System and method for controlling single inductor dual output DC/DC converters
View Patent ↗A DC to DC converter comprises voltage regulation circuitry for generating at least two output voltages responsive to an input voltage. The voltage regulation circuitry further includes a plurality of main switches connected to receive the input voltage. A plurality of auxiliary switches is connected to provide the at least two output voltages. A single inductor is connected between the plurality of main switches and the plurality of auxiliary switches. A dual-output PWM controller provides a first PWM control signal for controlling the operation of the plurality of main switches responsive to a first feedback voltage from a first output voltage using a first control loop and provides a second PWM control signal for controlling the operation of the plurality of auxiliary switches responsive to a second feedback voltage from a second output voltage using a second control loop. Current mode control can be used for each control loop to reduce the cross regulation problem.
1. A DC to DC converter, comprising:
voltage regulation circuitry for generating at least two output voltages responsive to an input voltage, wherein the voltage regulation circuitry further comprises:
a single inductor having a first side and a second side connected to provide each of the at least two output voltages;
a plurality of main switches connected to the first side of the single inductor and to no other inductors connected to receive the input voltage;
a plurality of auxiliary switches connected to the second side of the single inductor and to no other inductors, each of the plurality of auxiliary switches connected to provide one of the at least two output voltages;
a dual-output PWM controller generating a first PWM control signal for controlling the operation of the plurality of main switches responsive to a first feedback voltage from a first output voltage of the at least two output voltages using a first control loop and not responsive to a second feedback voltage from a second output voltage of the at least two output voltages and for providing a second PWM control signal for controlling the operation of the plurality of auxiliary switches responsive to the second feedback voltage from the second output voltage of the at least two output voltages using a second control loop and not responsive to the first feedback voltage from the first output voltage of the at least two output voltages;
wherein the first control loop further comprises:
a first error amplifier connected to compare the first feedback voltage with a reference voltage and generating a first error voltage signal responsive thereto;
a first comparator connected to compare the first error voltage signal with a slope compensation signal and generating a first PWM control signal at one of a first voltage level or a second voltage level responsive to the comparison;
a first PWM modulator generating the first PWM signal for driving the plurality of main switches responsive to the first PWM control signal;
wherein the second control loop further comprises:
a second error amplifier connected to compare the second feedback voltage with the reference voltage and generating a second error voltage signal responsive thereto;
a second comparator connected to compare the second error voltage signal with the slope compensation signal and generating a second PWM control signal at one of the first voltage level or the second voltage level responsive to the comparison;
a second PWM modulator generating the second PWM signal for driving the plurality of auxiliary switches responsive to the second PWM control signal;
a first driver circuit for driving the plurality of main switches responsive to the first PWM signal; and
a second driver circuit for driving the plurality of auxiliary switches responsive to the second PWM signal.
2. The DC to DC converter of claim 1 , further including:
a first proportional-integral-differential compensation network connected in a first feedback loop between an output of the first error amplifier and a first feedback input of the first error amplifier; and
a second proportional-integral-differential compensation network connected in a second feedback loop between an output of the second error amplifier and a first feedback input of the second error amplifier.
3. The DC to DC converter of claim 1 , further including:
a current sense network for monitoring a current through the inductor and generate a sensed inductor current waveform; and
at least one adder circuit for generating the slope compensation signal by adding the sensed inductor current waveform with a ramp signal.
4. A dual-output PWM controller for a single inductor dual output DC to DC converter, comprising:
a plurality of feedback inputs, each from an output of a network for monitoring an output voltage of the dual-output, single inductor DC to DC converter, the converter including voltage regulation circuitry for generating at least two output voltages responsive to an input voltage, the voltage regulation circuitry including a single inductor having a first side and a second side, a plurality of main switches connected to the first side of the inductor and no other inductor providing one of the at least two output voltages and a plurality of auxiliary switches connected to the second side of the inductor and no other inductor providing a second one of the at least two output voltages;
a first control loop for providing a first PWM signal for controlling the operation of a plurality of main switches of the DC to DC converter responsive to a first feedback voltage from a first feedback input and not responsive to a second feedback voltage from a second output voltage of the at least two output voltages, wherein the first control loop further comprises:
a first error amplifier connected to compare the first feedback voltage with a reference voltage and generating a first error voltage signal responsive thereto;
a first comparator connected to compare the first error voltage signal with a compensation signal and generating a first PWM control signal at one of a first voltage level or a second voltage level responsive to the comparison;
a first PWM modulator generating the first PWM signal for driving the first and the second main switches responsive to the first PWM control signal;
a second control loop for providing a second PWM signal for controlling the operation of a plurality of auxiliary switches of the DC to DC converter responsive to a second feedback voltage from a second feedback input and not responsive to the first feedback voltage from the first output voltage of the at least two output voltages, wherein the second control loop further comprises:
a second error amplifier connected to compare the second feedback voltage with the reference voltage and generating a second error voltage signal responsive thereto;
a second comparator connected to compare the second error voltage signal with the compensation signal and generating a second PWM control signal at one of the first voltage level or the second voltage level responsive to the first comparison;
a second PWM modulator generating the second PWM signal for driving the first and the second auxiliary switches responsive to the second PWM control signal; and
an output associated with each of the first and the second control loops providing the first and the second PWM signals.
5. The dual-output PWM controller of claim 4 , further including:
a first proportional-integral-differential compensation network connected in a first feedback loop between an output of the first error amplifier and a first feedback input of the first error amplifier; and
a second proportional-integral-differential compensation network connected in a second feedback loop between an output of the second error amplifier and a first feedback input of the second error amplifier.
6. The dual-output PWM controller of claim 4 further including:
a first adder circuit, within the first control loop, for generating a first slope compensation signal by adding a sensed inductor current waveform associated with an inductor of the DC to DC converter with a ramp signal; and
a second adder circuit, within the second control loop, for generating a second slope compensation signal by adding the sensed inductor current waveform associated with an inductor of the DC to DC converter with the ramp signal.
7. A method for providing DC to DC voltage regulation within a dual output, single inductor DC to DC voltage regulator, comprising the steps of:
receiving an input voltage;
monitoring a feedback voltage from a plurality of outputs of the voltage regulator;
providing a first PWM signal for controlling the operation of a plurality of main switches of the voltage regulator responsive to a first feedback voltage from a first output voltage using a first control loop and not responsive to a second feedback voltage from a second output voltage of the at least two output voltages, wherein the step of providing the first PWM signal further comprises the steps of:
comparing the first feedback voltage with a reference voltage;
generating a first error voltage signal one of a first voltage level and a second voltage level responsive to the comparison of the first feedback voltage and the reference voltage;
comparing the first error voltage signal with a slope compensation signal;
generating a first PWM control signal responsive the comparison of the first error voltage signal and the slope compensation signal;
generating the first PWM signal for driving the plurality of main switches responsive to the first PWM control signal;
providing a second PWM signal for controlling the operation of a plurality of auxiliary switches responsive to a second feedback voltage from a second output voltage using a second control loop and not responsive to the first feedback voltage from the first output voltage of the at least two output voltages, wherein the step of providing the second PWM signal further comprises the steps of:
comparing a second feedback voltage with the reference voltage;
generating a second error voltage signal responsive to the comparison of the second feedback voltage and the reference voltage;
comparing the second error voltage signal with the slope compensation signal;
generating a second PWM control signal one of the first voltage level and the second voltage level responsive the comparison of the second error voltage signal and the slope compensation signal;
generating the second PWM signal for driving the plurality of main switches responsive to the second PWM control signal;
switching the plurality of main switches connected to a first side of a single inductor and connected to no other inductors responsive to the first PWM signal;
switching the plurality of auxiliary switches connected to a second side of the single inductor and connected to no other inductors responsive to the second PWM signal; and
generating the first output voltage and the second output voltage responsive to the input voltage and the switching of the main switches and the auxiliary switches using the single inductor.
8. The method of claim 7 , further comprising the steps of:
driving the plurality of main switches responsive to the first PWM signal; and
driving the plurality of auxiliary switches responsive to the second PWM signal.
9. The method of claim 7 , further including the steps of:
providing a first proportional-integral-differential compensation network connected in a first feedback loop between an output of the first error amplifier and a first feedback input of the first error amplifier;
providing a second proportional-integral-differential compensation network connected in a second feedback loop between an output of the second error amplifier and a first feedback input of the second error amplifier;
altering the first feedback voltage responsive to the first proportional-integral-differential compensation network; and
altering the second feedback voltage responsive to the second proportional-integral-differential compensation network.
10. The method of claim 9 , further including steps of:
monitoring a current through an inductor of the voltage regulator;
generating a sensed inductor current waveform for the inductor of the voltage regulator; and
generating the slope compensation signal by adding the sensed inductor current waveform with a ramp signal.
11. A solar system comprising:
at least one solar panel;
a DC to DC converter connected to an output of each of the at least one solar panels, the DC to DC converter comprising:
voltage regulation circuitry for generating at least two output voltages responsive to an input voltage, wherein the voltage regulation circuitry further comprises:
a single inductor having a first side and a second side connected to provide each of the at least two output voltages;
a plurality of main switches connected to the first side of the single inductor and to no other inductors connected to receive the input voltage;
a plurality of auxiliary switches the second side of the single inductor and to no other inductors each of the plurality of auxiliary switches connected to provide one of the at least two output voltages;
a dual-output PWM controller generating a first PWM control signal for controlling the operation of the plurality of main switches responsive to a first feedback voltage from a first output voltage of the at least two output voltages using a first control loop and not responsive to a second feedback voltage from a second output voltage of the at least two output voltages and for providing a second PWM control signal for controlling the operation of the plurality of auxiliary switches responsive to a second feedback voltage from a second output voltage of the at least two output voltages using a second control loop and not responsive to the first feedback voltage from the first output voltage of the at least two output voltages;
wherein the first control loop further comprises:
a first error amplifier connected to compare the first feedback voltage with a reference voltage and generating a first error voltage signal responsive thereto;
a first comparator connected to compare the first error voltage signal with a slope compensation signal and generating a first PWM control signal at one of a first voltage level or a second voltage level responsive to the comparison;
a first PWM modulator generating the first PWM signal for driving the plurality of main switches responsive to the first PWM control signal;
wherein the second control loop further comprises:
a second error amplifier connected to compare the second feedback voltage with the reference voltage and generating a second error voltage signal responsive thereto;
a second comparator connected to compare the second error voltage signal with the slope compensation signal and generating a second PWM control signal at one of the first voltage level and the second voltage level responsive to the comparison;
a second PWM modulator generating the second PWM signal for driving the plurality of auxiliary switches responsive to the second PWM control signal;
a first driver circuit for driving the plurality of main switches responsive to the first PWM signal; and
a second driver circuit for driving the plurality of auxiliary switches responsive to the second PWM signal.