JPS5914376A - Inverter device - Google Patents

Abstract

PURPOSE:To avoid an interference to other equipment and an erroneous operation by forming two or more operating points of an inverter circuit with an LC resonance circuit of the inverter circuit and another resonance circuit and driving the inverter circuit at any operating point. CONSTITUTION:When a switch S is closed, a commercial power source Vs is connected, a transistor inverter circuit A is oscillated, and a high frequency output is obtained at the secondary side of an oscillation transformer 7. When a changeover switch S1 is provided at the terminal NC side, a choke coil 11b of an output alleviating reactance element is shortcircuited, and the secondary output of the transformer 7 is supplied through a choke coil 11a to a load 10. When a changeover switch S1 is switched to terminal NO side, a choke coil 11b is inserted in series with a choke coil 11a and a load 10 to reduce the output current, a capacitor 12 is simultaneously connected in parallel with the series circuit of the load 10 and the choke coil 11b.

Description

[Detailed description of the invention] The uninvented invention relates to an inverter device.

FIG. 1 shows a conventional example of this type of inverter device. This conventional inverter device is composed of a bush-pull type transistor inverter circuit A, etc., and a rectifier bridge 11) and a smoothing capacitor (31) are connected from a commercial power supply via a switch H to form a DC power supply, as shown in the figure. elI
The Il terminal is connected to the center tap of the primary winding Ns of the oscillation transformer 171 via the choke coil (2). , one end of this primary winding Ns is a transistor 14)
and the other f@ are connected to the collector of the transistor 161, and the three transistors 14) and 151 are collectively connected to both O terminals of the DC power supply. Furthermore, the feedback winding NB of the oscillation transformer +71 is connected to the bases of the transistors 14) and +51, and the resistor +81
, +91 to both terminals e of the DC power supply. A resonance capacitor (6) is connected between both ends of the primary winding Ns of the oscillation transformer (7), that is, between the collectors of transistors +41 and lfi+, and a resonance capacitor (6) is connected between both ends of the secondary winding N! of the oscillation transformer (71). A series circuit of a load 1101 and a choke coil for output variation is connected.

In this conventional example, the resistor 18) is connected to the DC power supply.

(When a drive current is applied to the base of each transistor +41 and 161 through 91, transistor (4) or #-
Either one of i+51 turns on. Now, if the transistor 14) is turned on, a current flows through the primary wire N1 of the oscillation transformer (7), and the secondary winding teeth and the feedback winding NBV
By inducing C back electromotive force and then turning transistors 141 and +51 on and off alternately by this electromotive force, the current flowing through the primary winding Ns is alternately reversed, and due to resonance operation with the capacitor (6). Secondary winding N! A high frequency sine wave output is obtained. This output is supplied to the load +101 via the output variable choke coil (Ill).

@Figure 2 (al shows the equivalent circuit when the resonance system of the transistor inverter circuit A is loaded.
(This is an equivalent circuit obtained by rewriting al.) Figure 2 f
C in al indicates the capacitance of the capacitor (61), the interface of the Lst'i oscillation transformer (71, excitation interface, and Lx is the old choke coil), and the resistance of the RVi load 1101. Also, FIG. L' in ibl
s is the impedance seen from the input terminals A and A' of this equivalent circuit, with frequency plotted on the horizontal axis, as shown in Figure 2 (
It will look like C1. That is, the point P is the parallel resonance point (anti-resonance point), and the self-excited inverter stably maintains oscillation at this point. In such a state, if the value of the coefficient y (61) shown in Fig. 1 is changed, the parallel resonant circuit impedance becomes wrinkled, and the anti-resonance point P of Fig. 2 In other words, when the capacitor capacity C is increased, the anti-resonance frequency becomes lower, and therefore the impedance of the choke coil +111 becomes smaller and the output to the load 101 increases, and vice versa when the capacitor capacity C is decreased. Also, if you change the excitation interface Ll of the oscillation transformer () 1 instead of changing the capacity C of the capacitor (6), the anti-resonance point changes as shown in Figure 2 (e). That is, A:/tactance If 1 is increased, the anti-resonant wave number becomes lower, so the impedance of the choke coil 111) becomes smaller and the load increases by 10
The output to 1 increases and vice versa if the excitation intertasis Ll is decreased.

