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EP-3783787-B1 - DC/DC CONVERTER, AND DC/DC CONVERTER CONTROL METHOD

EP3783787B1EP 3783787 B1EP3783787 B1EP 3783787B1EP-3783787-B1

Inventors

  • YUZURIHARA, ITSUO
  • HOSOYAMADA, Yu

Dates

Publication Date
20260506
Application Date
20180424

Claims (5)

  1. A DC/DC converter (1) comprising a main circuit (2) having an LC chopper circuit including a three-phase LC circuit (4) and a switching circuit (3) comprising switching devices (s 1A , s 1B , s 2A , s 2B , s 3A , s 3B ), and a control unit (6) configured to convert a DC input voltage intc high-frequency outputs at a plurality of different voltage levels to output power at different output power levels according to a High/Low two-level control, the LC circuit (4) including in each phase an inductance L connected in series with respect to the switching circuit and connectable to a load, and a capacitance C connected in parallel with respect to the switching circuit (3) and connectable in parallel to the load, the switching circuit (3) being configured to perform three-phase interleaving discrete switching control on an input voltage Vin to thereby supply the LC circuit (4) with an inductance current (iL), wherein the control unit (6) is configured to carry out constant-voltage control and constant-current control in combination to effect transition between two power levels of the High/Low two-level control, wherein the control unit (6) is configured to perform the following modes: a first mode , wherein the control unit (6) is configured to perform constant-current control tc implement a transition period between an output power level before transition and an output power level after transition, wherein in the first mode the control unit (6) is configured to determine a pulse width ΔT(k) to control ON/OFF operation of the switching device of the main circuit (2) is ΔT k = L 3 I Cref − L 3 − T s + T d 2 2 C i C − ave k s V in + T s + T d v o k s V in − T d T s ΔT k − 1 wherein k represents a control cycle of the main circuit and ks represents a corresponding control cycle of the control unit, ICref is a command value of the capacitance current, iC-ave(ks) is a detection value of a capacitance average current, vo(ks) is an output voltage, Ts denotes a time width for one control cycle of the control unit and Td is a delay time from the control unit control cycle ks with respect tc the main circuit control cycle k; a third mode wherein the control unit (6) is configured to perform constant-voltage control tc implement a retention period for retaining voltages of the output power level before transition and the output power level after transition, wherein in the third mode, the control unit (6) is configured to determine the pulse width ΔT(k) to control ON/OFF operation of the switching device of the main circuit (2) is ΔT k = T s + T d V ref − L 3 − T s + T d 2 2 C i C − ave k s V in − T d T s ΔT k − 1 wherein Vref denotes a voltage command value; and a second mode ,wherein the control unit (6) is configured to perform constant-voltage control tc implement a buffer period to shift from the transition period to the retention period, wherein in the second mode the control unit (6) is configured to determine the pulse width ΔT (k) to control ON/OFF operation of the switching device of the main circuit (2) is Δ T k = L 3 A 1 V ref − v 0 k s − L 3 − T s + T d 2 2 C i C − ave k s V in + T s + T d v o k s V in − T d T s Δ T k − 1 the output voltage in the first mode and the second mode being an estimated output voltage based on a capacitance current, wherein A1 in the second mode is a gain value that is smaller than a gain of the main circuit set to 3(Ts+Td)/L in the third mode, and the control unit is configured to repeat the three modes in sequence to output the high-frequency outputs at the plurality of voltage levels according to the High/ Low two-level control.
  2. A DC/DC converter (1) comprising a main circuit (2) having an LC chopper circuit including a three-phase LC circuit (4) and a switching circuit (3) comprising switching devices (s 1A , s 1B , s 2A , s 2B , s 3A , s 3B ), and a control unit (6) configured to convert a DC input voltage intc high-frequency outputs at a plurality of different voltage levels to output power at different output power levels according to a High/Low two-level control, the LC circuit (4) including in each phase an inductance L connected in series with respect to the switching circuit and connectable to a load, and a capacitance C connected in parallel with respect to the switching circuit (3) connectable in parallel to the load, the switching circuit (3) being configured to perform three-phase interleaving discrete switching control on an input voltage Vin to thereby supply the LC circuit (4) with an inductance current (iL), wherein the control unit (6) is configured to carry out constant-voltage control and constant-current control in combination to effect transition between two power levels of the High/Low two-level control, wherein the control unit is configured to perform the following modes: a first mode ,wherein the control unit (6) is configured to perform constant-current control tc implement a transition period between an output power level before transition and an output power level after transition, wherein in the first mode , the control unit (6) is configured to determine a pulse width ΔT(k; to control ON/OFF operation of the switching device of the main circuit (2) is ΔT k = L 3 I Cref − L 3 − T s + T d 2 2 C i C − ave k s V in + T s + T d v o k s V in − T d T s ΔT k − 1 wherein k represents a control cycle of the main circuit and ks represents a corresponding control cycle of the control unit, ICref is a command value of the capacitance current, iC-ave(ks) is a detection value of a capacitance average current, vo(ks) is an output voltage, Ts denotes a time width for one control cycle of the control unit and Td is a delay time from the control unit control cycle ks with respect tc the main circuit control cycle k; a third mode , wherein the control unit (6) is configured J to perform constant-voltage control to implement a retention period for retaining