The present invention discloses an analog photovoltaic power circuit, comprising: a photovoltaic device group for receiving photo energy to generate an input voltage; a power stage circuit for converting the input voltage to an output voltage; an optimum voltage estimation circuit for receiving a predetermined voltage and estimating an optimum voltage according to a direction of variation of the input voltage and a direction of variation of the power generated by the photovoltaic device group; and an analog comparison and control circuit for comparing the optimum voltage with the input voltage, to thereby control the operation of the power stage circuit.