DC/DC converter having a step-up converter supplying a step-down converter
A DC-DC converter has a Step-Up stage connected to a Step-Down stage. A common Step-Down controller is designed and configured such that a single reference voltage is compared to the output voltage of the Step-Down stage by a single comparator, producing a single error signal. The error signal is then compared to two different saw signals to generate first and second pulse-width modulated signals respectively. The first and second pulse-width modulated signals are inputted to a control unit that generates a first pair of control signals and a second pair of control signals, which control switching of the Step-Up stage and of the Step-Down stage.
1. A DC-DC converter, comprising:
an input terminal configured to receive an input voltage;
a Step-Up stage having a step-up stage input connected to the input terminal to receive the input voltage, and a step-up stage output, said Step-Up stage including a plurality of switches therein;
a Step-Down stage having a step-down stage input coupled to the step-up stage output and a step-down stage output, said Step-Down stage including a plurality of switches therein, said Step-Up stage and Step-Down stage being controlled by a first set of control signals and by a second set of control signals, respectively;
an output terminal connected to the step-down stage output so as to receive an output voltage of said Step-Down stage to drive a load coupled to said output terminal; and,
a controller configured to generate the first set of control signals and the second set of control signals, said controller comprising
a single error signal generator configured to generate a single error signal from a difference between a voltage at the step-down stage output and a single reference voltage, and to generate both the first set of control signals and the second set of control signals from said error signal, each one of the first set of control signals being directly and uniquely connected to one of the plurality of switches in the Step-Up stage, and each one of the second set of control signals being directly and uniquely connected to one of the plurality of switches in the Step-Down stage,
a first comparator configured to generate a first pulse-width modulated, PWM, control signal based on a comparison of the error signal with a first saw signal,
a second comparator configured to generate a second PWM control signal based on a comparison of the error signal with a second saw signal that is different from the first saw signal, and,
a control unit configured to generate the first control signals and the second control signals based on the first PWM control signal and the second PWM control signal, respectively,
wherein the controller is configured to control a magnitude of the first saw signal to be proportional to a voltage at the step-up stage output.
2. The DC-DC converter of claim 1 , wherein the step-down stage input is directly connected to the step-up stage output.
3. The DC-DC converter of claim 1 , wherein, in a first mode of operation, the controller is adapted to cause the first control signals and the second control signals to toggle so that the Step-Up stage and the Step-Down stage are simultaneously activated.
4. The DC-DC converter of claim 1 , wherein in a second mode of operation, the controller is configured to cause only the first control signals, not the second control signals to toggle so that only the Step-Down stage is activated.
5. The DC-DC converter of claim 1 , wherein the controller is configured to limit a maximum duty cycle for the Step-Up stage by pulse-width modulated, PWM, masking.
6. A DC-DC converter, comprising:
an input terminal configured to receive an input voltage;
a Step-Up stage having a step-up stage input connected to the input terminal to receive the input voltage, and a step-up stage output, said Step-Up stage including a plurality of switches therein;
a Step-Down stage having a step-down stage input coupled to the step-up stage output and a step-down stage output, said Step-Down stage including a plurality of switches therein, said Step-Up stage and Step-Down stage being controlled by a first set of control signals and by a second set of control signals, respectively;
an output terminal connected to the step-down stage output so as to receive an output voltage of said Step-Down stage to drive a load coupled to said output terminal; and,
a controller configured to generate the first set of control signals and the second set of control signals, said controller comprising
a single error signal generator configured to generate a single error signal from a difference between a voltage at the step-down stage output and a single reference voltage, and to generate both the first set of control signals and the second set of control signals from said error signal, each one of the first set of control signals being directly and uniquely connected to one of the plurality of switches in the Step-Up stage, and each one of the second set of control signals being directly and uniquely connected to one of the plurality of switches in the Step-Down stage,
a first comparator configured to generate a first pulse-width modulated, PWM, control signal based on a comparison of the error signal with a first saw signal,
a second comparator configured to generate a second PWM control signal based on a comparison of the error signal with a second saw signal that is different from the first saw signal,
a control unit configured to generate the first control signals and the second control signals based on the first PWM control signal and the second PWM control signal, respectively, and
means for controlling an offset of the first saw signal such that a minimum voltage value of said first saw signal to be proportional to the input voltage.
7. The DC-DC converter of claim 6 , wherein the step-down stage input is directly connected to the step-up stage output.
8. The DC-DC converter of claim 6 , wherein, in a first mode of operation, the controller is adapted to cause the first control signals and the second control signals to toggle so that the Step-Up stage and the Step-Down stage are simultaneously activated.
9. The DC-DC converter of claim 6 , wherein in a second mode of operation, the controller is configured to cause only the first control signals, not the second control signals to toggle so that only the Step-Down stage is activated.
10. The DC-DC converter of claim 6 , wherein the controller is configured to limit a maximum duty cycle for the Step-Up stage by pulse-width modulated, PWM, masking.
11. A DC-DC converter, comprising:
an input terminal configured to receive an input voltage;
a Step-Up stage having a step-up stage input connected to the input terminal to receive the input voltage, and a step-up stage output, said Step-Up stage including a plurality of switches therein;
a Step-Down stage having a step-down stage input coupled to the step-up stage output and a step-down stage output, said Step-Down stage including a plurality of switches therein, said Step-Up stage and Step-Down stage being controlled by a first set of control signals and by a second set of control signals, respectively;
an output terminal connected to the step-down stage output so as to receive an output voltage of said Step-Down stage to drive a load coupled to said output terminal; and,
a controller configured to generate the first set of control signals and the second set of control signals, said controller comprising
a single error signal generator configured to generate a single error signal from a difference between a voltage at the step-down stage output and a single reference voltage, and to generate both the first set of control signals and the second set of control signals from said error signal, each one of the first set of control signals being directly and uniquely connected to one of the plurality of switches in the Step-Up stage, and each one of the second set of control signals being directly and uniquely connected to one of the plurality of switches in the Step-Down stage,
a first comparator configured to generate a first pulse-width modulated, PWM, control signal based on a comparison of the error signal with a first saw signal,
a second comparator configured to generate a second PWM control signal based on a comparison of the error signal with a second saw signal that is different from the first saw signal, and,
a control unit configured to generate the first control signals and the second control signals based on the first PWM control signal and the second PWM control signal, respectively,
wherein a duty-cycle of the first PWM control signal and a duty-cycle of the second PWM control signal are managed by tuning a magnitude value and an average value of the first saw signal and of second saw signal, respectively.
12. The DC-DC converter of claim 11 , wherein the step-down stage input is directly connected to the step-up stage output.
13. The DC-DC converter of claim 11 , wherein, in a first mode of operation, the controller is adapted to cause the first control signals and the second control signals to toggle so that the Step-Up stage and the Step-Down stage are simultaneously activated.
14. The DC-DC converter of claim 11 , wherein in a second mode of operation, the controller is configured to cause only the first control signals, not the second control signals to toggle so that only the Step-Down stage is activated.
15. The DC-DC converter of claim 11 , wherein the controller is configured to limit a maximum duty cycle for the Step-Up stage by pulse-width modulated, PWM, masking.
16. A portable electronic device comprising:
a battery configured to provide a battery voltage;
a DC-DC converter configured to generate a supply voltage from the battery voltage, the supply voltage being higher than said battery voltage, the DC-DC converter including
an input terminal configured to receive the battery voltage;
a Step-Up stage having a step-up stage input connected to the input terminal to receive the input voltage and a step-up stage output, said Step-Up stage including a plurality of switches therein;
a Step-Down stage having a step-down input coupled to the step-up stage output, and a step-down output, said Step-Down stage including a plurality of switches therein, said Step-Up stage and Step-Down stage being controlled by a first set of control signals and by a second set of control signals, respectively;
an output terminal connected to the step-down stage output so as to receive the supply voltage from the step-down stage output; and,
a controller configured to generate the first set of control signals and the second set of control signals, said controller having
a single error signal generator configured to generate a single error signal from a difference between a voltage at the step-down stage output and a single reference voltage, and to generate both the first set of control signals and the second set of control signals from said error signal, each one of the first set of control signals being directly and uniquely connected to one of the plurality of switches in the Step-Up stage, and each one of the second set of control signals being directly and uniquely connected to one of the plurality of switches in the Step-Down stage,
a first comparator configured to generate a first pulse-width modulated, PWM, control signal based on a comparison of the error signal with a first saw signal,
a second comparator configured to generate a second PWM control signal based on a comparison of the error signal with a second saw signal that is different from the first saw signal, and,
a control unit configured to generate the first control signals and the second control signals based on the first PWM control signal and the second PWM control signal, respectively; and,
a Radio-Frequency Power Amplifier powered by the supply voltage,
wherein
the controller is configured to control a magnitude of the first saw signal to be proportional to a voltage at the step-up stage output,
the DC-DC converter further comprises means for controlling an offset of the first saw signal such that a minimum voltage value of said first saw signal to be proportional to the input voltage, and/or
a duty-cycle of the first PWM control signal and a duty-cycle of the second PWM control signal are managed by tuning a magnitude value and an average value of the first saw signal and of second saw signal, respectively.