JP2005192372A - Device for switching power source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize size reduction of the heat sink unit of a diode, by reducing the power loss of the diode, in a power source switching device, having a diode preferred circuit. <P>SOLUTION: In the power source switching device, the temperatures of the heat sink unit FIN1 and the diode 14 and the heat sink unit FIN2 of the diode 15 for the diode priority circuit are respectively detected by thermistors 18 and 19. Relays 21, 22 for supplying powers from power sources 11, 12 to a load unit 60 are provided, and a current transformer 24 is provided, in between these relays and the load unit. A relay on/off signal generator 30 controls the on/off of the relays 21, 22, based on the temperatures of the heat sink units FIN1, FIN2 detected by the thermistors 18, 19 and the detection current of the current transformer, reduces the losses of the diodes 14, 15, and prevents the currents to the power sources 11, 12 from reverse flow. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a power switching device, and more particularly to a power switching device including a diode priority circuit.

A power supply switching device including a diode priority circuit is known as a power supply switching device that selects a power supply having the highest output voltage from a plurality of power supplies and supplies the power of the power supply to a load device.
FIG. 5 is a block diagram showing a circuit configuration of such a conventional power supply switching device.
A power supply switching apparatus 100 shown in FIG. 5 includes two DC power supplies, that is, a power supply 101 and a power supply 102, and is configured to supply power to a load device 110 from a power supply with a high output voltage by a diode priority circuit. .

The power source 101 is, for example, a grid-connected power generation system such as a solar battery, and the power source 102 is a power source that generates DC power from AC power supplied from the system power source 103 (commercial AC power source or the like). The power supplies 101 and 102 are connected in parallel to the load device 110 via a diode 105 and a diode 106, respectively.

The diodes 105 and 106 are so-called stud type or flat type, and are attached to the heat radiating fins with screws (stud type), or have an external appearance (flat type) press-contacted with the heat radiating fins from both the upper and lower sides. Yes. FIN201 and FIN202 are radiators for the diodes 105 and 106, respectively.

FIG. 6 is a timing chart showing the overall operation of the power supply switching apparatus 100 configured as described above. In FIG. 6, (a) and (b) indicate the voltages of the power supplies 101 and 102, respectively. (C) is the load power (power consumption of the load device 110), (d) is the current I1 of the diode 105, (e) is the current I2 of the diode 106, and (f) is the loss W1 of the diode 105.
, (G) is the loss W2 of the diode 106, (h) is the temperature T1 of the radiator FIN201, (i
) Is the temperature T2 of the radiator FIN202. In addition, the T1 upper limit and T1 lower limit shown in FIG. 6H are an upper limit value (upper limit temperature) and a lower limit value (lower limit temperature), respectively, of the radiator FIN1 shown in FIG. . Moreover, the T2 upper limit and the T2 lower limit shown in FIG. 6 (i) are an upper limit value (upper limit temperature) and a lower limit value (lower limit temperature), respectively, of the radiator FIN2 shown in FIG. 1 described later, which is smaller than the radiator FIN202. .

As shown in FIGS. 6A and 6B, the output voltage of the power supply 101 (
V1) is higher than the output voltage (V2) of the power supply 102, and after time t2, the output voltage of the power supply 102 is higher than the output voltage of the power supply 101. The output voltage of the power supply 102 is the time t3
Reaches a predetermined rated value, and then keeps the voltage value. Therefore, power is supplied to the load device 110 from the power source 101 during the period from time t0 to time t2, and from the power source 102 after time t2.

The load device 110 starts operating at time t0 and enters a steady load state at time t1. Then, at time t4, the state shifts from the steady load to the maximum load state (see FIG. 6C). During this time, the load device 110 receives power supply from the power source 101 during the period of time t0 to t2, and receives power supply from the power source 102 after time t2.

Therefore, current (I1) flows only through the diode 105 at times t0 to t2, and current (I2) flows through only the diode 106 after time t2 (see FIGS. 6D and 6E). Along with this, time transitions of the loss (W1) of the diode 105 and the loss (W2) of the diode 106 change as shown in FIGS. 6 (f) and 6 (g), respectively.

The temperature of the heat sink FIN201 is the period during which a current flows through the diode 105 (time t0 to t
2) and gradually rises to near the upper limit at time t2. And it falls after time t2, returns to the original temperature after time t3 (refer FIG.6 (h)).
On the other hand, the temperature of the radiator FIN202 rises from time t2 when power supply from the power supply 102 to the load device 110 is started, and time t4 when the load device 110 shifts from the steady load to the maximum load.
Thereafter, it rises with a steep slope, exceeds the upper limit at time t6, and further rises (FIG. 6 (i
)reference).

Here, as shown in FIG. 6B, when the power supply 102 is momentarily cut off at time t7 due to a failure or the like, and the output voltage drops momentarily, power is supplied from the power supply 101 to the load device 110 during the momentary interruption. Supplied. Therefore, current flows again through the diode 105 until the power supply 102 recovers (period t7 to t8) (see FIG. 6D).

