JP2007259651A - Switching dc power supply and its power supply synchronizing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching DC power supply capable of essentially evading influence of switching noises, in equipment for which high stability is required, and its power source synchronizing method. <P>SOLUTION: The switching DC power supply is equipped with a power supply synchronizing circuit 10 actuating a switching circuit 3 in synchronization with a particular phase of a commercial AC power supply 1. The power supply synchronizing circuit 10 includes a high frequency oscillator 12 oscillating a stable clock signal of 1 MHz or more, a phase detection circuit 14 detecting the particular phase (for example, a zero cross point) of the commercial AC voltage, a dividing circuit 16 counting the clock signal and forming a switching clock of 1 to 100 kHz, and an enable circuit 18 outputting an approval signal approving counting of the dividing circuit in synchronization of the particular phase. The dividing circuit 16 counts the clock signal corresponding to the approval signal to output the switching clock to the switching circuit 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a switching DC power source that forms a DC power source from a commercial AC power source by a switching method, and a power source synchronization method thereof.

A switching DC power supply generally rectifies an AC power supply to obtain a DC power supply. The output of the DC power supply is temporarily converted into an AC voltage by an inverter switch or the like, and the AC voltage is transformed by a transformer. The output is converted by a rectifier circuit. It is converted again to a DC voltage.
Such a switching DC power supply is disclosed in Patent Document 1, Non-Patent Document 1, and the like.

FIG. 4 is a specific example of a conventional switching DC power supply. In this figure, the AC voltage of the commercial AC power supply 1 is smoothed by a full-wave rectification of a diode in the first rectifier circuit 2 and a filter by a resistor and a capacitor to become a DC voltage. This DC voltage is converted into a switching pulse of 1 kHz or more by a switching circuit 3 such as a transistor. The switching circuit 3 is controlled by the power supply control circuit 4.
The switching pulse voltage is stepped down (or stepped up) by the transformer 5. The switching pulse stepped down (or stepped up) by the transformer is full-wave rectified by the second rectifier circuit 6 and further converted into a DC voltage by a resistor and capacitor filter in the DC smoothing circuit 7, a stabilized voltage circuit by a transistor and a reference power supply IC. Converted.

    There is also a method of stabilizing the output voltage or current by controlling the switching circuit 3 from the deviation between the voltage of the DC smoothing circuit 7 and the reference voltage 9 by the deviation detection amplifier 8. Since this system performs transformer coupling of high frequency signals, a small transformer can be used, which helps to reduce the weight of the power supply.

  For the power supply control circuit 4, for example, a pulse width modulation element (PWM) is used. For the switching circuit 3, a transistor, an IGBT (insulated gate bipolar mode transistor), or the like is used.

    Even in a traditional chopper type switching regulator, the DC voltage of the output can be changed to some extent due to the time constant of the rectifying inductor L and the capacitor C connected immediately after the switching element and the switching frequency.

Japanese Patent Application Laid-Open No. 6-78535, “DC Power Supply Device” Toshiba website, Internet <URL: www. semicon. toshiba. co. jp / prd / pdf_presen / tr_PWMOSFET4_200502. pdf>

Since the conventional switching DC power supply described above performs power control by switching asynchronously with the input commercial AC power supply, switching noise is caused by a sharp pulse change (rising and falling) that occurs during power control by this switching circuit. Had occurred.
As a result, in this DC power supply, switching noise is generated on the input side asynchronously with the frequency of the input commercial AC power supply, and noise is radiated spatially as electromagnetic waves.

    The switching noise described above has a frequency of several kHz to several MHz corresponding to a switching pulse, and can be removed to such an extent that a general device is not affected by the filter.

However, for devices that require high stability, such as power supplies for accelerators for X-ray free electron lasers and power supplies for high-sensitivity seismometers, removal with a filter is not sufficient, and switching noise is adversely affected. There was a fear.
In addition, the filter may reduce the influence of this switching noise on the external device of the power supply, but it cannot be completely removed.

