Power supply device

Abstract

To protect a synchronous rectifying element by detecting its abnormality.SOLUTION: The power supply device includes an intermittent voltage generation circuit, a rectifying and smoothing circuit, a synchronous rectifying element drive circuit, an abnormality detection circuit, a load current detection circuit, and a protection circuit. The intermittent voltage generation circuit generates an intermittent voltage from an input voltage from an external power supply by a switching element that repeatedly turns on and off. The rectifying and smoothing circuit rectifies the intermittent voltage by a synchronous rectifying element that is turned on and off in synchronization with turning on and off of the switching element, smoothes the rectified voltage by a capacitor, and supplies the smoothed voltage to a load. The synchronous rectifier element drive circuit supplies a control signal for turning on and off the synchronous rectifier element to a control terminal of the synchronous rectifier element. The abnormality detection circuit detects an abnormality of the synchronous rectifier element drive circuit. The load current detection circuit detects a load current that is a current of the load supplied by the rectifying and smoothing circuit. The protection circuit performs a protection operation based on a detection result of the abnormality detection circuit and a detection result of the load current detection circuit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power supply device. [Background technology]

[0002] In switching power supplies and the like, power supply circuits that use synchronous rectification circuits in the rectification circuit on the secondary side are used (see, for example, Patent Document 1). This synchronous rectification is a method in which a synchronous rectification element such as a MOS transistor is used as a rectification element by switching between conducting and non-conducting states. This method can achieve lower loss than a rectification circuit that uses a diode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-292572 Summary of the Invention [Problem to be solved by the invention]

[0004] The driver circuit for this synchronous rectifier element detects the timing to turn the synchronous rectifier element on, generates a drive signal, and applies it to the gate of the MOS transistor that makes up the synchronous rectifier element.If a failure in this driver circuit or other reason prevents the control signal from being supplied to the gate of the MOS transistor that constitutes the synchronous rectifier element, the body diode of the MOS transistor will become conductive, causing an increase in loss in the MOS transistor.

[0005] Therefore, the present disclosure proposes a power supply device that detects and protects an abnormality in a synchronous rectifier element. [Means for solving the problem]

[0006] The power supply device of the present disclosure includes an intermittent voltage generation circuit that generates an intermittent voltage from an input voltage from an external power source using a switching element that repeatedly turns on and off; a rectifying and smoothing circuit that rectifies the intermittent voltage using a synchronous rectifying element that turns on and off in synchronization with the on and off of the switching element, smooths the voltage using a capacitor, and supplies the voltage to a load; a synchronous rectifying element drive circuit that supplies a control signal for turning the synchronous rectifying element on and off to a control terminal of the synchronous rectifying element; an abnormality detection circuit that detects an abnormality in the synchronous rectifying element drive circuit; a load current detection circuit that detects a load current, which is the current of the load supplied by the rectifying and smoothing circuit; and a protection circuit that performs protection operation based on the detection results of the abnormality detection circuit and the detection results of the load current detection circuit. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating an example of the configuration of a power supply device according to a first embodiment of the present disclosure. [Figure 2] 1 is a diagram illustrating an example of a synchronous rectifier element according to a first embodiment of the present disclosure. [Figure 3] 2 is a diagram illustrating a configuration example of an abnormality detection circuit according to a first embodiment of the present disclosure. FIG. [Figure 4] FIG. 2 is a diagram illustrating an example of abnormality detection according to the first embodiment of the present disclosure. [Figure 5] 1 is a diagram illustrating a configuration example of a load current detection circuit according to a first embodiment of the present disclosure. [Figure 6] 1 is a diagram illustrating a configuration example of a protection circuit according to a first embodiment of the present disclosure. [Figure 7] FIG. 10 is a diagram illustrating an example of the configuration of a power supply device according to a second embodiment of the present disclosure. [Figure 8] FIG. 10 is a diagram illustrating a configuration example of a current limiting circuit and a protection circuit according to a second embodiment of the present disclosure. [Figure 9] FIG. 10 is a diagram illustrating an example of the operation of the current limiting circuit and the protection circuit according to the second embodiment of the present disclosure. [Figure 10] FIG. 10 is a diagram illustrating an example of the configuration of a power supply device according to a third embodiment of the present disclosure. [Figure 11]FIG. 10 is a diagram illustrating an example of the configuration of a power supply device according to a fourth embodiment of the present disclosure. [Figure 12] FIG. 10 is a diagram illustrating an example of the configuration of a power supply device according to a fifth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be given in the following order. In the following embodiments, the same components are designated by the same reference numerals, and redundant description will be omitted. 1. First embodiment 2. Second embodiment 3. Third embodiment 4. Fourth Embodiment 5. Fifth Embodiment

[0009] (1. First embodiment) [Power supply configuration] 1 is a diagram showing an example of the configuration of a power supply device according to a first embodiment of the present disclosure. The figure is a circuit diagram showing an example of the configuration of power supply device 1. Power supply device 1 converts an input voltage from an AC power source 2 into a desired DC voltage and outputs it. Power supply device 1 in the figure supplies the DC voltage to a load 3.

[0010] The power supply device 1 includes a rectifier circuit 100, a capacitor 11, an intermittent voltage generating circuit 110, a transformer 12, a rectifying and smoothing circuit 120, synchronous rectifier element driving circuits 17 and 18, a resistor 19, a control unit 20, and an output voltage detecting unit 21. The power supply device 1 also includes an abnormality detecting circuit 130, a load current detecting circuit 150, and a protection circuit 160. The rectifier circuit 100, the capacitor 11, the intermittent voltage generating circuit 110, the transformer 12, the rectifying and smoothing circuit 120, the synchronous rectifier element driving circuits 17 and 18, the resistor 19, the control unit 20, the output voltage detecting unit 21, the abnormality detecting circuit 130, the load current detecting circuit 150, and the protection circuit 160 constitute a power supply circuit 10.

[0011] The rectifier circuit 100 is a circuit that rectifies an AC input voltage. The rectifier circuit 100 in the figure is configured as a bridge rectifier circuit. An AC power supply 2 is connected to a pair of input terminals of the rectifier circuit 100. The high-potential output terminal and the low-potential output terminal of the rectifier circuit 100 are connected to a capacitor 11 and an intermittent voltage generating circuit 110, which are connected in parallel.

[0012] The capacitor 11 smoothes the voltage output from the rectifier circuit 100 and input to the intermittent voltage generating circuit 110 .

[0013] The discontinuous voltage generating circuit 110 generates a discontinuous voltage from an input voltage from an external power source. The discontinuous voltage generating circuit 110 shown in the figure is an example configured as a half-bridge circuit. The discontinuous voltage generating circuit 110 includes switching elements 111 and 112 and capacitors 113 and 114. MOS transistors can be used for the switching elements 111 and 112. The switching elements 111 and 112 are alternately turned on and off, thereby generating a discontinuous voltage, which is a pulse voltage, from the output voltage of the rectifier circuit 100 smoothed by the capacitor 11. This discontinuous voltage is applied to the primary winding of the transformer 12. Note that circuits other than the half-bridge type, such as a full-bridge type circuit, can also be used for the discontinuous voltage generating circuit 110.

[0014] The transformer 12 insulates the primary and secondary sides of the power supply device 1 and converts the output voltage of the intermittent voltage generating circuit 110. The secondary winding of the transformer 12 is connected to the rectifying and smoothing circuit 120.

[0015] The rectifying and smoothing circuit 120 is a circuit that rectifies and smoothes the pulse voltage from the secondary winding of the transformer 12 to generate a DC voltage. The rectifying and smoothing circuit 120 includes switching elements 13 and 14, an inductor 15, and a capacitor 16. The switching elements 13 and 14 can be made of n-channel MOS transistors.

[0016] One end of the secondary winding of the transformer 12 is connected to the source of the switching element 13, and the other end of the secondary winding of the transformer 12 is connected to the source of the switching element 14. A center tap of the secondary winding of the transformer 12 is connected to one end of the inductor 15. The other end of the inductor 15 is connected to a wiring 41. The capacitor 16 is connected between the wiring 41 and a reference potential line 40. The drains of the switching elements 13 and 14 are commonly connected to the reference potential line 40. The gate of the switching element 13 is connected to a synchronous rectifier element drive circuit 17 via a signal line 50. The gate of the switching element 14 is connected to a synchronous rectifier element drive circuit 18 via a signal line 51. The rectifying and smoothing circuit 120 in the figure represents an example configured as a full-wave rectifier circuit.

[0017] Switching element 13 and switching element 14 correspond to synchronous rectification elements. Switching element 13 is driven to be turned on and off in synchronization with switching element 111. Furthermore, switching element 14 is driven to be turned on and off in synchronization with switching element 112. This allows synchronous rectification of switching elements 13 and 14. A control signal from synchronous rectification element drive circuit 17 is input to the gate of switching element 13. A control signal from synchronous rectification element drive circuit 18 is input to the gate of switching element 14. Furthermore, inductor 15 and capacitor 16 form a smoothing circuit.

[0018] The synchronous rectifier element drive circuit 17 generates a control signal for the switching element 13. This control signal is transmitted via a signal line 50. The drain voltage and source voltage of the switching element 13 are also input to the synchronous rectifier element drive circuit 17 via a signal line. The synchronous rectifier element drive circuit 17 detects on / off timing based on the drain-source voltage (Vds) of the switching element 13 and generates a control signal. The synchronous rectifier element drive circuit 18 generates a control signal for the switching element 14. This control signal is transmitted via a signal line 51. Similar to the synchronous rectifier element drive circuit 17, the drain voltage and source voltage of the switching element 14 are also input to the synchronous rectifier element drive circuit 18 via a signal line. The synchronous rectifier element drive circuit 18 generates a control signal based on the Vds of the switching element 14.

[0019] The wiring 41 is connected to the wiring 42 via a resistor 19. The wiring 42 and the reference potential line 40 are connected to the load 3 and supply a load current to the load 3. The resistor 19 is a resistor for detecting the load current.

[0020] The abnormality detection circuit 130 detects abnormalities in the synchronous rectifier element drive circuits 17 and 18. Such abnormalities occur when a control signal is not supplied to at least one of the synchronous rectifier element drive circuits 17 and 18. The above-mentioned signal lines 50 and 51 are wired to the abnormality detection circuit 130. The abnormality detection result of the abnormality detection circuit 130 is output to the protection circuit 160. The configuration of the abnormality detection circuit 130 will be described in detail later.

[0021] The load current detection circuit 150 detects the load current. This load current detection circuit 150 detects the load current based on the voltage between the terminals of the resistor 19. The detected load current is output to the protection circuit 160. The configuration of the load current detection circuit 150 will be described in detail later.

[0022] The protection circuit 160 performs a protection operation based on the detection results of the abnormality detection circuit 130 and the load current detection circuit 150. The configuration of the protection circuit 160 will be described in detail later.

[0023] The output voltage detection unit 21 detects the output voltage (the voltage of the wiring 41). The detected output voltage is output to the control unit 20.

[0024] The control unit 20 controls the switching elements 111 and 112. The control unit 20 controls the on / off of the switching elements 111 and 112 based on a signal from the output voltage detection unit 21, thereby stabilizing the output voltage of the power supply device 1.

[0025] [Synchronous rectification element] FIG. 2 is a diagram illustrating an example of a synchronous rectifier according to the first embodiment of the present disclosure. The diagram illustrates a MOS transistor 201 constituting the synchronous rectifier. When a drive signal (control signal) is input to the gate, the MOS transistor 201 becomes conductive and a current flows. The solid arrow in the diagram represents the current flowing from the source to the drain of the MOS transistor 201. In this case, a relatively small voltage drop occurs. If, for some reason, a drive signal is not input to the gate, the body diode 202 becomes conductive and a current flows through the body diode 202. The voltage drop across the body diode is approximately 0.6 V, which increases loss.

[0026] In this way, if the supply of the control signal to the synchronous rectifier element is stopped due to a failure of the synchronous rectifier element drive circuit 17 or a wiring problem, the loss of the synchronous rectifier element increases. If the synchronous rectifier element does not dissipate heat sufficiently, the synchronous rectifier element will be damaged.

[0027] Therefore, an abnormality detection circuit 130 is provided to detect abnormalities in the synchronous rectifier driving circuit 17 and the like.

[0028] [Configuration of the abnormality detection circuit] 3 is a diagram illustrating a configuration example of an abnormality detection circuit according to the first embodiment of the present disclosure. The same figure is a circuit diagram illustrating a configuration example of an abnormality detection circuit 130. The abnormality detection circuit 130 includes transistors 131 and 132, capacitors 133 and 134, resistors 135 to 138, comparators 139 and 140, and a NAND gate 141. NPN transistors can be used for the transistors 131 and 132. A two-input NAND gate can be used for the NAND gate 141. A power supply line Vcc that supplies power is wired to the abnormality detection circuit 130.

[0029] The base of transistor 131 is connected to signal line 51, and the collector of transistor 131 is connected to power supply line Vcc. The emitter of transistor 131 is connected to one end of capacitor 133, one end of resistor 135, and the non-inverting input terminal of comparator 140. The other end of capacitor 133 and the other end of resistor 135 are connected to reference potential line 40. The base of transistor 132 is connected to signal line 50, and the collector of transistor 132 is connected to power supply line Vcc. The emitter of transistor 132 is connected to one end of capacitor 134, one end of resistor 136, and the non-inverting input terminal of comparator 139. The other end of capacitor 134 and the other end of resistor 136 are connected to reference potential line 40. One end of resistor 137 is connected to power supply line Vcc, and the other end is connected to the inverting input terminal of comparator 139, the inverting input terminal of comparator 140, and one end of resistor 138. The other end of the resistor 138 is connected to the reference potential line 40. The output terminal of the comparator 139 and the output terminal of the comparator 140 are each connected to the input terminal of a NAND gate 141. The output terminal of the NAND gate 141 is connected to the signal line 52.

[0030] The transistors 131 and 132 form a buffer amplifier. The capacitor 133 is charged by a gate control signal of the switching element 14. The resistor 135 discharges the charge of the capacitor 133. As will be described later, the gate control signal is a pulse train. When the capacitor 133 is charged by the gate control signal, the voltage at the non-inverting input terminal of the comparator 140 increases. A threshold Vref generated by resistors 137 and 138 is applied to the inverting input terminal of the comparator 140. While the gate control signal is repeatedly input, the voltage at the non-inverting input terminal of the comparator 140 exceeds Vref, and the output terminal of the comparator 140 becomes H level.

[0031] When the control signal to the gate of the switching element 14 is interrupted, the voltage of the capacitor 133 drops due to the action of the resistor 135. When the voltage of the capacitor 133 drops below Vref, the output terminal of the comparator 140 goes low.

[0032] Capacitor 134 is charged by a control signal to the gate of switching element 13. Resistor 136 discharges the charge in capacitor 134. As will be described later, when capacitor 134 is charged by the gate control signal, the output terminal of comparator 139 becomes H level. On the other hand, when the control signal to the gate of switching element 13 is interrupted, the voltage of capacitor 134 drops due to the action of resistor 136. When the voltage of capacitor 134 drops below Vref, the output terminal of comparator 139 becomes L level.

[0033] When at least one of the output terminals of comparators 139 and 140 goes low, the output of NAND gate 141 goes high. This high-level signal indicates the detection of an abnormality. This signal is transmitted to protection circuit 160 via signal line 52.

[0034] [Anomaly Detection] 4 is a diagram illustrating an example of abnormality detection according to the first embodiment of the present disclosure. The diagram illustrates the operation of the abnormality detection circuit 130. In the diagram, "Vgs" represents the control signal waveform applied to the gate of the switching element 13 or 14. Furthermore, "detection voltage" represents the voltage waveform of the capacitor 133 or 134 in FIG. 3.

[0035] Under normal conditions, a pulsed control signal is applied, and the detection voltage exceeds Vref. In the event of an abnormality, for example, if the synchronous rectifier element drive circuit 17 or the like is damaged, the supply of the control signal is interrupted, causing the detection voltage to gradually decrease. When the detection voltage falls below Vref, the comparator 139 or the like outputs an H-level abnormality detection signal.

[0036] [Load current detection circuit configuration] FIG. 5 is a diagram illustrating a configuration example of a load current detection circuit according to the first embodiment of the present disclosure. This diagram is a circuit diagram illustrating a configuration example of a load current detection circuit 150. A resistor 19 is further illustrated in this diagram. The load current detection circuit 150 includes an operational amplifier 151 and resistors 152 to 155. The resistors 152 and 153 connected in series are connected between a wiring 41 and a reference potential line 40. The non-inverting input terminal of the operational amplifier 151 is connected to the midpoint between the resistors 152 and 153. The resistor 154 is connected between the wiring 42 and the inverting input terminal of the operational amplifier 151. The output terminal of the operational amplifier 151 is connected to a signal line 55. The resistor 155 is connected between the inverting input terminal and the output terminal of the operational amplifier 151.

[0037] The load current detection circuit 150 amplifies the voltage of the resistor 19 using a differential amplifier circuit formed by an OP amplifier 151, and generates an analog signal representing the load current. This signal representing the load current is transmitted to the protection circuit 160 via a signal line 55.

[0038] [Protection circuit configuration] 6 is a diagram showing a configuration example of a protection circuit according to the first embodiment of the present disclosure. The figure is a circuit diagram showing a configuration example of a protection circuit 160. The protection circuit 160 includes a comparator 161, resistors 162 and 163, and an AND gate 164. Note that a two-input AND gate can be used as the AND gate 164.

[0039] Resistors 162 and 163 connected in series are connected between the power supply line Vcc and the reference potential line 40. The non-inverting input terminal of comparator 161 is connected to signal line 55, and the inverting input terminal of comparator 161 is connected to the midpoint between resistors 162 and 163. The output terminal of comparator 161 and signal line 52 are connected to input terminals of AND gate 164, respectively. The output terminal of AND gate 164 is connected to signal line 56.

[0040] A threshold voltage set by resistors 162 and 163 is input to the inverting input terminal of comparator 161. A signal representing the load current is input to the non-inverting input terminal of comparator 161 via signal line 55. When the load current exceeds the threshold voltage, the output terminal of comparator 161 becomes H level. Due to the action of AND gate 164, an H level signal is input from abnormality detection circuit 130 and an H level alarm signal is generated when the load current exceeds the threshold.

[0041] When the current of the switching element 13, which is a synchronous rectifier element, is small, the synchronous rectifier element drive circuit 17 and the like may not be able to detect the voltage of the switching element 13 and may not generate a control signal. Even in this case, the abnormality detection circuit 130 detects the abnormality and outputs an H-level abnormality detection signal. Therefore, the protection circuit 160 disables the abnormality detection signal when the load current is less than a predetermined threshold. When the load current exceeds the threshold and the abnormality detection circuit 130 detects an abnormality, the protection circuit 160 generates an alarm signal and outputs it to the outside. In this way, the protection circuit 160 performs a protection operation of generating an abnormality detection signal when the abnormality detection circuit 130 detects an abnormality and the load current detection circuit detects a load current greater than a predetermined threshold.

[0042] In this way, the power supply device 1 according to the first embodiment of the present disclosure detects an abnormality in the synchronous rectifier element and protects it, thereby preventing damage to the synchronous rectifier element.

[0043] (2. Second Embodiment) The power supply device 1 of the first embodiment described above outputs an alarm signal when an abnormality is detected. In contrast, the power supply device 1 of the second embodiment of the present disclosure differs from the first embodiment described above in that it includes a current limiting circuit that limits the load current and adjusts the operating point of the current limiting circuit when an abnormality occurs.

[0044] [Power supply configuration] 7 is a diagram showing an example configuration of a power supply device according to a second embodiment of the present disclosure. Similar to FIG. 1, this figure is a circuit diagram showing an example configuration of the power supply device 1. The power supply device 1 in this figure differs from the power supply device 1 in FIG. 1 in that it includes a protection circuit 180 instead of the protection circuit 160 and further includes a current limiting circuit 170.

[0045] The current limiting circuit 170 is a circuit that limits the load current to a predetermined current. This current limiting circuit 170 performs current limiting based on the load current detected by the load current detection circuit 150. Specifically, when the load current detected by the load current detection circuit 150 reaches a predetermined threshold, the current limiting circuit 170 outputs a voltage drop signal to the output voltage detection unit 21, thereby preventing an increase in the load current. The configuration of the current limiting circuit 170 will be described in detail later.

[0046] The protection circuit 180 performs a protection operation by adjusting the threshold value of the current limiting circuit 170 when the abnormality detection circuit 130 detects an abnormality. The configuration of the protection circuit 180 will be described in detail later.

[0047] [Configuration of current limiting circuit and protection circuit] 8 is a diagram illustrating an example configuration of a current limiting circuit and a protection circuit according to a second embodiment of the present disclosure. The figure is a circuit diagram illustrating an example configuration of a current limiting circuit 170 and a protection circuit 180. The current limiting circuit 170 includes a comparator 171, resistors 172 and 173, and a diode 174.

[0048] Resistors 172 and 173 connected in series are connected between the power supply line Vcc and the reference potential line 40. The inverting input terminal of a comparator 171 is connected to the midpoint of the resistors 172 and 173. The non-inverting input terminal of the comparator 171 is connected to the signal line 55. The output terminal of the comparator 171 is connected to the anode of a diode 174. The cathode of the diode 174 is connected to the signal line 58. A signal line 57 from a protection circuit 180 is also connected to the midpoint of the resistors 172 and 173.

[0049] When the load current signal from the load current detection circuit 150 exceeds the threshold generated by resistors 172 and 173, the output terminal of the comparator 171 becomes H level. This H level signal is transmitted to the output voltage detection unit 21 via the signal line 58. Then, the output voltage detection unit 21 adjusts the signal to be output to the control unit 20 to reduce the output voltage. The diode 174 prevents the signal from flowing backward.

[0050] The protection circuit 180 includes a MOS transistor 182 and a resistor 181. One end of the resistor 181 is connected to the signal line 57. The other end of the resistor 181 is connected to the drain of the MOS transistor 182. The gate of the MOS transistor 182 is connected to the signal line 52, and the source is connected to the reference potential line 40.

[0051] When the abnormality detection circuit 130 detects an abnormality and outputs an H-level signal, the MOS transistor 182 becomes conductive. This connects the resistor 181 in parallel with the resistor 173. This reduces the threshold of the comparator 171. The operating point of the current limiting circuit 170 is adjusted.

[0052] [Operation of current limiting circuit and protection circuit] FIG. 9 is a diagram illustrating an example of the operation of the current limiting circuit and the protection circuit according to the second embodiment of the present disclosure. The diagram explains the operation of the current limiting circuit 170 and the protection circuit 180. The vertical axis of the diagram represents the output voltage, and the horizontal axis represents the output current. Normally, the current limiting circuit 170 limits the output current to "Io_max (normal)" in the diagram. Under abnormal conditions, that is, when the abnormality detection circuit 130 detects an abnormality, the protection circuit 180 adjusts the operating point of the current limiting circuit 170 to the dotted line position. Therefore, under abnormal conditions, the current limiting circuit 170 limits the output current to "Io_max (abnormal)" in the diagram.

[0053] The configuration of the power supply device 1 other than that described above is the same as the configuration of the power supply device 1 in the first embodiment of the present disclosure, and therefore description thereof will be omitted.

[0054] In this way, the power supply device 1 according to the second embodiment of the present disclosure performs control to lower the limit value of the output current when an abnormality occurs in the synchronous rectifier element, thereby preventing an increase in loss in the synchronous rectifier element.

[0055] (3. Third Embodiment) The power supply device 1 of the first embodiment described above includes the protection circuit 160. In contrast, the power supply device 1 of the third embodiment of the present disclosure differs from the first embodiment described above in that it further includes a current limiting circuit 170 and a protection circuit 180.

[0056] [Power supply configuration] 10 is a diagram showing an example configuration of a power supply device according to a third embodiment of the present disclosure. Similar to FIG. 1, this figure is a circuit diagram showing an example configuration of the power supply device 1. The power supply device 1 in this figure differs from the power supply device 1 in FIG. 1 in that it further includes a current limiting circuit 170 and a protection circuit 180.

[0057] The configuration of the power supply device 1 other than that described above is the same as the configuration of the power supply device 1 in the first embodiment of the present disclosure, and therefore description thereof will be omitted.

[0058] As described above, the power supply device 1 according to the third embodiment of the present disclosure includes the protection circuit 160 and the protection circuit 180. This makes it possible to detect and protect the synchronous rectifier elements from abnormalities, thereby reducing loss in the synchronous rectifier elements.

[0059] (4. Fourth Embodiment) In the power supply device 1 of the first embodiment described above, one power supply circuit 10 supplies power to the load 3. In contrast, the power supply device 1 of the fourth embodiment of the present disclosure differs from the first embodiment described above in that multiple power supply circuits 10 connected in parallel supply power to the load 3.

[0060] [Power supply configuration] Fig. 11 is a diagram showing an example configuration of a power supply device according to a fourth embodiment of the present disclosure. Similar to Fig. 1, Fig. 11 is a circuit diagram showing an example configuration of a power supply device 1. The power supply device 1 in Fig. 11 includes two power supply circuits 10 (power supply circuit 10a and power supply circuit 10b) and differs from the power supply circuit 10 in Fig. 1 in that it further includes MOS transistors 22 and 23. Note that the illustration of the power supply circuit 10 in Fig. 11 is simplified.

[0061] The output (wiring 42) of the power supply circuit 10a is connected to the load 3 via a MOS transistor 22. Similarly, the output (wiring 42) of the power supply circuit 10b is connected to the load 3 via a MOS transistor 23. In this way, the power supply circuits 10a and 10b are connected in parallel. This makes the power supply device 1 redundant. That is, even if either the power supply circuit 10a or the power supply circuit 10b fails, power can still be supplied to the load 3. The MOS transistors 22 and 23 prevent backflow of the output current if the power supply circuit 10 is damaged. The element for preventing backflow of the output current is not limited to a MOS transistor. For example, a diode can also be used.

[0062] A power supply device 1 configured as described above has the problem that, in addition to damage to the synchronous rectifier element of the power supply circuit 10, the user may not be able to detect a malfunction of the power supply circuit 10. This is because, even if the synchronous rectifier element drive circuit 17 or the like of the power supply circuit 10 is damaged, the synchronous rectifier element continues rectifying operation as long as the load current is small, and the power supply circuit 10 does not stop operating. In particular, because the power supply circuits 10 are duplicated, even if one of the power supply circuits 10 is damaged, the power supply device 1 continues operating in the range where the load current is small. In this state, if the normal power supply circuit 10 is removed to replace the power supply circuit 10 for maintenance or the like, the load will be concentrated on the malfunctioning power supply circuit 10.

[0063] 1, an alarm signal is output when the synchronous rectifier element drive circuit 17 or the like fails, allowing the user to recognize the malfunction of the power supply circuit 10.

[0064] 10, in addition to detecting failures in the synchronous rectifier element drive circuit 17, etc., the load current can be reduced in the event of an abnormality, thereby further protecting the synchronous rectifier element.

[0065] The configuration of the power supply device 1 other than that described above is the same as the configuration of the power supply device 1 in the first embodiment of the present disclosure, and therefore description thereof will be omitted.

[0066] In this way, the power supply device 1 according to the fourth embodiment of the present disclosure is configured by connecting multiple power supply circuits 10 in parallel, thereby improving redundancy.

[0067] (5. Fifth Embodiment) A modification of the power supply circuit 10 of the first embodiment will now be described.

[0068] [Power supply configuration] 12 is a diagram illustrating a configuration example of a power supply device according to a fifth embodiment of the present disclosure. The diagram illustrates an example including a switching power supply circuit configured as a boost chopper circuit. Note that an abnormality detection circuit 130, a load current detection circuit 150, a protection circuit 160, and the like are omitted. The switching element 13 in the diagram corresponds to a synchronous rectification element.

[0069] The effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0070] Some examples of combinations of the disclosed technical features are set out below. (1) an intermittent voltage generating circuit that generates an intermittent voltage from an input voltage from an external power supply by using a switching element that repeatedly turns on and off; a rectifying and smoothing circuit that rectifies the intermittent voltage using a synchronous rectifying element that turns on and off in synchronization with the on and off of the switching element, smooths the voltage using a capacitor, and supplies the smoothed voltage to a load; a synchronous rectifier element drive circuit that supplies a control signal for turning on and off the synchronous rectifier element to a control terminal of the synchronous rectifier element; an abnormality detection circuit that detects an abnormality in the synchronous rectification element drive circuit; a load current detection circuit that detects a load current that is a current of the load supplied by the rectifying and smoothing circuit; a protection circuit that performs a protection operation based on the detection result of the abnormality detection circuit and the detection result of the load current detection circuit; A power supply device having (2) The power supply device according to (1), wherein the abnormality detection circuit detects an abnormality when the control signal is not supplied from the synchronous rectifier element drive circuit. (3) The power supply device according to (1) or (2), wherein the protection circuit performs the protection operation of generating an abnormality detection signal when the abnormality detection circuit detects an abnormality and the load current detection circuit detects the load current greater than a predetermined threshold. (4) a current limiting circuit that limits the load current based on a predetermined threshold; The protection circuit performs a protection operation by adjusting the predetermined threshold value of the load current detection circuit when the abnormality detection circuit detects an abnormality. The power supply device according to any one of (1) to (3). (5) The power supply device according to any one of (1) to (4), wherein the intermittent voltage generating circuit comprises a transformer having a primary winding to which the switching element is connected and a secondary winding to which the rectifying and smoothing circuit is connected. (6) a plurality of power supply circuits each including the intermittent voltage generating circuit, the rectifying and smoothing circuit, the synchronous rectifying element driving circuit, the abnormality detecting circuit, the load current detecting circuit, and the protection circuit; The plurality of power supply circuits are commonly connected to the load. The power supply device according to any one of (1) to (5) above. [Explanation of symbols]

[0071] 1 Power supply 3. Load 10, 10a, 10b power circuit 13, 14, 111, 112 Switching elements 17, 18 Synchronous rectifier element drive circuit 110 Intermittent voltage generating circuit 120 Rectifier smoothing circuit 130 Abnormality detection circuit 150 Load current detection circuit 160, 180 protection circuit 170 Current limiting circuit

Claims

1. an intermittent voltage generating circuit that generates an intermittent voltage from an input voltage from an external power supply by using a switching element that repeatedly turns on and off; a rectifying and smoothing circuit that rectifies the intermittent voltage using a synchronous rectifying element that turns on and off in synchronization with the on and off of the switching element, smooths the voltage using a capacitor, and supplies the smoothed voltage to a load; a synchronous rectifier element drive circuit that supplies a control signal for turning on and off the synchronous rectifier element to a control terminal of the synchronous rectifier element; an abnormality detection circuit that detects an abnormality in the synchronous rectification element drive circuit; a load current detection circuit that detects a load current that is a current of the load supplied by the rectifying and smoothing circuit; a protection circuit that performs a protection operation based on the detection result of the abnormality detection circuit and the detection result of the load current detection circuit; A power supply device having

2. 2. The power supply device according to claim 1, wherein the abnormality detection circuit detects an abnormality when the control signal is not supplied from the synchronous rectifier element drive circuit.

3. 3. The power supply device according to claim 1, wherein the protection circuit performs the protection operation of generating an abnormality detection signal when the abnormality detection circuit detects an abnormality and the load current detection circuit detects the load current greater than a predetermined threshold.

4. a current limiting circuit that limits the load current based on a predetermined threshold; The protection circuit performs a protection operation by adjusting the predetermined threshold value of the load current detection circuit when the abnormality detection circuit detects an abnormality.

3. The power supply device according to claim 1 or 2.

5. 3. The power supply device according to claim 1, wherein the intermittent voltage generating circuit comprises a transformer having a primary winding connected to the switching element and a secondary winding connected to the rectifying and smoothing circuit.

6. a plurality of power supply circuits each including the intermittent voltage generating circuit, the rectifying and smoothing circuit, the synchronous rectifying element driving circuit, the abnormality detecting circuit, the load current detecting circuit, and the protection circuit; The plurality of power supply circuits are commonly connected to the load.

3. The power supply device according to claim 1 or 2.

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