voltages of the output power level before transition and the output power level after transition, wherein in the third mode , the control unit (6) is configured to determine the pulse width ΔT(k) to control ON/OFF operation of the switching device of the main circuit (2) is ΔT k = T s + T d V ref − L 3 − T s + T d 2 2 C i C − ave k s V in − T d T s ΔT k − 1 wherein Vref denotes a voltage command value; and a second mode ,wherein the control unit (6) is configured to perform constant-voltage control tc implement a buffer period to shift from the transition period to the retention period, wherein in the second mode ,the control unit (6) is configured to determine the pulse width ΔT(k) to control ON/OFF operation of the switching device of the main circuit (2) is Δ T k = L 3 A 1 V ref − v 0 k s − L 3 − T s + T d 2 2 C i C − ave k s V in + T s + T d v o k s V in − T d T s Δ T k − 1 the output voltage in the first mode being an estimated output voltage based on a capacitance current, the output voltage in the second mode being the detected output voltage; wherein A1 in the second mode is a gain value that is smaller than a gain of the main circuit set to 3(Ts+Td)/L in the third mode, and the control unit is configured to repeat the three modes in sequence to output the high-frequency outputs at the plurality of voltage levels according to the High/ Low two-level control.
  3. The DC/DC converter according to claim 1 or 2, wherein the capacitance current command value in the second mode is a difference between a voltage command value and a detected voltage value in the second mode and an integrated value of the gain A1, respectively.
  4. A control method for a DC/DC converter according to claim 1, wherein the control unit performs the following modes: a first mode to perform constant-current control to implement a transition period between an output power level before transition and an output power level after transition, wherein in the first mode a pulse width ΔT(k) for controlling ON/OFF operation of the switching device of the main circuit (2) is ΔT k = L 3 I Cref − L 3 − T s + T d 2 2 C i C − ave k s V in + T s + T d v o k s V in − T d T s ΔT k − 1 wherein k represents a control cycle of the main circuit and ks represents corresponding control cycle of the control unit, ICref is a command value of the capacitance current, iC-ave(ks) is a detection value of a capacitance average current, vo(ks) is an output voltage, Ts denotes a time width for one control cycle of the control unit and Td is a delay time from the control unit control cycle ks in respect to the main circuit control cycle k; a third mode to perform constant-voltage control to implement a retention period for retaining voltages of the output power level before transition and the output power level after transition, wherein in the third mode the pulse width ΔT(k) for controlling ON/OFF operation of the switching device of the main circuit (2) is ΔT k = T s + T d V ref − L 3 − T s + T d 2 2 C i C − ave k s V in − T d T s ΔT k − 1 wherein Vref denotes a voltage command value; and a second mode to perform constant-voltage control to implement a buffer period to shift from the transition period to the retention period, wherein in the second mode the pulse width ΔT(k) for controlling ON/OFF operation of the switching device of the main circuit (2) is ΔT k = L 3 A 1 V ref − v 0 k s − L 3 − T s + T d 2 2 C i C − ave k s V in + T s + T d v o k s V in − T d T s ΔT k − 1 the output voltage in the first mode and the second mode being an estimated output voltage based on a capacitance current, wherein A1 in the second mode is a gain value that is smaller than a gain of the main circuit set to 3(Ts+Td)/L in the third mode, and the control unit repeats the three modes in sequence to output the high-frequency outputs at the plurality of voltage levels according to the High/Low two-level control.
  5. A control method for a DC/DC converter according to claim 2, wherein the control unit (6) performs the following modes: a first mode to perform constant-current control to implement a transition period between an output power level before transition and an output power level after transition, wherein in the first mode a pulse width ΔT(k) for controlling ON/OFF operation of the switching device of the main circuit (2) is ΔT k = L 3 I Cref − L 3 − T s + T d 2 2 C i C − ave k s V in + T s + T d v o k s V in − T d T s ΔT k − 1 wherein k represents a control cycle of the main circuit and ks represents a corresponding control cycle of the control unit, ICref is a command value of the capacitance current, iC-ave(ks) is a detection value of a capacitance average current, vo(ks) is an output voltage, Ts denotes a time width for one control cycle of the control unit and Td is a delay time from the control unit control cycle ks in respect to the main circuit control cycle k; a third mode to perform constant-voltage control to implement a retention period for retaining voltages of the output power level before transition and the output power level after transition, wherein in the third mode the pulse width ΔT(k) for controlling ON/OFF operation of the switching device of the main circuit (2) is ΔT k = T s + T d V ref − L 3 − T s + T d 2 2 C i C − ave k s V in − T d T s ΔT k − 1 wherein Vref denotes a voltage command value; and a second mode to perform constant-voltage control to implement a buffer period to shift from the transition period to the retention period, wherein in the second mode the pulse width ΔT(k) for controlling ON/OFF operation of the switching device of the main circuit (2) is ΔT k = L 3 A 1 V ref − v 0 k s − L 3 − T s + T d 2 2 C i C − ave k s V in + T s + T d v o k s V in − T d T s ΔT k − 1 the output voltage in the first mode being an estimated output voltage based on a capacitance current, the output voltage in the second mode being the detected output voltage; wherein A1 in the second mode is a gain value that is smaller than a gain of the main circuit set to 3(Ts+Td)/L in the third mode, and the control unit repeats the three modes in sequence to output the high-frequency outputs at the plurality of voltage levels according to the High/Low two-level control.

Description

Technical Field The present invention relates to a DC/DC converter for switching a voltage level of a DC voltage, and a control method for the DC/DC converter. Background Art (High/Low Pulse Operation) In recent years, for example, high-frequency power (RF output) has been used in the field of plasma application, which power is generated by an ON/OFF pulse operation for turning ON/OFF in a cycle of several tens of Hz to several tens of kHz or a High/Low pulse operation for varying an amplitude of RF power at high speed. These pulse operations are said to be effective for suppressing abnormal discharge occurring due to particles produced during film formation and for microfabrication and others by using low-temperature plasma. The ON/OFF pulse operation is an operation mode of supplying intermittent high frequency power (RF output) to load. In this operation mode, plasma may be extinguished in an OFF period where the power is not supplied to the load. As a consequence, once the plasma is extinguished, the RF output will have a mismatch with a plasma impedance. By contrast, the High/Low pulse operation is an operation mode of periodically varying continuous high frequency power, which does not intermit at all times, to the load by dividing different two levels of a high level and a low level, thereby supplying power at a level different from the high level, instead of utilizing the OFF period of the ON/OFF pulse operation. For example, in the power supplying to the plasma, a continuous output is produced between power on a high side that is necessary to form a thin film and power on a low side that is necessary to maintain plasma discharge to thereby prevent the plasma from being extinguished and maintain constant stable plasma discharge. (DC/DC Converter) There is a method for performing the High/Low pulse operation to control a DC/DC converter section in an RF generator. Since it is required to make a fast transition between two different voltage levels to control the DC/DC converter section, a frequency limitation of the High/Low pulse operation is dependent on control responsivity of the DC/DC converter. Thus, in order to make the fast transition between the voltage levels, it is necessary to change the voltage quickly in the DC/DC converter and control the voltage stably. As a control method of the DC/DC converter, a PI control is well known. The PI control is a classic way of conducting the control in which a difference between a command value and a detection value is proportioned and integrated to calculate a manipulated variable. As an example, there is a PI control adopting a double closed loop control system comprising a minor loop using a capacitance current and a major loop using a detected output voltage. The PI control of the closed loop control type is classical, and the control responses of the major loop and the minor loop have the following limitations. 1) Since the minor loop is affected by, such as, dead time, the maximum control response thereof is a frequency of about 1/10 of a switching frequency.2) Due to the prevention of interference with the minor loop, the maximum control response of the major loop is a frequency of about 1/10 of the control response of the minor loop. Thus, the maximum control response of the major loop is a frequency of about 1/100 of the switching frequency. Due to this limitation in the control response, when the High/Low pulse operation is conducted at a frequency of 10 kHz or more, the switching frequency will exceed 1 MHz to thereby cause control complication, and the control response of the closed loop control will exceed the limitation. Accordingly, it is difficult in the PI control to achieve a stable High/Low pulse operation that can gain fast rise time and fall time. (Discrete Control) As a control method for a DC/DC converter with high responsivity, there is a discrete control. FIG. 20 shows a diagram of PI control and discrete control. PI control illustrated in FIG. 20(a) calculates a manipulated variable by detecting an error between an output and a command value, so as to gradually follow the command value according to a control response frequency. By contrast, the discrete control shown in FIG. 20(b) uses a model of a main circuit of the DC/DC converter and a detection value to calculate a manipulated variable required for matching a control value with a desired value after one sample. The manipulated variable is then fed to the main circuit to carry out non-linear control for matching a command value with the control value at a next sample point. The discrete control computes a pulse width ΔT(k) for each sampling period so that a control value of the (ks+1)-th sampling period becomes equal to the desired value for a state equation obtained by expanding a circuit state with an input and an output as state variables by a discrete model, and the output is then controlled by a switching operation according to the obtained pulse width ΔT(k). In the dis