JPH0321194Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention has a DC stabilized power supply, in particular, a plurality of self-excited forward converters connected in parallel,
It relates to a DC stabilized power supply that can approximately equalize the current level supplied to the load from each of these converters.

2. Description of the Related Art A DC stabilized power supply having a plurality of separately excited converters connected in parallel has already been used as a large-capacity power supply. For example, this DC stabilized power supply consists of a plurality of converters in which the primary winding of a transformer and a switching element are connected in series, and a stabilized DC output is extracted from the secondary winding of the transformer. The switching element is controlled by a control circuit having an oscillator provided commonly to each converter.

Problems to be Solved by the Invention In the conventional DC stabilized power supply configured as described above, a slight difference in the set value of the output voltage of each converter causes an imbalance in the load current shared by each converter. That is, all or most of the load current will flow to the converter whose output voltage setting is higher. Therefore, the amount of heat generated by the converter through which a large load current flows increases, and the life of the DC stabilized power supply is shortened. Additionally, when the allowable current supplied from one converter reaches its maximum, the current cannot be increased any further even if there is some margin in the current supplied from the other converter, which limits the range of use of the device itself. There are drawbacks. Furthermore, the control circuit becomes complicated, making it difficult to downsize.

The object of the present invention is to provide a compact DC stabilized power supply that has a plurality of self-excited forward converters connected in parallel to each other and can substantially equalize the current level supplied to the load from these converters. .

Means for Solving the Problems In the DC stabilized power supply of the present invention, the primary winding of the transformer and the switching element are connected in series, and the series circuit of the tertiary winding of the transformer and the capacitor is connected to the switching element. A stabilized DC output is provided from a common output terminal connected to the secondary winding of the transformer by connecting a control element to a control terminal of the element, and connecting a control element for controlling on/off of the switching element to the control terminal. In a DC stabilized power supply including a plurality of self-excited forward converters connected in parallel, each converter is provided with a peak current detection circuit for detecting the peak current flowing through the switching element, and a peak current detection circuit is provided at the common output terminal. A common error amplification circuit is provided, and the control element in the converter is driven for each converter based on the detection voltage of the peak current detection circuit in the converter and the output voltage of the common error amplification circuit. Configure.

Function: A peak current detection circuit detects the current flowing through each switching element of a plurality of self-excited forward converters, and a common error amplification circuit controls the current in accordance with the output voltage level. Therefore, the current flowing through each switching element becomes uniform, and the load current level of the converter becomes equal.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

First, FIG. 1 showing an embodiment of the present invention will be described. The DC stabilized power supply of the present invention has a plurality of self-excited forward converters 7 and 8 connected in parallel to a common input terminal 1 and a common output terminal 4. In one self-excited forward converter 7, the primary winding 11 of the transformer 9, the transistor 10, and the resistor 22 are connected in series between the positive terminal 2 and the negative terminal 3 of the common input terminal 1. be done. The resistor 22 has a function as a peak current detection element as described later. Secondary winding 12 of transformer 9
is connected to the common output terminal 4 through the rectifying and smoothing circuit 13.
It is connected to the positive side terminal 5 and the negative side terminal 6 of. The rectifying and smoothing circuit 13 includes a rectifying diode 14 and smoothing circuits 15 and 2 connected in series between one end of the secondary winding 12 and the positive terminal 5 of the common output terminal 4.
A diode 16 is connected between the other end of the secondary winding 12 and one end of the smoothing circuit 15, and a capacitor 17 is connected to the other end of the smoothing circuit 15 and the other end of the secondary winding 12. Common output terminal 4
is connected to a load (not shown), which is supplied with a stabilized DC output.

A drive circuit 20 is connected to the gate of the transistor 10.
is connected. That is, the drive circuit 20 is connected to the transformer 9
The tertiary winding 21 has a tertiary winding 21, and one end of the tertiary winding 21 is
It is connected to the gate of the transistor 10 through the capacitor 23, and the other end of the tertiary winding 21 is connected between the source of the transistor 10 and the resistor 22. The gate of the transistor 10 is connected to the starting resistor 1.
It is connected to the positive side terminal 2 through 8.

Further, the gate of the transistor 10 is connected via a diode 24 to the collector of a transistor 25 as a control element that controls on/off of the transistor 10, and the emitter of the transistor 25 is connected to the negative terminal 3.

A peak current detection circuit 26 is connected to the base of the transistor 25. Peak current detection circuit 2
6 consists of the resistor 22, a capacitor 27, and a resistor 28 connected in parallel. One end of each of the capacitor 27 and the resistor 28 is connected to the tertiary winding 21.
The other ends of the capacitor 27 and the resistor 28 are connected to the base of the transistor 25.

The base of the transistor 25 is further connected to an error amplification circuit 32 through a resistor 30 and a backflow blocking diode 31 connected in series. The error amplifier circuit 32 includes an error amplifier 33 and a reference voltage power supply 34 connected to an inverting input terminal of the error amplifier 33. The output terminal of the error amplifier 33 is connected to the diode 31, and the non-inverting input terminal of the error amplifier 33 is connected to the positive terminal 5 of the common output terminal 4. Further, the reference voltage power supply 34 is connected to the negative side terminal 6. Therefore, transistor 2
The output of the error amplifier circuit 32 and the output of the peak current detection circuit 26 are supplied to the base of the circuit 5.

The other self-excited forward converter 8 is configured in the same manner as the self-excited forward converter 7, and the same parts as those of the converter 7 are denoted by the same reference numerals, and the description thereof will be omitted.

In the above configuration, when the power is turned on, converter 7
Then, the capacitor 23 is charged through the starting resistor 18 and a voltage is applied to the gate of the transistor 10, so the transistor 10 is turned on.
Current flows through the positive terminal 2, the primary winding 11, the transistor 10, and the negative terminal 3. At this time,
A voltage that forward biases the diode 14 is induced in the secondary winding 12 of the transformer 9, and a current flows from the secondary winding 12 through the rectifying and smoothing circuit 13 to the load connected to the common output terminal 4. Supplied. Also,
Since a voltage that forward biases the transistor 10 is induced in the tertiary winding 21, a gate voltage obtained by adding the voltage of the tertiary winding 21 to the voltage of the capacitor 23 is applied to the transistor 10, and the transistor 10 Remains on. Primary winding 11
acts as an inductance coil, so the current flowing between the drain and source of the transistor 10 increases with time. However, when the current flowing through the resistor 22 increases and the voltage across the resistor 22 increases, the base current flows to the transistor 25 via the capacitor 27 and the resistor 28, and the transistor 2
5 turns on. As a result, the charge in the capacitor 23 is discharged, and the gate voltage of the transistor 10 begins to decrease. When the gate voltage of the transistor 10 decreases, the current between the drain and the source also decreases, so the gate voltage rapidly decreases and the transistor 10 is turned off. Thereafter, when the capacitor 23 is charged via the resistor 18, the transistor 10 is turned on again, and the above operation is repeated.

Next, when the output voltage to the common output terminal 4 increases and becomes higher than a predetermined set value, the output voltage of the error amplifier 33 increases, and base current is supplied to the transistor 25 through the diode 31 and the resistor 30. , the transistor 25 is turned on. As a result, the transistor 10 is turned on, the on period of the transistor 10 is shortened, and the output voltage is returned to the predetermined value. When the output voltage becomes low, the above operation is reversed.

Converter 8 also performs an operation similar to the above operation of converter 7, and a total output of converters 7 and 8 is generated at common output terminal 4.

The peak current flowing through each transistor 10 of the plurality of self-excited forward converters 7 and 8 is detected by a resistor 22, and this current is outputted to a common output terminal 4 by a common error amplification circuit 33. Since it is controlled according to the voltage level, the output voltage of the common output terminal 4 becomes a constant voltage, and the peak current flowing through each transistor 10 of each converter is equalized, so that the load current level is equalized. controlled.

FIG. 2 shows another embodiment of the invention, and this embodiment will be described. In FIG. 2, the same parts as those shown in FIG. 1 are designated by the same reference numerals, and the explanation thereof will be omitted. The gate of the transistor 10 of the self-excited forward converter 7 is connected to a resistor 40.
It is connected to one end of the tertiary winding 21 through the capacitor 23 and the capacitor 23 . One end of the resistor 40 is connected to the gate of the transistor 10, and a CR parallel circuit consisting of a resistor 41 and a capacitor 42 and a reverse current blocking diode 43 are connected in series between the other end of the resistor 40 and one end of the starting resistor 18. Connected. Converter 8 is also configured similarly to converter 7 described above. However, one ends of the starting resistors 18 of the converters 7 and 8 are connected to each other by a conductive wire 44, and an error amplification circuit 32 having a configuration different from that in FIG. 1 is connected to each transistor 25. The error amplifier circuit 32 is an error amplifier 4
5, a reference voltage power supply 49 connected to the inverting input terminal of the error amplifier 45, a light emitting diode 46 that emits light with the output of the error amplifier 45, and a light receiving transistor 47 that receives light from the light emitting diode 46. The emitter of the light receiving transistor 47 is connected to the base of each transistor 25 through the diode 31 and the resistor 30.
The collector of is connected to the negative side terminal 3 of the common input terminal 1 through a power supply 48.

In the above configuration, converters 7 and 8 perform on/off operations in synchronization with each other. This means that if one of the transistors 10 of converters 7 and 8 is turned on early, the starting resistor 18 will be connected to the positive terminal 2.
This is because most of the charging current that was flowing to the capacitor 23 through the converter now flows to the capacitor 23 of the other converter which is not turned on yet. Therefore, the turn-on timing of the other transistor 10 is advanced, and converters 7 and 8 are synchronized even though they are self-excited. In this case, the CR parallel circuit consisting of the resistor 41 and the capacitor 42 has the function of adjusting the current flowing to each capacitor 23 and compensating for the uneven threshold values of the plurality of transistors 10.

The constant voltage control is performed by operating the light emitting diode 46 and the light receiving transistor 47 with the output of the error amplifier 45 corresponding to the output voltage, and supplying a base current to the transistor 25 from the power source 48. Other operations are the same as the circuit shown in FIG.

The above embodiments of the present invention can be further modified within the same technical scope. For example, in the above example,
Although a DC stabilized power supply having two self-excited forward converters 7 and 8 is shown, the present invention can also be implemented in a DC stabilized power supply having three or more self-excited forward converters connected in parallel.

Effects of the invention In the DC stabilized power supply of the invention, a peak current detection circuit detects the current flowing through each switching element of a plurality of self-excited forward converters, and the current is detected by a common error amplification circuit. Since it is controlled according to the level of the output voltage issued to the common output terminal, the output voltage of the common output terminal becomes a constant voltage, and the peak current flowing through each switching element of each converter is equalized, and the load current is The level is controlled to be even.
Therefore, the amount of heat generated by each converter can be made approximately equal, and the life of the DC stabilized power supply is extended.
Additionally, the device is smaller than conventional devices.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of a DC stabilized power supply according to the present invention, and FIG. 2 is a circuit diagram showing another embodiment of the present invention. 1...Common input terminal, 2...Positive side terminal, 3...
...Negative side terminal, 4...Common output terminal, 5...Positive side terminal, 6...Negative side terminal, 7, 8...Self-excited forward converter, 9...Transformer, 10...Transistor (switching element), 11...primary winding,
12... Secondary winding, 13... Rectifier smoothing circuit, 20
... Drive circuit, 21 ... Tertiary winding, 22 ... Resistor, 25 ... Transistor (control element), 26 ...
...Peak current detection circuit, 31...Diode, 3
2...Error amplifier circuit, 33...Error amplifier.

Claims (1)

[Scope of utility model registration request] The primary winding of a transformer and a switching element are connected in series, the tertiary winding of the transformer and a series circuit of a capacitor are connected to a control terminal of the switching element, and the switching element is turned on to the control terminal.・DC stabilization is achieved by connecting multiple self-excited forward converters in parallel, connecting control elements for off-control and extracting stabilized DC output from a common output terminal connected to the secondary winding of the transformer. In the switching power supply, each of the converters is provided with a peak current detection circuit that detects the peak current flowing through the switching element, and a common error amplification circuit is provided at the common output terminal, A DC stabilized power supply characterized in that the control element in the converter is driven based on the detection voltage of the peak current detection circuit and the output voltage of the common error amplification circuit.