JP2815231B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp lighting device for lighting a discharge lamp via an inverter.

(Prior Art) Conventionally, a discharge lamp lighting device has a pair of a rectifier circuit 2 for rectifying an AC power supply 1 and a DC power supply circuit 4 including a smoothing circuit 3 connected in series to each other as shown in FIG. An inverter 6 is provided between the discharge lamp 5 and the inverter 6.
Is supplied from the DC power supply circuit 4 to turn on the discharge lamp 5 by the output of the inverter 6.

This type of conventional discharge lamp lighting device has the following problems. That is, (1) when power is applied when the discharge lamp 5 is not connected (no load), a high voltage is generated on the load circuit side, which is dangerous. (2) When the discharge lamp 5 enters an unstable lighting state at the end of its life, it becomes difficult to see due to flickering or the like. In addition, when the discharge lamp 5 is replaced due to the non-lighting state, it is dangerous, and an excessive load may be applied to the inverter 6. (3) When the discharge lamp 5 is in the half-wave discharge state at the end of its life and a DC component flows to the output side of the inverter 6, the transformer of the inverter 6 is demagnetized to cause abnormal heat generation, An excessive load is applied to the oscillation transistor and the like (exceeding the safe operation area), and the oscillation transistor may be destroyed instantaneously.

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

A device in which the unlit state of a discharge lamp is detected by an output voltage of a transformer of an inverter or CT (for example, Japanese Patent Application Laid-Open No. 61-158694)
issue).

Heating of electrical components due to excessive current of the inverter during half-wave discharge is detected, and the inverter is deactivated (for example, JP-A-62-51195).

An abnormal oscillation frequency at the time of half-wave discharge is detected to make the inverter inoperative (for example, JP-A-62-51196).

A detection winding is provided in the transformer of the inverter to detect the positive / negative balance and make it inactive (for example,
26198).

An abnormal voltage at the time of half-wave discharge is detected by a winding provided in a transformer of the inverter to make the inverter inoperative and a time limiter is provided (for example, Japanese Patent Laid-Open No. 59-146199).
No., JP-B-62-10000).

An increase in the current flowing through the discharge lamp is detected and the operation is disabled (for example, Japanese Patent Application Laid-Open No. 62-216196).

(Problems to be Solved by the Invention) However, the conventional discharge lamp lighting devices are not sufficiently improved and have the following disadvantages.

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

In such a case, the electric components may be destroyed by a short-time overload because the temperature has passed over time.

In the above case, the frequency also occurs due to voltage fluctuation, load fluctuation, and the like, and it is difficult to reliably detect an abnormality.

In the above case, it is possible to cope with the asymmetrical half-wave discharge. However, in the case of no load, there is no unbalance, so there is a disadvantage that it cannot be detected.

In the above case, the abnormal voltage is an abnormal voltage that is generated due to magnetic saturation or the like when the inverter transformer is magnetized and causes the transformer to operate abnormally.

In the above case, the increase in the current is an overcurrent due to the demagnetization or magnetic saturation of the output transformer of the inverter, and it is not possible to reliably detect abnormal lighting of the discharge lamp.

The present invention has been made in view of the above-described problems, and when an abnormality or a danger occurs in lighting of a discharge lamp, the abnormality can be reliably detected with a simple circuit configuration and the operation of the inverter can be quickly stopped. .

(Means for Solving the Problems) 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 supply and is connected in series with each other so as to be turned on by the output of the inverter 18. A discharge lamp lighting device including a pair of discharge lamps 15, a load current detection circuit 24 that detects a load current flowing through the pair of discharge lamps 15, and a load current detected by the load current detection circuit 24 is at least positive or negative. An inverter stop circuit 32 for stopping the operation of the inverter 18 when the current becomes equal to or less than a constant current on one of the poles, and a time limit circuit 38 for disabling the inverter stop circuit 32 until a predetermined time from when the power to the inverter 18 is turned on. And a reset circuit 41 for detecting the mounting of the two discharge lamps 15 at the midpoint of the pair of discharge lamps 15 and resetting the time limit circuit 38.

FIG. 1 shows a basic circuit of the present invention. In FIG. 1, reference numeral 14 denotes a DC power supply circuit, for example, a rectifier for full-wave rectification of an AC power supply. It is composed of a backward path and a smoothing circuit. Reference numeral 15 denotes a pair of discharge lamps connected in series with each other.

