Power converter

Abstract

A power converter is provided. The power converter includes an LLC converter, a feedback circuit, a first driving circuit, and a second driving circuit. The LLC converter includes a first bridge transistor set and a second bridge transistor set. The feedback circuit provides a feedback signal corresponding to a current value of the LLC converter. The first driving circuit drives the first bridge transistor set in response to the feedback signal and provides a control signal. The second driving circuit drives the second bridge transistor set in response to the control signal.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power conversion, and particularly to a power converter. BACKGROUND

[0002] The existing half-bridge LLC converter can be operated by a single driver. The half-bridge LLC converter is not suitable for high power applications. Therefore, in high power applications, the existing half-bridge LLC converter has to be added with another bridge transistor set to realize a full-bridge LLC converter. In the architecture of the half-bridge LLC converter plus another bridge transistor set, the driver mentioned above cannot drive the newly added bridge transistor set. Therefore, in the existing method, the driver is removed and a micro-controller unit (MCU) is added.

[0003] However, such a method requires modification of the micro-controller, such as writing firmware based on two bridge transistor sets. Therefore, the cost of modifying the half-bridge LLC converter to a full-bridge LLC converter is greatly increased due to the removal of the original driver, the addition of the micro-controller, and the rewriting of the firmware. SUMMARY

[0004] The present application provides a power converter capable of reducing the cost of modifying a half-bridge power converter to a full-bridge power converter.

[0005] The power converter of the present application includes an LLC converter, a feedback circuit, a first driving circuit, and a second driving circuit. The LLC converter includes a first bridge transistor set and a second bridge transistor set. The feedback circuit provides a feedback signal corresponding to a current value of the LLC converter. The first driving circuit is coupled to the feedback circuit and the first bridge transistor set. The first driving circuit drives the first bridge transistor set in response to the feedback signal and provides a control signal. The second driving circuit is coupled to the first driving circuit and the second bridge transistor set. The second driving circuit drives the second bridge transistor set in response to the control signal.

[0006] In an embodiment of the present application, the LLC converter includes a resonant circuit. The resonant circuit is coupled between a first node of the first bridge transistor set and a second node of the second bridge transistor set.

[0007] In an embodiment of the present application, the feedback circuit is inductively coupled with the resonant circuit to generate the feedback signal corresponding to the current value of the resonant circuit and to compensate the phase of the feedback signal.

[0008] In one embodiment of the present application, the feedback circuit includes a first feedback winding, a second feedback winding, a feedback resistor, and a feedback capacitor. The first feedback winding is coupled to the resonant circuit. The second feedback winding is coupled between the first drive circuit and the reference low voltage. The second feedback winding is inductively coupled to the first feedback winding to generate a current signal corresponding to a current value of the resonant circuit. The feedback resistor is connected in parallel to the second feedback winding. The feedback resistor converts the current signal to a sensed voltage signal. The feedback capacitor is coupled between the second feedback winding and the reference low voltage. The feedback capacitor compensates a phase of the sensed voltage signal to generate a feedback signal.

[0009] In one embodiment of the present application, the phase of the feedback signal lags behind the phase of the sensed voltage signal. The phase of the feedback signal is substantially the same as a current phase of the resonant circuit.

[0010] In one embodiment of the present application, the power converter further includes a coupling circuit. The coupling circuit is coupled between the first drive circuit and the second drive circuit. The coupling circuit transmits the control signal from the first drive circuit to the second drive circuit in an inductive coupling manner.

[0011] In one embodiment of the present application, the first bridge transistor set includes a first transistor and a second transistor. The second transistor is connected to the first transistor at the first node and connected in series with the first transistor between the input of the LLC converter and the reference low voltage. The second bridge transistor set includes a third transistor and a fourth transistor. The fourth transistor is connected to the third transistor at the second node and connected in series with the third transistor between the input of the LLC converter and the reference low voltage. The second drive circuit drives the third transistor and the fourth transistor based on the control signal.

[0012] In one embodiment of the present application, the coupling circuit includes a first loop and a second loop. The first loop is coupled between the control terminal of the first transistor and the first node. The second loop is coupled between the second drive circuit and the reference low voltage. The first loop and the second loop are isolated from each other.

