JPS62150697A - Discharge lamp burner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a chopper-type discharge lamp lighting device, which is used for high-pressure discharge lamps in which the discharge lamp voltage increases by a moment during lighting, including output fluctuations such as ripples. It is particularly suitable for lighting using a DC power source.

(Background Art) FIG. 4 is a circuit diagram showing a conventional example of a chopper type discharge lamp lighting device. In Fig. 4, 1 is a commercial power supply, 2 is a diode bridge, and 3 is a smoothing capacitor. It constitutes a DC type aE including: 4 is a transistor, 5 is an inductance, 6 is a flywheel diode, and 7 is a capacitor for high frequency bypass, and these circuit elements constitute a chopper circuit CHP. The electric power chopped at high speed by the transistor 4 is supplied to the discharge lamp 10 via the inductance 5, and when the transistor 4 is on, the electric power is transferred from the DC power supply E to the transistor 4, the inductance 5, and the discharge lamp 10 (or When a current flows through the capacitor 7), the resistor 8, and the path returning to the DC power supply E, and the transistor 4 is turned off, the energy stored in the inductance 5 is transferred from the inductance 5 to the discharge lamp 10 (or the capacitor 7), It passes through the resistor 8, the flywheel diode 6, and is emitted on the path back to the inductance 5. The capacitor 7 is a high frequency component bypass capacitor, and the discharge lamp 10 is supplied with a DC component.

In the circuit shown in FIG. 4, 8 is a resistor for detecting an output current, and 9 is a control circuit for driving a transistor. This control circuit 9 is a drive circuit that switches the transistor 4 at a constant frequency, and detects the instantaneous value of the output current from the output current detection resistor 8 to set the current value I set in advance.

When it reaches , transistor 4 is turned off. This makes it possible to suppress fluctuations in the output current IL with respect to fluctuations in the output of the commercial power supply 1. Here, the changes in the current ■L with respect to the output fluctuations of the commercial power supply 1 are shown in Fig. 6 (a) and (b).
Shown below. Figure (a) shows that when the output of commercial power supply 1 is large,
FIG. 2B shows a case where the output of the commercial power supply 1 is small. When the output of the commercial power supply 1 is large, the rising slope of the current I becomes steep when the transistor 4 is on, and the set value I. Since the time required to reach the voltage becomes faster, the on-time of the transistor 4 becomes shorter and an increase in output is suppressed. Conversely, when the output of the commercial power supply 1 drops by 1 degree Celsius, the on time of the transistor 4 increases, suppressing the drop in output. That is, in the chopper-type discharge lamp lighting device, in order to stabilize the output of the discharge lamp 10, the control circuit 9 detects the instantaneous value of the output current L, and adjusts the on/off duty ratio of the transistor 4. It's changing.

By the way, when the discharge lamp 10 is a high-pressure discharge lamp such as a metal halide discharge lamp, as the lighting time elapses, the discharge lamp voltage increases (the equivalent impedance of the discharge lamp increases). Even if the output of is constant, the slope of current ■ becomes gradually gentler. When the slope of the current IL becomes gentler, the on time of the transistor 4 becomes longer and the fluctuation of the current IL becomes smaller. However, the discharge lamp power increases by the amount that the discharge lamp voltage increases, so as the discharge lamp voltage increases, the discharge becomes more and more. There is also the problem of increased lighting power and overload.

Therefore, when the discharge lamp voltage increases, by lowering the switching frequency of the transistor 4, the current 1. It is possible to suppress the rise in the discharge lamp power while keeping the maximum value of I, i.In this case, the switching frequency will drop to the audible frequency range, causing noise problems and increasing the on time. A problem arises in that the drive power of the transistor 4 increases accordingly.

Another possible method is to limit the on-time of the transistor 4 to within a certain period of time to suppress the increase in discharge lamp power, but in this case, as shown in FIG. After reaching this point, as shown in FIG. 6(d), as the slope of current IL becomes smaller, the maximum value of current IL becomes smaller than set value Io. Electrician 1
In a region where the slope of - is relatively steep and the peak value Io is constant as shown in FIGS. 6(a) to (c), the output voltage of the smoothing capacitor 3 is ■.

