Surge protection circuit and system

Abstract

A power conversion device (200) comprising a bulk capacitor (115), a current limiting resistor (151) in series with the bulk capacitor (115), and a surge current control device configured to bypass the current limiting resistor (151) when activated. The power conversion device (200) further comprises a bypass device (210) in parallel with the current limiting resistor (151), the bypass device being configured to provide a low resistance path to the bulk capacitor (115) during a power surge.

Description

TECHNICAL FIELD

[0001] Aspects of the disclosure relate to electronic components, and in particular to surge protection and inrush current limitation for electronic components. BACKGROUND

[0002] Power converters are commonly used in a wide variety of systems, including telecommunications systems, fast chargers for electric vehicles, and other applications requiring high power density and high efficiency.

[0003] General power converter designs include a variety of protection devices designed to limit voltage spikes and current surges occurring at their input ports. A common metal oxide varistor is placed between the input ports to reduce voltage spikes occurring at the input. However, this alone is not sufficient to protect power switching transistors within the converter from lightning induced surges, particularly when the input power to the converter is disabled. SUMMARY

[0004] In one embodiment, a power conversion device is provided. The power conversion device includes a bulk capacitor, a current limiting resistor in series with the bulk capacitor, and an inrush current control device configured to bypass the current limiting resistor when activated.

[0005] The power conversion device further includes a bypass device in parallel with the current limiting resistor, the bypass device configured to provide a low resistance path to the bulk capacitor during a power surge.

[0006] In another embodiment, an inrush current limitation and surge protection circuit is provided. The inrush current limitation and surge protection circuit includes a bulk capacitor, a current limiting resistor in series with the bulk capacitor, and an inrush current control device configured to bypass the current limiting resistor when activated.

[0007] The inrush current limitation and surge protection circuit further includes a bypass device in parallel with the current limiting resistor, the bypass device configured to provide a low resistance path to the bulk capacitor during a power surge. BRIEF DESCRIPTION OF DRAWINGS

[0008] Many aspects of the disclosure can be better understood with reference to the following drawings. While several implementations are described in connection with these drawings, the disclosure is not limited to the implementations disclosed herein. On the contrary, it is intended to cover all alternatives, modifications, and equivalents.

[0009] Figure 1 An example prior art power converter circuit is illustrated.

[0010] Figure 2 An example power converter circuit with bridge rectifier including inrush current limiting and surge protection is illustrated.

[0011] Figure 3 An example power converter circuit with bridgeless power factor correction including inrush current limiting and surge protection is illustrated.

[0012] Figures 4A-4D An example bypass device to limit inrush current and provide surge protection for a power converter device is illustrated.

[0013] Figure 5 An example power converter circuit with bridgeless power factor correction including inrush current limiting and surge protection is illustrated.

[0014] Figure 6 An example power converter circuit with bridge rectifier and active power factor correction including inrush current limiting and surge protection is illustrated.

[0015] Figure 7 An example power converter circuit with bridge rectifier and active power factor correction including inrush current limiting and surge protection is illustrated. DETAILED DESCRIPTION

[0016] The example embodiments described herein illustrate different methods for limiting inrush current and providing surge protection for a power converter device. These embodiments limit inrush current at power on, and provide power surge protection to the power conversion device when it is connected to an alternating current (AC) power grid but the AC power is off.

[0017] Figure 1 An example prior art AC / DC power converter circuit 100 with bridge rectifier and active power factor correction is illustrated. This circuit includes input lines 102, neutral 104, and protective ground 106. This active power factor correction circuit includes inductor LI 131, diode D6 126, and power switch transistor Ql 141. Power switch transistor Ql 141 is susceptible to large voltage spikes and current surges and must be protected from damage.

[0018] In this prior art embodiment, the inrush current limiting component, current limiting resistor R1151 and relay K1161, are placed in series with the bulk capacitor C51115. In this embodiment, the relay K1161 acts as an inrush current control device. However, other embodiments can use a metal oxide semiconductor field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), etc., alone or in combination, as an inrush current control device. Initially, the voltage across the bulk capacitor C51115 is zero. When input power is applied to the power conversion device, inrush current charges the bulk capacitor C51115 until the voltage of the bulk capacitor C51115 reaches the peak value of the rectified input voltage.

[0019] During the positive half cycle, inrush current passes through diode D1121, diode D5125, and current limiting resistor R1151 to charge the bulk capacitor C51115, and back through diode D3123. During the negative half cycle, inrush current passes through diode D2122, diode D5125, and current limiting resistor R1151 to charge the bulk capacitor C51115, and back through diode D4124.

[0020] The current limiting resistor R1151 limits inrush current. Once the bulk capacitor C51115 is sufficiently charged, and the internal circuit begins to operate, the relay K1161 is activated to short out the current limiting resistor R1151 to reduce power loss.

[0021] Other components of this exemplary circuit include a metal oxide varistor MOV1107 connected across the input lines 102 and neutral 104 to clamp voltage spikes across the input. In addition, metal oxide varistors MOV2108 and MOV3109 are connected across the input along with a gas discharge tube GDT1105 in a configuration designed to clamp common mode power surges at the input. Typically, the metal oxide varistors (MOVs) or voltage dependent resistors (VDRs) used in power conversion devices are selected to meet the requirements of Annex G8.2 of IEC Standard IEC 62368-1 or Annex Q of ITE Standard IEC 61050-1, which specifies that the MOV / VDR's rated maximum continuous voltage should be at least 125% of the upper limit of the rated voltage of the power conversion device.

[0022] For example, if the power conversion device is rated for 100-240V AC, the MOV / VDR rating should be at least 300V AC. If the power conversion device is rated for 100-250V AC, the MOV / VDR rating should be at least 312.5V AC. To meet the ITE standard requirement, the clamping voltage of a suitable MOV / VDR is greater than 700V, as exemplified in Table 1 below.

[0023]

[0024] Table 1

[0025] This exemplary circuit also includes an electromagnetic interference (EMI) filter including capacitors CI 111, C2 112, C3 113, and C4 114 along with inductor L2 132. Capacitors CI 111 and C4 114 are X capacitors configured to reduce differential mode noise, while capacitors C2 112 and C3 112 are Y capacitors configured to reduce common mode noise.

[0026] If the power conversion device 100 is connected to the AC grid, but the AC is disconnected or disabled, the internal circuitry is not able to operate and the relay K1 161 remains open. If a lightning surge is coupled to the AC lines while the power conversion device 100 is in this state, the (lightning-induced) power surge is clamped only by the MOV / VDR and GDT at the input interface, and the power switch transistor Q1 141 is at risk of damage.

[0027] In this case the clamping voltage is high and the remaining power surge energy is not absorbed by the bulk capacitor C5 115, because the relay K1 161 is open. The power switch transistor Q1 141 is exposed to this remaining power surge voltage, resulting in an electrical overstress failure of the power switch transistor Q1 141.

[0028] Figure 2 An exemplary power converter circuit 200 with bridge rectification and active power factor correction including surge protection is exemplified. This exemplary power converter circuit 200 is the same as the power converter circuit 100 from Figure 1 , with the addition of a bypass device BD1 210 added in parallel to the current limiting resistor R1 151.

[0029] During normal power up, the power converter circuit 200 is the same as the power converter circuit 100 from Figure 1The power converter circuit 100 operates very similarly. When input power is applied to the power conversion device, the inrush current charges the bulk capacitor C5 115 until the voltage of the bulk capacitor C5 115 reaches the peak value of the rectified input voltage.

[0030] During the positive half cycle, the inrush current passes through diode D1 121, diode D5 125, and current limiting resistor R1 151 to charge the bulk capacitor C5 115, and back through diode D3 123. During the negative half cycle, the inrush current passes through diode D2 122, diode D5 125, and current limiting resistor R1 151 to charge the bulk capacitor C5 115, and back through diode D4 124.

[0031] The current limiting resistor R1 151 limits the inrush current. Once the bulk capacitor C5 115 is sufficiently charged, and the internal circuit begins to operate, the relay K1 161 is activated to short out the current limiting resistor R1 151 to reduce power losses. In this embodiment, the relay K1 161 acts as an inrush current control device. However, other embodiments can use MOSFETs, Insulated Gate Bipolar Transistors (IGBTs), etc., alone or in combination, as inrush current control devices.

[0032] If the power conversion device 200 is connected to an AC grid, but the AC is off or disabled, the internal circuit is not able to operate and the relay K1 161 remains open. If a lightning surge is coupled to the AC line while the power conversion device 200 is in this state, the (lightning-induced) power surge is first clamped by the MOV / VDR and GDT at the input interface. The remaining power surge then activates the bypass device BD1 210, which then provides a low resistance path to the bulk capacitor C5 115. The remaining power surge energy passes through the bypass device BD1 210 and is absorbed by the bulk capacitor C5 115, even though the relay K1 161 is open. Thus, the power switch transistor Q1 141 is protected from the power surge energy.

[0033] An embodiment of the bypass device BD1 210 is illustrated in Figures 4A-4D and is discussed in detail below.

[0034] Figure 3 An exemplary power converter circuit 300 with bridgeless power factor correction including inrush current limiting and surge protection is illustrated. This example power converter circuit 300 is similar to the power converter circuit 200 from Figure 2 but in a H-bridge bridgeless power factor correction configuration.

[0035] Here, the power factor correction circuit includes power switching transistors Q1 341 and Q2 342 along with inductor LI 331, and diodes D5 325 and D6 326.

[0036] During normal power up, the power converter circuit 300 operates very similarly to the power converter circuit 200 from Figure 2 When input power is applied to the power conversion device, the inrush current charges the bulk capacitor C5 115 until the voltage of the bulk capacitor C5 115 reaches the peak of the rectified input voltage.

[0037] During the positive half cycle, the inrush current passes through diode DI 121 and current limiting resistor Rl 151 to charge the bulk capacitor C5 115 and back through diode D3 123. During the negative half cycle, the inrush current passes through diode D2 122 and current limiting resistor Rl 151 to charge the bulk capacitor C5 115 and back through diode D4 124.

[0038] The current limiting resistor Rl 151 limits the inrush current. Once the bulk capacitor C5 115 is sufficiently charged and the internal circuit begins to operate, the relay Kl 161 is activated to short out the current limiting resistor Rl 151 to reduce power loss. In this embodiment, the relay Kl 161 acts as an inrush current control device. However, other embodiments can use MOSFETs, insulated gate bipolar transistors (IGBTs), etc. individually or in combination as inrush current control devices.

[0039] If the power conversion device 300 is connected to the AC grid, but the AC is off or disabled, the internal circuit is not able to operate and the relay Kl 161 remains open. If a lightning surge is coupled to the AC line while the power conversion device 300 is in this state, the (lightning-induced) power surge is first clamped by the MOV / VDR and GDT at the input interface. The remaining lightning surge then activates the bypass device BD1 310, which then provides a low resistance path to the bulk capacitor C5 115. The remaining lightning surge energy passes through the bypass device BD1 310 and is absorbed by the bulk capacitor C5 115, even though the relay Kl 161 is open. As a result, the power switching transistors Q1 341 and Q2 134 are protected from the lightning surge energy.

[0040] Embodiments of the bypass device BD1 310 are illustrated in Figures 4A-4D and are discussed in detail below.

[0041] While Figure 2 and Figure 3The embodiments illustrated in FIGS. 1-3 show the current limiting resistor R1 151, the relay K1 161, and the bypass devices BD1 210 and 310 adjacent to the bulk capacitor C5 115, but other implementations can place these elements somewhere on the line input 102 between the MOV 1107 and C4 114. However, when placed in this location, the relay K1 161 will need to be sized to handle more current than when adjacent to the bulk capacitor C5 115, which increases the size and cost of the relay K1 161.

[0042] Additionally, while Figure 2 and Figure 3 the embodiments illustrated in FIGS. 1-3 show AC / DC power converters, various other circuits can also use the various embodiments of the present application, including but not limited to DC / DC converters, high voltage DC converters, etc.

[0043] Figures 4A-4D Example bypass devices are illustrated to limit inrush current and provide surge protection for power converter devices. In these example embodiments, portions of power converter devices (such as power converter devices 200 and 300 from Figure 2 and Figure 3 respectively) are illustrated. These circuits all include a current limiting resistor R1 402, a relay K1 404, and a bulk capacitor C5 406. In these embodiments, the relay K1 404 acts as an inrush current control device. However, other embodiments can use MOSFETs, insulated gate bipolar transistors (IGBTs), etc. as inrush current control devices, either alone or in combination.

[0044] Figure 4A An example circuit is illustrated in which the bypass device is a gas discharge tube GDT1 400. In this embodiment, the gas discharge tube GDT1 400 is selected so that its DC breakdown voltage is higher than the maximum rectified input voltage, but lower than the rated voltage of the power switch transistor Q1 141 of Figure 2 or the power switch transistors Q1 341 and Q2 342 of Figure 3 .

[0045] Figure 4B An example circuit is illustrated in which the bypass device is a spark gap SG1 410. Figure 4C An example circuit is illustrated in which the bypass device is a transient voltage suppressor TVS1 420. Figure 4D An example circuit is illustrated in which the bypass device is a MOV / VDR MOV2 430. All of these various bypass devices are ideally selected to meet both the inrush current limit and the lightning surge requirements.

[0046] Note that additional embodiments of the present application can use any of these bypass devices, alone or in combination, in a particular application to provide inrush current limiting and lightning surge protection.

[0047] Figure 5 An exemplary power converter circuit 500 with bridgeless power factor correction including inrush current limiting and surge protection is illustrated. This example power converter circuit 500 is similar to the power converter circuit 300 from Figure 3 , but in a totem-pole bridgeless power factor correction configuration.

[0048] Here, the power factor correction circuit includes power switching transistors Q1 541 and Q2 542 along with inductor LI 531, and diodes D3 523 and D4 524.

[0049] During normal power up, the power converter circuit 500 operates very similarly to the power converter circuit 300 from Figure 3 . When input power is applied to the power conversion device, the inrush current charges the bulk capacitor C5 115 until the voltage of the bulk capacitor C5 115 reaches the peak value of the rectified input voltage.

[0050] During the positive half cycle, the inrush current passes through diode Dl 121 and current limiting resistor Rl 151 to charge the bulk capacitor C5 115, and back through diode D4 524. During the negative half cycle, the inrush current passes through diode D3 523 and current limiting resistor Rl 151 to charge the bulk capacitor C5 115, and back through diode D2 522.

[0051] The current limiting resistor Rl 151 limits the inrush current. Once the bulk capacitor C5 115 is sufficiently charged, and the internal circuitry begins to operate, the relay Kl 161 is activated to short out the current limiting resistor Rl 151 to reduce power losses. In this embodiment, the relay Kl 161 acts as an inrush current control device. However, other embodiments can use MOSFETs, insulated gate bipolar transistors (IGBT), etc., alone or in combination, as inrush current control devices.

[0052] If the power conversion device 500 is connected to the AC grid, but the AC is disconnected or disabled, the internal circuitry cannot operate and relay K1 161 remains open. If a lightning surge is coupled to the AC line while the power conversion device 500 is in this state, the power surge (caused by the lightning) is first clamped by the MOV / VDR and GDT at the input interface. The remaining power surge then activates bypass device BD1 510, which then provides a low-resistance path to bulk capacitor C5 115. The remaining power surge energy is transferred through bypass device BD1 510 and absorbed by bulk capacitor C5 115, even if relay K1 161 is open. As a result, power switching transistors Q1 541 and Q2 542 are protected from the power surge energy.

[0053] An embodiment of the bypass device BD1 510 is illustrated in Figures 4A-4D and are discussed in detail above.

[0054] Although Figure 2 、 Figure 3 and Figure 5 1 shows current limiting resistor R1 151, relay K1 161, and bypass devices BD1 210, 310, and 510 adjacent to bulk capacitor C5 115, but other embodiments may place these components somewhere on line input 102 between MOV1 107 and C4 114. However, when placed in this location, relay K1 161 will need to be sized to handle more current than when adjacent to bulk capacitor C5 115, which increases the size and cost of relay K1 161.

[0055] Figure 6 An exemplary power converter circuit 600 with bridge rectification and active power factor correction including inrush current limiting and surge protection is illustrated. This exemplary power converter circuit 600 is similar to the example power converter circuit 600 from Figure 2 1 , however this example circuit includes a MOSFET Q2 642 instead of the relay K1 161 as the inrush current control device.

[0056] MOSFET Q2 642 is placed in parallel with bulk resistor R1 151 and bypass device BD1610 and is similar to Figure 2 The relay K1 161 is running.

[0057] Figure 7 An exemplary power converter circuit 700 with bridge rectification and active power factor correction including inrush current limiting and surge protection is illustrated. This exemplary power converter circuit 700 is similar to the example power converter circuit 700 fromFigure 2 The power converter circuit 200 of FIG. 7, however, includes MOSFET Q2 742 in parallel with relay Kl 761 as the inrush current control device.

[0058] MOSFET Q2 742 is placed in parallel with body resistor Rl 151, bypass device BD1 710, and relay Kl 761. In this MOSFET Q2 742 and relay Kl 761 together operate in parallel as the inrush current control device.

[0059] The description and drawings describe specific embodiments to teach those skilled in the art how to make and use the best mode. Some conventional aspects have been simplified or omitted for the sake of teaching the inventive principles. Those skilled in the art will appreciate variations from these embodiments that fall within the scope of the invention. Those skilled in the art will also appreciate that the features described above can be combined in various ways to form many embodiments of the invention. Therefore, the invention is not limited to the specific embodiments described above, but only by the claims and their equivalents.

Claims

1. A power conversion device comprising: a bulk capacitor; a current limiting resistor in series with the bulk capacitor; a surge current control device in parallel with the current limiting resistor configured to bypass the current limiting resistor when activated; and a bypass device in parallel with the current limiting resistor configured to provide a low resistance path to the bulk capacitor during a power surge; wherein the bypass device is selected from the group of: a gas discharge tube, a spark gap, a transient voltage suppressor, and a metal oxide varistor.

2. The power conversion device of claim 1, wherein the bypass device is a gas discharge tube.

3. The power conversion device of claim 2, wherein the gas discharge tube has a direct current breakdown voltage greater than a maximum rectified input voltage of the power conversion device and less than a rated voltage of a power switch transistor within the power conversion device.

4. The power conversion device of claim 1, wherein the bypass device is a spark gap.

5. The power conversion device of claim 1, wherein the bypass device is a transient voltage suppressor.

6. The power conversion device of claim 1, wherein the bypass device is a metal oxide varistor.

7. The power conversion device of claim 1, wherein the bypass device comprises two or more devices selected from the group of: a gas discharge tube, a spark gap, a transient voltage suppressor, and a metal oxide varistor.

8. The power conversion device of claim 1, wherein the surge current control device comprises a device selected from the group of: a relay, a metal oxide semiconductor field effect transistor, and an insulated gate bipolar transistor.

9. The power conversion device of claim 1, further comprising: an input metal oxide varistor electrically coupled between two input ports; an electromagnetic interference filter electrically coupled with the input ports; and a power factor correction circuit electrically coupled with the electromagnetic interference filter.

10. The power conversion device of claim 9, wherein the bypass device is configured to protect a power switch transistor within the power factor correction circuit.

11. The power conversion device of claim 9, wherein the current limiting resistor, surge current control device, and bypass device are electrically coupled with the input ports between the input metal oxide varistor and the electromagnetic interference filter.

12. The power conversion device of claim 9, wherein the power factor correction circuit comprises a bridgeless power factor correction converter.

13. The power conversion device of claim 9, wherein the power factor correction circuit comprises a bridge rectifier.

14. A surge current limiting and surge protection circuit comprising: a bulk capacitor; a current limiting resistor in series with the bulk capacitor and configured to: receive a current from a bridge rectifier device; and provide the current to the bulk capacitor; ​ ​ a strike current control device in parallel with the current limiting resistor configured to bypass the current limiting resistor and provide the current to the bulk capacitor when activated; and a bypass device in parallel with the current limiting resistor configured to provide a low resistance path from the bridge rectifier device to the bulk capacitor to provide power surge energy during a power surge.

15. The strike current limiting and surge protection circuit of claim 14, wherein the bypass device is a gas discharge tube.

16. The strike current limiting and surge protection circuit of claim 15, wherein the gas discharge tube has a direct current breakdown voltage greater than a maximum rectified input voltage of the strike current limiting and surge protection circuit and less than a voltage rating of a power switching transistor within the strike current limiting and surge protection circuit.

17. The strike current limiting and surge protection circuit of claim 14, wherein the bypass device is a spark gap.

18. The strike current limiting and surge protection circuit of claim 14, wherein the bypass device is a transient voltage suppressor.

19. The strike current limiting and surge protection circuit of claim 14, wherein the bypass device is a metal oxide varistor.

20. The strike current limiting and surge protection circuit of claim 14, wherein the bypass device comprises two or more devices selected from the group of: a gas discharge tube, a spark gap, a transient voltage suppressor, and a metal oxide varistor.

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