JP2975032B2 - Discharge lamp lighting device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device using a resonance type inverter circuit, and is used for lighting a high-intensity discharge lamp (HID) at a high frequency. Is what is done.

[Prior Art] Conventional Example 1 FIG. 7 is a circuit diagram of a conventional example. Hereinafter, the circuit configuration will be described. The DC power supply V _1, the switching element
A series circuit of Q ₁ and Q ₂ is connected in parallel. Each switching element Q ₁ , Q ₂ is composed of a power MOSFET and has a parasitic anti-parallel diode. At both ends of the switching element Q _2, via the capacitor C ₂ for cutting direct current and inductor L of current limiting, the capacitor C ₁ for resonance is connected. The capacitor C ₁ for resonance, the discharge lamp R _L and the discharge detector
DET series circuits are connected in parallel. The switching elements Q ₁ and Q ₂ are alternately turned on and off by drive circuits DR ₁ and DR ₂ . Thereby, the inductor L and the capacitor
The resonant circuit consisting of C _1, flows an alternating current of substantially sinusoidal,
AC voltage generated across the capacitor C ₁ is applied to the discharge lamp R _L. Capacitance of the capacitor C ₂ of the DC blocking is set sufficiently larger than the capacitance of the capacitor C ₁ for resonance, it does not contribute to the resonance. In the steady state, when the ON periods of the switching elements Q ₁ and Q ₂ are equal, half the voltage of the DC power supply V ₁ is charged in the DC cut capacitor C ₂ .

The detection output V _DET of the discharge detector _DET is connected to the oscillator O via a resistor.
This is the control voltage Vc of the SC. The oscillation output of the oscillator OSC is frequency-divided by the frequency divider DIV, and the first and second frequency-divided outputs are supplied to the control electrodes of the switching elements Q ₁ and Q ₂ via drive circuits DR 1 and DR 2, respectively. .

Hereinafter, the configurations of the discharge detector DET, the oscillator OSC, the frequency divider DIV, and the drive circuits DR1 and DR2 will be briefly described.

First, the discharge detector DET has a low resistance connected in series to the discharge lamp _RL , an amplifier for amplifying the voltage generated across the low resistance, a rectifier for rectifying the amplified output, and smoothing the rectified output. And a Schmitt circuit that receives the smoothed output as an input. The output V _{DET of the} Schmitt circuit goes to the “High” level when the smoothed output of the CR integration circuit exceeds the first level, indicating that the discharge lamp _RL is in the discharge state. When the voltage falls below the second level, which is also low, the level becomes "Low", indicating that the discharge lamp _RL is in a non-discharge state (no-load state).

Next, the oscillator OSC includes a general-purpose timer IC (for example, NE555 manufactured by Signatures). This timer I
C has an external resistor and capacitor so as to form an astable multivibrator. When the control voltage Vc applied to its frequency control terminal (Pin 5) increases,
The frequency of the oscillation output Vo decreases.

Next, the frequency divider DIV is composed of the first and second AND circuits and D
It has a flip-flop. Oscillation output V of oscillator OSC
o is one of the inputs of the first and second AND circuits and the clock input C of the D flip-flop. The output of the D flip-flop is connected to the data input D. Therefore, as the output Q of the D flip-flop, an output obtained by dividing the oscillation output Vo of the oscillator OSC by half the frequency is obtained. D flip-flop output, Q
Are the other inputs of the first and second AND circuits, respectively.

Next, the drive circuits DR1 and DR2 will be described. Drive circuit DR2 of the switching element Q ₂ of the low voltage side, an input by connecting the base ends of the NPN transistor and the PNP transistor,
It is composed of a totem-pole circuit in which emitters are connected to each other to produce an output, and a control power supply voltage Vcc is applied between collectors, and a resistor for dividing the output of the totem-pole circuit. Driving circuit DR1 of the switching elements to Q ₁ high-pressure side
Is composed of the totem pole circuit described above, a pulse transformer that supplies the output of the totem pole circuit to the primary winding via a DC cut capacitor, and a resistor that divides the output of the pulse transformer. ing.

