The rechargeable strong light flashlight's constant current drive circuit ensures stable strong light output. Its core principle lies in a closed-loop control system that monitors and adjusts current in real time, mitigating the impact of current fluctuations on brightness. First, the circuit incorporates a reference voltage source as a stable reference standard. This reference source is unaffected by external voltage and temperature fluctuations and outputs a fixed voltage value, providing a precise "scale" for subsequent current control. Furthermore, a sampling resistor is connected in series with the rechargeable strong light flashlight's LED light source, forming a loop. When current flows through the sampling resistor, a corresponding voltage signal is generated across the resistor. This voltage signal directly reflects the actual current flowing through the LED, effectively providing the circuit with the ability to "sensing current status."
Next, a comparator and amplifier module compares the voltage signal generated by the sampling resistor with the fixed voltage of the reference voltage source. If the voltage signal corresponding to the actual current is lower than the reference voltage, the current in the LED is too low, potentially resulting in insufficient brightness. Conversely, if the actual voltage signal is higher than the reference voltage, the current is too high, potentially causing excessive brightness and increased power consumption and heat generation in the LED. If a discrepancy occurs between the two, the comparator and amplifier module immediately amplifies this tiny deviation signal and converts it into a control signal that drives subsequent actuators, providing sufficient "power" for current adjustment.
Actuators are typically semiconductor devices with current control capabilities, such as MOS transistors or transistors. These are connected in series in the LED's power supply circuit, acting as "flow valves" in the circuit. Upon receiving the control signal from the comparator and amplifier module, the actuator adjusts its conduction level accordingly: if the current is too low, it increases the conduction level, reducing the circuit resistance and allowing more current to flow to the LED; if the current is too high, it decreases the conduction level, increasing the circuit resistance and limiting the current. This dynamic adjustment ensures that the current flowing through the LED consistently fluctuates around the target current corresponding to the reference voltage, without significant deviation, thereby ensuring stable high-light output.
During the use of rechargeable strong light flashlights, the battery voltage gradually decreases as power is consumed, a common factor causing current fluctuations. A constant current drive circuit effectively addresses this fluctuation. Without constant current control, the current flowing through the LED decreases as the battery voltage drops, resulting in a noticeable decrease in brightness. However, through the aforementioned closed-loop control, the constant current circuit adjusts the actuator's on-duty cycle (i.e., the ratio of on-time to off-time) when the battery voltage drops, maintaining a constant average current per unit time. For example, when the voltage drops, the actuator's on-time is appropriately extended to compensate for the current loss caused by the voltage drop, ensuring that the current supplied to the LED consistently meets the requirements for strong light output.
The operating state of LED light sources is also affected by temperature. After prolonged operation, the LED's junction temperature rises, potentially causing changes in its forward voltage drop, leading to current fluctuations. The constant current drive circuit also addresses this situation. The sampling resistor captures subtle current changes caused by temperature fluctuations in real time and feeds the signal back to the comparator and amplifier module. Based on this feedback signal, the circuit promptly adjusts the actuator's state to offset the impact of the LED's forward voltage drop on the current, preventing dimming due to temperature increases or damage to the LED due to abnormal current increases, thereby maintaining stable, strong light output.
Furthermore, the constant current drive circuit incorporates corresponding protection mechanisms. These mechanisms ensure current stability while preventing abnormal conditions from damaging the circuit and LED. For example, when a short circuit or abnormal load causes a sudden increase in current, the voltage signal across the sampling resistor quickly exceeds the reference voltage. The comparator and amplifier module immediately outputs a strong control signal, causing the actuator to quickly cut or significantly limit the current. Normal constant-current control resumes after the abnormality is resolved. Furthermore, when the circuit temperature is too high, the overtemperature protection function appropriately reduces the current or adjusts the operating state to prevent excessive temperature from affecting component performance, indirectly ensuring long-term stability of the strong light output.
In practical use cases, whether battery performance degrades in low-temperature environments or LED heating increases in high-temperature environments, the constant-current drive circuit ensures a continuous and stable current flow through the LED through the coordinated operation of a reference voltage, real-time sampling, deviation amplification, dynamic adjustment, and abnormality protection. This comprehensive control logic ensures that the rechargeable strong light flashlight maintains consistent strong light output even under fluctuating power supply conditions and ambient temperature, eliminating flickering brightness and meeting user needs for stable lighting.
