Plug-in digital tubes, as common display devices, have performance closely related to their power supply voltage. Whether a plug-in digital tube can function properly in a low-voltage environment requires comprehensive analysis of its internal structure, driving method, and circuit design.
Plug-in digital tubes typically consist of multiple light-emitting diodes (LEDs), and the forward voltage of each LED is the key factor determining its lower operating limit. Generally, red LEDs have lower forward voltages, while green and blue LEDs have relatively higher ones. If the power supply voltage is lower than the forward voltage of the LED, the LED will not conduct, causing the digital tube to malfunction. Therefore, in low-voltage environments, it is necessary to ensure that the power supply voltage is higher than the forward voltage of all LEDs in the digital tube to guarantee its basic operation.
From the perspective of driving method, plug-in digital tubes are divided into two types: common anode and common cathode. Common anode digital tubes require a low-level drive; that is, when the control terminal outputs a low level, the corresponding LED conducts and illuminates. Common cathode digital tubes require a high-level drive. In low-voltage environments, common anode digital tubes may be more advantageous because their driving circuit only needs to output a low level to light the LED, resulting in relatively lower requirements for the power supply voltage. However, if the supply voltage is too low, even with a common anode structure, insufficient voltage may cause the LEDs to glow dimly or fail to light up.
Circuit design also significantly impacts the performance of the plug-in digital tube in low-voltage environments. To ensure stable operation of the digital tube under low voltage, a current-limiting resistor must be added to the circuit to prevent excessive current from damaging the LEDs. The value of the current-limiting resistor must be calculated appropriately based on the supply voltage and the forward voltage of the LEDs. If the supply voltage is low, the value of the current-limiting resistor should be reduced accordingly to ensure sufficient current flows through the LEDs for normal illumination. Furthermore, other components in the circuit, such as the driver chip and transistors, must also maintain stable operation under low voltage conditions; otherwise, the display effect of the digital tube may be affected.
The brightness of the plug-in digital tube may be affected to some extent under low voltage. Due to the reduced supply voltage, the current through the LEDs decreases, resulting in a weakened luminous intensity. Therefore, in applications requiring higher brightness, a low-voltage environment may not meet the requirements. In such cases, the brightness performance of the digital tube under low voltage can be improved by optimizing the circuit design, selecting LEDs with low forward voltage, or using a boost circuit. The stability of the plug-in digital tube in low-voltage environments is also a crucial factor to consider. Voltage fluctuations can cause instability in the digital tube display, resulting in flickering or uneven brightness. To improve stability, voltage regulators, such as Zener diodes or low-dropout linear regulators (LDOs), can be added to the circuit to ensure a stable supply voltage. Furthermore, proper circuit layout and wiring can also reduce the impact of voltage fluctuations on the digital tube.
In practical applications, the performance of the plug-in digital tube in low-voltage environments needs to be evaluated based on the specific scenario. For example, in battery-powered portable devices, because the battery voltage gradually decreases over time, the digital tube needs to maintain normal operation over a wide voltage range. In this case, selecting LEDs with low forward voltage, optimizing circuit design, and adding voltage regulators are particularly important.
