High-efficiency boost power factor correction circuit with shared pins and its conversion control circuit

Abstract

A high-efficiency boost power factor correction circuit with a shared pin and its conversion control circuit are disclosed. The boost power factor correction circuit includes: a switch and an inductor coupled to each other; a current sensing element for generating a current sensing signal based on the current flowing through the switch; a temperature sensing element non-contactly coupled to the inductor for generating a temperature sensing signal; and a conversion control circuit for operating the switch. The conversion control circuit is an integrated circuit and includes: a shared pin coupled to the temperature sensing element and the current sensing element; a current sensing circuit and a temperature sensing circuit for sensing multi-task sensing signals related to the current sensing signal and the temperature sensing signal respectively when the switch is on and off, respectively, via the shared pin; wherein the temperature sensing signal is related to the input voltage, the output voltage, and at least one electrical parameter of the temperature sensing element that changes with the measured temperature.

Description

Technical Field

[0001] This invention relates to a boost power factor correction circuit, and more particularly to a high-efficiency boost power factor correction circuit with shared pins. The invention also relates to a conversion control circuit for the high-efficiency boost power factor correction circuit. Background Technology

[0002] Please refer to Figure 1 , Figure 1 This is a schematic diagram of a boost converter power factor correction circuit in existing technology. For example... Figure 1 As shown, the prior art boost-type power factor correction circuit 1000 includes a boost-type power stage circuit 101, a control circuit 102, and a thermistor RT1. The boost-type power factor correction circuit 1000 is used to convert the input voltage VI to generate an output voltage VO with power factor correction. The boost-type power stage circuit 101 includes an inductor L, a switch SW11, and a switch SW12. The control circuit 102 is an integrated circuit that detects the feedback voltage VF via pin FB and the current sensing signal VC1 generated by the current sensing resistor RC1 via pin CS. Based on the feedback voltage VF and the current sensing signal VC1, it controls the switches SW11 and SW12 to switch according to their duty cycles via pin GA. In addition, the control circuit 102 needs to be connected to ground potential via pin GD. To prevent the boost power factor correction circuit 1000 from being damaged due to overheating, the control circuit 102 is coupled to the thermistor RT1 via pin TS, thereby detecting the temperature sensing signal VT1 generated by the thermistor RT1 and performing over-temperature protection (OTP).

[0003] The disadvantage of the prior art is that the control circuit 102 needs to use a dedicated pin for temperature sensing in order to achieve overheat protection of the boost power factor correction circuit 1000, which will increase the integrated circuit area and increase the cost. Summary of the Invention

[0004] This invention provides a boost power factor correction circuit for converting an input voltage to generate a power factor corrected output voltage. The circuit includes: a boost power stage circuit comprising a first switch and a first inductor coupled to each other; a current sensing element coupled to the first switch for generating a current sensing signal based on the current flowing through the first switch; a temperature sensing element non-contactly coupled to the first inductor for generating a temperature sensing signal; and a conversion control circuit for operating the first switch to control the first inductor to switch between the output voltage and a ground potential according to a duty cycle, thereby converting the input voltage to generate the output voltage. The conversion control circuit is an integrated circuit and includes a shared pin. The circuit includes a current sensing circuit coupled to the temperature sensing element and the current sensing element; a current sensing circuit for sensing a multitasking sensing signal through the shared pin when the first switch is turned on, wherein the multitasking sensing signal is related to the current sensing signal, and the switching control circuit for controlling the duty cycle based on the current sensing signal; and a temperature sensing circuit for sensing the multitasking sensing signal through the shared pin when the first switch is not turned on, wherein the multitasking sensing signal corresponds to the temperature sensing signal, wherein when the temperature sensing signal exceeds a temperature sensing threshold, it indicates that a measured temperature is higher than a preset temperature threshold; wherein the temperature sensing signal is related to the input voltage, the output voltage, and at least one electrical parameter of the temperature sensing element that changes with the measured temperature.

[0005] In some embodiments, the boost power factor correction circuit further includes a second inductor for coupling to the first inductor via electromagnetic induction, wherein a first terminal of the second inductor is coupled to the temperature sensing element, and wherein the temperature sensing signal is related to the difference between the input voltage and the output voltage.

[0006] In some embodiments, the second inductor and the first inductor form a transformer, the first inductor corresponding to a first winding of the transformer, and the second inductor corresponding to a second winding of the transformer.

[0007] In some embodiments, the temperature sensing circuit described above is used to sense the temperature sensing signal through the shared pin during a demagnetization period of the second inductor.

[0008] In some embodiments, the boost power factor correction circuit further includes a unidirectional conducting element coupled between the second inductor and the temperature sensing element, thereby ensuring that the voltage of the shared pin is not less than 0.

[0009] In some embodiments, the boost-type power factor correction circuit further includes: a voltage divider resistor coupled to the unidirectional conducting element; and a filter resistor coupled between the current sensing signal and the multitasking sensing signal to filter the current sensing signal and generate the multitasking sensing signal; wherein the second inductor generates an auxiliary voltage through electromagnetic induction, wherein when the first switch is not turned on, the voltage divider resistor, the temperature sensing element, the filter resistor, and the current sensing element are used to divide the auxiliary voltage to generate the multitasking sensing signal, at which time the multitasking sensing signal is related to the temperature sensing signal.

[0010] In some embodiments, the temperature sensing element is a thermistor with a positive or negative temperature coefficient, wherein the temperature sensing signal is proportional to the difference between the output voltage and the input voltage and inversely proportional to the resistance value of the thermistor.

[0011] In some embodiments, the current sensing element is a current sensing resistor connected in series with the first switch, wherein the temperature sensing signal is also proportional to a turns ratio between the second inductor and the first inductor, and the temperature sensing signal is also proportional to a voltage divider of the difference between the output voltage and the input voltage, wherein the voltage divider is related to the resistance value of the temperature-sensitive resistor and the resistance value of the current sensing resistor.