When the output voltage of the power source 102 is restored to a normal value at time t8, power supply from the power source 102 to the load device 110 is started again, and power supply from the power source 101 to the load device 110 is stopped (FIG. 6 (d), (See (e)). As shown in FIGS. 6D and 6F, during the momentary interruption (time t7 to t8), current flows through the diode 105 and loss occurs (for example, Patent Document 1).
2).

As described above, in the case of the power supply switching device 100 configured as described above, since all the current supplied from the power supply passes through the diode 105 or the diode 106, the diode 105 (1
06) is proportional to the load size of the load device 110. In particular, the load device 110
Is the maximum load, the current flowing through the diode 105 (106) is also maximum, so the loss of the diode 105 (106) is also maximum and the amount of generated heat is also maximum. For this reason, in order to reduce the power consumption of the system, it is necessary to reduce the loss of the diode 105 (106) when the load device 110 operates at the maximum load.
00 does not have such a function.

Moreover, since it is necessary to select a diode radiator in consideration of the maximum temperature when the system is used, if the maximum temperature is high, a large and expensive radiator must be used. This is a factor that increases the size and cost of the power supply switching device main body. As described above, the loss of the diode is maximized at the maximum load of the load device. Therefore, in order to reduce the maximum temperature of the radiator, it is necessary to reduce the loss of the diode at the maximum load of the load device. However, the conventional power supply switching device 100 does not have such a function.

In view of the problems of the power supply switching device 100 including such a diode priority circuit, a device that switches power by using a relay on / off method without using a diode is also conceivable. In the case of such a device, When the output voltage of each power source is substantially the same, the relay switching frequently occurs, causing the relay to be worn out, resulting in a problem that the useful life of the relay is shortened. Also,
In order to avoid a state where all the relays are opened and the power supply to the load device is interrupted, it is necessary to provide an overlap time (a state where any one of the relays is closed) in the relay switching operation,
There is also a problem that the circuit configuration for relay switching control becomes complicated.
Japanese Patent Laid-Open No. 5-108176 Japanese Patent Laid-Open No. 5-83884

As described above, the power supply switching device provided with the conventional diode priority circuit has a problem that when the load of the load device is large (particularly at the maximum load), the loss of the diode increases and the power consumption of the system increases. there were. In addition, it is difficult to reduce the size of the diode heatsink.
An object of the present invention is to reduce a loss of a diode in a power supply switching device including a diode priority circuit. It is another object of the present invention to enable use of a small diode heatsink having a low maximum allowable temperature.

The power supply switching apparatus according to the first aspect of the present invention includes diodes connected in series to a plurality of power supplies, and diodes that supply power to the load device from the power supply with the highest output voltage via each of the diodes. A power supply switching device having a circuit is assumed. A switch connected in parallel to each diode; a temperature detecting means for detecting a temperature related to each diode; and a switch connected in parallel to the diode based on the temperature related to the diode detected by the temperature detecting means And control means for controlling.

The control means, for example, sets each switch so that output power of each power source is supplied to the load device via each switch when the temperature of each diode reaches a predetermined upper limit value. Control. In this case, for example, when the temperature of each diode decreases from the upper limit value to a predetermined lower limit value, the control means supplies the output power of the power source to the load device via each diode. In addition, the switches are controlled.

The predetermined upper limit is a design value determined by taking into account factors such as diode loss, allowable temperature, and radiation capacity of the heat sink attached to the diode.For example, the safety factor is added to the allowable loss and allowable temperature of the diode. For example, the multiplied value. The specified lower limit is the same, and is a design value that is determined by taking into account factors such as diode loss, allowable temperature, and radiation capacity of the radiator attached to the diode. It is desirable that the upper limit value be reached immediately after rising and the switch not operate.

The power supply switching device according to the first aspect may be configured such that, for example, a radiator is attached to each diode, and the temperature detecting means detects the temperature of the radiator as a temperature related to the diode. .
According to the power supply switching device of the first aspect, the temperature of the diode is detected, and on / off switching of the switch connected in parallel to the diode is controlled based on the temperature, so that an increase in the temperature of the diode is suppressed. And the loss of the diode can be reduced. In addition, since on / off switching of the switch connected in parallel to the diode is controlled based on the temperature of the diode radiator, an increase in the temperature of the radiator can be suppressed, and a small radiator can be used. In addition, since power is supplied to the load device via the switch when the temperature of the diode reaches a predetermined upper limit value and when the temperature falls to the lower limit value, it is controlled according to the output voltage of the power source. Therefore, switching frequency is less than when switching relays. In addition, by adopting a method of detecting the temperature of the radiator of each diode and switching on / off of the switch based on the detected temperature, these functions can be realized with a simple circuit configuration. In addition, since a diode is used, there is no need to provide an overlapping time when switching the power supply.

The power supply switching device according to the second aspect of the present invention further includes a current detection means for detecting a current flowing through each of the switches in addition to the components included in the power supply switching device according to the first aspect. The control means detects a reverse current flowing into each power source via each switch based on the current detected by the current detection means, and turns off each switch during the detection. To do.

For example, all the switches may be configured to be connected to the current detection means.
According to the power supply switching device of the second aspect, the backflow of the current to the power supply that has supplied power to the load device via the switch is detected, and the power supply can be protected because the switch is turned off when the backflow occurs. .

