KR20010065378A - Apparatus for variableness of driving frequency power controller - Google Patents

Abstract

PURPOSE: An apparatus for variableness of driving frequency power controller is provided which controls the driving frequency of a piezoelectric transformer with a PWM IC and comparator corresponding to variations in input voltage and frequency in order to allow an inverter using the piezoelectric transformer to use the characteristics of the transformer. CONSTITUTION: A power controller for varying a driving frequency includes a piezoelectric transformer(T1) that has a predetermined driving frequency and boosts a DC driving voltage transmitted from outside to output the DC voltage as an AC driving voltage, and a cold cathode discharge lamp(12) for emitting light according to the AC driving voltage. The power controller further has a comparator for detecting voltages and currents input/output to/from the discharge lamp and compares them to send the compared result to the system, and a frequency converter for receiving the compared result to control a pulse width to change the driving frequency of the piezoelectric transformer and generating a fixed frequency. The power controller also has a switch(11) for receiving the fixed frequency to generate a corresponding switching frequency and transmitting the switching frequency to the piezoelectric transformer to determine if the transformer is driven or not.

Description

Power control device for variable driving frequency {Apparatus for variableness of driving frequency power controller}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power control apparatus for changing a driving frequency for changing a driving frequency of a DC / AC inverter using a piezoelectric transformer, and in particular, a pulse width modulation integrated circuit (PWM) and a comparator. The present invention relates to a power control device for changing a driving frequency that can increase the overall efficiency of an inverter by automatically adjusting the driving frequency according to an input or output condition.

In general, a DC / AC inverter is a kind of power conversion device, and means a device for exchanging DC power with AC power. A voltage is boosted to a predetermined level using a piezoelectric transformer.

As shown in FIG. 1 and FIG. 2, the piezoelectric transformer 1 has a rectangular parallelepiped shape, and an input voltage Vi having a constant driving frequency f ₀ and an amplitude is input to an input side thereof. The output side outputs an output voltage Vo having the same driving frequency as that of the input voltage and having an amplitude which is raised by a predetermined level from the amplitude of the input voltage.

At this time, an input voltage corresponding to the driving frequency must be input to the input side of the piezoelectric transformer 1. If the driving frequency of the piezoelectric transformer 1 and the driving frequency of the input voltage are different from each other, the piezoelectric transformer 1 may not function properly as a transformer, and a desired boost in the system may be performed at the output side of the piezoelectric transformer 1. Rain output voltage cannot be obtained. Therefore, the driving frequency of the piezoelectric transformer 1 should always be constant, and the driving frequency of the piezoelectric transformer 1 should not be changed according to the change of the input voltage or the load.

3 shows a configuration of a DC / AC inverter using the piezoelectric transformer 1.

A DC voltage supply unit 2 for supplying a DC input voltage to the system, a voltage fixing unit 3 for fixing the DC input voltage received from the DC voltage supply unit 2 to a constant voltage level, and the piezoelectric transformer 1 A switching element 4 for generating a switching frequency for determining whether to drive the driving element and transmitting the switching frequency to the piezoelectric transformer 1, and receiving the switching frequency of the switching element 4 to convert the DC input voltage into a predetermined AC output voltage. A piezoelectric transformer (1) for step-up and conversion, and a cold cathode tube discharge lamp (5) emitting light by generating a cold cathode fall phenomenon when an AC output voltage is transmitted through the piezoelectric transformer (1);

The AC output voltage output from the piezoelectric transformer 1 and the output current by the cold cathode tube discharge lamp 5 are detected and the PWM input voltage is fixed at a fixed level in the voltage fixing part 3 according to the detection result. The controller 6 is configured to change the duty cycle and to perform various control functions so that the switching frequency of the switching element 4 is fixed according to the driving frequency of the piezoelectric transformer 1.

In particular, the voltage fixing unit 3 is composed of a transistor (T), an inductor (L), and a diode (D) to obtain a fixed voltage using a buck-converter principle. A square wave signal is detected at the point A located at the base end of the transistor T and the control unit 6, and at the point B located between the switching element 4 and the piezoelectric transformer 1, a sine wave is detected. A signal of the form is to be detected.

In the operation of the conventional DC / AC inverter configured as described above, when the DC input voltage is transferred from the DC voltage supply unit 2 to the control unit 6, the control unit 6 outputs an AC output voltage output from the piezoelectric transformer 1. At the same time, the output current is detected through the cold cathode tube discharge lamp 5 which emits light by receiving the AC output voltage of the piezoelectric transformer 1.

The control unit 6 detects the output AC voltage and the output current, and changes the PWM duty cycle to fix the DC input voltage at a constant voltage level in the voltage fixing unit 3 according to the detection result. The piezoelectric transformer The switching frequency of the switching element 4 is fixed according to the driving frequency of (1).

Thus, the piezoelectric transformer 1 receiving the switching frequency of the switching device 4 outputs an AC output voltage in which the driving frequency is fixed and only the amplitude is changed.

However, in the related art, since only the duty cycle is controlled to set the DC input voltage to a predetermined voltage level while the frequency is fixed, there is a problem that efficiency is reduced. Furthermore, even if the DC input voltage is fixed at a constant voltage level, when the AC output voltage or the output current detected by the controller 6 becomes excessive, the voltage fixing part 3 must fix the DC input voltage at a lower voltage level. There is a problem that the efficiency is significantly reduced.

The present invention has been made to solve the above-mentioned problems of the prior art, the object of which is to respond to variations in input voltage or frequency with a PWM IC and a comparator in order to use the unique characteristics of the piezoelectric transformer in an inverter using a piezoelectric transformer. The present invention provides a power supply control apparatus for changing a driving frequency that can increase the efficiency of an inverter by adjusting a driving frequency of a piezoelectric transformer.

1 is a view showing a typical piezoelectric transformer,

2 is a view illustrating an input voltage and a driving frequency (a), an output voltage and a driving frequency (b) according to FIG.

3 is a block diagram showing the configuration of a DC / AC inverter using a piezoelectric transformer according to the prior art,

4 is a block diagram showing the configuration of a first embodiment of a power supply control device for variable drive frequency according to the present invention;

Figure 5 is a block diagram showing the configuration of a second embodiment of a power control device for variable drive frequency according to the present invention.

<Explanation of symbols on main parts of the drawings>

10, 20: voltage supply unit 11, 21: switching element

12, 22: cold cathode discharge lamp 13, 23: comparator

14, 24: PWM IC T1, T2: piezoelectric transformer

D1, D2: first and second diodes

According to the first feature of the drive frequency change power supply control apparatus according to the present invention for solving the above problems, a piezoelectric transformer for boosting the DC drive voltage transmitted from the outside while outputting as an AC drive voltage while having a constant drive frequency And a cold cathode tube discharge lamp that emits light by the AC drive voltage of the piezoelectric transformer, and a comparator which detects a voltage or current inputted to and outputs from the cold cathode tube discharge lamp, compares them with each other, and transmits the comparison result to the system. Passing the frequency change unit for controlling the output voltage and generating a fixed frequency by adjusting the pulse width so that the drive frequency of the piezoelectric transformer can be changed according to the comparison result of the comparison unit, and transmits the fixed frequency of the frequency change unit. Drive the piezoelectric transformer by generating a corresponding switching frequency It is configured to include a switching unit for transmitting a switching frequency to the piezoelectric transformer so that it can be determined.

According to a second aspect of the present invention, the operational amplifier may include a signal detector for selectively detecting any one of voltage and current inputted and outputted to the cold cathode tube discharge lamp, a detection result of the signal detector, and the frequency changer. Each of the reference voltages is received and compared with each other, the operation output unit is formed to deliver the comparison results to the system.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 4 is a block diagram showing a first embodiment of the power source control apparatus for changing the driving frequency according to the present invention, Figure 5 is a block diagram showing a first embodiment of the power source control apparatus for changing the driving frequency according to the present invention. to be.

First, referring to FIG. 4, a first embodiment of the present invention includes a voltage supply unit 10 for supplying power to drive a system; A piezoelectric transformer (T1) for boosting and converting a DC driving voltage transmitted from the outside while outputting the AC driving voltage while having a predetermined driving frequency; A cold cathode tube discharge lamp 12 emitting light while an electron emission phenomenon is generated by the AC driving voltage of the piezoelectric transformer T1; The voltage input to the cold cathode tube discharge lamp 12, that is, the AC drive voltage output from the piezoelectric transformer T1 and the output current output from the cold cathode tube discharge lamp 12 are respectively detected and compared with each other. A comparator 13 for delivering the to the system;

By receiving the comparison result of the comparator 13 and adjusting the pulse width so that the driving frequency of the piezoelectric transformer T1 can be changed accordingly, the output voltage is controlled so that a constant voltage and current flows and is fixed by the internal oscillation circuit. A PWM IC 14 having a frequency generated and a fixed frequency of the PWM IC 14 are received to generate a switching frequency corresponding thereto, so that the piezoelectric transformer T1 can be determined whether to drive the piezoelectric transformer T1. It consists of a switching element 11 for transmitting a switching frequency.

In particular, the PWM IC 14 is provided with a timing capacitor (CT) and a timing resistor (RT) terminal, respectively, and the frequency can be changed by the capacitor of the CT and the resistance of the RT.

Next, a second embodiment of the present invention will be described with reference to FIG. 5, but is similar to the first embodiment described above, but has a voltage input to the cold cathode discharge lamp 22 or a current output from the cold cathode discharge lamp 22. The first and second diodes D1 and D2 for detecting signals selectively installed to selectively detect any one of them, the detection result by the first and second diodes D1 and D2, and the PWM IC 24 The first embodiment is different from the first embodiment by the comparator 23 which receives each of the reference voltages, compares them with each other, and transmits the comparison results to the system.

According to the operation of the present invention according to the first and second embodiments configured as described above, when driving power is supplied to the voltage supply units 10 and 20, the PWM ICs 14 and 24 adjust the pulse width to adjust a constant voltage. And generating a fixed frequency by the internal oscillation circuit while controlling the output voltage to flow the current.

Then, the switching elements 11 and 21 receive the fixed frequency of the PWM ICs 14 and 24 and generate a switching frequency corresponding thereto, and transmit the same to the piezoelectric transformers T1 and T2 to transmit the piezoelectric transformers T1 and T2. ) Is determined whether to drive.

The piezoelectric transformers T1 and T2 are driven by the switching frequency to boost the DC driving voltage transmitted from the outside and convert the DC driving voltage into the AC driving voltage, and then transfer them to the cold cathode tube discharge lamps 12 and 22. In this case, the cold cathode tube discharge lamps 12 and 22 emit light while an electron emission phenomenon is generated by the AC driving voltages of the piezoelectric transformers T1 and T2.

Here, the comparator 13 according to the first embodiment detects an AC driving voltage of the piezoelectric transformer T1 input to the cold cathode tube discharge lamp 12 and an output current output from the cold cathode tube discharge lamp 12, respectively. The PWM IC 14 receives the comparison result of the comparator 13 and performs the pulse width adjustment again so that the driving frequency of the piezoelectric transformer T1 can be changed accordingly.

On the other hand, the comparator 23 according to the second embodiment selectively detects any one of the voltage or current input and output to the cold cathode tube discharge lamp 22 through the first and second diodes D1 and D2 and detects the same. The result is passed to the comparator 23. Then, the operational amplifier 23 compares the detection result of the first and second diodes D1 and D2 with the reference voltage received from the PWM IC 24, and transfers the comparison result to the PWM IC 24. The PWM IC 24 performs the pulse width adjustment function as described above. .

Therefore, the present invention automatically adjusts the driving frequency in response to the change in the input voltage or the load, so that the overall efficiency can be increased.

The power control device for changing the driving frequency of the present invention configured as described above drives the piezoelectric transformer in response to a change in input voltage or frequency by using a PWM IC and a comparator to use the unique characteristics of the piezoelectric transformer in an inverter using the piezoelectric transformer. By adjusting the frequency, the efficiency of the inverter can be increased.

Claims (2)

A piezoelectric transformer for boosting and converting a DC driving voltage transmitted from the outside while outputting the AC driving voltage while having a constant driving frequency, a cold cathode tube discharge lamp emitting light by the AC driving voltage of the piezoelectric transformer, and the cold cathode tube discharge The pulse width adjustment is performed so that the comparator which detects the voltage or current inputted to the lamp and compares them with each other and transmits the result of the comparison to the system, receives the comparison result of the comparator and changes the driving frequency of the piezoelectric transformer accordingly. And a switching frequency to control the output voltage and generate a fixed frequency, and generate a switching frequency corresponding to the fixed frequency of the frequency changing unit so as to determine whether to drive the piezoelectric transformer. It characterized in that it comprises a switching unit for transmitting Power control device for changing drive frequency. The method of claim 1, The operational amplifier unit receives a signal detection unit for selectively detecting any one of the voltage or current input and output to the cold cathode tube discharge lamp, and receives the detection result of the signal detection unit and the reference voltage by the frequency changer, respectively, A power control device for changing the driving frequency, characterized in that the operation output unit for transmitting the comparison result to the system is formed.