Instant heating semiconductor water heater capable of fixing-point keeping constant temperature

The utility model relates to an instant heating semiconductor water heating device capable of timing and constant temperature. The device is provided with a pressure limiting water valve (1) in front of a heating pipe (3) in a pipe structure of a water pipe. A fluid flow piezoelectric switch (6) is additionally arranged in front of a water outlet channel. A semiconductor electric heating element (4) is coated on the surface of the heating pipe (3). Thyristors (T1 and T2) are connected with the semiconductor electric heating element (4) in series. The conducting angles of the thyristors are controlled by a CPU according to the feedback information of a water temperature sensor and the requirements of constant temperature of a potentiometer, and the temperature and the energy are controlled. The utility model has the characteristics that the utility model accurately and fast controls temperature in a timing mode to save energy, the requirement to the water pressure of running water is not high, the utility model with high safety can work under low water pressure, does not leak electricity, and can be used at any time, the size is small, etc.