Method and apparatus for PWM control of multi-mode switching power supply using iterative average current mode control

A buck converter configured to receive a DC input voltage and provide a DC output voltage, the buck converter comprising:

• an inductor having a first terminal and a second terminal;
• a first controlled switch and a second controlled switch, each having a respective control terminal, a first terminal and a second terminal, wherein the second terminal of the first controlled switch and the first terminal of the second controlled switch are coupled to the first terminal of the inductor, the first terminal of the first controlled switch is coupled to the DC voltage input, and the second terminal of the second control switch is coupled to a common terminal;
• a rectifier device having a second terminal coupled to the second terminal of the inductor, and a first terminal configured to provide the DC output voltage;
• a current sense amplifier configured to output a current sense signal over a present switching cycle based on an inductor current through the inductor;
• a voltage error amplifier configured to output an error voltage based on a difference between a reference voltage and a representation of the DC output voltage;
• and
• a pulse width modulation (PWM) controller comprising:
• an iterative average current control circuit configured to receive the current sense signal over the present switching cycle and the error voltage, and to generate a pulse width modulation (PWM) signal for the present switching cycle based on the current sense signal for the present switching cycle and a current sense signal over a previous switching cycle that precedes the present switching cycle;
• wherein the buck converter further comprises a logic drivers control block configured to receive the PWM signal, and output control signals configured to drive the first and second controlled switches, via their respective control terminals, based on the PWM signal.

A boost converter configured to receive a DC input voltage and provide a DC output voltage, the boost converter comprising:

• an inductor having a first terminal and a second terminal, said first terminal coupled to the DC input voltage;
• a controlled switch having a control terminal, a first terminal and a second terminal;
• wherein the second terminal of the controlled switch is coupled to a common terminal, and the first terminal of the controlled switch is coupled to the second terminal of the inductor;
• a rectifier device having a second terminal coupled to the second terminal of the inductor, and a first terminal configured to provide the DC output voltage;
• a current sense amplifier configured to output a current sense signal over a present switching cycle based on an inductor current through the inductor;
• a voltage error amplifier configured to output an error voltage based on a difference between a reference voltage and a representation of the DC output voltage;
• a pulse width modulation (PWM) controller comprising:
• an error voltage modifier circuit configured to receive the error voltage, and output a modified error voltage corresponding to a product of the error voltage and a modifying coefficient;
• and
• an iterative average current control circuit configured to receive the current sense signal and the modified error voltage, and to generate a pulse width modulation (PWM) signal based on the current sense signal over the present switching cycle and a current sense signal over a previous switching cycle that precedes the present switching cycle;
• a logic drivers control block configured to receive the PWM signal, output the mode signal based on the DC input voltage and the DC output voltage, and output one or more control signals configured to drive the controlled switch, via its control terminal, based on the PWM signal.

A method of generating a pulse width modulation (PWM) signal for a converter configured to receive a DC input and provide a regulated DC output voltage, the method comprising:

• obtaining a current sense signal over a present switching cycle of the converter and a preceding switching cycle of the converter, both based on an inductor current through an inductor of the converter;
• determining a voltage representing an average inductor current over the present switching cycle;
• obtaining an error voltage based on a difference between a reference voltage and a representation of the regulated DC output voltage;
• selectively outputting the error voltage or a modified error voltage, the modified error voltage corresponding to a product of the error voltage and a modifying coefficient, based on an operating mode of the converter, and representing a target average inductor current;
• and
• generating the PWM signal based on a difference between said voltage representing the target average inductor current and said voltage representing the average inductor current over the present switching cycle.