JPH0545994U - LC resonance type drive circuit of discharge lamp - Google Patents

Abstract

(57) [Abstract] [Purpose] Avoiding a situation where the driving frequency is close to the acoustic resonance frequency is avoided by making a temporal transition of the driving frequency, and the lit HiD lamp is extinguished and extinguished. Prevent it from becoming. An LC of a discharge lamp having a feedback loop including an LC resonance circuit, controlling an output oscillation frequency by a resonance frequency output of the LC resonance circuit fed back by the feedback loop, and driving the discharge lamp by the output. In the resonance type drive circuit, the LC resonance circuit is a frequency transition type LC resonance circuit in which the resonance frequency transits with time.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an LC resonance type drive circuit of a discharge lamp, and more particularly to an LC resonance type drive circuit of a discharge lamp in which the resonance frequency of the LC resonance circuit transits with time.

[0002]

[Prior Art]

 A conventional LC resonance type drive circuit for a discharge lamp is shown in FIG. 4, for example.

The LC resonance type drive circuit of the discharge lamp shown in the figure is a typical circuit as an LC resonance type discharge lamp drive circuit.

The LC resonance type drive circuit 51 of this discharge lamp is composed of a driver circuit 52, an LC series resonance circuit 53, and a feedback circuit 54.

The driver circuit 52 includes a magnetic saturation type driver transformer T1, power transistors Q1 and Q2, and a non-saturation type output transformer T2. The driver transformer T1 is provided with a primary coil L1 and secondary coils L20 and L21 wound in the opposite direction to the primary coil L1. The secondary coil L20 and the secondary coil L21 are connected in series. A drive current circuit 56 1 is connected to a connection point between the secondary coil L20 and the secondary coil L21. The base terminal of the power transistor Q1 is connected to one terminal of the secondary coil L20. The base terminal of the power transistor Q2 is connected to one terminal of the secondary coil L21.

The emitter terminals of the power transistor Q1 and the power transistor Q2 are both connected to the ground line.

The output transformer T2 is provided with primary side coils L10 and L11 and a secondary side coil L02 wound in the same direction as the primary side coils L10 and L11.

The primary coil L10 and the primary coil L11 are connected in series. The collector terminal of the power transistor Q1 is connected to one terminal of the primary coil L10. The collector terminal of the power transistor Q2 is connected to one terminal of the primary coil L11. The drive current circuit 56 is connected to a connection point between the primary side coil L10 and the primary side coil L11.

The drive current circuit 56 is provided with a switch 56b for supplying the DC power generated by the battery 56a to the connection point.

One terminal of the secondary coil L 02 is connected to the LC series resonance circuit 53. On the other hand, the other terminal is connected to one terminal of the primary coil L1 of the driver transformer T1. The LC series resonance circuit 53 is composed of a series circuit of a capacitor C1 and a capacitor C2 and a coil 53a, and a HiD lamp 55 is connected to both ends of the capacitor C2.

The capacity of the capacitor C2 is sufficiently smaller than the capacity of the capacitor C1.

The feedback circuit 54 is connected to one terminal of the capacitor C2 and the other terminal of the primary coil L1 of the driver transformer T1.

Next, the operation of the LC resonance type drive circuit 51 of this discharge lamp will be described.

When the switch 56b of the drive current circuit 56 is closed, either the power transistor Q1 or Q2 is turned on. When the power transistor Q1 is turned on, the current IC1 flows through the primary coil L10 of the output transformer T2, and as a result, an electromotive force in the direction indicated by the solid line is generated in the secondary coil L02 of the output transformer T2. This electromotive force is fed back to the primary coil L1 of the driver transformer T1, and this time turns on the power transistor Q2. As a result, IC2 flows through the primary coil L11 of the output transformer T2, and electromotive force in the direction indicated by the broken line is generated in the secondary coil L02 of the output transformer T2. This electromotive force is supplied to the LC series resonance circuit 53 and further fed back to the driver transformer T1. Thereafter, the power transistors Q1 and Q2 are repeatedly turned on / off alternately, and oscillation is started at a resonance frequency determined by the capacitors C1 and C2 of the LC series resonance circuit 53 and the inductance of the coil 53a.

