JP2007134238A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably light a discharge lamp by suppressing going out of the discharge lamp due to the stoppage of arc discharge which is generated in many cases when the polarity of a current flowing in the discharge lamp is reversed. <P>SOLUTION: In on-off control of switching elements 14, 15 to generate a flyback voltage impressed on the discharge lamp 18 in secondary windings S1, S2 connected in series by switching the primary windings P1, P2 of transformers 12, 13, a control means 20 detects the discharge lamp current of the discharge lamp 18 by a current detecting resistance 20a, and controls the switching elements 14, 15 so as to set them from on to off by switching control signals Sa, Sb, timely when the polarity of the discharge current is reversed and the current becomes zero or almost zero. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, a secondary output voltage obtained by connecting the secondary outputs of two transformers generating flyback voltages in series is applied to a discharge lamp via a coil such as an igniter transformer and a resonant element such as a capacitor. The present invention relates to a discharge lamp lighting device for lighting a discharge lamp.

Examples of conventional discharge lamp lighting devices include the following.
In Conventional Example 1, in order to light a cold cathode discharge tube at a high frequency, a diode that prevents backflow is arranged at the power input terminal of one push-pull DC / AC converter transformer, and the fly when the switching element is turned off is arranged. A voltage sufficient for lighting the cold cathode discharge tube is obtained by applying the boosted flyback voltage generated in the secondary winding of the transformer to the cold cathode discharge tube without returning the back current to the power source. The discharge tube is turned on (see, for example, Patent Document 1).

  Further, in the conventional example 2, in order to light a discharge lamp, a transformer that generates a flyback voltage is connected to the discharge lamp, and the electrodes of the discharge lamp are broken down by the flyback voltage (for example, Patent Document 2). reference).

  In addition to the above, there are the following Patent Documents 3 to 9 as conventional techniques related to lighting of the discharge lamp.

JP 2000-133484 A JP 2005-50701 A JP-A-10-162974 Japanese Patent Laid-Open No. 10-321393 JP 2000-340383 A Japanese Patent Laid-Open No. 2002-117995 Japanese Patent Laid-Open No. 2003-1000047 JP 2003-264095 A JP-A-2005-004972

Since the conventional discharge lamp lighting device is configured as described above, in the discharge lamp using light emission by arc discharge, the stress applied to the glass bulb is alleviated by making the temperature of the arc / electrode uniform and the emission bright spot. In many cases, alternating current lighting is performed by alternately switching the polarity of the current so that the electrodes are consumed evenly.
For example, as in a discharge lamp lighting device for a high-intensity discharge lamp (HID lamp), when lighting is started, first, between the electrodes of the discharge lamp, a high voltage pulse of an igniter is used to cause dielectric breakdown, and then an electric current is applied. In a discharge lamp lighting device that emits light by arc discharge after forming a discharge, an inductance (L) component of an igniter that is a pulse transformer for generating a high voltage, and a capacitor that cancels this inductance (L) component and improves the power factor (C) A current including a specific frequency accompanied by a resonance operation flows to the discharge lamp, and the off timing of the switching element that flows the current to the transformer (flyback transformer) reverses the polarity of the current flowing to the discharge lamp. When the polarity of the current flowing through the discharge lamp is reversed, the energizing current is not necessarily the same as the point where the current becomes zero. Interrupted is over arc discharge, which can lead to extinction.

On the other hand, Conventional Example 1 is a technique for lighting a cold cathode discharge tube with a small lighting power, and does not consider the phase of the current flowing through the discharge lamp and the operation timing of the switching element, and the arc discharge is interrupted. The proper voltage application timing necessary for preventing the lamp from disappearing and stably lighting the discharge lamp is not devised.
In the conventional example 2, the dielectric breakdown between the electrodes of the discharge lamp is caused by the flyback voltage. However, the dielectric breakdown voltage of many high-intensity discharge lamps (HID lamps) is high, and the breakdown is caused only by the flyback voltage of the transformer. In such a case, it is essential to connect an igniter that generates a high voltage between the transformer and the discharge lamp. In this case, as described above, arc discharge occurs when the polarity of the current flowing through the discharge lamp is reversed. However, since the conventional example 2 has a configuration in which the igniter is not required, the conventional example 2 is necessary for preventing the above-described disappearance when the igniter is connected and lighting the discharge lamp stably. Appropriate voltage application timing is not devised.

  The present invention has been made to solve the above-described problems, and suppresses the extinction of the discharge lamp due to the arc discharge being interrupted when the polarity of the current flowing in the discharge lamp is reversed, or even when the arc discharge is interrupted. An object of the present invention is to obtain a discharge lamp lighting device that is immediately broken down again to continue arc discharge so that the discharge lamp can be lit stably.

  In the discharge lamp lighting device according to the present invention, one end of the primary winding is connected in series with the primary windings of two transformers connected to the DC power supply, and the power supply from the DC power supply is independently turned on and off. And an igniter for generating a high voltage pulse connected in series with the secondary windings of the two transformers, and the output of the secondary winding through a capacitor connected to the igniter. A voltage is applied to the discharge lamp, the polarity of the current flowing in the discharge lamp is reversed, and one of the two switching elements is controlled from on to off at a timing from negative to positive, and the other at a timing from positive to negative. Control means for controlling the switching element from on to off is provided.

  According to the present invention, the polarity of the current flowing through the discharge lamp is reversed, and one of the two switching elements is controlled from on to off at a timing from negative to positive, and the other switching is performed at a timing from positive to negative. Since the control means for controlling the element from on to off is provided, a high flyback voltage is generated on the secondary winding side of the transformer, and this high flyback voltage is zero in the discharge lamp current (the discharge lamp current is It is applied to the discharge lamp at the timing of going from negative to positive and from positive to negative), so it is possible to suppress the possibility that the arc discharge stops and the discharge lamp goes out, or when the discharge lamp goes out. In addition, it is possible to break down between the electrodes of the discharge lamp again and continue the arc discharge, and the discharge lamp can be lit stably.

An embodiment of the present invention will be described below.
Embodiment 1 FIG.
FIG. 1 is a configuration diagram for explaining the principle of a discharge lamp lighting device according to Embodiment 1 of the present invention.
In FIG. 1, the negative potential side of the DC power source 1 is connected to the source (S) of a switching element (FET (electrolytic effect transistor)) 2, and the drain (D) of the switching element 2 is the primary winding Po of the transformer 3. Connect to. The switching element 2 and the primary winding Po of the transformer 3 form a series connection. The other side of the primary winding Po of the transformer 3 is connected to the positive potential side of the DC power supply 1.

A switching control signal Sw having a required frequency for turning on / off the conduction between the drain (D) and the source (S) of the switching element 2 is input to the gate (G) of the switching element 2.
One end of the igniter 4 is connected to one end side of the secondary winding So of the transformer 3, and one end of the capacitor 5 is connected to the other end side. A discharge lamp 6 such as a high-intensity discharge lamp (HID bulb) is connected between the other end of the igniter 4 and the other end of the capacitor 5.

In the above configuration, the switching element 2 is turned on / off according to the switching control signal Sw having a required frequency input to the gate (G), and the voltage supply from the DC power source 1 to the primary winding Po of the transformer 3 is turned on / off.
The transformer 3 accumulates power energy from the DC power source 1 when the switching element 2 is in an on state, and when the switching element 2 transits from an on state to an off state, the transformer 3 applies a flyback voltage based on the accumulated power energy. 3 is generated at both ends of the secondary winding So.
The igniter 4 generates a high voltage pulse, and the high voltage pulse breaks down (dielectric breakdown) between the electrodes of the discharge lamp 6 to start the discharge lamp 6. The igniter 4 has an inductance (L) component.
The capacitor 5 cancels the inductance (L) component of the igniter 4 and improves the power factor with respect to the discharge lamp 6. However, the resonance circuit is composed of the inductance (L) component of the igniter 4 and the capacitance (C) component of the capacitor 5. Formed and there will be a resonant frequency. Due to the presence of this resonance frequency, the phase of the on / off switching timing by the switching element 2 on the primary winding Po side of the transformer 3 and the phase of the current flowing through the discharge lamp 6 do not coincide (described later).

Next, the operation of FIG. 1 will be described with reference to FIG.
FIG. 2 is a timing chart for explaining the principle of the discharge lamp lighting device according to Embodiment 1 of the present invention. FIG. 2 (a) is a switching timing chart of the switching element 2 by the switching control signal Sw, and FIG. ) Is a waveform diagram of a discharge lamp current flowing through the discharge lamp 6.
When the switching element 2 is turned on (OFF) at the switching timing as shown in FIG. 2A by the switching control signal Sw input to the gate (G), the primary winding Po of the transformer 3 is turned on. On the other hand, the voltage supply from the DC power source 1 is turned on and off, and a flyback voltage is generated at both ends of the secondary winding So of the transformer 3.

  On the other hand, the igniter 4 connected in series with the secondary winding So of the transformer 3 generates a high voltage pulse, and this high voltage pulse is superimposed on the output voltage from the secondary winding So of the transformer 3, and this high voltage The pulse between the electrodes of the discharge lamp 6 is broken down to start the discharge lamp 6. After the discharge lamp 6 is started up, the output voltage from the secondary winding So of the transformer 3 is applied to both electrodes of the discharge lamp 6 through the igniter 4 and the capacitor 5 to shift to steady lighting. A discharge lamp current having a waveform shown in 2 (b) flows. The discharge lamp current at the time of steady lighting shown in FIG. 2B is a current including a specific frequency accompanied by a resonance operation by the inductance (L) component of the igniter 4 and the capacitance (C) component of the capacitor 5. . Due to this resonance operation, the polarity of the current is reversed and the current of the discharge lamp 6 becomes zero. For example, the phase of each point such as the timings Tra, Trb, Trc and the like is the inductance (L) component of the igniter 4 and the capacitance (C ) Phase according to the resonance frequency determined by the component. Further, as shown at each timing point of Trb and Trc at which the current of the discharge lamp 6 becomes zero in FIG. 2B, between the ON timing or OFF timing of the switching element 2 in FIG. 2A and the timing Trb and Trc. Has a phase difference of θra or θrb, and the phase of each timing point of Trb and Trc is delayed with respect to the phase of the ON timing or the OFF timing of the switching element 2.

As described above, the phase of the switching timing of the switching element 2 in FIG. 2A and the phase in which the current of the discharge lamp 6 in FIG. Become. Due to this phase mismatch, when the polarity of the current flowing through the discharge lamp 6 is reversed even immediately after the high voltage pulse generated in the igniter 4 breaks down between the electrodes of the discharge lamp 6 and the arc discharge is reached. There is a negative effect that the arc discharge may be interrupted and may disappear. The reason for this disappearance is as follows.
As described above, the transformer 3 stores the power energy from the DC power source 1 when the switching element 2 is in the on state, and the flyback based on the stored power energy when the switching element 2 transitions from the on state to the off state. A voltage is generated across the secondary winding S of the transformer 3. In this case, since the power energy is fixed, the flyback voltage generated when the switching element 2 transitions from the on state to the off state is related to the discharge lamp current flowing on the secondary winding So side of the transformer 3. In contrast, when the discharge lamp current is not flowing, the flyback voltage becomes the highest, and the flyback voltage generated as the discharge lamp current increases becomes lower.

