Power circuit

Abstract

To provide a power supply circuit that can reduce the unevenness in output current and heat generation of switching elements without reducing power supply efficiency. [Solution] The power supply circuit according to the embodiment comprises a plurality of DC-DC converters, a temperature detection unit, and an adjustment unit. The plurality of DC-DC converters are connected in parallel to the load. The temperature detection unit is provided on the switching element of each of the plurality of DC-DC converters and detects the temperature of each switching element. The adjustment unit adjusts the switching control of the plurality of DC-DC converters so that the output current of each of the plurality of DC-DC converters becomes equal according to the temperature difference detected from each switching element.

Description

Technical Field

[0001] The present invention relates to a power supply circuit.

Background Art

[0002] Conventionally, in a power supply circuit that controls power supply to a load, in order to handle high-current output, multi-phase control in which a plurality of DCDC converters are connected in parallel and controlled is known (see, for example, Patent Document 1). In multi-phase control, by aligning the switching control of each of the plurality of DCDC converters, the output current is controlled to be evenly output from each DCDC converter.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the prior art, due to specific differences such as individual differences in electronic components of each DCDC converter and the positional relationship with peripheral components, the output current may not be equal even when the switching control is aligned. In this case, since the output current is biased, the degree of heat generation of the switching elements also varies between the DCDC converters. Regarding this point, a method of arranging current sensors in the output paths of each DCDC converter to monitor the output current and adjusting the switching control to equalize the output current can be considered. However, in this method, there is a risk that the power supply efficiency may decrease due to a decrease in the output voltage caused by the arrangement of the current sensors.

[0005] <00000…]] The present invention has been made in view of the above, and an object thereof is to provide a power supply circuit that can reduce the deviation of the output current and the heat generation of the switching elements without reducing the power supply efficiency. [Means for solving the problem]

[0006] To solve the above-mentioned problems and achieve the objective, the power supply circuit according to the present invention comprises a plurality of DC-DC converters, a temperature detection unit, and an adjustment unit. The plurality of DC-DC converters are connected in parallel to the load. The temperature detection unit is provided on the switching element of each of the plurality of DC-DC converters and detects the temperature of each switching element. The adjustment unit adjusts the switching control of the plurality of DC-DC converters so that the output current of each of the plurality of DC-DC converters becomes equal according to the temperature difference detected from each switching element. [Effects of the Invention]

[0007] According to the present invention, by controlling the switching so that the output currents of multiple DC-DC converters become equal according to the temperature difference detected from each switching element, variations in output current caused by temperature differences can be reduced. Furthermore, by suppressing variations in output current, variations in the temperature of the switching elements can also be reduced. In addition, in the present invention, by adjusting the output current according to the temperature detected by the temperature detection unit, it becomes unnecessary to place a current sensor in the output path of each DC-DC converter, thus preventing a decrease in output voltage caused by the current sensor. In other words, according to the present invention, it is possible to reduce the unevenness of output current and heat generation of switching elements without reducing power supply efficiency. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows an example of the configuration of a power supply circuit according to an embodiment. [Figure 2] Figure 2 shows the configuration of the first adjustment unit. [Figure 3] Figure 3 shows the connection configuration between the power supply circuit and the vehicle's battery. [Modes for carrying out the invention]

[0009] The power supply circuit according to the embodiment will be described in detail below with reference to the attached drawings. However, the present invention is not limited to the embodiments shown below.

[0010] First, the configuration and operation of the power supply circuit according to the embodiment will be described using Figure 1. Figure 1 is a diagram showing an example of the configuration of the power supply circuit according to the embodiment. The power supply circuit 1 shown in Figure 1 is a power supply circuit that performs multiphase control. In this disclosure, an example of performing multiphase control with two DC-DC converters is shown, but it may also be possible to perform multiphase control with three or more DC-DC converters.

[0011] Specifically, the power supply circuit 1 consists of a first DC-DC converter 10 and a second DC-DC converter 20 connected in parallel to a load (not shown). The load is connected to the output voltage Vout shown in Figure 1. The power supply circuit 1 also includes a first thermistor 100 and a second thermistor 200.

