TWI451680B - Dc-dc converter - Google Patents

Description

DC converter

The present invention relates to a DC-DC converter, and particularly relates to a zero current switching and pulse frequency modulation (ZCS) operating in a discontinuous conduction mode (DCM). -PFM) DC converter.

A DC converter is an electronic circuit that converts the potential of a DC power source. The DC converter usually uses a switched-mode conversion to achieve potential conversion, wherein the DC potential is converted by temporarily storing the input energy and then releasing it. The energy storage component used may be a magnetic storage component (inductor or transformer) or an electrical storage component (capacitor). With the switching device, energy can be input to the energy storage element or the output energy storage element.

However, switch-switched DC converters have their drawbacks, including the energy consumption caused by switching actions and electromagnetic interference (EMI).

A DC converter is disclosed in which a zero current switching pulse modulation technique is employed and operates in a discontinuous conduction mode.

The DC converter circuit according to an embodiment of the present invention includes a first switch, a second switch, an input diode, a magnetizing inductor, a first resonant capacitor, a first resonant inductor, and a first output. The diode and a first output filter capacitor. The first and second switches are operated in a conducting manner. When the first switch is turned on, an input potential is coupled to the anode of the input diode. The cathode of the input diode is coupled to a first end of the magnetizing inductance. The conductive state of the second switch is designed to short a second end of the magnetizing inductance to a ground. The first resonant capacitor and the first resonant inductor are arranged in series between the second end of the magnetizing inductance and the ground. A first connection node between the first resonant capacitor and the first resonant inductor is coupled to a first end of the first output filter capacitor by the first output diode to regulate the first output The potential of the filter capacitor. A second end of the first output filter capacitor is coupled to the ground. In addition, the first end of the first output filter capacitor is coupled to a first load to supply the first load to a first output potential.

In some embodiments, a first end of the first resonant capacitor is coupled to the second end of the magnetizing inductor, and a second end of the first resonant capacitor is coupled to the first connecting node, the first resonant A first end of the inductor is coupled to the first connection node, and a second end of the first resonant inductor is coupled to the ground. In such an embodiment, the anode and the cathode of the first output diode are respectively coupled to the first connection node and the first end of the first output filter capacitor. The gain between the first output potential and the input potential is a positive value.

Regarding the circuit structure of the foregoing positive gain DC converter, a second resonant inductor, a second resonant capacitor, a second output diode, and a second output filter capacitor may be further added thereto. The second resonant inductor and the capacitor are coupled in series between the second end of the magnetizing inductor and the ground. A second connection node between the second resonant inductor and the capacitor is coupled to a first end of the second output filter capacitor via the second output diode to regulate the potential of the second output filter capacitor. The second resonant inductor has a first end coupled to the second end of the magnetizing inductance and a second end coupled to the second connecting node. The second resonant capacitor has a first end coupled to the second connecting node and a second end coupled to the ground. An anode of the second output diode is coupled to the first end of the second output filter capacitor, and a cathode of the second output diode is coupled to the second connection node. The first end of the second output filter capacitor is further coupled to a second load to supply the second load to the second output potential. The gain between the second output potential and the input potential is a negative value.

The above described objects, features, and advantages of the invention will be apparent from the description and appended claims appended claims

The following description discloses various embodiments of the present invention, and is intended to be illustrative of the scope of the invention. The scope of the invention should be referred to the scope of the patent application.

1 is a diagram showing a DC converter implemented in accordance with an embodiment of the present invention, converting a input potential Vi to a first output potential Vpo with a positive gain, or converting the input potential Vi to a second with a negative gain. The potential Vno is output.

As shown, the DC converter includes a first switch Q1, a second switch Q2, an input diode Di, a magnetizing inductance Lm, a first resonant capacitor Cpr, a first resonant inductor Lpr, and a first The output diode Dp, a first output filter capacitor Cpo, a second resonant inductor Lnr, a second resonant capacitor Cnr, a second output diode Dn, and a second output filter capacitor Cno. The sizes of the first and second output filter capacitors Cpo and Cno may be larger than the sizes of the first and second resonance capacitors Cpr and Cnr by a specific ratio. The first switch Q1 and the second switch Q2 are turned on in an alternating manner to convert input energy.

The first switch Q1 is an anode designed to couple the input potential Vi to the input diode Di. The cathode of the input diode Di is coupled to a first end of the magnetizing inductance Lm. The second switch Q2 is disposed between a second end of the magnetizing inductance Lm and a ground end. Parallel to the second switch Q2, the first resonant capacitor Cpr and the first resonant inductor Lpr are coupled in series between the second end of the magnetizing inductance Lm and the ground, and further, the second resonant inductor Lnr and The second resonant capacitor Cnr is also coupled in series between the second end of the magnetizing inductance Lm and the ground. The circuit structure including the first resonant capacitor Cpr, the first resonant inductor Lpr, the first output diode Dp, and the first output filter capacitor Cpo is designed to generate a positive gain output potential Vpo to a first load Rpo use. The circuit structure including the second resonant inductor Lnr, the second resonant capacitor Cnr, the second output diode Dn, and the second output filter capacitor Cno is designed to generate a negative gain output potential Vno for a second load Rno is used.

This paragraph discusses the related component links for the positive gain conversion described above. The first resonant capacitor Cpr has a first end coupled to the second end of the magnetizing inductance Lm, and has a second end coupled to a first connecting node n1 for coupling to the first resonant inductor Lpr. The first resonant inductor Lpr has a first end coupled to the first connection node n1 and a second end coupled to the ground. The first output diode Dp has an anode coupled to the first connection node n1 and has a first end coupled to the first output filter capacitor Cpo. A second end of the first output filter capacitor Cpo is coupled to the ground. The first load Rpo is coupled to the first end of the first output filter capacitor Cpo. The first output potential Vpo is generated by the above-described element to be supplied to the first load Rpo.

This paragraph discusses the component connection relationship of the negative gain conversion technique. The second resonant inductor Lnr has a first end coupled to the second end of the magnetizing inductor Lm, and a second end coupled to a second connecting node n2 to further couple the second resonant capacitor Cnr. The second resonant capacitor Cnr has a first end coupled to the second connecting node n2 and a second end coupled to the ground. The second output diode Dn has a cathode coupled to the second connection node n2 and has a first end coupled to the second output filter capacitor Cno. A second end of the second output filter capacitor Cno is coupled to the ground. The second output potential Vno is generated by the above-described element and supplied to the second load Rno.

The following paragraphs discuss several control methods for the first and second switches Q1 and Q2 described above.

Refer to the flow chart shown in Figure 2, where the output potential Vpo or Vno is regulated. As shown in step S202, the conduction condition of the first switch Q1 may include: a first resonance potential difference (Vcpr, located between the first end and the second end of the first resonance capacitor Cpr) is locked (reached and maintained at a negative value of the first output potential (-Vpo); a second resonance potential difference (Vcnr, located between the first end and the second end of the second resonant capacitor Cnr) is locked at the second output potential (Vno a first resonant current (Ipr flowing from the first end of the first resonant inductor Lpr to the second end) and a second resonant current (Inr flowing from a first end of the second resonant inductor Lnr to the second end) The terminal has been pulled up to the zero level; and the first and second output diodes Dp and Dn are turned off. In some embodiments, the conduction of the first switch Q1 is operated in accordance with a dead-time control technique well known to those skilled in the art. Next, as shown in step S204, the turn-off of the first switch Q1 and the turn-on of the second switch Q2 are when the input current Ii falls to a zero value. As shown in step S206, the time point at which the second switch Q2 is turned off is when the first and second output diodes Dp and Dn are switched off. The loop formed by steps S202, S204, and S206 can regulate the output potentials Vpo and Vno.

The flowchart shown in FIG. 2 is not intended to limit the control flow of the first and second switches Q1 and Q2. The on/off switching time points of the first and second switches Q1 and Q2 can be adjusted with the design of other components in the DC converter.

According to the control flow shown in Fig. 2, the DC converter of Fig. 1 is repeatedly switched in four operation modes. Figure 3 illustrates the waveforms of several signals in Figure 1.

In a first time interval t1~t2, the DC converter is operated in a first mode of operation. The first switch Q1 is switched on, and the second switch Q2 is kept off. At the start time point (time point t1) of the first operation mode, the first and second resonance currents Ipr and Inr start from a zero value, the first resonance potential difference Vcpr starts from the potential -Vpo, and the second resonance potential difference Vcnr is from The potential Vno starts and the first and second output diodes Dp and Dn are off. The conductive state of the first switch Q1 causes the input current Ii to be generated, and the first and second resonant capacitors Cpr and Cnr are charged via the corresponding resonant network. When the first and second resonance potential differences Vcpr and Vcnr reach zero, the first and second resonance currents Ipr and Inr are at their maximum value. The first and second resonance potential differences Vcpr and Vcnr continue to rise until the first and second resonance currents Ipr and Inr and the input current Ii decrease to zero. As shown, the first and second output diodes Dp and Dn are reverse biased during the first time interval t1 to t2, and therefore, the first and second output diodes Dp and Dn are in the first operation. It remains off in the mode. The loop formed by the first output filter capacitor Cpo and the first load Rpo may cause the first output potential Vpo to drop slightly. The loop formed by the second output filter capacitor Cno and the second load Rno may cause the second output potential Vno to rise slowly.

At time point t2 (when input current Ii drops to zero), first switch Q1 switches to non-conducting, and second switch Q2 switches to conduct to expand a second mode of operation within second time interval t2~t3. At this stage, the input current Ii is locked at a value of zero, and the first and second resonance currents Ipr and Inr are decreased to a negative value. The shorted path provided by the turned-on second switch Q2 allows the first and second resonant capacitors Cpr and Cnr to be discharged by the corresponding resonant network. When the first and second resonance potential differences Vcpr and Vcnr fall to a value of zero, the first and second resonance currents Ipr and Inr are at their minimum values. At time t3, the first and second resonance potential differences Vcpr and Vcnr are reduced to the potentials -Vpo and Vno, respectively, and the first and second output diodes Dp and Dn are activated to the next time interval t3~t4. Currents I_Dp and I_Dn are generated.

In the third time interval t3 to t4, a third operation mode is expanded. At this stage, the first and second output diodes Dp and Dn are forward biased, and thus the first and second resonance potential differences Vcpr and Vcnr are locked at the potentials -Vpo and Vno, respectively. Due to the first and second output filter capacitors Cpo And the size of Cno can be much larger than the first and second resonant capacitors Cpr and Cnr, and the currents I_Dp and I_Dn traversing the first and second output diodes Dp and Dn respectively approximate the absolute values of the first and second resonant currents Ipr and Inr value. In the third time interval t3~t4, the first output potential Vpo slightly rises back to a higher level, and the second output potential Vno is slightly pulled back to a lower level. At the time point t4, the first and second resonance currents Ipr and Inr are locked at the zero value, and the first and second output diodes Dp and Dn are switched off.

At time t4, the second switch Q2 is switched to be non-conducting, and the DC converter is switched to a fourth mode of operation. Note that at this time, the first and second switches Q1 and Q2 are non-conductive and the first and second output diodes Dp and Dn are off. The first output filter capacitor Cpo and the loop formed by the first load Rpo again slightly pull down the first output potential Vpo to a lower level. The circuit formed by the second output filter capacitor Cno and the second load Rno slightly pulls the second output potential Vno to a higher level. Since the first resonance potential difference Vcpr is a negative value (-Vpo) locked to the first output potential, and the second resonance potential difference Vcnr is a value Vno locked to the second output potential, the first and second resonance currents Ipr and Inr are pulled up The zero return value and the first and second output diodes Dp and Dn are off. The first switch Q1 can be turned on again at time point t5 to expand another round of output potential regulation procedures. The point in time at which the first switch Q1 is turned on may depend on the values of the first and second loads Rpo and Rno. In the described embodiment, a dead-time control technique is a good choice.

