Power converter and current detection circuit

Abstract

A power converter and a current detection circuit are provided. The purpose of the present invention is to improve the detection accuracy of a current flowing in a coil provided in a power converter and to suppress the manufacturing cost of the power converter. A power converter (1) provided with a smoothing coil (Lo) is provided with: a detection winding (Ld) magnetically coupled to the smoothing coil (Lo); a detection resistor (Rd) and a detection capacitor (Cd) which are connected to each other in series and which are connected to the detection winding (Ld) in parallel; and a detection circuit (2) that detects the current flowing through the smoothing coil (Lo) on the basis of the voltage across the detection capacitor (Cd).

Description

Technical Field

[0001] The present invention relates to a technique for detecting a current flowing through a coil provided in a power converter. Background Art

[0002] As a current detection circuit, there is a structure including a detection circuit in which a detection resistor and a detection capacitor connected in series with each other are connected in parallel to a coil provided in a power converter, and a current flowing through the coil is detected based on a voltage drop of a DC resistance component of the coil obtained from both ends of the detection capacitor, and the detected current is corrected based on an error between the voltage at both ends of the detection capacitor and the voltage drop. As a related technique, there is Patent Document 1.

[0003] However, in the above current detection circuit, since the detection capacitor is directly connected to the coil, when detecting the current flowing through the coil based on the voltage drop of the DC resistance component of the coil, it is necessary to deviate the reference potential of the detection circuit to match the voltage at both ends of the detection capacitor, or to deviate the voltage at both ends of the detection capacitor to match the reference potential of the detection circuit. Therefore, it is feared that the manufacturing cost will increase corresponding to adding a function of deviating the reference potential of the detection circuit or the voltage at both ends of the detection capacitor in the detection circuit. In addition, since the voltage drop becomes a relatively small value, it is easily affected by quantization error when converting the voltage drop from an analog value to a digital value in the detection circuit, and it is feared that the current detection accuracy will decrease.

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2000-193687 Summary of the Invention

[0005] An object of one aspect of the present invention is to improve the detection accuracy of a current flowing through a coil provided in a power converter and to suppress the manufacturing cost of the power converter.

[0006] A power converter according to one form of the present invention is a power converter including a coil, and includes: a detection winding magnetically coupled to the coil; a detection resistor and a detection capacitor connected in series with each other and connected in parallel to the detection winding; and a detection circuit configured to detect a current flowing through the coil based on a voltage at both ends of the detection capacitor.

[0007] Thus, since the detection winding is magnetically coupled with the coil, the coil and the detection capacitor can be electrically isolated (insulated) from each other, and the reference potential of the detection capacitor can be arbitrarily set independently of the coil. Therefore, for example, by connecting the reference potential of the detection capacitor to the reference potential of the detection circuit, the current flowing through the coil can be detected based on the voltage across the detection capacitor without deviating the reference potential of the detection circuit or the voltage across the detection capacitor. Accordingly, there is no need to have a function of deviating the reference potential of the detection circuit or the voltage across the detection capacitor, and correspondingly, an increase in the manufacturing cost of the power converter can be suppressed. In addition, by increasing the winding turn ratio of the detection winding relative to the coil, the voltage applied to the detection capacitor can be increased. Therefore, in the detection circuit, when converting the voltage across the detection capacitor from an analog value to a digital value, it is less susceptible to quantization errors, and the current detection accuracy can be improved.

[0008] In addition, the coil may be a smoothing coil that smooths the current flowing into the power converter.

[0009] In addition, the smoothing coil may have a core portion, and the detection winding is wound around the core portion.

[0010] In addition, the core portion may have a gap.

[0011] In addition, when the number of turns of the coil is N1 and the number of turns of the detection winding is N2, N2 / N1≤10.

[0012] In addition, the power converter may be configured to include two offset resistors connected in series with each other and connected between a constant voltage source and the reference potential of the detection circuit. The two offset resistors offset the voltage across the detection capacitor by the potential difference between the potential at the connection point between the two offset resistors and the reference potential of the detection circuit.

[0013] Accordingly, the positive current flowing through the coil can be detected based on the voltage input to the detection circuit that is greater than the potential at the connection point between the two offset resistors, and the negative current flowing through the coil can be detected based on the voltage input to the detection circuit that is less than the potential at the connection point between the two offset resistors.

[0014] In addition, the smoothing coil may be disposed on at least one main surface of the substrate on which the power converter is mounted, and the detection winding is disposed side by side with respect to the smoothing coil in the thickness direction of the substrate.

[0015] Alternatively, the substrate may be a multi-layer substrate, and the detection winding may be arranged as a wiring pattern on an inner layer of the substrate.

[0016] In addition, a form of current detection circuit according to the present invention is a current detection circuit that detects a current flowing through a coil included in a power converter, and includes: a detection winding that is magnetically coupled to the coil; a detection resistor and a detection capacitor that are connected in series with each other and are connected in parallel with the detection winding; and a detection circuit that detects the current flowing through the coil based on the voltage across the detection capacitor.

[0017] In this way, since the detection winding is magnetically coupled to the coil, the coil and the detection capacitor can be electrically isolated (insulated) from each other, and the reference potential of the detection capacitor can be arbitrarily set independently of the coil. Therefore, for example, by connecting the reference potential of the detection capacitor to the reference potential of the detection circuit, it is possible to detect the current flowing through the coil based on the voltage across the detection capacitor without deviating the reference potential of the detection circuit or the voltage across the detection capacitor. As a result, there is no need to have a function that deviates the reference potential of the detection circuit or the voltage across the detection capacitor, and accordingly, an increase in the manufacturing cost of the power converter can be suppressed. In addition, by increasing the winding turn ratio of the detection winding with respect to the coil, the voltage applied to the detection capacitor can be increased. Therefore, in the detection circuit, when converting the voltage across the detection capacitor from an analog value to a digital value, it is possible to be less affected by quantization errors and improve the current detection accuracy.

[0018] According to the present invention, it is possible to improve the detection accuracy of the current flowing through the coil included in the power converter and suppress the manufacturing cost of the power converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a diagram showing an example of a power converter according to an embodiment.

