JPS60245431A - Battery charing/discharging control circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a battery charge/discharge control circuit in a power supply section of a device having a power failure compensation function using a rechargeable battery.

Conventional configurations and their problems Equipment that is used continuously for long periods of time and cannot tolerate instantaneous power outages is equipped with a built-in rechargeable battery, and in the event of a power outage, the built-in battery will not function properly. A method is taken to maintain it. In particular, when a microcomputer is used for calculation, control, etc. in order to provide flexibility in functions, a stable power supply is required for the microcomputer and computer.

Hereinafter, a conventional example of a battery charging/discharging circuit used in such equipment will be described.

FIG. 3 shows the configuration of a conventional battery charging/discharging control circuit, in which 1 is a DC constant voltage power supply, 2 is a charging control circuit,
3 is a rechargeable battery (hereinafter referred to as a battery); 4
is a voltage level converter, and 6 is a reverse current blocking diode.

The operation of the conventional battery charge/discharge control circuit of the power supply section configured as described above will be described below.

A power supply input (generally AC 100V of commercial frequency is used) is converted into a DC voltage (1) by a DC constant voltage power supply 1. The output of the DC constant voltage power supply 1 is branched into two parts, one of which is supplied to the charging control circuit 2 of the battery 3. The charging control circuit 2 includes a current limiting resistor R and a reverse current blocking diode D1, and maintains the charging current of the battery 3 at an appropriate value. The other output of the DC constant voltage power supply 1 is sent to the voltage level converter 4, where it is converted into a voltage 3 to be applied to the load and supplied to the rear load. Further, one of the input terminals of the battery 3 is connected to a load through a reverse current blocking diode D6. In the battery charge/discharge control circuit shown in FIG. 3, when there is power input, the battery 3 is charged and power is supplied to the load at the same time, and when there is no power input, the battery 3 supplies power to the load.

The output voltage of the DC constant voltage power supply 1 is set higher than the terminal voltage of the battery 3 in consideration of the voltage drop caused by the charging control circuit 2. For example, when using a 12V battery, the output voltage of the DC constant voltage power supply 1 is set to about 14V. The voltage level converter 4 generally uses the forward voltage drop of a diode to adjust the output voltage of the DC constant voltage power supply 1.
Outputs a voltage lower than 1. By setting the terminal voltage v2 of the battery 3 to be lower than the output voltage of the voltage level converter 3 when power is input, current does not flow through the reverse blocking diode 6 and the power is supplied to the load. is supplied only by the DC constant voltage power supply 1. Further, when there is no power input, that is, during battery operation, voltage v3' is supplied from the battery 3 to the load through the reverse current blocking diode 5. At this time, the diode D1. D2 prevents reverse discharge from the battery 3 to the DC constant voltage power supply 1.

The relationship between these voltages is shown in FIG.

Conventionally, with the above configuration, a system has been adopted in which charging and discharging of the battery is controlled in response to the presence or absence of power input. However, the above configuration has a problem in that the voltage (3) supplied to the load differs greatly depending on whether there is power input or not, as shown in FIG. That is, when there is a power input, the output voltage v3 of the voltage level converter, which is higher than the output voltage v2 of the charging control circuit, is supplied to the load.

On the other hand, when there is no power input, the terminal voltage v2' of the battery is supplied to the load as the voltage ■3' through the reverse current blocking diode. Therefore, during battery operation, the voltage supplied to the load is lower than when there is power input due to the following three factors.

(1) Output voltage V of the charging control circuit when there is power input
(2) Difference between charging voltage v2 and discharging voltage v2' of battery 3 (3) Forward voltage drop due to reverse blocking diode during battery operation (■2'- ■31) Secondly, in the above configuration, since the battery 3 is directly connected to the load during battery operation, the battery 3 continues to discharge until it runs out of charge.
This has the problem of degrading the performance of the battery. Furthermore, if a microcomputer or the like is connected as a load and the applied voltage during battery operation drops significantly, it will fall below the operating compensation voltage range of the load.

For example, if a voltage outside the operating compensation range is applied to a microcomputer, normal operation will not be guaranteed, and if the power is turned on again after the microcomputer has stopped functioning, it will be difficult to restart the microcomputer. There was a problem.

OBJECTS OF THE INVENTION The present invention solves the above problems and provides a battery charge/discharge control circuit that improves battery operating characteristics and stabilizes operation.

Structure of the Invention The present invention is a battery charging/discharging control circuit that includes a power input detection circuit that detects the presence or absence of power input, and a switch between the battery and the charging control circuit and between the charging control circuit and the load input. If there is no power input, turn on the first switch between the battery and charge control circuit.Turn off the second switch between the charge control circuit and load input.If there is no power input, turn on the second switch between the charge control circuit and load input. By turning on the switch of By turning off the first switch between the battery and the charging control circuit when the applied voltage falls below the load operation compensation range, over-discharge of the battery is prevented and load operation compensation is performed.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 shows the configuration of a battery charge/discharge control circuit in a first embodiment of the present invention. In Figure 1,
1 is a DC constant voltage power supply, 2 is a charging control circuit, 3 is an il-i rechargeable battery (hereinafter referred to as a battery), 4 is a voltage level converter, 6 is a power input detection circuit that detects the presence or absence of power input, 7 is a relay contact that operates with the output of the power input detection circuit 6, 8 is a capacitor, 9 is a voltage detector that detects the voltage applied to the load, 10 is a relay that operates with the output of the voltage detector, and 11 is operated with relay 10. It is a relay contact.

The operation of the battery charge/discharge control circuit configured as above will be described below.

When a power supply is input, the output of the DC constant voltage power supply 1 is supplied to the load through the voltage level converter 4.

The voltage applied to the negative terminal is guided to the voltage detector 9 and drives the transistor Q1 within the voltage detector 9.

The transistor Q1 includes a constant voltage diode D3 and a resistor R2.
A base current determined by flows. The operating level of the transistor Q1 can be determined by the constant voltage diode D3. If the voltage applied to the load 3 is sufficiently higher than the operating voltage of the constant voltage diode D3, the transistor Q1/'i is turned on and a collector current flows. As a result, relay 1
Q is driven, and the relay contact 11 becomes short-circuited.

In addition, the output of the power input detection circuit 6 causes the relay contact 7 to
will be released. As a result, the battery 3 is charged by the charging control circuit 2 by the DC constant voltage power supply 1. It is charged through the relay contact 11. The output of the DC constant voltage power supply 1 is supplied to the load through the diode D2 of the voltage level converter 4.

If the power supply input is cut off in this state, the input to the DC constant voltage power supply 1 becomes zero. At the same time, the power input detection circuit 6 detects the interruption of the power input, and the output of the power input detection circuit 6 short-circuits the relay contact 7.

Accordingly, the output of the battery 3 is supplied to the load through the relay contacts 11 and 7.

Note that reverse discharge from the battery 3 to the DC constant voltage power supply 1 is prevented by the diode D1 and the diode D2.

In order to prevent the power supply to the load from being cut off momentarily when switching the relay contact 7, a capacitor 8 is connected in parallel to the input of the load, and when switching the relay contact 7, the capacitor 8 is connected in parallel to the input of the load. Power is continuously supplied by discharging the 8 charges.

As the battery 3 continues to be discharged, the terminal voltage of the battery 3 gradually decreases, and as a result, the voltage applied to the load 3
′ also decreases. The voltage v31 applied to the load is detected by the voltage detector 9.
When the operating voltage of the constant voltage diode D3 is reached, the transistor Q1 is turned off, the relay 1Q is turned off, the relay contact 11 is opened, and the power supply from the battery to the load is stopped. Transistor Q1 in voltage detector 9
By setting the operating level at which the is turned on to be slightly higher than the minimum operation compensation voltage of the load, power is supplied from the battery 3 to the load only within the range in which the load operates normally.

According to this embodiment, during battery operation, the battery 3 is directly connected to the load through the relay contact 7 to supply power. This eliminates the need for the diode 6 of the conventional example shown in FIG. 3, and since there is no voltage drop in the forward direction of the diode 5 during battery operation, it is possible to supply the load with a voltage close to that during power input operation.

In addition, it is now possible to design the voltage level converter 4 and the charging control circuit 2 independently, so that the output voltage of the voltage level converter 4 during power input operation 3 and the discharge start voltage of the battery 3 during battery operation It becomes possible to match v3'.

Further, by providing a voltage detector 6 that detects the voltage applied to the load and controlling the connection of the battery terminals using the output of the voltage detector, it is possible to prevent characteristic deterioration due to overdischarge of the battery. Since the voltage applied to the load can be limited to within the operational compensation range of the load, the operation of the microcomputer etc. can be stabilized and restart can be ensured.

The power input detection circuit 6 is configured with a relay when performing battery operation when power input is cut off, and a second relay when performing battery operation even when the power supply voltage falls below a certain range.
Take the method shown in the example in the figure. In the power input detection circuit 6 shown in FIG. 2, 12 is a rectifying and smoothing circuit, 13 is a voltage detector, and 14 is a relay. Power input is rectifier smoothing circuit 12
The voltage is converted into direct current and applied to the voltage detector 13. This drives transistor Q1. A base current determined by a constant voltage diode D3 and a resistor R2 flows through the transistor Q1. The operating level of transistor Q1 can be determined by constant voltage diode D3. If the voltage corresponding to the power supply input, that is, the voltage applied to the collector of the transistor Q1 is sufficiently higher than that of the voltage regulator diode D3, the transistor Q1 is turned on and a collector current flows. As a result, the relay 14 is driven and the relay contact 7 shown in FIG. 2 becomes open. When the power input decreases,
The voltage applied to the collector of transistor Q1 also decreases.

When the voltage applied to the collector of transistor Q1 reaches the operating voltage of voltage regulator diode D3, transistor Q1 is turned off, relay 14 is turned off, and relay contact 7 in FIG. 4 is short-circuited and switched to battery operation. Change. If the transistor Q1 of the voltage detector 13 is set to turn off at the minimum operation compensation voltage of the DC constant voltage power supply 1, not only when the power input is cut off, but also when the power input is within the normal operating range of the DC constant voltage power supply 1. Below? It is possible to switch to battery operation even if the

Effects of the Invention As described above, the battery charging/discharging control circuit of the present invention is operated by the power input detection circuit that detects power input and the output of the power input detection circuit, and is equipped with a switch that switches to battery operation. It becomes possible to match the voltage applied to the load when there is input and when battery operation is performed without power input.

Furthermore, by providing the power supply input detection circuit with an accurate voltage detection function, it is possible to switch to battery operation even when the power supply input voltage falls below the normal operating range of the DC constant voltage power supply.

[Brief explanation of drawings]

FIG. 1 shows a charging/discharging control circuit in a sister example of the present invention, and a second
The figure shows an embodiment of the power input detection circuit in the actual example of FIG. 1. FIG. 3 shows a conventional battery charge/discharge control circuit, and FIG. 4 shows voltage waveforms of the circuit shown in FIG. 1... DC constant voltage power supply, 2... Charging control circuit, 3... Battery, 4... Voltage level converter, 5...・Backflow blocking diode, 6
...Power input detection circuit, 7...Relay contact, 8 Old...Capacitor, 9...Voltage detector, 1o...Relay, 11... ...Relay contact, 12... Rectifier smoothing circuit, 13...
Voltage detector, 14...Relay.

Claims (1)

[Claims] a DC constant voltage power supply, a rechargeable battery, and a charging control circuit that charges the battery using the output of the DC constant voltage power supply;
A first switch connected in series between the charging control circuit and the battery, a voltage level converter that converts the output of the DC constant voltage power supply to the voltage required for the load, and presence or absence of power input to the DC constant voltage power supply. a power input detection circuit that detects the voltage applied to the load, a second switch connected between the charging control circuit output and the load input, a capacitor connected in parallel to the input of the load, and a voltage detector that detects the voltage applied to the load. and a relay operated by a voltage detector, and when the input to the DC constant voltage power source is cut off, the output of the power input detection circuit short-circuits the second switch between the charge control circuit output and the load input, and the battery is It is characterized by switching the connection from the charge control circuit output to the load input, and opening the first switch between the charge control circuit and the battery upon detecting that the voltage applied to the load has fallen below the operation compensation voltage of the load. A battery charge/discharge control circuit,