TWI852766B - Switch-mode power converter - Google Patents

Abstract

A switch-mode power converter comprising an input node, a ground node, a switching node, a power node, a high side switching element, a low side switching element, an output node, a bootstrap capacitor, a variable resistor, and a feedback control circuit is provided. The high side switching element is coupled between the input node and the switching node. The low side switching element is coupled between the switching node and the ground node. The output node is electrically coupled to the switching node for generating an output voltage. The bootstrap capacitor is coupled between the power node and the switching node for raising the power voltage of the power node to generate a driving voltage. The variable resistor is located on the circuit between the bootstrap capacitor and the power node or the switching node. The feedback control circuit is for adjusting the variable resistor according to the output voltage.

Description

Switching power conversion circuit

The present invention relates to a switching power conversion circuit, and more particularly to a switching power conversion circuit with a bootstrap capacitor.

Self-supporting capacitors are commonly found in traditional switching power conversion circuits, and are particularly suitable for driving circuits on the high-voltage side of switching power conversion circuits. Self-supporting capacitors can be used to increase the voltage level at the power end to generate a driving voltage sufficient to drive the high-voltage side switching components.

However, traditional switching power conversion circuits are prone to overshoot or ringing when switching (especially on the high-voltage side). These phenomena will generate noise and cause unnecessary interference to the system.

The present invention provides a switching power conversion circuit. The switching power conversion circuit includes an input terminal, a ground terminal, a switching contact, a power terminal, a high-voltage side switching element, a low-voltage side switching element, an output terminal, a self-supporting capacitor, a variable resistor, and a feedback control circuit. The input terminal receives an input voltage. The power terminal provides a power voltage. The high-voltage side switching element is coupled between the input terminal and the switching contact. The low-voltage side switching element is coupled between the switching contact and the ground terminal. The output terminal is electrically coupled to the switching contact to generate an output voltage. The self-supporting capacitor is coupled between the power supply terminal and the switching contact to increase the power supply voltage to generate a driving voltage suitable for driving the high-voltage side switch element. The variable resistor is arranged in the circuit where the self-supporting capacitor is coupled to the power supply terminal or the circuit where the self-supporting capacitor is coupled to the switching contact. The feedback control circuit is coupled to the output terminal and the variable resistor to detect the output voltage and adjust the resistance value of the variable resistor accordingly to control the driving voltage.

In one embodiment of the present case, the switching power conversion circuit further includes a voltage detection circuit. The voltage detection circuit is electrically coupled to the output terminal, and generates a detection voltage signal according to the output voltage and provides it to the feedback control circuit. In another embodiment, the feedback control circuit includes an error amplifier and a control unit. The error amplifier receives the detection voltage signal and generates an error voltage signal according to the detection voltage signal. The control unit receives the error voltage signal and adjusts the resistance of the variable resistor according to the error voltage signal.

In one embodiment of the present case, the variable resistor is a digital variable resistor element.

In one embodiment of the present case, the variable resistor is an electromechanical variable resistor element.

In one embodiment of the present case, the switching power conversion circuit further includes a high-voltage side driving unit, which obtains a driving voltage and generates a high-voltage side driving signal according to a high-voltage side switch signal to drive the high-voltage side switch element. In another embodiment, the switching power conversion circuit further includes a negative voltage generating unit. The negative voltage generating unit is electrically coupled to the high voltage side driving unit and the high voltage side switching element, and is used to receive the high voltage side driving signal, and use the high voltage side driving signal to generate a high voltage side negative voltage driving signal to drive the high voltage side switching element. In addition, in one embodiment, the negative voltage generating unit includes a negative voltage generating capacitor and a negative voltage generating diode. The negative voltage generating capacitor has a first end and a second end, the first end is electrically coupled to the high voltage side driving unit, and the second end is electrically coupled to the high voltage side switching element. The negative voltage generating diode has a positive terminal and a negative terminal, the positive terminal is electrically coupled to the second terminal, and the negative terminal is electrically coupled to the switching contact. In addition, in one embodiment, the high voltage side switch element is a silicon carbide (SiC) switch element or a gallium nitride (GaN) switch element.

In one embodiment of the present case, the switching power conversion circuit further includes a low-voltage side driving unit, which obtains the power voltage and generates a low-voltage side driving signal according to a low-voltage side switch signal to drive the low-voltage side switch element.

In one embodiment of the present case, the switching power conversion circuit further includes a filter unit disposed in the circuit between the output terminal and the switching contact.

The self-supporting capacitor of the switching power conversion circuit provided in this case is connected in series with a variable resistor, and the feedback control circuit is used to adjust the resistance of the variable resistor according to the output voltage to control the voltage level of the driving voltage. In this way, the overshoot or ringing phenomenon generated when the driving voltage is switched between high and low can be improved.

The specific implementation of the present invention will be described in more detail below with reference to the schematic diagrams. The advantages and features of the present invention will become clearer based on the following description and the scope of the patent application. It should be noted that the diagrams are all in a very simplified form and are not in exact proportions, and are only used to conveniently and clearly assist in explaining the purpose of the present invention.

The first figure is a schematic diagram of a switching power conversion circuit 100 provided according to an embodiment of the present invention.

The present invention provides a switching power conversion circuit 100. The switching power conversion circuit 100 includes an input terminal P1, a ground terminal P2, a switching contact SW, a power terminal P3, a high-voltage side switch element QH, a low-voltage side switch element QL, an output terminal P4, a boot capacitor Cboot, a high-voltage side drive unit 120, a low-voltage side drive unit 140, a variable resistor Rv, and a feedback control circuit 160.

Among them, the input terminal P1 provides an input voltage VIN. The power terminal P3 provides a power voltage VCC. The high-voltage side switching element QH is coupled between the input terminal P1 and the switching contact SW. The low-voltage side switching element QL is coupled between the switching contact SW and the ground terminal P2. The output terminal P4 is electrically coupled to the switching contact SW to generate an output voltage VOUT to drive the load RL. In one embodiment, the aforementioned high-voltage side switching element QH and the low-voltage side switching element QL are both enhanced power transistor elements. However, it is not limited to this. In other embodiments, the aforementioned high-voltage side switching element QH and the low-voltage side switching element QL can also be depletion-type power transistor elements.

The self-support capacitor Cboot is coupled between the power terminal P3 and the switching point SW. The high voltage side of the self-support capacitor Cboot is coupled to the power terminal P3 through a diode D1, and the self-support capacitor Cboot is coupled to the switching point SW through a variable resistor Rv. The self-support capacitor Cboot is used to raise the voltage level of the power voltage VCC to generate a driving voltage Vboot to drive the high voltage side switch element QH.

The high-voltage side driver unit 120 is electrically coupled to the high-voltage side of the self-boot capacitor Cboot and the high-voltage side switch element QH. The high-voltage side driver unit 120 obtains a drive voltage Vboot from the self-boot capacitor Cboot, and generates a high-voltage side drive signal S2 according to a high-voltage side switch signal S1 to drive the high-voltage side switch element QH. The high-voltage side switch signal S1 can be a pulse width modulation (PWM) signal. In one embodiment, the high-voltage side driver unit 120 can include a power amplifier, which can be composed of a complementary metal oxide semiconductor device (CMOS). The power amplifier can utilize the driving voltage Vboot to amplify the high-voltage side switching signal S1 to generate a high-voltage side driving signal S2 sufficient to drive the high-voltage side switching element QH.

The low-voltage side driver unit 140 is electrically coupled to the power terminal P3 and the low-voltage side switch element QL. The low-voltage side driver unit 140 obtains the power voltage VCC from the power terminal P3, and generates a low-voltage side driver signal S4 according to a low-voltage side switch signal S3 to drive the low-voltage side switch element QL. The low-voltage side switch signal S3 can be a pulse width modulated signal. In one embodiment, the low-voltage side driver unit 140 can also include a power amplifier, which can be composed of a complementary metal oxide semiconductor device (CMOS).

The variable resistor Rv is arranged in a circuit where the self-supporting capacitor Cboot is coupled to the switching contact SW. The variable resistor Rv and the self-supporting capacitor Cboot are connected in series between the power terminal P3 and the switching contact SW. The feedback control circuit 160 is coupled to the output terminal P4 and the variable resistor Rv. The feedback control circuit 160 can detect the output voltage VOUT of the output terminal P4, and dynamically adjust the resistance value of the variable resistor Rv according to the output voltage VOUT, thereby adjusting the level of the driving voltage Vboot to improve the driving waveform when the high-voltage side switch element QH is turned on.

The variable resistor Rv of this embodiment is disposed in the circuit between the self-supporting capacitor Cboot and the switching contact SW. However, the present invention is not limited thereto. In other embodiments, the variable resistor Rv may also be disposed in the circuit where the self-supporting capacitor Cboot is coupled to the power supply terminal P3. In addition, the variable resistor Rv of this embodiment may be an electromechanical variable resistor element or a digital variable resistor element.

In one embodiment, the feedback control circuit 160 detects the output voltage VOUT of the output terminal P4 through a voltage detection circuit 170. The voltage detection circuit 170 may include a voltage divider circuit. The voltage detection circuit 170 is electrically coupled to the output terminal P4, and generates a detection voltage signal S5 according to the output voltage VOUT and provides it to the feedback control circuit 160. The feedback control circuit 160 may include an error amplifier 162 and a control unit 164. The error amplifier 162 compares the detection voltage signal S5 with a reference voltage Vr to generate an error voltage signal S6. The control unit 164 is used to receive the error voltage signal S6 and adjust the resistance of the variable resistor Rv according to the error voltage signal S6.

For example, when the output voltage VOUT is lower than the set value, the conduction time of the high-voltage side switch element QH needs to be prolonged. At this time, the control unit 164 can increase the resistance of the variable resistor Rv to slow down the slope of the driving signal when the high-voltage side switch element QH is turned on, thereby suppressing the ringing noise when the switch is turned on.

In one embodiment of the present case, the switching power conversion circuit 100 further includes a filter unit 180. The filter unit 180 is disposed in the circuit between the output terminal P4 and the switching contact SW. The filter unit 180 can make the output voltage VOUT generated by the output terminal P4 more stable.

FIG. 2 is a schematic diagram of a digital variable resistor element 200 provided according to an embodiment of the present invention. The digital variable resistor element 200 can be used as the variable resistor Rv in the switching power conversion circuit 100 of FIG. 1.

As shown in the figure, the digital variable resistor element 200 has a control interface 220, a register 240 and an analog resistor 260. The control interface 220 is used to receive an external control signal (e.g., the error voltage signal S6 from the feedback control circuit 160), and convert the control signal into a corresponding resistance setting value and store it in the register 240. The analog resistor 260 has a first connection terminal 262, a second connection terminal 264 and a variable terminal 266. The first connection terminal 262 is electrically coupled to the low voltage side of the boot capacitor Cboot, and the variable terminal 266 is electrically coupled to the switching contact SW. For example, the analog resistor 260 can be composed of a resistor string and a plurality of switch elements. The analog resistor 260 can generate a resistance value corresponding to the resistance setting value between the first connection terminal 262 and the variable terminal 266 according to the resistance setting value of the register 240.

FIG. 3 shows the driving waveform diagram of the high-voltage side switch element QH of the conventional switching power conversion circuit and the switching power conversion circuit 100 of the present invention. The solid line portion in the figure shows the driving waveform of the conventional switching power conversion circuit, that is, the driving waveform without adding the variable resistor Rv to adjust the driving voltage, and the dotted line portion shows the driving waveform of the switching power conversion circuit 100 of the present invention, that is, the driving waveform after adding the variable resistor Rv to adjust the high-voltage side driving signal S2.

As shown in the figure, by dynamically adjusting the waveform of the high-voltage side drive signal S2 through the variable resistor Rv, the rising slope of the leading edge of the drive waveform can be effectively slowed down when the high-voltage side switch element QH is turned on. This improves the overshoot or ringing phenomenon generated when the high-voltage side drive signal S2 switches between high and low, and effectively suppresses the noise generated when the high-voltage side switch element QH is turned on.

FIG. 4 is a schematic diagram of a switching power conversion circuit 400 provided according to another embodiment of the present invention.

Compared to the embodiment of the first figure, the switching power conversion circuit 400 of this embodiment further includes a high-voltage side negative voltage generating circuit 430 and a low-voltage side negative voltage generating circuit 450. The high-voltage side negative voltage generating circuit 430 is electrically coupled between the high-voltage side driving unit 120 and the high-voltage side switching element QH. The low-voltage side negative voltage generating circuit 450 is electrically coupled between the low-voltage side driving unit 140 and the low-voltage side switching element QL.

The high-voltage side negative voltage generating circuit 430 receives the first high-voltage side driving signal S11 generated by the high-voltage side driving unit 120, and uses the first high-voltage side driving signal S11 to generate a second high-voltage side driving signal S12 having a negative voltage.

The high-voltage side negative voltage generating circuit 430 includes a negative voltage generating capacitor C11 and a negative voltage generating diode D11. The negative voltage generating capacitor C11 has a first terminal P11 and a second terminal P12 opposite to each other. The first terminal P11 is electrically coupled to the high-voltage side driving unit 120 to obtain the first high-voltage side driving signal S11, and the second terminal P12 is electrically coupled to the gate of the high-voltage side switching element QH. The positive electrode of the negative voltage generating diode D11 is electrically coupled to the second end P12 of the negative voltage generating capacitor C11, and the negative electrode of the negative voltage generating diode D11 is electrically coupled to the switching contact SW.

When the high-voltage side switch element QH is turned on, due to the presence of the negative voltage generating diode D11, the gate potential of the high-voltage side switch element QH will be pulled up to a potential higher than the switching contact SW. Therefore, the negative voltage generating capacitor C11 will store a voltage difference. Subsequently, when the first high-voltage side driving signal S11 drops to 0V, the voltage difference stored in the negative voltage generating capacitor C11 will cause the gate potential of the high-voltage side switch element QH to drop to a negative voltage, thereby generating a second high-voltage side driving signal S12 with a negative voltage to drive the high-voltage side switch element QH. This high-voltage side negative voltage generating circuit 430 is suitable for driving power elements such as silicon carbide (SiC) power elements and gallium nitride (GaN) power elements that require negative voltage to ensure that the switching element is turned off.

Similar to the aforementioned high-voltage side negative voltage generating circuit 430, the low-voltage side negative voltage generating circuit 450 of the present embodiment receives the first low-voltage side driving signal S13 generated by the low-voltage side driving unit 140, and uses the first low-voltage side driving signal S13 to generate a second low-voltage side driving signal S14 with a negative voltage to drive the low-voltage side switching element QL. The design and operation principle of the low-voltage side negative voltage generating circuit 450 are similar to those of the aforementioned high-voltage side negative voltage generating circuit 430, and will not be elaborated here.

In summary, the boot capacitor Cboot of the switching power conversion circuit 100, 400 provided in the present case is connected in series with a variable resistor Rv, and the feedback control circuit 160 is used to adjust the resistance of the variable resistor Rv according to the output voltage VOUT to adjust the voltage level of the driving voltage Vboot. In this way, the overshoot or ringing phenomenon caused by the rapid switching of the driving voltage when the high-voltage side switching element QH is turned on can be improved. In addition, the switching power conversion circuit 400 provided in one embodiment of the present case has a high-voltage side negative voltage generating circuit 430 and a low-voltage side negative voltage generating circuit 450. The high-voltage side negative voltage generating circuit 430 and the low-voltage side negative voltage generating circuit 450 can generate a driving signal with a negative voltage, which is particularly suitable for driving silicon carbide power elements or gallium nitride power elements that require negative voltage to ensure that the switch element is turned off.

The above is only the preferred embodiment of this case and does not impose any restrictions on this case. Any technical personnel in the relevant technical field, within the scope of the technical means of this case, make any form of equivalent replacement or modification to the technical means and technical content disclosed in this case, which is within the scope of the technical means of this case and still within the scope of protection of this case.

100, 400: Switching power conversion circuit

120: High voltage side drive unit

140: Low voltage side drive unit

160: Feedback control circuit

162: Error amplifier

164: Control unit

170: Voltage detection circuit

180:Filter unit

200: Digital variable resistor element

220: Control Interface

240: Register

260:Analog resistor

262: First connection end

264: Second connection terminal

266: Variable end

430: High voltage side negative voltage generating circuit

450: Low voltage side negative voltage generating circuit

P1: Input terminal

P2: Ground terminal

P3: Power terminal

P4: Output terminal

SW: Switching contact

QH: High voltage side switch element

QL: Low voltage side switch element

Cboot: boot capacitor

Rv: variable resistor

RL: Load

VIN: Input voltage

VCC: power supply voltage

VOUT: output voltage

Vboot: driving voltage

Vr: reference voltage

S1: High voltage side switch signal

S2: High voltage side drive signal

S3: Low voltage side switch signal

S4: Low voltage side drive signal

S5: Detect voltage signal

S6: Error voltage signal

S11: First high voltage side drive signal

S12: Second high voltage side drive signal

S13: First low voltage side drive signal

S14: Second low voltage side drive signal

C11: Negative voltage generating capacitor

D1: Diode

D11: Negative voltage produces diode

P11: First end

P12: Second end

The first figure is a schematic diagram of a switching power conversion circuit provided according to an embodiment of the present invention; The second figure is a schematic diagram of a digital variable resistor element provided according to an embodiment of the present invention. The third figure shows the high-voltage side drive waveform diagram of a conventional switching power conversion circuit and the switching power conversion circuit of the present invention; and The fourth figure is a schematic diagram of a switching power conversion circuit provided according to another embodiment of the present invention.

100: Switching power conversion circuit

120: High voltage side drive unit

140: Low voltage side drive unit

160: Feedback control circuit

162: Error amplifier

164: Control unit

170: Voltage detection circuit

180: Filter unit

P1: Input terminal

P2: Ground terminal

P3: Power terminal

P4: Output port

SW: Switching contact

QH: High voltage side switch element

QL: Low voltage side switching element

Cboot: self-starting capacitor

Rv: variable resistor

RL: Load

VIN: Input voltage

VCC: power supply voltage

VOUT: output voltage

Vboot: driving voltage

Vr: reference voltage

S1: High voltage side switch signal

S2: High voltage side drive signal

S3: Low voltage side switch signal

S4: Low voltage side drive signal

S5: Detect voltage signal

S6: Error voltage signal

D1: diode

Claims (11)

A switching power conversion circuit comprises: an input terminal for receiving an input voltage; a ground terminal; a switching contact; a power terminal for providing a power voltage; a high-voltage side switch element coupled between the input terminal and the switching contact; a low-voltage side switch element coupled between the switching contact and the ground terminal; an output terminal electrically coupled to the switching contact and used to generate an output voltage; a self-supporting capacitor coupled between the power terminal and the switching contact and used to boost the power voltage to generate a driving voltage suitable for driving the high-voltage side switch element; A variable resistor is provided in the circuit where the self-supporting capacitor is coupled to the power supply terminal or the circuit where the self-supporting capacitor is coupled to the switching contact; and a feedback control circuit is coupled to the output terminal and the variable resistor to detect the output voltage and adjust the resistance of the variable resistor accordingly to control the driving voltage. The switching power conversion circuit as described in claim 1 further includes a voltage detection circuit, which is electrically coupled to the output end and generates a detection voltage signal according to the output voltage and provides it to the feedback control circuit. A switching power conversion circuit as described in claim 2, wherein the feedback control circuit includes an error amplifier and a control unit, the error amplifier receives the detection voltage signal and generates an error voltage signal according to the detection voltage signal, and the control unit receives the error voltage signal and adjusts the resistance of the variable resistor according to the error voltage signal. A switching power conversion circuit as described in claim 1, wherein the variable resistor is a digital variable resistor element. A switching power conversion circuit as described in claim 1, wherein the variable resistor is an electromechanical variable resistor element. The switching power conversion circuit as described in claim 1 further includes a high-voltage side driving unit, which obtains the driving voltage and generates a high-voltage side driving signal according to a high-voltage side switch signal to drive the high-voltage side switch element. The switching power conversion circuit as described in claim 6 further includes a low-voltage side driving unit, which obtains the power voltage and generates a low-voltage side driving signal according to a low-voltage side switch signal to drive the low-voltage side switch element. The switching power conversion circuit as described in claim 6 further includes a negative voltage generating unit, which is electrically coupled to the high voltage side driving unit and the high voltage side switching element, for receiving the high voltage side driving signal and utilizing the high voltage side driving signal to generate a high voltage side negative voltage driving signal for driving the high voltage side switching element. The switching power conversion circuit as described in claim 8, wherein the negative voltage generating unit comprises: a negative voltage generating capacitor having a first end and a second end, the first end being electrically coupled to the high voltage side driving unit, and the second end being electrically coupled to the high voltage side switching element; and a negative voltage generating diode having a positive end and a negative end, the positive end being electrically coupled to the second end, and the negative end being electrically coupled to the switching contact. A switching power conversion circuit as described in claim 9, wherein the high-voltage side switching element is a silicon carbide (SiC) switching element or a gallium nitride (GaN) switching element. The switching power conversion circuit as described in claim 1 further includes a filtering unit arranged in the circuit between the output end and the switching contact.

Images