Therefore, as shown in FIGS. 2 (a) and 2 (b), the flyback voltage generated is low when the discharge lamp current is flowing when the switching element 2 transitions from the on state to the off state.
Further, at the timing (Tra or the like) at which the polarity of the current of the discharge lamp 6 shown in FIG. 2B is reversed, the arc discharge may be interrupted and disappear as described above. In such a case, it is necessary to apply a high flyback voltage to the discharge lamp 6 quickly, break down the electrodes of the discharge lamp 6 again, and continue the arc discharge. However, since the timing of Tra and the like at which the polarity of the current of the discharge lamp 6 is reversed is out of the timing at which the switching element 2 transitions from the on state to the off state, the flybacks at both ends of the secondary winding S of the transformer 3 are performed. When the voltage is low and the arc discharge stops and goes out, it becomes difficult to break down the electrodes of the discharge lamp 6 again.

From the above, if the phase of the timing at which the switching element 2 switches from the on state to the off state is matched with the phase at which the current of the discharge lamp 6 becomes zero, it is highest at both ends of the secondary winding So of the transformer 3. A flyback voltage is generated, and this high flyback voltage is applied at the timing when the current of the discharge lamp 6 becomes zero, so that it is possible to suppress the possibility that the arc discharge stops and goes out.
Further, as described above, even when the phase at which the current of the discharge lamp 6 becomes zero and the phase of the timing at which the switching element 2 switches from the on state to the off state do not completely match, the current of the discharge lamp 6 is zero. Even when a high flyback voltage is generated in the secondary winding So of the transformer 3 immediately after passing the point, the arc discharge stops and even when the discharge lamp 6 is extinguished again, Breaking down between the electrodes, it is possible to continue the arc discharge.

Next, the basic configuration of the present invention will be described with reference to FIG.
FIG. 3 is a basic configuration diagram of the discharge lamp lighting device according to Embodiment 1 of the present invention.
In the configuration shown in FIG. 3, as described above, two transformers 12 (T1) and 13 (T2) are provided as transformers for generating a flyback voltage, and switching elements ( FET) 14 and switching element (FET) 15 are provided. The control unit 19 performs switching control of the switching element 14 and the switching element 15.
The basic functions (operations) of the transformer 12, the transformer 13, the switching element 14, and the switching element 15 are the same as those of the transformer 3 and the switching element 2 in FIG.

Further, other DC power source 11, igniter 16, capacitor (C) 17 and discharge lamp 18 in FIG. 3 are the same as DC power source 1, igniter 4, capacitor (C) 5 and discharge lamp 6 in FIG. These individual descriptions are omitted.
In FIG. 3, the transformer that generates the flyback voltage is composed of the transformer 12 and the transformer 13, so that the flyback voltage generated on the transformer secondary winding side is symmetrical between the high-side voltage and the low-side voltage. The AC voltage can be reduced.
In FIG. 3, “·” marks attached to the winding portions of the transformer 12 and the transformer 13 indicate the winding start side of each winding.
The primary winding P1 of the transformer 12 and the primary winding P2 of the transformer 13 are connected in parallel to the DC power supply 11 and are operated independently of each other. The positive potential side of the DC power source 11 is connected to the winding start side of the primary windings P1 and P2. The winding end side of the primary winding P1 is connected to the drain (D) of the switching element 14, and the winding end side of the primary winding P2 is connected to the drain (D) of the switching element 15.

The sources (S) of the switching elements 14 and 15 are connected to the negative potential side of the DC power supply 11, and the gates (G) are connected to the control means 19. The switching control signals Sa and Sb from the control means 19 are input.
Further, the secondary winding S1 of the transformer 12 and the secondary winding S2 of the transformer 13 are connected in series with the winding directions of these two windings being symmetrical. That is, the winding end side of the secondary winding S1 and the winding end side of the secondary winding S2 are connected to form a series connection. By this series connection, the polarities of the voltages generated in the secondary windings S1 and S2 of the transformers 12 and 13 become symmetrical, and the winding start side end of the secondary winding S1 and the winding start side end of the secondary winding S2 The flyback voltage generated between the high side voltage and the low side voltage is an alternating voltage that is symmetric. As a result, the secondary winding S1 and the secondary winding S2 connected in series generate a flyback voltage for alternating-current lighting of the discharge lamp 18, and the stress applied to the glass bulb of the discharge lamp 18 is alleviated. It is possible to obtain advantages such as even consumption.

The winding start side of the secondary winding S1 of the transformer 12 is connected to one end of the capacitor 17, and the winding start side of the secondary winding S2 of the transformer 13 is connected to one end of the igniter 16. The point that the discharge lamp 18 is connected between the other end of the igniter 16 and the other end of the capacitor 17 is the same as in FIG.
The control means 19 generates switching control signals Sa and Sb, and performs switching control via the gates (G) of the switching elements 14 and 15 based on the signals Sa and Sb. The switching control signal Sa and the switching control signal Sb have a phase relationship for alternately turning on and off the switching elements 14 and 15.
Further, the control means 19 detects the current of the discharge lamp 18 flowing on the secondary windings S1, S2 side of the transformers 12, 13, and detects the phase of the timing when the polarity of the current is reversed and the current becomes zero. A current phase detection circuit 19a is provided.