Reference numeral 18 denotes an inverter, which includes a pair of main transistors 21 and 22 that alternately conduct and an oscillation transformer 19, and a DC power supply circuit 1
4 is operated via a choke 20 and operates.
The discharge lamp 15 is turned on by the high-frequency output generated on the secondary winding side of No. 9.

23 is a stop switch for stopping the inverter. Reference numeral 24 denotes a load current detection circuit that detects a load current flowing through the discharge lamp 15 and includes resistors 25 and 26, diodes 27 and 28, and capacitors 29 and 30. When a load current flows, the load current
If the load current flows only on one of the positive and negative poles, only the corresponding capacitor 29 or 30 will be charged, and the load current will flow on both the positive and negative poles. When they are gone, both capacitors 29,3
0 is not charged together.

Reference numeral 32 denotes an inverter stop circuit, which includes a NAND circuit 33 and an AND circuit 34.
And a transistor 35 and a relay coil 36,
When the load current detected by the load current detection circuit 24 becomes equal to or less than a certain current on at least one of the positive and negative poles, the output of the NAND circuit 33 becomes a high voltage, thereby
The output of the D circuit 34 becomes high voltage, and the stop switch 23 is turned off.

Reference numeral 38 denotes a timed circuit which disables the inverter stop circuit 32 until a predetermined time required for the discharge lamp 15 to light from when the power is supplied to the discharge lamp lighting device.

Reference numeral 41 denotes a reset circuit which detects a voltage change at a midpoint position of the pair of discharge lamps 15 when the two discharge lamps 15 are mounted by a function of a choke 42 provided in parallel with one of the discharge lamps 15. It is configured to output a reset signal for resetting the timed circuit 38.

Next, the operation will be described. When power is applied to the discharge lamp lighting device, a low voltage is output from the timing circuit 38 until a predetermined time elapses after the power is applied, the AND circuit 34 has a closed gate, and the transistor 35 maintains an off state. 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, whereby the inverter 18 operates and a high frequency is generated in the secondary winding of the oscillation transformer 19. Then, the pair of discharge lamps 15 are turned on by high frequency. Then, when a predetermined time sufficient for the pair of discharge lamps 15 to light has elapsed since the power was turned on, a high voltage is output from the timing circuit 38, and the gate of the AND circuit 34 is opened.

If the discharge lamp 15 lights up normally, after turning on the power, the NAND circuit
33, the outputs of the time limit circuit 38 and the AND circuit 34 are as shown in FIG. That is, when the discharge lamp 15 is normally lit,
Since the load current flows in the discharge lamp 15 over a certain amount for both positive and negative electrodes, both the capacitors 29 and 30 are charged to a certain value or more, and as a result, the NAND circuit 33 outputs a low voltage, and the AND circuit 34 outputs a low voltage.
Becomes low voltage, the transistor 35 keeps the off state, the stop switch 23 keeps on, and the inverter 18
Keeps working.

When the discharge lamp 15 does not light or lights abnormally, after the power is turned on, the outputs of the NAND circuit 33, the time limit circuit 38, and the AND circuit 34 become as shown in FIG. That is, when power is applied when the discharge lamp 15 is not connected to the discharge lamp lighting device (when there is no load), or when the discharge lamp 15 is turned off at the end of its life, Since the load current stops flowing between the positive and negative electrodes, the charging voltages of the capacitors 29 and 30 are both lower than a certain value.As a result, the NAND circuit 33 outputs a high voltage, the output of the AND circuit 34 becomes a high voltage, and the transistor 35 As a result, the stop switch 23 is turned off, the base current is not supplied to the main transistors 21 and 22, and the operation of the inverter 18 is stopped. Then, when the pair of discharge lamps 15 are mounted, the reset signal from the reset circuit 41 resets the timing circuit 38, a low voltage is output from the timing circuit 38, and the inverter 18 can oscillate.

Also, when the discharge lamp 15 is in the half-wave discharge state at the end of its life, the load current flows through the discharge lamp 15 on only one of the positive and negative poles and does not flow to the other, so that the capacitors 29, 30
One of the charging voltages falls 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 the stop switch 23 is turned off to turn off the inverter 18. Operation stops.

