JPH10248261A - Redundant power-supply apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a redundant power-supply apparatus which can protect a normal power-supply apparatus in a failure or in the replacement of an apparatus even when a diode for reverse-current protection is omitted in the parallel operation of power-supply apparatus and which can reduce a power loss in an ordinary operation as compared with a conventional apparatus. SOLUTION: In a redundant power-supply apparatus in which a plurality of AC/DC converters 101, 102 are connected in parallel, the AC/DC converters 101, 102 are provided with an input converter 1 and an output converter 2 which convert an AC voltage into a DC voltage, with a capacitor C3 by which the DC output voltage of the output converter 2 is smoothed, with a transistor Q3, for capacitor control, which runs on or off the smoothing operation of the capacitor C3, with a voltage detection circuit 5 which detects the source-to- drain voltage of the transistor Q3 so as to output a voltage detecting signal S2 and with a control circuit 6 which controls the transistor Q3 so as to be turned on or off on the basis of a power-supply turning-on signal S1 indicating the turning-on-or-off operation of an AC power supply and on the basis of the voltage detecting signal S2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a redundant power supply suitable for a DC power supply such as a broadcasting station having a load device requiring continuous supply of power. More specifically, the smoothing operation of the smoothing capacitor of the DC power supply device is controlled on / off by a field effect transistor (hereinafter referred to as FET) so that the operation protection diode can be omitted when the power supply device is operated in parallel. At the same time, for controlling the capacitor, F
The present invention relates to a redundant power supply device capable of reducing power loss during normal operation by using ET.

[0002]

2. Description of the Related Art In recent years, in a broadcasting station or the like that requires continuous operation of load devices such as an image processing device and a switcher, a plurality of power supply devices are connected in parallel to the load devices, and one power supply device is connected to the load device. 2. Description of the Related Art A redundant power supply device that can supply DC power from another power supply device to a load device even when a device fails is used.

An output of this type of power supply is connected to a diode for operation protection, that is, a backflow prevention diode. The diode prevents the current from flowing from a normal power supply to a failed power supply. , To protect the normal operation of the power supply.

FIG. 9 shows an A-type device having such a diode.
FIG. 9 is a diagram illustrating a configuration of a conventional redundant power supply device in which C / DC converters (power supply devices) are connected in parallel. In this figure, a first AC / DC converter 301 is connected to a load device 4 via a connector 3A, and when the AC voltage is converted into a DC voltage by the AC / DC converter 301, the DC voltage is converted to a drive voltage. Is supplied to the load device 4.

In an AC / DC converter 301 shown in FIG.
The DC high voltage is converted by the output converter 2 into a low voltage for driving voltage.

A smoothing capacitor C3 is connected to the output stage of the output converter 2, and the DC low voltage is smoothed and stabilized by the capacitor C3.
On the output side of the capacitor C3, a diode D for preventing backflow is provided.
4 is provided, and the smoothed DC low voltage reaches the connector 3A via the diode D4.

Similarly, the second AC / DC converter 30
2 is connected to the load device 4 via the connector 3B so as to be in parallel with the first AC / DC converter 301, and D converted by the AC / DC converter 302.
The C low voltage is supplied to the load device 4 via the backflow preventing diode D4. Regarding the configuration of the input converter 1, the output converter 2, the smoothing capacitor C3, and the diode D4 in the AC / DC converter 302,
This is the same as the C converter 301.

In such a redundant power supply device having a pair of diodes D4 for preventing backflow, when power is supplied equally to the load device 4 by two normal AC / DC converters 301 and 302, Even if one of the AC / DC converters fails, the load device 4
Can be driven normally.

For example, when the smoothing capacitor C3 of the AC / DC converter 301 is short-circuited and the power cannot be supplied from the AC / DC converter 301 to the load device 4, the power shared by the AC / DC converter 301 is Can be promptly supplied from the AC / DC converter 302 to the load device 4. Since the function of a diode having such a configuration is similar to that of a two-input OR logic circuit, it is often referred to as a diode OR configuration.

