JPH01270769A - Converter - Google Patents

Abstract

PURPOSE:To suppress an unbalanced current by shortening the conducting time of one switching element in response to the amplitude of the input current of each forward type conversion circuit. CONSTITUTION:A DC voltage Vi is input to the inputs 1 of main circuits of forward conversion circuits A1, B1, high frequency-converted by switching circuits 12, 22, insulated and voltage-converted by transformers 13, 23, and rectified and smoothed by rectifying and smoothing circuits 14, 24 to obtain stable DC voltages V0 at the outputs 2. In order to detect the currents of the conversion circuits A1, B1, a transformer 4 in which one is connected to the input current, and the other is so connected that the input current becomes reverse in polarity, and an output proportional to the two input current difference is provided. The detected current controls the ON time of the output signal of a PWM comparator 35 through a rectifier 31, a voltage comparator 33, a differential amplifier 34, etc. Thus, the input currents of the two conversion circuits A1, B1 are equivalently controlled.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a converter device, and more specifically, when two forward conversion circuits are connected in parallel, the input current of each forward conversion circuit is The present invention relates to a converter device including means for correcting unbalance.

(Prior Art and Problems to be Solved by the Invention) In conventional converter devices, the circuit configuration is determined by the magnitude of output power, and the capacitance or transformer of the switching element used.

In order to reduce the size and weight of the reactor depending on the size of the reactor, the input and output sections of two forward conversion circuits are connected in parallel to increase the output capacity.

FIG. 3 is a block diagram showing a conventional converter device. In FIG. 0, 12.22 is a switching circuit, 13.
23 is a transformer, and 14.24 is a rectification and smoothing output circuit. Switching circuit 12. Trance 13. Rectification smoothing output circuit 14 and switching circuit 22. Trance 23. The rectifying and smoothing output circuit 24 constitutes one forward conversion circuit A and one forward conversion circuit B, respectively. The input and output of each of the forward conversion circuits A and Bo are commonly connected to input 1 and output 2, respectively.

Input DC voltage ■1 to input 1, and switch circuit 12
and 22 perform high frequency conversion, transformers 13 and 23 perform insulation and voltage conversion, and rectification and smoothing output circuits 14 and 24 perform rectification and smoothing to obtain a stable DC voltage V at output 2.

If the circuit constants of the two forward conversion circuits A and Bo are equal and the operations of the switching elements of the switching circuits 12 and 22 are exactly the same, then the two forward conversion circuits A and B are used.

The voltage and current waveforms within are the same.

However, in the actual forward converter circuits A and Bo, it is impossible to make the circuit constants and operations of the switching elements completely the same, resulting in unbalanced voltages and currents.

For example, the accumulation time due to the carrier accumulation effect of switching elements varies depending on the individual switching elements. Therefore, if the operating frequency of the converter device is high,
Alternatively, when the conduction rate of the switching elements is small, especially in an output short-circuit state, the difference in the storage time of each switching element cannot be ignored compared to the conduction time, so the current difference in each of the forward type conversion circuits A0 and B0 cannot be ignored. Equilibrium becomes significant.

Since the output sides of the two forward conversion circuits A6 and Bo are connected in parallel, the sum of the output currents of the forward conversion circuits A and B6 is a constant current equal to the load current. Therefore, for example, if the switching current of the switching element 12 of one forward type conversion circuit A becomes large, the switching current of the switching element 22 of the other forward type conversion circuit B0 inevitably becomes small.
Since the difference in storage time between switching elements 12 and 22 is further expanded, the current imbalance is further expanded.

Forward type conversion circuits A0 and Bo, where an excessive current flows compared to when operating in a balanced state, large capacity switching elements 12 and 22 are required, and the surge voltage due to wiring inductance also increases, which is not shown in the diagram. A large snubber circuit is also required.

For this reason, a conventional method has been to insert a balancing reactor 3 to balance the output current of the transformer 13, 23, but this method requires a large-capacity glue reactor and has the disadvantage of reducing efficiency. This placed constraints on the improvement of technology, economy, and credibility.

An object of the present invention was proposed to improve the above-mentioned drawbacks, and when the DC input and DC output parts of two forward conversion circuits are connected in parallel, the input current of each forward conversion circuit is It is an object of the present invention to provide a parallel-connected converter device that corrects unbalance and balances input terminals without increasing the size of the device or reducing efficiency.

(Means for Solving the Problems) In order to achieve the above object, the present invention connects in parallel the DC input and DC output parts of two forward conversion circuits that operate with a phase difference of 180 degrees, and In a converter device configured to convert an input voltage into a controlled DC voltage and obtain an output current twice the output current of each forward type conversion circuit, an input common to the forward type conversion circuits; a current detection means for detecting the magnitude and direction of the current flowing in the end circuit; an error increaser for feeding back the output voltage and outputting the error with respect to the output voltage reference; a threshold value set by the error output signal of the width amplifier; By performing comparison with the current detection output signal and controlling the pulse width for each pulse in current mode operation, the on-time of the switching circuit elements of the forward type conversion circuit where one input current is small can be extended. The present invention is characterized by comprising an operating time correction means for shortening the on-time of an element of a switching circuit of the other forward type conversion circuit having a larger input current, thereby balancing the currents of the forward type conversion circuits connected in parallel. The gist of the invention is a converter device.

(Example) Examples of the present invention will be described below. Note that the embodiments are merely illustrative, and it goes without saying that various changes and improvements can be made without departing from the spirit of the present invention.

FIG. 1 is a block diagram showing one embodiment of the present invention. In FIG. 1, the main circuits of forward conversion circuits A1 and B input a DC voltage Vi to input 1 as in FIG.
A switching circuit 12.22 performs high frequency conversion, a transformer 13.23 performs insulation and voltage conversion, and a rectification and smoothing output circuit 14.24 performs rectification and smoothing to obtain a stable DC voltage v0 at output 2.

In the present invention, in order to detect the current flowing through the two forward conversion circuits A and B, the - one is connected to receive its input current, and the other is connected so that its input current has opposite polarity. A current transformer 4 is provided which provides an output proportional to the difference between the two input terminals.

The current detected by the current transformer 4 is full-wave rectified by the rectifier circuit 31, inputted to the current comparator 33, and then input to the error amplifier 3.
The error signal output from step 4 is compared with the threshold value. The error amplifier 34 receives the output voltage ■ from the output 2 of the converter device.

is fed back, the error between the output voltage and the reference value of the reference 32 is amplified, and an error output signal is output as a dark value. The PWM comparator 35 receives from the oscillator 36 a clock signal with a frequency twice as high as the operating frequency of the switching circuit 12.22, and determines the timing of the rise of the signal sent to the switching circuit 12.22. Rectifier circuit 3 with IT clear stream comparison 33
1 and the error signal output from the error amplifier 34, and when the current value exceeds the error signal value, a pulse output is sent from the current comparator 33 to the PWM comparator 35. Sent out. PWM comparison section 35
The fall timing of the signal sent to the switching circuit is determined based on the output signal of the current comparator 33, and the on-time of the output signal of the PWM comparator 35 is controlled. Further, the signal from the PWM comparator 35 is multiplied by the flip-flop circuit 37, and this signal and the output from the PWM comparator 35 are input to the pulse distribution circuit 38. It is sent out as a control signal for the switching element No. 22.

FIG. 2 is an operation waveform diagram illustrating the operation of each part of the embodiment circuit shown in FIG. The input current of one DC-DC conversion circuit is shown, and the lower part shows the input current of the other one.

B in FIG. 2 is a signal waveform obtained by rectifying the waveform A in the rectifier circuit 31, and its magnitude is indicated by b. Second
C in the figure is the output of the error amplifier 34, which is an error signal between the output voltage and the output voltage reference 32, and the magnitude thereof is indicated by C. D in FIG. 2 is a clock signal output from the oscillator 36, which determines the timing of the rise of the output signal E from the PWM comparator 35. In B and C of Figure 2,
When the value of b becomes larger than the value of C, a signal is output from the current comparator 33 to the PWM comparator 35, which determines the fall timing of the output signal E. F and G in FIG. 2 are signals obtained by multiplying the signal of E. An output signal H to the switching circuit of one of the forward type conversion circuits is created from E and F. Further, from E and G, an output signal J to the switching circuit of the other forward conversion circuit, which is 180° out of phase with the output signal H, is generated.

In FIG. 2, before time t, the input currents of the two forward converter circuits A and B1 are balanced, and after time t, the input current of one forward converter circuit is balanced. When the value increases, the operating waveform of the output signal to the switching circuit changes.

When the input current of one of the forward conversion circuits increases due to variations in the components of the switching circuits 12 and 22 and variations in the operating time of the switching elements, the detected current of one of the forward conversion circuits A in FIG. 2 increases. , waveform B after rectification becomes larger (waveform B'), PW
The M comparator 35 converts the B° waveform to the error amplifier 34.
By comparing the error signal with the error signal, the width of the output signal, which is the conduction width of the switching circuit, is shortened and the increased current value is reduced, so that the input currents of the two forward converter circuits A1 and B1 are equalized. will be controlled by.

(Effects of the Invention) According to the present invention, as described above, in a converter device in which two forward type conversion circuits are connected in parallel to obtain an output current twice the output current of each forward type conversion circuit. , the conduction time of the switching circuit elements of one forward type conversion circuit is shortened in accordance with the magnitude of the input current of each forward type conversion circuit, and the conduction time of the switching circuit elements of one forward type conversion circuit is shortened. By extending the time, unbalanced current between two forward conversion circuits caused by variations in components or variations in storage time of elements of the switching circuit is suppressed.

As a result, there is no need to insert a reactor into the main circuit, and there is no need to add a large-capacity snubber circuit, making it possible to reduce the size and weight of the converter device, and improve economic efficiency and reliability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an operation waveform diagram explaining the operation of the embodiment of FIG. 1, and FIG. 3 is a block diagram showing a conventional converter device. l... Input 2... Output 4... Current transformer 12, 22... Switching circuit 13, 23... Transformer 14, 24... Rectification smoothing output circuit 31. ... Rectifier circuit 32 ... Output voltage reference 33 ... Current comparison section 34 ... Error amplifier 35 ... PWM comparison section 36 ... Oscillation section 37...Flip-flops 38, 39...Pulse distribution circuit

Claims (1)

[Claims] In a converter device that converts a DC input voltage into a controlled DC voltage by connecting the DC input and DC output parts of two forward type conversion circuits in parallel that operate with a phase difference of 180 degrees, the two forward type conversion circuits A current transformer that detects the input current of the conversion circuit, a means for determining the timing to turn on the switch of the forward type conversion circuit, and an error output of an error amplifier that feeds back the output voltage and outputs the error between the output voltage and the reference value. A converter device comprising means for comparing a signal and a signal obtained by rectifying the output of the current transformer to determine the timing for turning off the switch of the forward type conversion circuit.