[0012] In some embodiments, the switching control circuit further includes: a pulse width control circuit for generating a pulse width modulation signal based on the output voltage and a current-related signal associated with the current sensing signal and determining the duty cycle, wherein the pulse width modulation signal is used to control the first switch to switch according to the duty cycle, and wherein the pulse width control circuit is further used to generate an enable signal associated with the pulse width modulation signal; wherein the temperature sensing circuit includes: a comparison circuit coupled to the shared pin for comparing the temperature sensing signal with the temperature sensing threshold when the enable signal indicates that the first switch is off, to determine whether the temperature to be measured is higher than the preset temperature threshold.

[0013] In some embodiments, the conversion control circuit further includes a debounce circuit or a counter to reduce noise in the temperature sensing signal.

[0014] In some embodiments, the boost power factor correction circuit further includes a zero current sensing resistor, wherein the conversion control circuit further includes: a zero current sensing pin, wherein the zero current sensing resistor is coupled between the zero current sensing pin and a first terminal of the second inductor, wherein the first terminal of the second inductor is coupled to a temperature sensing element; and a clamping and detection circuit for clamping a zero current sensing voltage on the zero current sensing pin to ensure that it is not lower than a preset negative voltage, and for detecting the zero current sensing voltage to determine the zero current point when the current of the first inductor reaches 0.

[0015] In some embodiments, the conversion control circuit further controls the boost power stage circuit to operate in a boundary conduction mode or a discontinuous conduction mode based on the zero current point.

[0016] In some embodiments, the first terminal of the second inductor is coupled to the zero-current detection pin through the zero-current detection resistor, thereby generating the zero-current detection voltage on the zero-current detection pin.

[0017] In some embodiments, the clamping and detection circuitry further generates the temperature sensing threshold based on the zero-current detection voltage.

[0018] The present invention also provides a conversion control circuit for a boost power factor correction circuit, wherein the boost power factor correction circuit is used to convert an input voltage to generate an output voltage with power factor correction, and includes: a boost power stage circuit including a first switch and a first inductor coupled to each other; a current sensing element coupled to the first switch for generating a current sensing signal based on the current flowing through the first switch; and a temperature sensing element non-contactly coupled to the first inductor for generating a temperature sensing signal; the conversion control circuit is used to operate the first switch to control the first inductor to switch between the output voltage and a ground potential according to a duty cycle, thereby converting the input voltage to generate the output voltage, wherein the conversion control circuit is an integrated circuit, and the conversion control... The control circuit includes: a shared pin coupled to the temperature sensing element and the current sensing element; a current sensing circuit for sensing a multitasking sensing signal through the shared pin when the first switch is turned on, wherein the multitasking sensing signal is related to the current sensing signal, wherein the switching control circuit is used to control the duty cycle according to the current sensing signal; and a temperature sensing circuit for sensing the multitasking sensing signal through the shared pin when the first switch is not turned on, wherein the multitasking sensing signal corresponds to the temperature sensing signal, wherein when the temperature sensing signal exceeds a temperature sensing threshold, it indicates that a measured temperature is higher than a preset temperature threshold; wherein the temperature sensing signal is related to the input voltage, the output voltage, and at least one electrical parameter of the temperature sensing element that changes with the measured temperature.

[0019] This invention proposes a high-efficiency boost power factor correction circuit with shared pins, which can not only achieve over-temperature protection of the boost power factor correction circuit while reducing the area of ​​integrated circuits and lowering costs, but also improve the efficiency of the boost power factor correction circuit.

[0020] The following detailed description through specific embodiments will make it easier to understand the purpose, technical content, features and effects achieved by the present invention. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a boost power factor correction circuit in the prior art.

[0022] Figure 2 This is a schematic diagram of a boost power factor correction circuit in one embodiment of the present invention.

[0023] Figure 3 This is an operational waveform diagram of a boost power factor correction circuit in one embodiment of the present invention.

[0024] Figure 4A This is a graph showing the relationship between the resistance value and temperature of a temperature sensing element, which is a thermistor with a positive temperature coefficient, in one embodiment of the present invention.

[0025] Figure 4B This is a graph showing the relationship between the resistance value and temperature of a temperature sensing element, which is a thermistor with a negative temperature coefficient, in one embodiment of the present invention.

[0026] Figure 5A This is a schematic diagram of a boost power stage circuit in one embodiment of the present invention.

[0027] Figure 5B This is a schematic diagram of a boost power stage circuit in another embodiment of the present invention.

[0028] Figure 6 This is a schematic diagram of a boost power factor correction circuit in one embodiment of the present invention.

[0029] Figure 7 This is a schematic diagram of a boost power factor correction circuit in a specific embodiment of the present invention.

[0030] Figure 8 This is an operational waveform diagram of a boost power factor correction circuit in one embodiment of the present invention.

[0031] Figure 9 This is a schematic diagram of the conversion control circuit in a boost power factor correction circuit according to a specific embodiment of the present invention.

[0032] Explanation of symbols in the diagram

[0033] 10: Rectifier

[0034] 15: Differentiator

[0035] 101: Boost power stage circuit

[0036] 102: Control Circuit

[0037] 120: Boost power stage circuit

[0038] 121: Boost power stage circuit

[0039] 122: Boost power stage circuit

[0040] 1000: Boost power factor correction circuit

[0041] 20: Current sensing circuit

[0042] 220: Conversion control circuit

[0043] 226: Conversion Control Circuit

[0044] 227: Conversion Control Circuit

[0045] 229: Conversion Control Circuit

[0046] 2000: Boost power factor correction circuit

[0047] 30: Temperature sensing circuit

[0048] 31: Temperature sensing circuit

[0049] 40: Pulse Width Control Circuit

[0050] 50: Comparator Circuit

[0051] 60: Debounce circuit or counter

[0052] 6000: Boost power factor correction circuit

[0053] 70: Clamping and Detection Circuit

[0054] 71: Clamping and Detection Circuit

[0055] 7000: Boost power factor correction circuit

[0056] 80: Comparator

[0057] 90: Signal generation circuit

[0058] B1, B2, B3: Transistors

[0059] Cp: ​​Filter capacitor

[0060] CS: Pin

[0061] D1: Diode

[0062] Dt: Diode

[0063] Dz: Diode

[0064] EN: Enable signal

[0065] FB: Pin

[0066] Fb: Pin

[0067] GA: pin

[0068] GD: Pin

[0069] Gn: Pin

[0070] Gt: Pin

[0071] I1: Current

[0072] I2: Current

[0073] Ib: Current

[0074] IL: Current

[0075] IL1: Current

[0076] Irz: Current

[0077] kVin: signal

[0078] L: Inductance

[0079] L1: First Inductor

[0080] L2: Second inductor

[0081] Lc: coil

[0082] M1, M2: Transistors

[0083] n: Turns ratio

[0084] N1: Node

[0085] OTP: Over-temperature signal

[0086] OTP': Pre-loaded over-temperature signal

[0087] Pm: Shared pin

[0088] PWM: Pulse Width Modulation Signal

[0089] Q1: Transistor

[0090] R1: Resistor

[0091] RC1: Current sensing resistor

[0092] Rcs: Current sensing element

[0093] Rp: Filter resistor

[0094] Rset: Voltage divider resistor

[0095] Rt: Temperature sensing element

[0096] RT1: Thermistor

[0097] Rth1: Resistance value

[0098] Rth2: Resistance value

[0099] Rzc: Zero Current Sensing Resistor

[0100] Scs: Current sensing signal

[0101] Sts: Temperature sensing signal

[0102] SW11: Switch

[0103] SW12: Switch

[0104] t0~t4: Time points

[0105] T1, T2: Temperature

[0106] TS: Pin

[0107] Tth1: Preset temperature threshold

[0108] Tth2: Preset temperature threshold

[0109] Vaux: Auxiliary voltage

[0110] VC1: Current sensing signal

[0111] Vcmp: Comparison voltage

[0112] Vcs': Current-related signal

[0113] VF: Feedback voltage

[0114] Vfb: Feedback signal

[0115] Vg: Gate voltage

[0116] VI: Input Voltage

[0117] Vin: Input voltage

[0118] VL: Transpressure

[0119] Vlx: Voltage

[0120] Vms: Multi-task sensing signal

[0121] VO: Output voltage

[0122] Vout: Output voltage

[0123] Vref: Temperature sensing threshold

[0124] VT1: Temperature sensing signal

[0125] Vtr: Voltage threshold

[0126] Vzc: Zero Current Detection Voltage

[0127] Zc: Zero Current Detection Pin Detailed Implementation

[0128] The accompanying drawings in this invention are schematic and are primarily intended to illustrate the coupling relationships between circuits and the relationships between signal waveforms. The circuits, signal waveforms, and frequencies are not drawn to scale. For clarity, many practical details will be described in the following description, but this is not intended to limit the scope of the patent application.

[0129] Please refer to Figure 2 , Figure 2 This is a schematic diagram of a boost power factor correction circuit according to one embodiment of the present invention. In one embodiment, rectifier 10 rectifies AC voltage to generate input voltage Vin, and boost power factor correction circuit 2000 is used to convert input voltage Vin to generate output voltage Vout with power factor correction. In one embodiment, boost power factor correction circuit 2000 includes boost power stage circuit 120, current sensing element Rcs, temperature sensing element Rt, and conversion control circuit 220. In one embodiment, boost power stage circuit 120 includes a first switch, a second switch, and a first inductor L1. In one embodiment, the first switch corresponds to the lower bridge switch, and the second switch corresponds to the upper bridge switch, wherein the first switch can be a metal-oxide-semiconductor (MOS) transistor, and the second switch can be a switch or a diode. In this embodiment, the first switch is transistor Q1 (NMOS transistor), and the second switch is diode D1. In one embodiment, the first terminal of the first inductor L1, the first terminal of the transistor Q1, and the first terminal of the diode D1 are all coupled to node N1, thereby boosting the input voltage Vin to the output voltage Vout. In one embodiment, the current sensing element Rcs is a current sensing resistor connected in series between the transistor Q1 and ground potential.

[0130] In one embodiment, such as Figure 2As shown, a current sensing element Rcs is coupled to transistor Q1 to generate a current sensing signal Scs based on the current flowing through transistor Q1. A temperature sensing element Rt is non-contactly coupled to a first inductor L1 to generate a temperature sensing signal Sts. At least one electrical parameter of the temperature sensing element Rt, such as resistance, may have a positive or negative temperature coefficient relative to ambient temperature. In one embodiment, a conversion control circuit 220 operates transistor Q1 to control the first inductor L1 to switch between an output voltage Vout and a ground potential according to a duty cycle, thereby converting the input voltage Vin to generate the output voltage Vout. In one embodiment, the conversion control circuit 220 is an integrated circuit, including: a shared pin Pm, pin Gt, pin Gn, pin Fb, a current sensing circuit 20, a temperature sensing circuit 30, and a pulse width control circuit 40. In one embodiment, the shared pin Pm is coupled to the temperature sensing element Rt and the current sensing element Rcs, the pin Gt is coupled to the gate voltage Vg of transistor Q1, the pin Gn is coupled to the ground potential, and the pin Fb is coupled to the feedback signal Vfb.

