JPH01160375A - Inverter device - Google Patents

Abstract

PURPOSE:To improve reliability by providing an impedance element so that the charging current to the capacity component of a signal transfer circuit is not transferred. CONSTITUTION:An inverter device is constituted of AC power supply V, switching elements SW1-SW2, driver currents 1-2, a parallel circuit of a load Z and a capacitor C0 through inductance L0, current mirror circuits 3-4, an oscillation circuit 5 and so on. At this time, a capacitor C5 is provided as an impedance element bypassing so as the current charged to the capacity component C5 of the signal transfer circuit is not transferred to the first switching element SW1, and at the same time, the resistance Ra is provided as the impedance element in order that the current charged to the capacity component C5 makes hard to flow to the channel of signal transfer current 1B. Accordingly, the charging voltage to said capacity component C5 can be prevented from acting as if it was the signal transfer current.

Description

Detailed Description of the Invention (Technical Field) The present invention has a pair of switching elements, and is capable of connecting an oscillation circuit having the same potential as the negative switching element to the other switching element having a different potential through an insulating element such as a transformer. The present invention relates to an inverter device that transmits signals without delay.

(Background Art) Figure 11 is a circuit diagram of a conventional inverter device.
Figure 2 is a diagram of its operating waveforms. At both ends of the DC power supply V,
A series circuit of switching elements S W I and S W 2 is connected. The switching elements SW+ and SW2 are constituted by, for example, power bipolar transistors in which power transistors and diodes are connected in antiparallel. The switching elements SW, , SW2 are driven on and off by output signals V, , V2 of the driver circuit 1.2, respectively. A parallel circuit including a load Z and a capacitor C6 is connected to both ends of one switching element SW2 via an inductance L0. As the load Z, for example, a discharge lamp is used. When the load 2 is a discharge lamp, the reason why a resonant circuit including an inductance L0 and a capacitor C0 is used is to make the waveform of the load current sinusoidal in view of radiation noise and the like. The currents It and It of each switching element sw, , sw2 are shown in FIG. 12 (at).
, as shown in (1), starts in the negative direction and is interrupted in the positive direction. This is higher than the resonant frequency of the resonant circuit formed by the inductance L0 and the capacitor C6 of the switching element S W + .

This is because the drive frequency of SW2 is set high. With this setting, for example, the switching element SW
When , is turned off, the resonant current due to the load circuit first flows through the switching element SW2 in the negative direction,
Subsequently, the current flows in the positive direction of switching element SW2. Similarly, when the switching element SW2 is turned off, the resonant current caused by the load circuit first flows through the switching element SW+ in the negative direction, and then flows through the switching element SW in the positive direction. At this time, each switching element SW, SW2
element voltage V5. V, transitions to a high voltage when each turns off.

Resistor R1 and capacitor C connected across the DC power supply ■
The series circuit No. 1 is a power supply circuit of the lower circuit including the oscillation circuit 5 and the driver circuit 2, and the series circuit of the resistor R2 and capacitor C2 connected across the switching element SW is the power supply circuit of the upper circuit including the driver circuit 1. This is a power supply circuit. Capacitors C3 and C- are capacitive components of switching elements SW and SW2.

The oscillation circuit 5 supplied with power by the capacitor C1 outputs two drive signals vA and vday. drive signal v
A is input to the driver circuit 2, and a drive signal VB is input to the driver circuit 1 via the signal transmission circuit. The signal transmission circuit includes transistors T r + + T r
21 T r 31 T r 4, a diode D3, and a resistor R5, and performs signal transmission without using an insulating element such as a transformer. Transistor Tr.

Tr2 constitutes a current mirror circuit 3, and transistors Tr, Tr, constitute a current mirror circuit 4. Drive signal VB output from oscillation circuit 5
is one transistor Tr of the current mirror circuit 3,
The output of the other transistor Tr2 of the current mirror circuit 3 is input to one transistor Trs of the current mirror circuit 4. The other transistor Tr of the current mirror circuit 4 has a resistor R1 connected in series and is connected to both ends of a capacitor C2. Assuming that the current amplification factor hfe of each of the transistors Tr+ to Tr4 is sufficiently large, the signal transmission voltage mI is approximately the same as the input current flowing through the transistor Tr+ due to the drive signal VB. Closed transistor T r 21 T
The output current I to the transistor Tr is approximately the same as the signal transmission current I flowing to the transistor Tr3.

It flows like this. When the drive signal VB is at a high level, the transistors T r + and T r 2 conduct, and the signal transmission current 1. flows, and the transistor T r 3
1 T r 4 is also conductive. When the transistor Tr becomes conductive, an output current (4) flows through the resistor R2, a voltage drop occurs across the resistor R1, and the input signal (2) of the driver circuit 1 is generated.

is at a high level. When the drive signal VB is at a low level, the input signal V4 of the driver circuit 1 is at a low level. In addition, the transistor T of each current mirror circuit 3゜4
r, ~Tr< operates in an unsaturated region in order to perform high-speed operation.

When the transistor Tr2 is turned off, the diode D1 forms a bypass path for discharging the stored charge stored in the stray capacitance component Cs between the collector and emitter of the transistors Tr and z.

This is provided to reduce the reverse voltage between the base and emitter of the

In this conventional example, the input signal V synchronized with the drive signal VB can be transmitted to the driver circuit 1 at a different potential from the oscillation circuit 5 without using an insulating element such as a transformer or a photocoupler. The configuration is suitable for IC implementation of the control circuit. However, in this conventional example, when the drive signal V is at a low level and the element voltage increases, the capacitor C2 and the current mirror circuit 4
A charging current flows to the capacitive component Cs of the transistor Tr2 through one transistor Tr+, and this acts like a signal transmission current I8, sometimes resulting in malfunction.

This operation will be explained below with reference to FIG. First, time t. and drive signal VB (Fig. 12 (
b)) becomes low level, the current mirror circuits 3, 4
The currents IB', IB, I4 ((c), (d) in the same figure)
.

(e)) no longer flows, and the input signal V of driver circuit 1
< ((f) in the same figure) is at a low level, the output signal V + of the driver circuit 1 ((h) in the same figure) is at a low level, and the switching element SW is turned off. At this time, the element voltage v
,.

VS ((i), (j) in the same figure) changes in a gradient manner depending on the capacitance components Cs, C= of the switching elements SW, SW2, and the current changes at time t, and after that, the current in the negative direction due to the resonance effect of the load circuit. L ((1) in the same figure), and after time t2, the drive signal VA ((a) in the same figure)
When the voltage becomes high level, the switching element SW2 is turned on, and the current flows in the positive direction. As the element voltage ■ decreases, the charging voltage VS of the stray capacitance Cs of the transistor Tr2 of the current mirror circuit 3 (Fig. D
1 and capacitor C2, when the drive signal vA becomes a low level, the output signal V2 of the driver circuit 2 (FIG. 1(g)) becomes a low level, and the switching element SW2 is turned off. The element voltage V increases due to the resonance effect of the load circuit. At this time, the capacitive component Cs is charged through the current mirror circuit 4,
The charging voltage v6 also rises.Here, the charging current from the current mirror circuit 4 to the capacitive component C3 flows through the same path as the signal transmission current B due to the drive signal V, so the output current I4 flows, driver circuit 1
The level of the input signal V, to the driver circuit 1 increases, and the output signal V, of the driver circuit 1 becomes high level at time t. Therefore, the switching element SW1 is turned on, but since the element voltages V, V5 are still changing at this point, the capacitance components C, C, are rapidly charged and discharged. This current has a high peak value and causes a switching loss, sometimes causing destruction of the switching elements sw, sw2 and generation of noise.After time 6 t, the drive signal VB becomes high level, so the switching element SW1 continues to be on, and at time t6, when the current ■l (Fig. 12 (m)) flows in the positive direction, the drive signal VB becomes low level, and the switching element SW1 is turned off again. It supplies high-frequency power to the

As can be seen from the above explanation, in this conventional example,
Even if the drive signal v6 is at a low level, the element voltage ■,
As a result of the rise in , a charging current flows to the capacitive component Cs, and this becomes the signal transmission current 1. There is a problem in that the switching element SW1 is turned on due to the operation as shown in FIG.

(Object of the invention) The present invention has been made in view of the above points, and
The object is to provide an inverter device that improves reliability by preventing charging current to a capacitive component of a signal transmission circuit from acting like a signal transmission current.

(Disclosure of the Invention) The configuration of the inverter device according to the present invention will be explained with reference to the embodiment shown in FIG. and a load circuit that is AC driven by the output switched by the second switching element SW, SW2,
A first switch that turns on and off the first switching element SW1.
drive signal VB and the second switching element SW2
The oscillation circuit 5 is provided on the same potential side as the second switching element SW2, and generates a second drive signal vA that turns on and off so as not to turn on and off at the same time as the first switching element SW. The first drive signal VB is applied to the first switching element SWI while the current signal 1. In an inverter device comprising a signal transmission circuit (current mirror circuit 3.4) that transmits signals as a signal, an impedance element (capacitor C5 and a resistor Ra) are provided.

In the present invention, as described above, since the impedance element is provided so that the charging current to the capacitive component Cs of the signal transmission circuit is not transmitted to the first switching element SW,
This prevents the charging current to the capacitive component Cs of the signal transmission circuit from acting like a signal transmission current, thereby improving reliability.

Examples of the present invention will be described below. In the example circuit, parts having the same functions as those of the conventional example circuit are given the same reference numerals, and redundant explanation will be omitted.

Large 110- FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is an operating waveform diagram thereof. In this embodiment, in the conventional example shown in FIG. 11, a capacitor c5 is provided as an impedance element for bypassing so that the current charged in the capacitance component Cs of the signal transmission circuit is not transmitted to the first switching element SWI. , a resistor Ra is provided as an impedance element to prevent the current charging the capacitive component Cs from flowing into the path of the signal transmission current IB.

The operation will be described below with reference to FIG. 2 at time 0 [. , the drive signal V (Fig. 2(b)
) becomes a low level, currents ■8°, IB, and I4 ((c), (d), and (e) in the same figure) stop flowing.
Input signal V 4 to driver circuit 1 (same m (g)
) becomes low level, and the output signal of driver circuit 1 V +
((i) in the same figure) becomes a low level, and the switching element SW1 is turned off.

Capacitive components C3 and C4 of switching elements SW+ and SW2
Accordingly, the element voltage V3 ((j) in the same figure) decreases in a gradient manner. In addition, the accumulated charge of the capacitive component Cs is discharged through the capacitor C5 through a path passing through the diode D1 where the resistor Ra exists (because it is difficult to discharge).This causes the charging voltage vg of the capacitive component Cs ( (k)) decreases, the current flowing in the load circuit tries to continue flowing due to the resonance effect of the LC component, and after time 1+ flows through switching element SW2 in the negative direction.After time t2, drive signal VA( (a) in the same figure becomes a high level, the output signal V2 of the driver circuit 2 ((h) in the same figure) becomes a high level, the switching element SW2 is turned on, and the current I2
((1) in the same figure) flows in the forward direction. When the drive signal vA becomes low level at time t, the element voltage V and the charging voltage V6 increase in a gradient manner.The current flowing in the load circuit tries to continue flowing due to the resonance effect, and after time L4, The current flows through the switching element SW1 in the negative direction, and at this time,
Charging voltage ■6. The element voltage ■ is increasing.

The charging current required for the charging voltage V6 of the capacitive component Cs to rise is due to the presence of the resistor Ra.
, , T r , and flows as a current j cs (FIG. 6(f)) of the bypass capacitor C6.

Therefore, an unnecessary signal due to charging of the capacitive component Cs is not added to the signal transmission current IB, and the output signal V1 of the driver circuit 1 does not become high level. in this way,
In this embodiment, by inserting a resistor Ra, the charging current of the capacitive component Cs is prevented from flowing into the current mirror circuit 4, and by bypassing the charging current via the capacitor C6, the charging current is This is to prevent the switching element SWI from turning on.

