Power supply device

Abstract

This invention provides a power supply device. It includes an inrush current prevention circuit and a boost converter circuit, and reduces the cost of circuit components. The power supply device (100) of this invention converts an input voltage supplied by a power source into a predetermined DC voltage. The power supply device (100) includes: an inrush current prevention circuit (120) of the buck converter type, which suppresses inrush current from the power source to the power supply device (100); and a boost converter circuit (130), which outputs a predetermined DC voltage. The choke (104) in the inrush current prevention circuit (120) and the choke (104) in the boost converter circuit (130) are shared chokes, and the smoothing capacitor (107) in the inrush current prevention circuit (120) and the smoothing capacitor (107) in the boost converter circuit (130) are shared smoothing capacitors.

Description

Technical Field

[0001] This invention relates to power supply devices. Background Technology

[0002] Previously, power supply devices with surge current prevention circuits for suppressing surge current when the power is turned on were known (e.g., Patent Document 1 and Patent Document 2).

[0003] Furthermore, when the power supply device supplies voltage to a converter such as a DC-DC converter, it is preferable to supply a DC voltage suitable for the operation of the converter. If the power supply device has a boost converter circuit, the power supply device can output a DC voltage boosted to the desired voltage, and therefore can output a DC voltage suitable for the operation of the converter.

[0004] Therefore, the power supply device preferably includes an inrush current protection circuit and a boost converter circuit.

[0005] In power supply units equipped with inrush current protection circuits and boost converter circuits, there is room for improvement in the cost of circuit components.

[0006] Patent Document 1: Japanese Patent Publication No. 2017-183069

[0007] Patent Document 2: Japanese Patent Publication No. 2018-29415 Summary of the Invention

[0008] Therefore, the object of the present invention is to provide a power supply device that includes an inrush current prevention circuit and a boost converter circuit, and that can reduce the cost of circuit components.

[0009] Some embodiments of a power supply device convert an input voltage supplied by a power source into a predetermined DC voltage. The power supply device includes: a buck converter-type inrush current prevention circuit to suppress inrush current flow from the power source to the power supply device; and a boost converter circuit to output the predetermined DC voltage. The choke coil in the inrush current prevention circuit and the choke coil in the boost converter circuit are shared, and the smoothing capacitor in the inrush current prevention circuit and the smoothing capacitor in the boost converter circuit are shared. According to such a power supply device, both the inrush current prevention circuit and the boost converter circuit are included, and the cost of circuit components can be reduced.

[0010] In one embodiment of the power supply device, the power supply device may also include a mode control circuit for switching between a first mode and a second mode. The first mode is a mode in which the inrush current prevention circuit performs inrush current prevention operation, and the boost converter circuit does not perform boost converter operation. The second mode is a mode in which the inrush current prevention circuit does not perform inrush current prevention operation, and the boost converter circuit performs boost converter operation. Thus, by switching between the first mode and the second mode, the power supply device can operate as either the inrush current prevention circuit or the boost converter circuit.

[0011] In one embodiment of the power supply device, the inrush current prevention circuit may further include a first FET capable of switching whether current flows from the power supply to the inrush current prevention circuit. The power supply device also includes a voltage detector capable of detecting the voltage value between the drain and source of the first FET. When the voltage value between the drain and source of the first FET detected by the voltage detector falls below a predetermined threshold, the mode control circuit switches from the first mode to the second mode. Thus, by switching from the first mode to the second mode when the voltage value between the drain and source of the first FET falls below the predetermined threshold, the operation can be transitioned from acting as an inrush current prevention circuit to acting as a boost converter circuit at appropriate timing.

[0012] In one embodiment of the power supply device, the boost converter circuit may further include a second FET, which can adjust the output voltage of the boost converter circuit by adjusting its on / off duty cycle. The mode control circuit controls the second FET to always be off in the first mode and controls it to always be on in the second mode. By performing such control, the first mode and the second mode can be switched appropriately.

[0013] In one embodiment of the power supply device, a damping circuit may also be provided before the inrush current prevention circuit. Therefore, by providing a damping circuit, LC resonance can be suppressed.

[0014] According to the present invention, a power supply device is provided that includes an inrush current prevention circuit and a boost converter circuit, and the cost of circuit components can be reduced. Attached Figure Description

[0015] Figure 1 This is a diagram showing the general structure of an existing inrush current prevention circuit.

