A voltage generation circuit includes a high voltage detector (HVD), a clock signal control unit (CSCU), an oscillator, a pumping clock control unit (PCCU), and a charge pump. The HVD compares a high voltage applied to a memory cell array with at least one reference voltage to provide at least one comparison signal. The CSCU provides a clock control signal for changing a frequency of a clock signal in response to the at least one comparison signal. The oscillator generates the clock signal having a frequency according to the clock control signal. The PCCU passes or intercepts the clock signal to provide a pumping clock signal, in response to a control signal. The charge pump consecutively performs charge pumping operations to provide the high voltage while the pumping clock signal is applied to the charge pump.