FIG. 8 is an operation waveform diagram at the time of starting the discharge lamp _RL in the above-described circuit. The oscillation frequency f of the oscillator OSC, the detection output V _DET of the discharge detector _DET, and the control voltage Vc of the oscillator OSC are shown.
When, it shows the relationship between the voltage across V _RL of the discharge lamp R _L. First, when the power is turned on, the detection output V of the discharge detector DET is detected.
_{Since DET} is at “Low” level, the control voltage Vc of the oscillator OSC is
Is low. Accordingly, the oscillation frequency f = f ₁ of the oscillator OSC is set high. Next, when the current I _RL flows through the discharge lamp R _L , the detection output V _DET of the discharge detector _DET becomes “High” level, the control voltage Vc of the oscillator OSC increases, and the oscillation frequency f = f _{2 of the} oscillator OSC. Is set low. When the discharge lamp _RL starts, the impedance becomes lower than when there is no load.
The amplitude of the voltage across V _RL of the discharge lamp R _L decreases.

FIG. 9 shows the resonance characteristics of the above circuit. The horizontal axis f is the oscillation frequency of the oscillator OSC, the vertical axis V _RL is the voltage across the discharge lamp R _L. In no-load condition where the discharge lamp R _L is not lit, as described above, since the oscillator OSC operates at a frequency f = f _1, the resonant circuit is excited at a frequency higher than the resonance frequency f _0. At this time, the resonance current flowing through the inductor L becomes delayed phase relative to the excitation voltage generated across the switching element Q _2. This is called a slow mode.
On the other hand, when the discharge lamp _RL is turned on, the impedance of the discharge lamp _RL decreases, so that the slope of the resonance characteristic becomes gentle and the resonance frequency decreases. At this time, the oscillator OSC has the frequency f
= Because operating at f _2, the resonant current flowing in the resonant circuit becomes delayed phase with respect to the excitation voltage, operates also in the slow mode.

By the way, a high-intensity discharge lamp (HID) is often in a half-wave discharge state at the time of starting. If the current I _RL flows as shown in FIG. 7 in the half-wave discharge state,
The detection output V _DET of the discharge detector _DET becomes “High” level,
Oscillation frequency f is switched to the frequency f ₂ at the time of lighting from the frequency f ₁ at no load of the oscillator OSC. However, in the half-wave discharge state, since no load is applied to one polarity, the apparent impedance of the discharge lamp _RL is high, and the discharge lamp _RL exhibits a resonance characteristic close to that at the time of no load. Thus, when the oscillator OSC operates at frequency f ₂ at the time of lighting, will be operating at a frequency lower than the resonance frequency, the resonance current flowing in the resonant circuit, the flow advances against the excitation voltage phase. This is called an advanced phase mode.

Figure 10 (a), showing the relationship between (b) is an operation waveform diagram of the slow mode and the fast mode, respectively, the voltage across V _DS and current I _D of the switching elements Q ₁ and Q _2. First, in the slow mode, as shown in Figure 10 (a), the switching element Q ₁ is turned off at timing at which a forward current flows to the switching element Q _1, the switching element Q ₂ is turned on,
Resonance current flowing in the forward direction of the switching element Q ₁ is the flow through the reverse diode of the switching element Q _2, then the polarity of the resonant current reverses already been turned in the forward direction of the switching element Q ₂ Flows. Then, the switching element Q ₂ at the timing that a forward current flows through the switching element Q ₂ is turned on, the switching element Q ₁ is turned on, the resonance current flowing in the forward direction of the switching element Q ₂ is of the switching element Q ₁ flows through the backward diode, then the polarity of the resonant current reverses, flowing in the forward direction of the switching element Q ₁ which has already been turned on. Hereinafter, the same operation is repeated. Therefore, in the slow mode, the timing when the switching element Q _1, Q ₂ is turned on, and the reverse direction current flows to the switching element Q _1, Q _2, switching element Q _1, Q ₂ are turned on at the same time Such inconvenience does not occur.

On the other hand, in the phase advance mode, as shown in FIG.
The switching element Q ₁ is turned off at timing at which the reverse direction current flows through the switching element Q _1, the switching element Q ₂ is turned on, the resonance current flowing in the reverse direction diode of the switching element Q ₁ is the order of the switching element Q ₂ Flows in the direction. Therefore, until the reverse recovery time of the reverse diode of the switching element Q ₁ is passed, the switching element
Q ₁ and Q ₂ conduct simultaneously in the forward direction, and the DC power supply V
₁ is short-circuited and excessive current flows. The switching element Q ₂ is turned off, the switching element Q ₁ is turned on at the timing at which the reverse direction current flows through the switching element Q _2, the resonant current flowing in the reverse direction diode of the switching element Q ₂ is a switching element Q ₁ Flows in the forward direction. Therefore, until the reverse recovery time of the reverse diode of the switching element Q ₂ has passed, will be switching elements Q _1, Q ₂ conducts in the forward direction at the same time, the DC power supply V ₁ is being shorted, excessive current Flows. As described above, in the phase advance mode, at the timing when the switching elements Q ₁ and Q ₂ are turned on, the reverse current flows through the other switching elements Q ₂ and Q ₁ and until the reverse recovery time elapses. This causes a disadvantage that the switching elements Q ₁ and Q ₂ are simultaneously turned on.

