KR101022136B1 - Resonant piezo-powered boost converter circuit for harvesting piezoelectric energy - Google Patents

Abstract

PURPOSE: A resonant piezo-powered boost converter circuit for generating piezoelectric energy is provided to use a piezoelectric device which converts mechanical energy into electrical energy, thereby stably transferring the maximum energy to a load. CONSTITUTION: The first step of the first transistor is connected to the first step of a piezoelectric device. The first step of the second transistor is connected to the second step of the piezoelectric device. The first step of the third transistor is connected to the first step of the piezoelectric device. The first step of the fourth transistor is connected to the first step of the piezoelectric device. The first step of the fifth transistor is connected to the first step of a capacitor.

Description

RESONANT PIEZO-POWERED BOOST CONVERTER CIRCUIT FOR HARVESTING PIEZOELECTRIC ENERGY}

The present invention relates to a resonant self-boosting booster circuit, and more particularly, to a resonant self-boosting booster converter for energy harvesting using a piezoelectric element that converts mechanical energy into electrical energy without an external power source.

Recently, wireless electric and electronic products are becoming smaller and lighter based on circuit integration technology using advanced semiconductors. Most wireless electrical and electronic products use a small battery as the main energy source, and the limited battery capacity limits the use time. Research and development to extend battery life and enhance power density has been carried out steadily, and the concept of energy harvesting using solar, vibration, wind, heat, and manpower is applied to extend the usage time of low-voltage small-capacity wireless electric and electronic products. Research is actively conducted to power the load and attempt to extend the use time.

Due to the limitations of the characteristics of semiconductor switching devices used in power converters that supply harvested energy in accordance with load characteristics, and the limitation that harvestable energy is less than a few watts, research on development of energy harvesting systems until recently has been conducted. It was a level to test the ability. Recently, however, due to the rapid development of semiconductor devices, researches for developing piezoelectric energy harvesting have been attempted at various angles.

Among the energy harvesting elements, piezoelectric elements that convert mechanical energy due to vibration into electrical energy have a disadvantage in that harvestable energy is less than a few watts. Therefore, the development of the converter used in the energy harvesting system requires optimization considering the conversion efficiency. . Converters used for piezoelectric energy harvesting require simple structures and high efficiency, and must be able to operate on their own using only energy harvested from piezoelectric elements without using additional energy from outside.

Therefore, the technical problem to be achieved by the present invention is to provide a resonant boost converter that can be driven only by the energy generated from the piezoelectric element without an external energy source in order to efficiently harvest a small amount of electrical energy generated from the piezoelectric element.

According to an embodiment of the present invention, a resonance type self-boosting boost converter circuit includes a first transistor having a first end connected to a first end of a piezoelectric element and a first end to a second end of the piezoelectric element. A second transistor having a stage coupled thereto, a third transistor having a first stage coupled to the first end of the piezoelectric element, a fourth transistor having a first stage coupled to the second end of the piezoelectric element, and the first transistor A first diode having an anode connected to a second end of the transistor and a second end of the second transistor, a first end connected to a cathode of the first diode, and a second end of the third transistor and the fourth A capacitor having a second end connected to a second end of the transistor, a fifth transistor having a first end connected to the first end of the capacitor, and a second diode having an anode connected to the second end of the fifth transistor , The second An inductor having a first end connected to a cathode of a diode and an anode of the first diode, a first end connected to a second end of the inductor, and a second end connected to a second end of the capacitor, And a sixth transistor having a third end connected to the second end of the fifth transistor.

A first resistor may be further connected to an anode of the second diode and a second resistor may be connected to a second terminal of the fifth transistor.

A third diode having an anode connected to the second end of the inductor; and a second resistor having a first end connected to the cathode of the third diode and a second end connected to the second end of the capacitor. It may include.

When the first and fourth transistors or the second and third transistors are turned on, the voltage output from the piezoelectric element is rectified to a DC voltage, and the rectified DC voltage is charged to the capacitor through the first diode. Can be.

When the capacitor is charged with the maximum output voltage of the piezoelectric element, the fifth and sixth transistors may be turned on.

When the fifth and sixth transistors are turned on, the voltage charged in the capacitor may be discharged to the inductor through the fifth transistor, the first resistor, and the second diode.

As the resistance value of the first resistor increases, a rate at which the voltage charged in the capacitor is discharged to the inductor may be delayed.

When the voltage charged in the capacitor is discharged by the inductor, the fifth and sixth transistors may be turned off, and the voltage stored in the inductor may be transferred to the second resistor.

As described above, according to the present invention, the resonant self-boosting boost converter circuit for harvesting piezoelectric energy can perform a self-switching operation without a separate external energy source, and can stably transmit the maximum value of electric energy generated from the piezoelectric element to the load. Can be.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element in between. . In addition, when a part is said to "include" a certain component, which means that it may further include other components, except to exclude other components unless otherwise stated.

In addition, the expression that voltage is maintained throughout the specification indicates that even if the potential difference between two specific points changes over time, the change is within an allowable range in the design or the cause of the change is due to parasitic components that are ignored in the design practice of those skilled in the art. Include cases by. In addition, since the threshold voltage of a semiconductor device (transistor, diode, etc.) is very low compared to the discharge voltage, the threshold voltage is regarded as 0V and approximated.

1 is a diagram illustrating a general topology of an energy harvesting system using a piezoelectric element as an energy source. Piezoelectric element is a mechanical vibration energy It converts into electrical energy and outputs an AC voltage, which can be processed equivalently with an AC current source and a parallel capacitor (C _p ). AC voltage is rectified to DC voltage using a diode bridge circuit, and a step-up or step-down conversion is performed using a DC / DC converter depending on the load condition.

Hereinafter, the self-switching operation of the resonant boost converter circuit will be described with reference to FIGS. 2A and 2B. FIG. 2A is a circuit diagram illustrating a resonant boost converter circuit according to an exemplary embodiment of the present invention, and FIG. 2B is a circuit diagram illustrating a self-contained switch circuit included in the resonance type boost converter circuit of FIG. 2A.

As shown in FIGS. 2A and 2B, the resonant boost converter circuit includes six transistors S1, S2, S3, S4, S5, and S6, and the transistors S3, S4, and S5 in FIGS. 2A and 2B. An n-channel field effect transistor, in particular an n-channel metal oxide semiconductor (NMOS) transistor, is illustrated in these transistors S3, S4, and S5, and a body diode may be formed from a source to a drain direction.

2A and 2B, the transistors S1, S2, S6 are shown as p-channel field effect transistors, in particular p-channel metal oxide semiconductor (PMOS) transistors. A body diode can be formed in the source direction.

And other transistors having similar functions in place of NMOS transistors or PMOS transistors may be used as these transistors S1, S2, S3, S4, S5, S6. In addition, in FIGS. 2A and 2B, transistors S1, S2, S3, S4, S5, and S6 are shown as one transistor, respectively. It can be formed of a transistor of.

First, a resonance type boost converter circuit according to an exemplary embodiment of the present invention will be described with reference to FIG. 2A. The resonant boost converter circuit shown in FIG. 2A includes transistors S1, S2, S3, S4, S5, capacitor Co, diode D1, resistor Ro, and piezoelectric element PZT.

The first end of the piezoelectric element PZT is connected to the drain of the transistor S1, and the second end of the piezoelectric element PZT is connected to the drain of the transistor S4. The source of the transistor S1 is connected to the first stage of the inductor L and the self switching circuit, and the second stage of the inductor L is the anode of the diode D1 and the drain of the transistor S5. Connected with The cathode of the diode D1 is connected to the first end of the capacitor Co and the first end of the resistor Ro, respectively. In addition, the source of the transistor S4 is independently connected to the source of the self switching circuit and the transistor S5, respectively.

The drain of the transistor S5 is connected to the second terminal of the inductor L and the anode of the diode D1, and the gate of the transistor S5 is connected to a self switching circuit.

In addition, the source of the transistor S2 is connected to the source of the transistor S1, and the drain of the transistor S2 is connected to the second end of the piezoelectric element PZT. In addition, the drain of the transistor S3 is connected to the first end of the piezoelectric element PZT, and the source of the transistor S3 is connected to the source of the transistor S4.

In FIG. 2A, the transistors S1, S2, S3, and S4 function as active rectifiers for AC / DC rectification. That is, the AC voltage output from the piezoelectric element PZT is rectified to a positive DC voltage through the transistors S1, S2, S3, S4. According to the embodiment of the present invention, when the polarity of the piezoelectric element PZT is positive during the first half cycle, the transistors S1 and S4 are turned on to rectify the output voltage of the piezoelectric element PZT, and during the next half cycle. When the polarity of the piezoelectric element PZT is negative, the transistors S2 and S3 are turned on to rectify the output voltage of the piezoelectric element PZT.

According to an embodiment of the present invention, the switching is performed on and off using the polarity of the output voltage V _PZT of the piezoelectric element PZT without a separate gate drive circuit for switching transistors S1, S2, S3, and S4. Perform AC / DC conversion.

Next, a self switching circuit is connected to the contacts of transistor S2 and inductor L, the source of transistor S4, and the gate of transistor S5, as shown in FIG. 2A, and FIG. 2B. Self switching circuit according to an embodiment of the present invention as shown in the diode (D2, D3) capacitor (Cs), It consists of resistors Rs, RD and Rp and transistor S6.

The self-contained switch circuit according to the exemplary embodiment of the present invention illustrated in FIG. 2B may directly use the output energy of the piezoelectric element PZT without additional conversion for driving switching of the transistor S5 of the resonant boost converter circuit. do.

The anode of the diode D2 is connected to the source of the transistor S1 and the cathode is connected to the first end of the capacitor Cs. The first end of the capacitor Cs is also connected to the source of the transistor S6, and the second end is connected to the source of the transistor S4.

The diode D2 and the capacitor Cs not only sense a falling envelope of the piezoelectric element output voltage V _PZT but also store energy output from the piezoelectric element PZT.

The first end of the resistor Rs is connected to the anode of the diode D2, and the second end of the resistor Rs is connected to the gate of the transistor S6. The source of the transistor S6 is connected to the first end of the capacitor Cs, and the drain thereof is connected to the gate of the transistor S5.

The transistor S6 of the switch circuit has a function of detecting the maximum value of the piezoelectric element output voltage V _PZT by comparing the gate voltage of the transistor S6 with the voltage of the capacitor Cs by the turn-on characteristic. Has When the transistor S6 is turned on due to the voltage difference between the gate voltage V _G and the source voltage V _S of the transistor S6, the transistor S5 which is the main switch of the boost converter is turned on.

Then, the anode of the diode (D3) is connected to a first end of the resistor (R _D), a second terminal of the resistor (R _D) is connected to a first end of the resistance (Rp). The diode D3 and the resistor R _D form a discharge path.

Here, the turn-on time t _{S5 _ on} of the transistor S5 increases in proportion to the size of the resistor R _D inside the discharge path. Energy of the piezoelectric element stored in the capacitor Cs is regenerated to the loads Co and Ro through the diode D3 of the discharge path. When the capacitor Cs becomes zero voltage (0V) and the current flowing in the inductor L is maximum, the transistors S5 and S6 are turned off.

That is, the self-contained switch circuit shown in FIG. 2B detects the maximum value of the output voltage V _PZT of the piezoelectric element PZT through the diode D2 and the capacitor Cs, and the voltage V _Cs at both ends of the capacitor _Cs. Transistor S6 is turned on when the voltage difference between the piezoelectric element PZT and V _PZT is greater than the threshold voltage V _th of the transistor S6 in the comparator, and the transistor S5 is continuously Is turned on. The energy of the piezoelectric element stored in the capacitor Cs is regenerated to the load through the discharge path. Due to the threshold voltage V _th of the transistor S6, the transistor S5 operates in the delayed state t _d , not the maximum value of the piezoelectric element output voltage V _PZT , and the resistance of the discharge path ( R _D ) determines the turn-on time t _{S5 _ on} of the transistor S5. Energy is stored in the inductor L when the transistor S5 is turned on, and energy stored in the inductor L is transferred to the loads Co and Ro through the diode D1 when the transistor S5 is turned on.

Hereinafter, the operation of the resonance self-boosting boost converter circuit described with reference to FIGS. 2A and 2B will be described in detail with reference to FIGS. 3A to 4.

3A to 3D are diagrams illustrating an operation of a resonance self-boosting boost converter circuit according to an exemplary embodiment of the present invention, and FIG. 4 is a diagram illustrating waveforms for each operation mode illustrated in FIGS. 3A to 3D.

For convenience of description, in FIGS. 3A to 3D, the output voltage of the piezoelectric element is rectified by using the transistors S1 and S4 during the first half cycle, thereby operating the resonance self-boosting booster circuit.

In FIG. 4, (a) shows the amount of current flowing through the piezoelectric element PZT, (b) shows the output voltage of the piezoelectric element PZT, (c) shows the drain voltage of the transistor S5, and (d Denotes the amount of current flowing through the inductor L. In Fig. 4, (e) shows an enlarged drain voltage of the transistor S5 only for the periods of mode 3 (M3) and mode 4 (M4) in (c), and (f) shows mode 3 (M3) in (d). ) And the amount of current flowing in the inductor L is enlarged only for the period 4 (M4).

In mode 1 (M1) (t ₀ to t ₁ ), the transistor S1 and the transistor S4 are turned on, so as shown in FIG. 3A, the piezoelectric element PZT, the transistor S1, the diode D2, and the capacitor Cs are turned on. And a capacitor Cs is charged through the path of the transistor S4.

As described with reference to FIG. 1, the capacitor Cp inside the piezoelectric element is connected in parallel with an alternating current source ip in the piezoelectric element, and the alternating current source ip may be represented by Equation 1 below. The same waveform as in (a) is shown.

The piezoelectric element output voltage V _PZT may be represented by Equation 2, and represents a waveform as shown in FIG.

Where t _d is the time delayed by the threshold voltage V _th of the transistor S6 during the switching operation.

In mode 2 (M2) (t ₁ to t ₂ ), the voltage V _Cp of the capacitor _Cp and the voltage V _Cs of the capacitor _Cs are the maximum values of the piezoelectric element output voltage V _PZT . After being charged to, the voltage V _Cs of the capacitor Cs is fixed at the maximum value by the diode D2. In addition, the voltage V _Cp of the capacitor Cp in the piezoelectric element is reduced by the vibration of the piezoelectric element, and thus the piezoelectric element output voltage V _PZT is reduced again as shown in FIG. 3B. When the magnitude of V _Cs -V _PZT -V _D2 reaches the threshold voltage V _{th of} the transistor S6, the transistor S6 is turned on.

That is, the source voltage of the transistor S6 is kept constant by the capacitor Cs voltage V _Cs , and the gate voltage of the transistor S6 is reduced due to the reduction of the output voltage V _PZT of the piezoelectric element. Therefore, since the difference between the gate and source voltages of the transistor S6 becomes smaller than the threshold voltage V _th , the transistor S6 is turned on and the mode 2 M2 ends.

Here, assuming that there is no voltage decrease of the voltage V _Cs across the capacitor Cs with respect to the leakage current of the diode D2, the time t _d (= t ₂ ) delayed by the threshold voltage V _th of the transistor S6. t ₁ ) is expressed as Equation 3 below.

In the mode 3 (M3) (t ₂ to t ₃ ), when the transistor S6 is turned on, the transistor S5 is turned on as shown in FIG. 3C, and the capacitor Cs and the capacitor Cp are the inductor L and the resonance circuit. Configure That is, discharge paths of the capacitor Cp, the transistor S4, the capacitor Cs, the transistor S6, the resistor R _D , the diode D3 and the inductor L of the piezoelectric element PZT. The energy stored in the capacitor Cp and the capacitor Cs is transferred to the inductor L through. Here, the discharge is delayed as the resistance value of the resistor R _D increases.

In addition, since the transistor S5 is turned on, a closed circuit including the piezoelectric element PZT, the transistor S1, the inductor L, the transistor S5, and the transistor S4 is formed. As the energy is discharged into the inductor L, the drain voltage of the transistor S5 increases, and the drain voltage of the transistor S5 shows waveforms as shown in FIGS. 4C and 4E.

이며, 인덕터(L)에 흐르는 전류 초기값 i_L(t₂)은 0이다. 모드 3(M3)에서 인덕터(L)에 흐르는 전류는 다음의 수학식 4 및 수학식 5로 나타낼 수 있으며, 도 4의 (d), (f)와 같은 파형을 나타낸다. Here, the initial value of the output voltage Vc (t ₂ ) of the piezoelectric element is expressed by Equation 2 of Mode 1 (M1).

And initial current i _L (t ₂ ) flowing in the inductor L is zero. The current flowing through the inductor L in the mode 3 (M3) may be represented by the following Equations 4 and 5, and shows waveforms as shown in FIGS. 4 (d) and 4 (f).

의 1/4이고, R₃은 모드 3(M3)의 기생 저항 성분의 합이다. Mode 3 (M3) lasts until the piezoelectric element output voltage (V _PZT ) reaches zero voltage and the inductor current reaches its maximum value. The operating time t ₃ -t ₂ of mode 3 (M3) is the period of the resonant circuit consisting of the inductor L and Cs + Cp

Is 1/4 and R ₃ is the sum of parasitic resistance components of mode 3 (M3).

In mode 4 M4 (t ₃ to t ₄ ) as shown in FIG. 3D, energy stored in the inductor L is transferred to the loads Co and Ro through the diode D1 after the transistor S5 is turned off. . That is, in the process of transferring energy to the inductor L, the voltage V _Cs at both ends of the capacitor Cs decreases, and accordingly, the gate voltage of the transistor S5 decreases, so that the transistor S5 is turned off. In this case, energy accumulated in the inductor L is transferred to the loads Co and Ro.

이다. Here, the initial voltage Vc (t ₃ ) of the piezoelectric element is 0, and the initial value i _L (t ₃ ) of the current flowing in the inductor L is

to be.

The inductor current i _L (t) during mode 4 (M4) is given by Equation 6 below, and R ₄ is the sum of the parasitic resistance components during the mode 4 (M4) period.

The operating time t ₄ -t ₃ = t _{off in the} mode 4 (M4) is a time until the current of i _L (t) reaches 0 and can be expressed by Equation 7.

V _L (t) maintains V ₀ + V _D1 to deliver power to the load. When i _L = 0, the diode D1 is turned off. The power delivered to the load in the mode 4 (M4) is shown in Equation 8.

Thus, t ₀ to t ₀ corresponding to the half period (T / 2) shown in FIG. + The operation of Mode 1 (M1) to Mode 4 (M4) can be performed for T / 2 time, and when the operation of Mode 1 (M1) to Mode 4 (M4) is finished, the next half cycle (T / 2) is performed. Corresponding t ₀ The process of Mode 1 (M1) to Mode 4 (M4) is repeated again during + T / 2 to t ₀ + T time. Where the next half period (t ₀ In the period of + T / 2 to t ₀ + T), the piezoelectric element's output voltage (V _PZT ) is negative, and the transistors S2 and S3 are turned on to rectify the piezoelectric element's output voltage (V _PZT ) to be resonant. Let's run the boost converter circuit. The operation of operating the resonant self-boosting boost converter circuit by turning on the transistors S2 and S3 can be easily inferred from the operation of the modes 1 (M1) to 4 (M4) by those skilled in the art, and thus a detailed description thereof will be omitted. .

5 is a diagram illustrating a part of a resonance self-supporting boost converter circuit according to another exemplary embodiment of the present invention. As shown in FIG. 5, in accordance with another embodiment of the present invention, diodes D4, D5, D6, and D7 may be replaced as shown in FIG. 5 instead of transistors S1, S2, S3, and S4. In particular, the cathode and anode directions of the diodes D4, D5, D6, and D7 shown in FIG. 5 are the same as the directions of the body diodes included in the transistors S1, S2, S3, and S4 shown in FIG. 2A.

Accordingly, the output voltage of the piezoelectric element may be rectified through the diodes D4 and D7 during the first half cycle, and the output voltage of the piezoelectric element may be rectified through the diodes D5 and D6 during the next half cycle.

As described above, according to the exemplary embodiment of the present invention, the resonant self-boosting boost converter circuit for harvesting piezoelectric energy may perform a switching operation without a separate external energy source, and the maximum value of the electric energy generated by the piezoelectric element may be applied to the load. I can deliver it stably.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a diagram illustrating a general topology of an energy harvesting system using a piezoelectric element as an energy source.

2A is a circuit diagram illustrating a resonance type boost converter circuit according to an exemplary embodiment of the present invention.

FIG. 2B is a circuit diagram illustrating a self-switching circuit included in the resonance type boost converter circuit of FIG. 2A.

3A to 3D are diagrams illustrating an operation of a resonance self-supporting boost converter circuit according to an exemplary embodiment of the present invention.

4 is a diagram illustrating waveforms for each operation mode illustrated in FIGS. 3A to 3D.

5 is a diagram illustrating a part of a resonance self-supporting boost converter circuit according to another exemplary embodiment of the present invention.

Claims (8)

A first transistor having a first end connected to a first end of the piezoelectric element, A second transistor having a first end connected to a second end of the piezoelectric element, A third transistor having a first end connected to a first end of the piezoelectric element, A fourth transistor having a first end connected to a second end of the piezoelectric element, A first diode having an anode connected to a second end of the first transistor and a second end of the second transistor, A capacitor having a first end connected to a cathode of the first diode and a second end connected to a second end of the third transistor and a second end of the fourth transistor, A fifth transistor having a first end connected to a first end of the capacitor, A second diode having an anode connected to a second end of the fifth transistor, An inductor having a first end connected to the cathode of the second diode and the anode of the first diode, and A sixth transistor connected to a second end of the inductor, a second end connected to a second end of the capacitor, and a third transistor connected to a second end of the fifth transistor; Resonant self-boost boost converter circuit. The method of claim 1, And a first resistor connected to an anode of the second diode and a second end connected to a second end of the fifth transistor. The method of claim 2, A third diode having an anode connected to the second end of the inductor, and And a second resistor having a first end connected to the cathode of the third diode and a second end connected to the second end of the capacitor. The method of claim 3, When the first and fourth transistors or the second and third transistors are turned on, the voltage output from the piezoelectric element is rectified to a DC voltage, and the rectified DC voltage is charged to the capacitor through the first diode. Resonant self-boost boost converter circuit. The method of claim 4, wherein And the fifth and sixth transistors are turned on when the capacitor is charged with the maximum output voltage of the piezoelectric element. The method of claim 5, And a voltage charged in the capacitor during the turn-on of the fifth and sixth transistors is discharged to the inductor through the fifth transistor, the first resistor and the second diode. The method of claim 6, The resonant self-contained boost converter circuit of the delay rate of the voltage charged in the capacitor is discharged to the inductor as the resistance value of the first resistor is larger. The method of claim 6, And the fifth and sixth transistors are turned off and the voltage stored in the inductor is transferred to the second resistor when the voltage charged in the capacitor is discharged by the inductor.

Images