JP3329913B2 - Power supply - Google Patents

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 rectifying and smoothing an AC voltage supplied from an AC power supply, converting the rectified and smoothed DC voltage into a high-frequency AC voltage by an inverter, and driving a load. More particularly, the present invention relates to a power supply device having improved power factor and improved harmonic distortion of an input current from an AC power supply.

[0002]

2. Description of the Related Art Conventionally, as a power supply device as described above,
For example, there is one described in Japanese Patent Publication No. Hei 5-9918.
Figure 6 is a schematic circuit diagram showing those described above Kokoku No. 5-9918, inductor L ₂ for high-frequency cut
Full-wave rectified by a diode bridge DB with the AC voltage supplied from the AC power supply 1 via a supply DC voltage smoothed in the inverter circuit 3 in the smoothing capacitor C ₀ through the inductor L ₃ as a high-frequency cut filter The high-frequency AC voltage output from the inverter circuit 3 is supplied to the discharge lamp 4 serving as a load via the output transformer T, and the high-frequency AC voltage of the inverter circuit 3 is cut at a low frequency by the feedback winding n. It is fed back to the input side of the diode bridge DB via a capacitor C ₁ as use filter. Then, by through the inductor L ₃ charges the smoothing capacitor C ₀ by the output voltage of the high-frequency AC voltage superimposed diode bridge DB, input over substantially the entire area of one period of the AC voltage of the AC power supply 1 current , The input power factor from the AC power supply 1 can be improved, and the harmonic distortion of the input current can be improved. In addition, the cost can be increased because it can be realized with a relatively simple circuit configuration. It can be suppressed.

[0003]

However, in the above-mentioned conventional configuration, as shown in FIG. 7, when the AC voltage of the AC power supply 1 is near zero, the input current does not flow. There is a problem that occurs. Further, the high-frequency AC voltage of the inverter circuit 3 is fed back to the feedback winding n.
, The energy supplied from the output transformer T to the discharge lamp 4 is reduced by the amount fed back by the feedback winding n. Therefore, as shown in FIG. 8, there is also a problem that the lamp current flowing through the discharge lamp 4 generates a ripple synchronized with the cycle of the AC voltage of the AC power supply 1.

As a solution to the above problem at the same time, a device using a DC-DC converter circuit called a so-called active filter circuit has been proposed. However, the use of such an active filter circuit complicates the circuit configuration. There is a problem that the cost increases.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a power supply device capable of improving a power factor and improving harmonic distortion and having a simple circuit configuration without a pause section of an input current. is there.

[0005]

According to the first aspect of the present invention, an AC power supply, a rectifier for rectifying an AC voltage supplied from the AC power supply, and an output voltage from the rectifier are smoothed. A smoothing capacitor, an inverter that converts a DC voltage output from the smoothing capacitor into a high-frequency AC voltage and supplies the high-frequency AC voltage to a load, and a voltage feedback device that returns the high-frequency AC voltage output from the inverter to an input side of the rectifier,
An LC resonance circuit is connected between the AC power supply and the rectifier and resonates with the high-frequency AC voltage fed back by the voltage feedback device.

According to a second aspect of the present invention, in the first aspect, the resonance frequency of the LC resonance circuit is set higher than the frequency of the high-frequency AC voltage output from the inverter. According to a third aspect of the present invention, in the first aspect, the resonance frequency of the LC resonance circuit is set lower than the frequency of the high-frequency AC voltage output from the inverter.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the resonance frequency of the LC resonance circuit becomes substantially equal to the frequency of the high-frequency AC voltage according to a change in the frequency of the high-frequency AC voltage output from the inverter. And adjusting means for adjusting at least one of the inductance of the inductor and the capacitance of the capacitor.

[0008]

According to the first aspect of the present invention, an AC power supply, a rectifier for rectifying an AC voltage supplied from the AC power supply, a smoothing capacitor for smoothing an output voltage from the rectifier, and a DC voltage output from the smoothing capacitor And a voltage feedback device connected between the AC power supply and the rectifier, and a voltage feedback device that returns the high-frequency AC voltage output from the inverter to the input side of the rectifier. LC that resonates with high-frequency AC voltage fed back by
Since the high frequency AC voltage is increased by the resonance in the LC resonance circuit and superimposed on the output voltage of the rectifier, the voltage becomes higher than the voltage across the smoothing capacitor. It is possible to flow the input current from the AC power supply over substantially the entire area of one cycle, thereby eliminating the pause period of the input current.

