JP2007208718A - Switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize the whole power supply, to reduce manufacturing costs and to effectively prevent generation of noise by switching. <P>SOLUTION: The switching power supply 1 includes a tuner part 3 which converts a received signal of an antenna 2 into an intermediate frequency signal to restrict bands by a bandpass filter 11 and a built-in oscillator 13, a microcomputer 4 which selects any one of a plurality of switching frequencies set based on filter characteristics of the bandpass filter 11 according to receiving frequencies in the tuner part 3 and uses waveform generated by the built-in oscillator 13 based on the selected switching frequency as a switching frequency pulse and a switching power source 5 which performs a switching operation by being synchronized with the switching frequency pulse output from the microcomputer 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a switching power supply device.

  Conventionally, a switching power supply device has been used as a power source for electronic devices such as information devices and communication devices.

  Since this switching power supply device can in principle be made highly efficient and downsized, for example, it is possible to arbitrarily select reception frequencies for transmission signals of a plurality of frequencies transmitted from a transmitter to obtain desired information. Widely used in receivers and so on.

  However, the switching power supply device has a problem that noise having a frequency corresponding to an integral multiple (harmonic) of the switching frequency is likely to be generated. In particular, a device that is sensitive to noise requires countermeasures against switching noise. In particular, since receivers such as AM (amplitude modulation) and FM (frequency modulation) have a wide range of reception frequencies, it is necessary to take measures against noise at a frequency corresponding to an integral multiple of the switching frequency.

  Therefore, in recent years, a plurality of oscillating means different in oscillating frequency used as the switching frequency and switching means for switching the oscillating means in accordance with the receiving frequency and selecting a switching frequency with less interference to the receiving device are provided. A switching power supply device has been proposed (Patent Document 1).

Further, Patent Document 1 discloses an oscillation means that can continuously vary an oscillation frequency used as a switching frequency, and a two-dimensional plane in which a reception frequency is a horizontal axis and a switching frequency is a vertical axis. Control means for controlling the oscillating means so as to draw a repetitive waveform with respect to the reception frequency in a predetermined frequency range in advance and to continuously change the oscillation frequency according to the reception frequency within the repetition period; Has been proposed.
Japanese Patent No. 2668462

  However, the switching power supply device described in Patent Document 1 has a problem that the entire device cannot be reduced in size because it is necessary to provide a plurality of oscillation means on the substrate. This is particularly a problem for substrates that require higher density. In addition, the manufacturing cost increases due to the increase in the number of components.

  Further, when the oscillation frequency is switched continuously or repeatedly, there is a problem that a frequency having a sufficiently small influence may not be selected in order to suppress the generation of noise.

  The present invention has been made in view of such circumstances, and provides a switching power supply device that can downsize the entire device, reduce the manufacturing cost, and effectively prevent the generation of noise due to switching. It is intended to provide.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a switching power supply device, comprising a filter, receiving a carrier signal existing in one frequency band from among carrier signals received by an antenna, A tuner unit for converting the received signal into an intermediate frequency signal and band-limiting by the filter, and an oscillation unit are incorporated, and any one of a plurality of switching frequencies set based on the filter characteristics of the filter is A microcomputer that selects according to the reception frequency in the tuner unit and uses the waveform generated by the oscillation means based on the selected switching frequency as a switching frequency pulse, and synchronizes with the switching frequency pulse output from the microcomputer A switching power supply for performing a switching operation, and That.

  The invention according to claim 2 is the switching power supply device according to claim 1, wherein the microcomputer includes a table in which the reception frequency in the tuner unit and the plurality of switching frequencies are associated with each other. One of the plurality of switching frequencies is selected.

  The invention according to claim 3 is the switching power supply device according to claim 1 or 2, wherein the plurality of switching frequencies are a harmonic of a reception frequency in the tuner section and any one of the plurality of switching frequencies. The difference from the wave is set to be a value equal to or higher than the increase / decrease frequency with respect to the reception frequency when the output level is attenuated by a predetermined amount in the filter.

  According to the switching power supply according to the present invention, the microcomputer can incorporate the oscillating means, whereby the entire switching power supply can be reduced in size. Further, since the microcomputer uses the waveform generated by the oscillating means as the switching frequency pulse, it is not necessary to provide a plurality of oscillating means, and the manufacturing cost can be reduced by suppressing the number of components. In addition, since the microcomputer selects any one of a plurality of switching frequencies set based on the filter characteristics of the bandpass filter according to the reception frequency in the tuner section, it is sufficient to suppress noise generation. It is possible to select a frequency with less influence and generate a switching frequency pulse, thereby effectively preventing the generation of noise.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing the overall configuration of the switching power supply device 1 of the present embodiment.

  As shown in FIG. 1, the switching power supply device 1 includes an antenna 2, a tuner unit 3, a microcomputer 4, and a switching power supply 5.

  The antenna 2 receives a carrier signal modulated into a plurality of frequencies from a transmitter (not shown).

  The tuner unit 3 includes an RF amplification unit 6, an oscillator 7, a mixing unit 9, an IF amplification unit 10, a band pass filter 11 and a detection unit 12, and is received by the antenna 2 in accordance with a tuning control signal from the microcomputer 4. A carrier signal existing in one frequency band is received from the carrier signals, and the received signal is converted into an intermediate frequency signal.

  Among these, the RF amplification unit 6 includes a radio frequency (RF) amplifier (not shown), and amplifies a reception signal received by the antenna 2.

  The oscillator 7 includes a crystal oscillator 8 so as to generate a single-frequency waveform and output the waveform to the mixing unit 9.

  The mixing unit 9 includes a mixer (not shown), mixes the reception signal amplified by the RF amplification unit 6 and the single-frequency waveform output from the oscillator 7, and is a constant lower than the reception frequency. An intermediate frequency signal is generated and output to the IF amplifying unit 10.

  The IF amplifying unit 10 includes an intermediate frequency (IF) amplifier (not shown) and a band pass filter 11, and after band limiting the intermediate frequency signal input from the mixing unit 9 with the band pass filter 11, The band-limited intermediate frequency signal is amplified and output.

  The detector 12 detects the intermediate frequency signal input from the IF amplifier 10.

  Next, the microcomputer 4 includes a CPU, a ROM and a RAM (not shown), and controls the switching power supply device 1 in an integrated manner.

  Further, the microcomputer 4 determines a reception frequency in the tuner unit 3 by supplying a tuning control signal to the tuner unit 3.

  In addition, the microcomputer 4 selects any one of a plurality of switching frequencies set based on the filter characteristics of the bandpass filter 11 according to the reception frequency in the tuner unit 3, and based on the selected switching frequency. A switching frequency pulse is generated and output to the switching power supply 5.

  That is, the microcomputer 4 includes a built-in oscillator 13 including a crystal oscillator 14 as an oscillation means, and the built-in oscillator 13 generates a single-frequency waveform.

  The microcomputer 4 includes a table (LUT) in which the reception frequency in the tuner unit 3 is associated with a plurality of switching frequencies set based on the filter characteristics of the bandpass filter 11.

  Further, the microcomputer 4 selects one of a plurality of switching frequencies according to the reception frequency in the tuner unit 3 from the above table, and the waveform generated by the built-in oscillator 13 based on the selected switching frequency. Is subjected to pulse width modulation (PWM) to generate a switching frequency pulse and output it to the switching power supply 5.

  Here, a plurality of switching frequencies set based on the filter characteristics of the bandpass filter 11 will be described. First, a case where two types of switching frequencies are set will be described.

  FIG. 2 is a graph showing an example of filter characteristics of the bandpass filter 11. As shown in FIG. 2, the amount of attenuation of the output level with respect to the input level is a predetermined amount (about 50 dB in FIG. 2) when the increase / decrease frequency with respect to the reception frequency is about ± 30 kHz.

  In the microcomputer 4, two types of switching frequencies corresponding to the filter characteristics of the band pass filter 11 are set. That is, in the microcomputer 4, the difference Δf between the reception frequency and the switching frequency harmonic (integer multiple) in the tuner unit 3 becomes a value equal to or greater than the increase / decrease frequency (± 30 kHz) when the output level is attenuated by a predetermined amount. As described above, two types of switching frequencies are set. As a result, when one of the two types of switching frequencies is selected, the reception frequency does not overlap with the harmonics (integer multiples) of the switching frequency, so that generation of noise due to switching of the switching power supply 5 is prevented. .

  FIG. 3 shows an example of the relationship between the reception frequency in the tuner section 3 and the harmonics of the switching frequency output to the switching power supply 5.

  FIG. 3 shows an example in which the reception frequency is 729 kHz to 774 kHz. In FIG. 3, the switching frequency A (240 kHz) and the switching frequency B (260 kHz) are set so that the difference Δf between the reception frequency and the harmonics of the switching frequency (integer multiple) is ± 30 kHz.

  FIG. 4 shows an example of the relationship between the reception frequency in the tuner unit 3 and the switching frequency selected by the microcomputer 4.

  As shown in FIG. 4, when the reception frequency is 729 kHz, the difference from the harmonic b (780 kHz) is −51 kHz, and the reception frequency does not overlap with the harmonic b of the switching frequency B. Further, when the reception frequency is 774 kHz, the difference from the harmonic a (720 kHz) is +54 kHz, and the reception frequency does not overlap with the harmonic a of the switching frequency A. For this reason, generation of noise due to switching of the switching power supply 5 is prevented by selecting one of the two types of switching frequencies according to the reception frequency.

  That is, as shown in FIGS. 3 and 4, switching frequency B (260 kHz) is selected when the reception frequency is 729 to 747 kHz, and switching frequency A (240 kHz) is selected when the reception frequency is 756 to 774 kHz. Generation of noise due to is prevented.

  As another example, the relationship between the reception frequency and the harmonics of the switching frequency shown in FIG. 5 will be described. In FIG. 5, the difference between the reception frequency in the tuner unit 3 and either the harmonic c of the switching frequency C (960 kHz which is four times 240 kHz) or the harmonic d of the switching frequency D (1040 kHz which is four times 260 kHz). Is set to ± 80 kHz (± 30 kHz or more). Thereby, when the switching frequency C or the switching frequency D is selected according to the reception frequency, since the reception frequency does not overlap with either the harmonic c or the harmonic d, generation of noise due to switching is prevented. In addition, when the reception frequency does not overlap with either the harmonic c or the harmonic d, generation of noise is prevented even if either the switching frequency C or the switching frequency D is selected.

  FIG. 6 shows an example of the relationship between the reception frequency in the tuner unit 3 and the switching frequency selected by the microcomputer 4.

  As shown in FIG. 6, switching frequency D (260 kHz) is selected when the receiving frequency is 981 to 999 kHz, and switching frequency C (240 kHz) is selected when the receiving frequency is 1008 to 1026 kHz. Is prevented. As shown in FIG. 5, when the reception frequency is 999 kHz or 1008 kHz, the reception frequency does not overlap with either the harmonic c or the harmonic d, so either the switching frequency C or the switching frequency D is selected. Also good.

  Next, a case where three types of switching frequencies are set according to the filter characteristics of the bandpass filter 11 will be described. Note that the types of switching frequencies are not limited to two or three.

  FIG. 7 shows an example of the relationship between the reception frequency in the tuner unit 3 and the harmonics of the switching frequency output to the switching power supply 5 when the increase / decrease frequency with respect to the reception frequency is about ± 50 kHz as the filter characteristic of the bandpass filter 11. Indicates.

  FIG. 7 shows an example in which the reception frequency is 522 kHz to 756 kHz. In FIG. 7, the switching frequency E (160 kHz), the switching frequency F (180 kHz), and the switching frequency G (200 kHz) are set so that the difference Δf between the reception frequency and the harmonics of the switching frequency (integer multiple) is ± 50 kHz. Has been. As a result, when any one of the three types of switching frequencies is selected, the reception frequency does not overlap with the harmonics (integer multiples) of the switching frequency, thereby preventing the occurrence of noise due to switching of the switching power supply 5. ing.

  Further, the microcomputer 4 includes a frequency divider 15 that divides the generated switching frequency pulse and outputs it to the switching power supply 5.

  The switching power source 5 includes a switching element (not shown), and performs switching operation in synchronization with a switching frequency pulse output from the microcomputer 4 to switch a DC voltage / current from a DC power source (not shown). It is designed to output stable DC voltage / current.

  Next, the operation of the switching power supply device 1 according to this embodiment will be described. In the following, a case where two types of switching frequencies are set will be described.

  When the antenna 2 receives the carrier signal, the tuner unit 3 receives the carrier signal existing in one frequency band from among the carrier signals received by the antenna 2 in accordance with the tuning control signal from the microcomputer 4 and receives the received signal. Is converted to an intermediate frequency signal.

  That is, the RF amplification unit 6 amplifies the reception signal received by the antenna 2, and the mixing unit 9 mixes the reception signal amplified by the RF amplification unit 6 and the single frequency waveform output from the oscillator 7. The IF amplifying unit 10 generates an intermediate frequency signal, band-limits the intermediate frequency signal input from the mixing unit 9 with the bandpass filter 11, and then amplifies and outputs the band-limited intermediate frequency signal. Further, the detector 12 detects the intermediate frequency signal input from the IF amplifier 10.

  Next, the microcomputer 4 generates a switching frequency pulse based on a plurality of switching frequencies set according to the reception frequency in the tuner unit 3 and outputs the switching frequency pulse to the switching power supply 5.

  That is, the microcomputer 4 uses the table (LUT) in which the reception frequency in the tuner unit 3 and the two types of switching frequencies set based on the filter characteristics of the bandpass filter 11 are associated with each other. One of the two types of switching frequencies is selected according to the above. Then, when the switching frequency pulse is generated by performing pulse width modulation (PWM) on the waveform generated by the built-in oscillator 13 based on the selected switching frequency, the frequency divider 15 divides the switching frequency pulse and supplies it to the switching power source 5. Output.

  These two types of switching frequencies are set based on the filter characteristics of the bandpass filter 11. That is, when the increase / decrease frequency when the output level is attenuated by a predetermined amount is “± 30 kHz”, the difference Δf between the reception frequency and the harmonics of the switching frequency (integer multiple) in the tuner unit 3 is a value of ± 30 kHz or more. Thus, two types of switching frequencies are set.

  Subsequently, the microcomputer 4 outputs a switching frequency pulse corresponding to the reception frequency to the switching power supply 5 by performing pulse width modulation (PWM) on the waveform generated by the built-in oscillator 13 based on the selected switching frequency.

  Next, the switching power supply 5 performs a switching operation in synchronization with the switching frequency pulse output from the microcomputer 4 and switches a DC voltage / current from a DC power supply (not shown) to output a stable DC voltage / current. To do.

  As described above, according to the switching power supply device 1 according to the present embodiment, the microcomputer 4 includes the built-in oscillator 13, whereby the entire switching power supply device 1 can be downsized. Further, since the microcomputer 4 uses the waveform generated by the built-in oscillator 13 as the switching frequency pulse, it is not necessary to provide a plurality of oscillation means, and the manufacturing cost can be reduced by suppressing the number of components. In addition, since the microcomputer 4 selects any one of a plurality of switching frequencies set based on the filter characteristics of the bandpass filter 11 according to the reception frequency in the tuner unit 3, in order to suppress the generation of noise. It is possible to generate a switching frequency pulse by selecting a frequency that has a sufficiently small influence on the noise, and to effectively prevent noise generation.

  As described above in detail, according to the switching power supply device of the present invention, the entire device can be downsized, the manufacturing cost can be reduced, and the occurrence of noise due to switching can be effectively prevented.

It is a block diagram which shows the whole structure of the switching power supply device which concerns on this embodiment. It is a graph which shows the characteristic example of the filter with which the switching power supply concerning this embodiment is provided. It is a figure which shows the example of a relationship between a receiving frequency and the harmonic of a switching frequency. It is a table | surface which shows the example of a relationship between a receiving frequency and a switching frequency. It is a figure which shows the other example of a relationship between a receiving frequency and the harmonic of a switching frequency. It is a table | surface which shows the other relationship example of a receiving frequency and a switching frequency. It is a figure which shows the other example of a relationship between a receiving frequency and the harmonic of a switching frequency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Switching power supply device 2 Antenna 3 Tuner part 4 Microcomputer 5 Switching power supply 6 Amplifying part 7 Oscillator 8 Crystal oscillator 9 Mixing part 10 Amplifying part 11 Band pass filter 12 Detection part 13 Built-in oscillator 14 Crystal oscillator 15 Frequency divider

Claims (3)

A tuner that includes a filter, receives a carrier signal present in one frequency band from among the carrier signals received by the antenna, converts the received signal into an intermediate frequency signal, and limits the band by the filter;
Built-in oscillation means, selects any one of a plurality of switching frequencies set based on the filter characteristics of the filter according to the reception frequency in the tuner unit, and based on the selected switching frequency, the oscillation means A microcomputer having a switching frequency pulse as a waveform generated by
A switching power supply that performs a switching operation in synchronization with a switching frequency pulse output from the microcomputer;
A switching power supply device comprising:   The microcomputer includes a table in which a reception frequency in the tuner unit is associated with the plurality of switching frequencies, and any one of the plurality of switching frequencies is selected based on the table. Item 4. The switching power supply device according to Item 1.   The plurality of switching frequencies are equal to or higher than an increase / decrease frequency with respect to a reception frequency when a difference between a reception frequency in the tuner unit and a harmonic of any one of the plurality of switching frequencies is attenuated by a predetermined amount in the filter. 3. The switching power supply device according to claim 1, wherein the switching power supply device is set to have a value of.

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