[0020] FIG. 2 is a diagram showing an example of a smoothing coil, a core portion, and a detection winding.

[0021] Figure 3 is a diagram showing Modification 1 of the power converter according to the embodiment.

[0022] Figure 4 is a diagram showing Modification 2 of the power converter according to the embodiment.

[0023] Figure 5 is a diagram showing Modification 3 of the power converter according to the embodiment.

[0024] Figure 6This is a diagram showing a modification example 4 of the power converter according to the embodiment.

[0025] Figure 7 This is a diagram showing a modification example 5 of the power converter according to the embodiment.

[0026] Figure 8 This is a diagram showing a modification example 6 of the power converter according to the embodiment.

[0027] Description of Reference Numerals

[0028] 1... Power converter; 2... Control circuit; 3... Current detection circuit; 4... Detection circuit; B... Power supply; Load... Load; Cs, Cp... Capacitors; Q1 to Q6... Switches; T... Transformer; Lo... Smoothing coil; Co, Cb... Smoothing capacitors; Ld... Detection winding; Rd... Detection resistor; Cd... Detection capacitor; R1, R2... Deviation resistors; Re1, Re2... Relays; BH... High-voltage battery; BL... Low-voltage battery. Detailed Embodiment

[0029] The following describes the embodiment in detail based on the drawings.

[0030] Figure 1 This is a diagram showing an example of the power converter according to the embodiment.

[0031] Figure 1 The power converter 1 shown converts the DC power output from the power supply B into a predetermined DC power and supplies it to the load Load.

[0032] That is, the power converter 1 includes switches Q1 and Q2, capacitors Cp and Cs, transformer T, diodes Do1 and Do2, smoothing coil Lo, smoothing capacitor Co, control circuit 2, and current detection circuit 3. Additionally, switches Q1 and Q2 are formed of, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The drain terminal of switch Q1 is connected to one terminal of capacitor Cp, the source terminal of switch Q2, and one terminal of the primary coil Lp1 of transformer T. The source terminal of switch Q1 is connected to the other terminal of capacitor Cp and the negative terminal of power supply B. The drain terminal of switch Q2 is connected to the positive terminal of power supply B via capacitor Cs and is also connected to the other terminal of primary coil Lp1 via capacitor Cs. The cathode terminals of diodes Do1 and Do2 are connected to each other and are also connected to one terminal of smoothing capacitor Co and one terminal of load Load via smoothing coil Lo. The anode terminal of diode Do1 is connected to one terminal of the secondary coil Lp2 of transformer T. The anode terminal of diode Do2 is connected to the other terminal of secondary coil Lp2, the other terminal of smoothing capacitor Co, and the other terminal of load Load.

[0033] Control circuit 2 is formed of, for example, a CPU (Central Processing Unit), multi-core CPU, programmable devices (such as FPGA (Field Programmable Gate Array) and PLD (Programmable Logic Device)).

[0034] Furthermore, when converting the DC power output from power supply B into a predetermined DC power and supplying it to load Load, control circuit 2 alternately turns on and off switches Q1 and Q2 in such a way that the voltage of smoothing capacitor Co becomes the target voltage and the current detected by current detection circuit 3 becomes the target current.

[0035] First, when switch Q1 is turned on (when switch Q1 is on and switch Q2 is off), current flows from power supply B to primary coil Lp1, and current flows from secondary coil Lp2 through diode Do1, smoothing coil Lo, and smoothing capacitor Co to load Load.

[0036] Next, if switch Q1 is turned off (when switches Q1 and Q2 are off (dead time)), the current flows from the primary coil Lp1 to the capacitor Cp, charging the capacitor Cp. When the voltage across the capacitor Cp becomes the sum of the voltage of the power supply B and the voltage across the capacitor Cs, the capacitor Cs is charged by causing the current to flow from the primary coil Lp1 through the parasitic diode of the switch Q2 to the capacitor Cs. In addition, on the load Load side, the current continues to flow from the diode Do1 through the smoothing coil Lo and the smoothing capacitor Co to the load Load. Further, the energy stored in the primary coil Lp1 due to the charging of the capacitors Cp and Cs decreases, and thus the saturation state of the transformer T is alleviated. In addition, when the switch Q1 is turned off, the voltage across the capacitor Cp is 0 [V], and thus the switching operation loss is reduced.

[0037] Next, if switch Q2 is turned on (when switch Q1 is off and switch Q2 is on), the current flows from the primary coil Lp1 through the switch Q2 to the capacitor Cs, charging the capacitor Cs. In addition, on the load Load side, the current flows from the diode Do2 through the smoothing coil Lo and the smoothing capacitor Co to the load Load. Further, the energy stored in the primary coil Lp1 due to the charging of the capacitor Cs further decreases, and thus the saturation state of the transformer T is further alleviated. In addition, when the switch Q2 is turned on, a current flows through the parasitic diode of the switch Q2, and thus the switching operation loss is reduced. Moreover, during the period when the switch Q2 is on, the direction of the current reverses and the capacitor Cs discharges.

[0038] Next, if switch Q2 is turned off (when switches Q1 and Q2 are off (dead time)), the current flows from the capacitor Cp through the primary coil Lp1 to the power supply B, discharging the capacitor Cp. After the capacitor Cp is discharged, the current flows from the parasitic diode of the switch Q1 through the primary coil Lp1 to the power supply B. In addition, on the load Load side, the current continues to flow from the diode Do2 through the smoothing coil Lo and the smoothing capacitor Co to the load Load.

[0039] Hereinafter, the turning on and off of the switches Q1 and Q2 are alternately repeated. In addition, when the switch Q1 is turned on, a current flows through the parasitic diode of the switch Q1, and thus the switching operation loss is reduced.

[0040] The current detection circuit 3 includes a detection winding Ld, a detection resistor Rd, a detection capacitor Cd, and a detection circuit 4, and detects the current (alternating current) flowing through the smoothing coil Lo.

[0041] The detection winding Ld is magnetically coupled to the smoothing coil Lo by being wound around the core Cre of the smoothing coil Lo. Further, when the number of turns of the smoothing coil Lo is N1 and the number of turns of the detection winding Ld is N2, it is preferable that 0.3 ≤ N2 / N1 ≤ 10. More desirably, 1 ≤ N2 / N1 ≤ 10. Hereinafter, the winding turn ratio N2 / N1 is also represented as the winding turn ratio n. Thus, by making the winding turn ratio n relatively large, the voltage applied to the detection capacitor Cd can be increased. Therefore, in the detection circuit 4, when converting the voltage across the detection capacitor Cd from an analog value to a digital value, it is less susceptible to quantization errors and the current detection accuracy can be improved.

[0042] The detection resistor Rd and the detection capacitor Cd are connected in series with each other and are connected in parallel with the detection winding Ld. That is, one terminal of the detection capacitor Cd is connected to one terminal of the detection winding Ld via the detection resistor Rd, and the other terminal of the detection capacitor Cd is connected to the other terminal of the detection winding Ld and the reference potential of the detection circuit 4 (e.g., the ground portion of the power converter 1).

[0043] The detection circuit 4 detects the current flowing through the smoothing coil Lo based on the voltage across the detection capacitor Cd (the potential difference between the potential of one terminal of the detection capacitor Cd and the reference potential of the detection circuit 4).

[0044] For example, when the voltage across the smoothing coil Lo is VL, the current flowing through the smoothing coil Lo is iL, the inductance value of the smoothing coil Lo is L, the voltage across the detection capacitor Cd is Vc, the capacitance value of the detection capacitor Cd is C, the voltage across the detection resistor Rd is Vr, the resistance value of the detection resistor Rd is R, the current flowing through the detection capacitor Cd and the detection resistor Rd is is, the ratio of the number of turns of the detection winding Ld to the number of turns of the smoothing coil Lo is n, and the Laplace transform operator is s, the voltage VLd across the detection winding Ld is expressed as VLd = Vc + Vr. Here, VLd = n×VL = s×n×L×iL, Vc = is / (s×C), Vr = R×is, so it can be rewritten as s×n×L×iL = is / (s×C) + R×is. Solving this equation for is gives is = (s×n×L) / (1 / (s×C) + R)×iL, and thus it can be rewritten as Vr = R×is = R×(s×n×L) / (1 / (s×C) + R)×iL. Therefore, the voltage Vc across the detection capacitor Cd can be expressed as in Equation 1 below.

[0045] Vc = VLd - Vr = s × n × L × iL - R × (s × n × L) / (1 / (s × C) + R) × iL = (s × n × L × iL) / (1 + s × C × R) ··· Equation 1

[0046] Here, when R and C are set such that the cut-off frequency fc = 1 / (2π × R × C) of the filter circuit composed of the detection resistor Rd and the detection capacitor Cd is sufficiently lower than the switching frequency of the power converter 1, a condition of s × C × R >> 1 can be obtained. Thus, the "1" in the denominator of the above Equation 1 can be ignored, and therefore, the above Equation 1 can be transformed into the following Equation 2.

[0047] Vc = (n × L × iL) / (C × R) ··· Equation 2

[0048] That is, the detection circuit 4 obtains the current iL flowing through the smoothing coil Lo by substituting the voltage Vc across the detection capacitor Cd into the above Equation 2. In addition, the winding turn ratio n, the inductance value L, the capacitance value C, and the resistance value R are arbitrary values obtained in advance.

[0049] Thus, according to the power converter 1 of the embodiment, since the detection winding Ld is magnetically coupled with the smoothing coil Lo, the smoothing coil Lo and the detection capacitor Cd can be electrically isolated (insulated) from each other, and the reference potential of the detection capacitor Cd can be arbitrarily set independently of the smoothing coil Lo. Therefore, by connecting the other terminal (reference potential) of the detection capacitor Cd to the reference potential of the detection circuit 4, the current iL flowing through the smoothing coil Lo can be detected based on the voltage Vc across the detection capacitor Cd without deviating the reference potential of the detection circuit 4 or the voltage across the detection capacitor Cd. As a result, there is no need to have a function of deviating the reference potential of the detection circuit 4 or the voltage across the detection capacitor Cd, and accordingly, an increase in the manufacturing cost of the power converter 1 can be suppressed. In addition, after the current iL flowing through the smoothing coil Lo is detected, there is no need to correct the current iL, and therefore, an increase in the detection time of the current iL can be suppressed.

[0050] Alternatively, the current detection circuit 3 may be configured to detect the current flowing through the primary coil Lp1 or the secondary coil Lp2 having a core. When the current detection circuit 3 detects the current flowing through the primary coil Lp1 or the secondary coil Lp2, the detection winding Ld is wound around the core of the primary coil Lp1 or the secondary coil Lp2. Further, when the detection circuit 4 detects the current flowing through the primary coil Lp1 or the secondary coil Lp2 based on the voltage across the detection capacitor Cd, in the above formula 2, the winding turn ratio n represents the ratio of the number of turns of the detection winding Ld to the number of turns of the primary coil Lp1 or the secondary coil Lp2, and the inductance value L represents the inductance value of the primary coil Lp1 or the secondary coil Lp2.

[0051] Here, Figures 2A to 2D is a diagram showing an example of the smoothing coil Lo, the detection winding Ld, and the core Cre. Figure 2A is a perspective view of the multilayer substrate Sb on which the power converter 1 is mounted, the smoothing coil Lo, and the core Cre. Figure 2B is a cross-sectional view of the multilayer substrate Sb, the smoothing coil Lo, and the detection winding Ld. Figure 2C shows an example of the core Cre, Figure 2D shows another example of the core Cre.

[0052] Figure 2A and Figure 2B The smoothing coil Lo shown is composed of plate-shaped conductors L1 and L2 in a letter C shape. One plate-shaped conductor L1 is arranged on one main surface (the surface on the positive side in the Z direction) of the multilayer substrate Sb, and the other plate-shaped conductor L2 is arranged on the other main surface (the surface on the negative side in the Z direction) of the multilayer substrate Sb. For example, one terminal of the plate-shaped conductor L1 is connected to the wiring pattern on one main surface of the multilayer substrate Sb via solder or the like, the other terminal of the plate-shaped conductor L1 is connected to one terminal of the plate-shaped conductor L2 via a conductor in the multilayer substrate Sb, and the other terminal of the plate-shaped conductor L2 is connected to the wiring pattern on the other main surface of the multilayer substrate Sb via solder or the like. Thus, they are connected in series to form a two-turn smoothing coil Lo. Alternatively, the smoothing coil Lo may be composed of only the plate-shaped conductor L1 or the plate-shaped conductor L2. That is, the smoothing coil Lo is arranged on at least one main surface of the multilayer substrate Sb on which the power converter 1 is mounted.

[0053] Further, Figure 2B The detection winding Ld shown is a stacked coil composed of a wiring pattern and is arranged in the inner layer of the multilayer substrate Sb so as to face the smoothing coil Lo in the thickness direction (Z direction) of the multilayer substrate Sb. Figure 2BIn [the figure], the detection winding Ld is formed of a wiring pattern that forms four turns in a spiral shape, but the number of turns is not limited to four. Additionally, the detection winding Ld may be disposed on at least one main surface of the multilayer substrate Sb. That is, the detection winding Ld is arranged side by side with respect to the smoothing coil Lo in the thickness direction of the multilayer substrate Sb. Furthermore, the detection winding Ld is not limited to a structure where it is disposed in one inner layer of the multilayer substrate Sb, and it may also be configured by forming patterns in multiple inner layers and connecting the patterns of each layer in series. Additionally, it may be composed of a wire or the like and is not limited to a wiring pattern. Moreover, the substrate on which the power converter 1 is mounted may not be composed of a multilayer substrate.

[0054] Furthermore, Figure 2A The core Cre shown is composed of an E-shaped magnetic body Cre1 and an I-shaped magnetic body Cre2. Three through-holes H1 to H3 are arranged in the Y direction on the multilayer substrate Sb. Among the through-holes H1 to H3, the through-hole H2 is disposed inside the smoothing coil Lo, and the through-holes H1 and H3 are disposed outside the smoothing coil Lo. The core Cre is formed by passing three protruding portions of the magnetic body Cre1 through the through-holes H1 to H3 and then joining them to the magnetic body Cre2.

[0055] In addition, as Figure 2C shown, it may also be that the core Cre is cut to a length such that at least the end of one of the three protruding portions of the magnetic body Cre1 does not contact the magnetic body Cre2 when the magnetic body Cre1 and the magnetic body Cre2 are connected to each other, thereby providing a gap AG.

[0056] Or, as Figure 2D shown, it may also be that the core Cre is connected by the three protruding portions of the magnetic body Cre1 and the magnetic body Cre2 via a spacer S, thereby providing a gap AG.

[0057] Furthermore, it may also be that the core Cre does not have a gap.

[0058] The present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the gist of the present invention.

[0059] The power converter 1 of the embodiment is not limited to an active clamp forward converter and may also be composed of other converters.

[0060] <Variation 1>

[0061] Figure 3 It is a diagram showing Variation 1 of the power converter 1 of the embodiment. Additionally, Figure 3 in [the figure], the same reference numerals are assigned to the same structures as those Figure 1 shown, and their descriptions are omitted.

[0062] Figure 3 The power converter 1 shown is a non-insulated step-down converter that converts the DC power output from the power supply B into a predetermined DC power and supplies it to the load Load.

[0063] That is, Figure 3 The power converter 1 shown includes a switch Q1, a diode Do2, a smoothing coil Lo, a smoothing capacitor Co, a control circuit 2, and a current detection circuit 3. The drain terminal of the switch Q1 is connected to the positive terminal of the power supply B, the source terminal of the switch Q1 is connected to the cathode terminal of the diode Do2, and is connected to one terminal of the smoothing capacitor Co and one terminal of the load Load via the smoothing coil Lo. The anode terminal of the diode Do2 is connected to the negative terminal of the power supply B, the other terminal of the smoothing capacitor Co, and the other terminal of the load Load. In addition, Figure 3 The structure and operation of the current detection circuit 3 shown are the same as those of the current detection circuit 3 shown in Figure 1 Therefore, its description is omitted. In addition, the voltage across the load Load is lower than the voltage across the power supply B, and even if the load Load is composed of a battery, there is no situation where current flows from the load Load through the parasitic diode of the switch Q1 to the power supply B.

[0064] In addition, when converting the DC power output from the power supply B into a predetermined DC power and supplying it to the load Load, Figure 3 The control circuit 2 shown repeatedly turns on and off the switch Q1 so that the voltage of the smoothing capacitor Co becomes the target voltage and the current detected by the current detection circuit 3 becomes the target current. When the switch Q1 is turned on, current flows from the power supply B through the switch Q1, the smoothing coil Lo, and the smoothing capacitor Co to the load Load. In addition, when the switch Q1 is turned off, current continues to flow from the diode Do2 through the smoothing coil Lo and the smoothing capacitor Co to the load Load.

[0065] In Figure 3 In the power converter 1 shown, it is also not necessary to have a function that causes the reference potential of the detection circuit 4 or the voltage across the detection capacitor Cd to deviate when detecting the current flowing through the smoothing coil Lo. Therefore, accordingly, an increase in the manufacturing cost of the power converter 1 can be suppressed. In addition, in Figure 3 In the power converter 1 shown, the voltage applied to the detection capacitor Cd can also be increased by increasing the winding turn ratio n. Therefore, when converting the voltage across the detection capacitor Cd from an analog value to a digital value in the detection circuit 4, it is not easily affected by quantization errors, and the current detection accuracy can be improved. In addition, in Figure 3In the power converter 1 shown, it is also not necessary to correct the current iL after detecting the current iL flowing through the smoothing coil Lo. Therefore, an increase in the detection time of the current iL can be suppressed.