[0016] Figure 2This is a diagram showing the general structure of an existing boost converter circuit.

[0017] Figure 3 This is a diagram showing the outline of the power supply device for the comparative example.

[0018] Figure 4 This is a diagram showing the outline configuration of a power supply device according to one embodiment.

[0019] Figure 5 It means Figure 4 A diagram showing the portion of a power supply device that forms an inrush current prevention circuit.

[0020] Figure 6 It means Figure 4 A diagram showing the portion of the power supply unit that constitutes the boost converter circuit.

[0021] Figure 7 This is a diagram illustrating the operation of a power supply device in a first mode according to one embodiment.

[0022] Figure 8 This is a diagram illustrating the operation of a power supply device in a second mode according to one embodiment.

[0023] Figure 9 This is a diagram showing the outline configuration of the power supply device in the first modified example.

[0024] Figure 10 This is a diagram showing the outline configuration of the power supply device in the second variation.

[0025] Explanation of reference numerals in the attached figures:

[0026] 1: AC power supply; 2: Converter; 3: DC power supply; 100, 100a, 100b: Power supply unit; 101: Filter; 102: Rectifier; 103: First rectifier; 104: Choke; 105: Second rectifier; 106: Second FET; 107: Smoothing capacitor; 108: First FET; 109: Current detector; 110: Current control circuit; 111: Voltage detector; 112: Voltage control circuit; 113: Mode control circuit; 114: Damping circuit; 120: Impact 130: Boost converter circuit; 200a, 200b, 200c: Power supply unit; 201: Filter; 202: Rectifier; 210: Inrush current protection circuit; 211: Choke; 212: Diode; 213: Smoothing capacitor; 214: FET; 215: Current detector; 216: Current control circuit; 220: Boost converter circuit; 221: Choke; 222: Diode; 223: FET; 224: Smoothing capacitor; 225: Voltage control circuit. Detailed Implementation

[0027] (Inrush current prevention circuit)

[0028] First, the existing inrush current prevention circuit will be explained.

[0029] There are several types of surge current prevention circuits. For example, there are surge current prevention circuits with the following characteristics.

[0030] Parallel connection method of three-terminal bidirectional thyristor switch and temperature-sensitive fuse resistor

[0031] • Power thermistor method

[0032] Parallel connection of FET (Field Effect Transistor) and temperature-sensitive fuse resistor

[0033] Buck converter method

[0034] The various types of inrush current prevention circuits are explained.

[0035] Parallel connection method of three-terminal bidirectional thyristor switch and temperature-sensitive fuse resistor>

[0036] It is configured as follows: a circuit with a three-terminal bidirectional thyristor switch and a temperature-controlled fusible resistor connected in parallel is provided at the input section where a voltage is applied from the power supply.

[0037] When the power is turned on, the three-terminal bidirectional thyristor switch is turned off, and current flows through the temperature-sensitive fuse. At this time, the resistance value of the temperature-sensitive fuse suppresses the inrush current. In addition, the temperature-sensitive fuse melts when a current exceeding a specified value flows, thus preventing the power supply unit from malfunctioning due to high current.

[0038] Once the smoothing capacitor, charged by the current flowing from the power source, is fully charged, the triac switch is turned on. The resistance of the triac switch is less than that of the temperature-sensitive fuse, therefore the current flowing from the power source passes through the triac switch.

[0039] This method suffers from high cost due to the large number of components. Furthermore, the voltage drop of a three-terminal bidirectional thyristor switch during conduction is as large as about 1V, resulting in significant losses in the inrush current prevention circuit under steady-state conditions.

[0040] <Power Thermistor Method>

[0041] It is a configuration in which a power thermistor is placed at the input section where a voltage is applied from a power source. The power thermistor has the characteristic of having a high resistance value at low temperatures and a low resistance value at high temperatures.

[0042] Since the temperature of the power thermistor is low when the power is turned on, the resistance value of the power thermistor is large. Therefore, the large resistance value of the power thermistor can suppress the inrush current generated when the power is turned on. When a certain period of time elapses and a steady state is reached, the power thermistor itself generates heat and its temperature rises. Therefore, in the steady state, the resistance value of the power thermistor decreases, and the loss caused by the power thermistor can be reduced.

[0043] This method has the following problems: when the power is turned on at an early timing after the power is turned off, the temperature of the power thermistor remains high, so the resistance value of the power thermistor remains small, and the inrush current cannot be suppressed. In addition, even when the steady state is reached, the temperature of the power thermistor is in a high state, and since the resistance value of the power thermistor is relatively large at about several hundred mΩ, there is also a problem that the loss of the inrush current prevention circuit is large in the steady state.

[0044] <Parallel connection method of FET and thermal fuse resistor>

[0045] This is a configuration in which a circuit in which an FET and a thermal fuse resistor are connected in parallel is arranged at an input portion to which a voltage is applied from a power supply.

[0046] When the power is turned on, the FET is controlled to be off, and current flows through the thermal fuse resistor. At this time, the inrush current is suppressed by the resistance value of the thermal fuse resistor. In addition, the thermal fuse resistor fuses when a current exceeding a specified value flows, so that the power supply device can be prevented from malfunctioning due to a large current.

[0047] When the charging of the smoothing capacitor charged by the current flowing from the power supply is completed, the FET is controlled to be turned on. Since the on-resistance of the FET is smaller than the resistance value of the thermal fuse resistor, the current flowing from the power supply flows through the FET.

[0048] This method has a problem of high cost due to the large number of components.

[0049] <Step-down converter method>

[0050] Figure 1 This is a diagram showing a power supply device 200a provided with an inrush current prevention circuit 210 of a step-down converter method.

[0051] The power supply device 200a converts the input voltage supplied from the AC power supply 1 into a DC voltage and outputs it to the converter 2. The converter 2 may be, for example, a DC-DC converter.

[0052] The power supply device 200a includes a filter 201, a rectifier 202, and an inrush current prevention circuit 210 of a step-down converter method.

[0053] Filter 201 removes unwanted frequency components from the input voltage from AC power supply 1. Filter 201 can be, for example, a low-pass filter, a band-pass filter, etc.

[0054] Rectifier 202 is a circuit that makes current flow in only one direction.

[0055] The inrush current prevention circuit 210 includes: a choke 211, a diode 212, a smoothing capacitor 213, a FET 214, a current detector 215, and a current control circuit 216.

[0056] This section explains the operation of the inrush current prevention circuit 210, which is used as a buck converter.

[0057] When a voltage is applied from AC power source 1, FET 214 is controlled to conduct. If a voltage is applied from AC power source 1, current flows in the inrush current prevention circuit 210 as indicated by the solid arrow. That is, the current flows in the order of choke coil 211, smoothing capacitor 213, FET 214, and current detector 215. As the current flows in the manner described above, smoothing capacitor 213 is charged.

[0058] Current detector 215 detects the current flowing through FET 214. Current detector 215 outputs the detected current value to current control circuit 216.

[0059] If the current value obtained from the current detector 215 is above the specified current value, the current control circuit 216 disconnects the FET 214.

[0060] If FET214 is turned off, the magnetic energy stored in choke 211 is released, and current flows as shown by the dashed arrow. That is, the current flows in the order of choke 211, smoothing capacitor 213, and diode 212. As the current flows in this manner, smoothing capacitor 213 is charged.

[0061] Subsequently, if the current value obtained from the current detector 215 is less than the specified current value, the current control circuit 216 turns on the FET 214.

[0062] In this way, by repeatedly turning FET214 on and off, the surge current prevention circuit 210 can suppress surge current while charging the smoothing capacitor 213.

[0063] If the smoothing capacitor 213 has finished charging, no current flows through FET 214. In this state, the current control circuit 216 keeps FET 214 always on.

[0064] Because buck converters have fewer components, they are less expensive compared to other methods. Furthermore, buck converters are characterized by lower losses. Therefore, buck converter-based inrush current prevention circuits can be considered an advantageous configuration compared to the other inrush current prevention circuits described above.

[0065] (Boost converter circuit)

[0066] Next, the existing boost converter circuit will be described.

[0067] When AC voltage is input to a power supply unit, if only a smoothing capacitor is used for rectification, the input current will be distorted, generating high-order harmonic currents. The generation of high-order harmonic currents degrades efficiency. Furthermore, the generation of high-order harmonic currents can sometimes cause equipment malfunctions. Therefore, it is necessary to suppress high-order harmonics below the values ​​specified by the IEC (International Electrotechnical Commission).

[0068] Furthermore, when the power supply device supplies DC voltage to the converter, it is preferable to supply DC voltage suitable for the operation of the converter.

[0069] In order to reduce high-order harmonics and output a DC voltage suitable for the operation of the converter, the power supply device is generally configured with a boost converter circuit with APFC (Active Power Factor Correction) function.

[0070] Figure 2 This diagram shows a power supply unit 200b equipped with a boost converter circuit 220. The boost converter circuit 220 is a boost converter circuit with APFC function.

[0071] The power supply unit 200b converts the input voltage supplied from the AC power supply 1 into a DC voltage and outputs it to the converter 2. The converter 2 may be, for example, a DC-DC converter. The power supply unit 200b is capable of outputting a DC voltage suitable for the operation of the converter 2.

[0072] The power supply unit 200b includes a filter 201, a rectifier 202, and a boost converter circuit 220.

[0073] Filter 201 removes unwanted frequency components from the input voltage from AC power supply 1. Filter 201 can be, for example, a low-pass filter, a band-pass filter, etc.

[0074] Rectifier 202 is a circuit that makes current flow in only one direction.

[0075] The boost converter circuit 220 includes a choke 221, a diode 222, a FET 223, a smoothing capacitor 224, and a voltage control circuit 225.

[0076] The operation of the boost converter circuit 220 is explained.

[0077] When FET223 is turned on, current flows in the boost converter circuit 220 as shown by the solid arrow. That is, the current flows in the order of choke coil 221 and FET223. At this time, magnetic energy is stored in choke coil 221.

[0078] If FET223 is turned off, the voltage direction in choke 221 is reversed, the magnetic energy stored in choke 221 is released, and current flows as shown by the dashed arrow. That is, the current flows in the order of choke 221, diode 222, and smoothing capacitor 224.

[0079] By repeatedly turning FET223 on and off, the boost converter circuit 220 performs a boost operation.

[0080] The voltage control circuit 225 detects the voltage value of the smoothing capacitor 224 and controls the duty cycle of the FET 223 to make the detected voltage value close to the voltage suitable for the converter 2.

[0081] Therefore, by controlling the duty cycle of FET223's on / off state, the boost converter circuit 220 can output a specified DC voltage. Furthermore, the boost converter circuit 220 can reduce higher harmonics.

[0082] (Comparative Example)

[0083] Figure 3 This is a diagram showing the general configuration of the power supply device 200c of the comparative example.

[0084] The comparative example power supply device 200c includes a filter 201, a rectifier 202, and a reference. Figure 1 The inrush current prevention circuit 210 is described, and references are provided. Figure 2 The step-up converter circuit 220 is described.

[0085] Thus, by employing the inrush current prevention circuit 210 in a buck converter configuration, the power supply unit 200c can suppress inrush current from flowing through the AC power supply 1 when the voltage from the AC power supply 1 is applied. Furthermore, since the inrush current prevention circuit 210 is a buck converter, it features low cost and minimal losses.

[0086] Furthermore, by incorporating a boost converter circuit 220, the power supply unit 200c is able to output a specified DC voltage. Additionally, the power supply unit 200c can reduce high-order harmonics.

[0087] (The power supply device of the present invention)

[0088] Figure 4 This is a diagram showing the outline configuration of a power supply device 100 according to one embodiment. (Refer to...) Figure 4 The configuration and function of a power supply device 100 according to one embodiment will be described.

[0089] The power supply unit 100 converts the input voltage supplied from the AC power supply 1 into a specified DC voltage and outputs it to the converter 2.

[0090] Converter 2 may be, for example, a DC-DC converter. In the case that converter 2 is a DC-DC converter, converter 2 may be, for example, an isolated DC-DC converter.

[0091] The specified DC voltage output by the power supply unit 100 is a DC voltage suitable for the operation of the converter 2. In this way, by outputting a DC voltage suitable for the operation of the converter 2 from the power supply unit 100 and supplying it to the converter 2, the converter 2 can operate under optimal conditions.

[0092] The power supply device 100 includes a filter 101, a rectifier 102, a first rectifier 103, a choke 104, a second rectifier 105, a second FET 106, a smoothing capacitor 107, a first FET 108, a current detector 109, a current control circuit 110, a voltage detector 111, a voltage control circuit 112, and a mode control circuit 113.

[0093] Filter 101 removes unwanted frequency components from the input voltage from AC power supply 1. Filter 101 can be, for example, a low-pass filter, a band-pass filter, etc.

[0094] Rectifier 102 is a circuit that directs current in only one direction. The input of rectifier 102 is connected to filter 101. One end of the output of rectifier 102 is connected to one end of the first rectifier 103 and one end of the choke coil 104. The other end of the output of rectifier 102 is connected to current detector 109.

