JP2005160259A - High-voltage power circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-voltage power circuit with a simple structure capable of reducing total power consumption and increasing the service life of an ozone-absorbing filter by reducing power consumption and ozone generation when an internal temperature of an electronic apparatus at a low temperature. <P>SOLUTION: This high-voltage power circuit 1 is equipped with a high-voltage transformer 4 for increasing input voltage. A high-pressure power output increased by the high-voltage transformer 4 is supplied as a drive power supply for an ion air generator. Between the low-voltage side of a secondary coil 3 of the high-voltage transformer 4 and the ground, there is provided a resistor element 23 for current detection to detect the voltage across the resistor element 23 for current detection and control an output current so as to be constant. The resistor element 23 for current detection is a resistor element having a negative temperature characteristic such as a thermistor, and the high-voltage power circuit 1 performs current control so as to increase an output current when the ambient temperature of the resistor element 23 for current detection is high, and so as to decrease the output current when it is low. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a high-voltage power supply circuit, and more particularly to a high-voltage power supply circuit that can be suitably implemented in a high-voltage power supply circuit that supplies a high-voltage power supply to ion wind generating means for generating ion wind for internal cooling of electronic equipment.

  Conventionally, as a cooling means for protecting internal parts of an electronic device, a cooling means using a fan has been common. However, in the means for cooling using a fan, there is a problem that noise during operation of the fan is large and may be annoying. Therefore, in order to solve such a problem, cooling with ion wind using high pressure has been devised instead of cooling with a fan (see, for example, Patent Document 1).

  The principle of cooling with this ion wind will be specifically described. As shown in FIG. 3, when a high voltage is applied between the needle-like high-voltage electrode 30 and the mesh-like earth electrode 31, corona discharge occurs. At that time, air around the needle-like high-voltage electrode 30 is ionized, and an ion wind 32 is generated in the direction of the mesh-like ground electrode 31 due to an electric field generated between the electrodes. The amount of ion wind is almost proportional to the current due to corona discharge. Since no fan is used, there is almost no sound. Moreover, since ozone is generated together with the ions, the ozone adsorption filter 33 adsorbs ozone. Ion wind cooling is a cooling means using these ions with less noise.

Japanese Patent Laid-Open No. 10-241556

  However, in the above cooling means using ions, the output of the high voltage power supply circuit 34 for ion wind cooling is set when the ambient temperature of the electronic device is the highest, and even when the temperature inside the electronic device is low and the cooling is unnecessary, the output is high. Output is constant, consumes a lot of electric power, generates a lot of ozone, and accelerates the deterioration of the ozone adsorption filter 33.

  The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a high-voltage power supply circuit that can control the output current constant with a simple configuration, and more specifically. Provides a high-voltage power supply circuit with a simple configuration that reduces power consumption and ozone generation when the internal temperature of the electronic equipment is low, thereby reducing the total power consumption and extending the life of the ozone adsorption filter. is there.

  In order to achieve the above object, the invention according to claim 1 of the present invention includes a high voltage transformer that boosts the input voltage, and supplies a high voltage power output boosted by the high voltage transformer as drive power for the drive means. In the high voltage power supply circuit, a current detecting resistor is provided between the low voltage side of the secondary coil of the high voltage transformer and the ground, and the voltage across the current detecting resistor is detected to control the output current to be constant. It is characterized by that.

  With the above configuration, a high voltage power supply circuit capable of controlling the output current to be constant can be realized. In addition, there is a configuration in which voltage control by resistance division is performed in a relatively low-voltage power supply circuit, but applying such a voltage control power supply circuit to a high-voltage power supply circuit requires a plurality of resistance elements. This is not preferable from the viewpoint of reliability and the like. Since the high-voltage power supply circuit according to the present invention has a current control configuration, such a problem is solved.

