JP3326955B2 - Discharge lamp lighting device - Google Patents

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 device in which a DC-DC converter and a low frequency inverter are combined, and more particularly to a discharge lamp lighting device such as an HID lamp. is there.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a conventional discharge lamp lighting device. This device, after voltage conversion by a switching operation and the transformer Tf transistor Q DC power E, rectifying and smoothing by the diode D ₁ and capacitor C _1, switches the polarity through the inverter circuit consisting of transistors Q ₁ to Q ₄ This is a device for supplying a substantially rectangular alternating current to the discharge lamp. The transistor Q has a high frequency (for example,
Performs switching operation at about several 10 KHz), by switching the DC power source E, by rectifying a voltage whose pressure elevation by the transformer Tf a diode D _1, the capacitor C ₁
To generate a DC voltage. The capacitor C ₁ has a small capacity (for example, about several μF). DC voltage generated in the capacitor C _1, the transistor Q ₁ to Q ₄ polar low frequency by a full-bridge inverter circuit composed of (e.g., about several 100 Hz) while alternating with, is supplied to the discharge lamp 1 as a load You. The transistors Q _{1 to} Q ₄ are alternately driven at a low frequency by the inverter driving circuit 2.
When the discharge lamp 1 is turned on, the lamp voltage is detected by the voltage detection circuit 3 and the lamp current is detected by the current detection circuit 4, and in response to this, the power calculation circuit 5 calculates the lamp power. Then, the inputted respectively power command value given from the lamp were determined power and a reference power source E ₁ is the positive input of the error amplifier EA, to the negative input, receives the result, PWM control unit 6, it is equal As described above, the transistor Q is driven by the drive circuit 7. The opening / closing means SW is in a closed state at this time. By the above operation, when the discharge lamp is lit,
The transistor Q is PWM-controlled, and predetermined power is supplied to the discharge lamp 1.

Next, a description will be given of the start of the discharge lamp 1.
Before lighting, the discharge lamp 1 has a very high impedance, and the circuit is almost in a no-load state. The PWM control unit 6 controls the transistor Q by the drive circuit 7 with a predetermined duty.
Drive. Thus, the capacitor C _1, the energy from the DC power supply E is supplied, the voltage of the capacitor C ₁ increases. At this time, the voltage of the capacitor C ₁ is detected by the voltage detection circuit 3 is compared with the voltage of the reference power supply E ₂ by the comparator CP. Reference power source E _2, the capacitor C ₁ is set to a value such that the predetermined voltage (e.g., about 300 V). When the capacitor C ₁ exceeds a predetermined voltage value, the comparator CP outputs a low level,
In response to this, the opening / closing means SW is opened. At this time, the transistor Q is turned off. Then, the capacitor C ₁ drops below a predetermined voltage, the output of the comparator CP becomes a high level, the switching means SW becomes closed, the transistor Q is driven at a predetermined duty by the PWM control unit 6 again. By the above operation, the front lighting of the discharge lamp 1, a predetermined voltage is generated in the capacitor C _1. Here, when the starting circuit IG performs an operation of applying a high-voltage pulse (for example, ten and several KV) to the discharge lamp 1, the discharge lamp 1 causes dielectric breakdown and starts. In addition, the discharge lamp 1 changes from the state of dielectric breakdown to the state of arc discharge at the time of starting, and becomes stable.

[0004]

However, according to the above-described operation, at the time of starting the discharge lamp 1 or immediately thereafter, the transistor Q operates at a predetermined duty before starting. If the DC power supply E has a certain voltage range, such as a battery, and fluctuates, the duty is set in advance so that the desired power at the rated voltage is supplied to the discharge lamp 1 at startup. If specified, for example, when the power supply voltage is lower or higher than the rating, the power supply at the start becomes insufficient or excessive, and the discharge lamp 1 There is a problem that the light goes out before the state is changed to a stable state, and that an excessive flash is emitted due to the supply of overpower. In particular, extinction is a major problem because the discharge lamp 1 does not light. This is discharge lamp 1
Is that the startability of the battery depends on the power supply voltage.
There was a problem that stable starting performance could not be secured.

The present invention has been made in view of the above points, and an object thereof is to supply a substantially predetermined power to the discharge lamp at the time of starting the discharge lamp even when the power supply voltage fluctuates. To provide a discharge lamp lighting device capable of reducing start-up dependence on a power supply voltage, improving starting performance, and quickly starting a discharge lamp regardless of a power supply voltage. It is in.

[0006]

According to the present invention, in order to solve the above-mentioned problems, a converter for converting a voltage of a DC power supply, and a discharge lamp connected to an output of the converter and serving as a load are provided. an inverter unit for performing polarity switching of the voltage supplied to the power command value or conductive during lighting of the discharge lamp
In the discharge lamp lighting device in which the power supply to the load can be controlled by controlling the converter section based on the flow command value , when the discharge lamp is started , regardless of the command value,
It is characterized in that a means for controlling so as to be substantially constant regardless of the voltage of the DC power supply output power from the converter part no. Further, the converter unit is a flyback type DC-DC converter circuit that stores energy in the transformer when the switching means is on and discharges the energy from the transformer to the load side when the switching means is off. It is preferable that the power supplied to the load be controlled to be substantially constant by controlling the peak value of the current flowing through the transformer at the time of starting. Or the conver
A means for detecting the input voltage of the discharge lamp is provided to start the discharge lamp.
Sometimes, the switch of the converter block depends on the detected input voltage.
By controlling the on-duty of the switching means,
Output power from the converter is independent of the DC power supply voltage
The control may be performed so as to be substantially constant. Discharge lamp
When the converter starts, after the output voltage of the converter
Elapsed time or the output voltage rises to the specified voltage
What is necessary is just to detect as a period until it rises.

[0007]

According to the present invention, when the discharge lamp is started, the output power from the converter section is controlled so as to be substantially constant irrespective of the voltage of the DC power supply. In order to avoid the decrease in power supply at start-up by increasing the output of the converter unit, and to increase the power supply at start-up by decreasing the output of the converter unit when the voltage of the DC power supply rises. Can be eliminated. In this way, by performing control to make the power supplied at the time of starting substantially constant irrespective of the fluctuation of the DC power supply, the discharge lamp can be started quickly without depending on the voltage of the DC power supply.

[0008]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.
In the figure, reference numeral 8 denotes a duty command value generation circuit, and the other configuration is the same as that of the conventional example of FIG. The operation when the discharge lamp 1 is turned on is the same as that in the conventional example, and therefore, the operation when the discharge lamp 1 is started will be described. In the conventional example, the transistor Q is driven at a predetermined duty before and after the discharge lamp 1 is started. Therefore, when the voltage of the DC power supply E fluctuates, the power supplied to the discharge lamp 1 increases or decreases. In the embodiment, the duty of the transistor Q at the time of starting the discharge lamp 1 is changed by the voltage of the DC power supply E, so that almost constant power can be supplied even when the voltage of the DC power supply E changes. . That is, a duty command value generation circuit 8 that receives a voltage of the DC power supply E and gives a duty command at the time of starting is added to the PWM control unit 6.

FIG. 2 shows an example of the input / output relationship of the duty command value generating circuit 8, and shows the input voltage, that is, the DC power supply E.
When the voltage rises, a command is issued to reduce the duty (the ratio of the ON time to one cycle). As a result, when the voltage of the DC power supply E decreases, the duty increases, and the decrease in the power supply at the time of starting is eliminated. When the voltage of the DC power supply E increases, the duty decreases, and the duty at the time of starting increases. This eliminates an increase in power supply. Therefore, a discharge lamp lighting device capable of starting the discharge lamp 1 quickly without depending on the voltage of the DC power supply E, regardless of the fluctuation of the DC power supply E, is provided. Becomes possible. Note that after the starting stable discharge lamp 1, as described above, the power calculation circuit 5, a reference power source E _1, the duty is determined by the error amplifier EA and the like, the discharge lamp 1 is lighted.

FIG. 3 is a circuit diagram of a second embodiment of the present invention. Figure, Rs is the sense resistor, the amplifier circuit 9, a comparator 10, 11 is a timer circuit, 12 an AND circuit, T
r is a transistor, R _{1 to} R ₃ are resistors, and the other configuration is the same as that of the conventional example of FIG. The operation when the discharge lamp 1 is turned on is the same as that of the conventional example of FIG. The time of start of the discharge lamp 1, a predetermined voltage to the capacitor C ₁ before the start (e.g., about 300 V) for thereby generating is identical to a conventional example. However, at this time, the transistor Q is not driven with a predetermined duty, but performs a switching operation such that the peak value of the current flowing through the transistor Q becomes a predetermined value. The current flowing through the transistor Q increases with time while the transistor Q is on. The value of the current at that time is detected by the detection resistor Rs and amplified by the amplifier circuit 9, and then a signal is input to the negative input of the comparator 10. Also, the timer circuit 11
It is that the discharge lamp 1 is started, and detected by the voltage of the capacitor C ₁ drops after startup, then after a predetermined time, thereby changing the output from the high level to the low level.

Thus, before starting the discharge lamp 1, the transformer
The transistor Tr is off and the comparator 10
The voltage applied to the input is determined by changing the reference voltage Vref
R₁, R _TwoAnd the resistance R_ThreeIs the value obtained by dividing the pressure. Compa
The regulator 10 is flowing between this voltage and the transistor Q.
The output of the amplifier circuit 9 corresponding to the current is compared with the output of the amplifier circuit 9.
9 is high, ie, the transistor Q is
The flowing current is the resistance R₁, R _Two, R_ThreeValue set by
Outputs a low level when it becomes larger than. A
In response to this, the output of the
Thus, the opening / closing means SW is opened. The PWM control unit 6
At this time, a signal with a preset maximum duty is output
are doing. When the opening / closing means SW is opened,
The signal is not transmitted, and the drive circuit 7
And the transistor Q is turned off. Transistor
The energy stored in the transformer Tf by turning off Q
Is the secondary winding N_TwoIs supplied to the secondary side. Transi
When the star Q is off, the current flowing through the transistor Q is zero.
It is b. Capacitor C₁Is the reference power supply E_TwoBy
When the value falls below the set value, the output of the AND circuit 12 is output again.
The force becomes high level and the switching means SW is closed.
Thus, the signal of the PWM control unit 6 is transmitted to the drive circuit 7.
As a result, the transistor Q is turned on. Below, this operation
Is repeated, the path on the primary side of the transformer Tf is changed.
The peak value of the flowing current is the resistance R₁, R_Two, R _ThreeDetermined by
The switching of the transistor Q is performed so that the
Work and the capacitor C₁Voltage exceeds the specified voltage
The transistor Q keeps the off state
I do.

Next, the start circuit IG applies a pulse, so that the positive input of the comparator 10 remains the same for a predetermined time determined by the timer circuit 11 even after the discharge lamp 1 is started, as described above. Since the voltage is input, the peak value of the current flowing through the primary side of the transformer Tf becomes the same value as before starting. The timer circuit 11 outputs a high level until the discharge lamp 1 undergoes dielectric breakdown, shifts to arc discharge, and changes to a stable state, and turns off the transistor Tr.
Thereafter, the timer circuit 11 outputs a low level, the transistor Tr is turned on, the resistor R ₁ is short-circuited, and the voltage applied to the positive input of the comparator 10 is the resistor R
It will be determined by the partial pressures of ₂ and the resistor R _3, a higher value than before. Desired result, the transistor Q is operating the output of the error amplifier EA as described in the conventional example from a drive to a peak current and a predetermined value is controlled to be zero, i.e., the lamp power is set by the reference power source E ₁ To a state under PWM control so as to take the value of.

The above operation is similarly performed when the voltage of the DC power supply E fluctuates. That is, even when the power supply voltage is increased or decreased, the discharge lamp 1
Can be supplied to the discharge lamp 1 until a stable state is established after the start of the operation and the transition to the arc discharge lamp, so that even when the power supply voltage fluctuates, the light goes out and an excessive flash occurs. Without this, the discharge lamp 1 can be started, and the starting performance is improved.

In this embodiment, the timing at which the positive input value of the comparator 10 is switched by the timer circuit 11 is determined, but this timing may be determined by the output of the voltage detection circuit 3. That is, after the discharge lamp 1 is started, the lamp voltage gradually increases with the state of the discharge lamp 1, so that the output voltage value of the voltage detection circuit 3 also increases. When the voltage rises to a predetermined voltage, the transistor Tr may be turned on. In addition, the transistor Tr
May be turned on . By doing so, in the first embodiment, for example, the transformer
An excessive current may flow due to saturation of Tf and the circuit may be destroyed. However, in the second embodiment, the peak value of the current flowing through the transformer Tf is defined. Therefore, such a thing disappears.

FIG. 4 is a circuit diagram of a main part of a third embodiment of the present invention. This is because, in the first and second embodiments, the parts of the reference power source E ₁ is replaced with a power command value calculating circuit 13 and illustrates its periphery. Here, the power command value calculation circuit 13 is a circuit that receives the output of the voltage detection circuit 3 corresponding to the lamp voltage, generates a power command value, and outputs the power command value to the error amplifier EA. An operation of outputting a relatively large voltage and lowering the output voltage value as the input voltage increases is performed. Thus, when the discharge lamp 1 is started and the lamp voltage is relatively low,
That is, when the output of the voltage detection circuit 3 is low, the power command value calculation circuit 13 generates a command value so as to supply a larger power to the discharge lamp 1 than when the discharge lamp 1 is steadily lit, and the power command value Is faster than in the case where is fixed. In the first and second embodiment, after starting, even though to perform the control of power is substantially constant, by the reference power source E ₁ value (reference power source E ₁ value Is relatively low), the power control system (system at the time of lighting) is a control for determining the duty, and there is a case where the intended operation (the operation to make the power at the start almost constant) cannot be performed. It was possible,
In the present embodiment, the power command value is set higher at start-up than during steady-state lighting, so that such an event does not occur, and the intended operation can be reliably performed.

FIG. 5 shows a specific example of the power command value calculation circuit 13. The input terminal is supplied with the signal of the voltage detection circuit 3, the output terminal is connected is <br/> is to the negative input of the error amplifier EA. The meaning of each symbol is as follows. In the figure, OP ₁
～OP ₄ is an operational amplifier, D ₂ to D ₇ are diodes, C ₂
Is a capacitor, R _{4 to} R ₁₈ are resistors, and 14 is a power command value correction circuit. Briefly the operation, resistor R ₄ and R
_The voltage obtained by dividing the reference voltage Vref by ₅ is amplified by a circuit including an operational amplifier OP ₁ and resistors R ₆ , R ₇ , and R ₈ . The signals from the voltage detection circuit 3 are connected to the resistors R ₉ to R _9.
Amplified by the circuit consisting of ₁₂ and an operational amplifier OP _2. The higher one of the output voltages of the _two operational amplifiers OP ₁ and OP ₂ is selected by the diodes D ₂ and D ₃ , and the resistance R ₁₃
As the voltage input to the operational amplifier OP _3. The operational amplifiers OP _{3 to} OP ₅ constitute a voltage buffer, and the voltage obtained by the resistors R ₁₄ and R ₁₅ and the voltage obtained by the resistor R ₁₃ are respectively supplied to the diode D ₄ through a voltage buffer composed of the operational amplifiers OP ₄ and OP _3. , compared with D _5, lower voltage is output from the operational amplifier OP _5.
The output voltage of this circuit, that is, the upper limit of the power command value is
Determined by the resistor R _14, R _15.

Further, the resistors R ₄ and R ₅ determine the power command value when the discharge lamp 1 is steadily lit. A circuit consisting of the operational amplifier OP ₂ after the start, as the lamp voltage rises gradually, operates to lower the output value.
If, when the power command value correcting circuit 14 is not connected, at startup, the discharge lamp 1 command value output circuit consisting of an operational amplifier OP ₂ (provided that the resistor R _14, set at R ₁₅ upper limit value Is not exceeded), and thereafter, the lamp is lit with the command value determined by the resistors R ₄ and R ₅ , and the rated lighting is achieved. However, in this case, the discharge of a discharge lamp such as a metal halide lamp or the like occurs shortly after the start (about several seconds), and a smooth rise of light cannot be obtained. Therefore, the power command value is corrected so that the light transitions smoothly to the rated lighting state,
A power command value correction circuit 14 is provided. At startup,
The voltage Va rises from the ground potential to a predetermined potential (for example, the reference voltage Vref). At this time, the capacitor C
_A current flows through the diode ₂ through the diode D ₆ and the resistors R ₁₇ and R ₅ , and charges are accumulated with a time constant determined by the resistors R ₁₇ and R ₅ and the capacitor C ₂ . Thus, after start-up to the positive input of the operational amplifier OP _1, with a predetermined time constant, the voltage decreases to the voltage which is determined by the partial pressure of the capacitor C ₂ and the resistor R ₅ is applied. As a result, at the time of starting, the output of the power command value calculation circuit 13 performs an operation of decreasing to the rated value with a time constant, and the drop of the light output is corrected. Further, when the discharge lamp 1 is turned off, the operation is performed so that the voltage Va becomes the ground potential. Thereby, the capacitor C
Charges accumulated in the _2, is discharged through the diode D ₇ with a time constant determined by the capacitor C ₂ resistor R ₁₈ and the like. Thus, depending on the off time of the discharge lamp 1, the charge of capacitor C ₂ is discharged, the proper power command value can be obtained even in the case of restarting the discharge lamp 1, without causing overshooting or the like, smooth A high light output rise can be obtained. Incidentally, increasing the gain of the amplifier circuit consisting of an operational amplifier OP _1, it is possible to reduce the capacitance of the capacitor C _2, the capacitor C ₂ is enabled to a small.

