JPH0530929U - Electronics - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent ICs that are not backed up from entering the undefined area due to the voltage drop of the main power supply, and to prevent unnecessary power consumption of the backup power supply. [Structure] A normally open contact 41 of a relay inserted in a power supply line from a 5VIn power source to a second IC 40 and a 5V
When the voltage of the 5VIn power source becomes lower than 3.5V, the voltage output from the series voltage divider circuit falls below a predetermined reference voltage. A monitoring IC 32 that outputs a high-level voltage, and a relay exciting coil 38 that opens and closes the normally open contact 41 by the output of the monitoring IC 32.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an electronic device that includes a main power supply and a backup power supply, and is provided with a circuit to which power is supplied from the main power supply and the backup power supply, and a circuit to which power is supplied only from the main power supply.

[0002]

[Prior Art]

 Conventionally, for example, a main circuit of an electronic device as shown in FIG. 4 is known. Reference numeral 1 is a 5V rechargeable battery power source composed of a Ni-Cd (nickel-cadmium) battery or the like. The rechargeable battery power source 1 has its negative electrode terminal connected to the ground and its positive electrode terminal connected to the cathode terminal of the first diode 3 via the resistor 2. The anode terminal of the first diode 3 is connected to a 12V power source. Therefore, the 5V rechargeable battery power source 1 is charged by the power supplied from the 12V power source through the first diode 3 and the current adjusting resistor 2.

The positive electrode terminal of the rechargeable battery power source 1 is also connected to the ground via the electrolytic capacitor 4, and further connected to the input terminal of an IC (integrated circuit) 5 for constant voltage. The second diode 6 is connected from the output terminal to the input terminal of the constant voltage IC 5. The input terminal and the output terminal of the constant voltage IC 5 are connected to the ground via the first capacitor 7 and the second capacitor 8, respectively.

The output terminal of the constant voltage IC 5 is further connected to the collector terminal of a PNP transistor 10 via a third diode 9. The emitter terminal of the transistor 10 is connected to a power supply of 5V (hereinafter referred to as 5VIn in order to distinguish from 5V of a charging battery power supply) obtained by rectifying and smoothing a commercial power supply. A reset In circuit (not shown in detail) is connected to the base terminal of the transistor 10 via the base resistor 11. This reset In circuit monitors the voltage of the 5VIn power supply, and when the voltage of the 5VIn power supply drops to 4.5 to 4.7V, the voltage output via the base resistor 11 becomes high level. Is becoming.

The connection point between the cathode terminal of the third diode 9 and the collector terminal of the transistor 10 is connected to the power input terminal Vcc of the first IC 12. The input terminal IN of the first IC 12 is connected to the output terminal OUT of the second IC 13, and the 5VIn power supply is connected to the power supply input terminal Vcc of the second IC.

In the conventional example having such a configuration, first, the power from the 5VIn power source is input to the power source input terminals Vcc of the first IC 12 and the second IC 13. When the voltage of the 5VIn power supply drops to 4.5 to 4.7V, the output voltage of the reset In circuit becomes high level, and this output voltage is applied to the base terminal of the transistor 10 via the base resistor 11 and the transistor 10 To turn off. Then, the power supply from the 5VIn power supply is cut off by the transistor 10, and instead, the power from the 5V charging battery power supply 1 is input to the power supply input terminal Vcc of the first IC 12. On the other hand, the power source input terminal Vcc of the second IC 13 is directly supplied with power from the 5 VIn power source whose voltage has dropped.

[0007]

[Problems to be solved by the device]

 In a conventional electronic device having a circuit configuration shown in FIG. 4, for example, an IC generally has a power input terminal Vcc, for example, a TTL (transistor-transistor logic) level 5V IC such as the second IC 13, It is said that when a voltage of 2.5 to 2 V is input, it enters a so-called indefinite region where the operation becomes unstable.

The output terminal OUT of the second IC 13 which is not backed up by the rechargeable battery power supply 1 becomes unstable when the voltage of the 5VIn power supply is lower than 3.5V, and the output terminal OUT of the first IC 12 backed up by the rechargeable battery power supply 1 is A large amount of current flows from the input terminal IN to the output terminal OUT of the second IC 13 as compared with the normal case. When the voltage of the 5VIn power supply is 2.5V to 2V, the amount of current becomes maximum, and when it is near 0V, the current flows out of the undefined region and flows from the input terminal IN of the first IC12 to the output terminal OUT of the second IC13. Return to normal amount.

As described above, in a general electronic device, when the voltage input to the power supply input terminal of an IC that is not backed up drops to 2.5V, the IC enters an indeterminate region where the operation becomes unstable and malfunctions. There is a risk of accidents such as. Furthermore, since the operation of the IC is unstable, a phenomenon occurs in which a considerably large amount of current flows from the IC backed up by the backup power supply to the IC in the indefinite area as compared with the normal case. Due to this overcurrent phenomenon, the power of the backup power supply is wasted.

