JPH11252935A - High-voltage power supply and electronic device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-voltage power supply which suppresses a leakage current and improves the efficiency of the power supply by reducing the capacity coupling with peripheral parts. SOLUTION: A high-voltage power supply is provided with a high-frequency transformer 4a, which generates high-voltage AC power with high frequency, output connector 11, which enables an external load to be connected in such a way as to be freely detachable, and a printed circuit board 10, on which wiring patterns P are formed for an electrical connection between the high-frequency transformer 4a and the output connector 11. The width of the wiring pattern P is formed in the range of 0.1 mm to 0.5 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-voltage power supply including a high-frequency transformer for generating a high-frequency high-voltage AC power, which is used, for example, for driving a cold-cathode tube at a high frequency or generating static electricity.

[0002]

2. Description of the Related Art A high-voltage power supply is used in various fields such as a lighting circuit of a cold-cathode tube widely used as a backlight source of a liquid crystal display panel and a lighting apparatus, and a static electricity generating circuit in an electrophotographic copying machine. . Inside the high-frequency high-voltage power supply, a step-up transformer that operates with an alternating current of several tens of kHz to several hundreds of kHz is provided.

In a lighting circuit of a cold cathode tube, generally, several tens of kilohertz
In many cases, AC power having a voltage of several hundred volts is output at the frequency of z. However, recently, there is a tendency to increase the operating frequency in order to increase the brightness of the cold cathode fluorescent lamp.

The static electricity generating circuit employs a circuit system in which a rectifying element for rectifying the output of the step-up transformer is provided and a DC voltage is output. In order to reduce the size of the circuit, the operating frequency also tends to increase.

In such a circuit, the electrical connection from the step-up transformer to the output terminal is made by a wiring pattern formed on a printed circuit board, and the width of the wiring pattern is usually at least 2 mm or more. This is because the electric resistance of the wiring pattern is reduced as much as possible by increasing the width of the wiring pattern, thereby improving the efficiency of the power supply circuit.

[0006]

Liquid crystal display panels are widely used in small personal computers, so-called notebook personal computers. As the thickness of a notebook computer is reduced, a metal plate is provided on the back surface of the liquid crystal panel or a part thereof is reinforced with a metal frame in order to secure strength. When such a high-voltage power supply is housed in a small device, sufficient space for the high-voltage power supply cannot be secured, and the high-voltage power supply and the metal plate or metal frame of the liquid crystal display panel are often arranged close to each other. Then, capacitive coupling occurs between the high-voltage portion of the high-voltage power supply and the metal plate or metal frame, so that the AC impedance decreases and a leak current flows.

Although the output of the high-voltage power supply is DC, such as an electrophotographic copying machine, no leakage current flows. However, since the output wiring of the step-up transformer has a high frequency, the leakage current is generated by capacitive coupling at this portion. Flows.

Although the leakage current returns to the main power supply of the device, it does not pose a safety problem, but reduces the efficiency of the power supply circuit. Such a leakage current increases as the proximity distance between the high-voltage power supply and a metal component such as a metal frame decreases, and therefore, some measure is required as the device becomes smaller.

Further, in order to improve the brightness of the cold-cathode tube and reduce the size of the power supply circuit, a power supply circuit that operates at a high frequency is required. The higher the operating frequency, the lower the AC impedance tends to be.

An object of the present invention is to provide a high-voltage power supply capable of reducing leakage current and improving power supply efficiency by reducing capacitive coupling with peripheral components. It is another object of the present invention to provide an electronic device in which the efficiency of a high-frequency transformer does not decrease even when the device is made thin.

[0011]

SUMMARY OF THE INVENTION The present invention provides a high-frequency transformer for generating high-frequency, high-frequency AC power, an output connector for detachably connecting to an external load, and an electric connector between the high-frequency transformer and the output connector. And a printed circuit board on which a wiring pattern to be electrically connected is formed, wherein the width of the wiring pattern is formed in a range of 0.1 mm to 0.5 mm.

According to the present invention, the width of the wiring pattern for electrically connecting the high-frequency transformer and the output connector is set to 0.5.
When the thickness is set to be equal to or less than mm, capacitive coupling with peripheral metal parts can be significantly reduced as compared with the related art, so that an increase in leak current due to a decrease in AC impedance can be suppressed, and power supply efficiency can be greatly improved. Further, in such a high-voltage circuit, since the current is small, the influence on the increase in the electric resistance is small.

On the other hand, when the width of the wiring pattern is less than 0.1 mm, the pattern is easily cut in the pattern forming step of etching the printed circuit board, and the production yield is deteriorated. Therefore, the width of the wiring pattern is 0.
A range of 1 mm to 0.5 mm is preferred.

The present invention also provides a high-frequency transformer for generating high-frequency high-voltage AC power, an output connector for detachably connecting to an external load, a capacitor connected in series between the high-frequency transformer and the output connector, A printed circuit board on which a wiring pattern for electrically connecting between the high-frequency transformer and the capacitor and between the capacitor and the output connector is formed, and the width of the wiring pattern is in a range of 0.1 mm to 0.5 mm. A high-frequency high-voltage power supply characterized by being formed.

According to the present invention, the width of the wiring pattern for electrically connecting between the high-frequency transformer and the capacitor and between the capacitor and the output connector is formed to be 0.5 mm or less, so that the peripheral metal can be formed as compared with the prior art. Since capacitive coupling with components can be significantly reduced, an increase in leakage current due to a decrease in AC impedance can be suppressed, and power supply efficiency can be greatly improved. Further, in such a high-voltage circuit, since the current is small, the influence on the increase in the electric resistance is small.

On the other hand, when the width of the wiring pattern is less than 0.1 mm, the pattern is easily cut in the pattern forming step of etching the printed circuit board, and the production yield is deteriorated. Therefore, the width of the wiring pattern is 0.
A range of 1 mm to 0.5 mm is preferred.

According to the present invention, a high-frequency transformer for generating high-frequency high-voltage AC power, a rectifying element for rectifying the AC power, and a wiring pattern for electrically connecting the high-frequency transformer and the rectifying element are provided. And a printed circuit board having a width of 0.1 mm to 0.5 mm.
The high-voltage power supply is formed in the range of

According to the present invention, the width of the wiring pattern for electrically connecting the high-frequency transformer and the rectifying element is 0.5 mm.
By forming it below, capacitive coupling with peripheral metal parts can be significantly reduced as compared with the related art, so that an increase in leak current due to a decrease in AC impedance can be suppressed, and power supply efficiency can be greatly improved. Further, in such a high-voltage circuit, since the current is small, the influence on the increase in the electric resistance is small.

On the other hand, if the width of the wiring pattern is less than 0.1 mm, the pattern is likely to be cut in the pattern forming step of etching the printed circuit board, and the production yield is deteriorated. Therefore, the width of the wiring pattern is 0.
A range of 1 mm to 0.5 mm is preferred.

Further, the present invention is characterized in that the high-frequency transformer is a piezoelectric transformer that boosts voltage by mutual conversion between an electric signal and mechanical vibration.

According to the present invention, by using a piezoelectric transformer utilizing a piezoelectric effect as a high-frequency transformer,
Small and highly efficient boosting becomes possible. Further, the output current of the piezoelectric transformer is not so large, and even if the width of the wiring pattern on the transformer output side is reduced, the voltage drop does not increase. Therefore, it is more preferable to reduce the pattern width in a circuit using the piezoelectric transformer.

According to the present invention, there is also provided an electronic device incorporating the above-mentioned high-voltage power supply, comprising a metal frame or a metal plate, wherein a closest distance between the wiring pattern and the metal frame or the metal plate is 0.4 mm to 10 mm. An electronic device characterized by being set in a range.

The high-voltage power supply of the present invention has a particularly remarkable effect when used near a metal frame or a metal plate provided to reduce the thickness and strength of the device. For example, when a metal plate or a metal frame is used as a reinforcing member on the back surface or a part of the liquid crystal display panel of a notebook computer, the liquid crystal display panel can be made thinner. At this time, if the distance between the high-voltage wiring pattern on the printed board and the metal frame or metal plate is smaller than 0.4 mm, there is a possibility of discharge between the two. This distance is 10
If it is larger than mm, it is difficult to reduce the thickness of the electronic device.
Therefore, this distance is preferably in the range of 0.4 mm to 10 mm. The material of the metal frame or the metal plate is not particularly limited, and examples thereof include aluminum or an alloy thereof.

[0024]

FIG. 1 is a block diagram showing an embodiment of the present invention. The high-voltage power supply includes a power circuit unit 1 that supplies a high-voltage output VH to a load Q such as a cold-cathode tube or a corona charger, and a control unit 5 that controls the operating frequency of the power circuit unit 1.

The power circuit section 1 includes an AC generator 3 for converting a DC low voltage input VL supplied through a noise filter 2 into an AC waveform of a predetermined frequency, and an AC from the AC generator 3 to a high voltage. It is composed of a booster circuit 4 for conversion. The booster circuit 4 includes a high-frequency transformer such as a coil transformer using electromagnetic induction of a coil or a piezoelectric transformer using a piezoelectric effect.

The control unit 5 includes an output detection circuit 8 for detecting a load current I flowing to the load Q, a reference voltage generation circuit 6 for generating a constant reference voltage, a reference voltage and a detection signal from the output detection circuit 8. And an error amplifier 7 that outputs an error signal by comparing the two, and an oscillator 9 whose frequency can be controlled by the voltage of the error signal.

Next, the operation will be described. When the oscillator 9 oscillates at a certain frequency, the AC generator 3 converts the low voltage input VL into an AC waveform based on the frequency, and the booster circuit 4 generates the high voltage output VH to drive the load Q. If the output voltage of the booster circuit 4 has a characteristic that increases as the frequency increases, the fluctuation of the load current I is monitored by the output detection circuit 8, and the error amplifier 7 lowers the frequency of the oscillator 9 when the load current I increases, When the load current I decreases, the operation of the oscillator 9 increases. Therefore, when the load current I increases, the voltage of the high-voltage output VH decreases, and when the load current I decreases, the voltage of the high-voltage output VH increases. As a result, a feedback circuit that stabilizes the load current I is formed. Will be.

The operating frequency of such a high-voltage power supply is 20 k
Hz to 1 MHz, preferably 20 kHz to 200
It is set in the range of kHz. The output voltage of the high-voltage power supply is set in the range of 100 V to 10 kV.

FIG. 2 is a partial plan view showing an example of a wiring pattern on the output side of the high-frequency transformer 4a. The high-frequency transformer 4a is a component of the booster circuit 4, and is fixed on a printed board 10 such as a glass epoxy board. On the other hand, an output connector 11 for detachably connecting to an external load Q is also fixed on the printed circuit board 10.

A wiring pattern P made of copper or the like and having a width W is formed on the surface of the printed board 10 by etching or the like.
Terminal 4b and the terminal 11a of the output connector 11 by soldering or the like. Thus, the high-voltage output of the high-frequency transformer 4a is supplied to the output connector 11.

In such a configuration, the length of the wiring pattern P is set to 10 mm, the width W of the wiring pattern P is changed, and the power value of the low-voltage input VL and the power value of the The results obtained by measuring the ratio to the value as the power supply efficiency are shown in Table 1 below. An aluminum metal plate is placed 4 mm above the surface of the printed circuit board on which the high-frequency transformer is mounted, parallel to the printed circuit board, and another 0.1 mm thick insulating sheet is interposed between the printed circuit board and the opposite surface. An aluminum metal plate was placed. Thus, the measurement was performed with the printed board sandwiched between the two metal plates. A 120 kΩ resistor was used as the load Q.

[0032]

[Table 1]

Looking at the measurement results, the width W of the wiring pattern P
Was formed in the range of 0.1 mm to 0.5 mm, a high power efficiency of 80% or more was obtained. On the other hand, when the width W was 2.0 mm, the power supply efficiency was lower than 80%. In addition, it was difficult to prepare a sheet having a width W of 0.05 mm, and measurement was impossible.

By narrowing the width W of the wiring pattern P in this manner, it has been found that capacitive coupling with peripheral components can be greatly reduced, so that leakage current can be suppressed and power supply efficiency can be greatly improved.

