JP2005086948A - Switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching power supply which can detect various types of faults with a simple constitution in the switching power supply in which converter circuits are connected in parallel. <P>SOLUTION: The switching power supply 1 having converter circuits 2, 3 connected in parallel includes a plurality of current detecting means 4, 5 for detecting currents flowing to the converter circuits 2, 3, a plurality of differential amplifying means 41, 41 for amplifying a difference between a value based on the current detected by an arbitrary current detecting means and a value based on the current detected by a current detecting means except the arbitrary current detecting means, comparing means 42, 42 for comparing a value based on this amplified current difference with a fault judged value, and a control means 9 for controlling the plurality of the converter circuits 2, 3 to peak current by generating a drive signal for controlling to switch switching elements 10a-10b on the basis of the value based on a sum of the currents detected by the plurality of the current detecting means 4, 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a switching power supply apparatus in which converter circuits are connected in parallel.

  The switching power supply device has features such as small size, light weight and high efficiency, and is widely used as a power source for personal computers and automobiles. Some switching power supply devices are used as a power source for a load that requires a large current (large power) such as an electric device provided in a fuel cell vehicle. Some switching power supply devices for large power supply a plurality of converter circuits connected in parallel and supply a large current obtained by integrating the output currents of the plurality of converter circuits. Some of such switching power supply devices control a plurality of converter circuits by a plurality of control circuits, and some control a plurality of converter circuits by one control circuit.

In a switching power supply device having a plurality of converter circuits, when an abnormality such as a failure or overcurrent of any converter circuit among the plurality of converter circuits or an imbalance in output current between the converter circuits occurs, the abnormality is detected. It is necessary to stop all the converter circuits. For this purpose, there is a switching power supply device in which a control circuit is provided for each converter circuit, and each control circuit detects an abnormality of each converter circuit (see Patent Document 1). There is also a switching power supply device in which overcurrent protection circuits are provided for all converter circuits, and each overcurrent protection circuit detects an overcurrent of each converter circuit.
JP-A-6-105556

  However, the switching power supply device provided with the control circuits corresponding to all the converter circuits has a complicated configuration and a large circuit scale. This is because this switching power supply device provides each control circuit with a difference in current flowing in each converter circuit in order to detect an abnormality in the converter circuit, in addition to a circuit for switching control of the switching element of each converter circuit. This is because a circuit for detecting, a circuit for comparing the current difference with a reference value, and the like are required.

  In addition, a switching power supply device provided with an overcurrent protection circuit corresponding to all converter circuits can detect an overcurrent, but cannot detect a failure of the converter circuit. For example, in a switching power supply device in which two converter circuits are connected in parallel, the rated current value of the output current of the entire device is set to 200 A, the rated current value of the output current of each converter circuit is set to 100 A, and an overcurrent in each overcurrent protection circuit is set. The current detection determination value is 110A. In this switching power supply device, when 100 A is output at a load factor of 50%, it is assumed that one converter circuit fails and the output current of this converter circuit becomes 0 A. In this case, the other converter circuit outputs 100 A as the output current, but since the overcurrent detection determination value is 110 A, the overcurrent protection circuit determines that the other converter circuit is normal. In other words, even if one converter circuit fails, the other converter circuit may not flow overcurrent, so that one converter circuit failure cannot be detected.

  Accordingly, an object of the present invention is to provide a switching power supply device that can detect various abnormalities with a simple configuration in a switching power supply device in which converter circuits are connected in parallel.

  A switching power supply according to the present invention includes a plurality of converter circuits each including a switching element, connected in parallel, a plurality of current detection means for detecting currents flowing through the plurality of converter circuits, and a plurality of current detection means, respectively. Correspondingly provided, it amplifies the difference between a value based on a current detected by an arbitrary current detecting means among a plurality of current detecting means and a value based on a current detected by a current detecting means other than the arbitrary current detecting means. A plurality of differential amplifying means, a comparing means for comparing a value based on a current difference amplified by each of the plurality of differential amplifying means and an abnormality determination value, and a value based on a sum of currents respectively detected by the plurality of current detecting means And a control means for generating a drive signal for controlling the switching of the switching element based on the above and for controlling the peak current of the plurality of converter circuits.

  In this switching power supply device, an input voltage is converted into a predetermined voltage required by a load in a plurality of converter circuits each including a switching element, and an integrated current of each output current in the plurality of converter circuits is supplied to the load. In the switching power supply device, each current flowing through each converter circuit is detected by current detection means provided corresponding to each of the plurality of converter circuits. In the switching power supply device, one control means generates a drive signal for the switching elements of all the converter circuits using a value based on the sum of the plurality of detection currents, and turns on / off the switching elements by this drive signal. All converter circuits are peak current controlled by one control means. A value based on the sum of currents flowing through the converter circuits reflects changes in the current flowing through the converter circuits. Therefore, the control means generates a drive signal in consideration of current changes in all converter circuits. Further, in the switching power supply device, the differential amplifying means provided corresponding to the plurality of current detecting means respectively detects the value based on the current detected by the arbitrary current detecting means and the current detecting means other than the arbitrary current detecting means. Amplifies the difference from the current based value. Further, in the switching power supply device, the comparison unit compares the value based on the amplified current difference with the abnormality determination value, and determines that the value is based on the amplified current difference is larger than the abnormality determination value. In the switching power supply device, control is performed while balancing the current between the converter circuits. Therefore, in a normal state, the difference in current flowing between the converter circuits is 0 (ideal value) or a value close to 0. Therefore, when the switching power supply device is operating normally, the value based on the amplified current difference in all the differential amplifiers is 0 or a value close to 0. As a result, in the switching power supply device, the value based on the amplified current difference becomes smaller than the abnormality determination value, and is determined to be normal. However, in the switching power supply device, when an abnormality occurs, the value based on the current difference amplified by the differential amplification means increases. This is because an abnormality such as when a converter circuit fails (stops) and the current that flows becomes zero, when an overcurrent flows through a certain converter circuit, or when the current balance between the converter circuits is lost. In any of these abnormalities, the difference between the current flowing through the converter circuit in which the abnormality has occurred and the current flowing through another converter circuit, or the current difference between the converter circuits in which the current balance has been lost becomes very large. . Therefore, in the switching power supply device, the value based on the current difference amplified by the differential amplification means becomes larger than the abnormality determination value, and these various abnormalities can be detected. As described above, in this switching power supply device, although a plurality of converter circuits are provided, an abnormality can be detected with a simple configuration using a single control unit. Furthermore, in the switching power supply device, various types of abnormalities can be detected with a simple configuration using the differential amplification means and the comparison means.

  The value based on the detected current is a value based on the current detected by each of the plurality of current detection means. For example, the current detected by each current detection means itself and the current detected by each current detection means are smoothed. The average value of the current detected by the plurality of current detection means, and the average value of the values obtained by smoothing the current detected by the plurality of current detection means. The value based on the amplified current difference is a value based on the current difference amplified by each of the plurality of differential amplification units. For example, the current difference amplified by each differential amplification unit itself is amplified by each of the plurality of differential amplification units. The average value of the current difference. The value based on the sum of the currents is a value based on a value obtained by integrating all the currents detected by the plurality of current detection units, for example, the integrated value itself is an average value. The drive signal is a signal for turning on / off the switching element of the switching power supply device, and is, for example, a PWM signal, a PWM signal using phase shift control, or the like.

  In the switching power supply device of the present invention, when a plurality of converter circuits are provided on different substrates, and current detection means and differential amplification means corresponding to each converter circuit are provided on each substrate, they are provided on each substrate. The differential amplification means is preferably configured such that a terminal to which a value based on the current detected by the current detection means provided on a different substrate is input is connected to the ground of the substrate via a resistor.

  In this switching power supply device, a plurality of converter circuits, current detection means and differential amplification means corresponding to each converter circuit are provided on different boards, and the boards are connected by cables or the like to transmit and receive various signals. ing. Therefore, each differential amplification means receives a value based on the current detected by the current detection means provided on the same substrate at one input terminal and the current detection provided on a different substrate at the other input terminal. A value based on the current detected by the means is input. The other input terminal of the differential amplifying means is connected to the ground of the substrate via a resistor. For this reason, even if the cable connected between the substrates is disconnected, the other input terminal of the differential amplifying means is always 0 V. Therefore, the differential amplifying means amplifies the voltage difference between the input terminals. Can be output. As a result, in the switching power supply device, disconnection of the cable between the substrates can be detected as an abnormality. By the way, if the other input terminal of each differential amplification means is not connected to the ground of the board via a resistor, if the cable connected between the boards is disconnected, the other input terminal of the differential amplification means is Since it is in a floating state, differential amplification cannot be performed, and disconnection of a cable or the like between substrates cannot be detected as an abnormality.

  In the switching power supply device of the present invention, when a plurality of converter circuits, a plurality of current detection means, a plurality of differential amplification means and a comparison means are provided on the same substrate, the currents amplified by the plurality of differential amplification means respectively A current difference averaging means for averaging the difference is provided, and the comparison means is preferably configured to compare the current difference averaged by the current difference averaging means with the abnormality determination value.

  In this switching power supply device, a plurality of converter circuits, a plurality of current detection means, a plurality of differential amplification means and a comparison means are provided on the same substrate. In the switching power supply, the current difference averaged by the differential amplifier is averaged by the current difference averaging means, and the averaged current difference is compared with the abnormality determination value by one comparison means. The value obtained by averaging the amplified current differences reflects the current differences detected by all the differential amplification means. That is, when the amplified current difference in one differential amplifying means increases (that is, when an abnormality occurs), the increased current difference is also reflected in a value obtained by averaging the amplified current differences. . Therefore, in the switching power supply device, the abnormality can be detected by comparing the averaged values by the comparison means. For this reason, in this switching power supply apparatus, it is not necessary to provide each of the comparison means corresponding to the differential amplification means, so that the configuration is further simplified.

  The switching power supply device according to the present invention may be configured to include a plurality of smoothing units that are respectively provided corresponding to the plurality of current detection units and smooth the currents detected by the plurality of current detection units.

  In this switching power supply, the current detected by the current detecting means is smoothed by the smoothing means provided corresponding to each of the plurality of current detecting means to obtain a direct current. That is, in the switching power supply device, the current flowing through each converter circuit is pulsed, so that the pulsed detected current is smoothed so that it does not become low level even during the pulse off period. As described above, in the switching power supply device, the current detected by the current detecting means is a direct current, and the waveform is easy to handle by the differential amplifying means.

  According to the present invention, it is possible to detect various abnormalities in a switching power supply device in which converter circuits are connected in parallel with a simple configuration.

  Embodiments of a switching power supply apparatus according to the present invention will be described below with reference to the drawings.

