KR20120010636A - Boost converter - Google Patents

Abstract

PURPOSE: A boost converter is provided to reduce the internal pressure of a device without a separate loss snubber by clamping a voltage delivered to a device with a charging voltage or an output voltage during power source conversion. CONSTITUTION: A transformer(110) includes a first coil and a second coil. A preset winding ratio is formed through the electromagnetic coupling of the first coil and the second coil. A switching unit(120) includes a switch which switches an input power source delivered to the first coil according to a preset duty. A clamp unit(130) includes a first diode, a second diode, and a link capacitor transferring a power source. A stabilizing unit(140) includes a third diode and a capacitor stabilizing the power source outputted.

Description

Boost Converter {BOOST CONVERTER}

The present invention relates to a boost converter, and more particularly, to a boost converter that clamps the voltage delivered to the device to a charging voltage or an output voltage during power conversion to reduce the breakdown voltage of the device without employing a separate loss snubber.

Recently, various power supplies capable of boosting a low DC voltage have been researched and developed for fuel cell or battery-based electric drive systems, semiconductor manufacturing equipment, large display devices, ultrasonic and X-ray devices.

As such a power supply, the boost converter may be regarded as a typical power supply.

It is difficult to obtain a high boost ratio with a general boost converter. In the past, a plurality of boost converters were connected in series to obtain a high boost ratio. .

In order to solve this problem, a boost converter using a tap inductor has been disclosed, but it is essential to employ a lossy snubber for reducing a surge type voltage generated during power conversion switching.

However, this also causes a reduction in power conversion efficiency due to lossy snubbers, and a voltage in the form of a surge still occurs. Therefore, a problem that the manufacturing cost increases due to the adoption of a high breakdown voltage device still remains.

It is an object of the present invention to provide a boost converter that clamps the voltage delivered to an element to a charging or output voltage during power conversion to reduce the breakdown voltage of the element without employing a separate loss snubber.

In order to achieve the above object, one technical aspect of the present invention is a transformer having a first winding receiving an input power, and a second winding having a predetermined winding ratio in electromagnetic coupling with the first winding; A switching unit for switching on and off the input power delivered to the first winding according to a preset duty, and a link capacitor for charging a link voltage delivered to an output side by the switching of the switching unit. It is to provide a boost converter comprising a clamp unit for clamping the power output according to the result of the comparison between the level and the voltage level induced in the second winding, and a stabilization unit for stabilizing the power output from the clamp unit. .

According to one technical aspect of the present invention, the voltage level induced in the second winding may be higher than the voltage level charged in the link capacitor.

According to one technical aspect of the present invention, the transformer has a leakage inductance connected in series between one end of the first winding and one end of an input power terminal through which the input power is transmitted, and one end and the other end of the first winding. It may further include a magnetic inductance connected in parallel.

According to one technical aspect of the present invention, the switching unit includes a switch connected between the other end of the first winding and the ground, the clamp unit of the anode and the second winding is connected to the other end of the first winding A first diode having a cathode connected to one end and a second diode having an anode connected to ground and a cathode connected to the other end of the second winding, wherein the link capacitor includes a cathode of the first diode and a ground; Can be connected between.

According to one technical aspect of the present invention, the stabilization unit may include a third diode having an anode connected to the other end of the second winding, and a second capacitor connected to the cathode and the ground of the third diode.

According to one technical aspect of the present invention, the second diode turns off when the voltage level induced in the second winding is lower than the voltage level charged in the link capacitor, and the voltage level induced in the second winding. When the voltage level is higher than the voltage charged in the link capacitor, the voltage may be turned on to clamp the voltage across the third diode to the output voltage charged in the second capacitor.

According to one technical aspect of the present invention, the first winding and the second winding may have the same winding direction.

According to the present invention, the voltage delivered to the device is clamped to the charging voltage or the output voltage during power conversion to reduce the breakdown voltage of the device without employing a separate loss snubber, thereby preventing a reduction in power conversion efficiency due to the lost snubber. Since a device with a low breakdown voltage can be employed, manufacturing cost can be reduced.

1 is a schematic diagram of a boost converter of the present invention;
2 is a signal waveform diagram of a major part of the boost converter at turn off of the second diode of the present invention;
3A-3C are current flow diagrams in accordance with the signal waveform shown in FIG.
4 is a graph of current waveforms of first and third diodes when the second diode is turned off.
Fig. 5 is a signal waveform diagram of the main part of the boost converter at turn on of the second diode of the present invention.
6A-6C are current flow diagrams in accordance with the signal waveform shown in FIG.
7 is a graph of current waveforms of a link capacitor when the second diode is turned on.
8 is a graph showing the results of simulation of the boost converter when the second diode is turned off, and FIG. 9 is a graph showing the results of the simulation of the boost converter at the turn-on of the second diode.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a schematic diagram of a boost converter of the present invention.

Referring to FIG. 1, the boost converter 100 of the present invention may include a transformer 110, a switching unit 120, a clamp unit 130, and a stabilization unit 140.

 The transformer 110 may include a first winding Np and a second winding Ns, and the first winding Np and the second winding Ns may be electromagnetically coupled to each other to form a preset winding ratio. have.

The switching unit 120 may include a switch M for switching the input power transmitted to the first winding Np according to a preset duty.

The clamp unit 130 may include first and second diodes D1 and D2 and a link capacitor C _Link to transfer power.

The stabilization unit 140 may include a third diode D3 and a capacitor Co for stabilizing the output power.

One end of the first winding Np of the transformer 110 may be connected to one end of an input power terminal to which the input power Vin is input, and the other end of the first winding Np may be a switch M of the switching unit 120. Can be connected to one end of The other end of the switch M may be connected to ground, the other end of the link capacitor C _Link may be connected to ground, the anode of the first diode D1 is connected to one end of the switch M, and the cathode is a link capacitor. It can be connected to one end of (C _Link ). One end of the second winding Ns may be connected to one end of the link capacitor C _Link , and an anode of the second diode D2 may be connected to the other end of the second winding Ns and a cathode may be connected to ground. The anode of the third diode D3 may be connected to the cathode of the second diode D2 and the cathode of the third diode D3 may be connected to one end of the capacitor Co, and the other end of the capacitor Co may be connected to ground. Can be.

In the above-described boost converter 100, when the switch M is conductive, whether or not the second diode D2 is conductive is determined by Equation 1 below, and thus, when the second diode D2 is turned off. It can be operated in two ways, on and off.

<Equation 1>

That is, when the switch M is turned on, the turn ratio Ns / Np of the transformer 110 is small so that the voltage Vsec induced in the second winding Ns is the voltage V _{C _} of the link capacitor C _link . _When smaller than the _link ), the second diode D2 is always turned off because it is reverse biased. On the contrary, the voltage Vsec induced in the second winding Ns is large because the turn ratio Ns / Np of the transformer 110 is large. When greater than the voltage V _{C _ link} of the capacitor C _link , the second diode D2 becomes a forward bias to conduct.

On the other hand, when the switch M is cut off, the second diode D2 reverses the clamping of the voltages across the third diode D3 to the output voltage Vo.

First, an operation of turning off the second diode D2 will be described.

FIG. 2 is a signal waveform diagram of a main part of the boost converter when the second diode of the present invention is turned off, FIGS. 3A to 3C are current flow charts according to the signal waveform shown in FIG. 2, and FIG. The current waveforms of the first and third diodes at turn off.

Before explanation, the following assumptions are made for ease of interpretation. The leakage inductor Llk is very small compared to the magnetizing inductor Lm, the magnetizing inductor Lm is so large that the current ripple of the magnetizing inductor is negligibly small, the voltage of the link capacitor V _link , the voltage of the first capacitor ( It is assumed that Vc) and the capacitor's voltage Vo are constant, all operations are steady and all parasitic components are absent except for the portion shown.

Meanwhile, the illustrated load may be a light emitting diode light source body.

