JP2634807B2 - Inverter device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an insulating element such as a transformer having a pair of switching elements, and 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 that transmits a signal without passing through an inverter.

(Background Art) FIG. 8 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, power MOS transistors or power bipolar transistors in which diodes are connected in anti-parallel. Each switching element Q ₁ , Q ₂ is connected to the output V ₁ , V ₂
Are driven on and off, respectively. The one ends of the switching element Q _2, via the inductance L _0, a parallel circuit of the load Z and the capacitor C ₀ is connected. As the load Z, for example, a discharge lamp is used.

The series circuit of the resistor R ₁ and the capacitor C ₁ connected to both ends of the switching element Q ₁ is the power supply circuit of the upper drive circuit 1, and the series circuit of the resistor R ₂ and the capacitor C ₂ connected to both ends of the DC power supply V Is a power supply circuit of the lower drive circuit 2. Oscillation circuit 3 fed by the capacitor C _2, the two signals V _A, and outputs the V _B. Signal V _A is input to the drive circuit 2, the signal V _B via the signal transmission circuit, is inputted to the drive circuit 1.

The signal transmission circuit is composed of transistors Tr ₁ and Tr ₂ , diode D
_1, consists of Zener diodes ZD and a resistor R ₃ to R _6, and performs signal transmission without using an insulating element of transformer or the like.
Transistor Tr ₂ of the signal transmission circuit is connected to the resistor R _5, R ₆ in series, is connected across the capacitor C _1. Between the base and emitter of the transistor Tr _2, the resistance R ₄ is connected. The base of the transistor Tr ₂ via the Zener diode ZD, is connected to the collector of the transistor Tr _1. Signal V _B is at a high level, the base current flows through the transistor Tr ₁ via the resistor R _3, the transistor Tr ₁ is turned on. At this time, current flows through the Zener diode ZD, the voltage generated in the resistor R _4, the transistor Tr ₂ is turned on, the current I ₃ flows through the resistor R _5, R _6, resistor R _5, R
_A voltage V ₃ is generated at the connection point ₆ , and a high-level signal is input to the drive circuit 1. When the signal V _B is low,
A low-level signal is input to the drive circuit 1. In addition,
Zener diode ZD is used to share the voltage difference of the transistor Tr ₁ and Tr _2, the Zener voltage is set to approximately the same voltage as the power supply voltage. The diode D ₁ when the transistor Tr ₁ is turned off, to form a bypass path for releasing accumulated charges due to the stray capacitance of the Zener diode ZD, in order to reduce the base-emitter reverse voltage of the transistor Tr ₁ Is provided.

FIG. 9 is an explanatory diagram of the operation of the circuit in FIG. When the time t ₀ in the signal V _A (Figure 9 (a)) goes high, the output V ₂ of the drive circuit 2 (FIG. 9 (h)), the switching element Q ₂ is turned on. At this time, since the signal V _B is at a low level, no current flows through I _B is the transistor Tr _1. Therefore, since the voltage drop does not occur in the resistor R _4, the transistor Tr ₂ is turned off, the voltage V ₃ becomes low level, the output V ₁ of the drive circuit 1, the switching element Q ₁ is turned off.

Next, when the signal V _A becomes a low level at time t _1, the output V ₂ of the drive circuit 2, switching element Q ₂ is turned off. On the other hand, the signal V _B (FIG. 9 (b)) becomes high level, the transistor Tr ₁ current I _B (Figure 9 (c)) flows. This current I _B, the resistance R ₄ to the voltage drop V _R4 (FIG. 9 (d)) occurs, the base current flows through the transistor Tr _2, the transistor Tr ₂ is turned on. This current I ₃ (FIG. 9 (e)) to the transistor Tr ₂ flows, the resistance R
₅ , a voltage is applied to the series circuit of R ₆ , and the voltage V _{3 at} the voltage dividing point is applied.
(FIG. 9 (f)) becomes high level and the drive circuit 1
The output V ₁ (FIG. 9 (g)) of the switching element Q ₁
Turns on. Hereinafter, the same operation is repeated, whereby an alternating voltage _VL as shown in FIG. 9 (i) is supplied to the load circuit, and the switching element as shown in FIGS. 9 (j) and 9 (k). The currents I ₁ and I ₂ flow, and the load current I _Z flows as shown in FIG. 9 (l). When the load Z is a discharge lamp, the reason for using the resonance circuit of the inductance L ₀ and the capacitor C ₀ is to make the waveform of the load current I _Z into a sine wave from the relation of radiation noise and the like.

Here, each of the currents I ₁ of the switching element Q _1, Q _2,
I ₂ starts in the negative direction, as shown at times t ₀ , t ₁ , t ₂ ,
It shuts off in the forward direction. This is because if the resonance frequency of the resonance circuit in the inductance L ₀ and the capacitor C ₀ is f ₀ as shown in FIG. 10, the drive frequency fd of the switching element is set to be higher than the resonance frequency f ₀ . That's why. In this way, for example, when the switching element Q ₁ at time t ₀ is assumed that the off-resonance current by the load circuit, will be passing through the switching element Q ₂ is first in the negative direction, it followed switching element Q ₂ in the positive direction Turn on. Similarly, when the off switching element Q _2, the negative direction of the current flows first to the switching element Q _1, followed by the switching element Q ₁ is turned on in the forward direction. At this time, the voltage of each switching element Q ₁ , Q ₂ shifts to a high voltage when each turns off. When the element voltage rises at the time of off, it is reverse-biased by the drive circuits 1 and 2 and keeps the off state without fail.
Can be turned off.

On the other hand, when the drive frequency fd in the low frequency f ₁ than the resonance frequency f _0, the current of the switching element, a waveform as shown in FIG. 11. In this case, when one of the switching elements is turned on, a negative current flows through the other switching element. Therefore, since a high voltage is suddenly applied to the element in which the negative current flows at the moment when one of the switching elements is turned on, a recovery current or the like due to the negative current flows, so that the two switching elements are simultaneously turned on. A through current flows, resulting in a current waveform as shown in FIG. For this reason, there are disadvantages such as an increase in loss. To avoid this, the drive frequency fd
Must be higher than the resonance frequency f ₀ so that a waveform such as the switching element currents I ₁ and I ₂ in FIG. 9 can be obtained.

In this conventional example, signals can be transmitted from the lower oscillation circuit 3 to the upper drive circuit 1 having a different potential without using a transformer for a base drive or an insulating element such as a photocoupler. It can be said that the method. However, at time t _1, at the moment when the switching element Q ₂ is turned off, the current in the load circuit is to regenerated to the DC power source V through the switching element Q _1, this time the transistor
Because Tr ₁ is the current I _B for signal transmission in the ON state flows to other routes through the switching element Q ₁ back to the DC power supply V, the transistor Tr ₂ from the capacitor C _1, the Zener diode ZD, the transistor Tr A path for the shunt current _IX through ₁ is created. This is because the current at that moment is large and the capacitor
C ₁ is the high frequency is considered to lower interface. As a result, a large stress is applied to the transistor Tr ₂ , the zener diode ZD, and the transistor Tr ₁ , the loss increases, and the voltage V ₃ is affected, so that the operation of the drive circuit 1 is unstable. There was an inconvenience of becoming.

(Object of the Invention) The present invention has been made in view of the above-mentioned points, and an object of the present invention is to reduce the effect of regenerative current shunted to a signal transmission circuit to reduce the stress applied to circuit elements. An object of the present invention is to provide an inverter device with reduced reliability and higher reliability.

(Disclosure of the Invention) The configuration of the inverter device according to the present invention will be described with reference to the embodiment of FIG. _1. A series circuit of first and second switching elements Q ₁ and Q ₂ connected to a DC power supply V, A load circuit including an LC circuit that is AC-driven by outputs switched by the first and second switching elements Q ₁ and Q ₂ , and a _first circuit whose negative side is connected to a connection point between the two switching elements Q ₁ and Q ₂ . a power supply capacitor C _1, the first first the drive circuit 1, the negative electrode side second switching element Q ₂ at the same potential which is connected to the power supply capacitor C ₁ for driving the first switching element Q ₁ The second power supply capacitor C ₂ connected to
When, a second drive circuit 2 for driving the second of the second is connected to the power supply capacitor C ₂ of the switching element Q _2,
Is the connected second to the power supply capacitor C ₂ first and second
An inverter device comprising: an oscillation circuit 3 for outputting a drive signal to the drive circuits 1 and 2; and a signal transmission circuit for transmitting a drive signal from the oscillation circuit 3 to a signal input terminal of the first drive circuit 1. The signal transmission circuit,
A third switching element (transistor Tr ₁ ), which is turned on / off by receiving the output of the oscillation circuit 3, and operates in conjunction with the output signal of the third switching element to operate the first switching capacitor C ₁ A fourth switching element (transistor Tr ₂ ) inserted between the positive electrode side and the signal input terminal of the first drive circuit 1; and a fourth switching element (transistor Tr ₂ ) interposed in a signal transmission path between the third and fourth switching elements. And a current limiting element (resistance R ₀ ) to be inserted.

