JP6843094B2 - Switching power supply - Google Patents

Description

The present invention relates to a switching power supply device including a half-bridge current resonance type power converter.

The switching power supply generally has a function of detecting the output power or the output current supplied to the load in real time, and the detection result can be used to detect an abnormality in the load and the switching power supply. Used to protect loads and switching power supplies.

It is known that it is not easy to detect the output power and the output current of the half-bridge current resonance type converter, and various detection circuits have been conventionally proposed to solve this problem. For example, as disclosed in Patent Document 1, a current detection unit that detects a resonance capacitor current flowing through a resonance capacitor inserted in series with the primary winding of a transformer, and a detected resonance capacitor current are used. It is converted into a voltage signal, and without rectifying this voltage signal, half-cycle switching (half-cycle starting from the timing at which each switch element turns on) is averaged, and the averaged voltage value is calculated. There was a switching power supply device equipped with a load current extraction unit that was regarded as a value corresponding to the load current (output current). The load current extraction unit has an averaging circuit composed of a resistor, a capacitor, and a switch, and by turning the switch on and off at a predetermined timing, half a cycle of the voltage signal is averaged.

In the half-bridge current resonance type, when the set value of the output voltage is changed or the input voltage or the output current changes, the switching frequency changes and the magnitude and waveform of the resonance capacitor current also change significantly. Therefore, it is usually difficult to detect the output current by observing the resonance capacitor current, but in principle, the output current should be detected with a certain accuracy in the case of the configuration of the switching power supply device of Patent Document 1. Can be done.

Japanese Unexamined Patent Publication No. 2012-170218

The switching current device of Patent Document 1 is required to accurately average the half cycle of the voltage signal of the resonance capacitor current, but it is actually quite difficult. For example, when the above averaging circuit is used, a high voltage is applied to both ends of the switch at the moment the switch is turned off, and the switching noise generated by this is a large error factor, so the average value of the voltage signal is accurately extracted. It's not easy to do.

The present invention has been made in view of the above background technology, and is a half-bridge current resonance capable of detecting output power or output current with high accuracy even if the set value of output voltage is changed or the output current is changed. It is an object of the present invention to provide a type switching power supply device.

The present invention is a pair of elements arranged on the high side and the low side, and input / output is performed by a pair of main switching elements to which an input voltage is applied at both ends thereof , a primary winding and a secondary winding. insulation for transformers, the primary windings in series with the inserted resonance capacitor in position, and has a rectifying and smoothing circuit for generating a rectifying and smoothing the output voltage of the AC voltage generated in the secondary winding, wherein a pair of main switching element is connected to the primary winding through the resonant capacitor, the input voltage into a predetermined said output voltage by said main switching element is switched, for the load A half-bridge current resonance type power converter that outputs the voltage, a switching control unit that controls the output voltage by switching the main switching element and changing the switching frequency, and a resonance capacitor that flows through the resonance capacitor. A current characteristic value detection unit that detects a current characteristic value indicating the magnitude of the current and outputs it as current characteristic value information, an input voltage detection unit that detects the input voltage and outputs it as input voltage information, and the switching frequency. Output power information generation unit that acquires switching frequency information indicating values, the current characteristic value information, and the input voltage information, and generates output power information corresponding to the output power of the power conversion unit based on the respective information. With and
The current characteristic value has a switching frequency-dependent characteristic in which the value changes according to the switching frequency under a constant condition of the output power, and the output power information generation unit has the switching frequency dependence in advance. A formula for canceling the characteristics, which includes the input voltage as a variable, is set, and when the output power information generator acquires the current characteristic value information, the input voltage information and the switching at that time are obtained. The frequency information is acquired, the value of the input voltage recognized from the acquired input voltage information is substituted, and the calculation based on the formula is performed, and the current characteristic value recognized from the current characteristic value information is switched. It is a switching power supply device that corrects a frequency-dependent characteristic to a canceled value, regards the corrected value as a value corresponding to the output power, and generates the output power information.

The current characteristic value is preferably an absolute value of the peak value of the resonance capacitor current.

The output power information generation unit may be configured to output the generated output power information to the outside. Further, the switching control unit acquires the output power information, and when the value of the output power recognized from the output power information is equal to or less than the overpower reference value, the output voltage is held at a predetermined set value. As described above, the main switching element can be switched, and when the overpower reference value is exceeded, the switching of the main switching element can be forcibly stopped.

The switching power supply device of the present invention detects a current characteristic value (for example, the absolute value of the peak value) indicating the magnitude of the resonance capacitor current, and corrects the current characteristic value to a value that cancels the switching frequency dependence. , The corrected value is regarded as a value corresponding to the output power, and an output power signal is generated, which is a unique operation. By performing this operation, the output power (or output current) can be grasped with high accuracy even if the set value of the output voltage is changed or the output current changes.

Further, if the output power information generator is configured in the digital processor, a mathematical formula for canceling the switching frequency-dependent characteristic is set in advance, and the calculation based on the mathematical formula is performed to execute the above correction, the output is output. The power information generator can be configured more compactly.

It is a block diagram which shows the 1st Embodiment of the switching power supply device of this invention. It is a block diagram which shows an example of the internal structure of the switching control part of FIG. It is a block diagram which shows an example of the internal structure of the current characteristic value detection part of FIG. It is a graph (a) and (b) explaining the meaning of two mathematical formulas set in the output power information generation unit. It is a block diagram which shows the 2nd Embodiment of the switching power supply device of this invention. It is a block diagram which shows an example of the internal structure of the switching control part of FIG. It is a circuit diagram which shows the example which configured the output power information generation part of the switching power supply device of this invention by an analog circuit.

Hereinafter, the first embodiment of the switching power supply device of the present invention will be described with reference to FIGS. 1 to 4. As shown in FIG. 1, the switching power supply device 10 of this embodiment includes a half-bridge current resonance type power conversion unit 12. The power conversion unit 12 is provided with a series circuit of two main switching elements 16 (1) and 16 (2) between the input terminals 14a and 14b to which the input power supply 14 is connected. The main switching elements 16 (1) and 16 (2) are, for example, N-channel MOS FETs, and the main switching element 16 (1) is arranged on the high side side and the main switching element 16 (2) is arranged on the low side side. There is. Here, it is assumed that the fluctuation range of the input voltage Vi output by the input power supply 14 is very small.

A series circuit of the primary winding 18a of the transformer 18, the resonance capacitor 20, and the resonance inductor 22 is connected to both ends of the main switching element 16 (2) on the low side. The resonance inductor 22 may be replaced by the leakage inductor of the transformer 18. Two rectifying elements 24 and one smoothing capacitor 26 are connected to the secondary winding 18b of the transformer 18 to form a so-called center tap type rectifying and smoothing circuit.

In the power conversion unit 12, the main switching elements 16 (1) and 16 (2) switch in opposite phases to each other, generate an AC voltage in the primary winding 18a of the transformer 18, and generate an AC voltage in the secondary winding 18b. The output voltage Vo is generated by rectifying and smoothing the voltage. Then, the output voltage Vo and the output current Io (output power Po) are supplied to the load 28 connected between the output terminals 28a and 28b.

The power conversion unit 12 has a series circuit of the primary winding 18a, the resonance capacitor 20, and the resonance inductor 22 connected to both ends of the main switching element 16 (2) on the low side, but on the high side. It may be connected to both ends of the main switching element 16 (1). Further, although the rectifying element 24 is a diode, a synchronous rectifying element such as a MOS type FET may be used. The configuration of the secondary winding 18b and the rectifying / smoothing circuit is a center tap type, but may be changed to another configuration such as a bridge rectifying type.

The switching control unit 30 generates drive pulses Vg (1) and Vg (2) for switching the main switching elements 16 (1) and 16 (2), and changes the switching frequency Fsw to change the output voltage Vo. This is a block that controls the above, and can be composed of, for example, an error amplifier circuit 32 and a main switching element drive circuit 34, as shown in FIG.

The error amplifier circuit 32 has an inverting amplifier 32a that amplifies the difference between the detected value Vo1 of the output voltage Vo and the reference voltage Vr corresponding to the set value of the output voltage Vo, and outputs the output via a photocoupler 32b for insulation. Is output as the control current I32. The control current I32 increases / decreases in the direction of matching the output voltage Vo with the set value, increases when the output voltage Vo becomes higher than the set value, and decreases when the output voltage Vo becomes lower than the set value. The set value of the output voltage Vo can be changed by changing the reference voltage Vr through the external connection terminal 32c.

The main switching element drive circuit 34 includes an oscillator 34a and a drive pulse generation circuit 34b. The oscillator 34a determines the switching frequency Fsw based on the control current I32, and the drive pulse generation circuit generates the drive pulses Vg (1) and Vg (2) of the switching frequency Fsw determined by the oscillator 34a, and the main switching element. Output toward 16 (1) and 16 (2). The drive pulses Vg (1) and Vg (2) are voltage pulses that repeat high level and low level, and the main switching element 16 (1) is turned on when the drive pulse Vg (1) is at high level, and the main switching The element 16 (2) is turned on when the drive pulse Vg (2) is at a high level.

In general, a half-bridge current resonance type converter has a property that when the switching frequency Fsw is fixed, the output voltage Vo increases when the output current Io decreases, and the output voltage Vo decreases when the output current Io increases. Therefore, for example, when the output current Io becomes small and the output voltage Vo becomes higher than the set value, the control current I32 output by the error amplifier circuit 32 becomes large, and the main switching element drive circuit 34 responds to the change in the control current I32. The switching frequency Fsw of the drive pulses Vg (1) and Vg (2) is increased. As a result, the output voltage Vo drops and returns to the original set value. On the contrary, when the output current Io becomes large and the output voltage Vo becomes lower than the set value, the control current I32 becomes small, and the main switching element drive circuit 34 receives the drive pulse Vg (1), according to the change of the control current I32. Lower the switching frequency Fsw of Vg (2). As a result, the output voltage Vo drops and returns to the original set value.

In this way, the switching control unit 30 controls the output voltage Vo by varying the switching frequency Fsw. Further, the control current I32 changes almost in proportion to the output voltage Vo, and the switching frequency Fsw changes almost in proportion to the control current I32 .

The current characteristic value detection unit 36 is a block that detects a current characteristic value indicating the magnitude of the resonance capacitor current I20 flowing through the resonance capacitor 20. The resonance capacitor current I20 is an alternating current that oscillates substantially evenly in the positive and negative directions, and here, the absolute value of the peak value is the current characteristic value I20p.

As shown in FIG. 3, for example, the current characteristic value detection unit 36 connects a series circuit including the flow dividing capacitor 36a and the current detection resistor 36b in parallel to the resonance capacitor 20, and knows a part of the resonance capacitor current I20. Divide the current at the ratio of. Then, a peak-hold type rectifying and smoothing circuit composed of a diode 36c and a capacitor 36d is connected in parallel to the current detection resistor 36b, and the AC voltage generated in the current detection resistor 36b is peak-held and output. The resistor 36e connected in parallel to the capacitor 36d is a discharge resistor, and is set to a large value that does not interfere with the peak hold operation. Therefore, the current characteristic value detection unit 36 generates a voltage generated in the capacitor 36d, that is, a DC voltage substantially proportional to the current characteristic value I20p, and outputs the current characteristic information J (I20p).

Since the high voltage is not applied to both ends of the diode 36c at the moment when the diode 36c is turned off, the current characteristic value detection unit 36 hardly generates switching noise that causes an error, and detects the output current characteristic value I20p with high accuracy. Can be done. The rectifying and smoothing circuit composed of the diode 36c and the capacitor 36d has a configuration in which the AC voltage generated in the current detection resistor 36b is half-wave rectified and peak-held, but is configured to be full-wave rectified and peak-held. You may.

The output power information generation unit 38 acquires the switching frequency information J (Fsw) indicating the value of the switching frequency Fsw and the current characteristic value information J (I20P), and based on J (Fsw) and J (I20P), the power is supplied. This is a block that generates and outputs output power information J (Po) corresponding to the output power Po of the conversion unit 12. Here, it is provided in the digital processor.

As shown in FIG. 2, the output power information generation unit 38 inserts a current detection resistor 38a into the output of the photocoupler 32b, and the voltage generated in the current detection resistor 38a when the control current I32 flows, that is, switching. The DC voltage that is almost proportional to the frequency Fsw is acquired as the switching frequency information J (Fsw).

Further, the following mathematical formulas (formulas (1) and (2)) are set in advance in the output power information generation unit 38.

Equation (1) is an equation for calculating Ib (h) on the left side. In the right side, Ib and Fb are variables, and the other Ia1, Ia2, Fa1 and Fa2 are known constants. Equation (2) is an equation for calculating Po (B) on the left side. In the right side, Ib (h) is a variable, and the other Pk and Ia1 are known constants. Hereinafter, the meanings of the equations (1) and (2) will be described with reference to the graph of FIG. 4 (a).

In FIG. 4A, plots A1 and A2 are data measured by performing an energization test of the switching power supply device 10, and the output power Po is fixed to a constant reference value Pk and the set value of the output voltage Vo is set. The measured values of the current characteristic value I20p and the switching frequency Fsw when changed to different values are plotted. For example, plot A1 is a plot of "I20p = Ia1, Fsw = Fa1" measured under the condition of "Vo = 5V, Io = 20A, Po = 100W", and plot A2 is "Vo = 1V, Io =". It is a plot of "I20p = Ia2 (<Ia1), Fsw = Fa2 (> Fa1)" measured under the condition of "100A, Po = 100W". Therefore, for example, when a straight line passing through the plots A1 and A2 is drawn, the straight line is a straight line that approximately represents the relationship between the current characteristic value I20p and the switching frequency Fsw under the condition that the output power Po is constant.

The constants Ia1, Ia2, Fa1 and Fa2 in the equation (1) are the measured values of the above energization test, and the fractional part represents the slope of the straight line passing through the plots A1 and A2. Further, the constant Ia1 in the equation (2) is also a measured value of the energization test, and Pk is a reference value indicating the conditions of the energization test. In particular, the slope of the straight line passing through plots A1 and A2 can be said to be a numerical value that strongly indicates the characteristics of the switching frequency-dependent characteristic of the current characteristic value I20p.

In this way, the constants Ia1, Ia2, Fa1, Fa2, and Pk of the equations (1) and (2) are determined by performing the energization test of the switching power supply device 10, and the determined values are the output power information generator 38. Is initialized to.

When the switching power supply device 10 actually operates and supplies the output power Po (B) to the load 28, the output power information generation unit 38 grasps the output power Po (B) by the following procedure. First, the current characteristic value information J (I20p) is acquired to recognize that the current characteristic value I20p is Ib, and then the switching frequency information J (Fsw) is acquired to recognize that the switching frequency Fsw is Fb. .. That is, it is recognized that the switching power supply device 10 is operating in the plot B of FIG. 4 (a).

Then, Ib and Fb are substituted into the equation (1) to calculate Ib (h), which is a correction value of Ib. Equation (1) is the value of the current characteristic value I20p (= correction value Ib (= correction value Ib) when it is assumed that the switching power supply device 10 is operating at the switching frequency Fa1 under the condition of the output power Po (B). This is an equation that estimates h)) based on Ib and Fb of plot B. In other words, the correction value Ib (h) is a value obtained by normalizing Ib with reference to the switching frequency Fa1, and can be said to be a value that cancels the switching frequency dependence of the current characteristic value I20p.

The ratio Ia1 / Ib (h) of the current characteristic value Ia1 and the correction value Ib (h) is almost equal to the ratio Pk / Po (B) of the output power Pk and Po (B). Therefore, the output power information generation unit 38 can calculate the current output power Po (B) by substituting the correction value Ib (h) calculated in the equation (1) into the equation (2). Then, the output power information J (Po) corresponding to the calculated Po (B) is generated and output to the outside through the external connection terminal 40. If the value of the output voltage Vo (B) at that time is known, the output current Io (B) = Po (B) / Vo (B) is calculated, and the output current corresponding to the calculated Io (B) is calculated. It is also possible to generate information J (Io) and output it externally through the external connection terminal 40.

In the graph of FIG. 4A, plot B is below the straight line passing through plots A1 and A2, and Ib (h) <Ia1. Therefore, the current output power Po (B) is from the reference value Pk. You can see that it is small. Further, in the graph of FIG. 4B, the plot B is on the upper side of the straight line passing through the plots A1 and A2, and Ib (h)> Ia1. Therefore, the current output power Po (B) is larger than the reference value Pk. You can see that.

As described above, the switching power supply device 10 detects the current characteristic value I20p (absolute value of the peak value) indicating the magnitude of the resonance capacitor current I20, and cancels the switching frequency dependence of the current characteristic value I20p. It corrects to a value, regards the corrected value as a value corresponding to the output power Po, and generates output power information J (Po), which is a unique operation. By performing this operation, the output power Po (or output current Io) can be grasped with high accuracy even if the set value of the output voltage Vo is changed or the output current Io changes.

Further, in the output power information generation unit 38, all the configurations are provided in the digital processor, and the equations (1) and (2) for canceling the switching frequency-dependent characteristic are set in advance, and the equations (1) and (1), ( It is configured to perform the calculation based on 2) and execute the above correction. Therefore, the output power information generation unit can be configured more compactly than a configuration in which a plurality of discrete components are combined. Further, as described above, when the energization test is performed in the shipping inspection of the switching power supply device 10, the constants included in the equations (1) and (2) are determined based on the test results, so that the characteristics of each device vary. Can be easily absorbed.

Next, a second embodiment of the switching power supply device of the present invention will be described with reference to FIGS. 5 and 6. Here, the same configuration as that of the switching power supply device 10 is designated by the same reference numerals, and the description thereof will be omitted.

The switching power supply device 42 of this embodiment includes the same power conversion unit 12 and current characteristic value detection unit 36 as described above, and the difference in configuration is that a switching control unit 44 is provided instead of the switching control unit 30. The point is that the output power information generation unit 46 is provided in place of the output power information generation unit 38.

The output power information generation unit 46 performs the same operation as the output power information generation unit 38 described above to generate the output power information J (Po), but does not output the generated output power information J (Po) to the outside. , Output to the switching control unit 44.

The switching control unit 44 includes an oscillator 34a and a drive pulse generation circuit 34b similar to the output power information generation unit 30 described above, recognizes the output power Po from the output power information J (Po), and sets the output power Po as an overpower reference. When the value is Pth or less, the main switching elements 16 (1) and 16 (2) are switched so that the output voltage Vo is maintained at a predetermined set value, and the output power Po exceeds the overpower reference value Pth. At the time, the switching of the main switching elements 16 (1) and 16 (2) is forcibly stopped. When stopping the switching, for example, the operation of the oscillator 34a or the drive pulse generation circuit 34b may be stopped, or the high-level time ratio of the drive pulses Vg (1) and Vg (2) is maintained at 0%. You may.

According to the switching power supply device 42, the same effect as that of the switching power supply device 10 can be obtained, and further, excess power is output to prevent the switching power supply device 10 and the load 28 from being damaged or burned out. Overpower protection can be performed. For example, when the energization test shown in FIGS. 4A and 4B is performed, if the reference value Pk is set to a value equal to the overpower reference value Pth, the operating point of the overpower protection can be initially set with high accuracy. ..

The switching power supply device of the present invention is not limited to the above embodiment. For example, the equations (1) and (2) set in the output power information generators 38 and 46 described above are equations corresponding to the current characteristic value I20p and the switching frequency Fsw, but these equations are the current characteristic values. Depending on the form of information J (I20p) and switching frequency information J (Fsw), it can be replaced with substantially the same equation. For example, when the current characteristic value information J (I20p) is an analog voltage signal proportional to the current characteristic value I20p and the switching frequency information J (Fsw) is an analog voltage signal proportional to the switching frequency Fsw, Eqs. (1), ( By replacing 2) with an equation expressing the relationship between analog voltages, the output voltage Po (B) can be calculated by substituting each analog voltage into the equation as it is.

As described above, the current characteristic value I20p has a switching frequency-dependent characteristic in which the value of the output power Po changes according to the switching frequency Fsw under a constant condition, and the equations (1) and (2) are: This is a formula set to cancel the switching frequency-dependent characteristic of the current characteristic value I20p. The equations (1) and (2) are examples of the mathematical expressions, and the contents of the mathematical expressions can be appropriately changed in consideration of the detection accuracy required for the detection of the output power Po and the like. In the above embodiment, as described with reference to FIGS. 4 (a) and 4 (b), the switching frequency-dependent characteristic is specified based on the measured values of the two operating points (plots A1 and A2), and this is canceled. Equations (1) and (2) are set. For example, if the switching frequency-dependent characteristic is specified more accurately based on the measured values of three or more operating points and a equation is set to cancel this, the output will be output. The power detection accuracy can be further improved.

Since the fluctuation range of the input voltage Vi supplied from the input power supply 14 is small in the switching power supply devices 10 and 42, the influence of the input voltage Vi on the switching frequency-dependent characteristic of the current characteristic value I20p is constant, but the input voltage Vi When the fluctuation range of is large (in the case of a device having a wide input voltage range), it is preferable to consider the fluctuation of the input voltage Vi. In that case, it is advisable to provide an input voltage detection unit that detects the input voltage Vi and outputs the detection result as the input voltage information J (Vi), and sets a mathematical formula that includes the input voltage Vi as a variable in the output power information generation unit. .. The half-bridge current resonance type has the property that when the output voltage Vo and output current Io are constant and only the input voltage Vi fluctuates, the switching frequency Fsw changes almost in proportion to the input voltage Vi, so this property is taken into consideration. By setting the formula, the output power can be detected accurately even when the fluctuation range of the input voltage Vi is large.

Although the output power information generation units 38 and 46 are all provided in the digital processor, it is also possible to perform some or all of the above-mentioned functions in an analog circuit composed of a plurality of discrete components. For example, FIG. 7 shows an output power information generation unit 48 composed of a first amplifier circuit 50 composed of an operational amplifier and a resistor and a second amplifier circuit 52. The first amplifier circuit 50 is a so-called adder circuit, and by adjusting the values of the three resistors 50a, 50b, and 50c, input / output characteristics substantially equivalent to the arithmetic processing of the equation (1) are realized. It is possible to generate an analog voltage signal J (Ib (h)) proportional to the above correction value Ib (h). By adjusting the values of the two resistors 52a and 52b, the second amplifier circuit 52 in the subsequent stage can realize input / output characteristics that are almost equivalent to the arithmetic processing of equation (2), and the output voltage Po ( An analog voltage signal J (Po) proportional to B) can be generated.

2 and 6 show an example of the internal configuration of the switching control unit, and may be changed to another configuration if the operation intended by the present invention is possible.

FIG. 3 shows an example of the internal configuration of the current characteristic value detection unit, and may be changed to another configuration if the operation intended by the present invention is possible. In particular, the current characteristic value detected by the current characteristic value detector may be any one indicating the magnitude of the resonance capacitor current, and is not limited to the "absolute value of the peak value of the resonance capacitor current" such as I20p above. .. For example, the detection accuracy of the output power may be slightly reduced, but it is also possible to set the "average value of the waveform obtained by full-wave rectifying the resonance capacitor current" as the current characteristic value, and the current characteristic value detector can be used. You may change to such a configuration. Further, the resonance capacitor current may be observed at a position different from the position of the resonance capacitor, and may be observed at a position in series with the resonance inductor, for example.

In addition, as mentioned in the description of each embodiment and the description of the modification, the form of each information (current characteristic value information, switching frequency information and output power information) is an analog voltage signal, an analog current signal, and a digital signal. You can freely select from the above. Then, each block (switching control unit, current spot value detection unit, and output power information generation unit) may be configured so that information can be exchanged with the other block. Further, when the output power information is output to the outside, it may be output in the form of an electric signal as described above, or for example, it is output in the form of displaying the value of the output power on a display provided integrally with the power supply device. You may.

10, 42 Switching power supply 12 Half-bridge current resonance type power converter 16 (1), 16 (2) Main switching element 18 Transformer 18a Primary winding 18b Secondary winding 20 Resonant capacitor 30, 44 Switching control unit 36 Current characteristic value detection unit 38, 46, 48 Output power information generation unit
Fsw switching frequency
I20 resonant capacitor current
I20p Resonant capacitor current current characteristic value (absolute value of peak value)
Io output current
Po output power
Pth overpower reference value
Vi input voltage
Vo output voltage
J (Fsw) switching frequency information
J (I20p) Current characteristic value information
J (Po) output power information
J (Vi) input voltage information

Claims (1)

A pair of elements arranged on the high side and the low side, and a pair of main switching elements to which an input voltage is applied across them, and a transformer that insulates the input and output between the primary winding and the secondary winding. It has a resonance capacitor inserted in series with the primary winding, and a rectifying and smoothing circuit that rectifies and smoothes the AC voltage generated in the secondary winding to generate an output voltage, and the pair of main switching element is connected to the primary winding through the resonant capacitor, the input voltage into a predetermined said output voltage by said main switching element is switched to output to the load half Bridge current resonance type power converter and
A switching control unit that controls the output voltage by switching the main switching element and varying its switching frequency.
A current characteristic value detector that detects a current characteristic value indicating the magnitude of the resonance capacitor current flowing through the resonance capacitor and outputs it as current characteristic value information.
An input voltage detector that detects the input voltage and outputs it as input voltage information,
An output that acquires switching frequency information indicating the value of the switching frequency, the current characteristic value information, and the input voltage information, and generates output power information corresponding to the output power of the power conversion unit based on the respective information. Equipped with a power information generator
The current characteristic value has a switching frequency-dependent characteristic in which the value changes according to the switching frequency under a constant condition of the output power.
In the output power information generation unit, a mathematical formula for canceling the switching frequency-dependent characteristic, which includes the input voltage as a variable, is set in advance.
When the output power information generation unit acquires the current characteristic value information, it acquires the input voltage information and the switching frequency information at that time, and substitutes the value of the input voltage recognized from the acquired input voltage information. The calculation based on the above formula is performed to correct the current characteristic value recognized from the current characteristic value information to a value in which the switching frequency dependent characteristic is canceled, and the corrected value is regarded as a value corresponding to the output power. A switching power supply device characterized by generating the output power information.

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