Power protection circuit and power converting system

Abstract

A power protection circuit includes a control voltage generating circuit, a capacitor, and a first switch. The control voltage generating circuit is electrically connected between an input terminal and a reference terminal, and generates a control voltage based on an input voltage at the input terminal. The capacitor is electrically connected between an output terminal of the power protection circuit and the reference terminal. A first terminal of the first switch is electrically connected to the input terminal, a second terminal of the first switch is electrically connected to the output terminal, and a control terminal of the first switch is electrically connected to the control voltage generating circuit to receive the control voltage. When the input voltage exceeds a predetermined value, the first switch opens according to the control voltage, causing the output terminal to output an output voltage.

Description

Power protection circuit and power conversion system The present disclosure relates to a power protection circuit and a power conversion system with a power protection function, and in particular to a power conversion system with a power protection function. In the prior art, a bridge rectifier in a power converter can rectify an AC input voltage to generate a DC voltage and a ground voltage, wherein the AC input voltage can be a mains voltage of 110VAC, 220VAC or 230VAC, and the ground voltage can be used as a reference potential of 0V in the power converter. Typically, linear step-down circuits use high-voltage transistors as the primary high-voltage component to protect the back-end control circuitry and other low-voltage components. However, if the transistor is in the on state and subjected to high voltage, it will exceed the power rating and be damaged. Therefore, ensuring that linear power converters can operate normally at higher AC input voltages (250V-265V) has become a critical issue. One embodiment of the present disclosure provides a power protection circuit. The power protection circuit includes a control voltage generating circuit, a capacitor, and a first switch. The control voltage generating circuit is electrically connected between an input terminal and a reference terminal, and generates a control voltage based on an input voltage at the input terminal; the capacitor is electrically connected between an output terminal of the power protection circuit and the reference terminal; and the first switch has a first terminal, a second terminal, and a control terminal, wherein the first terminal of the first switch is electrically connected to the input terminal, the second terminal of the first switch is electrically connected to the output terminal of the power protection circuit, and the control terminal of the first switch is electrically connected to the control voltage generating circuit to receive the control voltage. When the input voltage is greater than a predetermined value, the control voltage generating circuit generates the control voltage, and the first switch is turned on based on the control voltage to enable the output terminal of the power protection circuit to output an output voltage. In one embodiment of the present disclosure, the control voltage generating circuit includes a first resistor, a second resistor, and a Zener diode. The first resistor is electrically connected between the input terminal and a voltage-dividing node; the second resistor is electrically connected between the control terminal of the first switch and the voltage-dividing node; and the Zener diode is electrically connected between the voltage-dividing node and the reference terminal. When the input voltage is greater than a predetermined value, the second resistor generates the control voltage at a terminal electrically connected to the control terminal of the first switch. The predetermined value is the breakdown voltage of the Zener diode. In one embodiment of the present disclosure, the control voltage generating circuit includes a second switch, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor. The second switch has a first terminal, a second terminal, and a control terminal, wherein the second terminal of the second switch is electrically connected to the reference terminal, and the control terminal of the second switch is electrically connected to a voltage dividing node; the third resistor is electrically connected between the input terminal and the voltage dividing node; the fourth resistor is electrically connected between the voltage dividing node and the reference terminal, wherein the third resistor and the fourth resistor generate a divided voltage based on the input voltage of the input terminal; the fifth resistor is electrically connected between the input terminal and the second terminal of the second switch; and the sixth resistor has a first terminal and a second terminal, wherein the first terminal of the sixth resistor is electrically connected to the second terminal of the second switch, the second terminal of the sixth resistor is electrically connected to the control terminal of the first switch, and when the second switch is turned on based on the divided voltage, the second terminal of the sixth resistor generates the control voltage. In one embodiment of the present disclosure, the second switch is an N-type high electron mobility transistor (HEMT) or an N-type field-effect transistor (MOSFET). In one embodiment of the present disclosure, the first switch is a PNP bipolar transistor. Another embodiment of the present disclosure provides a power conversion system. The power conversion system includes a power converter and a power protection circuit. The power converter includes at least a transistor and a first capacitor electrically connected to an output terminal of the power converter, wherein the transistor is controlled by the voltage across the first capacitor. The power protection circuit includes a control voltage generating circuit, a second capacitor, and a first switch. The above-mentioned control voltage generating circuit includes an input terminal electrically connected to the output terminal of the above-mentioned power converter, wherein the above-mentioned control voltage generating circuit is electrically connected between the output terminal of the above-mentioned power converter and a reference terminal via the above-mentioned input terminal, and generates a control voltage according to an output voltage of the output terminal of the above-mentioned power converter; the above-mentioned second capacitor is electrically connected between the output terminal of the above-mentioned power protection circuit and the above-mentioned reference terminal; and the above-mentioned first switch has a first terminal, a second terminal and a control terminal, wherein the first terminal of the above-mentioned first switch is electrically connected to the output terminal of the above-mentioned power converter, the second terminal of the above-mentioned first switch is electrically connected to the output terminal of the above-mentioned power protection circuit, and the control terminal of the above-mentioned first switch is electrically connected to the above-mentioned control voltage generating circuit to receive the above-mentioned control voltage, and when the output voltage of the output terminal of the above-mentioned power converter is higher than a predetermined value, the above-mentioned control voltage generating circuit generates the above-mentioned control voltage, and the above-mentioned first switch is turned on according to the above-mentioned control voltage so that the output terminal of the above-mentioned power protection circuit outputs an output voltage. In one embodiment of the present disclosure, the control voltage generating circuit includes a first resistor, a second resistor, and a Zener diode. The first resistor is electrically connected between the output terminal of the power converter and a voltage-dividing node; the second resistor is electrically connected between the control terminal of the first switch and the voltage-dividing node; and the Zener diode is electrically connected between the voltage-dividing node and the reference terminal. When the output voltage of the output terminal of the power converter is greater than a predetermined value, the second resistor is electrically connected to the control terminal of the first switch to generate the control voltage. The predetermined value is the breakdown voltage of the Zener diode. In one embodiment of the present disclosure, the control voltage generating circuit includes a second switch, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor. The second switch has a first terminal, a second terminal, and a control terminal, wherein the second terminal of the second switch is electrically connected to the reference terminal, and the control terminal of the second switch is electrically connected to a voltage dividing node. The third resistor is electrically connected between the output terminal of the power converter and the voltage dividing node. The fourth resistor is electrically connected between the voltage dividing node and the reference terminal, wherein the third and fourth resistors generate a divided voltage based on the output voltage of the output terminal of the power converter. The fifth resistor is electrically connected between the output terminal of the power converter and the second terminal of the second switch. The sixth resistor has a first terminal and a second terminal, wherein the first terminal of the sixth resistor is electrically connected to the second terminal of the second switch, the second terminal of the sixth resistor is electrically connected to the control terminal of the first switch, and when the second switch is turned on based on the divided voltage, the second terminal of the sixth resistor generates the control voltage. In one embodiment of the present disclosure, the second switch and the transistor are N-type high electron mobility transistors or N-type field effect transistors (the second switch and the transistor are even in number). In one embodiment of the present disclosure, the first switch is a PNP bipolar transistor. Please refer to FIG. 1 , which is a schematic diagram of a power conversion