIG. 2 as follows. That is, the burst dimming switching circuit 36 is inserted between the DC-DC converter circuit 32 and the inverter circuit 33 in the circuit of FIG. 2, and the detection / feedback circuit 35 is deleted.
[0026]
The control circuit 329 of the DC-DC converter circuit 32 ′ is an IC that operates in the same manner as the error amplifier 321, the dead time adjustment voltage generation circuit 322, the comparator 323, and the triangular wave generation circuit 324 of the DC-DC converter circuit 32 in FIG. (Integrated circuit).
[0027]
The smoothing coil 327 and the capacitor 328 are elements that stabilize the output of the DC-DC converter circuit 32 ′ so as not to adversely affect the operation of the subsequent burst dimming switching circuit 36.
[0028]
The burst dimming switching circuit 36 includes a switching transistor 364, a comparator 361, a burst dimming adjustment voltage generation circuit 362, and a triangular wave generation circuit 363.
[0029]
As shown in FIG. 3, the discharge lamp lighting device using the burst dimming system converts the output voltage of the DC power source 31 into a voltage of a predetermined level by the DC-DC converter circuit 32 ′, and the burst dimming switching circuit 36 is provided. And the power supply from the DC-DC converter circuit 32 ′ to the inverter circuit 33 is interrupted based on the burst signal generated by the burst dimming switching circuit 36, thereby The luminance of the cathode fluorescent tube 34 is changed. At this time, dimming can be performed by adjusting the intermittent ratio of energization to the inverter circuit 33.
[0030]
That is, the burst dimming switching circuit 36 turns on and off the DC voltage output from the DC-DC converter circuit 32 ′ in accordance with the on-state and off-state of the burst dimming system based on the burst signal.
[0031]
When the switching transistor 364 is on, the self-excited inverter circuit 33 oscillates and the cold cathode fluorescent tube 34 is lit by voltage application. When the switching transistor 364 is off, no voltage is input to the self-excited inverter circuit 33. Therefore, no voltage is applied to the cold cathode fluorescent tube 34, and the cold cathode fluorescent tube 34 is not lit.
[0032]
[Problems to be solved by the invention]
However, the above-described conventional discharge lamp lighting device using the burst dimming system has many components and is difficult to reduce in size and cost. In addition, during the lighting period, the input voltage to the inverter circuit 33 is only stabilized, and the tube current is not directly controlled. Therefore, the brightness varies depending on the characteristic variation of components and lamps and the ambient temperature.
[0033]
Furthermore, a roaring sound is generated from the transformer 331 and the choke coil 332, giving the user unpleasant feeling. This is caused by the magnetostriction of the winding transformer 331 and the choke coil 332 when the light-off state changes to the light-on state. The cause is the sudden increase in tube current and the exciting current that flows instantaneously immediately before lighting.
[0034]
For example, when a change in input voltage to the self-excited inverter circuit 33 when burst dimming is performed, a voltage waveform as shown in FIG. 4 is obtained. As a manifestation of the sound characteristics of the sound, it can be seen in the large and small overshoots immediately after entering the lighting state. A small overshoot is due to the excitation current.
[0035]
In addition, IC manufacturers have released dedicated ICs for burst dimming, and miniaturization can be achieved. However, since the smoothing capacitor is eliminated and the tube current signal is detected and controlled by the peak value in order to solve the above problem, the cost is low because the control is expensive. Furthermore, no measures against sounding are made. The voltage waveform when operating with a dedicated IC is also as shown in FIG.
[0036]
SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a burst dimming type discharge lamp lighting method capable of obtaining stable characteristics with inexpensive components and reducing the occurrence of roaring noise from a choke coil or winding transformer, and It is to provide such a device.
