JPH1023685A - Backup power circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the capacity of the backup power supply to electronic equipment by, when the engine switch of a vehicle is on, charging the backup power supply using the battery of the vehicle, and when the engine switch is off, alternately repeating a charging time and a pause time preset on the battery of the vehicle to intermittently charge the backup power supply. SOLUTION: When an engine switch 2 is on, a switching element 9 is kept on by means of a microcomputer 4, and a backup power supply 5 is charged through a 5V power supply 3 with AVR using a vehicle battery 1 as a power supply. When the engine switch 2 is off, the switching element 9 is on/off- controlled by means of the microcomputer 4, and the backup power supply 5 is intermittently charged through the 5-V power supply 3 using the vehicle battery 1 as a power supply, by repeating a charging time and a pause time predetermined. This enables providing a backup by means of a backup power supply 5 of small capacity, and redusing the power consumption of a vehicle battery 1, when the engine is at a stop.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backup power supply circuit for charging a backup power supply of a microcomputer of an electronic device mounted on a vehicle.

[0002]

2. Description of the Related Art FIG. 10 is a diagram showing a backup power supply circuit according to a conventional float charging system. In the figure, 1 is a vehicle battery (hereinafter referred to as "battery"), 2 is an engine switch, 3 is a 5V power supply composed of an AVR or the like using the battery 1 as an input source, and 4 is a microcomputer (hereinafter, "microcomputer"). 4a ~
4d is a component of the microcomputer 4, 4a is an input / output port (hereinafter referred to as "I / O port"), 4b is a CPU,
c is a RAM, and 4d is a ROM. 5 is a backup power supply composed of a secondary battery or the like, 6 is a current limiting resistor, 7 is a radio circuit of an electronic device controlled by the microcomputer 4, 8 is an operation input unit to the microcomputer 4, and a radio circuit 7 and an operation input The unit 8 is connected to the I / O port 4a.

Next, the operation will be described. 5V power supply 3
When the engine switch 2 is on, power is supplied to the microcomputer 4 and the backup power supply 5 is charged via the current limiting resistor 6. When the engine switch 2 is on, the microcomputer 4 is in the operation mode, and the operation input unit 8
The radio circuit 7 is controlled in accordance with the operation input from.

Next, when the engine switch 2 is turned off, the microcomputer 4 enters a non-operation mode. At this time, power is supplied to the microcomputer 4 from the backup power supply 5 through the current limiting resistor 6, and the information written in the RAM 4c is retained.

[0005]

Since the conventional backup power supply circuit is configured as described above, if the ON time of the engine switch is short, the backup power supply 5 may be insufficiently charged, and the engine switch may be turned off. If the time is long, the backup power supply 5 is overdischarged and R
AM4c information may be lost. Further, a microcomputer having a clock function needs to have a large-capacity backup power supply in order to prevent the clock from stopping due to overdischarge.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and a microcomputer can be backed up using a backup power supply such as a relatively small-capacity secondary battery or an electric double-layer capacitor. It is an object of the present invention to provide a backup power supply circuit that consumes less battery power while an engine switch is off.

[0007]

SUMMARY OF THE INVENTION A backup power supply circuit according to the present invention charges a backup power supply with a vehicle battery while an engine switch of the vehicle is on, and supplies the backup power supply to the vehicle while the engine switch is off. An intermittent charging means for charging the battery by alternately repeating a predetermined charging time and a pause time alternately is provided.

The intermittent charging means is controlled by control means for changing one or both of a charging time for the backup power supply and a pause time in accordance with the ON time of the engine switch.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. FIG. 1 is a block circuit diagram of the first embodiment, wherein 1 is a battery, 2 is an engine switch, 3 is a 5V power supply composed of an AVR or the like using the battery 1 as an input source, 4 is a microcomputer, 4a to 4e are 4a is an I / O port, 4b is a CPU,
4c is a RAM, 4d is a ROM, and 4e is a timer. 5
Is a backup power supply composed of a secondary battery or an electric double layer capacitor, 6 is a current limiting resistor, 7 is a radio circuit of an electronic device controlled by the microcomputer 4, and 8 is a microcomputer 4
9 is a switch element, and batteries 1 and 5
It is connected between V power supplies 3 and is on / off controlled by the microcomputer 4.

FIG. 2 is a diagram showing the relationship between the on / off state of the engine switch 2 and the on / off state of the switch element 9. FIG. 2 (a) shows the on / off state of the engine switch 2. 2 (b) shows the on / off state of the switch element 9.

Next, the operation of the first embodiment from the time when the engine switch 2 is turned on at time t0 to the time when the engine switch 2 is turned off at time t1 and then is turned on again at time t2 will be described.
This will be described with reference to the flowcharts of FIGS. 1, 2, and 3. Before time t0, the microcomputer 4 is supplied with power from the backup power supply 5 via the current limiting resistor 6, and is in a standby state. When the engine switch 2 is turned on at time t0 and the voltage of the battery 1 is applied to the I / O port 4a and the radio circuit 7, the CPU 4b proceeds to step 1
In (S1), it is determined that the engine switch 2 has been turned on by this voltage application, and in step 2 (S2), the switch element 9 is turned on.
Is turned on to start charging the backup power supply 5 and then proceed from step 3 (S3) to step 5 (S5),
The operation of the radio circuit 7 is controlled based on an input from the operation input unit 8 to the microcomputer 4.

Next, when the CPU 4b detects that the engine switch 2 has been turned off at time t1 in step 3 (S3), the timer 4e is reset in step 6 (S6) to start counting the charging time T1, If it is detected in step 7 (S7) that the charging time T1 has elapsed, the process proceeds to step 8
In step (S8), the switch element 9 is turned off.
In step 9), the timer 4e is reset to start counting the pause time T2, and when it is detected in step 10 (S10) that the pause time T2 has elapsed, the switch element 9 is turned on in step 11 (S11) and step 6 is performed. Returning to (S6), the operation of resetting the timer 4e and starting the counting of the charging time T1 is repeated, and the intermittent charging of the backup power supply 5 is repeated. When the engine switch 2 is turned on at time t2, step 1 (S1) ) And return to step 1 (S
The operation shifts from 1) to the operation of step (S3).

As described above, the backup power supply 5 supplies the charging time T1 and the pause time T2 while the engine switch 2 is off.
Are repeated intermittently, so that the charging time T1
If the length of the pause time T2 is set to an appropriate value based on the type and capacity of the backup power supply 5 and the backup power consumption of the microcomputer 4, the microcomputer 4 can be backed up by the small-capacity backup power supply 5. It is possible to reduce the power consumption of the battery 1 while the engine is stopped.

Embodiment 2 FIG. In the first embodiment, when the engine switch 2 is off, the charging time T1 and the pause time T2
Thus, intermittent charging is performed.
Is configured to increase or decrease the amount of intermittent charging according to the length of the ON time of the engine switch 2 (hereinafter, referred to as “TON”).

The circuit configuration of the second embodiment is the same as that of FIG. FIG. 4 is a flowchart of the second embodiment, and FIG. 5 is a standard time when TON is TON (hereinafter, referred to as TON).
Engine switch 2 when shorter than "TONS")
FIG. 6 is a diagram showing the ON / OFF state of the switch element 9 and FIG. 6 is a diagram showing the ON / OFF state of the engine switch 2 and the switch element 9 when TON is longer than TONS.

In FIG. 4, the operations of Step 1 (S1) to Step 6 (S6), Step 7 (S7) to Step 9 (S9), and Step 11 (S11) are the same as those in FIG. The description is omitted because it is the content, and the operation of the different steps will be described.

When the CPU 4b detects that the engine switch 2 has been turned off in step 3 (S3), the CPU 4b detects the time TON during which the engine switch 2 was on from the count value of the timer 4e in step 14 (S14). In step 15 (S15), the coefficient k is calculated based on the following equation. k = TON / TONS Here, TONS is a reference value of TON. Next, in step 16 (S16), the pause time T2 'is calculated based on the following equation. T2 '= T2 · k where T2 is the standard pause time when TON = TONS

The pause time T2 'is given to step 17 (S17) as the pause time T2' of the switch element 9. When the count value of the timer 4e reaches T2 ', the switch element 9 is turned on in step 11 (S11). Then, the operation returns to step 6 (S6), resets the timer 4e, starts counting the charging time T1 in step 7 (S7), repeats the intermittent charging of the backup power supply 5, repeats the engine switch 2 at time t2. Is turned on, the process returns to step 1 (S1) and shifts from step 1 (S1) to step 3 (S3).

Pause time T2 'in the intermittent charging operation
When TON is shorter than TONS, T2 '<T2 as shown in FIG. 5, and when TON is longer than TONS, T2'> T2 as shown in FIG. This is because TON is T
When it is shorter than ONS, the amount of charge of the backup power supply 5 while the engine switch 2 is on is small, so it is necessary to increase the amount of charge during intermittent charging. Conversely, when TON is longer than TONS, Since the amount of charge of the backup power supply 5 when the engine switch 2 is on is large, even if the charge amount during intermittent charging is reduced, the charge amount of the backup power supply 5 does not become insufficient, and overcharging is prevented. This is because the power consumption of the battery 1 can be reduced.

Embodiment 3 In the second embodiment, the charging time T1 is fixed and the pause time T2 'is variable.
In the third embodiment, the pause time T2 is fixed, and the charging time T1 'is variable.

The circuit configuration of the third embodiment is the same as that of FIG. FIG. 7 is a flowchart of the second embodiment, FIG. 8 is a diagram showing the on / off state of the engine switch 2 and the switch element 9 when TON is shorter than TONS, and FIG. 9 is an engine when TON is longer than TONS. FIG. 3 is a diagram showing on / off states of a switch 2 and a switch element 9.

In FIG. 7, from step 1 (S1) to step 6 (S6), from step 8 (S8) to step 11 (S11), and to step 14 (S1).
4), the operation of step 15 (S15) is the same as that of the same step in FIGS.
The operation of the different steps will be described.

In step 18 (S18), the CPU 4b calculates a charging time T1 'based on the following equation. T1 '= T1 / k where T1 is the standard charging time when TON = TONS

The charging time T1 'is given to step 19 (S19) as the charging time T1' of the switch element 9. When the count value of the timer 4e reaches T1 ', the switch element 9 is turned off in step 8 (S8). Step 9
The intermittent charging of the backup power supply 5 is repeated by repeating the operation of resetting the timer 4e in (S9) to start counting the pause time T2, and when the engine switch 2 is turned on at time t2, the process proceeds to step 1 (S1). Then, the process returns to step 3 (S3) from step 1 (S1).

Pause time T1 'in the above intermittent charging operation
When TON is shorter than TONS, T1 '> T1 as shown in FIG. 8, and conversely, when TON is longer than TONS, T1'<T1 as shown in FIG. This is because TON is T
When it is shorter than ONS, the amount of charge of the backup power supply 5 while the engine switch 2 is on is small, so it is necessary to increase the amount of charge during intermittent charging. Conversely, when TON is longer than TONS, Since the amount of charge of the backup power supply 5 when the engine switch 2 is on is large, even if the charge amount during intermittent charging is reduced, the charge amount of the backup power supply 5 does not become insufficient, and overcharging is prevented. This is because the power consumption of the battery 1 can be reduced.

It should be noted that both the charging time and the pause time of the backup power supply 5 may be changed in accordance with both the second and third embodiments, that is, the ON time of the engine switch.

[0027]

As described above, according to the present invention, the backup power supply is charged by the vehicle battery while the engine switch of the vehicle is on, and the backup power supply is previously stored by the battery of the vehicle while the engine switch is off. The provision of the intermittent charging means for performing charging alternately and repeatedly between the predetermined charging time and the pause time provides the effect of reducing the capacity of the backup power supply and reducing the power consumption of the vehicle battery.

Further, the control means for changing either one or both of the charging time and the rest time of the backup power supply in accordance with the on time of the engine switch being on is provided. This has the effect of further reducing the power consumption of the battery.

[Brief description of the drawings]

FIG. 1 is a block diagram of a backup power supply circuit according to Embodiment 1 of the present invention.

FIG. 2 is an operation explanatory diagram of the switch element according to the first embodiment;

FIG. 3 is a flowchart according to the first embodiment.

FIG. 4 is a flowchart according to a second embodiment of the present invention.

FIG. 5 is an operation explanatory diagram of the switch element according to the second embodiment.

FIG. 6 is an explanatory diagram of an operation of the switch element according to the second embodiment.

FIG. 7 is a flowchart according to a third embodiment of the present invention.

FIG. 8 is an operation explanatory diagram of the switch element according to the third embodiment.

FIG. 9 is an explanatory diagram of an operation of the switch element according to the third embodiment.

FIG. 10 is a block diagram of a conventional backup power supply circuit.

[Explanation of symbols]

1 battery, 2 engine switch, 35V power supply,
4 microcomputer, 4b CPU, 4e timer, 5 backup power supply, 6 current limiting resistor, 9 switch element.

Claims (2)

[Claims] 1. A backup power supply circuit for charging a backup power supply of a microcomputer of an electronic device mounted on a vehicle, wherein the backup power supply is charged by a vehicle battery while an engine switch of the vehicle is on. A backup power supply circuit comprising intermittent charging means for charging the backup power supply with the battery by alternately repeating a predetermined charging time and a pause time while the engine switch is off. 2. The intermittent charging means is controlled by a control means for changing one or both of a charging time for a backup power supply and a pause time in accordance with an ON time of an engine switch. Backup power circuit.