[0013] In one embodiment of the present application, the first loop includes a first coupling winding and a first capacitor. The first capacitor is connected in series with the first coupling winding between the control terminal of the first transistor and the first node. The first capacitor compensates a phase of the control signal.

[0014] In one embodiment of the present application, the second loop includes a second coupling winding, a second capacitor, and a diode. The second coupling winding is inductively coupled to the first coupling winding to receive the control signal. The second capacitor is connected in series with the second coupling winding between the second drive circuit and the reference low voltage. The second capacitor compensates a phase of the control signal. The cathode of the diode is coupled to the second drive circuit. The anode of the diode is coupled to the reference low voltage.

[0015] Based on the above, the feedback circuit provides a feedback signal corresponding to the LLC converter. The first driving circuit drives the first bridge transistor set in response to the feedback signal, and provides a control signal. The second driving circuit drives the second bridge transistor set in response to the control signal. In other words, the first driving circuit drives the first bridge transistor set, and the second driving circuit drives the second bridge transistor set in response to the driving of the first driving circuit. Therefore, in the case of adding the second bridge transistor set, the power converter can drive the LLC converter by the cooperation of the first driving circuit and the newly added second driving circuit. In this way, compared with the prior art, the cost of modifying the half-bridge LLC converter to the full-bridge LLC converter can be reduced.

[0016] In order to make the above features and advantages of the present application more apparent, the following embodiments are specifically described below, and the accompanying drawings are described in detail as follows. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a schematic diagram of a power converter according to a first embodiment of the present application.

[0018] Figure 2 is a schematic diagram of a power converter according to a second embodiment of the present application.

[0019] Figure 3 is a schematic diagram of a power converter according to a third embodiment of the present application.

[0020] REFERENCE NUMERALS

[0021] 100, 200, 300: power converter

[0022] 110, 210, 310: LLC converter

[0023] 120, 220, 320: feedback circuit

[0024] 130, 230, 330: first driving circuit

[0025] 140, 240, 340: second driving circuit

[0026] 250, 350: coupling circuit

[0027] 351: first loop

[0028] 352: second loop

[0029] BRI, D_HI, D_LO, IN_HI, IN_LO: pin of second driving circuit

[0030] C1: input capacitor

[0031] C2, C4, C5: capacitor

[0032] C3: feedback capacitor

[0033] C6: output capacitor

[0034] CL1: primary side coil

[0035] CL2, CL3: secondary side coil

[0036] CS, HB, ML, MU: pin of first driving circuit

[0037] D1, D2, Z1: diode

[0038] FB: feedback signal

[0039] GP1: first bridge transistor group

[0040] GP2: second bridge transistor group

[0041] L1: first feedback winding

[0042] L2: inductor

[0043] L3: second feedback winding

[0044] L4: first coupling winding

[0045] L5: second coupling winding

[0046] N1: first node

[0047] N2: second node

[0048] Q1, Q2, Q3, Q4: transistor

[0049] R1: feedback resistor

[0050] R2, R3: resistor

[0051] RT: resonance circuit

[0052] SC: control signal

[0053] Vin: input voltage

[0054] Vout: output voltage

[0055] VS: sense voltage signal DETAILED DESCRIPTION

[0056] Reference will now be made in detail to the exemplary embodiments of the present application, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used in the different drawings and the same or similar reference numbers will be used throughout this disclosure to refer to the same or similar parts.

