JP2004303519A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device with a simple circuit, constitution easy to assemble, high protection performance in abnormality of the lamp, a low price, and high productivity. <P>SOLUTION: The discharge lamp lighting device converting DC voltage of a DC power source E into high frequency voltage with a self-exciting inverter circuit IV of a load current feedback system and lighting a lamp LA with the high frequency voltage is equipped with a lamp abnormality detecting circuit NP1A detecting the abnormality of the lamp LA; an oscillation starting timer circuit NP1B letting flow starting current starting oscillation of the self-exciting inverter circuit IV from ON of a DC power source E for previously set time; and an oscillation stopping circuit NP1C having a capacitor C5 charged from oscillation starting of the inverter circuit IV, and stopping the oscillation of the inverter circuit IV by discharging charges charged in the capacitor C5 based on an output signal of the lamp abnormality detecting circuit NP1A. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device having a protection circuit for a lamp abnormality in a discharge lamp lighting device for lighting a discharge lamp with a high-frequency current generated by a switching element.
[0002]
[Prior art]
A conventional discharge lamp lighting device includes a transistor inverter that converts a DC voltage to a high-frequency voltage, and after supplying a base current to a main transistor for a predetermined time longer than a time required for lighting the discharge lamp from turning on a DC power supply. And an oscillation stopping means comprising a thermal protector for detecting an abnormal temperature rise of a circuit component of the transistor inverter and stopping the oscillation operation of the transistor inverter when an abnormal operation of the transistor inverter which is set to interrupt the current is detected (for example, Patent Document 1).
[0003]
[Patent Document 1]
Japanese Utility Model Publication No. 6-24159 (2-4 pages, Fig. 1)
[0004]
[Problems to be solved by the invention]
In the conventional discharge lamp lighting device as described above, the protection in the event of a lamp failure is such that abnormal heating of the main transistor 6 is detected by the thermal protector 16 of the oscillation stopping means 15 and the oscillation of the inverter circuit 2 is stopped. However, there is a problem that assembling the main transistor 6 and the thermal protector 16 is troublesome in order to reduce the mass production variation of the thermal response.
[0005]
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a simple circuit and a simple structure for assembling, has a high protection performance in the event of a lamp abnormality, is inexpensive, and has good mass productivity. The purpose is to obtain.
[0006]
[Means for Solving the Problems]
A discharge lamp lighting device according to the present invention converts a DC voltage of a DC power supply into a high-frequency voltage by a self-excited inverter circuit of a load current feedback system, and lights a discharge lamp (hereinafter abbreviated as a lamp) with the high-frequency voltage. In the lighting device, a lamp abnormality detection circuit for detecting an abnormality of the lamp, an oscillation start timer circuit for flowing a start current for starting the oscillation of the self-excited inverter circuit from turning on the DC power supply for a predetermined time, and the inverter An oscillation stop circuit that has a capacitor that is charged from the start of oscillation of the circuit and that stops the oscillation of the inverter circuit by discharging the charge charged in the capacitor based on the output signal of the lamp abnormality detection circuit. It is provided.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a circuit diagram of a discharge lamp lighting device according to Embodiment 1 of the present invention. In FIG. 1, a load current feedback type self-excited single-stone inverter circuit IV has a DC power supply E connected to an input section, and a discharge lamp load circuit LAC1 connected to an output section. Further, a lamp abnormality protection circuit NP1 for protecting the inverter circuit IV when the lamp is abnormal is connected to the discharge lamp load circuit LAC1 and the inverter circuit IV.
The discharge lamp load circuit LAC1 includes a series circuit of a coupling capacitor C2 connected to the electrode F2 of the lamp LA having the electrodes F1 and F2 and a ballast choke T2 for limiting the lamp current, and a starting capacitor connected to both ends of the lamp LA. The ballast choke T2 is provided with a primary winding N21 and a secondary winding.
