JP2879522B2 - Lighting circuit for vehicle discharge lamps - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel lighting circuit for a discharge lamp for a vehicle. More specifically, a lighting circuit for a vehicular discharge lamp that supplies a rectangular wave voltage to the discharge lamp and performs DC lighting of the discharge lamp during a predetermined period at the beginning of lighting of the discharge lamp includes a heavy load (for example, an engine). The use of a starter, etc.) causes a sudden drop in the power supply voltage, and even when this occurs with a cycle shorter than the cycle corresponding to the lighting frequency of the discharge lamp, the polarity switching of the rectangular wave voltage is performed. A lighting circuit for an electric lamp is provided.

[0002]

2. Description of the Related Art For AC lighting of a discharge lamp such as a metal halide lamp, a method of supplying a rectangular wave voltage to the discharge lamp is known.

FIG. 10 shows waveforms of a supply voltage Vout to a discharge lamp and a lamp current IL. A rectangular wave lamp current IL has a zero cross point when its polarity is switched.

[0004] The upper part of FIG. 11 is an enlarged view of a portion of a lamp current waveform in a circle in FIG. 10.

The lighting state of the discharge lamp is unstable for a while after the lamp is turned on. During this time, if the lamp current IL tries to pass through the zero cross point, the polarity is not inverted and the discharge current is not inverted. As shown in the figure, the lamp current I
L becomes zero, and the discharge lamp often goes out.

Therefore, in order to solve such inconveniences, it is conceivable to perform DC lighting of the discharge lamp during a period in which the lighting state of the discharge lamp is unstable.

That is, as shown in FIG. 12, a DC voltage is supplied to the discharge lamp until a period Td (hereinafter, referred to as a “DC lighting period”) elapses from the lighting time shown at t1 until the discharge lamp is turned on. It is only necessary to supply the rectangular wave voltage to the discharge lamp after exiting the unstable lighting state.

[0008]

However, in the above-described control, when the battery voltage, which is the input voltage of the lighting circuit, fluctuates periodically, there is a case where the transition from DC lighting to rectangular wave lighting is not performed. There is a problem that arises.

FIG. 13 schematically shows a change in the lamp current IL when the battery voltage B fluctuates.

When the battery voltage B drops sharply and the lamp current IL decreases and the discharge lamp temporarily goes out, the lighting discriminating circuit provided in the lighting circuit includes:
It is determined that the discharge lamp is in the non-lighting state during the period Tx in FIG. 13, and when it is determined that the lamp current IL has risen and the lamp has restarted after the period Tx, a signal is sent to a predetermined control circuit, and Shift to lighting.

By the way, if the fluctuation of the battery voltage is periodic and the period is shorter than the DC lighting period Td, the period will be continued forever.

That is, as shown in FIG. 14, every time the battery voltage B decreases, the lamp current IL temporarily decreases and instantaneous extinguishing of the discharge lamp occurs, after which the DC lighting period Td elapses. If the battery voltage B decreases beforehand, there is an inconvenience that the lighting does not shift from DC lighting to rectangular wave lighting forever.

[0013]

In order to solve the above-mentioned problems, a lighting circuit for a vehicle discharge lamp according to the present invention converts a DC voltage from a DC power supply circuit into a rectangular AC voltage and supplies the AC voltage to the discharge lamp. A lighting circuit for a vehicle discharge lamp provided with a DC-AC conversion means for performing lighting, a lighting determination circuit for determining whether the discharge lamp is lit or not, and a determination that the discharge lamp is lit by the lighting determination circuit. A DC lighting control circuit for stopping the polarity inversion of the rectangular wave in the DC-AC conversion means for a predetermined period of time and lighting the discharge lamp in a DC manner while the discharge lamp is in the DC lighting state. When it is determined that the discharge lamp is in the non-lighting state, the DC lighting control circuit sends a signal to the DC-AC conversion means to release the DC lighting of the discharge lamp, and then it is determined that the discharge lamp has been relighted. Is obtained by the again perform DC lighting of the discharge lamp waiting after being discriminated by the circuit of the polarity of the rectangular wave is inverted.

[0014]

According to the present invention, the lighting state of the discharge lamp is unstable by stopping the inversion of the polarity of the rectangular wave for a predetermined period of time after it is determined that the discharge lamp has been turned on and directing the discharge lamp to DC lighting. Of course, the discharge lamp can be DC-lit during the period, and when the discharge lamp is determined to be in the non-lighting state during the period when the discharge lamp is DC-lit, the DC lighting control circuit sends a signal to the DC-AC conversion means. The lamp is sent to release the DC lighting of the discharge lamp.After that, the lighting determination circuit determines that the discharge lamp has been re-lit, and then waits for the polarity of the rectangular wave to be reversed, and then performs the DC lighting of the discharge lamp again. By doing so, even when the DC power supply voltage fluctuates in a cycle shorter than the DC lighting period, the polarity of the rectangular wave is inverted, thereby making it possible to prevent the DC lighting from lasting.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the lighting circuit for a vehicle discharge lamp according to the present invention will be described below with reference to the illustrated embodiments. In the illustrated embodiment, the present invention is applied to a lighting circuit 1 of a metal halide lamp for an automobile using a rectangular wave lighting method.

FIG. 1 schematically shows a lighting circuit 1, in which a battery 2 is connected between DC voltage input terminals 3, 3 '.

Reference numerals 4 and 4 'denote DC power supply lines, and a lighting switch 5 is provided on one of the plus lines 4.

Reference numeral 6 denotes a DC booster circuit.
For example, a configuration of a chopper type DC-DC converter is used, and the boosting control is performed by a control circuit described later.

Reference numeral 7 denotes a DC-AC conversion circuit, which is provided at the subsequent stage of the DC boosting circuit 6 and converts a DC voltage sent from the DC boosting circuit 6 into a rectangular wave voltage.

This DC-AC conversion circuit 7 is shown in FIG.
As shown in FIG. 1, the bridge circuit 7A includes a semiconductor switch element 7 (i) (i = 1, 2, 3, 4) indicated by a switch symbol and a drive control circuit 7B. These semiconductor switch elements are paired with the semiconductor switch elements 7 (1) and 7 (4) and the semiconductor switch elements 7 (2) and 7 (3), respectively. Performs reciprocal switching control.

FIG. 2B shows only the semiconductor switching elements 7 (1) and 7 (2) connected in series, and shows the semiconductor switching elements 7 (2) located on the lower stage side of the bridge. ) Is switching-controlled by a signal from the drive control circuit 7B, and the higher-stage semiconductor switch element 7
(1) is configured to be turned on / off reciprocally to the semiconductor switch element 7 (2).

That is, when an FET is used as the semiconductor switch element, the gate of the N-channel MOSFET corresponding to the semiconductor switch element 7 (1) is connected to the source, and the output is taken out from the source. , A predetermined voltage Vcc is supplied to the anode of the diode D7, and the cathode of the diode D7 is connected to the capacitor C7.
And the resistor R7
Connected to the gate via Therefore, when the low-stage semiconductor switch element 7 (2) is in the ON state, the gate-source voltage of the high-stage FET becomes zero, and the F
ET is turned off, during which time the capacitor C7 is charged. Then, the lower-stage semiconductor switch element 7 (2)
Is turned off, the charged voltage of the capacitor C7 is supplied to the gate of the high-stage FET through the resistor R7,
ET is turned on. As described above, the ON state of the high-stage FET is maintained only by the energy of the capacitor C7.

The configuration of the drive control circuit 7B will be described later.

Reference numeral 8 denotes an igniter circuit, which is arranged at a stage subsequent to the DC-AC conversion circuit 7 and has AC output terminals 9 and 9 '.
A metal halide lamp 10 having a rated power of 35 W is connected between them.

Reference numeral 11 denotes a control circuit for controlling the output voltage of the DC booster circuit 6. The output of the DC booster circuit 6 is detected by voltage detecting resistors 12 provided between the output terminals of the DC booster circuit 6. A voltage detection signal corresponding to the voltage is input.

Further, a current detection signal corresponding to the output current of the DC booster circuit 6 is converted into a voltage by a current detection resistor 13 provided on a ground line connecting the DC booster circuit 6 and the DC-AC converter circuit 7. The data is input to the control circuit 11.

In this embodiment, the metal halide lamp 1 is used.
Although a signal corresponding to a lamp voltage or a lamp current of 0 is obtained from the output stage of the DC booster circuit 6, it is a matter of course that a configuration for directly detecting these may be employed.

The control circuit 11 generates a control signal corresponding to the above detection signal and sends it to the DC boosting circuit 6 to control the output voltage, thereby performing power control in accordance with the starting state of the metal halide lamp 10. The start time and the restart time of the lamp are shortened, and the control is promptly shifted to the constant power control. The V (voltage) -I (current) control unit 14 and the PWM (pulse width modulation) control unit 15 Having.

The VI control unit 14 is configured to control the lighting of the metal halide lamp 10 based on a predetermined control curve, and a detection signal relating to the output voltage of the DC booster circuit 6 is output from the voltage detection resistors 12 and 12. When they are sent,
A current command value corresponding to the detection signal is obtained by calculation, and this is compared with a current detection value by the current detection resistor 13 to send a command signal to the PWM control unit 15.

The PWM control unit 15 generates a signal having a variable pulse width in response to a command signal from the VI control unit 14 and sends out the signal as a control signal to the semiconductor switch element of the DC boost circuit 6. It has become.

Reference numeral 16 denotes a lighting discrimination circuit for discriminating the lighting or non-lighting state of the metal halide lamp 10 based on whether the current detected by the current detecting resistor 13 is equal to or greater than a predetermined reference value.

FIG. 3 shows an example of the configuration of the lighting discrimination circuit 16. The binarized output signal is obtained by comparing the amplified voltage of the terminal voltage of the current detection resistor 13 with a predetermined reference voltage. It is configured.

That is, the terminal voltage of the current detection resistor 13 is input to the amplifier 17, and the amplified output and the reference voltage Eref are compared by the comparator 18. When the amplified output is higher than the reference voltage, the metal halide is output. It is determined that the lamp 10 is turned on, and an H (high) signal is output. If the amplified output is equal to or lower than the reference voltage, it is determined that the metal halide lamp 10 is not turned on and L (low) is determined. Output a signal. Then, this lighting determination signal is sent to the subsequent DC lighting control circuit 19.

The DC lighting control circuit 19 performs DC lighting for a predetermined DC lighting period when the lamp is in an unstable state, such as at the beginning of lamp lighting. During this DC lighting period, the DC-AC conversion circuit is used. 7, the inversion of the polarity of the rectangular wave voltage is prohibited, and if the lamp goes out during the DC lighting period, the DC lighting is canceled. Then, even if the lamp is turned on again after the lamp has extinguished during the DC lighting period and before the polarity of the rectangular wave voltage is inverted, control is performed so as not to shift to DC lighting during this time.

FIG. 4 shows an example of the configuration of the DC lighting control circuit 19, which comprises two monostable multivibrators capable of triggering and resetting.

The monostable multivibrators 20, 21 are:
It has an A input terminal for a positive edge trigger, a B input terminal for a negative edge trigger, and a Q output terminal, and T1, T2
Time constant element (capacitor and resistor) externally connected to the terminal
Thus, the width of the output pulse can be set. The CD terminal, which is a reset terminal, is a negative edge input.

The discrimination signal from the lighting discrimination circuit 16 is NOT
The monostable multivibrator 2 at the preceding stage through the gate 22
0 input terminal and monostable multivibrator 2 at the subsequent stage
1 to the B input terminal.