[0012] The first DC-DC converter 10 comprises a first adjustment unit 11, a first switching element 12, a second switching element 13, a coil 14, and a capacitor 15.

[0013] The first adjustment unit 11 controls the switching of the first switching element 12 and the second switching element 13 using PWM (Pulse Width Modulation) control. Specifically, the first adjustment unit 11 generates the gate voltages to be applied to the gates of the first switching element 12 and the second switching element 13. The first adjustment unit 11 also adjusts the switching control of the first DC-DC converter 10 and the second DC-DC converter 20 according to the value of the resistive voltage divider of the first thermistor 100 and the second thermistor 200 connected in series, but the details of this will be described later.

[0014] The first switching element 12 is an N-channel type MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The first switching element 12 is positioned on the high-side, with its drain connected to a voltage source that supplies the input voltage Vin, and its source connected to the drain of the second switching element 13.

[0015] The second switching element 13 is an N-channel MOSFET. The second switching element 13 is a switching element located on the low-side, with its drain connected to the source of the first switching element 12 and its source connected to ground.

[0016] The coil 14 and capacitor 15 form a smoothing circuit that smooths the signals output from the first switching element 12 and the second switching element 13. The smoothed signal is output to the load as the output voltage Vout.

[0017] The second DC-DC converter 20 includes a second adjustment unit 21, a first switching element 22, a second switching element 23, a coil 24, and a capacitor 25.

[0018] The second adjustment unit 21 controls the switching of the first switching element 22 and the second switching element 23 by PWM control. Specifically, the second adjustment unit 21 generates gate voltages to be applied to the gates of the first switching element 22 and the second switching element 23. The second adjustment unit 21 also adjusts the switching control of the second DC-DC converter 20 according to the instructions of the first adjustment unit 11.

[0019] The first switching element 22 is an N-channel MOSFET. The first switching element 22 is a switching element located on the high-side, with its drain connected to a voltage source that supplies the input voltage Vin, and its source connected to the drain of the second switching element 23.

[0020] The second switching element 23 is an N-channel MOSFET. The second switching element 23 is a switching element arranged on the low side, with its drain connected to the source of the first switching element 22 and its source connected to the ground.

[0021] The coil 24 and the capacitor 25 are a smoothing circuit that smooths the signals output from the first switching element 22 and the second switching element 23. The smoothed signal is output to the load as the output voltage Vout.

[0022] The first thermistor 100 is provided on the first switching element 12 of the first DC-DC converter 10 and is a temperature detection unit that detects the temperature of the first switching element 12. Specifically, the first thermistor 100 is mounted near the first switching element 12. In the following, it is assumed that the first thermistor 100 is an NTC (Negative Temperature Coefficient) thermistor.

[0023] The second thermistor 200 is provided on the first switching element 22 of the second DC-DC converter 20 and is a temperature detection unit that detects the temperature of the first switching element 22. Specifically, the second thermistor 200 is mounted near the first switching element 22. In the following, it is assumed that the second thermistor 200 is an NTC thermistor.

[0024] The first thermistor 100 and the second thermistor 200 are connected in series. Specifically, one end of the first thermistor 100 is connected to a voltage source that outputs the reference voltage VCC of the first adjustment unit 11, and the other end is connected to one end of the second thermistor 200 and the first adjustment unit 11. Also, the other end of the second thermistor 200 is connected to the ground.

[0025] In this disclosure, the first adjustment unit 11 adjusts the switching control of the multiple DC-DC converters 10, 20 so that the output currents of each of the multiple DC-DC converters 10, 20 become equal according to the temperature difference detected from each switching element. As a result, according to this disclosure, by controlling the switching so that the output currents of each of the multiple DC-DC converters become equal according to the temperature difference detected from each switching element, variations in output current caused by temperature differences can be reduced. Furthermore, according to this disclosure, by suppressing variations in output current, variations in the temperature of the switching elements can also be reduced. In addition, according to this disclosure, by adjusting the output current according to the temperature detected by the thermistor, which is the temperature detection unit, it becomes unnecessary to place a current sensor in the output path of each DC-DC converter, and thus a decrease in output voltage due to the current sensor does not occur. In other words, according to this disclosure, the unevenness of output current and heat generation of switching elements can be reduced without reducing power supply efficiency.

[0026] Specifically, the first adjustment unit 11 compares the resistive voltage division of the reference voltage VCC by the first thermistor 100 and the second thermistor 200 with the reference voltage and adjusts the switching control based on the comparison result. This point will be explained using Figure 2.

[0027] Figure 2 shows the configuration of the first adjustment unit 11. As shown in Figure 2, the first adjustment unit 11 comprises a comparator 110 and a first driver 111. The comparator 110 receives a reference voltage at its positive terminal and the resistive voltage division of the first thermistor 100 and the second thermistor 200 at its negative terminal. The output terminal of the comparator 110 is connected to the first driver 111 and the second adjustment unit 21. The reference voltage is half the reference voltage VCC. In other words, the reference voltage is the reference voltage VCC divided by the number of DC-DC converters. The comparator 110 outputs a High signal when the resistive voltage division is lower than the reference voltage and outputs a Low signal when the resistive voltage division is higher than the reference voltage.

[0028] In the circuit configuration shown in Figure 2, the following two patterns will be explained. (1) Temperature of the first switching element 12 > Temperature of the first switching element 22 (2) Temperature of the first switching element 12 < Temperature of the first switching element 22

[0029] (1) Temperature of the first switching element 12 > Temperature of the first switching element 22 If the temperature of the first switching element 12 is higher than the temperature of the first switching element 22, this means that the output current of the first DC-DC converter 10 is greater than the output current of the second DC-DC converter 20. In other words, even though PWM control is performed with the same duty cycle PWM signal, the output current of the first DC-DC converter 10 is greater than the output current of the second DC-DC converter 20 due to individual differences in electronic components, etc.

[0030] In this case, the resistance of the first thermistor 100, which is an NTC thermistor, is lower than that of the second thermistor 200. As a result, the comparator 110 outputs a Low signal because the resistive voltage division becomes higher than the reference voltage.

[0031] When the first driver 111 receives a Low signal, it can determine that the temperature of the first switching element 12 is higher than the temperature of the first switching element 22. That is, the first driver 111 determines that the output current of the first DC-DC converter 10 is higher than the output current of the second DC-DC converter 20, and controls the switching to reduce the output current of the first DC-DC converter 10. Also, when the second adjustment unit 21 receives a Low signal, it controls the switching to increase the output current of the second DC-DC converter 20. In other words, the first adjustment unit 11 and the second adjustment unit 21 adjust the switching control until the resistive voltage divider and the reference voltage match.

[0032] (2) Temperature of the first switching element 12 < Temperature of the first switching element 22 If the temperature of the first switching element 12 is lower than the temperature of the first switching element 22, this means that the output current of the first DC-DC converter 10 is greater than the output current of the second DC-DC converter 20. In other words, even though PWM control is performed with the same duty cycle PWM signal, the output current of the second DC-DC converter 20 is greater than the output current of the first DC-DC converter 10 due to individual differences in electronic components, etc.

[0033] In this case, the first thermistor 100, which is an NTC thermistor, has a higher resistance than the second thermistor 200. As a result, the comparator 110 outputs a High signal because the resistive voltage division becomes lower than the reference voltage.

[0034] When the first driver 111 receives a High signal, it can determine that the temperature of the first switching element 12 is lower than the temperature of the first switching element 22. That is, the first driver 111 determines that the output current of the first DC-DC converter 10 is lower than the output current of the second DC-DC converter 20, and controls the switching to increase the output current of the first DC-DC converter 10. Also, when the second adjustment unit 21 receives a High signal, it controls the switching to decrease the output current of the second DC-DC converter 20. In other words, the first adjustment unit 11 and the second adjustment unit 21 adjust the switching control until the resistive voltage divider and the reference voltage match.

[0035] In this way, the first adjustment unit 11 and the second adjustment unit 21 can reduce variations in output current and temperature of switching elements by adjusting the switching control so that the resistive voltage divider and the reference voltage match.

