JP2015095927A - Power supply unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply unit with a wider range input voltage capable of achieving suppression of rectification section loss, size reduction, and high efficiency and output.SOLUTION: The power supply unit, having a rectification circuit with at least a part of a bridge diode comprised of a body diode of a field-effect transistor, includes control means for controlling to turn on and off the field-effect transistor according to the type of an input voltage of the bridge diode.

Description

  The present invention relates to a power supply device, and more particularly, to a power supply device that can output a desired DC voltage while supporting from a low-voltage DC input to a high-voltage AC input.

  FIG. 7 is an explanatory diagram showing a configuration example of a conventional AC (alternating current) -DC (direct current) converter. In FIG. 7, a rectifier circuit 20 is connected to the input voltage source 10, a DC-DC converter 40 is connected to the rectifier circuit 20 via a smoothing capacitor 30, and a load circuit 50 is connected to the DC-DC converter 40. ing.

  The input voltage source 10 is generally a commercial power source such as an AC 100V system or an AC 240V system, but includes an AC 24V system or a DC 12/24 / 48V system voltage source used in the industrial field.

  The voltage supplied from the input voltage source 10 is rectified by the rectifier circuit 20, then becomes a DC voltage with a ripple voltage reduced by the smoothing capacitor 30, and is supplied to the DC-DC converter 40.

  The DC-DC converter 40 converts the input DC voltage into a desired DC output voltage and outputs it to the load circuit 50.

  The DC-DC converter 40 can be properly used according to the presence / absence of an insulation function or the relationship between input and output voltages. When an insulation function is required, a flyback type or a forward type using a transformer is used, and when an insulation function is not required, a step-up type, a step-down type, a step-up / step-down type, or the like is used.

  FIG. 8 is a configuration explanatory diagram showing an example of the rectifier circuit 20 in the AC-DC converter of FIG. In FIG. 8, the rectifier circuit 20 includes a filter 21 and a bridge diode 22.

  The filter 21 is connected to the input voltage source 10 and has a function of reducing external noise from the input voltage source 10 and noise generated from inside the power supply.

  The bridge diode 22 is formed by connecting four diodes in a bridge shape with a predetermined polarity so as to rectify an input AC voltage to the same polarity. The output voltage is supplied to the smoothing capacitor 30 and the DC-DC converter 40. Supply. Specifically, the rectification operation is performed through a path indicated by a solid line when the L polarity of the input voltage source 10 is positive, and through a path indicated by a broken line when the N polarity is positive.

  FIG. 9 is a diagram illustrating a configuration example of a rectifier circuit in a conventional DC-DC converter, in which an input voltage source 10 is an example of a DC voltage, and FIG. 9A is an example in which a diode 23 is used as a rectifier circuit. (B) shows an example in which a field effect transistor 24 is used as a rectifier circuit.

  These rectifier circuits have a function of protecting the inside of the power source from being damaged when a power input of reverse polarity is applied. When there is no need to consider reverse polarity power input, the rectifier circuit is often omitted.

  Although the rectifier circuit using the diode 23 has a simple circuit configuration, there is a problem that loss due to a forward voltage drop becomes large.

  In a rectifier circuit using the field effect transistor 24, when a voltage is applied with a correct polarity, a drive circuit (not shown) operates to conduct the field effect transistor 24 to conduct rectification. Here, paying attention to the loss during conduction, only the loss due to the on-resistance of the field effect transistor 24 is obtained, so that the loss can be reduced as compared with the rectifier circuit using the diode 23.

  FIG. 10 is a configuration example diagram of a rectifier circuit in a conventional wide-range input-compatible power source. In the case of a power supply compatible with wide-range input, it is necessary to support a high-voltage AC power supply as described above, and thus a rectifier circuit configuration similar to that shown in FIG. 8 is adopted. In this case, since rectification is possible even at a low voltage DC input, as a result, the rectifier circuit at the time of low voltage DC input and the rectifier circuit at the time of high voltage AC input are combined.

  Patent Document 1 describes a switching power supply that can use a smoothing capacitor having a breakdown voltage comparable to that of a capacitor input type switching power supply and that can improve the power factor.

JP 2002-10463 A

  However, in the rectifier circuit configured as shown in FIG. 10, when it is intended to realize a power supply for a larger load circuit power or a power supply device in which the input voltage range is further expanded to the low voltage side, the loss of the bridge diode 22 is lost. There is a problem that becomes large.

For example, assuming that the forward voltage drop of the diode is 0.8V and the power supply efficiency is the same, when a power supply with an input current of 1A at a DC24V input is expanded to a DC12V input, the input current becomes 2A and the loss Ploss is
Ploss24V = 0.8V × 1A × 2 = 1.6W
Ploss12V = 0.8V × 2A × 2 = 3.2W
Will double.

  Actually, the loss further increases due to an increase in filter loss due to an increase in input current and an increase in diode forward voltage drop.

  Then, the heat generated by these causes an increase in product cost and product size, such as a decrease in reliability of the power supply device and addition of heat dissipating components to stop the rise in component temperature.

  The present invention solves such a problem, and an object of the present invention is to realize a power supply device with a high wide-range input that can reduce the loss of the rectification unit and is small in size and can efficiently obtain a high output.

In order to achieve such a problem, the invention according to claim 1 of the present invention is:
In a power supply device having a rectifier circuit in which at least a part of a bridge diode is configured by a body diode of a field effect transistor,
Control means for controlling on / off of the field effect transistor according to the type of input voltage of the bridge diode is provided.

The invention according to claim 2 is the power supply device according to claim 1,
When the input voltage is alternating current, each side of the bridge diode is composed of a body diode of a field effect transistor,
The control means selectively turns on / off field effect transistors on each side of the bridge diode.

The invention according to claim 3 is the power supply device according to claim 1,
When the input voltage is direct current, either one of the pair of sides of the bridge diode is composed of a body diode of a field effect transistor,
The control means selectively turns on a field effect transistor constituting the bridge diode.

According to a fourth aspect of the present invention, in the power supply device according to any one of the first to third aspects,
The control means includes
Polarity detection means for detecting the polarity of the input voltage of the bridge diode;
Voltage detecting means for detecting an output voltage of the bridge diode;
A logic unit that performs a logical operation based on output signals of the polarity detection unit and the voltage detection unit;
Drive means for selectively turning on and off the field effect transistors on each side of the bridge diode based on the output of the logic unit;
It is characterized by comprising.

According to a fifth aspect of the present invention, in the power supply device according to the fourth aspect,
A DC-DC converter is connected to the subsequent stage of the bridge diode,
The operation of the DC-DC converter is permitted or prohibited based on the output of the logic unit.

  As a result, it is possible to realize a power supply device that has a relatively small rectifier loss, can be used for a high wide-range input, and is small in size and can efficiently obtain a high output.

It is a configuration explanatory view showing an embodiment of the present invention. It is a circuit diagram which shows the specific example of the control part 60 used in FIG. It is a timing chart which shows the operation example at the time of AC input. It is a timing chart which shows the operation example at the time of DC input. It is composition explanatory drawing which shows the other Example of this invention. It is a circuit diagram which shows the specific example of the control part 60 used in FIG. It is composition explanatory drawing which shows an example of the conventional AC-DC converter. FIG. 8 is a configuration explanatory diagram illustrating an example of a rectifier circuit in the AC-DC converter of FIG. 7. It is a structural example figure of the rectifier circuit in the conventional DC-DC converter. It is a structural example figure of the rectifier circuit in the conventional wide range input corresponding | compatible power supply.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating the construction of an embodiment of the present invention, and the same reference numerals are given to the parts common to FIG. In FIG. 1, the bridge diode 25 constituting the rectifier circuit 20 is formed by connecting the body diodes of the four N-channel field effect transistors (MOSFETs) 25a to 25d in the same manner as the bridge diode 22 in FIG. It is configured.

The control unit 60 outputs five systems of output signals G1 to G4 and an enable signal CE of the DC-DC converter 40 based on four systems of input signals L _sig / S ₂ , N _sig / S ₄ , S ₁₃ / V ₋ , V ₊ . Is configured to output.

The signal terminal of the input signal L _sig / S ₂ is connected to the connection point of one output terminal L of the filter 21 and the field effect transistors 25a and 25b, and the signal terminal of the input signal N _sig / S ₄ is connected to the other end of the filter 21. Is connected to the connection point between the output terminal N and the field effect transistors 25c and 25d, and to the signal terminal of the input signal S ₁₃ / V ₋ , the connection point between the field effect transistors 25a and 25c is connected to the smoothing capacitor 30 and the DC−. One of the connection points of the DC converter 40 is connected, the connection point of the field effect transistors 25b and 25d is connected to the signal terminal of the input signal V ₊ , and the other connection point of the smoothing capacitor 30 and the DC-DC converter 40 is connected. It is connected.

  The gate of the field effect transistor 25a is connected to the signal terminal of the output signal G1, the gate of the field effect transistor 25b is connected to the signal terminal of the output signal G2, and the gate of the field effect transistor 25c is connected to the signal terminal of the output signal G3. Are connected, the signal terminal of the output signal G4 is connected to the gate of the field effect transistor 25d, and the signal terminal of the output signal CE is connected to the control terminal of the DC-DC converter 40.

  The control unit 60 includes a polarity / AC detection unit 61, a voltage level detection unit 62, a drive unit 63, and a logic unit 64.

FIG. 2 is a circuit diagram illustrating a specific example of the control unit 60. The polarity / AC detector 61 includes a differential output comparator 61a that compares the input signal L _sig / S ₂ and the input signal N _sig / S ₄ , and timer means that detects only the falling edge of the output signal of the differential output comparator 61a. 61b and timer means 61c for detecting only the rising edge of the output signal of the differential output comparator 61a.

The voltage level detection unit 62 includes two comparators 62a and 62b having hysteresis for detecting the level of the input signal V ₊ . Here, one comparator 62a detects a low voltage level, and the other comparator 62b detects a high level.

  The drive unit 63 generates and outputs four systems of output signals G1 to G4 for individually turning on / off the field effect transistors 25a to 25d constituting the bridge diode 25.

  Each output signal system is a positive voltage source E based on the sources of the field effect transistors 25a to 25d, and an insulation type that selectively turns on and off between the output of the voltage source E and the gates of the field effect transistors 25a to 25d. The switch SW and a resistor R that makes the gate and source of the field effect transistors 25a to 25d have the same potential when the switch SW is turned off. In the initial state immediately after energization, the field effect transistors 25a to 25d are turned off. Is set to The insulation type switch SW may be a unipolar switch such as a photocoupler.

  The logic unit 64 logically calculates the output signals of the two timer means 61b and 61c constituting the polarity / AC detection unit 61 and the output signals of the two comparators 62a and 62b constituting the voltage level detection unit 62. It is composed of four gate elements 64a to 64d, and generates a drive signal for each part of the drive unit 63 and an enable signal CE for the DC-DC converter 40.

  One input terminal of the gate element 64a is connected to the output terminal of the timer means 61b constituting the polarity / AC detector 61, and the other input terminal is connected to the output terminal of the comparator 62b constituting the voltage level detector 62. Has been. The output signal of the gate element 64a is connected to a switch SW of a predetermined output signal system of the drive unit 63 as a drive signal for driving on / off the switch SW of each output signal system that generates and outputs the output signals G1 and G4. .

  One input terminal of the gate element 64b is connected to the output terminal of the timer means 61c constituting the polarity / AC detector 61, and the other input terminal is connected to the output terminal of the comparator 62b constituting the voltage level detector 62. Has been. The output signal of the gate element 64b is connected to a switch SW of a predetermined output signal system of the drive unit 63 as a drive signal for driving on / off the switch SW of each output signal system that generates and outputs the output signals G2 and G3. .

  The first input terminal of the gate element 64c is connected to the output terminal of the timer means 61b constituting the polarity / AC detector 61, and the second input terminal of the timer means 61c constituting the polarity / AC detector 61 is connected. The output terminal is connected, and the output terminal of the comparator 62b constituting the voltage level detection unit 62 is connected to the third input terminal.

  The output terminal of the gate element 64c is connected to the first input terminal of the gate element 64d, and the output terminal of the comparator 62a constituting the voltage level detection unit 62 is connected to the second input terminal. The gate element 64d generates and outputs an enable signal CE for the DC-DC converter 40.

3A and 3B are timing charts showing an operation example at the time of AC input. FIG. 3A shows a potential difference between the input voltages L and N. FIG. 3B shows a differential output comparator constituting the polarity / AC detection unit 61. FIG. (C) shows the output of the timer means 61c constituting the polarity / AC detector 61, (d) shows the output of the timer means 61b constituting the polarity / AC detector 61, (e ) Shows the potential difference between the input signals V ₊ -V ₋ , (f) shows the output of the comparator 62 a constituting the voltage level detector 62, and (g) shows the output of the comparator 62 b constituting the voltage level detector 62. (H) shows the output of the drive unit 63, and (i) shows the output of the gate element 64 d constituting the logic unit 64.

  The differential output comparator 61a constituting the polarity / AC detection unit 61 generates an output corresponding to the potential difference between the inputs L and N of the input voltage shown in (a) as shown in (b). When the timer time TO of the timer means 61c and 61b constituting the polarity / AC detector 61 is set sufficiently larger than the AC input cycle, the outputs of the timer means 61c and 61b are positive logic as shown in (c) and (d). It will never be reversed.

In the initial state, the field effect transistors 25a to 25d constituting the bridge diode 25 are off, but the AC input is rectified by the body diode inside the field effect transistor, and the potential difference between the input signals V ₊ -V ₋ is shown in (e). Thus, a full-wave rectified waveform is obtained.

The comparators 62a and 62b constituting the voltage level detection unit 62 operate in accordance with respective threshold values (VthX ↑ / VthX ↓, X = 2, 3) with the potential difference between these input signals V ₊ -V ₋ as an input. .

  Here, the input signal of the drive unit 63 is controlled by the logic unit 64, and the output logic value of the timer means 61c and 61b is 0 as described above. Even so, the signal is not output to the drive unit 63. Therefore, the four systems of output signals G1 to G4 generated and output from the drive unit 63 are kept at the same potential as the source, and all the field effect transistors 25a to 25d remain in the off state.

  When the input voltage level rises from this state and the output of the comparator 62b is inverted to positive logic, the converter enable signal is output and the DC-DC converter 40 starts operation.

  That is, according to the configuration of FIG. 1 and FIG. 2, in the case of AC input, all the field effect transistors 25a to 25d perform rectification operation through the internal body diode in the off state, and the input voltage exceeds the threshold value of the comparator 62b. And the DC-DC converter 40 starts operation.

4A and 4B are timing charts showing an operation example at the time of DC input, in which FIG. 4A shows a potential difference between input voltage inputs +/−, and FIG. 4B shows a differential output comparator constituting the polarity / AC detection unit 61. (C) shows the output of the timer means 61c constituting the polarity / AC detector 61, (d) shows the output of the timer means 61b constituting the polarity / AC detector 61, (e ) Shows the potential difference between the input signals V ₊ -V ₋ , (f) shows the output of the comparator 62 a constituting the voltage level detector 62, and (g) shows the output of the comparator 62 b constituting the voltage level detector 62. (H) shows the outputs G2 and G3 of the drive unit 63, (i) shows the outputs G1 and G4 of the drive unit 63, and (j) shows the output of the gate element 64d constituting the logic unit 64. ing.

  The differential output comparator 61a constituting the polarity / AC detection unit 61 generates an output corresponding to the potential difference between the input +/− of the input voltage shown in (a) as shown in (b). In principle, the input polarity is not reversed because it is a DC input. However, in FIG. 4A, the voltage change is moderated and the polarity is reversed to illustrate the operation.

  When the potential difference between the inputs +/− becomes positive, after the set time T0 of the timer means 61c shown in (c) has elapsed, the output of the timer means 61b shown in (d) turns to positive logic, and between the inputs +/− It becomes negative logic immediately after the potential difference becomes negative. Further, after the time T0 elapses, the output of the timer means 61b turns to positive logic and becomes negative logic immediately after the input becomes zero.

  As described above, in the initial state, the field effect transistors 25a to 25d constituting the bridge diode 25 are off, but the DC input is rectified by the body diode inside the field effect transistor.

When the input +/- potential difference is positive, the body diodes of the field effect transistors 25b and 25c in FIG. 1 are conducting. For this reason, the potential difference between the input signals V ₊ -V ₋ is substantially equal to the absolute value of the potential difference between +/−. The comparators 62a and 62b having these as inputs operate according to respective threshold values (VthX ↑ / ↓, X = 2, 3).

At this time, in a state where the output logic of the timer means 61c is 1 and the output of the comparator 62b is 0, the output signals G2 and G3 of the drive unit 63 become active, and the field effect transistors 25b and 25c are turned on. As a result, the current that has been flowing through each body diode until then flows through the channel of the field effect transistor, and the forward loss of the diode can be reduced. For example, when the forward voltage drop is 0.8 V and the diode current is 1 A, a loss of 0.8 W occurs. However, when a field effect transistor having an on-resistance of 0.2Ω is selected, the loss is 0. Reduced to 2W.

  On the other hand, when the potential of the positive electrode becomes negative, the output signals G1 and G4 of the driving unit 63 become active during the period when the output logic value of the timer means 61b is 1, and the field effect transistors 25a and 25d are turned on.

  When the potential difference between the input +/− is further increased and the output of the comparator 62 b becomes positive, the output signal to the drive unit 63 is not output due to the configuration of the logic unit 64. As a result, the gates G1 to G4 are kept at the same potential as the source, and all the field effect transistors 25a to 25d are turned off and rectified by the internal body diode.

  In this case, since the input current is reduced due to the increase of the input voltage, the diode forward loss is smaller than that at the time of low voltage input. For example, when the threshold value of the comparator 62b is set to four times the minimum input voltage, the forward loss is reduced to about 1/4, which is not a big problem.

  If the output logic value of either the timer means 61b or the timer means 61c is 1 and the output of the comparator 62a is positive logic due to the configuration of the logic unit 64, the converter enable signal CE is output and the DC-DC Converter 40 starts operation. Since the converter enable signal remains active even after the input voltage further rises and the drive unit signal is turned off, the DC-DC converter 40 continues to operate.

That is, in the case of DC input, the operation is as follows.
a) [0V <comparator 62a threshold value ≦ +/− potential difference <comparator 62b threshold value]
After approximately T0 time has passed since the energization, the field effect transistors 25b and 25c are turned on to perform rectification operation, and the DC-DC converter 40 operates.

b) [0V> −comparator 62a threshold ≧≧ / −potential difference> comparator 62b threshold]
After approximately T0 time has passed since the energization, the field effect transistors 25a and 25d are turned on to perform a rectifying operation, and the DC-DC converter 40 operates.

c) [0V <Comparator 62b threshold value ≦ +/− potential difference] or [0V> −Comparator 62b threshold value ≧ +/− potential difference]
All the field effect transistors 25a to 25d are turned off, perform rectification operation through the body diode, and the DC-DC converter 40 operates.

d) [-comparator 62a threshold value≤ +/- potential difference <comparator 62a threshold value]
The DC-DC converter 40 does not operate.

  With such a configuration, it is possible to reduce the forward loss of the bridge diode, which is particularly effective for reducing the forward loss at the time of low voltage DC input.

  In addition, since the field effect transistor is not turned on using the timer means at the time of AC input, it is not necessary to increase the speed of the field effect transistor drive circuit, and the drive circuit can be configured with general-purpose inexpensive parts. Low power consumption of the drive circuit can also be realized.

  Since the DC input system is generally a 12V / 24V / 48V system, and the AC input system is generally a 100V system / 200V system, for example, the threshold value of the comparator 62b is about 60 to 70V of DC, and the threshold value of the comparator 62a. Is set to about 10V of DC, DC 12V / 24V / 48V system can be rectified by a field effect transistor, and AC 100 / 200V system can be rectified by a diode.

  FIG. 5 is an explanatory diagram showing the configuration of another embodiment of the present invention. Components common to those in FIG. In FIG. 5, the polarity of the terminals at the time of DC input is determined, and these input terminals are also used at the time of AC input.

  In FIG. 5, even if a DC input with reverse polarity is connected, it is not necessary to operate as a power source unless it is damaged. Therefore, a part of the bridge diode 25 (25a and 25d) is replaced with a simple diode from the field effect transistor. Yes.

  Although not shown in the figure, even when the field effect transistors 25b and 25c are connected in parallel to a bridge diode that is packaged as a single diode, the essential operation is the same as in FIG.

  However, if it operates as a power source during reverse polarity DC input, the loss of the diodes 25a and 25d substituted for low voltage input may increase, leading to damage. Therefore, it is necessary to control so that the DC-DC converter 40 does not operate in this state.

  FIG. 6 is a circuit diagram showing a specific example of the control unit 60 used in FIG. 5, and the same reference numerals are given to the parts common to FIG. The difference between FIG. 6 and FIG. 2 resides in the drive unit 63 and the logic unit 64. That is, the driving unit 63 is configured to generate and output two systems of output signals G2 and G3 for individually turning on and off the two field effect transistors 25b and 25c constituting the bridge diode 25. The part 64 is composed of three gate elements 64e to 64g.

  The logic unit 64 includes three logical operations for the output signals of the timer means 61b and 61c constituting the polarity / AC detection unit 61 and the output signals of the two comparators 62a and 62b constituting the voltage level detection unit 62. The gate elements 64e to 64g are configured to generate a drive signal for each part of the drive unit 63 and an enable signal CE for the DC-DC converter 40.

  One input terminal of the gate element 64e is connected to the output terminal of the timer means 61c constituting the polarity / AC detector 61, and the other input terminal is connected to the output terminal of the comparator 62b constituting the voltage level detector 62. Has been. The output signal of the gate element 64e is connected to a switch SW of a predetermined output signal system of the drive unit 63 as a drive signal for driving on / off the switch SW of each output signal system that generates and outputs the output signals G2 and G3. .

  One input terminal of the gate element 64f is connected to the output terminal of the timer means 61c constituting the polarity / AC detector 61, and the other input terminal is connected to the output terminal of the comparator 62b constituting the voltage level detector 62. Has been.

  The first input terminal of the gate element 64g is connected to the output terminal of the timer means 61b constituting the polarity / AC detection unit 61, and the second input terminal is connected to the output terminal of the gate element 64f. The input terminal is connected to the output terminal of the comparator 62a constituting the voltage level detector 62. The gate element 64g generates and outputs an enable signal CE for the DC-DC converter 40.

  In FIG. 5, when a low-voltage DC positive polarity is input, the field effect transistors 25b and 25c are made conductive. When a high-voltage AC is input, the field-effect transistors 25a to 25d remain in the OFF state. Operates as a DC converter.

  According to such a configuration, the converter does not operate when a low-voltage reverse polarity DC or a high-voltage bipolar DC is input, so that an unexpected input does not cause malfunction or damage.

  That is, by configuring the rectification unit and the control unit according to the required specifications for the power supply, it is possible to realize an inexpensive and small-sized power supply device with a smaller number of parts.

  Many control ICs used in general DC-DC converters have a built-in low-voltage lockout function for the purpose of preventing malfunction and damage of the DC-DC converter. These are configured such that the Vcc terminal voltage of the IC is monitored by a comparator with hysteresis, and the operation of the DC-DC converter is prohibited when a predetermined condition is not satisfied.

  A comparator for the low voltage lockout function built in the converter control IC is used in place of the comparator 62a of FIGS. 2 and 6, and an external start and stop circuit is provided so that the power supply start and stop becomes a desired value. By constructing, the same operation as in FIGS. 2 and 6 can be realized.

  According to such a configuration, it is not necessary to provide a comparator in the external circuit, and it is possible to realize an inexpensive and small-sized power supply device with a smaller number of parts.

  The positive voltage sources based on the sources of the field effect transistors in FIGS. 1 and 5 each have a large potential difference (in the case of an AC 200 V system input, several hundred volts), so that each is preferably insulated.

  Therefore, as such a positive voltage source, a plurality of insulated windings are provided in a transformer of a DC-DC converter, and a rectifier circuit is provided in a direction in which an output proportional to a constant controlled winding output is obtained. It is convenient to use one.

  For example, a photocoupler may be used as an insulating means between the gate driving means and the logic portion of the field effect transistor.

  As described above, according to the present invention, it is possible to realize a power supply device that can cope with a high wide-range input, and is small in size and can efficiently obtain a high output.

DESCRIPTION OF SYMBOLS 10 Input voltage source 20 Rectifier circuit 30 Capacitor 40 DC-DC converter 50 Load circuit 60 Control part 61 Polarity / AC detection part 62 Voltage level detection part 63 Drive part 64 Logic part

Claims (5)

In a power supply device having a rectifier circuit in which at least a part of a bridge diode is configured by a body diode of a field effect transistor,
A power supply apparatus comprising control means for controlling on / off of the field effect transistor according to a type of an input voltage of the bridge diode. When the input voltage is alternating current, each side of the bridge diode is composed of a body diode of a field effect transistor,
The power supply apparatus according to claim 1, wherein the control unit selectively turns on and off field effect transistors on each side of the bridge diode. When the input voltage is direct current, either one of the pair of sides of the bridge diode is composed of a body diode of a field effect transistor,
2. The power supply device according to claim 1, wherein the control means selectively turns on a field effect transistor constituting the bridge diode. The control means includes
Polarity detection means for detecting the polarity of the input voltage of the bridge diode;
Voltage detecting means for detecting an output voltage of the bridge diode;
A logic unit that performs a logical operation based on output signals of the polarity detection unit and the voltage detection unit;
Drive means for selectively turning on and off the field effect transistors on each side of the bridge diode based on the output of the logic unit;
The power supply device according to claim 1, wherein the power supply device is configured as follows. A DC-DC converter is connected to the subsequent stage of the bridge diode,
The power supply apparatus according to claim 4, wherein the operation of the DC-DC converter is permitted or prohibited based on an output of the logic unit.

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