阅读说明：本技术 电压转换电路及其控制电路 (Voltage conversion circuit and control circuit thereof ) 是由 李敬赞 杨珮婷 于 2018-08-17 设计创作，主要内容包括：本发明提供一种电压转换电路及其控制电路。控制电路包括电压选择电路、缓冲电路以及下拉开关。电压选择电路接收输入电压以及输出电压,并选择输入电压以及输出电压中电压值较小者作为选中电压。缓冲电路接收选中电压,并提供选中电压以作为参考电压。下拉开关的控制端接收致能信号,以依据致能信号而被导通或被断开,其中,下拉开关依据致能信号而导通,以将驱动开关的控制端的电压拉低至参考电压,并使驱动开关被断开。(The invention provides a voltage conversion circuit and a control circuit thereof. The control circuit comprises a voltage selection circuit, a buffer circuit and a pull-down switch. The voltage selection circuit receives the input voltage and the output voltage, and selects the smaller voltage value of the input voltage and the output voltage as a selected voltage. The buffer circuit receives the selected voltage and provides the selected voltage as a reference voltage. The control end of the pull-down switch receives an enabling signal to be conducted or disconnected according to the enabling signal, wherein the pull-down switch is conducted according to the enabling signal so as to pull down the voltage of the control end of the driving switch to a reference voltage and disconnect the driving switch.)

1. A control circuit for controlling a driving switch, wherein two ends of the driving switch respectively receive an input voltage and an output voltage, the control circuit comprising:

the voltage selection circuit receives the input voltage and the output voltage and selects the smaller voltage value of the input voltage and the output voltage as a selected voltage;

a buffer circuit coupled to the voltage selection circuit, receiving the selected voltage, and providing the selected voltage as a reference voltage; and

a pull-down switch connected in series between the control terminal of the driving switch and the reference voltage, the control terminal of the pull-down switch receiving an enable signal to be turned on or off according to the enable signal,

the pull-down switch is turned on according to the enable signal to pull down the voltage of the control end of the driving switch to the reference voltage and turn off the driving switch.

2. The control circuit of claim 1, wherein the voltage value of the reference voltage is greater than a voltage value of a ground voltage.

3. The control circuit of claim 1, wherein the voltage selection circuit comprises:

a first transistor, a first terminal of the first transistor receiving the input voltage, a control terminal of the first transistor receiving the output voltage, a second terminal of the first transistor being coupled to the buffer circuit; and

a second transistor, a first terminal of the second transistor receiving the output voltage, a control terminal of the second transistor receiving the input voltage, and a second terminal of the second transistor coupled to a second terminal of the first transistor.

4. The control circuit according to claim 3, wherein when the voltage value of the input voltage is greater than the voltage value of the output voltage, the second transistor is turned on according to the input voltage and outputs the output voltage to the buffer circuit as the selected voltage.

5. The control circuit according to claim 3, wherein when the voltage value of the output voltage is greater than the voltage value of the input voltage, the first transistor is turned on in accordance with the output voltage and outputs the input voltage to the buffer circuit as the selected voltage.

6. The control circuit of claim 1, wherein the voltage selection circuit comprises:

a comparator having a positive input terminal, a negative input terminal and an output terminal, wherein the positive input terminal of the comparator receives the output voltage, and the negative input terminal of the comparator receives the input voltage, wherein the comparator compares the voltage value of the output voltage with the voltage value of the input voltage to generate a comparison result at the output terminal of the comparator;

a first switch, a control terminal of which is coupled to an output terminal of the comparator, a first terminal of which receives the input voltage, and a second terminal of which is coupled to the buffer circuit, wherein the first switch is turned on or off according to the comparison result;

a second switch, a control terminal of which receives an inverse comparison result, a first terminal of which receives the output voltage, and a second terminal of which is coupled to a second terminal of the first switch, wherein the second switch is turned on or off according to the inverse comparison result; and the input end and the output end of the inverter are respectively coupled to the output end of the comparator and the control end of the second switch, and the inverter is used for receiving the comparison result and generating the inverse comparison result.

