Precise protection of LED switching power supply: design and practice

LED power supply overcurrent protection circuit switching

To shield the adjustment tube from harm in the case of a circuit short-circuit and an increase in current in the DC LED switching power supply circuit. Basically, the adjustment tube is in a reverse bias state and the circuit current is turned off when the output current goes above the predetermined value. Voltage divider resistors R4 and R5, along with a transistor (BG2) make up the overcurrent protection circuit.

In a typical operating state, BG2 is in a cut-off state and has no effect on the voltage stabilization circuit because its base potential is higher than its emitter potential due to the pressure exerted by R4 and R5. The adjustment tube BG1's base and emitter are close to a short circuit when it is short-circuited, the output voltage is zero, and the emitter is grounded. This accomplishes the protective goal of BG2 being in a saturated conduction condition.

Overvoltage safety circuit for LED switching power supply

Both input and output overvoltage protection are included in the switching regulator's overvoltage protection. Internal switching regulator components will be harmed by an unregulated DC power supply's excessive voltage (such as a battery and rectifier). For LED switching power supplies, an input overvoltage protection circuit is therefore necessary.

Transistors and relays make up this protection circuit. The transistor T turns on, the relay operates, and the input is disconnected when the breakdown voltage of the Zener diode is exceeded by the voltage of the input DC power source. An identification and overvoltage protection circuit for polarity protection can be created by combining the input polarity protection and input overvoltage protection circuits.

Protection methods and common faults of LED driver power supplies


In order to extend the life of LEDs, the design of LED driver power supplies is crucial. The following Ameya360 electronic component procurement network briefly analyzes it for everyone.

Common questions

1. LED driver circuit directly affects life

LED drivers are divided into two categories: digital and analog. RGB full-color changing and digital dimming control are examples of digital. DC constant current control circuits and switching power supplies with constant current in AC are examples of analog. Semiconductor parts, resistors, capacitors, and inductors make up the driving circuit. The circuit as a whole will fail if something goes wrong. The life of LEDs is 50,000-100,000 hours, which is much longer than the 2-3 years of switching power supplies. Therefore, the lighting factory needs to pay attention to the design of the drive circuit.

2. The problem of heat dissipation of LED driver power supply

LED cold light source, the operating temperature should not be too high. The design of lamps should consider the appearance, heat dissipation and other aspects. Some manufacturers use poor quality power supply, insufficient heat dissipation, resulting in failure. Therefore, it should be evaluated before design to ensure that the matching is appropriate.

3. The problem of designing LED driver power supply

Power design needs to leave enough margin to ensure long-term stable operation. LED power density is large, and heat dissipation is the key. When designing, the heat dissipation of LED and power supply should be fully considered to ensure the quality of lamps.

LED switching power supply soft start protection circuit

Upon turning on, the filter capacitor will produce a significant surge of current that might potentially burn the contacts. To prevent damage, a current limiting resistor should be attached when charging the capacitor. After the transient process ends, the relay automatically shorts the current limiting resistor to ensure normal power supply.

LED switching power supply overheating protection circuit

High-power LED switching power supply should be equipped with an overheating protection circuit to avoid premature failure of components.