After time t, the drive signal ■8 becomes high level, currents In', Ie, and I flow, the input signal ■ of the driver circuit 1 becomes high level, and its output signal ■ becomes high level. , the switching element SWl is turned on, and the current I, ((m) in the figure) flows in the positive direction. At time t6, the drive signal VB becomes low level again, and thereafter, power is supplied to the load Z by repeating this process.

Note that an impedance element such as a choke coil may be used instead of the resistor Ra, and if the impedance of the current mirror circuit 4 is very high compared to the impedance element (capacitor CS) for the noi bus, The resistor Ra may be omitted.

3(a) is a circuit diagram of a main part of a second embodiment of the present invention. In this embodiment, the connection position of the diode D is changed and the junction capacitance Cj of the diode D is used as a bypass impedance. FIG. 3(b) is a circuit diagram of a main part of a modified example of this embodiment, in which a capacitor C9 is connected in parallel with a diode D1 to further reduce the bypass impedance.

Scorch 1 FIG. 4 is a circuit diagram of a main part of a third embodiment of the present invention. In this embodiment, the charging current to the capacitive component Cs is supplied through a charging resistor Rb connected to a DC power supply V. Note that a capacitor or a choke coil may be used instead of the resistor Rb.

fire 1 renshi FIG. 5 is a circuit diagram of a fourth embodiment of the present invention.

In this embodiment, a capacitor C1l for suppressing voltage fluctuation is connected in parallel with the capacitance component Cs of the transistor Tr in the current mirror circuit 3. FIG. 6 is an operational waveform diagram of this embodiment.

Time t. Even if the element voltage V3 (FIG. 6(h)) decreases at - and -tl, the capacitance component Cs and the charging voltage v·6 of the capacitor C11 (FIG. 6(i)) hardly decrease. Therefore, even if the element voltage V increases from time t2 to time tL, the charging voltage of the capacitance component Cs and the capacitor C8 ■6
Since is originally high, charging current hardly flows, and unnecessary signals are not generated in the input signals (2) and (2) of the driver circuit 1.

X Lid]”- FIG. 7 is a circuit diagram of a fifth embodiment of the present invention.

In this embodiment, a diode D2 for blocking reverse flow is inserted in the signal transmission path between the current mirror circuits 3 and 4, so that the capacitance component Cs and the accumulated charge in the capacitor C8 are transferred to the element. It is designed so that it does not easily decrease even when the voltage (3) decreases. FIG. 8 is an operational waveform diagram of this embodiment. Time. ~t, the element voltage V
3 (FIG. 8(h)) decreases, the capacitance component Cs and the charging voltage V 6 of the capacitor C3 (FIG. 8(i)) hardly decrease. Therefore, even if the element voltage (3) increases between times t2 and t3, the capacitance component Cs and the capacitor C8
Since the charging voltage V6 is originally high, the charging current hardly flows, and the same effect as in the fourth embodiment is obtained.

Takei Example 6 FIG. 9 is a circuit diagram of a main part of a sixth embodiment of the present invention. In this embodiment, a resistor Rh is used in place of the capacitor C8 in FIG. 7 as an impedance element for preventing a decrease in the accumulated charge of the capacitive component Cs. This resistor Rb acts as an impedance element to continue charging the capacitance component Cs by the DC power supply V, and therefore,
Even if the element voltage V3 decreases, the charging voltage (6) hardly decreases.

Therefore, even if the element voltage (2) increases thereafter, almost no charging current flows to the capacitive component Cs.

Note that the impedance element for continuing to charge the capacitive component Cs is not limited to the resistor Rb, but may also be a capacitor,
A choke coil may also be used.

