Auxiliary power supply control circuit, auxiliary power supply and photovoltaic grid-connected inverter

Abstract

This invention provides an auxiliary power supply control circuit, an auxiliary power supply, and a photovoltaic grid-connected inverter. The auxiliary power supply control circuit includes a power supply chip, a flyback transformer, an undervoltage shutdown circuit, and a switching circuit. The first secondary side of the flyback transformer supplies power to the power supply chip through its power supply port. The primary side of the flyback transformer responds to a control signal from the output port of the power supply chip, causing the auxiliary power supply to start according to a corresponding startup voltage. The undervoltage shutdown circuit is powered by the first secondary side of the flyback transformer. The undervoltage shutdown circuit instructs the power supply chip to shut down the auxiliary power supply when the startup voltage of the primary side of the flyback transformer is less than the voltage at the undervoltage protection shutdown point. The switching circuit controls the undervoltage shutdown circuit to start after a preset delay time when the auxiliary power supply starts. By adding the switching circuit, the startup of the undervoltage shutdown circuit is delayed when the auxiliary power supply starts, thereby preventing leakage current from the undervoltage shutdown circuit from affecting the auxiliary power supply's startup at the normal startup voltage.

Description

Technical Field

[0001] This invention belongs to the field of switching power supply technology, and particularly relates to an auxiliary power supply control circuit, an auxiliary power supply, and a photovoltaic grid-connected inverter. Background Technology

[0002] The auxiliary power supply (hereinafter referred to as auxiliary power supply) of a household string photovoltaic grid-connected inverter is generally required to have a wide voltage and temperature operating range. Therefore, the auxiliary power supply is generally selected as a single-tube flyback power supply with an operating voltage range of 80 to 600Vdc.

[0003] In existing technologies, flyback power supplies typically place the power supply chip and undervoltage shutdown circuit on the same secondary side for power supply. However, in low-temperature environments, the auxiliary power supply often fails to start normally. To find the cause of this failure, the system ambient temperature was increased. The higher the temperature, the lower the power supply's startup voltage, confirming that temperature is indeed the cause of the auxiliary power supply's startup failure. However, heating the system in a low-temperature environment is impractical to solve the startup problem. Therefore, the reasons for the increased startup voltage at low temperatures were further analyzed. Capacitors degrade at low temperatures. Increasing the value of the voltage regulator capacitor did not significantly change the startup voltage at low temperatures. Removing the main power-consuming component of the undervoltage shutdown circuit resulted in a slight increase in the startup voltage at the same temperature, proving that the actual cause of the auxiliary power supply's startup failure was leakage current. The comparator in the undervoltage shutdown circuit generates a large leakage current, affecting the supply voltage of the power supply chip on the same secondary side, causing the auxiliary power supply to fail to start normally under normal startup voltage. Summary of the Invention

[0004] In view of this, the present invention provides an auxiliary power supply control circuit, an auxiliary power supply, and a photovoltaic grid-connected inverter, aiming to solve the problem that the auxiliary power supply cannot start normally in the prior art.

[0005] A first aspect of the present invention provides an auxiliary power control circuit, comprising: a power chip, a flyback transformer, an undervoltage shutdown circuit, and a switching circuit;

[0006] The primary side of the flyback transformer supplies power to the power chip through the power supply port of the power chip; the primary side of the flyback transformer responds to the control signal of the output port of the power chip, causing the auxiliary power supply to start according to the corresponding start-up voltage.

[0007] The undervoltage shutdown circuit is powered by the first secondary side of the flyback transformer; the undervoltage shutdown circuit is used to instruct the power chip to shut off the auxiliary power supply when the starting voltage of the primary side of the flyback transformer is less than the voltage of the undervoltage protection shutdown point.

[0008] In a switching circuit, it is used to control the undervoltage shutdown circuit to start after a preset delay time when the auxiliary power supply is started.

[0009] In some possible implementations, the switching circuit is an RC delay circuit; the RC delay circuit includes a transistor; the transistor is in the off state when the auxiliary voltage is not activated;

[0010] An RC delay circuit is used to control the transistor to switch from the off state to the on state after a preset delay time when the auxiliary power supply is started.

[0011] In some possible implementations, the undervoltage shutdown circuit includes a first power supply port and a second power supply port; the first power supply port is connected to a first secondary side; the second power supply port is connected to the drain of the transistor; and the source of the transistor is grounded.

[0012] In some possible implementations, the RC delay circuit includes a first resistor and a first capacitor;

[0013] The first terminal of the first resistor is connected to the reference value output port of the voltage chip; the second terminal of the first resistor is connected to the gate of the transistor; the first capacitor is connected in parallel between the gate and source of the transistor.

[0014] The source of the transistor is grounded; the drain of the transistor is connected to the undervoltage shutdown circuit.

[0015] In some possible implementations, the first capacitor is a temperature-sensitive capacitor with a negative temperature coefficient.

[0016] In some possible implementations, the RC delay circuit also includes a second resistor; the second resistor is connected in parallel with the first capacitor.

[0017] In some possible implementations, the second resistor is a thermistor with a negative temperature coefficient.

[0018] In some possible implementations, the switching circuit is a time-delay relay.

[0019] In some possible implementations, the voltage at the natural low-voltage shutdown point of the auxiliary voltage is the same as the voltage at the undervoltage protection shutdown point of the undervoltage shutdown circuit.

[0020] A second aspect of the present invention provides an auxiliary power supply, including: the auxiliary power supply control circuit as described in the first aspect above.

[0021] A third aspect of the present invention provides a photovoltaic grid-connected inverter, comprising: an auxiliary power supply as described in the second aspect above.

[0022] The auxiliary power supply control circuit, auxiliary power supply, and photovoltaic grid-connected inverter provided in this invention embodiment include: a power supply chip, a flyback transformer, an undervoltage shutdown circuit, and a switching circuit; the first secondary side of the flyback transformer supplies power to the power supply chip through the power supply port of the power supply chip; the primary side of the flyback transformer responds to the control signal of the output port of the power supply chip, causing the auxiliary power supply to start according to the corresponding start-up voltage; the undervoltage shutdown circuit is supplied by the first secondary side of the flyback transformer; the undervoltage shutdown circuit is used to instruct the power supply chip to shut down the auxiliary power supply when the start-up voltage of the primary side of the flyback transformer is less than the voltage of the undervoltage protection shutdown point; the switching circuit is used to control the undervoltage shutdown circuit to start after a preset delay time when the auxiliary power supply starts. By adding the switching circuit, the start-up of the undervoltage shutdown circuit is delayed when the auxiliary power supply starts, thereby avoiding the leakage current of the undervoltage shutdown circuit from affecting the auxiliary power supply to start according to the normal start-up voltage. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the auxiliary power control circuit provided in an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the auxiliary power supply main circuit provided in an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the undervoltage shutdown circuit provided in the embodiment of the present invention;

[0027] Figure 4 This is a schematic diagram of the switching circuit provided in an embodiment of the present invention. Detailed Implementation

[0028] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0029] Figure 1 This is a schematic diagram of the auxiliary power supply control circuit provided in an embodiment of the present invention. Figure 1As shown, in some embodiments, the auxiliary power control circuit includes: a power chip 11, a flyback transformer 12, an undervoltage shutdown circuit 13, and a switching circuit 14.

[0030] The first secondary side of the flyback transformer 12 supplies power to the power chip 11 through the power supply port of the power chip 11; the primary side of the flyback transformer 12 responds to the control signal of the output port of the power chip 11, causing the auxiliary power supply to start according to the corresponding start-up voltage; the undervoltage shutdown circuit 13 is powered by the first secondary side of the flyback transformer 12; the undervoltage shutdown circuit 13 is used to instruct the power chip 11 to shut down the auxiliary power supply when the start-up voltage of the primary side of the flyback transformer 12 is less than the voltage of the undervoltage protection shutdown point; the switching circuit 14 is used to control the undervoltage shutdown circuit 13 to start after a preset delay time when the auxiliary power supply starts.

[0031] In this embodiment of the invention, the power chip 11 has multiple ports, which may specifically include a power supply port, a compensation port, a feedback port, an output port, a reference value output port, a ground port, etc. The flyback transformer 12 includes a primary side and multiple secondary sides; the power supply port of the power chip 11 and the power supply port of the undervoltage shutdown circuit 13 are connected to the same secondary side, i.e., the first secondary side.

[0032] The power chip 11 is located at one end of the primary side of the flyback transformer 12, and the other end of the primary side of the flyback transformer 12 is connected to the bus. When the auxiliary power supply needs to be started, the bus provides a starting voltage to the other end of the primary side of the flyback transformer 12, and then the first secondary side supplies power to the power supply port of the power chip 11, thereby causing the output port of the power chip 11 to output a control signal to adjust the voltage of the primary side of the flyback transformer 12, thereby completing the start-up of the auxiliary power supply.

[0033] The undervoltage shutdown circuit 13 collects the start-up voltage of the primary side of the flyback transformer 12 and compares it with the voltage of the undervoltage protection shutdown point output by the reference value output port of the power chip 11 to realize the undervoltage protection of the auxiliary power supply.

[0034] In low-temperature environments, the undervoltage shutdown circuit 13 will generate a large leakage current. Since the undervoltage shutdown circuit is powered by the first secondary side, it will cause the equivalent load of the first secondary side to increase, causing the power chip 11, which is also connected to the first secondary side, to be de-energized, resulting in the auxiliary power supply being unable to start under normal startup voltage.

[0035] Since the auxiliary power supply is susceptible to leakage current during the startup phase, but the magnitude of leakage current has little impact on the power chip after startup and stable operation, in this embodiment of the invention, by adding a switching circuit, the startup of the undervoltage shutdown circuit is delayed when the auxiliary power supply starts up, thereby avoiding the leakage current of the undervoltage shutdown circuit from affecting the auxiliary power supply to start up according to the normal startup voltage.

[0036] In some embodiments, the switching circuit 14 is an RC delay circuit; the RC delay circuit includes a transistor; the transistor is in the off state when the auxiliary voltage is not started; the RC delay circuit is used to control the transistor to switch from the off state to the on state after a preset delay time when the auxiliary power supply is started.

[0037] In this embodiment of the invention, the RC delay circuit includes at least one resistor and at least one capacitor. When the auxiliary power supply starts up, the capacitor in the RC delay circuit will slowly charge until it is fully charged. Only then can the RC delay circuit reach the control voltage of the transistor, causing the transistor to switch states. The capacitor charging process is the aforementioned delay process. The transistor can be a switching device such as a MOSFET, and is not limited here. Since the leakage current of the MOSFET is small, and it is connected in series with the power supply point of the comparator in the undervoltage shutdown circuit, the leakage current can be further limited. Therefore, the combination of the RC delay circuit and the MOSFET can not only delay the start-up of the undervoltage shutdown circuit, but also limit the impact of leakage current on the auxiliary power supply during and after startup, thus enabling the auxiliary power supply to have better low-temperature adaptability.

[0038] The switching circuit can be located at either power supply terminal of the undervoltage shutdown circuit. In some embodiments, the undervoltage shutdown circuit includes a first power supply port and a second power supply port; the first power supply port is connected to a first secondary side; the second power supply port is connected to the drain of the transistor; and the source of the transistor is grounded.

[0039] In some embodiments, the RC delay circuit includes a first resistor and a first capacitor; a first end of the first resistor is connected to the reference value output port of the voltage chip; a second end of the first resistor is connected to the gate of the transistor; the first capacitor is connected in parallel between the gate and source of the transistor; the source of the transistor is grounded; and the drain of the transistor is connected to the undervoltage shutdown circuit 13.

[0040] In this embodiment of the invention, the size of the first capacitor increases as the temperature decreases, thereby enabling the undervoltage shutdown circuit to have a very short preset delay time when the temperature is normal, which is equivalent to normal turn-on, and to provide a relatively long preset delay time when the temperature is low, so as to avoid the influence of leakage current.

[0041] In some embodiments, the RC delay circuit further includes a second resistor; the second resistor is connected in parallel with the first capacitor.

[0042] In some embodiments, the second resistor is a thermistor with a negative temperature coefficient.

[0043] In this embodiment of the invention, in addition to the change in capacitance of the first capacitor itself, a resistor, namely a second resistor, can be connected in parallel across its two ends to adjust the capacitor charging time. The larger the resistance value of the second resistor, the longer the charging time required for the capacitor, i.e., the longer the preset delay time.

[0044] In some embodiments, the switching circuit 14 is a time-delay relay.

[0045] In this embodiment of the invention, when the auxiliary power supply is detected to be starting, the time-delay relay activates its contact switch after a delay time, energizing the undervoltage shutdown circuit and enabling it to start working. Compared to the undervoltage shutdown circuit and transistor described above, the time-delay relay has a more complex structure and can only limit the leakage current during startup (i.e., when there is no leakage current during the delay time), and no longer limits the leakage current after the auxiliary power supply is started.

[0046] In some embodiments, the voltage of the natural low-voltage shutdown point of the auxiliary voltage is the same as the voltage of the undervoltage protection shutdown point of the undervoltage shutdown circuit 13.

[0047] In this embodiment of the invention, if the voltage of the natural low-voltage shutdown point of the auxiliary voltage and the undervoltage protection shutdown point of the undervoltage shutdown circuit 13 are set to the same voltage point, the feedback loop of the auxiliary voltage can automatically shut off the auxiliary voltage when the voltage is low, which to some extent replaces the low-voltage shutdown circuit and ensures that the undervoltage shutdown circuit will not fail during the delayed start-up process.

[0048] The present invention is illustrated below by way of an implementation example, but is not intended to be limiting. Figure 2 This is a schematic diagram of the auxiliary power supply main circuit provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the undervoltage shutdown circuit provided in an embodiment of the present invention. Figure 2 and Figure 3 As shown, in this embodiment, the power supply chip 11 includes a power supply port VCC, a compensation port COM, a feedback port Vfb, a feedback port Is, an output port OUT, a reference value output port Vref, a ground port GND, and an operating frequency design port RC. The auxiliary winding includes multiple coils, where coils labeled 18 and 20 correspond to the primary winding, the others are auxiliary windings, and coils labeled 23 and 24 form the first secondary winding. R294, R295, and R264 in dashed box A are output buffer resistors, and R331 and R319 in dashed box B are current-limiting resistors. The power supply port VCC is powered by the VCC_+15V node on the first secondary winding, and the output port OUT is connected to the gate of the transistor on the primary winding of the flyback transformer 12.

[0049] When the auxiliary power supply needs to be started, the bus BUS provides a starting voltage to the other end of the primary side of the flyback transformer 12. Then, the VCC_+15V node on the first secondary side reaches the corresponding voltage, which powers the power chip 11 and starts it up. This causes the output port OUT to output a control signal, which controls the transistor to output a signal with the corresponding duty cycle to adjust the voltage on the primary side of the flyback transformer 12, thereby completing the start-up of the auxiliary power supply.

[0050] The undervoltage shutdown circuit 13 collects the voltage of the primary side HV node and the bus grounding point voltage (representing the bus BUS), compares it with the voltage of the undervoltage protection shutdown point output by the reference value output port Vref of the power chip 11, and sends the comparison result to the compensation port COM to realize the undervoltage protection of the auxiliary power supply.

[0051] Figure 3 The undervoltage shutdown circuit is an 8-port comparator, where ports 2, 3, 5, and 6 are input ports, ports 1 and 7 are output ports, and ports 4 and 8 are power supply ports. In low-temperature environments, the undervoltage shutdown circuit 13 generates a large leakage current. Since the undervoltage shutdown circuit is powered by the VCC_+15V_S node on the first secondary side, the increased leakage current causes the voltage at the VCC_+15V_S node to drop, effectively increasing the equivalent load on the first secondary side. At this point, the potential of VCC_+15V_S is lower than that of VCC_+15V, causing diode D29 to cut off, thus causing the VCC power supply port to lose its connection, preventing the auxiliary power supply from starting at the normal startup voltage.

[0052] Figure 4 This is a schematic diagram of the switching circuit provided in an embodiment of the present invention. Figure 4 As shown, the switching circuit includes a first resistor R12, a second resistor R13, and a first capacitor C5; the first end of the first resistor R12 is connected to the reference value output port of the voltage chip; the second end of the first resistor R12 is connected to the gate of transistor Q1; the first capacitor C5 is connected in parallel between the gate and source of transistor Q1; the source of transistor Q1 is grounded; the drain of transistor Q1 is connected to the undervoltage shutdown circuit 13; the second resistor R13 is connected in parallel with the first capacitor C5.

[0053] By setting a switching circuit between the power supply port and the bus ground terminal of the undervoltage shutdown circuit, the undervoltage shutdown circuit can be delayed during auxiliary power supply startup. This effectively avoids the influence of leakage current on the potential of VCC_+15V_S. After the auxiliary power supply is running stably, the influence of leakage current will have a smaller impact on the operation of the auxiliary power supply. Therefore, after the delay time, the undervoltage shutdown circuit can operate normally. Figure 3The MOSFET in the switching circuit shown is itself a device with low leakage current. Because it is connected in series with the undervoltage shutdown circuit, the switching circuit can still effectively limit the leakage current after completing the delayed start-up.

[0054] The auxiliary power supply feedback loop includes a protection signal introduced into the CS pin (corresponding to the feedback port Is of power chip 11). When the input PV voltage drops to a certain level, the difference between the feedback and the setpoint of the main output loop increases, causing the CS pin level to change to V_ref, thus shutting down the drive. Since the input PV voltage is too low to allow the self-powered flyback transformer to restart, the auxiliary power supply is reliably shut off. Therefore, if the voltage of the natural low-voltage shutdown point of the auxiliary voltage and the undervoltage protection shutdown point of the undervoltage shutdown circuit 13 are set to the same voltage point, the auxiliary voltage feedback loop can automatically shut off the auxiliary voltage at low voltage, partially replacing the low-voltage shutdown circuit and ensuring that the undervoltage shutdown circuit does not malfunction during delayed startup.

[0055] In summary, the beneficial effects of the present invention are as follows: by adding a switching circuit, the start-up of the undervoltage shutdown circuit is delayed when the auxiliary power supply starts, thereby avoiding the leakage current of the undervoltage shutdown circuit from affecting the auxiliary power supply to start up according to the normal start-up voltage.

[0056] This invention provides an auxiliary power supply, which is a single-transistor flyback power supply. The auxiliary power supply includes the auxiliary power supply control circuit as described in any of the above embodiments. In addition, the auxiliary power supply may also include devices / circuits for rectification, voltage regulation, protection, heat dissipation, etc.

[0057] The present invention also provides a photovoltaic grid-connected inverter, including the auxiliary power supply as described in the above embodiment, such as a photovoltaic inverter of the SPI5-40k model of a residential string photovoltaic grid-connected inverter.

[0058] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0059] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0060] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0061] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0062] In the embodiments provided by this invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0063] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0064] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. An auxiliary power supply control circuit, characterized by comprising: include: Power supply chip, flyback transformer, undervoltage shutdown circuit and switching circuit; The first secondary side of the flyback transformer supplies power to the power chip through the power supply port of the power chip; The primary side of the flyback transformer responds to the control signal at the output port of the power chip, causing the auxiliary power supply to start according to the corresponding startup voltage. The undervoltage shutdown circuit is powered by the first secondary side of the flyback transformer; The undervoltage shutdown circuit is used to instruct the power chip to shut off the auxiliary power supply when the starting voltage of the primary side of the flyback transformer is less than the voltage of the undervoltage protection shutdown point. The switching circuit is used to control the undervoltage shutdown circuit to start after a preset delay time when the auxiliary power supply is started. The switching circuit is an RC delay circuit; The RC delay circuit includes a transistor; the transistor is in the off state when the auxiliary power supply is not started. The RC delay circuit is used to control the transistor to switch from the off state to the on state after a preset delay time when the auxiliary power supply is started.

2. The auxiliary power supply control circuit of claim 1, wherein, The undervoltage shutdown circuit includes a first power supply port and a second power supply port; the first power supply port is connected to the first secondary side; the second power supply port is connected to the drain of the transistor; and the source of the transistor is grounded.

3. The auxiliary power supply control circuit according to claim 2, characterized in that, The RC delay circuit includes a first resistor and a first capacitor; The first end of the first resistor is connected to the reference value output port of the power chip; the second end of the first resistor is connected to the gate of the transistor; the first capacitor is connected in parallel between the gate and source of the transistor. The source of the transistor is grounded; the drain of the transistor is connected to the undervoltage shutdown circuit.

4. The auxiliary power supply control circuit according to claim 3, characterized in that, The RC delay circuit also includes a second resistor; the second resistor is connected in parallel with the first capacitor.

5. The auxiliary power supply control circuit according to claim 4, characterized in that, The second resistor is a thermistor with a negative temperature coefficient.

6. The auxiliary power supply control circuit according to claim 1, characterized in that, The switching circuit is a time-delay relay.

7. The auxiliary power supply control circuit according to claim 1, characterized in that, The voltage at the natural low-voltage shutdown point of the auxiliary power supply is the same as the voltage at the undervoltage protection shutdown point of the undervoltage shutdown circuit.

8. An auxiliary power supply, characterized in that, include: The auxiliary power control circuit as described in any one of claims 1-7 above.

9. A photovoltaic grid-connected inverter, characterized in that, include: The auxiliary power supply as described in claim 8 above.

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