Heating circuit of flowing type instantaneous electric water heater

The invention discloses a heating circuit of a flowing type instantaneous electric water heater, which comprises a first heating circuit (1) at least comprising a first heating tube, and a control circuit (2) for controlling the heating power of the first heating circuit (1), wherein the control circuit (2) comprises a switching power supply (21), a second filter capacitor, a third filter capacitor, a first normally open relay, a second normally open relay, a first protecting diode, a water flow switch, a bidirectional thyristor, a triggering diode, an alternating current capacitor, a potentiometer with a switch, a first protective resistor, a third protective resistor, a current limiting resistor, an electromagnetic valve and a tristate voltage stabilizer. Compared with the prior art, the heating circuit has the advantages that: the heating power of the first heating tube is adjusted from zero to the maximum heating power of the first heating tube by adjusting the resistance of the potentiometer with the swi