JPS5824865A - Voltage detector - Google Patents

Abstract

PURPOSE:To achieve a stable, accurate and effective detection of changes in the voltage by varying the quantity of emitted light of a light emitting diode depending on preset threshold voltage. CONSTITUTION:A circuit comprising a resistor R1, a Zener diode ZD, a green light emitting diode (LED) 1G and a circuit comprising a resistor R2, a red LED1R are connected in parallel between a battery B and a load L. Therefore, when the voltage of the battery B is normal, current flows both through the LED1G and the LED1R and a multicolor LED1' glows yellow mixing the green light emitted and the red light emitted. As the voltage falls below the threshold of the Zener diode ZD, current only flows through the LED1R, causing the multicolor LED1 to emit red light.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage detector, and particularly to a voltage detector that detects voltage by changing the amount of light emitted from an LED using a predetermined threshold voltage.

In electrical circuits, there is a minimum voltage required for normal operation of the electrical circuit. In battery-powered equipment, the voltage of the battery gradually decreases over time, so it is important to know whether the battery voltage is higher than the normal drive voltage n7.

Traditionally, using a moving coil type mini pilot meter or an LED? Used as a power pilot
The nV lightning voltage is detected by turning off the light below the voltage. However, the first conventional example, a mini-pilot meter, has a large volume that determines the limit of miniaturization when trying to miniaturize the device, and the second conventional example does not have LEDs. There is also a problem when using LEDs, which do not take up much space, because some users mistakenly think that the device is defective when the lights turn on.

The present invention has been proposed in order to effectively solve these disadvantages in the prior art, and its main purpose is to be suitable for miniaturization and to obtain stable and reliable operation. The present invention proposes a voltage detector that can effectively notify voltage changes.

Hereinafter, a detailed description will be given with reference to the accompanying drawings.

FIG. 1 shows a circuit diagram of a voltage detector using a Zener diode. In Figure 1, 1 is a green light emitting diode (hereinafter referred to as LE) in the same element using a gap.
(referred to as D) IG1 red light emitting 3- Diode (hereinafter referred to as LED) LED forming IR
This is a multicolor light emitting diode (hereinafter referred to as MLED) 1 that can emit light in intermediate colors such as orange and yellow by changing the ratio of current flowing through LED IG and LED IH.

L is an electric circuit supplied with power from battery B, and ZD is a Zener diode that turns off when the voltage supplied to L reaches nV or less.

In the above configuration, when the voltage of battery B is normal, current flows through both LED IG and LgD IR, so LED 1 emits yellow light by mixing green light and red light. When the voltage of battery B drops and approaches nV, the Zener diode ZD applies 0FFL, so 1G
While the current flowing through LED I suddenly decreases,
Since the Rff current does not change much, the green light emission is also weaker than the red light emission, and the MLEDI as a whole becomes orange. When the voltage further decreases to nV or less, current flows only through LED IH, so MLEDl begins to emit red light. As explained above, when the voltage of battery B drops, the light emission color of MLED1 becomes [yellow] (normal).

) → [orange] (normal, but it is better to replace battery B) → [red] (battery B voltage has dropped to such an extent that normal operation of the electric circuit cannot be guaranteed.) Change. Note that R1 and R2 are resistors for limiting the current flowing through the LEDIG and IIR.

FIG. 2 is a circuit diagram showing another embodiment of the present invention. Second
In the figure, transistor TR is a Zener diode Z.
While current is flowing through D2, current flows through the base resistor R5' and the transistor is turned on. R
3 and R4 are resistors for limiting the currents flowing through LEDIR and IG, respectively, and the other configurations are the same as in FIG. Reference numbers and symbols common to FIG. 1 indicate common structures.

Next, to explain the operation, if the voltage of battery B is normal, transistor TR is completely turned on, and LED
Since a voltage is applied to both ends of the IH, the LEDIR does not light up. On the other hand, since current flows through all of R3 and ZD in LEDIG, MLEDl emits green light.

When the voltage of battery B drops and approaches nv, the current flowing through the Zener diode ZD decreases, and the transistor TR
gradually becomes 0FFt, so the current also flows through LEDIR and becomes 1, and the current flowing through LEDIG decreases, so MLEDl starts to emit yellow light.

When the voltage of battery B further drops to near nV, the LED
While the current flowing through IR is largely limited by the Zener diode ZDK, the current supplied to the pace of the transistor TR through the pace resistor R5 is reduced.
Transistor TR becomes even more OFF.

Most of the current flowing through the resistor R4'e will be transferred from the transistor TR to the LEDIR, so
The green emission becomes even weaker t, b, and the red emission becomes even stronger.

One! Therefore, the MLED 1 as a whole exhibits an orange color.

When the voltage of battery B further drops below nv, the LED
At the same time that no current flows through IG, the transistor TR is also completely turned off, and current flows only through LEDIR, causing MLEDI to emit red light.

Therefore, in the example shown in Fig. 2, as the voltage of battery B decreases, it changes from [green] (normal) to [yellow] (normal, but it is better to replace the battery soon) → [ Orange] (normal, but the battery needs to be replaced.

) → [Red] (The voltage of battery B has dropped to the extent that normal operation of the electric circuit cannot be guaranteed.) and ML
The luminescent color of the entire ED1 changes.

Since the present invention is configured and operates as described above,
The user can reliably know the status of the power supply voltage of the battery, etc. by changing the color of the light emitted from the MLED.

Therefore, it becomes possible to replace the power supply or charge the battery before the electric circuit malfunctions. Furthermore, since the present invention can be constructed using only elements that can be made smaller, it can also be made smaller in equipment.

In the above description of the embodiment, an example in which a Zener diode is used as an element that produces a constant voltage drop has been disclosed.
The same effect can be produced even when connected in the forward direction.

Furthermore, in the above explanation, an example using an MLED having a plurality of light emitting parts in one chip was described, but L
Even if the EDIG and IR are each made up of independent LEDs and placed close enough to cause color mixing, the power status can be displayed in the same way. Note that if the degree of proximity is low, LEDIG and LEDIR will appear to be independent light emitting parts from the outside, and when the voltage of battery B is normal, both will emit light.

After that, when the voltage of battery B decreases, only the LEDIR emits light.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIG. 2 is a circuit diagram showing another embodiment. Here, B: battery, zD: Zener diode, MLED: multicolor light emitting diode, IG: green light emitting diode, IR: red light emitting diode. Patent applicant: Canon Co., Ltd. 11- Figure 1, 2N

Claims (1)

[Claims] 1. A circuit including at least one light emitting diode connected in parallel between a power source and a load, and a circuit further including an element that produces a constant voltage drop connected in series with the light emitting diode. A voltage detector, which is connected in parallel to detect a change in the power supply voltage based on a change in the amount of light emitted from the light emitting diode. 2. The voltage detector according to item 1, wherein the light emitting diode is a multicolor light emitting diode having two or more color light emitting parts in the same element. 3. Connecting an element that produces a constant voltage drop in series with at least one light emitting diode of the multicolor light emitting diodes, and connecting a transistor in parallel with at least one other light emitting diode to which the element is connected. 3. The voltage detector according to claim 2, wherein a change in voltage is detected by a change in color of a light emitting diode.