JPH072019B2 - Discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention uses an inverter circuit that supplies high-frequency power, and controls on-duty of a switching element by a voltage comparison circuit to perform preheating, starting, lighting, and dimming. The present invention relates to a discharge lamp lighting device.

[Prior Art] A conventional discharge lamp lighting device, as shown in FIG.
Is used as a power source, and an inverter circuit 3 that supplies high-frequency power to the discharge lamp 2 and a control circuit 5 that supplies a signal to the switching element 4 of the inverter circuit 3 are provided. The control circuit 5 includes the on-duty of the switching element 4. A voltage comparison circuit 6 that gradually increases and gradually increases the oscillation circuit is provided,
The voltage comparison circuit 6 compares the voltage with a reference voltage with a fixed time constant by the resistor R _S and the capacitor C ₅ at comparator CP _1, the reference voltage is two resistors connected in parallel to the control power source Vcc R ₆ , A series circuit of R _{7 and} a series circuit of a resistor R ₁₄ and a capacitor C ₄ connected to both ends of the negative side resistor R ₇ ,
After the power is turned on, the pressure is gradually increased. That is, the capacitor C ₄ of said previously connected to the output terminal of the comparator CP _2, the output terminal of the comparator CP ₂ fixed time after power is short-circuited, so that the reference voltage resistor R _6,
It becomes constant at the voltage division ratio set in the series-parallel circuit of R ₇ and R ₁₄ . After that, the output end of the comparator CP ₂ is opened, and the capacitor C ₄ is charged, so that the reference voltage is gradually increased to a voltage divided by the resistors R ₆ and R ₇ . During this time,
The on-duty of the switching element 4 gradually increases, and as a result, the oscillating voltage at the time of off gradually increases, and this voltage is applied to the discharge lamp 2 to turn on the discharge lamp 2.

[Problems to be Solved by the Invention] In the conventional discharge lamp lighting device, when an instantaneous voltage drop occurs in the DC power supply 1 at time t ₀ as shown in FIG. The voltage V ₆ of the Vcc capacitor C ₆ gradually decreases as shown in FIG. 8 (b), and the reference voltage Vk
Also decreases as shown in FIG. 8 (b). At this time, the reference voltage Vk
There at time t ₁ has reached the voltage across the capacitor C _4, the charge on capacitor C ₄ is discharged through the resistor R _14, R _7, reference voltage V
The falling of k decreases, and the voltage drop between the voltage Vc ₆ and the reference voltage Vk becomes unbalanced. Since the voltage drop of the voltage Vc ₆ and the reference voltage Vk is unbalanced, during operation of the comparator CP ₁ until t ₁ than and time t ₀ of FIG. 9 showing the time t ₀ previous state (a) As compared with the case of FIG. 9 (b) showing the state of FIG. 9B, the output off time becomes longer as shown in FIG. 9 (c) between time t ₁ and t ₂ . As a result, the off time of the transistor Q ₂ is long and the on time of the switching element 4 is long. Therefore, when the power supply voltage is restored at time t ₂ , the voltage applied to the switching element 4 at the time of the off state.
V _CE rises as shown in Fig. 8 (c). As a result, there is a problem that the rating of the switching element is exceeded and the switching element is destroyed.

The present invention has been made in view of such problems of the conventional technology, and the purpose thereof is to control so that the on-duty of the control circuit does not become abnormally long when the power supply voltage is restored after an instantaneous voltage drop, The purpose is to prevent the switching element from being destroyed by suppressing the voltage applied when the switching element is turned off within the maximum rated value.

[Means for Solving the Problem] In order to achieve the above object, in the discharge lamp lighting device according to the present invention, the falling of the reference voltage is prioritized over the falling of the control power supply at the same time or quickly when the voltage is instantaneously decreased. It was made to let.

[Operation] By giving priority to the fall of the reference voltage over the fall of the control power supply during the instantaneous voltage drop, the on-duty of the switching element does not become long, and the voltage exceeding the maximum rating of the switching element is restored even when the power supply voltage is restored. Is not applied.

[Example] With reference to the drawings embodiment, in FIG. 1, the diode D ₃ is connected between the resistor R ₁₄ and capacitor C _4, the anode resistance R ₁₄ side, the cathode capacitor C ₄ Connected to the side. The other parts having the same reference numerals as those in the conventional example shown in FIG. 7 are the same.

