Electronic device and method for DC-DC conversion with variable bias current

1. An electronic device comprising a switch mode DC-DC converter comprising a comparator for generating one of a pulse width modulated (PWM) or pulse frequency modulated (PFM) output signal for driving a power switch of the switch mode DC-DC converter, the electronic device being configured to reduce a bias current of the comparator independent of a voltage control loop of the converter from a first value to a second value wherein speed at which the bias current is reduced is fixed in time to generate a change over several cycles of the converter and with a first slope in response to a load current decreasing to substantially zero and to increase the bias current of the comparator from the second value to the first value time wherein speed at which the bias current is increased is fixed in time with a second slope in response to the load current increasing from substantially zero, wherein the second slope is steeper than the first slope, and wherein the comparator operates at a low bias when inductor current is substantially zero and at a higher bias when the inductor current exceeds zero in order to operate at maximum speed and being further configured to generate a pause signal as an indicator of whether a magnitude of an inductor current of the DC-DC converter is zero, wherein a transition of the pause signal is used to start a reduction of the bias current of the comparator with the first slope.

2. The electronic device according to claim 1 , being further configured to generate the first slope with a transistor configured to operate as a variable resistor.

3. The electronic device according to claim 2 , being configured to compensate a loss of gain of the comparator if the bias current is reduced.

4. The electronic device according to claim 1 , being configured to compensate a loss of gain of the comparator if the bias current is reduced.

5. A method of operating an electronic device comprising for switch mode DC-DC conversion, the method comprising: reducing a bias current of comparator independent of a voltage control loop of the converter for generating one of a pulse width modulated (PWM) or pulse frequency modulated (PFM) output signal for driving a power switch of the switch mode DC-DC converter from a first value to a second value wherein speed at which the bias current is reduced is fixed in time to generate a change over several cycles of the converter with a first slope in response to a load current decreasing to substantially zero, and increasing the bias current of the comparator from the second value to the first value wherein speed at which the bias current is increased is fixed in time with a second slope in response to the load current increasing from substantially zero, wherein the second slope is steeper than the first slope and, wherein the comparator operates at a low bias when inductor current is substantially zero and at a higher bias when the inductor current exceeds zero in order to operate at maximum speed, further comprising generating a pause signal as an indicator of whether a magnitude of an inductor current of the DC-DC converter is zero, wherein a transition of the pause signal is used to start a reduction of the bias current of the comparator with the first slope.