Power supply over-voltage protection

A power supply input circuit (1,2,3) comprising

• a disconnecting circuit (1) coupled to receive an AC-input voltage (Vac) and a disconnecting signal (Vd) for disconnecting the AC-input voltage (Vac) from output terminals (T1,T2) of the disconnecting circuit (1) if the disconnecting signal (Vd) is active,
• a series arrangement of a first and a second smoothing capacitor (C1,C2) coupled between output terminals (T3,T4) of the power supply input circuit (1,2,3),
• a voltage doubler circuit (20) coupled to said output terminals (T1,T2) for supplying a rectified output voltage across the series arrangement of the first and the second smoothing capacitor (C1,C2) in a first situation where no voltage doubling is required, and for supplying one polarity of the AC-input voltage (Vac) across said first smoothing capacitor (C1) and the other polarity of the AC-input voltage (Vac) across said second smoothing capacitor (C2), to provide a doubled rectified output voltage across the series arrangement of the first and the second smoothing capacitor (C1,C2) in a second situation where a voltage doubling is required, and
• an over-voltage detection circuit (3) having an output for supplying the disconnecting signal (Vd),
• characterized in that
• the over-voltage detection circuit (3) comprises a first over-voltage prevention circuit (30) to detect an over-voltage across said first smoothing capacitor (C1), and a second over-voltage prevention circuit (31) to detect an over-voltage across said second smoothing capacitor (C2), the over-voltage detection circuit (3) activating the disconnecting signal (Vd) if an over-voltage is detected across at least one of said smoothing capacitors (C1,C2).