JPH0810985B2 - Inverter device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device, which is used for lighting a discharge lamp, for example, and has a simple circuit configuration, a high input power factor and a high frequency with a low frequency ripple. The present invention relates to an inverter device capable of outputting a voltage.

[Prior Art] Conventionally, for example, an inverter device shown in FIG. 6 is known as an inverter device used in a discharge lamp lighting device. The device shown in the figure has a rectifying circuit 1 composed of a diode bridge DB that rectifies a commercial power supply AC, a smoothing capacitor 2,
It is connected between the rectifier circuit 1 and the smoothing capacitor 2 and has a choke coil CH1, a diode D3 and a transistor Q.
3, chopper circuit 3 consisting of switching control circuit CT1
And an inverter circuit 4. The discharge lamp 5 is connected to the output of the inverter circuit 4 via the choke coil CH2. That is, in the device of FIG. 6, the output of the rectifier circuit 1 is connected to the smoothing capacitor 2 via the chopper circuit 3 having a good power factor, and the inverter circuit 4 is supplied with power to improve the input power factor. Was.
However, in such a conventional example, there is a problem that the circuit configuration becomes complicated and the apparatus becomes expensive.

Therefore, as an inverter device in which the input power factor is improved by a simple configuration, the one shown in FIG. 7 has been conventionally proposed. That is, in the circuit of FIG. 7, the positive side output end of the rectifier circuit 1 is connected to one end a of the inverter circuit 4 via the choke coil CH1.
Is a series circuit of transistors Q1 and Q2 that are alternately turned on and off and connected to both ends of smoothing capacitor 2 (between points a and c), and a diode D connected in parallel to each transistor Q1 and Q2.
It is formed as a half-bridge circuit including a series circuit of capacitors C1 and C2 and capacitors D1 and C2. Further, a series circuit of a choke coil CH2 which is a stabilizing element and a discharge lamp 5 is connected between the connection point (point b) of the transistors Q1 and Q2 and the connection point of the capacitors C1 and C2, and the negative output of the rectifier circuit 1 is connected. The end is connected to the connection point (point b) of the transistors Q1 and Q2. The switching control circuit CT2 that alternately turns on and off the transistors Q1 and Q2 of the inverter circuit 4 is composed of an oscillator such as an astable multivibrator.

In the circuit of FIG. 7, when the transistor Q1 is turned on by the switching control circuit CT2, the choke coil CH1 and the transistor Q1 start from the positive output terminal of the rectifier circuit 1.
A series circuit of a discharge lamp 5 and a choke coil CH2, which is a stabilizing element, that divides the voltage of the smoothing capacitor 2 by the capacitors C1 and C2 as well as a current that flows through 1 to the choke coil CH1 and accumulates electromagnetic energy. Apply to. At this time, the current flowing through the discharge lamp 5 is a transistor.
It flows to Q1. Therefore, a combined current of the current for accumulating electromagnetic energy in the choke coil CH1 from the commercial power supply AC and the current flowing in the discharge lamp 5 flows in the transistor Q1. Next, when the transistor Q1 is turned off and the transistor Q2 is turned on, the electromagnetic energy accumulated in the choke coil CH1 is discharged through the commercial power source AC, the diode bridge DB, the choke coil CH1, the smoothing capacitor 2 and the diode D2, The smoothing capacitor 2 is charged. On the other hand, the voltage of the smoothing capacitor 2 is divided by the capacitors C1 and C2,
The voltage of the capacitor C2 is applied to the choke coil CH2 and the discharge lamp 5, and the voltage is supplied to the discharge lamp 5. In this case, the transistors Q1 and Q2, the diodes D1 and D2, the choke coil CH2, the discharge lamp 5 and the capacitors C1 and C2 form a half-bridge type inverter circuit.
A step-up chopper circuit is formed by CH1, transistor Q1, smoothing capacitor 2 and diode D2. Therefore, by sharing transistor Q1 and diode D2 in both circuits, the circuit configuration is simplified. That is, according to the circuit of FIG. 7, the input power factor can be improved with a relatively simple circuit configuration.

[Problems to be Solved by the Invention] However, in the inverter device shown in FIG. 7, the voltage across the smoothing capacitor is about twice the peak value of the AC input voltage, and the voltage is extremely high as a switching element of the inverter circuit. There was the inconvenience that things were needed. In particular, when the AC input voltage is 200 V, even if the AC input voltage is 100 V, an element having a higher withstand voltage is required, but such a switching element is also difficult to obtain.

