JPH02172194A - Discharge lamp lightup device - Google Patents

Abstract

PURPOSE:To provide controllability for a discharge lamp in a simple circuit configuration by raising the switching frequency in accordance with increase in the current flowing through a resonance capacitor. CONSTITUTION:The switching frequency of an inverter circuit equipped with a resonance capacitor C1 installed in parallel with an inductor L1 and a discharge lamp 2 is set higher than the natural frequency of a load circuit. The current flowing through this capacitor C1 is divided by a resistance R1 and integrated with the aid of a diode D3, resistances R2, R3, and capacitor C2 to be sensed in the form of a voltage value. Through an inverting amplifier 5, V-F converter 6, and frequency divider 3, this voltage value controls the switching frequency of switching elements Q1, Q2 of the inverter. By this frequency control the discharge lamp 2 is controlled into optimum condition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a discharge lamp lighting device for lighting a discharge lamp at high frequency using an inverter having a resonant circuit.

[Prior Art] Conventionally, in an inverter-type discharge lamp lighting device, methods for detecting the state of the discharge lamp include a method of detecting the lamp voltage of the discharge lamp by dividing it with a high resistance, and a method of detecting the lamp voltage of the discharge lamp by dividing it with a high resistance. Methods have been proposed in which the lamp current is detected by inserting a resistor or current transformer.

These methods directly detect the lamp voltage and lamp current of a discharge lamp, and are applied to various types of control. On the other hand, as a method for indirectly detecting the state of a discharge lamp, it is possible to determine whether or not the discharge lamp is in a half-wave discharge state by determining the magnitude of the current in a resonance capacitor connected in parallel to both ends of the discharge lamp. A method for determining this has been proposed.

Figure 8 shows an example of the circuit (see Japanese Patent Application No. 62-6493). At both ends of the DC power supply E, there are transistors Q,...
A commutating diode D, , D, is connected in antiparallel to each transistor Q, , Q2, to which a series circuit of Q, is connected in parallel. The drive circuit 1 includes a transistor Q,
, Q are generated to alternately turn them on. By the on/off operation of transistors Q, Q2,
A rectangular wave-like high frequency voltage is applied to a series resonant circuit consisting of an inductor and a capacitor C3, and an LC resonant current flows. The discharge lamp 2 is connected in parallel with the capacitor C8, both of which are driven by the 1i voltage. When the discharge lamp 2 is a thermionic emission type discharge lamp such as a fluorescent lamp, the thermionic emission material (hereinafter referred to as emitter) applied to the filament decreases at the end of the life of the discharge rod. As a result, it may become difficult to discharge, a phenomenon called half-wave discharge may occur, or the discharge may stop. At the end of the life of a fluorescent lamp, it is rare for the emitters of two filaments to disappear at the same time, and the emitter of one filament always disappears first, so the half-wave discharge phenomenon occurs from the filament whose emitter has disappeared. This phenomenon occurs because electrons are not emitted.

This state in which the emitter disappears is called an emitterless state.

In the circuit of FIG. 8, in order to detect this emissionless state, a first detection resistor R0 is connected to the emitter side of the transistor Q2, and a second detection resistor R0 is connected in series with the resonance capacitor C1.
detection resistor R7 is connected, and each resistor n
o , the voltage drop that occurs on R+ is connected to the diode D o ,
Rectified by D3, comparator CMPI, CMr'2
The signal is compared with the reference voltages V, , V, and a detection signal is obtained via an OR circuit Ort.

Suppose now that the emitter of the filament on one side of the discharge lamp 2 disappears, and the discharge lamp 2 enters a half-wave discharge state in which it conducts only in the direction shown by the arrow a. In this field 3, the Q of the series resonance increases in C1 during the high frequency half cycle when the lamp current is blocked, so the inductor L is transferred from the capacitor C1.
An excessive current will flow in the direction of 1. This excessive current is caused by electromagnetic energy accumulated in inductor L1 when transistors 1 to Q are conductive, flowing through detection resistor R,,R, and capacitor C1, and as a voltage drop across detection resistor R0, D0 and comparator CM
Detected by P 1.

On the contrary, assume that the emitter of the filament on the other side of the discharge lamp 2 disappears, and the discharge lamp 2 enters a half-wave discharge state in which conduction occurs only in the direction indicated by the arrow. In this case,
For similar reasons, inductor and capacitor C1
Excessive current flows in the direction of. This excessive current flows from the DC power supply E to I and transistor Q when transistor Q is conductive.
, , inductor L, capacitor C3, and detection resistor R3, and is detected as a voltage drop across detection resistor R1 by diode D and comparator CMP2.

The detection outputs of the comparators CMPI and CMP2 are input to the drive circuit 1 via the OR circuit OR, and in the case of emission reduction, transistors Q, , Q are both turned off to stop the oscillation operation of the inverter circuit.

Figure 9 is a circuit diagram of another conventional example. In this circuit, the magnitude of the current flowing through the resonance capacitor C3 is determined by the resistor R1, the diode D5, the reference voltage V2, and the comparator CMP2.
Since there is a possibility that an overcurrent may flow through the transistors Q, Q2, an operation stop signal is transmitted to the drive circuit 1. Also, resistor Rs, diode D! , the reference voltage V1 and the comparator CMP3 determine the magnitude of the lamp current flowing through the discharge lamp 2, and the determination result is transmitted to the drive circuit 1.
is being communicated to. Furthermore, resistors R,,,R,,,diodes D,. , the magnitude of the lamp voltage applied to the discharge lamp 2 is determined by the reference voltage V1 and the comparator CMP4,
The determination result is transmitted to the drive circuit 1. 13i11
For example, in a high-pressure discharge lamp, the lamp voltage changes immediately after starting and as it approaches a stable state.
to communicate. Note that the lamp current and lamp voltage are not limited to binary discrimination, but may also be linearly detected and used to control the drive circuit 1.

[Problems to be Solved by the Invention] In the above-mentioned conventional example 1, the state of the discharge lamp 2 is indirectly detected by the current flowing through the resonance capacitor C1. It merely detects that the discharge lamp 2 has fallen into a normal state, and does not detect and control the state of the discharge lamp 2 when the discharge lamp 2 is in a normal state.

Furthermore, in the conventional S2 described above, the current of the resonance capacitor CI is not used for any control, but is merely used to stop oscillation when an overcurrent flows. Moreover, in order to control the state of the discharge lamp 2, both the lamp current and the lamp voltage are detected, so there is a problem that the configuration of the detection circuit becomes complicated. Furthermore, when detecting only either the lamp current or the lamp voltage, there is a problem in that the lamp current or the lamp voltage can only be controlled to a constant level. Furthermore, if a voltage divider circuit using resistors is used to detect lamp voltage, for example, in discharge lamps that require high voltage for starting,
There is a problem that it is necessary to use a resistor with sufficiently high voltage resistance, which makes it expensive.

As described above, in the conventional example, although the current flowing through the resonance capacitor C1 connected in parallel with the discharge lamp 2 is detected, the presence or absence of an overcurrent is simply determined based on binary values. and the state of discharge lamp 2 is i'1tlltill
I couldn't. Therefore, there is a problem in that the configuration for detecting and controlling the state of the discharge lamp 2 becomes complicated.

The present invention has been made in view of the above points, and its purpose is to detect the current flowing through the resonance capacitor connected in parallel with the discharge lamp.
An object of the present invention is to provide a discharge lamp lighting device that allows controlling the state of a discharge lamp.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, the first
As shown in the figure, there is an inverter circuit including a series resonant circuit of an inductor L1 and a capacitor C1, and a load circuit in which a discharge lamp 2 is connected in parallel with the capacitor CI, and the switching frequency f of the inverter circuit is controlled by the load circuit. The discharge lamp lighting device is characterized in that it is provided with a current detection means for detecting the current flowing through the capacitor C3, and a frequency control means for increasing the switching frequency when the detected current value increases. That is.

[Operation] In the present invention, the lamp voltage V1a of the discharge lamp 2 can be detected because the current detection means for detecting the current flowing through the capacitor CI connected in parallel with the discharge lamp 2 is provided. In other words, the current Ic flowing through the resonance capacitor C2 is I e= 2 yr rx C+
fXVi'a, and the detected voltage Vdt is proportional to the lamp voltage .mu., and also proportional to the switching frequency r of the inverter circuit. Therefore, by changing the switching frequency r based on the detected voltage Vdt, the discharge lamp 2 can be controlled to an appropriate state.

For example, if the discharge lamp 2 is an HID (high-intensity discharge lamp), the discharge lamp 2 will be almost short-circuited immediately after starting! By chance,
Lamp voltage Vim becomes low. Until this is detected and the discharge lamp 2 approaches a stable state, the switching frequency r can be changed to smoothly bring the discharge lamp 2 close to a stable state.

In addition, as in the embodiment shown in FIG. 6, by arithmetically combining the lamp current generator 1u and the current Ic of the capacitor C6, it is also possible to perform further control for stable lighting of the discharge lamp 2.

[Embodiment 1] Figure 1 is a circuit diagram of the first embodiment of the present invention, and Figure 2 (
a) to (c) are the main circuit diagrams, and Fig. 3 (n), (
b) is an explanatory diagram of its operation.8 In this embodiment, parts having the same functions as those in the conventional example are given the same reference numerals, and duplicate explanations are omitted.0 In this embodiment, the capacitor C1
The current ■c flowing through the circuit is taken out as a voltage drop at a resistor R1, and divided through a diode D by resistors R2 and R3 and a capacitor C2 to obtain a detection voltage Vdt. This detection voltage Vdt is inverted and amplified by the inverting amplifier 5. When the current Te increases, the output voltage of the inverting amplifier 5 decreases, and when the current Ic decreases, the output voltage of the inverting amplifier 5 increases. The output voltage is input to the V-F converter 6, and the voltage change is converted into a change in the oscillation frequency. The V-F converter 6 is composed of a well-known timer IC (NE555 manufactured by Sidanetics or μPCl555 from Nippon Electric Layer, which is compatible with this).
Operating power supply E + , E i and resistance R = , R to C4
s and a capacitor C3 are added to form an astable multivibrator. The 5th bin of timer IC4 is a frequency control terminal, and when the voltage of this 5th bin is increased,
The oscillation frequency becomes lower, and when the voltage of the 5th bin is lowered,
The oscillation frequency becomes higher. Therefore, as the current Ic increases, the oscillation frequency of the V-F converter 6 increases, and the current Ic increases.
As c decreases, the oscillation frequency of the V-F converter 6 becomes lower. The oscillation frequency output from this V-F converter 6 is
The frequency is divided by two in the frequency divider circuit 3, and each divided frequency output is inputted to the control terminals of l transistors Q, , Q2 through one drive circuit IA, IB, and the transistors Q, , Q, are alternately connected. It controls on/off.

FIG. 2(a) shows a circuit I1 configuration of the inverting amplifier 5. In FIG. This inverting amplifier 5 has an input resistor r and a feedback resistor r connected to the inverting input terminal of the operational amplifier OP, and a reference voltage E' is applied to the non-inverting input terminal, and outputs an input voltage whose phase is inverted. Generates voltage.

FIG. 2(b) shows the circuit configuration of the frequency divider circuit 3. The input of the frequency divider circuit 3 is connected to the trigger input of the T flip-flop FFl, and the AND circuits G, , G
, is connected to one input of . AND circuit G +
, the other input of G2 is a T flip-flop FF
The outputs Q and 'Q of , are connected, and the AND circuit G, ,
The output of G2 is a pair of frequency-divided outputs.

FIG. 2(e) shows the circuit configuration of drive circuits IA and IB. The input signal is applied to the base of transistor Q, via base resistor r,. When the transistor Qj is turned on, the current from the operation 4 power supply E flows through the pulse transformer P.
flows into the primary winding of T, and its secondary winding output is the base resistance r
4 and is supplied between the base and emitter of the transistor Q or G2.

FIGS. 3(a) and 3(b) are explanatory diagrams of the operation of this embodiment.

The figure (n) shows the lamp voltage V1a of the discharge lamp 2 and the detected voltage V
The relationship between dt and switching frequency f is shown. As is clear from the figure, when the lamp voltage V1a increases, the current Ic flowing through the resonance capacitor c1 increases, so the detection voltage VdL increases and the switching frequency f
will also rise, and vice versa.

FIG. 3(b) shows a different discharge lamp 11. ．． 12,1. It shows the relationship between the lamp voltage ia and the switching frequency r when both are lit by the same lighting device. Now, there is a discharge lamp,
is lit at frequency r=r, and the lamp voltage is Vt'a.

Suppose that another discharge lamp 12 is lit using the same lighting device. Here, a discharge lamp! , ,1. The impedance of the discharge lamp 12 is not necessarily the same due to variations, and the impedance of the discharge lamp 12 is the discharge lamp! , then the frequency t=r.

Then, the lamp voltage V1a2 of the discharge lamp 12 becomes higher than the lamp voltage V1a+ of the discharge lamp 11. Therefore, the detected value VdL of the current of the capacitor C8 when the discharge lamp 12 is lit is higher than the detected value Vdt of the current of the capacitor C1 when the discharge lamp 11 is lit. As a result, the output voltage of the inverting amplifier 5 becomes low, the oscillation frequency of the VF converter 6 becomes high as r=r, >r, and the operating point is at the third
Move from point A to point B in figure (b), and the lamp voltage V
l'a, decreases. On the contrary, a discharge lamp with lower impedance than discharge lamp 11! , when lit by the same lighting device, the lamp voltage Vi at frequency r= r
Since a is lower than V1a+, the oscillation frequency is r=
r becomes low as <f+, and the operating point is point A in Fig. 3(b).
The lamp voltage Vfa increases as the lamp moves from point C toward point C.

If controlled in this way, even when lighting a discharge lamp such as a high-pressure sodium lamp with high color rendering, whose emitted color temperature differs significantly depending on the lamp voltage VNa,
Variations in lamp voltage due to variations between discharge lamps are reduced, and differences in color temperature between discharge lamps can be reduced.

In addition, in the present invention, the switching frequency f is set higher than the natural oscillation frequency of the load circuit because if the switching frequency f is set lower than the natural oscillation frequency of the load circuit, the transistor Q,... At the moment when Q, are turned on, diodes D2, . Since current is flowing through diode D2. D.
This is to prevent the transistor Q and the diode D, or the transistor Q2 and the diode DI, from being turned on simultaneously until the reverse recovery time elapses.

In this way, when the switching frequency f is set higher than the natural oscillation frequency of the inverter circuit, the phase of the current flowing through the load circuit lags behind the voltage applied to the load circuit, so this is called a slow phase mode. I'm here. In the slow phase mode, as shown in FIG. 3(b), as the switching frequency increases, the voltage applied to the resonance capacitor C1 decreases, so the resonance current re also decreases. When the detected value VCIt of Ic increases, by controlling the switching frequency r to increase, the resonance current Ie can be controlled to be stabilized.

[Embodiment 2] Figure 4 is a circuit diagram of a second embodiment of the present invention, and Figure 5 (
u) and (b) are diagrams explaining the operation.0 In this embodiment,
It uses a high-pressure discharge lamp that requires high voltage to start. Therefore, in this embodiment, a low frequency oscillation circuit 7 is provided in order to intermittently generate a high voltage for starting at the time of starting. This low frequency oscillation circuit 7 is a well-known timer IC 40 (
NE555 manufactured by Signetics or compatible μPCl555 manufactured by NEC
, a capacitor Cs, a diode D, and an operating power supply E2 are added to form an astable multi-by-break, and a low-frequency rectangular wave signal is obtained at its output terminal (bin 3).

The operating power source E2 is voltage-divided by resistors R, .

Therefore, the voltage signal 6 outputted from the low frequency oscillation circuit 7 becomes high when the output terminal (bin 3) is at the "Higl+" level, and becomes low when the output terminal (No. 3 bin) is at the "Low" level. This voltage signal V, at the time of starting, is
,,V,, the diode DI is on and the diode D,,D, is off. Therefore, at the time of starting, the switching frequency f changes according to the voltage signal V6 as shown in FIG.
<r, and now the frequency r, ,r, is shown in Fig. 5(b)
As shown in , for the natural vibration frequency r0 of the inverter circuit under no load, ".<".

Assuming that the relationship is <r2, when r=r2, the resonant voltage generated in the capacitor C3 becomes high, and a high voltage is applied to the discharge lamp 2. The discharge lamp 2 is started by this high voltage.

By the way, the impedance of this heel high pressure discharge lamp becomes extremely low immediately after starting. At this time, it is important to quickly bring the discharge lamp 2 into a stable lighting state t'A 15 by flowing a sufficient lamp current. However, if the lighting frequency f4 during stable lighting remains unchanged, this sufficient current may not flow at the time of starting, and it is desirable to set the frequency f low at the time of starting.

Therefore, in this embodiment, the resonance capacitor C1
The current Ic flowing through the current transformer T1 and the resistor R1
～Detected by R1, diode D3, and capacitor C2,
The inverting amplifier 5 performs inversion amplification to obtain a voltage signal V, and this voltage signal V is passed through a diode D to V-F.
It is applied to the frequency control terminal (pin 5) of the converter 6. Immediately after starting, the voltage signal ■, the voltage signal V
, ,V, is designed so that the circuit constant is higher than that of V, so that the diodes Ds and Dt are off and the diode D is on, and the switching frequency f is controlled according to the voltage signal v. Ru. Eventually, when the discharge lamp 2 reaches a stable state, the voltage signal V changes to the voltage signal V7.
becomes lower than , diode D is on, diode D
=, DI is turned off, and the oscillation frequency r of the V-F converter IA 6 becomes a constant frequency r4 determined by the voltage signal V7.
becomes. Here, the voltage signal V is determined by detecting the lamp current of the discharge lamp 2 using a current transformer T3, resistors R5 to R, diode D1, and capacitor C4, and detecting the presence or absence of the detected voltage using a comparator CMP and a reference voltage E4. This is a constant voltage obtained by determining the value, and when the discharge lamp 2 is lit, the voltage is higher than the voltage signal V6. The voltage signal 7 is higher than the voltage signal 7 immediately after the discharge lamp 2 starts until it reaches a stable state. , the circuit constants are designed to be lower than .

In addition, during the period from immediately after the start of the discharge lamp 2 until reaching a stable state, the temperature of the discharge lamp 2 rises, the lamp voltage 1a rises, and the frequency r rises, causing the capacitor to Since the current in C1 also increases, the frequency f increases at an accelerating rate, and the frequency r is not set low for an unnecessarily long period of time, but is quickly adjusted according to the state IB of the discharge lamp 2. It is something that can be transitioned to a stable state.

[Embodiment 3] Fig. 6 is a circuit diagram of a third embodiment of the present invention, and Fig. 7 is an explanatory diagram of its operation.
The first input winding N of the lance T detects the resonant current 1c flowing to the resonance capacitor CI, the second input winding N2 detects the lamp current TNu flowing to the discharge lamp 2, and the output winding N , outputs a composite current of the resonant current Ic and the lamp current 11n. A voltage signal proportional to this composite weight K I - is generated across a resistor R1, and rectified and smoothed by a diode D1, resistors Rt and R2, and a capacitor C1 to obtain a detection voltage Vdt. The other configurations are the same as in the first embodiment.

The value of the current I obtained in the output winding N3 of the current transformer T is, if the phase difference between the resonance current Ic and the lamp current 11a is ignored, N 2X I 1m N +X I c= N3X
I becomes 3. Therefore, the detection voltage VdL is Vdt-(R+/Nz)(NtX r t'a-N,
x I c), and if the impedance of the discharge lamp 2 is Z, then VlrL=I la/Z, so Vd
t=(R+/N5)(Ntx r 1aN + X 2
x r X r la/Z )=(k f)XI
t'a, where k is a constant.

In this embodiment, it is assumed that the DC power supply E operates at a switching frequency of r=r when the DC power supply E has the rated voltage.

Now, for some reason, the voltage of the DC current HE is EL4 (>E).
If the discharge lamp 2 is a high-pressure sodium lamp, for example, the impedance 2 will hardly change, so if it remains as rr, the lamp voltage Via will rise and the lamp current 11m will increase, so the detection voltage VdL increases. Therefore, the switching frequency f increases, the switching frequency changes to r=r, and the lamp voltage V
j'a decreases, the lamp current 11a also decreases, and the detection voltage VdL is maintained at a constant value.On the other hand, if the voltage of the DC power supply E decreases to EL (<E) for some reason, the opposite occurs. As a result, a circuit for compensating the lamp voltage V1a against fluctuations in the power supply voltage can be easily realized.

[Effects of the Invention] As described above, the present invention provides a discharge lamp lighting device having a resonance capacitor connected in parallel with the discharge lamp and an inverter circuit operating in a slow phase mode. Since the current flowing through the capacitor is detected and the switching frequency is controlled to increase as the detected current increases, the effect is that the state of the discharge lamp can be detected and controlled with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of the first embodiment of the present invention, FIGS. 2(a) to (c) are main circuit diagrams of the same as above, and FIGS. 3(a) and (b) are operation explanatory diagrams of the same as above. FIG. 4 shows the second embodiment of the present invention.
Figure P1, Figures 5(a) and (b) are diagrams for explaining the same operation as above, Figure 6 is a circuit diagram of the third embodiment of the present invention, Figure 7 is a diagram for explaining the operation of the same as above, and Figure 8 is the conventional diagram. The example circuit diagram, FIG. 9, is a circuit diagram of another conventional example. Q and Q are transistors, E is a DC power supply, L is an inductor, C3 is a capacitor, R1 is a resistor, 2 is a discharge lamp, and 6 is a V-F converter.

Claims (2)

[Claims] (1) Including a series resonant circuit of an inductor and a capacitor,
In a discharge lamp lighting device having an inverter circuit including a load circuit in which a discharge lamp is connected in parallel with the capacitor, and in which the switching frequency of the inverter circuit is set higher than the natural oscillation frequency of the load circuit, the current flowing through the capacitor is A discharge lamp lighting device comprising a current detection means for detecting a current, and a frequency control means for increasing a switching frequency when a detected current value increases. (2) The discharge lamp is a high-pressure discharge lamp, and further comprises a control means for operating the current detection means and the frequency control means during a period from immediately after the high-pressure discharge lamp starts to when the high-pressure discharge lamp reaches a stable state. 1. The discharge lamp lighting device according to 1.