JPS6399769A - Dc/dc converter - Google Patents

Abstract

PURPOSE:To enable high-speed switching to be performed, and attenuate noise, by generating false random number pulse from a false random number generator, and by controlling a switching element with the pulse. CONSTITUTION:A DC power source 11 is switched by a switching element 12, and is rectified from the secondary side of a transformer 13 via switching gates 14-15, and current is fed to a load 17 via a smoothing circuit 16. In this case, a pseudo random number generator 18 is set, and by a clock from a clock generator 19, the false random number generator 18 is driven, and a false random number pulse train is generated, and by the pulse train, the switching element 12 is switching-controlled. Said gates 14-15 rectifying the secondary side output voltage or the transformer 13 are opened or closed via a preset counter 29 and a flipflop 28 through a correlation unit 22. Then, the false random number pulse is almost generated at random, and so the pulse is not fed back to the primary side and can be controlled by the secondary side only.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention is used in DC power supplies, chargers, uninterruptible power supplies, etc. for electronic equipment, and switches DC power, supplies the switching output to a transformer, This invention relates to a DC/DCC/formula that obtains desired DC power by rectifying and smoothing the output of the transformer.

``Prior Art'' This type of DC/DC converter is generally referred to as a switching regulator. Various methods are used to adjust the voltage on the load side. The current mainstream method is a pulse width modulation method that adjusts the on period for switching the DC power supply output to 3Pl. That is, the deviation of the load voltage from the set value is detected, and the pulse width for controlling the primary side switching element is adjusted in accordance with this deviation.

At this time, in order to avoid mixing between the primary and secondary sides and to provide direct current isolation, a photocoupler or 1% auxiliary transformer is used to convert the deviation detected on the secondary side into the primary side. There are 17 people on the side. This made the circuit complicated.

Currently, the greatest effort in the development of this type of DC/DC converter is to increase the switching frequency. This reduces the size of transformers and smoothing circuit components,
This is due to the fact that it can be implemented at a high μ degree. The current standard is generally considered to be high if the switching frequency is 500 ktLz or higher. However, MO3-FE for electric power
The performance of T is significantly improved, and experimental results have been reported in the United States for switching at 1.5 Mllz.

The loss during high-speed switching is 11 due to switching.
It is said that the on-resistance value is more important than the loss. Transistors with a cutoff frequency of 5 MHz or higher and low on-resistance values are already commercially available. Therefore, high-speed switching is possible in this respect. However, a pure digital control system using a microcomputer
/DC comparator is also being researched, but there is a limit to processing speed with the method of importing numerical values, calculating and outputting them.
It is still under development.

An object of the present invention is to provide a C/DC converter which performs digital control, is capable of high-speed switching, has low noise, and has a simple structure.

[Means for Solving the Problems] According to the present invention, one pseudo-random number pulse is generated from the td(U random number generator, and the switching element is controlled by this pseudo-random number pulse to switch the DC power. The DC output thus generated is supplied to the transformer, and the output on the secondary side of the transformer is branched and supplied to the correlator, which generates a pulse every period of the pseudorandom number. The output of the next side is rectified, further smoothed by a smoothing circuit, and supplied to the load.The deviation of the load voltage from the reference voltage is detected by a comparator, and the digital value corresponding to the deviation is applied to the transformer. The secondary side output pulses are counted by a counter every time a pulse is obtained from the correlator.The gate is controlled by the output of the counter, and a period corresponding to the counting period, that is, a counting period or a non-counting period. The rectified output of the secondary side output of the transformer is supplied to the smoothing circuit.

For example, for M-series pseudo-random numbers, when using an n-stage shift register, (2''-1> pseudo-random number sequences are obtained. Even if you use l-focus software, the cross correlation between each pseudo-random number sequence is On the other hand, autocorrelation alone is significant, so if you select a specific random number sequence and input M-sequence pseudo-random numbers to an autocorrelator specific to that random number sequence, the correlator will produce , (2'-1) bits.If the interval between these correlation output pulses is one frame, within that frame, from the end of the frame, a pulse is generated for any length from 0 to (2'-1). )) bit strings can be created. The counting period of the counter corresponds to the length from the frame end within one frame according to the deviation value, and since the rectified output is supplied to the smoothing circuit during this period, a voltage corresponding to the deviation is output. become. Note that the pseudorandom number pulse has approximately the same number of "1"s and 0s within one frame,
Since these occur almost randomly, the output voltage can be controlled with an accuracy of approximately 2 n-+ .

It can be controlled only on the secondary side without feedback to the primary side, almost digitally, and pseudo-random pulses can be generated relatively easily even at high frequencies.

"Example" The present invention will be described in detail with reference to FIG.

The DC output of the DC power supply 11 is switched by the switching element 12 and output to the transformer 1 as AC including a DC component.
I am guided by 3. Both ends of the secondary side of the transformer 13 are connected to one end of each of the switching gates 14 and 15, and the other ends of the switching gates 14 and 15 are connected to each other. The point is connected to a load 17 via a smoothing circuit 16. The AC power obtained on the secondary side of the transformer 13 is double-wave rectified by the switching gates 14 and 15, and the rectified output is converted to DC by the smoothing circuit 16.

In this invention, a pseudo-random number generator 18 is provided, and the pseudo-random number generator 18 is driven by a clock from a clock generator 19 to generate a pseudo-random number pulse train, and switching of the switching element 12 is controlled by this pseudo-random number pulse train. Therefore, the input voltage waveform of the transformer 13 becomes a pseudo-random pulse waveform. The secondary voltage waveform of the transformer 13 is an alternating current of pseudo-random number pulses.

The secondary output voltage of the transformer 13 is half-wave rectified by a waveform shaper 21 and guided to a correlator 22 as a pulse waveform.

The correlator 22 outputs one pulse each time a set pseudo-random number pulse train is input.

For example, the correlator 22 is provided with a shift register 23 having shift stages equal to one frame of the pseudo-random number pulse train of the pseudo-random number generator 18. The sum of the outputs of the remaining shift stages is added to the inverted version, and a pulse is output when the value exceeds a predetermined value. The load voltage is detected by the voltage detection circuit 24, and compared with the reference voltage of the reference voltage source 25 by the comparator 26 to determine the basis of the load voltage! 1! Deviations to the voltage are detected. This deviation signal is sent to the A/D converter 27
is converted to a digital value. When a pulse is output from the correlator 22, the flip-flop 28 is turned on, and its output opens the switching gate 14.15. At the same time, the deviation digital value of the A/D converter 27 is preset in the preset counter 29 by the output pulse of the correlator 22, and the counter 29 starts counting down.Each output from both ends of the secondary side of the transformer 13 has a waveform. Shaping circuit 2
1.31, and the output pulse trains from these waveform shaping circuits 21 and 31 are inputted to the preset counter 29 as a counting clock through an OR gate 32.

When the preset counter 29 counts pulses by the preset value, the preset counter 29 sends a reset pulse to the flip-flop 28, and at the same time the switching gates 14 and 15 close, the preset counter 29
8 itself also stops counting. When the pseudo-random number generator 18 is configured with, for example, a seven-stage shift register, the length of one frame of the pseudo-random number pulse train is 127 bits, the preset counter 29 is configured with 7 bits, and the A/D converter 2
7 is a 7-bit 7-bit output. The correlator 22 may be configured using a surface acoustic wave device, a charge-coupled device, or the like, other than the 127-stage shift register 23, an adder, and a phase inverter.

If the clock frequency of the clock generator 19 is approximately 3 MHz, and the repetition bit length of the pseudorandom pulse train, that is, one frame is 127 bits, the repetition frequency of the output pulse of the correlator 22 is 23.6 kHz, which is an audio frequency. The output digital value of the A/D converter 27 is set to 127 at maximum load, which is a sufficiently higher value and does not generate audible frequency noise. Comparator 2 during normal use negative part
6 becomes 0, and the A/D converter 27 adjusts so as to output the optimal preset value when the analog human power is 0. Sensitivity adjustment can be performed by adjusting the gain of the comparator 26. When integral control and differential control are added, respective analog circuits (which can be realized by circuits using operational amplifiers) may be inserted between the comparator 26 and the A/D converter 27.

When the load voltage becomes higher than the reference voltage, the precent value for the counter 29 decreases and switching control is performed)14.
15 becomes shorter and the load voltage decreases. Conversely, when the load voltage becomes lower than the reference voltage, the preset value increases and the switching control 1-1
4. The time spent during each step of 15 becomes longer and the load voltage increases.

In this way the load voltage is held constant.

The output pulse of the correlator 22 resets the flip-flop 28, the output of the preset counter 29 sets the flip-flop 28, and the value preset to the preset counter 29 correspondingly increases as the load voltage increases. You can.

``Effects of the Invention'' As described above, according to the present invention, since the control signal is not routed from the secondary side to the primary side of the transformer, there is no need for direct current insulation coupling of the control signal. The circuit is simplified accordingly, and there is essentially no need to worry about contact between the primary and secondary sides of the transformer.

Since it can be operated at a high frequency, main circuit elements such as the transformer 13, the choke of the smoothing circuit 16, and the capacitor can be made smaller.

Control systems using normal IC elements have a frequency limit of 1
Although on the order of 0MTo, the frequency limit of pseudorandom number systems is much higher. For example, the frequency limit of a surface acoustic wave device is about 1.5 GHz, and the determining factor for the operating frequency limit is rather the frequency characteristics of the main circuit switching element, but as mentioned above, the on-resistance of a transistor is There are low loss types, and low loss types can be easily obtained.

By changing the bit length of one frame of the pseudorandom pulse train, design accuracy can be freely selected, and in order to increase control accuracy, the bit length of one frame can be increased.

- In the case of a DC/DC converter that is implemented in a C-type manner, there is noise emission from a specific frequency, and it is necessary to take countermeasures against this.
Four considerations have been made. However, in the present invention, since the direct current is switched using pseudo-random numbers, the frequency spectrum is spread over a wide band and low-level white noise is produced, so that noise radiation can be easily dealt with.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the DC/DC converter of the present invention. Patent applicant: Asahi Kasei Industries Co., Ltd. Agent: Takashi Kusano

Claims (1)

[Claims] (1) Switch the output of the DC power supply with a switching element, supply the switched output to the transformer,
DC/D that rectifies the AC power obtained on the secondary side of the transformer, smooths the rectified output with a smoothing circuit, and supplies it to the load.
In the C converter, a pseudo-random number generator generates pseudo-random number pulses and supplies them as a switching control signal to the switching element, and the secondary output of the transformer is branched and supplied, and a pulse is output for each period of the pseudo-random number. a comparator that detects the deviation of the voltage of the load from the reference voltage; and a comparator that detects the deviation of the voltage of the load from the reference voltage, and a digital value corresponding to the deviation detected by the comparator. a counter that counts pseudorandom pulses of the secondary side output; and a gate that is controlled by the output of the counter and supplies the rectified output of the secondary side output of the transformer to the smoothing circuit for a period corresponding to the counting period. A DC/DC converter comprising: