JPH04155798A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To improve a lighting device which operates via an inverter by providing a load current detecting circuit, an inverter stopping circuit which is actuated under a preset current or less, a time limiting circuit for the period of no operation of the inverter, and a reset circuit for a discharge lamp installation- time timing circuit. CONSTITUTION:A load current detecting circuit 24 which detects the load current flowing through a discharge lamp 15, and an inverter stopping circuit 32 which stops the operation of an inverter 18 when the current detected by the circuit is no greater than the specified current value on at least one side of either positive or negative electrode, are provided; and a lighting abnormality can be detected by a simple circuit configuration so as to surely stop the operation of the inverter 18, so that dangers or damages, etc., can be prevented, either when the discharge lamp 15 is not in connection or when end of life causes mis-lighting or half wave discharge state. And, the circuit 32 is disabled in its operation so that the inverter 18 is surely operated to perform normal lighting, by means of a timing circuit 38 after turning on of the power supply until lighting comes on, or further by means of a resetting circuit 41 when the discharge lamp 15 is installed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a discharge lamp lighting device that lights a discharge lamp via an inverter.

<Prior Art> As shown in FIG. 5, a discharge lamp lighting device conventionally includes a DC power supply circuit 4 comprising a rectifier circuit 2 for rectifying an AC power supply 1 and a smoothing circuit 3, and a discharge lamp 5. Some lamps are provided with an inverter 6, and the inverter 6 is supplied with power from the DC power supply circuit 4, so that the output of the inverter 6 lights up the discharge lamp 5.

This type of conventional discharge lamp lighting device has the following problems. That is, (1) when the discharge lamp 5 is not connected (
If power is applied during a no-load condition, high voltage will be generated on the load circuit side, which is dangerous. (When the 2-in discharge lamp 5 reaches the end of its life and is in an unstable lighting state, it becomes unsightly due to flickering, etc.) Also, it is dangerous when replacing the discharge lamp 5 when it is not lighting up, and the inverter (3) When the discharge lamp 5 reaches the end of its life and enters a half-wave discharge state, and a portion of direct current flows to the output side of the inverter 6, the transformer of the inverter 6 may become unbalanced. This may cause abnormal heat generation, place an excessive load on the inverter's transistors, etc. (beyond the safe operation range), and cause instantaneous destruction.

Therefore, in order to solve the above-mentioned problems, the following various inventions have been made.

■Those that detect the non-lighting state of discharge lamps using the output voltage of the inverter transformer or CT (for example, Japanese Patent Laid-Open No. 61-158
No. 694).

(2) Detecting heat generation in electrical components due to excessive current in the inverter during half-wave discharge and disabling the inverter (for example, Japanese Patent Laid-Open No. 62-51195).

■Detect abnormal oscillation frequency during half-wave discharge and disable the inverter (for example, Japanese Patent Application Laid-open No. 62-51196)■
A detection winding is installed in the inverter transformer to detect its positive/negative balance and disable it (for example,
No. 6198).

■Half-wave ε due to the winding installed in the inverter transformer
Detects abnormal voltage during discharge and deactivates the inverter ν
In addition, a timer is installed (for example, special
Kai No. 59-146199, Special Publication No. 62-10000
issue).

-■ Detects an increase in the current flowing through the discharge lamp and indicates that it is inoperable.
(For example, JP-A-62-216196).

<Problem to be solved by the invention> However, conventional discharge lamp lighting devices have not been sufficiently improved;
Each has the following drawbacks.

In the case of (2) above, only the lighting and non-lighting of the discharge lamp can be detected, and the half-wave discharge state etc. cannot be detected.

In the case of (2) above, since the temperature changes over time, electrical components may be destroyed by short-term overload.

In the case of (2) above, the frequency also occurs due to voltage fluctuations, load fluctuations, etc., and it is difficult to reliably detect abnormalities.

In the case of (2) above, it can be handled when the half-wave discharge is asymmetrical, but it has the disadvantage that it cannot be detected when there is no load because no unbalance occurs.

In the case of (2) above, the abnormal voltage is an abnormal voltage that is generated due to magnetic saturation due to biased magnetization of the inverter transformer, causing the transformer to operate abnormally.

In the case of (2) above, the increase in current is an overcurrent due to biased magnetization or magnetic saturation of the output transformer of the inverter, and it is not possible to reliably detect the lighting abnormality of the discharge lamp.

In view of the above-mentioned problems, the present invention makes it possible to reliably detect an abnormality or danger in the lighting of a discharge lamp with a simple circuit configuration and quickly stop the operation of the inverter. .

<Means for Solving the Problem> The technical means of the present invention for solving this technical problem includes an inverter 18 that is operated by being supplied with power from a power source, and a discharge lamp 15 that is lit by the output of this inverter 18. The discharge lamp lighting device includes a load current detection circuit 24 that detects the load current flowing through the discharge lamp 15, and a load current detected by the load current detection circuit 24 that is lower than a constant current at least on either the positive or negative pole side. Then, an inverter stop circuit 32 that stops the operation of the inverter 18, and a time limit circuit 38 that makes the inverter stop circuit 32 inactive until a predetermined time after power is turned on to the inverter 18.
A reset circuit 41 is provided for resetting the timer circuit 38 when the discharge lamp 15 is attached.

<Example> Hereinafter, the present invention will be explained according to the illustrated example.
The figure shows the basic circuit of the present invention. In FIG. 1, 14 is a DC power supply circuit, and 15 is a discharge lamp.

Reference numeral 18 denotes an inverter, which is equipped with a pair of main transistors 21 and 22 that conduct alternately and an oscillation transformer 19, and is operated by being supplied with power from the DC power supply circuit 14 via the choke 2o. The discharge lamp 15 is lit according to the output.

23 is a stop switch for stopping the inverter.

24 is a load current detection circuit that detects the load current flowing through the discharge lamp 15, and includes resistors 25 and 26 and diodes 27 and 28.
, and a capacitor 29.30. When a load current flows to either the positive or negative pole side of the discharge lamp 15, the capacitor 29.30 is charged by the load current, and only one of the positive and negative pole sides is charged. When a load current flows through the capacitor 29 or 30, only one of the capacitors 29 and 30 corresponding to it is charged, and when the load current stops flowing to both the positive and negative poles, both capacitors 29 and 30 are not charged. It is configured.

32 is an inverter stop circuit, which is connected to the NAND circuit 33 and AN
It is composed of a D circuit 34, a transistor 35, and a relay coil 36, and when the load current detected by the load current detection circuit 24 becomes less than a certain current at least on either the positive or negative pole side, the output of the NAND circuit 33 is The voltage becomes high, so that the output of the AND circuit 34 becomes a high voltage, and the stop switch 23 is turned off.

Reference numeral 38 denotes a time limit circuit that makes the inverter stop circuit 32 inoperable until a predetermined time period required for the discharge lamp 15 to light up after the power is turned on to the discharge lamp lighting device.

Reference numeral 41 denotes a reset circuit, which is configured to output a signal for resetting the time limit circuit 38 when the discharge lamp 15 is attached.

Next, the operation will be explained. When power is turned on to the discharge lamp lighting device, a low voltage is output from the timer circuit 38 until a predetermined period of time has elapsed since the power was turned on, the gate of the AND circuit 34 is closed, and the transistor 35 is kept off. , the stop switch 23 is kept in the on state. Therefore,
A base current can be supplied to the main transistors 21 and 22, and power is supplied from the DC power supply circuit 14 to the inverter 18, which operates the inverter 18 and generates a high frequency in the secondary winding of the oscillation transformer 19. discharge lamp 15
lights up due to high frequency. When a predetermined time period sufficient for the discharge lamp 15 to light up after the power is turned on has elapsed, a high voltage is output from the timer circuit 38, and the gate of the AND circuit 34 is in an open state.

If the discharge lamp 15 lights up normally, after turning on the power, the NAND
The outputs of the circuit 33, time limit circuit 38 and AND circuit 34 are as shown in FIG. That is, when the discharge lamp 15 is lit normally, the load current flows through the discharge lamp 15 at a constant level or more for both positive and negative poles, so both the capacitors 29 and 30 are charged to a constant value or higher, and as a result, the NAND circuit 33
outputs a low voltage, the output of the AND circuit 34 becomes a low voltage, and the transistor 3ε remains off, so the stop switch 23 remains on and the inverter 18 continues to operate.

If the discharge lamp 15 does not light up or lights up abnormally, after turning on the power, the NAND circuit 33, the time limit circuit 38, and the AND
The output of circuit 34 is as shown in FIG.

That is, when power is applied when the discharge lamp 15 is not connected to the discharge lamp lighting device (no load), or when the discharge lamp 15
When discharge lamp 1 reaches the end of its life and is not lit,
5, the load current stops flowing to both the positive and negative poles, so the charging voltages of the capacitors 29 and 30 both become below a certain value, and as a result, the NAND circuit 33 outputs a high voltage, and the A
The output of the ND circuit 34 becomes a high voltage, and the transistor 35
is turned on, the stop switch 23 is turned off, the base current is no longer supplied to the main transistors 21 and 22, and the operation of the inverter 18 is stopped. Then, when the discharge lamp 15 is attached, a reset signal from the reset circuit 41 resets the timer circuit 38, a low voltage is output from the timer circuit 38, and the inverter 18 becomes able to oscillate.

Furthermore, when the discharge lamp 15 reaches the end of its life and enters a half-wave discharge state, the load current flows through the discharge lamp 15 only to one of the positive and negative poles and does not flow to the other, so the capacitor 29
．． 30 becomes below a certain value, and as a result the NAND circuit 33 outputs a high voltage, the output of the AND circuit 34 becomes a high voltage, the transistor 35 is turned on, and when the stop switch 23 is turned off, the inverter 18 is turned on. operation will stop.

FIG. 4 shows a specific circuit of the present invention. In the figure, the inverter 18 includes a pair of transistors 11 and 2 which are alternately conductive, a resonance capacitor C1, an inverter transformer T3, etc. is the primary coil 1l11, the secondary coil m2 and the pair of preheating coils fl+
h.

The load current detection circuit 24 includes a diode D. 1. D.

4. Capacitor CI (I CIO? and resistor R111+
It has RI+2+RI+3. Inverter stop circuit 32
includes a NAND circuit 33, an AND circuit 34, a transistor 35 that outputs an inverter stop signal, and the like. NAN
The D circuit 33 includes an operational amplifier OP2 and a transistor 07.
1 bite6. Q9, capacitor C1゜2, diode D1゜5. Dl. 6th grade. The AND circuit 34 includes a diode DI09 and a resistor R1zff. The timer circuit 38 includes an operational amplifier OPI and resistors R+zs, R
+z4 is provided.

The reset circuit 41 is a Zener diode DII! s diode DIIDIDIlIIDI+3, capacitor C
l09 and resistor R136, R+3+, RI! t・R1
33, RI3< will be described below. When the discharge lamp 15 operates normally, when the power is turned on, the capacitor Cs and Zener diode D11
．． Apply a DC voltage of 8■ to the control circuit side. At the same time, a capacitor. 5. Resistance R1゜1. The voltage at point P1□ of the power supply reset circuit constituted by R1°3, diodes o+z, and n+3 rises. The voltage level at point P1□ is 3.5 higher than the reference voltage at point P6+PI3 of the control circuit.
It is set to above ■ (approximately 4.0 ■) and does not affect all control operations. Then, as the voltage at point p+z rises, the voltage at time limit circuit 38 rises to the voltage at point PIZ of the power supply reset circuit at a slope determined by the time constant of electrolytic capacitor C112 and resistor R0°. Point PR
The voltage is applied to the positive terminal of the operational amplifier OP+ of the time limit circuit 38 via the resistors R1 and R3. operational amplifier OPl
At the same time, the voltage at point Pl+ rises at point Pb, which is the negative terminal of resistor R1□4. A reference voltage of 3.5■ determined by the voltage division ratio of R1□5IRI□6 is applied.

