JPS62296396A - Discharge lamp lighter - 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 3. Detailed Description of the Invention (Technical Field) The present invention relates to a discharge lamp lighting device using an inverter circuit.

(Background technology) FIG. 8 is a circuit diagram of a conventional discharge lamp lighting device.

The power supply voltage of the alternating current power supply AC is rectified by the diode bridge DB, smoothed by the capacitor C0, and made into a direct current voltage. This DC voltage is 1 of the leakage transformer T.
It is applied to the series circuit between the next side and the semiconductor switching element Q1. Discharge lamps DL, DL2 are connected to the secondary side of the leakage transformer T1 via a capacitor C2, and actance elements (capacitors Ci, DL2) are connected to the non-power side of each discharge lamp.
C-) is connected to constitute a discharge lamp filament preheating circuit. A diode D1 is connected in antiparallel to the semiconductor switch cable Q. Further, a capacitor C1 that resonates with the inductance component of the circuit is connected in parallel to both ends of the switch element Q.

The capacitor C1 may be connected to both ends of the primary coil of the leakage transformer T1.

The output of the separately excited signal generating circuit sG is connected to the control pole of the semiconductor switching element Q, and the conduction inhibiting circuit B and the drive transformer T2.
and is input through. The separately excited signal generation circuit SG is
Power is supplied from the control section power supply circuit PW connected to the smoothing capacitor C0.

FIG. 9(a) shows a separately excited signal for turning on and off the semiconductor switch element Q1 (when it is at the "Higb" level, it is called a separately excited on signal, and when it is at a "Low" level, it is called a separately excited off signal. ), when the semiconductor switching element Q is turned on by a separately excited ON signal, 1 of the leakage transducer T1 is turned on.
A switch element current as shown in FIG. 9(c) flows through the next side. When the semiconductor switching element Q is turned off by a separately excited off signal, the leakage transformer T1 resonates with the capacitor C2 due to the energy stored in the LC component of the circuit, and as shown in FIG. A resonant capacitor current flows, and across the semiconductor switch element Q1,
A resonant voltage as shown in FIG. 9(b) is generated. When this resonant voltage becomes zero, the resonant current flows through the diode D1, and when the diode current (FIG. 9 (Po)) becomes zero, the separately excited signal causes the semiconductor switching element Q,
A current flows in the same way as in the previous cycle (Fig. 9 (c)),
In this way, oscillation continues, and the voltage generated on the secondary side of the leakage transformer T due to this resonance is applied to the discharge lamps DL, DL2 via the leakage inductance and the capacitor C2, causing them to light up.

By the way, when the filament is disconnected, when the discharge lamp is not connected, or when there is no load, such as in a transient state when the discharge lamp is attached or detached, the reactance element is not connected, so the natural oscillation period of the circuit is It changes greatly and one cycle is large. Therefore, the natural oscillation frequency of the circuit under no load is lower than when the discharge lamp is lit. In this way, even when the natural oscillation period of the circuit changes, in a separately excited drive type inverter, the semiconductor switching element Q1 is forcibly turned on according to the period of the separately excited signal, so the voltage of the resonant capacitor C1 is high. In some cases, the semiconductor switching element Q1 may be turned on, and a rush current from the capacitor C1 flows to the semiconductor switching element Q1, causing a large power loss and also causing damage to the semiconductor switching element Q. It may occur. Therefore, in the circuit shown in FIG. 8, a switch element voltage detection circuit A and a conduction prohibition circuit B are provided. The voltage across the semiconductor switch element Q is detected by the switch element voltage detection circuit A. Switch element voltage detection port &! The detection output of 8A is NO in the conduction prohibition circuit B.
It is input to R circuit G2. The other input of the NOR circuit G2 receives the separately excited signal from the separately excited signal generating circuit SG.
An inverted signal is input to the T circuit G1. This conduction prohibition circuit B prohibits conduction of the semiconductor switch element Q even if a separately excited ON signal is generated during a period when the semiconductor switch element Q1 has a voltage across both ends.

