JP2001110585A - Discharge lamp lightening apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rationalize a detecting circuit to detect the abnormality of the discharge lamp. SOLUTION: The discharge lamp lightening apparatus drives a discharge lamp 3 by an inverter 2 controlled by an inverter control device 1. A voltage detecting circuit 4 is provided to rectify and detect the secondary voltage of the discharge lamp 3. A voltage converting circuit 5 is provided for the output side of the voltage detecting circuit 4, to rise the output voltage when its output voltage rises as well as lowered. The discharge tube lightening apparatus can protect the inverter 2 by stopping the output of the inverter 2 when the output voltage of the voltage converting circuit 5 rises higher than designated by feeding the output of the voltage converter circuit to the inverter control device 1.

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 device provided with a detection circuit for detecting an abnormality of a discharge lamp when the discharge lamp is driven by an inverter.

[0002]

2. Description of the Related Art In this type of discharge lamp lighting device, various detection circuits for detecting abnormality of the discharge lamp are provided to protect the inverter, and detection of the end of discharge lamp life and detection of disconnection of the discharge lamp are performed. Is going.

[0003]

However, it is necessary to provide separate detection circuits according to the purpose of detection. Then, an object of the present invention is to rationalize a detection circuit for detecting an abnormality of a discharge lamp.

[0004]

Means for solving the problems are as described in the claims.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described. However, this is merely an exemplary embodiment adopted based on the present invention, and the present invention will be described based on matters unique to the embodiment. Therefore, the technical scope of the present invention should be determined based on the matters stated in the claims and matters substantially equivalent to the matters.

In the illustrated embodiment, the inverter control means 1
A discharge lamp lighting device for driving a discharge lamp 3 by an inverter 2 controlled by a voltage detection circuit 4 for rectifying and detecting a secondary voltage of the discharge lamp 3;
A voltage conversion circuit 5 is provided on the output side of the voltage detection circuit 4 for increasing the output voltage regardless of whether the output voltage rises or falls below the normal voltage, and inputs the output of the voltage conversion circuit 5 to the inverter control means 1. The discharge lamp lighting device protects the inverter 2 by, for example, stopping the output of the inverter 2 when the output voltage of the voltage conversion circuit 5 rises above a predetermined voltage.

In this embodiment, a chopper 6 is provided at a stage preceding the inverter 2 for the purpose of reducing power supply harmonics. That is, in the present embodiment, the rectifier 8
And the discharge lamp 3 is driven via the chopper 6 and the inverter 2, and the chopper 6 is controlled by the chopper control means 9,
The inverter 2 is a discharge lamp lighting device controlled by the inverter control means 1. The inverter 2 is provided with a voltage detection circuit 4 for rectifying and detecting the secondary voltage of the discharge lamp 3, and its output voltage is higher than the normal voltage. A voltage conversion circuit 5 for increasing the output voltage whether rising or falling is provided on the output side of the voltage detection circuit 4, and the output of the voltage conversion circuit 5 is input to the chopper control means 9 and the inverter control means 1, This is also a discharge lamp lighting device that reduces the output voltage VDC of the chopper 6 when the output voltage of the voltage conversion circuit 5 rises above a predetermined voltage. Q1 is a switching element of the chopper 6, and Q2
And Q3 are switching elements of the inverter 2, and the inverter control means 1 controls opening and closing of the switching elements Q2 and Q3 alternately via a driving means 2a as appropriate.

The voltage detecting circuit 4 may be a known one comprising a capacitor, a resistor and a rectifying element as shown in the figure, and does not require any particular explanation. The voltage conversion circuit 5 is provided at a stage subsequent to the voltage detection circuit 4, and includes, for example, a transistor 10 and a resistor 1
1 to 13, and one end of the resistor 13 has, for example, +12
A voltage of V is applied. The output of the voltage detection circuit 4 is connected to a connection point between the resistances 11 and 12 and the resistance 13, and this connection point is connected to the control terminal 14 of the inverter control means 1,
This connection point is also connected to a control terminal 16 of the chopper control means 9 via a Zener diode 15.