After a predetermined time (5 seconds) has elapsed since the power was turned on, the voltage at point P changes to point P by capacitor CI+□ and resistor RIIO.
6, and the output of the operational amplifier OP is inverted from a low voltage to a high voltage. During those 5 seconds, the transistor 35 is not biased and the inverter 18 continues its oscillation operation. When the discharge lamp 15 lights up during those 5 seconds, the discharge lamp current flows through the resistor RIS, and a voltage is generated at point P2. From the voltage at point P2, the load current detection circuit 24
The capacitor C+oi+C1°7 is charged with a DC voltage including positive and negative ACC voltages.

In the forward direction, transistor Q8 is on and transistor q is off, and in the reverse direction, transistor Q8 is on and transistor q is off.
7 is turned off due to reverse bias, the diodes DIO5+DI06 are turned off, and the electrolytic capacitor ClO2 is charged by the DC voltage at the point Pl+ via the resistor R1□2. The voltage at point P7 of electrolytic capacitor C1゜2 is applied to the negative terminal of operational amplifier OP2, and a resistor R1241LzS is applied to the positive terminal of operational amplifier OP2.
, LZ&, a voltage at point PI3 is applied. After the power is turned on, a high voltage is output to point P, which is the output terminal of operational amplifier OP2, for a while, but after the discharge lamp 150 is turned on, the voltage at point P becomes higher than the voltage at point pus, and the voltage at point P
, the output will be a low voltage. Therefore, 5 seconds after the power is turned on, the output of the operational amplifier OP, point P4, is the resistor R1□,
As a result, the voltage becomes low through the diode D1.9, the transistor 35 is not driven, and the inverter 18 continues to oscillate.

In addition, after the power is turned on, the output of the operational amplifier OP4, which forms the discharge lamp removal/removal restart circuit, at point P9 becomes a high voltage, and the resistor R1° and capacitor C are connected to the base of the transistor Q6.
A one-pulse voltage is applied from a differentiating circuit constituted by 106, and the charge of capacitor C5,2 is transferred by transistor Q6 to resistor R1oa and diode D. 1. As described above, charging starts after the voltage at point P8 drops to 0■ immediately after the power is turned on. Even after the discharge lamp is turned on, the output at point P of operational amplifier OP4 continues at a high voltage level, no voltage is applied to the base of transistor Q6, and the voltage at point P8 is not dropped by transistor Qh. In the above manner, the discharge lamp 15 continues to be lit normally. The circuit operation when the discharge lamp 15 is attached and detached will be described later.

Next, the operation when the discharge lamp 15 reaches the end of its life without emitting light will be explained. Since the load current to the discharge lamp 15 becomes a half-wave during EMI-RES, the capacitor C of the load current detection circuit 24
3゜6. Either charge of C+o7! No voltage is generated. In the case of forward emission, transistor Q8 is turned off, current flows from resistor R1111, and transistor Q is turned on. When transistor Q is turned on, capacitor C1゜2 becomes resistor R1! + and diode D,. 6 and is discharged by the transistor RO.

When the voltage at point P becomes lower than the voltage at point P13, the output from point P of the operational amplifier becomes a high voltage. The operational amplifier will be activated 5 seconds after the power is turned on.

Since the output of point P4 is a high voltage, when point P5 becomes high voltage, the diode 0107. Transistor 35 is turned on through D+os. Then, the inverter inserted into the baseline of main transistors Q+ and Qz
The base of the stop switch 23 for stopping the motor is grounded, and the sub-transistor Q is turned off.

As a result, no current is supplied to the bases of the main transistors Q, , Q, and the inverter 18 stops oscillating. Also, in the case of Emiles in the opposite direction, the train stops in the same way. Furthermore, even when there is no load, the capacitor Cl0t is not charged and therefore stops. That is, the inverter 18 maintains oscillation only when a normal current is flowing through the discharge lamp 15.

The restart operation by attaching the discharge lamp 15 will be explained.