FIG. 3 is a partial plan view showing another example of the wiring pattern on the output side of the high-frequency transformer 4a. The high-frequency transformer 4a is fixed on the printed circuit board 10, the output connector 11 is also fixed on the printed circuit board 10, and the capacitor 12 connected in series between the high-frequency transformer 4a and the output connector 11 is also mounted on the printed circuit board 10. Fixed.

A wiring pattern P having a width W is formed on the surface of the printed board 10 by etching or the like. The terminal 4b of the high-frequency transformer 4a, the terminal 11a of the output connector 11, and the terminal 12a of the capacitor 12 are formed by the wiring pattern P. Electrically connected. In such a configuration, the same measurement results as in Table 1 were obtained.

FIG. 4 is a partial plan view showing still another example of the wiring pattern on the output side of the high-frequency transformer 4a. The high-frequency transformer 4a is fixed on the printed circuit board 10,
The output connector 11 is also fixed on the printed circuit board 10. Further, a rectifying element 13 for rectifying the AC power from the high-frequency transformer 4a is interposed between the high-frequency transformer 4a and the output connector 11, and is similarly fixed on the printed circuit board 10.

On the surface of the printed circuit board 10, a wiring pattern P having a width W is formed by etching or the like, and the terminal 4b of the high-frequency transformer 4a, the terminal 11a of the output connector 11, and the terminal 13a of the rectifier 13 are connected to the wiring pattern P. Electrically connected by In such a configuration, the same measurement results as in Table 1 were obtained.

[0039]

As described above in detail, according to the present invention, the width of the wiring pattern provided on the output side of the high-frequency transformer is formed in the range of 0.1 mm to 0.5 mm, thereby making it possible to reduce Since the capacitive coupling with metal parts can be greatly reduced, an increase in leakage current can be suppressed, and power supply efficiency can be greatly improved.

Further, by using a piezoelectric transformer utilizing a piezoelectric effect as the high-frequency transformer, a compact and highly efficient boosting is possible.

In an electronic device using a metal frame or a metal plate, the closest distance between the high-voltage wiring pattern on the printed board and the metal frame or the metal plate is set to 0.
By setting the thickness in the range of 4 mm to 10 mm, the thickness of the device can be reduced while reliably preventing discharge.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a partial plan view showing an example of a wiring pattern on the output side of a high-frequency transformer 4a.

FIG. 3 is a partial plan view showing another example of the wiring pattern on the output side of the high-frequency transformer 4a.

FIG. 4 is a partial plan view showing still another example of a wiring pattern on the output side of a high-frequency transformer 4a.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power circuit part 4 Booster circuit 4a High frequency transformer 4b, 11a, 12a, 13a Terminal 5 Control part 10 Printed circuit board 11 Output connector 12 Capacitor 13 Rectifier

Claims (5)

[Claims] A high-frequency transformer for generating high-frequency high-frequency AC power, an output connector for detachably connecting to an external load, and a wiring pattern for electrically connecting the high-frequency transformer and the output connector are formed. A high-voltage power supply, comprising: a printed circuit board, wherein a width of the wiring pattern is formed in a range of 0.1 mm to 0.5 mm. 2. A high-frequency transformer for generating high-frequency high-frequency AC power, an output connector for detachably connecting to an external load, a capacitor connected in series between the high-frequency transformer and the output connector, and a high-frequency transformer. A printed circuit board on which a wiring pattern for electrically connecting between the capacitor and between the capacitor and the output connector is formed, wherein the width of the wiring pattern is formed in a range of 0.1 mm to 0.5 mm. A high-voltage power supply characterized in that: 3. A high-frequency transformer for generating high-frequency high-voltage AC power, a rectifying element for rectifying the AC power, and a wiring pattern for electrically connecting the high-frequency transformer and the rectifying element are formed. A high-voltage power supply comprising a printed circuit board, wherein the width of the wiring pattern is formed in a range of 0.1 mm to 0.5 mm. 4. The high-voltage power supply according to claim 1, wherein the high-frequency transformer is a piezoelectric transformer that boosts a voltage by mutual conversion between an electric signal and mechanical vibration. 5. An electronic device incorporating the high-voltage power supply according to claim 1, further comprising a metal frame or a metal plate, wherein a closest distance between the wiring pattern and the metal frame or the metal plate is reduced. 0.4mm
An electronic device characterized by being set in a range of 10 to 10 mm.