Furthermore, even if the intertasis Lv of the choke coil 111) is changed, the impedance of the parallel resonant circuit changes, and the anti-resonance point P of fcl in FIG.
In other words, interface L! When increasing , the anti-resonant wave number becomes lower, and in this case, the choke coil's A:7
Since the tactance L2 is increased, the output to the load (lO) decreases even if the frequency becomes lower. Of course interface L
The opposite is true if you reduce it by 1. Note that the case where a capacitor is used instead of the choke coil 1111 to vary the output can be explained in the same way as the choke coil +111, but in that case, as the anti-resonance point frequency becomes higher, the capacitor impedance becomes smaller, so the output increases. However, using a capacitor instead of a choke coil (older choke coil) causes a phase-advanced current to flow through switching elements such as transistors, which may destroy these elements, increase the loss of the transistor inverter circuit A, or increase waveform distortion. Because of the drawbacks such as increased noise generation, it is not used much other than for special purposes.

It has been explained above that when the circuit constants of the circuit shown in FIG.
If this is used, the inverter load can be easily controlled.

By the way, the method of changing the capacitor capacitance jlC of the capacitor (6) does not have a means of continuously changing the capacitor capacitance C, and the method of switching the capacitor capacitance C generates surge voltage and current when switching, and the switching elements such as transistors There is a risk of destroying the
Significantly change the output of the base (for example, change the output from 100% to 5
0%), the capacitor capacitance C needs to be changed significantly more than that, and there is a risk that the transistor inverter circuit A may cause abnormal oscillation, so this is hardly a preferable method.

In addition, an oscillation transformer using a saturable reactor has been considered as a method of changing the excitation intufftance Lt of the oscillation transformer (71), but since the structure is quite rough and large-scale, it is not suitable for other than special purposes. For this reason, a choke coil (11) as shown in FIG. 1 is often used. However, when controlling the output by changing the circuit constants and changing the oscillation frequency of the inverter circuit, it is possible to control the output by changing the circuit constants. In an inverter device, frequency fluctuations are inevitable, and when the output is controlled by changing the tactance L! of the choke coil dll shown in Figure 1, the tactance L! There is a drawback that if the output is reduced by increasing Ll, the same wave number necessarily decreases.

For example, in the circuit shown in @1, the load is +101,! - then F
Using CL32W and FCL40W fluorescent lamp loads (series connection), switching the E7 tactance of the old choke coil) resulted in 100% lighting and 60% lighting, resulting in 100% lighting.
The frequency at % is 40KH2, the same wave number at 6ON is 25K
It became H2. As is well known, fluorescent lamps emit near-infrared rays, and if the lighting frequency is 1/2 or the same as the inter-carrier frequency of communication equipment that uses infrared rays, it can cause interference and cause malfunction of communication equipment. It has been known.

Currently, the frequency used for such communication equipment using infrared rays is 30KHz to 50KHz, so the lighting frequency of a fluorescent lamp is 15 to 24KH2130 to 48K.
If H2 is used, it will result in interference, so in order to exclude this band, it will be necessary to use I/''i25 to 29KH2 and frequencies above 49KHz.In order to set the same wave number of the lighting device in such a range, There is no other way than to set the lighting to 49KH2 or more for 100% lighting and 60% lighting, and if the lighting is set to 9kHz for 60% lighting, the same wave number at 100% lighting will rise to 80kHz, which will increase radiation noise and switch This creates new problems such as increased loss, so frequency control is required in order to effectively use the same wavenumber within a limited range.In response to these demands, separately excited inverter devices are attracting attention. However, since the circuit is more complex than the variable speed type, issues such as cost and reliability remain.Therefore, there is a need for a simple method to control the same wave number when changing the output of a self-excited inverter. It can be said that the sex is very large.

The invention was made in view of the points mentioned above, and its purpose is to provide a self-excited inverter device in which two or more operating points can be set for the inverter when the output is reduced, and the oscillation frequency can be taken into account. With this design, it is possible to easily avoid interference and malfunction with equipment such as communication equipment installed near X1, and by adjusting the circuit constants, the oscillation frequency when output is reduced can be varied over a wide range. An object of the present invention is to provide an inverter device that has a simple configuration and is advantageous in terms of cost and reliability.

The present invention will be explained below with reference to Examples. First, the uninvented operating principle will be explained. Figure 3 (al~(cl) shows an equivalent circuit when the resonant system of the inverter circuit is loaded to explain the uninvented principle; R, provided in series with
Also, capacitor C is connected in parallel with load R1! are provided, and a changeover switch So is configured to set the state in which these capacitors C2 are pushed in and the state in which they are removed. That is, if the switch So is an NCI)lii1 child sub, these elements L1 and Cs are removed from the circuit, and the inverter circuit oscillates at a frequency determined by the capacitor CI and the tactance L1 of the oscillation transformer. Switch S here. If you make it a NO terminal picture, the intertasis element L
3.] Njinsa C! is inserted in the circuit, the inverter circuit has a series resonant circuit consisting of the capacitor C2 and the tactance L in addition to the parallel resonant circuit of the capacitor Ct and the tactance Ls. When such a situation is expressed as a frequency characteristic of circuit impedance, it becomes as shown in FIG. In other words, when the switch So is an NC terminal picture, there is a parallel resonance frequency Po of the capacitor C1 (!: intance L1, and the circuit impedance at that time is maximum, but at a frequency lower than the same wave number po)
o l, l< old 1. ．． Therefore, it shows an inductive impedance, and at frequencies higher than the same wave number re,
The characteristics are shown in Figure 4 (al).If we assume that the feedback signal of the self-excited inverter device is obtained from an oscillation transformer, as is well known, the same wave number of oscillation is the same wave number of the parallel resonance point, that is, the anti-resonance point. It is determined at P6, and is unstable at other points.However, when the switch So is set to NOf@child, the following three resonance points are formed as shown in Fig. 4 (bl).In other words, ωL!<< The capacitance of C1 and the capacitance of capacitor C1 are added to form a parallel resonance with the interface L1.In addition, at the same wave number of the pair, a series resonance is formed between the interface C! and the capacitor C!.This resonance point is P. ! Furthermore, it interfaces with the interface LL and becomes parallel, forming parallel resonance with the capacitor C1.The parallel resonance point corresponding to this is Ps.

Of these three resonance points, P snow is a series resonance point, which is an unstable region in a self-commutated inverter device that uses parallel resonance, but P+ and Pg are both anti-resonance points and stable. The oscillation can be sustained, and by switching the switch So from the operating point P of Fig. 4 (al), @ Fig. 4 (
It can be seen that the same wave number can be controlled to either of the two operating points of PI and PI of bl. According to experiments by the inventors, if fpo > fpo, then Ps, and if fpo < f
If it was po, it became Ps.

@3 Figure Tbl is one in which a current-limiting interface element L4 is added. That is, if the switch So is on the NC terminal side, the current-limiting interface element L4 used as an actance element is short-circuited, and the capacitor Cs is also not connected. Therefore, the inverter device
The interface element Ls functions as a stabilizing element of the output current, and the operating point in this case is the Pa point in FIG. 4 (al).

Next, when the switch So is switched to the NO terminal mode, the current limiting tactance element L4 is inserted in series with the load R to reduce the output current, and at the same time, the capacitor C8 is inserted in parallel. Therefore, the inverter device has a capacitor C1 and an interface! parallel circuit and interface element L1
, Coyden'J'Cx is formed, and as mentioned above, three resonance points as shown in FIG. 4 (bl) are obtained.

This shows that when adjusting the output by narrowing down the output current, the oscillation frequency can be set either high or low by selecting the P point with a low same wave number and the 21 points with a high same wave number. Figure 3 (The equivalent circuit of cl is shown in Figure 3.
Further, the same explanation can be given by replacing the capacitor Ct with the interface element L1.

The circuit shown in FIG. 5 was formed based on this principle. That is, in this embodiment, in the transistor inverter circuit A, the secondary winding Ns of the oscillation transformer (7)
A load +101 is connected to both ends of the @1 choke coil (11a) and a second choke coil (llb), and the first. @2 choke coil (1la)
, (llb) to the common terminal COM of the changeover switch s1, and the load +101 and the second choke coil (llb).
At the point where the NC terminal of the changeover switch s1 is connected to the connection point of l lb), and the capacitor [+21 is connected between the connection point of the secondary winding island and the load (101) and the NO terminal of the changeover switch S, This is different from the conventional circuit shown in FIG.

When the switch S is turned on now, the commercial power supply v5 is connected, and the transistor inverter circuit A operates in oscillation in the same manner as the conventional example shown in FIG. 1, and a high-frequency output is obtained on the secondary screen of the oscillation transformer (7). If the selector switch S1 is now on the NC terminal side, the choke coil (1lb
) is short-circuited, so the 2 of the oscillating transformer (7)
The next output is the load +10 via the choke coil (lla).
1. Next, changeover switch Ss t NOI
When set to II, the choke coil (11a) and load 110
) is inserted in series with the choke coil (llb) to reduce the output current.At the same time, the capacitor (121 is the load +
+01 and a choke coil (lit)) in parallel. The oscillation same wave number of the transistor inverter circuit A at this time can be considered in two ways as explained in Fig. 4 (bl). As mentioned in the principle explanation, if you set the frequency in advance, you can make the frequency higher or lower when the output is reduced. The same wave number before switching of the selector switch S1 is set so that the same wave number is obtained, and the operating point is selected so as not to cause noise interference to the communication equipment even when the output is reduced.

After switching the selector switch S+ to the NO terminal, for example, by providing a short circuit switch SWa and an open switch SWb as shown in Fig. 6, and changing the circuit t-mode momentarily by operating these switches, the t You can also switch between high and low frequency. Furthermore, the oscillation station wave number can be varied over a wide range by changing the capacitance value of the converter αt, and of course the interface value of the choke coil (lla) can also be changed. Since this is done by a parallel resonant circuit of LC, the other resonant circuit formed when reducing the output is a series resonant circuit, but in the case of an inverter circuit using a series resonant circuit, another resonance formed when reducing the VCI/'i output. The circuit is preferably a parallel resonant circuit.

The uninvented device has an inverter circuit that performs self-excited oscillation by an LC resonance circuit of a capacitor and an interface of an oscillation transformer, and sets an output reduction state by switching the reactance value, or uses an actance element as the secondary output of the oscillation transformer. In an inverter circuit inserted in series between a load, the LC resonant circuit of the inverter circuit and the another resonant circuit are provided, including another resonant circuit including the above-mentioned reactasis element and a switching means when in an output reduction state. Since 2 or more operating points of the inverter circuit are formed by 2 and t and the isolator circuit is driven at any of the operating points, the oscillation station wave number is set so as not to become a source of interference noise from nearby communication equipment, etc. This has the effect of increasing the design margin when considering the following: Therefore, interference with other nearby equipment and malfunction can be easily avoided, and noise filters for this purpose:
In addition, by adjusting the circuit constants, the same wave number of oscillation when the output decreases can be changed over a wide range, and by simply forming another resonant circuit using a switching means. Since it can be realized with a simple configuration, it is advantageous in terms of cost and reliability.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of the conventional example, @Figure 2 fat * (bl
1 (cl + fdl, (pi is the same operation explanatory diagram as above, Fig. 3 (al, (bl, (cl
) is an explanatory diagram of the same operation, Figure 5 is a circuit diagram of an embodiment of the invention yet to be invented, Figure @6 is a partially omitted circuit diagram of another embodiment of the present invention, and (7) is an oscillation transformer. , t+01 is the load, (
lla) and (llb) are choke coils, 021 is a capacitor, AVi controller, 7-digital inverter, and Sl is a changeover switch. Agent Patent Attorney Ishi 1) Choshichi

Claims (1)

[Claims] 111 It has an inverter circuit that performs self-excited oscillation by an LC resonance circuit of a capacitor and the interface of an oscillation transformer, and a reactance element that switches the reactance value to set the output reduction state is connected between the secondary output of the oscillation transformer and the load. In an inverter device inserted in series between
Another resonant circuit including the reactance element and a switching means are provided in the output reduction state, and two or more operating points of the inverter circuit are formed by the LC resonant circuit of the inverter circuit and the resonant circuit on the side. An inverter device characterized in that it drives an inverter circuit at any operating point.