JP2008289285A - Dc voltage conversion circuit, record device, and control method for dc voltage conversion circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent output voltage from becoming unstable due to temperature variation and to output a stable voltage in a switching type DC voltage conversion circuit. <P>SOLUTION: This DC voltage conversion circuit has a switching device, an inductor, and a capacitor. This circuit converts an input voltage to a pulse voltage with the switching device, and is smoothened by the inductor and capacitor for output. This circuit has a control circuit which controls the switching device, and the control circuit controls drive frequency of the switching device corresponding to the assumed temperature of the capacitor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a switching type DC voltage conversion circuit having an LPF (low pass filter) using an electrolytic capacitor or the like, a recording apparatus, and a control method for the DC voltage conversion circuit.

  In recent years, from the viewpoint of environmental consideration, an efficient switching type DC voltage conversion circuit is often used as a DC voltage conversion circuit. The switching type DC voltage conversion circuit includes an LPF in which an inductor and a capacitor are connected, and smoothes the output voltage.

  As a DC voltage conversion circuit of the above switching method, a method of changing a switching frequency and a duty according to an output voltage and an output current has been proposed in order to improve efficiency fluctuation due to load fluctuation (see Patent Document 1).

In order to improve operation stability at low temperatures, a method has been proposed in which the gain of the error amplifier is varied according to the duty of the pulse voltage and the ambient temperature (see Patent Document 2).
Japanese Patent No. 2,607,569 Japanese Patent No. 3574394

  In a switching-type DC voltage conversion circuit, in a method of smoothing a voltage output by connecting an LPF with an inductor and a capacitor, ripple-like fluctuations are superimposed on the smoothed voltage. The voltage (ripple voltage) on which the ripple-like fluctuation is superimposed is greatly influenced by the ESR (Equivalent Series Resistance) characteristic of the LPF capacitor, and the ripple voltage increases when the ESR is large. A large ripple voltage is not desirable as a power source because a stable voltage cannot be output.

  An electrolytic capacitor is often used as the LPF capacitor. The ESR of the electrolytic capacitor generally has temperature dependency, and the ESR increases as the temperature decreases. That is, when the ESR of the electrolytic capacitor is large at a low temperature, there is a problem that the ripple voltage increases and becomes undesirable as a power source.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a switching type DC voltage conversion circuit and a control method therefor that do not prevent stable voltage output due to temperature changes.

The present invention for solving the above-described problem includes a switching element, an inductor, and a capacitor. The input voltage is converted into a pulse voltage by the switching element, and is smoothed and output by the inductor and the capacitor. A voltage conversion circuit comprising:
A control circuit for controlling the switching element;
The control circuit controls a driving frequency of the switching element according to an assumed temperature of the capacitor.

Another aspect of the present invention for solving the above-described problems includes a switching element, an inductor, and a capacitor. The input voltage is converted into a pulse voltage by the switching element, and is smoothed by the inductor and the capacitor. DC voltage conversion circuit that outputs
A control circuit for controlling the switching element;
A capacitor temperature detection circuit for detecting the temperature of the capacitor;
Have
When the temperature detected by the capacitor temperature detection circuit is equal to or lower than a predetermined specified temperature, the control circuit drives the capacitor until the temperature of the capacitor exceeds the specified temperature. If the temperature detected by the capacitor temperature detection circuit exceeds a predetermined temperature, the switching element is controlled to drive at a relatively high driving frequency. Control is performed so that the element is driven.

Another aspect of the present invention for solving the above-described problems includes a switching element, an inductor, and a capacitor. The input voltage is converted into a pulse voltage by the switching element, and is smoothed by the inductor and the capacitor. A method for controlling a DC voltage conversion circuit that outputs
The driving frequency of the switching element is controlled in accordance with an assumed temperature of the capacitor.

Furthermore, another present invention for solving the above-mentioned problems includes a switching element, an inductor, and a capacitor. The input voltage is converted into a pulse voltage by the switching element, and is smoothed by the inductor and the capacitor. A method for controlling a DC voltage conversion circuit that outputs
A capacitor temperature detecting step for detecting the temperature of the capacitor;
When the temperature detected by the capacitor temperature detecting step is equal to or lower than a predetermined specified temperature, the drive frequency is relatively high until the temperature of the capacitor exceeds the specified temperature by driving the capacitor. The switching element is controlled so as to be driven, and when the temperature detected by the capacitor temperature detection circuit exceeds a predetermined specified temperature, the switching element is driven at a relatively low driving frequency. A control process to control,
It is characterized by having.