  In this embodiment, the switching power supply device according to this embodiment is applied to a switching power supply circuit in which two or three DC / DC converter circuits are connected in parallel. The switching power supply according to the present embodiment includes one control IC [Integrated Circuit] that controls a plurality of DC / DC converter circuits, and performs feedback control of the DC / DC converter circuit by peak current control. Furthermore, the switching power supply apparatus according to the present embodiment includes a protection circuit for detecting various abnormalities. In this embodiment, there are four embodiments depending on the difference in the number of DC / DC converter circuits and the configuration of the protection circuit, and the first to third embodiments include two DC / DC converter circuits. The fourth embodiment includes three DC / DC converter circuits, and the first embodiment includes a comparator for each of the two differential amplifiers. The second embodiment has one comparator for two differential amplifiers, and the third embodiment has one comparator for two differential amplifiers and a differential. In this embodiment, the current values input to the amplifiers are averaged. In the fourth embodiment, comparators are provided for each of the three differential amplifiers.

  With reference to FIGS. 1-3, the structure of the switching power supply device 1 which concerns on 1st Embodiment is demonstrated. FIG. 1 is a configuration diagram of the switching power supply device according to the first embodiment. FIG. 2 is a circuit configuration diagram of the switching power supply device of FIG. FIG. 3 shows input / output characteristics of the differential amplifier of FIG.

The switching power supply device 1 is a power supply circuit that converts a DC input voltage V _I into a DC output voltage V _O (<V _I ) and can supply a large current (for example, 200 A) and a large power (for example, 3 kW). Yes, it is used for various purposes. The switching power supply device 1 is a switching regulator that turns on / off the switching element by PWM control. The input voltage V _I is variable, and an input voltage range (for example, 300 to 400 V) is set. The output voltage V _O is set to a constant target voltage (for example, 12 V) according to the load L. The load L corresponds to, for example, an electric device such as a fan or a heater in an automobile (particularly, a fuel cell automobile that requires a large amount of power for stack temperature management, etc.), and the load current varies greatly depending on the processing load. is there.

The switching power supply apparatus 1 includes, as main components, a first DC / DC converter circuit 2, a second DC / DC converter circuit 3, a first current detection circuit 4, a second current detection circuit 5, an averaging circuit 6, and a first protection circuit. 7, a second protection circuit 8 and a control IC 9 are provided. In the switching power supply device 1, two DC / DC converter circuits 2 and 3 are connected in parallel to supply a large current, and a combined current of the output currents of the two DC / DC converter circuits 2 and 3 is output. . Further, in the switching power supply device 1, in order to simplify the configuration, control two DC / DC converter circuit 2 in one control IC9, the output in the control IC9 voltage _{V o} and the DC / DC converter circuit 2, The peak current control is performed based on the average currents of the currents I ₁ and I ₂ flowing through the primary side circuits of the three primary circuits. Further, in the switching power supply device 1, the peak current is controlled by one control IC 9, so that the first current detection circuit 4 detects the current I ₁ flowing through the first DC / DC converter circuit 2 and the second current detection circuit 5 The current I ₂ flowing through the _second DC / DC converter circuit 3 is detected, and the two currents I ₁ and I ₂ are averaged by the averaging circuit 6 and input to the control IC 9. Further, in the switching power supply device 1, various abnormalities in the switching power supply device 1 are detected by the first protection circuit 7 and the second protection circuit 8.

  Further, the switching power supply device 1 is constituted by two first substrates 1a and second substrates 1b. A first DC / DC converter circuit 2, a first current detection circuit 4, an averaging circuit 6, a first protection circuit 7 and a control IC 9 are provided on the first substrate 1a. A second DC / DC converter circuit 3, a second current detection circuit 5, and a second protection circuit 8 are provided on the second substrate 1b. The first board 1a and the second board 1b are connected by a large number of cables 1c,..., And signals are transmitted and received between the first board 1a and the second board 1b.

The two DC / DC converter circuits 2 and 3 have the same configuration, and include a full bridge circuit 10, a transformer 11, diodes 12 and 13, and a smoothing circuit 14 as main configurations. The full bridge circuit 10 includes a first FET [Field Effect Transistor] 10a, a second FET 10b, a third FET 10c, and a fourth FET 10d as switching elements. The drains of the first FET 10a and the second FET 10b are connected to the positive side of the power supply 15, and the third FET 10c And the source of the fourth FET 10d is connected to the ground side of the power supply 15, and the primary winding of the transformer 11 between the connection terminal of the source of the first FET 10a, the drain of the third FET 10c, the connection terminal of the source of the second FET 10b, and the drain of the fourth FET 10d. 11a is connected. In the full bridge circuit 10, the first FET 10 a, the fourth FET 10 d, the second FET 10 b, and the third FET 10 c are alternately turned on, and a current that flows in the reverse direction in the primary winding 11 a of the transformer 11 is alternately passed. Smoothing circuit 14 is composed of an inductor 14a and the capacitor 14b, the amplitude is input pulse voltage equal to the input voltage V _I is the switching operation of the full bridge circuit 10 averages the pulse voltage. When the second FET 10b and the third FET 10c are turned on, a pulse voltage is input to the smoothing circuit 14 from the secondary side first winding 11b of the transformer 11 through the diode 12, and the first FET 10a and the fourth FET 10d are turned on. In this case, a pulse voltage is input from the second winding 11 c on the secondary side of the transformer 11 via the diode 13.

The two current detection circuits 4 and 5 have the same configuration and include a transformer 20, a diode 21, and a resistor 22. The primary winding 20 a of the transformer 20 is connected between the sources of the third FET 10 c and the fourth FET 10 d and the ground side of the power supply 15. The secondary winding 20b of the transformer 20 has one end connected to the anode of the diode 21 and the other end connected to the ground. The resistor 22 has one end connected to the cathode of the diode 21 and the other end connected to the ground. In the transformer 20, in order to reduce power loss in the DC / DC converter circuits 2 and 3, the number of turns of the primary winding 20a is extremely smaller than the number of turns of the secondary winding 20b (for example, the turn ratio is 1: 100). ~ 1: 200). In the current detection circuits 4 and 5, the secondary side of the transformer 20 is half-wave rectified, and the currents I ₁ and I ₂ flowing in the primary side circuits of the DC / DC converter circuits 2 and 3 are converted to voltages V ₁ and V across the resistor 22. Detect as ₂ respectively. Hereinafter, the both-end voltages are referred to as a first current detection voltage V ₁ and a second current detection voltage V ₂ , respectively. The reason why the transformer is used for current detection is that the primary side and the secondary side can be insulated and the power loss can be reduced.

The averaging circuit 6 includes two resistors 30 and 31. The resistor 30 has one end connected to one end of the resistor 22 of the first current detection circuit 4 and the other end connected to the other end of the resistor 31. One end of the resistor 31 is connected to one end of the resistor 22 of the second current detection circuit 5. The connection end of the resistor 30 and the resistor 31 is connected to the control IC 9. The resistor 30 and the resistor 31 have the same resistance value. In the averaging circuit 6, the first current detection voltage V ₁ is input from one end of the resistor 30, the second current detection voltage V ₂ is input from one end of the resistor 31, and the first end is connected from the connection end of the resistor 30 and the resistor 31. A voltage V _AV obtained by averaging the current detection voltage V ₁ and the second current detection voltage V ₂ is output to the control IC 9. Since the second current detection circuit 5 and the averaging circuit 6 are provided on different substrates 1a and 1b, respectively, one end of the resistor 31 and one end of the resistor 22 of the second current detection circuit 5 are connected by a cable 1c. Is done.

The current detection voltages V ₁ and V ₂ are voltages corresponding to the currents I ₁ and I ₂ flowing through the primary side circuits of the DC / DC converter circuits 2 and 3, and the direct current components include windings of the inductor 14 a and the transformer 11. It consists of pulsed voltage components V ₁₁ ,..., V ₂₁ ,. The current detection voltages V ₁ and V ₂ include voltage components V ₁₁ , V ₁₃ ,..., V ₂₁ , V ₂₅ when the first FET 10 a and the fourth FET 10 d are turned on (a negative excitation current flows through the transformer 11). , ... and the voltage components V ₁₂ , V ₁₄ , ..., V ₂₂ , V ₂₆ , ... when the second FET 10b and the third FET 10c are turned on (when a positive excitation current flows through the transformer 11). Appear alternately. Current averaging voltage _{V AV,} since voltage obtained by averaging the two current detection voltages _V 1, _{V 2,} the change in the DC / DC converter two currents _I 1 flowing through the primary circuit of the circuit 2,3, _{I 2} Reflects.

The two protection circuits 7 and 8 have the same configuration, and include a smoothing circuit 40, a differential amplifier 41, a comparator 42, a determination reference power supply 43, and resistors 44 to 47. The first protection circuit 7, the overcurrent of the 1 DC / DC converter circuit 2, a failure of the 2DC / DC converter circuit 3, the current imbalance (first current _{I 1} between the DC / DC converter circuit 2 second If greater than current I _2), a protective circuit for detecting various abnormalities such as breakage of the cable 1c. The second protection circuit 8, an overcurrent of the 2DC / DC converter circuit 3, a failure of the 1 DC / DC converter circuit 2, a current imbalance (second current _{I 2} between the DC / DC converter circuit 2 first If greater than current I _1), a protection circuit for detecting an abnormality such as disconnection of the cable 1c.

The smoothing circuit 40 includes resistors 40a and 40b and a capacitor 40c. One end of the resistor 40a is connected to one end of the resistor 22 of the current detection circuits 4 and 5, and the other end is connected to one end of the resistor 40b and one end of the capacitor 40c. The other end of the capacitor 40c and the other end of the resistor 40b are connected to the ground. In particular, the resistor 40b of the smoothing circuit 40 of the first protection circuit 7 is a resistor 40b connected to the inverting input terminal of the differential amplifier 41 of the second protection circuit 8 via the resistor 45, and is not the substrate 1a but the substrate 1b. Provided. The resistor 40b of the smoothing circuit 40 of the second protection circuit 8 is a resistor 40b connected to the inverting input terminal of the differential amplifier 41 of the first protection circuit 7 via the resistor 45, and is not the substrate 1b but the substrate 1a. Provided. Therefore, the resistor 40a and the resistor 40b are connected via the cable 1c. The smoothing circuit 40 of the first protection circuit 7 averages the pulse-like voltage component of the first current detection voltage V ₁ to generate the first smoothed voltage V _S1 (see FIGS. 5A and 5C). . The smoothing circuit 40 of the second protection circuit 8, a pulse-like voltage component of the second current detection voltage _{V 2} averaged to produce a second smoothed voltage _{V S2} (FIG. 5 (b), (d) see) .

Incidentally, the first current detection voltage V ₁ and the second current detection voltage V ₂ have pulse-like voltage components, and the pulse-like voltage components are smoothed to obtain the first smoothing voltage V _S1 and the second current detection voltage V _S1 . By setting the smoothed voltage V _S2 , the voltage is set so as not to become 0 V in the off period in which no pulsed voltage component is generated. As described above, the first current detection voltage V ₁ and the second current detection voltage V ₂ are DC voltages, and are easily handled by the differential amplifier 41.