[0095] The power supply device 100 is equipped with a reference Figure 1 The circuit diagram illustrates the inrush current prevention circuit for a buck converter, and is equivalent to the reference circuit. Figure 2 The circuit diagram of the boost converter is described.

[0096] First, refer to Figure 5 ,illustrate Figure 4The power supply device 100 shown is equipped with an inrush current prevention circuit of the buck converter type. Figure 5 It is to extract Figure 4 The diagram shows the circuit elements associated with the surge current prevention circuit in the power supply device 100.

[0097] Reference Figure 5 The power supply device 100 includes a first rectifier 103, a choke 104, a smoothing capacitor 107, a first FET 108, a current detector 109, and a current control circuit 110, which together constitute an inrush current prevention circuit 120.

[0098] If Figure 5 The surge current prevention circuit 120 shown is... Figure 1 Comparing it with the surge current prevention circuit 210 shown, then... Figure 5 The first rectifier 103, choke 104, smoothing capacitor 107, first FET 108, current detector 109, and current control circuit 110 of the inrush current prevention circuit 120 shown correspond to respectively Figure 1 The surge current prevention circuit 210 shown includes diode 212, choke 211, smoothing capacitor 213, FET 214, current detector 215, and current control circuit 216.

[0099] Next, refer to Figure 6 ,illustrate Figure 4 The power supply device 100 shown is equipped with a boost converter circuit. Figure 6 It is to extract Figure 4 The diagram shows the circuit elements associated with the boost converter circuit in the power supply device 100.

[0100] Reference Figure 6 The choke 104, second rectifier 105, second FET 106, smoothing capacitor 107 and voltage control circuit 112 of the power supply device 100 constitute a boost converter circuit 130.

[0101] If Figure 6 The boost converter circuit 130 shown is... Figure 2 Comparing it with the boost converter circuit 220 shown, then... Figure 6 The choke 104, second rectifier 105, second FET 106, smoothing capacitor 107, and voltage control circuit 112 of the boost converter circuit 130 shown correspond to respectively Figure 2 The boost converter circuit 220 shown includes a choke 221, a diode 222, a FET 223, a smoothing capacitor 224, and a voltage control circuit 225.

[0102] For reference Figure 5 and Figure 6 As explained, the power supply unit 100 includes a buck converter-type inrush current prevention circuit 120 and a boost converter circuit 130. Here, Figure 5 The surge current prevention circuit 120 shown includes a choke 104 and Figure 6 The choke 104 in the boost converter circuit 130 shown is a shared choke. Furthermore, Figure 5 The surge current prevention circuit 120 shown includes a smoothing capacitor 107 and Figure 6 The smoothing capacitor 107 included in the boost converter circuit 130 shown is a common smoothing capacitor. Therefore, if the power supply device 100 of one embodiment and Figure 3 Compared to the power supply device 200c of the comparative example, the power supply device 100 of one embodiment has one less choke coil and one less smoothing capacitor. That is, the power supply device 100 of one embodiment can implement an inrush current prevention circuit 120 and a boost converter circuit 130 with fewer circuit elements than the power supply device 200c of the comparative example.

[0103] Return to Figure 4 Let me explain.

[0104] The first rectifier 103 is a circuit that directs current in only one direction. The first rectifier 103 can be, for example, a diode, a FET, etc. Figure 4 In the first rectifier 103, the current flows from the bottom to the top.

[0105] One end of the first rectifier 103 is connected to the output of the rectifier 102 and one end of the choke coil 104. The other end of the first rectifier 103 is connected to the source of the second FET 106, the negative terminal of the smoothing capacitor 107, and the drain of the first FET 108.

[0106] The choke coil 104 can be any coil. One end of the choke coil 104 is connected to the output of the rectifier 102 and one end of the first rectifier 103. The other end of the choke coil 104 is connected to one end of the second rectifier 105 and the drain of the second FET 106.

[0107] The second rectifier 105 is a circuit that directs current in only one direction. The second rectifier 105 can be, for example, a diode, a FET, etc. Figure 4 In the middle, the second rectifier 105 causes the current to flow from the left to the right.

[0108] One end of the second rectifier 105 is connected to the other end of the choke coil 104 and the drain of the second FET 106. The other end of the second rectifier 105 is connected to the positive terminal of the smoothing capacitor 107.