As described above, when the discharge lamp _RL is a high-intensity discharge lamp, it may be in a half-wave discharge state during the starting process, and in this half-wave discharge state, the detection output V _DET of the discharge detector _DET becomes “ becomes a High "level, the oscillator OSC operates at a frequency f = f ₂ at the time of lighting, the leading phase mode. For this reason, an overcurrent flows due to the simultaneous turning on of the switching elements Q ₁ and Q ₂ , which may cause deterioration and destruction of the elements.

Conventional Example 2 FIG. 11 is a circuit diagram of another conventional example. This circuit is configured to switch the oscillation frequency of the oscillator OSC only when the discharge lamp _RL is in a double-wave discharge state.
Hereinafter, the main circuit configuration will be described. The primary winding of the current transformer CT is connected in series to the discharge lamp _RL . The current transformer CT has first and second secondary windings. The voltage obtained at the first secondary winding is input to the first comparator CMP1 via a rectifying and smoothing circuit. Further, the voltage obtained at the second secondary winding is input to the second comparator CMP2 via the rectifying / smoothing circuit. Discharge lamp
When the current I _RL flows through R _L in the direction shown by the arrow in FIG. 11, the input voltage of the first comparator CMP1 rises, and the output Vd
t ₁ is the "High" level. Further, when the current in the reverse direction flows through the discharge lamp R _L, the input voltage of the second comparator CMP2 is increased, the output Vdt ₂ is "High" level. Since the input voltages of the comparators CMP1, CMP2 is briefly held by the capacitor of the rectifying and smoothing circuit, the discharge lamp when R _L is-wave discharge state, the output Vdt ₁ of the first and second comparators CMP1, CMP2, Vdt ₂ At the same time, the output of the AND circuit AND becomes the "High" level, and the oscillation frequency of the oscillator OSC is switched to the frequency at the time of lighting.

FIG. 12 is an operation waveform diagram of the circuit, the oscillation frequency f of the oscillator OSC, and the voltage across V _RL of the discharge lamp R _L, discharge lamp R _L
A current I _RL flowing through the first and second comparators CMP1,
The relation between outputs Vdt ₁ and Vdt ₂ of CMP2 is shown. Immediately after the power is turned on, the discharge lamp R _L is unloaded condition, no current flows I _RL, the amplitude of the voltage V _RL increases. Thereafter, when the discharge lamp _RL enters a half-wave discharge state and, for example, a current _IRL flows in a direction indicated by an arrow in FIG. 11, the output V1 of the first comparator CMP1 is output.
dt ₁ becomes “High” level, but the second comparator CMP2
Since the output Vdt ₂ is at the “Low” level, the AND circuit AND
Is at the "Low" level, and the oscillation frequency f of the oscillator OSC remains the frequency at the time of no load. After that, discharge lamp R _L
There is a double-wave discharge state, when the current I _RL becomes to flow in both directions, the output Vdt ₁ of the first and second comparators CMP1, CMP2, Vdt ₂ becomes "High" level at the same time. Therefore, the output of the AND circuit AND becomes “High” level, and the oscillation frequency f of the oscillator OSC switches to the frequency at the time of lighting.

In this conventional example, the phase is not set in the half-wave discharge state. However, when the oscillation frequency is f = f ₁ in the half-wave discharge state, the current I flowing through the discharge lamp _RL is
There is a problem that _RL is small and it takes a long time to transition from the half-wave discharge state to the double-wave discharge state. For this reason, there is a problem that flickering or the like in a half-wave discharge state is long and the life of the discharge lamp _RL is shortened. Therefore, in the half-wave discharge state, it is desired that the discharge lamp _RL be quickly heated by flowing a larger amount of current to quickly shift to the double-wave discharge state.

