Power supply device

Abstract

The power supply device includes a pair of input terminals, a bridge rectifier circuit, a voltage divider circuit, an attenuation circuit, and a voltage drop detection circuit. A direct-current input voltage and an alternating-current input voltage having an effective value substantially equal to that of the direct-current input voltage are applied to the input terminal. The AC input terminal of the bridge rectifier circuit is connected with the input terminal, and the DC output terminal is connected with the input end of the load circuit. The voltage division circuit is connected to the input terminal and outputs a midpoint voltage of the input voltage. The attenuation circuit outputs a DC output voltage obtained by attenuating a waveform of a midpoint voltage of the voltage divider circuit at a predetermined ratio when a DC input voltage is applied to the input terminal. And outputs an AC output voltage in which the waveform of the midpoint voltage of the voltage divider circuit when an AC input voltage is applied to the input terminal is attenuated to a waveform such that the peak voltage is substantially equal to the DC output voltage. The voltage drop detection circuit detects a drop in the voltage input to the input terminal by detecting a drop in either the DC output voltage or the AC output voltage.

Description

Technical Field

[0001] The invention relates to a power supply device. Background Art

[0002] A power supply device is used, which uses a switching power supply circuit. In recent years, a power supply device has been used, which forms an input current with a waveform substantially equal to that of an input voltage by adopting a switching power supply circuit having a power factor improvement function. With respect to such a power supply device, the following problems may arise, such as if the input voltage drops, the input current increases, and the loss of the switching transistor of the switching power supply circuit increases. Therefore, a power supply device is proposed, which is provided with a power failure detection circuit for detecting a decrease in the input voltage such as a power failure, and controls the switching power supply circuit (flyback circuit) to stop when the input voltage drops (for example, refer to Patent Document 1).

[0003] The power failure detection circuit detects a power failure or the like based on the peak voltage of the full-wave rectified input voltage.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2015-042093

[0005] However, in the above-mentioned prior art, there is a problem that when the power supply device is operated by a DC voltage having a voltage equal to the effective value of the AC input voltage, the operating point when a decrease in the input voltage is detected varies between the AC input and the DC input. Therefore, there is a problem that when a DC input voltage is applied, a decrease in the input voltage is detected by a voltage different from the effective voltage when the AC input voltage is applied. Summary of the invention

[0006] The present invention provides a power supply device that makes detection voltages when detecting a decrease in input voltage consistent with respect to an AC input voltage and a DC input voltage.

[0007] The power supply device of the present invention has a pair of input terminals, a bridge rectifier circuit, a voltage divider circuit, an attenuation circuit, and a voltage drop detection circuit. A DC input voltage and an AC input voltage of an effective value substantially equal to the DC input voltage are applied to the input terminal. The AC input terminal of the bridge rectifier circuit is connected to the input terminal, and the DC output terminal is connected to the input of the load circuit. The voltage divider circuit is connected to the input terminal and outputs a midpoint voltage of the input voltage. The attenuation circuit outputs a DC output voltage after the waveform of the midpoint voltage of the voltage divider circuit when the DC input voltage is applied to the input terminal is attenuated at a predetermined ratio, and outputs an AC output voltage after the waveform of the midpoint voltage of the voltage divider circuit when the AC input voltage is applied to the input terminal is attenuated to a waveform having a peak voltage substantially equal to the DC output voltage. The voltage drop detection circuit detects a decrease in the voltage input to the input terminal by detecting a decrease in either the DC output voltage or the AC output voltage.

[0008] Effects of the Invention

[0009] According to the present invention, the detection voltages when a decrease in input voltage is detected can be made consistent with respect to an AC input voltage and a DC input voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a diagram showing a configuration example of a power supply device according to a first embodiment of the present invention.

[0011] Figure 2 It is a diagram showing a configuration example of an attenuation circuit, a voltage drop detection circuit, a peak voltage detection circuit, and a starting voltage detection circuit according to the first embodiment of the present invention.

[0012] Figure 3 This is a diagram showing an example of attenuation of input voltage according to the embodiment of the present invention.

[0013] Figure 4 It is a diagram showing another configuration example of the attenuation circuit and the peak voltage detection circuit according to the first embodiment of the present invention.

[0014] Figure 5 It is a diagram showing a configuration example of a power supply device according to a second embodiment of the present invention.

[0015] Figure 6 It is a diagram showing a configuration example of an attenuation circuit according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0016] Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings. The description will be given in the following order. In addition, in each of the following embodiments, the same reference numerals are given to the same parts and repeated descriptions are omitted.

[0017] 1. First Implementation Method

[0018] 2. Second Implementation Method

[0019] 3. Third Implementation Method

[0020] (1. First Implementation Method)

[0021] [Structure of power supply device]

[0022] Figure 1 1 is a diagram showing a configuration example of a power supply device according to a first embodiment of the present invention. The diagram is a circuit diagram showing a configuration example of a power supply device 10. The power supply device 10 converts a power source such as an AC voltage source or a DC voltage source into a desired DC voltage and supplies it to other instruments. Here, for example, a commercial power source is equivalent to an AC voltage source. The diagram shows an AC voltage source 11. In addition, for example, a battery is equivalent to a DC voltage source. The diagram shows a DC voltage source 12. The DC voltage source 12 outputs a DC voltage equal to the effective value of the output voltage of the AC voltage source 11.

[0023] The power supply device 10 has an input terminal 101 and an input terminal 102 as a pair of input terminals, a bridge rectifier circuit 110, a DC stabilized power supply circuit 120, a voltage divider circuit 130, an attenuation circuit 140, a voltage drop detection circuit 170, a peak voltage detection circuit 150 and a starting voltage detection circuit 160.

[0024] The input terminals 101 and 102 are a pair of input terminals connected to the AC voltage source 11 or the DC voltage source 12 .

[0025] The bridge rectifier circuit 110 is a circuit that performs full-wave rectification on an AC input voltage. Regarding the bridge rectifier circuit 110, the AC input terminal is connected to the input terminals 101 and 102, and the DC output terminal is connected to the input end of the DC stabilized power supply circuit 120. In addition, the bridge rectifier circuit 110 in the figure shows an example of being connected to the input terminal 101 via the fuse 103. In addition, the negative terminal of the DC output terminal of the bridge rectifier circuit 110 is grounded.

[0026] The DC stabilized power supply circuit 120 is a circuit that converts the full-wave rectified waveform output from the bridge rectifier circuit 110 into a DC voltage of a desired voltage and supplies it to other devices as a power supply. The DC stabilized power supply circuit 120 includes a power factor improvement circuit 121, a smoothing capacitor 122, and a switching power supply circuit 123. In addition, the DC stabilized power supply circuit 120 is an example of the "load circuit" of the present invention.

[0027] The power factor improvement circuit 121 is a circuit that sets the power factor of the DC stabilized power supply circuit 120 to approximately 1. The power factor improvement circuit 121 is composed of, for example, a step-up chopper circuit, and performs switching on and off (switching) of the output voltage of the bridge rectifier circuit 110 to convert it into a DC voltage of a specified voltage. At this time, the power factor improvement circuit 121 adjusts the on-off cycle in such a way that an input current having a waveform substantially equal to the input voltage waveform flows. By configuring the power factor improvement circuit 121, the input voltage of the switching power supply circuit 123 in the subsequent stage can be made equal when the AC voltage source 11 is connected and when the DC voltage source 12 is connected. A known circuit can be used for the power factor improvement circuit 121.

[0028] The smoothing capacitor 122 is connected to the output terminal of the power factor improvement circuit 121 , and is a capacitor that smoothes the output voltage of the power factor improvement circuit 121 .

[0029] The switching power supply circuit 123 is a circuit that switches the output voltage of the power factor improvement circuit 121 smoothed by the smoothing capacitor 122 on and off to convert it into a desired voltage DC. A known circuit can be used for the switching power supply circuit 123. The switching power supply circuit 123 of the figure is assumed to be a feedforward type or a flyback type circuit, and has a transformer 124, a MOS transistor 125, and a control circuit 126. In addition, the transformer 124 only describes the primary winding. The primary winding of the transformer 124 and the MOS transistor 125 connected in series are connected to the input end of the switching power supply circuit 123.

[0030] The MOS transistor 125 is turned on and off to apply a pulsed AC voltage to the primary winding of the transformer 124. The AC voltage is stepped up or down by the transformer 124 and output from the secondary winding. The voltage of the secondary winding of the transformer 124 is rectified and smoothed to be converted into a DC and output from the DC stabilized power supply circuit 120. The control circuit 126 controls the ratio of the on and off of the MOS transistor 125 so that the output voltage of the DC stabilized power supply circuit 120 is stabilized. In addition, the control circuit 126 further controls to start the on and off of the MOS transistor 125 when the voltage applied to the input terminals 101 and 102 reaches a predetermined voltage. That is, the control circuit 126 stops the on and off of the MOS transistor 125 when the voltage applied to the input terminals 101 and 102 is low. In addition, the start voltage detection circuit 160 described later detects whether the voltage applied to the input terminals 101 and 102 reaches a predetermined voltage. The control circuit 126 performs control to stop the on / off operation of the MOS transistor 125 based on a signal from the startup voltage detection circuit 160 .

[0031] The voltage divider circuit 130 is a circuit that is connected between the input terminals 101 and 102 and outputs the midpoint voltage of the input voltage. The voltage divider circuit 130 in the figure shows an example of being connected to the input terminal 101 via the fuse 103. The voltage divider circuit 130 is composed of a resistor 131 and a resistor 132 connected in series. The resistor 131 and the resistor 132 can be set to have equal resistance values. A midpoint voltage (Vvd in the figure) is output from the midpoint of the resistor 131 and the resistor 132 connected in series.

[0032] The attenuation circuit 140 is a circuit that outputs a DC output voltage after the waveform of the midpoint voltage of the voltage divider circuit 130 is attenuated at a predetermined ratio when a DC input voltage is input to the input terminals 101 and 102. In addition, the attenuation circuit 140 further outputs an AC output voltage by attenuating the waveform of the midpoint voltage of the voltage divider circuit 130 when an AC input voltage is applied to the input terminals 101 and 102 to a waveform in which the peak voltage is substantially equal to the DC output voltage. The output of the attenuation circuit 140 (Vout2 in the figure) is output to the voltage drop detection circuit 170 and the peak voltage detection circuit 150. The structure of the attenuation circuit 140 will be described in detail later.

[0033] The voltage drop detection circuit 170 is a circuit that detects a drop in the voltage input to the input terminals 101 and 102 by detecting a drop in either the DC output voltage or the AC output voltage from the attenuation circuit 140. The voltage drop detection circuit 170 outputs a voltage drop detection signal as a detection result to an external device. The configuration of the voltage drop detection circuit 170 will be described in detail later.

[0034] The peak voltage detection circuit 150 is a circuit that detects and outputs the peak voltage of the DC output voltage and the AC output voltage. The peak voltage detection circuit 150 outputs the detected peak voltage (Vout1 in the figure) to the startup voltage detection circuit 160.

[0035] The startup voltage detection circuit 160 is a circuit that detects the startup voltage of the switching power supply circuit 123 by detecting the increase in the output voltage of the peak voltage detection circuit 150. The detection result is output to the control circuit 126.