In the present invention, when heat generation increases due to diode loss, such as when the load of the load device is large, power supply from the power source is performed via a switch instead of a diode.
The loss of the diode can be reduced, and the diode radiator can be downsized. As a result, the overall size of the device can be reduced, the power loss in the entire device can be reduced, and the manufacturing cost of the device can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a system configuration of a power supply switching device 10 according to an embodiment of the present invention.
In FIG. 1, the power source 11 and the power source 12 are both DC power sources. The power supply 11 and the power supply 12 are connected in parallel to the load device 60 via the diode 14 and the diode 15, respectively. The diode 14 and the diode 15 are attached with a radiator FIN1 and a radiator FIN2 for releasing heat generated by these elements to the outside. Also, heatsink FIN1, FIN
2 are attached with thermistors 18 and 19 for outputting voltage values indicating their temperatures, respectively.

The power source 11 is connected to the first relay 21, and the power source 12 is connected to the second relay 22. The other terminals of the first relay 21 and the second relay 22 are both connected to the current transformer 24. Thus, the power supply 11 and the power supply 12 are respectively connected to the relay 21.
, 22 is connected to one end of a current transformer (CT) 24. This relay 21
The relay 22 can be replaced by a single latching relay.

The other end of the current transformer 24 is connected to the cathodes of the diode 14 and the diode 15 and the load device 60. The current transformer 24 is a current detection element provided for detecting a reverse flow of a current flowing from one power supply to the other power supply via the relay 21 or the relay 22, and flows to the relay 21 or the relay 22 that is turned on. Detect current. The current transformer 24 outputs the detected values of those currents to the relay ON / OFF signal generation circuit 30.

The relay ON / OFF signal generation circuit 30 is a circuit that forms the core of the present system, and the relay 21 is based on the temperatures of the radiators FIN1 and FIN2 detected by the thermistors 18 and 19.
, 22 is controlled to turn on / off the current flowing through the diodes 14, 15 to the relays 21, 2
The temperature is controlled so that the temperature of the radiators FIN1 and FIN2 does not exceed a predetermined upper limit value. Further, based on the detected current value of the current transformer 24, the backflow of current from one power supply 11 (power supply 12) to the other power supply 12 (power supply 11) is detected. When a reverse flow is detected, the relay that is currently turned on (relay 21 or relay 22) is instantaneously turned off so that the reverse current does not flow into the power source (power source 11 or power source 12). Protect the power supply.

Table 1-1 below shows a method in which the relay ON / OFF signal generation circuit 30 controls the ON / OFF of the relay 21 based on the temperature T1 of the radiator FIN1 detected by the thermistors 18 and 19.

上記表１−１に示すように、リレーＯＮ／ＯＦＦ信号生成回路３０は、
（１）リレー２１の現在の状態がオフ（ＯＦＦ）のとき、放熱器ＦＩＮ１の温度Ｔ１が上
限値Ｍ１未満であれば、リレー２１をオフのままにする。
（２）リレー２１の現在の状態がオフのとき、放熱器ＦＩＮ１の温度Ｔ１が上限値Ｍ１以
上であればリレー２１をオン（ＯＮ）にし、ダイオード１４ではなくリレー２１を介して
電源１１から負荷装置６０へ電力が供給されるようにする。
（３）リレー２１の現在の状態がオンのとき、放熱器ＦＩＮ１の温度Ｔ１が下限値Ｌ１以
上であれば、リレー２１をオンのままにする。
（４）リレー２１の現在の状態がオンのとき、放熱器ＦＩＮ１の温度Ｔ１が下限値Ｌ１未
満であれば、リレー２１をオフにし、リレー２１ではなくダイオード１５を介して電源１
５から負荷装置６０へ電力が供給されるようにする。

As shown in Table 1-1 above, the relay ON / OFF signal generation circuit 30 includes:
(1) When the current state of the relay 21 is OFF (OFF), if the temperature T1 of the radiator FIN1 is lower than the upper limit value M1, the relay 21 is kept off.
(2) When the current state of the relay 21 is off, the relay 21 is turned on (ON) if the temperature T1 of the radiator FIN1 is equal to or higher than the upper limit value M1, and the load is applied from the power source 11 via the relay 21 instead of the diode 14. Power is supplied to the device 60.
(3) When the current state of the relay 21 is on, if the temperature T1 of the radiator FIN1 is equal to or higher than the lower limit L1, the relay 21 is kept on.
(4) When the current state of the relay 21 is on and the temperature T1 of the radiator FIN1 is less than the lower limit value L1, the relay 21 is turned off and the power source 1 is not connected via the diode 15 but the relay 21.
Power is supplied from 5 to the load device 60.

The relay ON / OFF signal generation circuit 30 controls on / off of the relay 21 based on the direction (polarity) of the detected current of the current transformer (CT) 24 as shown in Table 1-2 below.

