JP4723343B2 - Discharge lamp lighting device - Google Patents

Description

  The present invention relates to a discharge lamp lighting device that performs output control of an inverter circuit section using a microcomputer.

  In the conventional method using an oscillation control IC (Integrated Circuit) using a CR time constant, the frequency can be set freely. In addition, as shown in Japanese Patent No. 2647495 (Patent Document 1), it is relatively easy to control the output current of the inverter circuit unit for those that do not use a microcomputer for inverter control.

  However, as the use of a microcomputer becomes indispensable for the multi-functionalization of the circuit and the simplification of the circuit, the output control of the inverter circuit section using the microcomputer is as follows. There is an inconvenience.

When the rectangular wave voltage is generated by the microcomputer and the oscillation frequency of the inverter circuit unit is controlled, the oscillation frequency f is the clock frequency used for the microcomputer fc, and an arbitrary integer n (n = 1, 2, 3 ...)
f = fc / n
Determined by For this reason, the frequency cannot be finely adjusted unless the clock frequency is very large (and therefore the output current cannot be finely adjusted).

  For example, when a 4 MHz clock is used and an oscillation frequency of about 80 kHz is desired, 78.4 kHz (n = 51), 80.0 kHz (n = 50), 81.6 kHz (n = 49) You can only choose from the inside. For this reason, each difference is about 1.6 kHz, and the change of the output current of an inverter circuit part will become very rough.

FIG. 5 shows a resonance curve of a load circuit unit (for example, equivalent to a load circuit unit 4 of FIG. 2 described later) of the discharge lamp lighting device. The horizontal axis is frequency and the vertical axis is output current. The frequency on the horizontal axis is the above formula f = fc / n
Corresponds to f.

  As shown in FIG. 5, usually, design may be performed at a steep portion of a resonance curve (resonance curve) like frequencies Fa, Fb, and Fc. In such a case, the output current at the frequencies Fa, Fb, and Fc changes greatly as Ia, Ib, and Ic.

A microcomputer has a limit in the clock frequency that can be used, and the larger the clock frequency, the higher the power consumption and the higher the cost. In addition, since the output current of the inverter circuit unit is controlled by varying the oscillation frequency, the coarser the change in the oscillation frequency, the coarser the change in the output current of the inverter circuit unit, and the fine adjustment of the output current cannot be performed. .
Japanese Patent No. 2647495

  An object of the present invention is to make it possible to finely adjust an output current of an inverter circuit unit in a discharge lamp lighting device that performs output control of an inverter circuit unit using a rectangular wave voltage output from a microcomputer.

The discharge lamp lighting device of the present invention,
In a discharge lamp lighting device for lighting a discharge lamp,
An inverter circuit which has a switching element, inputs a DC voltage, converts the input DC voltage into a high-frequency voltage by switching of the switching element, and outputs a current corresponding to the converted high-frequency voltage to the discharge lamp as an output current And
A rectangular wave voltage generator that generates and outputs a rectangular wave voltage having a predetermined duty ratio, and that can change the duty ratio of the generated rectangular wave voltage; and
By inputting the rectangular wave voltage of the predetermined duty ratio output from the rectangular wave voltage generation unit, by switching the switching element of the inverter circuit unit based on the input rectangular wave voltage of the predetermined duty ratio, A drive circuit unit that outputs the output current to the inverter circuit unit;
The rectangular wave voltage generator is
The drive circuit unit controls the magnitude of the output current to be output to the inverter circuit unit by changing a duty ratio of the rectangular wave voltage generated by itself.

  According to the present invention, the output current of the inverter circuit unit can be finely adjusted in the discharge lamp lighting device that controls the output of the inverter circuit unit using the rectangular wave voltage output from the microcomputer (rectangular wave voltage generating unit).

Embodiment 1 FIG.
The first embodiment will be described with reference to FIGS. Embodiment 1 is an embodiment of a discharge lamp lighting device that controls the magnitude of the output current of an inverter circuit unit by changing the duty ratio of a rectangular wave voltage of a constant frequency output from a microcomputer.

  FIG. 1 is a block diagram of a discharge lamp lighting device 100 according to the first embodiment. The discharge lamp lighting device 100 includes a rectifying circuit unit 1, an active filter circuit unit 2, an inverter circuit unit 3, a load circuit unit 4, a drive circuit unit 5, and a microcomputer 11.

  The load circuit unit 4 includes a discharge lamp. The microcomputer 11 includes a duty ratio storage unit 21 that stores the duty ratio, and a rectangular wave voltage generation unit that generates and outputs a rectangular wave voltage of the duty ratio based on the duty ratio stored in the duty ratio storage unit 21. 20. A detailed description of the function of each component will be given in the description of FIG.

  An outline of the operation of the discharge lamp lighting device 100 will be described with reference to FIG.

(1) The rectangular wave voltage generation unit 20 of the microcomputer 11 generates and outputs a rectangular wave voltage having a predetermined frequency and a duty ratio stored in the duty ratio storage unit 21. In this case, the rectangular wave voltage generator 20 can change the duty ratio of the generated rectangular wave voltage. For example, the duty ratio storage unit 21 stores a plurality of different duty ratios, and the rectangular wave voltage generation unit 20 generates rectangular wave voltages having a plurality of different duty ratios, thereby generating rectangular wave voltages. The duty ratio can be changed.
(2) The drive circuit unit 5 receives a rectangular wave voltage having a predetermined frequency and a predetermined duty ratio output from the rectangular wave voltage generation unit 20, and an inverter circuit unit according to the frequency and the duty ratio of the input rectangular wave voltage The switching circuit 3 (not shown) is switched (ON / OFF) to cause the inverter circuit unit 3 to output an output current. Thus, the drive circuit unit 5 turns on and off the switching element at a switching frequency corresponding to the frequency of the input rectangular wave voltage and a ratio corresponding to the duty ratio.
(3) The inverter circuit unit 3 has a switching element (not shown), receives a DC voltage from the active filter circuit unit 2, and converts the input DC voltage into a high-frequency voltage by switching (ON / OFF) of the switching element. The output current corresponding to the converted high-frequency voltage is output to the discharge lamp of the load circuit unit 4.
(4) With the above configuration, by changing the duty ratio of the rectangular wave voltage generated by the rectangular wave voltage generator 20 of the microcomputer 11, the ratio of ON / OFF of the switching element of the inverter circuit unit 3 is changed. Thus, the magnitude of the output current output from the inverter circuit unit 3 is controlled. By this control, the effective value of the high-frequency power supply voltage of the inverter circuit unit 3 is changed by increasing or decreasing the ON-DUTY of the rectangular wave voltage output from the rectangular wave voltage generating unit 20 of the microcomputer 11, and the inverter The magnitude of the output current of the circuit unit 3 can be controlled.

  FIG. 2 is a diagram illustrating a specific circuit configuration of the discharge lamp lighting device 100. The circuit configuration of the discharge lamp lighting device 100 will be described with reference to FIG.

  The rectifier circuit unit 1 is a circuit that rectifies a power supply voltage and removes noise.

  The active filter circuit unit 2 is a circuit that boosts the power supply voltage to a predetermined DC voltage by switching along the power supply voltage waveform and shapes the input current waveform to improve the power factor.

  The inverter circuit unit 3 converts the direct-current voltage boosted by the active filter circuit unit 2 into a reverse polarity voltage output from the drive circuit unit 5, an FET (Field Effect Transistor) Q <b> 1 (6) (switching element), and an FET Q <b> 2. (7) A circuit that generates a high-frequency voltage by alternately switching (switching on / off) the (switching element) and outputs an output current corresponding to the high-frequency voltage to the lamp LA10 (discharge lamp).

  The load circuit unit 4 is a circuit for lighting the lamp LA10 (discharge lamp) by utilizing the resonance of the inductor L1 (8) and the capacitor C1 (9).

  The drive circuit unit 5 outputs a rectangular wave voltage having a predetermined frequency and a predetermined duty ratio output from the microcomputer 11 to a totem pole output formed by the transistor Q1 (12) and the transistor Q2 (13), and the inductor L2 1 From the inductor L2 secondary side (15) and the inductor L2 secondary side (16) applied to the secondary side (14) and having different polarities, the FET Q1 (6) and FET Q2 (7) of the inverter circuit unit 3 are This is a circuit that performs switching (on / off) alternately according to the frequency and duty ratio of the input rectangular wave voltage. The drive circuit unit 5 has FET Q1 (6) and FET Q2 (FETs) which are switching elements at substantially the same frequency and duty ratio and on / off ratio with respect to the frequency and duty ratio of the input rectangular wave voltage. 7) is turned on / off. Here, "substantially" the same frequency and duty ratio and "substantially" the same on / off ratio are used. This is because, in theory, the switching element of the inverter circuit unit 3 switches at the same switching frequency and the same ON / OFF ratio as the duty ratio with respect to the frequency and duty ratio of the rectangular wave voltage. This is because there may be cases where the components are not necessarily physically the same due to variations in the characteristics of the components constituting the portion 5.

  The microcomputer 11 generates and outputs a rectangular wave voltage having a predetermined frequency and a predetermined duty ratio. Further, the microcomputer 11 can change the duty ratio of the output rectangular wave voltage. This is as described in FIG.

  With the polarity of the inductor L2 shown in FIG. 2, the ON-DUTY of the rectangular wave voltage output from the microcomputer 11 matches the ON-DUTY of the output voltage of the inverter circuit unit 3.

  For example, if the ON-DUTY of the rectangular wave voltage output from the microcomputer 11 is 70%, the ON-DUTY of the output voltage of the inverter circuit unit 3 is also approximately 70%. Therefore, when the ON-DUTY of the rectangular wave voltage is set to 70% when the operation is performed at the same frequency with “ON-DUTY 50%”, the output voltage of the inverter circuit unit 3 is decreased (ON is set to LOW). You can).

  For example, if the ON-DUTY of the rectangular wave voltage output from the microcomputer 11 is 30%, the ON-DUTY of the output voltage of the inverter circuit unit 3 is also approximately 30%. Accordingly, when the ON-DUTY of the rectangular wave voltage is set to 30% when the operation is performed at the same frequency with “ON-DUTY 50%”, the output voltage of the inverter circuit unit 3 is increased (ON is set to LOW). You can).

  FIG. 3 is a diagram showing the relationship between the oscillation frequency of the inverter circuit unit 3 and the output current. The horizontal axis is the oscillation frequency, and the vertical axis is the output current. As shown in FIG. 3, when the frequency of the rectangular wave voltage output from the microcomputer 11 (which is the same as the oscillation frequency of the inverter circuit unit 3) is Fb, the output voltage of the inverter circuit unit 3 varies depending on the change of the duty ratio. When increasing, the output current increases from Ib2 to Ib3. On the other hand, when the output voltage of the inverter circuit unit 3 decreases, the output current decreases from Ib2 to Ib1.

  As described above, the change in the frequency is large and the fine adjustment cannot be performed with respect to the point that “the coarser the change in the oscillation frequency, the more the change in the output current becomes coarser and the fine adjustment of the output current cannot be performed”. For the portion, the output current of the inverter circuit unit can be finely adjusted by finely adjusting the ON-DUTY of the rectangular wave voltage output from the microcomputer 11. Fine adjustment of the output current is particularly useful in the case of preheating the discharge lamp.

  In the above, for example, the duty ratio storage unit 21 stores a plurality of different duty ratios, and the rectangular wave voltage generation unit 20 generates the rectangular wave voltages having a plurality of different duty ratios. The case of changing the duty ratio of the rectangular wave voltage was assumed. However, not only a plurality of duty ratios, but also when the duty ratio storage unit 21 stores one duty ratio, and the rectangular wave voltage generation unit 20 generates a rectangular wave voltage of the duty ratio according to the duty ratio. Of course, the output current can be finely adjusted. For example, assume that an output current of Id is desired in FIG. On the other hand, the frequencies that can be output by the microcomputer 11 are Fa, Fb, Fc..., And it is assumed that a rectangular wave voltage having the frequency Fd cannot be generated. In that case, for example, the frequency of the rectangular wave voltage is set to Fa, and the duty ratio at which the output current Id is obtained at the frequency Fa is stored in the duty ratio storage unit 21 of the microcomputer 11. Alternatively, the frequency of the rectangular wave voltage is set to Fb, and the duty ratio at which the output current Id is obtained at the frequency Fb is stored in the duty ratio storage unit 21 of the microcomputer 11. As a result, the output current Id can be obtained. For example, the duty ratio stored in the duty ratio storage unit 21 is any value from 0% to 50%. Alternatively, the duty ratio stored in the duty ratio storage unit 21 is any value of 50% or more and less than 100%. The duty ratio to be stored in the duty ratio storage unit 21 is determined in advance by experiments or the like, and can be stored and shipped in the case of commercialization.

  In the discharge lamp lighting device 100 according to the first embodiment, the rectangular wave voltage generation unit 20 changes the duty ratio of the rectangular wave voltage generated by the rectangular wave voltage generation unit 20 so that the drive circuit unit 5 outputs the output current to the inverter circuit unit 3. The output current of the inverter circuit unit 3 can be finely adjusted.

  In the discharge lamp lighting device 100 according to the first embodiment, the duty ratio storage unit 21 stores the duty ratio, and the rectangular wave voltage generation unit 20 stores the duty ratio storage unit 21, but generates a rectangular wave voltage based on the duty ratio. Therefore, the output voltage of the inverter circuit can be easily finely adjusted.

Embodiment 2. FIG.
Next, Embodiment 2 will be described with reference to FIG. FIG. 4 is a diagram illustrating a circuit configuration of the discharge lamp lighting device 200 according to the second embodiment. The point which provided the electric current detection part 30 differs with respect to FIG. 2 which shows the discharge lamp lighting device 100 of Embodiment 1. FIG.

  In the discharge lamp lighting device 200 of the second embodiment, the current detection unit 30 detects the magnitude of the output current output from the inverter circuit unit 3 to the discharge lamp. The rectangular wave voltage generator 20 changes the duty ratio of the rectangular wave voltage generated by itself based on the magnitude of the output current detected by the current detector 30. With the above configuration, the magnitude of the output current of the inverter circuit unit 3 can be finely adjusted with certainty.

  Specifically, it is assumed that the duty ratio storage unit 21 stores a plurality of different duty ratios. The rectangular wave voltage generator 20 can generate rectangular wave voltages having a plurality of different duty ratios. Further, the rectangular wave voltage generator 20 stores a target range of the output current as a target range.

In such a configuration,
(1) First, the rectangular wave voltage generation unit 20 outputs a rectangular wave voltage having a duty ratio at which the output current of the inverter circuit unit 3 is the smallest, and the magnitude of the output current when the rectangular wave voltage is output is determined as the current. Obtained from the detection unit 30. It is determined whether the magnitude of the acquired output current belongs to the target range. If it belongs, the rectangular wave voltage generator 20 continues to output the rectangular wave voltage with the duty ratio.
(2) On the other hand, when the target range is not reached, a rectangular wave voltage having a duty ratio with the next largest output current is output, and similarly, a determination is made based on the value of the current detection unit 30.
(3) By repeating this, the magnitude of the output current can be finely adjusted reliably.

  In the discharge lamp lighting device 100 of the second embodiment, the current detection unit 30 detects the output current of the inverter circuit unit 3, and the rectangular wave voltage generation unit 20 outputs based on the output current detected by the current detection unit 30. Since the duty ratio of the rectangular wave voltage to be changed is changed, the output current of the inverter circuit unit 3 can be finely adjusted with certainty.

  In the above embodiment, a DC power source obtained by boosting or stepping down a commercial power source, an inverter circuit for converting DC supplied from the DC power source into a high-frequency current, a choke coil connected to the inverter circuit, A discharge lamp load circuit comprising a lamp and a coupling capacitor, wherein the oscillation frequency control of the inverter circuit is controlled by a rectangular wave voltage generated from a microcomputer, and the output current control of the inverter circuit is controlled from the microcomputer A discharge lamp lighting device having means for controlling by changing the effective value of the high-frequency power supply voltage by increasing or decreasing the ON-DUTY of the generated rectangular wave voltage has been described.

1 is a block diagram of a discharge lamp lighting device 100 according to Embodiment 1. FIG. 1 is a circuit diagram of a discharge lamp lighting device 100 according to Embodiment 1. FIG. FIG. 4 is a diagram illustrating a relationship between an oscillation frequency of the inverter circuit unit 3 and an output current in the first embodiment. 6 is a circuit diagram of a discharge lamp lighting device 200 according to Embodiment 2. FIG. It is a figure which shows a prior art example.

Explanation of symbols

  1 rectifier circuit section, 2 active filter circuit section, 3 inverter circuit section, 4 load circuit section, 5 drive circuit section, 6 FET Q1, 7 FET Q2, 8 inductor L1, 9 capacitor C1, 10 lamp LA, 11 microcomputer, 12 Transistors Q1, 13 Transistors Q2, 14 Inductor L2 Primary side, 15 Inductor L2 Secondary side, 16 Inductor L2 Secondary side, 20 Rectangular wave voltage generation unit, 21 Duty ratio storage unit, 30 Current detection unit.

Claims (2)

In a discharge lamp lighting device for lighting a discharge lamp,
The switching element has a DC voltage and converts the input DC voltage into a high-frequency voltage by turning on and off the switching element, and outputs a current corresponding to the converted high-frequency voltage as an output current to the discharge lamp. An inverter circuit unit
A duty ratio storage unit for storing a duty ratio set corresponding to the switching frequency F of the switching element during preheating of the discharge lamp ;
Advance said a set frequency during the preheating is the frequency of the switching frequency F, and the rectangular wave voltage generator for outputting generates a rectangular wave voltage of said duty ratio in which the duty ratio storage unit is stored,
The switching element of the inverter circuit unit receives the rectangular wave voltage output from the rectangular wave voltage generation unit , and has a frequency corresponding to the frequency of the input rectangular wave voltage and a duty ratio of the input rectangular wave voltage. A discharge lamp lighting device comprising : a drive circuit unit that causes the inverter circuit unit to output the output current at the time of preheating by turning on and off the inverter. In a discharge lamp lighting device for lighting a discharge lamp,
The switching element has a DC voltage and converts the input DC voltage into a high-frequency voltage by turning on and off the switching element, and outputs a current corresponding to the converted high-frequency voltage as an output current to the discharge lamp. An inverter circuit unit
A square wave voltage generator you generates and outputs a rectangular wave voltage of each duty ratio corresponding to the magnitude the output current of a different a rectangular wave voltage of a predetermined frequency,
The rectangular wave voltage output from the rectangular wave voltage generating unit is input, and the switching element of the inverter circuit unit is turned on and off according to the frequency and duty ratio of the input rectangular wave voltage, thereby outputting the output to the inverter circuit unit. e Bei a drive circuit section for outputting the current,
The discharge lamp lighting device further includes:
A current detection unit for detecting the magnitude of the output current output to the discharge lamp by the inverter circuit unit;
The rectangular wave voltage generator is
And outputs to the order of the rectangular wave voltage of a duty ratio corresponding to the largest the output current from the rectangular wave voltage of a duty ratio corresponding to the lowest said output current, a rectangular duty ratio corresponding to the output current of each size Each time a wave voltage is output, it is determined whether or not the magnitude of the output current detected by the current detector belongs to a preset target range. If it is determined that the output current belongs to the target range, the current rectangle The discharge lamp lighting device is characterized in that the output of the wave voltage is continued, and when it is determined that the output voltage does not belong to the target range, a rectangular wave voltage having a duty ratio at which the output current becomes the next largest is output.

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