JPH08255690A - Discharge lamp lighting circuit - Google Patents

Abstract

PURPOSE: To control the acceptance or declining of power supply to a discharge lamp so that the discharge lamp can be lighted as much as possible with respect to a temporary abnormality cause. CONSTITUTION: A power source interrupting relay circuit 6 is provided between a battery 2 and a DC booster circuit 7 in a lighting circuit 1, and the acceptance or declining of power supply to a discharge lamp 11 is controlled by the opening and closing of a relay contact 6a. When an abnormal state based on a permanent abnormality cause for a circuit part situated on the discharge lamp 11 side seen from the power source interrupting relay circuit 6 or the discharge lamp 11 is detected by an abnormality judging circuit 22 or an output current abnormality detecting circuit 26, the power supply to the discharge lamp 11 is interrupted by the power source interrupting relay circuit 6, and this state is held. When an abnormal state based on a temporary abnormality cause for battery voltage is detected by a low voltage reset circuit 23 or an overvoltage detecting circuit 24, the power supply to the discharge lamp 11 is temporarily stopped, and when the battery voltage is thereafter returned to the normal range, the power supply to the discharge lamp 11 is restarted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting circuit for detecting the occurrence of an abnormal state in a discharge lamp, a lighting circuit and its power supply and stopping the power supply to the discharge lamp.

[0002]

2. Description of the Related Art For the lighting of a small discharge lamp (for example, a metal halide lamp) which has recently been attracting attention as a light source for a vehicle, some kind of circuit protection measure is taken because the voltage supplied to the discharge lamp is high. There is a need.

For example, an abnormality detection circuit for detecting an abnormality in the discharge lamp or the lighting circuit or an abnormality in the power source of the lighting circuit is provided, and when the abnormality is detected, the discharge lamp is supplied with power at the next power source. There is known a circuit provided with a means for shutting it off until it is turned on.

[0004]

However, regardless of the cause of the abnormality, the power supply to the discharge lamp is uniformly cut off when an abnormality is detected, and this cutoff state is maintained until the next power-on. However, there is a problem that the electric power is not supplied to the discharge lamp even when the normal state is recovered after that.

For example, when the power supply voltage supplied to the lighting circuit is temporarily lowered to a predetermined value or less, the power supply to the discharge lamp is cut off, and this state is maintained until the next power supply. Therefore, even if the power supply voltage value returns to the normal range due to the subsequent recovery of the power supply voltage, the discharge lamp is not lit. Therefore, the adverse effects caused by such a discharge lamp off state (for example, a discharge lamp lighting circuit When applied to a vehicular lamp, the driver of the vehicle may be at risk of traveling in the dark.).

Therefore, an object of the present invention is to control permission / prohibition of power supply to the discharge lamp so as to light the discharge lamp as much as possible for a temporary cause of abnormality.

[0007]

In order to solve the above-mentioned problems, the discharge lamp lighting circuit of the present invention is based on a permanent abnormality cause of the circuit section or the discharge lamp located on the discharge lamp side as seen from the breaking means. When the abnormal state is detected by the abnormality detecting means, the shutoff means shuts off the power supply to the discharge lamp and maintains this state, and is located on the power source side of the lighting circuit or the shutoff means. When the abnormal state due to the temporary cause of abnormality in the circuit section is detected by the abnormality detecting means, the shut-off means temporarily stops the power supply to the discharge lamp and then releases it when returning to the normal state. The power supply to the electric light is restarted.

According to the present invention, the power supply to the discharge lamp is cut off and kept for the cause of permanent abnormality,
Regarding the temporary cause of the abnormality, the power supply to the discharge lamp is temporarily stopped, and the power supply to the discharge lamp is restarted when returning to the normal state.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the discharge lamp lighting circuit of the present invention will be described below with reference to the illustrated embodiments.

(A. Outline of Configuration) [FIG. 1] The lighting circuit 1 will be described by dividing it into three parts: a power supply system for a lamp, a lighting control system, and a circuit protection system.

(A-1. Power feeding system) 1 is a lighting circuit.

A battery 2 is connected between the DC voltage input terminals 3 and 3 '.

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

Reference numeral 6a is a relay contact, and the plus line 4
It is provided in series with the lighting switch 5 above.
The relay contact 6a is opened and closed by a power cutoff relay circuit described later.

Reference numeral 7 is a DC boosting circuit, the positive side input terminal of which is connected to the output side terminal of the relay contact 6a, and the other input terminal (ground side) of which is connected to the DC voltage input terminal 3 '. The DC boosting circuit 7 is a circuit for boosting the battery voltage, and the boosting control is performed by a control circuit described later.

Reference numeral 8 denotes a high-frequency booster circuit, which is provided in the subsequent stage of the DC booster circuit 7 and is a circuit for converting the DC voltage from the DC booster circuit 7 into a sine wave AC voltage. As the high-frequency booster circuit 8, for example, a push-pull type self-excited inverter circuit is used.

Reference numeral 9 denotes an igniter circuit, which is arranged in the latter stage of the high frequency booster circuit 8 and has its AC output terminals 10 and 1
Between 0 ', metal halide lamp 11 with rated power of 35W
Is connected.

(A-2. Lighting control system) 12 is a control circuit for controlling the output voltage of the DC boost circuit 7, and
Voltage dividing resistors 13 and 1 provided between output terminals of the booster circuit 7.
A voltage detection signal corresponding to the output voltage of the DC booster circuit 7 detected by 3 '(this is referred to as " _VO ") is input. Further, the current detecting resistor 14 provided on the ground line connecting the DC boosting circuit 7 and the high frequency boosting circuit 8
The output current of the DC booster circuit 7 (which "I _O"
It is written. The current detection signal corresponding to () is input to the control circuit 12 via the amplifier 15 in a voltage-converted form. Then, the control circuit 12 generates a control signal (which will be referred to as “P _S ”) corresponding to these detection signals, and the DC boost circuit 7 generates the control signal via the gate drive circuit 16.
To control the output voltage.

The control circuit 12 includes a timer circuit 1
The output voltage V _O of the DC boost circuit 7 is input via
When a predetermined time corresponding to the extinguishing time of the lamp elapses from the start of lighting the lamp, the control is switched to the constant power control of the lamp.

Reference numeral 18 is a supply voltage drop detecting circuit, in which a voltage (hereinafter referred to as "+ B") applied to a power supply terminal 19 taken out from the output side terminal of the relay contact 6a through a diode is below a predetermined value. When this happens, a signal is sent to the control circuit 12 to control the lighting of the metal halide lamp 11 with a control power smaller than the rated power.

Reference numeral 20 denotes a lighting / non-lighting detection circuit, which judges whether or not the metal halide lamp 11 is lit depending on whether or not the output of the amplifier 15 is at a predetermined level or higher, and detects the detection signal according to the judgment result. "S ₂₀ ") is output.

Reference numeral 21 denotes an idle period control section, which is related to lighting control when the voltage applied to the DC voltage input terminals 3, 3'has dropped below a predetermined value. That is, when the lamp non-lighting detection signal S ₂₀ is received from the lighting / non-lighting detection circuit 20, it is determined whether the power supply voltage B is equal to or lower than a predetermined value, and when the voltage B is equal to or lower than the predetermined value, Is the control circuit 12
A signal (hereinafter referred to as “S ₂₁ ”) is sent to control the pause period of the control pulse P _{S to change} the upper limit value of the output voltage V _O of the DC booster circuit 7. Then, during this time, the signal for temporarily stopping the operation of the supply voltage drop detection circuit 18 (this referred to as _"S'21".)
Is sent to the supply voltage drop detection circuit 18.

(A-3. Circuit protection system) 6 is a relay circuit for shutting off the power source, and is used for a circuit in the subsequent stage (that is,
It is provided so as to cut off the supply of the battery voltage to the DC booster circuit 7 and the circuits thereafter. That is, when the power cutoff relay circuit 6 receives signals from an abnormality determination circuit, a low voltage reset circuit, an overvoltage detection circuit, and an output current abnormality detection circuit, which will be described later, the internal relay is turned off to open the relay contact 6a. Works like.

Reference numeral 22 denotes an abnormality judging circuit, which is between the judgment reference value of the output current corresponding to the output voltage V _O of the DC boosting circuit 7 and the signal level corresponding to the output current of the DC boosting circuit 7 from the amplifier 15. It is determined whether or not the circuit has fallen into an abnormal state based on the magnitude relation, and the control signal to the power cutoff relay circuit 6 is sent out upon receiving the detection signal S ₂₀ from the lighting / non-lighting detection circuit 20. There is. Examples of the abnormal state of the circuit include abnormal lighting of the metal halide lamp 11 (a short circuit or an open state of the lamp) and a case where the high-frequency booster circuit 8 is opened at the output stage. When the abnormality determination circuit 22 detects an abnormal state of such a circuit, it sends a signal to the power cutoff relay circuit 6 to cut off the supply of the power supply voltage from the battery 2 to the DC booster circuit 7.

A low voltage reset circuit 23 sends a signal to the power cutoff relay circuit 6 through a delay recovery circuit, which will be described later, when the battery voltage becomes abnormally low and the lamp cannot be kept lit. The supply of the battery voltage to the booster circuit 7 is cut off. Incidentally, such an operation is performed only when the detection signal S ₂₀ sent from the lighting / non-lighting detection circuit 20 is received and it is informed that the lamp is not lit. . That is, the low-voltage reset circuit 23 does not determine whether to permit power supply to the DC booster circuit 7 only based on the magnitude of the battery voltage, but always monitors the lighting state of the lamp and determines that the lamp is in the non-lighting state. Then, it is first determined whether or not the battery voltage is equal to or lower than a predetermined value, and whether or not to permit the supply of the battery voltage to the power feeding system is determined.

An overvoltage detection circuit 24 detects that the value of the battery voltage exceeds a predetermined value, and at this time, sends a signal to the power cutoff relay circuit 6 via the delay recovery circuit 25 to send it to the power feeding system. It is provided to cut off the supply of battery voltage.

When the delay recovery circuit 25 receives an abnormality detection signal from the low voltage reset circuit 23 or the overvoltage detection circuit 24, the delay recovery circuit 25 promptly turns off the relay in the power cutoff relay circuit 6 to open its contact 6a. After that, when the battery voltage returns to the normal range, the relay contact 6a is closed with a predetermined delay time.

Reference numeral 26 denotes an output current abnormality detection circuit, which is a circuit when the high-frequency booster circuit 8 is short-circuited at the output stage or a short circuit occurs in another circuit section and the output current I _O becomes abnormally large. It is provided for protection. That is, when the detection signal relating to the output current I _O of the DC booster circuit 7 is input to the output current abnormality detection circuit 26 via the amplifier 15 and the output current I _O of the DC booster circuit 7 exceeds a certain reference value. When it is judged to be abnormal, a signal is sent to the power cutoff relay circuit 6 to cut off the supply of the battery voltage to the DC booster circuit 7.

The output current abnormality detection circuit 26 constantly monitors the output voltage V _O of the DC booster circuit 7 to determine whether the metal halide lamp 11 is in the initial lighting state or in a steady state. This is a variable comparison reference value for the output current I _O of the DC booster circuit 7.

