JP2012230602A - Electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of conventional failures due to instantaneous interruption or the like.SOLUTION: The electronic apparatus includes: a main IC with a reset terminal; and an additional circuit connected to the reset terminal. The additional circuit includes: a first input terminal which inputs a power supply voltage to be supplied to the main IC; a second input terminal which inputs a control signal to be output from the main IC when the main IC is put in an operating state; and a switch element to which the control signal from the second input terminal is input, and which is put in an ON state when the level of the power supply voltage in the first input terminal becomes less than a predetermined threshold which is higher than a predetermined level, in which a reset signal is applied to the reset terminal when the switch element is put in the ON state, and the main IC is shifted to a reset state when the reset signal is applied to the reset terminal.

Description

  The present invention relates to an electronic device having a reset function.

  The power supply from the external commercial power source to the electronic device may be suddenly cut off or temporarily cut off (instantaneous interruption or instantaneous interruption). In such a case, the power supply voltage of a predetermined level that has been supplied to a control unit (IC: Integrated Circuit) included in the operating electronic device suddenly drops, causing the IC to freeze or malfunction. After that, it may not operate normally. In general, it is considered that a detection circuit for detecting such a momentary interruption is provided in a power supply circuit included in an electronic device, and the protection function for the IC is activated when the momentary interruption is detected by the detection circuit. obtain.

  As a related technology, there is known a reset circuit that supplies a reset signal voltage for initializing the microcomputer to the reset terminal of the microcomputer before the output voltage to the microcomputer drops below the operation guarantee voltage of the microcomputer (Patent Literature). 1). In addition, a configuration is known in which a control error or a CPU runaway does not occur by detecting a momentary power interruption / shutdown or a power supply voltage drop and shifting the microcomputer to a reset state (Patent Document 2,). 3).

Japanese Patent Laid-Open No. 2000-207065 JP 2010-186336 A JP 2001-296587 A

  Here, when an electronic device is assembled and manufactured, if it is intended to efficiently manufacture a product using a power supply circuit already unitized, measures such as providing the detection circuit in the power supply circuit are taken. It is difficult. Further, there is room for further improvement as a measure for more reliably preventing IC freeze and malfunction due to instantaneous interruption or the like.

  The present invention has been made to solve the above-described problems, and provides an electronic apparatus that can more reliably prevent the occurrence of a malfunction of a control unit that has been conventionally seen due to a momentary interruption or the like.

  One aspect of the present invention is an electronic device that resets the control unit before the power supply voltage supplied to the control unit drops below a predetermined level, and includes a main IC as the control unit including a reset terminal; An additional circuit connected to the reset terminal, the additional circuit having a first input terminal for inputting a power supply voltage supplied to the main IC, and a control output from the main IC when the main IC is in an operating state. A second input terminal for inputting a signal and an ON state when a control signal is input from the second input terminal and the power supply voltage level at the first input terminal falls below a predetermined threshold value higher than the predetermined level. When the switch element is turned on, a reset signal is given to the reset terminal, and the main IC is given a reset signal to the reset terminal. It is constituted to shift to the reset state when.

  According to this configuration, the main IC is reset when the level of the power supply voltage supplied to the main IC falls below the threshold value. Therefore, even when the level of the power supply voltage supplied to the main IC suddenly drops to a level (voltage lower than the predetermined level) that causes a malfunction such as freeze or malfunction in the main IC due to a momentary interruption or the like, Before such a problem occurs, the main IC can be surely reset to a safe state. Further, since such a configuration is realized by providing an additional circuit, it is also suitable when an electronic device is to be manufactured using a unitized power supply circuit.

It is a figure which shows an example of a structure of an electronic device roughly. It is a figure which shows the structure of an additional circuit. It is a figure which shows the sequence of a control signal. It is a figure which shows the timing which the reset terminal at the time of providing an additional circuit switches to L level, and the timing which the output of the conventional reset IC switches to L level.

As an embodiment of the present invention, the additional circuit is equivalent to a state in which the control signal is input from the second input terminal even after the control signal is interrupted by holding the charge by the control signal from the second input terminal. It is good also as a structure provided with CR circuit which maintains a state for a predetermined period.
In addition, as an embodiment of the present invention, at least two supply systems for supplying power to the additional circuit are provided, and a voltage supplied to the additional circuit when the external power supply is cut off. It is good also as a structure which connected the supply system | strain and the said 1st input terminal of the one that falls earlier.

  Further, as a more detailed embodiment of the present invention, an electronic device that resets the control unit before the power supply voltage supplied to the control unit drops below a predetermined level, which is connected to an external commercial power source and input A power supply circuit capable of generating and outputting a predetermined power supply voltage by AC-DC conversion of the commercial power supply, and a first power supply voltage output from the power supply circuit regardless of whether the electronic device is in an operating state or a standby state. A sub IC that outputs a first control signal for operating an electronic device when an instruction to turn on the power supply is received from the outside, and the first control signal is input and output from the power supply circuit An IC as the control unit that operates by inputting the second power supply voltage, and includes a main IC having a reset terminal, and an additional circuit connected to the reset terminal. A first input terminal for inputting a source voltage, a second input terminal for inputting a second control signal output from the main IC when the main IC is in an operating state, and a third input terminal for inputting a first power supply voltage And an NPN-type first transistor having a base connected to the second input terminal and an emitter connected to the ground, a cathode connected to the first input terminal, and an anode connected to the collector side of the first transistor. A base is connected to a Zener diode that flows current to the anode side when a voltage higher than a predetermined threshold is applied to the first input terminal, and a path that connects the anode of the Zener diode and the collector of the first transistor. And a PNP-type second transistor having an emitter connected to the third input terminal and a collector connected to the ground, the third input terminal and the second transistor When the reset terminal is connected to the path connecting the emitter of the first and second emitters and the second control signal is input from the second input terminal, the first transistor is turned on and the level of the second power supply voltage at the first input terminal When the threshold voltage falls below the above threshold value, the second transistor is turned on to give a reset signal to the reset terminal, and the main IC shifts to the reset state when the reset signal is given to the reset terminal. Has a state equivalent to the state in which the second control signal is input from the second input terminal even after the second control signal is interrupted by holding the electric charge by the second control signal from the second input terminal in the capacitor. A CR circuit for maintaining time, and a second power source among a supply system for supplying a first power supply voltage to an additional circuit and a supply system for supplying a second power supply voltage The supply system that supplies the voltage may be configured such that when the supply from the commercial power supply is cut off, the voltage supplied to the additional circuit decreases more quickly.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.
FIG. 1 illustrates a schematic configuration of an electronic apparatus 10 according to the present embodiment. The electronic device 10 corresponds to, for example, a liquid crystal television. However, the electronic device assumed by the present invention is any electronic device such as a recorder, a player, or a monitor as long as it is a product that includes a power supply circuit and is controlled by an external remote control device (remote control device) operated by the user. Is applicable. The electronic device 10 includes a power supply circuit 11, a DC-DC converter 12, a main IC 13, a sub IC 14, an additional circuit 15, a tuner circuit 16, a signal processing circuit 17, a panel drive circuit 18, a liquid crystal module 19, and the like.

  The power supply circuit 11 is, for example, a transformer that inputs and transforms an AC voltage acquired from an external commercial power supply via a power cord (AC cord) on the primary side and outputs it to the secondary side, or a secondary side of the transformer Includes a rectifier circuit, a smoothing circuit, and the like that convert the alternating current extracted into direct current into The DC voltage output from the power supply circuit 11 is input to the DC-DC converter 12. The DC-DC converter 12 converts the input DC voltage to a predetermined level, and supplies the converted DC voltage to each drive target as a power supply voltage for each drive target. As an example, a constant voltage Vall (first power supply voltage) of about +3.3 V is supplied from the DC-DC converter 12 to the sub IC 14 and the additional circuit 15. Further, a power supply voltage Vcc (second power supply voltage) of about + 12V can be supplied from the DC-DC converter 12 to the main IC 13 and the additional circuit 15.

  The constant voltage Vall is a voltage output from the DC-DC converter 12 regardless of whether the electronic device 10 is in an operating state or a standby state when the electronic device 10 is connected to a commercial power source via a power cord. . Therefore, the sub IC 14 is always operated by receiving the voltage Vall even when the electronic device 10 is in the standby state. The power supply circuit 11 and the DC-DC converter 12 may be collectively referred to as a power supply circuit. When the electronic device 10 is in a standby state, the sub IC 14 receives a power-on (P-ON) instruction from the user via a remote controller or various keys provided on the electronic device 10. A first control signal (P-ON1 signal) for setting the signal to the operating state is output to the main IC 13. The P-ON1 signal is an H level signal among predetermined high (H) level or low (L) level signals output from the sub IC 14.

  The main IC 13 is connected to each part and each circuit constituting the electronic device 10 via a bus, and includes a CPU, a RAM, and a ROM. In an operating state, the CPU stores a predetermined memory stored in the ROM while using the RAM as a work area. The process according to the program is executed to control the entire electronic device 10. The main IC 13 operates by inputting a P-ON1 signal and inputting a power supply voltage Vcc of about +12 V from the DC-DC converter 12. Further, the main IC 13 outputs a second control signal (P-ON2 signal) to the additional circuit 15 after a while from the start of operation (see FIG. 3). The P-ON2 signal is an H level signal among predetermined H level or L level signals output from the main IC 13. The main IC 13 includes a reset terminal 13a. When a reset signal is given to the reset terminal 13a, the main IC 13 shifts to a reset state and executes its own initialization.

  The tuner circuit 16 receives a broadcast signal through an antenna (not shown) under the control of the main IC 13. The signal processing circuit 17 performs various signal processing such as demodulation of the video / audio signal from the received broadcast signal, image quality adjustment and scaling processing on the video signal, and the like. It is generated and output to the panel drive circuit 18. The panel drive circuit 18 drives the liquid crystal panel in the liquid crystal module 19 based on the supplied frame, and displays an image based on the frame on the liquid crystal panel. The liquid crystal module 19 includes a liquid crystal panel, a backlight for illuminating the liquid crystal panel, an inverter circuit for driving the backlight, and the like. In addition to the above-described configuration, the electronic device 10 can include known configurations required for configuring a television, such as an audio signal processing circuit, a speaker, and an external input terminal.

  FIG. 2 is a diagram showing a configuration of the additional circuit 15. The additional circuit 15 includes a first input terminal 15a, a second input terminal 15b, and a third input terminal 15c. The first input terminal 15a receives the power supply voltage Vcc. The second input terminal 15b inputs the P-ON2 signal. The third input terminal 15c receives the constant voltage Vall. The additional circuit 15 includes an NPN transistor Q1 (first transistor) having a base connected to the second input terminal 15b via the resistor R1 and an emitter connected to the ground GND. A capacitor C is provided between a path connecting the base of the transistor Q1 and the resistor R1 and the ground GND. The resistor R1 and the capacitor C constitute a CR circuit having a predetermined time constant. The additional circuit 15 includes a Zener diode Z having a cathode connected to the first input terminal 15a and an anode connected to the collector side of the transistor Q1. The Zener diode Z is applied when a voltage equal to or higher than a predetermined threshold (zener voltage) higher than the minimum operating voltage (predetermined level, for example, about +4 to 6 V) of the main IC 13 is applied to the first input terminal 15a. It has a characteristic of flowing current to the anode side, and the Zener voltage is, for example, about + 9.1V. The main IC 13 is operated under the condition that the supplied power supply voltage Vcc is equal to or higher than the minimum operating voltage.

  A diode D and a resistor R2 are provided between the anode of the Zener diode Z and the collector of the transistor Q1, and a PNP transistor that connects the base to the path connecting the diode D and the resistor R2 via the resistor R3. Q2 (second transistor) is provided. The transistor Q2 has an emitter connected to the third input terminal 15c via the resistor R4 and a collector connected to the ground GND. Further, a reset terminal 13a is connected to a path connecting the resistor R4 and the emitter of the transistor Q2.

  In such an additional circuit 15, when the control signal (P-ON2 signal) is input from the second input terminal 15b and the level of the power supply voltage Vcc at the first input terminal 15a falls below the Zener voltage, the transistor Q2 ( The switch element) is turned on, and the emitter and collector of the transistor Q2 are conducted. When the transistor Q2 is turned on, the voltage level of the reset terminal 13a becomes "L". The reset terminal 13a is always pulled up to a predetermined H level by the voltage Vall when the transistor Q2 is in the OFF state. Thus, switching the level of the reset terminal 13a to the L level corresponds to giving a reset signal to the reset terminal 13a.

  More specifically, when the electronic device 10 is in a normal operation state, the base voltage of the transistor Q1 increases due to the input of the P-ON2 signal from the second input terminal 15b when the electronic device 10 is in a normal operating state. The transistor Q1 is turned on (conducting between the collector and emitter of the transistor Q1). Further, since the power supply voltage Vcc higher than the zener voltage is applied to the first input terminal 15a, a current flows from the cathode side to the anode side of the zener diode Z, and the transistor Q2 is turned off ( Reset terminal 13a is at H level). On the other hand, when a momentary interruption or the like occurs in the electronic device 10 and the level of the power supply voltage Vcc falls below the Zener voltage, the base voltage of the transistor Q2 drops to turn on the transistor Q2. Thereby, the reset terminal 13a becomes L level, and the main IC 13 is reset.

  Note that once the main IC 13 is reset, the input of the P-ON2 signal from the main IC 13 to the second input terminal 15b is interrupted at that moment, so the level of the reset terminal 13a becomes unstable (the reset terminal 13a is maintained at the L level). In some cases, the function of resetting the main IC 13 by the additional circuit 15 as described above may be lost. Therefore, the additional circuit 15 is provided with a CR circuit as described above. According to the CR circuit, the charge due to the P-ON2 signal from the second input terminal 15b is held in the capacitor C, so that the P-ON2 signal can be input from the second input terminal 15b even after the P-ON2 signal is interrupted. Since a state equivalent to a certain state is maintained for a predetermined time, the ON state of the transistor Q1 and the ON state of the transistor Q2 can be maintained for a certain period of time, and thereby the main IC 13 can be reliably reset.

  FIG. 3 shows a sequence such as a P-ON2 signal output from the main IC 13. As shown in FIG. 3, in the electronic device 10, when a power-on (P-ON) instruction is received from the user, a P-ON1 signal is output from the sub IC 14 toward the main IC 14, and an output of the P-ON1 signal is output. At substantially the same time, the power supply voltage Vcc to the main IC 13 rises. As a result, the main IC 13 starts operation, and a P-ON2 signal is output from the main IC 13 at a later timing (for example, 50 msec after the P-ON instruction). When receiving a power-off (P-OFF) instruction from the user, the main IC 13 turns off the P-ON2 signal, and the sub-IC 14 performs P- at a later timing (for example, 50 msec after the P-OFF instruction). The ON1 signal is turned off and the power supply voltage Vcc to the main IC 13 decreases. That is, according to the sequence, when a power on / off instruction is received from the user, the P-ON2 signal is output from the main IC 13 and the power supply voltage Vcc is reduced (below the Zener voltage). Therefore, it is possible to prevent a malfunction that the main IC 13 is reset when the user instructs to turn on / off the electronic device 10.

  In the electronic device 10 according to the present embodiment, the power supply voltage Vcc is selected from the supply system for supplying the power supply voltage Vcc to the additional circuit 15 and the supply system for supplying the constant voltage Vall (see FIG. 1). The supply system to be supplied is characterized in that the voltage supplied to the additional circuit 15 starts to decrease when the supply from the commercial power supply is cut off (when an instantaneous interruption or the like occurs). Such characteristics are determined by the capacitance of a capacitor (not shown) provided in the middle of each supply system. In the configuration of a conventional electronic device, there is a case in which a reset IC is employed that constantly monitors by inputting the voltage Vall, and detects that the level of the voltage Vall has constantly decreased to reset the main IC 13.

  FIG. 4 shows the timing at which the reset terminal 13a switches to the L level when the additional circuit 15 according to the present embodiment is provided, and the output of the conventional reset IC (the output from the reset IC to the reset terminal of the main IC) is L. It is a figure which shows the timing which switches to a level. Here, the change of the signal when the power cord is suddenly disconnected while the electronic device 10 is operating (AC-OFF) is shown. As shown in FIG. 4, when the AC-OFF is set, the output of the conventional reset IC is lower when the reset terminal 13a is switched to the L level when the additional circuit 15 according to the present embodiment is provided. It can be seen that it is about 1 second earlier than the timing of switching to the level. This is because the additional circuit 15 causes the level of the reset terminal 13a to be L level based on the transition of the power supply voltage Vcc that starts to decrease earlier when the supply from the commercial power supply is cut off. That is, according to the present embodiment, the main IC 13 can be reset by reacting more quickly when a momentary interruption or the like occurs, compared to the case where a conventional reset IC is used.

  Thus, according to the present embodiment, the main IC 13 is reset when the level of the power supply voltage Vcc supplied to the main IC 13 falls below a predetermined threshold value that is higher than the minimum operating voltage of the main IC 13. Therefore, even when the level of the power supply voltage Vcc supplied to the main IC 13 drops to a level that causes a malfunction such as freezing or malfunction in the main IC 13 due to an instantaneous interruption or the like, the main IC 13 is surely connected before such a malfunction occurs. IC13 is reset. In addition, in order to realize such a configuration and effect by providing the additional circuit 15, it is also suitable when the electronic device 10 is manufactured using the unitized power supply circuit 11.

DESCRIPTION OF SYMBOLS 10 ... Electronic device, 11 ... Power supply circuit, 12 ... DC-DC converter, 13 ... Main IC, 13a ... Reset terminal, 14 ... Sub IC, 15 ... Additional circuit, 15a ... 1st input terminal, 15b ... 2nd input terminal , 15c ... third input terminal

Claims (4)

An electronic device that resets the control unit before the power supply voltage supplied to the control unit drops below a predetermined level,
A main IC as the control unit including a reset terminal;
An additional circuit connected to the reset terminal,
The additional circuit includes a first input terminal for inputting a power supply voltage supplied to the main IC, a second input terminal for inputting a control signal output from the main IC when the main IC is in an operating state, and a second input. A switching element that is turned on when a control signal is input from the terminal and the level of the power supply voltage at the first input terminal falls below a predetermined threshold value that is higher than the predetermined level. Give a reset signal to the reset terminal when
An electronic device characterized in that a main IC shifts to a reset state when a reset signal is given to a reset terminal.   The additional circuit maintains a state equivalent to a state in which a control signal is input from the second input terminal for a predetermined time even after the control signal is interrupted by holding the charge by the control signal from the second input terminal. The electronic apparatus according to claim 1, further comprising a circuit.   A supply system that includes at least two supply systems for supplying power to the additional circuit, and of which the voltage supplied to the additional circuit decreases more quickly when the external power supply is cut off. The electronic device according to claim 1, wherein the electronic device is connected to the first input terminal. An electronic device that resets the control unit before the power supply voltage supplied to the control unit drops below a predetermined level,
A power supply circuit that can be connected to an external commercial power supply, AC-DC converted from the input commercial power supply to generate a predetermined power supply voltage, and output;
Regardless of whether the electronic device is in an operating state or a standby state, the electronic device is operated by inputting the first power supply voltage output from the power supply circuit, and the electronic device is set in the operating state when an external power-on instruction is received. A sub IC that outputs the first control signal of
A main IC provided with a reset terminal, which is an IC as the control unit that operates by inputting a first control signal and inputting a second power supply voltage output from a power supply circuit;
An additional circuit connected to the reset terminal,
The additional circuit includes a first input terminal for inputting a second power supply voltage, a second input terminal for inputting a second control signal output from the main IC when the main IC is in an operating state, and a first power supply voltage. A third input terminal for input, an NPN-type first transistor having a base connected to the second input terminal and an emitter connected to ground, a cathode connected to the first input terminal, and an anode connected to the collector side of the first transistor And a path connecting the anode of the Zener diode and the collector of the first transistor when a voltage higher than a predetermined threshold level and higher than a predetermined threshold is applied to the first input terminal. And a PNP-type second transistor having a base connected, an emitter connected to a third input terminal, and a collector connected to the ground, and a third input terminal The reset terminal is connected to the path connecting the emitter of the second transistor and the emitter of the second transistor, the second control signal is input from the second input terminal, the first transistor is turned on, and the second power source at the first input terminal When the voltage level falls below the threshold value, the second transistor is turned on to give a reset signal to the reset terminal,
The main IC shifts to the reset state when a reset signal is given to the reset terminal,
The additional circuit is in a state equivalent to a state in which the second control signal is input from the second input terminal even after the second control signal is interrupted by holding the charge by the second control signal from the second input terminal in the capacitor. Including a CR circuit for maintaining a predetermined time,
Further, of the supply system for supplying the first power supply voltage to the additional circuit and the supply system for supplying the second power supply voltage, the supply system for supplying the second power supply voltage is supplied from the commercial power supply. An electronic device characterized in that the voltage supplied to the additional circuit decreases more quickly when the power is cut off.

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