system 1 disclosed in a first embodiment of the present disclosure. As shown in FIG. 1 , the power conversion system 1 includes a power converter 100 and a power protection circuit 10 . The power converter 100 includes an output terminal OUTPUT1 , and the power protection circuit 10 includes an input terminal INPUT1 electrically connected to the output terminal OUTPUT1 of the power converter 100 . In one embodiment, the power converter 100 includes a bridge rectifier 101 , a voltage divider circuit 201 , resistors R1 and R2 , transistors Q1 and Q2 , a Zener diode D1 , and a capacitor C1 . In one embodiment, the bridge rectifier 101 may include four rectifier diodes D2 - D5 . Rectifier diodes D2 - D5 may be Schottky barrier diodes (SBDs). The voltage divider circuit 201 may include resistors R3 and R4 . Bridge rectifier 101 rectifies an AC input voltage VAC-IN to generate a DC voltage VDC-IN and a ground voltage GND. For example, the AC input voltage VAC-IN can be 110VAC, 220VAC, or 230VAC mains power, and ground voltage GND can serve as a reference potential of 0V in voltage conversion circuit 100. In one embodiment, transistor Q2 can be an N-type high electron mobility transistor (HEMT) or an N-type metal-oxide-semiconductor field-effect transistor (MOSFET), where the reference symbols D, G, and S represent the drain, gate, and source of transistor Q2, respectively. In one embodiment, transistor Q1 can be an NPN bipolar transistor, where the reference symbol B represents the base of transistor Q1. As shown in FIG1 , the cathode of Zener diode D1 is electrically connected to an output terminal OUTPUT1, and the anode of Zener diode D1 is electrically connected to base B of transistor Q1. One end of resistor R3 is electrically connected to DC voltage VDC-IN, and one end of resistor R4 is electrically connected to ground voltage GND. A contact 202 is electrically connected to the other end of resistor R3 and the other end of resistor R4, and is located between resistors R3 and R4. Contact 202 is further electrically connected to base B of transistor Q1. As shown in FIG1 , the voltage at contact 202 is determined by the resistance values ​​of resistors R3 and R4. For example, when resistor R3 is 10k ohms and resistor R4 is 7k ohms, the voltage at contact 202 is 7 / 17 × (DC voltage VDC-IN). Therefore, the voltage at base B electrically connected to contact 202 is also applied with a voltage of 7 / 17 × (DC voltage VDC-IN). As the DC voltage VDC-IN gradually increases from a low level, the voltage at base B also rises with it. When DC voltage VDC-IN reaches a predetermined voltage, the voltage at base B also rises, turning on transistor Q1. This causes gate G of transistor Q2 to receive ground voltage GND through the conducting transistor Q1, causing transistor Q2 to turn off (turn off). After transistor Q2 turns off, DC voltage VDC-IN can no longer charge capacitor C1. Thus, as long as the DC voltage VDC-IN exceeds the predetermined voltage, the DC voltage VDC-IN will be turned off by transistor Q2, and capacitor C1 will no longer be charged. This prevents transistor Q2 from burning out due to excessive drain-to-source voltage and high current. In other words, the power converter 100 can be designed to provide power near the voltage valleys of the DC voltage VDC-IN and stop providing power at the voltage peaks of the DC voltage VDC-IN. This function is referred to herein as valley powering. Furthermore, the predetermined voltage corresponds to the resistance ratio of resistors R3 and R4. As shown in FIG1 , the power protection circuit 10 includes an input terminal INPUT1, a control voltage generating circuit A, a capacitor C2, and a first switch S1. The control voltage generating circuit A is electrically connected between the output terminal OUTPUT1 of the power converter 100 and a ground voltage GND (i.e., a reference terminal) via the input terminal INPUT1. In one embodiment, the control voltage generating circuit A may include a first resistor R11, a second resistor R22, and a Zener diode D2. In one embodiment, the first switch S1 has a first terminal S1T1, a second terminal S1T2, and a control terminal S1TC. The first terminal S1T1 of the first switch S1 is electrically connected to the output terminal OUTPUT1 of the power converter 100, the second terminal S1T2 of the first switch S1 is electrically connected to the output terminal OUTPUT of the power protection circuit 10, and the control terminal S1TC of the first switch S1 is electrically connected to the second resistor R22 to receive a control voltage VC. In one embodiment, the first switch S1 may be a PNP bipolar transistor. As shown in FIG1 , the first resistor R11 is electrically connected between the output terminal OUTPUT1 of the power converter 100 and a voltage dividing node DN via the input terminal INPUT1. The second resistor R22 is electrically connected between the control terminal of the first switch S1, such as the base of the first switch S1, and the voltage dividing node DN. The Zener diode D2 is electrically connected between the voltage dividing node DN and the ground voltage GND. As shown in FIG1 , the capacitor C2 is electrically connected between