JP2573268B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp lighting device provided with a filament preheating circuit.

(Background Art) FIG. 3 is a circuit diagram of a conventional discharge lamp lighting device (Japanese Patent Application No. 60-113720) using an inverter circuit. DC power supply E
A series circuit of capacitors C ₁ and C _{2 and} a series circuit of transistors Q ₁ and Q _{2 which} are main switching elements are connected in parallel to both ends of the circuit. Diodes D ₁ and D ₂ are connected in anti-parallel to the transistors Q ₁ and Q ₂ , respectively. Transistor
Between the connection points of Q ₁ and Q _{2 and} the connection points of the capacitors C ₁ and C ₂ , there are current transformers T ₁ and T ₂ for feeding back the load current,
Through the inductor L _1, a hot cathode type discharge lamp LA is connected. Between the discharge lamp LA filament f _1, f ₂ of the non-power supply side terminal of the capacitor C ₃ of the filament current for energization is connected. The capacitor C _3, together with the inductor L _1,
It constitutes an LC resonance circuit, the load current I ₀ becomes oscillating current. This oscillating current is the primary winding N ₁ of the current transformers T ₁ and T ₂ ,
flowing through the n _1. In the secondary windings N ₂ and N ₃ of the current transformer T ₂ , a voltage whose polarity changes according to the oscillating current flowing through the discharge lamp LA is induced, and this induced voltage is applied to the bases and emitters of the transistors Q ₁ and Q _2. The switching is performed so that the transistors Q ₁ and Q ₂ are alternately turned on.

This inverter circuit includes a starting circuit for starting the self-excited oscillation operation when the voltage of the DC power supply E is applied. The starting circuit capacitor C is charged via the resistor R when the power source is turned on, the charging voltage is reaches the breakover voltage diode thyristor Q is on diode thyristor Q, diode thyristor to the base of the transistor Q ₂ Transistor with base current through Q
Q ₂ is turned on first to start the inverter circuit.

Further, between the bases and the emitters of the transistors Q ₁ and Q ₂ , the transistors Q ₃ and Q _{4 serving as} dimming switching elements are provided.
Is connected between the bases and the emitters of the transistors Q ₃ and Q ₄ , the secondary windings n ₂ and n ₃ of the current transformer T ₁ are connected to the diodes D ₃ and D ₄ and the impedances Z ₁ and Z ₂ , respectively. Light switch SW
_1, connected via the SW _2, by turning off or on the dimming switch SW _1, SW _2, and is capable of switching the full lighting state and dimming state. In FIG. 3, impedance Z ₁ , Z ₂ and diode D ₃ ,
D _4, the base current of the transistor Q _3, Q ₄ is set to a predetermined value, but the breakdown voltage between the base and emitter of the transistor Q _3, Q ₄ may be omitted if there is no problem.

Figure 4 (a) the switch SW ₁ for dimming, SW ₂ are shown respective parts of an operation waveform at full lighting time turning off, FIG. (B) The dimming switch SW _1, tone and turns on the SW ₂ light The operation waveform of each part at the time of lighting is shown. In the figure, I ₀ represents the load current flowing through the inductor L _1, I ₁ denotes a lamp current flowing to the discharge lamp LA. The collector current I _Q1, I _Q2 is flowing through the transistor _{Q 1, Q 2, I D1} , I D2 represents the current flowing through the diode D _1, D _2.

In the case of FIG. 4A in which the dimming switches SW ₁ and SW ₂ are turned off, the transistors Q ₁ and Q ₂ are turned on and off alternately by the current fed back by the current transformer T ₂ , and the output of the inverter circuit is output. There is applied to the resonant circuit consisting of the discharge lamp LA and the parallel capacitor C ₃ and the series inductor L _1, the discharge lamp LA is predetermined load current I ₀ is supplied, the full lighting state.

Here, when the switches SW ₁ and SW ₂ are turned on to be in the dimming state, during the on-period of the transistor Q ₁ , the base of the transistor Q ₃ , which is a dimming switching element, is passed from the current transformer T ₁ via the diode D _3. current is supplied, the transistor Q ₃ is turned on. That transistor to Q ₁ base current flowing until now because of the cut, therewith the charge accumulated in the stray capacitance between the base and the emitter of the transistor Q ₁ simultaneously flows through the transistor Q _3, the transistor Q ₁ is rapidly Turn off. Similarly, in another on-period transistor Q _2, by the transistor Q ₄ is turned on, the transistor Q ₂ is rapidly turned off. as a result,
As shown in FIG. 4 (b), the oscillation frequency of the inverter circuit becomes higher than in the case of full lighting in FIG. 4 (a), and the impedance of the inductive load becomes higher, so that dimming is performed.

Here, the load current I ₀ flowing through the primary winding n ₁ of the current transformer T ₁ includes a lamp current I ₁ flowing through the discharge lamp LA filaments
The current I ₀ = I ₁ + I ₂ obtained by combining the filament current I ₂ flowing through the resonance capacitor C ₃ via f ₁ and f ₂ . The filaments f ₁ and f ₂ of the discharge lamp LA are cold immediately after lighting, and heat up with the elapse of time after lighting. Therefore, the filament current I ₂ immediately after lighting increases, and then decreases,
Eventually, the value becomes constant. Thus, over time after the lighting, Firanmento current I ₂ is changed. Further, the characteristics of the filaments f ₁ and f ₂ of the discharge lamp LA change with the use time, and the characteristics change between a new filament and a filament before the end of life. Therefore, the filament current I ₂
Also changes with the passage of time from the new article to the end of the life.
Furthermore, Firan for electron emission amount by applying conditions of the electron emitting material of the filament f _1, f ₂ varies, variations in the characteristics of the filament f _1, f ₂ of the discharge lamp LA is increased, therefore, even with this variability instrument current I ₂ will vary.

When the filament current I ₂ varies, also vary the control conditions of the transistors Q _3, Q ₄ for to fluctuate the load current I ₀ flowing through the primary winding n ₁ of the current transformer T _1, dimming, the discharge lamp LA However, there is a disadvantage that the output fluctuates greatly.

FIG. 5 is a circuit diagram of another conventional example (Japanese Patent Application No. 60-113716). In the conventional example, both ends of the transistor Q _1, coupling capacitor C for cutting the DC component
₁ and current transformers T ₁ , T ₂ ,
And the discharge lamp LA is connected via an inductor L _1.
Between the non-power side terminals of the filaments f ₁ and f ₂ of the discharge lamp LA,
Capacitor C ₃ is connected, and an LC resonance circuit by the capacitor C ₃ and the inductor L _1. Serving as a switching element for the dimming transistor Q _3, the transistor
Only it is connected to the side of Q _2. During dimming Therefore, the on-interval the transistor Q ₂ is shorter than the on-interval the transistor Q _1. This is shown in a waveform diagram,
It looks like the figure. Figure 6 (a) is, for dimming switch SW ₁
There off by the transistor Q ₁ at the time of full lighting was, Q ₂ of the on period, (b) shows the ON period of the transistor Q _1, Q ₂ at the time of dimming switch SW ₁ is dimming is turned on.

As described above, in this circuit, the transistor
By making the on-periods of Q ₁ and Q ₂ unbalanced, a smaller current flows through the discharge lamp LA than when the transistors Q ₁ and Q ₂ are on during the same period.

This is also in the conventional example, similarly Firanmento current I ₂ through the filament f _1, f ₂ flows through the primary winding n ₁ of the current transformer T _1, the same disadvantages as the conventional example of FIG. 3 There is.

(Object of the Invention) The present invention has been made in view of the above points, and an object of the present invention is to provide a discharge lamp lighting device capable of detecting a lamp current without being affected by a filament current. To provide.

(Disclosure of the Invention) In the discharge lamp lighting device according to the present invention, in order to achieve the above object, as shown in FIG. 1 or FIG. 2, a filament f ₁ in a hot cathode discharge lamp LA is used. , the impedance element (capacitor for preheating current supply to the non-power supply side of the f ₂
C ₃ ), the discharge lamp lighting device
Current transformer T _{1 in} series with the power supply side of the filaments f ₁ and f ₂
Connect the primary winding n _1, the non-power side of the discharge lamp LA is connected to the primary winding n ₁ becomes opposite polarity the secondary winding n _2, 3 of the current transformer T ₁ Tsugimaki the line n ₃ is obtained by a lamp current detection winding.

Therefore, in the present invention, the filaments f ₁ and f ₂
To remove the influence of the current I ₂ flowing through, it is capable of detecting only the lamp current I _1.

 Hereinafter, examples of the present invention will be described.

Embodiment 1 FIG. 1 is a circuit diagram of one embodiment of the present invention. In this embodiment, portions having the same functions as those of the conventional example shown in FIG. 5 are denoted by the same reference numerals, and redundant description will be omitted. Discharge lamp
Connect the primary winding n ₁ of the current transformer T ₁ to the power supply side of Firanmento f _1, f ₂ of the LA, is connected to the secondary winding n ₂ of the current transformer T ₁ to the non-power supply side. Here, the primary winding n ₁ and the secondary winding
n ₂ is wound with reduced polarity. Current tertiary winding n ₃ of the transformer T ₁ is the impedance Z _1, diode D _3, which is connected between the base and emitter through a switch SW ₁ for dimmer dimming transistor Q _3.

With this configuration, the capacitor C _1, the filament f _1, a capacitor C _3, 2 winding n ₂ of the current transformer T _1, filaments f _2, 1 winding n ₁ of the current transformer T _1, the inductor L ₁ Although flows preheating current I ₂ through, this preheating current I _2, the voltage induced in the secondary winding n ₂ of the current transformer T _1, is induced in the primary winding n ₁ of the current transformer T ₁ The voltage is
The current transformer T ₁ is turned on by the filament current I _{2 in} order to have voltages of opposite polarities as seen from the tertiary winding n ₃ and cancel each other out.
The voltage induced in the tertiary winding n ₃ of zero. Then, the capacitor C _1, the discharge lamp LA, 1 winding n ₁ of the current transformer T _1,
Only by the lamp current I ₁ flowing through the inductor L _1, a voltage is induced in the tertiary winding n ₃ of the current transformer T _1, is fed between the base and emitter of the transistor Q _3. Thus, in the present embodiment, the lamp current can only be supplied to the transistor Q ₃ for dimming the components I _1, components of Firanmento current I ₂ is canceled, tone transistor Q ₃ for optical
Since not supplied to the without being affected by the Firanmento current I _2, it is possible to perform the dimming control.

Embodiment 2 FIG. 2 is a circuit diagram of another embodiment of the present invention. In this embodiment, a separately-excited inverter circuit that drives the transistors Q ₁ and Q ₂ by the external oscillation circuit 4 is used. Detecting a lamp current by a current transformer T _1, and converted into a DC voltage by rectifying and smoothing circuit 1 consisting of the diode D ₅ and the capacitor C _5, and compared with a set value by the comparison circuit 2, the lamp current is larger than the set value In such a case, the oscillation frequency of the oscillation circuit 4 is changed by the stabilizing circuit 3 so that the lamp current is controlled to decrease. Conversely, when the lamp current is smaller than the set value, the lamp current is increased. , And controls the oscillation frequency of the oscillation circuit 4 to stabilize the lamp current. Comparison circuit 2, stabilization circuit 3, and oscillation circuit 4
Since the specific circuit configuration can be easily realized,
Details are omitted.

In such a separately-excited inverter circuit, if control is performed so as to stabilize the load current, the lamp current will fluctuate due to the fluctuation of the filament current, and the luminous flux will fluctuate. By canceling the filament current component, only the lamp current component of the load current is detected, and control is performed to stabilize the component, thereby stabilizing the lamp current regardless of the fluctuation of the filament current. It becomes possible.

(Effects of the Invention) As described above, the present invention relates to a discharge lamp lighting device having a filament preheating circuit, in which a power supply side of a filament of a discharge lamp and a primary winding of a DC current transformer are connected to each other. A secondary winding having a polarity opposite to that of the primary winding is connected to the non-power supply side, and a tertiary winding of the current transformer is used as a lamp current detection winding, so that a filament current component is removed from the load current. As a result, only the lamp current component can be detected, and therefore, there is an effect that the fluctuation of the detected current due to the fluctuation of the filament current can be prevented.

If dimming control or luminous flux stabilization control is performed using the detected lamp current, stable control that is not affected by the filament current can be performed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention, FIG. 2 is a circuit diagram of another embodiment of the present invention, FIG. 3 is a circuit diagram of a conventional example, FIG. FIG. 5 is a circuit diagram of another conventional example, and FIG. 6 is an operation explanatory diagram of the same. E is a DC power supply, LA is a discharge lamp, f ₁ and f ₂ are filaments, C ₃
Capacitor, T ₁ denotes a current transformer, n ₁ is the primary winding, n ₂ is the secondary winding, n ₃ is a third winding.

Claims (2)

(57) [Claims] 1. A discharge lamp lighting device comprising a hot cathode type discharge lamp in which an impedance element for supplying a preheating current is connected to a non-power supply side of a filament in a hot cathode type discharge lamp. Connect the next winding,
A discharge lamp lighting device, wherein a secondary winding having a polarity opposite to that of the primary winding is connected to a non-power supply side of the discharge lamp, and a tertiary winding of the current transformer is a lamp current detection winding. . 2. A discharge lamp, comprising: a current feedback type inverter circuit as a driving power source; and a dimming switching element connected in parallel to a feedback input terminal of a main switching element constituting the inverter circuit. 2. The discharge lamp lighting device according to claim 1, wherein said tertiary winding is connected to a control input terminal of said switching element via a switch turned on at the time of dimming.