Even if it is a pulsating flow including ripples as shown in FIG. 5 (LL), the current 1. The maximum value of is constant as shown in FIG. 5(b), the optical output waveform is also flat, and flicker-free light can be obtained. However, the discharge lamp voltage increased and the 6th
As shown in FIG. 5(d), when the on-time of the transistor 4 reaches a region where the on-time is limited, the peak value of the current IL changes with respect to the instantaneous value of the voltage , as shown in FIG. The optical output waveform also includes ripples, which has the disadvantage of causing flickering. Also, regarding output fluctuations other than ripples, the on-time of transistor 4 is not controlled in this region, so current 1. The problem is that the fluctuations in

(Object of the Invention) The present invention has been made to solve the above-mentioned problems, and its purpose is to respond to changes in power supply voltage and discharge lamp impedance without reducing the switching frequency. Another object of the present invention is to provide a chopper-type discharge lamp lighting device that can suppress output fluctuations and prevent flickering without limiting the on-time of a switching element.

(Disclosure of the Invention) To explain the discharge lamp lighting device according to the present invention with reference to the illustrated embodiment, as shown in FIGS. 1 to 3, a DC power source E and a high frequency A short circuit including a transistor 4 which is a high-speed switching element to perform the switching, an inductor 9 and a capacitor 7 which smooth the voltage that has been chipped, and a diode 6 which forms a release path for the energy stored in the inductance 5. The circuit CHP, the high-pressure discharge lamp 10 connected to the output end of the chopper circuit CHP, the current detection resistor 8 inserted in series in the main current path of the chopper circuit CHP, and the transistor 4, which is the high-speed switching element, are connected at a constant cycle. The current I + detected by the current detection resistor 8
- a control circuit 9 that turns off the transistor 4, which is a high-speed switching element, when the current reaches a predetermined maximum current value I0. In a complete discharge lamp lighting device, a discharge lamp voltage detection circuit Dv is connected in parallel with the discharge lamp 10,
Detection voltage V detected by the discharge lamp voltage detection circuit Dv
b7! When IC increases, the maximum current value I in the control circuit 9. A maximum current value control circuit 13 is provided to control the current value to be low.

In this way, in the present invention, when the discharge lamp voltage increases, the main current of the chopper circuit CHP increases.

Since the maximum value I0 of t is controlled to be small,
This makes it possible to suppress a rise in discharge lamp power with respect to a rise in discharge lamp voltage. Therefore, since there is no need to reduce the switching frequency to prevent overload, problems such as noise will not occur. Also, there is no need to limit the ON time of the switching elements, so the output fluctuation of the DC power supply E No flickering occurs.

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

FIG. 1(a) shows a main circuit of a discharge lamp lighting device according to an embodiment of the present invention, and FIG. 1(b) shows a detailed configuration of a control circuit used in this discharge lamp lighting device. The main circuit shown in FIG. 1(a) is the same as the conventional example in FIG.
Identical parts are given the same reference numerals and explanations will be omitted. A discharge lamp voltage detection circuit Dv is connected to both ends of the discharge lamp 10.

This detection circuit Dv includes voltage dividing resistors 11 and 12, and the voltage at the voltage dividing point S is inputted to the control circuit 9.

The control circuit 9 includes a maximum current value control circuit 13, a comparator 22, a pulse generation circuit 23, 29, and a transistor base drive circuit 37.

First, the maximum current value control circuit 13 includes a diode 14, a capacitor 15, a DC power supply 16, resistors 17 to 20, 48 .
49 and an operational amplifier 21.

The voltage at point b in the discharge lamp voltage detection circuit Dv described above is input to the input terminal of the maximum current value control circuit 13. The voltage input through the terminal charges the capacitor 15 via the diode 14.

Since the reverse current blocking diode 14 is connected, the capacitor 15 is charged to the peak value of the voltage input from the terminal. This voltage vb is applied to the inverting input terminal of the operational amplifier 21 via the resistor 17.
Reference voltages 1 and 6 of a DC power supply 16 are applied to the non-inverting input terminal t1 of 1 through a resistor 18. The operational amplifier 21 outputs the difference voltage between the voltage of the capacitor 15 and the reference voltage.

