JP3890688B2 - Discharge lamp lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a discharge lamp lighting device.
[0002]
[Prior art]
In a discharge lamp lighting device that lights a discharge lamp at a high frequency, when the load state becomes an abnormal mode such as the end of life, the discharge amount in the tube of the discharge lamp decreases due to half-wave discharge or the like, the impedance of the discharge lamp increases, and the discharge lamp discharges. The first problem is that stress due to heat generation, voltage, current, etc. of various components such as the main switching element and the discharge lamp current limiting element in the lamp lighting device increases. As means for solving the first problem, means for detecting an abnormality of the load and stopping the oscillation of the inverter circuit or intermittently oscillating or reducing the output of the discharge lamp is often used.
[0003]
As an example, a circuit diagram of a conventional example according to the present invention is shown in FIG.
This circuit includes an inverter circuit that converts a DC power supply voltage E into an AC high-frequency voltage and supplies it to the load circuit side via a ballast choke L1. Here, the inverter circuit is a so-called half-bridge type inverter circuit composed of a series circuit of field effect transistors (hereinafter referred to as switching elements) Q1 and Q2 connected to both ends of the DC power supply E. The load circuit includes a series-parallel circuit including a discharge lamp La1 and capacitors C1 and C3 connected to both ends of the switching element Q2 via a ballast choke L1 and a balancer T1, and a discharge lamp La2 and capacitors C2 and C4. It consists of a series-parallel circuit. The capacitors C1 and C2 are resonance capacitors and preheating capacitors, and the capacitors C3 and C4 are DC component cutting capacitors. Further, the resistors R4 and R5, one end of which is connected to the source of the switching element Q2, the diode D1, the capacitor C7, the comparator CP1, and the reference voltage Vref1 constitute the Emiless detection circuit A, and the series including the capacitor C5 and the resistors R6 and R7. The circuit, the series circuit composed of the capacitor C6, the resistors R8 and R9, the transistors Tr1 and Tr2, the diode D2, the resistors R10 and R11, the capacitor C7, the comparator CP1, and the reference voltage Vref1 constitute an Emiles detection circuit B. Furthermore, a series circuit of a resistor R1 and a secondary winding n2 of a ballast choke L1 is connected between the gate and source of the switching element Q1, and a series circuit of resistors R2 and R3 is connected to both ends of the series circuit of the switching element Q2 and the resistor R4. Is connected. An ON / OFF signal is supplied from the control circuit 1 to the gate of the switching element Q2.
[0004]
The operation will be briefly described below with reference to the operation waveform diagram shown in FIG.
By alternately turning on and off the switching elements Q1 and Q2, resonance occurs between the ballast choke L1 and the capacitor C1, the ballast choke L1 and the capacitor C2, and the discharge lamp La1 and the discharge lamp La2 are turned on. Further, by supplying the dimming signal 2 to the control circuit 1, the on-section of the switching element Q2 is varied, and the discharge lamp La1 and the discharge lamp La2 are dimmed.
[0005]
In such a circuit configuration, when at least one of the discharge lamp La1 or the discharge lamp La2 reaches the end of its life, voltage stress, current stress, and temperature stress applied to the inverter circuit increase, so that the emiless detection circuits A and B The control for suppressing the stress is performed via this. For example, when one end of the filament of the discharge lamp La1 becomes Emires, the current flowing through the discharge lamp La1 and the discharge lamp La2 is unbalanced, so that T1 generates a voltage in the direction of correcting the imbalance. As a result, the potential at the connection point between the resistors R6 and R7 and the potential at the connection point between the resistors R8 and R9 become imbalanced, and the difference between the two connection point potentials is applied to the resistor R10. Due to this potential difference, the transistor Tr1 or the transistor Tr2 is turned on, a current flows through the diode D2 and the resistor R11, and the comparator CP1 operates when the voltage value across the capacitor C7 exceeds a predetermined level Vref1, thereby switching. The stress is reduced by controlling the element Q2 to stop oscillating.
[0006]
On the other hand, when both the discharge lamps La1 and La2 become Emires, it is conceivable that an imbalance of the currents flowing through the discharge lamp La1 and the discharge lamp La2 does not occur and the Emires detection circuit B does not work. At this time, an excessive current flows through the switching elements Q1 and Q2, but the overcurrent is detected by the resistor R4, the current flows through the resistor R5 and the diode D1, and the voltage value across the capacitor C7 has a predetermined level Vref1. When the value exceeds the value, the comparator CP1 operates, so that the switching element Q2 is controlled to stop oscillation and the stress is reduced.
[0007]
[Problems to be solved by the invention]
However, the above-described conventional example has the following second problem.