When the instantaneous voltage drop as in the FIG. 2 (a) to a DC power source 1 at time t ₀ of FIG. 2 occurs, the voltage Vc ₆ and the reference voltage Vk of the capacitor C ₆ is gradual, as in the second view (b) Fall to. Also the reference voltage Vk is equal to or less than the voltage across the capacitor C _4, since the discharge current of the capacitor C ₄ does not flow through the resistor R ₇ by the diode D _3, the voltage drop of the voltage Vc ₆ and the reference voltage Vk is balances, Ondeyuti switching element 4, the output is the third diagram of the comparator CP ₁ (a) not long since seems that the (b), the second figure at time t ₁ the power supply voltage is recovered when the switching element 4 also (c There is no danger of exceeding the maximum rating when a voltage such as) is applied. Incidentally, FIG. 3 (a) shows the operation of the comparator CP _{1 in} the state before time t _{0 in} FIG. 2, and FIG. 3 (b) shows the operation from the time t ₀ to t _{1 in} FIG. The operation of CP ₁ is shown.

In FIG. 4, the power supply voltage detection circuit 7 connects a series circuit of a zener diode ZD ₂ and resistors R ₁₅ and R ₁₆ to the DC power source 1, and the connection point of the resistors R ₁₅ and R _16n is connected to the base of the transistor Q _5. Then, the collector of the transistor Q ₅ is connected to the control power supply Vcc via the resistor R ₁₇ and the base of the transistor Q ₆ . The collector and emitter of transistor Q ₆ are connected across resistor R ₇ . The other parts having the same reference numerals as those in the conventional example shown in FIG. 7 are the same.

The direct current power supply 1 at the time of instantaneous voltage drop at time t ₀ in FIG. 5 is as Figure 5 (a), and becomes equal to or less than the Zener diode ZD ₂ zener voltage V _ZD2, the transistor Q ₅ is FIG. 5 (b) As a result, the transistor Q ₆ is turned on as shown in FIG. 5 (c), and the reference voltage Vk is changed to FIG. 5 (d).
Thus, the charge of the capacitor C ₄ is left at the same time as the on-voltage (≈0.6 V) of the transistor Q ₆ is lowered. In this way, the on-duty of the switching element 4 during the instantaneous voltage drop is minimized to suppress the voltage V _CE applied to the switching element 4 when the DC power supply 1 is restored at time t ₁ . FIG. 6 (a) shows the comparator CP _{1 in} the state before time t _{0 in} FIG.
6 (b) also shows the operation of the comparator CP _{1 in} the state from time t ₀ to t _{1 in} FIG.

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it is possible to perform control so that the on-duty of the control circuit for power supply voltage recovery after an instantaneous voltage drop does not become long, and the voltage applied to the switching element at the time of turning off is suppressed to a low level. Therefore, there is an effect that it is possible to prevent the breakdown when the rating is exceeded.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is an operation time chart of the above, FIG. 3 is an operation explanatory diagram of the same, and FIG. 4 is a circuit diagram of another embodiment of the present invention. FIG. 5 is an operation time chart of the above, FIG. 6 is an operation illustration of the above, FIG. 7 is a circuit diagram of a conventional example, FIG. 8 is a time chart of the same, and FIG. 9 is an operation illustration of the same. 1 ... DC power supply, 2 ... discharge lamp, 3 ... inverter circuit, 4 ... switching element, 5 ... control circuit, 6 ...
Voltage comparator _{circuit, R 6, R 7, R} 14 ...... resistance, C ₄ ...... capacitor, Vcc ...... control power.

Claims (1)

[Claims] 1. An inverter circuit that supplies high-frequency power to a discharge lamp using a DC power supply as a power source, a control circuit that supplies a signal to a switching element of the inverter circuit, and an on-duty of the switching element is gradually increased to generate an oscillating voltage. And a voltage comparison circuit provided in the control circuit for gradually boosting the voltage. The voltage comparison circuit compares a voltage having a constant time constant with a reference voltage, and the reference voltage is connected in parallel to a control power supply. In a discharge lamp lighting device in which a series circuit of a plurality of resistors and a series circuit of a resistor and a capacitor connected to both ends of the negative side resistor of the two resistors are used to gradually increase the voltage after the power is turned on, the above-mentioned reference is provided at the momentary voltage drop. A discharge lamp lighting device, characterized in that a voltage fall is prioritized over a control power supply fall.