TWM639160U - Power adapter - Google Patents

Abstract

A power converter is provided, including a transformer, first and second power switch tubes, first and second current sources, first, second, third and fourth switch tubes, and a switch control circuit. The first electrodes of the first, second, third, and fourth switch tubes are respectively connected to the first, second, third, and fourth output ends of the switch control circuit, and the second electrodes of the first and third switch tubes The electrodes are respectively connected to the first and second current sources, the second electrode of the second switch tube is connected to the third electrode of the first switch tube and the base of the first power switch tube, and the second electrode of the fourth switch tube is connected to The third electrode of the third switching tube and the base of the second power switching tube, the collector of the first power switching tube is connected to the primary winding of the transformer, the emitter is connected to the base of the second power switching tube, the second power switching tube The collector of the tube is connected to the primary winding of the transformer and the emitter is grounded via a current sense resistor.

Description

power converter

The invention relates to the field of integrated circuits, in particular to a power converter.

In the field of small and medium power power converters, the flyback converter occupies an absolute dominant position in the application market below 100W due to its advantages such as simple circuit, high conversion efficiency, and wide input voltage range. In recent years, power switching tubes (also known as bipolar transistors) have been widely used in low-power markets below 10W because of their good switching characteristics and low price advantages.

With more and more functions of mobile devices such as mobile phones and tablet computers, the capacity of batteries powering mobile devices has increased explosively, and the output power of chargers or adapters powering mobile devices has continued to increase, and has developed from the original 5W To 20W, 30W, 45W, 65W or even higher. How to improve the overall efficiency and power density of the power converter system on the basis of low cost, so that the power converter can not only meet the development needs of the miniaturization of the charger or adapter, but also meet the increasingly stringent energy efficiency standards of the power supply, has become the research topic of today. focus.

The power converter according to the embodiment of the invention includes a transformer, first and second power switch tubes, first and second current sources, first, second, third, and fourth switch tubes, and a switch control circuit, Wherein: the first electrodes of the first, second, third, and fourth switch tubes are respectively connected to the first, second, third, and fourth output ends of the switch control circuit, and the first and third switch tubes The second electrodes are respectively connected to the first and second current sources, the second electrode of the second switch tube is connected to the third electrode of the first switch tube and the base of the first power switch tube, and the second electrode of the fourth switch tube connected to the third electrode of the third switching tube and the base of the second power switching tube, the third electrode of the second switching tube is grounded or connected to the third electrode of the third switching tube and the second electrode of the fourth switching tube, The third electrode of the fourth switching tube is grounded, and the collector of the first power switching tube is connected to the transformer The primary winding, the base is connected to the third electrode of the first switching tube and the second electrode of the second switching tube, the emitter is connected to the base of the second power switching tube, and the collector of the second power switching tube is connected to the transformer The primary winding, the base of which is connected to the third electrode of the third switching tube and the second electrode of the fourth switching tube, and the emitter is grounded through the current sensing resistor.

1,2,3,4,5,6,7,8: pins

100A, 100B: power converter

102: switch control circuit

104: chip power supply circuit

106: Feedback control circuit

108: Current sensing control circuit

110: Oscillator circuit

112: logic control circuit

114: protection circuit

CS: current sense pin

D1: the first switch tube

D2: The second switch tube

D3: The third switch tube

D4: The fourth switch tube

FB, VDD: pin

Hfe: magnification

I _B1 : the first driving current

I _B2 : the second driving current

Ic: current

Iref: reference current

Is: Primary current

I _source 1: the first current source

I _source 2: the second current source

OVP: overvoltage protection pin

Q1: The first power switch tube

Q2: The second power switch tube

Rs: current sense resistor

T: Transformer

U1, U1A, U1B: control chip

VBUS: power line

Vcs: voltage

Vref: reference voltage

The invention can be better understood from the following description of specific embodiments of the invention with reference to the drawings, wherein: FIG. 1A shows an example circuit diagram of a power converter according to an embodiment of the invention.

FIG. 1B shows another example circuit diagram of a power converter according to an embodiment of the invention.

FIG. 2 shows a working waveform diagram of multiple signals in the power converter shown in FIG. 1A/1B.

FIG. 3A shows an example block diagram of a control die in the power converter shown in FIG. 1A .

FIG. 3B shows an example block diagram of a control die in the power converter shown in FIG. 1B .

FIG. 4 shows a schematic diagram of an example package of the first and second power switch tubes in the power converter shown in FIG. 1A/1B .

FIG. 5 shows a schematic diagram of an example package of the first and second power switch tubes and the control chip in the power converter shown in FIG. 1A/1B .

Features and exemplary embodiments of various aspects of the present invention will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the invention may be practiced without some of these specific details. The following description of the embodiments is only to provide a better understanding of the invention by showing an example of the invention. The invention is in no way limited to any specific configuration set forth below, but rather covers any modifications, substitutions and improvements of elements and parts without departing from the spirit of the invention. In the illustrations and the following description, well-known structures and techniques have not been shown in order to avoid unnecessarily obscuring the present invention. In addition, it should be noted that the term "A is connected to B" used herein may mean "A and B are directly connected" or "A and B are indirectly connected via one or more other elements".

At present, the main reason why the power switch tube can only be used in the low-power market is that the conduction of the power switch tube is driven by current, and there must be sufficient driving current to make the power switch tube conduct. In addition, the driving loss of the power switch tube is large, the conduction loss is large, and the turn-off speed is slow, these factors also limit its application in the higher power market.

In view of the above, a power converter according to an embodiment of the present invention is proposed, in which four switching tubes are used to drive the power switching tubes in combination, so as to reduce the driving current consumption of the power switching tubes, increase the turn-on speed of the power switching tubes and/or Turn off speed, and/or reduce the turn off loss of the power switch tube.

FIG. 1A shows an example circuit diagram of a power converter 100A according to an embodiment of the present invention. As shown in FIG. 1A , the power converter 100A includes a transformer T, first and second power switch tubes Q1 and Q2 , first and second current sources I _source1 and I _source2 , first, second, third, and third Four switch tubes D1 to D4, and the switch control circuit 102, wherein: the first electrodes of the first, second, third, and fourth switch tubes D1 to D4 are respectively connected to the first, second, and second electrodes of the switch control circuit 102. In the third and fourth output ends, the second electrodes of the first and third switch tubes D1 and D3 are respectively connected to the first and second current sources I _source1 and I _source2 , and the second electrode of the second switch tube D2 is connected to The third electrode of the first switching tube D1 and the base of the first power switching tube Q1, the second electrode of the fourth switching tube D4 are connected to the third electrode of the third switching tube D3 and the base of the second power switching tube Q2 , the third electrode of the second switch tube D2 and the third electrode of D4 are grounded, the collector of the first power switch tube Q1 is connected to the primary winding of the transformer T, and the base is connected to the third electrode of the first switch tube D1 and the third electrode of the first switch tube D1. The second electrode and emitter of the second switching tube D2 are connected to the base of the second power switching tube Q2, the collector of the second power switching tube Q2 is connected to the primary winding of the transformer T, and the base is connected to the third switching tube D3. The third electrode and the second electrode and the emitter of the fourth switch tube D4 are grounded via the current sensing resistor Rs.

FIG. 1B shows an example circuit diagram of a power converter 100B according to an embodiment of the present invention. The main difference in structure between the power converter 100B shown in FIG. 1B and the power converter 100A shown in FIG. 1A is that the third electrode of the second switching tube D2 is connected to the third electrode and the fourth electrode of the third switching tube D3 The second electrode of the switch tube D4 (that is, connected to the first power switch tube The emitter of Q1 and the base of the second power switch tube Q2), the connection relationship of other parts is the same as the corresponding parts shown in FIG. 1 , and will not be repeated here.

FIG. 2 shows the working waveform diagram of multiple signals in the power converter 100A/100B shown in FIG. 1A/1B, wherein D1 to D4 represent the conduction for driving the first to fourth switching tubes D1 to D4 respectively. I _B1 represents the first drive current for the second power switch tube Q2, I _B2 represents the second drive current for the second power switch tube Q2, and Is represents the flow through the current sensing resistor Rs the primary current.

As shown in FIG. 1A/1B and FIG. 2 , in some embodiments, when the second power switch tube Q2 changes from the off state to the on state, the first switch tube D1 and the first power switch tube Q1 are in conduction. state and the second, third, and fourth switching tubes D2 to D4 are in the off state, the base current of the second power switching tube Q2 is supplied by the first current source I _source1 via the first switching tube D1 and the first power switching tube Q1 provides (that is, uses the first driving current I _B1 as the driving current of the second power switch transistor Q2 ).

As shown in FIG. 1A/1B and FIG. 2, in some embodiments, when the second power switch tube Q2 is in the on state, before the voltage Vcs on the current sensing resistor Rs reaches a predetermined set value, the first switch tube D1 and the first power switch tube Q1 is in the on state and the second, third, and fourth switch tubes D2 to D4 are in the off state, the base current of the second power switch tube Q2 is supplied by the first current source I _source1 through the first The switching tube D1 and the first power switching tube Q1 provide (that is, use the first driving current I _B1 as the driving current of the second power switching tube Q2 ).

As shown in FIG. 1A/1B and FIG. 2 , in some embodiments, when the second power switch tube Q2 is in the on state, after the voltage Vcs on the current sensing resistor Rs reaches a predetermined set value, the first switch tube D1 , the fourth switching tube D4, and the first power switching tube Q1 are in an off state, the second and third switching tubes D2 and D3 are in a conducting state, and the base current of the second power switching tube Q2 is supplied by the second current source I _source2 Provided via the third switch tube D3 (that is, using the second drive current I _B2 as the drive current of the second power switch tube Q2 ).

As shown in FIG. 1A/1B and FIG. 2, in some embodiments, when the second power switch tube Q2 is in the off state, the first switch tube D1, the third switch tube D3, and the first power switch tube The power switch tube Q1 is in the off state, and the second and fourth switch tubes D2 and D4 are in the on state.

In the power converter 100A/100B shown in FIG. 1A/1B, the first and second switching tubes D1 and D2 are used to control whether the first driving current I _B1 is used as the driving current of the second power switching tube Q2 (the first A drive current I _B1 is also used as the drive current of the first power switch tube Q1, so the first and second switch tubes D1 and D2 are actually used to control the on and off of the first power switch tube Q1), the third and the second The four switch tubes D3 and D4 are used to control whether the second drive current I _B2 is used as the drive current of the second power switch tube Q2 . When the second power switch tube Q2 is in the conduction state, the first and second drive currents I _B1 and I _B2 are used as the drive current of the second power switch tube Q2 in different periods. In the process of the second power switch tube Q2 changing from the off state to the on state, the first drive current I _B1 is used as the drive current of the second power switch tube Q2, in this case the first drive current I _B1 should be sufficient is large, so that the second power switch tube Q2 can quickly enter the saturation region, so as to minimize the turn-on loss of the second power switch tube Q2 and increase the switching speed of the second power switch tube Q2. However, if the driving current of the second power switch tube Q2 is too high, the turn-off speed of the second power switch tube Q2 will be reduced, and the turn-off loss of the second power switch tube Q2 will be increased. Before the process of the off-state starts, the driving current of the second power switch tube Q2 is switched from the first driving current I _B1 to the second driving current I _B2 (also referred to as the pre-shutdown driving current), which can make the second power switch The minority carriers stored in the base region rapidly recombine during the conduction state of the tube Q2 to reduce the turn-off time of the second power switch tube Q2, reduce the turn-off loss of the second power switch tube Q2, and improve the power converter 100A/ 100B system efficiency and output power.

