JP2758705B2 - Hot-swap circuit - Google Patents

Description

Description: 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 a package during maintenance of an electronic device such as a computer. .

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

Conventionally, an example of this kind of hot-swap circuit 6 is a circuit shown in FIG. 5, which includes a resistor R1 for limiting an inrush current when a package is inserted, and a switch for short-circuiting the same after a predetermined time. SW and a bypass capacitor C. That is, when the package is inserted with the switch SW opened, the charging of the bypass capacitor C is started through the resistor R1, and the charging is completed for a certain period of time (for example, up to 99.3% if 5τ = 5CR1 seconds later). After being charged, the resistor R1 was short-circuited by a manual switch operation.

The terminals 1 to 4 correspond to the terminals 1 to 4 in FIG. 2, respectively.

However, the conventional hot-swap circuit described above has a risk of erroneous operation since human intervention is always required. That is, if the package is inserted while the switch SW is turned on, an inrush current is generated.
However, there is a drawback that not only does it go down due to overcurrent, but also damages the bypass capacitor C.

On the other hand, if the operation is performed with the switch SW turned off, the power supply that has caused a voltage drop due to the resistor R1 continues to be supplied to the logic circuit 7, which causes a malfunction of the logic circuit 7, especially an intermittent failure. there were.

Further, the time from when the package is inserted to when the switch is turned on must be measured by a human, but there is a disadvantage that the time until the switch is turned on must be adjusted according to the size of the bypass capacitor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional disadvantages, and an object of the present invention is to provide a hot-swap circuit capable of automatically short-circuiting a charging resistor.

A 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 hot-line state where a voltage is supplied from a power supply device. A time constant circuit provided between the voltage supply device and the power supply device, the capacitor including a capacitor and a charging resistor for charging the capacitor with the voltage; and a short circuit at both ends of the charging resistor. An electromagnetic relay for canceling the short circuit, and a control means for receiving the charging voltage value of the capacitor as an input, having a hysteresis characteristic in a relationship between the input and the output, and controlling the electromagnetic relay with the output, the electromagnetic relay comprising: The first contact is connected in parallel to both ends of the charging resistor, and one end of the coil is connected to a terminal of the charging resistor on the power supply device side; A series circuit of a zener diode and a second contact of the electromagnetic relay; a second zener diode connected in parallel with the series circuit and having a higher zener voltage than the first zener diode; and the second contact A control resistor having one end connected to a connection point of the second Zener diode, a base connected to the other end of the control resistor, a collector connected to the other end of the coil of the electromagnetic relay, and an emitter connected to the ground point. A transistor which is connected to each other and performs an on / off operation as the output with respect to the input.

Embodiment Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing a configuration of an embodiment of a hot-swap circuit according to the present invention, and a logic circuit 7 shown in FIG.
And facilitates insertion and removal of the DC power supply 5 from the live line via the connector 8.

In FIG. 1, 6a is a relay drive circuit including an NPN transistor Q1, an electromagnetic relay RL driven by the collector output of the transistor Q1, a base resistor R3, and a wheeling diode D1, and 6b is an inrush current limiting resistor R1.
A rush current limiting circuit comprising a first make contact rl1 of the relay RL for short-circuiting both ends of the resistor R1, 6c a first reference voltage circuit comprising a zener diode Z1 and a resistor R2, 6d
Is the second make contact of zener diode Z2 and relay RL,
This is a second reference voltage circuit comprising a series connection circuit with rl2. That is, the hot-swap circuit 6 in FIG.
It corresponds to. 1 to 4 correspond to the terminals 1 to 4 in FIG. 2, respectively.

Next, the operation of FIGS. 1 and 2 will be described with reference to FIG. 3 showing a time chart at the time of hot-swap.

First, when the package 10 including the hot-swap circuit 6 is inserted into the DC power supply 5 via the connector 8 at time t0, charging of the bypass capacitor C through the inrush current limiting resistor R1 is started. Then, as shown in FIG. 3, the output voltage E2 of the hot-swap circuit rises 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, generally, package replacement at the time of maintenance is performed manually, so chattering at the connector 8 always occurs. Therefore, here, a case where chattering (period T0) occurs at time t1 will be described. At this time, the input voltage E1 of the hot-swap circuit 6 has a pulse-like waveform as shown in FIG.
Due to the time constant of the capacitor C and the capacitor C, the charge and discharge increase while repeating charging and discharging.

However, the transistor Q1 remains off until the voltage exceeds the first specified voltage VZ1 + VBE1 determined by the Zener voltage VZ1 of the Zener diode Z1 and the base-emitter voltage VBE1 of the transistor Q1 (time t0 to t2). Therefore, the relay RL also does not operate, and the contacts rl1 and rl2 remain broken.

Then, at time t2, the output voltage E2 becomes the first specified voltage VZ1 +
When VBE1 is exceeded, transistor Q1 turns on and relay R
To drive L, contacts rl1 and rl2 make. Contact r
Both ends of the inrush current limiting resistor R1 are short-circuited by the make of l1, and the output voltage of the DC power supply 5 is directly applied to the logic circuit 7.

On the other hand, the Zener diodes Z1 and Z
And 2 are connected in parallel. Here, since these zener voltages are selected so that VZ1> VZ2, the relay drive circuit 6a
The on / off characteristic, which is the input / output characteristic, has a hysteresis characteristic as shown in FIG. Therefore, as shown in FIG. 3, the contacts rl1 and rl2 can operate (break → make) without chattering.

That is, referring to FIG. 4, in order for the relay contact rl1 for short-circuiting both ends of the inrush current limiting resistor R1 to change from the break state to the make state, the output voltage E1 is required.
2, that is, the charging voltage of the capacitor C must exceed the voltage value of VZ1 + VBE1. On the other hand, in order for the relay contact rl1 to change from the make state to the break state, the charged voltage of the capacitor C must be lower than the voltage value of VZ2 + VBE1. Therefore, chattering of the relay contact rl1 at the time of insertion and removal can be effectively prevented.

As described above, the logic circuit performs a predetermined operation in the make state of the contacts rl1 and rl2 due to the package insertion operation.

Next, a case where the package is removed at time t3 will be described. At this time, since human intervention also occurs, chattering (period T1) occurs in the connector 8 as shown in FIG. The input voltage E1 of the hot-swap circuit has a pulse-like waveform as in the case of the period T0, but its output voltage E2 is equal to the resistance R1.
The charge and discharge of the capacitor C and the capacitor C are repeated while repeating the charging and discharging based on the time constant. However, due to the above-described hysteresis characteristic, until the voltage falls below the second specified voltage VZ2 + VBE1 determined by the Zener voltage VZ2 of the Zener diode Z2 and the base-emitter voltage VBE1 of the transistor Q1 (at time t3).
Tt4), the transistor Q1 keeps on and drives the relay RL, and the contacts rl1 and rl2 remain made.

Then, at time t4, the output voltage E2 becomes the second specified voltage VZ2 +
When the voltage falls below VBE1, the transistor Q1 is turned off and the relay RL does not operate. Therefore, the contacts rl1 and rl2
Because of the hysteresis characteristic shown in FIG. 4, break occurs without chattering and returns to the initial state.

In FIG. 1, the diode D1 is connected to the transistor Q1.
Is a wheeling diode for returning the exciting current flowing through the relay RL when is turned off. The resistance R3 is
The leakage current of the Zener diode Z1 causes the transistor Q1
Is a bypass resistor for preventing accidentally turning on.

As described above, the present invention requires no manual intervention by detecting the supply voltage level to the logic circuit and automatically performing short-circuit control at both ends of the inrush current limiting resistor by the relay contact. In addition, it is possible to eliminate the problem caused by the erroneous operation, and to make the time until the inrush current control resistor is short-circuited independent of the size of the bypass capacitor. Furthermore, by giving the hysteresis to the make and break operations of the relay, there is an effect that adverse effects (malfunctions due to noise, etc.) due to chattering in the connector portion at the time of insertion / removal are not given to the logic circuit.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a hot-swap circuit according to an embodiment of the present invention,
FIG. 2 is a block diagram showing a configuration of an electronic device package including a hot-swap circuit, FIG. 3 is a time chart showing changes in input voltage and output voltage at the time of insertion and removal, and FIG. FIG. 5 is a characteristic diagram showing a make operation and a break operation of a short-circuit control relay contact, and FIG. 5 is a circuit diagram of a conventional hot-swap circuit. Explanation of Signs of Main Parts C: Capacitor R1 to R3: Resistance RL: Relay rl1, rl2: Relay contact Q1: Transistor Z1, Z2: Zener diode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02H 9/02 H02J 1/00 H05K 7/14 G06F 1/00-3/00

Claims (1)

(57) [Claims] 1. A live-line insertion / extraction circuit for protecting a voltage-supplied device when the voltage-supplied device is inserted into or removed from the power-supply device in a live-line state where a voltage is supplied from the power-supply device. Provided between the device and the power supply,
A time constant circuit comprising a capacitor and a charging resistor for charging the capacitor with the voltage, an electromagnetic relay for short-circuiting or canceling the short-circuit at both ends of the charging resistor, and a charging voltage value of the capacitor as an input. The relationship between the input and the output has a hysteresis characteristic, and includes control means for controlling the electromagnetic relay with the output.The electromagnetic relay has a first contact connected in parallel to both ends of the charging resistor. One end of the coil is connected to a terminal of the charging resistor on the power supply device side, and the control means is connected in parallel with a series circuit of a first zener diode and a second contact of the electromagnetic relay; and A second Zener diode having a higher Zener voltage than the first Zener diode, and a connection point between the second contact and the second Zener diode One end is connected to a control resistor, the base is connected to the other end of the control resistor, the collector is connected to the other end of the coil of the electromagnetic relay, and the emitter is connected to the ground point.・
A hot-swap circuit comprising a transistor performing an off operation.