[Problems to be Solved by the Invention] As described above, when the discharge lamp is lit by the resonance type inverter device, the impedance of the discharge lamp changes between when the discharge lamp is not loaded and when the discharge lamp is lit. The characteristics change greatly. Therefore, as in Conventional Example 1, it has been proposed to detect the start of discharge and switch the oscillation frequency of the inverter device from the frequency at no load to the frequency at lighting when the discharge starts. However, in a high-intensity discharge lamp, it often shifts from a no-load state to a double-wave discharge state via a half-wave discharge state. When the switching elements are turned on, an overcurrent flows when the switching elements are simultaneously turned on, which causes a problem that the elements are deteriorated or destroyed. Therefore,
As in Conventional Example 2, it has been proposed to detect the double-wave discharge state of the discharge lamp and switch the operating frequency of the inverter device to the frequency at the time of lighting after the discharge lamp enters the double-wave discharge state. However, if the inverter device is operated at the no-load frequency in the half-wave discharge state, a large amount of current does not flow through the discharge lamp, and it takes a long time to shift to the double-wave discharge state. Flickering caused by
There is a problem that the life of the discharge lamp is shortened.

The present invention has been made in view of such a point, and an object of the present invention is to provide a discharge lamp lighting device for lighting a high-intensity discharge lamp using a resonance type inverter device, in which a half of a discharge lamp is generated during a starting process. An object of the present invention is to promptly shift to a double-wave discharge state while avoiding a phase advance mode in a wave discharge state.

[Means for Solving the Problems] In the present invention, in order to solve the above-mentioned problems, as shown in FIG. 1, first and second switching elements Q ₁ , a series circuit Q ₂ 'in parallel connected to the DC power supply V _1, first and second switching elements Q _1, Q
Drive circuits DR ₁ and DR ₂ that alternately turn on and off ₂
In the discharge lamp lighting device comprising a resonant circuit is excited by the inductor L and the first and second voltage obtained at the connection point of the switching elements Q _1, Q ₂ comprises a capacitor C ₁ and the high-intensity discharge lamp R _L, release A discharge detector DET for detecting the start of discharge of the discharge lamp _RL when the lamp current of the lamp _RL starts flowing in at least one direction, and a first detector for detecting the start of discharge by the discharge detector DET. And second switching element
Frequency control means for gradually moving the operating frequency f of Q ₁ and Q ₂ from the no-load frequency f ₁ to the lighting frequency f ₂ so that the current flowing through the resonance circuit does not enter the advanced mode. It is a feature.

[Operation] According to the present invention, a lighting device for a high-intensity discharge lamp using a resonance-type inverter device as described above
When the start of the half-wave discharge of _RL is detected, the operating frequency of the switching elements Q ₁ and Q ₂ is gradually changed from the frequency at the time of no load to the frequency at the time of lighting so that the current flowing through the resonance circuit does not become the advanced mode. So that it can be prevented from going into the fast-phase mode in the half-wave discharge state immediately after the start of discharge, and as the half-wave discharge state approaches the double-wave discharge state, the frequency at the time of lighting becomes closer. As a result, the current flowing through the discharge lamp _RL can be increased to quickly shift to the double-wave discharge state.

Embodiment 1 FIG. 1 is a circuit diagram of a first embodiment of the present invention. Less than,
The circuit configuration will be described. DC power supply V ₁ and the switching element Q _1, Q _2, the inductor L, and configuration of the main circuit including a capacitor C _1, C ₂ and the discharge lamp R _L, similar to that in the conventional example shown in Figure 7 or Figure 11 Therefore, duplicate description will be omitted.
The configurations of the driving circuits DR1 and DR2, the frequency divider DIV, and the oscillator OSC are the same as those of the conventional example shown in FIG. Further, the configuration of the discharge detector DET is different from the conventional example shown in FIG. 11 in that the outputs Vdt ₁ and Vdt ₂ of the first and second comparators CMP1 and CMP2 are output via an OR circuit instead of the AND circuit AND. It is configured to be. Therefore, in the present embodiment, when the discharge lamp _RL is in the half-wave discharge state, the detection output V _DET of the discharge detector _DET is at the “High” level regardless of the direction of the current I _RL . Detection output V _DET of the discharge detector DET is connected to the base of NPN transistor Q ₃ through a resistor. N
The emitter of the PN transistor Q ₃ are connected to ground, collector is connected to the base and collector of the PNP transistor Q ₄ via a resistor R _1, is connected to the base of PNP transistor Q _5. The emitter of the PNP transistor Q ₄ are, is connected to the emitter of the PNP transistor Q _5, and is connected to the control power source voltage Vcc. Hfe of the PNP transistors Q ₄ and Q ₅ are substantially equal, and these constitute a current mirror circuit. The collector of the PNP transistor Q ₅ is connected to one end of the capacitor C _3, the other end of the capacitor C ₃ is grounded. Voltage Vx obtained capacitor C ₃ is low impedance via the impedance converter ZCV consisting operational amplifier, the oscillator via a diode D OSC
Control voltage Vc. The impedance converter ZCV
Has a high input impedance, low output impedance, gain is 1 amp, the voltage of the capacitor C ₃ Vx
It is used as a buffer amplifier to prevent the oscillator OSC from affecting.

