Power source circuit

Abstract

To provide a power source circuit comprising a switching element and having a low component failure rate by leveling the uneven heat generation of the switching element.SOLUTION: A power source circuit according to an embodiment comprises: a plurality of switching elements connected in parallel, connected to a power source input, and converting DC voltage provided from the power source input to AC voltage; a transformer including primary winding wire and secondary winding wire and inducing voltage on the secondary winding wire from voltage from the primary winding wire; a plurality of rectifying switching elements connected in parallel, connected between the secondary winding wire and a load, and synchronously rectifying the voltage induced on the secondary winding wire; a control portion controlling the switching operation of the plurality of the switching elements and the plurality of rectifying switching elements; and a plurality of temperature sensors detecting temperature of each of the plurality of switching elements and outputting temperature data indicating the temperature to the control portion, the control portion controls each of the time at which each of the plurality of switching elements turns on based on the temperature data.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a power supply circuit. [Background technology]

[0002] A switching element (FET: Field effect transistor) is used as a power supply circuit for supplying power to a load.

[0003] Generally, as is known from the Arrhenius model, semiconductors deteriorate and their lifespan shortens when exposed to temperature. Therefore, there is a problem that temperature deviations can cause reliability to decrease and failure rates to increase.

[0004] For example, Patent Document 1 discloses a technology for improving the efficiency of a power supply by detecting the temperature and correcting the operation timing since the recovery current time (current drop rate) changes depending on the temperature of a synchronous rectifier element. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-116016 A Summary of the Invention [Problem to be solved by the invention]

[0006] Conventionally, multiple switching elements are controlled by using the same control signal when they are turned on or off. However, each switching element has individual differences in the on-resistance, switching speed, parasitic capacitance, etc. Therefore, there is a problem that the amount of heat generated by the switching elements varies, resulting in uneven heat generation.

[0007] The present invention has been made in view of the above circumstances, and has as its object to provide a power supply circuit with a low component failure rate by leveling out uneven heat generation in switching elements. [Means for solving the problem]

[0008] A power supply circuit according to an embodiment includes a plurality of switching elements connected in parallel to a power supply input and converting a DC voltage supplied from the power supply input into an AC voltage, a primary winding connected to the plurality of switching elements, and a secondary winding connected to a load, a transformer that induces a voltage from the primary winding in the secondary winding, a plurality of rectifying switching elements connected in parallel between the secondary winding and the load and synchronously rectifying the voltage induced in the secondary winding, a control unit that controls the switching operation of the plurality of switching elements and the plurality of rectifying switching elements, and a plurality of temperature sensors that are arranged in correspondence with each of the plurality of switching elements, detect the temperature of each of the plurality of switching elements, and output temperature data indicating the temperature to the control unit, and the control unit controls the on-time of each of the plurality of switching elements based on the temperature data. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing an example of a power supply circuit according to the present embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of the operational relationship between the control unit, the temperature sensor, and the switching elements. [Diagram 3] FIG. 3 is a flowchart showing an example of an operation procedure of the power supply circuit according to the embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a conceptual diagram relating to temperature data and ON time of a control signal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The power supply circuit will be described in detail below with reference to the drawings. In the following embodiments, parts with the same numbers perform the same operation, and will not be described again. For example, when there are a plurality of identical or similar elements, a common reference number may be used to describe each element without distinguishing between them, and a subnumber may be used in addition to the common reference number to describe each element with distinction between them.

[0011] [Embodiment] (composition) FIG. 1 is a block diagram showing an example of a power supply circuit according to the present embodiment. As illustrated in FIG. 1, the power supply circuit 1 includes a power supply input 11, four switching element groups 12-1, 12-2, 12-3, 12-4, a transformer 13, two rectifying switching element groups 14-1, 14-2, a smoothing inductor 15, a smoothing capacitor 16, an output voltage detection circuit 17, a control unit 18, and a temperature sensor TS.

[0012] The power supply input 11 is a DC voltage that serves as an input to the power supply circuit 1. The power supply input 11 is connected to an arbitrary power supply and supplies the DC voltage to the switching element groups 12-1, 12-2, 12-3, and 12-4.

[0013] Each of the four switching element groups 12-1, 12-2, 12-3, and 12-4 is composed of a plurality of switching elements connected in parallel. The four switching element groups are connected to a power supply input 11 and a primary winding of a transformer 13, which will be described later. FIG. 1 shows an example in which each of the switching elements of the four switching element groups 12-1, 12-2, 12-3, and 12-4 is composed of an N-channel MOSFET. However, each switching element may be composed of any FET, such as a MOSFET, a MESFET, or a JFET. In the following description, when there is no need to distinguish between the four switching element groups 12-1, 12-2, 12-3, and 12-4, they will simply be referred to as the switching element group 12.

[0014] A control signal is supplied from the control unit 18 to a control terminal (gate) of each switching element of the switching element group 12. Each switching element performs a switching operation based on the control signal from the control unit 18, and switches the DC voltage supplied from the power supply input. In the example of FIG. 1, the four switching element groups 12-1, 12-2, 12-3, and 12-4 are connected in a full bridge configuration, and serve as a primary side circuit to convert a DC voltage into an AC voltage based on a control signal from the control unit and supply the AC voltage to the primary winding of the transformer 13.

[0015] The transformer 13 is an isolation transformer including a primary winding and a secondary winding. The primary winding is connected to the four switching element groups as described above, and the secondary winding is connected to the load LO. The winding direction of the secondary winding is opposite to that of the primary winding. The transformer 13 converts the primary voltage (voltage of the primary winding) into a secondary voltage (voltage of the secondary winding) proportional to the turns ratio between the primary winding and the secondary winding.

[0016] Each of the two rectifier switching element groups 14-1 and 14-2 is composed of a plurality of switching elements connected in parallel. The two rectifier switching element groups 14-1 and 14-2 are connected between the secondary winding of the transformer 13 and the load LO. The two rectifier switching element groups 14-1 and 14-2 synchronously rectify the voltage induced in the secondary winding of the transformer 13 using each switching element. FIG. 1 shows an example in which each switching element of the two rectifier switching element groups 14-1 and 14-2 is composed of an N-channel MOSFET. However, each switching element may be composed of any FET, for example, a MOSFET, a MESFET, a JFET, or the like. Here, in the following description, when there is no need to distinguish between the two rectifier switching element groups 14-1 and 14-2, they will simply be referred to as the rectifier switching element group 14.

[0017] The smoothing inductor 15 and the smoothing capacitor 16 form a smoothing circuit, which smoothes the voltage rectified by the rectification switching element group 14 and outputs it as a DC output voltage. This DC output voltage is supplied to a load LO.

[0018] The output voltage detection circuit 17 is a circuit that monitors the DC output voltage and outputs the result to the control unit 18.

[0019] The temperature sensors TS are sensors provided corresponding to each switching element of the switching element group 12 and the rectifier switching element group 14. Therefore, the temperature sensors TS are provided in the same number as the switching elements of the switching element group 12 and the rectifier switching element group 14. The temperature sensors TS detect the temperature of each switching element and output temperature data indicating the detected temperature to the control unit 18.

[0020] The control unit 18 is provided to control each device shown in Fig. 1. The control by the control unit 18 may be realized by hardware, software, or a combination of hardware and software. The control unit 18 may include, for example, one or more processors such as an MPU (micro processing unit) or a CPU (central processing unit), a program memory in which a program executed by the processor is recorded, and a data memory in which data required when the control unit 18 performs processing is stored.

[0021] The control unit 18 generates a pulse-shaped control signal for switching and driving each of the switching elements of the switching element group 12 and the rectification switching element group 14 based on, for example, the detection result from the output voltage detection circuit 17 and the temperature data from the temperature sensor TS. Then, the control unit 18 outputs the generated control signal to each of the switching elements. That is, the control unit 18 controls the switching operation of the switching elements. Then, the control unit 18 controls the switching operation of the switching elements so that the output voltage applied to the load LO becomes a target voltage.

[0022] Furthermore, the control unit 18 controls the ON time of the switching elements of the switching element group 12 and the rectifying switching element group 14 based on the temperature data. For example, the control unit 18 calculates a reference temperature based on the temperature data, and controls the ON time of the switching element corresponding to the temperature sensor that outputs temperature data exceeding the reference temperature to be shortened. In this way, the control unit 18 controls the ON time of each switching element to be changed according to the temperature of the individual switching element, thereby leveling out the temperature of each switching element. Note that the control unit 18 may also control the ON time of at least one of the switching elements of the switching element group 12 and the rectifying switching element group 14 to be shortened.

