JPH09322551A - Power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a voltage across both terminals of a smoothing capacitor from increasing abnormally, for example, if a dimmer lamp is on when an input current distortion is reduced by a simple circuit configuration and at the same time the oscillation frequency of an inverter circuit is increased. SOLUTION: A pulsive current Id is allowed to flow from a rectifier DB at a high frequency, and input current harmonic distortion is reduced and power factor is improved with a simple circuit configuration according to the relationship among three voltages of a voltage Vc4 across the terminals of a capacitor C4, a voltage Vdc across the terminals of a smoothing capacitor C1, and a pulsation current DC voltage Vin and a high-frequency operation of an inverter circuit consisting of switching elements Q1 and Q2 and diodes D1 and D2 that are connected inversely in parallel with each both terminals of the switching elements Q1 and Q2. Then, the capacitance value of the capacitor C4 is set in a direction for setting the current waveform of an input current Iin to nearly sinusoidal waveform near the center value of the variable range of the oscillation frequency of the inverter circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply.

[0002]

2. Description of the Related Art In a power supply device for converting an AC power supply Vs into a high frequency power and supplying it to a load, an input current harmonic distortion can be improved and a power factor can be improved with a simple circuit configuration. There is Japanese Patent Publication No. 5-38161, and a circuit diagram thereof is shown in FIG. (First Conventional Example) In this circuit system, the voltage Vc4 across the capacitor C4, which is connected between the rectifier DB and the smoothing capacitor C1, the voltage Vdc across the smoothing capacitor C1, the AC power supply Vs through the filter circuit F, the rectifier DB. The relationship between the three voltages of the pulsating current direct-current voltage Vin obtained by full-wave rectification with the switching elements Q1 and Q2 and the diodes D1 and D2 connected in antiparallel to both ends of each of the switching elements Q1 and Q2. Rectifier DB by the high frequency operation of the inverter circuit
Is a method in which a pulse current Id is caused to flow in a high frequency. In this circuit system, charging / discharging with the capacitor C4 greatly contributes to improving input current high tide distortion. Note that a diode D3 is connected in parallel with the capacitor C4, and the positive output terminal of the rectifier DB and the switching element Q
An inverter load Z1 is connected between the contacts 1 and Q2, and a part of the high-frequency output of the inverter circuit is fed back to the output terminal of the rectifier DB via the inverter load Z1. Further, a control means 1 for controlling the switching elements Q1 and Q2 is provided, and the inverter load Z1 is connected in parallel between a series circuit including the coupling capacitor C3, the discharge lamp La and the choke L1, and a non-power supply terminal of the discharge lamp La. The capacitor C4 forms the impedance element Z2.

Next, the circuit operation of this circuit will be briefly described. First, the operation when the pulsating DC voltage Vin is near zero, that is, in the valley will be described.

When the switching element Q2 is turned on, the resonance current is supplied from the smoothing capacitor C1 as a power source, and the resonance current is changed from the smoothing capacitor C1, the capacitor C4, the coupling capacitor C3,
The discharge lamp La, the capacitor C2, the choke L1, the switching element Q2, and the smoothing capacitor C1 flow through the path to charge the capacitor C4 and the choke L.
Energy is stored in 1. When the charging voltage Vc4 of the capacitor C4 becomes substantially equal to the voltage Vdc across the smoothing capacitor C1, the resonance current I1 flowing in the capacitor C4.
Stops and the current Id flows from the rectifier DB to try to continue the inverter operation. At the moment when the switching element Q2 is turned off and the switching element Q1 is turned on, a regenerative current due to the energy stored in the choke L1 flows through the diode D1 to charge the smoothing capacitor C1.
The current Id flowing at this time becomes a charging current from the rectifier DB to the smoothing capacitor C1 to charge the smoothing capacitor C1. When the energy stored in the choke L1 disappears, the resonance operation is inverted and the inverter operation using the coupling capacitor C3 as a power supply causes the coupling capacitor C3 → the capacitor C4 → the switching element Q1 → the choke L1 → the discharge lamp La, A resonance current flows through the path from the capacitor C2 to the coupling capacitor C3, and the charge stored in the capacitor C4 is discharged. When the charge stored in the capacitor C4 is exhausted, the resonance current flows through the diode D3.

