JPH02199798A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To eliminate the probability of a rush current running by power source short circuit by constituting a resonance circuit in such a manner as sending a current of lag phase to an inverter load even when operated at the switching frequency of lighting time in the no-load state and operated at the switching frequency of no-load time in the lighting state. CONSTITUTION:The resonance frequency f1 of series resonance circuits L1, C1, the resonance frequency f2 of parallel resonance circuits L2, C2, and the higher f3 of resonance frequencies of a resonance circuit formed of the series resonance circuits L1, C1 and the parallel resonance circuits L2, C2 are set to f1<f2<f3. The switching frequency fA of no-load time and the switching frequency fB of lighting time are bet to fA>f2 and f1<fB<f2. Thus, a current of lag phase is sent to an inverter load even when the resonance circuit is operated at the switching frequency fB of lighting time in no-load state and operated at the switching frequency fA of no-load time in the lighting state. Hence, even if an error judgment of no-load state and lighting state occurs, there is no possibility of a rush current by power source short circuit.

Description

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

[Conventional technology] FIG. 5 is a circuit diagram of a conventional discharge lamp lighting device.

The circuit configuration will be explained below. A series circuit of capacitors C, 1 and CO2 and a series circuit of switching elements Q, Q2 are connected in parallel to both ends of the DC power supply E. Each switching element Q1. Diodes D t and D 2 are connected in antiparallel to Q 2 , respectively. A parallel circuit of a capacitor C2 and a discharge lamp l is connected between the connection point of the capacitors C, , C, and the connection point of the switching element Q and h via an inductor Ll.

The switching elements Q,,Q, are turned on and off alternately,
As a result, a high frequency AC voltage is applied to the inverter load consisting of the discharge lamp 1, the capacitor C2, and the inductor. Capacitor C2 and inductor L1 constitute a series resonant circuit, and by bringing the switching frequency of switching elements Q, Q2 close to the resonant frequency of the series resonant circuit, a high voltage is generated across capacitor C2 due to resonance. , the discharge lamp l starts. When the discharge lamp l starts and transitions from a no-load state to a lighting state, a load resistor is connected in parallel with the capacitor C2, so
As shown in FIG. 6, the resonance characteristics change.

In Fig. 6 (1), the horizontal axis is the switching frequency f,
Vertical motion indicates the imaginary part of the impedance Z of the inverter load. Further, in FIG. 6(b), the horizontal axis represents the switching frequency f, and the vertical axis represents the current I flowing through the inductor Ll. f is the resonant frequency under no load, and the switching frequency at this time is set to fA. In other words, the switching frequency fA at no load is the switching frequency fA of the switching elements Q, ,Q.

The resonant frequency f at no load,
is set to a value larger than and close to the resonant frequency f. On the other hand, fl is the resonance frequency during lighting, and the switching frequency at this time is set to f. In other words, the switching frequency for one day when lighting is the switching element Q,
, Q2 is set to a value that is larger than the resonant frequency fI during lighting and not far from the resonant frequency f, so that the phase of the current flowing through Q2 is slow and the rated current flows through the discharge lamp l.

[Problems to be Solved by the Invention] In the conventional example described above, a method for determining whether the discharge lamp l is in a no-load state or a lit state is to detect the lamp current flowing through the discharge lamp l and determine its magnitude. A common method is to determine the However, with this discrimination method, for example, if a HID lamp (high-intensity high-pressure discharge lamp) does not smoothly transition from glow discharge to arc discharge, or if a fluorescent lamp enters a half-wave discharge state, It may not be possible to clearly distinguish between a no-load state and a lighting state. For example, if it is erroneously determined that the lighting state has shifted to the no-load state,
As shown in Figure 6(a), on the resonance characteristics at no load,
Since it will operate at the switching frequency r8 during lighting, the phase of the current flowing through the inductor L1 will be in the advance mode, and a rush current may flow due to a short circuit in the power supply.For example, when current flows through the diode D, When the switching element Q2 is turned on, the diode D,
Until the reverse recovery time elapses, diode D and switching element Q will be conductive at the same time.
A rush current due to short-circuiting of the power supply flows in a path from the DC power supply E through the diode D switching element Q2. Therefore, it is necessary to use a switching element with a large current withstand capacity. Further, there is a problem that the rush current may lead to destruction of the switching element, reducing the reliability of the entire lighting device.