When the discharge lamp 15 is installed, the point PI4 is connected to the negative line through the filament of the discharge lamp 15 and the diode D113, so the voltage at the point PI4 is approximately 0■, but the discharge lamp 15 When you remove the resistor R13
The voltage divided by ゜ and resistor RIffl + RI32 is at point PI
4, and the voltage at point P3 increases. When the voltage at point P becomes higher than the voltage at point pH, the operational amplifier o
The output at point P, of p, is inverted from high voltage to low voltage. At this time, the charge of the capacitor CI 04 is the operational amplifier o
Discharge at p.

Next, when the discharge lamp 15 is connected, the voltage at point PI4 is approximately 0■
The voltage at point P3 becomes lower than the voltage at point PIff. At that time, the output of the point P9 of the operational amplifier OP4 shifts from a low voltage to a high voltage, and the voltage of the rising edge by the differentiating circuit turns on the transistor Q, and the resistor R1.4 and the diode D. The sea case is reset by discharging the capacitor C1.5 through C1.1 and restarts from the initial state.

<Effects of the Invention> According to the present invention, the load current detection circuit 24 that detects the load current flowing through the discharge lamp 15;
When the load current detected by the inverter 1 becomes equal to or less than a certain current on at least one of the positive and negative poles, the inverter 1
Since the inverter stop circuit 32 is provided to stop the operation of the discharge lamp 15, it can be used when the discharge lamp 15 is not connected (at no load), when the discharge lamp 15 reaches the end of its life and is not lit, and when the discharge lamp 15 is not lit. In all cases when the lamp 15 reaches the end of its life and enters a half-wave discharge state, any abnormality in the lighting of the discharge lamp 15 can be detected with a simple circuit configuration, and the operation of the inverter 18 can be reliably stopped. In addition, even when a half-wave discharge state occurs, it is possible to respond quickly, and therefore dangers caused by abnormal lighting of the discharge lamp 150 and damage to electrical parts can be prevented.

Moreover, since the presence or absence of positive or negative load current is detected, unlike the case where an abnormal voltage generated in a transformer is detected, the transformer of the inverter 18 is not burdened with biased magnetism or the like. In addition, since a time limit circuit 38 is provided that disables the inverter stop circuit 32 for a predetermined time after the power is turned on to the inverter 18, the inverter stop circuit 32 is activated from the time the power is turned on until the discharge lamp 15 is lit. This also eliminates the inconvenience of disabling normal lighting of the discharge lamp 15. Furthermore, since a reset circuit 41 is provided that resets the timer circuit 38 when the discharge lamp 15 is attached, if the discharge lamp 15 is attached from a state where the discharge lamp 15 is not connected, the inverter stop circuit 32 is activated. In order to make the inverter stop circuit 32 inoperative for a predetermined time after the installation of the inverter 15,
It is now possible to operate the inverter 18 to light the discharge lamp 15, and there is no possibility that the discharge lamp 15 cannot be lit due to the inverter stop circuit 32 even though the discharge lamp 15 is normal. By attaching the discharge lamp 15, the discharge lamp 15 can be turned on, and its practical effect is significant.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a basic circuit of the present invention, FIGS. 2 and 3 are waveform diagrams for explaining operation, and FIG. 4 is a circuit diagram showing a specific circuit of the present invention. FIG. 5 is a circuit diagram showing a conventional example. 15...discharge lamp, 18...inverter, 24...
Load current detection circuit, 32... Inverter stop circuit, 3
8... Time limit circuit, 41... Reset circuit. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) Inverter (18) that operates by being supplied with power from the power source
and a discharge lamp (15) that is lit by the output of the inverter (18), which includes a load current detection circuit (24) that detects a load current flowing through the discharge lamp (15), and a load current detection circuit (24) that detects a load current flowing through the discharge lamp (15); When the load current detected by the current detection circuit (24) becomes less than a certain current on at least one of the positive and negative poles, the inverter (18)
an inverter stop circuit (32) that stops the operation of the inverter (32), and a time limit circuit (3) that makes the inverter stop circuit (32) inactive for a predetermined time after power is applied to the inverter (18).
8) and a reset circuit (41) that resets the timer circuit (38) when the discharge lamp (15) is attached.