JPH07108093B2 - Inverter device - Google Patents

Description

Description: TECHNICAL FIELD The present invention has a pair of switching elements, and an insulating element such as a transformer from an oscillation circuit having the same potential as one switching element to a drive circuit of another switching element having a different potential. The present invention relates to an inverter device configured to perform signal transmission without intervention.

(Background Art) FIG. 6 is a circuit diagram of a conventional inverter device. A series circuit of switching elements Q ₁ and Q ₂ is connected to both ends of the DC power supply V. The switching elements Q ₁ and Q ₂ are composed of, for example, transistors in which diodes are connected in antiparallel. The switching elements Q ₁ and Q ₂ are driven on / off by the outputs V ₁ and V ₂ of the drive circuits 1 and ₂ , respectively. A parallel circuit of a load Z and a capacitor C ₀ is connected to both ends of one switching element Q ₂ via an inductance L ₀ . As the load Z, for example, a discharge lamp is used.

A series circuit of a resistor R ₁ and a capacitor C ₁ connected to both ends of the switching element Q ₁ is a power supply circuit of the upper drive circuit 1, and a series circuit of a resistor R ₂ and a capacitor C ₂ connected to both ends of the DC power supply V. Is a power supply circuit of the lower drive circuit 2. The oscillating circuit 3 fed by the capacitor C ₂ is
Two signals V _A and V _B are output. The signal V _A is input to the drive circuit 2, and the signal V _B is passed through the signal transmission circuit,
It is input to the drive circuit 1.

The signal transmission circuit includes transistors Tr ₁ and Tr ₂ , a Zener diode ZD, and resistors R _{3 to} R ₆ , and performs signal transmission without using an insulating element such as a transformer. The transistor Tr ₂ of the signal transmission circuit has resistors R ₅ and R ₆ connected in series, and is connected to both ends of the capacitor C ₁ . Transistor Tr ₂
A resistor R ₄ is connected between the base and emitter of the. The base of the transistor Tr ₂ is connected to the collector of the transistor Tr ₁ via the Zener diode ZD. When the signal V _B is high level, a base current flows through the transistor Tr ₁ through the resistor R ₃ and the transistor Tr ₁
Turns on. At this time, a current flows through the Zener diode ZD, and the voltage generated in the resistor R ₄ causes the transistor T
r ₂ is turned on, the current I ₃ flows through the resistor R _5, R _6, resistor R _5, R ₆
A voltage V ₃ is generated at the connection point of, and a high level signal is input to the drive circuit 1. When the signal V _B is low level, the low level signal is input to the drive circuit 1. The Zener diode ZD is used to share the voltage difference between the transistors Tr ₁ and Tr ₂ .

FIG. 7 shows a circuit example of the drive circuit 1. In the figure, the parts denoted by the symbols A to D correspond to the circuit of FIG.
In the drive circuit 1, a series circuit of a resistor R ₇ and a transistor Tr ₃ and a totem pole circuit composed of transistors Tr ₄ and Tr ₅ are connected between terminals A and C which are connected to both ends of a capacitor C _1. The collector output of Tr ₃ is made into a low impedance by a totem pole circuit composed of transistors Tr ₄ and Tr ₅ , and is output through a parallel circuit of a forward bias resistor R ₈ and a reverse bias diode D _1. It is output to D. In the drive circuit 1, when the input terminal B is at a high level, the transistor Tr ₃ is on, the transistor Tr ₄ is off, the transistor Tr ₅ is on, and the output terminal D is at a low level. When the terminal B is at the low level, the output terminal D is at the high level.

FIG. 8 shows a circuit example of the drive circuit 2. In the figure, the parts denoted by E to H correspond to the circuit of FIG.
In the drive circuit 2, between the terminals E and G connected to both ends of the capacitor C ₂ , a series circuit of a resistor R ₉ and a transistor Tr _6, a series circuit of a resistor R ₁₀ and a transistor Tr ₇ ,
Totem pole circuit consisting of transistor Tr _8, Tr ₉ is connected, the collector output of the transistor Tr ₆ is connected to the base of the transistor Tr _7, the collector output of the transistor Tr ₇ consists of a transistor Tr _8, Tr ₉ The impedance is reduced by the totem pole circuit and is output to the output terminal H via the parallel circuit of the forward bias resistor R ₁₁ and the reverse bias diode D ₂ . In the drive circuit 2, when the input terminal F is at high level, the transistor Tr ₆ is on, the transistor Tr ₇ is off, the transistor Tr ₈ is on, the transistor Tr ₉ is off, and the output terminal H is at high level. Therefore, when the input terminal F is at low level, the output terminal H is at low level.

FIG. 9 is a diagram for explaining the operation of the circuit shown in FIG. In FIG. 9, times t _{0 to} t ₁ (t _{4 to} t ₅ ) and times t _{2 to} t ₃ are dead-off times, and both switching elements Q ₁ and Q ₂ should be turned off. At time t ₀ , the signal V _B (FIG. 9 (b)) becomes high level, and at time t ₁ , the signal V _A
When (FIG. 9 (a)) becomes high level, the drive circuit 2
The input terminal F of is at a high level and the output terminal H (Fig. 9 (g)).
Is output at a high level, and the switching element Q ₂ is turned on. At this time, the transistor Tr ₁ is turned on by the signal V _B , the current I _B (FIG. 9 (c)) flows through the Zener diode ZD, and the transistor Tr ₂ is turned on by the voltage generated in the resistor R ₄ and the current. I ₃ (Fig. 9 (d)) flows. Therefore, the voltage V ₃ (FIG. 9 (e)) obtained by the resistors R ₅ and R ₆ becomes high level, the input terminal B becomes high level, and the output terminal D (FIG. 9 (f)) becomes low level. And
The switching element Q ₁ is off. Therefore, the voltage V _{L at} the connection point of the switching elements Q ₁ and Q ₂ becomes low level.

When the signal V _A becomes low level at time t ₂ , the switching element Q ₂ is turned off through the drive circuit 2 and the voltage V _L
While the signal V _B goes low at time t ₃ ,
The transistor Tr ₁ turns off, the current I _B and the current I ₃ stop flowing, the voltage V ₃ becomes low level, and the switching element Q ₁ turns on.

When V _B becomes high level again at time t ₄ and V _A becomes high level at time t ₅ , the above operation is repeated. As a result, the voltage V _L shown in FIG. 9 (j) is obtained, the alternating voltage is supplied to the load circuit, and the switching element currents I ₁ and I ₁ shown in FIG. 9 (h) (i) are supplied. ₂ flows, and a load current I _z as shown in FIG. 9 (k) flows. When the load Z is a discharge lamp, the reason why the resonant circuit of the inductance L ₀ and the capacitor C ₀ is used is to make the waveform of the load current I _z sinusoidal due to the relation of radiation noise and the like.

Here, the current I _{1 of} each switching element Q ₁ , Q ₂
As shown at time t ₀ and time t ₂ , I ₂ starts in the negative direction and shuts off in the positive direction. This is the resonance frequency of the resonance circuit in the inductance L ₀ and the capacitor C ₀ ,
When f ₀ as shown in FIG. 10, because the drive frequency fd of the switching elements is set at higher than the resonance frequency f _0. In this way, if the switching element Q ₁ is turned off at time t ₀ , for example, the resonance current due to the load circuit tends to keep the switching element current I ₁ flowing in the positive direction.
₂ flows in the negative direction first, and then the switching element Q ₂ turns on in the positive direction. Similarly, when turning off the switching element Q ₂ is the negative direction of the current flows first to the switching element Q _1, followed by the switching element Q ₁ is turned on. At this time, the voltage of each of the switching elements Q ₁ and Q ₂ shifts to a high voltage when each of them is turned off. When the element voltage rises when it is turned off, it is reverse-biased by the drive circuit and reliably keeps the off state, so stable on / off operation can be performed even when the element voltage changes.

On the other hand, when the drive frequency is set to the frequency f ₁ lower than the resonance frequency f ₀ , the current of the switching element has a waveform as shown in FIG. In this case, when one switching element is turned on, a negative current is flowing through the other switching element. Therefore, since a high voltage is suddenly applied to the element in which the current in the negative direction was flowing at the moment when one of the switching elements was turned on, a recovery current due to the current in the negative direction flows, so that the two switching elements are turned on at the same time. A through current flows and the current waveform becomes as shown in FIG. Therefore, there is an inconvenience such as an increase in loss, and in order to avoid this, the drive frequency fd
Is required to be higher than the resonance frequency f ₀ so that waveforms such as the switching element currents I ₁ and I ₂ in FIG. 9 can be obtained.

In this conventional example, the lower oscillation circuit 3 is used without using a transformer for a base drive or an insulating element such as a photocoupler.
Therefore, the signal can be transmitted to the drive circuit 1 having a different potential on the upper side, and thus it can be said that the method is suitable for an IC. However, at the instant when the switching element Q ₂ is turned off at time t ₂ , the current of the negative circuit tries to regenerate to the DC power supply V through the switching element Q _1, but at this time, the transistor Tr ₁ is in the on state and the transistor Tr ₁ for signal transmission is used. Since the current I _B flows, a path for the shunt current Ix passing from the capacitor C ₁ to the transistor Tr ₂ , the Zener diode ZD, and the transistor Tr ₁ is formed in addition to the path for returning to the DC power source V via the switching element Q _1. . This is because the current at that moment is large and the capacitor C ₁ is considered to have low impedance at high frequencies. As a result, a large stress is applied to the transistor Tr ₂ , the Zener diode ZD, and the transistor Tr ₁ , and the loss increases, and the voltage V ₃ is also affected, so that the operation of the drive circuit 1 is unstable. There was an inconvenience.

