JP3146228B2 - Switching regulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching regulator.

[0002]

2. Description of the Related Art A conventional switching regulator will be described with reference to a basic circuit of a flyback system shown in FIG. Since the circuit operation of the switching regulator of FIG. 7 is well known, a detailed description thereof will be omitted. Briefly, in this switching regulator, the controller 9
Switch 4 in response to a switching signal given from
Turns on and off. Thereby, the DC power supply 3 and the transformer 2
And the primary side 2a is interrupted. Due to this interruption, a voltage is induced on the secondary side 2b of the transformer 2. This induced voltage is converted to a direct current by a direct current conversion circuit 7 including a rectifier diode 5 and a smoothing capacitor 6 to obtain an output voltage to be supplied to a load 8. It is well known that the magnitude of this output voltage is determined by the on / off duty of the switch 4 which is turned on / off in response to a switching signal given from the controller 9. The on / off duty is a ratio between the time when the switch 4 is on and the time when it is off, and the ratio does not change regardless of the frequency of the switching signal. That is, in this type of switching regulator, the magnitude of the output voltage depends on the on / off duty of the switch 4, but does not depend on the frequency of the switching signal, that is, the switching frequency. In order to stabilize the output voltage at a constant level, it is preferable to detect the magnitude of the output voltage and output a switching signal from the controller 9 whose on / off duty is controlled so that the output voltage is kept constant.

In such a switching regulator, a slight side wave component is generated due to not only the switching frequency and its harmonics but also subtle fluctuations of the switching frequency. Such switching frequency, its harmonics and side wave components may appear as noise affecting the operation of electronic devices around it, for example, when listening to the radio near this switching regulator It is well known that the influence of the noise disturbs the reception operation and causes the noise to be heard, and also the television image and the sound to be disturbed.

[0004]

In such a switching regulator, a circuit system is used to prevent the switching frequency, its harmonics, and side wave components from becoming a noise that interferes with the reception operation of an electronic device such as a radio or a television. Can be reduced to some extent by the improvement of, but it cannot be reduced to zero because it is unique to the switching regulator. Therefore, in the related art, the entire switching regulator is covered with a shield cover so that such noise does not leak to the outside as much as possible.

However, in order to prevent the noise from being leaked by such a shield cover, a large-sized and thick-walled one is required in order to enhance the effect of preventing the leakage. There is a problem that the advantages of small size and light weight are greatly impaired.

According to the present invention, each frequency component such as a switching frequency of a switching signal, a harmonic thereof, or a side wave thereof prevents leakage of noise which affects a receiving operation of an electronic device such as a radio or a television around a switching regulator. For the purpose of providing a switching regulator that solves the above problem without providing a shield cover for the electronic device so that the receiving operation of the electronic devices is not obstructed and the advantages of small size and light weight are not impaired. I have.

[0007]

In order to solve such a problem, a switching regulator according to the present invention is connected in parallel to a DC power supply and turned on / off in response to a switching signal to switch the DC power supply. An electrically intermittent switch means, a controller for outputting the switching signal to control the on / off operation of the switch means, and a direct current for converting a voltage output to an output side of the switch means into a direct current and outputting an output voltage A switching signal in which the output voltage does not change with a switching frequency that is the frequency of the switching signal, the request signal requesting the controller to switch the switching frequency to one of a plurality of switching regulators. Output frequency switching circuit Connected, the controller provides a switching signal having a switching frequency corresponding to the request signal from the plurality of switching frequency in response to said request signal to said switch means, said plurality of scan
The least common multiple of the switching frequency is the operating frequency of the electronic device.
It is characterized in that it is set out of several bands .

[0008]

According to the present invention, the switching frequency switching circuit may be configured to select the request signal by an external operation and output the selected signal to the controller.

[0010] The present invention is set in the configuration of claim 1, wherein the switching frequency switching circuit is configured by microcomputers, the microcomputer previously
When the specified condition is detected, the controller
Request signal for switching to the switching frequency
It can also be characterized by outputting a signal.

[0011]

According to the present invention, in response to a request signal from a switching frequency switching circuit, a controller operates to switch to one of a plurality of switching frequencies, and a switch having a signal having the switched switching frequency is used. Since the switching means can be turned on and off, when the switching means is operated with a signal at any one of the switching frequencies, the switching frequency, its harmonics or its side wave components are changed to the surrounding radio, television, or other. If the noise causes the operation of the electronic device, the signal can be switched to a signal of another switching frequency so that the noise does not affect the operation of the electronic device. I can help you. Moreover, multiple switching frequencies
Set the least common multiple of the numbers outside the operating frequency band of the electronic device.
In this case, one of the switching frequency signals
May affect the operation of the electronic device.
Other switches that have a least common multiple relationship with the switching frequency
When the signal of the switching frequency is selected, the operation of the electronic device
All frequencies within the operating frequency band are
It is no longer an integral multiple of the switching frequency,
Operation is selected for other switching frequency signals.
Operating state can be maintained.

[0012]

[0013] The present invention having the above structure as claimed in claim 2, wherein the switching frequency switching circuit, when configured to output to the controller selects the request signal externally operated, the electronic apparatus When the operation is affected by the frequency component generated from the switching regulator, the operator can manually switch to another switching frequency to operate to eliminate the effect.

[0014] The present invention having the above structure as claimed in claim 3, wherein the switching frequency switching circuit is configured by microcomputers, time the microcomputer detects a preset condition, the controller
To switch to the specified switching frequency
If the electronic device is configured to output a request signal , the microcomputer determines that the operation of the electronic device is affected by the switching frequency and automatically switches to another switching frequency. This eliminates the need for the operator to manually operate.

[0015]

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

FIG. 1 is a circuit diagram of a switching regulator according to an embodiment of the present invention. Referring to FIG. 1, a switching regulator 1 of this embodiment has a basic configuration of a flyback system. The switching regulator 1 includes a transformer 2. A primary side 2a of the transformer 2 is connected in parallel to a DC power supply 3 via a switch 4 composed of electronic means such as a transistor. A secondary side 2b of the transformer 2 has a rectifier diode 5 and a smoothing capacitor. 6 are connected in parallel to a load 8 via a direct current conversion circuit 7 consisting of Although the basic operation of the switching regulator 1 of the flyback type is well-known, the DC power supply 3 accompanying the on / off of the switch 4 is simply described.
The voltage induced on the secondary side 2b of the transformer 2 due to the interruption of the primary side 2a of the transformer 2 with respect to
The DC voltage is supplied to the load 8 as an output voltage.

As described above, the switch 4 is connected to the controller 9
The primary side 2a of the transformer 2 is interrupted with respect to the DC power supply 3 by this switching signal, and the voltage induced on the secondary side 2b is converted into direct current by this interruption, so that the load 8 operates in a known manner. DC voltage is supplied in accordance with the following equation. The level of the output voltage supplied to the load 8 is controlled by controlling the pulse width of the level and the pulse width of the low level.

As described above, the magnitude of the output voltage of the switching regulator 1 is normally determined depending on the on / off duty of the switch 4, and does not depend on the frequency of the switching signal, that is, the switching frequency. Therefore, even if the frequency of the switching signal from the controller 9 changes, the magnitude of the output voltage of the switching regulator does not change.

In this embodiment, the switching regulator 1 includes a switching frequency switching circuit 10 connected to a controller 9. The switching frequency switching circuit 10 outputs a request signal requesting the controller 9 to switch the switching frequency. The controller 9 switches the switching frequency to a plurality of stages in response to the request signal. In this case, the plurality of switching frequencies are set such that their least common multiple is outside the operating frequency band of the electronic device. In this way, when the switching regulator 1 is operating with a switching signal having any arbitrary switching frequency, the switching frequency and the harmonic components and side-wave components which are the frequencies related thereto are determined by the operation of the electronic device. The switching frequency switching circuit 10
The controller 9 switches to another switching frequency in response to a request signal from the electronic device. Since the other switching frequency is not an integral multiple of the operating frequency of the electronic device within the band, the electronic device performs In the frequency band, the operation can be performed without being affected by the other switching frequency. Specifically, for example, the controller 9 is provided with a switching frequency switching circuit 10.
Switching frequency is 19 in response to the request signal from
In the case where the electronic device is, for example, an AM radio, the switching frequency, its harmonics, and its side wave components become noise within the reception band of 522 kHz to 1629 kHz when the electronic device is switched to three of 0, 230, and 290 kHz. In order to prevent the reception operation from being hindered, the least common multiple of each switching frequency is set to 127 MHz, which is outside the band of the AM radio reception frequency, and is set to be outside the reception band, that is, larger than 1,629 kHz. With this setting, even if the switching frequency is switched to any arbitrary switching frequency, the least common multiple of the switching frequency is out of the reception band, and all the frequencies in the band are at least one of the switching frequencies. It is no longer an integral multiple of the frequency. As a result, reception interference of AM radio can be eliminated. For example,
When the switching regulator is operating at a switching frequency of 230 kHz and a 690 kHz radio broadcast is being received near this switching regulator, the switching frequency switching circuit 10 outputs two signals.
A request signal for switching to a switching frequency of 90 kHz is output to the controller 9. Then, the controller 9 turns the switch 4 on and off at a switching frequency of 290 kHz. Therefore, for the radio receiving the radio broadcast, the switching frequency is used for all the reception frequencies within the reception frequency band. Will not be any noise.

Next, specific examples of the switching frequency switching circuit of the switching regulator of FIG. 1 will be described with reference to FIGS.
This will be described with reference to FIG. The switching frequency switching circuit 10 of FIG. 2A includes a switching frequency selection switch 11 for enabling selection of a switching frequency by an external operation. The switching frequency selection switch 11 has a first individual contact 11a corresponding to a switching frequency of 190 kHz, a second individual contact 11b corresponding to a switching frequency of 230 kHz, and 290 kHz.
Individual contact 11c corresponding to the switching frequency of
And a movable contact 11d that moves between these individual contacts in accordance with the selection of the switching frequency. Each of the individual contacts 11a to 11c is connected to a power supply via resistors 12 to 14 having the same resistance value Ra, and a resistor 15 having a resistance value Rb (where Ra >> Rb) is provided between the movable contact 11d and the ground. Is connected. Each individual contact 11a
11c are individually connected to the input sections A, B, and C of the controller 9, respectively. Since the input impedance Zin of the input section of the controller 9 is in a relationship of Zin >> Ra, the potential of the input section corresponding to the individual contact not connected to the movable contact 11d becomes high level, and the movable contact 11d is connected. The potential of the input section corresponding to the individual contact becomes low level. Therefore, the controller 9
When the movable contact 11d is connected to the first individual contact 11a, for example, as shown in the drawing, the potential of the input section A becomes low level, and it can be detected that the switching frequency is selected to 190 kHz. Although the number of switching of the switching frequency is three in the embodiment, the number can be arbitrarily increased or decreased.

Therefore, as shown in the figure, the movable contact 11d of the switching frequency selection switch 11 is connected to the first individual contact 11a so that noise generated from the switching regulator during use of the switching regulator can be received by surrounding electronic equipment such as a radio. When the operation is adversely affected and noise is emitted from the radio, by connecting the movable contact 11d to the second individual contact 11b, noise can be prevented from being emitted from the radio.

Here, as described with reference to FIG. 2B, the controller 9 internally includes three oscillation circuits 9a and 9a.
b, 9c, the first oscillating circuit 9a has an input section A, and when the potential of the input section A is low,
The second oscillation circuit 9b oscillates at a frequency of 230 kHz when the potential of the input portion b is low.
The third oscillation circuit 9c has an input section C and oscillates when the potential of the input section C is at a low level, and the switch 4 is turned on and off by a switching signal output from each oscillation circuit. It is supposed to be.

