JPH10312893A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a self-exciting inverter device at a low cost for conducting a frequency control for preheating and starting a discharge lamp, and an operation frequency control corresponding to load current fluctuation. SOLUTION: A self-exciting inverter circuit is provided with a drive circuit driven by using a current transistor 8' input with the load current of the transistor 3 being an output switching element of a high frequency conversion means. Therein, since the driving circuit of the transistor 3 has a thermistor 13, a temperature depending variable resistant element, the resistant value of the thermistor 13 changes by temperature change resulting from the increasing and decreasing of self generation or the fluctuation of an ambient temperature so that the current and the phase of a secondary winding changes comparing with the current (the load current) phase of the primary winding side of the current transformer 8'. Therefore, the timing of the transistor 3 changes so that the operation frequency of the inverter device can be changed without any special control circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-excited inverter device for lighting a discharge lamp, and more particularly to a self-excited oscillating frequency of the self-excited oscillating frequency which is automatically controlled by a temperature change due to its ambient temperature or self-heating using a temperature-dependent variable resistance element. In which the operating frequency is changed.

[0002]

2. Description of the Related Art FIG.
FIG. 1 is a circuit diagram of a conventional half-bridge type self-excited inverter device disclosed in Japanese Unexamined Patent Publication (Kokai) Publication. In the figure, a self-excited inverter circuit having a DC power supply 1 as an input is represented by transistors 2
3, a diode 20, 20; a driving current transformer 8; and a capacitor 4. A driving circuit for the transistors 2, 3 is constituted by a secondary winding of the current transformer 8, resistors 14, 15, a capacitor 16, and a variable resistor 17. The load circuit is constituted by a resonance circuit including a choke coil 7, a capacitor 6 and a discharge lamp 5, and the starting circuit is constituted by a resistor 9 and a capacitor 10.
And the voltage sensitive element 11.

Next, the operation of a conventional half-bridge type self-excited inverter device will be described. When the DC power supply 1 is turned on, the capacitor 10 is charged via the resistor 9 in the starting circuit, and when the charged voltage reaches the breakover voltage of the voltage sensing element 11, discharge is performed via the base to emitter of the transistor 3 on the low side. When started, the transistor 3 is turned on. As a result, the self-excited inverter circuit starts operating, and the DC power supply 1 → capacitor 4 → discharge lamp 5 (discharge lamp 5 filament capacitor 6 → discharge lamp 5 filament) → choke coil 7 → current transformer 8
A current flows through the path of n1 → transistor 3 → DC power supply 1 to charge the capacitor 4. Since this current flows through the primary winding n1 of the current transformer 8, the two secondary windings n
A voltage is induced in 2 ′ and n2 to flow a current. The induced current flowing through the secondary winding n2 initially flows in a polarity (a direction flowing into the base terminal of the transistor 3) for maintaining the conduction state of the transistor 3. At this time, the induced current flows by shunting the capacitor 16 and the variable resistor 17, and negative charges are accumulated on the current transformer side of the capacitor 16.

[0004] Thereafter, the current for charging the capacitor 4 increases, but as the charging proceeds, the increase slows down, and eventually decreases. At this time, the voltage induced in the secondary winding of the current transformer 8 is also inverted, so that the transistor 3 is turned off and the transistor 2 is turned on. At this time, the charge accumulated in the capacitor 16 also acts in the direction of applying a negative voltage to the base terminal so as to turn off the transistor 3. The magnitude of the electric charge stored in the capacitor 16 changes depending on the value of the variable resistor 17 connected in parallel. When the resistance value is large, the electric charge increases, and the transistor 3 is turned off quickly. Will be higher. Conversely, if the resistance value of the variable resistor 17 is small, the charge stored in the capacitor 16 is also small.
The timing for turning off the inverter does not advance, and the operating frequency of the inverter decreases.