[0057] Reference is made to Figure 1 , Figure 1 is a schematic diagram of a power converter according to a first embodiment of the present application. In this embodiment, the power converter 100 comprises an LLC converter 110, a feedback circuit 120, a first driving circuit 130 and a second driving circuit 140. The LLC converter 110 comprises a first bridge transistor set GP1 and a second bridge transistor set GP2. The feedback circuit 120 provides a feedback signal FB corresponding to a current value of the LLC converter. For example, the first bridge transistor set GP1 comprises transistors Q1, Q2. The transistors Q1 and Q2 are connected at a first node N1. The transistors Q1, Q2 are connected in series between an input of the LLC converter and a reference low voltage (e.g. ground). The second bridge transistor set GP2 comprises transistors Q3, Q4. The transistors Q3, Q4 are connected at a second node N2. The transistors Q3, Q4 are connected in series between the input of the LLC converter and the reference low voltage. The LLC converter 110 further comprises a resonant circuit RT. The resonant circuit RT is arranged between the first node N1 and the second node N2. The feedback circuit 120 senses a current value at the resonant circuit RT and provides a feedback signal FB corresponding to the current value at the resonant circuit RT. In some embodiments, the resonant circuit RT can be coupled in series with a primary side winding of the LLC converter 110 between the first node N1 and the second node N2. In some embodiments, the resonant circuit RT is coupled between the first node N1 and the second node N2, and an inductor of the resonant circuit RT is coupled in parallel with a primary side winding of the LLC converter 110. The present application is not limited to the configuration of the resonant circuit RT and the primary side winding.

[0058] In this embodiment, the first driving circuit 130 is coupled to the feedback circuit FB and the first bridge transistor set GP1. The first driving circuit 130 receives the feedback signal FB and drives the first bridge transistor set GP1 in response to the feedback signal FB. That is, the first driving circuit 130 drives the first bridge transistor set GP1 in response to the operation of the LLC converter. In addition, the first driving circuit 130 also provides a control signal SC. In this embodiment, the control signal SC is associated with the state of the first driving circuit 130 driving the first bridge transistor set GP1. In this embodiment, the first driving circuit 130 is implemented by a single half-bridge controller. For example, the first driving circuit 130 can be a half-bridge controller such as NCP13992, L6599, etc.

[0059] It is noted that the power converter 100 can utilize the first driving circuit 130 and the feedback circuit 120 to form a closed loop driving architecture, thereby stabilizing the operation of the first driving circuit 130.

[0060] In this embodiment, the second driving circuit 140 is coupled to the first driving circuit 130 and the second bridge transistor set GP2. The second driving circuit 140 receives the control signal SC from the first driving circuit 130. The second driving circuit 140 drives the second bridge transistor set GP2 in response to the control signal SC. The second driving circuit 140 is implemented, for example, by a single half-bridge driver. For example, the second driving circuit 140 can be a NCP5106A, NCP5304, or the like half-bridge driver.

[0061] In this embodiment, the second driving circuit 140 drives the second bridge transistor set GP2 in response to the control signal SC of the first driving circuit 130. Therefore, in the case of adding the second bridge transistor set, the power converter 100 can be driven by the cooperation of the first driving circuit and the newly added second driving circuit 140 to drive the LLC converter. In modifying the half-bridge architecture of the LLC converter 110 to the full-bridge architecture, this embodiment only needs to add the feedback circuit 120 and the second driving circuit 140. This embodiment does not need to replace the first driving circuit 130 by a microcontroller. In this way, compared with the prior art, the cost of modifying the half-bridge LLC converter to the full-bridge LLC converter can be reduced.

[0062] In this embodiment, the secondary side circuit of the LLC converter can be an asynchronous rectification circuit. In some embodiments, the secondary side circuit of the LLC converter can be a synchronous rectification circuit. The present application is not limited to the architecture of the secondary side circuit of the LLC converter 110.

[0063] Please refer to Figure 2 , Figure 2 is a schematic diagram of a power converter according to the second embodiment of the present application. In this embodiment, the power converter 200 includes an LLC converter 210, a feedback circuit 220, a first driving circuit 230, a second driving circuit 240, and a coupling circuit 250. The cooperation between the LLC converter 210, the feedback circuit 220, and the first driving circuit 230 can be sufficiently taught in the first embodiment, and thus will not be repeated here. The coupling circuit 250 is coupled between the first driving circuit 230 and the second driving circuit 240. The coupling circuit 250 transmits the control signal SC from the first driving circuit 230 to the second driving circuit 240 in an inductive coupling manner.

