TWI820741B - Dual-input power switching system and method of operating the same - Google Patents

Abstract

A dual-input power switching system includes a first DC power source, a second DC power source, a DC conversion circuit, and a boost-up circuit. The first DC power source provides a first DC voltage, and the second DC power source provides a second DC voltage. The DC conversion circuit receives the first DC voltage or the second DC voltage being an input voltage, and converts the input voltage to supply power to a load. The boost-up circuit provides a hold-up voltage to boost up the input voltage when the first DC power source stops supplying power to lead to power drop of the input voltage, such that the input voltage reaches to a specific voltage that is greater than the second DC voltage and afterward naturally decreases to be less than or equal to the second DC voltage.

Description

Dual input power switching system and its operation method

The present invention relates to a power switching system and an operating method thereof, in particular to a dual-input DC power switching system and an operating method thereof.

In the application of dual-input power switching systems, the power switch is used to switch one input power (first input power) to another input power (second input power) to ensure continuous operation in the event of a power outage or outage. Supply power to the load. However, if the first input power supply is directly switched to the second input power supply (for example, hard switching), the voltage difference between the two input power supplies will generate a large current (also called surge current or inrush current) at the moment of switching. inrush current). Inrush current may damage the switching elements at the input of the power switching system. Or, for the power protection mechanism of the input power supply, the inrush current may cause the input current to exceed the maximum safe current and trigger the power protection mechanism, causing the input power supply to automatically shut down. Furthermore, in the power supply protection mechanism, because the power is equal to the product of current and voltage (P=I*V), when the inrush current causes the input current to rise, the input power supply will automatically reduce the input voltage to maintain the rated output power, and thus As a result, the power supply capacity of the front stage is insufficient, and the entire system shuts down without warning.

Taking the application of dual-input AC power supplies as an example, by switching the power supply when the AC power supply is at zero voltage for phase switching, the inrush current caused by the voltage difference between the dual AC power supplies can be avoided. However, in the application of dual input DC power supplies, the voltage difference between the dual DC power supplies will be inevitable, and the generation of inrush current will be inevitable.

For this reason, how to design a dual-input DC power switching system and its operating method to solve the problems and technical bottlenecks of the existing technology is an important issue in the industry.

One purpose of the present invention is to provide a dual-input power switching system to solve the problems of the prior art.

In order to achieve the aforementioned purpose, the dual-input power switching system proposed by the present invention includes a first DC power supply, a second DC power supply, a DC conversion circuit and a boosting circuit. The first DC power supply is used to provide a first DC voltage. The second DC power supply is used to provide a second DC voltage. The DC conversion circuit is coupled to the output side of the second DC power supply and the output side of the first DC power supply, for receiving the first DC voltage or the second DC voltage as an input voltage, and converting the input voltage to power the load. The boosting circuit is coupled to the input side of the DC conversion circuit, the output side of the first DC power supply, and the output side of the second DC power supply, and is used to provide a maintaining voltage when the first DC power supply stops supplying power and causes the input voltage to lose power. The input voltage is raised so that the input voltage reaches a specific voltage greater than the second DC voltage and then naturally decreases to less than or equal to the second DC voltage.

Through the proposed dual-input power switching system, when the first DC power supply stops supplying and the input voltage drops out, the boost circuit is activated to provide a maintaining voltage to boost the input voltage. When the input voltage drops out Maintain the load operation; at the same time, the boost circuit makes the maintenance voltage reach a specific voltage greater than the second DC voltage, which can avoid the surge current caused by the voltage difference between the first DC voltage and the second DC voltage, thereby protecting the power switching system Furthermore, after the boost circuit has been turned off, the input voltage can naturally connect from the higher specific voltage to the lower second DC voltage, and no surge current will be generated during the natural decrease of the input voltage.

Another object of the present invention is to provide an operating method of a dual-input power switching system to solve the problems of the prior art.

In order to achieve the aforementioned purpose, the operating method of the dual-input power switching system proposed by the present invention includes: (a) providing the first DC voltage as the input voltage from the first DC power supply, and converting the input voltage to power the load; ( b) Determine whether the input voltage has lost power; (c) When the input voltage has lost power, start the booster circuit to gradually increase the maintenance voltage as the input voltage; (d) Determine whether the input voltage has reached a specific voltage; (e ), until the maintenance voltage reaches a specific voltage and is maintained for a specific period of time, the second DC power supply is switched to provide the second DC voltage as the input voltage.

Through the operation method of the proposed dual-input power switching system, when the first DC power supply stops supplying and the input voltage drops out, the boost circuit is activated to provide a maintaining voltage to boost the input voltage. Maintains load operation during power outage; at the same time, the boost circuit causes the maintenance voltage to reach a specific voltage greater than the second DC voltage, which can avoid surge current caused by the voltage difference between the first DC voltage and the second DC voltage, thereby protecting Power switching system; furthermore, after the boost circuit has been turned off, the input voltage can naturally connect from the higher specific voltage to the lower second DC voltage, and no inrush current will be generated during the natural decrease of the input voltage. .