The output voltage of the operational amplifier 21 is divided by resistors 48 and 49 to become the output voltage of the maximum current value control circuit 13. The resistance values of resistors 17 to 20 are R17 to R2°, and Rl 7
= R+ as R2゜=R+9, the output voltage of the operational amplifier 21 is ■. is V O= R20 (V 16
Vb)/R17. As is clear from this equation, when the partial voltage vb of the discharge lamp voltage increases, the operational amplifier output voltage ■. becomes smaller. Maximum current value control circuit 13
The output voltage vb of this operational amplifier 21 is the output voltage ■.

is divided by a resistor of 47.48.

The comparator 22 is provided to define the peak value of the current IL by the output voltage vh of the maximum current value control circuit 13, and the comparator 22 is provided to define the peak value of the current IL by the output voltage vh of the maximum current value control circuit 13.
The voltage Va at point a obtained by the detection resistor 8 is compared, and the comparison output is input to a pulse generation circuit 29 for setting the on-time of the transistor.

The pulse generation circuit 23 is provided to set the switching frequency of the transistor 4, and includes a general-purpose timer IC 28 and a resistor 24 added to the timer IC 28.
, 25, and capacitors 26 and 27. As the timer IC 28, M51841P (commonly known as 555) is used. The terminal ■ of the timer IC 28 is a single terminal, and when the voltage of this terminal becomes 1/3 Vcc or less,
The timer IC28 is triggered and the output terminal ■ (8 points) becomes I.
] level. Resistance 24. When the time determined by the capacitor 26 has elapsed and the terminal ■ reaches 2/3 Vcc, the output terminal ■ goes to L level, conduction occurs between the terminal ■ and the terminal ■ of the timer IC 28, and the voltage is accumulated in the capacitor 26. Energy is released through resistor 25. and,
When the voltage across the capacitor 26 becomes 1/3 Vcc or less, the timer (2) C28 is triggered again, and the output terminal (2) becomes H level. Thereafter, the same operation is repeated, and a voltage Ve as shown in FIG. 2(a) is obtained at the output terminal (3).

The pulse generating circuit 29 is provided to set the on-time of the transistor 4, and includes a general-purpose timer IC 36, resistors 33-35, and capacitors 30-32 added to the timer IC 36. General purpose timer IC
36 is the same as timer IC28<M51841P
(commonly known as 555) is used. Resistance 33. One circuit of the timer IC 36 composed of the capacitor 30 generates a pulse from the output terminal of the timer IC 28 (see Fig. 2).
a)), the waveform at one point is as shown in Figure 2(b), and the fall from H level to L level, that is, the fall from L level to H level at the output terminal ■ of the timer IC28. At the rising edge, the timer IC 36 is triggered. This trigger operation causes the output terminal of the timer IC 36 to
point g) remains at H level for a certain period of time as shown in FIG. 2(C).

The transistor base drive circuit 37 is provided to drive the base of the transistor 4 in the chopper circuit CHP, and includes a pulse transformer 47 whose output terminals c and d are connected between the base and emitter of the transistor 4, and this pulse transformer. A transistor 46 for driving 47, a diode 44, 45, and a resistor 38 to 4
1 and capacitors 42 and 43. The base of the transistor 47 is connected to the output of the pulse generating circuit 29, and the drive circuit 37 turns on the transistor 4 during the period when the output terminal (2) (point g) of the timer IC 36 is at H level.

When the transistor 4 is turned on, a current {circle around (2)} flows into the inductance 5. This current (2) is detected as a voltage Va by the current detection resistor 8. This voltage V
a is compared with the output voltage vh of the maximum current value control circuit 13 related to the discharge lamp voltage by the comparator 22, and the discharge lamp voltage can be increased. When Vh>Va, the output terminal i of the comparator 22 becomes H level, and when Va≧VI+, the output ii of the comparator 22 becomes L level.

The output terminal i of the comparator 22 is connected to the timer IC 3 in the pulse generation circuit 29 for setting the ON time of the transistor 4.
It is connected to the reset terminal ■ of 6.

When an L level signal is input to the reset terminal ■ of the timer rC36, the timer IC36 is reset, and the timer IC36
The output terminal ■ (point g) becomes L level (m2 diagram (c)
, (d)). In other words, transistor 4 is turned on and current I
When L increases and reaches a certain value (Va≧\lh), the reset terminal ■ (1 point) of the timer IC36 becomes L level,
The output terminal (2) (point g) of the timer IC 36 also becomes L level, and the transistor 4 is turned off. As a result, the current I decreases (:jS2 (e)).

As is clear from the above description, in the circuit of this embodiment, when the discharge lamp voltage increases, the maximum current value control circuit 13
The output voltage vh of the discharge lamp decreases, and the output of the resistor 8 capacitor 22 becomes L level, resetting the ON signal of the transistor 4. As the discharge lamp voltage rises, the chopper circuit CHP
It is possible to perform control to reduce the maximum value I of the main current.

FIG. 3 shows a main circuit of a discharge lamp lighting device according to another embodiment of the present invention. In this embodiment, an external pressure type chopper circuit CHP is used as the main circuit for lighting the discharge lamp. In this chopper circuit CHP, when the transistor 4 is on, current flows in a loop from the capacitor 3, through the inductance 5, the transistor 4, the resistor 8, and back to the capacitor 3, and when the transistor 4 is off, the current flows through the inductance 5. The stored energy is released through the inductance 5 through a diode 6, a discharge lamp 10 (or a capacitor 7), a resistor 8, a capacitor 3, and a loop returning to the inductance 5. At both ends of the discharge lamp 10, a voltage dividing resistor I for current detection is installed, as in the previous embodiment.
I, 12 are connected, and the voltage at the voltage dividing point is input to the control circuit 9. As for the control circuit 9, the same one as in the previous embodiment is used.

Note that the chopper circuit type is not limited to the circuits described in each of the above embodiments, and other circuit configurations may also be used.

(Effects of the Invention) As described above, the present invention controls the maximum value of the main current flowing through the chamber circuit so that it becomes smaller when the discharge lamp voltage increases, so that the discharge lamp voltage increases during lighting. When lighting a high-pressure discharge lamp whose voltage rises, it is possible to suppress a rise in discharge lamp power with respect to a rise in discharge lamp voltage, and to prevent overload. Further, in the present invention, unlike the conventional example, there is no need to reduce the switching frequency to prevent overload, so problems such as noise do not occur. Furthermore, in the present invention, the maximum value of the main current is reduced as the discharge lamp voltage increases, so the maximum value of the main current is sufficient to withstand fluctuations in the output of the DC power supply due to ripples, etc. It is stable, and therefore, the discharge lamp current does not fluctuate in response to output fluctuations of the DC power supply, unlike in the conventional case where overload was prevented by limiting the on-state rPf of the switching element. , no flickering occurs.

[Brief explanation of drawings]

FIG. 1(a) is a circuit diagram showing the main circuit of a discharge lamp lighting device according to an embodiment of the present invention, FIG. 1(b) is a circuit diagram of a control circuit used in the same discharge lamp lighting device, and FIG. 3 is a circuit diagram showing the main circuit of a discharge lamp lighting device according to another embodiment of the present invention, FIG. fj44 is a circuit diagram of a conventional example, FIG. The figure is an explanatory diagram of the operation of the conventional example same as above. E is a DC power supply, CHP is a chopper circuit, Dv is a discharge lamp voltage detection circuit, 4 is a transistor, 5 is an inductance, 6 is a diode, 7 is a capacitor, 8 is a current detection resistor, 9 is a control circuit, 1o is a discharge lamp , 13 is a maximum current value control circuit.

Claims (1)

[Claims] (1) A chopper circuit including a DC power source, a high-speed switching element that chops the DC power source at high frequency, an inductance and a capacitor that smooth the chopped voltage, and a diode that forms a release path for the energy stored in the inductance. a high-pressure discharge lamp connected to the output end of the chopper circuit; a current detection resistor inserted in series in the main current path of the chopper circuit;
A chopper-type discharge lamp lighting device including a control circuit that turns on the high-speed switching element at a constant cycle and turns off the high-speed switching element when the current detected by the current detection resistor reaches a predetermined maximum current value. A discharge lamp voltage detection circuit is connected in parallel with the discharge lamp, and when the detection voltage detected by the discharge lamp voltage detection circuit increases, the maximum current value in the control circuit is controlled to be lower. A discharge lamp lighting device characterized by being provided with a current value control circuit.