JPH032869Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage drop display circuit that detects and displays a voltage drop in a battery used in a portable wireless device such as a tape recorder.

As the voltage drop display circuit used in such wireless equipment, a method using a meter pointer or a method using a light emitting element such as a light emitting diode is generally used. Although the method using a meter is certainly superior in accurately displaying the degree of current consumption, it is expensive and is not suitable for small wireless devices because it cannot be made small. .

The present invention aims to provide a voltage drop display circuit using a light emitting element that is suitable for downsizing wireless devices, and will be described in detail below with reference to the drawings.

The illustrated circuit is one embodiment of the voltage drop indicating circuit of the present invention. In the figure, 1 is a battery as a DC power source, 2 is a voltage drop detection section provided between a power line 3 and ground, and a resistor 4, a Zener diode 5, and a resistor 6 are connected in series. Reference numeral 7 designates a first transistor whose base is connected to the connection point a between the Zener diode 5 and the resistor 6 and whose emitter is grounded, and whose collector is connected to the power supply line 3 via the resistor 8. .
Reference numeral 9 denotes a second transistor whose base is connected to the collector of the first transistor 7 and whose emitter is grounded, and whose collector is connected to the power supply line 3 via a resistor 10.
11 is the base of the first transistor 7 and the second transistor 7;
A capacitor 12 connected between the collector of the transistor 9 and the collector 12 is a light emitting diode whose anode is connected to the connection point b between the collector of the second transistor 9 and the resistor 10 and whose cathode is grounded. In such a configuration, the values of the resistors 4 and 6 are such that the voltage on the power supply line 3 is the first
The voltage of the power supply line 3 is higher than the first reference value, and the voltage of the power supply line 3 is higher than the first reference value. When the second reference value or more is present, the first transistor 7
is set to a value that biases the first transistor 7 into an active state when it is equal to or greater than the first reference value and less than the second reference value.

The voltage drop display circuit of the present invention is constructed as described above, and the operation of this circuit will now be described. When the voltage of the battery 1, which is a DC power source, is sufficiently high and the voltage of the power supply line 3 is higher than the second reference value, the first transistor 7 is sufficiently biased by the voltage drop detection section 2 and is in a saturated state. When the first transistor 7 is in a saturated state, the collector potential of the first transistor 7 becomes approximately ground potential, so the second transistor 9, whose base is connected to the collector of the first transistor 7, is reverse biased and becomes non-active. It is in a conductive state. In this way, when the voltage of the power supply line 3 is equal to or higher than the second reference value, the second transistor 9 is in a non-conducting state, so that the connection point b
becomes a high potential, and the light emitting diode 12 is in a conductive and lit state.

As described above, when the voltage of the power supply line 3 is higher than the second reference value, the light emitting diode 12 is in the lighting state, but then the voltage of the power supply line 3 drops and the voltage becomes higher than the first reference value and the second reference value is reached. The operation when the value becomes less than the value will be explained. When the voltage of the power supply line 3 reaches such a value, the first transistor 7 is biased to an active state by the voltage drop detection section 2 , so that the voltage between the collector and emitter of the first transistor 7 increases, and the collector potential of the first transistor 7 increases. Rise. When the collector potential of the first transistor 7 rises, the second transistor 9, which had been in a reverse bias state, becomes a forward bias state and transitions to a conductive state. When the second transistor 9 becomes conductive, its collector potential drops, but as a result of this potential drop being positively fed back to the base of the first transistor 7 through the capacitor 11, the first transistor 7 becomes less active. The second transistor 9 shifts to the cut-off state, and as the second transistor 9 shifts to the cut-off state, the second transistor 9 becomes saturated. When the capacitor 11 is charged with a time constant determined by the resistor 4 and the capacitor 11, the base potential of the first transistor 7 rises, and the first transistor 7 shifts from the cut-off state to the active state. When the first transistor 7 becomes active, the collector potential of the first transistor 7 decreases, so the bias of the second transistor 9 becomes shallower.
Correspondingly, the collector potential of the second transistor 9 increases. When the collector potential of the second transistor 9 rises, the rise in potential is positively fed back to the base of the first transistor 7 through the capacitor 11, and as a result, the first transistor 7 shifts from an active state to a saturated state, and then reaches the saturated state. With the transition of , the second transistor 9 becomes non-conductive. Then, when the charge stored in the capacitor 11 is discharged, the first transistor 7 shifts from the saturated state to the active state, so that the above-described operation is repeated. In this way, when the voltage of the power supply line 3 is higher than the first reference value and lower than the second reference value, the second transistor 9 repeats the conductive state and the non-conductive state at a predetermined period. Result light emitting diode 1
2 is in a blinking state.

As described above, the operation is performed when the voltage of the power line 3 is equal to or higher than the first reference value.Next, the case where the battery 1 is exhausted and the voltage of the power line 3 drops below the first reference value will be described. When the voltage of the power supply line 3 drops below the first reference value, the Zener diode 5 constituting the voltage drop detection section 2 becomes non-conductive, so that no bias current flows to the base of the first transistor 7 and the first transistor 7
is in a non-conducting state. When the first transistor 7 is in a non-conducting state, the collector potential of the first transistor 7 is at a high potential, so that the second transistor 9 is sufficiently biased and is in a conducting state. Therefore, the potential at the collector of the second transistor 9, that is, the connection point b, is approximately at ground potential, and the light emitting diode 12 is in a non-lighting state.

In this embodiment, the light emitting diode 12 is configured to turn on, blink, and turn off in the order of lighting as the voltage of the power supply line 3 drops. When connected, the light emitting diode 12 is turned off as the voltage of the power supply line 3 drops.
The blinking and lighting states can be changed in this order. Furthermore, although a light emitting diode was used as the light emitting element in this embodiment, it is of course possible to use other light emitting elements.

As explained above, the voltage drop display circuit of the present invention changes the light emitting element into three different states of lighting, blinking, and non-lighting in response to changes in the power supply voltage. By selecting the optimum operating voltage value for electrical equipment and the first reference value as the lowest usable voltage value, you can easily check the voltage status of the battery used as a power source, especially when the light emitting element blinks. This has the advantage that it is possible to easily recognize when it is time to replace the battery based on the operation. Further, in the present invention, the bias state of the first transistor is changed in response to the voltage drop in the power supply line, and the oscillation operation is performed by the cooperation of the first transistor, the second transistor, and the capacitor. In other words, since the oscillation circuit is configured with two transistors, one for voltage detection and one for controlling the lighting operation of the light emitting element, the circuit configuration is simpler than when a special oscillation circuit is provided. Therefore, the practical value of the present invention is extremely high.

[Brief explanation of drawings]

The illustrated circuit is one embodiment of the voltage drop indicating circuit of the present invention. Explanation of main drawing numbers, 1... Battery, 2 ... Voltage drop detection section, 3... Power line, 5... Zener diode, 7... First transistor, 9... Second transistor, 11... Capacitor , 12...
light emitting diode.

Claims (1)

[Scope of utility model registration request] A Zener diode that is in a conductive state when the power supply voltage is equal to or higher than a first reference value and becomes non-conductive when it drops below the reference value, and a bias current is supplied through the Zener diode when the Zener diode is in a conductive state. biased to the saturated state when the power supply voltage is higher than the first reference value and higher than the second reference value, and biased to the active state when the power supply voltage is higher than the first reference value and less than the second reference value. a first transistor whose base is connected to the collector of the first transistor, whose collector is connected to the base of the first transistor via a capacitor, and when the first transistor is in an active state, the first transistor is connected to the collector of the first transistor; The second transistor operates in oscillation in cooperation with the first transistor, and the light emitting element is connected so that the light emitting operation is controlled by conduction/nonconduction of the second transistor,
When the power supply voltage is higher than the first reference value, the second transistor is non-conductive to cause the light emitting element to turn on or off, and when the power supply voltage is lower than the first reference value, the second transistor is turned on or off. The conduction operation of the transistor causes the light emitting element to turn off or on, and when the power supply voltage is higher than the first reference value and less than the second reference value, the light emission is caused by the repeated conduction and non-conduction operation of the second transistor. A voltage drop display circuit characterized in that an element is made to blink.