JPH05191976A - Switching power supply - Google Patents

Abstract

PURPOSE:To reduce normal mode noise generated from a power factor improving circuit. CONSTITUTION:A choke coil 31 is split into two coil parts 32A, 32B having the same turns and applied on one core 32 with reverse polarities to be connected with the output line of a rectifying circuit 7 at the opposite ends thereof. According to the constitution, a common mode noise appears in reverse phase between the voltage supply side line of the rectifying circuit 7 and a ground terminal FG and between the minus side line of the rectifying circuit 7 and the ground terminal FG, and thereby the normal mode noise is offset between the voltage supply side line and the minus side line of the rectifying circuit 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply device having a power factor correction circuit on the input side of an inverter.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 6, in a power supply device of this type, a power supply 2 is connected to both ends of a commercial power supply 1 via input terminals + V1 and -V1, and the power supply 2 has an inductance. A noise filter circuit 6 formed of capacitors 3 and 4 and a capacitor 5 removes normal mode noise of the AC power supply voltage supplied from the commercial power supply 2 via the input terminals + V1 and -V1.
7A, 7B, 7C, 7D connected to both ends of
The AC power supply voltage is rectified by the rectifier circuit 7 formed by connecting the bridges to the power factor correction circuit 8. The power factor correction circuit 8 is connected to the voltage supply line of the rectifier circuit 7 and is connected to a choke coil 10 in which a coil portion 9A is wound around a core 9 and an energy M that controls the energy stored in the choke coil 10.
The switching element 11 comprises an OS-type FET, a diode 13 inserted and connected between the choke coil 10 and a primary winding 12A of a transformer 12 for insulating the primary side and the secondary side from each other. The output voltage switched by the smoothing capacitor 14 is smoothed, and the DC input voltage Vi is transferred to the transformer 12 and the MOS type FET 15.
By applying to the inverter consisting of
Rectifier diode 1 for the voltage induced in 12 secondary windings 12B
The DC output voltage Vo is supplied between the output terminals + V2 and -V2 after being rectified and smoothed by 6, 17, the inductance 18 and the smoothing capacitor 19. Then, the DC output voltage Vo is supplied to the pulse width control circuit 22 as an output detection voltage divided by the resistors 20 and 21, and the pulse width control circuit 22.
Supplies a drive signal to the FET 15 so that the output voltage Vo becomes constant according to the level of the output detection voltage.

The DC input voltage Vi is divided by the resistors 23 and 24, and the pulse width control circuit 25 controls the conduction pulse width of the switching element 11 based on the divided input detection voltage. That is, when the switching element 11 is on, the DC current from the rectifier circuit 7 stores energy in the choke coil 10, while when the switching element 11 is off, the energy stored in the choke coil 10 is supplied from the rectifier circuit 7. The voltage is superimposed on the generated voltage and output from the power factor correction circuit 8. Then, the pulse width control circuit 25 detects a change in the DC input voltage Vi via the resistors 23 and 24, and brings the voltage waveform and the current waveform from the AC power source close to each other to improve the input power factor. It controls the energy stored in the choke coil 10 via 11.

[0004]

In the above-mentioned conventional example, the choke coil 10 is connected to the voltage supply side line from the rectifier circuit 7, while nothing is connected to the negative side line from the rectifier circuit 7. Between the voltage supply side line of the rectifier circuit 7 and the ground terminal FG due to noise in a high frequency region such as a ripple current generated from the input side of the power factor correction circuit 8 due to the on / off operation of the switching element 11 which is not connected. There is a difference between the common-mode noise level generated at 1) and the common-mode noise level generated between the minus side line of the rectifier circuit 7 and the ground terminal FG.
Therefore, the choke coil provided in the power factor correction circuit 8
Due to 10, normal mode noise is generated between the voltage supply side line and the minus side line of the rectifier circuit 7, and this noise is superimposed on the AC power supply 1 as noise terminal voltage from the input terminals + V1 and -V1 of the power supply 2. Therefore, there is a problem that it causes a malfunction in other electronic devices.

Therefore, an object of the present invention is to provide a switching power supply device capable of reducing the normal mode noise generated by the power factor correction circuit.

[0006]

According to the present invention, an AC power supply voltage is rectified by a rectifier circuit, and a choke coil and a switching element for controlling energy stored in the choke coil are provided. In a switching power supply device including a power factor correction circuit that brings a voltage waveform and a current waveform of the AC power supply voltage close to each other, the choke coil is divided into half turns, and each of the divided coil parts has a reverse polarity. It is wound around the same core so as to be inserted and connected to both ends of the output line of the rectifier circuit.

[0007]

With the above structure, noises in a high frequency region such as ripple currents generated on the voltage supply side line and the minus side line of the rectifier circuit from the power factor correction circuit due to the ON / OFF operation of the switching element have phases opposite to each other. The normal mode noise that appears and is generated between the voltage supply side line and the minus side line of the rectifier circuit is canceled, and the noise level is reduced.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The same parts as in FIG.
Detailed description of the same part is omitted.

FIG. 1 shows an embodiment of the present invention. In the same drawing, a choke coil 31 divides each coil portion 32A, 32B into half turns, and the coil portions 32A, 32B have opposite polarities. The choke coil 31 is wound around the same core 32 so that the coil portions 32A and 32B of the choke coil 31 are inserted and connected to both ends of the output line of the rectifier circuit 7 to improve the power factor correction circuit 8.
6 is the same as FIG. 6 except that it constitutes A.

Next, the operation of the above configuration will be described.

When the power is turned on, the AC power supply voltage from the commercial power supply 1 is supplied to the rectifier circuit via the noise filter circuit 6, and this rectified voltage is applied to the power factor correction circuit 8A. The power factor correction circuit 8A stores the direct current from the rectifier circuit 7 as electromagnetic energy of the choke coil 31 when the switching element 11 is on, and the energy stored in the choke coil 31 when the switching element 11 is off. Is superimposed on the output voltage from the rectifier circuit 7 and supplied to the primary winding 12A and the smoothing capacitor 14 of the transformer 12, and the rectifying diode 16, from the secondary winding 12B of the transformer 12.
A DC output voltage Vi is output via 17, the inductance 18 and the smoothing capacitor 19. Then, noise in a high frequency region such as a ripple current from the input side of the power factor correction circuit 8A generated by repeating the on / off operation of the switching element 11 is on the voltage supply side line and the minus side line of the rectifier circuit 7. And are respectively superimposed. At this time, since the coil portions 32A and 32B of the choke coil 31 are wound around the core 33 so as to have polarities opposite to each other,
The common mode noise generated between the voltage supply side line of the rectifier circuit 7 and the ground terminal FG and the common mode noise generated between the minus side line of the rectifier circuit 7 and the ground terminal FG have mutually opposite phases. The normal mode noise generated between the voltage supply side line and the minus side line of the rectifier circuit 7 cancels each other because their voltage levels are opposite to each other, and the total voltage level of this normal mode noise is extremely high. Get smaller.

Next, in the conventional example and the present example,
The measurement results of the waveforms of the noise terminal voltage indicating the magnitude of the noise returning to the commercial power supply side and the common mode noise and the normal mode noise for the output line of the rectifier circuit 7 are shown below.

FIG. 2 shows a method of measuring the noise terminal voltage generated from the power source 2A in FIG. 1 and the power source 2 in FIG. 6, and frequency analysis is performed between the commercial power source 1 and the input terminals + V1, -V1. The disturbing wave measuring device 41 such as a spectrum analyzer used for the power source 2 and 2A side impedance Z is maintained at a prescribed 50Ω,
A pseudo power supply network 42 for eliminating the influence of external noise on A and performing an accurate measurement is connected. Further, there are common mode noise generated between the voltage supply side line and the minus side line of the rectifier circuit 7 and the ground terminal FG, and normal mode noise generated between the voltage supply side line and the minus side line of the rectifier circuit 7. All waveforms are measured by a synchroscope (not shown). At this time, the measurement conditions for each of the power supplies 2 and 2A are shown in Table 1 below. Under each measurement condition, the choke coils 10 and 31 inserted and connected to the power supply 2 or the power supply 2A have substantially the same number of turns and inductance.

[0014]

[Table 1]

Sample 1 uses the choke coil 10 of the power supply 2 shown in FIG. 6 in the conventional example, and its noise terminal voltage and waveforms of common mode noise and normal mode noise are shown in FIGS. 3 (A) and 3 (B). Show. At this time,
The maximum value of the noise terminal voltage generated from the power supply 2 in (A) is the limit of the type I information device used in the commercial and industrial area, which is defined by VCCI (Voluntary Control Council for Radio Interference such as Information Processing Devices). For values, 150kHz to 5M
It can be seen that there is only a margin of about 3 dB in the range of Hz. Further, in FIG. 3B, there is a difference in the high frequency voltage generated between the voltage supply side line of the rectifier circuit 7 and the ground terminal FG and between the negative side line of the rectifier circuit 7 and the ground terminal FG. Therefore, the maximum peak value is 300 V between the voltage supply side line and the minus side line of the rectifier circuit 7.
A large high-frequency voltage that reaches even

On the other hand, as shown in Samples 2 and 3, each coil portion is formed by bifilar winding and split winding.
When the choke coil 31 in which 32A and 32B are wound around the core 32 is used, the noise terminal voltage from the power supply 2A and the waveforms of the common mode noise and the normal mode noise are shown in FIGS. 4 (A), 4 (B) and FIG. It becomes like 5 (A) and (B). That is, the maximum value of the noise terminal voltage generated from the power supply 2A in FIGS. 4 (A) and 5 (A) is the ICI of VCCI in the range of 150 kHz to 5 MHz in the choke coil 31 of bifilar winding and split winding. It can be seen that there is a margin of 15 dB or more with respect to the limit value of the seed information device, and the voltage level thereof is greatly reduced compared to the conventional example. Further, as shown in FIGS. 4B and 5B, between the voltage supply side line of the rectifier circuit 7 and the ground terminal FG, and between the negative side line of the rectifier circuit 7 and the ground terminal FG. Generate high frequency voltages having opposite phases to each other, so that the voltage between the voltage supply side line and the minus side line of the rectifier circuit 7 is canceled, and the voltage level thereof is 50%.
It can be seen that the voltage drops below V.

As described above, in the above embodiment, the choke coil in which the coil portions 32A and 32B are inserted and connected to the voltage supply side line and the minus side line of the rectifier circuit 7, respectively.
The normal mode noise generated between the voltage supply side line and the minus side line of the rectifier circuit 7 is canceled by 31 and the noise terminal voltage generated from the power supply 2A is reduced to prevent the malfunction of peripheral devices from being induced. You can

Further, since the noise terminal voltage from the power supply 2A is reduced, the noise component passing through the noise filter circuit 6 provided between the commercial power supply 1 and the rectifying circuit 7 is reduced, which reduces the noise filter. It is possible to reduce the size and weight of each element such as the inductances 3 and 4 of the circuit 6 and the capacitor 5.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist of the present invention. For example, the switching element is a MOS
A transistor may be used instead of the type FET, and the power factor correction circuit can be adapted to various types.

[0020]

The present invention rectifies an AC power supply voltage by a rectifier circuit and has a choke coil and a switching element for controlling energy stored in the choke coil. The switching element is switched to switch the AC power supply voltage. In a switching power supply device including a power factor correction circuit for approximating the voltage waveform and the current waveform, the choke coil is divided into half turns, and the divided coil parts have the same polarity so as to have opposite polarities. A switching power supply device that is wound around the core and inserted and connected to both ends of the output line of the rectification circuit, and can reduce the normal mode noise generated by the power factor correction circuit.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram showing a method for measuring a noise terminal voltage.

FIG. 3 is a waveform diagram showing a noise terminal voltage and high-frequency voltage levels in a common mode and a normal mode in Sample 1.

FIG. 4 is a waveform diagram showing a noise terminal voltage and a high frequency voltage level in a common mode and a normal mode in Sample 2.

FIG. 5 is a waveform diagram showing a noise terminal voltage and a high frequency voltage level in a common mode and a normal mode in Sample 3;

FIG. 6 is a circuit configuration diagram showing a conventional example.

[Explanation of symbols]

 1 Commercial power supply 7 Rectifier circuit 8A Power factor correction circuit 11 Switching element 31 Choke coil 32 Core 32A, 32B Coil part

Claims (1)

[Claims] 1. An AC power supply voltage is rectified by a rectifier circuit, and a choke coil and a switching element for controlling energy stored in the choke coil are provided, and the switching element is switched to form a voltage waveform of the AC power supply voltage. In a switching power supply device including a power factor correction circuit that makes the current waveform and the current waveform closer to each other, the choke coil is divided into half turns, and the divided coil parts have the same core so as to have opposite polarities. A switching power supply device, which is wound and inserted and connected at both ends of the output line of the rectifier circuit.