上記表１−２に示すように、リレーＯＮ／ＯＦＦ信号生成回路３０は、電流トランス２
４の検出電流が正方向（電流がリレー２１から電流トランス２４の方に流れる向き）であ
れば、上述した表１−１に示す方法で、放熱器ＦＩＮ１の温度Ｔ１に基づいてリレー２１
のオン／オフを制御する。また、電流トランス２４の検出電流が逆方向（電流が電流トラ
ンス２４からリレー２１の方に流れる向き）であれば、リレー２１をオフして電源１１へ
の電流の逆流を阻止する。

As shown in Table 1-2 above, the relay ON / OFF signal generation circuit 30 includes the current transformer 2
4 is in the positive direction (the direction in which the current flows from the relay 21 toward the current transformer 24), the relay 21 is detected based on the temperature T1 of the radiator FIN1 by the method shown in Table 1-1.
Control on / off of. If the detected current of the current transformer 24 is in the reverse direction (the direction in which the current flows from the current transformer 24 toward the relay 21), the relay 21 is turned off to prevent the reverse flow of current to the power source 11.

By the way, the upper limit value M1 and the lower limit value L1 of the temperature T1 of the radiator FIN1 are determined in consideration of factors such as the loss of the diode 14, the allowable temperature, and the radiation capability of the radiator FIN1. The same applies to the heatsink FIN2, and the upper limit M2 and the lower limit L of the temperature T2 of the heatsink FIN2.
2 is determined in consideration of the loss of the diode 15, the allowable temperature, the radiation capability of the heatsink FIN2, and the like.

The relay ON / OFF signal generation circuit 30 is configured by the method shown in Table 2-1 below.
Based on the temperature T2 of IN2, ON / OFF of the relay 22 is controlled.

上記表２−１に示すように、リレーＯＮ／ＯＦＦ信号生成回路３０は、
（１）リレー２２の現在の状態がオフ（ＯＦＦ）のとき、放熱器ＦＩＮ２の温度Ｔ２が上
限値Ｍ２未満であれば、リレー２２をオフのままにする。
（２）リレー２２の現在の状態がオフのとき、ＦＩＮ２の温度Ｔ２が上限値Ｍ２以上であ
れば、リレー２２をオン（ＯＮ）にし、ダイオード１５ではなくリレー２２を介して電源
１２から負荷装置６０へ電力が供給されるようにする。
（３）リレー２２の現在の状態がオンのとき、ＦＩＮ２の温度Ｔ２が下限値Ｌ２以上であ
れば、リレー２２をオンのままにする。
（４）リレー２２の現在の状態がオンのとき、ＦＩＮ２の温度Ｔ２が下限値Ｌ２未満であ
れば、リレー２２をオフにし、リレー２２ではなくダイオード１６を介して電源１２から
負荷装置６０へ電力が供給されるようにする。

As shown in Table 2-1 above, the relay ON / OFF signal generation circuit 30
(1) When the current state of the relay 22 is OFF (OFF), if the temperature T2 of the radiator FIN2 is lower than the upper limit value M2, the relay 22 is kept off.
(2) When the current state of the relay 22 is OFF, if the temperature T2 of FIN2 is equal to or higher than the upper limit M2, the relay 22 is turned ON (ON), and the load device is connected from the power source 12 via the relay 22 instead of the diode 15. Power is supplied to 60.
(3) When the current state of the relay 22 is on, if the temperature T2 of FIN2 is equal to or higher than the lower limit L2, the relay 22 is kept on.
(4) When the current state of the relay 22 is ON, if the temperature T2 of FIN2 is less than the lower limit L2, the relay 22 is turned OFF, and power is supplied from the power supply 12 to the load device 60 via the diode 16 instead of the relay 22. To be supplied.

The relay ON / OFF signal generation circuit 30 controls the ON / OFF of the relay 22 based on the direction of the detected current of the current transformer (CT) 24 as shown in Table 2-2 below.

上記表２−２に示すように、リレーＯＮ／ＯＦＦ信号生成回路３０は、電流トランス２
４の検出電流が正方向（電流がリレー２２から電流トランス２４の方に流れる向き）であ
れば、上述した表２−１に示す方法により、放熱器ＦＩＮ２の温度Ｔ２に基づいてリレー
２２のオン／オフを制御する。また、電流トランス２４の検出電流が逆方向（電流が電流
トランス２４からリレー２２の方に流れる向き）であれば、リレー２２をオフして電源１
２への電流の逆流を阻止する。

As shown in Table 2-2 above, the relay ON / OFF signal generation circuit 30 includes the current transformer 2
4 is in the positive direction (the direction in which the current flows from the relay 22 toward the current transformer 24), the relay 22 is turned on based on the temperature T2 of the radiator FIN2 by the method shown in Table 2-1. Control off / off. If the detected current of the current transformer 24 is in the reverse direction (the direction in which the current flows from the current transformer 24 toward the relay 22), the relay 22 is turned off and the power source 1
Block the backflow of current to 2.

FIG. 2 is a diagram illustrating a configuration example of the relay ON / OFF signal generation circuit 30 of FIG.
The relay ON / OFF signal generation circuit 30 shown in FIG. 2 includes a first relay control circuit 40 (40-1) that controls on / off of the relay 21 based on the temperature T1 of the radiator FIN1, and the radiator FIN2 A second relay control circuit 40 (40-2) for controlling on / off of the relay 22 based on the temperature T2 is provided.

Furthermore, a voltage (output of the thermistor 18) indicating the temperature T1 of the radiator FIN1 (hereinafter simply referred to as FIN1) and a voltage (Typically referred to as FIN2) indicating the temperature T2 of the radiator FIN1 (hereinafter simply referred to as FIN1). A binary signal T indicating the comparison result by comparing the output of the thermistor 19)
A comparator 51 that outputs H and a comparator 53 that determines whether the detected value (current) of the current transformer (CT) 24 is positive and outputs a binary signal CT according to the determination result are provided.

The comparator 51
(1-1) “1” (H level signal) when FIN1 temperature T1> FIN2 temperature T2.
(1-2) When FIN1 temperature T1 ≦ FIN2 temperature T2, “0” (L level signal) is
Output.

The comparator 53 is
(2-1) “1” (H level signal) when the detected value of the current transformer 24 (CT detected value)> 0,
(2-2) “0” (L level signal) when current transformer 24 detection value (CT detection value) ≦ 0,
Output.

The relay control circuit 40-1 includes comparators 41 and 43, latches 44 and 46, an inverter 45, a 3-input OR gate 47, and a 4-input AND gate 48.
The comparator 41 inputs a voltage indicating the FIN1 temperature T1 to the + terminal, and inputs a voltage indicating the FIN1 temperature upper limit M1 to the-terminal.
(3-1) If FIN1 temperature T1 ≧ FIN1 temperature upper limit M1, “1” (H level signal) is set.
(3-2) If FIN1 temperature T1 <FIN1 temperature upper limit M1, “0” (L level signal) is output to the clock input terminal of latch 44 and 3-input OR gate 47.

The comparator 43 inputs a voltage indicating the FIN1 temperature T1 to the + terminal, and inputs a voltage indicating the FIN1 temperature lower limit L1 to the-terminal.
(4-1) If FIN1 temperature T1 ≧ FIN1 temperature lower limit L1, “1” (H level signal) is set.
(4-2) If FIN1 temperature T1 <FIN1 temperature lower limit L1, “0” (L level signal) is output to inverter 45 and 4-input AND gate 48.

The latch 44 and the latch 46 are latches that hold the current state of the ON / OFF control signal of the relay 21 (hereinafter, the ON / OFF signal of the relay 21) output from the 4-input AND gate 48.
The latch 44 is a relay 2 having a 4-input AND gate 48 output inputted to the data input terminal D.
1 ON / OFF signal is latched at the rising edge of the output signal of the comparator 41 (change from “0” to “1”) input to the clock input terminal. As a result, the temperature T1 of FIN1
Becomes equal to or higher than the upper temperature limit M1 of FIN1, the ON / OFF signal of the relay 21 output from the 4-input AND gate 48 is latched.

The inverter 45 inverts the output (binary signal) of the comparator 43 and outputs the inverted signal to the clock input terminal of the latch 46. The latch 46 latches the ON / OFF signal of the relay 21 input to the data input terminal D at the rising edge (change from “0” to “1”) of the output signal of the inverter 45 input to the clock input terminal. As a result, FIN1
When the temperature T1 becomes less than the temperature lower limit L1 of FIN1, the ON / OFF signal of the relay 21 output from the 4-input AND gate is latched in the latch 46.

The signal held by the latch 44 and the latch 46 (ON / OFF signal of the relay 21) is 3
Input to the input OR gate 47.
The 3-input OR gate 47 inputs the outputs of the comparator 41 and the latches 44 and 46 and outputs the 3-input OR logic operation result to the 4-input AND gate 48. For this reason, the 3-input OR gate 47 is ANDed with “1” as 4-input AND when any one of the above 3 inputs becomes “1”.
The signal is output to the gate 48, and “0” is output to the 4-input AND gate 48 only when all the three inputs are “0”. Therefore, the 3-input OR gate 47 has a FIN1 temperature T1 ≧ FI.
If the temperature upper limit value M1 of N1 or the ON / OFF signal of the relay 21 is ON, “1” is output to the 4-input AND gate 48. Conversely, when the temperature T1 of FIN1 <the upper temperature limit M1 of FIN1 and the ON / OFF signal of the relay 21 is OFF, “0” is input 4
Output to D gate 48. Therefore, when the relay 21 is off and the temperature T1 of FIN1 is lower than the upper limit M1, the ON / OF of the relay 21 output from the 4-input AND gate 48 is output.
Since the F signal is “0”, the relay 21 maintains the OFF state.

The 4-input AND gate 48 outputs the output of the comparator 43, the output of the 3-input OR gate 47,
The output of the comparator 51 and the output of the comparator 53 are input, and the input signals AN
The D logical operation result is output to the relay 21. Therefore, the 4-input AND gate 48 is
When any one of the inputs becomes “0”, “0” is output to the relay 21 and the relay 21 is turned off. Further, only when all the four inputs are “1”, “1” is output to the relay 21 and the relay 21 is turned on.

The comparator 51 inputs a voltage value indicating the FIN1 temperature T1 to the + terminal and a voltage value indicating the FIN2 temperature T2 to the-terminal.
(1-1) “1” when FIN1 temperature T1> FIN2 temperature T2.
(1-2) “0” when FIN1 temperature T1 ≦ FIN2 temperature T2.
The signal TH shown is output to the 4-input AND gate 48.

Therefore, when the temperature T2 of FIN2 is equal to or higher than the temperature T1 of FIN1, the 4-input AND gate 48 sets the ON / OFF signal of the relay 21 to “0” to turn off the relay 21.
The comparator 53 is
(2-1) “1” when current transformer 24 detection value (CT detection value)> 0,
(2-2) “0” when current transformer 24 detection value (CT detection value) ≦ 0,
The signal CT shown is output to the 4-input AND gate 48.

Since the detected value of the current transformer 24 is equal to or less than 0 when backflow occurs, the comparator 53 outputs “0” to the 4-input AND gate 48 when backflow occurs. Therefore, 4-input AND
The gate 48 sends an ON / OFF signal to the relay 21 when a reverse flow to the power source 11 occurs.
0 "and the relay 21 is immediately turned off.

The inputs of the 4-input AND gate 48 are all “1” because the output of the comparator 43, the output TH of the comparator 51, the output CT of the comparator 53, and the 3-input OR gate 4
7 when all the outputs of 7 are “1”, the relay 21 that the 4-input AND gate 48 outputs.
The ON / OFF signal of (1) FIN1 temperature T1 is equal to or higher than the upper temperature limit M1, (
2) It becomes “1” only when the temperature T1 of FIN1 is higher than the temperature T2 of FIN2 and (3) both the latch 44 and the latch 46 hold “1”. The latch 44 and the latch 4
The initial state of 6 is set to “1”. As a result, the relay 21 is turned on for the first time when both the above conditions (1) and (2) are satisfied.

The relay control circuit 40-2 has substantially the same configuration as the relay control circuit 40-1, and inverts the output TH of the comparator 51 to the configuration of the relay control circuit 40-1, and outputs the inverted signal to 4
An inverter 55 that outputs to the input AND gate 48 'is added. The output of the comparator 51 is “0” when the temperature T1 of FIN1 is equal to or lower than the temperature T2 of FIN2.
The output of the inverter 55 becomes “1” when the temperature T2 of FIN2 is equal to or higher than the temperature T1 of FIN1. Therefore, the ON / OFF signal of the relay 22 output from the 4-input AND gate 48 ′ is
It is “1” only when FIN1 temperature T1 ≦ FIN2 temperature T2. Therefore, the relay control circuit 40-2 turns on the relay 22 only when the temperature of FIN1 ≦ the temperature of FIN2. On the other hand, as described above, the relay control circuit 40-1 has the temperature T1 of FIN1.
The relay 21 is turned on only when the temperature T2 of> FIN2. Therefore, for example, when the temperatures of both the FIN1 and FIN2 radiators exceed the upper limit values M1 and M2, the switch corresponding to the higher-temperature radiator is preferentially turned on.

In the relay control circuit 40-2, the same components as those of the relay control circuit 40-1 are denoted by the same reference numerals with a symbol added to them. The difference between the relay control circuit 40-1 and the relay control circuit 40-2 is that the radiator FIN is connected to the + terminals of the comparators 41 ′ and 43 ′.
The voltage value indicating the temperature T2 of 2 is input, the ON / OFF signal of the relay 22 is input to the data input terminal D of the latches 44 ′ and 46 ′, the latch 44 ′ and the latch 46 ′ are the relay 2
2 holds the current ON / OFF signal of 4 and the 4-input AND gate 48 ′
The point is that an N / OFF signal is output. Since the relay control circuit 40-2 operates in the same manner as the relay control circuit 40-1, except that the control target is the relay 22, the description of the operation is omitted.

Next, the operation of the power supply switching apparatus 10 of the first embodiment of the present invention having the above-described configuration will be described with reference to the timing chart of FIG.
FIGS. 3A and 3B show changes in voltage values of the power supplies 11 and 12 over time, respectively. FIG.
c) shows the time change of the load power consumed by the load device 60. 3D shows the time change of the current (I1) flowing through the diode 14, FIG. 3E shows the time change of the ON / OFF signal of the relay 21, and FIG. 3F shows the current flowing through the relay 21 (Ir1). ). Further, FIG. 3G shows the time change of the detected current of the current transformer (CT) 24, and FIG.
FIG. 3 (i) shows the time change of the ON / OFF signal of the relay 22 and the time change of the current (Ir2) flowing therethrough. Further, FIG. 3 (j) shows the time change of the loss (W1) of the diode 14, and FIG. 3 (k) shows the time change of the loss (W2) of the diode 15. 3 (l) shows the time change of the temperature (T1) of FIN1, and FIG.
The time change of the temperature (T2) of IN2 is shown.

As shown in FIGS. 3A and 3B, the output voltage V of the power source 11 is applied during the period from time t0 to time t2.
1 is higher than the output voltage V <b> 2 of the power supply 12, so that the power supply to the load device 60 is the power supply 11.
Is done by. During this period, the load of the load device 60 becomes a steady load at time t1, and this state continues until time t6. Therefore, during the period from time t0 to time t2, the diode 14
Current flows only through the diode 15 and no current flows through the diode 15 (see FIGS. 3D and 3H).

