JP2694833B2 - Discharge lamp ▼ Ten ▲ Light device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp lighting device capable of automatically stopping operation when a discharge lamp is removed and restarting when the discharge lamp is reattached. is there.

[Conventional technology]

Conventionally, in this type of discharge lamp lighting device equipped with a switching element and an LC resonance circuit, which has an inverter circuit for converting a DC power supply into an AC power supply and outputting from an output end to a discharge lamp, a discharge lamp is provided at an output end of the inverter circuit. It is inconvenient that it operates even in a no-load state where is not connected, which is a problem in terms of safety, reliability, and power consumption. FIG. 8 shows a circuit example of a discharge lamp lighting device provided with a one-stone inverter circuit. Here, the LC resonance circuit is configured by the capacitor C ₁ and the inductance L ₁ ,
High-frequency oscillation is performed by turning on and off the switching element Q ₁ to which the DC power source E is applied via this LC resonance circuit, and the load circuit 2 including the discharge lamp FL and the capacitor C ₂ is connected via the inductance L _2. Supplying high voltage. However, in the case where such an LC resonance circuit is added, when the discharge lamp FL is removed and a no-load state is set, a high voltage is output to the output terminal of the discharge lamp FL, which causes the following problems.

A. If the worker touches the output terminal with the discharge lamp FL removed and no load is applied, there is a danger of electric shock due to the high voltage generated.

B. When the secondary voltage exceeds 300V, it is not compliant with the Electrical Appliance and Material Control Law and JIS standards.

Therefore, in order to solve the above-mentioned problems, the discharge lamp lighting device is provided with a no-load detection unit, and when the no-load detection signal is obtained, the operation of the switching element Q ₁ of the inverter circuit 1 is stopped or suppressed. It is possible. However, when the operation of the inverter circuit 1 is stopped or suppressed when there is no load, it is necessary to have a function of detecting the reattachment of the discharge lamp and operating the inverter circuit 1 normally.

FIG. 9 shows a schematic configuration diagram of a conventional example. This discharge lamp lighting device has an inductance L ₁ and a capacitor C ₁
A parallel circuit of a LC resonance circuit consisting of a parallel circuit of and a switching element Q ₁ consisting of a transistor is connected in parallel to the DC power supply E, and the LC resonance circuit is discharged via an inductance L ₂ and a DC cutting capacitor C _0. The load circuit 2 including the lamp FL is connected, and the load side of the capacitor C ₀ is connected to the no-load detection unit 3b including a voltage detection circuit.
An output control unit 4 is provided which controls the operation of the switching element Q ₁ to stop or control the output of the inverter circuit 1 when the no-load detection signal is obtained. In the figure, 5 is a drive unit for driving the switching element Q ₁ of the inverter circuit 1 based on the output of the output control unit 4.

[Problems to be solved by the invention]

However, in the above-described conventional example, the DC cutting capacitor C ₀ that is originally unnecessary for the inverter circuit 1 is used.
It is necessary to add DC to cut the DC component.
Without this capacitor C _0, it is impossible to detect whether the discharge lamp (load circuit 2) is mounted or not due to the influence of the DC component on the circuit, and the inverter circuit 1 cannot be automatically restarted. However, when such a capacitor C ₀ is connected in series to the load circuit 2, the voltage applied to the load circuit 2 becomes low and the operation of the inverter circuit 1 is affected, which makes the circuit design troublesome. There was a problem.

The present invention has been made in view of the above points, and it is an object of the present invention to perform no-load detection without adding a DC cut capacitor, and to provide a DC cut capacitor. It is an object of the present invention to provide a discharge lamp lighting device that can eliminate the inconvenience.

[Means for solving the problem]

The discharge lamp lighting device of the present invention includes a switching element and
An inverter circuit equipped with an LC resonance circuit that converts DC power to AC power and outputs it to the output end, and detects whether a discharge lamp is connected to the output end based on the operating current or operating voltage of the inverter circuit. A load detection section, an intermittent oscillation section that receives a no-load detection signal from the no-load detection section and outputs a control signal for intermittently oscillating the inverter circuit, and an intermittent circuit that receives the control signal from this intermittent oscillation section and interrupts the inverter circuit. The output control section oscillates and continuously oscillates the inverter circuit when no load detection signal is obtained.

(Operation)

The present invention is configured as described above, and detects whether or not the discharge lamp is connected to the output terminal based on the operating current or operating voltage of the inverter circuit by the no-load detecting unit, and The intermittent oscillation section that outputs a control signal for intermittently oscillating the inverter circuit in response to the load detection signal is provided, and the control circuit from this intermittent oscillation section causes the inverter circuit to intermittently oscillate, and the no-load detection signal is An output control unit that continuously oscillates the inverter circuit when it is no longer available is provided.When no load is applied, the inverter circuit is alternately switched between the stopped state and the operating state to perform intermittent oscillation operation, and the operation during intermittent oscillation is performed. No-load detection is performed by the current or operating voltage, so no-load detection should be performed without adding a DC cut capacitor. Can, and to be able to eliminate the inconvenience due to the provision of the capacitor DC blocking. In addition, stress on circuit components due to a stopped state of the inverter circuit under no load is reduced, and the output voltage can be adjusted easily. Further, if the operation state during the intermittent oscillation operation is changed to the continuous oscillation, the voltage at the time of the transition can be set higher than the discharge start voltage of the discharge lamp and the restart can be easily performed.

〔Example〕

FIG. 1 is a block circuit diagram showing a schematic configuration of one embodiment of the present invention. The DC power supply E is formed by a constant voltage power supply obtained by rectifying an AC power supply. In addition, the inverter circuit 1
The load circuit 2 connected to the output terminal of is composed of a discharge lamp FL and a capacitor C ₂ . Further, the inverter circuit 1 is formed of a switching element Q ₁ and an LC resonance circuit including an inductance L ₁ and a capacitor C ₁ as in the conventional example, and the operating frequency is changed by turning the switching element Q ₁ on and off. It is controllable and does not form a closed circuit when the discharge lamp FL is removed and there is no load, so that no output current flows from the inverter circuit 1 when there is no load. On the other hand, the no-load detection unit 3a is formed of a current detection circuit that detects the current at the output end of the inverter circuit 1, and detects the operating current of the inverter circuit 1 at the output end and the discharge lamp FL is installed. For example, a current transformer is inserted in series with the load circuit 2 and no-load detection is performed based on the secondary side output of the current transformer.

Further, the output control unit 4 selectively controls whether to perform the intermittent oscillation operation or the continuous oscillation operation of the inverter circuit 1 based on the output of the no-load detection unit 3a, and turns on the switching element Q ₁ of the inverter circuit 1. The output is controlled by controlling the frequency (set it higher than the normal operating frequency at the start of operation and gradually approaching the normal operating frequency), and the switching element Q ₁ of the inverter circuit ₁ uses the output control unit 4 output. It is designed to be controlled via the drive unit 5.

Further, the intermittent oscillation unit 6 gives a control signal for intermittently oscillating the inverter circuit 1 to the output control unit 4 when the no-load detection signal is output from the no-load detection unit 3a. It is formed by using a crystal oscillator or CR time constant circuit to set the time and period, and outputs a pulse signal of a constant pulse width output at constant time intervals as a control signal.

As shown in FIG. 2, a no-load detection unit 3b including a voltage detection circuit may be provided. In this case, when the inverter circuit 1 intermittently oscillates under no load, the output voltage of the inverter circuit 1 is changed. If the voltage does not stabilize immediately, it is necessary to provide the voltage detection prohibition timer 7 for prohibiting the voltage detection operation because the voltage at the output end becomes stable.

Further, in each of the above-described embodiments, the current detection or the voltage detection is performed at the output end of the inverter circuit 1 to detect whether or not the discharge lamp FL is attached, but the inverter circuit 1 is detected at an appropriate detection point other than the output end. It goes without saying that the operating current or the operating voltage may be checked to detect whether or not the discharge lamp FL is mounted.

Hereinafter, the operation of the embodiment will be described. Now, when the operation of the inverter circuit 1 is stopped under no load, the output of the no-load detection unit 3a becomes "L" and a no-load detection signal is output. In response to this, the intermittent oscillation unit 6 operates. It starts and outputs a control signal to the output control unit 4. Then, the output control unit 4 fixes the operating frequency of the inverter circuit 1 to a high mode, and when the control signal becomes “H”, the driving unit 5 causes the switching element Q ₁ of the inverter circuit 1 to be operated at a frequency higher than the normal operating frequency. Also drives at high frequencies. However, since the control signal becomes “L” immediately, the driving of the switching element Q ₁ is stopped. Therefore, when the control signal is “H”, the inverter circuit 1 operates in a pulsed manner,
When the discharge lamp FL is not attached, the output end of the inverter circuit 1 is open, so that "L" is output from the no-load detector 3a, and the discharge lamp FL is reattached. The above intermittent oscillation operation in which the stopped state and the operating state alternately occur is repeated until. In this case, since the inverter circuit 1 oscillates intermittently, a high voltage is not output to the output end of the inverter circuit 1, and there is no danger of an electric shock to the worker when the discharge lamp FL is reattached. It is possible to realize a discharge lamp lighting device that complies with the standards and the Electrical Appliance and Material Control Law. In addition, since there is a stopped state of the inverter circuit when there is no load, stress on circuit components is reduced and output voltage adjustment is facilitated.

On the other hand, when the discharge lamp FL is reattached, the operating current of the inverter circuit 1 operating in intermittent oscillation at no load is detected, and "H" indicating load reattachment is output from the no load detector 3a. The control signal is no longer output from the intermittent oscillating unit 6, the inverter circuit 1 performs continuous oscillating operation, and at the same time, the operating frequency of the inverter circuit 1, which is fixed at a frequency higher than the normal operating frequency, gradually shifts to the normal operating frequency. Then, the inverter circuit 1 automatically restarts and the discharge lamp
Power is supplied to FL (load circuit 2). When the no-load detection unit 3b is formed by using the voltage detection circuit, the voltage detection prohibit timer 7 immediately after the inverter circuit 1 intermittently oscillates.
Operates, and voltage detection is prohibited until the output terminal voltage stabilizes.

Here, when the inverter circuit 1 is in the intermittent oscillation operation, the no-load detection is performed during the oscillation period. Therefore, the output voltage of the inverter circuit 1 in the intermittent oscillation operation is equal to or higher than the discharge start voltage of the discharge lamp FL. If set to
Even when the discharge lamp FL is reattached during the intermittent oscillation operation, the discharge lamp FL can be safely and reliably restarted. Therefore, the operation period in the intermittent oscillation may be set to a period in which no load can be detected, and can be freely set in seconds or minutes. That is, the effective value voltage of the output of the inverter circuit 1 which is a problem due to the continuous oscillation operation under no load may be freely extended to the desired desired effective value voltage by extending the cycle of the intermittent oscillation operation. , It is possible to set separately the voltage required for restarting when re-installing the discharge lamp FL and the suppression of the excessive effective value voltage, which has the advantage that the degree of freedom in design is high and that it can be performed accurately. is there.

Incidentally, the inverter circuit 1 comprised of an LC resonant circuit and the switching elements Q _1, at the switching element Q ₁
When the switching element Q ₁ is turned on and off by applying the DC power supply E via the LC resonance circuit, in the transient state at the time of starting the start, a resonance current and a resonance voltage higher than those in the steady state are generated, and the switching element Q 1 Both the current flowing in ₁ and the applied voltage have high values. In addition, switching elements
The longer the Q ₁ on period, the higher their values become. This is because as the ON period of the switching element Q ₁ becomes longer, the current flowing through the inductance L ₁ increases and the electromagnetic energy L ₁ I ² /
It is considered that this is because when the switching element Q ₁ is turned off due to the increase of 2, the increased energy is charged to the capacitor C ₁ and becomes a high value. Also,
In general, when the discharge lamp is lit, the lamp voltage is kept lower than the discharge start voltage at the start of the operation of the discharge lamp lighting device, and a preheating current is supplied to the filament of the discharge lamp for a certain period of time, just after the power is turned on. It is considered to be good for the life of the lamp to start the discharge by making the lamp voltage higher than the discharge start voltage after being sufficiently preheated. Therefore, in particular, when the discharge lamp is lit at a high frequency using the inverter circuit, the preheating and transient state of the discharge lamp are taken into consideration, and a high operating frequency period (preheating period) is set immediately after the start of the operation of the inverter circuit. After performing pre-heating, it is necessary to lower the operating frequency and start the discharge. Therefore, in the embodiment, the output control unit 4 is configured so that the operating frequency immediately after the start of the operation of the inverter circuit 1 is set higher than the normal operating frequency and is gradually lowered to the normal operating frequency. I am doing it.

FIG. 3 shows a concrete circuit example, in which the present invention is applied to a discharge lamp lighting device using a one-stone type inverter circuit 1, and a direct current power source E is a constant voltage power source obtained by rectifying an alternating current power source. The switching element Q _{1, which} is formed and to which the DC power supply E is applied via the LC resonance circuit including the capacitor C ₁ and the inductance L ₁ , is turned on and off by the drive circuit 5a. The voltage is applied to the load circuit 2 including the discharge lamp FL and the capacitor C ₂ via the inductance L ₂ . In the figure, CP ₁ and CP ₂ are comparators, Q _{2 to} Q ₅ are transistors, D _{1 to} D ₄ are diodes, R _{1 to} R ₁₄ are resistors, C ₃ and C ₄ are capacitors, and diode D ₁ is feedback. A diode for passing current, control power supply
Vc is supplied from the DC power source E via the resistor R ₁ .

Here, the no-load detection unit 3b that detects the non-power supply side voltage of the inductance L ₂ is formed using the comparator CP _2, and the voltage at the detection point is the reverse current blocking diode D ₄
Resistor R ₁₃ through, is applied to the series circuit of the R _14, resistors R _13, R
_The voltage divided by ₁₄ and the reference voltage Vs ₂ set by the resistors R ₁₁ and R ₁₂ are compared by the comparator CP ₂ and output when the discharge lamp FL is mounted. The voltage at the “H” output of comparator CP ₂ is determined by resistor R ₁₀ .

Here, when the discharge lamp FL is removed and there is no load, the output of the comparator CP ₂ of the no load detector 3b is "L".
Then, the no-load detection signal is output. At this time, in the output control unit 4, the limited power source Vc is connected to the capacitor via the resistor R _8.
When C ₄ is charged and the voltage across capacitor C ₄ becomes higher than the reference voltage Vs ₁ set by resistors R ₆ and R ₇ , the output of comparator CP ₁ becomes “H” and the preheat recovery signal is output. It When this preheat recovery signal is input to the driving unit 5a, the operating frequency of the inverter circuit 1 is set higher than the normal operating frequency by the driving unit 5a, and the overvoltage applied to the discharge lamp FL (load circuit 2) in the transient state. Keep it low enough. At the same time it stops the driving of the switching element Q ₁ by turning on the switching element Q ₂ by "H" output of the comparator CP ₁ by grounding the base of the switching element Q _1.

Further, the intermittent oscillation unit 6, the capacitor C ₃ is charged from the control power supply Vc via a resistor R _5, when the capacitor C ₃ is charged to a predetermined voltage, the transistor Q ₃ via the resistor R ₄
Is turned on, the base of the transistor Q ₂ is grounded, and the transistor Q ₂ is turned off. Therefore, the switching element Q ₁ is driven at a high frequency according to the drive signal of the drive circuit 5a, and the inverter circuit 1 operates for a certain time. At this time, since the capacitor C ₁ and the inductance L ₁ resonate even in the no-load state, the comparator CP ₂ outputs the “H” signal indicating the load state to turn on the transistor Q ₄ and discharge the capacitor C ₃ . Then, the transistor Q ₃ is turned off. Furthermore, the “H” output of the comparator CP ₂ turns on the transistor G ₅ to discharge the capacitor C ₄ , and the comparator CP ₁ outputs “L”.
Is output. However, when the operation of the inverter circuit 1 passes the transient state, the voltage at the detection point drops because it is in the no-load state, the output of the comparator CP ₂ becomes “L”, and the switching element continues until the capacitor C ₃ is charged. Q ₁
Stop driving. Since the LC resonance circuit consisting of the inductance L ₁ and the capacitor C ₁ has internal resistance, the vibration due to the LC resonance circuit becomes a damping vibration, and if the switching element Q ₁ does not turn on, it damps and stops, and the output No high voltage is output at the end.

Next, when the discharge lamp FL is reattached, when the intermittent oscillation of the inverter circuit 1 is started, the voltage at the detection point fluctuates greatly due to the resonance of the LC resonance circuit, and the comparator CP ₂ outputs “H”, "L" is alternately output according to the operating frequency of the inverter circuit 1. Thus, the capacitor C ₄ is repeatedly charged and discharged, the comparator CP ₁ output always the voltage across the capacitor C ₄ is no longer reaches the reference voltage Vs ₁ of the comparator CP ₁ "L", and the preheated return signal to the drive circuit 5a Will not be entered. Further, since the transistor Q ₂ which has stopped driving the switching element Q ₁ is turned off, as a result, the switching element Q ₁ gradually shifts from the high frequency to the normal operating frequency, and the inverter circuit 1 also continuously oscillates according to the frequency. It operates and the load circuit 2 is automatically fed with power from the inverter circuit 1 and the discharge lamp FL lights up.

4 (a) is the base voltage of the switching element Q ₁ during the intermittent oscillation operation in the no-load state, (b) is the voltage at the detection point when the discharge lamp FL is remounted from the no-load state, ( c) shows the voltage at the detection point in the no-load state. The voltage at the detection point exceeds the reference voltage Vs ₂ under load, but does not exceed the reference voltage Vs ₂ under no load, so the capacitor C ₄ is not discharged.

FIG. 5 shows another embodiment, which is a half-bridge type inverter formed by a pair of switching elements Q _1a and Q _1b driven by drive circuits 5a and 5b, a capacitor C ₁₀ and an inductance L ₁₀ . is obtained by applying the present invention to the discharge lamp lighting apparatus using the circuits 1a, in FIG., CP ₃ comparator, I ₁ is the inversion circuit, Q ₁₀ to Q ₁₃ are transistors, D _1a, D
_1b and D ₁₃ are diodes, R _{12 to} R ₂₆ are resistors, C ₁₁ is a capacitor, T ₁ is an isolation transformer, and CT is a current transformer.

Now, when the discharge lamp FL is removed and unloaded state, since the output terminal of the inverter circuit 1a (non-power side of the capacitor C ₁₀₎ no current flows, the secondary current of the state current transformer CT Detect. That is, when a current flows in the primary side of the current transformer CT, a current also flows in the secondary side through the diode D ₁₃ , the resistors R ₂₅ and R ₂₆ , and a voltage is generated across the resistor R _26. The transistor Q ₁₃ is turned on, the charge of the capacitor C ₁₁ that has been charged via the resistor R ₂₂ is discharged, and the voltage across the capacitor C ₁₁ is lower than the reference voltage Vs ₃ determined by the resistors R ₂₁ , R ₂₃ , and R ₂₄ . It goes low, and the comparator CP ₃ output goes low.

On the contrary, in the case of no load condition, 2 of the current transformer CT
Since the current does not flow to the secondary side and the transistor Q ₁₃ does not turn on, the charge of the capacitor C ₁₁ is not discharged and the comparator C ₁₃ is not discharged.
P ₃ output becomes "H". This comparator CP ₃ output is “H”
Then, the preheat recovery signal is input to the drive circuits 5a and 5b,
The operating frequencies of the drive circuits 5a and 5b are fixed to the preheating mode which is higher than the normal operating frequency. Further, the transistor Q ₁₁ is turned on via the insulating transformer T ₁ , the base of the transistor Q _1b is grounded, and the driving of the transistor Q _1b is stopped.

Further, from the intermittent oscillator 6 to the period T as shown in FIG.
The control signal for the on period t is output, the control signal is inverted by the inverting circuit I ₁ and applied to the base of the transistor Q ₁₀ via the transistor Q ₁₂ , and the comparator C
When the output of P ₃ becomes "H", the output of the inverting circuit I ₁ transistor Q ₁₂ is turned on is input to the base of the transistor Q _10, the control signal is outputted from the intermittent oscillator section 6 "H"
At this time, the transistor Q _1a is driven by the drive circuit 5a, and the intermittent oscillation operation is started. If the discharge lamp FL is reattached while the transistor Q _1a is intermittently driven and the inverter circuit 1a is intermittently oscillating at a high frequency, the output of the comparator CP ₃ becomes “L” and the operating frequency is the preheat mode. The discharge lamp FL is safely and normally lit by gradually shifting from the high frequency to the normal lighting frequency.

7 (a) to 7 (c) show the base voltage of the transistor _Q1a and the current transformer with and without load.
It shows the primary current of CT, and no current flows in the primary side of current transformer CT when there is no load.

〔The invention's effect〕

The present invention is configured as described above, and detects whether or not the discharge lamp is connected to the output terminal based on the operating current or operating voltage of the inverter circuit by the no-load detecting unit, and The intermittent oscillation section that outputs a control signal for intermittently oscillating the inverter circuit in response to the load detection signal is provided, and the control signal from this intermittent oscillation section causes the inverter circuit to intermittently oscillate, and the no-load detection signal is An output control unit that continuously oscillates the inverter circuit when it is no longer available is provided.When no load is applied, the inverter circuit is alternately switched between the stopped state and the operating state to perform intermittent oscillation operation, and the operation during intermittent oscillation is performed. No-load detection is performed by the current or operating voltage, so no-load detection should be performed without adding a DC cut capacitor. It is possible to eliminate the inconvenience caused by providing a DC cut capacitor, and because the inverter circuit is stopped when there is no load, stress on circuit components is reduced, output voltage adjustment is easier, and intermittent oscillation is also achieved. If the operating state during operation is changed to continuous oscillation, the voltage at the time of transition can be set higher than the discharge start voltage of the discharge lamp for easy restart, and the oscillation frequency of the inverter circuit can be changed by the intermittent oscillation operation. Does not enter the phase advancing mode or does not pass through the phase advancing mode, so that the stress applied to the switching element of the inverter circuit can be reduced.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of an embodiment of the present invention, FIG. 2 is a block circuit diagram of another embodiment of the above, FIG. 3 is a specific circuit diagram of the above, FIG. FIG. 5 is a concrete circuit diagram of another embodiment, FIGS. 6 and 7 are operation explanatory diagrams of the same, FIG. 8 is a block circuit diagram of a conventional example, and FIG. 9 is a block circuit diagram of another conventional example. is there. Reference numeral 1 is an inverter circuit, 2 is a load circuit, 3a and 3b are no-load detecting sections, 4 is an output control section, 5 is a drive section, and 6 is an intermittent oscillation section.

Claims (1)

(57) [Claims] 1. An inverter circuit comprising a switching element and an LC resonance circuit for converting a DC power supply into an AC power supply and outputting the AC power from an output terminal to a discharge lamp, and discharging to an output terminal based on an operating current or an operating voltage of the inverter circuit. A no-load detector that detects whether or not a lamp is connected, an intermittent oscillator that receives a no-load detection signal from the no-load detector and outputs a control signal to intermittently oscillate the inverter circuit, and this intermittent oscillator. A discharge lamp lighting device, comprising: an output control unit that intermittently oscillates an inverter circuit in response to a control signal from the unit and continuously oscillates the inverter circuit when a no-load detection signal is no longer obtained.