PWM LED street lighting dimming method by inductor

 

PWM LED street lighting dimming method by inductor

 

Circuit, when the inductor through current, the inductor will produce a magnetic field that is part of the current way to convert magnetic energy “stored in the inductor; when no longer current to the inductor, inductors the magnetic energy by the current in the released from the loop. This current mutation is the inductor, the inductance of this charge and discharge “principle, which is used to average the PWM LED street lighting dimming discontinuous current.

 

To ensure that the PWM cycle is less than the inductance of τ time, because if the PWM cycle is greater than τ, then there is likely to appear in the case of the PWM duty cycle changes, the current in a circuit to achieve a DC current of the inductor saturation, affecting LED street lighting current regulation. When C8051330 clock frequency is 25 MHz, the choice of PWM cycle current change stalls. If the cycle is the greater, the stalls of the PWM duty cycle is more, on the contrary, the less. Intended duty cycle of 256 stalls, the frequency of the PWM wave should choose below 100kHz, the cycle of more than 10 μs, DC sense of 10Ω, the inductance value should be selected greater than 0.1 mH to Figure 2, the PWM frequency of 100kHz, duty cycle 90%, the inductance of 0.1 mH to 1 mH to 40 mH, the simulation results of the circuit current.

 

This voltage is the voltage on a 20-Ω resistor in series circuit for led high bay light, stable voltage of 340 mV, the circuit current is 17 mA, because the actual circuit current loss, so the actual current value is smaller than the analog current value. But the current trend and simulation.