[0131] Please refer to the following at the same time Figure 2 and Figure 3 , Figure 3 This is an operational waveform diagram of a boost-type power factor correction circuit according to one embodiment of the present invention. In one embodiment, at... Figure 3 During the time period from time t0 to time t1, transistor Q1 is turned on under the control of the gate voltage Vg. The current IL1 flowing through the first inductor L1 increases over time. The current sensing circuit 20 senses the multi-task sensing signal Vms through the shared pin Pm to generate a current-related signal Vcs'. At this time (during the time period from time t0 to time t1), the multi-task sensing signal Vms is related to the current sensing signal Scs. Figure 3During the time period from time point t2 to time point t3, transistor Q1 is controlled by the gate voltage Vg and is not turned on. The current IL1 flowing through the first inductor L1 decreases over time. The temperature sensing circuit 30 senses the multi-task sensing signal Vms through the shared pin Pm. At this time (during the time period from time point t2 to time point t3), the multi-task sensing signal Vms corresponds to the temperature sensing signal Sts. The temperature sensing signal Sts is related to the temperature to be measured. When the temperature sensing signal Sts exceeds the temperature sensing threshold Vref, the temperature sensing circuit 30 indicates that the temperature to be measured is higher than the preset temperature threshold. The relevant details are described later. In one embodiment, the temperature sensing signal Sts is related to at least one electrical parameter of the input voltage Vin, the output voltage Vout, and the temperature sensing element Rt as a function of the temperature to be measured. In one embodiment, the pulse width control circuit 40 generates a pulse width modulation signal PWM based on the feedback signal Vfb and the current-related signal Vcs' related to the current sensing signal Scs, and determines its duty cycle. The pulse width modulation signal PWM is used to control transistor Q1 to switch according to the duty cycle.

[0132] In one embodiment, the temperature sensing element Rt is a thermistor with a positive or negative temperature coefficient. Please also refer to... Figure 4A and Figure 4B , Figure 4A In one embodiment of the present invention, the temperature sensing element is a thermistor with a positive temperature coefficient, and the relationship between the resistance value and temperature is shown in the graph. Figure 4B This is a graph showing the relationship between the resistance value and temperature of a temperature sensing element, specifically a thermistor with a negative temperature coefficient, in one embodiment of the present invention. Please also refer to... Figure 2 and Figure 4A In one embodiment, when the temperature sensing element Rt is a thermistor with a positive temperature coefficient, such as Figure 4A As shown, the resistance value increases with increasing temperature. The preset temperature threshold Tth1 corresponds to the resistance value Rth1. In this embodiment, the resistance value Rth1 also corresponds to the temperature sensing threshold Vref. Therefore, when the temperature sensing signal Sts exceeds the temperature sensing threshold Vref, the temperature sensing circuit 30 generates an over-temperature signal OTP to indicate that the measured temperature is higher than the preset temperature threshold Tth1. The pulse width control circuit 40 then controls the transistor Q1 to turn off based on the over-temperature signal OTP to perform over-temperature protection. Please also refer to... Figure 2 and Figure 4B In one embodiment, when the temperature sensing element Rt is a thermistor with a negative temperature coefficient, such as Figure 4BAs shown, the resistance value decreases as the temperature increases. The preset temperature threshold Tth2 can correspond to the resistance value Rth2. In this embodiment, the resistance value Rth2 can also correspond to the temperature sensing threshold Vref. Therefore, when the temperature sensing signal Sts is lower than the temperature sensing threshold Vref, the temperature sensing circuit 30 generates an over-temperature signal OTP to indicate that the temperature to be measured is higher than the preset temperature threshold Tth2. The pulse width control circuit 40 controls the transistor Q1 to turn off according to the over-temperature signal OTP to perform over-temperature protection.

[0133] Please refer to the following at the same time Figure 5A and Figure 5B , Figure 5A This is a schematic diagram of a boost power stage circuit in one embodiment of the present invention. Figure 5B This is a schematic diagram of a boost power stage circuit in another embodiment of the present invention. Figure 5A The boost power stage circuit 121 is similar to Figure 2 In one specific embodiment, the boost power stage circuit 121 further includes a coil Lc and a differentiator 15. The coil Lc is used to detect the current IL of the first inductor L1, and the differentiator 15 is used to differentiate the current IL to generate the voltage VL across the first inductor L1, thereby causing the temperature sensing element Rt to generate a temperature sensing signal Sts based on the voltage VL. Figure 5B The boost power stage circuit 122 is similar to Figure 2 In one specific embodiment, the boost power stage circuit 122 further includes a second inductor L2, which is coupled to the first inductor L1 by electromagnetic induction. In this embodiment, the temperature sensing signal Sts is related to the difference between the input voltage Vin and the output voltage Vout.

[0134] Please refer to Figure 6 , Figure 6 This is a schematic diagram of a boost power factor correction circuit in one embodiment of the present invention. Figure 6 The boost power factor correction circuit 6000 is similar to Figure 2The boost power factor correction circuit 2000, in one embodiment, further includes a second inductor L2, a unidirectional conducting element, a voltage divider resistor Rset, a filter resistor Rp, a filter capacitor Cp, and a zero-current detection resistor Rzc. The unidirectional conducting element is, for example, a diode or a synchronous rectifier switch. In this embodiment, the unidirectional conducting element is a diode Dt, used to ensure that the voltage at the shared pin Pm is not less than 0. In one embodiment, the conversion control circuit 226 further includes a clamping and detection circuit 70 and a zero-current detection pin Zc. In one embodiment, the temperature sensing circuit 31 includes a comparator circuit 50 and a debounce circuit or counter 60. The comparator circuit 50 is coupled to a shared pin Pm and is used to compare the temperature sensing signal Sts with the temperature sensing threshold Vref to generate a pre-overtemperature signal OTP'. The debounce circuit or counter 60 is used to generate an overtemperature signal OTP based on the pre-overtemperature signal OTP', thereby reducing the noise of the temperature sensing signal Sts (e.g., ringing noise caused by switching of the boost power stage circuit 120).

[0135] In one embodiment, such as Figure 6As shown, the second inductor L2 is coupled to the first inductor L1 via electromagnetic induction to generate an auxiliary voltage Vaux. In this embodiment, the second inductor L2 and the first inductor L1 form a transformer, with the first inductor L1 corresponding to the first winding and the second inductor L2 corresponding to the second winding, wherein the turns ratio of the first winding to the second winding is 1:n. In one embodiment, the first terminal of the second inductor L2 is coupled to the temperature sensing element Rt, and the diode Dt is coupled between the second inductor L2 and the temperature sensing element Rt, thereby ensuring that the voltage of the shared pin Pm is not less than 0, that is, that the voltage of the multi-tasking sensing signal Vms is not less than 0. In one embodiment, the voltage divider resistor Rset is coupled between the diode Dt and the second inductor L2, or between the diode Dt and the temperature sensing element Rt, to divide the auxiliary voltage Vaux or limit the current flowing through the second inductor L2. In one embodiment, a filter resistor Rp is coupled between the current sensing signal Scs and the multi-task sensing signal Vms, and a filter capacitor Cp is coupled between the multi-task sensing signal Vms and the ground potential. In one embodiment, the pulse width control circuit 40 is also used to generate an enable signal EN related to the pulse width modulation signal PWM. In one embodiment, a zero-current detection resistor Rzc is coupled between the zero-current detection pin Zc and the first terminal of the second inductor L2. The first terminal of the second inductor L2 is coupled to the zero-current detection pin Zc through the zero-current detection resistor Rzc, thereby generating a zero-current detection voltage Vzc at the zero-current detection pin Zc. The clamping and detection circuit 70 is used to clamp the zero-current detection voltage Vzc through the zero-current detection pin Zc, ensuring that it is not lower than a preset negative voltage and not higher than a preset positive voltage. The clamping and detection circuit 70 is also used to detect the zero-current detection voltage Vzc to determine the zero-current point when the current IL of the first inductor L1 reaches 0.

[0136] Please refer to the following at the same time Figure 3 and Figure 6 In one embodiment, during the excitation period of the second inductor L2, i.e. Figure 3 During the time period from time t0 to time t1, the current sensing circuit 20 senses the multi-task sensing signal Vms through the shared pin Pm. At this time, the multi-task sensing signal Vms is related to the current sensing signal Scs. Specifically, during the time period from time t0 to time t1, the pulse width modulation signal PWM generated by the pulse width control circuit 40 controls the gate voltage Vg of transistor Q1 to a high level via the pin Gt, causing transistor Q1 to turn on. The filter resistor Rp is used to filter the current sensing signal Scs to generate the multi-task sensing signal Vms, thereby making the multi-task sensing signal Vms correspond to the filtered current sensing signal Scs during the time period from time t0 to time t1. It should be noted that... Figure 6 In one embodiment, during the time period from time t0 to time t1, the auxiliary voltage Vaux is -n. Vin.

[0137] In one embodiment, during the demagnetization period of the second inductor L2 (i.e., before the current of the second inductor L2 drops to 0), Figure 3 During the time period from time point t2 to time point t3, the temperature sensing circuit 31 senses the temperature sensing signal Sts through the shared pin Pm. Specifically, during the time period from time point t2 to time point t3, the pulse width modulation signal PWM generated by the pulse width control circuit 40 controls the gate voltage Vg of transistor Q1 to a low level via the pin Gt, so that transistor Q1 is not turned on, and the pulse width control circuit 40 generates an enable signal EN to indicate that transistor Q1 is turned off. This allows the comparison circuit 50 to compare the temperature sensing signal Sts with the temperature sensing threshold Vref based on the enable signal EN to determine whether the temperature to be measured is higher than the preset temperature threshold. It should be noted that during the time period from time point t2 to time point t3, the multi-task sensing signal Vms corresponds to the temperature sensing signal Sts. For example, in one embodiment, when the temperature sensing element Rt is a thermistor with a positive temperature coefficient, during the time period from time point t2 to time point t3, when the temperature to be measured is temperature T1, as... Figure 3 The waveform of Vms (T1) corresponds to the voltage of the multi-task sensing signal Vms of the temperature sensing signal Sts being lower than the voltage of the temperature sensing threshold Vref. The comparator circuit 50 determines that the measured temperature (T1) is not higher than the preset temperature threshold. When the measured temperature is temperature T2, such as Figure 3 The waveform of Vms (T2) corresponds to the voltage of the multi-task sensing signal Vms of the temperature sensing signal Sts being higher than the voltage of the temperature sensing threshold Vref. The comparator circuit 50 generates a pre-set over-temperature signal OTP' to indicate that the temperature to be measured (T2) is higher than the preset temperature threshold. The debounce circuit or counter 60 generates an over-temperature signal OTP based on the pre-set over-temperature signal OTP'. The pulse width control circuit 40 controls the transistor Q1 to turn off based on the over-temperature signal OTP to perform over-temperature protection.

[0138] Figure 6 In the embodiment, during the time period from time point t2 to time point t3, the auxiliary voltage Vaux is n. (Vout-Vin), the voltage divider resistor Rset, the temperature sensing element Rt, the filter resistor Rp, and the current sensing element Rcs are used to divide the auxiliary voltage Vaux to generate a multi-task sensing signal Vms, which can be expressed by the following equation 1: Vms = [(Vout - Vin)] n-VDt] (Rcs+Rp) / (Rset+Rt+Rcs+Rp) Formula 1 In Equation 1, Vms is the voltage of the multi-task sensing signal Vms, corresponding to the voltage of the temperature sensing signal Sts; n is the turns ratio of the second inductor L2 to the first inductor L1; VDt is the voltage of the diode Dt; and Rset, Rt, Rp, and Rcs are the resistance values ​​of the voltage divider resistor Rset, the temperature sensing element Rt, the filter resistor Rp, and the current sensing element Rcs, respectively. In this embodiment, the voltage divider resistor Rset is a resistor with a relatively low temperature coefficient, and the temperature sensing element Rt is a thermistor with a relatively high temperature coefficient. As shown in Equation 1, the voltage of the temperature sensing signal Sts is proportional to a voltage divider of the difference between the output voltage Vout and the input voltage Vin, and also proportional to the turns ratio n between the second inductor L2 and the first inductor L1, and inversely proportional to the resistance value of the thermistor. This voltage divider is related to the resistance value of the thermistor and the resistance value of the current sensing resistor.

[0139] Please refer to Figure 7 , Figure 7 This is a schematic diagram of a boost power factor correction circuit in a specific embodiment of the present invention. Figure 7 The boost power factor correction circuit 7000 is similar to Figure 6 In one embodiment, the boost power factor correction circuit 6000, Figure 7 The clamping and detection circuit 71 in the conversion control circuit 227 includes a comparator 80, transistors B1, B2, B3, M1, M2, a resistor R1, and a diode Dz. In one embodiment, transistors B1, B2, and B3 are bipolar junction transistors (BJTs) of the same conductivity type, wherein transistors B1 and B2 are diode-coupled BJTs, and transistors M1 and M2 are metal-oxide-semiconductor (MOS) transistors of the same conductivity type. In one embodiment, diode Dz is a Zener diode, which clamps the zero-current detection voltage Vzc through the zero-current detection pin Zc to ensure that it is not lower than a preset negative voltage and not higher than a preset positive voltage. In this embodiment, the preset negative voltage is the opposite of the forward bias voltage of the Zener diode, and the preset positive voltage is the opposite of the reverse bias voltage of the Zener diode.

[0140] Please refer to the following at the same time Figure 3 and Figure 7In one embodiment, transistors B1, B2, and B3, and diode Dz are used to mirror the current Ib generated by the current source to generate current I1. Transistors M1 and M2 are used to mirror current I1 to generate current I2. Resistor R1 generates a signal kVin related to the input voltage Vin based on current I2, and current Irz is also generated based on current I2. It should be noted that in... Figure 3 During the time interval from time point t0 to time point t1, since the auxiliary voltage Vaux is related to the input voltage Vin, and the current Irz is related to the auxiliary voltage Vaux, the current I2 is related to the input voltage Vin, which in turn makes the signal kVin related to the input voltage Vin.

[0141] Please continue to refer to Figure 3 and Figure 7 In one embodiment, comparator 80 is used to detect the zero-current detection voltage Vzc and compare it with a voltage threshold Vtr to generate a comparison voltage Vcmp, thereby determining when the current IL1 of the first inductor L1 reaches zero (in steady state, the valley of the current IL1 of the first inductor L1 is 0). Specifically, as follows... Figure 3 As shown, when the zero-current detection voltage Vzc is less than the voltage threshold Vtr, the comparison voltage Vcmp indicates the knee point of the zero-current detection voltage Vzc, and thus determines the zero-current point (time point t3) when the current IL1 of the first inductor L1 reaches 0. Consequently, the pulse width control circuit 40 controls the comparator circuit 50 to switch to an inactive state based on the comparison voltage Vcmp. In one embodiment, the comparison voltage Vcmp can also be used to determine time point t2. In one embodiment, the pulse width control circuit 40 also controls the boost power stage circuit 120 to operate in discontinuous conduction mode (DCM) based on the aforementioned zero-current point (time point t3). Figure 3 As shown, when the comparison voltage Vcmp detects the knee point and indicates that it has reached the zero current point (time point t3), the PWM signal controls the transistor Q1 to remain non-conducting. At this time, the diode D1 also turns off until the start of the next cycle (time point t4). Therefore, during the period from time point t3 to time point t4, the auxiliary voltage Vaux, the zero current detection voltage Vzc, and the multi-task sensing signal Vms will all exhibit oscillating waveforms.

[0142] Please refer to the following at the same time Figure 7 and Figure 8 , Figure 8This is an operational waveform diagram of a boost power factor correction circuit in one embodiment of the present invention. In one embodiment, the pulse width control circuit 40 further controls the boost power stage circuit 120 to operate in Boundary Conduction Mode (BCM) based on the aforementioned zero current point (point t3), such as... Figure 8 As shown, when the comparison voltage Vcmp detects the knee point and indicates that it has reached the zero current point (time point t3), the PWM signal controls the transistor Q1 to turn on, thus starting a new cycle. It should be noted that in the boundary conduction mode, when the current IL1 of the first inductor L1 reaches 0 (time point t3), the next cycle immediately begins. Therefore, the auxiliary voltage Vaux, the zero current detection voltage Vzc, and the multi-task sensing signal Vms will not exhibit oscillating waveforms. It should also be noted that the voltage Vlx at the first terminal of the first inductor L1 is related to the input voltage Vin during the time period from time point t0 to time point t1, and is related to the difference between the output voltage Vout and the input voltage Vin during the time period from time point t2 to time point t3.

[0143] Please refer to Figure 9 , Figure 9 This is a schematic diagram of the conversion control circuit in a boost power factor correction circuit according to a specific embodiment of the present invention. Figure 9 The conversion control circuit 229 is similar to Figure 7 In one embodiment, the conversion control circuit 229 further includes a signal generation circuit 90, which generates a temperature sensing threshold Vref based on a zero current detection voltage Vzc.

[0144] In summary, the boost power factor correction circuit of the present invention uses a shared pin, which allows the current sensing circuit and the temperature sensing circuit to detect the current and temperature respectively when the first switch is on and off. Therefore, it can achieve over-temperature protection of the boost power factor correction circuit while reducing the area of ​​the integrated circuit and lowering the cost, and can also improve the efficiency of the boost power factor correction circuit.

[0145] The present invention has been described above with reference to preferred embodiments. However, the above description is only intended to facilitate understanding of the invention by those skilled in the art and is not intended to limit the broadest scope of the invention. The described embodiments are not limited to individual application and can also be used in combination. For example, two or more embodiments can be used in combination, and some components of one embodiment can be used to replace corresponding components in another embodiment. Furthermore, within the same spirit of the invention, those skilled in the art can conceive of various equivalent changes and combinations. For example, the phrase "processing or calculating based on a signal or generating an output result" in the present invention is not limited to the signal itself, but also includes, when necessary, performing voltage-to-current conversion, current-to-voltage conversion, and / or proportional conversion on the signal, and then processing or calculating based on the converted signal to generate an output result. Therefore, within the same spirit of the invention, those skilled in the art can conceive of various equivalent changes and combinations, and there are many ways to combine them, which will not be listed here. Therefore, the scope of the present invention should cover the above and all other equivalent changes.

Claims

1. A boost-type power factor correction circuit, characterized in that, Used to convert an input voltage to produce an output voltage with power factor correction, including: A boost power stage circuit includes a first switch and a first inductor coupled to each other; A current sensing element is coupled to the first switch to generate a current sensing signal based on the current flowing through the first switch. A temperature sensing element is coupled to the first inductor in a non-contact manner to generate a temperature sensing signal. A second inductor is used to be coupled to the first inductor by electromagnetic induction, wherein a first end of the second inductor is coupled to the temperature sensing element. A zero-current sensing resistor; as well as A conversion control circuit is used to operate the first switch to control the first inductor to switch between the output voltage and a ground potential according to a duty cycle, so as to convert the input voltage and generate the output voltage. The conversion control circuit is an integrated circuit and includes: A shared pin is coupled to the temperature sensing element and the current sensing element; A current sensing circuit is used to sense a multitasking sensing signal through the shared pin when the first switch is turned on. At this time, the multitasking sensing signal is related to the current sensing signal, and the switching control circuit is used to control the duty cycle according to the current sensing signal. A temperature sensing circuit is used to sense the multitasking sensing signal through the shared pin when the first switch is not turned on. At this time, the multitasking sensing signal corresponds to the temperature sensing signal. When the temperature sensing signal exceeds a temperature sensing threshold, it indicates that the temperature to be measured is higher than a preset temperature threshold. A zero-current sensing pin, wherein the zero-current sensing resistor is coupled between the zero-current sensing pin and a first terminal of the second inductor; and A clamping and detection circuit is used to clamp a zero current detection voltage on the zero current detection pin to ensure that it is not lower than a preset negative voltage, and to detect the zero current detection voltage to determine the zero current point when the current of the first inductor reaches 0. The temperature sensing signal is related to the difference between the input voltage and the output voltage, and at least one electrical parameter of the temperature sensing element that changes with the measured temperature.

2. The boost power factor correction circuit as described in claim 1, wherein, The second inductor and the first inductor form a transformer, the first inductor corresponding to a first winding of the transformer, and the second inductor corresponding to a second winding of the transformer.

3. The boost power factor correction circuit as described in claim 1, wherein, The temperature sensing circuit is used to sense the temperature sensing signal through the shared pin during a demagnetization period of the second inductor.

4. The boost power factor correction circuit as described in claim 1, wherein, It also includes a unidirectional conducting element coupled between the second inductor and the temperature sensing element, thereby ensuring that the voltage of the shared pin is not less than 0.

5. The boost power factor correction circuit as described in claim 4, wherein, Also includes: A voltage divider resistor is coupled to the unidirectional conducting element; and A filter resistor is coupled between the current sensing signal and the multitasking sensing signal to filter the current sensing signal and generate the multitasking sensing signal. The second inductor generates an auxiliary voltage through electromagnetic induction. When the first switch is not turned on, the voltage divider resistor, the temperature sensing element, the filter resistor, and the current sensing element are used to divide the auxiliary voltage to generate the multitasking sensing signal. At this time, the multitasking sensing signal is related to the temperature sensing signal.

6. The boost power factor correction circuit as described in claim 1, wherein, The temperature sensing element is a thermistor with a positive or negative temperature coefficient, wherein the temperature sensing signal is proportional to the difference between the output voltage and the input voltage and inversely proportional to the resistance value of the thermistor.

7. The boost power factor correction circuit as described in claim 6, wherein, The current sensing element is a current sensing resistor connected in series with the first switch. The temperature sensing signal is also proportional to the turns ratio between the second inductor and the first inductor, and the temperature sensing signal is also proportional to a voltage divider of the difference between the output voltage and the input voltage. The voltage divider is related to the resistance value of the temperature-sensitive resistor and the resistance value of the current sensing resistor.

8. The boost power factor correction circuit as described in claim 1, wherein, The conversion control circuit also includes: A pulse width control circuit is used to generate a pulse width modulation signal and determine the duty cycle based on the output voltage and a current correlation signal related to the current sensing signal, wherein the pulse width modulation signal is used to control the first switch to switch according to the duty cycle, and wherein the pulse width control circuit is also used to generate an enable signal related to the pulse width modulation signal. The temperature sensing circuit includes: A comparison circuit, coupled to the shared pin, is used to compare the temperature sensing signal with the temperature sensing threshold when the enable signal indicates that the first switch is off, in order to determine whether the temperature to be measured is higher than the preset temperature threshold.

