JP2001126895A - Electric power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure that prevents magnetic saturation of a transformer immediately after starting and also make the transformer miniaturized, in the condition of requiring large power in the state that impedance is low immediately after starting such as a HID lamp and high impedance and low supplying power when the load is stable, increases efficiency when load is stable, and decreases size of the transformer. SOLUTION: In a power supply unit boosting voltage of a direct current power supply and converting it into an alternating current by an inverter circuit and supplying it to a load it comprises a transformer for boosting voltage, a switching element for intermittently connecting a first winding of the transformer to a direct current power supply, and a controlling circuit for controlling the switching element to permit output power supplied to the load to be larger immediately after starting than when load is stable, wherein the magnetic circuit of the transformer comprises a first gap part g1 suitable for the output power when the load is stable state and a second gap part g2 suitable for the output power immediately after starting.

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 used for a discharge lamp lighting device and the like.

[0002]

2. Description of the Related Art FIG. 12 shows a configuration example of a conventional discharge lamp lighting device. Hereinafter, the circuit configuration will be described. The DC power supply E is composed of, for example, an on-vehicle battery, and its DC voltage is stabilized by the capacitor C1 and applied to a series circuit of the primary windings N11 and N12 of the transformer T and the switching element Q1. The secondary winding N2 of the transformer T is connected to a capacitor C2 via a diode D1. Capacitors C1, C2, transformer T, switching element Q
1 and the diode D1 constitute a DC booster circuit 1. When the switching element Q1 repeats ON / OFF at a high frequency, a voltage obtained by boosting the DC voltage of the DC power supply E is obtained in the capacitor C2. A series circuit of switching elements Q2 and Q3 and a series circuit of switching elements Q4 and Q5 are connected in parallel to the capacitor C2. The switching elements Q2 to Q5 alternately operate in such a manner that one of a pair of switching elements Q2, Q5 and Q3, Q4 arranged in a diagonal direction is turned on and the other is turned off in a low-frequency manner. An inverter circuit 2 that outputs a wave voltage is configured. A discharge lamp 4 is connected via an igniter unit 3 between a connection point between the switching elements Q2 and Q3 and a connection point between the switching elements Q4 and Q5.

FIG. 13 shows the structure of a transformer T of the DC booster circuit 1. In this example, a pair of substantially E-shaped cores 5 and 6 are arranged so that both side legs thereof abut each other to form a sun-shaped magnetic circuit as a whole. The center leg of one core 5 is formed to be slightly shorter than the two side legs, thereby forming a gap g. A primary winding N11, a secondary winding N2, and a primary winding N12 are sequentially arranged from the inner layer to the outer layer so as to surround the center leg piece.

[0004] The operation of the conventional discharge lamp lighting device will be described below. First, at the time of starting the discharge lamp 4, which is a load, the switching element Q1 repeats ON / OFF,
The voltage of the capacitor C <b> 2 is boosted to a no-load secondary voltage of about 300 V to 400 V, and the no-load secondary voltage is applied to both ends of the discharge lamp 4. In this state, the igniter unit 3 generates a high-voltage pulse of about 20 kV. Thereby, discharge starts between the electrodes of the discharge lamp 4 and the discharge lamp 4 starts. After the discharge lamp 4 is turned on, the switching element Q2
Q5 to O5 alternately at a frequency suitable for stable lighting of the discharge lamp 4.
N / OFF is repeated. As a result, a rectangular wave voltage is applied to the discharge lamp 4. Switching element Q1
Is controlled to supply electric power suitable for stable lighting of the discharge lamp 4.

[0005] The power required from the start of the discharge lamp 4 to the stable lighting state immediately after the start of the discharge lamp 4 is not constant. Depending on the application, for example, when a light source for a vehicle headlamp or a projector is used as a load, a quick light flux is required. Swift transition to stable lighting due to the rise of the LED is required. Conventionally, in order to achieve this, as shown in FIG. 14A, the control of the output power Wout supplied to the load 4 is performed by setting the area immediately after the start to the section A, the area of stable lighting to the section C, Assuming that the transition area is section B, the area immediately after startup (section A)
By setting the power Wout> the power Wout in the stable region (section C), the transition time to stable lighting is shortened.

[0006]

FIG. 14B shows a temporal change of the impedance R4 of the load 4 when an HID lamp is used as the load 4. HID
In the case of a lamp, the impedance is low immediately after starting (for example, 5Ω), and gradually increases as the operation shifts to stable lighting (for example, 200Ω). For this reason, the operation of the DC booster circuit 1 for controlling the output power is such that the load 4 has a low impedance and supplies a relatively large power in the region (section A) immediately after the start-up. The next current enters a continuous mode including a DC component as shown in FIG. 15A, and the peak value of the current increases.
On the other hand, in the stable region (section C), the impedance of the load 4 increases, and the output power Wout also decreases to the power at the time of stable lighting.
As shown in FIG. 5B, the DC component can be greatly reduced, and the peak value decreases.

[0007] The two greatly different modes of operation are referred to as 1
In the case of designing with one transformer (for example, in the case of a flyback transformer), in order to avoid a magnetic saturation phenomenon when the current of the transformer increases, as shown in FIG. It was necessary to increase the size or the cross section of the magnetic path of the magnetic circuit. However, if the gap g of the magnetic circuit is increased, the magnetic coupling between the primary winding and the secondary winding is weakened, and the circuit efficiency during stable lighting is also reduced. Further, when the magnetic circuit cross section of the magnetic circuit is enlarged, the shape of the transformer becomes large, which leads to an increase in the size and cost of the lighting device.

An object of the present invention is to reduce the size and size of a DC booster circuit transformer for performing load power control under the above-described load conditions and power control conditions while increasing the circuit efficiency.

[0009]

According to the present invention, in order to solve the above-mentioned problems, as shown in FIG. 12, a DC power supply E and a boosted DC power supply E supplied to a load 4 are provided. In a power supply device comprising a DC booster circuit 1 for controlling power, an inverter circuit 2 for converting a boosted DC voltage to an AC voltage, and a load 4 connected to an output of the inverter circuit 2, the DC booster circuit 1 is a step-up transformer T
A switching element Q1 for intermittently connecting a primary winding of the transformer T to a DC power supply E, and the switching element Q1 so that the output power supplied to the load 4 becomes larger immediately after startup than when the load is stable. And a control circuit for controlling Q1. The magnetic circuit of the transformer T includes, as shown in FIG.
It has a first gap portion g1 suitable for output power when the load is stable and a second gap portion g2 suitable for output power immediately after startup. According to the configuration of the present invention, the coupling coefficient of the first gap g1 is larger than that of the second gap g2, so that the efficiency at the time of stable load is improved.

[0010]

(Embodiment 1) FIG. 1 shows a configuration of a magnetic circuit of a transformer used in a power supply device according to Embodiment 1 of the present invention. The circuit configuration of the present embodiment is the same as the conventional example of FIG. 12, and the configuration of the magnetic circuit of the transformer T of the DC booster circuit 1 is replaced with the configuration shown in FIG. 1 instead of the configuration shown in FIG. Only the point is different. Assuming that the area immediately after startup is section A, the area of stable lighting is section C, and the transition area is section B, the power Wout supplied to the discharge lamp 4 is power Wout in section A> power Wout in section C. The first magnetic circuit includes a first gap portion g1 that is optimal for output power in a stable region (section C) and a second gap portion g2 that takes into account output power in a region immediately after startup (section A). .
In the first gap portion g1, the coupling coefficient is larger than in the second gap portion g2, and the efficiency increases. Therefore, FIG.
As shown in the figure, without increasing the size of the transformer,
The circuit efficiency η at the time of stable lighting can be greatly improved as compared with the conventional example.

(Embodiment 2) FIGS. 3 and 4 show how to form a first gap g1 and a second gap g2.
Each drawing (a) is a cross-sectional view taken along line AA ′ in each drawing (b). In the example of FIG. 3, a pair of ferrite cores having a substantially E-shaped cross section are arranged so that the end faces of both legs abut against each other, and a central leg inserted into the center of the winding is formed in a columnar shape. The first gap portion g1 is formed by making the length of the leg slightly shorter than that of the two-sided leg, and the second leg is formed by shaving off portions of the central leg that are respectively opposed to the two-sided leg. A gap portion g2 is formed. Further, in the example of FIG. 4, the second gap g2 is formed by cutting off a part of the center leg into a substantially semicircular shape. Such a two-stage gap can be provided on both side legs of the magnetic circuit (core).
As shown in FIG. 4, if the first gap g1 is provided on the center leg, the first gap g1 is magnetically saturated in a region (section A) immediately after startup.
Even when the second gap g2 operates, the unnecessary radiation noise leaking to the outside of the transformer can be reduced.

(Embodiment 3) FIG. 5 shows an embodiment of a sectional structure including a transformer winding. In the present embodiment, the core is substantially adhered to a substrate having excellent thermal conductivity such as the metal substrate 10. This improves the heat dissipation of the self-heating,
The efficiency can be improved by reducing the heat of the transformer. For a winding having a large current (for example, a primary winding N1), as shown in FIG. 6, by using a winding N in which a rectangular wire is wound edgewise, the occupancy rate of the winding itself is also improved. Therefore, a large amount of current can be passed through a small volume. As a result, the size of the transformer can be reduced.

When the secondary side of the transformer is used in a center tap type circuit as shown in FIG.
For secondary windings that have a relatively high voltage and require an insulation distance between the windings and an insulation distance between layers, the winding itself can be formed by using a winding in which a flat wire is edgewise wound. Since the withstand voltage is high and the skin effect is reduced, the occupancy rate of the winding of the transformer can be reduced, and the DC booster circuit 1 can be downsized.

(Embodiment 4) FIG. 7 shows Embodiment 4 of the present invention.
FIG. Hereinafter, the circuit configuration will be described. The DC power supply E is composed of, for example, an on-vehicle battery,
The DC voltage is applied to a series circuit of the primary winding N1 of the transformer T and the switching element Q1. The secondary winding of the transformer T has a center tap. One of the secondary windings N21 is connected to a series circuit of a diode D1, a switching element Q2, and a capacitor C2 with the center tap interposed therebetween. The secondary winding N22 is a diode D2,
The switching element Q3 and the capacitor C2 are connected to a series circuit. The connection point between the switching elements Q2 and Q3 is grounded, and is connected to one end of the discharge lamp 4. The discharge lamp 4 is connected in parallel to both ends of the capacitor C2 via the secondary winding of the pulse transformer PT. An igniter unit 3 for applying a high-voltage pulse when the discharge lamp 4 as a load is started is connected to the primary winding of the pulse transformer PT.

The switching elements Q2 and Q3 alternate at a low frequency, and one of them is turned on and the other is turned off. Further, the switching element Q1 is turned ON / OFF at a high frequency to appropriately control the power supplied to the discharge lamp 4. Now, switching element Q2 is ON and switching element Q3 is OF
F, when the switching element Q1 is turned on, a current flows from the DC power supply E to the primary winding N1 of the transformer T, and the secondary winding N21 of the transformer T causes the diode D
1, a current flows through the switching element Q2 and the capacitor C2. Thus, the capacitor C2 is charged in a direction in which the ground terminal of the discharge lamp 4 becomes positive. On the other hand, the switching element Q2 is OFF and the switching element Q3 is ON
When the switching element Q1 is turned on, a current flows from the DC power supply E to the primary winding N1 of the transformer T, and a current flows from the secondary winding N22 of the transformer T to the capacitor C
2. A current flows through the switching element Q3 and the diode D2. As a result, the capacitor C2 is charged in a direction in which the ground terminal of the discharge lamp 4 becomes negative. By repeating the above operation, a rectangular wave voltage whose polarity is inverted according to the alternating of the switching elements Q2 and Q3 is obtained at both ends of the capacitor C2.

Hereinafter, the operation of the lighting device will be described. First, when starting the discharge lamp 4 as a load, one of the switching elements Q2 and Q3 is ON and the other is OFF, the switching element Q1 repeats ON / OFF, and the voltage of the capacitor C2 is about 300V to 400V. The voltage is boosted to a no-load secondary voltage, and the no-load secondary voltage is applied to both ends of the discharge lamp 4. In this state, the igniter unit 3 applies a pulse voltage to the primary winding of the pulse transformer PT. Thereby, a high-voltage pulse of about 20 kV is applied to both ends of the discharge lamp 4 via the capacitor C2,
Discharge starts between the electrodes of the discharge lamp 4, and the discharge lamp 4 starts. After the discharge lamp 4 is turned on, the switching elements Q2, Q2
3 is alternately turned ON at a frequency suitable for stable lighting of the discharge lamp 4.
Repeat OFF. As a result, a rectangular wave voltage is applied to the discharge lamp 4. The switching element Q1 is controlled so as to supply electric power suitable for stable lighting of the discharge lamp 4. These switching elements Q1, Q2, Q3 are controlled by the control circuit 7. Note that the switching element Q
3 is driven via a level shift circuit 11.

(Embodiment 5) FIG. 8 shows another circuit configuration of a power supply device using the transformer of the present invention. In this example, the output polarity of the secondary winding with respect to the primary winding of the transformer T is opposite to that in the example of FIG. 7, and the secondary winding has no center tap. Switching element Q1
Is turned on, a current flows through the primary winding N1 of the transformer T, and magnetic energy is accumulated in the transformer T. At this time, the diode D1 is OFF, and no current flows through the secondary winding N2. When the switching element Q1 is turned off,
A back electromotive force is generated in the secondary winding N2 of the transformer T due to the magnetic energy stored in the transformer T, and the diode D1
Through the capacitor C2. As a result, a DC voltage is supplied to the load circuit. Even in such a circuit configuration, when the load circuit includes the rectangular wave lighting circuit of the HID lamp, the output power Wout is controlled so as to be large immediately after the start, and the output power Wout is decreased as the operation shifts to the stable lighting. The transformer T may be magnetically saturated. Therefore, the magnetic gap of the transformer T is a two-stage gap, and a first gap portion g1 optimal for output power during stable lighting and a second gap portion g2 considering output power immediately after startup are provided. As a result, the circuit efficiency during stable lighting can be improved without increasing the size of the transformer.

(Embodiment 6) FIG. 9 shows still another configuration example of a power supply device using the transformer of the present invention. In this example, a DC / DC converter having a configuration shown in FIG. 8 is combined so as to alternately operate in a pair in parallel. Hereinafter, the circuit configuration will be described. DC power supply E
Includes the primary winding of the transformer T1 and the switching element Q1.
1 series circuit is connected, and the transformer T2
Are connected in parallel with a series circuit of the primary winding and the switching element Q12. Each switching element Q11, Q1
2 is alternately turned ON / OFF by a control signal output from the same control circuit 7 and a drive signal (see FIG. 10) having a phase difference of only 180 degrees via a drive circuit 8. The secondary winding of the transformer T1 is connected to a capacitor C2 via a diode D1, and the secondary winding of the transformer T2 is connected in parallel to the capacitor C2 via a diode D2. A series circuit of the switching elements Q2 and Q3 and a series circuit of the switching elements Q4 and Q5 are connected in parallel to both ends of the capacitor C2. A discharge lamp 4 is connected via an igniter unit 3 between a connection point between the switching elements Q2 and Q3 and a connection point between the switching elements Q4 and Q5.

In the discharge lamp lighting device having such a configuration, the control of the output power Wout supplied to the load 4 is performed by controlling the area immediately after the start-up to section A, the stable lighting area to section C, and the transition area to section B. Then, the area immediately after startup (section A)
Is controlled such that the power Wout of the power supply> the power Wout of the stable region (section C). Further, by providing the transformers T1 and T2 of the DC / DC converter section in parallel and connecting them alternately to the DC power supply E, the DC power supply E
The utilization rate has been improved. Further, at the time of stable lighting, by controlling the current modes of the transformers T1 and T2 to operate under the critical condition so that the switching elements Q11 and Q12 shown in FIG. 10 are alternately turned on, the power supply E and the transformers T1 and T2 are controlled. The utilization factor is improved, and the efficiency of the power supply device can be improved. Also, two transformers T
1 and T2 have a shape as shown in FIG. 11 and share a two-stage gap type core. Thereby, the transformers T1, T2
It is possible to improve the circuit efficiency while reducing the size of the device.

As shown in FIG. 12, two primary windings N11 and N12 may be connected in parallel so that a large current can flow immediately after the start. In this case, the two primary windings N11 and N12 are connected to the secondary winding N as shown in FIG.
It is convenient to wind the wire 2 so as to be sandwiched from both sides, so that the magnetic coupling becomes good.

[0021]

According to the present invention, a DC power supply, a DC booster circuit for boosting the DC power supply to control power supplied to a load, and an inverter circuit for converting the boosted DC voltage to an AC voltage, In a power supply device including a load connected to an output of an inverter circuit, the DC booster circuit includes a boosting transformer, and a switching element intermittently connecting a primary winding of the transformer to a DC power supply; A control circuit for controlling the switching element so that the output power supplied to the load is larger than that at the time of load stabilization immediately after the start-up. By having the first gap portion and the second gap portion suitable for the output power immediately after starting, the circuit efficiency at the time of stability is greatly improved as compared with the conventional one without increasing the size of the transformer. It is possible to above.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration example of a magnetic circuit according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing changes over time in circuit efficiency, load impedance, and output power according to the first embodiment of the present invention.

3A and 3B are diagrams illustrating a configuration example of a magnetic circuit according to a second embodiment of the present invention, wherein FIG. 3A is a cross-sectional view, and FIG.

4A and 4B are diagrams illustrating another configuration example of the magnetic circuit according to the second embodiment of the present invention, where FIG. 4A is a cross-sectional view and FIG.

FIG. 5 is a sectional view of a transformer according to a third embodiment of the present invention.

FIG. 6 is a perspective view showing an appearance of a winding used in the transformer of FIG.

FIG. 7 is a circuit diagram according to a fourth embodiment of the present invention.

FIG. 8 is a circuit diagram according to a fifth embodiment of the present invention.

FIG. 9 is a circuit diagram according to a sixth embodiment of the present invention.

FIG. 10 is an operation explanatory diagram of Embodiment 6 of the present invention.

FIGS. 11A and 11B are diagrams showing a configuration of a core used in a sixth embodiment of the present invention, wherein FIG. 11A is a cross-sectional view and FIG.

FIG. 12 is a circuit diagram of a conventional example.

FIG. 13 is a sectional view of a conventional transformer.

FIG. 14 is an explanatory diagram showing a temporal change in output power and load impedance in a conventional example.

FIG. 15 shows a first example of a transformer at start-up and when the load is stabilized in the conventional example
FIG. 4 is a waveform diagram showing a next current waveform.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 DC booster circuit 2 inverter circuit 3 igniter section 4 discharge lamp 5 core 6 core g1 first gap section g2 second gap section

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Nakai 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. Inventor Shinji Okamoto 1048 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Works, Ltd. (reference)

Claims (14)

[Claims] 1. A DC power supply, a DC booster circuit for boosting the DC power supply to control power supplied to a load, an inverter circuit for converting a boosted DC voltage to an AC voltage, and an output of the inverter circuit. A DC boosting circuit, a boosting transformer, a switching element intermittently connecting a primary winding of the transformer to a DC power supply, and an output supplied to the load. A control circuit for controlling the switching element so as to increase the power immediately after the start-up, compared to when the load is stable; a magnetic circuit of the transformer includes a first gap portion suitable for output power when the load is stable and a start-up A power supply device comprising: a second gap portion suitable for immediately following output power. 2. The power supply device according to claim 1, wherein the first gap is set to be narrower than the second gap. 3. The magnetic circuit according to claim 1, wherein the magnetic circuit is formed by abutting both side legs of a pair of cores each having a substantially E-shaped cross section, and wherein the first gap portion and the second gap portion are formed of the magnetic circuit. A power supply device formed between end faces of opposed central legs of the pair of cores. 4. The power supply device according to claim 3, wherein the pair of central legs facing each other across the gap portion has a substantially cylindrical shape, and a winding is mounted around the central leg. 5. The second gap according to claim 4, wherein at least one of the pair of central legs opposed to each other across the first gap portion has a surface facing at least one of both end surfaces in the vicinity of one end surface of the pair of central legs. A power supply device characterized by forming a part. 6. The second gap portion according to claim 4, wherein a cross-sectional shape near at least one end face of a pair of central legs facing each other across the first gap portion is substantially semicircular. A power supply device characterized by the above-mentioned. 7. The method according to claim 1, wherein
The windings mounted around the center leg consist of a primary winding wound separately on the inner layer and the outer layer, and a secondary winding wound on the middle layer between the two primary windings. A power supply device characterized by the above-mentioned. 8. The method according to claim 1, wherein
A power supply device characterized by using a winding in which a flat wire is edgewise wound as a winding of a transformer. 9. The method according to claim 1, wherein
A power supply device having a structure in which a core portion of a transformer is substantially adhered to a heat dissipation substrate. 10. The load according to claim 1, wherein the load connected to the output of the inverter circuit is a discharge lamp, and a high-voltage pulse is applied between the output of the inverter circuit and the discharge lamp when the discharge lamp is started. A power supply device comprising: 11. The HI according to claim 10, wherein the load impedance of the load is substantially short-circuited immediately after start-up, and the load impedance becomes higher as the load shifts to stable lighting.
A power supply device comprising a D lamp. 12. The transformer according to claim 1, further comprising a center tap in a secondary winding of the transformer, one end of an output capacitor being connected to the center tap, and the other end of the output capacitor being connected to the secondary tap. A power supply device comprising a pair of switching elements that are alternately turned on and off alternately connected between both ends of a winding, and the output capacitor is used as an output of an inverter circuit. 13. The step-up transformer according to claim 1, wherein the step-up transformer and a switching element for intermittently connecting a primary winding of the transformer to a DC power supply are paired in parallel with the DC power supply. A power supply device, wherein the pair of switching elements are controlled so that current flows alternately from a DC power supply to primary windings of the pair of transformers. 14. The power supply device according to claim 13, wherein the pair of transformers share a core.