When there is no load, the natural oscillation period of the inverter circuit is longer than when the light is on, and the switch element voltage becomes a long-period oscillating voltage, as shown in Figure 9 (f). is detected by the switch element voltage detection circuit A, and during the period when its detection output (Fig. 9 (G)) is at the "°H" level, the conduction prohibited circuit n!3 prevents the passage of the separately excited ON signal. Therefore, the drive signal of the semiconductor switch element Q1 becomes as shown in FIG.
1 has a voltage across the semiconductor switching element Q.

Therefore, when there is no load, even if the natural oscillation frequency of the inverter circuit is lower than when the light is on, the semiconductor switching element Q1 is turned on by the separately excited signal while the voltage of the resonant capacitor C1 is high. Therefore, the rush current from the resonant capacitor C1 can be prevented from flowing to the semiconductor switching element Q.

By the way, in the circuit shown in Fig. 8, the ON/OFF state of the separately excited signal is
By changing the duty, the current flowing through the semiconductor switching element Q1 changes, so the resonance current value changes and the voltage applied to the discharge lamp can be changed, preheating the discharge lamp without causing it to light up. It is possible to set the state, lighting condition, and dimming condition. The duty of the separately excited signal can be easily changed by switching the resistance value in the CR time constant circuit for determining the oscillation frequency inside the separately excited signal generating circuit SG using the duty switching signal generating circuit CHG. .

However, in a transient state at the time of duty switching, the conductance of the discharge lamp changes and it takes time to reach a constant state, so it takes time for the vibration of the inverter circuit to reach a steady state. In this transient state, if the above-mentioned operation of inhibiting the separately excited signal when the semiconductor switch element voltage is >> 0 is performed, the transition to another oscillation mode as shown in FIG. 10 occurs, and in this oscillation mode, If the frequency drops significantly and the inverter output voltage drops, the discharge lamp will not turn on when switching from on-duty for preheating to on-duty for lighting, or when switching to on-duty for dimming. It was found that the discharge lamp sometimes went out.

Since this operation mode has a preheating circuit including reactance elements (capacitors Cx and C4) on the non-power supply side of the discharge lamp, vibrations on the secondary side of the leakage transformer T, The waveform is superimposed on the vibration on the next side. As mentioned above, if there is a prohibition operation of the separately excited signal when (semiconductor switch element voltage)>O, the semiconductor switch element voltage will become zero due to a sudden change in the conductance of the discharge lamp in the transient state at the time of duty switching. If it does not return to normal, it will remain stable in this vibration mode and will not return to its original state.

Such a phenomenon may occur not only during duty switching but also in a transient state when a discharge lamp is inserted from a no-load state. In addition to the above-mentioned driving method that prohibits the external excitation signal during the switching element voltage generation period, this phenomenon can also be solved by the driving method shown in Fig. 7, which sets a constant conduction period after the switching element voltage returns to zero. This is a problem that also occurs in drive systems such as In the circuit shown in Fig. 7, the current flowing through the diode D1 is detected by the current transformer CT when the switch element voltage becomes zero, and the monostable multivibrator MV is triggered by the detection output. The on period is set. This circuit also stabilizes in the vibration mode shown in FIG. 10 in a transient state when switching on-duty. When the vibration mode is stabilized, a sufficient starting voltage cannot be obtained and the discharge lamp cannot be lit.

(Object of the invention) The present invention has been made in view of the above-mentioned points,
The purpose is to: In the transient state of the discharge lamp,
To provide a discharge lamp lighting device using an inverter circuit that can prevent falling into an oscillation mode in which a slight discharge occurs at a low frequency.

(Disclosure of the Invention) As shown in FIGS. 1 to 7, the discharge lamp lighting device according to the present invention includes a DC power supply VDC, a semiconductor switching element Q1 that is in the forward direction with respect to the DC power supply VDC, and a DC A diode D1 connected in parallel to the semiconductor switch element Q in a direction opposite to the power supply VDC, and a semiconductor switch element Q.
A drive signal generation circuit F that repeatedly controls the conduction of an inductance element such as a one-cage transformer T1 that is connected in series with the inductance element, a capacitor C3 that exhibits a resonance state with the inductance element, and a semiconductor switch element Q, and turns on and off the semiconductor switch element Q1. In an inverter circuit including a resonant voltage generated by the discharge lamps DL, DL2 applied via a stabilizing element, a slight discharge mode detection circuit M is provided for detecting an oscillation mode in which the discharge lamp is stable in a state of slight discharge. , a circuit is provided for feeding back the detection output of the slight discharge mode detection circuit M to the drive signal generation circuit F.

That is, one aspect of the present invention includes a slight discharge mode detection circuit M that detects a low frequency oscillation mode (hereinafter referred to as "micro discharge mode") caused by changes in the conductance of the discharge lamp during a transient state of the discharge lamp. By feeding back the detection output to the drive signal generation circuit F, for example, the switch element Q of the inverter is forced to be driven by the separately excited ON signal, and the transient state can be overcome until the conductance of the discharge lamp is stabilized. , to shift to normal oscillation mode. Alternatively, when the slight discharge mode is detected, control is performed such as turning off the power once, or canceling the state switching of the discharge lamp and returning to the initial state, to prevent the slight discharge mode from continuing indefinitely. It is something.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Note that in the example circuit, the same elements as those in the conventional example circuit are given the same reference numerals and redundant explanations will be omitted.

Large 11U - Figure 1 is a circuit diagram of the main parts of a discharge lamp lighting device according to an embodiment of the present invention, and Figure 2 is an explanatory diagram of its operation. As a circuit, the 8th
The first example uses the same circuit as the conventional example circuit in the figure.
The figure shows only the control circuit.

In this embodiment, the generation period of the switch element voltage in the slight discharge mode is longer and includes two or more periods of separately excited ON signals, and this is used to count the separately excited ON signals during the generation period of the switch element voltage. However, when the number of counts becomes two or more, it is determined that the mode is a slight discharge mode. The slight discharge mode detection circuit M includes two D flip-flops FF, FF2, and is configured to count the number of times a separately excited ON signal is generated during a period when the switch element voltage is high. Each D flip-flop FF.

FF2's set human power S is both connected to the ground,
It is considered to be 'Low' level.For reset human power R,
A signal obtained by inverting the detection output of the switch element voltage detection circuit A by the NOT circuit is input. The output of the separately excited signal generation circuit SG is input to the clock input cp of the first stage D flip processor 1FF, and the clock input cp of the second stage D flip processor 1FF2 is inputted to the clock input cp of the first stage D flip processor 1FF. The output of the flip-flop FF is input.

Further, the output of each D flip-flop FF, FF2 is connected to its own D input. therefore,
D flip flop b knob FF1. FF constitutes a counter circuit, and its count output is obtained as the output of the D flip-flop FF, and is input to the timer circuit TM. The output of the timer circuit TM is input to an AND circuit.

The detection output of the switch element voltage detection circuit A is input to the other input of the AND circuit circuit. AND circuit G4
The output of is input to the NOR circuit G2. The other input of the NOR circuit G2 receives the separately excited signal t! outputted from the separately excited signal generating circuit SG. A signal inverted by the -NOT circuit G1 is input.

The output of the NOR circuit G2 is input to the control pole of the switching element Q1 via the drive transformer T2.

By taking the logic M between the timer output of the dimer circuit TM and the detection output of the switch element voltage detection circuit A, during the timer period τ, the output of the AND circuit is °''
During this period, the switching element Q is forcibly driven only by the external excitation signal.The switching element Q is forcibly driven by only the separately excited signal.The switching element Q is forcibly driven during this period.
Turn on the discharge lamp.

Note that the generation period of the switch element voltage under no load is shorter than the generation period of the slight discharge mode, and is long enough to include one period of the separately excited ON signal, so it cannot be detected as the slight discharge mode. There isn't.

Figure 3 is a circuit diagram of a main part of another embodiment of the present invention, and
The figure is an explanatory diagram of its operation.0 In this embodiment, the same elements as in the previous embodiment are given the same reference numerals, and duplicate explanations are omitted. Similarly, in the slight discharge mode, the generation period of the switch element voltage is longer, and the slight discharge mode is detected by utilizing the fact that the separately excited ON signal includes two cycles during the voltage generation period.

In this embodiment, as the switch element voltage detection circuit A, a voltage dividing circuit including resistors R, , R2 is used.

A Zener diode ZD for regulating the detection output of the switch element voltage detection circuit A is connected in parallel to the resistor R2. This switch element voltage detection circuit A is connected to both ends of a switch element Q1 made of a transistor.

In the slight discharge mode, the switch element voltage ■ is as shown in FIG. 4 (a). ε is manually input to the switch element voltage detection circuit A, and from the switch element voltage detection circuit A,
4th [4! A detection output as shown in I(b) is obtained. This detection output is the first stage D flip-flop FF,
Since the D input of the first stage is set as the D input of the first stage (l!!
Q output of Flip Flora 1F F + (Figure 4 (d))
becomes a “High” level.

This Q output is the D of the second stage D flip-flop FF2.
It is considered an input. Therefore, due to the second separately excited signal during the period when the switch element voltage is high, the Q signal (fourth!] (e) of the second stage D flip-flop FF is
The level becomes "High". Since the detection output of the switch element voltage detection circuit A and the separately excited signal are input to the AND circuit G5, the separately excited signal during the period when the switch element voltage is high is outputted from the AND circuit. This separately excited signal and the Q of the second stage D flip-flop FF2
The output is input to the AND circuit. Therefore, the waveform of the second separately excited ON signal is obtained as the output of the AND circuit G4, and this is used as the output of the slight discharge mode detection circuit M.

Figure 5 is a circuit diagram of an embodiment of the present invention;
The figure is an explanatory diagram of its operation.6 In this embodiment, the same elements as in the previous embodiment are given the same reference numerals, and redundant explanation will be omitted.

In this embodiment, in order to detect the slight discharge mode,
The differential detection output of the switch element voltage is used. That is, since the waveform of the switch element voltage in the slight discharge mode is a waveform in which waveforms with different periods are superimposed, when the differential detection circuit K detects the differential waveform of the switch element voltage, it is detected that the switch element voltage is being generated. A plurality of differential detection outputs are generated as shown in FIG. 6(C).

In normal vibration mode or when there is no load, the differential detection output is only 1 g. Therefore, when this differential detection output is counted and the count is 2g or more,
It is sufficient to determine that it is in the slight discharge mode.

In the differential detection circuit K of FIG. 5, a CR@ division circuit is configured by a capacitor C6 and a resistor R3. A Zener diode Z D 2 for regulating the detection output to the differential detection circuit is connected in parallel to the resistor R. The detection output of this differential detection circuit I (is counted by a counter circuit consisting of two D flip-flops FF, FF2, and when the count is 2 or more, it is output as the Q output of the D flip-flop 1FF2 of 2 VlEl. , a slight discharge mode detection output can be obtained.

In each of the embodiments described above, the slight discharge mode is detected, and the detection signal drives the switch element with a separate excitation ON signal for a certain period of time. A preheating mode that shortens the on-duty by sending a signal to the circuit and preheating the discharge lamp by applying a voltage that does not turn it on! You can also set it to

Okata Eshi V The seventh figure is a circuit diagram of another embodiment of the present invention.

This embodiment relates to an improvement on the previous example shown in Fig. 11. That is, the present invention is not limited to separately excited drive type inverter circuits, but also applies to switch element voltages as shown in Fig. 7 [21]. The switch element Q returns to zero for a certain period of time.
, can be used in a one-way inverter circuit that conducts.

In the circuit shown in Fig. 7, the diode current is detected by a current transformer CT, and the monostable multivibrator MV is triggered by the detection output, and the switch element is activated for a certain period of time, as in the case of the conventional example shown in Fig. 11. However, in the slight discharge mode, as shown in Figure 10, it is difficult for the switch element voltage to return to zero, so the output of the monostable multivibrator MV turns the switch element Q1 on. When conducting conduction control, the oscillation frequency becomes very low and the output of the inverter also decreases. Therefore, when detecting the slight discharge mode, the multiplexer MPX is switched to the side of the separately excited signal generation circuit SG by the detection output of the slight discharge mode detection circuit 118M. As a result, the switch element Q1 is forcibly driven by the separately excited signal, so that the discharge lamps DL, DL2 survive the transient state and shift to a normal oscillation mode. After that, the multiplexer MPX is switched to the monostable multivibrator MV side by the detection output of the slight discharge mode detection circuit M, and the normal oscillation state is maintained using the same operation as in Fig. 7. be.

(Effects of the Invention) As described above, in the present invention, even if the discharge lamp enters the slight discharge mode, the state is detected by the slight discharge mode detection circuit, and the detection output is fed back to the drive signal generation circuit. This has the effect of preventing the discharge lamp from remaining in the slight discharge mode indefinitely.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a main part of a discharge lamp lighting device according to an embodiment of the present invention, FIG. FIG. 4 is an explanatory diagram of the same operation as the above, FIG. 5 is a main circuit diagram of still another embodiment of the present invention, FIG. 6 is an explanatory diagram of the same as the above, and FIG. 7 is a diagram of another embodiment of the present invention. Circuit diagram, Figure 8 is the circuit diagram of the conventional example, Figures 9 and 10
This figure is an explanatory diagram of the same operation as above, and FIG. 11 is a circuit diagram of another conventional example. VDC is a DC power supply, Ql is a semiconductor switch element, D is a diode, CI is a capacitor, T is a beam cage transformer, D L + , D L z are discharge lamps, F is a drive signal generation circuit, M is a slight discharge mode It is a detection circuit.

Claims (3)

[Claims] (1) A DC power supply, a semiconductor switching element in the forward direction with respect to the DC power supply, a diode connected in parallel to the semiconductor switching element in the reverse direction with respect to the DC power supply, and an inductance element connected in series with the semiconductor switching element. , a capacitor that exhibits a resonance state with an inductance element, a drive signal generation circuit that repeatedly controls conduction of a semiconductor switch element, and a discharge lamp that applies a resonant voltage generated by turning on and off of the semiconductor switch element via a stabilizing element. The inverter circuit is provided with a slight discharge mode detection circuit that detects an oscillation mode that is stable when the discharge lamp is in a state of slight discharge, and a circuit that feeds back the detection output of the slight discharge mode detection circuit to the drive signal generation circuit. A discharge lamp lighting device characterized by: (2) The drive signal generation circuit includes a separately excitation signal generation circuit that generates a separately excitation signal for the semiconductor switch element, and a separately excitation signal that generates a separately excitation signal for the semiconductor switch element during a period in which the semiconductor switch element has a voltage across the semiconductor switch element at least when no load is applied. and a conduction prohibition circuit that prohibits input to the conduction control pole of the element,
2. The discharge lamp lighting device according to claim 1, wherein the conduction prohibition circuit is a circuit whose operation is stopped by the detection output of the slight discharge mode detection circuit. (3) the drive signal generation circuit is a circuit that applies an on signal to the semiconductor switch element for a predetermined period after the voltage across the semiconductor switch element becomes zero when there is no detection output of the slight discharge mode detection circuit; The discharge lamp according to claim 1, further comprising a circuit that applies a separately excited signal to the semiconductor switch element to repeatedly conduct conduction control of the semiconductor switch element when there is a detection output of the slight discharge mode detection circuit. lighting device.