9. The boost power factor correction circuit as described in claim 1, wherein, The conversion control circuit also includes a debounce circuit or a counter to reduce noise in the temperature sensing signal.

10. The boost power factor correction circuit as described in claim 1, wherein, The conversion control circuit also controls the boost power stage circuit to operate in a boundary conduction mode or a discontinuous conduction mode based on the zero current point.

11. The boost power factor correction circuit as described in claim 1, wherein, The first terminal of the second inductor is coupled to the zero-current detection pin through the zero-current detection resistor, thereby generating the zero-current detection voltage at the zero-current detection pin.

12. The boost power factor correction circuit as described in claim 1, wherein, The clamping and detection circuit also generates the temperature sensing threshold based on the zero-current detection voltage.

13. A conversion control circuit, characterized in that, A boost power factor correction circuit is used to convert an input voltage to generate a power factor corrected output voltage, and includes: a boost power stage circuit including a first switch and a first inductor coupled to each other; a current sensing element coupled to the first switch for generating a current sensing signal based on the current flowing through the first switch; a temperature sensing element non-contactly coupled to the first inductor for generating a temperature sensing signal; a second inductor coupled to the first inductor via electromagnetic induction, wherein a first terminal of the second inductor is coupled to the temperature sensing element; and a zero-current sensing resistor; a conversion control circuit for operating the first switch to control the first inductor to switch between the output voltage and a ground potential according to a duty cycle, thereby converting the input voltage to generate the output voltage, wherein the conversion control circuit is an integrated circuit, and the conversion control circuit includes: A shared pin is coupled to the temperature sensing element and the current sensing element; A current sensing circuit is used to sense a multitasking sensing signal through the shared pin when the first switch is turned on. At this time, the multitasking sensing signal is related to the current sensing signal, and the switching control circuit is used to control the duty cycle according to the current sensing signal. A temperature sensing circuit is used to sense the multitasking sensing signal through the shared pin when the first switch is not turned on. At this time, the multitasking sensing signal corresponds to the temperature sensing signal. When the temperature sensing signal exceeds a temperature sensing threshold, it indicates that the temperature to be measured is higher than a preset temperature threshold. A zero-current sensing pin, wherein the zero-current sensing resistor is coupled between the zero-current sensing pin and a first terminal of the second inductor; and A clamping and detection circuit is used to clamp a zero current detection voltage on the zero current detection pin to ensure that it is not lower than a preset negative voltage, and to detect the zero current detection voltage to determine the zero current point when the current of the first inductor reaches 0. The temperature sensing signal is related to the difference between the input voltage and the output voltage, and at least one electrical parameter of the temperature sensing element that changes with the measured temperature.

14. The conversion control circuit as described in claim 13, wherein, The second inductor and the first inductor form a transformer, the first inductor corresponding to a first winding of the transformer, and the second inductor corresponding to a second winding of the transformer.

15. The conversion control circuit as described in claim 13, wherein, The temperature sensing circuit is used to sense the temperature sensing signal through the shared pin during a demagnetizing period of the second inductor.

16. The conversion control circuit as described in claim 13, wherein, The boost power factor correction circuit also includes a unidirectional conducting element coupled between the second inductor and the temperature sensing element, thereby ensuring that the voltage of the shared pin is not less than 0.

17. The conversion control circuit as described in claim 16, wherein, The boost power factor correction circuit also includes: A voltage divider resistor is coupled to the unidirectional conducting element; and A filter resistor is coupled between the current sensing signal and the multitasking sensing signal to filter the current sensing signal and generate the multitasking sensing signal. The second inductor generates an auxiliary voltage through electromagnetic induction. When the first switch is not turned on, the voltage divider resistor, the temperature sensing element, the filter resistor, and the current sensing element are used to divide the auxiliary voltage to generate the multitasking sensing signal. At this time, the multitasking sensing signal is related to the temperature sensing signal.

18. The conversion control circuit as described in claim 13, wherein, The temperature sensing element is a thermistor with a positive or negative temperature coefficient, wherein the temperature sensing signal is proportional to the difference between the output voltage and the input voltage and inversely proportional to the resistance value of the thermistor.

19. The conversion control circuit as described in claim 18, wherein, The current sensing element is a current sensing resistor connected in series with the first switch. The temperature sensing signal is also proportional to the turns ratio between the second inductor and the first inductor, and the temperature sensing signal is also proportional to a voltage divider of the difference between the output voltage and the input voltage. The voltage divider is related to the resistance value of the temperature-sensitive resistor and the resistance value of the current sensing resistor.

20. The conversion control circuit as described in claim 13, wherein, Also includes: A pulse width control circuit is used to generate a pulse width modulation signal and determine the duty cycle based on the output voltage and a current correlation signal related to the current sensing signal, wherein the pulse width modulation signal is used to control the first switch to switch according to the duty cycle, and wherein the pulse width control circuit is also used to generate an enable signal related to the pulse width modulation signal. The temperature sensing circuit includes: A comparison circuit, coupled to the shared pin, is used to compare the temperature sensing signal with the temperature sensing threshold when the enable signal indicates that the first switch is off, in order to determine whether the temperature to be measured is higher than the preset temperature threshold.

21. The conversion control circuit as described in claim 13, wherein, It also includes a debounce circuit or a counter to reduce noise in the temperature sensing signal.

22. The conversion control circuit as described in claim 13, wherein, The boost power stage circuit is controlled to operate in either a boundary conduction mode or a discontinuous conduction mode based on the zero current point.

23. The conversion control circuit as described in claim 13, wherein, The first terminal of the second inductor is coupled to the zero-current detection pin through the zero-current detection resistor, thereby generating the zero-current detection voltage at the zero-current detection pin.

24. The conversion control circuit as described in claim 13, wherein, The clamping and detection circuit also generates the temperature sensing threshold based on the zero-current detection voltage.

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