DC-to-DC converter including flying capacitor
A DC-to-DC converter includes a first capacitor, first, second, third, and fourth switches connected in series between first and second electrodes of the first capacitor, a second capacitor connected to a connection node of the first switch and the second switch and a connection node of the third switch and the fourth switch, an inductor connected to a connection node of the second switch and the third switch, and a controller that controls an on/off state of each of the first to fourth switches on the basis of a value obtained by applying a reciprocal of a detection current that is a measured current flowing through the inductor to a difference between a first detection voltage and a first voltage instruction value and a difference between a second detection voltage and a second voltage instruction value.
1. A DC-to-DC converter comprising:
a first capacitor;
a first switch, a second switch, a third switch, and a fourth switch connected in series between a first electrode and a second electrode of the first capacitor;
a second capacitor having a first electrode and a second electrode respectively connected to a connection node of the first switch and the second switch and a connection node of the third switch and the fourth switch;
an inductor connected to a connection node of the second switch and the third switch at a first terminal thereof; and
a controller that controls an on/off state of each of the first to fourth switches on a basis of a calculation result using a difference between a first detection voltage and a first voltage instruction value, a difference between a second detection voltage and a second voltage instruction value, and a reciprocal of a detection current that is a measured current flowing through the inductor,
wherein the first detection voltage is a measured voltage between the first electrode and the second electrode of the first capacitor or a measured voltage between a second terminal of the inductor and a connection node of the first capacitor and the fourth switch.
2. The DC-to-DC converter according to claim 1 , wherein the controller controls the on/off state of each of the first to fourth switches on a basis of a value obtained by applying a preset proportional control constant to the difference between the second detection voltage and the second voltage instruction value and by multiplying a resultant value of the application of the preset proportional control constant by the reciprocal of the detection current.
3. The DC-to-DC converter according to claim 2 , wherein when the detection current has a magnitude that is within a preset range in a vicinity of zero, the controller determines the reciprocal of the detection current as a preset constant value.
4. The DC-to-DC converter according to claim 2 , wherein when the detection current has a magnitude that is within a preset range in a vicinity of zero, the controller determines the reciprocal of the detection current as a preset constant value that linearly changes within the preset range.
5. The DC-to-DC converter according to claim 1 , wherein the controller comprises:
a voltage controller that generates a current instruction value with respect to a current flowing through the inductor on a basis of the difference between the first detection voltage and the first voltage instruction value;
a current controller that generates a first control voltage instruction value on a basis of a difference between the current instruction value and the detection current; and
a flying capacitor voltage controller that generates a second control voltage instruction value on a basis of the difference between the second detection voltage and the second voltage instruction value and the reciprocal of the detection current.
6. The DC-to-DC converter according to claim 5 , wherein the flying capacitor voltage controller comprises:
a subtractor that calculates the difference between the second detection voltage and the second voltage instruction value;
a proportional controller that outputs a value obtained by applying a proportional control value to a calculation result of the subtractor;
a reciprocal calculator that calculates the reciprocal of the detection current; and
a multiplier that multiplies the value output by the proportional controller by a calculation result of the reciprocal calculator and outputs a product resulting from the multiplication as the second control voltage instruction value.
7. The DC-to-DC converter according to claim 6 , wherein when the detection current has a magnitude that is within a preset range in a vicinity of zero, the reciprocal calculator determines the reciprocal of the detection current as a preset constant value.
8. The DC-to-DC converter according to claim 6 , wherein when the detection current has a magnitude that is within a preset range in a vicinity of zero, the reciprocal calculator determines the reciprocal of the detection current as a preset constant value that linearly changes within the preset range.
9. The DC-to-DC converter according to claim 5 , wherein the controller comprises:
a first adder that adds the first control voltage instruction value and the second control voltage instruction value to produce a first duty instruction value;
a subtractor that subtracts the first control voltage instruction value from the first detection voltage;
a second adder that adds an output value of the subtractor to the second control voltage instruction value to produce a second duty instruction value;
a first switching controller that determines an on/off state of each of the first switch and the fourth switch according to a result of comparison between the first duty instruction value and a triangular wave signal having a predetermined frequency; and
a second switching controller that determines an on/off state of each of the second switch and the third switch according to a result of comparison between the second duty instruction value and the triangular wave signal.
10. The DC-to-DC converter according to claim 1 , further comprising a voltage sensor for obtaining the measured voltage between the first electrode and the second electrode of the first capacitor or the measured voltage between the second terminal of the inductor and the connection node of the first capacitor and the fourth switch.
11. The DC-to-DC converter according to claim 1 , further comprising a current sensor for obtaining the measured current flowing through the inductor.