JP2013013237A - Power supply control method and power supply controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply control method and power supply controller, capable of facilitating identification of a starting point of switching control in use of a switching power supply.SOLUTION: The power supply control method or the power supply controller, rectifying alternating currents and obtaining an output voltage by switching control, generates a control signal with a predetermined waveform, compares an output voltage detecting signal to a control signal and implements switching control on the basis of a comparison result. Each opening point of the switching control is uniquely defined with a control signal generating point as an original point.

Description

  The present invention relates to a power supply control method and a power supply control apparatus using a switching power supply.

  In recent years, lighting devices using light-emitting diodes (hereinafter referred to as “LEDs”) have attracted attention as lighting devices that achieve both energy saving and environmental consideration. The LED emits light when a current is passed through, and its brightness is proportional to the current value. Therefore, the current LED lighting equipment controls the brightness of the LED, that is, the current value. Be controlled. In addition to LED lighting devices, various household appliances are controlled by direct current.

  In general, as one method for obtaining a DC voltage from a commercial AC power supply, it is known to use a power supply control device using a pulse modulation type switching power supply. An example of a power supply control apparatus using a pulse modulation type switching power supply is shown in FIG. The power supply control device 100 in FIG. 5 includes a noise filter 101 for noise prevention connected to a commercial AC power supply, a rectifier circuit 102 that rectifies the output of the noise filter 101, and a smoothing circuit that smoothes the pulsating current rectified by the rectifier circuit 102. 105 and a switching power supply 103 (hereinafter referred to as “SW power supply 103”) for converting the output voltage of the smoothing circuit 105 into a predetermined voltage.

  FIG. 6 is a diagram showing a schematic configuration of the SW power supply 103. The SW power supply 103 includes a switching element 6 (hereinafter referred to as “SW element 6”) made of a power MOSFET, a transformer 7, a rectifier diode 8, a smoothing capacitor 9, and a switching control unit 130 (hereinafter referred to as “SW control unit 130”). Consists of. In the SW power source 103, the input voltage smoothed by the smoothing circuit 105 is converted to a high-frequency pulse by high-speed switching by the switching element 6 and sent to the transformer 7. Then, rectification is performed by the rectifier diode 8 and smoothed by the smoothing capacitor 9 to obtain an output voltage.

  The SW control unit 130 is a control unit that feeds back the output voltage and performs ON / OFF control of the SW element 6, and includes an output voltage detection circuit 321, a comparator 331, an abnormality detector 341, a SW element drive circuit 351, It comprises an oscillator 360 and a triangular wave generator 361. In the SW control unit 130, the square wave generated by the oscillator 360 is converted into a symmetrical triangular wave by the triangular wave generation unit 361 and input to one end of the comparator 331. The output voltage detected by the output voltage detection circuit 321 is input to the other end of the comparator 331. Then, as shown in FIG. 6, the comparator 331 compares the triangular wave with the output voltage, and outputs a drive signal that turns on the SW element 6 only during a period when the triangular wave is larger than the output voltage. The SW element drive circuit 351 drives the SW element 6 based on the drive signal.

  With such a configuration, when the output voltage from the SW power supply 103 increases, the period during which the triangular wave is larger than the output voltage is shortened, and the ON time of the SW element 6 is shortened. The output voltage is adjusted by the duty ratio of the ON state and the OFF state of the SW element 6 controlled in this way. When an abnormality such as an overcurrent, overvoltage, undervoltage or temperature abnormality is detected by the abnormality detector 341, a stop signal is sent from the abnormality detector 341 to the SW element driving circuit 351, and the operation of the SW element 6 is performed. Stopped.

  Subsequently, an operation waveform diagram in the power supply control device 100 of FIG. 5 is shown in FIG. First, the AC voltage output from the commercial AC power supply is subjected to full-wave rectification by the rectifier circuit 102 after the noise is removed by the noise filter 101. FIG. 7A shows an input voltage waveform after rectification by the rectifier circuit 102. Then, the pulsating flow rectified by the rectifying circuit 102 is smoothed by the smoothing circuit 105, resulting in a voltage waveform shown in FIG. In this case, the current waveform flowing on the primary side (commercial AC power supply side) of the smoothing circuit 105 is a short pulse wave having a high peak value as shown in FIG. Here, since the pulse wave as shown in FIG. 7 (c) contains a large amount of harmonics, if it flows to the outside through the power supply line, it causes a failure due to noise. In addition, there is a problem that although power saving is on average, power generation / power supply / distribution equipment is required to guarantee high peak power. In order to solve such problems, it has been proposed to adopt a power factor correction circuit (PFC) that improves the power factor of the power source and suppresses the generation of harmonics.