[0008]
In the circuit of the inverter circuit IV, a series circuit of a tank circuit in which an output transformer T1 and a resonance capacitor C1 are connected in parallel and a main transistor Q1 that switches at a high frequency is connected to a DC power supply E, and a capacitor C1 and a collector of the main transistor Q1 are connected. The ballast choke T2 of the discharge lamp load circuit LAC1 is connected to the connection point. Further, a series circuit of the inductor choke T3, the secondary winding N22, and the starting resistors R7 and R8 is connected between the positive electrode of the DC power supply E and the base of the main transistor Q1 via the electrode F1.
A series circuit of a resistor R1 and a diode D1 is connected between the base and the emitter of the main transistor Q1, and a capacitor C4 is connected between a connection point of the secondary winding N22 and the resistor R7 and a negative electrode of the DC power supply E.
[0009]
The lamp abnormality protection circuit NP1 includes a lamp abnormality detection circuit NP1A for electrically detecting an abnormality of the lamp LA, and an oscillation activation for supplying a startup current for starting the oscillation of the self-excited inverter circuit when the DC power supply is turned on for a predetermined time. The timer circuit NP1B includes an oscillation stop circuit NP1C that stops the oscillation of the self-excited inverter circuit IV based on the output of the lamp abnormality detection circuit NP1A.
[0010]
In the lamp abnormality detection circuit NP1A, a series circuit of the resistors R10 and R11 is connected between the electrode F2 of the lamp LA and the negative electrode of the DC power supply E. Further, a series circuit of a capacitor C10 and a diode D5 is connected in parallel to the resistor R11, and a series circuit of a diode D4 and a zener diode DZ1 is connected to a connection point between the capacitor C10 and the diode D5. Further, a capacitor C9 is connected between a connection point between the diode D4 and the Zener diode DZ1 and the negative electrode of the DC power supply E.
[0011]
In the oscillation start timer circuit NP1B, a parallel circuit of the resistor R4 and the diode D3 and a series circuit of the capacitor C8 are connected between the positive electrode and the negative electrode of the DC power supply E via the electrode F1.
A transistor Q5 is connected between the contacts of the starting resistors R7 and R8 and the negative electrode of the DC power supply E, and a parallel circuit of a resistor R4 and a diode D3 and a series circuit of a capacitor C8 are connected to the positive and negative electrodes of the DC power supply E via an electrode F1. Connected between them. Further, a Zener diode DZ2 is connected between a connection point between the resistor R4 and the capacitor C8 and the base of the transistor Q5.
[0012]
In the oscillation stop circuit NP1C, a series circuit of a capacitor C5 and a diode D2 is connected between the base and the emitter of the main transistor Q1, and a thyristor Q2 is connected in parallel with the diode D2. Further, a capacitor C6 and a resistor R2 are connected between the gate of the thyristor Q2 and the negative electrode of the DC power supply E. Further, the Zener diode DZ1 of the lamp abnormality detection circuit NP1A is connected to the gate of the thyristor Q2.
[0013]
Next, the operation of the discharge lamp lighting device configured as described above will be described with reference to FIG.
First, when the DC power supply E is turned on, a base current is supplied to the main transistor Q1 from the DC power supply E via the electrode F1, the oscillation starting resistors R8 and R7, the secondary winding N22 of the ballast choke T2, and the inductor choke T3. Goes on. As a result, a current flows through the main transistor Q1 to a series circuit of the output transformer T1 or the electrode F1, the starting capacitor C3, the electrode F2, the coupling capacitor C2, and the ballast choke T2, and this load current is transferred to the secondary winding of the ballast choke T2. Positive feedback is made to the input of the main transistor Q1 via N22, and the state further shifts to the ON state.
