Power converter and current detection circuit

Abstract

To suppress the manufacturing cost of a power converter, while enhancing the accuracy of detecting currents flowing in a coil of the power converter.SOLUTION: A power converter 1 with a smooth coil Lo includes: a detection coil Ld magnetically coupled to the smooth coil Lo; a detection resistor Rd and a detection capacitor Cd connected in series with each other and connected to the detection coil Ld in parallel; and a detection circuit 2 for detecting a current flowing in the smooth coil Lo on the basis of the dual-end voltages of the detection capacitor Cd.SELECTED DRAWING: Figure 1

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, 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 based on a voltage drop of a DC resistance component of the coil obtained from the voltage across the detection capacitor, the current flowing through the coil is detected, and a detection circuit that corrects the detected current based on an error between the voltage across the detection capacitor and the voltage drop is provided. 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 offset the reference potential of the detection circuit to match the voltage across the detection capacitor, or to offset the voltage across the detection capacitor to match the reference potential of the detection circuit. Therefore, there is a risk that the manufacturing cost will increase due to adding a function to offset the reference potential of the detection circuit or the voltage across the detection capacitor to the detection circuit. In addition, since the voltage drop is a relatively small value, when converting the voltage drop from an analog value to a digital value in the detection circuit, it is easily affected by quantization error, and there is a risk that the current detection accuracy will decrease.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[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 that are connected in series with each other and connected in parallel to the detection winding, and a detection circuit that detects the current flowing through the coil based on the voltage across the detection capacitor.

[0007] Thus, since the detection winding is magnetically coupled to the coil, the coil and the detection capacitor can be electrically separated (insulated) from each other, and the reference potential of the detection capacitor can be set arbitrarily 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 offsetting the reference potential of the detection circuit or the voltage across the detection capacitor. As a result, an increase in the manufacturing cost of the power converter can be suppressed because there is no need to provide a function for offsetting the reference potential of the detection circuit or the voltage across the detection capacitor. Also, by increasing the winding number ratio of the detection winding with respect to the coil, the voltage applied to the detection capacitor can be increased, so that it is possible to make it difficult to be affected by quantization error when converting the voltage across the detection capacitor from an analog value to a digital value in the detection circuit, and the current detection accuracy can be improved.

[0008] Further, the coil may be a smoothing coil that smooths the current flowing through the power converter.

[0009] Further, the smoothing coil may have a core, and the detection winding may be wound around the core.

[0010] Further, the core may have a gap.

[0011] Also, when the number of turns of the coil is N1 and the number of turns of the detection winding is N2, N2 / N1≦10 may be satisfied.

[0012] Further, the power converter includes 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 are configured to offset the voltage across the detection capacitor by the potential difference between the potential of the connection point of the two offset resistors and the reference potential of the detection circuit.

[0013] Thereby, among the voltages input to the detection circuit, the forward current flowing through the coil can be detected based on the voltage higher than the potential of the connection point of the two offset resistors, and among the voltages input to the detection circuit, the reverse current flowing through the coil can be detected based on the voltage lower than the potential of the connection point of the two offset resistors.

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

[0015] Further, the substrate is a multilayer substrate, and the detection winding may be arranged as a wiring pattern in the inner layer of the substrate.

[0016] Also, a current detection circuit according to one aspect of the present invention is a current detection circuit that detects a current flowing through a coil provided in a power converter, and includes a detection winding magnetically coupled to the coil, and a detection resistor and a detection capacitor connected in series with each other and connected in parallel to the detection winding. The detection circuit detects a current flowing through the coil based on the voltage across the detection capacitor.

[0017] Thus, since the detection winding is magnetically coupled to the coil, the coil and the detection capacitor can be electrically separated (insulated) from each other, and the reference potential of the detection capacitor can be set arbitrarily 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 offsetting the reference potential of the detection circuit or the voltage across the detection capacitor. As a result, since there is no need to provide a function for offsetting the reference potential of the detection circuit or the voltage across the detection capacitor, an increase in the manufacturing cost of the power converter can be suppressed. Also, by increasing the winding number ratio of the detection winding to the coil, the voltage applied to the detection capacitor can be increased, so that when converting the voltage across the detection capacitor from an analog value to a digital value in the detection circuit, the influence of quantization error can be made less likely to occur, and the current detection accuracy can be improved.

Advantages of the Invention

[0018] According to the present invention, it is possible to improve the detection accuracy of the current flowing through the coil provided in the power converter while suppressing the manufacturing cost of the power converter.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0020] The embodiments will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing an example of the power converter in the embodiment.

[0021] The power converter 1 shown in FIG. 1 is an active clamp forward converter, which converts the DC power output from the power supply B into a predetermined DC power and supplies it to the load Load.

[0022] 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. The switches Q1 and Q2 are constituted by, 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 terminal of diode Do1 is connected to the cathode terminal of diode Do2 and is 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.

[0023] The control circuit 2 is composed of, for example, a CPU (Central Processing Unit), a multi-core CPU, or a programmable device (such as an FPGA (Field Programmable Gate Array) or a PLD (Programmable Logic Device)).

[0024] Also, when the control circuit 2 converts the DC power output from the power supply B into a predetermined DC power and supplies it to the load Load, the switch Q1 and Q2 are 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.

[0025] First, when the switch Q1 is turned on (when the switch Q1 is on and the switch Q2 is off), current flows from the power supply B to the primary coil Lp1, and current flows from the secondary coil Lp2 to the load Load through the diode Do1, the smoothing coil Lo, and the smoothing capacitor Co.

[0026] Next, when the switch Q1 is turned off (when the switches Q1 and Q2 are off (dead time)), current flows from the primary coil Lp1 to the capacitor Cp, and the capacitor Cp is charged. 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, current flows from the primary coil Lp1 through the parasitic diode of the switch Q2 to the capacitor Cs, and the capacitor Cs is charged. Also, on the load Load side, current continues to flow from the diode Do1 through the smoothing coil Lo and the smoothing capacitor Co to the load Load. Note that since the energy stored in the primary coil Lp1 decreases due to the charging of the capacitors Cp and Cs, the saturation state of the transformer T is alleviated. Also, when the switch Q1 is turned off, the voltage across the capacitor Cp is 0 [V], so the switching loss is reduced.

[0027] Next, when switch Q2 turns on (when switch Q1 is off and switch Q2 is on), current flows from primary coil Lp1 through switch Q2 to capacitor Cs, and capacitor Cs is charged. Also, on the load side, current flows from diode Do2 through smoothing coil Lo and smoothing capacitor Co to load Load. Note that since the energy stored in primary coil Lp1 further decreases due to the charging of capacitor Cs, the saturation state of transformer T is further alleviated. Also, when switch Q2 turns on, current flows through the parasitic diode of switch Q2, so the switching loss is reduced. And during the on-period of switch Q2, the direction of the current reverses and capacitor Cs discharges.

[0028] Next, when switch Q2 turns off (when switches Q1 and Q2 are off (dead time)), current flows from capacitor Cp through primary coil Lp1 to power supply B, and capacitor Cp is discharged. After the discharge of capacitor Cp, current flows from the parasitic diode of switch Q1 through primary coil Lp1 to power supply B. Also, on the load side, current continues to flow from diode Do2 through smoothing coil Lo and smoothing capacitor Co to load Load.

[0029] Thereafter, the on and off of switches Q1 and Q2 are alternately repeated. Note that when switch Q1 turns on, current flows through the parasitic diode of switch Q1, so the switching loss is reduced.

[0030] 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.

[0031] The detection winding Ld is magnetically coupled to the smoothing coil Lo by being wound around the core Cre of the smoothing coil Lo. 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 preferably, 1 ≦ N2 / N1 ≦ 10. By making the winding ratio n relatively large in this way, the voltage applied to the detection capacitor Cd can be increased. 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 make it less susceptible to the influence of quantization error and improve the current detection accuracy.

[0032] The detection resistor Rd and the detection capacitor Cd are connected in series with each other and connected in parallel to 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 (for example, the ground of the power converter 1).

[0033] 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).

[0034] 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 operator is s, the voltage VLd across the detection winding Ld is VLd = Vc + Vr Here, VLd = n×VL = s×n×L×iL, Vc = is / (s×C), and Vr = R×is. Therefore, s×n×L×iL = is / (s×C) + R×is It is rewritten as. Solving this equation for is gives is=(s×n×L) / (1 / (s×C)+R)×iL Since it is Vr=R×is=R×(s×n×L) / (1 / (s×C)+R)×iL It can be rewritten as. Therefore, the voltage Vc across the detection capacitor Cd can be expressed as in the following Equation 1.

[0035] 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

[0036] 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 smaller than the switching frequency of the power converter 1, the condition C×R>>>1 can be obtained. Then, since the "1" in the denominator of the above Equation 1 can be ignored, the above Equation 1 can be transformed into the following Equation 2.

[0037] Vc=(n×L×iL) / (C×R)···Equation 2

[0038] 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. Note that the winding turns ratio n, the inductance value L, the capacitance value C, and the resistance value R are arbitrary values obtained in advance.

[0039] According to the power converter 1 of the embodiment in this way, since the detection winding Ld is magnetically coupled to the smoothing coil Lo, the smoothing coil Lo and the detection capacitor Cd can be electrically separated (insulated) from each other, and the reference potential of the detection capacitor Cd can be set arbitrarily 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 offsetting the reference potential of the detection circuit 4 or the voltage across the detection capacitor Cd. As a result, since there is no need to provide a function for offsetting the reference potential of the detection circuit 4 or the voltage across the detection capacitor Cd, an increase in the manufacturing cost of the power converter 1 can be suppressed. Further, since it is not necessary to correct the current iL after detecting the current iL flowing through the smoothing coil Lo, an increase in the detection time of the current iL can be suppressed.

[0040] Note that 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 ratio n indicates 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 indicates the inductance value of the primary coil Lp1 or the secondary coil Lp2.

[0041] Here, FIGS. 2A to 2D are diagrams showing an example of the smoothing coil Lo, the detection winding Ld, and the core Cre. FIG. 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. FIG. 2B is a cross-sectional view of the multilayer substrate Sb, the smoothing coil Lo, and the detection winding Ld. FIG. 2C shows an example of the core Cre, and FIG. 2D shows another example of the core Cre.

[0042] The smoothing coil Lo shown in FIGS. 2A and 2B is composed of C-shaped plate conductors L1 and L2 of the alphabet. One plate 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 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 conductor L1 is connected to a wiring pattern on one main surface of the multilayer substrate Sb via solder or the like, the other terminal of the plate conductor L1 is connected to one terminal of the plate conductor L2 via a conductor in the multilayer substrate Sb, and the other terminal of the plate conductor L2 is connected to a wiring pattern on the other main surface of the multilayer substrate Sb via solder or the like, so that they are connected in series to form a two-turn smoothing coil Lo. Note that the smoothing coil Lo may be composed of only the plate conductor L1 or the plate 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.

[0043] Also, the detection winding Ld shown in FIG. 2B is a multilayer 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 plate thickness direction (Z direction) of the multilayer substrate Sb. In FIG. 2B, the detection winding Ld is formed in a spiral wiring pattern with four turns, but the number of turns is not limited to four turns. Note that the detection winding Ld may be arranged on at least one main surface of the multilayer substrate Sb. That is, the detection winding Ld is arranged side by side with the smoothing coil Lo in the plate thickness direction of the multilayer substrate Sb. Also, the detection winding Ld is not limited to a configuration in which it is arranged in one inner layer of the multilayer substrate Sb, and may be configured by forming patterns in a plurality of inner layers and connecting the patterns of each layer in series. Also, it may be composed of a conducting wire or the like and is not limited to a wiring pattern. Also, the substrate on which the power converter 1 is mounted does not have to be composed of a multilayer substrate.

[0044] In addition, the core Cre shown in Fig. 2A is composed of a magnetic body Cre1 of alphabetical E type and a magnetic body Cre2 of alphabetical I type. Three through-holes H1 to H3 are provided side by side in the Y direction in the multilayer substrate Sb. Among the through-holes H1 to H3, the through-hole H2 is provided inside the smoothing coil Lo, and the through-holes H1 and H3 are provided outside the smoothing coil Lo. The core Cre is formed by three protrusions of the magnetic body Cre1 passing through the through-holes H1 to H3 and being joined to the magnetic body Cre2.

[0045] Note that, as shown in Fig. 2C, when the magnetic body Cre1 and the magnetic body Cre2 are connected to each other, the core Cre may be provided with a gap AG by shaving at least one tip of the three protrusions of the magnetic body Cre1 so as not to contact the magnetic body Cre2.

[0046] Alternatively, as shown in Fig. 2D, the core Cre may be provided with a gap AG by connecting the three protrusions of the magnetic body Cre1 and the magnetic body Cre2 via a spacer S.

[0047] In addition, the core Cre may not be provided with a gap.

[0048] 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.

[0049] The power converter 1 of the embodiment is not limited to an active clamp forward converter, and may be composed of other converters.

[0050] <Modification 1> Fig. 3 is a diagram showing Modification 1 of the power converter 1 in the embodiment. In Fig. 3, the same components as those shown in Fig. 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0051] The power converter 1 shown in Fig. 3 is a non-insulated step-down converter, which converts the DC power output from the power supply B into a predetermined DC power and supplies it to the load Load.

[0052] That is, the power converter 1 shown in FIG. 3 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, and the source terminal of the switch Q1 is connected to the cathode terminal of the diode Do2 and is also 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. Note that since the configuration and operation of the current detection circuit 3 shown in FIG. 3 are the same as those of the current detection circuit 3 shown in FIG. 1, the description thereof is omitted. Also, it is assumed that the voltage across the load Load is lower than the voltage across the power supply B, and even if the load Load is constituted by a battery, no current flows from the load Load to the power supply B through the parasitic diode of the switch Q1.

[0053] Also, when the control circuit 2 shown in FIG. 3 converts the DC power output from the power supply B into a predetermined DC power and supplies it to the load Load, the control circuit 2 repeatedly turns the switch Q1 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 Q1 turns on, current flows from the power supply B to the load Load through the switch Q1, the smoothing coil Lo, and the smoothing capacitor Co. Also, when the switch Q1 turns off, current continues to flow from the diode Do2 to the load Load through the smoothing coil Lo and the smoothing capacitor Co.

[0054] Also in the power converter 1 shown in FIG. 3, when detecting the current flowing through the smoothing coil Lo, there is no need to provide a function of offsetting the reference potential of the detection circuit 4 or the voltage across the detection capacitor Cd. Therefore, the increase in the manufacturing cost of the power converter 1 can be suppressed accordingly. Also in the power converter 1 shown in FIG. 3, by increasing the winding ratio n, the voltage applied to the detection capacitor Cd can be increased. 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 make it less susceptible to the influence of quantization error and improve the current detection accuracy. Also in the power converter 1 shown in FIG. 3, after detecting the current iL flowing through the smoothing coil Lo, there is no need to correct the current iL. Therefore, the increase in the detection time of the current iL can be suppressed.

[0055] <Modification 2> FIG. 4 is a diagram showing a second modification of the power converter 1 in the embodiment. In FIG. 4, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0056] The power converter 1 shown in FIG. 4 is an isolated forward converter, which converts the DC power output from the power supply B into a predetermined DC power and supplies it to the load Load.

[0057] That is, the power converter 1 shown in FIG. 4 includes a switch Q1, a transformer T, diodes Do1 and 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. Note that the circuit configuration for resetting the transformer T in the isolated forward converter shown in FIG. 4 is not shown. Also, since the configuration and operation of the current detection circuit 3 are the same as those of the current detection circuit 3 shown in FIG. 1, the description thereof is omitted.

[0058] Also, when the control circuit 2 shown in FIG. 4 converts the DC power output from the power supply B into a predetermined DC power and supplies it to the load Load, the switch Q1 is 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 Q1 turns 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 to the load Load through the diode Do1, the smoothing coil Lo, and the smoothing capacitor Co. When the switch Q1 turns off, current continues to flow from the diode Do2 to the load Load through the smoothing coil Lo and the smoothing capacitor Co.

[0059] Also in the power converter 1 shown in FIG. 4, when detecting the current flowing through the smoothing coil Lo, there is no need to provide a function of offsetting the reference potential of the detection circuit 4 or the voltage across the detection capacitor Cd. Therefore, the increase in the manufacturing cost of the power converter 1 can be suppressed accordingly. Also in the power converter 1 shown in FIG. 4, by increasing the turns ratio n, the voltage applied to the detection capacitor Cd can be increased. Therefore, when converting the voltage across the detection capacitor Cd from an analog value to a digital value in the detection circuit 4, the influence of quantization error can be made less likely to occur, and the current detection accuracy can be improved. Also in the power converter 1 shown in FIG. 4, after detecting the current iL flowing through the smoothing coil Lo, there is no need to correct the current iL. Therefore, the increase in the detection time of the current iL can be suppressed.

[0060] <Modification Example 3> FIG. 5 is a diagram showing a modification example 3 of the power converter 1 in the embodiment. In FIG. 5, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0061] The power converter 1 shown in FIG. 5 is an isolated push-pull converter, which converts the DC power output from the power supply B into a predetermined DC power and supplies it to the load Load.

[0062] That is, the power converter 1 shown in FIG. 5 includes switches Q1 and Q2, transformer T, diodes Do1 and Do2, smoothing coil Lo, smoothing capacitor Co, control circuit 2, and 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 primary coil Lp1. The positive terminal of power supply B is connected to the center tap of primary coil Lp1. The cathode terminal of diode Do1 is connected to the cathode terminal of diode Do2 and is connected to one terminal of smoothing capacitor Co and one terminal of load Load via smoothing coil Lo, and 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. Note that since the configuration and operation of current detection circuit 3 shown in FIG. 5 are the same as those of current detection circuit 3 shown in FIG. 1, the description thereof is omitted.

[0063] Also, when the control circuit 2 shown in FIG. 5 converts the DC power output from power supply B into a predetermined DC power and supplies it to load Load, it alternately and repeatedly turns on and off switches Q1 and Q2 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. When switch Q2 turns off and switch Q1 turns on, current flows from power supply B to primary coil Lp1 through the center tap of primary coil Lp1, and current flows from secondary coil Lp2 to load Load through diode Do1, smoothing coil Lo, and smoothing capacitor Co. When switch Q1 turns off and switch Q2 turns on, current flows from power supply B to primary coil Lp1 through the center tap of primary coil Lp1, and current flows from secondary coil Lp2 to load Load through diode Do2, smoothing coil Lo, and smoothing capacitor Co.

[0064] Also in the power converter 1 shown in FIG. 5, when detecting the current flowing through the smoothing coil Lo, there is no need to provide a function for offsetting the reference potential of the detection circuit 4 or the voltage across the detection capacitor Cd. Therefore, the increase in the manufacturing cost of the power converter 1 can be suppressed accordingly. Also in the power converter 1 shown in FIG. 5, by increasing the winding turns ratio n, the voltage applied to the detection capacitor Cd can be increased. 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 make it less susceptible to the influence of quantization error and improve the current detection accuracy. Also in the power converter 1 shown in FIG. 5, after detecting the current iL flowing through the smoothing coil Lo, there is no need to correct the current iL. Therefore, the increase in the detection time of the current iL can be suppressed.

[0065] <Modification Example 4> FIG. 6 is a diagram showing a modification example 4 of the power converter 1 in the embodiment. In FIG. 6, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0066] The power converter 1 shown in FIG. 6 is an isolated half-bridge converter, which converts the DC power output from the power supply B into a predetermined DC power and supplies it to the load Load.

[0067] That is, the power converter 1 shown in FIG. 6 includes switches Q1 and Q2, a capacitor Cr, a transformer T, diodes Do1 and Do2, a smoothing coil Lo, a smoothing capacitor Co, a control circuit 2, and a 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. Note that since the configuration and operation of the current detection circuit 3 shown in FIG. 6 are the same as those of the current detection circuit 3 shown in FIG. 1, the description thereof is omitted.

[0068] Also, when converting the DC power output from power supply B into a predetermined DC power and supplying it to load Load, the control circuit 2 shown in FIG. 6 alternately and repeatedly turns on and off switches Q1 and Q2 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.

[0069] First, when switch Q1 turns 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.

[0070] Next, when switch Q1 turns 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.

[0071] Next, when switch Q2 turns on (when switch Q1 is off and switch Q2 is 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. Note that when switch Q2 turns on, current is flowing through the parasitic diode of switch Q2, so switching loss is reduced.

[0072] Next, when switch Q2 turns off (when switches Q1 and Q2 are 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.

[0073] Thereafter, the on and off of switches Q1 and Q2 are alternately repeated. Note that when switch Q1 turns on, current is flowing through the parasitic diode of switch Q1, so switching loss is reduced.

[0074] Also in the power converter 1 shown in FIG. 6, when detecting the current flowing through the smoothing coil Lo, there is no need to provide a function of offsetting the reference potential of the detection circuit 4 or the voltage across the detection capacitor Cd. Therefore, the increase in the manufacturing cost of the power converter 1 can be suppressed accordingly. Also in the power converter 1 shown in FIG. 6, by increasing the winding turns ratio n, the voltage applied to the detection capacitor Cd can be increased. 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 make it less susceptible to the influence of quantization error and improve the current detection accuracy. Also in the power converter 1 shown in FIG. 6, after detecting the current iL flowing through the smoothing coil Lo, there is no need to correct the current iL. Therefore, the increase in the detection time of the current iL can be suppressed.

[0075] <Modification Example 5> FIG. 7 is a diagram showing Modification Example 5 of the power converter 1 in the embodiment. In FIG. 7, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0076] The power converter 1 shown in FIG. 7 is an isolated full-bridge converter that converts the DC power output from the power source B into a predetermined DC power and supplies it to the load Load.

[0077] That is, the power converter 1 shown in FIG. 7 includes switches Q1 to Q4, a transformer T, diodes Do1 and Do2, a smoothing coil Lo, a smoothing capacitor Co, a control circuit 2, and a current detection circuit 3. Note that the switches Q3 and Q4 are constituted by, for example, MOSFETs. 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, and 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 terminal of the diode Do1 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, and 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. Note that since the configuration and operation of the current detection circuit 3 shown in FIG. 7 are the same as those of the current detection circuit 3 shown in FIG. 1, the description thereof is omitted.

[0078] Also, when the control circuit 2 shown in FIG. 7 converts the DC power output from the power supply B into a predetermined DC power and supplies it to the load Load, after turning on switches Q1 and Q4 and turning off switches Q2 and Q3 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, it repeats turning off switches Q1 and Q4 and turning on switches Q2 and Q3. When switches Q1 and Q4 are turned on (when switches Q1 and Q4 are on and switches Q2 and Q3 are off), current flows from the positive terminal of the power supply B through switches Q1, primary coil Lp1, and switch Q4 to the negative terminal of the power supply B, and current flows from the secondary coil Lp2 through diode Do1, smoothing coil Lo, and smoothing capacitor Co to the load Load. When switches Q2 and Q3 are turned on (when switches Q1 and Q4 are off and switches Q2 and Q3 are on), current flows from the positive terminal of the power supply B through switch Q3, primary coil Lp1, and switch Q2 to the negative terminal of the power supply B, and current flows from the secondary coil Lp2 through diode Do2, smoothing coil Lo, and smoothing capacitor Co to the load Load.

[0079] Also in the power converter 1 shown in FIG. 7, when detecting the current flowing through the smoothing coil Lo, there is no need to provide a function of offsetting the reference potential of the detection circuit 4 or the voltage across the detection capacitor Cd, so the increase in the manufacturing cost of the power converter 1 can be suppressed accordingly. Also in the power converter 1 shown in FIG. 7, by increasing the turns ratio n, the voltage applied to the detection capacitor Cd can be increased, so when converting the voltage across the detection capacitor Cd from an analog value to a digital value in the detection circuit 4, the influence of quantization error can be made less likely to occur, and the current detection accuracy can be improved. Also in the power converter 1 shown in FIG. 7, after detecting the current iL flowing through the smoothing coil Lo, there is no need to correct the current iL, so the increase in the detection time of the current iL can be suppressed.

[0080] <Modification Example 6> FIG. 8 is a diagram showing a modification 6 of the power converter 1 in the embodiment. In FIG. 8, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0081] The power converter 1 shown in FIG. 8 is an active clamp forward converter, which 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.

[0082] That is, the power converter 1 shown in FIG. 8 includes relays Re1 and Re2, a smoothing capacitor Cb, switches Q1 and Q2, a capacitor Cs, a transformer T, switches Q5 and Q6, a smoothing coil Lo, a smoothing capacitor Co, a control circuit 2, and a current detection circuit 3. The switches Q5 and Q6 are constituted by, for example, MOSFETs. The drain terminal of the switch Q1 is connected to the source terminal of the switch Q2 and one terminal of the primary coil Lp1 of the transformer T. The source terminal of the switch Q1 is connected to the negative terminal of the power supply B via the relay Re1 and is also connected to one terminal of the smoothing capacitor Cb. The drain terminal of the switch Q2 is connected to the positive terminal of the power supply B via the capacitor Cs and the relay Re2, is also connected to the other terminal of the primary coil Lp1 via the capacitor Cs, and is also connected to the other terminal of the smoothing capacitor Cb via the capacitor Cs. The drain terminal of the switch Q5 is connected to the drain terminal of the switch Q6 and is also connected to one terminal of the smoothing capacitor Co and the positive terminal of the low-voltage battery BL via the smoothing coil Lo. The source terminal of the switch Q5 is connected to one terminal of the secondary coil Lp2 of the transformer T, the other terminal of the smoothing capacitor Co, and the negative terminal of the low-voltage battery BL. The source terminal of the switch Q6 is connected to the other terminal of the secondary coil Lp2.

[0083] The current detection circuit 3 shown in FIG. 8 includes a detection winding Ld, a detection resistor Rd, a detection capacitor Cd, a detection circuit 4, and offset resistors R1 and R2.

[0084] The detection winding Ld is wound around the core Cre of the smoothing coil Lo.

[0085] The detection resistor Rd and the detection capacitor Cd are connected in series with each other and are connected in parallel to the detection winding Ld.

[0086] The offset 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. Also, the connection point of the offset resistors R1 and R2 is connected to the connection point of the detection winding Ld and the detection capacitor Cd, and the total voltage of the voltage across both ends of the detection capacitor Cd and the voltage across both ends of the offset resistor R2 is input to the detection circuit 4. That is, by the offset resistors R1 and R2, the voltage across both ends of the detection capacitor Cd is offset by the potential difference between the potential of the connection point of the offset resistors R1 and R2 and the reference potential of the detection circuit 4, and the voltage across both ends of the detection capacitor Cd after the offset is input to the detection circuit 4. The detection circuit 4 obtains the current iL flowing through the smoothing coil Lo by substituting the voltage Vc across both ends of the detection capacitor Cd after the offset into the above formula 2. Thereby, among the voltages input to the detection circuit 4, the forward current flowing through the smoothing coil Lo can be detected based on the voltage higher than the potential of the connection point of the offset resistors R1 and R2, and among the voltages input to the detection circuit 4, the reverse current flowing through the smoothing coil Lo can be detected based on the voltage lower than the potential of the connection point of the offset resistors R1 and R2.

[0087] In the power converter 1 shown in FIG. 8, before startup, the potential of the smoothing capacitor Cb is zero. Before the normal operation in which the control circuit 2 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, the smoothing capacitor Cb is pre-charged with the power supplied from the low-voltage battery BL with the relays Re1 and Re2 cut off, and then the relays Re1 and Re2 are turned on to supply power from the high-voltage battery BH to the low-voltage battery BL. Thereby, it is possible to suppress a relatively large inrush current from flowing from the high-voltage battery BH to the smoothing capacitor Cb when the relays Re1 and Re2 transition from the cut-off state to the conduction state.

[0088] For example, assume that the direction of the current flowing from the high-voltage battery BH to the low-voltage battery BL is the forward direction, and the direction of the current flowing from the low-voltage battery BL to the high-voltage battery BH is the reverse direction. Also, assume that the input voltage range of the AD conversion of the detection circuit 4 is 0 [V] to 5 [V], and the potential of the connection point of the offset resistors R1 and R2 is 2.5 [V]. Further, let the voltage across both ends of the detection capacitor Cd after offset be Vc.

[0089] In this case, first, the control circuit 2 shuts off the relays Re1 and Re2, and keeps the switch Q1 off at all times so that the reverse current detected by the current detection circuit 3 becomes the target current, and repeatedly turns on and off the switches Q2, Q5, and Q6. When the switch Q6 turns on (when the switches Q1, Q2, and Q5 are off and the switch Q6 is on), current flows from the low-voltage battery BL to the secondary coil Lp2, and current flows from the primary coil Lp1 to the smoothing capacitor Cb. At this time, the current in the smoothing coil Lo is in the reverse direction. Also, when the switch Q6 turns off (when the switches Q1 and Q6 are off and the switches Q2 and Q5 are on), the transformer T resets, and the reverse current in the smoothing coil Lo increases. That is, also in this case, the current in the smoothing coil Lo is in the reverse direction. Therefore, the voltage input to the detection circuit 4 is a voltage less than 2.5 [V] and a voltage of 0 [V] or more, and the detection circuit 4 detects the reverse current flowing through the smoothing coil Lo. Thereby, the smoothing capacitor Cb can be charged before the relays Re1 and Re2 are turned on. Note that the switch Q1 may be turned on / off in synchronization with the switch Q6.

[0090] 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.

[0091] Then, when the voltage of the smoothing capacitor Co reaches the target voltage and the forward current detected by the current detection circuit 3 reaches the target current, 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. When switches Q1 and Q6 turn on (when switches Q1 and Q6 are on and switches Q2 and Q5 are off), current flows from the high-voltage battery BH to the primary coil Lp1, and from the secondary coil Lp2, through switches Q6, the smoothing coil Lo, and the smoothing capacitor Co, to the low-voltage battery BL. When switch Q2 turns on (when switches Q1 and Q6 are off and switches Q2 and Q5 are on), current flows from the primary coil Lp1, through switch Q2, to the capacitor Cs, and the saturation state of the transformer T is alleviated. Also, on the low-voltage battery BL side, current flows from 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 greater than 2.5 [V] and less than or equal to 5 [V], and the detection circuit 4 detects the forward current flowing through the smoothing coil Lo.

[0092] Also in the power converter 1 shown in FIG. 8, by increasing the turns ratio n, the voltage applied to the detection capacitor Cd can be increased. Therefore, when converting the voltage across the detection capacitor Cd from an analog value to a digital value in the detection circuit 4, the influence of quantization error can be reduced, and the current detection accuracy can be improved. Also, in the power converter 1 shown in FIG. 8, after detecting the current iL flowing through the smoothing coil Lo, it is not necessary to correct the current iL, so an increase in the detection time of the current iL can be suppressed.

Explanation of Symbols

[0093] 1 Power converter 2 Control circuit 3 Current detection circuit 4 Detection circuit B Power supply Load Load Cs, Cp Capacitor Q1~Q6 Switch T Transformer Lo Smoothing Coil Co, Cb Smoothing Capacitor Ld Detection Coil Rd Detection Resistor Cd Detection Capacitor R1, R2 Offset Resistors Re1, Re2 Relays BH High-Voltage Battery BL Low-Voltage Battery

Claims

1. A power converter comprising a coil, a detection winding 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 to the detection winding, and a detection circuit that detects a current flowing through the coil based on a voltage across the detection capacitor, A power converter comprising the above.

2. The power converter according to Claim 1, wherein the coil is a smoothing coil that smooths a current flowing through the power converter A power converter.

3. The power converter according to Claim 2, wherein the smoothing coil has a core, and the detection winding is wound around the core A power converter.

4. The power converter according to Claim 3, wherein the core has a gap A power converter.

5. The power converter according to Claim 1, wherein when the number of turns of the coil is N1 and the number of turns of the detection winding is N2, N2 / N1 ≤ 10 A power converter.

6. The power converter according to Claim 1, comprising two offset resistors that are connected in series with each other and are connected between a constant voltage source and a reference potential of the detection circuit, wherein the two offset resistors offset a voltage across the detection capacitor by a potential difference between a potential at a connection point of the two offset resistors and the reference potential of the detection circuit A power converter.

7. The power converter according to Claim 2, wherein the smoothing coil is disposed on at least one main surface of a substrate on which the power converter is mounted, and the detection winding is disposed side by side with respect to the smoothing coil in a thickness direction of the substrate A power converter.

8. The power converter according to Claim 7, wherein the substrate is a multilayer substrate, and the detection winding is disposed as a wiring pattern in an inner layer of the substrate A power converter.

9. A current detection circuit that detects a current flowing through a coil provided in a power converter, a detection winding 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 to the detection winding, and a detection circuit that detects a current flowing through the coil based on a voltage across the detection capacitor, A current detection circuit comprising the above.

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