INCREASING PWM RESOLUTION BY MODULATION
A method for generating a pulse width modulated (PWM) signal includes determining a PWM period and/or a pulse width of the pulse width modulated signal by counting the number of clock cycles of a reference clock signal and by switching the pulse width modulated signal when a predetermined number of clock cycles is reached. The reference clock signal comprises clock cycles of at least a first clock period and a second clock period. The first clock period and the second clock period differ by an amount of time, which is substantially smaller than both half of the first clock period and half of the second clock period.
1 . A method for generating a pulse width modulated (PWM) signal, comprising:
determining a PWM period and/or a pulse width of the pulse width modulated signal by counting a number of clock cycles of a reference clock signal and by switching the pulse width modulated signal when a predetermined number of clock cycles is reached; wherein the reference clock signal comprises clock cycles of at least a first clock period and a second clock period, and the first clock period and the second clock period differ by an amount of time, which is substantially smaller than both half of the first clock period and half of the second clock period.
2 . The method according to claim 1 , further comprising:
generating a first clock signal having the first clock period, generating a second clock signal having the second clock period, and composing the reference clock signal by using at least one clock cycle of both the first clock signal and the second clock signal.
3 . The method according to claim 1 , wherein at least one clock cycle of the first period and one clock cycle of the second period are used within one period of the pulse width modulated signal.
4 . The method according to claim 1 , wherein the number of clock cycles having the first clock period and the number of clock cycles having the second clock period are selectively and variably chosen over a plurality of PWM periods of the pulse width modulated signal, such that the pulse width of the pulse width modulated signal is averaged over a plurality of PWM periods of the pulse width modulated signal.
5 . The method of claim 1 , wherein the number of clock cycles of the first clock period and the number of clock cycles of the second clock period is periodically varied over a modulation period.
6 . An electronic device including circuitry for generating a pulse width modulated signal, the circuitry comprising:
a counter adapted to be increased in response to a reference clock signal;
a comparator for comparing the count of the counter to a predefined number;
a logic circuitry coupled to the counter output and to the comparator for producing the pulse width modulated signal;
a switch to switch the clock cycles of the reference clock signal between first clock cycles having a first clock period and second clock cycles having a second clock period, such that the first clock period and the second clock period differ by an amount of time which is substantially smaller than both half of the first clock period and half of the second clock period; and
a controlling means adapted to control the switching mechanism.
7 . The electronic device according to claim 6 , further comprising circuitry for setting the first clock period and the second clock period to differ by the amount of time which is substantially smaller than both half of the first clock period and half of the second clock period.
8 . The electronic device according to claim 6 , comprising circuitry for generating a first clock signal having the first clock period, generating a second clock signal having the second clock period.