JP2006149078A - Power supply instantaneous shutoff prevention system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply instantaneous shutoff prevention system capable of being used by switching it to the internal battery of a battery drive apparatus without causing power supply instantaneous shutoff of a battery drive apparatus body when an external battery is removed from the battery drive apparatus body during using the external battery. <P>SOLUTION: In a power supply switching structure for supplying the power by switching the internal battery V1 and the attachable/detachable external battery V2 by switching circuits (1), (2), a clamping circuit comprising a diode 46 in which the output of a secondary battery 45 in the battery drive apparatus is as a voltage for clamping is connected to a power supply line O to prevent the instantaneous shutoff of the voltage of the power supply line caused by the attaching/detaching external battery V2. The voltage of the secondary battery used as a static memory and a backup battery of a clock or the like is used for the clamping. When the external battery is intentionally or suddenly removed, the power supply interruption can be prevented during use of the external battery. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a method for preventing power supply interruption when a second battery (external battery) is removed, and in particular, power supply interruption of an electronic device (battery drive device) that is operated by a battery power supply such as a mobile phone device to which an external battery can be attached. It relates to prevention methods.

  In recent years, thinning of component parts such as batteries, PWBs, LCDs, etc., and improvement of mounting technology have made it possible to realize mounting of narrow pitch components, etc., and it has become possible to realize small and thin mobile phone devices such as credit card type mobile phones. The situation has been reached.

  On the other hand, as a result of the downsizing and thinning of the mobile phone device, there are also concerns such as shortening the call time due to the decrease in the capacity of the internal battery, and as a means to solve this, an external battery is appropriately attached to the mobile phone device It can be used to suppress the consumption of the internal battery.

However, in such power supply by switching between the two power sources, there is a possibility that the supply voltage may cause a momentary interruption due to the attachment / detachment of one of the power sources, and it is important to have a power supply configuration that can prevent the momentary interruption.
As such a power supply structure, a structure in which two power supplies are respectively supplied to a power supply line via a diode is known (see Patent Document 1).

  FIG. 7 is a diagram showing a circuit principle of a power supply system using a diode. A diode OR configuration is adopted so that power is always supplied to the load from both the power sources V1 and V2 via the diodes D1 and D2, respectively, so that even if one of the power sources V1 or V2 is removed, the power source is not momentarily interrupted. Is.

  However, in the power supply configuration shown in FIG. 7, a voltage drop is generated from the power supply voltage by the forward voltage drop VF (about 0.4 V to 0.8 V) of the diode, the voltage value is low, and a narrow usage range (for example, 4. In the case of a battery power source of 2V to 3.3V, etc., VF has a disadvantage that it causes a loss of operable voltage and leads to shortening of battery life, and power sources V1 and V2 as viewed from the device receiving power supply. Are not independent of each other, interfere with each other between power sources, and cannot be designed on the device side such as changing the operation mode depending on whether the battery is an internal battery or an external battery.

  FIG. 8 is a diagram showing a power supply switching circuit configuration that can be used so that the two power supplies V1 and V2 are independent (see Non-Patent Document 1). The diode of the circuit shown in FIG. 7 is replaced with a switch circuit composed of two P-channel insulated gate transistors (PMOS transistors) whose sources are connected to each other. According to this circuit configuration, a control signal is output from the controller 31 and the control circuit 32 based on the voltage values of the input terminals of the power supplies V1 and V2, and the on / off states of the switch circuits are controlled in opposite directions. Thus, the two power sources V1 and V2 can be switched independently.

JP 2003-9424 A "LINEAR technology, Product Bulletin, Final Electrical Specification LTC4412 9th page" Internet homepage http://www.linear-tech.co.jp/datasheet/html/jp_pdf/j4412f.pdf

  As described above, it is possible to supply power from two power supplies to battery-powered equipment by using two switch circuits. In such a power supply switching system, one power supply can be attached or detached. If the switch circuit is switched, the switch circuit that should switch and output the battery may not be turned on immediately due to a delay in operation when switching the switch circuit. is there.

For example, when this power supply switching method is applied to an internal battery and an external battery of a mobile terminal device or the like, the power supply is not instantaneously switched to the internal battery V1 when the external battery V2 is unexpectedly removed from the mobile terminal device body. The supply is momentarily interrupted, the voltage of the power supply line drops to 0V, and the circuit does not move. For this reason, switching to the internal battery V1 is not automatically performed, and there is a problem that the mobile phone device or the like needs to be turned on again.
(the purpose)
An object of the present invention is to provide an instantaneous power supply prevention method that can be used by reliably switching to an internal battery of a battery-driven device without causing an instantaneous power supply interruption when the external battery is removed from the battery-driven device main body when using the external battery. It is to provide.