[0066] <Modified Example 2>

[0067] Figure 4 It is a diagram showing a modified example 2 of the power converter 1 of the embodiment. In addition, Figure 4 in, for Figure 1 the same structure as the structure shown is labeled with the same reference numeral and its description is omitted.

[0068] Figure 4 The power converter 1 shown is an isolated flyback converter, and converts the DC power output from the power supply B into a predetermined DC power and supplies it to the load Load.

[0069] That is, Figure 4 the power converter 1 shown includes a switch Q1, a transformer T, diodes Do1, Do2, a smoothing coil Lo, a smoothing capacitor Co, a control circuit 2, and a current detection circuit 3. The drain terminal of the switch Q1 is connected to the positive terminal of the power supply B via the primary coil Lp1 of the transformer T, and the source terminal of the switch Q1 is connected to the negative terminal of the power supply B. In addition, Figure 4 the circuit structure for resetting the transformer T is omitted in the isolated flyback converter shown. In addition, the structure and operation of the current detection circuit 3 are the same as those of the current detection circuit 3 shown in Figure 1 so its description is omitted.

[0070] In addition, when converting the DC power output from the power supply B into a predetermined DC power and supplying it to the load Load, Figure 4 the control circuit 2 shown repeatedly turns on and off the switch Q1 so that the voltage of the smoothing capacitor Co becomes the target voltage and the current detected by the current detection circuit 3 becomes the target current. When the switch Q1 is turned on, current flows from the power supply B to the primary coil Lp1, and current flows from the secondary coil Lp2 of the transformer T through the diode Do1, the smoothing coil Lo, and the smoothing capacitor Co to the load Load. When the switch Q1 is turned off, current continues to flow from the diode Do2 through the smoothing coil Lo and the smoothing capacitor Co to the load Load.

[0071] In Figure 4 the power converter 1 shown, it is also not necessary to have a function of deviating the reference potential of the detection circuit 4 or the voltage across the detection capacitor Cd when detecting the current flowing through the smoothing coil Lo. Therefore, accordingly, an increase in the manufacturing cost of the power converter 1 can be suppressed. In addition, in Figure 4In the power converter 1 shown, the voltage applied to the detection capacitor Cd can also be increased by increasing the winding turn ratio n. Therefore, when converting the voltage across the detection capacitor Cd from an analog value to a digital value in the detection circuit 4, it is possible to be less affected by quantization errors and improve the current detection accuracy. In addition, in Figure 4 In the power converter 1 shown, it is not necessary to correct the current iL after detecting the current iL flowing through the smoothing coil Lo. Therefore, an increase in the detection time of the current iL can be suppressed.

[0072] <Modified Example 3>

[0073] Figure 5 FIG. is a diagram showing a modified example 3 of the power converter 1 of the embodiment. In addition, Figure 5 In, the same reference numerals are given to the same structures as those Figure 1 shown, and their description is omitted.

[0074] Figure 5 The power converter 1 shown is an isolated push-pull converter, and converts the DC power output from the power supply B into a predetermined DC power and supplies it to the load Load.

[0075] That is, Figure 5 The power converter 1 shown includes switches Q1, Q2, a transformer T, diodes Do1, Do2, a smoothing coil Lo, a smoothing capacitor Co, a control circuit 2, and a current detection circuit 3. The source terminal of switch Q1 is connected to the negative terminal of power supply B, and the drain terminal of switch Q1 is connected to one terminal of the primary coil Lp1 of transformer T. The source terminal of switch Q2 is connected to the negative terminal of power supply B, and the drain terminal of switch Q2 is connected to the other terminal of the primary coil Lp1. The positive terminal of power supply B is connected to the center tap of the primary coil Lp1. The cathode terminals of diodes Do1 and Do2 are connected, and are connected to one terminal of the smoothing capacitor Co and one terminal of the load Load via the smoothing coil Lo. The anode terminal of diode Do1 is connected to one terminal of the secondary coil Lp2 of transformer T. The anode terminal of diode Do2 is connected to the other terminal of the secondary coil Lp2. The center tap of the secondary coil Lp2 is connected to the other terminal of the smoothing capacitor Co and the other terminal of the load Load. In addition, Figure 5 The structure and operation of the current detection circuit 3 shown are the same as those of the current detection circuit 3 Figure 1 shown, and therefore, its description is omitted.

[0076] In addition, when converting the DC power output from the power supply B into a predetermined DC power and supplying it to the load Load, Figure 5The control circuit 2 shown causes the switches Q1 and Q2 to be alternately and repeatedly turned on and off, so that the voltage of the smoothing capacitor Co becomes the target voltage and the current detected by the current detection circuit 3 becomes the target current. When the switch Q2 is off and the switch Q1 is on, current flows from the power supply B through the center tap of the primary coil Lp1 to the primary coil Lp1, and current flows from the secondary coil Lp2 through the diode Do1, the smoothing coil Lo, and the smoothing capacitor Co to the load Load. When the switch Q1 is off and the switch Q2 is on, current flows from the power supply B through the center tap of the primary coil Lp1 to the primary coil Lp1, and current flows from the secondary coil Lp2 through the diode Do2, the smoothing coil Lo, and the smoothing capacitor Co to the load Load.

[0077] In Figure 5 the power converter 1 shown, it is also not necessary to have a function of causing the reference potential of the detection circuit 4 or the voltage across the detection capacitor Cd to deviate when detecting the current flowing through the smoothing coil Lo. Accordingly, an increase in the manufacturing cost of the power converter 1 can be suppressed. Further, in Figure 5 the power converter 1 shown, the voltage applied to the detection capacitor Cd can also be increased by increasing the winding turn ratio n. Therefore, when converting the voltage across the detection capacitor Cd from an analog value to a digital value in the detection circuit 4, it is less susceptible to quantization errors and the current detection accuracy can be improved. Further, in Figure 5 the power converter 1 shown, it is also not necessary to correct the current iL after detecting the current iL flowing through the smoothing coil Lo. Therefore, an increase in the detection time of the current iL can be suppressed.