Referring to FIGS. 2, 3A to 3C and FIG. 4 together with FIG. 1, first, operation in mode 1, which is time t0 to t1, starts the winding starting point of the transformer 110 when the switch M is turned on at time t0. since positive voltage is applied to the first diode (D1) there is applied voltage (V _{C _ link)} of the output voltage (Vo) and the link capacitor (C _link), the second diode (D2), the link capacitor (C _link ) voltage (V _{C _ link)} and a primary winding (Np) voltage (Vpri (Ns / Np multiplied by the voltage (Vpri) with turns ratio (Ns / Np) of the transformer (110))), and is applied to, a third of the Since the output voltage Vo and the voltage V _{C _ link} of the link capacitor C _link are applied to the diode D3, the first to third diodes D1, D2, and D3 are turned off. The same conduction path is formed.

In addition, an input voltage Vin is applied to the primary side of the transformer 110 so that the input current iin increases with a slope of Vin / Lm.

On the other hand, at the moment when the switch M is turned on, resonance occurs between the inductance component of the leakage inductor Lk of the transformer 110 and the parasitic capacitor Cj3 of the third diode D3, but is caused by the output voltage Vo. Clamped.

Next, in operation 2 of time t1 to t2, when the switch M is turned off, as shown in FIG. 3B, the input current iin of the transformer 110 follows the link capacitor C _link along the first diode D1. Since the negative voltage is applied to the start point of the winding of the transformer 110, the second diode D2 is turned off. The current ipri of the first winding Np of the transformer 110 flows by the difference between the input current iin and the current iLm of the magnetizing inductor Lm, and the second winding Ns of the transformer 110 is present. Since the third diode D3 conducts due to the current isec flowing through it, a voltage of-(Vo-V _{C _ link} ) / (Ns / Np) is applied to the magnetizing inductor Lm as shown in FIG. 3 (b). The voltage of Vin + V _{C _ link-} (Vo-V _{C _ link} ) / (Ns / Np) is applied to the leakage inductor Lk. Therefore, the input current iin is reduced by the slope of {Vin + V _{C _ link-} (Vo-V _{C _ link} ) / (Ns / Np)} / Lm. On the other hand, the energy stored in the magnetization inductor (Lm) in the previous mode 1 is transferred to the secondary side through the transformer 110, the energy stored in the leakage inductor (Lk) is the drain (source) source of the switch (M) The capacitor between the capacitor and resonance generate a resonance and the voltage VDS between the drain and the source of the switch M is rapidly increased, but the voltage of the switch M is V _{C _ link} because the first diode D1 is conductive. Is clamped.

Lastly, in the mode 3 of the time t2 to t3, when the input current iin becomes '0', the first diode D1 is turned off as shown in FIG. 3C, and the current iLm of the magnetizing inductor Lm. ) Are all transmitted to the output side through the transformer (110).

Thereafter, the above-described modes 1 to 3 are repeatedly operated.

On the other hand, since the average current of the capacitor (Co) should be '0' by the charge balance principle, the following equation (2).

<Equation 2>

Therefore, since the average current of the first diode D1 must be equal to the average current of the third diode D3, if the magnetization inductor Lm is very large and the ripple of the current iLm of the magnetization inductor is negligibly small, the drop period ( Tfall) may be derived from Equation 3 below.

<Equation 3>

Here, since the current iLm of the magnetizing inductor Lm is equal to the sum of the input current iin and the current ipri of the first winding Np of the transformer 110, the following Equation 4 may be derived. have.

<Equation 4>

Accordingly, the output voltage Vo is expressed by Equation 5 below by Equation 3 and Equation 4.

<Equation 5>

Meanwhile, since the average voltage of the magnetizing inductor Lm is '0' as shown in the signal waveform of FIG. 2, the following Equation 6 must be satisfied.

<Equation 6>

Therefore, the voltage of the link capacitor (C _link) by the following equation 5 and equation 6 (V _{C _ link)} is shown in Equation 7 of.

<Equation 7>

Next, an operation of turning on the second diode D2 will be described.

5 is a signal waveform diagram of a main part of the boost converter at turn-on of the second diode of the present invention, FIGS. 6A to 6C are current flow charts according to the signal waveform shown in FIG. 5, and FIG. 7 is a turn of the second diode. This is the current waveform of the link capacitor when it is turned on.

Prior to the description, the same assumptions as above are made for the convenience of interpretation.

Referring to FIGS. 5, 6A to 6 and 7, together with FIG. 1, first, the operation in Mode 1 of time t0 to t1 is positive at the starting point of winding of the transformer 110 when the switch M is turned on. Since the voltage is applied, the second diode D2 is turned on, the voltage V _{C _ link} of the link capacitor C _link is applied to the first diode D1, and the output voltage Vo is applied to the third diode D1. Is applied to turn off the first and third diodes D1 and D3, thereby forming a conductive path such as the solid line of FIG. 6A. Accordingly, the voltage V _{C _ link} / Ns / Np of the link capacitor C _link is applied to the magnetizing inductor Lm, and Vin-V _{C _ link} / ( The voltage of Ns / Np) is bowed and the input current iin rises with the slope of {Vin-V _{C _ link} / (Ns / Np)} / Lk. At this time, the difference between the input current iin and the magnetization inductor current iLm is transferred to the second winding Ns of the transformer to charge the link capacitor C _link . In addition, although resonance occurs due to the inductance component of the leakage inductor Lk of the transformer 110 and the capacitance component of the parasitic capacitor Cj3 of the third diode D3, the second diode D2 conducts to the third diode ( The voltage VD3 of D3) is clamped to the output voltage Vo.

Next, in operation 2 of time t1 to t2, when the switch M is turned off, as shown in FIG. 6B, the input current iin of the transformer 110 is along the first diode D1 and the link capacitor C _link . Since a negative voltage is applied to the start point of the winding of the transformer, the second diode D2 is turned off. At this time, since the current iLm of the magnetizing inductor Lm is transferred to the second winding Ns of the transformer 110 and flows to the output side through the third diode D3, the magnetizing inductor Lm is as shown in FIG. 5. the voltage _{(Vo-V C _ link)} / (Ns / Np) - - (Vo-V C _ link) / (Ns / Np) voltage is applied, leakage inductor (Lk) is Vin + V _{C _ link} Is approved. Therefore, the input current iin decreases with the slope of {Vin + V _{C _ link-} (Vo-V _{C _ link} ) / (Ns / Np)} / Lm and then equals the current iLm of the magnetizing inductor Lm. Once it is done, as shown in Figure 5 gradually decrease until the charge balance of the link capacitor (C _link ) is achieved. At this time, the current iD3 of the third diode D3 equal to the current of the second winding Ns of the transformer 110 is equal to the current iLm and the input current iin of the magnetizing inductor Lm as shown in FIG. 5. It will flow by the difference. In addition, resonance occurs between the leakage inductor Lk and the diode of the switch M, so that the voltage VDS between the drain and the source of the switch M rises sharply, but because the first diode D1 is conducting, the switch ( The voltage of M) is clamped to V _{C _ link} .

Lastly, in the mode 3 of the time t2 to t3, when the input current iin becomes '0', the first diode D1 is turned off as shown in FIG. 6C, and the current iLm of the magnetizing inductor Lm. ) Are all transmitted to the output side through the transformer (110).

Thereafter, the above-described modes 1 to 3 are repeatedly operated.

As shown in FIG. 7, since the average current of the link capacitor C _link should be '0' by the charge balance principle, the following Equation 8 may be derived.

<Equation 8>

Here, since the average input current <i _in > is equal to the sum of the current iLm of the magnetizing inductor and the current i _{C _ Link} of the link capacitor, Equation 9 is derived.

<Equation 9>

Accordingly, the average input current < i _in >

<Equation 10>

Further, since the output current io is equal to the average current of the link capacitor C _link in the turn-off period, the following equation (11) holds.

