JP2828658B2 - 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 for lighting a discharge lamp by converting a DC voltage into a high-frequency voltage by an inverter circuit.

[Prior Art] Fig. 4 shows a conventional example, a pair of switching elements serving transistor for turning on and off alternately at both ends of the DC power source E ₁
A series circuit of Q ₁ and Q ₂ is connected. One transistor Q
It connects the load circuit Z which includes a series circuit of the inductance L ₁ and the discharge lamp l via the capacitor C ₀ to _1. Also,
Capacitor C ₁ in parallel to the discharge lamp l is is connected. Yes and two secondary windings (feedback winding) n _1, n ₂ is provided in the inductance L _1, the secondary winding n _1, n ₂ are then respectively connected to the bases of the transistors Q _1, Q ₂ is there.

The oscillating current flowing through the load circuit Z is passed through the secondary windings n ₁ , n ₂ at a predetermined cycle determined by the oscillating current to the two transistors Q ₁ , Q
₂ is turned on and off alternately. Where transistor Q
The winding directions of the secondary windings n ₁ and n ₂ are reversed to alternately turn on and off ₁ and Q ₂ .

Figure 5 shows another conventional example, the base is a control terminal of the transistor Q _1, Q ₂ is not returned from the oscillating current flowing through the load circuit Z, alternately two transistors Q _1, Q ₂ There is provided a control circuit ₁₁ for performing on / off control.

FIG. 6 shows still another conventional example, in which one transistor
The base for Q ₁ are controlled by feeding back the oscillating current by the secondary winding n ₁ of the inductance L _1, the other transistor Q ₂
It is provided with a control circuit 1 ₂ having a timer circuit which operates in at least off-period of the transistor Q _1. In this circuit, connects the voltage dividing circuit of resistors R ₁ and R ₂ in parallel with the transistor Q _2, when the transistor Q ₁ is on, the input terminal of the control circuit 1 ₂ Type H level signal, transistor when Q ₁ is off, type L-level signal to the input terminal of the control circuit 1 ₂ is controlled by the control circuit 1 ₂ so as to turn on the transistor Q ₂ receives this signal. In other words, detecting that _one transistor Q1 is turned off,
The Q ₂ are to be turned on. Also, so that dimming discharge lamp l to input dimming signal to the control circuit 1 _2.

[Problem to be Solved by the Invention] The circuit of FIG. 4 has a problem that it is difficult to reduce the value of the oscillating current flowing through the load circuit Z, to dimming the discharge lamp l, and to add an additional function.

In the circuit of FIG. 5, without simultaneously turned on the two transistors Q _1, Q _2, and the control circuit 1 ₁ for controlling two transistors Q _1, Q ₂ smoothly becomes complex, and costly There is a problem that it becomes.

Further, in the circuit of FIG. 6, when the transistor Q ₂ is on, the inductance L ₁ by abnormality such as a discharge lamp l or power
Abnormal current flows, has a risk of the transistor Q ₁ is turned on. That is, when the two transistors Q ₁ and Q ₂ are simultaneously turned on, the power supply is short-circuited, and the transistors
There is a problem that Q ₁ and Q ₂ are destroyed.

The present invention has been provided in view of the above points,
It is an object of the present invention to provide a reliable and low-cost discharge lamp lighting device.

[Means for Solving the Problems] The present invention provides feedback means for returning an oscillating current flowing in a load circuit to a control terminal of one switching element, and for controlling the one switching element to be turned on and off at a predetermined cycle determined by the oscillating current. A control circuit for turning on and off the other switching element by a timer circuit, a delay circuit provided between the feedback means and the control terminal of one of the switching elements for delaying the ON operation of the switching element for a fixed time, and a load circuit. Control means for receiving a signal having the same phase as a signal for driving one of the switching elements from the feedback means and forcibly turning off the other switching element when the flowing oscillating current becomes abnormal.