  Further, when the power supply control device 100 is turned on, a large capacity smoothing capacitor of the smoothing circuit 105 in an empty state is charged, so that a large current as shown in FIG. Flowing. When such a rush current is generated, it is conceivable that the fuse is blown, the power supply voltage is unstable, and the equipment is affected accordingly. In order to prevent such an effect, it is possible to use a member that can withstand the magnitude of the rush current. However, the use of such a member causes unnecessary costs, and the fuse is abnormal during normal use. There are drawbacks such as the possibility of not functioning.

  Therefore, various methods have been considered to prevent the generation of rush current. Patent Document 1 includes, as an example, a smoothing capacitor bank circuit including a smoothing capacitor for a large capacity bank and a charging resistor for charging the capacitor, in addition to the smoothing capacitor. A configuration for preventing generation of rush current is disclosed. In addition to the method described in Patent Document 1, it is conceivable to reduce the capacity of the smoothing capacitor in the smoothing circuit 105 or to eliminate the smoothing circuit 105 itself.

JP-A-9-322539

  Here, since the power factor correction circuit is a step-up type constant voltage power supply, adopting a power factor correction circuit to solve the problem of pulse waves including harmonics means that an extra power supply. This means that installation is necessary, leading to an increase in cost, a reduction in efficiency, and an increase in size of the power supply control device.

  Further, when a smoothing capacitor bank circuit is separately provided as described in Patent Document 1 in order to suppress rush current, the number of parts increases, leading to an increase in product cost and an increase in size. There's a problem. Further, when the capacity of the smoothing capacitor is reduced or the smoothing circuit 105 itself is eliminated, when the processing by the SW power source 103 is performed according to the pulsating flow rectified by the rectifying circuit 102, the input current waveform is shown in FIG. ), The waveform has two peaks. In this case as well, there are problems of noise due to harmonics and peak guarantee, as in the case of the current waveform shown in FIG. Even when the smoothing circuit 105 is eliminated, a rush current may be generated to charge the smoothing capacitor 9 in the SW power supply 103.

  Further, in the conventional SW power supply 103, a symmetrical triangular wave is generated, and this is compared with the output voltage to perform ON / OFF control of the SW element 6. In this case, the SW element 6 is controlled. Since the starting point is indeterminate, there is a problem when the control method is used in which the inside is processed in chronological order according to a predetermined procedure. For example, when the inside is digitally processed, there is a problem that the processing becomes very complicated because the start position varies.

  The present invention has been made in view of the above problems, and when a switching power supply is used, it is possible to easily specify the starting point of the switching control, thereby preventing the complicated internal processing. It is an object to provide a method and a power supply control device.

  In order to solve the above problems, according to the present invention, a power supply control method for rectifying alternating current and obtaining an output voltage by performing switching control, the power supply control method generates a control signal having a predetermined waveform, and outputs the output voltage. The control signal is compared with the control signal and switching control is performed based on the comparison result, and each starting point of the switching control is uniquely determined starting from the point at which the control signal is generated. A featured power supply control method is provided.

  In addition, the predetermined waveform in the power supply control method may have a triangular wave starting from each starting point of the switching control or may be a sawtooth wave. Further, the portions other than the start point to the end point of the switching control in the predetermined waveform may be arbitrarily set.

  Furthermore, according to the present invention, there is provided a power supply control device comprising a rectifying circuit for rectifying a commercial AC power supply and a switching power supply for obtaining an output voltage based on an input voltage rectified by the rectifying circuit, wherein the switching power supply is a predetermined power supply. A switching control unit that generates a control signal having the following waveform, compares the control signal with the signal that has detected the output voltage, and performs switching control based on the comparison result, and the switching control unit starts each switching control A power supply control device is provided in which a point is uniquely determined starting from a point at which a control signal is generated.

The power control method and power control device of the present invention have the following effects.
1. Since the starting point of the switching control is uniquely determined, it is possible to easily specify and control the starting position even when digital processing is performed.
2. By preventing the generation of pulsed current and reducing the peak current value, the current capacity required for power generation, power supply, and distribution facilities can be reduced. In addition, since the power generation capacity and power transmission equipment of the power plant need to be prepared according to the peak current value, the smaller the peak current value, the less current capacity etc. actually required. As a result, the cost required for these social infrastructures can be reduced.
3. Since the current waveform can be made close to a sine wave, a low radiation noise operation with less unnecessary radiation is possible.
4). Since the generation of harmonics can be reduced without using a power factor correction circuit, miniaturization and cost reduction are possible at the same time.
5. By controlling the ON time of the SW element when the power is turned on, generation of rush current can be prevented.
6). The SW element ON time is measured, and based on this information, the pulsating current output from the rectifier circuit is divided into a plurality of sections, and the logical scale is kept small compared to the case where the ON time control is performed for each section. be able to.

It is a block diagram which shows the outline of the power supply control apparatus in embodiment of this invention. It is a figure which shows the structure of the switching power supply of FIG. It is a flowchart which shows the flow of the process in a control signal production | generation part. It is a figure which shows the operation | movement waveform in the power supply control apparatus of FIG. It is a block diagram which shows the outline of the power supply control apparatus in a prior art. It is a figure which shows the structure of the switching power supply in a prior art. It is a figure which shows the operation | movement waveform in the power supply control apparatus of a prior art. It is a figure which shows the operation | movement waveform in the modification of this invention.

  Hereinafter, a power supply control device according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a power supply control device 10 according to an embodiment of the present invention. The power supply control device 10 includes a noise filter 1, a rectifier circuit 2, and a switching power supply 3 (hereinafter referred to as “SW power supply 3”). The SW power supply 3 of the present embodiment is a pulse modulation type switching power supply, and obtains an output voltage based on a pulsating voltage input directly from the rectifier circuit 2 without passing through a power factor correction circuit or a smoothing circuit. It is. Moreover, although the power supply control apparatus 10 is connected to the commercial AC power supply, the power supply control apparatus 10 of the present invention can be used in addition to the commercial AC power supply.

  The noise filter 1 is for preventing noise generated from the SW power source 3 from radiating or propagating to the outside and not being affected by noise from the outside. The rectifier circuit 2 includes a rectifier diode and performs full-wave rectification on the output from the noise filter 1.

  Next, the configuration of the SW power supply 3 of the present embodiment will be described with reference to FIG. The SW power source 3 includes a switching element 6 such as a power MOFET (hereinafter referred to as “SW element 6”), a transformer 7, a rectifier diode 8, a smoothing capacitor 9, and a switching control unit 30 (hereinafter referred to as “SW control unit 30”). Consists of. In the SW power source 3, the pulsating voltage rectified by the rectifier circuit 2 is sent to the transformer 7 as a high-frequency pulse by high-speed switching by the switching element 6. Then, rectification is performed by the rectifier diode 8 and smoothed by the smoothing capacitor 9 to obtain a DC output voltage. The SW control unit 30 is a control unit that feeds back an output voltage and performs ON / OFF control of the SW element 6, and includes a control signal generation unit 31, an output voltage detection circuit 32, a comparator 33, an abnormality detector 34, and an SW element. A drive circuit 35 is included. In addition, the process of each part of SW control part 30 in this embodiment can be easily implement | achieved using FPGA (Field-Programmable Gate Array) and a gate array with a small logic scale.

  The control signal generation unit 31 generates a control signal to be compared with the output voltage detected by the output voltage detection circuit 32, and includes a time measurement unit 311, a clock control unit 312, and a D / A converter 313. Consists of. The time measuring unit 311 has a timer and a storage unit (not shown), and measures and stores a time width exceeding a predetermined detection level as a pulse width WL for each pulsating wave rectified by the rectifying circuit 2. /Update. Further, the time measuring unit 311 divides the stored pulse width WL into n, and sets the stage counter CNT (0 to n−1) for each divided time Tn.