[0064] Further explanation, please refer to Figure 3 , Figure 3is a schematic diagram of a power converter according to the third embodiment of the present application. In this embodiment, the power converter 300 comprises an LLC converter 310, a feedback circuit 320, a first driving circuit 330, a second driving circuit 340, and a coupling circuit 350. The LLC converter 310 comprises a first bridge transistor set GP1, a second bridge transistor set GP2, a resonance circuit RT, and a secondary side circuit. The first bridge transistor set GP1 and the second bridge transistor set GP2 are connected in parallel with an input capacitor CI. The first bridge transistor set GP1 comprises transistors Q1, Q2. The transistors Q1 and Q2 are connected to a first node N1. The transistors Q1, Q2 are connected in series between an input terminal of the LLC converter 310 and a reference low voltage. The input terminal of the LLC converter 310 is configured to receive an input voltage Vin. The second bridge transistor set GP2 comprises transistors Q3, Q4. The transistors Q3, Q4 are connected to a second node N2. The transistors Q3, Q4 are connected in series between the input terminal of the LLC converter and the reference low voltage. The resonance circuit RT is coupled between the first node N1 and the second node N2.

[0065] In this embodiment, the resonance circuit RT is coupled between the first node N1 and the second node N2. The feedback circuit 320 comprises a first feedback winding LI, a second feedback winding L3, a feedback resistor R1, and a feedback capacitor C3. The first feedback winding LI is coupled in series with the resonance circuit RT between the first node N1 and the second node N2. The resonance circuit RT comprises an inductor L2, a primary side coil CL1, and a capacitor C2. The first feedback winding LI, the inductor L2, the capacitor C2, and the primary side coil CL1 are coupled in series. In some embodiments, the order of the first feedback winding LI, the inductor L2, the capacitor C2, and the primary side coil CL1 can be changed according to actual requirements. In some embodiments, the inductor L2 can be designed to be connected in parallel with the primary side coil CL1. The present application is not limited to the coupling manner of the resonance circuit RT and the primary side coil CL1 in this embodiment.

[0066] In this embodiment, the first driving circuit 330 comprises at least pins MU, HB, ML, CS. The pin MU is coupled to a control terminal of the transistor Q1. The first driving circuit 330 drives the transistor Q1 through the pin MU. The pin ML is coupled to a control terminal of the transistor Q2. The first driving circuit 330 drives the transistor Q2 through the pin ML. The pin HB is coupled to the first node N1. The first driving circuit 330 receives a feedback signal FB through the pin CS. In this embodiment, the feedback circuit 320 inductively couples with the resonance circuit RT to generate the feedback signal FB corresponding to the current value of the resonance circuit RT. In addition, the feedback circuit 320 also compensates the phase of the feedback signal FB.

[0067] In this embodiment, the feedback capacitor C3 is coupled between the first driving circuit 330 (i.e., the pin CS) and the reference low voltage. The second feedback winding L3 is inductively coupled with the first feedback winding LI to generate a current signal corresponding to the current value of the resonant circuit RT. In this embodiment, the second feedback winding L3 is inductively coupled with the first feedback winding LI. That is, the second feedback winding L3 generates a current signal corresponding to the current value flowing through the first feedback winding LI. The feedback resistor Rl is in parallel with the second feedback winding L3. The feedback resistor Rl converts the current signal into a sensed voltage signal VS. The feedback capacitor C3 is coupled between the first driving circuit 330 (i.e., the pin CS) and the reference low voltage. The feedback capacitor C3 compensates the phase of the sensed voltage signal VS to generate the feedback signal FB. In this embodiment, based on the inductive coupling, the phase of the sensed voltage signal VS is substantially the same as the current phase of the resonant circuit RT. It is noted that the phase of the sensed voltage signal VS causes the first driving circuit 330 in half-bridge driving mode to malfunction. Therefore, the feedback capacitor C3 compensates the phase of the sensed voltage signal VS to generate the feedback signal FB, such that the phase of the feedback signal FB lags behind the current phase of the resonant circuit RT. Thus, the operation of the first driving circuit 330 is normal. In this embodiment, the first feedback winding LI and the second feedback winding L3 can be part of a current transformer (CT).

[0068] In this embodiment, the feedback circuit 320 can further include a resistor R2. The resistor R2 is coupled between the first end of the feedback resistor Rl and the first end of the feedback capacitor C3. The second end of the feedback resistor Rl and the second end of the feedback capacitor C3 are coupled to the reference low voltage. Thus, the feedback resistor Rl, the resistor R2 and the feedback capacitor C3 collectively form a resistor-capacitor network. In some embodiments, the resistor-capacitor network is not limited to only the feedback resistor Rl, the resistor R2 and the feedback capacitor C3.

[0069] In this embodiment, the second driving circuit 340 includes at least the pins IN_HI, D_HI, IN_LO, D_LO, BRI. The pin IN_HI is coupled to the pin ML. The pin D_HI is coupled to the control terminal of the transistor Q3. Based on the signal received by the pin IN_HI, the second driving circuit 340 drives the transistor Q3 through the pin D_HI. Thus, the transistors Q2, Q3 are substantially turned on or turned off at the same time. The second driving circuit 340 receives the control signal SC through the pin IN_LO. The pin D_LO is coupled to the control terminal of the transistor Q4. Based on the control signal SC, the second driving circuit 340 drives the first bridge arm transistor set GP1 (i.e., the transistors Q3, Q4) through the pin D_LO. In addition, the pin BRI is coupled to the second node N2.

[0070] In this embodiment, the coupling circuit 350 comprises a first loop 351 and a second loop 352. The first loop 351 is coupled between the control terminal of the transistor Q1 and the first node N1. The second loop 352 is coupled between the second driving circuit 340 and the reference low voltage. Further, the first loop 351 can be regarded as coupled between the pin MU and the pin HB. The second loop 352 can be regarded as coupled between the pin IN LO and the reference low voltage. It is noted that the first loop 351 and the second loop 352 are isolated from each other. The reference point (or common point) of the first driving circuit 330 and the reference point of the second driving circuit 340 can be different. The isolation between the first loop 351 and the second loop 352 can avoid abnormal operation or malfunction of the second driving circuit 340. In this embodiment, the coupling circuit 350 helps the LLC converter 310 to achieve zero voltage switching (ZVS) in the full-bridge architecture.

[0071] In this embodiment, the first loop 351 comprises a first coupling winding L4 and a capacitor C4. The capacitor C4 and the first coupling winding L4 are coupled in series between the control terminal of the transistor Q1 and the first node N1. The capacitor C4 compensates the phase of the control signal SC. It is noted that the control signal SC is associated with the signal used to drive the transistor Q1.

[0072] In this embodiment, the first loop 351 further comprises a resistor R3. The resistor R3, the capacitor C4 and the first coupling winding L4 are coupled in series between the control terminal of the transistor Q1 and the first node N1. The series order of the resistor R3, the capacitor C4 and the first coupling winding L4 can be changed according to actual requirements. The present application is not limited to the series order of the first loop 351 in this embodiment.

[0073] In this embodiment, the second loop 352 comprises a second coupling winding L5, a capacitor C5 and a diode Z1. The second coupling winding L5 is inductively coupled with the first coupling winding L4 to receive the control signal SC. The capacitor C5 and the second coupling winding L5 are coupled in series between the second driving circuit 340 and the reference low voltage. The capacitor C5 compensates the phase of the control signal SC. The cathode of the diode Z1 is coupled to the second driving circuit 340 (i.e. the pin IN LO). The anode of the diode Z1 is coupled to the reference low voltage. In this embodiment, the diode Z1 is used to limit the voltage value of the control signal SC. In this embodiment, the diode Z1 can be implemented by a zener diode. In this embodiment, the first coupling winding L4 and the second coupling winding L5 can be part of a potential transformer (PT).

[0074] In the present embodiment, the secondary-side circuit is configured to provide an output voltage Vout. In the present embodiment, the secondary-side circuit includes the secondary-side coils CL2, CL3, diodes D1, D2, and an output capacitor C6. The first terminal of the secondary-side coil CL2 is connected to the first terminal of the secondary-side coil CL3. The second terminal of the secondary-side coil CL2 is coupled to the anode of the diode D1. The second terminal of the secondary-side coil CL3 is coupled to the anode of the diode D2. The cathode of the diode D1 is coupled to the cathode of the diode D2. In addition, the output capacitor C6 is coupled between the first terminal of the secondary-side coil CL2 and the cathode of the diode D1.

[0075] In summary, the power converter includes an LLC converter, a feedback circuit, a first driving circuit, and a second driving circuit. The feedback circuit is configured to provide a feedback signal corresponding to the LLC converter. The first driving circuit is configured to drive the first bridge transistor set in response to the feedback signal, and to provide a control signal. The second driving circuit is configured to drive the second bridge transistor set in response to the control signal. Thus, in the case of adding the second bridge transistor set, the power converter can drive the LLC converter by the cooperation of the first driving circuit and the newly added second driving circuit. In this way, the cost of modifying a half-bridge LLC converter to a full-bridge LLC converter can be reduced compared to the prior art. In some embodiments, the power converter further includes a coupling circuit. The coupling circuit includes a first loop and a second loop. The first loop is coupled between the control terminal of the first transistor and the first node. The second loop is coupled between the second driving circuit and a reference low voltage. The first loop and the second loop are isolated from each other, so as to avoid abnormal or erroneous operation of the second driving circuit.

[0076] Finally, it should be noted that the above-described embodiments are merely intended to illustrate the technical solutions of the present application, rather than limit the same. Even though the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still make modifications to the technical solutions recorded in the above embodiments, or equivalently replace some or all of the technical features thereof; and these modifications or replacements do not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A power converter, characterized by, The power converter comprises: an LLC converter including a first bridge transistor set and a second bridge transistor set; a feedback circuit configured to provide a feedback signal corresponding to a current value of the LLC converter; a first driving circuit coupled to the feedback circuit and the first bridge transistor set, configured to drive the first bridge transistor set in response to the feedback signal and provide a control signal; and a second driving circuit coupled to the first driving circuit and the second bridge transistor set, configured to drive the second bridge transistor set in response to the control signal.

2. The power converter of claim 1, wherein, The LLC converter comprises: a resonant circuit coupled between a first node of the first bridge transistor set and a second node of the second bridge transistor set.

3. The power converter of claim 2, wherein, The feedback circuit is inductively coupled with the resonant circuit to generate the feedback signal corresponding to the current value of the resonant circuit and compensate a phase of the feedback signal.

4. The power converter of claim 2, wherein, The feedback circuit comprises: a first feedback winding coupled to the resonant circuit; a second feedback winding coupled between the first driving circuit and a reference low voltage and inductively coupled with the first feedback winding to generate a current signal corresponding to the current value of the resonant circuit; a feedback resistor connected in parallel to the second feedback winding and converting the current signal to a sensed voltage signal; and a feedback capacitor coupled between the second feedback winding and the reference low voltage, compensating a phase of the sensed voltage signal to generate the feedback signal.

5. The power converter of claim 4, wherein: a phase of the feedback signal is substantially the same as a phase of the sensed voltage signal, and the phase of the feedback signal lags a current phase of the resonant circuit.

6. The power converter of claim 2, wherein, The power converter further comprises: a coupling circuit coupled between the first driving circuit and the second driving circuit, configured to transmit the control signal from the first driving circuit to the second driving circuit in an inductive coupling manner.

7. The power converter of claim 6, wherein: the first bridge transistor set comprises: a first transistor; and a second transistor connected to the first node with the first transistor and connected in series with the first transistor between an input of the LLC converter and a reference low voltage, and the second bridge transistor set comprises: a third transistor; and a fourth transistor connected to the second node with the third transistor and connected in series with the third transistor between the input of the LLC converter and the reference low voltage, the second driving circuit driving the third and fourth transistors based on the control signal.

8. The power converter of claim 7, wherein, The coupling circuit comprises: a first loop coupled between a control terminal of the first transistor and the first node; and a second loop coupled between the second driving circuit and the reference low voltage, wherein the first loop and the second loop are isolated from each other.

9. The power converter of claim 8, wherein, The first loop comprises: a first coupling winding; and a first capacitor connected in parallel to the first coupling winding. a first capacitor coupled in series with the first coupling winding between the control terminal of the first transistor and the first node, configured to compensate for a phase of the control signal.

10. The power converter of claim 9, wherein, The second loop includes: a second coupling winding inductively coupled with the first coupling winding to receive the control signal; a second capacitor coupled in series with the second coupling winding between the second drive circuit and the reference low voltage, configured to compensate for a phase of the control signal; and a diode having a cathode coupled to the second drive circuit and an anode coupled to the reference low voltage.

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