Then, the reset circuit 41 detects the mounting of both the discharge lamps 15 from the voltage change at the midpoint position of the pair of discharge lamps 15,
The timed circuit 38 can be reset by detecting the installation of the discharge lamp 15 with a very simple circuit configuration. That is, in order to detect the mounting of the pair of discharge lamp 15, from the point P ₂₁ and P ₂₂ each independently for a pair of the discharge lamp 15 as shown in FIG. 5, be taken out a signal for detecting the presence or absence of a mounted considered, but such a case, it is necessary to take the aND of the output signal of the point P ₂₁ and the point P _22, the order requires complicated processing circuit, the circuit configuration of the reset circuit 41 is very complex Become. Also, in this case, the DC is 200V and the discharge lamp is about 280V.
Since the starting voltage for 152 lamps needs to be 400 V to 600 V, it is not possible to reliably determine the presence or absence of the discharge lamp 15. So chalk
By providing 42, the mounting of both discharge lamps 15 can be detected with a simple circuit configuration from the voltage fluctuation at the midpoint of the pair of discharge lamps 15.

FIG. 4 shows a specific circuit of the present invention.
Inverter 18 is a pair of transistors that conduct alternately.
Q ₁ and Q ₂ , a resonance capacitor C ₁₀ , an inverter transformer T _{3, and the} like. The inverter transformer T ₃ has a primary coil m ₁ , a secondary coil m _2, and a pair of preheating coils f ₁ and f _2. I have.

Load current detection circuit 24 includes a diode D _103, D _104, a capacitor C _106, C ₁₀₇ and resistor _{R 111, R 112, R 113} . The 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.
The NAND circuit 33 includes an operational amplifier OP ₂ , transistors Q ₇ , Q ₈ ,
Q ₉ , a capacitor C ₁₀₂ , diodes D ₁₀₅ , D _{106 and the} like. The AND circuit 34 has a diode D ₁₀₉ and a resistor R ₁₂₇ . The timed circuit 38 includes an operational amplifier OP ₁ and resistors R ₁₂₃ and R ₁₂₃ .
_{It has 124} .

The reset circuit 41 includes a Zener diode D ₁₁₂ , diodes D ₁₁₀ , D ₁₁₁ , D ₁₁₃ , a capacitor C _109, and resistors R ₁₃₀ , R
_131, and includes a _{R 132, R 133, R 134} .

Next, the operation will be described. If the pair of the discharge lamp 15 to the normal lighting operation, when turning on the power supply, applying a DC voltage of 6.8V by the capacitor C ₈ and the Zener diode D ₁₁ to the control circuit side. At the same time, capacitor C ₁₀₁ , resistors R ₁₀₁ , R
_103, the voltage of the diode D _12, the power reset circuit point P ₁₂ of which is constituted by D ₁₃ rises. High voltage 3.5V or higher than the voltage level of the point P ₁₂ is the reference voltage of the P _6, P ₁₃ point control circuit (4.0V
Degree), and does not affect all control operations. Then, the voltage of the point P ₁₂ is by rises, rises at an inclination determined by the time constant voltage of timing circuit 38 is due to electrolytic capacitor C ₁₁₂ and a resistor R ₁₁₀ to the voltage of the point P ₁₂ of the power reset circuit. Operational amplifier OP _{1 of} timed circuit 38 from point P ₈
Is applied to the plus terminal of R via a resistor _R123 . Operational amplifier
The P ₆ that it is the negative terminal of the OP _1, the voltage of the point P ₁₁ is at the same time rises, the reference voltage 3.5V determined by the voltage division ratio of the resistors R _124, R _125, R ₁₂₆ is applied. After a predetermined time (5 seconds) has elapsed since the power was turned on, the capacitor C ₁₁₂ and resistor R ₁₁₀
Voltage P ₈ becomes higher than the voltage of the point P _6, the output of the operational amplifier OP ₁ is inverted from a low voltage to a high voltage. During the five seconds, the transistor 35 is not biased and the inverter 18 continues the oscillating operation. When the discharge lamp 15 is lighted at its 5 seconds, the discharge lamp current resistance R ₁₅ flows, a voltage is generated at point P _2. Than the voltage of the point P _2, charging the capacitor C _106, C ₁₀₇ of the load current detection circuit 24 a DC voltage including positive and negative, respectively of AC Rippuri.