[0014]
On the other hand, since the input circuit of the main transistor Q1 is formed with the self-inductance of the secondary winding N22 of the ballast choke T2 and the LC series resonance circuit of the capacitor C4, the secondary winding N22 of the ballast choke T2 → the inductor choke T3 → The base current flowing in the closed loop of the base coil / emitter of the main transistor Q1 → the capacitor C4 → the secondary winding N22 of the ballast choke T2 flows in the opposite direction due to oscillation, and the secondary winding N22 of the ballast choke T2 → capacitor. Since the current flows through C4 → diode D1 → resistance R1 → inductor choke T3 → secondary winding N22 of ballast choke T2, the main transistor Q1 rapidly turns off when the accumulated charge at the base-emitter junction of the main transistor Q1 is erased.
[0015]
Thereafter, the charge of the resonance capacitor C1 is discharged mainly through the series circuit of the electrode F1, the starting capacitor C3, the electrode F2, the coupling capacitor C2, and the ballast choke T2, so that an oscillating load current flows. Due to this load current, a current is generated in the secondary winding N22 of the ballast choke T2, and the secondary winding N22 of the ballast choke T2 → the capacitor C4 → the diode D1 → the resistor R1 → the inductor choke T3 → the secondary winding N22 of the ballast choke T2. Current flows in the opposite direction, and the transistor Q1 is kept off.
[0016]
Then, due to the oscillating load current, the positive feedback current mainly to the base of the transistor Q1 again flows through the secondary winding N22 of the ballast choke T2, and the main transistor Q1 turns on to repeat the above operation. The main transistor Q1 performs switching at a high frequency of about 20 to 50 kHz.
At this time, the ON period of the main transistor Q1 is mainly determined by the resonance frequency of the capacitor C4 and the inductor choke T3, and the OFF period is mainly determined by the resonance frequency of the capacitor C1, the starting capacitor C3, and the ballast choke T2.
[0017]
At this time, since the capacity of the starting capacitor C3 is set to a value that causes LC resonance with the ballast choke T2, a high-frequency resonance current flows through the electrodes F1 and F2 of the lamp LA, and at the same time, a high voltage is generated across the starting capacitor C3. The lamp LA is turned on by this voltage. After the lamp LA is turned on, the impedance of the lamp LA is connected in parallel with the starting capacitor C3, and this is used as a load circuit, and the inverter circuit IV continues the oscillating operation in the same manner as described above. A high-frequency current limited by the ballast choke T2 flows.
[0018]
On the other hand, in the oscillation start timer circuit NP1B, the capacitor C8 is charged in the closed loop of the DC power source E → the electrode F1 → the resistor R4 → the capacitor C8 → the DC power source E at the same time as the DC power source E is turned on. When the voltage exceeds the Zener voltage of the Zener diode DZ2, the transistor Q5 turns on and the starting current supplied via the starting resistor R8 is cut off.
[0019]
Next, at the end of the life of the lamp LA, when the rectified lighting is continued, or when the electrodes F1 and F2 are preheated due to the non-lighting of the lamp LA, a resonance voltage larger than that during the normal lighting of the lamp LA is applied to the starting capacitor C3. Occurs continuously.
This large resonance voltage is divided by the resistors R10 and R11 of the lamp abnormality detection circuit NP1A, and detected as a peak-to-peak voltage by the capacitor C9. When this detection voltage becomes equal to or higher than the voltage set in advance by the Zener diode DZ1, current is supplied to the gate of the thyristor Q2 of the oscillation stop circuit NP1C, and the thyristor Q2 is turned on.
[0020]
On the other hand, the capacitor C5 is charged from the start of the oscillation of the inverter circuit IV, and when the thyristor Q2 is turned on, the charge charged in the capacitor C5 is transferred from the capacitor C5 → the thyristor Q2 → the base / emitter of the main transistor Q1 → the capacitor C5. By discharging in a closed loop, the main transistor Q1 is turned off, and the oscillation of the inverter circuit IV stops.