Figure 2 is an operation waveform diagram of the present embodiment, the oscillation frequency f of the oscillator OSC, the detection output V _DET of the discharge detector DET, a control voltage Vc of the oscillator OSC, and a discharge lamp R both voltage V _RL of _L Shows the relationship. Hereinafter, the operation of the present embodiment will be described.

_Assuming that the collector-emitter voltages of the transistors Q ₃ and Q ₄ are V _CE3 and V _CE4 , respectively, the current I _R1 flowing through the resistor R ₁ is given by the following equation.

I _R1 = (Vcc−V _CE3 −V _CE4 ) / R ₁ As described above, since the transistors Q ₄ and Q _{5 form} a current mirror circuit, the current flowing through the transistor Q ₅
I _Q5, the current flowing through the resistor R ₁ via the transistor Q ₄ I _R1
Is approximately equal to Therefore, the voltage obtained in the capacitor C ₃
Vx is given by the following equation.

Vx = I _Q5 · t / C ₃ = ｛(Vcc−V _CE3 −V _CE4 ) / R ₁ · C ₃ ｝ · t where t is the detection output V _DET of the discharge detector _DET is “High”
This is the elapsed time after the level has been reached. This voltage Vx (the voltage minus the forward voltage drop V _F of the diode D from strictly voltage Vx) is, until it exceeds the (2/3) Vcc is an oscillator OS
The oscillation frequency f of C is fixed at f = f ₁ (operating frequency at no load). When it exceeds (2/3) Vcc, the oscillation frequency f of the oscillator OSC gradually decreases as the voltage Vx increases. , F
= To migrate to f ₂ (the operating frequency at the time of lighting). Because, as the oscillator OSC, the timer I as shown in FIG.
When C (Signetics NE555) is used,
This is because a voltage of (2/3) Vcc appears at the frequency control terminal (5th pin). That is, the voltage Vx is (2/3) V
When the voltage is lower than cc, the diode D is cut off, so that the oscillation frequency f of the oscillator OSC does not change even when the voltage Vx increases. When the voltage Vx exceeds (2/3) Vcc, the diode D becomes conductive. Therefore, as the voltage Vx increases, the control voltage Vc increases and the oscillation frequency f of the oscillator OSC increases.
Decreases. The voltage Vx is the control power supply voltage Vc
c since (strictly voltage minus the collector-emitter voltage V _CE5 of the transistor Q ₅ from the voltage Vcc) can not be higher than the oscillation frequency f is f = f ₂ (operating frequency at the time of lighting)
Stop at

With this control, even if the discharge lamp _RL is in a half-wave discharge state, it does not enter the early phase mode at the beginning, so that an overcurrent does not flow and deterioration and destruction of the element can be prevented. Further, since the frequency f changes in a direction to gradually increase the current, the power supplied to the discharge lamp _RL also gradually increases, and the half-wave discharge state does not continue for a long time, and quickly shifts to the double-wave discharge state. Therefore, there is no problem of flicker due to continuation of the half-wave discharge state and deterioration of the discharge lamp _RL .