According to the second aspect of the present invention, since the resonance frequency of the LC resonance circuit is set higher than the frequency of the high-frequency AC voltage output from the inverter, the load is loaded with the high-frequency AC voltage having a frequency higher than the normal frequency. When driving, the frequency of the high-frequency AC voltage of the inverter rises and L
By approaching the resonance frequency of the C resonance circuit, it becomes possible to flow the input current from the AC power supply over substantially the entire period of one cycle of the AC voltage of the AC power supply, thereby eliminating the pause period of the input current. is there.

According to the third aspect of the invention, since the resonance frequency of the LC resonance circuit is set lower than the frequency of the high-frequency AC voltage output from the inverter, the load is loaded with the high-frequency AC voltage having a frequency lower than the normal frequency. When driving, the frequency of the high-frequency AC voltage of the inverter falls to L
By approaching the resonance frequency of the C resonance circuit, it becomes possible to flow the input current from the AC power supply over substantially the entire period of one cycle of the AC voltage of the AC power supply, thereby eliminating the pause period of the input current. is there.

According to a fourth aspect of the present invention, in response to a change in the frequency of the high-frequency AC voltage output from the inverter,
Since the adjusting means for adjusting at least one of the inductance of the inductor and the capacitance of the capacitor is provided so that the resonance frequency of the LC resonance circuit becomes substantially equal to the frequency of the high-frequency AC voltage, when the frequency of the high-frequency AC voltage of the inverter changes. Also, according to the change by the adjusting means, LC
By making the resonance frequency substantially equal to the resonance frequency of the resonance circuit, the input current can flow from the AC power supply over substantially the entire period of one cycle of the AC voltage of the AC power supply, thereby eliminating the pause period of the input current. It is.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic circuit configuration diagram of a power supply device according to the present embodiment. As shown in FIG. 1, the power supply, an AC power supply 1, the inductor L ₁ and capacitor C ₁
, A diode bridge DB, a smoothing capacitor C ₀ , an inverter circuit 3, an output transformer T, and a feedback winding for feeding a high-frequency AC voltage of the inverter circuit 3 from the output transformer T to the resonance circuit 2. A discharge lamp 4 is connected as a load to the secondary side of the output transformer T. Note that the inductor L ₂ and capacitor C ₂ connected to an AC power source 1 constitutes a filter for high-frequency cut.

The output side of the feedback winding n is connected in series with the capacitor C ₁ of the resonance circuit 2, and the capacitor C ₁
And a series circuit of a feedback winding n is connected to the AC power supply 1 in parallel with the diode bridge DB. The AC voltage supplied from the AC power supply 1 is full-wave rectified in the diode bridge DB, further smoothed by the smoothing capacitor C _0, and input to the inverter circuit 3.

The inverter circuit 3 includes a serially connected one.
Pair of switching transistors Q₁, Q_TwoAlternately conducting
By shutting off, the smoothing capacitor C₀Through
A high-frequency AC voltage is obtained from the input DC voltage,
Frequency AC voltage to the current feedback transformer CT and capacitor C_Three
And the output transformer T
To supply a high-frequency AC voltage to the discharge lamp 4 via the
Starts and lights the discharge lamp 4
is there. The switching transistor Q₁, Q_TwoGuide
The switching operation of the cutoff is performed by the switching transistor Q
₁, Q_TwoFeedback loop with a secondary winding connected to each base
This is a self-excited operation by a lance CT. Also switching
Transistor Q₁, Q_TwoStart the inverter circuit 3 in parallel with
A starting circuit 5 for operating the motor is connected to the starting circuit.
Path 5 is coupling capacitor C _Four, Resistance R₁, Daio
Code D₁And Diac Q_ThreeIt is composed of

On the other hand, the resonance frequency f of the resonance circuit 2₀Is
Nacta L₁The inductance of L ₁, Capacitor C₁
The capacity of C₁Then, it is expressed by the following equation.

[0016]

(Equation 1)

The above resonance frequency f₀Is inverter circuit 3
Becomes almost equal to the frequency f of the high-frequency AC voltage output from the
So, the inductor L₁Inductance and condensation
Sa C₁Is set. Circuit operation in the above configuration
The operation will be described with reference to FIG. First, the AC voltage of AC power supply 1
Is in the positive half cycle. Connected to the resonant circuit 2
The feedback winding n corresponds to the operating frequency of the inverter circuit 3.
The high-frequency AC voltage obtained in FIG.₁Direction and its
Inverse v_TwoIt occurs alternately with the direction. And return winding
The frequency f of the high-frequency AC voltage generated in the line n and the resonance circuit 2
Resonance frequency f₀Is to be approximately equal as described above
The high-frequency AC power generated in the feedback winding n
The resonance current 2 is applied to the resonance circuit 2 by the pressure.₁Is flowing
Become. Therefore, the capacitor C ₁High frequency at both ends
An AC voltage is generated, and the capacitor C₁Of both ends
Voltage and the high-frequency AC voltage generated in the feedback winding n
(See FIG. 3 (a)), and a diode
Full-wave rectified in bridge DB and smoothing capacitor C
₀Is to charge.

