Pulse drive circuit

Abstract

To reduce ripples of a current pulse.SOLUTION: A pulse drive circuit 100 comprises: a DC voltage generation circuit 1 for generating a DC voltage that corresponds to a selected reactor current command Ci or a reactor both ends voltage command Cvl; a smoothing reactor 2; a current pulse generation circuit 4 for generating a current pulse Iout from a reactor current Il having been smoothed by the smoothing reactor 2; a reactor current control circuit 6 for outputting a reactor current command Ci on the basis of an error of the reactor current Il with respect to a reactor current target value; a reactor both ends voltage control circuit 9 for outputting a reactor both ends voltage command Cvl on the basis of an error of a voltage Vla deriving from the reactor both ends voltage detected by a reactor both ends voltage sensor 7 with respect to 0 V which is a reactor both ends voltage target value or a voltage close to prescribed 0 V; and a command selection circuit 10 for selecting a reactor current command or a reactor both ends voltage command in accordance with on / off of a current pulse.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pulse drive circuit. [Background technology]

[0002] Laser processing machines that use laser diodes (LDs) to perform processes such as cutting and marking metals are known. Such laser processing machines require a large drive current and a laser pulse with a short pulse width that matches the processing conditions. On the other hand, since laser diodes are current-driven elements, a constant-current power supply circuit that can supply a constant current of the drive current required to oscillate the laser at a desired output is used as a power supply. In such constant-current power supply circuits, a highly efficient switching power supply method is adopted, and therefore a smoothing reactor is generally used. Therefore, even if an attempt is made to output a current pulse with a short pulse width that matches the processing conditions, the response speed of the output current is slow and it does not become a square wave.

[0003] Therefore, a laser processing machine for such an application is provided with a pulse drive circuit. In this pulse drive circuit, a switching element is arranged in parallel with the laser diode, and by turning this switching element on and off, the flow path of the output current output from the constant current source is switched between the supply path to the laser diode and the feedback path to the constant current source, thereby supplying the required square wave current pulse to the laser diode with a high-speed current response (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Republished Patent Publication WO2016 / 167019 (see especially FIG. 5 and embodiment 2) Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional pulse drive circuit described above, when the pulse width of the current pulse is increased, the ripple of the current pulse becomes large, causing distortion of the waveform.

[0006] The present invention has been made to solve the above-mentioned problems, and has an object to provide a pulse drive circuit capable of improving the ripple of a current pulse. [Means for solving the problem]

[0007] In order to achieve the above object, a pulse drive circuit according to an aspect of the present disclosure includes: a DC voltage generation circuit that generates and outputs a DC voltage according to a reactor current command or a reactor voltage command selected by a command selection circuit; a smoothing reactor having one end connected to a high potential output terminal of the DC voltage generation circuit and smoothing a reactor current output from the DC voltage generation circuit; a first output terminal and a second output terminal, the second output terminal being connected to the other end of the smoothing reactor and the first output terminal being connected to a low potential output terminal of the DC voltage generation circuit, an output terminal to which a load to be driven by a current pulse is connected between the second output terminal and the first output terminal; a current pulse generating circuit that generates a current pulse from the reactor current smoothed by a reactor and outputs the current pulse to the load via the output terminal; a reactor current sensor that detects the reactor current; a reactor current control circuit that outputs a reactor current command based on an error of the reactor current detected by the reactor current sensor with respect to a reactor current target value; a voltage sensor that detects a voltage across the reactor of the smoothing reactor; and a voltage control circuit that outputs a voltage command across the reactor based on an error of a voltage derived from a voltage across the reactor detected by the voltage sensor with respect to a target value of a voltage across the reactor of 0 V or a voltage close to a predetermined 0 V; and the command selection circuit that receives the pulse signal from an external source, selects and outputs the reactor current command during the current pulse on period, and selects and outputs the voltage command across the reactor during the current pulse off period. Effect of the Invention

[0008] The present disclosure provides an effect of providing a pulse drive circuit capable of improving ripples in a current pulse. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing an example of a configuration of a pulse drive circuit according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a circuit diagram showing an example of a specific circuit configuration of the DC / DC conversion circuit of FIG. [Diagram 3] FIG. 3 is a circuit diagram showing an example of a specific circuit configuration of a main part of the pulse drive circuit of FIG. [Figure 4] FIG. 4 is a circuit diagram showing an example of a specific circuit configuration of a control system of the pulse drive circuit of FIG. [Diagram 5] FIG. 5 is a waveform diagram showing the results of an operation simulation of a pulse drive circuit that performs only feedback control of the reactor current in a DC / DC conversion circuit when the frequency of the current pulse is 1 kHz. [Figure 6] FIG. 6 is a waveform diagram showing the results of an operation simulation of a pulse drive circuit that performs only feedback control of the reactor current in a DC / DC conversion circuit when the frequency of the current pulse is 10 kHz. [Figure 7] FIG. 7 is a waveform diagram showing the results of an operation simulation of a pulse drive circuit that performs only feedback control of the reactor current in a DC / DC conversion circuit when the frequency of the current pulse is 50 kHz. [Figure 8] FIG. 8 is a waveform diagram showing the results of an operation simulation of a pulse driving circuit that performs feedback control of the voltage across a reactor during the off period of the current pulse and feedback control of the reactor current during the on period of the current pulse when the frequency of the current pulse is 1 kHz in a DC / DC conversion circuit. [Figure 9] FIG. 9 is a waveform diagram showing the results of an operation simulation of a pulse driving circuit that performs feedback control of the voltage across a reactor during the off period of the current pulse and feedback control of the reactor current during the on period of the current pulse when the frequency of the current pulse is 10 kHz in a DC / DC conversion circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A pulse drive circuit according to an aspect of the present disclosure includes: a DC voltage generation circuit that generates and outputs a DC voltage according to a reactor current command or a reactor end voltage command selected by a command selection circuit; a smoothing reactor having one end connected to a high potential output terminal of the DC voltage generation circuit and smoothing a reactor current output from the DC voltage generation circuit; a first output terminal and a second output terminal, the second output terminal being connected to the other end of the smoothing reactor and the first output terminal being connected to a low potential output terminal of the DC voltage generation circuit, an output terminal to which a load to be driven by a current pulse is connected between the second output terminal and the first output terminal; The smoothing reactor includes a current pulse generating circuit that generates a current pulse from the smoothed reactor current and outputs the current pulse to the load via the output terminal, a reactor current sensor that detects the reactor current, a reactor current control circuit that outputs a reactor current command based on an error of the reactor current detected by the reactor current sensor with respect to a reactor current target value, a voltage sensor that detects a voltage across the reactor of the smoothing reactor, a voltage control circuit that outputs a voltage command across the reactor based on an error of a voltage derived from a voltage across the reactor detected by the voltage sensor with respect to a target value of a voltage across the reactor, which is 0V or a voltage close to a predetermined 0V, and the command selection circuit that receives the pulse signal from an external source, selects and outputs the reactor current command during the current pulse on period, and selects and outputs the voltage command across the reactor during the current pulse off period. Here, the technical meaning of "a voltage close to 0V or a predetermined 0V" will be described.In the feedback control of the voltage across the reactor, the ideal target value of the voltage across the reactor is 0V when the resistance component of the smoothing reactor is 0Ω (for example, when the smoothing reactor is in a superconducting state), and when the resistance component of the smoothing reactor is not 0Ω, it is a voltage equivalent to the voltage drop due to the resistance component of the smoothing reactor (hereinafter referred to as the resistance drop voltage). However, since the resistance drop voltage varies depending on the magnitude of the reactor current, in reality, the target value of the voltage across the reactor cannot be set to an ideal voltage value, and the target value of the voltage across the reactor is set to a second-best voltage value. Therefore, the target value of the voltage across the reactor is set to 0V or a second-best voltage value, taking into account the resistance component of the smoothing reactor and the range of change in the reactor current. This 0V or second-best voltage value is "a voltage close to 0V or a predetermined 0V." The more the target voltage value across the reactor deviates from the ideal voltage value, the less effective the feedback control becomes in matching the output energy of the DC voltage generation circuit with the energy consumed by the load (here, the internal resistance of the constant current source) when the load on the constant current source (DC voltage generation circuit + smoothing reactor) suddenly decreases. "0V or a voltage close to a specified 0V" can be obtained by design, experiment, simulation, etc.

[0011] According to the above configuration, in the DC voltage generating circuit, feedback control of the reactor current is performed during the current pulse ON period, but feedback control of the voltage across the reactor is performed during the current pulse OFF period.

[0012] First, when the feedback control shifts from the current pulse on period to the current pulse off period, the load voltage of the constant current source becomes 0V due to the off of the current pulse. This is because the current pulse generating circuit shorts between the second output terminal and the first output terminal, and the first output terminal is connected to the low potential output terminal of the DC / DC conversion circuit. Then, in the smoothing reactor, the output voltage of the DC voltage generating circuit is applied to the terminal on the DC voltage generating circuit side, and the potential on the load side becomes 0V. On the other hand, in the feedback control of the voltage across the reactor, since the target value of the voltage across the reactor is 0V or a voltage close to a predetermined 0V, in the DC voltage generating circuit, the output voltage is reduced toward 0V or a voltage close to the predetermined 0V by the feedback control so that the voltage across the reactor becomes 0V or a voltage close to the predetermined 0V. On the other hand, in this process, the DC voltage generating circuit is controlled to substantially maintain the current reactor current. This is because when the reactor current changes, a potential difference due to an induced voltage occurs across the smoothing reactor. As a result, the DC voltage generating circuit performs feedback control so that the output voltage is approximately 0 V, which is the voltage required for the reactor current to substantially maintain the current value (reactor current target value in the feedback control of the reactor current). As a result, the output energy of the DC voltage generating circuit is quickly made to match the energy consumed by the load (here, the internal resistance of the constant current source).