[Operation] According to the present invention, the signal is in-phase with the control means received from the feedback means, and when the oscillating current flowing through the load circuit becomes abnormal, the control means forcibly switches the other switching element. The switching element is turned off, and one of the switching elements is turned on after being delayed for a predetermined time by a delay circuit, thereby preventing both switching elements from being turned on at the same time.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. Figure 1 shows a block circuit diagram, and the one transistor Q ₁ is fed back via the secondary winding n ₁ delay circuit 2 oscillating current from the inductance L _1. Further, the inductance L ₁ to the control circuit 1 for turning on and off the other transistor Q ₂
And it is fed back to oscillating current from the secondary winding n _2. here,
The outputs of the secondary windings n ₁ and n ₂ are in phase, and if the voltage of the secondary winding n ₁ is at L level, the voltage of the secondary winding n ₂ is also at L level. On the other hand, when the signal is at the H level, the H level is output. Also, the secondary windings n ₁ and n _{2 of} the inductance L ₁ constitute feedback means. Note that, using the secondary windings n ₁ and n ₂ , the off state of the transistor Q ₁ can be detected. Alternatively, a detection method as shown in FIG. 6 may be used.

Figure 2 shows an operation waveform diagram, the signal of the same phase are output to the secondary winding n _1, n ₂ of the inductance L ₁ as shown in FIG. 2 (a) (b). Now, has been entered on the base of the transistor Q ₁ through a delay circuit 2 by the secondary winding n ₁ of the signal, the signal from the secondary winding n ₁ is at the L level,
When the transistor Q ₁ is turned off, the transistor Q ₁ is inputted to be turned off to the control circuit 1 is detected by the above method, the control circuit 1 in this off time, it triggers the internal timer circuit timer Start operation. As shown in FIG. 2 (c) by the timer output of the timer circuit, and the transistor Q ₂ so as to a certain period on. Then, the transistor Q ₂ is turned off, the signal from the secondary winding n ₁ of the inductance L ₁ is input to the delay circuit 2 is outputted after a predetermined time. Here, in the delay circuit 2, the second
Delayed by a time t as shown in FIG. (D), turn on the transistor Q ₁ after this delay.

Here, when the transistor Q ₂ is on, the abnormality of ₁ such as a discharge lamp l or DC power source E, the inductance L abnormal current flows in the _1, series to the base of the transistor Q ₁ through a secondary winding n ₁ An H level signal is input to the connected delay circuit 2. At the same time Fig. 2 (b) H-level signal above a predetermined value as shown in via the secondary winding n ₂ enters the control circuit 1. The control circuit 1 receives this H level signal,
As shown in FIG. 2 (c), the transistor Q ₁ is forcibly turns off the transistor Q ₂ before turning on the delay in circuit 2 outputs. After off of the transistor Q _2, is turned on the transistor Q ₁ is in time t lag as shown in FIG. 2 (d). Therefore, at the time of abnormality, both transistors Q ₁ and Q ₂
Are not turned on at the same time.

FIG. 3 shows a specific circuit diagram, wherein a delay circuit 2 is constituted by a resistor R ₁ and a capacitor C _2, and a monostable multivibrator 3
If, constitute a control circuit 1 from transistor Q ₃ to Q ₅ and the like. Also, the secondary windings n ₁ and n _{2 of} the inductance L ₁ constitute feedback means, and one transistor Q ₁ has a load circuit Z
The oscillating current is fed back. The FET Q _{2, which} is the other switching element, is on / off controlled by the monostable multivibrator 3. This monostable multivibrator 3
Is a general-purpose integrated circuit (for example, μPD4538 manufactured by NEC Corporation)
After the falling trigger input terminal B changes from H level to L level, the output terminal Q is at H level and the output terminal is at L level for a certain period. And turn on the FETs Q ₂ in this state. Here, by connecting the switching element serving FETs Q ₂ voltage dividing resistors of the resistor R ₄ and R ₅ in parallel, by dividing the voltage across V _Q2 of FETs Q ₂ by the resistor R ₄ and R _5, the transistor Q _A signal in which ₁ is off is detected as a trigger signal for the monostable multivibrator 3. The time when the output terminal Q of the monostable multivibrator 3 is at the H level (the time when the output terminal is at the L level) is the resistance R ₉
To be determined by the time constant of the capacitor C _3.

