JP4114802B2 - Lamp lighting device - Google Patents

Description

  The present invention relates to a lamp lighting device that uses arc discharge such as a high-intensity discharge lamp.

  In general, a conventional lamp lighting device that employs an AC lighting system controls the output power to be constant based on the difference between the reference value and the output power. For example, in Patent Document 1, as shown in FIG. 4, the rectifier circuit 2 includes a rectifier circuit 2, a buck-boost converter circuit 3, an inverter circuit 4, an arithmetic control circuit 6, and a discharge lamp 5. The difference is detected, and the pulse width of the semiconductor switch Q1 of the step-up / step-down converter circuit 3 is controlled in accordance with the difference, and the output power is controlled to be constant. The inverter circuit 4 is composed of four semiconductor switches Q2 to Q5. The first set of semiconductor switches Q2 and Q5 and the second set of semiconductor switches Q3 and Q4 are alternately turned on and off, and the arm is short-circuited. In order to prevent this, a dead time period in which all the semiconductor switches Q2 to Q5 are simultaneously turned off is provided.

  However, according to the conventional example, the reference value used in power control is maintained at a constant value even during the dead time that occurs when the polarity of the inverter circuit 4 is switched. The output voltage of the pressure converter circuit 3 rises, and when this voltage rises, a large current flows through the lamp and overshoot occurs.

  When such an overshoot occurs, more current than necessary flows through the lamp, increasing the stress on the electrode, affecting the life of the electrode. Furthermore, there is a problem that noise generated from the apparatus is increased.

A technique for preventing overshoot that occurs at the time of polarity switching is already known, and is disclosed in Patent Document 2, for example. In Patent Document 2, the reference value is decreased by a predetermined period at the time of polarity switching in synchronization with the polarity switching signal, the difference between the detected value and the reference value at the time of polarity switching is reduced, and the output voltage is controlled to be constant. ing.
Japanese Patent Laid-Open No. 08-096973 JP 2003-203796 A

  However, in the above conventional example, there is a device that provides a predetermined fixed reference value, and in order to subtract the preset decrease value in the control device from the reference value, several reduction values are set in advance in the microcomputer or the like. In addition, it was necessary to select a decrease value according to the lamp current. The present invention has been made in view of the above points, and in the AC lighting system, when the lamp power is controlled by reducing the difference between the detection value and the reference value, the reduction value is not set. It is an object of the present invention to reliably reduce the difference between the detected value and the reference value at the time of polarity switching with a simple circuit configuration and prevent overshoot of the output current.

The invention of claim 1 is a power conversion circuit capable of converting input power into a DC voltage and controlling an output current, a polarity switching circuit for converting a DC voltage output from the power conversion circuit into an AC voltage, and the power a detecting means connected in series between the converter circuit and the polarity switching circuit, and a detection voltage adjusting circuit connected in parallel to said detecting means, a voltage of the detecting means to adjust year on the detection voltage adjusting circuit test A current control circuit that compares the output voltage with a reference voltage and controls the power conversion circuit so as to follow the reference voltage, and the detection voltage adjustment circuit is arranged before and after the polarity of the lamp voltage is switched to a steady state. The detection voltage of the detection voltage adjusting circuit is changed during a predetermined period of time, and the output current is controlled to be constant so that the detection voltage and the reference voltage are equal in a steady state. The predetermined period before and after the polarity of the lamp voltage is switched to provide a lamp lighting device, characterized in that to reduce the output current value than the output current of the detection voltage in a previous period the steady state by greater than the reference voltage Is.

  According to the first aspect of the present invention, since the detected value of the lamp current is made larger than the reference voltage for a predetermined period before and after the lamp polarity is switched, it is possible to prevent overshoot that occurs at the time of polarity switching. Therefore, it is possible to prevent electrode deterioration due to overshoot overcurrent, and to prevent noise generated from the apparatus due to overshoot.

The invention of claim 2 is a power conversion circuit capable of converting input power into a DC voltage and controlling an output current, a polarity switching circuit for converting a DC voltage output from the power conversion circuit into an AC voltage, and the power Detection means connected in series between the conversion circuit and the polarity switching circuit, a detection voltage adjustment circuit connected in parallel to the detection means, and detection in which the voltage of the detection means is adjusted by the previous detection voltage adjustment circuit A current control circuit that compares the voltage with a reference voltage and controls the power conversion circuit to follow the reference voltage, and the detection voltage adjustment circuit includes a first resistor, a second resistor, includes a semiconductor switch, wherein the first and the resistor the second resistor and the semiconductor switch are connected in series, a predetermined period before the polarity of the lamp voltage is switched, by turning off the semiconductor switch, Maintaining without dividing the voltage of the serial detection means, after a predetermined time period in which the polarity is switched, the semiconductor switch is turned on, dividing the voltage of said detecting means by said second resistor and the first resistor The lamp lighting device characterized by the above is provided.

  According to the second aspect of the present invention, it is possible to easily adjust the voltage level of the detection voltage at the time of switching the polarity only by controlling the semiconductor switch and obtain the effect of the first aspect.

According to a third aspect of the present invention, there is provided a power conversion circuit capable of converting input power into a DC voltage and controlling an output current, a polarity switching circuit for converting a DC voltage output from the power conversion circuit into an AC voltage, and the power Detection means connected in series between the conversion circuit and the polarity switching circuit, a detection voltage adjustment circuit connected in parallel to the detection means, and detection in which the voltage of the detection means is adjusted by the previous detection voltage adjustment circuit A current control circuit that compares the voltage with a reference voltage and controls the power conversion circuit to follow the reference voltage, and the detection voltage adjustment circuit includes a first resistor, a second resistor, , but are connected in series, the semiconductor switches are connected in parallel with the first resistor or the second resistor, a predetermined period before the polarity of the lamp voltage is switched, by turning on the semiconductor switches, photoelectric of said detecting means Was maintained without dividing, after a predetermined time period in which the polarity is switched, the semiconductor switches turn off, and wherein dividing the voltage of said detecting means by said second resistor and the first resistor lamp A lighting device is provided.

  According to the invention of claim 3, the effect of claim 1 can be obtained by easily adjusting the voltage level of the detection voltage at the time of switching the polarity only by controlling the semiconductor switch.

  According to a fourth aspect of the present invention, in the second or third aspect, the voltage dividing ratio between the first resistor and the second resistor is arbitrarily set according to a lamp voltage at the time of polarity switching. A lamp lighting device is provided.

  According to the invention of claim 4, it is possible to select a resistance value that does not overshoot by arbitrarily setting the voltage dividing ratio between the first resistor and the second resistor in accordance with the lamp voltage at the time of polarity switching. Therefore, in addition to the effect of the first aspect, optimal control can be performed according to the lamp load.

  In the alternating current lighting system, an effect is obtained that overshoot of the output current at the time of polarity switching can be suppressed.

  First, Example 1 which shows the best mode for carrying out the present invention will be described.

  FIG. 1 shows a lamp lighting device 100 according to a first embodiment of the present invention. The lamp lighting device 100 includes a power conversion circuit 1 that can convert input power into a DC voltage and control output current, a polarity switching circuit 2 that switches the output polarity of the power conversion circuit 1, a lamp 3, and a power conversion circuit. A detection resistor R3 for detecting an output current and a control unit 11 are included.

  The control unit 11 includes a polarity switching signal S1 and S2 of the polarity switching circuit 2, a polarity switching signal generation circuit 4 that generates a short-time adjustment signal S3 at the time of polarity switching in synchronization with the polarity switching signals S1 and S2, and a detection resistor. The detection voltage adjustment circuit 6 that adjusts the voltage of R3, and the current that controls the control signal S4 of the power conversion circuit 1, for example, the pulse width modulation signal, so that the adjusted detection voltage Vs and the reference voltage Vr are equal to each other. A control circuit 7 and a control circuit 5 are included.

  The power conversion circuit 1 is a switching regulator such as a step-down chopper circuit that converts a DC voltage of about DC 300 to 400 V into a lower power DC voltage. A capacitor C is provided at the output stage of the power conversion circuit 1.

  The polarity switching circuit 2 is an inverter configured by a semiconductor switch such as a MOSFET or IGBT that switches a DC voltage, for example.

  The output voltage of the power conversion circuit 1 is detected by the divided voltage of the resistors R1 and R2. The detected value of the output voltage is converted into a reference value of the lamp current by the control circuit 5 so that the output power becomes constant, and is input to one of the current control circuits 7 as the reference voltage Vr.

  The detection resistor R3 is connected to the subsequent stage of the capacitor C in the output stage of the power conversion circuit 1, and detects the voltage Vd proportional to the output current Io. The detection voltage Vd becomes the detection voltage Vs through the detection voltage adjustment circuit 6 and is given to the other input of the current control circuit 7. The current control circuit 7 changes the power so that the detection voltage Vs follows the reference voltage Vr. The pulse width control signal S4 of the apparatus 1 is controlled.

  The detection voltage adjustment circuit 6 includes two series resistors R4 and R5 connected in series across the detection resistor R3, and the semiconductor switch 10. The detection voltage Vs is obtained from the connection point between the resistors R4 and R5. The semiconductor switch 10 preferably has a small internal resistance when conducting, and a MOSFET is used in this embodiment. The resistors R4 and R5 may be configured by connecting several resistors in series or in parallel as long as each resistance value is a predetermined value. Furthermore, you may comprise with a variable resistor.

  Here, the connection point between the resistor R2 and the resistor R3 serves as a reference potential of the signal system, that is, the control unit 11, and is grounded. However, it is not necessarily grounded, but means the reference potential.

  FIG. 2 is a waveform diagram for explaining the operation of this embodiment. 2A shows polarity switching signals S1 and S2 for controlling a semiconductor switch (not shown) of the polarity switching circuit 2, and FIG. 2B shows an adjustment signal S3 for controlling the semiconductor switch 10. As shown in FIG. (C) shows the output current of the lamp. As shown in FIG. 2C, the polarity of the output current of the lamp is switched at time t2 during which the polarity switching signals S1 and S2 are simultaneously turned off at times t1 to t3.

  The polarity switching signal generation circuit 4 generates an adjustment signal S3 for controlling the semiconductor switch 10 separately from the polarity switching signals S1 and S2 given to the polarity switching circuit 2. The adjustment signal S3 outputs an ON signal when the polarity switching signals S1 and S2 are steady, and outputs an OFF signal during a period in which the polarity switching signals S1 and S2 are simultaneously OFF.

  That is, the off signal of the adjustment signal S3 covers the off period between t1 and t2 and between t2 and t3 with reference to the time t2 when the polarity of the output current switches. For example, the polarity switching signals S1 and S2 are 100 Hz. If there is, a period of several tens of μs is provided between t1 and t2 and between t2 and t3, and an off signal is output for a period of about 50 to 100 μs as a whole between t1 and t3. The off period can be changed by the polarity switching signal generation circuit 4 according to the load condition of the lamp. The term “steady” refers to a state of a flat portion after the polarity switching signals S1 and S2 rise. The polarity of the output voltage of the output polarity switching circuit 2 corresponds to the polarity of the polarity switching signals S1 and S2.

  First, an ON signal is given to the semiconductor switch 10 in a steady state after the polarity of the output polarity switching circuit 2 is switched. When the semiconductor switch 10 is turned on, the detection voltage Vd is input to the current control circuit 7 as the detection voltage Vs divided by the resistors R4 and R5. For example, assuming that the resistors R4 and R5 have the same value and the semiconductor switch 10 is an ideal switch, the detection voltage Vs is Vd / 2. Here, since the current control circuit 7 controls the reference voltage Vr and the detection voltage Vs to be at the same level, the reference voltage Vr is set to Vd / 2, which is the value of the detection voltage in the steady state. .

  Next, as shown in FIG. 2B, the adjustment signal S3 gives an off signal of about 50 to 100 μs to the semiconductor switch 10 at the time of polarity switching when the polarity switching signals S1 and S2 are simultaneously turned off. As a result, the semiconductor switch 10 is turned off, and the detection voltage Vd of the detection resistor R3 is input to the current control circuit 7 as the detection voltage Vs without being divided.

  Since the reference voltage Vr of the current control circuit 7 is set to Vd / 2, since the detection voltage Vs apparently rises to Vd, the pulse width control signal of the power conversion circuit 1 is narrowed so that the detection voltage is the reference The output current is decreased so as to be Vd / 2 which is the set value of the voltage Vr. That is, in this embodiment, the output current is controlled to decrease to Io / 2.

  When the adjustment signal S3 returns to the on state after the off period at the time of polarity switching, the semiconductor switch 10 is turned on to be in a steady state, and Vd / 2 is input to the current control circuit 7 as the detection voltage Vs. As a result, the output current is controlled to Io.

  In this embodiment, in the steady state other than during polarity switching, the detection voltage is divided and the output voltage is controlled to be constant so that the detection voltage and the reference voltage are at the same level. Since control is performed without dividing the detection voltage for a predetermined period, the output current is reduced, and overshoot can be prevented.

  Further, since the resistance value that does not overshoot can be selected by adjusting the ratio of the resistance values of the series resistors R4 and R5, optimal control can be performed according to the lamp load.

  FIG. 3 shows a lamp lighting device 200 according to the second embodiment of the present invention. In this embodiment, resistors R4 and R5 are connected in series across the current detection resistor R3, and the semiconductor switch 10 is connected in parallel to the non-grounded resistor R5. The semiconductor switch 10 is controlled by an adjustment signal S3 having a phase opposite to that of the first embodiment. That is, the semiconductor switch 10 is turned off in a steady state and turned on for a short time when switching the polarity. Accordingly, if the resistances R4 and R5 are set to the same value, the detection voltage Vs is Vd / 2 in the steady state, and the detection voltage Vs becomes Vd at the time of polarity switching, and the polarity switching is performed as in the first embodiment. Time overshoot can be prevented.

It is a circuit diagram which shows the lamp lighting device 100 of the 1st Example of this invention. It is a wave form diagram for operation | movement description of the 1st Example of this invention. It is a circuit diagram which shows the lamp lighting device 200 of the 2nd Example of this invention. It is a circuit diagram which shows the lamp lighting device in a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Power conversion circuit 2 ... Polarity switching circuit 3 ... Lamp 4 ... Polarity switching signal generation circuit 5 ... Control circuit 6 ... Detection voltage adjustment circuit 7 ... Current control circuit 10 ... Semiconductor switch 11 ... Control unit

Claims (4)

A power conversion circuit that can convert input power to DC voltage and control output current,
A polarity switching circuit that converts a DC voltage output from the power conversion circuit into an AC voltage;
Detection means connected in series between the power conversion circuit and the polarity switching circuit;
A detection voltage adjustment circuit connected in parallel to the detection means ;
It said voltage detection means by comparing the detection voltage is adjusted year on the detection voltage adjusting circuit with a reference voltage, and a current control circuit for controlling the power conversion circuit to follow the reference voltage, the detection The voltage adjustment circuit changes the detection voltage of the detection voltage adjustment circuit between a steady state and a predetermined period before and after the polarity of the lamp voltage is switched, so that the detection voltage and the reference voltage become equal in the steady state. controlled so that the output current constant, thereby decreasing the output current value than the output current of the year on the steady state the detection voltage by greater than said reference voltage at a predetermined period before and after the polarity of the lamp voltage is switched A lamp lighting device characterized by that. A power conversion circuit that converts input power into DC voltage and controls output current;
A polarity switching circuit that converts a DC voltage output from the power conversion circuit into an AC voltage;
Detection means connected in series between the power conversion circuit and the polarity switching circuit;
A detection voltage adjustment circuit connected in parallel to the detection means;
A current control circuit that controls the power conversion circuit so as to follow the reference voltage by comparing a detection voltage obtained by adjusting the voltage of the detection means with a detection voltage adjustment circuit in the previous period with a reference voltage;
The detection voltage adjustment circuit includes:
A first resistor;
A second resistor;
A semiconductor switch;
And the first resistor, the second resistor, and the semiconductor switch are connected in series , and the semiconductor switch is turned off before a predetermined period when the polarity of the lamp voltage is switched, and the voltage of the detection means Is maintained without being divided, and after a predetermined period when the polarity is switched, the semiconductor switch is turned on, and the voltage of the detection means is divided by the first resistor and the second resistor. Lighting device. A power conversion circuit that converts input power into DC voltage and controls output current;
A polarity switching circuit that converts a DC voltage output from the power conversion circuit into an AC voltage;
Detection means connected in series between the power conversion circuit and the polarity switching circuit;
A detection voltage adjustment circuit connected in parallel to the detection means;
A current control circuit that controls the power conversion circuit so as to follow the reference voltage by comparing a detection voltage obtained by adjusting the voltage of the detection means with a detection voltage adjustment circuit in the previous period with a reference voltage;
The detection voltage adjustment circuit includes:
A first resistor;
A second resistor;
There are connected in series, the semiconductor switches are connected in parallel with the first resistor or the second resistor, a predetermined period before the polarity of the lamp voltage is switched, by turning on the semiconductor switches, the voltage of said detecting means The lamp lighting characterized by maintaining the voltage without voltage division and turning off the semiconductor switch and dividing the voltage of the detection means by the first resistance and the second resistance after a predetermined period when the polarity is switched. apparatus. In claim 2 or claim 3,
A lamp lighting device, wherein a voltage division ratio between the first resistor and the second resistor is arbitrarily set according to a lamp voltage at the time of polarity switching.

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