JPH0359997A - Discharge lamp lighting device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a discharge lamp lighting device, and in particular to a common reset circuit that accurately resets each circuit necessary for lighting a discharge lamp and a circuit for detecting the end of lamp life. The present invention relates to a discharge lamp lighting device that can perform the following operations.

(Conventional technology) FIG. 2 shows a schematic configuration of a conventional discharge lamp lighting device.

In the device shown in the figure, when alternating current (AC) power is input, the AC power is normally converted into DC by a rectifier circuit 1 and applied to an inverter circuit 3, and the inverter circuit 3 generates high-frequency power to lamp the lamp. Drive load 5. In this case, since the inverter circuit 3 is driven by the oscillation signal of the oscillator 7, the output power frequency of the inverter circuit 3 can be changed by controlling the oscillation frequency of the oscillator 7, and the output power frequency of the inverter circuit 3 can be changed according to this oscillation frequency. The voltage level applied to the lamp load can be varied. That is, when the oscillation frequency of the oscillator 7 increases, the output voltage of the inverter circuit 3 decreases, and conversely, when the oscillation frequency decreases, the output voltage of the inverter circuit 3 increases. Therefore, by utilizing this property, it is possible to perform a soft start operation when the power is turned on, stop or reduce the output of the inverter circuit 3 at the end of the lamp life, and perform other controls.

That is, in the circuit shown in FIG. 2, the lamp voltage detection circuit 9 outputs a voltage corresponding to the voltage applied to the discharge lamp to the node a. This voltage causes the voltage at node b to gradually rise with a time constant determined primarily by resistor R1 and capacitor C1. On the other hand, the voltage at node a is divided by a voltage dividing circuit made up of resistors R5 and R6R7 and output to node C. The voltage at node C is resistor R
A relatively high voltage is applied to the frequency control terminal of the oscillator 7 via the diode D1. Therefore, the oscillator 7 oscillates at a relatively high frequency and is supplied to the four-way inverter 3. As a result, the voltage applied from the inverter circuit 3 to the lamp load 5 becomes a relatively low value, and the discharge lamp is preheated.

The voltage at node b gradually increases and when it reaches a predetermined value, transistor T1 turns on and short-circuits resistor R7. As a result, the voltage at node C is the same as the voltage at node a between resistors R5 and R.
6, and is applied to the oscillator 7 via the diode D1 at a relatively low voltage value. As a result, the oscillator 7 oscillates at a lower frequency, a high voltage is supplied from the inverter circuit 3 to the lamp load 5, the discharge lamp is lit, and a so-called soft start operation is performed.

Immediately after the AC power is turned on, the output voltage of the lamp voltage detection circuit 9, that is, the voltage at the node a, does not rise immediately, and in order to prevent the oscillator 7 from oscillating at a low frequency, the transistor T2, capacitor C3, and resistor R9 are used. , RIO, R1
1, R12, etc. is provided. This circuit is supplied with a power supply that rises quickly, for example, the output power of the rectifier circuit 1. When the power is turned on, the collector voltage of the transistor T2, and hence the voltage at the node d, is rapidly pulled up by the action of the capacitor C3. Therefore, a relatively positive voltage is applied to the oscillator 7 via the diode D2, and the oscillator 7 is approximately
j, It oscillates at a relatively high frequency at the same time as it is turned on. This prevents high voltage from being applied to the discharge lamp when the power is turned on. And capacitor C3 and resistor R9
, RIO and R8, etc., the collector voltage of the transistor T2, and thus the voltage at the node d, gradually decreases and reaches a predetermined value, the diode D2 is cut off, and the oscillator 7 is connected to the diode D1.
Voltage is now supplied from node C via.

Furthermore, when the discharge lamp used in the lamp load circuit 5 reaches the end of its life, the lamp voltage increases due to phenomena such as half-wave discharge. Therefore, when the voltage at node a also increases and exceeds a predetermined value, current is supplied from Zener diode ZDI to the base of transistor T3. This results in
The transistor T3 is turned on and the collector of the transistor T3 becomes low level. Therefore, the base voltage of the transistor T2 is pulled down to a low level via the flip-flop FFI, and the transistor T2 is turned on. As a result, the voltage at the node d becomes high level, and the oscillator 7 oscillates at a relatively high frequency.

That is, when the end of life of the discharge lamp is detected, the output of the inverter circuit is lowered to protect each part of the circuit from high voltage.

Furthermore, in the circuit shown in FIG. 2, a lamp installation detection circuit 11 is provided, and this detection circuit 11 receives a signal of a different voltage depending on whether or not a discharge lamp is installed in the discharge lamp lighting device and the number of installed discharge lamps. Output. For example, when one lamp is attached to the lighting device and another lamp is attached, the voltage of the lamp attachment detection circuit 11 increases from the predetermined voltage by, for example, several volts. This results in
The first output node e of the reset circuit 13 becomes high level for a predetermined period of time to reset the flip-flop FFI. Further, in the reset circuit 13, the inverter circuit I
The output f of NVI is at a low level for a predetermined period of time, turning on transistor T2 and discharging the charge in capacitor C3.

In this case, Soph!・The charge of the timing capacitor C1 of the start circuit is transferred to the inverter NV of the reset circuit 13 via the diode D4, resistor R13, and diode D5.
It is discharged to 1. Further, when no lamp is attached to the lighting device, a lamp-unattached detection signal V is applied from the lamp attachment detection circuit 11 to the oscillator 7, and the oscillator 7
oscillation is stopped. This signal V is the transistor T4
is also applied to the transistor T4 when the lamp is not installed.
is turned on, discharging the capacitor C1 of the soft start circuit via the diode D4, and resetting the soft start circuit. In this way, in the circuit shown in FIG. 2, when a new lamp is installed, each part of the circuit is reset to ensure accurate starting of the discharge lamp and protection of the lamp.

(Problem to be Solved by the Invention) However, in the conventional discharge lamp lighting device shown in Fig. 2, the charge in the capacitor used in the time constant circuit of the soft start circuit is not completely discharged even by the operation of the reset circuit. There was an inconvenience that it was not done. In addition, since a differentiating circuit is used to determine the timing in the reset circuit, the width of the reset pulse, that is, the reset period, cannot be made too long, and this also prevents the reset operation of each part of the circuit from being performed properly. This has the disadvantage that cases may occur. Furthermore, in order to lengthen the reset period, a large capacitance capacitor is required, making it difficult to integrate the circuit.

SUMMARY OF THE INVENTION In view of the above-mentioned problems in the conventional device, an object of the present invention is to enable a common reset circuit to reset each part of a discharge lamp lighting device with a simple circuit configuration, and to ensure that the reset operation is carried out reliably. The purpose is to make it happen.

(Means for solving the problem 811) A discharge lamp lighting device according to the present invention includes an oscillation software circuit having an inverter circuit for lighting the discharge lamp, and a timing circuit for controlling the oscillation frequency at the time of starting oscillation of the inverter circuit. a soft start circuit having a timing circuit for controlling the output voltage of the inverter circuit when starting the discharge lamp; an end-of-life detection circuit having a flip-flop circuit that operates at the end of the lamp life; a mounting detection circuit that outputs a corresponding signal;
A common reset circuit is provided that resets the timing circuits of the oscillation soft circuit and the soft start circuit, and the flip-flop of the end-of-life detection circuit based on at least the output of the attachment detection circuit.

(Function) In the above-described configuration, when the number of lamps mounted on the discharge lamp lighting device is increased, the level of the output signal of the mounting detection circuit changes. In response to this level change, a reset circuit uses, for example, an integral four-way circuit to set a predetermined
Outputs a reset signal for 1 development. In response to this reset signal, both ends of the capacitors forming the timing circuits of the oscillation soft circuit and the soft start circuit are short-circuited by, for example, a transistor, and each capacitor is discharged.

Further, a reset signal is applied from the reset circuit to the flip-flop circuit of the lamp end-of-life detection circuit, and the flip-flop circuit is reset at the same time.

(Example) Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows the main parts of a discharge lamp lighting device according to an embodiment of the present invention. The device shown in the figure includes an oscillation circuit 21, a soft start circuit 23, an end-of-life detection circuit 25, an oscillation software circuit 27, a reset circuit 29, and the like. An inverter circuit and a lamp load (not shown) are connected to the output of the oscillation circuit 21. Furthermore, a power supply circuit that rectifies and smoothes the AC power supply to generate the operating power supply Vcc and the like is not shown.

The soft start circuit 23 includes a resistor R21, etc., a capacitor C21, and a capacitor C21 that constitute a time constant circuit.
The reset transistor Q2 is connected in parallel to the reset transistor Q2. The end-of-life detection circuit 25 includes a comparator CMP2 and N
It has a flip-flop composed of OR gates Nl, N2°N3, and an output transistor Q6. The oscillation software circuit 27 includes transistors Q3. Q4, resistors R28 and R29, capacitor C22 for timing setting, and inverter INV2
and an output transistor Q5. The two reset circuits include an inverter INv3, a resistor R32 and a capacitor C23 that are connected to the output of the inverter INv3 and constitute an integrating circuit for timing setting.
It is composed of a NOR gate N4, a transistor Q9, and the like.

In the device shown in FIG. 1, when the power is turned on, DC power VCC is first supplied to the oscillation software circuit 27 from a rectifier circuit (not shown). In the oscillation software circuit 27, since the voltage across the capacitor C22 is initially approximately O, the input of the inverter circuit INV2 is at a low level, and therefore the output of the inverter circuit INV2 and the emitter of the transistor Q5 are at a high level. This high-level voltage is divided by resistors R30 and R31, and a relatively high voltage is applied to oscillator 21 as frequency control voltage Vf via transistor Q7.

As a result, the oscillator 21 starts oscillating at a high frequency such as 80 KHz when the power is turned on, and the output of the inverter circuit (not shown) has a relatively low voltage value. Next, when a predetermined period of time passes and the voltage across the capacitor C22 increases, the inverter circuit INV2 is inverted and the output of the inverter circuit INV2 becomes low level. As a result, the transistor Q5 is cut off, and the output voltage of the oscillation software circuit 27 is reduced to approximately Ov.

Shortly before the output of the oscillation software circuit 27 decreases, the lamp voltage vL applied from a lamp voltage detection circuit (not shown)
has risen, and therefore, this lamp voltage VL is applied to the oscillator 21 via the transistor Q1, a voltage divider circuit composed of resistors R25, R26, and R27, and the transistor Q8.
is applied as a control signal Vf to cause the oscillator 21 to continue oscillating at a relatively high frequency. And transistor Q1
Soft start circuit 2 from the emitter through resistor R21
The capacitor C21 of No. 3 is gradually charged, and when the voltage across the capacitor 21 reaches a predetermined value or higher, the comparator CMP1
output changes from high level to low level. As a result, the base voltage of the transistor Q8 also becomes lower than the previous voltage value, and this lower voltage value is applied to the oscillator 21 as the control signal Vf. As a result, the oscillation frequency of the oscillator 21 is further lowered, the output of the inverter circuit (not shown) is increased, and the discharge lamp is started.

That is, a so-called soft start operation is performed.

Next, when the discharge lamp reaches the end of its life, the lamp detection voltage v
L increases abnormally. As a result, the end-of-life detection circuit 2
The voltage at the negative input terminal of comparator CMP2 of No. 5 becomes higher than the reference voltage V, and the output of comparator CMP2 of No. 1 is inverted from high level to low level.

As a result, NOR game) N1. N2. The output of the flip-flop composed of N3 changes from low level to high level, turning on transistor Q6. Therefore, the power of the inverter circuit INV2 of the oscillation software circuit 27 becomes low level, and the power of the transistor Q5. Oscillator 2 via Q7 etc.
1 is applied with a high control voltage Vf. This reduces the output of the oscillator 21 and prevents the generation of high voltage at the end of the lamp life.

