JP2004282944A - Switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To superpose a plurality of detection signals on one main detection signal and to transmit the superposed signal to a primary side by insulating via one photocoupler. <P>SOLUTION: A switching power supply (10A) includes first to N-th detecting means (21, 22 and 23) at a secondary side and includes a primary side controller (40) for controlling on, off a main switching element (13) at a primary side. A modulator (50) provided at the secondary side superposes a signal obtained by modulating a carrier by second and third detection signals on a first detection signal, and outputs the superposed detection signal. One photocoupler (31) sends the superposed detection signal to the primary side as a superposed feedback signal. A demodulator (60) provided at the primary side obtains first to third feedback signals by demodulating the superposed feedback signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a switching power supply device including a primary side to which an input AC voltage from an AC power supply is applied and a secondary side for outputting a secondary side output voltage, and in particular, changes the state of the secondary side to the primary side. The present invention relates to a switching power supply device having feedback means.
[0002]
[Prior art]
In the switching power supply device, primary-side rectifying and smoothing means for rectifying and smoothing an input AC voltage supplied from an AC power supply to a primary-side DC voltage, switching means for switching the primary-side DC voltage and converting the same to an AC voltage, Secondary rectifying and smoothing means for rectifying and smoothing the AC voltage to a secondary DC voltage. The secondary DC voltage is also called a secondary output voltage. The switching means includes a main transformer having a primary winding to which a primary DC voltage is applied and a secondary winding for outputting a converted AC voltage, and a main switching element for turning on and off the primary DC voltage. In the switching power supply having such a configuration, the primary-side rectifying / smoothing means, the main switching element, and the primary winding of the main transformer are called a primary side, and the secondary winding and the secondary-side rectifying / smoothing means of the main transformer are used as secondary sides. Called the next side.
[0003]
In such a switching power supply, the primary side and the secondary side need to be electrically insulated and separated in order to prevent an accident such as electric shock. As means for electrically insulating and separating, a photocoupler is generally used. Also, in the switching power supply, in order to perform constant voltage control, it is necessary to return a change in the secondary output voltage to the primary side as a constant voltage control signal. In this case, the constant voltage control signal is returned to the primary side via the photo coupler.
[0004]
In other cases, it may be necessary to transmit a signal for entering the standby mode, an overcurrent / overvoltage detection signal, and the like to the primary side.
[0005]
When it is necessary to transmit a signal other than the constant voltage control signal to the primary side, conventionally, information is transmitted to the primary side using the same number of photocouplers as necessary signals and information.
[0006]
Hereinafter, a conventional switching power supply device will be described with reference to FIG. The illustrated switching power supply device 10 includes a primary-side rectifying / smoothing circuit 11, a main transformer 12 having a primary winding 121 and a secondary winding 122, a main switching element 13, a diode 14, and an output capacitor 15. ing.
[0007]
The primary side rectifying / smoothing circuit 11 rectifies and smoothes an input AC voltage supplied from an AC power supply to a primary side DC voltage. The primary side rectifying and smoothing circuit 11 includes, for example, a diode bridge and an input capacitor.
[0008]
This primary side DC voltage is applied to the primary winding 121 of the main transformer 12. The main switching element 13 turns on and off the primary DC voltage. By turning on and off the main switching element 13, an AC voltage is induced in the secondary winding 122 of the main transformer 12. This induced AC voltage is called the converted AC voltage. That is, the secondary winding 122 of the main transformer 12 outputs the converted AC voltage. Therefore, the combination of the main transformer 12 and the main switching element 13 operates as switching means for switching the primary DC voltage and converting it into the AC voltage.
[0009]
The converted AC voltage is rectified by the diode 14 and then smoothed by the output capacitor 15. From the output capacitor 15, a secondary DC voltage (secondary output voltage) is output. Therefore, the combination of the diode 14 and the output capacitor 15 functions as a secondary rectifying / smoothing means for rectifying and smoothing the converted AC voltage into a secondary DC voltage.
[0010]
The illustrated conventional switching power supply device includes a voltage detection circuit 21, an overcurrent detection circuit 22, and a standby mode detection circuit 23 as means for detecting the state on the secondary side. The voltage detection circuit 21 detects a change in the secondary output voltage and outputs a constant voltage detection control signal. The overcurrent detection circuit 22 detects an overcurrent on the secondary side and outputs an overcurrent detection signal. The standby mode detection circuit 23 detects a standby mode command and outputs a standby mode detection signal.
[0011]
In the illustrated example, only three detection circuits 21 to 23 are provided as means for detecting the state of the secondary side, but the present invention is not limited to this. In addition to these, an overvoltage detection circuit for detecting overvoltage is provided. Etc. may be provided.
[0012]
In the illustrated example, since three detection circuits 21 to 23 are provided, the illustrated conventional switching power supply device 10 includes first to third circuits as means for electrically insulating and separating the primary side and the secondary side. Photocouplers 31, 32, and 33 are provided. The first photocoupler 31 receives a constant voltage detection control signal from the voltage detection circuit 21 as a first detection signal, emits a first light signal, and emits a first light signal. And a first light receiving transistor 31r for transmitting a first feedback signal to the primary side. The second photocoupler 32 receives the overcurrent detection signal from the overcurrent detection circuit 22 as a second detection signal, emits a second optical signal, and emits a second optical signal. And a second light receiving transistor 32r for transmitting a second feedback signal to the primary side. The third photocoupler 33 receives a standby mode detection signal from the standby mode detection circuit 23 as a third detection signal and emits a third optical signal, and emits a third optical signal. And a third light receiving transistor 33r for transmitting a third feedback signal to the primary side.
[0013]
The first to third feedback signals are supplied to the primary side control unit 40. The primary side control unit 40 controls on / off of the main switching element 13 in response to the first to third feedback signals.
[0014]
As described above, the conventional switching power supply device 10 has a problem that a plurality of photocouplers are required. In order to solve this problem, an overvoltage protection signal (or remote control signal) is superimposed on a feedback signal (constant voltage detection control signal) of the main output voltage induced on the secondary side by using a single switch. 2. Description of the Related Art There is known a technology in which a photocoupler is insulated by a plurality of photocouplers and transmitted to a primary side (for example, see Patent Document 1).
[0015]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-156972
[Problems to be solved by the invention]
In Patent Literature 1, since one switch is used as the superimposing means, only one signal can be superimposed on the constant voltage detection control signal. That is, in Patent Literature 1, a signal obtained by performing an OR operation of an overvoltage protection signal and a remote control signal by an OR circuit is superimposed on a constant voltage detection control signal by controlling a switch.
[0017]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a switching power supply device capable of superimposing a plurality of detection signals on one main detection signal, insulating the signal by one photocoupler, and transmitting the signal to the primary side.
[0018]
[Means for Solving the Problems]
According to the present invention, there is provided a switching power supply device (10A) including a primary side to which an input AC voltage from an AC power supply is applied and a secondary side to output a secondary side output voltage, wherein the secondary side Comprises first to Nth detection means (21, 22, 23) for detecting the state of the secondary side and outputting first to Nth (N is an integer of 3 or more) detection signals, A primary side control unit (40) that receives the first to Nth detection signals as first to Nth feedback signals and controls on / off of a main switching element (13) disposed on the primary side; In the switching power supply device, a signal obtained by modulating a carrier wave with the second to Nth detection signals is provided on the secondary side and is superimposed on the first detection signal. A modulating means (50) for outputting a signal; One photocoupler (31) for transmitting a signal to the primary side as a superimposed feedback signal in a state where the primary side and the secondary side are electrically insulated and separated from each other; and provided on the primary side. And a demodulating means (60) for demodulating the superimposed feedback signal to obtain the first to Nth feedback signals.
[0019]
In the above switching power supply, the primary side includes, for example, a primary side rectifying / smoothing means (11) for rectifying and smoothing the input AC voltage to a primary side DC voltage, and a main transformer (12) to which the primary side DC voltage is applied. A primary winding (121) and the main switching element (13) for turning on and off the primary side DC voltage, and the secondary side is, for example, a main transformer (12) for outputting a converted AC voltage. And secondary side rectifying / smoothing means (14, 15) for rectifying and smoothing the converted AC voltage to the secondary side output voltage. Further, it is preferable that the first to Nth detection means (21 to 23) and the modulation means (50) are realized by one integrated circuit, and the primary side control unit (40) and the demodulation means (60) is preferably realized by one integrated circuit.
[0020]
Further, when the N is 3, the modulating means (50) includes, for example, a first oscillator (51) for oscillating a first carrier having a first oscillation frequency, the first carrier (51) and the second carrier (51). A first multiplier (53) for multiplying the first detection signal by the first detection signal and a second modulation signal for outputting a second carrier having a second oscillation frequency lower than the first oscillation frequency. An oscillator (52), a second multiplier (54) that multiplies the second carrier and the third detection signal to output a second modulation signal, An adder (55) that adds the first modulation signal and the second modulation signal and outputs the superimposed detection signal. The demodulation means (60) extracts, for example, the first detection signal from the superimposed feedback signal and outputs the first feedback signal to the low-pass filter (61), and the superimposed signal. A high-pass filter (62) for extracting the first modulated signal from the feedback signal; a first demodulation unit for demodulating the extracted first modulated signal and outputting the second feedback signal; A band-pass filter (63) for extracting the second modulated signal from the superimposed feedback signal, and demodulating the extracted second modulated signal to output the third feedback signal. And a second demodulation unit.
[0021]
It is to be noted that the reference numerals in the parentheses are provided for facilitating the understanding of the present invention, are merely examples, and are not limited thereto.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0023]
Referring to FIG. 2, a switching power supply device 10A according to one embodiment of the present invention will be described.
[0024]
The illustrated switching power supply device 10A has the second and third photocouplers 32 and 33 eliminated, and instead includes a modulator 50 as a superimposing means on the secondary side and a demodulator 60 as a separating means on the primary side. Except for this point, it has the same configuration as the conventional switching power supply device 10 shown in FIG. Therefore, components having the same functions as those of the components shown in FIG. 1 are denoted by the same reference numerals, and descriptions thereof will be omitted for simplification of description.
[0025]
That is, the conventional switching power supply device 10 includes three photocouplers 31 to 33, whereas the switching power supply device 10A according to the present embodiment includes only one photocoupler 31.
[0026]
The modulator 50 superimposes a signal obtained by modulating the carrier with the second and third detection signals on the first detection signal, and outputs the superimposed detection signal. One photocoupler 31 sends the superimposed detection signal to the primary side as a superimposed feedback signal in a state where the primary side and the secondary side are electrically insulated and separated. The demodulator 60 demodulates the superimposed feedback signal to obtain first to third feedback signals.
[0027]
The illustrated modulator 50 includes first and second oscillators 51 and 52, first and second multipliers 53 and 54, and an adder 55. The first oscillator 51 oscillates a first carrier having a first oscillation frequency. The second oscillator 52 oscillates a second carrier having a second oscillation frequency lower than the first oscillation frequency. The first multiplier 53 performs RF (high-frequency) modulation of the first carrier with the second detection signal by multiplying the first carrier and the second detection signal, and converts the first modulation wave. Output. The second multiplier 54 performs RF modulation of the second carrier with the third detection signal by multiplying the second carrier by the third detection signal, and outputs a second modulated wave. The adder 55 superimposes the first and second modulation waves on the first detection signal by adding the first detection signal, the first modulation wave, and the second modulation wave. The detected signal is output.
[0028]
The illustrated demodulator 60 includes a low-pass filter 61, a high-pass filter 62, and a band-pass filter 63. The low-pass filter 61 extracts a first detection signal from the superimposed feedback signal and outputs a first feedback signal. The high-pass filter 62 extracts the first modulated wave from the superimposed feedback signal. The extracted first modulated wave is supplied to a first demodulation unit (not shown). The first demodulation section demodulates the first modulated wave using the first carrier to reproduce a second detection signal, and outputs a second feedback signal. The band-pass filter 63 extracts a second modulated wave from the superimposed feedback signal. The extracted second modulated wave is supplied to a second demodulation unit (not shown). The second demodulation unit demodulates the second modulated wave using the second carrier to reproduce a third detection signal and outputs a third feedback signal. These first to third feedback signals are sent to the primary side control unit 40.
[0029]
As described above, in the present embodiment, by providing the modulator 50 on the secondary side and the demodulator 60 on the primary side, the first detection signal (constant voltage detection control signal) and the second detection signal (constant voltage detection control signal) are provided. Three types of detection signals including an overcurrent detection signal) and a third detection signal (standby mode detection signal) can be transmitted from the secondary side to the primary side using one photocoupler 31.
[0030]
Note that the voltage detection circuit 21, the overcurrent detection circuit 22, the standby mode detection circuit 23, and the modulator 51 can be realized by one integrated circuit (IC). Also, the primary side control circuit 40 and the demodulator can be realized by one integrated circuit (IC).
[0031]
Further, in the above-described embodiment, the modulator 50 includes the two oscillators 51 and 52. Alternatively, the modulator 50 may include one oscillator and a frequency divider.
[0032]
FIG. 3 shows a timing chart of the switching power supply device 10A. 3A shows a state of switch control of the main switching element 13, FIG. 3B shows a primary current, and FIG. 3C shows a secondary current.
[0033]
The switching power supply 10A shown in FIG. 2 is an RCC switching power supply. In the switching power supply of the RCC system, when the main switching element 13 is turned on, current energy from the primary side is stored in the main transformer 12 as magnetic flux energy, and when the main switching element 13 is turned off, energy is discharged to the secondary side as current. I do.
[0034]
In the vicinity of the arrow in FIG. 3, the change in current and voltage is large, and a lot of noise is generated. Therefore, if information is transmitted from the secondary side to the primary side while avoiding such a period in which noise is generated, the influence of noise is reduced.
[0035]
As described above, the present invention has been described with reference to the preferred embodiments, but the present invention is not limited to the above-described embodiments. For example, in the above-described embodiment, an example is described in which three types of detection signals are transmitted (returned) from the secondary side to the primary side, but four or more types of detection signals are transmitted from the secondary side to the primary side ( Needless to say, the present invention can be applied to the case of returning. Further, in the above-described embodiment, an example is described in which the modulator 50 provided on the secondary side uses RF modulation as its modulation method, but may be replaced with quadrature modulation or various pulse modulations.
[0036]
【The invention's effect】
As is clear from the above description, in the present invention, by providing a modulator as a superimposing means on the secondary side and a demodulator as a separating means on the primary side, three or more types of detection signals can be converted into one photo. There is an effect that the signal can be transmitted from the secondary side to the primary side using the coupler.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram showing a conventional switching power supply device.
FIG. 2 is a circuit block diagram showing a switching power supply according to one embodiment of the present invention.
FIG. 3 is a timing chart of the switching power supply device shown in FIG. 2;
[Explanation of symbols]
10A Switching power supply 11 Primary rectifying and smoothing circuit 12 Main transformer 121 Primary winding 122 Secondary winding 13 Main switching element 14 Diode 15 Output capacitor 21 Voltage detection circuit 22 Overcurrent detection circuit 23 Standby mode detection circuit 31 Photocoupler 40 Primary Side control unit 50 Modulator 51 First oscillator (OSC1)
52 Second oscillator (OSC2)
53 first multiplier 54 second multiplier 55 adder 60 demodulator 61 low-pass filter 62 high-pass filter 63 band-pass filter

Claims (4)

A switching power supply device comprising a primary side to which an input AC voltage from an AC power supply is applied and a secondary side for outputting a secondary side output voltage, wherein the secondary side detects a state of the secondary side. And first to Nth detection means for outputting first to Nth detection signals (N is an integer of 3 or more), and the primary side converts the first to Nth detection signals to the first to Nth detection signals. The switching power supply device further comprising a primary-side control unit that receives an N-th feedback signal and controls on / off of a main switching element arranged on the primary side.
A modulator provided on the secondary side, superimposing a signal obtained by modulating a carrier with the second to Nth detection signals on the first detection signal, and outputting a superimposed detection signal;
One photocoupler that sends the superimposed detection signal to the primary side as a superimposed feedback signal in a state where the primary side and the secondary side are electrically insulated and separated,
Demodulation means provided on the primary side to demodulate the superimposed feedback signal to obtain the first to Nth feedback signals;
A switching power supply device comprising: The primary side includes a primary side rectifying / smoothing means for rectifying and smoothing the input AC voltage to a primary side DC voltage, a primary winding of a main transformer to which the primary side DC voltage is applied, and turning on / off the primary side DC voltage. Having the main switching element,
The secondary side includes a secondary winding of a main transformer that outputs a converted AC voltage, and a secondary-side rectifying and smoothing unit that rectifies and smoothes the converted AC voltage to the secondary-side output voltage. The switching power supply device according to claim 1. The said 1st thru | or Nth detection means and the said modulation means are implement | achieved by one integrated circuit, The said primary side control part and the said demodulation means are implemented by one integrated circuit. Switching power supply. Said N is 3,
A modulating means for multiplying the first carrier and the second detection signal by a first oscillator for oscillating a first carrier having a first oscillation frequency, and outputting a first modulation signal; 1 multiplier, a second oscillator that oscillates a second carrier having a second oscillation frequency lower than the first oscillation frequency, and a multiplier that multiplies the second carrier and the third detection signal. A second multiplier for outputting a second modulation signal, and adding the first detection signal, the first modulation signal, and the second modulation signal to output the superimposed detection signal. And an adder,
The demodulation means extracts the first detection signal from the superimposed feedback signal, and outputs a first feedback signal to the low-pass filter; and the first modulation signal from the superimposed feedback signal. A high-pass filter that extracts a signal, a first demodulation unit that demodulates the extracted first modulated signal and outputs the second feedback signal, and a second demodulator that outputs the second feedback signal from the superimposed feedback signal. And a second demodulation unit that demodulates the extracted second modulation signal and outputs the third feedback signal.
The switching power supply device according to claim 1.

Images