In the present invention, thus, in the path for transmitting the drive signal of the switching element to Q ₁ different sides of the oscillation circuit 3 and the potential not through the insulating element, a current limiting element such as a resistor R ₀ since inserted, even branched into regenerative current signal transmission path from the load side switching element Q ₂ is turned off in the oscillation circuit 3 the same potential side to the power source side, since the flow limited by the limiting device, conventional Such a large shunt current does not flow, and the stress applied to the circuit element is reduced.

Hereinafter, examples of the present invention will be described. In the circuit of the embodiment, portions having the same functions as those of the circuit of the conventional example are denoted by the same reference numerals, and redundant description will be omitted.

Embodiment 1 FIG. 1 is a circuit diagram of one embodiment of the present invention. FIG. 2 is an explanatory diagram of the operation of the present embodiment, and illustration of parts common to FIG. 9 is omitted. In the present embodiment, the eighth
In conventional example, Zener diode in signal transmission path
A resistor _R0 is inserted as a current limiting element in series with ZD. In the prior art shown in FIG. 8, since the zener voltage is set to be close to the power supply voltage, there is no element for limiting the current from the power supply exceeding the zener voltage, the impedance becomes very low, and the Although the shunt current _IX was flowing, in the present embodiment, the disadvantageous current _IX is significantly reduced by providing the resistor _R0 as compared with the conventional example, and the stable current with less loss is obtained. The operation becomes possible.

Here, the resistance value of the resistor _R0 is set to a high impedance to the extent that the above-mentioned inconvenient current _IX is suppressed. Since decreasing the current I _B by limiting action of the resistor R _0, by increasing the resistance of the resistor R _4, and to stabilize the operation of the transistor Tr _2. Further, with the insertion of the resistor _R0 , the zener voltage of the zener diode ZD is changed to a low value. Other configurations and operations are the same as those of the conventional example shown in FIGS. 8 and 9.

In the present embodiment, the reverse voltage applied between the base and the emitter of the transistor Tr ₂ at times t ₀ and t ₂ can be reduced by the resistor R ₀ , and a diode for bypassing the reverse voltage is used. D ₁ may be omitted. The same applies to the following embodiments.

Embodiment 2 FIG. 3 is a main part circuit diagram of a second embodiment of the present invention. In this embodiment, the Zener diode ZD is omitted from the circuit of the embodiment shown in FIG. 1, and the resistance value of the resistor _R0 is made higher instead. At time t ₁ ~t ₂ the switching element Q ₂ is turned off, the voltage V _L of the load circuit is high level, the voltage V of the capacitor C _1
The voltage of the sum of _C1 and voltage _VL is almost stable. Therefore, if properly choose a resistor R ₀ the value of the resistor R _4, be omitted Zener diode ZD, it is capable of transmitting a stable signal between times t ₁ ~t _2. In addition, the higher impedance of the resistor _R0 causes the above-mentioned disadvantageous current
I _X can be further suppressed.

Embodiment 3 FIG. 4 is a circuit diagram of a third embodiment of the present invention. In the present embodiment, not operate the transistor Tr ₁ in the saturation region, which is operated in the active region, the oscillation circuit 3
A constant current determined by the current flowing through the transistor Tr _3, the output flowing in transistor Tr _1, and those using the constant current for signal transmission. Therefore, nearly constant current value for signal transmission by fluctuation of voltage V _L and the voltage of the capacitor C ₁ of the load circuit, in which it is possible to stable signal transmission.

In the conventional circuit of FIG. 8, the transistor Tr
By using a current mirror circuit consisting of ₁ and Tr ₃ , the shunt current _IX can be made constant, but in reality, 100% perfect Miller effect cannot be easily obtained. To more completely eliminate the effects of _IX ,
It is necessary to adopt the configuration of the present invention.

Embodiment 4 FIG. 5 is a circuit diagram of a fourth embodiment of the present invention. In the present embodiment, in the embodiment of FIG. 4, in place of the resistor R ₄ is connected to the transistor Tr ₄ so as to constitute a current mirror circuit, those constant-Ryuka also the current flowing through the transistor Tr ₂ It is. Thereby, since the transistors Tr ₁ and Tr ₂ for signal transmission operate not in the saturation region but in the active region, this is an effective method for performing higher-speed operation. Also in this case, by inserting a high-impedance resistor _R0 in the signal transmission path, it is possible to suppress an undesired shunt current due to a regenerative current from the load circuit. In the present embodiment, the voltage drop value generated in the resistor R ₀ by the current flowing through the resistor R ₀ is the voltage of the sum of the voltage V _L and the voltage V _C1 of the capacitor C ₁ at the time of the off-switching element Q ₂ Collector-emitter voltage V of transistor Tr ₁
Do not larger than the voltage obtained by subtracting the sum of the minimum value and the base-emitter voltage of the transistor Tr ₄ of the _CE.

Incidentally, in the embodiment circuit shown in FIG. 5, to remove the lower switching element Q ₂ and the drive circuit 2, even when the Ichiseki type inverter circuit as shown in FIG. 6, the oscillation circuit when 3 and the ground level is transmitted to different switching elements to Q ₁ drive circuit 1 in drive signal V _B, if by inserting a resistor R ₀ in the signal transduction pathway,
It is possible to suppress the shunt current of the regenerative current from the load circuit. However, in the Ichiseki formula inverter circuit as shown in FIG. 6, the need for signaling it is eliminated by providing the oscillator 3 on the side of the capacitor C ₁ which supplies the operating power to the drive circuit 1. Therefore, the present invention is particularly effective when two switching elements Q ₁ and Q ₂ having different ground levels are driven by one oscillation circuit 3 as shown in the circuit of FIG.

Embodiment 5 FIG. 7 is a circuit diagram of a fifth embodiment of the present invention. In the present embodiment, a full-bridge inverter circuit, that is, a series circuit of the third and fourth switching elements Q ₃ and Q ₄ is connected in parallel with the DC power supply V, and the load circuits are connected to the first and fourth switching elements. 2 switching elements Q _1, Q connection point ₂ and is connected between a connection point of the third and fourth switching elements Q _3, Q _4, the switching elements to Q ₁ diagonal directions, Q _4, Q ₂ , and an inverter circuit which is adapted to supply a current to turn on and off the Q ₃ at the same time, alternating to the load circuit. In the present embodiment, the operating power supply of the driving circuit 5 of the switching element Q ₄ are, although from the capacitor C ₂ in the same manner as the drive circuit 2, the operation power supply of the driving circuit 4 of the switching element Q ₃ are switched connected to both ends of the element Q ₃ resistor R ₇ and capacitor C ₃
It is obtained by the series circuit. This is because the load circuit is interposed, it can not be used to supply the voltage of the capacitor C _1. Transistors Tr _{5 to} Tr ₈ , diode D ₂ ,
The configuration and operation of the signal transmission circuit of the switching element Q ₃ consisting of resistors R ₈ to R _10, are the same as those of the signal transmission circuit of the switching element Q _1, a repetition of the same explanation is avoided.

Also in this embodiment, by inserting the resistors R ₀ and R ₁₀ in the signal transmission paths for transmitting the drive signals to the oscillation circuit 3 and the drive circuits 1 and 4 on the different potential side, respectively, the inconvenience due to the regenerative current from the load circuit is caused. It is possible to suppress a large shunt current.

(Effect of the Invention) As described above, in the present invention, the current limiting element is inserted in the path for transmitting the drive signal of the switching element having a different potential from the oscillation circuit without passing through the insulating element. Even if the switching element on the same potential side is turned off and the regenerative current from the load side to the power supply side is shunted to the signal transmission path, the current is limited by the current limiting element, so that a large shunt current does not flow and the circuit element There is an effect that it is possible to provide a highly reliable inverter device with less applied stress, stable operation, and high reliability.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of the first embodiment, FIG. 3 is a main part circuit diagram of a second embodiment of the present invention, and FIG. FIG. 5 is a circuit diagram of a fourth embodiment of the present invention, FIG. 6 is a circuit diagram of a modification of the above embodiment, FIG. 7 is a circuit diagram of a fifth embodiment of the present invention, 8 is a circuit diagram of a conventional example, FIG. 9 is an operation explanatory diagram of the above example, FIG. 10 is a diagram showing resonance characteristics of a load circuit, and FIG. 11 is a diagram showing a current waveform flowing through a switching element. R ₀ is a resistor.

Claims (1)

(57) [Claims] 1. A series circuit of first and second switching elements connected to a DC power supply, and a load circuit including an LC circuit that is AC-driven by an output switched by the first and second switching elements. A first side in which the negative electrode side is connected to a connection point of the two switching elements;
A first drive circuit connected to the first power supply capacitor for driving the first switching element; and a second power supply capacitor having a negative electrode side connected to the same potential as the second switching element. A capacitor; a second drive circuit connected to the second power supply capacitor for driving a second switching element; and a drive signal connected to the second power supply capacitor for the first and second drive circuits. An inverter device comprising: an oscillation circuit that outputs a signal; and a signal transmission circuit that transmits a drive signal from the oscillation circuit to a signal input terminal of a first drive circuit. A third switching element to be turned off, and an interlocking operation in response to an output signal of the third switching element, and the first power supply capacitor A fourth switching element interposed between the positive electrode side and a signal input terminal of the first drive circuit; and a current limiting element interposed in a signal transmission path between the third and fourth switching elements. An inverter device comprising: