JPH03278214A - Hot-line inserting/extracting circuit - Google Patents

Abstract

PURPOSE:To efficiently execute the extension or eliminating work of circuits without exerting influence upon other circuit functions even when a printed board is inserted/extracted in a power ON state by using an hot-line inserting/ extracting circuit for a device having a bus line. CONSTITUTION:When a connector 8 is connected to the device, respective signals from the bus line 5, a power supply line 6 and a control line 7 are supplied to a CKT (main circuit) 3 to start the operation of the CKT 3. Since the operation of respective elements can not be forecasted immediately after starting the operation, a signal to be outputted from the CKT 3 to an IC 2 can not be forecasted. However, since no power is supplied to the IC 2 in the OFF state of a SW 4, the state is equivalent to the disconnection of the IC 2 to the bus line 5. After starting the normal operation of the CKT 3, i.e. after the lapse of a prescribed time from the detection of the insertion of the printed board 1 into the device, the SW 4 is automatically turned on and a normal signal is outputted to the bus line 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hot-swap circuit that allows a printed board on which a circuit is mounted to be inserted and removed while the device is powered on.

[Conventional technology]

In devices with bus lines, such as microprocessor-applied devices, if you try to add or remove circuits hanging from the bus line (by inserting or removing a printed board) while the power is on, the shock of inserting or removing the printed board will affect other circuits. Conventionally, the power has been turned off before adding or deleting circuits.

[Problem to be solved by the invention]

Once a device into which a printed circuit board has been inserted is put into service, it is generally very difficult to turn off the power in order to change a particular part without stopping the functions of other parts. Therefore, there is a need for a method that allows circuits (printed boards) to be inserted and removed while the power is on.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hot-swap technology that has not been previously available.

[Means to solve the problem]

The hot-swapping circuit of the present invention includes a printed circuit board that is connected to a live bus line and a power supply line through a connector.
connecting the power supply line to a main circuit via the connector and connecting it to a TTL integrated circuit via a switch circuit;
The bus line is connected to the main circuit via the connector and the TTL integrated circuit, and the switch circuit is turned on after a predetermined time has elapsed after the connector is inserted. Further, the present invention is characterized in that the TTL integrated circuit is of a normal type or a Schottky type.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the hot-swap circuit of the present invention, and FIGS. FIG. 7 is an equivalent circuit diagram showing a second example.

In Figure 1, 1 is a printed board that is inserted and removed from the device, 2 is a TTL integrated circuit (hereinafter referred to as an IC), 3 is a main circuit (hereinafter referred to as a CRT) for realizing the functions of the printed board 1, and 4 is a power supply supplied from the device. 5 is a bus line on the device side, 6 is a power line that supplies power from the device, 7 is a control line for CKT 3, and 8 is a bus line 5. Power supply m6. This is a connector that accommodates the control line 7.

FIG. 2 shows a typical equivalent circuit of the output stage of a normal type TTL integrated circuit. ~12 are NPN transistors (hereinafter referred to as QN), and 1.3 to 15 are resistors (hereinafter referred to as R).
), 16 is a diode (hereinafter referred to as D), 17 is an output terminal (hereinafter referred to as OT), 1.8 is a power supply terminal (hereinafter referred to as PW), and 19 is a ground (hereinafter referred to as G). In FIG. 2, when the power is off, the power line is equivalently regarded as ground, so in TTL integrated circuits other than the normal type, current may flow from the output terminal toward the power source.

However, the output stage of the normal type TTL integrated circuit in this example has D16 and Qs12, both of which are ○T17.
Since the polarity is oriented in the opposite direction, no current will flow even when the power is turned off.

In other words, when the power is turned off, there is no effect on the circuit connected to 0T17. This example utilizes the properties of this normal type TTL integrated circuit.

Now, consider the case where the printed board 1 is inserted into the device. The moment connector 8 is connected to the device, bus line 5. Power line 6. Each signal on the control line 7 is supplied and the CKT 3 starts operating. Immediately after the start of operation, the operation of each element cannot be predicted, so the signal from CKT3 to IC2 cannot be predicted. However, if SW4 is turned off at this time, no power is supplied to IC2, so its output is equivalent to not being connected to bus line 5.

After CKT 3 starts operating normally, that is, when a predetermined period of time has elapsed after detecting that the printed circuit board 1 was inserted into the device, SW4 is automatically turned on or turned on manually. As a result, a normal signal from CKT3 passes through IC2 and is output to bus line 5.

Figure 3 shows a typical equivalent circuit of the output stage of a Schottky type (S type) TTL integrated circuit, with QN20~2.
4 and R25 to R29. When the power is off, the power line is equivalently regarded as ground, so in TTL integrated circuits other than the Schottky type (S type), current may flow from the output terminal toward the power source.

However, in this example, the Schottky type (S type) T
The output stage of the TL integrated circuit has 0T through QN23 and 24.
Since diodes of opposite polarity are formed from 17 to PWI 8 and G19, no current flows even when the power is turned off. In other words, when the power is off, it is 0T.
It does not affect the circuit connected to 17.

This example utilizes the properties of this Schottky type (S type) TTL integrated circuit.

The operation when inserting the printed circuit board 1 into the apparatus is the same as the operation in the first example shown in FIG. 2, so the explanation will be omitted.

In other words, the first. According to the second example, once the power is turned on, IC2 does not output a signal to bus line 5 while the circuit is unstable, but outputs a signal to bus line 5 after the circuit starts operating stably. It can be output.

〔Effect of the invention〕

As explained above, by using the hot-line insertion/removal circuit according to the present invention in a device having a bus line, it is possible to insert/remove a printed circuit board while the power is on without affecting other circuit functions. This has the effect of making it possible to efficiently add or delete circuits.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the hot-swap circuit of the present invention, and FIGS. 2 and 3 show the first embodiment of the output stage of the TTL integrated circuit in FIG. FIG. 7 is an equivalent circuit diagram showing a second example. 1... Printed board, 2... TTL integrated circuit (IC)
, 3... Main circuit (CKT), 4... Switch turn l
¥8 (SW), 5...bus line, 6...power line,
7... Control line, 8... Connector, 10. ~12,2
0 to 24...NPN type transistor (QN), 13
．． ~15°25, ~29...Resistor (R>-1,6・
...Diode (D), 17...Output terminal (OT),
18...Power terminal (PW), 19...Ground (G
).

Claims (2)

[Claims] (1) In a printed board connected to a live bus line and a power supply line through a connector, the power supply line is connected to the main circuit through the connector and to a TTL integrated circuit through a switch circuit; The bus line is connected to the main circuit via the connector and the TTL integrated circuit, and the switch circuit is turned on after a predetermined time has elapsed after the connector is inserted. circuit. (2) The hot-swap circuit according to claim 1, wherein the TTL integrated circuit is either a normal type or a Schottky type.