Analog photovoltaic power circuit with auto zero calibration

摘要

The invention provides an analog photovoltaic power circuit with auto zero calibration, which judges whether the current trend or voltage trend has the same direction as or different direction from the power trend, and adjusts an input/output power conversion accordingly, so that an input current approaches to an optimum current corresponding to a maximum power point, in which the judgments of the current trend, voltage trend and power trend is calibrated with auto-zero circuitry.

主权项

1. A photovoltaic power circuit with auto zero calibration, for converting an input current and an input voltage generated by a photovoltaic device to an output current and an output voltage, the photovoltaic power circuit comprising:
a trend judgment circuit having a storage mode and a comparison mode, the trend judgment circuit including:
a current trend indicator circuit configured to operably judge a slope direction of the input current at a present time point as compared with the input current at a previous time point in the comparison mode to generate a current trend signal, or a voltage trend indicator circuit configured to operably judge a slope direction of the input voltage at the present time point as compared with the input voltage at the previous time point in the comparison mode to generate a voltage trend signal;a power trend indicator circuit configured to operably judge a slope direction of the power at the present time point as compared with the power at the previous time point according to the input current and the input voltage in the comparison mode to generate a power trend signal; anda trend comparison circuit configured to operably generate a trend comparison result according to the current trend signal and the power trend signal, or according to the voltage trend signal and the power trend signal; and a power output control circuit which is coupled to the photovoltaic device at an input terminal and extracts electric energy at the input terminal to generate the output current and the output voltage at an output terminal, the power output control circuit adjusts the power conversion from the input terminal to the output terminal directly or indirectly according to an output from the trend judgment circuit so that the input current approaches an optimum current of the photovoltaic device,wherein the power trend indicator circuit includes:
an analog multiplication circuit configured to operably receive a signal related to the input current and a signal related to the input voltage, and multiply them to obtain a signal related to power; a comparison and amplification circuit having an input terminal configured to operably receive the signal related to power; a capacitor having a high voltage terminal coupled to another input terminal of the comparison and amplification circuit; and a switch coupled between an output terminal of the comparison and amplification circuit and the high voltage terminal of the capacitor, the switch being controlled by a clock signal.