[0109] The second FET 106 can be any FET. The drain of the second FET 106 is connected to the other end of the choke 104 and one end of the second rectifier 105. The source of the second FET 106 is connected to the other end of the first rectifier 103, the negative terminal of the smoothing capacitor 107, and the drain of the first FET 108. The gate of the second FET 106 is connected to the voltage control circuit 112.

[0110] The smoothing capacitor 107 has the function of reducing pulsation components. The smoothing capacitor 107 can be any type of capacitor. The positive terminal of the smoothing capacitor 107 is connected to the other end of the second rectifier 105. The negative terminal of the smoothing capacitor 107 is connected to the other end of the first rectifier 103, the source of the second FET 106, and the drain of the first FET 108.

[0111] The first FET 108 can be any FET. The drain of the first FET 108 is connected to the other end of the first rectifier 103, the source of the second FET 106, and the negative terminal of the smoothing capacitor 107. The source of the first FET 108 is connected to the current detector 109. The gate of the first FET 108 is connected to the current control circuit 110.

[0112] The first FET 108 has the function of switching whether current flows from AC power supply 1 to surge current prevention circuit 120. When the first FET 108 is turned on, current flows from AC power supply 1 to surge current prevention circuit 120. When the first FET 108 is turned off, current does not flow from AC power supply 1 to surge current prevention circuit 120.

[0113] Current detector 109 detects the current flowing through the first FET 108. Current detector 109 can be, for example, a resistor. Current detector 109 outputs the detected current value to current control circuit 110.

[0114] If the current value obtained from the current detector 109 is above a predetermined current value, the current control circuit 110 turns off the first FET 108. Conversely, if the current value obtained from the current detector 109 is less than a predetermined current value, the current control circuit 110 turns on the first FET 108. In this case, to prevent frequent switching of the first FET 108's on / off state, the threshold values ​​for turning on and off the first FET 108 can be set to different threshold values.

[0115] Furthermore, the control by which the current control circuit 110 turns on the first FET 108 is not limited to the control described above. For example, the current control circuit 110 can turn on the first FET 108 after a predetermined time has elapsed after turning it off. The predetermined time may be, for example, tens of μs.

[0116] Voltage detector 111 detects the voltage value between the drain and source of the first FET 108.

[0117] The voltage control circuit 112 detects the voltage value of the smoothing capacitor 107 and controls the duty cycle of the second FET 106 to make the detected voltage value close to a specified DC voltage. The specified DC voltage is a DC voltage suitable for the operation of the converter 2. That is, the voltage control circuit 112 performs feedback control on the on / off of the second FET 106 to output a DC voltage suitable for the operation of the converter 2 to the converter 2.

[0118] When the voltage of the smoothing capacitor 107 is less than the specified DC voltage, the voltage control circuit 112 controls the duty cycle of the second FET 106 to make the period during which the second FET 106 is turned on longer. When the voltage of the smoothing capacitor 107 is greater than the specified DC voltage, the voltage control circuit 112 controls the duty cycle of the second FET 106 to make the period during which the second FET 106 is turned on shorter.

[0119] The mode control circuit 113 switches between the first mode and the second mode.

[0120] The first mode is as follows: Figure 5 The surge current prevention circuit 120 of the power supply device 100 shown performs surge current prevention operation. Figure 6 The boost converter circuit 130 of the power supply device 100 shown does not perform boost converter operation. The operation of the power supply device 100 in the first mode will be described later.

[0121] The second mode is as follows: Figure 5 The surge current prevention circuit 120 of the power supply device 100 shown does not perform surge current prevention operation. Figure 6 The boost converter circuit 130 of the power supply device 100 shown performs boost converter operation. The operation of the power supply device 100 in the second mode will be described later.

[0122] When the power is turned on, the mode control circuit 113 causes the power supply device 100 to operate in a first mode. In the first mode, the mode control circuit 113 causes the current control circuit 110 to operate normally. That is, if the current value obtained from the current detector 109 is greater than or equal to a predetermined current value, the current control circuit 110 turns off the first FET 108. Conversely, if the current value obtained from the current detector 109 is less than the predetermined current value, the current control circuit 110 turns on the first FET 108. Thus, the inrush current prevention circuit 120 included in the power supply device 100 performs inrush current prevention operation.

[0123] Furthermore, when operating in the first mode, the mode control circuit 113 controls the voltage control circuit 112 to keep the second FET 106 always off. As a result, the boost converter circuit 130 included in the power supply device 100 does not perform boost converter operation.