[0078] <Variation Example 4>

[0079] Figure 6 is a diagram showing Variation Example 4 of the power converter 1 of the embodiment. Additionally, Figure 6 in, the same reference numerals are given to the same structures as those Figure 1 shown, and their description is omitted.

[0080] Figure 6 The power converter 1 shown is an isolated half-bridge converter and converts the DC power output from the power supply B into predetermined DC power and supplies it to the load Load.

[0081] That is, Figure 6The power converter 1 shown includes switches Q1 and Q2, capacitor Cr, transformer T, diodes Do1 and Do2, smoothing coil Lo, smoothing capacitor Co, control circuit 2, and current detection circuit 3. The drain terminal of switch Q1 is connected to the positive terminal of power supply B, and the source terminal of switch Q1 is connected to the drain terminal of switch Q2 and one terminal of the primary coil Lp1 of transformer T. The source terminal of switch Q2 is connected to the other terminal of primary coil Lp1 via capacitor Cr and is also connected to the negative terminal of power supply B. The cathode terminals of diodes Do1 and Do2 are connected to each other and are connected to one terminal of smoothing capacitor Co and one terminal of load Load via smoothing coil Lo. The anode terminal of diode Do1 is connected to one terminal of secondary coil Lp2 of transformer T. The anode terminal of diode Do2 is connected to the other terminal of secondary coil Lp2. The center tap of secondary coil Lp2 is connected to the other terminal of smoothing capacitor Co and the other terminal of load Load. Additionally, Figure 6 the structure and operation of the current detection circuit 3 shown are Figure 1 the same as those of the current detection circuit 3 shown, and thus, its description is omitted.

[0082] Furthermore, when converting the DC power output from power supply B into a predetermined DC power and supplying it to load Load, Figure 6 the control circuit 2 shown causes switches Q1 and Q2 to be alternately turned on and off repeatedly so that the voltage of smoothing capacitor Co becomes the target voltage and the current detected by current detection circuit 3 becomes the target current.

[0083] First, when switch Q1 is turned on (when switch Q1 is on and switch Q2 is off), current flows from power supply B through switch Q1 to primary coil Lp1, and current flows from secondary coil Lp2 through diode Do1, smoothing coil Lo, and smoothing capacitor Co to load Load.

[0084] Next, when switch Q1 is turned off (when switches Q1 and Q2 are off (dead time)), current flows from the other terminal of primary coil Lp1 through capacitor Cr and the parasitic diode of switch Q2 to one terminal of primary coil Lp1, and current continues to flow from secondary coil Lp2 through diode Do1, smoothing coil Lo, and smoothing capacitor Co to load Load.

[0085] Next, if switch Q2 is turned on (when switch Q1 is turned off and switch Q2 is turned on), current flows from one terminal of capacitor Cr through primary coil Lp1 and switch Q2 to the other terminal of capacitor Cr, and current flows from secondary coil Lp2 through diode Do2, smoothing coil Lo, and smoothing capacitor Co to load Load. Additionally, when switch Q2 is turned on, current flows through the parasitic diode of switch Q2, thus reducing the switching operation loss.

[0086] Next, if switch Q2 is turned off (when switches Q1 and Q2 are turned off (dead time)), current flows from the negative terminal of power supply B through capacitor Cr, primary coil Lp1, and the parasitic diode of switch Q1 to the positive terminal of power supply B, and current continues to flow from secondary coil Lp2 through diode Do2, smoothing coil Lo, and smoothing capacitor Co to load Load.

[0087] Hereinafter, the turning on and off of switches Q1 and Q2 are alternately repeated. Additionally, when switch Q1 is turned on, current flows through the parasitic diode of switch Q1, thus reducing the switching operation loss.

[0088] In Figure 6 the power converter 1 shown, it is also not necessary to have a function that causes the reference potential of detection circuit 4 or the voltage across detection capacitor Cd to deviate when detecting the current flowing through smoothing coil Lo. Accordingly, an increase in the manufacturing cost of power converter 1 can be suppressed. Further, in Figure 6 the power converter 1 shown, the voltage applied to detection capacitor Cd can also be increased by increasing the winding turn ratio n. Therefore, when converting the voltage across detection capacitor Cd from an analog value to a digital value in detection circuit 4, it is less susceptible to quantization error, and current detection accuracy can be improved. Further, in Figure 6 the power converter 1 shown, it is also not necessary to correct current iL after detecting the current iL flowing through smoothing coil Lo. Therefore, an increase in the detection time of current iL can be suppressed.

[0089] <Example of Variation 5>

[0090] Figure 7 is a diagram showing Example of Variation 5 of power converter 1 of the embodiment. Additionally, Figure 7 in Figure 1 structures identical to those shown are denoted by the same reference numerals, and their description is omitted.

[0091] Figure 7 the power converter 1 shown is an isolated full-bridge converter that converts the DC power output from power supply B into predetermined DC power and supplies it to load Load.

[0092] That is, Figure 7 the power converter 1 shown includes switches Q1 to Q4, a transformer T, diodes Do1, Do2, a smoothing coil Lo, a smoothing capacitor Co, a control circuit 2, and a current detection circuit 3. In addition, the switches Q3 and Q4 are constituted by MOSFETs, for example. The drain terminal of the switch Q1 is connected to the positive terminal of the power supply B and the drain terminal of the switch Q3. The source terminal of the switch Q1 is connected to one terminal of the primary coil Lp1 of the transformer T and the drain terminal of the switch Q2. The source terminal of the switch Q2 is connected to the negative terminal of the power supply B and the source terminal of the switch Q4. The source terminal of the switch Q3 is connected to the other terminal of the primary coil Lp1 and the drain terminal of the switch Q4. The cathode terminals of the diodes Do1 and Do2 are connected to each other and are connected to one terminal of the smoothing capacitor Co and one terminal of the load Load via the smoothing coil Lo. The anode terminal of the diode Do1 is connected to one terminal of the secondary coil Lp2 of the transformer T. The anode terminal of the diode Do2 is connected to the other terminal of the secondary coil Lp2. The center tap of the secondary coil Lp2 is connected to the other terminal of the smoothing capacitor Co and the other terminal of the load Load. In addition, Figure 7 the structure and operation of the current detection circuit 3 shown are Figure 1 the same as those of the current detection circuit 3 shown, and therefore, the description thereof is omitted.

