Power circuit

Abstract

The present invention provides a power supply circuit that can detect the timing at which the inductor current reaches a predetermined value without using an auxiliary coil. [Solution] A power supply circuit that generates a target output voltage from an AC voltage, comprising: a full-wave rectifier circuit for rectifying the AC voltage; first and second inductors to which the full-wave rectified voltage is applied; a first transistor for controlling the first inductor current flowing through the first inductor; a second transistor for controlling the second inductor current flowing through the second inductor; a first common-mode choke having a first coil connected between the positive side of the full-wave rectifier circuit and the first inductor, and a second coil connected between the negative side of the full-wave rectifier circuit and the low-potential side of the first transistor; a first resistor for detecting the first inductor current; a second resistor for detecting the second inductor current; and a switching control circuit for controlling the switching of the first and second transistors based on the first and second inductor currents and the output voltage.

Description

Technical Field

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

Background Art

[0002] Among power factor correction circuits, there is an interleaved power factor correction circuit configured by a plurality of circuit groups. Some power factor correction circuits operate in a critical mode in which a transistor is turned on when an inductor current reaches a predetermined value (for example, zero). When a plurality of circuit groups perform interleaved operation, there are cases where the inductor current cannot be correctly detected by a resistor provided on each ground line of the plurality of circuit groups. For this reason, there are cases where a transformer having a main coil and an auxiliary coil is used, and detection that the inductor current flowing through the main coil has reached a predetermined value is performed based on the voltage of the auxiliary coil (for example, Patent Documents 1 to 5).

Prior Art Literature

Patent Literature

[0003]

Patent Literature 1

Patent Literature 2

Patent Literature 3

Patent Literature 4

Patent Literature 5

Summary of Invention

Problem to be Solved by Invention

[0004] However, designing a transformer to accommodate changes in the voltage level of full-wave rectified voltage is often complicated. Accordingly, it may sometimes be difficult to detect that the inductor current flowing through the main coil has reached a predetermined value using the voltage of the auxiliary coil.

[0005] The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a power supply circuit that can detect the timing at which the inductor current reaches a predetermined value without using an auxiliary coil. [Means for solving the problem]

[0006] A first aspect of the power supply circuit according to the present invention, which solves the aforementioned problems, is a power supply circuit that generates an output voltage of a target level from an AC voltage, comprising: a full-wave rectifier circuit that rectifies the AC voltage and outputs a full-wave rectified voltage; first and second inductors to which a voltage corresponding to the full-wave rectified voltage is applied; a first transistor that controls the first inductor current flowing through the first inductor; a second transistor that controls the second inductor current flowing through the second inductor; a first common-mode choke having a first coil connected between the positive output node of the full-wave rectifier circuit and the first inductor, and a second coil connected between the negative output node of the full-wave rectifier circuit and the low-potential electrode of the first transistor; a first resistor that detects the first inductor current; a second resistor that detects the second inductor current; and a switching control circuit that controls the switching of the first and second transistors based on the first and second inductor currents detected by the first and second resistors, respectively, and the output voltage.

[0007] A second aspect of the power supply circuit according to the present invention, which solves the aforementioned problems, is a power supply circuit that generates an output voltage of a target level from an AC voltage, comprising: a full-wave rectifier circuit that rectifies the AC voltage and outputs a full-wave rectified voltage; n inductors (n is an integer of 3 or more) to which a voltage corresponding to the full-wave rectified voltage is applied; n transistors that control the inductor current flowing through each of the n inductors; (n-1) common-mode chokes having a first coil connected between the positive output node of the full-wave rectifier circuit and each of the (n-1) inductors, and a second coil connected between the negative output node of the full-wave rectifier circuit and each of the low-potential electrodes of the (n-1) transistors; n resistors that detect the inductor current flowing through each of the n inductors; and a switching control circuit that controls the switching of the n transistors based on the inductor current flowing through each of the n inductors detected by each of the n resistors and the output voltage.