For this reason, during the period from time t0 to time t2, FIN1 temperature T1 rises due to the heat generated by the diode 14, and reaches time t2 near its upper limit value M1. However, since the output voltage V2 of the power source 12 becomes higher than the output voltage V1 of the power source 11 after time t2, the power supply from the power source 11 to the load device 60 is stopped, and after time t2, the power supply to the load device 60 is stopped. It is performed by the power supply 12. For this reason, no current flows through the diode 14, so that FIN1
The temperature T1 gradually decreases, and after time t3, the temperature T1 decreases to the lower limit L1 or less (FIG. 3 (
l)).

The voltage V2 of the power source 12 rises to a predetermined rated value at time t4 and maintains the rated value after time t4. In this way, while the load device 60 is driven with a steady load (time t2 to t6).
), A predetermined constant current flows through the diode 15 (see FIG. 3H). Along with this, the temperature T2 of FIN2 gradually increases under the influence of heat generation of the diode 15, but does not reach its upper limit M2 (see FIG. 3 (m)).

Thereafter, the load device 60 is driven at the maximum load from time t6 (see FIG. 3C). For this reason, the electric power supplied from the power supply 12 to the load device 60 increases, and accordingly, the current I2 flowing through the diode 15 also increases (see FIG. 3 (h)). Thus, the loss W2 of the diode 15 also increases, and the temperature T2 of FIN2 also rises to its upper limit M2 at time t7 (FIG. 3 (
m)).

The relay ON / OFF signal generation circuit 30 is detected by the detected temperature signal from the thermistor 19.
When it is detected that the temperature T2 of FIN2 has reached the upper limit M2, the relay 22 is turned on (ON).
(See FIG. 3I). Thereby, after time t7, power supply from the power source 12 to the load device 60 is performed via the relay 22, and the power source does not flow to the diode 15 (see FIG. 3 (h)). For this reason, the loss of the diode 15 becomes zero (FIG. 3 (k
)) And FIN2 temperature T2 also decreases. Then, the temperature T2 of FIN2 falls to its lower limit L2 at time t8 (see FIG. 3 (m)). The relay ON / OFF signal generation circuit 30 determines that the temperature T2 of FIN2 is lower than the lower limit L2 by the detected temperature signal input from the thermistor 19.
When it is detected that the value is less than the value, the relay 22 is turned off again (see FIG. 3I).

In this way, the relay ON / OFF signal generation circuit 30 receives the FIN2 input from the thermistor 19 during the period when the load device 60 is driven at the maximum load (period from time t7 to t14).
If the temperature T2 of FIN2 rises to its upper limit M2 based on the temperature detection signal of
After that, when the temperature T2 of FIN2 falls below its lower limit L2, relay 22
The control to turn off is repeated (see FIGS. 3H and 3M).

When the relay ON / OFF signal generation circuit 30 periodically controls the ON / OFF of the relay 22 in this way, the voltage V2 of the power source 12 at the time t14 when the relay 22 is ON.
When the power supply is interrupted due to a failure or the like, the voltage V1 of the power supply 11 becomes higher than the voltage V2 of the power supply 12, so that a current flows from the power supply 11 to the power supply 12 (see FIG. 3D). Relay ON
The / OFF signal generation circuit 30 detects the backflow of current to the power supply 12 based on the backflow current detected by the current transformer 24 (see FIG. 3G).

The relay ON / OFF signal generation circuit 30 immediately turns off the relay 22 when this reverse flow is detected (see FIG. 3I). Since switching of the relay 22 from on to off is performed instantaneously, the reverse current flowing through the relay 22 is only a very short time, so that the power supply 12 is protected (
(Refer FIG.3 (i)).

Thus, the relay ON / OFF signal generation circuit 30 immediately turns off the relay 22 when the voltage of the power source 12 suddenly drops due to a failure or the like when the relay 22 is on, and the power source 11 Prevents the backflow of current from the power source 12 to the power source 12 to protect the power source 12.
At time t15, the power supply 12 is restored, and the voltage V2 returns to normal (see FIG. 3B). Since the temperature T2 of FIN2 is lower than the upper limit value M2 at time t15, the relay ON / OFF signal generation circuit 30 does not turn on the relay 22. For this reason, the power supply from the power source 12 to the load device 60 is performed via the diode 15. As a result, a current I2 flows through the diode 15 and a loss W2 occurs in the diode 15 (see FIGS. 3 (h) and 3 (k)). As a result, the temperature T2 of FIN2 starts to rise again and reaches its upper limit M2 at time t16 (see FIG. 3 (m)).

When the relay ON / OFF signal generation circuit 30 detects that the FIN2 temperature T2 has reached its upper limit M2 by the FIN2 detection value temperature signal input from the thermistor 19, the relay ON / OFF signal generation circuit 30 turns on the relay 22 (FIG. 3 (i)). )reference). The relay ON / OFF signal generation circuit 30
Is the detected temperature T of FIN2 input from the thermistor 19 in the same manner as before the failure of the power supply 12.
2, the control to turn on / off the relay 22 is performed to adjust the temperature T <b> 2 of FIN <b> 2.

Eventually, at time t17, when the load device 60 is again driven with a steady load, the power source 1
2 also decreases the power supplied to the load device 60, so that the current I2 flowing through the diode 15
And the temperature T2 of FIN2 is also maintained at its lower limit L2 (see FIGS. 3C and 3M).

