JP7341178B2 - switching power supply - Google Patents

Description

The present invention relates to a current resonance half-bridge type switching power supply device in which a resonant capacitor and a resonant inductor are provided in series with the input winding of a transformer.

In a current resonant half-bridge type switching power supply, a unique resonant operation is performed by a transformer, a resonant capacitor, and a resonant inductor. By detecting this resonant operation, the status of power conversion operation (actual resonant frequency, It is known that it is possible to grasp the output power, output current, etc.). Therefore, conventionally, the state of resonance operation is detected and the detection results are used for various control and protection functions.

For example, the LLC converter (current resonant half-bridge converter) disclosed in Patent Document 1 detects a resonant voltage and a resonant current, and uses the detection results to improve load responsiveness and facilitate phase compensation design. It is used to improve.

The LLC converter of Patent Document 1 includes a capacitor C4 between the input winding of the transformer and the connection point of the resonance capacitor and the ground line as a circuit for detecting a resonance voltage (hereinafter referred to as a resonance voltage signal generation section). , C6 are connected in series, and a circuit is provided which outputs the voltage generated in the capacitor C6 as a resonant voltage signal VCR. The series circuit of capacitors C4 and C6 is a so-called voltage divider circuit, which converts the resonant voltage generated at the connection point between the input winding and the resonant capacitor into a resonant voltage signal (for example, a low voltage signal of several volts or less) that can be easily handled by the control circuit. Performs an operation to lower the voltage.

In addition, as a circuit for detecting a resonant current (hereinafter referred to as a resonant current signal generating section), a series circuit of a capacitor C3 and a resistor R6 is installed between the input winding of the transformer and the connecting point of the resonant capacitor and the ground line. A circuit is provided which connects the resistor R6 and outputs the voltage generated across the resistor R6 as a resonant current signal VIS. The capacitor C4 and the resistor R6 operate to shunt a part of the resonant current flowing through the input winding of the transformer and convert it into a resonant current signal (for example, a low voltage signal of several volts or less) that can be easily handled by the control circuit.

JP2020-78155A

When the configuration of the resonant voltage signal generating section and the resonant current signal generating section disclosed in Patent Document 1 is applied to a switching power supply device into which a commercial AC voltage is input, the connection point between the input winding and the resonant capacitor is over 100 Since a high voltage of ten volts to several hundred volts is generated, capacitors C3 and C4 disclosed in the drawings of Patent Document 1 must be selected to have a withstand voltage of at least 100 volts or more.

Generally, surface-mounted ceramic capacitors are suitable for applications such as the capacitors C3, C4, and C6 described above. Commercially available ceramic capacitors have a rich lineup and are relatively inexpensive when the withstand voltage is 50 V or less, but when the withstand voltage exceeds 50 V, the lineup tends to be limited and the prices tend to be relatively high. Furthermore, even if the withstand voltage inside the capacitor element is guaranteed, small elements with two external electrodes close to each other may experience creeping discharge when a high voltage of 100-100 volts to several hundred volts is applied. Since there is a risk of this occurring, it cannot be used, and a sufficiently large external shape must be selected.

Therefore, when configuring the resonant voltage signal generating section and the resonant current signal generating section disclosed in Patent Document 1, there is a problem that the plurality of capacitors (capacitors C3 and C4) must be made into large and expensive elements. was there. Furthermore, in recent years, there has been a desire to increase the number of resonant voltage signal generators and resonant current signal generators in order to perform more advanced control or to further improve safety by enhancing protection functions. The challenge was to suppress the increase in costs and increase in costs.

The present invention has been made in view of the above-mentioned background art, and provides a current resonant half-bridge type switching power supply device in which a resonant voltage signal generating section, a resonant current signal generating section, or both can be configured compactly and inexpensively. The purpose is to

The present invention provides an input line and a ground line to which an input voltage is supplied from an input power source, a first switching element whose one end is connected to the input line, and a connection between the other end of the first switching element and the ground line. a second switching element connected between them, a transformer having an input winding and an output winding, one end of the input winding being connected to the connection point of the first and second switching elements; is connected to the other end of the input winding, and the other end is connected to the input line or the ground line, and a resonance inductor inserted in a position adjacent to the input winding in series; A current resonance type comprising a rectifying and smoothing circuit that rectifies and smoothes the voltage generated in the output winding to generate an output voltage, and a first control section that controls switching operations of the first and second switching elements. A switching power supply device comprising:
A resonant operation monitoring circuit for monitoring resonant operation by the transformer, the resonant capacitor, and the resonant inductor is provided, and the resonant operation monitoring circuit includes a step-down capacitor whose one end is connected to one end of the resonant capacitor; n (n: natural number) resonant voltage signal generators connected between the other end of the step-down capacitor and the ground line; k (k: natural number) resonant current signal generators;
The resonant voltage signal generating section is composed of a series circuit of a plurality of signal generating capacitors, and a waveform approximately similar to the resonant voltage generated across the resonant capacitor is applied to a specific connection point in the series circuit. It generates a voltage and outputs this voltage as a resonant voltage signal.
The resonant current signal generating section is composed of a series circuit of a shunt capacitor and a current-voltage conversion resistor, and a resonant current flowing through the input winding is connected to a connection point between the shunt capacitor and the current-voltage conversion resistor. It generates voltages with approximately similar waveforms and outputs this voltage as a resonant current signal.
The capacitance of the step-down capacitor is smaller than the capacitance of the resonance capacitor, and is set so that the voltage generated at the other end of the step-down capacitor is 50V or less, and the signal generation capacitor and the shunt capacitor are This is a switching power supply device that uses a capacitor element with a withstand voltage of 50V or less.

The present invention also provides an input line and a ground line to which an input voltage is supplied from an input power source, a first switching element whose one end is connected to the input line, and the other end of the first switching element and the ground line. and a transformer having an input winding and an output winding, one end of the input winding being connected to a connection point between the first and second switching elements. , a resonant capacitor having one end connected to the other end of the input winding and the other end connected to the input line or the ground line, and a resonant inductor inserted in a position adjacent to the input winding in series. a rectifying and smoothing circuit that rectifies and smoothes the voltage generated in the output winding to generate an output voltage; and a first control section that controls switching operations of the first and second switching elements. A resonant switching power supply device,
A resonant operation monitoring circuit for monitoring resonant operation by the transformer, the resonant capacitor, and the resonant inductor is provided, and the resonant operation monitoring circuit includes a step-down capacitor whose one end is connected to one end of the resonant capacitor; comprising n (n≧2) resonant voltage signal generating units connected between the other end of the step-down capacitor and the ground line;
The resonant voltage signal generating section is composed of a series circuit of a plurality of signal generating capacitors, and a waveform approximately similar to the resonant voltage generated across the resonant capacitor is applied to a specific connection point in the series circuit. It generates a voltage and outputs this voltage as a resonant voltage signal.
The capacitance of the step-down capacitor is smaller than the capacitance of the resonance capacitor, and is set so that the voltage generated at the other end of the step-down capacitor is 50V or less, and the signal generation capacitor has a withstand voltage of 50V. This is a switching power supply device that uses the following capacitor elements.

The present invention also provides an input line and a ground line to which an input voltage is supplied from an input power source, a first switching element whose one end is connected to the input line, and the other end of the first switching element and the ground line. and a transformer having an input winding and an output winding, one end of the input winding being connected to a connection point between the first and second switching elements. , a resonant capacitor having one end connected to the other end of the input winding and the other end connected to the input line or the ground line, and a resonant inductor inserted in a position adjacent to the input winding in series. a rectifying and smoothing circuit that rectifies and smoothes the voltage generated in the output winding to generate an output voltage; and a first control section that controls switching operations of the first and second switching elements. A resonant switching power supply device,
A resonant operation monitoring circuit for monitoring resonant operation by the transformer, the resonant capacitor, and the resonant inductor is provided, and the resonant operation monitoring circuit includes a step-down capacitor whose one end is connected to one end of the resonant capacitor; k (k≧2) resonant current signal generators connected between the other end of the step-down capacitor and the ground line;
The resonant current signal generating section is composed of a series circuit of a shunt capacitor and a current-voltage conversion resistor, and a resonant current flowing through the input winding is connected to a connection point between the shunt capacitor and the current-voltage conversion resistor. It generates voltages with approximately similar waveforms and outputs this voltage as a resonant current signal.
The capacitance of the step-down capacitor is smaller than the capacitance of the resonance capacitor, and is set so that the voltage generated at the other end of the step-down capacitor is 50V or less, and the shunt capacitor has a withstand voltage of 50V or less. This is a switching power supply device that uses a capacitor element.