[0018] That is, as shown in FIG. 3 (a), the voltage across the capacitor C _1, the AC voltage of the feedback winding AC power source 1 and the high-frequency alternating voltage is superimposed occurring n is approximately one period thereof The voltage E across the smoothing capacitor C _0
Since it is higher than ₀ , a charging current flows through the smoothing capacitor C0 as a chopping current in substantially the entire region described above (see FIG. 3B). As a result, the input current flows over substantially the entire area of one cycle of the AC voltage of the AC power supply 1, so that the pause period of the input current as in the conventional example can be eliminated (FIG. 3B). reference).

At this time, the discharge lamp 4, which is a load,
As shown in FIG. 4, a lamp current having a low ripple and a favorable current waveform flows. Furthermore, according to the configuration of the present invention, the smoothing capacitor C ₀ is charged with energy by resonance obtained from the resonance circuit 2 of the inductor L ₁ and the capacitor C ₁ , so that when the AC voltage of the AC power supply 1 is near zero. , And a good light output can be obtained. As shown in FIG. 5, in place of the inductor L ₂ of the high-frequency cut, by connecting the configured passive filter 6 to the AC power supply 1 two windings wound in the same core, the AC power source The harmonic distortion of the input current supplied from 1 can be further improved.

In the case where the load is the discharge lamp 4, in the dimming operation mode in which the light output of the discharge lamp 4 is reduced, or in the filament preheating mode immediately after the power supply to the discharge lamp 4 is started. The frequency of the high-frequency AC voltage of the inverter circuit 3 is higher than the frequency in the normal lighting mode. Therefore, the resonance circuit 2
Inductance and a capacitor C of the resonant frequency f ₀ of the inverter circuit inductor L ₁ to be higher than the frequency f of the high frequency AC voltage of 3 in the normal lighting mode of
If the capacity of ₁ is set, even when the discharge lamp 4 is turned on in the above-described mode, the resonance frequency f ₀ approaches the set resonance frequency f ₀ as the frequency of the high-frequency AC voltage of the inverter circuit 3 increases, AC power supply 1 as described above
When the AC voltage is near zero, the lamp current hardly decreases, and a good light output can be obtained.

The inductance of the inductor L ₁ and the capacitance of the capacitor C ₁ are set so that the resonance frequency f ₀ of the resonance circuit 2 is lower than the frequency f of the high-frequency AC voltage of the inverter circuit 3 in the normal lighting mode. ,
Even when the frequency f of the high-frequency AC voltage of the inverter circuit 3 is decreased from the frequency in the normal lighting mode as in a no-load state, the resonance of the resonance circuit 2 set as the frequency of the high-frequency AC voltage of the inverter circuit 3 decreases. When the frequency approaches the frequency f ₀ and the AC voltage of the AC power supply 1 is near zero as described above, there is almost no decrease in the lamp current.
Good light output can be obtained.

Furthermore, to be able to change the resonance frequency f ₀ of the resonant circuit 2, the adjusting means for adjusting at least one of the inductance and capacitance of the capacitor C ₁ of the inductor L ₁ is provided, as described above According to the frequency f of the high-frequency AC voltage of the inverter circuit 3 that changes according to various operation states of the inverter circuit 3, the adjusting means adjusts the resonance frequency f ₀ of the resonance circuit 2 to approach the frequency f of the high-frequency AC voltage. Inverter circuit 3
As described above, in all the operating states, the lamp current hardly decreases when the AC voltage of the AC power supply 1 is near zero, and a good light output can be obtained.

In this embodiment, the case where the load is a discharge lamp has been described, but the present invention is not limited to this. Further, the inverter circuit is not limited to that of the present embodiment,
For example, various types such as a one-stone type and an L-push-pull type can be used.

[0024]

According to the first aspect of the present invention, there is provided an AC power supply, a rectifier for rectifying an AC voltage supplied from the AC power supply, a smoothing capacitor for smoothing an output voltage from the rectifier, and a DC voltage output from the smoothing capacitor. And a voltage feedback device connected between the AC power supply and the rectifier, and a voltage feedback device that returns the high-frequency AC voltage output from the inverter to the input side of the rectifier. And the LC resonance circuit that resonates, the returned high-frequency AC voltage is L
By being increased by resonance in the C resonance circuit and superimposed on the output voltage of the rectifier, the voltage becomes higher than the voltage across the smoothing capacitor. It is possible to flow. As a result, there is an effect that a so-called pause section of the input current can be eliminated, and the power factor and the harmonic distortion can be improved with a simple circuit configuration.

According to the second aspect of the present invention, the resonance frequency of the LC resonance circuit is set to be higher than the frequency of the high-frequency AC voltage output from the inverter. By approaching the frequency, it is possible to flow the input current from the AC power supply over substantially the entire period of one cycle of the AC voltage of the AC power supply, and it is possible to eliminate the pause period of the input current, which is higher than the normal frequency. When a load is driven by a high-frequency AC voltage having a frequency, the power factor and the harmonic distortion can be improved.

According to the third aspect of the present invention, since the resonance frequency of the LC resonance circuit is set lower than the frequency of the high-frequency AC voltage output from the inverter, the frequency of the high-frequency AC voltage of the inverter decreases and the resonance frequency of the LC resonance circuit decreases. By approaching the frequency, it is possible to flow the input current from the AC power supply over substantially the entire period of one cycle of the AC voltage of the AC power supply, and it is possible to eliminate the pause period of the input current, which is lower than the normal frequency. When a load is driven by a high-frequency AC voltage having a frequency, the power factor and the harmonic distortion can be improved.

According to a fourth aspect of the present invention, the inductance of the inductor and the inductance of the capacitor are adjusted so that the resonance frequency of the LC resonance circuit becomes substantially equal to the frequency of the high-frequency AC voltage according to the change in the frequency of the high-frequency AC voltage output from the inverter. Since there is provided an adjusting means for adjusting at least one of the capacity and the capacitance, the adjusting means makes the resonance frequency of the LC resonance circuit substantially equal to the frequency of the high-frequency AC voltage according to a change in the frequency of the high-frequency AC voltage output from the inverter. This allows the input current to flow from the AC power supply over substantially the entire period of one cycle of the AC voltage of the AC power supply, thereby eliminating a pause in the input current and changing the frequency of the high-frequency AC voltage of the inverter. Also in this case, there is an effect that the power factor can be improved and the harmonic distortion can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram showing an embodiment.

FIG. 2 is a circuit diagram showing a main part of the above.

FIGS. 3 (a) and 3 (b) are waveform diagrams for explaining the operation of the above.

FIG. 4 is a waveform diagram of a lamp current of the discharge lamp.

FIG. 5 is a schematic circuit diagram showing another example of the above.

FIG. 6 is a schematic circuit diagram showing a conventional example.

FIG. 7 is a waveform chart showing a power supply voltage and an input current according to the embodiment.

FIG. 8 is a waveform diagram of a power supply voltage and a lamp current of a discharge lamp according to the first embodiment.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 AC power supply 2 Resonant circuit 3 Inverter circuit 4 Discharge lamp L ₁ Inductor C ₁ Capacitor n Feedback winding

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/48 H02M 1/12 H02M 7/06 H05B 41/24

Claims (4)

(57) [Claims] An AC power supply, a rectifier for rectifying an AC voltage supplied from the AC power supply, a smoothing capacitor for smoothing an output voltage from the rectifier, and converting a DC voltage output from the smoothing capacitor into a high-frequency AC voltage. An inverter that supplies a high-frequency AC voltage output from the inverter to the input side of the rectifier, and a high-frequency AC voltage that is connected between the AC power supply and the rectifier and is fed back by the voltage feedback device. And a LC resonance circuit that resonates with the power supply device. 2. The power supply device according to claim 1, wherein the resonance frequency of the LC resonance circuit is set higher than the frequency of the high-frequency AC voltage output from the inverter. 3. The power supply device according to claim 1, wherein the resonance frequency of the LC resonance circuit is set lower than the frequency of the high-frequency AC voltage output from the inverter. 4. At least one of the inductance of the inductor and the capacitance of the capacitor such that the resonance frequency of the LC resonance circuit becomes substantially equal to the frequency of the high-frequency AC voltage according to the change in the frequency of the high-frequency AC voltage output from the inverter. The power supply device according to claim 1, further comprising an adjusting unit that adjusts the power.