In order to change the operating frequency of the inverter in this method, it is necessary to change the resistance value of the variable resistor 17 by some method. FIG. 11 shows an operation frequency control for actually preheating and starting the discharge lamp 5 and changing the operation frequency to protect the inverter device from excessive voltage and current generated due to a load abnormality or the like. There is another conventional half-bridge type self-excited inverter device. This inverter device includes a capacitor 16
A resistor 18 and a switch 19 are connected in parallel with each other, and the control circuit 22 having a timer function and a voltage / current detection function controls on / off of the switch 19 to change the parallel resistance value of the capacitor 16. is there.

[0006]

As described above, in the conventional inverter device, the operating frequency cannot be automatically changed, or if the operation frequency can be changed automatically, a control circuit for that is necessary. However, there is a problem that it becomes expensive. The present invention has been made to solve the above problems, and has as its object to provide a self-excited inverter device capable of automatically changing an operating frequency without a complicated control circuit.

[0007]

According to a first aspect of the present invention, there is provided an inverter apparatus comprising: a DC power supply; and a high-frequency converter having at least one output switching element for converting a DC voltage of the DC power supply into a high-frequency voltage by switching. A resonant load circuit composed of a choke coil, a capacitor, and a discharge lamp to which a high-frequency voltage of a high-frequency converter is applied, and a drive circuit that drives an output switching element using a current transformer that receives a load current of the resonant load circuit as an input. In the self-excited inverter device provided, the drive circuit has a temperature-dependent variable resistance element connected to a control terminal of an output switching element.

According to a second aspect of the present invention, there is provided an inverter device comprising:
A resonance comprising a DC power supply, high frequency conversion means having at least one output switching element for converting a DC voltage of the DC power supply into a high frequency voltage by switching, and a choke coil, a capacitor and a discharge lamp to which the high frequency voltage of the high frequency conversion means is applied; In a self-excited inverter device including a load circuit and a drive circuit for driving an output switching element using a current transformer having a load current of a resonance load circuit as an input, the drive circuit includes a secondary winding of the current transformer. And a series circuit of a temperature-dependent variable resistance element connected to a control terminal of the output switching element.

According to a third aspect of the present invention, there is provided an inverter device comprising:
A resonance comprising a DC power supply, high frequency conversion means having at least one output switching element for converting a DC voltage of the DC power supply into a high frequency voltage by switching, and a choke coil, a capacitor and a discharge lamp to which the high frequency voltage of the high frequency conversion means is applied; In a self-excited inverter device including a load circuit and a drive circuit for driving an output switching element using a current transformer having a load current of a resonance load circuit as an input, the drive circuit includes a secondary winding of the current transformer. And a parallel circuit of a frequency setting capacitor and a temperature-dependent variable resistance element connected in series with the secondary winding.

According to a fourth aspect of the present invention, there is provided an inverter device comprising:
DC power supply, high-frequency conversion means including a pair of output switching elements connected in series for converting a DC voltage of the DC power supply into a high-frequency voltage by switching, a choke coil, a capacitor, and a discharger to which the high-frequency voltage of the high-frequency conversion means is applied. In a self-excited inverter device including a resonance load circuit including an electric lamp and a drive circuit that drives an output switching element using a current transformer that receives a load current of the resonance load circuit as an input, the drive circuit includes a current transformer. It has an added auxiliary winding and a temperature-dependent variable resistance element connected to the auxiliary winding.

The high frequency conversion means in the inverter device according to the present invention is constituted by a one-stone resonance circuit comprising a parallel circuit of a coil and a capacitor and an output switching element connected in series to the parallel circuit. The driving circuit for the switching element has a temperature-dependent variable resistance element.

According to a sixth aspect of the present invention, in the inverter device, the high-frequency converting means is constituted by a half-bridge type inverter circuit comprising a pair of output switching elements connected in series to each other, and at least one of the output switching elements of the inverter circuit. Has a temperature-dependent variable resistance element.

The temperature-dependent variable resistance element used in the drive circuit in the inverter device according to claim 7 of the present invention is NTC.
It is a thermistor.

The temperature-dependent variable resistance element used in the drive circuit in the inverter device according to claim 8 of the present invention is a PTC.
It is a thermistor.

According to a ninth aspect of the present invention, the temperature-dependent variable resistance element used in the drive circuit in the inverter device is thermally coupled to the output switching element.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a circuit diagram showing an inverter device according to Embodiment 1 of the present invention, FIG. 2 is a circuit diagram showing a drive circuit portion of the inverter device, and FIG. 3 is a diagram showing a phase and a waveform of a drive current of the inverter device. is there. 1, the same components as those of the conventional example are denoted by the same reference numerals, and the description of the duplicated components will be omitted. A transistor 3 as an output switching element and a diode 21 are connected in parallel with a parallel circuit of a coil 23 and a resonance capacitor 24 to form a one-piece resonance circuit as a high-frequency converter.

Reference numeral 8 'denotes a driving current transformer for driving the transistor 3 with a current flowing through a load circuit composed of the discharge lamp 5, the capacitor 6, and the choke coil 7 as an input. The thermistor is a temperature-dependent variable resistor that is connected to the next winding and changes the magnitude and phase of the base current of the transistor 3.
Here, the resistance value of the thermistor 13 changes due to a temperature change due to an ambient temperature or self-heating. As the resistance value changes, the induced current flowing through the secondary winding of the current transformer 8 '(base terminal of transistor 3 → resistance 15 →
The phase of the thermistor 13 → the secondary winding n2) of the current transformer 8 ′ changes. As a result, the timing at which the transistor 3 turns on → off changes, and the operating frequency changes.

The phase of the secondary current of the current transformer is
How it changes with the load resistance connected to the next current circuit will be described with reference to FIGS. FIG. 2 shows a primary winding n1 of the current transformer 8 'in FIG. 1, a secondary winding n2 constituting a drive circuit of the transistor 3, a base resistor 15 (r) and a thermistor 13 (Rt) on the secondary side. 3A shows the phase of the secondary current I ₂ , and FIG. 3B shows the current waveform.
Assuming that the primary current I ₁ and the secondary current I ₂ are the exciting current of the current transformer 8 ′ ≒ 0, the secondary current circuit has the same phase when the load resistance R (= r + Rt) = 0, and the load resistance R Becomes larger, the phase of the secondary current (drive current) is advanced (up to 90 degrees) as compared with the primary current (load current).

In FIG. 3, the load resistance R of the secondary current circuit
But 0, rl, r2 the secondary current I ₂ in the case of (0 <r1 <r2), indicated by 31, 32 and 33. The phase of the secondary current 31 is the same as the phase of the primary current. As described above, the larger the resistance value of the secondary side of the current transformer 8 ′, the more the secondary current I ₂ , that is, the phase of the base current for driving the switching of the transistor 3 is advanced. As a result, the earlier timing Since the transistor 3 is switched, the inverter device operates at a high frequency. As described above, since the operating frequency of the inverter device changes depending on the value of the load resistance of the secondary current circuit, that is, the load resistance of the drive circuit of the transistor 3, the thermistor 13 which is a temperature-dependent variable resistance element is used as the load resistance of the drive circuit. The operating frequency of the thermistor 13 can be automatically changed in accordance with the temperature change of the thermistor 13 due to self-heating or ambient temperature fluctuation and the resulting resistance value change.

For example, when the power is turned on and the operation is started, the thermistor 13, which is a temperature-dependent variable resistance element, changes its resistance value due to a rise in temperature due to its own heat generation and the like, and the steady-state operation frequency is changed from the operating frequency at startup. It can be automatically swept to the operating frequency during operation. Here, if an NTC thermistor whose resistance value decreases as the temperature rises is used as the temperature-dependent variable resistance element, the frequency can be gradually reduced from a high operating frequency at startup to an operating frequency at steady operation.