Further, by eliminating the input of the circuit, even without the portion of the circuit consisting of the operational amplifier OP _2, it is obtained substantially the same effect. Further, determination in this case, even when the lamp voltage is no longer rise to the rated by temporarily pressure leak or the like occurs in the discharge lamp 1, as long as a state of eliminating a circuit consisting of an operational amplifier OP _2, the resistor R _4, R ₅ Since only the rated power to be supplied is supplied to the discharge lamp 1 and no excessive power is supplied, there is no trouble such as destruction of the discharge lamp 1 and the lighting of the lamp is increased by increasing the stress of the circuit. The advantage of increased safety without destroying the device results.

In the above embodiment, the case where the lamp power is controlled by the command value to turn on the discharge lamp has been described. However, the present invention is not limited to this. For example, the lamp current is controlled by the command value to turn on the discharge lamp. Even in such cases, the present invention can be applied. In addition, another method may be adopted as a method of controlling the peak value at the time of starting (a predetermined value). The DC power supply E may be a rectified and smoothed AC. Also,
Although the flyback type DC-DC converter has been described, the present invention can also be applied to a forward type or the like.

[0020]

According to the discharge lamp lighting device of the present invention, the DC
In a discharge lamp lighting device in which a DC converter unit and a low frequency inverter unit are combined, a means is provided for controlling the output power from the converter unit to be substantially constant regardless of the voltage of the DC power supply when the discharge lamp is started. Therefore, the energy supplied to the discharge lamp at the time of starting can be set to a substantially predetermined value irrespective of the power supply voltage, and even when the power supply voltage fluctuates, the discharge lamp can be started quickly, such as an HID lamp. It is possible to improve the startability when turning on the discharge lamp.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the first embodiment of the present invention.

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

FIG. 4 is a main part circuit diagram of a third embodiment of the present invention.

FIG. 5 is a circuit diagram of an arithmetic circuit used in a third embodiment of the present invention.

FIG. 6 is a circuit diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge lamp 2 Inverter drive circuit 3 Voltage detection circuit 4 Current detection circuit 5 Power calculation circuit 6 PWM control unit 7 Drive circuit 8 Duty command value generation circuit

Claims (4)

(57) [Claims] 1. A a converter unit that performs voltage conversion of a DC power source is connected to the output of the converter, an inverter unit for performing polarity switching of the voltage supplied to a load discharge lamp, the lighting of the discharge lamp Sometimes power command value or current command value
In the discharge lamp lighting device in which the power supplied to the load can be controlled by controlling the converter based on the DC power, the output power from the converter is supplied regardless of the command value when the discharge lamp is started. A discharge lamp lighting device provided with means for controlling the voltage to be substantially constant irrespective of the voltage of the discharge lamp. 2. The flyback type DC-DC converter circuit which stores energy in a transformer when the switching means is turned on and discharges the energy from the transformer to the load side when the switching means is turned off. And means for controlling the power supplied to the load to be substantially constant by controlling the peak value of the current flowing through the transformer when the discharge lamp is started. Item 10. The discharge lamp lighting device according to Item 1. 3. A means for detecting an input voltage of a converter unit.
At the start of the discharge lamp according to the detected input voltage.
Controls the on-duty of the switching means in the inverter
2. The discharge according to claim 1, further comprising means for performing a discharge.
Lighting device. 4. After the output voltage of the converter section decreases,
After a certain period of time, or when the output voltage reaches a predetermined voltage
Equipped with a means to detect the period until rising as the starting time
The release according to any one of claims 1 to 3,
Lighting device.