[0013] Next, when the feedback control shifts from the current pulse off period to the current pulse on period, when the load voltage becomes a predetermined voltage (for example, 120 V, which is the rated load voltage of the load) due to the on of the current pulse, the reactor current output from the DC voltage generating circuit is suddenly reduced. Here, if the feedback control of the reactor current is performed for the DC voltage generating circuit during the current pulse off period, the reactor current output from the DC voltage generating circuit is in a state in which it is increased above the reactor current target value at the end of the current pulse off period, and therefore, when the current pulse on period is entered, the DC voltage generating circuit is feedback controlled to increase the reactor current until the reactor current output from the DC voltage generating circuit falls below the reactor current target value. Therefore, the DC voltage generating circuit cannot be feedback controlled immediately so that the reactor current becomes the reactor current target value. However, according to the above configuration, feedback control of the voltage across the reactor is performed for the DC voltage generating circuit during the current pulse off period, and the reactor current is substantially controlled to the reactor current target value. Therefore, when the current pulse on period is entered, the reactor current detected by the reactor current sensor substantially decreases from the reactor current target value, and the DC voltage generating circuit is immediately feedback controlled so that the reactor current becomes the reactor current target value. This allows the output energy of the DC voltage generating circuit to quickly match the energy consumed by the load. In this way, the output energy of the DC voltage generating circuit is quickly matched to the energy consumed by the load (the internal resistance of the constant current source or the load driven by the current pulse) during the current pulse off period and the current pulse on period, and as a result, the action of the smoothing reactor is suppressed and the ripple of the current pulse is fundamentally improved.

[0014] The 0V or a predetermined voltage close to 0V may be a voltage within 5% of the rated output voltage of the pulse drive circuit. The rated output voltage of the pulse drive circuit is a rated value of the voltage output from the output terminal, and is set to, for example, a rated load voltage of a load assumed to be connected to the output terminal of the pulse drive circuit. The voltage within 5% of the rated output voltage of the pulse drive circuit is a voltage in a range whose lower limit is 0V and whose upper limit is 5% of the rated output voltage of the pulse drive circuit. The absolute value of the voltage across the reactor can become the rated output voltage of the pulse drive circuit at the moment when the load of the constant current source is suddenly decreased, when feedback control of the voltage across the reactor is started. Therefore, a voltage of 5% of the rated output voltage of the pulse drive circuit can be said to be a voltage close to 0V as a target value of the voltage across the reactor in feedback control of the voltage across the reactor.

[0015] According to this configuration, when the load of the constant current source suddenly decreases, the output energy of the DC voltage generating circuit can be suitably matched to the energy consumed by the load (here, the internal resistance of the constant current source) by feedback control of the voltage across the reactor.

[0016] the DC voltage generating circuit is a DC / DC conversion circuit that generates and outputs a PWM-controlled square wave DC voltage from a DC voltage input from a DC power source using one or more switching elements that are turned on / off in response to a PWM signal, the smoothing reactor is a reactor having one end connected to a high potential output end of the DC / DC conversion circuit and smoothing a reactor current output from the DC / DC conversion circuit, the first output end of the output end is connected to a low potential output end of the DC / DC conversion circuit, and the pulse current generating circuit is The pulse signal may be input from a control device, the reactor current control circuit may receive the reactor current target value from the control device, the pulse signal may be input from the control device to the command selection circuit, and the pulse drive circuit may include a PWM signal generation circuit that generates one or more PWM signals corresponding to the one or more switching elements in response to the output current command or the reactor voltage command from the command selection circuit and outputs the one or more PWM signals to the one or more switching elements, respectively.

[0017] According to this configuration, the DC / DC conversion circuit generates a PWM-controlled rectangular wave DC voltage using one or more switching elements that are turned on / off in response to a PWM signal generated in response to a reactor current command or a reactor-end voltage command, so that a DC voltage in response to a reactor current command or a reactor-end voltage command can be efficiently generated.

[0018] The inverter may further include a voltage averaging circuit that generates and outputs a voltage obtained by averaging the voltage across the smoothing reactor detected by the reactor voltage sensor as a voltage derived from the voltage across the smoothing reactor detected by the reactor voltage sensor, and the reactor voltage control circuit may be a circuit that outputs the reactor voltage command based on an error between the voltage output from the voltage averaging circuit and the target voltage value. With this configuration, an accurate reactor voltage command can be output.

[0019] Hereinafter, specific embodiments of the present disclosure will be described with reference to the drawings. In addition, the same or corresponding elements are given the same reference numerals throughout all the drawings below, and their repeated description will be omitted. In addition, since the following drawings are for explaining the present disclosure, elements unrelated to the present disclosure may be omitted, dimensions may be inaccurate due to exaggeration, or may be simplified, and the shapes of corresponding elements in multiple drawings may not match. In addition, in the specification and claims, the fact that an electric circuit is electrically connected may be abbreviated as simply "connected". In addition, the present disclosure is not limited to the following embodiments.

[0020] (Embodiment) In the embodiment of the present disclosure, the DC voltage generating circuit is configured with a DC / DC conversion circuit, and a pulse signal and a reactor current target value are input to the pulse driving circuit from a control device external to the pulse driving circuit.

[0021] [composition] Fig. 1 is a block diagram showing an example of a configuration of a pulse drive circuit according to an embodiment of the present disclosure. Referring to Fig. 1, the pulse drive circuit 100 includes, as a main part, a DC / DC conversion circuit 1, which is an example of a DC voltage generation circuit, a smoothing reactor 2, an output terminal 3, and a current pulse generation circuit 4. Furthermore, the pulse drive circuit 100 includes, as a control system, a reactor current sensor 5, a reactor current control circuit 6, a reactor voltage sensor 7, a voltage averaging circuit 8, a reactor voltage control circuit 9, a command selection circuit 10, and a PWM signal generation circuit 11.

[0022] These elements are explained in more detail below.

[0023] <Rated output voltage of the pulse driving circuit 100> The rated output voltage of the pulse drive circuit 100 is the rated value of the voltage output from the output terminal 3, and is set to, for example, the rated load voltage of the load 32 assumed to be connected to the output terminal 3 of the pulse drive circuit 100.

[0024] <DC / DC conversion circuit 1> A DC voltage is input from a DC power supply 31 to a pair of input terminals 1c, 1d of the DC / DC conversion circuit 1. The DC / DC conversion circuit 1 generates a PWM-controlled square-wave DC voltage from this DC voltage using one or more switching elements that are turned on and off according to a PWM signal Spwm, and outputs this from a pair of low-potential output terminal 1a and high-potential output terminal 1b. The DC / DC conversion circuit 1 may be capable of generating a PWM-controlled square-wave DC voltage. Examples of the DC / DC conversion circuit 1 include a combination of a full-bridge or half-bridge inverter and a rectifier circuit, a step-down chopper, and the like. The DC power supply 31 is not particularly limited as long as it can output a DC voltage.

[0025] 2 is a circuit diagram showing an example of a specific circuit configuration of the DC / DC conversion circuit 1 of FIG. 1. Referring to FIG. 2, the DC / DC conversion circuit 1 is composed of a full-bridge inverter 41, a transformer 42 and a pair of rectifier elements 43 that constitute a two-phase half-wave rectifier circuit. This configuration is well known, so it will be briefly described. A DC voltage is input from the DC power source 31 of FIG. 1 to a pair of input terminals 1c, 1d of the inverter 41. In addition, four PWM signals Spwm are input to each of the four switching elements Q1 to Q4. In response to this PWM signal Spwm, a set of switching elements Q1 and Q2 and a set of switching elements Q3 and Q4 are alternately turned on, thereby generating a rectangular wave AC voltage having a pulse width according to the PWM signal Spwm, and this AC voltage is input to the primary winding of the transformer 42. A center tap is provided on the secondary winding of the transformer 42, and this center tap is connected to the low potential output terminal 1a of the DC / DC conversion circuit 1, and both ends of the secondary winding are connected to the anodes of the pair of rectifier elements 43, the diodes D1 and D2, respectively, and the cathodes of the pair of diodes D1 and D2 are connected to the high potential output terminal 1b of the DC / DC conversion circuit 1. As a result, the square wave AC voltage input to the primary winding of the transformer 42 is transformed according to the turn ratio and output as a two-phase square wave AC voltage between both ends of the secondary winding and the center tap. The two-phase square wave AC voltage is rectified by the pair of diodes D1 and D2, respectively, and a square wave full-wave rectified DC voltage having a pulse width according to the PWM signal Spwm is output from the low potential output terminal 1a and the high potential output terminal 1b of the DC / DC conversion circuit 1.

[0026] 3 is a circuit diagram showing an example of a specific circuit configuration of the main part of the pulse drive circuit of FIG. 1. Referring to FIG. 3, the DC / DC conversion circuit 1 is configured to include a switching element Q5 and a freewheeling diode D3 as another example of a specific circuit configuration. A high-potential side main terminal (here, the collector of the IGBT) of the switching element Q5 is connected to a high-potential output terminal of a constant voltage source 51, and a low-potential side main terminal (here, the emitter of the IGBT) of the switching element Q5 is connected to a smoothing reactor 2. A PWM signal Spwm is input to a control terminal (here, the gate of the IGBT) of the switching element Q5. A cathode of the freewheeling diode D3 is connected to a low-potential side main terminal of the switching element Q5, and an anode of the freewheeling diode D3 is connected to a low-potential output terminal of the constant voltage source 51. Therefore, the anode of the freewheeling diode D3 corresponds to the low potential output terminal 1a of the DC / DC conversion circuit 1, and the cathode of the freewheeling diode D3 corresponds to the high potential output terminal 1b of the DC / DC conversion circuit 1.

[0027] The constant voltage source 51 is similar to the DC power source 31 in FIG. 1, and it is sufficient if it can output a DC voltage.

[0028] The switching element Q5 is configured with a transistor such as a FET, a bipolar transistor, an IGBT, etc. Here, the switching element Q5 is configured with an IGBT.

[0029] The switching element Q5, the freewheel diode D3, and the smoothing reactor 2 constitute a step-down chopper. The switching element Q5 turns on and off in response to the PWM signal Spwm input to the control terminal, thereby generating a square-wave DC voltage having a pulse width in response to the PWM signal Spwm from the DC voltage input from the constant voltage source 51, and outputs this to the smoothing reactor 2. The smoothing reactor 2 generates a voltage in response to the on and off of the switching element Q5. As a result, during the on period of the switching element Q5, a current is supplied to the load side by the constant voltage source 51, and during the off period of the switching element Q5, a current is supplied to the load side by the smoothing reactor 2 through the freewheel diode D3.

[0030] <Smoothing reactor 2> 1, one end of the smoothing reactor 2 is connected to the high potential output terminal 1b of the DC / DC conversion circuit 1, and the other end is connected to the second output terminal 3b. Referring to Fig. 3, in an example of a specific circuit configuration of a main part of the pulse drive circuit 100, one end of the smoothing reactor 2 is connected to the low potential side main terminal of the switching element Q5, and the other end is connected to the second output terminal 3b.

[0031] The smoothing reactor 2, as part of the constant current source, serves to smooth out fluctuations in the reactor current (hereinafter sometimes simply referred to as the "reactor current") output from the DC / DC conversion circuit 1, which are caused by the PWM signal Spwm, and also serves to smooth out fluctuations in the reactor current, which are caused by current pulse generation.

[0032] It is preferable that the inductance value of the smoothing reactor 2 is large, but since an increase in inductance value increases the size of the smoothing reactor 2, the magnitude of the inductance value of the smoothing reactor 2 is restricted by the installation space of the smoothing reactor 2 in the device in which the pulse drive circuit 100 is mounted. Therefore, an appropriate inductance value of the smoothing reactor 2 is selected in consideration of the installation space of the smoothing reactor 2 in the device in which the pulse drive circuit 100 is mounted. In this case, the carrier frequency of the PWM signal Spwm is much higher than the pulse frequency of the current pulse (the frequency of the pulse signal), so that the fluctuation in the reactor current caused by the PWM signal Spwm is sufficiently smoothed.

[0033] <Output terminal 3> 2 and 3, the output terminal 3 includes a first output terminal 3a and a second output terminal 3b. The first output terminal 3a is a low potential output terminal, and is grounded in an example of a specific circuit configuration of the main part of the pulse driving circuit 100. The second output terminal 3b is a high potential output terminal. A load 32 is connected between the first output terminal 3a and the second output terminal 3b.

[0034] The load 32 is a load that is driven by a current pulse. Examples of the load 32 include a laser diode and a light emitting diode.

[0035] <Current pulse generating circuit 4> 1, the current pulse generating circuit 4 is connected between the first output terminal 3a and the second output terminal 3b. A pulse signal Spls is input from the control device 33 to the current pulse generating circuit 4.

[0036] The control device 33 is, for example, a device that controls a processing machine that performs processing using the elements of the load 32. The control device 33 includes a processor Pr and a memory Me. That is, the control device 33 has a hardware control circuitry configured with the processor Pr and the memory Me. A processing program is stored in the memory Me, and the processor Pr reads out the processing program from the memory Me and executes the processing program. This causes the control device 33 to operate as follows. The control device 33 controls the processing machine according to the processing program, and outputs a pulse signal Spls to the pulse drive circuit 100 as part of the control. In addition, the control device 33 outputs a reactor current target value Ilset to the pulse drive circuit 100, as described later. The pulse signal Spls is, for example, a binary signal (see the waveform diagrams in the 10th row of FIG. 5 to FIG. 9) that alternates between a low-level section that represents a current pulse on period in which a current pulse is output (the current pulse is on) and a high-level section that represents a current pulse off period in which a current pulse is not output (the current pulse is off). The pulse signal Spls may be a binary signal that alternates between a high-level section representing a current pulse on period and a low-level section representing a current pulse off period. In this case, the circuit to which the pulse signal Spls is input may be configured to perform an operation to be performed during the current pulse on period and an operation to be performed during the current pulse off period in the high-level section and the low-level section of the pulse signal Spls, respectively.

[0037] The current pulse generating circuit 4 shorts the second output terminal 3b and the first output terminal 3a during the current pulse off period, and opens the second output terminal 3b and the first output terminal 3a during the current pulse on period, thereby generating a current pulse from the reactor current Il smoothed by the smoothing reactor 2. This current pulse is output to the load 32 via the output terminal 3. Therefore, this current pulse is the output current Iout.

[0038] 3, in one example of a specific circuit configuration of the main part of the pulse drive circuit 100, the current pulse generation circuit 4 includes a switching element Q6 having a high potential side main terminal (here, the drain of an N-channel FET) connected to the second output terminal 3b and a low potential side main terminal (here, the source of an N-channel FET) connected to the first output terminal 3a. A pulse signal Spls is input from the control device 33 to a control terminal (here, the gate of the N-channel FET) of the switching element Q6 via a drive circuit (not shown). A snubber circuit is connected in parallel with the switching element Q6.

[0039] The switching element Q6 is composed of a transistor such as a FET, a bipolar transistor, an IGBT, etc. Here, the switching element Q6 is composed of an N-channel FET. Here, the snubber circuit is composed of a high-pass filter in which a resistor R1 and a capacitor C1 are connected in series.

[0040] When a high-level pulse signal Spls is input to a control terminal of the switching element Q6, the switching element Q6 turns on and shorts the second output terminal 3b and the first output terminal 3a. As a result, the reactor current Il output from the high-potential output terminal 1b (cathode of the freewheel diode D3) of the DC / DC conversion circuit 1 returns to the low-potential output terminal 1a (anode of the freewheel diode D3) of the DC / DC conversion circuit 1 through the smoothing reactor 2 and the switching element Q6. When a low-level pulse signal Spls is input to a control terminal of the switching element Q6, the switching element Q6 turns off and opens the second output terminal 3b and the first output terminal 3a. As a result, the reactor current output from the high potential output terminal 1b (cathode of the freewheel diode D3) of the DC / DC conversion circuit 1 passes through the smoothing reactor 2, the second output terminal 3b, the load 32, and the first output terminal 3a and returns to the low potential output terminal 1a (anode of the freewheel diode D3) of the DC / DC conversion circuit 1. In this manner, a current pulse is generated by the current pulse generating circuit 4, and this is output to the load 32 via the output terminal 3.

[0041] <Reactor current sensor 5> 1 and 3, the reactor current sensor 5 is disposed in a portion of the flow path of the reactor current Il between the high potential output terminal 1b of the DC / DC conversion circuit 1 and the connection point Nd between the second output terminal 3b and the current pulse generating circuit 4. The reactor current sensor 5 detects the reactor current Il in the portion between the high potential output terminal 1b and the connection point Nd between the second output terminal 3b and the current pulse generating circuit 4, and outputs the detected reactor current Ild. Examples of the reactor current sensor 5 include a resistance type sensor, a Hall element type sensor, and a magnetic impedance type sensor.

[0042] <Reactor current control circuit 6> Referring to FIG. 1, the reactor current control circuit 6 is an error amplification circuit for the reactor current Il, and outputs a reactor current command Ci based on the error of the reactor current Ild detected by the reactor current sensor 5 relative to a reactor current target value Ilset input from the control device 33.

[0043] Fig. 4 is a circuit diagram showing an example of a specific circuit configuration of the control system of the pulse drive circuit 100 of Fig. 1. Referring to Fig. 4, in an example of a specific circuit configuration of the control system of the pulse drive circuit 100, the reactor current control circuit 6 is configured as an arithmetic circuit including an operational amplifier 52. The non-inverting input terminal of the operational amplifier 52 is connected to the ground. Resistors R1 and R2 are connected in parallel to the inverting input terminal. A capacitor C2 is connected between the inverting input terminal and the output terminal of the operational amplifier 52, and further, a resistor R3 and a capacitor C3, which are connected in series with each other, are connected in parallel to the capacitor C2.

[0044] Therefore, in this calculation circuit, the resistors R1, R2, and the capacitor C2 form an integrating circuit for the operational amplifier 52, the resistors R1, R2, R3, and the capacitor C3 form a PI compensator, and the resistors R1 and R2 form an adding circuit. A voltage corresponding to the reactor current target value Ilset with its sign inverted is input to the resistor R1. A voltage corresponding to the reactor current Ild detected by the reactor current sensor 5 is input to the resistor R2. As a result, the difference between the detected reactor current Ild and the reactor current target value Ilset is amplified, imperfectly integrated, and inverted, and output from the operational amplifier 52. In other words, the error of the detected reactor current Ild with respect to the reactor current target value Ilset is PI controlled and output from the operational amplifier 52 as a reactor current command Ci.

[0045] <Voltage sensor 7 at both ends of reactor> 1 and 3, the reactor voltage sensor 7 detects the voltage Vl across the smoothing reactor 2 and outputs the detected voltage Vld (hereinafter, referred to as the detected reactor voltage). Examples of the reactor voltage sensor 7 include a resistance type sensor and a capacitor type sensor.

[0046] <Both-end voltage averaging circuit 8> 1, the both-ends voltage averaging circuit 8 generates and outputs a voltage (hereinafter referred to as averaged reactor both-ends voltage) Vla obtained by averaging the detected reactor both-ends voltage Vld of the smoothing reactor 2 detected by the reactor both-ends voltage sensor 7. Referring to FIG. 4, in one example of a specific circuit configuration of the control system of the pulse drive circuit 100, the both-ends voltage averaging circuit 8 includes resistors R4, R5, and a capacitor C4. The high potential end of the resistor R4 is connected to the on-off switch 53, and the other end of the resistor R4 is connected to the ground. A resistor R5 and a capacitor C4, which are connected in series to each other, are connected to both ends of the resistor R4. The connection point between the resistor R5 and the capacitor C4 is connected to a resistor R7, which is an input element of the reactor both-ends voltage control circuit 9.

[0047] The on-off switch 53 receives the pulse signal Spls from the control device 33 and the detection reactor voltage Vld detected by the reactor voltage sensor 7. When a high-level pulse signal Spls indicating a current pulse off period is input, the on-off switch 53 turns on and inputs the detection reactor voltage Vld to the high potential end of resistor R4, and when a low-level pulse signal Spls indicating a current pulse on period is input, the on-off switch 53 turns off and stops the input of the detection reactor voltage Vld. Meanwhile, resistor R5 and capacitor C4 form a low-pass filter, and the detection reactor voltage Vld input to resistor R4 is averaged (smoothed) by this low-pass filter, and the averaged reactor voltage Vla is input to resistor R7, which is an input element of the reactor voltage control circuit 9.

[0048] <Reactor voltage control circuit 9> 1, the reactor voltage control circuit 9 is an error amplifier circuit for the reactor voltage Vl, and outputs a reactor voltage command Cvl based on the error of the average reactor voltage Vla averaged by the reactor voltage averaging circuit 8 with respect to the reactor voltage target value Vlset. The reactor voltage target value Vlset is stored in a reactor voltage target value storage unit 22. The reactor voltage target value storage unit 22 is composed of elements such as an appropriate circuit or memory.

[0049] 4, the reactor voltage control circuit 9 includes a constant voltage source 54 and an arithmetic circuit including an operational amplifier 55 in an example of a specific circuit configuration of the control system of the pulse drive circuit 100. The voltage of the constant voltage source 54 is set to a predetermined reactor voltage target value Vlset. Therefore, the constant voltage source 54 constitutes the reactor voltage target value storage unit 22 in FIG. 1. The reactor voltage target value Vlset is set to "0V or a voltage close to a predetermined 0V". The reactor voltage target value Vlset is set to 0V or a second best voltage value in consideration of the resistance component of the smoothing reactor 2 and the range of change of the reactor current Il. This 0V or second best voltage value is "0V or a voltage close to a predetermined 0V". The more the target value Vlset of the voltage across the reactor deviates from the ideal voltage value, the less the function of the feedback control of the voltage Vl across the reactor to match the output energy of the DC / DC conversion circuit 1 with the energy consumed by the load (here, the internal resistance of the constant current source) when the load of the constant current source (DC / DC conversion circuit 1 and smoothing reactor 2) suddenly decreases. The "0V or a voltage close to a predetermined 0V" is obtained by design, experiment, simulation, etc. The "0V or a voltage close to a predetermined 0V" is, for example, a voltage within 5% of the rated output voltage of the pulse drive circuit 100. The voltage within 5% of the rated output voltage of the pulse drive circuit 100 is a voltage whose lower limit is 0V and is in a range that is 5% of the rated output voltage of the pulse drive circuit 100. The absolute value of the voltage Vl across the reactor can become the rated output voltage of the pulse drive circuit 100 at the moment when the feedback control of the voltage Vl across the reactor is started and the load of the constant current source suddenly decreases. Therefore, a voltage of 5% of the rated output voltage of the pulse drive circuit 100 can be said to be a voltage close to 0 V as the target value Vlset of the voltage across the reactor in feedback control of the voltage Vl across the reactor. If the target value Vlset of the voltage across the reactor is a voltage within 5% of the rated output voltage of the pulse drive circuit 100, the output energy of the DC / DC conversion circuit 1 can be suitably matched to the energy consumed by the load by feedback control of the voltage Vl across the reactor when the load of the constant current source suddenly decreases.Here, the "0 V or a predetermined voltage close to 0 V" is set to about 50 mV (about 0.04% of the rated output voltage (for example, 120 V) of the pulse driving circuit 100).

[0050] The non-inverting input terminal of the operational amplifier 55 is connected to ground. Resistors R6 and R7 are connected in parallel to the inverting input terminal. A capacitor C5 is connected between the inverting input terminal and the output terminal of the operational amplifier 55. Furthermore, a resistor R8 and a capacitor C6, which are connected in series to each other, are connected in parallel to the capacitor C5.

[0051] Therefore, in this calculation circuit, the resistors R6, R7, and the capacitor C5 form an integrating circuit for the operational amplifier 55, the resistors R6, R7, R8, and the capacitor C6 form a PI compensator, and the resistors R6 and R7 form an adding circuit. The resistor R6 receives the target reactor voltage Vlset, the sign of which is inverted. The resistor R7 receives the averaged reactor voltage Vla, which is averaged by the voltage averaging circuit 8. As a result, the difference between the averaged reactor voltage Vla and the target reactor voltage Vlset is amplified and incompletely integrated, and is inverted and output from the operational amplifier 55. In other words, the error of the averaged reactor voltage Vla with respect to the target reactor voltage Vlset is PI controlled and output from the operational amplifier 55 as a reactor voltage command Cvl.

[0052] <Command selection circuit 10> 1, the command selection circuit 10 receives a pulse signal Spls from the control device 33, selects a reactor current command Ci during a current pulse-on period and outputs it as a selection command Cmd, and selects a reactor voltage command Cvl during a current pulse-off period and outputs it as a selection command Cmd. Referring to FIG. 4, the command selection circuit 10 is composed of a changeover switch 56 in an example of a specific circuit configuration of the control system of the pulse drive circuit 100.

[0053] A pulse signal Spls is input from the control device 33 to the switching switch 56. When a low-level pulse signal Spls representing the current pulse on period is input to the switching switch 56, the connection destination of the PWM signal generation circuit 11 is switched to the reactor current control circuit 6. Thereby, a reactor current command Ci is input from the reactor current control circuit 6 to the PWM signal generation circuit 11 as a selection command Cmd. When a high-level pulse signal Spls representing the current pulse off period is input to the switching switch 56, the connection destination of the PWM signal generation circuit 11 is switched to the reactor terminal voltage control circuit 9. Thereby, a reactor terminal voltage command Cvl is input from the reactor terminal voltage control circuit 9 to the PWM signal generation circuit 11 as a selection command Cmd.

[0054] <PWM signal generation circuit 11> Referring to FIG. 1, the PWM signal generation circuit 11 generates one or more PWM signals Spwm corresponding to one or more switching elements (Q1 to Q4 (see FIG. 2) or Q5 (see FIG. 3)) of the DC / DC conversion circuit 1 according to a reactor current command Ci or a reactor terminal voltage command Cvl as a selection command Cmd output from the command selection circuit 10, and outputs the one or more PWM signals Spwm to the one or more switching elements (Q1 to Q4 or Q5), respectively.

[0055] Referring to FIG. 4, in an example of a specific circuit configuration of the control system of the pulse drive circuit 100, the PWM signal generation circuit 11 includes a first PWM signal generation unit 11a and a second PWM signal generation unit 11b connected in parallel to the command selection circuit 10. This configuration is applied when the DC / DC conversion circuit 1 is configured by a circuit using the full-bridge type inverter 41 of FIG. 2.

[0056] The first PWM signal generating unit 11a includes a comparator 57, a signal source 58, an AND circuit 59, and a signal source 60. The selection command Cmd from the command selection circuit 10 is input to a non-inverting input terminal of the comparator 57. A triangular wave with a predetermined carrier frequency (for example, 200 kHz) is input to an inverting input terminal of the comparator 57 from a signal source 58 connected to the ground. As a result, a PWM signal having a pulse width according to the value of the selection command Cmd is output from the comparator 57. This PWM signal is input to one input terminal of the AND circuit 59. A first binary signal with an on-duty of 50% and a frequency (100 kHz) that is 1 / 2 the predetermined carrier frequency is input from a signal source 60 connected to the ground to the other input terminal of the AND circuit 59. As a result, during the high-level period of the first binary signal, the PWM signal from the comparator 57 is output from the AND circuit 59 as a first PWM signal Spwm.

[0057] The second PWM signal generating unit 11b includes a comparator 61, a signal source 62, an AND circuit 63, and a signal source 64. The selection command Cmd from the command selection circuit 10 is input to a non-inverting input terminal of the comparator 61. A triangular wave of the predetermined carrier frequency (200 kHz) is input to an inverting input terminal of the comparator 61 from a signal source 62 connected to the ground. As a result, a PWM signal having a pulse width according to the value of the selection command Cmd is output from the comparator 61. This PWM signal is input to one input terminal of an AND circuit 63. A second binary signal with an on-duty of 50% and a frequency (100 kHz) that is half the predetermined carrier frequency is input to the other input terminal of the AND circuit 63 from a signal source 64 connected to the ground. However, the phase of this second binary signal is delayed by 180° from the phase of the first binary signal of the first PWM signal generating unit 11a. As a result, during a high-level period of the second binary signal corresponding to a low-level period of the first binary signal, the PWM signal from the comparator 61 is output from the AND circuit 63 as a second PWM signal Spwm.

[0058] The first PWM signal Spwm and the second PWM signal Spwm are input to the pair of switching elements Q1 and Q2 and the pair of switching elements Q3 and Q4 of the DC / DC conversion circuit 1 in FIG. 2, respectively.

[0059] On the other hand, when the DC / DC conversion circuit 1 is configured as a step-down chopper of FIG. 3, the PWM signal output from the comparator 57 of the first PWM signal generating unit 11a is input as the PWM signal Spwm to the switching element Q5 of the DC / DC conversion circuit 1 of FIG. 3.

[0060] The reactor current control circuit 6, the both-end voltage averaging circuit 8, the both-end reactor voltage control circuit 9, and the command selection circuit 10 may be configured by software.

[0061] [Operation] Next, the operation of the pulse drive circuit 100 configured as above will be described with reference to Fig. 1. Referring to Fig. 1, the DC / DC conversion circuit 1 outputs a square-wave DC output voltage Vout having a pulse width according to the PWM signal Spwm input from the PWM signal generation circuit 11 from the DC voltage input from the DC power supply 31 by turning on and off one or more switching elements according to the PWM signal Spwm input from the PWM signal generation circuit 11. The smoothing reactor 2 smoothes the reactor current Il according to the square-wave DC output voltage Vout output from this DC / DC conversion circuit 1. From this smoothed reactor current Il, the current pulse generation circuit 4 generates a current pulse that is the output current Iout according to the pulse signal Spls input from the control device 33. Specifically, the current pulse generating circuit 4 generates a current pulse, which is the output current Iout, from the reactor current Il by shorting between the second output terminal 3b and the first output terminal 3a during a current pulse off period in the pulse signal Spls and opening between the second output terminal 3b and the first output terminal 3a during a current pulse on period in the pulse signal Spls.

[0062] Meanwhile, the reactor current sensor 5 detects the reactor current Il. The reactor current control circuit 6 outputs a reactor current command Ci based on the error of the reactor current Ild detected by the reactor current sensor 5 with respect to the reactor current target value Ilset input from the control device 33. Furthermore, the reactor voltage sensor 7 detects the reactor voltage Vl of the smoothing reactor 2. The reactor voltage averaging circuit 8 generates and outputs a voltage obtained by averaging the reactor voltage Vld of the smoothing reactor 2 detected by the reactor voltage sensor 7. The reactor voltage control circuit 9 outputs a reactor voltage command Cvl based on the error of the average reactor voltage Vla averaged by the reactor voltage averaging circuit 8 with respect to the reactor voltage target value Vlset. The command selection circuit 10 receives the pulse signal Spls from the control device 33, selects a reactor current command Ci during a current pulse-on period of the pulse signal Spls and outputs it as a selection command Cmd, and selects a reactor voltage command Cvl during a current pulse-off period of the pulse signal Spls and outputs it as a selection command Cmd. The PWM signal generation circuit 11 generates one or more PWM signals Spwm corresponding to one or more switching elements (Q1 to Q4 or Q5) in accordance with the reactor current command Ci or the reactor voltage command Cvl, which is the selection command Cmd from the command selection circuit 10, and inputs them to the DC / DC conversion circuit 1.

[0063] [Effects] The effects of the pulse driving circuit 100 configured and operating as described above will be described using simulation results.

[0064] {simulation} This simulation was performed for the pulse driving circuit 100 shown in Figs. 3 and 4. In this simulation, Examples 1 and 2 of the present disclosure and Comparative Examples 1 to 3 were performed. The implementation conditions are shown in Table 1. The set duty ratio of the current pulse, which is the output current Iout, is 50%. The "set output voltage value" was set to the rated output voltage of the pulse driving circuit 100 here.

[0065] [Table 1] In this simulation, the following parameters were measured: the output current Iout, which is a current pulse supplied to the load 32; the reactor current Il; the output voltage Vout1 of the DC / DC conversion circuit 1; the voltage Vout2 on the output side (the connection point Nd side between the second output terminal 3b and the current pulse generating circuit 4) of the smoothing reactor 2; the detection reactor voltage Vld, which is the detection voltage of the reactor voltage Vl (corresponding to Vout1-Vout2); the average reactor voltage Vla, which is the output voltage of the voltage averaging circuit 8; the voltage of the reactor current command Ci (the output voltage of the operational amplifier 52 in FIG. 4); the voltage of the reactor voltage command Cvl (the output voltage of the operational amplifier 55 in FIG. 4); the voltage of the selection command Cmd; and the voltage of the pulse signal Spls. The waveforms of these parameters are shown in FIG. 5 to FIG. 9.

[0066] {Waveform diagram} The waveform diagrams in Figures 5 to 9 were created by tracing the waveforms of the images output from a simulation device. In addition, the regions indicated by reference characters A to C in the waveform diagrams in the fourth and fifth rows of Figure 5 and the regions indicated by reference characters D to E in the waveform diagrams in the fourth and fifth rows of Figure 8 are areas in which pulses having an on-duty of nearly 100% are densely packed at minute intervals, and if these pulse waveforms were drawn with a solid line of normal thickness, they would be filled in with the solid line and would not be able to be drawn, so they are shown with an appropriate transparent pattern.

[0067] FIG. 5 is a waveform diagram showing the result of an operation simulation (Comparative Example 1) of a pulse drive circuit that performs only feedback control of the reactor current Il when the frequency of the current pulse is 1 kHz for the DC / DC conversion circuit 1. FIG. 6 is a waveform diagram showing the result of an operation simulation (Comparative Example 2) of a pulse drive circuit that performs only feedback control of the reactor current Il when the frequency of the current pulse is 10 kHz for the DC / DC conversion circuit 1. FIG. 7 is a waveform diagram showing the result of an operation simulation (Comparative Example 3) of a pulse drive circuit that performs only feedback control of the reactor current Il when the frequency of the current pulse is 50 kHz for the DC / DC conversion circuit 1. FIG. 8 is a waveform diagram showing the result of an operation simulation (Example 1) of a pulse drive circuit 100 that performs feedback control of the voltage Vl across the reactor during the OFF period of the current pulse and feedback control of the reactor current Il during the ON period of the current pulse when the frequency of the current pulse is 1 kHz for the DC / DC conversion circuit 1. FIG. 9 is a waveform diagram showing the results of an operation simulation (Example 2) of a pulse drive circuit 100 that performs feedback control of the voltage Vl across the reactor during the off period of the current pulse and feedback control of the reactor current Il during the on period of the current pulse when the frequency of the current pulse is 10 kHz for a DC / DC conversion circuit 1.

[0068] 5 to 9, the horizontal axis of each waveform diagram indicates time (ms) common to all the diagrams, as shown in the bottom waveform diagram, and the vertical axis of each waveform diagram indicates a physical quantity specific to each waveform diagram.

[0069] The top waveform diagram shows the waveform of the output current Iout. The vertical axis shows the current (A). The second waveform diagram shows the waveform of the output current Iout with the vertical axis scaled up. The vertical axis shows the current (A) with the scaled up. The third waveform diagram shows the waveform of the reactor current Il. The vertical axis shows the current (A) with the same scale as the second waveform diagram.

[0070] The waveform diagram in the fourth row shows waveform diagrams of the output voltage Vout1 of the DC / DC conversion circuit 1 and the voltage Vout2 on the output side of the smoothing reactor 2. The vertical axis shows voltage (V). In the waveform diagram in this row, the solid line shows the waveform diagram of the output voltage Vout1 of the DC / DC conversion circuit 1, and the dashed dotted line shows the waveform diagram of the voltage Vout2 on the output side of the smoothing reactor 2. In the waveform diagram of the output voltage Vout1 of the DC / DC conversion circuit 1, a square wave DC voltage pulse appears having a pulse width and frequency according to the pulse width and carrier frequency of the PWM signal Spwm.

[0071] The fifth waveform diagram shows the detection reactor voltage Vld (reactor voltage Vl). This waveform diagram shows the waveform of Vout1-Vout2. When the reactor voltage Vl is a positive value, the reactor voltage Vl suppresses an increase in the reactor current Il while storing energy in the smoothing reactor 2. When the detection reactor voltage Vld is a negative value, the reactor voltage Vl suppresses a decrease in the reactor current Il while storing energy in the smoothing reactor 2 while releasing stored energy.

[0072] The sixth waveform diagram shows the averaged reactor voltage Vla. The vertical axis shows voltage (V). The averaged reactor voltage Vla shows the voltage of a signal obtained by averaging the detected reactor voltage Vld, which is the reactor voltage Vl, using a low-pass filter and multiplying the gain by 1 / 25.

[0073] The seventh waveform diagram shows the waveform of the reactor current command Ci. The vertical axis indicates voltage (V). The reactor current command Ci corresponds to the on-duty of the square wave DC voltage of the DC / DC conversion circuit 1. 0V to 3V corresponds to an on-duty of 0% to 100%.

[0074] The eighth waveform diagram shows a waveform diagram of a voltage command Cvl across the reactor. The vertical axis indicates voltage (V). The voltage command Cvl across the reactor corresponds to the on-duty of the square wave DC voltage of the DC / DC conversion circuit 1. 0V to 3V corresponds to an on-duty of 0% to 100%.

[0075] The ninth waveform diagram shows the waveform diagram of the selection command Cmd. The vertical axis shows voltage (V). In Comparative Examples 1 to 3 (FIGS. 5 to 7), the selection command Cmd is always the reactor current command Ci, so the waveform diagram of the selection command Cmd is the same as the seventh waveform diagram of the reactor current command Ci. In Examples 1 and 2 (FIGS. 8 and 9), the selection command Cmd is the reactor current command Ci when the pulse signal Spls is in the current pulse on period (low level), and is the reactor voltage command Cvl when the pulse signal Spls is in the current pulse off period (high level), so the waveform diagram of the selection command Cmd is the same as the seventh waveform diagram of the reactor current command Ci when the pulse signal Spls is in the current pulse on period (low level), and is the same as the eighth waveform diagram of the reactor voltage command Cvl when the pulse signal Spls is in the current pulse off period (high level).

[0076] The tenth row shows a waveform diagram of the pulse signal Spls, which is at a low level during the current pulse ON period and at a high level during the current pulse OFF period.

[0077] {evaluation} Comparative Example 1 5, in the first and second waveform diagrams, in Comparative Example 1, a ripple of ΔI=39 A occurs in the output current Iout.

[0078] In the waveform diagram of the third stage, the reactor current Il is not sufficiently smoothed by the smoothing reactor 2 because the pulse frequency is relatively low at 1 kHz, and the waveform of this insufficiently smoothed reactor current Il during the current pulse on period appears as is in the waveform of the output current Iout, generating a ripple of ΔI = 39 A.

[0079] In the waveform diagram of the fourth stage, the voltage Vout2 (dashed line) on the output side of the smoothing reactor 2 suddenly changes between 120V and 0V between the current pulse on period and the current pulse off period. In addition, the output voltage Vout1 of the DC / DC conversion circuit 1 changes between a constant amplitude voltage and approximately 0V with a delay with respect to the change in the voltage Vout2 on the output side of the smoothing reactor 2, which is the load voltage. This means that the feedback control of the reactor current Il follows the sudden change in the load voltage with a delay. Furthermore, the output voltage Vout1 of the DC / DC conversion circuit 1 is divided into a period where pulses corresponding to the PWM signal are densely packed (area indicated by reference characters A to C) and a period where no pulses are generated at all. In the period indicated by reference characters A to C, the width of the pulse corresponding to the PWM signal is proportional to the magnitude of the reactor current command Ci in the waveform diagram of the seventh stage.

[0080] In the waveform diagrams of the fifth and sixth rows, the detection reactor voltage Vld and the averaging reactor voltage Vla are positive during the beginning of the current pulse off period. This means that the increase in the reactor current Il is suppressed by the smoothing reactor 2 during the current pulse off period.

[0081] In the waveform diagram of the seventh stage, the reactor current command Ci is generally close to a voltage corresponding to 100% on-duty during the current pulse on period, and is 0V corresponding to 0% on-duty during the current pulse off period. However, the reactor current command Ci gradually increases from 0V to a value close to the voltage corresponding to 100% on-duty with a delay from the switch from the current pulse off period to the current pulse on period, and gradually decreases from a value close to the voltage corresponding to 100% on-duty to 0V with a delay from the switch from the current pulse on period to the current pulse off period.

[0082] Taking the waveform diagrams from the 4th to 7th stages into consideration, during the current pulse off period, the reactor current Il is delayed in responding to a sudden change in the load voltage due to feedback control of the reactor current Il, so that the reactor current Il increases far beyond the reactor current target value Ilset, although the increase is suppressed by the smoothing reactor 2, and even if the reactor current command Ci becomes 0V, the reactor current Il at the end of the current pulse off period does not decrease to the reactor current target value Ilset. Also, in the steady state, the energy stored by the smoothing reactor 2 is equal to the energy released from the smoothing reactor 2, so that conversely, at the end of the current pulse on period, the reactor current Il falls below the reactor current target value Ilset. In fact, the waveform of the reactor current Il in the 2nd stage is like that.

[0083] In the eighth waveform diagram, the reactor voltage command Cvl is not output because feedback control of the reactor voltage is not performed in Comparative Example 1. Therefore, in the ninth waveform diagram, the selection command Cmd has the same waveform as the reactor current command Ci in the seventh waveform diagram.

[0084] Comparative Example 2 6, in the first and second waveform diagrams, in Comparative Example 2, a ripple of ΔI=14 A occurs in the output current Iout.

[0085] In the waveform diagram of the third stage, the reactor current Il has a relatively high pulse frequency of 10 kHz, so it is smoothed to a certain extent by the smoothing reactor 2, and the waveform of this somewhat smoothed reactor current Il during the current pulse on period appears as is in the waveform of the output current Iout, generating a ripple of ΔI = 14 A.

[0086] In the waveform diagram of the fourth stage, the voltage Vout2 (dashed line) on the output side of the smoothing reactor 2 changes suddenly between 120 V and 0 V between the current pulse-on period and the current pulse-off period. On the other hand, the pulse corresponding to the PWM signal of the output voltage Vout1 of the DC / DC conversion circuit 1 (hereinafter, sometimes referred to as the "pulse of the output voltage Vout1") has a constant amplitude regardless of the change in the voltage Vout2 on the output side of the smoothing reactor 2, which is the load voltage. However, the pulse width of the output voltage Vout1 of the DC / DC conversion circuit 1 changes in response to the change in the reactor current Il.

[0087] In the fifth waveform diagram, the detection reactor voltage Vld is negative during the current pulse ON period and positive during the current pulse OFF period. In the seventh waveform diagram, the reactor current command Ci increases monotonically during the current pulse ON period and decreases monotonically during the current pulse OFF period.

[0088] As a result, during the current pulse ON period, the decrease in the reactor current Il is suppressed by the voltage Vl across the reactor, and during the current pulse OFF period, the increase in the reactor current Il is suppressed by the voltage Vl across the reactor.

[0089] To summarize the above, in Comparative Example 2, since the pulse frequency is relatively high at 10 kHz, the feedback control of the reactor current Il cannot follow the sudden change in the load voltage at all, and it is clear that the reactor current Il, which fluctuates due to the sudden change in the load voltage, is smoothed only by the smoothing reactor 2.

[0090] Comparative Example 3 Referring to FIG. 7, in the first and second waveform diagrams, in Comparative Example 3, almost no ripple occurs in the output current Iout.

[0091] In the waveform diagram of the fourth stage, the voltage Vout2 (dashed line) on the output side of the smoothing reactor 2 changes suddenly between 120 V and 0 V between the current pulse on period and the current pulse off period. On the other hand, the pulse of the output voltage Vout1 of the DC / DC conversion circuit 1 has a nearly constant amplitude and width regardless of changes in the voltage Vout2 on the output side of the smoothing reactor 2, which is the load voltage.

[0092] In the fifth waveform diagram, the detection reactor voltage Vld is negative during the current pulse ON period and positive during the current pulse OFF period. In the seventh waveform diagram, the reactor current command Ci increases slightly monotonically during the current pulse ON period and decreases slightly monotonically during the current pulse OFF period.

[0093] As a result, during the current pulse ON period, the decrease in the reactor current Il is slightly suppressed by the voltage Vl across the reactor, and during the current pulse OFF period, the increase in the reactor current Il is slightly suppressed by the voltage Vl across the reactor.

[0094] To sum up the above, in Comparative Example 3, since the pulse frequency is remarkably high at 50 kHz, the feedback control of the reactor current Il cannot keep up with the sudden change in the load voltage at all, and therefore it is clear that the reactor current Il, which fluctuates due to the sudden change in the load voltage, is almost completely smoothed out by only the smoothing reactor 2.

[0095] Example 1 8, in the first and second waveform diagrams, a ripple of ΔI=3.0 A occurs in the output current Iout in Example 1. This is a marked improvement in ripple compared to Comparative Examples 1 and 2.

[0096] In the waveform diagram of the third stage, the reactor current Il is almost constant. The waveform of this almost constant reactor current Il during the current pulse on period appears as it is in the waveform of the output current Iout, generating an improved ripple of ΔI=3.0A.

[0097] In the waveform diagram of the fourth stage, the voltage Vout2 (dotted line) on the output side of the smoothing reactor 2 changes suddenly between 120V and 0V between the current pulse on period and the current pulse off period. On the other hand, the pulse of the output voltage Vout1 of the DC / DC conversion circuit 1 has a waveform of the period indicated by reference character D during the current pulse on period in accordance with the change in the voltage Vout2 on the output side of the smoothing reactor 2, which is the load voltage, and changes to have a waveform having a constant amplitude and a very thin width having an on-duty close to 0% during the current pulse off period. During the period indicated by reference character D, the pulse of the output voltage Vout1 of the DC / DC conversion circuit 1 has a constant amplitude and a width corresponding to a value (magnitude) close to the voltage corresponding to the 100% on-duty of the selection command Cmd (reactor current command Ci) shown in the waveform diagram of the ninth stage. As a result, the output voltage Vout1 of the DC / DC conversion circuit 1 becomes 120V, which is the set output voltage, during the current pulse on period, and becomes almost 0V during the current pulse off period.

[0098] In the fifth waveform diagram, the voltage Vld across the detection reactor has a waveform in the period indicated by reference character E during the current pulse on period, and has a waveform in the current pulse off period that has an amplitude that is approximately 0 V smaller than the waveform in the current pulse off period of the fourth waveform diagram. In the period indicated by reference character E, the pulse of the output voltage Vout1 of the DC / DC conversion circuit 1 has an amplitude that is the same as that in the period indicated by reference character D in the fourth waveform diagram, but has an amplitude that is reduced by "120 V" and has inverted polarity.

[0099] In the waveform diagram in the sixth stage, the averaging reactor voltage Vla is nearly 0V. This means that the smoothing of the reactor current Il by the smoothing reactor 2 is hardly working. This is natural because during the current pulse off period, the reactor voltage Vl is controlled to be "0V or a predetermined voltage close to 0V" by feedback control of the reactor voltage Vl. However, even during the current pulse off period, the averaging reactor voltage Vla is nearly 0V, even though feedback control of the reactor voltage Vl is not performed, which has an interesting technical significance.

[0100] In the seventh waveform diagram, the reactor current command Ci has a constant value (magnitude) that is approximately close to the voltage corresponding to an on-duty of 100%.

[0101] In the waveform diagram of the eighth stage, the reactor voltage command Cvl has a value close to 0V during the current pulse off period, and has a voltage value corresponding to an on-duty of about 30% during the current pulse on period. This phenomenon is not desirable, but since the reactor voltage command Cvl is not output as the selection command Cmd during the current pulse on period, this phenomenon does not affect the ripple of the output current Iout. Therefore, this phenomenon can be ignored. However, the cause will be explained for the time being. During the current pulse on period, the on-off switch 53 is turned off, so the detected reactor voltage Vld is not input to the voltage averaging circuit 8. On the other hand, the charge of the capacitor C4 is discharged through the resistors R4 and R5, so that the average reactor voltage Vla falls below the reactor voltage target value Vlset, which is a "predetermined voltage close to 0V," and as a result, the reactor voltage command Cvl gradually rises. This is the cause of the above phenomenon. In order to fundamentally eliminate this phenomenon, for example, the both-end voltage averaging circuit 8 and the both-end reactor voltage control circuit 9 can be configured using software, and during the current pulse ON period, the previous averaged both-end reactor voltage Vla can be stored and output.

[0102] In the waveform diagram of the ninth stage, the selection command Cmd has a constant value close to the voltage corresponding to 100% on-duty of the reactor current command Ci of the seventh stage during the current pulse on period, and has a value close to approximately 0V of the reactor voltage command Cvl of the eighth stage during the current pulse off period. As a result, as described above, the pulse of the output voltage Vout1 of the DC / DC conversion circuit 1 has a waveform that has a relatively wide width during the current pulse on period and an extremely narrow width during the current pulse off period, whereby the output voltage Vout1 of the DC / DC conversion circuit 1 becomes the set output voltage of 120V during the current pulse on period and becomes "approximately 0V" required to maintain the reactor current target value Ilset during the current pulse off period.

[0103] Example 2 Example 2 is similar to Example 1 except that the pulse frequency is relatively higher than that of Example 1. However, since the pulse frequency is relatively higher than that of Example 1, the effect of the present disclosure is clear.

[0104] 9, in the first and second waveform diagrams, a ripple of ΔI=1.5 A occurs in the output current Iout in Example 2. This is a marked improvement in ripple compared to Comparative Examples 1 and 2.

[0105] In the waveform diagram of the fourth stage, the voltage Vout2 (dashed line) on the output side of the smoothing reactor 2 changes suddenly between 120V and 0V between the current pulse on period and the current pulse off period. Meanwhile, the pulse of the output voltage Vout1 of the DC / DC conversion circuit 1 changes to have a waveform that has a constant amplitude and a relatively wide width during the current pulse on period, and has a constant amplitude, a very thin width, and a relatively long pulse interval during the current pulse off period, in accordance with the change in the voltage Vout2 on the output side of the smoothing reactor 2, which is the load voltage. As a result, the output voltage Vout1 of the DC / DC conversion circuit 1 becomes the set output voltage of 120V during the current pulse on period, and becomes approximately 0V during the current pulse off period.

[0106] In the fifth waveform diagram, during the current pulse on period, the voltage Vld across the detection reactor has the same width as the pulse of the output voltage Vout1 in the fourth waveform diagram, and an amplitude with "120 V" subtracted and the polarity reversed, and during the current pulse off period, the waveform has an amplitude that is approximately 0 V smaller than the waveform in the current pulse off period in the fourth waveform diagram.

[0107] The sixth to eighth waveform diagrams are generally similar to those in the second embodiment.

[0108] In the waveform diagram of the ninth stage, the selection command Cmd has a constant value close to the voltage corresponding to 100% on-duty of the reactor current command Ci of the seventh stage during the current pulse on period, and has a value close to approximately 0V of the reactor voltage command Cvl of the eighth stage during the current pulse off period. As a result, as described above, the pulse of the output voltage Vout1 of the DC / DC conversion circuit 1 has a waveform that has a relatively wide width during the current pulse on period and an extremely thin width and a relatively long pulse interval during the current pulse off period, whereby the output voltage Vout1 of the DC / DC conversion circuit 1 becomes the set output voltage of 120V during the current pulse on period and becomes approximately 0V during the current pulse off period.

[0109] {Causes of current pulse ripple} From the results of Comparative Examples 1 to 3, the following can be concluded. In the pulse drive circuit 100, when viewed from the constant current source (DC / DC conversion circuit 1 and smoothing reactor 2), the load voltage changes significantly and suddenly between a predetermined voltage (for example, 120V) and 0V due to the on / off of the current pulse, which is the output current Iout. In this case, a mismatch occurs between the output energy of the DC / DC conversion circuit 1 and the energy consumed by the load (the internal resistance of the constant current source or the load 32. Hereinafter, this may be simply referred to as the "load"), and if this mismatch is not resolved, the smoothing reactor 2 balances the output energy of the DC / DC conversion circuit 1 and the energy consumed by the load by storing and releasing energy equivalent to the mismatch. In the energy balancing action of this smoothing reactor 2, the reactor current Il output from the DC / DC conversion circuit 1 is smoothed, but the waveform of this smoothed reactor current Il appears as a ripple in the current pulse, which is the output current Iout.

[0110] Here, as in Comparative Examples 1 to 3, if only feedback control of the reactor current Il is performed for the DC / DC conversion circuit 1, the output energy of the DC / DC conversion circuit 1 cannot be quickly made to match the energy consumed by the load due to a response delay of the reactor current Il, and this mismatch between the output energy and the energy consumed by the load must be resolved by the energy balancing action of the smoothing reactor 2. Therefore, the ripple of the current pulse cannot be fundamentally improved.

[0111] {Action and effect} According to the above analysis results, when the load voltage changes suddenly due to the on / off of the current pulse, if the output energy of the DC / DC conversion circuit 1 can be quickly made to match the energy consumed by the load, the effect of the smoothing reactor 2 can be suppressed and the ripple of the current pulse can be fundamentally improved.

[0112] From the results of Examples 1 and 2, the following can be concluded.

[0113] According to the pulse drive circuit 100 of the present disclosure, in the DC / DC conversion circuit 1, feedback control of the reactor current Il is performed during the current pulse ON period, but feedback control of the reactor voltage Vl is performed during the current pulse OFF period.

[0114] First, when the feedback control shifts from the current pulse on period to the current pulse off period, the load voltage of the constant current source (DC / DC conversion circuit 1 and smoothing reactor 2) becomes 0V due to the off of the current pulse. This is because the current pulse generating circuit 4 shorts between the second output terminal 3b and the first output terminal 3a, and the first output terminal 3a is connected to the low potential output terminal 1a of the DC / DC conversion circuit 1. Then, in the smoothing reactor 2, the output voltage Vout1 of the DC / DC conversion circuit 1 is applied to the terminal on the DC / DC conversion circuit 1 side, and the terminal on the load side becomes substantially 0V. On the other hand, in the feedback control of the voltage Vl across the reactor, since the target value Vlset of the voltage across the reactor is 0V or a voltage close to a predetermined 0V, in the DC / DC conversion circuit 1, the output voltage Vout1 is reduced toward 0V or a voltage close to a predetermined 0V by the feedback control so that the voltage Vl across the reactor becomes 0V or a voltage close to a predetermined 0V. Meanwhile, in this process, the DC / DC conversion circuit 1 is controlled so as to substantially maintain the current reactor current Il. This is because when the reactor current Il changes, a potential difference occurs across the smoothing reactor 2 due to an induced voltage. As a result, the DC / DC conversion circuit 1 feedback controls the output voltage Vout to a voltage of "almost 0 V", which is the voltage required for the reactor current Il to substantially maintain the current current value (reactor current target value Ilset in feedback control of the reactor current). As a result, the output energy of the DC / DC conversion circuit 1 is quickly made to match the energy consumed by the load (here, the internal resistance of the constant current source).

[0115] Next, when the feedback control shifts from the current pulse off period to the current pulse on period, when the load voltage becomes a predetermined voltage (for example, 120 V which is the rated load voltage of the load) due to the on of the current pulse, the reactor current Il of the DC / DC conversion circuit 1 suddenly decreases. Here, if feedback control of the reactor current Il is performed for the DC / DC conversion circuit 1 during the current pulse off period, the reactor current Il of the DC / DC conversion circuit 1 is in a state where it is increased above the reactor current target value Ilset at the end of the current pulse off period (see Comparative Example 1), so when the current pulse on period is entered, the DC / DC conversion circuit 1 is feedback controlled to increase the reactor current Il until the reactor current Il of the DC / DC conversion circuit 1 falls below the reactor current target value Ilset. Therefore, the DC / DC conversion circuit 1 cannot be feedback controlled immediately so that the reactor current Il becomes the reactor current target value Ilset. However, according to the pulse drive circuit 100 of the present disclosure, feedback control of the voltage Vl across the reactor is performed for the DC / DC conversion circuit 1 during the current pulse off period, and the reactor current Il is substantially controlled to the reactor current target value Ilset. Therefore, when the current pulse on period is entered, the reactor current Il detected by the reactor current sensor 5 substantially decreases from the reactor current target value Ilset. Therefore, the DC / DC conversion circuit 1 is immediately feedback controlled so that the reactor current Il becomes the reactor current target value Ilset. This allows the output energy of the DC / DC conversion circuit 1 to quickly match the energy consumed by the load. In this way, the output energy of the DC / DC conversion circuit 1 is quickly matched to the energy consumed by the load during the current pulse off period and the current pulse on period, and as a result, the action of the smoothing reactor 2 is suppressed and the ripple of the current pulse is fundamentally improved.In other words, the present invention is an original invention that combines feedback control of the voltage Vl across the reactor during the current pulse off period with feedback control of the reactor current Il during the current pulse on period, thereby making it possible to quickly match the output energy of the DC / DC conversion circuit 1 with the energy consumed by the load while substantially maintaining the reactor current Il at the reactor current target value Ilset, thereby fundamentally improving the ripple of the current pulse.

[0116] (Other embodiments) In the above embodiment, the voltage averaging circuit 8 may be omitted. Examples of such cases include a case where an averaged reactor voltage Vla can be acquired in the reactor voltage sensor 7, a case where the detected reactor voltage Vl is smoothed (averaged) due to a parasitic impedance of a reactor voltage detection path from the reactor voltage sensor 7 to the reactor voltage control circuit 9, and a case where the detected reactor voltage Vl is smoothed (averaged) because the carrier frequency of the PWM signal is extremely high.

[0117] In the above embodiment, the DC / DC conversion circuit 1 may be replaced with a DC voltage generation circuit that generates a variable DC voltage by an analog circuit rather than by PWM control.

[0118] In the above embodiment, the reactor current target value Ilset may be stored in an appropriate location other than the control device 33.

[0119] In the above embodiment, the pulse drive circuit 100 may include a control device including a processor and a memory, and the control device may output the pulse signal Spls and the reactor current target value Ilset.

[0120] Numerous modifications and other embodiments will be apparent to those skilled in the art in light of the above description, and therefore the above description is to be construed as illustrative only. [Industrial Applicability]

[0121] The pulse drive circuit of the present disclosure is useful as a pulse drive circuit capable of improving ripples in a current pulse. [Explanation of symbols]

[0122] 1 DC / DC conversion circuit (DC voltage generation circuit) 1a Low potential output terminal 1b High potential output terminal 1c,1d A pair of input terminals 2 Smoothing reactor 3 Output terminal 3a 1st output terminal 3b 2nd output terminal 4 Current pulse generating circuit 5 Reactor current sensor 6 Reactor current control circuit 7 Voltage sensor at both ends of reactor 8. Voltage averaging circuit 9. Reactor voltage control circuit 10 Command selection circuit 11 PWM signal generation circuit 22 Reactor end voltage target value storage section 31 DC power supply 32 Load 33 Control device 41 Inverter 42 Trans 43 Pair of rectifier elements 51,54 Constant voltage source 52,55 Op-amps 53 On-Off Switch 56 Changeover switch 57 Comparator 58, 60 signal source 59 AND Circuit 100 Pulse drive circuit Ci Reactor current command Cmd Selection command Cvl Reactor voltage command Il Reactor current Ilset Reactor current target value Iout Output current Spls Pulse signal Spwm PWM signal Vl Voltage across reactor Vla Average reactor voltage Vlset Reactor voltage target value Vout1 Output voltage of DC / DC conversion circuit Vout2 Voltage on the output side of the smoothing reactor

Claims

1. A DC voltage generation circuit that generates and outputs a DC voltage corresponding to the reactor current command or reactor terminal voltage command selected by the command selection circuit, A smoothing reactor is connected at one end to the high-potential output terminal of the DC voltage generation circuit, and smooths the reactor current output from the DC voltage generation circuit. It has a first output terminal and a second output terminal, the second output terminal being connected to the other end of the smoothing reactor and the first output terminal being connected to the low-potential output terminal of the DC voltage generation circuit, and between the second output terminal and the first output terminal, there is an output terminal to which a load driven by current pulses is connected, A current pulse generation circuit receives an externally input pulse signal that alternately includes a current pulse off period and a current pulse on period, short-circuits the second output terminal and the first output terminal during the current pulse off period, and opens the second output terminal and the first output terminal during the current pulse on period, thereby generating a current pulse from the reactor current smoothed by the smoothing reactor, and outputs the current pulse to the load via the output terminal, A reactor current sensor for detecting the reactor current, A reactor current control circuit that outputs a reactor current command based on the error of the reactor current detected by the reactor current sensor relative to the reactor current target value, A reactor voltage sensor for detecting the voltage across the reactor of the smoothing reactor, A reactor voltage control circuit that outputs a reactor voltage command based on the voltage error originating from the reactor voltage detected by the reactor voltage sensor relative to a target value of 0V or a predetermined voltage close to 0V, A pulse drive circuit comprising: a command selection circuit that receives the pulse signal from an external source, selects and outputs the reactor current command during the current pulse on period, and selects and outputs the reactor terminal voltage command during the current pulse off period.

2. The pulse drive circuit according to claim 1, wherein the voltage of 0V or a predetermined voltage close to 0V is a voltage within 5% of the set output voltage of the DC voltage generation circuit.

3. The DC voltage generation circuit is a DC / DC conversion circuit that generates and outputs a PWM-controlled square wave DC voltage from a DC voltage input from a DC power supply using one or more switching elements that turn on and off in response to a PWM signal. The smoothing reactor is a reactor whose one end is connected to the high-potential output terminal of the DC / DC conversion circuit, and which smooths the reactor current output from the DC / DC conversion circuit. The first output terminal of the output terminal is connected to the low-potential output terminal of the DC / DC conversion circuit. The pulse signal is input to the current pulse generation circuit from the control device. The reactor current control circuit receives the reactor current target value from the control device. The command selection circuit receives the pulse signal from the control device, and The pulse drive circuit according to claim 1, further comprising a PWM signal generation circuit that generates one or more PWM signals corresponding to one or more switching elements in response to the reactor current command or the reactor terminal voltage command from the command selection circuit, and outputs the one or more PWM signals to the one or more switching elements, respectively.

4. The circuit further comprises a voltage averaging circuit that generates and outputs a voltage derived from the voltage across the smoothing reactor detected by the reactor voltage sensor, which is the average of the voltages across the smoothing reactor detected by the reactor voltage sensor. The pulse drive circuit according to any one of claims 1 to 3, wherein the reactor terminal voltage control circuit is a circuit that outputs a reactor terminal voltage command based on the error of the voltage output from the terminal voltage averaging circuit with respect to the terminal voltage target value.

Images