FIG. 4 is a block diagram showing a system configuration of a power supply switching device 70 according to another embodiment of the present invention. In FIG. 4, the same components as those of the power supply switching device 10 of FIG.
The system configuration of the power supply switching device 70 is different from that of the power supply switching device 10 in that the power supply 81 is a power supply that rectifies an AC voltage supplied from a system power supply 71 that is an AC power supply, converts it to a DC voltage, and outputs it. is there.

Since the operation of the power supply switching device 70 is the same as that of the power supply switching device 10, a detailed description thereof will be omitted.
Also in the power supply switching device 70, the relay ON / OFF signal generation circuit 30 includes the thermistor 18,
On / off switching control of the relays 21 and 22 is performed based on the temperatures T1 and T2 of the FINs 1 and 2 detected by the circuit 19, and the losses W1 and W2 of the diodes 14 and 15 are suppressed. The relay ON / OFF signal generation circuit 30 detects the backflow of the current Ir1 (or Ir2) to the power source 12 flowing through the relay 21 (or relay 22) from the detected current value input from the current transformer 24, and from the backflow The power supply 11 (or power supply 12) is protected.

As described above, in this embodiment, the temperature of the diode is indirectly detected by the temperature of the radiator by detecting the temperature of the radiator attached to the diode.
When the temperature of the radiator reaches a predetermined upper limit value, power is supplied from the power source via a switch instead of the diode so that the diode does not exceed the upper limit value. . For this reason, according to the present Example, the loss of a diode can be reduced and the size of the radiator can be reduced.

Also, the temperature of the diode heatsink is detected, and the switch is turned on / off based on the detected temperature.
Since the system is switched off, the entire circuit configuration is simplified. Furthermore, when a reverse current flows into the power supply via the switch that is turned on, the switch is turned off instantaneously, so that the power supply can be protected.

In the above embodiment, the radiators (FIN) attached to the diodes (14, 15), respectively.
1, 2) is detected, but the temperature of the diode (14, 15) is directly detected by a thermistor or the like, and based on the detected temperature, it is based on the temperature of the radiator (FIN 1, 2) described above. Similarly to the method, on / off switching of the relays 21 and 22 may be controlled. Further, although a current transformer is used as the current detection element, the power supply switching device of the present invention only needs to have a function of detecting the direction of the current. Therefore, an inexpensive shunt resistor is used instead of the current transformer. Alternatively, a Hall element or the like may be used.

In addition, both of the above-described two embodiments are systems having two power supplies, but the present invention can be easily applied to a system having three or more power supplies. This can be easily conceived by those skilled in the art. The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  The present invention can be applied to a wide range of systems that use a plurality of power sources together.

It is a block diagram which shows the system configuration | structure of the power supply switching apparatus of one Example of this invention. (Example 1) It is a figure which shows the structural example of a relay ON / OFF signal generation circuit. 3 is a timing chart for explaining the operation of the power supply switching apparatus according to the first embodiment. It is a block diagram which shows the system configuration | structure of the power supply switching apparatus of the other Example of this invention. (Example 2) It is a block diagram which shows the system configuration | structure of the conventional power supply switching device. It is a timing chart explaining operation | movement of the conventional power supply switching device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Power supply switching device 11, 12 Power supply 14,15 Diode FIN1, FIN2 Radiator 18, 19 Thermistor 21, 22 Relay 24 Current transformer (CT)
30 Relay ON / OFF signal generation circuit 40 (40-1, 40-2) Relay control circuit 41, 41 ', 43, 43' Comparator 44, 44 ', 46, 46' Latch 45, 45 'Inverter 47, 47' OR gate 48, 48 'AND gate 51, 53 Comparator 70 Power supply switching device 71 System power supply (AC power supply)
81 Power supply (DC power supply)
M1, M2 Upper limit L1, L2 Lower limit

Claims (6)

In a power supply switching device having a diode priority circuit that has a diode connected in series to each of a plurality of power supplies, and supplies power from the power supply with the highest output voltage to the load device via each of the diodes.
A switch connected in parallel to each of the diodes;
Temperature detecting means for detecting the temperature of each diode;
Control means for controlling a switch connected in parallel to the diode based on the temperature of the diode detected by the temperature detection means;
A power supply switching device comprising: The control means controls each switch so that output power of each power source is supplied to the load device via each switch when the temperature of each diode reaches a predetermined upper limit value. The power supply switching device according to claim 1. The control means is configured so that the output power of the power source is supplied to the load device via each diode when the temperature of each diode decreases from the upper limit value to a predetermined lower limit value. The power supply switching device according to claim 2, wherein the power supply switching device is controlled. Furthermore, a current detection means for detecting a current flowing through each switch is provided,
The control means detects a reverse current flowing into each power source via each switch based on the current detected by the current detection means, and turns off each switch during the detection. Item 4. The power supply switching device according to item 1, 2 or 3. 5. The power supply switching device according to claim 4, wherein all the switches are connected to the current detection means. 2. The power supply switching device according to claim 1, wherein a radiator is attached to each of the diodes, and the temperature detecting means detects a temperature of the radiator as a temperature related to the diode.

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