JPH04289724A - Used power source discriminator - Google Patents

Abstract

PURPOSE:To provide a device for discriminating which power source is used, in equipment wherein an AC adaptor and a secondary battery are used jointly. CONSTITUTION:The terminal 1 of a three-terminal DC jack 10, which is equipped with contacts a and b by which the circuit between terminals 2 and 3 is switched by the plug in of an AC adaptor, is connected to GND, and the terminal 2 is connected to the (+) terminal of equipment, and the terminal 3 is connected to the (+) terminal of secondary battery 11. A regulator 12 and a used power source discriminating circuit 13 are connected each in series between the (+) electrode of the equipment and the GND, and by this used power source discriminating circuit 13, it judges which power currently is in use.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to small devices that use both an AC adapter and a secondary battery, whether the power source used is a secondary battery, a semi-stabilized power source, or a stabilized power source. This invention relates to a power source identification circuit that identifies whether the device is powered by an AD converter within the device.

0002

2. Description of the Related Art As is well known, many small devices that operate using an AC adapter and a secondary battery have come to be seen on the market. In particular, more and more devices use secondary batteries, and they can be used over and over again. Also, 2
AC adapters for charging batteries used to be semi-stabilized AC adapters using commercial transformers, but recently many AC adapters using switching power supplies have been used. For devices, switching between an AC adapter and a secondary battery is usually performed using a DC jack. Since the DC jack has specifications as shown in FIG. 1, it is difficult for the device to determine whether power is being supplied from the AC adapter or the secondary battery. For example, if a commercial transformer is used for operation, the voltage will drop as the load increases. When this voltage drop is below the voltage at which the secondary battery is dead, it is impossible for the device to determine whether the battery is dead or the AC adapter voltage has dropped.

0003

SUMMARY OF THE INVENTION An object of the present invention is to provide a circuit that detects and identifies which power source is driving a device itself.

0004

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and includes a circuit that can detect the ripple voltage of the power supply voltage in the machine, thereby reducing the voltage drop in the voltage of the AC adapter. It is designed to determine whether it is due to a drop in the battery life or a dead battery in the secondary battery.

[0005]

[Operation] Equipment that uses both an AC adapter and a secondary battery receives power from the DC jack shown in FIG. 1 as described above. Since the input ports are the same, it is impossible to determine which power source is receiving power. Normally, the power source can be identified by the voltage level, but if the AC adapter uses a commercial transformer, it becomes impossible to distinguish it from a secondary battery if the primary voltage drops. In the case of an AC adapter that uses a commercial transformer, power is supplied to the secondary side using a primary power supply at 50Hz (hertz) or 60Hz (hertz), but even if smoothed with a capacitor, the A ripple voltage of milliV or more is generated. The present invention converts this voltage difference into an AD in the device.
The measurement is performed using a power source identification circuit using a converter. That is, when a secondary battery or a switching AC adapter (stabilized power supply) is used, this ripple voltage difference is so small that it is hardly measured. Therefore, by measuring the ripple of the power supply, it is possible to determine whether the power supply is an AC adapter using a commercial transformer (semi-stable power supply), a secondary battery, or a switching power supply (stabilized power supply).

[0006]

[Embodiment] FIG. 2 shows an embodiment of the present invention, in which terminal 1 of the AC adapter jack 10 is connected to GND, terminal 2 is connected to the (+) electrode of the device, and terminal 3 is connected to the (+) electrode of the secondary battery 11. ) connected to the pole. 12 is a +5V regulator connected between the (+) electrode of the device and GND, 13 is a logic section 14
, an AD converter section 15 , and a display section 16 . As shown in FIG. 3, the logic section 14 includes a CPU 141, a ROM 142, a RAM 143
and an I/O port 144, and the AD converter section 15 includes an AD converter 151 and voltage dividing resistors R1 and R2. The broken line shows the flow of current when the secondary battery 11 is in use, and since contacts a and b are turned on, the current flows in the direction of the arrow. As shown in FIG. 3, the CPU 141 in the logic section 14 measures the applied V1 voltage via the AD converter section 15. AD converter 151 of AD converter section 15 in the embodiment
Since it is an 8-bit type, it is possible to measure the V1 voltage in 256 levels. Resistors R1 and R of the AD converter section 15
2 is provided to divide the V1 voltage applied to meet the specifications of the AD converter 151, and the voltage input to the AD converter 151 is 2.5V maximum value (V voltage 10.3V maximum value). . The divided voltage of the V1 voltage applied to the AD converter 151 is applied to the logic section 14.
is measured. The maximum and minimum values of the measurement results are sent to the logic section 1.
The CPU 141 of No. 4 recognizes this and calculates the difference. FIG. 7 shows the measurement results. When the V1 voltage is measured with a synchro oscilloscope when the secondary battery 11 is used, it is a constant voltage as shown in FIG. FIG. 4 shows the flow of current when the AC adapter is used. Since contacts a and b are turned off, the current flows as shown by the arrow. When operated with an AC adapter using a commercial transformer, the AD converter section 1
When the V1 voltage applied to V1 is measured with a synchro oscilloscope, a ripple voltage as shown in FIG. becomes. This CPU1
As can be seen from the difference between the minimum value and maximum value according to No. 41, the difference is large in the case of an AC adapter using a commercial transformer. A using a commercial transformer depends on whether this difference is larger or smaller than a certain value (3 in the example).
It is detected whether the C adapter or the secondary battery 11 is being used. In addition, in the case of an AC adapter using a switching power supply, since it is a stabilized power supply, the difference between the maximum value and minimum value measurement results at the AD converter is the same as that of a secondary battery, as can be seen from FIG. However, since the AC adapter must charge the secondary battery, the voltage becomes high as shown in FIG. In other words, a certain value (in the example, V
1 is 7.5V, the AD converter value is 184), depending on whether it is larger or smaller, the A using a switching power supply
Determine whether it is a C adapter or a secondary battery. As mentioned above, by measuring the ripple voltage of the power supply used, you can choose between an AC adapter that uses a commercial transformer (semi-stable power supply), a secondary battery, or an AC adapter that uses a switching power supply (
It is possible to detect which one of the stabilized power supplies is being used. In the embodiment, these states are displayed using the LED of the display section 16.

[0007]

[Effects of the Invention] According to the present invention, an AC adapter using a commercial transformer can be used even if a voltage drop occurs due to load fluctuations.
It is no longer falsely detected as a low voltage check for the next battery. Additionally, since the device can determine the power source being used, it can be provided with special functions depending on the power source being used.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a DC jack.

FIG. 2 is a block diagram of an embodiment of the present invention.

FIG. 3 is a block diagram showing details of a used power source identification circuit.

FIG. 4 is an explanatory diagram showing the effect when using the AC adapter.

[Figure 5] V when using secondary battery and switching power supply
1 is a diagram showing one voltage.

FIG. 6 is a diagram showing the V1 voltage when an AC adapter is connected using a commercial transformer.

FIG. 7 is a diagram showing the measured minimum value, measured maximum value, and difference thereof for each power source used.

[Explanation of symbols]

10 DC jack 11 Secondary battery 12 Regulator 13　　　　　　　Power supply identification circuit used 14 Logic section 15 AD converter section

Claims (1)

[Claims] [Claim 1] By inserting the AC adapter, the terminal (2
), (3) Connect the terminal (1) of the 3-terminal DC jack (10) equipped with contacts a and b that are OFF to GND,
Terminal (2) connects to the (+) electrode of the device, and terminal (3)
) is a device connected to the (+) electrode of the secondary battery (11), and a regulator (
12) and a power source identification circuit (13) are connected in parallel, respectively.