(Object of the Invention) The present invention has been made in view of the above points,
It is an object of the present invention to provide an inverter device in which the influence of a regenerative current shunted to a signal transmission circuit is reduced, stress applied to a circuit element is reduced, and reliability is improved.

DISCLOSURE OF THE INVENTION In the inverter device according to the present invention, the first and second
Connect a series circuit of switching elements to a DC power supply, and provide a load circuit including an LC circuit that is AC-driven by the outputs switched by the first and second switching elements, and set each switching element to the resonance of the LC circuit. An oscillation circuit that generates a signal that turns on alternately at a frequency higher than the frequency after a dead-off time in which both switching elements are turned off at the same potential side as one switching element, and when one of the switching elements is off In addition, in a period other than the dead-off time, a signal transmission circuit for transmitting the ON signal of the other switching element to the other switching element by passing a current without passing through the insulating element is provided.

In the present invention, as described above, in the inverter device which includes the load circuit including the LC circuit and is switched at a frequency higher than its resonance frequency, when the switching element on the same potential side as the oscillation circuit is off and During the period other than the dead-off time, the current is passed and transmitted without passing through the insulation element of the ON signal of the switching element on the side with a different potential from the oscillation circuit.
By conducting the signal transmission path after the regenerative current from the load side to the power supply side is reduced, a large shunt current as in the conventional example does not flow, and the stress applied to the circuit element is reduced.

Examples of the present invention will be described below.

Embodiment 1 FIG. 1 is a circuit diagram of a main part of an embodiment of the present invention, and FIG. 2 is an operation waveform chart thereof. In the circuit of FIG. 1, the same parts as those of the conventional example of FIG. 6 are not shown. In this embodiment, in the conventional example shown in FIG.
The signal V _B obtained by inverting the signal V _B by the inverter gate G ₁ of the '(FIG. 2 (b) see), driving the transistor Tr _1. As the drive circuit 1 for driving the upper transistor Q ₁ , the same circuit as the drive circuit 2 shown in FIG. 8 is used.

In FIG. 2, when the signal V _B ′ becomes low level at time t ₀ and the signal V _A becomes high level at time t ₁ , the switching element Q ₂ is turned on by the drive circuit 2 and also by the signal V _B ′. , Transistor Tr ₁ is off and transistor
Tr ₂ is turned off, voltage V ₃ becomes low level, and voltage V ₁
Becomes a low level, and the switching element Q _{1 is} turned off.

At time t ₂ , the signal V _A becomes low level, the switching element Q ₂ is turned off, at time t ₃ , the signal V _B ′ becomes high level, the transistor Tr ₁ is turned on, and the resistance flows due to the current flowing through the Zener diode ZD. A voltage is generated in R ₄ , the transistor Tr ₂ is turned on, the voltage V ₃ becomes high level, the voltage V ₁ also becomes high level through the drive circuit 1, and the switching element Q ₁ is turned on. After that, at time t ₄ , the switching element Q ₁ is turned off again, and the above operation is repeated.

In the present embodiment, the transistor Tr ₁ is turned on and the signal is transmitted to the upper drive circuit 1 during the time t _{3 to} t ₄ as shown in FIG. 2 (c). . The current flowing in the negative direction of the switching element Q ₁ when the switching element Q ₂ is turned off (time t ₂ ), that is, the current regenerated on the side of the DC power supply V becomes maximum, and then gradually decreases. In the conventional example, the transistor Tr ₁ has already been turned on at time t ₂ and a large negative current has flowed. However, in the present invention, the transistor Tr ₁ is turned on for the first time at time t ₃ , so that it is shown in FIG. 2 (h). Such a low level negative current becomes the shunt current Ix. Therefore, this inconvenient current Ix is greatly reduced as compared with the conventional example, and stable operation with less loss becomes possible.

Second Embodiment FIG. 3 is a circuit diagram of a second embodiment of the present invention. In this embodiment, the transistor Tr ₁ is not operated in the saturation region but is operated in the active region, and a constant current I _B determined by the current flowing through the transistor Tr ₁₀ via the resistor R ₃ is transmitted. It was used for. Therefore, the value of the current I _B by fluctuation of voltage V _L and the voltage of the capacitor C _1, substantially kept in the set current value determined by the value or the like of the resistor R _3, it is possible to stable signal transmission. The other components are the same as in Example 1, with reversing the driving signals of the transistor Tr ₁ by the inverter gate G _1, as a drive circuit 1 for driving the upper transistors Q _1, shown in FIG. 8 Using the same circuit as the drive circuit 2, the current I _{B is} generated when the switching element Q ₂ is off.
By flowing, and transmits an ON signal of the switching element Q ₁ to the switching element Q _1.

Even in the conventional circuit shown in FIG. 6, the transistor Tr ₁
By using a current mirror circuit composed of Tr ₁₀ and Tr ₁₀ , the shunt current Ix can be made constant, but in reality, it is not possible to easily obtain a 100% perfect mirror effect. To remove the effect more completely,
It is necessary to adopt the configuration of the present invention.

Third Embodiment FIG. 4 is a circuit diagram of a third embodiment of the present invention. In this embodiment, the transistor Tr ₁ is operated in the saturation region,
A function of a constant current circuit is obtained by a constant current element Is, and a stable operation is obtained as in the case of the second embodiment by converting the signal transmission current I _B into a constant current. Is.

Fourth Embodiment FIG. 5 is a circuit diagram of a fourth embodiment of the present invention. In this embodiment, the transistor Tr ₁₁ is connected instead of the resistor R ₄ in the second embodiment, and the current flowing through the transistor Tr ₂ is also made constant. As a result, the transistors Tr ₁ and Tr ₂ for signal transmission operate in the active region rather than the saturation region, which is an effective method for higher-speed operation.

Although not particularly shown, a full-bridge type inverter circuit, that is, a series circuit of third and fourth switching elements is connected in parallel with a power source, and load circuits are connected to the first and second load circuits.
Connected between the connection point of the switching element and the connection point of the third and fourth switching elements, and simultaneously turns on and off the switching elements in diagonal directions to supply alternating current to the load circuit. Also in the circuit, the same effect can be obtained by transmitting the ON signal of the drive circuit on the side of the different potential from that of the oscillation circuit by flowing the current when the switching element on the side of the same potential is turned off.

(Effect of the invention) As described above, the present invention includes the load circuit including the LC circuit,
In an inverter device that is switched at a frequency higher than its resonance frequency, when a switching element on the same potential side as the oscillation circuit is off and during a period other than the dead off time, the switching element on a different potential side from the oscillation circuit is on. Since the signal is transmitted by passing the current without passing through the insulating element, the signal transmission path is made conductive after the regenerative current from the load side to the power source side is reduced. There is an effect that a large shunt current does not flow, a stress on a circuit element is small, an operation is stable, and a highly reliable inverter device can be provided.

[Brief description of drawings]

1 is a circuit diagram of a first embodiment of the present invention, FIG. 2 is an operation explanatory diagram of the same as above, FIG. 3 is a circuit diagram of a second embodiment of the present invention, and FIG. 4 is a third embodiment of the present invention. An example circuit diagram, FIG. 5 is a circuit diagram of a fourth embodiment of the present invention, FIG. 6 is a circuit diagram of a conventional example, FIGS. 7 and 8 are main part circuit diagrams, and FIG. 9 is the same as above. FIG. 10 is an operation explanatory diagram, FIG. 10 is a diagram showing a resonance characteristic of the load circuit, and FIG. 11 is a diagram showing a current waveform flowing in the switching element. G ₁ is an inverter gate.

Claims (3)

[Claims] 1. A LC circuit in which a series circuit of first and second switching elements is connected to a DC power source, and AC is driven by the outputs switched by the first and second switching elements.
A load circuit including a circuit is provided, and each switching element is
An oscillation circuit that generates a signal that turns on alternately at a frequency higher than the resonance frequency of the LC circuit after a dead-off time in which both switching elements are turned off at the same potential side as one switching element When the element is off and during a period other than the dead-off time, a signal transmission circuit for transmitting an on signal of the other switching element to the other switching element by passing a current without passing through the insulating element is provided. Characteristic inverter device. 2. A capacitor serving as a driving power source for the other switching element is connected in parallel via a resistor, and one end of the capacitor is connected to a connection point of both switching elements. The inverter device according to claim 1. 3. A first current mirror circuit for converting an ON signal of the other switching element output from the oscillation circuit into a current signal is provided on the same potential side as the oscillation circuit, and receives the current signal. 3. The inverter device according to claim 2, wherein a second current mirror circuit that reproduces an ON signal of the other switching element is provided on the potential side of the other switching element.