KR100252251B1 - Electromagnetic interference prevention apparatus - Google Patents

Abstract

PURPOSE: An electromagnetic interference prevention apparatus is provided to minimize a generation of an electro magnetic interference by excluding a click signal and thus minimizing a length of a clock line. CONSTITUTION: A clock generating part(60) generates a plurality of clock signals. A clock buffer(70) receives the clock signals and outputs the pertinent clock signals by being controlled by an input of predetermined output enable signals(BOE1-BOEn). A control part(80) judges whether an extension card is mounted on extension slots(S1-Sn,14) and outputs the pertinent output enable signals(BOE1-BOEn). The clock buffer(70) has a plurality of three phase buffers which are controlled by the output enable signals(BOE1-BOEn). A plurality of series termination resistances(R1-Rn) are connected to clock lines which are formed on the clock generating part(60) and the clock buffer(70). A plurality of series termination resistances(RT1-RTn) are connected to clock lines which are formed on the clock buffer(70) and the extension slots(S1-Sn).

Description

ELECTRO MAGNETIC INTERFERENCE PREVENTION APPARATUS

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electromagnetic interference preventing apparatus, and more particularly, to an electromagnetic interference preventing apparatus for preventing electromagnetic interference from occurring in a system using a clock signal .

At present, the occurrence of electromagnetic interference is inevitable in a computer system using a clock signal, an embedded control system, and other electronic devices.

EMI (Electro Magnetic Interference) refers to a phenomenon in which electromagnetic waves radiated directly from an electric or electronic device or electromagnetic waves conducted by the device cause interference to other devices. As the use of various electronic devices increases, electromagnetic interference generated from the electromagnetic wave interference due to the development of digital technology has caused a great problem due to mutual noise interference, mutual erroneous operation of precision electronic devices, and adverse effects on the human body. Is treated as an extremely important standard. The regulations that restrict the electromagnetic disturbance to a certain value or less are established and regulated internationally.

There are many causes of electromagnetic interference, but the most significant one is the clock signal used in the system or equipment. In order to suppress the electromagnetic wave radiation generated from the clock signal, the following methods have been proposed and used.

A transmission line effect occurs when the length of a clock line for providing a clock signal exceeds a certain length in the relationship between the frequency of the clock signal and the rise time of the clock signal. At this time, termination of the clock line is performed by exactly matching the impedance of the clock driver with the impedance of the clock line. In this way, it is theoretically possible to eliminate the occurrence of electromagnetic interference.

Termination methods include series termination, load termination, split termination, and RC termination. Although each problem exists, the fundamental problem is that impedance matching is practically impossible because the output impedance of the clock generating part is different between the rising edge and the falling edge. It is therefore inevitable that electromagnetic interference will occur in transmission lines that are not properly terminated.

On the other hand, in a system having an extension slot, the length of a clock line from a clock generating unit to an extension slot is long in most systems, so it must be treated as a termination line. However, the clock signal is always applied to all expansion slots regardless of whether the extension card is not installed in the expansion slot.

1 is a perspective view showing a general internal structure of a conventional computer system.

1, the internal structure of a conventional computer system 100 includes a power supply unit 8, a floppy disk drive (FDD) 20, a hard disk drive (HDD) 22, a main board 10, an extension slot 14 provided on the main board 10, a plurality of extension boards 16 inserted therein, , And a memory (18).

The main board 10 is a PCB (Printed Circuit Board) on which a plurality of semiconductor chips and various circuit elements are mounted, including a CPU (Central Processing Unit) 12. The expansion slot 14 is a slot into which additional devices necessary for the computer system 100, for example, a video board for outputting an image signal to a monitor, and the like are inserted.

2 is a block diagram showing a general circuit configuration of a conventional computer system.

As shown in FIG. 2, the general circuit configuration of a conventional computer system is configured as follows. A CPU 12, an expansion slot 14, various buses 24, 26 and 28, address and data buffers 30, 34, 32 and 36, a direct memory access controller 38, An address latch 40, a page register, a memory buffer 44 and memories 18 and 46, a keyboard controller 50, an interrupt controller an interrupt controller 52, a timer 54, a real time clock 56, and the like.

In the case of the expansion slot 14 configured in the computer system 100 as described above, the clock is supplied to the expansion slot 14. Since the length of the clock line supplied to the expansion slot 14 through the bus 26 is long, . However, regardless of whether the expansion card is not installed in the expansion slot, the clock signal is always applied to all expansion slots.

3 is a diagram for explaining a case where electromagnetic interference is generated in an open clock line.

3, when the clock signal is being applied from the clock generating unit 60 to the open clock line 62, the clock line 62 and the ground plane 64 cause a stand- A standing wave may be generated. That is, since the clock line 62 opened without a load serves as an antenna, there is a problem that a standing wave is generated and electromagnetic interference is generated.

An object of the present invention is to solve the above-mentioned problems, and it is an object of the present invention to provide a method and a system for controlling a path of a clock line supplied to an expansion slot, So that the occurrence of electromagnetic interference is minimized.

1 is a perspective view showing a general internal structure of a conventional computer system,

2 is a block diagram showing a general circuit configuration of a conventional computer system,

3 is a diagram for explaining a case where electromagnetic interference is generated in an open clock line,

4 is a detailed circuit diagram of an electromagnetic interference preventing device according to an embodiment of the present invention,

5 is a circuit diagram showing a case where an electromagnetic interference (EMI) device according to an embodiment of the present invention is installed in a computer system.