The present invention can also be used for automatically adjusting the operating frequency of the inverter device with respect to fluctuations in the load and the like of the inverter device. Load of the inverter apparatus is the secondary current I ₂ also increases, which is the primary current becomes larger when the induction of I ₁ of the current transformer 8 'varies, its temperature is increased self heating value of the temperature-dependent family variable resistive element As a result, the resistance value changes and the operating frequency of the inverter changes. In this case, the frequency of the operation of the inverter device is reduced by using an NTC thermistor whose resistance value is reduced by a temperature rise as a temperature-dependent resistance element, and reduced by using a PTC thermistor whose resistance value is increased by a temperature rise. Can be raised.

Embodiment 2 FIG. FIG. 4 is a circuit diagram showing an inverter device according to Embodiment 2 of the present invention. This embodiment includes a half-bridge type inverter circuit having a pair of transistors 2 and 3 connected in series to each other as high-frequency conversion means. A drive circuit connected to the base terminals of the transistors 2 and 3 has a base resistor 14.
15 are connected in series with the secondary windings n2 ′ and n2 of the current transformer 8 and thermistors 12 and 13 that are temperature-dependent variable resistors.

When the resistance value of the thermistors 12 and 13 changes due to a temperature change due to ambient temperature or self-heating,
Induced current flowing through the secondary winding of the current transformer 8 (base terminal of transistor 2 → resistor 14 → thermistor 12 → secondary winding n2 ′ of current transformer 8 and base terminal of transistor 3 → resistor 15 → thermistor 13 → The phase of the secondary winding n2) of the current transformer 8 changes. As a result, the timing of turning on and off the transistors 2 and 3 changes, and the operating frequency changes. How the phase of the secondary current I ₂ of the current transformer 8 changes with the load resistance connected to the secondary current circuit will be described with reference to FIGS.
This is the same as described with reference to FIG.

Embodiment 3 FIG. FIG. 5 is a circuit diagram showing an inverter device according to Embodiment 3 of the present invention. In this embodiment, a transistor 3 as an output switching element and a diode 21 are connected in parallel with a parallel circuit of a coil 23 and a resonance capacitor 24, and are connected to the base terminal of the transistor 3 of a one-stone resonance circuit as high-frequency conversion means. , In series with the base resistor 15 and the secondary winding n2 of the current transformer 8,
The parallel circuit of the capacitor 16 and the thermistor 13 is connected.

When the resistance value of the thermistor 13 increases due to temperature change, the electric charge accumulated in the capacitor 16 increases due to the base current flowing when the transistor 3 is on, and the timing for turning off the transistor 3 is advanced, so that the operating frequency of the inverter device is increased. Grows. Further, when the resistance value of the thermistor 13 decreases, the electric charge stored in the capacitor 16 by the transistor 3 decreases, and the timing of turning off the transistor 3 is delayed, so that the operating frequency of the inverter decreases. In this embodiment, the resistance value of the thermistor 13 changes from a resistance value determined by its ambient temperature at startup to a resistance value determined by self-heating during steady operation. As a result, the operating frequency of the inverter device also automatically transitions from the starting frequency to the steady operating frequency. Further, when the current flowing through the load circuit, that is, the current flowing through the primary winding of the current transformer 8 fluctuates due to the fluctuation of the load of the inverter device, the secondary winding current fluctuates, and the current flowing through the thermistor 13 also fluctuates. As a result, thermistor 1
3, the operating frequency is automatically adjusted.

Embodiment 4 FIG. 6 is a circuit diagram showing an inverter device according to Embodiment 4 of the present invention. This embodiment includes a half-bridge type inverter circuit having a pair of transistors 2 and 3 connected in series to each other as high-frequency conversion means. The variable resistor 17 of the drive circuit in the conventional inverter device shown in FIG. This is an alternative to the thermistor 13 which is a dependent variable resistance element. Also in this embodiment, the resistance value of the thermistor 13 changes from a resistance value determined by its ambient temperature at the time of startup to a resistance value determined by self-heating during steady operation. As a result, the operating frequency of the inverter device also automatically transitions from the starting frequency to the steady operating frequency. Further, when the current flowing through the load circuit, that is, the current flowing through the primary winding of the current transformer 8 fluctuates due to the fluctuation of the load of the inverter device, the secondary winding current fluctuates, and the current flowing through the thermistor 13 also fluctuates. As a result, the resistance value of the thermistor 13 changes and the operating frequency is automatically adjusted.