[0023] (operation) Next, the operation of the power supply circuit 1 configured as above will be described.

[0024] FIG. 2 is a diagram showing an example of the operational relationship between the control unit 18, the temperature sensor TS, and the switching elements. The switching elements shown in FIG. 2 may be the switching elements of the switching element group 12 or the rectifying switching element group 14, or may be the switching elements of both the switching element group 12 and the rectifying switching element group 14.

[0025] As shown in Fig. 2, the control unit 18 acquires temperature data from a temperature sensor TS. In the example of Fig. 2, temperature data A to Z are acquired from each switching element. Then, the control unit 18 outputs control signals A to Z corresponding to the temperature data A to Z to the switching elements. That is, in this embodiment, the control unit 18 does not output a uniform control signal to each switching element of the switching element group 12 or the rectification switching element group 14, but outputs individual control signals based on the temperature data of each switching element.

[0026] FIG. 3 is a flowchart showing an example of an operation procedure of the power supply circuit 1 according to the embodiment. This flowchart begins, for example, by starting to supply a DC output voltage to a load LO via the power supply circuit 1.

[0027] In step ST101, the control unit 18 acquires temperature data from the temperature sensor TS. The temperature sensor TS detects the temperature from each of the switching elements in the switching element group 12 and the rectifying switching element group 14, and generates temperature data. The temperature sensor TS then outputs the generated temperature data to the control unit 18. For example, the period for detecting the temperature and the period for outputting the temperature data may be any period. The control unit 18 acquires temperature data of each switching element from the temperature sensor TS corresponding to each switching element in the switching element group 12 and the rectifying switching element group 14.

[0028] In step ST102, the control unit 18 calculates the reference temperature. The control unit 18 operating as a calculation unit calculates the reference temperature based on the temperature data. The reference temperature is the average value or median value of the acquired temperature data. The control unit 18 may calculate the reference temperature for each of the switching element group 12 and the rectifying switching element group 14, or may calculate the reference temperature from the temperature data of all of these switching elements. It is possible to change whether to use the average value or the median value as the reference temperature according to the mode. For example, when starting operation, the control unit 18 may adopt the median value as the reference temperature, and after a predetermined time has passed, use the reference temperature switched from the median value to the average value. Alternatively, the control unit 18 may determine whether to use the average value or the median value as the reference temperature according to an instruction from an administrator who manages the power supply circuit 1.

[0029] In step ST103, the control unit 18 judges whether the temperature data is greater than the reference temperature. The control unit 18 operating as a judgement unit judges whether the temperature data of each switching element is greater than the reference temperature. For example, the control unit 18 makes a judgment for each piece of temperature data acquired from each temperature sensor TS. If the temperature data is less than the reference temperature, the process proceeds to step ST105. On the other hand, if the temperature data exceeds the reference temperature, the process proceeds to step ST104.

[0030] In step ST104, the control unit 18 calculates the amount of reduction. The control unit 18 operating as a calculation unit calculates the amount of reduction based on a reference temperature and temperature data. For example, the control unit 18 calculates the deviation between the reference temperature and the temperature data. Then, the control unit 18 calculates the amount of reduction by applying a predetermined formula or a predetermined proportional value to the calculated deviation. The amount of reduction is a time that does not affect the operation of the power supply circuit, for example, an amount that reduces the time by about several percent from the original time.

[0031] In step ST105, the control unit 18 outputs a control signal. The control unit 18 operating as an output unit outputs an output signal corresponding to each switching element of the switching element group 12 and the rectification switching element group 14. That is, for a switching element whose temperature exceeds the reference temperature, the control unit 18 outputs a control signal so as to reduce the on-time of the control signal according to the amount of reduction. On the other hand, for a switching element whose temperature is below the reference temperature, the control unit 18 outputs a control signal with a normal on-time.

