lithium 3400mah 3.7v 18650 battery

　　Introduction to LED drive power electronic circuit

　　Half-bridge and full-bridge are commonly used topologies for switching power supplies, and "shoot-through" poses a great threat to them. Shoot-through is a phenomenon in which two transistors on the same bridge arm are turned on at the same time at the same time.

　　Thru circuit

　　Half-bridge and full-bridge are commonly used topologies for switching power supplies, and "shoot-through" poses a great threat to them. Shoot-through is a phenomenon in which two transistors on the same bridge arm are turned on at the same time at the same time.

　　During the commutation period, the switching power supply is susceptible to interference and causes shoot-through. Excessive shoot-through current will damage the power electronic devices used for inversion. Once a shoot-through phenomenon occurs, it must be detected as soon as possible and the driver must be turned off immediately to prevent the PN junction of the switching device from accumulating excessive heat and causing burnout.

　　overcurrent circuit

　　When unexpected situations such as load short circuit, overload or control circuit failure occur, the current flowing through the switching tube will be too large, causing the tube to increase power consumption and generate heat. If there is no overcurrent protection device, the high-power switching tube may be damaged; Failure of the regulation circuit may also cause overcurrent damage to the LED.

　　Overcurrent protection generally detects and compares through sampling resistors or Hall sensors to achieve protection, but they all have the disadvantages of large size and high cost.

　　overshoot circuit

　　Stabilized current switching power supplies can easily cause current overshoot when starting up and shutting down. Loads such as LEDs are not allowed to have ms-level current overshoots. The impact of a large instantaneous current may damage the LED device.

　　Overvoltage circuit

　　If the load of a steady-flow power supply is disconnected, the voltage across the current detection resistor drops to zero. Once the given value is not zero, the regulator will cause the output voltage to surge sharply to the maximum value, which is very dangerous when the load connection is in poor contact. .

　　For loads such as LED and semiconductor refrigeration, when overvoltage occurs, the first task is to protect the load, followed by protecting the switching power tube.

　　In order to solve the above problems, two protection methods are used at the same time. One is to place a bidirectional TVS to protect against instantaneous impulse voltage.

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