JPH0334305B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an inverter device that converts a commercial frequency power supply voltage to a high frequency voltage of several tens of KHz.

(Background technology) As the need for power saving becomes established,
Inverter-type lighting devices that energize and light discharge lamps with high-frequency power of several tens of KHz are now well-known technology, and this method is popular because the luminous efficiency of the lamp is improved compared to commercial frequency. It is being

However, simply converting the commercial input power to a high frequency and energizing the discharge lamp does not improve the lamp power factor compared to the lamp power factor when using the commercial frequency, and therefore the power loss in the inverter lighting device increases. Since the input rectified voltage obtained through the full-wave rectifier 2 connected to the commercial AC power supply 1 is smoothed through the smoothing circuit 3, as shown in FIG. A method of energizing using high frequency power with a small amount of energy is used. Note that 5 in the figure is an inverter. To smooth this input rectified voltage, smoothing using a large capacitance capacitor or smoothing using partial feedback of the inverter output is used. However, if the input rectified voltage to the inverter is completely smoothed in this way, the power factor of the lamp becomes almost 1, reducing loss in the inverter and realizing a highly efficient lighting device, but on the other hand, the input power factor decreases. A deteriorating disadvantage occurs. This is because while the input commercial power supply supplies 50Hz or 60Hz ripple power, the input smoothing section converts it into smoothed power (voltage), which naturally results in a decrease in power factor.

In order to prevent such a decrease in the input power factor, the following methods have been considered. A concrete example of this is shown in FIG.
In Fig. 2, a lagging current i _L due to the AC side choke 6 and a leading phase current i _C due to the AC side capacitor 7 are shown.
By combining these, the input power factor is improved. However, even in this method, although the power factor is certainly improved, there is a drawback that there are many real harmonic components of the input current i. This is due to the voltage discrimination effect of the three-phase full-wave rectifier 2. The state of the input current i is shown and explained in FIG. 3b. To make it easier to understand,
FIG. 3 is drawn with the smoothing circuit 3 of FIG. 2 removed. The inverter 5 and the discharge lamp 4 can be considered to have a power factor of approximately 1 in the operating state, and therefore can be easily thought of as resistive loads. At this time, it is clear that the output voltage V _D of the full-wave rectifier 2 has the waveform shown by the solid line in FIG. 3a. This is because the lagging current i _L of the chain 6 and the leading phase current i _C of the capacitor 7 try to form rectified voltages V _L and V _C (including the broken line) as shown in the figure a, but the voltage of the rectifier 2 Due to the discrimination action, a voltage V _D is generated as shown by the solid line, and the lagging current i _L and leading current i _C at this time are formed as shown in c and d in the same figure, and the input current i is finally shown in b in the same figure. It can be seen that the input power factor is naturally improved. However, as is clear from FIG. 5B, the input current i has a rectangular waveform, and it can be understood that the number of odd harmonics including the third harmonic increases. Note that the waveform _Vs in a and b of the figure is a power supply voltage waveform.

As mentioned above, in the conventional example, if the input power factor is improved and the low frequency ripple of the high frequency voltage that energizes the discharge lamp is reduced, the harmonic component of the input current increases. Ta. Furthermore, in order to smooth the input rectified voltage, a smoothing capacitor of considerably large capacity is also required, which also has the drawback of increasing the shape and cost of the lighting device. Furthermore, when the load of the lighting device is made to have a high capacity, for example,
When lighting multiple discharge lamps, or
When the load is a discharge lamp of several hundred W, such as an HID lamp, there is only one inverter device, so the current and voltage withstand capacity of the elements that make up the inverter must be considerably large, resulting in a very large size. ,
Also, the cost is high, and for high capacity loads,
There were also drawbacks that made it difficult to put it into practical use.

(Object of the Invention) The present invention was made in view of the above-mentioned drawbacks, and its purpose is to reduce the low-frequency ripple of the envelope of the high-frequency output voltage in an inverter device that converts a commercial frequency power supply voltage into a high-frequency voltage. The purpose is to reduce the input power, improve the input power factor, and further reduce the harmonic components of the input current to improve the input characteristics.

(Disclosure of the Invention) FIG. 4 is a circuit diagram showing an embodiment of the present invention, in which 5a and 5b each indicate a constant current push-pull inverter. First, to explain the circuit related to the first constant current push-pull inverter 5a, one end of the AC input side of the first full-wave rectifier 2a is connected to one line of the single-phase commercial power supply 1 via the chain yoke 6. Full wave rectifier 2 for other wires
Connect to the other end of the AC input side of a. Full wave rectifier 2
A constant current switch 8 connects the anode side of the DC side output terminal of a.
a to the intermediate tap of the primary winding of the transformer 9a, and the collectors of the pair of transistors 11a and 12a are connected to both terminals of the primary winding of the transformer 9a, and the common emitter of each The connection terminal is connected to the negative electrode side of the DC output terminal of the full-wave rectifier 2a. A capacitor 10a is connected in parallel to both ends of the primary winding of the transistor 9a, and a resistor 13 is connected between the base terminals of both transistors 11a and 12a.
a, 14a are connected, and the anode terminal of the DC power supply 15a is connected to the common connection terminal of the resistors 13a, 14a, and the negative terminal is connected to the negative terminal of the full-wave rectifier 2a.

On the other hand, a second full-wave rectifier 2 is connected via a capacitor 7 to the same line as the commercial power supply 1 connected to the yoke 6.
One end of the AC input side of the full-wave rectifier 2b is connected, and the other line of the commercial power supply 1 is connected to the other end of the AC input side of the full-wave rectifier 2b. The DC side output end of the full-wave rectifier 2b is connected to the second constant-current push-pull inverter 5b, which has the same specifications and the same configuration as the constant-current push-pull inverter 5a, and the output end of the first full-wave rectifier 2a. The connection is made in the same way as the connection with the inverter 5a of No. 1. Also, the output windings 1 of transformers 9a and 9b of both inverters 5a and 5b
One end of each of 7a and 17b is connected, and a discharge lamp 4 is connected between the other ends. Both transformers 9a, 9b
A capacitor 18 and a transformer 19 are connected in series to the non-common connection ends of the output windings 17a and 17b, and both terminals of the two secondary windings 16a and 16b of the transformer 19 are connected to the transistors 11a and 11a of both inverters 5a and 5b, respectively. It is connected between the base terminals of transistors 12a and between the base terminals of transistors 11b and 12b.

Next, the operation of the inverter device will be explained with reference to the operation waveform diagram shown in FIG. When a power supply voltage _Vs is generated from the commercial AC power supply 1, full-wave rectified voltages _VL and _VC of the power supply voltage _Vs appear at the output terminals of the first and second full-wave rectifiers 2a and 2b. Next, the operation of the first inverter 5a will be described. The full-wave rectified voltage V _L appearing in the first full-wave rectifier 2a is applied between the collector and emitter of the transistors 11a and 12a via the choke 8a and the primary winding of the transformer 9a. As a result, since the transistors 11a and 12a are conductive, a collector current flows through the transistors 11a and 12a, and the collector current flows from the intermediate tap point of the primary winding of the transformer 9a to both transistors 11a and 12a. One of them saturates first, and from this point on, output winding 1
A voltage v _I is generated at 7a. Now, when voltage v _I is generated in the direction shown in FIG. 4, transistors 11a and 1
A voltage v _N is generated between the base ends of 2a in the direction shown,
Transistor 12a is turned off and transistor 11 is turned off.
It operates to turn on a. On the other hand, due to the presence of the capacitor 10a, the voltage v _I exhibits an oscillating voltage, and when the polarity of the voltage v _I is reversed, the voltage v _N
The polarity of is also reversed, and transistor 11a is now turned off and transistor 12a is turned on. At the time of this inversion, electromagnetic energy is stored in the primary winding of the transformer 9a on the side of the transistor 11a through which the collector current of the transistor 11a was flowing, and when the transistor 11a is off, it is released as a charging current to the capacitor 10a, and the voltage It works to maintain the vibration of v _I , and from then on, a sinusoidal oscillating voltage is generated in the voltage v _I , which is isolated from the primary winding.
Similarly, a sinusoidal oscillating voltage is generated in the secondary winding 17b of the transformer 9b of the second inverter 5b. At this time, transistor 11a and transistor 12a, transistor 11b and transistor 1
2b is in the same state because the inversion operation is controlled by the secondary windings 16a, 16b of the transformer 19 containing the same signal, and therefore both output windings 17a, 17
A synchronized oscillating voltage can be obtained as the voltage generated between each terminal of b.

Now, in this way, the voltage generated across the discharge lamp 4 becomes a high frequency voltage with less low frequency ripple.
This is due to the following reason. In the present invention, since the output high frequency voltage is synthesized in series from the outputs of the two constituent inverters,
The result is the same as adding the instantaneous values of the input DC voltages. On the other hand, since each inverter 5a, 5b is connected in series with the AC power supply via the choke 6 and capacitor 7, the first full-wave rectifier 2a has a lagging phase current i _L with respect to the power supply voltage _Vs. , and an advanced phase current i _C flows through the second full-wave rectifier 2b. Also, both rectifiers 2
Since the load power factor when looking at both inverters 5a and 5b from a and 2b is approximately 1 at low frequencies, they are considered to be almost resistance, and the AC side input terminal voltages of both rectifiers 2a and 2b are respectively relative to the power supply voltage. A lagging phase voltage v _L and a leading phase voltage v _C are generated. This situation is shown in FIG. 5a. Therefore, since the input current i is a combination of the lagging current i _L and the leading phase current i _C , it is clear that the input current i has a high power factor.

Also, the lagging current i _L and leading phase current i _C are as in the conventional example,
It is clear that the input current i becomes a sine wave rather than a rectangular wave due to the voltage discrimination effect of the full-wave rectifier, and the input current i has a sine wave shape since I = I = _L + I = _C holds in the vector. From the above, according to the present invention, the input power factor of the inverter-type lighting device for a discharge lamp is set to a high power factor, and the input power factor of the inverter-type lighting device is made high, and the high-frequency voltage with little low-frequency ripple is controlled without smoothing the input rectified voltage to the inverter. generated, maximizing the luminous efficiency of the discharge lamp,
A highly efficient lighting device can be realized.

In the present invention, the low frequency ripple is the slow phase current
Since it is determined by the phase angle θ between i _L and leading current i _C , the lagging phase angle for both currents i _L and i _C is set from π/3 to 2π/3.
It is also clear that within the range of , the luminous efficiency of the discharge lamp can be almost maximized. This is due to the following reason. Now, if the lagging phase current i _L and leading phase current i _C are set as i _C = I sin (ωt) i _L = I sin (ωt - θ), both full-wave rectifiers 2a and 2b shown in Fig. 4
The input voltages v _L and v _C are expressed by the following equations.

v _C =R·I sin(ωt) v _L =R·I sin(ωt−θ) Here, R is the equivalent impedance on the output side seen from the full-wave rectifiers 2a and 2b.

Therefore, since the output voltage v _put in the present invention is determined by adding the output voltages of each inverter 5a and 5b,
The low frequency envelope of the output voltage v _put can be found using the following equation.

Low frequency envelope of output voltage v _put = k × ( | v _C | + | v _L |) = k・R・I { | sinωt | + | sin (ωt − θ) | | ……(1) Here k is the ratio of the maximum instantaneous value of the output high-frequency voltage to the instantaneous value of the input voltage of the inverters 5a and 5b. Figure 6 shows the relationship between phase angle θ and low frequency ripple ratio (maximum value of low frequency envelope of output voltage v _put ÷ minimum value of low frequency envelope of output voltage v _put ) from equation (1) above. It can be seen that the ripple ratio is minimum when the phase angle θ is π/2. Therefore, it can be seen that when the phase angle θ is π/2, the ripple ratio is the smallest, the power required to re-ignite the discharge lamp is lower, and the luminous efficiency is maximized compared to when ripple is included in the commercial frequency. Ru. However, when adjusting the phase angle θ to π/2, there are differences in the type of discharge lamp, variations within the same type,
Alternatively, in view of variations in circuit constants and variations in load capacity (variations in the number of discharge lamps), the phase angle θ actually varies from π/3 to 2π/3.

It should be noted that the present invention is not limited to the above embodiments, and can of course be modified within the scope of the claims.

(Effects of the Invention) As described above, the present invention connects the AC input end of a first full-wave rectifier to both ends of an AC power source via an element exhibiting inductive impedance with respect to the power frequency, and The output terminal is connected to the DC input terminal of the first high-frequency conversion circuit having an output isolation transformer, and the second full-wave rectifier is connected via an element exhibiting capacitive impedance with respect to the power frequency at both ends of the AC power supply. having an isolation transformer connecting the AC input end and outputting the DC output end of the rectifier;
It is connected to the DC input terminal of a second high frequency conversion circuit having substantially the same specifications as the first high frequency conversion circuit, and operates the first and second high frequency conversion circuits in synchronization, and also isolates both high frequency conversion circuits. Since each output is serially combined and a load is connected to the combined output terminal, a high frequency output with an envelope with little low frequency ripple can be obtained, and the input power factor can be made high. We have been able to provide an inverter device that has low input current waveform distortion, reduces odd-order harmonic components, and can also improve power transmission and distribution efficiency.

Note that if such an inverter device is used to light a discharge lamp, it is possible to provide a highly efficient lighting device with high luminous efficiency, and it is also possible to connect a high-capacity load such as a multi-lamp lighting device such as an HID lamp or a fluorescent lamp. Also, since the high frequency conversion section is divided into two parts, a sufficient function can be achieved even if an element with a small withstand capacity is used, and both cost and size can be reduced.

[Brief explanation of the drawing]

Figures 1 and 2 are simplified circuit diagrams of the conventional example;
4 is a circuit diagram showing an embodiment of the present invention, FIG. 5 is an operating waveform diagram of the above embodiment, and FIG. 6 shows the ripple ratio with respect to the phase angle. It is a characteristic diagram.

Claims (1)

[Claims] 1. The AC input end of a first full-wave rectifier is connected to both ends of an AC power source via an element exhibiting inductive impedance with respect to the power frequency, and the DC output end of the rectifier is connected to an output isolation transformer. is connected to the DC input end of a first high frequency conversion circuit having a high frequency conversion circuit, and the AC input end of a second full wave rectifier is connected to both ends of the AC power supply via an element exhibiting capacitive impedance with respect to the power frequency. , the DC output end of the rectifier is connected to the DC input end of a second high frequency conversion circuit having substantially the same specifications as the first high frequency conversion circuit and having an output isolation transformer, and the first and second high frequency conversion circuits are connected to each other. An inverter device in which the circuits are operated synchronously, the isolated outputs of both high frequency conversion circuits are combined in series, and a load is connected to the combined output terminal. 2. The inductive impedance and the capacitive impedance have constants such that different phase angles of current flowing through each impedance are set between π/3 and π/2. The inverter device described. 3. The inverter device according to claim 1 or 2, wherein the first and second high frequency conversion circuits are constant current push-pull inverter circuits.