Protection circuit for dimmer, and dimmer

A protection circuit for use in a dimmer, the dimmer comprising:

• a pair of input terminals configured to be electrically connected in series between a lighting load and an AC power supply;
• a bidirectional switch configured to selectively cut off or pass a bidirectional current between the pair of input terminals;
• and a control unit configured to control the bidirectional switch so as to turn the bidirectional switch from ON to OFF at a point in time when an amount of time, varying according to a lighting level, passes since a starting point of a half cycle of an AC voltage of the AC power supply,
• the bidirectional switch having a control terminal, to which a capacitive element is electrically connected, the bidirectional switch turning from OFF to ON when a voltage between both terminals of the capacitive element becomes equal to or greater than a threshold voltage,
• the protection circuit comprising a charging/discharging regulator circuit configured to make a rate of fall of the voltage between both of the terminals of the capacitive element when the control unit turns the bidirectional switch from ON to OFF lower than a rate of rise of the voltage between both of the terminals of the capacitive element when the control unit turns the bidirectional switch from OFF to ON.