JP2011147285A - Power supply device and power supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem with multi-output power supply, wherein the efficiency of using power is poor although rated power is designed to exceed the sum of maximum power consumption of a load L1 and a load L2. <P>SOLUTION: The power supply includes: a power supply circuit 10 for output of the rated power; a current detection unit 31 for detecting drive current driving the load L1 and the load L2 and for output of a detection signal; an overcurrent determiner 41 for receiving the detection signal, for comparing it with a threshold and for output of a control signal; and a power control unit 42 controlling supply of the drive current to the load L2 by receiving the control signal. Thus, the efficiency of use as a power supply is improved since surplus power can be supplied to the load L2 while power supply to the load L1 is secured. When the power supply is constituted to supply power to the load L2 of a common board 80 from a plurality of circuit boards 70 having the power supplies, power can be saved and the power supply can be miniaturized without practically stopping the load L2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a multi-output type power supply device and a power supply system including the power supply device, and in particular, when the power consumption of a main load is less than the rated power, the redundant load is supplementarily used. The present invention relates to a multi-output type power supply device and a power supply system for outputting.

  Conventionally, in a multi-output type power supply device, when an overcurrent flows through a load, this is detected and the result is fed back to the control circuit of the power supply to limit the overcurrent and guarantee an appropriate current value. A power supply device having an overcurrent protection function is known. Patent Document 1 describes such a multi-output type power supply device having an overcurrent protection function.

  FIG. 11 is a schematic circuit diagram showing a configuration of a conventional power supply device described in Patent Document 1. In FIG.

  A conventional power supply device having an overcurrent protection function includes a direct current (hereinafter referred to as “DC”) power supply E, a transformer 1, and a switching transistor 2. The transformer 1 and the transistor 2 convert the voltage and supply power to the main load L1 and the subordinate load L2. Here, when it is detected by the current detection resistor 6 that the supply current to the main load L1 has increased beyond the specified value (overcurrent), the transistor 7 is activated, and the overcurrent detection signal is transmitted via the photocoupler 8 to the control circuit. 3 is transmitted. As a result, the control circuit 3 protects the load L1 by operating the transistor 2 so as to limit power supply to the main load L1 and the subordinate load L2.

JP 2000-253655 A

However, the conventional power supply apparatus has the following problems.
Normally, the power supply device is designed so that the rated power can be output. In the conventional case, the power supply device is designed so that the sum of the maximum power consumption of the main load L1 and the subordinate maximum power consumption can be output. However, it is extremely rare to use it at rated power at all times, and it is often used at 70 to 80% or less of the rated power. As a result, the utilization efficiency with respect to the rated power is low, and the supply capability of the difference between the rated power and the actual used power is wasted.

  The power supply device of the present invention includes a power supply unit that outputs a rated power for supplying a drive current to the first load and one or more second loads, the first load, and the second load. A current detection unit that detects the drive current supplied to the load and outputs a detection signal, and receives the detection signal, compares it with a predetermined threshold value, and determines that there is surplus power when the detection signal is less than the threshold value Then, when the drive current is supplied to the second load and the detection signal exceeds the threshold, it is determined that there is no surplus power and the surplus power control unit cuts off the drive current to the second load. And have.

  Another power supply device of the present invention further has a first threshold value and a second threshold value, and the surplus power control unit is supplied with the drive current to the first and second loads. When the detection signal is less than the first threshold value, it is determined that there is surplus power, and the supply of the drive current to the second load is continued, and the detection signal is the first threshold value. Is exceeded, it is determined that there is no surplus power, and the drive current to the second load is cut off.

  In a state where the drive current to the second load is cut off, when the detection signal becomes less than the second threshold, it is determined that there is surplus power and the drive current to the second load is determined. When the drive current exceeds the second threshold, it is determined that there is no surplus power, and the state where the drive current to the second load is cut off is continued.

  Another power supply device according to the present invention outputs the first detection signal and the second detection signal, and the surplus power control unit is configured to output the drive current to the first and second loads. In the supplied state, when the first detection signal is less than the threshold value, it is determined that there is surplus power, the supply of the drive current to the second load is continued, and the first detection signal is When the threshold value is exceeded, it is determined that there is no surplus power, and the drive current to the second load is cut off.

  In a state where the drive current to the second load is cut off, when the second detection signal becomes less than the threshold, it is determined that there is surplus power and the drive current to the second load is determined. When the second detection signal exceeds the threshold value, it is determined that there is no surplus power, and the state where the drive current to the second load is cut off is continued.

  The power supply system of the present invention includes a plurality of the power supply devices, and a common line that connects an output side of the surplus power control unit provided in each of the plurality of power supply devices and one or more of the second loads. Have.

  Another power supply system of the present invention includes a plurality of the power supply devices and a common line connected to an output side of the surplus power control unit, and the common line is further connected to the plurality of power supply devices. Each is connected to the corresponding first load.

  According to the power supply device of the present invention, since the surplus power is supplied to the second load while securing the power supply to the first load, the use efficiency as a power source is increased and wasteful power consumption is suppressed. can do. As a result, it can contribute to power saving and downsizing of the power supply device, and cost reduction can be expected.

  Moreover, even if the power consumption of the second load temporarily increases due to a failure or malfunction of the second load, the power supply device can perform a stable operation by disconnecting the second load. .

  According to another power supply device of the present invention, in addition to the above effects, there are the following effects (1) and (2).

  (1) Since the first threshold value and the second threshold value are configured, the power consumption of the second load increases, and the power supply to the second load is temporarily interrupted by the first threshold value. In order for power to be supplied to the second load again after the operation is performed, whether or not the transition from the cutoff state to the supply state is possible is determined based on the second threshold value. Power supply is not started. The power supply to the second load can be resumed when the power consumption of the first load decreases and becomes sufficient surplus power. For this reason, even when the second load requires a large starting current, the second load can stably start operation without causing a malfunction due to insufficient current.

  (2) By using the first and second threshold values and the comparator, the operation of the power control unit can be set freely and with high accuracy.

  According to another power supply device of the present invention, the following effects (3) and (4) are obtained in addition to the above effects.

  (3) Since it is configured to have the first detection signal and the second detection signal, the power consumption of the second load increases, and the power to the second load is temporarily increased by the first detection signal. In order for power to be supplied to the second load again after the supply is cut off, whether or not the transition from the cut-off state to the supply state is possible is determined by the second detection signal. The power supply to the load is not started. The power supply to the second load can be resumed when the power consumption of the first load decreases and becomes sufficient surplus power. For this reason, similarly to the effect (1), even when the second load requires a large starting current, the second load can stably start operation without causing a malfunction due to insufficient current.

  (4) Since an auxiliary power source for operating the circuit is not used, it can be realized with a simple circuit.

  The power supply system of the present invention has the following effects (5) to (7).

  (5) By supplying power from one or more power supply systems to one or more second loads, the probability of interruption of power supply to the second load is reduced without a dedicated power supply circuit. be able to.

  (6) When the minimum power that can be reliably supplied from a plurality of power supply devices to one or a plurality of second loads is known, only power that is insufficient to operate the second load is supplied. If another power supply circuit is provided in the second load, the power supply is completely cut off and the reliability is improved, and the rated power of the other power supply circuit can be reduced, so that the power supply circuit can be made smaller and cheaper. it can.

  (7) By distributing the power necessary for the operation of the second load to each power supply device in advance and designing the power supply unit, it is possible to delete the power circuit of the common second load, and further reduce the size and It can be made cheap. In addition, since the electric power supplied to a 2nd load from a power supply part becomes so small that there are many power supply devices, it can respond, without making a power supply part large sized and expensive.

  According to another power supply system of the present invention, the following effects (8) to (10) are obtained.

  (8) Normally, when the power supply unit in the power supply apparatus fails, the first load stops functioning even though the first load is normal. According to another power supply system of the present invention, when a failure occurs in the power supply unit, it is possible to supply power from the other power supply device to the first load of the failed power supply device while sending an alarm to the outside. Therefore, even if a large redundant configuration is not adopted, the probability that the function of the power supply system is stopped is reduced until the maintenance person takes measures such as replacement of the failed power supply, and the reliability of the power supply system is improved. Can do.

  (9) Even when a failure occurs in the power supply units of a plurality of power supply devices, the probability that the entire power supply system stops can be greatly reduced.

  (10) When there are a large number of power supply devices, the reliability can be further increased by setting the capacity of the power supply unit that assumes failure of a plurality of power supply devices.

FIG. 1 is a schematic first functional block diagram showing a configuration of a power supply device according to Embodiment 1 of the present invention. FIG. 2 is a circuit diagram showing a configuration example of the power supply device of FIG. FIG. 3 is a circuit diagram showing a configuration example of the power supply circuit in FIG. FIG. 4 is a circuit diagram showing a configuration example of the power supply device according to the second embodiment of the present invention. FIG. 5 is a schematic second functional block diagram showing the configuration of the power supply device according to the third embodiment of the present invention. FIG. 6 is a circuit diagram showing a configuration example of the power supply device of FIG. FIG. 7 is a schematic perspective view showing a configuration example of the power supply system according to the fourth embodiment of the present invention. FIG. 8 is a circuit block diagram showing a configuration example of the power supply system of FIG. FIG. 9 is a schematic perspective view showing a configuration example of a power supply system in Embodiment 5 of the present invention. FIG. 10 is a circuit block diagram showing a configuration example of the power supply system of FIG. FIG. 11 is a schematic circuit diagram showing a configuration of a conventional power supply apparatus.

  Modes for carrying out the present invention will become apparent from the following description of the preferred embodiments when read in light of the accompanying drawings. However, the drawings are only for explanation and do not limit the scope of the present invention.

(Configuration of Power Supply Device of Example 1)
FIG. 1 is a schematic first functional block diagram illustrating a configuration of a power supply device according to a first embodiment of the present invention.

  The power supply device includes a power supply unit (for example, a power supply circuit) 10 including a DC-DC power supply circuit that outputs a rated power based on a DC power supply E, and a surplus power supply circuit 30 that controls supply of surplus power. . The surplus power supply circuit 30 is connected to the positive electrode 10a and the negative electrode 10b of the power supply circuit 10, and includes a current detection unit 31 that detects a drive current that drives the main first load L1 and the subordinate second load L2, and this current. It has a surplus power control unit 40 that controls supply and cut-off of surplus power to the load L2 by a detection signal from the detection unit 31.

  The surplus power control unit 40 detects an occurrence of overcurrent based on a detection signal from the current detection unit 31 and outputs a control signal. The surplus power control unit 40 receives an output signal of the overcurrent determination unit 41 and receives the load L2 It is comprised from the electric power control part 42 which supplies and interrupts | blocks the electric power to.

  Here, the current detection unit 31 is connected to the positive electrode 10a of the power supply circuit 10, and the current detection unit 31 is connected to the overcurrent determination unit 41 through a signal line. One end of the load L1 and the power control unit 42 are connected to the output side of the current detection unit 31. A power control unit 42 is connected to the output side of the overcurrent determination unit 41, and one end of a load L <b> 2 is connected to the output side of the power control unit 42. The other end of the load L2, the power control unit 42, and the other end of the load L1 are connected to the negative electrode 10b of the power supply circuit 10.

FIG. 2 is a circuit diagram showing a configuration example of the power supply device of FIG.
The current detection unit 31 includes a first resistance element 31a having a resistance value R1, and the overcurrent determination unit 41 includes a first transistor (eg, a PNP transistor, hereinafter referred to as “PNPTR”) 41a. The power control unit 42 includes a second transistor (for example, PNPTR) 42a and a second resistance element 42b having a resistance value R2.

  The first electrode (for example, emitter) of the PNPTR 41a is connected to the positive electrode 10a of the power supply circuit 10 and one end of the resistance element 31a, and the second electrode (for example, collector) is the control electrode (for example, base) of the PNPTR 42a. And the resistance element 42b. The control electrode (for example, base) of the PNPTR 41a is connected to the first electrode (for example, emitter) of the PNPTR 42a, the other end side of the resistance element 31a, and one end of the load L1. Further, the second electrode (for example, collector) of the PNPTR 42a is connected to one end of the load L2. The other end of the load L1, the other end of the resistance element 42b, and the other end of the load L2 are connected to the negative electrode 10b of the power supply circuit 10.

FIG. 3 is a circuit diagram showing a configuration example of the power supply circuit in FIG.
The power supply circuit 10 includes a DC power supply E and a transformer 11. An NPN transistor for switching (hereinafter referred to as “NPNTR”) 22 is provided between the DC power source E and the transformer 11, and the switching operation of the NPNTR 22 can be controlled by the control circuit 21. ing. The anode of the rectifying diode 12 is connected to one end on the output side of the transformer 11, and the cathode is connected to the positive electrode 10 a via the inductor 14. One end of a capacitor 15 is connected between the output side of the inductor 14 and the positive electrode 10a. The inductor 14 and the capacitor 15 constitute a smoothing circuit.

  The other end on the output side of the transformer 11 is connected to the anode of the commutation diode 13, the other end of the capacitor 15, and the negative electrode 10b. Between the positive electrode 10a and the negative electrode 10b, a resistance element 16, a light emitting diode 20a constituting a photocoupler 20, and a shunt regulator 17 are connected in series, and in parallel with this, a resistance element 18 for voltage division, 19 is connected. The collector of the NPNTR 20 b constituting the photocoupler 20 is connected to the first terminal of the control circuit 21. The emitter of the NPNTR 20b is connected to the second terminal of the control circuit 21, the emitter of the NPNTR 22, and the DC power source E.

(Operation of Power Supply Circuit in Power Supply Device in Embodiment 1)
In the power supply circuit 10 of FIG. 3, the DC voltage supplied from the DC power supply E is converted into an alternating current (hereinafter referred to as “AC”) voltage by switching of the NPNTR 22, and is transferred to the secondary side (output side) via the transformer 11. Communicated. The transmitted AC voltage is rectified by the diodes 12 and 13 and smoothed by the inductor 14 and the capacitor 15 to become a DC voltage, which becomes an output voltage.

  The output voltage is divided by the resistance element 18 and the resistance element 19, and an error from the reference voltage is amplified inside the shunt regulator 17. A signal corresponding to the amplified error is transmitted to the control circuit 21 via the photocoupler 20, and the control circuit 21 determines the on-duty according to the signal and drives the NPNTR 22. Here, the on-duty means a time ratio during which the NPNTR 22 occupies during the switching cycle.

(Operation of Surplus Power Supply Circuit in Power Supply Device in Embodiment 1)
Regarding the operation of the surplus power supply circuit 30 in the power supply apparatus according to the first embodiment, (1) the operation when the power consumption of the load L1 and the load L2 is in the normal state, and (2) the power consumption of the load L1 increases. (3) Operation when the power consumption of the load L1 increases and then returns to the normal state, (4) Operation when the power consumption of the load L2 increases, and (5) Consumption of the load L2 The following description will be divided into operations when the power returns to the normal state after the power increase.

(1) Operation when the power consumption of the load L1 and the load L2 is in the normal state When the total power consumption of the load L1 and the load L2 is in the normal state within the rated power of the power supply circuit 10, the PNPTR 41a is in the non-conduction state ( The base voltage of the PNPTR 42a is pulled down by the resistance element 42b and becomes the second potential (for example, the base-emitter threshold voltage VBE (th)). , PNPTR 42a is in a conductive state (hereinafter referred to as “on state”). Therefore, power is supplied to the load L1 via the resistance element 31a, and power is supplied to the load L2 via the resistance element 31a and the PNPTR 42a.

(2) Operation when the power consumption of the load L1 increases (a) The sum of the current I1 flowing through the load L1 and the current I2 flowing through the load L2 flows through the resistance element 31a having the resistance value R1. That is, when the current flowing through the resistance element 31a is I (R1), the following equation (1) is established.
I (R1) = I1 + I2 (1)

    (B) When the power consumption of the load L1 increases, the current I1 flowing through the load L1 increases, and the current I (R1) increases from Equation (1).

    (C) When the current I (R1) increases, the potential difference due to the current I (R1) (for example, the voltage drop of the resistance element 31a) increases.

    (D) When the drop voltage of the resistance element 31a increases, this drop voltage reaches the threshold value of the PNPTR 41a (for example, the base-emitter threshold voltage VBE (th)) (= reference voltage).

(E) When the drop voltage of the resistance element 31a reaches the reference voltage, the PNPTR 41a becomes conductive. That is, when the following formula (2) is established, the PNPTR 41a transitions from the off state to the on state.
VBE (th) = I (R1) × R1 (2)

    (F) When the PNPTR 41a is turned on, a first potential (for example, a voltage across the resistance element 31a) (= VBE (th)) is applied between the base and emitter of the PNPTR 42a, but the base potential of the PNPTR 42a is It becomes higher than the emitter potential and enters a reverse bias state.

    (G) Therefore, the PNPTR 42a transitions from the on state to the off state.

    (H) As a result, power supply to the load L1 is ensured, and power supply to the load L2 is interrupted.

(3) Operation when the power consumption of the load L1 increases and then returns to the normal state (a) When the power consumption of the load L1 decreases, the current I1 flowing through the load L1 decreases, and the current I (R1) decreases.

    (B) When the current I (R1) decreases, the voltage drop across the resistance element 31a due to the current I (R1) decreases.

    (C) When the voltage drop of the resistance element 31a decreases, the voltage drop becomes smaller than the threshold value of the PNPTR 41a (for example, the base-emitter threshold voltage VBE (th)) (= reference voltage).

(D) When the drop voltage of the resistance element 31a becomes smaller than the reference voltage, the PNPTR 41a is turned off. That is, when the following expression (3) is established, the PNPTR 41a transitions from the on state to the off state.
VBE (th)> I (R1) × R1 (3)

    (E) When the PNPTR 41a is turned off, the base voltage of the PNPTR 42a is pulled down by the resistance element 42b to become a second potential (for example, the base-emitter threshold voltage VBE (th)), and the PNPTR 42a is turned on. It becomes a state.

    (F) When the PNPTR 42a is turned on, power is supplied to the load L2 via the resistance element 31a and the PNPTR 42a.

(4) Operation when the power consumption of the load L2 increases (a) When the power consumption of the load L2 increases, the current I2 flowing through the load L2 increases, and the current I (R1) increases from Equation (1).

  Thereafter, operations similar to the operations (c) to (h) in (2) are performed, power supply to the load L1 is ensured, and power supply to the output load L2 is interrupted.

(5) Operation when the normal state returns after the power consumption of the load L2 increases (a) Since the power supply to the load L2 is cut off, the current I (R1) decreases from the equation (1).

  Thereafter, the operations (b) to (f) of (3) are executed, and power is again supplied to the load L2 via the resistance element 31a and the PNPTR 42a.

In the operations (1) to (5), the boundary point at which the PNPTR 41a transitions from the off state to the on state is the same as in the equation (2).
VBE (th) = I (R1) × R1 (4)
It becomes. At this time, if the resistance value R1 of the resistance element 31a is set so as to satisfy the following expression (5), the rated power of the power supply circuit 10 can be used effectively to the maximum.
VBE (th) = Io × R1 (5)
However, Io: Rated current of the power supply circuit 10

Next, the cases (4) and (5) will be described.
In the cases (4) and (5), once the power consumption of the load L2 increases and the power supply to the load L2 is interrupted, the current I (R1) immediately decreases and the load L2 is supplied. Power supply is started. At this time, if the power consumption of the load L2 continues to increase, the power supply to the load L2 is interrupted again.

  As described above, in the power supply device according to the first embodiment, when the power consumption of the load L2 increases, the power supply to the load L2 and the interruption thereof may be repeated continuously. Therefore, it is desirable to apply the power supply device according to the first embodiment to a case where the fluctuation of the power consumption of the load L2 is small as shown in the third embodiment described later. However, the load L2 may have a case where the power consumption increases only at the time of startup due to an initialization operation or the like, or a case where the fluctuation of the power consumption is large, such as a transmission / reception circuit. This correspondence will be described using a power supply device having a hysteresis characteristic of Example 2 or Example 3 described later.

(Effect of Example 1)
The power supply device according to the first embodiment has the following effects (i) to (iii).

  (I) A value obtained by subtracting the power supplied to the load L1 from the rated power of the power supply circuit 10, that is, surplus power, is supplied to the load L2 while securing the power supply to the load L1, so that the utilization efficiency as a power source And wasteful power consumption can be suppressed.

  (Ii) Since the rated power of the power supply circuit 10 is (maximum power consumption of the load L1 + maximum power consumption of the load L2), it is not necessary to design with a large capacity, thereby contributing to downsizing of the power supply circuit 10 and cost reduction Can also be expected.

  (Iii) When power is supplied as an auxiliary power source to a circuit with high power consumption, such as the control circuit 21 of the power supply circuit 10 that uses power that is stepped down and generated from a high voltage by a regulator, the entire power consumption is expected to be suppressed. it can.

(Configuration of Surplus Power Circuit of Example 2)
FIG. 4 is a circuit diagram showing a configuration example of the power supply device according to the second embodiment of the present invention, and the functional blocks thereof are shown in FIG. In FIG. 4, elements common to the elements in FIG. 2 illustrating the first embodiment are denoted by common reference numerals.

  The power supply device according to the second embodiment includes a power supply circuit 10 similar to that of the first embodiment and a surplus power supply circuit 30A having a configuration different from that of the surplus power supply circuit 30 according to the first embodiment. The surplus power supply circuit 30A has a Hall element 31b instead of the resistance element 31a of the first embodiment.

  Further, the surplus power supply circuit 30A includes an overcurrent determination unit 41A having a configuration different from that of the first embodiment, and a power control unit 42A configured by a P-channel MOS field effect transistor (hereinafter referred to as “PMOS”) 42c. The overcurrent determination unit 41A includes a comparator 41b serving as a detection signal determination unit, a first switch (for example, an N-channel MOS field effect transistor, hereinafter referred to as “NMOS”) 41c, and a reference voltage VREF1. The first reference voltage generation unit (for example, the reference voltage generation unit) 41d for generating the reference voltage and the second reference voltage generation unit (for example, the reference voltage generation unit) 41e for generating the reference voltage VREF2.

  In the overcurrent determination circuit 41A, the source of the NMOS 41c is connected to the inverting input terminal of the comparator 41b via the reference voltage generators 41d and 41e connected in series. The source of the NMOS 41c is connected to one end of the output terminal of the Hall element 31b, and the other end of the output terminal of the Hall element 31b is connected to the non-inverting input terminal of the comparator 41b. Further, the input side of the Hall element 31b is connected to the positive electrode 10a of the power supply circuit 10, and one end of the load L1 and the source of the PMOS 42c are connected to the output side of the Hall element 31b. The drain of the NMOS 41c is connected between the reference voltage generator 41d and the reference voltage generator 41e connected in series.

  The gate of the NMOS 41c and the gate of the PMOS 42c are connected to the output side of the comparator 41b. The drain of the PMOS 42c is connected to one end of the load L2, and the other end of the load L1 and the load L2 is connected to the negative electrode 10b of the power supply circuit 10.

  The characteristic of the power supply device according to the second embodiment is that the overcurrent determination unit 41A is configured to have hysteresis characteristics.

  Since the power consumption of the load L1 or the load L2 increases and the power supply to the load L2 is cut off due to the configuration having the hysteresis characteristics, the first threshold (for example, the reference voltage VREF1 + the reference voltage VREF2) and the load Since the second threshold value (for example, the reference voltage VREF2) when the power consumption of L1 decreases and returns to the normal state is different, the phenomenon that the power supply to the load L2 and the interruption are continuously repeated is prevented. It is configured to be able to. This operation will be described below.

(Operation of Power Supply Device in Embodiment 2)
In FIG. 4, the Hall element 31b has a function similar to that of the resistance element 31a in FIG. 2. If the current flowing through the Hall element 31b is I (H), I (H ) To output a potential difference (for example, Hall voltage) VH proportional to the output terminal.
VH = K × I (H) (6)
Where K is a proportional constant, where I (H) is
I (H) = I1 + I2 (7)
It becomes.

  When the power consumption of the load L1 or the load L2 increases, the current I1 or the current I2 increases.

  When the current I1 or the current I2 increases, the current I (H) increases from the equation (7). When the current I (H) increases, the Hall voltage VH of the Hall element 31b due to the current I (H) eventually reaches the sum of the reference voltages VREF1 and VREF2.

When the current I (H) further increases and the Hall voltage VH exceeds the sum of the reference voltages VREF1 and VREF2 (Equation (8)), the output voltage of the comparator 41b becomes the first logic level (eg, low level, “ The level is changed from “L” to a second logic level (for example, high level, hereinafter referred to as “H”), and the PMOS 42c changes from the on state to the off state.
VREF1 + VREF2 <VH (8)

  As a result, power supply to the load L1 is ensured and power supply to the load L2 is interrupted.

  When the output of the comparator 41b changes from “L” to “H”, the NMOS 41c is turned on at the same time, and both ends of the reference voltage generator 41d are short-circuited. Therefore, the sum of the reference voltages VREF1 and VREF2 in the comparator 41b is the reference voltage. It changes to VREF2 only.

When the power consumption of the load L1 decreases and the surplus power increases, the Hall voltage VH decreases as shown in the following equation (9), and becomes smaller than the reference voltage VREF2. For this reason, since the comparator 41b outputs “L”, the PMOS 42c transits from the off state to the on state.
VREF2> VH (9)
As a result, in addition to supplying power to the load L1, power supply to the load L2 is also started.

  Here, when the output voltage of the comparator 41b changes from “H” to “L”, the NMOS 41c is simultaneously turned off to open both ends of the reference voltage generation unit 41d, so that the reference voltage in the comparator 41b again becomes the reference voltage VREF1. And return to the sum of VREF2.

  As described above, in the second embodiment, the reference voltage generation unit 41d and the reference voltage generation unit 41e are provided, and the hysteresis width is set to the reference voltage for the comparator 41b. In the above operation, the Hall voltage VH or the reference voltage VREF1 and the reference voltage of the Hall element 31b are changed so that the output voltage of the comparator 41b transitions from “L” to “H” when the current I (H) = Io. If the sum of VREF2 is set, the rated power of the power supply circuit 10 can be used effectively to the maximum.

(Effect of Example 2)
According to the surplus power supply circuit 30A of the second embodiment, in addition to the effects of the first embodiment, there are the following effects (i) to (iii).

  (I) Since the overcurrent detection circuit 41A is configured to have hysteresis characteristics, when the power consumption of the load L2 increases and the power supply to the load L2 is once interrupted, as a result, the Hall element Although the current I (H) flowing through 31b decreases, the reference voltage also decreases from VREF1 + VREF2 to VREF2, so that power supply to the load L2 is not easily started. The power supply to the load L2 can be resumed when the power consumption of the load L1 decreases and becomes a sufficient surplus power. As a result, the load L2 can stably operate without malfunction even in the case where the power consumption increases only at the time of startup, such as in an initialization operation, or in the case where the power consumption fluctuates significantly, such as a transmission / reception circuit.

  (Ii) By using the reference voltages VREF1 and VREF2 and the comparator 41b, the current I1 + I2 for turning on / off the PMOS 42c can be set freely and with high accuracy.

  (Iii) By using the NMOS 41c and the PMOS 42c for the overcurrent determination unit 41A and the power control unit 42A, the power consumption in the circuit can be reduced as compared with the case where a bipolar transistor is used.

(Configuration of Power Supply Device of Example 3)
FIG. 5 is a schematic second functional block diagram showing the configuration of the power supply device according to the third embodiment of the present invention. In FIG. 5, the first functional block diagram of the first embodiment is shown in common with the elements in FIG. Are marked with a common sign.

  The power supply device includes a power supply circuit 10 and a surplus power supply circuit 30B different from the first and second embodiments. The surplus power supply circuit 30B includes a current detection unit 31B having a configuration different from that of the second embodiment, and realizes systemization by the current detection unit 31B instead of the hysteresis by the overcurrent determination unit 41A.

  The surplus power supply circuit 30B is connected to the positive electrode 10a and the negative electrode 10b of the power supply circuit 10, and includes a current detection unit 31B that detects a drive current that drives the main first load L1 and the subordinate second load L2, and this current. And a surplus power control unit 40B that controls supply and cut-off of surplus power to the load L2 by a detection signal from the detection unit 31B.

  The surplus power control unit 40B receives an overcurrent determination unit 41B that detects the occurrence of an overcurrent based on a detection signal from the current detection unit 31B and outputs a control signal, and receives the control signal from the overcurrent determination unit 41B and receives the load L2 It is comprised from the electric power control part 42B which supplies and interrupts | blocks the electric power to.

  Here, the input side of the current detection unit 31B is connected to the positive electrode 10a of the power supply circuit 10, and the output side of the current detection unit 31B is connected to one end of the load L1 and the input side of the power control unit 42B. The current detection unit 31B is connected to the overcurrent determination unit 41B through a signal line. The power control unit 42B is connected to the output side of the overcurrent determination unit 41B, and one end of the load L2 is connected to the output side of the power control unit 42B. The other end of the load L2, the power control unit 42B, the current detection unit 31B, and the other end of the load L1 are connected to the negative electrode 10b of the power supply circuit 10.

  FIG. 6 is a circuit diagram showing a configuration example of the power supply device of FIG. 5, and the same reference numerals are given to the same elements as those in FIG.

  The current detection unit 31B generates a first detection signal generation unit (for example, a resistive element 31d having a resistance value R4) that generates a first detection signal, and a second detection signal that is different from the first detection signal. A second detection signal generator (for example, a resistance element 31c and a resistance element 31d having a resistance value R3 connected in series), a second switch (for example, PMOS 31e), and a resistance element 31f having a resistance value R5 It is configured.

  The overcurrent determination unit 41B is configured by a PNPTR 41f, and the power control unit 42B is configured by a PMOS 42d and a resistance element 42e having a resistance value R6.

  The emitter of the PNPTR 41f is connected to the positive electrode 10a of the power supply circuit 10, one end of the resistance element 31c, and the source of the PMOS 31e, and the base is connected to one end of the resistance element 31d, one end of the load L1, and the source of the PMOS 42d. Has been. The collector of the PNPTR 41f is connected to the gate of the PMOS 31e, one end of the resistance element 31f, one end of the resistance element 42e, and the gate of the PMOS 42d.

  The drain of the PMOS 31e is connected to the other end of the resistance element 31c and the other end of the resistance element 31d. The drain of the PMOS 42d is connected to one end of the load L2. The other end of the load L1, the other end of the resistance element 42e, the other end of the load L2, and the other end of the resistance element 31f are connected to the negative electrode 10b of the power supply circuit 10.

(Operation of Surplus Power Supply Circuit in Power Supply Device in Embodiment 3)
Regarding the operation of the surplus power supply circuit 30B in the power supply device according to the third embodiment, (1) the operation when the power consumption of the load L1 and the load L2 is in the normal state, and (2) the power consumption of the load L1 increases. (3) Operation when the power consumption of the load L1 increases and then returns to the normal state, (4) Operation when the power consumption of the load L2 increases, and (5) Consumption of the load L2 The following description will be divided into operations when the power returns to the normal state after the power increase.

(1) Operation when the power consumption of the load L1 and the load L2 is in the normal state When the total power consumption of the load L1 and the load L2 is in the normal state within the rated power of the power supply circuit 10, the PNPTR 41f is set to the off state. Therefore, the gate voltage of the PMOS 42d is pulled down by the resistance element 42e and becomes the second potential (for example, the potential of the negative electrode 10b of the power supply circuit 10), so the PMOS 42d is in the on state. Further, the gate voltage of the PMOS 31e is pulled down by the resistance element 31f to become the second potential (for example, the potential of the negative electrode 10b of the power supply circuit 10), so that the PMOS 31e is turned on and both ends of the resistance element 31c are short-circuited. Therefore, power is supplied to the load L1 via the PMOS 31e and the resistance element 31d, and to the load L2 via the PMOS 31e, the resistance element 31d and the PMOS 42d. Hereinafter, it is assumed that the on-resistance of the PMOS 31e is sufficiently smaller than the resistance element 31d, and the voltage drop in the on-state can be ignored.

(2) Operation when power consumption of load L1 increases (a) The sum of current I1 flowing through load L1 and current I2 flowing through load L2 flows through resistance element 31d. That is, when the current flowing through the resistance element 31d is I (R4), the following equation (10) is established.
I (R4) = I1 + I2 (10)

    (B) When the power consumption of the load L1 increases, the current I1 flowing through the load L1 increases, and the current I (R4) increases from Equation (10).

    (C) When the current I (R4) increases, the voltage drop across the resistance element 31d due to the current I (R4) increases.

    (D) When the voltage drop of the resistance element 31d increases, this voltage drop reaches the threshold value of the PNPTR 41f (for example, the base-emitter threshold voltage VBE (th)) (= reference voltage).

(E) When the drop voltage of the resistance element 31c reaches the reference voltage, the PNPTR 41f becomes conductive. That is, when the following formula (11) is established, the PNPTR 41f transitions from the off state to the on state.
VBE (th) = I (R4) × R4 (11)

    (F) When the PNPTR 41f is turned on, a first potential (for example, a base-emitter voltage of the PNPTR 41f) (= VBE (th)) is applied as the gate potential of the PMOS 31e.

    (G) Therefore, the PMOS 31e transitions from the on state to the off state.

    (H) As a result, the current I (R4) flowing through the resistance element 31d also flows through the resistance element 31c.

(I) At this time, the resistance value R3 of the resistance element 31c is added to the resistance value R4 of the resistance element 31d to increase the combined resistance value. However, the resistance between the base and the emitter of the PNPTR 41f is equivalent to a PN junction diode. And the series drop voltage of the resistance element 31d are equal to VBE (th) of the PNPTR 41f as shown in the equation (12).
VBE (th) = I (R4) × (R3 + R4) (12)

    (J) Also, when the PNPTR 41f is turned on, a first potential (for example, the sum of voltages across the resistance element 31c and the resistance element 31d) (= VBE (th)) is applied between the gate and source of the PMOS 42d. However, the gate potential of the PMOS 42d becomes higher than the source potential and is in a reverse bias state.

    (K) Therefore, the PMOS 42d transitions from the on state to the off state.

    (L) As a result, power supply to the load L1 is ensured and power supply to the load L2 is interrupted.

(3) Operation when the power consumption of the load L1 increases and then returns to the normal state (a) When the power consumption of the load L1 decreases, the current I1 flowing through the load L1 decreases, and the current I (R4) decreases.

    (B) When the current I (R4) decreases, the voltage drop across the resistance element 31c and the resistance element 31d due to the current I (R4) decreases.

    (C) When the drop voltage of the resistance element 31c and the resistance element 31d decreases, this drop voltage becomes smaller than the threshold value of the PNPTR 41f (for example, the base-emitter threshold voltage VBE (th)) (= reference voltage).

(D) When the voltage drop across the resistive element 31c and the resistive element 31d becomes smaller than the reference voltage, the PNPTR 41f is turned off. That is, when the following equation (13) is satisfied, the PNPTR 41f transitions from the on state to the off state.
VBE (th)> I (R4) × (R3 + R4) (13)

    (E) When the PNPTR 41f is turned off, the gate potential of the PMOS 31e is applied with the second potential (for example, the potential of the negative electrode 10b of the power supply circuit 10).

    (F) Therefore, the PMOS 31e transitions from the off state to the on state.

    (G) As a result, the current I (R4) flowing through the resistance element 31c flows through the PMOS 31e where the voltage drop can be ignored.

    (H) When the PNPTR 41f is turned off, the gate voltage of the PMOS 42d is pulled down by the resistance element 42e to become the second potential (for example, the potential of the negative electrode 10b of the power supply circuit 10), and the PMOS 42d is turned on.

    (I) When the PMOS 42d is turned on, power is supplied to the load L2 via the PMOS 31e, the resistance element 31d, and the PMOS 42d.

(4) Operation when the power consumption of the load L2 increases (a) When the power consumption of the load L2 increases, the current I2 flowing through the load L2 increases, and the current I (R4) increases from Equation (10).

  Thereafter, operations similar to the operations (c) to (l) in (2) are performed, power supply to the load L1 is ensured, and power supply to the output load L2 is interrupted.

(5) Operation when the normal state returns after the power consumption of the load L2 increases (a) Since the power supply to the load L2 is cut off, the current I (R4) decreases from the equation (10).

  Thereafter, the operations (b) to (i) of (3) are executed, and power is again supplied to the load L2 via the PMOS 31e, the resistance element 31d, and the PMOS 42d.

In the operations (1) to (5), the boundary point at which the PNPTR 41f transitions from the off state to the on state is obtained from the equation (11).
VBE (th) = I (R4) × R4 (14)
It becomes. At this time, if the resistance value R4 of the resistance element 31d is set so as to satisfy the following equation (15), the rated power of the power supply circuit 10 can be used effectively to the maximum.
VBE (th) = Io × R4 (15)
However, Io: Rated current of the power supply circuit 10

(Effect of Example 3)
The power supply device according to the third embodiment has the following effects.

  As in the second embodiment, since the surplus power supply circuit is configured to have hysteresis characteristics, the same effect as in the second embodiment can be obtained. However, in this embodiment, since the comparator is not used, the circuit is operated. Therefore, it can be expected to be realized with a simple circuit.

(Configuration of power supply system in Embodiment 4)
FIG. 7 is a schematic perspective view illustrating a configuration example of a power supply system according to the fourth embodiment of the present invention.

  In the first to third embodiments, a single use example of the power supply device has been described. However, in the fourth embodiment, a plurality of different loads L1 (= L1-1, L1-2,... When power is supplied to the power supply device to -N), power is supplied from a plurality of power supply devices to the load L2, which is a common circuit.

  That is, the power supply system of the fourth embodiment includes a unit 90, a plurality of circuit boards 70, and a common board 80. The unit 90 includes a plurality of circuit boards 70 having a power supply device and a load L1, A common board 80 having a load L2 supplied with power from a plurality of circuit boards 70 is mounted.

  FIG. 8 is a circuit block diagram illustrating a configuration example of the power supply system in FIG. 7, and elements common to the elements in FIG. 1 illustrating the first embodiment are denoted by common reference numerals.

  Output sides of the plurality of circuit boards 70 are connected to a load circuit 81 (= load L2) in the common board 80 via a common line 73. The plurality of circuit boards 70 (= 70-1, 70-2,..., 70-N) are configured by a power supply device substantially the same as the power supply device described in the first embodiment and a load L1. The power supply device includes a power supply circuit 10 (= 10-1, 10-2,..., 10-N) and a current detector 31 (= 31-1, 31-2,..., 31-N). , Overcurrent determination unit 41 (= 41-1, 41-2,..., 41-N), power control unit 42 (= 42-1, 42-2,..., 42-N), And a plurality of diodes 71 (= 71-1, 71-2,..., 71-N) for preventing a backflow of current.

  The common board 80 has a load L <b> 2 and is supplied with power from a plurality of circuit boards 70 through a common line 73.

(Operation of Power Supply System in Embodiment 4)
Usually, power is supplied to the load L <b> 2 in the common panel 80 from the power supply device in each of the plurality of circuit boards 70. In the first to third embodiments, when the power consumption of the load L1 increases, the power supply to the load L2 is cut off. However, in the fourth embodiment, the power consumption of any one of the loads L1 of the plurality of circuit boards 70. Even if the power supply to the common panel 80 is cut off, the remaining circuit boards 70 continue to supply power to the common panel 80.

(Effect of Example 4)
The power supply system according to the fourth embodiment has the following effects (i) to (iii).

  (I) By supplying power from the plurality of circuit boards 70 to the load L2 of the common board 80, the probability of interruption of the power supply to the load L2 with a simple circuit without the common board 80 having a dedicated power supply circuit. The reliability can be expected to be improved.

  (Ii) When the minimum power that can be reliably supplied from the plurality of circuit boards 70 to the load L2 of the common board 80 is known, the power that is insufficient to operate the load L2 (= the required power of the load L2−) Since the power supply circuit for supplying only the minimum power supply for each circuit board 70 may be provided in the common board 80, the circuit can be reduced in size and cost. This also prevents the power supply to the load L2 from being cut off.

  (Iii) By distributing the power necessary for the operation of the load L2 in advance to each circuit board 70 and designing the power supply circuit 10, the power supply circuit of the common board 80 can be eliminated, and the size and cost can be further reduced. be able to. In addition, since the electric power supplied to the load L2 from the power supply circuit 10 becomes so small that the number of the circuit boards 70 is large, it can respond without making the power supply circuit 10 large-sized and expensive.

(Configuration of power supply system in Embodiment 5)
FIG. 9 is a schematic perspective view illustrating a configuration example of the power supply system according to the fifth embodiment of the present invention.

  The configuration of the power supply system of the fifth embodiment is substantially the same as the configuration of the fourth embodiment. A plurality of circuit boards 70A having a power supply device and a load L1 are mounted on the unit 90A.

  FIG. 10 is a circuit block diagram illustrating a configuration example of the power supply system of FIG. 9, and elements common to those in FIG. 8 illustrating the fourth embodiment are denoted by common reference numerals.

  The power supply system according to the fifth embodiment includes a plurality of power supply devices and a common line 73A that connects the output side of the surplus power control unit 40 provided in each of the plurality of power supply devices and the load L1 in the circuit board 70A. Yes.

  The configuration of the power supply device according to the fifth embodiment is substantially the same as the configuration of the power supply device according to the fourth embodiment, but differs in the following points. That is, the cathode of the backflow prevention diode 71 is connected to the common line 73A, and the common line 73A is connected to one end of the load L1 in the plurality of circuit boards 70A. The anode of the backflow preventing diode 72 (= 72-1, 72-2,..., 72-N) is connected, and the cathode of the diode 72 is connected to one end of the load L1. It is different from the configuration. Other configurations are the same as those of the fourth embodiment.

(Operation of Power Supply System in Embodiment 5)
In the power supply system of the fifth embodiment, when the power supply circuit 10 of any circuit board 70A fails, the load L1 of the circuit board 70A that has failed from the remaining other circuit board 70A via the backflow prevention diode 71 and the common line 73A. Is supplied with power. At this time, since the backflow of the supplied current is blocked by the backflow prevention diode 72, the current does not flow into the failed power supply circuit 10.

(Effect of Example 5)
The power supply system according to the fifth embodiment has the following effects (a) to (c).

  (A) Normally, when the power supply circuit 10 in the circuit board 70A fails, the circuit board 70A itself stops functioning even though the load L1 is normal. By adopting the configuration of the fifth embodiment, it is possible to supply power from the other circuit board 70A to the failed circuit board 70A while sending an alarm to the outside due to the failure of the power supply circuit 10, so that the maintenance person has failed. Until the circuit board 70A is replaced, the probability of stopping the function of the device is reduced, and the reliability of the device can be improved.

  (B) In communication equipment and the like, the power supply circuit may have a redundant configuration in order to ensure reliability. Normally, an N + 1 redundant configuration is used by using a power supply panel provided with only a power supply circuit. That is, the maximum power required by the load is secured by N power panels, and one power panel is added as a spare. In this case, the operation of the device is ensured even if one power supply panel fails.

  However, it is necessary to secure a large space for the power supply panel, which is a large scale. Furthermore, when two power supply panels fail, the function of the entire device is not guaranteed, or the entire device is forcibly stopped to prevent malfunction. By adopting the configuration of the fifth embodiment, even if a power supply circuit failure occurs in a plurality of circuit boards 70A, the probability of stopping the entire device with a simple circuit that saves space can be greatly reduced.

  (C) When there are many component circuit boards 70A, it is possible to further increase the reliability by setting the capacity of the power supply circuit 10 assuming a plurality of failure.

(Modification)
The present invention is not limited to the above-described embodiments, and various usage forms and modifications are possible. For example, the following forms (a) to (i) are used as the usage forms and modifications.

(A) In the first embodiment, the example in which the power supply to the load L2 is interrupted when the rated current Io flows through the resistance value R1 of the resistance element 31a has been described. However, if the power supplied to the load L2 is small, the load L2 may not be started or stopped normally. In this case, the resistance value R1 may be set so that the minimum operating current of the load L2 is equal to or greater than a current value that can be secured. For example, the resistance value R1 is set to satisfy the equation (5a) when the minimum operating current of the load L2 is I2 (min).
VBE (th) ≦ (I1 + I2 (min)) × R1 (5a)

  (B) In the second and third embodiments, the PNPTRs 41a and 41f are directly connected to the current detection units 31 and 31B, but the base currents of the PNPTRs 41a and 41f are adjusted / suppressed by inserting resistors into the detection signal lines. can do. As a result, the PNPTRs 41a and 41f can be protected and the operation of the PNPTRs 41a and 41f and the PNPTRs 42a and 42d, that is, the switching of power supply to and interruption of the load L2, can be smoothed, and radiation noise can be reduced due to the change in the current I2. Voltage fluctuations (overshoot and undershoot) can be suppressed. Furthermore, when the circuit is applied to the fourth and fifth embodiments, the probability of power interruption of the load L2 can be reduced.

  (C) In the first to fifth embodiments, the load L2 is described as one. However, the load L2 is not limited to one, and a plurality of surplus power control units 40 are connected in parallel or in cascade. A plurality of loads L2 can be connected.

  (D) In the first to fifth embodiments, the load L2 has a specification such that the same power as that of the load L1 is supplied at the maximum, but the current detection unit 31 is divided and the load L1 is connected to the intermediate point. By doing so, the power supplied to the load L2 can be limited, and a function as overcurrent protection for the load L2 can be provided.

  (E) In the first to fifth embodiments, the surplus power supply circuit 30 is directly connected to the subsequent stage of the power supply circuit 10, but the distance between the power supply circuit 10 and the surplus power supply circuit 30 is not limited. You may connect through the element and circuit.

  (F) In the first to fifth embodiments, the surplus power supply circuit 30 is configured alone, but may be configured integrally with the power supply circuit 10.

  (G) In the first to fifth embodiments, it has been described that the same voltage is supplied to the load L1 and the load L2. However, the applied voltage is applied to the load L2 using a booster, a step-down, and a step-up / down circuit. It may be converted.

  (H) In the first to fifth embodiments, the power supply circuit 10 is a DC-DC type connected to the DC power supply E. However, an AC-DC type power supply connected to the AC power supply A may be used.

  (I) In the first to fifth embodiments, the surplus power supply circuit 30 added to the positive electrode 10a of the power supply circuit 10 has been described. For example, this can be realized by replacing the PNPTR 41a and the PNPTR 42a of the first embodiment with NPN transistors, respectively.

  (J) Although the PMOS 31d is used in the third embodiment, any switch (for example, PNPTR) that becomes non-conductive when the PNPTR 41b is conductive can be realized.

  (K) In the fourth and fifth embodiments, the configuration based on the first functional block illustrated in FIG. 1 has been described. However, the configuration can be realized based on the second functional block illustrated in FIG. is there.

  (L) In Examples 4 and 5, the backflow prevention element is shown by the diodes 71 and 72. However, it is possible to use a field effect transistor such as LTC4358 manufactured by LINEAR TECHNOLOGY. In this case, the forward voltage drop and loss are reduced. It becomes possible to reduce.

  (M) In the first embodiment, the configuration and operation of the power supply circuit 10 described with reference to FIG. 3 is merely an example, and does not limit the element, circuit system, and insulation characteristics (insulation / non-insulation). .

DESCRIPTION OF SYMBOLS 10 Power supply circuit 30 Surplus power supply circuit 31 Current detection part 40 Surplus power control part 41 Overcurrent determination part 42 Power control part
70, 70A Circuit board 80, 80A Common board L1 First load L2 Second load 73, 73A Common line

Claims (13)

A power supply unit that outputs electric power for supplying a driving current to the first load and one or more second loads;
A current detector that detects the drive current supplied to the first load and the second load and outputs a detection signal;
Based on the detection signal, it is compared with a predetermined threshold value. When the detection signal is less than the threshold value, it is determined that there is surplus power and the drive current is supplied to the second load, and the detection signal exceeds the threshold value. The surplus power control unit that determines that there is no surplus power and cuts off the drive current to the second load;
A power supply device comprising: The surplus power control unit
Based on the detection signal, an overcurrent determination unit that compares the predetermined threshold with the detection signal and outputs a control signal;
A power control unit that controls supply of the drive current to the second load based on the control signal;
The power supply device according to claim 1, further comprising: The overcurrent determination unit
Based on a first electrode, a second electrode, a control electrode for controlling a conduction state between the first electrode and the second electrode, and a threshold voltage between the first electrode and the control electrode The power supply device according to claim 2, comprising a first transistor having the threshold value. The overcurrent determination unit
When the detection signal reaches the threshold value, the control signal of the first potential is output,
3. The power supply device according to claim 2, wherein when the detection signal is less than the threshold value, the control signal having a second potential is output. The power control unit
5. The power supply device according to claim 2, further comprising: a second transistor; and a second resistance element connected between the second transistor and ground. The current detector is
6. The device according to claim 1, further comprising: a first resistance element or a Hall element that generates a potential difference when the driving current flows and outputs the potential difference as the detection signal. The power supply device described in 1. The surplus power control unit
Having the first threshold and the second threshold different from the first threshold;
In a state where the driving current is supplied to the first and second loads, when the detection signal is less than the first threshold, it is determined that there is surplus power and the second load is supplied to the second load. Continue to supply drive current,
When the detection signal exceeds the first threshold, it is determined that there is no surplus power, and the drive current to the second load is cut off,
In a state where the drive current to the second load is cut off, when the detection signal becomes less than the second threshold, it is determined that there is surplus power and the drive current to the second load is determined. Supply
2. The power supply according to claim 1, wherein when the detection signal exceeds the second threshold value, it is determined that there is no surplus power, and the state where the drive current to the second load is cut off is continued. apparatus. The surplus power control unit
Based on the detection signal, an overcurrent determination unit that compares the detection signal with the first threshold value or the second threshold value, and outputs the control signal;
A power control unit that controls supply of the drive current to the second load based on the control signal;
The power supply device according to claim 7, further comprising: The overcurrent determination unit
First and second reference voltage generators for generating the first threshold;
A second reference voltage generator for generating the second threshold;
When the detection signal is less than the first or second threshold value, the control signal of the first logic level is output, and when the detection signal exceeds the first or second threshold value, the second logic level is output. A detection signal determination unit that outputs the control signal of a level;
A first switch that switches between the first threshold and the second threshold based on the control signal;
The power supply device according to claim 8, further comprising: The current detector is
A first detection signal generator for generating the first detection signal;
A second detection signal generation unit that generates the second detection signal different from the first detection signal;
In a state where the driving current is supplied to the first and second loads, when the first detection signal is less than the threshold, the output of the first detection signal is continued, and the first detection signal is output. When the detection signal exceeds the threshold, the output of the first detection signal is stopped and the second detection signal is output.
In a state where the drive current to the second load is cut off, when the second detection signal exceeds the threshold value, the output of the second detection signal is continued, and the second detection signal A second switch that stops the output of the second detection signal and outputs the first detection signal when the value is less than the threshold value;
The power supply device according to claim 1, wherein The surplus power control unit
In a state where the driving current is supplied to the first and second loads, when the first detection signal is less than the threshold value, it is determined that there is surplus power and the second load is supplied to the second load. Continue to supply drive current,
When the first detection signal exceeds the threshold, it is determined that there is no surplus power, and the drive current to the second load is interrupted,
In a state where the drive current to the second load is cut off, when the second detection signal becomes less than the threshold, it is determined that there is surplus power and the drive current to the second load is determined. Supply
11. The power supply according to claim 10, wherein when the second detection signal exceeds the threshold value, it is determined that there is no surplus power and the state where the drive current to the second load is cut off is continued. apparatus. A plurality of power supply devices according to any one of claims 1 to 11,
A common line connecting the output side of the surplus power control unit provided in each of the plurality of power supply devices and one or more of the second loads;
A power supply system comprising: A plurality of power supply devices according to any one of claims 1 to 11,
A common line connecting an output side of the surplus power control unit provided in each of the plurality of power supply devices and the first load corresponding to each of the plurality of power supply devices;
A power supply system characterized by comprising:

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