JPH07230888A - High intensity discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To shorten rise time, and flatten light output by detecting an electric current and voltage impressed on a discharge lamp, and controlling the electric current and the voltage according to an added value of a detecting result so that the added value coincides with a reference value. CONSTITUTION:DC voltage is supplied from DC electric power supply 12 by a DC-DC converter 11, and a high frequency pulse is impressed on a discharge lamp 15 by a PWM regulator 13 and a full bridge circuit 14. Respective ones of these impression voltage and impression electric current are detected by a voltage detecting circuit 16 and an electric current detecting circuit 17, and a detecting result is added by an adder 30, and they are controlled by the regulator 13 so that an added result coincides with a prescribed reference value. A high intensity discharge lamp lighting circuit whose rise time is short and light output is flat is attained by this feedback electric power control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-intensity discharge lamp lighting device for lighting a high-intensity discharge lamp used in a vehicle or the like.

[0002]

2. Description of the Related Art Conventionally, a high-intensity discharge lamp lighting device shown in FIG. 10 has been known (Japanese Patent Laid-Open No. 3-8).
299). In FIG. 10, 1 is a battery 2
DC / DC converter (step-up circuit) for stepping up the DC voltage of 3 is a high-frequency step-up circuit for converting the output voltage of the DC / DC converter 1 into a sine wave AC voltage, and 4 is a high-intensity discharge lamp 5 such as a metal halide lamp. A current limiting load and an igniter circuit for supplying electric power, 6 an igniter starting circuit for outputting a starting signal to the current limiting load and igniter circuit 4,
A control circuit 7 controls the output voltage of the DC / DC converter 1.

The control circuit 7 includes a voltage calculation unit 7a for detecting the output voltage of the DC / DC converter 1, a current calculation unit 7b for detecting the output current of the DC / DC converter 1, and the calculation units 7a and 7b. Generates a rectangular pulse with a duty cycle according to the signal and outputs it to DC / DC.
The converter 1 comprises a pulse width modulator 7c for sending to the gate of the FET 1a.

In the above high-intensity discharge lamp lighting device, when the lighting switch S is turned on, a starting pulse is first generated by a signal sent from the igniter starting circuit 6 to the current limiting load and the igniter circuit 4, and the discharge lamp 5 is triggered. Then, the output voltage of the DC / DC converter 1 is controlled by the control circuit 7 at any time, and finally, the discharge lamp 5 is switched to the steady state lighting.

[0005]

However, such a high-intensity discharge lamp lighting device is not provided with the feedback control means for making the electric power supplied to the load (discharge lamp 5) constant. Therefore, it takes a considerable time from turning on the lighting switch S until the discharge lamp 5 emits a predetermined amount of light. That is, there is a problem that the rising is slow. Further, there is a problem that it is difficult to obtain the flatness of the light output because the feedback control means is not provided.

Further, since the feedback control means for the output fluctuation of the battery 2 is not provided,
When the battery voltage drops significantly, a large current inversely proportional to it may flow from the battery and burn out the circuit pattern.Therefore, the circuit pattern must be made thicker, and the circuit board becomes larger accordingly. There was a problem.

The present invention has been made in view of such problems, and an object thereof is to shorten the rise time and to obtain the flatness of the optical output.
Moreover, it is another object of the present invention to provide a high-intensity discharge lamp lighting device that can make the printed circuit board small.

[0008]

A high-intensity discharge lamp lighting device according to the present invention comprises boosting means for boosting a battery voltage,
High-intensity discharge lamp lighting including pulse generating means for converting the output voltage from the boosting means into a pulse voltage having a variable pulse width and outputting the pulse voltage, and a full bridge circuit for applying the pulse voltage to the discharge lamp. In the device, voltage detection means for detecting a voltage applied to the discharge lamp, current detection means for detecting a current flowing in the discharge lamp, voltage detection signal detected by the voltage detection means and detection by the current detection means. Output from the adding means based on a detection output from the battery voltage detecting means, and a battery voltage detecting means for detecting a voltage drop of the battery voltage equal to or higher than a predetermined voltage. And an additional value adjusting means for switching the magnitudes of the outputs of the voltage detecting means and the current detecting means so that the additional value of the voltage detecting means matches the preset reference value.

[0009]

The high-intensity discharge lamp lighting device according to the present invention, when the battery voltage drops, changes in accordance with the degree of the drop.
One of the current detection signal and the voltage detection signal added by the adder circuit is adjusted so that the addition result is always constant, and power control is performed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a high-intensity discharge lamp lighting device according to the present invention will be described below with reference to the drawings. First, the basic circuit configuration will be described. In FIG. 1, 11 is a battery 1.
The DC / DC converter (step-up means) for stepping up the DC voltage of 2 is composed of a switching transistor Qf, a transformer T, a pulse width modulator 35, etc.
PWM (pulse width modulation) that generates a pulse voltage from the DC voltage boosted by the C converter 11
The regulator inputs the output from the adder circuit 30 described later to the pulse width modulator 35 to perform pulse width modulation.

Reference numeral 14 is the P smoothed by the smoothing circuit 10.
An output from the WM regulator 13, that is, a full-bridge circuit that converts the pulse voltage into a rectangular wave AC voltage and applies it to a high-intensity discharge lamp (hereinafter, referred to as a discharge lamp) 15. Although not shown in FIG. 1, it will be described later. The full bridge driver 33 causes the switching transistor Q1,
Each of Q2, Q3 and Q4 is time-division driven.

Reference numeral 16 is a voltage detection circuit (voltage detection means) for detecting the voltage applied to the discharge lamp 15 by the full bridge circuit 14, and 17 is current detection for detecting the current flowing through the discharge lamp 15 by the full bridge circuit 14. Circuits (current detecting means) 31, 32 are amplifiers, and the amplifier 31
When the voltage V ₁ '= -αV ₁ output from the amplifier and the voltage V ₂ ' = -βV ₂ output from the amplifier 32, the output voltage V ₃ of the adder 30 is

V ₃ = αV ₁ '+ βV ₂ ' However, α and β are the amplification degrees of the amplifiers 31 and 32,
V ₁ and V ₂ are the voltages of the detection signals output by the voltage detection circuit 16 and the current detection circuit 17.

The PWM regulator 13 controls the conduction time, which is the pulse width of the pulse voltage, and controls so that Er = V _A3 = αV ₁ + βV ₂ (A) (that is, voltage detection). Control is performed so that the sum of the detection signal detected by the circuit 16 and the detection signal detected by the current detection circuit 17 becomes a constant value Er).

Here, the lamp current is also the rated current It so that Vt = αV ₁ when the voltage applied to the discharge lamp 15 is the rated voltage Vt. Moreover, if αV ₁ = βV ₂ = (1/2) Er ... (B) is set (however, V ₂ is detected by the current detection circuit 17 when the current flowing through the discharge lamp 15 is the rated current It). The power Pt supplied to the discharge lamp 15 (which is the voltage of the detection signal) is Pt = Vt · It = (αV ₁ ) · (βV ₂ ), and the outputs of the amplifiers 31 and 32 are equal to each other and Er / 2.
Has become.

Now, assuming that the voltage V of the discharge lamp 15 deviates from the rated value Vt by ± X percent, (A) and (B).
From the formula

[Equation 1] Becomes

The expressions (C) and (D) show that the lamp current increases when the lamp voltage decreases, and conversely the lamp current decreases when the lamp voltage increases.

At this time, the electric power P _X is calculated as follows: P _X = Vt (1-X) It (1 + X) = VtIt (1-
X ²⁾ = a Pt (1-X ^2). That is, where the lamp voltage is close to the rated value Vt, it is almost constant near the top of the graph as shown in FIG. For example, the change in power when Vt changes by 20 percent is 1- (0.2) ² = 0.96, which is only improved by 4 percent.
By the way, when it is driven with a constant current, it changes ± 20%.

Further, since the lamp voltage is low at the time of start-up, the current can flow nearly twice the rated value It, so that the rising speed is faster than the constant current drive.

FIG. 3 is a circuit diagram of the high-intensity discharge lamp lighting device shown in FIG. In FIG. 3, a full-bridge driver 33 turns on and off the transistors Q1 to Q4 of the full-bridge circuit 14, and when the transistors Q1 to Q4 are turned on and off, an AC voltage having a frequency of several 10 Hz to several 100 Hz is discharged. It is applied to the electric lamp 15.

In the PWM regulator 13, the width of the output pulse voltage is determined by the conduction time of the switching transistor Qf. The conduction time is determined by the pulse width modulator 35. The pulse width modulator 35 lengthens the conduction time when the addition signal Vc output from the adder 30 is lower than the internal reference voltage, and vice versa. When the addition signal Vc is higher than the internal reference voltage, the conduction time is shortened. That is, the pulse width modulator 35 includes the adder 3
The pulse width of the pulse voltage is controlled so that the output voltage Vc of 0 becomes constant. Reference numeral 36 denotes a trigger circuit for starting the initial lighting, which applies a trigger voltage to the discharge lamp 15 when the lighting switch S is turned on to start the discharge.

The full bridge driver 33 and the trigger circuit 36 are omitted in FIGS. 1 and 5.

Here, the voltage V ₀ applied to the discharge lamp 15
(It can be regarded as equivalent to the input voltage of the full-bridge circuit 14), the output voltage V ₁ ′ of the amplifier 31 is V ₁ ′ = −V ₀ · (R ₂ / (R ₁ + R ₂ )) · (R ₄ / R ₃ ) ... (1) However, R ₂ << R ₃ .

On the other hand, assuming that the current flowing through the discharge lamp 15 is Ir, the output voltage V ₂ ′ of the amplifier 32 is V ₂ ′ = −IrRr (R ₆ / R ₅ ) ... (2) However, Rr << R ₅ .

Therefore, the output voltage Vc of the adder circuit 30 is Vc = {V ₀ · R ₂ · R ₄ / R ₃ (R ₁ + R ₂ )} + (Ir · Rr · R ₆ / R ₅ ) ... (3) Further, the equation (3) can be expressed as Vc = h · V ₀ + I · Ir (4), and is therefore equivalent to the equation (A).

If Vc = Er, h = α and I = β, the same format as described above is obtained. The start-up characteristic at such a setting is as shown in FIG. 3, a fast start-up characteristic can be obtained, and a stable lighting characteristic is provided.

By doing so, the rated power can be supplied almost even if the lamp voltage deviates from the rated value, so that the rise time of the discharge lamp 15 can be considerably shortened. In FIG. 4, φ is the amount of light emitted from the discharge lamp 15, V ₀ is the applied voltage to the discharge lamp 15, and Ir is the discharge lamp 1.
5 shows the electric current flowing in 5.

Next, an example will be described in which the amplifiers 31 and 32 in the circuit configuration shown in FIG. 1 are replaced with attenuators 51 and 52 in order to change the lighting characteristics at the time of startup. In FIG. 8, 51 and 52 are non-linear attenuators connected to the preceding stage of the adder 30 and correspond to the amplifiers 31 and 32.

Reference numeral 52 is connected to improve the lighting characteristics as follows. That is, the response shown in FIG. 5 for a large current at startup is very small.
Further, at the time of start-up, the lamp voltage V _V is low, and the voltage detection circuit 16
Since the voltage V ₁ detected by is low, the equilibrium condition V ₁ '+ V
_The lamp current has a very large value in order to satisfy ₂ '= Er. Therefore, as shown in FIG. 7, the lamp current at startup is set so that 100 W of electric power is applied to the 35 W discharge lamp. The applied power has the fastest response when adjusted along the allowable power curve (solid line). In this embodiment, this curve is continuously approximated to accelerate the rise.

When the discharge lamp 15 is heated and the lamp voltage rises, the lamp current decreases to satisfy the equilibrium condition, and the voltage V _{2 of the} current detection signal output from the current detection circuit 17 becomes It is decreasing. That is, as shown in FIG. 6, a large change in the lamp current (3a part) is followed by a slightly gradual change (2a part), and then a linear change.

Next, in the attenuator 51 in the circuit configuration shown in FIG. 5, as shown in FIG. 8, the reference voltage Es is changed to Ra, Rb,
The voltage is divided by Rc, and the divided voltage is output to the comparator C.
It is input to the non-inverting terminal as a reference voltage of 1 to C3. The output terminals of the comparators C1 to C3 are resistors R
It is connected to the current detection circuit via 1 to R3 and R. A4 is an operational amplifier. When the output voltage V ₂ of the current detection circuit 17 is zero, all the comparators C1 to C3 are turned off and R1 to R3 are not connected.

In the comparator C1, when the output voltage V ₂ of the current detection circuit 17 rises, the reverse phase input voltage through R and R1 exceeds the divided voltage value of Es, and the comparator C1 is turned on. As a result, the voltage V ₂ is attenuated by R1 / (R + R1). The point where this attenuation occurs is point 1 in FIG. 7, and Rc is selected so that the partial pressure value is exceeded at this point 1.

Further, when V ₂ rises, the comparator C
2 is turned on, and the voltage Vb is attenuated by the parallel combined resistance of R1 and R2. This attenuation is {R1R2 / (R1 + R2)} / {R + (R1R2 /
(R1 + R2))} = R1R2 / {R (R1 + R2) +
R1R2}. The point that receives this attenuation is point 2 in FIG.
Rb may be selected so that the partial pressure value is exceeded at point 2.

Further, V ₂ rises and the comparator C3
When is turned on, the voltage V ₂ is attenuated by the parallel resistance of the resistors R1, R2 and R3. Then, the point receiving this attenuation is point 3 in FIG. 7, and Ra is selected so as to exceed the partial pressure value at this point 3.

Due to the operation of the attenuator 51, when the lamp voltage is lower than the rated voltage (85 V), the discharge lamp 15 is promptly started and shifts to a steady state.

When the lamp voltage exceeds the rated voltage, the voltage applied to the discharge lamp 15 gradually decreases along the quadratic curve. Then, the output voltage V ₁ of the voltage detection circuit 16 rises, but since this voltage V ₁ is attenuated by the attenuator 52, the decrease in the current flowing through the discharge lamp 15 is suppressed,
The constant power characteristic is further improved.

That is, when the voltage V ₂ rises and C4 turns on, V ₂ becomes (R5R6 / (R5 + R6)) / {R +
It is attenuated by (R5R6 / (R5 + R6))}.

If the lamp voltage is above the rated value, the output voltage V ₂ of the current detection circuit 17 will be below the standard value.
The voltage V ₂ decreases linearly as shown in FIG.

Next, with reference to FIG. 9, a case where the output voltage of the battery 12 drops below a predetermined level when the discharge lamp 15 is started will be described. FIG. 9 shows only a part of FIG. 5, that is, a part necessary for explanation. In the figure, the power line connected to the DC / DC converter 11 from the output of the lighting switch S is branched on the way and connected to the comparison circuit 61, and the output line is the reference voltage switching circuit 6
Connected to 2.

The comparison circuit 61 is, for example, a minimum operating voltage of an on-vehicle battery of 10 volts (generally, a voltage which should not be used at a voltage lower than this, which is a reference voltage E.
_{Let T.} ) Is set as a reference voltage, and when the output voltage of the battery 12 is lower than this minimum operating voltage, the reference voltage of the reference voltage switching circuit 62 is switched from the high voltage Eh to the lower voltage E _s , This is supplied as the reference voltage Es of the attenuator 51.

That is, when the output voltage of the battery 12 drops below the reference value E _T , the reference voltage switching circuit 62 is switched to the lower reference voltage E _S.
As a result, the electric power supplied to the discharge lamp 15 is initially supplied with the characteristic along the alternate long and short dash line as shown in FIG. 7, so that the starting lighting gradually rises.
In other words, the lighting current is suppressed to a predetermined value or less at the time of starting to reduce the lighting characteristics within a usable range, and without this control, it is assumed that the voltage of the battery 15 is about 10 volts at the initial stage, and the lighting is performed. When the switch S is turned on, the battery voltage drops significantly to a non-reusable voltage in order to supply the lighting current.

[0042]

As described above, according to the present invention, the rise time can be shortened, the flatness of the light output can be obtained, and the printed circuit board can be made small. It

[Brief description of drawings]

FIG. 1 is a circuit block explanatory diagram showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the amount of voltage deviation applied to the discharge lamp 15 and the electric power.

FIG. 3 is a diagram showing a specific circuit diagram of the circuit block explanatory diagram in FIG. 1.

FIG. 4 is a graph showing a response characteristic.

FIG. 5 is a diagram showing the amplifier in FIG. 1 replaced with an attenuator.

FIG. 6 is a graph showing the relationship between the output of the attenuator and the detection voltage of the voltage detection circuit.

7 is a graph showing the relationship between the voltage applied to the discharge lamp 15 and the power supplied to the discharge lamp 15. FIG.

FIG. 8 is a graph showing the relationship between the output of the attenuator and the detection voltage of the voltage detection circuit.

FIG. 9 is a circuit block explanatory diagram showing a main part of an embodiment of the present invention.

FIG. 10 is an explanatory diagram of a circuit block for explaining a conventional example.

[Explanation of symbols]

 12 Battery 11 DC / DC Converter 13 PWM Regulator 14 Full Bridge Circuit 15 Discharge Lamp 16 Voltage Detection Circuit 17 Current Detection Circuit 30 Addition Circuit 31, 32 Amplification Circuit 51, 52 Attenuator 61 Comparison Circuit 62 Reference Voltage Switching Circuit

Claims (1)

[Claims] 1. A boosting means for boosting a battery voltage, a pulse generating means for converting an output voltage from the boosting means into a pulse voltage having a variable pulse width and outputting the pulse voltage, and applying the pulse voltage to a discharge lamp. In a high-intensity discharge lamp lighting device comprising: a full bridge circuit, a voltage detecting means for detecting a voltage applied to the discharge lamp, a current detecting means for detecting a current flowing through the discharge lamp, and the voltage detecting means. Adding means for taking the sum of the voltage detection signal detected by the means and the current detection signal detected by the current detecting means, battery voltage detecting means for detecting a voltage drop of the battery voltage above a predetermined voltage, and the battery voltage detecting means The output magnitudes of the voltage detecting means and the current detecting means are adjusted so that the added value output from the adding means matches the preset reference value based on the detection output from the means. A high-intensity discharge lamp lighting device, comprising: an addition value adjusting means for switching the height.