JPH0591749A - Inverter - Google Patents

Abstract

PURPOSE:To prevent a stress to a switching element. CONSTITUTION:A switching element Q1 is closed after a switching element Q2 is opened by feeding back by a feed-back circuit FB1. The element Q2 is driven by a pulse signal of an oscillator OS. The drive of the element Q2 is stopped until the element Q1 is opened by a feed-back circuit FB2. The element Q2 is forcibly driven to be closed after the element Q1 is opened by a feed-back circuit FB3. Accordingly, current is prevented from flowing in a diode D1 connected in parallel with the element Q1 before the element Q2 is closed, and a reverse recovery current of the diode D1 is prevented from being fed as a power source short-circuit current when the element Q2 is closed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called self-excited control system inverter device used in a discharge lamp lighting device or the like.

[0002]

2. Description of the Related Art An example of a conventional inverter device of this type is shown in FIG. 7, and its configuration and operation will be described below (see Japanese Patent Application No. 1-182850). This inverter device
As shown in FIG. 7, a DC power supply E ₁ (which may be an AC power supply converted into a DC voltage) may be connected to a main switching element Q ₁ composed of transistors via a power switch SW.
By connecting a series circuit of Q ₂ , each main switching element Q ₁ ,
It has a half-bridge structure in which diodes D ₁ and D ₂ are connected in parallel to Q ₂ , respectively, and an LC resonance circuit including an inductor L ₁ and a capacitor C ₁ and a load LD such as a discharge lamp.
Of the main switching element Q ₁
Further, a vibration circuit VB is connected in parallel with the vibration circuit VB, and a starting circuit ST for starting the main switching element Q ₂ is also provided. The starting circuit ST comprises a resistor R ₈ , a capacitor C ₄ , a diode D ₄ and a voltage response switching element Q ₅ . It should be noted that the starter circuit is not shown in the example circuits of FIGS. 4 and 6 described later.

The inductor L ₁ is composed of a primary winding n ₁ and secondary windings n ₂ and n ₃ . The primary winding n ₁ constitutes a vibration circuit VB, one end of the secondary winding n ₂ is connected to the base terminal of the main switching element Q ₁ by the resistor R _{1, and the} other end is connected to the emitter terminal of the main switching element Q _1. It is connected. That is, the secondary winding n ₂ is operative to return the oscillating current flowing through the inductor L ₁ to the base terminal of the main switching element Q _1, turns on driving the main switching element Q ₁ after the main switching element Q ₂ Off .. On the other hand, the secondary winding n ₃ is connected to the drive circuit DR ₁ through the rectifying diode D ₃ , operates so as to feed back a part of the output signal of the vibration circuit VB to the drive circuit DR ₁ , and the main switching element Q ₂ Drive is stopped until the main switching element Q ₁ is turned off.

The oscillator circuit OS has two standard C-MOSs.
It is composed of an astable multivibrator composed of gates IC ₁ and IC ₂ (4069, 4049, etc.), a capacitor C ₂ and resistors R ₄ and R _5, and generates a pulse signal of a constant cycle. The oscillation cycle T of the oscillation circuit OS is determined by the following equation, and the duty of the oscillation output is 50%. T≈2.2C ₂ × R ₅ Here, the oscillation period T of the oscillation circuit OS is set shorter than the natural oscillation period of the oscillation circuit VB.

Drive circuit DR₁Is output from the oscillator circuit OS
The main switching element Q in response to the pulse signal₂To
Two transistors connected in series that are driven on.
Star Q₃, Q_FourAnd resistance R₂, R₃, R₇Composed of and
There is. Drive circuit DR₁And the power supply of the oscillation circuit OS is direct current
Power E₁Resistance R₆And capacitor C₃Can be split with
Obtained by (DC power supply E₂). Capacitor C ₃
Is for smoothing.

FIG. 8 shows a time chart of each part of the inverter device shown in FIG. FIG. 3A shows the waveform of the oscillating current I ₁ flowing in the oscillating circuit VB, and I _Q1 , I _Q2 , I _D1 ,
I _D2 represents the collector current flowing through the transistors Q ₁ and Q ₂ and the current flowing through the diode, respectively. FIG. 11B shows a voltage waveform of the output terminal a of the oscillation circuit OS. The period t ₁₁ is “High” level (level of the DC power supply E ₂ ) and the period t ₁₂ is “Low” level (ground level). Is becoming FIG (c) shows the induced voltage V _n2 of the secondary winding n ₂ of the inductor L _1, FIG. (D) shows the induced voltage V _n3 of the secondary winding n ₃ of the inductor L _1. FIG. _6E shows the output voltage of the diode D ₃ , that is, the base voltage V _BE2 of the main switching element Q ₂ .

Next, the operation will be described with reference to FIG.
It When the power switch SW is turned on, first the start circuit ST
Operates and the main switching element Q₂Turns on. Start-up
Since the circuit ST is a well-known circuit that is often used in the past,
The description is omitted. Main switching element Q₂Is turned on
And DC power supply E₁→ Power switch SW → Capacitor C ₀
→ Vibration circuit VB → Main switching element Q₂→ DC power supply E
₁Current flows through the path of the inductor L₁Secondary winding n₃
A voltage is induced in the direction indicated by the arrow in FIG. At this time
At the same time, the power supply voltage of the oscillator circuit OS is DC power supply E.₂More companion
Since it has been supplied, the operation has started and the transistor Q
₃Turns on and the secondary winding n₃More diode D₃，
Resistance R₇, Transistor Q₃And resistance R₂Through the
Switching element Q₂The base current is supplied to the
The oscillation operation of the barter device is started. Inda at this time
Kuta L₁Secondary winding n₂Is the main switching element Q₁of
Apply reverse bias voltage between base and emitter
The main switching element Q is wound with various polarities.₁Is off
Stay in the state.

Eventually, the output terminal a of the oscillator circuit OS is
Interval t₁₁Changes from "High" level to "Low" level after
And transistor Q₃Off, transistor Q_FourIs on
And the main switching element Q₂Base emitter
The main switching element Q₂Is off
It At this time, inductor L₁Oscillating current I₁Is
Since it tries to flow in the same direction, diode D₁Is on
And the current I_D1Flows. On the other hand, the main switching element
Q₂When the switch is turned off, the main switching element Q ₂This
Inductor L due to the reduced inductor current₁Residual
Since the inductance produces the opposite induced voltage,
Kuta L₁Secondary winding n₂The polarity of the induced voltage of
Switching element Q₁Forward bias. As a result,
Flow I_D1Becomes zero, the capacitor C₀Power source
Main switching element Q₁Collector current I_Q1Flows
It At this time, inductor L₁Core goes to saturation flux
And is linearly magnetized. Eventually, the core reaches saturation flux
Then inductor L₁The inductance value of
Direction, and as a result, the main switching element Q₁The
Rector current I_Q1The change over time becomes infinite. That is,
Collector current I_Q1Is the base current I_b1H_feDouble (I_Q1= I
_b1× h_fe), The main switching element Q₁Is unsaturated
And inductor L₁Each winding n₁~ N₃Induced voltage
Is reduced, the base current being supplied is also reduced.
Switching element Q₁Turns off.

In this conventional example, the main switching element is
Child Q₂Drive circuit DR₁Inductor L₁Secondary winding n
₃Since the resonance signal is fed back more, the main switching element
Child Q ₁Is turned off, then the drive circuit DR₁Secondary winding n
₃Is applied. At this time, the output of the oscillator circuit OS is
Already inverted from “Low” level to “High” level
Transistor Q₃Is on, transistor Q_FourBut
It turns off and the main switching element Q₂Is forward biased
Main switching element Q₂Turns on. Because
In this conventional example, the main switching element Q₁But
After surely turning off, the main switching element Q₂Is the oscillation time
Since it is turned on by the output of the path OS, the main switching element
Child Q₁, Q₂Never turn on at the same time. Main switch
Element Q₁After the inductor is turned off, the inductor L₁Flow
Oscillating current I₁Try to flow in the same direction,
Iodo D₂Turns on and the current I_D2Is the vibration circuit VB →
Capacitor C₀→ DC power supply E₁Flowing in a loop. Electric current
I_D2After the power becomes zero, the DC power supply E₁More capacitors
C₀→ Vibration circuit VB → Main switching element Q₂→ DC power
Source E₁Collector current I in the loop_Q2Flows. Below, above
The oscillating operation of the inverter is continued by the operation described above.