Embodiment 5 FIG. FIG. 7 is a circuit diagram showing an inverter device according to Embodiment 5 of the present invention. This embodiment includes a half-bridge type inverter circuit having a pair of transistors 2 and 3 connected in series to each other as high-frequency conversion means. Instead of using a temperature-dependent variable resistance element in the drive circuit connected to the base terminals of the transistors 2 and 3, an auxiliary winding n3 is provided in the current transformer 8 ', and the temperature-dependent variable resistance element is used in the auxiliary winding circuit. A certain thermistor 25 is connected.

When the resistance value connected to the auxiliary winding n3 increases, the advance of the current phase (relative to the primary current) generated on the secondary winding side n2'.n2 (switching element drive circuit side) of the current transformer increases. In addition, since the current value increases, the switching timing of the transistors 2 and 3 is advanced, and the operating frequency of the inverter device is increased. Conversely, when the resistance value connected to the auxiliary winding n3 decreases, the advance of the current phase (relative to the primary current) generated on the secondary winding side n2 ′ · n2 (switching element drive circuit side) of the current transformer 8 increases. Since the current becomes smaller and the current value becomes smaller, the switching timing of the transistors 2 and 3 is delayed, and the operating frequency is reduced. Therefore, if a PTC thermistor is used as the thermistor 25, the operating frequency can be automatically changed from a low frequency to a high frequency in response to self-heating or an increase in ambient temperature. The operating frequency can be automatically changed from a high frequency to a low frequency according to the temperature rise.

In this embodiment, the auxiliary winding n3
Although only the temperature-dependent variable resistance element is connected to the variable resistance element, various fixed impedance elements in addition to the temperature-dependent variable resistance element are connected in parallel or in series, and the magnitude and phase of the current flowing through the auxiliary winding are adjusted. In addition, it is possible to set the transition of the operating frequency according to the self-heating or the change in the ambient temperature in various patterns.

Embodiment 6 FIG. FIG. 8 is a circuit diagram showing an inverter device according to Embodiment 6 of the present invention. This embodiment includes a half-bridge type inverter circuit having a pair of transistors 2 and 3 connected in series to each other as high-frequency conversion means. The transistors 2 and 3 are thermally coupled with a thermistor 13 which is a temperature-dependent resistance element used in a drive circuit. The basic operation is the same as in the first embodiment. However, the resistance value of the thermistor 13 changes under the influence of heat generation (that is, loss) of the transistors 2 and 3, and changes the operating frequency of the inverter device. The inverter device changes the current flowing through the transistors 2 and 3 due to power supply voltage fluctuations and load fluctuations, and the loss increases, resulting in excessive heat generation and destruction.
By selecting the characteristics of the thermistor so as to change to an operating frequency at which the loss in the transistors 2 and 3 decreases as the temperature rises, it is possible to obtain an inverter device that prevents a heat generation failure of the transistor due to a load change or the like.

FIG. 9 is a diagram showing an example of thermal coupling between the output switching element and the temperature-dependent resistance element of the inverter device. In the figure, the thermistor 13 and two transistors 2 and 3 are thermally coupled by placing them on one heat radiation fin 25. A resistance value of the thermistor 13 changes due to a temperature change due to heat generation of the transistors 2 and 3, and a thermistor having a characteristic that changes the operating frequency of the inverter device so as to suppress heat generation of the transistors 2 and 3 is selected and configured. Note that, in this embodiment, an example has been described in which the two switching elements connected in series are thermally coupled, but the switching element may be thermally coupled to either one of the two switching elements.