  The present invention has been developed to solve such problems. That is, an object of the present invention is to provide a switching DC power supply and a power supply synchronization method thereof that can essentially avoid the influence of switching noise in a device that requires high stability.

According to the present invention, a first rectifier circuit that rectifies a commercial AC voltage into a first DC voltage, a switching circuit that generates a switching pulse by switching control of the first DC voltage, and a transformer that converts the voltage of the switching pulse. And a switching DC power supply having a second rectifier circuit that rectifies the switching pulse voltage-converted by the transformer into a second DC voltage,
There is provided a switching DC power supply comprising a power supply synchronization circuit that operates a switching circuit in synchronization with a specific phase of a commercial AC power supply.

According to a preferred embodiment of the present invention, the power supply synchronization circuit includes a high-frequency oscillator that oscillates a stable clock signal of 1 MHz or more;
A phase detection circuit for detecting a specific phase of the commercial AC voltage;
A frequency divider that counts the clock signal to form a switching clock of 1 kHz or more and less than 100 kHz;
An enable circuit that outputs a permission signal that permits counting of the frequency divider circuit in synchronization with the specific phase, and
The frequency divider circuit counts the clock signal according to the permission signal and outputs a switching clock to the switching circuit.

The specific phase of the commercial AC voltage is a zero cross point,
Furthermore, it is preferable to have a phase shift setting circuit that shifts the zero cross point and the rising point of the clock signal so as not to coincide with each other.

Further, according to the present invention, a first rectifier circuit that rectifies a commercial AC voltage to a first DC voltage, a switching circuit that generates a high-frequency pulse of 1 kHz or more and less than 100 kHz from the first DC voltage, and a voltage of the high-frequency pulse A power source synchronization method for a switching DC power source, comprising: a transformer that converts the voltage; and a second rectifier circuit that rectifies the high-frequency pulse voltage-converted by the transformer into a second DC voltage,
There is provided a power supply synchronization method for a switching DC power supply, characterized in that a switching pulse generated in the switching circuit is synchronized with a frequency of a commercial AC power supply.

According to a preferred embodiment of the present invention, a high frequency oscillation step for oscillating a stable clock signal of 1 MHz or higher,
A phase detection step for detecting a specific phase of the commercial AC voltage;
A count permission step for outputting a permission signal in synchronization with the specific phase;
A frequency dividing step of counting the clock signal according to the permission signal to form a switching clock of 1 kHz or more and less than 100 kHz,
The switching clock is output to the switching circuit to operate the switching circuit.

The specific phase of the commercial AC voltage is a zero cross point,
Further, it is preferable to shift the zero cross point and the rising point of the clock signal so as not to coincide with each other.

According to the apparatus and method of the present invention, since the switching circuit is operated in synchronization with a specific phase of the commercial AC power supply by the power supply synchronization circuit, the influence of the switching noise on the external device of the switching DC power supply is temporally affected. Can be constant.
This means that the influence of switching noise on the external device can be greatly reduced. In other words, since the noise generation timing is known, analog data can be converted into digital data and imported into the computer while avoiding the timing.
Therefore, as a result, it is possible to improve the detection sensitivity and stability of the detection apparatus or device in which the power supply of the present invention and a circuit driven by the power supply are incorporated.

As described above, it is impossible to completely eliminate the switching noise by the filter. Moreover, although there is no problem in a general electronic device, a high-precision device that requires extremely high stability and low noise requires further measures against switching noise.
In high-precision experimental equipment, in order to reduce the influence of pulse noise from the switching DC power supply, it is easy to take measures against noise in external equipment by making the noise generation constant in time and space.
Specifically, if the generation of noise is made constant, the influence on the external device is almost known, so that it becomes possible to add a filter in the device or to operate the device at a timing with no influence. If the device is operated at a constant power output timing, the device can be operated at a time when the output fluctuations are always constant without any influence of noise (effectively always a constant power output). It means to increase the operational stability effectively.

From the above viewpoint, the means of the present invention detects the voltage zero-cross point of the input commercial power of the power supply circuit, and starts counting of a stable signal of 1 MHz or more from the crystal oscillator by the detection timing by the enable circuit. Let As a result, the switching timing (phase) of the DC power supply can be matched (synchronized) with the phase of the commercial power.
In addition, the counter signal is frequency-divided by this counter, and a power supply switching clock in the order of kHz is generated. Here, instead of detecting the zero cross point, the phase of the commercial AC power supply may be detected accurately.
The reason why the zero cross timing or phase of the commercial AC power supply is detected with a high frequency signal such as crystal oscillation is to increase the time accuracy of detection / phase setting (phase detection / setting accuracy).

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

FIG. 1 is a block diagram of a switching DC power supply according to the present invention.
As shown in this figure, the switching DC power supply according to the present invention includes a first rectifier circuit 2, a switching circuit 3, a transformer 5, and a second rectifier circuit 6.
The first rectifier circuit 2 includes a diode, a resistor, and a capacitor (not shown), and rectifies the AC voltage of the commercial AC power source 1 of, for example, 60 Hz or 50 Hz into the first DC voltage.
The switching circuit 3 is a transistor, for example, and generates a switching pulse by switching control of the first DC voltage.
The transformer 5 converts the voltage of the switching pulse. This voltage conversion may be either step-down or step-up.
The second rectifier circuit 6 rectifies the switching pulse voltage-converted by the transformer 5 into a second DC voltage.

In FIG. 1, the switching DC power supply of the present invention further includes a DC smoothing circuit 7 and a deviation detection amplifier 8. The DC smoothing circuit 7 is a filter composed of a resistor and a capacitor, and further smoothes the second DC voltage.
The deviation detecting amplifier 8 controls the switching circuit 3 based on the deviation between the voltage of the DC smoothing circuit 7 and the reference voltage 9 to stabilize the output voltage or current.

    In FIG. 1, the switching DC power supply of the present invention further includes a power supply synchronization circuit 10. The power supply synchronization circuit 10 has a function of operating the switching circuit 3 in synchronization with a specific phase of the commercial AC power supply 1.

FIG. 2 is a configuration diagram of the power supply synchronization circuit of FIG. In this figure, the power supply synchronization circuit 10 includes a high-frequency oscillator 12, a phase detection circuit 14, a frequency divider circuit 16, and an enable circuit 18.
The high-frequency oscillator 12 is a crystal oscillator, for example, and oscillates a stable clock signal of 1 MHz or higher (12.8 MHz in this example).
The phase detection circuit 14 is a comparator, for example, and detects a specific phase (for example, a zero cross point) of the commercial AC voltage.
The frequency dividing circuit 16 is, for example, a plurality (two in this example) of counters or shift registers, and counts the clock signal (1 MHz or more) of the high-frequency oscillator 12 and divides this into, for example, 1/10 to 1/1000. Rotate to form a switching clock of 1 kHz or more and less than 100 kHz.
The frequency dividing circuit 16 counts the clock signal according to the permission signal output from the enable circuit 18 to form the above-described switching clock, and outputs the switching clock to the switching circuit 3. .
The enable circuit 18 outputs a permission signal that permits the frequency dividing circuit 16 to count in synchronization with a specific phase (for example, zero cross point) detected by the phase detection circuit 14.

  The specific phase of the commercial AC voltage is preferably the zero cross point. Further, in this case, the power supply synchronization circuit 10 further includes a phase shift setting circuit 17, which is shifted so that the zero cross point and the rising point of the clock signal do not coincide with each other.

    In this figure, reference numeral 13 denotes a waveform shaper, which shapes the waveform of the clock signal of the high-frequency oscillator 12 into a pulse shape. Reference numeral 11 denotes a transformer that transforms the commercial AC voltage to a voltage suitable for the phase detection circuit 14 (for example, 10 V).

    In FIG. 2, a high-frequency oscillator 12 is a crystal oscillator, for example, and generates a sine wave of 1 MHz or more (12.8 MHz in this example). The signal of the crystal oscillator is shaped into a pulse by the waveform shaper 13 shaping the waveform. The frequency divider circuit 16 counts down the pulses to generate a switching clock for the switching circuit 3. In this process, the pulse is converted by the counter of the frequency dividing circuit 16 to a frequency of 1 MHz or more to 1 kHz or more and less than 100 kHz.

    The phase detection circuit 14 (comparator) detects the voltage zero cross timing (zero cross point) of the commercial AC power supply 1 input to the switching DC power supply. The enable circuit 18 generates a permission signal at this detection timing and inputs it to the frequency dividing circuit 16, and the frequency dividing circuit 16 starts counting at this timing.

With the above-described configuration, the phase detection circuit 14 performs accurate phase detection of each cycle of the commercial AC power supply 1, thereby ensuring accurate synchronization of the counter operation in the frequency divider circuit 16 with respect to the commercial AC power supply 1. .
The generated switching pulse is applied to the switching circuit 3 (switching element such as a transistor or IGBT) installed in front of the transformer 5 (upstream side) through the first rectifier circuit 2 of FIG.
The electric power pulsed by the switching circuit 3 is adjusted in voltage by the transformer 5 and rectified by the second rectifier circuit 6 and the DC smoothing circuit 7 to become stable DC power.

    The power supply synchronization method for a switching DC power supply according to the present invention is characterized in that the switching pulse generated in the switching circuit 3 described above is synchronized with the frequency of the commercial AC power supply 1.

That is, the power supply synchronization method of the switching DC power supply of the present invention has a high frequency oscillation step, a phase detection step, a count permission step, and a frequency division step,
In a high-frequency oscillation step, oscillate a stable clock signal of 1 MHz or more,
In the phase detection step, a specific phase of commercial AC voltage is detected,
In the count permission step, a permission signal is output in synchronization with the specific phase,
In the frequency dividing step, the clock signal is counted according to the permission signal to form a switching clock of 1 kHz or more and less than 100 kHz.
By outputting this switching clock to the switching circuit 3 and operating the switching circuit 3, the switching pulse generated in the switching circuit 3 is synchronized with the frequency of the commercial AC power supply 1.

    In particular, the specific phase of the commercial AC voltage is a zero cross point, and it is preferable to shift the zero cross point and the rising point of the clock signal so as not to coincide with each other.

FIG. 3 is an operation explanatory diagram of the switching DC power supply according to the present invention. This figure shows a time chart of specific switching pulse generation.
In this figure, (A) is an AC voltage signal of the commercial AC power supply 1, and (B) is an enlarged view of one cycle. (C) is an output signal of the frequency dividing circuit 16, that is, a switching pulse of 1 kHz or more and less than 100 kHz.
Further, (D) is an enlarged schematic diagram of the switching pulse according to the present invention. In the present invention, the switching pulse is generated by the high-frequency oscillator 12 (crystal) at the timing of the zero cross point of the AC voltage in synchronization with 0 V of the commercial AC power supply. Start counting signals (1MHz and above). Then, a switching pulse is formed by frequency division by the counter of the frequency divider circuit 16.
Therefore, the switching noise to the external device of the switching DC power supply according to the present invention is generated at a fixed timing from the zero cross point as indicated by a vertical thin line in (D). Thereby, the influence of switching noise can be made constant over time.
Note that if the count permission signal of the zero cross timing matches the rising timing of the crystal signal, it may become unstable. Therefore, the phase shift setting circuit 17 in FIG. 2 is shifted so that the timings of the two do not match.

  (E) and (F) in FIG. 3 show an asynchronous case where there is no power supply synchronization. In these cases, the generation timing of the switching noise indicated by the thin line is generated randomly without being synchronized with the zero cross point. As a result, the influence of the switching noise cannot be made constant over time, and may have an adverse effect as described above.

  The switching DC power supply of the present invention described above can be used in all fields including scientific experiments that dislike noise, and has a wide range of application to accelerator science, earth science, engineering, and the like. In particular, it can be used as a power source for experimental equipment that requires high stability, for example, an X-ray free electron laser accelerator component equipment. In addition, it can also be used in equipment such as stages in geodetic fields such as high-sensitivity seismometers and high-sensitivity strain gauges that dislike noise, and electron microscopes that measure positions with high sensitivity and lithography fields for semiconductor manufacturing.

  In addition, this invention is not limited to embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.

It is a block diagram of the switching DC power supply by this invention. It is a block diagram of the power supply synchronizing circuit of FIG. It is operation | movement explanatory drawing of the switching DC power supply of this invention. It is a block diagram of the conventional switching DC power supply.

Explanation of symbols

1 commercial AC power supply, 2 first rectifier circuit, 3 switching circuit,
4 power control circuit, 5 transformer, 6 second rectifier circuit,
7 DC smoothing circuit, 8 deviation detection amplifier, 9 reference voltage,
10 power supply synchronization circuit, 11 transformer, 12 high frequency oscillator,
13 waveform shaper, 14 phase detection circuit, 16 frequency divider,
17 Phase shift setting circuit, 18 Enable circuit

Claims (6)

A first rectifier circuit that rectifies a commercial AC voltage into a first DC voltage; a switching circuit that generates a switching pulse by switching control of the first DC voltage; a transformer that converts the voltage of the switching pulse; A switching DC power supply having a second rectification circuit for rectifying the converted switching pulse into a second DC voltage,
A switching DC power supply comprising a power supply synchronization circuit that operates a switching circuit in synchronization with a specific phase of a commercial AC power supply. The power supply synchronization circuit includes a high-frequency oscillator that oscillates a stable clock signal of 1 MHz or higher;
A phase detection circuit for detecting a specific phase of the commercial AC voltage;
A frequency divider that counts the clock signal to form a switching clock of 1 kHz or more and less than 100 kHz;
An enable circuit that outputs a permission signal that permits counting of the frequency divider circuit in synchronization with the specific phase, and
2. The switching DC power supply according to claim 1, wherein the frequency dividing circuit counts the clock signal according to the permission signal and outputs a switching clock to the switching circuit. The specific phase of the commercial AC voltage is a zero cross point,
3. The switching DC power supply according to claim 2, further comprising a phase shift setting circuit that shifts the zero cross point and the rising point of the clock signal so as not to coincide with each other. A first rectifier circuit that rectifies a commercial AC voltage to a first DC voltage, a switching circuit that generates a high-frequency pulse of 1 kHz or more and less than 100 kHz from the first DC voltage, a transformer that converts the voltage of the high-frequency pulse, A power supply synchronization method for a switching DC power supply comprising a second rectifier circuit that rectifies a high-frequency pulse voltage-converted by a transformer into a second DC voltage,
A power supply synchronization method for a switching DC power supply, wherein a switching pulse generated in the switching circuit is synchronized with a frequency of a commercial AC power supply. A high-frequency oscillation step for oscillating a stable clock signal of 1 MHz or higher;
A phase detection step for detecting a specific phase of the commercial AC voltage;
A count permission step for outputting a permission signal in synchronization with the specific phase;
A frequency dividing step of counting the clock signal according to the permission signal to form a switching clock of 1 kHz or more and less than 100 kHz,
5. The switching DC power supply synchronization method according to claim 4, wherein the switching clock is output to the switching circuit to operate the switching circuit. The specific phase of the commercial AC voltage is a zero cross point,
6. The method according to claim 5, further comprising shifting the zero cross point and the rising point of the clock signal so as not to coincide with each other.

Images