The resonance capacitor has one end connected to the other end of the input winding, the other end connected to the input line, a first resonance capacitor, and one end connected to the other end of the input winding, The second resonant capacitor may be configured with a second resonant capacitor whose other end is connected to the ground line. Further, the resonance inductor may be replaced by a leakage inductance of the transformer. Furthermore, a second control unit is provided that includes a digital processor capable of rewriting an internal control program, and the resonance operation monitoring circuit generates a plurality of signals related to the resonance operation, and selects a specific signal among them. The second control unit outputs the other signal to the first control unit and the other signal to the second control unit, and the second control unit outputs the other signal acquired from the resonance operation monitoring circuit to the second control unit. The analysis may be performed using a digital processor, and the operation of the first control unit may be changed based on the analysis result.

The switching power supply device of the present invention includes a new and unique resonance operation monitoring circuit, and can easily obtain resonance voltage signals and resonance current signals useful for various controls and the like. Moreover, since the current flowing into the resonance operation monitoring circuit can be made very small, the power loss generated in the resonance operation monitoring circuit can be suppressed to a minimum.

Further, in the case of this resonant operation monitoring circuit, it is only necessary to select a large and expensive capacitor element for the step-down capacitor, and for the other capacitors, capacitor elements with a withstand voltage of 50V or less are used. Therefore, capacitors other than the step-down capacitor can be small and inexpensive, and the resonance operation monitoring circuit can be configured compactly and inexpensively. In addition, even if the number of resonant voltage signal generators and resonant current signal generators that make up the resonant operation monitoring circuit is increased, the mounting space and cost increase can be kept to a minimum, allowing more advanced control and protection. It is easy to enhance functionality and improve safety.

FIG. 1 is a circuit diagram showing a first embodiment of a switching power supply device of the present invention. FIGS. 7A and 7B are circuit diagrams showing a modification of the switching power supply device of the first embodiment. FIGS. FIGS. 7A and 7B are circuit diagrams showing other modifications of the switching power supply device of the first embodiment. FIGS. FIG. 3 is a circuit diagram showing a second embodiment of the switching power supply device of the present invention. FIG. 7 is a circuit diagram showing a modification of the resonant voltage signal generating section.

Hereinafter, a first embodiment of a switching power supply device of the present invention will be described based on FIG. 1. The switching power supply device 10 of the first embodiment is a so-called current resonance half-bridge type switching converter, which converts the input voltage Vi supplied from the input power supply 12 into a predetermined output voltage Vo, and outputs the converted voltage to the load 14. Outputs output voltage Vo and output current Io (output power Po = Vo × Io).

The switching power supply device 10 has an input line 16 and a ground line 18 to which an input voltage Vi is supplied from an input power supply 12. One end of a first switching element 20 is connected to the input line 16, and the first switching element 20 One end of the second switching element 22 is connected to the other end, and the other end of the second switching element 22 is connected to the ground line 18.

The transformer 24 has an input winding 24a and an output winding 24b, and one end of the input winding 24a is connected to a connection point between the first and second switching elements 20 and 22. A resonance capacitor 26 is connected between the other end of the input winding 24a and the ground line 18, and a resonance inductor 28 is inserted in series and adjacent to the input winding 24a. A resonance system is formed by the capacitor 26 and the resonance inductor 28. The output winding 24b of the transformer 24 is connected to a rectifying and smoothing circuit 30 that rectifies and smoothes the voltage generated in the output winding 24b to generate an output voltage Vo.

The first control unit 32 is a block that controls switching operations of the first and second switching elements 20 and 22. Here, in order to stabilize the output voltage Vo to a constant voltage, an output voltage signal S(Vo) corresponding to the output voltage Vo is obtained, and the output voltage signal S(Vo) is maintained at a predetermined target value. , the on-time and off-time of the first and second switching elements 20 and 22 are variably adjusted. Specifically, the High time and Low time of the drive pulses Vg20 and Vg22 for driving the first and second switching elements 20 and 22 are changed.

In addition, the switching power supply device 10 is provided with a unique resonance operation monitoring circuit 34 in order to monitor the resonance operation of the transformer 24, the resonance capacitor 26, and the resonance inductor 28. The resonance operation monitoring circuit 34 is connected between a step-down capacitor 36 whose one end is connected to the connection point between the resonance capacitor 26 and the input winding 24a, and the other end of the step-down capacitor 36 and the ground line 18. One resonant voltage signal generator 38 (38(1)) and two resonant current signal generators 40 (40(1), 40(2) connected between the other end of the step-down capacitor and the ground line 18. )). The resonant voltage signal generator 38(1) is composed of a series circuit of two signal generating capacitors 42a and 42b, and the resonant current signal generators 40(1) and 40(2) are configured with a shunt capacitor 44a and a current Each of them is constituted by a series circuit of a voltage conversion resistor 44b.

Here, the relationship between the capacitances of the capacitors in each part and the like will be explained. The capacitance of the step-down capacitor 36 is set to be sufficiently smaller than the capacitance of the resonance capacitor 26 so that the resonance operation monitoring circuit 34 does not affect the resonance operation, and the capacitance of the step-down capacitor 36 is set to be sufficiently smaller than that of the resonance capacitor 26. The voltage generated at the opposite end of the line 24a is set to be 50V or less.

The capacitance ratio of the signal generation capacitors 42a and 42b is such that the voltage generated at the other end of the step-down capacitor 36 is further reduced, and the first control unit 32 has a voltage that is easy to handle (for example, several volts) across the signal generation capacitor 42b. low voltage below) is set to occur. The capacitance of the shunt capacitor 44a is set so that the impedance is sufficiently larger than that of the current-voltage conversion resistor 44b, and by adjusting the resistance value of the current-voltage conversion resistor 44b, , the first control unit 32 generates a voltage that is easy to handle (for example, a low voltage of several volts or less).

At one end of the step-down capacitor 36 (one end on the input winding 24a side), a voltage is generated in which a sinusoidal resonant voltage is superimposed on the DC voltage Vi/2. Since the DC voltage Vi/2 cannot pass through the step-down capacitor 36, the other end of the step-down capacitor 36 (one end on the opposite side from the input winding 24a) has a resonant voltage reduced to 50 V or less, which is abbreviated as a resonant voltage. Voltages with similar waveforms are generated. Then, the resonant voltage signal generating section 38(1) generates a low voltage having a waveform substantially similar to the resonant voltage across the signal generating capacitor 42b, and uses this voltage as the resonant voltage signal Sv(1) to generate the first signal. It is output to the control section 32.

A sinusoidal resonant current flows through the input winding 24a of the transformer 24. Therefore, a part of the resonant current is shunted through the step-down capacitor 36. Then, the resonant current signal generating section 40(1) shunts a part of the current that has passed through the step-down capacitor 36 through the shunt capacitor 44a, and applies a resonant current to both ends of the current-voltage conversion resistor 44b. A low voltage with a similar waveform is generated, and the voltage is outputted to the first control circuit 32 as a resonant current signal Si(1). Similarly, the resonant current signal generator 40(2) shunts a part of the current that has passed through the step-down capacitor 36 through the shunt capacitor 44a, and supplies the resonant current and the current to both ends of the current-voltage conversion resistor 44b. A low voltage having a substantially similar waveform is generated, and the generated voltage is output to the first control section 32 as a resonance current signal Si(2).

The magnitude of the resonant voltage has a strong correlation with the output power Po supplied to the load 14. Therefore, the first control circuit 32 detects the output power Po by, for example, analyzing the resonance voltage signal Sv(1), and performs processing to optimize the control characteristics of the output voltage control system according to the output power Po. conduct.

Further, the magnitude of the resonant current has a strong correlation with the output current Io supplied to the load 14. Therefore, the first control unit 32 detects the output current Io by, for example, analyzing the resonance current signal Si(1), and when the output current Io reaches a permissible value, the first control unit 32 quickly switches the first and second switching elements. The switching frequency is changed to prevent the output current Io from exceeding the allowable value (overcurrent protection).

Furthermore, the timing at which the resonant current crosses zero becomes important information for causing the first and second switching elements 20 and 22 to perform zero-volt switching. Therefore, the first control unit 32 detects the timing at which the resonance current crosses zero by, for example, analyzing the resonance current signal Si(2), and determines the timing to turn on the first and second switching elements 20 and 24. Perform the processing to determine.

As explained above, the switching power supply 10 includes a new and unique resonance operation monitoring circuit 34, and generates resonance voltage signals Sv(1) and resonance current signals Si(1), Si(2) useful for various controls. can be easily obtained. Moreover, since the current flowing into the resonance operation monitoring circuit 34 can be made very small, the power loss generated in the resonance operation monitoring circuit 34 can be minimized.

In addition, in the case of the resonance operation monitoring circuit 34, it is only the step-down capacitor 36 that requires selection of a large and expensive capacitor element, and the other capacitors (signal generation capacitors 42a, 42b, shunt capacitor 44a) In this case, a capacitor element with a withstand voltage of 50V or less is used. Therefore, for the 36 capacitors other than the step-down capacitor, capacitors having a small external size and low cost can be used, and the resonance operation monitoring circuit 34 can be configured compactly and inexpensively. Furthermore, even if the number of resonant voltage signal generators 38 and resonant current signal generators 40 that constitute the resonant operation monitoring circuit 34 is increased, the mounting space and cost increase can be minimized, allowing more advanced control. It is easy to improve safety by enhancing protection functions.

Next, four modification examples regarding the connection structure of the elements (input winding 24a, resonance capacitor 26, and resonance inductor 28) constituting the resonance system of the switching power supply device 10 will be explained based on FIGS. 2 and 3. . In the modified switching power supply device 10a shown in FIG. 2A, the resonant inductor 28 is omitted, and a leakage inductance (not shown) inside the transformer 24 is used instead. In addition, in the switching power supply device 10b of the modified example shown in FIG. 2(b), the resonance inductor 28 is inserted into one end of the input winding 24a on the resonance capacitor 26 side, instead of at one end on the switching elements 20, 24 side. has been done. Even when the configuration of the switching power supply devices 10a and 10b is changed, the same effects as those of the switching power supply device 10 described above can be obtained.

In the switching power supply device 10c of the modified example shown in FIG. In addition, in the switching power supply device 10d of the modified example shown in FIG. The second resonance capacitor 26(1) has one end connected to the other end of the input winding 24a (one end on the opposite side to the switching elements 20, 22), and the other end connected to the input line 16. The capacitor 26(2) has one end connected to the other end of the input winding 24a (one end on the opposite side to the switching elements 20 and 22), and the other end connected to the ground line 18. Even when the configuration of the switching power supply devices 10c and 10d is changed, the same effects as those of the switching power supply device 10 described above can be obtained.

Next, a second embodiment of the switching power supply device of the present invention will be described based on FIG. 4. Here, the same configuration as the switching power supply device 10 described above is given the same reference numeral and the description thereof will be omitted.

The switching power supply device 46 of the second embodiment has a configuration of the switching power supply device 10 including a second control section 48 and a resonant voltage signal Sv(2) that generates a resonance voltage signal Sv(2) and outputs it to the second control section 48. A signal generating section 38(2) and a resonant current signal generating section 40(2) that generates a resonant current signal Si(3) and outputs it to the second control section 48 are attached. The configuration is similar.

The resonant voltage signal generator 38(2), like the resonant voltage signal generator 38(1) described above, is composed of a series circuit of two signal generating capacitors 42a and 42b, and has a resonant current signal generator 40(3). ) is constituted by a series circuit of a shunt capacitor 44a and a current-voltage conversion capacitor 44b, similar to the above-mentioned resonant current signal generators 40(1) and 40(2). In FIG. 4, a circuit in which two signal generating units 38(2) and 40(3) are added to the above-mentioned resonant electric operation monitoring circuit 34 is collectively referred to as a resonant electric operation monitoring circuit 50.

The second control unit 48 includes a digital processor that can rewrite the internal control program, analyzes the resonant voltage signal Sv(2) and the resonant current signal Si(3) with the digital processor, and uses the digital processor to analyze the resonant voltage signal Sv(2) and resonant current signal Si(3). , performs control to change the operation of the first control unit 32. As will be explained in detail later, the processing executed by the digital processor does not require high speed, and relatively inexpensive general-purpose products can be used.

The first control section 32 described above is usually constructed by preparing a commercially available general-purpose control IC and adding a small number of individual circuit elements around it. In the first control section 32, the output stage that outputs the drive pulses Vg20 and Vg22 is required to operate at high speed, and other parts that do not require such high speed are required to have low power consumption. Therefore, it is preferable that the control IC has a BiCMOS structure in which the output stage has a bipolar structure and the other parts have a CMOS structure.

General-purpose control ICs are sold by multiple manufacturers, and each has its own characteristics. However, since these are general-purpose products, they cannot meet the needs of all power supply designers, and there are many cases in which they do not have the desired functions, or they have the desired functions but are not satisfied with their performance. . Therefore, the switching power supply device 46 is provided with a second control section 48 in order to add new functions or supplement the insufficient performance of the control IC.

First, the first control of the two controls performed by the second control section 48 will be explained. The first control unit 32 performs high-speed overcurrent protection using the functions of a commercially available control IC. Because the threshold value for determining whether or not the overcurrent protection occurs varies and fluctuates depending on the environmental temperature, it takes time and effort to design and evaluate overcurrent protection. Therefore, the second control section 48 executes the second overcurrent protection based on the second overcurrent threshold set in advance, separately from the first control section 32. The second overcurrent threshold is numerical information written into the control program of the digital processor, so it does not change.

The second control unit 48 detects the output current Io by analyzing the resonant current signal Si(3), determines whether there is an overcurrent state based on a second overcurrent threshold, and determines that the overcurrent state exists. Then, a signal is output to the first control section 32 to forcibly stop the switching operations of the first and second switching elements 20 and 22. Therefore, even if the overcurrent threshold of the first control unit 32 fluctuates and the overcurrent protection does not operate, the second overcurrent protection operates and safety is ensured.

However, since the second overcurrent protection operates at a slower speed than the overcurrent protection of the first control section 32, it is difficult to simply omit the overcurrent protection of the first control section 32. Therefore, by using the overcurrent protection of the first control section 32 and the second overcurrent protection together, more reliable overcurrent protection can be realized.

Further, regarding the second overcurrent protection, it is possible to set the second overcurrent threshold according to the user's request, for example, by customization. This customization can be done easily by simply rewriting the second overcurrent threshold value (numerical information) in the digital processor, without making any changes to the hardware. In addition, as another application, it may be possible to configure the second overcurrent threshold value to be externally variable by the user, so that the switching power supply device 46 can be used as a constant current power supply.

Next, the second control performed by the second control section 48 will be explained. The first control unit 32 described above does not perform overpower protection to prevent the output power Po from exceeding a permissible value, but detects the output power Po by analyzing the resonance voltage signal Sv(1) and It is relatively easy to provide overpower protection using the functions of the product's control IC. However, it is not easy to implement overpower protection in which, for example, the operation of the switching power supply device 46 is stopped when the overpower state continues for more than a specified time (for example, one minute). Therefore, the second control unit 48 uses a counter included in the digital processor to perform overpower protection in consideration of time. The overpower threshold and specified time can be easily set in the control program of the digital processor.

The second control unit 48 detects the output power Po by analyzing the resonance voltage signal Sv(2), and determines whether the output power Po exceeds the overpower threshold. If the overpower state continues for more than a specified time, a signal is output to the first control section 32 to forcibly stop the switching operations of the first and second switching elements 20 and 22. Therefore, the second control unit 48 can easily implement overpower protection that takes time into account, in which switching operation is stopped if the overpower state continues beyond a specified time.

As explained above, according to the switching power supply device 46, it is possible to obtain the same effects as the switching power supply device 10, and also to improve safety by complementing the functions of the switching power supply device 10. Additional functionality may be added to the device 10.

Note that the switching power supply device of the present invention is not limited to the above embodiment. For example, the resonant voltage signal generating sections 38(1) and 38(2) described above are a series circuit of two signal generating capacitors 42a and 42b, but for example, the resonant voltage signal generating section 38(3) shown in FIG. It is also possible to configure a series circuit of three signal generation capacitors 42a, 42b, and 42c as shown in the figure, and output resonant voltage signals Sv(3H) and Sv(3L) with different magnitudes from each connection point. It is.

The content of the control performed by the first and second control units using the resonance voltage signal Sv and the resonance current signal Si is not limited to the content of control performed by the first and second control units 32 and 48, It may also be used to control completely different contents.

The resonance operation monitoring circuit 34 in FIG. 1 has a configuration that outputs three signals (one resonance voltage signal Sv and two resonance current signals Si), and the resonance operation monitoring circuit 50 in FIG. 4 has a configuration that outputs five signals. (Two resonant voltage signals Sv and three resonant current signals Si), but if the number of signals output by the resonant operation monitoring circuit is two or more in total, the effect aimed at by the present invention can be achieved. is obtained. Furthermore, if the only signal necessary for control by the first and second control sections 32 is the resonance voltage signal Sv, the resonance current signal generation section is not necessary, and the signal necessary for control by the first and second control sections 32 is In the case of only the resonant current signal Sv, the resonant voltage signal generator is not necessary.

10, 10a to 10d, 46 Switching power supply device 12 Input power supply 16 Input line 18 Ground line 20 First switching element 22 Second switching element 24 Transformer 24a Input winding 24b Output winding 26 Resonance capacitor 28 Resonance inductor 30 Rectifying and smoothing circuit 32 First control section 34, 50 Resonant operation monitoring circuit 36 Step-down capacitor 38, 38(1), 38(2) Resonant voltage signal generating section 40, 40(1) to 40(3) Resonant current signal Generating parts 42a, 42b, 42c Signal generation capacitor 44a Shunting capacitor 44b Current-voltage conversion capacitor 48 Second control part
Sv, Sv(1), Sv(2) Resonant voltage signal
Si, Si(1) to Si(3) resonant current signal

Claims (6)

An input line and a ground line to which an input voltage is supplied from an input power source, a first switching element whose one end is connected to the input line, and a first switching element connected between the other end of the first switching element and the ground line. a second switching element; a transformer having an input winding and an output winding; one end of the input winding connected to the connection point of the first and second switching elements; a resonant capacitor connected to the other end of the line and the other end connected to the input line or the ground line; a resonant inductor inserted in series and adjacent to the input winding; and the output winding. a current resonance type switching power supply device comprising: a rectifying and smoothing circuit that rectifies and smoothes a voltage generated in the circuit to generate an output voltage; and a first control section that controls switching operations of the first and second switching elements. In,
A resonant operation monitoring circuit for monitoring resonant operation by the transformer, the resonant capacitor, and the resonant inductor is provided, and the resonant operation monitoring circuit includes a step-down capacitor whose one end is connected to one end of the resonant capacitor; n (n: natural number) resonant voltage signal generators connected between the other end of the step-down capacitor and the ground line; k (k: natural number) resonant current signal generators;
The resonant voltage signal generating section is composed of a series circuit of a plurality of signal generating capacitors, and a waveform approximately similar to the resonant voltage generated across the resonant capacitor is applied to a specific connection point in the series circuit. It generates a voltage and outputs this voltage as a resonant voltage signal.
The resonant current signal generating section is composed of a series circuit of a shunt capacitor and a current-voltage conversion resistor, and a resonant current flowing through the input winding is connected to a connection point between the shunt capacitor and the current-voltage conversion resistor. It generates voltages with approximately similar waveforms and outputs this voltage as a resonant current signal.
The capacitance of the step-down capacitor is smaller than the capacitance of the resonance capacitor, and is set so that the voltage generated at the other end of the step-down capacitor is 50V or less, and the signal generation capacitor and the shunt capacitor are A switching power supply device characterized in that a capacitor element having a withstand voltage of 50V or less is used. An input line and a ground line to which an input voltage is supplied from an input power source, a first switching element whose one end is connected to the input line, and a first switching element connected between the other end of the first switching element and the ground line. a second switching element; a transformer having an input winding and an output winding; one end of the input winding connected to the connection point of the first and second switching elements; a resonant capacitor connected to the other end of the line and the other end connected to the input line or the ground line; a resonant inductor inserted in series and adjacent to the input winding; and the output winding. a current resonance type switching power supply device comprising: a rectifying and smoothing circuit that rectifies and smoothes a voltage generated in the circuit to generate an output voltage; and a first control section that controls switching operations of the first and second switching elements. In,
A resonant operation monitoring circuit for monitoring resonant operation by the transformer, the resonant capacitor, and the resonant inductor is provided, and the resonant operation monitoring circuit includes a step-down capacitor whose one end is connected to one end of the resonant capacitor; comprising n (n≧2) resonant voltage signal generating units connected between the other end of the step-down capacitor and the ground line;
The resonant voltage signal generating section is composed of a series circuit of a plurality of signal generating capacitors, and a waveform approximately similar to the resonant voltage generated across the resonant capacitor is applied to a specific connection point in the series circuit. It generates a voltage and outputs this voltage as a resonant voltage signal.
The capacitance of the step-down capacitor is smaller than the capacitance of the resonance capacitor, and is set so that the voltage generated at the other end of the step-down capacitor is 50V or less, and the signal generation capacitor has a withstand voltage of 50V. A switching power supply device characterized by using the following capacitor elements. An input line and a ground line to which an input voltage is supplied from an input power source, a first switching element whose one end is connected to the input line, and a first switching element connected between the other end of the first switching element and the ground line. a second switching element; a transformer having an input winding and an output winding; one end of the input winding connected to the connection point of the first and second switching elements; a resonant capacitor connected to the other end of the line and the other end connected to the input line or the ground line; a resonant inductor inserted in series and adjacent to the input winding; and the output winding. a current resonance type switching power supply device comprising: a rectifying and smoothing circuit that rectifies and smoothes a voltage generated in the circuit to generate an output voltage; and a first control section that controls switching operations of the first and second switching elements. In,
A resonant operation monitoring circuit for monitoring resonant operation by the transformer, the resonant capacitor, and the resonant inductor is provided, and the resonant operation monitoring circuit includes a step-down capacitor whose one end is connected to one end of the resonant capacitor; k (k≧2) resonant current signal generators connected between the other end of the step-down capacitor and the ground line;
The resonant current signal generating section is composed of a series circuit of a shunt capacitor and a current-voltage conversion resistor, and a resonant current flowing through the input winding is connected to a connection point between the shunt capacitor and the current-voltage conversion resistor. It generates voltages with approximately similar waveforms and outputs this voltage as a resonant current signal.
The capacitance of the step-down capacitor is smaller than the capacitance of the resonance capacitor, and is set so that the voltage generated at the other end of the step-down capacitor is 50V or less, and the shunt capacitor has a withstand voltage of 50V or less. A switching power supply device characterized by using a capacitor element of. The resonance capacitor has one end connected to the other end of the input winding, the other end connected to the input line, a first resonance capacitor, and one end connected to the other end of the input winding, 4. The switching power supply device according to claim 1, further comprising a second resonant capacitor whose other end is connected to the ground line. 5. The switching power supply device according to claim 1, wherein the resonance inductor is replaced by a leakage inductance of the transformer. A second control section equipped with a digital processor that can rewrite the internal control program is provided,
The resonance operation monitoring circuit generates a plurality of signals related to the resonance operation, outputs a specific signal among them toward the first control section, and outputs other signals toward the second control section. output,
The second control section analyzes the other signal acquired from the resonance operation monitoring circuit with the digital processor, and changes the operation of the first control section based on the analysis result. 5. The switching power supply device according to any one of 5.

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