JPH0213536B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply circuit, and more particularly to a control circuit for switching between active and standby power supplies to improve the reliability of a power supply device.

Conventionally, this type of switching circuit for active and standby power supplies was
It was constructed as shown in Figure 1. In this drawing, PU1 is the current DC stabilized power supply circuit, PU2
is a preliminary DC stabilized power supply circuit, 1 and 11 are unregulated DC power supplies, 2 and 12 are main control circuits, 3
and 13 are error amplifier circuits, 4 and 14 are reference voltage generation circuits, 9 is a load, and D1 and D11 are reverse current blocking diodes. In this circuit, the voltage is detected between the terminals of the load 9 in order to improve the accuracy of output voltage detection, and the active unit PU1 is the standby unit.
It is set to obtain an output voltage slightly higher than that of PU2, so diode D1 is normally in a forward conduction state, and constant voltage controlled DC is supplied from active unit PU1 to load 9. .

In this state, the detection voltage given to the error amplification circuit 13 of the standby unit PU2 is V _L , and
This is the reference voltage given to the error amplifier circuit 13.
Since the voltage is slightly higher than Vr ₂ , the main control circuit 12 always operates to lower the output voltage Vc ₂ , and in a steady state, the value of the output voltage Vc ₂ is approximately zero volts.

If the active unit PU1 were to stop due to a failure in this state, the standby unit PU2 would have to start up from an output voltage of zero volts and supply DC to the load 9 instead of the active unit PU1. , there is a drawback that large transient voltage fluctuations occur during switching, and in the case of an intermittent drop in the output of the active unit PU1, DC is supplied from the active unit PU1 again after recovery. It is necessary to set the output voltage somewhat low, and when using it stably at a low output voltage, there is a drawback that it is difficult to satisfy a predetermined voltage fluctuation rate.

The object of the present invention is that even if the output voltages of the active unit and the standby unit are set to exactly the same value, the one with a slower output voltage rise time will be the standby unit, and the output voltage of the standby unit will be controlled by a reverse current blocking diode. By switching the output voltage detection point so that the voltage across the terminal stays at zero volts, that is, the same voltage as the load voltage, the above drawbacks are eliminated and a very stable and highly accurate DC voltage can be supplied to both the working machine and the standby machine. It is an object of the present invention to provide a control circuit for switching between active and standby power sources that can output from

Describing the structure of the present invention, the present invention has two
In the current and standby power supply switching control circuit, the outputs of the DC stabilized power supply circuits PU1 and PU2 are connected in parallel to the load via diodes D1 and D11, respectively.
If the diode D1 input voltage of one PU1 of the two DC stabilized power supply circuits is higher than the diode D11 output voltage of the other PU2, then
PU1 is operated as a working power source, and its diode D1 output voltage is supplied as an output voltage detection signal, and if the diode D11 output voltage of the other PU2 is higher than the diode D1 input voltage of one PU1, the other PU2 is A current/standby power source switching control circuit, characterized in that a switch circuit that operates as a current power source and supplies the output voltage of the diode D11 as an output voltage detection signal is added to each of the two DC stabilized power source circuits. It is.

The present invention will be explained below by way of examples with reference to the drawings.

FIG. 2 shows a circuit diagram of an embodiment of the invention. Second
In the figure, the current/standby power supply switching control circuit of the present invention includes an unregulated DC power supply 1, a main control circuit 2,
A known DC stabilized power supply circuit PU1 consisting of an error amplification circuit 3, a reference voltage generation circuit 4, a power supply output terminal 6, a detection signal input terminal 7, a common retrace terminal 8, an overvoltage detection shot circuit 5, and a Stabilized DC power supply 11, main control circuit 12, and error amplification circuit 13
, a reference voltage generation circuit 14 , and a power output terminal 16
, a detection signal input terminal 17 , and a common retrace terminal 18
, a known DC stabilized power supply circuit PU2 consisting of an overvoltage detection shot circuit 15, and a power supply output terminal 6.
and diodes D1 and D11 whose anodes are connected to 16 and whose cathodes are connected to each other.
and a load 9 connected to the cathodes of diodes D1 and D11 and common return terminals 8 and 18, respectively.
The emitter and collector were connected to the anode and detection signal input terminal 7 of the diode D1, respectively.
PNP transistor Q1 and PNP transistor Q
1 and the cathode of the diode D1, the output terminal is connected to the base of the PNP transistor Q1 through the resistor R1, the positive input terminal is connected to the cathode of the diode D1, and the negative input terminal is connected to the cathode of the diode D1. The terminal is diode D1
1, a PNP transistor Q11 whose emitter is connected to the anode of the diode D11, and whose collector is connected to the detection signal input terminal 17, respectively.
A resistor R connected between the collector of PNP transistor Q11 and the cathode of diode D11
12, and a comparator Z whose output terminal is connected to the base of the PNP transistor Q11 through a resistor R11, whose positive input terminal is connected to the cathode of the diode D11, and whose negative input terminal is connected to the anode of the diode D11 through the resistor R4.
11 and a resistor R connected between the output of comparator Z1 and the negative side of comparator Z11.
3 and a resistor R1 connected between the output of comparator Z11 and the negative side of comparator Z1.
3 and a capacitor C1 connected in parallel to the load 9.
It is made up of.

In the circuit shown in FIG. 2, the voltages after passing through the diodes of the known DC stabilized power supply circuits PU1 and PU2 are set in advance to approximately the same voltage V3, and the rise time of the output voltage of the DC stabilized power supply circuit PU1 is If the rise time of the output voltage of the stabilized power supply circuit PU2 is earlier, the diode D1 becomes forward biased first, and the potential on the negative side of the comparator Z11 becomes higher than the positive side input, turning on the transistor Q11 and stabilizing the DC current. The power supply circuit PU2 operates so that the potential of the anode of the diode D11 is the same as the potential of the cathode, and therefore cannot supply direct current to the load 9.
On the other hand, the negative input of comparator Z1 is pulled to a low level by the output of comparator 11 through resistor R13, so if R14 is chosen appropriately, it will be slightly lower than the positive input, so transistor Q1 is off, so the DC The stabilized power supply circuit PU1 operates so that the potential of the cathode of the diode D1 becomes V3, and therefore supplies direct current to the load 9, and becomes a working device.

Next, if the current machine is unable to supply DC to the load 9 due to some kind of failure, or if the overvoltage protection short circuit 5 is activated, the diode D
The potential at the anode of diode D1 drops rapidly, but the potential at the cathode of diode D1 drops only gradually due to the accumulated charge in capacitor C1. Therefore, the negative input potential of comparator Z11 becomes lower than the positive input potential, the output of Z11 becomes high level, transistor Q11 is turned off, and DC stabilizing power supply circuit PU2 is connected to diode D.
The operation is started so that the potential of the cathode 11 becomes V3, and direct current is supplied to the load 9.

In this way, capacitor C1, resistor R
By selecting appropriate values for R1, R3, R4, R11, R13, and R14, it is possible to extremely reduce the transient voltage fluctuation when switching from the active machine to the standby machine for the load 9, and also to reduce the steady voltage. It is also possible to make fluctuations due to switching extremely small.

In addition, in the circuit shown in Figure 2, once the active machine becomes unable to supply output and switches to backup machine operation in the sequence described above, even if the active machine's output supply capacity is restored, it switches to active machine operation. It is characterized by excellent maintainability because it does not change.

As described above, by configuring the circuit of the present invention, there is an effect that transient fluctuations and steady voltage fluctuations with respect to the load during switching between working and standby can be extremely reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional example, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. Note that the symbols used in the drawings indicate the following. PU1, PU2...DC stabilized power supply circuit, 1,1
DESCRIPTION OF SYMBOLS 1... Unregulated DC power supply, 2, 12... Main control circuit, 3, 13... Error amplifier circuit, 4, 14... Reference voltage generation circuit, 5, 15... Overvoltage detection shot circuit, 6, 16 ...Power output terminal, 7, 17...
...Detection signal input terminal, 8, 18...Common return terminal, 9...Load, R1-4, R11-14...Resistor, Z1, Z11...Comparator, Q1, Q
11...Transistor, D1, D11...Diode, C1...Capacitor.

Claims (1)

[Scope of Claims] 1. The positive outputs of the first and second DC stabilized power supply circuits are connected to the load via the first and second diodes, respectively, and the first and second DC stabilized power supply circuits are connected to the load. In a power supply device configured to operate one of the units as a working unit and the other unit to operate as a backup unit when the active unit is stopped, a first resistor is connected to the anode of the second diode. a first comparator having an inverting input terminal connected to the cathode of the second diode, and a non-inverting input terminal connected to the cathode of the second diode; an inverting input terminal connected to the anode of the first diode through a second resistor; The terminal is
a second comparator having a non-inverting input terminal connected to the cathode of the first diode; a base connected to the output terminal of the first comparator via a third resistor, and an emitter connected to the first diode; a first PNP transistor whose collector is respectively connected to the cathode of said first diode through a fourth series resistor; whose base is connected to said second comparison transistor through a fifth resistor; to the output terminal of the device.
An emitter is connected to the anode of the second diode,
The collectors each have a second diode connected to the cathode of the second diode through a sixth resistor.
a PNP transistor; a voltage detection terminal of the error amplifier in the first DC stabilized power supply circuit connected to the collector of the first PNP transistor; a voltage detection terminal of the error amplifier in the first DC stabilized power supply circuit connected to the collector of the second PNP transistor; Current use characterized by comprising a voltage detection terminal of an error amplifier in a DC stabilized power supply circuit,
Standby power supply switching control circuit.