JPS61296696A - Discharge lamp lighting apparatus - 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 discharge lamp lighting device using a separately excited inverter circuit.

[Background technology]

The discharge lamp lighting device that forms the basis of this invention is a commercial type BAc, diode DI, as shown in FIG.

Power is supplied to the separately excited inverter circuit 2 from the DC type #l consisting of D2, and a series circuit of an inductor L1, a parallel circuit of a capacitor C3, and a discharge lamp 3 is connected as a load of the separately excited inverter circuit 2, and A preheating transformer TI is also connected as a load. The excitation and operating frequency control of the separately excited inverter circuit 2 is controlled by V/F (
voltage/frequency) conversion circuit 7. Variable resistance VR, oscillation circuit 6
This is performed by an excitation circuit 8 consisting of a drive circuit 5 and a drive circuit 5.

This discharge lamp lighting device boosts the high-frequency output voltage of a separately excited inverter circuit 2 using a series resonant circuit consisting of an inductor L1 and a capacitor C3 and applies it to the discharge lamp 3, and also preheats the filament of the discharge lamp 3 using a preheating transformer T1. As a result, the discharge lamp 3 is started, and when the discharge lamp 3 is started, the discharge lamp 3 is lit in a state where the current is limited by the inductor L1. C4 is a capacitor for cutting direct current.

And V/F conversion circuit 7. Variable resistance VR, seeding circuit 6
The operating frequency of the separately excited inverter circuit 2 is periodically switched alternately between a first frequency and a second frequency by an excitation circuit 8 comprising a drive circuit 5.
The first frequency is configured to be changed by adjusting the variable resistor VR, and the discharge lamp 3 is dimmed by adjusting the first frequency.

Also, the second frequency is determined by the inductor L1 and capacitor C.
By setting the frequency to a fixed frequency near the series resonance frequency of 3 (for example, the frequency f+ in the fully lit state), a high voltage is applied across the discharge lamp 3 even when the discharge lamp 3 goes out due to deep dimming. The lights are re-ignited to keep them lit.

4 is an advance preheating circuit that eliminates the second frequency section for a certain period of time immediately after the power is turned on, so that lighting is not performed.
The discharge lamp 3 is preheated in advance.

FIG. 8 shows the frequency characteristics of the voltage across the capacitor C3 when the discharge lamp 3 is not lit (no load), where f is the resonance frequency determined by the inductor L1 and the capacitor C3, and is expressed as follows. fl is the frequency of the rated lighting state (second frequency)
, f2 is the frequency of the lowest level dimming state.

The circuit shown in FIG. 7 will be explained in detail below.

IC, is an astable multi-pipe rake (general-purpose timer C
r555J), and the oscillation frequency is determined by the resistors R5 and Rs, the capacitor C5, and the input voltage at the No. 5 terminal.

IC2 is a D flip-flop, which divides the output of the astable multivibrator TC, and divides the output of the astable multivibrator TC into a transistor Tr3.
．． Tr4 is turned on and off alternately. Transistor Tt3
When transistor T r H is turned on, transistor T r H is turned off, and when transistor T r 3 is turned off, transistor T r 1 is turned on. The transistor T r 2 also operates in the same manner, so that the transistors Try and Tr 2 are alternately turned on and off. On the other hand, diode bridge DB,
is full-wave rectification of the commercial power supply AC, and the resistance Rg.

The operational amplifier IC compares the voltage value divided by R9 and the voltage value divided by the control cylinder fiVcc by the resistors RIO and R11, and the output of the operational amplifier IC4 becomes high level during a period when the latter is high. Inverter G5° and gate G6. The circuit consisting of the resistor R12 and the capacitor Ce is a fall detection circuit, and when the output voltage of the operational amplifier IC4 changes from a high level to a low level, a high level appears as the output of the AND gate G6 for a certain period of time. This high level period is determined by the time constants of resistor R12 and capacitor C8.