[0093] In addition, when converting the DC power output from the power supply B into a predetermined DC power and supplying it to the load Load, Figure 7 the control circuit 2 shown repeatedly performs an operation of turning on the switches Q1 and Q4 and turning off the switches Q2 and Q3, and then turning off the switches Q1 and Q4 and turning on the switches Q2 and Q3, so that the voltage of the smoothing capacitor Co becomes a target voltage and the current detected by the current detection circuit 3 becomes a target current. When the switches Q1 and Q4 are turned on (when the switches Q1 and Q4 are turned on and the switches Q2 and Q3 are turned off), current flows from the positive terminal of the power supply B through the switch Q1, the primary coil Lp1, and the switch Q4 to the negative terminal of the power supply B, and current flows from the secondary coil Lp2 through the diode Do1, the smoothing coil Lo, and the smoothing capacitor Co to the load Load. When the switches Q2 and Q3 are turned on (when the switches Q1 and Q4 are turned off and the switches Q2 and Q3 are turned on), current flows from the positive terminal of the power supply B through the switch Q3, the primary coil Lp1, and the switch Q2 to the negative terminal of the power supply B, and current flows from the secondary coil Lp2 through the diode Do2, the smoothing coil Lo, and the smoothing capacitor Co to the load Load.

[0094] In Figure 7In the power converter 1 shown, it is also not necessary to have a function of deviating the reference potential of the detection circuit 4 or the voltage across the detection capacitor Cd when detecting the current flowing through the smoothing coil Lo. Therefore, accordingly, an increase in the manufacturing cost of the power converter 1 can be suppressed. In addition, in Figure 7 In the power converter 1 shown, the voltage applied to the detection capacitor Cd can also be increased by increasing the winding turn ratio n. Therefore, when converting the voltage across the detection capacitor Cd from an analog value to a digital value in the detection circuit 4, it is less susceptible to quantization errors, and the current detection accuracy can be improved. In addition, in Figure 7 In the power converter 1 shown, it is also not necessary to correct the current iL after detecting the current iL flowing through the smoothing coil Lo. Therefore, an increase in the detection time of the current iL can be suppressed.

[0095] <Variation 6>

[0096] Figure 8 FIG. is a diagram showing Variation 6 of the power converter 1 of the embodiment. In addition, Figure 8 In, the same reference numerals are given to the same structures as those Figure 1 shown, and the description thereof is omitted.

[0097] Figure 8 The power converter 1 shown is an active clamp forward converter, and converts the DC power output from the high-voltage battery BH into a predetermined DC power and supplies it to the low-voltage battery BL.

[0098] That is, Figure 8The power converter 1 shown includes relays Re1, Re2, smoothing capacitor Cb, switches Q1, Q2, capacitor Cs, transformer T, switches Q5, Q6, smoothing coil Lo, smoothing capacitor Co, control circuit 2, and current detection circuit 3. Further, switches Q5, Q6 are formed of MOSFETs, for example. The drain terminal of switch Q1 is connected to the source terminal of switch Q2 and one terminal of the primary coil Lp1 of transformer T. The source terminal of switch Q1 is connected to the negative terminal of high-voltage battery BH via relay Re1 and is also connected to one terminal of smoothing capacitor Cb. The drain terminal of switch Q2 is connected to the positive terminal of high-voltage battery BH via capacitor Cs and relay Re2, is also connected to the other terminal of primary coil Lp1 via capacitor Cs, and is also connected to the other terminal of smoothing capacitor Cb via capacitor Cs. The drain terminals of switches Q5 and Q6 are connected to each other and are also connected to one terminal of smoothing capacitor Co and the positive terminal of low-voltage battery BL via smoothing coil Lo. The source terminal of switch Q5 is connected to one terminal of secondary coil Lp2 of transformer T, the other terminal of smoothing capacitor Co, and the negative terminal of low-voltage battery BL. The source terminal of switch Q6 is connected to the other terminal of secondary coil Lp2.

[0099] In addition, Figure 8 The current detection circuit 3 shown includes detection winding Ld, detection resistor Rd, detection capacitor Cd, detection circuit 4, deviation resistors R1, R2.

[0100] Detection winding Ld is wound around the core Cre of smoothing coil Lo.

[0101] Detection resistor Rd and detection capacitor Cd are connected in series with each other and are connected in parallel with detection winding Ld.

[0102] The deviation resistors R1 and R2 are connected in series with each other and are connected between the constant voltage source Pvc and the reference potential of the detection circuit 4. In addition, the connection point between the deviation resistors R1 and R2 is connected to the connection point between the detection winding Ld and the detection capacitor Cd, and the sum of the voltages across both ends of the detection capacitor Cd and the voltages across both ends of the deviation resistor R2 is input to the detection circuit 4. That is, through the deviation resistors R1 and R2, the voltage across both ends of the detection capacitor Cd is deviated from the potential difference between the potential of the connection point between the deviation resistors R1 and R2 and the reference potential of the detection circuit 4, and the deviated voltage across both ends of the detection capacitor Cd is input to the detection circuit 4. The detection circuit 4 solves for the current iL flowing through the smoothing coil Lo by substituting the voltage Vc across both ends of the deviated detection capacitor Cd into the above formula 2. Thereby, it is possible to detect the forward current flowing through the smoothing coil Lo based on the voltage in the voltage input to the detection circuit 4 that is greater than the potential of the connection point between the deviation resistors R1 and R2, and it is possible to detect the reverse current flowing into the smoothing coil Lo based on the voltage in the voltage input to the detection circuit 4 that is less than the potential of the connection point between the deviation resistors R1 and R2.

[0103] Figure 8 Before starting, the potential of the smoothing capacitor Cb in the power converter 1 shown is zero. Before the normal operation of converting the DC power output from the high-voltage battery BH into predetermined DC power and supplying it to the low-voltage battery BL, the control circuit 2 pre-charges the smoothing capacitor Cb with the power supplied from the low-voltage battery BL in a state where the relays Re1 and Re2 are open, and then, makes the relays Re1 and Re2 conductive to supply power from the high-voltage battery BH to the low-voltage battery BL. Thereby, it is possible to suppress the situation where a relatively large inrush current flows from the high-voltage battery BH to the smoothing capacitor Cb when the relays Re1 and Re2 migrate from the open state to the conductive state.

[0104] For example, consider a case where the direction of the current flowing from the high-voltage battery BH to the low-voltage battery BL is defined as the forward direction and the direction of the current flowing from the low-voltage battery BL to the high-voltage battery BH is defined as the reverse direction. In addition, the input voltage range of the AD conversion of the detection circuit 4 is set to 0 [V] to 5 [V], and the potential of the connection point between the deviation resistors R1 and R2 is set to 2.5 [V]. In addition, the voltage across both ends of the deviated detection capacitor Cd is set to Vc.

[0105] In this case, first, the control circuit 2 keeps the switch Q1 open all the time and repeatedly turns on and off the switches Q2, Q5, and Q6 to open the relays Re1 and Re2 and make the reverse current detected by the current detection circuit 3 become the target current. When the switch Q6 is turned on (when the switches Q1, Q2, and Q5 are off and the switch Q6 is on), the current flows from the low-voltage battery BL to the secondary coil Lp2, and the current flows from the primary coil Lp1 to the smoothing capacitor Cb. At this time, the current in the smoothing coil Lo becomes reverse. In addition, when the switch Q6 is turned off (when the switches Q1 and Q6 are off and the switches Q2 and Q5 are on), the transformer T is reset, and the reverse current in the smoothing coil Lo increases. In other words, in this case, the current in the smoothing coil Lo also becomes reverse. Therefore, the voltage input to the detection circuit 4 is a voltage smaller than 2.5 [V] and a voltage equal to or higher than 0 [V], and the detection circuit 4 detects the reverse current flowing in the smoothing coil Lo. Thus, the smoothing capacitor Cb can be charged before the relays Re1 and Re2 are turned on. In addition, the switch Q1 can also be turned on and off synchronously with the switch Q6.

[0106] Next, when the voltage of the smoothing capacitor Cb becomes equal to or higher than the voltage threshold (for example, the voltage of the high-voltage battery BH), the control circuit 2 turns on the relays Re1 and Re2.

[0107] Moreover, the control circuit 2 alternately and repeatedly turns on and off the switches Q5 and Q6 and alternately and repeatedly turns on and off the switches Q1 and Q2 to make the voltage of the smoothing capacitor Co become the target voltage and make the forward current detected by the current detection circuit 3 become the target current. When the switches Q1 and Q6 are turned on (when the switches Q1 and Q6 are on and the switches Q2 and Q5 are off), the current flows from the high-voltage battery BH to the primary coil Lp1, and the current flows from the secondary coil Lp2 through the switch Q6, the smoothing coil Lo, and the smoothing capacitor Co to the low-voltage battery BL. When the switch Q2 is turned on (when the switches Q1 and Q6 are off and the switches Q2 and Q5 are on), the current flows from the primary coil Lp1 through the switch Q2 to the capacitor Cs, and the saturation state of the transformer T is relieved. In addition, on the low-voltage battery BL side, the current flows from the switch Q5 through the smoothing coil Lo and the smoothing capacitor Co to the low-voltage battery BL. At this time, the voltage input to the detection circuit 4 is a voltage greater than 2.5 [V] and a voltage equal to or lower than 5 [V], and the detection circuit 4 detects the forward current flowing in the smoothing coil Lo.

[0108] In Figure 8In the power converter 1 shown, the voltage applied to the detection capacitor Cd can also be increased by increasing the winding turn ratio n. Therefore, in the detection circuit 4, when converting the voltage across the detection capacitor Cd from an analog value to a digital value, it is less susceptible to quantization errors, and the current detection accuracy can be improved. In addition, in Figure 8 the power converter 1 shown, it is not necessary to correct the current iL after detecting the current iL flowing through the smoothing coil Lo. Therefore, an increase in the detection time of the current iL can be suppressed.

Claims

1. A power converter comprising a coil, characterized in that: have: A detection winding, which is magnetically coupled to the coil; a detection resistor and a detection capacitor, wherein the detection resistor and the detection capacitor are connected in series with each other and connected in parallel with the detection winding; as well as A detection circuit detects a current flowing through the coil based on a voltage across the detection capacitor.

2. The power converter according to claim 1, characterized in that The coil is a smoothing coil that smoothes the current flowing to the power converter.

3. The power converter according to claim 2, characterized in that: The smooth coil has a core, The detection winding is wound around the core.

4. The power converter according to claim 3, characterized in that: The core has a gap.

5. The power converter according to claim 1, characterized in that When the number of turns of the coil is N1 and the number of turns of the detection winding is N2, N2 / N1≤10.

6. The power converter according to claim 1, characterized in that having two deviation resistors connected in series with each other and connected between the constant voltage source and the reference potential of the detection circuit, The two offset resistors cause the voltage across both ends of the detection capacitor to deviate from a potential difference between a potential at a connection point between the two offset resistors and a reference potential of the detection circuit.

7. The power converter according to claim 2, characterized in that The smoothing coil is arranged on at least one main surface of a substrate on which the power converter is mounted. The detection winding is arranged in parallel with the smoothing coil in the thickness direction of the substrate.

8. The power converter according to claim 7, characterized in that: The substrate is a multi-layer substrate, The detection winding is arranged as a wiring pattern on an inner layer of the substrate.

9. A current detection circuit for detecting a current flowing through a coil provided in a power converter, characterized in that: have: A detection winding, which is magnetically coupled to the coil; a detection resistor and a detection capacitor, the detection resistor and the detection capacitor are connected in series with each other and connected in parallel with the detection winding; as well as, A detection circuit detects a current flowing through the coil based on a voltage across the detection capacitor.

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