JPH09120894A - Abnormality detection circuit in power discharge lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect abnormality by using a single integrating means. SOLUTION: A comparator 131 detects the opening of a power discharge light 3, and a comparator 132 detects the short-circuit of the power discharge light 3. A capacitor 121 starts charging when a power source 1 is turned ON, and a comparator 129 suspends the output of a failure judgment signal while a charge voltage Vc reaches at least a forth reference voltage Vs4 (a first specified value). The capacitor 121 is charged toward a third reference voltage Vs3 (a second specified value) when the comparator 131 or the comparator 132 detects the opening or short-circuit ofthe power discharge light 3, and the comparator 129 outputs a failure judgment signal to a PWN 10 when the charge voltage Vc of the capacitor 121 raises the third reference voltage Vs3 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality detection circuit in a discharge lamp lighting device, and more particularly to a discharge lamp lighting device for lighting a discharge lamp such as a metal halide lamp used as a vehicle headlight. The present invention relates to an abnormality detection circuit that detects an abnormality (also referred to as an abnormality in a discharge lamp) in a discharge lamp lighting device such as a disconnection or a short circuit of a wiring between control devices.

[0002]

2. Description of the Related Art Generally, when lighting a discharge lamp, a high voltage pulse is applied to the discharge lamp with an open voltage of several hundreds of volts to shift from glow discharge to arc discharge and start lighting. .

By the way, as the abnormal mode of this type of discharge lamp, there may be a defect in the high-voltage pulse generation circuit, a disconnection of the wiring between the discharge lamp and the control device, a short circuit, etc. It is necessary to promptly stop the generation of the voltage pulse, or promptly stop the power supply to avoid excessive power consumption due to a short circuit.

However, when the discharge lamp is turned on, it is necessary to apply an open circuit voltage of several hundred volts to the discharge lamp as described above, and it is necessary to apply a high voltage pulse in this state. Further, since the discharge lamp has a negative resistance, the discharge voltage immediately after the start of lighting is extremely small, and the discharge voltage thereafter increases with time and stabilizes.

Therefore, when detecting the abnormality of the discharge lamp, for example, when detecting a short circuit of the wiring leading to the discharge lamp, it is effective to detect that the terminal voltage of the discharge lamp is small. Since the discharge voltage immediately after is extremely small, it is necessary to delay the abnormality determination at least during the period from power-on to immediately after the start of lighting.

Further, in detecting the disconnection of the wiring leading to the discharge lamp, it is effective to detect that the terminal voltage of the discharge lamp is a large voltage corresponding to the open voltage. Since the terminal voltage immediately after that is an open circuit voltage of several hundred volts, it is necessary to delay the abnormality determination during the period corresponding to the delay time from power-on to the start of discharge.

Further, in a discharge lamp, the discharge may rarely be interrupted due to a mechanical shock or the like. In such a case, a voltage of several hundreds of volts is applied and a high voltage is applied for prompt relighting. Pulse has to be applied,
Therefore, it is necessary to delay the abnormality determination until the discharge lamp is turned on again.

As described above, when determining the abnormality of the discharge lamp, it is necessary to delay the determination from the time the power is turned on to immediately after the start of lighting, the determination delay for the open detection during stable lighting, and the rapid abnormality determination during short circuit during stable lighting. Therefore, a plurality of timer circuits are required for this.

[0009]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of replacing these timer circuits with an extremely simple circuit including a single integrating means. In addition,
As a conventional abnormality detection circuit in the discharge lamp lighting device,
Japanese Utility Model Publication No. 4-119996, Japanese Utility Model Publication No. 4-11999.
There is one described in Japanese Patent No. 8 and the like.

[0010]

According to a first aspect of the present invention, a single integrating means is provided, and the abnormality determination signal is output during the period from when the integrated value is turned on until the integrated value reaches at least the first predetermined value. The feature is that it is set to grace. Here, the first predetermined value is set to a value at which the output of the abnormality determination signal can be postponed at least until immediately after the discharge lamp starts lighting after the power is turned on.

Therefore, according to the first aspect of the present invention, the abnormality determination is performed by the single integrating means (including the time integration by the capacitor or the pulse counting by the counter) at least during the period from the power-on to the time immediately after the start of lighting. You can grace.

The invention of claim 2 is an example in which a capacitor for performing time integration is adopted as a single integrating means.