[0036] Furthermore, the first adjustment unit 11 can generate a reference voltage itself, thereby enabling it to accurately determine the reference voltage used for comparison by the comparator 110.

[0037] Next, the connection configuration between the power supply circuit 1 and the vehicle's battery 50 will be explained using Figure 3. Figure 3 is a diagram showing the connection configuration between the power supply circuit 1 and the vehicle's battery 50.

[0038] As shown in Figure 3, a fuse 51, a harness 52, and a protection element 53 are arranged in order between the input side of the power supply circuit 1 and the battery 50. The protection element 53 is a component that protects against overcurrent from the battery 50 to the power supply circuit 1.

[0039] As described above, the power supply circuit 1 reduces the bias in output current among multiple DC-DC converters, thus lowering the current capacity required for each switching element. As a result, overcurrent limiting can also be suppressed, and the rated currents of the protection element 53 and harness 52 can be reduced. This enables miniaturization and cost reduction of the product through the miniaturization of each component.

[0040] As described above, the power supply circuit 1 according to the embodiment comprises a plurality of DC-DC converters, a temperature detection unit (thermistors 100, 200), and an adjustment unit (first adjustment unit 11 and second adjustment unit 21). The plurality of DC-DC converters are connected in parallel to the load. The temperature detection unit is provided on the switching element of each of the plurality of DC-DC converters and detects the temperature of each switching element. The adjustment unit adjusts the switching control of the plurality of DC-DC converters so that the output current of each of the plurality of DC-DC converters becomes equal according to the temperature difference detected from each switching element.

[0041] According to this disclosure, by controlling the switching so that the output currents of multiple DC-DC converters become equal according to the temperature difference detected from each switching element, variations in output current caused by temperature differences can be reduced. Furthermore, according to this disclosure, by suppressing variations in output current, variations in the temperature of the switching elements can also be reduced. In addition, according to this disclosure, by adjusting the output current based on the temperature detected by the thermistor, which is the temperature detection unit, it becomes unnecessary to place a current sensor in the output path of each DC-DC converter, thus preventing a decrease in output voltage caused by a current sensor. In other words, according to this disclosure, it is possible to reduce the unevenness of output current and heat generation of switching elements without reducing power supply efficiency.

[0042] Further effects and modifications can be readily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents. [Explanation of Symbols]

[0043] 1 Power circuit 10. First DC-DC Converter 11 1st adjustment section 12, 22 First switching element 13, 23 Second switching element 14 coils 15 Capacitors 20. Second DC-DC converter 21 2nd adjustment section 24 coils 25 Capacitors 50 batteries 51 Fuse 52 Harness 53 Protective elements 100 Thermistor No. 1 110 Comparator 111 First Driver 200 Thermistor No. 2

Claims

1. Multiple DC-DC converters connected in parallel to the load, A temperature detection unit is provided in each switching element of the plurality of DC-DC converters to detect the temperature of each switching element, An adjustment unit that adjusts the switching control of the plurality of DCDC converters so that the output current of each of the plurality of DCDC converters becomes equal according to the temperature difference detected from each switching element, A power supply circuit equipped with the following features.

2. The temperature detection unit is a thermistor with one end connected to a reference voltage source. The adjustment unit is, The other end of the thermistor is connected to a reference voltage corresponding to the voltage of the reference voltage source, and the switching control is adjusted based on the comparison result. The power supply circuit according to claim 1.

3. The thermistors provided on each of the switching elements are connected in series. The adjustment unit is, It is connected between two adjacent thermistors connected in series, and compares the voltage between the thermistors with the reference voltage, adjusting the switching control based on the comparison result. The power supply circuit according to claim 2.

4. The aforementioned reference voltage is half the voltage of the reference voltage source. The adjustment unit is, Adjust the switching control so that the voltage across the thermistor matches the reference voltage. The power supply circuit according to claim 3.

5. The voltage of the reference voltage source is the voltage generated by the adjustment unit. The power supply circuit according to claim 2.

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