Patent ID: 8922290

Claim:
A pulse width modulator (PWM), comprising: a driver coupled to output a first and a subsequent period of a PWM signal, wherein each period includes the PWM signal changing between first and second states; a two-way oscillator to generate an oscillator signal, the two-way oscillator including: a first frequency adjust current source coupled to source a first frequency adjust current; a second frequency adjust current source coupled to sink a second frequency adjust current; a first capacitor coupled to integrate the first frequency adjust current by charging with the first frequency adjust current source during the first period of the PWM signal, wherein the first capacitor is further coupled to integrate the second frequency adjust current by discharging with the second frequency adjust current source during the subsequent period of the PWM signal; a first switching reference coupled to output a first reference voltage during the first period of the PWM signal responsive to the oscillator signal, and to output a second reference voltage during the subsequent period of the PWM signal responsive to oscillator signal; and a first comparator coupled to compare the output of the first switching reference with a voltage on the first capacitor and to generate the oscillator signal in response thereto, wherein the driver determines a frequency of the PWM signal in response to the oscillator signal, and wherein first and second frequency adjust current sources vary the first and second frequency adjust currents, respectively, to vary the frequency of the PWM signal to spread energy of switching harmonics over a frequency band and to reduce electromagnetic interference (EMI).