The failed AC / DC converter 30
The one diode D4 functions as a diode switch (backflow prevention) to prevent current from flowing from the AC / DC converter 302 during normal operation to the AC / DC converter 301. Therefore, even when the AC / DC converter 301 after the repair is connected to the load device 4 (hereinafter referred to as device replacement), a large charge current flows from the AC / DC converter 302 to the smoothing capacitor C3 due to the presence of the newer diode D4. Does not flow. That is, the diode D4 functions as a backflow preventing element.

As a result, power is continuously supplied to the load device 4 without causing a voltage change to the load device 4 at the time of failure or replacement of the device.

[0012]

However, in the conventional redundant power supply device, if the output current of the AC / DC converters 301 and 302 is designed to be large in accordance with the power demand of the load device 4, the power loss in the diode 4 becomes large. , The heat generated by this cannot be ignored.

Here, as shown in FIG.
Consider the power loss of the diode D4 by taking the configuration of the power supply device A as an example. Generally, a plurality of diodes are connected in parallel in order to reduce power loss in a diode for blocking backflow.

FIG. 11 is a diagram showing instantaneous output characteristics (considering characteristic changes due to heat generation) in which the vertical axis is an instantaneous forward current on a semilog scale and the horizontal axis is an instantaneous forward voltage on an equally divided scale. Current Schottky diode (product name; C) when four diodes D4 are connected in parallel and used.
120P04QE (average rectified current Io = 120 A, reverse breakdown voltage VRRM = 40 V).

The output current shared by one diode is 1
Since 20/4 = 30 A, the instantaneous forward voltage at this time is about 0.45 V as can be read from FIG.
Assuming that one diode can supply an output current of 120 A, the instantaneous forward voltage becomes about 0.75 V.

If the increase in the line resistance due to the connection of the diode is estimated to be about 1 mΩ, the voltage drop due to the line resistance is 0.12 V. Accordingly, the simple power loss Ploss of the diode D4 is Ploss = 120 × 0.57 = 68.4 W since the sum of the voltage drops is 0.57V.

However, considering the power conversion efficiency from the AC voltage to the DC voltage, the power loss in the diode D4 further increases. For example, assuming that the power conversion efficiency of the input converter 1 is 90% and the power conversion efficiency of the output converter 2 is 80%, the power loss is: Ploss = (120 × 0.57) / (0.9 × 0.8) =
It will be as large as 95W.

Therefore, according to the present invention, even if the diode for preventing backflow during the parallel operation of the power supply device is omitted, one of the power supply devices which is operating normally at the time of failure or replacement of the device can be protected. It is an object of the present invention to provide a redundant power supply that can reduce power loss during normal operation.

[0019]

In the redundant power supply according to the present invention, normally, only about 10 to 20% of the output current of the smoothing capacitor is supplied with the smoothing charging current (hereinafter referred to as ripple current). It is a redundant power supply unit that connects multiple power supply units in parallel and supplies DC power to load equipment.These power supply units receive AC power supply and convert AC voltage to DC power. A voltage conversion circuit provided with a rectifying diode having a function of blocking a reverse current while converting the voltage into a voltage, a capacitor for smoothing the DC output voltage of the voltage conversion circuit, and turning on or off the smoothing operation of the capacitor. A field effect transistor for controlling a capacitor to be turned off, and a voltage between a source and a drain of the field effect transistor is detected to output voltage detection information. A voltage detection circuit, a power-on detection circuit that detects whether the AC power supply is on or off and outputs power-on information, and an electric field based on voltage detection information from the voltage detection circuit and power-on information from the power-on detection circuit. And a control circuit for controlling the gate of the effect transistor.

In the redundant power supply device according to the present invention, when the power supply device is normal without any failure such as short-circuit in the smoothing capacitor, the power-on detection circuit supplies "power-on" power-on information and the voltage detection circuit outputs "voltage on". By turning on the capacitor control field-effect transistor, the voltage control circuit that has input the voltage detection information of "no abnormality" can flow ripple current to the smoothing capacitor, and the power supply device can operate normally. .

In the case where the power supply fails due to a short circuit of the smoothing capacitor or the like, even if the power-on information of "power on" is input from the power-on detection circuit in the failed power supply, the voltage detection circuit will Input voltage detection information indicating "voltage abnormal", the voltage control circuit turns off the capacitor control field effect transistor.

Thus, the smoothing capacitor of the failed power supply is disconnected from the load device, so that the failed power supply can be operated using the smoothing capacitor of another power supply.

Therefore, even if the operation protection diode as in the conventional power supply device is omitted, one normal power supply device can be protected at the time of failure or replacement of the device, and can be continuously connected to the load equipment without instantaneous interruption. Power can be supplied.

Further, in the redundant power supply of the present invention, the ripple current flowing through the capacitor-controlling field effect transistor during normal operation is smaller than the DC output current. Power loss is 1/5 to that of the conventional method
It can be reduced to 1/10.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

(1) First Embodiment FIG. 1 is a diagram showing a configuration of a redundant power supply device according to a first embodiment. In the present embodiment, when a plurality of power supply devices are connected in parallel to supply DC power to load devices, in order to protect a normal power supply device at the time of failure of these power supply devices or replacement of the device, a smoothing capacitor is provided. The smoothing operation can be controlled to be on or off.

This control focuses on the fact that the originally provided rectifying diode can also be used as a backflow preventing diode. This is because it is easier to switch the smoothing capacitor and to reduce the power loss than to switch directly with a diode.

In this embodiment, two AC / DC converters 1 as shown in FIG.
The case where the configuration is made up of 01 and 102 will be described. In this figure, a first AC / DC converter 101 is connected to a load device 4 via a connector 3A, and when the AC voltage is converted to a DC voltage by the AC / DC converter 101, the DC voltage is converted to the load device. 4.

Similarly, the second AC is connected via the connector 3B.
/ DC converter 102 is connected to the load device 4, and the AC voltage is
When converted into the C voltage, this DC voltage is supplied to the load device 4.

That is, the first AC / DC converter 10
Reference numeral 1 denotes an input converter 1 and an output converter 2. The input converter 1 is connected to the AC power supply,
When the power is turned on, the AC voltage is converted into a DC high voltage by the input converter 1. Although not shown in FIG. 1, the power-on detection circuit provided in the input converter 1 as shown in FIG. 2 detects ON or OFF of the power. The power on / off detected here is output from a power-on detection circuit as a power-on signal (power-on information) S1 as described later.

An output converter 2 is connected to the output side of the input converter 1, and the high DC voltage is converted by the output converter 2 into a low DC voltage. A smoothing capacitor C3 is connected to the output stage of the output converter 2, and the DC low voltage converted by the output converter 2 is smoothed by the capacitor C3.

The smoothing capacitor C3 is provided with an n-channel field effect transistor (hereinafter simply referred to as "transistor") Q3 for controlling the capacitor in series with the smoothing capacitor C3. The ripple current flowing through the capacitor C3 is turned on or off by the transistor Q3. Is done.

A voltage detection circuit 5 is connected to a connection point p3 between the drain of the transistor Q3 and the negative terminal of the capacitor C3. The voltage VSD between the source and the drain of the transistor Q3 is detected by the voltage detection circuit 5. When,
The detected voltage VSD is compared with a preset reference voltage (Vak). As a result, a low-level voltage detection signal (voltage detection information) S2 indicating that there is no abnormal voltage is output from the voltage detection circuit 5. It is supposed to be. The internal configuration of the voltage detection circuit 5 will be described with reference to FIG.

A control circuit 6 is connected to the input converter 1, the transistor Q3, and the voltage detection circuit 5, and receives a power-on signal S1 from the input converter 1 and a voltage detection signal S2 from the voltage detection circuit 5. The transistor Q3 for controlling the capacitor is
Are controlled on / off.

The input converter 1, output converter 2, smoothing capacitor C3, transistor Q3, voltage detection circuit 5 and control circuit 6 in the second AC / DC converter 102 are the same as those in the first AC / DC converter 101. Therefore, the description is omitted.

As shown in FIG. 2A, the input converter 1 for converting the AC voltage into a DC high voltage has a bridge rectifier circuit 11, a pair of resistors R1 and R2 for detecting a voltage, a capacitor C2 for holding an output, and a power supply. The detection circuit 12 is configured.

In this figure, a bridge rectifier circuit 11 is connected to an AC voltage via a fuse F, and the AC voltage is full-wave rectified by the bridge rectifier circuit 11. An output holding capacitor C2 is connected to the output stage of the bridge rectifier circuit 11, and the rectified output is stored in the capacitor C2.

A pair of resistors R1 and R2 are connected to the rectification output side. When the rectified output voltage is detected by the resistors R1 and R2 when the AC power is turned on, the pair is connected to the connection point p1 of the resistors R1 and R2. By the power-on detection circuit 12,
The detection voltages of the resistors R1 and R2 are compared with a preset reference value. As a result, when the detected voltage becomes equal to or higher than the reference value, for example, a low-level power-on signal S1 indicating power-on is output from the power-on detection circuit 12 to the control circuit 6. When the power is off, a high-level signal S1 is output from the power-on detection circuit 12 that has been supplied with the auxiliary power.

As a result, the input converter 1
The level signal S1 is input, and a low
The control circuit 6 to which the level signal S2 is input can turn on the capacitor controlling transistor Q3.

The circuit format of the input converter 1 may be constituted by a boost type input converter 1 'as shown in FIG. 2B. This input converter 1 'includes a bridge rectifier circuit 11, a pair of resistors R1 and R2 for detecting an input voltage, a capacitor C1 for attenuating noise, a choke coil L1 for flyback, a transistor Q1 for switching, and a capacitor C2 for holding output. , And a pair of resistors R3 and R4 for detecting an output voltage and a voltage control circuit 13.

In this figure, a bridge rectifier circuit 11 is connected to an AC voltage via a fuse F, and the AC voltage is full-wave rectified by the bridge rectifier circuit 11. The output stage of the bridge rectifier circuit 11 is connected to a noise attenuating capacitor C1.
Attenuated by 1.

A pair of resistors R1 and R2 are connected to the rectification output side, and when the rectified output voltage is detected by the resistors R1 and R2 when the AC power is turned on, the pair is connected to a connection point p1 of the resistors R1 and R2. The voltage control circuit 13 compares the voltage detected by the resistors R1 and R2 with a reference value. As a result, when the detected voltage becomes equal to or higher than the reference value, a power-on signal S1 indicating power-on is output from the voltage control circuit 13 to the control circuit 6, and the switching of the transistor Q1 is controlled.

By the flyback operation by the switching control, a high voltage is stored in the capacitor C2. When the storage voltage of the capacitor C2 is detected by the pair of resistors R3 and R4, the voltage control circuit 13 outputs the resistors R3 and R4.
Is compared with a reference value. As a result, when the detected voltage becomes equal to or higher than the reference value, a start command signal (DC-OK) is output from the voltage control circuit 13 to the output converter 2.

Thus, the output converter 2 is activated,
In the control circuit 6, the power-on signal S from the input converter 1 'is output.
The control circuit 6, which inputs 1 and receives the voltage detection signal S2 from the voltage detection circuit 5, can control the transistor Q3 for capacitor control on and off.

As shown in FIG. 3, the output converter 2 includes a transformer T1, diodes D1 and D2, a choke coil L2 for smoothing, a comparator 14, a reference power supply 15, a pulse width modulator (PWM) 16, an oscillator 17, It is composed of a high frequency amplifier (RF amplifier) 18 and a switching transistor Q2.

Although not shown in FIG. 3, a transistor Q2 is connected to the output stage of the output holding capacitor C2 (see FIG. 2) via a transformer T1.
2 is converted into an alternating current by the switching operation of the transistor Q2. The AC-converted primary voltage is stepped down by a transformer T1 having a predetermined turns ratio.

Diodes D1 and D2 for rectification (also used to prevent backflow) are connected to the output side of the transformer T1, and the output voltage of the transformer T1 is full-wave rectified by the diodes D1 and D2. A choke coil L2 is connected to the rectification output side, and the rectification output is smoothed by the choke coil L2 and the above-described capacitor C3.

The smoothed output voltage is applied to the load device 4. In order to stabilize the output of the output converter 2, the load device 4 and the comparator 14 are connected via the connector 3 A as shown in FIG. Connected to the load equipment 4
And a comparator 14 which receives a receiving end voltage (driving voltage of a load end) from a reference power supply 15 and a reference voltage VREF from a reference power supply 15.
As a result, the receiving end voltage is compared with the reference voltage VREF.
Based on the comparison result, a pulse width control signal for setting the duty of transistor Q2 to a specified value is output.

A pulse width modulator 16 is connected to the output side of the comparator 14. A pulse width control signal is input from the comparator 14, and a pulse width modulator 16 receives a pulse signal of a reference frequency from an oscillator 17. The width is adjusted to the specified value.

The output stage of the pulse width modulator 16 has a transformer T
2 is connected, and the pulse signal adjusted to the specified value is input to the primary side of the transformer T2 and boosted. Transformer T
A high frequency amplifier 18 is connected to the secondary side of 2, and the boosted pulse signal is amplified by the high frequency amplifier 18.

A switching transistor Q2 is connected to the output stage of the high-frequency amplifier 18. The switching operation of the transistor Q2 to which the amplified pulse signal has been input causes a DC high voltage (held by the capacitor C2) with a specified duty. Voltage) is exchanged.

Thus, feedback control can be performed, and a stable low voltage and large current can be supplied from the output converter 2 to the load device 4.

As shown in FIG. 4, the voltage detecting circuit 5 for detecting the source-drain voltage VSD includes a constant voltage diode D3, resistors R5 and R7 for voltage feedback, resistors R6 and R8 for voltage detection, and a comparator. 19. Thyristor 2
0, constituted by a pnp bipolar transistor Q4 for switching.

The comparator 1 is connected to the connection point p3 between the smoothing capacitor C3 and the capacitor controlling transistor Q3.
9 (+ terminal) is connected, and the voltage VSD between the source and the drain of the transistor Q3 is inputted, and the voltage (reference voltage) Vak between the anode and the cathode of the constant voltage diode D3 is inputted.
The voltage VSD and the voltage V
ak are compared.

As a result, for example, when the capacitor C3 is operating normally, the voltage VSD becomes lower than the voltage Vak.
21 is output. When the capacitor C3 is short-circuited and abnormally operated, the voltage VSD becomes higher than the voltage Vak, so that the comparator 19 outputs a high-level signal S21.

The output stage of the comparator 19 includes a resistor R6
A thyristor 20 connected to the gate via
The anode of the thyristor 20 is connected to the resistor R7, and the cathode is connected to the ground line (GND). The base of the transistor Q4 is connected to the anode of the thyristor 20, and the emitter of the transistor Q4 is connected to the resistor R5.
Is connected to the negative terminal of the comparator 19 through
A resistor R8 is connected to the collector.

In such a connection configuration, for example, since the thyristor 20 to which the low-level signal S21 is input from the comparator 19 remains off, no current flows through the resistor R7. As a result, no current flows through the resistor R8 while the transistor Q4 remains off. Accordingly, when the capacitor C3 is normal, the voltage detection circuit 5
A low level voltage detection signal S2 is output.

The thyristor 20, which has received the high-level signal S21 from the comparator 19, is turned on.
A current flows through the resistor R7. Thereby, the transistor Q
Since 4 is turned on, a current flows through the resistor R8. Therefore,
When the capacitor C3 is abnormal, the voltage detection circuit 5 outputs a high-level voltage detection signal S2 to the control circuit 6.

The output stage of the voltage detection circuit 5 has a two-input NOR
(Negative OR) circuit, and a transistor Q3 for controlling the capacitor is connected to the control circuit 6.
On / off control.

That is, only when the low-level power-on signal S1 is input from the input converter 1 and the low-level voltage detection signal S2 is input from the voltage detection circuit 5, the control circuit 6 outputs the capacitor control transistor Q3. A high level control signal S3 is output to the gate of
This transistor Q3 turns on.

The other input logic, that is, the signal S1 =
When the signal S2 is low and the signal S2 is high, the signal S2
When 1 = high level and the signal S2 = low level and when the signal S1 = high level and the signal S2 = high level, the low level control signal S3 is supplied from the control circuit 6 for controlling the capacitor. Is output to the gate of the transistor Q3, so that the transistor Q3 is turned off.

The operation of the thus configured redundant power supply at the time of normal operation, at the time of failure, and at the time of device replacement will be described. Usually, in the redundant power supply, each AC / D
The C converters 101 and 102 independently have sufficient facility capacity to meet the power demand (100%) of the load equipment 4. Here, a case where parallel operation is performed using two AC / DC converters 101 and 102 having the same power supply capacity will be described as an example.

Under such power supply conditions, for example, the AC / DC
When converters 101 and 102 are normal, source-drain voltage VSD of transistor Q3 is lower than anode-cathode voltage Vak of constant voltage diode D3. Therefore, as shown in FIG. 2A, the control circuit 6, which receives the low-level power-on signal S1 from the power-on detection circuit 12 and the low-level voltage detection signal S2 from the voltage detection circuit 5, inputs a transistor for controlling a capacitor. Since the high-level control signal S3 is output to Q3, the transistor Q is turned on.

As a result, a ripple current having a switching frequency flows through the transistor Q3 of each of the AC / DC converters 101 and 102, and a half of the current flows to the load device 4.
Power can be supplied (normal operation) by the AC / DC converters 101 and 102.

The two AC / DC converters 10
In a state in which the power supply units 1 and 102 are already operating in parallel so as to share power by 負荷 for the load device 4, for example, the smoothing capacitor C3 of the AC / DC converter 101 is short-circuited and a malfunction occurs. In this case, the voltage VSD between the source and the drain of the transistor Q3 of the AC / DC converter 101 becomes higher than the voltage Vak between the anode and the cathode of the constant voltage diode D3.

Therefore, a low-level power-on signal S1 is input from the power-on detection circuit 12, and the voltage detection circuit 5
The low-level control signal S3 is output to the transistor Q3 for controlling the capacitor by the control circuit 6 to which the high-level voltage detection signal S2 is input, and the transistor Q is turned off. As a result, the smoothing capacitor C3 of the AC / DC converter 101 is disconnected from the load device 4.

Therefore, no current flows into the short-circuited capacitor C3. Further, since the current does not flow to the secondary winding side of the transformer T1 due to the presence of the diodes D1 and D2, the drive voltage value to the load device 4 does not change. At this time, the smoothing capacitor C of the AC / DC converter 102
The AC / DC converter 101 is continuously operated using an electrolytic capacitor called a bypass capacitor of the load device 3 and the load device 4. That is, the half power is still shared by the AC / DC converter 101.

The abnormal state of the AC / DC converter 101 can be determined, for example, by monitoring a control signal S3 from the control circuit 6. In this case, a buzzer sounds or a warning lamp is turned on. Good.

The failed AC / DC converter 10
When the AC / DC converter 101 is released from the parallel operation, the AC / DC converter 101 may be disconnected from the load device 4 with the power supply of the AC / DC converter 101 turned off. At this time, when the power of the AC / DC converter 101 is turned off, the normal AC / DC converter 102
% Of electric power to the load equipment 4 and AC / D
Since only the current is not supplied from the C converter 101 to the load device 4, there is no change in the receiving end voltage (the drive voltage to the load device 4).

AC / DC converter 101 after repair
When the AC / DC converter 101 is returned to the parallel operation, the AC / DC converter 101 is connected to the load device 4 with the power supply of the AC / DC converter 101 turned off. At this time, the charging route to the capacitor C3 is cut off by the transistor Q3 for controlling the capacitor. However, when the power is turned on, the transistor Q3 is turned on by the operation of the control circuit 6 to be in a parallel state.

Next, a DC output, 5 V / 120 A AC /
The power loss of the transistor Q3 for controlling the capacitors of the DC converters 101 and 102 is calculated.

FIG. 5 is a diagram showing an output portion of the forward type AC / DC converters 101 and 102. In this example, an electrolytic capacitor having a rated voltage of 6.3 V, a capacitance of 10,000 μF, an impedance of 39 mΩ (at a frequency of 100 Kz), and an allowable ripple current of 2.12 A (at a frequency of 100 Kz) is used as the smoothing capacitor C3 shown in FIG. Is used. In this calculation example, eight capacitors C3 are connected in parallel.

