TWI854441B - Two-stage voltage conversion system and method thereof - Google Patents

Abstract

The present invention is a two-stage voltage conversion system and method thereof, comprising a first-stage voltage converter, a second-stage voltage converter and an adaptive control unit, wherein the adaptive control unit is connected to the first-stage voltage converter and the second-stage voltage converter, and adjusts the voltage gain ratio of the first-stage voltage converter and the second-stage voltage converter to meet the overall gain ratio of the variable input power source converted into the gain output power source. A cycle adjustment signal and a frequency adjustment signal are variably generated according to the gain, so that the first-stage voltage converter converts the variable input power into the first voltage conversion power according to a first trigger command related to the cycle adjustment signal, and the second-stage voltage converter converts the first voltage conversion power into the gain output power according to a second trigger command related to the frequency adjustment signal.

Description

Two-stage voltage conversion system and method thereof

The present invention relates to a voltage conversion system and method thereof, and in particular to a two-stage voltage conversion system and method thereof for dynamically adjusting the gain ratio between two voltage converters to achieve efficiency optimization.

Battery-powered devices usually have a wide input voltage characteristic, and the power supply they require must also have a wide voltage gain ratio. Single-stage non-isolated circuits usually find it difficult to meet this requirement, let alone take into account both efficiency and performance. Using a two-stage isolated boost circuit is easier to achieve a wide voltage gain ratio and is therefore often used.

The most common circuit structure of a traditional DC-DC converter is a two-stage boost circuit that combines a boost converter with an LLC resonant converter. The LLC resonant converter can switch at zero voltage, which not only improves efficiency but also allows the circuit to operate at high frequency and reduce size. In the case of a variable input voltage, the LLC resonant converter can achieve a stable output voltage by changing the frequency.

As shown in FIG1 , a two-stage boost circuit 1 is shown, in which the boost converter 10 and the LLC resonant converter 12 each have a separate control circuit to adjust their output voltage. Under the requirement of a wide input voltage, the boost converter 10 provides a gain ratio for most high input voltages. Under a lower input voltage, the LLC converter 12 provides a secondary boost to meet the requirement of a wide input voltage.

However, the first control circuit 14 of the boost converter 10 includes a first voltage controller 140, a first current controller 142 and a pulse-width modulation (PWM) 144, and the second control circuit 16 of the LLC resonant converter 12 includes a second voltage controller 160, a second current controller 162 and a voltage-controlled oscillator (VCO) 164. The designs of the first control circuit 14 and the second control circuit 16 are complicated, which makes the operation integration between the first control circuit 14 and the second control circuit 16 more difficult. In addition, the current two-stage boost circuits are all optimized by the developer in advance to meet the specification requirements. This method may reduce the circuit efficiency and performance, or even make it unstable, during the circuit production process or when the circuit operating point deviates from the original design point due to environmental changes.

Therefore, how to integrate the first control circuit 14 and the second control circuit 16 to make the two-stage boost circuit more reliable and stable and ensure the circuit performance and reliability of the two-stage boost circuit is a problem that needs to be solved urgently.

In view of the problems of the prior art, the purpose of the present invention is to integrate the control circuit of the first-stage voltage converter of the two-stage voltage conversion circuit and the control circuit of the second-stage voltage converter as an interrelated control circuit group, so that the control circuit group is more reliable and stable, and can be adaptively adjusted in real time to optimize the efficiency of the conversion voltage gain, ensure the performance and reliability of the two-stage voltage conversion circuit, and control the temperature rise of the two-stage circuit.

According to the purpose of the present invention, a two-stage voltage conversion system is provided, including a first-stage voltage converter, a second-stage voltage converter and an adaptive control unit, wherein the first-stage voltage converter receives a variable input power source and converts the variable input power source into a first voltage conversion power source according to a first trigger command. The second-stage voltage converter is connected to the first-stage voltage converter, receives the first voltage conversion power source, and converts the first voltage conversion power source into a gain output power source according to a second trigger command and a third trigger command. The adaptive control unit is connected to the first-stage voltage converter and the second-stage voltage converter. The adaptive control unit receives the input voltage fed back by the variable input power supply, and receives the output voltage and output current fed back by the gain output power supply. The adaptive control unit adjusts the input current command obtained according to the output voltage adjustment, and adjusts the voltage gain ratio of the first-stage voltage converter and the second-stage voltage converter according to the input voltage, the input current command, the output voltage and the output current, so as to meet the variable input power conversion. The overall gain required for the gain output power supply is obtained by variably generating a cycle adjustment signal and a frequency adjustment signal, wherein the cycle adjustment signal is related to the gain of the variable input power supply converted into the first voltage conversion power supply, and the frequency adjustment signal is related to the gain of the first voltage conversion power supply converted into the gain output power supply, so as to output a first trigger command related to the cycle adjustment signal to the first-stage voltage converter, and output a second trigger command and a third trigger command related to the frequency adjustment signal to the second-stage voltage converter.

The adaptive control unit includes an adaptive controller, a first-stage control module and a second-stage control module. The adaptive controller receives and records the adjustment input current command, and compares the current adjustment input current command and the current frequency adjustment signal with the previous adjustment input current command and the previous frequency adjustment signal, and generates a comparison result. The voltage gain ratio of the first-stage voltage converter and the second-stage voltage converter is adjusted according to the comparison result, and the cycle adjustment signal and the frequency adjustment signal are variably generated. The first-stage control module is connected to the first-stage voltage converter and includes a voltage controller, a current controller and a pulse width modulator. The voltage controller receives the output voltage and adjusts the obtained adjustment input current command according to the output voltage. The current controller is connected to the voltage controller. The current controller receives the input current of the variable input power source and the input current adjustment command, and compares the output current and the input current adjustment command to output the control voltage command. The pulse width modulator is connected to the current controller and receives the control voltage command and the cycle adjustment signal, and outputs the first trigger command to the first-stage voltage converter according to the control voltage command and the cycle adjustment signal. The second-stage control module is a block wave signaler, which is connected to the second-stage voltage converter. The block wave signaler has a duty cycle of 50%. The block wave signaler adjusts the signal according to the frequency to output the second trigger command and the third trigger command to the second-stage voltage converter.

The first-stage voltage converter is a boost converter, which includes a first inductor, a first diode and a first transistor. The input end of the first inductor is connected to the positive electrode of the variable input power source, the input end of the first diode is connected to the output end of the first inductor, the output end of the first diode outputs the positive power source of the first voltage conversion power source, and the drain of the first transistor is connected to the output end of the first inductor and the drain of the first transistor. The input end of the first transistor, the source of the first transistor is connected to the negative pole of the variable input power supply, the gate of the first transistor is connected to the pulse width modulator, and receives the first trigger command, so as to control the first transistor to maintain the same switching frequency according to the first trigger command, change the duty cycle size of the first transistor, so as to control the gain size of the boost converter to the variable input power supply, and output the first voltage conversion power supply.

The first voltage measuring circuit is also included, one end of which is connected to the line between the positive electrode of the variable input power source and the input end of the first inductor, and the other end of which is connected to the line between the negative electrode of the variable input power source and the source of the first transistor, so as to measure the output voltage.

It also includes a first current measuring circuit, which is connected to the line between the positive pole of the variable input power source and the input end of the first inductor to measure the input current.

The second voltage measuring circuit is also connected to the line between the input end of the first diode and the source of the first transistor to measure the first voltage conversion power supply.

The second-stage voltage converter is an LLC resonant converter, including a second transistor, a third transistor, a second inductor, a second capacitor and a transformer. The drain of the second transistor is connected to the positive electrode of the first voltage conversion power source, the gate of the second transistor is connected to the block wave signaler, and receives a second trigger command to control the action of the second transistor according to the frequency adjustment signal. The drain of the third transistor is connected to the source of the second transistor, the drain of the third transistor is connected to the negative electrode of the first voltage conversion power source, the gate of the third transistor is connected to the block wave signaler, and receives a third trigger command to control the action of the third transistor according to the third switching frequency. The input end of the second inductor is connected to the line between the source of the first transistor and the drain of the second transistor. The input end of the second capacitor is connected to the drain of the third transistor. The positive pole of the primary side of the transformer is connected to the output end of the second inductor, and the negative pole of the primary side of the transformer is connected to the output end of the second capacitor, so as to control the second transistor and the third transistor to maintain the same duty cycle according to the second trigger command and the third trigger command, change the switching frequency of the second transistor and the third transistor, and control the gain of the LLC resonant converter to the first voltage conversion power supply, so that the secondary side of the transformer outputs the required gain output power supply. Among them, the switching frequency of the second transistor and the third transistor is the frequency value in the frequency adjustment signal.

It also includes a second current measuring circuit, which is connected to the positive pole of the secondary side of the transformer to measure the output current.

It also includes a bridge rectifier circuit, which is connected between the positive and negative poles of the secondary side of the transformer to output the current of the power supply with a stable output gain.

It also includes a third voltage measurement circuit, which is connected between the output end of the bridge rectifier circuit and the load to measure the output voltage.

Among them, the variable input power source is a battery.

According to the purpose of the present invention, a two-stage voltage conversion method is provided, which is applied to a two-stage voltage conversion system, and the voltage gain ratio of the first-stage voltage converter and the second-stage voltage converter is adjusted by an adaptive control unit, so that the process of converting the variable input power supply into the gain output power supply can achieve the maximum efficiency of the overall gain.

The adaptive control unit variably generates a cycle adjustment signal and a frequency adjustment signal to adjust the voltage gain ratio of the first-stage voltage converter and the second-stage voltage converter, and the step of the adaptive control unit variably generating the cycle adjustment signal and the frequency adjustment signal includes reading the last adjustment input current command and the frequency adjustment signal, and reading the current adjustment input current command and the frequency adjustment signal, and adjusting the voltage gain ratio of the first-stage voltage converter and the second-stage voltage converter by comparing the last adjustment input current command and the frequency adjustment signal, and the current adjustment input current command and the frequency adjustment signal.

Among them, if the current adjustment input current command is greater than the previous adjustment input current command, and the frequency value of the current frequency adjustment signal is greater than the frequency value of the previous frequency adjustment signal, then the frequency value of the next frequency adjustment signal is reduced to reduce the voltage gain of the second-stage voltage converter, and the duty cycle of the next cycle adjustment signal is increased to increase the voltage gain of the first-stage voltage converter, and then the cycle adjustment signal and the frequency adjustment signal are updated accordingly.

Among them, if the current adjustment input current command is greater than the previous adjustment input current command, and the frequency value of the current frequency adjustment signal is less than the frequency value of the previous frequency adjustment signal, the frequency value of the next frequency adjustment signal is increased to increase the voltage gain of the second-stage voltage converter, and the duty cycle of the next cycle adjustment signal is reduced to reduce the voltage gain of the first-stage voltage converter, and then the frequency values of the cycle adjustment signal and the frequency adjustment signal are updated accordingly.

Among them, if the current adjustment input current command is less than the previous adjustment input current command, and the frequency value of the current frequency adjustment signal is less than the frequency value of the previous frequency adjustment signal, then the frequency value of the next frequency adjustment signal is reduced to reduce the voltage gain of the second-stage voltage converter, and the duty cycle of the next cycle adjustment signal is increased to increase the voltage gain of the first-stage voltage converter, and then the frequency value of the cycle adjustment signal and the duty cycle of the frequency adjustment signal are updated accordingly.

Among them, if the current adjustment input current command is less than the previous adjustment input current command, and the frequency value of the current frequency adjustment signal is greater than the previous frequency adjustment signal, the frequency value of the next frequency adjustment signal is increased to increase the voltage gain of the second-stage voltage converter, and the duty cycle of the next cycle adjustment signal is reduced to reduce the voltage gain of the first-stage voltage converter, and then the cycle adjustment signal and the frequency adjustment signal are updated accordingly.

The frequency value of the frequency adjustment signal is between the resonant frequency of the second-stage voltage converter and the minimum switching frequency of the second-stage voltage converter.

The adaptive control unit receives a first operating temperature of the first-stage voltage converter and a second operating temperature of the second-stage voltage converter. When the adaptive control unit adjusts the cycle adjustment signal and the frequency adjustment signal, the first operating temperature and the second operating temperature do not exceed a first safe operating temperature of the first-stage voltage converter and a second safe operating temperature of the second-stage voltage converter.

In summary, the present invention integrates and controls the first-stage control module and the second-stage control module, so that the two-stage voltage conversion system maintains the best conversion efficiency for boosting, making the two-stage voltage conversion system more reliable and stable, and ensuring the circuit performance and reliability of the two-stage boost circuit.

The embodiments of the present invention will be further explained below with the help of the relevant drawings. As far as possible, the same reference numerals in the drawings and the specification represent the same or similar components. In the drawings, the shapes and thicknesses may be exaggerated for the sake of simplicity and convenience. It is understood that the components not specifically shown in the drawings or described in the specification have the form known to the ordinary technicians in the relevant technical field. The ordinary technicians in this field can make various changes and modifications based on the content of the present invention.

Please refer to FIG. 2 , the present invention is a two-stage voltage conversion system, including a first-stage voltage converter 2, a second-stage voltage converter 3 and an adaptive control unit 4. The first-stage voltage converter 2 receives a variable _input power source vin , and converts the variable _input power source _vin into _{a first voltage conversion power source vd} according to a first trigger command GQm _. The second-stage voltage converter 3 is connected to the first-stage voltage converter ₂ , receives the first voltage conversion power source vd , and converts the first voltage conversion power source _vd into a gain output power source _vout according to a second trigger command GQa and a _third trigger command GQb .

Furthermore, the adaptive control unit 4 is connected to the first-stage voltage converter 2 and the second-stage voltage converter 3. The adaptive control unit 4 receives the input voltage vi of the variable _input power source vin , and receives the output voltage v0 _and the output current i0 _fed back by _the gain output power source _vout . The adaptive control unit 4 adjusts the adjusted input current command i _LC according to the output voltage v _o , and calculates _{the input power according to the input voltage v i} and _the adjusted input current command i _LC , and calculates the output power according to the output voltage v _o and the output current i _o according to the input voltage v i and _the adjusted input current command i _LC , and _compares the input power with the output power to generate a comparison result. According to the comparison result, the voltage gain ratio of the first-stage voltage converter 2 and the second-stage voltage converter 3 is adjusted to meet the overall gain of the variable input power source v _in converted into the gain output power source v _out , so that the adaptive control unit 4 variably generates the cycle adjustment signal f _{s 1} and the frequency adjustment signal fs , so that the adaptive control unit 4 outputs _a first _trigger command _GQm related to the period adjustment signal fs1 to the first-stage voltage converter 2, and outputs a second trigger command _GQa and a third trigger command GQb _related to the frequency adjustment signal fs _to the second-stage voltage converter 3.

In one embodiment of the present invention, the variable input power source vin _is a battery, more specifically a rechargeable battery. The first-stage voltage converter 2 is a boost converter, which includes a first inductor L , a first diode D1 , and a first transistor Qm _. The input end of the first inductor L is connected _to the positive electrode _of the variable input power source vin , the input end of _the first diode D1 _is connected to the output end of the first inductor L , the output end of the first diode D1 outputs the positive power _of the first voltage conversion power source vd , the drain of the first transistor Qm _is connected to the output end of the first inductor L and the input end of _the first diode D1 , the source of _the first transistor Qm is connected to the negative electrode _of the variable input power source vin , the gate of the first transistor Qm _is connected to the pulse width modulator, and receives _the first trigger command GQm , according to the first trigger command, the _first transistor Qm _is controlled to maintain the same switching frequency, the duty cycle of the first transistor is changed, the gain of the boost converter to the variable input power source vin is controlled, and the first voltage conversion power source vd _is output. In detail, the cycle adjustment signal fs1 is the basis for the first trigger command GQm _{to change} the duty cycle of the first transistor.

In this embodiment, a first voltage measuring circuit 50, a second voltage measuring circuit 51 and a first current measuring circuit 52 are further _included . One end of the first voltage measuring circuit 50 is connected to the line between the positive electrode of the variable _input power source vin and the input end of the first inductor L , and the other end of the first voltage measuring circuit 50 is connected _to the line between the negative electrode of the variable input power source vin and the source of the first transistor Qm to measure the output voltage vi . The second voltage measuring circuit 51 is connected to the line between the _input end of the first diode D1 and _the source of the first transistor Qm to measure the first voltage conversion power source _{vd .} The first current measuring circuit 52 is connected to a line between the positive electrode of _the variable input power source vin and the input terminal of the first inductor L to measure the input _current iL .

In this embodiment, the second-stage voltage converter 3 is an LLC resonant converter, including _a second transistor Qa , _a third transistor Qb _, a second inductor Lr _, a second capacitor Cr and a transformer 30. The drain of the second transistor Qa _is connected to the positive electrode of the first voltage conversion power source vd , and the gate of _{the second transistor Qa} is connected _to the block wave signal and receives _the second trigger command GQa _to control the action of _{the second transistor Qa} according to the frequency adjustment signal fs . The drain of the _third transistor Qb is connected _to the source of _{the second transistor Qa} , the drain of the third transistor Qb is connected to the negative electrode _of the first voltage conversion power source vd , the gate of _the third transistor Qb is connected _to the block wave signal, and receives the third trigger command GQb to control the action of the third transistor Qb according to the third switching frequency. The input end of the second inductor Lr is connected _to the line between the source of the first transistor _Qm and _the drain _{of the} second transistor Qa . The input end of the second capacitor Cr _is connected to the drain of the third transistor Qb . The positive pole of the primary side of the transformer 30 is connected to the output end of the _{second inductor} Lr , and the negative pole of the primary side of the transformer 30 is connected to the output end _of the second capacitor Cr . In addition, there is an inductance Lm between the positive and negative poles of the primary side of the transformer 30, and a load Rload is connected between the positive _and negative poles of the gain output power supply _vout . By controlling _the second transistor Qa and the third transistor Qb to _maintain the same duty cycle according to the second trigger command and the third trigger command _, the switching frequency of _the second transistor Qa and the third transistor Qb is changed to control the actions _of the second transistor Qa and the third transistor Qb , thereby adjusting the gain of the LLC resonant converter to the first voltage _conversion power source vd , so that the secondary side of _the transformer outputs the required gain output power _source vout . In further detail, the actions of the second transistor Qa _and the third transistor Qb controlled by the second trigger command and _the third trigger command are usually one on and one off. The duty cycles of _the second transistor Qa and the third transistor Qb are 50% each, and the second trigger command and the third trigger command use the frequency adjustment signal fs as a basis _for changing the switching frequency of the second transistor Qa and the third transistor Qb . In other words, the switching frequency of the second transistor Qa _{and the} third transistor Qb _is the frequency value in _the frequency adjustment _signal fs .

In this embodiment, a second current measuring circuit 54, a third voltage measuring circuit 56 and a bridge rectifier circuit 58 are further included. The second current measuring circuit 54 is connected to the positive electrode of the secondary side of the transformer 30 to measure the output current i _o . The bridge rectifier circuit 58 is connected between the positive electrode and the negative electrode of the secondary side of the transformer 30 so that the stable output gain output power v _out is output to the load R _load in the form of direct current. The third voltage measuring circuit 56 is connected between the output end of the bridge rectifier circuit 58 and the load R _load to measure the output voltage v _o .

As can be seen from the above, the boost converter and LLC resonant converter of the present invention are similar to the two-stage boost circuit formed by combining the conventional boost converter and LLC resonant converter. However _, the boost converter and LLC resonant converter of the present invention can dynamically adjust the switching frequency of the first transistor Qm , the second transistor Qa and the third transistor _Qb simultaneously by using the adaptive control unit 4 , thereby changing the gain ratio of the boost converter and the LLC resonant converter, so that the two-stage voltage conversion system maintains the best efficiency _and boosts to the required overall gain.

>0)表示效率逐漸增加。當超過最高效率點所對應的頻率調整訊號f _s 時，效率變化量(△η)與頻率調整訊號f _s 的頻率變化量(△f _s )的比值小於零(

>0)表示效率逐漸增加。 Please refer to Figure 3, which is a curve showing the relationship between the efficiency of the variable input power source vin of the two-stage voltage conversion system _in converting the variable _input power source vin into the gain output power source vout and the change in the frequency adjustment signal fs _. For the highest efficiency point in Figure 3, when the frequency adjustment signal _fs corresponding to the highest efficiency point has not been _exceeded , the ratio of the efficiency change (△ η ) to the frequency change (△ fs ₎ of the frequency adjustment signal fs is greater than zero (

>0) indicates that the efficiency gradually increases. When the frequency adjustment _signal fs corresponding to the highest efficiency point is exceeded, the ratio of the efficiency change (△η) to the frequency change of the frequency adjustment _signal fs ( _△ fs ) is less than zero (

>0) indicates a gradual increase in efficiency.

>0)表 示效率逐漸增加。當超過最高效率點所對應的頻率調整訊號f _s 時，調整輸入電流命令i _LC 的電流變化量(△i _LC )與頻率調整訊號f _s 的頻率變化量(△f _s )的比值小於零(

>0)表示效率逐漸增加。 Please refer to Figure 4. When the output power and input voltage vi of the gain output power supply v _out are the _same , the lower the input current i _L , the higher the efficiency. When the actual efficiency is calculated by adjusting the input current command i _LC , the lowest adjusted input current command i _LC corresponds to the frequency adjustment signal f _s of the highest efficiency. When the frequency adjustment signal f _s corresponding to the highest efficiency point is not exceeded, the ratio of the current change (△ i _LC ) of the adjusted input current command i _LC to the frequency change (△ f _s ) of the frequency adjustment signal f _s is greater than zero (

>0) indicates that the efficiency gradually increases. When the frequency adjustment _signal fs corresponding to _the highest efficiency point is exceeded, the ratio of the current change (△ iLC ) of the adjustment input current command iLC to the frequency change (△ _fs ) of the frequency adjustment signal fs _is less _than zero (

>0) indicates a gradual increase in efficiency.

According to the relationship among the efficiency of converting the variable input power source vin _into the gain output power source _vout , the frequency adjustment _signal fs and the adjustment input current command iLC _, an adaptive control unit 4 is designed in this embodiment to integrate the first-stage control module 42 and the second-stage control module 44, so that the first-stage control module 42 and the second-stage control module 44 can adjust the voltage gain of the first-stage voltage converter 2 and the voltage gain of the second-stage voltage converter 3 in real time.

In this embodiment, the adaptive control unit 4 includes an adaptive controller 40, a first-stage control module 42, and a second-stage control module 44. The adaptive controller 40 receives and compares the previous adjustment input current command i _LC with the next adjustment input current command i _LC , and receives and compares the previous adjustment input current command i _LC with the next adjustment input current command to generate a comparison result, and adjusts the voltage gain ratio requirements of the first-stage voltage converter 2 and the second-stage voltage converter 3 according to the comparison result to meet the overall gain required for converting the variable input power source v _in into the gain output power source v _out , and variably generates the cycle adjustment signal f _s1 and the frequency adjustment signal f _s . In addition, the adaptive control unit 4 also receives the input voltage vi _{, the output} voltage v0 and the output current i0 , and calculates _the input power and the output power according to the input voltage vi _, the input current adjustment command iLC , the output voltage v0 and _the output current _i0 to confirm the power adjustment status.

In this embodiment, the first-stage control module 42 is connected to the first-stage voltage converter 2, and includes a voltage controller 420, a current controller 422, and a pulse width modulator 424. The voltage controller 420 receives the output voltage v _o and adjusts the adjusted input current command i _LC according to the output voltage v _o . The current controller 422 is connected to the voltage controller 420, and the current controller 422 receives the input current i _L of the variable input power source vi _n and the adjusted input current command i _LC , and compares the output current i _o and the adjusted input current command i _LC , and outputs the control voltage command v _con . The pulse width modulator 424 is connected to the current controller 422 and receives the control voltage command v _con and the cycle adjustment signal f _{s 1} , and outputs the first trigger command GQ _m to the first-stage voltage converter 2 according to the control voltage command v _con and the cycle adjustment signal f _{s 1} .

In this embodiment, the second-stage control module 44 is a block wave signal device, and is connected to the second-stage voltage converter 3. The duty cycle of the block wave signal device is ₅₀ %. The block wave signal device outputs the _second trigger command GQa and the third trigger command GQb to the second-stage voltage converter 3 according to the frequency adjustment signal fs _{. By changing the adjustment input current command iLC} , _the cycle adjustment signal fs1 and the frequency adjustment signal fs _are adjusted, so that the first transistor Qm can adjust the gain of the first-stage voltage converter ₂ in real time with the adjusted cycle adjustment signal _fs1 , and _the second transistor Qa and the third transistor Qb can adjust the gain of the first _- stage voltage converter 2 in real _time . , to adjust the gain of the second-stage voltage converter 3. At this time, the ratio of the adjusted gain of the first-stage voltage converter 2 to the gain of the second-stage voltage converter 3 is the aforementioned voltage gain ratio for adjusting the first-stage voltage converter 2 to the second-stage voltage converter 3.

In the embodiment of the present invention, please refer to FIG5. Since the frequency adjustment signal is given by an open loop, the present invention does not need the zero current switch protection required by the LLC resonant converter of the general closed loop control, and the circuit is more reliable. The switching frequency given by the present invention under normal operation is the resonant frequency f _r of L _r - C _r , as shown in FIG5, the normal operating point, so under light load (Light load) or positive load (Max load, Q _max = 0.4), the same gain can be maintained, and the circulating current of the switch is the lowest, resulting in better efficiency.

Please refer to FIG. 5. The present invention is a two-stage voltage conversion method, _which is applied to the aforementioned two _- stage voltage conversion system. The adaptive control unit 4 variably generates a period adjustment signal fs1 and a frequency adjustment signal fs _to adjust the voltage gain ratio to achieve the maximum efficiency ( η ) of the overall gain. The steps of the adaptive control unit 4 variably generating the period adjustment signal fs1 and _the frequency adjustment signal fs include: (S101) reading the last adjustment input current command i _LC and the frequency adjustment signal fs _; (S102) reading the current adjustment input current command i _LC and the frequency adjustment _signal fs ; (S103) determining whether the current adjustment input current command i _LC is greater than the last adjustment input current command i _LC . If yes, proceed to step (S104), otherwise proceed to step (S107); (S104) Determine whether the frequency value of the current frequency adjustment signal f _s is greater than the frequency value of the last frequency adjustment signal f _s . If yes, proceed to step (S105), otherwise proceed to step (S106); (S105) Reduce the frequency value of the next frequency adjustment signal f _s to increase the voltage gain of the second-stage voltage converter 3 and increase the next cycle adjustment signal f _{s 1} duty cycle to reduce the voltage gain of the first _- stage voltage converter 2, and then proceed to step (S108); (S106) increase the frequency value of the next frequency adjustment signal fs to reduce the voltage gain of the second-stage voltage converter 3, and reduce the duty cycle of the next cycle adjustment signal fs1 to increase the voltage gain of the first-stage voltage converter 2; (S107) determine whether the frequency value of the current frequency adjustment signal fs is less _than the frequency value of the previous frequency adjustment signal fs _. If the frequency value of the cycle adjustment signal _fs1 is _correct , proceed _to step (S105); otherwise, proceed to step (S106); (S108) after the duty cycle of _the cycle adjustment signal fs1 and the frequency value of the frequency adjustment signal fs are adjusted, the duty cycle of the cycle adjustment signal fs1 and the frequency value of the frequency adjustment signal fs are _updated and then transmitted to the first-stage voltage converter 2 and the second-stage voltage converter 3 respectively to change the voltage gain ratio of the first-stage voltage converter 2 and the second-stage voltage converter 3, and then the process is looped according to step (S101) and its subsequent steps.

In the present invention, the frequency value of the frequency adjustment signal fs is between the resonance frequency of the second _- stage voltage converter 3 and the minimum switching frequency of the second-stage voltage converter 3. In addition, the adaptive control unit 4 receives a first operating temperature _T1 of the first-stage voltage converter 2 and a second operating temperature _T2 of _the second-stage voltage converter 3. When the adaptive control unit 4 adjusts the frequency values of the cycle adjustment signal fs1 and the frequency adjustment signal fs , the first operating temperature _T1 and _the second operating temperature _T2 do not exceed a first safe operating temperature of the first-stage voltage converter 2 and a second safe operating temperature of the second-stage voltage converter 3.

In summary, the present invention integrates the first-stage control module 42 and the second-stage control module 44 _to adjust the period adjustment signal fs1 of the first-stage voltage converter 2 in real time to control the first-stage voltage converter 2 _to convert the variable input power source vin into the gain of the first voltage conversion power source vd _, and adjusts the frequency adjustment signal fs of the second-stage voltage converter ₃ to control the second-stage voltage converter 3 to convert the variable input power source vin _into the gain of the second voltage conversion power source, so that the two-stage voltage conversion system maintains the best conversion efficiency for boosting, making the two-stage voltage conversion system more reliable and stable, and ensuring the circuit performance and reliability of the two-stage boost circuit.

The above is only an example to illustrate the preferred implementation of the present invention, and is not intended to limit the scope of implementation. All simple substitutions and equivalent changes made according to the scope of the patent application of the present invention and the content of the patent specification are within the scope of the patent application of the present invention.

1: Two-stage boost circuit

10: Boost converter

12: LLC resonant converter

14: First control circuit

140: First voltage controller

142: First current controller

144: Pulse Width Modulator

16: Second control circuit

160: Second voltage controller

162: Second current controller

164: Voltage-controlled oscillator

2: First stage voltage converter

3: Second stage voltage converter

30: Transformer

4: Adaptive control unit

40: Adaptive controller

42: First level control module

420: Voltage controller

422: Current controller

424: Pulse Width Modulator

44: Second level control module

v _in : variable input power

50: First voltage measurement circuit

51: Second voltage measurement circuit

52: First current measurement circuit

54: Second current measurement circuit

56: The third voltage measurement circuit

58: Bridge rectifier circuit

GQ _m : First trigger command

GQ _a : Second trigger command

GQ _b : The third trigger command

v _d : First voltage conversion power source

v _out : Gain output power

v _o : output voltage

v _i : Input voltage

i _LC : Adjust input current command

i _o : output current

f _{s 1} : cycle adjustment signal

f _s : frequency adjustment signal

L : First inductor

D ₁ : First diode

Q _m : First transistor

Q _a : Second transistor

Q _b : The third transistor

L _r : Second inductor

C _r : Second capacitor

R _load : load

L _m : The inductance of the primary side of the transformer

S101~S108: Process steps

Figure 1 is a schematic diagram of a two-stage boost circuit of the prior art.

Figure 2 is a schematic diagram of an embodiment of the two-stage voltage conversion system of the present invention.

Figure 3 is a schematic diagram showing the relationship between the frequency adjustment signal and efficiency of the present invention.

Figure 4 is a schematic diagram showing the relationship between the input current adjustment command and the frequency adjustment signal of the present invention.

Figure 5 is a schematic diagram showing the relationship between the voltage gain and the frequency adjustment signal of the present invention under different loads.

Figure 6 is a schematic diagram of the process of the two-level voltage conversion method of the present invention.

2: First stage voltage converter 3: Second stage voltage converter 30: Transformer 4: Adaptive control unit 40: Adaptive controller 42: First stage control module 420: Voltage controller 422: Current controller 424: Pulse width modulator 44: Second stage control module : Variable input power supply 50: First voltage measurement circuit 51: Second voltage measurement circuit 52: First current measurement circuit 54: Second current measurement circuit 56: Third voltage measurement circuit 58: Bridge rectifier circuit ：First trigger command : Second trigger command ：The third trigger command ：First voltage conversion power supply : Gain output power : Output voltage : Input voltage : Adjust input current command : Output current ：Cycle adjustment signal : Frequency adjustment signal ：First Inductor ：First diode ：First transistor ：Second transistor ：Third transistor ：Second inductor ：Second capacitor : Load : The inductance of the primary side of the transformer

Claims (14)

A two-stage voltage conversion system includes: a first-stage voltage converter, receiving a variable input power source, and converting the variable input power source into a first voltage conversion power source according to a first trigger command; a second-stage voltage converter, connected to the first-stage voltage converter, receiving the first voltage conversion power source, and converting the first voltage conversion power source into a gain output power source according to a second trigger command and a third trigger command; and an adaptive control unit, connected to the first-stage voltage converter and the second-stage voltage converter, the adaptive control unit receiving an input voltage of the variable input power source and an output voltage feedback from the gain output power source. The adaptive control unit obtains an adjusted input current command according to the output voltage, and adjusts the voltage gain ratio of the first-stage voltage converter and the second-stage voltage converter according to the input voltage, the adjusted input current command, the output voltage and the output current, so as to meet the overall gain of the variable input power source converted into the gain output power source, and variably generates a cycle adjustment signal and a frequency adjustment signal, so as to output the first trigger command to the first-stage voltage converter according to the cycle adjustment signal, and output the second trigger command and the third trigger command to the second-stage voltage converter according to the frequency adjustment signal. The two-stage voltage conversion system as described in claim 1, wherein the adaptive control unit comprises: an adaptive controller, receiving and recording the adjustment input current command, the frequency adjustment signal and the period adjustment signal, and generating a comparison signal according to the comparison between the current adjustment input current command and the previous adjustment input current command, and the current frequency adjustment signal and the previous frequency adjustment signal. The first-stage control module is connected to the first-stage voltage converter and includes: a voltage controller, which receives the output voltage and adjusts the adjusted input voltage according to the output voltage. a current controller connected to the voltage controller, the current controller receives an input current of the variable input power source and the adjustment input current command, compares the output current and the adjustment input current command, and outputs a control voltage command; and a pulse width modulator connected to the current controller, receives the control voltage command and the cycle adjustment signal, and adjusts the control voltage command according to the control voltage command. and the cycle adjustment signal to output the first trigger command to the first-stage voltage converter; a second-stage control module connected to the second-stage voltage converter, the second-stage control module is a block wave signaler, the block wave signaler has a duty cycle of 50%, and the block wave signaler adjusts the signal according to the frequency to output the second trigger command and the third trigger command to the second-stage voltage converter. A two-stage voltage conversion system as described in claim 2, wherein the first-stage voltage converter is a boost converter, and the boost converter includes: a first inductor, the input end of the first inductor is connected to the positive electrode of the variable input power source; a first diode, the input end of the first diode is connected to the output end of the first inductor, and the output end of the first diode outputs the positive power of the first voltage conversion power source; and a first transistor, the drain of the first transistor The output end of the first inductor is connected to the input end of the first diode, the source of the first transistor is connected to the negative pole of the variable input power source, the gate of the first transistor is connected to the pulse width modulator, and receives the first trigger command to maintain the same switching frequency according to the first trigger command, change the duty cycle size of the first transistor, so as to control the gain size of the boost converter to the variable input power source, and output the first voltage conversion power source. The two-stage voltage conversion system as described in claim 3 includes a first voltage measuring circuit, one end of which is connected to the line between the positive electrode of the variable input power source and the input end of the first inductor, and the other end of which is connected to the line between the negative electrode of the variable input power source and the source of the first transistor to measure the output voltage. The two-stage voltage conversion system as described in claim 3 includes a first current measuring circuit, which is connected to the line between the positive electrode of the variable input power source and the input end of the first inductor to measure the input current. The two-stage voltage conversion system as described in claim 3 further includes a second voltage measurement circuit connected to the line between the input terminal of the first diode and the source of the first transistor to measure the first voltage conversion power source. The two-stage voltage conversion system as described in claim 3, wherein the second-stage voltage converter is an LLC resonant converter, comprising: a second transistor, the drain of the second transistor is connected to the positive electrode of the first voltage conversion power source, the gate of the second transistor is connected to the block wave signaler, and receives the second trigger command to control the second trigger command according to the second trigger command. The second transistor is controlled to maintain the same duty cycle, and the switching frequency of the second transistor is changed; a third transistor, the drain of the third transistor is connected to the source of the second transistor, the drain of the third transistor is connected to the negative electrode of the first voltage conversion power source, the gate of the third transistor is connected to the block wave signal, and receives the third trigger command, to control the third transistor to maintain the same duty cycle according to the third trigger command, and change the switching frequency of the third transistor; a second inductor, the input end of the second inductor is connected to the line between the source of the first transistor and the drain of the second transistor; a second capacitor, the input end of the second capacitor is connected to the drain of the third transistor; and a transformer, the positive pole of the primary side of the transformer is connected to the output end of the second inductor, the negative pole of the primary side of the transformer is connected to the output end of the second capacitor, and the secondary side of the transformer outputs the gain output power; wherein the switching frequency of the second transistor and the third transistor is the frequency value in the frequency adjustment signal. The two-stage voltage conversion system as described in claim 7 includes a second current measuring circuit connected to the positive pole of the secondary side of the transformer to measure the output current. The two-stage voltage conversion system as described in claim 7 includes a bridge rectifier circuit connected between the positive and negative poles of the secondary side of the transformer to stabilize the current of the gain output power supply. The two-stage voltage conversion system as described in claim 9 includes a third voltage measurement circuit, which is connected between the output terminal of the bridge rectifier circuit and a load to measure the output voltage. A two-stage voltage conversion system as described in claim 1, wherein the variable input power source is a battery. A two-stage voltage conversion method is applied to a two-stage voltage conversion system as in any one of claim items 1 to 10, wherein the adaptive control unit variably generates the cycle adjustment signal and the frequency adjustment signal to adjust the voltage gain ratio, so as to improve the overall gain of the two-stage voltage conversion system at the best efficiency. The steps of the adaptive control unit variably generating the cycle adjustment signal and the frequency adjustment signal include: reading the last adjustment input current command and the frequency adjustment signal; reading the current adjustment input current command and the frequency adjustment signal; and When the current adjustment input current command is greater than the previous adjustment input current command, and the frequency value of the frequency adjustment signal is greater than the frequency value of the previous frequency adjustment signal, the frequency value of the frequency adjustment signal is reduced to reduce the voltage gain of the second-stage voltage converter, and the duty cycle of the next cycle adjustment signal is increased to increase the voltage gain of the first-stage voltage converter; when the current adjustment input current command is greater than the previous adjustment input current command, and the frequency value of the frequency adjustment signal is less than the frequency value of the previous frequency adjustment signal, the frequency value of the frequency adjustment signal is reduced to reduce the voltage gain of the second-stage voltage converter, and the duty cycle of the next cycle adjustment signal is increased to increase the voltage gain of the first-stage voltage converter. When the frequency value of the frequency adjustment signal of the current frequency adjustment signal is smaller than the frequency value of the frequency adjustment signal of the previous frequency adjustment signal, the frequency value of the frequency adjustment signal of the next frequency adjustment signal is increased to increase the voltage gain of the second-stage voltage converter, and the duty cycle of the next cycle adjustment signal is reduced to reduce the voltage gain of the first-stage voltage converter; when the current adjustment input current command is smaller than the previous adjustment input current command, and the frequency value of the frequency adjustment signal of the current frequency adjustment signal is smaller than the frequency value of the frequency adjustment signal of the previous frequency adjustment signal, the frequency value of the frequency adjustment signal of the next frequency adjustment signal is reduced to reduce the voltage gain of the second-stage voltage converter. The voltage gain of the first-stage voltage converter is increased, and the duty cycle of the next cycle adjustment signal is increased to increase the voltage gain of the first-stage voltage converter; and when the current adjustment input current command is less than the previous adjustment input current command, and the frequency value of the current frequency adjustment signal is greater than the frequency value of the previous frequency adjustment signal, the frequency value of the next frequency adjustment signal is increased to increase the voltage gain of the second-stage voltage converter, and the duty cycle of the next cycle adjustment signal is reduced to reduce the voltage gain of the first-stage voltage converter. A two-stage voltage conversion method as described in claim 12, wherein the frequency value of the frequency adjustment signal is between the resonant frequency of the second-stage voltage converter and the minimum switching frequency of the second-stage voltage converter. A two-stage voltage conversion method as described in claim 12, wherein the adaptive control unit receives a first operating temperature of the first-stage voltage converter and a second operating temperature of the second-stage voltage converter, and when the adaptive control unit adjusts the frequency value of the cycle adjustment signal and the duty cycle of the frequency adjustment signal, the first operating temperature and the second operating temperature do not exceed a first safe operating temperature of the first-stage voltage converter and a second safe operating temperature of the second-stage voltage converter.