Negative voltage generating circuit

A negative voltage generating circuit, comprising:

• a pulse generator having a positive voltage input pin coupled to a power supply, an oscillating output pin alternately outputting a high level signal and a low level signal, and a negative voltage input pin;
• a switch having a first terminal coupled to the oscillating output pin of the pulse generator, a second terminal coupled to the power supply via a resistor, and a third terminal grounded;
• a first capacitor having one terminal coupled to the first terminal of the switch;
• at least one first diode, the anode of the at least one first diode coupled to another terminal of the capacitor, the cathode of the at least one first diode coupled to ground;
• a second diode, the anode of the second diode coupled to the negative voltage input pin of the pulse generator, the cathode of the second diode coupled to the anode of the at least one first diode;
• and
• a second capacitor coupled between the anode of the second diode and ground.