[0036] [Structures of attenuation circuit, voltage drop detection circuit, peak voltage detection circuit, and start-up voltage detection circuit]

[0037] Figure 2 1 is a diagram showing a configuration example of an attenuation circuit, a voltage drop detection circuit, a peak voltage detection circuit, and a startup voltage detection circuit according to the first embodiment of the present invention. This figure is a circuit diagram showing a configuration example of an attenuation circuit 140, a voltage drop detection circuit 170, a peak voltage detection circuit 150, and a startup voltage detection circuit 160.

[0038] The attenuation circuit 140 includes resistors 141 to 144, a capacitor 145, and a transistor 146. The resistors 141 and 142 connected in series are connected between the input terminal and the ground line. The capacitor 145 connected in parallel with the resistor 143 and the circuit connected in series with the resistor 144 are connected between the input terminal and the ground line. The base of the transistor 146 is connected to the midpoint of the resistors 141 and 142 connected in series. The emitter of the transistor 146 is connected to the midpoint of the resistor 143 and the capacitor 145 connected in series. The collector of the transistor 146 is grounded. In addition, the midpoint of the resistor 143 and the capacitor 145 connected in series constitutes the output terminal of the attenuation circuit 140, and Vout2 is output. A pnp transistor can be used for the transistor 146.

[0039] The capacitor 145 connected in parallel with the resistor 143 and the circuit connected in series with the resistor 144 are circuits for attenuating the input voltage. The circuit is composed of a voltage divider circuit in which a plurality of impedance elements including a reactance element are connected in series. By configuring the reactance element in the circuit, different attenuation amounts can be set for the DC input voltage and the AC input voltage.

[0040] The circuit of the resistors 141 and 142 and the transistor 146 is a circuit that discharges the voltage of the capacitor 145 when the input voltage (Vvd) decreases. By configuring this circuit, a decrease in the input voltage can be detected at high speed.

[0041] The voltage drop detection circuit 170 includes a comparator 171 , a delay circuit 172 , and a signal generation circuit 173 .

[0042] The comparator 171 compares the signal ( Vout2 ) output from the attenuation circuit 140 with the threshold voltage Vth2 , and outputs an H-level (high-level) signal when Vout2 is smaller than Vth2 .

[0043] The delay circuit 172 is a circuit that delays the output signal of the comparator 171. The delay circuit 172 is a circuit that prevents detection of a voltage drop when the AC input voltage is near 0 V. The delay circuit 172 delays the signal output from the comparator 171 by a predetermined time. When a signal is output from the comparator 171 even after the delay, the delay circuit 172 outputs a signal to the signal generating circuit 173.

[0044] The signal generating circuit 173 is a circuit that generates and outputs a voltage drop detection signal based on the output signal of the delay circuit 172 .

[0045] The peak voltage detection circuit 150 includes a diode 151, a capacitor 152, and a resistor 153. The anode of the diode 151 is connected to the input terminal, and the cathode is connected to the output terminal. The capacitor 152 is connected between the output terminal and the ground line. The resistor 153 is connected between the output terminal and the ground line. The peak voltage of the output (Vout2) of the attenuation circuit 140 is detected by the diode 151 and the capacitor 152. Vout1 in the figure represents the detected peak voltage. In addition, the resistor 153 discharges the capacitor 152 when no input voltage is applied.

[0046] The startup voltage detection circuit 160 includes a comparator 161 . The comparator 161 compares the signal ( Vout1 ) output from the peak voltage detection circuit 150 with the threshold voltage Vth1 , and outputs an H-level signal when Vout1 is greater than Vth1 . This signal is transmitted to the control circuit 126 .

[0047] [Attenuation circuit operation]

[0048] Figure 3 This is a diagram showing an example of attenuation of an input voltage involved in an embodiment of the present invention. This figure is a diagram showing an example of attenuation of an input voltage of an attenuation circuit 140. The operation of the attenuation circuit 140 and the peak voltage detection circuit 150 is described using this figure. The left side of the figure shows when AC input occurs, and the right side shows when DC input occurs. In addition, "Vvd", "Vout2" and "Vout1" in the figure represent the waveforms of Vvd, Vout2 and Vout1. In addition, this figure shows an outline of the signal waveform, which may not be the same as the actual one.

[0049] Vvd is a full-wave rectified waveform when AC input occurs. Vp1 in the figure represents the peak voltage, and Ve represents the effective voltage. This voltage waveform is attenuated by the attenuation circuit 140. Vout2 represents the attenuated waveform. Vp2 represents the peak voltage of the attenuated waveform. Next, the peak voltage is detected using the peak voltage detection circuit 150. Vout1 represents the detected peak voltage. The waveform of Vout1 is the waveform obtained by smoothing the waveform of Vout2.

[0050] Vvd is a DC waveform when DC input occurs. Vdc1 in the figure represents a DC voltage. This Vdc1 is a voltage substantially the same as Ve. This DC waveform is attenuated by the attenuation circuit 140 and becomes Vdc2. This Vdc2 is a voltage substantially the same as Vp2. In addition, the waveform of Vout1 is substantially the same as that of Vout2.

[0051] In this way, the attenuation circuit 140 attenuates the waveform so that the peak voltage Vp1 of the waveform during AC input becomes Vp2 which is substantially the same as Vdc2 during DC input. Thus, the voltage of Vout2 can be made the same during AC input and DC input.

[0052] Furthermore, by the circuit action of the resistors 141 and 142 and the transistor 146 arranged in the attenuation circuit 140, when Vvd decreases to a voltage near 0 V, Vout2 can be decreased to a voltage near 0 V. Thus, the voltage drop detection circuit 170 can detect the voltage drop at high speed.

[0053] In addition, when it is not necessary to discharge the voltage of the capacitor 145 when Vvd decreases, for example, when the voltage drop detection circuit 170 is omitted, the resistors 141 and 142 and the transistor 146 of the attenuation circuit 140 can be omitted. In this case, the attenuation circuit 140 is composed of the resistors 143 and 144 and the capacitor 145.

[0054] [Other structures of attenuation circuit and peak voltage detection circuit]

[0055] Figure 4 140 and 150. FIG. 140 is a diagram showing another configuration example of the attenuation circuit and the peak voltage detection circuit according to the first embodiment of the present invention.

[0056] The attenuation circuit 140 of the figure has resistors 147 and 148 connected in series instead of the resistor 144. The voltage at the midpoint of the resistors 147 and 148 connected in series is output to the voltage drop detection circuit 170. By adjusting the ratio of the resistors 147 and 148, the voltage output to the voltage drop detection circuit 170 can be adjusted.

[0057] The peak voltage detection circuit 150 of the figure has resistors 154 and 155 connected in series instead of the resistor 153. The voltage at the midpoint of the resistors 154 and 155 connected in series is output to the startup voltage detection circuit 160. By adjusting the ratio of the resistors 154 and 155, the voltage output to the startup voltage detection circuit 160 can be adjusted.

[0058] In this way, the power supply device 10 can make the detection voltages when detecting a decrease in input voltage for the AC input voltage and the DC input voltage consistent.

[0059] (2. Second Implementation Method)

[0060] [Structure of power supply device]

[0061] Figure 5 2 is a diagram showing a configuration example of a power supply device according to a second embodiment of the present invention. Figure 1 Similarly, FIG. 1 is a circuit diagram showing a configuration example of a power supply device 10. The power supply device 10 of this figure is similar to FIG. 1 in that it further includes a buffer circuit 180. Figure 1 The power supply device 10 is different.

[0062] The buffer circuit 180 is a circuit that is disposed between the voltage divider circuit 130 and the attenuation circuit 140 to separate the voltage divider circuit 130 from the attenuation circuit 140. The buffer circuit 180 may be formed, for example, of an emitter follower circuit. By configuring the buffer circuit 180, the influence of the attenuation circuit 140 on the voltage divider circuit 130 can be reduced. In contrast, in the case where the buffer circuit 180 is not provided, the attenuation circuit 140 is connected in parallel with either the resistor 131 or the resistor 132 of the voltage divider circuit 130, and an error may occur in the midpoint voltage.

[0063] The configuration of the power supply device 10 other than this is the same as that of the power supply device 10 according to the first embodiment of the present invention, and thus the description thereof will be omitted.

[0064] As described above, the power supply device 10 according to the second embodiment of the present invention can reduce the change in the output voltage of the voltage dividing circuit 130 by providing the buffer circuit 180 .

[0065] (3. Third Implementation Method)

[0066] [Structure of attenuation circuit]

[0067] Figure 6 1 is a diagram showing a configuration example of an attenuation circuit according to a third embodiment of the present invention. Figure 2 Similarly, FIG. 1 is a circuit diagram showing a configuration example of an attenuation circuit 140. The attenuation circuit 140 of this figure is similar to FIG. 1 in that it further includes a correction circuit 190. Figure 2The attenuation circuit 140 is different.

[0068] The correction circuit 190 is composed of a resistor 191 and a capacitor 192 connected in series. The correction circuit 190 is connected to the resistor 143 in parallel.

[0069] In this figure, the resistors 141, 142, 143 and 144 can be set to 100 kΩ, 47 kΩ, 7.8 kΩ and 10 kΩ respectively. In addition, the capacitor 145 can be set to 3.3 μF. In this case, the resistor 191 can be set to 100 Ω. In addition, the capacitor 192 can be set to 0.47 μF.

[0070] The correction circuit 190 is a circuit that adjusts the attenuation of the attenuation circuit 140 according to the frequency of the AC input voltage. By configuring the correction circuit 190, even when the AC input voltage changes from 50 Hz to 60 Hz, the attenuation can be kept constant.

[0071] Will Figure 6 The attenuation circuit 140 is applied to Figure 5 The operation of the power supply device 10 was confirmed by simulation. In addition, the gain of the buffer circuit 180 was set to 1 and the simulation was performed. The results are as follows.

[0072] (1) When applying 110V DC input voltage

[0073] Vout1: 18.3V, Vout2: 18.9V

[0074] (2) When an AC input voltage of 110 Vrms (50 Hz) is applied

[0075] Vout1 (peak voltage): 18.8V, Vout2 (peak voltage): 19.4V

[0076] (3) When an AC input voltage of 110 Vrms (60 Hz) is applied

[0077] Vout1 (peak voltage): 18.2V, Vout2 (peak voltage): 18.7V

[0078] In this way, Vout1 and Vout2 can be made consistent with each other for the DC input voltage and the AC input voltage. In addition, even when the AC input voltage changes from 50 Hz to 60 Hz, the correction circuit 190 can reduce the change in Vout1 and Vout2.

[0079] The configuration of the power supply device 10 other than this is the same as that of the power supply device 10 according to the first embodiment of the present invention, and thus the description thereof will be omitted.

[0080] As described above, the power supply device 10 according to the third embodiment of the present invention can maintain the attenuation amount of the attenuation circuit 140 substantially constant even when the frequency of the AC input voltage changes by providing the correction circuit 190 in the attenuation circuit 140 .

[0081] In addition, the effects described in this specification are merely illustrative and are not limiting, and other effects may be possible.

[0082] Several examples of combinations of disclosed technical features are described below.

[0083] (1) A power supply device, wherein:

[0084] The power supply device comprises:

[0085] a pair of input terminals to which a DC input voltage and an AC input voltage having an effective value substantially equal to the DC input voltage are applied;

[0086] a bridge rectifier circuit having an AC input terminal connected to the input terminal and a DC output terminal connected to an input of a load circuit;

[0087] A voltage divider circuit connected to the input terminal and outputting a midpoint voltage of the input voltage;

[0088] an attenuation circuit that outputs a DC output voltage obtained by attenuating the waveform of the midpoint voltage of the voltage divider circuit when the DC input voltage is applied to the input terminal at a predetermined ratio, and outputs an AC output voltage obtained by attenuating the waveform of the midpoint voltage of the voltage divider circuit when the AC input voltage is applied to the input terminal to a waveform having a peak voltage substantially equal to the DC output voltage; and

[0089] The voltage drop detection circuit detects a drop in the voltage input to the input terminal by detecting a drop in either the DC output voltage or the AC output voltage.

[0090] (2) The power supply device according to (1), wherein:

[0091] The attenuation circuit is composed of a voltage dividing circuit in which a plurality of impedance elements are connected in series.

[0092] (3) The power supply device according to (1) or (2), wherein:

[0093] The power supply device also has:

[0094] a peak voltage detection circuit, which detects the peak voltages of the DC output voltage and the AC output voltage; and

[0095] The startup voltage detection circuit detects the startup voltage of the load circuit by detecting the increase of the output voltage of the peak voltage detection circuit.

[0096] (4) The power supply device according to any one of (1) to (3), wherein:

[0097] The power supply device further includes a buffer circuit disposed between the voltage dividing circuit and the attenuation circuit.

[0098] (5) The power supply device according to any one of (1) to (4), wherein:

[0099] The attenuation circuit further includes a correction circuit that adjusts an output voltage according to a frequency of a voltage input to the input terminal.

[0100] (6) The power supply device according to any one of (1) to (5), wherein:

[0101] The load circuit is a DC stabilized power supply circuit.

[0102] Description of the label

[0103] 10 Power supply unit

[0104] 11 AC voltage source

[0105] 12 DC voltage source

[0106] 101, 102 Input terminals

[0107] 110 bridge rectifier circuit

[0108] 120 DC stabilized power supply circuit

[0109] 130 voltage divider circuit

[0110] 140 Attenuation Circuit

[0111] 150 Peak Voltage Detection Circuit

[0112] 160 Startup voltage detection circuit

[0113] 170 Voltage drop detection circuit

[0114] 180 Buffer Circuit

[0115] 190 Correction Circuit

Claims

1. A power supply device, wherein: The power supply device comprises: a pair of input terminals to which a DC input voltage and an AC input voltage having an effective value substantially equal to the DC input voltage are applied; a bridge rectifier circuit having an AC input terminal connected to the input terminal and a DC output terminal connected to the input end of the load circuit; A voltage divider circuit connected to the input terminal and outputting a midpoint voltage of the input voltage; an attenuation circuit that outputs a DC output voltage obtained by attenuating the waveform of the midpoint voltage of the voltage divider circuit when the DC input voltage is applied to the input terminal at a predetermined ratio, and outputs an AC output voltage obtained by attenuating the waveform of the midpoint voltage of the voltage divider circuit when the AC input voltage is applied to the input terminal to a waveform having a peak voltage substantially equal to the DC output voltage; as well as The voltage drop detection circuit detects a drop in the voltage input to the input terminal by detecting a drop in either the DC output voltage or the AC output voltage.

2. The power supply device according to claim 1, wherein: The attenuation circuit is composed of a voltage dividing circuit in which a plurality of impedance elements are connected in series.

3. The power supply device according to claim 1 or 2, wherein: The power supply device also has: a peak voltage detection circuit, which detects the peak voltages of the DC output voltage and the AC output voltage; and The startup voltage detection circuit detects the startup voltage of the load circuit by detecting the increase of the output voltage of the peak voltage detection circuit.

4. The power supply device according to claim 1 or 2, wherein: The power supply device further includes a buffer circuit disposed between the voltage dividing circuit and the attenuation circuit.

5. The power supply device according to claim 1 or 2, wherein: The attenuation circuit further includes a correction circuit that adjusts an output voltage according to a frequency of a voltage input to the input terminal.

6. The power supply device according to claim 1 or 2, wherein: The load circuit is a DC stabilized power supply circuit.

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