Power supply device for a light box including first and second DC to DC convertors and energy reserve

A supply device for powering a light box from an unstable power supply, comprising:

• a first regulating DC to DC convertor of the booster type configured to provide stable power to the light box and coupled between the power supply and the light box and including a diode on an output thereof configured to protect against reversals of polarity and outages of the power supply;
• a capacitor coupled to the output of the first DC to DC converter so as to be charged thereby and so as to form an energy reserve for the light box;
• a second regulating DC/DC converter of the step-down type coupled to the output of the first DC to DC convertor and including galvanic isolation and configured to generate from an output voltage of the first DC to DC converter a plurality of stabilized supply voltages provided to an electronic control card of a display device illuminated by the light box,
• wherein the first DC to DC converter is powered directly and permanently by the power supply, and
• a link between the control card and the display device is effected with a galvanic isolation device.