The third aspect of the present invention is characterized in that the integral ratio from the first predetermined value to the second predetermined value is varied depending on the abnormal mode. Therefore, if the abnormality mode is discharge lamp open, by setting the integration rate to a small value, it is not necessary to determine an abnormality even if temporary extinguishing occurs during stable lighting, and to prompt re-lighting of the discharge lamp. When the abnormality mode is short-circuiting of the discharge lamp, the integration rate is set to a large value, whereby an abnormality determination can be made immediately and excessive power consumption due to short-circuiting can be avoided.

According to the fourth aspect of the present invention, the abnormality determination is performed when the integrated value reaches the second predetermined value, and the power supply to the discharge lamp is stopped. Therefore, the abnormality detection means when the discharge lamp is opened. It is conceivable that the level of the input side of will decrease and the abnormality detecting means will not be able to detect the abnormality. However, since the integral ratio of the integral value increases even after the integral value reaches the second predetermined value, the abnormality occurs. It is possible to continuously output the abnormality determination signal from the determination means.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a discharge lamp lighting device including an abnormality detection circuit according to an embodiment.

In FIG. 1, 1 is a battery, 2 is a power switch, 3 is a discharge lamp, 10 is a PWM (pulse width modulation circuit), 20 is a DC / DC converter, 30 is a high voltage pulse generation circuit, 40 is an inverter, 50 is a power control circuit,
Reference numeral 60 represents a constant voltage circuit, and 100 represents an abnormality detection circuit.

The DC / DC converter 20 starts its operation when the power switch 2 is turned on, and causes the power MOS transistor 21 to perform a switching operation by the PWM 10 to generate AC power on the secondary side of the transformer 22. The diode 23 and the capacitor 2
The DC voltage is applied to the inverter 40 after being rectified and smoothed by the inverter 4.

The high-voltage pulse generation circuit 30 applies a high-voltage pulse to the discharge lamp 3 at the time of starting the discharge lamp 3 and at the time of extinguishing during stable lighting to start and relight the lamp.

The inverter 40 is the bridge control circuit 4
It is composed of full-bridge connected MOS transistors 41 to 44 which are switched by 6, 6 and 47, and is configured to convert direct current into alternating current and apply it to the discharge lamp 3.

The power control circuit 50 receives the terminal voltage V _L of the discharge lamp 3 detected by the capacitor 24 and the discharge current I _L detected by the current detection resistor 45, and inputs the discharge lamp terminal voltage V _L and the discharge voltage. The PWM 10 is controlled to control the electric power supplied to the discharge lamp 3 based on the current I _L.

The constant voltage circuit 60 converts the voltage of the battery 1 into a constant voltage when the power switch 2 is turned on, and the constant voltage Vc
c is applied to the abnormality detection circuit 100.

The abnormality detection circuit 100 determines whether or not the discharge lamp 3 is abnormal on the basis of the terminal voltage V _L of the discharge lamp 3 detected by the capacitor 24, and supplies power to the discharge lamp 3 when the abnormality is determined. The PWM 10 is controlled so as to stop.

Specifically, the abnormality detection circuit 100 divides the terminal voltage V _L of the discharge lamp 3 and divides the divided voltage V _L1 into the positive input terminal of the comparator 131 and the comparator 13.
Voltage dividing resistor 11 to be input to the negative input terminal of 2 respectively
9, 133. On the negative input terminal side of the comparator 131 and the positive input terminal side of the comparator 132,
The first reference voltage V _S1 and the second reference voltage V _{S2, respectively.}
A constant voltage circuit 60 for inputting (<first reference voltage V _S1 ).
Voltage dividing resistors 116 to 118 for dividing the constant voltage Vcc by
Is connected. Here, the first reference voltage V _S1 is set to a value smaller than the voltage value obtained by dividing the open circuit voltage of the discharge lamp 3 by the voltage dividing resistors 119 and 133, while the second reference voltage V _S2 is Short voltage of discharge lamp 3 is divided by voltage dividing resistor 1
It is set to a value larger than the voltage value divided by 19, 133, and the comparator 131 outputs a Hi level when the discharge lamp is open, while the comparator 13
2 is configured to output a Hi level when the discharge lamp 3 is short-circuited.