In the normal lighting state of the discharge lamp 3, the output voltage of the voltage conversion circuit 5 is, for example, 3 V (corresponding to the above-mentioned normal voltage), and this voltage is applied to the control terminal 14 of the inverter control means 1. . In this state, the transistor 10 is on. At the end of the life of the discharge lamp 3, the discharge lamp 3 is mostly in a half-wave discharge state, and the voltage across the discharge lamp 3 increases. Therefore, the output voltage of the voltage detection circuit 4 increases, and the voltage at the connection point between the resistors 12 and 13 also increases. When this voltage becomes equal to or higher than the reference voltage (predetermined voltage) of the control terminal 14, for example, 5 V, a timer count is started inside the inverter control means 1. 1 shifts to the protection state of the inverter 2 by stopping the oscillation output of the inverter 2 or the like.
In this way, it is possible to prevent an excessive current from flowing through the inverter 2 at the end of the life of the discharge lamp 3 and increase stress and heat generation of the components. The reference voltage of the control terminal 14 in the protection state is controlled so as to change from 5V to 1.5V. That is, if the input voltage to the control terminal 14 is 1.5 V or more, the control is performed so that the oscillation stop of the inverter 2 is continued.

The operation in which the control terminal 14 becomes 5 V or more and the timer count is performed is a mask operation inside the inverter control means 1 for a predetermined time from turning on the AC power supply 7 to preheating and starting the discharge lamp 3. It is controlled and prevents the adverse effect that the normal discharge lamp 3 is not turned on. In other words, the oscillation of the inverter 2 is controlled at least until the discharge lamp 3 is turned on, regardless of the voltage of the control terminal 14, even if the discharge lamp 3 is at the end of its life.

Next, when the discharge lamp 3 is removed from a socket (not shown) and the inverter 2 is in a no-load state, the output voltage of the voltage detection circuit 4 becomes zero. Then, the transistor 10 is turned off, and the voltage of the control terminal 14 is pulled up to +12 V via the resistor 13. Thereafter, the state shifts to the protection state of the inverter 2 in the same manner as at the end of the life of the discharge lamp 3. In this way, when the discharge lamp 3 comes off or the inverter 2 is in a no-load state, the switching element Q
It can be prevented that spike-shaped currents flow through 2 and Q3 to increase heat generation. Note that the mask control inside the inverter control means 1 during a predetermined time from turning on the AC power supply 7 to preheating and starting the discharge lamp 3 is the same as described above.

The present embodiment also has a function of reducing the output voltage VDC of the chopper 6 at the end of the life of the discharge lamp 3 or when the inverter 2 is in a no-load state.
As described above, the output voltage of the voltage conversion circuit 5 increases when the discharge lamp 3 is abnormal, but when this voltage reaches the Zener voltage of the Zener diode 15, a current flows into the control terminal 16 of the chopper control means 9. The chopper control means 9 functions to reduce the output voltage VDC of the chopper 6. In this example, the degree of reduction of the output voltage VDC of the chopper 6 is controlled in accordance with the current flowing through the Zener diode 15. For example, the output voltage VDC of the Is controlling.

In this way, when the discharge lamp 3 is abnormal, it is possible to prevent an excessive voltage output from being generated in the inverter 2, and it is possible to avoid an increase in the size of components and an increase in withstand voltage. The Zener diode 15 is connected in series with a diode 17 for preventing backflow. Although the Zener diode 15 is used in the illustrated example, a transistor may be used to amplify the amount of current flowing into the control terminal 16, or a comparator may be used. Further, depending on the setting of the control terminal 16, there may be a case where these means such as the Zener diode 15 are not particularly required.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inverter control means 2 Inverter 3 Discharge lamp 4 Voltage detection circuit 5 Voltage conversion circuit 6 Chopper 7 AC power supply 8 Rectifier 9 Chopper control means

Continued on the front page F term (reference) 3K072 AA02 BA05 BB01 BB10 BC01 BC03 DB03 EA01 EA02 EB01 EB05 GA02 GB12 GC04 HB03

Claims (2)

[Claims] 1. A discharge lamp lighting device for driving a discharge lamp by an inverter controlled by an inverter control means, comprising: a voltage detection circuit for rectifying and detecting a secondary voltage of the discharge lamp; A voltage conversion circuit is provided on the output side of the voltage detection circuit, and the output of the voltage conversion circuit is input to the inverter control means even if the voltage rises or falls below the normal voltage. A discharge lamp lighting device that protects the inverter by stopping the output of the inverter when the output voltage of the inverter rises above a predetermined voltage. 2. A discharge lamp lighting device controlled by an AC power supply via a rectifier, a chopper and an inverter, wherein the chopper is controlled by chopper control means, and the inverter is controlled by the inverter control means. A voltage detection circuit is provided to rectify and detect the secondary voltage of the voltage detection circuit. The output voltage of the voltage detection circuit increases even if the output voltage rises or falls below the normal voltage. A discharge lamp lighting device which is provided with an output of the voltage conversion circuit and inputs the output of the voltage conversion circuit to the chopper control means and the inverter control means, and reduces the output voltage of the chopper when the output voltage of the voltage conversion circuit rises above a predetermined voltage.