  Since the resistor 40b of the smoothing circuit 40 is a resistor connected in series with the resistor 40a and in parallel with the capacitor 40c, it is usually arranged in the vicinity of the elements 40a and 40c. However, in the switching power supply device 1, the resistor 40 b of the smoothing circuit 40 of one protection circuit is arranged on a different substrate on which the differential amplifier 41 of the other protection circuit is provided. This is because the smoothing voltage is input to the inverting input terminal of the differential amplifier 41 on one board from the smoothing circuit 40 on the other board via the cable 1c. Therefore, if the cable 1c is disconnected, the differential amplifier This is because the inverting input terminal 41 is open and the output of the differential amplifier 41 is always 0V. When the differential amplifier 41 is constantly at 0V, the comparator 42 always has a low signal (0V), and an abnormality cannot be detected. Therefore, the inverting input terminal of the differential amplifier 41 is effectively grounded by using the resistor 40b of the smoothing circuit 40 so that the inverting input terminal of the differential amplifier 41 does not open even if the cable 1c is disconnected.

The differential amplifier 41 of the first protection circuit 7 has a non-inverting input terminal connected via a resistor 44 to the connection end of the resistor 40a, the resistor 40b, and the capacitor 40c of the smoothing circuit 40 of the first protection circuit 7, and an inverting input. A terminal is connected to a connection end of the resistor 40 a, the resistor 40 b, and the capacitor 40 c of the smoothing circuit 40 of the second protection circuit 8 via a resistor 45. The differential amplifier 41 of the second protection circuit 8 has a non-inverting input terminal connected to the connection end of the resistor 40a, the resistor 40b, and the capacitor 40c of the smoothing circuit 40 of the second protection circuit 8 via a resistor 44, and an inverting input. A terminal is connected to a connection end of the resistor 40a, the resistor 40b, and the capacitor 40c of the smoothing circuit 40 of the first protection circuit 7 via a resistor 45. Further, the differential amplifier 41 has an output terminal connected to an inverting input terminal via a resistor 46. In the differential amplifier 41 of the first protection circuit 7, first smoothing voltage _{V S1} is the case larger than the second smoothed voltage _{V S2} obtained by subtracting the second smoothed voltage _{V S2} from the first smoothing voltage _{V S1} The differential voltage is amplified, and when the first smoothed voltage V _S1 is equal to or lower than the second smoothed voltage V _S2 , the first differential amplified voltage V _A1 is output as 0 V (FIGS. 3, 5 (c) to 5). (See (e)). In the differential amplifier 41 of the second protection circuit, when the second smoothed voltage _{V S2} is greater than the first smoothed voltage _{V S1} is the difference obtained by subtracting the first smoothing voltage _{V S1} from the second smoothing voltage _{V S2} The voltage is amplified, and when the second smoothed voltage V _S2 is equal to or lower than the first smoothed voltage V _S1 , the second differential amplified voltage V _A2 is set to 0 V (FIG. 3, FIG. 5 (c), ( d) and (f)). In FIG. 3, the horizontal axis is (first smoothed voltage V _S1 −second smoothed voltage V _S2 ) or (second smoothed voltage V _{S2 −first} smoothed voltage V _S1 ), and the vertical axis is first. The differential amplification voltage V _A1 or the second differential amplification voltage V _A2 indicates the output characteristics of the differential amplifier 41. Since the first protection circuit 7 and the second protection circuit 8 are provided on different substrates 1a and 1b, respectively, the resistor 45 connected to the inverting input terminal of the differential amplifier 41 of one protection circuit and the other protection circuit The smoothing circuit 40 is connected by a cable 1c.

Incidentally, since current balance is normally established between the DC / DC converter circuits 2 and 3, the first current I ₁ that flows through the first DC / DC converter circuit 2 and the second current that flows through the second DC / DC converter circuit 3. A current that is the same as or close to I ₂ flows. Thus, the first current detection voltages V ₁ and pulsed voltage component of the second current detection voltage V ₂ has a same or close to that voltage component. Therefore, the first smoothed voltage V _S1 and the second smoothed voltage V _S2 are the same or close to each other, and the first differential amplified voltage V _A1 and the second differential amplified voltage V _A2 are 0 V or The voltage is close to 0V. However, when an abnormality occurs in the switching power supply device 1 and one of the first current I ₁ and the second current I ₂ becomes an abnormal current, the first differential amplification voltage V _A1 or the second differential amplification voltage V _A2 becomes larger. For example, when the first DC / DC converter circuit 2 fails, the first current I ₁ does not flow, and therefore the second differential amplification voltage V _A2 increases. Conversely, since the case where the 2DC / DC converter circuit 3 has failed is not the second current _{I 2} flows through the first differential amplifier voltage _{V A1} becomes larger. The first current _{I 1} is the case of overcurrent, the first differential amplifier voltage _{V A1} becomes larger. Conversely, the second current _{I 2} is the case of overcurrent, the second differential amplifier voltage _{V A2} is increased.

The comparator 42 has a non-inverting input terminal connected to the output terminal of the differential amplifier 41 via the resistor 47, an inverting input terminal connected to the plus terminal of the determination reference power supply 43, and an output terminal connected to the control IC 9. . The negative terminal of the determination reference power supply 43 is connected to the ground. Criterion power supply 43 is a power supply for generating an abnormality judgment reference voltage V _R for the first differential amplifier voltage V _A1, the second differential amplifier voltage V _A2 to determine whether it is increased to an abnormal voltage . Failure determination reference voltage _{V R} is the voltage for detecting a voltage difference corresponding to 20-30% of the rated voltage of the DC / DC converter circuit 2 is set. Incidentally, since current imbalance occurs between the DC / DC converter circuits 2 and 3 due to variations in the elements of the DC / DC converter circuits 2 and 3, the rated voltage of the DC / DC converter circuits 2 and 3 is caused by the current imbalance. A voltage difference corresponding to about 10% at maximum may occur. In the comparator 42 of the first protection circuit 7, when the first differential amplification voltage V _A1 is larger than the abnormality determination reference voltage V _R , the signal becomes a high signal, and the first differential amplification voltage V _A1 becomes the abnormality determination reference voltage V _R. outputting a first abnormality detection signals S ₁ serving as a low signal (0V) in the following cases. In the comparator 42 of the second protection circuit 8 becomes a high signal is greater than the second differential amplifier voltage V _A2 is failure determination reference voltage V _R, the second differential amplifier voltage V _A2 is failure determination reference voltage V _R and outputs a second abnormality detection signal S ₂ as the low signal in the following cases. Since the second protection circuit 8 and the control IC 9 are provided on different substrates 1a and 1b, the output terminal of the comparator 42 of the second protection circuit 8 and the control IC 9 are connected by a cable 1c.

The control IC 9 performs feedback control of the two DC / DC converter circuits 2 and 3 by peak current control. Control in IC 9, 2 two output voltage _{V O} at the DC / DC converter circuit 2 and 3 are formed so that the target voltage, the output voltage _{V O} and the current averaging voltage based on _{V AV} second 1PWM signal _{P 1} and the 2PWM signal to generate a P _2. The control IC 9 also controls the first PWM signal P ₁ and the second PWM signal P ₂ based on the current average voltage V _AV so as to suppress the partial excitation of the transformers 11 and 11 of the two DC / DC converter circuits 2 and 3. Is generated.

Note that the 1PWM signal _{P 1} is a signal for turning on / off the first 1FET10a and second 4FET10d. The 2PWM signal _{P 2} is a signal for turning on / off the first 2FET10b and second 3FET10c. As for the ON signals of the _first PWM signal P ₁ and the second PWM signal P ₂ , the rise is defined by the clock of the control IC 9 and the fall is defined by the control signal CS and the current average voltage V _AV (FIG. ) To (c)). The 1PWM signal P ₁ and the second 2PWM signal P _2, the same period, the rise of the ON signal of one signal is set between the rising of the ON signal of the other signal (FIG. 4 (b), ( c)). The same signal is used in the two DC / DC converter circuits 2 and 3 for the _first PWM signal P ₁ and the second PWM signal P ₂ .

Further, the control IC 9, when the first abnormality detection signal S ₁ and the second abnormality detection signal on the basis of the S ₂ determines whether an abnormality in the switching power supply device 1 has occurred, it is determined that the abnormal DC / DC converter circuits 2 and 3 in order to stop, the first 1PWM signal _{P 1} and the second 2PWM all off signal signals _{P 2.} The control IC 9 determines that an abnormality has occurred when at least one of the first abnormality detection signal S ₁ and the second abnormality detection signal S ₂ is a high signal, and is normal when both signals are low signals. judge. When an abnormality due to current imbalance between the DC / DC converter circuits 2 and 3 occurs, the control IC 9 does not use all the OFF signals, but the first PWM signal P1 and the _first PWM signal P1 for eliminating the current imbalance. the 2PWM signal _{P 2} may be generated.

The operation of the switching power supply device 1 will be described with reference to FIGS. Here, first, the basic operation of the switching power supply device 1 and the control IC 9 will be described, and then, the operation of the protection circuits 7 and 8 when one of the DC / DC converter circuits 2 and 3 fails. 5 described along the timing chart, the operation of the first current detection voltages V ₁ and the second current detection voltage protection for various patterns of the pulse voltage components in V ₂ circuits 7 and 8 shown in FIG. FIG. 5 is a timing chart when the DC / DC converter circuit fails in the switching power supply device of FIG. 1, (a) is the first current detection voltage detected by the first current detection circuit, and (b) is A second current detection voltage detected by the second current detection circuit, (c) is a first smoothing voltage in the first protection circuit, (d) is a second smoothing voltage in the second protection circuit, (E) is a first differential amplification voltage in the first protection circuit, (f) is a second differential amplification voltage in the second protection circuit, and (g) is a first abnormality detection signal in the first protection circuit. (H) is a second abnormality detection signal in the second protection circuit. FIG. 6 shows changes in each voltage and each signal for various patterns of pulse voltage components in the first current detection voltage and the second current detection voltage. FIG. 6A shows the first detected by the first current detection circuit. (B) is the second current detection voltage detected by the second current detection circuit, (c) is the first smoothing voltage in the first protection circuit, and (d) is the second protection voltage. (E) is the first differential amplification voltage in the first protection circuit, (f) is the second differential amplification voltage in the second protection circuit, and (g) is the second smoothing voltage in the circuit. It is a first abnormality detection signal in the first protection circuit, and (h) is a second abnormality detection signal in the second protection circuit.

In the switching power supply device 1, the input voltage V _I is input to the two DC / DC converter circuits 2 and 3, respectively. In each of the DC / DC converter circuits 2 and 3, the first FET 10a and the fourth FET 10d are turned on based on the ON signal of the _first PWM signal P1 from the control IC 9, and the second FET 10b and the second FET 10b are based on the OFF signal of the _second PWM signal P2. When the 3FET 10c is turned off, a negative exciting current flows in the primary winding 11a of the transformer 11, and a current flows from the secondary winding 11c through the diode 13 to the smoothing circuit 14. In each of the DC / DC converter circuits 2 and 3, the _second FET 10b and the third FET 10c are turned on based on the ON signal of the _second PWM signal P2 from the control IC 9, and the first FET 10a based on the OFF signal of the _first PWM signal P1. When the fourth FET 10 d is turned off, a positive exciting current flows through the primary winding 11 a of the transformer 11, and a current flows from the secondary first winding 11 b to the smoothing circuit 14 through the diode 12. Furthermore, in the DC / DC converter circuit 2, averages the input voltage _{V I} to output as pulse ON period FET10a~10d in the smoothing circuit 14, and outputs a voltage _{V O.} Then, in the switching power supply device 1, and applies the voltage V _o to a load L, and outputs a current obtained by integrating the output currents of the two DC / DC converter circuit 2.

In the switching power supply device 1, the currents I ₁ and I ₂ flowing through the primary side circuits of the DC / DC converter circuits 2 and 3 are converted into the first current detection voltage V ₁ and the second current detection voltage by the current detection circuits 4 and 5. respectively detected as V _2. In the switching power supply device 1, the averaging circuit 6 averages the first current detection voltage V ₁ and the second current detection voltage V ₂ and feeds back the current average voltage V _AV to the control IC 9. In the switching power supply device 1, the output voltage V _O is fed back to the control IC 9.

At this time, the control IC 9, and subtracts the output voltage V _O from the target voltage, and generates a control signal CS by multiplying the gain in the subtracted value. Then, in the control IC 9, the control signal CS is compared with the current averaged voltage V _AV as the ramp signal by a comparator (see FIG. 4A). Further, the control IC 9, when the first 2PWM signal _{P 2} of the OFF signal, raises the first 1PWM off signal of the signal _{P 1} to the ON signal for each fixed period, current averaging voltage _{V AV} control signal CS is less than the period Then, the ON signal is continued, and when the current averaged voltage V _AV reaches the control signal CS, it falls from the ON signal to the OFF signal, and the first PWM signal P ₁ is generated (see FIGS. 4A and 4B). The control IC 9 outputs the generated first PWM signal P ₁ to the gates of the first FETs 10 a and 10 a and the fourth FETs 10 d and 10 d of the two DC / DC converter circuits 2 and 3. Further, the control IC 9, when the first 1PWM signal _{P 1} is OFF signals launched a first 2PWM off signal of the signal _{P 2} ON signal every predetermined period, the current averaged voltage _{V AV} control signal CS is less than the period in continuing the oN signal, the current averaging voltage _{V AV} reaches the control signal CS falls from the oN signal to the oFF signal, to generate a first 2PWM signal _{P 2} (see FIG. 4 (a), (c) ). Then, the control IC 9, and outputs the generated first 2PWM signal _{P 2} of the two DC / DC converter circuit 2 first 2FET10b, 10b and the 3FET10c, to the gates of 10c.

In this way, the control IC 9 can perform peak current control using one detected current waveform (current averaged voltage V _AV ) despite controlling the two DC / DC converter circuits 2 and 3. . Therefore, the control IC 9 reduces the processing load and simplifies the configuration because only one comparator or the like is required. Further, the control IC 9 does not generate the _first PWM signal P ₁ and the second PWM signal P ₂ for each of the DC / DC converter circuits 2 and 3, and controls them using the same signal. Therefore, in the control IC 9, even if the output power of one of the DC / DC converter circuits 2, 3 is biased or the load current suddenly changes, the current balance of each DC / DC converter circuit 2, 3 is lost. There is no.

A case where one of the DC / DC converter circuits 2 and 3 fails will be described. In the example of FIG. 5, the two DC / DC converter circuits 2 and 3 are normal, the second DC / DC converter circuit 3 is faulty, and the first DC / DC converter circuit 2 is faulty. Further, in the example of FIG. 5, the pulse-like voltage components of the first current detection voltage V ₁ and the second current detection voltage V ₂ have the same pulse width for easy understanding. Causes of failure of the DC / DC converter circuits 2 and 3 include failure of at least one of the FETs 10a to 10d, a mistake in the manufacturing process, and the like.

In the normal case, since the currents I ₁ and I ₂ normally flow in the two DC / DC converter circuits 2 and 3, normal pulse voltage components V ₁₁ and V ₁₂ are represented in the first current detection voltage V _1. Therefore, normal pulse voltage components V ₂₁ and V ₂₂ also appear in the second current detection voltage V ₂ (see FIGS. 5A and 5B). In the two smoothing circuits 40, 40, the first smoothing voltage V _S1 and the second smoothing voltage V _S2 are the same voltage (see FIGS. 5C and 5D). Therefore, since there is no difference between the first smoothed voltage V _S1 and the second smoothed voltage V _{S2 in} the two differential amplifiers 41 and 41, the first differential amplified voltage V _A1 and the second differential amplified voltage V S _{As A2} , 0V is output to the comparators 42 and 42 (see FIGS. 5E and 5F). As a result, the two comparators 42 and 42, first differential amplifying voltage _{V A1,} since the second differential amplifier voltage _{V A2} is smaller than the abnormality detection reference voltage _{V R,} the first abnormality detection signal _{S 1,} the as second abnormality detection signals _{S 2} and outputs a low signal (0V) to the control IC 9 (see FIG. 5 (g), (h) ). In this case, the control IC 9, it is determined that an abnormality has not occurred in the switching power supply 1 to generate a first 1PWM signal _{P 1} and the second 2PWM signal _{P 2} corresponding to the peak current control.

When the second DC / DC converter circuit 3 fails, the second current I ₂ does not flow in the second DC / DC converter circuit 3, and therefore no pulse voltage component appears in the second current detection voltage V ₂ (FIG. 5 ( b)). Therefore, in the smoothing circuit 40 of the second protection circuit 8, the second smoothing voltage V _S2 is 0 V (see FIG. 5D). Therefore, the first smoothing voltage V _S1 is significantly larger than the second smoothing voltage V _S2 , and the differential amplifier 41 of the first protection circuit 7 has (first smoothing voltage V _S1 −second smoothing voltage V _A first differential amplification voltage V _A1 obtained by amplifying _S2 ) is output (see FIG. 5E). Since this first differential amplifier voltage V _A1 becomes larger than the abnormality detection reference voltage V _R, the comparator 42 of the first protection circuit 7 outputs the high signal to the control IC9 as a first abnormality detection signal S ₁ (Fig. 5 (g)). Incidentally, the differential amplifier 41 of the second protection circuit 8 outputs 0 V as the second differential amplification voltage V _A2 (see FIG. 5F), and the comparator 42 of the second protection circuit 8 has a second abnormality. and it outputs a low signal to the control IC9 as the detection signal _{S 2} (see FIG. 5 (h)). In this case, the control IC 9, it is determined that an abnormality has occurred in the switching power supply 1 to generate a first 1PWM signal _{P 1} and the second 2PWM signal _{P 2} all consisting OFF signal. Then, in the switching power supply device 1, all the FETs 10a to 10b of the two DC / DC converter circuits 2 and 3 are turned off, and the DC / DC converter circuits 2 and 3 are stopped.

Incidentally, even when the cable 1c connecting the differential amplifier 41 of the first protection circuit 7 and the smoothing circuit 40 of the second protection circuit 8 is disconnected, the inverting input terminal of the differential amplifier 41 of the first protection circuit 7 is always connected. since the 0V, the first abnormality detection signals S ₁ becomes high signal, can detect the abnormality. Further, even when the cable 1c which connects the control IC9 and the second 2DC / DC converter circuit 3 is disconnected, it can not send a second 1PWM signal _{P 1} and the second 2PWM signal _{P 2,} the 2DC / DC converter circuit 3 is stopped second current I ₂ stops flowing Te, the first abnormality detection signals S ₁ becomes high signal, can detect the abnormality.

When the first DC / DC converter circuit 2 breaks down, the first current I ₁ does not flow in the first DC / DC converter circuit 2, and therefore no pulse voltage component appears in the first current detection voltage V ₁ (FIG. 5 ( a)). Therefore, in the smoothing circuit 40 of the first protection circuit 7, the first smoothing voltage V _S1 is 0 V (see FIG. 5C). Therefore, the second smoothing voltage V _S2 is significantly larger than the first smoothing voltage V _S1 , and the differential amplifier 41 of the second protection circuit 8 has (second smoothing voltage V _S2 −first smoothing voltage V _A second differential amplification voltage V _A2 obtained by amplifying _S1 ) is output (see FIG. 5F). Since the second differential amplifier voltage V _A2 is greater than the abnormality detection reference voltage V _R, the comparator 42 of the second protection circuit 8, and outputs a high signal to the control IC9 as second abnormality detection signal S ₂ (Fig. 5 (h)). Incidentally, the differential amplifier 41 of the first protection circuit 7 outputs 0 V as the first differential amplification voltage V _A1 (see FIG. 5E), and the comparator 42 of the first protection circuit 7 has a first abnormality. and it outputs a low signal to the control IC9 as a detection signal _{S 1} (see FIG. 5 (g)). In this case, the control IC 9, it is determined that an abnormality has occurred in the switching power supply 1 to generate a first 1PWM signal _{P 1} and the second 2PWM signal _{P 2} all consisting OFF signal.

Incidentally, even when the cable 1c connecting the differential amplifier 41 of the second protection circuit 8 and the smoothing circuit 40 of the first protection circuit 7 is disconnected, the inverting input terminal of the differential amplifier 41 of the second protection circuit 8 is always connected. since the 0V, the second abnormality detection signal S ₂ becomes high signal, it can detect the abnormality. Also, when the cable 1c which connects the control IC9 and the first 1 DC / DC converter circuit 2 is broken, can not send a second 1PWM signal _{P 1} and the second 2PWM signal _{P 2,} the 1 DC / DC converter circuit 2 is stopped The first current I ₁ stops flowing, and the second abnormality detection signal S ₂ becomes a high signal, and this abnormality can be detected.

The operation of the protection circuits 7 and 8 for various patterns of pulse voltage components in the first current detection voltage V ₁ and the second current detection voltage V ₂ will be described. In the example of FIG. 6, when the two DC / DC converter circuits 2 and 3 are normal (patterns of the pulse voltage components V ₁₁ and V ₁₂ and the pulse voltage components V ₂₁ and V ₂₂ ), the second DC / DC converter circuit 3 When the second current I ₂ is a small current (pattern of pulse voltage components V ₁₃ , V ₁₄ and pulse voltage components V ₂₃ , V ₂₄ ), the first current I ₁ of the first DC / DC converter circuit 2 is a small current. (Pattern of pulse voltage components V ₁₅ and V ₁₆ and pulse voltage components V ₂₅ and V ₂₆ ) is shown. In the example of FIG. 6, the pulse-like voltage components of the first current detection voltage V ₁ and the second current detection voltage V ₂ have the same pulse width for easy understanding.

When both the first current I ₁ of the first DC / DC converter circuit 2 and the second current I ₂ of the second DC / DC converter circuit 3 are flowing normally, the pulse voltage component V _{11 of} the first current detection voltage V ₁ , the same pulses as the V ₁₂ and the second current detection voltage _{V 2} of the pulse voltage component _{V 23, V 24} (see FIG. 6 (a), (b) ). Therefore, the first smoothed voltage V _S1 and the second smoothed voltage V _S2 have the same voltage value (see FIGS. 6C and 6D), and the differential amplifier 41 of the first protection circuit 7 has the first difference. 0V is output as the dynamic amplification voltage V _A1 (see FIG. 6E), and the differential amplifier 41 of the second protection circuit 8 outputs 0V as the second differential amplification voltage V _A2 (see FIG. 6F). ). Accordingly, since the first differential amplifier voltage V _A1 and a second differential amplifier voltage V _A2 is smaller than the abnormality detection reference voltage V _R, the low as a comparator in 42 first abnormality detection signals S ₁ of the first protection circuit 7 outputs a signal to the control IC9 (see FIG. 6 (g)), the comparator 42 of the second protection circuit 8 outputs a low signal to the control IC9 as second abnormality detection signal _{S 2} (FIG. 6 (h) see) . In this case, the control IC 9, it is determined that an abnormality has not occurred in the switching power supply 1 to generate a first 1PWM signal _{P 1} and the second 2PWM signal _{P 2} corresponding to the peak current control.

When the second current I ₂ of the second DC / DC converter circuit 3 becomes a small current, the pulse voltage components V ₂₃ and V _{24 of} the second current detection voltage V ₂ are also reduced (see FIG. 6B). Therefore, the smoothing circuit 40 of the second protection circuit 8 outputs a second smoothed voltage V _S2 having a small voltage corresponding to the pulse voltage components V ₂₃ and V ₂₄ (see FIG. 6D). Therefore, the second smoothing voltage V _S2 is smaller than the first smoothing voltage V _S1 , and the differential amplifier 41 of the first protection circuit 7 has (first smoothing voltage V _S1 −second smoothing voltage V _A first differential amplification voltage V _A1 obtained by amplifying _S2 ) is output (see FIG. 6E). Since the first differential amplifier voltage V _A1 is greater than the abnormality detection reference voltage V _R, the comparator 42 of the first protection circuit 7 outputs the high signal to the control IC9 as a first abnormality detection signal S ₁ (Fig. 6 (g)). Incidentally, the differential amplifier 41 of the second protection circuit 8 outputs 0 V as the second differential amplification voltage V _A2 (see FIG. 6F), and the comparator 42 of the second protection circuit 8 has a second abnormality. and it outputs a low signal to the control IC9 as the detection signal _{S 2} (see FIG. 6 (h)). In this case, the control IC 9, it is determined that an abnormality has occurred in the switching power supply 1 to generate a first 1PWM signal _{P 1} and the second 2PWM signal _{P 2} all consisting OFF signal.

When the first current _{I 1} of the first 1 DC / DC converter circuit 2 becomes small current, also decreases the first current detection voltage _{V 1} of the pulsed voltage component _{V 15, V 16} (see FIG. 6 (a)). Therefore, the smoothing circuit 40 of the first protection circuit 7 outputs the first smoothed voltage V _S1 having a small voltage corresponding to the pulse voltage components V ₁₅ and V ₁₆ (see FIG. 6C). Therefore, the first smoothing voltage V _S1 is smaller than the second smoothing voltage V _S2 , and the differential amplifier 41 of the second protection circuit 8 has (second smoothing voltage V _S2 −first smoothing voltage V _A second differential amplification voltage V _A2 obtained by amplifying _S1 ) is output (see FIG. 6F). Since the second differential amplifier voltage V _A2 is greater than the abnormality detection reference voltage V _R, the comparator 42 of the second protection circuit 8, and outputs a high signal to the control IC9 as second abnormality detection signal S ₂ (Fig. 6 (h)). Incidentally, the differential amplifier 41 of the first protection circuit 7 outputs 0V as the first differential amplification voltage V _A1 (see FIG. 6E), and the comparator 42 of the first protection circuit 7 has a first abnormality. and it outputs a low signal to the control IC9 as a detection signal _{S 1} (see FIG. 6 (g)). In this case, the control IC 9, it is determined that an abnormality has occurred in the switching power supply 1 to generate a first 1PWM signal _{P 1} and the second 2PWM signal _{P 2} all consisting OFF signal.

  According to this switching power supply device 1, it is possible to perform peak current control of the two DC / DC converter circuits 2 and 3 with one control IC 9 with a very simple configuration, and to detect an abnormality in the switching power supply device 1. Can do. In addition, the switching power supply device 1 has a simple configuration including the smoothing circuit 40, the differential amplifier 41, the comparator 42, and the like in the two protection circuits 7 and 8, and the DC / DC converter circuits 2 and 3 fail, overcurrent, DC Various abnormalities such as current imbalance between the DC / DC converter circuits 2 and 3 and disconnection of the cable 1c can be detected. Further, in the switching power supply device 1, although there is only one control IC 9, a failure of the DC / DC converter circuit on one side is provided by providing the protection circuits 7 and 8 corresponding to the DC / DC converter circuits 2 and 3, respectively. And overcurrent can be detected.

  Further, in the switching power supply device 1, since the resistor 40b of the smoothing circuit 40 on one substrate is used as a resistor for grounding the inverting input terminal of the differential amplifier 41 on the other substrate, the differential amplifier 41 on the other substrate is used. Even when the cable 1c connected to the inverting input terminal is disconnected, the differential amplifier 41 can be operated normally, and the disconnection abnormality of the cable 1c can be detected.

  With reference to FIG. 7, the structure of the switching power supply device 51 which concerns on 2nd Embodiment is demonstrated. FIG. 7 is a circuit configuration diagram of the switching power supply according to the second embodiment. In the second embodiment, the same components as those in the switching power supply device 1 according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The switching power supply device 51 has almost the same configuration as that of the switching power supply device 1 according to the first embodiment. However, the switching power supply device 51 is configured on one substrate (not shown), and for each differential amplifier in the two protection circuits. It is composed of one comparator. The switching power supply 51 includes, as main components, a first DC / DC converter circuit 2, a second DC / DC converter circuit 3, a first current detection circuit 4, a second current detection circuit 5, an averaging circuit 6, and a first protection circuit. 57, a second protection circuit 58, and a control IC 9, all of which are provided on one substrate.

  The two protection circuits 57 and 58 have basically the same configuration as that of the protection circuits 7 and 8 according to the first embodiment, but one comparator is provided depending on the provision on one substrate. As well as reducing, the arrangement of the resistors of the smoothing circuit changes. The two protection circuits 57 and 58 have the same configuration, and each includes a smoothing circuit 60, a differential amplifier 41, and resistors 44 to 46, and an averaging circuit 61, a comparator 62, and a determination reference power source 63 are two. Only one circuit is provided. The two protection circuits 57 and 58 are protection circuits for detecting various abnormalities such as an overcurrent and failure of the DC / DC converter circuits 2 and 3 and an abnormal current balance between the DC / DC converter circuits 2 and 3. . Note that the protection circuits 57 and 58 cannot detect which one of the DC / DC converter circuits 2 and 3 has an abnormality.

  The smoothing circuit 60 is a smoothing circuit similar to the smoothing circuit 40 according to the first embodiment, and includes resistors 60a and 60b and a capacitor 60c. Since the switching power supply device 51 is configured on one board, it is not necessary to connect the boards with a cable. Therefore, as in the first embodiment, it is not necessary to take measures against the open state of the inverting input terminal of the differential amplifier 41 due to cable disconnection. Therefore, the resistor 60 b of the first protection circuit 57 is disposed in the vicinity of the resistor 60 a of the first protection circuit 57 without being used for grounding the inverting input terminal of the differential amplifier 41 of the second protection circuit 58. Similarly, the resistor 60 b of the second protection circuit 58 is disposed in the vicinity of the resistor 60 a of the second protection circuit 58 without being used for grounding the inverting input terminal of the differential amplifier 41 of the first protection circuit 57.

The averaging circuit 61 includes resistors 61a and 62b. One end of the resistor 61a is connected to the output terminal of the differential amplifier 41 of the first protection circuit 57, and the other end is connected to the other end of the resistor 61b. One end of the resistor 61 b is connected to the output terminal of the differential amplifier 41 of the second protection circuit 58. The resistor 61a and the resistor 61b have the same resistance value. The averaging circuit 61 averages the first differential amplification voltage V _A1 and the second differential amplification voltage V _A2 and outputs the differential amplification average voltage V _AA .

The comparator 62 is a comparator similar to the comparator 42 according to the first embodiment, but does not compare the first differential amplification voltage V _A1 and the second differential amplification voltage V _A2 , respectively. Compare the average voltages. The comparator 62 has a non-inverting input terminal connected to the connection end of the resistors 61 a and 61 b of the averaging circuit 61, an inverting input terminal connected to the plus terminal of the determination reference power supply 63, and an output terminal connected to the control IC 9. Is done. The negative terminal of the determination reference power supply 63 is connected to the ground. Since the differential amplification average voltage V _AA is an average voltage of the first differential amplification voltage V _A1 and the second differential amplification voltage V _A2, it reflects the voltage change of the two voltages, but the degree of the voltage change is Get smaller. Therefore, the abnormality judgment reference voltage V _R generated by the judgment reference power supply 63 is set to a voltage lower than the abnormality judgment reference voltage V _R according to the first embodiment. In the comparator 62, a high signal when the differential amplifier averaged voltage V _AA is larger than the abnormality judgment reference voltage V _R, when the differential amplifier averaged voltage V _AA is less failure determination reference voltage V _R is An abnormality detection signal S that is a low signal is output.

In the second embodiment, since only the abnormality detection signal S from one comparator 62 is input, the control IC 9 determines whether or not the switching power supply 51 is abnormal based on the abnormality detection signal S. to stop the DC / DC converter circuit 2 and 3 when it is determined, a second 1PWM signal _{P 1} and the second 2PWM all off signal signals _{P 2.} In the control IC 9, when the abnormality detection signal S becomes a high signal, it is determined as abnormal, and when it is low, it is determined as normal.

The operation of the switching power supply device 51 will be described with reference to FIG. Compared with the operation of the switching power supply device 1 according to the first embodiment, the operation of the switching power supply device 51 uses the first differential amplification voltage V _A1 and the second differential amplification voltage V _A2 in the protection circuits 57 and 58. Since only the comparison is made by averaging, the operation of the protection circuits 57 and 58 will be described when the switching power supply device 51 is normal and when the switching power supply device 51 is abnormal. Regarding the abnormality in the switching power supply 51, a case where the second DC / DC converter circuit 3 fails and a case where the first DC / DC converter circuit 3 fails will be described.

When the switching power supply device 51 is normal, the currents I ₁ and I ₂ normally flow in the _two DC / DC converter circuits 2 and 3, and therefore a normal pulse voltage component is represented in the first current detection voltage V _1. We, the normal pulse voltage component to the second current detection voltage V ₂ is appearing. In the two smoothing circuits 60, 60, the first smoothing voltage V _S1 and the second smoothing voltage V _S2 are the same voltage. Therefore, since there is no difference between the first smoothed voltage V _S1 and the second smoothed voltage V _{S2 in} the two differential amplifiers 41 and 41, the first differential amplified voltage V _A1 and the second differential amplified voltage V S 0V is output to the averaging circuit 61 as _A2 . Therefore, even an averaging circuit 61, and outputs 0V to the comparator 62 as a differential amplifier averaged voltage _{V AA.} As a result, the comparator 62, since the differential amplifier averaged voltage V _AA is smaller than the abnormality detection reference voltage V _R, and outputs a low signal to the control IC9 as abnormality detection signal S. In this case, the control IC 9, it is determined that an abnormality in the switching power supply 51 has not occurred, and generates a first 1PWM signal _{P 1} and the second 2PWM signal _{P 2} corresponding to the peak current control.

When the second DC / DC converter circuit 3 fails, the second current I ₂ does not flow in the second DC / DC converter circuit 3, and therefore no pulse voltage component appears in the second current detection voltage V ₂ . Therefore, in the smoothing circuit 60 of the second protection circuit 58, the second smoothing voltage V _S2 is 0V. Accordingly, the second smoothing voltage V _S2 becomes smaller than the first smoothing voltage V _S1 , and the differential amplifier 41 of the first protection circuit 57 ((first smoothing voltage V _S1 −second smoothing voltage V _S2 )). a first differential amplifier voltage V _A1 obtained by amplifying the output to the averaging circuit 61. On the other hand, the differential amplifier 41 of the second protection circuit 58 outputs 0 V to the averaging circuit 61 as the second differential amplification voltage V _A2 . In the averaging circuit 61, the first differential amplification voltage V _A1 and the second differential amplification voltage V _A2 are averaged, and the differential amplification average voltage V _AA reflecting a large voltage of the first differential amplification voltage V _A1. Is output to the comparator 62. Since the differential amplifier averaged voltage V _AA is greater than the abnormality detection reference voltage V _R, the comparator 62 outputs a high signal to the control IC9 as abnormality detection signal S. In this case, the control IC 9, it is determined that an abnormality has occurred in the switching power supply 51, generates a first 1PWM signal _{P 1} and the second 2PWM signal _{P 2} all consisting OFF signal.

When the first DC / DC converter circuit 2 fails, the first current I ₁ does not flow in the first DC / DC converter circuit 2, and therefore no pulse voltage component appears in the first current detection voltage V ₁ . Therefore, in the smoothing circuit 60 of the first protection circuit 57, the first smoothing voltage V _S1 is 0V. Accordingly, the first smoothed voltage V _S1 becomes smaller than the second smoothed voltage V _S1 , and the differential amplifier 41 of the second protection circuit 58 has (second smoothed voltage V _{S2 −first} smoothed voltage V _S1 ). _Is output to the averaging circuit 61. On the other hand, the differential amplifier 41 of the first protection circuit 57 outputs 0 V to the averaging circuit 61 as the first differential amplification voltage V _A1 . In the averaging circuit 61, the first differential amplification voltage V _A1 and the second differential amplification voltage V _A2 are averaged, and the differential amplification average voltage V _AA that reflects a large voltage of the second differential amplification voltage V _A2. Is output to the comparator 62. Since the differential amplifier averaged voltage V _AA is greater than the abnormality detection reference voltage V _R, the comparator 62 outputs a high signal to the control IC9 as abnormality detection signal S. In this case, the control IC 9, it is determined that an abnormality has occurred in the switching power supply 51, generates a first 1PWM signal _{P 1} and the second 2PWM signal _{P 2} all consisting OFF signal.

  According to the switching power supply device 51, the peak current control of the two DC / DC converter circuits 2 and 3 can be performed by one control IC 9 with a very simple configuration, and an abnormality in the switching power supply device 51 can be detected. it can. In addition, the switching power supply device 51 has a simple configuration including the smoothing circuit 60, the differential amplifier 41, the comparator 62, and the like in the two protection circuits 57 and 58, so that the DC / DC converter circuits 2 and 3 fail, overcurrent, DC Various abnormalities such as current imbalance between the DC / DC converter circuits 2 and 3 can be detected.

  With reference to FIG. 8, the structure of the switching power supply device 71 which concerns on 3rd Embodiment is demonstrated. FIG. 8 is a circuit configuration diagram of the switching power supply according to the third embodiment. In the third embodiment, the same components as those of the switching power supply device 51 according to the second embodiment are denoted by the same reference numerals, and the description thereof is omitted.

The switching power supply device 71 has almost the same configuration as the switching power supply device 51 according to the second embodiment, but the first smoothing voltage V _S1 and the second smoothing are applied to the non-inverting input terminals of the two differential amplifiers. In this configuration, an averaged voltage with the voltage V _S2 is input. The switching power supply device 71 includes, as main components, a first DC / DC converter circuit 2, a second DC / DC converter circuit 3, a first current detection circuit 4, a second current detection circuit 5, an averaging circuit 6, and a first protection circuit. 77, a second protection circuit 78, and a control IC 9.

  The two protection circuits 77 and 78 have basically the same configuration as that of the protection circuits 57 and 58 according to the second embodiment, but the voltage input to the differential amplifier is changed. The two protection circuits 77 and 78 have the same configuration, and each includes a smoothing circuit 60, an averaging circuit 87, a differential amplifier 81, and resistors 84 to 86, an averaging circuit 61, a comparator 62, and a determination. One reference power supply 63 is provided with two circuits. The two protection circuits 77 and 78 are protection circuits for detecting various abnormalities such as an overcurrent and failure of the DC / DC converter circuits 2 and 3 and an abnormal current balance between the DC / DC converter circuits 2 and 3. . The protection circuits 77 and 78 cannot detect which one of the DC / DC converter circuits 2 and 3 has an abnormality.

The averaging circuit 87 includes resistors 87a and 87b. One end of the resistor 87a is connected to the connection end of the smoothing circuit 60 of the first protection circuit 77 between the resistor 60a, the resistor 60b, and the capacitor 60c, and the other end is connected to the other end of the resistor 87b. One end of the resistor 87b is connected to a connection end of the resistor 60a, the resistor 60b, and the capacitor 60c of the smoothing circuit 60 of the second protection circuit 78. The resistor 87a and the resistor 87b have the same resistance value. The averaging circuit 87 averages the first smoothed voltage V _S1 and the second smoothed voltage V _S2 and outputs a smoothed average voltage V _SA .

The differential amplifier 81 of the first protection circuit 77 has a non-inverting input terminal connected to the connection end of the resistors 87 a and 87 b of the averaging circuit 87 via the resistor 84, and an inverting input terminal of the first protection circuit 77. The smoothing circuit 60 is connected to a connection end of the resistor 60a, the resistor 60b, and the capacitor 60c via a resistor 85. The differential amplifier 81 of the second protection circuit 78 has a non-inverting input terminal connected to the connection end of the resistors 87 a and 87 b of the averaging circuit 87 via the resistor 84, and an inverting input terminal of the second protection circuit 78. The smoothing circuit 60 is connected to a connection end of the resistor 60a, the resistor 60b, and the capacitor 60c via a resistor 85. Further, the differential amplifier 81 has an output terminal connected to the inverting input terminal via the resistor 86. In the differential amplifier 81 of the first protection circuit 77, smoothed average voltage _{V SA} is the greater than the first smoothed voltage _{V S1} obtained by subtracting the first smoothing voltage _{V S1} from the smoothed average voltage _{V SA} The differential voltage value is amplified, and when the smoothed average voltage V _SA is equal to or lower than the first smoothed voltage V _S1 , the first differential amplified voltage V _A1 is output as 0V. In the differential amplifier 81 of the second protection circuit 78, smoothed average voltage _{V SA} is the larger than the second smoothed voltage _{V S2} obtained by subtracting the second smoothed voltage _{V S2} from the smoothed average voltage _{V SA} The differential voltage value is amplified, and when the smoothed average voltage V _SA is equal to or lower than the second smoothed voltage V _S2 , the second differential amplified voltage V _A2 is output as 0V.

  The operation of the switching power supply device 71 will be described with reference to FIG. Since the operation in the switching power supply 71 is different from the operation in the switching power supply 51 according to the second embodiment, only the voltages input to the differential amplifiers 81 and 81 in the two protection circuits 77 and 78 are different. The operations in 77 and 78 will be described when the switching power supply 71 is normal and when an abnormality occurs in the switching power supply 71. Regarding the abnormality in the switching power supply device 71, a case where the second DC / DC converter circuit 3 fails and a case where the first DC / DC converter circuit 2 fails will be described.

When the switching power supply device 71 is normal, the currents I ₁ and I ₂ normally flow in the _two DC / DC converter circuits 2 and 3, and therefore a normal pulse voltage component is represented in the first current detection voltage V _1. We, the normal pulse voltage component to the second current detection voltage V ₂ is appearing. In the two smoothing circuits 60, 60, the first smoothing voltage V _S1 and the second smoothing voltage V _S2 are the same voltage. Therefore, the averaging circuit 87 outputs the same voltage as the first smoothed voltage V _S1 (second smoothed voltage V _S2 ) to the two differential amplifiers 81 and 81 as the smoothed average voltage V _SA . Therefore, in the two differential amplifiers 81 and 81, there is no difference between the smoothed average voltage V _SA and the first smoothed voltage V _S1 or the second smoothed voltage V _S2, and thus the first differential amplified voltage V _A1. , 0 V is output to the averaging circuit 61 as the second differential amplification voltage V _A2 . Therefore, even an averaging circuit 61, and outputs 0V to the comparator 62 as a differential amplifier averaged voltage _{V AA.} As a result, the comparator 62, since the differential amplifier averaged voltage V _AA is smaller than the abnormality detection reference voltage V _R, and outputs a low signal (0V) to the control IC9 as abnormality detection signal S. In this case, the control IC 9, it is determined that an abnormality in the switching power supply 71 has not occurred, and generates a first 1PWM signal _{P 1} and the second 2PWM signal _{P 2} corresponding to the peak current control.

When the second DC / DC converter circuit 3 fails, the second current I ₂ does not flow in the second DC / DC converter circuit 3, and therefore no pulse voltage component appears in the second current detection voltage V ₂ . Therefore, in the smoothing circuit 60 of the second protection circuit 78, the second smoothing voltage V _S2 is 0V. On the other hand, since the first current I ₁ normally flows in the first DC / DC converter circuit 2, a normal pulse voltage component appears in the first current detection voltage V ₁ . Therefore, the smoothing circuit 60 of the first protection circuit 77 outputs the first smoothed voltage V _S1 according to the first current detection voltage V ₁ . In the averaging circuit 87, the first smoothed voltage V _S1 and the second smoothed voltage V _S2 are averaged, and the smoothed average voltage V _SA that is about half of the first smoothed voltage V _S1 is converted into two differential amplifiers. 81 and 81, respectively. Therefore, the second smoothed voltage V _S2 (0 V) is smaller than the smoothed average voltage V _SA , and the differential amplifier 81 of the second protection circuit 78 has (smoothed average voltage V _SA −second smoothed voltage). A second differential amplification voltage V _A2 obtained by amplifying V _S2 ) is output to the averaging circuit 61. On the other hand, the differential amplifier 81 of the first protection circuit 77 outputs 0 V to the averaging circuit 61 as the first differential amplification voltage V _A1 . In the averaging circuit 61, the first differential amplification voltage V _A1 and the second differential amplification voltage V _A2 are averaged, and the differential amplification average voltage V _AA that reflects a large voltage of the second differential amplification voltage V _A2. Is output to the comparator 62. Since the differential amplifier averaged voltage V _AA is greater than the abnormality detection reference voltage V _R, the comparator 62 outputs a high signal to the control IC9 as abnormality detection signal S. In this case, the control IC 9, it is determined that an abnormality in the switching power supply apparatus 71 has occurred, and generates a first 1PWM signal _{P 1} and the second 2PWM signal _{P 2} all consisting OFF signal.

When the first DC / DC converter circuit 2 fails, the first current I ₁ does not flow in the first DC / DC converter circuit 2, and therefore no pulse voltage component appears in the first current detection voltage V ₁ . Therefore, in the smoothing circuit 60 of the first protection circuit 77, the first smoothing voltage V _S1 is 0V. On the other hand, since the 2DC / DC converter in the circuit 3 and the second current I ₂ flows normally, the normal pulse voltage component to the second current detection voltage V ₂ is appearing. Therefore, the smoothing circuit 60 of the second protection circuit 58, and outputs a second smoothed voltage _{V S2} corresponding to the second current detection voltage _{V 2.} In the averaging circuit 87, the first smoothed voltage V _S1 and the second smoothed voltage V _S2 are averaged, and the smoothed average voltage V _SA that is about half of the second smoothed voltage V _S2 is converted into two differential amplifiers. 81 and 81, respectively. Therefore, the first smoothed voltage V _S1 (0 V) is smaller than the smoothed average voltage V _SA , and the differential amplifier 81 of the first protection circuit 77 has (smoothed average voltage V _SA −first smoothed voltage). The first differential amplification voltage V _A1 obtained by amplifying V _S1 ) is output to the averaging circuit 61. On the other hand, the differential amplifier 81 of the second protection circuit 78 outputs 0 V to the averaging circuit 61 as the second differential amplification voltage V _A2 . In the averaging circuit 61, the first differential amplification voltage V _A1 and the second differential amplification voltage V _A2 are averaged, and the differential amplification average voltage V _AA reflecting a large voltage of the first differential amplification voltage V _A1. Is output to the comparator 62. Since the differential amplifier averaged voltage V _AA is greater than the abnormality detection reference voltage V _R, the comparator 62 outputs a high signal to the control IC9 as abnormality detection signal S. In this case, the control IC 9, it is determined that an abnormality in the switching power supply apparatus 71 has occurred, and generates a first 1PWM signal _{P 1} and the second 2PWM signal _{P 2} all consisting OFF signal.

  The switching power supply device 71 has the same effect as the switching power supply device 51 according to the second embodiment.

  A first protection circuit 90, a second protection circuit 91, and a third protection circuit 92 of the switching power supply according to the fourth embodiment will be described with reference to FIG. FIG. 9 is a circuit diagram of a protection circuit in the switching power supply according to the fourth embodiment. In FIG. 9, the smoothing circuit in the protection circuit is not drawn. In the fourth embodiment, the same components as those of the switching power supply device 1 according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The switching power supply device (not shown) according to the fourth embodiment is the same switching power supply device as the switching power supply device 1 according to the first embodiment, but can supply a larger current than the switching power supply device 1. Power circuit. Therefore, this switching power supply device is a switching power supply device in which three DC / DC converter circuits 2 (3) in the switching power supply device 1 are connected in parallel, and each output of the three DC / DC converter circuits (not shown). Outputs the combined current. In this switching power supply device, a current detection circuit is provided for each of the three DC / DC converter circuits, and the three currents (voltages) detected by the three current detection circuits are averaged to obtain a control IC (not shown). The peak current control is performed using this current average voltage. Further, in this switching power supply device, various abnormalities in the switching power supply device are detected by the first protection circuit 90, the second protection circuit 91, and the third protection circuit 92 provided corresponding to the three current detection circuits.

  The three protection circuits 90, 91, and 92 have the same configuration, and include a smoothing circuit (not shown), a differential amplifier 41, a comparator 42, a determination reference power supply 43, and resistors 44 to 47. The first protection circuit 90 has an overcurrent of the first DC / DC converter circuit, a failure of the second DC / DC converter circuit, a current balance abnormality between the first DC / DC converter circuit and the second DC / DC converter circuit (the first current is the first current). This is a protection circuit for detecting various abnormalities such as when larger than 2 currents. The second protection circuit 91 includes an overcurrent of the second DC / DC converter circuit, a failure of the third DC / DC converter circuit, a current balance abnormality between the second DC / DC converter circuit and the third DC / DC converter circuit (the second current is the second current). This is a protection circuit for detecting an abnormality such as when larger than 3 currents. The third protection circuit 92 includes an overcurrent of the third DC / DC converter circuit, a failure of the first DC / DC converter circuit, a current balance abnormality between the third DC / DC converter circuit and the first DC / DC converter circuit (the third current is the first current). This is a protection circuit for detecting various abnormalities such as when the current is larger than one current.

The differential amplifier 41 of the first protection circuit 90 has a non-inverting input terminal connected to the smoothing circuit output terminal of the first protection circuit 90 via the resistor 44 and an inverting input terminal output of the smoothing circuit of the second protection circuit 91. The end is connected via a resistor 45. The differential amplifier 41 of the second protection circuit 91 has a non-inverting input terminal connected to the output terminal of the smoothing circuit of the second protection circuit 91 via the resistor 44 and an inverting input terminal of the smoothing circuit of the third protection circuit 92. The output terminal is connected via a resistor 45. The differential amplifier 41 of the third protection circuit 92 has a non-inverting input terminal connected to the smoothing circuit output terminal of the third protection circuit 92 via the resistor 44, and an inverting input terminal output of the smoothing circuit of the first protection circuit 90. The end is connected via a resistor 45. Further, the differential amplifier 41 has an output terminal connected to an inverting input terminal via a resistor 46. In the differential amplifier 41 of the first protection circuit 90, first smoothing voltage _{V S1} is the case larger than the second smoothed voltage _{V S2} obtained by subtracting the second smoothed voltage _{V S2} from the first smoothing voltage _{V S1} The differential voltage value is amplified, and when the first smoothed voltage V _S1 is equal to or lower than the second smoothed voltage V _S2 , the first differential amplified voltage V _A1 is output as 0V. In the differential amplifier 41 of the second protection circuit 91, a second smoothing voltage _{V S2} is the case larger than the third smoothing voltage _{V S3} by subtracting the third smoothing voltage _{V S3} from the second smoothing voltage _{V S2} The differential voltage value is amplified, and when the second smoothed voltage V _S2 is equal to or lower than the third smoothed voltage V _S3 , the second differential amplified voltage V _A2 is output as 0V. In the differential amplifier 41 of the third protection circuit 92, a third smoothing voltage _{V S3} is the greater than the first smoothed voltage _{V S1} obtained by subtracting the first smoothing voltage _{V S1} from the third smoothing voltage _{V S3} The differential voltage value is amplified, and when the third smoothed voltage V _S3 is equal to or lower than the first smoothed voltage V _S1 , the third differential amplified voltage V _A3 is set to 0V.

  With reference to FIG. 9, the operation of the protection circuits 90, 91, 92 of the switching power supply according to the fourth embodiment will be described. Here, the operation in the protection circuits 90, 91, 92 will be described when the switching power supply device is normal and when the switching power supply device is abnormal. Regarding the abnormality in the switching power supply device, the case where the second DC / DC converter circuit fails, and the case where the third DC / DC converter circuit and the first DC / DC converter circuit fail are described.

When the switching power supply device is normal, the currents normally flow in the three DC / DC converter circuits. Therefore, a normal pulse voltage component appears in the first current detection voltage, and the second current detection voltage is also normal. Thus, a normal pulse voltage component appears in the third current detection voltage. In the three smoothing circuits, the first smoothing voltage V _S1 , the second smoothing voltage V _S2 , and the third smoothing voltage V _S3 are the same voltage. Therefore, in the three differential amplifiers 41, 41, 41, the first smoothed voltage V _S1 and the second smoothed voltage V _S2 , the second smoothed voltage V _S3 , the third smoothed voltage V _S3 , and the third smoothed voltage are used. Since there is no difference between the voltage V _S3 and the first smoothed voltage V _S1 , 0 V is set as the comparator 42 as the first differential amplification voltage V _A1 , the second differential amplification voltage V _A2 , and the third differential amplification voltage V _A3. , 42, 42. As a result, the three comparators 42,42,42, first differential amplifying voltage _{V A1,} the second differential amplifier voltage _{V A2,} the third differential amplifier voltage _{V A3} is smaller than the abnormality detection reference voltage _{V R} Therefore, a low signal (0 V) is output to the control IC as the first abnormality detection signal S ₁ , the second abnormality detection signal S ₂ , and the third abnormality detection signal S ₃ . In this case, the control IC determines that no abnormality has occurred in the switching power supply device, and generates the first PWM signal and the second PWM signal corresponding to the peak current control.

When the second DC / DC converter circuit fails, the second current does not flow in the second DC / DC converter circuit, so that no pulse voltage component appears in the second current detection voltage. Therefore, in the smoothing circuit 40 of the second protection circuit 91, the second smoothing voltage V _S2 is 0V. Therefore, the second smoothing voltage V _S2 becomes smaller than the first smoothing voltage V _S1 , and the differential amplifier 41 of the first protection circuit 90 has (first smoothing voltage V _S1 −second smoothing voltage V _S2 ). _Is output as a first differential amplification voltage V _A1 . Since this first differential amplifier voltage V _A1 becomes larger than the abnormality detection reference voltage V _R, the comparator 42 of the first protection circuit 90, outputs a high signal to the control IC as a first abnormality detection signal S _1. Incidentally, in the differential amplifier 41 of the second protection circuit 91 and outputs a 0V as the second differential amplifying voltage V _A2, a low signal as a comparator in 42 second abnormality detection signal S ₂ of the second protection circuit 91 Output to the control IC. The third and outputs 0V as the third differential amplifier voltage V _A3 in the differential amplifier 41 of the protection circuit 92, a low signal as the third abnormality detection signal S ₃ in the comparator 42 of the third protection circuit 92 Output to the control IC. In this case, the control IC determines that an abnormality has occurred in the switching power supply device, and generates the first PWM signal and the second PWM signal that are all off signals.

When the third DC / DC converter circuit fails, the third current does not flow in the third DC / DC converter circuit, and therefore no pulse voltage component appears in the third current detection voltage. Therefore, in the smoothing circuit 40 of the third protection circuit 92, the third smoothing voltage V _S3 is 0V. Therefore, the third smoothing voltage V _S3 becomes smaller than the second smoothing voltage V _S2 , and the differential amplifier 41 of the second protection circuit 91 has (second smoothing voltage V _{S2 −third} smoothing voltage V _S3 ). _Is output as a second differential amplification voltage V _A2 . Since the second differential amplifier voltage V _A2 is greater than the abnormality detection reference voltage V _R, the comparator 42 of the second protection circuit 91, outputs a high signal to the control IC as the second abnormality detection signal S _2. Incidentally, the differential amplifier 41 of the first protection circuit 90 outputs 0 V as the first differential amplification voltage V _A1 , and the comparator 42 of the first protection circuit 90 outputs a low signal as the first abnormality detection signal S _1. Output to the control IC. The third and outputs 0V as the third differential amplifier voltage V _A3 in the differential amplifier 41 of the protection circuit 92, a low signal as the third abnormality detection signal S ₃ in the comparator 42 of the third protection circuit 92 Output to the control IC. In this case, the control IC determines that an abnormality has occurred in the switching power supply device, and generates the first PWM signal and the second PWM signal that are all off signals.

When the first DC / DC converter circuit fails, the first current does not flow in the first DC / DC converter circuit, so that no pulse voltage component appears in the first current detection voltage. Therefore, in the smoothing circuit 40 of the first protection circuit 90, the first smoothing voltage V _S1 is 0V. Accordingly, the first smoothed voltage V _S1 becomes smaller than the third smoothed voltage V _S3 , and the differential amplifier 41 of the third protection circuit 92 has (third smoothed voltage V _{S3 −first} smoothed voltage V _S1 ). _Is output as a third differential amplification voltage V _A3 . Since the third differential amplifier voltage V _A3 is greater than the abnormality detection reference voltage V _R, the comparator 42 of the third protection circuit 92 outputs a high signal to the control IC as a third abnormality detection signal S _3. Incidentally, the differential amplifier 41 of the first protection circuit 90 outputs 0 V as the first differential amplification voltage V _A1 , and the comparator 42 of the first protection circuit 90 outputs a low signal as the first abnormality detection signal S _1. Output to the control IC. Further, in the differential amplifier 41 of the second protection circuit 91 and outputs a 0V as the second differential amplifying voltage V _A2, a low signal as a comparator in 42 second abnormality detection signal S ₂ of the second protection circuit 91 Output to the control IC. In this case, the control IC determines that an abnormality has occurred in the switching power supply device, and generates the first PWM signal and the second PWM signal that are all off signals.

  According to the switching power supply according to the fourth embodiment, it is possible to control the peak current of the three DC / DC converter circuits with one control IC with a very simple configuration, and to detect an abnormality in the switching power supply. Can be detected. In addition, this switching power supply device has a simple configuration including a smoothing circuit, a differential amplifier 41, a comparator 42, and the like in the three protection circuits 90, 91, and 92. It is possible to detect various abnormalities such as current imbalance between DC / DC converter circuits. Further, in this switching power supply apparatus, there is one control IC, but by providing three protection circuits 90, 91, 92 corresponding to each DC / DC converter circuit, one of the three DC / DCs is provided. It is possible to detect a converter circuit failure or overcurrent.

  As mentioned above, although embodiment which concerns on this invention was described, this invention is implemented in various forms, without being limited to the said embodiment.

  For example, in this embodiment, the present invention is applied to a switching power supply circuit in which two or three DC / DC converter circuits are connected in parallel. However, the present invention is applied to a switching power supply circuit in which four or more DC / DC converter circuits are connected in parallel. Also good.

  In this embodiment, a full bridge circuit is applied as the bridge circuit, but other bridge circuits such as a half bridge circuit and a push-pull circuit may be applied. Moreover, although applied to the switching power supply device provided with a bridge circuit in this Embodiment, you may apply to the switching power supply device which is not provided with a bridge circuit.

  In this embodiment, the averaging circuit is configured as a circuit that generates a value based on the sum of currents (voltage values) detected by the current detection circuit. However, another circuit such as integration may be configured. Alternatively, the current (voltage value) detected by the current detection circuit may be directly taken into the control IC and averaged or integrated by the control IC.

  In the present embodiment, the control means is configured by an analog circuit (control IC), but may be configured by a digital circuit. Further, in the present embodiment, the comparator or the like in the protection circuit is configured by an analog circuit, but may be configured by a digital circuit using a microcomputer or the like.

  In this embodiment, the PWM signal is applied as the drive signal, but a signal of another modulation method such as a PWM signal using phase shift may be applied.

  Further, in the present embodiment, when an abnormality is detected, both DC / DC converter circuits are stopped. However, the DC / DC converter circuit on the side where the abnormality has occurred may be stopped, or It may be configured to display a warning signal or display indicating an abnormality.

1 is a configuration diagram of a switching power supply device according to a first embodiment. FIG. It is a circuit block diagram of the switching power supply device of FIG. It is the input-output characteristic of the differential amplifier of FIG. FIG. 2 is an explanatory diagram of peak current control in the switching power supply device of FIG. 1, where (a) is a current average voltage and a control signal compared by a control IC, and (b) is a first PWM signal generated by the control IC. , (C) is a second PWM signal generated by the control IC. 2 is a timing chart when a DC / DC converter circuit fails in the switching power supply device of FIG. 1, wherein (a) is a first current detection voltage detected by a first current detection circuit, and (b) is a second current detection. (C) is a first smoothing voltage in the first protection circuit, (d) is a second smoothing voltage in the second protection circuit, and (e) is a second current detection voltage detected by the circuit. (F) is a second differential amplification voltage in the second protection circuit, (g) is a first abnormality detection signal in the first protection circuit, h) is a second abnormality detection signal in the second protection circuit. The change of each voltage and each signal with respect to various patterns of the pulse voltage component in the first current detection voltage and the second current detection voltage is shown, and (a) is the first current detection voltage detected by the first current detection circuit. (B) is the second current detection voltage detected by the second current detection circuit, (c) is the first smoothing voltage in the first protection circuit, and (d) is the second current detection voltage in the second protection circuit. (E) is the first differential amplification voltage in the first protection circuit, (f) is the second differential amplification voltage in the second protection circuit, and (g) is the first protection circuit. (H) is a second abnormality detection signal in the second protection circuit. It is a circuit block diagram of the switching power supply device which concerns on 2nd Embodiment. It is a circuit block diagram of the switching power supply device which concerns on 3rd Embodiment. It is a circuit diagram of the protection circuit in the switching power supply device concerning a 4th embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,51,71 ... Switching power supply device, 1a ... 1st board | substrate, 1b ... 2nd board | substrate, 1c ... Cable, 2 ... 1st DC / DC converter circuit, 3 ... 2nd DC / DC converter circuit, 4 ... 1st electric current detection Circuit 5, 5 Second current detection circuit 6 Average circuit 7, 57, 77 First protection circuit 8, 58, 78 Second protection circuit 9 Control IC 10 Full bridge circuit 10a ... 1st FET, 10b ... 2nd FET, 10c ... 3rd FET, 10d ... 4th FET, 11 ... Transformer, 11a ... Primary winding, 11b ... 1st winding, 11c ... 2nd winding, 12, 13 ... Diode, 14 ... smoothing circuit, 14a ... inductor, 14b ... capacitor, 15 ... power supply, 20 ... transformer, 20a ... primary winding, 20b ... secondary winding, 21 ... diode, 22 ... resistor, 30, 31 ... resistor, 40 60 ... smoothing circuit, 40a, 40b, 60a, 60b ... resistor, 40c, 60c ... capacitor, 41, 81 ... differential amplifier, 42, 62 ... comparator, 43, 63 ... judgment reference power supply, 44-47 ... resistor, 61 ... Averaging circuit, 61a, 61b ... Resistor, 84-86 ... Resistor, 87 ... Averaging circuit, 87a, 87b ... Resistor, 90 ... First protection circuit, 91 ... Second protection circuit, 92 ... Third protection circuit

Claims (4)

A plurality of converter circuits each including a switching element and connected in parallel;
A plurality of current detecting means for detecting each of the currents flowing through the plurality of converter circuits;
A current value provided by each of the plurality of current detection means and based on a current detected by an arbitrary current detection means among the plurality of current detection means and a current detected by a current detection means other than the arbitrary current detection means A plurality of differential amplification means for amplifying a difference from a value based on
Comparison means for comparing a value based on the current difference amplified by each of the plurality of differential amplification means and an abnormality determination value;
Control means for generating a drive signal for switching control of the switching element based on a value based on a sum of currents detected by the plurality of current detection means, and for controlling peak current of the plurality of converter circuits. A switching power supply device. When the plurality of converter circuits are provided on different substrates, and the current detection means and the differential amplification means corresponding to each converter circuit are provided on each substrate,
The differential amplifying means provided on each substrate is characterized in that a terminal to which a value based on a current detected by a current detecting means provided on a different substrate is input is connected to the ground of the substrate via a resistor. The switching power supply device according to claim 1. When the plurality of converter circuits, the plurality of current detection means, the plurality of differential amplification means and the comparison means are provided on the same substrate,
Current difference averaging means for averaging current differences amplified by the plurality of differential amplification means,
2. The switching power supply device according to claim 1, wherein the comparison unit compares the current difference averaged by the current difference averaging unit with an abnormality determination value. 4. The apparatus according to claim 1, further comprising a plurality of smoothing units that are respectively provided corresponding to the plurality of current detection units and smooth the currents detected by the plurality of current detection units. A switching power supply device according to claim 1.

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