Then, the forward direction transistor Q ₈ is a transistor Q ₉ ON is turned off, and the reverse in the OFF state for the transistors Q ₇ is reverse biased, the diode
D _105, D ₁₀₆ is turned off, the resistor R by the DC voltage of the point P _11
The electrolytic capacitor C ₁₀₂ is charged via ₁₂₂ . Voltage P ₇ points of the electrolytic capacitor C ₁₀₂ is applied to the minus terminal of the operational amplifier OP _2, the voltage of the resistor R _124, R _125, determined points by R ₁₂₆ P ₁₃ is applied to the plus terminal of the operational amplifier OP ₂ . The power-on after P ₅ that it is a while the output terminal of the operational amplifier OP _2, the high voltage is output, the voltage of the lighting after the point P ₇ of the discharge lamp 15 becomes higher than the voltage of the point P _13, the point P The output of ₅ becomes low voltage. Thus, 5 seconds after the power is turned on the output of the point P ₄ of the operational amplifier OP ₁ is the resistance P ₁₂₇ diode D
_The voltage becomes low through ₁₀₉ , the transistor 35 is not driven, and the inverter 18 continues oscillating. Also, an operational amplifier that forms a discharge lamp detachable restart circuit after power-on
Output point P ₉ of OP ₄ becomes a high voltage, the base of the transistor Q _6, the voltage of the single pulse is applied from the differentiating circuit composed of a resistor R ₁₀₇ and a capacitor C _106, the capacitor
Charge of C ₁₁₂ is discharged through the resistor R ₁₀₄ and the diode D ₁₀₁ by the transistor Q _6. The voltage at point P ₈ starts charging from after falling to 0V after as power-on as described above. Output point P ₉ of the discharge lamp after lighting also operational amplifier OP ₄ continues the high voltage level, no voltage is applied to the base of the transistor Q _6, is not the voltage of the point P ₈ is turned off by the transistor Q ₆ . The normal operation of the discharge lamp 15 is continued as described above. The circuit operation by attaching and detaching the discharge lamp 15 will be described later.

Next, the operation at the time of Emiless when the discharge lamp 15 reaches the end of its life will be described. At the time of Emiless, since the load current to the discharge lamp 15 becomes a half wave, the capacitors C ₁₀₆ and C
Either one of ₁₀₇ charging voltages is not generated. In the case of forward Emiresu, the transistor Q ₈ is turned off, the resistor R ₁₁₈
More current flows, the transistor Q ₉ is turned on. When the transistor Q ₉ is turned on, the capacitor C ₁₀₂ is discharged by the transistor Q ₉ through the resistor R ₁₂₁ and a diode D _106. When the voltage of the point P ₇ is a lower level than the voltage of the point P _13, the output of the point P ₅ of Opeaanpu OP ₂ becomes a high voltage. Since 5 seconds after power output point P ₄ of the operational amplifier OP ₁ has a high voltage, the diode D when the point P ₅ has a higher voltage
_The transistor 35 is turned on through ₁₀₇ and _D108 . And
The base of the stop switch 23 for stopping the inverter, which is placed in the baseline of the main transistors Q ₁ and Q ₂ , is grounded, and the sub-transistor Q ₃ is turned off. As a result, no current is supplied to the bases of the main transistors Q ₁ and Q ₂ , and the inverter 18 stops oscillating.
Also, in the case of the backward Emiless, the operation is similarly stopped. Further, even when there is no load, the operation is stopped because the capacitor _C102 is not charged. That is, only when a normal current flows through the discharge lamp 15, the inverter 18 maintains the oscillation.

A restart operation by mounting the discharge lamp 15 will be described. In a state where the discharge lamp 15 is mounted, the point P _14, because they are connected to the negative line through the filament and the diode D ₁₁₃ of the discharge lamp 15, the voltage of the point P ₁₄ is about 0V, release removing the lamp 15, the divided voltage by the resistor R ₁₃₀ resistor R _131, R ₁₃₂ is applied to a point P _14, the voltage at point P ₃ rises. When the voltage at the point P ₃ is higher than the voltage of the point P _13,
Output point P ₉ of the operational amplifier OP ₄ is inverted from high voltage to low voltage. At this time, the charge of the capacitor C ₁₀₄ is
Discharge at ₄ .

Now connects the discharge lamp 15, drops to approximately the voltage at point P ₁₄ 0V, the voltage at point P ₃ is lower than the voltage at the point P _13. At that time, the output of the point P ₉ of the operational amplifier OP ₄ shifts to higher voltage than the low voltage, the transistor Q ₆ is turned on, the capacitor C ₁₀₅ is discharged through the resistor R ₁₀₄ and the diode D ₁₀₁ at a voltage of a rising edge by differentiator This resets the sea case and restarts from the initial state.

(Effects of the Invention) According to the present invention, a load current detection circuit 24 for detecting a load current flowing through a pair of discharge lamps 15 and the load current detection circuit
When the load current detected by 24 becomes a constant current or less on at least one of the positive and negative poles, the inverter
Since the inverter stop circuit 32 for stopping the operation of the lamp 18 is provided, when the discharge lamp 15 is not connected (no load), when the discharge lamp 15 becomes unlit at the end of its life, and For all cases when the electric lamp 15 is in the half-wave discharge state at the end of its life, the lighting abnormality 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, it is possible to promptly respond to a half-wave discharge state, so that danger due to abnormal lighting of the discharge lamp 15 and damage to electric components can be prevented. In addition, since the presence or absence of the load current is detected, unlike the case of detecting an abnormal voltage generated in the transformer, the transformer of the inverter 18 is not subjected to a load such as magnetization. In addition, the inverter 18
The inverter stop circuit until a predetermined time from power-on to the inverter
Since a timed circuit 38 that disables the 32 is provided, the inverter stop circuit is
The inconvenience that the normal operation of the discharge lamp 15 is disabled by the operation of the discharge lamp 15 is also eliminated. Furthermore, since the reset circuit 41 for resetting the timed circuit 38 when the two discharge lamps 15 are mounted is provided from a change in current flowing to the connection point of the pair of discharge lamps 15,
If the discharge lamp 15 is mounted in a state where the pair of discharge lamps 15 are not connected, the inverter stop circuit 32 disables the inverter stop circuit 32 until a predetermined time from the mounting of the pair of discharge lamps 15. Activate a pair of discharge lamps
15 can be turned on, and although the discharge lamp 15 is normal, the discharge lamp 15 is
Can be turned on simply by mounting the discharge lamp 15. Moreover, since the mounting of the two discharge lamps 15 is detected from the current change at the connection point of the discharge lamps 15, the circuit configuration of the reset circuit 41 is different from the case where the presence / absence of the mounted state of the pair of discharge lamps 15 is separately detected. It can be done very easily and its practical effect is significant.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing a basic circuit of the present invention, FIGS. 2 and 3 are waveform diagrams for explaining the operation, and FIG. 4 is a circuit diagram showing a specific circuit of the present invention. It is. FIG. 5 is a circuit diagram showing a comparative example with the present invention. FIG. 6 is a circuit diagram showing a conventional example. 15: discharge lamp, 18: inverter, 24: load current detection circuit, 32: inverter stop circuit, 38: timed circuit, 41
.... Reset circuit.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-62-163293 (JP, A) JP-A-2-126597 (JP, A) JP-A-2-172190 (JP, A) JP-A-2- 189898 (JP, A) JP-A-61-240595 (JP, A) JP-A-59-146199 (JP, A) JP-A-56-56199 (JP, U) (58) Fields investigated (Int. ⁶ , DB name) H05B 41/24

Claims (1)

(57) [Claims] 1. A discharge lamp lighting device comprising: an inverter (18) operated by being supplied with power from a power source; and a pair of discharge lamps (15) connected in series with each other so as to be turned on by an output of the inverter (18). In the device, a load current detection circuit (24) for detecting a load current flowing through the pair of discharge lamps (15), and the load current detected by the load current detection circuit (24) is at least one of the positive and negative poles. An inverter stop circuit (32) for stopping the operation of the inverter (18) when the current becomes lower than a certain current; and a time limit circuit for disabling the inverter stop circuit (32) until a predetermined time from when the power to the inverter (18) is turned on. (38) and a reset circuit (41) that detects the mounting of both discharge lamps (15) at the midpoint of the pair of discharge lamps (15) and resets the timed circuit (38). Characteristic discharge lamp Lighting device.