AC-DC converter

Abstract

The invention provides an AC-to-DC converter, comprising: a voltage dividing network configured to divide an AC input characterization voltage when the AC input characterization voltage is a non-zero voltage to generate an AC input characterization divided voltage and provide the AC input characterization divided voltage to a control chip through a predetermined pin of the control chip, and when the AC input characterization voltage is zero voltage, a chip temperature characterization voltage is generated based on a predetermined current flowing out of a predetermined pin of the control chip, and the chip temperature characterization voltage is provided for the control chip through the predetermined pin of the control chip, the alternating-current input characterization voltage and the alternating-current input voltage of the alternating-current-to-direct-current converter are completely and synchronously changed; and the control chip is configured to realize detection of the alternating current input voltage based on the alternating current input characterization partial voltage when the alternating current input characterization voltage is non-zero voltage, and realize off-chip over-temperature protection of the control chip based on the chip temperature characterization voltage when the alternating current input characterization voltage is zero voltage.

Description

Technical Field

[0001] The present invention generally relates to the field of circuits, and in particular to an AC-to-DC converter. Background Art

[0002] Currently, real-time monitoring and fault detection of AC input voltage by the control chips in AC-DC converters is a core technology for ensuring the safety and reliability of these devices. Fluctuations in the AC input voltage or sudden power outages can pose various safety risks, leading to an increasing number of integrated line voltage detection and protection features in the control chips of AC-DC converters. Summary of the Invention

[0003] According to an embodiment of the present invention, an AC-to-DC converter includes a voltage divider network and a control chip, wherein: the voltage divider network is configured to divide the AC input characterization voltage to generate an AC input characterization divided voltage when the AC input characterization voltage is a non-zero voltage, and provide the AC input characterization divided voltage to the control chip via a predetermined pin of the control chip; and when the AC input characterization voltage is zero voltage, generate a chip temperature characterization voltage based on a predetermined current flowing out of the predetermined pin of the control chip, and provide the chip temperature characterization voltage to the control chip via the predetermined pin of the control chip, wherein the AC input characterization voltage changes completely synchronously with the AC input voltage of the AC-to-DC converter; the control chip is configured to detect the AC input voltage based on the AC input characterization divided voltage when the AC input characterization voltage is a non-zero voltage, and to implement external over-temperature protection for the control chip based on the chip temperature characterization voltage when the AC input characterization voltage is zero voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The present invention can be better understood from the following description of specific embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0005] Figure 1 is a schematic diagram showing an example circuit structure of a conventional flyback AC-DC converter.

[0006] Figure 2 FIG. 1 is a schematic diagram showing another example circuit structure of a conventional flyback AC-DC converter.

[0007] Figure 3 It shows Figure 2 The filtered AC input voltage V AC ' and BO terminal voltage waveforms.

[0008] Figure 4 is a schematic diagram showing an example circuit structure of an AC-DC converter according to an embodiment of the present invention.

[0009] Figure 5It shows Figure 4 The diagram shows an example circuit structure of an AC state detection voltage divider network and circuit parts related to AC voltage detection and chip over-temperature protection in a control chip.

[0010] Figure 6 It shows Figure 5 The following are example waveform diagrams of the AC state detection voltage divider network and multiple related signals of the control chip.

[0011] Figure 7 It shows Figure 5 FIG. 1 is a schematic diagram of an example circuit structure of an AC voltage detection unit shown in FIG.

[0012] Figure 8 It shows Figure 5 A schematic diagram of an example circuit structure of a chip over-temperature protection unit is shown.

[0013] Figure 9 It shows Figure 8 The following are example waveform diagrams of multiple signals in the chip over-temperature protection unit.

[0014] Figure 10 It shows Figure 4 The diagram shows another example circuit structure of the AC state detection voltage divider network and the circuit parts related to AC voltage detection and chip over-temperature protection in the control chip. DETAILED DESCRIPTION

[0015] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In the detailed description below, many specific details are proposed in order to provide a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is by no means limited to any specific configuration and algorithm proposed below, but covers any modification, replacement and improvement of elements, components and algorithms without departing from the spirit of the present invention. In the accompanying drawings and the following description, well-known structures and technologies are not shown in order to avoid unnecessary ambiguity in the present invention. In addition, it should be noted that the term "A is connected to B" used herein can mean "A is directly connected to B" or "A is indirectly connected to B via one or more other elements."

[0016] Figure 1 : is a schematic diagram showing an example circuit structure of a conventional flyback AC-DC converter. Figure 1 In the flyback AC-DC converter 100 shown in FIG. 1 , the AC input voltage V AC After the electromagnetic interference filter and rectifier processing, the AC line voltage Vline The control chip 102 detects the voltage V on the auxiliary winding of the transformer T. aux To achieve the AC line voltage V line The detection of AC input voltage V AC Detection; when the power switch tube inside the control chip 102 is in the off state, the secondary winding of the transformer T discharges, and the voltage V on the auxiliary winding of the transformer T at this time aux is the DC output voltage V DC When the power switch tube inside the control chip 102 is in the on state, the primary winding of the transformer T is charged, and the voltage V on the auxiliary winding of the transformer T is aux is the AC line voltage V line Proportional negative pressure:

[0017]

[0018] Among them, N P Indicates the number of turns of the primary winding of transformer T, N aux Indicates the number of turns of the auxiliary winding of the transformer T. When the AC line voltage is detected during the charging process of the primary winding of the transformer T, the voltage V at the demagnetization detection pin (ie, DEM pin) of the control chip 102 is DEM is fixed to a predetermined voltage (e.g., V DEM =0.1V), at this time, due to the voltage V on the auxiliary winding of the transformer T aux When the voltage is negative, the DEM pin of the control chip 102 flows out a current. According to the magnitude of the current, the AC line voltage V line Detection of the size.

[0019] Combine Figure 1 The line voltage detection scheme described can detect the AC line voltage V when the AC power is normally connected. line However, it cannot detect the AC line voltage V after the AC power is unplugged. line This is because the presence of capacitor Cbuck makes the AC line voltage V line The voltage V on the auxiliary winding of the transformer T does not change immediately after the AC power is unplugged. aux It will not immediately return to 0 potential, so that the control chip 102 cannot immediately detect the AC input voltage V AC changes.

[0020] Figure 2 1 is a schematic diagram showing another example circuit structure of a conventional flyback AC-DC converter. Figure 2 In the flyback AC-DC converter 200 shown in FIG. 1 , the AC input voltage VAC After the electromagnetic interference filter is processed, the filtered AC input voltage V AC '; The voltage divider network composed of resistors R1 and R2 is used to filter the AC input voltage V AC 'Produce AC input voltage divider; the control chip 202 detects the AC input voltage divider via the over-voltage protection pin (ie, BO pin) and then realizes the AC input voltage V AC Detection.

[0021] Figure 3 It shows Figure 2 The filtered AC input voltage V AC ' and BO terminal voltage waveform. Combined Figure 2 and Figure 3 It can be seen that when the AC power supply is normally connected, the BO terminal voltage (i.e., the AC input voltage at the BO pin of the control chip 202) will exceed the power-off detection threshold Vref_off inside the control chip 202. At this time, the filtered AC input voltage V AC 'The size of the detection is then realized to detect the AC input voltage V AC When the AC power is unplugged, the voltage at the BO terminal drops below the unplug detection threshold Vref_off. At this time, the filtered AC input voltage V can be quickly detected based on the change in the BO terminal voltage. AC ' changes and detects the AC input voltage V AC changes.

[0022] Combine Figure 2 and Figure 3 The AC input voltage detection scheme described can not only detect the AC input voltage V when the AC power is normally connected, but also AC The size of the detection can be realized after the AC power is unplugged. AC Because the control chip 202 integrates a power switch, the temperature rise of the control chip 202 is relatively high. To improve reliability, the control chip 202 is generally required to have an off-chip over-temperature protection (OTP) function. However, the traditional solution of using the current sensing pin (i.e., the CS pin) to implement the off-chip OTP function is not suitable for control chips with integrated power switches.

[0023] Given the combination Figures 1 to 3 In order to address one or more problems existing in the flyback AC-DC converter described above, an AC-DC converter according to an embodiment of the present invention is proposed, wherein the line voltage and temperature detection pin (i.e., LTD pin) of the control chip can be used to detect the AC input voltage while realizing off-chip over-temperature protection of the control chip.

[0024] Figure 4 1 is a schematic diagram showing an example circuit structure of an AC-DC converter according to an embodiment of the present invention. Figure 4 As shown, the AC-DC converter 400 includes an AC state detection voltage divider network 402 and a control chip 404, wherein: the AC state detection voltage divider network 402 is configured to detect the AC input voltage V AC ' is a non-zero voltage for AC input characterization voltage V AC 'Dividing the voltage to generate the AC input characterizing divided voltage and providing the AC input characterizing divided voltage to the control chip 404 via the LTD pin of the control chip 404, and AC When the voltage is zero, the chip temperature characterization voltage is generated based on the predetermined current flowing out of the LTD pin of the control chip 404 and the chip temperature characterization voltage is provided to the control chip 404 via the LTD pin of the control chip 404, wherein the AC input characterization voltage V AC ' is the AC input voltage V AC Fully synchronous voltage changes (for example, EMI filter to AC input voltage V AC The filtered AC input voltage V AC '); The control chip 404 is configured to characterize the AC input voltage V AC 'When the voltage is non-zero, the AC input voltage V is realized based on the AC input characterization voltage division AC The detection and characterization voltage V AC When the voltage is zero, the off-chip over-temperature protection of the control chip 402 is realized based on the chip temperature characterization voltage.

[0025] Figure 5 It shows Figure 4 The schematic diagram of the example circuit structure of the AC state detection voltage divider network and the circuit parts related to AC voltage detection and chip over-temperature protection in the control chip is shown. Figure 5 As shown, in some embodiments, the AC state detection voltage divider network 402 includes a first resistor R1, a second resistor R2, and a negative temperature coefficient resistor R3, wherein: the first resistor R1 and the second resistor R2 are connected in series at the AC input representative voltage V AC ' and the circuit reference ground, the first resistor R1 and the negative temperature coefficient resistor R3 are connected in series at the AC input characterizing the voltage V AC ' and the LTD pin of the control chip 404, the second resistor R2 and the negative temperature coefficient resistor R3 are connected in series between the LTD pin of the control chip 404 and the circuit reference ground.

[0026] like Figure 5As shown, in some embodiments, the control chip 404 includes an AC voltage detection unit 4042 and a chip over-temperature protection unit 4044, wherein: the AC voltage detection unit 4042 is connected to the LTD pin of the control chip 404 via a first switch S1, and is configured to implement one or more of power-on detection, power-off detection, under-voltage protection, and over-voltage protection for the AC input voltage based on the AC input characteristic voltage division when the first switch S1 is in a closed state; the chip over-temperature protection unit 4044 is connected to the LTD pin of the control chip 404 via a second switch S2, and is configured to provide a predetermined current I to the LTD pin of the control chip 404 when the second switch S2 is in a closed state. OTP Based on the chip temperature characterization voltage, the off-chip over-temperature protection of the control chip 402 is realized, wherein the first switch S1 is at the AC input characterization voltage V AC ' is in the closed state when it is non-zero voltage and represents the voltage V at the AC input AC ' is in the off state when the voltage is zero, the second switch S2 is in the AC input characterizing the voltage V AC ' is in the disconnected state when it is non-zero voltage and the AC input characterizes the voltage V AC 'When the voltage is zero, it is in the closed state, and the predetermined current I OPT It is a constant current with a good temperature coefficient.

[0027] Figure 6 It shows Figure 5 The example waveforms of the AC state detection voltage divider network and multiple related signals of the control chip are shown, where V AC ' represents the AC input voltage, V LTD represents the voltage at the LTD pin of the control chip 404, S1 represents the signal for controlling the closing and opening of the first switch S1, and S2 represents the signal for controlling the closing and opening of the second switch S2. Figure 6 As shown, when the first switch S1 is in the closed state and the second switch S2 is in the open state, the control chip 404 is in the AC voltage detection state (corresponding to the AC input characteristic voltage V AC ' is a half cycle of non-zero voltage), the voltage V at the LTD pin of the control chip 404 LTD Characterize the voltage divider for AC input, that is:

[0028]

[0029] In addition, if Figure 6 As shown, when the first switch S1 is in the open state and the second switch S2 is in the closed state, the control chip 404 is in the chip over-temperature protection state (corresponding to the AC input characteristic voltage V AC ' is a half cycle of zero voltage), the current source provides a constant current I to the LTD pin of the control chip 404OPT , the voltage V at the LTD pin of the control chip 404 LTD The chip temperature characterization voltage is:

[0030] V LTD =I OTP *((R1||R2)+R3) (3)

[0031] When the control chip 404 is in the AC voltage detection state, for the sake of chip voltage resistance, a lower voltage needs to be generated at the LTD pin of the control chip 404. Therefore, a first resistor R1 with a large resistance is used in combination with a second resistor R2 with a small resistance to detect the AC input voltage V AC 'Perform voltage division, then the above equation (3) can be approximated as:

[0032] V LTD =I OTP *(R2+R3 ) (4)

[0033] The resistance of the negative temperature coefficient resistor R3 decreases as the temperature increases. Therefore, when the control chip 404 is in the chip over-temperature protection state, the voltage V at the LTD pin of the control chip 404 is LTD It will gradually decrease as the temperature of the control chip 404 increases.

[0034] Figure 7 It shows Figure 5 Schematic diagram of an example circuit structure of an AC voltage detection unit shown in FIG. Figure 7 As shown, in some embodiments, the AC voltage detection unit 4042 can be configured to divide the AC input voltage V at the LTD pin of the control chip 404 by LTD The AC input voltage V is compared with one or more different internal reference voltages to achieve AC One or more of power-on detection, power-off detection, undervoltage protection, and overvoltage protection.

[0035] like Figure 7 As shown, in some embodiments, the AC voltage detection unit 4042 includes comparators comp1, comparator comp2, comparator comp3, comparator comp4, and an AC state detection timer, wherein: the comparator comp1 is configured to divide the AC input voltage V at the LTD pin of the control chip 404 by LTD With the AC input voltage V AC The AC voltage power-on detection signal (not shown) is generated by comparing the AC voltage power-on detection reference voltage AC_on_ref of the power-on detection; the comparator comp2 is configured to represent the AC input voltage V at the LTD pin of the control chip 404 LTD With the AC input voltage VAC The AC voltage unplug detection signal (not shown) is generated by comparing the reference voltage AC_off_ref of the unplug detection; the comparator comp3 is configured to divide the AC input voltage V at the LTD pin of the control chip 404 by LTD With the AC input voltage V AC The comparator comp3 is configured to generate an AC voltage undervoltage detection signal (not shown) by comparing the AC input voltage at the LTD pin of the control chip 404 with the reference voltage Brown_ref. LTD With the AC input voltage V AC The AC voltage overvoltage detection signal is generated by comparing the AC voltage with the reference voltage OVP_ref of the overvoltage protection (not shown in the figure); the AC status detection timer is configured to generate the AC voltage power-on indication signal AC_on, the AC voltage unplugging indication signal AC_off, the AC voltage undervoltage protection signal Brown_out, and the AC voltage overvoltage protection signal Line_OVP by performing timer debounce on the AC voltage power-on detection signal, the AC voltage unplugging detection signal, the AC voltage undervoltage detection signal, and the AC voltage overvoltage detection signal, respectively.

[0036] like Figure 7 As shown, in some embodiments, if the AC voltage power-on indication signal AC_on is high, it indicates that the AC input voltage V AC Powered on, otherwise it indicates the AC input voltage V AC Not powered on; if the AC voltage unplug indication signal AC_off is high, it means that the AC input voltage V AC The power is unplugged, otherwise it indicates that the AC input voltage V AC If the AC voltage undervoltage protection signal Brown_out is high, it means that the AC input voltage V AC In undervoltage state, otherwise it indicates that the AC input voltage V AC Not in undervoltage state; if the AC voltage overvoltage protection signal Line_OVP is high, it means that the AC input voltage V AC In overvoltage state, otherwise it indicates that the AC input voltage V AC Not in overvoltage condition.

[0037] Figure 8 It shows Figure 5 Schematic diagram of an example circuit structure of a chip over-temperature protection unit shown in FIG. Figure 8 As shown, in some embodiments, the chip over-temperature protection unit 4044 can be configured to control the chip 404 by representing the chip temperature at the LTD pin to a voltage V LTDThe over-temperature protection indication signal EX_OTP is generated by comparing the over-temperature protection threshold Vref_OTP with the internal over-temperature protection threshold Vref_OTP to indicate whether the control chip 404 needs to be protected from over-temperature.

[0038] like Figure 8 As shown, in some embodiments, the chip over-temperature protection unit 4044 includes an OTP comparator and an OTP timer, wherein: the OTP comparator is configured to control the chip temperature representative voltage V at the LTD pin of the chip 404 when the signal used to control the closing and opening of the second switch S2 is enabled. LTD The chip over-temperature detection signal is compared with the internal over-temperature protection threshold Vref_OTP to generate a chip over-temperature detection signal (not shown in the figure); the OTP counter is configured to generate an over-temperature protection indication signal EX_OTP by performing a timer debounce on the chip over-temperature detection signal.

[0039] Figure 9 It shows Figure 8 The example waveform diagram of multiple signals in the chip over-temperature protection unit is shown, where: Vref_OTP represents the internal over-temperature protection threshold, V LTD The chip temperature representative voltage V at the LTD pin of the control chip 404 is represented by LTD , EX_OTP indicates the over-temperature protection indication signal. Figure 9 As shown, the chip temperature representative voltage V at the LTD pin of the control chip 404 LTD As the temperature of the control chip 400 increases, it gradually decreases; when the chip temperature at the LTD pin of the control chip 404 represents the voltage V LTD When the temperature is higher than the internal over-temperature protection threshold voltage Vref_OTP, the over-temperature protection indication signal EX_OTP is low, indicating that the control chip 400 does not need to be protected from over-temperature by the chip; when the chip temperature at the LTD pin of the control chip 404 is higher than the internal over-temperature protection threshold voltage Vref_OTP, the over-temperature protection indication signal EX_OTP is low, indicating that the control chip 400 does not need to be protected from over-temperature by the chip; LTD After the voltage is lower than the internal over-temperature protection threshold voltage Vref_OTP and a short period of time has passed, the over-temperature protection indication signal EX_OTP changes from a low level to a high level, indicating that the control chip 400 needs to be protected from over-temperature off-chip.

[0040] Figure 10 It shows Figure 4 The diagram shows another example circuit structure of the AC state detection voltage divider network and the circuit parts related to AC voltage detection and chip over-temperature protection in the control chip. Figure 10 The circuit structure shown is Figure 4 The difference between the circuit structures shown is that in the AC state detection voltage divider network 402', the first resistor R1, the second resistor R2, and the negative temperature coefficient resistor R3 are connected in series at the AC input representative voltage V AC' and the circuit reference ground, the second resistor R2 and the negative temperature coefficient resistor R3 are connected in series between the LTD pin of the control chip 404 and the circuit reference ground.

[0041] exist Figure 10 In the circuit structure shown, when the first switch S1 is in the closed state and the second switch S2 is in the open state, the control chip 404 is in the AC voltage detection state (corresponding to the AC input characteristic voltage V AC ' is a half cycle of non-zero voltage), the AC input at the LTD pin of the control chip 404 represents the divided voltage V LTD As shown in equation (5), when the first switch S1 is in the open state and the second switch S2 is in the closed state, the control chip 404 is in the chip over-temperature protection state (corresponding to the AC input characteristic voltage V AC ' is a half cycle of zero voltage), the chip temperature at the LTD pin of the control chip 404 represents the voltage V LTD As shown in equation (6):

[0042]

[0043] V LTD =I OTP *((R2+R3)||R1)≈I OTP *(R2+R3) (6)

[0044] In summary, in the AC-DC converter according to the embodiment of the present invention, the control chip 404 can realize one or more of AC unplug detection, AC power-on detection, AC voltage undervoltage protection, and AC voltage overvoltage protection while realizing external over-temperature protection of the control chip 404 using only one LTD pin, thereby improving the pin utilization of the control chip 404 (combined with Figure 1 The line voltage detection scheme and the combination Figure 2 It should be understood that although the accompanying drawings only show a flyback AC-DC converter as an example of an AC-DC converter according to an embodiment of the present invention, the AC-DC converter according to an embodiment of the present invention may also adopt other system architectures and be combined with Figures 4 to 10 The AC voltage detection solution and chip over-temperature protection solution can also be applied to AC-DC converters of other system architectures.

[0045] The present invention may be implemented in other specific forms without departing from its spirit and essential characteristics. For example, the algorithms described in the specific embodiments may be modified without departing from the basic spirit of the present invention. Therefore, the present embodiments are to be considered in all respects as illustrative and not restrictive, and the scope of the present invention is defined by the appended claims rather than the foregoing description. All modifications that come within the meaning and scope of the claims and equivalents are intended to be included within the scope of the present invention.