According to an aspect of the present invention, there is provided an electromagnetic interference preventing apparatus comprising: a clock generating unit generating a plurality of clock signals; A clock buffer for receiving the clock signal and controlling the input of a predetermined output enable signal to output a corresponding clock signal; And a controller for determining whether or not the expansion card is installed in the expansion slot and outputting the corresponding output enable signal.

In this embodiment, the clock buffer includes a plurality of three-phase buffers controlled by the output enable signal.

In this embodiment, the clock generating unit includes a plurality of continuous termination resistors connected to the respective clock lines formed in the clock generating unit and the clock buffer.

In this embodiment, the clock buffer includes a plurality of continuous termination resistors coupled to the respective clock lines configured in the clock buffer and the expansion slot.

Example

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a detailed circuit diagram of an electromagnetic interference preventing apparatus according to an embodiment of the present invention.

4, the electromagnetic interference preventing apparatus of the present invention mainly includes a clock generating unit 60, a clock buffer 70, and a control unit 80. The clock buffer 70 may include a plurality of three-phase buffers.

First, the clock signals (Clock1 to Clockn) generated in the clock generating unit 60 are provided to the expansion slots S1 to Sn, 14 through the clock buffer 70. FIG. The clock generating unit 60 and the clock buffer 70 are arranged as close to each other as possible so as not to exhibit the transmission line effect between the two clock lines and the clock generating unit 60 and the clock buffer 70, (R1 to Rn) for series termination.

The control unit 80 determines whether or not an expansion card (not shown) is installed in the expansion slots S1 to Sn, 14 and controls the clock buffer 80 so that only the corresponding clock signal is output. That is, the presence or absence of the expansion card is determined based on the card detection signals P11, P12 to Pn1, and Pn2 input through the expansion slots S1 to Sn and 14. And outputs the output enable signals BOE1 to BOEn to the clock buffer 70 to control the output of the corresponding clock signal.

The clock buffer 70 enables / disables the output of the clock signal output to the corresponding slot according to whether the output enable signals BOE1 to BOEn are active or not. Therefore, a clock signal is supplied to the expansion slots (S1 to Sn, 14) to which the expansion card is attached. Since the supply of the clock signal to the expansion slots S1 to Sn and 14 to which the expansion card is not attached is interrupted and the corresponding three-phase buffer of the clock buffer 70 maintains the tri-state, The effect of shortening the length can be obtained. Therefore, occurrence of electromagnetic interference can be prevented as much as possible.

On the other hand, in the case of a computer system, there are signals for indicating whether or not an expansion card is installed in each of the expansion slots S1 to Sn and 14, and the PRSTN1 # and PRSTN2 # signals are defined on the PCI bus. Table 1 shows the results.

PRSNT # 1 PRSNT2 # Expansion Configuration open open No expansion board ground open Expansion board mounting, 25 W open ground Expansion board mounting, 15 W ground ground Expansion board mounting, 7.5 W

In the case of the ISA bus, there is no signal indicating the existence of an expansion card. Therefore, the MASTER # signal is a signal that is not used well in the current AT system, so the MASTER # signal should be a signal Pn1 indicating whether a makeup card is present and the other signal Pn2 being pulled up or pulled down pull down.

In addition, a reserved pin or an unused pin, which is also reserved in the S bus, the VL bus, the micro channel bus, the Nu bus, and the other bus, is selected and set to the signals Pn1 and Pn2 indicating the presence or absence of the expansion card Can be used.

(RT1 to RTn) for the continuous termination can be inserted into the clock line between the output terminal of the clock signal and the clock signal input pin of each of the expansion slots (S1 to Sn, 14), or any one of RC, Apply one. Therefore, when the expansion card is mounted in the expansion slots S1 to Sn, the characteristic impedance of the clock line can be matched to minimize the occurrence of electromagnetic interference.

A case in which the electromagnetic interference prevention device as described above is installed in a computer system is shown in FIG. 5 of the accompanying drawings. When the electromagnetic interference prevention device is installed in the computer system as shown in FIG. 5, when the expansion card is not installed in the expansion slot 14, the supply of the clock is interrupted, so that the conventional electromagnetic waves are not generated.

According to the present invention, when the expansion card is mounted to determine whether or not the expansion card is mounted, the clock signal is normally supplied to the expansion slot. When the expansion card is not mounted, the supply of the clock signal is blocked. Thereby minimizing transmission line effects. Therefore, it is possible to obtain a cost saving effect by simplifying or eliminating the electromagnetic interference preventing devices added to the apparatus and the circuit to minimize the occurrence of electromagnetic interference and to prevent electromagnetic interference.

Claims (4)

A clock generating unit (60) for generating a plurality of clock signals; A clock buffer 70 for receiving the clock signal and controlling the input of predetermined output enable signals BOE1 to BOEn to output a corresponding clock signal; And a control unit (80) for determining whether or not an expansion card is installed in the expansion slots (S1 to Sn, 14) and outputting corresponding output enable signals (BOE1 to BOEn) 2. The apparatus of claim 1, wherein the clock buffer (70) comprises: a plurality of three-phase buffers controlled by the output enable signals (BOE1 to BOEn) The electromagnetic interference preventing apparatus according to claim 1, further comprising a plurality of continuous termination resistors (R1 to Rn) connected to the respective clock lines formed in the clock generating unit (60) and the clock buffer (70). The electromagnetic interference suppressor according to claim 1, further comprising a plurality of continuous termination resistors (RT1 to RTn) connected to the clock buffer (70) and each clock line formed in the expansion slots (S1 to Sn).