JP2505058B2 - Abnormality detection method in battery charging circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention relates to a method for detecting an abnormality in a battery charging circuit, which aims to detect disconnection of a connector (6) and open failure of a battery (5) even when power is turned on. An output control transistor (1) for converting an input voltage into an output voltage for battery charging, and detecting the output voltage,
A stabilization control circuit (3) that stabilizes the output voltage by comparing it with the reference voltage (16) and generating an error voltage and feeding it back to the output control transistor (1), and detecting an excessive output current. To control the output control transistor (1) to limit the current, an overcurrent protection circuit (2) that detects an excessive output voltage and outputs an abnormal signal, and an output voltage to a battery ( In the battery charging circuit consisting of the output terminals (7, 7 ') for supplying to the 5), the stabilization control circuit (3) has an output voltage detection circuit (10) including a delay circuit (15), The delay circuit (15) acts so that the output of the stabilization control circuit (3) temporarily raises the output voltage of the output control transistor (1) when the input voltage is applied. When applying the input voltage of The overvoltage detection circuit (4) detects a high voltage output from the output control transistor (1) due to an abnormal connection of the battery (5) at the output terminal (7, 7 ') or an open failure of the battery (5). In this configuration, the connection abnormality of the battery (5) or the open failure of the battery (5) is determined.

[Industrial applications]

The present invention relates to abnormality detection for detecting an abnormal connection between an output terminal and a battery and an open failure of the battery when the battery is being charged by a battery charging circuit.

The trickle charge method is generally used to charge the backup battery that is used instead when the normal power supply fails, and it is possible to use a low charging voltage while the load is being driven by the normal power supply. It is always charged. Then, in order to detect the connection abnormality between the output terminal of the charging circuit and the battery, the connector is provided with a dedicated pin for connection detection, and when it is disconnected, the output of the connection detection pin changes to the outside. I was trying to report a connection error.

In such a conventional abnormality detecting method, only the disconnection of the connector is detected, and the open failure of the battery cannot be detected.

The present invention provides a method for detecting an abnormality in a battery charging circuit that does not require a special connector having a connector connection detection terminal and can detect not only an abnormal connection of the connector but also an open failure of the battery. To do.

[Conventional technology]

A conventional method for detecting an abnormality in a battery charging circuit will be described with reference to FIG.

In the figure, 50 is a voltage stabilizing circuit and a current limiting circuit, 51
Is an overvoltage detection circuit that monitors and detects the output voltage so that the charging voltage applied to the battery is not too high.
Is a load resistance when a connection abnormality signal is output to the outside when the connector is disconnected, 53 is a diode for preventing current from flowing backward from the battery to the charging circuit side, 54 is a connector connecting the charging circuit and the battery , 55 is the battery, 5
6,56 'are connection terminals on the charging circuit side of the connector 54, 57,57'
Is a connection terminal on the battery side of the connector 54, 58 is a charging circuit side terminal of the connection abnormality detection pin in the connector, 59 is a battery side terminal of the connection abnormality detection pin in the connector,
60 is a terminal for outputting a connection abnormality signal.

The method of detecting an abnormality in the battery charging circuit in FIG. 4 is as follows.

When the terminal 58 on the charging circuit side and the terminal on the battery side in the connector 54 are normally connected, the level of the connection abnormality signal output terminal 60 outputs 0 V, which is the same potential as the negative side of the battery.

Therefore, even if a warning lamp or the like is connected to the tip of the connection abnormality signal output terminal 60, the warning lamp does not light.

However, if the connector 54 is disconnected and the terminals 58 and 59 of the connection abnormality detection pins on the charging circuit side and the battery side are not connected,
The level of the connection abnormality signal output terminal 60 becomes equal to the positive side of the charging circuit, and the warning lamp connected to the end of the connection abnormality signal output terminal 60 lights up.

[Problems to be Solved by the Invention]

In the conventional abnormality detection method as described above, it is necessary to provide the connector with the dedicated pin for detecting the connection abnormality,
Moreover, only the disconnection of the connector could be detected.

However, in reality, although it is desired to be able to detect a failure in which the battery is open, it has been impossible with the conventional abnormality detection method.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for detecting an abnormality in a battery charging circuit, which can detect not only the disconnection of a connector but also an open failure of a battery.

[Means for solving the problem]

According to the present invention, a delay capacitor is connected to the voltage detection input side of the voltage stabilizing circuit so that a change in output voltage can be detected with a delay, so that the battery charging circuit is turned on without a load, such as when the battery is disconnected. If so, an error voltage is excessively generated, an abnormally high output voltage is generated, and a battery connection check can be performed.

In other words, at startup, it detects whether the output terminal of the charging circuit is not connected to the battery or the battery has an open circuit failure by detecting whether an excessive output is generated, and detects the abnormality of the charging circuit. did.

 FIG. 1 is a principle diagram of the charging circuit of the present invention.

In the figure, 1 is an output control transistor, 2 is an overcurrent protection circuit which detects a current and controls the output control transistor (1) to limit a current, and 3 detects an output voltage and compares it with a reference voltage to determine an error voltage. A stabilization control circuit 4 for stabilizing the output voltage by generating and feeding back to the output control transistor (1) is an overvoltage detection circuit. , Which outputs a signal notifying an external device of abnormality, 5 is a battery, 6 is a connector for connecting an output terminal of a charging circuit and a battery terminal, 7 and 7'is an output terminal on the voltage stabilizing circuit side of the connector, 8, 8'is a battery terminal of the connector, 10 is an output voltage detection circuit for detecting an output voltage including a delay circuit, 11 is a current detection resistor for detecting an output current, 12 is a current detection resistor. Differential amplifiers such as operational amplifiers that amplify the voltage at the ends, 13 and 14 are voltage dividing resistors that detect the output voltage of the voltage stabilization circuit, 15 is a delay circuit that consists of a delay capacitor, and 16 is a battery, zener diode, etc. Reference numeral 17 is a differential amplifier such as an operational amplifier which compares the detected output voltage with the reference voltage and the output voltage and amplifies the difference voltage.

[Action]

The operation of the principle of the charging circuit of FIG. 1 will be described with reference to FIG. If necessary, refer to FIG.

FIG. 2 shows the voltage output characteristics of the charging circuit of FIG. 1 when the power is turned on.

In the figure, 18 is the voltage output characteristic when the power is turned on when there is a connection abnormality in the battery or an open failure in the battery, Va is the overvoltage detection point at which the overvoltage detection circuit operates, Vb is the open circuit failure in the battery, and the charging circuit Normal output voltage when there is no abnormality in the connection between the terminal and the battery terminal,
Reference numeral 19 is a delay time of the operation of the stabilization control circuit caused by the capacitor of the delay circuit 15.

First, the operation when the power is turned on will be described for the case where the connector 6 is detached and the output terminals 7 and 7'and the battery terminals 8 and 8'are not connected.

A reference voltage applied to the positive input of the differential amplifier 17 when the power is turned on (a constant voltage diode is generally used)
The output detection voltage applied to the negative input rises slowly after the actual output voltage change due to the action of the delay circuit 15. As a result, the differential amplifier 17 generates an excessive error voltage, and voltage stabilization control is disabled for a certain period of time. At this time, the output voltage rapidly becomes excessive when the battery is disconnected and there is no load or when the battery has an open failure.

Then, when the output voltage reaches the overvoltage detection point of the overvoltage detection circuit (4), the overvoltage detection circuit operates. For example,
An overvoltage detection circuit is connected in parallel between the output terminals 7 and 7 '. A thyristor (not shown) of the overvoltage detection circuit.
It is turned on by the overvoltage and outputs an abnormal signal to an external device.

On the other hand, when a normal battery is connected to the output terminals 7 and 7 ', an excessive output voltage generated during the delay period by the delay capacitor causes an excessive charging current to the battery, resulting in an overcurrent. Since the protection circuit operates and the output voltage is suppressed, the overvoltage detection circuit (4) does not operate,
No abnormal signal is output. Then, when the delay capacitor is charged and the transient period at power-on has passed,
A stable voltage is always output near the normal value indicated by Vb.

In the above description, the abnormality is detected only when the power is turned on. However, the delay capacitor may be provided with a periodic discharge circuit to detect the connection abnormality periodically.

〔Example〕

 FIG. 3 shows an embodiment of the present invention.

In the figure, 20-1 is an output control transistor, 20-2
Is a current protection circuit, 20-3 is a stabilization control circuit, 20-4 is an overvoltage detection circuit, 21 is a bias resistance of the output control transistor 20-1, 22 is the base of the output control transistor 20-1,
The protection diode 23 prevents the reverse voltage from being applied between the emitters, and is an operational amplifier in the overcurrent protection circuit, which inputs the voltage generated across the current detection resistor, amplifies and outputs it, and controls the output control transistor. 24 is an operational amplifier in a voltage stabilization control circuit, which inputs an error voltage generated by fluctuation of the output voltage, amplifies and outputs the control voltage of the output control transistor 20-1, and 25 and 26 are Protective diodes of operational amplifiers 23 and 24, 27 is a current detection resistor for detecting the output current, 2
Reference numerals 8, 29, 30, 31 are voltage dividing resistors for detecting the voltage between both terminals of the current detection resistor 27, and the voltage detected by the resistors 28, 29 is input to the judgment input terminal side of the operational amplifier 23. ,
The voltage detected by the resistors 30 and 31 is input to the non-inverting input side of the operational amplifier 23, and 32 is a reference voltage source that determines the error of the output voltage. The reference voltage is input to the non-inverting input side of the operational amplifier 24. 33, 34, and 35 are output voltage detection resistors that input the detection voltage to the inverting input side of the operational amplifier 24, 36 is a delay capacitor in the output voltage detection circuit, and 37 is a high voltage on the output side. A diode to prevent it from being added to the base of the output control transistor, 38 is a load resistance of the thyristor in the overvoltage detection circuit, 39 is a thyristor in the overvoltage detection circuit, which operates by an excessive output voltage and outputs from the abnormal signal output terminal. Abnormality is notified by cutting off the voltage, and at the same time, the output control transistor 20-
The base voltage of 1 is set to 0V so that the output of the output control transistor does not output. 40, 41, 42 are detection circuits for excessive voltage, 41 is a Zener diode for keeping the gate voltage of the thyristor constant, 40 and 42 are voltage dividing resistors that determine the gate voltage of the thyristor, 43 is a backflow prevention diode that prevents current from flowing from the battery side to the charging circuit side, 44 is a battery, 45 and 45 'are output terminals, 46 is an abnormal signal It is an output terminal.

 The operation of the embodiment shown in FIG. 3 is as follows.

The output voltage characteristic of the circuit of FIG. 3 immediately after power-on is the same as that of FIG.

Consider the operation when the power is turned on in the case where the terminals 45 and 45 'on the charging circuit side are not connected to the battery.

When the power is turned on, the voltage of the delay capacitor 36 rises slowly from 0V, so the error voltage output from the operational amplifier 24 becomes excessive at first. Therefore, the feedback to the output control transistor 20-1 becomes impossible and an excessive output voltage is generated.

Therefore, the gate voltage of the thyristor 39 generated at both ends of the resistor 42 of the overvoltage detection circuit 20-4 becomes high, and the thyristor 39 becomes high.
39 turns on and informs the abnormality to the outside.

At the same time, the base voltage of the output control transistor 20-1 also drops and the operation is stopped.

Next, when the battery 44 is connected, the overvoltage generated during the delay period is absorbed by the battery even when the power is turned on, and the overvoltage does not occur.

Therefore, the overvoltage detection circuit does not operate, the output of the abnormality signal output terminal 46 does not change while still outputting a high voltage, and the outside is notified of no abnormality.

When the charging circuit and the battery are connected,
The open failure of the battery can be detected in the same manner as when the output terminal of the charging circuit and the battery are not connected.

In the illustrated embodiment, the abnormality can be detected only when the power is turned on, but the delay capacitor 36 can be periodically discharged to detect the abnormality of the charging circuit regularly.

〔The invention's effect〕

According to the present invention, without providing a special terminal for detecting connection in the connector for connecting the charging circuit and the battery, the presence or absence of the connection can be surely confirmed every time the power is turned on, and at the same time, with a simple structure, during charging. It is also possible to check whether or not there is an open failure in the battery.

[Brief description of drawings]

FIG. 1 is a principle diagram of the charging circuit of the present invention. FIG. 2 is a diagram showing a voltage output characteristic of the present invention when the power is turned on. FIG. 3 is a diagram showing an embodiment of the present invention. FIG. 4 is a diagram showing a conventional method for detecting an abnormality in a battery charging circuit. In FIG. 1, 1: output control transistor, 2: overcurrent protection circuit, 3: stabilization control circuit, 4: overvoltage detection circuit, 5: battery, 6: connector, 7, 7 ': output terminal, 8, 8 ′: Battery terminal, 1
0: Output voltage detection circuit, 11: Current detection resistor, 12: Differential amplifier, 13, 14: Voltage dividing resistor, 15: Delay circuit, 16: Reference voltage, 17:
Differential amplifier.

Claims (1)

(57) [Claims] 1. An output control transistor (1) for converting an input voltage into an output voltage for charging a battery, and detecting the output voltage, comparing the output voltage with a reference voltage (16), and generating an error voltage to output the output. A stabilization control circuit (3) that stabilizes and controls the output voltage by feeding back to the control transistor (1), and an overcurrent that detects an excessive output current and controls the output control transistor (1) to limit the current. Protection circuit (2)
And a battery charging circuit comprising an overvoltage detection circuit (4) for detecting an excessive output voltage and outputting an abnormal signal, and output terminals (7, 7 ') for supplying the output voltage to a battery (5). The stabilization control circuit (3) has an output voltage detection circuit (10) including a delay circuit (15), and the delay circuit (15) outputs the output of the stabilization control circuit (3) when an input voltage is applied. The output control transistor (1) acts to temporarily increase the output voltage, and when the input voltage is applied to the battery charging circuit, the overvoltage detection circuit (4) causes the output terminal (7, 7) to operate. Due to the abnormal connection of the battery (5) or the open failure of the battery (5) at ′), the high voltage output from the output control transistor (1) is detected and the connection of the battery (5) is abnormal or the battery (5) is open. Abnormality detecting method of the battery charging circuit and judging a.