JP2003125582A - Power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sharply reduce the noise of a power unit which has power factor improving function. SOLUTION: A power factor improving converter PFC 5 sets the ripple voltage in the frequency of AC power appearing in the output voltage to a DC-DC converter 6 to 10 Vp-p or higher, whereby the DC-DC converter 6 changes its oscillation frequency, according to the ripple voltage contained in the DC voltage from the power factor improving converter PFC 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device having a power factor improving function, and more particularly to a power supply device capable of significantly reducing noise.

[0002]

2. Description of the Related Art Conventionally, as a power supply device, as shown in FIG. 15, an active power factor correction converter for inputting an AC power supply and outputting direct current, and a DC output from this active power factor correction converter are input. There is known a DC-DC converter that outputs another direct current.

Now, the operation of the conventional power supply device shown in FIG. 15 will be described. When the AC power supply 1 is applied to the power supply device, the sine wave voltage supplied from the AC power supply 1 passes through the filter 2, is full-wave rectified by the rectifier 3 and passes through the filter 4, and is transmitted to the power factor correction converter PFC5. Wave rectified waveform is provided. At this time, the filters 2 and 4 remove noise components leaking from the power supply device to the AC power supply 1 side.

First, one end of the criticality detection winding 61b is G
It is connected to ND, and the other end is input to the + input terminal of the comparator 54 via the resistor 60, and at the same time, the first reference voltage 53 is input to the − input terminal of the comparator 54. In the comparator 54, both input voltages are compared, and the low level set signal is output from the comparator 54 to the flip-flop 59. The flip-flop 59 is set according to the set signal from the comparator 54, a high-level drive signal is output from the Q output terminal, and the switching element 62 is on-controlled. When the switching element 62 is turned on, the filter 4 moves to the main winding 61.
A, a switching current flows to GND through the drain-source of the switching element 62 and the current detection resistor 63, and energy is stored in the choke coil 61.

At this time, the switching current flowing through the switching element 62 is the source-source of the switching element 62.
A current target value V output from the multiplier 55 in the comparator 56 after being converted into a voltage by the current detection resistor 63 provided between the GNDs and input to the + input terminal of the comparator 56.
compared with m.

When the switching current reaches the current target value Vm, the comparator 56 outputs a high-level reset signal to the flip-flop 59. The flip-flop 59 is reset in response to the reset signal from the comparator 56, the high level drive signal output from the Q output terminal is switched to the low level, and the switching element 62 is off-controlled. When the switching element 62 is turned off, the energy stored in the choke coil 61 and the voltage supplied from the filter 4 are combined, and the output capacitor 65 is charged through the rectifying diode 64. As a result, the output capacitor 65 outputs a voltage boosted higher than the peak value of the full-wave rectified waveform supplied from the filter 4.

The voltage from the condenser 65 is the resistance 66, 6
The voltage is divided by 7 and input to the operational amplifier 57, compared with the second reference voltage 58 by the operational amplifier 57, and this error signal is supplied to the multiplier 55. The full-wave rectified waveform from the filter 4 is divided by the resistors 51 and 52 and input to the multiplier 55. The multiplier 55 multiplies the full-wave rectified waveform and this error signal to obtain the target current value V of the switching current.
m is supplied to the-input terminal of the comparator 56.

Next, when the release of the energy stored in the choke coil 61 is completed, the criticality detection winding 61 is formed.
The voltage of b is inverted. This voltage is compared with the first reference voltage 53 by the comparator 54, and the comparator 54 outputs a low level set signal to the flip-flop 59. As a result, the flip-flop 59 is set according to the set signal from the comparator 54, and the drive signal is input again to the switching element 62 to be turned on. After that, the output voltage of the output capacitor 65 of the power factor correction converter PFC5 is kept constant by repeating such operations. At the same time, the current of the AC power supply 1 has a sinusoidal current waveform that follows the voltage of the AC power supply 1.

[0009]

As described above, in the power supply device having the power factor improving function, the power factor improving converter P is used.
The DC-DC converter 6 is connected to the output side of the FC5. For this reason, two switching power supply circuits are connected in series although they are one power supply device. Each switching power supply circuit handles a large amount of energy and is prone to generate switching noise.

Moreover, in this type of power supply device, since there are two switching power supply circuits, the noise generated by the entire power supply device becomes large, so many noise countermeasures are taken in order to comply with the noise standards of each country. There is a need to do.
As measures against individual noises, measures such as adding a filter immediately before the input / output terminal or slowing the switching speed to make the voltage change rate dv / dt gentle are taken.

Since the conventional power supply device has taken such measures against noise, the addition of parts has been a factor of cost increase. At the same time, it causes an increase in switching loss, forcing a decrease in conversion efficiency and an increase in the size of the device. The present invention has been made in view of the above, and an object of the present invention is to significantly reduce noise in a power supply device having a power factor improving function.

[0012]

The invention according to claim 1 is
In order to solve the above problems, a power factor correction converter that inputs an AC power source, converts it into a DC voltage and outputs it, and a DC-DC that converts a DC voltage from this power factor correction converter into another DC voltage and outputs it. A power supply device including a converter, wherein the power factor correction converter includes ripple voltage setting means for setting a ripple voltage at a frequency of an AC power source appearing in an output voltage to the DC-DC converter to 10 Vp-p or more. The gist of the DC-DC converter is that the oscillation frequency changes according to the ripple voltage included in the DC voltage from the power factor correction converter.

In order to solve the above-mentioned problems, the invention as set forth in claim 2 is a power factor improving converter for inputting a full-wave rectified waveform from an AC power source through a choke coil, turning it on and off by a switching element, and converting it into a DC voltage. And a DC-DC converter that converts the DC voltage from the power factor correction converter into another DC voltage and outputs the converted DC voltage, wherein the power factor correction converter converts the DC voltage to the DC-DC converter. Error signal amplifying means for setting and outputting an amplification gain of the error signal consisting of the difference between the output voltage and the reference voltage;
Current target value generating means for generating a current target value linked with the full-wave rectified waveform from the full-wave rectified waveform from the AC power source and the error signal from the error signal amplification means, and switching that flows during the ON period of the switching element. Switching current detection means for detecting a current and outputting it as a current detection value, and the current detection value of the switching current from the switching current detection means, when the current target value from the current target value generation means reaches the current target value, the switching OFF control means for turning off the element, and the error signal amplification means adjusts the amplification gain so that the ripple voltage at the frequency of the AC power supply appearing in the output voltage to the DC-DC converter becomes 10 Vp-p or more. Set the DC-DC
The gist of the converter is that the oscillation frequency fluctuates according to the ripple voltage included in the DC voltage from the power factor correction converter.

In order to solve the above-mentioned problems, a power factor correction converter for inputting a full-wave rectified waveform from an AC power source through a choke coil, turning it on and off by a switching element, and converting it into a DC voltage is provided. And a DC-DC converter that converts a DC voltage from the power factor correction converter into another DC voltage and outputs the converted DC voltage, wherein the power factor correction converter is provided in the choke coil. Set signal generating means for generating a set signal when the ringing voltage generated in the criticality detection winding reaches the first reference voltage, and turning on the switching element in response to the set signal from the set signal generating means. ON control means, and a triangular wave generator which is activated in response to the set signal from the set signal generating means to oscillate a triangular wave signal having a predetermined frequency. Means, an error signal amplifying means for setting and outputting an amplification gain of an error signal composed of a difference between an output voltage to the DC-DC converter and a reference voltage, and a voltage value of the triangular wave signal from the triangular wave oscillating means, OFF control means for turning off the switching element when the error signal from the error signal amplification means is reached, wherein the error signal amplification means has a frequency of the AC power supply appearing in an output voltage to the DC-DC converter. The amplification gain is set so that the ripple voltage at 10 Vp-p or more becomes, and the DC-DC converter changes the oscillation frequency according to the ripple voltage included in the DC voltage from the power factor correction converter. Use as a summary.

According to a fourth aspect of the invention, in order to solve the above-mentioned problems, the DC-DC converter is a self-excited oscillation type DC.
The gist is that it is a frequency control type DC-DC converter such as a DC converter, a voltage quasi-resonance type DC-DC converter, a current resonance type DC-DC converter.

In order to solve the above-mentioned problems, the fifth aspect of the present invention is characterized in that the DC-DC converter is a DC-DC converter having a frequency modulation function.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a diagram showing a configuration of a power supply device according to a first embodiment of the present invention. The configuration of the power supply device will be described with reference to FIG.

In FIG. 1, an AC power source 1 to a filter 2
The sine wave voltage that has passed through the filter 2 is full-wave rectified by the rectifier 3 and passes through the filter 4, and the full-wave rectified waveform from the filter 4 is supplied to the power factor correction converter PFC5. It The filters 2 and 4 remove noise components leaking from the power supply device to the AC power supply 1 side.

The DC output of the power factor correction converter PFC5 is input to the DC-DC converter 6, and DC-
The DC converter 6 converts the DC voltage input from the power factor correction converter PFC5 into another DC voltage and outputs it to the output terminal 7
Output from a and 7b. The filters 2 and 4 are shown in FIG.
The π-type normal mode filter shown in FIG. 3, the simplest normal mode filter shown in FIG. 3, the normal mode filter + common mode filter shown in FIG. 4 and the like can be omitted.

Next, the structure of the power factor correction converter PFC5 will be described in detail.

The power factor correction converter PFC5 has, as a basic configuration, a boost chopper circuit composed of a main winding 61a of a choke coil 61, a switching element 62, a rectifying diode 64, and an output capacitor 65. The choke coil 61 includes a main winding 61a and a criticality detection winding 61b.
Is provided. One end of the main winding 61a is connected to one output terminal of the filter 4 and the resistor 51.
The other end of 1a is connected to the drain of the switching element 62 and the anode of the rectifying diode 64. Further, one end of the criticality detection winding 61b is connected to the + input terminal of the comparator 54 via the resistor 60, and the other end of the criticality detection winding 61b is connected to GND. The cathode of the rectifying diode 64 described above is connected to one end of the output capacitor 65 and the input terminal 5 a of the DC-DC converter 6.

Next, the structure of the control system of the power factor correction converter PFC5 will be described. The + input terminal of the comparator 54 is connected to the GN via the resistor 60 and the criticality detection winding 61b.
Connected to D. The first reference voltage 53 is input to the-input terminal of the comparator 54. The comparator 54 compares both input voltages, and when the voltage generated in the criticality detection winding 61b input to the + input terminal is lower than the first reference voltage 53, a low level set signal is flip-flopted. It is output to the set terminal of the switch 59.

The set input terminal of the flip-flop 59 is connected to the output terminal of the comparator 54, the reset input terminal is connected to the output terminal of the comparator 56, and the Q output terminal is connected to the switching element 62. The gate terminal of is connected. The flip-flop 59 outputs a high level drive signal to the Q output terminal when a low level set signal is input from the comparator 54. When a high level reset signal is input from the comparator 56, a low level is output to the Q output terminal.

The voltage between the terminals of the capacitor 65 is divided by the resistors 66 and 67 and input to the-input terminal of the operational amplifier 57, and the second reference voltage 58 is input to the + input terminal.
Is input, and a variable resistor 68 is connected between the − input terminal and the output terminal of the operational amplifier 57.
The amplification gain of the operational amplifier 57 is set by the resistors 66 and 67 and the variable resistor 68, and the amplification gain of the error signal formed by the difference between the divided voltage corresponding to the output voltage of the capacitor 65 and the second reference voltage 58 is set. It is set, amplified, and supplied to the multiplier 55.

A voltage obtained by dividing the full-wave rectified waveform from the filter 4 by the resistors 51 and 52 is input to one input terminal of the multiplier 55, and the operational amplifier 57 is input to the other input terminal.
The error signal from is input, the multiplier 55 multiplies the full-wave rectified waveform and this error signal, and the result is supplied to the-input terminal of the comparator 56 as the current target value Vm linked with the full-wave rectified waveform.

The current target value Vm of the switching current is supplied from the multiplier 55 to the-input terminal of the comparator 56, the current detection resistor 63 is connected to the + input terminal of the comparator 56, and the switching element 62 is turned on. The voltage corresponding to the drain-source current during the period is input as the current detection value. When the switching current reaches the current target value Vm linked with the full-wave rectified waveform, the comparator 56 outputs a high-level reset signal to the flip-flop 59.

Next, the operation of the power supply device according to the first embodiment of the present invention will be described. When the AC power supply 1 is applied to the power supply device, the sine wave voltage supplied from the AC power supply 1 passes through the filter 2, is full-wave rectified by the rectifier 3 and passes through the filter 4, and is transmitted to the power factor correction converter PFC5. Wave rectified waveform is provided.

(1) Operation at Startup First, the + input terminal of the comparator 54 has a resistor 60,
It is in a state of being connected to GND through the criticality detection winding 61b, and at the same time, the first reference voltage 53 is input to the-input terminal of the comparator 54. In the comparator 54, both input voltages are compared, and the voltage at the + input terminal has a lower potential, so the comparator 54 outputs a low-level set signal to the flip-flop 59. The flip-flop 59 is set according to the set signal from the comparator 54, and a high-level drive signal is output from the Q output terminal to turn on the switching element 62 at timing t1 shown in FIG.

When the switching element 62 is turned on, FIG.
As shown at timing t1 in FIG.
Drain voltage Vd of the device drops to near 0V. Then, a switching current flows from the filter 4 to the GND via the main winding 61a, the drain-source of the switching element 62, and the current detection resistor 63, and energy is stored in the choke coil 61. At this time, the switching element 62
As shown in FIG. 5, the switching current flowing in the voltage Vs is converted into a voltage Vs by the current detection resistor 63 provided between the source of the switching element 62 and GND, and is input to the + input terminal of the comparator 56. The current target value Vm linked with the full-wave rectified waveform output from the multiplier 55 is compared.

(2) Current target value Vm A variable resistor 68 is provided between the minus input terminal and the output terminal of the operational amplifier 57, and the output voltage from the output capacitor 65 is divided by the resistors 66 and 67 to obtain the operational amplifier 57.
Of the differential voltage value of the output voltage and the second reference voltage 58, which is input to the negative input terminal, is amplified and set with an amplification gain, and the error signal output from the operational amplifier 57 is multiplied. Is supplied to the container 55. The waveform B shown in FIG. 6 represents the error signal output from the operational amplifier 57. Here, the amplitude level of the error signal is adjusted so that the amplification gain (feedback gain) of the output voltage of the power factor correction converter PFC5 is reduced by the variable resistor 68 connected between the − input terminal and the output terminal of the operational amplifier 57. It

On the other hand, the full-wave rectified waveform from the filter 4 is divided by the resistors 51 and 52 and input to the multiplier 55. The waveform A shown in FIG. 6 represents a full-wave rectified waveform output from the filter 4, which is 2 times the frequency of the commercial power source.
It is a double cycle. In the multiplier 55, the operational amplifier 5
A voltage obtained by multiplying the error signal from 7 and the full-wave rectified waveform from the filter 4 is generated, and is supplied to the-input terminal of the comparator 56 as the current target value Vm linked with the full-wave rectified waveform.

(3) OFF control of switching element At the timing t2 shown in FIG. 5, the target current value Vm in which the detected current value of the switching current is linked with the full-wave rectified waveform
Then, the comparator 56 outputs a high-level reset signal to the flip-flop 59. The flip-flop 59 is reset in response to the reset signal from the comparator 56, the high level drive signal output from the Q output terminal is switched to the low level, and the switching element 62 is off-controlled.

When the switching element 62 is turned off, the energy stored in the choke coil 61 and the voltage supplied from the filter 4 are combined, and the rectifying diode 6
4, the output capacitor 65 is charged. As a result, the output capacitor 65 outputs a voltage boosted higher than the peak value of the full-wave rectified waveform supplied from the filter 4. The waveform C shown in FIGS. 7 and 6 is a diagram showing the state of the output voltage between the output terminals 5a and 5b of the power factor correction converter PFC5. As shown in this figure, the output voltage from the conventional power factor correction converter PFC has no ripple voltage, whereas the output voltage from the power factor correction converter PFC5 in the present embodiment is approximately 10 Vp-p. It has a ripple voltage.

(4) On-Control of Switching Element Next, when the energy stored in the choke coil 61 is released, a ringing voltage is generated in the criticality detection winding 61b, and the voltage of the criticality detection winding 61b is generated. Is reversed. This voltage is the first reference voltage 53 and the comparator 54.
And the low level set signal is output from the comparator 54 to the flip-flop 59 at the timing t3. As a result, the flip-flop 59 is set according to the set signal from the comparator 54, and the drive signal is input again to the switching element 62 and is turned on at timing t3 shown in FIG.

(5) Amplification Gain (Feedback Gain) In this embodiment, a variable resistor 68 for adjusting the amplification gain is connected between the − input terminal and the output terminal of the operational amplifier 57, and the output capacitor 65 Output voltage is divided by resistors 66 and 67 and input to the-input terminal of the operational amplifier 57, and is compared with the second reference voltage 58 by the operational amplifier 57. The operational amplifier 57 has a variable resistor 68.
Since the amplification gain is determined according to the adjustment value of, the error signal decreases as the amplification gain of the operational amplifier 57 decreases.
The variable resistor 68 is adjusted to set the amplification gain so that the ripple voltage appearing in the output voltage to the DC-DC converter at the frequency of the AC power supply becomes 10 Vp-p or more, and an error signal of a small amplification level is sent to the multiplier 55. Supplied.