[0008] According to the present invention, it is possible to provide a power supply circuit that can detect the timing at which the inductor current reaches a predetermined value without using an auxiliary coil. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of the configuration of the AC-DC converter 10. [Figure 2] This figure shows an example of the configuration of the power factor correction IC27. [Figure 3] This figure shows an example of the operation of the common mode choke 22a. [Figure 4] This figure shows an example of the operation of the common mode choke 22a. [Figure 5] This figure shows an example of the operation of the common mode choke 22a. [Figure 6] This figure shows an example of electric currents Ipa, Ina, Inb, and Ipb. [Figure 7] This figure shows the simulation results. [Figure 8]It is a diagram illustrating an example configuration of an AC-DC converter 13. [Figure 9] It is a diagram illustrating an example of currents Ipa, Ina, Inb, and Ipb. [Figure 10] It is a diagram illustrating simulation results. [Figure 11] It is a diagram illustrating an example configuration of an AC-DC converter 14. [Figure 12] It is a diagram illustrating an example configuration of an AC-DC converter 15. DETAILED DESCRIPTION OF EMBODIMENTS

[0010] Based on the descriptions of the present specification and the accompanying drawings, at least the following matters will be made clear. In the following description, the same or equivalent components, members, and the like shown in each drawing are denoted by the same reference numerals, and duplicate descriptions may be omitted as appropriate.

[0011] ===== Present Embodiment ===== FIG. 1 is a diagram illustrating an example configuration of an AC-DC converter 10 according to an embodiment of the present invention. The AC-DC converter 10 is a boost chopper-type power supply circuit that generates an output voltage Vout of a target level from an AC voltage Vac of a commercial power supply. The AC-DC converter 10 applies the output voltage Vout to a load 12 to supply electric power thereto. Further, as will be described in detail later, the AC-DC converter 10 includes NMOS transistors 25a and 25b (described later) that are switched to perform interleaved operation, and operates as a power factor correction circuit that operates in critical conduction mode.

[0012] The AC-DC converter 10 includes common-mode chokes 11, 22a, and 22b, a full-wave rectifier circuit 20, capacitors 21 and 30, inductors 23a and 23b, diodes 24a and 24b, NMOS transistors 25a and 25b, resistors 26a, 26b, 31, and 32, and a power factor correction IC 27.

[0013] The common mode choke 11 prevents noise generated by switching of NMOS transistors 25a and 25b (described later) from leaking out to the commercial power supply side. The common mode choke 11 applies an AC voltage Vac, from which common mode noise has been removed, to a full-wave rectifier circuit 20 (described later). The common mode choke 11 includes a coil L1 connected between a node N1 to which the AC voltage Vac is applied and an input node Nin1 of the full-wave rectifier circuit 20, and a coil L2 connected between a node N2 to which the AC voltage Vac is applied and an input node Nin2 of the full-wave rectifier circuit. The common mode choke 11 corresponds to a "third common mode choke". The node N1 corresponds to a "first node", the node N2 corresponds to a "second node", the input node Nin1 corresponds to a "first input node", and the input node Nin2 corresponds to a "second input node".

[0014] The full-wave rectifier circuit 20 performs full-wave rectification on the AC voltage Vac from which ripple components have been removed and outputs the rectified voltage as a full-wave rectified voltage Vrec, which is applied to a capacitor 21 and common mode chokes 22a and 22b via a positive output node No of the full-wave rectifier circuit 20. The AC voltage Vac is, for example, a voltage having an effective value of 140 to 240 V and a frequency of 50 to 60 Hz. Hereinafter, in the present embodiment, voltages are basically potential differences relative to a reference point (GND in FIG. 1), while the AC voltage Vac indicates a voltage between terminals.

[0015] The capacitor 21 smoothes an input voltage Vrec, and the capacitor 30 constitutes a boost chopper circuit together with inductors 23a, 23b and NMOS transistors 25a, 25b. Therefore, the charging voltage of the capacitor 30 becomes a DC output voltage Vout.

[0016] The common mode chokes 22a and 22b, which will be described in detail later, prevent noise from propagating to the commercial power supply side, and match each of currents Ipa and Ipb flowing from the node No to the inductors 23a and 23b with each of currents Ina and Inb flowing from resistors 26a and 26b to a node Ng, respectively.

[0017] The common mode choke 22a has a coil L1a connected between node No and inductor 23a, and a coil L2a connected between the negative output node Ng of the full-wave rectifier circuit 20 and the low-potential electrode of the NMOS transistor 25a. The common mode choke 22a also applies the full-wave rectification voltage Vrec to inductor 23a. The current flowing through coil L1a corresponds to current Ipa, and the current flowing through coil L2a corresponds to current Ina.

[0018] The common mode choke 22b has a coil L1b connected between node No and inductor 23b, and a coil L2a connected between the negative output node Ng of the full-wave rectifier circuit 20 and the low-potential electrode of the NMOS transistor 25b. The common mode choke 22a also applies the full-wave rectification voltage Vrec to inductor 23a. The current flowing through coil L1b corresponds to current Ipb, and the current flowing through coil L2b corresponds to current Inb.

[0019] Furthermore, common mode choke 22a corresponds to the "first common mode choke," and common mode choke 22b corresponds to the "second common mode choke." Also, coils L1a and L1b correspond to the "first coil," and coils L2a and L2b correspond to the "second coil."

[0020] Diodes 24a and 24b each charge capacitor 30 with inductor currents ILa and ILb, respectively, corresponding to the voltages generated across inductors 23a and 23b, during the periods when NMOS transistors 25a and 25b (described later) are off. As a result, an output voltage Vout is generated in capacitor 30.

[0021] Each of the NMOS transistors 25a and 25b controls the inductor currents ILa and ILb flowing through the respective inductors 23a and 23b, respectively, and is a switching element for controlling the power supplied to the load 12 of the AC-DC converter 10. In this embodiment, the NMOS transistors 25a and 25b are N-type MOS (Metal Oxide Semiconductor) transistors, but they may also be bipolar transistors, IGBTs, etc.

[0022] Furthermore, the gate electrode of NMOS transistor 25a is connected to terminal OUT1 of power factor correction IC 27, and the gate electrode of NMOS transistor 25b is connected to terminal OUT2 of power factor correction IC 27. Also, inductor 23a corresponds to the "first inductor," inductor 23b corresponds to the "second inductor," NMOS transistor 25a corresponds to the "first transistor," and NMOS transistor 25b corresponds to the "second transistor." Inductor current ILa corresponds to the "first inductor current," and inductor current ILb corresponds to the "second inductor current."

[0023] Resistors 26a and 26b each detect the inductor currents ILa and ILb flowing through NMOS transistors 25a and 25b, respectively, or the inductor currents ILa and ILb flowing through capacitor 30, respectively. The voltages Vcs1 and Vcs2 generated across resistors 26a and 26b, respectively, according to the inductor currents ILa and ILb, are applied to terminals CS1 and CS2 of power factor correction IC 27, respectively. Resistors 26a and 26b are also provided between the source electrodes of NMOS transistors 25a and 25b and node Ng, respectively.

[0024] Furthermore, as described above, resistors 26a and 26b each detect the inductor currents ILa and ILb, respectively. However, if common-mode chokes 22a and 22b are absent, the inductor currents ILa and ILb merge at capacitor 30 and then are divided according to the impedance of the ground line to which resistors 26a and 26b are provided. As a result, resistors 26a and 26b cannot detect only the inductor currents ILa and ILb, respectively.

[0025] Furthermore, detecting the current by connecting a resistor in series with inductor 23a or inductor 23b is not directly feasible because the voltage across resistors 26a and 26b is less than 0.1V, while the voltage relative to the ground potential, which is the reference potential of the power factor correction IC27 (described later), is generally around 400V. Methods using isolation amplifiers are also available, but these are expensive.

[0026] Furthermore, resistor 26a corresponds to the "first resistor," resistor 26b corresponds to the "second resistor," the source electrode of NMOS transistor 25a corresponds to the "low-potential side electrode of the first transistor," and the source electrode of NMOS transistor 25b corresponds to the "low-potential side electrode of the second transistor."

[0027] The power factor correction IC 27 is an integrated circuit that interleaves and switches NMOS transistors 25a and 25b to improve the power factor of the AC-DC converter 10 while ensuring that the output voltage Vout reaches a target level (e.g., 400V). Specifically, the power factor correction IC 27 controls the switching of NMOS transistors 25a and 25b so that it turns on when the inductor currents ILa and ILb reach predetermined values ​​(e.g., zero amperes) and turns off after a period corresponding to the output voltage Vout has elapsed. The power factor correction IC 27 is also provided with terminals OUT1, OUT2, CS1, CS1g, CS2, CS2g, and FB. In this embodiment, terminals other than OUT1, etc., of the power factor correction IC 27 are omitted for convenience. The power factor correction IC 27 corresponds to a "switching control circuit".

[0028] Furthermore, as shown in Figure 2, the power factor correction IC 27 operates with the ground potential of capacitor 30 as the reference potential, detects the voltage across resistors 26a and 26b, and detects the inductor currents ILa and ILb, respectively. The power factor correction IC 27 also switches the NMOS transistors 25a and 25b based on the inductor currents ILa and ILb, respectively, and the feedback voltage Vfb.

[0029] The power factor correction IC27 is composed of differential amplifier circuits (DIFF) 50, 51, a drive signal output circuit 52, and driver circuits 53, 54.

[0030] Each of the differential amplifier circuits 50 and 51 detects the inductor currents ILa and ILb based on the voltages generated across the respective resistors 26a and 26b.

[0031] The drive signal output circuit 52 outputs drive signals to drive the NMOS transistors 25a and 25b, respectively, based on the detection results of the differential amplifier circuits 50 and 51 and the feedback voltage Vfb (described later). The differential amplifier circuits 50 and 51 and the drive signal output circuit 52 operate based on the voltage Vdd, which is generated internally from the power supply voltage Vcc, with the ground potential of the capacitor 30 as the reference potential.

[0032] Driver circuits 53 and 54 each amplify the respective drive signals from the drive signal output circuit 52, output voltages Vo1 and Vo2 respectively, and switch NMOS transistors 25a and 25b respectively. Driver circuits 53 and 54 use the ground potential of capacitor 30 as their reference potential and operate based on the power supply voltage Vcc.

[0033] The resistors 31 and 32 in Figure 1 form a voltage divider circuit that divides the output voltage Vout, generating the feedback voltage Vfb used when switching the NMOS transistors 25a and 25b. The feedback voltage Vfb generated at the node to which resistors 31 and 32 are connected is applied to terminal FB.

[0034] ==Operation of Common Mode Chokes 22a and 22b== Figures 3-5 show an example of the operation of common mode chokes 22a and 22b. In Figures 3-5, the positive output node No and the negative output node Ng of the full-wave rectifier circuit 20 are connected to the A side electrode, and either the inductor 23a or 23b and either the resistor 26a or 26b are connected to the B side electrode.

[0035] Figure 3 shows an example of magnetic fluxes Φ1 and Φ2 generated in the core 100 of the common mode choke 22a (or common mode choke 22b) when currents I1 and I2 flow from electrode A to electrode B via coils L1a and L2a (or coils L1b and L2b).

[0036] When current I1 flows from side A to side B through coil L1a, a magnetic flux Φ1 is generated within core 100. Similarly, when current I2 flows from side A to side B through coil L2a, a magnetic flux Φ2 is generated within core 100. Since magnetic fluxes Φ1 and Φ2 are generated in the same direction within core 100, the magnetic flux within core 100 strengthens, and as a result, electromotive forces are generated at both ends of coils L1a and L2a, respectively, in a direction that opposes currents I1 and I2. Therefore, the currents I1 and I2 flowing from side A to side B decrease in proportion to the magnetic fluxes Φ1 and Φ2 generated within core 100. In this way, the common mode chokes 22a and 22b can remove the currents flowing in the same direction through coils L1a and L2a.

[0037] Figure 4 shows an example of magnetic fluxes Φ1 and Φ2 generated in the core 100 of the common mode choke 22a (or common mode choke 22b) when current I1 flows from side A to side B through coil L1a (or coil L1b) and current I2 flows from side B to side A through coil L2a (or coil L2b).

[0038] When current I1 flows from side A to side B through coil L1a, a magnetic flux Φ1 is generated within core 100. Similarly, when current I2, with the same value as current I1, flows from side B to side A through coil L2a, a magnetic flux Φ2 of the same magnitude as magnetic flux Φ1 is generated within core 100. Since magnetic fluxes Φ1 and Φ2 are generated in opposite directions within core 100, the magnetic flux within core 100 is canceled out. Therefore, currents I1 and I2 are unaffected because the magnetic flux within core 100 is canceled out. As a result, common mode chokes 22a and 22b have no effect on currents I1 and I2, which have the same value and flow in opposite directions through coils L1a and L2a.

[0039] Figure 5 shows an example of magnetic fluxes Φ1 and Φ2 generated in the core 100 of the common mode choke 22a (or common mode choke 22b) when current I1 flows from side A to side B through coil L1a (or coil L1b) and current I2 flows from side B to side A through coil L2a (or coil L2b).

[0040] When current I1 flows from side A to side B through coil L1a, a magnetic flux Φ1 is generated within core 100. Similarly, when current I2, for example, with a value greater than current I1, flows from side B to side A through coil L2a, a magnetic flux Φ2 is generated within core 100. Since magnetic fluxes Φ1 and Φ2 are generated in opposite directions within core 100, a magnetic flux Φdiff, which is the difference between magnetic fluxes Φ1 and Φ2, is generated within core 100. Because of the magnetic flux Φdiff within core 100, current I1 increases and current I2 decreases. As a result, the common mode chokes 22a and 22b operate to make the currents I1 and I2 flowing in opposite directions through coils L1a and L2a equal in value.

[0041] Therefore, the common-mode choke 22a removes currents Ipa and Ina flowing in the same direction, and operates so that currents Ipa and Ina flowing in different directions have the same value. Similarly, the common-mode choke 22b removes currents Ipb and Inb flowing in the same direction, and operates so that currents Ipb and Inb flowing in different directions have the same value. As a result, the currents flowing through resistors 26a and 26b match the inductor currents ILa and ILb flowing through inductors 23a and 23b of the respective boost chopper circuits. This makes it possible to provide a power supply circuit that can detect the timing at which the inductor current reaches a predetermined value without using an auxiliary coil.

[0042] However, the common-mode chokes 22a and 22b match the AC components of the inductor currents Ipa and Ina, as well as the currents Ipb and Inb. On the other hand, since the electromotive force generated across the coil is proportional to the change in magnetic flux, it does not generate an electromotive force for the DC component that does not involve a change in magnetic flux, and as a result, as shown in Figure 6, the DC component may not match. However, as shown in Figure 6, if the currents Ipa, Ina, Ipb, and Inb fall below the ground voltage, the power factor correction IC 27 can detect that the inductor currents ILa and ILB have reached predetermined values.

[0043] ==Simulation Results== Figure 7 shows the simulation results. In Figure 7, the thin solid line represents the current flowing through inductor 23b, the dashed line represents the current flowing through resistor 26b, the dotted line represents the current flowing through inductor 23a, and the thick solid line represents the current flowing through resistor 26a. In order to check the conditions, including cases where the current flowing through resistors 26a and 26b has a waveform unsuitable for control, the simulation model also directly detects the currents of inductors 23a and 23b separately and performs switching control based on these detections.

[0044] The simulation results on the left side of Figure 7 are for the case without using common mode chokes 22a and 22b, while the simulation results on the right side of Figure 7 are for the case with common mode chokes 22a and 22b.

[0045] In the simulation results on the left, the currents flowing through inductor 23a and resistor 26a do not match, and the currents flowing through inductor 23b and resistor 26b also do not match.

[0046] On the other hand, in the simulation results on the right, the AC components of the current flowing through inductor 23a and resistor 26a match, and the AC components of the current flowing through inductor 23b and resistor 26b also match. However, the DC components are slightly different.

[0047] Thus, when using common-mode chokes 22a and 22b, if we ignore the shift in the DC component, we can see that the current flowing through inductors 23a and 23b can be detected by resistors 26a and 26b, respectively.

[0048] Furthermore, a modified method for roughly matching the DC components in order to detect when the inductor currents ILa and ILb have reached predetermined values ​​is described below.

[0049] ===Literal translation=== Figure 8 shows an example of the configuration of the AC-DC converter 13. The AC-DC converter 13 is composed of common mode chokes 11, 22a, 22b, a full-wave rectifier circuit 20, capacitors 21, 30, inductors 23a, 23b, diodes 24a, 24b, 28a, 28b, 29a, 29b, NMOS transistors 25a, 25b, resistors 26a, 26b, 31, 32, and a power factor correction IC 27.

[0050] Diodes 28a and 28b are impedance elements that prevent the inductor currents ILa and ILb from the source electrodes of the NMOS transistors 25a and 25b from flowing to the lower-potential electrode of the capacitor 30. Specifically, when the NMOS transistor 25a is turned on, diode 28a prevents the inductor current ILa from flowing to the lower-potential side of the capacitor 30. Diodes 28a and 28b are also placed between the source electrodes of the NMOS transistors 25a and 25b and the lower-potential electrode of the capacitor 30.

[0051] Furthermore, diode 28a has an anode connected to the low-potential electrode of capacitor 30 and a cathode connected to the source electrode of NMOS transistor 25a. Similarly, diode 28b has an anode connected to the low-potential electrode of capacitor 30 and a cathode connected to the source electrode of NMOS transistor 25b. Also, since diodes 28a and 28b only need to prevent current leakage, they may be diodes with a lower voltage rating compared to diodes 24a and 24b.

[0052] Furthermore, diode 28a corresponds to the "first impedance element" and the "first diode," while diode 28b corresponds to the "second impedance element" and the "third diode."

[0053] Diodes 29a and 29b, respectively, suppress the potential fluctuations of the source electrodes of NMOS transistors 25a and 25b that occur due to the presence of diodes 28a and 28b, respectively. Specifically, diode 29a turns on when the potential of the source electrode of NMOS transistor 25a rises above ground potential by the forward voltage of diode 29a (e.g., 0.3 volts), thereby limiting the potential fluctuation of the source electrode of NMOS transistor 25a to 0.3 volts. Diode 29b functions similarly.

[0054] Diode 29a has an anode connected to the source electrode of NMOS transistor 25a and a cathode connected to the low-potential electrode of capacitor 30. Diode 29b also has an anode connected to the source electrode of NMOS transistor 25b and a cathode connected to the low-potential electrode of capacitor 30.

[0055] Alternatively, instead of diodes 29a and 29b, a nonlinear element may be used that exhibits a resistance greater than the impedance of the ground line for small current values ​​and a small resistance for relatively large current values. Furthermore, diode 29a corresponds to the "second diode," and diode 29b corresponds to the "fourth diode."

[0056] Furthermore, by providing diodes 28a, 28b, 29a, and 29b, as shown in Figure 9, the DC components of currents Ipa and Ina and the DC components of currents Ipb and Ina will be approximately equal, and it will be possible to detect relatively accurately when the inductor currents ILa and ILb have reached predetermined values. This makes it possible to provide a power supply circuit that can detect the timing at which the inductor current reaches a predetermined value without using an auxiliary coil.

[0057] Figure 10 shows the simulation results. In Figure 10, the thin solid line represents the current flowing through inductor 23b, the dashed line represents the current flowing through resistor 26b, the dotted line represents the current flowing through inductor 23a, and the thick solid line represents the current flowing through resistor 26a. In order to check the conditions, including cases where the current flowing through resistors 26a and 26b has a waveform unsuitable for control, the simulation model also directly detects the currents of inductors 23a and 23b separately and performs switching control based on these detections.

[0058] The simulation results on the left side of Figure 10 are for the case using common mode chokes 22a and 22b, while the simulation results on the right side of Figure 10 are for the case using common mode chokes 22a and 22b, and diodes 28a, 28b, 29a, and 29b.

[0059] In the simulation results on the left, the AC components of the current flowing through inductor 23a and resistor 26a match, and the AC components of the current flowing through inductor 23b and resistor 26b also match. However, the DC components are slightly different.

[0060] On the other hand, in the simulation results on the right, the currents flowing through inductor 23a and resistor 26a coincide and overlap, and the currents flowing through inductor 23b and resistor 26b also coincide and overlap.

[0061] Thus, when using common-mode chokes 22a and 22b, and diodes 28a, 28b, 29a and 29b, the current flowing through inductors 23a and 23b can be detected by resistors 26a and 26b, respectively, and it can be seen that the DC components are also nearly identical.

[0062] Figure 11 shows an example of the configuration of the AC-DC converter 14. The AC-DC converter 14 is composed of common mode chokes 11, 22a, 22b, a full-wave rectifier circuit 20, capacitors 21, 30, inductors 23a, 23b, diodes 24a, 24b, 28a, 28b, 29a, 29b, NMOS transistors 25a, 25b, resistors 26a, 26b, 31, 32, and a power factor correction IC 27.

[0063] In the AC-DC converter 14, similar to the AC-DC converter 13, diodes 28a, 28b, 29a, and 29b are provided, so the potential of the source electrodes of the NMOS transistors 25a and 25b is maintained at a predetermined level. Therefore, even if resistors 26a and 26b are placed between the cathodes of diodes 29a and 29b and the low-potential side electrode of capacitor 30, the inductor currents ILa and ILb when the NMOS transistors 25a and 25b are off can be detected.

[0064] Figure 12 shows an example of the configuration of the AC-DC converter 15. In the AC-DC converter 15, n NMOS transistors (for example, NMOS transistors 25a to 25n) are switched to perform interleaved operation.

[0065] The AC-DC converter 15 consists of common-mode chokes 11, 22a~22n, a full-wave rectifier circuit 20, capacitors 21, 30, inductors 23a~23n, diodes 24a~24n, 28a~28n, 29a~29n, NMOS transistors 25a~25n, resistors 26a~26n, 31, 32, and a power factor correction IC 27. The operation of each component in the AC-DC converter 15 is the same as that of the AC-DC converter 13, so a description is omitted.

[0066] Furthermore, in AC-DC converters 10, 13, 14, and 15, a common-mode choke (for example, common-mode chokes 22a and 22b) was provided for each group of circuits that perform interleaved operation. However, since the common-mode choke 22a controls the inductor current ILa to flow through resistor 26a, only the inductor current ILb naturally flows through resistor 26b, so the common-mode choke 22b is not necessarily required in AC-DC converters 10, 13, and 14.

[0067] Similarly, if all other circuits in the AC-DC converter 15 have a common-mode choke (for example, a common-mode choke 22a), then the common-mode choke 22n is not necessarily required in the circuit group that contains the NMOS transistor 25n.

[0068] Furthermore, although common mode chokes 11 are provided in AC-DC converters 10, 13, 14, and 15, if a common mode choke 22a or the like is present, the common mode choke 11 is not necessarily required.

[0069] ===Summary=== The AC-DC converter 10 of this embodiment has been described above. The AC-DC converter 10 includes a full-wave rectifier circuit 20, inductors 23a, 23b, NMOS transistors 25a, 25b, a common-mode choke 22a, resistors 26a, 26b, and a power factor correction IC 27. This makes it possible to provide a power supply circuit that can detect the timing at which the inductor current reaches a predetermined value without using an auxiliary coil.

[0070] Furthermore, the AC-DC converter 10 is equipped with a common-mode choke 22b. Because the AC-DC converter 10 has common-mode chokes 22a and 22b, a current Ina with the same value as the inductor current ILa flows through resistor 26a, and a current Inb with the same value as the inductor current ILb flows through resistor 26b. As a result, when the inductor currents ILa and ILb of the NMOS transistors 25a and 25b are turned off, it is possible to detect that they have reached predetermined values ​​using resistors 26a and 26b without using an auxiliary coil.

[0071] Furthermore, the AC-DC converter 10 is equipped with a common-mode choke 11. This prevents noise generated by the switching of the NMOS transistors 25a and 25b (described later) from flowing out to the commercial power supply side.

[0072] Furthermore, the AC-DC converter 13 includes a capacitor 30 and an impedance element. This prevents the inductor current ILa from flowing back to the low-potential electrode of the capacitor 30 when the NMOS transistor 25a is turned on.

[0073] Furthermore, the impedance element is diode 28a. This prevents the inductor current ILa from flowing back to the low-potential electrode of capacitor 30 when NMOS transistor 25a is ON, and also allows the use of a diode with a lower voltage rating than diode 24a as diode 28a, resulting in a lower forward voltage drop and minimizing the reduction in efficiency due to conduction losses.

[0074] Furthermore, the AC-DC converter 13 includes a diode 29a. This allows the potential of the source electrode of the NMOS transistor 25a to be limited to a potential less than or equal to the forward voltage of the diode 29a (for example, 0.3 volts).

[0075] Furthermore, the AC-DC converter 13 is equipped with two impedance elements. This prevents the inductor currents ILa and ILb from flowing back to the low-potential electrode of the capacitor 30 when the NMOS transistors 25a and 25b are turned on, respectively.

[0076] Furthermore, the two impedance elements are diodes 28a and 28b. This prevents the inductor currents ILa and ILb from flowing back to the low-potential electrode of the capacitor 30 when the NMOS transistors 25a and 25b are turned on, and also allows the use of diodes with lower voltage ratings than diodes 24a and 24b as diodes 28a and 28b, resulting in a lower forward voltage drop and minimizing the reduction in efficiency due to conduction losses.

[0077] Furthermore, the AC-DC converter 13 includes diodes 29a and 29b. This allows the potential of the source electrodes of the NMOS transistors 25a and 25b to be limited to a potential less than or equal to the forward voltage of the diodes 29a and 29b (for example, 0.3 volts).

[0078] Furthermore, resistor 26a is provided between the source electrode of NMOS transistor 25a and node Ng, and resistor 26b is provided between the source electrode of NMOS transistor 25a and node Ng. This allows the inductor currents ILa and ILb to be detected whether NMOS transistors 25a and 25b are on or off. In other words, resistors 26a and 26b can detect when the inductor currents ILa and ILb reach predetermined values ​​after NMOS transistors 25a and 25b have been turned off.

[0079] Furthermore, resistor 26a is provided between the cathode of diode 29a and the low-potential electrode of capacitor 30, and resistor 26b is provided between the cathode of diode 29b and the low-potential electrode of capacitor 30. This allows for the detection of inductor currents ILa and ILb when NMOS transistors 25a and 25b are off, and allows for the detection of the inductor currents ILa and ILb reaching predetermined values ​​after NMOS transistors 25a and 25b have been turned off.

[0080] Furthermore, the AC-DC converter 15 includes a full-wave rectifier circuit 20, n inductors 23a to 23n, n NMOS transistors 25a to 25n, (n-1) common-mode chokes 22a to 22(n-1), n ​​resistors 26a to 26n, and a power factor correction IC 27. As a result, the AC-DC converter 15 can interleave n (where n is an integer of 3 or more) NMOS transistors 25a to 25n.

[0081] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. Furthermore, the present invention may be modified or improved without departing from its spirit, and it goes without saying that equivalents thereof are included. [Explanation of Symbols]

[0082] 10, 13~15 AC-DC converters 11,22a~22n Common Mode Choke 12 loads 20 Full wave rectifier circuit 21,30 Capacitors 23a~23n Inductor 24a~24n, 28a~28n, 29a~29n diodes 25a~25n NMOS transistors 26a~26n,31,32 Resistor 27 Power Factor Correction IC 50, 51 Differential amplifier circuit 52 Drive signal output circuit 53, 54 Driver Circuit 100 cores

Claims

1. A power supply circuit that generates an output voltage of a target level from an AC voltage, A full-wave rectifier circuit that rectifies the AC voltage and outputs a full-wave rectified voltage, First and second inductors to which a voltage corresponding to the full-wave rectified voltage is applied, A first transistor controls the first inductor current flowing through the first inductor, A second transistor controls the second inductor current flowing through the second inductor, A first common-mode choke having a first coil connected between the positive output node of the full-wave rectifier circuit and the first inductor, and a second coil connected between the negative output node of the full-wave rectifier circuit and the low-potential electrode of the first transistor, A first resistor for detecting the current of the first inductor, A second resistor for detecting the current of the second inductor, A switching control circuit controls the switching of the first and second transistors based on the first and second inductor currents detected in each of the first and second resistors and the output voltage, A power supply circuit equipped with the following features.

2. A power supply circuit according to claim 1, A second common-mode choke having a first coil connected between the positive output node of the full-wave rectifier circuit and the second inductor, and a second coil connected between the negative output node of the full-wave rectifier circuit and the low-potential electrode of the second transistor, A power supply circuit equipped with the following features.

3. A power supply circuit according to claim 1 or 2, A third common-mode choke having a first coil connected between a first node to which the AC voltage is applied and a first input node of the full-wave rectifier circuit, and a second coil connected between a second node to which the AC voltage is applied and a second input node of the full-wave rectifier circuit, A power supply circuit equipped with the following features.

4. A power supply circuit according to claim 1, A capacitor to which the aforementioned output voltage is applied, A first impedance element is provided between the low-potential electrode of the first transistor and the low-potential electrode of the capacitor, A power supply circuit equipped with the following features.

5. The power supply circuit according to claim 4, The first impedance element is, The first diode has an anode connected to the low-potential electrode of the capacitor and a cathode connected to the low-potential electrode of the first transistor. power circuit.

6. The power supply circuit according to claim 5, A second diode having an anode connected to the low-potential electrode of the first transistor and a cathode connected to the low-potential electrode of the capacitor, A power supply circuit equipped with the following features.

7. The power supply circuit according to claim 2, A capacitor to which the aforementioned output voltage is applied, A first impedance element is provided between the low-potential electrode of the first transistor and the low-potential electrode of the capacitor, A second impedance element is provided between the low-potential electrode of the second transistor and the low-potential electrode of the capacitor, A power supply circuit equipped with the following features.

8. The power supply circuit according to claim 7, The first impedance element is, The first diode has an anode connected to the low-potential electrode of the capacitor and a cathode connected to the low-potential electrode of the first transistor. The second impedance element is, The third diode has an anode connected to the low-potential electrode of the capacitor and a cathode connected to the low-potential electrode of the second transistor. power circuit.

9. The power supply circuit according to claim 8, A second diode having an anode connected to the low-potential electrode of the first transistor and a cathode connected to the low-potential electrode of the capacitor, A fourth diode having an anode connected to the low-potential electrode of the second transistor and a cathode connected to the low-potential electrode of the capacitor, A power supply circuit equipped with the following features.

10. A power supply circuit according to claim 1, The first resistor is A facility is provided between the low-potential electrode of the first transistor and the negative output node, The second resistor is A component is provided between the low-potential electrode of the second transistor and the negative output node, power circuit.

11. The power supply circuit according to claim 9, The first resistor is A device is provided between the cathode of the second diode and the low-potential electrode of the capacitor, The second resistor is A device is provided between the cathode of the fourth diode and the low-potential electrode of the capacitor. power circuit.

12. A power supply circuit that generates an output voltage of a target level from an AC voltage, A full-wave rectifier circuit that rectifies the AC voltage and outputs a full-wave rectified voltage, n inductors (where n is an integer of 3 or more) to which a voltage corresponding to the full-wave rectified voltage is applied, n transistors that control the inductor current flowing through each of the n inductors, (n-1) common-mode chokes, each having a first coil connected between the positive output node of the full-wave rectifier circuit and each of the (n-1) inductors, and a second coil connected between the negative output node of the full-wave rectifier circuit and each of the low-potential electrodes of the (n-1) transistors, n resistors for detecting the inductor current flowing through each of the n inductors, A switching control circuit controls the switching of the n transistors based on the inductor current flowing through each of the n inductors detected by each of the n resistors and the output voltage, A power supply circuit equipped with the following features.

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