JPH08126303A - Power supply - Google Patents

Abstract

PURPOSE: To eliminate the need of adding peripheral parts to a power unit or changing the peripheral parts of the power unit at the time of adding a function by controlling the opening/closing of a switching element which controls the output voltage of the power unit by using software only. CONSTITUTION: An A/D converter incorporated in a microcomputer 8 measures voltage V and converts the voltage V into digital data. When the value of the digital data are larger than a prefixed reference value, the close period of a switching element 7 is made shorter and, when the data are smaller than the reference value, the close period of the element 7 is made longer. Such control can be realized when the timer function generally incorporated in the program of the microcomputer 8 is used. In other words. the open/close period of the element 7 and control value (reference value) of the output voltage depend only on the software of the microcomputer 8. Therefore, even when the specification of the power supply is changed, the power supply can be made to cope with the change by only modifying the software without requiring the addition of other parts or change of used parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device.

[0002]

2. Description of the Related Art Conventionally, a converter type power supply for converting an alternating current into a direct current has a discrete component and some dedicated ICs.
Was composed of.

[0003]

Since the conventional power source is composed entirely of hardware, it is necessary to add or replace parts every time the specifications are changed. Also, when adding a new function such as a protection function, it is necessary to add a dedicated circuit.

[0004]

A converter type power supply circuit is controlled by using an AD converter and a microcomputer. AD
The converter converts the output voltage, input voltage, etc. of the power supply circuit into digital data. Based on the conversion result, the microcomputer performs a calculation by a predetermined program process to open / close the switch element. The switch element here is to chop the input voltage, and energy is accumulated in the choke coil while the switch element is closed. On the contrary, in the open period, the energy is output as the output voltage. Therefore, the output voltage can be controlled by controlling the opening / closing time of the switch element.

[0005]

According to the present invention, the open / close control of the switch element for controlling the output voltage is entirely executed by software. Therefore, even when the value of the output voltage to be controlled is changed, only the software needs to be changed, and the peripheral components are not added or changed. If the output voltage and input voltage are monitored by the AD converter built in the microcomputer, even if these voltages become abnormally high, it is possible to perform a protective operation such as stopping the operation of the switch element by judging it by software. is there. All of these functions can also be implemented by software, so there is no need to add or change peripheral components as the functions are added.

[0006]

EXAMPLE An example of the present invention will be described with reference to FIG. In the figure, 1 is an AC power supply, 2 is a rectifier, 3 is a choke coil,
Reference numeral 4 is a diode, 5 is a capacitor, 6 is a load, 7 is a switching element, and 8 is a microcomputer with a built-in AD converter.
The microcomputer 8 controls opening / closing of the switch element 7. The energy of the AC power supply 1 rectified by the rectifier 2 is accumulated in the choke coil 3 while the switch element 7 is closed. After that, the energy accumulated when the switch element 7 is opened is smoothed by the capacitor 5 via the diode 4 and output as a DC voltage. The output voltage V at this time increases as the energy stored in the choke coil 3 increases. The energy accumulated in the choke coil 3 increases as the closing period of the switch element 7 increases. Therefore, it can be seen that the voltage V can be controlled by the length of the closing period of the switch element. That is, if the closing period is lengthened, the voltage V increases, and if it is shortened, the voltage V decreases. Utilizing this, the voltage V is measured by the AD converter incorporated in the microcomputer 8 and converted into digital data, and if the value is larger than a predetermined reference value, the closing period of the switch element 7 is shortened. If it is small, the voltage V can be controlled to be constant by increasing the closing period. Such control can be realized by executing a program of a microcomputer or by using a timer function generally incorporated in the microcomputer. The timer function is a function in which when a microcomputer sets a value in the timer by a program, a hardware timer operates and an interrupt or the like occurs after a time corresponding to the set value has elapsed. Since it is not necessary to measure the time programmatically, the load on the software can be reduced. The process using the timer function will be described with reference to FIG. First, the value of the closed period of the switch element 7 is set in the timer, and the switch element 7 is closed. The timer measures time independently of the program using a clock of a predetermined frequency. The program monitors whether the time according to the value set in the timer has elapsed. When the time has passed, the switching element 7
The value of the open period of is newly set in the timer and the switch element 7 is opened. After that, the AD converter is activated to measure the voltage V, and the error from the reference value is calculated. The closing period and the opening period of the switch element 7 are updated based on the calculation result. After that, when the time corresponding to the value set by the timer has been measured, the process returns to the beginning. As a means for the program to recognize the end of the time measurement of the timer, either means for periodically monitoring the measured value of the timer as described above or an interrupt generated by the timer at the end of the time measurement of the timer may be used. In the above operation, the open / close cycle of the switch element 7 and the control value (reference value) of the output voltage all depend only on the software of the microcomputer 8. Therefore, even if the specifications of the power supply typified by this change, it is not necessary to add or change other parts if only the software is modified. In addition, the effect of the present invention does not change even if the filter processing is applied to the flow of FIG. For example, the method of calculating the error may be the average value of the errors of the past N times. In this case, the system is resistant to noise mixed in the terminals of the AD converter.

Another embodiment of the present invention will be described with reference to FIG. The basic processing flow of the microcomputer in this case is the same as in FIG. In addition, the microcomputer 8 is a built-in AD converter that monitors the output of the rectifier 2 and detects a momentary interruption of the input voltage. If a momentary interruption is detected, the switch element 13 is closed for a predetermined period of time, and power is supplied from the capacitor 12. Diode 12 is intended to prevent discharge of capacitor 12 during normal operation. This allows
Even if the input voltage drops for a certain period of time, stable power can be supplied.

Another embodiment of the present invention will be described with reference to FIG. In the figure, 9 is a current detecting means, which outputs a voltage substantially proportional to the current to the microcomputer 8. The closing period of the switch element 7 is determined by the timer built in the microcomputer as in the flow of FIG. 2, but during the opening period, the microcomputer 8 monitors the output of the current detecting means 9 and opens when the current becomes zero. After the period ends, the switch element 7 is closed again. In this method, since the switch element 7 is closed after the current value is always zero, if the closing period of the switch element 7 is almost constant, the locus of the peak value of the current is substantially proportional to the input voltage as shown in FIG. To do. This is because the current value I when the switching element 7 is closed for T seconds when the current is zero is L, where the inductance of the choke coil 3 is V, and V is the input voltage.

[0009]

This is because I = V × T / L, which is proportional to the input voltage V. Here, the closed period T of the switch element 7 is sufficiently shorter than the changing period of the input voltage V, and the input voltage V can be regarded as constant during the period. In FIG. 5, 30 is an input voltage, 31 is an input current, 3
Reference numeral 2 is a signal for controlling the switch element 7. Switch element 7 closes when 32 is high. From FIG. 5, that is, the average value of the input current is proportional to the input voltage, which means that the power factor is higher than that of a rectifier circuit composed of a simple diode and a capacitor. There is also an effect that the harmonic components generated by the power source are small.

Another embodiment of a power supply that provides a high power factor will be described with reference to FIG. In this embodiment, the microcomputer 8 AD-converts the output of the rectifier 2 to detect the time A when the voltage becomes zero. After that, the open / close period of the switch element 7 may be controlled so that the output of the current detection unit 9 draws a sine waveform according to the elapsed time from the time A. Specifically, the microcomputer has a reference of a current value according to the elapsed time from time A as a table, and when the AD conversion result of the output of the current detection means 9 is larger than this reference value, the switch element 7 Is opened to stop the current, and when the current is small, the switch element 7 is closed and the operation of passing the current is repeated. To change the output voltage value, each reference value may be multiplied by N. However, N is a positive real number here. In this method, the current waveform approaches the voltage waveform as shown in FIG. 6, and the peak value of the current becomes lower than that in FIG. 5, so the withstand current value of the switch element can be reduced, and the input voltage due to harmonic interference or wiring resistance can be reduced. Can be prevented.

In the microcomputer used in the above-mentioned embodiment,
Furthermore, by providing a communication function, the output voltage is turned on externally,
If it can be turned off or the voltage value can be controlled, the power supply device can be applied in a wider range. Further, the control signal for opening and closing the switch element 7 is generated by hardware different from the microcomputer, and if the open period, the closed period, the repetition frequency, etc. can be set by software, the effect of the present invention will not change. Absent. Further, in the above-described embodiments, the boost converter is taken as an example, but the effect of the present invention is the same in any method as long as the output voltage can be controlled by opening / closing the switch element.

[0012]

According to the present invention, the output voltage value and the abnormality detection level are set by the software of the microcomputer. Therefore, when these specifications are changed, no parts are added or changed. As a result, it is possible to use one type of hardware as a power source with various specifications by simply changing the software, and productivity is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart of a microcomputer process of the first embodiment.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a third embodiment of the present invention.

FIG. 5 is a current and voltage waveform diagram of the third embodiment.

FIG. 6 is a current / voltage waveform diagram of the fourth embodiment.

[Explanation of symbols]

 1 ... AC power supply, 2 ... Rectifier, 3 ... Inductance, 4 ... Diode, 5 ... Capacitor, 6 ... Load, 7 ... Switch element, 8 ... Microcomputer, 9 ... Current detection means, 11 ... Diode, 12 ... Capacitor, 13 ... Switch element, 30 ... Voltage waveform, 31 ... Current waveform, 32 ... Switch control signal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Motohiro Sugino, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture, Hitachi Image Information Systems Co., Ltd. (72) Kenji Kawabata, 888, Fujihashi, Ome, Tokyo 888, Hitachi Factory Living Equipment Division

Claims (4)

[Claims] 1. A rectifying means for rectifying an AC voltage, an inductance, a switch means, and a control means, wherein the inductance stores electric power output by the rectifier means during a closed period of the switch means, In the power supply device that discharges the electric power accumulated in the open period of the means to drive the load, the control means measures the voltage applied to the load, and the microcomputer performs a predetermined program processing on the result and executes the processing. A power supply device characterized in that the voltage applied to the load is controlled by opening and closing the switch means at a timing based on the result. 2. The power supply device according to claim 1, wherein, in the program processing, the open period and the closed period of the switch means or one of them is measured by using a timer function built in a microcomputer. 3. The output of the rectifying means is grounded via a diode and a capacitor, has a second switch means connected in parallel with the diode, and the microcomputer has an output voltage of the rectifying means. 2. The power supply device according to claim 1, wherein the second switch means is closed and the power is continuously supplied from the capacitor when the period is decreased. 4. The microcomputer has communication means with the outside, transmits the internal state to the outside, and changes the output voltage and stops or starts the operation according to an external command. The power supply device according to item 1.