7. The control circuit of claim 1, wherein the buffer circuit comprises:

a first current mirror circuit, receiving the selected voltage as an operating voltage, receiving a reference current at a first end thereof, and generating a first current at a second end thereof according to the reference current; and

a second current mirror circuit coupled to the first current mirror circuit, receiving and mirroring the first current to draw a second current from the second terminal of the pull-down switch,

the voltage value of the second end of the pull-down switch is pulled down to be equal to the voltage value of the reference voltage according to the second current.

8. The control circuit of claim 7, wherein the first current mirror circuit comprises:

a first transistor, a first terminal of the first transistor being coupled to the voltage selection circuit, a control terminal and a second terminal of the first transistor being coupled to each other;

a second transistor, a first terminal of the second transistor being coupled to a second terminal of the pull-down switch, a control terminal of the second transistor being coupled to a control terminal of the first transistor, a second terminal of the second transistor outputting the first current; and

the current source is coupled between a ground voltage and the second end of the first transistor and is used for providing the reference current.

9. The control circuit of claim 8, wherein the second current mirror circuit comprises:

a third transistor, wherein a first terminal and a control terminal of the third transistor are coupled to a second terminal of the second transistor, and a second terminal of the third transistor receives the ground voltage; and

a fourth transistor, a first terminal of the fourth transistor being coupled to the second terminal of the pull-down switch, a control terminal of the fourth transistor being coupled to the control terminal of the third transistor, a second terminal of the fourth transistor receiving the ground voltage,

wherein a width-to-length ratio of the fourth transistor is N times a width-to-length ratio of the third transistor, where N is a real number not less than 1.

10. The control circuit of claim 1, wherein the buffer circuit comprises:

the operational amplifier has a positive input terminal, a negative input terminal and an output terminal, the positive input terminal of the operational amplifier is coupled to the voltage selection circuit, the negative input terminal and the output terminal of the operational amplifier are coupled to each other, wherein the positive input terminal of the operational amplifier receives the selected voltage and provides the selected voltage to the output terminal of the operational amplifier as the reference voltage.

11. The control circuit of claim 1, further comprising:

a charge pump device coupled to the control terminal of the driving switch for boosting the voltage value of the control terminal of the driving switch;

a voltage shifter coupled to the control terminal of the pull-down switch and the control terminal of the driving switch, receiving a control signal as an operating voltage, and generating a pull-down switch signal by shifting the enable signal to control an on or off state of the pull-down switch; and

a ground switch, a first end of the ground switch being coupled to the control end of the driving switch, the control end of the ground switch receiving a shutdown signal, a second end of the ground switch receiving a ground voltage, wherein the ground switch is turned on according to the shutdown signal to pull down a voltage of the control end of the driving switch to the ground voltage.

12. A voltage conversion circuit, comprising:

a drive switch; and

the control circuit of any of claims 1 to 11, coupled to the drive switch and providing the reference voltage to pull down a voltage of a control terminal of the drive switch to the reference voltage and cause the drive switch to be turned off.

Technical Field

The present invention relates to a voltage converting circuit and a control circuit thereof, and more particularly, to a voltage converting circuit capable of rapidly restarting a driving switch and a control circuit thereof.

Background

In the prior art, a power conversion circuit provides a driving switch and supplies an output voltage by turning on the driving switch. In addition, when a circuit protection mechanism needs to be activated under a condition of an input voltage, such as entering a state of overcurrent protection, overvoltage protection, and reverse voltage protection, the conventional power conversion circuit may generate a control signal to pull down a voltage of the control terminal of the driving switch to a ground voltage to turn off the driving switch.

However, when the circuit protection mechanism is released, the driving switch is restarted, and the voltage at the control end of the driving switch is gradually raised, and it takes a long time to charge the load capacitor at the output end and the gate-source capacitor of the driving switch again. Therefore, it is an important issue how to increase the restart speed of the driving switch when the circuit protection mechanism is finished.

Disclosure of Invention

The invention provides a voltage conversion circuit and a control circuit thereof, which can achieve the function of rapidly restarting a drive switch.