Figure 3 shows that the first output potential Vpo is regulated near a positive value (e.g., about +5.6 volts), and the second output potential Vno is regulated at a negative value (example) For example, around -5.6 volts). The DC converter disclosed in FIG. 1 can successfully convert the input potential Vi to a positive gain output potential Vpo and a negative gain output potential Vno.

The control flow of the first and second switches Q1 and Q2 is based on a zero current switching technique and a voltage switching technique. At time point t1, the first switch Q1 is turned on, but the input current Ii is zero; zero current switching is formed. At time t2, the first switch Q1 is switched to non-conducting, and the input current Ii returns to a value of zero; a zero current switching is also formed. At time t3, the first and second output diodes Dp and Dn are switched in a zero voltage switching event; at this time, the voltages V_Dp and V_Dn on the first and second output diodes Dp and Dn are close to zero volts. . At time t4, the first and second output diodes Dp and Dn are turned off under zero current switching conditions; at this time, the currents I_Dp and I_Dn on the first and second output diodes Dp and Dn are zero.

In some embodiments, the first and second switches Q1 and Q2 are implemented as double junction transistors (BJT) for the purpose of reducing energy consumption. Since the wear current of the tailing current can be avoided, the characteristics of the double junction transistor are quite suitable for the zero current switching technique disclosed herein. Furthermore, in order to reduce current stress, unnecessary energy transfer operations should be avoided; therefore, a unidirectional switch can be employed.

In another embodiment, the DC converter provides only the positive gain conversion described above. This type of DC converter does not include the components required for negative gain conversion (eg, does not include the second resonant inductor and the capacitors Lnr and Cnr, the second output diode Dn, and the second output filter capacitor Cno). In such an embodiment, the conduction condition of the first switch Q1 includes: the first resonance potential difference Vcpr has been locked at a negative value of the first output potential (-Vpo); the first resonance current Ipr has been pulled to zero level; and the first output diode Dp is off. In addition, when the input current Ii falls to the zero level, the first switch Q1 can be switched to be non-conductive and the second switch Q2 can be switched to be turned on. Then, when the first output diode Dp is again switched to the off state, the second switch Q2 can be switched to be non-conductive.

In another embodiment, the DC converter only provides the negative gain conversion described above. This type of DC converter does not include the components required for positive gain conversion (eg, does not include the first resonant capacitor and the inductors Cpr and Lpr, the first output diode Dp, and the first output filter capacitor Cpo). In such an embodiment, the conduction condition of the first switch Q1 includes: the second resonance potential difference Vcnr has been locked at the second output potential Vno; the second resonance current Inr has been pulled up to the zero level; and the second output diode Dn has been switched to the off state. In addition, when the input current Ii falls to the zero level, the first switch Q1 can be turned off and the second switch turned on. Then, when the second output diode Dn is again switched to the off state, the second switch Q2 can be turned off.

The following paragraphs describe the design guidelines for DC converters.

Figure 4 illustrates a design criterion for a symmetric positive/negative gain converter in a flow chart. The user-determinable DC conversion design parameters include: the overall energy consumption upper limit Ptotal, the input potential Vi, the predetermined positive gain amount Anor, the positive gain upper limit Amax, the output potential regulated frequency f, and the upper limit of the chain of the positive gain output potential Vpo. △ Vpo. The following discloses several equations for design use:

The following discussion assumes a Vto value of 0.5 watts for Ptotal, 2.8 volts for Vi, 2 for Aor, 3 for Amax, 5 MHz for f, and ±1% for ΔVpo. In step S402, Anor is substituted into Equation 1 to calculate the value of L1/Lpr, and the reliability margin can be more considered in design, so L1/Lpr can be set to 0.5. Step S404 substitutes the values of L1/Lpr and Amax into Equation 2 to calculate the rp value. Therefore, the rp value is 8.989. Step S406 substitutes the values of Vi, Anor, and Ptotal into Equation 3 to calculate the minimum value Rpo(min) of the first load. Rpo(min) can be set to 125 ohms. Step S408 substitutes Rpo(min) and rp into Equation 4 to calculate the Zp value, and takes the values of Anor, Rpo (set based on Rpo(min)) and f into Equation 5 to calculate the first resonance capacitance Cpr. the size of. The calculated result shows that Zp is 14 ohms and the first resonant capacitor Cpr is 2.2 nF. Step S410 substitutes Zp and Cpr into Equation 6 to find the first resonant inductor Lpr. The result of the first resonance inductance Lpr is 0.47 uH. Step S412 substitutes Lpr and Anor into Equation 1 to calculate the magnitude of the magnetizing inductance L1 (i.e., Lm). The calculation results show that the magnetizing inductance L1 should be designed to be 0.22 uH. Step S414 incorporates the chain-wave limitation ΔVpo into design considerations to calculate the value of the first output filter capacitor Cpo. According to the following equation: The first output filter capacitor Cpo is set to 0.18 uF. In step S416, based on the first resonant capacitor Cpr, the first resonant inductor Lpr, and the first output filter capacitor Cpo calculated above, the second resonant capacitor Cno, the second resonant inductor Lnr, and the second output filter capacitor Cno are obtained. value.

It is specifically stated that the flow shown in Figure 4 and the calculated L1, Cpr, Lpr, Cpo, Cnr, Lnr, and Cno are not intended to limit the scope of the invention. Those skilled in the art will also be able to design the DC converter disclosed in FIG. 1 with other design criteria.

While the present invention has been described in its preferred embodiments, the present invention is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is subject to the definition of the scope of the patent application.

Cno, Cpo. . . Second, first output filter capacitor

Cnr, Cpr. . . Second, first resonant capacitor

Di. . . Input diode

Dn, Dp. . . Second, first output diode

I_Dn, I_Dp. . . Current flowing through Dn, Dp

Ii. . . Input Current

Inr, Ipr. . . Second, first resonant current

N1, n2. . . First and second connection nodes

Lm. . . Magnetizing inductance

Lnr, Lpr. . . Second, first resonant inductor

Rno, Rpo. . . Second, first load

Q1, Q2. . . First and second switches

Vcnr, Vcpr. . . Second, first resonance potential difference

V_Dn, V_Dp. . . Cross pressure on Dn, Dp

Vi. . . Input potential

as well as

Vno, Vpo. . . Second, first output potential

Figure 1 illustrates a DC-DC converter in accordance with an embodiment of the present invention;

Figure 2 is a flow chart illustrating a control flow of the disclosed DC converter;

Figure 3 illustrates the waveforms of several signals on Figure 1;

Figure 4 illustrates in a flow chart a design guideline for the disclosed DC converter.

Cno, Cpo. . . Second, first output filter capacitor

Cnr, Cpr. . . Second, first resonant capacitor

Di. . . Input diode

Dn, Dp. . . Second, first output diode

I_Dn, I_Dp. . . Current flowing through Dn, Dp

Ii. . . Input Current

Inr, Ipr. . . Second, first resonant current

N1, n2. . . First and second connection nodes

Lm. . . Magnetizing inductance

Lnr, Lpr. . . Second, first resonant inductor

Rno, Rpo. . . Second, first load

Q1, Q2. . . First and second switches

Vcnr, Vcpr. . . Second, first resonance potential difference

V_Dn, V_Dp. . . Cross pressure on Dn, Dp

Vi. . . Input potential

as well as

Vno, Vpo. . . Second, first output potential

Claims (13)

A DC converter includes: an input diode, a first output diode, and a first output filter capacitor; a first switch for coupling an input potential to an anode of the input diode; a magnetizing inductor having a first end and a second end, wherein the first end of the magnetizing inductor is coupled to a cathode of the input diode; and the second switch is configured to couple the magnetizing inductor a second resonant port and a grounding terminal; and a first resonant capacitor and a first resonant inductor connected in series between the second end of the magnetizing inductor and the grounding end, wherein the first resonant capacitor and the first resonant inductor A first connection node is coupled to a first end of the first output filter capacitor via the first output diode to regulate a potential on the first output filter capacitor; wherein: the first output filter a first end of the first output filter capacitor is coupled to a first load to supply the first load to a first output potential; and the first switch and the first The second switch is operated in the polling conduction mode. . The DC converter of claim 1, wherein the first resonant capacitor has a first end coupled to the second end of the magnetizing inductance, and a second end coupled to the first connecting node The first resonant inductor has a first end coupled to the first connecting node and a second end coupled to the ground end; and the first output diode has an anode coupled to the first connecting node and has A cathode is coupled to the first end of the first output filter capacitor. The DC converter of claim 2, wherein: the first switch reaches a negative value at a first resonance potential and maintains a negative value of the first output potential, and a first resonant current is pulled to a value of zero and Switching the first output diode to a conducting state; the first resonant potential difference is between the first and second ends of the first resonant capacitor; and the second resonant current flows through the first resonant inductor , from the first end to the second end. The DC converter of claim 3, wherein the first switch is turned off and the second switch is turned on when an input current falls to a zero level. The DC converter of claim 4, wherein the second switch is switched to be non-conducting when the first output diode is again turned off. The DC converter of claim 1, wherein the first resonant inductor has a first end coupled to the second end of the magnetizing inductance, and a second end coupled to the first connecting node The first resonant capacitor has a first end coupled to the first connecting node and a second end coupled to the ground end; and the first output diode has a cathode coupled to the first connecting node, and The first end of the first output filter capacitor is coupled to the anode. The DC converter of claim 6, wherein: the first switch is reached at a first resonance potential difference and maintained at the first output potential, a first resonant current is pulled to a zero level and the first The first output diode is turned off to be turned on; the first resonant potential difference is between the first and second ends of the first resonant capacitor; and the first resonant current flows through the first resonant inductor, The first end flows to the second end. The DC converter of claim 7, wherein the first switch is turned off and the second switch is turned on when an input current falls to a zero level. The DC converter of claim 8, wherein the second switch is turned off when the first output diode is again switched to be non-conducting. The DC converter of claim 2, further comprising: a second output diode and a second output filter capacitor; and a second resonant inductor and a second resonant capacitor connected in series to the magnetizing inductor Between the second end and the ground, wherein: a second connection node between the second resonant inductor and the second resonant capacitor is coupled to the second output filter capacitor via the second output diode a first end is configured to regulate the second output filter capacitor; the second resonant inductor has a first end coupled to the second end of the magnetizing inductor, and a second end coupled to the second connecting node; The second resonant capacitor has a first end coupled to the second connecting node and has a second end coupled to the ground. The second output diode has a cathode coupled to the second connecting node. And having a first end coupled to the second output filter capacitor; the first end of the second output filter capacitor is further coupled to a second load to supply the second load and the second output potential; a second output filter capacitor The two ends are coupled to the ground. The DC converter of claim 10, wherein: the first switch is at a first resonance potential difference and is maintained at a negative value of the first output potential, and a second resonance potential difference is reached and maintained at the The second output potential, a first resonant current, and a second resonant current are pulled to a zero level, and the first and second output diodes are turned off to be switched to an on state; the first resonant potential difference is present in the first Between the first and second ends of the resonant capacitor; the second resonant potential difference is between the first and second ends of the second resonant capacitor; the first resonant current flows through the first resonant inductor The first end flows to the second end; and the second resonant current flows through the second resonant inductor, from the first end to the second end. The DC converter of claim 11, wherein the first switch is turned off and the second switch is turned on when an input current drops to a zero level. The DC converter of claim 12, wherein the second switch is turned off when the first and second diodes are again turned off.