JPH04101621A - Inserting and removing circuit for hot-line - Google Patents

Abstract

PURPOSE:To automatically short-circuit a charging resistance by detecting a supply voltage level to a logic circuit, and automatically controlling a short- circuit of a rush current limiting resistance by a relay contact. CONSTITUTION:When a package 10 is inserted to a DC power source 5 at a time t0, an output voltage E2 of a hot-line inserting and removing circuit is raised. If a chattering occurs at a time t1, an output voltage E2 of the hot-line inserting and removing circuit 6 is raised while repeating charging and discharging. However, a relay RL is not operated until it exceeds a first predetermined voltage (VZ1+VZ2+VBE1), and contacts rl1, rl2 remain broken. When the voltage E2 exceeds the predetermined voltage (VZ1+VZ2+VBE1) at a time t2, a transistor Q1 is turned ON, the relay RL and the transistor Q2 are driven, and hence the contacts rl are made. On the other hand, since a Zener diode Z1 is short-circuited when the transistor Q2 is turned ON, the contacts rl are operated without chattering.

Description

Detailed Description of the Invention Technical Field The present invention relates to a hot-swap circuit, and more particularly to a hot-swap circuit for solving various problems that occur when hot-swapping packages during maintenance of electronic devices such as computers. .

Prior Art FIG. 2 is a block diagram showing the positional relationship in an actual device of a hot-swap circuit 6, which is mounted between a DC power supply 5 and a logic circuit 7 that is a load of this power supply. The hot-swap circuit 6 is packaged together with the logic circuit 7, and this package 10 is electrically connected to the DC power supply 5 via the connector 8. Incidentally, the capacitor C is a bypass capacitor and operates in cooperation with the hot-swap circuit 6, as will be described later.

Conventionally, as an example of this type of hot-swap circuit 6, there is a circuit shown in FIG. 5, which includes a resistor R1 to limit the rush current when inserting a package, and a switch to short-circuit this after a certain period of time. It consisted of SW and bypass capacitor C. In other words, when the package is inserted with the switch SW open, charging of the bypass capacitor C starts through the resistor R1, and charging is completed for a certain period of time (for example, if 5τ-5CR1 second has elapsed, 99
．． After the battery was charged to 3%), the resistor R1 was short-circuited by manual switch operation.

Note that terminals 1 to 4 in FIG. 5 correspond to terminals ] to 4 in FIG. 2.

However, the above-mentioned conventional hot-swap circuit requires manual intervention, and there is a risk of erroneous operation. In other words, if a package is inserted with the switch SW turned on, an inrush current will occur, which will cause the DC power supply 5 to
This has the disadvantage that not only does it go down due to overcurrent, but it also damages the bypass capacitor C.

On the other hand, if the operation is continued with the switch SW turned off, the voltage drop caused by the resistor R1 will continue to be supplied to the logic circuit 7, resulting in malfunction of the logic circuit 7, especially intermittent failure. there were.

Another disadvantage is that the time from inserting the package to turning on the switch must be measured by a human, or the time from turning on to turning on must be adjusted depending on the capacitance of the bypass capacitor.

OBJECTS OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and its purpose is to provide a hot-swap circuit that can automatically short-circuit a charging resistor.

Composition of the Invention The hot-swap circuit according to the present invention is a hot-swap circuit that protects both devices when a voltage-supplied device is inserted into or removed from the power supply device in a live state where voltage is being supplied from the power supply device. A time constant circuit provided between the voltage supply device and the power supply device and comprising a capacitor and a charging resistor for the capacitor, and a switching device for short-circuiting or releasing the short-circuit between both ends of the charging resistor. a switching transistor that shorts one of the first and second Zener diodes; When the Zener voltage value exceeds the sum of the Zener voltage values caused by the second Zener diode, the switching means controls the short-circuiting of both ends of the charging resistor, and the switching transistor is turned on and the charging voltage value of the capacitor is short-circuited. and means for controlling release of the short circuit between both ends of the charging resistor by the switching means when the Zener voltage value of the Zener diode becomes lower than that of the other Zener diode.

Example Next, embodiments of the present invention will be described using the drawings.

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the hot-swap circuit according to the present invention, which is located before the logic circuit 7 shown in FIG. This makes it easy to insert and remove the wire into a live wire.

In FIG. 1, 6a is an NPN) transistor Ql,
A relay live circuit consisting of an electromagnetic relay RL driven by the collector output of this transistor Ql, a base resistor R4, and a wheeling diode DI, 6b is an inrush current limiting resistor R1, and a relay RL that short-circuits both ends of this resistor R1. Inrush current limiting circuit consisting of contact point ``g'' and 6c is a Zener diode Z connected in series with 11.
1 and Z2, resistor R2, PNP transistor Q2 that shorts Zener diode Z1, and this transistor Q
This is a reference voltage circuit consisting of two base bias resistors R5 and R3. In other words, the hot-swap circuit 6 in FIG. 2 corresponds to these 6a to 6c. Further, 1 to 4 correspond to ends T] to 4 in FIG. 2, respectively.

Next, the operations shown in FIGS. 1 and 2 will be explained with reference to FIG. 3, which shows a time chart during hot insertion and removal.

First, at time to, the package 10 including the hot-swap circuit 6
When is inserted into the DC power supply 5 via the connector 8, charging of the bypass capacitor C is started through the inrush current limiting resistor R1. Then, as shown in FIG. 3, the output voltage E2 of the hot-swap circuit increases with the time constant of the capacitor C and the resistor R1 for charging the capacitor C and limiting the rush current.

