JP2878349B2 - Discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an inverter device for controlling one of a pair of switching elements connected in series to both ends of a DC power supply to be separately excited and the other to be self-excited and turned on and off. The present invention relates to a discharge lamp lighting device constituted by using the above.

[Prior Art] A conventional discharge lamp lighting device of this kind is shown in FIG. The discharge lamp lighting device includes a DC power supply (including a DC power supply obtained by rectifying or rectifying and smoothing the AC power supply) across the diode E ₁
The transistors Q ₁ and Q _{2 in} which D ₁ and D ₂ are connected in anti-parallel are connected in series, and both ends of the transistor Q ₁ are connected via a capacitor C ₀ to a discharge lamp la and _a primary winding of _a driving transformer T ₁ . l Connected to ₁ . Here, the discharge lamp l capacitor C ₁ connected in parallel to the non-power supply side of _a can, with preheating of the filaments of the discharge lamp l _a, constitutes a resonant circuit in primary winding l ₁ and the drive transformer T _l those with secondary winding to l ₂ with called self-excited at the voltage induced in the transistor Q ₁ on the drive transformer T _l by the resonance current flowing in the resonant circuit, and controls the off. Note that the capacitor C ₀ is connected to the capacitor C ₁
In this case, the capacitance is made larger than that described above so as not to contribute to resonance. Then, in the discharge lamp lighting apparatus, the on the other transistor Q _2, off Yes as controlled by called separately excited at the control circuit 1, the control circuit 1 and the driving unit 1a for driving the transistor Q _2, a timer 1b to send a drive signal to set the time for turning on the transistor Q ₂ in the driving unit 1a, Yes constituted by a trigger portion 1c which gives a trigger to start the time limiting operation of the timer 1b, the timer 1b and trigger portion oN the transistor Q ₂ with a 1c, it is to form an oscillation controller 1d that controls the off. Incidentally, in this discharge lamp lighting device for turning on the transistor Q ₂ after the transistor Q ₁ is turned off, a detection circuit 2 for detecting that the transistor Q ₁ is turned off from the voltage across the transistor Q _2, the detection circuit 2 is composed of resistors R ₁ and R ₂ . That, in this discharge lamp lighting device detects that the detection circuit 2 transistor Q ₁ is turned off, the trigger circuit 1c and triggers the timer 1b to start the time limiting operation by the output of the detection circuit 2, the the control circuit 1 operates to turn on the transistor Q ₂ to limit operation period of the timer 1b. Therefore,
The transistors Q ₁ and Q ₂ are turned on and off alternately, and the DC power supply E ₁
It will supply replacement to the discharge lamp l _a to AC power of high frequency DC power supplied from.

By the way, in this discharge lamp lighting device, the load circuit 4 is opened when there is no load, so that the transistors Q ₁ and Q ₂ are turned off and on at this time. In such a discharge lamp lighting device to stop the operation if it becomes no-load condition, the discharge lamp l _a is it is necessary to reset the control circuit 1 to put the restart when mounted. Therefore, in order in the conventional to detect the mounting of the discharge lamp l _a, it had been provided with a diode D ₃ and resistor R _3, the mounting detection circuit 3 consisting of R _4. That is, in the mounting detection circuit 3, when the discharge lamp l _a is attached, since the potential at the point A (the connection point of the capacitor C ₀ and the discharge lamp l _a) is increased, the control circuit 1 in this After resetting, the discharge lamp lighting device is restarted.

[Problems to be Solved by the Invention] However, the mounting detection circuit 3 shown in FIG. 7 has the following problem. That is, since high potential at point A where the mounting detection circuit 3 detects the mounting state of the discharge lamp l _a, it is necessary to use a high breakdown voltage as a component, increases the cost. In addition, when such a mounting detection circuit 3 is provided, two detection inputs of the control circuit 1 are required, and when the control circuit 1 is considered as an IC, an increase in the number of inputs leads to an increase in the number of pins, which is preferable. is not.

The present invention has been made in view of the above points, and an object of the present invention is to detect the mounting of a discharge lamp without the need for a component having a high withstand voltage, and to discharge a discharge lamp suitable for use as an IC in a control circuit. It is to provide a device.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, a control circuit is provided with a mounting determination circuit for determining a mounting state of a discharge lamp from an output of a detection circuit.

[Operation] The present invention focuses on the fact that a change occurs in the voltage across the second switching element when the discharge lamp is mounted, and provides a mounting determination circuit in the control circuit. The state of mounting the discharge lamp is determined based on the voltage between both ends of the element. Since a high voltage is not applied to both ends of the second switching element,
Since high-voltage components are not required, and the control circuit only needs to be provided with input terminals for the detection circuit, there is no increase in the number of input terminals for the control circuit, making it suitable for use as an integrated control circuit. It is like that.

Embodiment 1 FIGS. 1 to 4 show an embodiment of the present invention. In the discharge lamp lighting device of this embodiment, as shown in FIG. 1, the mounted state of the discharge lamp l _a from the output state of the detection circuit 2 for detecting that the transistor Q ₁ is turned off from the voltage across the transistor Q ₂ The difference from the conventional circuit shown in FIG. 7 is that a mounting discriminating circuit 6 for discriminating is provided in the control circuit 1.

Here, the voltage across the transistor Q _2, that is, the potential of the point a in FIG. 1 (the connection point transistors Q _1, Q _2), varies as shown in FIG. 2 by a connection state of the discharge lamp l _a I do.
When the discharge lamp l _a as shown from time t ₀ in FIG. 2 in a period of t ₁ is the steady lighting is turned on transistors Q _1, Q ₂ are alternately, since the off, a point Is a rectangular waveform.

Now, when the discharge lamp l _a at time t ₁ in Figure 2 is that in unloaded state removed, the series resonance consisting of a primary winding l ₁ of the capacitor C ₁ and the driving transformer T _l is the time the Since no circuit is formed, the operation of the discharge lamp lighting device stops, and the potential at point a drops to 0V.

When wearing the discharge lamp l _a in time t _2, the capacitor C _0, C _1, the driving transformer T 1 winding l ₁ of _l, resistors R _1, time in FIG. 2 through R ₂ t transient current flows as indicated by ₂ in the time t _3, the potential of the point a in the changes to the state shown. Therefore, the discharge lamp l _a from the change in the potential of the point a can be determined that it has been mounted.

FIG. 3 shows a specific circuit of the circuit shown in FIG. In this embodiment, the MOSFET Q ₂ ′ is used as the second switching element. In the control circuit 1 of the present embodiment, the timer 1b and the trigger unit 1c are constituted by a monostable multivibrator (such as a general-purpose IC 4528) 10, and the drive unit 1a is constituted by an inverter buffer (general-purpose IC).
4049 etc.) 11. Here, the monostable multivibrator 10, by changing the value of the variable resistor R _5,
MOSFET Q ₂ by varying the ON period of ', are output to be supplied to the discharge lamp l _a to allow the adjustment to the dimming control. The control circuit 1 is provided with an astable multivibrator (555 or the like of a general-purpose IC) 12 as a starting circuit for starting the monostable multivibrator 10, and outputs the output of the astable multivibrator 12 to an inverter gate I _3. in the inverted output, the inverter gate I ₁ of the detection circuit 2, so as to start the discharge lamp lighting device triggers OR monostable multivibrator 10 at the output of the OR gate G ₁ to take the output through the I ₂ It is. Then, the mounting discrimination circuit 6, a comparator CP _1, the transistor Q _3, Yes and a capacitor C ₃ and resistor R ₆ to R _9, an AND of the outputs of the inverter gate I ₁ of the mounting discrimination circuit 6 astable multivibrator 12 capacitors at the output of the aND gate G ₂ to take
Connected to both ends on-transistor Q ₄ of C _4, and controls the off is so as to start the monostable multivibrator 10 when the discharge lamp l _a is mounted by the output of the astable multivibrator 12 . Incidentally, in this FIG. 3 by connecting the Zener diode ZD ₁ in parallel to the resistor R ₂ of the detection circuit 2, are as detection output does not become higher than a predetermined voltage.