Embodiment 2 FIG. 3 is a circuit diagram of a second embodiment of the present invention. Less than,
The circuit configuration will be described. DC power supply V ₁ and the switching element Q _1, Q _2, the inductor L, and configuration of the main circuit including a capacitor C _1, C ₂ and the discharge lamp R _L, similar to that in the conventional example shown in Figure 7 or Figure 11 Therefore, duplicate description will be omitted.
The configurations of the drive circuits DR1 and DR2 and the discharge detector DET are the same as those in the first embodiment. The detection output V _DET of the discharge detector _DET is a switching control signal of the switch SW. Discharge detector DE
When the T detection output V _DET is at the “Low” level, the changeover switch SW is connected to the terminal b. At this time, the reference voltage Vr is applied to the resistor R _2, the control voltage Vc becomes equal to the reference voltage Vr. Further, the capacitor Cx is the reference voltage Vr through a resistor R ₃ is applied, the charged voltage becomes equal to the reference voltage Vr. Next, when the detection output V DET of the discharge detector _DET becomes “High” level, the changeover switch SW is connected to the terminal a. At this time, the reference voltage Vr is applied to the parallel circuit via a resistor R ₃ resistor R ₂ and a capacitor Cx. Therefore, the control voltage Vc from the reference voltage Vr, which resistor R _2, gradually shifts to the R ₃ divided voltage _{R 2 · Vr / (R 2} + R 3).

This control voltage Vc is a voltage for controlling the pulse width of the monostable multivibrator MM, and when the control voltage Vc rises,
The pulse width increases. The output Q of the monostable multivibrator MM is used as one input of the AND circuits AND1 and AND2, and is used as the trigger input T of the T flip-flop FF. As the output Q and the negative output of the T flip-flop FF, an output obtained by dividing the trigger input T to a half frequency is obtained. These outputs are used as one inputs of AND circuits AND3 and AND4. The outputs of the detectors ZD2 and ZD1 are supplied to the other inputs of the AND circuits AND3 and AND4, respectively. The outputs of the AND circuits AND3 and AND4 are used as the other inputs of the AND circuits AND1 and AND2, respectively, and the OR circuit OR
Trigger input of the monostable multivibrator MM via. And the outputs of the AND circuits AND1 and AND2 are
The switching elements Q ₁ ,
It is supplied to the control electrode of Q _2.

In this embodiment, when the phase advance mode is set, 2
In order to prevent two switching elements Q ₁ and Q ₂ from turning on at the same time, a simultaneous on prevention circuit including detectors ZD 1 and ZD 2 and AND circuits AND 3 and AND 4 is provided. The detector ZD1 is
And detecting a reverse current flowing through the switching element Q ₁ via a current transformer, the output of the detector ZD1 only when a reverse current flows through the switching element Q ₁ "Low"
Level. Similarly, the detector ZD2 has detected a reverse current flowing through the switching element Q ₂ via a current transformer, the output of the detector ZD2 only when a reverse current flows through the switching element Q ₂ " Low "level.

Hereinafter, the operation of the present embodiment will be described. The monostable multivibrator MM is triggered by the rising edge of the output of the OR circuit OR. When the output Q of the monostable multivibrator MM falls, the output of the T flip-flop FF is inverted. Now, the negative output of the T flip-flop FF is inverted from “High” level to “Low” level, and the output Q
Is inverted from “Low” level to “High” level, the output of the AND circuit AND2 changes from “High” level to “Low” level at the falling timing of the output Q of the monostable multivibrator MM. . Therefore, the switching element Q ₂ becomes a state to block forward current, this time, if the reverse current flows through the switching element Q _1, a slow mode, immediately on signal to the switching element Q ₁ Does not occur at the same time. In this case,
Since the output of the detector ZD2 is at the “High” level, the output of the AND circuit AND3 is at the “High” level, and the monostable multivibrator MM is triggered via the OR circuit OR.
As a result, the output Q of the monostable multivibrator MM is at the “High” level for a certain period, during which the AND circuit A
When the output of ND1 becomes “High” level, the switching element
ON signal is applied to Q _1.

On the other hand, as described above, the output of the AND circuit AND2 is “Hig
When changes to Low "level" level "h, when a reverse current flows through the switching element Q ₂ is a phase advance mode, given immediately on signal to the switching element Q _1, the simultaneous ON In this case, since the output of the detector ZD2 is at the “Low” level, the AND circuit AND
The output of 3 becomes “Low” level, and the monostable multivibrator MM is not triggered. Then the switching element
Reverse current stops of Q _2, comes to the other state reverse current flowing through the switching element Q _1, the output of the detector ZD2 becomes "High" level, the output of the AND circuit AND3 at this timing " It becomes High level, and the monostable multivibrator MM is triggered. As a result, the output Q of the monostable multivibrator MM is at the “High” level for a certain period, during which the output of the AND circuit AND1 is “High”.
Level so that, on signal is applied to the switching element Q _1. Therefore, the phase advance mode can be prevented, and the two switching elements Q ₁ and Q ₂ do not turn on at the same time.

The above operation timing of the switching element Q ₁ is turned on, a case has been described in which the control by the AND circuit AND3 and detector ZD2, the detector ZD1 a timing when the switching element Q ₂ is turned on and the AND circuit AND4 It goes without saying that the same holds when controlling.

The feature of the present embodiment is that the pulse width of the monostable multivibrator MM is made variable by an externally applied control voltage Vc in an inverter device having such a simultaneous ON prevention circuit.

FIG. 4 is an operation waveform diagram of the present embodiment. The operation frequency f of the inverter device (in other words, the pulse width control voltage Vc of the monostable multivibrator MM), the detection output V _DET of the discharge detector _DET , and the discharge shows the relationship between the voltage across V _RL of the lamp R _L. At power-on, the detection output V _DET of the discharge detector _DET
Is at the “Low” level, the switch SW is connected to the terminal b, and the control voltage Vc is equal to the reference voltage Vc.
After that, when the discharge lamp _RL enters the half-wave discharge state, the discharge detector
Since the detection output V _DET of the _DET becomes “High” level, the changeover switch SW is connected to the terminal “a”, and the control voltage Vc is the reference voltage.
Gradually decreases from Vc, a predetermined time constant _{R 2 · Vc (R 2 +} R 3)
Move to In this process, the pulse width of the monostable multivibrator MM becomes gradually wider, a discharge lamp R sufficient energy _L is supplied, the voltage across V _RL of the discharge lamp R _L is reduced, to the full-wave discharge state The transition is smooth.

Third Embodiment FIG. 5 is a circuit diagram of a third embodiment of the present invention. Less than,
The circuit configuration will be described. DC power supply V ₁ and the switching element Q _1, Q _2, the inductor L, and configuration of the main circuit including a capacitor C _1, C ₂ and the discharge lamp R _L, similar to that in the conventional example shown in Figure 7 or Figure 11 Therefore, duplicate description will be omitted.
In addition, the driving circuits DR1 and DR2, the frequency divider DIV and the discharge detector DET
Is the same as that of the first embodiment. Detection output V _DET of the discharge detector DET is supplied to the base of the transistor Q ₃ via the resistor R _4. The emitter of the transistor Q ₃ are is grounded, and the collector resistor R ₆ through the resistor R ₅ capacitors
It is connected to one end of each of the C _3. The other end of the capacitor C ₃ is grounded, the other end of the resistor R ₆ is connected to the control power source voltage Vcc.

In this embodiment, three oscillators OSC1 to OSC3 are provided. The first oscillator OSC1 is an oscillator for periodically changing a control voltage applied to the second oscillator OSC2. The second oscillator OSC2 is a voltage-controlled oscillator whose oscillation frequency fa changes according to the output voltage of the first oscillator OSC1.
Third oscillator OSC3 is an oscillator of the voltage controlled oscillation frequency fb is changed in accordance with the control voltage Vc obtained in the capacitor C ₃ above. The oscillation output of oscillator OSC2 is AND circuit AND2
The oscillation output of the oscillator OSC3 is used as one input of the AND circuit AND1. AND circuit AN
A detection output V _DET of the discharge detector _DET is supplied to the other input of D1, and a signal obtained by inverting the detection output V _DET of the discharge detector _DET by the NOT circuit is supplied to the other input of the AND circuit AND2. Has been entered. The outputs of the AND circuits AND1 and AND2 are input to the frequency divider DIV via the OR circuit OR.

FIG. 6 is an operation waveform diagram of the present embodiment, in which the oscillation frequency fa of the oscillator OSC2, the detection output V _DET of the discharge detector DET, the oscillation frequency fb of the oscillator OSC3, and the output frequency f _{0 of the} OR circuit OR.
When, it shows the relationship between the voltage across V _RL of the discharge lamp R _L. At power-on, the detection output V _DET of the discharge detector _DET is “L”.
because it is ow "level, the AND circuit AND1 is a signal passage prohibiting state, the AND circuit AND2 is a signal passable condition. Therefore, the output frequency f ₀ of the OR circuit OR is an oscillator
It is determined by the oscillation frequency fa of OSC2. This oscillation frequency fa
It is decreased to a frequency close to the resonance point of the predetermined time intervals determined by the oscillator OSC1, each time, the voltage across V _RL of the discharge lamp R _L increases. As a result, a high voltage pulse for starting is periodically applied to the discharge lamp _RL . In this state,
Since the transistor Q ₃ are being turned off, the capacitor C ₃ is charged to the level of the control power supply voltage Vcc via a resistor R _6, the oscillation frequency fb of oscillator OSC3 is set higher.

Now, when the discharge lamp _RL starts discharging by the high voltage pulse, the detection output V _DET of the discharge detector _DET goes to the “High” level, so that the AND circuit AND1 is in a signal passable state, and the AND circuit AND2 is The signal passage is prohibited. Accordingly, the output frequency f ₀ of the OR circuit OR is determined by the oscillation frequency fb of oscillator OSC3. Detection output V _DET of discharge detector _DET
There becomes the "High" level, the transistor Q ₃ are turned on, the capacitor C ₃ is resistor R ₅ is connected in parallel. Therefore, the control voltage Vc obtained in the capacitor C _3, the control power supply voltage Vcc as the initial value, with a predetermined time constant R ₅ · Vcc /
It drops to (R ₅ + R _6). Accordingly, the oscillation frequency fb of the oscillator OSC3 gradually decreases, and finally reaches the operating frequency at the time of lighting.

In each of the above embodiments, the switching elements Q ₁ , Q
₂ is not limited to a power MOSFET, but may be a bipolar transistor with an anti-parallel diode added. Generally, any semiconductor switch element that does not block reverse current can be used.

Also, the circuit configuration of the inverter device is not limited to the modified half-bridge circuit as exemplified in the embodiment, but may be a half-bridge circuit or a full-bridge circuit, or the like. The present invention can be applied. Here, the full bridge circuit is a series circuit of the first and second switching elements and a series circuit of the third and fourth switching elements connected in parallel to a DC power supply, and the first and second switching elements are connected in parallel. Switching element connection point and third
And a connection point between the fourth switching element and a connection point of the fourth switching element. The third switching element is a circuit in which a reverse polarity voltage is alternately applied to the LC resonance circuit. The fourth switching element is turned on and off simultaneously with the first switching element, and the fourth switching element is turned on and off simultaneously with the first switching element. The half-bridge circuit is a circuit in which the third and fourth switching elements in the full-bridge circuit are each replaced with a capacitor.

[Effect of the Invention] According to the present invention, in a discharge lamp lighting device for lighting a high-intensity discharge lamp using a so-called resonance type inverter device, when a start of a half-wave discharge of the discharge lamp is detected, a switching element is provided. The operating frequency is controlled so that the current flowing through the resonance circuit gradually changes from the frequency at no load to the frequency at lighting so that the current does not enter the phase advance mode.
A phase advance mode can be prevented in the half-wave discharge state immediately after the start of discharge.In addition, as the half-wave discharge state approaches the double-wave discharge state, the operating frequency approaches the frequency at the time of lighting, and sufficient current is supplied to the discharge lamp. And it can be quickly moved to the double-wave discharge state.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention, FIG. 2 is an operation waveform diagram of the above embodiment, FIG. 3 is a circuit diagram of a second embodiment of the invention, FIG. 5 is a circuit diagram of a third embodiment of the present invention, FIG. 6 is an operation waveform diagram of the above example, FIG. 7 is a circuit diagram of a conventional example, FIG. 8 is an operation waveform diagram of the above example, and FIG. FIGS. 10 (a) and 10 (b) are operation waveform diagrams respectively showing the operation in the slow mode and the fast mode,
FIG. 11 is a circuit diagram of another conventional example, and FIG. 12 is an operation waveform diagram of the same. V ₁ was DC power source, Q _1, Q ₂ are switching elements, L is the inductor, C ₁ -C ₃ are capacitors, R _L is the discharge lamp, DET discharge detector, OSC an oscillator, R ₁ is the resistance.

Claims (1)

(57) [Claims] A drive circuit for connecting a series circuit of first and second switching elements which does not block a reverse current to a DC power supply in parallel, and for driving the first and second switching elements alternately on and off. A discharge lamp lighting device comprising a resonance circuit including an inductor, a capacitor, and a high-intensity discharge lamp and excited by a voltage obtained at a connection point between the first and second switching elements. And a discharge detector for detecting the start of discharge of the discharge lamp when the discharge starts to flow in one direction, and when the discharge start is detected by the discharge detector, the operating frequencies of the first and second switching elements are set at no load. Frequency control means for gradually moving the current flowing through the resonance circuit from the frequency of the lamp to the frequency at the time of lighting so as not to be in the advanced mode. Location.