(FR2756677-A1)      Thermal energy, using e.g. seebeck effect devices to exploit relatively low temperature differentials, is obtainable from several suggested sources - e.g. animal (including human) skin, house walls or window-panes, soil, etc., ambient air constituting, usually, the lower temperature component. DC voltage, obtained (1) e.g. from several series-connected devices, with appreciable internal resistance (2), is applied to a transformer primary (3) in series with an FET (5) coupled to earth via a resistance (8) and by capacitance (9) to one of two earthed (7) secondaries (6',6).    The secondaries feed alternately operating chopper-booster circuits, comprising MOSFETs (11,12) and inductances (13,14), with output via Schottky diodes (15,16). A high-value capacitance (17) and peak-lopping diode (18) stabilise the output (U,U).    A reversible variant tolerates sources of changing polarity. Manufacturing methods are also described.    USE -   Autonomous low-power supplies.    (FR2767418-A1)      Thermal energy, using e.g. seebeck effect devices to exploit relatively low temperature differentials, is obtainable from several suggested sources - e.g. animal (including human) skin, house walls or window-panes, soil, etc., ambient air constituting, usually, the lower temperature component. DC voltage, obtained (1) e.g. from several series-connected devices, with appreciable internal resistance (2), is applied to a transformer primary (3) in series with an FET (5) coupled to earth via a resistance (8) and by capacitance (9) to one of two earthed (7) secondaries (6',6).    The secondaries feed alternately operating chopper-booster circuits, comprising MOSFETs (11,12) and inductances (13,14), with output via Schottky diodes (15,16). A high-value capacitance (17) and peak-lopping diode (18) stabilise the output (U,U).    A reversible variant tolerates sources of changing polarity. Manufacturing methods are also described.    USE -   Autonomous low-power supplies.    (EP972335-A2)      Thermal energy, using e.g. seebeck effect devices to exploit relatively low temperature differentials, is obtainable from several suggested sources - e.g. animal (including human) skin, house walls or window-panes, soil, etc., ambient air constituting, usually, the lower temperature component. DC voltage, obtained (1) e.g. from several series-connected devices, with appreciable internal resistance (2), is applied to a transformer primary (3) in series with an FET (5) coupled to earth via a resistance (8) and by capacitance (9) to one of two earthed (7) secondaries (6',6).    The secondaries feed alternately operating chopper-booster circuits, comprising MOSFETs (11,12) and inductances (13,14), with output via Schottky diodes (15,16). A high-value capacitance (17) and peak-lopping diode (18) stabilise the output (U,U).    A reversible variant tolerates sources of changing polarity. Manufacturing methods are also described.    USE -   Autonomous low-power supplies.