JPH02290164A - Power unit - Google Patents

Abstract

PURPOSE:To prevent noise interference with the other electrical equipment, connected to an AC power supply, by providing a capacitor between input terminals of a rectifier, connected to the AC power supply, while interposing a constant current inductor between one output terminal of the rectifier and an emitter side common connection point of each transistor of an inverter. CONSTITUTION:A capacitor 3 is provided between input terminals of an output rectifier 2 of an AC power supply 1, while a constant current inductor 9 is interposed between one output terminal of the rectifier 2 and an emitter side common connection point of a pair of push pull type transistors 6, 7. A pair of power supply lines are equivalently shared for a high frequency by the capacitor 3 in the input side of the rectifier 2 further with the constant current inductor 9 effectively utilized. Thus, a high frequency noise, generated at the time of switching the transistors 6, 7, can be prevented from being transmitted to the other electrical equipment connected to the AC power supply 1 through the power supply lines or the like.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is intended to prevent the adverse effects of high frequency noise generated by the switching transistors of a push-pull type transistor inverter on other electrical equipment. Regarding the power supply device.

(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 effective when lighting a discharge lamp at high frequency.

However, this push-pull transistor inverter continuously generates high-frequency noise due to its switching operation. Therefore, for example, if a push-pull transistor inverter is connected to an AC power source (commercial power source) through a rectifier, the noise generated by the switching operation of the transistor will be transmitted to other electrical equipment connected to the AC power source via power lines etc. transmitted and have adverse effects. This is so-called radio noise. For example, such noise is defined as 5 2 5 k in the Electrical Appliances and Materials Control Law.
High frequency noise of Hz to 1605 kHz is required to be kept below 65 dB.

For this reason, conventionally, the noise has been reduced by providing a filter circuit including an inductor and a capacitor between the AC power source and the rectifier. Furthermore, a push-pull type transistor inverter has been proposed in which an auxiliary inductor is inserted between one of the input terminals connected to the storage battery and the emitters of a pair of commonly connected transistors (Japanese Unexamined Patent Application Publication No. 1973-1972-1). 38429
Publication No.).

(Problems to be Solved by the Invention) However, in devices provided with a filter circuit, there is a limit to the miniaturization of the inductor and capacitor that constitute the filter circuit, which poses a major obstacle to miniaturization of the entire device.

Furthermore, the need for extra capacitors and inductors inevitably increases the price. Also, JP-A-4
8-'18429 is intended to obtain an auxiliary DC voltage source for driving transistors, and is not intended to reduce high frequency noise in equipment subject to high frequency noise interference. Furthermore, regarding the configuration, the one in the above publication uses a storage battery as an input power source (Japanese Patent Laid-Open No. 48-384
Publication No. 29, page 2, line 9 in the bottom left column, lines 2 to 2 in the right column
(line 8) and does not use an AC power source that connects other electrical equipment, such as a commercial power supply, so when other electrical equipment is installed, it is necessary to reduce the high frequency noise to this electrical equipment. No configuration shown. Furthermore, in the above-mentioned publication, when other electrical equipment is connected to the storage battery, an auxiliary inductor is inserted between one of the input terminals and the emitters of a pair of commonly connected transistors. Even if there is an effect of reducing high frequency noise, it is only between the ground and the line on the one input terminal side where the auxiliary inductor is connected, and the noise will be reduced on the other input terminal side where the auxiliary inductor is not inserted. Since the auxiliary inductor is not present in the conduction circuit,
This does not contribute in any way to noise reduction between the line and the ground on the other input terminal side.

The present invention has been made to eliminate these conventional drawbacks, and can effectively prevent high frequency noise caused by switching transistors from being transmitted to other electrical equipment via power lines, and can also reduce the size of the entire device. The purpose of this invention is to provide a power supply device that can be used at a low cost.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a capacitor between the input terminals of a rectifier that rectifies the output of an AC power source, and a push-pull type capacitor that is connected to one output terminal of the rectifier. The structure is characterized in that a constant current inductor is inserted between a common connection point on the emitter side of a pair of transistors.

(Function) The present invention uses a capacitor on the input side of a rectifier to make a pair of power supply lines equivalently a common line for high frequencies, and conducts electricity through the pair of power supply lines by effectively utilizing a constant current inductor. This effectively reduces the problem of high frequency noise. Further, by providing the capacitor between the input terminals of the rectifier, it is effectively possible to reduce the tendency of high frequency noise generated by the rectifier to be conducted to the power supply line side.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

1 is, for example, an AC power source which is a commercial power source, and a rectifier 2 is connected to this AC power source 1. This rectifier 2
A capacitor 3 is provided between the input terminals of. Further, another capacitor 4 is connected between the two output terminals of the rectifier.
is provided. Reference numeral 5 denotes a push-pull transistor inverter, which 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, 7, and the input winding of the inverter transformer 8 is connected between the collectors of these transistors 8, 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 transformer 8 is connected to the positive output terminal of the rectifier 2.

Further, a resonance capacitor 10 is connected in parallel to the input winding of the inverter transformer 8. A load l1 is connected to this transistor inverter 5. The constant current inductor 9 is connected to the inverter 5
The inverter 5 has the function of making the input current constant, thereby allowing the inverter 5 to operate stably, and is well known in itself. In the inductor 9 of this embodiment, for example, as shown in FIG. 5, a coil 9C is wound around the central leg 9b of an E-shaped core 9a, and a gap 9r is provided at the tip of each leg 9bs 9d, 9e. This is a configuration in which a flat core 9g is provided through the core. The present invention is characterized in that the inductor 9 is provided between the common connection point on the emitter side of the transistors 6.7 and one output terminal of the rectifier 2, and the capacitor 3 is provided between the input terminals of the rectifier 2. This allows the high frequency noise generated when the transistors 6 and 7 are switched to be transmitted to other electrical equipment (
Not shown. ).

The inductor 9 may be of several mH, for example.

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. Load l1 is supplied with this high frequency power.

By the way, push-pull type transistor inverter 5
Transistors 6 and 7 generate several hundred kHz during switching.
Generates high frequency noise above z.

However, the present invention includes an inductor 9 inserted between the emitters of the transistors 6 and 7 and one output terminal of the rectifier 2, and a capacitor 3 on the manual side of the rectifier 2.
This prevents the high frequency noise from being transmitted to other electrical equipment via power lines or the like. This effect will be explained with reference to FIGS. 2 to 4. Figure 2 is the first
This is an equivalent circuit shown assuming that transistors 6 and 7 in the figure are noise sources 20 and 21, respectively. In Figure 2, 22
．． 23 equivalently represents 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 problem of distributed capacitance between ground and ground is substantially only in the collector.

24.25 is the distributed capacitance between the load 1l and the earth, 26.
27 represents the composite inductance component of the human power winding and the output winding of the inverter transformer 8, and 28.29 represents the capacitor component obtained by equivalently replacing the resonance capacitor 10 between the input winding and the output winding of the transformer 8. ing. Other parts that are the same as those in FIG. 1 are given the same reference numerals. However, if we further simplify this Figure 2, we can see that Figure 3
It will look like the illustration.

In FIG. 3, 30 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, and reducing the noise voltage across this element 30 is
The purpose of this invention is to reduce noise interference from other high-frequency noise interference equipment connected to the AC power supply l.

In Figure 3, the power supply line can be shown as a single line because
This is because, as shown in FIG. 2, a capacitor 3 is provided, and since this capacitor 3 has a low impedance to high frequencies, it can be considered to be equivalently short-circuited. Note that even without this capacitor 3, if a pair of power supply lines are close to each other and routed over a long distance, the power supply line can be considered as one line due to the distributed capacitance between the lines, but if the power line is long Routing over long distances causes problems such as voltage drop and an increase in the number of wires used, so usually efforts are made to shorten the length of the wires. 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. 31.32 is a composite of distributed capacitance 22.23 and distributed capacitance 24.25 in FIG. 2. This figure 3 is expressed as one noise source 20
If we focus only on this, we get the result shown in Figure 4. Therefore, the noise voltage V30 of the element 30 exhibiting the impedance
is expressed as follows.

Here, z24... Impedance Z9 of one capacitor 28 with the resonant capacitor lO replaced on one winding side... Impedance 230 of the inductor 9... Impedance Z31 of the element 30...
Impedance V20 of the composite distributed capacitance 3l 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 human power side of the rectifier 2, the above equation (^) can be used to calculate the noise source 2.
It is clear that the same holds true for l. As is clear from the above equation (^), by inserting the inductor 9 between the emitter of the transistor 6.7 and one output terminal of the rectifier 2, the noise voltage of the transistor 6.7 can be reduced to a high impedance at high frequencies. The inductor 9 shown in FIG. 1 can significantly reduce the amount of noise, thereby preventing or reducing noise interference from other electrical equipment (high frequency noise interference equipment) connected to the AC power source 1. On the other hand, inductor 9
In the case where is provided on the collector side of the transistor 6.7,
As is clear from the equivalent circuits in FIGS. 2 to 4, noise source 20 or 2l, element 30, distributed capacitance 22 or 23
A closed circuit is formed, and the above-mentioned effect of the inductor 9 cannot be obtained. This is also clear from the fact that the windings 28 and 27 of the inverter transformer 8 shown in FIG. 2 hardly contribute to noise reduction. That is, in a transistor, a large distributed capacitance exists between the collector and the ground. Furthermore, the condenser 3
Even if the diodes of the rectifier 2 generate high-frequency noise during switching at low voltage, this is bypassed, and as a result, the problem of high-frequency noise to the high-frequency noise interference equipment can be reduced. According to experiments conducted by the inventors, in the configuration of this embodiment, the AC power supply 1 is a commercial power supply of 50Hz 100V, and the oscillation frequency of the inverter 5 is 3.
3kHz, when inductor 9 is approximately 5mH and load 11 is a discharge lamp, 525kHz16 is regulated by the Electrical Appliance and Material Control Law.
The high frequency noise of 0.05 kHz between each power supply line and the ground can be reduced by 10 dB or more compared to the case where the inductor 9 is not provided or the inductor 9 is provided on the collector side of the transistor 6.7.

Note that the present invention is not limited to the above-mentioned embodiments, and can be modified in various ways. For example, a 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 other inductor may be provided between the common connection point on the emitter side and the output terminal of the rectifier. It is readily understood that the following devices may be provided.

[Effects of the Invention] As detailed above, the present invention is a power supply device that rectifies the output of an AC power supply to which other high-frequency noise interference devices can be connected and converts it into high-frequency power using a push-pull type transistor inverter. A capacitor is provided between the input terminals of the rectifier connected to the AC power source, and a constant current inductor is provided between one of the output terminals of the rectifier and a common connection point on the emitter side of each transistor of the inverter. is inserted, the pair of power supply lines can be made into a common line to prevent high frequency noise generated when each of the transistors switches, and the high frequency noise can be reduced by the constant current inductor which exhibits high impedance to high frequencies. Therefore, it is possible to prevent noise disturbances to other electrical equipment (high frequency noise interference equipment) connected to the AC power source. 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.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIGS. 2 to 4 are equivalent circuit diagrams illustrating the same operation, and FIG. 5 is a simplified front view of an embodiment of the inductor. DESCRIPTION OF SYMBOLS 1... AC power supply, 2... Rectifier, 3... Capacitor 5... Transistor inverter, 6, 7... Transistor 9... Inductor for constant current. Patent Applicant Toshiba Lighting & Technology Co., Ltd. Agent Patent Attorney Yoshihiro Onoda Ishitak Ikon

Claims (1)

[Claims] (1) An AC power source to which a high-frequency noise disturbance device can be connected, a rectifier that rectifies the output of this AC power source, a capacitor installed between the input terminals of this rectifier, and a high-frequency power source that converts the output of the rectifier into high-frequency power. a push-pull type transistor inverter for converting into A power supply device featuring: