CN102545614A - Resonant power conversion circuit - Google Patents

Abstract

The invention provides a resonant power conversion circuit, which receives the electric energy of input voltage and converts the electric energy into output voltage, and comprises: a switching circuit; a resonant circuit connected to the switching circuit; a transformer including a primary winding and a secondary winding, the primary winding being connected to the switching circuit and the resonant circuit; a rectifying circuit connected to the secondary winding of the transformer to rectify a voltage of the secondary winding to generate an output voltage; the control unit is connected with the output ends of the switching circuit and the resonant power conversion circuit and used for controlling the switching circuit to be switched on or switched off according to the output voltage so that the electric energy of the input voltage is selectively transmitted to the primary winding of the transformer through the switching circuit; the control unit adjusts the operating frequency and the operating mode of the switch circuit when the switch circuit is switched on according to the voltage value change of the output voltage. The invention can not cause the voltage value of the output voltage to exceed the rated voltage value because of the parasitic capacitance of the output rectifying element and the transformer.

Description

Resonant power conversion circuit

technical field

The invention relates to a power conversion circuit, in particular to a resonant power conversion circuit.

Background technique

In recent years, with the advancement of science and technology, electronic products with various functions have been gradually developed. These electronic products with various functions not only meet the various needs of people, but also integrate into everyone's needs. Daily life makes people's life more convenient.

These various electronic products with different functions are composed of various electronic components, and each electronic component needs to operate normally under an appropriate voltage. Therefore, it is necessary to use a power conversion circuit to provide an appropriate voltage value to each electronic component. Electronics can function normally. In order to improve the efficiency of power conversion circuits, LLC resonant power conversion circuits with high efficiency are used in some electronic products. However, the gain of traditional LLC resonant power conversion circuits drops limited in the high frequency band (higher than the resonance frequency), and the output The parasitic capacitance of the rectifier and transformer will increase the gain in the high frequency band (Peak Charge), causing the output voltage to be unstable at light load or no load, or even exceed the rated voltage.

In order to increase the efficiency of the power conversion circuit, the power conversion circuit will select a MOSFET with a lower on-resistance (Rds) to reduce the conduction loss when the MOSFET is turned on. However, MOSFETs with low on-resistance (Rds) have large parasitic capacitance, and when used in traditional LLC resonant power conversion circuits, the output voltage of traditional LLC resonant power conversion circuits will exceed the rated voltage at light load or no load value. Currently there are several solutions as follows:

(1) Adding a dummy load (Dummy Load): This method requires additional load components to be connected to the output of the LLC resonant power conversion circuit. In addition to failing to meet the actual load conditions, it will also increase losses and reduce efficiency. At present It is not applicable under the conditions of emphasizing high-efficiency power supply and energy saving and environmental protection.

(2) Burst Mode Control: When the LLC resonant power conversion circuit is under light load or no load, the MOSFET will be operated intermittently to reduce the output voltage of the LLC resonant power conversion circuit. However, this method will This causes the ripple (Ripple) and noise (Noise) of the output voltage to become larger.

(3) Notch Filter: By adding an additional resonant element, the gain of the LLC resonant power conversion circuit in the high-frequency section is rapidly reduced to meet the low gain requirement at light load or no load, but it will affect to the originally optimized resonance parameter design value, resulting in a drop in efficiency.

(4) Dead Time Control: Since the length of the dead time will affect the output voltage of the LLC resonant power conversion circuit, in the high frequency band, the influence of the parasitic capacitance effect can be reduced by adjusting the length of the dead time. However, this method will limit the length of the dead time to be less than four times the period of the maximum operating frequency (1/(4×fmax)), which increases the complexity of the LLC resonant power conversion circuit. In addition, the parasitic capacitance Cds of the current MOSFET is large, which will also cause the stagnation time to become small.

When the voltage values of the input voltage and the output voltage are adjustable and have a wide range, the above four methods also cannot solve the problem of unstable output voltage under light load or no load. Therefore, how to develop a resonant power conversion circuit that can improve the defects of the above-mentioned known technologies is an urgent problem to be solved in the relevant technical field.

Contents of the invention

The purpose of the present invention is to provide a resonant power conversion circuit to provide a rated output voltage, no matter when the resonant power conversion circuit operates at the operating frequency in the high frequency range, light load or no load, it can provide the rated output voltage. The output voltage will not cause the voltage value of the output voltage to exceed the rated voltage value. Even if the voltage values of the input voltage and the output voltage are adjustable and have a wide range, a stable output voltage can be provided, and when a stable load is provided, the voltage value of the output voltage will not exceed the rated voltage value. At the same time, it will not reduce efficiency due to increased losses, will not increase the ripple and noise of the output voltage, and will not limit the operating frequency of the resonant power conversion circuit to increase complexity.

To achieve the above purpose, a broad implementation of the present invention is to provide a resonant power conversion circuit for receiving electric energy from an input voltage and converting it into an output voltage. The resonant power conversion circuit includes: a switch circuit; a resonant circuit, Connected to the switching circuit; Transformer, including primary winding and secondary winding, and the primary winding is connected to the switching circuit and resonant circuit; Rectifier circuit, connected to the secondary winding of the transformer, used to rectify the voltage of the secondary winding to generate the output voltage and a control unit, connected to the output of the switch circuit and the resonant power conversion circuit, to control the switch circuit to be turned on or off according to the output voltage, so that the electric energy of the input voltage is selectively transmitted to the primary winding of the transformer through the switch circuit; , the control unit adjusts the operating frequency and the operating mode of the switching circuit according to the voltage value change of the output voltage.

To achieve the above purpose, another broad implementation of the present invention is to provide a resonant power conversion circuit for receiving electric energy from an input voltage and converting it into an output voltage. The resonant power conversion circuit includes: a switch circuit; a resonant circuit , connected to the switching circuit; transformer, including the primary winding and the secondary winding, and the primary winding is connected to the switching circuit and the resonant circuit; the rectifier circuit, connected to the secondary winding of the transformer, is used to rectify the voltage of the secondary winding to generate an output voltage; and a control unit, connected to the output of the switching circuit and the resonant power conversion circuit, for controlling the switching circuit to be turned on or off according to the output voltage, so that the electric energy of the input voltage is selectively transmitted to the primary winding of the transformer through the switching circuit, And control the rectification circuit to turn on or cut off, so that the rectification circuit rectifies the voltage of the secondary winding; wherein, the control unit adjusts the operating frequency of the switch circuit and the operation mode when the rectification circuit is turned on according to the voltage value change of the output voltage.

The resonant power conversion circuit of the present invention can provide a rated output voltage, regardless of whether the resonant power conversion circuit operates at the operating frequency of the high-frequency range, light load or no load, it can provide the rated output voltage without causing output The voltage value of the voltage exceeds the rated voltage value. Since the resonant power conversion circuit of the present invention adjusts the operating mode of the rectifier circuit, the operating frequency, the operating mode and the dead time of the switching circuit, even if the voltage values of the input voltage and the output voltage are adjustable and have a wide range or operating In the high frequency band (higher than the resonant frequency), the rated output voltage can also be provided, and the output voltage will not exceed the rated voltage due to the parasitic capacitance of the output rectifying element and the transformer. At the same time, it will not reduce efficiency due to increased loss, will not increase the ripple and noise of the output voltage, and will not limit the operating frequency of the resonant power conversion circuit to increase complexity.

Description of drawings

FIG. 1 is a schematic circuit diagram of a resonant power conversion circuit according to a preferred embodiment of the present invention.

FIG. 2 is a detailed schematic diagram of a resonant power conversion circuit according to a preferred embodiment of the present invention.

FIG. 3 is a schematic circuit diagram of a resonant power conversion circuit according to another preferred embodiment of the present invention.

The reference numerals in the above-mentioned accompanying drawings are explained as follows:

1: Resonant power conversion circuit 11: Switching circuit

12: Resonant circuit 13: Rectifier circuit

14: Control unit 141: Switch drive circuit

142: Drive power circuit 143: Feedback circuit

144: Control Circuit 1441: Controller

1442: Signal processing circuit 145: Rectification drive circuit

15: Filter circuit T _r : Transformer

N _p : primary winding N _s : secondary winding

OP1～OP3: first to third operational amplifiers

R _p : Compensation resistors R ₁ ~ R ₇ : The first ~ seventh resistors

Q ₁ to Q ₄ : first to fourth switches Q _a : first rectifier switch

Q _b : second rectifier switch D ₁ : first diode

D ₂ : second diode V ₁ , V ₂ : voltage drop

V _ref1 ~V _ref3 : first to third reference voltages

V _g1 ~ V _g4 : first to fourth switch drive signals

V _r1 : first rectification drive signal V _r2 : second rectification drive signal

V _e1 : first error signal V _e2 : second error signal

V _T : Voltage adjustment signal V _a : Driving voltage

V _cc : auxiliary voltage V _f : feedback signal

V _in : Input voltage V _o : Output voltage

C _p : Compensation capacitance C _o : Output capacitance

C _r : Resonant capacitance L _r : Resonant inductance

Detailed ways

Some typical embodiments embodying the features and advantages of the present invention will be described in detail in the description in the following paragraphs. It should be understood that the present invention is capable of various changes in different ways without departing from the scope of the present invention, and that the description and drawings therein are illustrative in nature rather than limiting the present invention.

Please refer to FIG. 1 , which is a schematic circuit diagram of a resonant power conversion circuit according to a preferred embodiment of the present invention. As shown in Figure 1, the resonant power conversion circuit 1 is used to receive the electric energy of the input voltage V _in and convert it into an output voltage V _o , the resonant power conversion circuit 1 includes a switch circuit 11, a resonant circuit 12, a transformer T _r , and a rectifier circuit 13. A control unit 14 and a filter circuit 15. Wherein, the switch circuit 11 is connected to the resonant circuit 12. In this embodiment, the switch circuit 11 is composed of the first switch _Q1 and the second switch _Q2 to form a half-bridge switch circuit 11, and the first switch _Q1 and the second switch Q2 The control terminals of the switch Q ₂ are respectively connected to the switch driving circuit 141 .

The resonant circuit 12 is connected to the switch circuit 11 and the primary winding _Np of the transformer _Tr to generate a resonant response in the circuit. In this embodiment, the resonant circuit 12 is composed of a resonant capacitor _Cr and a resonant inductor _Lr connected in series. The transformer T _r includes a primary winding N _p and a secondary winding N _s , and the primary winding N _p is connected to the switch circuit 11 and the resonant circuit 12. In this embodiment, the secondary winding N _s of the transformer T _r also includes a center tap ( center tap) is connected to the output of the resonant power conversion circuit 1. The rectifier circuit 13 is connected to the secondary winding _Ns of the transformer _Tr , and the filter circuit 15 is connected to the output of the rectifier circuit 13 and the resonant power conversion circuit 1. In this embodiment, the filter circuit 15 can be but not limited to an output capacitor C _o , and the rectification circuit 13 is a full-wave rectification circuit composed of the first diode D ₁ and the second diode D ₂ .

The voltage of the secondary winding N _s is respectively rectified and filtered by the rectifier circuit 13 and the filter circuit 15 to generate a rated output voltage V _o . The control unit 14 is connected to the output of the switch circuit 11 and the resonant power conversion circuit 1, and is used to generate a corresponding first switch drive signal V _g1 and a second switch drive signal V _g2 according to the output voltage V _o to control the switch circuit 11 to turn on or off. Turn off, so that the power of the _input voltage Vin is selectively delivered to the primary winding N _p of the transformer T _r via the switch circuit 11 .

In this embodiment, the control unit 14 includes a switch driving circuit 141 , a driving power circuit 142 , a feedback circuit 143 and a control circuit 144 . Wherein, the switch drive circuit 141 is respectively connected to the drive power supply circuit 142, the control circuit 144, the control terminal of the first switch _Q1 and the control terminal of the second switch _Q2 to generate the first switch drive signal V _g1 and the second switch Q2. The driving signal V _g2 turns on or off the switch circuit 11 correspondingly. The driving power supply circuit 142 is respectively connected to the switch driving circuit 141 and the control circuit 144, in order to receive the electric energy of the auxiliary voltage _Vcc , and generate the driving voltage _Va to the switch driving circuit 141, so as to provide the electric energy required by the switch driving circuit 141, so that The voltage amplitudes of the first switch driving signal V _g1 and the second switch driving signal Vg2 vary with the voltage of the driving voltage _Va . The feedback circuit 143 is respectively connected to the output of the control circuit 144 and the resonant power conversion circuit 1 for generating a corresponding feedback signal V _f according to the output voltage V _o .

In some embodiments, the control circuit 144 can be implemented using a digital signal processor (DSP). During operation, the control circuit 144 controls the switch drive circuit 141 and the drive power supply circuit respectively according to the feedback signal V _f and the first reference voltage V _ref1 142 operates to change the frequency and voltage amplitude (amplitude) of the first switch driving signal V _g1 and the second switch driving signal V _g2 , and the running modes of the first switch _Q1 and the second switch _Q2 are turned on respectively according to The voltage amplitudes of the first switch driving signal V _g1 and the second switch driving signal V _g2 change the operation mode.

When the load of the system circuit 2 becomes smaller (the load is sufficient to stabilize the output voltage) and the output voltage V _o rises above the rated voltage value, the feedback signal V _f will also rise correspondingly. At this time, the control circuit 144 passes the rising feedback signal V _f determines that the output voltage V _o rises above the rated voltage value, and correspondingly controls the switch drive circuit 141 to increase the frequency of the first switch drive signal V _g1 and the second switch drive signal V _g2 , so that the output voltage V _o drops to the rated voltage value, Therefore, the voltage value of the feedback signal V _f drops to the voltage value of the first reference voltage V _ref1 . At this time, the operation mode in which the first switch _Q1 and the second switch _Q2 are turned on is a linear mode (linear mode), that is, the first switch _Q1 and the second switch _Q2 operate in a linear region (linear region) when they are turned on. . Since the operation mode in which the first switch _{Q1 and} the second switch _Q2 are turned on is a linear mode, the voltage drop (Voltage drop) _V1 and _V2 between the first switch Q1 and _the second switch Q2 is relatively small, even The system circuit 2 is heavily loaded, and the switching loss of the first switch _Q1 and the second switch _Q2 will only increase by a small value.

Conversely, when the load of the system circuit 2 increases and the output voltage V _o drops below the rated voltage value, the feedback signal V _f will also drop correspondingly. At this time, the control circuit 144 will correspondingly control the switch drive circuit 141 to reduce the first The frequencies of the switch driving signal V _g1 and the second switch driving signal V _g2 make the output voltage V _o rise to a rated voltage value, so that the voltage value of the feedback signal V _f rises to the voltage value of the first reference voltage V _ref1 . At this time, the operating mode in which the first switch _Q1 and the second switch _Q2 are turned on is also a linear mode.

When the system circuit 2 is not running or the load is very low, the resonant power conversion circuit 1 will run at no load (no load) or very light load (light load), such as 1-10% of the rated output power, the output In addition to the voltage V _o rising beyond the rated voltage value, the difference between the voltage value of the output voltage V _o and the rated voltage value will be relatively large. Correspondingly, the voltage value of the feedback signal V _f and the first reference voltage V _ref1 The difference will also be larger. At this time, if the control circuit 144 only controls the switch driving circuit 141 to increase the frequency of the first switch driving signal _Vg1 and the second switch driving signal Vg2, the output voltage V _o cannot be effectively reduced to the rated voltage value due to the limitation of the minimum gain. Therefore, the control circuit 144 will further control the driving power supply circuit 142 to reduce the voltage value of the driving voltage _Va , so that the voltage amplitudes of the first switch driving signal V _g1 and the second switch driving signal V _g2 are reduced, so as to change the first switch Q1 and the second switch _Q1. The operation mode in which the second switch _Q2 is turned on is a saturation mode or an active mode, that is, the first switch _Q1 and the second switch _Q2 operate in a saturation region or an active region (activeregion). Since the operation mode in which the first switch _Q1 and the second switch _Q2 are turned on is the saturation mode or the active mode, the voltage drops _V1 and _V2 of the first switch _Q1 and the second switch _Q2 are compared with those in the linear mode It is much larger. Under the same frequency, the larger output voltage V _o can be reduced by a larger voltage value, so that the voltage value of the output voltage V _o is the rated voltage value.

Please refer to FIG. 2 together with FIG. 1 , which is a detailed schematic diagram of a resonant power conversion circuit according to a preferred embodiment of the present invention. As shown in FIG. 2 , the feedback circuit 143 is realized by a voltage divider circuit formed by the first resistor R ₁ and the second resistor R ₂ , and the feedback signal V _f is generated by dividing the output voltage V _o by the voltage divider circuit. The control circuit 144 includes a controller 1441 and a signal processing circuit 1442, wherein the signal processing circuit 1442 is connected to the controller 1441, the feedback circuit ₁₄₃ and the driving power supply circuit ₁₄₂ to generate corresponding The first error signal V _e1 , the second error signal V _e2 , and the voltage adjustment signal V _T . The magnitude of the first error signal V _e1 is proportional to the difference between the feedback signal V _f and the first reference voltage V _ref1 (V _ref1 -V _f ), and the magnitude of the second error signal V _e2 is proportional to the difference between the first error signal V _e1 and the third The difference between the reference voltage V _ref3 (V _ref3 −V _e1 ), the magnitude of the voltage adjustment signal V _T is proportional to the difference between the first error signal V _e1 and the second reference voltage V _ref2 (V _ref2 −V _e1 ).

The controller 1441 is connected to the switch driving circuit 141 and the signal processing circuit 1442, and is used to obtain the difference between the voltage value of the output voltage V _o and the rated voltage value by using the first error signal V _e1 , and the controller 1441 will use the first error signal V e1 The signal V _e1 changes the frequencies of the first switch driving signal V _g1 and the second switch driving signal Vg2 correspondingly. When the output voltage V _o rises above the rated voltage value, the controller 1441 will increase the frequency of the first switch driving signal V _g1 and the second switch driving signal V _g2 , on the contrary, when the output voltage V _o drops below the rated voltage value , the controller 1441 reduces the frequencies of the first switch driving signal V _g1 and the second switch driving signal V _g2 .

When the difference between the voltage value of the output voltage V _o and the rated voltage value exceeds the first set value, it means that the resonant power conversion circuit 1 is operating in a no-load or very light-load state. At this time, the signal processing circuit 1442 The voltage adjustment signal V _T produced will make the driving power supply circuit 142 provide a driving voltage V _a of a lower voltage value to the switch driving circuit 141, so the switch driving circuit 141 will output the first switch driving signal V g1 and the second switching driving signal V _g1 with a smaller voltage amplitude. The operating mode in which the first switch _Q1 and the second switch _Q2 are turned on by the second switch driving signal V _g2 is a saturation mode or an active mode. Conversely, when the difference between the voltage value of the output voltage V _o and the rated voltage value does not exceed the first set value, it means that the resonant power conversion circuit 1 is not operating in a no-load or very light-load state. At this time, The voltage adjustment signal V _T produced by the signal processing circuit 1442 will cause the driving power supply circuit 142 to provide a driving voltage V _a of a higher voltage value to the switch driving circuit 141, and the switch driving circuit 141 outputs a first switch driving signal with a larger voltage amplitude The operating mode in which the first switch _Q1 and the second switch Q2 are turned on by V _g1 and the _second switch driving signal V _g2 is a linear mode.

On the whole, when the resonant power conversion circuit 1 is operating at no-load or very light-load state, the control unit 14 will not only increase the frequency of the first switch driving signal V _g1 and the second switch driving signal V _g2 , but also Reduce the voltage value of the driving voltage V _a , so that the voltage amplitudes of the first switch driving signal V _g1 and the second switch driving signal V _g2 are reduced, so as to change the conduction mode of the first switch _Q1 and the second switch _Q2 to saturation mode or active mode. In this embodiment, when the resonant power conversion circuit 1 is running in a no-load or very light-load state, that is, the difference between the voltage value of the output voltage V _o and the rated voltage value exceeds the first set value or the second set value When the value is constant, the controller 1441 further adjusts the dead time (Dead Time) of the first switch driving signal V _g1 and the second switch driving signal V _g2 according to the second error signal V _e2 . In other words, the greater the difference between the voltage value of the output voltage V _o and the rated voltage value, the greater the stagnation time between the first switch drive signal V _g1 and the second switch drive signal V _g2 , so that the voltage value of the output voltage V _o The rated voltage can be maintained more stably.

In this embodiment, the compensation capacitor _Cp and the compensation resistor _Rp are connected in series between the non-inverting input terminal and the output terminal of the first operational amplifier (Operational Amplifier) OP1, and the third resistor R3 is connected to the first operational amplifier OP1. Between the output terminal and the controller 1441, the non-inverting input terminal and the inverting input terminal of the first operational amplifier OP1 are respectively the first reference voltage V _ref1 and the feedback signal V _f , and are connected via the first operational amplifier OP1 and the compensation capacitor C _p The first error circuit constituted by the compensating resistor R _p generates the first error signal V _e1 , and its relationship is: V _e1 ∝ _{V ref1} −V _f .

In this embodiment, the sixth resistor _R6 is connected between the output terminal of the first operational amplifier OP1 and the inverting input terminal of the third operational amplifier OP3, and the seventh resistor _R7 is connected to the output terminal of the third operational amplifier OP3 Between and the inverting input terminal, the non-inverting input terminal of the third operational amplifier OP3 is the third reference voltage V _ref3 , and the second error formed by the third operational amplifier OP3, the sixth resistor R ₆ and the seventh resistor R ₇ The circuit generates the second error signal V _e2 , and the controller 1441 is connected to the output terminal of the third operational amplifier OP3 to obtain the second error signal V _e2 , the relationship is: V _e2 ∝(V _ref3 −V _e1 )×( -R ₇ /R ₆ ).

In this embodiment, the fourth resistor _R4 is connected between the output terminal of the first operational amplifier OP1 and the inverting input terminal of the second operational amplifier OP2, and the fifth resistor _R5 is connected to the output terminal of the second operational amplifier OP2 Between the inverting input terminal and the output terminal of the second operational amplifier OP2, the output terminal of the second operational amplifier OP2 is further connected to the driving power supply circuit 142. The non-inverting input terminal of the second operational amplifier OP2 is the second reference voltage V _ref2 , and is connected via the second operational amplifier OP2, The third error circuit formed by the fourth resistor R ₄ and the fifth resistor R ₅ generates the voltage adjustment signal V _T , and its relationship is: V _T ∝(V _ref2 -V _e1 )×(-R ₅ /R ₄ ).

Please refer to FIG. 3 together with FIG. 1 , which is a schematic circuit diagram of a resonant power conversion circuit according to another preferred embodiment of the present invention. The switch circuit 11, rectifier circuit 13 and control unit 14 of FIG. 3 are different from FIG _. 1. As shown in FIG. 3, the switch circuit 11 includes a third switch Q3 in addition to the first switch _Q1 and the second switch _Q2 . With the fourth switch Q ₄ , four switches form a full-bridge switch circuit 11 . The rectification circuit 13 is a full-wave rectification circuit composed of a first rectification switch _Qa and a second rectification switch _Qb , and the control terminals of the first rectification switch _Qa and the second rectification switch _Qb are connected to the rectification drive circuit 145 of the control unit 14 , and turn on or off according to the first rectification driving signal V _r1 and the second rectification driving signal V _r2 .

As for the control unit 14, in addition to the switch drive circuit 141, the drive power circuit 142, the feedback circuit 143 and the control circuit 144, it also includes a rectification drive circuit 145. In this embodiment, the drive power circuit 142 is connected to the rectification drive circuit 145 respectively. The control circuit 144 and the rectification drive circuit 145 are connected to the control circuit 144, the drive power supply circuit 142, the control terminals of the first rectification switch Q _a and the second rectification switch Q _b , respectively, to generate the first rectification drive signal V r1 and the second rectification drive signal V _r1 The second rectification drive signal V _r2 makes the first rectification switch Q _a and the second rectification switch Q _b correspondingly turned on or off.

Different from FIG. 1 , the auxiliary voltage V _cc provided to the switch driving circuit 141 with a fixed voltage value corresponds to the first switch driving signal V _g1 , the second switch driving signal V _g2 , the third switch driving signal V _g3 and the fourth switch The driving signal V _g4 has a fixed voltage amplitude, therefore, the operating mode in which the first switch Q ₁ , the second switch Q ₂ , the third switch Q ₃ and the fourth switch Q ₄ is turned on is fixed as a linear mode. Another difference from Fig. 1 is that the electric energy required by the rectification drive circuit 145 is provided by the drive voltage _Va generated by the drive power supply circuit 142, therefore, the voltage amplitudes of the first rectification drive signal V _r1 and the second rectification drive signal V _r2 Will vary with the voltage value of the driving voltage V _a

In this embodiment, when the difference between the voltage value of the output voltage V _o and the rated voltage value does not exceed the first set value, it means that the resonant power conversion circuit 1 is not operating in a no-load or light-load state. At this time , the voltage adjustment signal V _T generated by the control circuit 144 will cause the drive power supply circuit 142 to provide a drive voltage V _a of a higher voltage value to the rectification drive circuit 145, and the rectification drive circuit 145 outputs a first rectification drive signal with a larger voltage amplitude V _r1 and the second rectification drive signal V _r2 are sent to the control terminals of the first rectification switch Q _a and the second rectification switch Q _b , and the operation mode corresponding to the conduction of the first rectification switch Q _a and the second rectification switch Q _b is linear model. Conversely, when the difference between the voltage value of the output voltage V _o and the rated voltage value exceeds the first set value, it means that the resonant power conversion circuit 1 is operating in a no-load or light-load state. At this time, the control circuit 144 In addition to increasing the frequency of the first switch driving signal V _g1 , the second switch driving signal V _g2 , the third switch driving signal V _g3 and the fourth switch driving signal V _g4 , by reducing the voltage value of the driving voltage V _a , The voltage amplitudes of the first rectifying driving signal V _r1 and the second rectifying driving signal V _r2 are reduced to change the conduction mode of the first rectifying switch Q _a and the second rectifying switch Q _b into a saturation mode or an active mode.

In general, when the resonant power conversion circuit 1 is operating in the no-load or light-load state, the control circuit 144 will increase the first switch driving signal V _g1 , the second switch driving signal V _g2 , the third switch driving signal V In addition to the frequencies of _g3 and the fourth switch driving signal V _g4 , the voltage amplitudes of the first rectifying driving signal V _r1 and the second rectifying driving signal V _r2 are lowered to change the first rectifying switch Q _a and the second rectifying switch Q a The operating mode of _b conduction is saturation mode or active mode. In this embodiment, when the resonant power conversion circuit 1 is operating in a no-load or light-load state, the control circuit 144 will further adjust the first rectification driving signal according to the difference between the feedback signal V _f and the first reference voltage V _ref1 The dead time between V _r1 and the second rectification drive signal V _r2 . In other words, the greater the difference between the voltage value of the output voltage V _o and the rated voltage value, the greater the stagnation time between the first rectification drive signal V _r1 and the second rectification drive signal V _r2 , so that the voltage value of the output voltage V _o The rated voltage can be maintained more stably.

The above-mentioned first switch Q ₁ , second switch Q ₂ , third switch Q ₃ and fourth switch Q ₄ , first rectifier switch Q _a and second rectifier switch Q _b may be but not limited to metal oxide semiconductor field Effect transistor (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET) or bipolar junction transistor (Bipolar Junction Transistor, BJT).

In summary, the resonant power conversion circuit of the present invention can provide a rated output voltage, regardless of whether the resonant power conversion circuit operates at the operating frequency of the high frequency range, light load or no load, it can also provide the rated output voltage , will not cause the voltage value of the output voltage to exceed the rated voltage value. Since the resonant power conversion circuit of the present invention adjusts the operating mode of the rectifier circuit, the operating frequency, the operating mode and the dead time of the switching circuit, even if the voltage values of the input voltage and the output voltage are adjustable and have a wide range or operating In the high frequency band (higher than the resonant frequency), the rated output voltage can also be provided, and the output voltage will not exceed the rated voltage due to the parasitic capacitance of the output rectifying element and the transformer. At the same time, it will not reduce efficiency due to increased losses, will not increase the ripple and noise of the output voltage, and will not limit the operating frequency of the resonant power conversion circuit to increase complexity.

The present invention can be modified in various ways by those skilled in the art without departing from the protection scope of the appended claims.

Claims (20)

1. A resonant power conversion circuit, which receives electric energy of an input voltage and converts it into an output voltage. The resonant power conversion circuit comprises: a switching circuit; a resonant circuit connected to the switching circuit; a transformer including a primary winding and a secondary winding, and the primary winding is connected to the switch circuit and the resonant circuit; a rectification circuit connected to the secondary winding of the transformer to rectify the voltage of the secondary winding to generate the output voltage; and A control unit, connected to the output of the switching circuit and the resonant power conversion circuit, to control the switching circuit to be turned on or off according to the output voltage, so that the electric energy of the input voltage is selectively transmitted to the transformer through the switching circuit of the primary winding; Wherein, the control unit adjusts the operating frequency and the operating mode of the switching circuit according to the voltage value change of the output voltage. 2. The resonant power conversion circuit according to claim 1, wherein when the difference between the voltage value of the output voltage and the rated voltage value exceeds a first set value, the control unit controls the switch circuit to be turned on The operating mode is saturation mode or active mode. 3. The resonant power conversion circuit according to claim 2, wherein when the difference between the voltage value of the output voltage and the rated voltage value does not exceed the first set value, the control unit controls the switch circuit to be turned on The operating mode is linear mode. 4. The resonant power conversion circuit as claimed in claim 2, wherein when the difference between the voltage value of the output voltage and the rated voltage value exceeds the first set value or a second set value, the control unit The dead time controlling the switching circuit varies according to the voltage value of the output voltage. 5. The resonant power conversion circuit as claimed in claim 1, further comprising a filter circuit connected to the output of the rectifier circuit and the resonant power conversion circuit. 6. The resonant power conversion circuit as claimed in claim 5, wherein the filter circuit is an output capacitor. 7. The resonant power conversion circuit as claimed in claim 1, wherein the control unit comprises: A switch drive circuit, connected to the control terminal of the switch circuit, to generate at least one first switch drive signal to turn on or off the switch circuit correspondingly; A drive power supply circuit connected to the switch drive circuit to receive the power of an auxiliary voltage and generate a drive voltage to the switch drive circuit to provide the power required by the switch drive circuit; a feedback circuit, connected to the output of the resonant power conversion circuit, to generate a corresponding feedback signal according to the output voltage; and A control circuit, connected to the switch drive circuit, the drive power circuit and the feedback circuit, to control the operation of the switch drive circuit and the drive power circuit according to the feedback signal and a first reference voltage, so as to change the first switch drive The frequency and voltage amplitude of the signal; Wherein, the operation mode in which the switch circuit is turned on changes according to the voltage amplitude of the first switch driving signal. 8. The resonant power conversion circuit as claimed in claim 7, wherein the control circuit is a digital signal processor. 9. The resonant power conversion circuit as claimed in claim 7, wherein the control circuit comprises: a signal processing circuit, connected to the feedback circuit and the driving power supply circuit, to generate a corresponding first error signal and a voltage adjustment signal according to the feedback signal and the first reference voltage; and a controller, connected to the switch driving circuit and the signal processing circuit, to correspondingly change the frequency of the first switch driving signal according to the first error signal; Wherein, the magnitude of the first error signal is proportional to the difference between the feedback signal and the first reference voltage, the magnitude of the voltage adjustment signal is proportional to the difference between the first error signal and the second reference voltage, and the driving voltage With this voltage adjustment signal changes. 10. The resonant power conversion circuit as claimed in claim 9, wherein the signal processing circuit further generates a corresponding second error signal according to the feedback signal and the first reference voltage, and the magnitude of the second error signal is proportional to the first The difference between an error signal and a third reference voltage, and the controller adjusts the dead time of the first switch driving signal according to the second error signal. 11. The resonant power conversion circuit as claimed in claim 1, wherein the switching circuit is a half-bridge or full-bridge switching circuit. 12. The resonant power conversion circuit as claimed in claim 1, wherein the resonant circuit comprises a resonant capacitor and a resonant inductor. 13. The resonant power conversion circuit as claimed in claim 12, wherein the resonant capacitor is connected in series with the resonant inductor. 14. A resonant power conversion circuit, which receives electric energy of an input voltage and converts it into an output voltage, the resonant power conversion circuit comprising: a switching circuit; a resonant circuit connected to the switching circuit; a transformer including a primary winding and a secondary winding, and the primary winding is connected to the switch circuit and the resonant circuit; a rectification circuit connected to the secondary winding of the transformer to rectify the voltage of the secondary winding to generate the output voltage; and A control unit, connected to the output of the switching circuit and the resonant power conversion circuit, to control the switching circuit to be turned on or off according to the output voltage, so that the electric energy of the input voltage is selectively transmitted to the transformer through the switching circuit and controlling the rectification circuit to be turned on or off so that the rectification circuit rectifies the voltage of the secondary winding; Wherein, the control unit adjusts the operating frequency of the switching circuit and the operating mode when the rectifying circuit is turned on according to the voltage value change of the output voltage. 15. The resonant power conversion circuit as claimed in claim 14, wherein when the difference between the voltage value of the output voltage and the rated voltage value exceeds a first set value, the control unit controls the conduction of the rectifier circuit The operating mode is saturation mode or active mode. 16. The resonant power conversion circuit according to claim 15, wherein when the difference between the output voltage and the rated voltage does not exceed the first set value, the control unit controls the rectifier circuit to be turned on The operating mode is linear mode. 17. The resonant power conversion circuit as claimed in claim 15, wherein when the difference between the voltage value of the output voltage and the rated voltage value exceeds the first set value or a second set value, the control unit The dead time controlling the rectification circuit varies according to the voltage value of the output voltage. 18. The resonant power conversion circuit as claimed in claim 14, further comprising a filter circuit connected to the output of the rectifier circuit and the resonant power conversion circuit. 19. The resonant power conversion circuit as claimed in claim 14, wherein the control unit comprises: A switch drive circuit, connected to the control terminal of the switch circuit, to generate at least one first switch drive signal to turn on or off the switch circuit correspondingly; A rectification drive circuit connected to the control terminal of the rectification circuit to generate at least one first rectification drive signal to make the rectification circuit turn on or off correspondingly; A drive power circuit, connected to the switch drive circuit, to receive the power of an auxiliary voltage, and generate a drive voltage to the rectification drive circuit, so as to provide the power required by the rectification drive circuit; a feedback circuit, connected to the output of the resonant power conversion circuit, to generate a corresponding feedback signal according to the output voltage; and A control circuit, connected to the switch drive circuit, the drive power circuit, the rectification drive circuit and the feedback circuit, to control the switch drive circuit, the rectification drive circuit and the drive power supply according to the feedback signal and a first reference voltage the circuit operates to change the frequency of the first switch drive signal, the drive voltage and the voltage amplitude of the first rectified drive signal; Wherein, the operation mode in which the rectification circuit is turned on changes according to the voltage amplitude of the first rectification driving signal. 20. The resonant power conversion circuit as claimed in claim 19, wherein the control circuit further adjusts the dead time of the first rectification driving signal according to the difference between the feedback signal and the first reference voltage.

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