[0124] If the voltage value between the drain and source of the first FET 108 detected by the voltage detector 111 is below a specified threshold, the mode control circuit 113 switches from the first mode to the second mode.

[0125] The mode control circuit 113 may, for example, calculate the average value of the drain-source voltage of the first FET 108 over a specified period, and switch from the first mode to the second mode when the calculated average value falls below a specified threshold. In the first mode, if the smoothing capacitor 107 continues to charge, the current flowing through the first FET 108 decreases, and therefore the frequency at which the first FET 108 turns off decreases. Consequently, the average value of the drain-source voltage of the first FET 108 gradually decreases. If the calculated average value falls below a specified threshold, the mode control circuit 113 switches from the first mode to the second mode.

[0126] When operating in the second mode, the mode control circuit 113 controls the current control circuit 110 to keep the first FET 108 always on. As a result, the inrush current prevention circuit 120 of the power supply device 100 does not perform inrush current prevention operation.

[0127] Furthermore, when operating in the second mode, the mode control circuit 113 causes the voltage control circuit 112 to operate normally. That is, the voltage control circuit 112 detects the voltage value of the smoothing capacitor 107 and controls the duty cycle of the second FET 106 to make the detected voltage value close to a predetermined DC voltage. As a result, the boost converter circuit 130 included in the power supply device 100 performs boost converter operation.

[0128] Reference Figure 7 This describes the operation of the power supply device 100 when operating in the first mode.

[0129] When operating in the first mode, the mode control circuit 113 controls the voltage control circuit 112 to keep the second FET 106 always off.

[0130] When a voltage is applied from AC power source 1, the first FET 108 is controlled to conduct. When a voltage is applied from AC power source 1, current flows in the power supply device 100 as indicated by the solid arrow. That is, the current flows in the order of choke coil 104, second rectifier 105, smoothing capacitor 107, first FET 108, and current detector 109. As the current flows in the manner described above, the smoothing capacitor 107 is charged.

[0131] The current detector 109 detects the current flowing through the first FET 108. The current detector 109 outputs the detected current value to the current control circuit 110.

[0132] If the current value obtained from the current detector 109 is above a specified current value, the current control circuit 110 disconnects the first FET 108.

[0133] If the first FET 108 is disconnected, the magnetic energy stored in the choke coil 104 is released, and current flows as shown by the dashed arrow. That is, the current flows in the order of choke coil 104, second rectifier 105, smoothing capacitor 107, and first rectifier 103. As the current flows in the manner described above, the smoothing capacitor 107 is charged.

[0134] Subsequently, if the current value obtained from the current detector 109 is less than the specified current value, the current control circuit 110 turns on the first FET 108.

[0135] Thus, by repeatedly turning the first FET108 on and off, the power supply device 100 can charge the smoothing capacitor 107 while suppressing the inrush current.

[0136] If the charging voltage of the smoothing capacitor 107 increases, the current flowing through the smoothing capacitor 107 decreases. Consequently, the drain-source voltage of the first FET 108 decreases. If the drain-source voltage of the first FET 108 detected by the voltage detector 111 falls below a predetermined threshold, the mode control circuit 113 switches from the first mode to the second mode.

[0137] Reference Figure 8 This explains the operation of the power supply device 100 when operating in the second mode.

[0138] When operating in the second mode, the mode control circuit 113 controls the current control circuit 110 to keep the first FET 108 always on.

[0139] When the second FET 106 is turned on, current flows in the power supply device 100 as shown by the solid arrow. That is, the current flows in the order of choke coil 104, second FET 106, first FET 108, and current detector 109. At this time, magnetic energy is stored in choke coil 104.

[0140] If the second FET 106 is disconnected, the voltage direction in the choke 104 is reversed, the magnetic energy stored in the choke 104 is released, and current flows as shown by the dashed arrow. That is, the current flows in the order of choke 104, second rectifier 105, smoothing capacitor 107, first FET 108, and current detector 109. Through this operation, the power supply device 100 performs a boost operation.

[0141] The voltage control circuit 112 detects the voltage value of the smoothing capacitor 107 and controls the duty cycle of the second FET 106 to make the detected voltage value close to the specified DC voltage.

[0142] The power supply unit 100 outputs a specified DC voltage, adjusted by the voltage control circuit 112 in the manner described above, to the converter 2.

