JPH0348746B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a high frequency power supply device that aims to reduce high frequency noise voltage between a line and the ground.

(Prior Art) Push-pull type transistor inverters have already been proposed and are well known, and are widely used in various technical fields. For example, it is also used when lighting discharge lamps at high frequencies. It is known that devices having high frequency switching means, including such push-pull type transistor inverters, continuously generate noise at a frequency higher than the fundamental oscillation frequency due to the switching operation. Therefore, when a push-pull type transistor inverter is connected to an AC power source, which is a commercial power source, through a rectifier, the high frequency noise acts as a radio frequency noise voltage source. This was applied as a noise voltage to the impedance, causing noise interference to the equipment receiving noise interference. Regarding such noise, for example, the Electrical Appliance and Material Control Law requires that high frequency noise of 525 kHz to 1605 kHz be reduced to 65 dB or less.

For this reason, a conventional filter circuit formed by combining an inductor and a capacitor has been provided between the AC power supply and the rectifier in an attempt to reduce the high frequency noise voltage. However, in the case where the filter circuit is provided, there is a limit to the miniaturization of the inductor constituting the filter circuit, and this poses a major obstacle to miniaturization and weight reduction of the entire device. In addition, the provision of special parts made the device that much more expensive.

Therefore, the present inventors have proposed a push-pull type transistor inverter in which a constant current inductor is inserted between a common connection point on the emitter side of a pair of transistors and one output terminal of an input side rectifier. This device utilizes the high frequency blocking effect of the constant current inductor by intervening the constant current inductor in each circuit for transmitting high frequency noise voltage from each transistor that is a high frequency noise source to the noise disturbed device. As a result, high frequency noise to the noise-disturbing device can be reduced. In other words, the problem of high frequency noise can be reduced by using the constant current inductor that the push-pull type inverter has.
There is no need to provide a special filter, and it can be provided in a small size and at low cost, and is extremely effective.

(Problems to be Solved by the Invention) The present invention has been made to further improve the above. In other words, in the above-mentioned constant current inductor, the distance from the core to the winding start side and the winding end side of the coil and the total dielectric constant between each side and the core are usually different, and it is extremely difficult to make them the same. Have difficulty. Distributed capacitance (electrostatic capacitance) is proportional to dielectric constant and area, and inversely proportional to distance. Therefore, due to the difference in distance and dielectric constant, the distributed capacitance between the core and the winding start side and winding end side is As a result, the distributed capacitance between the core and the ground through the core, which has a much larger area than the wire of the coil, also differs. The present inventors focused on the difference in the distributed capacitance with respect to the ground, and discovered that high frequency noise can be reduced more effectively by inserting an inductor in consideration of the difference in the distributed capacitance.

This invention was made based on such knowledge, and an object of the present invention is to provide a high frequency power supply device that can significantly reduce high frequency noise between a line and the ground.

In addition, the constant current inductor is electrically located between the output end of the rectifier on the input side and the resonant circuit on the inverter main circuit side, and is used to detect the difference between the DC voltage and the resonant output (sine wave voltage). It shares the voltage of the inverter, and flows a current containing ripples synchronized with a half cycle of the oscillation frequency of the inverter. Therefore, the above constant current inductor is
When there is no load connected, or when the load is light such as before starting a discharge lamp, the current consumed by the load is small, so the current consumption is synchronized with the half cycle of the oscillation frequency of the inverter. This attempts to cause a reactive current to flow in the opposite direction to the polarity of the input DC voltage. This reactive current tries to flow through the rectifier at the beginning of a cycle in which the reactive current flows, but is interrupted during one cycle. When this reverse reactive current is cut off, the constant current inductor generates a high pulse voltage across both ends due to its back electromotive force. This high pulse voltage can destroy the rectifier and
High frequency noise is generated by generating the pulse voltage. Therefore, the present invention
Another object of the present invention is to simultaneously prevent the generation of high pulse voltage and high frequency noise caused by such a constant current inductor.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a first capacitor between the input terminals of a rectifier that rectifies the output of an AC power supply, and a first capacitor that is connected to one output terminal of the rectifier. A constant current inductor is connected between the common connection point on the emitter side of a pair of push-pull type transistors, and the terminal on the side with the smaller distributed capacitance between the core and the winding start side and the winding end side of the coil is connected to the above transistor. The configuration is characterized in that a second capacitor is further provided between the output terminals of the rectifier.

(Function) The present invention provides a constant current inductor in the high frequency noise transmission circuit from each of a pair of high frequency noise sources (a pair of transistors) to a noise disturbed device, thereby reducing the high frequency of the constant current inductor. By utilizing the blocking effect, the problem of high frequency noise that attempts to be transmitted through a pair of input power supply lines is effectively reduced.

Furthermore, since the one with the smaller distributed capacitance between the core and the winding start side and the winding end side of the coil of the constant current inductor is set as the transistor inverter side, the transistor inverter side is connected to the ground via the core. The distributed capacitance can be made small (the impedance is large). Therefore, of the high frequency noise (radio frequency noise) voltage generated by the transistors of the transistor inverter, a considerable portion of the noise voltage appearing across the constant current inductor is applied to the impedance due to the relatively smaller distributed capacitance. Therefore, it is possible to reduce the noise voltage applied to the high frequency noise interference device connected to the terminal side with relatively large distributed capacitance.

Furthermore, by providing the first capacitor between the input terminals of the rectifier, it is possible to reduce the high frequency noise voltage between the pair of power lines, and also to absorb the high frequency noise generated by the rectifier, and to It also effectively reduces the amount of conduction.

Furthermore, the second capacitor forms a current path for the reactive current that the constant current capacitor attempts to flow during no load or light load, and a high pulse voltage is generated when the reactive current is interrupted midway. prevent the occurrence of This protects the rectifier and prevents generation of high frequency noise.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 7. Reference numeral 1 denotes an AC power source, which is a commercial power source, for example, and a rectifier 2 is connected to this AC power source 1. A first capacitor 3 is provided between the input terminals of this rectifier 2 . Further, a second capacitor 4 is provided between the two output terminals of the rectifier. 5 is a push-pull type transistor inverter, and the rectifier 2
The rectifier 2 is connected to the rectifier 2 and converts the output of the rectifier 2 into high frequency power. In this embodiment, unsmoothed DC power is converted to high frequency power.
The push-pull type transistor inverter 5 includes a pair of transistors 6 and 7, and the input winding of an inverter transformer 8 is connected between the collectors of these transistors 6 and 7, respectively. Then, the emitters of the pair of transistors 6 and 7 are connected, and the common connection point of these emitters is connected to the negative output terminal of the rectifier 2 via a constant current inductor 9, which will be described later.
The midpoint of the input winding of the inverter transformer 8 is connected to the positive output terminal of the rectifier 2. Also,
A resonance capacitor 10 is connected in parallel to the input winding of the inverter transformer 8.
This resonance capacitor 10 and the inductance component of the inverter transformer 8 form a parallel resonance circuit. The transistor inverter 5 has a load 1 receiving the resonant output.
1 is connected. As described above, the constant current inductor 9 shares the voltage difference between the DC voltage and the resonant output (sinusoidal voltage),
A current containing ripples is passed in synchronization with a half cycle of the inverter's oscillation frequency. This makes it possible to make the input current to the inverter 5 a constant current at high frequency during normal loads, and to operate the inverter 5 stably to obtain the required resonant output, which itself is well known. . A feature of the present invention is that the distributed capacitance between the inductor 9 and the common connection point on the emitter side of the transistors 6 and 7 and one output terminal of the rectifier 2, and between the inductor 9 and the ground is small. The side terminal is provided on the transistor inverter side, and the first capacitor 3 is connected to the rectifier 2.
The second capacitor 4 is provided between the input terminals of the rectifier 2, and the second capacitor 4 is provided between the output terminals of the rectifier 2. 2
The high frequency noise generated by the noise is caused by other electrical equipment (not shown) connected to the AC power supply 1 via power lines etc.
This is to prevent the information from being transmitted to the Further, when the constant current inductor 9 attempts to flow a reactive current having a polarity opposite to the output voltage of the rectifier 2, a current path is formed for this reactive current to prevent the generation of a high pulse voltage. be.

The inductor 9 may be of several mH, for example. As shown in FIG. 5, the inductor 9 has a coil 13 wound around the central leg 12a of an E-shaped core 12, and each leg 12a, 12
A flat core 15 is provided at the tips of b and 12c via a gap 14. In the inductor 9 having such a configuration, the distance from the core 12 is different between the winding start side a and the winding end side b of the coil 13, and there is also a distance between the coil 13 and the core, such as a bobbin, insulating tape, air, etc. Since the overall permittivity of core 1 is different, core 1
The electrostatic coupling between 2 and 2 is different, and the former is generally larger. As a result, if such an inductor 9 were to be housed in a grounded case 16 as shown in FIG. 6, the core 12 and the case 16 would be
Since the distributed capacitance 17 between coils 1 and 1 is large,
The distributed capacitance between the winding start side and the ground of No. 3 is larger than that at the winding end side. Therefore, in this embodiment, the winding start side a of the coil with a large distributed capacitance between the ground and the coil is connected to the negative terminal of the rectifier 2, and the winding end side b of the coil with a small distributed capacitance between the ground and the ground is connected to the negative terminal of the rectifier 2. is connected to the emitter side of transistors 6 and 7. The magnitude of the distributed capacitance between the winding start side or the winding end side and the core can often be estimated by visually comparing the distance to the core and taking into account the dielectric constant. However, in delicate cases, the capacitance between the start of winding and the case 16 and between the end of winding and the case 16 can be measured using a well-known high-frequency LCR meter while the capacitance is housed in the case 16 as shown in Figure 6. It is.

Next, the effect will be explained. The transistor inverter 5 is supplied with DC power rectified by the rectifier 2 from the AC power supply 1 and operates to output high frequency power. The load 11 is supplied with this high frequency power.

By the way, the transistors 6 and 7 of the push-pull type transistor inverter 5 generate high frequency noise of several hundred kHz or more, which is a harmonic with respect to the fundamental oscillation frequency, when switching. However, in the present invention, the high-frequency This prevents noise from being transmitted to other electrical equipment via power lines, etc. This effect can be expressed as
This will be explained with reference to FIGS. FIG. 2 shows transistors 6 and 7 in FIG. 1 as noise sources 20 and 2, respectively.
This is an equivalent circuit that is assumed to be 1. In FIG. 2, 22 and 23 equivalently represent the distributed capacitance between the collectors of the transistors 6 and 7 and the ground. It should be noted here that transistors have a large power loss in their collectors, and in order to improve heat dissipation, the collectors are designed to have a large area. Therefore, in a transistor, the distributed capacitance between ground and ground is essentially only the collector. 24 and 25 are distributed capacitances between the load 11 and the ground, 26 and 27 are composite inductance components of the input and output windings of the inverter transformer 8, and 28 and 29 are the input windings of the transformer 8 that connect the resonance capacitor 10. And capacitors 30 and 31 equivalently replaced between the output windings represent distributed capacitances between both ends of the inductor 9 and the ground, respectively. Other parts that are the same as those in FIG. 1 are given the same reference numerals.

Here, if this FIG. 2 is further simplified, it becomes as shown in FIG. 3. In FIG. 3, 32 is an element that indicates the impedance of the pseudo power supply circuit used in the noise measurement circuit between the power supply line and the ground. The objective is to reduce noise interference from high-frequency noise-disturbing equipment. The reason why the power supply line can be shown as one in Figure 3 is because a capacitor 3 is provided as shown in Figure 2, and this capacitor 3 has a low impedance to high frequencies, so it can be equivalently shown as This is because it can be considered as a short circuit. Note that even if there is no capacitor 3, if a pair of power lines are close to each other and routed over a long distance, the power line can be considered as one line due to the distributed capacitance between the lines. Since wiring over long distances causes problems such as voltage drop and an increase in the number of wires used, usually efforts are made to shorten the wiring length. Therefore, the capacitor 3 is required to make the pair of power supply lines a common line for high frequencies. In addition, in FIG. 3, for simplicity, only the case when the rectifier 2 is conductive is considered. Reference numerals 33 and 34 represent a composite of the distributed capacitances 22 and 23 and the distributed capacitances 24 and 25 in FIG. If this FIG. 3 is shown focusing only on one noise source 20, it will become as shown in FIG. 4. Therefore, if the distributed capacitances 30 and 31 between both ends of the inductor 9 and the ground are omitted, the noise voltage V32 of the element 32 exhibiting the impedance is expressed as follows.

V ₃₂ =｜Z28｜/｜Z28+Z9｜・｜Z32｜/｜Z33+Z32｜
V20...(A) Here, Z28... Impedance of one capacitor 28 with the resonant capacitor 10 replaced on one winding side Z9... Impedance of inductor 9 Z32... Impedance of element 32 Z33... Impedance of composite distributed capacitance 33 V20 ... is the noise voltage of the noise source 20.

Since the pair of power supply lines are made into a common line by the capacitor 3 on the input side of the rectifier 2, it is clear that the above equation (A) holds true for the other noise sources 21 as well. In FIGS. 3 and 4, it is clear from the above equation (A) that the constant current inductor 9 is interposed in series in the high frequency noise transmission circuit to the element 32, and the inductor 9 is connected to the transistors 6 and 7. By inserting the emitter into one output end of the rectifier 2, the noise voltage of the transistors 6 and 7 can be significantly reduced by the inductor 9, which exhibits high impedance at high frequencies. It is possible to prevent or reduce noise interference from other connected electrical equipment (high-frequency noise interference equipment). In other words, the voltage of the noise voltage source 20 or 21 applied to the impedance 32 is divided by the inductor 9 and the capacitor 28 or 29, so the presence of the inductor 9 reduces the high frequency noise applied to the impedance 32. This means that it can be reduced.

In the present invention, the inductor 9 is further inserted at the above position in consideration of the distributed capacitance between both ends of the inductor 9 and the ground. That is, the voltage across the inductor 9 attempts to apply a high frequency noise voltage to the impedance 32 in the circuit of the inductor 9 - impedance 32 - ground - distributed capacitance 31 - inductor 9. On the other hand, as described above, the distributed capacitance 31 between the transistor inverter 5 side terminal of the inductor 9 and the ground is at the winding end side of the inductor 9, and the distributed capacitance 31 between the ground and the transistor inverter 5 side terminal is relatively small. Because it is small and has high impedance, it shares most of the high frequency noise voltage. As a result, the noise voltage applied to the impedance 32 can be reduced. Moreover, in this case, the distributed capacitance 30 connected in parallel with the impedance 32 is
Since the distributed capacitance between the winding start side of the inductor 9 and the ground is relatively large and the impedance is small, the noise voltage applied to the impedance 32 can also be reduced from this point of view.

In contrast to the present invention, when the inductor 9 is provided on the collector side of the transistors 6 and 7,
That is, in the case of the one provided between the positive side output terminal of the rectifier 2 and the composite inductance components 26 and 27 in FIG. 2, the high-frequency noise voltage transmission circuit to the element 32 in the equivalent circuit of FIG. Since a closed circuit of noise source 20 or 21 - element 32 - distributed capacitance 22 or 23 is formed without the presence of constant current inductor 9, the above-mentioned effect of inductor 9 cannot be obtained in the first place. This is also clear from the fact that the windings 26 and 27 of the inverter transformer 8 shown in FIG. 2 do not contribute to noise reduction.

Furthermore, in this embodiment, the diodes of the rectifier 2 generate high frequency noise when switching, although at low voltage. However, the capacitor 3 absorbs this, and as a result, the problem of high frequency noise for the high frequency noise interference device can be reduced.
Furthermore, the capacitor 3 is also effective in reducing high frequency noise voltage between a pair of power supply lines.

Next, at both ends of the constant current inductor 9,
During the operation of the inverter 5, the voltage shown in FIG. 7A is generated. As mentioned above, this means that the constant current inductor 9 outputs DC voltage and resonance output (sinusoidal voltage).
This is because the voltage difference between the two is shared. Also,
During normal load, the current shown in Figure 2 flows. This is also because the inverter 5 generates a resonant output as described above, and ripples are superimposed in synchronization with the half cycle of the resonant output. Furthermore, Figures 7A and 7B show the periods of the high-frequency voltage and current in an enlarged manner, and one peak of the sinusoidal waveform in Figure 7A corresponds to a half cycle of the high-frequency output voltage of the inverter 5 (hereinafter the same applies). ). By the way, when there is no load or a light load, the current consumed by the load 11 decreases and the input current decreases accordingly, so the current flowing through the constant current inductor 9 is become that way. The negative current (reactive current) in Figure 7 C is:
It flows through the second capacitor 4. Therefore, the current of the constant current inductor 9 is not interrupted, and high pulse voltage is not generated.

On the other hand, without the second capacitor 4,
As shown in Figure 8A, the negative current is interrupted in the middle of the cycle in which it should flow, and at this time, the constant current inductor 9 generates a pulse-like high voltage as shown in Figure 8B due to the back electromotive force. do. This high voltage may destroy the rectifier 2, and
This generates high-frequency noise, causing high-frequency noise problems to other electrical devices.

That is, in the present invention, the second capacitor 4 can prevent the destruction of the rectifier 2 caused by the constant current inductor 9, the generation of high pulse voltage, and the problems of high frequency noise affecting other electrical equipment.

Note that the present invention is not limited to the above-mentioned embodiments, and can be modified in various ways. For example, the inductor may be one in which a coil 41 is wound around a drum-shaped core 40, as shown in FIG. In this case, it is understood from the capacitance that the distributed capacitance between the winding start side and the core is clearly larger, and the distributed capacitance with respect to the ground is also larger. In addition, the shape of the inductor is not limited; the inductor should just be installed so that the side with the smaller distributed capacitance between the coil and the core is on the side of the transistor inverter between the winding start side and the winding end side of the coil. . The constant current inductor may be provided between the common connection point on the emitter side of each transistor and one of the output terminals of the rectifier, and the constant current inductor may be provided between the common connection point on the emitter side of each transistor and the output terminal of the rectifier. It is understood that devices may be provided.

[Effects of the Invention] As described in detail above, the present invention is a high-frequency power supply device that rectifies the output of an AC power source and converts it into high-frequency power using a push-pull type transistor inverter. A first capacitor is provided between the input terminals, and a second capacitor is provided between the output terminals of the rectifier, and one of the output terminals of the rectifier and a common connection point on the emitter side of each transistor of the inverter. In between, connect the constant current inductor to the ground so that the terminal with the smaller distributed capacitance between the coil is on the transistor side, and the distributed capacitance between the core and the winding start side and the winding end side is smaller. This is inserted with one side facing the transistor.

Therefore, the constant current inductor exhibiting a high impedance to high frequencies can be interposed in the transmission circuit for transmitting high frequency noise voltage from each of the transistors, which are sources of high frequency noise, to the equipment subject to noise interference. Since the high-frequency noise voltage across the constant current inductor can be divided by the large distributed capacitance, it is possible to prevent or reduce noise interference to other electrical equipment (high-frequency noise disturbing equipment) connected to the AC power supply. . Furthermore, since a constant current inductor is used, no special parts are required, the overall size of the device does not increase, and the price does not increase.

Furthermore, the first capacitor between the input terminals of the rectifier can reduce the high frequency noise voltage between the pair of power supply lines, and since the rectifier absorbs the high frequency noise generated, as a result, the high frequency noise This makes it possible to more reliably reduce the problem of high frequency noise caused by interfering equipment.

Furthermore, the second capacitor between the output terminals of the rectifier forms a current path for the reactive current that flows through the constant current inductor when there is no load or when the load is light, so that the reactive current is cut off. This prevents the constant current inductor from generating a high pulse voltage, thereby preventing damage to the rectifier due to the high pulse voltage and generation of high frequency noise due to the generation of the high pulse voltage.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figure 2 is a circuit diagram showing an embodiment of the present invention.
Figures 4 to 4 are equivalent circuit diagrams that also explain the action.
5 and 6 are simplified front views of one embodiment of the inductor, FIG. 7 is a voltage and current waveform diagram illustrating the operation of the above embodiment, and FIG. 8 is a voltage and current waveform diagram illustrating the conventional operation. and a current waveform diagram, and FIG. 9 is a simplified front view of another embodiment of a constant current inductor. 1... AC power supply, 2... Rectifier, 3... Capacitor, 5... Transistor inverter, 6, 7
...Transistor, 9...Inductor for constant current.

Claims (1)

[Claims] 1. An AC power source; A rectifier that rectifies the output of the AC power source; A first capacitor provided between the input terminals of the rectifier; A first capacitor provided between the output terminals of the rectifier; a second capacitor; a push-pull type transistor inverter that converts the output of the rectifier into high-frequency power; between one of the output terminals of the rectifier and a common connection point on the emitter side of each transistor of the transistor inverter; A high frequency power supply characterized by comprising: a constant current inductor inserted with the terminal having a smaller distributed capacitance between the core and the coil at the inverter side among the winding start side and the winding end side of the coil; Device.