JP2007304986A - Overcurrent control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid breakdown of a power source module by inrush current when the power is turned on without designing the power source module with over specification and without designing the overcurrent protection characteristic, in an overcurrent control circuit. <P>SOLUTION: A selection signal 6 from a module 3 is supplied to a current detection resistance selecting circuit 8 existing in each slot of a base board 1. The current detection resistance selecting circuit 8 detects current 7 supplied to the module 3 by switching and using the current detection resistance. The value of the detected current 7 is transmitted to a current control circuit 10 through a current detection result signal 9. The current control circuit 10, based on the current detection result signal 9, suppresses the current 7 so that current more than the electric current value shown by the selection signal 6 does not flow. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an overcurrent control circuit. In particular, the present invention relates to an overcurrent control circuit that includes a power supply circuit and a plurality of other circuits to which a power supply current is supplied from the power supply circuit, and is suitable for a base board of a programmable controller.

  Conventionally, for overcurrent control in a programmable controller equipped with a power supply module, the power supply module mounted on the base board has an overcurrent protection function, and this protection function collects the power supply current supplied to other modules. There was something to limit. Alternatively, each module has a component for protecting from overcurrent (for example, a fuse, a fuse resistor, etc.) to individually limit the power supply current.

  In this application, NRI search formula = (programmable controller) * ((mother board) + (base board) + (back board)) * (protection) was used to conduct a prior art search. I didn't find it.

  In the base board of a programmable controller in which the power module has an overcurrent protection function, for example, when a CPU module, an IO module, or a functional module is mounted, an electrolytic capacitor for smoothing the power included in each module when the power module is turned on Charges rapidly. For this reason, the overcurrent protection function of the power supply module is activated by an inrush current that is an excessively large current flowing through each module. As a result of this protection function, the power supply module stops functioning for safety. There was a case. In order to avoid such an outage, the power supply module must be designed with over-spec with a margin higher than the normally required rating, and must respond to an inrush current that is a sudden load. Or it was necessary to devise the overcurrent protection characteristics of the power supply module.

  The purpose of the present invention is to avoid overcurrent that can avoid power module malfunction due to inrush current when power is turned on without designing the power supply module with overspec and without having to devise overcurrent protection characteristics. It is to provide a control circuit.

  One aspect of the circuit device according to the present invention to achieve the above object includes a power supply circuit having an overcurrent protection function for limiting a power supply current to be output, and each slot provided in a power supply line. In an overcurrent control circuit comprising a plurality of other circuits to which the power supply current is supplied, information for acquiring consumption current information about individual power supply currents consumed by the plurality of other circuits for each slot Collecting means and current control means provided corresponding to each of the slots, each of which suppresses the individual power supply current to other corresponding circuits based on the current consumption information to prevent overcurrent A plurality of current control means.

  In another aspect of the circuit device according to the present invention, the current control unit detects the individual power source current based on the consumption current information, and controls the current so as not to flow more than the detected current. May be provided.

  Furthermore, in another aspect of the circuit device according to the present invention, the information collecting means includes an error detection resistor provided in the other circuit and an error signal output when a voltage across the resistor exceeds a predetermined value. Detecting means, and the current control means controls the individual power supply current so as not to exceed a predetermined value based on the signal.

(Function)
According to the circuit device according to the present invention of each aspect described above, the power supply current from the power supply circuit is supplied to the plurality of other circuits based on the current consumption information about the individual power supply current consumed by the plurality of other circuits. Since the power supply current is suppressed for each slot, it is possible to operate so that the overcurrent protection function of the power supply circuit does not work against a transient load increase.

FIG. 1 is a functional block diagram of an overcurrent control circuit according to the present invention.
A power supply module 2, a CPU module 3a, an IO module 3b, a functional module 3c, and other modules (not shown) are mounted on the base board 1, which is an overcurrent control circuit according to the present invention. The power supply module 2 has an overcurrent protection function. The number of modules mounted on the base board 1 differs for each product, and what is shown here is an example and does not limit the present invention. The power supply current generated by the power supply module 2 is supplied from the power supply line 4 to the modules 3a, 3b, 3c,. Each slot is provided with current control circuits 5a, 5b, 5c,... Corresponding to the modules 3a, 3b, 3c,.

  The current control circuits 5a, 5b, 5c,... Acquire current consumption information 6a, 6b, 6c,. These pieces of information are information about individual power supply currents consumed by the modules 3a, 3b, 3c,. The current control circuits 5a, 5b, 5c,... Control and suppress the currents 7a, 7b, 7c,... That supply each individual power source current to each module based on the consumption current information 6a, 6b, 6c,. It operates to prevent overcurrent independently for each module.

  As a result, when the power supply module 2 is turned on, the power supply module 2 can cope with a temporary load increase as in the case where the electrolytic capacitor for smoothing the power supply included in each of the modules 3a, 3b, 3c,. The overcurrent protection function that the power module has does not work, and the power supply module 2 has the maximum capability.

(Embodiment 1)
FIG. 2 is a circuit diagram of an overcurrent control circuit according to Embodiment 1 in which the above functions provided by the present invention are implemented. In the present embodiment, the above functions of the present invention are implemented by a current detection resistor selection method, and can be used for a programmable controller. In FIG. 2, the above function is shown only for one module 3 other than the module 2, and illustration of the other modules is omitted. In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is simplified.

  In FIG. 2, a selection signal 6 from a module 3 having an electrolytic capacitor or the like in a power supply line for smoothing is supplied as current consumption information to a current detection resistor selection circuit 8 in each slot provided in the base board 1. The current detection resistor selection circuit 8 supplied with the selection signal 6 detects the current 7 supplied to the module 3 by switching the current detection resistor. The value of the detected current 7 is transmitted to the current control circuit 10 by the current detection result signal 9. Based on the current detection result signal 9, the current control circuit 10 performs control to suppress the current 7 so that no current exceeding the current value indicated by the selection signal 6 that is current consumption information from the module 3 flows.

  As the current control circuit 10, a generally known constant current circuit can be used.

  According to the present embodiment, the inrush current, which is the charging current of the built-in power supply line capacitor flowing in each module when the power supply module is turned on, is set for each module with a value set by the selection signal from each module to the base board. As shown in FIG. FIG. 4 shows an inrush current that is not suppressed for comparison with the conventional circuit.

  Therefore, when the power supply of the power supply module is turned on, it can be avoided that the overcurrent protection function of the power supply module works against the temporary load increase and the function is stopped. In addition, since the inrush current of each module can be suppressed to a value suitable for each module, it is possible to allow for a surplus in the inrush current simply by confirming that the total current consumption of each module does not exceed the rated current capacity of the power supply module. In addition, it is possible to estimate the current of the programmable controller system. In the design of the power supply module, it is unnecessary to design the overcurrent protection function with an allowance exceeding the rating, which can contribute to the cost reduction and size reduction of the circuit device.

(Embodiment 2)
FIG. 5 is a circuit diagram of an overcurrent control circuit according to a second embodiment in which the above function provided by the present invention is implemented. In this embodiment, the above-described functions of the present invention are implemented by an error amplifier system, and an error amplifier signal is received from each module and used for control. It can be used for a programmable controller. In FIG. 5, the above function is shown only for one module 3 other than the module 2, and illustration of the other modules is omitted. In FIG. 5, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is simplified.

  The module 3 includes a current detection resistor 11 on a power supply line to the internal circuit 14, and a potential across the current detection resistor 11 is input to an error amplifier 12 configured by a photocoupler. The error amplifier 12 causes a current proportional to the potential at both ends detected by the current detection resistor 11 to flow through the base board 1. The current detection circuit including the current detection resistor 11 and the error amplifier 12 is an example of an element that supplies an analog signal from the module 3 to the base board 1 and does not limit the present invention.

  When the potential 7 across the current detection resistor 11 increases due to an increase in the current 7 to the module 3, the light-emitting diode that constitutes the photocoupler of the error amplifier 12 is turned on and a forward current starts to flow. When the potential at both ends is further increased, the forward current increases. The error amplifier 12 supplies a current proportional to the forward current to the current control circuit 10 of the base board 1 as an error amplifier signal 13.

  The current control circuit 10 can be composed of a constant current circuit, and the current control circuit 10 controls the current 7 to the module 3 so that the error amplifier signal 13 becomes zero, and suppresses it to a certain current or less.

  In the module 3, the value of the current detection resistor 11 can be adjusted by adjusting the forward drop characteristic of the light emitting diode constituting the photocoupler of the error amplifier 12. Therefore, in the present embodiment, the circuit configuration of the current control circuit 10 may be simple as long as the current 7 to the module 3 can be controlled so that the current that is the error amplifier signal 13 is simply zero. Furthermore, the effects described in the first embodiment can also be obtained by this embodiment.

It is a functional block diagram of the overcurrent control circuit which concerns on this invention. 1 is a circuit diagram of Embodiment 1 of an overcurrent control circuit according to the present invention. FIG. It is a figure which shows a mode that the rush current of the built-in power line capacitor | condenser which flows into each module at the time of power activation of a power supply module in Embodiment 1 and 2 was suppressed. It is a figure which shows a mode that an inrush current is not suppressed in a conventional circuit. It is a circuit diagram of Embodiment 2 of the overcurrent control circuit which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base board 2 Power supply module 3 Module 3a CPU module 3b IO module 3c Function module 4 Power supply line 5a, 5b, 5c, 10 Current control circuit 6a, 6b, 6c Current consumption information 7a, 7b, 7c Current supplied to each module 8 Current detection resistor selection circuit 9 Current detection result signal 11 Current detection resistor 12 Error amplifier 13 Error amplifier signal

Claims (3)

In an overcurrent control circuit comprising a power supply circuit having an overcurrent protection function for limiting a power supply current to be output, and a plurality of other circuits to which the power supply current is supplied through each slot provided in a power supply line ,
Information collecting means for acquiring current consumption information about individual power supply current consumed by the plurality of other circuits for each slot;
Current control means provided corresponding to each of the slots, and a plurality of currents for preventing overcurrent by suppressing the individual power supply currents to other circuits corresponding to each slot based on the consumption current information And an overcurrent control circuit. The overcurrent control circuit according to claim 1,
An overcurrent control circuit, wherein the current control means comprises means for detecting the individual power supply current based on the consumption current information, and means for controlling so that no more current than the detected current flows. . The overcurrent control circuit according to claim 1,
The information collecting unit includes a current detection resistor provided in the other circuit, and an error detection unit that outputs an error signal when a voltage across the resistor exceeds a predetermined value,
The overcurrent control circuit, wherein the current control means controls based on the signal so that the individual power supply current does not exceed a predetermined value.

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