[0010]

[SUMMARY OF THE INVENTION However, the conventional example described above, the variations in characteristics of the main switching element Q _1, turned off the main switching element Q ₁ is early, the current I _D2 becomes zero Oscillation circuit OS even after
There is a case that the output of is still "Low" level and not inverted to "High" level. In such a case, there is a problem that a short-circuit current flows and stress on the main switching elements Q ₁ and Q ₂ increases. This point will be described with reference to FIG. 9A shows the waveforms of the currents I _D1 and I _Q1 , FIG. 9B shows the waveforms of the currents I _D2 and I _Q2 , and FIG. 9C shows the output from the output terminal a of the oscillator circuit OS. The waveform of the signal is shown in FIG. 7D, which shows the secondary winding n ₃ of the inductor L _1.
Shows the waveform of the induced voltage V _n3 of the inductor L ₁ , the waveform of the induced voltage V _n2 of the secondary winding n ₂ of the inductor L ₁ is shown, and the waveform (f) of the same is the base voltage of the main switching element Q ₂ . V _BE2 is shown.

That is, as described above, the pulse signal is "Hi
Before switching to gh "level, main switching element Q₁Is o
If the output is off, the output of the oscillation circuit OS is "Low".
 The transistor Q₃Is off
Langista Q_FourTurns on and the main switching element Q₂
Remains off, the oscillating current I₁Is originally
Main switching element Q₂Figure 9 where you should pass
As shown in (a), the diode D₁→ Capacitor C₀
→ Current I in the loop of the vibration circuit VB_D1Flow as and then
The output of the oscillator circuit OS is higher than “Low” level.
Diode D from time A₁Of reverse recovery time
Between (diode D₁Until it turns off), FIG. 9 (a),
As shown in (b), the DC power source E₁→ Diode D₁→
Main switching element Q₂Short circuit current I in the loop_XFlows
It As a result, the main switching element Q ₁, Q₂Su
There was a problem that tresses increased.

An object of the present invention is to prevent simultaneous turning-on of a pair of main switching elements with a simple structure, and to allow reverse recovery current of a diode connected in antiparallel to the main switching element to flow as a power supply short-circuit current through the main switching element. And to provide a highly reliable inverter device.

[0013]

In the inverter device of the present invention, a pair of main switching elements are connected in series between both ends of a DC power source, and a pair of diodes are respectively connected in antiparallel to the pair of main switching elements. ing. An oscillating circuit including an LC resonance circuit and a load is connected in parallel to one of the pair of main switching elements. Further, an oscillating circuit that generates a pulse signal of a constant cycle is provided, and a drive circuit that turns on the other of the pair of main switching elements in response to the pulse signal generated from the pulse oscillating circuit is provided
Further, first to third feedback circuits are provided.

The first feedback circuit feeds back the oscillating current or the oscillating voltage generated in the oscillating circuit to one of the pair of main switching elements, thereby turning off the other of the pair of main switching elements. One of them is turned on. The second feedback circuit feeds the oscillating current or the oscillating voltage generated in the oscillating circuit back to the drive circuit, thereby stopping the driving of the other of the pair of main switching elements until one of the pair of main switching elements is turned off. ..
The third feedback circuit feeds an oscillating current or an oscillating voltage generated in the oscillating circuit back to the drive circuit, thereby making a pair of periods during which a pulse signal is generated from the oscillating circuit after turning off at least one of the pair of main switching elements. The other main switching element is forcibly turned on.

[0015]

According to the structure of the present invention, the third feedback circuit feeds back the oscillating current or the oscillating voltage generated in the oscillating circuit to the drive circuit, so that a pair of main signals is generated before the pulse signal is generated from the oscillating circuit. Even when one of the switching elements is turned off, at least one of the pair of main switching elements is forcibly turned on for a period of time after one of the pair of main switching elements is turned off until a pulse signal is generated from the oscillation circuit. You can As a result, it is possible to prevent current from flowing in the diode connected in antiparallel to one of the pair of main switching elements before the other of the pair of main switching elements is turned on, and the reverse recovery current of the diode is It is possible to prevent the power supply short circuit current from flowing when the other of the switching elements is turned on.

