JPS5897294A - Device for firing discharge lamp - 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] The present invention relates to a discharge lamp lighting device.

In general, in a discharge lamp lighting device using a high-frequency transistor inverter, the discharge lamp may cause a half-wave discharge at the end of its life due to an unbalance of the electrodes, or an abnormal discharge may occur due to a change in gas components, and the normal impedance of the discharge lamp may be reduced. It may become. In this case, the inverter circuit supplies a large amount of power compared to the normal state, and the heat generated by the transformer and transistor of the inverter circuit increases, causing the internal temperature of the lighting device to rise significantly. Therefore, in the conventional inverter lighting device, in order to withstand the heat generated in such an abnormal lighting state, the lighting circuit is configured with an inverter circuit having a considerably larger capacity than normally required. However, such measures are disadvantageous in terms of cost, as they increase the capacity of the parts, making the device unusable, and creating a heat dissipation structure for abnormal loads.

Therefore, in order to protect the transistors by suppressing abnormal lighting conditions of discharge lamps, a thermostat equipped with a thermostat that is thermally coupled to the transistor of the inverter circuit and stops the operation of the inverter circuit when the temperature of the transistor rises abnormally is recommended. The one proposed by the applicant is already known. In addition, we have also proposed a method in which the thermostat is thermally coupled to a constant current inductor, full-wave rectifier, etc., rather than directly to the transistor, and indirectly stops the inverter circuit when the transistor temperature rises abnormally. has been done.

An example of a specific circuit configuration and its operation will be explained with reference to FIG. A thermostat (4) and an inverter circuit (5) are connected to the capacitor C1, and a discharge lamp (6) is connected to the output 11 of the inverter circuit (5).
) are connected in series. Here, the inverter circuit (5) connects the output end of the full-wave rectifier (3) to the intermediate point of the constant current inductor (7) and the negative winding N+ of the inverter transformer (8). The collector and emitter of a pair of push-pull transistors (9) (g) are connected between each end of the transistor (9) and the output end of the full-wave rectifier (3).
The base of (G) is connected to a full-wave rectifier (3) using a resistor RhR5.
The base winding Na is connected to one end of the base winding Na, and each of the base windings Na is connected to one end of the base winding Na. Note that a capacitor Cm that resonates with the primary winding N1 is connected to both ends of the negative winding Nl. In addition, the discharge lamp (6) is connected in series to the secondary winding II Nm of the inverter transformer (8), and the pair of preheating windings NH of the inverter transformer (8) are connected to the discharge lamp (6). (Filamen) (6
a) Connected to (u). Next, the thermostat (4) is a normally closed type, such as a bimetal, and is thermally coupled to the full-wave rectifier (3).
It becomes open when an abnormal temperature is detected.

In such a configuration, when the AC power supply (2) is connected to the input side of the inverter circuit (5), the transistor (9
) αQ, the one with larger (base current (III)) x (DC current amplification factor (hFl)) is in the ON state. Now, hypothetically, suppose that transistor (9) is ONt, then the DC current will be from −next winding JI Nt to transistor (
9) and the secondary winding Nm of the inverter transformer (8)
and induces a back electromotive force in the base winding N■. At this time, a voltage is generated in the base winding Nu in a direction that biases the transistor (9) positively and biases the transistor αQ negatively. This voltage becomes almost a sine wave due to the capacitor C3, but when this voltage change becomes zero, the transistor (
9) is in the OFF state. At this moment, the inductance of the primary winding N1 generates a back electromotive force, and the base winding N1
The polarity of the voltage generated by m is also reversed. That is, the transistor αO is now positively biased and turned t, and the transistor (9) is negatively biased and turned OFF.

This pair of transistors (9) (a)
By repeating the N.OF''F' operation, that is, the push-pull operation, a high frequency voltage is generated at the secondary winding MA of the inverter transformer (8), and power is supplied to the discharge lamp (6).

However, during such operation, if the temperature of the transistor (9) rises abnormally for some reason, the temperature of the full-wave rectifier (3) also rises in response to this temperature rise, and the temperature of the full-wave rectifier (3) also rises. ) thermally coupled with thermostat)
(4) If the O operating temperature is exceeded, the thermostat (4)
changes to the open state and automatically cuts off the input to the inverter circuit (5). At this time, the oscillation operation of the inverter circuit (5) immediately stops and the discharge lamp (6) goes out. During this light-off period, when the temperature of the transistor (9) gradually decreases due to heat radiation and reaches the return temperature of the thermostat (4), the thermostat (4) closes the power supply circuit and the inverter circuit (5) restarts. The discharge lamp (6) is automatically relit by the operation. This repeated operation of turning on and off continues until the cause of the abnormality is removed. The same thing applies when the temperature of the transistor increases abnormally.

In addition, in order to protect transistors (9) (g), the temperature rise of these transistors (9) αO is controlled by thermos I).
The temperature rise in the full-wave rectifier (3) is detected without being detected by the controller (4), but now the thermostat (4) is forcibly turned on in the discharge lamp lighting device (1) shown in Figure 1. Connect a short-circuited, normal discharge lamp and a discharge lamp at the end of its life, and measure the surface temperature of the transistor (9) (or (to)) that has become hot and the surface temperature of the Kinba rectifier (3). As a result, the surface temperature of the former was 87℃ under a normal discharge lamp.
The surface temperature of the latter is 93°C, and in the case of a discharge lamp at the end of its life, the former is 100°C and the latter is 106°C. ) also shows the same tendency as the temperature increase of +13°C, so there is no problem with such an indirect detection method.