On the other hand, the multiplier 55 multiplies the error signal by the full-wave rectified waveform to obtain the current target value Vm linked with the full-wave rectified waveform.
Is generated, a voltage having a cycle twice the frequency of the commercial power supply always occurs in the target current value Vm. As a result,
A large ripple voltage is generated in the output voltage of the power factor correction converter PFC5 as compared with the conventional power supply device. After that,
By repeating such operations, the average voltage of the output voltage of the output capacitor 65 of the power factor correction converter PFC5 is kept constant while having the ripple voltage. At the same time, the current of the AC power supply 1 has a sinusoidal current waveform that follows the voltage of the AC power supply 1.

Next, effects of the power supply device according to the first embodiment of the present invention will be described. According to the present embodiment, the variable resistor 68 is provided between the negative input terminal and the output terminal of the operational amplifier 57, and the amplification gain (feedback gain) of the output voltage of the power factor correction converter PFC5 is significantly reduced, and the power factor correction converter is provided. Since a large ripple voltage is generated in the output voltage of the PFC 5, the output voltage ripple can be set to 10 Vp-p or more by appropriately adjusting the variable resistor 68, and as a result, the following effects appear. .

As the DC-DC converter 6, for example, as shown in FIG. 8, a self-excited flyback converter whose switching frequency fluctuates according to an input voltage is used. Since the output voltage of the power factor correction converter PFC5 has the ripple voltage as described above, that is, the input voltage of the DC-DC converter 6 changes, the switching frequency of the DC-DC converter 6 is large. fluctuate. As a result, the frequency components of the noise generated from the DC-DC converter 6 are dispersed without being concentrated at a specific frequency.

By the way, the noise generated from electronic equipment is regulated by the international standard CISPR, and in particular, the bandwidth of the receiver used for noise measurement is determined to be 9 kHz. Therefore, a ripple voltage is generated in the output voltage of the power factor correction converter PFC5,
By changing the input voltage of the DC-DC converter 6, the fluctuation band of the switching frequency of the DC-DC converter 6 can be dispersed to 9 kHz or more, and noise can be significantly reduced.

Application Example 1 FIG. 8 is a self-excited flyback DC-DC converter 1 applicable to the DC-DC converter 6 of the power supply device according to the first embodiment of the present invention.
It is a figure which shows 6. Here, the operation of the self-excited flyback DC-DC converter 16 will be described with reference to FIG. Output terminal 5 of power factor correction converter PFC5
a and 5b are input terminals 16 of the DC-DC converter 16
a and 16b, respectively, and a power factor correction converter P
The output voltage of FC5 is supplied as the input voltage Vi of the DC-DC converter 16.

First, from the input voltage Vi, the starting resistor R6,
A charging current flows through the capacitor C4 through the route of the resistor R7, the capacitor C4, the auxiliary winding P2, and the current detection resistor R3. The voltage of the capacitor C4 is the threshold value Vt of the switching element Q1.
When it reaches h, the switching element Q1 is turned on and a voltage is applied to the primary winding P1. When a voltage is applied to the primary winding P1, a feedback voltage is generated in the auxiliary winding P2 to be added to the voltage of the capacitor C4, and the switching element Q1 is rapidly turned on.

The current of the primary winding P1 rises with the lapse of time, and energy is stored in the transformer T1. The combined value of the voltage detected by the current detection resistor R3 and the bias voltage of the capacitor C3 is Vbe (Vt of the control transistor Q2.
h) When the voltage is reached, the control transistor Q2 is turned on and the switching element Q1 is turned off.

When the switching element Q1 is turned off, the energy stored in the transformer T1 is transferred to the secondary winding S.
Is rectified and smoothed by the diode D21 and the capacitor C21 and output. When the release of the energy stored in the transformer T1 ends, a ringing voltage is generated in each winding of the transformer T1. Then, the ringing voltage generated in the auxiliary winding P2 turns on the switching element Q1 again. After that, the oscillation operation is continued by repeating this operation.

The output voltage Vo is the voltage detection circuit 1 on the secondary side.
7 and the error signal is transmitted to the primary side by the photocoupler PC1. This error signal controls the transistor side of the photocoupler PC1 to adjust the voltage of the capacitor C3. The voltage charged in the capacitor C3 controls the timing at which the switching element Q1 is turned off, and the output voltage becomes constant.

In the DC-DC converter 16, the peculiar oscillation frequency is determined by the turns ratio of the primary winding P1 and the secondary winding S of the transformer T1, the input voltage Vi and the output voltage Vo. Even in a general self-excited flyback converter, the input voltage fluctuates by 10V,
The switching frequency fluctuates by several kHz. Since the bandwidth of the switching frequency generally has a bandwidth of about 10 kHz, the bandwidth of the switching frequency is 9
It spreads beyond kHz and goes out of the band of the filter of the receiver used for noise measurement, and the frequency component of noise can be dispersed outside the band of measurement of this receiver.

Therefore, the DC-DC converter 16 having the output voltage of the power factor correction converter PFC5 as the input voltage Vi
In the case of DC-D, since the switching frequency greatly changes according to the fluctuation of the ripple voltage of the input voltage Vi.
The fluctuation band of the switching frequency of the C converter 16 is 9
Since it can be dispersed at a frequency of not less than kHz, a great effect can be obtained in reducing noise.

Application Example 2 FIG. 9 is a diagram showing a voltage quasi-resonant type DC-DC converter 26 applicable to the DC-DC converter 6 of the power supply device according to the first embodiment of the present invention. . Here, the operation of the voltage quasi-resonant type DC-DC converter 26 will be described with reference to FIG.
The output terminals 5a and 5b of the power factor correction converter PFC5 are
The output voltage of the power factor correction converter PFC5 is supplied as the input voltage Vi of the DC-DC converter 26, which is connected to the input terminals 26a and 26b of the DC-DC converter 26, respectively.

First, the flip-flop FF is set by the pulse output from the oscillator OSC and the switching element Q1 is turned on. When the switching element Q1 turns on, the switching current increases with the passage of time. The switching current is converted into a voltage by the current detection resistor R2, combined with the error signal from the secondary side by the resistor R1 and the capacitor C1, and compared with the reference voltage ES1 by the comparator COMP1.

When the combined value of the switching current and the error signal reaches the reference voltage ES1, the output of the comparator COMP1 becomes high level, the flip-flop FF is reset and the output Q1 is turned off. Flip flop FF
When the output Q1 is turned off, the energy stored in the transformer T1 is rectified and smoothed by the diode D21 and the capacitor C21 from the secondary winding S and output.

When the discharge of the energy stored in the transformer T1 is completed, a ringing voltage is generated in each winding of the transformer T1. The ringing voltage generated in the auxiliary winding P2 is compared with the reference voltage ES2 by the comparator COMP2. That is, the generation of the ringing voltage is detected, the flip-flop FF is set, and the switching element Q1 is turned on again. After that, the oscillation operation is continued by repeating this operation. The output voltage is detected by the voltage detection circuit 27 on the secondary side, and the error signal is transmitted to the primary side by the photocoupler PC1. The transistor side of the photocoupler PC1 is controlled by this error signal and is combined with the detection voltage of the switching current by the resistor R1 and the capacitor C1 to control the off timing of the switching element Q1 and make the output voltage constant.

Also in this DC-DC converter 26, the winding number ratio of the primary winding P1 and the secondary winding S of the transformer T1, the input voltage Vi and the output voltage Vo, and the transformer T1.
The intrinsic oscillation frequency is determined by the quasi-resonant frequency due to the inductance L of 1 and the capacitor C2. Therefore, in the DC-DC converter 26 that uses the output voltage of the power factor correction converter PFC5 as the input voltage Vi, the switching frequency greatly changes according to the fluctuation of the ripple voltage of the input voltage Vi, and thus the DC-DC converter 26.
The fluctuation band of the switching frequency can be dispersed to 9 kHz or more, and a great effect can be obtained in noise reduction.

(Application Example 3) FIG. 10 is a diagram showing a DC-DC converter 36 having a frequency modulation function, which is applicable to the DC-DC converter 6 of the power supply device according to the first embodiment of the present invention. . Here, the operation of the DC-DC converter 36 having the frequency modulation function will be described with reference to FIG. The output terminals 5a and 5b of the power factor correction converter PFC5 are connected to the input terminals 36a and 36b of the DC-DC converter 36, respectively, and the output voltage of the power factor correction converter PFC5 becomes the input voltage Vi of the DC-DC converter 36. Supplied.

First, the ON timing of the switching element Q1 is always determined by the pulse output from the oscillator OSC. When the switching element Q1 turns on, the switching current increases with the passage of time. The switching current is converted into a voltage by the current detection resistor R6 and compared with the error signal from the secondary side by the comparator COMP1.

When the switching current reaches the value of this error signal, the output of COMP1 becomes high level, the flip-flop FF is reset and Q1 is turned off. When the switching element Q1 is turned off, the energy stored in the transformer T1 is transferred from the secondary winding S to the diode D2.
1, rectified and smoothed by the capacitor C21 and output. Eventually, the switching element Q1 is turned on again by the output of the oscillator OSC regardless of whether or not all the energy stored in the transformer T1 has been discharged.

The oscillation frequency of the DC-DC converter 36 is determined by the charge / discharge cycle of the capacitor C1. The capacitor C1 is charged by a current flowing from the reference voltage ES2 through the resistor R2 and an input voltage Vi from the resistor R1.
Is determined by the current flowing through. Generally, the current ratio of the resistor R2 is set high, and the charging cycle is mainly determined by the resistor R2. The capacitor C1 is discharged by the oscillator OS.
It is performed by the discharge circuit inside C. Where input voltage V
When i changes, the current of the resistor R1 also changes, and the charging cycle slightly changes. Therefore, when the input voltage Vi changes, the oscillation frequency changes depending on the ratio of the resistors R1 and R2. Therefore, in the DC-DC converter 36 in which the output voltage of the power factor correction converter PFC5 is the input voltage Vi, the switching frequency greatly changes according to the fluctuation of the ripple voltage of the input voltage Vi, and thus the switching of the DC-DC converter 36. The frequency fluctuation band can be dispersed to 9 kHz or more, and a great effect can be obtained in noise reduction.

Application Example 4 FIG. 11 is a diagram showing a current resonance type DC-DC contour 46 applicable to the DC-DC converter 6 of the power supply device according to the first embodiment of the present invention. Here, referring to FIG. 11, a current resonance type DC
The operation of the DC converter 46 will be described. The output terminals 5a and 5b of the power factor correction converter PFC5 are DC-
The output voltage of the power factor correction converter PFC5 is connected to the input terminals 46a and 46b of the DC converter 46, respectively, and supplied as the input voltage Vi of the DC-DC converter 46.

The switching elements Q1 and Q2 are alternately turned on and off with a dead time provided by the two gate control signals output from the control circuit 47. The leakage inductance Lr of the transformer T1 and the capacitor C are turned on by being alternately turned on by the switching elements Q1 and Q2.
A resonance current due to 3 flows.

At the same time, an exciting current flows through the inductance Lp1 of the primary winding P1 of the transformer T1. This exciting current charges and discharges the capacitor C3 regardless of the load current.
In order to adjust the output voltage, it is necessary to change the amplitude voltage of the capacitor C3 by controlling the charging / discharging of the capacitor C3 by this exciting current. These are switching elements Q1,
This is possible by varying the oscillation frequency of Q2 that is turned on and off alternately, and the output voltage can be adjusted by so-called frequency control.

Now, this DC- which makes the output voltage a constant voltage
In the DC converter 46, when the load is constant, its oscillation frequency is also constant. Also, when the input voltage changes, the oscillation frequency fluctuates and the output voltage is made constant. Therefore, in the DC-DC converter 46 in which the output voltage of the power factor correction converter PFC5 is the input voltage Vi, the switching frequency greatly changes according to the fluctuation of the ripple voltage of the input voltage Vi, and thus the switching of the DC-DC converter 46. The frequency fluctuation band can be dispersed to 9 kHz or more, and a great effect can be obtained in noise reduction.

(Second Embodiment) FIG. 12 is a diagram showing a configuration of a power supply device according to a second embodiment of the present invention. The configuration of the power supply device will be described with reference to FIG. In the first embodiment, referring to FIG. 1, the set signal of the flip-flop 59 is the choke coil 61.
When the release of the energy stored in the coil is completed, the voltage of the criticality detection winding 61b is inverted. That is, FIG. 1 shows a power factor correction converter PFC in the discontinuous current mode, and the current flowing through the choke coil 61 decreases to zero.

On the other hand, the feature of the second embodiment is that the power factor correction converter PF in the continuous current mode is used.
This is to input a rectangular wave output from the oscillator 71 to the flip-flop 59 as a set signal. That is, every time the rectangular wave output from the oscillator 71 becomes low level, the set signal is flip-flop 59.
Is input to the choke coil 61, the current flowing in the choke coil 61 continuously flows without decreasing to zero.

Regarding the operation of the power supply device according to the second embodiment of the present invention, for example, a rectangular wave output from the oscillator 71 is input to the flip-flop 59 as a set signal, and a high level drive signal is output from the Q output terminal. Is output and the switching element 62 is turned on, and the other operations are the same as those in the first embodiment, and therefore the description thereof is omitted. Further, since the same effects can be obtained from the power supply device according to the second embodiment of the present invention (Application Example 1) to (Application Example 4), the description thereof will be omitted.

(Modifications 1 to 3) FIG. 13 shows the first embodiment of the present invention.
FIG. 11 is a diagram showing a modified example of the error signal amplifier circuit applicable to the power supply device according to the second embodiment. The configuration of the error signal amplifier circuit will be described with reference to FIG. First
In addition, in the second embodiment, the DC resistance is adjusted by the variable resistor 68.

On the other hand, in the modified example 1, FIG.
As shown in (A), a capacitor 81 is provided between the negative input terminal and the output terminal of the operational amplifier 57 to significantly reduce the AC gain (feedback gain) of the output voltage of the power factor correction converter PFC5, thereby reducing the power factor correction converter PFC5. A large ripple voltage is generated in the output voltage of.

Here, the output voltage ripple can be set to 10 Vp-p or more by adjusting the AC gain by appropriately adjusting the capacitance of the capacitor 81. In the second modification, as shown in FIG.
A capacitor 83 and a resistor 85 are connected in series between the negative input terminal and the output terminal of the operational amplifier 57 to significantly reduce the AC gain (feedback gain) of the output voltage of the power factor correction converter PFC5, and the output of the power factor correction converter PFC5. A large ripple voltage is generated in the voltage. here,
The output voltage ripple can be set to 10 Vp-p or more by appropriately adjusting the capacitance of the capacitor 83 and the resistance value of the resistor 85 to adjust the AC gain and the cutoff frequency.

Further, in the modified example 3, as shown in FIG. 13C, a capacitor 81 and a resistor 87 are connected in parallel between the negative input terminal and the output terminal of the operational amplifier 57, and the output of the power factor correction converter PFC5. The DC gain of the voltage is adjusted and the AC gain (feedback gain) is significantly reduced, and a large ripple voltage is generated in the output voltage of the power factor correction converter PFC5. Where capacitor 8
The output voltage ripple can be reduced to 1 by adjusting the AC gain so that the capacitance of 1 and the resistance of the resistor 87 are adjusted appropriately.
It can be set to 0 Vp-p or more.

(Third Embodiment) FIG. 14 is a diagram showing a configuration of a power supply device according to a third embodiment of the present invention. The configuration of the power supply device will be described with reference to FIG. The feature of the third embodiment is that the power factor correction converter PF using a triangular wave current that does not change the width of the ON period of the switching element 62 within a half cycle of the frequency of the AC power supply 1.
A feedback circuit is formed in the booster type power factor correction converter PFC by using a control circuit that operates in the quasi-resonant type voltage mode.

That is, the multiplier 55 and the current detection resistor 63 provided in the first embodiment are deleted,
Further, a triangular wave oscillator 9 that triggers in response to a set signal output from the comparator 54 and oscillates a triangular wave
1 and the reset signal when the voltage value of the amplified error signal output from the operational amplifier 57 reaches the voltage value of the triangular wave output from the triangular wave oscillator 91.
This is because the comparator 56 for outputting to 9 is provided. The voltage value of the amplified error signal output from the operational amplifier 57 has a substantially constant value equal to or longer than a half cycle of the frequency of the AC power supply 1 because the response is sufficiently delayed by the variable resistor 68 and the capacitor 93.

Here, the inductance value (L value) of the choke coil 61 is selected so that the current flowing through the choke coil 61 is always a triangular wave, and the feedback response time is set to a half cycle or more of the frequency of the AC power supply. so,
The width of the ON period of the switching element 62 within the half cycle is substantially fixed.

Further, since the width of the ON period of the switching element 62 is fixed, the switching current Ip becomes
By fixing T and L,

[Equation 1] Ip = E × T / L (1) A value proportional to the input voltage E is determined.

Therefore, the current flowing through the choke coil 61 is filled with the triangular wave having an ascending gradient and the triangular wave having a descending gradient, so that 1/2 of the peak current becomes the input current. That is, the sine wave current waveform is proportional to the input current waveform.

Next, the operation of the power supply device according to the third embodiment of the present invention will be described. When the AC power supply 1 is applied to the power supply device, the sine wave voltage supplied from the AC power supply 1 passes through the filter 2, is full-wave rectified by the rectifier 3 and passes through the filter 4, and is transmitted to the power factor correction converter PFC5. Wave rectified waveform is provided.