As described above, the power cutoff relay circuit 6 determines whether to supply the battery voltage to the power feeding system according to the signals from the circuits 22, 23, 24 and 26. For an abnormality detection signal based on a permanent cause of abnormality such as a signal from the circuit 22 or the output current abnormality detection circuit 26, this is held, and the power supply cutoff state is continued unless the lighting switch 5 is turned on again. Further, like the signals from the low voltage reset circuit 23 and the overvoltage detection circuit 24, the power supply cutoff state is not held for an abnormality detection signal due to a temporary cause such as an increase (or decrease) in battery voltage, When the battery voltage returns to the normal range, the power supply voltage is again supplied to the power feeding system.

(B. Circuit Configuration of Each Part) [FIGS. 2 to 4] Next, each part of the lighting circuit 1 will be described in detail.

(B-1. Power feeding system) [FIG. 2] (b-1-a. DC boosting circuit) The DC boosting circuit 7 is configured as a chopper type DC-DC converter.
A control pulse P, which is provided between the inductor 27 provided on the plus line 4 and the plus line 4 and the ground line 4 ′ in the subsequent stage, and which is sent from the control circuit 12 via the gate drive circuit 16. An N-channel FET 28 that is switched by _S , a rectifying diode 29 whose anode is connected to the drain of the FET 28 on the plus line 4, and a smoothing provided between the cathode of the diode 29 and the ground line 4 '. It is composed of a capacitor 30. And
In the DC booster circuit 7, the inductor 27 stores energy when the FET 28 is turned on by the control pulse P _S , releases the stored energy when the FET 28 is turned off, and inputs a voltage corresponding to this. DC voltage boosting is performed by superimposing it on the voltage.

(B-1-b. High-frequency booster circuit) As the high-frequency booster circuit 8, a self-exciting push-pull type inverter circuit is used.

That is, one end of the choke coil 31 is connected to the positive side output terminal of the DC booster circuit 7, and the other end is connected to the center tap of the primary winding 32a of the transformer 32.

Reference numerals 33 and 33 'are N-channel FETs, the sources of which are both connected to one end of the current detection resistor 14, the drain of the FET 33 is connected to the terminal on the starting end side of the primary winding 32a, and the FET 33'. The drain is connected to the terminal on the terminal side of the primary winding 32a.

Reference numeral 34 is a feedback winding provided on the primary side of the transformer 32. The voltage induced in the feedback winding is sent to a two-phase gate drive circuit 35, where two drive signals having an antiphase relationship with each other are provided. Are produced and sent to the FETs 33 and 33 ', respectively.

Reference numerals 36 and 36 'denote resistors provided between the gates and sources of the FETs 33 and 33', respectively, and 37 denotes a zener inserted between the center tap of the primary winding 32a and the common source of the FETs 33 and 33 '. It is a diode.

Reference numeral 38 is a capacitor provided on the primary side of the transformer 32, and 39 is a capacitor provided on the secondary side.

Therefore, the high frequency booster circuit 8 includes the feedback winding 3
Gate drive circuit 3 based on the voltage induced in 4
FET33,33 by the drive signal generated by
′ Is reciprocally switched, whereby a sinusoidal AC voltage is generated across the secondary winding 32b of the transformer 32.

(B-1-c. Igniter circuit) The igniter circuit 9 comprises a trigger transformer 40 and a trigger pulse generator 41.

That is, the secondary winding 4 of the trigger transformer 40
0b is provided on the line connecting one output terminal of the high-frequency booster circuit 8 and the AC output terminal 10, and the pulse output from the trigger pulse generating section 41 is applied to the primary winding 40a.

The trigger pulse generator 41 has a capacitor and a spark gap element (not shown) therein, and when the capacitor is charged when the lamp is started and its terminal voltage exceeds a predetermined value, the trigger gap generator 41 operates. Upon conduction, a trigger pulse is generated, which is boosted by the trigger transformer 40 and superposed on the AC output of the high-frequency booster circuit 8 and then applied to the metal halide lamp 11.

(B-2. Lighting control system) [FIG. 3] Regarding the lighting control system, the control circuit 12 and the timer circuit 1
7. The lighting / non-lighting detection circuit 20 will be described in detail. still,
The control circuit 12 is composed of an output voltage V _O of the DC booster circuit 7, an output voltage detection unit for detecting the output current I _O , an output current detection unit, and a PWM (pulse width modulation) control unit.

(B-2-a. Output voltage detecting unit) 42 is an output voltage detecting unit, and is connected to D via the voltage dividing resistors 13 and 13 '.
The output voltage V _O of the C booster circuit 7 is detected, this is compared with a predetermined reference value, and the difference voltage is output as an error output.

Reference numeral 43 is an error amplifier, which is an operational amplifier 4
The non-inverting input terminal of No. 4 has voltage dividing resistors 13 and 13 via resistors.
, And a voltage detection signal (this is referred to as “S _V ”) is input. Then, a predetermined reference voltage (referred to as "V ₁ ") defined by the voltage dividing resistors 45 and 45 'is applied to the inverting input terminal. A predetermined voltage (referred to as “V _ref ”) by a reference voltage generator (not shown) is applied to one end of the resistor 45, and this V _ref is a constant value that is not affected by fluctuations in the battery voltage. Has been done.

[0046] (b-2-b. The output current detection unit) 46 is an output current detecting unit, detects a voltage conversion value output current I _O through the current detection resistor 14 of the DC booster circuit 7,
It is provided to compare this with a predetermined reference value and take out the difference voltage as an error output.

As the amplifier 15, an operational amplifier 47 to which negative feedback is applied by a resistor is used. The non-inverting input terminal of the operational amplifier 47 is connected to the output terminal of the current detection resistor 14 via the resistor 48, and thus the current detection signal (this is referred to as “S _I ”) is input, and The inverting input terminal is grounded via the resistor 49.

Reference numeral 50 denotes an operational amplifier as an error amplifier, the non-inverting input terminal of which is connected to the output terminal of the operational amplifier 47 via the resistor 51. Then, a reference voltage generated by the reference voltage generator 52 (this is referred to as "V ₂ ") is applied to the inverting input terminal.

The reference voltage generator 52 is composed of resistors 53 and 53 'connected in series, and a voltage buffer 54 for extracting a voltage from between the resistors 53 and 53', and the output of the voltage buffer 54. Is applied to the inverting input terminal of the operational amplifier 50 via a resistor. The voltage V _ref is applied to one end of the resistor 53. Further, the value of V ₂ is changed by the signal sent from the supply voltage drop detection circuit 18 to the reference voltage generator 52 as the power supply voltage B drops,
As a result, the lamp 11 is controlled with electric power below the rated electric power according to the decrease in the battery voltage.

(B-2-c. Timer circuit) The timer circuit 17 is a circuit provided for shifting to the constant power control after a lapse of a predetermined time corresponding to the extinguishing time of the lamp from the start of lighting. Yes, it consists of an active switch element and a time constant circuit.

Reference numeral 55 is an NPN transistor, the collector of which is connected to the positive output terminal of the DC booster circuit 7, and the emitter of which is connected to the non-inverting input terminal of the operational amplifier 50 via the resistor 56.

The base of the transistor 55 is connected to the anode of the diode 57, and the cathode of the diode 57 is grounded via the capacitor 58 (whose capacitance is "C ₅₈ ").

Reference numeral 59 is a resistor provided between the base and collector of the transistor 55 (its resistance value is "R ₅₉ "), and 60 is a resistor provided between the cathode of the diode 57 and the collector of the transistor 55. (The resistance value is “R ₆₀ ”).

(B-2-d. PWM control section) 61 is a PW
M control unit, which compares its input voltage in its comparator 62 with the triangular wave from the oscillator 63, and has a control pulse P having a duty cycle corresponding to the input voltage.
It is what causes _S.

That is, the minus input terminal of the comparator 62 is connected to each output terminal of the operational amplifiers 44 and 50, and the plus input terminal thereof is connected to the output terminal of the oscillator 63.

Reference numeral 64 denotes a quiescent period adjusting comparator, which controls the quiescent period of the control pulse P _S , and as a result, the upper limit value of the output voltage V _O of the DC booster circuit 7 (this is referred to as "V _m ". , The value of V _m is not a fixed value but is variable by the rest period control unit 21.). Then, the signal from the oscillator 63 is input to the plus input terminal thereof, and when the voltage applied to the other minus input terminal is increased, the pause period of the pulse output from the comparator 64 is lengthened.

Reference numeral 65 is an AND circuit, and the comparator 6
A final control pulse P _S can be obtained by performing an AND operation on the output pulses from 2 and 64 and outputting the result via the buffer 66.

Therefore, in the AND circuit 65, one of the output pulses of the comparators 62 and 64 having a smaller duty cycle is selected.

A voltage obtained by dividing the reference voltage V _ref by the voltage dividing resistors 67 and 68 is normally applied to the negative input terminal of the idle period adjusting comparator 64, but the idle period is generated depending on the operating condition of the circuit. voltage of different value by the signal S ₂₁ from the control unit 21 is added, whereby D
The allowable range of the output voltage V _O of the C booster circuit 7 (that is, the upper limit value V _m ) is variable.

To summarize the above description, the PWM control unit 6
The duty cycle of the control pulse P _S obtained by 1 is regulated to a value corresponding to the output voltage of the output voltage detection unit 42 and the output current detection unit 46, and the voltage level applied to the negative input terminal of the idle period adjustment comparator 64. Defines the upper limit value of the duty cycle of the control signal P _S. Then, the control pulse P _S passes through the gate drive circuit 16 and the FET 28 of the DC booster circuit 7.
Is fed back to control the output voltage V _O.

(B-2-e. Lighting / non-lighting detection circuit) 7
4 is a comparator, the negative input terminal of which is connected to the output terminal of the amplifier 15 via the resistor 75,
The output of the amplifier 15 (this is referred to as “S ₁₅ ”) is input. The predetermined reference voltage to the positive input terminal (this referred to as "V _3".) Is added.

That is, the comparator 74 compares the output voltage S ₁₅ of the amplifier 15 with the reference voltage V ₃ and outputs a signal S ₂₀ as the comparison result. When the lamp is on, S _Since the level of ₁₅ is V ₃ or more, an L (low) signal is output as the signal S ₂₀ , and when the lamp is not lit, the level of S ₁₅ is less than V ₃ and the signal S ₂₀ is H (high). Output a signal.

Reference numeral 76 is a capacitor inserted between the negative input terminal of the comparator 74 and the ground line.

Reference numeral 77 is an NPN transistor whose emitter is grounded, and a voltage obtained by dividing the output voltage of the comparator 74 by the resistors 78 and 78 'is applied to its base.
The collector is connected to the non-inverting input terminal of the operational amplifier 50 of the output current detector 46. Therefore, when the output signal of the comparator 74 becomes H level, the transistor 77 is turned on and the potential of the non-inverting input terminal of the operational amplifier 50 is forcibly lowered to near zero.

(B-3. Circuit protection system) [FIG. 4] (b-3-a. Power cutoff relay circuit) 98 is a power supply terminal, and is an output side of the lighting switch 5 via a reverse voltage prevention diode. It is connected to the terminal. The voltage applied to the power supply terminal 98 will be referred to as “+ B ′”.

Reference numeral 99 is a relay, one end of the coil 99a of which is connected to the power supply terminal 98 and the other end of which is connected to the collector of the NPN transistor 100. This coil 9
The relay contact 6a is opened and closed depending on the presence or absence of the exciting operation of 9a.

Reference numeral 101 denotes a signal holding circuit, which has an input terminal 1
01a includes an abnormality determination circuit 22 and an output current abnormality detection circuit 2
The signal from the transistor 6 is sent, and when the input terminal 101a becomes H level, this state is held and the transistor 100 is turned off.

As a result, the relay 99 is turned off and DC
The supply of power supply voltage to the booster circuit 7 is cut off.
This state is continued unless the lighting switch 5 is once turned off and then turned on again.

Further, the L signal from the low voltage reset circuit 23 or the overvoltage detection circuit 24 is sent to the base of the transistor 100 via the delay recovery circuit 25 when an abnormality relating to the battery voltage is detected. Therefore, the transistor 100 is turned off and the relay 99 is turned off. When the battery voltage returns to the normal range, the H signal from the delay recovery circuit 25 turns on the transistor 100, and the relay 9
The contact 6a is closed by the operation 9 and the lighting operation is restarted.

(B-3-b. Low voltage reset circuit) 11
9 is a resistor, one end of which is connected to the power supply terminal 98,
The other end is grounded via resistors 120 and 121.

Reference numeral 122 denotes a Zener diode provided in parallel with the resistors 120 and 121, the cathode of which is connected between the resistors 119 and 120, and the anode of which is grounded.

Reference numeral 123 is a comparator, whose negative input terminal is connected between the resistors 120 and 121, and whose positive input terminal divides the voltage applied to the power supply terminal 98 by voltage dividing resistors 123a and 123a '. Is added via a resistor.

That is, the resistors 119, 120, 121 and the Zener diode 122 generate the reference voltage of the comparator 123, and when the divided value of the power supply voltage B'is below this reference voltage, the comparator 123 outputs the L signal. It is supposed to do.

However, such a detecting operation is carried out only when the lamp is in a non-lighting state, and is carried out when the lamp is in a lighting state or until a predetermined time elapses after the lighting switch 5 is turned on. There is no such thing.

That is, a two-stage NP that is switched according to the signal S ₂₀ from the lighting / non-lighting detection circuit 20.
N-transistors 124 and 125 (both of which have their emitters grounded) and a delay operation circuit 126 including a capacitor and a comparator are provided.

That is, the lighting / non-lighting detection signal S ₂₀ is input to the base of the transistor 124 via the resistor, the collector voltage of the transistor 124 is applied to the base of the transistor 125 via the resistor, and the transistor 125 is turned on.
Is connected to the minus input terminal of the comparator 123 via the resistor 127.

Therefore, when the signal S ₂₀ is the L signal, the transistor 124 is turned off and the transistor 125 is turned on, so that the potential of the negative input terminal of the comparator 123 is lowered and the output of the comparator 123 is forced to be the H signal. The operation related to the detection of the power supply voltage drop is not performed.
In other words, such a detecting operation is performed only when the signal S ₂₀ is the H signal.

In the delay operation circuit 126, one end of the resistor 128 is connected to the power supply terminal 98 and the other end is grounded via the capacitor 129.
A terminal voltage of 29 is applied to the positive input terminal of the comparator 130 via a resistor. Then, the comparator 13
Power supply voltage B'is connected to the negative input terminal of 0
The voltage divided by 1, 131 'is applied, and an output signal corresponding to the comparison result between this voltage and the terminal voltage of the capacitor 129 is sent to the minus input terminal of the comparator 123 via the resistor 132.

That is, immediately after the lighting switch 5 is turned on, charging of the capacitor 129 is started, and until the terminal voltage thereof exceeds the reference voltage (3.5 V) (about 0.2 seconds), the output of the comparator 130 becomes L. Since it is a signal, the output of the comparator 123 is forcibly set to the H signal.

(B-3-c. Overvoltage detection circuit) 133 is a resistor, one end of which is connected to the power supply terminal 98, and the other end of which is grounded via the resistors 134 and 135.

Reference numeral 136 is a Zener diode, the cathode of which is connected between the resistors 133 and 134 and the anode of which is grounded.

Reference numeral 137 is a comparator, the positive input terminal of which is connected between the resistors 134 and 135 via the resistor. Then, a voltage obtained by dividing the power supply voltage B ′ by the resistors 138 and 138 ′ is applied to the negative input terminal.

That is, the battery voltage is high, and the potential of the negative input terminal of the comparator 137 is equal to that of the resistors 133 and 1.
It outputs an L signal when the reference voltage created by 34, 135 and Zener diode 136 is exceeded.

(B-3-d. Delay recovery circuit) 139 is an NPN transistor whose emitter is grounded, and its base receives signals from the low voltage reset circuit 23 and the overvoltage detection circuit 24 via a resistor. The switching operation is performed by the signal.

The collector of the transistor 139 is a resistor 14
It is connected to the power supply terminal 98 via 0, and is also connected to the base of the NPN transistor 144 via the diode 141 and the resistors 142 and 143.

Transistor 144 has its collector connected to the resistance of the base of transistor 100,
A resistor 145 is provided between the emitters.

A capacitor 146 has one end connected between the resistors 142 and 143 and the other end grounded.

In the delay recovery circuit 25, however, the transistor 139 is turned off when at least one of the output signals of the low voltage reset circuit 23 and the overvoltage detection circuit 24 is the L signal, and therefore the transistor 144.
Is immediately turned on, the transistor 100 is turned off, and the relay 99 is turned off. After that, when the output signals of the low voltage reset circuit 23 and the overvoltage detection circuit 24 become the H signal, the transistor 139 is turned on this time. However, the transistor 144 does not turn off immediately but is composed of the resistors 143 and 145 and the capacitor 146. The time constant circuit turns off after a predetermined time.

(C. Operation) [FIGS. 5 to 7] Next, the operation of the lighting circuit 1 will be described with reference to the metal halide lamp 11
The lighting control operation and the circuit protection operation will be described separately. still,
FIG. 5 shows the output voltage V _O (V), the output current I _O (A), the lamp current I _L (A), and the lamp voltage V 0 of the DC boost circuit 7.
_L (V), and the luminous flux L of the metal halide lamp 11
The time course of (lm) is schematically shown, and the origin of the time axis t is immediately after the lighting switch 5 is turned on. Also,
FIG. 6 is a graph showing the relationship between the output voltage V _O on the horizontal axis and the output current I _O on the vertical axis. (C-
1. Lighting Control Operation) [FIGS. 5 and 6] The lighting control operation of the circuit 1 when the voltage applied between the DC voltage input terminals 3 and 3 ′ is in a normal range will be described.

First, the situation when the lighting is started from the cold state of the lamp (hereinafter referred to as "cold start") will be described.

In this case, immediately after the lighting switch 5 is turned on, the capacitor 58 of the timer circuit 17 is in an empty state, and the emitter potential of the transistor 55 is low. Therefore, only the output of the amplifier 15 is applied to the non-inverting input terminal of the operational amplifier 50 in the output current detector 46.

Immediately after the lighting, the lamp voltage V _L is low and D is low, as can be seen from the graph curve shown by the solid line in FIG.
Output current I _O of C booster circuit 7 is relatively small.

That is, the output S _{15 of the} amplifier 15 is smaller than the reference voltage V ₂ generated by the reference voltage generator 52.

Further, while the lamp is not lit, S ₁₅ is V
Since it is smaller than _3, the output signal of the lighting / non-lighting detection circuit 20 is the H signal, and the transistor 77 is in the ON state, so the input voltage of the operational amplifier 50 is forcibly set to the L level.

From the time when the lighting switch 5 is turned on until the lamp light is detected, the duty cycle of the control pulse P _S changes the input voltage of the idle period adjusting comparator 64, that is, the voltage V _ref to the resistor 67. It is defined by the voltage value divided by 68 and this value defines the upper limit of the output voltage V _O of the DC booster circuit 7.

After that, when the lighting of the lamp is detected, the duty cycle of the control pulse P _S is changed to the output voltage detection unit 4
2 is defined by the output voltage of the error amplifier 43, and the control pulse P _S from the PWM control unit 61 to the gate drive circuit 16 and the FET 28 of the DC boost circuit 7.
Sent to

[0097] indicates the state of point a immediately after the start lights in FIG. 6, from this point a, the output voltage V _O is increased by going control region A _V output until the output current I _O at a substantially constant from the point b This is an area under the control of the voltage detection unit 42.

Thereafter, the capacitor 58 is gradually charged (if the time constant at this time is "τ ₁ ", then τ ₁ = (R
₅₉ // R ₆₀ ) ・ C ₅₈ . However, "//" represents parallel combination of resistance values. ), And accordingly, transistor 5
The emitter potential of 5 rises, and the potential of the non-inverting input terminal of the operational amplifier 50 rises.

When this reaches a level corresponding to the reference voltage V ₂ , thereafter, the duty cycle of the control pulse P _S is regulated by the output voltage of the operational amplifier 50.

That is, since the duty cycle of the control pulse P _S decreases as the output voltage of the operational amplifier 50 increases, the output voltage V _O that has been kept at the maximum value until then.
Gradually decreases.

Regarding the reference voltage V ₂ , when the battery voltage is a predetermined value, for example, 10 V or more, the reference voltage V ₂ is determined by the value obtained by dividing V _ref by the resistors 53 and 53 '.

In FIG. 6, the control region A _I from the point b to the point d via the peak point c of the output current I _O is a region under the control of the output current detecting section 46.

When the capacitor 58 is fully charged, the transistor 55 is turned on, its emitter potential becomes substantially equal to the output voltage V _O of the DC booster circuit 7, and thereafter the constant power control is started.

That is, the value obtained by dividing the output voltage V _O by the resistors 51 and 56 and the amplified output S ₁₅ corresponding to the output current I _O is controlled so as to be a constant value corresponding to V _2. Therefore, constant power control of V _O · I _O = constant is realized in the form of linear approximation.

The area A _S from point d to point e in FIG. 6 is a constant power area, and the rated power is supplied to the metal halide lamp 11 in this area.

However, as can be seen from the curve indicated by the solid line, the lamp light flux L transitions to a steady state after showing a sharp rise immediately after lighting and then overshooting.

Next, the relighting operation after the metal halide lamp 11 is turned off will be described.

While the lamp is off, the charge stored in the capacitor 58 of the timer circuit 17 has a time constant τ.
₂ (= R ₆₀ · C ₅₈ ), it is gradually discharged.

Since the time constant τ ₂ is set to a value corresponding to the degree of temperature decrease of the lamp after the light is turned off, when the lighting switch 5 is turned on again, the lighting from the control area according to the terminal voltage of the capacitor 58 is performed. The operation is started.

That is, proper lighting control is performed according to the elapsed time required from turning off the light to relighting it.

For example, when the lamp is turned on again after several tens of seconds have passed since the lamp was turned off, since the lighting is started from the operating point in the control area A _I and the constant power control is started, the alternate long and short dash line in FIG. As shown by, the output voltage V _O and the output current I _O have a curve that gradually decreases immediately after the start of lighting, and the lamp luminous flux L first rises sharply and stabilizes after an overshoot.

When the lamp is turned on again a few seconds after the lamp is turned off, the glass bulb of the metal halide lamp 11 is still hot, and the lamp voltage immediately after the lamp is turned on again as shown by the chain double-dashed line in FIG. Since V _L is high and the output current I _O is large, the constant power control is immediately performed, and the luminous flux L is stabilized at the rated power.

The reason for providing the timer circuit 17 is to shorten the starting time.