Specifically, in the process of changing the second power switch tube Q2 from the off state to the on state, the first drive current I _B1 is used as the drive current of the second power switch tube Q2, due to the amplification effect of the first power switch tube Q1 , the base current of the second power switch tube Q2 is hfe*I _B1 (hfe is the amplification factor of the first power switch tube Q1), and the larger base current impels the second power switch tube Q2 to enter the saturation region rapidly, reducing the The turn-on loss of the second power switch tube Q2; during the period when the second power switch tube Q2 is in the conduction state, the primary side current Is=Ic+hfe*I _B1 flowing through the current sensing resistor Rs (Ic is the primary current Is=Ic+hfe*I B1 flowing through the transformer T winding current); after the voltage Vcs on the current sensing resistor Rs reaches a predetermined setting value (for example, 90% of the maximum voltage value Vcsmax on the current sensing resistor Rs), use the second driving current I _B2 as the second power switch The drive current of tube Q2, because I _B2 << I _B1 , so when using the second drive current I _B2 to maintain the second power switch tube Q2 in the on state, the second power switch tube Q2 stores the carriers in the base region Less, when the second power switch tube Q2 is turned off, the carriers with fewer base regions can quickly recombine to reduce the turn-off time of the second power switch tube Q2 and reduce the turn-off loss of the second power switch tube Q2 .

FIG. 3A shows an example block diagram of control die U1A in power converter 100A shown in FIG. 1A . FIG. 3B shows an example block diagram of the control die U1B in the power converter 100B shown in FIG. 1B . In the following, for simplicity, the control chips U1A and U1B are collectively referred to as the control chip U1. As shown in FIG. 3A/3B, the first to fourth switch tubes D1 to D4 and the switch control circuit 102 can be included in the control chip U1, and the control chip U1 can also include: chip power supply circuit 104: connected to the control chip U1 VDD pin, including under voltage protection (Under Voltage Lock Out, UVLO), over voltage protection pin (Over Voltage Protection, OVP), reference voltage and reference current (Vref&Iref) three parts, used to provide operating voltage for the internal circuit of the chip , a reference voltage Vref, and a reference current Iref. When the voltage at the VDD pin exceeds the UVLO voltage, the internal circuit of the chip starts to work. When the voltage at the VDD pin exceeds the OVP threshold, the internal circuit of the chip enters an automatic recovery protection state to prevent damage to the control chip U1.

Feedback control circuit 106: connected to the FB pin of the control chip U1, including continuous conduction mode (Continuous Conduction Mode, CCM)/quasi-resonant (Quasi-resonant, QR) mode/green mode/high load mode control, pulse width modulation (Pulse Width Modulation, PWM) comparator, pulse width modulation pre-shutdown (PWM_pre) comparator three parts. The PWM comparator and the PWM_pre comparator compare the output voltage feedback signal received by the FB pin with the current sense signal received by the CS current sense pin (for example, the voltage Vcs on the current sense resistor Rs) to generate a PWM signal and PWM_pre signal, and output the PWM signal and the PWM_pre signal to the logic control circuit 112 . In addition, the CCM/QR mode/green mode/high load mode control part realizes CCM, QR mode, and green mode according to the output voltage feedback signal received by the FB pin. mode, and switching control of the high-load mode, and output the mode control signal to the logic control circuit 112 .

Current sensing control circuit 108: connected to the CS current sensing pin of the control chip U1, including leading edge blanking (Leading Edge Blanking, LEB), slope compensation, over current protection (Over Current Protection, OCP) comparator, over current protection Pre-shutdown (OCP_pre) comparator four parts. When the system operating mode is detected to be in deep CCM via the CS current sense pin, slope compensation is required to maintain system stability. The OCP comparator compares the current sensing signal received by the CS current sensing pin with the OCP threshold, and outputs an OCP shutdown signal to the logic control circuit 112 . The OCP_pre comparator compares the current sensing signal received by the CS current sensing pin with the OCP pre-shutdown threshold, and outputs the OCP pre-shutdown signal to the logic control circuit 112 .

Oscillator (Oscillator, OSC) circuit 110 : used to generate a high-frequency sawtooth wave signal and provide it to the logic control circuit 112 for the logic control circuit 112 to generate a square wave signal with an adjustable duty cycle.

Logic control circuit 112 : for logically analyzing the input signals from each circuit module, and outputting logic control signals to the switch control circuit 102 .

The protection circuit 114 is used to enable the control chip U1 to enter an automatic recovery protection state when abnormal fault information is detected, so as to prevent the control chip U1 from being damaged.

Here, it should be noted that the switch control circuit 102 is used to generate four control signals for respectively controlling the on and off of the first to fourth switch tubes D1 to D4 according to the logic control signal provided by the logic control circuit 112, the first The first to fourth switching transistors D1 to D4 are turned on and off under the control of the switch control circuit 102 to form the first and second driving currents I _B1 and I _B2 . The first to fourth switching transistors D1 , D2 , D3 , D4 can be realized by using N-type metal oxide semiconductor field effect transistor (N-MOSFET) or bipolar junction transistor (Bipolar Junction Transistor, BJT). The first and third switching transistors D1 and D3 can also be realized by P-type metal oxide semiconductor field effect transistors (P-MOSFET).

In some embodiments, the first switch control circuit can be used to control the on and off of the first and second switch transistors D1 and D2, and the second switch control circuit can be used to control the third and the turn-on and turn-off of the fourth switch tubes D3 and D4. In addition, the first and second power switch tubes Q1 and Q2 can be two independent power switch tubes, and can also be formed in one chip package; or the control chip U1 can be formed with the first and second power switch tubes Q1 and Q2 in a three-die package.

FIG. 4 shows a schematic diagram of an example package of the first and second power switch transistors Q1 and Q2 in the power converter 100A/100B shown in FIG. 1A/B. As shown in FIG. 4, the first and second power switch transistors Q1 and Q2 may be included in the same single-substrate island chip package (wherein, the collectors of the first and second power switch transistors Q1 and Q2 are connected), and The detailed pin information of the single-base island chip package is as follows: pin 1 is the first current pin, which is used to receive the first driving current I _B1 and is connected to the base region of the first power switch tube Q1; pin 2 is The second current pin is used to receive the second driving current I _B2 and is connected to the emitter area of the first power switch tube Q1 and the base area of the second power switch tube Q2; 3/4 pins are emitter pins , connected to the emitter region of the second power switch tube Q2, in order to increase the heat dissipation area and reduce the temperature, multiple bonding wires and multi-pin packaging can be used, for example, two pins are connected by two sets of bonding wires, and each group of bonding wires contains The specific number of bonding wires can be determined according to the area of the emitter area of the second power switch tube Q2; pins 5~8 are collector pins, connected to the collector areas of the first and second power switch tubes Q1 and Q2 , for the convenience of heat dissipation and printed circuit board layout, a multi-pin package is used, and the collector regions of the first and second power switch tubes Q1 and Q2 are located on the back of the transistor, so the first and second power switch tubes Q1 and Q2 can be used The conductive glue is connected to the chip base island, no need to wire, and the impedance is the smallest.

FIG. 5 shows an example package diagram of the first and second power switch transistors Q1 and Q2 and the control chip U1 in the power converter 100A/100B shown in FIG. 1A/B. As shown in FIG. 5 , the first and second power switch tubes Q1 and Q2 are packaged in a flat form, and the control chip U1 and the second power switch tube Q2 are packaged in an iterative form. The specific package form can be adjusted according to the number and shape of the base islands, and is not limited to the 8-pin package form. The detailed pinout information for the example package shown in Figure 5 is as follows: Pins 1, 2, and 3 are control pins for controlling the chip U1, which are connected to the internal pad of the control chip U1; pins 4 are emitter pins, which are connected to the emitter area of the second power switch tube Q2, In order to increase the heat dissipation area and reduce the temperature, multiple bonding wires can be used to reduce the bonding resistance. The specific number of bonding wires can be determined according to the area of the emitter area of the second power switch tube Q2; pins 5~8 are collector pins , connected to the collector areas of the first and second power switch tubes Q1 and Q2, for the convenience of heat dissipation and printed circuit board layout, a multi-pin package is used, and the collector areas of the first and second power switch tubes Q1 and Q2 are located at The back of the transistor is connected to the base island with conductive glue, no wiring is required, and the impedance is the smallest.

The example package shown in Figure 5 can add redundant pins without increasing the cost of system pins. The entire system circuit is simple, with few peripheral components and low system cost.

To sum up, in the power converter according to the present invention, four switching tubes are combined to drive the power switching tubes, which reduces the driving current loss of the power switching tubes and increases the turn-on speed of the power switching tubes. In addition, by setting the pre-turn-off driving current when the power switch tube is ready to change from the on state to the off state, the carriers in the base region during the on state of the power switch tube are reduced, so that the power switch can be quickly extracted when the power switch is turned off. The remaining minority carriers in the base region of the tube can increase the turn-off speed and reduce the turn-off loss, thereby improving the application range of the power switch tube in the medium power system.

This creation can be realized in other specific forms without departing from its spirit and essential characteristics. The current embodiments are to be considered in all respects as illustrative rather than restrictive, and the scope of the present creation is defined by the appended claims rather than the above description, and what falls within the meanings and equivalents of the claims All changes are included within the scope of this work.

100A: power converter

102: switch control circuit

CS: current sense pin

FB, VDD: pin

D1: the first switch tube

D2: The second switch tube

D3: The third switch tube

D4: The fourth switch tube

I _B1 : the first driving current

I _B2 : the second driving current

Ic: current

Is: Primary current

I _source1 : the first current source

I _source2 : the second current source

Q1: The first power switch tube

Q2: The second power switch tube

Rs: current sense resistor

U1A: Control chip

VBUS: power line

Claims (11)

A power converter, characterized in that it includes a transformer, first and second power switch tubes, first and second current sources, first, second, third, and fourth switch tubes, and a switch control circuit, wherein : the first electrodes of the first, second, third, and fourth switch tubes are respectively connected to the first, second, third, and fourth output terminals of the switch control circuit, and the first and The second electrode of the third switch tube is respectively connected to the first and second current sources, and the second electrode of the second switch tube is connected to the third electrode of the first switch tube and the first power switch the base of the power switch, the second electrode of the fourth switch tube is connected to the third electrode of the third switch tube and the base of the second power switch tube, and the third electrode of the second switch tube is grounded Or connected to the third electrode of the third switching tube and the second electrode of the fourth switching tube, the third electrode of the fourth switching tube is grounded, and the collector of the first power switching tube is connected to the The primary winding and the base of the transformer are connected to the third electrode of the first switch tube and the second electrode of the second switch tube, and the emitter is connected to the base of the second power switch tube. The collector of the second power switching tube is connected to the primary winding of the transformer, the base is connected to the third electrode of the third switching tube and the second electrode of the fourth switching tube, and the emitter is grounded through a current sensing resistor . The power converter according to claim 1, wherein, when the second power switch tube is turned from the off state to the on state, the first switch tube and the first power switch tube are in the on state And the second, third, and fourth switching tubes are in an off state, and the base current of the second power switching tube is supplied by the first current source via the first switching tube and the first power switching tube. switch provided. The power converter according to claim 1, wherein, during the period when the second power switch tube is in the on state, before the voltage on the current sensing resistor reaches a predetermined setting value, the first switch tube and the The first power switch tube is in the conduction state and the second, The third and fourth switching tubes are in an off state, and the base current of the second power switching tube is provided by the first current source via the first switching tube and the first power switching tube. The power converter according to claim 1, wherein, during the period when the second power switch tube is in the on state, after the voltage on the current sensing resistor reaches a predetermined setting value, the first switch tube, the The fourth switch tube and the first power switch tube are in the off state, the second and third switch tubes are in the on state, and the base current of the second power switch tube is controlled by the second current source provided via the third switch tube. The power converter according to claim 1, wherein, during the period when the second power switch tube is in the off state, the first switch tube, the third switch tube, and the first power switch tube are in the In the off state, the second and fourth switch tubes are in the on state. The power converter according to claim 1, wherein the first, second, third and fourth switching transistors are implemented as power switching transistors or field effect transistors. The power converter according to claim 1, further comprising a control chip, the first, second, third, and fourth switch tubes and the switch control circuit are included in the control chip. The power converter according to claim 1, wherein the first and second power switch tubes are included in the same single-island chip package. The power converter according to claim 8, wherein the single base island chip package has a first current pin, a second current pin, at least one emitter pin, and at least one collector pin. The power converter according to claim 7, wherein the first and second power switch tubes and the control chip are included in the same chip package. The power converter according to claim 10, wherein the first and second power switch tubes are packaged in a flat form, and the control chip and the second power switch tube are packaged in an iterative form.

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