JPH10174448A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect whether a load is normal or abnormal, even if the output voltage to the load is DC or DC-superposed by making a difference in induced voltages between both U cores a specified value or below, when the load is normal and making it a larger value than that when the load is normal, when the load is abnormal. SOLUTION: When the output voltage to a load is DC-superposed, leakage magnetic flux is different at the A side (negative side) and B side (positive side) of a secondary winding. Therefore, low resistors R1, R2 are set to such values that the voltages V1 , V2 at points A, B are nearly the same at normal operation. With the appropriate setting of the values of the low resistors R1, R2, current is not made to flow into a detection resistor R5, because V1 becomes equal to V2 and R3 becomes equal to R4 in the case that each neon tube is correctly connected, and therefore the neon tube emits light. When one of the neon tubes is broken or the like, however, the voltages induced in both the U cores are greatly different, and a specified voltage Vdet appears in a second high resistor R5. By this method, it can be told clearly distinguished whether a load is normal or abnormal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply.

[0002]

FIG. 6 shows a conventional high frequency power supply for lighting a neon tube. As shown in the figure,
A commercial power supply (in the example shown, AC 220 V) is connected to a full-wave rectifier circuit 1
To the rectifier, where it is rectified,
Is smoothed by the smoothing capacitor 2 connected to the output side of the circuit. An inverter circuit 3 is connected between both terminals of the smoothing capacitor 2, where the frequency is converted to a predetermined high frequency. Further, the inverter circuit 3 is connected to the primary side of the step-up transformer 4 so that the transformer 4 steps up the high-frequency signal. Then, the secondary side of the transformer 4 is connected to the neon tube 6. And
Usually, a plurality of neon tubes 6 are connected in series.

[0003] The inverter circuit 3 includes a switching element 3a for supplying or interrupting a current to the primary side of the transformer 4, and a control circuit 3b for controlling ON / OFF of the switching element 3a.

FIG. 7 shows an equivalent circuit of the secondary part. Each neon tube 6 is represented by a capacitor C and a resistor R connected in parallel, and they are connected in series. Then, a stray capacitance C1 is generated between each neon tube 6 and the ground. If the neon tube 6 serving as a load breaks or gas escapes, the resistance R increases, so that light cannot be emitted and the device is opened. The output voltage rises due to the resonance in addition to the lift due to the open state, and there is a possibility that the signboard to which the neon tube 6 is attached may discharge or the lead wire may burn.

Therefore, when the output voltage is high, it is difficult to directly detect the current on the secondary side. Therefore, a protection circuit 7 is conventionally provided as shown in FIG. Is monitored, and when the input current exceeds a certain value, the control circuit 3b is forcibly stopped and the switching element 3a is turned off (the switch is opened) as an abnormality is determined.

More specifically, a detection circuit 7a for detecting a current is provided on the primary side of the transformer 4 to detect an input current (AC). The output of the detection circuit 7a is sent to the detection and rectification circuit 7b, where it is rectified and smoothed to determine the level of the input current. Further, the detection value after the smoothing is stored in the cutoff holding circuit 7.
When the detected value exceeds a certain reference value, a predetermined signal is sent to the control circuit 3b to stop the operation. Further, the cutoff holding circuit 7c has a function of holding the stopped state once the operation is stopped.

[0007] However, in the conventional device, since the cutoff is performed only when the input current becomes large, only a part of the abnormal state on the secondary side can be detected. That is, for example, even if one end of the neon tube 6 is grounded to the ground, the load current flowing to the secondary side is reduced or does not change much. Therefore, since the input current does not change, the above-described conventional apparatus cannot detect such an abnormality.
However, if one end is grounded, there is a danger that sparks may be discharged at that portion and sparks may be emitted. In particular, if it occurs at the end of the neon tubes 6 connected in series, the above problem becomes significant because the current value is large.

When one side of the neon tube 6 is off, a high open-circuit voltage is generated at the connection terminal of the neon tube 6. Therefore, there is a risk of electric shock if the connection terminal is touched by mistake. However, since the secondary side is in an open state, the input current does not increase, and the conventional state cannot detect such an abnormal state.

[0009] Further, because of the high frequency, the length of the lead wire connecting the transformer 4 and the neon tube 6 is regulated, for example, to within 2 m. However, in actual construction, there is a possibility that the length is longer than the regulated length. . However, even if such a phenomenon occurs, the effect on the input current is small,
Since there is no significant change, it cannot be detected as abnormal. Therefore, in the conventional device, it is only possible to detect an abnormality such that the voltage increases due to resonance on the secondary side.

Further, since the current flowing to the primary side is as large as about several A, the detection resistor and the current detection transformer used in the detection circuit 7a need to be large, and the device becomes large. Further, heat loss due to heat generated by the flow of a large current cannot be ignored.

Therefore, the present inventor has provided a high frequency power supply device comprising an inverter circuit and a step-up type transformer for generating an AC voltage having a predetermined frequency on a secondary side of the transformer.
The transformer includes a primary winding and a secondary winding attached to the core in a mutually insulated state, detects an induced voltage generated in the core, and outputs when the induced voltage is equal to or more than a certain value. A power supply unit was designed to stop the operation.

That is, in the case of a neon tube or the like in which a plurality of loads are connected in series, since the loads are balanced in a normal state, the ground voltages at both ends of the core are equal. Therefore, no induced voltage is generated in the core from the secondary winding side, or the value becomes very small, if at all. On the other hand, when an abnormality such as a pipe crack or a ground fault occurs, the load balance is lost, and a difference occurs between the ground voltages at both ends of the core. As a result, an induced voltage is generated in the core. Therefore, the presence or absence of an abnormality on the secondary side can be determined by monitoring the induced voltage of the core.

Therefore, for example, if the core is connected to the ground via a detecting member such as a detecting resistor, a current flows from the core to the ground through the detecting resistor when an induced voltage is generated. Accordingly, a predetermined voltage is generated at both ends of the detection resistor, and its magnitude is proportional to the induced voltage. Therefore, the voltage is monitored, and when the voltage exceeds a certain value, it is determined that there is an abnormality, and the output is stopped. With this configuration, the current value on the primary side does not increase so much, and a voltage is induced in the core even in the case of a ground fault or pipe breakage, so that an abnormal state can be reliably detected.

By the way, in the case of the above-mentioned power supply,
Since the secondary (output) side is a high-frequency AC / positive / negative target output, it is possible to accurately detect an abnormality on the secondary side by monitoring the induced voltage of the core according to the above-described principle. However, in the case of high-frequency output, the adjacent neon tube is lit by electrostatic induction, and if the wiring is lengthened, the leakage current increases and the lighting performance decreases, and furthermore, the central part is caused by the leakage current. Has a problem that it becomes dark with respect to the edge.

Therefore, when the output voltage on the secondary side is DC or D
The present inventors have considered applying a configuration for monitoring the presence or absence of an abnormality on the secondary side by monitoring the above-described induced voltage of the core with respect to a power supply device that is superimposed on C. However, the following problem newly arises and cannot be applied as it is.

That is, since the winding of the transformer is usually wound uniformly, if such a winding is used, the balance between both ends of the core is lost even in a normal state, and an induced voltage is generated. Then, comparison and discrimination with the abnormal state cannot be sufficiently performed, and the abnormal state cannot be detected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and has as its object to solve the above-mentioned problems and to solve the problem when the load is normal even if the output method is DC or DC superposition. An object of the present invention is to provide a power supply device capable of reducing an induced voltage induced in a core to a predetermined value or less and accurately discriminating between normal and abnormal loads based on the magnitude of the induced voltage in the core. .

[0018]

In order to achieve the above object, a power supply device according to the present invention includes an inverter circuit and a transformer, and further comprises a DC or DC superimposed output voltage. Is
A primary winding and a secondary winding attached to each other in an insulated state with respect to a core, wherein the core is divided into two parts;
By arranging the end faces of the cores to face each other with an insulating sheet interposed therebetween, a closed magnetic path is formed by both U cores while maintaining an electrically insulating state. And by providing the voltage dividing circuit in the both cores, the difference between the induced voltages generated in the two U cores based on the leakage magnetic flux of the secondary winding when the load is normal becomes equal to or less than a certain value. The difference between the induced voltages generated in the core when the load is abnormal is larger than that in the normal state (claim 1).

In order to actually discriminate between normal and abnormal, for example, an adding / subtracting circuit may be connected to the voltage dividing circuit, and the difference between the induced voltages may be obtained by the adding / subtracting circuit. 2). More specifically, the voltage dividing circuit is a low resistance (R1, R2) disposed between the cores and ground, respectively, and the adding / subtracting circuit is connected to the low resistance in parallel. , The first high resistance (R
3, R4) and a second high resistance (R5) connected in series to both first high resistances and falling to the ground (claim 3).

That is, when the output voltage is DC or DC superimposed, the directions of the voltages generated in the secondary windings are equal.
If the winding state of the secondary winding is made uniform, an induced voltage is generated in the core as it is even when the load is normal. Therefore, by interposing an insulating sheet on the joint surface of the two U cores constituting the core, both U cores are electrically insulated,
An induced electromotive force is generated independently for each U core. Then, by appropriately setting the parameters (the resistance values of the low resistances R1 and R2 in the embodiment) of the voltage dividing circuit connected to the U core, the induced voltage generated in the normal state (in the third embodiment and the embodiment). The difference in the low-resistance voltage between both terminals is minimized.

If there is an abnormality in the load, the load balance greatly differs from the normal state, and the induced voltage generated in both U cores also changes, so that there is a difference between the two. Therefore, normal / abnormal can be discriminated by monitoring the degree of the difference. If the parameters are set according to the assumed load, more accurate normal / abnormal discrimination can be performed. In particular, when the load is a neon tube as in the embodiment, the state of the load can be specified to some extent, and the present invention effectively contributes.

Note that the loads targeted by the present invention include:
A plurality of neon tubes connected in series are used. Therefore, when an abnormality such as a pipe crack or a ground fault occurs, the load balance is broken as compared with that in a normal state, and a large difference is generated due to the ground voltage at both ends of the core. As a result, the induced voltage generated in the U core greatly differs, and an abnormality can be detected based on the above-described principle.

[0023]

FIG. 1 shows an example of a power supply device on which a power supply device according to the present invention is mounted. As shown in FIG. 1, the power supply device 10 has an input side connected to a commercial power supply (not shown), converts power supplied from the commercial power supply into a desired output method, and loads the load ( A neon tube 11) in which a plurality of tubes are connected in series is driven.

Specifically, first, the inverter circuit 12
And a step-up type transformer 13. The commercial power supply is converted to a predetermined high frequency by the inverter circuit 12 provided on the input side. The inverter circuit 12 is connected to the primary side of the step-up type transformer 13, and boosts the high-frequency signal to about 15000 V by the transformer 13. The transformer 13 attaches the primary winding 13b and the secondary winding 13c to the leg of the core 13a having a predetermined shape. Furthermore, in order to suppress the fluctuation of the output due to the fluctuation of the load, a leakage type structure is adopted.

Further, in this embodiment, a capacitor 16 is inserted in series between the secondary winding 13c of the transformer 13 and the output terminal 15, and a diode 17 is inserted so as to connect between the output terminals 15. The neon tube 11 can be connected to both output terminals 15. Thus, when the neon tube 11 is connected to the output terminal 15, a closed loop is formed in which the secondary winding 13c, the capacitor 16, and the neon tube 11 are connected in series.

Further, a diode 17 is connected between the output terminals 15.
Since the negative side is short-circuited, the output voltage is half-wave rectified without a waveform appearing on the negative side. Therefore, a high frequency DC superimposed waveform in which the high frequency is shifted to one side is obtained. However, the output current becomes an alternating current due to resonance between the neon tube 11 and the secondary winding 13c.

As described above, since the output voltage is superimposed on DC, the electrostatic induction and the leakage current are reduced, so that the adverse effects due to the AC voltage as described in the section "Background of the Invention" are eliminated. In addition, since the output current is alternating current, it is possible to provide an excellent power supply device that can emit light from a low voltage, stably discharge with a small current, and exhibit the advantages of a high-frequency system such as high conversion efficiency.

Further, in this embodiment, a voltage detection circuit 20 for detecting an electrostatic induction voltage from the secondary winding 13c to the core 13a is provided in order to detect a load balance on the secondary side. Specifically, the core 13a is grounded via a detection resistor, and the voltage between both terminals of the detection resistor is detected. The ground may be the ground in the circuit or the ground may be used.

Then, the output of the detection circuit 20 is connected to the detection rectification circuit 21. The detection and rectification circuit 21 detects an AC voltage generated by the detection circuit 20, rectifies and smoothes the converted AC voltage, converts the DC voltage into a DC voltage, and converts the DC voltage into a cutoff holding circuit 2.
2 is given. Then, the cutoff holding circuit 22
Thus, when the level of the DC voltage is equal to or higher than the reference value, an operation stop command is sent to the inverter 12.

On the other hand, as an example of a specific configuration of the transformer 13, the one shown in FIGS. 2 and 3 can be used. As shown in FIG.
Using two U-cores 26, 26, a fixture 27 is mounted in a groove 26 a formed on the side surface of the U-core 26. Then, the two U-cores 26 are formed by the spring force of the fixture 27.
Is fixed.

Further, a primary winding 13b and a secondary winding 13c are mounted on the leg 26b of the U core 26, respectively. The primary winding 13b has a winding 29 around the square bobbin 28.
The square bobbin 28 includes:
Four lead pins 30 are attached. The two ends of the winding 29 are electrically connected to the two lead pins 30, and are connected to a circuit board (not shown) via the lead pins 30.

Since the transformer is mounted on the circuit board by inserting the lead pins 30 into the predetermined holes formed in the circuit board in this manner, the four lead pins 30 are connected.
Provided so that the transformer 13 can be fixed in a stable state. Therefore, when both ends of the winding 29 are connected to the lead pins, the remaining two lead pins are normally electrically unconnected and used for fixing.

On the other hand, the secondary winding 13c is
Is formed by applying a winding 32 to the periphery of the wire. In addition, the winding structures of the primary winding 13b and the secondary winding 13c are both uniform. That is, the uniform winding structure means that the number of turns is equal in each part in the axial direction, and the windings 29, 3
2 is a state in which the distance between the inner peripheral surface of the core 2 and the outer peripheral surface of the leg portion 26b of the core 26 is constant in the axial direction, which is a conventional winding structure generally used.

In the present invention, the U cores 26 are electrically insulated from each other by interposing the film sheet 33 between the front end joining surfaces 26c of the U cores 26. In addition, the tip 27a of the fixture 27 is coated with a resin, and a portion of the U-core 26 that is in contact with the groove 26a is insulated so that electrical conduction between the two cores 26 via the fixture 27 is suppressed. In addition, the tip 27 of the fixture 27
a may be fitted with an insulating tube instead of being coated with a resin.
It may itself be made of an insulating material, and various configurations can be adopted.

Further, both U-cores 26 and the two lead pins 30 to which the winding 29 is not connected are electrically connected. Specifically, both are connected using a conductive tape 34 or other various materials. Then, both U cores 26
It becomes conductive with a predetermined lead pin 30 via the conductive tape 34. Therefore, by connecting the lead pin 30 to the detection circuit 20 mounted on the circuit board, the voltage generated in the core 13a can be easily taken out.

In this way, it is possible to extract the voltage generated in the core through the lead pin which has conventionally been used only for fixing. A new member required for that purpose is the conductive tape 34, and the configuration can be simplified. Then, the connection with the detection circuit 20 can be easily performed only by mounting on the circuit board.

On the other hand, in the detection circuit 20, as shown in FIGS. 4 and 5, both U cores 26 are grounded via low resistances R1 and R2 constituting a voltage dividing circuit. Further, a first high resistance R3, R4 is connected in parallel with the low resistances R1, R2, and a first high resistance R3, R4
Is connected to one end of a second high resistance R5, and the second high resistance R5
The other end of 5 is grounded. These high resistance R3 ~
R5 forms an addition / subtraction circuit. And R1
The resistance value of R5 is such that R1, R2 << R3, R4, R5 R3 = R4.

With this configuration, an equivalent circuit as shown in FIG. 5 is obtained. That is, a predetermined induced voltage is generated in the U core 26 by the leakage magnetic flux from the secondary winding 13c. Then, as described in the “Background of the Invention” section above, if the output voltage to the load is DC superimposed,
When the winding structure of the secondary winding 13c is uniform, the leakage flux on the A side (the negative side of the output voltage) and the B side (the positive side of the output voltage) of the secondary winding 13c are different. That is, the leakage flux from the coil is larger on the B side (positive side) than on the A side (negative side),
A voltage tends to be induced on the B side even in a normal state (see FIG. 1). On the other hand, in the present example, both the U cores 28 are electrically insulated by the film sheet 33 and the impedance of the cores is sufficiently high, so that each can be regarded as a current source. Therefore, in the present invention, the low resistances R1 and R2 are appropriately set so that the voltages V1 and V2 at both points A and B are almost equal in a normal state. Note that the low resistance R1 (R2) and the second high resistance R3 (R4) are connected in parallel to the U core 26, but since the resistance values of both are greatly different, the resistance value on the low resistance side is large. By adjusting the low resistances R1 and R2, the voltages V1 and V2 generated during normal operation can be made substantially equal.

Then, when the neon tubes 11 are normally connected, the voltage Vdet generated across the second high resistance R5, which is the detection resistance, is obtained from V1 = V2 and R3 = R4.
Becomes 0. Therefore, no current flows through the detection resistor R5 connected to the core 13a. Therefore, the cutoff holding circuit 22 does not operate, and the inverter 12 performs a normal switching operation, so that a current of a predetermined high frequency flows through the primary winding 13 b of the transformer 13. Then, a high voltage is generated in the secondary winding 13c, causing the neon tube 11 to emit light.

On the other hand, Vdet can be expressed by the following equation.

[0041]

(Equation 1) Therefore, for example, one of the serially connected neon tubes 11
The book is broken, the neon tube 11 comes off, the secondary terminal 15 of the transformer 13 is opened, one end of the neon tube 11 is grounded, or the secondary winding 13c of the transformer 13 is connected to the neon tube 11. If the length of the lead wire to be used is longer than the specified length, the resistance value and the capacitance in the equivalent circuit on the load side shown in FIG. 6 locally change, and the balance is lost as a whole.

Then, since a large voltage is induced in the core 13a, the voltage balance between the two U cores 26 is greatly different (V1 = V2 is not satisfied). Then, the predetermined voltage Vdet (not 0) is changed to the second high resistance R5 according to the above equation.
Therefore, by detecting such a voltage, it is possible to determine whether the voltage is normal or abnormal.

At this time, since the detected voltage is an AC voltage, the AC voltage is rectified by the detection rectifier circuit 21 and is further smoothed and converted into a DC voltage. Then, the DC voltage is compared with a reference value in the cutoff holding circuit 22, and when the DC voltage is equal to or more than the reference value, it is determined that the above is the case, and the inverter 12 is stopped.

Therefore, no voltage is generated in the secondary winding 13c of the transformer 13, and no resonance occurs on the secondary side.
Further, even if one end of the neon tube 11 comes off to open the output terminal 15 or one end of the neon tube 11 is grounded, the output voltage of the secondary winding 13c of the transformer 13 is 0 as described above. Therefore, there is no danger of electric shock or sparks. Further, even when the length of the lead wire is longer than the specified length, if the load balance on the secondary side is lost due to this, it is possible to detect.

In each of the above-described embodiments, an example is shown in which the power supply device to be mounted is applied to a device that outputs a DC superposition, but the present invention is not limited to this.
A DC output may be used, and the output voltage and the output current may be direct current (DC). That is, the present invention can be applied to a type in which the output is not full-wave rectified and an induced electromotive force is generated in the core even in a normal state.

[0046]

As described above, in the power supply device according to the present invention, even if the output method is DC or DC superposition, the values of the elements constituting the voltage dividing circuit are appropriately set, so that the power supply device can be divided in the normal state. The voltage generated in each of the two cores can be made substantially equal (the difference is within a predetermined margin). Therefore, it is possible to accurately discriminate between the normal load and the abnormal load based on the magnitude of the induced voltage of the U core.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an embodiment of a power supply device according to the present invention.

FIG. 2 is an exploded perspective view showing an example of a transformer which is a main part of the present invention.

FIG. 3 is a perspective view showing an example of a transformer which is a main part of the present invention.

FIG. 4 is a plan view showing a transformer and a detection circuit which are main parts of the present invention.

FIG. 5 is an equivalent circuit thereof.

FIG. 6 is a diagram illustrating an example of a conventional power supply device.

FIG. 7 is an equivalent circuit thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Power supply apparatus 11 Neon tube (load) 12 Inverter 13 Transformer 13a Core 13b Primary winding 13c Secondary winding 20 Detection circuit 26 U core 33 Film sheet

Claims (3)

[Claims] 1. A power supply device comprising an inverter circuit and a transformer, and generating a DC or DC superimposed output voltage, wherein the transformer has a primary winding and a secondary winding attached to a core in a mutually insulated state. The core is arranged so that the end faces of the U core divided into two parts are opposed to each other with an insulating sheet interposed therebetween, thereby providing a closed magnetic path with both U cores while maintaining an electrically insulated state. Further, by providing a voltage dividing circuit in the two cores, a difference between induced voltages generated in the two U cores based on leakage magnetic flux of the secondary winding when the load is normal is constant. And a difference between the induced voltages generated in the core when the load is abnormal is larger than that in a normal state. 2. The power supply device according to claim 1, wherein an addition / subtraction circuit is connected to the voltage dividing circuit, and the difference between the induced voltages is obtained by the addition / subtraction circuit. 3. The voltage dividing circuit includes low resistances (R1, R2) respectively disposed between the cores and ground, and the addition / subtraction circuit is connected in parallel to the low resistance.
3. The method according to claim 2, further comprising a first high resistance (R3, R4) and a second high resistance (R5) connected in series to both first high resistances and falling to ground. Power supply.