<Equation 11>

Therefore, according to the energy conservation law, the input power should be the same as the output power.

<Equation 12>

Meanwhile, as shown in FIG. 5, since the average voltage of the magnetizing inductor Lm is '0', the following Equation 13 must be satisfied.

<Equation 13>

Therefore, the voltage (V _{_ C link)} of the link capacitor (C _link) by Equation 12 and Equation 13 are shown in the equation (14) of.

<Equation 14>

8 is a graph illustrating a simulation result of a boost converter when the second diode is turned off, and FIG. 9 is a graph illustrating a simulation result of a boost converter when the second diode is turned on.

As shown, the resonance between the leakage inductor component of the transformer and the parasitic capacitors of each element occurs at the turn-off or turn-on of the second diode of the boost converter of the present invention, but the breakdown voltage of each element is determined by the voltage of the link capacitor or By clamping to the output voltage, it can be seen that it has the effect of reducing the breakdown voltage without the need for a separate loss snubber.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the particular forms disclosed. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

100 ... Boost Converter
110 ... Transformers
120 ... switching part
130.Clamp
140.Stabilizer

Claims (12)

A transformer having a first winding receiving an input power and a second winding electromagnetically coupled to the first winding, the second winding having a preset winding ratio;
A switching unit for switching on and off the input power delivered to the first winding according to a preset duty;
A clamp unit including a link capacitor for charging a link voltage transmitted to an output side by switching of the switching unit, and clamping a power output according to a result of comparing a level of the link voltage with a voltage level induced in the second winding; And
Stabilization unit for stabilizing the power output from the clamp unit
Boost converter comprising a. The method of claim 1,
And the voltage level induced in the second winding is higher than the voltage level charged in the link capacitor. The method of claim 1,
The transformer further includes a leakage inductance connected in series between one end of the first winding and one end of an input power terminal to which the input power is transmitted, and a magnetic inductance connected in parallel to one end and the other end of the first winding. Boost converter. The method of claim 3,
The switching unit includes a switch connected between the other end of the first winding and the ground,
The clamp part includes a first diode having an anode connected to the other end of the first winding and a cathode connected to one end of the second winding, an anode connected to ground, and a cathode connected to the other end of the second winding. 2 more diodes,
And the link capacitor is connected between the cathode of the first diode and ground. The method of claim 4, wherein
And the stabilizing unit includes a third diode having an anode connected to the other end of the second winding, and a second capacitor connected to the cathode and the ground of the third diode. The method of claim 5,
The second diode is turned off when the voltage level induced in the second winding is lower than the voltage level charged in the link capacitor, and when the voltage level induced in the second winding is higher than the voltage level charged in the link capacitor. And turning on to clamp the voltage across the third diode to an output voltage charged in the second capacitor. The method of claim 1,
Boost converter, characterized in that the first winding and the second winding is the same winding direction. The method of claim 7, wherein
And the voltage level induced in the second winding is higher than the voltage level charged in the link capacitor. The method of claim 7, wherein
The transformer further includes a leakage inductance connected in series between one end of the first winding and one end of an input power terminal to which the input power is transmitted, and a magnetic inductance connected in parallel to one end and the other end of the first winding. Boost converter. 10. The method of claim 9,
The switching unit includes a switch connected between the other end of the first winding and the ground,
The clamp part includes a first diode having an anode connected to the other end of the first winding and a cathode connected to one end of the second winding, an anode connected to ground, and a cathode connected to the other end of the second winding. 2 more diodes,
And the link capacitor is connected between the cathode of the first diode and ground. The method of claim 10,
And the stabilizing unit includes a third diode having an anode connected to the other end of the second winding, and a second capacitor connected to the cathode and the ground of the third diode. The method of claim 11,
The second diode is turned off when the voltage level induced in the second winding is lower than the voltage level charged in the link capacitor, and when the voltage level induced in the second winding is higher than the voltage level charged in the link capacitor. And turning on to clamp the voltage across the third diode to an output voltage charged in the second capacitor.

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