D flip-flop IC, transistor T r 4
The on/off operation of the transistor T r 5 is synchronized with the on/off operation, and a voltage obtained by inverting the D input appears at the d output, turning the transistor T r 5 on and off. When the transistor T r 5 turns on, the output of the operational amplifier IC5 becomes R,4+ V R □・Vcc R13 + R14 + V R , and the diode D7 compares this value with R15 + R16 , and if the former is low, the output of the operational amplifier IC6 becomes -07 (ON), which is R13+R+a+VR, is the on-voltage of diode D7. When the transistor 7r6 is off, the output of the operational amplifier ICs becomes Vcc, so the diode D7
is turned off, and the output of the operational amplifier IC6 becomes □・Vcc R+5" R1B. The output of the operational amplifier IC6 becomes the 5th terminal input voltage of the astable multi-by-break IC, and the 5th terminal voltage becomes □・Vcc in the interval TA. R+s + R16 is added, and R13+R14'' V R is added in the section TB. Note that when R13+R14+V RRIs ” R16, IG □・Vcc RI5+ R16 always becomes the input voltage of the No. 5 terminal (at this time, the discharge lamp 3 is in the rated lighting state).

Then, in section TA, the astable multivibrator IC
, the input voltage at terminal 5 is always constant, and its value changes depending on the resistance value of the variable resistor VR in the interval TB, and in the interval T
^ ensures that the lighting is maintained during dimming, and achieves the desired dimming level in section TB.

The operation of the advance preheating circuit 4 is as follows. That is, after the power is turned on, a charging current flows through the capacitor C9 via the resistor R17, and the voltage across the capacitor C9 changes to the resistor R1?
, increases due to the time constant of capacitor C9. While the voltage across capacitor C9 is lower than the voltage divided by resistors RIR and R19, the output of operational amplifier IC7 is at a high level, transistor Tr6 is on, and the voltage across capacitor C9 is the voltage divided by resistors R18 and R19. When the voltage becomes higher, the output of the operational amplifier lc7 becomes a low level, and the transistor Tr6 is turned off. When the transistor Tr6 is on, the output voltage of the operational amplifier Ics is □・Vc
c R13" R14, and the state is VR-0. Naturally, R13+R14RI5+R16, so the input voltage at the 5th terminal of the astable multivibrator IC becomes □・Vcc R13" R14. The on-period of the transistor Tr6 is: Regardless of whether the transistor T r 5 is on or off, the input voltage at the No. 5 terminal is the above value. In other words, since there is no TA section mentioned above to ensure lighting maintenance, the discharge lamp 3 does not light up. The discharge lamp 3 is preheated in advance.

By the way, as mentioned above, in this discharge lamp lighting device, in order to enable dimming down to a low level, a method is used in which interval TA and interval 1 day are provided periodically. To explain the above operation during dimming,
As shown in Fig. 8, the section T^ is the separately excited inverter circuit 2.
The operating frequency of is set to fl, and the interval TB is set to f2. In order to stabilize the lighting state of the discharge lamp 3 during this lowest level dimming, the following steps must be taken.

FIG. 9(A), CB) and FIG. 10(A).

(B) shows the waveforms of the lamp voltage and lamp current during the lowest level dimming, and FIGS. 9 and 10 show the same light output. As is clear from this figure, the higher the lamp lighting maintenance voltage (voltage in section TA), the more
Since the lamp current rises rapidly, it is necessary to narrow the section TA. At this time, if the width of the section TA fluctuates due to some reason (such as noise), it is easily understood that the narrower the width of the section TA, the greater the fluctuation in the lamp current due to the fluctuation, and the more likely it is to flicker.

In other words, for flickering during lowest level dimming, it is more advantageous to widen the width of section TA and lower the lighting sustaining voltage. must be kept away from the resonant frequency fo. When the frequency f1 is moved away from rO, the voltage across the capacitor C3 at the frequency ft decreases along the curve shown in FIG. Lowering the voltage across the capacitor C3 means lowering the starting voltage when lighting the discharge lamp 3 at its rated value. In other words, it means that the starting condition is poor in the rated lighting condition.

Here, it seems that if the starting performance at the rated lighting becomes poor, it will be impossible to maintain the lighting at the lowest level dimming, but the voltage required to maintain the lighting at the lowest level dimming is actually the rated lighting. The starting voltage will be higher than that under normal conditions. The reason is explained as follows.

Although FIGS. 9 and 10 show the pump voltage and lamp current waveforms for ease of explanation, the actual waveforms are as shown in FIG. 11. FIG. 11(A) shows the input voltage at the fifth terminal of the astable multi-by-break IC+, and the slope W1 is a region where the operating frequency transiently passes through fo. (B) in the same figure shows the lamp voltage, and when the operating frequency transiently passes through fo, the starting voltage increases to Vll. ■12
is the starting voltage at frequency r1. (C) in the same figure shows the lamp current.

In order to alternately switch the operating frequency of the separately excited inverter circuit 2 between f and f2, an astable multi-vibration IC is used.
, the waveform of the voltage input to the fifth terminal is as shown in FIG. This is due to the characteristics of the circuit.

This inclined part W.

If you pay attention to this, it is an astable multi-by-break IC.

The voltage at the No. 5 terminal of
Or, it changes continuously from f2 to f1.

Therefore, in this inclined portion WI, the separately excited inverter circuit 2
The operating frequency transiently passes through the resonant frequency fo, which increases the lighting sustaining voltage during lowest level dimming. Here, the passage of the frequency fo is only transient, and the operating frequency changes before the voltage across the capacitor C3 becomes very high, so circuit components such as semiconductors are not destroyed and almost no stress is applied.

On the other hand, at the time of starting in the rated lighting state, the voltage is low because the frequency is fixed to f1.

As explained above, in such a discharge lamp lighting device, the starting layer in the rated lighting state becomes poor.

[Purpose of the invention]

An object of the present invention is to provide a discharge lamp lighting device that can improve startability.

[Disclosure of the invention]

The discharge lamp lighting device of the present invention includes a series circuit including a DC power source, a separately excited inverter circuit supplied with power from the DC power source, and a parallel circuit of an inductor, a capacitor, and a discharge lamp serving as a load of the separately excited inverter circuit. an excitation circuit that excites the separately excited inverter circuit; and a starting circuit that controls the excitation circuit so that the operating frequency of the separately excited inverter circuit transiently passes through the resonant frequency of the inductor and capacitor when starting the discharge lamp. The configuration includes the following.

In this way, when the discharge lamp starts, the operating frequency of the separately excited inverter circuit is changed so that it transiently passes through the resonance frequency of the inductor and capacitor, so when the operating frequency passes through the resonance frequency, the discharge lamp The applied voltage becomes higher, and starting performance can be improved.

Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 to 6. This discharge lamp lighting device, as shown in Fig. 1,
A series circuit of a DC power supply 1, a separately excited inverter circuit 2 supplied with power from the DC power supply 1, a parallel circuit of an inductor I serving as a load of the separately excited inverter circuit 2, a capacitor C3, and a discharge lamp 3; an excitation circuit 8 that excites the separately excited inverter circuit 2; and an excitation circuit that excites the separately excited inverter circuit 2 so that the operating frequency of the separately excited inverter circuit 2 transiently passes through the resonant frequency of the inductor L1 and capacitor c3 when the discharge lamp 3 is started. In addition to this, a preliminary preheating circuit 4 is provided.

The excitation circuit 8 includes a drive circuit 51 and an oscillation circuit 6°V/F.
It is composed of a (voltage/frequency) conversion circuit 7 and a variable resistor VR, and excites the separately excited inverter circuit 2 and controls the operating frequency.

This discharge lamp lighting device starts the discharge lamp 3 by boosting the high frequency output voltage of the separately excited inverter circuit 2 using a series resonant circuit consisting of an inductor L1 and a capacitor C3 and applying it to the discharge lamp 3. After starting, the discharge lamp 3 is current-limited by the inductor L1.
It is designed to light up.

Then, by the excitation circuit 8, the separately excited inverter circuit 2
The operating frequency is periodically switched alternately between a first frequency and a second frequency, and the first frequency is configured to be changed by adjusting a variable resistor VR. Discharge lamp 3 by adjusting the frequency of 1
It is designed to perform dimming. Further, the second frequency is a fixed frequency near the series resonance frequency of the inductor L1 and the capacitor C3 (for example, the frequency f+ in the rated lighting state).
Even when the discharge lamp 3 goes out due to deep dimming, a high voltage is applied across the discharge lamp 3 to re-ignite it and keep it lit.

The advance preheating circuit 4 performs advance preheating of the discharge lamp 3 by eliminating the second frequency section and preventing lighting for a certain period of time immediately after the power is turned on.

Hereinafter, the circuit shown in FIG. 1 will be explained in detail with reference to FIGS. 2 to 4.

First, in the main circuit, a diode DI+02° and capacitors cl and c2 double the voltage, rectify and smooth the commercial power supply AC, and use it as a DC fl source 1 for the separately excited inverter circuit 2. This separately excited inverter circuit 2 includes a transistor Tr
y, Tr2 is turned on and off alternately, causing the load (Ll, C].

3) has a so-called separately excited half-bridge configuration that supplies high-frequency power. The discharge lamp 3 is started and lit by a series resonant circuit including an inductor L1 and a capacitor C3. The filament of the discharge lamp 3 is constantly preheated by the preheating transformer T1 e D3. D4 is a diode, and C4 is a capacitor for DC cant.

Next, the oscillation circuit 6 and drive circuit 5 will be explained.

IC, is astable multi-pipe leak (general-purpose timer TCr
555J), the frequency of which is determined by resistors R5 and R6, capacitor C5, and the input voltage at the 5th terminal, and the output voltage is obtained from the 3rd terminal. IC2 is a D flip-flop, which works as a frequency divider by connecting the Q output and D input, and the Q output and Q output are connected to the Nant gate G3.
゜Transistor Tr3. through G4. It becomes the gate input of transistor Tr4, and becomes the gate input of transistor Tr3. Tr4 is turned on and off alternately. When the transistor Tr3 is turned on, a voltage is induced in the transformer T2 in the direction shown by the solid line in the figure, and the transistor Tr1 is turned off.

When the transistor T r 3 is turned off, a flyback voltage is generated in the transformer T2 in the direction shown by the dotted line in the figure, and the transistor Trl is turned on. After the transistor Tr1 is turned on, the emitter current is fed back to the base current to maintain the on state. That is, when the transistor T r 3 is on, the transistor Tr1 is off, and the transistor T r
When transistor Tr3 is off, transistor Trl is turned on, and similarly when transistor Tr4 is on, transistor Trl is turned on.
2 is off, and when the transistor Tr4 is off, the transistor Tr2 is turned on. As described above, the transistor T
r1 and Tr2 are alternately turned on and off.

R1-R4 are resistors, D5. D6 is a diode. C
6 is a capacitor, R7 is a resistor, and G2 is an inverter.

FIG. 2 is a waveform diagram showing how the oscillation circuit 6 and drive circuit 5 operate. The same figure (A) shows the 3rd terminal voltage of the astable multivibrator IC, the same figure (B) shows the Q voltage of the D flip-flop IC2, the same figure (C) shows the 5th voltage of the D flip-flop IC2, the same figure (D ) is the transistor T r
4, the gate voltage of transistor T r
3, (F) is the base current of the transistor Trl, and (G) is the collector current of the transistor TrI.

Next, the V/F conversion circuit 7 will be explained.

The operational amplifier ■C4 is for obtaining a power synchronization signal, and here operates as a comparator. Diode bridge DB for commercial power AC.

A voltage obtained by dividing the voltage rectified by the resistors R8 and Rg is applied to the inverting input terminal of the operational amplifier IC. On the other hand, a value obtained by dividing the control power supply Vcc by resistors RIO and R11 is applied to the non-inverting input terminal of the operational amplifier IC4. When the non-inverting input terminal voltage > the inverting input terminal voltage of the operational amplifier IC, the output voltage of the operational amplifier IC becomes high level, and conversely, when the non-inverting input terminal voltage <the inverting input terminal voltage, the output voltage of the operational amplifier IC becomes low level. ec7 is a small capacitor.

Inverter G5. ANDGATE G6. and resistance R12,
The circuit consisting of the capacitor C9 is a fall detection circuit, and the high level section of the output voltage of the analog gate G6 is determined by the resistor R12 and the capacitor C9. The output voltage of AND gate G6 is applied to the data input terminal (D) of D flip-flop IC2, and in synchronization with the on/off of transistor Tr4 (synchronized with the operating frequency of separately excited inverter circuit 2), the Q output is applied to the data input terminal (D) of D flip-flop IC2. T: “Manpower will be applied to gate 5.

When the Q output of D flip-flop IC2 is high level,
Transistor Tr5 is turned on, and resistor RI3. R
14. The value R, 4+ V R □ Vcc R13+ R14+ V R determined by the variable resistor VR is added to the non-inverting input terminal voltage of the operational amplifier +C5, and this value becomes the output of the operational amplifier IC5 as it is.

Diode D7 compares R,4+ V R □ Vcc R13+ R,4+ V R and IG □ Vcc R16+ R16, and if R13+ R14+ V R <--V c c RI5+ R16, R11"R14+VR is the operational amplifier. This becomes the output voltage of IC6, and the input voltage of the 5th terminal of the astable multi-by-break IC.Here,
D? (ON) is a voltage for turning on the diode D7, and is about 0.7V. Therefore, when the transistor T r 5 is on, by changing the variable resistor VR, the input voltage at the No. 5 terminal of the astable multi-by-break IC changes. However, R14+VR (max) −・V c c + D 7 (ON) R13+
R14+ VR(llaX)111i ≧□・Vcc R16" R16, and at this time it is an astable multi-vibration IC.

The 5th terminal input terminal of □・Vcc RIs + R16 It remains as it is.

When the Q output is at a low level, the transistor T r 5 is off, and approximately +Vcc is applied to the non-inverting input terminal of the operational amplifier IC5 via the resistor RI3, and the operational amplifier I
The output voltage of C5 becomes +Vcc.

Therefore, the voltage □-・ determined by the resistors R16 and R16
Diode D7 compares Vcc R15 + R16 and the output voltage of operational amplifier C5, and in this case, since Vcc>□・Vcc RIs + R16, diode D7 is off, so the non-inverting input voltage of operational amplifier C6 is Vcc RIs + R16, and this voltage becomes the No. 5 terminal input voltage of the astable multi-by-break IC.

However, when the transistor T r 5 is turned on, R+3"R
14+VR > −-V c c RIEI + R16, the output of the operational amplifier ■C6 becomes IG □・Vcc R16+ RIs, regardless of whether the transistor Tr5 is on or off (at this time, the so-called discharge lamp 3 is turned on at its rated value) ).

As mentioned above, the output voltage of the operational amplifier IC6 becomes the input voltage of the astable multivibrator IC117) at the 5th terminal, and the discharge lamp 3 is lit at the operating frequency according to this voltage (astable multivibrator IC1 is the 5th terminal of the astable multivibrator IC1). The lower the input voltage, the lower the oscillation frequency, and therefore the lower the operating frequency of the separately excited inverter circuit 2).

The above operation is shown in the waveforms of each part as shown in FIG.

In FIG. 3, (A) shows the variable resistance VRO value. The same [m (B) shows the input voltage of the operational amplifier IC4, V21 is the inverting input terminal voltage, and V22 is the non-inverting input terminal voltage, which is RIO+R11.The same figure (C) shows the output voltage of the operational amplifier ■c4. ing. The same figure (D) shows the output voltage of AND gate G6,
That is, it shows the D input of the D flip-flop IC3. Part (E) of the same figure shows the gate voltage of the transistor Tr4, that is, the C input of the D flip-flop IC3. (F) of the same figure shows the Q output of the D flip-flop IC3, that is, the gate power of the transistor T r 5. (G) of the same figure shows the output voltage of the operational amplifier IC6, that is, the input voltage of the No. 5 terminal of the astable multi-by-break IC, which is V23. V 2a, 'br ha+atsure Rl! + + R16 +D? (ON), (H) in the figure shows changes in the operating frequency of the separately excited inverter circuit 2, where f is the frequency corresponding to the rated lighting state, r2 is the frequency corresponding to the predetermined level dimming state, and f3
is the frequency corresponding to the lowest level dimming state. Same figure (
+) indicates the lamp voltage, and (J) in the figure indicates the lamp current.

In addition, FIG. 11 is an enlarged view of the part surrounded by a dashed line in FIG. 3.

Next, the preliminary preheating circuit 4 and the starting circuit 9 will be explained. The advance preheating circuit 4 and the starting circuit 9 include an operational amplifier Ice, an AND gate G? .

OR gate CB,) IE resistor R17-R20, capacitor C9, CIQ, diode D8. Transistor T r
Consists of 6.

The operation is as follows.

After the power is turned on, a charging current flows through the capacitor C9 via the resistor R17, and the voltage c9 across the capacitor C9 rises due to a time constant determined by the resistors R17 and R19. The operational amplifier IC is connected to this voltage and the resistor R8. R19
Compare the voltage □・Vcc R18+R19 divided by
When it reaches R19, it becomes a low level. When the output of operational amplifier IC7 is high level, the input of OR gate G8 is high level,
Regardless of the output of AND gate G7, the output of OR gate G8 becomes high level. Therefore, the transistor Tr6 is turned on, and at this time, the output voltage of the operational amplifier IC becomes □.Vcc Rl:l + R14, regardless of whether the transistor Tr5 is on or off. This state is equivalent to VR-0, and the diode D7 is on, so the output of the operational amplifier IC6 becomes R13+R14. When the transistor Tr6 is on, the □Vcc RIs + R16 obtained when the transistor Tr5 is off does not appear as the output of the operational amplifier IC6, so the discharge lamp 3 is not lit and is in a preheating state. operational amplifier IC
? When the output of the capacitor CIO becomes low level, the charge stored in the capacitor CIO starts discharging via the resistor R20.

Even if the voltage of capacitor CIO decreases due to discharge, the AND gate G? The input terminal is accepted as high level.

Therefore, an operational amplifier IC? After the output of the AND gate G7 becomes low level, the Q output of the D flip-flop IC3 appears as the output of the AND gate G7 for a while, and the OR gate G8 becomes
Since one of the input terminals is at a low level, the output is
It is the same as the Q output of the D flip-flop IC3. That is, the transistors T r 5 and Tr 6 are repeatedly turned on and off at the same time. Transistors Try, Tr6
When both are off, the output of the operational amplifier IC5 is Vcc, and therefore the output of the operational amplifier IC6 is R15+R16. On the other hand, when both transistors Try and Tr6 are on, the output of the operational amplifier [Cs becomes R13+R14, so the diode D7 is turned on, and the output of the operational amplifier TC6 becomes R13+R14, that is, the state at the lowest level dimming. The discharge lamp 3 is slightly discharged. After that, as the discharge of capacitor CIO progresses and the input terminal of AND gate G7 comes to be regarded as low level, the output of AND gate G7 becomes low level, and since both the inputs of OR gate Ge are low level, the output also becomes a low level, and the transistor T r
6 is off. After the transistor T r 6 is turned off, the discharge lamp 3 is lit in a dimming state set by the variable resistor VR. At this time, suppose the VR value is VR(max),
In other words, assuming that the rated lighting state is set, the discharge lamp 3 will start a slight discharge at the lowest level dimming state at the time of startup, and this will lower the starting voltage of the discharge lamp 3, and when the discharge lamp 3 shifts to the rated lighting state, it will smoothly switch to the rated lighting state. lights up. In other words, as shown in Fig. 11, during lowest level dimming, the lighting sustaining voltage becomes higher than the starting voltage in the rated lighting state by transiently passing through the resonance frequency of the inductor LI and capacitor C3. Even in the rated lighting condition, the resonant frequency is transiently passed through when the discharge lamp 3 is started, and the discharge lamp 3 is once slightly discharged, so that the starting performance in the rated lighting condition is improved. This situation is shown in FIG.

Is Fig. 4 (A) an operational amplifier IC? denotes the input voltage of v
3□ is the inverting input terminal voltage, V32 is the non-inverting input terminal voltage, R111+R19, and (B) in the same figure is the output voltage of the operational amplifier IC. (C) in the figure is the 0-point voltage of the AND gate G7, (D) is the 0-point voltage of the AND gate Gv, and V33 is the boundary voltage at which the output of the AND gate G7 changes. The same figure (E
) is the 0-point voltage of OR gate G8, (F) is the 0-point voltage of OR gate G8, and (G) is the output voltage of OR gate G8. (H) in the same figure shows the resistance value of variable resistor VR, and V
R(llax), (1) in the same figure is the operational amplifier ■C5
The output voltage is R13+R14.The figure (J) is the output voltage of the operational amplifier ■C6, which is R13+R14 RI5+R16.The figure (K) is the lamp voltage, and the figure (L) is the lamp current. , FIG. 11 is an enlarged view of the area surrounded by the dashed-dotted line.

In the discharge lamp lighting device shown in Fig. 7, the width of the lighting sustaining voltage generation period is widened to suppress flickering during lowest level dimming.
In this example, when starting at rated lighting condition, the starting performance was poor when starting at rated lighting condition due to lowering the voltage value.
Since a period during which the resonant frequency is transiently passed is provided, and the discharge lamp 3 is slightly discharged, the discharge lamp 3 shifts to the rated lighting state, so that the starting performance of the discharge lamp 3 can be improved.

Note that the DC type Al in the above embodiment may be configured to undergo full-wave rectification using a diode bridge and smoothing using a capacitor.

Further, the present invention not only improves the starting performance of the discharge lamp lighting device shown in FIG. 7, but can also be used generally when lighting a discharge lamp at its rated value (without dimming). In this case, starting performance can be ensured by transiently passing the operating frequency of the separately excited inverter circuit, and the starting voltage in the rated lighting state can therefore be lowered, making it possible to downsize the inductor or reduce power loss. It is possible to reduce the

Furthermore, in the explanation of FIG. 11, it has been stated that due to the characteristics of the circuit, there is a slope in the rise and fall of the voltage at the No. 5 terminal of the astable multi-vibration IC, so the resonance point is passed transiently. , Figure 5 (A), (
As shown in B), it is also conceivable to shift the operating frequency of the separately excited inverter circuit 2 to a position very close to the resonant frequency for a period of time that does not cause heat generation or destruction of the circuit components.

In other words, lIJ! on the circuit characteristics! In addition to utilizing the oblique portion W, a period may be intentionally provided in which the operating frequency is brought close to the resonant frequency.

Furthermore, in the case of the circuit shown in Fig. 1, since the output voltage of the separately excited inverter circuit 2 (which can be thought of as the voltage across the preheating transformer T1) is a rectangular wave, the resonance frequency of the inductor L1 and capacitor C3 is Since it has a resonant frequency that is an odd multiple of the frequency, for example, as shown in FIG. 6, the resonant frequency fo' for the third harmonic and the resonant frequency f for the fundamental wave.

Similar improvements in starting performance can be obtained by transiently passing through the two resonant frequencies.

In any case, in the present invention, the starting performance is improved by passing the resonant frequency transiently, and it goes without saying that a plurality of resonant frequencies may be passed.

〔Effect of the invention〕

The discharge lamp lighting device of the present invention changes the operating frequency of the separately excited inverter circuit so as to transiently pass the resonant frequency of the inductor and capacitor when starting the discharge lamp, so that the operating frequency passes the resonant frequency. In some cases, the voltage applied to the discharge lamp is increased, which improves starting performance.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of an embodiment of this invention, Figures 2 to 5 are waveform diagrams for explaining its operation, Figure 6 is a frequency characteristic diagram of capacitor voltage, and Figure 7 is the basis of this invention. FIG. 8 is a frequency characteristic diagram of the capacitor voltage, and FIGS. 9 to 11 are waveform diagrams for explaining its operation. ■...DC power supply, 2...Separately excited inverter circuit, 3
...discharge lamp, 8...excitation circuit, 9...starting circuit Fig. 2 Fig. 3 Fig. 6

Claims (1)

[Claims] A series circuit of a DC power supply, a separately excited inverter circuit supplied with power from the DC power supply, a parallel circuit of an inductor, a capacitor, and a discharge lamp serving as a load of this separately excited inverter circuit, and an excitation that excites the separately excited inverter circuit. A discharge lamp lighting device comprising: a circuit; and a starting circuit that controls the excitation circuit so that the operating frequency of the separately excited inverter circuit transiently passes through the resonant frequency of the inductor and capacitor when starting the discharge lamp.