First, the DC power source E ₁ is turned, the discharge lamp lighting device will be described operation when it is started. During this startup, the transistor Q ₁ is in OFF, the output of the detection circuit 2 at this time holds the low level, the transistor Q ₃ of the mounting discrimination circuit 6 maintains the OFF state. Therefore, the voltage across the capacitor C ₃ is held in a state of exceeding the reference voltage determined by the resistors R _8, R _9, the output of the comparator CP ₁ this time is at a low level, the output of the AND gate G ₂ is an inverter It is maintained at a low level regardless of the output state of I _1. In this case the transistor Q ₄ are in the OFF, astable multivibrator 12 is kept in the operating state. At this time,
The output (terminal 3) of the astable multivibrator 12 changes to high and low levels at a predetermined cycle. At this start, the potential at the point a is at the low level, so the OR gate G ₁
The output state output appears as it is obtained by inverting the output of the astable multivibrator 12 in the inverter gate I _3. Here, as the monostable multivibrator 10, a trigger is activated when a control input (B in FIG. 3) falls from a high level to a low level. Thus, the output of the astable multivibrator 12 is a trigger is the monostable multivibrator 10 by the falling of the output of the OR gate G ₁ at the time of ramps up from a low level to a high level, the output at this time becomes the low level. Therefore, the output of the MOSFET Q ₂
Is turned on for a predetermined time, and the operation shifts to a steady operation in which the transistor Q ₁ and the MOSFET Q ₂ ′ are turned on and off alternately.

When the transistor Q ₁ and the MOSFET Q ₂ ′ are turned on and off alternately in this manner, the output of the detection circuit 2 becomes the transistor
Changes to a high level and a low level in response to the switching of the Q _1, MOSFET Q ₂ '. When the transistor Q ₃ in accordance with the output of the detection circuit 2 is turned on, is turned off, Fig. 4 (d)
The voltage of the capacitor C ₃ as shown in is so as not to rise above the reference voltage, thus the output of the comparator CP ₁ is held at the high level. Therefore, AND gate G ₂
The output of the output obtained by inverting the output of the detection circuit 2 by the inverter I ₁ appears as it is. Further, the transistor Q ₄ is turned on by the output of the AND gate G ₂ at this time, when it is turned off, since the voltage across the capacitor C ₄ are so as not reach the predetermined voltage at which the output is inverted alternately, astable oscillation of the vibrator 12 is stopped, this time the output is held at a high level in, so that the output of the OR gate G ₁ is detecting circuit 2
High level and low level in accordance with the output of. Therefore, Tolga is applied to the monostable multivibrator 10 at the output of the detection circuit 2 when the transistor Q ₁ is turned off.

Here, when the discharge lamp l _a is removed at time t ₁ in FIG. 4, the potential at point a as described above when this is reduced to 0V. Therefore, the transistor Q ₃ is held in the OFF state, the capacitor C ₃ is charged through the resistor R _7, across voltage rises as shown in FIG. 4 (d). Accordingly, the monostable multivibrator 10 operates in such a manner that the output of the astable multivibrator 12 changes to a high level and a low level in a predetermined cycle and the MOSFET Q ₂ ′ is turned on and off in the same manner as described above at the time of starting. I do. However, at this time, since the load circuit 1 is open, the discharge lamp lighting device does not operate.

Now, for example, when the discharge lamp l _a is attached at the time indicated by t ₂ in FIG. 4, as described in Figure 2, the load circuit 1
, The potential at point a rises. While the potential at the point a is rising, the transistor Q ₃
There turned on, charges of the capacitor C ₃ at this time is discharged, the output of the comparator CP ₁ becomes high level. However, in this case, the output of the detection circuit 2 is an inverter gate.
It is higher than the threshold value of I _1, the output of the AND gate G ₂ is kept at a low level, thereby the transistor Q ₄ is kept turned off, astable multivibrator
Operation 12 continues. However, the potential of a point in this case is at a high level, the output of the inverter gate I ₂ is at the high level, the output of the OR gate G ₁ is held at the high level, no in this case stable multivibrator
The twelve outputs cannot trigger the monostable multivibrator 10. Then, after the potential at point a falls below the threshold value of the inverter gate I _1, when the output of the astable multivibrator 12 becomes high level, the output of the OR gate G ₁ is a low level, starting at this time The monostable multivibrator 10 is triggered. When the monostable multivibrator 10 is thus triggered, the above-described steady oscillation operation is started.

Embodiment 2 FIGS. 5 and 6 show another embodiment of the present invention. Which was constructed using astable multivibrator 13 capable of changing the oscillation frequency of the oscillation control unit 1d of the control circuit 1 in this embodiment, the outputs of the inverter gate I ₄ of the astable multivibrator 13 Nando to Nandgate
By taking in G _3, on the MOSFET Q ₂ 'in synchronization with the OFF of the transistor Q _1, it is to be OFF control. In addition, the mounting determination circuit 6 includes an inverter gate I ₅ , a transistor Q ₅ , capacitors C ₄ and C ₅ , a diode D _3, and resistors R ₂₀ and R 5.
It consists of ₂₁ . Further, in the discharge lamp lighting device is adapted to be turned after preheated once discharge lamp l _a at the time of mounting of the starting and the discharge lamp l _a. Therefore, the timer 14 that is triggered by the output of the mounting determination circuit 6 and the timer circuit 14
And a frequency control unit 15 for controlling the oscillation frequency of the astable multivibrator 13 to a high frequency during the time-limited operation period. Here, the timer 14, comparator CP _2, Yes and a capacitor C ₆ and a resistor R ₂₂ to R _24, the frequency control unit
15, voltage follower B _1, transistor Q _6, are constituted by a capacitor C ₇ and the resistance R ₂₅ to R _26.

First, at the time of starting, the potential at the point a is low level.
The output of the inverter gate I ₄ keeps the high level, since at this time the diode D ₃ is reverse biased, maintains a state where the capacitor C ₅ is charged, the inverter gate I ₅
Threshold has been exceeded. Thus, the output of the inverter gate I ₅ is in the state the capacitor C ₄ is that is discharged at a low level. At this time, the transistor
Q ₅ is off, the capacitor C ₆ is so through the resistor R ₂₂ are in a state of being charged, the output of the comparator CP ₂ is at the low level, the transistor Q ₆ is also turned off. Thus, kept in a state of the capacitor C ₇ is charged via the resistor R _27, the control input of the astable multivibrator 13 (fifth terminal) is maintained at a higher voltage determined by the resistors R _25, R _26.
In this case, the astable multivibrator 13 operates at a low oscillation frequency. In this case, the inverter gate I ₄
Since the output of the is kept at a high level, the output of the astable multivibrator 13 (pin 3) is when it becomes a high level, the output of the NAND gate G ₃ becomes low level. Therefore, at this time, the MO
SFETQ ₂ ′ is turned on for a certain period. That is, the discharge lamp lighting device is activated by this turning on.

When the MOSFET Q ₂ ′ is turned off, the potential at the point a goes high. At this time, the output of the inverter gate I ₄ becomes a low level, charges the capacitor C ₅ is discharged, the output of the inverter gate I ₅ becomes the high level. In this state, the transistor Q ₁ and the MOSFET Q ₂ ′
Are alternately turned on and off. Thus the output of the inverter gate I ₅ becomes high level, transient current through the capacitor C ₄ this time the transistor Q ₅
Since supplied to the base, the transistor Q ₅ is instantaneously turned on, it charges the capacitor C ₆ is discharged. Then, the capacitor C ₆ is gradually charged, and the comparator is operated until the voltage across the capacitor C ₆ reaches the reference voltage.
The output of CP ₂ becomes high level (period t ₃ ~t ₄ in FIG. 6). Period the output of the comparator CP ₂ is at a high level, since a low voltage determined by the resistor R ₂₅ to R _27, the oscillation frequency at this time astable multivibrator 13 is higher than the steady state. Note that the astable multivibrator 13
Is set higher than the resonance frequency of the load circuit 1. Thus low-level period of the NAND gate taking NAND of the outputs of the astable multivibrator 13 of the inverter gate I ₄ obtained by inverting the output of the detection circuit 2 becomes shorter than the time constant, the ON period of the MOSFET Q ₂ 'to the Becomes shorter. Therefore, the output supplied to the discharge lamp l _a is suppressed low, the discharge lamp l _a in this period is preheating.

When the time limit of the timer elapses, the output of the comparator CP ₂ becomes low level, and at this time, the capacitor C ₇ is gradually charged, so that the control input voltage of the astable multivibrator 13 is gradually increased. . Therefore, the oscillation frequency of the astable multivibrator 13 gradually decreases, the output of the NAND gate G ₃ take the NAND between the inverter gate I ₄ period gradually becomes longer at a low level accordingly. That is,, MOSFET Q ₂ ON period of 'becomes longer toward the stationary on-period, a discharge lamp l _a power level also increases gradually supplied to and hence the discharge lamp l _a is started on, are steady lighting after. In the discharge lamp lighting device can be used to adjust the power supplied to the discharge lamp l _a changing value of the resistance R ₂₅ of the frequency control unit 15, a discharge lamp l _a can be continuously dimmed.

Here, when the discharge lamp l _a at time t ₁ of FIG. 6 is removed, the output after this point the inverter gate I ₄ holds the high level, is charged capacitor C _5, the inverter gate I The output of ₅ goes low. However, no base current in the transistor Q ₅ is supplied in this case, therefore astable multivibrator 13
The oscillation frequency of the MOSFET Q ₂ ′ is maintained by the output of the astable multivibrator 13 via the NAND gate G ₃ and the inverter buffer 11 in this case.
A signal to turn on and off is applied.
Since l _a is off, MOSFET Q ₂ ′ does not turn on.

When the discharge lamp l _a is attached at the time t ₂ in FIG. 6, the potential at point a as shown in the diagram (a) is high in this case, the output of the inverter gate I ₄ is low level next, this time charges the capacitor C ₅ is discharged to, it falls below the threshold value of the inverter gate I _5, the output of the inverter gate I ₅ becomes high level. Thus, the transistor Q ₅ is turned on, in the same manner as described in the operation at the start after, after preheating the discharge lamp l _a, the oscillation frequency of the astable multivibrator 13 is lowered gradually, the discharge lamp l _a Lights up at the start and shifts to a steady operation thereafter.

[Effects of the Invention] In the present invention, as described above, since the mounting circuit is provided in the control circuit, the mounting state of the discharge lamp can be determined from the voltage across the second switching element by the mounting circuit, Since a high voltage is not applied to both ends of the second switching element, components with a high withstand voltage are not required. In addition, since the control circuit only needs to be provided with the input terminal for the detection circuit, there is no increase in the input terminals of the control circuit.
This makes it suitable for control circuit integration.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention, FIG. 2 is an explanatory diagram showing an output state of a detection circuit when a discharge lamp is attached / detached, FIG. 3 is a specific circuit diagram, and FIG. FIG. 5, FIG. 5 is a circuit diagram of the embodiment, FIG. 6 is an operation explanatory diagram of the embodiment, and FIG. 7 is a circuit diagram of a conventional example. 1 is a control circuit, 2 is a detection circuit, 4 is a load circuit, 6 is a mounting discrimination circuit, Q ₁ and Q ₂ are transistors, T _l is a driving transformer, l
_a discharge lamp, E ₁ is a DC power source.

Continuation of the front page (56) References JP-A-3-129699 (JP, A) JP-A-3-167793 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 41 / twenty four

Claims (1)

(57) [Claims] 1. A load circuit having a resonance circuit configuration including first and second switching elements connected in series to both ends of a DC power supply, a discharge lamp connected in parallel to the first switching element, and a current flowing through the load circuit. Feedback means for feeding the resonance current back to the control terminal of the first switching element to turn on and off the first switching element at a predetermined period, and for determining the off state of the first switching element from the voltage across the second switching element. A detection circuit for detecting a signal; and a second circuit corresponding to an output of the detection circuit.
And a control circuit for turning on and off the first switching element and turning on and off the second switching element alternately with the first switching element. A discharge lamp lighting device comprising a control circuit provided with a mounting determination circuit for determining a mounting state of a discharge lamp from an output.