JPH0469048A - Overcurrent detecting circuit for power supply - Google Patents

Abstract

PURPOSE:To protect a power supply itself and each load from overcurrent by providing a body side overcurrent detecting circuit, a load side overcurrent detecting circuit and an allowable current setting circuit. CONSTITUTION:A body side current detecting circuit 6 and a load side current detecting circuit 7 are inserted between a power supply unit 1 and a load 10. When a current higher than the allowable current of the load 10 flows through the load 10, the load side overcurrent detecting circuit 7 functions to detect the overcurrent. Furthermore, allowable current of the load side overcurrent detecting circuit 7 can be modified according to the current capacity of the load 10 connected with an allowable current setting circuit 14. When a current higher than the actual current capacity of the power supply 1 flows through the power supply under a state where a plurality of loads 10 are connected and the current capacity of the power supply 1 is higher than the total allowable current of the loads 10, the body side overcurrent detector 6 functions to detect the overcurrent. According to the arrangement, each load 10 and the power supply 1 can be protected from overcurrent.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention relates to a power supply device that supplies current to a load, and particularly to a power supply device for protecting the power supply device itself and the load from overcurrent. This invention relates to an overcurrent detection circuit.

(Prior Art) For example, in a large-capacity power supply device that supplies DC power to various electronic devices, the output terminal of the power supply device may be accidentally short-circuited, or the load connected to the output terminal may malfunction. When a short circuit occurs, a large current flows. As a result, various electronic components built into the power supply device are damaged. In order to prevent such a situation from occurring, an overcurrent detection circuit is built into the power supply, and the output current is set to the maximum allowable value based on the maximum output current value of the power supply itself. An overcurrent detection circuit that outputs a warning signal when the current value exceeds 1max is incorporated. Note that the maximum allowable current value 1 max is usually 110 to 15 of the rated output current value.
It is set to a value of about 0%.

However, even in a power supply device incorporating the above-mentioned overcurrent detection circuit, there are the following problems that must be solved.

That is, it is assumed that various loads are connected to the power supply device. Therefore, the current capacity of the connected load also varies greatly depending on the type of load. In other words, each load has an allowable current value 1r for the current flowing through that load, and if a current exceeding this allowable current value I flows, there is a risk that the load will be damaged.Therefore, the current value flowing into each load Needless to say, it is necessary to control the current value to be less than the allowable current value Ir set for the relevant load.

However, when this load is connected to the power supply, if the load's allowable current value 1r is significantly lower than the power supply's maximum allowable current value 1wax, a current exceeding the allowable current value Ir flows through the load. However, since the overcurrent detection circuit does not operate, there is a risk that the load may be damaged without the operator noticing.

In order to avoid such a situation, the operating current value of the overcurrent detection circuit built into the power supply device should be set to the allowable current value of the load 1r.
If the type of load connected to this power supply device changes, is it necessary to replace the overcurrent detection circuit each time? Furthermore, when a plurality of loads are connected in parallel to one power supply device, the operating current value of the overcurrent detection circuit must be equal to the total current value of the allowable current values of each load. but,
If the operating current value is set to the total current value in this way, even if an overcurrent flows through one of the remaining operating loads when there is one load that is not operating among multiple loads, the overcurrent will not be affected. The current is not detected by the overcurrent detection circuit described above. Therefore, there is a risk of damage due to load.

In addition, when a large number of loads that are operated intermittently are connected, there is a very low probability that all the loads will be operated at the same time. If the total current value is set as the total current value, it is necessary to significantly increase the current capacity of the power supply device, which is undesirable, so the current capacity is set lower than the total current value. In case 2, if all the loads are operated at the maximum rating at the same time, the current capacity of the power supply device will be exceeded, so it is necessary to operate the overcurrent detection circuit at the maximum allowable current value corresponding to the actual current capacity.

(Problem to be solved by the invention) As described above, in the overcurrent detection circuit of the conventional power supply device, it was not possible to accurately detect the overcurrent of each load, so it is necessary to reliably protect the loads from overcurrent. I couldn't.

The present invention was made in view of these circumstances, and
By providing two types of overcurrent detection circuits, one for detecting overcurrent of the power supply itself and the other for detecting overcurrent of each load, the power supply itself and each load can be protected from overcurrent at the same time, increasing reliability. The present invention aims to provide an overcurrent detection circuit for a power supply device that can significantly improve performance.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the overcurrent detection circuit of the power supply device of the present invention includes an a main unit-side overcurrent detection circuit that detects when the current value of the current output from the power supply main body exceeds a maximum allowable current value set based on the maximum output current value of the power supply main body itself; a load side overcurrent detection circuit that is inserted between the main body side overcurrent detection circuit and the output terminal and detects that the current flowing to the load exceeds an allowable current value;
The load-side overcurrent detection circuit is provided with an allowable current setting circuit that can variably set the allowable current value according to the current capacity of the load.

(Function) In the overcurrent detection circuit of the power supply device configured as described above, the main body side overcurrent detection circuit and the load side overcurrent detection circuit are interposed between the power supply device body and the load. and,
If a current exceeding the allowable current value of this load flows through the load,
The load side overcurrent detection circuit is activated and overcurrent is detected.

Furthermore, the allowable current value of the load-side overcurrent detection circuit can be changed according to the current capacity of the connected load. In addition, if multiple loads are connected and the current capacity of the power supply is larger than the total allowable current value of each load, and a current exceeding the actual current capacity flows through the power supply, an overcurrent will occur on the main unit side. The detection circuit operates and detects an overcurrent. Therefore, each load and power supply are protected from overcurrent.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a schematic configuration of a power supply device incorporating an overcurrent detection circuit according to an embodiment. A three-phase voltage supplied from an external three-phase AC power source is applied to the primary winding of a power transformer 2 within the power supply main body 1. A choke coil 4 is connected to both ends of the secondary winding of the power transformer 2 via diodes 3a and 3b with the polarities shown. The other end of this choke coil 4 is connected to the (+) side pressure terminal 5a of this power supply device. Further, the intermediate point of the secondary winding is connected to the (-) side pressure terminal 5b of this power supply device via the main body side overcurrent detection circuit 6 and the load side overcurrent detection circuit 7. Further, a smoothing capacitor 8 is inserted between the output terminal of the choke coil 4 and the intermediate point of the secondary winding, and the output terminal 5a.

A capacitor 9 is also connected between 5b and 5b. A load 10 is connected between the output terminals 5a and 5b. That is, the three-phase voltage input to the power supply main body 1 is rectified by the diodes 3a and 3bb, and is rectified by the choke coil 4. After being converted to DC by the smoothing capacitor 8, the output terminals 5a, 5b
is supplied to the load]0 via the load.

In the main body side overcurrent detection circuit 6, the voltage across the detection resistor]1 inserted in the current path to the load 10 is the resistance R.
2, after being amplified by the amplifier 13 via R2, the comparator 1
It is input to one input terminal of 4. Also, this comparator 1
A reference signal is input to the other input terminal of 4. Further, a reference voltage VRI is applied to one input terminal of the amplifier 12 via a resistor R1.

In such a main body side overcurrent detection circuit 6, the value of the current flowing through the detection resistor 11, that is, the current I supplied from the power supply main body 1 to the load]0 via the output terminals 5a and 5b, or this power supply main body When the maximum permissible current value llll1ax determined based on the current capacity of 1 is exceeded, the voltage across the detection resistor 11 increases, and the output signal of the comparison circuit 13 is inverted. The inversion conditions of this comparison circuit 13 are determined by the resistors R, , R2 and the M'I voltage □. Therefore, the resistance value R of the detection resistor 13 and the reference voltage VRI are adjusted so that the output signal of the comparison circuit 13 is inverted when the maximum allowable current I max flows.

Further, in the load side overcurrent detection circuit 7, the load 10
An allowable current setting circuit] 4 is inserted in the current path for the The voltage across the allowable current setting circuit 14 is amplified by the amplifier 15 via resistors R2 and R2, and then input to one input terminal of the comparator 16. Further, a reference signal is input to the other input terminal of the comparator 16. Further, a reference voltage VR2 is applied to one input terminal of the amplifier 12 via a resistor R1.

The allowable current setting circuit 14 includes three resistors 17a and 17a, each having different resistance values x, y, and z, as shown in the figure.
7b and 17c are connected in parallel via shoot pins 18a, 18b, and 18c, and shoot pins 18a,
By appropriately cutting off 18b and 18c, the combined resistance value R6 at both ends of this allowable current setting circuit 14 can be selectively set to seven types. For example, all shoot pins 18a to 18
In a state where b is not cut, the combined resistance RC is Rc - (XY+YZ + ZX)/XYZ. Also,
If shoot pins 18b and 18C are cut, Rc-
It becomes X.

The basic operation of this load side overcurrent detection circuit 7 is almost the same as that of the main body side overcurrent detection circuit 6 described above. Therefore, in this load side overcurrent detection circuit 7, the comparator 1
When the output signal of 6 is inverted, the allowable current setting circuit 1
4, that is, the allowable current value 1r flowing through the load 10 is determined by the combined resistance RC of the allowable current setting circuit 14. This combined resistance Rc is
The operating current value of the load-side overcurrent detection circuit 7 can be variably set by appropriately disconnecting the chute pins 18a to 18C.

According to the overcurrent detection circuit of the power supply device configured in this way, by appropriately setting the disconnection state of each chute bin 18a to 18b of the allowable current setting circuit 14 of the load side overcurrent detection circuit 7, the power supply device The output signal of the comparator circuit 16 can be inverted at the current value closest to the allowable current value 1r corresponding to the current capacity of the load 10 connected to the output terminals 5a and 5b. That is, when the current flowing through the load 10 exceeds the allowable current value 1r corresponding to the current capacity of the load 10, the load-side overcurrent detection circuit 7 outputs an overcurrent detection signal.

Therefore, since the operating current value of the load-side overcurrent detection circuit 7 can be variably set according to the current capacity of the load 10 connected to this power supply device, even if the load 10 is connected, An overcurrent detection signal is immediately output when a current exceeding the allowable current set in the load 10 flows.

Therefore, the safety of the load 10 can be improved.

In addition, the operating current of the overcurrent detection circuit 6 on the main body side is the maximum allowable current value 1111 based on the maximum output current value of this power supply device.
Since it is set to 8X, the power supply main body 1 is reliably protected. In other words, if a large number of loads are connected to this power supply, the total current value is the sum of the allowable current values set for all loads, assuming that all loads are not operated at once. The maximum allowable current value of this power supply unit may be exceeded. In such a case, if all the loads are operated at once, the current value output from the power supply main body may exceed the maximum allowable current value. Under this condition, each load-side overcurrent detection circuit provided for each load does not output an overcurrent detection signal. However, since the overcurrent detection signal is output from the overcurrent detection circuit on the main body side, damage to the main body of the power supply device due to overcurrent can be prevented.

FIG. 2 is a block diagram showing a schematic configuration of a power supply device that can supply current to a plurality of loads at a time.

The same parts as in FIG. 1 are given the same reference numerals. That is, the current output from the power supply main body 1 is transmitted to the main body side overcurrent detection circuit 6. Load side overcurrent detection circuit 7 and output terminal 5a
, 5b to the load 10, and is also supplied to the load 10 via the same body-side overcurrent detection circuit 6, another load-side overcurrent detection circuit 7a, and another output terminal 5aa, 5ba.
supplied to a. The operating current value of the load-side overcurrent detection circuit 7 is set based on the current capacity of the load 10, and the operating current value of the load-side overcurrent detection circuit 7a is set based on the current capacity of the load 10a.

According to the overcurrent detection circuit of the power supply device configured in this manner, the allowable current value is set for each load 10, 10a, so that damage caused by overcurrent to each load can be reliably prevented. Furthermore, damage to the power supply device itself due to overcurrent can be prevented.

Note that the present invention is not limited to the embodiments described above. In the allowable current setting circuit 14 of the embodiment, the combined resistance value is variably set by cutting off the chute pins 18a to 18c, or a changeover switch or the like may be used, for example.

[Effects of the Invention] As explained above, the overcurrent detection circuit of the power supply device of the present invention has two types of overcurrent detection: a circuit for detecting overcurrent of the power supply itself and a circuit for detecting overcurrent of each load. A current detection circuit is provided. Further, the operating current value of the load-side overcurrent detection circuit that detects overcurrent of each load is configured to be variable. Therefore, the power supply device itself and each load can be protected from overcurrent at the same time, and the reliability of the entire power supply device can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an overcurrent detection circuit of a power supply device according to one embodiment of the present invention, and FIG. 2 is a block diagram showing an overcurrent detection circuit of a power supply device according to another embodiment of the present invention. . 1. Power supply unit, 5a, 5b... Output terminal, 6.
- Main body side overcurrent detection circuit, 7... Load side overcurrent detection circuit, 10... Load, 11... Detection resistor, 14... Allowable current setting circuit. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] The maximum allowable current value of the current that is inserted between the power supply main body and the output terminal to which a load is connected, and is output from the power supply main body is set based on the maximum output current value of the power supply main body itself. An overcurrent detection circuit on the main body side that detects that the current value has been exceeded, and an overcurrent detection circuit on the main body side that is inserted between the overcurrent detection circuit on the main body side and the output terminal to detect that the current flowing to the load has exceeded the allowable current value. A load side overcurrent detection circuit to detect,
An overcurrent detection circuit for a power supply device, comprising: an allowable current setting circuit provided in the load side overcurrent detecting circuit and capable of variably setting the allowable current value according to the current capacity of the load.