JPS5911265B2 - transistor inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 5 The present invention relates to a transistor inverter device in which an inductance element is inserted in the input circuit of a bushable transistor inverter to provide a constant current function, thereby reducing switching loss in the transistors.

As shown in a typical circuit example in FIG. Each terminal is connected to a transistor T.
R, , is connected to the input terminal P2 via the collector-emitter path of TR2.

Also, the intermediate tap of the feedback winding NB of the transformer T is set to 2.
are connected to the transistors TRI and TR through the diode D.
2, and connect each terminal of the winding NB to resistors R1, R2 and '! 0 Capacitor C
The transistor TR0 is connected to the transistor TR0 through a parallel circuit with C2.
, connected to the base of TR2. The secondary winding Ns of the transistor T is connected between output terminals P3 and P4, and the base of the transistor TRI is connected to the input terminal P1 via a starting resistor R3. As shown in FIG. 1, this bush bull type transistor inverter connects a load L between output terminals P3 and P4,
When the DC power supply E is connected between the input terminals P and P2, the base current of the transistor 30TR first flows through the resistor R3, and thereby the collector current of the transistor TRI starts to flow.

As a result, a voltage is generated in the feedback winding NB, and a base current is applied from the feedback winding NB to the transistor TRI via a parallel circuit of the resistor R and the capacitor Cl so that the collector current 35 further increases. This turns on the transistor TRI. Then, when the collector IC of the transistor TRI is equal to the product of the base q゜-current 1b and the DC current amplification factor HFE of the transistor,
The increase in the collector current 1C is stopped, thereby the voltage of the primary winding Np decreases, and the base current of the transistor TRl also decreases.

When the collector current decreases due to the decrease in base current,
A feedback voltage of opposite polarity is generated in the feedback winding NB, which reverse biases the transistor TRl to turn it off, and forward biases the transistor TR2. Therefore, the transistor TR is turned off, a base current begins to flow through the transistor TR2, and a collector current begins to flow through the transistor TR2. This transistor TR2 is then turned off similarly to the transistor TRl, and the collector current starts flowing through the transistor TRl again as in the case of the transistor TR2. That is, the transistors TR, TR2 continue to perform an oscillating operation by alternately repeating on and off operations, thereby supplying an alternating current voltage to the load L connected between the output terminals P3 and P4. Therefore, this type of push-pull type transistor inverter has the following drawbacks because it has an operating mechanism in which one transistor in the on state turns off and then the other transistor turns on. .

That is, the trigger for turning off the transistor that has been on is given when the collector current 1C and base current 1b reach IchFE-1b as described above. However, the direct current amplification factor HFE varies depending on the individual transistors, and even in the same transistor, it is not constant due to the influence of temperature, drift, etc. Therefore, in a device in which the timing for turning off the transistor is determined by the DC current amplification factor HFE as described above, there may be a significant difference in input/output characteristics including the scanning frequency, making it difficult to mass-produce. lacking in sex. For this reason, as a means of not depending on the DC current amplification factor HFE for changing the timing of turning the transistor from the on state to the off state, a method can be considered in which capacitors Cl and C2 are connected in parallel with resistors R1 and R2, as shown in the figure.

By doing this, when transistor TRl is currently on and a reverse bias is applied between the base and emitter of transistor TR2, transistor TR2 is off, but as time passes, capacitor C changes to the polarity shown in the figure. Therefore, the transistor T
The base potential of R2 rises. And transistor T
When the base potential of R2 becomes higher than the emitter potential,
Transistor TR2 turns on even though transistor TRl is in the on state. and,
When the transistor TR2 is turned on, the discharge current of the capacitor C1 flows through the parallel circuit of the feedback winding NBL resistor R2 and the capacitor C2, the base-emitter path of the transistor TR2, and the emitter-base path of the transistor TRl.
A reverse bias is applied to the transistor TRl to turn it off. Therefore, since the transistors TRl and TR2 can be switched by the capacitors Cl and C2 irrespective of their DC current amplification factors HFE, compared to the case where the switching operations are performed in relation to the DC current amplification factors. It should be possible to make the oscillation frequency and output characteristics of the inverter stable, unaffected by the DC current amplification factor of the transistors.

However, as mentioned above, the base of the transistor TRl
Even if the discharge current of the capacitor C1 is applied to the emitter path to apply a reverse bias, the transistor TRl will not turn off immediately due to its accumulation time and fall time characteristics, and the collector current of the transistor TRl will continue to flow for a while. In the end, both transistors T
It was found that the collector current started to flow through Rl and TR2 at the same time.

In this way, both transistors TRl and TR2
When a collector current flows at the same time, the magnetic flux generated in the primary winding Np of the inverter transformer T due to the collector current cancels each other, and during that period, the voltage of the primary winding Np becomes approximately zero, Moreover, the transistor TRl,
Since TR2 is turned on at the same time, it becomes short-circuited, the oscillation operation stops, and the transistors TR1 and TR2 are destroyed, and it has been found that the above idea cannot be put into practical use as is. On the other hand, in the case of an inductive load in a transistor inverter, for example, in the case where the load L is inductive in the transistor inverter shown in FIG. The result will be as shown in the figure.

As can be seen from the figure, when a transistor switches, especially when it turns off, a sudden pulse-like voltage is generated between its collector and emitter, which causes transistor loss and ultimately reduces the conversion efficiency of the inverter. It's summery. Furthermore, when an LC oscillation system is installed on the load side, the collector current of the transistor also oscillates in accordance with the oscillation of the oscillation, that is, the oscillation of the load current, and as a result, the peak value of the input current is lower than its average value. There were also problems with much larger values. Furthermore, since the collector current changes, the base current must be designed to be larger than the average value in accordance with the peak value of the collector current, and as a result, power loss due to the base current also increases. Furthermore, since the collector current, that is, the input current fluctuates, it includes a high frequency component (generally because the oscillation frequency is from several KHz to several +KHz), there is also the problem of high frequency noise. Note that a push-pull type thyristor inverter has been proposed that attempts to reduce the pulse-like voltage shown in FIG. 2 that occurs when a pair of thyristors are switched (Japanese Patent Publication No. 43-27010).

This is an inductance element inserted in series between a DC power source and an inverter to prevent pulsed voltage and rush current during switching. However, in this case, the inductance element does not act on fluctuations in the human power current after switching. Therefore, although this device attempts to absorb fluctuations after switching by using a resistor, there is a problem in that the resistor causes power loss. By inserting an inductance element having a specific inductance value in series between a DC power supply and a push-pull type transistor inverter, this invention not only suppresses inrush current during switching of the input current of the inverter. , the current remains constant even after switching, which solves the various problems mentioned above, stabilizes the oscillation frequency and input/output characteristics, and also enables switching after turning on a pair of transistors at the same time when switching transistors. The present invention provides a transistor inverter device with high conversion efficiency and low power loss due to switching loss and base current in transistors. Embodiments of the present invention will be described below with reference to the drawings.

Note that the same parts as those of the conventional device shown in FIG. 1 will be described with the same reference numerals. FIG. 3 shows an embodiment of the present invention, and the feature of this device is that an inductance element CH such as a chiyoke coil is connected between a bushable transistor inverter I and a DC power supply E, and its inductance value will be described later. The reason is that a specific value is selected and inserted in series.

With such a configuration, the transistor TR is now turned on and a reverse bias is applied between the base and emitter of the transistor TR2, and when time passes while the transistor TR2 is turned off, the transistor TRl is turned on. However, the base potential of the transistor TR2 rises due to the charging potential of the capacitor C, and the transistor T
Base current begins to flow through R2, thereby reverse biasing transistor TRl.

In this case as well, as mentioned above, the transistor TRl
, TR2 temporarily flows through both of the collector currents at the same time, and the primary winding voltage of the inverter transformer T becomes approximately zero, but the inductance element prevents the inrush current from the DC power supply E from becoming a problem. Since CH exhibits high impedance, the human power current flowing from DC power supply E to inverter I is kept constant. Therefore, even if the transistors TRl and TR2 are turned on at the same time as described above, this will not cause an accident such as a short circuit, so the inverter IV is determined by the charging time constant of the capacitors Cl and C2. It will oscillate normally at regular intervals. Therefore, even if transistors with varying DC current amplification factors HFF are used, the oscillation frequency of the inverter and the input/output characteristics can be adjusted and set to a predetermined value, and can be made fixed. In addition, as mentioned above, the inductance element CH can make the inverter's 1V human power current a constant current, so even if the load is inductive, a pair of transistors can be turned on at the same time during transistor switching operation. The voltage generated between the collector and emitter can be made close to zero, thereby making the switching loss in the transistor extremely small.
Conversion efficiency as an inverter can be improved.

Furthermore, even if the load L side includes an LC vibration system and the load current attempts to oscillate, the inductance element CH
As a result, the peak value of the input current can be made very close to its average value, as shown by the collector current in Figure 5, because the human input current to the inverter can be suppressed from oscillating in response to it. The maximum collector current can be selected to be sufficiently smaller than that in the conventional device shown in FIG. 2, and as a result, a transistor with a small capacity can be used.

Furthermore, since the base current can be designed to be close to the average value of the collector current, it can be made smaller than the conventional one, reducing power loss due to the base current and also reducing the problem of high frequency noise. Here, in order to clarify the appropriate value range of the inductance value L of the inductance element CH that can produce the above-mentioned action and effect, the inductance element CH
impedance value ωL (where ω is the inverter IV
angular frequency) and input impedance Zin of inverter IV at load (however, this Zin is input current 11 when the power supply voltage is In), then Vin(i)LZin=
? This is what I asked for.

) The change in the efficiency η (to) of the inverter IV with respect to the ratio -11nZin was investigated, and the results will be described with reference to FIG.

In this test, the DC power supply voltage was set to 12 (V), the oscillation frequency of the inverter was set to approximately 15 (KHz), and a series circuit of a capacitor ballast and a 10 W fluorescent lamp was used as the load. In addition, other tests with different conditions yielded results similar to the above test.
These results are approximately equal to the results shown in FIG. As is clear from FIG. 4, when the inductance value of the inductance element is L, the input current of the inverter can be made constant both during and after switching, and sufficiently good efficiency can be obtained. It can be seen that the above-mentioned effects can be fully exhibited.

However, if the inductance value L becomes large, the iron core, winding, etc. will become large and loss will occur, so it is most desirable in practice to set the inductance value L to .

Next, make the load L inductive and make the inductance element CH
The current and cage pressure waveforms at each part of the inverter IV were investigated using an inductor with an inductance L, and the results are shown in FIG.

In this case, unlike the case of the conventional device shown in Figure 2, no pulse-like voltage is generated between the collector and emitter of the transistor even during the switching operation of the transistor, and the switching loss of the transistor is extremely reduced. It can be seen that even when the inductance value of the inductance element is at the above value, the constant current effect is sufficiently exhibited during switching and during the entire period after switching. Furthermore, even when the inductance value of the inductance element is the above-mentioned value, as is clear from FIG. 4, a considerable improvement in efficiency is achieved, although it is not sufficient. In the above embodiment, the base circuit of the transistor includes capacitors C, C2, but as in the embodiment shown in FIG. 6, the capacitor C4 is connected in parallel to the load L, As shown in the figure, in the case where a series circuit of a capacitor ballast C5 and a fluorescent lamp La is used as a load, parallel or series vibration occurs between the capacitors C4 and C5 and the windings of the inverter transformer T, and each winding of the transformer T The generated voltage takes a form close to a sine wave due to its oscillations, and the voltage between the bases of the transistors also changes accordingly, which allows the transistors to perform switching operations.
Depending on the switching time of R2, etc., the capacitor Cl,
As in the case of using C2, there is a period in which a pair of transistors are turned on at the same time, and there are problems such as fluctuations in load current, so the present invention can also be applied to such an inverter.

In addition, if a capacitor is not used on the load side, vibrations caused by the capacitors Cl and C2 tend to have an adverse effect, so in that case, as in the embodiment shown in FIG.
Dummy resistors R4 and R5 are installed in each base circuit of l and TR2.
Just insert .

Furthermore, in the embodiment shown in FIG. 3, when the load condition becomes extremely light compared to the rated load, the power source impedance is high due to the inductance element CH, and reactive power is not returned to the power source. This may result in abnormal oscillation of the inverter IV, but in such a case, as in the embodiment shown in FIG. CH
Connect the capacitor C6 through the capacitor C6
It is sufficient if the function of temporarily storing reactive power is left unused. However, if the capacitance of the capacitor C6 is too large, there will be an inconvenience that the role of the inductance element CH during the important rated load is diminished. In other words, the impedance due to capacitor C6 is the inductance element C
There are limitations compared to the impedance due to H. So, what is the ratio of both impedances ωL? The change in inverter efficiency η (%) with respect to 1/(!)C characteristics was investigated.

Note that the test conditions in this case are the same as in the test described above. In this case, the results shown in FIG. 10 were obtained, and it was found that it is desirable to set this from now on.

Note that, as in this embodiment, an LC circuit is inserted between the power supply and the inverter circuit, which is seen in single transistor inverter devices. This is a so-called filter to prevent noise from affecting other loads. In other words, an inductance element is used to prevent the generation of noise, and a capacitor is used to convert the state of the power supply seen from the inverter side into a constant voltage source. It's something completely different. In addition, conventional devices insert a minute conductance element into the collector circuit or power supply of the transistor, but this is only used for the purpose of suppressing the rise of the current flowing through the transistor and reducing switching loss. This is also completely different since it does not have a constant current function like the one of the present invention. As detailed above, in the present invention, an inductance element having a specific inductance value is inserted in series between a DC power supply and a push-pull type transistor inverter, so that the inductance element can cause an inrush during switching of a pair of transistors of an inverter. It has both the function of blocking current and the function of making the input current constant after switching, so there is no power loss, the number of parts can be reduced, it operates stably, and small-capacity transistors can be used. It is inexpensive, has low power loss due to base current, has low high-frequency noise, and can reduce power loss by turning on a pair of transistors simultaneously and reducing the collector-emitter voltage to near zero before switching. This makes it possible to provide an inverter device with fewer transistors.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional device, Fig. 2 is a current/voltage waveform diagram of each part in the same device, Fig. 3 is a circuit diagram showing an embodiment of the present invention, and Fig. 4 is used in the same embodiment. Figure 5 is a characteristic diagram showing the relationship between the inductance value of the inductance element and the efficiency of the inverter. Figure 5 is a current/voltage waveform diagram of each part when an inductive load is used in the same example.
9 are circuit diagrams showing other embodiments of the present invention, and FIG. 10 is a characteristic diagram showing the relationship between the capacitance of the capacitor and the efficiency of the converter used in the embodiment shown in FIG. V...Push-pull type transistor inverter, TR,, TR2...Transistor, T...
...Inverter transformer, E...DC power supply,
L...Load, CH...Inductance element.

Claims (1)

[Scope of Claims] 1. A push-pull type transistor inverter connected to this power supply and having a period in which a pair of transistors are simultaneously turned on during switching, and an inductance inserted in series between the DC power supply and the inverter. The inductance value L of the inductance element is L≧1/5, where Zin is the input impedance of the push-pull transistor inverter under load and ω is the output angular frequency of the inverter. A transistor inverter device characterized in that Z^i^n_ω is set.