In the above description, the pulsating DC voltage Vin is at the valley, but even if the pulsating DC voltage Vin is not near zero,
The voltage Vdc across the smoothing capacitor C1 is Vin + Vc4
Is substantially equal to the above, the inverter operation using the smoothing capacitor C1 as a power supply as described above is not performed, and the current Id flows from the rectifier DB to continue the inverter operation. In this way, the inverter circuit repeats the resonance operation, and the capacitor C4 repeatedly charges and discharges. The period during which the input current Iin flows is a period during which the current Id flows from the rectifier DB after the switching element Q2 is turned on and the smoothing capacitor C1 is charged to Vc4 + Vin. Thus, in this circuit system, the capacitor C4
It can be understood that charging / discharging greatly contributes to supplying the input current Iin. In order for the input current Iin to flow in the entire section of the pulsating direct current voltage Vin, Vin + Vc4>
The condition of Vdc is necessary, and when Vin = 0, Vc4> V
The condition of dc is required.

However, the first conventional example has the following first problem. Here, for example, in the case of performing dimming control for reducing the light output of the discharge lamp La, a method of increasing the oscillation frequency of the switching element forming the inverter circuit to reduce the output of the inverter circuit is well known. ing. Therefore, in the present circuit method, if the oscillation frequency of the switching elements Q1 and Q2 is increased to perform dimming lighting, the charging frequency of the capacitor C4 due to the resonant operation of the inverter circuit becomes short because the oscillation frequency becomes high, and The charging voltage Vc4 of C4 decreases. When Vc4 becomes Vdc, pulsating current DC voltage Vin
In the vicinity of the valley portion of, there is a section where the current Id does not flow. That is, when the oscillation frequency f = f1,
Although the input current Iin was flowing in all the sections of the pulsating direct current voltage Vin, the input current Iin becomes a waveform with a pause section by increasing the oscillation frequency f from f1 to f2.

As a means for solving the above-mentioned first problem,
There is one shown in Japanese Patent Application No. 7-254212 filed by the present applicant, and its circuit diagram is shown in FIG. (Second conventional example) In this conventional example, the input current distortion can be improved with a simple circuit configuration, and the output control can be easily performed. Especially, when the load is the discharge lamp, the dimming control of the discharge lamp can be performed. Power supply device.

The difference from the first conventional example shown in FIG. 1 is that the capacitor C4, which is greatly involved in the input current waveform distortion, is divided into a capacitor C41 and a capacitor C42, and
This is because SW is connected in series to the capacitor C42, and the same configurations as those of the other first conventional example are denoted by the same reference numerals and the description thereof will be omitted. Note that C4 = C41 + C42.

Next, the operation of the switch SW will be briefly described with reference to the time chart shown in FIG.

When the oscillation frequency of the inverter circuit is f1, as shown in FIG. 15A, the switch SW is turned on to set the capacitance of the impedance element Z2 to the combined capacitance C4 of the capacitors C41 and C42, and the impedance element Z2 voltage Vz2 (= C4 voltage Vc4)
By satisfying the relationship of Vc4> Vdc, it is possible to obtain an input current waveform without a pause section and improve the input current distortion.

When the oscillation frequency is increased from f1 to f2, the switch SW is turned off as shown in FIG. 15, and the capacitance value of the impedance element Z2 is changed from C4 to C41.
By increasing the resonance frequency to f2 by decreasing the resonance frequency to f2, the voltage Vz2 across the impedance element Z2 (the voltage Vc41 across C41) becomes Vc41> near the valley of the pulsating current DC voltage.
The relationship of Vdc can be satisfied, the input current Iin flows even in the valley portion of the pulsating direct current voltage, an input current waveform without a pause section can be obtained, and the input current distortion can be improved.

With such a configuration, it is possible to easily obtain an input current waveform having no pause section even during dimming lighting, etc., without changing other circuit constants only by changing the capacitance value of the impedance element Z2. It is possible to improve the input current high power wave distortion.

[0013]

However, the second conventional example has the following second problem.

Even during dimming lighting, the impedance value of the impedance element Z2 is varied to obtain an input current waveform having no pause section. Therefore, when the oscillation frequency of the inverter circuit is increased, for example, during dimming lighting, the output power Wout to the discharge lamp La is reduced, so that the input power Win> the output power Wout, and the oscillation frequency of the inverter circuit is changed. When it is lowered, for example, at the time of rated lighting, the load output to the discharge lamp La is increased, so that the input power Win <output power Wout. That is, when the oscillation frequency of the inverter circuit is increased, the power supplied from the smoothing capacitor C1 to the discharge lamp La is reduced as compared with the case where the oscillation frequency of the inverter circuit is decreased, so the voltage Vdc across the smoothing capacitor C1 is reduced. Will cause an abnormal rise in.

