JP2002373038A - Power source control circuit and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a malfunction when turning on a power source by performing the power source control for a peripheral circuit using the reset of a microcomputer and a plurality of power sources. SOLUTION: The output of a reset circuit 105 is connected to the reset input terminal of a first electronic circuit 106 and the control terminal of a switch 109. When the voltage of a power source 101 exceeds a prescribed voltage value, the operation of the first electronic circuit 106 is started and the switch 109 is changed over. The switch 109 is provided on the GND line of the power source 101 and whether or not the GND line is to be disconnected is controlled by the output of the reset circuit 105. This GND line is made into GND line common for a plurality of electronic circuits 107 and 108 to be operated by different voltages so that the ON/OFF of power sources of electronic circuits 106, 107 and 108 can be simultaneously controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply control circuit for controlling a power supply of an electronic circuit and an electronic apparatus.

[0002]

2. Description of the Related Art Conventional power supply control circuits and electronic devices include:
For example, an output of a reset circuit is input to a reset terminal of a microcomputer and a circuit for controlling power to a peripheral circuit, such as a power supply control circuit described in JP-A-6-243269, so that the microcomputer is reset and the power supply of the peripheral circuit is reduced. There is an invention that performs control to prevent malfunction.

[0003]

However, conventional power supply control circuits and electronic equipment have a problem in that when controlling peripheral circuits using a plurality of power supplies, it is necessary to provide a power supply control circuit for each of different power supplies. are doing. In addition, when the voltage rises after charging the secondary battery, a malfunction may occur if the rise time of the power supply is long.

According to the present invention, even when a plurality of power supplies, which are the problems of the prior art, are used, the microcomputer and peripheral circuits do not malfunction even if a power supply control circuit is not provided for each of the power supplies, and the power supply rises steeply. To prevent malfunction.

[0005]

SUMMARY OF THE INVENTION The present invention provides a power supply for supplying power, a plurality of voltage conversion circuits for converting the voltage of the power supply to respective voltages, and a plurality of voltage conversion circuits converted by the plurality of voltage conversion circuits. A plurality of electronic circuits that are driven by a voltage and share the power supply and the ground, and a switch that opens and closes the ground to the ground connected to the power supply and the plurality of electronic circuits; and And a reset circuit that outputs a reset signal by detecting the voltage of the power supply.

According to the present invention, the reset circuit is further connected to at least one of the plurality of electronic circuits,
A power supply control circuit that resets the remaining electronic circuits by resetting the at least one electronic circuit.

According to the present invention, there is provided a power supply control circuit in which the plurality of electronic circuits include an electronic circuit that operates with at least two or more power supply voltages, and a ground of the power supply voltage of the certain electronic circuit is shared.

According to the present invention, the power supply circuit is a secondary battery, and a charge control circuit for charging the secondary battery and selecting whether or not to charge the secondary battery via the transmission control circuit. The power supply control circuit according to any one of claims 1 to 3, further comprising: a power supply selection circuit that performs switching when the output of the power supply selection circuit is higher than a predetermined voltage. is there.

According to the present invention, the power supply selection circuit has at least two inputs, and outputs a first input when the power supply selection circuit has a predetermined voltage or less, and the power supply selection circuit outputs the first input when the power supply selection circuit has a predetermined voltage or less. 5. The method according to claim 4, wherein the second input is output when the signal is high.
It is a power supply control circuit as described.

[0010] The present invention is an electronic apparatus having these power control circuits.

An output signal of a reset IC which detects a voltage of a power supply and outputs a reset signal at a predetermined voltage is connected to at least two or more input terminals. One is connected to the reset input terminal of the first electronic circuit having the reset input terminal, and starts the operation of the first electronic circuit when the secondary battery voltage exceeds a predetermined voltage value. Another connection destination of the output signal of the reset IC is a control signal input terminal of the switch. The switch is provided on a GND line of a power supply, and controls whether to disconnect or connect the GND line by an output signal of a reset IC. The GND line has a common GND in the second electronic circuit that operates at a plurality of power supply voltages. For example, the secondary battery is charged and the voltage gradually increases.
Changes from “L level” to “H level” to cause the first electronic circuit to perform a reset operation, and at the same time, controls a switch to turn on the power supply to operate the second electronic circuit. If the second electronic circuit does not receive a reset signal and has only a power-on reset circuit, an accurate reset operation is performed by the power-on reset circuit, so that more accurate operation can be guaranteed.

In addition, when charging is performed from a place where the capacity of the secondary battery is not sufficient, it takes some time since the voltage of the secondary battery rises to a voltage at which the electronic circuit operates normally. In order to eliminate the time for the secondary battery voltage to rise, it is possible to select and use both methods of supplying the power of the electronic circuit from the secondary battery and supplying the electronic circuit directly from the charging DC power supply to the electronic circuit. By doing so, the power supply can rise steeply and malfunctions can be prevented.

[0013]

Embodiments of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram showing a first embodiment according to the present invention. The power supply 101 is a secondary battery or a capacitor such as a lithium ion secondary battery, a lithium polymer secondary battery, or a nickel hydride secondary battery used in a portable device or the like. Further, the power supply 101 may be a primary battery that performs only discharge. Each of the electronic circuits is supplied with power from the power supply 101 and is converted to a predetermined voltage using the voltage conversion means 102, 103, and 104 in order to use each of the electronic circuits at a voltage that does not cause malfunction. Voltage conversion means 102, 1
03 and 104 are voltage regulators and the like.

The first voltage conversion circuit 102 supplies power to the first electronic circuit 106. Second voltage conversion circuit 10
3 supplies power to the second electronic circuit 107. The third voltage conversion circuit 104 supplies power to the third electronic circuit 108. First electronic circuit 106, second electronic circuit 10
The seventh and third electronic circuits 108 perform voltage conversion of signals between the respective electronic circuits, and input / output signals without concern for operating voltages of the respective electronic circuits.

The reset circuit 105 detects the voltage of the power supply 101. The detected input voltage is compared with a reference voltage.
If the input voltage is lower than the reference voltage, an "L level" signal is output, and if the input voltage is higher than the reference voltage, an "H level" signal is output. Further, when the voltage is gradually increased or decreased, the output voltage does not oscillate even if the level of the input voltage slightly fluctuates (fluctuates), so that a hysteresis is provided. The voltage detected by the reset circuit 105 is set to a voltage value at which the electronic circuits 106, 107, and 108 do not malfunction.

The output of the reset circuit 105 is connected to at least two places. One is a reset terminal of the first electronic circuit 106. The other is a signal input terminal of the switch 109. The first electronic circuit 106 has a built-in reset circuit. The first electronic circuit 106 is in a reset state when the output signal of the reset circuit 105 is at “L level”, and performs a normal operation when it is at “H level”. Switch 1
An output terminal 09 is connected to GND of the second electronic circuit 107 and the third electronic circuit 108, and an input terminal is connected to GND of the voltage conversion circuits 102, 103, 104 and the power supply 101. When the voltage of the power supply 101 is lower than the predetermined voltage,
The output of the reset circuit 105 becomes “L level”. Then, the switch 109 is turned off, so that the power is turned off. Conversely, when the voltage of the power supply 101 is higher than the predetermined voltage, the output of the reset circuit 105 goes to “H level”. Then, the switch 109 is turned on,
Power supply is connected. When the switch 109 changes from OFF to ON, current starts flowing. The built-in power-on reset circuit operates in the second electronic circuit 107 and the third electronic circuit 108, and normal operation starts after the reset.

That is, when the voltage of the reset circuit 105 changes from the "L level" to the "H level" when the voltage exceeds a predetermined value, the first electronic circuit 106 starts the operation after reset, and the second electronic circuit 106 operates. The circuit 107 and the third electronic circuit 108 are turned on, the power-on reset circuit operates, and the reset operation starts.

(Second Embodiment) FIG. 2 is a circuit diagram showing a second embodiment according to the present invention. The power supply 201 is a lithium secondary battery. Although not shown, charging can be performed using an external charger.

The memory 207 has a power-on reset circuit inside. However, there is no reset input terminal and 0V
If the rise time of the power supply from 10 V to 2.7 V takes 10 milliseconds or more, a malfunction occurs. The operating power supply range of the memory 207 is 2.7V to 3.3V. Usually, 3.
Operate at 0V. The display circuit 208 is an LCD display circuit, and the CPU 206 controls display. The operating power supply range of the display circuit 208 is from 3.0 to 3.6 V, and usually is 3.
Operate at 3V.

The CPU 206 operates according to a program stored in the memory 207, and has an operating power supply range from 1.8 to 2.
2V, and is usually operated at 2.0V.

The first voltage regulator 202 is C
The power supply for PU outputs 2.0V. The second voltage regulator 203 outputs 3.0 V with a memory power supply. The third voltage regulator 202 outputs 3.3 V with a power supply for a display circuit. The memory 207 includes a flash memory and a RAM, and is also used as a work area for storing programs and performing calculations. The CPU 20
Reference numeral 6 controls the display circuit 208 to perform display on the LCD, and operates according to a program stored in the memory 207 for various controls and calculations. The reset IC 205 includes a power supply 201
When the voltage is less than 2.8 V, a signal of “L level” is output, and when the voltage is 2.8 V or more, a signal of “H level” is output. Reset IC
The output of 205 is the reset terminal of CPU 206 and NchM
Connected to the gate of OSFET 209.

The Nch MOSFET 209 has a reset C
If the output of I205 is "L level", it is OFF, and if it is "H level", it is ON. The source of the Nch MOSFET 209 is connected to the power supply GND, and the drain is connected to the CPU 206, the memory 207, and the GND of the display circuit 208. With this configuration, if the voltage of the power supply 201 is lower than 2.8V, the power of the CPU 206, the memory 207, and the display circuit 208 is turned off.
The power sources of the U 206, the memory 207 and the display circuit 208 are connected and operable. By the switching operation of the Nch MOSFET 209, the rising of the power supply of the CPU 206, the memory 207, and the display circuit 208 becomes steep, and the malfunction of the memory 207 can be prevented. The NchMOSFET is advantageous because the smaller the resistance between the source and the drain, the smaller the voltage drop. It is desirable that the resistance is 0.1Ω or less.

(Third Embodiment) FIG. 3 is a circuit diagram showing a third embodiment according to the present invention. The power supply 301 is a secondary battery. The plus of the power supply 301 is connected to the charge control circuit 311, the power supply selection circuit 312, and the cathode of the diode 313. The minus of the power supply 301 is the charge control circuit 311, the reset IC 312, the source of the FET 309, and the GND and C of the first voltage regulator 302.
Connected to GND of PU306. Charge control circuit 311
Performs constant-current charging until the battery voltage reaches a predetermined voltage, and then performs constant-voltage charging. The CPU 306 controls the ON / OFF of the function. CPU306
Is in a non-operating state, the charging control circuit 311 may malfunction. Therefore, the power supply 301
02 to the charging terminal 310 during charging.
A power supply selection circuit 312 is provided so that power can be supplied to the CPU 302 from the power supply. Power supply selection circuit 3
The power supply selected by the power supply 12 becomes the power supply voltage of 2.0 V by the first voltage regulator 302,
306. The power supply selected by the power supply selection circuit 312 has a power supply voltage of 3.0 V by the second voltage regulator 302 and is supplied to the memory 307. The memory 307 is a memory for storing programs of the CPU 306 and for storing data such as calculations. The power supply selected by the power supply selection circuit 312 becomes a power supply voltage of 3.0 V by the third voltage regulator 304, is supplied to the display circuit 306, and becomes a power supply for driving display. The memory 307 and the display circuit 308 have a common GND line, and are connected to the drain of an NchMOS FET 309. The source of the FET 309 is connected to the negative terminal of the battery, and the power of the display circuit 308 and the memory 307 can be turned off or connected by a gate signal.

The reset IC 305 is connected to the power supply selection circuit 31
The output signal is monitored at 2.8 V and the output signal is varied. The reset IC outputs an “L” signal when the detected voltage is lower than 2.8V, and outputs an “H” signal when the detected voltage is higher than 2.8V. The reset signal output line 314 is F
It is connected to the gate of the ET 309 and the CPU 306. That is, if the output of the power supply selection circuit 312 is less than 2.8V,
The CPU 306 enters a reset state. Then, memory 3
07 and the display circuit 308 are turned off and inactive. If the output of the power supply selection circuit 312 is 2.8 V or more, the reset of the CPU 306 is released. Then, the power of the memory 307 and the display circuit 308 is turned on and the memory 307 and the display circuit 308 are operated. By being in the operating state, the CPU
306 is a charge control circuit 3 via the CPU output signal line 315
11 to start the operation of the charge control circuit 311.

The diode 313 is connected to a power supply selection circuit 312
Is higher than the voltage of the power supply 301, a current flows, and the power supply 301 is charged. That is, when charging is started from a place where the power supply 301 has no capacity, the power supply voltage gradually rises, and it takes time to reach a voltage at which the electronic circuit operates normally. In order to shorten this time, the power supply selection circuit 312 may be used to supply power directly from the charging terminal 310 to the electronic circuit. That is, the power supply selection circuit 3
12, the current from the charging terminal 310 and the current from the power source 301 are selectively output.

Here, an example of the power supply selection circuit 312 will be described with reference to the drawings. FIG. 4 is a circuit diagram illustrating an example of a power supply selection circuit 312 used in the third embodiment. A power supply selection circuit 31 shown in FIG.
It corresponds to 2. The first input terminal 402 is connected to the charging terminal 31
Current is supplied from the plus of zero. Second input terminal 40
3, the current is supplied from the output of the charge control circuit 311 or the positive pole of the power supply 301. The 3.0 V voltage regulator 404 controls the input voltage between GND and IN to GND.
The output is converted so that the voltage between -OUT becomes 3.0 V. The first diode 405 is a backflow prevention diode that prevents a current from flowing into the OUT terminal. The second diode is a backflow prevention diode that prevents a current from flowing into the second input terminal 403. The output terminal selects and outputs the output of the diode having the higher voltage of either the first diode 405 or the second diode 406. That is, if the voltage of the second input terminal 403 is 3.0 V or less, the output terminal 407 outputs 3.0 V, and if the voltage of the second input terminal 403 is 3.0 V or more, the output terminal 407 is the second input terminal. An output from the power supply 301 or the charge control circuit 311 input to 403 is output.

