JPH07122382A - Discharge lamp lighting apparatus - Google Patents

Abstract

PURPOSE:To provide a discharge lamp lighting apparatus in which the output of an circuit is made optimum at either starting time or lighting time. CONSTITUTION:At the starting time of a discharging lamp FL, since a capacitor C16 is not charged, a transistor Q3 keeps in OFF state and thus a field effect transistor FET1 keeps in OFF state. Since a Zener diode ZD4 is in OFF state, a transistor Q4 also keeps in OFF state and gate voltage is applied to a field effect transistor FET2 at a voltage valve of a capacitor C8 and the resultant capacitor of the capacitors C7, C8 is changed and the voltage of an inverter circuit 2 is kept constant. In the case of low temperature, the resistance of a thermister R17 having positive temperature coefficient lowers and the voltage of the inverter circuit 2 increases. When lighting is started and the capacitor C16 is charged, the Zener diode ZD4 is turned ON and since no gate voltage is applied to the field effect transistor FET2, the oscillation frequency of the transistor Q1 is determined based on the resultant capacity of the capacitors C6, C8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for appropriately adjusting the output of an inverter circuit both when starting and lighting a discharge lamp.

[0002]

2. Description of the Related Art As a conventional discharge lamp lighting device, for example, a structure described in Japanese Patent Application Laid-Open No. 2-192695 is known.

The discharge lamp lighting device disclosed in Japanese Unexamined Patent Publication No. 2-192695 changes the oscillation frequency of a transistor, which is a switching element of an inverter circuit, so that even if the load current of the discharge lamp or the like changes. The output voltage of the circuit is kept constant. Further, a resonance circuit of a capacitor and an inductor that sets the oscillation frequency of the transistor is connected to the base of the transistor. Then, in order to change the oscillation frequency of the transistor, the capacitance of the capacitor connected to the base of the transistor is changed, and the gate voltage of the field effect transistor connected in series to the capacitor is changed to apparently. By changing the resistance value and the resonance frequency of the resonance circuit, the oscillation frequency of the transistor is changed and the output voltage of the inverter circuit is made constant.

[0004]

However, in the case of the discharge lamp lighting device described in Japanese Patent Laid-Open No. 192695/1990, the starting voltage of the discharge lamp depends on the output voltage at the time of lighting. The output voltage cannot be optimized.

If the temperature of the discharge lamp or the ambient temperature is low at the time of starting the discharge lamp, it is difficult to start the discharge lamp. .

Therefore, there are problems that the discharge lamp does not light up and the life of the discharge lamp is affected.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a discharge lamp lighting device capable of optimizing the output of the inverter both at the time of starting and at the time of lighting.

[0008]

A discharge lamp lighting device according to claim 1, which has a switching element, and an inverter circuit for lighting the discharge lamp by changing the output by changing the oscillation of the switching element. An oscillation control circuit that controls the oscillation of the switching element of the inverter circuit, and a lamp start time that controls the oscillation control circuit for a predetermined time until the discharge lamp starts to set the output of the inverter circuit to the first output. An output control circuit and a lamp lighting output control circuit for controlling the oscillation control circuit to set the output of the inverter circuit to the second output after the discharge lamp is started.

A discharge lamp lighting device according to a second aspect of the present invention includes a switching element, an inverter circuit for lighting the discharge lamp by changing the output by changing the oscillation of the switching element, and the switching of the inverter circuit. An oscillation control circuit for controlling the oscillation of the element, a lamp start time output control circuit for controlling the oscillation control circuit to set the output of the inverter circuit for a predetermined time until the discharge lamp is started, and a lamp start for detecting the temperature. A correction means for increasing the output set by the lamp start output control circuit when the temperature is lower than a predetermined value is provided.