the output terminal OUTPUT of the power protection circuit 10 and the ground voltage GND. As shown in FIG. 1 , the control terminal S1TC of the first switch S1 does not receive the control voltage VC until the output voltage VOUT at the output terminal OUTPUT1 of the power converter 100 (equivalent to the input voltage VIN at the input terminal INPUT1) exceeds a predetermined value. In one embodiment of the present disclosure, the predetermined value is the breakdown voltage of the Zener diode D2, for example, 40V. When the output voltage VOUT at the output terminal OUTPUT1 of the power converter 100 is less than the breakdown voltage of the Zener diode D2, the control voltage VC is not transmitted to the control terminal S1TC of the first switch S1. When the input voltage VIN exceeds the predetermined value, the Zener diode D2 breaks down, causing the breakdown voltage of the Zener diode D2 to appear at the voltage divider node DN. This causes the second resistor R22 to be electrically connected to the control terminal S1TC of the first switch S1, generating the control voltage VC. When the first switch S1 is turned on in response to the control voltage VC, current flowing through the first switch S1 charges the capacitor C2, thereby generating the output voltage VOUT at the output terminal OUTPUT of the power protection circuit 10. That is, before the output voltage VOUT at the output terminal OUTPUT1 of the power converter 100 exceeds the breakdown voltage of the Zener diode D2, the first switch S1 is closed, and the power protection circuit 10 does not output the output voltage VOUT. Because the power protection circuit 10 does not output the output voltage VOUT until the output voltage VOUT at the output terminal OUTPUT1 of the power converter 100 exceeds the breakdown voltage of the Zener diode D2, the power protection circuit 10 ensures that the transistor Q2 is completely turned off before outputting the output voltage VOUT, thereby preventing the transistor Q2 from burning out. Please refer to FIG. 2 , which is a schematic diagram of a power protection circuit 20 according to a second embodiment of the present invention. The difference between power protection circuit 20 and power protection circuit 10 lies in the circuit architecture of a control voltage generating circuit A1 included in power protection circuit 20, which differs from the circuit architecture of control voltage generating circuit A included in power protection circuit 10. As shown in FIG. 2 , control voltage generating circuit A1 includes an input terminal INPUT1, a second switch S2, a third resistor R33, a fourth resistor R44, a fifth resistor R5, and a sixth resistor R6. The second switch S2 has a first terminal S2T1, a second terminal S2T2, and a control terminal S2TC. As shown in FIG. 2 , the second terminal S2T2 of the second switch S2 is electrically connected to the ground voltage GND, and the control terminal S2TC of the second switch S2 is electrically connected to a voltage-dividing node DN; the third resistor R33 is electrically connected between the input terminal INPUT1 and the voltage-dividing node DN; the fourth resistor R44 is electrically connected between the voltage-dividing node DN and the ground voltage GND, wherein the third resistor R33 and the fourth resistor R44 generate a divided voltage VD according to the input voltage VIN at the input terminal INPUT1; the fifth resistor R5 is electrically connected between the input terminal INPUT1 and the first terminal S2T1 of the second switch S2; and the sixth resistor R6 has a first terminal and a second terminal, wherein the first terminal of the sixth resistor R6 is electrically connected to the first terminal S2T1 of the second switch S2, and the second terminal of the sixth resistor R6 is electrically connected to the control terminal S1TC of the first switch S1. In one embodiment of the present invention, the second switch S2 is an N-type metal-oxide-semiconductor field-effect transistor (MOSFET). However, in another embodiment of the present invention, the second switch S2 is an N-type gallium nitride high electron mobility transistor (GaN High Electron Mobility Transistor, GaN HEMT). As shown in FIG. 2 , the divided voltage VD increases as the output voltage VOUT at the output terminal OUTPUT1 of the power converter 100 (equivalent to the input voltage VIN at the input terminal INPUT1) increases. Therefore, before the input voltage VIN exceeds a predetermined value (e.g., 40V) (i.e., before the divided voltage VD turns on the second switch S2), the control terminal S1TC of the first switch S1 does not receive the control voltage VC. When the input voltage VIN exceeds the predetermined value, the divided voltage VD turns on the second switch S2, thereby generating the control voltage VC at the second end of the sixth resistor R6. When the first switch S1 turns on in response to the control voltage VC, the current flowing through the first switch S1 charges the capacitor C2, generating the output voltage VOUT at the output terminal OUTPUT of the power protection circuit 10. In other words, before the input voltage VIN exceeds the predetermined value, the first switch S1 is closed, and the power protection circuit 10 does not output the output voltage VOUT. Because the power protection circuit 20 outputs the output voltage VOUT only after the input voltage VIN is greater than the predetermined value, the power protection circuit 20 can ensure that the transistor Q2 is completely turned off before outputting the output voltage VOUT to prevent the transistor Q2 from being burned. Please refer to FIG. 3 , which is a schematic diagram of a power conversion system 400 according to a third embodiment of the present disclosure. The power conversion system 400 includes a power converter 100, a power protection circuit 10, and a DC / DC conversion circuit 402. The power protection circuit 10 is electrically connected to the output terminal OUTPUT1 of the power converter 100, and the DC / DC conversion circuit 402 is electrically connected to the output terminal OUTPUT of the power protection circuit 10. Reference may be made to the power converter 100 and the power protection circuit 10 in FIG. In another embodiment, the power protection circuit 10 may be replaced by the power protection circuit 20. As shown in FIG3 , a power conversion system 400 can perform a two-stage buck-stepping operation on an AC input voltage VAC-IN, wherein the power converter 100 is an AC / DC converter and is configured to perform a first-stage buck-stepping operation on the AC input voltage VAC-IN to generate an output voltage VOUT (e.g., 40V), and a DC / DC conversion circuit 402 is configured to perform a second-stage buck-stepping operation on the output voltage VOUT to generate a low output voltage VOUTL (e.g., 3.3V) and a high output current IOUTH (e.g., 200mA). Therefore, as shown in Figure 3, the input of the power conversion system 400 is an AC input voltage VAC-IN (e.g., 90V~260V), and the output of the power conversion system 400 is a low output voltage VOUTL (e.g., 3.3V) and a high output current IOUTH (e.g., 200mA), wherein the load coupled to the output terminal OUTPUTL of the power conversion system 400 can be, for example, a wireless hotspot (Wi-Fi) module, and the power conversion system 400 provides the low output voltage VOUTL (e.g., 3.3V) and the high output current IOUTH (e.g., 200mA) to the above-mentioned wireless hotspot (Wi-Fi) module. In summary, the power protection circuit disclosed in this disclosure is designed to output the output voltage only after the input voltage at the input terminal to which it is electrically connected exceeds the predetermined value. Furthermore, the linear AC / DC step-down and output current boosting circuit disclosed in this disclosure can be used to provide the low output voltage and the high output current to a load coupled to the circuit. Therefore, compared to the prior art, the power protection circuit can ensure that the transistor electrically connected to the input terminal is completely turned off before outputting the output voltage to prevent the transistor from burning out, while still providing the high output current to the load. The above description is merely a preferred embodiment of this disclosure, and all equivalent changes and modifications made within the scope of the patent claims of this disclosure are intended to be covered by this disclosure. 1.400: Power conversion system 10.20: Power protection circuit 100: Power converter 101: Bridge rectifier 201: Voltage divider circuit 202: Contact 402: DC / DC conversion circuit A, A1: Control voltage generation circuit B: Base C1, C2: Capacitors D1, D2: Zener diodes D2-D5: Rectifier diodes D: Drain DN: Voltage divider node G: Gate GND: Ground voltage IOUTH: High output current INPUT1: Input terminal OUTPUT1, OUTPUT, OUTPUTL: Output terminal Q1 , Q2: transistor R1, R2, R3, R4: resistor R11: first resistor R22: second resistor R33: third resistor R44: fourth resistor R5: fifth resistor R6: sixth resistor S: source S1: first switch S1T1, S2T1: first terminal S1T2, S2T2: second terminal S1TC, S2TC: control terminal S2: second switch VDC-IN: DC voltage VAC-IN: AC input voltage VC: control voltage VOUT: output voltage VOUTL: low output voltage VIN: input voltage VD: divided voltage FIG1 is a schematic diagram of a power protection circuit disclosed in the first embodiment of the present disclosure. FIG2 is a schematic diagram of a power protection circuit disclosed in the second embodiment of the present disclosure. FIG3 is a schematic diagram of a linear AC / DC voltage step-down and output current boosting circuit disclosed in the third embodiment of the present disclosure. 1: Power conversion system 10: Power protection circuit 100: Power Converter 101: Bridge Rectifier 201: Voltage divider circuit 202:Contact A: Control voltage generating circuit B: Base C1, C2: capacitors D1, D2: Zener diodes D2-D5: rectifier diodes D: Drain DN: voltage divider node G: Gate GND: Ground voltage INPUT1: input terminal OUTPUT1, OUTPUT: output terminal Q1, Q2: transistors R1, R2, R3, R4: resistors R11: first resistor R22: Second resistor S: Source S1: First switch S1T1: First End S1T2: Second end S1TC: Control terminal VDC-IN: DC voltage VAC-IN: AC input voltage VC: control voltage VOUT: output voltage VIN: input voltage

Claims

1. A power protection circuit, comprising: a control voltage generating circuit electrically connected between an input terminal and a reference terminal, and generating a control voltage based on an input voltage at the input terminal, wherein the control voltage generating circuit comprises: a first resistor electrically connected between the input terminal and a voltage divider node; a second resistor electrically connected between a control terminal of a first switch and the voltage divider node; and a Zener diode electrically connected between the voltage divider node and the reference terminal, wherein when the input voltage is greater than a predetermined value, the second resistor electrically connected to one end of the control terminal of the first switch generates the control voltage, and the predetermined value is the breakdown voltage of the Zener diode; A capacitor is electrically connected between an output terminal of the power protection circuit and a reference terminal; and a first switch has a first terminal, a second terminal, and a control terminal, wherein the first terminal of the first switch is electrically connected to the input terminal, the second terminal of the first switch is electrically connected to the output terminal of the power protection circuit, the control terminal of the first switch is electrically connected to a control voltage generating circuit to receive the control voltage, and when the input voltage is greater than the predetermined value, the control voltage generating circuit generates the control voltage, and the first switch is turned on according to the control voltage so that the output terminal of the power protection circuit outputs an output voltage.

2. The power protection circuit as claimed in claim 1, wherein the first switch is a PNP bipolar transistor.

3. A power conversion system, comprising: a power converter, including at least a transistor and a first capacitor electrically connected to an output terminal of the power converter, wherein the transistor is controlled by a voltage across the first capacitor; and a power protection circuit, comprising: a control voltage generating circuit, including an input terminal electrically connected to the output terminal of the power converter, wherein the control voltage generating circuit is electrically connected between the output terminal of the power converter and a reference terminal via the input terminal, and generates a control voltage based on an output voltage of the output terminal of the power converter, wherein the control voltage generating circuit includes: a first switch having a first terminal, a second terminal and a control terminal, wherein the second terminal of the first switch is electrically connected to the reference terminal, and the control terminal of the first switch is electrically connected to a voltage divider node; a third resistor electrically connected between the output terminal of the power converter and the voltage divider node; and a fourth resistor electrically connected between the voltage divider node and the reference terminal, wherein the third resistor and the fourth resistor generate a voltage divider based on the output voltage of the output terminal of the power converter; A fifth resistor having a first terminal and a second terminal, wherein the first terminal of the fifth resistor is electrically connected to the output terminal of the power converter and the second terminal of the fifth resistor is electrically connected to the first terminal of the first switch; and a sixth resistor having a first terminal and a second terminal, wherein the first terminal of the sixth resistor is electrically connected to the first terminal of the first switch and the second terminal of the sixth resistor is electrically connected to the control terminal of the second switch, and when the first switch is turned on according to the voltage divider, the second terminal of the sixth resistor generates the control voltage; A second capacitor is electrically connected between an output terminal of the power protection circuit and a reference terminal; and a second switch has a first terminal, a second terminal, and a control terminal, wherein the first terminal of the second switch is electrically connected to the output terminal of the power converter, the second terminal of the second switch is electrically connected to the output terminal of the power protection circuit, and the control terminal of the second switch is electrically connected to a control voltage generating circuit to receive the control voltage, and when the output voltage of the output terminal of the power converter is higher than a predetermined value, the control voltage generating circuit generates the control voltage, and the second switch is turned on according to the control voltage to cause the output terminal of the power protection circuit to output an output voltage.

4. The power conversion system as claimed in claim 3, wherein the first switch and the transistor are an N-type high electron mobility transistor or an N-type field-effect transistor.

5. The power conversion system as claimed in claim 3, wherein the second switch is a PNP bipolar transistor.

Images