JP3811958B2 - Discharge lamp lighting circuit - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a discharge lamp lighting circuit using an inverter circuit.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is a capacitor input type power supply unit as shown in FIG. That is, the full-wave rectifying circuit 2 is connected between the AC power supply 1, the full-wave rectification circuit 2 is connected to the smoothing capacitor C ₁ between the DC power source which is full-wave rectified, the both ends of the smoothing capacitor C ₁ The obtained smoothed voltage is provided as a power source for the subsequent inverter circuit (not shown).
[0003]
[Problems to be solved by the invention]
For such a capacitor input type, although smoothness is good, the input current I _IN flowing from the commercial AC power source 1 side is as shown in FIG. (B) with respect to the input voltage V _IN, the pause interval In addition, since the peak value becomes large, the harmonic distortion of the input current I _IN becomes large.
[0004]
There is a boost chopper type as a means for improving the occurrence of such a pause period. According to this, the input current distortion is improved, but there is a drawback that the configuration becomes complicated.
[0005]
[Means for Solving the Problems]
A smoothing capacitor is connected between the full-wave rectified DC power supplies , and an inverter circuit having a resonant inductor, a resonant capacitor, and first and second switching elements is provided between both ends of the smoothing capacitor. In a discharge lamp lighting circuit in which the two switching elements are alternately controlled to turn on and off the discharge lamp at a high frequency , the positive side of the DC power source is the anode side between the DC power source and the smoothing capacitor. 1 diode connected, said second diode connected to the positive side of the DC power supply as the anode side between the DC power source and the resonant capacitor, the first diode, said smoothing capacitor from said DC power source electric current, off in a section where both end voltages V _C1 of the smoothing capacitor is V _C1> V in respect DC voltage V in of the direct current power supply When the first switching element is turned on, a current is passed through the resonant inductor to store energy, and when turned off, a current is passed through the resonant capacitor to resonate the resonant inductor and the resonant capacitor, and the second diode is wherein the resonant capacitor voltage across V _C0 is equal to the DC voltage V _C0 on, said from the DC power supply second switching element, the resonance inductor through by passing a power factor correction current to the smoothing capacitor V _C1> V in , the second switching element is turned off to regenerate the resonant inductor, and the first switching element is turned on again, whereby the smoothing capacitor, the resonant inductor, and the first switching element In order to make the voltage V _C1 across the smoothing capacitor constant by passing a current through .
[0006]
[Action]
When the resonant inductor voltage generated by the resonance between the resonant inductor and the resonant capacitor in the inverter circuit becomes equal to the power supply voltage, the second diode is turned on, so that the power factor improving current flows from the second switching element through the resonant inductor to the smoothing capacitor. Therefore, a high peak current for the smoothing capacitor can be suppressed. Therefore, the power factor can be improved with a simple configuration, and the low distortion circuit can keep the smooth voltage constant. Therefore, the voltage applied to the discharge lamp is almost flat.
[0007]
【Example】
An embodiment of the present invention will be described with reference to FIGS. First, a full-wave rectifier circuit 4 is connected to the AC power source 3, and a DC power source that obtains a DC voltage as an input voltage Vin between output terminals of the full-wave rectifier circuit 4 is configured. A smoothing capacitor C ₁ is connected between the output terminals of the full-wave rectifier circuit 4 via a first diode D ₁ . An inverter circuit 5 for the smoothing capacitor C ₁ and the power supply is connected to the both ends of the smoothing capacitor C _1. (Specifically, composed of a transistor or the like) the first and second switching elements S ₁ inverter circuit 5 is on-off controlled alternately, S ₂ and each first and second switching elements S _1, S ₂ and anti-parallel diodes D ₂ and D ₃ connected to ₂ and an LC resonance circuit 6 including a resonance inductor L ₀ and a resonance capacitor C ₀ . Here, the resonant inductor L ₀ is connected in series to the first switching element S ₁ , and this series circuit is connected between both ends of the full-wave rectifier circuit 4 and the first diode D ₁ . The resonant capacitor C ₀ is connected in series to the second switching element S ₂ , and this series circuit is connected in parallel between both ends of the first switching element S ₁ . Further, a second diode D ₄ for power factor improvement is connected between one end (the second switching element S ₂ side) of the resonant capacitor C ₀ and one of the output terminals of the full-wave rectifier circuit 4. .
[0008]
The resonant inductor L ₀ that forms the output portion of the inverter circuit 5 is also used as the primary winding of the inverter transformer 7, and a load 8 serving as a discharge lamp is connected via the secondary winding L _1. Yes.
[0009]
In such a configuration, the operation will be described with reference to the voltage waveform and current waveform shown in FIG. The illustrated example shows a transient operation waveform when the full-wave rectified input voltage Vin is Vin = 100 V (meaning a point of 100 V in the full-wave rectified half-wave waveform as shown in FIG. 7). V _S1 is the voltage across the first switching element S ₁ , V _C0 is the voltage across the resonant capacitor C ₀ , I _S1 is the current flowing through the first switching element S ₁ , I _S2 is the current flowing through the second switching element S ₂ , I _D4 represents the current flowing through the second diode D ₄ .
[0010]
First, power is turned on, electric charge is accumulated in the smoothing capacitor C ₁ via the diode D ₁ , and the diode D ₁ is turned off in a section where the voltage V _{C1 at} both ends thereof is V _C1 > Vin. On the other hand, in the inverter circuit 5, when the first switching element S ₁ is turned on (current I _S1 flows), current flows in the resonant inductor L ₀ to store energy, and when the first switching element S ₁ is turned off, the reverse parallel connection is performed. A current flows to the resonant capacitor C ₀ through the diode D ₃ . As a result, the LC resonance state is substantially achieved, and the voltage V _L0 of the resonance inductor L ₀ rises and falls due to resonance between the resonance inductor L ₀ and the resonance capacitor C ₀ . In parallel with this, since the first and second switching elements S ₁ and S ₂ are alternately turned on and off, when the voltage across the capacitor V _C0 becomes V _C0 ≈Vin, as shown in FIG. At the same time, the second diode D ₄ is turned on to become a power factor correction current I _D4 , which flows along the path of the second switching element S ₂ → the resonant inductor L ₀ → the smoothing capacitor C ₁ . In other words, will be current directly flows through the smoothing capacitor C ₁ from the DC power supply side, the portion shown hatched in FIG. 2 contributes to power factor correction. By this power factor correction current I _D4 , V _C1 > Vin. When the second switching element S ₂ is turned off, the resonance inductor L ₀ is regenerated by the anti-parallel diode D ₂ , and the first switching element S ₁ is turned on again, so that the smoothing capacitor C ₁ → the resonance inductor L ₀ → Current flows through the path of the first switching element S ₁ . Thereafter, the same operation is repeated.
[0011]
Therefore, when the voltage and current waveforms of the input part are shown in this embodiment, the input current obtained at the output part of the full-wave rectifier circuit 4 with respect to the AC voltage E of the sinusoidal AC power supply 3 as shown in FIG. Iin is as shown in the figure, and the power factor improving current continues to flow from the power source side even in the phase portion where the AC voltage E is low, so that no pause period occurs. As a result, in the operation control of the inverter circuit 5, the on-duty and frequency control of the _first and second switching elements S ₁ and S ₂ can be easily performed. Eventually, the smoothing voltage obtained in the smoothing capacitor C ₁ is also made constant while improving the power factor. Therefore, the output (output voltage) applied to the load 8 through the inverter circuit 5 operating with the smoothing capacitor C ₁ as a power source. A waveform obtained by enlarging the half-wave rectified with respect to V _L and output current I _L ) is almost flat as shown in FIG.
[0012]
Further, when considering the operation of the present embodiment, the first and second switching elements S ₁ and S ₂ are alternately turned on and off, and the resonance current I _L0 is used with a delay, so that there is no switching loss. Further, since the voltage applied to the second switching element S ₂ is the input voltage Vin = 100 V, an element having a lower withstand voltage than the first switching element S ₁ can be used.
[0013]
5 is an enlarged waveform diagram corresponding to FIG. 2 showing a transient voltage and current state of the inverter operation when the input voltage Vin is 50 V, and FIG. 6 is an inverter waveform operation when the input voltage Vin is 0 V. FIG. 9 is an enlarged waveform diagram showing transient voltage and current states corresponding to FIG. 2 (refer to FIG. 7 for Vin = 50V and 0V).
[0014]
FIG. 8 shows a modification in which, in addition to the resonant capacitor C _0, a resonant capacitor C ₀₁ is connected in parallel to the first switching element S ₁ . According to such a configuration, alternately relates first and second switching elements S _1, S _2, which is on-off controlled, it shall have the dead time first and second switching elements S _1, S ₂ is turned off together Since partial resonance occurs, switching noise is reduced.
[0015]
【The invention's effect】
According to the present invention, an inverter circuit including a smoothing capacitor connected between full-wave rectified DC power supplies and a resonant inductor, a resonant capacitor, and first and second switching elements between both ends of the smoothing capacitor is provided. In a discharge lamp lighting circuit, wherein the first and second switching elements are alternately turned on / off so that the discharge lamp is turned on at a high frequency , the plus of the DC power supply is provided between the DC power supply and the smoothing capacitor. connect the first diode side as an anode side, wherein connecting the second diode to the positive side of the DC power supply as the anode side between the DC power source and the resonant capacitor, the first diode, the DC power supply current flows to the smoothing capacitor from, V _C1 across the voltage V _C1 of the smoothing capacitor with respect to the DC voltage V in of the direct current power source> and V in When the first switching element is turned on, a current is passed through the resonant inductor to store energy, and when turned off, a current is passed through the resonant capacitor to cause the resonant inductor and the resonant capacitor to resonate. The two diodes are turned on when the voltage V _C0 across the resonant capacitor becomes equal to the DC voltage V _C0, and a power factor improving current is passed from the DC power source to the smoothing capacitor via the second switching element and the resonant inductor. V _C1 > V in , the second switching element is turned off to regenerate the resonant inductor, and the first switching element is turned on again, so that the smoothing capacitor, the resonant inductor, A current is passed through the path of the first switching element to keep the voltage V _C1 across the smoothing capacitor constant. Since so as to reduction, the resonant inductor voltage generated by the resonance between the resonant inductor and resonant capacitor in the inverter circuit is equal to the supply voltage, the second diode is turned on, the smoothing capacitor through the resonant inductor from the second switching element Since the power factor correction current flows through the capacitor, it is possible to suppress a high peak current for the smoothing capacitor. Therefore, it is possible to provide a low distortion circuit capable of improving the power factor with a simple configuration and keeping the smooth voltage constant, and the load. The high-frequency voltage applied to the discharge lamp can be made substantially flat, and the voltage applied to the second switching element is equivalent to a DC power supply, so that an element with a low breakdown voltage can be used.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an embodiment of the present invention.
FIG. 2 is an enlarged waveform diagram showing a transient voltage and current at Vin = 100V.
FIG. 3 is an enlarged waveform diagram showing a transient state of an AC voltage E and an input current Iin.
FIG. 4 is an enlarged waveform diagram showing a transient state of output voltage and current with respect to a load.
FIG. 5 is an enlarged waveform diagram showing a transient voltage and current at Vin = 50V.
FIG. 6 is an enlarged waveform diagram showing a transient voltage and current at Vin = 0V.
FIG. 7 is a waveform diagram of a full-wave rectified voltage showing each point of Vin.
FIG. 8 is a circuit diagram showing a modification.
9A and 9B show a conventional example, in which FIG. 9A is a circuit diagram, and FIG. 9B is a waveform diagram showing its input current.
[Explanation of symbols]
4 DC power supply 5 Inverter circuit 8 Discharge lamp C ₀ Resonance capacitor C ₁ Smoothing capacitor D ₁ First diode D ₄ Second diode L ₀ Resonance inductors S ₁ and S ₂ Switching elements

Claims (1)

A smoothing capacitor is connected between the full-wave rectified DC power supplies , and an inverter circuit having a resonant inductor, a resonant capacitor, and first and second switching elements is provided between both ends of the smoothing capacitor. In a discharge lamp lighting circuit in which the switching lamp is alternately turned on / off to turn on the discharge lamp at a high frequency,
The positive side of the DC power source a first diode connected as the anode side, the anode side the plus side of the DC power supply between the resonant capacitor and the DC power supply between the DC power supply and the smoothing capacitor a second diode connected as,
Said first diode, the DC power from the electric current to the smoothing capacitor, off in a section where both end voltages V _C1 of the smoothing capacitor is V _C1> V in respect DC voltage V in of the direct current power supply And
When the first switching element is turned on, a current is passed through the resonant inductor to store energy, and when turned off, a current is passed through the resonant capacitor to resonate the resonant inductor and the resonant capacitor;
The second diode is turned on when the voltage V _C0 across the resonance capacitor becomes equal to the DC voltage V _C0, and a power factor improving current is supplied from the DC power source to the smoothing capacitor via the second switching element and the resonance inductor. To make V _C1 > V in ,
When the second switching element is turned off, the resonance inductor is regenerated, and when the first switching element is turned on again, a current flows through the path of the smoothing capacitor, the resonance inductor, and the first switching element. The discharge lamp lighting circuit is characterized in that the voltage V _C1 across the smoothing capacitor is made constant .

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