SUMMARY OF THE INVENTION In view of the above-mentioned problems in the conventional device, it is an object of the present invention to simplify the circuit configuration of an inverter device and to use a switching element having a relatively low breakdown voltage. It is another object of the present invention to apply a DC voltage, which is almost completely smoothed and has a low frequency ripple, which is almost completely smooth.

[Means for Solving the Problems] An inverter device according to the present invention includes a bridge type inverter circuit having a rectifying circuit for rectifying an input AC power source, a smoothing capacitor, and at least one pair of switching elements connected in series with each other, A series circuit of a first inductance element and a first diode connected between a rectifier circuit output and the smoothing capacitor, an intermediate of a pair of switching elements of the inverter circuit, a first inductance element of the series circuit, and a series circuit. And a coupling capacitor connected to the middle of the diode. Further, an impedance element is connected in series with the coupling capacitor as needed.

Further, as a second configuration, a second diode is connected in series with the coupling capacitor on the side of the first output terminal of the inverter circuit of the coupling capacitor, and an intermediate portion between the second diode and the coupling capacitor. A second inductance element can be connected between the second output terminal of the inverter circuit and the second output terminal of the inverter circuit. Where "first output end"
Means the middle of the pair of switching elements.
The term "second output terminal" means the middle of the other pair of switching elements in a full-bridge inverter circuit having another pair of switching elements connected in series with each other, and the other pair of switching elements. In the half-bridge type inverter circuit having first and second capacitors connected in series to each other instead of the switching element of
It means the middle of the second capacitor.

Further, as a third configuration, the first of the inverter circuits is used.
A series circuit of a third inductance element and a third capacitor is connected between the output end of the third inductance element and the one end of the smoothing capacitor, and the middle of the third inductance element and the third capacitor and the first inductance. The coupling capacitor may be connected between the element and the middle of the first diode. Also, a fourth capacitor can be connected in series with the third inductance element.

[Operation] In the configuration described above, at least a pair of switching elements forming the inverter circuit are turned on / off at a high frequency of, for example, several tens KHz. Then, due to this on / off, the voltage at the connection point (first output end) of the pair of switching elements changes to a high level or a low level at the frequency. This change in voltage is applied to the connection point of both elements in the series circuit of the first inductance element and the first diode via the coupling capacitor. As a result, this first diode is turned on and off at high frequency, so that the AC input current flows even when the instantaneous value of the AC voltage is low or near the peak value, and the effective current decreases with respect to the average current. It is possible to increase the input power factor.

In the second configuration, by turning on / off the pair of switching elements, a current is alternately reversed to a series circuit of the second diode and the coupling capacitor or a circuit including the coupling capacitor and the second inductance element. Flow in the direction. Thereby, the energy stored in the first inductance element connected to the output of the rectifier circuit turns on / off the first diode connected to the first inductance element according to the on / off operation of the switching element.

Further, in the third configuration, a high frequency voltage is generated in accordance with ON / OFF of the pair of switching elements via the series circuit of the third inductance element and the third capacitor, and the coupling capacitor. It is supplied to the connection point of both elements in the series circuit of the first diode. This causes the first diode to switch at high frequency.

Embodiments Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an inverter device according to an embodiment of the present invention. The device shown in the figure has a rectifying circuit 1 including a diode bridge for rectifying commercial power AC, a smoothing capacitor 2, switching transistors Q1 and Q2, and a diode D.
1, D2, capacitors C1, C2, C3, choke coil CH4, and an inverter circuit for lighting the discharge lamp 5. One output of the rectifier circuit 1 is connected to one end of the smoothing capacitor 2 via the series circuit of the choke coil CH3 and the diode D4, and the other output of the rectifier circuit 1 is connected to the other end of the smoothing capacitor 2. Transistors Q1 and Q2 forming the inverter circuit are connected in series at both ends of the smoothing capacitor 2. Diodes D1 and D2 are connected between the collector and emitter of the transistors Q1 and Q2, respectively. Capacitors C1 and C2 are further provided on both ends of the smoothing capacitor 2.
Are connected in series, and the discharge lamp 5 is connected via a choke coil CH4 between the connection point of these capacitors C1 and C2 and the connection point of the transistors Q1 and Q2. A switching control circuit (not shown) is connected to each of the switching transistors Q1 and Q2.
Turn 2 on and off alternately. Further, a series circuit of a coupling capacitor C4 and an impedance element Z1 is connected between the connection point of the switching transistors Q1 and Q2 and the connection point of the choke coil CH3 and the diode D4. As the impedance element Z1, for example, an inductor and /
Or resistors are used.

In the inverter device of FIG. 1, the commercial power supply AC is rectified by the rectifier circuit 1 and applied to the smoothing capacitor 2 via the series circuit of the choke coil CH3 and the diode D4. On the other hand, each of the switching transistors Q1 and Q2 operates in accordance with the operation of a switching control circuit (not shown),
It is turned on and off alternately at a frequency of KHz. The switching control circuit can be configured by, for example, an astable multivibrator. By alternately turning on and off the transistors Q1 and Q2 in this way, a high-frequency AC voltage is generated between the connection point of these transistors and the connection point of the capacitors C1 and C2, and this voltage turns on the discharge lamp 5. .

In the above-mentioned operation, the high frequency voltage generated at the connection point of the transistors Q1 and Q2 is applied to the connection point of the choke coil CH3 and the diode D4, that is, the anode of the diode D4 via the series circuit of the impedance element Z1 and the coupling capacitor C4. . As a result, the diode D4 is repeatedly turned on and off at high frequencies. Therefore, the AC input current has a conduction period even when the instantaneous value of the input AC voltage is low. Therefore, the input current comes to flow even in the vicinity of the peak value of the AC voltage, the effective current decreases with respect to the average current, and the input power factor can be increased. The impedance element Z1 is used, for example, to adjust the magnitude of the high frequency signal applied to the diode D4, but it is also possible to omit this impedance element and apply the high frequency voltage only by the coupling capacitor C4. It is possible. In this case, for example, the capacitance of the coupling capacitor C4 can be adjusted to optimize the level of the high frequency signal applied to the diode D4.

As shown in FIG. 2, it is possible to connect a series circuit of the choke coil CH3 and the diode D4 between the negative output terminal of the rectifier circuit 1 and the negative terminal of the smoothing capacitor 2. In this case, it is clear that the same effect as that of the device shown in FIG. 1 can be achieved.

Furthermore, the present invention is not limited to the half-bridge type inverter device shown in FIG. 1 and the like, but can be applied to the full-bridge type inverter device shown in FIG. 3, for example. That is, the device of FIG. 3 uses transistors Q4 and Q5 instead of the capacitors C1 and C2 in the device of FIG. 1, and diodes D6 and D7 are connected to the transistors Q4 and Q5, respectively. ing. In the device of FIG.
The transistors Q1 and Q5 and the transistors Q2 and Q4 are turned on and off alternately to turn on the discharge lamp.
In this case as well, the input power factor can be improved in the same manner as described above by the functions of the capacitor C4, the impedance element Z1, the choke coil CH3, and the diode 4 as described above.

FIG. 4 shows the configuration of an inverter device according to still another embodiment of the present invention. In the device shown in the figure, the connection point of the switching transistors Q1 and Q2 and the choke coil CH3
And a coupling capacitor between the connection point of diode D4 and
A series circuit of C4 and diode D5 is connected, and a choke coil L1 is connected between the connection point of the coupling capacitor C4 and the diode D5 and the connection point of the capacitors C1 and C2.

In the device of FIG. 4, when the switching transistors Q1 and Q2 are turned on and off as in the device of FIG. 1, the high frequency voltage generated at the connection point of these transistors Q1 and Q2 is the diode D5, the coupling capacitor C4, and the choke. It is applied to the anode of the diode D4 through the circuit including the coil L1. That is, for example, when the switching transistor Q2 is on, a current flows from the positive terminal of the rectifier circuit 1 through the choke coil CH3, the coupling capacitor C4, the diode D5, and the transistor Q2, and a predetermined energy is accumulated in the choke coil CH3. It In contrast, the transistor
When Q2 is off, current flows from the connection point of the capacitors C1 and C2 to the diode D4 via the choke coil L1 and the coupling capacitor C4. That is, at this time, the choke coil CH
By releasing the energy stored in 3, diode D4 conducts. In this way, the diode D4 is turned on / off by the high frequency signal and has a conduction period even when the instantaneous value of the input AC voltage is low.

FIG. 5 shows the configuration of an inverter device according to still another embodiment of the present invention. In the device shown in the figure, the connection point of each switching transistor Q1 and Q2 and the choke coil CH3
And a coupling capacitor between the connection point of diode D4 and
A series circuit of C4 and choke coil L2 is connected, and a capacitor C5 is connected between the connection point of coupling capacitor C4 and choke coil L2 and the negative side output terminal of rectifier circuit 1, that is, the negative side terminal of smoothing capacitor 2. Has been done. It is also possible to insert the capacitor C6 in series with the choke coil L2.

In the device shown in FIG. 5, when the switching transistors Q1 and Q2 are turned on and off as in the device shown in FIG. 1, a high frequency signal generated at the connection point of these switching transistors Q1 and Q2 is turned on and off. Is choke coil L2, coupling capacitor C4, capacitor C5
Is applied to the anode of the diode D4 via a circuit including. That is, the high frequency signal generated at the connection point of the transistors Q1 and Q2 is applied to the division circuit composed of the inductor L2 and the capacitor C5, and the output of this division circuit is input to the anode of the diode D4 via the coupling capacitor C4. It As a result, the diode D4 is repeatedly turned on and off at a high frequency, and has a conduction period even when the instantaneous value of the input AC voltage is low. Therefore, the input current can flow even in the vicinity of the peak value of the AC voltage, the effective current decreases with respect to the average current, and the input power factor can be increased.
In this case, further increase the input power factor by selecting the resonance frequency of the choke coil L2 and the capacitor C5 or the resonance frequency of the series circuit of the choke coil L2 and the capacitors C5 and C6 close to the operating frequency of the inverter. You can That is, in this case, the current waveform of the input power source can be approximated to, for example, a sine wave to increase the input power factor. It should be noted that it is convenient to set the value of the capacitor C4 to a value sufficiently larger than the value of the capacitor C5.

[Advantages of the Invention] As described above, according to the present invention, it is possible to increase the input power factor with a simple circuit configuration, and the DC voltage applied to the inverter circuit is almost completely smoothed. To be Further, the DC voltage applied to the inverter circuit is almost completely smoothed. Further, since the DC voltage applied to the inverter circuit is slightly higher than the peak value of the AC input voltage, for example, about 1.1 times the peak value, it is not necessary to use a switching element having a particularly high breakdown voltage.

[Brief description of drawings]

1 to 5 are electric circuit diagrams showing the configuration of an inverter device according to an embodiment of the present invention, and FIGS. 6 and 7 are electric circuits showing a conventional inverter device, respectively. It is a circuit diagram. 1: Rectifier circuit, 2: Smoothing capacitor, 4: Inverter circuit, 5:
Discharge lamps, Q1, Q2, ..., Q5: Switching transistors, D1, D
2,…, D7: Diode, CH1, CH2, CH3, CH4: Choke coil, C1, C2, C3, C4: Capacitor, Z1: Impedance element, D5: Diode, L1, L2: Choke coil, C5, C6: Capacitor .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Aoike Nanjo 1-28-3, Mita, Minato-ku, Tokyo, Toshiba Electric Materials Co., Ltd. Mishima factory

Claims (3)

[Claims] 1. A bridge-type inverter circuit having a rectifying circuit for rectifying an input AC power source, a smoothing capacitor, and at least one pair of switching elements connected in series with each other; connected between the rectifying circuit output and the smoothing capacitor. A series circuit of a first inductance element and a first diode; connected between the middle of the pair of switching elements of the inverter circuit and the middle of the first inductance element and the first diode of the series circuit An inverter device comprising: a coupling capacitor; 2. A bridge type inverter circuit having a rectifying circuit for rectifying an input AC power supply, a smoothing capacitor, a pair of switching elements connected in series with each other, and first and second capacitors connected in series with each other; A series circuit of a first inductance element and a first diode connected between the rectifier circuit output and the smoothing capacitor; an intermediate of a pair of switching elements of the inverter circuit and a first inductance element of the series circuit; A series circuit of a second diode and a coupling capacitor connected between the middle of the first diode and the middle of the second diode and the coupling capacitor, and a middle of the first and second capacitors of the inverter circuit. A second inductance element connected between the two; and an inverter device. 3. A bridge-type inverter circuit having a rectifying circuit for rectifying an input AC power source, a smoothing capacitor, and at least one pair of switching elements connected in series with each other; connected between the rectifying circuit output and the smoothing capacitor. A series circuit of a first inductance element and a first diode; and a third inductance element and a third capacitor connected between the middle of the pair of switching elements of the inverter circuit and one end of the smoothing capacitor. A series circuit; and a coupling capacitor connected between the middle of the third inductance element and the third capacitor and the middle of the first inductance element and the first diode. Inverter device.