JP2009195095A - Input voltage adaptive system power supply apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To expand an operating time and reduce the size and cost in a battery device by improving efficiency of a power supply apparatus. <P>SOLUTION: The apparatus consists of an A/D converter 11, a ROM12, a PWM generator 13, an FET drive circuit 14, an insulating transformer 15, an error amplifier 16, an input portion 10, and an output portion 11. A switching frequency and a duty are optimized to ensure high efficiency in response to an input voltage, by using an inexpensive microcomputer and an ASIC (general logic IC, etc.). Moreover, input information is read by the A/D converter 11, and control data corresponding to the read data is extracted from the ROM 12. The optimized switching frequency, which varies depending on the input voltage, is outputted to the PWM generator 13, to be synthesized with feedback information. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a switching power supply apparatus.

  Electric power is supplied mainly from a direct current (DC) power source represented by a battery and a commercial power source (AC) power source. With the recent development of low-voltage and power-saving technologies, there are various types of power supply required for these power supply devices (power supplies), and research and development on multiple outputs, high efficiency, and miniaturization are progressing daily. ing. These power sources have been developed based on a feedback technique called an analog method. However, in order to respond to technological progress in recent years, there are situations where it is impossible to respond due to control problems, etc. Various power supply devices are trying to solve these problems by introducing digital control system Proposed.

  Among the requirements for the power supply, there are many demands for improving the efficiency of the power supply. In order to respond to such demands, various approaches have been made, such as careful selection of parts used, improvement, and examination of control methods. Specific examples of this include reduction of the ON resistance of the FET that is the switch used, reduction of the input capacitance, and the introduction of a technique called soft switching using a resonant circuit.

  Higher efficiency of the power supply not only brings about economic effects such as reduction of power consumption, but also benefits such as high reliability and long life due to a decrease in heat generation. The so-called battery-powered device that operates in the above-described manner operates with limited energy, so that the operation time of the device is also affected, so that there is an increasing demand for a highly efficient power source.

  These battery drive devices are often premised on the combined use with power supply from commercial power, and in a normal state, power supply from a stable power source with little temporal change is assumed. However, since the output voltage of the battery device decreases with discharge due to its electrochemical characteristics, stable power supply such as a constant input voltage cannot be expected.

  On the other hand, many power supplies respond to input voltage fluctuations, but generally have input fluctuation characteristics in which output efficiency characteristics change. This is because the design is designed so that the rated input at the time of design and the output efficiency at the rated load are maximized based on the power supply from a stable commercial power source that occupies most of the usage time. As a means for solving these problems, it is conceivable to cope with a narrow control range of the conventional analog control, but the correspondence is not simple and is not economical including development costs. In addition, since there are many demands for additional functions such as soft start and overcurrent protection, there are many problems such as cost increase due to the addition of parts and difficulty in miniaturization.

As a method of solving these various problems, as described in Patent Document 1, for example, a digital control type power supply apparatus that responds to fluctuations in output voltage has been proposed.
JP2007-306769

In the case of an input source in which the input voltage fluctuation characteristic can be considered constant for a short time, such as a battery, but the voltage changes due to the discharge characteristic, a decrease in the efficiency of the power supply affects the operation time of the apparatus. From another point of view, it is uneconomical because the maximum possible output efficiency cannot be obtained when using an input voltage value other than the rated value within the input voltage range. In addition, when it is dealt with by adding an additional function, the number of parts increases, which may cause an increase in parts cost and adverse effects on downsizing. In order to solve this problem, even when a digital control technique is introduced, if a microcomputer or the like that consumes a large amount of power is used for the control unit, the efficiency characteristics of the power supply device are affected, which can be a negative effect of higher efficiency. In order to solve the above problems, it is desired to optimize the control method in accordance with the input voltage and the state of the load by using a necessary minimum control microcomputer with low power consumption and improve the efficiency. .
As a patent using these concepts, as disclosed in Japanese Patent Application Laid-Open No. 2003-88110, a proposal has been made to improve efficiency by switching a switching frequency according to an input source. However, in the embodiment, only analog and digital switching methods are used. In addition, the continuous control proposed internally requires a high-performance CPU due to an increase in the amount of calculation in the conventional digital control.
Therefore, the present invention provides a power supply device that can be changed to a more desirable control method at a lower cost while monitoring the input voltage and load conditions, and solves the above-mentioned problems.

  In order to solve the above problem, a control method is used in the power supply apparatus, which monitors the input voltage and the output voltage, and changes the switching frequency and the duty so that the output efficiency is maximized according to each input voltage. A controller capable of changing the switching frequency and duty is provided on the primary side. Further, in order to reduce power consumption in the control unit, the switching frequency and duty are controlled using a microcomputer, ASIC, or the like having relatively low performance for the control unit. This is a technique for reducing the power consumption required for computation because advanced computation required in the digital power supply causes an increase in power consumption.

  In order to minimize the computation, the control for load fluctuations and input fluctuations that are relatively fluctuating is left to the conventional analog method, and the part that cannot be handled by the control is complemented by digital control, and excessive digital computing ability This is a method that is established with a configuration that does not require the above. By using a relatively low speed computer, it is possible to achieve both reduction in power consumption and cost and improvement in efficiency. As a specific calculation method, a method of performing control by making a table of the relation between the result of the calculation in advance and the calculation condition and referring to the table is used. This technique reduces the computation time that requires a lot of time, and makes it possible to implement the necessary functions even with the addition of lower-function hardware.

Moreover, in this power supply device, the overcurrent and overvoltage protection functions in the power supply device are realized by determining the maximum duty using a microcomputer, ASIC, ROM, or the like.

  Therefore, in the switching power supply device of the present invention, the calculation is simplified by using the reference table of the relationship between the input voltage and the optimum switching frequency recorded in the microcomputer, ASIC, ROM, etc. Reduce power consumption of ASIC.

  Optimal control according to the input voltage can be obtained, and operation is possible with the highest possible output efficiency. As a result, it is possible to expect an increase in the operation time of a device that is required to operate with limited energy such as a battery. In addition, the calculation time and the increase in power consumption caused by the addition of control can be reduced by using the tabulation method to minimize the increase in power consumption of microcomputers, ASICs, etc. The effect on efficiency characteristics can also be reduced.

  In addition, the control unit provided on the primary side by adding a microcomputer, ASIC, etc. can also be used for the additional function of the power supply device, contributing to cost reduction and size reduction by reducing the number of parts.

  FIG. 1 is a block diagram of a power supply device. First, this block diagram will be described. This circuit includes an A / D converter 11, a ROM 12, a PWM generator 13, an FET drive circuit 14, an insulating transformer 15, an error amplifier 16, an input unit 10, and an output unit 11. In the power supply circuit, the A / D converter 11, the ROM 12, and the PWM generator 13 are regarded as having an equivalent block configuration even when they are configured by an integrated ASIC or a microcomputer (hereinafter referred to as a microcomputer). In some cases, a microcomputer integrated up to the error amplifier 16 may be used.

The feature of this method is that the information input to the input unit 10 is taken in by the A / D converter 11 and the corresponding control amount is taken out from the ROM 12 which is a data table, and the information obtained from the error amplifier 16 and the PWM generator 13 superimposing is to linearly combine different controls of the input system and the feedback system.
This is to change the basic frequency of PWM, which has been conventionally performed by an analog control IC, at such a speed that does not affect the response characteristics of the analog feedback. In other words, since the frequency uniquely determined in the design stage is dynamically changed according to the use conditions, it is not greatly different from switching the power supply of two dedicated designs. Therefore, it can be seen that if the switching timing is properly performed, it is obvious that the conventional technique is an extension of the prior art, and that it can be easily put into practical use.

The creation of the table is the same as the design method of a general analog control power supply, and is equivalent to storing and using numerically parameters such as a capacitor and a resistor that could not be changed dynamically. If the parameter determined by the conventional design method is switched by a comparator and an analog switch, the equivalent of the present invention can be easily realized, but a more economical and simple method is to use a microcomputer. Good These control parameters may of course be obtained by calculation, but data obtained from experiments may also be used. What is important is that these can be made into a table to reduce the amount of calculation and can be realized with simple hardware.

  The table data created by either method is used for control as follows. First, input information is read by an A / D converter, control data corresponding to the read data is taken out from the ROM 12, and an optimized switching frequency that differs depending on the input voltage is output to the PWM generator 13 to provide feedback information. Let's synthesize. As a result, the calculation time of the microcomputer is shortened and the power consumption is reduced.

  The switching frequency and maximum duty are determined by the input microcomputer. By using this, it is possible to provide additional functions such as overcurrent and overvoltage protection in order to prevent smoke, fire, etc. due to overload, load short circuit, application of excessive voltage, and the like.

  The output voltage adjustment is generated mainly by an error signal from the error amplifier 16 as in the conventional analog switching power supply. When the output power supply is an insulation type, there are a method of obtaining insulation with a photocoupler on the primary side and a secondary side, and a method using an auxiliary transformer, and the position of the error amplifier can be on the primary side or the secondary side. Absent. Therefore, there is no practical problem even if the power source is not only an insulation type but also a non-insulation type.

FIG. 2 shows an embodiment of how to superimpose the feedback control amount and the switching frequency. The phototransistor side is connected to both ends of the primary-side resistor, and the duty is adjusted by using the Schmitt inverter and the change in charge / discharge time by the primary-side capacitor and resistor.
FIG. 3 shows a configuration example in which no photocoupler is used. The output voltage is extracted to the primary side by the auxiliary transformer, and the output voltage is adjusted by changing the duty according to the fluctuation of the voltage. High efficiency and high functionality can be achieved by changing the control method and switching frequency according to the input voltage.

  By increasing the efficiency and functionality of the power supply device, the operation time of the battery drive device can be extended, and by consolidating the control unit, the power supply device can be expected to be reduced in size and cost.

Block Diagram Illustration when using a photocoupler Illustration when the photocoupler is not used

Explanation of symbols

10 Input unit 11 A / D converter 12 ROM
13 PWM generator 14 FET drive circuit 15 transformer (insulation)
16 Error amplifier (insulated)
17 Output section

Claims (3)

  In the power supply device, the input voltage and load conditions are monitored using an inexpensive microcomputer or ASIC (general-purpose logic IC, etc.), and the output efficiency is maximized based on the information on the obtained input voltage values and load conditions. A power supply device characterized by controlling an optimal switching frequency and duty.   In the power supply device described above, the microcomputer, ASIC, etc., use the correspondence table of the input voltage calculated in advance and the optimum switching frequency, thereby shortening the calculation time and reducing the power consumption. The power supply device is characterized in that it can be controlled with a simple and inexpensive device because it requires only a low computing capacity. In the above power supply device, a power supply device capable of realizing an overcurrent, overvoltage function, etc. without adding components by controlling a pair of switching frequency and maximum duty using a microcomputer, ASIC (general-purpose logic IC, etc.) .

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