JPH0567153U - Battery charging circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize a dummy load with a simple configuration to empty the battery before charging the battery. [Configuration] An AC adapter that generates a DC voltage from a commercial power source, a DC-DC converter that inputs a DC voltage output from the AC adapter and outputs a stabilized DC voltage, and an electric power from the DC-DC converter. When charging a battery by providing a power switch, a charging switch, and a discharging switch in a battery charging circuit that has a load circuit that receives power supply and a battery that is charged when energized and that supplies backup power to the load circuit when a power failure occurs Switch control means having a backup step, a complete discharging step of continuing discharging to the load circuit until the amount of charge of the battery becomes zero even in the energized state, and a charging step and a charging completion step. ..

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a charging circuit suitable for use in a battery backup circuit or the like, and more particularly to improving a charging sequence.

[0002]

[Prior Art]

 FIG. 4 is a configuration block diagram of a conventional device. In the figure, an AC adapter 10 is connected to a commercial AC power source and outputs a DC current. The DC-DC converter 20 inputs the DC power sent from the AC adapter 10 and supplies a stabilized DC voltage to the load circuit 30. The battery 40 supplies electric power in place of the AC power supply during a power failure, and trickle charges from the AC power supply when energized. Since the load circuit 30 receives power from the battery 40 at the time of power failure, it does not hinder the operation even if there is a momentary power failure. The dummy load 50 is a load for discharging the battery 40 before charging, and reliably charges the battery 40 after the battery 40 is completely discharged.

FIG. 5 shows a charging current monitoring circuit for the battery 40. The current supplied from the charging circuit 22 to the battery 40 is detected by the current detection resistor R1, and the voltage generated at this resistor R1 is amplified by the operational amplifier and the amplification resistors R2 and R3 and output as the charging current monitor signal. .. FIG. 6 is a phase diagram of the charging current and the output voltage of the battery 40. At the beginning of charging, the output voltage rises at a constant value of the charging current since the battery 40 is almost empty, and the output voltage becomes constant after a while. As the charging progresses, the output voltage maintains a constant value, but the charging current gradually decreases and the battery 40 becomes fully charged.

[0004]

[Problems to be solved by the device]

 However, if the dummy load 50 is exclusively provided in a portable device, there is a problem that the cost of parts increases and it becomes necessary to consider heat dissipation, which complicates the design. Further, if the charge current is used to detect the end of charge of the battery 40, it is difficult to determine whether the battery 40 is unconnected or the charge is completed because the voltage generated in the current detection resistor is very small, and backup is performed. There was a problem that it was not possible to judge whether or not it could be done reliably.

The present invention solves such a problem, and a first object thereof is to realize a dummy load for emptying the battery before charging the battery with a simple configuration. The second purpose is to provide a battery charging circuit that can reliably detect whether or not a battery backup is possible.

[0006]

[Means for Solving the Problems]

 A first invention for achieving the above first object is an AC adapter that generates a DC voltage from a commercial power source, and a DC adapter that inputs a DC voltage output from this AC adapter and outputs a stabilized DC voltage. -A DC converter, a load circuit that receives power from the DC-DC converter, and a battery charging circuit that has a battery that is charged when energized and supplies backup power to the load circuit when a power failure occurs. It is a composition.

That is, a power switch provided between the AC adapter and the DC-DC converter, a charging switch provided between the AC adapter and the battery, and between the battery and the DC-DC converter. When the battery is charged, the backup step of turning off the power switch and the charging switch and turning on the discharge switch, and the charge amount of the battery even in the energized state. The discharging process continues until the battery charge reaches zero, the charging process turns on the power switch and the charging switch and turns off the discharging switch after the battery is completely discharged in this discharging process, and the charging process charges the battery. A switch control means having a charging completion step of turning off the charging switch after the completion of It has a feature.

A second invention for achieving the above second object is to input a DC voltage output from this AC adapter to an AC adapter that generates a DC voltage from a commercial power source, and generate a stabilized direct current voltage. A DC-DC converter for outputting and a battery charging circuit having a battery that is charged when energized and supplies backup power to the load circuit when a power failure occurs are configured as follows.

That is, it comprises a remote sense line connected to the battery, and a comparator for measuring the output voltage of the battery via the remote sense line and comparing it with a backup reference voltage to output a backup enable signal. It is characterized by doing.

[0010]

[Action]

 In the first invention, the switch control means operates the power switch, the charging switch, and the discharging switch so that when the battery is charged, the load circuit is first used to empty the battery and then the battery is completely charged. At this time, since the load circuit is used as the discharging load, the dummy load is not required and the configuration is simplified.

In the second invention, a remote sense line for voltage detection is provided independently of the load line through which current flows to the battery. Then, the charge state of the battery is measured by the comparator, and after the battery is charged to a certain voltage or higher, backup is possible, and a signal to that effect is output.

[0012]

【Example】

 Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention. In FIG. 1, the same elements as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted. In the figure, the switch circuit 60 has a power switch 61, a charge switch 62, and a discharge switch 63. The power switch 61 is provided between the output terminal of the AC adapter 10 and the input terminal of the DC-DC converter 20. The charging switch 62 is provided between the output terminal of the AC adapter 10 and the battery 40. The discharge switch 63 is provided between the battery 40 and the input terminal of the DC-DC converter 20, and operates in cooperation with the power switch 61. The diode D1 is provided between the discharge switch 63 and the input terminal of the DC-DC converter 20, and inhibits power supply to the battery 40 when energized. Semiconductor switches such as transistors and FETs may be used for these switches. The switch control circuit 70 opens and closes each switch of the switch circuit 60, and the details will be described with reference to FIG.

FIG. 2 is a waveform diagram for explaining the operation of the circuit of FIG. 1, where (A) is the on / off state of the main power supply, (B) is the power interruption state of the AC power supply, (C) is the opening and closing of the power switch 61, ( D) is an opening / closing of the discharge switch 63, (E) is an opening / closing of the charging switch 62, (F) is a charge amount of the battery 40, and (G) is an explanatory diagram of an operation mode. Until time T1, the power switch 61 is on, the power switch 61 is on, and the discharge switch 63 and the charge switch 62 are off. Since a power failure occurs at time T1, the switch control circuit 70 that has detected the power failure turns off the power switch 61, turns on the discharge switch 63, and keeps the charge switch 62 off. As a result, the load circuit 30 is backed up by the battery 40. When power is restored at time T2, the charging sequence of the battery 40 is started. The switch control circuit 70 keeps each switch the same as that at the time of backup and continues discharging until the charge amount of the battery 40 becomes zero. Here, the load circuit 30 is used instead of the dummy load. It is preferable to increase the power consumption in the load circuit 30 in order to complete the complete discharge early. At time T3, the charge amount of the battery 40 becomes zero, so charging is started. Therefore, the power switch 61 is turned on, the discharge switch 63 is turned off, and the charge switch 62 is turned on. Since charging of the battery is completed at time T4, the charging switch 62 is turned off. In this way, the battery is reliably charged.

FIG. 3 is a configuration block diagram for explaining the second device. Here, the charger 22 and the battery 40 are connected using a connector 80. The connector 80 connects three poles at the same time, and includes a load line 81 through which a current flows, a remote sense line 82 for voltage detection, and a common line 83. The comparator U1 compares the output voltage of the battery 40 detected by the remote sense line 82 with the voltage dividing resistors R1 and R2 and the reference voltage Vref, and outputs a backup enable signal. The reference voltage Vref is set to be slightly lower than the constant voltage of the output voltage shown in FIG. 6, and is set to a value at which the battery 40 can recognize that the load circuit 30 can be backed up. Note that the back-up enable signal can also be used as an alarm signal for the battery 40 not connected.

Next, the relationship with the battery over-discharge prevention circuit 90 will be described. The timer 91 inputs the backup enable signal of the comparator U1 and detects that the voltage of the battery 40 has dropped. When the battery 40 becomes unchargeable when over-discharge occurs, it is necessary to stop the backup. Therefore, the timer 91 receives the alarm signal indicating that the output voltage of the battery 40 has dropped due to the backup enable signal, and then drives the relay 92 after a predetermined time has elapsed to stop the backup operation by the battery 40. . The circuit composed of the resistor R3 and the diode D2 is a circuit for charging the battery 40. That is, when the battery 40 is in the uncharged state, the backup enable signal of the comparator U1 is in the L state and the relay 92 is in the OFF state, so that the charger 22 and the battery 40 are disconnected. Therefore, a series circuit of a resistor R3 and a diode D2 is inserted in parallel with the relay 92 so that the battery 40 can be charged by the charger 22. When the battery 40 is charged more than the backup reference voltage, the relay 92 is turned on to shift to constant current charging. The diode D3 is connected in parallel with the charger 22, and supplies backup power from the battery 40 to the DC-DC converter 20 to operate the load circuit 30 at the time of power failure.

[0016]

[Effect of the device]

 As described above, according to the first aspect of the present invention, the switch circuit is controlled by the switch control circuit to connect the battery 40 to the load circuit 30 so that the charge amount is once set to zero before charging. You can charge it easily. Further, since the load circuit 30 is used, the manufacturing cost is reduced and the design is facilitated as compared with the case where the dummy load is provided. In the second invention, the output voltage of the battery is measured by using the remote sense line and is compared with the reference voltage that can be backed up, so there is an effect that it is possible to reliably determine whether backup by the battery is possible.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a first device.

FIG. 2 is a waveform diagram illustrating the operation of the device of FIG.

FIG. 3 is a configuration block diagram illustrating a second device.

FIG. 4 is a configuration block diagram of a conventional device.

FIG. 5 is a battery charging current monitoring circuit diagram.

FIG. 6 is a phase diagram of a charging current and an output voltage of a battery.

[Explanation of symbols]

 10 AC Adapter 20 DC-DC Converter 30 Load Circuit 40 Battery 60 Switch Circuit 70 Switch Control Circuit 22 Charger 82 Remote Sense Line

Claims (2)

[Scope of utility model registration request] 1. An AC adapter for generating a DC voltage from a commercial power source, a DC-DC converter for inputting a DC voltage output from the AC adapter and outputting a stabilized DC voltage, and the DC-DC converter. In a charging circuit of a battery having a load circuit that receives supply of electric power and a battery that is charged when energized and supplies backup power to the load circuit when a power failure occurs, a power provided between the AC adapter and the DC-DC converter. A switch, a charging switch provided between the AC adapter and the battery, the battery and the DC-
A discharge switch provided between the DC converters, and a backup step of turning off the power switch and the charge switch and turning on the discharge switch when the battery is charged, and the battery even in the energized state. In the complete discharge process, which continues discharging until the amount of charge becomes zero, the charging process in which the power switch and the charge switch are turned on and the discharge switch is turned off after the completion of discharging of the battery in this complete discharge process, and this charging process. A charging circuit for a battery, comprising switch control means having a charging completion step of turning off a charging switch after charging of the battery is completed. 2. An AC adapter that generates a DC voltage from a commercial power source, a DC-DC converter that inputs a DC voltage output from the AC adapter and outputs a stabilized DC voltage, and a power failure that is charged when energized. At this time, in a battery charging circuit having a battery that supplies backup power to the load circuit, a remote sense line connected to the battery and the output voltage of the battery are measured via this remote sense line to obtain a backup reference voltage. A battery charging circuit comprising: a comparator that outputs a backup enable signal for comparison.