Claims

1. An AC-to-DC converter, comprising a voltage divider network and a control chip, wherein: The voltage divider network is configured to, when the AC input characterizing voltage is a non-zero voltage, divide the AC input characterizing voltage to generate an AC input characterizing divided voltage and provide the AC input characterizing divided voltage to the control chip via a predetermined pin of the control chip, and, when the AC input characterizing voltage is zero voltage, generate a chip temperature characterizing voltage based on a predetermined current flowing out of the predetermined pin of the control chip and provide the chip temperature characterizing voltage to the control chip via the predetermined pin of the control chip, wherein the AC input characterizing voltage changes completely synchronously with the AC input voltage of the AC-to-DC converter; The control chip is configured to detect the AC input voltage based on the AC input characteristic voltage division when the AC input characteristic voltage is a non-zero voltage, and to implement off-chip over-temperature protection for the control chip based on the chip temperature characteristic voltage when the AC input characteristic voltage is zero voltage.

2. The AC-to-DC converter according to claim 1, wherein: The AC input representative voltage is a filtered AC input voltage generated by processing the AC input voltage through an electromagnetic interference filter.

3. The AC-to-DC converter according to claim 1, wherein: The voltage divider network includes a first resistor, a second resistor, and a negative temperature coefficient resistor. The first resistor and the second resistor are connected in series between the AC input characterization voltage and the circuit reference ground. The first resistor and the negative temperature coefficient resistor are connected in series between the AC input characterization voltage and the predetermined pin of the control chip. The second resistor and the negative temperature coefficient resistor are connected in series between the predetermined pin of the control chip and the circuit reference ground.

4. The AC-to-DC converter according to claim 1, wherein: The voltage divider network includes a first resistor, a second resistor, and a negative temperature coefficient resistor. The first resistor, the second resistor, and the negative temperature coefficient resistor are connected in series between the AC input characterizing voltage and the circuit reference ground. The second resistor and the negative temperature coefficient resistor are connected in series between the predetermined pin of the control chip and the circuit reference ground.

5. The AC-to-DC converter according to claim 1, wherein: The control chip includes: an AC voltage detection unit, connected to the predetermined pin of the control chip via a first switch, and configured to implement one or more of power-on detection, power-off detection, undervoltage protection, and overvoltage protection for the AC input voltage based on the AC input characteristic voltage division when the first switch is in a closed state; a chip over-temperature protection unit, connected to the predetermined pin of the control chip via a second switch, and configured to provide the predetermined current to the predetermined pin of the control chip and implement off-chip over-temperature protection of the control chip based on the chip temperature characterizing voltage when the second switch is in a closed state; The first switch is in a closed state when the AC input characteristic voltage is non-zero voltage and is in an open state when the AC input characteristic voltage is zero voltage, and the second switch is in an open state when the AC input characteristic voltage is non-zero voltage and is in a closed state when the AC input characteristic voltage is zero voltage.

6. The AC-to-DC converter according to claim 5, wherein: The AC voltage detection unit is further configured to implement one or more of power-on detection, power-off detection, undervoltage protection, and overvoltage protection for the AC input voltage by comparing the AC input characteristic divided voltage with one or more internal reference voltages.

7. The AC-to-DC converter according to claim 6, wherein: The AC voltage detection unit is further configured to generate an AC voltage power-on detection signal, an AC voltage power-off detection signal, an AC voltage undervoltage detection signal, and an AC voltage overvoltage detection signal by comparing the AC input characterization voltage with the internal reference voltages used for power-on detection, power-off detection, undervoltage protection, and overvoltage protection of the AC input voltage, respectively, and to generate an AC voltage power-on indication signal, an AC voltage power-off indication signal, an AC voltage undervoltage indication signal, and an AC voltage overvoltage indication signal by performing timer debouncing on the AC voltage power-on detection signal, the AC voltage power-off detection signal, the AC voltage undervoltage detection signal, and the AC voltage overvoltage detection signal, respectively.

8. The AC-to-DC converter according to claim 5, wherein: The chip over-temperature protection unit is further configured to generate an over-temperature protection indication signal indicating whether the control chip needs to be over-temperature protected by comparing the chip temperature representative voltage with an internal over-temperature protection threshold.

9. The AC-to-DC converter according to claim 8, wherein: The chip over-temperature protection unit is further configured to generate a chip over-temperature detection signal by comparing the chip temperature characterization voltage with the internal over-temperature protection threshold when the signal used to control the closing and opening of the second switch is enabled, and generate an over-temperature protection indication signal by timer debouncing the chip over-temperature detection signal.

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