[0008]
In the above conventional example, when the output level of the discharge lamp La1 or the discharge lamp La2 is lowered according to the dimming signal, even if the discharge lamp is Emires, the Emires detection circuits A and B detect the Emires at a certain output level or less. Will not work and the stress cannot be reduced. Further, as shown in FIG. 5A, in a circuit system in which a pulse is applied to the discharge lamp La1 or the discharge lamp La2 at a predetermined cycle in order to light the discharge lamp La1 or the discharge lamp La2 while maintaining a low luminous flux, Although the lighting performance at the time of low luminous flux is improved, as shown in FIG. 5B, the ON width of the switching element Q2 is periodically widened, so that the voltage applied to the ballast choke L1 and the resistor R1 is increased. Furthermore, stress becomes large. In addition, it is very difficult to perform control so that the reference voltage Vref1 is varied in accordance with the dimming level (for example, Japanese Patent Laid-Open No. Hei 2-144896) to enable detection of Emires during dimming.
[0009]
The present invention has been made in view of all the above-mentioned problems, and an object of the present invention is to provide a discharge lamp lighting device capable of reliably detecting lamp emires during dimming and thus reducing circuit stress. It is.
[0010]
[Means for Solving the Problems]
In order to solve the above problem, according to the invention described in claim 1, an inverter circuit for supplying a high frequency voltage to a discharge lamp, a current limiting element for limiting an output current of the inverter circuit, and the current limiting element In the discharge lamp lighting device for supplying a high-frequency voltage to at least two of the discharge lamps via the balancer, as a physical arrangement relationship, a temperature sensing element is provided. Is disposed between the current limiting element and the balancer , and as an electrical connection relationship, a temperature sensing element is inserted into a path through which the inverter circuit supplies a high frequency voltage to the discharge lamp, and the temperature sensing the temperature sensitive device when the temperature is above a predetermined value of the element, together with the inverter circuit to block the path for supplying high frequency power to said discharge lamp, said current limiting element and the temperature sensing element and heat generating component , In the longitudinal direction of and the printed circuit board on the same printed circuit board, the current limiting element, the temperature sensitive device, characterized in that it is implemented arranged in the order of the heat generating component.
[0011]
According to a second aspect of the present invention, the current limiting element is a ballast choke .
[0012]
According to a third aspect of the present invention, the temperature sensitive element is a thermal protector .
[0013]
According to a fourth aspect of the present invention, the inverter circuit is capable of varying the light output of the discharge lamp .
[0018]
[Embodiment]
(Embodiment 1)
FIG. 3 is a circuit diagram of the first embodiment according to the present invention, FIG. 1A is a schematic upper view of the main part, and FIG. 1B is a side view thereof.
[0019]
4 differs from the circuit diagram of the conventional example shown in FIG. 4 in that a resistor R13 connected to both ends of the switching element Q1, a temperature sensing element (for example, a thermal protector) TP inserted between the ballast choke L1 and the balancer T1, and a capacitor C1. A resistor R14 connected to both ends of the resistor, a series circuit of resistors R15 and R16 connected to both ends of the capacitor C3, and a diode D3 having an anode side terminal connected to a connection point of the resistors R15 and R16, and between the diode D3 and the ground A no-load detection circuit A on the discharge lamp La1 side composed of a resistor R20 connected to the capacitor R2 and a capacitor C8 connected to both ends of the resistor R20, a resistor R13, a temperature sensitive element TP, and a resistor connected to both ends of the capacitor C2. R17, a series circuit of a resistor R18 and a resistor R19 connected to both ends of the capacitor C4, a resistor R18 and a resistor The connection point of R19 is provided with a no-load detection circuit B on the discharge lamp La2 side composed of a diode D3 having an anode side terminal connected, a resistor R20, and a capacitor C8, and has the same configuration as the other conventional examples. Are omitted by giving the same reference numerals. As the DC power source E, in this circuit, an AC power source Vs, a rectifier DB connected to both ends of the AC power source Vs via the filter circuit F, and a so-called step-up chopper circuit connected to the output terminal of the rectifier DB. It is composed. The step-up chopper circuit includes an inductor L12, a diode D11, a switching element Q11, and a smoothing capacitor C11. The switching element Q11 is controlled by the control circuit 11.
[0020]
Further, as shown in FIGS. 1A and 1B, the temperature sensing element TP is inserted between the ballast choke L1 and the balancer T1, and is mounted and disposed close to the ballast choke L1 and the balancer T1. Yes.
[0021]
The operation will be briefly described below.
In this circuit, when any one of the discharge lamp La1 or the discharge lamp La2 becomes Emires, the Emires detection circuit B operates to perform control such as oscillation stop and intermittent oscillation of the switching element Q2. In addition, when the output of the discharge lamps La1 and La2 is decreased upon receiving the dimming signal 2, the voltage difference between the discharge lamp La1 and the discharge lamp La2 becomes small, the Emileless detection circuit B does not work, and the L1 and the balancer T1 are gradually increased. Stress is applied, and the temperature of the ballast choke L1 and the balancer T1 rises. When the temperature rises above a certain level, the temperature sensing element TP operates to cut off the path of the no-load detection circuit and stop the oscillation of the inverter circuit. Thereafter, when the temperature sensing element TP reaches a temperature below a certain level, the inverter circuit starts to oscillate again.
[0022]
When both the discharge lamp La1 and the discharge lamp La2 become Emires, the Emires detection circuit A operates to perform control such as oscillation stop and intermittent oscillation of the switching element Q2. When the output of the discharge lamp La1, La2 receives a dimming signal 2 is lowered, since the current flowing through the inverter circuit is reduced, no longer work is Emiresu detection circuit B, and gradually stress ballast choke L1 and the balancer T1 The temperature of the ballast choke L1 and the balancer T1 rises. When the temperature rises above a certain level, the temperature sensing element TP operates to cut off the path of the no-load detection circuit and stop the oscillation of the inverter circuit. Thereafter, when the temperature sensing element TP reaches a temperature below a certain level, the inverter circuit starts to oscillate again.
[0023]
The temperature sensing element TP is inserted between the circuit ballast choke L1 and the balancer T1, but any temperature sensor TP may be used as long as it is on a path that interrupts the no-load detection circuit. However, on the circuit, it is more advantageous to insert the ballast choke L1 between the ballast choke L1 and the balancer T1 as shown in FIG.
[0024]
(Embodiment 2)
FIG. 2A shows a schematic upper view of the main part of the second embodiment according to the present invention, and FIG. 2B shows a side view thereof.
[0025]
The difference from the first embodiment shown in FIG. 1 is that the temperature sensing element TP is inserted between the ballast choke L1 and the resistor R1 and mounted in close proximity to the ballast choke L1 and the resistor R1. Therefore, the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0026]
In this embodiment, when one of the discharge lamp La1 or the discharge lamp La2 becomes Emires, or when both the discharge lamp La1 and the discharge lamp La2 become Emires, the dimming signal 2 is received. When the outputs of the discharge lamps La1 and La2 decrease, the voltage applied to the resistor R1 increases in addition to the ballast choke L1 and the balancer T1, so the temperature of the resistor R1 increases. When the temperature rises above a certain level, the temperature sensing element TP operates to cut off the path of the no-load detection circuit and stop the oscillation of the inverter circuit. Thereafter, when the temperature sensing element TP reaches a temperature below a certain level, the inverter circuit starts to oscillate again.
[0027]
【The invention's effect】
According to the invention described in claims 1 to 4, dimming reliably detects Ranpuemiresu of single-lamp or Oto upon, thus it is possible to reduce the circuit stress, also insert the temperature sensitive device between the parts Therefore, it is possible to provide a discharge lamp lighting device that can be realized at a low cost, can reduce the positional deviation of the temperature sensing element, and can maintain high detection accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic (a) upper view and (b) side view of a main part of a first embodiment according to the present invention.
FIGS. 2A and 2B are schematic (a) an upper view and (b) a side view of a main part of a second embodiment according to the present invention.
FIG. 3 shows a circuit diagram of an embodiment according to the present invention.
FIG. 4 shows a circuit diagram of a conventional example according to the present invention.
FIG. 5 shows an operation waveform diagram according to the conventional example.
[Explanation of symbols]
L1 Ballast choke La Discharge lamp Q Switching element TP Temperature sensing element

Claims (4)

An inverter circuit that supplies a high-frequency voltage to the discharge lamp; a current limiting element that limits an output current of the inverter circuit; and a balancer disposed near the current limiting element, the inverter circuit including the balancer In a discharge lamp lighting device that supplies a high-frequency voltage to at least two of the discharge lamps, a temperature sensing element is disposed between the current limiting element and the balancer as a physical arrangement relationship , and As a simple connection relationship, the temperature sensing element is inserted and disposed in a path where the inverter circuit supplies a high frequency voltage to the discharge lamp, and when the temperature of the temperature sensing element exceeds a certain value, the temperature sensing element is with blocking the path for supplying high frequency power to the discharge lamp, wherein a current limiting element and the temperature sensitive device and the heat generating component, the same printed circuit board and in a longitudinal direction of the printed circuit board The current limiting element, the temperature sensitive device, a discharge lamp lighting apparatus characterized by being implemented arranged in the order of the heat generating component. The discharge lamp lighting device according to claim 1 , wherein the current limiting element is a ballast choke . The discharge lamp lighting device according to claim 1 , wherein the temperature sensitive element is a thermal protector . The discharge lamp lighting device according to any one of claims 1 to 3 , wherein the inverter circuit is capable of changing a light output of the discharge lamp.

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