[0016]

Embodiments of the present invention will now be described with reference to the drawings. [First Embodiment] FIG. 1 is a block diagram of an inverter device according to a first embodiment of the present invention. In FIG. 1, main switching elements Q ₁ and Q ₂ formed of, for example, bipolar transistors are connected in series at both ends of a DC power source E ₁ , and diodes D ₁ and Q ₂ are connected in the reverse direction to the main switching elements Q ₁ and Q ₂ , respectively. D ₂ is connected. At least one of the main switching elements Q ₁ and Q ₂ is connected to an LC resonance circuit KS including an inductor and a capacitor and a vibration circuit VB including a load LD in the main switching element Q ₁ in this circuit. The oscillating current (which may be an oscillating voltage) flowing in the oscillating circuit VB is supplied to the first feedback circuit FB ₁
By by feeding back to the base terminal is a control terminal of the main switching element Q _1, for turning on and off the main switching element Q ₁ at a predetermined cycle determined by the oscillating current (or oscillating voltage). In this case, the main switching element Q ₁ is turned on after the main switching element Q ₂ is turned off.

On the other hand, the main switching element Q ₂ has an oscillator circuit OS which continuously generates a pulse signal of a constant cycle by itself without receiving a pulse from another, and a drive circuit which operates by the signal of the oscillator circuit OS. It is driven on by DR ₁ . The aforementioned drive circuits DR _1, stops driving of the main switching element Q ₂ by feedback oscillating current generated in the oscillating circuit VB (or oscillating voltage) to the drive circuit DR ₁ to the main switching element Q ₁ is turned off Second
Feedback circuit FB ₂ is attached, and the oscillating current (or oscillating voltage) generated in the oscillating circuit VB is supplied to the drive circuit DR.
_A third feedback circuit FB ₃ is provided for forcibly driving the main switching element Q ₂ on by turning back the main switching element Q ₁ until the pulse signal is generated from the oscillation circuit OS after the main switching element Q ₁ is turned off. .. The second and third
The output signals of the feedback circuits FB ₂ and FB ₃ can also be fed back to the oscillation circuit OS.

With such a configuration, since the oscillating current (or oscillating voltage) generated in the oscillating circuit VB is fed back to the driving circuit DR ₁ by the third feedback circuit FB ₃ , a pulse signal is generated from the oscillating circuit OS. Even when the main switching element Q ₁ is turned off before the generation, the main switching element Q ₂ is forcibly turned on for at least the period after the main switching element Q ₁ is turned off until the pulse signal is generated from the oscillation circuit OS. Can be made As a result, it is possible to prevent a current from flowing through the diode D ₁ that is connected in antiparallel with the main switching element Q ₁ before the main switching element Q ₂ is turned on, and the reverse recovery current of the diode D ₁ is the main switching element. When Q ₂ is turned on, it can be prevented from flowing as a power supply short-circuit current.

The inverter device will be described below with reference to the specific circuit shown in FIG. The inverter circuit of this embodiment is obtained by adding a feedback circuit FB ₃ to the conventional example shown in FIG. 7, and other configurations are similar to those of FIG. 7. That is, by controlling the input signal to the drive circuit DR ₁ by the feedback circuit FB _3, before the pulse signal, that is, the ON signal of the main switching element Q ₂ , that is, the “High” level signal is output from the oscillation circuit OS, Even when the main switching element Q ₁ is turned off, the input signal to the drive circuit DR ₁ is forced during the period from when the main switching element Q ₁ is turned off until the pulse signal from the oscillation circuit OS becomes “High” level. The main switching element Q ₂
To the ON signal (that is, a “High” level signal).

Feedback circuit FB₃Is the resistance R₈， Zenada
Iodo ZD₁And standard C-MOS gate
AND circuit AN₁, Inversion circuit IN₁, OR circuit OR₁
It is composed of Resistance R₈And Zener diode ZD
₁Series circuit is diode D ₃Cathode and ground
Connected between the line and the resistance R₈And Zener Daio
De ZD₁The voltage at the connection point is AND circuit AN₁One of
It is input to the force terminal b. Zener diode ZD₁A
AND circuit AN₁For input protection. AND circuit
AN₁Output from the oscillator circuit OS to the other input terminal c of
Inverting circuit for pulse signal₁The signal inverted by
I will be forced. And AND circuit AN₁Output terminal d signal
Signal and the signal at the output terminal a of the oscillator circuit OS are OR circuit OR
₁Is input to the OR circuit OR₁Signal from the output terminal e of
In the signal of the output terminal a of the oscillation circuit OS in the conventional example.
Instead, the drive circuit DR₁Is being supplied to.

FIG. 3 shows a time chart of each part in the above-mentioned configuration. FIG. 3A shows the waveforms of the current I _D1 and the current I _Q1 , and FIG. 3B shows the current I _D2 and the current I _Q1 .
The waveform of _Q2 is shown, the figure (c) shows the signal voltage waveform of the output terminal a of the oscillation circuit OS, and the figure (d) shows the diode D _3
Shows the waveform of the output voltage V _D3 of the AND circuit, (e) shows the signal voltage waveform of one input terminal b of the AND circuit AN ₁ , and (f) shows the waveform of the base voltage of the main switching element Q _2. shown, FIG. (g) shows the waveform of the induced voltage V _n2 of the secondary winding n ₂ of the inductor L _1, and FIG. (h) inductor L ₁
Indicates the secondary winding waveform of the induced voltage V _n3 of n _3, FIG. (I) represents the other signal voltage waveform at the input terminal c of the AND circuit AN _1, FIG. (J) the AND circuit AN ₁ The signal voltage waveform at the output terminal d of the OR circuit OR is shown in FIG.
The signal voltage waveform of the output terminal e of ₁ is shown.

Next, the operation of the inverter device shown in FIG. 2 will be described with reference to FIG. When the power switch SW is turned on, the starting circuit ST first operates, and thereafter, the main switching element Q ₂ is turned on, the main switching element Q ₁ is turned off, and the output voltage of the output terminal a of the oscillation circuit OS is higher than the “High” level. The main switching element Q ₂ is turned off and the main switching element Q ₁ is turned on by inversion to the “Low” level, and the oscillation operation of the inverter device continues, as in the conventional example shown in FIG. 7.

Then, for example, as shown in FIG. 3, the ON period of the main switching element Q ₁ becomes long and the oscillation circuit O
A period T during which the main switching element Q ₁ is turned off after the output of S is inverted from “Low” level to “High” level.
_In the case of ₁ , the feedback circuit FB ₃ has no effect, and the feedback circuit FB ₃ has no effect.
The input signal (the signal at the output terminal e of the OR circuit OR ₁ ) to the drive circuit DR ₁ shown in FIG.
Becomes the same as the output signal of, as in the conventional example, after the main switching element Q ₁ off, the drive circuit DR ₁ to the secondary winding n ₃
Is applied, the transistor Q ₃ is turned on, the transistor Q ₄ is turned off, and the main switching element Q ₂
Is forward biased, and the main switching element Q ₂ is turned on.

And time t₁Then, the output signal of the oscillator circuit OS
When the signal inverts from the "High" level to the "Low" level,
Main switching element Q₂Turns off and diode D₁
Conducts, and then the main switching element Q₁Is on
It Next, time t₁From time t_FourUntil period T₂No
Sea urchin main switching element Q₁ON time is shortened,
The output of the oscillator circuit OS is higher than “Low” level.
Time t₃Previous time t₂Mainly on switching
Element Q₁Is turned off, that is, the main switch
Holding element Q₁Is turned off, the current I_D2After is zero
In addition, the output terminal a of the oscillation circuit OS is at "Low" level.
In such a case, time t₂Than time t₃Between
Feedback circuit FB₃The operation of will be described. AND circuit A
N₁One input terminal c is an output terminal a of the oscillation circuit OS.
Since the inversion signal of is input, as shown in FIG.
At “High” level, time t₃At “Hig
Invert from “h” level to “Low” level.
Circuit AN₁The other input terminal b of the main switching element
Child Q₁Is off, diode D₃Output voltage V_D3
(See Fig. 3 (d)) has a positive voltage, so
t₂Than time t_FourAt the output terminal a of the oscillator circuit OS
Is shown from "High" level to "Low" level
The "High" level is maintained as shown in 3 (e). did
Therefore, period T₂In the AND circuit AN₁Output of
As shown in FIG. 3 (j), the signal at the terminal d is the main switch.
Element Q₁Is off at time t₂More oscillator circuit output
Force signal is inverted from "Low" level to "High" level
Time t ₃Remains at “High” level, and remains at “Low” during other periods
 "Keep the level.

The input signal to the drive circuit DR ₁ , that is, the signal at the output terminal e of the OR circuit OR ₁ is shown in FIG.
As shown in FIG. 3, the OR circuit OR ₁ outputs the logical sum of the signal at the output terminal d of the AND circuit AN ₁ and the signal at the output terminal a of the oscillator circuit OS, so that the main switching element Q ₁
After being turned off, the signal surely inverts from the “Low” level to the “High” level, and thereafter, at time t ₄ , the signal at the output terminal a of the oscillator circuit OS inverts from the “High” level to the “Low” level. Invert from “High” level to “Low” level.

Feedback circuit FB as described above₃By the action of
Time t₂Main switching element Q ₁After turn off
Is the drive circuit DR₁The input signal to the
And the main switching element Q₂Is forward biased
Since it is turned on, the main switch is turned on as in the conventional example shown in FIG.
Holding element Q₁Turns off and current I_D2Even after the
Main switching element Q₂Is turned off
DC power supply E ₁→ Diode D₁→ Main Sui
Touching element Q₂Prevents excessive short circuit current in the
Can be stopped. In other words, this example is a drawback of the conventional example.
Main switching element Q₂When forward current flows to
The output of the oscillator circuit OS remains at the “Low” level.
, The main switching element Q₂Is turned off.
DC power source E due to₁→ Diode D₁→ Main Sui
Touching element Q₂The short circuit current of the
It can be stopped and the main switching element Q₁, Q₂Of stress
Occurrence can be prevented.

[Second Embodiment] FIG. 4 shows a block diagram of an inverter device according to a second embodiment of the present invention. In this embodiment, not the oscillating current of the oscillating circuit VB but the oscillating voltage is fed back to the output terminal of the oscillating circuit OS to prevent the main switching elements Q ₁ and Q ₂ from being simultaneously turned on. Is applied.

[0028] In this embodiment, the main switching element a bipolar transistor in Q _1, the main switching element Q is adopted MOS · FET to _2, the main switching element Q ₂ resistor R ₁₁ connected in parallel to the , R ₁₂ in series, the oscillating voltage of the oscillating circuit VB, in this case, the divided voltage of the drain-source voltage V _Q2 of the main switching element Q ₂ is detected, which is inverted by the inverting circuit IN ₂ and then oscillated. in addition to the aND circuit aN ₂ together with the signal of the output terminal a of the circuit OS, and inputs a signal output terminal f of the aND circuit aN ₂ to the OR circuit OR _1. With this configuration, the main switching element Q ₁ is turned off and the resistor R ₁₁ ,
When the voltage at the connection point of R ₁₂ drops to the ground level, the AND circuit AN ₂ opens and the pulse signal from the oscillation circuit OS is added to the drive circuit DR ₂ through the OR circuit OR ₁ and the main switching element Q 2 ₂ is turned on. The drive circuit DR ₂ is composed of a non-inverter buffer.

In this circuit, the anti-parallel diode for the main switching element Q ₂ is not shown,
It exists as a parasitic diode in MOS FET. Also in this embodiment, since the main switching element Q ₁ is turned off and then the main switching element Q ₂ is turned on as in the conventional example shown in FIG. 7, the main switching elements Q ₁ and Q ₂ are simultaneously operated. It can be prevented from turning on.

Also in the above configuration, the feedback circuit FB₃To
By connecting as shown in FIG. 4, the embodiment shown in FIG.
The same effect as can be obtained. With the above configuration
FIG. 5 shows a time chart of each part in FIG. Figure 5 (a)
Is the current I_D1And current I_Q1Shows the waveform of
Current I_D2And current I_Q2Shows the waveform of
The signal voltage waveform of the output terminal a of the oscillation circuit OS is shown in FIG.
(D) is an AND circuit AN ₁Signal voltage of one input terminal b
The pressure waveform is shown in FIG.₁The other of
The signal voltage waveform at the input terminal c is shown in FIG.
Circuit AN₁The signal voltage waveform of the output terminal d of
(G) is an AND circuit AN₂Signal voltage waveform of output terminal f
FIG. 6 (h) shows an OR circuit OR.₁Output terminal e
Shows the signal voltage waveform. Figure (i) shows the main switching element Q.
₂Gate voltage V_GS2Figure (j) shows the inductor
L₁Secondary winding n₂Induced voltage V_n2Shows the waveform of
(K) is the main switching element Q₂Drain voltage V_Q2of
The waveform is shown.