The present invention has been made in view of these points, and an object of the present invention is to provide a discharge lamp lighting device that can prevent stress on a switching element when transitioning from a no-load state to a lighting state. It's about doing.

[Means for Solving the Problems] In order to solve the above problems, in the discharge lamp lighting device according to the present invention, as shown in FIGS. 1 and 2, an inductor constituting a series resonant circuit is used. and a capacitor C1, an inductor L2 and a capacitor C2 forming a parallel resonant circuit, a DC power source E, and a switching circuit Q that switches the DC power source E at high frequency and applies it to the series resonant circuit and the parallel resonant circuit. The resonant frequency of the series resonant circuit is f1, the resonant frequency of the parallel resonant circuit is f2,
When f3 is the higher resonant frequency of a resonant circuit composed of a series resonant circuit and a parallel resonant circuit, f, < [2
<f3, and the switching frequency at no load is fA
, the switching frequency at the time of lighting is adjusted to fB, fA
>fa, and fl<fB<r2.

[Function] As is clear from FIGS. 2(a) and 2(b), in the present invention, even if the switching frequency f at the time of lighting is operated in the no-load state, the no-load Even when operating at a switching frequency of 18, a current with a delayed phase flows through the inverter load, so even if the no-load state and the lighting state are incorrectly determined, the current with the leading phase will flow through the inverter load as in the conventional example. Therefore, there is no risk of rush current flowing due to a short circuit in the power supply.

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

The circuit configuration will be explained below. The DC power supply E is switched by the switching circuit Q, and the terminals X,
A high frequency switched voltage is generated between Y.

The primary winding (inductor L) of the high-frequency transformer PT and the capacitor C2 constitute a parallel resonant circuit, one end of which is connected to the terminal X via the inductor L1, and the other end of the parallel resonant circuit connected to the terminal It is connected to terminal Y via. The inductor L1 and the capacitor Ct constitute a series resonant circuit. High frequency transformer PT.

A discharge lamp l is connected to the secondary winding of.

In the inverter circuit shown in FIG.
Let fl be the resonant frequency of the series resonant circuit consisting of the inductor 2 and the capacitor C1, f2 be the resonant frequency of the parallel resonant circuit consisting of the inductor 2 and the capacitor C2, and let the inductor L
,,L, and capacitors C,,C.

Among the resonant frequencies of the resonant circuit, the higher one is f3, and the lower one is [, l. In addition, the switching frequency when no load is "A", and the switching frequency when lighting is fB
shall be. Then, as shown in Fig. 2 (a) and (b), each resonance frequency is set so that E + < r 2 < r 3, and the switching frequency is set as fA > fs,
Also, set so that f, < r, < r. Switching between the switching frequency fA during no-load and the switching frequency ts during lighting is determined by detecting the lamp current flowing through the discharge lamp l and determining its magnitude.

With this configuration, when transitioning from the no-load state to the lighting state, it is possible to prevent rush current from flowing through the switching circuit Q even if it is mistakenly determined that the lighting state is in the no-load state. It can be prevented. In other words, in this embodiment, the switching frequency rB at the time of lighting is f +
Since it is set so that < f s < r 2, even if it is incorrectly determined that the lighting is in the no-load state, the phase of the current flowing through the switching circuit Q will be as shown in Fig. 2 (a) and (b). As is clear from the figure, the rush current does not flow because it is in the slow phase mode. Note that the capacitor CI
If the capacitance of the high-frequency transformer PT is set sufficiently larger than that of the capacitor C2, most of the voltage generated during resonance will be shared between both ends of the capacitor C2.
, can be downsized.

[Example 2] FIG. 3 is a circuit diagram of a second embodiment of the present invention.

In this embodiment, an inductor which is not affected by the descendants is added to the parallel circuit of the high frequency transformer PT and capacitor C2 in the circuit of FIG. is the inductor Ll.

Example 1 except that f2 is the higher of the resonant frequencies of the series-parallel circuit composed of inductors L2, L3 and capacitors Ct and C2, and f2 is the resonant frequency of the parallel circuit of inductors L2, L3 and capacitor C2. It is similar to

Further, a circuit that directly supplies power to the discharge lamp l from an inductor without going through the high frequency transformer PT can also provide the same effects as in the first embodiment.

[Example 3] FIG. 4 is a circuit diagram of a third embodiment of the present invention.

In this embodiment, the inverter device uses a half-bridge configuration similar to the conventional example shown in FIG.
,, By devising the configuration of the inverter load connected between the connection point of Q2, it is possible to easily start the discharge lamp 1 with a high starting voltage. The primary winding L2 of the high-frequency transformer PT and the capacitor C2 form a parallel resonant circuit, one end of which is connected to the connection point of the switching elements Q, , Q, via the inductor L1, and the other The end is connected to capacitor C via capacitor C1.
It is connected to the connection point of 6,,C,,. Inductor L1 and capacitor C4 constitute a series resonant circuit. A discharge lamp 1 is connected to the secondary winding of the high frequency transformer PT via a capacitor C11. One end of the capacitor C1 is connected to the connection point of the capacitor C01°CO2, and the other end is connected to the switching element Q1. through the inductor L11. Connected to the connection point of Q2. The capacitance of capacitor C1 is set to be sufficiently larger than the capacitance of capacitor C7. Then, when the circuit is operated at the switching frequency fA under no load to cause the circuit to resonate, most of the resonant voltage is shared between both ends of the capacitor C2. Therefore, a high voltage is generated across the capacitor C2, and a starting voltage can be applied to the discharge lamp l via the high frequency transformer PT and the capacitor C11. When the discharge lamp l is lit, the lamp current is detected and shifts to the switching frequency fB at the time of lighting.

In this embodiment, as in each of the above-mentioned embodiments, the resonant frequency of the series resonant circuit consisting of the inductor L1 and the capacitor C1 is set to fl, and the inductor L2 and the capacitor C
When the resonant frequency of the parallel resonant circuit consisting of 2 is f2, if it is set as r, < rB < r, a leading phase current will flow even if it is operated at the switching frequency fB during lighting in a no-load state. Even if the transition from the no-load state to the lighting state is misjudged, no rush current will flow.

[Effects of the Invention] According to the present invention, in a discharge lamp lighting device using an inverter device including a resonant circuit, even if the discharge lamp lighting device is operated at the switching frequency during lighting in a no-load state, Even when operated at the no-load switching frequency,
Since the resonant circuit is configured so that a current with a delayed phase flows through the inverter load, there is no risk of rush current flowing due to a short circuit in the power supply, which has the effect of increasing reliability.
Further, since the current withstand capacity of the switching element can be reduced, there is an effect that cost can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of the first embodiment of the present invention, Fig. 2(a)
, (b) is an explanatory diagram of the same operation as above, and FIG. 3 is the second diagram of the present invention.
FIG. 4 is a circuit diagram of a third embodiment of the present invention, FIG. 5 is a circuit diagram of a conventional example, and FIGS. 6(a) and 6(b) are explanatory diagrams of the same operation. C1 and C2 are capacitors, L + and L2 are inductors, l is a discharge lamp, Q is a switching circuit, and E is a DC power supply. Figure 1 Figure 3 Figure 2 Figure 4

Claims (1)

[Claims] (1) An inductor and a capacitor that constitute a series resonant circuit, an inductor and a capacitor that constitute a parallel resonant circuit, a DC power supply, and switching that switches this DC power supply at high frequency and applies it to the series resonant circuit and the parallel resonant circuit. A resonant circuit consisting of a circuit and a discharge lamp to which a voltage generated in the resonant circuit is applied, the resonant frequency of the series resonant circuit is f_1, and the resonant frequency of the parallel resonant circuit is f_2. When the higher one of the resonance frequencies of is f_3, f_1<f_2<f
Set the switching frequency at no load to f_A.
, when the switching frequency at the time of lighting is f_B, f
A discharge lamp lighting device characterized in that _A>f_3 and f_1<f_B<f_2.