[0032]

According to the first aspect of the present invention, there is provided a self-excited inverter circuit having a drive circuit for driving an output switching element using a current transformer having a load current of a resonance load circuit as an input. Has a temperature-dependent variable resistance element, the resistance value of the temperature-dependent variable resistance element changes due to a change in temperature due to an increase or decrease in self-heating or a change in ambient temperature, and the current on the primary winding side of the current transformer ( Since the phase and magnitude of the current on the secondary winding side compared to the load current phase change, the switching timing of the output switching element changes, and as a result, the operating frequency of the inverter can be changed without a special control circuit. It is possible to control the preheating and lighting frequency of the discharge lamp and to protect against abnormalities such as overcurrent without complicated control circuits. There is a kill effect.

According to a second aspect of the present invention, in a self-excited inverter circuit including a drive circuit for driving an output switching element using a current transformer having a load current of a resonance load circuit as an input, the switching element is driven. Since the circuit has a series circuit of the secondary winding of the current transformer and the temperature-dependent variable resistor connected to the control terminal of the output switching element, the temperature-dependent variable due to the temperature change due to increase / decrease of self-heating and fluctuation of the ambient temperature When the resistance value of the resistance element increases, the advance of the current phase on the secondary winding side compared to the current (load current) phase on the primary winding side of the current transformer increases, and as a result, the operating frequency of the inverter increases. ,
Conversely, when the resistance value is reduced, the advance of the current phase on the secondary winding side is reduced, and as a result, the operating frequency of the inverter is reduced. And the operating frequency can be automatically changed in response to a change in self-heating caused by a change in circuit current due to a load change or the like.

According to a third aspect of the present invention, in a self-excited inverter circuit having a drive circuit for driving an output switching element using a current transformer having a load current of a resonance load circuit as an input, the switching element is driven. The circuit has a secondary winding of the current transformer and a parallel circuit of a capacitor for setting the frequency and a temperature-dependent variable resistance element connected in series with the secondary winding. When the resistance value of the temperature-dependent variable resistance element increases due to a temperature change caused by the temperature increase, the accumulated charge of the capacitor connected in parallel with the element increases, and the timing for turning off the switching element is advanced, so that the operating frequency of the inverter increases, Conversely, when the resistance value decreases,
Since the accumulated charge of the capacitor connected in parallel with the element becomes small and the timing of turning off the switching element becomes late, the operating frequency of the inverter becomes low.
The operating frequency is changed from the starting operating frequency to the steady-state operating frequency without a special control circuit, or the operating frequency is automatically changed in response to self-heating fluctuations caused by circuit current changes due to load fluctuations and the like. There is an effect that can be.

According to a fourth aspect of the present invention, in a self-excited inverter circuit having a drive circuit for driving an output switching element using a current transformer having a load current of a resonance load circuit as an input, the switching element is driven. Since the circuit has an auxiliary winding added to the current transformer and a temperature-dependent variable resistance element connected to the auxiliary winding, if the resistance value increases due to a change in temperature due to an increase or decrease in self-heating or a change in ambient temperature, etc. In addition, the current flowing through the auxiliary winding of the current transformer is reduced, the current flowing through the secondary winding (switching element driving circuit) is increased, and the phase lead for the primary winding current (load current) is also increased. When the operating frequency of the inverter is increased by earliering the timing of turning on and off the element, and when the resistance value decreases, the current flows through the auxiliary winding. In order to increase the current, the current flowing to the secondary winding side is reduced, the phase lead is also reduced, the timing of turning on and off the switching element is delayed, and the operating frequency of the inverter is reduced, so that special control is performed. The operating frequency can be changed from the operating frequency at start-up to the operating frequency at steady state without a circuit, or the operating frequency can be automatically changed in response to changes in self-heating due to changes in circuit current due to load fluctuations, etc. effective.

According to the fifth aspect of the present invention, the high-frequency converting means is constituted by a one-stone resonance circuit comprising a parallel circuit of a coil and a capacitor and an output switching element connected in series to the parallel circuit. Since the drive circuit of the output switching element of the circuit has a temperature-dependent variable resistance element, the resistance value changes due to a temperature change due to an increase or decrease in self-heating or a change in the ambient temperature, and the current (load) on the primary winding side of the current transformer. In order to change the phase and magnitude of the current on the secondary winding side compared to the current) phase, the switching timing of the output switching element of the single-pole resonant circuit changes, and as a result, the operating frequency of the inverter can be reduced without a special control circuit. Since it can be changed, it is possible to control the preheating and lighting frequency of the discharge lamp and to protect against abnormalities such as overcurrent without complicated control circuits. There is an effect that can be.

According to the sixth aspect of the present invention, the high-frequency converting means is constituted by a half-bridge type inverter circuit comprising a pair of output switching elements connected in series with each other, and at least one of the output switching elements of the inverter circuit. Since the drive circuit has a temperature-dependent variable resistance element, the resistance value changes due to a temperature change due to an increase or decrease in self-heating or a change in the ambient temperature, and is compared with the current (load current) phase on the primary winding side of the current transformer. In order to change the phase and magnitude of the current on the secondary winding side, the switching timing of the output switching element of the half-bridge type inverter circuit in which the temperature-dependent variable resistance element is connected in the drive circuit changes, and as a result, a special Since the operating frequency of the inverter can be changed without a control circuit, it is possible to control the preheating / falling frequency of the discharge lamp. And, a protection operation against the abnormality such as overcurrent, there is an effect that can be achieved without complicated control circuits.

According to the seventh aspect of the present invention, the temperature-dependent variable resistance element that changes the operating frequency of the inverter device due to the temperature fluctuation is an NTC thermistor. When the temperature rises, the resistance value decreases, and the operating frequency of the inverter device changes from the frequency at the original resistance value to the frequency at the reduced resistance value. Conversely, when the temperature of the NTC thermistor falls, the resistance value increases. Become
Since the operating frequency of the inverter is changed from the frequency of the original resistance value to the frequency of the increased resistance value, the operation frequency of the inverter device can be automatically changed.

According to the eighth aspect of the present invention, the temperature-dependent variable resistance element that changes the operating frequency of the inverter device due to the temperature fluctuation is a PTC thermistor. When the temperature rises, the resistance value increases, and the operating frequency of the inverter device is changed from the frequency at the original resistance value to the frequency at the increased resistance value. Conversely, PTC
As the temperature of the thermistor decreases, its resistance value decreases, and the operating frequency of the inverter changes from the frequency at the original resistance value to the frequency at the reduced resistance value.
There is an effect that the operating frequency of the inverter device can be automatically changed.

According to the ninth aspect of the present invention, the temperature-dependent variable resistance element for changing the operating frequency of the inverter device due to the temperature fluctuation is thermally coupled to the output switching element. Accordingly, the temperature of the temperature-dependent variable resistance element fluctuates, and the resistance value changes, thereby changing the operation frequency of the inverter device and automatically changing the operation frequency to the operation frequency corresponding to the heat generation amount of the output switching element. Therefore, there is an effect that the operating frequency can be changed to a safe operating frequency in which the inverter device does not fail according to the heat generation amount of the output switching element.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an inverter device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a drive circuit portion of the inverter device.

FIG. 3 is a diagram showing a phase and a waveform of a drive current of the inverter device.

FIG. 4 is a circuit diagram showing an inverter device according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing an inverter device according to Embodiment 3 of the present invention.

FIG. 6 is a circuit diagram showing an inverter device according to Embodiment 4 of the present invention.

FIG. 7 is a circuit diagram showing an inverter device according to a fifth embodiment of the present invention.

FIG. 8 is a circuit diagram showing an inverter device according to Embodiment 6 of the present invention.