The control circuit of the invention is used for controlling the driving switch. Two ends of the driving switch respectively receive an input voltage and an output voltage. The control circuit comprises a voltage selection circuit, a buffer circuit and a pull-down switch. The voltage selection circuit receives the input voltage and the output voltage, and selects the smaller voltage value of the input voltage and the output voltage as a selected voltage. The buffer circuit is coupled to the voltage selection circuit, receives the selected voltage, and provides the selected voltage as a reference voltage. The pull-down switch is connected in series between the control end of the driving switch and the reference voltage, the control end of the pull-down switch receives the enabling signal and is switched on or switched off according to the enabling signal, and the pull-down switch is switched on according to the enabling signal so as to pull down the voltage of the control end of the driving switch to the reference voltage and switch off the driving switch.

Based on the above, the present invention provides a control circuit, and selects the smaller of the voltage values of the input voltage and the output voltage as the selected voltage. To provide the selected voltage as a reference voltage. The pull-down switch is turned on according to the enabling signal to pull down the voltage of the control end of the driving switch to the reference voltage and turn off the driving switch. Therefore, after the circuit protection mechanism is released, when the driving switch is to be restarted, the voltage value of the control end of the driving switch is raised from the voltage value of the reference voltage, so that the time required for recovering the voltage of the control end of the driving switch can be reduced, and the aim of quickly restarting the driving switch is fulfilled.

In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.

Drawings

Fig. 1 shows a schematic diagram of a control circuit according to an embodiment of the invention.

Fig. 2 shows a schematic diagram of a control circuit according to another embodiment of the invention.

FIG. 3 shows a schematic diagram of another implementation of a voltage selection circuit of an embodiment of the invention.

FIG. 4 shows a schematic diagram of another implementation of a buffer circuit of an embodiment of the invention.

Fig. 5 is a schematic diagram of a voltage conversion circuit according to an embodiment of the invention.

Description of the reference numerals

100. 200, 510: control circuit

110. 210, 310: voltage selection circuit

120. 220, 420: buffer circuit

130. 230: charge pump device

240: voltage shifter

500: voltage conversion circuit

520: driver

COM: comparator with a comparator circuit

Con: pull-down switch signal

CTL: control signal

DSW: driving switch

En: enabling signal

INCR: result of inverse comparison

INV: reverser

IS: current source

OP: operational amplifier

CR: comparison results

PLSW: pull-down switch

SDS (sodium dodecyl sulfate): shutdown signal

SW 1: first switch

SW 2: second switch

SWG: grounding switch

T11-T12, T21-T24: transistor with a metal gate electrode

VIN: input voltage

Vm 1: selected voltage

VOUT: output voltage

Vr 1: reference voltage

Detailed Description

Referring to fig. 1, fig. 1 is a schematic diagram of a control circuit according to an embodiment of the invention. The control circuit 100 may be configured to control the driving switch DSW, wherein two terminals of the driving switch DSW respectively receive the input voltage VIN and the output voltage VOUT. The control circuit 100 includes a voltage selection circuit 110, a buffer circuit 120, a charge pump device 130, and a pull-down switch PLSW. The voltage selection circuit 110 receives the input voltage VIN and the output voltage VOUT, and selects the smaller of the input voltage VIN and the output voltage VOUT as the selected voltage Vm 1. The buffer circuit 120 is coupled to the voltage selection circuit 110, receives the selected voltage Vm1, and provides the selected voltage Vm1 as the reference voltage Vr 1. The charge pump device 130 is coupled to the control terminal of the driving switch DSW and is used for boosting the voltage value of the control terminal of the driving switch DSW. The pull-down switch PLSW is connected in series between the control terminal of the driving switch DSW and the reference voltage Vr1, the control terminal of the pull-down switch PLSW receives the enable signal En to be turned on or off according to the enable signal En, wherein the pull-down switch PLSW is turned on according to the enable signal En to pull down the voltage of the control terminal of the driving switch DSW to the reference voltage Vr1, and turn off the driving switch DSW.

Specifically, in the present embodiment, after receiving the input voltage VIN and the output voltage VOUT, the voltage selection circuit 110 in the control circuit 100 selects the voltage value of the input voltage VIN and the voltage value of the output voltage VOUT according to the voltage value of the input voltage VIN and the voltage value of the output voltage VOUT, for example, when the voltage value of the input voltage VIN is greater than the voltage value of the output voltage VOUT, the output voltage VOUT with a smaller voltage value is selected as the selected voltage Vm1 to be transmitted to the buffer circuit 120. On the other hand, if the voltage value of the output voltage VOUT is larger than that of the input voltage VIN, the input voltage VIN having a smaller voltage value is selected as the selected voltage Vm 1.

After receiving the selected voltage Vm1, the buffer circuit 120 generates the reference voltage Vr1 according to the selected voltage Vm1 and provides the reference voltage Vr1 to the second terminal of the pull-down switch PLSW, wherein the voltage value of the reference voltage Vr1 is substantially equal to the voltage value of the selected voltage Vm1, and the voltage value of the reference voltage Vr1 is greater than the voltage value of the ground voltage. In addition, the control terminal of the pull-down switch PLSW receives the enable signal En and is turned on or off according to the enable signal En.

In addition, the charge pump device 130 is coupled to the control terminal of the driving switch DSW. The charge pump device 130 is used for turning on the driving switch DSW by increasing the voltage value of the control terminal of the driving switch DSW under normal circuit operation (i.e. under the conditions of no over-current protection, over-voltage protection and reverse voltage protection).

Accordingly, when the protection mechanism is activated, the pull-down switch PLSW is turned on according to the enable signal En, which is an enable voltage level, so as to pull down the voltage of the control terminal of the driving switch DSW to the reference voltage Vr1, and turn off the driving switch DSW. Since the voltage value of the reference voltage Vr1 is greater than the voltage value of the ground voltage, when the driving switch is restarted after the circuit protection mechanism is released, the voltage value of the control terminal of the driving switch DSW is raised from the voltage value of the reference voltage Vr1, so as to reduce the time required for recovering the voltage of the control terminal of the driving switch DSW, thereby achieving the purpose of quickly restarting the driving switch DSW.

Referring to fig. 2, fig. 2 is a schematic diagram of a control circuit according to another embodiment of the invention. In the present embodiment, the control circuit 200 is used to control the on and off operations of the driving switch DSW. The control circuit 200 includes a voltage selection circuit 210, a buffer circuit 220, a charge pump device 230, a voltage shifter 240, a pull-down switch PLSW, and a ground switch SWG. The voltage selection circuit 210 includes a transistor T11 and a transistor T12. The transistor T11 has a first terminal receiving the input voltage VIN, a control terminal receiving the output voltage VOUT, and a second terminal coupled to the buffer circuit 220. The transistor T12 has a first terminal receiving the output voltage VOUT, a control terminal receiving the input voltage VIN, and a second terminal coupled to the second terminal of the transistor T11.

Regarding the circuit operation, the first terminal of the transistor T11 and the first terminal of the transistor T12 in the voltage selection circuit 210 respectively receive the input voltage VIN and the output voltage VOUT, and select the first terminal according to the voltage value of the input voltage VIN and the voltage value of the output voltage VOUT. For example, when the voltage value of the input voltage VIN is greater than the voltage value of the output voltage VOUT, the transistor T12 is turned on according to the input voltage VIN, and the output voltage VOUT is outputted to the buffer circuit 220 as the selected voltage Vm1, and at the same time, the transistor T11 is turned off. On the other hand, when the voltage value of the input voltage VIN is smaller than the voltage value of the output voltage VOUT, the transistor T11 is turned on according to the output voltage VOUT and outputs the input voltage VIN to the buffer circuit 220 as the selected voltage Vm1, and at the same time, the transistor T12 is turned off.

The buffer circuit 220 includes a first current mirror circuit MR1 and a second current mirror circuit MR 2. The first current mirror circuit MR1 receives the selected voltage Vm1 as an operating voltage, and has a first terminal receiving the reference current Iref and generates a first current I1 at a second terminal according to the mirrored reference current Iref. The second current mirror circuit MR2 is coupled to the first current mirror circuit MR1, receives and mirrors the first current I1 to draw a second current I2 from the second terminal of the pull-down switch PLSW, wherein the voltage value at the second terminal of the pull-down switch PLSW is pulled down to a voltage value equal to the reference voltage Vr1 according to the second current I2.

In detail, in the present embodiment, the first current mirror circuit MR1 includes transistors T21 to T22 and a current source IS. The transistor T21 has a first terminal coupled to the voltage selection circuit 210, and a control terminal and a second terminal coupled to each other. The transistor T22 has a first terminal coupled to the second terminal of the pull-down switch PLSW, a control terminal coupled to the control terminal of the transistor T21, and a second terminal outputting the first current I1. The current source IS coupled between the ground voltage GND and the second terminal of the transistor T21 for providing the reference current Iref.

On the other hand, the second current mirror circuit MR2 includes transistors T23 to T24. The first terminal and the control terminal of the transistor T23 are coupled to the second terminal of the transistor T22, and the second terminal thereof receives the ground voltage GND. The transistor T24 has a first terminal coupled to the second terminal of the pull-down switch PLSW, a control terminal coupled to the control terminal of the transistor T23, and a second terminal receiving the ground voltage GND.

When the selected mid-voltage Vm1 is provided to the first terminal of the transistor T21, the transistor T21 is turned on correspondingly, and the voltage at the control terminal and the second terminal of the transistor T21 is made equal to the selected voltage Vm1 minus the threshold voltage (Vth) of the transistor T21. The control terminal of the transistor T22 receives the same voltage (Vm 1-Vth) as that at the control terminal of the transistor T21 and generates the first current I1 accordingly. The first current I1 flows through the transistors T22 and T23 and makes the voltage at the first terminal of the transistor T22 substantially equal to the voltage value of the selected voltage Vm 1. Here, the voltage at the first terminal of the transistor T22 is provided to the second terminal of the pull-down switch PLSW as the reference voltage Vr 1.

It should be noted that, in this embodiment, the width-to-length ratio of the current channel of the transistor T24 in the second current mirror circuit MR2 is increased to be larger than the width-to-length ratio of the current channel of the transistor T23 in the second current mirror circuit MR2 (for example, N times, where N is a real number larger than 1), so as to boost the second current I2 drawn from the second end of the pull-down switch PLSW. Since the voltage value at the second terminal of the pull-down switch PLSW is pulled down to a voltage value equal to the reference voltage Vr1 according to the second current I2, the larger second current I2 can speed up the time for pulling down the voltage at the control terminal of the driving switch DSW to the reference voltage Vr 1.

On the other hand, in the embodiment, the transistors T21 and T22 and the transistors T23 and T24 have different conductive types, and fig. 2 shows that two P-type transistors T21 and T22 and two N-type transistors T23 and T24 are used to respectively construct the first current mirror circuit MR1 and the second current mirror circuit MR 2.

On the other hand, the charge pump device 230 is coupled to the control terminal of the driving switch DSW. The charge pump device 230 is used for turning on the driving switch DSW by raising the voltage value of the control terminal of the driving switch DSW under normal operation. The voltage shifter 240 is coupled to the control terminal of the pull-down switch PLSW and the control terminal of the driving switch DSW, receives the control signal CTL on the control terminal of the driving switch DSW as an operation voltage, and generates the pull-down switch signal Con to the control terminal of the pull-down switch PLSW by shifting the enable signal En to control the on or off state of the pull-down switch PLSW. The voltage shifter 240 may pull up a voltage level of the offset enable signal En to generate the pull-down switch signal Con when the offset enable signal En is an enable voltage level, and may switch off the pull-down switch PLSW according to the pull-down switch signal Con. The ground switch SWG has a first terminal coupled to the control terminal of the driving switch DSW, a control terminal receiving the shutdown signal SDS, and a second terminal receiving the ground voltage GND, wherein the ground switch SWG is turned on according to the shutdown signal SDS to pull down the voltage of the control terminal of the driving switch DSW to the ground voltage GND.

Referring to fig. 3, fig. 3 is a schematic diagram of another embodiment of a voltage selection circuit according to the embodiment of the invention. In the present embodiment, the voltage selection circuit 310 includes a comparator COM, a first switch SW1, a second switch SW2, and an inverter INV. The comparator COM has a positive input terminal receiving the output voltage VOUT, a negative input terminal receiving the input voltage VIN, and an output terminal, wherein the comparator COM is capable of comparing the voltage value of the output voltage VOUT with the voltage value of the input voltage VIN and generating a comparison result CR at the output terminal of the comparator COM. The control terminal of the first switch SW1 is coupled to the output terminal of the comparator COM, the first terminal thereof receives the input voltage VIN, and the second terminal thereof is coupled to the buffer circuit, wherein the first switch SW1 is turned on or off according to the comparison result CR. The control terminal of the second switch SW2 receives the inverted comparison result INCR, the first terminal thereof receives the output voltage VOUT, and the second terminal thereof is coupled to the second terminal of the first switch SW1, wherein the second switch SW2 is turned on or off according to the inverted comparison result INCR. The input end and the output end of the inverter INV are respectively coupled to the output end of the comparator COM and the control end of the second switch SW2, for receiving the comparison result CR and generating the inverse comparison result INCR.

Regarding the detailed circuit operation, when the voltage value of the input voltage VIN is greater than the voltage value of the output voltage VOUT, the comparator COM may generate the comparison result CR at a first logic level (e.g., a low logic level). The inverter INV receives the comparison result CR at the low logic level and generates an inverted comparison result INCR at a second logic level (e.g., a high logic level). In this way, the second switch SW2 can be turned on, and the first switch SW1 is turned off, so that the output voltage VOUT is transmitted to the buffer circuit as the selected voltage Vm 1. On the other hand, when the voltage value of the output voltage VOUT is greater than the voltage value of the input voltage VIN, the second switch SW2 is turned off, and the first switch SW1 is turned on, so that the input voltage VIN is used as the selected voltage Vm1 to be transmitted to the buffer circuit.

Referring to fig. 4, fig. 4 is a schematic diagram illustrating another embodiment of a buffer circuit according to the present invention. In the present embodiment, the buffer circuit 420 in the control circuit includes an operational amplifier OP. The operational amplifier OP has a positive input terminal coupled to the voltage selection circuit, a negative input terminal coupled to the voltage selection circuit, and an output terminal coupled to the negative input terminal and the output terminal, wherein the positive input terminal of the operational amplifier OP receives the selected voltage Vm1 and provides the selected voltage Vm1 to the output terminal of the operational amplifier OP as the reference voltage Vr 1.

It should be noted that the buffer circuit 420 of the present embodiment may be an operational amplifier OP coupled in a voltage follower type, and the voltage follower may be a single gain amplification circuit (unity gain amplification circuit) and is used to provide the reference voltage Vr1 equal to the selected voltage Vm1 to the second terminal of the pull-down switch.

Referring to fig. 5, fig. 5 is a schematic diagram of a voltage converting circuit according to an embodiment of the invention. The voltage conversion circuit 500 includes a driving switch DSW, a control circuit 510, and a driver 520, and the voltage conversion circuit 500 has a plurality of pins for receiving an input voltage VIN and an output voltage VOUT, respectively.

The driver 520 is used for generating a control signal CTL to control the on/off state of the driving switch DSW. The control circuit 510 is coupled to an output of the driver 520. The control circuit 510 receives the input voltage VIN and the output voltage VOUT, selects the smaller of the voltage value of the input voltage VIN and the voltage value of the output voltage VOUT as a selected voltage, and provides the selected voltage as a reference voltage, so as to pull down the voltage of the control terminal of the driving switch DSW to the reference voltage through the pull-down switch in the control circuit 510, and turn off the driving switch DSW.

Details of the implementation of the control circuit 510 have been set forth in many of the above embodiments, and are not repeated herein.

In summary, in the voltage converting circuit of the present invention, the voltage of the control terminal of the driving switch is pulled down to the reference voltage when the pull-down switch is turned on according to the enable signal by selecting the smaller of the voltage values of the input voltage and the output voltage at the two ends of the driving switch as the selected voltage and providing the selected voltage as the reference voltage, so that the driving switch is turned off. Therefore, after the circuit protection mechanism is released, the voltage value of the control end of the driving switch can be raised from the voltage value of the reference voltage, the time required by the voltage recovery of the control end of the driving switch is reduced, and the purpose of rapidly restarting the driving switch is achieved.

Although the present invention has been described with reference to the above embodiments, it should be understood that the invention is not limited to the embodiments, and various changes and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention.