Shoot-Through Circuits
Half-bridge and full-bridge topologies are commonly used in switching power supplies. "Shoot-through" poses a significant threat to these topologies. Shoot-through occurs when two transistors in the same bridge arm are simultaneously conducting.
During the commutation period, switching power supplies are susceptible to interference that can cause shoot-through. Excessive shoot-through current can damage the power electronics used for inversion. Once shoot-through occurs, it must be detected and the driver shut down immediately to prevent excessive heat accumulation and burnout in the PN junction of the switching device.
Overcurrent Circuits
Unexpected conditions such as load short circuits, overloads, or control circuit failures can cause excessive current to flow through the switching transistor, increasing power consumption and heat generation. Without overcurrent protection, high-power switching transistors can be damaged. Failure of the regulation circuit can also cause overcurrent damage to the LED.
Overshoot Circuits
Regulated current switching power supplies are prone to current overshoot during startup and shutdown. Loads like LEDs cannot tolerate current overshoots even in the millisecond range. Such sudden surges of high current can damage the LED device.
Overvoltage Circuit
If a load in a regulated current power supply experiences a short circuit, the voltage across the current sense resistor drops to zero. However, if the setpoint is non-zero, the regulator will cause the output voltage to surge to its maximum value, which can be dangerous if the load connection is poor.
For loads such as LEDs and semiconductor refrigeration, when an overvoltage occurs, the primary priority is to protect the load, followed by protecting the switching power transistors.
To address these issues, two protection methods can be used simultaneously. One is to use a bidirectional TVS to provide protection against transient surge voltages.
