KR19980060968U - Power Supply Circuit for Memory Back Up - Google Patents

Abstract

A memory backup power supply circuit for checking a voltage of a backup battery and displaying the result thereof to a user, the memory backup power supply circuit having a backup battery and supplying backup power to the memory, wherein the voltage of the backup battery is provided. And a first NPN bipolar junction transistor configured to compare the reference voltage with a reference voltage and output a signal according thereto, and to turn on the buzzer and the light emitting diode according to the output signal of the comparator and display the abnormality of the backup battery. The reliability of the device can be improved.

Description

Power Supply Circuit for Memory Back Up

The present invention relates to a memory backup power supply circuit, and more particularly, to a memory backup power supply circuit used in a credit card inquiry machine.

As shown in FIG. 1, the power supply circuit for a conventional memory backup includes a backup battery BAT ₁ , a first diode D ₁ having an anode connected to a positive electrode of the backup battery BAT ₁ , A second diode D ₂ , a first diode and a second diode D ₁ (D ₂ ) having a cathode connected to the cathode of the first diode D ₁ and supplied with + 5V operating power through the anode. The (V _BB ) terminal of the cathode of the memory 10 is commonly connected.

The operation of the conventional memory backup power supply circuit configured as described above is as follows.

First, when the operating power is normally supplied, the memory 10 receives the + 5V operating power through the second diode D ₂ and preserves the stored data.

Meanwhile, when the operation power supply is stopped, at the same time, the power of the backup battery BAT ₁ is supplied through the first diode D ₁ and the memory 10 is supplied with the memory 10 to prevent the stored data from being lost. In this case, the first and second diodes D ₁ and D ₂ are configured to prevent the reverse flow of the current. The backup battery BAT ₁ has a capacity set according to the consumption current and the driving voltage of the memory 10.

The memory backup power supply circuit according to the prior art has a problem in that the state of the backup battery, i.e., the voltage, is not known, so that the replacement time of the battery may be missed and data is lost.

Therefore, the present invention has been made to solve such a problem, and the object of the present invention is to provide a memory backup power supply circuit that can notify the user when the voltage of the backup battery is less than the minimum voltage to perform the backup operation. .

1 is a circuit diagram showing a memory backup power supply circuit according to the prior art;

2 is a circuit diagram showing a power supply circuit for memory backup according to the present invention,

3 is a circuit diagram illustrating a detailed configuration of a comparison unit of FIG. 2.

* Description of the symbols for the main parts of the drawings *

10: memory BAT ₁ : backup battery

D ₁ , D ₂ : diode SW ₁ : first switch

R ₁ to R ₁₀ : resistance VR ₁ : variable resistor

20: comparison unit Q _1, Q ₂ : the first and second transistors (BJT)

OR ₁ : ORA gate A ₁ : OP AMP

BUZ ₁ : Buzzer LED ₁ : Light emitting diode

30: CPU40: interface unit

The present invention is a memory backup power supply circuit having a backup battery for supplying the backup power to the memory, the comparison unit for comparing the voltage of the backup battery and the reference voltage and outputs a signal according to the output signal of the comparison unit, the comparison unit is turned on And a first NPN bipolar junction transistor for driving the buzzer and the light emitting diode to display an abnormality of the backup battery.

Hereinafter, a memory backup power supply circuit according to the present invention will be described with reference to the accompanying drawings.

2 is a circuit diagram showing a memory backup power supply circuit according to the present invention, Figure 3 is a circuit diagram showing a detailed configuration of the comparison unit of FIG.

Memory back-up power supply circuit includes a memory 10 having the same connection configuration with the conventional technique, as shown in Figure 2 according to the present invention, the first and second diode (D ₁₎ (D _2), a backup battery ( BAT ₁ ), the first contact point (a) connected to the (+) pole of the backup battery BAT ₁ , the second contact point (b) connected to the + 5v operating power through the resistor R ₃ , and according to the user's operation. The first switch SW ₁ connected to the first contact point a or the second contact point b is backed up through the first contact point a to the input terminal V _IN according to the switching of the first switch SW ₁ . Comparator 20 receiving a voltage of the battery BAT ₁ or a + 5v voltage through the second contact b and comparing it with a reference voltage V _REF to output a 0g high 0h or 0g low 0h signal Ora gate OR ₁ and OR gate OR _{1 for} ORing an output signal of the interface unit 40 and an output signal of the comparison unit 20 for connecting the data of the CPU 30 to each unit. of Is turned on in accordance with an output signal the second transistor (Q _2), the second transistor buzzer (BUZ ₁₎ and a light emitting diode connected to the collector in parallel with the (Q ₂₎ being received is each of the + 5V operating power having a (LED ₁₎ It is configured by. At this time, the reference voltage V _REF of the comparator 20 is the lowest voltage capable of performing a memory backup operation, and its value is determined by the voltage divider resistor R ₁ (R ₂ ) connected to the reference voltage V _REF terminal. This is determined. In addition, as shown in FIG. 3, the comparator 20 has an input terminal V _IN connected to a non-inverting terminal (+) through a resistor R ₇ and a reference voltage V _REF terminal having a variable resistor VR ₁ . OP amplifier (A ₁ ) and OP amplifier (A ₁ ) connected to inverting terminal (-) and resistor (R ₈ ) connected to variable resistor (VR ₁ ) of input terminal (V _IN ) and reference voltage terminal (V _REF ) ) the base is connected via a resistor (R ₉₎ to the output of and through the collector + 5V operating power is applied to the collector via a resistor (R ₁₀₎ consisting of the output (V _OUT) between the resistor (R ₁₀₎ and the collector It consists of the first transistor Q ₁ . In this case, the resistor R ₈ and the variable resistor VR ₁ are configured to compensate for the offset voltage of the OP amplifier A ₁ .

The operation of the memory backup power supply circuit configured as described above is as follows.

First, the user of the first switch (SW ₁₎ for operation with the second contact (b) when connected to the comparison unit 20, the voltage of the backup battery (BAT ₁₎ to check the status of the back-up battery (BAT ₁₎ It is applied to the input terminal V _IN . Subsequently, the OP amplifier A ₁ of the comparator 20 operates as a differential amplifier and outputs a 0g low 0h signal due to its operation characteristic when the input voltage of the backup battery BAT ₁ is less than or equal to the reference voltage V _REF . . The 0g low 0h signal, which is the output of the OP amplifier A ₁ , is applied to the base of the first transistor Q ₁ . Therefore, since the first transistor Q ₁ is turned off, a 0g high 0h signal is output to the output terminal V _OUT of the comparator 20. Then the comparison unit output 0g high 0h signals 20 outputs the 0g high 0h signal regardless of Iowa gate (OR ₁₎ type and Iowa input of the gate (OR ₁₎ operating characteristic interface section 40 of the. And Iowa gate (OR ₁₎ output 0g high 0h signal drives the second transistor is applied to a (Q ₂₎ the second transistor (Q ₂₎ is turned on and a buzzer (BUZ ₁₎ and the LED (LED ₁₎ . Therefore, the buzzer BUZ ₁ and the light emitting diode LED ₁ generate buzzer sounds and light, respectively, to inform the user that the voltage of the backup battery BAT ₁ is lower than the reference voltage, and take appropriate measures such as replacing the battery.

On the other hand, when the voltage of the backup battery BAT ₁ is greater than the reference voltage, the OP amplifier A ₁ of the comparator 20 outputs a 0g high 0h signal. The 0g high 0h signal, which is the output of the OP amplifier A ₁ , is applied to the base of the first transistor Q ₁ . Therefore, since the first transistor Q ₁ is turned on, a 0g low 0h signal is output to the output terminal V _OUT of the comparator 20 and input to the OR gate OR ₁ . At this time, the CPU 30 performs a control operation, and when an error occurs, the CPU 30 inputs corresponding data to the interface unit 40 through the data bus. Subsequently, if there is no abnormality in the system according to the data input from the CPU 30, the interface unit 40 outputs a 0g low 0h signal through the output port Port1. Therefore, OR gate OR ₁ receives these two signals and performs an OR operation to output 0g low 0h signal. And Iowa 0g gate output signal of the low 0h (OR ₁₎ is applied to the second transistor (Q ₂₎ the second transistor (Q ₂₎ is turned off. Therefore, since the buzzer BUZ ₁ and the light emitting diode LED ₁ do not operate, the user recognizes that the voltage of the backup battery BAT ₁ is normal.

On the other hand, when the CPU 30 detects an abnormality of the system and outputs corresponding data to the interface unit 40, the interface unit 40 outputs a 0g high 0h signal. Therefore, the OR gate OR ₁ outputs a 0g high 0h signal regardless of the output signal of the comparator 20 and drives the buzzer BUZ ₁ and the light emitting diode LED ₁ to inform the user of an abnormal circuit. .

The memory backup power supply circuit according to the present invention checks the voltage of the backup battery and informs the user in case of an error to prevent the loss of memory, thereby improving the reliability of the device using the same.

Claims (3)

A memory backup power supply circuit having a backup battery and supplying backup power to a memory, A comparator for comparing a voltage of the backup battery with a reference voltage and outputting a signal according thereto; And a first NPN bipolar junction transistor which is turned on in response to an output signal of the comparator and displays an abnormality of a backup battery by driving a buzzer and a light emitting diode. The method of claim 1, The comparison unit An OP amplifier which receives the voltage of the backup battery to the non-inverting terminal (+) through a first resistor and receives the reference voltage to the inverting terminal (-) through a second resistor, differentially amplifies and outputs the reference voltage; And a level maintaining part for maintaining a voltage of an output signal of the OP amplifier above a predetermined level. The method of claim 2, The level maintaining part The output signal of the OP amplifier is input to the base through a third resistor, and a power supply voltage of a predetermined level is applied to the collector through a fourth resistor, and the output signal of the OP amplifier is output through an output terminal configured between the fourth resistor and the collector. And a second NPN bipolar junction transistor which outputs a signal inverted by the signal and whose voltage level is maintained above a predetermined level.