Therefore, this invention prevents an IC that is not backed up from entering an undefined area due to a drop in the voltage of the main power supply, and minimizes the current flowing from the backed up IC to the unbacked IC. Therefore, it is an object of the present invention to provide an electronic device that can prevent unnecessary power consumption of a backup power supply.

[0011]

[Means for Solving the Problems]

 This invention comprises a main power supply and a backup power supply that backs up power when the voltage of the main power supply drops, and a main power supply, a circuit supplied with the backup power supply, and a circuit supplied with only the main power supply are provided. In the provided electronic device, the voltage detection means detects the voltage of the main power supply, and the reference voltage set higher than the voltage at which the circuit supplied with power from the main power supply operates unstable. Main power supply voltage determining means for determining whether or not the voltage of the main power supply is low, and when the main power supply voltage determining means determines that the voltage of the main power supply is lower than the reference voltage, power is supplied from the main power supply only. And a disconnection means for disconnecting the power supply line from the main power supply to the circuit.

[0012]

[Action]

 In the present invention having such a configuration, when the voltage of the main power supply drops, the power supplied from the main power supply and the backup power supply is backed up by the backup power supply.

The voltage of the main power supply is detected by the voltage detection means. The main power supply determination means determines that the voltage of the main power supply detected by the voltage detection means is lower than the reference voltage set higher than the voltage at which the circuit supplied with power from only the main power supply operates unstable. Then, the disconnection means disconnects the power supply line from the main power supply to the circuit to which power is supplied only from the main power supply.

[0014]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of an essential part of an electronic device to which the present invention is applied. Reference numeral 21 is a 5V rechargeable battery power source as a backup power source composed of a Ni—Cd (Nickel-Cadmium) battery or the like. The rechargeable battery power source 21 has its negative electrode terminal connected to the ground, and its positive electrode terminal connected to the cathode terminal of the first diode 23 via the resistor 22 for current adjustment. The anode terminal of the first diode 23 is connected to a 12V power source. Therefore, the 5V rechargeable battery power source 21 is charged by the electric power supplied from the 12V power source through the first diode 23 and the current adjusting resistor 22.

The positive terminal of the rechargeable battery power source 21 is also connected to the ground via the electrolytic capacitor 24, and further connected to the input terminal of the IC 25 for constant voltage. The second diode 26 is connected from the output terminal to the input terminal of the constant voltage IC 25. The input terminal and the output terminal of the constant voltage IC 25 are connected to the ground via a first capacitor 27 and a second capacitor 28, respectively.

The output terminal of the constant voltage IC 25 is further connected to a collector terminal of a PNP type first transistor 30 via a third diode 29. The emitter terminal of the first transistor 30 is connected to a power source of 5V (hereinafter referred to as 5VIn in order to distinguish from 5V of a charging battery power source) as a main power source obtained by rectifying and smoothing a commercial power source. Further, a reset In circuit (not shown in detail) is connected to the base terminal of the first transistor 30 via the first base resistor 31. The reset In circuit monitors the voltage of the 5VIn power supply, and when the voltage of the 5VIn power supply drops to 4.5 to 4.7V, the voltage output via the base resistor 31 becomes high level. It is like this.

The connection point between the cathode terminal of the third diode 29 and the collector terminal of the first transistor 30 is connected to the power source input terminal Vcc of the monitoring IC 32 and the first IC 33 as main power source voltage determining means. It is connected. To the input terminal IN of the monitoring IC 32, a connection point (division output point) of a series voltage dividing circuit of a resistor 34 and a resistor 35 as a voltage detecting means connected to a power source of 5VIn is connected. When the voltage of the 5VIn power supply drops to 3.5V or less, the divided output from the connection point becomes lower than a predetermined reference voltage, and the output of the output terminal OUT of the monitoring IC 32 becomes high level. .. The output terminal OUT is connected to the base terminal of an NPN type second transistor 37 via a second base resistor 36. The emitter terminal of the second transistor 37 is connected to the ground, and the collector terminal is connected to the 12V power source through the exciting coil 38 of the relay. Further, a diode 39 is connected in parallel with the exciting coil 38.

The input terminal IN of the first IC 33 is connected to the output terminal OUT of the second IC 40, and the power supply input terminal Vcc of the second IC 40 is opened / closed by the exciting coil 38 of the relay. The 5VIn power source is connected through a normally open contact 41 as a disconnection means.

In the present embodiment having such a configuration, since the power source of 5VIn normally outputs a voltage of 5V, the resistor 34 and the resistor 35 connected in series to the input terminal IN of the monitoring IC 32 are connected. Since the divided voltage of the voltage circuit is higher than the predetermined reference voltage, the output voltage of the output terminal OUT of the monitoring IC 32 becomes high level, the second transistor 37 is turned on, and the exciting coil 38 of the relay is turned on. Is energized, and the normally open contact point 41 of the relay is closed. Therefore, the voltage of 5V is input to the power supply input terminal Vcc of the second IC 40 from the power supply of 5VIn.

Also in the reset In circuit that monitors the power supply of 5VIn, since the voltage of the power supply of 5VIn is 5V, a low level voltage is output and the first transistor 30 is turned on. Therefore, a voltage of 5V is input from the 5VIn power supply to the power supply input terminal Vcc of the first IC 33 via the emitter-collector of the first transistor 30.

When the voltage of the power supply of 5VIn drops to 4.5 to 4.7V, the first transistor 30 is turned off by the high level output from the reset In circuit, and the voltage of 5VIn The power supply from the power supply to the first IC 33 is cut off. At this time, the voltage of 5V from the rechargeable battery power source 21 is input to the power source input terminal Vcc of the first IC 33, instead of the power source of 5VIn.

Further, when the voltage of the power supply of 5VIn drops to 3.5V or less, the divided voltage of the series voltage dividing circuit of the resistor 34 and the resistor 35 becomes lower than the reference voltage. Therefore, the output voltage of the output terminal OUT of the monitoring IC 32 is reduced. Becomes a low level, and the second transistor 41 is turned off. Then, the exciting coil 38 of the relay is de-energized, and the normally open contact point 41 of the relay is opened. Therefore, the power supply from the 5VIn power supply to the second IC 40 is cut off.

FIG. 2 shows the timing of power supply from various power supplies. First, the power from the 12V power supply is supplied. As a result, the charging battery power source 21 of 5V can be charged, and the relay can be driven. Next, the power supply from the 5VIn power supply is started, and the 5V power supply from the rechargeable battery power supply 21 becomes possible.

If the voltage of the power supply of 5VIn may drop to 4.5 to 4.7V, the reset In is turned on (the output voltage becomes high level) as shown at the time point A. .

FIG. 3A shows a graph A of the output voltage when the voltage of the power supply of 5VIn drops, and FIG. 3B shows the voltage input to the power supply input terminal Vcc of the second IC 40. Shows the graph. Note that the graph B in FIG. 3A shows the current consumption amount in the conventional case, and the graph C shows the current consumption amount in the present embodiment.

As described above, according to this embodiment, when the voltage of the power source of 5VIn drops to 3.5V or less, the normally-open contact 41 of the relay supplies power to the second IC 40 from the power source of 5VIn. Can be shut off. Therefore, the second IC 40 can be prevented from entering the indefinite region, and as a result, the current from the rechargeable battery power source 21 flowing through the first IC can be minimized.

That is, it is possible to prevent the second IC 40 from entering the indefinite area, and it is possible to prevent useless power consumption. Further, the constant voltage IC 25 for stabilizing the output voltage of the rechargeable battery power source 21 has conventionally used an IC with a large capacity in consideration of the overcurrent in the indefinite region. Therefore, it is possible to use a constant-voltage IC with a small capacitance.

[0029]

[Effect of the device]

 As described above in detail, according to the present invention, it is possible to prevent an IC that is not backed up from entering an undefined area due to a drop in the voltage of the main power supply, and minimize the current flowing from the backed up IC to the unbacked up IC. Therefore, it is possible to provide an electronic device that can suppress the power consumption and thus prevent unnecessary power consumption of the backup power supply.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a main part showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating a power supply and reset I of various power sources according to the embodiment.
The figure which shows the high level output timing of n.

FIG. 3 is a graph of a voltage when the voltage of the 5VIn power supply of the embodiment is dropped, a graph of a voltage input to the power supply input terminal of the second IC, and a graph of power consumption of the conventional example and the present embodiment.

FIG. 4 is a circuit diagram of a main part showing a conventional example.

[Explanation of symbols]

21 ... Rechargeable battery power source, 25 ... Constant voltage IC, 32 ... Monitoring IC, 33 ... First IC, 34, 35 ... Resistors (series voltage dividing circuit), 38 ... Relay exciting coil, 40 ... Second IC, 41 ... Normally open contact of relay,

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location H02H 3/24 A 9061-5G H02J 9/06 D 8021-5G 7165-5B G06F 1/00 335 C

Claims (1)

[Scope of utility model registration request] 1. A main power supply and a backup power supply for backing up the power when the voltage of the main power supply drops,
In an electronic device provided with a circuit supplied with power from the main power supply and the backup power supply and a circuit supplied with power from only the main power supply, only voltage detection means for detecting the voltage of the main power supply, and only the main power supply. Main power supply voltage determining means for determining whether or not the voltage of the main power supply detected by the voltage detecting means is lower than a reference voltage set higher than a voltage at which a circuit supplied with power from an unstable operation,
When the main power supply voltage determining means determines that the voltage of the main power supply is lower than the reference voltage, a disconnection for disconnecting a power supply line from the main power supply to a circuit to which power is supplied only from the main power supply. An electronic device comprising means.