JP2865411B2 - Discharge lamp lighting device - Google Patents

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> Conventionally, a discharge lamp lighting device includes, between a discharge lamp 5 and a DC power supply circuit 4 including a rectifying circuit 2 for rectifying an AC power supply 1 and a smoothing circuit 3 as shown in FIG. In some inverters, an inverter 6 is provided, and power is supplied from the DC power supply circuit 4 to the inverter 6 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 method in which the non-lighting state of a discharge lamp is detected by an output voltage of a transformer of an inverter or CT (for example, Japanese Unexamined Patent Publication No. 61-158694).
issue).

Detects heat generation of electrical components due to excessive current of the inverter during half-wave discharge and disables the inverter (for example,
No. 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, and the positive / negative balance is detected to make it inactive (for example, Japanese Patent Publication No. 61-2619).
No. 8).

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 Application 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 have not been 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 generated due to magnetic saturation or the like of the inverter transformer when the transformer is demagnetized, causing 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 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 supply, and a discharge lamp 15 that is turned on by an output of the inverter 18. In the discharge lamp lighting device, a load current detection circuit 24 that detects a load current flowing through the discharge lamp 15 and a load current detected by the load current detection circuit 24 is reduced to a certain current or less on at least one of the positive and negative poles. Then, an inverter stop circuit 32 for stopping the operation of the inverter 18 and a time limit circuit 38 for disabling the inverter stop circuit 32 until a predetermined time after the power supply to the inverter 18 is provided, and the load current detection circuit 24 A capacitor charged by a current of one polarity, positive or negative, flowing through the discharge lamp 15; and a capacitor charged by a current of the other polarity flowing through the discharge lamp 15. Wherein the inverter stop circuit 32, when it becomes the load current one of the charging voltage of the pair of capacitors of the detection circuit 24 is low, the point that is configured to stop the operation of the inverter 18.

<Embodiment> Hereinafter, the present invention will be described with reference to the illustrated embodiment. FIG. 1 shows a basic circuit of the present invention. In FIG. 1, reference numeral 11 denotes a rectifying circuit for full-wave rectifying an AC power supply 12, and 13 denotes a smoothing circuit. In the circuit,
These constitute a DC power supply circuit 14. 15 is a discharge lamp.

An inverter 18 includes a pair of main transistors and an oscillating transformer 19 which are alternately conductive, and operates by being supplied with power from the DC power supply circuit 14 via a choke 20.
The discharge lamp 15 is turned on by the high frequency output generated on the next winding side.

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 a 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.

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 relay coil 36 maintains the demagnetized state, and the stop switch 23 is maintained in the on state. Accordingly, power is supplied from the DC current circuit 14 to the inverter 18, whereby the inverter 18 operates to generate a high frequency in the secondary winding of the oscillation transformer 19, and the discharge lamp 15 is lit by the high frequency. Then, when a predetermined time sufficient for the discharge lamp 15 to light up after the power is turned on,
The high voltage is output from the timed circuit 38, and the AND circuit 34 has its gate open.

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 poles, 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
Becomes low voltage, the transistor 35 is kept off, the relay coil 36 is kept demagnetized, the stop switch 23 is kept on, and the inverter 18 continues to operate.

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 To turn on, the relay coil 36 is excited, the stop switch 33 is turned off, and the operation of the inverter 18 is stopped.

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, the relay coil 36 is excited, and the stop switch is turned off. When the switch 23 is turned off, the operation of the inverter 18 stops.

FIG. 4 shows a specific circuit of the present invention.
Inverter 18 is a pair of transistors that conduct alternately.
Q _1, Q _2, resonant capacitor C _10, an inverter transformer T ₃
Comprising a like, the inverter transformer T ₃ has a primary coil m _1, 2 primary coil m ₂ and a pair of preheating coils f _1, f _2.

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} .
Inverter stop circuit 32 includes a NAND circuit 33, the AND circuit 34, the transistor Q ₅ for outputting an inverter stop signal. The NAND circuit 33 includes an operational amplifier OP ₂ , transistors Q ₇ and 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 the operational amplifier OP ₁ and the resistor R
_123, comprising the R _124.

41 is a reset circuit, a Zener diode D _112, the diode _{D 110, D 111, D 113} , a capacitor C ₁₀₉ and resistor
R ₁₃₀ , R ₁₃₁ , R ₁₃₂ , R ₁₃₃ , R ₁₃₄
Is configured to output a reset signal for resetting the timed circuit 38 when the device is mounted.

Next, the operation will be described. If 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, a power reset circuit composed of a capacitor C ₁₀₁ , resistors R ₁₀₁ and R ₁₀₃ , and diodes D ₁₂ and D _13.
Voltage of the P ₁₂ rises. Point of the voltage level of the point P ₁₂ is the control circuit
The voltage is set to 3.5 V or more (about 4.0 V) higher than the reference voltages of P ₆ and P ₁₃ 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. Via a resistor R ₁₂₃ is applied to the plus terminal of the operational amplifier OP ₁ timed circuit 38 from the point P _8. Operational amplifier OP
The P ₆ that it is the _first negative terminal, the voltage at 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 power-up than the predetermined time (5 seconds) elapses, higher than the voltage of the capacitor C ₁₁₂ and a resistor R ₁₁₀ voltage point P ₆ of the point P _8, the output of the operational amplifier OP ₁ is inverted from a low voltage to a high voltage. Part 5 seconds, the transistor Q ₅ is not be biased, the inverter 18 continues the oscillation 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 R ₁₂₇ diode D
Becomes low voltage through _109, the transistor Q ₅ is not driven, the inverter 18 continues oscillation.

After the power is turned on, the output at the point P ₉ of the operational amplifier OP ₄ forming the discharge lamp detaching / restarting circuit becomes a high voltage, and the differentiating circuit configured by the resistor R ₁₀₇ and the capacitor C _{106 at} the base of the transistor Q _6. voltage Waparusu is applied from the charge of the capacitor C ₁₁₂ discharges 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
Either one of the charging voltage of the C ₁₀₇ does not occur. 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 the operational amplifier OP ₂ is a higher voltage. Since 5 seconds after power output point P ₄ of the operational amplifier OP ₁ has a high voltage, when the point P ₅ is a high voltage diode
Transistor Q ₅ is turned on through D _107, D _108. Then, will be the base of the sub-transistor Q ₃ of the inverter stop have put the baseline of the main transistor Q _1, Q ₂ is grounded, the sub-transistor Q ₃
Turns 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, the inverter 18 keeps oscillating only when the discharge lamp 15 is flowing a normal current.

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 ₄ 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 of the P _13. At that time,
Output point P ₉ of the operational amplifier OP ₄ is shifted to the high voltage from the low voltage transistor with a voltage of a rising edge by differentiator
Q ₆ is turned on, Sea case by capacitor C ₁₁₂ is discharged through the resistor R ₁₀₄ and the diode D ₁₀₁ is reset to restart from the initial state.

In the case of the specific circuit shown in Figure 4, the transistor Q ₅ is a switch element, it can stop the oscillating operation of the inverter 18 in the switch elements of very small capacity. That is, to stop the oscillation of the inverter 18 comprising a pair of transistors Q _1, Q ₂ which conduct alternately, to cut off the power supply loop of the inverter 18, or transistor Q _1,
It is conceivable to stop the supply of the base current to the Q _2. However, when the inverter 18 is stopped, these current loops require a switch element for cutting the current, and the element requires a base current and an element having a capacity for supplying the current flowing to the inverter 18. , Need a very large capacity. Therefore, by providing the transistor Q ₅ for interrupting the base current of the transistor Q ₃ which constitutes a control circuit for controlling the base current of a pair of transistors Q _1, Q ₂ as shown in FIG. 5, the very small volume The switch element can cut off the base currents of the transistors Q ₁ and Q ₂ and stop the inverter 18.

<Effects of the Invention> According to the present invention, a load current detection circuit 24 that detects a load current flowing through the discharge lamp 15 and a load current detected by the load current detection circuit 24 is at least one of the positive and negative poles. When the discharge lamp 15 is not connected (when no load is applied), the discharge lamp 15 reaches the end of its life when the discharge lamp 15 is not connected (when no load is applied). In all cases when the lamp is in the non-lighting state and when the discharge lamp 15 is in the half-wave discharge state at the end of its life, the lighting abnormality of the discharge lamp 15 is detected with a simple circuit configuration, and the operation of the inverter 18 is performed. Can be stopped reliably and a half-wave discharge state can be promptly dealt with. Therefore, danger due to abnormal lighting of the discharge lamp 15 and damage to electric components can be prevented beforehand. 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. Further, a time limit circuit 38 for disabling the inverter stop circuit 32 for a predetermined time after the power is supplied to the inverter 18 is provided.
There is no inconvenience such that the inverter stop circuit 32 operates and the discharge lamp 15 cannot be turned on normally until the lamp 15 is turned on.

Further, the load current detection circuit 24 includes a capacitor charged by a current of one polarity, positive or negative, flowing through the discharge lamp 15, and a capacitor charged by a current of the other polarity flowing through the discharge lamp 15, The inverter stop circuit 32
Is configured to stop the operation of the inverter 18 when the charging voltage of one of the pair of capacitors of the load current detection circuit 24 becomes low, so that one of the positive and negative flowing through the discharge lamp 15 is If the polarity current becomes smaller,
In response to this, the charging voltage of the corresponding capacitor is reliably lowered. For example, when the discharge lamp 15 is in the half-wave discharge state, the charging voltage of one capacitor is 0, and the half-wave discharge state is accurately and reliably detected. It is possible to detect the abnormal lighting of the discharge lamp 15 with high accuracy, and to operate the inverter 18 only when there is an abnormal lighting of the discharge lamp 15 without error.
Can be reliably stopped, and the practical effect is remarkable.

[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, FIG. 4 is a circuit diagram showing a specific circuit of the present invention, and FIG. FIG.
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.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05B 41/24

Claims (1)

(57) [Claims] An inverter (18) and the inverter (1)
8) A discharge lamp lighting device provided with a discharge lamp (15) that is lit by the output of (8), a load current detection circuit (24) for detecting a load current flowing through the discharge lamp (15), and the load current detection circuit (24). If the load current detected in step (1) falls below a certain level on at least one of the positive and negative poles, an inverter stop circuit (32) for stopping the operation of the inverter (18) and a power supply to the inverter (18) A time limit circuit (38) for disabling the inverter stop circuit (32) by a predetermined time is provided, and the load current detection circuit (24) is provided with a positive or negative current flowing through the discharge lamp (15). And a capacitor charged by a current of the other polarity flowing through the discharge lamp (15). The inverter stop circuit (32) is connected to a pair of capacitors of the load current detection circuit (24). A discharge lamp lighting device characterized in that the operation of the inverter (18) is stopped when the charging voltage of one of the two becomes low.