[0032] FIG. 4 is a diagram showing an example of a conceptual diagram relating to temperature data and ON time of a control signal. As shown in Fig. 4, when the temperature data acquired by one of the temperature sensors TS (temperature sensor TS A in the example of Fig. 4) is higher than the reference temperature, the control unit 18 generates a control signal A for controlling the switching element corresponding to the temperature sensor TS to reduce the on-time, and outputs the control signal A to the switching element. By doing so, the on-time of the switching element with a temperature higher than the reference temperature is shortened, so that the amount of heat generated can be suppressed to be smaller than that of the other switching elements.

[0033] In step ST106, the control unit 18 judges whether or not to end the operation. The control unit 18 judges whether or not an operation end signal has been input from the administrator. If an operation end signal has not been input, the process returns to step ST101. The control unit 18 may display data indicating to the administrator which switching element is being controlled to have its on time shortened.

[0034] The control unit 18 calculates the reference temperature based on the temperature data of each switching element, and therefore it is possible to control the ON time of a switching element having a relatively high temperature to be shorter. This makes it possible to suppress the amount of heat generated by a switching element having a higher temperature compared to other switching elements.

[0035] (Effects of the embodiment) According to the embodiment described above, a temperature sensor is provided corresponding to each of a plurality of switching elements connected in parallel, and temperature data of each of the plurality of switching elements is acquired from the temperature sensor. Then, the time when the switching element is turned on is controlled based on the temperature data. This makes it possible to provide a power supply circuit with a low component failure rate by leveling out the uneven heat generation of the switching elements.

[0036] [Other embodiments] In this embodiment, the control unit 18 controls the switching element whose temperature exceeds the reference temperature calculated from the temperature data to have a shorter on-time than the normal on-time (the on-time of the switching element whose temperature does not exceed the reference temperature). However, the control unit 18 may control the switching element whose temperature is below the reference temperature to have a longer on-time than the switching element whose temperature exceeds the reference temperature.

[0037] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0038] 1…Power circuit 11…Power input 12...Switching element group 13...Trans 14...Rectification switching elements 15…Smoothing inductor 16…Smoothing capacitor 17...Output voltage detection circuit 18...Control section

Claims

1. A plurality of switching elements connected in parallel to a power supply input for converting a DC voltage supplied from the power supply input to an AC voltage; a transformer including a primary winding connected to the plurality of switching elements and a secondary winding connected to a load, the transformer inducing a voltage from the primary winding in the secondary winding; a plurality of rectifying switching elements connected in parallel, the rectifying switching elements being connected between the secondary winding and the load and performing synchronous rectification of a voltage induced in the secondary winding; a control unit that controls switching operations of the plurality of switching elements and the plurality of rectifying switching elements; a plurality of temperature sensors arranged in association with the plurality of switching elements, each of which detects a temperature of the plurality of switching elements and outputs temperature data indicating the temperature to the control unit; and the control unit controls the ON times of the plurality of switching elements based on the temperature data. power circuit.

2. a plurality of rectification temperature sensors arranged in correspondence with the plurality of rectification switching elements, each of which detects a temperature of the plurality of rectification switching elements, and outputs rectification temperature data indicating the temperature to the control unit; The control unit controls the ON times of the plurality of rectifying switching elements based on the rectifying temperature data.

2. The power supply circuit according to claim 1.

3. the control unit calculates a reference temperature based on the temperature data, and controls the ON times of the plurality of switching elements based on the reference temperature and the temperature data.

3. The power supply circuit according to claim 1 or 2.

4. the control unit determines whether the temperature data exceeds the reference temperature, and when it is determined that the temperature data exceeds the reference temperature, controls to shorten an on-time of a first switching element corresponding to the temperature sensor that outputs the temperature data exceeding the reference temperature.

4. The power supply circuit according to claim 3.

5. the control unit controls the first switching element so as to shorten an on-time of the first switching element based on a deviation between the reference temperature and the temperature data.

5. The power supply circuit according to claim 4.

6. 6. The power supply circuit according to claim 5, wherein the on-time of said first switching element is shortened for a period of time that does not affect the operation of said power supply circuit.

7. The reference temperature is an average or median of the temperature data.

4. The power supply circuit according to claim 3.

8. The control unit switches between using the average value or the median value as the reference temperature according to a mode.

8. The power supply circuit according to claim 7.

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