Since the capacity of the capacitor C2 is sufficiently smaller than the capacity of the capacitor C1, the terminal voltage of the capacitor C2 becomes large in the resonance state. Since the input impedance of the HiD lamp is large at the time of starting, a high voltage of about 10 KV is applied to the HiD lamp 55, and the HiD lamp 55 starts discharging.

After the discharge is started, the input impedance of the HiD lamp 55 becomes extremely small, so that the capacitor C2 becomes close to a short-circuited state, and thereafter, the driving determined by the capacitor C1 and the inductance of the coil 53a. The oscillation continues at the frequency f.

The frequency of mechanical vibration generated in the discharge gas or arc inside the HiD lamp by the electromagnetic force due to the supplied current approaches the frequency unique to the HiD lamp, which is determined by the size of the arc or the gas pressure. , The vibration is increased by resonance. The frequency unique to the HiD lamp in this case is called the acoustic resonance frequency, and when electromagnetic mechanical vibration generated in the discharge gas or arc is increased, the arc bends or extinguishes. .. Therefore, the drive frequency f is selected in advance so as not to match the acoustic resonance frequency of the HiD lamp 55.

[0018]

[Problems to be solved by the device]

 However, in such a conventional LC resonance type drive circuit for a HiD lamp, the drive frequency is constant, whereas the acoustic resonance frequency of the HiD lamp is not uniform in the characteristics of the HiD lamp or changes with time. Therefore, if the acoustic resonance frequency approaches the driving frequency, electromagnetic mechanical vibration generated in the discharge gas is increased and the lit HiD lamp is extinguished. There was a problem that it disappeared.

The present invention has been made by paying attention to such a conventional problem, and the drive frequency is brought close to the acoustic resonance frequency by changing the drive frequency temporally. The purpose is to avoid and solve the above problems.

[0020]

[Means for Solving the Problems]

 The LC resonance type drive circuit of the discharge lamp of the present invention has a feedback loop including an LC resonance circuit, and controls the output oscillation frequency by the resonance frequency output of the LC resonance circuit fed back by the feedback loop. In the LC resonance type drive circuit of the discharge lamp for driving and lighting the discharge lamp, the LC resonance circuit is a frequency transition type LC resonance circuit in which the resonance frequency transits with time.

[0021]

In the LC resonance type drive circuit of the discharge lamp according to the present invention, the resonance frequency is temporally transited by the frequency transition type LC resonance circuit, and the output oscillation frequency is controlled to transit temporally. To drive the discharge lamp. Therefore, even if the acoustic resonance frequency of the discharge lamp changes, the output oscillation frequency that drives the discharge lamp constantly changes over time, so that the acoustic resonance frequency and the output oscillation frequency are close to each other, and It is possible to prevent the state from being maintained, and to prevent the discharge lamp that had been lit from being extinguished by being extinguished.

[0022]

【Example】

 The invention will be described below with reference to the drawings. FIG. 1 is an electric circuit diagram showing an embodiment of the present invention. In this figure, parts that are the same as or equivalent to those in FIG.

The LC resonance type drive circuit 1 of this discharge lamp is provided with an LC series resonance circuit 7. In the LC series resonance circuit 7, a secondary coil L32 of an inductance adjusting transformer T3 is connected in series to a series circuit of a capacitor C1, a capacitor C2 and a coil 53a.

One terminal of the primary coil L31 of the inductance varying transformer T3 is connected to one terminal of the secondary coil L02 of the output transformer T2. The inductance varying transformer T3 is provided with secondary coils L32 and L33 wound in the same direction as the primary coil L32. The secondary coils L32 and L33 are connected in series, and the connection point is connected to the ground line.

One terminal of the secondary coil L32 is connected to the drain terminal of the transistor Q3. One terminal of the secondary coil L33 is connected to the drain terminal of the transistor Q4. The source terminals of the transistors Q3 and Q4 are connected to the ground line. The gate terminals of the transistor Q3 and the transistor Q4 are commonly connected and further connected to the AC power supply Ef. A direct current power source Eb is connected in series with the alternating current power source Ef. The negative terminal of the DC power source Eb is connected to the ground line.

Next, the operation will be described.

The driving frequency f after the HiD lamp 5 is turned on, that is, the resonance frequency of the LC series resonance circuit 7 after the HiD lamp 5 is turned on, is determined by the inductance of the capacitor C1 and the coil 53a and the transformer for varying the inductance. It is the inductance of the primary coil L31 of T3. Therefore, if the inductance of the primary coil L31 is changed, the resonance frequency of the LC series resonance circuit changes, and the drive frequency f changes with time.

The principle of changing the drive frequency f by changing the inductance of the primary coil L31 will be described below. FIG. 2 shows an equivalent circuit when the inductance varying transformer T3 side is viewed from both ends of the primary coil L31. As shown in FIG. 2, it can be represented as a parallel circuit of the self-inductance Lo of the primary coil L31 and the internal resistance R of the transistor Q3 or the transistor Q4. The impedance Zab of this equivalent circuit has a winding ratio n of 1.

[0029]

[Equation 1]

Can be represented by The locus drawn by the impedance vector Za b when the internal resistance R is changed from 0 to infinity can be represented by FIG. That is, when the internal resistance R is infinite, the impedance vector Zab becomes jωLo and only the reactance component of the primary coil L31. When the internal resistance R is ωLo

[0031]

[Equation 2]

The reactance component in this case is jωLo / 2, which is half. When the internal resistance R is 0, the impedance vector Zab becomes zero. As described above, the equivalent inductance of the impedance Zab changes from Lo to zero with respect to the change of the internal resistance R of the transistor Q3 or the transistor Q4.

The internal resistance R of the transistor Q3 or the transistor Q4 can be changed by the bias applied to the gates of the transistors Q3 and Q4 by the AC power supply Ef and the DC power supply Eb.

Therefore, in the circuit configuration shown in FIG. 2, when the bias applied to the gates of the transistors Q3 and Q4 is changed by the AC power supply Ef and the DC power supply Eb, the transistor in response to the current in the broken line direction The internal resistance of Q3 acts, and the internal resistance of the transistor Q4 acts on the current in the direction shown by the solid line. By changing the internal resistance R, the drive frequency transitions and the repetition cycle (sweep frequency) ) Can also be changed.

In this embodiment, since the transistors Q3 and Q4 are provided symmetrically with respect to the secondary coils L32 and L33, it is necessary to use transistors Q3 and transistors Q4 having uniform characteristics. Is.

[0036]

[Effect of the device]

 As described above, according to the present invention, since the configuration is provided with the frequency transition type LC resonance circuit in which the resonance frequency transits in time, the acoustic resonance frequency and the output oscillation frequency are close to each other, and It is possible to prevent the discharge lamp from being maintained, and to prevent the discharge lamp that had been lit from being extinguished by being extinguished.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of an LC resonance type drive circuit of a discharge lamp of the present invention.

FIG. 2 is an equivalent circuit diagram when the inductance variable transformer T3 side is viewed from the primary side coil L31.

FIG. 3 is a locus diagram drawn by an impedance vector Zab.

FIG. 4 is an electric circuit diagram showing an LC resonance type drive circuit of a conventional discharge lamp.

[Explanation of symbols]

 1 LC resonance type drive circuit for discharge lamp T3 Inductance changing transformer L31 Primary coil L32, L33 Secondary coil Q3, Q4 Transistor Ef AC power supply Eb DC power supply

Claims (1)

[Scope of utility model registration request] 1. A discharge lamp having a feedback loop including an LC resonance circuit, wherein an output oscillation frequency is controlled by a resonance frequency output of the LC resonance circuit fed back by the feedback loop, and a discharge lamp is driven and lit by the output. In the LC resonance type drive circuit, the LC resonance circuit is a frequency transition type LC whose resonance frequency is temporally changed.
An LC resonance type drive circuit for a discharge lamp, which is a resonance circuit.