FIG. 9 is a diagram showing an example of thermal coupling between an output switching element and a temperature-dependent resistance element of the inverter device.

FIG. 10 is a circuit diagram showing a conventional inverter device.

FIG. 11 is a circuit diagram showing another conventional inverter device.

[Explanation of symbols]

1 DC power supply, 3 transistor, 5 discharge lamp, 6 capacitor, 7 choke coil, 8 'current transformer,
13 Thermistor.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koji Shibata 5-1-1, Ofuna, Kamakura City, Kanagawa Prefecture Inside Mitsubishi Electric Lighting Co., Ltd. (72) Inventor Tetsuya Kobayashi 5-1-1, Ofuna, Kamakura City, Kanagawa Prefecture Mitsubishi Electric Lighting Co., Ltd.

Claims (9)

[Claims] 1. A high-frequency converter having a DC power supply, at least one output switching element for converting a DC voltage of the DC power supply into a high-frequency voltage by switching, a choke coil to which the high-frequency voltage of the high-frequency converter is applied,
A self-excited inverter device including: a resonance load circuit including a capacitor and a discharge lamp; and a drive circuit that drives an output switching element using a current transformer that receives a load current of the resonance load circuit as an input. An inverter device having a temperature-dependent variable resistance element connected to a control terminal of a switching element. 2. A high-frequency converter having a DC power supply, at least one output switching element for converting a DC voltage of the DC power supply into a high-frequency voltage by switching, and a choke coil to which the high-frequency voltage of the high-frequency converter is applied.
A self-excited inverter device comprising: a resonance load circuit including a capacitor and a discharge lamp; and a drive circuit that drives an output switching element using a current transformer that receives a load current of the resonance load circuit as an input. An inverter device comprising a series circuit of a secondary winding of a current transformer and a temperature-dependent variable resistance element connected to a control terminal of the output switching element. 3. A high-frequency converter having a DC power supply, at least one output switching element for converting a DC voltage of the DC power supply into a high-frequency voltage by switching, and a choke coil to which the high-frequency voltage of the high-frequency converter is applied.
A self-excited inverter device comprising: a resonance load circuit including a capacitor and a discharge lamp; and a drive circuit that drives an output switching element using a current transformer that receives a load current of the resonance load circuit as an input. Secondary winding of current transformer and its 2
An inverter device, which is connected in series with a next winding and has a parallel circuit of a frequency setting capacitor and a temperature-dependent variable resistance element. 4. A high-frequency converter comprising a DC power supply, a pair of output switching elements connected in series to convert a DC voltage of the DC power supply into a high-frequency voltage by switching, and a choke to which the high-frequency voltage of the high-frequency converter is applied. A self-excited inverter device comprising: a resonance load circuit including a coil, a capacitor, and a discharge lamp; and a drive circuit that drives an output switching element using a current transformer that receives a load current of the resonance load circuit as an input. An inverter device comprising: an auxiliary winding added to the current transformer; and a temperature-dependent variable resistance element connected to the auxiliary winding. 5. The high-frequency conversion means comprises a one-stone resonance circuit including a parallel circuit of a coil and a capacitor and an output switching element connected in series to the parallel circuit,
The driving circuit for a switching element of the one-stone resonance circuit includes a temperature-dependent variable resistance element.
The inverter device according to 2 or 3. 6. A high-frequency conversion means comprising a half-bridge type inverter circuit comprising a pair of output switching elements connected in series to each other, wherein at least one of the output switching elements of the inverter circuit has a temperature-dependent variable circuit. 4. The inverter device according to claim 1, further comprising a resistance element. 7. The inverter device according to claim 1, wherein the temperature-dependent variable resistance element is an NTC thermistor. 8. The inverter device according to claim 1, wherein the temperature-dependent variable resistance element is a PTC thermistor. 9. The inverter device according to claim 1, wherein the temperature-dependent variable resistance element is thermally coupled to the output switching element.