TWI879198B - Power converter having clamping mechanism - Google Patents

Abstract

A power converter having a clamping mechanism is provided. The power converter includes a high-side switch, a resonant inductor, a low-side switch, an output inductor, a clamp capacitor, an auxiliary switch and a control circuit. A first terminal of the resonant inductor is connected to a second terminal of the high-side switch. A first terminal of the low-side switch is connected to a second terminal of the resonant inductor. A first terminal of the output inductor is connected to the second terminal of the resonant inductor and the first terminal of the low-side switch. A first terminal of the clamp capacitor is connected to the second terminal of the high-side switch and the first terminal of the resonant inductor. A first terminal of the auxiliary switch is connected to a second terminal of the clamp capacitor.

Description

Power converter with clamping mechanism

The present invention relates to a power converter, and more particularly to a power converter with a clamping mechanism.

With the rapid development of technology, portable electronic products have been widely used in people's lives. Power management is an important part of these electronic products. It must be able to provide stable power to each subsystem in the electronic product to enable it to operate normally.

As greenhouse effects become more serious, the power converters in these products are mostly moving towards smaller footprints, high power density, and high efficiency to achieve energy conservation. In terms of improving power density, the required inductance and capacitance values can be reduced by increasing the switching frequency of the power converter. However, increasing the switching frequency in traditional power converters will increase switching losses, which is not conducive to further improving the efficiency of traditional power converters.

The present invention provides a power converter with a clamping mechanism to address the deficiencies of the prior art. The power converter with a clamping mechanism of the present invention comprises an upper bridge switch, a resonant inductor, a lower bridge switch, an output inductor, an output capacitor, a clamping capacitor, an auxiliary switch and a control circuit. The first end of the upper bridge switch is connected to the positive end of the input power supply. The first end of the resonant inductor is connected to the second end of the upper bridge switch. The first end of the lower bridge switch is connected to the second end of the resonant inductor. The second end of the lower bridge switch is connected to the negative end of the input power supply. The first end of the output inductor is connected to the second end of the resonant inductor and the first end of the lower bridge switch. The first end of the output capacitor is connected to the second end of the output inductor and a load. The second end of the output capacitor is connected to the negative end of the input power supply. The first end of the clamping capacitor is connected to the second end of the upper bridge switch and the first end of the resonant inductor. The first end of the auxiliary switch is connected to the second end of the clamping capacitor. The second end of the auxiliary switch is connected to the negative end of the input power supply. The control circuit is connected to the control end of the upper bridge switch, the control end of the lower bridge switch and the control end of the auxiliary switch. The control circuit is configured to control the operation of the upper bridge switch, the lower bridge switch and the auxiliary switch.

As described above, the present invention provides a power converter with a clamping mechanism. The power converter of the present invention utilizes a clamping circuit element to generate a negative current to achieve zero-voltage switching of the switch element, thereby further improving the efficiency of the converter. In terms of switch control, a non-complementary control method different from the past is used, which can further reduce the converter loss compared to the traditional complementary control method. In addition, the power converter of the present invention can further perform feedback control, that is, adopt the adaptive closing time control in the ripple control, so that when the input voltage, output voltage, and load current change, the same switching frequency can be maintained, thereby reducing the electromagnetic interference (EMI) problem of the switching power supply.

To further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are only used for reference and description and are not used to limit the present invention.

The following is an explanation of the implementation of the present invention through specific concrete embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments. The details in this specification can also be modified and changed in various ways based on different viewpoints and applications without departing from the concept of the present invention. In addition, the drawings of the present invention are only for simple schematic illustrations and are not depicted according to actual sizes. Please note in advance. The following implementation will further explain the relevant technical contents of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention. In addition, the term "or" used in this article may include any one or more combinations of the related listed items depending on the actual situation.

Please refer to FIG. 1 , which is a circuit diagram of a power converter with a clamping mechanism according to an embodiment of the present invention.

The power converter with a clamping mechanism of the present invention includes an upper bridge switch Sw, a resonant inductor Lr, a lower bridge switch Sr, an output inductor Lo, an output capacitor Co, a clamping capacitor Cclamp, an auxiliary switch Sa and a control circuit CTR.

The first end of the upper bridge switch Sw is connected to the positive end of an input power source Vin. The second end of the upper bridge switch Sw is connected to the first end of the resonant inductor Lr. The second end of the resonant inductor Lr is connected to the first end of the lower bridge switch Sr. The second end of the lower bridge switch Sr is connected to the negative end of the input power source Vin.

The first end of the output inductor Lo is connected to the second end of the resonant inductor Lr and the first end of the lower bridge switch Sr. The first end of the output capacitor Co is connected to the second end of the output inductor Lo and the first end of the load (the current of the load is indicated by ILoad in FIG. 1 ). That is, the first end of the output capacitor Co or the second end of the inductor Lo can be connected to the load as the output end of the power converter of the present invention. The second end of the output capacitor Co is connected to the negative end of the input power Vin.

It is worth noting that the first end of the clamping capacitor Cclamp is connected to the second end of the upper bridge switch Sw and the first end of the resonant inductor Lr. The first end of the auxiliary switch Sa is connected to the second end of the clamping capacitor Cclamp. The second end of the auxiliary switch Sa is connected to the negative end of the input power supply Vin.

The control circuit CTR is connected to the control end of the upper bridge switch Sw, the control end of the lower bridge switch Sr, and the control end of the auxiliary switch Sa. The control circuit CTR is configured to output a plurality of control signals to the control end of the upper bridge switch Sw, the control end of the lower bridge switch Sr, and the control end of the auxiliary switch Sa to control the operation of the upper bridge switch Sw, the lower bridge switch Sr, and the auxiliary switch Sa, including controlling the conduction time of the upper bridge switch Sw, the lower bridge switch Sr, and the auxiliary switch Sa.

The output terminal of the power converter of the embodiment of the present invention is used to supply the output voltage Vout as shown in FIG1. If necessary, the control circuit CTR of the power converter of the embodiment of the present invention can adjust the operation of the upper bridge switch Sw, the lower bridge switch Sr and the auxiliary switch Sa according to the output voltage Vout (the divided voltage) of the output terminal of the power converter, including controlling the conduction time of the upper bridge switch Sw, the lower bridge switch Sr and the auxiliary switch Sa.

For example, the control circuit CTR may include a comparator, a flip-flop, an on-time timer, and a driver, which are not shown in the figure because they are not intended to be limiting of the present invention. The first input terminal of the comparator of the control circuit CTR, such as the non-inverting input terminal, may be connected to the output terminal of the power converter of the present invention to receive the output voltage Vout, or the input terminal of the voltage divider circuit may be connected to the output terminal of the power converter of the present invention and the first input terminal of the comparator, such as the non-inverting input terminal, may be connected to the output terminal of the voltage divider circuit to receive the divided voltage of the output voltage Vout from the voltage divider circuit.

A second input terminal of the comparator, such as an inverting input terminal, can be coupled to a reference voltage.

The comparator compares the output voltage Vout (divided voltage) of the power converter of the present invention with the reference voltage to output a comparison signal to the first input terminal of the flip-flop (e.g., the S terminal of the SR flip-flop). The second input terminal of the flip-flop (e.g., the R terminal of the SR flip-flop) is connected to the output terminal of the on-time timer to receive an on-time count signal.

The flip-flop generates a logic signal according to the level of a comparison signal received and the level of an on-time count signal, and outputs a logic inversion signal opposite to the level of the logic signal. The on-time timer can perform timing according to the received logic inversion signal, and the driver can control the on-time of the upper bridge switch Sw, the lower bridge switch Sr and the auxiliary switch Sa according to the received logic inversion signal.

Please refer to FIG. 1 to FIG. 10 , wherein FIG. 2 to FIG. 9 are schematic diagrams of current flow of a power converter with a clamping mechanism according to an embodiment of the present invention, and FIG. 10 is a waveform diagram of a signal of the power converter with a clamping mechanism according to an embodiment of the present invention.

The control circuit CTR shown in FIG1 can output a plurality of control signals to the control end of the upper bridge switch Sw, the control end of the lower bridge switch Sr, and the control end of the auxiliary switch Sa, respectively, to control the operation of the upper bridge switch Sw, the lower bridge switch Sr, and the auxiliary switch Sa.

For example, when the control circuit CTR controls the operation of the upper bridge switch Sw, the lower bridge switch Sr and the auxiliary switch Sa, a control signal Vgssw at the control end (e.g., the gate end) of the upper bridge switch Sw is as shown in FIG10 , a voltage signal Vdssw at the first end (e.g., the drain end) of the upper bridge switch Sw is as shown in FIG10 , a control signal Vgssa at the control end (e.g., the gate end) of the auxiliary switch Sa is as shown in FIG10 , and a control signal Vgssr at the control end (e.g., the gate end) of the lower bridge switch Sr is as shown in FIG10 . As a result, the current signal ILr of the resonant inductor Lr, the current ILoad of the output inductor Lo, the current signal Isa of the auxiliary switch Sa, and the current signal Isr of the lower bridge switch Sr are shown in FIG10 .