[0021]
At this time, since the starting current is in the cutoff state, the inverter circuit IV is not restarted until the DC power supply E is turned on again or the lamp LA is replaced, and the inverter circuit IV is protected. In this case, the diode D3 has the effect of shortening the discharge time constant of the charge discharging loop of the capacitor C8 (capacitor C8 → diode D3 → starting resistor R8 → transistor Q6 → capacitor C8).
[0022]
As described above, the oscillation stop circuit NP1C does not require the conventional current transformer or thermal protector, and is a simple circuit composed of a small oscillation stop capacitor C5 and a small-capacity thyristor Q2 for discharging this charge. It is easy to assemble, inexpensive, and has good mass productivity.
Further, the protection performance at the time of lamp abnormality can be enhanced.
[0023]
Embodiment 2 FIG.
In the present embodiment, the oscillation start timer circuit NP1B of the first embodiment has a mask function for invalidating the output of the lamp abnormality detection circuit NP1A.
FIG. 2 is a circuit diagram of a discharge lamp lighting device according to Embodiment 2 of the present invention.
2, the same or corresponding parts as those in FIG. 1 of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0024]
In the lamp abnormality detection circuit NP2A of the lamp abnormality protection circuit NP2, the transistor Q6 is connected in parallel to the capacitor C9, and the base of the transistor Q6 is connected to the connection point between the resistors 7 and 8.
[0025]
Next, the operation of the discharge lamp lighting device configured as described above is the same as that of the first embodiment in that the inverter circuit IV performs the oscillating operation after the DC power supply E is turned on. The operation of NP1 will be described.
[0026]
In the lamp abnormality protection circuit NP1, in order to turn on the lamp LA, when the DC power supply E is turned on, the DC power supply E passes through the electrode F1, the oscillation starting resistors R8, R7, the secondary winding N22 of the ballast choke T2, and the inductor choke T3. Thus, a base current is supplied to the main transistor Q1, and the main transistor Q1 is turned on. Thereafter, the main transistor Q1 is turned on and off, the inverter circuit IV starts oscillating, and the lamp LA is turned on. Since the starting current flowing through R8 is supplied to the base of the transistor Q6, the transistor Q6 is turned on, the capacitor C9 for voltage detection is short-circuited, and the lamp abnormality detection circuit NP1A is in a mask state in which it does not operate.
[0027]
On the other hand, in the oscillation start timer circuit NP1B, at the same time as the transistor Q5 is turned on in the first embodiment, the start current supplied to the base of the transistor Q6 of the lamp abnormality detection circuit NP2A is cut off, and the transistor Q6 is turned off to detect the lamp abnormality. The circuit NP2A becomes operable.
As described above, the transistor Q5 and the transistor Q6 operate in synchronization, and the lamp abnormality detection circuit NP1A becomes operable at the same time when the starting current is cut off.
With this configuration, when the lamp abnormality detection circuit NP2A operates, the starting current is always shut off in a masked state, so that the circuit can be surely protected and the circuit is advantageously simplified.
[0028]
Since the base current of the main transistor Q1 is supplied from the ballast choke T2 via the secondary winding N22, the oscillation of the inverter circuit IV continues. Further, since the resistance value of the starting resistor R7 is set to a large value of several tens of kΩ, the turning on of the transistor Q5 does not affect the oscillation operation of the inverter circuit IV.
[0029]
Next, at the end of the life of the lamp LA, when the rectified lighting is continued, or when the electrodes F1 and F2 are preheated due to the non-lighting of the lamp LA, a resonance voltage larger than that during the normal lighting of the lamp LA is applied to the starting capacitor C3. Occurs continuously.
This large resonance voltage is divided by the resistors R10 and R11 of the lamp abnormality detection circuit NP2A and detected by the capacitor C9 as a peak-to-peak voltage. When this detection voltage becomes equal to or higher than the voltage set in advance by the Zener diode DZ1, current is supplied to the gate of the thyristor Q2 of the oscillation stop circuit NP1C, and the thyristor Q2 is turned on.
[0030]
On the other hand, the capacitor C5 is charged from the start of the oscillation of the inverter circuit IV, and when the thyristor Q2 is turned on, the charge charged in the capacitor C5 is transferred from the capacitor C5 → the thyristor Q2 → the base / emitter of the main transistor Q1 → the capacitor C5. By discharging in a closed loop, the main transistor Q1 is turned off, and the oscillation of the inverter circuit IV stops.
[0031]
At this time, since the starting current is in the cutoff state, the inverter circuit IV is not restarted until the DC power supply E is turned on again or the lamp LA is replaced, and the inverter circuit IV is protected. In this case, the diode D3 has the effect of shortening the discharge time constant of the charge discharging loop of the capacitor C8 (capacitor C8 → diode D3 → starting resistor R8 → transistor Q6 → capacitor C8).
[0032]
Next, when the DC power supply E is turned on and the load current does not flow through the ballast choke T2, for example, when no load is considered, the starting current flowing through the main transistor Q1 via the starting resistors R8 and R7 as described above. Before the temperature of the main transistor Q1 starts to rise, the inverter circuit IV is protected by setting the transistor Q5 to be turned on for a few seconds, for example.
[0033]
As described above, since the oscillation start timer circuit NP1B also has a mask function for disabling the output of the lamp abnormality detection circuit NP2A, it can be a simple circuit, and can be inexpensive and have good mass productivity. .
Further, when the lamp abnormality detection circuit NP2A operates, the starting current is always cut off in a masked state, and the circuit can be reliably protected.
[0034]
【The invention's effect】
As described above, according to the present invention, a DC voltage of a DC power supply is converted into a high-frequency voltage by a self-excited inverter circuit of a load current feedback system, and a discharge lamp (hereinafter abbreviated as a lamp) is lit by the high-frequency voltage. In the electric lamp lighting device, a lamp abnormality detection circuit for detecting abnormality of the lamp, an oscillation start timer circuit for flowing a start current for starting the oscillation of the self-excited inverter circuit from the turning on of the DC power supply for a predetermined time, An oscillation stop circuit that has a capacitor charged from the start of oscillation of the inverter circuit, and stops the oscillation of the inverter circuit by discharging the charge charged in the capacitor based on the output signal of the lamp abnormality detection circuit; , It is easy to assemble with a simple circuit, enhances the protection performance in the event of a lamp abnormality, and is inexpensive for mass production. It can be.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a discharge lamp lighting device according to a first embodiment of the present invention.
FIG. 2 is a circuit diagram of a discharge lamp lighting device according to a second embodiment of the present invention.
[Explanation of symbols]
C5 capacitor, E DC power supply, IV inverter circuit, LA lamp, NP1 lamp abnormality protection circuit, NP1A, lamp abnormality detection circuit, NP1B oscillation start timer circuit, NP1C oscillation stop circuit.

Claims (2)

In a discharge lamp lighting device that converts a DC voltage of a DC power supply into a high-frequency voltage by a self-excited inverter circuit of a load current feedback system and turns on a discharge lamp (hereinafter abbreviated as a lamp) with the high-frequency voltage,
A lamp abnormality detection circuit that detects abnormality of the lamp;
An oscillation start timer circuit for flowing a start current for starting oscillation of the self-excited inverter circuit from turning on the DC power supply for a predetermined time,
An oscillation stop circuit that has a capacitor that is charged from the start of oscillation of the inverter circuit and that stops the oscillation of the inverter circuit by discharging the charge charged in the capacitor based on the output signal of the lamp abnormality detection circuit; A discharge lamp lighting device comprising: 2. The discharge lamp lighting device according to claim 1, wherein the oscillation start timer circuit also has a mask function for disabling an output of the lamp abnormality detection circuit for a predetermined time from when the DC power is turned on.

Images