The present invention has been made in view of all the above problems, and an object of the present invention is to improve the input current distortion with a simple circuit configuration and to increase the oscillation frequency of the inverter circuit. In this case, it is an object of the present invention to provide a power supply device capable of preventing the voltage across the smoothing capacitor from abnormally increasing during dimming lighting.

[0016]

In order to solve the above problems, according to the present invention, a rectifier for rectifying an AC power supply and a smoothing connected between the output terminals of the rectifier via a diode. A capacitor, an inverter circuit that converts the voltage across the smoothing capacitor into a high-frequency voltage and supplies it to the load, and a high-frequency output feedback means that returns a part of the high-frequency voltage output from the inverter circuit to the output terminal of the rectifier and the contact of the diode. And an impedance element connected in parallel to both ends of the diode, and in the vicinity of the center value of the variable range of the oscillation frequency of the inverter circuit, the impedance of the impedance element in the direction in which the input current waveform from the AC power supply has a substantially sinusoidal shape. It is characterized by setting a value.

According to the second aspect of the present invention, in the vicinity of the center value of the variable range of the oscillation frequency of the inverter circuit, the impedance is increased in the direction in which the input power from the AC power supply and the output power supplied to the load become substantially equal. It is characterized by setting the impedance value of the element.

According to a third aspect of the invention, the impedance element changes its impedance value within a variable range of the oscillation frequency of the inverter circuit.

According to the fourth aspect of the invention, the average impedance value of the impedance elements within the variable range of the oscillation frequency of the inverter circuit is near the center value of the variable range,
The input current waveform from the AC power supply is a value that is substantially sinusoidal, and the impedance value of the impedance element is changed in a direction in which the input power from the AC power supply and the output power supplied to the load are substantially equal. And

According to a fifth aspect of the invention, a series circuit including a charging circuit for charging the smoothing capacitor and an impedance element is connected in parallel to both ends of the load.

According to the sixth aspect of the present invention, the impedance element is composed of a plurality of capacitors and a plurality of switches, and the connection of the plurality of capacitors is switched by controlling the switches, whereby the impedance of the impedance element is changed. It is characterized by changing the value.

According to the seventh aspect of the present invention, the impedance element is composed of a plurality of inductance elements and a plurality of switches, and by controlling the switches, the connection of the plurality of inductance elements is switched to make the impedance element. The impedance value of is variable.

According to the eighth aspect of the present invention, the impedance element includes a plurality of capacitors, a plurality of inductance elements, and a plurality of switches, and the switches are controlled to control the plurality of capacitors and the plurality of inductance elements. It is characterized in that the impedance value of the impedance element is changed by switching the connection with and.

According to a ninth aspect of the present invention, the load includes a discharge lamp.

According to the invention of claim 10, the load is:
It is characterized in that it is configured to include a transformer having a secondary winding and a discharge lamp connected in parallel to the secondary winding of the transformer.

According to the invention described in claim 11, the charging circuit is configured to include a capacitor.

According to a twelfth aspect of the present invention, the charging circuit is configured to include an inductance element.

According to a thirteenth aspect of the present invention, the charging circuit is configured to include a capacitor and an inductance element.

[0029]

[Embodiment]

(First Embodiment) The circuit configuration of the first embodiment according to the present invention is the same as that of the first conventional example shown in the circuit diagram of FIG.
Since only the operation is different, the operation of the present embodiment will be briefly described with reference to FIGS.

In the circuit shown in FIG. 14, the capacitor C
When the amplitude of the voltage Vc4 between both ends of 4 is small, Vin <Vdc
Since it is + Vc4, as shown in FIG. 2C, a pause section in which the value of the input current Iin becomes zero occurs in the current waveform of the input current Iin. Hereinafter, this is called a pause in the input current waveform. Further, when the amplitude of the voltage Vc4 across the capacitor C4 is large, Vin> Vdc + Vc4.
As shown in FIG. 2A, the current waveform of the input current Iin is inverted before the value of the input current Iin reaches zero. Less than,
This is called a jump in the input current waveform. FIG.
In (b), a current waveform of the substantially sine wave-shaped input current Iin is shown.

Here, for example, when the dimming control is performed with the value of the capacitor C4 kept constant, the current waveform of the input current Iin increases as the oscillation frequency of the inverter circuit increases.
2 (a)-> FIG. 2 (b)-> FIG. 2 (c).
In order to eliminate this point and always obtain the current waveform of the substantially sinusoidal input current Iin as shown in FIG. 2B, the oscillation frequency f of the inverter circuit increases as shown by the solid line in FIG. However, the current waveform of the input current Iin may not always be substantially sinusoidal as long as it does not affect other power supply devices. The present invention utilizes this point to prevent abnormal boosting of the voltage Vdc across the smoothing capacitor C1 due to the imbalance between the input power Win and the output power Wout as described above. In FIG. 3, the shaded area above the solid line shows a region where the input current waveform has a pause, and the below the solid line shows a region where a jump occurs in the input current waveform.

When the oscillation frequency of the inverter circuit is increased to perform dimming control or the like, the output power Wout is small, so that the input power Win is decreased, that is, the input current waveform is stopped. When the oscillation frequency of the inverter circuit is lowered to perform full lighting control or the like, the output power Wout is large. Therefore, when the control is performed in the direction in which the input power Win increases, in other words, in the direction in which the input current waveform jumps, the smoothing capacitor is controlled. The rise of the voltage Vdc across C1 can be reduced.

When the oscillation frequency is kept constant, both the input power Win and the output power Wout decrease as the capacitance value of the capacitor C4 increases, as shown in FIG. 4, and the rate of change is the input power Win. Output power W
When it is larger than out and the capacitance value of the capacitor C4 is small, Win> Wout, a jump occurs in the current waveform of the input current Iin, and the voltage Vdc across the smoothing capacitor C1 rises. When the capacitance value of the capacitor C4 is large, Win <Wout, the current waveform of the input current Iin is paused, and the voltage Vdc across the smoothing capacitor C1 is reached.
Is reduced.

From the above, when the oscillation frequency of the inverter circuit is changed within a certain range, the current waveform of the input current Iin having a substantially sine wave shape as shown in FIG. To obtain the capacitor C
A value of 4 may be set.

Further, within the range of change of the oscillation frequency, the capacitance value of the capacitor C4 is varied so that the voltage Vdc across the smoothing capacitor C1 does not rise abnormally.
The average value of the capacitor C4 within the change range of the oscillation frequency is set to a value that can obtain the current waveform of the substantially sinusoidal input current Iin as shown in FIG. 2B at the oscillation frequency at the center of the change width. If it is set so that the input current surge current distortion can be further improved.

FIG. 5 shows the input current high power wave distortion and the input power W.
FIG. 9 is a characteristic diagram showing the relationship between the capacitance value of a capacitor C4 and the oscillation frequency of the inverter circuit in in and output power Wout.

(1) When the oscillation frequency f of the inverter circuit and the capacitance value of the capacitor C4 are controlled so as to change on the solid line (b) shown in FIG. 5, a substantially sinusoidal waveform as shown in FIG. 2 (b) is obtained. The current waveform of the input current Iin can be obtained, and the input current storm surge can be optimally improved. In addition,
In FIG. 5, the upper side of the solid line (b) shows a region (c) where the input current waveform is paused, and the lower side of the solid line (b) shows a region (a) where the input current waveform jumps. .

(2) When the oscillation frequency f of the inverter circuit and the capacitance value of the capacitor C4 are controlled so as to change along the solid line (d) shown in FIG. 5, the relationship of Win = Wout is maintained, and the smoothing capacitor C1 is maintained. The voltage Vdc between both ends of the capacitor is substantially constant, and the voltage Vdc across the smoothing capacitor C1 can be prevented from rising.

(3) The capacitance value of the capacitor C4 is kept substantially constant, and the oscillation frequency f of the inverter circuit is changed on the solid line (e) including the intersection A between the solid line (b) and the solid line (d) shown in FIG. In addition, the current waveform of the input current Iin having a substantially sinusoidal waveform as shown in FIG. 2B can be obtained at the oscillation frequency approximately at the center of the variation width (dimming range) of the oscillation frequency f of the inverter circuit. By controlling as much as possible, the input current harmonic distortion can be improved with a simple configuration.

(4) Furthermore, the capacitance value of the capacitor C4 is made variable so that the oscillation frequency f of the inverter circuit and the capacitor C
4 so that the average capacitance value of 4 changes on the solid line (f) including the intersection A of the solid line (b) and the solid line (d) shown in FIG.
In addition, the control is performed so that the current waveform of the substantially sine wave-shaped input current Iin as shown in FIG. 2B can be obtained at the oscillation frequency approximately at the center of the variation width (dimming range) of the oscillation frequency f of the inverter circuit. Then, it approaches the direction of Win = Wout,
While improving the input current harmonic distortion with a simple configuration,
Voltage Vdc across smoothing capacitor C1 during dimming control
The abnormal rise of can be reduced.

From the characteristic diagram of FIG. 5, if the capacitance value of the capacitor C4 is set so that it passes through the intersection point A and the slope approaches the solid line (b), the input current storm surge distortion can be improved,
On the other hand, if the capacitance value of the capacitor C4 is set so as to pass the intersection point A and the slope approaches the solid line (d), it is possible to reduce the abnormal increase in the voltage Vdc across the smoothing capacitor C1. FIG.
The shaded area in FIG. 2 indicates the allowable range for both the improvement of the input current high-tide wave distortion and the reduction of the abnormal increase in the voltage Vdc across the smoothing capacitor C1. That is, even if the capacitor C4 is changed so as to operate the circuit within this allowable range, the average value thereof is set to the oscillation frequency approximately at the center of the change width (dimming range) of the oscillation frequency f of the inverter circuit as shown in FIG. It may be controlled so as to obtain a substantially sinusoidal current waveform of the input current Iin as shown in b).

The present embodiment is the second embodiment shown in FIG.
You may use for a conventional example. (Embodiment 2) FIG. 6 shows a circuit diagram of a second embodiment according to the present invention.

The difference from the first conventional example shown in FIG. 1 is that instead of the capacitor C4, a series circuit including a capacitor C5n and a switch SW5n (n is a positive integer) is used.
Since the diode D3 is connected in parallel, the same configurations as those of the other first conventional example are denoted by the same reference numerals and the description thereof will be omitted. In FIG. 6, n = 3, and the field effect transistors (hereinafter, referred to as switching elements Q1 and Q2).
It is called a switching element. ) Is used.

Next, the operation will be briefly described. As shown in FIG. 7A, the voltage Vdc across the smoothing capacitor C1 is the pulsating current voltage Vin obtained by rectifying the AC power supply Vs by the rectifier DB, and the contact voltage Va at the positive output terminal of the rectifier DB and the anode terminal of the diode D3. (Hereinafter, referred to as contact voltage Va). Here, capacitors C51, C52, C
Assuming that the relationship of the respective capacitance values of 53 is C51 <C52 <C53, the voltage Vdc across the smoothing capacitor C1 for each capacitor at the same oscillation frequency f is as shown in FIG.
As shown in (a), it decreases as the capacitance of the capacitor C5n increases. In addition, the input current I to each capacitor
As shown in FIG. 7B, the current waveform of in is an input current waveform with a jump in the case of the capacitor C51, the input current waveform is a substantially sine wave in the case of the capacitor C52, and is in the case of the capacitor C53. It has a current waveform with a pause. Therefore, the input power in each case of the capacitors C51, C52, C53 is Win1, Win2, W
If in3, Win1 <Win2 <Win3.

When the discharge lamp La is subjected to dimming control in a direction in which the speed of light gradually decreases, the lamp power (=) in the discharge lamp La is changed by switching in the direction in which the capacity value increases in the order of C51 → C52 → C53. (Output power) WLa gradually decreases, the lamp power WLa gradually approaches the input power Win, and when the lamp power WLa and the input power Win become substantially constant, the voltage Vdc across the smoothing capacitor C1 increases abnormally. Can be prevented.

During the dimming control of the discharge lamp La, the resonance current flowing through the inverter circuit decreases, so in this case, if the capacitance of the capacitor connected in parallel with the diode D3 is increased, the input current Iin Although the quiescent section of the current waveform becomes longer, the input current high-tide distortion is most improved at the average value Cav of the capacitors C51, C52, and C53 and the oscillation frequency approximately at the center of the variation width of the oscillation frequency f of the inverter circuit. Similarly, capacitors C51, C52,
When each capacitance value of C5 is selected, a current waveform of the input current Iin having a substantially sinusoidal shape as shown in FIG. 2B can be obtained, and the input current high tide over the entire variation range of the oscillation frequency f of the inverter circuit. The wave distortion can be alleviated, and an abnormal rise in the voltage Vdc across the smoothing capacitor C1 during dimming control can be reduced.

(Third Embodiment) FIG. 8 shows a circuit diagram of a third embodiment according to the present invention.

The difference from the second embodiment shown in FIG. 6 is that an inductance element L5n (n is a positive integer) is provided in series with the capacitor C5n and the switch SW5n, and the other second embodiment. The same configurations as those in Embodiment 1 are designated by the same reference numerals and description thereof will be omitted. In addition, in FIG.
n = 3.

In the first embodiment shown in FIG. 6, the idle section of the input current waveform is controlled by the voltage amplitude of the capacitor C5n connected in parallel with the diode D3, but in the present embodiment, the capacitor C5n and the inductance are controlled. Element L
By changing the impedance of the series circuit with 5n, the voltage amplitude of the series circuit of the capacitor C5n and the inductance element L5n at the time of dimming control is changed to control the idle section of the input current waveform, thereby performing dimming control. The input power Win at the time is controlled.

Then, at the average value Zav of the impedance values of the series circuit composed of the capacitor C5n and the inductance element L5n and the oscillation frequency approximately at the center of the variation width of the oscillation frequency f of the inverter circuit, the input current high-tide distortion is the highest. If the impedance value of each of the series circuits including the capacitor C5n and the inductance element L5n is selected so as to be improved, a current waveform of the input current Iin having a substantially sine wave shape as shown in FIG. 2B can be obtained. Therefore, it is possible to reduce the input current surge wave distortion over the entire range of variation of the oscillation frequency f of the inverter circuit, and reduce the abnormal rise in the voltage Vdc across the smoothing capacitor C1 during dimming control.

(Fourth Embodiment) FIG. 9 shows a circuit diagram of a fourth embodiment according to the present invention.

The difference from the second embodiment shown in FIG. 6 is that a parallel circuit of a diode D3 and a series circuit composed of a capacitor C5n and a switch SW5n is connected to the positive output terminal of the rectifier DB and one end of the discharge lamp La. Connected between the positive output terminal of the rectifier DB and the contacts of the switching elements Q1 and Q2, and the inductance element L2 and the capacitor C6.
The charging circuit for the smoothing capacitor C1 consisting of the above is provided, and the same configurations as those of the other second embodiment are denoted by the same reference numerals and the description thereof will be omitted. In FIG. 9, n = 3.

Here, in the circuits of the first and second conventional examples shown in FIGS. 1 and 14, a load current including a low-frequency ripple as shown in FIG. When the load is the discharge lamp La, the third problem that flicker of the discharge lamp La occurs and the like occurs, but in the present embodiment, this third problem can also be solved. Hereinafter, this point will be briefly described.

When Vin + Vz2 <Vdc when switching element Q1 is off and switching element Q2 is on, smoothing capacitor C1 → impedance element Z2 → coupling capacitor C3 → discharge lamp La, capacitor C
2 → choke L1 → switching element Q2 → smoothing capacitor C1. A charging current of impedance element Z2 flows, and when Vin + Vz2> Vdc, AC power supply Vs
→ Rectifier DB → Coupling capacitor C3 → Discharge lamp L
a, capacitor C2 → choke L1 → switching element Q2 → rectifier DB → alternating current power supply Vs input current Ii
n flows. Next, when the switching element Q1 is turned on and the switching element Q2 is turned off, the discharge current of the impedance element Z2 is generated along with the regenerative current and the impedance element Z2.
2 → switching element Q1 → choke L1 → discharge lamp L
a, capacitor C2 → coupling capacitor C3 → impedance element Z2. As described above, the discharge lamp La includes the current flowing from the AC power supply Vs to the discharge lamp La and the impedance element Z2 due to the smoothing capacitor C1.
And the total charging and discharging current flows.

