JP3022748B2 - Precharge circuit for active device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precharge circuit for a power supply circuit for an active device, which applies a precharge voltage to an external circuit to be actively inserted and removed and then applies a main voltage to the external circuit. About.

[0002]

2. Description of the Related Art When an external circuit 1, such as a PC card, is inserted into or removed from an apparatus 2, such as a computer, through an ordered connector 2, a power supply voltage and other various signals are applied as shown in FIG. (Hereinafter referred to as active insertion and removal) in some cases.

[0003] The ordered connector 2 has a plurality of terminals 2a to 2d.
A power supply capacitor C and some ICs are connected to these various terminals. When the external circuit 1 is inserted, first, the precharge terminal 2b and the ground terminal 2d are connected, and the precharge The voltage Vp is applied. next,
When the main voltage terminal 2a and the signal terminal 2c are connected, the main voltage V
m is applied and the signal S is input.

The precharge voltage Vp is supplied from a precharge circuit provided in a power supply circuit, which will be described later, of the device (hereinafter, referred to as an active device) 3. From this precharge circuit, a relatively small precharge current is supplied. Then, the power supply capacitor C is charged. This precharge circuit suppresses noise generated due to a steep charging current entering the power supply capacitor C during charging, and protects the pins of the connector 2 from excessive charging current.

FIG. 8 shows a power supply circuit 4 ′ of the activation device 3.
The power supply circuit 4 'is composed of a main voltage circuit 4a and a precharge voltage circuit 4b', and is provided with a terminal for outputting the main voltage Vm and the precharge voltage Vp and a ground terminal. The main voltage Vm and the precharge voltage Vp are output to the circuit 1.

The main voltage circuit 4a includes resistors R1 and R2 for dividing the main voltage Vm, an error amplifier AMP1 for detecting and amplifying an error of the voltage divided by the resistors R1 and R2 with respect to the reference voltage Vref1, and This error amplifier AM
A main voltage control circuit CNT1 that controls the main voltage Vm based on the output of P1 and outputs the same through circuit elements such as the choke coil L1.

The precharge circuit 4b 'has substantially the same configuration as the main voltage circuit 4a and operates in a similar manner. In other words, the precharge circuit 4b 'outputs the precharge voltage Vp
R3 and R4 for dividing the voltage, and these resistors R3 and R4
4, an error amplifier AMP2 'for detecting and amplifying an error with respect to the reference voltage Vref2', and a precharge voltage Vp is controlled based on the output of the error amplifier AMP2 'to control the choke coil L2 and the like. And a precharge voltage control circuit CNT2 that outputs via a circuit element. Further, a diode D for protecting the main voltage circuit 4a from a reverse bias is provided.

Here, reference voltages Vref1 and Vref
2 'is set to a constant value to output a predetermined main voltage Vm and a precharge voltage Vp.

As shown in FIG. 9, the precharge voltage Vp is set lower than the main voltage Vm so that a relatively small precharge current flows.

[0010]

In the precharge circuit for an active device as described above, the main voltage Vm drops due to a load fluctuation of the external circuit 1 during or after the active insertion of the external circuit 1. Then, the main voltage Vm becomes lower than the precharge voltage Vp, and power to the external circuit 1 is supplied from the precharge circuit 4b '(hereinafter, referred to as a reverse mode).

For this reason, the precharge circuit 4b 'must be provided with high output and measures against heat generation, which leads to an increase in size and cost of the device.

In order to prevent this, as shown in FIG. 10, the voltage difference A between the main voltage Vm and the precharge voltage Vp must be set somewhat larger in advance in anticipation of the drop of the main voltage Vm and variation in accuracy. There was a problem that did not become.

If the voltage difference A is set to a somewhat large value, the pre-charge voltage Vp is too low, causing a problem in the operation of the device when the ordered connector is connected halfway. The precharge output characteristics required from the external circuit 1 could not be sufficiently satisfied.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to ensure a substantially equal precharge voltage slightly smaller than a main voltage while reliably preventing a reverse rotation mode. An object of the present invention is to provide a precharge circuit for an active device.

[0015]

In order to achieve the above object, in the precharge circuit for an active device according to the present invention, when power is supplied to an external circuit which is actively inserted and removed, a precharge voltage is applied to the external circuit. A pre-charge circuit of an activation device power supply circuit for applying a main voltage after the application; a main voltage detection means for detecting the main voltage; a pre-charge voltage detection means for detecting the pre-charge voltage; Error detection means for detecting an error of the output signal of the precharge voltage detection means with respect to the output signal of the voltage detection means, wherein the precharge voltage is controlled based on the output signal of the error detection means.

[0016]

The precharge voltage is controlled based on an output signal of the error detection means for detecting an error of an output signal of the precharge voltage detection means with respect to an output signal of the main voltage detection means. The precharge voltage is controlled. Therefore, even if the main voltage fluctuates, the precharge voltage also fluctuates in synchronization with the main voltage, so that it is possible to reliably prevent the precharge voltage from becoming higher than the main voltage and supplying power from the precharge circuit to the external circuit. . For this reason, the precharge voltage can be set to a substantially equal voltage that is slightly smaller than the main voltage.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a precharge circuit for an active device according to the present invention will be described with reference to FIGS.

FIG. 1 shows a power supply circuit diagram including an active device precharge circuit 4b of the present embodiment, which differs from the conventional configuration shown in FIG. 8 in the following points.

In the conventional circuit shown in FIG. 8, the reference voltage Vref2 'of the error detecting means AMP2' is fixed. In this embodiment, however, the reference voltage is applied to the main voltage Vm by the resistors R1 'and R2'. It is a divided voltage.

Except for the above differences, the configuration is basically the same as that of the conventional example shown in FIG. 8, and the same parts are denoted by the same reference numerals, description thereof will be omitted, and differences will be mainly described.

In FIG. 1, as described above, the reference voltage Vref2 of the precharge voltage circuit 4b changes the main voltage Vm to the resistance R
Since the voltage is divided by 1 'and R2', the precharge voltage Vp is controlled based on the main voltage Vm. Therefore, even if the main voltage Vm fluctuates, the precharge voltage Vp also fluctuates in synchronization with the fluctuation.

As a result, as shown in FIG. 2, even if the main voltage Vm drops due to a load change or the like, the precharge voltage Vp also drops synchronously. Therefore, in order to prevent the device from falling into the reverse mode as in the prior art, the main voltage V
There is no need to set a large voltage difference A between the main voltage Vm and the precharge voltage Vp in anticipation of the drop of m. Therefore, as shown in FIG. 3, the voltage difference A can be reduced by at least the drop of the main voltage Vm as compared with the related art, and the precharge voltage Vp can be set to be substantially equal to the main voltage Vm, which is slightly smaller.

Therefore, a high-precision precharge voltage V
It is possible to satisfy the precharge output characteristics required from an external circuit, for example, to output p.

Further, when used in a device having a large tolerance in voltage accuracy, the impedance of the power supply line of the external circuit that is hot-swapped can be increased, so that, for example, the wiring pattern can be made thinner or the IC inside the external circuit can be connected to the input terminal. It becomes possible to arrange it in a remote place.

Here, the precharge voltage Vp is changed to the main voltage V
The variation characteristic of the precharge voltage Vp with respect to the variation of the main voltage Vm when the voltage was set to be substantially the same as that of m was confirmed. As shown in FIG. 4, the loads A and B are connected to the power supply circuit 4, the main voltage Vm is applied to the load A, the precharge voltage Vp is applied to the load B, and the steps shown in FIG. A current Im having a shape like that shown in FIG. As a result, as shown in FIG. 6, the precharge voltage Vp also fluctuates in accordance with the fluctuation of the main voltage Vm, and the precharge voltage Vp is set to a substantially equal voltage slightly smaller than the main voltage Vm. However, it was confirmed that the reverse mode did not occur.

The present invention can be applied not only to a PC card or the like which is directly inserted and removed as an external circuit, but also to an external circuit which is indirectly inserted and removed via a relay cable or the like.

[0027]

As described above, in the precharge circuit for an active device according to the present invention, a precharge voltage substantially equal to the main voltage, which is slightly smaller than the main voltage while reliably preventing the inversion mode, is prevented. And a highly accurate precharge output can be obtained.

Further, since it is possible to surely prevent the reversal mode from being entered, it is not necessary to take measures for increasing the output and generating heat in the precharge circuit, thereby making it possible to prevent an increase in size and cost.

[Brief description of the drawings]

FIG. 1 is a power circuit diagram including a precharge circuit for an active device according to an embodiment of the present invention.

FIG. 2 is an operation characteristic diagram showing a change in a precharge voltage Vp with respect to a change in a main voltage Vm of a precharge circuit for an activation device according to an embodiment of the present invention.

FIG. 3 shows a precharge voltage Vp with respect to a main voltage Vm of an active device precharge circuit according to an embodiment of the present invention;
5 is an operation characteristic diagram showing a voltage difference A of FIG.

FIG. 4 is a block circuit diagram showing a state in which loads A and B are connected to a power supply circuit including a precharge circuit for an active device according to one embodiment of the present invention.

FIG. 5 is an operation characteristic diagram showing that a current Im is caused to flow to a load A in FIG. 4 in a stepwise manner.

6 is an operation characteristic diagram showing a change in a precharge voltage Vp when a main voltage Vm is applied to a load A in FIG. 4;

FIG. 7 is a block circuit diagram showing an external circuit which is hot-swappable according to a conventional example and an embodiment of the present invention.

FIG. 8 is a power supply circuit diagram including a precharge circuit for an active device according to a conventional example.

FIG. 9 shows a main voltage V of a conventional precharge circuit for an activation device.
FIG. 9 is an operation characteristic diagram showing a voltage difference A of a precharge voltage Vp with respect to m.

FIG. 10 is an operation characteristic diagram showing a change in precharge voltage Vp with respect to a change in main voltage Vm of a conventional precharge circuit for an activation device.

[Explanation of symbols]

 Reference Signs List 1 external circuit 4 active device power supply circuit 4b precharge circuit R1 to R4 resistance R1 ', R2' resistance AMP1, 2 error amplifier CNT1 main voltage control circuit CNT2 precharge voltage control circuit D diode Vm main voltage Vp precharge voltage Vref1, 2, 2 'reference voltage

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Kamada 5-36-11 Shimbashi, Minato-ku, Tokyo Inside Iwaki Electronics Co., Ltd. (56) References JP-A-4-157514 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) G06F 3/00

Claims (1)

(57) [Claims] When supplying power to an external circuit (1) to be actively inserted and removed, a precharge voltage is applied to the external circuit (1), and then a power supply circuit (4) for an active device for applying a main voltage is provided. A precharge circuit (4b), a main voltage detection means (R2 ') for detecting the main voltage, and a precharge voltage detection means (R4) for detecting the precharge voltage
And an error detection means (AMP2) for detecting an error of an output signal of the precharge voltage detection means (R4) with respect to an output signal of the main voltage detection means (R2 '). A precharge circuit for an active device, wherein the precharge voltage is controlled based on an output signal.