(1) Operation at Startup First, the + input terminal of the comparator 54 has a resistor 60,
It is in a state of being connected to GND through the criticality detection winding 61b, and at the same time, the first reference voltage 53 is input to the-input terminal of the comparator 54. In the comparator 54, both input voltages are compared, and the voltage at the + input terminal has a lower potential, so the comparator 54 outputs a low-level set signal to the flip-flop 59. The flip-flop 59 is set according to the set signal from the comparator 54, and a high-level drive signal is output from the Q output terminal to turn on the switching element 62 at timing t1 shown in FIG.

When the switching element 62 is turned on, FIG.
As shown at timing t1 in FIG.
Drain voltage Vd of the device drops to near 0V. Then, a switching current flows from the filter 4 to the GND via the main winding 61a and the drain-source of the switching element 62, and energy is stored in the choke coil 61.

(2) The variable resistor 68 and the capacitor 93 are connected in parallel between the minus input terminal and the output terminal of the error signal operational amplifier 57, and the output voltage from the output capacitor 65 is divided by the resistors 66 and 67. The error signal output from the operational amplifier 57 is input to the negative input terminal of the operational amplifier 57, and an amplification gain is set and amplified with respect to the error signal formed of the difference between the divided value of the output voltage and the second reference voltage 58. The signal is supplied to the-input terminal of the comparator 56. The waveform B shown in FIG. 6 represents the error signal output from the operational amplifier 57.

Here, the amplitude level of the error signal is adjusted so that the amplification gain (feedback gain) of the output voltage of the power factor correction converter PFC5 is reduced by the variable resistor 68 connected between the minus input terminal and the output terminal of the operational amplifier 57. Is adjusted and supplied to the minus input terminal of the comparator 56.

(3) When the low level set signal is output from the comparator 54 to the flip-flop 59 at the time of activating the OFF control of the switching element, at the same time, the set signal is input to the triangular wave oscillator 91 to trigger and generate a triangular wave. Is oscillated. The triangular wave output from the triangular wave oscillator 91 is input to the + input terminal of the comparator 56. In the triangular wave oscillator 91, the comparator 5
4 to the next set signal is input, for example, about 10
It oscillates a triangular wave at a frequency of 0 kHz.

In the comparator 56, the voltage value of the amplified error signal output from the operational amplifier 57 is the triangular wave oscillator 9
When the voltage value of the triangular wave output from 1 is reached, the reset signal is output to the flip-flop 59. The flip-flop 59 is reset in response to the reset signal from the comparator 56, the high-level drive signal output from the Q output terminal is switched to the low level, and the switching element 62 is off-controlled.

When the switching element 62 is turned off, the energy stored in the choke coil 61 and the voltage supplied from the filter 4 are combined, and the rectifying diode 6
4, the output capacitor 65 is charged.

As a result, the output capacitor 65 outputs a voltage boosted higher than the peak value of the full-wave rectified waveform supplied from the filter 4. The waveform C shown in FIGS. 7 and 6 is the output terminals 5a, 5 of the power factor correction converter PFC5.
It is a figure which shows the mode of the output voltage between b. As shown in this figure, the output voltage from the conventional power factor correction converter PFC has no ripple voltage, whereas the output voltage from the power factor correction converter PFC5 in the present embodiment is approximately 10 Vp-p. It has a ripple voltage.

(4) ON Control of Switching Element Next, when the energy stored in the choke coil 61 is released, a ringing voltage is generated in the criticality detection winding 61b, and the voltage of the criticality detection winding 61b is generated. Is reversed. This voltage is the first reference voltage 53 and the comparator 54.
And a low level set signal is output from the comparator 54 to the flip-flop 59. As a result, the flip-flop 59 is set according to the set signal from the comparator 54, and the drive signal is input again to the switching element 62 to be turned on. At the same time, the set signal is input to the triangular wave oscillator 91 and triggered, and the triangular wave oscillation is synchronized with the set signal.

(5) Amplification Gain (Feedback Gain) In this embodiment, the variable resistor 68 and the capacitor 93 for adjusting the amplification gain are connected in parallel between the − input terminal and the output terminal of the operational amplifier 57, Output capacitor 6
The output voltage from 5 is divided by resistors 66 and 67 and input to the-input terminal of the operational amplifier 57.
7 is compared with the second reference voltage 58. Since the amplification gain of the operational amplifier 57 is determined according to the adjustment value of the variable resistor 68 and the capacitor 93, the error signal decreases as the amplification gain of the operational amplifier 57 decreases.

The variable resistor 68 is adjusted so that the ripple voltage appearing in the output voltage to the DC-DC converter becomes 10 Vp-p or more, and the amplification gain is set so that the error signal of a small amplification level is detected by the comparator. 56. Here, the voltage value of the error signal after amplification output from the operational amplifier 57 has a substantially constant response for a half cycle or more of the frequency of the AC power supply 1 because the response is sufficiently delayed by the variable resistor 68 and the capacitor 93. On the other hand, since the current flowing through the choke coil 61 is always a triangular wave, the feedback response time can be set to a half cycle or longer of the frequency of the AC power supply, and the width of the ON period of the switching element 62 within the half cycle is almost fixed. Like

Further, since the width of the ON period of the switching element 62 is fixed, the switching current Ip becomes
Since T and L are fixed, a value proportional to the input voltage E is determined by the above equation (1). As a result, the current flowing through the choke coil 61 is filled with a rising triangle wave and a descending triangle wave, so that half of the peak current becomes the input current, and the sinusoidal current waveform is proportional to the input current waveform.

As a result, a large ripple voltage is generated in the output voltage of the power factor correction converter PFC5 as compared with the conventional power supply device. Thereafter, by repeating such operations, the output capacitor 65 of the power factor correction converter PFC5
The output voltage at is maintained at a constant average voltage with a ripple voltage. At the same time, the current of the AC power supply 1 has a sinusoidal current waveform that follows the voltage of the AC power supply 1.

Although FIG. 14 shows an example of the error signal amplifier circuit in which the variable resistor 68 and the capacitor 93 are connected to the operational amplifier 57, the present embodiment is not limited to such a case. The modifications 1 to 3 of the error signal amplifier circuit as shown in FIG. 13 can be applied.

[0087]

As described above, according to the present invention, since a large ripple voltage of 10 Vp-p or more, which is twice the frequency of the commercial power supply, is generated in the output voltage of the power factor correction converter, it is supplied. DC- whose frequency changes with the power supply voltage
The switching frequency of the DC converter is also frequency-modulated according to these ripple voltages. Therefore, DC-
The noise level at the switching frequency of the DC converter is dispersed by the frequency modulation, and the noise level can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a power supply device according to a first embodiment of the present invention.

FIG. 2 is a circuit of a π-type normal mode filter applicable to filters 2 and 4.

FIG. 3 is a circuit of a normal mode filter applicable to filters 2 and 4.

FIG. 4 is a circuit of a normal mode filter + common mode filter applicable to filters 2 and 4.

FIG. 5 is a timing chart for explaining the operation of the power factor correction converter PFC5.

FIG. 6 is waveforms A, B, and C at various places for explaining the operation of the power factor correction converter PFC5.

FIG. 7 is a waveform for explaining the operation of the power factor correction converter PFC5.

8 is a circuit of a self-excited flyback DC-DC converter 16 applicable to the DC-DC converter 6. FIG.

9 is a circuit of a voltage quasi-resonant type DC-DC converter 26 applicable to the DC-DC converter 6. FIG.

10 is a circuit of a DC-DC converter 36 having a frequency modulation function applicable to the DC-DC converter 6. FIG.

11 is a circuit of a current resonance type DC-DC converter 46 applicable to the DC-DC converter 6. FIG.

FIG. 12 is a diagram showing a configuration of a power supply device according to a second embodiment of the present invention.

FIG. 13 is a modification example 1 to 3 of the error signal amplifier circuit applicable to the power supply device according to the first and second embodiments of the present invention.
(A), (B), (C) showing.

FIG. 14 is a diagram showing a configuration of a power supply device according to a third embodiment of the present invention.

FIG. 15 is a circuit diagram of a conventional power supply device.

[Explanation of symbols]

1 AC power supply 2,4 filter 3 rectifier 5 Power factor improvement converter PFC 6 DC-DC converter 54, 56 comparator 55 multiplier 59 flip flops 57 operational amplifier 61 choke coil 62 switching element 64 rectifier diode 65 Output capacitor 66, 67, 85, 87 resistance 68 Variable resistance 71 oscillator 81,83,93 capacitors 91 triangular wave oscillator

Claims (5)

[Claims] 1. A power factor correction converter which inputs an AC power source and converts it into a DC voltage and outputs it, and a D which converts a DC voltage from this power factor correction converter into another DC voltage and outputs it.
A power supply device including a C-DC converter, wherein the power factor correction converter sets a ripple voltage at an AC power supply frequency appearing in an output voltage to the DC-DC converter to 10 Vp-p or more. A power supply device, comprising: means, wherein the DC-DC converter has an oscillation frequency that varies in accordance with a ripple voltage included in a DC voltage from the power factor correction converter. 2. A power factor correction converter for inputting a full-wave rectified waveform from an AC power supply through a choke coil, turning it on and off by a switching element to convert it into a DC voltage, and a DC voltage from this power factor correction converter. And a DC-DC converter for converting and outputting the DC voltage to the DC-DC converter, wherein the power factor correction converter outputs an error signal including a difference between an output voltage to the DC-DC converter and a reference voltage. An error signal amplifying means for setting and outputting an amplification gain, and a current target for generating a current target value linked with the full-wave rectified waveform from the full-wave rectified waveform from the AC power supply and the error signal from the error signal amplifying means. A value generating means, a switching current detecting means for detecting a switching current flowing in the ON period of the switching element and outputting the current as a current detection value, The current detection value of the switching current from the switching current detection means, an OFF control means for turning off the switching element when reaching the current target value from the current target value generation means, and the error signal amplification means, The amplification gain is set so that the ripple voltage at the frequency of the AC power supply appearing in the output voltage to the DC-DC converter is 10 Vp-p or more, and the DC-DC converter uses the DC from the power factor correction converter. A power supply device characterized in that the oscillation frequency changes in accordance with the ripple voltage included in the voltage. 3. A power factor correction converter for inputting a full-wave rectified waveform from an AC power source through a choke coil, turning it on and off by a switching element and converting it into a DC voltage, and a DC voltage from this power factor correction converter. And a DC-DC converter for converting the DC voltage into a DC voltage and outputting the converted DC voltage, wherein the power factor correction converter has a first ringing voltage generated in a criticality detection winding provided in the choke coil. Set signal generating means for generating a set signal when reaching the reference voltage, ON control means for turning on the switching element in response to the set signal from the set signal generating means, and set from the set signal generating means Triangular wave oscillating means for activating in response to a signal to oscillate a triangular wave signal having a predetermined frequency, and output to the DC-DC converter Error signal amplification means for setting and outputting an amplification gain of the error signal consisting of the difference between the voltage and the reference voltage, and the voltage value of the triangular wave signal from the triangular wave oscillation means reaches the error signal from the error signal amplification means. OFF control means for turning off the switching element when the output voltage of the AC / DC converter is turned off. The amplification gain is set to, and the DC-DC converter has an oscillation frequency that varies according to a ripple voltage included in the DC voltage from the power factor correction converter. 4. The DC-DC converter is a self-excited oscillation type DC-DC converter, a voltage quasi-resonant type DC.
4. The power supply device according to claim 1, wherein the power supply device is a frequency control type DC-DC converter such as a -DC converter or a current resonance type DC-DC converter. 5. The power supply device according to claim 1, wherein the DC-DC converter is a DC-DC converter having a frequency modulation function.