In order to further understand the technology, means and effects adopted by the present invention to achieve the intended purpose, please refer to the following detailed description and drawings of the present invention. It is believed that the purpose, features and characteristics of the present invention can be understood in depth and For specific understanding, however, the attached drawings are only for reference and illustration, and are not intended to limit the present invention.

The technical content and detailed description of the present invention are as follows with reference to the drawings.

Please refer to FIG. 1 , which is a block diagram of a dual-input power switching system 1 according to the first embodiment of the present invention. The dual-input power switching system 1 of the present invention is used for the application of dual DC inputs, especially using the first switch SW ₁ and the second switch SW ₂ to switch the first DC power supply V _DC1 to the second DC power supply V _DC2 . It should be able to continuously supply power to the load 100 in the event of a power outage or blackout. One of the first DC power supply V _DC1 and the second DC power supply V _DC2 may be a backup power.

The dual-input power switching system 1 includes a first DC power supply V _DC1 , a second DC power supply V _DC2 , a first switch SW ₁ , a second switch SW ₂ , a DC conversion circuit 10 , a boost circuit 20 and a control circuit 30 . The first DC power supply V _DC1 is used to provide the first DC voltage V ₁ . The second DC power supply V _DC2 is used to provide the second DC voltage V ₂ . The input side of the DC conversion circuit 10 is coupled to the first DC power supply V _DC1 and the second DC power supply V _DC2 for receiving the first DC voltage V ₁ or the second DC voltage V ₂ as the input voltage V of the DC conversion circuit 10 _IN . The DC conversion circuit 10 is further used to convert the first DC voltage V ₁ or the second DC voltage V ₂ into the output voltage V _OUT and then supply power to the load 100 to maintain the operation of the load 100 .

The first switch SW ₁ is coupled between the output side of the first DC power supply V _DC1 and the input side of the DC conversion circuit 10 . When the first switch SW ₁ is turned on, the first DC voltage V ₁ is provided to the DC conversion circuit. 10 as input voltage V _IN . The second switch SW ₂ is coupled between the output side of the second DC power supply V _DC2 and the input side of the DC conversion circuit 10 , wherein when the second switch SW ₂ is turned on, the second DC voltage V ₂ is provided to the DC conversion circuit 10 as input voltage V _IN .

The first DC power supply V _DC1 is coupled to the input side of the DC conversion circuit 10 through the first switch SW ₁ , and the second DC power supply V _DC2 is coupled to the input side of the DC conversion circuit 10 through the second switch SW ₂ . When the first switch SW ₁ is turned on, the first DC voltage V ₁ is provided to the DC conversion circuit 10 ; or, when the second switch SW ₂ is turned on, the second DC voltage V ₂ is provided to the DC conversion circuit 10 . Therefore, the first switch SW ₁ and the second switch SW ₂ play the role of input power switching. In one embodiment, the first switch SW ₁ and the second switch SW ₂ may be relays.

The boosting circuit 20 is coupled to the input side of the DC conversion circuit 10, the output side of the first DC power supply V _DC1 and the output side of the second DC power supply V _DC2 , and is used to cause the input when the first DC power supply V _DC1 stops supplying power. When the voltage V _IN is powered off, the maintaining voltage V _BUCK is provided to boost the input voltage V _IN . From another perspective, the first DC power supply V _DC1 , the second DC power supply V _DC2 , the boost circuit 20 and the DC conversion circuit 10 are coupled in parallel, which means that the positive and negative polarities of the first DC voltage V ₁ , the second DC voltage V 1 and the DC conversion circuit 10 are connected in parallel. The positive and negative polarities of the voltage V ₂ and the positive and negative polarities of the sustaining voltage V _BUCK are respectively coupled to the positive terminal and the negative terminal of the input side of the DC conversion circuit 10 (ie, the positive and negative polarities of the input voltage V _IN ).

The control circuit 30 is coupled to the first switch SW ₁ , the second switch SW ₂ , the DC conversion circuit 10 and the boosting circuit 20 , and is used to generate the first control signal C 1 to the first control signal C ₁ to the first control signal C according to the input voltage V _IN of the DC conversion circuit 10 . A switch SW ₁ generates a second control signal C ₂ to the second switch SW ₂ and a boost signal _CA to the boost circuit 20 .

In operation, when the control circuit 30 detects that the first DC power supply V _DC1 provides the first DC voltage V ₁ as the input voltage V _IN , the control circuit 30 turns on the first switch SW ₁ through the first control signal C ₁ . Or when the control circuit 30 detects that the second DC power supply V _DC2 provides the second DC voltage V ₂ as the input voltage V _IN , the control circuit 30 turns on the second switch SW _{2 through the second control signal C 2 .} When the control circuit 30 detects that the first DC power supply V _DC1 stops supplying power and causes the input voltage V _IN to lose power, such as an abnormal power outage or voltage abnormality caused by overvoltage, undervoltage, or phase loss, or the user replaces the power supply voluntarily, The control circuit 30 activates the boosting circuit 20 through the boosting signal _CA. The boosting circuit 20 increases the sustaining voltage V _BUCK according to the boosting signal _CA , and provides the sustaining voltage V _BUCK to the DC conversion circuit 10 to boost the input voltage V _IN . Until the maintenance voltage V _BUCK reaches a specific voltage greater than the second DC voltage V ₂ , the control circuit 30 turns off the boosting circuit 20 through the boosting signal _CA , and turns off the first switch SW ₁ through the first control signal C ₁ . Until the specific voltage is maintained for a specific period of time, the control circuit 30 turns on the second switch SW ₂ through the second control signal C ₂ , so that the second DC power supply V _DC2 provides the second DC voltage V ₂ as the input voltage V _IN to the load 100 . Power supply.

In this way, when the first DC power supply V _DC1 stops supplying power and the input voltage V _IN is powered down, the boost circuit 20 provides the maintaining voltage V _BUCK to boost the input voltage V _IN to maintain the operation of the load 100; at the same time, the boost circuit 20 The circuit 20 causes the input voltage V _IN (or the maintenance voltage V _BUCK ) to reach a specific voltage greater than the second DC voltage V ₂ and then naturally decrease to less than or equal to the second DC voltage V ₂ to avoid the first DC voltage V ₁ and the second DC voltage V 2 . The surge current caused by the voltage difference between the DC voltages _V2 protects the dual-input power switching system 1.

Please refer to FIG. 2 , which is a block diagram of a dual-input power switching system 2 according to a second embodiment of the present invention. In FIGS. 1 and 2 , elements with the same functions are represented by the same reference numerals, but this does not limit the present invention. As shown in Figure 2, the dual-input power switching system 2 includes a first DC power supply V _DC1 (not shown in Figure 2, please refer to Figure 1), a second DC power supply V _DC2 (not shown in Figure 2, please refer to Figure 1) , the first switch SW ₃ , the second switch SW ₄ , the DC conversion circuit 10 , the boost circuit 20 and the control circuit 32 .

In one embodiment, the dual-input power switching systems 1 and 2 further include a first input protection circuit F ₁ and a second input protection circuit F ₂ ; the first input protection circuit F ₁ is coupled in series to the first DC power supply V The positive path between _DC1 and the first switch SW ₃ ; the second input protection circuit F ₂ is coupled in series to the positive path between the second DC power supply V _DC2 and the second switch SW ₄ ; where the input protection circuits F ₁ and F ₂ can be various types of fuses, such as current, voltage, thermal fuses, etc.

In one embodiment, the dual-input power switching systems 1 and 2 further include electromagnetic compatibility filters (not shown in FIGS. 1 and 2 ), which can be built into the DC conversion circuit 10 or coupled in parallel to the DC conversion circuit 10 The input side is used to filter the input voltage V _IN .

The first switch SW ₃ includes a first power transistor Q ₁₁ , a second power transistor Q ₁₂ , a third power transistor Q ₁₃ and a fourth power transistor Q ₁₄ . The first power transistor Q ₁₁ and the second power transistor Q ₁₂ are connected back to back to form a bidirectional switch group, which is coupled in series to the positive path between the first DC power supply V _DC1 and the DC conversion circuit 10 . The third power transistor Q ₁₃ and the fourth power transistor Q ₁₄ are connected back to back to form a bidirectional switch group, which are coupled in series to the negative path between the first DC power supply V _DC1 and the DC conversion circuit 10 .

Similarly, the second switch SW ₄ includes a fifth power transistor Q ₂₁ , a sixth power transistor Q ₂₂ , a seventh power transistor Q ₂₃ and an eighth power transistor Q ₂₄ . The fifth power transistor Q ₂₁ and the sixth power transistor Q ₂₂ are connected back to back to form a bidirectional switch group, which is coupled in series to the positive path between the second DC power supply V _DC2 and the DC conversion circuit 10 . The seventh power transistor Q ₂₃ and the eighth power transistor Q ₂₄ are connected back to back to form a bidirectional switch group, which are coupled in series to the negative path between the second DC power supply V _DC2 and the DC conversion circuit 10 . In the second embodiment of the present invention, the power transistors Q ₁₁ , Q ₁₂ , Q ₁₃ , Q ₁₄ , Q ₂₁ , Q ₂₂ , Q ₂₃ , and Q ₂₄ are N-channel enhancement power field effect transistors (N-channel enhancement). type power MOSFET), however, those with ordinary knowledge in the art can replace the N-channel transistor with a P-channel transistor and appropriately modify the control signal level according to actual needs, but are not limited to this.

The control circuit 32 is coupled to the first switch SW ₃ , the second switch SW ₄ , the DC conversion circuit 10 and the boosting circuit 20 , and is used to generate the first control signal S 1 and the first control signal S ₁ according to the input voltage V _IN of the DC conversion circuit 10 . The third control signal S ₃ is sent to the first switch SW ₃ , the second control signal S ₂ and the fourth control signal S ₄ are sent to the second switch SW ₄ , and the boost signal _CA is sent to the boost circuit 20 . In the embodiments of FIGS. 1 and 2 , the control circuits 30 and 32 may be any type of control circuit, such as but not limited to a digital or analog microcontroller, a microprocessor, a general-purpose integrated circuit, or an application-specific integrated circuit.

In operation, when the control circuit 32 detects that the first DC power supply V _DC1 provides the first DC voltage V ₁ as the input voltage V _IN , the control circuit 32 turns on the first switch SW ₃ through the first control signal S ₁ The first power transistor Q ₁₁ , the third power transistor Q ₁₃ and the fourth power transistor Q ₁₄ are connected, and the second power transistor Q ₁₂ of the first switch SW ₃ is turned on through the third control signal S ₃ . When the control circuit 32 detects that the first DC voltage V ₁ is powered off and the input voltage V _IN is powered off, the control circuit 32 activates the boosting circuit 20 through the boosting signal _CA. The boosting circuit 20 increases the sustaining voltage V _BUCK according to the boosting signal _CA , and provides the sustaining voltage V _BUCK to the DC conversion circuit 10 to boost the input voltage V _IN .

When the input voltage V _IN starts to rise, the control circuit 32 turns off the second power transistor Q ₁₂ through the third control signal S ₃ . Until the maintenance voltage V _BUCK reaches a specific voltage greater than the second DC voltage V ₂ , the control circuit 32 turns off the boost circuit 20 through the boost signal _CA , and turns off the first switch SW ₃ through the first control signal S ₁ The first power transistor Q ₁₁ , the third power transistor Q ₁₃ and the fourth power transistor Q ₁₄ . Until the input voltage V _IN maintains at a specific voltage for a specific period of time, the control circuit 32 turns on the fifth power transistor Q ₂₁ , the seventh power transistor Q ₂₃ and the eighth power transistor of the second switch SW ₄ through the second control signal S ₂ The power transistor Q ₂₄ is used to prepare the second DC power supply V _DC2 to provide the second DC voltage V ₂ . Until the input voltage V _IN naturally drops to less than or equal to the second DC voltage V ₂ , the control circuit 32 turns on the sixth power transistor Q ₂₂ of the second switch SW ₄ through the fourth control signal S ₄ , so that the second DC power supply V _DC2 provides the second DC voltage V ₂ as the input voltage V _IN . Alternatively, the body diode of the sixth power transistor Q ₂₂ naturally conducts forward, so that the second DC power supply V _DC2 provides the second DC voltage V ₂ as the input voltage V _IN .

In this way, when the first DC voltage V ₁ loses power and the input voltage V _IN loses power, the boost circuit 20 provides the maintaining voltage V _BUCK to boost the input voltage V _IN to maintain the operation of the load 100 ; at the same time, the boost circuit 20 so that the maintenance voltage V _BUCK reaches a specific voltage greater than the second DC voltage V ₂ and then naturally drops to less than or equal to the second DC voltage V ₂ to avoid the voltage between the first DC voltage V ₁ and the second DC voltage V ₂ The surge current caused by the difference, thereby protecting the power switching system 2.

Please refer to Figure 3, which is a schematic waveform diagram of the boost circuit 20 of the dual-input power switching system 1 and 2 of the present invention being activated. See Figures 1 and 2 together. Before time t1, the first DC power supply V _DC1 provides the first DC voltage V ₁ (for example, 48 volts), and the first switches SW ₁ and SW ₃ are turned on to deliver the first DC voltage V ₁ to the DC conversion circuit 10 as the input voltage. V _IN . Between time t1 and t2, the first DC voltage _V1 is powered off causing the input voltage V _IN to power down to the minimum operating voltage of the power switching system 1, 2 (for example, 34 volts), so the boost circuit 20 is activated. Between time t2 and t3, the boost circuit 20 provides the sustaining voltage V _BUCK to boost the input voltage V _IN to a specific voltage (eg, 74 volts) greater than the second DC voltage V ₂ (eg, 68 volts).

Please refer to FIG. 4 , which is a schematic waveform diagram of power switching of the dual-input power switching system 2 of the present invention. See also FIG. 2 . The first control signal S ₁ controls the first power transistor Q ₁₁ , the third power transistor Q ₁₃ and the fourth power transistor Q ₁₄ of the _first switch SW 1 ; the second control signal S ₂ controls the second power transistor Q 14 of the second switch SW ₂ the fifth power transistor Q ₂₁ , the seventh power transistor Q ₂₃ and the eighth power transistor Q ₂₄ ; the second power transistor Q ₁₂ of the first switch SW ₁ controlled by the third control signal S ₃ ; and the fourth control The signal S ₄ controls the sixth power transistor Q ₂₂ of the second switch SW ₂ .

Before time t1, the third control signal S ₃ is at a high level to turn on the second power transistor Q 12 of the first switch SW ₃ , and the first control signal S ₁ is at a high level to turn on the second power transistor Q ₁₂ of the first switch SW ₃ The first power transistor Q ₁₁ , the third power transistor Q ₁₃ and the fourth power transistor Q ₁₄ enable the first DC power supply V _DC1 to provide the first DC voltage V ₁ (for example, 48 volts) to the DC conversion circuit 10 as Input voltage V _IN . At this time, the second control signal S ₂ is at a low level to turn off the fifth power transistor Q ₂₁ , the seventh power transistor Q ₂₃ and the eighth power transistor Q ₂₄ of the second switch SW ₄ , and the second DC The power supply V _DC2 is in the power supply standby state. Assume that the first DC power supply V _DC1 stops supplying power at time t1 (as shown in Figure 4, the first DC voltage V ₁ drops from 48 volts to 0 volts). At this time, the input voltage V _IN provided to the DC conversion circuit 10 gradually decreases. (e.g. down to 34 volts).

At time t2, the boost circuit 20 is activated, and the third control signal S ₃ is at a low level to turn off the second power transistor Q ₁₂ of the first switch SW ₁ to avoid the maintenance voltage provided by the boost circuit 20 The voltage difference between V _BUCK and the first DC voltage V ₁ (0 volts) generates a current that flows into the first DC power supply V _DC1 . When the boost circuit 20 is activated from time t2 to t3, the boost circuit 20 gradually increases the maintenance voltage V _BUCK to a specific voltage. In one embodiment, the maintaining voltage V _BUCK is generated by an auxiliary power supply. The auxiliary power supply can be provided by an energy storage component (such as, but not limited to, a capacitor, a supercapacitor, etc.) to provide power when the power supply is turned off. Or when the power is off, the output voltage can still maintain the output level normally within the hold-up time to provide stable power supply. Therefore, when the boost circuit 20 is activated, the boost circuit 20 is used to gradually increase the voltage (maintaining voltage V _BUCK ) as the auxiliary power supply. At this time, neither the first DC power supply V _DC1 nor the second DC power supply V _DC2 supplies power, and the maintaining voltage V _BUCK provided by the auxiliary power supply temporarily supplies power to the load 100 .

When the maintenance voltage V _BUCK increases to a specific voltage, in this embodiment, the specific voltage is 74 volts greater than the second DC voltage V ₂ (which is 68 volts), that is, at time t3, the maintenance voltage V _BUCK Increased to 74 volts, the first control signal S ₁ is at a low level to turn off the first power transistor Q ₁₁ , the third power transistor Q ₁₃ and the fourth power transistor Q ₁₄ of the first switch SW ₃ , so as to Turn off the power supply path of the first DC power supply V _DC1 . Until the specific voltage is maintained for a specific period of time from time t3 to t4, the second control signal S ₂ is at a high level to turn on the fifth power transistor Q ₂₁ , the seventh power transistor Q ₂₃ and the second switch SW ₄ The eight power transistors Q ₂₄ are used to prepare the second DC power supply V _DC2 to provide the second DC voltage V ₂ . Until the input voltage V _IN naturally drops to less than or equal to the second DC voltage V ₂ from time t4 to t5, the control circuit 32 turns on the sixth power transistor Q ₂₂ of the second switch SW ₄ through the fourth control signal S ₄ , so that The second DC power supply V _DC2 provides the second DC voltage V ₂ as the input voltage V _IN .

At time t4, the input voltage V _IN is pulled up by the sustaining voltage V _BUCK to a specific voltage (74 volts) greater than the second DC voltage V ₂ (68 volts), and the boost circuit 20 is turned off, so the input voltage V _IN will naturally drop from 74 volts to 68 volts. In this way, the input voltage V _IN can naturally connect from the higher specific voltage to the lower second DC voltage V ₂ , and no surge current will be generated during the natural decrease of the input voltage V _IN , thus avoiding the second DC voltage V 2 . The surge current caused by the voltage difference between the DC voltage V ₁ and the second DC voltage V ₂ further protects the power switching system 2 .

In one embodiment, the specific voltage is the maximum operating voltage of the power switching systems 1 and 2; it should be noted that the maximum operating voltage of the power switching systems 1 and 2 should be greater than the first DC voltage provided by the first DC power supply V _DC1 V ₁ and the second DC voltage V ₂ provided by the second DC power supply V _DC2 to ensure that the voltage received from the DC power supply does not exceed the safe operating range.

In one embodiment, the specific voltage is a voltage greater than the second DC voltage V ₂ . For example, when the first DC voltage V ₁ is 68 volts and the second DC voltage V ₂ is 48 volts, since the first DC voltage V ₁ has been powered down to zero volts at time t1 , the boosting circuit 20 only needs to At time t3, the maintaining voltage V _BUCK is raised to a specific voltage (for example, 54 volts) greater than the second DC voltage V ₂ (48 volts), so that surge current can be avoided.

After time t4, the boost circuit 20 no longer boosts the sustain voltage V _BUCK and pulls up the input voltage V _IN . When the input voltage V _IN naturally drops to less than the second DC voltage V ₂ , the second switch SW ₄ The body diode of the six-power transistor Q ₂₂ will naturally conduct in the forward direction. Since the boosting circuit 20 has been turned off, the sustaining voltage V _BUCK is no longer boosted, so the sustaining voltage V _BUCK will gradually decrease to the minimum operating voltage of the power switching system 2 (for example, 34 volts). Therefore, in one embodiment, there is no need to use the fourth control signal S ₄ to turn on the sixth power transistor Q ₂₂ at time t5; or, the sixth power transistor Q ₂₂ may be replaced with a diode. In one embodiment, turning on the sixth power transistor Q ₂₂ through the fourth control signal S ₄ at time t5 can reduce the on-resistance and voltage of the sixth power transistor Q ₂₂ to speed up the increase of the second DC voltage V ₂ Power supply.

In this way, through the power switching operation of the power switching system 2 in FIG. 4 , the inrush current caused by the voltage difference between the dual DC power supplies can be avoided, thereby protecting the power switching system 2 .

Please refer to Figure 5, which is a flow chart of the operating method of the dual-input power switching system 1 and 2 of the present invention, see Figures 1 to 4. The method is used to operate the dual-input power switching systems 1 and 2. The specific description of the dual-input power switching systems 1 and 2 can be found in the foregoing content (see Figures 1 to 4, and the corresponding instructions. ), no further details will be given here.

The steps of the operation method include: first, the first DC power supply V _DC1 provides the first DC voltage V ₁ as the input voltage V _IN , and converts the input voltage V _IN to power the load 100 (step S11 ). Then, it is determined whether the input voltage V _IN is powered off (step S12). When the input voltage V _IN does not lose power, the first DC power supply V _DC1 continues to supply power to the load 100 (return to step S11).

When the input voltage V _IN is powered off, it is determined that the first DC power supply V _DC1 stops supplying power, and the boost circuit 20 is started (step S13) to gradually increase the sustaining voltage V _BUCK as the input voltage V _IN (step S14). Among them, the maintenance voltage V _BUCK is the voltage of the auxiliary power supply. The auxiliary power supply can be provided by an energy storage component (such as, but not limited to, a capacitor, a supercapacitor, etc.) to provide power when the power supply is shut down or powered off. At this time, the output voltage can still maintain the output level normally within the hold-up time to provide stable power supply.

Then, it is determined whether the input voltage V _IN has reached a specific voltage (step S15). When the sustaining voltage V _BUCK has not reached the specific voltage, the boost circuit 20 is continuously activated to increase the sustaining voltage V _BUCK as the input voltage V _IN . Until the input voltage V _IN reaches a specific voltage, it is determined whether the input voltage V _IN has been maintained for a specific period of time (step S16). If the input voltage V _IN has not been maintained for a specific period of time, the determination of step S16 continues. If the input voltage V _IN has been maintained for a specific period of time, the second DC power supply V _DC2 is switched to provide the second DC voltage V ₂ as the input voltage V _IN (step S17 ).

To sum up, the present invention has the following characteristics and advantages: when the first DC power supply V _DC1 stops supplying and causes the input voltage V _IN to lose power, the boost circuit 20 is activated to provide the sustaining voltage V _BUCK to boost the input voltage. V _IN can maintain the operation of the load 100 when the input voltage V _IN is powered off; at the same time, the boost circuit 20 allows the maintenance voltage V _BUCK to reach a specific voltage greater than the second DC voltage V ₂ , which can prevent the first DC voltage V ₁ from being connected with the second DC voltage V 2 . The surge current caused by the voltage difference between the two DC voltages V ₂ thus protects the power switching systems 1 and 2; furthermore, after the boost circuit 20 has been turned off, the input voltage V _IN can naturally change from a higher specific value. The voltage is connected to the lower second DC voltage V ₂ , and no inrush current is generated during the natural decrease of the input voltage V _IN .

The above are only detailed descriptions and drawings of the preferred embodiments of the present invention. However, the characteristics of the present invention are not limited thereto and are not used to limit the present invention. The entire scope of the present invention should be determined by the following patent application scope. Subject to the present invention, all embodiments that are within the spirit of the patentable scope of the present invention and similar changes thereof shall be included in the scope of the present invention. Anyone familiar with the art can easily think of such changes or modifications in the field of the present invention. Modifications may be covered by the following patent scope of this case.

1: Dual input power switching system 2: Dual input power switching system V _DC1 : First DC power supply V _DC2 : Second DC power supply V ₁ : First DC voltage V ₂ : Second DC voltage 10: DC conversion circuit 20: Boost circuit 30: Control circuit 32: Control circuit SW ₁ : first switch SW ₂ : second switch SW ₃ : first switch SW ₄ : second switch F ₁ : first input protection circuit F ₂ : second Input protection circuit Q ₁₁ ~ Q ₁₄ : first ~ fourth power transistors Q ₂₁ ~ Q ₂₄ : fifth ~ eighth power transistor 100: load V _IN : input voltage V _BUCK : maintenance voltage V _OUT : output voltage C ₁ : First control signal C ₂ : Second control signal C _A : Boost signal S ₁ : First control signal S ₂ : Second control signal S ₃ : Third control signal S ₄ : Fourth control signal t1~t5 :Time S11~S17:Steps

FIG. 1 is a block diagram of a dual-input power switching system according to the first embodiment of the present invention.

FIG. 2 is a block diagram of a dual-input power switching system according to a second embodiment of the present invention.

FIG. 3 is a schematic waveform diagram of the boost circuit of the dual-input power switching system of the present invention being activated.

FIG. 4 is a schematic waveform diagram of power switching of the dual-input power switching system of the present invention.

FIG. 5 is a flow chart of the operating method of the dual-input power switching system of the present invention.

1:Dual input power switching system

V _DC1 : the first DC power supply

V _DC2 : Second DC power supply

V ₁ : first DC voltage

V ₂ : Second DC voltage

10: DC conversion circuit

20: Boost circuit

30:Control circuit

SW ₁ : first switch

SW ₂ : Second switch

100:Load

V _IN :Input voltage

V _BUCK : maintaining voltage

V _OUT :Output voltage

C ₁ : First control signal

C ₂ : Second control signal

C _A : Boost signal

Claims (20)

A dual-input power switching system, including: a first DC power supply for providing a first DC voltage; a second DC power supply for providing a second DC voltage; A DC conversion circuit is coupled to the output side of the second DC power supply and the output side of the first DC power supply, for receiving the first DC voltage or the second DC voltage as an input voltage, and converting the input voltage supply power to a load; and A boosting circuit, coupled to the input side of the DC conversion circuit, the output side of the first DC power supply, and the output side of the second DC power supply, used to cause the input voltage to drop when the first DC power supply stops supplying power. When the power supply is powered on, a maintenance voltage is provided to boost the input voltage, so that the input voltage reaches a specific voltage greater than the second DC voltage and then naturally decreases to less than or equal to the second DC voltage. The dual-input power switching system as described in claim 1 further includes: A first switch is coupled between the output side of the first DC power supply and the input side of the DC conversion circuit, wherein when the first switch is turned on, the first DC voltage is provided to the DC conversion circuit as the DC conversion circuit. input voltage; and a second switch coupled between the output side of the second DC power supply and the input side of the DC conversion circuit, wherein when the second switch is turned on, the second DC voltage is provided to the DC conversion circuit as the input voltage. The dual-input power switching system as described in claim 2 further includes: A control circuit, coupled to the first switch, the second switch, the DC conversion circuit and the boost circuit, is used to generate a first control signal to the first switch and generate a second control signal according to the input voltage. signal to the second switch and generate a boost signal to the boost circuit; When the control circuit detects that the first DC power supply provides the first DC voltage as the input voltage, the control circuit turns on the first switch through the first control signal; or when the control circuit detects that When the second DC power supply provides the second DC voltage as the input voltage, the control circuit turns on the second switch through the second control signal. The dual-input power switching system as described in claim 3, wherein: When the control circuit detects that the first DC power supply stops supplying and causes the input voltage to lose power, the control circuit activates the boost circuit through the boost signal, so that the boost circuit provides the maintenance voltage to the DC converter. circuit to boost the input voltage; Until the maintenance voltage reaches the specific voltage greater than the second DC voltage, the control circuit turns off the boost circuit through the boost signal, and turns off the first switch through the first control signal; and Until the specific voltage is maintained for a specific period of time, the control circuit turns on the second switch through the second control signal, so that the second DC power supply provides the second DC voltage as the input voltage. The dual-input power switching system of claim 2, wherein the first switch includes a first power transistor, a second power transistor, a third power transistor and a fourth power transistor, wherein: The first power transistor and the second power transistor are connected back-to-back to form a first switch group with bidirectional conduction. The first switch group is coupled in series to a positive electrode between the first DC power supply and the DC conversion circuit. path; and The third power transistor and the fourth power transistor are connected back-to-back to form a second switch group with bidirectional conduction. The second switch group is coupled in series to a negative electrode between the first DC power supply and the DC conversion circuit. path. The dual-input power switching system of claim 5, wherein the second switch includes a fifth power transistor, a sixth power transistor, a seventh power transistor and an eighth power transistor, wherein: The fifth power transistor and the sixth power transistor are connected back-to-back to form a third switch group with bidirectional conduction. The third switch group is coupled in series to a positive path between the second DC power supply and the DC conversion circuit. , and the sixth power transistor is coupled to the second power transistor; and The seventh power transistor and the eighth power transistor are connected back-to-back to form a fourth switch group with bidirectional conduction. The fourth switch group is coupled in series to a negative path between the second DC power supply and the DC conversion circuit. , and the eighth power transistor is coupled to the fourth power transistor. The dual-input power switching system as described in claim 6 further includes: A control circuit coupled to the first switch, the second switch, the DC conversion circuit and the boost circuit for generating a first control signal and a third control signal to the first switch according to the input voltage , generate a second control signal and a fourth control signal to the second switch, and generate a boost signal to the boost circuit. The dual-input power switching system as described in claim 7, wherein: When the control circuit detects that the first DC power supply provides the first DC voltage as the input voltage, the control circuit turns on the first power transistor, the third power transistor and the third power transistor through the first control signal. The fourth power transistor turns on the second power transistor through the third control signal; and When the control circuit detects that the input voltage is powered down due to a power outage of the first DC voltage, the control circuit activates the boosting circuit through the boosting signal, so that the boosting circuit provides the maintaining voltage to the DC converter. circuit to boost the input voltage. The dual-input power switching system as described in claim 8, wherein: When the input voltage begins to rise, the control circuit turns off the second power transistor through the third control signal; Until the maintaining voltage reaches the specific voltage greater than the second DC voltage, the control circuit turns off the boosting circuit through the boosting signal, and turns off the first power transistor and the third power transistor through the first control signal. three power transistors and the fourth power transistor; and Until the input voltage maintains at the specific voltage for a specific period of time, the control circuit turns on the fifth power transistor, the seventh power transistor and the eighth power transistor through the second control signal to prepare the third power transistor. Two DC power supplies provide the second DC voltage. The dual-input power switching system as described in claim 9, wherein until the input voltage naturally drops to less than or equal to the second DC voltage: The control circuit turns on the sixth power transistor through the fourth control signal, so that the second DC power supply provides the second DC voltage as an input voltage. The dual-input power switching system as described in claim 9, wherein until the input voltage naturally drops to less than or equal to the second DC voltage: The body diode of the sixth power transistor naturally conducts forward, so that the second DC power supply provides the second DC voltage as the input voltage. The dual-input power switching system of claim 1, wherein the specific voltage is a maximum operating voltage of the dual-input power switching system, and the maximum operating voltage is greater than the first DC voltage and the second DC voltage. The dual-input power switching system of claim 1, wherein the boost circuit is activated when the first DC voltage is powered off causing the input voltage to power down to a minimum operating voltage of the dual-input power switching system. . The dual-input power switching system of claim 13, wherein when the boost circuit is turned off, the maintaining voltage is the minimum operating voltage of the dual-input power switching system. An operating method for a dual-input power switching system, including: (a) Provide a first DC voltage as an input voltage from a first DC power source, and convert the input voltage to power a load; (b) Determine whether the input voltage is powered off; (c) When the input voltage is powered off, a boost circuit is activated to gradually increase a maintenance voltage as the input voltage; (d) Determine whether the input voltage has reached a specific voltage; and (e) Until the input voltage has reached the specific voltage and maintained for a specific period of time, switch to provide a second DC voltage as the input voltage from a second DC power supply. The operation method as described in request item 15 further includes: When the input voltage does not lose power, the first DC voltage is provided by the first DC power supply as the input voltage; and When the input voltage has not reached the specific voltage, the boost circuit is continuously activated to increase the maintaining voltage as the input voltage. The operation method as described in claim 15, wherein step (c) includes: When the first DC voltage is powered off causing the input voltage to power down to a minimum operating voltage of the dual-input power switching system, the boost circuit is activated. The operation method as described in claim 15, wherein step (e) includes: After the input voltage has reached the specific voltage and maintained for a specific period of time, the boost circuit is turned off so that the input voltage naturally drops to less than or equal to the second DC voltage. The operation method of claim 18, wherein after the boost circuit is turned off, the maintaining voltage naturally drops to a minimum operating voltage of the dual-input power switching system. The operation method of claim 15, wherein the specific voltage is a maximum operating voltage of the dual-input power switching system, and the maximum operating voltage is greater than the first DC voltage and the second DC voltage.

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