Maximum power point tracking controllers and maximum power point tracking methods

A maximum power point tracking system, comprising:

• a power converter, converting an energy, outputted from an energy harvester, to an output voltage according to a PWM signal for driving a loading;
• a voltage detector, outputting a detection signal corresponding to the output voltage;
• and
• a maximum power point tracking controller, coupled to the voltage detector to receive the detection signal, comprising:
• a slope detection unit, calculating whether the output voltage is in a positive trend or in a negative trend according to the detection signal to output a trend signal, wherein a voltage level of the trend signal is a first voltage level or a second voltage level when the output voltage is in the positive trend or the negative trend, wherein the slope detection unit comprises:
• a first voltage detection unit, integrating the detection signal within a first time interval from a first time point to output a first amplified signal;
• a second voltage detection unit, integrating the detection signal within the first time interval from a second time point later than the first time point to output a second amplified signal, wherein a difference between the first time point and the second time point is a second time interval;
• and
• a comparison unit, calculating a trend of the output voltage from the first time point to the second time point according to a difference between the first amplified signal and the second amplified signal, and determining the voltage level of the trend signal according to the trend of the output voltage;
• and
• a control unit, having a first operation mode and a second operation mode to respectively increase and decrease a duty cycle of the PWM signal, wherein the control unit switches a current operation mode when the trend signal is changed from the first voltage level to the second voltage level, thereby performing a maximum power point tracking procedure.

A maximum power point tracking method, comprising:

• maintaining a current operation mode of a maximum power point tracking controller in a first state;
• entering a second state from the first state when an output voltage of a power converter is changed from a positive trend to a negative trend;
• switching the current operation mode of the maximum power point tracking controller in the second state and entering a third state;
• counting clock periods in the third state;
• and
• entering the second state from the third state and recounting the clock periods when a trend of the output voltage is not changed within N clock periods,
• wherein the first state is entered to from the third state and the clock periods stop being counted when the output voltage is changed from the negative trend to the positive trend within N clock periods.

A maximum power point tracking method, comprising:

• determining whether an output voltage of a power converter is changed from a positive trend to a negative trend;
• switching a current operation mode of a maximum power point tracking controller and starting to count clock periods when the output voltage is changed from the positive trend to the negative trend;
• and
• detecting whether the output voltage has been changed from the negative trend to the positive trend within N clock periods, wherein the current operation mode is switched when the output voltage is in the negative trend for N clock periods;
• and
• stopping the counting of the clock periods when the output voltage is changed from the negative trend to the positive trend within N clock periods.