Next, the operation of the reset circuit will be explained. A voltage V corresponding to the lamp installation state is output from a lamp installation detection circuit (not shown) to each comparator CMP3. It is applied to CMP4.

For example, in a lighting device using two discharge lamps, this voltage V is 0V1 if both lamps are installed.
2. If only one is installed. OV, and if no lamps are installed, it can be 3.0V, etc.

Therefore, from the state where one lamp is installed, one additional lamp is installed.
When an additional lamp is attached, the voltage V 2 decreases from 2, Ov to OV, and the output of the comparator CMP3 changes from a high level to a low level. Therefore, the output of inverter INV3 becomes high level. Then, the low level output of the comparator CMP3 and the voltage across the capacitor C23 are NOR gated)
Although applied to N4, the voltage across the capacitor C23 is initially O■. Therefore, the output of NOR gate N4 becomes high level, resetting the flip-flop of end-of-life detection circuit 25 and turning on transistor Q6. As a result, the capacitor C22 of the oscillation software circuit 27 is short-circuited, and its charge is discharged. In addition, reset circuit 2
As a result of the output of NOR gate N4 of 9 becoming high level,
The transistor Q9 is turned on, and the transistor Q2 of the soft start circuit 23 is also turned on. As a result, capacitor C22 of oscillation soft circuit 27 and capacitor C21 of soft start circuit 23 are both short-circuited and discharged. When a predetermined period of time has elapsed and the peak power of the integrating circuit made up of resistor R32 and capacitor C23 becomes high level, the output of NOR gate N4 becomes low level and the reset period ends. Note that if both lamps are not attached, the oscillation of the oscillator 21 is stopped by the output voltage V 1 of the comparator CMP4.

(Effects of the Invention) 5 As described above, according to the present invention, the timing circuit of the oscillation soft circuit and the soft start circuit and the flip-flop of the end-of-life detection M path can be reliably reset by a reset circuit with a simple configuration. I can do it. Further, the circuit for resetting each of these circuits can be shared. Furthermore, since an integrator circuit is used as a timing circuit to determine the time width of the reset signal, it is possible to obtain a signal with a sufficient time width with a relatively small capacitor, ensuring that the reset is performed reliably and the device can be easily integrated into integrated circuits.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing the main parts of a discharge lamp lighting device according to an embodiment of the present invention, and FIG. 2 is a block circuit diagram showing the configuration of a conventional discharge lamp lighting device. 1: Rectifier circuit, 3: Inverter circuit, 5: Lamp load, 7.21: Oscillator, 9: Lamp voltage detection port, 11: Lamp attachment detection circuit, 13.29: Reset circuit, 23: Soft start circuit, 25 : End of life detection circuit, 27: Oscillation software circuit, C21, C22, C23: Capacitor, CMPI, CM
P2. ..., CMP4: Comparator, INVl,, I N
V2. I NV3: In/<-Even, Nl, N2. N
3. N4: NOR gate, Ql, Q2. ..., Q9
:l-transistor, R21, R22,..., R34:
resistance.

Claims (1)

[Claims] 1. An inverter circuit that generates power for lighting the discharge lamp,
an oscillation soft circuit having a timing circuit for controlling an oscillation frequency at the time of starting oscillation of the inverter circuit; a soft start circuit having a timing circuit for controlling the output voltage of the inverter circuit at the time of starting the discharge lamp; and a lamp. an end-of-life detection circuit having a flip-flop circuit that operates at the end of life; a mounting detection circuit that outputs a signal corresponding to the mounting state of the discharge lamp; and at least the oscillation soft circuit and the soft start based on the output of the mounting detection circuit. A discharge lamp lighting device comprising a common reset circuit for resetting a timing circuit of the circuit and a flip-flop of the end-of-life detection circuit.