The total impedance when the smoothing capacitor C3 is connected in parallel is 39 mΩ / 8 = 5 mΩ. However, since the pattern resistance and the inductance of the capacitor C3 enter, the value is larger than the above value. Therefore, in order to reduce the impedance, it is necessary to minimize the on-resistance of the capacitor controlling transistor Q3.

Therefore, a plurality of ultra-low on-resistance field effect transistors (FETs) are used in parallel for the transistor Q3. In FIG. 6, the vertical axis indicates the on-resistance of the equally divided scale.
It is a figure which shows the ON characteristic whose horizontal axis is the drain current of the equally divided scale. As the transistor Q3 for controlling the capacitor, a TMOS power FET having an ON characteristic as shown in FIG. 6 (trade name: MTP75N05HD, etc., Id = 7)
5A, VDSS = 50V, RDS (on) = 9.5 mΩ) are suitable.

Here, assuming that the ripple current Ir flowing through the smoothing capacitor C3 is 20% of the output current I0 = 120A, Ir = 120A × 0.2 = 24A _PP .

If four FETs each having a source-drain ON resistance of 10 mΩ are connected in parallel and used as the transistor Q3, the ON resistance Ron becomes 2.5 mΩ. Therefore, the power loss Plo in the transistor Q3
ss is given by Ploss = (Ir / 2√3) ² × Ron (1), and when a specific numerical value is substituted into equation (1), Ploss = (24 / 2√3) ² × 2 .5 = 0.12W, and the power loss (95W) by the conventional method in which the DC output current Io is always supplied to the backflow preventing diode D4.
Power loss can be greatly reduced as compared with It can be said that the loss is negligible even when considering the power conversion efficiency and the line resistance. The ripple current Ir can be further reduced by increasing the inductance value of the choke coil L2 or increasing the switching frequency.

Next, it is calculated whether the short-circuit current can be cut off by the transistor Q3 when the smoothing capacitor C3 is short-circuited.

For example, if the ripple current Ir when the output current Io = 120 A is 24 A _PP and the on-resistance of the transistor Q 3 is 2.5 mΩ, the transistor Q
The source-drain voltage VSD of No. 3 is about 30 mV. When the capacitor C3 is short-circuited, the power loss of the transistor Q3 is 1.4 even if the ripple current Ir twice the steady state flows and the voltage VSD = 60 mV is detected.
Since it is about W, the transistor Q3 itself is not destroyed by the short-circuit current.

As described above, in the redundant power supply of this embodiment, the transistor Q3 for controlling the capacitor is provided between the smoothing capacitor C3 and the ground line, and the transistor Q3 is turned off when the power is turned off and when the capacitor C3 is abnormal. Accordingly, even if there is no diode having an OR configuration as in the conventional power supply device, the power supply device can be operated as a redundant power supply device, and even if one of the power supply devices fails, power is continuously supplied to the load device 4. be able to.

Further, since the backflow preventing diode D4 is not used as in the conventional system, the heat generation is reduced, and the rise in the temperature inside the device is reduced. Therefore, since a large current diode and a radiator are not required, the cost can be reduced.

As a transistor Q3, a sense FET (trade name: M) having current detection M and K terminals in addition to the gate G, source S, and drain D terminals as shown in FIG.
If TP10N10M) is used, the detection sensitivity of the ripple current Ir can be further increased, and the smoothing capacitor C
3 can be detected early. (2) Second Embodiment FIG. 8 is a diagram showing a configuration of a redundant power supply device according to a second embodiment. In the second embodiment, a current limiting resistor R9 is further connected in parallel between the source and the drain of the capacitor controlling transistor Q3. The components having the same reference numerals and the same names as those in the first embodiment have the same functions, and the description thereof will be omitted.

In the redundant power supply of the present embodiment, for example, while one AC / DC converter 201 is already operating, the other AC / DC converter 202
Are connected, the connector 3B is connected to the load device 4 with the power of the AC / DC converter 202 turned off.

