JPH0475430A - Rechargeable power unit - Google Patents

Abstract

PURPOSE:To obtain a power having an overdischarge preventing mechanism and an overcharge preventing function by constituting a discharging circuit and a charging circuit of elements incorporating parasitic diodes in a charging power supply comprising a quick charge secondary battery. CONSTITUTION:Upon droppage of battery 3 voltage below a predetermined level due to discharge, output voltage of a control means 5 causes transition of a MOSFET 41 from conducting state to interrupted state thus interrupting a battery 3 discharge circuit. When the battery 3 voltage is recovered due to charging through the parasitic diode 41A of the MOSFET 41, normal (low loss) charging takes place. When the battery 3 voltage exceeds a predetermined level due to charging, output voltage of the control means 5 causes transition of a MOSFET 42 from conducting state to interrupted state thus interrupting a battery 3 charging circuit. When the battery 3 voltage is recovered due to charging through the parasitic diode 42A of the MOSFET 42, normal (low loss) discharge takes place.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention relates to a rechargeable power supply device having a secondary battery that can be charged quickly, and particularly relates to a power supply device having an over-discharge prevention mechanism and an overcharge prevention function. Regarding equipment.

[Prior Art 1] With the development of portable equipment, radios, cassette tape recorders with radios, and portable VTRs were developed.

For the power supply of electronic devices such as portable computers, communication devices such as mobile phones, power devices such as portable power tools, etc.
Rechargeable batteries and secondary batteries are becoming widely used. In particular, the use of secondary batteries has increased significantly in recent years.

In general secondary batteries, when overcharged beyond proper charging conditions, gas is generated as the electrolyte decomposes.

In open or drained cells, the gas generated is allowed to escape, but the electrodes suffer some damage as a result of this overcharging.

On the other hand, in sealed batteries, the gas pressure builds up inside, causing an explosion. For this reason, some sealed batteries are equipped with a safety valve to prevent overcharging in order to cope with the increase in gas pressure. However, with these batteries equipped with a safety valve, gas may not be removed reliably. This caused problems in terms of reliability. Furthermore, when highly corrosive gas is released due to the operation of this safety valve, there is also the drawback that it corrodes equipment in which the battery is installed.

In addition, if overcharging is severe, a short circuit may occur inside the battery, leading to the battery bursting.

Therefore, a device is needed to prevent batteries from being charged beyond normal charging conditions.

Generally, with commercially available secondary batteries, a thermostat or temperature fuse is connected in series with the battery, and when the battery is overcharged beyond the appropriate charging conditions, it detects the heat generation of the battery and shuts off the charging circuit. I am trying to solve the above problems.

[Problem to be Solved by the Invention] However, with devices such as thermostats or temperature fuses that detect heat generation during overcharging and shut off the charging circuit, by the time this is detected, the battery has already exceeded the proper charging condition. Overcharging was progressing, and not only did battery performance deteriorate, but abnormal conditions such as leakage and rupture often occurred.

Additionally, when using a rechargeable power supply attached to a device, the power supply is often left attached to the device for a long period of time, which may completely discharge the secondary battery inside the power supply. Ta.

As described above, when a secondary battery is completely discharged, the performance of many secondary batteries deteriorates significantly and cannot withstand repeated use. Moreover, many (many) devices do not have devices to prevent over-discharging of power supplies, and removable rechargeable power supplies used in various devices are It often happens that the battery in the power supply unit is left unused for a long period of time, leading to over-discharge.

In particular, with non-aqueous secondary batteries, once over-discharge occurs, a short circuit occurs inside the battery during subsequent charging, causing not only performance deterioration but also serious safety problems such as rupture. was there. In this case, especially if charging after overdischarging leads to overcharging, this risk becomes even higher.

The purpose of the present invention is to solve the above-mentioned problems by preventing over-discharging of the secondary battery in a rechargeable power supply when the rechargeable power supply is left attached to a device. In addition, even if the charging device malfunctions or is charged with a charging device other than the dedicated charging device, the secondary battery in the rechargeable power supply device is protected from overcharging, and the secondary battery is It is an object of the present invention to provide a rechargeable power supply device that prevents deterioration of performance and prevents a secondary battery from becoming dangerous due to overcharging.

[Means for Solving the Problems j] In order to achieve the above object, the present invention provides a switch means in which a rechargeable battery and a first and second switch element each having a parasitic diode therein are connected in series. , control means for detecting the voltage across the battery and controlling the switch means, and the first switch element is configured such that the forward direction of its parasitic diode is in the discharging direction of the battery,
The second switch element is connected to the battery such that the forward direction of its parasitic diode is in the charging direction of the battery, and the control means is configured such that the voltage of the battery is lower than the first voltage near the chargeable voltage. When the battery voltage drops, the first switch element is made conductive, and when the voltage of the battery rises above a second voltage that is near the chargeable voltage and higher than the first voltage, the first switch element is turned off. When the voltage of the battery rises above a third voltage near the dischargeable voltage, the second switch element is made conductive, and when the voltage of the battery is near the dischargeable voltage and the third The second switching element is brought into a non-conducting state when the voltage drops below a fourth voltage lower than the voltage of .

[Function 1] According to the present invention, when the control means detects that the remaining capacity of the battery has decreased below the dischargeable voltage, the control means controls the switch means to cut off the discharge circuit, and the charging of the battery is stopped. When the control means detects that the voltage has exceeded the allowable voltage, the control means controls the switch means to cut off the charging circuit. Furthermore, the circuit can be simplified by selecting the switch element constituting the switch means as an element having a parasitic diode inside and constructing the discharging circuit and the charging circuit using the parasitic diode.

[Example] Hereinafter, an example of a power supply device having an overcharge prevention function and an overcharge prevention function according to the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the basic configuration of the present invention.

As shown in FIG. 1, a load or charger 1 is connected to a power supply device 2. As shown in FIG. The power supply device 2 includes a battery 3, a switch means 4, and a control means 5.

Here, the term "battery" as used in the present invention refers to not only a single battery but also an assembled battery in which multiple batteries are connected to each other, a battery with additional functions such as a safety device related to short circuits, a remaining capacity display, etc., and an assembled battery. It also includes.

Note that the switch element constituting the switch means in the present invention is preferably a voltage-driven switch in order to reduce power loss and reduce power consumption during normal use. As a device that satisfies this condition, a field effect transistor (FET) has favorable conditions, but among these, using a MOS FET, which has a parasitic diode inside the device, significantly simplifies the circuit and reduces the size. can do.

That is, two switch elements are connected in series and connected to the battery, and these two switch elements are used as a cutoff switch (sw") of a discharging circuit to prevent over-discharge, and a cut-off switch (sw") of a charging circuit to prevent over-charge, respectively. Used independently as a cutoff switch (3woc).

At this time, the cutoff switch (SW) of the discharge circuit for overdischarge prevention
”) is the cutoff switch (sw) of the discharge circuit for overdischarge prevention.
oo) The internal parasitic diode is set so that the charging current is in the forward direction, and the charging circuit cutoff switch (SWoo) for overcharging prevention is connected to the charging circuit cutoff switch (swo C) for overcharging prevention. The discharge circuit cutoff switch (swap) for overdischarge prevention and the charging circuit cutoff switch (SWoc) for overcharge prevention are connected in series so that the parasitic diode is in the forward direction of the discharge current. Connect with battery. By connecting in this way, the parasitic diode inside the switch element can be used as part of the charging circuit or discharging circuit of the power supply, and part of the charging circuit and discharging circuit within the power supply can be omitted. , it can be used as a two-terminal component in the same way as a conventional power supply device. Here, a third terminal or the like for externally controlling the control means within the power supply device is not necessarily required.

Next, FIG. 2 shows an embodiment of a power supply device equipped with an overcharge prevention function and an overcharge prevention function. As shown in Fig. 2, the switch means includes a MOS FET 41 loaded with an internal parasitic diode 41A as a cutoff switch (sro) of the discharge circuit for overdischarge protection, and a cutoff switch (SWOC) of the charging circuit for overcharge prevention. ) is used as a MOS FET 42 having an internal parasitic diode 42A. The battery 3 consists of a single cell or an assembled battery connected in series or parallel.

The control means 5 can be composed of a comparator, a reference voltage circuit, etc., and as shown in the circuit diagram shown in FIG.
Connect the non-inverting input terminal (■) to the negative terminal of the battery 3 and the positive terminal of the battery 3. The control means 5 supplies the output (yooQut) to the cutoff switch (SW") of the discharging circuit for overdischarge prevention to the gate of the MOS FET 41, and outputs the cutoff switch (SW") of the charging circuit for overcharge prevention to the gate of the MOS FET 41. (V",
, t) MO5FET42 (7)K)! , : supply.

The negative terminal of the battery 3 is connected to the drain of the MOS FET 42, the source of the MOS FET 42 is connected to the source of the MOS FET 41, the train of the MOS FET 41 is connected to the negative terminal 7 of the power supply 2, and the positive terminal of the battery 3 is connected to the drain of the power supply 2. Connect to the positive terminal 6 of the In addition, MOS FET41
and MOSFET42 may be interchanged in position as long as the polarity is not changed.

An example of the back cover turn of the control means 5 is shown in FIG. FIGS. 3(a) and 3(b) show examples of patterns of outputs (VODa, . . . ) to the cutoff switch (SWoo) of the discharge circuit for overdischarge prevention. Also, (c) 8 and (d) in Figure 3
The charging circuit cutoff switch 5- (SWo
c) Heno pressure (■0c,,ut) An example of tube turn is shown.

As shown in FIG.
oil +V”out toil), the gate cutoff voltage of the MOS FET (■61°1.
)), and the two outputs of the control means 5 (■
00°Lltl Vocaut) is off (yoo.

ut+offl+ ”°out +6ffl), both need to be lower than the MOS FET (7) gate cutoff voltage (V, s (.tt+). However, the cutoff switch (s
output voltage when on (voo.,...l) to wan)
The output format shown in FIG. 3 (a) or (b) may be used. Similarly, the output voltage (V0cout+ofi+) when the cutoff switch (SWoc) of the charging circuit for overcharging prevention is turned on is (cl
or (d), either of the output formats is acceptable.

According to the above configuration, when the voltage across the battery 3 becomes less than a certain voltage (vOD in the third section. Voltage (yooo, t) is VOm16ft+
From the above ■. t. ff+ and below, MOS FE
T41 changes from a conductive state to a cutoff state and cuts off the discharge circuit of 03.

Then, by charging via the parasitic diode 41A of the MOS FET 41, the voltage across the battery 3 increases to the above yOD, 1
When the voltage exceeds , (■ODo in Figure 3), the discharge circuit cutoff switch (SW
The output voltage of the control means 5 to oo) changes from the off state to the on state, the MOS FET 41 changes from the cutoff state to the conduction state, and normal (low loss) charging is performed.

Similarly, when the voltage across the battery 3 exceeds a certain voltage (■0coef in Fig. 3), the output voltage of the control means 5 to the cutoff switch (SW'') of the charging circuit for overcharging prevention changes to Voc( Off1 or more becomes V''ostott or less, and the MOS FET 42 changes from a conductive state to a cutoff state, thereby cutting off the charging circuit for the battery 3.

Then, due to discharge through the parasitic diode 42A of the MOS FET 42, the voltage across the battery 3 becomes the voltage V0C6f.
When the voltage becomes lower than f (yoc6° in Fig. 3), the cutoff switch fsW of the charging circuit for overcharging prevention is activated.
The output voltage of the voltage detection means 5 to 0c) changes from the off state to the on state, the MOS FET 42 changes from the cutoff state to the conduction state, and a normal (low loss) discharge is performed.

By the way, assuming that the dischargeable voltage is Vt, ow and the chargeable voltage is VH+gh, and considering the magnitude of hysteresis to be described later, yV0Dott≦V1. OW＜V”Q.＜
Vt4 + Kh+ ■LOW〈voco,〈■14
11. ≦■0c0. If there is a setting thread, usually,
MOS FET 41 and MOS FET 42 are never in a cutoff state at the same time.

Note that the positions of the switch elements and the output turns of the control means shown in FIGS. 2 and 3 are based on the N-channel type MO
When using another switch element that corresponds to the S FET, it is necessary to select the arrangement and output pattern of the control means depending on the characteristics of the switch element.

Here, as a result of examining MOS FETs used as cutoff switches for charging and discharging circuits, we found that MOSFE
T is the on-resistance between drain and source (Ro=+
. . , ) is preferable, and it has been found that the on-resistance (RD, t...) between the drain and source needs to be equal to or smaller than the internal resistance of the battery in the power supply. Ta. Of course, MOS FET
can be used in parallel; in this case, MOS
On-resistance between drain and source of FET (R-+.n
It is necessary that the combined resistance value of +) be equal to or smaller than the internal resistance of the battery in the power supply device.

On-resistance between drain and source of MOS FET (RD
s+. . )) is larger than the internal resistance of the battery in the power supply device, the power loss due to the MOS FET becomes large (not only does this result in a significantly large temperature deviation in the power supply device, which is undesirable).

Note that if the switch element is a device that has a parasitic diode inside, it can be
Similar to the OS FET, the circuit within the power supply device can be simplified.

Further, the control means has two independent outputs, one of which is a discharge circuit cutoff switch (swo) for overdischarge prevention.
l+), and the other is connected to the input of a charging circuit cutoff switch (SW") for overcharging prevention.

Then, turn off the discharge circuit cutoff switch (S) to prevent overdischarge.
l! The output (vOD.ut) of the control means to the overdischarge detection voltage (■00°ff), that is, the reset voltage ( voo.,) and the magnitude of the hysteresis (Voo..).

VODot+') is about 0.05V to 5.0V.

If the hysteresis is smaller than 0.05V, the voltage between the battery terminals recovers by cutting off the discharge current and exceeds the reset voltage (■0D0°) again.As a result, the cutoff switch (SW0f) of the discharge circuit for overdischarge prevention ') will turn on and the power supply will discharge intermittently, so it is undesirable for the hysteresis to be too small.

On the other hand, if the hysteresis is larger than 5.0■, when the power supply starts charging from the discharge cutoff state, the voltage of the battery in the power supply does not exceed the reset voltage (yoo..), which prevents overdischarge. Discharge circuit cutoff switch (3woo)
Since the output (■00°ut) of the control means to the
Since the charging current flows only through the parasitic diode of the over-discharge prevention cut-off switch (SW'') while the switch remains off, the power loss in the over-discharge prevention cut-off switch (SW'') continues to be large.

Therefore, it is undesirable for the hysteresis to be too large (,
The hysteresis must be large enough to immediately reset the output (voDout) of the control means to the overdischarge prevention cutoff switch (SWoD) as the battery voltage increases due to the start of charging.

Considering the above, the magnitude of hysteresis is 0.05V
It is preferable that it is about 5.0 .

Similarly, the charging circuit cutoff switch (SW) is used to prevent overcharging.
The output of the control means (■00゜ut) to oD) is a reset voltage (■00゜ut) lower than the overcharge detection voltage (v0c=rr), that is, the detection voltage that turns off the cutoff switch (SWoc) of the charging circuit for overcharge prevention. ), and the magnitude of hysteresis (Vocate −V
ocon) is better at about 0.05V to 5.0V.

If the hysteresis is smaller than 0.05V, the voltage between the battery terminals decreases due to the cutoff of the charging current, which causes the voltage to drop below the reset voltage (Voc, wa) again. ) is turned on and the power supply continues to be charged intermittently, so it is undesirable for the hysteresis to be too small.

On the other hand, if the hysteresis is larger than 5.0■, when the power supply enters discharge from the charging cutoff state, the voltage of the battery in the power supply does not fall below the reset voltage (VOCQ,), and the Charging circuit cutoff switch (SWoc)
) is not reset, the charging circuit cutoff switch (S
woe) remains off, the discharge current flows only through the parasitic diode of the overcharge prevention cutoff switch (SWOC), so the overcharge prevention cutoff switch (SWOC)
Therefore, it is undesirable for the hysteresis to be too large, and as the battery voltage drops due to the start of discharging, the output of the voltage detection means to the overcharge prevention cutoff switch (swOc) will continue (. voo.u
The hysteresis must be large enough to reset t). Considering the above, the magnitude of hysteresis is o, osv ~ 5. It is preferable to have about Ov.

In addition, the working voltage range of battery 3 is VLOW≦■≦vs+
gn, normally V”Off≦VLOW<■
QD... <v,,,h,v,. , ＜v”..＜
It is necessary to set V++gn≦V0c0rt.

By the way, electronic circuits used as control means include bipolar IC, MOS IC, CMOS IC, Bi-MO
Although it can be configured with an S IC1, a pie grid IC, etc., it is preferable that the current consumption is small, and it is desirable that the current consumption is at least smaller than the self-discharge current of the secondary battery in the rechargeable power supply device. In particular, with a removable rechargeable power supply, if you store the battery in a charged state, the remaining capacity of the rechargeable power supply may run out in a very short period of time if you leave it unused. It is unbearable for practical use.

Next, a case where the secondary battery disclosed in Japanese Patent Application Laid-Open No. 62-90863 is used as the battery 3 will be specifically explained. Below, a case where two secondary batteries are combined in series as the battery 3 will be explained in detail.

The standard operating voltage range of batteries is ■2.75 per cell.
V~4.2■, and when two batteries are combined in series, it becomes 5.5V~8.4■.

In this example, a power supply device with a capacity of 2.0 Ah was prototyped as a power source for a video movie. Prototype power supply unit 9
It has a size of 0 mm x 46 mm x 26 mm, and 0.
It has an internal resistance of 15Ω to 0.30Ω. In addition, the internal resistance of the single cell of the battery 3 is 0.02Ω to 0.08Ω,
The self-discharge current at 25° C. is about 200 μA.

Here, in the battery 3, when the voltage between the terminals of the single cell becomes about 0.5 V or less, not only does the performance deteriorate more than normal cycle deterioration, but also a cause of an internal cell short circuit occurs. Therefore, when two batteries are combined in series, it is necessary for safety to ensure that the voltage of the power supply device does not fall below at least 1V.

Furthermore, when the voltage between the terminals of the battery 3 exceeds about 4.5 .ANG., it not only causes a greater deterioration in performance than normal cycle deterioration, but is also unfavorable from a safety standpoint. Furthermore, if it exceeds 4.8■, abnormal heat generation will occur, resulting in a dangerous situation. Therefore, when two batteries are combined in series, it is necessary for safety to ensure that the voltage of the power supply device during charging does not exceed 9.0 µ.

For example, the switch element used here is 2SK12.
86 (NEC), 23 to 1136 (Mitsubishi), 2S
K1137 (Mitsubishi).

If you use a MOS FET such as 2SKl114 (Toshiba), the on-resistance (R
o(..1) can be between 0.04Ω and 0.12Ω. Of course, by using a MOS FET with a higher rating, it is possible to further reduce the on-resistance (Rns+o) between the drain and source of the MOS FET.

Further, the control means 5 may use a comparator, a reference voltage circuit, etc., and the detection circuit for overdischarge prevention and the detection circuit for overcharge prevention may each be constituted by a Schmitt circuit. In such a circuit, the discharge cutoff voltage (voo, rf) is set to 5.2V.
~5.5V, charge cutoff voltage (vocorr) 8.5
Set to V~8.8■. Furthermore, the control means 5 is a CMO
If it is constructed using an SIC or the like, it is easy to suppress the average current consumption of the voltage detection means 5 to 100μ8 or less. Also,
If the power supply is short-circuited externally, the current leaking to the external circuit of the power supply when the MOS FET is cut off (Ios
-) is 1.0μ8 or less.

With the above configuration, within the operating voltage range of this power supply (5.5V to 8.4V), it can be used in the same way as when two batteries are connected in series. Therefore, the power loss in the MOS FET can be suppressed to about 5% or less of the power capacity of the power supply device.

Here, we tested the effect on overdischarge by connecting a 5Ω resistor between the external terminals of the power supply for one week, discharging the battery inside the power supply, and comparing the capacity before and after with a conventional battery. We conducted an evaluation.

As a result, conventionally, when two secondary batteries were simply connected in series, a decrease in capacity of 5% to 80% was observed, but in the prototype power supply device, there was no decrease in capacity at all. Furthermore, even if the power supply unit and conventional batteries are left unused for a month after being discharged, if two conventional secondary batteries are simply connected in series, % to 50% decrease in capacity was observed, but no decrease in capacity was observed in the prototype power supply device.

Furthermore, if the power supply device 2 is under normal charging conditions (charging current is 2A)
(and the voltage between the terminals of the power supply device 2 is 8.4V or less), when charging is performed, the voltage between the terminals of the battery 3 in this power supply device 2 is the charging cutoff voltage. (v
oCort), the charging circuit is immediately cut off and the battery 3 in the power supply device 2 can be prevented from reaching a dangerous state.

For example, if a battery pack in which two secondary batteries are connected in series and this power supply device 2 are used, 2. Comparing the case of constant current charging of OA, a battery pack with two batteries connected in series starts to generate abnormal heat when the voltage between the terminals exceeds 9.6V.
Eventually it will rupture. In particular, if the battery is overcharged after being overdischarged, it may generate abnormal heat at a voltage lower than 9.6cm and suddenly burst.

However, in this power supply device 2, if the voltage between the terminals of the battery 3 in the power supply device 2 exceeds the charging cutoff voltage (vocotr), the charging circuit is immediately shut off, so a dangerous situation can be prevented. That is, compared to normal charging, the deterioration of characteristics may be several percent greater, but dangerous conditions such as explosion are avoided, and the battery can be used safely thereafter.

In particular, in the removable rechargeable power supply device according to the present invention, no matter what kind of device it is and how it is used, over-discharging of the secondary battery in the power supply device can be prevented, and Even when the battery is charged with a charging device other than the dedicated charging device, overcharging of the secondary battery in the power supply device can be prevented.

[Advantageous Effects of the Invention 1] As explained above, according to the present invention, it has a very simple structure and can be used in exactly the same way as a normal secondary battery. To protect the battery from over-discharge, shut off the discharge circuit of the power supply before
However, before the battery is overcharged beyond normal charging conditions, the charging circuit of the power supply device can be cut off to protect the battery from overcharging, thereby reducing the danger and characteristics of overdischarging and overcharging. It is possible to eliminate the risk of deterioration.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing the basic configuration of the present invention, Fig. 2 is a circuit diagram of an embodiment of the present invention, Fig. 3 (a), (b), (c) , (d) is a diagram showing an example of an output pattern of the control means. DESCRIPTION OF SYMBOLS 1...Load or charger, 2...Power supply device, 3...Battery, 4...Switch means, 5...Control means, 6...Positive terminal, 7...Negative terminal, 41.42...MOS FET. 41A, 42A...parasitic diode. (a) (c) Figure 3 (b)

Claims (1)

[Claims] 1) A switch means including a rechargeable battery and a first and second switch element each having a parasitic diode connected in series; and a control means for controlling the first switch element such that the forward direction of its parasitic diode is in the discharging direction of the battery, and the second switch element is configured such that the forward direction of its parasitic diode is in the charging direction of the battery. The control means is connected to the battery so that the voltage of the battery becomes conductive when the voltage of the battery falls below a first voltage in the vicinity of a chargeable voltage, and the control means conducts the first switch element so that the voltage of the battery When the voltage of the battery rises above a second voltage that is near the chargeable voltage and higher than the first voltage, the first switch element is made non-conductive, and the voltage of the battery is set to a third voltage that is near the dischargeable voltage. When the voltage of the battery is higher than the voltage, the second switch element is made conductive, and when the voltage of the battery is lower than the fourth voltage, which is near the dischargeable voltage and lower than the third voltage, the second switch element is turned on. A rechargeable power supply device characterized by making an element non-conductive.