Next, the operation of FIG. 3 will be described with reference to FIG.
FIG. 4 is a timing diagram for explaining the basic configuration of the discharge lamp lighting device according to Embodiment 1 of the present invention. FIG. 4 (a) is a switching timing diagram of the switching element 14 by the switching control signal Sa, and FIG. 4 (b). Is a switching timing diagram of the switching element 15 by the switching control signal Sb, and FIG. 4C is a waveform diagram of a discharge lamp current flowing through the discharge lamp.
The operation of turning on and off the voltage supply from the DC power supply 11 by switching of the switching element 14 to generate a flyback voltage at both ends of the secondary winding S1 of the transformer 12 and the voltage from the DC power supply 11 by switching of the switching element 15 Each operation of turning on and off the supply and generating a flyback voltage at both ends of the secondary winding S2 of the transformer 13 is the same as the operation by the switching element 2 and the transformer 3 described in FIG.

The switching of the switching element 14 and the switching of the switching element 15 are performed by switching control signals Sa and Sb generated by the control means 19 and sent to the gates (G) of the switching elements 14 and 15, respectively. The switching control signal Sa and the switching control signal Sb have a phase relationship in which the switching elements 14 and 15 are alternately turned on (OFF) or turned off (OFF) as shown in FIGS. 4 (a) and 4 (b). Yes.
Due to this phase relationship, flyback voltages are alternately generated in the secondary winding S1 of the transformer 12 and the secondary winding S2 of the transformer 13 when each of the switching elements 14 and 15 transitions from the on state to the off state. To do. Further, as described above, since the secondary windings S1 and S2 are connected in series so that the polarities of the voltages generated in the secondary windings S1 and S2 of the transformers 12 and 13 are symmetric with respect to positive and negative, this series The flyback voltage generated between the winding start end of the connected secondary winding S1 and the winding start end of the secondary winding S2 is an AC voltage in which the high side voltage and the low side voltage are symmetric.

On the other hand, the igniter 16 connected in series with the secondary winding S2 of the transformer 13 generates a high voltage pulse, and this high voltage pulse is superimposed on the output voltage from the secondary windings S1 and S2 connected in series, The high voltage pulse breaks down the electrodes of the discharge lamp 18 to start the discharge lamp 18. After the discharge lamp 18 is started, the output voltage from the secondary windings S1 and S2 connected in series is applied to both electrodes of the discharge lamp 18 via the igniter 16 and the capacitor 17 to shift to steady lighting. The discharge lamp current having the waveform shown in FIG. The discharge lamp current at the time of steady lighting shown in FIG. 4C is specified with resonance operation by the inductance (L) component of the igniter 16 and the capacitance (C) component of the capacitor 17 as in the description of FIG. The current includes the frequency of.
The control means 19 detects the discharge lamp current shown in FIG. 4C by the built-in current phase detection circuit 19a, and the polarity of the discharge lamp current is reversed from positive to negative or from negative to positive, and the current becomes zero. Is detected.

As shown in FIGS. 4A to 4C, the control means 19 alternately switches the switching element 14 and the switching element 15 in accordance with the timing when the detected discharge lamp current is inverted in polarity and the current becomes zero. Set from on to off. Alternatively, the control unit 19 alternately sets the switching element 14 and the switching element 15 from on to off in accordance with the timing immediately after the point at which the discharge lamp current becomes zero.
As a result, the phase at which the current of the discharge lamp 18 becomes zero coincides with the phase of the timing at which the switching elements 14 and 15 are switched from the on state to the off state, and the secondary windings S1 and S1 of the transformers 12 and 13 are matched. The highest flyback voltage is generated in S2, and this high flyback voltage is applied at the timing when the current of the discharge lamp 18 becomes zero, so that the possibility that the arc discharge stops and disappears is suppressed.

The current of the discharge lamp 18 also becomes zero when the phase at which the current of the discharge lamp 18 becomes zero and the phase of the timing at which the switching elements 14 and 15 each switch from the on state to the off state do not completely match. Immediately after passing the point, a high flyback voltage is generated and applied to each of the secondary windings S1, S2 of the transformers 12, 13, so that even when the arc discharge is interrupted and goes out, the discharge lamp 18 again. Breaking down between the electrodes, arc discharge is continued.
In general, the breakdown voltage that restores the arc discharge once stopped increases with the passage of time, so it is better to apply the voltage within the shortest possible time immediately after the arc discharge stops. And the current supply to the discharge lamp 18 can be resumed, so that a high flyback voltage is generated and applied to the discharge lamp 18 immediately after the point where the current of the discharge lamp 18 becomes zero as described above. Therefore, preferable arc discharge can be continued.

Next, a specific configuration example based on the basic configuration of FIG. 3 will be described with reference to FIG.
FIG. 5 is a block diagram of a discharge lamp lighting device according to Embodiment 1 of the present invention. In addition, the same code | symbol is attached | subjected about the same thing as FIG.
The configuration shown in FIG. 5 embodies the configuration of the control means 19 of FIG. Other structural elements other than the control means 20 are the same as those in FIG. 3, and individual descriptions of those given the same reference numerals as those in FIG. 3 are omitted.
The control means 20 includes a current detection resistor 20a, a buffer circuit 20b, an inverting circuit 20c, a control circuit 20d, and a control circuit 20e.
In the configuration of the control means 20, the current detection resistor 20a is connected between the winding start end of the secondary winding S2 of the transformer 13 and the ground, and the current flowing through the discharge lamp 18 during steady lighting is a voltage at the current detection resistor 20a. Detect as a descent.

The buffer circuit 20b amplifies a voltage signal corresponding to the current of the discharge lamp 18 detected by the current detection resistor 20a, and outputs it as a rectangular wave signal.
The inverting circuit 20c outputs a rectangular wave signal obtained by inverting the phase of the output of the buffer circuit 20b.
The control circuit 20d generates a switching control signal Sa for the switching element 14 based on the rectangular wave signal from the inverting circuit 20c. The switching control signal Sa is a signal in which the on-duty factor of switching is made variable. For this reason, the control circuit 20d includes a monostable multivibrator (not shown) capable of variably setting the pulse width.
The control circuit 20e generates a switching control signal Sb for the switching element 15 based on the rectangular wave signal from the buffer circuit 20b. The switching control signal Sb is also a signal in which the switching on-duty factor is made variable in the same manner as the switching control signal Sa. For this reason, the control circuit 20e is also provided with a monostable multivibrator (not shown) capable of variably setting the pulse width.

Next, the operation of FIG. 5 will be described focusing on the operation of the control means 20. A description of the same operations as those in FIG. 3 except for the operation of the control means 20 will be omitted.
The current flowing through the discharge lamp 18 after the discharge lamp 18 breaks down and shifts to steady lighting is detected as a voltage drop across the current detection resistor 20a, and a voltage signal corresponding to this discharge lamp current is input to the buffer circuit 20b. To do. This voltage signal corresponds to the discharge lamp current affected by the resonance frequency due to the inductance (L) component of the igniter 16 and the capacitance (C) component of the capacitor 17.
The voltage signal is amplified in the buffer circuit 20b, shaped into a rectangular wave signal, branched and sent to the inverting circuit 20c and the control circuit 20e.
The inverting circuit 20c inverts the phase of the rectangular wave signal from the buffer circuit 20b and sends the phase-inverted rectangular wave signal to the control circuit 20d.

This control circuit 20d detects, as one function, the rising or falling of the rectangular wave signal sent from the inverting circuit 20c as the timing when the polarity of the current flowing through the discharge lamp 18 is reversed and the current becomes zero. Here, the rising or falling portion of the rectangular wave signal has a time of rising or falling which is not zero but takes a little time. Therefore, the current corresponds to zero at the rising or falling detection timing.
The control circuit 20d sets the switching element 14 from on to off in accordance with the timing when the detected current becomes zero. Alternatively, the control circuit 20d sets the switching element 14 from on to off in accordance with the timing when the discharge lamp current becomes zero immediately after the point at which the discharge lamp current becomes zero.

Further, as another function, the control circuit 20d sets an on-duty factor that represents the on-period of the switching control signal Sa. By setting this on-duty factor, the lighting power of the discharge lamp 18 can be subjected to pulse width control (PWM control), and this lighting power can be set to an appropriate power.
The on-duty factor is set by a built-in monostable multivibrator according to a PWM control signal (not shown).
As described above, the control circuit 20d sets the switching element 14 from ON to OFF in accordance with the timing when the current of the discharge lamp 18 becomes zero, while setting an ON duty factor indicating the ON period of the switching element 14. The switched control signal Sa is output.

The control circuit 20e also operates in the same manner as the control circuit 20d based on the rectangular wave signal sent from the buffer circuit 20b, and switches the switching element 15 from on to off at the timing when the current of the discharge lamp 18 becomes zero. On the other hand, the switching control signal Sb in which the on-duty factor representing the on period of the switching element 15 is set is output.
Further, as described above, since the phase of the rectangular wave signal input to the control circuit 20d is inverted with respect to the phase of the rectangular wave signal input to the control circuit 20e, the switching control signal Sa output from the control circuit 20d; The switching control signal Sb output from the control circuit 20e is a signal having an alternating relationship of on / off timing.

Next, details of the control means 20 of FIG. 5 will be described with reference to FIG.
FIG. 6 is a detailed block diagram of the control means 20 of the discharge lamp lighting device according to Embodiment 1 of the present invention.
In addition, the same code | symbol is attached | subjected about the same thing as FIG. 5, and duplication description is abbreviate | omitted.
In FIG. 6, the current detection resistor 20a, the capacitor 201, the resistor 202, the inverting circuit 203, the inverting circuit 204, the capacitor 205, the inverting circuit 206, and the resistor 207 form a current phase detecting circuit 20f. Two coupling capacitors 208 and 209 are provided at the output terminal of the current phase detection circuit 20f.
The control circuit 20d includes a monostable multivibrator formed of a transistor 210, a resistor 212, a capacitor 214, and a comparator (comparator) 216. The control circuit 20e includes a transistor 211, a resistor 213, a capacitor 215, and a comparator (comparator). 217 and a monostable multivibrator formed by the
A positive feedback loop is formed by the control means 20 having the above configuration, the switching elements 14 and 15 and the transformers 12 and 13 (primary windings P1 and P2, secondary windings S1 and S2) of FIG. An astable multivibrator that oscillates is formed. The current phase detection circuit 20f corresponds to the input amplifier of the astable multivibrator.

Next, the operation of FIG. 6 will be described with reference to FIG.
FIG. 7 is a diagram for explaining the operation of the control means 20 in the discharge lamp lighting device according to Embodiment 1 of the present invention. FIG. 7 (a) shows a voltage corresponding to the current of the discharge lamp 18 generated at both ends of the current detection resistor 20a. FIG. 7B is a waveform diagram of the voltage signal Sc1 of the collector (C) of the transistor 210, and FIG. 7C is a switching control that is the output of the comparator 216 and the output of the control circuit 20d. FIG. 7D is a waveform diagram of the voltage signal Sc2 of the collector (C) of the transistor 211. FIG. 7E is a switching control that is the output of the comparator 217 and the output of the control circuit 20e. It is a wave form diagram of signal Sb.
A voltage signal Sr shown in FIG. 7A corresponding to the discharge lamp current after the discharge lamp 18 has shifted to steady lighting is generated at both ends of the current detection resistor 20a forming the current phase detection circuit 20f, and this voltage signal Sr. Is input to the inverting circuit 203 through the capacitor 201. A circuit formed by the inverting circuits 203 and 204, the resistor 202, the capacitor 205, and the like after the capacitor 201 amplifies the voltage signal Sr and shapes the waveform into a rectangular wave signal. The rectangular wave signal output from the inverting circuit 204 is sent to the inverting circuit 206, and is sent to the base (B) of the transistor 210 forming the control circuit 20d via the coupling capacitor 208.

The inverting circuit 206 inverts the phase of the rectangular wave signal from the inverting circuit 204 and sends the phase-inverted rectangular wave signal to the base (B) of the transistor 211 forming the control circuit 20e via the coupling capacitor 209.
A voltage is applied from the DC power supply Vcc to the collector (C) of the transistor 210 forming the control circuit 20d and forming the monostable multivibrator through the resistor 212, and the rectangular wave signal input to the base (B) The collector (C) and the grounded emitter (E) are turned on / off. A charging / discharging capacitor 214 is provided between the collector (C) of the transistor 210 and the ground, and the capacitor 214 is charged through the resistor 212.
The voltage charged in the capacitor 214 is discharged from the collector (C) of the transistor 210 through the emitter (E) when it is turned on by the rectangular wave signal at the base (B) of the transistor 210. By charging and discharging the capacitor 214, a triangular wave voltage signal Sc1 shown in FIG. 7B is generated at the collector (C) of the transistor 210.

The phase relationship between the generated triangular wave voltage signal Sc1 shown in FIG. 7B and the voltage signal Sr corresponding to the discharge lamp current shown in FIG. 7A is as shown in FIG. The phase relationship is such that the voltage zero point at which the polarity switches to positive coincides with the point at which the triangular wave of the voltage signal Sc1 returns from the positive peak to the negative peak.
The generated triangular wave voltage signal Sc1 is input to the positive phase input terminal (+) of the comparator 216. A pulse width control (PWM) signal Sp representing a direct current level (voltage) is input and set to the negative phase input terminal (−) of the comparator 216. As a result, the relationship between the voltage signal Sc1 at the positive phase input terminal (+) and the pulse width control signal Sp at the negative phase input terminal (−) in the comparator 216 becomes as shown in FIG. The signal Sc1 is a signal that changes to the positive side and the negative side with the pulse width control signal Sp representing the DC level as a boundary.

As described above, the voltage signal Sc1 is input to the positive phase input terminal (+), and the pulse width control signal Sp representing the DC level is set to the negative phase input terminal (−). The switching control signal Sa having the rectangular wave shown in c) is output. The switching element 14 is turned off in the period Tf of the switching control signal Sa shown in FIG. 7C, and the switching element 14 is turned on in the period Tn. The timing of turning from on to off coincides with the point at which the voltage signal Sc1 shown in FIG. 7B returns from the positive peak to the negative peak, and the voltage signal Sr shown in FIG. 7A changes from negative to positive. It coincides with the zero voltage point at which the polarity switches. The voltage zero point of the voltage signal Sr is a point where the polarity of the current flowing through the discharge lamp 18 is reversed and the current becomes zero. As a result, the switching control signal Sa for setting the switching element 14 from on to off is output from the control circuit 20d to the switching element 14 at the timing when the discharge lamp current becomes zero.
Further, by changing (shifting) the level of the pulse width control signal Sp in the positive direction or the negative direction, the widths of the period Tf and the period Tn of the switching control signal Sa change, and the level of the pulse width control signal Sp is changed in the negative direction. As the shift is performed, the width of the period Tn during which the switching element 14 is turned on becomes wider, and the on-duty factor increases.

As described above, the on-duty factor of the switching control signal Sa is set by the pulse width control signal Sp, and the pulse width is controlled.
In the above description, the rising or falling portion of the rectangular wave signal representing the discharge lamp current obtained by shaping the waveform in the current phase detection circuit 20f formed by the inverting circuits 203, 204, etc., the voltage signal in FIG. The part of Sc1 returning from the positive peak to the negative peak, and the part where the switching control signal Sa of FIG. The required time is not zero, but it takes a little time. Therefore, there is a case where the switching element 14 is not necessarily set from on to off at the timing when the discharge lamp current becomes zero. In this case, the switching element 14 is set from on to off at a timing when the discharge lamp current is substantially zero.

  On the other hand, the control circuit 20e including the monostable multivibrator formed by the transistor 211, the resistor 213, the capacitor 215, and the comparator 217 has the same operation as the control circuit 20d having the same configuration except for the phase relationship. Therefore, in the following, this phase relationship will be described, and the description of the operation overlapping with that of the control circuit 20d will be omitted. The circuit elements of the transistor 211, resistor 213, capacitor 215, and comparator 217 of the control circuit 20e correspond to the circuit elements of the transistor 210, resistor 212, capacitor 214, and comparator 216 of the control circuit 20d, respectively. The basic operation of each circuit element is the same.