Output terminal Q of the monostable multivibrator 3 is connected through a resistor R ₆ is connected to the base of the transistor Q ₃ for driving, the output terminal is connected to the base of the transistor Q ₄ for driving through a resistor R ₇ . The collector of the transistor Q ₃ are the positive electrode of the DC power source E _2, the emitter of the transistor Q ₄ is connected to the negative electrode of the DC power source E _2, the collector of the emitter and the transistor Q ₄ of the transistor Q ₃ are via a resistor R ₁₀ FET
It is connected to the base of Q _2. Thus, the monostable multivibrator 3 operates as a timer circuit for determining the ON period of the FETs Q _2.

The abnormality of the discharge lamp l or DC power source E _1, when an abnormal current flows through the inductance L _1, a predetermined value or more signals from the secondary winding n ₂ is output, the base of the transistor Q ₅ is H
Level, and the transistor Q ₅ is turned on. Thus, monostable, the CD input terminal of the vibrator 3 contains the L level signal, the output terminal Q is L level, the output terminal becomes H level, the base of the transistor Q ₂ is contains the L level signal, FETs Q ₂ is turned off. The monostable multivibrator 3 and the transistors Q ₅ , Q ₃ , and Q ₄ , which constitute the main parts of the control circuit 1, constitute control means for forcibly turning off the FET Q ₂ .

Incidentally, in the embodiment, although the circuit which also serves as a current transformer of the feedback means of the oscillation inductance L ₁ and a switching element, but may be separately.

[Effects of the Invention] As described above, according to the present invention, feedback means for returning an oscillating current flowing in a load circuit to a control terminal of one switching element and controlling the one switching element to be turned on / off at a predetermined cycle determined by the oscillating current. A control circuit for turning on and off the other switching element by a timer circuit; a delay circuit provided between the feedback means and the control terminal of one of the switching elements for delaying the on operation of the switching element for a predetermined time; and a load circuit. When the flowing oscillating current becomes abnormal, control means for receiving a signal in phase with the signal for driving one of the switching elements from the feedback means and forcibly turning off the other switching element is provided. The signal is in phase with the control means received from the feedback means, and when the oscillating current flowing through the load circuit becomes abnormal, the control means The other switching element can be forcibly turned off, and one switching element can be turned on after being delayed for a certain time by a delay circuit. Therefore, when an abnormal current flows in the load circuit, one of the switching elements is turned off. Before the switching element is turned on, the other switching element can be always turned off, which has the effect of being easy to design and reducing the cost, and preventing both switching elements from being turned on at the same time. Therefore, the power supply is not short-circuited, and the safety is achieved.

[Brief description of the drawings]

FIG. 1 is a basic circuit diagram of an embodiment of the present invention, FIG. 2 is an operation waveform diagram of the above, FIG. 3 is a concrete circuit diagram of the above, FIG. 4 is a circuit diagram of a conventional example, and FIG. FIG. 6 is a circuit diagram of a conventional example, and FIG. 6 is a circuit diagram of still another conventional example. 1 the control circuit, the second delay circuit, E ₁ denotes a DC power source, Q _1, Q ₂ are transistors, C ₀ is the capacitor, l the discharge lamp, L ₁ is the inductance, Z is the load circuit.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-1444891 (JP, A) JP-A-2-144892 (JP, A) JP-A-2-172195 (JP, A) JP-A-2-142 280673 (JP, A) JP-A-2-295098 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 41/24

Claims (1)

(57) [Claims] 1. A DC power supply, a pair of switching elements connected in series at both ends of the DC power supply and alternately turned on and off, and at least one of the switching elements is connected in parallel via a capacitor to at least one of the switching elements. And a load circuit including a series circuit of the discharge lamps. An oscillating current flowing through the load circuit is fed back to a control terminal of one switching element, and the one switching element is turned on / off at a predetermined cycle determined by the oscillating current. Return means,
A control circuit for turning on and off the other switching element by a timer circuit; a delay circuit provided between the feedback means and the control terminal of one of the switching elements for delaying the on operation of the switching element for a predetermined time; Control means for receiving a signal in phase with a signal for driving one of the switching elements from the feedback means when the current becomes abnormal, and forcibly turning off the other switching element. Lighting device.