1. Overcurrent protection
In the Fog light driver plus light source system, overcurrent protection is a key function. For the driver, when an abnormally large current appears in the circuit, it may be caused by a short circuit of the light source or other circuit failures. To achieve overcurrent protection, a current detection element, such as a precision resistor, is usually set in the circuit. When the current passing through the resistor increases, the voltage across it will also increase accordingly. Once this voltage exceeds the set threshold, the protection circuit will start. Inside the driver, a current limiting chip or a power management chip with a current limiting function can be used. These chips can automatically adjust the output of the driver according to the detected overcurrent signal, limit the further increase of current, and thus protect the driver and light source from the impact of excessive current. For example, when a part of the light source has a short circuit failure, causing a sudden increase in current, the overcurrent protection mechanism will act quickly to prevent the excessive current from burning the power components (such as MOSFET, etc.) in the driver and the light source itself.
2. Overvoltage protection
Overvoltage protection is equally important. The input voltage of the driver may be too high due to abnormal conditions in the automotive electrical system (such as voltage regulator failure). At the input stage of the driver, an overvoltage protection circuit can be set, such as a varistor. When the input voltage exceeds the normal operating voltage range, the resistance of the varistor will drop sharply, shunting the excess voltage to protect the subsequent circuit. In addition, some advanced driver chips have integrated overvoltage protection functions. For light sources, excessive voltage may cause the bulb filament to fuse or the LED light source chip to be damaged. Through the overvoltage protection function of the driver, it can be ensured that the voltage output to the light source is always within the safe range to maintain the normal working state of the light source.
3. Undervoltage protection
Undervoltage protection is mainly for the situation where the input voltage of the driver is too low. When the car battery is low or the voltage drop is too large at the start-up moment, undervoltage may occur. In the driver, the input voltage can be monitored by a voltage comparator. Once the input voltage is lower than the set undervoltage threshold, the driver can stop working or enter low power consumption mode. This is done to prevent the driver from malfunctioning in the undervoltage state, thereby avoiding damage to the light source, such as preventing the LED light source from flickering and uneven brightness at low voltage, and also protecting the circuit components inside the driver.
4. Short-circuit protection
Short-circuit protection is to prevent short circuits that may occur in the connection lines between the light source and the driver and inside the light source. At the output end of the driver, a short-circuit protection circuit can be used, such as setting a fuse or an electronic switch with short-circuit protection function in the output circuit. When a short circuit is detected, the fuse blows or the electronic switch disconnects the circuit, thereby preventing the abnormal flow of current and preventing the driver and light source from being damaged by the large current generated by the short circuit. At the same time, for some intelligent drivers, it is also possible to determine whether there is a short circuit by detecting abnormal conditions in the output current and voltage, and take protective measures in time, so that normal operation can be automatically restored after the fault is eliminated.