Next, FIG. 2C will be described. In this figure, a switching frequency switching circuit is a microcomputer 10 mounted on a synthesizer tuner, and a controller 9 has two inputs a and b, and the inputs a and b are two data lines with the microcomputer 10. D0 and D1 are individually connected. Then, the microcomputer 10 supplies combination data of a high-level signal and a low-level signal to the input units a and b of the controller 9 via the data lines D0 and D1, respectively. Then, when the data of state 1 of the combination in which both the input sections a and b of the controller 9 are at the high level are given, the switching frequency of 190 kHz, the state of the state 2 in which the input section a is at the high level and the input section b is at the low level 230kHz given data
The switching frequency of 290 kHz is selected when the data of the state 3 of the combination in which the input section a is at the low level and the input section b is at the high level is given. As an example of an electronic device that is adversely affected by noise generated from the switching regulator, for example, a synthesizer tuner equipped with the microcomputer, the microcomputer 10 of the synthesizer tuner has the input unit a at a low level and the input unit b at a high level. 690 kHz in the state 2 of the combination of
When trying to receive a radio broadcast, 690 kHz is 2
Since the frequency is 30 times the frequency of 30 kHz, the microcomputer uses the switching frequency of the switching regulator of 23 kHz.
It is determined that if the frequency remains at 0 kHz, the reception operation of the synthesizer tuner is adversely affected by noise, and the input section a is set to the high level and the input section b is set to the low level, and the switching frequency is set to 290 kHz.
Switching the radio reception frequency to 690 kHz eliminates any noise.

Here, the controller 9 includes a state discriminating circuit 9d for discriminating data of a state given from the microcomputer 10 as described with reference to FIG.
It has the same three oscillating circuits 9a, 9b, 9c as in FIG. 2 (a), and the state discriminating circuit 9d has three output units c, d, e, respectively, and these output units c, d , E are connected to the respective input sections A, B, C of the respective oscillation circuits 9a, 9b, 9c. The state determination circuit 9d outputs a low level from the output section c to the input section A of the first oscillation circuit 9a when the combination data of the state 1
Is low from the output d to the input b of the second oscillation circuit 9b, and is low from the output e to the input c of the third oscillation circuit 9c for the combination of state 3. By outputting a signal, each oscillation circuit 9
a, 9b, 9c are 190, 230, 290 kHz, respectively.
An oscillation output having a switching frequency of z is output as a switching signal.

Although the switching regulator of the above embodiment is of the flyback type, the switching regulator 16 of the forward type can be similarly implemented as shown in FIG. Since the basic configuration and operation of the forward type switching regulator 16 are well known, a detailed description thereof will be omitted. However, the magnitude of the output voltage depends on the on / off duty of the switch 4 as in the flyback type. It does not depend on the switching frequency. Therefore, the switching frequency switching circuit 10 having the same configuration as that described in the above embodiment is connected to the controller 9 in the same manner so that the switching frequency can be switched, so that the switching operation can be performed for the reception operation of the surrounding electronic equipment, for example, the radio. When the switching frequency has an adverse effect, the adverse effect can be eliminated by switching the switching frequency in response to a request signal from the switching frequency switching circuit 10.

As is well known, the forward type switching regulator 16 of FIG. 3 has lower noise than the flyback type switching regulator 16 and is therefore more effective in eliminating the above-mentioned adverse effects.

A forward type switching regulator 1 in which the current waveform of the switch shown in FIG.
Even when the switching frequency switching circuit 10 is connected to the controller 9 in the same manner as in the above-described embodiment, the same operation and effect as described above can be obtained. The switching regulator 1 shown in FIG.
In 7, the current waveform of the switch 4 becomes sinusoidal due to the resonance capacitor 18 parallel to the primary side 2a of the transformer 2 and the resonance coil 19 in series between one end of the primary side 2a and the switch 4. Since the noise is lower than that of a normal forward type switching regulator, the above-mentioned effect is more remarkable.

Further, even when the switching frequency switching circuit 10 is connected to the controller 9 of the switching regulator 20 of the half-bridge type shown in FIG. Since the half-bridge type has lower noise than the forward type depending on the design, the above-mentioned effect is more remarkable.
In FIG. 5, the switch 4 is connected between one end of the primary side 2a of the transformer 2 and the DC power supply 3 and between the other end of the primary side 2a and the DC power supply 3, respectively. In response to the request signal from the frequency switching circuit 10, the on / off operation of both switches 4 is controlled in the same manner as described above.

Further, even when the switching frequency switching circuit 10 is connected to the half-bridge type switching regulator 21 in which the current waveform of the switch shown in FIG. . In the switching regulator 19 of FIG. 6, the current waveform of the switch 4 becomes sinusoidal due to the leakage inductance between the resonance capacitor 22 and the transformer 2. The switching regulator 21 shown in FIG. 6 in which the voltage and / or current of the switch 4 is sinusoidal has a lower noise than that of the normal half-bridge type, so that the above-mentioned effect is more remarkable. In the switching regulator 21 of FIG. 6 as well, the switch 4 is connected between one end of the primary side 2a of the transformer 2 and the DC power supply 3 and between the other end of the primary side 2a and the DC power supply 3 as in FIG. The controller 9 responds to a request signal from the switching frequency switching circuit 10 to control the on / off operation of both switches 4 in the same manner as described above. In this system, the output voltage does not depend on the switching frequency.
It does not depend on the on-off duty.

[0030]

According to the present invention as described above, according to the present invention, it is in when Zureka one switch means switching signal of the switching frequency is operating, the switching frequency, the electronic device its harmonics etc. in surrounding For example, if it becomes noise for the operation of radio or television,
By switching to other switching frequencies, it will be able to avoid the electronic equipment noise, thereby, <br/> traditional so noise does not affect the electronic device according to the switching frequency and frequency associated therewith a weight was set only, also thick shield cover thickness is not required, small size is an advantage of the switching regulator by the shield cover, it is unnecessary to advantage light is impaired.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a switching regulator according to an embodiment of the present invention.

FIGS. 2A and 2B are specific circuit diagrams of the switching regulator of FIG. 1 of the present invention, wherein FIG. 2A is a circuit diagram specifically showing a switching frequency switching circuit particularly when the switching frequency is switched by an external operation, and FIG. (a) is a specific circuit diagram of a controller used in (a), (c) is a circuit diagram specifically showing a switching frequency switching circuit particularly when a switching frequency is switched using a microcomputer mounted on a synthesizer tuner, and (d) is (c) FIG. 2 is a specific circuit diagram of a controller used in (1).

FIG. 3 is a circuit diagram of a switching regulator according to another embodiment of the present invention.

FIG. 4 is a circuit diagram of a switching regulator according to another embodiment of the present invention.

FIG. 5 is a circuit diagram of a switching regulator according to another embodiment of the present invention.

FIG. 6 is a circuit diagram of a switching regulator according to another embodiment of the present invention.

FIG. 7 is a circuit diagram of a conventional switching regulator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Switching regulator 2 Transformer 2a Transformer primary side 2b Transformer secondary side 3 DC power supply 4 Switch 7 DC conversion circuit 8 Load 9 Controller 10 Switching frequency switching circuit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 3/28

Claims (3)

(57) [Claims] A switch connected in parallel to the DC power supply and electrically turning on and off the DC power supply in response to a switching signal; and an on / off operation of the switch outputting the switching signal. And a DC conversion circuit that converts the voltage output to the output side of the switch means into a direct current and outputs an output voltage, while the output voltage does not change due to the switching frequency that is the frequency of the switching signal. In a switching regulator, a switching frequency switching circuit that outputs a request signal requesting the controller to switch the switching frequency to any one of a plurality of switching regulators is connected, and the controller responds to the request signal by a plurality of switching frequency switching circuits. Of the switching frequencies Gives a switching signal having a switching frequency corresponding to the No. to the switch means, the least common multiple of said plurality of switching frequency, the electronic device
A switching regulator set outside the operating frequency band of the switch. 2. The switching frequency switching circuit according to claim 1, wherein
Select the request signal by operating the
The switching regulator according to claim 1, characterized in that the force. 3. The switching frequency switching circuit according to claim 1 ,
The microcomputer is composed of an microcomputer.
When the computer detects a preset condition, it
The controller switches to the specified switching frequency.
2. The switching regulator according to claim 1, wherein the switching regulator outputs a request signal for requesting the switching.