Next, the operation will be described with reference to FIG. Continuation of the oscillation operation of the inverter device and the feedback circuit F due to the repeated operation in which the main switching element Q ₂ is on and the main switching element Q ₁ is off and the main switching element Q ₂ is off and the main switching element Q ₁ is on.
The operation of B ₃ is similar to that of the embodiment shown in FIG.
As shown in (i), when the main switching element Q ₁ and the diode D ₁ are off, that is, when the currents I _D2 and I _Q2 are flowing, the gate voltage V _GS2 of the main switching element Q ₂ is always at the “High” level. next, the DC power source E ₁ → diode D ₁ → can prevent the occurrence of excessive short-circuit current of the main switching element Q ₂ loop, the main switching element Q _1, Q
_{It is possible} to prevent the occurrence of stress on ₂ .

[Third Embodiment] FIG. 4 shows a block diagram of an inverter device according to a second embodiment of the present invention. This embodiment differs from the embodiment of FIG. 4 in that the main switching element Q ₂
The main switching element Q ₂ is turned on by connecting the drain terminal of the main switching element Q _{1 to} the base terminal of the main switching element Q ₁ and connecting the diode D ₅ between the emitter and the base of the main switching element Q ₁ in the forward direction. The present invention is applied to an inverter device having a structure in which the main switching element Q ₁ is always turned off.
The points other than the above are the same as those of the embodiment of FIG.

This embodiment has the same effect as that of the embodiment shown in FIG. 2 and can provide a more reliable inverter device.

[0034]

According to the inverter device of the present invention, since the oscillating current or the oscillating voltage generated in the oscillating circuit is fed back to the drive circuit by the third feedback circuit, before the pulse signal is generated from the oscillating circuit. Even when one of the pair of main switching elements is turned off, the other of the pair of main switching elements is forcibly turned on for at least the period until the pulse signal is generated from the oscillation circuit after turning off one of the pair of main switching elements. It can be driven. As a result, it is possible to prevent current from flowing in the diode connected in antiparallel to one of the pair of main switching elements before the other of the pair of main switching elements is turned on, and the reverse recovery current of the diode is It is possible to prevent the power supply short circuit current from flowing when the other of the switching elements is turned on. Therefore, it is possible to prevent the occurrence of stress on the main / main switching element with a simple configuration.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing a specific configuration of the inverter device according to the first embodiment of the present invention.

FIG. 3 is a time chart of each part of the inverter device according to the first embodiment.

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

FIG. 5 is a time chart of each part showing the operation of the inverter device of the second embodiment.

FIG. 6 is a circuit diagram showing a specific configuration of an inverter device according to a third embodiment of the present invention.

FIG. 7 is a circuit diagram showing a configuration of a conventional inverter device.

FIG. 8 is a time chart of each part showing the operation of the conventional inverter device.

FIG. 9 is a time chart of each part showing a drawback of the conventional inverter device.

[Explanation of symbols]

E ₁ DC power supply Q ₁ , Q ₂ Main switching element D ₁ , D ₂ Diode VB Oscillation circuit KS LC resonance circuit LD load FB ₁ First feedback circuit FB ₂ Second feedback circuit FB ₃ Third feedback circuit OS oscillation Circuit DR ₁ drive circuit

Claims (1)

[Claims] 1. A DC power supply, a pair of main switching elements connected in series between both ends of the DC power supply, a pair of diodes respectively connected in anti-parallel to the pair of main switching elements, an LC resonance circuit, and An oscillating circuit composed of a load and connected in parallel to one of the pair of main switching elements, an oscillating circuit for generating a pulse signal of a constant period, and the pair of main switching elements in response to a pulse signal generated from the pulse oscillating circuit. And a drive circuit for driving the other of the pair of ON switching elements, and an oscillating current or an oscillating voltage generated in the oscillating circuit is fed back to one of the pair of main switching elements to turn off the other of the pair of main switching elements. A first feedback circuit that turns on one of the switching elements, and an oscillating current or an oscillating current generated in the oscillating circuit. A second feedback circuit that stops driving the other of the pair of main switching elements by returning the pressure to the drive circuit until one of the pair of main switching elements is turned off; and a vibration generated in the vibrating circuit. By feeding back the current or the oscillating voltage to the drive circuit, the other of the pair of main switching elements is forcibly turned on for at least the period until the pulse signal is generated from the oscillation circuit after turning off one of the pair of main switching elements. An inverter device comprising a third feedback circuit for driving.