JP2014053981A - Switching power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation of the power-supply characteristics of a switching power supply without depending on an input voltage range or an output voltage variable range.SOLUTION: A switching power supply having an LLC resonant circuit and switch elements Q1 and Q2 detects error between a voltage value of an output voltage and a target value of the output voltage determined by power supply voltage of a reference voltage source Vref, and passes a current according to the detection result to a phototransistor PC2. Further, an input voltage detection unit 20 detects an input voltage or a voltage according to the input voltage, and a current source S passes a current according to the detection result.

Description

  The present invention relates to a switching power supply.

  Conventionally, a switching power supply having a resonant circuit has been proposed (see, for example, Patent Documents 1 and 2).

[Configuration of Switching Power Supply 100]
FIG. 9 is a circuit diagram of a switching power supply 100 according to a conventional example. The switching power supply 100 includes a transformer T, a primary circuit connected to the primary winding W1 of the transformer T, and a secondary circuit connected to the secondary windings W2 and W3 of the transformer T.

  First, the primary side circuit will be described. The primary side circuit includes switch elements Q1 and Q2 configured by N-channel MOSFETs, a control circuit 10, a capacitor C1, an inductor L, and a phototransistor PC2.

  The switch elements Q1 and Q2 form a half bridge circuit, and the input terminal IN is connected to the drain of the switch element Q1. An input terminal GND connected to a reference potential source is connected to the source of the switch element Q2. One end of the primary winding W1 is connected to the source of the switch element Q1 and the drain of the switch element Q2 via the capacitor C1 and the inductor L. Capacitor C1, inductor L, and primary winding W1 form an LLC resonant circuit. An input terminal GND is connected to the other end of the primary winding W1.

  A control circuit 10 is connected to the gate of the switch element Q1 and the gate of the switch element Q2. The control circuit 10 is connected to the input terminal GND and to the collector of the phototransistor PC2 at the terminal P1. The input terminal GND is connected to the emitter of the phototransistor PC2.

  Next, the secondary circuit will be described. The secondary circuit includes diodes D1 and D2, capacitors C2 and C3, resistors R1 to R4, a reference voltage source Vref, an error amplifier AMP, and a photodiode PC1.

  One end of the secondary winding W2 is connected to the anode of the diode D1, and the other end of the secondary winding W3 is connected to the anode of the diode D2. The output terminal OUT1 is connected to the cathode of the diode D1 and the cathode of the diode D2. The output terminal OUT2 is connected to the other end of the secondary winding W2 and one end of the secondary winding W3. The output terminal OUT1 and the output terminal OUT2 are connected through a capacitor C2 and are connected through resistors R3 and R4.

  The output terminal OUT1 is connected to one end of the resistor R3, one end of the resistor R4 is connected to the other end of the resistor R3, and the output terminal OUT2 is connected to the other end of the resistor R4. An inverting input terminal of the error amplifier AMP is connected to the other end of the resistor R3 and one end of the resistor R4, and an output terminal of the error amplifier AMP is connected via the capacitor C3 and the resistor R2. The positive terminal of the reference voltage source Vref is connected to the non-inverting input terminal of the error amplifier AMP, and the output terminal OUT2 is connected to the negative electrode of the reference voltage source Vref. The resistors R2 to R4, the error amplifier AMP, the capacitor C3, and the reference voltage source Vref constitute output voltage detecting means.

  The output terminal of the error amplifier AMP is connected to the cathode of the photodiode PC1, and the anode of the photodiode PC1 is connected to the output terminal OUT1 via the resistor R1. The photodiode PC1 is provided in a pair with the phototransistor PC2, and the photodiode PC1 and the phototransistor PC2 constitute a photocoupler.

[Operation of Switching Power Supply 100]
In the switching power supply 100 having the above configuration, the control circuit 10 controls the on / off frequency of the switch elements Q1 and Q2 according to the voltage of the terminal P1, and the input voltage input from the input terminals IN and GND is predetermined. And output from the output terminals OUT1 and OUT2 as output voltages.

  The voltage at the terminal P1 changes according to the output voltage. Specifically, the error amplifier AMP detects an error voltage that is an error between the voltage value of the output voltage and the target value of the output voltage determined by the power supply voltage of the reference voltage source Vref, and the amount of light corresponding to the detection result is detected. From the photodiode PC1 to the phototransistor PC2. The phototransistor PC2 allows a current corresponding to the amount of light received from the photodiode PC1 to flow from the control circuit 10 toward the input terminal GND. According to this, the voltage at the terminal P1 changes according to the error voltage.

JP 2004-343855 A JP 2007-252144 A

  FIG. 10 is a diagram illustrating gain phase characteristics of the switching power supply 100. In FIG. 10, the vertical axis represents the gain or phase, and the horizontal axis represents the response frequency of the switching power supply 100.

  In a switching power supply having a resonance circuit such as the switching power supply 100, the proportional gain becomes maximum at the lower limit of the input voltage as shown in FIG. For this reason, in order to stabilize the output voltage, a negative feedback control constant is set at the lower limit of the input voltage. However, if the input voltage range is wide, the proportional gain decreases as shown in FIG. 10 at the time of normal operation or at the upper limit of the input voltage, so that the power supply characteristics may be deteriorated.

  Therefore, in order to suppress the above-described deterioration of the power supply characteristics, it is conceivable to take measures such as providing a power factor correction circuit (boost converter) to narrow the input voltage range. However, even when this measure is taken, the above-described deterioration of the power supply characteristics cannot be suppressed because the effect of the boost converter is lost during a power failure.

  Further, as another problem, even when the output voltage is varied similarly to the input voltage fluctuation, the proportional gain fluctuation occurs. In this case, the proportional gain becomes maximum at the upper limit of the output voltage. However, even in this case, if the variable range of the output voltage is wide, the proportional gain decreases at the time of normal operation or at the lower limit of the output voltage, similarly to the case where the negative feedback control constant is set at the upper limit of the input voltage. In some cases, power supply characteristics deteriorate.

  In view of the above-described problems, an object of the present invention is to suppress deterioration of power supply characteristics of a switching power supply regardless of an input voltage range or an output voltage variable range.

The present invention proposes the following items in order to solve the above-described problems.
(1) The present invention relates to a resonance circuit (e.g., equivalent to an LLC resonance circuit formed by the capacitor C1, the inductor L, and the primary winding W1 in FIG. 1) and a switch element (for example, the switch element Q1, FIG. Q2) is a switching power supply (e.g., equivalent to the switching power supply 1 in FIG. 1 or the switching power supply 1A in FIG. 3) according to the input voltage, the voltage according to the input voltage, the output voltage, or the output voltage Voltage detection means (for example, corresponding to the input voltage detection unit 20 in FIG. 1) and correction means (for example, the current in FIG. 1) that controls the proportional gain in accordance with the voltage detected by the voltage detection means. And a switching power supply including a source S and a control circuit 10A in FIG.

  According to this invention, the voltage detection means and the correction means are provided in the switching power supply having the resonance circuit and the switch element. The voltage detection means detects the input voltage, the voltage corresponding to the input voltage, the output voltage, or the voltage corresponding to the output voltage. Further, the proportional gain is controlled by the correcting means in accordance with the voltage detected by the voltage detecting means.

  For this reason, when the voltage detection means detects the input voltage or the current corresponding to the input voltage, the proportional gain can be controlled according to the input voltage. Therefore, it is possible to suppress the proportional gain from fluctuating according to the fluctuation of the input voltage, and it is possible to suppress the deterioration of the power supply characteristics of the switching power supply regardless of the input voltage range.

  Further, when the output voltage or the voltage corresponding to the output voltage is detected by the voltage detection means, the proportional gain can be controlled according to the output voltage. Therefore, it is possible to suppress the proportional gain from fluctuating according to the fluctuation of the output voltage, and it is possible to suppress the deterioration of the power supply characteristics of the switching power supply regardless of the output voltage variable range.

  (2) According to the present invention, for the switching power source of (1), an output voltage or a voltage corresponding to the output voltage is detected, and an output voltage detecting means for supplying a current corresponding to the detection result, and the output voltage detecting means flows Control means for controlling the on / off frequency of the switching element in accordance with the current, and the correction means controls the current that the output voltage detection means flows to control the proportional gain. A switching power supply is proposed.

  According to this invention, the output voltage detecting means and the control means are provided in the switching power source of (1). Then, the output voltage detection means detects the output voltage or a voltage corresponding to the output voltage, and flows a current corresponding to the detection result. Also, the on / off frequency of the switch element is controlled by the control means in accordance with the current flowing through the output voltage detection means. Further, the proportional gain is controlled by controlling the current flowing through the output voltage detecting means by the correcting means. For this reason, the effect similar to the effect mentioned above can be produced.

  (3) In the switching power supply according to (2), the correction unit may change the current flowing through the output voltage detection unit linearly or nonlinearly according to the voltage detected by the voltage detection unit. We have proposed a switching power supply.

  According to the present invention, in the switching power supply of (2), the current flowing through the output voltage detecting means is changed linearly or non-linearly by the correcting means according to the voltage detected by the voltage detecting means. For this reason, the proportional gain can be changed linearly or non-linearly with respect to the voltage detected by the voltage detecting means, and the same effect as described above can be obtained.

  (4) According to the present invention, in the switching power supply of (1), the correction unit (for example, equivalent to the control circuit 10A in FIG. 3) determines the relationship between the voltage detected by the voltage detection unit and the proportional gain. Information (e.g., corresponding to a calculation formula described later) is stored in advance, and using the information, a value of a proportional gain corresponding to the voltage detected by the voltage detection unit is obtained, and the proportional gain is obtained from the obtained value. We propose a switching power supply characterized by controlling

  According to the present invention, in the switching power source of (1), the correction unit stores in advance information indicating the relationship between the voltage detected by the voltage detection unit and the proportional gain, and using this information, The value of the proportional gain corresponding to the voltage detected by the voltage detecting means is obtained, and the proportional gain is controlled to the obtained value. Therefore, the proportional gain can be controlled to an input voltage, a voltage corresponding to the input voltage, an output voltage, or a value corresponding to a voltage corresponding to the output voltage. Therefore, the same effects as those described above can be achieved.

  (5) In the switching power supply of (4), the present invention relates to a voltage detected by the voltage detection means in which the correction means (for example, equivalent to the control circuit 10A in FIG. 3) holds information in advance, a proportional gain, , Has proposed a switching power supply characterized by being linear or non-linear.

  According to the present invention, in the switching power supply of (4), the relationship between the voltage detected by the voltage detecting means in which the correcting means holds information in advance and the proportional gain is linear or nonlinear. For this reason, the proportional gain can be changed linearly or non-linearly with respect to the voltage detected by the voltage detecting means, and the same effect as described above can be obtained.

  (6) In the switching power supply of (4) or (5), the present invention is configured to turn on the switch element based on the proportional gain controlled by the correction unit and the output voltage or a voltage corresponding to the output voltage. A switching power supply characterized by comprising a control means (for example, corresponding to the control circuit 10A in FIG. 3) for controlling the off frequency is proposed.

  According to the present invention, the switching power source of (4) or (5) has an on / off frequency of the switch element based on the proportional gain controlled by the correcting means and the output voltage or the voltage according to the output voltage. Control means for controlling the above is provided. For this reason, the effect similar to the effect mentioned above can be produced.

  (7) The present invention provides the switching power supply according to any one of (2), (3), and (6), wherein the output voltage or the voltage corresponding to the output voltage is a voltage value of the output voltage and a target of the output voltage. And a switching power supply characterized by an error voltage of the value.

  According to the present invention, in any one of the switching power supplies of (2), (3), or (6), the output voltage or the voltage corresponding to the output voltage is the output voltage value, the output voltage target value, Error voltage. For this reason, it is possible to achieve the same effect as described above by controlling the on / off frequency of the switch element based on the error between the voltage value of the output voltage and the target value.

  (8) In the switching power supply according to any one of (2), (3), (6), and (7), the control means is provided on a primary side of the switching power supply, and the output voltage Or switching means characterized by comprising transmission means (for example, equivalent to the photodiode PC1 and the phototransistor PC2 in FIG. 1) for transmitting a signal corresponding to the output voltage from the secondary side to the primary side of the switching power supply Proposed power supply.

  According to the present invention, in any one of the switching power supplies of (2), (3), (6), or (7), the control means is provided on the primary side of the switching power supply, and the output voltage or the output voltage is determined. Transmission means for transmitting a voltage signal from the secondary side to the primary side of the switching power supply is provided. For this reason, even when the control means is on the primary side of the switching power supply, the output voltage or a voltage corresponding to the output voltage can be transmitted to the control means, and the same effects as described above can be obtained. it can.

  (9) In the switching power supply according to any one of (2), (3), (6), and (7), the control means is provided on the secondary side of the switching power supply, and the switch element A control signal for controlling the on / off frequency of the switching power source is transmitted to the switch element via a transmission means (for example, equivalent to the insulating circuit 41 in FIG. 7) for transmitting a signal from the secondary side to the primary side of the switching power supply. A switching power supply characterized by transmission is proposed.

  According to the present invention, in any one of the switching power supplies of (2), (3), (6), or (7), the control means is provided on the secondary side of the switching power supply. The control signal for controlling the on / off frequency is transmitted to the switch element via a transmission means for transmitting a signal from the secondary side to the primary side of the switching power supply. For this reason, even when the control means is on the secondary side of the switching power supply, the on / off frequency of the switch element can be controlled by the control means, and the same effects as described above can be obtained. .

  (10) The present invention provides the switching power supply according to any one of (1) to (9), wherein the correction unit is configured when the input voltage is equal to or lower than a predetermined threshold (for example, at the time of a power failure described later). The switching power supply is characterized by controlling the proportional gain.

  According to the present invention, in any one of the switching power supplies of (1) to (9), the proportional gain is controlled by the correcting means when the input voltage is equal to or less than a predetermined threshold value. For this reason, when the input voltage is equal to or lower than a predetermined threshold, the same effect as described above can be obtained.

  (11) In the switching power supply according to any one of (1) to (10), the present invention includes a power factor correction circuit (e.g., equivalent to the power factor correction circuit 30 in FIG. 6) at the input portion of the switching power supply. We propose a switching power supply characterized by

  According to this invention, in the switching power supply of any one of (1) to (10), the power factor correction circuit is provided at the input portion of the switching power supply. For this reason, during the period when electric power is supplied to the power factor correction circuit, the power factor correction circuit can suppress the deterioration of the power supply characteristics of the switching power supply.

  According to the present invention, it is possible to suppress the deterioration of the power supply characteristics of the switching power supply regardless of the input voltage range or the output voltage variable range.

1 is a circuit diagram of a switching power supply according to a first embodiment of the present invention. It is a figure which shows the gain phase characteristic of the said switching power supply. It is a circuit diagram of the switching power supply concerning a 2nd embodiment of the present invention. It is a circuit diagram of the switching power supply which concerns on 3rd Embodiment of this invention. It is a circuit diagram of the switching power supply which concerns on 4th Embodiment of this invention. It is a circuit diagram of the switching power supply concerning a 5th embodiment of the present invention. It is a circuit diagram of the switching power supply which concerns on 6th Embodiment of this invention. It is a circuit diagram of the switching power supply which concerns on 7th Embodiment of this invention. It is a circuit diagram of the switching power supply concerning a prior art example. It is a figure which shows the gain phase characteristic of the said switching power supply.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the constituent elements in the following embodiments can be appropriately replaced with existing constituent elements, and various variations including combinations with other existing constituent elements are possible. Accordingly, the description of the following embodiments does not limit the contents of the invention described in the claims.

<First Embodiment>
[Configuration of Switching Power Supply 1]
FIG. 1 is a circuit diagram of a switching power supply 1 according to the first embodiment of the present invention. The switching power supply 1 is different from the switching power supply 100 according to the conventional example shown in FIG. 9 in that it includes an input voltage detection unit 20 and a current source S. In the switching power supply 1, the same components as those of the switching power supply 100 are denoted by the same reference numerals, and the description thereof is omitted.

  The current source S is connected in parallel with the phototransistor PC2.

[Operation of switching power supply 1]
In the switching power supply 1, the input voltage detection unit 20 detects an input voltage or a voltage corresponding to the input voltage, and sends a signal corresponding to the detection result to the current source S.

  Here, the voltage corresponding to the input voltage is a voltage that changes following the change of the input voltage. For example, the input voltage is divided using a resistor, or input using an amplifier circuit. It is an amplified version of the voltage.

  The current source S passes a current corresponding to the voltage detected by the input voltage detection unit 20 based on the signal sent from the input voltage detection unit 20. According to this, the current flowing through the phototransistor PC2 changes according to the voltage detected by the input voltage detector 20, and the proportional gain is controlled.

  Here, the current corresponding to the voltage detected by the input voltage detection unit 20 is a current that changes linearly or nonlinearly with respect to the voltage detected by the input voltage detection unit 20.

  When the current flowing through the current source S is changed linearly, for example, the current flowing through the current source S is decreased linearly as the voltage detected by the input voltage detection unit 20 increases. According to this, as the voltage detected by the input voltage detection unit 20 increases, the current flowing through the phototransistor PC2 increases linearly, and the proportional gain increases linearly.

  When the current flowing through the current source S is changed nonlinearly, for example, if the voltage detected by the input voltage detection unit 20 is less than a predetermined threshold, the current value flowing through the current source S is changed to the first value. Set to a value of 1. On the other hand, if the voltage detected by the input voltage detection unit 20 is equal to or greater than a predetermined threshold, the current value that the current source S flows is set to a second value that is smaller than the first value. According to this, when the voltage detected by the input voltage detection unit 20 is equal to or higher than the above-described threshold value, the current flowing through the phototransistor PC2 becomes larger than when the voltage is lower than the above-described threshold value, and the proportional gain is increased. Will rise. That is, the proportional gain changes nonlinearly with whether or not the voltage detected by the input voltage detection unit 20 is equal to or higher than the above threshold.

  FIG. 2 is a diagram illustrating gain phase characteristics of the switching power supply 1. In FIG. 2, the vertical axis indicates the gain or phase, and the horizontal axis indicates the response frequency of the switching power supply 1.

  As described above, when the current flowing through the current source S is changed according to the voltage detected by the input voltage detection unit 20, as shown in FIG. 2, the proportionality at the upper limit of the input voltage with respect to the lower limit of the input voltage. The decrease in gain is suppressed compared to the case shown in FIG.

  According to the above switching power supply 1, the following effects can be produced.

  The switching power supply 1 controls the proportional gain by changing the current flowing through the phototransistor PC2 in accordance with the input voltage or the voltage corresponding to the input voltage. For this reason, it can suppress that a proportional gain fluctuates according to the fluctuation | variation of an input voltage, and can suppress degradation by the input voltage range about the power supply characteristics of the switching power supply 1, such as a sudden load change characteristic and a regulation characteristic. According to this, the capacity of the capacitor C2 can also be reduced.

Second Embodiment
[Configuration of Switching Power Supply 1A]
FIG. 3 is a circuit diagram of a switching power supply 1A according to the second embodiment of the present invention. The switching power supply 1A is different from the switching power supply 1 according to the first embodiment of the present invention shown in FIG. 1 in that the control circuit 10A is provided instead of the control circuit 10 and the current source S is not provided. . In the switching power supply 1A, the same components as those of the switching power supply 1 are denoted by the same reference numerals, and the description thereof is omitted.

[Operation of Switching Power Supply 1A]
In the switching power supply 1 </ b> A, the control circuit 10 </ b> A controls the proportional gain according to the voltage detected by the input voltage detection unit 20 based on the signal sent from the input voltage detection unit 20. Specifically, the control circuit 10A stores in advance a calculation formula indicating the relationship between the voltage detected by the input voltage detection unit 20 and the proportional gain. Then, by substituting the voltage detected by the input voltage detection unit 20 into this calculation formula, the value of the proportional gain corresponding to the voltage detected by the input voltage detection unit 20 is obtained, and the proportional gain is controlled to the obtained value. To do.

  Here, the calculation formula is a mathematical formula in which the relationship between the voltage detected by the input voltage detection unit 20 and the proportional gain is linear or non-linear.

  When the relationship between the voltage detected by the input voltage detector 20 and the proportional gain is linear, for example, the proportional gain is increased linearly as the voltage detected by the input voltage detector 20 increases. .

  Further, when the relationship between the voltage detected by the input voltage detection unit 20 and the proportional gain is non-linear, for example, if the voltage detected by the input voltage detection unit 20 is less than a predetermined threshold value. For example, the proportional gain is set to the first value. On the other hand, if the voltage detected by the input voltage detection unit 20 is equal to or greater than a predetermined threshold value, the proportional gain is set to a second value larger than the first value. According to this, when the voltage detected by the input voltage detection unit 20 is equal to or higher than the above-described threshold, the proportional gain increases as compared with the case where the voltage is lower than the above-described threshold. That is, the proportional gain changes nonlinearly with whether or not the voltage detected by the input voltage detection unit 20 is equal to or higher than the above threshold.

  Further, the control circuit 10A controls the on / off frequencies of the switch elements Q1 and Q2 based on the controlled proportional gain and the voltage at the terminal P1.

  According to the above switching power supply 1 </ b> A, the same effects as those described above that can be achieved by the switching power supply 1 can be achieved.

<Third Embodiment>
[Configuration of Switching Power Supply 1B]
FIG. 4 is a circuit diagram of a switching power supply 1B according to the third embodiment of the present invention. The switching power supply 1B is different from the switching power supply 1 according to the first embodiment of the present invention shown in FIG. 1 in the connection of the current source S and the phototransistor PC2. In the switching power supply 1B, the same components as those of the switching power supply 1 are denoted by the same reference numerals, and the description thereof is omitted.

  A voltage source V1 is connected to the collector of the phototransistor PC2, and a terminal P1 of the control circuit 10 is connected to the emitter of the phototransistor PC2. The current source S is connected in parallel with the phototransistor PC2.

  According to the above switching power supply 1B, the same effect as the above-mentioned effect which the switching power supply 1 can show | play can be show | played.

<Fourth embodiment>
[Configuration of Switching Power Supply 1C]
FIG. 5 is a circuit diagram of a switching power supply 1C according to the fourth embodiment of the present invention. The switching power supply 1C is different from the switching power supply 1A according to the second embodiment of the present invention shown in FIG. 3 in the connection of the phototransistor PC2. In the switching power supply 1C, the same components as those of the switching power supply 1A are denoted by the same reference numerals, and the description thereof is omitted.

  A voltage source V1 is connected to the collector of the phototransistor PC2, and a terminal P1 of the control circuit 10A is connected to the emitter of the phototransistor PC2.

  According to the above switching power supply 1C, the same effects as those described above that can be achieved by the switching power supply 1A can be achieved.

<Fifth Embodiment>
[Configuration of Switching Power Supply 1D]
FIG. 6 is a circuit diagram of a switching power supply 1D according to the fifth embodiment of the present invention. The switching power supply 1D is different from the switching power supply 1 according to the first embodiment of the present invention shown in FIG. 1 in that a power factor correction circuit 30 is provided in the input section. In the switching power supply 1D, the same components as those of the switching power supply 1 are denoted by the same reference numerals and description thereof is omitted.

  The power factor correction circuit 30 forms a boost converter and operates when the input voltage of the switching power supply 1D is higher than a predetermined threshold. On the other hand, when the input voltage of the switching power supply 1D is less than or equal to the threshold value, the input voltage detection unit 20 transmits a signal corresponding to the detection result to the current source S as described above, and the input voltage of the switching power supply 1D is equal to the threshold value. If it is higher, transmission of the signal to the current source S is stopped.

  For this reason, when the input voltage is higher than the threshold value, the power factor correction circuit 30 boosts the input voltage and narrows the input voltage range.

  On the other hand, when the input voltage is equal to or lower than the threshold (for example, during a power failure), the power factor correction circuit 30 does not operate. However, the input voltage detection unit 20 detects the input voltage or a voltage corresponding to the input voltage, and sends a signal corresponding to the detection result to the current source S. For this reason, the current source S passes a current corresponding to the received signal, and changes the current flowing through the phototransistor PC2.

  According to the above switching power supply 1D, in addition to the above-described effects that the switching power supply 1 can exhibit, the following effects can be achieved.

  When the input voltage is higher than the threshold, the switching power supply 1D can narrow the input voltage range by the power factor correction circuit 30 and suppress the deterioration of the power supply characteristics of the switching power supply 1D.

<Sixth Embodiment>
[Configuration of Switching Power Supply 1E]
FIG. 7 is a circuit diagram of a switching power supply 1E according to the sixth embodiment of the present invention. The switching power supply 1E is different from the switching power supply 1A according to the second embodiment of the present invention shown in FIG. 3 in place of the control circuit 10A, the phototransistor PC2, the photodiode PC1, and the resistor R1. 41 and 42 are different. In the switching power supply 1E, the same components as those of the switching power supply 1A are denoted by the same reference numerals, and the description thereof is omitted.

  The control circuit 10B is provided on the secondary side of the switching power supply 1E. Specifically, the control circuit 10B is directly connected to the output terminal of the error amplifier AMP. Further, the control circuit 10B is connected to the gate of the switch element Q1 and the gate of the switch element Q2 through the insulating circuit 41, and is connected to the input voltage detection unit 20 through the insulating circuit 42.

[Operation of switching power supply 1E]
In the switching power supply 1E, the control circuit 10B receives the voltage detected by the input voltage detection unit 20 via the insulation circuit 42, and controls the proportional gain according to this voltage. A control signal corresponding to the controlled proportional gain and the voltage at the terminal P1 is transmitted to the switch elements Q1 and Q2 via the insulating circuit 41 to control the on / off frequency of the switch elements Q1 and Q2. To do.

  According to the switching power supply 1E described above, the same effects as those described above that can be achieved by the switching power supply 1A can be achieved.

<Seventh embodiment>
[Configuration of switching power supply 1F]
FIG. 8 is a circuit diagram of a switching power supply 1F according to the seventh embodiment of the present invention. The switching power supply 1F is different from the switching power supply 1E according to the sixth embodiment of the present invention shown in FIG. 7 in that a control circuit 10C is provided instead of the control circuit 10B, the input voltage detection unit 20, and the insulation circuit 42. Different. Further, the switching power supply 1F controls the current supplied by the output voltage detection means composed of the resistors R2 to R4, the error amplifier AMP, the capacitor C3, and the reference voltage source Vref to control the proportional gain. Different from 1E. In the switching power supply 1F, the same components as those of the switching power supply 1E are denoted by the same reference numerals, and the description thereof is omitted.

  The control circuit 10C is provided on the secondary side of the switching power supply 1F similarly to the control circuit 10B, and is connected to the output terminal OUT1.

[Operation of switching power supply 1F]
In the switching power supply 1F, the control circuit 10C controls the proportional gain according to the detection result of the output voltage detected by the output voltage detection means. Specifically, the control circuit 10C stores in advance a calculation formula that indicates the relationship between the output voltage and the proportional gain. Then, the detected output voltage is substituted into this calculation formula, the value of the proportional gain corresponding to the output voltage is obtained, and the proportional gain is controlled to the obtained value.

  Here, the calculation formula is a mathematical formula in which the relationship between the output voltage and the proportional gain is linear or non-linear.

  When the relationship between the output voltage and the proportional gain is linear, for example, the proportional gain is increased linearly as the output voltage increases.

  When the relationship between the output voltage and the proportional gain is non-linear, for example, if the output voltage is less than a predetermined threshold, the proportional gain is set to the first value. On the other hand, if the output voltage is greater than or equal to a predetermined threshold, the proportional gain is set to a second value that is greater than the first value. According to this, when the output voltage is equal to or higher than the above threshold value, the proportional gain increases as compared with the case where the output voltage is lower than the above threshold value. That is, the proportional gain changes non-linearly with whether or not the output voltage is equal to or higher than the above threshold value.

  Further, the control circuit 10C transmits a control signal corresponding to the controlled proportional gain and the voltage at the terminal P1 to the switch elements Q1 and Q2 via the insulation circuit 41, and turns on / off the switch elements Q1 and Q2. Control off frequency.

  According to the above switching power supply 1F, the following effects can be produced.

  The switching power supply 1F can control the proportional gain according to the output voltage. Therefore, it is possible to suppress the proportional gain from fluctuating according to the fluctuation of the output voltage, and it is possible to suppress the deterioration of the power supply characteristics of the switching power supply 1F regardless of the output voltage variable range.

  The present invention is not limited to the above-described embodiment, and various modifications and applications can be made without departing from the gist of the present invention.

  For example, in each of the above-described embodiments, the half-bridge circuit is provided in the primary circuit, but the present invention is not limited thereto, and for example, a full-bridge circuit may be provided.

  In each of the above-described embodiments, the transformer T has a so-called center tap. However, the present invention is not limited to this.

  Further, in each of the above-described embodiments, the primary side circuit is provided with the LLC resonant circuit as the resonant circuit. However, the present invention is not limited to this.

  In the first and third embodiments described above, the signal sent to the current source S is an input voltage or a signal corresponding to a detection result of a voltage corresponding to the input voltage. However, the present invention is not limited to this. For example, an output voltage or a signal corresponding to a detection result of a voltage corresponding to the output voltage may be used. When the signal sent to the current source S is an output voltage or a detection signal of a voltage corresponding to the output voltage, the proportional gain can be controlled according to the output voltage. According to this, it is possible to suppress the proportional gain from fluctuating according to the fluctuation of the output voltage, and it is possible to suppress the deterioration of the power supply characteristics of the switching power supply regardless of the output voltage variable range.

  In the second embodiment and the fourth embodiment described above, the proportional gain is controlled according to the input voltage or the detection result of the voltage corresponding to the input voltage. However, the present invention is not limited to this. For example, the proportional gain may be controlled in accordance with the output voltage or the detection result of the voltage corresponding to the output voltage. When controlling the proportional gain according to the output voltage or the detection result of the voltage according to the output voltage, it is possible to suppress the proportional gain from fluctuating according to the fluctuation of the output voltage, and the output voltage variable range. Regardless, the deterioration of the power supply characteristics of the switching power supply can be suppressed.

  In the first and third embodiments described above, the current source S is connected in parallel to the phototransistor PC2. However, the present invention is not limited to this. For example, a resistor or an element or a circuit that can flow a current is used. If it is.

  Moreover, although the example which provided the power factor improvement circuit 30 in the above-mentioned 5th Embodiment was demonstrated, the power factor improvement circuit 30 can be provided also in other embodiment.

1, 1A, 1B, 1C, 1D, 1E, 1F, 100; switching power supply 10, 10A, 10B, 10C; control circuit 20; input voltage detection unit 30; power factor correction circuit 41, 42; insulation circuit AMP; PC1; Photodiode PC2; Phototransistor Q1, Q2; Switch element S; Current source T; Transformer

Claims (11)

A switching power supply having a resonant circuit and a switch element,
Voltage detection means for detecting an input voltage, a voltage according to the input voltage, an output voltage, or a voltage according to the output voltage;
And a correction means for controlling a proportional gain in accordance with the voltage detected by the voltage detection means. An output voltage detecting means for detecting an output voltage or a voltage corresponding to the output voltage and flowing a current corresponding to the detection result;
Control means for controlling the on / off frequency of the switch element according to the current flowing by the output voltage detection means,
2. The switching power supply according to claim 1, wherein the correcting unit controls a proportional gain by controlling a current flowing through the output voltage detecting unit.   3. The switching power supply according to claim 2, wherein the correction unit changes a current flowing through the output voltage detection unit linearly or nonlinearly according to a voltage detected by the voltage detection unit. The correction means includes
Information indicating the relationship between the voltage detected by the voltage detection means and the proportional gain is held in advance,
The switching power supply according to claim 1, wherein a value of a proportional gain corresponding to the voltage detected by the voltage detection unit is obtained using the information, and the proportional gain is controlled to the obtained value.   5. The switching power supply according to claim 4, wherein a relationship between a voltage detected by the voltage detection unit that holds information in advance by the correction unit and a proportional gain is linear or non-linear.   5. A control unit that controls an on / off frequency of the switch element based on the proportional gain controlled by the correction unit and the output voltage or a voltage corresponding to the output voltage. Or the switching power supply of 5.   The output voltage or a voltage corresponding to the output voltage is an error voltage between a voltage value of the output voltage and a target value of the output voltage, according to any one of claims 2, 3 and 6. Switching power supply. The control means is provided on the primary side of the switching power supply,
8. The transmission device according to claim 2, further comprising a transmission unit configured to transmit the output voltage or a voltage corresponding to the output voltage from a secondary side to a primary side of the switching power supply. 9. The switching power supply described.   The control means is provided on the secondary side of the switching power supply, and includes a transmission means for transmitting a control signal for controlling the on / off frequency of the switching element from the secondary side to the primary side of the switching power supply. The switching power supply according to claim 2, wherein the switching power supply is transmitted to the switch element.   The switching power supply according to claim 1, wherein the correction unit controls the proportional gain when the input voltage is equal to or lower than a predetermined threshold value. The switching power supply according to any one of claims 1 to 10,
A switching power supply comprising a power factor correction circuit at an input section of the switching power supply.

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