By the way, since package replacement during maintenance is generally done manually, chattering in the connector 8 is bound to occur. Therefore, here, chattering (
A case in which the period TO) occurs will be explained. At this time, the input voltage E1 of the hot-swap circuit 6 has a pulse-like waveform as shown in FIG. , rises through repeated charging and discharging.

However, the zener 11i of the zener diode Zl and Z2
voltages VZl and VZ2 and the voltages VZl and VZ2 and the voltage of transistor Ql
Until the first specified voltage VZI+ VZ2+ VBEI determined by the emitter voltage VBEI is exceeded (time t
O~t2), transistor Q1 remains off.

Therefore, relay RL also does not operate and contacts rg1 and r
g2 remains broken.

Then, at time t2, the output voltage E2 becomes the first specified voltage V.
Z1+ V Z2+ V BIEI is exceeded, transistor Ql turns on, relay RL and transistor Q
2, contacts r and Q are made. Contact “g”
By making this, both ends of the inrush current limiting resistor R1 are short-circuited, and the output voltage of the DC current #5 is directly applied to the logic circuit 7.

On the other hand, since the Zener diode Zl is short-circuited by turning on the transistor Q2, the on-off characteristic, which is the input/output characteristic of the relay drive circuit 6a, has a hysteresis characteristic as shown in FIG. therefore,
As shown in FIG. 3, the contact rΩ can operate (break-make) without chattering.

That is, referring to FIG. 4, in order for the relay contact "g" to short-circuit both ends of the inrush current limiting resistor R1 to change from the break state to the make state, the output voltage E must be
2, that is, the charging voltage of capacitor C is VZI + VZ
The voltage value of 2+ VnEI must be exceeded. On the other hand, in order for relay contact "9 to change from the make state to the break state, the charging voltage of capacitor C must be V
It must be lower than the voltage value of Z2 + V CIE24- V BEI.

Therefore, chattering of the relay contact rΩ during insertion and removal can be effectively prevented.

As described above, the logic circuit performs a predetermined operation when the contact "g" is in the make state due to the package insertion operation.

Next, the case where the package is removed at time t3 will be explained. At this time as well, due to manual intervention, chattering (period TI) occurs in the connector 8 as shown in FIG. The input terminal E1 of the hot-swap circuit has a pulse-like waveform as in the case of period TO, but its output voltage E2 falls while repeating charging and discharging due to the time constant of resistor R1 and capacitor C. . However, due to the above-mentioned hysteresis characteristic, the Zener voltage VZ2 of the Zener diode Z2 and the collector-emitter voltage Ver72 of the transistor Q2
and the heath-emitter voltage VnEI of transistor Q1
The second specified voltage VZ2+ V CIE2 determined by
+V rllll (at time t3-t4)
), h transistor Q1 remains on and drives relay RL, and contact ``g'' remains closed.

Then, at time t4, the output voltage E2 reaches the second specified voltage VZ.
When 2+VCl and 2+VBl are turned F, the transistor Ql turns off, so the relay RL stops moving. Therefore, due to the hysteresis characteristic shown in FIG. 4, the contact rl breaks and returns to the initial state without causing chattering.

Note that in FIG. 1, the diode DI is the transistor Q.
This is a wheeling diode for returning the excitation current flowing through relay RL when relay RL is turned off. Also, the resistance R
3 is a bypass resistor for preventing the transistor Q1 from being erroneously turned on due to the leakage current of the Zener diode Z1.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the present invention detects the supply voltage level to a logic circuit and automatically controls the short circuit between both ends of an inrush current limiting resistor using a relay contact, thereby eliminating the need for human intervention. First, problems caused by erroneous operations can be eliminated, and the time required to short-circuit the inrush current control resistor can be made independent of the capacitance of the bypass capacitor. Further, by specifying hysteresis in the make and break operations of the relay, there is an effect that the logic circuit is not affected by chattering at the connector section during insertion and removal (malfunctions due to noise, etc.).

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a hot-swap circuit according to an embodiment of the present invention;
Figure 2 is a block diagram showing the configuration of an electronic device package including a hot-swap circuit, Figure 3 is a time chart showing changes in input voltage and output voltage during insertion and removal, and Figure 4 is a diagram of the inrush current limiting resistor. A characteristic diagram showing the make operation and break operation of the relay contact for short circuit control, and FIG. 5 is a circuit diagram of a conventional hot-swap circuit. Explanation of symbols of main parts C...Capacitor R1-R5...Resistor RL...Relay rD...Relay contact Ql, Q2...・Transistor Zl, Z2・
...Zena diode Ganto Ibaraki NEC'f+

Claims (1)

[Claims] (1) A hot-line insertion/extraction circuit that protects both devices when a voltage-supplied device is inserted into or removed from the power supply device in a live-line state where voltage is being supplied from the power supply device, the voltage-supplied device and the power supply device, a time constant circuit consisting of a capacitor and a charging resistor for the capacitor, a switching means for short-circuiting or releasing the short-circuit between both ends of the charging resistor, and a first circuit connected in series with each other. and second
a Zener diode, a switching transistor that shorts one of the first and second Zener diodes, and a charging voltage value of the capacitor that is set to the first and second
means for controlling the short-circuiting of both ends of the charging resistor by the switching means when the sum of the Zener voltage values due to the Zener diodes exceeds the sum of the Zener voltage values caused by the Zener diodes; and means for controlling the switching transistor to be turned on; and means for controlling release of the short circuit between both ends of the charging resistor by the switching means when the Zener voltage value of the Zener diode becomes lower than the Zener voltage value of the Zener diode.