The present invention relates to an energy supply circuit for instantly supplying power without a power converter and an electronic device which operates only when energy is supplied from an energy source using the same. An energy supply circuit without a power converter according to the present invention comprises: an energy extraction unit 10 for generating power from an energy source; and output unit 20 for supplying power to an external electronic circuit; a switch unit 30 interposed between the energy extraction unit and the output unit 20 to connect an output end of the energy extraction unit 10 to the output unit 20 when switched on; and a maximum power point tracking control unit 40 for generating an open/closed signal for opening or closing the switch unit 30 according to the voltage and current of the energy extraction unit 10. The present invention has a technical feature wherein a turn-on point of the open/closed signal comes at a time when the output end voltage of the energy extraction unit 10 is Vh, and a turn-off point comes at a time when the output end voltage of the energy extraction unit 10 is Vl. Accordingly, the present invention has a simple configuration, low manufacturing costs, has no energy loss due to the power conversion, and has no reduction in life due to charging and discharging of an energy storage device.