TWI419455B - Power converter - Google Patents

Description

Power converter

The present invention relates to a power converter, and more particularly to a switched power converter.

Switching power converters usually include a DC/DC controller, an upper bridge switch, a lower bridge switch, and an impedance circuit composed of components such as an inductor and a capacitor. Among them, the switching power converter controls the conduction of the upper bridge switch and the lower bridge switch through the DC-to-DC controller, thereby adjusting the current flowing through the impedance circuit. Thereby, the switched power converter will convert the input voltage to the corresponding output voltage.

In addition, existing switching power converters mostly generate a sense current related to the output current through a down-bridge sensing circuit. Thereby, the switching power converter can determine the magnitude of the output current according to the sensing result, thereby achieving an overcurrent protection mechanism. However, for the existing switching power converter, when the driven load is too small, the down-bridge sensing circuit tends to be inoperable due to the reverse current generated by the inductance. At this time, the lower bridge sensing circuit will not be able to sense the current, which in turn causes the switching power converter to fail to determine the magnitude of the output current, thereby reducing the stability of the system.

In addition, for a multi-channel switching power converter, when the driven load is too small, the switching power converter will not be able to discriminate the output current generated by each channel, and thus the output current of each channel cannot be balanced. In other words, when the existing switching power converter drives the light load, due to the insufficient sensing range of the lower bridge sensing circuit, the output current of the switching power converter cannot be balanced, resulting in a decrease in system stability.

The invention provides a power converter, which improves the stability of the system by increasing the sensing range of the sensing unit.

The present invention provides a power converter that continuously receives sense currents corresponding to respective channels during reverse current generation to maintain a balance of currents for each channel.

The invention provides a power converter comprising a switching unit, an impedance unit, a sensing unit and a controller, and the sensing unit comprises a resistor, an operational amplifier, an N-channel transistor, a current replica circuit, and a calculation circuit. The switching unit switches the plurality of transmission paths according to the plurality of pulse signals. The impedance unit is electrically connected to the switching unit to form a node, and generates an output current according to switching of the transmission paths. The sensing unit can sense the current back. Thereby, the controller determines the magnitude of the output current according to the sensing current, and controls the pulse signals according to the determination result, so that the output current is less than a current threshold.

In the case of the sensing unit, the first end of the resistor is electrically connected to the node. The negative input of the operational amplifier is electrically connected to the second end of the resistor, and the positive input of the operational amplifier is maintained at a positive voltage. The gate of the N-channel transistor is electrically connected to the output of the operational amplifier, and the source of the N-channel transistor is electrically connected to the negative input terminal of the operational amplifier. The current replica circuit is electrically connected to the drain of the N-channel transistor and generates a replica current when the N-channel transistor is turned on. The calculation circuit subtracts the replica current from a predetermined current to generate a sense current.

In an embodiment of the invention, the sensing unit further includes a voltage source. The voltage source is electrically connected between the positive input terminal and the ground terminal of the operational amplifier, and is used to provide a positive voltage.

In an embodiment of the invention, the positive input terminal of the operational amplifier is electrically connected to the ground terminal, and the positive voltage is derived from the offset voltage of the operational amplifier itself.

The invention further provides a power converter comprising N switching units, N impedance units, N sensing units and a controller, N being an integer greater than one. The i-th switching unit includes a plurality of transmission paths, and switches the transmission paths according to the plurality of pulse signals. The N impedance units are electrically connected one-to-one with the N switching units to form N nodes, and generate N output currents. Further, the i-th impedance unit generates an i-th output current according to switching of the transmission paths in the i-th switching unit. The N sensing units are used to generate N sensing currents. The controller determines the magnitude of the output currents according to the N sensing currents, and controls the pulse signals of each switching unit according to the determination result, so that the N output currents reach a balance.

In addition, the ith sensing unit includes a resistor, an operational amplifier, an N-channel transistor, a current replica circuit, and a calculation circuit. The first end of the resistor is electrically connected to the i-th node. The negative input of the operational amplifier is electrically connected to the second end of the resistor, and the positive input of the operational amplifier is maintained at a positive voltage. The gate of the N-channel transistor is electrically connected to the output of the operational amplifier, and the source of the N-channel transistor is electrically connected to the negative input terminal of the operational amplifier. The current replica circuit is electrically connected to the drain of the N-channel transistor and generates a replica current when the N-channel transistor is turned on. The calculation circuit subtracts the replica current from a predetermined current to generate an ith sense current.

In an embodiment of the invention, the ith sensing unit further includes a voltage source. The voltage source is electrically connected between the positive input terminal and the ground terminal of the operational amplifier, and is used to provide a positive voltage.

Based on the above, the present invention maintains the positive input terminal of the operational amplifier at a positive voltage to increase the sensing range of the sensing unit. Thereby, as the sensing range of the sensing unit increases, the system stability of the power converter can be improved. In addition, for a multi-phase power converter, it can maintain the balance of the current of each channel through the increase of the sensing range of the sensing unit.

The above described features and advantages of the present invention will be more apparent from the following description.

1 is a circuit diagram of a power converter in accordance with an embodiment of the present invention. Referring to FIG. 1, the power converter 100 includes a switching unit 110, an impedance unit 120, a sensing unit 130, and a controller 140. The switching unit 110 is electrically connected to the impedance unit 120 to form a node N11. In addition, the switching unit 110 switches the plurality of transmission paths according to the plurality of pulse signals to adjust the current flowing through the impedance unit 120. On the other hand, the impedance unit 120 generates the output current IO ₁ according to the switching of the transmission path of the switching unit 110.

For example, in the present embodiment, the switching unit 110 includes a switch SW11 and a switch SW12. In addition, in this embodiment, the buck impedance unit 120 is taken as an example, so the impedance unit 120 includes the inductor L1 and the capacitor C1. The first end of the switch SW11 is electrically connected to the voltage VD ₁₁ , and the second end of the switch SW11 is electrically connected to the node N11. The first end of the switch SW12 is electrically connected to the node N11, and the second end of the switch SW12 is electrically connected to the ground. In addition, the first end of the inductor L1 is electrically connected to the node N11. The first end of the capacitor C1 is electrically connected to the second end of the inductor L1, and the second end of the capacitor C1 is electrically connected to the ground.

In operation, the controller 140 generates a plurality of pulse signals PU ₁₁ ~ PU ₁₂ . Wherein, based on the pulse signal switch SW11 ~ ₁₁ PU PU PU ₁₂ of the first pulse signal ₁₁ is determined in its conducting state, and the switch SW12 is based on the pulse signal PU PU ~ ₁₁ second pulse signal PU _{12 12} to determine its conduction state. Thereby, as the conduction state of the switch SW11 and the switch SW12 changes, the switching unit 110 and the impedance unit 120 will constitute different current loops, thereby causing a corresponding change in the current flowing through the inductor L1.

For example, FIG. 2 is a schematic diagram of an inductor current in accordance with an embodiment of the present invention. Referring to FIGS. 1 and 2, when the switch SW11 is turned on and the switch SW12 is not turned off, the current I _L flowing through the inductor L1 will gradually rise with time. In addition, when the switch SW11 is not turned on and the switch SW12 is turned on, the current I _L flowing through the inductor L1 will gradually decrease with time. Thereby, as the current I _L of the inductor L1 changes, the capacitor C1 and the inductor L1 will generate the output current IO ₁ , that is, the average current I _AV of the current I _L in FIG. 2 .

On the control of the switching unit 110, the controller 140 determines the magnitude of the output current IO ₁ according to the sensing current IS ₁ returned by the sensing unit 130. Thereby, the controller 140 controls the pulse signal PU ₁₁ PUPU ₁₂ according to the discrimination result, thereby causing the output current IO _{1 to be} smaller than the current threshold. As a result, the power converter 100 will achieve an overcurrent protection mechanism.

Looking further, the sensing unit 130 includes a resistor R1, an N-channel transistor NM1, an operational amplifier 131, a current replica circuit 132, a calculation circuit 133, and a voltage source 134. The first end of the resistor R1 is electrically connected to the node N11. The negative input terminal of the operational amplifier 131 is electrically connected to the second end of the resistor R1, and the positive input terminal of the operational amplifier 131 is electrically connected to the voltage source 134. The gate of the N-channel transistor NM1 is electrically connected to the current replica circuit 132. The source of the N-channel transistor NM1 is electrically connected to the negative input terminal of the operational amplifier 131, and the gate of the N-channel transistor NM1 is electrically connected to the operational amplifier 131. The output.

In operation, voltage source 134 is used to provide a positive voltage such that the positive input of operational amplifier 131 is maintained at a positive voltage. Although the present embodiment maintains the positive input terminal of the operational amplifier 131 at a positive voltage through the voltage source 134, in practical applications, those skilled in the art can also electrically connect the positive input terminal of the operational amplifier 131 to the ground terminal. And maintaining its positive input terminal at a positive voltage through the offset voltage of the operational amplifier 131 itself. Furthermore, the feedback loop formed by the operational amplifier 131 and the N-channel transistor NM1 will cause the node N12 to maintain a positive voltage.

On the other hand, as the conduction path of the switching unit 110 is switched, the voltage level of the node N11 will produce a corresponding change. Wherein, when the voltage level of the node N12 is greater than the voltage level of the node N11, the voltage difference between the nodes N11 and N12 will cause the N-channel transistor NM1 to be turned on, thereby generating the current IM ₁₁ . At this point, current replica circuit 132 will receive current IM ₁₁ and replicate current IM ₁₁ to produce replica current IM ₁₂ . In addition, the calculation circuit 133 will operate on the replica current IM ₁₂ to sense the current IS ₁ to the controller 140.

It is worth mentioning that FIG. 3 is a relationship diagram between the current IM ₁₁ and the output current IO ₁ , wherein the curve 310 is used to indicate the relative relationship between the two currents IM ₁₁ and IO ₁ when the node N12 is maintained at the ground voltage, and the curve 320 It is used to indicate the relative relationship between the two currents IM ₁₁ and IO ₁ when the node N12 is maintained at a positive voltage. In practical applications, when the power converter 100 drives a light load, the reverse current generated by the inductor L1 will cause the voltage level of the node N11 to be greater than zero.

In view of the above, as shown by curve 310, if node N12 is maintained at ground voltage, the reverse current will cause the voltage level of node N11 to be greater than node N12. At this time, the current IM ₁₁ will not be generated, which in turn causes the sensing unit 130 to fail to sense the current IS ₁ to the controller 140. However, referring to the curve 320, when the node N12 is maintained at a positive voltage, although the reverse current causes the voltage level of the node N11 to be greater than 0, the voltage level of the node N12 is set to be larger than the node N11, thus sensing Unit 130 can still sense current IS ₁ to controller 140.

Accordingly, this embodiment maintains the positive input of operational amplifier 131 at a positive voltage such that node N12 is maintained at a positive voltage. On the other hand, in the present embodiment, since the acquisition of the replica current IM ₁₂ is relative to the positive voltage, the calculation circuit 133 subtracts the replica current IM _{12 by} a predetermined current, and accordingly obtains the sensing current IS. ₁ . Thereby, through the return of the sensing current IS ₁ , the controller 140 can determine the magnitude of the output current IO ₁ and control the pulse signals PU ₁₁ PU PU ₁₂ according to the determination result, so that the output current IO _{1 is} smaller than the current threshold. value.

Further, as shown in FIG. 1, in the present embodiment, the current replica circuit 132 includes a P-channel transistor PM11 and a P-channel transistor PM12. The source of the P-channel transistor PM11 is electrically connected to the voltage VD ₁₂ , and the gate and the drain of the P-channel transistor PM11 are electrically connected to the drain of the N-channel transistor NM1. The source of the P-channel transistor PM12 is electrically connected to the voltage VD ₁₂ , and the gate of the P-channel transistor PM12 is electrically connected to the gate of the P-channel transistor PM11. Thereby, the P-channel transistors PM11 and PM12 will form a current mirror to replicate the current IM ₁₁ received by the P-channel transistor PM11 and generate a replica current IM ₁₂ through the source of the P-channel transistor PM12.

In general, this embodiment maintains the positive input of operational amplifier 131 at a positive voltage such that the voltage level of node N12 is maintained at a positive voltage. As such, when the power converter 100 drives the light load, the sensing unit 130 can still sense the current IS ₁ to the controller 140 despite the reverse current generated by the inductor L1. In other words, the sensing unit 130 of the present embodiment has a larger sensing range, which can increase the stability of the system of the power converter 100.

4 is a circuit diagram of a power converter in accordance with another embodiment of the present invention. Referring to FIG. 4, the power converter 400 includes N switching units 410_1 410410_N, N impedance units 420_1 420 420_N, N sensing units 430_1 430 430_N, and a controller 440, N being an integer greater than one. The power converter 400 is a multi-phase power converter, and the switching unit 410_1 and the impedance unit 420_1 can be regarded as one channel or a single phase. By analogy, the switching units 410_1~410_N and the impedance units 420_1~420_N will form N channels or N phases.

Further, the switching unit 410_1 includes a plurality of transmission paths, and the impedance unit 420_1 generates an output current IO ₄₁ according to switching of the transmission path of the switching unit 410_1. By analogy, the switching units 410_1~410_N and the impedance units 420_1~420_N will generate the output currents IO ₄₁ ~ IO _4N . On the other hand, the sensing units 430_1~430_N are used to detect N channels, and accordingly generate N sensing currents IS ₄₁ ~IS _4N . The controller 440 determines the magnitude of the output currents IO ₄₁ ~ IO _4N according to the sensing currents IS ₄₁ ~ IS _4N , and controls the pulse signals P ₁₁ ~ P ₁₂ , P ₂₁ ~ P ₂₂ , ..., P according to the discrimination result. _N1 ~ P _N2 . Thereby, the switching units 410_1~410_N will cause the N outputs generated by the impedance units 420_1~420_N under the control of the pulse signals P ₁₁ ~ P ₁₂ , P ₂₁ ~ P ₂₂ , ..., P _N1 ~ P _N2 . The current IO ₄₁ ~ IO _4N reaches equilibrium.

Further, the circuit architecture of each channel is the same. For example, the circuit structures of the switching units 410_1~410_N are the same, and the circuit structures of the impedance units 420_1~420_N are also the same. In addition, the sensing units 430_1 ～ 430_N also have the same circuit architecture. In order to make the present invention more familiar to those skilled in the art, the switching mechanism 410_1, the impedance unit 420_1, and the sensing unit 430_1 will be taken as an example to further illustrate the working mechanism of the power converter 400.

Referring to FIG. 4, the switching unit 410_1 includes a switch SW41 and a switch SW42. The impedance unit 420_1 includes an inductor L4 and a capacitor C4. Further, the sensing unit 430_1 includes a resistor R4, an N-channel transistor NM4, an operational amplifier 431, a current replica circuit 432, a calculation circuit 433, and a voltage source 434. The switching unit 410_1, the impedance unit 420_1, and the sensing unit 430_1 have the same or similar circuit architectures as the switching unit 110, the impedance unit 120, and the sensing unit 130 in FIG. 1, respectively.

In operation, the unit switches 410_1, the switch SW41 and the switch SW42 respectively in response to the pulse signals P ₁₁ and P ₁₂ to decide the conduction state thereof. In addition, as the conduction state of the switch SW41 and the switch SW42 changes, the switching unit 410_1 and the impedance unit 420_1 will constitute different current loops, thereby causing a corresponding fluctuation in the current flowing through the inductor L4. On the other hand, as the conduction path of the switching unit 410_1 is switched, the voltage level of the node N41 will also produce a corresponding change.

In addition, the feedback loop formed by the operational amplifier 431 and the N-channel transistor NM4 maintains the node N42 at a positive voltage. Thereby, when the voltage level of the node N42 is greater than the voltage level of the node N41, the voltage difference between the nodes N41 and N42 will cause the N-channel transistor NM4 to be turned on, thereby generating the current IM ₄₁ . Current replica circuit 432 will receive current IM ₄₁ and replicate current IM ₄₁ to produce replica current IM ₄₂ . In addition, the calculation circuit 433 subtracts the replica current IM _{42 by} a predetermined current and accordingly obtains the sense current IS ₄₁ .

It is worth mentioning that this embodiment maintains the positive input terminal of the operational amplifier 431 at a positive voltage so that the voltage level of the node N42 can be maintained at a positive voltage. As such, when the power converter 400 drives the light load, the sensing unit 430_1 can still sense the current IS ₄₁ to the controller 440 despite the reverse current generated by the inductor L4. Similarly, for the sensing units 430_2~430_N, although the inductances in the impedance units 420_1~420_N generate reverse currents, the sensing units 430_2~430_N can still return the sensing currents IS ₄₂ ~IS _4N to the controller 440. Further, the balance of the N output currents IO ₄₁ to IO _4N is maintained. The detailed structure and working principle of the present embodiment are included in the above embodiments, and thus will not be described herein.

In summary, the present invention maintains the positive input terminal of the operational amplifier at a positive voltage to increase the sensing range of the sensing unit. Thereby, when the power converter drives the light load, although the inductor generates a reverse current, the sensing unit can still sense the current to the controller. Thereby, the system stability of the power converter can be improved. In addition, for a multi-phase power converter, it can maintain the balance of the current of each channel through the increase of the sensing range of the sensing unit.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

100, 400. . . Power converter

110, 410_1~410_N. . . Switching unit

SW11, SW12, SW41, SW42. . . switch

VD ₁₁ , VD ₁₂ . . . Voltage

120, 420_1~420_N. . . Impedance unit

L1, L4. . . inductance

C1, C4. . . capacitance

130, 430_1~430_N. . . Sensing unit

131, 431. . . Operational Amplifier

132,432. . . Current replica circuit

133, 433. . . Calculation circuit

134, 434. . . power source

R1, R4. . . resistance

NM1, NM4. . . N-channel transistor

PM11, PM12. . . P channel transistor

IM ₁₁ , IM ₄₁ . . . Current

IM ₁₂ , IM ₄₂ . . . Copy current

140, 440. . . Controller

PU ₁₁ ~ PU ₁₂ , P ₁₁ ~ P ₁₂ , P ₂₁ ~ P ₂₂ , PN ₁ ~ PN ₂ . . . Pulse signal

IO ₁ , IO ₄₁ ~ IO _4N . . . Output current

IS ₁ , IS ₄₁ ~ IS _4N . . . Sense current

N11, N12, N41, N42. . . node

I _L . . . Inductor current

I _AV . . . Average current

310, 320. . . curve

1 is a circuit diagram of a power converter in accordance with an embodiment of the present invention.

2 is a schematic diagram of an inductor current in accordance with an embodiment of the present invention.

Figure 3 is a graph of current IM ₁₁ versus output current IO ₁ .

4 is a circuit diagram of a power converter in accordance with another embodiment of the present invention.

100. . . Power converter

110. . . Switching unit

SW11, SW12. . . switch

VD ₁₁ , VD ₁₂ . . . Voltage

120. . . Impedance unit

L1. . . inductance

C1. . . capacitance

130. . . Sensing unit

131. . . Operational Amplifier

132. . . Current replica circuit

133. . . Calculation circuit

134. . . power source

R1. . . resistance

NM1. . . N-channel transistor

PM11, PM12. . . P channel transistor

IM ₁₁ . . . Current

IM ₁₂ . . . Copy current

140. . . Controller

PU ₁₁ ~ PU ₁₂ . . . Pulse signal

IO ₁ . . . Output current

IS ₁ . . . Sense current

N11, N12. . . node

Claims (12)

A power converter includes: a switching unit that switches a plurality of transmission paths according to a plurality of pulse signals; an impedance unit electrically connected to the switching unit to form a node, and generates an output current according to switching of the transmission paths A sensing unit includes: a resistor, the first end of which is electrically connected to the node; an operational amplifier whose negative input terminal is electrically connected to the second end of the resistor, and the positive input terminal of the operational amplifier is maintained at a Under positive voltage; an N-channel transistor whose gate is electrically connected to the output end of the operational amplifier, the source of the N-channel transistor is electrically connected to the negative input terminal of the operational amplifier; a current replica circuit is electrically connected a drain of the N-channel transistor, and generating a replica current when the N-channel transistor is turned on; and a calculation circuit that subtracts a predetermined current from the replica current to generate a sense current; and a control And determining the magnitude of the output current according to the sensing current, and controlling the pulse signals according to the determination result, so that the output current is less than a current threshold. The power converter of claim 1, wherein the current replica circuit comprises: a first P-channel transistor, the source of which is electrically connected to a first voltage, and the gate of the first P-channel transistor Electrode is electrically connected to the drain of the N-channel transistor; and a second P-channel transistor is electrically connected to the first voltage, and the gate of the second P-channel transistor is electrically connected to the first A gate of a P-channel transistor, the source of the second P-channel transistor is used to generate the replica current. The power converter of claim 1, wherein the switching unit comprises: a first switch, the first end of which is electrically connected to a second voltage, and the second end of the first switch is electrically connected to the node And the first switch determines a conduction state according to a first pulse signal of the pulse signals; and a second switch, the first end of which is electrically connected to the node, and the second end of the second switch The ground is electrically connected to the ground, and the second switch determines the conduction state according to a second pulse signal of the pulse signals. The power converter of claim 1, wherein the impedance unit comprises: an inductor, the first end of which is electrically connected to the node; and a capacitor whose first end is electrically connected to the second end of the inductor The second end of the capacitor is electrically connected to a ground. The power converter of claim 1, wherein the sensing unit further comprises: a voltage source electrically connected between the positive input terminal and the ground terminal of the operational amplifier, and configured to provide the positive voltage . The power converter of claim 1, wherein the positive input terminal of the operational amplifier is electrically connected to a ground, and the positive voltage is derived from an offset voltage of the operational amplifier itself. A power converter includes: N switching units, wherein the i-th switching unit includes a plurality of transmission paths, and switches the transmission paths according to a plurality of pulse signals, where N is an integer greater than 1; N impedance units, One-to-one electrical connection with the switching units to form N nodes, and generating N output currents, wherein the i-th impedance unit generates an ith output according to switching of the transmission paths in the i-th switching unit The current sensing unit generates N sensing currents, wherein the ith sensing unit comprises: a resistor, the first end of which is electrically connected to the ith node; and an operational amplifier whose electrical input is electrically connected a second end of the resistor, and the positive input terminal of the operational amplifier is maintained at a positive voltage; an N-channel transistor whose gate is electrically connected to the output end of the operational amplifier, the source of the N-channel transistor Connected to the negative input terminal of the operational amplifier; a current replica circuit electrically connected to the drain of the N-channel transistor, and generates a replica current when the N-channel transistor is turned on; and a calculation circuit that copies the Current reduction a preset current to generate an ith sense current; and a controller, determining the magnitudes of the output currents according to the sense currents, and controlling the pulse waves of each of the switching units according to the determination result a signal such that the N output currents are balanced. The power converter of claim 7, wherein the current replica circuit comprises: a first P-channel transistor, the source of which is electrically connected to a first voltage, and the gate of the first P-channel transistor Electrode is electrically connected to the drain of the N-channel transistor; and a second P-channel transistor is electrically connected to the first voltage, and the gate of the second P-channel transistor is electrically connected to the first A gate of a P-channel transistor, the source of the second P-channel transistor is used to generate the replica current. The power converter of claim 7, wherein the i-th switching unit comprises: a first switch, the first end of which is electrically connected to a second voltage, and the second end of the first switch is electrically connected An i-th node, wherein the first switch determines a conduction state according to a first pulse signal of the pulse signals; and a second switch, the first end of which is electrically connected to the i-th node, the first The second end of the two switches is electrically connected to a ground, and the second switch determines the conduction state according to a second pulse signal of the pulse signals. The power converter of claim 7, wherein the ith impedance unit comprises: an inductor, the first end of which is electrically connected to the ith node; and a capacitor whose first end is electrically connected to the inductor The second end of the capacitor is electrically connected to a ground. The power converter of claim 7, wherein the ith sensing unit further comprises: a voltage source electrically connected between the positive input terminal and the ground terminal of the operational amplifier, and configured to provide the Positive voltage. The power converter of claim 7, wherein the positive input terminal of the operational amplifier is electrically connected to a ground, and the positive voltage is derived from an offset voltage of the operational amplifier itself.