  A second aspect of the present invention is the high-voltage power supply circuit according to the first aspect, wherein a switching element provided between the low-voltage side of the primary coil of the high-voltage transformer and the ground, and a current detection resistor An output control circuit that detects a voltage across the element and outputs a pulsed control signal that controls opening and closing of the switching element, and the output control circuit generates a pulse in accordance with a change in the voltage across the current detection resistor element. The output current is controlled to be constant by changing the pulse width of the state control signal so as to control the voltage across the current detecting resistor to be constant.

  As described above, as a specific configuration for controlling the output current constantly, it is only necessary to include a switching element and an output control circuit. Therefore, a high-voltage power supply circuit that controls the output current constantly can be realized with a simple circuit configuration.

  The invention according to claim 3 is the high-voltage power supply circuit according to claim 1 or 2, wherein the resistance element for current detection is a resistance element having negative temperature characteristics, and the ambient temperature of the resistance element is high. The current control is sometimes performed such that the output current is sometimes increased and the output current is decreased at a low temperature.

  With the above configuration, power consumption at low temperatures can be reduced.

  The invention as set forth in claim 4 is the high-voltage power supply circuit according to any one of claims 1 to 3, wherein the driving means is a cooling means.

  The cooling means is not limited to the ion wind generating means, but includes other cooling means.

  The invention according to claim 5 is the high-voltage power supply circuit according to claim 4, wherein the cooling means is an ion wind generating means for generating an ion wind for cooling the inside of the electronic equipment.

  With the above configuration, when the temperature inside the electronic equipment is high, there is a large amount of high-voltage current and the effect of cooling by ion wind is large. At low temperatures where cooling is not required, the high-voltage current is suppressed, reducing power consumption and generating less ozone. The life of the ozone adsorption filter can be extended.

  According to the present invention, it is possible to realize a high voltage power supply circuit capable of controlling the output current to be constant with a simple configuration. In particular, when the current detecting resistor element is a resistor element having negative temperature characteristics and the cooling means is an ion wind generating means, when the temperature in the electronic device is high, there is a large amount of high-voltage current, and the cooling effect by the ion wind However, at low temperatures where cooling is not necessary, high voltage current can be suppressed, power consumption can be reduced, ozone generation can be reduced, and the lifetime of the ozone adsorption filter can be extended.

  In the following embodiments, an example will be described in which the high-voltage power supply circuit according to the present invention is applied to a high-voltage power supply circuit for supplying drive power to ion cooling air generating means for internal cooling of an electronic device such as a liquid crystal projector.

(Embodiment)
[Configuration of high-voltage power supply circuit]
FIG. 1 is a circuit diagram of a high-voltage power supply circuit according to the present invention. The high voltage power supply circuit 1 is used to supply driving power for the ion wind generating means. Here, the ion wind generating means includes the needle-like high-voltage electrode 30 and the mesh-like ground electrode 31 shown in FIG.

  The high voltage power supply circuit 1 includes a high voltage transformer 4 composed of a primary coil 2 and a secondary coil 3. On the primary side of the high-voltage transformer 4, a field effect transistor 6 is provided between the low-voltage side of the primary coil 2 and the ground. Between the source and drain of the transistor 6, a parallel circuit composed of a backflow prevention diode 7 and a capacitor 8 is connected in parallel. Further, a pulsed control signal M from the output control circuit 9 is given to the gate of the transistor 6. The frequency of the control signal M is constant, and the output current is controlled as described later by changing the ON period and OFF period of the transistor 6 by changing the pulse width. That is, output current control is performed by duty control of the control signal M.

  Further, a reverse current prevention diode 11 is provided between the high voltage side of the primary coil 2 and the input terminal 10 to which the DC input voltage Vin is applied. The diode 11 and the high voltage side of the primary coil 2 are provided. One end of the capacitor 12 is connected to the connection line connecting the two, and the other end of the capacitor 12 is grounded.

  On the secondary side of the high-voltage transformer 4, a rectification / smoothing circuit 15 is provided on the high-voltage side of the secondary coil 3. The rectifying / smoothing circuit 15 is a triple voltage rectifying / smoothing circuit including diodes 16, 17, 18 and capacitors 19, 20, 21. A smoothing capacitor 22 is provided between the low voltage side of the secondary coil 3 and the ground. One end of a current detection resistance element 23 for detecting an output current is connected to a connection point A between the smoothing capacitor 22 and the low voltage side of the secondary coil 3, and the other end of the current detection resistance element 23 is grounded. Yes. Then, the fluctuation of the output current flowing through the current detecting resistance element 23 is converted into the voltage level at the connection point A and is detected by the output control circuit 9. The output control circuit 9 changes the pulse width of the control signal M, changes the magnetic energy accumulated in the primary coil 2, and changes the back electromotive force so that the voltage level at the connection point A becomes constant. Thus, the output current from the secondary side is controlled to be constant. That is, constant current control is performed.

  Here, it should be noted that in the present embodiment, the resistance element for current detection 23 is realized by a thermistor or the like. The resistance value decreases as the temperature increases, and conversely, the resistance value increases as the temperature decreases. In other words, a resistive element having a so-called negative temperature characteristic is used. This increases the output current at high temperatures and decreases the output current at low temperatures. Therefore, by installing the entire high-voltage power supply circuit 1 or only the current detection resistor element 23 near the part where temperature management is required in the electronic device, the high-voltage output current increases when the part is at a high temperature, and the ion wind is generated. Many cooling effects can be increased. On the contrary, when the temperature is low, the high-voltage output current becomes small, and the cooling effect can be reduced with less ion wind.

[Operation of high-voltage power supply circuit]
FIG. 2 is a waveform diagram for explaining the operation of the high-voltage power supply circuit. 2 (1) shows the ON / OFF state of the transistor 6, FIG. 2 (2) is a current waveform diagram at point C of the high-voltage power supply circuit of FIG. 1, and FIG. 2 (3) is the high-voltage power supply circuit of FIG. FIG. 2 (4) is a voltage waveform diagram at point D of the high-voltage power supply circuit in FIG. 1, FIG. 2 (5) is a voltage waveform diagram at point E in the high-voltage power supply circuit in FIG. FIG. 2 (6) is a voltage waveform diagram at point A of the high voltage power supply circuit of FIG. In the voltage waveform diagram at point B in FIG. 2 (3), since the level of the input voltage Vin is low, the ON period of the transistor 6 is drawn as 0 V from the viewpoint of drawing preparation.
Hereinafter, the operation of the high-voltage power supply circuit having the above configuration will be described with reference to FIG.

(Operation during steady operation)
The output control circuit 9 outputs a control signal M to the gate of the transistor 6. Thereby, during the high level period of the control signal M, the transistor 6 is turned on as shown in FIG. 2A, and the input current flows to the ground through the diode 11, the primary coil 2, and the transistor 6. As a result, a current flows in the primary coil 2 in a changing state as shown in FIG. 2B, and magnetic energy is accumulated. When the transistor 6 is turned off, a back electromotive force based on the stored magnetic energy is generated in the primary coil 2, and is generated in the primary coil 2 by a resonance circuit composed of the primary coil 2 and the capacitor 8. Generates a large pulse voltage VB (see FIG. 2 (3)). As a result, the secondary coil 3 generates a pulsed voltage VD (see FIG. 2 (4)) boosted in accordance with the turn ratio of the primary coil 2 and the secondary coil 3. Then, it is rectified and smoothed by the rectifying / smoothing circuit 15 to become a high-voltage DC voltage of voltage VE (see FIG. 2 (5)), and is supplied to the ion wind generating means as a high-voltage output current.

  On the other hand, an output current also flows through the current detecting resistance element 23 on the low voltage side of the secondary coil, and the change in the amount of current is converted to a voltage at point A and applied to the output control circuit 9. Thereby, the output control circuit 9 changes the pulse width of the control signal M so that the voltage at the point A (see FIG. 2 (6)) becomes constant. Thus, the output current is controlled to be constant.

