JPH0241274B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a switching type power source, and particularly to a switching type power source for parallel operation that is used in parallel operation.

[Conventional technology]

Conventionally, when power supplies are operated in parallel, a backflow prevention diode is provided at the output of each power supply, and the output voltage of each power supply is monitored inside the backflow prevention diode. Figure 4 is a diagram showing an example of when two power supplies are operated in parallel using this method.
02 is a power supply, 103 is a load device, 104, 105
1 represents a backflow prevention diode, and 106 and 107 represent output voltage monitoring circuits, respectively. However, when the circuit shown in FIG. 4 is used, when the current consumption of the load device 103 increases, heat generation due to power loss in the backflow prevention diodes 104 and 105 becomes a major problem.

Therefore, in parallel operation of switching type power supplies, a method has been considered in which the backflow prevention diode is removed and the outputs of each power supply are directly connected, as shown in FIG. The method of output voltage monitoring in this case is
Overvoltage is detected by the shared overvoltage monitoring circuit 204,
Instead of monitoring the undervoltage, switching operation is monitored by switching stop detection circuits 206 and 207. Here, the reason why undervoltage is not monitored is because the voltage applied to the load 203 is determined by the power supply that generates the highest output voltage among the power supplies connected in parallel, so the power supply that generates a voltage lower than this is normal. This is because it is not possible to monitor whether

FIG. 6 is a circuit diagram showing a partial configuration example of a switching type power supply equipped with a conventional switching stop detection circuit used when the outputs of power supplies are directly connected and operated in parallel. Next, the circuit shown in FIG. 6 will be explained.

The voltage at the input 1 is converted into a rectangular wave by the switching transistor 11 of the switching circuit 10, and is stepped up or down by the transformer 21 of the step-up/down circuit 20. The rectifying and smoothing circuit 30 includes rectifying diodes 31 and 32, a choke coil 33, and a smoothing capacitor 34, and generates a DC voltage at the output 2.

The switching stop detection circuit 80 consists of a rectifier diode 81 and a smoothing capacitor 82, and extracts a part of the switching waveform appearing at the connection point between the transformer 21 and the rectifier diode 32, rectifies and smoothes it, and outputs it to the outside as the switching stop detection signal output 3. Output. If the switching circuit 10 fails and switching stops, the switching stop detection signal output 3 becomes OV. Therefore,
By monitoring this output 3, switching stop can be detected.

[Problem that the invention seeks to solve]

However, with such a configuration, it is only in the switching circuit 10 that switching is completely stopped.
This is not limited to cases where there is a failure.

For example, in FIG. 5, the output voltage of the switching type power supply 201 is normal, but the output voltage of the switching type power supply 202 has increased abnormally. In this case, switching type power supply 2
In the switching of 01, negative feedback works as the output voltage increases, so the switching duty gradually narrows and eventually stops.

At this point, the switching stop detection time 206 of the normal switching type power supply 201 (8 in Fig. 6) is detected.
0) may be activated, causing the switching stop error to be displayed on the error display circuit 205, and the actual overvoltage error may not be displayed.

As another example, even though the output setting voltages of switching type power supplies connected in parallel are within the normal range, a switching type power supply that generates a low voltage even when there is a difference in the output setting voltages of each switching type power supply is within the normal range. , the switching duty may gradually become narrower due to negative feedback and eventually come to a halt. In this case, even though the switching circuit 10 itself operates normally, the switching stop detection circuit 80 (if the output setting voltage of the switching type power supply 201 is lower than the switching type power supply 202, the switching stop detection circuit 206) is working. , a switching stop abnormality is displayed on the abnormality display circuit 205.

The present invention provides that when at least two or more switching type power supplies are operated in parallel by directly connecting their outputs,
By preventing switching from completely stopping even if the feedback voltage of a normal switching type power supply falls outside of the allowable value due to a difference in output setting voltage or an increase in output voltage due to a failure, errors in the switching stop detection circuit described above can be prevented. The object of the present invention is to provide a switching type power supply for parallel operation that can prevent detection.

[Means and actions for solving problems]

The switching type power supply for parallel operation according to the present invention includes a switching circuit that converts an input DC voltage into a rectangular wave, a circuit that steps up and down the rectangular wave voltage, and an output DC voltage that rectifies and smoothes the stepped up and down rectangular wave voltage. a rectifying and smoothing circuit that extracts the voltage, a reference voltage source that supplies a constant reference voltage, a voltage dividing circuit that divides the output DC voltage to generate a feedback voltage, and a comparison circuit that compares the feedback voltage and the reference voltage. and a switching control circuit that performs negative feedback control of switching of the switching circuit based on the output of the comparison circuit, and a switching stop detection circuit that extracts a part of the switching waveform and monitors the switching operation. At the same time, a feedback voltage adjustment circuit for adjusting the feedback voltage is connected to the output of the switching stop detection circuit, and the output of the feedback voltage adjustment circuit is connected to a connection point between the voltage dividing circuit and the comparison circuit. Accordingly, when at least two or more switching type power supplies are operated in parallel with their outputs directly connected,
The feedback voltage adjustment circuit adjusts the feedback voltage so that the feedback voltage of a normal switching type power supply does not fall outside of a permissible value and stop the switching operation due to a difference in output setting voltages or an increase in output voltage due to a failure. This makes it possible to prevent the switching stop detection circuit from erroneously detecting a switching stop.

〔Example〕

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

FIG. 1 is a block diagram showing the configuration of a switching type power supply for parallel operation according to the present invention. In FIG. 1, 1 is an input terminal and 2 is an output terminal.
This switching type power supply has switching circuit 1.
0, a step-up/down circuit 20, a rectifying and smoothing circuit 30, a voltage dividing circuit 40, a comparison circuit 50, a reference voltage source 60, and a switching control circuit 70. A switching stop detection circuit 80 is connected to the connection point between the step-up/down circuit 20 and the rectification/smoothing circuit 30. A feedback voltage adjustment circuit 90 is connected to the output of the switching stop detection circuit 80. This feedback voltage adjustment circuit 90 adjusts the feedback voltage obtained by dividing the voltage in the voltage dividing circuit 40, so that switching will not stop under any circumstances if the switching circuit 10 is normal.

FIG. 2 is a circuit diagram showing a first embodiment of the present invention. Next, the present invention will be explained in detail with reference to FIG.

The voltage switched by the switching transistor 11 of the switching circuit 10 is stepped up or down by the transformer 21 of the step-up/down circuit 20. In this embodiment, the switching stop detection circuit 80 is composed of a diode 81 and a capacitor 82, and extracts a part of the switching waveform appearing at the connection point between the transformer 21 and the diode 32 of the rectifying and smoothing circuit 30, and rectifies and smoothes it. Therefore, when the switching transistor 11 is switching normally, a positive DC voltage is generated on the cathode side of the diode 81, and when the switching operation of the switching transistor 11 is completely stopped, the cathode voltage of the diode 81 is becomes OV.

The feedback voltage adjustment circuit 90 is composed of resistors 91 and 92 and a diode 93, and one side of the resistor 91 is connected to the output of the switching stop detection circuit 80, that is, the cathode of the diode 81. The output of the feedback voltage adjustment circuit 90 is the anode of the diode 93, and is connected to the output of the voltage dividing circuit 40. Here, the resistance value of the resistors 91 and 92 is the output 2
When the voltage of the diode 93 is normal, the cathode voltage of the diode 93 is set to be higher than the anode voltage.

In the voltage dividing circuit 40, a resistor 41 and a resistor 42 divide the voltage of the output 2, and output the divided voltage to the comparator circuit 50 as a feedback voltage. Comparison circuit 50 includes an operational amplifier 51, compares the feedback voltage with a reference voltage supplied from reference voltage source 60, and outputs a DC voltage to switching control circuit 70. The switching control circuit 70 controls the switching duty of the switching transistor 11 according to the output voltage of the comparison circuit 50.

Now, consider a state in which output 2 is connected in parallel with at least one other power supply output, and the output voltage of the other power supply has increased. In this case, since the reverse current prevention diode shown in FIG. 4 is not used, the highest voltage among the output voltages of the other power supplies connected in parallel appears at output 2. Therefore, the voltage divider circuit 4
The zero output voltage, ie, the feedback voltage, also increases.

When the anode voltage of the diode 93 becomes higher than the sum of the cathode voltage and the forward voltage of the diode 93, the diode 93 becomes forward biased, and a portion of the current flowing from the output 2 through the resistor 41 is transferred to the diode. Flows into resistor 92 through 93. As a result, the resistor 42 and the resistor 92 are connected in parallel, and the feedback voltage is applied to the diode 9.
The voltage becomes lower than the voltage before 3 becomes conductive. Therefore, since the switching control circuit 70 acts to widen the switching duty, the switching operation of the switching transistor 11 does not stop.

Therefore, switching stop detection signal output 3
In this case, if the switching of the switching transistor 11 is in operation, some kind of DC voltage always appears, and only when the switching stops, the switching stop detection signal output 3 becomes OV, so if this signal is monitored externally, Switching stop abnormalities can be displayed without fail.

Note that the feedback voltage adjustment circuit 90 shown in this embodiment
The circuit configuration is an example of the simplest configuration, but
It goes without saying that a circuit configuration other than this embodiment may be used as long as it is possible to adjust the feedback voltage according to the signal from the switching stop detection circuit.

The same applies to the switching stop detection circuit 80, and any circuit configuration other than this embodiment may be used as long as it is capable of monitoring the voltage waveform switched by the transistor 11.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention, and circuits having the same functions as those in FIG. 2 are given the same symbols and their explanations will be omitted.

First, the switching stop detection circuit 80 provides a tertiary winding 83 in the transformer 21 to extract the switching waveform of the switching transistor 11, and full-wave rectifies the switching waveform obtained from this winding using rectifier diodes 84 and 85. , a DC voltage is obtained by a smoothing capacitor 86. The output of the switching stop detection circuit 80 is connected to the feedback voltage adjustment circuit 9.
A reference voltage source 95 is connected to an inverting input of a comparator circuit 94 of zero, and a reference voltage source 95 is connected to a non-inverting input of the comparator circuit 94 . Similar to the example shown in FIG. 2, when the switching circuit 10 is operating normally, a positive DC voltage is generated at the output of the switching stop detection circuit 80. It is set lower than the voltage so that the output of the comparator circuit 94 becomes low level. At this time, since the transistor 96 is in an off state, the feedback voltage adjustment circuit 90 does not affect the feedback voltage at all.

Next, consider a case where the switching duty becomes narrow due to negative feedback due to a difference in the output setting voltages of the power supplies connected in parallel or an increase in the output voltage due to a failure or the like.

At this time, when the output voltage of the switching stop detection circuit 80 decreases and becomes lower than the set voltage of the reference voltage source 95, the output of the comparison circuit 94 is inverted and changes to a high level. Then, since the transistor 96 is turned on, part of the current that has flowed from the output 2 through the resistor 41 of the voltage dividing circuit 40 flows through the resistor 97 and the transistor 96. As a result, the resistor 42 and the resistor 97 are connected in parallel, and the feedback voltage is
The voltage becomes lower than before the transistor 96 turns on.

The subsequent operations are as explained using Figure 2.
By monitoring the switching stop detection signal output 3 externally, a switching stop abnormality can be definitely displayed.

It should be noted that the above-mentioned embodiment is a typical example, and it goes without saying that the same applies to various switching type power supplies including push-pull/flyback type power supplies.

〔Effect of the invention〕

As explained above, according to the present invention, a switching power supply for parallel operation is provided with a switching stop detection circuit and a feedback voltage adjustment circuit that extract a part of the switching waveform and monitor the switching operation. By preventing switching from completely stopping, there is an effect that false detection of switching stop can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of a switching type power supply for parallel operation according to the present invention, Fig. 2 is a circuit diagram showing a first embodiment of the invention, and Fig. 3 is a circuit diagram showing a second embodiment of the invention. Fig. 4 is a block diagram showing an example of parallel operation of conventional power supplies; Fig. 5 is a block diagram showing an example of parallel operation of switching type power supplies equipped with a conventional switching stop detection circuit; FIG. 6 is a block diagram showing a partial configuration of a switching type power supply equipped with the switching stop detection circuit shown in FIG. 5. 10... Switching circuit, 20... Buck-boost circuit, 30... Rectifying and smoothing circuit, 40... Voltage dividing circuit,
50... Comparison circuit, 60... Reference voltage source, 70...
... Switching control circuit, 80 ... Switching stop detection circuit, 90 ... Feedback voltage adjustment circuit.

Claims (1)

[Claims] 1 A switching type power supply used when at least two or more units are operated in parallel with their outputs directly connected, which includes a switching circuit that converts the input DC voltage into a rectangular wave, a circuit that steps up and down the rectangular wave voltage, and a switching circuit that converts the input DC voltage into a rectangular wave. A rectifier and smoothing circuit that rectifies and smoothes a rectangular wave voltage that has been stepped up and down to obtain an output DC voltage, a reference voltage source that supplies a constant reference voltage, and a voltage divider circuit that divides the output DC voltage and generates a feedback voltage. In a switching type power supply, the switching type power supply is composed of a comparison circuit that compares the feedback voltage and the reference voltage, and a switching control circuit that performs negative feedback control of switching of the switching circuit using the output of the comparison circuit. A switching stop detection circuit for monitoring switching operation and the output of the switching stop detection circuit are inputted, and the output is connected to a connection point between the voltage dividing circuit and the comparison circuit to adjust the feedback voltage. A switching type power supply for parallel operation characterized by being equipped with a feedback voltage adjustment circuit.