In detail, the power converter of the embodiment of the present invention performs the action interval in the non-complementary control mode, for example but not limited to the time interval from time point t0 to time point t1 (i.e., the first time interval described herein), the time interval from time point t1 to time point t2 (i.e., the second time interval described herein), the time interval from time point t2 to time point t3-1 (i.e., the third time interval described herein), the time interval from time point t3-1 to time point t3-2 (i.e., the fourth time interval described herein), the time interval from time point t3-2 to time point t4 (i.e., the fifth time interval described herein), the time interval from time point t4 to time point t5 (i.e., the sixth time interval described herein), and the time interval from time point t5 to time point t6 (i.e., the seventh time interval described herein) as shown in FIG. 10. , the time period from time point t6 to time point t7 (i.e. the eighth time period described herein), and the time period from time point t7 to time point t8 (i.e. the ninth time period described herein).

In the time interval from time point t0 to time point t1 as shown in FIG10 (i.e., the first time interval described herein), the control circuit CTR turns on the upper bridge switch Sw and turns off the lower bridge switch Sr and the auxiliary switch Sa. At this time, as shown in FIG2 , the current of the input power source Vin flows sequentially through the upper bridge switch Sw and the resonant inductor Lr to the output inductor Lo, causing the current of the resonant inductor Lr and the current ILoad of the output inductor Lo to increase. The current of the resonant inductor Lr is equal to the current of the output inductor Lo.

In the time interval from time point t1 to time point t2 as shown in FIG10 (i.e., the second time interval described herein), the control circuit CTR turns off the upper bridge switch Sw and keeps the lower bridge switch Sr and the auxiliary switch Sa turned off. At this time, as shown in FIG3 , the current of the output inductor Lo charges the parasitic capacitance Csw of the upper bridge switch Sw, and discharges the parasitic capacitance Csa of the auxiliary switch Sa and the parasitic capacitance Csr of the lower bridge switch Sr.

In the time interval from time point t2 to time point t3-1 as shown in FIG10 (i.e., the third time interval described herein), the control circuit CTR turns off the upper bridge switch Sw and the auxiliary switch Sa and turns on the lower bridge switch Sr. At this time, the resonant inductor Lr resonates with the clamping capacitor Cclamp, and the auxiliary switch Sa is not turned on, as shown in FIG4, so that the current of the resonant inductor Lr flows sequentially through the lower bridge switch Sr and the body diode Dsa of the auxiliary switch Sa to the clamping capacitor Cclamp, so that the energy of the resonant inductor Lr is transferred to the clamping capacitor Cclamp for energy storage. At the same time, the current Isr of the lower bridge switch Sr flows to the output inductor Lo.

The voltage across the parasitic capacitor Csr of the lower bridge switch Sr is reduced to zero in the time period from time point t1 to time point t2 (i.e., the second time period described herein), and the voltage across the parasitic capacitor Csa of the auxiliary switch Sa is zero at time point t2, so the lower bridge switch Sr and the auxiliary switch Sa can achieve zero-voltage switching at time point t2.

That is to say, the power converter with a clamping mechanism of the present invention can achieve zero-voltage switching by setting a clamping capacitor Cclamp and an auxiliary switch Sa, and configuring an upper bridge switch Sw, a resonant inductor Lr, a lower bridge switch Sr, an output inductor Lo, an output capacitor Co and a control circuit CTR to reduce the loss of the upper bridge switch Sw and the lower bridge switch Sr during switching. In this way, the power converter with a clamping mechanism of the present invention can maintain high-efficiency operation.

In the time period from time point t3-1 to time point t3-2 as shown in FIG10 (i.e., the fourth time period described herein), the control circuit CTR keeps closing the upper bridge switch Sw and the auxiliary switch Sa and opens the lower bridge switch Sr. As shown in FIG5 , the current Isr of the lower bridge switch Sr continues to flow to the output inductor Lo.

In the time interval from time point t3-2 to time point t4 as shown in FIG10 (i.e., the fifth time interval described herein), the control circuit CTR keeps closing the upper bridge switch Sw and opens the auxiliary switch Sa and the lower bridge switch Sr. At this time, as shown in FIG6 , the current of the clamping capacitor Cclamp flows sequentially through the auxiliary switch Sa and the lower bridge switch Sr to the resonant inductor Lr, and the current Isr of the lower bridge switch Sr continues to flow to the output inductor Lo.

As shown in FIG. 10 , in the time period from time point t3-2 to time point t4 (ie, the fifth time period described herein), the current ILr flowing through the resonant inductor Lr gradually decreases to a value less than zero.

As shown in FIG10 , the time during which a control signal Vgssa at the control terminal (e.g., gate terminal) of the auxiliary switch Sa maintains a high voltage level (i.e., the time period from time point t3-2 to time point t4) is short, so that the conduction time of the auxiliary switch Sa is short, that is, the control circuit CTR controls the conduction time of the auxiliary switch Sa within a conduction time length threshold range. In this way, the loss caused by the conduction of the auxiliary switch Sa can be reduced, and the converter efficiency can be further improved.

In the time interval from time point t4 to time point t5 as shown in FIG10 (i.e., the sixth time interval described herein), the control circuit CTR turns off the upper bridge switch Sw, the auxiliary switch Sa, and the lower bridge switch Sr. At this time, as shown in FIG7 , the current of the parasitic capacitor Csw of the upper bridge switch Sw flows to the input power supply Vin, the current of the resonant inductor Lr flows to the parasitic capacitor Csa of the auxiliary switch Sa, and the current of the body diode Dsr of the lower bridge switch Sr flows to the output inductor Lo.

In the time interval from time point t5 to time point t6 as shown in FIG10 (i.e., the seventh time interval described herein), the control circuit CTR keeps closing the upper bridge switch Sw, the lower bridge switch Sr, and the auxiliary switch. At this time, as shown in FIG8 , the current of the resonant inductor Lr flows through the body diode Dsw of the upper bridge switch Sw to the input power supply Vin, and the current Isr of the body diode Dsr of the lower bridge switch Sr flows to the output inductor Lo.

In the time interval from time point t6 to time point t7 as shown in FIG10 (i.e., the eighth time interval described herein), the control circuit CTR turns on the upper bridge switch Sw, and keeps the lower bridge switch Sr and the auxiliary switch closed. At this time, as shown in FIG9 , the current of the resonant inductor Lr flows through the upper bridge switch Sw to the input power supply Vin, and the current Isr of the body diode Dsr of the lower bridge switch Sr flows to the output inductor Lo.

As shown in FIG. 10 , when the polarity of the resonant inductor Lr and the current ILr is reversed, the resonant inductor Lr enters the ninth time period (i.e., the time period from time point t6 to time point t7) from the eighth time period (i.e., the time period from time point t7 to time point t8).

In the time period from time point t7 to time point t8 as shown in FIG. 10 (i.e., the ninth time period described herein), the current of the input power source Vin (not shown) flows through the upper bridge switch Sw to the resonant inductor Lr (this current is opposite to the direction of the current in the time period from time point t6 to time point t7), and the current Isr of the body diode Dsr of the lower bridge switch Sr flows to the output inductor Lo.

As shown in FIG. 10 , when the resonant inductor current ILr rises to the same level as the current ILoad of the output inductor Lo, the body diode Dsr of the lower bridge switch Sr is turned off, and the time period from time point t7 to time point t8 (ie, the ninth time period described herein) ends.

In summary, the present invention provides a power converter with a clamping mechanism. The power converter of the present invention utilizes a clamping circuit element to generate a negative current to achieve zero-voltage switching of the switch element, thereby further improving the efficiency of the converter. In terms of switch control, a non-complementary control method different from the previous one is used, which can further reduce the converter loss compared to the traditional complementary control method. In addition, the power converter of the present invention can further perform feedback control, that is, adopt the adaptive closing time control in the ripple control, so that when the input voltage, output voltage, and load current change, the same switching frequency can be maintained, thereby reducing the electromagnetic interference (EMI) problem of the switching power supply.

The contents disclosed above are only preferred feasible embodiments of the present invention and are not intended to limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made using the contents of the specification and drawings of the present invention are included in the scope of the patent application of the present invention.

Vin: input power Sw: upper bridge switch Sa: auxiliary switch Sr: lower bridge switch Dsw, Dsa, Dsr: body diode Csw, Csa, Csr: parasitic capacitance Lr: resonant inductance Lo: output inductance Co: output capacitance Cclamp: clamping capacitance Vout: output voltage ILoad: current CTR: control circuit Vgssw, Vgssa, Vgssr, Vdssw: control signal

FIG. 1 is a circuit diagram of a power converter with a clamping mechanism according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of current flow in a power converter with a clamping mechanism according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of current flow in a power converter with a clamping mechanism according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of current flow in a power converter with a clamping mechanism according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of current flow in a power converter with a clamping mechanism according to an embodiment of the present invention.

FIG. 6 is a schematic diagram of current flow in a power converter with a clamping mechanism according to an embodiment of the present invention.

FIG. 7 is a schematic diagram of current flow in a power converter with a clamping mechanism according to an embodiment of the present invention.