A rectangular wave signal corresponding to the discharge lamp current from the inverting circuit 206 is input to the base (B) of the transistor 211 forming the control circuit 20e and forming the monostable multivibrator through the capacitor 209. The phase of the rectangular wave signal is inverted with respect to the rectangular wave signal input to the base (B) of the transistor 210 of the control circuit 20d. Therefore, a triangular wave voltage signal Sc2 shown in FIG. 7D is generated at the collector (C) of the transistor 211.
The triangular wave voltage signal Sc2 shown in FIG. 7 (d) has a phase difference of 180 degrees with respect to the triangular wave voltage signal Sc1 shown in FIG. 7 (b). Therefore, the comparator 217 to which the triangular wave voltage signal Sc2 shown in FIG. 7D is inputted outputs the switching control signal Sb having the waveform shown in FIG. The phase of the switching control signal Sb has a phase difference of 180 degrees with respect to the switching control signal Sa shown in FIG.
As described above, the control circuit 20d and the control circuit 20e output the switching control signal Sa and the switching control signal Sb in which the switching elements 14 and 15 are alternately turned on and off.

Next, the state before and after breakdown of the discharge lamp 18 in the configuration of FIGS. 5 and 6 will be described with reference to FIG. In this description, FIGS. 5 and 6 are used together.
FIG. 8 is a timing diagram for explaining the state before and after breakdown of the discharge lamp 18 in the discharge lamp lighting device according to Embodiment 1 of the present invention, and FIG. 8 (a) is a waveform diagram of the discharge lamp current flowing through the discharge lamp 18. 8B is a waveform diagram of a current phase detection signal that has been shaped into a rectangular wave in the current phase detection circuit 20f (FIG. 6) formed by the inverting circuits 203, 204, etc., and FIG. FIG. 8D is a waveform diagram of the switching control signal Sb for the switching element 15, and FIG. 8E is a waveform diagram of the voltage applied to the discharge lamp 18. The waveform diagram of the current phase detection signal shown in FIG. 8B corresponds to FIG. 8D, and the waveform diagram of the current phase detection signal corresponding to FIG. 8C is omitted.
The description of FIG. 5 or FIG. 6 is for the steady lighting of the discharge lamp 18.
As described above, the discharge lamp 18 is activated by the breakdown between the electrodes of the discharge lamp 18 due to the high voltage pulse generated by the igniter 16 and then shifts to steady lighting.

In FIG. 8A, while no discharge lamp current flows through the discharge lamp 18 (Ta), no voltage is generated in the current detection resistor 20a (FIG. 6). The current phase detection circuit 20f does not output a current phase detection signal based on the detection of the current detection resistor 20a.
As described above, in the configuration of FIG. 5, the control means 20, the switching elements 14 and 15, and the transformers 12 and 13 form an astable multivibrator.
Therefore, during the period when the discharge lamp current is not flowing (Ta), the rectangular wave discharge lamp current phase detection signals (W1, W2, etc.) shown in FIG. 8B are generated by the self-oscillation by the astable multivibrator. Based on these generated signals, the control circuit 20d and the control circuit 20e are operated.
As a result, the switching control signal Sa shown in FIG. 8C is output from the control circuit 20d (W3 to W5, etc.), and the switching control signal S2 shown in FIG. 8D is output from the control circuit 20e ( W6-W8 etc.).

Further, during the period when the discharge lamp current is not flowing (Ta), as described above, the flyback voltage in the AC form generated on the secondary windings S1 and S2 side of the transformers 12 and 13 becomes a high voltage. As shown in (e), a high-voltage AC flyback voltage (e1, e2, e3, etc.) is applied to the discharge lamp 18.
Next, as shown in FIG. 8 (e), when a high voltage pulse (ei) is generated from the igniter 16 and this high voltage pulse (ei) is applied to the discharge lamp 18 to cause a breakdown, immediately after the breakdown, As shown in FIG. 8 (a), a current starts to flow through the discharge lamp 18 (i1), and after a transient period of several current interruptions (Tb, Tc, Td, etc.), steady lighting without current interruption is performed. Time current (i2).

When current begins to flow through the discharge lamp 18 in this way, current phase detection based on the current detection resistor 20a is activated, and the control circuit 20d and the control circuit 20e are activated based on this detection. Thereby, as shown in FIG. 8B, the current phase detection signal output from the current phase detection circuit 20f shifts from a signal based on self-oscillation to a signal synchronized with the discharge lamp current (W9 to W10, etc.) Accordingly, the switching control signal Sa output from the control circuit 20d and the switching control signal Sb output from the control circuit 20e also shift from a signal based on self-oscillation to a signal synchronized with the discharge lamp current (W11 to W14, etc.). As a result, the switching elements 14 and 15 are set from on to off at an appropriate timing of zero current at which the polarity of the discharge lamp current is reversed, and the extinction of the discharge lamp 18 is suppressed.
When the current starts to flow through the discharge lamp 18, the flyback voltage generated on the secondary windings S1, S2 side of the transformers 12, 13 decreases according to the discharge lamp current as described above. The applied voltage gradually decreases as shown in FIG. 8E (e4 to e7, etc.) and reaches the voltage (e8) during steady lighting. Here, a high flyback voltage is applied to the jumped portions of the voltages e5, e6, e7, etc. corresponding to the current interruption (Tb, Tc, Td, etc.) of the discharge lamp 18 shown in FIG. Indicates that This voltage application suppresses the extinction of the discharge lamp 18.

  As described above, according to the first embodiment, the primary windings P1 and P2 of the transformers 12 and 13 are switched, and the flyback voltage applied to the discharge lamp 18 to the secondary windings S1 and S2 connected in series. In the on / off control of the switching elements 14 and 15 that generate the power, the control means 20 sets the switching elements 14 and 15 from on to off at the timing when the polarity of the current flowing through the discharge lamp 18 is reversed and the current becomes zero. Since the on / off control is performed by the switching control signals Sa and Sb, a high flyback voltage is generated in the secondary windings S1 and S2 of the transformer, and this high flyback voltage causes the current of the discharge lamp 18 to be zero. Is applied to the discharge lamp 18, and the application of this voltage suppresses the possibility that the arc discharge is interrupted and the discharge lamp 18 is extinguished. Is effected even if the discharge lamp reaches the lighting failure even to breakdown between again discharge lamp electrodes, it is possible to continue the arc discharge, the discharge lamp can be stably lighted.

  Further, since the control means 20 is configured to include a current phase detection circuit that detects the current flowing through the discharge lamp 18 and detects the phase at which the polarity of the current is reversed and the current becomes zero, the discharge lamp 18 The switching control signals Sa and Sb can be generated in accordance with the phase of the current flowing through the switch, and the switching elements 14 and 15 are controlled to be turned on / off by the switching control signals Sa and Sb. The frequency is naturally determined by the influence of the resonance frequency due to the inductance (L) component of 16 and the capacitance (C) component of the capacitor 17, and the oscillation state can be maintained as a self-excited circuit as a circuit.

  Further, the control means 20 controls the lighting power of the discharge lamp 18 by the ON period of the switching elements 14 and 15, and the current flowing through the discharge lamp 18 at the timing when the ON period ends and the switching elements 14 and 15 are turned OFF. Since the polarity is reversed and the control is performed so as to synchronize with the timing when the current becomes zero, the lighting power of the discharge lamp 18 can be set to an appropriate power and the polarity of the current flowing through the discharge lamp 18 It is possible to maintain stable lighting in which arc discharge does not stop during reversal.

  The control means 20 in FIG. 6 forms an astable multivibrator in the configuration of FIG. 5 and oscillates at its own frequency when no current flows through the discharge lamp 18. , 15 can always be turned on and off, and even if a special sequence is not provided, the switching operation is performed even in the non-steady operation before the discharge lamp 18 is turned on, or the non-steady operation after the discharge lamp 18 is extinguished. can do.

It is a block diagram for demonstrating the principle of the discharge lamp lighting device by Embodiment 1 of this invention. It is a timing diagram for demonstrating the principle of the discharge lamp lighting device by Embodiment 1 of this invention, (a) is a switching timing diagram of the switching element by a switching signal, (b) is the discharge lamp electric current waveform which flows into a discharge lamp. FIG. 1 is a basic configuration diagram of a discharge lamp lighting device according to Embodiment 1 of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a timing diagram for basic composition explanation of the discharge lamp lighting device by Embodiment 1 of this invention, (a) and (b) are the switching timing diagrams of the switching element by a switching control signal, (c) flows into a discharge lamp. It is a discharge lamp electric current waveform diagram. It is a block diagram of the discharge lamp lighting device by Embodiment 1 of this invention. It is a detailed block diagram of the control means of the discharge lamp lighting device by Embodiment 1 of this invention. It is operation | movement explanatory drawing of the control means in the discharge lamp lighting device by Embodiment 1 of this invention, (a) is a waveform diagram of a voltage signal corresponding to the discharge lamp current generated at both ends of the current detection resistor, (b) and (D) is a waveform diagram of a voltage signal at the collector (C) of the transistor, and (c) and (e) are waveform diagrams of a switching control signal output by the control circuit. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a timing diagram for explaining states before and after a breakdown of a discharge lamp in a discharge lamp lighting device according to Embodiment 1 of the present invention, (a) is a waveform diagram of a discharge lamp current flowing through the discharge lamp, and (b) is a current phase. The waveform diagram of the current phase detection signal shaped into a rectangular wave in the detection circuit, (c) and (d) are the waveform diagrams of the switching control signal for the switching element, and (e) is the waveform diagram of the voltage applied to the discharge lamp. is there.

Explanation of symbols

  1,11 DC power supply, 2,14,15 switching element, 3,12,13 transformer, 4,16 igniter, 5,17 capacitor, 6,18 discharge lamp, 19,20 control means, 19a, 20f current phase detection circuit 20a current detection resistor, 20b buffer circuit, 20c inversion circuit, 20d, 20e control circuit, 201, 205, 208, 209, 214, 215 capacitor, 202, 207, 212, 213 resistance, 203, 204, 206 inversion circuit, 210, 211 Transistor, 216, 217 Comparator.

Claims (3)

Two transformers with one end of the primary winding connected to a DC power source;
Two switching elements that are respectively connected in series with the primary windings of the two transformers and that independently turn on and off the power supply from the DC power supply;
The secondary windings are connected in series so that the polarities of the output voltages output from the secondary windings of the two transformers are different from each other, and high voltage pulses connected in series with the secondary windings In a discharge lamp lighting device in which an output voltage of the secondary winding is applied to a discharge lamp via an igniter that is generated and a capacitor connected in series to the igniter,
The polarity of the current flowing through the discharge lamp is reversed, and one of the two switching elements is controlled from on to off at a timing from negative to positive, and the other switching element is switched from on to off at a timing from positive to negative. A discharge lamp lighting device comprising control means for controlling the discharge lamp.   2. The discharge unit according to claim 1, wherein the control means includes a current phase detection circuit that detects a current flowing through the discharge lamp and detects a phase at which the polarity of the current is reversed and the current becomes zero. Electric light lighting device. The control means controls the lighting power of the discharge lamp according to the ON period of the switching element, and the timing at which the ON period ends and the switching element is turned OFF is such that the polarity of the current flowing through the discharge lamp is reversed and the current is zero. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is controlled so as to be synchronized with the timing.

Images