Incidentally, even during normal operation, the temperature of the detection portion of the full-wave rectifier (3) whose temperature is detected by the thermostat (4) changes with the ambient temperature, as shown by the straight line in FIG. 2, for example. In addition, the temperature of the same part during an abnormality changes as shown by straight line B in FIG. 2 even if the ambient temperature is the same. Therefore, for example, if the threshold value of the detected temperature at which the thermostat (4) operates is TC, even during normal operation, if the ambient temperature is 35°C or higher, it will be judged as a circuit abnormality, and the abnormality as shown by straight line B. During operation, if the ambient temperature is 15° C. or higher, it exceeds the threshold value T° C., so the thermostat (4) determines that there is an abnormality.

However, even if the state changes from a normal operating state to an abnormal state, at a low ambient temperature of 15°C or less, the threshold value T°C
Since the temperature does not exceed 1, the thermostat (4)K does not determine that there is an abnormality, and the operation of the inverter circuit (4) is not stopped. That is, there is a problem in the abnormality detection ability when the ambient temperature is low.

The present invention has been made in view of these points, and provides a discharge lamp lighting device that can reliably detect abnormalities in the inverter and discharge lamp and protect the transistors even when the ambient temperature is low. The purpose is to

The present invention detects the ambient temperature of the thermostat using the temperature detection means, and when the temperature is low, the heating means auxiliarily heats the thermostat and therefore the detection part, so that when an abnormality occurs, the temperature at tt. It is configured so that the operation of the inverter circuit can be stopped by detecting it from the thermostat K.

An embodiment of the present invention will be described based on FIGS. 3 and 4. Components that are the same as those shown in FIGS. 1 and 3 are denoted by the same reference numerals, and descriptions thereof will be omitted. In this embodiment, a positive temperature coefficient thermistor RP is used as a temperature detection means. A full-wave rectifier (3
), and the positive characteristic thermistor RPrH senses the temperature around the thermostat (4) (8), and the full-wave rectifier (3), which is the detection part, is connected near the thermostat (4). A resistor RH is provided.

In such a configuration, the positive characteristic circulator Rp-rH
The resistance value of the resistor RH changes depending on the ambient temperature, and the resistance is low at low temperatures and high at high temperatures. Therefore, the power consumption and calorific value of the resistor RH are large at low temperatures and small at high temperatures. Therefore, the thermostat (4), i.e., the sensing part, is configured such that when the ambient temperature is low, such as below IIS'C, K is this resistance RH.
Even during normal operation, the full-wave rectifier (3) exhibits characteristics like curve A in Figure 4, and if the temperature of the full-wave rectifier (3) rises due to an abnormality, it will exceed the threshold T°C. This is detected by the thermostat (4), and the inverter circuit (5) stops operating. In this way, even when the ambient temperature is low, the temperature is corrected by supplementary heating by the resistor RH, so that an abnormal operation can be reliably detected by the thermostat (4).

As an ambient temperature detection means, a thermistor Rtu whose resistance is high at low temperatures and low at high temperatures is used as shown in Figure 2 (a).
It may be connected in parallel with the resistor RH as shown in FIG. 2, where the resistor - is for protection when the resistance value of the thermostat H becomes extremely low. This method is suitable for voltage circuits as shown in Figure 3, for example, an AC power supply (2), both ends of a full-wave rectifier (3) as in the example (one diode is also acceptable), and a full-wave rectifier (3). ) can be used. t
In addition, as shown in (4) in the same figure, the resistor RH and thermistor Rt
If only a parallel circuit with n is used, it is suitable for a current circuit.
A power supply or full-wave rectifier output and series circuit can be used.

By the way, in this embodiment, the thermostat (4) is thermally coupled to the full-wave rectifier (3), but it may also be directly thermally coupled to the transistor (9) αQ, or it may be connected to the constant current inductor (7). ) K may be thermally coupled, and it goes without saying that the power source may be either alternating current or direct current. In addition, the thermostat (4) can be connected to any part where the transistors (9) and (2) are inactive, in addition to the DC or AC power supply path. It is possible to use a thermostat (4). And this thermostat (4
) is made of bimetal, which facilitates thermal coupling and has a simple structure, but it may also be of an electronic circuit type, such as a combination of a temperature sensing element and a switching circuit.

As described above, the present invention uses a thermostat that is directly or indirectly thermally coupled to the transistors of the inverter circuit to stop the operation of the inverter circuit when the temperature rises abnormally. Since a heating means for auxiliary heating is provided, even if abnormal operation occurs at low ambient temperatures, it can be reliably detected and the operation of the inverter circuit can be stopped. This makes it possible to keep the rice cake unaffected by the ambient temperature.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a conventional example, Fig. 2 is an explanatory diagram of its operation, Fig. 3 is a circuit diagram showing an embodiment of the present invention, Figure 4 is an explanatory diagram of its operation, and Fig. 5 (α). (k) is a circuit diagram showing a modified example. 2...Power supply, 3...Full wave rectifier, 4...Thermostat, 5...Inverter circuit, 6...Discharge lamp, 7
...Constant current, current inductor, 9-10...Transistor, cabinet...Positive characteristic sensor (temperature detection means),
RH...Resistor (heating means) sRtM-・Thermistor (temperature detection means) Applicant: Tokyo Electric Co., Ltd., 2-11 Agent: Akira Aiki
・1st ward, -10th figure U and 5th (a) (6′ υ″

Claims (1)

[Claims] A power supply, a transistor-based inverter circuit that uses this power supply as input to perform oscillation operation and generate high-frequency voltage, a discharge lamp that is energized by the output of this inverter circuit, and a transistor that directly or indirectly connects to the transistor of this inverter circuit. a thermostat that is thermally coupled to the transistor and stops the operation of the inverter circuit when the temperature of the transistor rises abnormally; and a heating means that supplementally heats the thermostat at low temperatures based on temperature detection means that detects the ambient temperature of the thermostat. A discharge lamp lighting device characterized by: