JP5764680B2 - Inrush current prevention device - Google Patents

Description

  The present invention relates to an apparatus for preventing the occurrence of an inrush current when power is supplied to an electrical device.

  When turning on electrical equipment with inductive loads such as solenoids, motors, transformers and relay coils, electrical equipment with capacitors, or incandescent lamps, a much larger current than that in the steady state is momentarily applied. It is generally known to flow. This instantaneous large current is called inrush current, and electrical equipment is usually designed to withstand this inrush current.

On the other hand, in recent years, secondary batteries such as lithium-ion batteries have become widespread, and electric devices using this as a power source are spreading.
However, the lithium ion battery has a safety problem because the normal area and the dangerous area are very close to each other. In order to protect the battery from overcharge, overdischarge, overcurrent, etc., various protection circuits are provided on the battery itself. Is provided. From the viewpoint of ensuring safety, these protection circuits are designed to operate immediately if a slight abnormality occurs. If an inrush current occurs when the electrical equipment is turned on, the lithium ion battery is protected. The circuit works immediately and power is turned off.
For this reason, when a lithium-ion battery is used as the power source, the battery side protection circuit is activated even though the electrical equipment has the performance to withstand this inrush current due to the inrush current generated when the power is turned on. As a result, there is a problem that the power supply to the electrical equipment is interrupted (see FIG. 4).

In this regard, when using a lithium ion battery, it is common to use a lithium ion battery having a large capacity so that the battery side can withstand an inrush current generated when the electric device is turned on. In other words, if the inrush current generated when the power is turned on is within the allowable range of the protection circuit of the lithium ion battery to be used, the protection circuit will not operate. The range is expanded so that the protection circuit does not operate even if an inrush current occurs.
However, such a method it is inevitable to use a lithium ion battery comprising a over-over specifications with respect to electrical equipment, physically and economically there is a problem that waste occurs.

For this problem, for example, an invention described in Japanese Patent Application Laid-Open No. 2004-179016 has been proposed.
In the present invention, a variable resistance mechanism is interposed between a lamp, which is a load, and a power source, and the resistance value of the variable resistance mechanism is set to be higher than that in a steady state for a predetermined time immediately after the power is turned on. By doing so, the occurrence of inrush current can be suppressed. As the variable resistance mechanism, it is disclosed that a thermistor is used or a switch that operates after a predetermined time elapses after power is turned on and a fixed resistor are connected in parallel.
According to the present invention, since the generation of inrush current can be suppressed by increasing the resistance value only until a predetermined time elapses after the power is turned on, the protection circuit of the lithium ion battery is operated by the inrush current. Therefore, it is not necessary to use a large capacity lithium ion battery.
JP 2004-179016 A

However, in the present invention, since it is indispensable to use a resistor, there is a problem that a loss due to the resistor inevitably occurs in a steady state, and the circuit becomes large, weak against heat and short in life.
In addition, when a thermistor is used as the variable resistance mechanism, the resistance value of the thermistor becomes low when the power is turned on again immediately after the device that is energized in the steady state is turned off. However, when the variable resistance mechanism is configured by connecting the timer switch and the fixed resistor in parallel, there is a problem that the circuit becomes complicated.

It is an object of the present invention to provide a device capable of reliably preventing the occurrence of an inrush current when power is applied to an inductive load using a lithium ion battery as a driving power source with a simple circuit configuration without using a resistor. And

The inrush current prevention device of the present invention controls a switching element and on / off control of the switching element between an inductive load using a lithium ion battery as a driving power source and a power switch for supplying power to the inductive load. connect the switching circuit and control means for controlling program carried out in the chopper control is stored, said control program, said inductive load is set the time until a steady state, said control means, said Based on a control program, after the power is turned on by the power switch, until the inductive load reaches a steady state, the switching element is chopper controlled to suppress an increase in the actual voltage value of the inductive load. .

As the switching element used in the switching circuit, a transistor, a field effect transistor (FET), an insulated gate bipolar transistor (IGBT), a thyristor, and the like can be considered, but any element that can be switched with low voltage and low power consumption can be used. It is not limited to this.
The control means includes a microcomputer or a digital IC storing a control program for turning on / off the switching element by chopper control until the inductive load reaches a steady state after the power is turned on by a power switch. Conceivable. This chopper control is started by turning on the power switch and is performed until the inductive load reaches a steady state.

Here, after the power is turned on, whether or not the inductive load has reached a steady state is determined by the passage of a predetermined time or the state of the load current.
That is, when it is determined whether or not the inductive load has reached a steady state after a lapse of a predetermined time, the time until the inductive load reaches a steady state is preset in the control program according to the inductive load to be used. The chopper control is terminated when the set time has elapsed (claim 1) .
On the other hand, when determining whether or not the inductive load has reached a steady state according to the state of the load current, current detection means is connected to the primary side or the secondary side of the switching circuit, and the current detected by this current detection means. A value is input to the control means of the switching circuit, and the control means determines whether or not the inductive load has reached a steady state based on the current value. In this case, in the control program, a current value in a steady state of the inductive load to be used is set in advance, and the set current value is compared with the current value detected by the current detection means by the control means. The chopper control is terminated when the current value detected by the current detection means reaches a set current value (claim 2) .

The ratio of the on and off time in one cycle of the on and off states of the switching elements by the chopper control can also be adapted gradually ON time becomes longer (claim 3).
For example, the ON / OFF time ratio in one cycle of switching element ON / OFF is set to gradually increase the ON time. For example, the ON time is fixed and the OFF time is gradually shortened over time. It is conceivable to set the ON / OFF duty ratio to gradually increase the ON time.

According to the present invention, between the inductive load using a lithium ion battery as a driving power source and the power switch for supplying power to the inductive load, the switching element and on / off control of the switching element can be performed by chopper control. A switching circuit including a control unit storing a control program to be performed, and a time until the inductive load reaches a steady state is set in the control program, and the control unit stores the control program in the control program Based on the above, since the switching element is controlled by the chopper until the inductive load reaches a steady state after the power is turned on, an increase in the actual voltage value immediately after the power is turned on can be suppressed. Occurrence can be prevented. Thereby, it can be set as the inrush current prevention apparatus of a simple circuit structure, without using resistance.

According to the invention of claim 2, the current detection means is connected to the primary side or the secondary side of the switching circuit, the current value detected by the current detection means is input to the control means of the switching circuit, and the control the program, together with the current value I _S for the steady state of the inductive load is set, the detected current value by comparing the detected current value I ₁ and the set current value I _S by the current detecting means program to end the chopper control is incorporated in the case where I ₁ has reached the set current value I _S, the inductive load is steady state from turning on the power by the power switch on the basis of the control means the control program until reaching, since shall chopper control said switching element, said control means determines whether the inductive load based on the current value has reached a steady state, induced It can end chopper control at an appropriate timing according to the state of sexual load.

According to the invention of claim 3 , the ratio of the on / off time in one cycle of on / off of the switching element by the chopper control is gradually increased so that the substantial voltage applied to the inductive load is increased. It is possible to raise the value gradually from 0 to a steady voltage, and it is possible to reliably prevent the occurrence of an inrush current when the power is turned on.

The figure which shows the outline | summary of 1st Example of this invention The figure which similarly shows the relationship between chopper control and load current until it reaches a steady state The figure which shows the outline | summary of 2nd Example of this invention The figure which shows the state where the power supply was cut off by the generation of the inrush current and the battery protection function

FIG. 1 is a block diagram showing an outline of a first embodiment of the present invention.
A power switch 3 for turning on / off the power supply to the DC motor 1 is connected between the electric device having the DC motor 1 that is an inductive load and the lithium ion battery 2 that is a power source of the electric device. Has been. A switching circuit 4 is connected between the power switch 3 and the DC motor 1.

The switching circuit 4 includes a switching element 41 and a microcomputer 42 that is a control unit that performs switching control of the switching element 41. The microcomputer 42 is branched and connected to a load side line of the power switch 3 in order to detect opening and closing of the power switch 3.
As the switching element 41, for example, a semiconductor element capable of switching control with low voltage and low power consumption such as a transistor, a field effect transistor (FET), an insulated gate bipolar transistor (IGBT), or a thyristor can be used.

In the microcomputer 42, a control program for chopper-controlling the switching element 41 for a predetermined time t1 after the power is turned on by the power switch 3 is recorded in advance.
In this control program, the ratio of the on / off time in one cycle of on / off of the switching element by chopper control to the time t1 until the DC motor 1 used reaches a steady state and the on-time gradually increases. Is set to
When power is turned on by the power switch 3, the control program is activated to start chopper control of the switching element 41 until the time t <b> 1 set according to the connected DC motor 1 elapses in advance. The switching element 41 is chopper-controlled according to the set on / off control pattern. When the time set according to the DC motor 1 (time to reach a steady state) t1 elapses, the chopper control is finished, and thereafter switching until the power switch 3 is opened (until the power switch 3 is turned off). The on state of the element 41 is continued.

The on / off control pattern of the switching element 41 is appropriately set according to the electric equipment to be used. In this embodiment, the ratio of the on-time to the off-time in one cycle of on / off of the switching element 41 by chopper control is set so that the on-time gradually becomes longer as time elapses. By setting in this way, it is possible to reach a steady voltage while gradually increasing the actual voltage, and it is possible to reliably prevent the occurrence of an inrush current (see FIG. 2).
Here, as a setting in which the ratio of the on time to the off time in one cycle of on / off of the switching element 41 is gradually increased, the off time is gradually shortened while keeping the on time constant. And a method of gradually increasing the on-time duty ratio (voltage pattern b in FIG. 2).

  The power switch 3 and the switching circuit 4 may be incorporated in an electric device provided with the DC motor 1 or may be configured as separate devices without being incorporated in the electric device itself, and the DC motor 1 and the lithium ion battery 2. You may connect between. In short, the switching circuit 4 only needs to be connected between the power switch 3 and the DC motor 1.

According to this inrush current preventing apparatus, the current is controlled by chopper-controlling the semiconductor switching element 41 for a predetermined time after the power is turned on until the connected inductive load reaches a steady state with a simple circuit configuration without using a resistor. By repeating ON / OFF, it is possible to suppress the increase of the actual voltage value and prevent the inrush current from occurring.
As described above, since the occurrence of the inrush current can be prevented, even when the lithium ion battery 2 is used as the power source of the DC motor 1, it is not necessary to consider the battery overcurrent protection circuit. A lithium ion battery having an appropriate capacity corresponding to the DC motor 1 can be used.

FIG. 3 shows an embodiment in which the chopper control is canceled by determining whether or not the inductive load has reached a steady state based on the current flowing through the inductive load.
The configuration of the first embodiment is that current detection means 5 is connected to the secondary side of the switching circuit 4, and the current value I ₁ detected by this current detection means 5 is sent to the microcomputer 42 that is control means of the switching circuit 4. point so as to be inputted, the control program stored in the microcomputer 42, together with the current value I _S steady state of the inductive load to be used is set, the current value detected by the current detecting means 5 I ₁ and by comparing the set current value I _S, the detected current value I ₁ is a difference in that that is teamed up a program to end the chopper control when it reaches the set current value I _S. Other configurations are the same as those of the first embodiment.
The current detection means 5 for detecting the current value I ₁ flowing through the inductive load can be connected to the primary side of the switching circuit 4 and input to the microcomputer 42 as the control means (not shown). .

According to this embodiment, inputted to the microcomputer 42 detects the load current I ₁ by the current detection means 5 connected to the secondary side of the switching circuit 4, the current value I _S steady state of the inductive load 1 A program that ends the chopper control when the detected current value I ₁ reaches the set current value I _S by comparing the set current value I ₁ and the set current value I _S detected by the current detection means 5. Since the recorded microcomputer 42 determines whether or not the inductive load 1 has reached a steady state, the chopper control can be terminated at an appropriate timing according to the state of the inductive load 1.

The present invention relates to an inrush current preventing device for an electric device having an inductive load using a lithium ion battery as a driving power source, and has industrial applicability.

1 Load (DC motor)
2 Lithium ion battery 3 Power switch 4 Switching circuit 41 Switching element 42 Microcomputer (control means)
5 Current detection means

Claims (3)

A switching element and a control program for performing on / off control of the switching element by chopper control are stored between an inductive load driven by a lithium ion battery and a power switch for supplying power to the inductive load. switching circuits and control means are connected,
In the control program, a time until the inductive load reaches a steady state is set, and when this set time elapses, a program for terminating the chopper control is incorporated,
The control means performs chopper control of the switching element and increases the substantial voltage value of the inductive load from when the power is turned on by the power switch until the inductive load reaches a steady state based on the control program. To suppress
Inrush current prevention device. A switching element and a control program for performing on / off control of the switching element by chopper control are stored between an inductive load driven by a lithium ion battery and a power switch for supplying power to the inductive load. A switching circuit provided with a control means,
Wherein the primary side or secondary side of the switching circuit is connected to the current detecting means, a current value detected by the current detecting means is inputted to the control means of the switching circuit,
Wherein the control program, the with current I _S of the steady state of the inductive load is set, the detection by comparing the detected current value I ₁ and the set current value I _S by the current detecting means program to end the chopper control is included if the current value I ₁ has reached the set current value I _S,
The control means performs chopper control of the switching element and increases the substantial voltage value of the inductive load from when the power is turned on by the power switch until the inductive load reaches a steady state based on the control program. To suppress
Inrush current prevention device. The ratio of on / off time in one cycle of switching element on / off by chopper control was made to gradually increase the on time.
The inrush current preventing device according to claim 1 or 2.

Images