  Another object of the present invention is to provide a power supply interruption prevention system that enables an external battery and an internal battery to be switched independently without interfering with each other, and can prevent an interruption of the power supply when the external battery is removed. is there.

  The power supply interruption prevention system of the present invention can supply power to a power supply line (for example, O in FIG. 1) by an internal battery (for example, V1 in FIG. 1) and a removable external battery (for example, V2 in FIG. 1). In a method for preventing instantaneous power interruption of a battery-driven device (for example, 4 in FIG. 1), a clamp circuit that clamps the power supply line by an output voltage of a secondary battery (for example, 45 in FIG. 1) inside the battery-driven device is provided. The clamp circuit is constituted by a diode (for example, 46 in FIG. 1) connected between the output of the secondary battery and the power supply line.

  In addition, the battery-driven device includes a changeover switch (for example, switch circuits (1) and (2) in FIG. 1) for switching power supply from the internal battery or an external battery, and a control circuit for the changeover switch (for example, FIG. 1). 3), and the control circuit switches to supply power preferentially from the external battery when the external battery is connected, and the secondary battery is the internal battery or the external battery. The secondary battery is backed up to supply power to a logic processing unit (for example, 41 in FIG. 1) including at least a static memory and a clock circuit of an internal circuit even when the power of the battery-powered device is stopped. It is a battery.

  In particular, the battery-powered device is a mobile phone, and the voltage value of the secondary battery is lower than a specified value which is a detection threshold value on the lower limit side of a voltage range used as a battery power source specified by the mobile phone, and the circuit A voltage value that can be maintained is set, and the changeover switch includes two drain-source current paths connected in series between the internal battery and external battery and a power supply line, and a gate electrode controlled by the control circuit. It is characterized by comprising P-channel MOS transistors (for example, D10 to D21 in FIG. 1).

(Function)
By connecting a clamp circuit that uses the output of a secondary battery in a battery-powered device such as a cellular phone as a clamping voltage, the voltage of the power-supply line caused by an external battery attached to or detached from the battery-powered device can be reduced. Prevent momentary interruptions. In the configuration in which power is supplied by controlling the internal battery and the external battery, even when the external battery is disconnected from the battery-driven device main body, it can be used without causing a power interruption. The voltage of a secondary battery used as a backup battery for a static memory, a clock circuit or the like in a battery-driven device is used for clamping. During use of the external battery, it is possible to prevent an instantaneous power interruption when the external battery is intentionally and unexpectedly disconnected.

  According to the present invention, the power supply line is provided with a clamp circuit that uses the output voltage of the secondary battery inside the battery-driven device as a clamp voltage, so that power can be supplied even when the attached external battery is intentionally or unexpectedly removed. Since the power supply to the line is maintained, it is possible to prevent the harmful effects caused by the instantaneous power interruption of the battery-driven device.

  The clamp circuit can be realized with a simple configuration in which a diode is provided between the secondary battery and the power supply line.

  Furthermore, as a power supply switching circuit, it is possible to prevent the interference between batteries by switching the supply of power from the internal battery or the external battery by a changeover switch or the like composed of two P-channel MOS transistors. Is possible.

  As the secondary battery, it is possible to use a backup battery that is charged from an internal battery or an external battery and supplies power to internal circuits such as a static memory and a clock circuit even when the power is stopped.

  In particular, by applying to a mobile phone device, it is possible to realize a sufficient usable time even with a PCMCIA type mobile phone by attaching and detaching an external battery.

(Description of configuration)
FIG. 1 is a block diagram showing a power supply switching circuit according to an embodiment of the present invention.

  The present embodiment is a battery-driven device 4 that operates with a battery power source, and two batteries for supplying power to the battery-driven device 4, for example, an internal battery 1 (hereinafter referred to as V 1) built in the electronic device 4. A detachable external battery 2 (hereinafter referred to as V2) attached from the outside of the electronic device 4 via the connection terminal I, and four P-channel MOS transistors for supplying power to the battery-driven device 4 from any one of the batteries V1 and V2. A switching circuit including PMOS 10, PMOS 11, PMOS 20, and PMOS 21, and a control circuit 3 that controls the gate of each PMOS transistor and controls conduction / non-conduction of each of the PMOS transistors are provided.

  The switching circuit is configured as two switch circuits PMOS10, PMOS11, PMOS20, and PMOS21 in which two P-channel MOS transistors each having a parasitic diode between the source and the drain are connected in series between the source and the drain for each of the batteries V1 and V2. The drains of the output side PMOS transistors PMOS11 and PMOS21 of each switch circuit are connected in common and connected to the power supply line O of the battery drive device 4. Also, since the internal battery V1 and the external battery V2 operate independently without interfering with each other in the switching circuit, the parasitic diodes D10 and D11 and D20 and D21 are reversely connected so that no current flows through the circuit block through the parasitic diode. In this way, the source is connected to each other.

  In addition, the battery-driven device 4 includes various circuit blocks 47 as portable electronic devices and an AD conversion circuit ADC (analog-digital converter) (1) that inputs the voltages of the power supply lines O of the two switch circuits and converts them into digital signals. ) 42, an AD converter circuit ADC (2) 43 that inputs the voltage of the connection terminal I of the external battery V2 and converts it into a digital signal, and outputs of the ADCs 42 and 43, and various processes including processing as a clock circuit A central processing unit for processing and a logic processing unit 41 constituted by a logic circuit CPU / Logic, a secondary battery 45 as a backup power source, and a voltage of the power supply line O are inputted to charge the secondary battery 45. The output of the charging IC 44 and the secondary battery 45 is supplied to the power supply line O and the logic processing unit (CPU / Logic) 4. It comprises a supply diode 46 to the battery-driven device 4 etc., the.

  Here, the logic processing unit 41 outputs a control signal to the control circuit according to the voltage of the power supply line O and the connection terminal I of the external battery V2, and the control circuit 3 controls the gate electrodes of the four P-channel MOS transistors. Then, one of the two switch circuits is turned on, and when the external battery V2 is attached, only the switch circuit (2) PMOS 20 and PMOS 21 are turned on and power is supplied with priority over the internal battery V1. In a state where the external battery V2 is removed, only the switch circuit (1) PMOS10 and PMOS11 are made conductive (ON) and power is supplied from the internal battery V1.

  For the above control, the logic processing unit 41 detects the voltage VO of the power supply line O from the AD conversion circuit ADC (1) 42 and the voltage of the connection terminal I of the external battery V2 from the AD conversion circuit ADC (2) 43. An arithmetic processing function that inputs VI and sets a specified value, which is a detection threshold on the lower limit side of the voltage range used as a battery power supply, as a low voltage detection voltage value and outputs the following control signals based on the voltage VO and the voltage VI Have

(A) When the voltage at the terminal I exceeds the low voltage detection voltage value, a control signal for turning off the switch circuit 1 and turning on the switch circuit 2 is output to the control circuit 3.
(B) When the voltage at the terminal I is equal to or lower than the low voltage detection voltage value, a control signal for turning on the switch circuit 1 and turning off the switch circuit 2 is output to the control circuit 3.
(C) When the switch circuit 1 is in the off state and the switch circuit 2 is in the on state, when the voltage VO (voltage at the terminal I) of the power supply line O drops to the low voltage detection voltage value, the switch circuit 1 is turned on. A control signal for switching the circuit 2 to the OFF state is output to the control circuit 3.

  The control circuit 3 controls the gate electrodes of the PMOS transistors constituting each switch circuit by the control signal from the logic processing unit 41, and sets the on / off states of the switch circuits (1) and (2) to (a) to (c). ).

(Description of operation)
First, with respect to the power supply switching circuit shown in FIG. 1, the operation when the clamping circuit, which is a feature of the present invention, is not provided will be described.
FIG. 2 is a diagram showing a power supply switching circuit configuration when no clamp circuit is provided. In the circuit configuration shown in FIG. 1, the circuit composed of the charging IC 44, the secondary battery 45 and the diode 46 is excluded.

  When the external battery V2 normally supplies a voltage exceeding the low voltage detection voltage value to the battery-driven device 4 and is disconnected from the connection terminal I, the external battery V2 is disconnected from the state (b). The operation circuit (a) of the logic processing unit 41 should switch the switch circuit (1) to the on state and switch circuit (2) to the off state. However, since the switching operation of the switch circuit (1) including the switch circuit (1) itself or the logic processing unit 41 or the like to the ON state is delayed even by a normal circuit delay, the switch circuit (1) is switched from the internal battery V1. The power supply to the power supply line O via the delay is also delayed, and an instantaneous interruption occurs.

FIG. 3 is a time chart showing a voltage change of the power supply line when the external battery V2 is unexpectedly disconnected in a circuit having no clamp circuit.
When the external battery V2 is disconnected after the external battery V2 is attached to the battery-driven device 4 and the power supply line O is supplied with power from the external battery V2 via the switch circuit (2) (t1) As a result of the operation delay of the switch circuit, in particular, the switch circuit (1) is not instantaneously turned on, the voltage value of the power supply line O is instantaneously lowered to 0V as shown in the excessive characteristic shown in FIG. As a result, the power supply to the battery-powered device 4 is stopped, and the battery-powered device 4 enters an instantaneous power interruption state. Thereafter, the battery-powered device 4 is operated by the internal battery V1 when the user turns on the new power.

Next, the operation for preventing the instantaneous power interruption when the external battery V2 is disconnected in the power supply switching circuit of the present embodiment shown in FIG. 1 will be described.
FIG. 4 is a diagram illustrating a timing chart of the operation of the present embodiment.

In the present embodiment, the output voltage of the secondary battery as a backup power source charged by the constant charging IC 44 from the power supply line O can be supplied to the logic processing unit 41 via the diode 46 and supplied to the power supply line O. It has a connection configuration. Here, the clamp voltage by the secondary battery is a voltage value obtained by subtracting the forward voltage drop VF of the diode from the output voltage of the secondary battery, and is a voltage lower than the low voltage detection voltage value set by the battery drive device 4. Although it is a value, it is set to a voltage value at which the circuit of each part of the battery-driven device 4 operates normally.
With this configuration and the set voltage, the diode 44 is always in the reverse bias state and in the off state in the normal operation state where the voltage value of the power supply line O other than the momentary interruption is higher than the low voltage detection voltage value.

  When the external battery V2 is disconnected while the power supply line O is supplied with power from the external battery V2 via the switch circuit (2) (t1), the operation delay of the switch circuit, in particular, the switch circuit (1) Is not instantaneously turned on, the voltage of the power supply line O rapidly decreases. However, when the voltage of the power supply line O reaches the clamp voltage, the diode 44 is turned on, and a decrease to the lower level is prevented.

  With the above clamping operation, even if the external battery V2 is intentionally or unintentionally removed while the external battery V2 is in use, the diode 44 becomes conductive during a transient short period of time when the external battery V2 is switched to, and the output of the secondary battery The operation of the battery-powered device 4 is maintained when the voltage suppresses the decrease in the voltage of the power supply line O.

  In addition, since the output voltage of the secondary battery is supplied to the main circuit such as the logic processing unit 41 even in the power-off state, the switch circuit (1) is switched on at time (t2) within the short period, Thereafter, power is supplied from the internal battery V <b> 1 to the battery-driven device 4.

  In the setting example of the present embodiment shown in FIG. 4, the batteries V1 and V2 have an initial value (voltage value of the charge state initial value) of 4.2V, the low voltage detection voltage value of the battery drive circuit is 3.6V, and the secondary The battery voltage is set to 3.7V (clamping voltage is 3.3V) with the forward voltage drop VF being 0.4V. In this example, when the battery is disconnected (t1), the power supply line tries to drop to 0V, but the output voltage of the secondary battery 3.7V clamps the power supply line O to 3.3V through the diode. Thus, the power supply line O is maintained at 3.3 V even when no power is supplied from both switch circuits. Thereafter, the logic processing unit 41 detects a decrease in the low voltage detection voltage value of 3.6 V or less from the output of the ADC 42 and outputs a control signal to the control circuit 3, and the control circuit 3 switches the switch circuits (1), (2 ) Is controlled to switch from the battery V2 to the internal battery V1 (t2), and the power supply state of the original internal battery V1 is set to prevent the power supply line from being momentarily cut to 0V.

  FIG. 5 is a block diagram showing a mobile phone to which the instantaneous power interruption prevention system of the present invention is applied, and FIG. 6 is a perspective view showing a PCMCIA card size mobile phone in which a thin lithium ion battery is detachably configured as an external battery. is there.

  As shown in FIG. 5, the mobile phone main body 5 includes an antenna for a telephone call and a high frequency circuit RF, a memory circuit 55, a display unit LCD, a key input unit KEY, a receiver / vibrator for incoming calls, a microphone / speaker for transmission and reception, A central processing unit CPU that is connected to a clock display or the like and performs each processing, and a logic processing unit BB51 that includes a logic circuit LOGIC.

  The mobile phone 5 includes a built-in battery (V 1) 56, a power switching circuit 57 connected to the built-in battery 56 and an external battery (V 2) 6 that can be attached to and detached from the mobile phone terminal device 5, and the power switching circuit 57 A power control circuit 58 that supplies power to each block by output is provided.

  Further, in the mobile phone main body, a secondary battery 53 as a backup power source when the power is cut off (when the power is off), a charging IC 52 for charging the secondary battery 53 from the built-in battery 56 or the external battery 6, and the 2 The output voltage of the secondary battery 53 is applied to the logic processing unit 51 and the memory 55 via the diode 54, and applied to a power supply line (not shown) on the output side of the power supply switching circuit 57.

  With the above configuration, problems such as a reduction in call time due to a reduction in the capacity of the internal battery due to a reduction in the size and thickness of the mobile phone can be solved, and an adverse effect of a momentary interruption of the power supply line due to the attachment / detachment of the external battery can be eliminated.

It is a block diagram which shows the power supply switching circuit of one Embodiment of the power supply instantaneous interruption prevention system of this invention. It is a figure which shows the power supply switching circuit structure when not having a clamp circuit. It is a time chart which shows the voltage change of the power supply line when the external battery V2 comes off in the circuit which does not have a clamp circuit. It is a figure which shows the timing chart of the operation | movement of this Embodiment. It is a block diagram showing a mobile phone to which the instantaneous power interruption prevention method of the present invention is applied, It is a perspective view which shows the mobile telephone of the PCMCIA card size which comprised the thin lithium ion battery detachably as an external battery. It is a figure which shows the circuit principle of the power supply system which uses a diode. It is a figure which shows the power supply switching circuit structure which can be used so that two power supplies V1 and V2 may become independent.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,56 Internal battery 2, 6 External battery 3 Control circuit 4 Battery drive apparatus 5 Cellular phone 41, 51 CPU / Logic (logic processing part)
42, 43 ADC
44, 52 Charging IC (Charge Integrated Circuit)
45, 53 Secondary battery 46, 54 Diode 47 Each circuit block 51 Logic treatment unit 57 Power switching circuit 58 Power control circuit D10, D11, D20, D21 Parasitic diode PMOS10, PMOS11, PMOS20, PMOS21 P channel MOS transistor

Claims (9)

In the power supply prevention method for battery-powered equipment that can supply power to the power supply line with an internal battery and a removable external battery,
A power supply interruption prevention system comprising: a clamp circuit that clamps the power supply line by an output voltage of a secondary battery inside a battery-driven device.   2. The instantaneous power interruption prevention system according to claim 1, wherein the clamp circuit comprises a diode connected between an output of the secondary battery and the power supply line.   The battery-powered device includes a changeover switch for switching supply of power from the internal battery or an external battery, and a control circuit for the changeover switch. The control circuit has priority from the external battery when the external battery is connected. 3. The power supply interruption prevention method according to claim 1, wherein switching is performed so as to supply electric power.   4. The power supply interruption prevention method according to claim 1, wherein the secondary battery is charged from the internal battery or an external battery.   5. The instantaneous power interruption prevention system according to claim 1, wherein the secondary battery is a backup battery that supplies power to an internal circuit even in a power-off state of a battery-driven device.   6. The power supply interruption prevention system according to claim 5, wherein the internal circuit is at least a static memory and a clock circuit of a battery-driven device.   The voltage value of the secondary battery is set as a voltage value that is lower than a specified value that is a detection threshold value on a lower limit side of a voltage range to be used as a battery power source and that can maintain circuit operation. The power supply interruption prevention method according to any one of claims 1 to 6.   The power supply interruption prevention method according to any one of claims 1 to 7, wherein the battery-powered device is a mobile phone device.   The changeover switch is composed of two P-channel MOS transistors in which a drain-source current path is connected in series between the internal battery and the external battery and a power supply line, and a gate is controlled by the control circuit. The instantaneous power interruption prevention method according to any one of claims 3 to 8.

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