(Operation when the ambient temperature is high)
When the ambient temperature rises, the resistance value of the current detection resistor element 23 decreases, and the voltage level at the point A decreases transiently. For example, the voltage level decreases transiently as indicated by a point P1 shown in FIG. Then, this is detected by the output control circuit 9, and the output control circuit 9 increases the pulse width of the control signal M so that the voltage level at the point A becomes constant. As a result, the magnetic energy accumulated in the primary coil 2 increases, and the back electromotive force generated when the transistor 6 is turned off increases. As a result, the amount of high voltage output current increases. As a result, the output of the ion wind generating means is increased, the amount of ion wind generated is increased, and the internal components of the electronic device can be efficiently cooled.

(Operation when the ambient temperature is low)
When the ambient temperature decreases, the resistance value of the current detection resistor element 23 increases, and the voltage level at the point A increases transiently. For example, the voltage level rises transiently as indicated by a point P2 shown in FIG. Then, this is detected by the output control circuit 9, and the output control circuit 9 reduces the pulse width of the control signal M so that the voltage level at the point A becomes constant. As a result, the magnetic energy accumulated in the primary coil 2 is reduced, and the back electromotive force generated when the transistor 6 is OFF is reduced. As a result, the amount of high-voltage output current is reduced. As a result, the output of the ion wind generating means is reduced, and the amount of ion wind generated is reduced. As a result, high temperature current can be suppressed at low temperatures when cooling is not required, power consumption can be reduced, ozone generation can be reduced, and the lifetime of the ozone adsorption filter can be extended.

(Other matters)
In the above embodiment, the high voltage power supply circuit for supplying the driving power for the ion wind generating means has been described. However, the present invention is not limited to this, and the driving means as other cooling means, other than the cooling means. The present invention can be widely applied to a high-voltage power supply circuit for driving power supply of the driving means.

  The present invention can be applied to a high-voltage power supply circuit for supplying power to an ion wind generating means for cooling internal components of electronic equipment such as a liquid crystal projector.

1 is a circuit diagram of a high voltage power supply circuit according to a first embodiment of the present invention. It is a wave form diagram for demonstrating operation | movement of a high voltage power supply circuit. It is a figure for demonstrating the principle of cooling with an ion wind.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 34: High voltage power supply circuit 2: Primary coil 3: Secondary coil 4: High voltage transformer 6: Transistor 9: Output control circuit 15: Rectification / smoothing circuit 23: Resistance element for current detection (thermistor)
30: Needle-like high-voltage electrode 31: Mesh-like ground electrode 33: Ozone adsorption filter

Claims (5)

In a high-voltage power supply circuit that includes a high-voltage transformer that boosts an input voltage and supplies a high-voltage power output boosted by the high-voltage transformer as a drive power supply for the drive means.
A resistance element for current detection is provided between the low-voltage side of the secondary coil of the high-voltage transformer and the ground, and a voltage across the current detection resistance element is detected to control the output current to be constant. High voltage power circuit. A switching element provided between the low voltage side of the primary coil of the high voltage transformer and the ground;
An output control circuit that outputs a pulsed control signal that detects the voltage across the current detection resistor element and controls the switching of the switching element;
With
By controlling the output control circuit so that the voltage across the current detection resistor element is constant by changing the pulse width of the pulse-shaped control signal according to the variation in the voltage across the current detection resistor element. The high-voltage power supply circuit according to claim 1, wherein the output current is configured to be controlled at a constant level.   The current detection resistor element is a resistor element having a negative temperature characteristic, and current control is performed so that an output current is increased when an ambient temperature of the resistor element is high, and an output current is decreased when the temperature is low. The high-voltage power supply circuit according to 1 or 2.   The high-voltage power supply circuit according to claim 1, wherein the driving unit is a cooling unit. The high-voltage power supply circuit according to claim 4, wherein the cooling unit is an ion wind generating unit that generates an ion wind for cooling the inside of an electronic device.

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