Control device with magnetic flux density calculation
A switching loss of a power conversion device is sufficiently reduced. A DC-DC converter includes a switching circuit that converts input first DC power into AC power, a transformer that performs voltage conversion of the AC power, and an output circuit that converts the AC power subjected to the voltage conversion by the transformer into second DC power. The control circuit that controls the DC-DC converter calculates a magnetic flux density value B of the transformer and controls a drive frequency of the switching circuit based on the calculated magnetic flux density value B.
1. A control device that controls a power conversion device that converts input first DC power into second DC power and outputs the second DC power, the control device comprising:
a voltage control unit that calculates a duty instruction value for controlling an output voltage of an output circuit;
a switching carrier frequency setting unit that calculates a magnetic flux density value based on the duty instruction value and an input voltage of a switching circuit and sets a switching carrier frequency according to a drive frequency based on the calculated magnetic flux density value; and
a signal generation unit that generates an output signal for driving the switching circuit based on the duty instruction value and the switching carrier frequency and supplies the generated output signal to the switching circuit,
wherein the power conversion device includes the switching circuit that converts the first DC power into AC power, a transformer that performs voltage conversion of the AC power, and the output circuit that converts the AC power subjected to the voltage conversion by the transformer into the second DC power,
wherein the control device calculates the magnetic flux density value of the transformer and controls the drive frequency of the switching circuit based on the calculated magnetic flux density value,
wherein the switching carrier frequency setting unit sets the switching carrier frequency so that the drive frequency is lowered in a case where the magnetic flux density value is smaller than a predetermined magnetic flux density command value based on a saturation magnetic flux density of the transformer and so that the drive frequency is increased in a case where the magnetic flux density value is larger than the predetermined magnetic flux density command value, and
wherein the power conversion device further includes a temperature detector that detects a temperature of the transformer, and
the switching carrier frequency setting unit changes the predetermined magnetic flux density command value based on the temperature of the transformer detected by the temperature detector.
2. The control device according to claim 1 , further comprising a clock unit that controls execution timings of the voltage control unit and the switching carrier frequency setting unit.
3. The control device according to claim 1 , wherein
the power conversion device further includes a current detector that detects an output current from the output circuit, and
the switching carrier frequency setting unit changes the predetermined magnetic flux density command value based on the detected value of the output current detected by the current detector.
4. The control device according to claim 1 , wherein
the switching carrier frequency setting unit has a PI control unit that performs proportional-integral control based on a difference between the magnetic flux density value and the predetermined magnetic flux density command value by using a predetermined control gain, and
the predetermined control gain is changed based on at least one of the switching carrier frequency and an output current from the output circuit.
5. The control device according to claim 1 , wherein
the switching circuit is connected to the control device via an insulating gate driver provided with an insulating transformer,
the switching carrier frequency setting unit has a frequency limiting unit that limits the switching carrier frequency to a predetermined minimum frequency or higher, and
the predetermined minimum frequency is determined based on at least one of a saturation magnetic flux density of the insulating transformer and a current ripple in an output current from the output circuit.
6. A control device that controls a power conversion device that converts input first DC power into second DC power and outputs the second DC power, the control device comprising:
a voltage control unit that calculates a duty instruction value for controlling an output voltage of an output circuit;
a switching carrier frequency setting unit that calculates a magnetic flux density value based on the duty instruction value and an input voltage of a switching circuit and sets a switching carrier frequency according to a drive frequency based on the calculated magnetic flux density value; and
a signal generation unit that generates an output signal for driving the switching circuit based on the duty instruction value and the switching carrier frequency and supplies the generated output signal to the switching circuit,
wherein the power conversion device includes the switching circuit that converts the first DC power into AC power, a transformer that performs voltage conversion of the AC power, and the output circuit that converts the AC power subjected to the voltage conversion by the transformer into the second DC power,
wherein the control device calculates the magnetic flux density value of the transformer and controls the drive frequency of the switching circuit based on the calculated magnetic flux density value,
wherein the switching carrier frequency setting unit sets the switching carrier frequency so that the drive frequency is lowered in a case where the magnetic flux density value is smaller than a predetermined magnetic flux density command value based on a saturation magnetic flux density of the transformer and so that the drive frequency is increased in a case where the magnetic flux density value is larger than the predetermined magnetic flux density command value, and
wherein the power conversion device further includes a current detector that detects an output current from the output circuit, and
the switching carrier frequency setting unit changes the predetermined magnetic flux density command value based on the detected value of the output current detected by the current detector.
7. The control device according to claim 6 , further comprising a clock unit that controls execution timings of the voltage control unit and the switching carrier frequency setting unit.
8. The control device according to claim 6 , wherein
the power conversion device further includes a temperature detector that detects a temperature of the transformer, and
the switching carrier frequency setting unit changes the predetermined magnetic flux density command value based on the temperature of the transformer detected by the temperature detector.
9. The control device according to claim 6 , wherein
the switching carrier frequency setting unit has a PI control unit that performs proportional-integral control based on a difference between the magnetic flux density value and the predetermined magnetic flux density command value by using a predetermined control gain, and
the predetermined control gain is changed based on at least one of the switching carrier frequency and the output current from the output circuit.
10. The control device according to claim 6 , wherein
the switching circuit is connected to the control device via an insulating gate driver provided with an insulating transformer,
the switching carrier frequency setting unit has a frequency limiting unit that limits the switching carrier frequency to a predetermined minimum frequency or higher, and
the predetermined minimum frequency is determined based on at least one of a saturation magnetic flux density of the insulating transformer and a current ripple in the output current from the output circuit.
11. A control device that controls a power conversion device that converts input first DC power into second DC power and outputs the second DC power, the control device comprising:
a voltage control unit that calculates a duty instruction value for controlling an output voltage of an output circuit;
a switching carrier frequency setting unit that calculates a magnetic flux density value based on the duty instruction value and an input voltage of a switching circuit and sets a switching carrier frequency according to a drive frequency based on the calculated magnetic flux density value; and
a signal generation unit that generates an output signal for driving the switching circuit based on the duty instruction value and the switching carrier frequency and supplies the generated output signal to the switching circuit,
wherein the power conversion device includes the switching circuit that converts the first DC power into AC power, a transformer that performs voltage conversion of the AC power, and the output circuit that converts the AC power subjected to the voltage conversion by the transformer into the second DC power,
wherein the control device calculates the magnetic flux density value of the transformer and controls the drive frequency of the switching circuit based on the calculated magnetic flux density value,
wherein the switching carrier frequency setting unit sets the switching carrier frequency so that the drive frequency is lowered in a case where the magnetic flux density value is smaller than a predetermined magnetic flux density command value based on a saturation magnetic flux density of the transformer and so that the drive frequency is increased in a case where the magnetic flux density value is larger than the predetermined magnetic flux density command value, and
wherein the switching carrier frequency setting unit has a PI control unit that performs proportional-integral control based on a difference between the magnetic flux density value and the predetermined magnetic flux density command value by using a predetermined control gain, and
the predetermined control gain is changed based on at least one of the switching carrier frequency and an output current from the output circuit.
12. The control device according to claim 11 , further comprising a clock unit that controls execution timings of the voltage control unit and the switching carrier frequency setting unit.
13. The control device according to claim 11 , wherein
the power conversion device further includes a temperature detector that detects a temperature of the transformer, and
the switching carrier frequency setting unit changes the predetermined magnetic flux density command value based on the temperature of the transformer detected by the temperature detector.
14. The control device according to claim 11 , wherein
the power conversion device further includes a current detector that detects the output current from the output circuit, and
the switching carrier frequency setting unit changes the predetermined magnetic flux density command value based on the detected value of the output current detected by the current detector.
15. The control device according to claim 11 , wherein
the switching circuit is connected to the control device via an insulating gate driver provided with an insulating transformer,
the switching carrier frequency setting unit has a frequency limiting unit that limits the switching carrier frequency to a predetermined minimum frequency or higher, and
the predetermined minimum frequency is determined based on at least one of a saturation magnetic flux density of the insulating transformer and a current ripple in the output current from the output circuit.