The capacitance of the capacitor 23 and the resistance of the resistor 24 externally connected to the T1 terminal and the T2 terminal of the monostable multivibrator 20 are such that the pulse width of the Q output is a half of the period of the rectangular wave voltage. The period is set so as to be equal to or more than one time.

The Q output of the monostable multivibrator 20 is sent to the B input terminal of the monostable multivibrator 21 via the diode 25. A predetermined power supply voltage Vcc is supplied to the B input terminal and the CD terminal of the monostable multivibrator 20.

In the monostable multivibrator 21, the B input terminal is used, and the pulse width corresponding to the DC lighting period is determined by the capacitance of the capacitor 26 and the resistance of the resistor 27 externally connected to its T1 and T2 terminals. Is set.

Then, the Q output of the monostable multivibrator 21 is sent as an output signal of the DC lighting control circuit 19 to the drive control circuit 7B of the DC-AC conversion circuit 7 via the diode 28.

Reference numerals 29 and 30 denote diodes, and 31 a NOT gate.
A voltage Vcc is applied to the input terminal of the T gate 31. The cathode of the diode 29 is connected to the A input terminal of the monostable multivibrator 20, and the cathode of the diode 30 is connected to the Q output terminal of the monostable multivibrator 21. The output of the NOT gate 31 is connected to the diode 3 connected in reverse to the NOT gate 31.
2 is connected to a CD terminal of the monostable multivibrator 21, and the CD terminal is pulled up by a resistor 33.

The drive control circuit 7B of the bridge circuit 7A
As shown in FIG. 5, the output of the counter 35 includes an oscillating unit 34, a counter 35, and a flip-flop 36. Element 7
(2) and 7 (4) are sent out as control signals.

The basic clock signal generated by the oscillator 34 is sent to the clock input terminal (negative edge) of the counter 35 and the clock input terminal (positive edge) of the flip-flop 36, respectively.

As the counter 35, a ripple carry counter is used. The output (Q10) of the specified number of stages is sent to the D input terminal of the flip-flop 36,
The signal is sent to the reset terminal (R) of the flip-flop 36 via the OT gate 39. The output signal of the DC lighting control circuit 19 is input to the reset terminal (R) of the counter 35, and the Q output of the flip-flop 36 is supplied via the diode 40.

FIG. 6 is a time chart for explaining the operation of the DC lighting control circuit 19 when the metal halide lamp 10 is normally turned on. "So (16)" is an output signal of the lighting discrimination circuit 16, and "Sb" (21) ”is a B input signal of the monostable multivibrator 21, and“ So (2)
1) "is the Q output signal of the monostable multivibrator 21;
“So (35)” indicates an output signal of the counter 35, respectively.

FIG. 7 shows the drive control circuit 7 of the bridge circuit 7A when the output signal of the DC lighting control section is an L signal.
It is a time chart for explaining the operation of B,
“Scl (34)” is a clock signal from the oscillation unit 34,
“S￣cl (34)” is an anti-phase signal of Scl (34),
"So (36)" is the Q output of the flip-flop 36,
“S￣o (36)” indicates the Q bar output of the flip-flop 36, respectively. “So (35)” is an output signal of the counter 35.

By turning on the metal halide lamp 10,
When an H level lighting determination signal is input to the DC lighting control circuit 19, the B input Sb of the monostable multivibrator 21 is input.
(21) falls and the Q output So (21) of the monostable multivibrator 21 during the set DC lighting period.
Becomes the H signal.

Therefore, the counter 35 of the drive control circuit 7B is reset during this time, so that the output So of the counter 35 is
Since (35) is fixed to the L signal and the switching control of the semiconductor switch element of the bridge circuit 7A is not performed, the DC lighting of the metal halide lamp 10 is performed.

After the DC lighting period has elapsed, the Q output So of the monostable multivibrator 21 of the DC lighting control circuit 19 is output.
When (21) becomes the L signal, the reset for the counter 35 is released.

Therefore, the counter 35 outputs a predetermined number of divided outputs of the clock signal to the flip-flop 36
The Q output So (36) of the flip-flop 36 is supplied to the counter 35 via the diode 40.
, The output of the counter 35 is a pulse signal generated instantaneously. This signal is further divided by the flip-flop 37 at the subsequent stage, and the duty cycle is shaped into a 50% rectangular pulse. The Q output and Q bar output of the flip-flop 37 pass through the dead time setting unit 38, and the semiconductor switch elements 7 (2), 7 (7) on the lower stage side of the bridge circuit 7A.
Since these are sent to (4), these semiconductor switching elements are switched almost alternately.

As described above, in the DC lighting control circuit 19,
The DC lighting period is set by the monostable multivibrator 21, and the DC lighting control circuit 1
When the output signal of No. 9 is an H signal, the inversion of the polarity of the rectangular wave is prohibited, and the DC lighting of the metal halide lamp 10 is performed.

FIG. 8 is a time chart for explaining the operation of the DC lighting control circuit 19 when a rapid change in the battery voltage repeatedly occurs in a cycle shorter than the set DC lighting period. FIG. 5 mainly shows the relationship between the fluctuation of the battery voltage and the lamp current, and FIG. 6B shows the time axis of the instantaneous change ts of the battery voltage in FIG. In the figure, "B"
Is the battery voltage, “IL” is the lamp current, and “Scd
(21) "indicates a CD input signal of the monostable multivibrator 21. In addition, So (16), Sb
(21) and So (21) are as described above.

As described above, the metal halide lamp 10
Is turned on shortly after turning on, but when the metal halide lamp 10 temporarily goes out during the DC lighting period as shown by an arrow D in FIG. When the discrimination signal becomes the L signal, the cathodes of the diodes 29 and 30 of the DC lighting control circuit 19 both become H level. Therefore, the input of the NOT gate 31 is at the H level, the output thereof is at the L level, and the CD input of the monostable multivibrator 21 is at the L level, which is reset, so that the Q output signal So (21)
Becomes the L signal. As described above, when this signal is an H signal, So (21) is used as a reset signal for the counter 35 of the drive control circuit 7B. During this time, the DC lighting of the metal halide lamp 10 is performed. It means release of lighting.

When the lighting discrimination signal changes from the H signal to the L signal, the A input of the monostable multivibrator 20 at the preceding stage of the DC lighting control circuit 19 rises, and the
The H signal is output to the output terminal for a period defined by the resistor 23 and the capacitor 24 (a period that is equal to or more than one half and less than one time of the period of the rectangular wave), during which the polarity of the rectangular wave is switched. You.

Then, after the elapse of this period, DC lighting is started. That is, the monostable multivibrator 2 in the preceding stage
The 0 Q output goes to the L level, and the monostable multivibrator 21 at the subsequent stage operates.

As described above, during the period from the time when the lamp goes out to the time when the polarity of the rectangular wave is inverted, control is performed so as not to shift to DC lighting even if the lamp is immediately turned on again.

When the DC lighting is restarted, the DC lighting period is not shortened, and the DC lighting is canceled when the lamp instantaneously goes out during the DC lighting period. As described above, a new DC lighting starts from the time when the waiting period for the polarity inversion of the rectangular wave by the monostable multivibrator 20 at the preceding stage has elapsed, and the preset DC lighting period is always guaranteed.

[0059]

As is apparent from the above description, according to the lighting circuit for a vehicle discharge lamp of the present invention, the inversion of the rectangular wave polarity is stopped for a predetermined period after it is determined that the discharge lamp has been turned on. And direct the discharge lamp to DC lighting,
The discharge lamp can be DC-lit during the period when the lighting state of the discharge lamp is unstable, and when the discharge lamp is determined to be in the non-lighting state during the period when the discharge lamp is DC-lit, the DC After the lighting is released, and after it is determined that the discharge lamp has been re-lit, the DC light of the discharge lamp is performed again after the polarity of the rectangular wave is inverted, thereby reducing the heavy load (engine starter, etc.). It is possible to prevent the DC lighting state from becoming permanent due to the periodic fluctuation of the power supply voltage due to use.