FIG. 8 is a schematic diagram of current flow in a power converter with a clamping mechanism according to an embodiment of the present invention.

FIG. 9 is a schematic diagram of current flow in a power converter with a clamping mechanism according to an embodiment of the present invention.

FIG. 10 is a waveform diagram of a signal of a power converter with a clamping mechanism according to an embodiment of the present invention.

Vin: Input power

Sw: bridge switch

Sa: Auxiliary switch

Sr: Down bridge switch

Dsw, Dsa, Dsr: body diode

Csw, Csa, Csr: parasitic capacitance

Lr: resonant inductance

Lo: output inductance

Co: output capacitance

Cclamp: clamping capacitor

Vout: output voltage

ILoad: current

CTR: Control circuit

Claims (9)

A power converter with a clamping mechanism, comprising: an upper bridge switch, wherein the first end of the upper bridge switch is connected to the positive end of an input power source; a resonant inductor, wherein the first end of the resonant inductor is connected to the second end of the upper bridge switch; a lower bridge switch, wherein the first end of the lower bridge switch is connected to the second end of the resonant inductor, and the second end of the lower bridge switch is connected to the negative end of the input power source; an output inductor, wherein the first end of the output inductor is connected to the second end of the resonant inductor and the first end of the lower bridge switch; an output capacitor, wherein the first end of the output capacitor is connected to the second end of the output inductor and the load, and the second end of the output capacitor is connected to the negative end of the input power source; A clamping capacitor, the first end of which is connected to the second end of the upper bridge switch and the first end of the resonant inductor; An auxiliary switch, the first end of which is connected to the second end of the clamping capacitor, and the second end of which is connected to the negative end of the input power supply; and A control circuit, connected to the control end of the upper bridge switch, the control end of the lower bridge switch and the control end of the auxiliary switch, configured to control the operation of the upper bridge switch, the lower bridge switch and the auxiliary switch; Wherein, within a first time period, the control circuit turns on the upper bridge switch and turns off the lower bridge switch and the auxiliary switch; Wherein, in a second time period, the control circuit turns off the upper bridge switch and keeps the lower bridge switch and the auxiliary switch turned off, and the current of the output inductor charges a parasitic capacitor of the upper bridge switch and discharges a parasitic capacitor of the auxiliary switch and a parasitic capacitor of the lower bridge switch. A power converter with a clamping mechanism as described in claim 1, wherein, during the first time period, the current of the input power source flows sequentially through the upper bridge switch and the resonant inductor to the output inductor. A power converter with a clamping mechanism as described in claim 1, wherein, in a third time period, the control circuit closes the upper bridge switch and the auxiliary switch and opens the lower bridge switch, and the current of the resonant inductor flows sequentially through the lower bridge switch and the body diode of the auxiliary switch to the clamping capacitor, and the current of the lower bridge switch flows to the output inductor. A power converter with a clamping mechanism as described in claim 3, wherein, in a fourth time period, the control circuit keeps the upper bridge switch and the auxiliary switch closed and keeps the lower bridge switch open, and the current of the lower bridge switch continues to flow to the output inductor. A power converter with a clamping mechanism as described in claim 4, wherein, in a fifth time period, the control circuit maintains closing the upper bridge switch and opens the auxiliary switch and the lower bridge switch, the current of the clamping capacitor flows sequentially through the auxiliary switch and the lower bridge switch to the resonant inductor, and the current of the lower bridge switch continues to flow to the output inductor. A power converter with a clamping mechanism as described in claim 5, wherein, in a sixth time period, the control circuit turns off the upper bridge switch, the auxiliary switch and the lower bridge switch, the current of the parasitic capacitance of the upper bridge switch flows to the input power supply, the current of the resonant inductor flows to the parasitic capacitance of the auxiliary switch, and the current of the body diode of the lower bridge switch flows to the output inductor. A power converter with a clamping mechanism as described in claim 6, wherein, in a seventh time interval, the control circuit turns off the upper bridge switch, the lower bridge switch and the auxiliary switch, the current of the resonant inductor flows through the body diode of the upper bridge switch to the input power supply, and the current of the body diode of the lower bridge switch flows to the output inductor. A power converter with a clamping mechanism as described in claim 7, wherein, in an eighth time interval, the control circuit turns on the upper bridge switch and keeps the lower bridge switch and the auxiliary switch closed, the current of the resonant inductor flows to the upper bridge switch, and the current of the body diode of the lower bridge switch flows to the output inductor. A power converter with a clamping mechanism as described in claim 1, wherein the control circuit controls the on-time of the auxiliary switch within a on-time length threshold range.

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