[0037]
[Means for Solving the Problems]
The present invention achieves the above object by claim 1. The winding An inverter circuit having a transformer and a switching transistor, and a tube that rectifies a tube current flowing through a discharge lamp to be lit and charges a smoothing capacitor, and outputs a voltage corresponding to the tube current value based on the charging voltage of the smoothing capacitor A current value detection circuit, an error amplifier that outputs a voltage difference between the voltage output from the tube current value detection circuit and the first reference voltage as an error voltage, and the inverter circuit and the DC power source are connected in series. A switching transistor for driving that is switched on and off based on a control signal to supply power to the inverter circuit, means for generating a dead time adjustment voltage having a dead time voltage value, means for generating a triangular wave voltage, and the triangular wave voltage When the switching time for the drive is higher than the dead time adjustment voltage and the error voltage. Pulse width modulation means for outputting the control signal for turning on the transistor, and adjusting the dead time voltage value to change the ratio of the on / off period of the drive switching transistor to change the lighting state and extinguishing state of the discharge lamp. In a discharge lamp lighting method in which brightness adjustment is performed by a burst dimming method that is alternately switched, a current that does not cause the discharge lamp to light in accordance with an adjusted dead time voltage value during a period in which the discharge lamp is turned off. A discharge lamp lighting method is proposed in which a voltage having a voltage value equal to or higher than the voltage value of the smoothing capacitor when the winding transformer is energized and the brightness of the discharge lamp is set to the maximum is applied to the smoothing capacitor.
[0038]
According to the discharge lamp lighting method, in the period in which the discharge lamp is turned off, the voltage value of the dead time adjustment voltage is switched, and the ratio of the ON period of the drive switching transistor is reduced to the inverter circuit. By reducing the power supplied, a current that does not lead to the lighting of the discharge lamp is energized in the winding transformer, so that when the discharge lamp changes from the unlit state to the lit state, A sharp change does not occur in the energization current value, the cause of the sounding noise related to the small overshoot of the waveform in FIG. 4 is reduced, and the voltage value of the smoothing capacitor when the brightness of the discharge lamp is set to the maximum. A voltage having the above is applied to the smoothing capacitor during a period in which the discharge lamp is turned off, and a voltage drop of the smoothing capacitor By preventing excessive supply of power to the inverter circuit for compensating the voltage drop, the sounding-related causes large overshoot of the waveform in FIG. 4 can be reduced. Since these functions and effects can be obtained with main components of the conventional current dimming method, the effects of achieving a burst dimming function with an inexpensive configuration can be obtained at the same time.
[0039]
Thus, basically, the same operation as that of the conventional current dimming method is performed during the lighting period of the dimming pulse. Accordingly, the main component configuration is the same as that of the current dimming method.
[0040]
In addition, since the voltage is applied to the smoothing capacitor that rectifies and charges the tube current during the extinguishing period and is charged, the current value of the winding transformer is steep when the discharge lamp changes from the extinguished state to the illuminated state. There is no change. If this charging is not performed, the following problems will occur.
[0041]
That is, the charging voltage Vc1 of the smoothing capacitor is reduced by discharging through the resistors R2 and R3 during the extinguishing period, and an overshoot is caused in which an excessive voltage is applied to the inverter circuit immediately after the transition to the lighting period. As a result, the tube current also increases corresponding to the amount of overshoot and becomes brighter than desired. This is because the longer the extinction period is, and the higher the input DC power supply voltage is, the more prominent it is. Not practical.
[0042]
Also, Claim 2 Then, a smoothing capacitor is charged by rectifying the tube current flowing through the discharge lamp to be lit and an inverter circuit having a winding transformer and a switching transistor, and a voltage corresponding to the tube current value based on the charging voltage of the smoothing capacitor Between the inverter circuit and the DC power source, a tube current value detection circuit that outputs a difference voltage between the voltage output from the tube current value detection circuit and the first reference voltage, and an error amplifier. Are connected in series to each other and switched on and off based on a control signal to supply power to the inverter circuit, a drive switching transistor for generating a dead time adjustment voltage, a means for generating a triangular wave voltage, and the triangular wave voltage The drive switching transistor is turned on when the dead time adjustment voltage and the error voltage are higher. A discharge lamp lighting device comprising: a pulse width modulation means for outputting the control signal to generate a dimming pulse generation means for generating a dimming pulse signal for adjusting the brightness of the discharge lamp according to a pulse width; The dead time adjustment voltage is set to a first dead time voltage value when the dimming pulse is at one level, and the dead time adjustment voltage is set to the first dead time voltage value when the dimming pulse is at the other level. Means for mixing a voltage having a second dead time voltage value higher than the dead time voltage value of 1 and lower than the maximum value of the triangular wave voltage; and changing the pulse width of the dimming pulse to change the voltage of the discharge lamp. A voltage applied to the smoothing capacitor when the dimming pulse is at the other level is a voltage having a voltage value equal to or higher than the voltage value of the smoothing capacitor when the brightness is set to the maximum. Suggest discharge lamp lighting apparatus provided with means.