  According to the present invention, in a switching type DC voltage conversion circuit, it is possible to prevent an output voltage from becoming unstable due to a temperature change and to output a stable voltage.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  The switching type DC voltage conversion circuit of the present invention can be preferably used in a recording apparatus such as an inkjet recording apparatus.

  FIG. 10 is an external perspective view showing an outline of the configuration of an ink jet recording apparatus which is a typical embodiment of the present invention.

  As shown in FIG. 10, an ink jet recording apparatus (hereinafter referred to as a recording apparatus) includes a recording head 3 that performs recording by discharging ink in accordance with an ink jet system. The driving force generated by the carriage motor M1 is transmitted from the transmission mechanism 4 to the carriage 2 on which the recording head 3 is mounted, and the carriage 2 is reciprocated (reciprocated scanning) in the direction of arrow A which is the main scanning direction. Along with this reciprocating scanning, for example, a recording medium P such as recording paper is fed through the paper feeding mechanism 5 and conveyed to a recording position, and ink is ejected from the recording head 3 to the recording medium P at the recording position. Make a record.

  In addition to mounting the recording head 3 on the carriage 2 of the recording apparatus, an ink tank 6 for storing ink to be supplied to the recording head 3 is mounted. The ink tank 6 is detachable from the carriage 2.

  The recording apparatus shown in FIG. 10 is capable of color recording. For this reason, the carriage 2 has four ink tanks containing magenta (M), cyan (C), yellow (Y), and black (K) inks, respectively. It is installed. These four ink tanks can be attached and detached independently.

  The carriage 2 and the recording head 3 can achieve and maintain a required electrical connection by properly contacting the joint surfaces of both members. The recording head 3 applies energy according to a recording signal to selectively eject ink from a plurality of ejection ports for recording. In particular, the recording head 3 of the present embodiment employs an ink jet system that ejects ink using thermal energy, and includes an electrothermal transducer to generate thermal energy. The electrical energy applied to the electrothermal converter is converted to thermal energy, and the ink is ejected from the discharge port using the pressure change caused by the growth and contraction of bubbles caused by film boiling caused by applying the thermal energy to the ink. To discharge. The electrothermal transducer is provided corresponding to each of the ejection ports, and ink is ejected from the corresponding ejection port by applying a pulse voltage to the corresponding electrothermal transducer in accordance with the recording signal.

  As shown in FIG. 10, the carriage 2 is connected to a part of the driving belt 7 of the transmission mechanism 4 that transmits the driving force of the carriage motor M <b> 1, and slides in the direction of arrow A along the guide shaft 13. It is guided and supported freely. Accordingly, the carriage 2 scans back and forth along the guide shaft 13 by forward and reverse rotations of the carriage motor M1. Further, a scale 8 is provided for indicating the position of the carriage 2 along the main scanning direction (arrow A direction) of the carriage 2.

  Further, the recording apparatus is provided with a platen (not shown) facing the discharge port surface where the discharge port (not shown) of the recording head 3 is formed, and the recording head 3 is driven by the driving force of the carriage motor M1. The mounted carriage 2 is scanned back and forth. At the same time, recording is performed over the entire width of the recording medium P conveyed on the platen by supplying a recording signal to the recording head 3 and discharging ink.

  The recording apparatus is provided with a recovery device 10 for recovering a discharge failure of the recording head 3 at a position outside the range of reciprocating motion (outside the recording area) for the recording operation of the carriage 2 on which the recording head 3 is mounted. Has been.

  The recovery device 10 includes a capping mechanism 11 that caps the ejection port surface of the recording head 3 and a wiping mechanism 12 that cleans the ejection port surface of the recording head 3. Then, in conjunction with the capping of the ejection port surface by the capping mechanism 11, ink is forcibly discharged from the ejection port by a suction means (a suction pump or the like) in the recovery device. As a result, an ejection recovery operation such as removing ink or bubbles with increased viscosity in the ink flow path of the recording head 3 is performed.

  Further, when the recording head 3 is not in operation or the like, the ejection port surface of the recording head 3 is capped by the capping mechanism 11 to protect the recording head 3 and to prevent ink evaporation and drying. On the other hand, the wiping mechanism 12 is arranged in the vicinity of the capping mechanism 11 and wipes ink droplets adhering to the discharge port surface of the recording head 3.

  In addition, the recording apparatus is configured such that preliminary ejection can be performed by ejecting ink not related to recording to the capping mechanism 11.

  The ink discharge state of the recording head 3 can be kept normal by the suction operation and preliminary discharge operation using the capping mechanism 11 and the wiper operation using the wiping mechanism 12.

  Although FIG. 10 shows a configuration in which the ink tank 6 and the recording head 3 are separated, a head cartridge in which the ink tank and the recording head are integrally formed may be used.

  FIG. 11 is a block diagram showing a control configuration of the recording apparatus shown in FIG.

  As shown in FIG. 11, the controller 600 includes a ROM 602 that stores an MPU 601, a required table, and other fixed data. Further, it has a special application integrated circuit (ASIC) 603 that generates control signals for controlling the carriage motor M1, the conveyance motor M2, and the recording head 3. In addition, a system bus 605 is provided to connect the RAM 604, the MPU 601, the ASIC 603, and the RAM 604, which are provided with an image data development area, a work area for program execution, and the like to exchange data. Furthermore, an analog signal input from a sensor group described below is A / D converted into a digital signal, and an A / D converter 606 that supplies the digital signal to the MPU 601 is configured.

  Reference numeral 610 denotes a computer or the like serving as a supply source of image data, and is collectively referred to as a host. Image data, commands, status signals, and the like are transmitted and received between the host 610 and the recording apparatus via an interface (I / F) 611.

  Further, reference numeral 620 denotes a switch group, which includes a power switch 621, a print switch 622 for instructing the start of printing, and a recovery switch 623 for instructing the start of the recovery operation. Composed. Reference numeral 630 denotes a sensor for detecting an apparatus state including a position sensor 631 such as a photocoupler for detecting a home position, a temperature sensor 632 provided at an appropriate position of the recording apparatus for detecting an environmental temperature, and the like. A group.

  Further, 640 is a carriage motor driver that drives the carriage motor M1, and 642 is a conveyance motor driver that drives the conveyance motor M2. A recording head driver 644 drives the recording head 3. The switching type DC voltage conversion circuit of the present invention can be used for the printhead driver 644 to supply a drive voltage to the printhead 3, for example. Further, for example, it can be used for the transport motor driver 642 to supply power to the transport motor M2.

  FIG. 1 is a circuit diagram for explaining the DC voltage conversion circuit of this embodiment.

  The input voltage Vin101 is pulse-converted by switching of the bipolar transistor 102, which is a switching element, and input to an LPF (low-pass filter) composed of an inductor 103 and a capacitor 104 and smoothed. Here, an electric field capacitor is used as the capacitor 104. An SBD (Schottky barrier diode) 105 is disposed on the wiring connecting the emitter of the transistor 102 and the ground (GND), and charges flow according to the potential generated by the inductor 103 when the transistor 102 is turned off. A method in which the SBD is arranged between the emitter of the transistor 102 and GND in this way is called an asynchronous method. On the other hand, there is also a control system in which a transistor is arranged in place of the SBD 105 and the transistor arranged between the emitter of the transistor 102 and the GND is turned on when the transistor 102 is turned off. Call it. A predetermined voltage 109 obtained by dividing the smoothed voltage Vout 106 by the resistor 107 and the resistor 108 is fed back to the DC / DC control block 110 which is a control circuit of the transistor 102. The DC / DC control block 110 controls switching of the transistor 102 so that the fed back voltage 109 is stabilized.

  FIG. 2 is a graph showing a representative example of the temperature characteristics of the ESR of the electrolytic capacitor used for the LPF. As shown in the graph of FIG. 2, the ESR of the electrolytic capacitor is larger at lower temperatures. The rate of change increases rapidly as the temperature decreases.

  FIG. 3 is a diagram illustrating a waveform of a voltage input to the LPF in a normal cycle and a waveform of a voltage output from the LPF in the DC voltage conversion circuit.

  The voltage waveform 301 input to the LPF in the normal cycle is subjected to switching control every regular cycle T1 302 which is the normal cycle. In this waveform, the transistor is turned on for the period Ton1 303. Hereinafter, a state in which switching control is performed at regular intervals, which are normal cycles, is referred to as normal frequency driving. When such a switching waveform is input to the LPF, a ripple voltage in which ripple-like fluctuations are superimposed on the smoothed voltage is output as indicated by a voltage waveform 304 output from the LPF at normal temperature. Here, when the temperature of the electrolytic capacitor used for the LPF is low, the ESR increases as shown in FIG. For this reason, when the temperature of the electrolytic capacitor used for the LPF is low, the ripple voltage peak value of the voltage waveform 305 output from the LPF at low temperature is compared with the ripple voltage peak value 306 of the voltage waveform 304 output from the LPF at normal temperature. 307 becomes large and the voltage becomes unstable.

  FIG. 4 is a diagram illustrating a waveform of a voltage input to the LPF in a short cycle and a waveform of a voltage output from the LPF in the DC voltage conversion circuit.

  The switching control cycle T2 402 shown in the voltage waveform 401 input to the LPF in a short cycle is controlled at a cycle shorter than the cycle T1 302 which is the switching control cycle of FIG. Yes. However, the ratio between the period T2 402 of the switching control and the period Ton2 403 in which the transistor is on is substantially the same as the ratio between the period T1 302 in FIG. 3 and the period Ton1 303 in which the transistor is on. Yes. Hereinafter, the state of driving by switching control for each short cycle is referred to as high-speed frequency driving. The ripple voltage peak value 405 of the voltage waveform 404 output from the LPF at a low temperature in FIG. 4 is smaller than the ripple voltage peak value 307 of the voltage waveform 305 output from the LPF at a low temperature in FIG. . Thus, when the switching control cycle is shortened under the same conditions, the ripple voltage is reduced.

  However, if the switching control cycle is shortened, the number of times of switching per unit time increases, so that the switching loss of the transistor 102 in FIG. 1 increases. Due to this switching loss, there is a demerit that the amount of heat generated in the capacitor 104 (electrolytic capacitor) or the like increases in addition to the transistor 102 in FIG. The present invention also avoids this disadvantage.

  FIG. 5 shows a flowchart for explaining the present embodiment.

  When processing by the DC voltage conversion circuit is started (step S110), the DC voltage conversion circuit performs high-frequency driving (step S140). Before operating the DC voltage conversion circuit, the environmental temperature and the temperature of the LPF electrolytic capacitor may be low. In this case, the ESR of the electrolytic capacitor of the LPF is high. If the ESR of the electrolytic capacitor is high, the ripple voltage peak value of the output voltage from the DC voltage conversion circuit increases as described above, and this output voltage becomes unstable. In order to avoid such a state, at the start of the processing by the DC voltage conversion circuit (at the time of start-up), control is performed so that the ripple voltage peak value is kept small by operating at high frequency drive (step S140).

  The electrolytic capacitor rises in temperature due to self-heating of the electrolytic capacitor when the charging and discharging of the ripple current accompanying the operation of the DC voltage conversion circuit is repeated. When the DC voltage conversion circuit is started, there is no problem even if a switching loss occurs due to high frequency driving because there is no temperature rise due to self-heating of the electrolytic capacitor. For this reason, the high frequency driving is maintained for a predetermined time (step S150). By doing so, the electrolytic capacitor for LPF rises in temperature due to self-heating of the electrolytic capacitor as described above, and ESR is lowered. Here, the specified time for maintaining the high frequency drive is an electrolytic capacitor from the operation guarantee lower limit temperature of the DC voltage conversion circuit to a temperature at which the output voltage from the DC voltage conversion circuit is assumed to be stable due to self-heating. It is desirable to set the time required for heating.

  Then, after maintaining a predetermined time high frequency drive until a predetermined specified time elapses (step S150), the process shifts to a normal frequency drive (step S160), and a normal operation state that is a normal operation state (step S170). )become.

  FIG. 6 is a circuit diagram for explaining the DC voltage conversion circuit of the present embodiment.

  The DC voltage conversion circuit of the present embodiment is configured to further include an ambient temperature detection circuit 701 connected to the DC / DC control block 110 in addition to the DC voltage conversion circuit of the first embodiment shown in FIG. The DC / DC control block 110 can switch the control of the DC voltage conversion function according to the temperature of the use environment of the DC voltage conversion circuit detected by the ambient temperature detection circuit 701. The rest of the configuration is common to the DC voltage conversion circuit of the first embodiment shown in FIG.

  FIG. 7 shows a flowchart for explaining the present embodiment.

  When processing by the DC voltage conversion circuit is started (step S110), the ambient temperature detection circuit 701 detects the temperature of the usage environment of the DC voltage conversion circuit (step S120). When the temperature of the usage environment of the DC voltage conversion circuit is equal to or lower than a predetermined specified temperature, the DC voltage conversion circuit is driven at a high frequency (step S140). The specified value temperature is a temperature at which the ESR becomes high and the stable voltage output becomes difficult when the temperature of the electrolytic capacitor of the LPF is equal to or lower than the specified value temperature. When the temperature of the environment in which the DC voltage conversion circuit is used exceeds a predetermined temperature, the DC voltage conversion circuit is driven at a normal frequency (step S160). Steps S140 to S170 are the same as those in FIG.

  FIG. 8 is a circuit diagram for explaining the DC voltage conversion circuit of this embodiment.

  The DC voltage conversion circuit according to the present embodiment is similar to the DC voltage conversion circuit according to the first embodiment shown in FIG. 1 and further includes a temperature detection circuit (capacitor temperature detection circuit) 801 for an electrolytic capacitor connected to the DC / DC control block 110. It is the composition provided with. The DC / DC control block 110 can switch the control of the DC voltage conversion function in accordance with the temperature of the electrolytic capacitor detected by the temperature detection circuit 801 of the electrolytic capacitor. The electrolytic capacitor temperature detection circuit 801 has a structure in which, for example, a temperature detection element is disposed in contact with the body of the electrolytic capacitor. The rest of the configuration is common to the DC voltage conversion circuit of the first embodiment shown in FIG.

  FIG. 9 shows a flowchart for explaining the present embodiment.

  When the processing by the DC voltage conversion circuit is started (step S110), the electrolytic capacitor temperature is detected by the electrolytic capacitor temperature detection circuit 801 (step S130). When the temperature of the electrolytic capacitor is equal to or lower than a predetermined specified temperature, the DC voltage conversion circuit is driven at a high frequency (step S140). The specified value temperature is a temperature at which the ESR becomes high and the stable voltage output becomes difficult when the temperature of the electrolytic capacitor of the LPF is equal to or lower than the specified value temperature. Then, the DC voltage conversion circuit is driven at a high frequency by repeating step S130 and step S140 until the temperature of the electrolytic capacitor exceeds a predetermined specified temperature. In step S130, when the temperature of the electrolytic capacitor exceeds a predetermined specified temperature, the DC voltage conversion circuit is driven at a normal frequency (step S160).

  It is possible to always detect the temperature of the electrolytic capacitor during the operation of the DC voltage conversion circuit, and periodically switch the switching cycle of the DC voltage conversion circuit according to the detected temperature. Further, a plurality of switching periods that can be switched may be provided. When there are a plurality of switching periods, when the temperature of the electrolytic capacitor is high and the ESR is small, it is possible to provide a long switching period and control that is advantageous in terms of life while suppressing the heat generation of the electrolytic capacitor.

  As described in the above embodiments, according to the present invention, in the switching type DC voltage conversion circuit, the output voltage is prevented from becoming unstable due to the influence of the ESR temperature characteristic of the electrolytic capacitor used in the LPF, and stable. It becomes possible to output a voltage.

FIG. 3 is a circuit diagram for explaining the DC voltage conversion circuit according to the first embodiment. It is a graph which shows the representative example of the temperature characteristic about ESR of an electrolytic capacitor. It is a figure which shows the waveform of the voltage input into LPF in a normal period, and the waveform of the voltage output from LPF in a DC voltage converter circuit. It is a figure which shows the waveform of the voltage input into LPF in a short period in a DC voltage converter circuit, and the waveform of the voltage output from LPF. 3 is a flowchart for explaining the operation of the DC voltage conversion circuit according to the first embodiment. FIG. 6 is a circuit diagram for explaining a DC voltage conversion circuit according to a second embodiment. 6 is a flowchart for explaining an operation of the DC voltage conversion circuit according to the second embodiment. FIG. 6 is a circuit diagram for explaining a DC voltage conversion circuit according to a third embodiment. 10 is a flowchart for explaining the operation of the DC voltage conversion circuit according to the third embodiment. 1 is an external perspective view showing an outline of a configuration of an ink jet recording apparatus that is a typical embodiment of the present invention. It is a block diagram which shows the control structure of an inkjet recording device.

Explanation of symbols

102 transistor 103 inductor 104 capacitor 110 DC / DC control block

Claims (10)

A DC voltage conversion circuit having a switching element, an inductor, and a capacitor, converting an input voltage into a pulse voltage by the switching element, and smoothing and outputting the pulse voltage by the inductor and the capacitor;
A control circuit for controlling the switching element;
The DC voltage conversion circuit, wherein the control circuit controls a driving frequency of the switching element in accordance with an assumed temperature of the capacitor.   The control circuit performs control so that the switching element is driven at a relatively high drive frequency before a predetermined specified time elapses, and a relatively low drive frequency after the specified time elapses. The DC voltage conversion circuit according to claim 1, wherein the switching element is controlled so as to be driven. A detection circuit for detecting the temperature of the environment in which the DC voltage conversion circuit is used;
When the temperature detected by the detection circuit exceeds a predetermined specified temperature, the control circuit causes the switching element to operate at a relatively low driving frequency before the predetermined specified time has elapsed. The direct-current voltage conversion circuit according to claim 2, wherein the direct-current voltage conversion circuit is controlled so as to be driven. A DC voltage conversion circuit having a switching element, an inductor, and a capacitor, converting an input voltage into a pulse voltage by the switching element, and smoothing and outputting the pulse voltage by the inductor and the capacitor;
A control circuit for controlling the switching element;
A capacitor temperature detection circuit for detecting the temperature of the capacitor;
Have
When the temperature detected by the capacitor temperature detection circuit is equal to or lower than a predetermined specified temperature, the control circuit drives the capacitor until the temperature of the capacitor exceeds the specified temperature. If the temperature detected by the capacitor temperature detection circuit exceeds a predetermined temperature, the switching element is controlled to drive at a relatively high driving frequency. A direct-current voltage conversion circuit, wherein the element is controlled to be driven.   5. The DC voltage conversion circuit according to claim 1, wherein the capacitor is an electrolytic capacitor. 6. The switching element is a bipolar transistor,
6. The DC voltage conversion circuit according to claim 1, wherein a Schottky barrier diode is disposed between the emitter of the bipolar transistor and the ground.   7. A recording apparatus using the DC voltage conversion circuit according to claim 1. A recording head for recording on a recording medium, a recording head driver for driving the recording head, a transport motor for transporting the recording medium, and a transport motor driver for driving the transport motor,
The recording apparatus according to claim 7, wherein the DC voltage conversion circuit is used in at least one of the recording head driver and the transport motor driver. A control method of a DC voltage conversion circuit having a switching element, an inductor, and a capacitor, converting an input voltage into a pulse voltage by the switching element, and smoothing and outputting the pulse voltage by the inductor and the capacitor,
A control method for a DC voltage conversion circuit, wherein the drive frequency of the switching element is controlled in accordance with an assumed temperature of the capacitor. A control method of a DC voltage conversion circuit having a switching element, an inductor, and a capacitor, converting an input voltage into a pulse voltage by the switching element, and smoothing and outputting the pulse voltage by the inductor and the capacitor,
A capacitor temperature detecting step for detecting the temperature of the capacitor;
When the temperature detected by the capacitor temperature detecting step is equal to or lower than a predetermined specified temperature, the drive frequency is relatively high until the temperature of the capacitor exceeds the specified temperature by driving the capacitor. The switching element is controlled so as to be driven, and when the temperature detected by the capacitor temperature detection circuit exceeds a predetermined specified temperature, the switching element is driven at a relatively low driving frequency. A control process to control,
A method for controlling a DC voltage conversion circuit, comprising:

Images