JP3920361B2 - Microcomputer protection system - Google Patents

Description

[0001]
[Industrial application fields]
The present invention is a microcomputer applied to a device using a microcomputer that switches from a normal power consumption mode in which power is supplied from an AC power supply to a low power consumption mode in which power is supplied from a backup battery when the AC power supply is off. Concerning protection system.
[0002]
[Prior art]
FIG. 6 is an explanatory diagram of power consumption mode switching according to the prior art. As can be seen from the figure, an AC power plug P is connected to the primary side of the transformer Tr, and a diode D and a capacitor C are connected in series to the secondary side. A resistor R and a Zener diode ZD are further connected in series with the capacitor C. An electric wire is connected from the connection point of the resistor R and the Zener diode ZD to an alternating current (AC) detection port of a microcomputer (not shown). The microcomputer is supplied with power from a backup battery (not shown) in a normal power consumption mode in which power is supplied from an AC power supply when the voltage level DC at the AC detection port is high. Switch to low power consumption mode.
[0003]
[Problems to be solved by the invention]
In the power consumption mode switching according to the above-described prior art, when the contact failure occurs between the AC power plug and the AC power outlet receiving it, the voltage level DC is pulsed when the AC power is turned on and off instantaneously. The high level and the low level are repeatedly changed so that the microcomputer malfunctions, and sometimes an excessive pulse is inputted to the AC detection port of the microcomputer and the microcomputer is destroyed. There is also a problem that the microcomputer malfunctions due to pulse noise.
[0004]
SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a microcomputer protection system which does not have the above-mentioned problem, that is, eliminates malfunction of the microcomputer and protects the microcomputer from destruction. Another object is to provide a microcomputer protection system in which the microcomputer does not malfunction due to pulse noise.
[0005]
[Means for Solving the Problems]
FIG. 1 is a basic block diagram of the present invention. The microcomputer protection system of the present invention that solves the above problems is connected to an alternating current power supply, converts the alternating current into a constant voltage direct current when the alternating current power is on and supplies it to the microcomputer 7, and is built in when the alternating current power is off. A constant voltage circuit 3 for supplying direct current from a backup battery to the microcomputer 7, a rectifier circuit 4 connected to an alternating current power source for converting alternating current to direct current, and receiving the output of the rectifier circuit 4, the alternating current power source is turned off. When the switch is turned on, charging is started and a high level voltage is output after a predetermined time. When the AC power supply is switched from on to off, the charge / discharge circuit 5 starts discharging and immediately outputs a low level voltage. When the output voltage is low level, a low level voltage is output, and when the output voltage is high level, the output voltage is high. The mode switching circuit 6 that outputs the bell voltage and the output voltage of the mode switching circuit 6 are switched. When the output voltage is low level, the mode is switched to the low power consumption mode. When the output voltage is high level, the normal power consumption is achieved. And a microcomputer 7 for switching to the mode.
In the microcomputer protection system of the present invention, the charge / discharge circuit 5 and the mode switching circuit 6 are configured to include an element that absorbs pulse noise.
[0006]
[Action]
In the microcomputer protection system of the present invention, the charging / discharging circuit 5 receiving the output of the rectifying circuit 4 starts charging when the AC power source is switched from OFF to ON, and outputs a high level voltage after a predetermined time. Is switched from on to off, discharge starts and a low level voltage is immediately output. Therefore, the mode switching circuit 6 that receives the output voltage of the charge / discharge circuit 5 has the output voltage of the charge / discharge circuit 5 of low level. When the output voltage is high, the microcomputer 7 outputs a high level voltage for setting the microcomputer 7 in the normal power consumption mode. These outputs are input to the microcomputer AC detection port. The microcomputer 7 is constantly supplied with constant voltage direct current from the constant voltage circuit 3, but the microcomputer 7 switches itself to the low power consumption mode when the voltage of the AC detection port becomes low level. The operation is performed by the electric power supplied from the backup battery 8 incorporated in the circuit 3. Therefore, even if a sudden power on / off occurs, the voltage to the AC detection port of the microcomputer 7 is kept at a low level during the transient time, so the microcomputer 7 does not malfunction and an excessive pulse is detected by the microcomputer. The microcomputer is protected from destruction without input to the AC detection port.
Since the microcomputer protection system of the present invention further includes an element that absorbs pulse noise, the microcomputer does not malfunction.
[0007]
【Example】
FIG. 2 is a circuit diagram of an embodiment according to the present invention. In this figure, the portions surrounded by a square with a broken line indicate the constant voltage circuit 3, the rectifier circuit 4, the charge / discharge circuit 5, the mode switching circuit 6 and the battery 8, respectively, and the portion surrounded by a solid line with a rectangle indicates the microcomputer 7. Show. The microcomputer protection system according to the embodiment of the present invention supplies AC 100V power to the primary side of the transformer Tr by turning on the switch SW connected in series to the primary side of the transformer Tr. The constant voltage circuit 3 is connected to the secondary side of the transformer Tr. One end of the secondary side of the transformer Tr is connected to the constant voltage regulator 9 via the diode D3. Is converted to a constant voltage direct current and supplied to the microcomputer 7 through the diode D4. When the AC power is off, direct current is supplied from the built-in backup battery 8 to the microcomputer 7. The diode D4 is a diode provided to prevent backflow from the battery 8. The rectifier circuit 4 includes a diode D1 and a resistor R1 connected in series, and converts alternating current into direct current. The charge / discharge circuit 5 is a circuit that charges the capacitor C3 when the switch SW is on and discharges the capacitor C3 when the switch SW is off. The mode switching circuit 6 receives the output of the charge / discharge circuit 5 and outputs a low level voltage when the microcomputer 7 is operated in the low power consumption mode according to the potential of the capacitor C5, that is, the potential at the point F. When operating in the normal power consumption mode, the circuit switches to output a high level voltage. The output DC of the mode switching circuit 6 is input to the AC detection port of the microcomputer 7. The battery 8 is a battery that supplies power to the microcomputer 7 to back up the microcomputer 7 when the AC power is off. The capacitors C2, C4, C5 and the inductance L1 are elements provided for absorbing pulse noise. The operation of the circuit diagram shown in FIG. 2 will be described below with reference to time charts of voltage levels of the respective parts. In the time charts described below with reference to FIGS. 3 to 5, the horizontal axis indicates time, and the vertical axis indicates voltage level.
[0008]
FIG. 3 is a time chart when the potential at each point in the circuit diagram of the embodiment is switched from power on to off. When the power supply is switched from on to off, the voltage on the secondary side of the transformer Tr becomes 0, the negative potential of the diode D1 disappears, and the capacitor C7 is sufficiently larger than the capacitor C1, so the potential at the point A changes from negative to positive high level. The transistor TR1 is turned on, the capacitor C3 is instantaneously discharged through the transistor TR1 and the resistor R6, the potential at the point B becomes 0V, the transistor TR2 is turned off, and the potential at the point E changes from 0V to the high level. TR3 is turned on and the potential at the point F changes from high level to low level, and the microcomputer 7 receiving this switches the normal power consumption mode to the low power consumption mode. However, the capacitor C6 is switched from the power-on to the off-state by preventing the backflow of the diode D2, and then maintains the potential for a predetermined time. Immediately after the power-off, the charge stored in the capacitor C6 flows to the base of the transistor TR3 via the resistor R4. The transistor TR3 is turned on and the point F is set to the low level.
[0009]
FIG. 4 is a time chart when the potential at each point in the circuit diagram of the embodiment is switched from power-off to on. When the power supply is switched from OFF to ON, a voltage is generated on the secondary side of the transformer Tr, a negative potential of the diode D1 is generated, and the potential at the point A is changed from a positive high level by the ratio of the resistors R1 and R2. The transistor TR1 is turned off, the capacitor C3 is charged through the resistor R3 and discharged through the resistor R6, the potential at the point B rises, and the transistor TR2 is turned on for a predetermined time T seconds after the power is turned on. The potential at point E is changed from high level to 0 V, the transistor TR3 is turned off, and the potential at point F is changed from low level to high level. The microcomputer 7 receiving this changes from the low power consumption mode to the normal power consumption mode.
[0010]
FIG. 5 is a time chart at the time of repeatedly switching the power supply off / on at each point in the circuit diagram of the embodiment. This figure shows a time chart when the power source is repeatedly switched off, on, off, on from the power source on state. The charging time for the capacitor C3 is determined by the values of the resistor R3, the resistor R6, and the capacitor C3. By these selections, a time T seconds until the transistor TR2 is turned on after the power is turned on is set. When the AC power source is repeatedly turned off, on, off, and on while the AC power source is on, when the power source is first switched from on to off at time t1, the secondary voltage of the transformer Tr becomes 0, and the diode D1 Since the capacitor C7 is sufficiently larger than the capacitor C1, the potential at the point A changes from negative to positive high level, the transistor TR1 is turned on, and the capacitor C3 is instantaneously discharged through the transistor TR1 and the resistor R6. The potential at the point B is 0V, the transistor TR2 is turned off, the potential at the point E is changed from 0V to the high level, the transistor TR3 is turned on, and the potential at the point F is changed from the high level to the low level. Switch from normal power consumption mode to low power consumption mode.
[0011]
Thereafter, when the power source is switched from OFF to ON at time t2, a voltage is generated on the secondary side of the transformer Tr, a negative potential of the diode D1 is generated, and the potential at the point A is positive due to the ratio between the resistors R1 and R2. The transistor TR1 is turned off, the capacitor C3 is charged through the resistor R3 and discharged through the resistor R6, and the potential at the point B rises, but within a predetermined time T seconds from the time t2. Since the power source is switched from on to off at time t3, the transistor TR2 does not turn on from time t2 to t3, the potential at point E remains high, and the transistor TR3 remains on and F The potential at the point remains at a low level, and the microcomputer 7 receiving this maintains the power consumption mode in the low power consumption mode.
[0012]
Thereafter, when the power source is switched from OFF to ON at time t4, the capacitor C3 is similarly charged through the resistor R3 and discharged through the resistor R6, and the potential at point B rises, and T seconds after time t4. At time t5, the transistor TR2 is turned on, the potential at the point E is changed from high level to 0 V, the transistor TR3 is turned off, and the potential at the point F is changed from low level to high level. To normal power consumption mode.
[0013]
【The invention's effect】
As described above, according to the microcomputer protection system of the present invention, the charging / discharging circuit that receives the output of the rectifier circuit starts charging when the AC power source is switched from OFF to ON, and the high level voltage after a predetermined time. When the AC power supply is switched from ON to OFF, the discharge starts and immediately outputs a low level voltage. Therefore, the mode switching circuit that receives the output voltage of the charge / discharge circuit has the output voltage of the charge / discharge circuit When it is low level, it outputs a low level voltage that sets the microcomputer to the low power consumption mode. When the output voltage is high level, it outputs a high level voltage that sets the microcomputer to the normal power consumption mode. Those outputs are sent to the microcomputer's AC detection port, so even if a sudden power on / off occurs, the microcomputer Without generating operation, it is protected against destruction, even longer and thus of a backup battery life.
According to the microcomputer protection system of the present invention, the microcomputer further includes an element that absorbs pulse noise, so that the microcomputer does not malfunction.
[Brief description of the drawings]
FIG. 1 is a basic block configuration diagram of the present invention.
FIG. 2 is a circuit diagram of an embodiment according to the present invention.
FIG. 3 is a time chart at the time of switching from the power-on to the power-off of the potential at each point in the circuit diagram of the embodiment.
FIG. 4 is a time chart at the time of switching from the power-off to the power-on of the potential at each point in the circuit diagram of the embodiment.
FIG. 5 is a time chart at the time of repeated switching off and on of the potential of each point in the circuit diagram of the embodiment.
FIG. 6 is an explanatory diagram of power consumption mode switching according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 3 ... Constant voltage circuit 4 ... Rectifier circuit 5 ... Charge / discharge circuit 6 ... Mode switching circuit 7 ... Microcomputer 8 ... Battery

Claims (2)

Connected to an AC power source, when the AC power source is turned on, the AC is converted to a constant voltage DC and supplied to the microcomputer (7). When the AC power source is turned off, a direct current is supplied from a built-in battery (8) to the microcomputer (7). A constant voltage circuit (3) to be supplied to
A rectifier circuit (4) connected to the AC power source and converting AC to DC and outputting;
When a parallel circuit of a transistor (TR1) and a capacitor (C3) controlled by the output of the rectifier circuit (4) is provided and the AC power source is switched from OFF to ON, the output voltage of the rectifier circuit (4) said transistor (TR1) is turned off, the starts charging the capacitor (C3) from the constant-voltage circuit (3) outputs a high level voltage after a predetermined time has elapsed, turn off the AC power supply from on the When switched, said by the output voltage of the rectifier circuit (4) transistor (TR1) is turned on, performs the discharge of electric charges charged in the capacitor (C3) via the transistor (TR1), immediately a low level A charge / discharge circuit (5) for outputting a voltage;
A mode switching circuit that receives the output voltage of the charge / discharge circuit (5), outputs a low level voltage when the output voltage is low level, and outputs a high level voltage when the output voltage is high level ( 6) and
A microcomputer (7) that receives the output voltage of the mode switching circuit (6), switches to a low power consumption mode when the output voltage is low, and switches to a normal power consumption mode when the output voltage is high; ,
A microcomputer protection system comprising: The charge / discharge circuit (5) and the mode switching circuit (6) each include an element that absorbs pulse noise , and at least one of the elements of the mode switching circuit (6) is an inductance. A microcomputer protection system according to claim 1.

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