[0043]
According to the discharge lamp lighting device, the dimming pulse generating means generates a dimming pulse signal for adjusting the luminance of the discharge lamp in accordance with the pulse width, and the dimming pulse is at one level. For example, when the level is low, the dead time adjustment voltage is set to a first dead time voltage value, and when the dimming pulse is at the other level, that is, when the level is high, the dead time adjustment voltage is set to the first dead time voltage. Is set to a second dead time voltage value higher than the dead time voltage value.
[0044]
Thus, when the dimming pulse is at the one level, the drive switching transistor is turned on when the triangular wave voltage is larger than the dead time adjustment voltage having the first dead time voltage value and the error voltage. Then, the inverter circuit is energized, and the discharge lamp is turned on.
[0045]
Further, when the dimming pulse is at the other level, the drive switching transistor is turned on when the triangular wave voltage is larger than the dead time adjustment voltage having the second dead time voltage value and the error voltage. The inverter circuit is energized. Here, since the second dead time voltage value is set to a value higher than the first dead time voltage value and lower than the maximum value of the triangular wave voltage, the dimming pulse is When the level is low, the ratio of the on period of the drive switching transistor is decreased, the power supplied to the inverter circuit is decreased, the discharge lamp is turned off, and burst dimming is performed. The transformer is kept energized.
[0046]
Thereby, even when the discharge lamp is turned off, the winding transformer is energized with a current that does not cause the discharge lamp to turn on, so when the discharge lamp changes from the turned off state to the turned on state. In addition, there is no steep change in the energization current value of the winding transformer.
[0047]
Further, a voltage having a voltage value equal to or higher than the voltage value of the smoothing capacitor when the brightness of the discharge lamp is set to a maximum is applied to the smoothing capacitor by the voltage applying means during a period in which the discharge lamp is turned off. Is done. As a result, when the discharge lamp is changed from a light-off state to a light-on state, a change larger than the voltage of the smoothing capacitor does not occur.
[0048]
Accordingly, the voltage output from the tube current value detection circuit does not change greatly, so that the ratio of the on / off period of the drive switching transistor does not change abruptly.
[0049]
Also, Claim 3 Then Claim 2 In the discharge lamp lighting device described above, Second Dead time voltage value is The discharge lamp is turned off and energization to the winding transformer is maintained. A discharge lamp lighting device set to a voltage value is proposed.
[0050]
According to the discharge lamp lighting device, Second Dead time voltage value is The discharge lamp is turned off and energization to the winding transformer is maintained. Since the voltage value is set, unnecessary power consumption is avoided.
[0051]
Also, Claim 4 Then Claim 2 In the discharge lamp lighting device described above, a discharge lamp lighting device provided with means for detecting a maximum value of a voltage input to the inverter circuit and determining the second dead time voltage value from the maximum value voltage is proposed. .
[0052]
According to the discharge lamp lighting device, the maximum value of the voltage input to the inverter circuit is detected, and the second dead time voltage value is determined from the maximum value voltage. When changed, the second dead time voltage value is set corresponding to the changed voltage.
[0053]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0054]
FIG. 5 is a block diagram showing a discharge lamp lighting device according to the first embodiment of the present invention. In the figure, the same components as those of the conventional example shown in FIG. The difference between the first embodiment and the conventional example is that a dimming pulse generation circuit 41, NPN-type switching transistors 42 and 43, and a resistor 44 are provided. In the first embodiment, the detection / feedback circuit 35 ′ excluding the variable resistor VR1 is provided.
[0055]
The dimming pulse generation circuit 41 can change the pulse width of the dimming pulse P1, for example, by generating the dimming pulse P1 having a frequency of 500 Hz and changing the resistance value of the variable resistor VR. That is, the ratio between the high level period and the low level period of the dimming pulse P1 can be changed.
[0056]
A dimming pulse P1 is input to the base of the transistor 42, and the transistor 42 is set to an on state when the dimming pulse P1 is at a high level. A predetermined voltage V1 is applied to the collector of the transistor 42, and the emitter is connected to the connection point between the smoothing capacitor C1 and the cathode of the diode D1. Here, the value of the voltage V1 is set to be equal to or higher than the voltage value of the smoothing capacitor C1 when the ON period of the pulse of the output of the comparator 323 is maximized and the luminance of the fluorescent tube 34 is maximized.
[0057]
The dimming pulse P1 is input to the base of the transistor 43, and the transistor 43 is set to an on state when the dimming pulse P1 is at a high level. A predetermined voltage V 2 is applied to the collector of the transistor 43, and the emitter is a first dead time voltage generated by one inverting input terminal of the comparator 323 via the resistor 44, that is, the dead time adjustment voltage generation circuit 322. It is connected to the inverting input terminal to which DT1 is applied. As a result, the second dead time voltage DT2 is applied to the inverting input terminal via the transistor 43 and the resistor 44 when the transistor 43 is on.
[0058]
Here, the first dead time voltage DT1 is set to a value slightly higher than the minimum value of the triangular wave voltage TR, and the second dead time voltage DT2 is set to a voltage value slightly lower than the maximum value of the triangular wave voltage TR. ing.
[0059]
In the discharge lamp lighting device configured as described above, dimming is performed by changing the ratio between the high level period and the low level period of the pulse signal output from the dimming pulse generation circuit 41.
[0060]
That is, as shown in the signal waveform diagram of FIG. 6, when the dimming pulse P1 is at a low level, the transistors 42 and 43 are turned off, and the first dead time voltage is applied to one inverting input terminal of the comparator 323. DT1 is applied. As a result, the voltage of the error signal ER becomes higher than the first dead time voltage DT1, and the control signal CS based on the comparison result of the voltage of the error signal ER and the triangular wave voltage TR is sent from the comparator 323 to the base of the drive switching transistor 325. And the ratio at which the transistor 325 is turned on is increased. Accordingly, the supply current to the inverter circuit 33 is increased and the fluorescent tube 34 is turned on.
[0061]
On the other hand, when the dimming pulse P1 is at the high level, the transistors 42 and 43 are turned on, and the second dead time voltage DT2 is applied to one inverting input terminal of the comparator 323. Thus, when the triangular wave voltage TR is larger than the second dead time voltage DT2, the drive switching transistor 325 is turned on and the inverter circuit 33 is energized. Here, since the voltage value of the second dead time voltage DT2 is set to be higher than the first dead time voltage DT1 and slightly lower than the maximum value of the triangular wave voltage TR, the dimming pulse signal P1 is At the high level, the ratio of the ON period of the drive switching transistor 325 is reduced, the power supplied to the inverter circuit 33 is reduced, and the fluorescent tube 34 is turned off, but the winding transformer 331 and the choke coil 332 The energized state is maintained.
[0062]
As a result, during the period in which the fluorescent tube 34 is turned off, a current that does not lead to the lighting of the fluorescent tube 34 is applied to the winding transformer 331 of the inverter circuit 33. Therefore, the fluorescent tube 34 is changed from the turned off state to the turned on state. When changed, since there is no steep change in the energization current value of the winding transformer 331, magnetostriction, resonance, and resonance generated in the winding transformer 331 and the choke coil 332 due to the abrupt change in the energization current value are reduced. The roaring sound generated from these is reduced. Therefore, the user does not feel uncomfortable due to the roaring sound.
[0063]
Further, when the transistor 42 is turned on, a voltage having a voltage value equal to or higher than the voltage value of the smoothing capacitor C1 when the luminance of the fluorescent tube 34 is set to the maximum is applied to the smoothing capacitor C1.
[0064]
As a result, the following effects are obtained.
[0065]
That is, if the smoothing capacitor C1 is not charged during such a light extinction period, the voltage Vc1 of the smoothing capacitor C1 decreases due to the discharge through the resistors R2 ′ and R3 ′ during the light extinction period, and immediately after the transition to the lighting period. In addition, an excessive voltage is applied to the inverter circuit 33, causing overshoot. As a result, the tube current is increased by the amount of overshoot, and becomes brighter than desired. This is more noticeable as the light extinction period is longer and the input DC power supply voltage is higher, so it does not darken even if the dimming setting is set dark, and the brightness varies depending on the input voltage even if the brightness setting is the same. Can not.
[0066]
Therefore, in the above configuration, since the energization current to the winding transformer 331 and the choke coil 332 does not increase or decrease rapidly, magnetostriction, resonance, and resonance generated in the winding transformer 331 and the choke coil 332 are further reduced, The roaring sound generated from these is further reduced.
[0067]
Next, a second embodiment of the present invention will be described.
[0068]
FIG. 7 is a configuration diagram showing a discharge lamp lighting device according to the second embodiment of the present invention. In the figure, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. The difference between the second embodiment and the first embodiment is that a DC-DC converter circuit 32 ″ is provided instead of the DC-DC converter circuit 32.
[0069]
In this DC-DC converter circuit 32 ″, a two-input comparator 323A is used in place of the three-input comparator 323, and the first dead time voltage DT1 and the first dead-time voltage DT1 are obtained by diode OR coupling with diodes 329A and 329B at the inverting input terminals. A dead time voltage DT2 of 2 is applied in this way, so that a general-purpose IC or the like can be used by using the diode OR coupling.
[0070]
Next, a third embodiment of the present invention will be described.
[0071]
FIG. 8 is a block diagram showing a discharge lamp lighting device according to the third embodiment of the present invention. In the figure, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. The difference between the third embodiment and the first embodiment is that a Zener diode 51 and a resistor 52 are provided to generate a third dead time voltage DT3 from the output voltage of the DC-DC converter circuit 32. That is, the first and second dead time voltages DT1 and DT2 are mixed and applied to one inverting input terminal of the comparator 323.
[0072]
The cathode of the Zener diode 51 is connected to the output terminal of the DC-DC converter circuit 32, that is, the connection point between the choke coil 327 and the capacitor 328, and the anode is connected to one inverting input terminal of the comparator 323 via the resistor 52. Has been.
[0073]
According to the above configuration, when the power supply voltage of the DC power supply 31 is changed, the voltage value of the third dead time voltage DT3 changes corresponding to the changed power supply voltage, so the first dead time voltage DT1. Instead, the third dead time voltage DT3 prevents the overcurrent from flowing to the inverter circuit 33.
[0074]
Next, a fourth embodiment of the present invention will be described.
[0075]
FIG. 9 is a block diagram showing a discharge lamp lighting device according to the fourth embodiment of the present invention. In the figure, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. The difference between the fourth embodiment and the first embodiment is that a peak hold circuit 61, a comparator 62, an electronic switch 63, and a resistor 64 are provided in place of the transistor 43 and the resistor 44. is there.
[0076]
When the dimming pulse signal P1 is at a low level, the peak hold circuit 61 has its input side connected to the output terminal of the DC-DC converter circuit 32, that is, the connection point between the choke coil 327 and the capacitor 328, and the DC-DC converter. The peak value of the output voltage of the circuit 32 is detected, and this voltage Vpk is held and output to the inverting input terminal of the comparator 62.
[0077]
The comparator 62 inputs the voltage V3 to the non-inverting input terminal, and outputs the difference voltage between the voltage V3 and the voltage Vpk applied to the inverting input terminal via the electronic switch 63 and the resistor 64 to the second dead. Output as time voltage DT2. Here, the voltage V3 can be changed so that it can be finely adjusted.
[0078]
The electronic switch 63 is set to an on state when the dimming pulse signal P1 is at a low level.
[0079]
According to the above configuration, the peak hold circuit 61 detects the maximum value of the voltage input to the inverter circuit 33, and the voltage value of the second dead time voltage DT2 is determined from this maximum value voltage. When the voltage of the power supply 31 is changed, the voltage value of the second dead time voltage DT2 can be easily set corresponding to the changed voltage.
[0080]
Therefore, when the voltage of the DC power supply 31 is changed, the second dead time voltage DT2 is set corresponding to the changed voltage. Therefore, even if the power supply voltage is changed, it is the same without making a significant change. It can be used in a state with functions.
[0081]
Each embodiment described above is a specific example of the present invention, and the present invention is not limited to these.
[0082]
【The invention's effect】
As described above, the discharge lamp lighting method according to claim 1 of the present invention is used. According to the basics The typical operation is the same as the conventional current dimming method during the lighting period of the dimming pulse. Therefore, the main component configuration is the same as that of the current dimming method, and the number of components and the cost can be reduced. In addition, since the voltage is applied to the smoothing capacitor that is charged by the tube current even during the extinguishing period, the current supplied to the winding transformer does not increase or decrease rapidly. As a result, magnetostriction, resonance, and resonance generated in the winding transformer and the choke coil are reduced, and generation of roaring sound generated therefrom is reduced. Therefore, the user does not feel uncomfortable due to the roaring sound.
[0083]
Also, Claim 2 According to the described discharge lamp lighting device, since the current that does not lead to the lighting of the discharge lamp is applied to the winding transformer of the inverter circuit even during the period in which the discharge lamp is turned off, the discharge lamp is turned off. When the state is changed from the lighting state to the lighting state, there is no steep change in the energization current value of the winding transformer, so magnetostriction, resonance, and resonance generated in the winding transformer and choke coil due to the steep change in the energization current value. And the roaring sound generated from these is reduced. Furthermore, since the voltage output from the tube current value detection circuit does not change greatly when the discharge lamp changes from the off state to the on state, the ratio of the on / off period of the drive switching transistor changes rapidly. Therefore, the energization current to the winding transformer does not increase or decrease rapidly. As a result, magnetostriction, resonance, and resonance generated in the winding transformer and the choke coil are further reduced, and the roaring sound generated therefrom is further reduced. Therefore, the user does not feel uncomfortable due to the roaring sound.
[0084]
Also, Claim 3 According to the described discharge lamp lighting device, in addition to the above effects, Second Dead time voltage value is The discharge lamp is turned off and energization to the winding transformer is maintained. Since the voltage value is set, unnecessary power consumption is avoided.
[0085]
Also, Claim 4 According to the described discharge lamp lighting device, in addition to the above effect, when the voltage of the DC power supply is changed, the second dead time voltage value is set corresponding to the changed voltage. Even if the voltage is changed, it can be used in a state having the same function without making a significant change.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a conventional discharge lamp lighting device.
FIG. 2 is a block diagram showing a conventional discharge lamp lighting device using a current dimming method.
FIG. 3 is a block diagram showing a conventional discharge lamp lighting device using a burst dimming method.
FIG. 4 is a diagram for explaining problems in a conventional example
FIG. 5 is a configuration diagram showing a discharge lamp lighting device according to the first embodiment of the present invention.
FIG. 6 is a signal waveform diagram for explaining the operation of the discharge lamp lighting device according to the first embodiment of the present invention.
FIG. 7 is a configuration diagram showing a discharge lamp lighting device according to a second embodiment of the present invention.
FIG. 8 is a configuration diagram showing a discharge lamp lighting device according to a third embodiment of the present invention.
FIG. 9 is a configuration diagram showing a discharge lamp lighting device according to a fourth embodiment of the present invention.
[Explanation of symbols]
11, 21, 31 ... DC power supply, 12, 22, 32, 32 ', 32 "... DC-DC converter circuit, 13, 23,33 ... self-excited inverter circuit, 14 ... current detection circuit, 15, 25 ... cold Cathode fluorescent tube (discharge lamp), 24 ... burst signal oscillation circuit, 34 ... cold cathode fluorescent tube (discharge lamp), 35, 35 '... detection / feedback circuit, 321 ... error amplifier, 322 ... dead time adjustment voltage generation circuit, 323 ... Comparator, 324 ... Triangle wave generation circuit, 325 ... Switching transistor for drive, 326 ... Diode, 327 ... Choke coil, 328 ... Capacitor, 331 ... Wound transformer, 332 ... Choke coil, 333,334 ... Switching transistor, 335 ... Resistance 336,337 ... capacitor, R1, R2, R2 ', R3, R3' ... resistor, D1 ... diode, C1 ... smoothing capacitor, 41 ... dimming pulse generator circuit, 42, 43 ... Switching transistor, 44 ... resistor, VR ... variable resistor, 51 ... zener diode, 52 ... resistor, 61 ... peak hold circuit, 62 ... comparator, 63 ... electronic switch, 64 ... resistor.

Claims (4)

An inverter circuit having a winding transformer and a switching transistor and a tube current flowing through a discharge lamp to be lit are rectified to charge a smoothing capacitor, and a voltage corresponding to the tube current value is output based on the charging voltage of the smoothing capacitor A tube current value detecting circuit that outputs a difference voltage between the voltage output from the tube current value detecting circuit and the first reference voltage as an error voltage, and a series connection between the inverter circuit and the DC power source. A switching transistor for driving that is switched on and off based on a control signal and supplies power to the inverter circuit; means for generating a dead time adjustment voltage having a dead time voltage value; means for generating a triangular wave voltage; When the triangular wave voltage is higher than the dead time adjustment voltage and the error voltage, the drive switch Pulse width modulation means for outputting the control signal for turning on the transistor, and adjusting the dead time voltage value to change the ratio of the on / off period of the drive switching transistor to change the lighting state and extinguishing state of the discharge lamp. In the discharge lamp lighting method that adjusts the brightness by burst dimming method that switches alternately,
During the period in which the discharge lamp is turned off, a current that does not lead to the lighting of the discharge lamp according to the adjusted dead time voltage value is supplied to the winding transformer,
A discharge lamp lighting method, wherein a voltage having a voltage value equal to or higher than a voltage value of the smoothing capacitor when the luminance of the discharge lamp is set to a maximum is applied to the smoothing capacitor. An inverter circuit having a winding transformer and a switching transistor and a tube current flowing through a discharge lamp to be lit are rectified to charge a smoothing capacitor, and a voltage corresponding to the tube current value is output based on the charging voltage of the smoothing capacitor A tube current value detecting circuit that outputs a difference voltage between the voltage output from the tube current value detecting circuit and the first reference voltage as an error voltage, and a series connection between the inverter circuit and the DC power source. A switching transistor for driving which is switched on and off based on a control signal and supplies power to the inverter circuit, means for generating a dead time adjustment voltage having a first dead time voltage value, and means for generating a triangular wave voltage And the drive switch when the triangular wave voltage is higher than the dead time adjustment voltage and the error voltage. In the discharge lamp lighting device that includes a pulse width modulation means for outputting said control signal for turning on the quenching transistor,
A dimming pulse generating means for generating a dimming pulse signal for adjusting the luminance of the discharge lamp corresponding to the pulse width;
The dead time adjustment voltage is set to a first dead time voltage value when the dimming pulse is at one level, and the first dead time adjustment voltage is set with respect to the dead time adjustment voltage when the dimming pulse is at the other level. Means for mixing a voltage having a second dead time voltage value that is higher than the dead time voltage value and lower than the maximum value of the triangular wave voltage;
A voltage having a voltage value equal to or higher than the voltage value of the smoothing capacitor when the brightness of the discharge lamp is set to a maximum by changing a pulse width of the dimming pulse, and the smoothing capacitor when the dimming pulse is at the other level. A discharge lamp lighting device, characterized in that a voltage applying means for applying to is provided. The discharge lamp lighting device according to claim 2, wherein the second dead time voltage value is set to a voltage value at which the discharge lamp is extinguished and the energization to the winding transformer is maintained . The discharge lamp lighting device according to claim 2, further comprising means for detecting a maximum value of the voltage input to the inverter circuit and determining the second dead time voltage value from the maximum value voltage.

Images