Charging Circuit And, Charging Method

Various embodiments of the teachings herein include a charging circuit to charge a capacitor of an optical alarm device, connected between the capacitor and a charging bus. The capacitor supplies power to a light-emitting unit. The charging circuit comprising: a voltage detection circuit to detect a first voltage of the charging bus; a boost circuit connected to the charging bus to perform voltage boosting, to charge the capacitor with the boosted voltage; and a controller. The controller controls charging the boost circuit to the capacitor, so the voltage of the capacitor is equal to a second voltage after the light-emitting unit emits light at a target light intensity. The second voltage is equal to the sum of the first voltage and a predetermined difference.