JP2002345261A - Power supply unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply unit capable of correcting both input current distortion and a peak factor of output current and reducing cost without increasing the number of parts even when the device is mounted inside a ferromagnetic metallic case. SOLUTION: A parallel circuit of a diode D3 and a capacitor C2 is connected with one end of a sinewave rectifier DB, a series circuit of switching devices Q1, Q2 is connected between the other end of the sinewave rectifier DB and the other end of the diode D3, and a series circuit of an impedance device Z of a ballast element, a DC cut-off capacitor C1 and a primary winding of a linkage transformer T is connected between a connection point of the switching devices Q1, Q2 and one end of the diode D3. There are provided a charging diode D1 for flowing charging current from the output of the sinewave rectifier DB to a filter capacitor C0 through the linkage transformer T and the switching device Q2, and a discharging diode D2 for supplying DC voltage from the filter capacitor C0 to the series circuit of the switching devices Q1, Q2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for converting an AC voltage from an AC power supply into a DC voltage, converting the DC voltage into a high-frequency voltage, and supplying a high-frequency voltage to a load.

[0002]

2. Description of the Related Art Conventionally, in order to efficiently turn on a fluorescent lamp, an AC voltage from an AC power supply is rectified and smoothed and converted into a DC voltage. A power supply device that supplies high-frequency power to a load resonance circuit including a load as a load is widely used.

(Conventional Example 1) FIG. 9 is a circuit diagram showing such a conventional power supply device (Japanese Patent Application No. 10-270418). This power supply device includes a full-wave rectifier DB for full-wave rectification of an AC voltage from a power supply AC to a DC voltage, and a full-wave rectifier D
A diode D3 having an anode connected to the positive output terminal of B, a cathode of the diode D3 and a full-wave rectifier D
Switching elements Q1 and Q2 formed of FETs connected in series with the negative output terminal of B; a capacitor C1 connected to one end of the positive output terminal of the full-wave rectifier DB;
The connection point between the switching elements Q1 and Q2 and the capacitor C1
Having a primary winding connected to the other end of the discharge lamp La and connected in parallel to each end of both filaments of the discharge lamp La.
Leakage transformer T having secondary winding and discharge lamp La
A load circuit composed of a capacitor C4 connected in parallel with the other end of each of the two filaments, a smoothing capacitor C0 connected to a drain of a switching element Q1 composed of an FET and a positive terminal, and a switching element composed of an FET A diode D2 connected between the source of Q2 and the negative terminal of the capacitor C0 for flowing the discharge current of the capacitor C0;
The diode D1 is connected between the connection point of the capacitor C0 and the negative terminal of the capacitor C0 to flow the charging current of the capacitor C0; And a capacitor C2 connected in parallel.

In this power supply device, a leakage transformer T
The LC resonance circuit is constituted by the leakage inductance and the capacitor C4. In this case, the LC
The specifications of the primary winding of the leakage transformer T are determined by a saturation design or the like in order to apply a voltage sufficient for starting to the discharge lamp La by the resonance operation of the resonance circuit.

For this reason, the input voltage (FIG.
10 (a), and the input current (FIG. 10).
Although the waveform shown by the broken line in (a) is taken in, the appropriate smoothed voltage cannot be obtained at the valley of the voltage applied to both ends of the inverter (see FIG. A large current cannot flow. That is, FIG.
As shown in (c), a high-frequency current having a poor crest factor flows through the discharge lamp La.

(Conventional Example 2) Next, a power supply device in which the crest factor which is a weak point of Conventional Example 1 is improved (Japanese Patent Application No. 11-6 / 1999).
No. 9191) is shown in FIG. The power supply device shown in FIG. 11 includes a full-wave rectifier DB for full-wave rectification of an AC voltage to a DC voltage, a first diode D3 having one end connected to one output terminal of the full-wave rectifier DB in a forward direction, A capacitor C2 connected in parallel to the first diode D3; and a capacitor C2 connected in series between the other output terminal of the full-wave rectifier DB and the other end of the first diode D3, and alternately at a frequency higher than the AC voltage. A pair of switching elements Q1 and Q2 to be turned on and off;
A series circuit of a chopper choke Lc, a DC cut capacitor C1, and a primary winding of a leakage transformer T, which is connected between a connection point of Q2 and the one end of the first diode D3; A discharge lamp load La connected to the side, a resonance capacitor C4 connected in parallel to the discharge lamp load La, a smoothing capacitor C0 for supplying a DC voltage to a series circuit of the pair of switching elements Q1 and Q2, A charging diode D1 for flowing a charging current from the output of the full-wave rectifier DB to the smoothing capacitor C0 via the choke Lc for the chopper and the switching element Q2, and a series connection of the pair of switching elements Q1 and Q2 from the smoothing capacitor C0. A discharge diode D2 for supplying a DC voltage to a circuit, and the pair of switching elements And a capacitor C3 connected in parallel to the series circuit of 1, Q2.

In the power supply device having the above configuration, the switching elements Q1 and Q2 are turned on / off alternately by a drive signal from a control circuit (not shown). Then, the capacitance value of the capacitor C4 and the leakage inductance component of the leakage transformer T are set so that a desired voltage is generated across the capacitor C4 by resonance of the LC resonance circuit,
Next, the smoothing capacitor C0 and the choke Lc for the step-down chopper are set so that the smoothing capacitor C0 is appropriately charged by the step-down chopper operation.

Thus, in the circuit configuration shown in FIG.
LC so that an appropriate voltage can be applied to the discharge lamp load La
A resonance circuit can be set. However, when mounted on a case made of a ferromagnetic material, the leakage inductance component of the leakage transformer T may fluctuate greatly. In the above-described circuit configuration, the leakage inductance is a ballast element of the inverter. When mounted on a case, the effect of the case on the output is large, making it difficult to use a leakage transformer.It is necessary to divide the transformer into a transformer and a ballast choke, leading to an increase in the number of parts and a factor that leads to an increase in cost. Become.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has an advantage that both the input current distortion and the output current crest factor are made appropriate, and the ferromagnetic metal case is provided. It is an object of the present invention to provide a power supply device that can be reduced in cost without increasing the number of components even when mounted.

[0010]

In order to solve the above-mentioned problems, a power supply device according to the first aspect of the present invention has a full-wave rectifier D for full-wave rectification of an AC voltage to a DC voltage as shown in FIG.
B, a first diode D3 having one end connected to one output terminal of the full-wave rectifier DB in the forward direction, a capacitor C2 connected in parallel to the first diode D3, and the other of the full-wave rectifier DB Output terminal and the first diode D3
And a pair of switching elements Q1 and Q2, which are connected in series between the other ends thereof and are alternately turned on and off at a frequency higher than the AC voltage, and a pair of switching elements Q1 and Q2.
, And a DC cut capacitor C1 and one of the leakage transformer T, which are connected between a connection point of the first diode D3 and the one end of the first diode D3.
A series circuit of a next winding, a load La connected to the secondary side of the leakage transformer T, a smoothing capacitor C0 for supplying a DC voltage to a series circuit of the pair of switching elements Q1 and Q2, A charging diode D1 for flowing a charging current from the output of the full-wave rectifier DB to the smoothing capacitor C0 via the transformer T and the switching element Q2, and a series circuit of the pair of switching elements Q1 and Q2 from the smoothing capacitor C0. A discharge diode D2 for supplying a DC voltage. A capacitor C3 is connected in parallel to a series circuit of the pair of switching elements Q1 and Q2.

In this configuration, for example, the leakage inductance component of the leakage transformer T is used as the inductance component for the step-down chopper.
It is possible to set an appropriate smoothed voltage to 0. The inductance component of the chopper choke is much smaller than the inductance component of the resonance inductor. For this reason, it is possible to adopt a structure in which the leakage flux of the leakage transformer T does not leak outside the leakage transformer T. As a result, the inductance component for the step-down chopper, which is composed of the leakage inductance component of the leakage transformer T, is less affected by the ferromagnetic material. Therefore, it is possible to reduce the change in output when the ferromagnetic material is mounted on the case, and to design a circuit that appropriately adjusts both the input current distortion and the crest factor.

Further, as shown in FIG. 4, an LC resonance circuit including a resonance capacitor C4 and a resonance inductor L may be provided so that a resonance current flows through the load. With this configuration, a ballast choke and a leakage transformer are provided, and the leakage inductance component of the leakage transformer can be used as the inductance component of the step-down chopper. As a result, it is possible to reduce the change in output when the ferromagnetic material is mounted on the case, and to design a circuit that appropriately adjusts both the input current distortion and the crest factor. It should be noted that the number of parts is small and the cost can be reduced.

Further, as shown in FIG. 7, the DC cut capacitor C1 may be connected to a path for charging the smoothing capacitor C0 and to a path on which a resonance current flows (claim 3). With this configuration, the input current distortion can be more appropriately improved.

As shown in FIG. 8, a second diode D4 is connected in series in the forward direction between a parallel circuit of the first diode D3 and the capacitor C2 and the output terminal of the diode bridge DB. Two diodes D
3, a capacitor C5 connected in parallel between both ends of D4 may be provided. Also in this configuration,
Input current distortion can be more appropriately improved.

[0015]

(Embodiment 1) FIG. 1 is a circuit diagram of a first embodiment of the present invention. Hereinafter, the circuit configuration will be described. An AC power supply AC is connected to an AC input terminal of the full-wave rectifier DB. On the positive polarity side of the DC output terminal of the full-wave rectifier DB, the drain of the switching element Q1 composed of a MOSFET, the positive polarity side of the smoothing capacitor C0, and one end of the capacitor C3 are connected. The drain of the switching element Q2 composed of a MOSFET is connected to the source of the switching element Q1. The other end of the capacitor C3 is connected to the source of the switching element Q2, and the anodes of the diodes D2 and D3 are connected. A capacitor C2 is connected in parallel to both ends of the diode D3. The cathode of the diode D3 is connected to the negative side of the DC output terminal of the full-wave rectifier DB. One end of a ballast impedance component Z is connected to the negative polarity side of the DC output terminal of the full-wave rectifier DB via a DC cut capacitor C1, and the other end of the ballast impedance component Z and the switching elements Q1, Q
The primary winding of the leakage transformer T is connected between the two connection points. A discharge lamp load La is connected in parallel between both ends of the secondary winding of the leakage transformer T. The connection point between the primary winding of the leakage transformer T and the ballast impedance component Z is connected to the cathode of a diode D1. The anode of the diode D1 and the cathode of the diode D2 are connected to the negative side of the smoothing capacitor C0. The diode D1 is for charging the smoothing capacitor C0, and the diode D2 is for discharging the smoothing capacitor C0.

In the power supply device having the above configuration, the switching elements Q1 and Q2 are turned on / off alternately by a high-frequency control signal from a control circuit (not shown). Due to the impedance component Z serving as a ballast, the desired voltage is
The step-up ratio of the leakage transformer T is set so as to occur in the step S1.
Is set to an appropriate value so that the voltage of the step-down chopper, which includes the leakage inductance components of the smoothing capacitor C0 and the leakage transformer T, is appropriately charged.

As described above, by employing the circuit configuration shown in FIG. 1, it is possible to set the inductance component of the chopper choke and the smoothing capacitor C0 so that an appropriate voltage is applied to the discharge lamp load La. .

FIGS. 2 and 3 are explanatory diagrams of the operation of the power supply device shown in FIG. Hereinafter, an example of the operation of the power supply device illustrated in FIG. 1 will be described with reference to these drawings. First, when the switching element Q1 is turned on, as shown in FIG. 2 (a), the load current is such that the smoothing capacitor C0 becomes a DC power supply, and the smoothing capacitor C0 → the switching element Q1 → the leakage transformer T → the ballast impedance Z → DC Cut capacitor C1 → capacitor C2 → diode D2
, And supplies power to the discharge lamp load located on the secondary side of the leakage transformer T via the leakage transformer T.

The input current is V _AC (AC power supply voltage)
In the period where> V _T (voltage across leakage transformer T) + V _C1 (voltage across capacitor C1), AC power supply AC → diode bridge DB → switching element Q1 → leakage transformer T → ballast impedance Z → DC cut capacitor C1 → Diode bridge D
It flows on the path of B.

Next, when the switching element Q1 is turned on and _VAC
In the period where (AC power supply voltage) <V _T (voltage across leakage transformer T) + V _C1 (voltage V _C1 across capacitor C ₁ ), the input current is not drawn in, and the load current is reduced as shown in FIG. ), As shown in FIG.
Flows along the same path as.

Next, when the switching element Q1 is turned off and the switching element Q2 is turned on, FIG.
As shown in (c), the load current flows on the path of the leakage transformer T → ballast impedance Z → DC cut capacitor C1 → capacitor C2 → parasitic diode of the switching element Q2 due to the energy stored in the leakage transformer T. Power is supplied to the discharge lamp load located on the secondary side of the leakage transformer T via the transformer T.

The input current is V _AC (AC power supply voltage)
In the period where> V _C0 (voltage across the smoothing capacitor C0) + V _Z (voltage across the impedance Z) + V _C1 (voltage across the capacitor C1), the AC power supply AC → the diode bridge DB → the smoothing capacitor C0 → the diode D
1 → ballast impedance Z → DC cut capacitor C1 → flow through the path of diode bridge DB.

When the energy stored in the leakage transformer T disappears, as shown in FIG.
The load currents are DC cut capacitor C1 and capacitor C
2, the power flows through the path of the DC cut capacitor C1, the ballast impedance Z, the leakage transformer T, the switching element Q2, and the capacitor C2, and the power is supplied to the discharge lamp load located on the secondary side of the leakage transformer T via the leakage transformer T. Supply.

The input current is V _AC (AC power supply voltage)
+ V _C2 (voltage across capacitor C2)> V _C0 (voltage across smoothing capacitor C0) + V _T (leakage transformer T
), The AC power supply AC → the diode bridge DB → the smoothing capacitor C0 → the diode D1 → the leakage transformer T → the switching element Q2
→ flows through the path of the capacitor C2 → the diode bridge DB.

When the energy stored in the capacitor C2 is exhausted, the diode D3 connected in parallel to the capacitor C2 is turned on, and the load current is reduced as shown in FIG.
Using the DC cut capacitor C1 as a power source, the discharge lamp flows on the path of the DC cut capacitor C1, the ballast impedance Z, the leakage transformer T, the switching element Q2, and the diode D3, and is located on the secondary side of the leakage transformer T via the leakage transformer T. Supply power to the load.

The input current is V _AC (AC power supply voltage)
> V _C0 (voltage across the smoothing capacitor C0) + V _T (voltage across the leakage transformer T)
The current flows along the path of AC power supply AC → diode bridge DB → smoothing capacitor C0 → diode D1 → leakage transformer T → switching element Q2 → diode D3 → diode bridge DB.

Next, when the switching element Q2 is turned off and the switching element Q1 is turned on, FIG.
As shown in (f), the load current is caused by the energy stored in the leakage transformer T, the path of the leakage transformer T → the parasitic diode of the switching element Q1 → the smoothing capacitor C0 → the path of the diode D1, or the leakage transformer T → the switching element. Power is supplied to the discharge lamp load located on the secondary side of the leakage transformer T via the leakage transformer T through the path of the parasitic diode of Q1 → the capacitor C3 → the diode D3 → the DC cut capacitor C1 → the ballast impedance Z. By a series of these operations, the high-frequency power is supplied to the discharge lamp load, and at the same time, the input current is taken in and the input current distortion can be suppressed.

As described above, according to the first embodiment, since the leakage inductance of the leakage transformer T is used as the inductor of the step-down chopper, by setting the leakage inductance arbitrarily, the full-wave rectifier D
Within the range up to the output peak voltage of B, the smoothing capacitor C
It is possible to set the smoothed voltage by 0 to an arbitrary voltage. As a result, it is possible to design a circuit that appropriately sets both the input current distortion and the output crest factor.

The inductance component of the chopper choke according to the present embodiment is a leakage component of the leakage transformer T, and the leakage flux of the leakage transformer T is structured so as not to leak outside the leakage transformer T. preferable. By doing so, the inductance for the step-down chopper, which is the leakage inductance component of the leakage transformer T, is less likely to be affected by the ferromagnetic material. That is, compared with the leakage magnetic flux of the leakage transformer shown in the conventional example, the magnetic flux leaking out of the leakage transformer used in the present embodiment is very small. And the change in leakage inductance is small, and the ballast component is the impedance Z, so that the change in output as in the conventional example is small. As a result, it is possible to reduce the change in output when mounted in the case of a ferromagnetic material, and to design a circuit that appropriately adjusts both the input current distortion and the crest factor.

(Embodiment 2) FIG. 4 is a circuit diagram of a second embodiment of the present invention. Hereinafter, the circuit configuration will be described. The power supply device shown in FIG. 4 is different from the first embodiment shown in FIG. 1 in that a resonance inductor L is connected as a ballast impedance Z, and a resonance capacitor C4 is connected to both ends of a discharge lamp load connected to the secondary side of the leakage transformer T. This is the configuration. In this embodiment, the switching elements Q1,
An inverter is configured by Q2, a leakage transformer T, a resonance inductor L, a DC cut capacitor C1, a diode D3, a capacitor C2, a resonance capacitor C4, a load resonance circuit including a discharge lamp load La, and the like.

An example of a procedure for setting each value of the LC resonance circuit in the power supply device having the above configuration will be described. The resonance of the LC resonance circuit causes a desired voltage to be generated across the capacitor C4 or a desired current to be discharged. Light load La
First, the capacitance value of the capacitor C4 and the inductance value of the inductor L are determined with priority given to the capacitance value of the capacitor C4. Next, an appropriate voltage is supplied to the capacitor C0 by the step-down chopper circuit.
The inductance value of the step-down chopper choke composed of the leakage inductance of the leakage transformer T and the capacitance value of the capacitor C0 are determined.

As described above, by employing the circuit configuration shown in FIG. 4, it is possible to set the chopper choke component and the capacitor C0 so that an appropriate voltage is applied to the discharge lamp load. Here, the discharge lamp load includes an inductor L
The voltage generated at both ends of the capacitor C4 is applied to the discharge lamp load by the resonance action of the LC resonance circuit constituted by the capacitor C4 and the capacitor C4. Therefore, by controlling the switching frequency of the switching elements Q1 and Q2, It is possible to control the voltage applied to the lamp load.

FIGS. 5 and 6 are explanatory diagrams of the operation of the power supply device shown in FIG. The circuit operation of the present embodiment is substantially the same as the circuit operation of the first embodiment, and the description of the circuit operation will be omitted.

Also in this embodiment, since the leakage inductance of the leakage transformer T is used as the inductor of the step-down chopper, by setting the leakage inductance arbitrarily, the leakage inductance can be set within the range up to the output peak voltage of the full-wave rectifier DB. The smoothing voltage by the smoothing capacitor C0 can be set to an arbitrary voltage.
As a result, it is possible to design a circuit that appropriately sets both the input current distortion and the output crest factor.

Further, since the leakage transformer of this embodiment uses a leakage transformer with a reduced leakage magnetic flux similarly to the first embodiment, the ferromagnetic case is closer to the leakage transformer than the leakage transformer of the conventional example 2. The change in leakage inductance due to contact with the lamp is small, and the change in discharge lamp output is also small.

(Embodiment 3) FIG. 7 is a circuit diagram of a third embodiment of the present invention. The power supply device shown in FIG. 7 includes a DC cut capacitor C1 in the first embodiment shown in FIG.
In this configuration, the switching element is connected between a connection point of the switching elements Q1 and Q2 and the leakage transformer T. The circuit operation of the present embodiment is substantially the same as the circuit operation of the first embodiment, and a detailed description of the circuit operation will be omitted.

The feature of the circuit operation of this embodiment is that, during the period in which the input current is drawn by the step-down chopper circuit operation, the AC power supply AC → the diode bridge DB → the capacitor C0 → the diode D1 → the leakage transformer T → the capacitor C1 → the switching element Q2 → The input current flows through the path of the capacitor C2 or the diode D3 → the diode bridge DB, but the input power supply is the AC power supply AC, the capacitor C2, and the DC cut capacitor C1, and even at the valley of the AC power supply AC, the capacitor C2 and the DC cut capacitor. Since C1 serves as a power supply, it is possible to design a circuit that better improves input distortion and also has an appropriate output crest factor. In addition, even when mounted on a ferromagnetic case or the like, the influence on the leakage magnetic flux is small, and the change in the discharge lamp output due to the change in the leakage magnetic flux is small.

(Embodiment 4) FIG. 8 is a circuit diagram of a fourth embodiment of the present invention. In the power supply device shown in FIG. 8, the diode D4 is connected in the forward direction of the input current between the cathode of the diode D3 and the output terminal on the negative polarity side of the diode bridge DB in the second embodiment shown in FIG. The circuit configuration is such that a capacitor C5 is connected between a connection point between the source side of the switching element Q2 and the capacitor C2 and a connection point between the diode bridge DB and the diode D4. The capacitor C5 serves as an input power supply when the step-down chopper circuit operates, and the capacitor C2 also serves as the input power supply and the resonance capacitor of the resonance circuit. Therefore, the capacitor C5 cannot sufficiently serve as the input power supply in the power supply voltage trough of the AC power supply AC. Therefore, a capacitor C5 is provided.

The circuit operation of this embodiment is substantially the same as the circuit operation of the second embodiment, and a detailed description of the circuit operation will be omitted. The feature of the circuit operation of the present embodiment is that, during the period in which the input current is drawn by the step-down chopper circuit operation, the AC power supply AC → the diode bridge DB → the capacitor C0 → the diode D1 → the leakage transformer T → the switching element Q2 → the capacitor C5 or the diode D3. Although the input current flows through the series circuit of D4 → diode bridge DB, the input power source is the AC power source AC and the capacitor C5.
Since the capacitor C5 serves as a power supply, it is possible to design a circuit in which the input distortion is further improved and the output crest factor is also appropriate. Also in the present embodiment, the second
As in the embodiment, it is possible to design a circuit that appropriately sets both the input distortion and the output crest factor. In addition, even when mounted on a ferromagnetic case or the like, the influence on the leakage magnetic flux is small, and the change in the discharge lamp output due to the change in the leakage magnetic flux is small.

[0040]

According to the first aspect of the present invention, a full-wave rectifier for full-wave rectification of an AC voltage to a DC voltage, and a first end connected to one output terminal of the full-wave rectifier in a forward direction. , A capacitor connected in parallel to the first diode, and alternately connected in series between the other output terminal of the full-wave rectifier and the other end of the first diode at a frequency higher than the AC voltage. A pair of switching elements to be turned on and off, an impedance element serving as a ballast component, a DC cut capacitor, and a primary of a leakage transformer, which are connected between a connection point of the pair of switching elements and the one end of the first diode. A series circuit of windings, a load connected to the secondary side of the leakage transformer, and a smoothing capacitor for supplying a DC voltage to the series circuit of the pair of switching elements. A charging diode for flowing a charging current from the output of the full-wave rectifier to the smoothing capacitor via the leakage transformer and the switching element; and supplying a DC voltage from the smoothing capacitor to a series circuit of the pair of switching elements. Circuit that optimizes both input distortion and crest factor.The output due to the change in leakage inductance component of the leakage transformer even when mounted in a ferromagnetic case. There is little change.

According to the second aspect of the present invention, since an LC resonance circuit for flowing a resonance current to a load is provided, the output can be controlled by controlling the switching frequency of the switching element, and the input distortion and the crest factor can be controlled. It is possible to design a circuit that makes both of them appropriate, and even when mounted on a ferromagnetic case, there is little change in output due to a change in leakage inductance of the leakage transformer.

According to the third aspect of the present invention, since the DC cut capacitor is provided on a path for charging the smoothing capacitor and a path on which a resonance current flows, the input current is sufficiently drawn even in the valley of the AC power supply. It becomes possible.

According to the fourth aspect of the present invention, the second diode is connected in series in the forward direction between the parallel circuit of the first diode and the capacitor and the output terminal of the diode bridge.
Since a capacitor connected in parallel between both ends of the two diodes connected in series is provided, it is possible to sufficiently draw the input current even in the valley of the AC power supply.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a circuit operation explanatory diagram of the first embodiment of the present invention.

FIG. 3 is a circuit operation explanatory diagram of the first embodiment of the present invention.

FIG. 4 is a circuit diagram of a second embodiment of the present invention.

FIG. 5 is a circuit operation explanatory diagram of a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of a circuit operation according to a second embodiment of the present invention.

FIG. 7 is a circuit diagram of a third embodiment of the present invention.

FIG. 8 is a circuit diagram of a fourth embodiment of the present invention.

FIG. 9 is a circuit diagram of Conventional Example 1.

FIG. 10 is a signal waveform diagram of each unit in FIG. 9;

FIG. 11 is a circuit diagram of a second conventional example.

[Explanation of symbols]

 Q1 Switching element Q2 Switching element DB Full-wave rectifier C0 Smoothing capacitor D1 Charging diode D2 Discharge diode D3 First diode La Discharge lamp C1 DC cut capacitor Z Ballast impedance T Leakage transformer

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H05B 41/24 H05B 41/24 L F Term (Reference) 3K072 AA02 AC11 BA03 BB01 BC02 DB03 GA02 GB12 5H006 AA02 AA07 BB08 CA02 CA07 CB08 CC08 HA09 5H007 AA02 AA08 BB03 CA02 CB17 CC01 CC32

Claims (4)

[Claims] 1. A full-wave rectifier for full-wave rectification of an AC voltage to a DC voltage, a first diode having one end connected to one output terminal of the full-wave rectifier in a forward direction, and a parallel to the first diode. A pair of switching elements that are connected in series between the other output terminal of the full-wave rectifier and the other end of the first diode and that are alternately turned on and off at a frequency higher than the AC voltage; A series circuit of an impedance element serving as a ballast component, a DC cut capacitor, and a primary winding of a leakage transformer, which is connected between a connection point of the pair of switching elements and the one end of the first diode; A load connected to a secondary side of the switching element; a smoothing capacitor for supplying a DC voltage to a series circuit of the pair of switching elements; A charging diode for flowing a charging current from the output of the full-wave rectifier to the smoothing capacitor via a lance and a switching element; and a discharging diode for supplying a DC voltage from the smoothing capacitor to a series circuit of the pair of switching elements. A discharge lamp lighting device comprising: a diode. 2. An LC for flowing a resonance current to the load.
The power supply device according to claim 1, further comprising a resonance circuit. 3. The power supply device according to claim 2, wherein the DC cut capacitor is connected to a path for charging the smoothing capacitor and to a path through which a resonance current flows. 4. A second diode is connected in series in a forward direction between the one end of the first diode and one output terminal of the full-wave rectifier, and the first and second diodes are connected in series. The power supply device according to claim 1, further comprising a capacitor connected in parallel between both ends.