Here, with respect to the charging / discharging current of the impedance element Z2 by the smoothing capacitor C1, the coupling capacitor C3 has a sufficiently large capacity with respect to the capacitors C4, C41, C42 and the like which constitute the impedance element Z2. Further, since the impedance element Z2 is connected in series, the combined capacitance of the coupling capacitor C3 and the impedance element Z2 becomes substantially equal to the capacitance of the impedance element Z2, that is, a value that is sufficiently smaller than the coupling capacitor C3. Therefore, the coupling capacitor C3 does not function as a coupling capacitor. At this time, the voltage Vc3 across the coupling capacitor C3 is negligible. Moreover, since the impedance element Z2 is not included in the path of the current flowing from the AC power supply Vs to the discharge lamp La,
The coupling capacitor C3 sufficiently functions as a coupling capacitor, and the coupling capacitor C at that time is used.
The voltage waveform of the voltage Vc3 at both ends of 3 is the switching element Q
When the on-duty of No. 2 is 50%, as shown in FIG. 11, the amplitude of the pulsating current DC voltage Vin is about half the amplitude. Therefore, as shown in FIG. 13A, the load current waveform flowing from the AC power source Vs to the discharge lamp La has substantially positive and negative amplitudes and a substantially sinusoidal envelope. Further, as shown in FIG. 12, the voltage Vz2 across the impedance element Z2 has a voltage waveform substantially equal to the difference between the voltage Vdc across the smoothing capacitor C1 and the pulsating current DC voltage Vin that changes in a substantially sinusoidal manner. Will be things. The charging / discharging current waveform of the impedance element Z2 at this time has the envelope shown in FIG. 13B, and the discharge lamp La has the current shown in FIG.
A sum including the current shown in FIG. 13B, that is, a current including a low-frequency ripple as shown in FIG. 13C flows. The low frequency ripple is caused by the discharge lamp La and the impedance element Z2.
It changes depending on the impedance and other conditions.

In the present embodiment shown in FIG. 9, an AC power source V
The input current Iin from s flows through the charging circuit of the smoothing capacitor C1 including the inductance element L2 and the capacitor C6, and does not flow into the discharge lamp La through the capacitors C51 to C53 and the diode D3.
The low frequency ripple of the input current Iin from the AC power supply Vs does not affect the load current waveform flowing through the discharge lamp La. On the other hand, using the smoothing capacitor C1 as a power source, the switching elements Q1 and Q2, the discharge lamp La, the capacitor C2,
The choke L1 and the coupling capacitor C3 form a so-called half-bridge inverter circuit. Since the coupling capacitor C3 functions as the coupling capacitor of the half-bridge inverter circuit, the discharge lamp La
The low frequency ripple of the load current flowing through is greatly reduced. As described above, a load current with a low-frequency ripple reduced as shown in FIG. 10 can be passed through the discharge lamp La, and radiation noise, flicker of the discharge lamp La particularly when the load is the discharge lamp La, and the like. Can be reduced.

Although one end of the charging circuit of the smoothing capacitor C1 including the inductance element L2 and the capacitor C6 is connected to the contacts of the switching elements Q1 and Q2, it is connected to the contacts of the choke L1 and the coupling capacitor C3. Alternatively, the charging circuit may be composed of only an inductor or only a capacitor.

[0058]

According to the inventions of claims 1 to 4 and 6 to 8, the input current distortion can be improved with a simple circuit configuration and the oscillation frequency of the inverter circuit can be improved. It is possible to provide a power supply device capable of preventing the voltage across the smoothing capacitor from abnormally rising when the voltage is increased.

According to the fifth and eleventh to thirteenth aspects of the invention, the input current distortion can be improved with a single circuit configuration, the low frequency ripple of the load current can be reduced, and the inverter can be used. It is possible to provide a power supply device capable of preventing the voltage across the smoothing capacitor from abnormally increasing when the oscillation frequency of the circuit is increased.

According to the ninth and tenth aspects of the present invention, the input current distortion can be improved with a single circuit configuration, the low frequency ripple of the load current can be reduced, and the oscillation frequency of the inverter circuit can be reduced. It is possible to provide a power supply device capable of preventing the voltage across the smoothing capacitor from abnormally increasing when the light is turned on by turning on.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention and a first conventional example.

2A is a diagram showing an input current waveform with a jump, FIG. 2B is a diagram showing a substantially sinusoidal input current waveform according to the present invention;
(C) shows an input current waveform diagram with a pause.

FIG. 3 is an oscillation frequency f of an inverter circuit according to the present invention.
It is a characteristic view which shows the relationship between the capacitance value of the capacitor C4.

FIG. 4 is a characteristic diagram showing a relationship between a capacitance value of a capacitor C4 and input power Win and output power Wout according to the present invention.

FIG. 5 is an oscillation frequency f of an inverter circuit according to the present invention.
It is another characteristic view showing the relationship between the capacitance value C4 of the capacitor and.

FIG. 6 is a circuit diagram showing a second embodiment according to the present invention.

FIG. 7A is a waveform diagram of a voltage across a smoothing capacitor C1, and FIG. 7B is a waveform diagram of an input current waveform according to the embodiment.

FIG. 8 is a circuit diagram showing a third embodiment according to the present invention.

FIG. 9 is a circuit diagram showing a fourth embodiment according to the present invention.

FIG. 10 shows a waveform diagram of a load current waveform according to the above embodiment.

FIG. 11 is a waveform diagram of a voltage waveform across a coupling capacitor C3 according to the first and second conventional examples.

FIG. 12 shows waveform diagrams of voltage waveforms across the impedance element Z2 according to the first and second conventional examples.

13A is a waveform diagram of a load current waveform flowing from an AC power source to a load according to the first and second conventional examples, and FIG. 13B is a waveform diagram of a charging / discharging current waveform of an impedance element Z2;
(C) shows a waveform diagram of a load current waveform.

FIG. 14 is a circuit diagram showing a second conventional example according to the present invention.

FIG. 15 shows an operation waveform diagram of a second conventional example according to the present invention.

[Explanation of symbols]

 C capacitor DB rectifier f oscillation frequency Iin input current L inductance element La discharge lamp Q switching element SW switch T transformer Vac AC power supply Win input power Wout output power WLa lamp power Z2 impedance element

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Claims (13)

[Claims] 1. A rectifier for rectifying an AC power supply, a smoothing capacitor connected between output terminals of the rectifier via a diode, and an inverter circuit for converting a voltage across the smoothing capacitor into a high frequency voltage and supplying the high frequency voltage to a load. And a high-frequency output feedback means for returning a part of the high-frequency voltage output from the inverter circuit to the output terminal of the rectifier and the contact of the diode, and an impedance element connected in parallel to both ends of the diode. In the above, in the vicinity of the center value of the variable range of the oscillation frequency of the inverter circuit, the impedance value of the impedance element is set in a direction in which the waveform of the input current from the AC power source becomes substantially sinusoidal. Power supply. 2. In the vicinity of the center value of the variable range of the oscillation frequency of the inverter circuit, the input power from the AC power supply and the output power supplied to the load are substantially equal to each other,
The power supply device according to claim 1, wherein an impedance value of the impedance element is set. 3. The power supply device according to claim 1, wherein the impedance element changes an impedance value within a variable range of an oscillation frequency of the inverter circuit. 4. A value in which an average current impedance value of the impedance element within a variable range of an oscillation frequency of the inverter circuit is near a center value of the variable range and an input current waveform from the AC power supply has a substantially sinusoidal shape. And
4. The impedance value of the impedance element is changed in a direction in which the input power from the AC power supply and the output power supplied to the load are substantially equal to each other. Power supply. 5. A series circuit comprising a charging circuit for charging the smoothing capacitor and the impedance element is connected in parallel to both ends of the load. Power supply. 6. The impedance element comprises a plurality of capacitors and a plurality of switches, and controls the switches to switch the connection between the plurality of capacitors to change the impedance value. The power supply device according to any one of claims 1 to 5. 7. The impedance element is composed of a plurality of inductance elements and a plurality of switches, and controls the switch to switch the connection between the plurality of inductance elements to change the impedance value. The power supply device according to any one of claims 1 to 5. 8. The impedance element includes a plurality of capacitors, a plurality of inductance elements, and a plurality of switches, and controls the switches to connect the plurality of capacitors to the plurality of inductance elements. The power supply device according to any one of claims 1 to 5, wherein the power supply device is switched to change the impedance value. 9. The power supply device according to claim 1, wherein the load includes a discharge lamp. 10. The load is configured to include a transformer having a secondary winding and a discharge lamp connected in parallel to the secondary winding of the transformer.
6. The power supply device according to claim 5. 11. The power supply device according to claim 5, wherein the charging circuit includes a capacitor. 12. The charging circuit is configured to include an inductance element.
The power supply as described. 13. The power supply device according to claim 5, wherein the charging circuit includes a capacitor and an inductance element.