JPH02290165A - Power unit - Google Patents

Abstract

PURPOSE:To prevent a rectifier from being damaged by providing an inductor between an emitter side common connection point of transistors an output terminal of the rectifier, first capacitor between input terminals of the rectifier and the second capacitor between output terminals of the rectifier. CONSTITUTION:The first capacitor 3 is provided between input terminals of a rectifier 2, which rectifies an output of an AC power supply 1, while the second capacitor 4 is provided in an output side of the rectifier 2, further a constant current inductor 9 is interposed between one of the output terminals 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 first capacitor 3, and further a high frequency noise, which tends to be propagated through the power supply lines, is reduced by the second capacitor 4. In this way, damage of the rectifier 2 by the constant current inductor 9 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a power supply device equipped with a push-pull type transistor inverter.

(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
The device disclosed in Japanese Patent Publication No. 8-38429 is intended to obtain an auxiliary DC voltage source for driving a transistor, and is not intended to reduce high frequency noise in equipment subject to high frequency noise interference. Furthermore, in terms of structure, the one in the above publication is
A device that uses a storage battery as an input power source (Japanese Patent Application Laid-Open No. 48-3842
Publication No. 9, page 2, line 9 in the bottom left column, lines 2 to 3 in the right column
(line), 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 a configuration for reducing high frequency noise to this electrical equipment. is not 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 interposed in the conduction circuit, it does not contribute to noise reduction between the line and ground on the other input terminal side.

Further, when a push-pull transistor inverter is used and a resonant circuit is used to obtain a resonant output, a constant current inductor is usually provided on the input side of the inverter. However, this constant current inductor may try to flow a current in the opposite direction to the polarity of the input power supply, especially when the load is light. Moreover, if this reverse direction of current is interrupted, both ends of the constant current inductor The high pulse voltage generated could destroy the rectifier.

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.

At the same time, the present invention aims to prevent the destruction of the rectifier and the generation of high frequency noise caused by the 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 source, and a second capacitor on the output side of the rectifier. , and a constant current inductor is inserted between one output terminal of the rectifier and a common connection point on the emitter side of a pair of push-pull transistors. It is something to do.

(Function) The present invention makes a pair of power supply lines equivalently a common line for high frequencies using the first capacitor on the human power side of the rectifier, and effectively utilizes the constant current inductor and connects the pair of power supply lines by using the second capacitor. This effectively reduces the problem of high frequency noise that tends to be transmitted through the power supply line.

Further, the second capacitor protects the rectifier by bypassing the reverse current caused by the constant current inductor during light loads and the like. Furthermore, the first capacitor effectively reduces transmission of high frequency noise generated by the rectifier to the power supply line side.

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

1 is an AC power source which is a commercial power source, for example, and a rectifier 2 is connected to this AC power source 1. This rectifier 2
A first capacitor 3 is provided between the input terminals of. Further, a second capacitor 4 is provided between the two output terminals of the rectifier. 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,
The input winding of an inverter transformer 8 is connected between the reflectors of these transistors 6 and 7. Then, the emitters of the pair of transistors 6.7 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 lO is connected in parallel to the input winding of the inverter transformer 8. A load 11 is connected to this transistor inverter 5. The constant current inductor 9 functions to make the input current to the inverter 5 a constant current, thereby allowing the inverter 5 to operate stably, and is well known in itself. The inductor 9 of this embodiment, for example, as shown in FIG. 7, has a coil 9C wound around the central leg 9b of an E-shaped core 9a, and
A flat core 9g is provided at the tip of each leg 9b, 9d, 9e via a gap 9r. The features of the present invention are that the inductor 9 is provided between the common connection point on the emitter side of the transistors 6 and 7 and one output terminal of the rectifier 2, and that the first capacitor 3 is connected to the input of the rectifier 2. The second capacitor 4 is provided between the terminals and the second capacitor 4 is provided between the output terminals of the rectifier 2, thereby preventing the high frequency noise generated when the transistors 6 and 7 are switching from being transmitted through the power line etc. This prevents the signal from being transmitted to other electrical equipment (not shown) connected to the AC power source 1. Furthermore, even if the constant current inductor 9 attempts to flow a current with a polarity opposite to that of the input power source, this prevents the rectifier 2 from being destroyed. 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. The load 11 is supplied with this high frequency power.

By the way, push-pull type transistor inverter 5
The transistor 6.7 generates several hundred kHz during its switching.
Generates high frequency noise above z.

However, in the present invention, the high frequency noise is removed from the power supply line by the inductor 9 inserted between the emitters of the transistors 6 and 7 and one output terminal of the rectifier 2, and the first capacitor 3 on the human power side of the rectifier 2. This is to prevent the information from being transmitted to other electrical equipment via other devices.

This effect will be explained with reference to FIGS. 2 to 4. FIG. 2 shows transistors 8 and 7 in FIG. 1 as noise sources 2 (1
．． This is an equivalent circuit shown assuming that 21. In FIG. 2, 2223 equivalently represents the distributed capacitance between the collectors of 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 11 and the ground, 26.27 is the inverter transformer 8
The combined inductance component of the input winding and output winding of
28 and 29 represent capacitors equivalently replacing the resonance capacitor 10 between the input winding and the output winding of the transformer 8, respectively. Other parts that are the same as those in FIG. 1 are given the same reference numerals. Therefore, when this FIG. 2 is further simplified, it becomes as shown in FIG. 3. 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. 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 FIG. 3 is because the first capacitor 3 is provided as shown in FIG.
This is because it has a low impedance to high frequencies, so it can be considered to be equivalently short-circuited.

Note that even if there is no first 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. However, wiring 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 wiring length. Therefore, the first 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 the distributed capacitance 22.2 in Figure 2
3, and the distributed capacity 24. 25 is synthesized and shown. If this FIG. 3 is shown focusing only on one noise source 20, it will become as shown in FIG. 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 10 replaced on one winding side... Impedance Z30 of the inductor 9... Impedance 231 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 first capacitor 3, it is clear that the above equation (A) holds true for the other noise sources 2l as well.

As is clear from the above equation (^), by inserting the inductor 9 between the emitters of the transistors 6 and 7 and one output terminal of the rectifier 2, the noise voltage of the transistors 6 and 7 can be reduced to a high impedance at high frequencies. Inductor 9 shown
As a result, it is possible to prevent or reduce noise interference in other electrical equipment (high-frequency noise interference equipment) connected to the AC power supply l. On the other hand, in the case where the inductor 9 is provided on the collector side of the transistor 6.7, as is clear from the equivalent circuits of FIGS. 2 to 4,
A closed circuit of the noise source 20 or 2l, the element 30, and the distributed capacitance 22 or 23 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, even if the diodes of the rectifier 2 generate high frequency noise during switching at low voltage, the first capacitor 3 bypasses the high frequency noise, and as a result, the high frequency noise is transmitted to the high frequency noise interference device. It can reduce the problem of

Next, a voltage shown in FIG. 5(a) appears at both ends of the constant current inductor 9 while the inverter 5 is in operation. Also, during normal load, the current shown in the figure below flows. This is because the inverter 5 is configured to generate a resonant output using the resonant capacitor IO, the inverter transformer 8, etc., as described above. In addition, Figure 5 (a),
(b) shows an enlarged view of the period of high-frequency voltage and current, and one peak of the sinusoidal waveform in FIG. By the way, when the load is light, the input current decreases, so the current flowing through the constant current inductor 9 becomes as shown in FIG. 5(C). The negative current (reactive current) in FIG. 5(c) 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, if the second capacitor 4 is not present, the negative current will be cut off as shown in FIG. 6 (a), and at this time, the constant current inductor 9 will be Generates a pulse-like high voltage. This high voltage has the risk of destroying the rectifier 2 and also generates high frequency noise, causing high frequency noise problems to other electrical equipment. That is, in the present invention, the second capacitor 4 can prevent problems such as destruction of the rectifier 2 caused by the constant current inductor 9, generation of high pulse voltage, and high frequency noise to other electrical equipment.

According to experiments conducted by the present inventors, in the configuration of this embodiment,
The AC power supply 1 is a commercial power supply of 50Hz 100V, the oscillation frequency of the inverter 5 is 33kHz, and the inductor 9 is approximately 5V.
mH, when the load it is a discharge lamp, the high frequency noise of 525 kHz to 1605 kHz regulated by the Electrical Appliance and Materials Control Law should be removed between each power supply line and the ground. The reduction was achieved by more than 10 dB compared to what was installed. Further, even under light load, no high pulse voltage was generated across the constant current inductor 9.

Note that the present invention is not limited to the above-mentioned embodiments, and can be modified in various ways. For example, it is sufficient that a constant current inductor is 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 is 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 first capacitor is provided between the input terminals of the rectifier connected to the AC power supply, and a second capacitor is provided between the output terminals of the rectifier, and one of the output terminals of the rectifier, Since a constant current inductor is inserted between the common connection point on the emitter side of each transistor of the inverter, the pair of power supply lines can be made into a common line for high frequency noise generated when each transistor switches, and, The constant current inductor exhibiting high impedance to high frequencies can reduce high frequency noise, and therefore can prevent or reduce noise interference to other electrical equipment (high frequency noise interference equipment) connected to the AC power source. . However, since it uses a constant current inductor, it does not require any special parts or increase the size of the entire device.
It also does not cause the price to rise.

Further, it is possible to prevent the generation of high pulse voltage by the constant current inductor and damage to the rectifier due to this high pulse voltage, and also to prevent high frequency noise accompanying the generation of the high pulse voltage.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIGS. 2 to 4 are equivalent circuit diagrams explaining the same operation, FIG. 5 is a voltage and current waveform diagram explaining the operation, and FIG. A current and voltage waveform diagram explaining the conventional operation, and FIG. 7 is a simplified front view showing one embodiment of an inductor. DESCRIPTION OF SYMBOLS 1... AC power supply, 2... Rectifier, 3... Capacitor, 4... Second capacitor 5... Transistor inverter 6. 7... Transistor, 9... For constant current inductor. Patent applicant: Toshiba Lighting & Technology Co., Ltd. Agent: Patent attorney: Yoshihiroichi Onoda, 384 years old

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 first capacitor provided between the input terminals of this rectifier; Output of the rectifier a second capacitor provided between the terminals; a push-pull type transistor inverter that converts the output of the rectifier into high-frequency power; a common emitter side of one of the output terminals of the rectifier and each transistor of the transistor inverter; A power supply device comprising: a constant current inductor inserted between connection points;