  The clock control unit 312 is a control unit that controls the clock frequency in the D / A converter 313. The clock control unit 312 sets a different frequency f for each stage counter CNT set in the time measurement unit 311 with respect to one wave of pulsating flow. Thereby, the time value for which the SW element 6 operates for each stage counter CNT can be controlled. The D / A converter 313 is a digital-analog converter including, for example, a 4-bit resistor ladder, and outputs a control signal according to the clock frequency set by the clock control unit 312. Specifically, the D / A converter 313 can be configured by a counter and a resistance ladder. In this case, the counter is counted up / down at the clock frequency f from the clock control unit 312 and a voltage level corresponding to the counter output value is generated by the resistor ladder. According to this configuration, by adjusting the clock frequency f of the clock control unit 312, a control signal having a desired falling (or rising) waveform can be generated and input to the comparator 33.

  The SW power supply 3 in the present embodiment measures the pulse width WL exceeding a predetermined voltage level for each wave of the pulsating current rectified by the rectifier circuit 2 by the SW control unit 30, and measures each wave in the width direction. The current value is gradually increased (gradually increased) so that a sharp current increase does not occur at the rising edge of the voltage of each section, and the voltage decreases at the falling edge of the voltage of each section. In order to prevent a sudden increase in current, the current value is gradually decreased (gradually decreased), and this gradual increase and decrease control is repeated for each wave to suppress a steep increase in current and obtain a current waveform with less harmonics. It is to make. In particular, in the present embodiment, the control signal generator 31 is configured to obtain the current waveform as described above by generating a control signal to be compared with the output voltage by the comparator 33 for each section.

  Specific processing in the control signal generation unit 31 will be described with reference to the flowchart of FIG. 3 and the operation waveform of FIG. 3 and 4, an example in which one wave pulsating flow is divided into four in the width direction will be described. In this process, first, the voltage level of the pulsating current rectified by the rectifying circuit 2 is detected and compared with a predetermined detection level (S1). Here, the predetermined detection level is an operation lower limit voltage value of the SW power supply 3. Then, as shown in FIG. 4A, in the time measuring unit 311, from the time when the pulsating current voltage becomes larger than the detection level (S1: YES) to the time when it becomes smaller (S8, S9: NO) (that is, the pulse). The time width from the time when the current voltage exceeds the operation lower limit value of the SW power supply 3 until it can operate until it becomes less than the operation lower limit value and becomes inoperative is measured as the pulse width WL (FIG. 4B). ) And store (S10). Further, the stored pulse width WL is divided into four, and Tn of each section is obtained (S11). In addition, since the waveform may not be stable when the power is turned on, the pulse width is measured as WL after the lapse of two or more pulsating flows.

  In parallel with the measurement of the pulse width WL, a control signal is generated for each divided section, and the ON time of the SW element 6 is controlled. Specifically, when the voltage value of the rectified pulsating voltage is larger than the detection level (S1: YES), the timer of the time measuring unit 311 is started (S2). Then, in the clock control unit 312, the value of the stage counter CNT is set to 0, and the variable T is set to Tn (S3). Here, the time Tn is obtained by dividing the pulse width WL measured in the previous process by the time measuring unit 311 (that is, the pulse width of the previous pulsating flow) into four.

  Subsequently, the clock frequency f of the D / A converter 313 is set to a value (f0) corresponding to the stage counter CNT (in this case, 0) (S4). Here, in the present embodiment, the frequency (f0) corresponding to the stage counter CNT (0) is set so as not to cause a steep current increase at the rising portion. Specifically, the ON time of the SW element 6 is controlled by the width of the triangular wave output from the D / A converter 313, that is, the inclination (FIGS. 4E to 4H). More specifically, as the slope of the triangular wave becomes steeper, the ON time of the SW element 6 becomes shorter, and as the slope becomes gentler, the ON time becomes longer. Further, the slope of the triangular wave output from the D / A converter 313 becomes steep as the clock frequency f is increased. Therefore, by setting the frequency (f0) corresponding to the stage counter CNT (0) at the time of rising high, the ON time of the SW element 6 can be shortened and the current value can be suppressed.

  Subsequently, it is determined whether or not the time T has elapsed (S5). If the time T has not elapsed (S5: NO), the process waits until it elapses. During this time, the D / A converter 313 is operated at the clock frequency f0. On the other hand, when the time T has elapsed (S5: YES), 1 is added to the stage counter CNT, and Tn is added to the time T (S6). Then, it is determined whether or not the stage counter CNT is smaller than 4 (S7). If the stage counter CNT is smaller than 4 (S7: YES), it is determined in S9 whether or not the pulsating voltage is larger than the detection level. If the pulsating voltage is greater than the detection level (S9: YES), the process returns to S4. In S4, the clock frequency of the D / A converter 313 is set to a value (f1) corresponding to the stage counter CNT (1 in this case). In this way, the processes from S4 to S6 are repeated until the stage counter CNT is equal to or greater than the number of divisions (4) (S7: NO) or the pulsating voltage is below the detection level (S9: NO). The frequency at is set.

  If the stage counter CNT is 4 or more (S7: NO), it is determined in S8 whether or not the pulsating voltage is larger than the detection level as in S9. Then, when the pulsating voltage is larger than the detection level (S8: YES), it waits until it becomes equal to or lower than the detection level. If it is determined in S8 that the pulsating voltage is below the detection level (S8: NO), and if a similar determination is made in S9 (S9: NO), the value of the timer at that time is changed to the pulse. Stored as the pulse width WL of the flow (S10). Thereafter, the newly stored pulse width WL is divided into four and the time Tn is updated (S11). Then, the timer is reset (S12), the process returns to S1, and the same process is performed for the next pulsating flow.

  4C and 4E to 4H show output waveforms of the D / A converter 313 in the stage counters CNT (0 to 3) when the pulsating flow is divided into four. Here, FIGS. 4E to 4H are enlarged views of the waveforms shown in FIG. As shown in FIG. 4C, the D / A converter 313 outputs triangular waves having different slopes for each section, and the repetition frequency of the triangular wave in each section is, for example, about 100 kHz when it is low and high. Is set to about 1 MHz. When the stage counter CNT = 0 (FIG. 4 (e)) and the stage counter CNT = 3 (FIG. 4 (h)), a relatively high clock frequency is set so that the triangle with a steep slope is obtained. A waveform is output. On the other hand, in the case of the intermediate stage counter CNT = 1 (FIG. 4 (f)) and the stage counter CNT = 2 (FIG. 4 (g)), a relatively low clock frequency is set so that the triangular shape has a gentle slope. A waveform is output.

  The output waveform of the D / A converter 313 (FIG. 4C) is input to the comparator 33 as a control signal. Then, the comparator 33 compares with the output voltage detected by the output voltage detection circuit 32 to generate the drive signal shown in FIG. FIG. 4 (i) is an enlarged view of the waveform shown in FIG. 4 (d). As shown in FIG. 4I, when the stage counter CNT = 0 and the stage counter CNT = 3, the ON time of the SW element 6 in each cycle is shortened, and the intermediate stage counter CNT = 1. When the stage counter CNT = 2, the ON time becomes longer. By controlling the SW element 6 in this way, the output current waveform can be made a waveform close to a sine wave as shown in FIG.

  In the present embodiment, the control signal is generated with the point indicated by “SP” of each waveform in FIGS. 4E to 4H at the time of comparison in the comparator 33 as a starting point. That is, the position of each starting point SP where control of the SW element 6 is started is uniquely determined without fluctuation. 4 (e) to 4 (h), the point where the triangular wave has finished is the end point of the operation of the SW element 6. Here, since what is necessary to generate the drive waveform is a waveform from the start point SP to the end point, any waveform from the end point to the next start point may be used. With such a configuration, it is also possible to easily set an OFF period between pulsating flows.

  As described above, in the above embodiment, by generating a control signal having a predetermined waveform for each section and comparing it with the output voltage, generation of a pulsed current is prevented and the peak current value is reduced. Is possible. In addition, since the current waveform can be made close to a sine wave, a low radiation noise operation with less unnecessary radiation is possible. Furthermore, since the generation of harmonics can be reduced without using a power factor correction circuit, miniaturization and cost reduction can be achieved at the same time.

  As a method of dividing the pulsating flow and controlling the SW element 6 for each section, the ON time of the SW element when there is no restriction on the operation of the SW power source 103 is measured, and the stage is based on this information. It is also possible to perform ON time control for each counter value. However, in this case, a high-speed clock is required to measure the ON time. Further, when the measured number of clocks is divided, the logical scale is greatly increased. On the other hand, by configuring the SW power supply 3 as in the above-described embodiment, the logic scale can be kept small without requiring a high-speed clock number.

  Further, by controlling the ON time of the SW element 6 to be short at first and gradually increase when the power is turned on, generation of rush current can be prevented. In addition, it is possible to easily specify the start position even when digital processing is performed by uniquely defining a start point for starting control of the SW element 6 in the control signal and generating a triangular wave starting from this point. This makes it possible to prevent complication of processing.

  Further, the SW power supply 3 of the present embodiment can be used as a substitute for the power factor correction circuit. Here, while the power factor correction circuit can generally only boost the voltage, the SW power supply 3 of the present embodiment is more useful in that it can also step down. Furthermore, when the SW power supply 3 of the present embodiment is used in a power control device for an LED lighting apparatus, the luminance of the LED lighting device can be reduced by connecting to a phase control type dimming device compatible with an incandescent bulb. It is also possible to control (dimming).

The above is the description of the exemplary embodiments of the present invention. Specific aspects of the embodiments of the present invention are not limited to those described above, and can be arbitrarily changed within the scope of the technical idea expressed by the description of the scope of claims. For example, in the above-described embodiment, the case where the pulsating flow is divided into four parts has been described. However, the present invention is not limited to this and can be divided into an arbitrary number. However, when performing digital processing, it is practical to divide into ²ⁿ . Moreover, the setting of the frequency in each section is not limited to the above embodiment, and various current waveforms can be obtained by setting the frequency to an arbitrary value.

  Further, in the above embodiment, the case where the pulsating flow is divided into a plurality of sections and each start point SP of the control signal in each section is uniquely determined has been described, but the present invention is limited to the case where the pulsating flow is divided. It is not something. For example, as shown in FIG. 8, the present invention can also be applied when not divided into sections. Also in this case, each start point SP of the waveform (control signal) shown in FIG. 8C is uniquely determined (in the case of FIG. 8C, the falling start position of the triangular wave is set as the start point SP. ).

DESCRIPTION OF SYMBOLS 1 Noise filter 2 Rectifier circuit 3 Switching power supply 6 Switching element 7 Transformer 8 Rectifier diode 9 Smoothing capacitor 10 Power supply control apparatus 30 Switching control part 31 Control signal generation part 32 Output voltage detection circuit 33 Comparator 34 Abnormality detector 35 Switching element drive circuit 311 Time Measurement Unit 312 Clock Control Unit 313 D / A Converter

Claims (8)

A power supply control method for rectifying alternating current and switching to obtain an output voltage,
The power control method includes:
Generating a control signal having a predetermined waveform;
Comparing the control signal with the signal that detected the output voltage,
Performing switching control based on the comparison result;
Including
Each starting point of the switching control is uniquely determined from a point where the control signal is generated as a starting point.   The power supply control method according to claim 1, wherein the predetermined waveform has a triangular wave starting from each starting point of the switching control.   The power supply control method according to claim 1, wherein the predetermined waveform is a sawtooth wave.   4. The power supply control method according to claim 1, wherein a portion other than the start point to the end point of the switching control in the predetermined waveform can be arbitrarily set. 5. A rectifier circuit for rectifying commercial AC power;
A switching power supply that obtains an output voltage based on the input voltage rectified by the rectifier circuit, and a power supply control device comprising:
The switching power supply is
Generating a control signal having a predetermined waveform;
Comparing the control signal with the signal that detected the output voltage,
A switching control unit that performs switching control based on the comparison result,
The switching control unit uniquely determines each starting point of the switching control from a point where the control signal is generated as a starting point.   The power supply control device according to claim 5, wherein the predetermined waveform includes a triangular wave starting from each starting point of the switching control.   The power supply control device according to claim 5, wherein the predetermined waveform is a sawtooth wave. 8. The power supply control method according to claim 5, wherein a portion other than each start point to end point of the switching control in the predetermined waveform can be arbitrarily set.

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