Method and circuit for controlling switching frequency signal

A circuit for controlling a switching frequency signal used in a direct current to direct current (DC to DC) converter, wherein said DC to DC converter generates an output voltage to drive a system and said switching frequency signal is generated by inputting a modulation frequency to a pulse width modulation (PWM) circuit, comprising:

• a plurality of comparative circuits including a plurality of corresponding predetermined voltages for comparing said output voltage and said plurality of corresponding predetermined voltages when a signal is received by said system to stop said switching frequency signal and generating a plurality of output signals when said output voltage is smaller than said plurality of corresponding predetermined voltages;
• and
• a multiplexer electrically connected to said plurality of comparative circuits for determining one of said plurality of comparative circuits according to said system and transferring one of said plurality of output signals corresponding to said determined comparative circuit to said pulse width modulation (PWM) circuit for restarting said pulse width modulation (PWM) circuit to generate said switching frequency signal, thereby increasing said output voltage to drive said system.

A circuit for controlling a switching frequency signal used in a direct current to direct current (DC to DC) converter, wherein said DC to DC converter generates an output voltage to drive a system and said switching frequency signal is generated by inputting a modulation frequency to a pulse width modulation (PWM) circuit, comprising:

• a comparative circuit including a predetermined voltage for comparing said output voltage and said predetermined voltage when a signal is received by said system to stop said switching frequency signal and generating an output signal to said pulse width modulation (PWM) circuit for restarting said pulse width modulation (PWM) circuit to generate said switching frequency signal to increase said output voltage to drive said system when said output voltage is smaller than said predetermined voltage.