A series circuit of a resistor 107 and a capacitor 121 is connected between the output terminals of the constant voltage circuit Vcc. The capacitor 121 includes a transistor 123.
And a resistor 108 having a resistance value substantially equal to the resistance value of the resistor 107 are connected in parallel. The transistor 123 performs switching operation according to the operation of the transistor 124 which performs switching operation according to the output of the comparator 131.

A series circuit composed of a transistor 126 and a resistor 110 is connected in parallel to the resistor 107 in order to change the charging time constant of the capacitor 121. The transistor 126 performs a switching operation according to the switching operation of the transistor 125 and the switching operation of the transistor 127. Here, the transistor 125 is the comparator 12 described later.
The switching operation is performed according to the output of 9.
On the other hand, the transistor 127 is the comparator 1 described later.
The switching operation is performed according to the output operation of the transistor 128 and the output operation of the comparator 132.

The positive electrode of the capacitor 121 is connected to the positive input terminal of the comparator 129 and the comparator 130.
The negative input terminals of are connected respectively. A third reference voltage V _S3 (corresponding to the second predetermined value according to the invention) and a fourth reference voltage V are respectively provided on the negative input terminal side of the comparator 129 and the positive input terminal side of the comparator 130. _S4 (corresponding to the first predetermined value in the present invention, the third
_Is smaller than the reference voltage V _S3 . ), The voltage dividing resistor 104 for dividing the constant voltage Vcc by the constant voltage circuit 60 to
106 is connected. The PWM 10 is connected to the output terminal of the comparator 129. Note that reference numeral 10
1 to 103, 109, 111 to 115 are resistors,
Reference numeral 120 represents a diode.

Next, an example of the operation of the discharge lamp lighting device configured as described above will be described by classifying it according to the abnormal mode of the discharge lamp and the time when the abnormality occurs.

When the discharge lamp is opened during stable lighting of the discharge lamp (FIG. 2) When the power switch 2 is turned on at time t ₀ , the PWM 10
Starts the operation, and the power M of the DC / DC converter 20
The OS transistor 21 is driven and AC power is generated on the secondary side of the transformer 22. This AC power is diode 2
It is rectified and smoothed by the capacitor 3 and the capacitor 24 and supplied to the inverter 40. In the inverter 40, the DC voltage (open circuit voltage) _VL of several hundred volts of this capacitor 24 is used.
Is converted into alternating current and applied to the discharge lamp 3. Then, when a high voltage pulse is generated from the high voltage pulse generation circuit 30, the discharge lamp 3 starts discharging. The power control circuit 50 calculates the power to be applied to the discharge lamp 3 based on the output signal (discharge current) I _L and (terminal voltage of the discharge lamp 3) the terminal voltage of the capacitor 24 V _L of the current sensing resistor 45, PWM10 To control.

Further, when the power switch 2 is turned on, the constant voltage circuit 60 generates a constant voltage Vcc, and the abnormality detection circuit 100
A constant voltage Vcc is applied to.

In the abnormality detection circuit 100, when the power is turned on, the capacitor 121 is not charged, so the output of the comparator 129 is at Lo level, and the abnormality determination signal is not output to the PWM 10. When the power is turned on, the transistor 125 is off because the output of the comparator 129 is at the Lo level, and the transistor 128 is on and the transistor 127 is off because the output of the comparator 130 is at the Hi level. Therefore, the transistor 126 is off.
Therefore, the capacitor 121 is charged with a relatively large charging time constant by the resistor 107.

After that, when the terminal voltage V _L of the capacitor 24 rises to an open circuit voltage of several hundreds of volts and a high voltage pulse is generated from the high voltage pulse generation circuit 30, the discharge lamp 3 starts lighting and the discharge lamp 3 operates. The discharge causes the terminal voltage V _L of the capacitor 24 to drop instantaneously. At this point,
Since the charging voltage Vc of the capacitor 121 is still smaller than the fourth reference voltage V _S4 of the comparator 130, the output of the comparator 129 is Lo level and the abnormality determination signal is not output to the PWM 10. Further, at this time, since the output of the comparator 129 is at the Lo level as described above, the transistor 128 is still on,
Since the transistor 126 is off and the output of the comparator 131 is inverted to the Lo level, the transistor 124 is switched off and the transistor 123 is switched on. Therefore, from the time when the discharge lamp 3 starts lighting, the capacitor 121 has the resistors 107 and 108.
1/2 the constant voltage Vcc with a relatively large charging time constant due to
The battery is charged toward the voltage value of, that is, 1/2 Vcc (third predetermined value).

After that, at time t ₁ , when the charging voltage Vc of the capacitor 121 rises to the fourth reference voltage V _S4 , the output of the comparator 130 is inverted to the Lo level, and the transistor 128 is switched off. But,
The output of the comparator 132 at this time is at the Lo level because the discharge lamp 3 is in the stable lighting state, and therefore the transistor 127 is still off and the transistor 126 is still off. Therefore, the capacitor 12
Even after the charging voltage Vc of 1 has risen to the fourth reference voltage V _S4 , the capacitor 121 is charged toward 1/2 Vcc with a relatively large charging time constant due to the resistors 107 and 108.

After that, the charging voltage Vc of the capacitor 121 is
Rises to 1/2 Vcc, the capacitor 121 stops charging and the charging voltage Vc of the capacitor 121 becomes 1/2
It is held at Vcc.

Then, at time t_Two , The discharge lamp 3 is abnormal.
Terminal voltage V of capacitor 24 _L Rises to open circuit voltage
Then, the output of the comparator 131 is inverted to Hi level.
I do. Therefore, the transistor 124 is turned on and transitioned.
The switch 123 switches off and the capacitor 1
Reference numeral 21 is a charging time constant by the resistor 107, which is directed to the constant voltage Vcc.
It will be charged once.

After that, at time t ₃ , when the charging voltage Vc of the capacitor 121 rises to the third reference voltage V _S3 , the output of the comparator 129 is inverted to the Hi level. That is, the abnormality determination signal is output to the PWM 10. In PWM10, when this abnormality determination signal is input,
The power MOS transistor 21 is held in the off state, and the power supply to the discharge lamp 3 is stopped.

When the output of the comparator 129 is inverted to the Hi level as described above, the transistor 125 is turned on and the transistor 126 is turned on, and the capacitor 121 has a constant voltage with a very small charging time constant of the resistors 107 and 110. It is rapidly charged to Vcc. As a result, the terminal voltage V _L of the capacitor 24 decreases due to the stop of the power supply to the discharge lamp 3, and the comparator 13
Even if the output of No. 1 is inverted to the Lo level and the transistor 123 is turned on to form the discharge path of the capacitor 121, the terminal voltage Vc of the capacitor 121 can be held at a substantially constant voltage Vcc, so the output of the comparator 129 is at the Hi level. , That is, the comparator 129 can continue to output the abnormality determination signal.

As described above, in the period T ₁ from the power-on time t ₀ to the open generation time t ₂ , the terminal voltage V _L of the capacitor 24 rises to the same open voltage as when the discharge lamp is open immediately before the start of discharge. In some cases, the abnormality determination signal is not output, and when the terminal voltage V _L of the capacitor 24 drops to a relatively small voltage when the discharge lamp is short-circuited immediately after the start of discharge, the abnormality determination signal is output. Therefore, it is possible to prevent erroneous abnormality determination.

Further, the discharge lamp 3 may be temporarily extinguished at the time of stable lighting due to a mechanical shock or the like.
_{Even if the} discharge lamp 3 opens in ₂ , the abnormality determination signal is not output instantaneously, and the grace period T ₂ for outputting the abnormality determination signal is set.
Since the above is provided, the terminal voltage V _L of the capacitor 24 and the high voltage pulse of the high voltage pulse generation circuit 30 can prompt the relighting of the discharge lamp 3.

When the discharge lamp is short-circuited during stable lighting of the discharge lamp (FIG. 3) When the discharge lamp 3 is short-circuited at time t ₂ during stable lighting of the discharge lamp 3, the terminal voltage V _L of the capacitor 24 becomes extremely small. The output of the comparator 132 is inverted to the Hi level. For this reason, the transistor 128 may be maintained in the off state, so that the transistor 1
27 is turned on, the transistor 126 is turned on, and the capacitor 121 is rapidly charged to the constant voltage Vcc with a very small charging time constant by the resistors 107 and 110. During this charging, time t ₃ extremely close to the point in time t ₂
Therefore, the terminal voltage Vc of the capacitor 121 is the third reference voltage Vc.
_When rising to _S3 , the output of the comparator 129 is inverted to the Hi level, and the abnormality determination signal is output to the PWM10. After the output of the abnormality determination signal, the same operation as when the discharge lamp is opened as described above can be performed, and the power supply to the discharge lamp 3 can be reliably stopped.

As described above, when the discharge lamp is short-circuited, the abnormality determination signal is instantaneously output to the PWM 10, so that excessive power consumption due to the occurrence of the short-circuit can be avoided.

Although not shown, when the discharge lamp 3 is already open when the power is turned on, the terminal voltage V _L of the capacitor 24 is held at the open voltage, so the output of the comparator 131 is Hi. The level is held, the transistor 124 is held in the on state, the transistor 123 is held in the off state, and the capacitor 121 is charged toward the constant voltage Vcc with the charging time constant of the resistor 107. The charging voltage Vc of the capacitor 121 is the third
When the voltage rises to the reference voltage V _S3 of
An abnormality determination signal is output from 9, and the power supply to the discharge lamp 3 is stopped.

Although not shown, when the discharge lamp 3 is already short-circuited when the power is turned on, the terminal voltage V _L of the capacitor 24 is held at an extremely small voltage, so that the output of the comparator 132 is It is held at Hi level. Therefore, at the time point t ₁ shown in FIG.
The output of 30 is inverted to Lo level and the transistor 128
When the transistor is switched off, the transistor 127
Is turned on, the transistor 126 is turned on, the capacitor 121 is rapidly charged toward the constant voltage Vcc with an extremely small charging time constant by the resistors 107 and 110, and the charging voltage Vc of the capacitor 121 is the third voltage.
When the voltage rises to the reference voltage V _S3 of
An abnormality determination signal is output from 9, and the power supply to the discharge lamp 3 is stopped.

In the above-described embodiment, the capacitor is used as the integrating means to perform the time integration, but as an alternative to this, a counter may be used to count the pulses.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a discharge lamp lighting device including an abnormality detection circuit according to an embodiment.

FIG. 2 is a waveform chart showing an example of the operation.

FIG. 3 is a waveform diagram showing another operation example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Battery (power supply) 2 Power switch 3 Discharge lamp 100 Abnormality detection circuits 131 and 132 Comparator 129 that is a main part of abnormality detection means 129 Comparator that is a main part of abnormality determination means 121 Capacitor (integration means) 110, 126 Integration rate A resistance and a transistor that form the main part of the increasing means Vc Integrated value V _S3 Third reference voltage (second predetermined value) V _S4 Fourth reference voltage (first predetermined value) 1/2 Vcc Third predetermined value

Claims (4)

[Claims] 1. An abnormality detecting means for detecting an abnormality in a discharge lamp lighting device, and an integration operation that starts an integration operation when a power is turned on and continues until the integration value reaches at least a first predetermined value. While continuing, when an abnormality detection signal is input from the abnormality detecting means, an integrating means that restarts or continues the integrating operation, and a period until the integrated value of the integrating means reaches the first predetermined value. A second delay in which the output of the abnormality determination signal is delayed and the integral value of the integrator is larger than the first predetermined value.
An abnormality detection circuit that outputs an abnormality determination signal when the predetermined value of is reached, the abnormality detection circuit in the discharge lamp lighting device. 2. An abnormality detecting means for detecting an abnormality in the discharge lamp lighting device, and an integrating operation which starts the integrating operation when the power is turned on and which continues until the integrated value reaches at least a first predetermined value. When the abnormality detection signal is not input from the abnormality detection means after the integrated value reaches the first predetermined value while continuing, the integrated value is set to a third predetermined value larger than the first predetermined value. On the other hand, when an abnormality detection signal is input from the abnormality detection means, the integration means restarts or continues the integration operation, and until the integrated value of the integration means reaches the first predetermined value. A second delay in which the output of the abnormality determination signal is delayed and the integral value of the integrating means is larger than the third predetermined value.
An abnormality detection circuit that outputs an abnormality determination signal when the predetermined value of is reached, the abnormality detection circuit in the discharge lamp lighting device. 3. The integrator means performs an integration operation in which an integration ratio from the first predetermined value to the second predetermined value is different depending on an abnormal mode. An abnormality detection circuit in the discharge lamp lighting device according to. 4. An integration rate increasing means for further increasing an integration rate in the integration operation of the integrating means when the integrated value of the integrating means reaches the second predetermined value. An abnormality detection circuit in the discharge lamp lighting device according to any one of 1 to 3.