Abstract:
A digital electric power inverter comprising: a CPU, a PWM driving circuit, a PWM converting circuit, a rectifying circuit, an AC driving circuit, a DC/AC inverting circuit, an overload detecting circuit, a current detecting circuit and an alarm circuit, the power inverter is characterized by that: the entire circuitry of the electric power inverter is designed to be controlled by the CPU; with the CPU, the overload detecting and inductive load distinction ability, the output of the power inverter can be accurately controlled.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention is related to a digital electric power inverter, and especially to a DC to AC power inverter particularly suitable to be used as a protection circuit module structure to control and protect the elements of the power inverter from being damaged and to be able to provide actuating power for a machine.  
           [0003]    2. Description of the Prior Art  
           [0004]    A conventional electric power inverter is comprised of a plurality of IC&#39;s, when one of the IC&#39;s is lacking, a similar IC shall be changed for it, this will make the entire performance of working influenced, and can increase difficulty of designing. The inferiority in designing thereof for overload protection is shown in FIG. 1; to satisfy the requirement for activating a heavy tool machine in the markets, huge electric power is required, if such a machine is to be actuated, several folds of monetary amount must be paid to purchase an electric power inverter with several folds of functional specification for actuating a small machine.  
           [0005]    For example, a sand wheel needs 200W for running, while the transient power for actuating is over 1000W; therefore, in using such a machine, an electric power inverter of 1000W must be purchased. The reason is that, a conventional electric power inverter triggers a protecting loop to shut outputting in corresponding to the detecting signal from a detecting loop when the output terminal is given a heavy load, to thereby protect the interior electronic elements; this is because that conventional designing has to trigger a protecting line according to the detecting of the output state to turn off the system to protect the product. And this is the defect of the conventional design.  
           [0006]    And a conventional electric power inverter may render the internal detecting loop thereof to mistake a case for a loading short circuit when the output terminal thereof is connected with an inductive load or in actuating a load with a larger current; thereby, a protection loop is triggered to shut outputting, to in turn make a machine not work. This is an unsolvable problem and technical bottleneck of the conventional electric power inverter in that it is unable to distinguish a short circuit from an inductive load.  
           [0007]    Therefore, the motive of the present invention is to improve the conventional electric power inverters to get rid of the above stated defects, and to provide a digital electric power inverter which sufficiently uses the control character of a CPU (a microcomputer). Thereby, the CPU turns off output in time before the output power makes the elements crumbled, in order that the elements can restore their functions; a short time after restoration, the CPU turns on output again, till it once more turns off before the elements are crumbled. The process is repeated again and again, so that the CPU  4  can accurately distinguish a short circuit from a false short circuit according to variation of current and makes suitable disposing and to accumulate the low power outputs made in many times to get the required high actuating power for a load.  
         SUMMARY OF THE INVENTION  
         [0008]    The primary object of the present invention is to provide an intermittently actuated digital electric power inverter that can gradually supply step by step the required actuating transient power output and can effectively automatically judge between a false short circuit and a large power actuating loading to thereby protect the electronic elements therein.  
           [0009]    To achieve the above stated object, the present invention is comprised of a CPU, a PWM driving circuit, a PWM converting circuit, a rectifying circuit, an AC driving circuit, a DC/AC inverting circuit, an overload detecting circuit, a current detecting circuit and an alarm circuit. The present invention is characterized by that: the entire circuitry thereof is designed to be controlled by the CPU; with the CPU, the overload detecting and inductive load distinction ability, the output of the power inverter can be accurately controlled.  
           [0010]    The present invention will be apparent in its content and other features after reading the detailed description of the preferred embodiment thereof in reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a drawing of a current vs. time coordinate showing that a conventional power inverter is unable to satisfy the requirement of a transient current supply;  
         [0012]    [0012]FIG. 2 is a drawing showing comparison of power outputs between the conventional power inverter and the present invention;  
         [0013]    [0013]FIG. 3 is an electric block diagram showing of the present invention;  
         [0014]    [0014]FIG. 4 shows the entire electric circuitry of the present invention; FIG. 5 is an output current curve diagram of the present invention;  
         [0015]    [0015]FIG. 6 is a diagram showing the mode of current output of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    Referring firstly to FIGS. 3 and 4, the present invention is comprised of a current detecting circuit  1 , an overload detecting circuit  2 , a CPU  4 , a high voltage detecting circuit  5 , an alarm circuit  6 , a PWM driving circuit  7 , an AC driving circuit  8 , a voltage regulation circuit (5V)  9 , a PWM converting circuit  10 , a rectifying circuit  11 , a DC/AC inverting circuit  12  and a switch  13 .  
         [0017]    Wherein, the voltage regulation circuit  9  is provided for power supplying for normal operation of the entire circuitry of the power inverter; the CPU  4  is provide for connecting all the detecting circuits; the current detecting circuit  1  is connected with one end thereof to the DC/AC inverting circuit  12 , and with another end thereof to the CPU  4 ; the overload detecting circuit  2  is also connected with one end thereof to the DC/AC inverting circuit  12 , and with another end thereof to the CPU  4 ; the high voltage detecting circuit  5  is connected with one end thereof to the rectifying circuit  11 , and with another end thereof to the CPU  4 ; the alarm circuit  6  is directly connected with the CPU  4 ; the PWM driving circuit  7  is connected with one end thereof to the CPU  4 , with another end thereof to a PWM converting circuit  10 ; the AC driving circuit  8  is connected with one end thereof to the CPU  4 , with another end thereof to the DC/AC inverting circuit  12 ; the PWM converting circuit  10  is connected with one end thereof to the PWM driving circuit  7 , with another end thereof to the rectifying circuit  11 ; the rectifying circuit  11  is connected with one end thereof to the PWM converting circuit  10 , with another end thereof to the DC/AC inverting circuit  12 , it has a high voltage AC output connecting point; the DC/AC inverting circuit  12  connected with the AC driving circuit  8  and the rectifying circuit  11 , the other end thereof is connected separately with the current detecting circuit  1  and the overload detecting circuit  2 , it further has an AC output connecting point.  
         [0018]    Thereby, the CPU  4  controls by cooperation the working of the overload detecting circuit  2 , it turns off output in time before the output power makes the elements crumbled, a short time after restoration, the CPU  4  turns on output again. The process is repeated again and again intermittently to protect the elements from being damaged, and the normal working power for a machine load can be afforded, the larger actuating power for the machine can be provided.  
         [0019]    As shown in FIG. 5, under the outputting mode of serially turning on/off, the CPU  4  can clearly distinguish a short circuit from a false short circuit according to whether the current is always the same or is gradually reduced, and makes suitable disposing.  
         [0020]    And the more detailed combination and functions of present invention are as follows:  
         [0021]    The current detecting circuit  1  is comprised of an operation amplifier (OPA) and a Zener diode connected therewith and a plurality of resistances connected therewith too, it is provided for detecting whether an output means a short circuit or a false short circuit;  
         [0022]    the overload detecting circuit  2  is comprised of an operation amplifier (OPA), a plurality of diodes, resistances and capacitors; it is provided for detecting whether it is overloading and whether the input DC voltage is overly high or overly low;  
         [0023]    the CPU  4  includes a transistor, a plurality of resistances and capacitors, a diode, an operation amplifier (OPA) and an LED  41  composing a microcomputer control loop, in order to provide signals for the PWM driving circuit  7  and the AC driving circuit  8 ;  
         [0024]    the high voltage detecting circuit  5  is comprised of a plurality of transistors, Zener diodes, resistances, a variable resistance and a plurality of capacitors; it is provided for detecting a high voltage state;  
         [0025]    the alarm circuit  6  is comprised of a transistor, a plurality of diodes and resistances, and a buzzer  61 ; it is provided for detecting an abnormal state of the circuitry to provide an alarm;  
         [0026]    the PWM driving circuit  7  is comprised of a plurality of transistors, diodes, resistances and capacitors; it is provided for amplifying and reshaping the output PWM signals output from the CPU  4 ;  
         [0027]    the AC driving circuit  8  is comprised of a plurality of transistors and resistances; it is provided for amplifying the output AC driving signals of the CPU  4 ;  
         [0028]    the voltage regulation circuit  9  is comprised of a voltage regulation IC  91 , a plurality of diodes and capacitors;  
         [0029]    the PWM converting circuit  10  is comprised of a plurality of FET power transistors, resistances, capacitors and two transformers  101 ,  102 ; it is directly supplied with electric power in the mode of DC inputting, and is provided for increasing the voltage of the driving signals amplified and reshaped by the PWM driving circuit  7  through the transformers to generate high frequency AC signals;  
         [0030]    the rectifying circuit  11  is comprised of a plurality of diodes capacitors and resistances; it is directly supplied with electric power in the mode of DC inputting, and is provided for rectifying the high frequency AC signals generated by the PWM converting circuit  10  to generate an AC high voltage;  
         [0031]    the DC/AC inverting circuit  12  is comprised of a plurality of transistors, FET power transistors, diodes, Zener diodes, resistances, capacitors and a heat sensitive resistance; it is provided for converting DC high voltage signals provided by the AC driving circuit  8  into an AC high voltage output.  
         [0032]    The above stated circuitry assembled can make the present invention execute the following actions when the switch  13  is closed to actuate the CPU  4 :  
         [0033]    1. The CPU  4  renders the PWM (pulse wide modulation) driving circuit  7  to generate, amplify and reshape signals, the signals amplified and reshaped are increased in voltage by the transformers  101 ,  102  of the PWM converting circuit  10 , the high frequency AC signals generated after increasing of voltage is rectified by the rectifying circuit  11  to get an AC high voltage.  
         [0034]    2. The CPU  4  renders the AC driving circuit  8  to generate and amplify signals, the signals amplified renders the DC/AC inverting circuit  12  to convert DC high voltage into AC high voltage to generate an AC output.  
         [0035]    3. The DC/AC inverting circuit  12  provides a current signal which is sent to the overload detecting circuit  2 ; the detecting state is sent back to the CPU  4  for analysis and judgment, if it is judged abnormal, the CPU  4  immediately adjust the PWM driving circuit  7  and the AC driving circuit  8  to protect the elements from being damaged.  
         [0036]    4. The high voltage detecting circuit  5  detects a high voltage state and sends the state back to the CPU  4  which executes suitable modulation for the abnormal potential state to make the power supplying state normal.  
         [0037]    5. Under the outputting mode of serially turning on/off, the CPU  4  can clearly distinguish between a short circuit and a false short circuit according to whether the current is always the same or is gradually reduced, and makes suitable disposing.  
         [0038]    Referring to FIGS. 2, 4, the present invention sufficiently utilizes the characteristic of the CPU  4 , thereby, when a machine with the actuating transient power of more than 200W is actuated (such as a sand wheel machine with the actuating transient power of more than 1000W), the present invention nonetheless provides a load with an output power, but the CPU  4  turns off output in time within the tolerated scope of safety before the output power makes the elements crumbled, in order that the elements can restore their functions, a short time after restoration, the CPU  4  turns on output again, till it once more turns off before the elements are crumbled. The process is repeated again and again to protect the elements from being damaged, and the actuating power for a machine can be provided. Therefore, although this is not able to provide all the power to transiently afford the machine requirement, it can gradually supply step by step the required actuating power. In view of this, this mode of operation can provide a 200W electric power inverter for actuating a 200W sand wheel machine, it does not require a 1000W electric power inverter for actuating as is the case of a conventional power inverter.  
         [0039]    In using the electric power inverter of the present invention, to avoid loading short-circuit which may induce extreme large current at the output terminal to burn out the power inverter; in reactivating of many electric inductive machines, the current required is far larger than that for normal using, this may make a quasi short circuit (hence it is called a false short circuit) which is unable to be distinguished. In this view, as shown in FIGS. 5, 6, the present invention adopts the outputting mode of serially turning on/off, it is very hard to distinguish between a genuine short circuit and false short circuit during the initial detecting; but after serially turning on/off, the CPU  4  can clearly distinguish according to whether the current is always the same or is gradually reduced to thereby easily judge between a genuine short circuit and false short circuit. If the detecting gives the result of being gradually reduced, the outputting is going on till the load is actuated to run as is normal; on the contrary, every time when the on/off current is abnormally large and there is no tendency of becoming smaller, the CPU  4  makes suitable disposing to turn off the output to thereby protect the electronic elements therein.  
         [0040]    In conclusion, the present invention can surely obtain the object stated above after one reviewing the content disclosed hereinbefore, it thereby provides the digital power inverter that can gradually supply step by step the required actuating transient power output. Having thus described the present invention with practicability,