Totem-pole PFC equipped with surge protection circuit and surge protection method for use in totem-pole PFC

Abstract

To provide a totem pole PFC provided with a surge protection circuit.SOLUTION: A totem pole PFC comprises: at least one bypass-diode branch with at least two bypass-diodes; at least one switch branch with at least two switches; at least one polarity changer branch with at least two switches; an input bridge connecting the switch branch(es) with an input voltage source; and at least one bypass branch connecting the input bridge in parallel with the bypass-diodes of the bypass-diode branch(es). A surge protection circuit comprises: at least one current sensor configured to detect a current flowing through at least one of the bypass-diodes of the bypass-diode branch(es); and a control unit configured to receive a detected current value from the current sensor(s) and to switch at least one switch of the totem pole PFC at least in dependence on the detected current value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a totem-pole PFC (power factor correction circuit) equipped with a surge protection circuit and a surge protection method for use in a totem-pole PFC. [Background technology]

[0002] Conventional PFC power converters, for example known from US 2012 / 0294053 A1 or US 2020 / 0161962 A1, are generally used for reducing power grid interference due to power harmonics and reducing power grid noise. In particular, during initial product testing of the PFC and during its use, the voltage supplied from the input voltage source (e.g., the power grid) tends to generate surge voltages. In such cases, surge protection circuits are commonly used to protect the device from destruction caused by these surge voltages and their induced currents. However, no conventional surge protection circuit can adequately and reliably protect a totem-pole PFC. In particular, conventional surge protection circuits do not provide suitable surge protection for a totem-pole PFC with a polarity converter. Summary of the Invention [Problem to be solved by the invention]

[0003] An object of the present invention is to provide a totem-pole PFC with a surge protection circuit that can adequately, reliably and quickly react to a surge voltage and protect the totem-pole PFC. Another object of the present invention is to provide a surge protection method for a totem-pole PFC that can adequately, reliably and quickly protect the totem-pole PFC from a surge voltage.

[0004] The solution to this object is achieved by the subject matter of the independent claims. The dependent claims contain advantageous embodiments of the invention. [Means for solving the problem]

[0005] The present invention relates to a totem-pole PFC with a surge protection circuit, where the totem-pole PFC includes at least one bypass diode branch with at least two bypass diodes, at least one switch branch with at least two switches, at least one polarity converter branch with at least two switches, and an input bridge connecting the switch branch with an input voltage source. The totem-pole PFC also includes at least one bypass branch connecting the input bridge in parallel with a bypass diode of the bypass diode branch. The surge protection circuit includes at least one current sensor configured to detect a current flowing through at least one bypass diode of the bypass diode branch. The surge protection circuit further includes a control unit configured to receive a detected current value from the current sensor and switch at least one switch of the totem-pole PFC based at least on the detected current value.

[0006] A totem-pole PFC with a surge protection circuit has the advantage that a current sensor can adequately detect the surge voltage by detecting the current flowing through at least one bypass diode in the bypass diode branch.

[0007] Preferably, the at least one current sensor is a current transducer, preferably a Hall effect sensor, more preferably a magneto resistive (AMR) sensor. Additionally or alternatively, the at least one current sensor is preferably a shunt resistor.

[0008] Preferably, current flows through the bypass diode branch only during and immediately after the initial start-up of the PFC device and when the input voltage source receives a surge voltage. Thus, the present invention quickly and reliably detects the occurrence of a surge voltage by detecting the current flowing through the bypass diode branch.

[0009] Preferably, the term "initial start-up" refers to the state when the device is turned on, especially for the first time and / or after being completely shut down.

[0010] In addition to advantageously detecting and protecting against surge voltages, the surge protection circuitry is preferably also able to detect and accordingly protect against power line disturbances (PLDs).

[0011] Preferably, the totem pole PFC includes a capacitor, particularly at its output side, which is charged during start-up of the totem pole PFC. Preferably, current flows through the bypass diode branch only during the capacitor charging, in the absence of a surge voltage. In other words, when the capacitor is fully charged, no current flows through the bypass diode during operation of the totem pole PFC, unless a surge voltage is present.

[0012] Preferably, the term "no current" means "essentially no current". In other words, small induced currents, e.g., due to electromagnetic interference, are not necessarily excluded by the term "no current". Also, for example, "no current" preferably means "no intentional current", i.e., the totem-pole PFC and surge protection circuits are designed such that there is no intentional current flowing at the time and / or location referred to by the term "no current", e.g., via explicit switching of devices supplying current.

[0013] Preferably, the current sensor is arranged in the bypass branch, more preferably at a node of the bypass branch, in particular between the connection point of the bypass branch with the input bridge and the connection point of the bypass branch with the bypass diode branch.

[0014] Preferably, the surge protection circuit includes a plurality of current sensors, where each bypass diode of the bypass diode branches is connected in series with at least one of the current sensors, and preferably, each bypass diode of the one or more bypass diode branches is connected to at least one current sensor of the plurality of current sensors.

[0015] Advantageously, at least one bypass diode branch is connected in parallel with at least one switch branch, whereby one or more current sensors are respectively arranged at a node between a junction point of the bypass diode branch and the bypass branch and a junction point of the bypass diode branch and the switch branch.

[0016] More preferably, the first current sensor is arranged at a node between a connection point between the bypass diode branch and the bypass branch and a connection point between the bypass diode branch and at least one high-side switch of the switch branch. More preferably, the second current sensor is arranged at a node between a connection point between the bypass diode branch and the bypass branch and a connection point between the bypass diode branch and the low-side switch of the switch branch.

[0017] Advantageously, the totem-pole PFC includes one or more of the above-mentioned switch branches and one polarity converter branch. In case of multiple switch branches, the switch branch closest to the bypass diode branch may be referred to as the first switch branch. The first switch branch has a direct connection point with the bypass diode branch. One or more other switch branches may be referred to as the second or more switch branches, and have a direct connection point with the first switch branch while preferably not having a direct connection point with one or more or any of the bypass diode branches.

[0018] Preferably, when the totem-pole PFC includes multiple current sensors, at least one current sensor is arranged at each node connecting the junction of the bypass diode branch and the bypass branch and the junction of the first switch branch, i.e. at least one of the high-side node and the low-side node between the bypass diode branch and the first switch branch, preferably in addition to or as an alternative to the at least one current sensor arranged in the bypass branch.

[0019] In one advantageous embodiment, the totem-pole PFC includes just one bypass diode branch.

[0020] Preferably, the totem pole PFC comprises one or more, preferably two or more, preferably three or more, more preferably four or more switch branches. Preferably, the totem pole PFC comprises exactly one or exactly two or exactly three switch branches. More preferably, each switch branch comprises exactly two switches.

[0021] More preferably, the totem-pole PFC comprises exactly one polarity converter branch. Advantageously, the polarity converter branch comprises exactly two switches.

[0022] Preferably, any or all of the switches of the totem-pole PFC are connected with anti-parallel diodes, in particular each switch, in the illustrative example of MOSFET switches, these switches are preferably anti-parallel body diodes.

[0023] Preferably, the bypass diode branch is coupled in parallel with the two switch branches.More preferably, the polarity converter branch is coupled in parallel with the switch branch and the bypass diode branch.

[0024] Advantageously, the polarity converter branch is additionally coupled in parallel with the input voltage source, in particular via a bypass branch.More preferably, the totem-pole PFC comprises a polarity converter bridge connecting the polarity converter branch with the input voltage source.

[0025] In one embodiment, the control unit preferably includes a latch for switching off at least one switch of the totem-pole PFC and a latch reset input for resetting the latch, where the latch reset input is particularly configured to receive a latch reset signal from a digital signal processor, preferably included in the totem-pole PFC, particularly in a surge protection circuit of the totem-pole PFC.

[0026] Preferably, the latch is an integrated logic latch.More preferably, the latch is a discrete transistor / MOSFET circuit, in particular implemented with diode feedback.More preferably, the latch is an integrated driver, in particular implemented with diode feedback for self-holding.

[0027] Preferably, the latch is of the edge-triggered flip-flop type.

[0028] Preferably, the latch actively switches off each switch (via an OFF signal) or passively switches off the switch (without an ON signal), depending in particular on whether each switch is a normally-on switch or a normally-off switch.

[0029] More preferably, the control unit includes a comparator for comparing the detected current with a predetermined protective current value.

[0030] Preferably, the comparator is an integrated operation amplifier (OPV). More preferably, the comparator is an integrated comparator (IC). More preferably, the comparator is an integrated driver, in particular using a constant input level of the driver.

[0031] Preferably, the predetermined protection current value is a predetermined value higher than the start-up current value of the PFC. For example, during start-up of the totem-pole PFC, a current of, for example, 30A may be generated in one or more bypass diodes of the bypass diode branch. Preferably, the predetermined protection current value is set higher than 30A, preferably between 30A and 100A. However, preferably, the predetermined protection current value is less than 300A.

[0032] In one advantageous embodiment, the comparator outputs a latch input signal for use in a latch of the control unit, and thus, preferably, when the comparator determines that the detected current is greater than or equal to a predefined protection current value, the comparator outputs a latch input signal, which controls the latch to switch at least one switch of the totem-pole PFC.

[0033] Preferably, the comparator is a Schmitt trigger or an analog comparator. If the comparator is preferably a Schmitt trigger, its lower threshold is preferably set within a predetermined range of the start-up current through the bypass diode branch. More preferably, its upper threshold is preferably set at a pre-defined protection current value. Thus, the comparator does not output a latch input signal during start-up of the totem-pole PFC. If the protection circuit is triggered during start-up or PLD (power line interference), the control unit recognizes this and resets the latch. The PFC continues and normal operation can then proceed.

[0034] Preferably, the control unit is configured to switch the at least one switch of the totem-pole PFC based on the detected current and a predefined duration after the totem-pole PFC is switched on. Thus, preferably, the surge protection circuit does not switch the at least one switch of the totem-pole PFC in response to a current through the at least one diode resulting from start-up of the device.

[0035] Preferably, the control unit, in particular the latch of the control unit, is configured to switch off all switches of the totem-pole PFC. In particular, the control unit is preferably configured to switch off all switches of all switch branches and all polarity converter branches.

[0036] Preferably, said switching OFF of each switch is realized by the control unit outputting an active OFF signal, in particular in the preferred case where the switch or switches are of a normally ON type. Alternatively or additionally, in the preferred case where the switch or switches are of a normally OFF type, the control unit is configured to switch off each switch by not providing an ON signal and / or by ceasing to output an ON signal.

[0037] The invention further relates to a surge protection method for a totem-pole PFC, the totem-pole PFC comprising at least one bypass diode branch with at least two bypass diodes, at least one switch branch with at least two switches, at least one polarity converter branch with at least two switches, an input bridge connecting the switch branch with an input voltage source, and at least one bypass branch connecting the input bridge in parallel with bypass diodes of the bypass diode branch, the surge protection method comprising the steps of: detecting and / or measuring a current through at least one bypass diode of the bypass diode branch by means of at least one current sensor; comparing the detected current value with a predefined protection current value; switching at least one switch of the totem-pole PFC to a switched state, in particular to an off state, if the detected current value is equal to or greater than the protection current value.

[0038] Preferably, the surge protection method is performed by a totem-pole PFC including a surge protection circuit according to any one of the above-mentioned embodiments. In particular, the surge protection method is preferably performed by a control unit of the totem-pole PFC including a surge protection circuit according to any one of the above-mentioned embodiments.

[0039] Preferably, the surge protection method includes the step of holding the switched state, preferably the off state, with a latch for a predetermined latch duration, wherein the surge protection method includes the step of resetting the latch after the predetermined latch duration.

[0040] Preferably, the surge protection method resets the latch when the detected current value is less than or equal to the protection current value and the latch duration time has elapsed.

[0041] More preferably, all the switches of the totem-pole PFC are switched to an off state when the detected current value is equal to or greater than the protection current value.

[0042] In one preferred embodiment, the method includes waiting a predetermined duration after the totem-pole PFC is shut on before switching the at least one switch to an off state. Preferably, the waiting step is performed by isolating at least one of a comparator and a latch of the surge protection circuit from the totem-pole PFC.

[0043] Preferably, the steps of holding the OFF state for a predefined latch duration and comparing the detected current value with the predefined protection current value are preferably repeated alternately. In other words, the surge protection method includes, once the predefined latch duration has elapsed, the surge protection method (again) compares the detected current value with the predefined protection current value and resets the latch if the detected current value is less than or equal to the protection current value. If in this case the detected current value is (still) not less than or equal to the protection current value, the surge protection method does not reset the latch after the predefined latch duration. Preferably, if the detected current value is not less than or equal to the protection current value, the surge protection method resets the predefined latch duration and holds the OFF state for the predefined latch duration (again).

[0044] Preferably, and particularly as an alternative to the above-mentioned re-measuring and comparing the current value, the surge protection method resets the latch after a predefined latch duration without re-measuring and re-comparing the current value, where if the current value is (still) equal to or greater than the protection current value, the surge protection method re-latches the switch to the off state.

[0045] Preferably, the latch is reset to allow normal operation of the totem-pole PFC. [Brief description of the drawings]

[0046] Further details, advantages and features of the preferred embodiment of the present invention are described in detail with reference to the drawings. [Figure 1] 1 shows a circuit diagram and a schematic diagram of an input surge voltage of a totem-pole PFC with a surge protection circuit according to a first embodiment of the present invention; [Diagram 2]1 shows a circuit diagram and a schematic diagram of an input surge voltage of a totem-pole PFC with a surge protection circuit according to a first embodiment of the present invention; [Diagram 3] 1 shows a circuit diagram and a schematic diagram of an input surge voltage of a totem-pole PFC with a surge protection circuit according to a first embodiment of the present invention; [Figure 4] 1 shows a circuit diagram of a totem-pole PFC with a surge protection circuit according to a first embodiment of the present invention and a schematic diagram of an input surge voltage and an input signal of a polarity converter of the totem-pole PFC; [Diagram 5] 1 shows a functional circuit schematic diagram of a surge protection circuit and a control unit of a totem-pole PFC with a surge protection circuit according to a first embodiment of the present invention; [Figure 6] 1 shows a circuit diagram of a totem-pole PFC with a surge protection circuit according to a second embodiment of the present invention. [Figure 7] 1 shows a schematic block diagram of a surge protection method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] In particular, Figures 1-4 show a first embodiment of a totem-pole PFC 1 with a surge protection circuit 2. As shown in Figures 1-3, a surge voltage is introduced by an input voltage source 10. In Figure 4, the inlet shows a wrong switching operation of the polarity converter 7, and a surge current is also introduced into the totem-pole PFC 1.

[0048] As can be seen in detail from the circuit diagram of Figure 1, the totem-pole PFC 1 of this embodiment includes one bypass diode branch 3 with two bypass diodes 4. For simplicity, the two bypass diodes 4 shown in the drawing are referred to as elements of a single bypass diode branch 3, and the presence of additional coupling or connection points therein (e.g., in the description of bypass branch 11 below) does not affect this representation. The same or similar representation is used for the switch branch 5 and polarity converter branch 7.

[0049] The totem-pole PFC 1 includes one or more switch branches 5. In this embodiment, the totem-pole PFC 1 includes two switch branches 5. Each switch branch 5 includes two switches 6.

[0050] The totem-pole PFC 1 also includes a polarity converter branch 7 that includes two switches 8 (polarity converter switches 8). The polarity converter branch 7 is used to change the polarity of the signal output from the switch branch 5 to an appropriate DC voltage at the capacitor branch 12 with the capacitor 13 and output 14 of the totem-pole PFC 1.

[0051] The totem-pole PFC 1 also includes an input bridge 9 connecting each of the switch branches 5 with an input voltage source 10. The input bridge 9 includes one inductance branch 15 for each switch branch 5, connecting each switch branch 5 with the input voltage source 10.

[0052] The totem-pole PFC 1 also includes an electromagnetic interference filter 16 (EMI filter 16).

[0053] The totem-pole PFC 1 further includes a bypass branch 11 connecting the input bridge 9 in parallel with the bypass diodes 4 of the bypass diode branch 3. As will be explained in more detail below, current flows through the bypass branch 11 only during start-up of the totem-pole PFC 1, in particular during the charging operation of the capacitor 13 and during the introduction of a surge voltage by the input voltage source 10.

[0054] In the following description of the surge input voltage, it is assumed that the capacitor 13 is already charged, in particular fully charged, or in other words, that a predefined start-up time has elapsed.

[0055] A voltage source 10, for example a power grid, introduces an AC voltage, as shown in the introductory portion of Figure 1. In the case shown in Figure 1, the voltage source 10 introduces a high surge voltage into a positive phase of the (otherwise regular) AC voltage.

[0056] 1, the polarity converter branch 7 is in the intended or correct state via its polarity converter switch 8, i.e., the high-side polarity converter switch 8 is OFF and the low-side polarity converter switch 8 is ON. In this case, "high-side" and "low-side" refer to the polarity of the output signal voltage at the output 14 of the totem-pole PFC 1.

[0057] In the case of a high surge voltage in FIG. 1, the current, i.e., the surge current, flows through the bypass branch 11. surge As shown in FIG. 1, the surge current generated by the high surge voltage flows out of the voltage source 10, through the bypass branch 11, the high-side bypass diode 4, the capacitor 13, the low-side polarity converter switch 8 in the ON state, through the polarity converter bridge 17 to the EMI filter 16 and the voltage source 10.

[0058] This causes high surge currents to flow especially through the low-side switch 8 of the polarity converter branch 7, which can cause destruction of the device.

[0059] To mitigate this, the totem-pole PFC 1 includes a surge protection circuit 2, as shown in FIGS.

[0060] Fig. 5 shows a detailed functional circuit diagram of the control unit 21 of the surge protection circuit 2 of this embodiment. Fig. 1 shows the current sensor 18 of the surge protection circuit 2. In this embodiment, the current sensor 18 is arranged in the bypass branch 11.

[0061] Preferably, the current sensor 18 is arranged at a node of the bypass branch 11 between a first connection point 24 of the bypass branch 11 and the input bridge 9 and a second connection point 25 of the bypass branch 11 and the bypass diode branch 3.

[0062] The control unit 21 includes a comparator 19, in particular a hardware-based comparator, which compares the current measured by the current sensor 18 (see also FIG. 1) with a predefined protective current value 27. The current measured by the current sensor 18 is represented as “i surge_measure " is expressed as follows.

[0063] The predetermined protection current value 27 is a current value, particularly an absolute value, such that a surge current having (and / or higher than) this value may cause damage and / or destruction of the totem-pole PFC 1. The protection current value 27 is input to the comparator 19 via the signal processing unit 23 and is particularly set to a constant value.

[0064] The signal processing unit 23 is preferably an element of the totem-pole PFC 1 and / or the surge protection circuit 2. Preferably, the signal processing unit 23 is further configured to control the totem-pole PFC 1, especially during normal operation. Further preferably, the signal processing unit 23 is part of the control unit 21 or, preferably, is a separate unit thereto. Preferably, the signal processing unit 23 is a digital signal processor.

[0065] The control unit 21 of the surge protection circuit 2 also includes a latch 20, which detects the current measured by the current sensor 18, i.e., the detected “i surge_measure If the current is greater than or equal to the predetermined protection current value 27, the comparator 19 inputs a latch signal to the latch 20.

[0066] In this embodiment, the latch 20 is further configured to output an OFF signal to all switches 6, 8 of the totem-pole PFC 1. This causes all switches 6, 8, including the switches in switch branch 5 and the switches in polarity converter branch 7, to be switched to an OFF state. In this regard, depending on whether each switch is a normally-on switch or a normally-off switch, the latch 20 can either actively switch off the switches (via an OFF signal) or passively switch off the switches 6, 8 (without an ON signal).

[0067] Thereby, the surge protection circuit 2 reliably and quickly switches off all the switches 6, 8 to protect the totem-pole PFC 1 from destruction when a surge voltage occurs.

[0068] The signal processing unit 23 is also configured to output a latch reset signal 22 to the latch 20 to reset the latch 20 and thereby restore normal operation of the totem-pole PFC 1 .

[0069] The signal processing unit 23 is particularly configured to output a latch reset signal 22 after a predefined latch duration, after which the signal processing unit 23 outputs the latch reset signal 22. If the current sensed by the current sensor 18 is then below the protection current value 27, normal operation of the totem-pole PFC 1 resumes. On the other hand, if the current sensed by the current sensor 18 is (still or again) above the protection current value 27, the latch 20 latches again and switches off all the switches 6, 8.

[0070] As previously mentioned, during normal start-up operation of the totem-pole PFC 1 , as the capacitor 13 charges, current flows through the bypass diode 4 and the current sensor 18 .

[0071] In order to prevent the latch 20 from switching off the switches 6, 8 during normal start-up operation (i.e. no surge voltage is input via the input voltage source), the control unit 21 and / or the signal processing unit 23 are preferably configured to set the protection current value 27 to a suitable level that is equal to or greater than the start-up current surge value that flows during normal start-up operation.

[0072] Additionally or alternatively, the control unit 21 and / or the signal processing unit 23 are preferably configured to switch the switches 6, 8 according to a predefined duration after the totem-pole PFC 1 is switched on, in particular via the latch 20. Preferably, the predefined duration is the time required to at least partially, in particular fully, charge the capacitor 13 after an initial start-up of the totem-pole PFC 1.

[0073] To achieve this, the control unit 21 and / or the signal processing unit 23 are preferably configured to turn off at least one of the comparator 19 and the latch 20 for a predefined duration. Preferably, the signal processing unit 23 is configured to output a constant latch reset signal to the latch 20 within the predefined activation duration, such that the latch 20 does not latch.

[0074] In a preferred embodiment, the comparator 19 is a Schmitt trigger having a lower threshold and an upper threshold. In this case, the lower threshold is preferably set at least to the startup surge current flowing through the bypass diode 4 during startup operation of the totem-pole PFC 1. For example, the current is about 30A, but it can be larger or smaller depending on device characteristics and usage. Also, the upper threshold is preferably set to a predetermined protection current value. Thereby, when the upper threshold, i.e., the protection current value, is reached, the Schmitt trigger only outputs a latch signal (e.g., a high signal, i.e., "1"), and when the detected current is below the startup surge current, the Schmitt trigger does not output a latch signal (e.g., a low signal, i.e., "0").

[0075] In a preferred embodiment, the output of comparator 19 is input to signal processing unit 23, which outputs a latch signal to latch 20. In this case, when comparator 19 outputs a high signal, signal processing unit 23 preferably outputs a latch signal to latch 20, and preferably when comparator 19 outputs a low signal, signal processing unit 23 outputs a latch reset signal to latch 20.

[0076] This allows the surge protection circuit 2 to properly and reliably protect the totem-pole PFC 1 from an overcurrent caused by a surge voltage input from the input voltage source 10. The charged capacitor 13 makes it possible to prevent an interruption in the output of the totem-pole PFC 1 during surge protection.

[0077] FIG. 2 shows a circuit schematic and an input surge voltage schematic of a totem-pole PFC 1 with a surge protection circuit 2 according to a first embodiment of the present invention.

[0078] As can be seen from the introductory part of Fig. 2, in this example, the input voltage source 10 inputs a negative or low surge voltage during the (normal) positive phase period of the input AC voltage. In this case, since the phase of the input AC voltage is positive before the low surge, the polarity converter branch 7 is switched as shown in Fig. 1. The high side polarity switch 8 is OFF and the low side polarity switch 8 is ON.

[0079] In this case, the generated surge current "i surge " flows out of the voltage source 10, flows through the polarity converter bridge 17, the low-side polarity switch 8 in the ON state, the low-side bypass diode 4, and the bypass branch 11, and returns to the voltage source 10. This can cause damage to the low-side polarity switch 8 in particular due to the high surge current that flows through it. This is prevented by the surge protection circuit 2, as the surge current flows through the bypass branch 11, in which the current sensor 18 is located.

[0080] 3 shows a further example of a surge voltage, where the input voltage source 10 inputs a negative or low surge voltage during a (normal) positive phase of the input AC voltage, and then abruptly switches to the negative phase of the AC voltage, causing the AC voltage to become negative after the surge voltage.

[0081] In this case, an initial positive phase of the input AC voltage causes the polarity converter branch 7 to switch as shown in Figures 1 and 2. However, a sudden switch to a negative phase of the input AC voltage causes the polarity converter branch 7 to essentially go into a faulty switching configuration. In contrast to the case shown in Figure 3, in normal operation, during the negative phase, the low-side polarity converter switch 8 should be OFF and the high-side polarity converter switch 8 should be ON.

[0082] Thus, a surge or short circuit current flows from the voltage source 10 through the polarity converter bridge 17, the low-side polarity converter switch 8 in the ON state, the low-side bypass diode 4, and the bypass branch 11 back to the voltage source 10. This can cause damage to the low-side polarity switch 8 in particular due to the high surge current that flows through it. This is prevented by the surge protection circuit 2 as the surge current flows through the bypass branch 11 in which the current sensor 18 is located.

[0083] FIG. 4 shows a circuit diagram of a totem-pole PFC 1 with a surge protection circuit 2 according to a first embodiment of the present invention, and a schematic diagram of the input surge voltage and the input signal of the polarity converter 7 of the totem-pole PFC 1.

[0084] In the example shown in FIG. 4, instead of the input voltage source 10 receiving a surge voltage, the polarity converter branch 7 is switched on incorrectly.

[0085] 4 shows the input voltage (inlet bottom) and the control signal (inlet top) of the polarity converter branch 7, where a positive signal corresponds to the low side polarity converter switch 8 being ON, a negative signal corresponds to the low side polarity converter switch 8 being OFF, and the high side polarity converter switch 8 being switched in the opposite manner.

[0086] In normal operation, as also described above with respect to Figures 1-3, when the AC input voltage switches from positive to negative, the high-side polarity converter switch 8 switches from OFF to ON and the low-side polarity converter switch 8 switches from ON to OFF. In other words, during a positive phase of the AC input voltage, the high-side polarity converter switch 8 should be in the OFF state (which is correctly switched as shown in Figures 1-3) and the low-side polarity converter switch 8 should be in the ON state.

[0087] Thus, in the case of FIG. 4, due to the negative phase of the input AC voltage being reached, the high-side polarity converter switch 8 should be in the ON state. The low-side polarity converter switch 8 should accordingly be in the OFF state. However, now the low-side polarity converter switch 8 is mistakenly switched back to the ON state. As shown in the horizontal center of the top inlet of FIG. 4, the switch signal of the low-side polarity converter switch 8 is first switched from a positive signal (corresponding to ON) to a negative signal (corresponding to OFF), as shown in the circuit diagram of FIG. 4, which is correct, but then mistakenly switched back to a positive signal (corresponding to ON).

[0088] In this case, the surge current will flow in the same way as in Fig. 3, because the incorrect switching in Fig. 4 is essentially equivalent to the correct switching when a reverse surge voltage is introduced by the AC voltage shown in Fig. 3. This may result in, in particular, the low-side polarity switch 8 being damaged due to the high surge current that will flow through it. This is prevented by the surge protection circuit 2, because the surge current will flow through the bypass branch 11, in which the current sensor 18 is located, and will be detected in the bypass branch 11.

[0089] In this way, in any of the above cases, as well as in the case of surge voltages and / or faulty switching of the polarity converter 7, the surge protection circuit 2 can protect the switches 6, 8 of the protective totem-pole PFC 1 from overcurrent and potential breakdown thereof.

[0090] FIG. 6 shows a second preferred embodiment of a totem-pole PFC 1 with a surge protection circuit 2 .

[0091] In particular, Figure 6 shows an alternative or additional arrangement of the current sensor 18 compared to Figures 1 to 4. Preferably, the second embodiment includes a control unit 21 and / or a digital signal processor 23 of the surge protection circuit 2 as described above, with particular reference to Figures 1 and 5.

[0092] Here, the surge protection circuit 2 includes two additional current sensors 18, each detecting the current flowing through one of the high-side and low-side bypass diodes 4. If the surge protection circuit 2 preferably includes only these two additional current sensors 18, especially if there is no current sensor 18 in the bypass branch 11, the surge protection circuit 2 can more reliably detect and protect against all surge voltage situations since the surge current always flows through one of the bypass diodes 4.

[0093] Preferably, each of these current sensors 18 is connected in series with one bypass diode 4 .

[0094] As can be seen from Figs. 1 to 4 and 6, the bypass diode branch 3 is connected in parallel with at least one (in this case exactly two) switch branch 5. Thereby, a third connection point 26 between the bypass diode branch 3 and the switch branch 5 is formed. Preferably, the current sensor 18 is arranged at a node between the second connection point 25 between the bypass branch 11 and the bypass diode branch 3 and the corresponding third connection point 26. Preferably, the first current sensor 18 is arranged at a node between the second connection point 25 and the third connection point 26 on the low side. Furthermore, the second current sensor 18 is arranged at a node between the second connection point 25 and the third connection point 26 on the high side.

[0095] The control unit 21 also preferably includes two or more comparators 19 and / or two or more latches 20 to account for multiple current sensors 18 .

[0096] Additionally or alternatively, the control unit 21 preferably includes at least one combiner circuit for combining current value outputs from different current sensors 18 into a common signal for use in particular by the comparator 19. Additionally or alternatively, the control unit 21 preferably includes at least one combiner circuit for combining output signals of corresponding comparators 19 for use in the latch 20 into a common signal for use in particular by the latch 20.

[0097] The above-described configuration of two current sensors 18 should be understood as being in addition to or as an alternative to the current sensor 18 located in the bypass bridge 11.

[0098] 7 shows a schematic block diagram of a surge protection method for a totem-pole PFC 1 according to one embodiment of the present invention. Preferably, the surge protection method is performed in or using the totem-pole PFC 1 described above with reference to FIGS. 1 to 6, which will be described later. Any of the above embodiments and examples describing the functional configuration of the totem-pole PFC 1 and / or the surge protection circuit 2 and / or the control unit 21 and / or the digital signal processor 23 should also be understood as a preferred embodiment and example of the surge protection method used for the totem-pole PFC 1.

[0099] Preferably, the surge protection method is separate from, and in particular in addition to, the normal operation method of the PFC 1, ie the power factor correction method which drives the switches 6, 8 in response to a (normal, non-surge) input voltage.

[0100] The surge protection method includes the step 100 of measuring the current through at least one bypass diode 4 of the bypass diode branch 3 by means of at least one current sensor 18 .

[0101] The surge protection method further includes a step 200 of comparing the current value 100 detected by the current sensor 18 with a predetermined protective current value 27. Step 200 is particularly performed using the comparator 19.

[0102] The surge protection method further comprises step 300, in which at least one switch 6, 8 of the totem-pole PFC 1 is preferably switched to an OFF state if the detected current is equal to or greater than the protective current value 27. In particular, said switching operation 300 is preferably performed only if the detected current is equal to or greater than the protective current value. Preferably, said switching operation does not correspond to a (normal) switching operation of the switches 6, 8 for normal operation (i.e. power factor correction of the PFC 1).

[0103] Preferably, the switching operation 300 switches off all the switches 6, 8.

[0104] The surge protection method according to the present embodiment further includes step 400, specifically utilizing latch 20 to maintain the off state for a predetermined latch duration.

[0105] Preferably, the latch duration is between 50 μs and 100 μs, inclusive.

[0106] The surge protection method also includes a step 500 of resetting the latch 20 after a predetermined latch duration has elapsed, preferably if the detected current value is less than or equal to the protection current value 27 .

[0107] If the detected current value after the predetermined latch duration may not be less than or equal to the protective current value 27, i.e., if the latch 20 is reset in step 500, the surge protection method includes an additional preferred loop back to step 100. Then, during and / or after the reset 500 of the latch 20, the surge protection method again detects or measures the current by the current sensor 18 (step 100) and repeats steps 200-500.

[0108] The surge protection method also includes an optional and preferred step 600, which includes waiting a predefined duration after the totem-pole PFC 1 has been shut on before performing a switch-off of any or all switches 6, 8 in response to a surge current. The optional step 600 may be performed before step 100, such that the surge protection method comprising steps 100-500 is initiated only after the predefined duration. Additionally or alternatively, the optional step 600 is preferably performed before the switching step 300, preferably after the detection step 100 and / or after the comparison step 200.

[0109] As explained above with respect to FIG. 1, in addition to or as an alternative to optional step 600, the surge protection method preferably switches off the switches 6, 8 only if the surge current is higher than the starting surge current by setting the predetermined protection current value 27 higher than the (typical) surge current (start-up surge current), e.g. higher than 30A.

[0110] The above surge protection method is preferably performed by the surge protection circuit 2, in particular by the preferably control unit 21 and / or the preferably signal processing unit .

[0111] By using the surge protection method of the present embodiment, the totem-pole PFC 1 can be reliably and quickly protected from damage or destruction caused by surge voltage and / or surge current and / or PLD (power line interference).

[0112] In addition to the above written description of the invention, explicit reference is made to Figures 1 to 7, which show the features of the invention in detail. The drawings show specific technical details regarding the circuit configurations of the branches and elements described above, in particular the parallel and series connections. However, it should be emphasized that in a technical sense, the circuit configurations shown in the drawings also encompass equivalents of these circuit principle diagrams, so-called "redrawings" or "simplifications". [Explanation of symbols]

[0113] 1. Totem Pole PFC 2. Surge protection circuit 3. Bypass diode branch 4. Bypass diode 5. Switch branch 6. Switch 7. Polarity converter branch 8. Switch 9. Input Bridge 10. Input voltage source 11. Bypass branch 12. Capacitor branch 13. Capacitor 14. Totem pole PFC output 15. Inductance branch 16. EMI filters 17. Polarity converter bridge 18. Current sensor 19. Comparator 20. Latch 21. Control unit 22. Latch reset signal 23. Digital signal processor 24. Bypass branch connection point 25. Bypass branch connection point 26, bypass diode branch connection point 27. Prescribed protective current value 100, detecting a current through a bypass diode 200, a step of comparing the detected current values 300, Switching Steps 400, a step of maintaining the switched OFF state of the switch 500, step to reset the latch 600, Step to wait after starting Totem Pole PFC

Claims

1. 1. A totem-pole power factor correction (PFC) circuit with surge protection circuitry, comprising: at least one bypass diode branch comprising at least two bypass diodes of the same polarity; at least one switch branch having at least two switches; at least one polarity converter branch having at least two switches; an input bridge connecting the switch branches with an input voltage source; at least one bypass branch connecting the input bridge with bypass diodes of the bypass diode branches, the bypass branch being connected to the input bridge at a first node and to the bypass diode branch at a second node; The surge protection circuit comprises: at least one current sensor configured to detect a current through at least one bypass diode of the bypass diode branch; a control unit configured to receive a detected current value from the at least one current sensor and to switch at least one switch of the totem-pole PFC based at least on the detected current value; The control unit a comparator for comparing the detected current value with a predetermined protection current value; a latch for switching off the at least one switch of the totem-pole PFC; a signal processing unit for controlling the totem-pole PFC; Including, The totem-pole PFC, wherein the signal processing unit is further used for switching the at least one switch of the totem-pole PFC based on the detected current value and a predetermined duration after the totem-pole PFC is switched on.

2. 2. The totem-pole PFC of claim 1, wherein when the detected current value is greater than or equal to the predetermined protection current value, the comparator inputs a latch signal to the latch, and the latch is used to switch off the at least one switch in the switch branch and the polarity converter branch based on the latch signal.

3. 2. The totem-pole PFC of claim 1, wherein if the detected current value is greater than or equal to the predetermined protection current value, the signal processing unit causes all the switches in the switch branch and the polarity converter branch to remain in an off state for the predetermined duration.

4. 3. The totem pole PFC of claim 2, wherein the signal processing unit is further adapted for providing a latch reset input to the latch when the detected current value is less than or equal to the predetermined protection current value and the predetermined time duration has elapsed.

5. 2. The totem-pole PFC of claim 1, wherein the surge protection circuit is further adapted for preventing current from flowing through the bypass diode branch when the detected current value is equal to or greater than the predetermined protection current value.

6. 2. The totem pole PFC of claim 1, wherein the surge protection circuit is further adapted to allow current to flow through the at least one bypass branch only during start-up, charging operation, or introduction of a surge voltage of the totem pole PFC.

7. The totem-pole PFC of claim 1 , wherein the at least one bypass diode branch is connected in parallel with the at least one switch branch.

8. The totem-pole PFC of claim 1 , wherein the at least one current sensor is disposed between a plurality of connection points of the bypass branch and the bypass diode branch.

9. 9. The totem-pole PFC of claim 8, wherein each of the at least one current sensor is disposed at a node between a junction of the bypass branch and the bypass diode branch and a junction of the bypass diode branch and the switch branch.

10. 9. The totem-pole PFC of claim 8, wherein each of the at least one current sensors is disposed at a node of the bypass branch between a connection point of the bypass branch with the input bridge and a connection point of the bypass branch with the bypass diode branch.

11. 9. The totem pole PFC of claim 8, wherein the at least one current sensor is a plurality of current sensors, the plurality of current sensors being arranged such that each bypass diode of the bypass diode branch is connected in series with at least one of the plurality of current sensors.

12. The totem pole PFC of claim 1 , wherein a predetermined protection current value is equal to or greater than a start-up current value of the totem pole PFC.

13. 1. A surge protection method for a totem-pole PFC, the totem-pole PFC including at least one bypass diode branch with at least two bypass diodes of the same polarity, at least one switch branch with at least two switches, at least one polarity converter branch with at least two switches, an input bridge connecting the switch branch with an input voltage source, and at least one bypass branch connecting the input bridge with bypass diodes of the bypass diode branch, the input bridge being connected to the input bridge at a first node and to the bypass diode branch at a second node, the surge protection method comprising: detecting a current through at least one bypass diode of the bypass diode branch by at least one current sensor; comparing the detected current value with a predetermined protection current value; and switching at least one switch of the totem-pole PFC to an off state if the detected current value is equal to or greater than the predetermined protection current value. The surge protection method further comprises waiting a predetermined duration after the totem-pole PFC is shut on before switching the at least one switch to the switched state.

14. 14. The surge protection method of claim 13, further comprising the steps of: using a latch to hold the switched state for a predetermined latch duration; and resetting the latch after the predetermined latch duration.

15. 15. The surge protection method of claim 14, wherein if the detected current value is greater than or equal to the predetermined protection current value, all switches of the totem-pole PFC are switched to an off state for the predetermined latch duration.

16. 15. The surge protection method of claim 14, further comprising resetting the latch after the predetermined latch duration has elapsed and if the detected current value is less than or equal to the predetermined protection current value.

17. 14. The method of surge protection of claim 13, further comprising the step of: allowing current to flow through the at least one bypass branch if the detected current value is greater than or equal to the predetermined protective current value.

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