[0010]

In the discharge lamp lighting device according to the first aspect of the present invention, the oscillation control circuit is controlled by the lamp start output control circuit to set the output of the inverter circuit to the first output for a predetermined time until the discharge lamp is started. After the discharge lamp has started, the output control circuit controls the oscillation control circuit by the lamp lighting output control circuit to set the output of the inverter circuit to the second output. The discharge lamp can be reliably started, and the discharge lamp can be efficiently turned on after the discharge lamp is started.

In the discharge lamp lighting device according to the second aspect of the present invention, during the predetermined time until the discharge lamp is started, the oscillation control circuit is controlled by the lamp start-up output control circuit to set the output of the inverter circuit to detect the temperature. If the detected temperature is low, the output set by the output control circuit at lamp start is increased to increase the output of the inverter circuit.Therefore, even if the temperature of the discharge lamp is low, the discharge lamp can be started reliably. In addition, the discharge lamp can be efficiently turned on after starting.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the discharge lamp lighting device of the present invention will be described below with reference to the drawings.

In FIG. 1, E is a commercial AC power supply, and the full-wave rectifier circuit 1 is connected to the commercial AC power supply E.
Between the output terminals of this full-wave rectifier circuit 1, a surge absorption element
The TNR and the capacitor C1 are connected, and the inverter circuit 2 is connected.

The inverter circuit 2 includes a capacitor
A series circuit for smoothing the valley filling of the capacitor C2, the inductor L1 and the diode D1 is connected in parallel with C1.

Further, a series circuit of a primary winding Tr1a having an inductance for resonance of the inverter transformer Tr1 and a transistor Q1 as a switching element is connected between both terminals of the capacitor C2 and the inductor L1.
A resonance capacitor C3 is connected in parallel with Tr1a, and a diode D2 is connected to the collector of the transistor Q1 from the connection point of the inductor L1 and the diode D1.

Further, the secondary winding Tr1b of the inverter transformer Tr1 is connected to the discharge lamp via the detection winding CT1a of the current transformer CT of the oscillation control circuit 3, the capacitor C4 and the resistor R1.
Connect FL filaments FLa and FLb. Further, the filaments FLa and FLb have a capacitor C5 for starting.
Connect. And the control winding CT of this current transformer CT
A diode D3 is connected to 1b, the diode D3 is connected to the base of the transistor Q1, and a series circuit of a capacitor C6 and a field effect transistor FET1, a series circuit of a capacitor C7 and a field effect transistor FET2,
Transistor via diode D4 and capacitor C8
It is connected to the emitter of Q1. Also, the transistor Q1
Between the base and emitter of the diode D5 and resistor R2
Is connected to the positive electrode of the full-wave rectifier circuit 1 via a starting resistor R3.

Further, a series circuit of a voltage dividing capacitor C10 and a capacitor C11 is connected in parallel to the capacitor C5, and a rectifying diode D6 and a diode D7, a resistor R4, a capacitor C12 and a timer circuit 4 are connected to the capacitor C10. It is connected. This timer circuit 4 is composed of a capacitor C13, a diode D8 and a resistor R5, and a transistor is provided at the connection point of the capacitor C13 and the resistor R5.
The base of Q2 is connected, and between the collector of this transistor Q2 and diode D6, capacitor C14 and resistor R6
And the light emitting diode LED1 are connected, and the transistor Q2
A series circuit of a Zener diode ZD1 and a light emitting diode LED2 is connected between the emitter of the diode and the cathode of the diode D6.

On the other hand, a voltage detection circuit 5 is connected to the output terminal of the full-wave rectification circuit 1, and the voltage detection circuit 5 has a resistance.
R7 and capacitor C15 are connected, and zener diode ZD2 and resistor R8 are connected to capacitor C15.

A lamp lighting output control circuit 6 is connected to the voltage detection circuit 5. This lamp lighting output control circuit 6 is connected to a series circuit of a resistor R9 and a capacitor C16. The capacitor C16 has a resistor R10, an emitter and collector of a transistor Q3, a resistor R11 and a resistor C11.
A series circuit of R12 is connected, and the connection point of the resistors R11 and R12 is connected to the gate of the field effect transistor FET1. In addition, the base of transistor Q3 has a resistor
A series circuit of R14 and variable resistor R15 for variable output is connected. A Zener diode ZD3, a phototransistor PTr1 photocoupled to the light emitting diode LED1 and a phototransistor PTr2 photocoupled to the light emitting diode LED2 are connected in parallel to the capacitor C16.

Further, a lamp starting output control circuit 7 is connected to the full-wave rectifier circuit 1. The output control circuit 7 at the time of starting the lamp is such that the resistor R16
And a series circuit of capacitor C17 is connected, and a series circuit of Zener diode ZD4 and base and emitter of transistor Q4 is connected in parallel with capacitor C17.The collector of this transistor Q4 serves as a correction means A positive temperature characteristic thermistor R17 is connected to the positive side of the full-wave rectifier circuit 1
A resistor R18 is connected between the collector and emitter of Q4.

Next, the operation of the circuit shown in FIG. 1 will be described.

First, when the power is turned on, the full-wave rectification circuit 1 performs full-wave rectification, and a pulsating current is applied to the capacitor C1. Then, the inverter circuit 2 performs switching control of the direct current voltage supplied from the capacitor C1 on the transistor Q1 at a high frequency, and the primary winding Tr of the inverter transformer Tr1.
A voltage that resonates with the inductance of 1a and the capacitance of capacitor C3 is induced in the secondary winding Tr1b, and the discharge lamp FL
Is supplied to. Then, the capacitor C5 preheats the filaments FLa and FLb of the discharge lamp FL, and at the same time, the capacitor C5
The generated voltage is applied to the discharge lamp FL to start and light the discharge lamp FL.

When the discharge lamp FL is started, no charge is stored in the capacitor C13 of the timer circuit 4, and the transistor Q2 is kept in the ON state until the light emitting diode LED1 Light up. When the light emitting diode LED1 is turned on, the phototransistor PTr1 is turned on, and the capacitor C16 is not charged.

Since the capacitor C16 is not charged and the transistor Q3 is kept in the off state, no voltage is applied to the gate of the field effect transistor FET1 and the field effect transistor FET1 is kept in the off state.
C6 is in an open state and does not contribute to the switching operation of the transistor Q1.

On the other hand, since the Zener diode ZD4 is in the OFF state until the capacitor C17 is charged, the transistor Q4 also maintains the OFF state, and the positive temperature characteristic thermistor
With the voltage value set by the voltage division of R17 and resistor R18,
A gate voltage is applied to the field effect transistor FET2 to determine the output voltage of the inverter circuit 2 when the discharge lamp FL is turned on.

When the temperature of the discharge lamp FL or the ambient temperature is low at the time of starting the discharge lamp FL, the resistance value of the positive temperature characteristic thermistor R17 becomes low, and the voltage across the resistor R18 becomes high. Therefore, the field effect transistor FE
The gate voltage of T2 increases, the apparent capacitance of capacitor C7 increases, and the combined capacitance of capacitors C7 and C8 increases, so the base current of transistor Q1 increases and the output of inverter circuit 2 increases. Then, the voltage applied to the discharge lamp FL at the time of starting the lamp at a low temperature is increased, and the discharge lamp FL is reliably turned on.

When the discharge lamp FL is started, the transistor Q2 is turned off and the light emitting diode LED1 is turned off.
The phototransistor PTr1 is also turned off, and after the time set by the time constant of the resistor R9 and the capacitor C16, the capacitor
C16 is charged. Then, by charging the capacitor C16, the transistor Q3 is turned on, and the gate voltage is applied to the gate of the field effect transistor FET1.
Adjust to the normal control level. The capacitor C17
The zener diode ZD4 is turned on by the charging of, and the transistor Q4 is turned on, so that the current flowing in the resistor R18 is bypassed and the gate voltage of the field effect transistor FET2 is not applied, so the capacitor C7 is opened.
The oscillation frequency of the transistor Q1 is determined by the combined capacitance of the capacitors C6 and C8.

First, when the output from the full-wave rectifier circuit 1 rises and the voltage detected by the voltage detection circuit 5 rises, the base current of the transistor Q3 increases and the gate voltage of the field effect transistor FET1 is changed. The output of the inverter circuit 2 is reduced by decreasing the output of the inverter Q1 by increasing the switching speed of the transistor Q1.

On the other hand, when the output from the full-wave rectifier circuit 1 decreases and the voltage detected by the voltage detecting circuit 5 decreases, the base current of the transistor Q3 decreases and the gate voltage of the field effect transistor FET1 changes. The output of the inverter circuit 2 is increased by slowing the switching of the transistor Q1.

Thus, when the output voltage of the full-wave rectifier circuit 1 increases, the output of the inverter circuit 2 decreases, and conversely, when the output voltage of the full-wave rectifier circuit 1 decreases, the output of the inverter circuit 2 increases. Therefore, the output of the inverter circuit 2 can be always kept constant.

When the voltage of the discharge lamp FL increases by a predetermined value or more, the Zener diode ZD1 is turned on to turn on the light emitting diode LED2, and the phototransistor PTr2 is turned on to turn on the field effect transistor FE.
The gate voltage of T1 is eliminated, the output of the inverter circuit 2 is minimized, and the inverter circuit 2 is protected.

The positive temperature characteristic thermistor R17 may be a general resistor when the output correction due to the temperature at the time of starting is unnecessary.

[0033]

In the discharge lamp lighting device according to the first aspect of the present invention, during the predetermined time until the discharge lamp is started, the oscillation control circuit is controlled by the lamp start time output control circuit to output the output of the inverter circuit to the first output. After the discharge lamp has started, the output control circuit of the lamp lighting controls the oscillation control circuit to set the output of the inverter circuit to the second output. Since it can be adjusted to the lighting state, the discharge lamp can be surely started, and the discharge lamp can be efficiently turned on after the start.

In the discharge lamp lighting device according to claim 2,
For a predetermined time until the discharge lamp starts, the output control circuit at lamp start controls the oscillation control circuit to set the output of the inverter circuit, and if the detected temperature is low, the output at lamp start is output. To increase the output set by the control circuit and increase the output of the inverter circuit,
Even when the temperature of the discharge lamp is low, the discharge lamp can be reliably started even if the temperature is low, and the discharge lamp can be efficiently lit after the start.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a discharge lamp lighting device of the present invention.

[Explanation of symbols]

 2 Inverter circuit 3 Oscillation control circuit 6 Output control circuit at lamp lighting 7 Output control circuit at lamp startup FL Discharge lamp Q1 Transistor R17 as switching element Positive temperature characteristic thermistor as correction means

Claims (2)

[Claims] 1. An inverter circuit having a switching element, which changes an output by changing an oscillation of the switching element to light a discharge lamp, and an oscillation control circuit which controls an oscillation of the switching element of the inverter circuit. A lamp start-time output control circuit that controls the oscillation control circuit for a predetermined time until the discharge lamp starts to set the output of the inverter circuit to a first output; and the oscillation control after the discharge lamp starts. A discharge lamp lighting device, comprising: a lamp lighting output control circuit for controlling a circuit to set an output of the inverter circuit to a second output. 2. An inverter circuit which has a switching element and changes the output of the switching element to change the output to light a discharge lamp, and an oscillation control circuit which controls the oscillation of the switching element of the inverter circuit. And a lamp start-up output control circuit that controls the oscillation control circuit to set the output of the inverter circuit for a predetermined time until the discharge lamp starts, and if the temperature is detected and the temperature is below a predetermined value when the lamp is started. 2. A discharge lamp lighting device, further comprising: a correction unit that increases the output set by the lamp start-up output control circuit.