FIG. 5 is a waveform chart showing the operation of the third embodiment. The battery voltage 501 indicating the operation of the voltage of the power supply 301, the reset IC output 314 of the reset IC 305
Of reset IC 502 showing operation of
9 shows a switch state 503 indicating the state of the switch No. 9 and an output 504 of the power supply selection circuit indicating the operation of the output of the power supply selection circuit 312.

The battery voltage 501 is a diagram showing a process in which the battery is charged and the voltage gradually rises when there is no battery capacity. When a 6.0 V DC power supply is connected to the charging terminal 310, charging starts. When the power supply 301 is 3.0 V or less, 3.0 V is output from the power supply selection circuit 312, which serves as a load power supply, and further charges the power supply 301 via the diode 313. 2. The power supply 301 is charged.
When the voltage exceeds 0 V, the power supply 301
Is output. The output 504 of the power supply selection circuit is indicated by a broken line a just where the output of the power supply selection circuit 312 changes. The one-dot broken line of the output 504 of the power supply selection circuit
1 is shown. Since the reset IC 305 starts charging and the output of the power supply selection circuit 312 is 3.0 V,
The state 502 of the output of the reset IC becomes “H” upon the start of charging, and the CPU 306 becomes an operating state. Further, the state of the FET 309 indicated by the switch state 503 also changes from the OFF state to the ON state at the start of charging, and power flows to the peripheral circuits.

By providing the power supply selection circuit 312 in this manner, even when the voltage of the power supply 301 is low, the power supply selection circuit 31
Since the power is supplied to the load via the load 2, the load can operate.

[0030]

As described above, even in a circuit using a plurality of voltages, the reset means 105 and the switch means 109 can prevent a malfunction at the time of turning on the power of the electronic device or at the time of charging with one power supply control circuit. When an NchMOS FET is used, the rise time of the power supply is shortened, so that the voltage gradually increases during charging, thereby preventing loss and malfunction due to through current occurring near the threshold. In addition, NchMOS type FE
Since the resistance between the source and the drain of T is low, there is no need to worry about voltage drop due to the transistor. When the secondary battery is charged from a state where there is no capacity, the electronic device can be used immediately after the start of charging.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment.

FIG. 2 is a block diagram showing a second embodiment.

FIG. 3 is a block diagram showing a third embodiment.

FIG. 4 is a circuit diagram illustrating an example of a power supply selection circuit used in a third embodiment.

FIG. 5 is a waveform chart showing an operation of the third embodiment.

[Explanation of symbols]

 201 power supply 209 NchMOSFET 301 power supply 309 FET 310 charging terminal 313 diode 401 wavy line 402 first input terminal 403 second input terminal 404 3.0 V voltage regulator 405 first diode 406 second diode 407 output terminal

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5B011 DA06 EA02 EA08 MA01 MA12 MB11 5B054 AA11 AA13 BB01 CC01 DD01 EE05 5G065 BA00 DA01 DA07 EA02 FA02 GA04 GA06 HA04 KA02 LA01 MA09 MA10 NA06

Claims (6)

[Claims] A power supply for supplying power; a plurality of voltage conversion circuits for converting the voltage of the power supply to respective voltages; and a power supply driven by the respective voltages converted by the plurality of voltage conversion circuits. A plurality of electronic circuits having a common ground; a switch for opening and closing the ground to the ground connected to the power supply and the plurality of electronic circuits; and a reset signal connected to the switch and detecting a voltage of the power supply. And a power supply control circuit comprising: 2. The power supply control according to claim 1, wherein the reset circuit is further connected to at least one electronic circuit of the plurality of electronic circuits, and resetting the at least one electronic circuit also resets the remaining electronic circuits. circuit. 3. The power supply control circuit according to claim 2, wherein the plurality of electronic circuits include an electronic circuit that operates with at least two or more power supply voltages, and a common ground of the power supply voltage of the certain electronic circuits is used. . 4. The power supply circuit is a secondary battery, a charge control circuit for charging the secondary battery, and a power supply for selecting whether or not to charge the secondary battery via the transmission control circuit. The power supply control circuit according to any one of claims 1 to 3, further comprising: a selection circuit; and a diode configured to switch to charge the secondary battery when an output of the power supply selection circuit is higher than a predetermined voltage. 5. The power supply selection circuit has at least two inputs, and outputs a first input when the power supply selection circuit is lower than a predetermined voltage, and outputs a first input when the power supply selection circuit is higher than a predetermined voltage. 5. The power supply control circuit according to claim 4, wherein said output circuit outputs a second input. 6. An electronic apparatus comprising the power supply control circuit according to claim 1.