[0143] According to one embodiment of the power supply device 100 described above, an inrush current prevention circuit and a boost converter circuit are provided, and the cost of circuit components can be reduced. More specifically, the power supply device 100 includes an inrush current prevention circuit 120 and a boost converter circuit 130, and the choke coil 104 provided in the inrush current prevention circuit 120 and the choke coil 104 provided in the boost converter circuit 130 are shared choke coils. Furthermore, the smoothing capacitor 107 provided in the inrush current prevention circuit 120 and the smoothing capacitor 107 provided in the boost converter circuit 130 are shared smoothing capacitors. Therefore, one embodiment of the power supply device 100 and... Figure 3 Compared to the configuration of the power supply device 200c shown in the comparative example, one choke coil and one smoothing capacitor can be eliminated, thereby reducing the cost of circuit components.

[0144] (First variation)

[0145] Figure 9 This is a diagram showing the general configuration of the power supply device 100a in the first modified example. Figure 4 The power supply device 100 shown is configured to be supplied with voltage from AC power supply 1, but the power supply device 100a of the first modified example is configured to be supplied with voltage from DC power supply 3.

[0146] The power supply device 100a of the first modification and Figure 4 The power supply device 100 shown differs in that it does not have a rectifier 102.

[0147] Like the power supply device 100a in the first modification, even if the configuration is supplied with voltage from the DC power supply 3, it can achieve the same functionality as... Figure 4 The power supply device 100 shown has the same function.

[0148] (Second variation)

[0149] Figure 10 This is a diagram showing the general configuration of the power supply device 100b in the second modified example.

[0150] The power supply device 100b in the second variation and Figure 9 The power supply device 100a shown differs in that it has a damping circuit 114 in the stage after the filter 101, that is, before the inrush current prevention circuit 120.

[0151] For example, in Figure 9 In the power supply device 100a shown, under special circumstances such as when the cable connected to the input section is long or when the inductive component of the filter 101 is very large, LC resonance may occur and the operation of the power supply device 100a may become unstable.

[0152] Even under these conditions, the power supply device 100b of the second modification can reduce the AC impedance of the input section through the damping circuit 114, thereby suppressing LC resonance. Therefore, the power supply device 100b of the second modification can suppress the generation of LC resonance that would cause the operation of the power supply device 100b to become unstable.

[0153] Those skilled in the art will understand that the present invention can be implemented in other prescribed ways besides the described embodiments without departing from its spirit or essential characteristics. Therefore, the above description is illustrative and not limiting. The scope of the disclosure is not defined by the above description, but by the appended claims. All modifications within the scope thereof are included therein.

[0154] For example, the arrangement and number of the aforementioned components are not limited to the contents illustrated in the above description and figures. The arrangement and number of the components can be arbitrarily configured as long as their functions can be achieved.

Claims

1. A power supply device that converts an input voltage supplied by a power source into a predetermined DC voltage, characterized in that, have: A buck converter-type inrush current prevention circuit suppresses inrush current from the power source to the power supply device; A boost converter circuit that outputs the specified DC voltage; The mode control circuit switches between the first mode and the second mode. as well as A voltage detector is capable of detecting the voltage between the drain and source of the first FET. The surge current prevention circuit includes a first FET, which is capable of switching whether current flows from the power supply to the surge current prevention circuit. The choke coil in the inrush current prevention circuit and the choke coil in the boost converter circuit are shared choke coils. The smoothing capacitor in the inrush current prevention circuit and the smoothing capacitor in the boost converter circuit are shared smoothing capacitors. The first mode is as follows: the inrush current prevention circuit performs inrush current prevention action, and the boost converter circuit does not perform boost converter action. The second mode is as follows: the inrush current prevention circuit does not perform inrush current prevention, and the boost converter circuit performs boost converter operation. When the voltage value between the drain and source of the first FET detected by the voltage detector falls below a predetermined threshold, the mode control circuit switches from the first mode to the second mode.

2. The power supply device according to claim 1, characterized in that, The boost converter circuit also includes a second FET, which can adjust the output voltage of the boost converter circuit by controlling its on / off duty cycle. The mode control circuit controls the operation in the first mode to keep the second FET always off. The mode control circuit controls the second mode to keep the first FET always on.

3. The power supply device according to claim 1 or 2, characterized in that, The inrush current prevention circuit also includes a damping circuit in the preceding stage.

Images