In each of the above embodiments, a current mirror circuit 3.4 operating in an unsaturated region is used as a signal transmission circuit, but a transistor T as shown in FIG.
r2. The present invention can also be applied to a case where a saturation type switching circuit using T r is used. 1st
In the signal transmission circuit shown in Figure 0, the transistor Tr
< is connected in series with resistors R7 and Rs, and capacitor C
2 (not shown). A resistor R6 is connected between the base, emitter, and ivy of the transistor Tr. The base of the transistor Tr4 is connected to the collector of the transistor Tr2 via a resistor R5. When the drive signal V is at a high level, a base current flows to the transistor Tr2 via the resistor R4, and 1.
Transistor Tr2 is turned on. At this time, a current flows through the resistor R6, and the voltage generated across the resistor R6 turns on the transistor Tr4, and the resistor R? , a current flows through Rs, and a signal ■4 is generated at the connection point of resistors Rt and R3,
A high level signal is input to a driver circuit 1 (not shown). When the drive signal VB is at a low level, a low level signal is input to the driver circuit 1. Even in such a signal transmission circuit, when the transistor Tr2 is turned off, a malfunction occurs due to the charging current to the capacitance component Cs between its collector and emitter, so it is meaningful to apply the present invention.

Note that the inverter device with a full bridge configuration, that is, the series circuit of the third and fourth switching elements is connected to the DC power supply V.
and a load circuit is connected between the connection point of the first and second switching elements and the connection point of the third and fourth switching elements, and the diagonal switching elements are turned on and off at the same time. The present invention can also be applied to an inverter device that is turned off and supplies alternating current to a load circuit.

(Effects of the Invention) As described above, the present invention has first and second switching elements connected in series, and from an oscillation circuit having the same potential as the second switching element to the first switching element having a different potential. In an inverter device that performs signal transfer without going through an insulating element, an impedance element is provided to prevent the charging current to the capacitive component of the signal transmission circuit from being transmitted to the first switching element, so that the impedance element is provided at both ends of the switching element. This has the effect of preventing unnecessary switching element current from flowing when the voltage changes, and improving reliability.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is an operation waveform diagram of the same as above, FIG. 3(a) is a main part circuit diagram of a second embodiment of the present invention, and FIG. Main part circuit diagram of a modified example of the above, No. 4
The figure is a circuit diagram of a main part of a third embodiment of the present invention, FIG. 5 is a circuit diagram of a fourth embodiment of the present invention, FIG. 6 is an operation waveform diagram of the same as above, and FIG. Example circuit diagram, FIG. 8 is an operation waveform diagram of the same as above, FIG. 9 is a main part circuit diagram of the sixth embodiment of the present invention,
FIG. 10 is a circuit diagram of another signal transmission circuit used in the present invention,
FIG. 11 is a circuit diagram of a conventional example, and FIG. 12 is an operation waveform diagram of the same. ■ is a DC power supply, SW+, SW2 are switching elements, 3
, 4 is a current mirror circuit, 5 is an oscillation circuit, vA, vB
is a drive signal, Ra and 'Rb are resistances, cs is a capacitance component, and Cs and Ce are capacitors.

Claims (4)

[Claims] (1) A series circuit of first and second switching elements is connected to a DC power source, and a load circuit is driven by AC by the outputs switched by the first and second switching elements, and the first switching element An oscillation circuit that generates a first signal that turns on and off the second switching element and a second signal that turns on and off the second switching element such that it does not turn on and off at the same time as the first switching element. In an inverter device comprising a signal transmission circuit which is provided on the same potential side as the oscillation circuit and which transmits a first signal from the oscillation circuit to the first switching element as a current signal without going through an insulating element, the capacitance component of the signal transmission circuit The charging current is the first
An inverter device characterized in that an impedance element is provided to prevent transmission to the switching element. (2) The inverter device according to claim 1, wherein the impedance element includes a capacitor that bypasses the current charged in the capacitance component of the signal transmission circuit from being transmitted to the first switching element. . (3) The inverter device according to claim 1, wherein the impedance element includes a voltage fluctuation suppressing capacitor connected in parallel to a capacitance component of the signal transmission circuit. (4) The inverter device according to claim 1, wherein the impedance element includes a diode that prevents discharge of electric charge stored in a capacitive component of the signal transmission circuit.