JP3614011B2 - Inverter device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inverter device that converts a DC voltage obtained by rectifying and smoothing an AC power source into a high-frequency voltage and supplies it to a load.
[0002]
[Prior art]
(Conventional example 1)
FIG. 10 is a circuit diagram of a conventional half-bridge inverter. C1 is a relatively large-capacity electrolytic capacitor that supplies a DC voltage to the inverter, and is connected to a voltage obtained by rectifying an AC power source to generate the DC voltage Vdc. A series circuit of switching elements Q1, Q2 is connected in parallel to both ends of the capacitor C1, and a series circuit of capacitors C31, C32 having a smaller capacity than the capacitor C1 is connected in parallel. An inverter load circuit is connected between the connection point of the switching elements Q1, Q2 and the connection point of the capacitors C31, C32. The inverter load circuit includes a series resonant circuit of an inductor L1 and a capacitor C2, and a load load is connected in parallel to the capacitor C2. The load load is not particularly limited, but a discharge lamp or the like is used. The switching elements Q1 and Q2 are alternately turned on and off, and the high frequency voltage Vinv is applied to the inverter load circuit. The high frequency voltage Vinv has an amplitude that is approximately half of the voltage Vdc of the capacitor C1.
[0003]
In this half-bridge inverter, the voltage applied to the inverter load circuit is only half the power supply voltage Vdc to the inverter. Since the applied voltage is low, the circuit current is inevitably increased to obtain the same output, and therefore the circuit loss is increased and the circuit efficiency is not good. In addition, it is necessary to increase the current rating of the component, leading to an increase in cost.
[0004]
(Conventional example 2)
FIG. 11 is a circuit diagram of a conventional full bridge inverter. Compared with the circuit of FIG. 10, the series circuit of capacitors C31 and C32 is replaced with a series circuit of switching elements Q3 and Q4. In operation, the switching elements Q1 and Q4 are driven on / off in synchronization, and the switching elements Q2 and Q3 are also driven on / off in synchronization. Switching elements Q1 and Q2 and switching elements Q3 and Q4 connected in series are alternately turned on / off and controlled so as not to be turned on simultaneously. In this circuit, the voltage applied to the inverter load circuit is the voltage Vdc of the capacitor C1, which is twice that of the half-bridge inverter. Accordingly, the circuit current is relatively small, the circuit efficiency is increased, and the drawbacks of the half-bridge inverter are improved. However, the full bridge inverter has a large number of switching elements of four. As a result, the number of drive circuits for the switching elements increases, and the entire circuit becomes complicated and large.
[0005]
(Conventional example 3)
FIG. 12 shows a conventional two-switch forward converter. C1 is a capacitor serving as a DC power supply, and supplies a DC voltage Vdc. In parallel with the capacitor C1, switching elements Q1, Q2 are connected via a primary winding n1 of the transformer T. The diodes D1 and D2 are connected between the connection point between the primary winding n1 of the transformer T and the switching elements Q1 and Q2 and both ends of the capacitor C1, and the regenerative current of the primary winding n1 of the transformer T is fed back to the capacitor C1. Current path is formed. Switching elements Q1, Q2 are driven on and off in synchronization. When the switching elements Q1 and Q2 are turned on, the voltage Vdc of the capacitor C1 is applied to the primary winding n1 of the transformer T. When the switching elements Q1 and Q2 are turned off, the residual energy is passed through the diodes D1 and D2. Regenerate to C1. At this time, the voltage Vdc is applied to the primary winding n1 of the transformer T in the reverse direction.
[0006]
Diodes D3 and D4, an inductor L2, and a capacitor C2 are connected to the secondary winding n2 of the transformer T to generate a DC voltage. A load circuit load is connected to both ends of the capacitor C2. In this circuit, the amplitude of the voltage applied to the primary winding n1 of the transformer T is the voltage Vdc of the capacitor C1, but this is an application example of a DC / DC converter circuit and does not supply a high frequency to the load.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above points, eliminates the drawbacks described in the prior art, applies a high voltage to the inverter load circuit, and therefore reduces the circuit current and reduces the number of highly efficient inverter devices. This is intended to be realized with the number of parts.
