Switch-mode power supply controllers

A switch mode power supply (SMPS) controller for combined pulse width and pulse frequency modulation of a power switching device of said SMPS, the controller comprising:

• an input to receive a feedback signal responsive to an output voltage of said SMPS;
• and
• a pulse generator for driving said power switching device, said pulse generator being configured to generate first and second ramp signals, one rising the other falling, and to output a drive pulse with a first period timed by a duration of said first ramp signal for controlling said power switching device on and with a second period timed by a duration of said second ramp signal for controlling said power switching device off;
• and
• wherein said pulse generator is further configured to initiate said first ramp signal at a level responsive to said feedback signal.

A switch mode power supply (SMPS) controller circuit for generating a rising and falling voltage ramp for controlling the timing of switching of a power switching device of said SMPS, the circuit comprising:

• a current input for a feedback signal current;
• a first current mirror circuit having an input coupled to said current input and having first and second first current mirror outputs;
• a constant current generator to generate a substantially constant current;
• a second current mirror circuit having an input coupled to said substantially constant current generator and having first, second and third constant current outputs;
• a resistor coupled to said first output of said first current mirror and to said first output of said second current mirror to provide an initialisation voltage;
• a junction coupled to said second output of said first current mirror and to said second output of said second current mirror to form a difference current, said difference current being dependent upon a difference between said constant current and said feedback signal current;
• a capacitor;
• and
• switches to selectively couple said capacitor to said initialisation voltage, to said third constant current output of said second current mirror to charge said capacitor, and to a supply of said difference current to discharge said capacitor, to generate said rising and falling voltage ramps.

A method of controlling a switch mode power supply (SMPS), the method comprising:

• initialising a voltage on a capacitor responsive to a feedback signal current dependent upon an output voltage of said SMPS;
• charging said capacitor at a substantially constant rate to determine an on period for a power switching device of said SMPS;
• and
• discharging said capacitor at a rate dependent upon said feedback signal current to determine an off period for said power switching device of said SMPS.

A PWM and PFM SMPS controller for controlling a power switching device of said SMPS, the controller comprising:

• a first input to received a feedback signal from an output of said SMPS;
• a second input to receive a current sense signal sensing a current through said switching device;
• a first ramp generator coupled to said first input to generate a first ramp for controlling a switching frequency of said switching device responsive to said feedback signal;
• and
• a second ramp generator coupled to said second input to generate a second ramp for controlling an on time of said switching device responsive to said current sense signal.

A PWM and PFM SMPS controller for controlling a power switching device of said SMPS, the controller comprising:

• a first input to receive a feedback signal from an output of said SMPS;
• a second input to receive a current sense signal sensing a current through said switching device;
• a first ramp generator responsive to at least one of said feedback signal and said current sense signal for controlling one or both of a pulse width and pulse frequency of a control signal to said power switching device;
• a slope compensation ramp generator to generate a compensation ramp for waveform modulating said pulse width of said switching device;
• and
• wherein said compensation ramp waveform is responsive to said current sense signal.

A PWM and PFM SMPS controller for controlling a power switching device of said SMPS, the controller comprising:

• a first input to received a feedback signal from an output of said SMPS;
• a second input to receive a current sense signal sensing a current through said switching device;
• and
• a control system to provide a pulse width and frequency modulation control signal to said switching device responsive to both said feedback signal and said current sense signal.

A current limiting current translation circuit, the circuit being configured to receive an input current and to translate said input current to an output current substantially linearly dependent on said input current, one or both of a maximum and minimum value of said output current being limited at one or both of a maximum and minimum limiting current value of said input current, one or both of said maximum and minimum said limiting current values being dependent on a reference current, the circuit comprising:

• a first input for said input current;
• a second input for said reference current;
• at least one current mirror connected to form an intermediate current, said intermediate current having a value of substantially zero at one or both of said maximum and minimum limiting current values;
• and
• an output node coupled to an output of said at least one current mirror.