The circuit diagram on the left shows an AC/DC power converter without power factor correction. In the waveform on the right hand side, the red sinusoidal waveform is AC input voltage, and the blue waveform represents the AC line input current. Due to the non-linear nature of the diode rectifier bridge, the current waveform lags the input AC voltage in phase and is non-sinusoidal. The distortion in current waveform results in poor Power Factor, which causes inefficient power grid usage and harmonic current contamination on the grid. The problem can be severe enough in some commercial enterprises that a Power Factor penalty may be levied from the utility companies.