JPH0521191A - Discharge lamp lighting circuit - Google Patents

Abstract

PURPOSE:To make the current of a discharge lamp variable easily without increasing the bearing force of a switch, by using a diode with a different reverse restoring time inserted between the base emitters of a switching element to convert so as to make the current flowing to the discharge lamp variable. CONSTITUTION:A cathode of a switch 17 and a diode 16 is connected in parallel to a diode 11, and a circuit of connecting its anode and an anode of the diode 11 is provided. A current flowing to a discharge lamp 6 is returned by a current transformer 8, and by charging and discharging the charge accumulated to a capacitor 10 by utilizing the voltage and a magnetic saturation generated to both ends of the secondary winding, the ON and OFF of a transistor(Tr) 5 is controlled, and a high voltage generated to a resonance circuit of a capacitor 2 and an inductor 3 is divided by a capacitor 9 and an inductor 7, and thereby, the discharge lamp 6 is lighted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting circuit.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional example of a discharge lamp lighting circuit. As shown in the figure, the discharge lamp lighting circuit has a circuit as described below. A parallel resonance circuit of the positive side of the DC power supply 1, the capacitor 2 and the inductor 3. This resonant circuit and the anode of diode 4,
A circuit that reaches the negative side of the DC power supply 1 via its cathode and the collector and emitter of the transistor 5. The discharge lamp 6, the inductor 7, and the current transformer 8 are arranged in parallel with the resonance circuit.
A circuit consisting of the primary winding. A circuit that reaches the emitter of the transistor 5 via the capacitor 9, the secondary winding of the current transformer 8 and the capacitor 10 in parallel with the discharge lamp 6. A circuit in which the base of the transistor 5 and the other of the secondary windings are connected. A circuit that reaches the emitter through the base of the transistor 5, the cathode of the diode 11, and its anode and the resistor 12. It is composed of a circuit in which the anode of the diode 11 and the anode of the diode 13 are connected, and the cathode of the diode 13 and the anode of the diode 4 are connected. In the figure, 14 is a switch and 15 is a capacitor. In the discharge lamp lighting circuit configured as described above, conventionally, the current flowing in the discharge lamp 6 is changed by the capacitors 10 and 1 of the control circuit.
The composite capacitance of the capacitors was changed by switching the number 5. With this, the switching element (transistor) 5 is on / off controlled.

[0003]

In the above-mentioned prior art, it is necessary to increase the current withstanding capacity of the changeover switch 14 (both see FIG. 3) due to the inrush current generated when the capacitor 15 is changed over. The present invention has been made in view of the above points, and an object of the present invention is to provide a discharge lamp lighting device capable of easily changing the current flowing through the discharge lamp without increasing the withstand voltage of the switch. .

[0004]

The above object is achieved by connecting a diode having a different reverse recovery time in parallel with the diode through a switch so as to change the current flowing through the discharge lamp.

[0005]

Since the above means is provided, the current flowing through the discharge lamp can be varied by switching the diodes having different reverse recovery times inserted between the base and the emitter of the switching element.

[0006]

EXAMPLES Next, the present invention will be specifically described by way of examples. 1 and 2 show an embodiment of the present invention. Since the same parts as those in the past are designated by the same reference numerals, the description thereof will be omitted. In this embodiment, a diode 16 having a different reverse recovery time is connected in parallel with the diode 11 via a switch 17 so as to change the current flowing through the discharge lamp 6. By doing so, the current flowing through the discharge lamp 6 can be changed by switching the diodes 11 and 16 having different reverse recovery times inserted between the base and the emitter of the switching element 5, and the withstand voltage of the switch 17 can be increased. It is possible to obtain a discharge lamp lighting device capable of easily changing the current flowing through the discharge lamp 6 without raising it. That is, a circuit in which the switch 17 and the cathode of the diode 16 are connected in parallel with the diode 11 and the anode thereof is connected to the anode of the diode 11 is provided. By doing so, the circuit operation becomes as follows. The discharge lamp lighting circuit feeds back the current flowing in the discharge lamp 6 by the current transformer 8 and charges and discharges the electric charge stored in the capacitor 10 by utilizing the voltage and magnetic saturation generated across the secondary winding of the current transformer 8. By controlling the on / off of the transistor 5 and turning on / off the transistor 5,
The high voltage generated in the resonance circuit of the capacitor 2 and the inductor 3 is divided by the capacitor 9 and the inductor 7 to light the discharge lamp 6. When the transistor 5 shifts from on to off in such a lighting circuit, the negative side of the DC power supply 1 of the capacitor 10 is positive and the secondary side of the current transformer 8 is negative, so that the transistor 5 is reverse biased and turned off. The electric charge remaining in the capacitor 10 after the transistor 5 is turned off flows through the resistor 12 and the diode 11. Next, when the secondary side of the current transformer 8 of the capacitor 10 becomes positive, the transistor 5 is forward biased and turns from off to on. FIG. 2 shows current and voltage waveforms when the switch 17 is opened and closed. (A) to (d) show the case where the switch 17 is opened and (a) shows the transistor 5 of FIG.
And a current waveform flowing in the diode 13, (b) is a base-emitter voltage waveform of the transistor 5 of FIG.
Similarly, (c) shows the base current waveform of the transistor 5 in FIG. 1, and (d) also shows the diode 11 or the combined current waveform of the diodes 11 and 16 in FIG.
(A ') to (d') are when the switch 17 is closed, and (a ') is the same as (a).
3, the waveform of the current flowing through the transistor 3, the waveform of the base-emitter voltage of the transistor 5 in (b ') as in (b), and the base current waveform of the transistor 5 in (c') as in (c).
Similarly to (d), (d ') is a diode 11 or a combined current waveform of the diodes 11 and 16. First, replace the diode 11 with a diode with a fast reverse recovery time
Connect a diode with a slow reverse recovery time to. Switch 1
When the transistor 7 is opened, a current determined only by the diode 11 flows when the transistor 5 is off, and the reverse recovery time is short as shown in FIG. The current flowing from the capacitor 10 is divided into the diode 11 and the base current of the transistor 5. Next, when the switch 17 is closed, the reverse recovery time of the diode 16 is slow, so the combined current with the diode 11 is the same as shown in FIG.
As a result, the current flowing in the opposite direction of the diodes 11 and 16 increases as compared with the previous one. Therefore, transistor 5
, The on-time of the transistor is shortened as shown in FIG. 9 (b '), and the current flowing through the transistor 5 and the diode 13 is also reduced. Therefore, the discharge lamp 6
The current flowing through is proportional to the current shown in FIG. In this way, the current flowing through the discharge lamp 6 can be changed easily and at low cost simply by connecting the diodes having different reverse recovery times in parallel. That is, the diode 11 transfers the electric charge accumulated in the capacitor 10 when the transistor 5 is off to the resistor 12 and the diode 11
The anode is discharged from the anode through the secondary side of the current transformer 8. Next, the secondary side of the current transformer 8 of the capacitor 10 becomes the positive side, and the transistor 5 is forward biased and turned on. At this time, the current from the capacitor 10 flows through the transistor 5 through the secondary side of the current transformer 8 and the base / emitter of the transistor 5,
At the same time, during the reverse recovery time of the diode 11, a part of this current flows to the secondary side of the current transformer 8, the diode 1
1 through the cathode, the anode and the resistor 12. If this current is large, the current that drives the transistor 5 is reduced, and the ON period of the transistor 5 is shortened. As a result, the current flowing through the discharge lamp 6 is reduced. On the contrary, if the amount is small, the current that drives the transistor 5 increases and the transistor 5
The ON period of becomes longer. As a result, the current flowing through the discharge lamp 6 increases. In this way, by connecting the diode 11 and the diode 16 having a different reverse recovery time, the discharge lamp 6
It is possible to change the current flowing through. As described above, according to the present embodiment, the current flowing through the discharge lamp can be varied simply by connecting in parallel diodes having different reverse recovery times, so that it can be realized at a very low cost and in a small size.

[0007]

As described above, according to the present invention, the current flowing through the discharge lamp can be easily changed without increasing the withstand voltage of the switch, and the current flowing through the discharge lamp can be easily increased without increasing the withstand voltage of the switch. It is possible to obtain the discharge lamp lighting device capable of changing the current.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a discharge lamp lighting circuit of the present invention.

FIG. 2 is also a switch opening of one embodiment ((a)-
(D)) shows current and voltage waveforms when the switch is closed ((a ') to (d')). (A) and (a ') are waveform diagrams of current flowing through transistors and diodes, (b). ,
(B ') is a base-emitter voltage waveform diagram of the transistor, (c) and (c') are base current waveform diagrams of the transistor, (d) and (d ') are diodes or diodes having different reverse recovery times from the diode. 5 is a combined current waveform diagram of FIG.

FIG. 3 is a circuit diagram of a conventional discharge lamp lighting circuit.

[Explanation of symbols]

1 ... DC power supply 2 ... Capacitor 3 ... Inductor 5 ... Transistor (switching element) 6 ... Discharge lamp 7 ... Inductor 9, 10 ... Capacitor 11 ... Diode 12 ... Resistor 16 ... Diode 17 ... Switch

Claims (1)

Claim: What is claimed is: 1. A circuit in which a resonance circuit in which a DC power source, an inductor and a capacitor are connected in parallel is connected to a switching element, a circuit in which an inductor and a capacitor are connected in series in parallel with the resonance circuit, and this circuit. A discharge lamp connected in parallel with the capacitor, a control circuit for feeding back a current flowing in the discharge lamp to turn on / off the switching element, and a resistor and a diode for discharging the electric charge of the capacitor of the control circuit are connected in series. A discharge lamp lighting circuit comprising a circuit, wherein a diode having a different reverse recovery time is connected in parallel with the diode via a switch to change a current flowing through the discharge lamp.