扩频调制抑制LLC开关电源传导干扰

使用扩频调制技术对具备软开关能力的开关电源扩频调制,抑制开关电源传导EMI。通过公式推导分析扩频调制抑制EMI的原理,并在具体的LLC开关电源电路上进行实验测试,观察扩频调制的EMI抑制效果。对DSP芯片的EPWM模块程序进行编写,生成经过调制信号调制后的PWM波进行开关电源控制,无须增加外部时钟电路实现扩频调制。通过多次改变调制信号,分别以正弦波、三角波、锯齿波进行调制并进行实验测试,验证LLC开关电源电路中使用扩频调制抑制传导EMI的有效性,扩频调制后的EMI得到有效抑制,能够满足EN55032 ClassB标准下的限值。

The spread spectrum modulation technique is used to modulate the switching power supply with soft switching capability to suppress the EMI conduction of the switching power supply.The principle of suppressing EMI by spread spectrum modulation is analyzed by deducing the formula,and the EMI suppressing effect of spread spectrum modulation is observed by experiment test on a specific LLC switching power supply circuit.The EPWM module program of DSP chip is programmed to generate PWM wave modulated by modulated signal for switching power supply control,without adding external clock circuit to realize spread spectrum modulation.By changing the modulated signal several times,modulated by sine wave,triangle wave and sawteeth wave respectively,and conducted experimental tests to verify the effectiveness of using spread spectrum modulation to suppress conducted EMI in LLC switching power supply circuit.Through spread spectrum modulation,EMI can be effectively suppressed,which can meet the limit value under the EN55032 ClassB standard.