The specific circuit configurations shown in the above embodiments are merely examples for embodying the present invention, and the technical scope of the present invention is interpreted in a limited manner. Not something.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing an outline of a lighting circuit of a vehicular discharge lamp according to the present invention.

FIGS. 2A and 2B are diagrams showing a configuration example of the DC-AC conversion circuit of FIG. 1, wherein FIG. 2A is a diagram showing the entire configuration, and FIG. 2B is a circuit corresponding to a circle surrounded by a dashed line in FIG. FIG. 3 is a diagram showing a specific configuration of a part.

FIG. 3 is a circuit diagram illustrating a configuration example of a lighting determination circuit.

FIG. 4 is a circuit diagram illustrating a configuration example of a DC lighting control circuit.

FIG. 5 is a circuit diagram illustrating a configuration example of a drive control circuit in the DC-AC conversion circuit.

FIG. 6 is a time chart for explaining the operation of the DC lighting control circuit when the discharge lamp is normally lit.

FIG. 7 is a time chart for explaining an operation of the bridge circuit in a state where DC lighting is released.

FIG. 8 is a time chart for explaining the operation of the DC lighting control circuit when a rapid change in the battery voltage repeatedly occurs in a cycle shorter than the set DC lighting period; (B) mainly shows the relationship between the fluctuation of the battery voltage and the lamp current, and (b) shows the state of each part by expanding the time axis for the instant ts of the sudden change in the battery voltage in (a).

FIG. 9 is a time chart for explaining the relationship between the instantaneous extinguishing of the lamp during the DC lighting period and the subsequent DC lighting period.

FIG. 10 shows the supply voltage Vout to the discharge lamp and the lamp current I.
FIG. 6 is a diagram showing each waveform of L.

FIG. 11 is a diagram for describing a zero cross of a lamp current.

FIG. 12 is a diagram illustrating DC lighting of a discharge lamp.

FIG. 13 is a diagram schematically showing a change in lamp current IL when a battery voltage B fluctuates.

FIG. 14 is a diagram for describing the continuation of the DC lighting period that occurs when the battery voltage fluctuates periodically and the cycle is shorter than the DC lighting period.

[Explanation of symbols]

 Reference Signs List 1 lighting circuit for vehicle discharge lamp 2, 6 DC power supply circuit section 7 DC-AC conversion means 10 discharge lamp (metal halide lamp) 16 lighting discrimination circuit 19 DC lighting control circuit

Claims (2)

(57) [Claims] 1. A lighting circuit for a vehicular discharge lamp comprising a DC-AC converter for converting a DC voltage from a DC power supply circuit unit into a rectangular wave AC voltage and supplying the AC voltage to the discharge lamp.
A lighting discriminating circuit for discriminating the lighting or non-lighting state of the discharge lamp, and stopping the polarity inversion of the rectangular wave in the DC-AC converter for a predetermined period after the lighting discriminating circuit determines that the discharge lamp is turned on. A DC lighting control circuit for DC lighting the discharge lamp; and a DC lighting control circuit for controlling the DC-light when the lighting determination circuit determines that the discharge lamp is in a non-lighting state while the discharge lamp is DC lighting. A signal is sent to the AC conversion means to release the DC lighting of the discharge lamp,
After that, the lighting circuit determines that the discharge lamp has been re-lit, and then waits for the polarity of the rectangular wave to be reversed before performing the DC lighting of the discharge lamp again. circuit. 2. A lighting circuit for a discharge lamp for a vehicle according to claim 1, wherein the DC lighting control circuit sends a signal to a DC-AC conversion means to cancel the DC lighting of the discharge lamp, and then the discharge lamp is turned on. A lighting circuit for a vehicular discharge lamp, wherein DC lighting of the discharge lamp is restarted in a predetermined period after re-lighting and the polarity of the rectangular wave is switched.