That is, if the output voltage V _O of the DC boosting circuit 7 is directly applied to the non-inverting input terminal of the operational amplifier 50 via the resistor 56 without providing the timer circuit 17, the physical state of the lamp is reduced. This is because the constant power control is performed from the start of lighting regardless of the situation, so that the light emission of the lamp in the control areas A _V and A _I is not promoted and the rise of the light flux L is delayed.

(C-2. Circuit protection operation) Next, the protection operation when an abnormal state of the lighting circuit 1 is detected will be described. (C-2-a. Operation of Low Voltage Reset Circuit) [FIG. 7] FIG. 7 is a diagram for explaining the relationship between the fluctuation of the battery voltage V _B and the signals and operating states of the respective parts. V _B "
Indicates the battery voltage, “ΔV _L ” indicates the range of variation regarding the lower limit value of the battery voltage (its central level is “V _L ”), and “ΔV _H ” indicates the range of variation regarding the upper limit value (its center). The level is "V _H ".)
These variations are caused as an error in the manufacture of individual lamps and lighting devices. Also, the lower limit value of the allowable range of the battery voltage V _B (“V ^* _L ”)
It is written. ) As a ^{_{V * L = V L + ΔV}} L / 2, the upper limit value ( "V
^* _H ". ) When was the ^{_{V * H = V H -ΔV H}} / 2, V
Tolerance of _B [Delta] V _B is _{ΔV B = V H -V L -} (ΔV L + Δ
V _H ) / 2.

The level (H / L) of the non-lighting detection signal S ₂₀ and the comparator 123 are provided below the battery voltage V _B.
Output signal (this is referred to as "CMP (123)".) Level (H / L), and the operating state of the relay 99 (this is indicated by " _Ry (99)", "ON" or "OFF"). , Which is represented by any one of the two binary states.

Input voltage B by the low voltage reset circuit 23
The drop detection of 'is performed only when the non-lighting detection signal is sent from the lighting / non-lighting detection circuit 20.

That is, as shown by the solid line, the detection signal S ₂₀ is L
At the level (that is, when the lamp is lit), the output voltage of the comparator 123 remains the H signal even when the battery voltage V _B drops and passes the point P of V _B = V ^* _L. This causes transistor 124 to turn off and transistor 125 to
This is because the reference voltage of the comparator 123 is low because the is turned on. Therefore, the comparator 12
Since the transistor 139 is turned on and the transistor 144 is turned off by the H signal output from the relay 3,
9 is in the ON state, and the relay contact 6a is closed.

When the signal S ₂₀ is the H signal (that is, the lamp is not lit) at the point P as shown by the chain line, the transistor 124 is turned on and the transistor 125 in the subsequent stage is turned off. 12
A reference voltage of 3 is defined by resistors 119, 120, 121 and Zener diode 122.

Then, since the comparator 123 determines that the input voltage B'is lower than the reference value, the output signal of the comparator 123 becomes L level.

Therefore, the transistor 139 of the delay recovery circuit 25 is turned off and the transistor 144 is turned on immediately so that the transistor 100 of the power cutoff relay circuit 6 is turned off and the relay 99 is turned off to open its contact 6a.

When the battery voltage V _B remains below V ^* _L even after passing the point P as shown by the broken line, the relay contact 6a remains open, but the battery voltage V _B drops. Is a temporary one, and V _B = V ^* _L at point Q as shown by the solid line, and then returns to V ^* _L ≦ V _B ≦ V ^* _H at the point Q as shown by the chain line. The output of the comparator 123 becomes the H signal.

Incidentally, in FIG. 7, a point P is shown in order to simplify the explanation.
Although the level at the point Q is set to the same level, the comparator 123 actually has a hysteresis characteristic. The reason is that the output voltage of the battery 2 is not directly detected in detecting the decrease of the voltage B ', but the input voltage between the DC voltage input terminals 3 and 3', that is, the battery voltage is detected. This is because the voltage obtained by subtracting the voltage drop corresponding to the consumed current is detected. That is, if the detection level of the comparator 123 does not have the hysteresis characteristic, a kind of chattering phenomenon occurs in the relay 99.

Therefore, as a practical problem, V_BIs about
Lamp non-lighting condition is detected at 7.5V or less
Relay 99 is turned off, and then V_BIs about
After returning to 9.5V or higher, turn on the relay 99.
Is desirable. In addition, the cell starter
Battery voltage fluctuations that occur when starting the engine
(V _B= 5 to 8 V), the comparator 123
Having a hysteresis characteristic is effective.

If the width of the hysteresis characteristic is set to the above value, for example, when the lighting switch 5 is turned on with V _B = 8 V, the relay 99 remains in the off state. Will occur. In order to avoid this, as described above, the delay operation circuit 126 prevents the drop in the voltage B ′ from being temporarily detected from immediately after the lighting switch 5 is turned on until a predetermined time elapses. There is.

When the output of the comparator 123 becomes H level, the transistor 139 is turned on immediately, but the transistor 144 is turned off when the terminal voltage of the capacitor 146 becomes lower than a predetermined value. Delay time (“Δt”)
It is written. ) Is a value that meets two conditions (for example,
Δt = 0.15 seconds).

The two conditions are: (1) A momentary interruption of the power supply of the vehicle body caused by a defective connection (or contact) of the connector for the wiring connecting the battery terminal and the DC voltage input terminals 3, 3 '. If it repeats intermittently in response to vibration, the power supply is cut off continuously during this period. (2) When repeatedly turning on / off the lighting switch as during passing, the power supply is switched according to the switch operation. The on / off operation of is performed.

That is, with respect to (1), since the power source is temporarily cut off and the energized state is repeated, the capacitor 146 is gradually charged and the transistor 144 is turned on while the output of the comparator 123 is at the L level. , Once the transistor 144 is turned on, the resistors 143, 14
5. Since the value of the time constant Δt defined by the capacitor 146 is large, the transistor 144 is not turned off even if the instantaneous interruption and the energization are repeated. The condition (2) is a condition for enabling the power to be turned on / off according to the speed of the switch operation by the driver, and in this case, while the power is turned on and off repeatedly. At 146, the capacitor 146 is not fully charged.

However, when the output signal of the comparator 123 becomes H level, the transistor 144 is turned off after Δt seconds, the transistor 100 is turned on and the relay 99 is turned on. Therefore, the relay contact 6a is closed and the lamp 11 is turned on. The lighting operation is restarted, and the lamp 11 is lit after a certain time has elapsed from the point P.

(C-2-b. Operation of Overvoltage Detection Circuit) When the power supply voltage B ′ becomes an excessive value and the potential of the negative input terminal of the comparator 137 exceeds the reference voltage, the L signal output from the comparator 137. Is sent to the transistor 139 of the delay recovery circuit 25, the relay contact 6a
Is opened immediately.

After that, when the voltage B'becomes low and returns to the normal range, the output signal of the comparator 137 becomes the H signal, so that a predetermined delay time has elapsed after the H signal was input to the delay recovery circuit 25. After a lapse of time, the relay contact 6a is closed.

(D. Function) Then, the signals of the low voltage reset circuit 23 and the overvoltage detection circuit 24 are delayed by the delay recovery circuit 25.
This state is not maintained even if the relay 99 is turned off by being sent to the transistor 100 of the power cutoff relay circuit 6 via (the abnormality determination circuit 22 and the output current abnormality detection circuit 26 detect an abnormality. Therefore, the driver does not have to take the troublesome work of canceling the cutoff state by turning off the lighting switch 5 and then turning it on again. That is, when the battery voltage returns to the normal range, the relay contact 6a is closed and the power supply to the lamp 11 is restarted.

Even if the battery voltage drops to V ^* _L or less, if the lamp 11 is still lit, the relay 99
In the ON state, the battery voltage is supplied to the DC boost circuit 7.

[0134]

As is apparent from the above description, according to the invention of claim 1, it is unlikely that a permanent cause of abnormality will be recovered to a normal state, or if it is temporarily recovered. However, since there is a risk of inducing the spread of damage, the safety of the circuit operation is guaranteed by continuously cutting off the power supply to the discharge lamp.
By resuming the power supply to the discharge lamp and controlling the discharge lamp to be lit as much as possible at the time of recovery to the normal state, it is possible to prevent the harmful effects caused by the non-illuminated state of the discharge lamp.

According to the second aspect of the present invention, the discharge lamp is detected when the abnormality of the lighting state of the discharge lamp or the abnormality of the output voltage and / or the output current of the lighting circuit is detected among the permanent causes of abnormality. By interrupting the power supply to the power supply until the next power-on, it is possible to prevent the discharge lamp and the lighting circuit from being fatally damaged or destroyed.

According to the third aspect of the invention, by detecting an abnormality in the input voltage value to the lighting circuit as a cause of the temporary abnormality, it is possible to prevent a temporary variation in the input voltage when the power is turned on. Thus, power can be supplied to the discharge lamp when the input voltage is restored to the normal range, and the discharge lamp can be controlled to be lit as much as possible unless there is another abnormality.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an overall circuit configuration.

FIG. 2 is a circuit diagram showing a power feeding system.

FIG. 3 is a circuit diagram centering on a lighting control system.

FIG. 4 is a circuit diagram mainly showing a low voltage reset circuit and an overvoltage detection circuit.

FIG. 5 is a graph diagram schematically showing a temporal change of current, voltage value, and lamp luminous flux of each part of the circuit for explaining a control operation.

FIG. 6 is a graph showing the relationship between the output voltage and the output current of the DC boost circuit.

FIG. 7 is an explanatory diagram showing the operation of the low voltage reset circuit.

[Explanation of symbols]

1 ... Discharge lamp lighting circuit, 2 ... Power supply, 6 ... Breaking means, 11 ...
Discharge lamps, 22, 23, 24, 26 ... Abnormality detecting means, 2
3, 24 ... Input voltage detecting means

Front page continuation (72) Inventor Hiromi Shibata 500 Kitawaki, Shimizu City, Shizuoka Prefecture Koito Manufacturing Co., Ltd. Shizuoka Factory

Claims (3)

[Claims] 1. A discharge lamp lighting circuit comprising a cutoff means for cutting off power supply to a discharge lamp, based on a permanent cause of an abnormality in a circuit section or a discharge lamp located on the discharge lamp side as seen from the cutoff means. When the abnormal state is detected by the abnormality detecting means, the shutoff means shuts off the power supply to the discharge lamp and maintains this state, and is located on the power supply side as seen from the power source of the lighting circuit or the shutoff means. When the abnormal state due to the temporary cause of abnormality in the circuit section is detected by the abnormality detecting means, the shut-off means temporarily stops the power supply to the discharge lamp and then releases it when returning to the normal state. A discharge lamp lighting circuit characterized by restarting power supply to an electric lamp. 2. The discharge lamp lighting circuit according to claim 1, wherein the lighting state of the discharge lamp is abnormal, or the output voltage of the lighting circuit and /
Alternatively, when an abnormal state of the output current is detected by the abnormality detecting means, the shutoff means shuts off the power supply to the discharge lamp and maintains this state until the next power-on, and the discharge lamp lighting. circuit. 3. The discharge lamp lighting circuit according to claim 1 or 2, further comprising input voltage detection means for detecting an input voltage to the lighting circuit, wherein the input voltage is detected by a detection signal from the input voltage detection means. When it is detected that the voltage is out of the specified range, the cutoff means stops the power supply to the discharge lamp, and when it is detected that the input voltage returns to the specified range, the power is supplied to the discharge lamp. A discharge lamp lighting circuit characterized by restarting.