JP2005237044A - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver where the reception will not be obstructed by the noise generated from a separately-excited switching power unit. <P>SOLUTION: A microcomputer 2 stores the information of received frequency and controls a receiving circuit 4, based on the information of received frequency. Furthermore, the microcomputer 2 receives the input of the DC output voltage V<SB>OUT</SB>from a separately-excited switching power unit 1, and generates a control signal, where N (N is a natural number) times of the frequency and the received frequency are not substantially the same and which stabilizes DC output V<SB>OUT</SB>, according to the stored information of received information and the information of the DC output voltage V<SB>OUT</SB>inputted from a separately-excited switching power unit 1, and sends out the generated control information to the separately-excited switching power unit 1, and switches on or switches off the switching element (not shown) within the separately-excited switching power unit 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a receiving device including a separately excited switching power supply device.

  An example of the configuration of a conventional receiving apparatus is shown in FIG. The receiving apparatus of FIG. 4 is a receiving apparatus including a separately-excited switching power supply device, which is a separately-excited switching power supply device 1 ′, a microcomputer (hereinafter also referred to as a microcomputer) 2 ′, an antenna 3, and a receiving device. The circuit 4, the power amplifier 5, and the speaker 6 are included.

The separately excited switching power supply device 1 ′ converts the commercial AC voltage V _IN into a DC output voltage V _OUT and supplies the DC output voltage V _OUT to the microcomputer 2 ′, the receiving circuit 4, and the power amplifier 5. The microcomputer 2 ′ controls the receiving circuit 4 so that the receiving circuit 4 receives and demodulates a reception signal having a desired frequency. The demodulated signal output from the receiving circuit 4 is transmitted to the power amplifier 5. The power amplifier 5 drives the speaker 6 according to the input demodulated signal.

Next, a configuration example of the separately excited switching power supply device 1 ′ is shown in FIG. The commercial AC voltage V _IN is rectified by the rectifier circuit 11 and smoothed by the smoothing capacitor 12 to be converted into a DC voltage. The DC voltage is supplied to a series circuit including the primary winding 13 a of the switching transformer 13 and the switching transistor 14.

The switching transistor 14 is turned on and off by a control signal output from the control circuit 19. When the switching transistor 14 is in the ON state, a DC voltage is supplied to the primary winding 13a of the switching transformer 13, and excitation energy is accumulated in the primary winding 13a of the switching transformer 13. On the other hand, when the switching transistor 14 is in the OFF state, the excitation energy accumulated in the primary winding 13 a of the switching transformer 13 is taken out from the secondary winding 13 b of the switching transformer 13. Therefore, the induced voltage output from the secondary winding 13b of the switching transformer 13 is a rectangular wave AC voltage. This rectangular wave AC voltage is rectified by the rectifier diode 15 and smoothed by the smoothing capacitor 16 to become the DC output voltage V _OUT .

The circuit composed of the rectifier diode 15 and the smoothing capacitor 16 averages the voltage during the period in which the induced voltage output from the secondary winding 13b of the switching transformer 13 is positive, and obtains the average value of the voltage integrated value in one cycle of the switching cycle. Get proportional output. Therefore, the DC output voltage V _OUT is a value proportional to the ON period of the switching transistor 14.

The feedback amplifier 17 compares the DC output voltage V _OUT with the internal reference voltage, and sends the comparison result to the control circuit 19 through the photocoupler 18 as a comparison signal. The control circuit 19 generates a control signal based on the comparison signal, shortens the ON period of the switching transistor 14 if the DC output voltage V _OUT is greater than the reference voltage, and switches if the DC output voltage V _OUT is not greater than the reference voltage. The on period of the transistor 14 is lengthened. The off-period of the switching transistor 14 is fixed. As a result, the DC output voltage V _OUT is maintained at a predetermined value.
Japanese Patent Laid-Open No. 5-198150

  However, in the separately excited switching power supply apparatus of FIG. 5, the ON period of the switching transistor 14 has no relation to the reception frequency of the reception circuit 4 and is determined only according to the state of the load such as the power amplifier 5. In many cases, the switching noise of the excitation type switching power supply 1 ′ reaches the receiving circuit 4 due to radiation or the like, and the receiving circuit 4 receives the switching noise. In such a case, the received signal that should be received is obstructed by the switching noise and cannot be received properly.

According to the configuration of the separately excited switching power supply apparatus of FIG. 5, the commercial AC voltage V _IN is converted into an AC pulse voltage by switching of the switching transistor 4 after being full-wave rectified and smoothed. _When the effective value of _IN is 100 V, switching noise is generated from an AC pulse voltage of about 140 V peak-to-peak.

  The fundamental frequency of switching noise determined by the ON period of the switching transistor 4 is generally 50 kHz to 200 kHz, which corresponds to 1/9 to 1/11 of the reception frequency 522 kHz to 1629 kHz of AM radio broadcasting in Japan. Since the switching noise is composed of the fundamental wave of the fundamental frequency and its harmonics, if the reception circuit 4 is a reception circuit for receiving AM radio broadcasts, reception is disturbed by the ninth to eleventh harmonic components of the switching noise. Is done.

  In order to prevent such reception interference due to switching noise, a method of reducing harmonic components of switching noise generated from a separately-excited switching power supply device is conceivable. However, the arrangement of components and the printed wiring board are greatly involved. The implementation of this method was very difficult.

  In view of the above problems, an object of the present invention is to provide a receiving apparatus in which reception is not disturbed by noise generated from a separately excited switching power supply apparatus.

  In order to achieve the above object, a separately-excited switching power supply according to the present invention converts a DC input voltage into an AC voltage by an on / off operation and supplies it to the primary winding of the switching transformer. A switching element, a conversion circuit that converts an AC voltage induced in the secondary winding of the switching transformer into a DC output voltage, and outputs information related to the value of the DC output voltage output from the conversion circuit. And external input means for inputting a control signal for controlling on / off of the switching element from the outside and supplying the control signal to the control terminal of the switching element.

  According to such a configuration, information on the value of the DC output voltage is output to the outside, and a control signal for on / off control of the switching element is input from the outside. Therefore, the control signal is set to only the DC output voltage. The signal can be determined according to the DC output voltage and other parameters without being determined according to the signal. Then, by using the separately-excited switching power supply device having the above configuration as the receiving device and setting the other parameter as the reception frequency, reception is prevented from being interrupted by switching noise generated from the separately-excited switching power supply device. It becomes possible.

  In order to achieve the above object, in the receiving apparatus according to the present invention, a separately excited switching power supply having the above-described configuration and a receiving circuit using a DC output voltage output from the separately excited switching power supply as a driving voltage. And receiving frequency information, controlling the receiving circuit based on the received frequency information, and according to the received frequency information and information output from the external output means of the separately excited switching power supply device N times the frequency (N is a natural number) and the reception frequency are not substantially the same, and a control signal that stabilizes the DC output voltage is generated, and the generated control signal is generated outside the separately excited switching power supply device. And a control circuit for sending out to the input means.

  According to such a configuration, since N times the frequency of the control signal is not substantially the same as the reception frequency, N times the switching frequency of the separately excited switching power supply device is not substantially the same as the reception frequency. Thereby, reception can be prevented from being disturbed by switching noise generated from the separately excited switching power supply device.

  The receiving device having the above-described configuration may further include a power supply device that supplies the control circuit with a voltage that serves as a drive voltage for the control circuit.

  According to such a configuration, since the control circuit can be started before starting the separately excited switching power supply, it is not necessary to separately provide a control circuit for starting the separately excited switching power supply.

  According to the present invention, it is possible to realize a receiving apparatus in which reception is not disturbed by noise generated from a separately excited switching power supply apparatus.

  An embodiment of the present invention will be described with reference to the drawings. A configuration example of a receiving apparatus according to the present invention is shown in FIG. 1 that are the same as those in FIG. 4 are denoted by the same reference numerals. The receiving apparatus of FIG. 1 is a receiving apparatus provided with a separately-excited switching power supply, and includes a separately-excited switching power supply 1, a microcomputer 2, an antenna 3, a receiving circuit 4, a power amplifier 5, and a speaker. 6 and the sub power supply device 7.

The separately excited switching power supply device 1 converts the commercial AC voltage V _IN into a DC output voltage V _OUT and supplies the DC output voltage V _OUT to the receiving circuit 4 and the power amplifier 5. The microcomputer 2 controls the receiving circuit 4 so that the receiving circuit 4 receives and demodulates a received signal having a desired frequency, and simultaneously controls the separately excited switching power supply 1. Further, since the microcomputer 2 needs to be activated before the separately excited switching power supply 1 is activated, a sub power supply device 7 for supplying power to the microcomputer 2 is provided separately from the separately excited switching power supply 1. The demodulated signal output from the receiving circuit 4 is transmitted to the power amplifier 5. The power amplifier 5 drives the speaker 6 according to the input demodulated signal. As an example of the configuration of the sub power supply device 7, there can be cited a configuration including a transformer that uses the commercial AC voltage V _IN as a primary voltage and a rectifier circuit that rectifies the secondary voltage of the transformer and supplies it to the microcomputer 2.

  Next, a configuration example of the separately excited switching power supply device 1 is shown in FIG. 2 that are the same as those in FIG. 5 are denoted by the same reference numerals.

A commercial AC voltage V _IN is applied to the input side of a rectifier circuit 11 formed by bridge-connecting four diodes, and a smoothing capacitor 12 is connected to the output side of the rectifier circuit 11. The commercial AC voltage V _IN is rectified by the rectifier circuit 11 and smoothed by the smoothing capacitor 12 to be converted into a DC voltage.

  A series circuit including a primary winding 13 a of the switching transformer 13 and a switching transistor 14 which is an n-type channel MOSFET is connected to both ends of the smoothing capacitor 12. One end of the primary winding 13 a of the switching transformer 13 is connected to the positive polarity side of the smoothing capacitor 12, and the source of the switching transistor 14 is connected to the negative polarity side of the smoothing capacitor 12.

  The secondary winding 13 b of the switching transformer 13 is connected to a rectifying / smoothing circuit including the rectifying diode 15 and the smoothing capacitor 16. That is, one end of the secondary winding 13b of the switching transformer 13 is connected to the positive polarity side of the smoothing capacitor 16 via the rectifier diode 15, and the other end of the secondary winding 13b of the switching transformer 13 is the negative polarity of the smoothing capacitor 16. Connected to the side.

Furthermore, a terminal 20 connected to the positive polarity side of the smoothing capacitor 16 and a terminal 21 connected to the negative polarity side of the smoothing capacitor 16 are connected to the microcomputer 2 (not shown in FIG. 2). Thereby, the microcomputer 2 can detect the DC output voltage V _OUT of the separately excited switching power supply device 1. A terminal 22 is also connected to the microcomputer 2. The microcomputer 2 generates a pulse signal corresponding to the DC output voltage V _OUT according to a control flowchart described later, and outputs the pulse signal to the terminal 22. The pulse signal input to the terminal 22 is sent to the gate of the switching transistor 14 through the photocoupler 18.

The switching transistor 14 is turned on and off by a pulse signal sent from the terminal 22 through the photocoupler 18. When the pulse signal is at a high level, that is, when the switching transistor 14 is on, a DC voltage that is a voltage across the smoothing capacitor 12 is supplied to the primary winding 13a of the switching transformer 13, and the primary winding 13a of the switching transformer 13 Excitation energy is accumulated in On the other hand, when the pulse signal is at the low level, that is, when the switching transistor 14 is in the OFF state, the excitation energy accumulated in the primary winding 13a of the switching transformer 13 is extracted from the secondary winding 13b of the switching transformer 13. Therefore, the induced voltage output from the secondary winding 13b of the switching transformer 13 is a rectangular wave AC voltage. This rectangular wave AC voltage is rectified by the rectifier diode 15 and smoothed by the smoothing capacitor 16 to become the DC output voltage V _OUT .

The rectifying / smoothing circuit including the rectifying diode 15 and the smoothing capacitor 16 averages the voltage during the period in which the induced voltage output from the secondary winding 13b of the switching transformer 13 is positive, and averages the voltage integrated value in one cycle of the switching cycle. Get an output proportional to the value. Therefore, the DC output voltage V _OUT is a value proportional to the ON period of the switching transistor 14.

  Next, the control operation performed by the microcomputer 2 will be described with reference to the control flowchart of FIG. The microcomputer 2 reads the set value of the Low level period and the initial value of the High level period stored in the internal memory immediately after startup, generates a pulse signal based on the read data, and outputs the pulse signal to the terminal 22 ( Step # 10). Thereby, the switching operation of the separately excited switching power supply device 1 is started.

  In the subsequent step # 20, the microcomputer 2 controls the receiving circuit 4 to set the receiving frequency. As for the reception frequency, the microcomputer 2 may store a predetermined value, or an input device may be provided in the receiving device so that the user inputs a set value to the input device and sends the set value to the microcomputer 2. Good. What is important here is that there is information on the reception frequency in the microcomputer 2.

In subsequent step # 30, the microcomputer 2 determines whether or not the DC output voltage V _OUT is smaller than a predetermined value.

If the DC output voltage V _OUT is smaller than the predetermined value (Yes in Step # 30), the microcomputer 2 extends the High level period of the pulse signal by 0.1 μsec from the current state (Step # 60). The microcomputer 2 calculates the frequency of the pulse signal after execution of step # 60 (hereinafter referred to as pulse frequency), and N times the pulse frequency (N is a natural number) is within ± 5 kHz of the reception frequency set in step # 20. (Step # 70), and if N times the pulse frequency is within ± 5 kHz of the reception frequency set in Step # 20 (Yes in Step # 70), return to Step # 60 and return to the pulse frequency The calculation is repeated until N times the frequency falls within ± 5 kHz of the reception frequency set in step # 20. When N times the pulse frequency deviates from within ± 5 kHz of the reception frequency set in step # 20, the process proceeds to step # 80 described later. The pulse frequency is the reciprocal of the added value of the high level period and the low level period.

On the other hand, if the DC output voltage V _OUT is not smaller than a predetermined value (No in Step # 30), the microcomputer 2 shortens the High level period of the pulse signal by 0.1 μsec from the current state (Step # 40). Then, the microcomputer 2 calculates the pulse frequency after execution of Step # 40, and determines whether N times the pulse frequency (N is a natural number) is within ± 5 kHz of the reception frequency set in Step # 20 ( Step # 50) If N times the pulse frequency is within ± 5 kHz of the reception frequency set in Step # 20 (Yes in Step # 50), return to Step # 40 and set N times the pulse frequency in Step # 20 The calculation is repeated until the received frequency falls within ± 5 kHz. When N times the pulse frequency deviates from within ± 5 kHz of the reception frequency set in step # 20, the process proceeds to step # 80 described later.

  In step # 80, the microcomputer 2 outputs to the terminal 22 a pulse signal whose frequency has been changed based on the result of the calculation. Thereafter, the microcomputer 2 determines whether or not the reception frequency has been changed (step # 90). If there is a change in the reception frequency (Yes in step # 90), the process proceeds to step # 20, the reception frequency is reset, and then the calculation for obtaining the high level period is repeated. On the other hand, if there is no change in the reception frequency (No in Step # 90), the process proceeds to Step # 30, and the calculation for obtaining the High level period is repeated.

  When the microcomputer 2 performs the control operation according to the control flowchart of FIG. 3, the high level period of the pulse signal is set so that N times the pulse frequency deviates from ± 5 kHz of the reception frequency. It is possible to prevent reception from being disturbed by the generated switching noise.

When the microcomputer 2 performs the control operation according to the control flowchart of FIG. 3, if it is determined in step # 50 or step # 70 that N times the pulse frequency is always outside ± 5 kHz of the reception frequency, step # 80 Since the DC output voltage V _OUT is accurately fed back during the High level period of the pulse signal output at, the DC output voltage V _OUT is in the most stable state. However, even if it is determined in step # 50 or step # 70 that N times the pulse frequency is within ± 5 kHz of the reception frequency, the DC output voltage _VOUT can be stabilized on average. For example, when it is determined in step # 50 that N times the pulse frequency is within ± 5 kHz of the reception frequency, the high level period of the pulse signal output in step # 80 is a period for stabilizing the DC output voltage _VOUT. The DC output voltage V _OUT is lowered more than necessary. However, in the next step # 30, since the DC output voltage V _OUT should be determined to be smaller than the specified value, step # 60. Then, the process proceeds to step # 70, where the processing is performed in the direction of increasing the High level period, that is, in the direction of increasing the DC output voltage _VOUT . Further, in the next process, the DC output voltage V _OUT is processed in a decreasing direction, and the DC output voltage V _OUT can be stabilized on average.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, the control of the high level period of the pulse signal shown in FIG. 3 is until it is devised so that the calculation of the microcomputer becomes easy. Even if the microcomputer generates the pulse signal using another control method, I do not care. Further, the receiving circuit is not limited to a receiving circuit for receiving AM radio broadcasts, and may be a receiving circuit for receiving FM radio broadcasts, for example. The separately excited switching device is not limited to a flyback switching power supply device, and may be a forward switching power supply device, for example.

These are figures which show the example of 1 structure of the receiver which concerns on this invention. These are figures which show one structural example of the separately excited switching power supply device with which the receiver of FIG. 1 is provided. These are the control flowcharts of the microcomputer with which the receiver of FIG. 1 is provided. These are figures which show the example of 1 structure of the conventional receiver. These are figures which show one structural example of the separately excited switching power supply device with which the receiver of FIG. 4 is provided.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Separately excited switching power supply device 2 Microcomputer 4 Receiving circuit 7 Sub power supply device 13 Switching transformer 14 Switching transistor 19 Control circuit 20-22 Terminal

Claims (3)

A switching transformer,
A switching element that converts a DC input voltage into an AC voltage by an on / off operation and supplies it to the primary winding of the switching transformer;
A conversion circuit that converts an AC voltage induced in the secondary winding of the switching transformer into a DC output voltage and outputs the DC voltage;
External output means for outputting information on the value of the DC output voltage output from the conversion circuit to the outside;
An external input means for inputting a control signal for controlling on / off of the switching element from the outside and supplying the control signal to a control terminal of the switching element;
A separately excited switching power supply device comprising: The separately excited switching power supply device according to claim 1;
A receiving circuit using a DC output voltage output from the separately excited switching power supply as a driving voltage;
The reception frequency information is stored, the reception circuit is controlled based on the reception frequency information, and the frequency according to the reception frequency information and the information output from the external output means of the separately excited switching power supply device N times (N is a natural number) and the reception frequency are not substantially the same, and a control signal for stabilizing the DC output voltage is generated, and the generated control signal is used as an external input unit of the separately excited switching power supply device. A control circuit for sending to
A receiving apparatus comprising:   The receiving device according to claim 2, further comprising: a power supply device that supplies a voltage that is a driving voltage of the control circuit to the control circuit.

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