[0008]
[Means for Solving the Problems]
In the inverter apparatus of the present invention, in order to solve the above problem, as shown in FIG. 1, first and second switching connected to each one end positive and negative poles of the DC power source such as a capacitor C1 Means for synchronously turning on / off the elements Q1, Q2 and the first and second switching elements Q1, Q2 so as to have a period of turning off at the same time as the first and second switching elements Q1, Q2; Q1, Q2 and the inverter load circuit 1 connected between the other ends of the inverter load circuit 1 and the first and second switching elements Q1, each regenerative current between the positive and negative electrodes of the connection point between the DC power source of Q2 There and first and second diodes D1, D2 connected in a direction to return to the DC power source, regeneration by the residual energy at the same time off the first and second switching elements Q1, Q2 It is characterized in that the inductor L2 for simultaneously turning on the first and second diodes D1, D2 by flow connected in parallel with the inverter load circuit 1. Here, the inverter load circuit 1 has a series resonant circuit of an inductor L1 and a capacitor C2, and a load load is connected in parallel with the capacitor C2.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
(Example 1)
FIG. 1 is a circuit diagram of Embodiment 1 of the present invention. C1 is a capacitor serving as a DC power supply, and supplies a DC voltage Vdc. In parallel with the capacitor C1, switching elements Q1, Q2 are connected via an inverter load circuit 1. The inverter load circuit 1 has a series resonance circuit of an inductor L1 and a capacitor C2, and a load load is connected in parallel with the capacitor C2. The load load is not particularly limited, but a discharge lamp or the like is used. The diodes D1 and D2 are connected between the connection point between the inverter load circuit 1 and the switching elements Q1 and Q2 and between both ends of the capacitor C1, thereby forming a current path for feeding back the regenerative current of the inverter load circuit 1 to the capacitor C1. . Further, an inductor L2 is connected in parallel with the inverter load circuit 1. Switching elements Q1, Q2 are driven on and off in synchronization.
[0010]
When the switching elements Q1 and Q2 are on, the voltage Vdc of the capacitor C1 is applied to the inverter load circuit 1 in the direction indicated by the arrow Vinv, and at the same time, the same voltage is applied to the inductor L2. The current path at this time is shown in FIG. When the switching elements Q1 and Q2 are turned off, the inverter load circuit 1 and the inductor L2 enter a regeneration mode, turn on the diodes D1 and D2, and regenerate residual energy to the capacitor C1. At this time, the voltage Vdc is applied to the inverter load circuit 1 and the inductor L2 in the direction opposite to the arrow Vinv illustrated. The current path at this time is shown in FIG. The current of the inverter load circuit 1 gradually decreases, and when there is no inductor L2, it becomes zero and no current flows. In this circuit, since the inductor L2 exists, when the current of the inverter load circuit 1 becomes zero, the current flows in the reverse direction along the path of the inductor L2, the inductor L1, the capacitor C2, and the load load → the inductor L2, using the inductor L2 as a power source. Flows. The current path at this time is shown in FIG.
[0011]
Although this circuit has a configuration of a two-switch forward converter, an alternating current can be passed through the load circuit, so it can be said that this circuit is a two-switch forward inverter. According to the present invention, an AC voltage having an amplitude of the voltage Vdc of the capacitor C1 is applied to the inverter load circuit 1, and the circuit current flowing through the inverter load circuit 1 is reduced as in the full bridge inverter. Moreover, two switching elements are the same as a half-bridge inverter, and there are few. Additional components are the diodes D1 and D2 and the inductor L2, but the diodes D1 and D2 do not require a drive circuit, and the control circuit is simple. The inductor L2 is also a passive component, and the control circuit does not increase. Therefore, a high voltage is applied to the inverter load circuit 1, a circuit current is small, and a highly efficient inverter can be realized.
[0012]
Further, in this circuit, since the switching elements Q1 and Q2 are driven on and off in synchronization, the switching elements Q1 and Q2 can be easily driven as compared with the conventional half-bridge circuit and full-bridge circuit. That is, in the conventional examples of FIG. 10 and FIG. 11, it is described that the switching elements in series are alternately turned on / off, but strictly speaking, both switching elements are provided so that there is no period during which the switching elements are simultaneously turned on. It is necessary to provide a slight dead-off time for simultaneously turning off. 3A is a drive signal for the switching elements Q1 and Q2 of the half-bridge circuit of FIG. 10, and FIG. 3B is a drive signal of the switching elements Q1 to Q4 of the full-bridge circuit of FIG. , T2 is the dead-off time. This dead-off time needs to be set appropriately according to the constant and drive frequency of the inverter load circuit, and complicates the control circuit. On the other hand, in the present circuit, as shown in FIG. 3C, the switching elements Q1 and Q2 are controlled to be turned on / off in synchronization, so that it is not necessary to provide a dead-off time, and the control circuit is simple. Become.
[0013]
(Example 2)
FIG. 4 is a circuit diagram of Embodiment 2 of the present invention. In the present embodiment, in the circuit of FIG. 1, the load load is a discharge lamp la and is applied to an inverter lighting device. Although the discharge lamp la requires a high voltage for starting, it can be seen that the circuit is suitable for the discharge lamp lighting device due to the characteristic that the applied voltage becomes high as described in the first embodiment. In this embodiment, the resonance capacitor C2 also serves as a preheating capacitor for the discharge lamp la.
[0014]
(Example 3)
FIG. 5 is a circuit diagram of Embodiment 3 of the present invention. In this embodiment, in the inverter having the discharge lamp la as a load, the output is variable, and the discharge lamp la can be dimmed. An oscillator 2 for generating a basic oscillation signal, a level shifter 3 for driving the switching element Q1 on the high potential side, and a pulse width for changing the ON time of the driving signal for the switching element Q2 in accordance with the dimming signal 4 A modulation circuit 5 is added. As shown in the control example of FIG. 6, dimming control is performed by keeping the frequency of the drive signal of the switching elements Q1 and Q2 constant and shortening the ON time of the switching element Q2.
[0015]
In the control example of FIG. 6, since the operating frequency of the inverter load circuit is fixed and only the on-time of the switching element Q2 needs to be adjusted, the control is easy. In addition, by selecting an operating frequency close to the no-load resonance point, the applied voltage of the discharge lamp la can be maintained high, which is effective in preventing extinction at the dimming lower limit. Further, as shown in the control example of FIG. 7, it goes without saying that the light can be adjusted even if the frequency of the drive signal of the switching elements Q1, Q2 is changed.
[0016]
(Example 4)
FIG. 8 is a circuit diagram of Embodiment 4 of the present invention. In the present embodiment, the switching element Q2 on the low voltage side and the diode D2 connected in series with the switching element Q2 are combined as components of the chopper circuit for improving the input power factor. Compared with the circuit of FIG. 1, the difference is that the voltage obtained by rectifying the AC power supply Vs by the full-wave rectifier DB is connected to both ends of the switching element Q2 via the inductor L3. The switching elements Q1 and Q2 are driven on and off in synchronization as in the first embodiment. When the switching element Q2 is turned on, the power supply voltage rectified by the full-wave rectifier DB is short-circuited through the inductor L3, and a current flows through the inductor L3. When the switching element Q2 is off, the electrolytic capacitor C1 is charged via the diode D2 by superimposing the induced electromotive voltage of the inductor L3 on the power supply voltage rectified by the full-wave rectifier DB. That is, the switching element Q2 and the diode D2 are also used as a switching element of the boost chopper circuit. In this embodiment, there is an advantage that an inverter circuit having a high input power factor is obtained. Other effects are the same as in the previous embodiment.
[0017]
(Example 5)
FIG. 9 is a circuit diagram of Embodiment 5 of the present invention. This embodiment is a combination of the dimming inverter of the third embodiment and the chopper switch combined inverter of the fourth embodiment. In this embodiment, the switching element Q2 also serves as a chopper switching element. Further, only the ON time of the switching element Q2 is shortened according to the dimming signal. That is, when dimming, the frequency remains constant and only the ON time of the switching element Q2 is shortened. This is because when viewed as a chopper circuit, the input power decreases, and the method of reducing the input power is greater than the dimming control by increasing the frequency. The voltage Vdc is difficult to increase. Therefore, it is advantageous in terms of the breakdown voltage of the element.
[0018]
【The invention's effect】
According to the first aspect of the present invention, the inverter load circuit is connected between the positive and negative electrodes of the DC power source via the first and second switching elements, and the first and second switching elements are simultaneously turned on and simultaneously turned off. synchronously driven on and off so as to have a first and in a direction regenerative current between the positive and negative electrodes of the inverter load circuit and a DC power source and each of the connection points of the first and second switching elements is returned to the DC power supply A second diode is connected , and an inductor for simultaneously turning on the first and second diodes by a regenerative current due to residual energy when the first and second switching elements are simultaneously turned off is connected in parallel with the inverter load circuit. Therefore, a high voltage can be applied to the inverter load circuit, a circuit current is small, a highly efficient inverter can be realized, and the number of parts is small. , There is an advantage that control is easy.
[0019]
According to the invention of claim 2, since the inverter load circuit includes the LC series resonance circuit, the voltage applied to the load can be increased, which is advantageous when the load is a discharge lamp. Further, according to the invention of claim 3, since one of the switching elements and the diode can be used as an element of the step-up chopper circuit, the input power factor can be improved with a simple circuit configuration, and the applied voltage to the load can be increased. can do.
[0020]
According to the invention of claim 4 or 5, the output to the load can be adjusted by duty control or frequency control of the switching element. In particular, according to the invention of claim 4, only control of one switching element is possible. Since the output can be adjusted with this, the control circuit for adjusting the output can be simplified.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of Embodiment 1 of the present invention.
FIG. 2 is an explanatory diagram for explaining a current path according to the first embodiment of the present invention;
FIG. 3 is a waveform diagram for explaining a dead-off time according to the first embodiment of the present invention.
FIG. 4 is a circuit diagram of Embodiment 2 of the present invention.
FIG. 5 is a circuit diagram of Embodiment 3 of the present invention.
FIG. 6 is an explanatory diagram of a dimming operation by duty control according to the third embodiment of the present invention.
FIG. 7 is an explanatory diagram of a dimming operation by frequency control according to the third embodiment of the present invention.
FIG. 8 is a circuit diagram of Embodiment 4 of the present invention.
FIG. 9 is a circuit diagram of Embodiment 5 of the present invention.
10 is a circuit diagram of Conventional Example 1. FIG.
FIG. 11 is a circuit diagram of a second conventional example.
12 is a circuit diagram of Conventional Example 3. FIG.
[Explanation of symbols]
Q1, Q2 Switching element L1, L2 Inductor C1, C2 Capacitor D1, D2 Diode load Load 1 Inverter load circuit

Claims (5)

The first and second switching elements whose one ends are connected to both positive and negative poles of the DC power supply, and the first and second switching elements are simultaneously turned on and off so as to have a period of turning off at the same time. Means for driving; inverter load circuit connected between the other ends of the first and second switching elements; connection points of the inverter load circuit and the first and second switching elements; And a first diode and a second diode connected in a direction in which the regenerative current returns to the DC power source between the two electrodes, and the first and second diodes are generated by the regenerative current due to the residual energy when the first and second switching elements are simultaneously turned off. inverter device is characterized in that an inductor for co-turn on the diode connected in parallel with the inverter load circuit. 2. The inverter device according to claim 1, wherein the inverter load circuit is formed by connecting an inductor in series with a parallel circuit of a load and a capacitor. 3. The inverter device according to claim 1, wherein a DC output terminal of a full-wave rectifier that rectifies an AC power source is connected to both ends of one switching element via a chopper choke. 4. The inverter device according to claim 1, wherein the on / off frequency of the first and second switching elements is constant and the on-time of one of the switching elements is variable. 4. The inverter device according to claim 1, wherein the on / off frequency of the first and second switching elements is variable.

Images