JP4311213B2 - Discharge lamp lighting device - Google Patents

Description

  The present invention relates to a discharge lamp lighting device for lighting a discharge lamp such as a metal halide lamp, and in particular, a discharge lamp lighting in which a high voltage can be applied to the discharge lamp at the start without causing an increase in the size of the start coil. Relates to the device.

  2. Description of the Related Art Conventionally, there is known a discharge lamp lighting device configured to boost a direct current power source with a DC / DC converter and convert a direct current output of the DC / DC converter into alternating current with an H bridge circuit to light the discharge lamp with alternating current. (For example, refer to Patent Documents 1 and 2).

In this type of discharge lamp lighting device, a starting coil is provided on the output side of the H bridge circuit, and the DC voltage of the DC / DC converter is applied to the primary side coil of the starting coil, whereby a high voltage is applied to the secondary side coil. And the high voltage is applied to the discharge lamp to start the discharge lamp.
Japanese Patent Laid-Open No. 09-120894 (FIG. 1) JP 09-82483 A

  In order to start the discharge lamp, it is desirable to generate a voltage as high as possible in the secondary coil of the starting coil. For this reason, it is conceivable to increase the output voltage of the DC / DC converter applied to the primary coil of the starting coil. In this case, however, the breakdown voltage of the elements around the booster coil of the DC / DC converter must be increased. . Further, it is conceivable to increase the step-up ratio (turn ratio) of the starting coil. In this case, however, the starting coil is increased in size and cost.

  The present invention solves the above-described problems, does not increase the output voltage of the DC / DC converter, and does not increase the step-up ratio of the starting coil, and the secondary coil of the starting coil is as high as possible. It is an object of the present invention to provide a discharge lamp lighting device that can reliably start a discharge lamp by generating a voltage.

The discharge lamp lighting device of the present invention includes a DC / DC converter that boosts a DC power supply, an H-bridge circuit that converts a DC output of the DC / DC converter into AC and outputs the AC to the discharge lamp, and the discharge lamp at the start A starting coil for applying a starting voltage, a switching element connected in series to a primary side coil of the starting coil, a series circuit of the switching element and the primary coil, and a positive side on the positive side A starting capacitor connected to a high voltage side output side of the H bridge circuit and having a negative electrode side connected to a GND side output side of the DC / DC converter; and a high voltage side output and a low voltage side output of the H bridge circuit And when the pair of switching elements of the H bridge circuit is turned on, the high voltage side output of the H bridge circuit is at a high level and the low voltage side. When the output becomes low level, the starting capacitor and the voltage doubler capacitor are charged, and then the other pair of switch elements of the H bridge circuit is turned on, the high voltage side output of the H bridge circuit is low level, The low voltage side output is inverted to a high level, respectively, and a voltage in which the output voltage of the DC / DC converter and the terminal voltage of the voltage doubler capacitor are superimposed is applied to the charged starting capacitor. It is characterized by that.
According to the present invention, the highest possible voltage can be generated on the secondary side of the starting coil without increasing the output voltage of the DC / DC converter and without increasing the step-up ratio of the starting coil.

  The step-up ratio of the starting coil is 230/3 or less, and the starting coil is relatively small.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit diagram of a discharge lamp lighting device according to an embodiment of the present invention, and FIG. 2 is an operation explanatory diagram of the circuit.

  In FIG. 1, a DC / DC converter 1 is connected to a + B terminal and a GND terminal of a DC power supply, and an output voltage of the DC power supply is boosted by the DC / DC converter 1.

  Connected to the output side of the DC / DC converter 1 is an H-bridge circuit 2 composed of four switch elements 2A, 2B, 2C, 2D (for example, a MOS FET), and the DC output of the DC / DC converter 1 is The switching elements 2A, 2B, 2C, and 2D of the H bridge circuit 2 are converted to alternating current. A discharge lamp (bulb) (not shown) is connected to the high-voltage side output terminal Hi and the low-voltage side output terminal Lo of the H-bridge circuit 2, and the discharge lamp is lit in an alternating current by the output of the H-bridge circuit 2.

  The secondary side coil 3b of the starting coil 3 is connected to the high voltage side output (point A in the figure) of the H bridge circuit 2, and the starting coil 3 applies the starting voltage to the discharge lamp to start the discharge lamp. Let A switch element 4 (for example, a thyristor) is connected in series to the primary coil 3a of the starting coil 3, and when the switch element 4 is turned on, the primary coil 3a is energized. The number of turns of the primary coil 3a is 3 turns, the number of turns of the secondary coil 3b is 215 turns, and the turn ratio (step-up ratio) of the starting coil 3 is 230/3 or less, the conventional primary side 3 turns, Small compared to 235 turns on the secondary side. A starting capacitor 5 is connected in parallel to the series circuit of the primary coil 3a and the switch element 4, and when the switch element 4 is turned on, the starting capacitor 5 is discharged, and a large current flows in the primary coil 3a. A high voltage is generated in the secondary coil 3b. The positive side of the starting capacitor 5 is connected to the high voltage side output (point A) of the H bridge circuit 2 via the voltage doubler rectifier circuit 6, while the negative side is the GND side of the DC / DC converter 1. It is connected to the output (D point in the figure).

  A voltage doubler rectifier circuit 6 is connected to a high voltage side output (point A) and a low voltage side output (point B in the figure) of the H-bridge circuit 2, and the voltage doubler rectifier circuit 6 includes a rectifier diode 7 and a voltage doubler capacitor 8. Is provided. The rectifier diode 7 is connected to the high voltage side output (point A) of the H bridge circuit 2. The positive electrode side of the voltage doubler capacitor 8 is connected to the positive electrode side of the starting capacitor 5 via another diode 9. A Zener diode 10 is connected to the positive side of the voltage doubler capacitor 8 and the high voltage side output (point C in the figure) of the DC / DC converter 1.

  The control circuit 11 inputs a lamp current, a lamp voltage, and the like as detection signals, and outputs a control signal to the DC / DC converter 1, the H bridge circuit 2, and the switch element 4 at a predetermined timing.

  Next, the operation of the circuit configured as described above will be described with reference to FIG.

  When a reset period of about 4 ms elapses after the DC power supply (+ B) is turned on, the DC / DC converter 1 starts to operate, and the output voltage of the DC / DC converter 1 (the voltage between the points C and D) is about 400V. When about 10 ms elapses after the power is turned on, two switch elements 2A, 2B among the four switch elements 2A, 2B, 2C, 2D of the H bridge circuit 2 that have been turned off until then are turned on. The potential of the high voltage side output (point A) is 400V, and the potential of the low voltage side output (point B) is 0V. At this time, the starting capacitor 5 is charged from the point A through the rectifier diode 7, the resistor 12, and the diode 9, and the voltage doubler capacitor 8 is charged through the rectifier diode 7, the resistor 12, and the resistor 13, and about 16 ms has elapsed since the power was turned on. When the time has elapsed, the potentials at the point E and the point F in the figure are both about 400V.

  When about 16 ms elapses after the power is turned on, the switch elements 2A and 2B of the H-bridge circuit 2 are switched off, and the other switch elements 2C and 2D are switched on. By this switching operation, the point A becomes 0V and the point B becomes 400V. Since the point B rises from 0V to 400V with a voltage of 400V at both ends of the voltage doubler capacitor 8, the point E rises instantaneously toward 800V and is already charged to 400V. Is further charged through the resistor 13 and the diode 9. If all the energy stored in the voltage doubler capacitor 8 (C = 0.33 μF) is transferred to the starting capacitor 5 (C = 0.47 μF), the F point becomes 735 V, but in reality the voltage doubler capacitor Since there is a part remaining in 8, the F point becomes about 500V.

  Further, when about 22 ms elapses after the power is turned on, the H-bridge circuit 2 is reversed again, and when the point A becomes 400V and the point B becomes 0V, the voltage doubler capacitor 8 is charged with 400V. Furthermore, when about 28 ms has passed since the power was turned on, when the H bridge circuit 2 is reversed and the point A becomes 0V and the point B becomes 400V, the point E rises to 800V instantly and is already charged to about 500V. The starting capacitor 5 that has been started is further charged, but the switching element (thyristor) 4 is turned on when about 400 μS has elapsed since the inversion of the H-bridge circuit 2 this time. The electric charge stored in is discharged through the primary coil 3a of the starting coil 3, a high voltage of about 22 kV is generated in the secondary coil 3b, the breakdown between the electrodes of the discharge lamp is broken down, and the discharge lamp starts to light up, that is, starts. To do. The voltage of the starting capacitor 5 at the time of discharging is about 520V. The Zener diode 10 serves to limit the potential at the point E that tends to increase toward 800V.

  As described above, the discharge lamp lighting device of the present embodiment applies the voltage obtained by the voltage doubler rectifier circuit 6 to the primary side of the starting coil 3. Since the voltage on the primary side of the starting coil 3 is increased using the voltage doubler rectifier circuit 6 in this way, the output voltage of the DC / DC converter 1 is not increased, and the step-up ratio of the starting coil 3 is increased. Without doing so, a voltage as high as possible can be generated on the secondary side of the starting coil 3.

  The step-up ratio of the starting coil 3 is 230/3 or less, and the starting coil 3 is relatively small.

  Further, the discharge lamp lighting device of the present embodiment includes a DC / DC converter 1 that boosts a DC power supply, an H bridge circuit 2 that converts a DC output of the DC / DC converter 1 into an AC and outputs the AC to a discharge lamp, and a start In parallel, a starting coil 3 for applying a starting voltage to the discharge lamp, a switching element 4 connected in series to the primary coil 3a of the starting coil 3, and a series circuit of the switching element 4 and the primary coil 3a are connected in parallel. And a voltage doubler rectifier circuit 6 for applying a voltage higher than the output voltage of the DC / DC converter 1 to the starting capacitor 5 based on the switching operation of the H-bridge circuit 2. At the time of starting, a voltage higher than the output voltage of the DC / DC converter 1 is applied to the starting capacitor 5 by the voltage doubler rectifier circuit 6, and when the switching element 4 is turned on, the starting capacitor 5 is instantaneously discharged. A large current flows through the primary coil 3a, a high voltage is generated in the secondary coil 3b, and the discharge lamp starts. Therefore, the highest possible voltage can be generated on the secondary side of the starting coil 3 without increasing the output voltage of the DC / DC converter 1 and without increasing the step-up ratio of the starting coil 3.

It is a circuit diagram of the discharge lamp lighting device concerning one embodiment of the present invention. It is operation | movement explanatory drawing of a circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC / DC converter 2 H bridge circuit 3 Starting coil 3a Primary side coil 3b Secondary side coil 4 Switch element 5 Starting capacitor 6 Double voltage rectifier circuit 8 Double voltage capacitor

Claims (2)

A DC / DC converter that boosts a DC power supply;
An H-bridge circuit for converting the direct current output of the DC / DC converter into alternating current and outputting it to a discharge lamp;
A starting coil for applying a starting voltage to the discharge lamp at the time of starting;
A switch element connected in series to the primary coil of the starting coil;
The switching element and the primary side coil are connected in parallel to each other, and the positive side is connected to the high voltage side output side of the H bridge circuit and the negative side is connected to the GND side output side of the DC / DC converter. A starting capacitor,
A voltage doubler capacitor connected between the high voltage side output and the low voltage side output of the H-bridge circuit;
With
When the pair of switch elements of the H bridge circuit is turned on, the high voltage side output of the H bridge circuit is high level, the low voltage side output is low level, and the starting capacitor and the voltage doubler capacitor are charged,
Thereafter, when the other pair of switch elements of the H bridge circuit are turned on, the high voltage side output of the H bridge circuit is inverted to a low level and the low voltage side output is inverted to a high level, respectively, and the output of the DC / DC converter A voltage obtained by superimposing a voltage and a terminal voltage of the voltage doubler capacitor is applied to the charged starting capacitor.
A discharge lamp lighting device configured as described above .   The discharge lamp lighting device according to claim 1, wherein a boosting ratio of the starting coil is 230/3 or less.

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