At this time, although the transistor Q3 for controlling the capacitor of the AC / DC converter 202 is off, the smoothing capacitor C3 of the other AC / DC converter 202 is shifted from the already operating AC / DC converter 201.
Charging current flows into the

In this case, since the charging current at that time can be limited by the resistor R9, the voltage fluctuation at the load terminal can be suppressed to a negligible level.

[0085]

As described above, the redundant power supply of the present invention is provided with the field effect transistor for controlling the smoothing operation of the smoothing capacitor on or off according to the power-on information and the voltage detection information.

Accordingly, by turning off the field effect transistor for controlling the capacitor when the power is turned off and when the smoothing capacitor is abnormal, etc.
Even if there is no backflow preventing diode in the configuration, a normal power supply device can be protected and stable DC power can be supplied to load devices.

In the redundant power supply of the present invention, the ripple current flowing through the capacitor controlling transistor during normal operation is smaller than the DC output current, and the on-resistance of the field effect transistor can be reduced. The power loss is reduced to 1/5 to 1/10 compared to the conventional method in which the output current is always supplied to the backflow prevention diode.
Can be reduced.

Further, since no backflow preventing diode is used, heat generation is reduced, and a rise in the temperature inside the apparatus can be suppressed. In addition, since a large current diode and a radiator are not required, a cooling means or the like is not required, and the cost of the power supply device can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a redundant power supply device according to a first embodiment.

FIG. 2 is a diagram illustrating a configuration example of an input converter according to each embodiment.

FIG. 3 is a diagram illustrating a configuration example of an output converter according to each embodiment.

FIG. 4 is a diagram illustrating a configuration example of a voltage detection circuit and a control circuit for a capacitor.

FIG. 5 is a diagram illustrating a calculation example of power loss of a transistor Q3 for controlling a capacitor.

FIG. 6 is a diagram showing characteristics of the on-resistance of a transistor Q3 for controlling a capacitor.

FIG. 7 is a diagram showing a configuration example of a sense FET having high current detection sensitivity.

FIG. 8 is a diagram illustrating a configuration of a redundant power supply device according to a second embodiment.

FIG. 9 is a diagram showing a configuration of a conventional redundant power supply device having an OR configuration using a diode for preventing backflow.

FIG. 10 is a diagram illustrating a calculation example of a power loss of a diode for blocking backflow.

FIG. 11 is a diagram showing output characteristics of a backflow preventing diode.

[Explanation of symbols]

1 ... input converter, 2 ... output converter, 3
A, 3B ... connector, 4 ... load equipment (RL),
5 ... voltage detection circuit, 6 ... control circuit, 11 ...
Bridge rectifier circuit, 12 ... power-on detection circuit, 13
... voltage control circuits, 14, 19 ... comparators,
15: Reference power supply, 16: Pulse width modulator (PW
M), 17 ... oscillator, 18 ... high frequency amplifier (R
F amplifier), 20 ... thyristor, 101, 102,
201, 202, 301, 302... AC / DC converters, Q1 to Q4.
..Capacitors, R1 to R9 ... resistors, D1 to D4
..Diodes, T1, T2 ... transformers, L1, L2
···choke coil.

Claims (2)

[Claims] 1. A redundant power supply device for connecting a plurality of power supply devices in parallel to supply DC power to a load device, wherein the power supply device receives an AC power supply, converts an AC voltage into a DC voltage, A voltage conversion circuit including a rectifying diode having a function of blocking a backflow current; a capacitor for smoothing a DC output voltage of the voltage conversion circuit; and a capacitor control for turning on or off a smoothing operation of the capacitor. A field-effect transistor, a voltage detection circuit that detects voltage between the source and the drain of the field-effect transistor and outputs voltage detection information, and a power-on detection that detects on or off of the AC power supply and outputs power-on information. Circuit, and the electric field effect based on voltage detection information from the voltage detection circuit and power-on information from the power-on detection circuit. Ridandando power supply, characterized in that it comprises a control circuit for the gate control of the transistor. 2. The redundant power supply device according to claim 1, wherein a current limiting resistor is connected in parallel between the source and the drain of the field effect transistor.