common LED drive circuit analyzes this paper important

electronic fever Friends Network,www.12vgridtiepowerinverters***. The buck circuit capacitor is a common small-current power circuit, because of their sizes small, cost is low, the current is constant absolute strengths are often applied to the LED drive circuit.

Figure 1 for the the actual take capacitance buck LED driver circuit. Careful and utilize local convergence varistor or transient voltage restraint transistor circuit, Initiative connection on varistor or transient voltage system made transistor

voltage gradient moment (such as lightning, electricity equipment starting) effectively gradient current discharge, thus maintaining two shut with the other transistor, the response time of the individual micro-millisecond.

circuit works:

of

capacitor C1 for the buck with limited flow: As we all know, the characteristics of the capacitor is through exchange, every DC, When the capacitor convergence in exchange circuit, its capacitance calculations formula: XC = 1/2πf C

, XC performance capacitive reactance, f performance input AC power frequency, C represents the buck capacitor.

flows through the capacitor step-down circuit current calculations formula: I = U / XC

where I said that the current flowing through the capacitor, said power supply voltage U, XC, said the capacitance of the capacitor when the load voltage is much less than 220V, 220V, 50Hz AC circuit, the current and capacitance relational : I = 69C wherein the capacitor unit is uF, the current in units of mA

following table for 220V, 50Hz AC circuit current of practice with actual measuring current analogy

the

resistor R1 is the bleeder resistor, and its role as follows: When the sine wave at the maximum peak instant been intercepted, the residual charge on the capacitor C1 helpless release, long long existence in the repair if the human body is exposed to C1 of the metal sector strong electric shock may be the presence of resistor R1 residual charge can release let go, in order to protect human, machine insurance. Bleed resistor and capacitor size, the greater the capacity of the normal capacitor more remnants charge, bleeder resistor on the resistance would choose. Lessons following table, for the design of reference:

The role of

D1 ~ D4 is rectified, its role is the AC power is rectified to a pulsating DC voltage. The role of the C2, C3 for the filter,power inverter, its role is the rectified pulsating DC voltage into a stable DC voltage filtering. Varistor (or transient voltage system made transistor) the role of the input pulse high-voltage power supply in an instant on release let go, which cover LED transient high voltage breakdown. Depending on the number of LED series may be forward breakover voltage (Vf), 220V AC circuits, can be up to about 80.

component selection of the capacitor voltage is individual requests greater than the peak value of the input supply voltage, 220V, 50Hz AC circuit, the trade-offs withstand voltage of 400 volts or more polyester capacitors or paper media capacitor. D1 ~ D4 can choose IN4007. The filter capacitor C2, C3 of the breakdown voltage according to the load voltage, Common to 12 times the load voltage. Its capacitance depending on the size of the load current.

driver circuit capacitor buck

following schematic other situations, for design reference:

in the circuit of Figure 2, the thyristor SCR and R3 maintenance circuit, when the flow through the LED current is greater than the set value, the SCR conduction a certain angle, so the circuit current shunt, so that LED working in constant current situation, to prevent the LED from damage due to high-voltage transient.

composed of low-level power supply filtering circuit

circuit in Figure 3, C1, R1, varistors, L1, R2, able to enter an instant high-pressure filter composed of step-down circuit,Grid tie inverter, C2, R2, C3, C4, L2, and pressure sensitive resistor is composed of a filter circuit rectified. This circuit

take dual filter circuit to cover the LED is not an instant high-voltage breakdown destruction.

Figure 4 is a schematic capacitance antihypertensive use circuit, the application of two anti-parallel LED circuit for rectifying an AC voltage after the buck, can be generally applied to the luminous lights, buttons instigation lamp request not high the status of guidance lights and other places.