Frequency divider circuit and a frequency synthesizer circuit

A frequency synthesizer circuit, comprising:

• a frequency divider circuit, wherein the frequency divider circuit comprises:
• a first flip-flop;
• a second flip-flop;
• a phase inverter, wherein an output electrode of the first flip-flop is electrically connected to each of an input electrode of the second flip-flop, two gate electrodes of the second flip-flop, and an output electrode of the phase inverter, wherein an output electrode of the second flip-flop is electrically connected to each of an input electrode of the phase inverter, two gate electrodes of the phase inverter, and an input electrode of the first flip-flop, and wherein a control electrode of the phase inverter is connected to a control signal;
• and
• a control module, wherein the first flip-flop is connected to a voltage source through the control module, wherein the control module is connected to the control signal and controls the connection between the first flip-flop and the voltage source, and wherein when the control signal is a first-mode signal, the first flip-flop is disconnected from the voltage source, providing a functionality of a N-division frequency divider;
• when both the control signal and an output signal of the second flip-flop are a second-mode signal, a functionality of a N+1-division frequency divider is provided, wherein N is an integer greater than or equal to 2.