TWI761945B - Power factor corrector - Google Patents

Abstract

A power factor corrector(PFC) includes a rectifier unit, a single-ended primary inductance converter(SEPIC), a current sensor, a resonance unit, and a control unit. The control unit is electrically connected to the rectifier unit to detect a DC input voltage converted by the rectifier unit to an AC output voltage, and is electrically connected to the current sensor to obtain the magnitude of a first inductor current flowing through a first inductor of the SEPIC, and is also electrically connected to a load to detect the DC output voltage, and also electrically connected to the SEPIC and the resonant unit to control a corresponding main switch and an auxiliary switch to achieve zero-voltage switching, thereby realizing a power factor corrector with high overall efficiency and high power factor.

Description

Power Factor Corrector

The present invention relates to a power factor corrector, in particular to a power factor corrector using a single-ended primary inductor converter (Single ended primary inductor converter, SEPIC) structure.

The power factor is the ratio of the effective power consumed by the load to the apparent power, which to a certain extent reflects the utilization ratio of the generator capacity of the power system, and is an indicator of reasonable electricity consumption. And some loads (such as electrical products) have a very low power factor because of their internal impedance characteristics. Therefore, in order to improve the power factor of the load, a power corrector must be installed at the power input end. Existing power factor correctors are divided into active and passive types. Passive power factor correctors are, for example, LC-type or π-type low-pass filters, but their power factor value can only reach about 70%, and the volume is relatively large. Therefore, active power factor correctors are usually used when more stringent power factor requirements are required. There is room for improving efficiency and power factor in the design of various active power factor correctors.

Therefore, an object of the present invention is to provide a power factor corrector utilizing a single-ended primary inductance converter (SEPIC) architecture.

Therefore, the present invention provides a power factor corrector, which is suitable for receiving an AC input voltage and a load, and includes a rectifier unit, a single-ended primary inductance converter, a current sensor, a resonance unit, and a control unit .

The rectifier unit receives the AC input voltage and converts it to output the DC input voltage. The single ended primary inductor converter (SEPIC) is electrically connected to the rectifier unit and the load to receive the DC input voltage and convert it to output a DC output voltage to the load, and includes a first inductor and a Main switch.

The current sensor detects the magnitude of a first inductor current flowing through the first inductor of the single-ended primary inductor converter. The resonant unit is electrically connected to the single-ended primary inductance converter, and includes an auxiliary switch, a resonant inductor, and a clamping capacitor to form a resonant path.

The control unit is electrically connected to the rectifier unit to detect the DC input voltage, electrically connected to the current sensor to obtain the magnitude of the first inductor current, and also electrically connected to the load to detect the DC output voltage, and also The single-ended primary inductance converter and the resonance unit are electrically connected to control the main switch and the auxiliary switch to achieve zero-voltage switching.

In some implementations, the control unit generates a main control signal and an auxiliary control signal according to the DC input voltage, the first inductor current, and the DC output voltage to respectively control the main switch and the auxiliary switch Operates on or off.

In some embodiments, the rectifier unit is a diode bridge including four diodes.

In other embodiments, the main switch of the single-ended primary inductance converter and the auxiliary switch of the resonant unit both include a back diode and a parasitic capacitor connected in parallel.

In other embodiments, the rectifier unit includes a positive output terminal and a negative output terminal for outputting the DC input voltage, and the single-ended primary inductance converter further includes a first capacitor, a second inductor, a a first diode and an output capacitor, the first inductor includes a first terminal and a second terminal electrically connected to the positive output terminal of the rectifier unit, the main switch includes the second terminal electrically connected to the first inductor a first terminal of the terminal, a control terminal receiving the main control signal, and a second terminal electrically connected to the negative output terminal of the rectifier unit, the first capacitor includes a first terminal electrically connected to the second terminal of the first inductor One end and a second end, the second inductor includes a first end electrically connected to the second end of the first capacitor, and a second end electrically connected to the negative output end of the rectifier unit, the first diode The body includes an anode end and a cathode end that are electrically connected to the first end of the second inductor, the output capacitor includes a first end that is electrically connected to the cathode end of the first diode, and the rectifier unit that is electrically connected to the first end. A second terminal of the negative output terminal, the load is connected in parallel with the output capacitor.

In some implementation aspects, the clamping capacitor of the resonant unit is connected in series with the auxiliary switch, and is then connected in parallel with the main switch of the single-ended primary inductance converter, and the resonant inductor is electrically connected to the single-ended primary inductor between the second end of the first capacitor of the converter and the first end of the second inductor.

The effect of the present invention is: through the resonance path of the resonance unit, the control unit controls the main switch and the auxiliary switch to achieve zero-voltage switching according to the first inductor current, the DC input voltage, and the DC output voltage , thereby realizing a power factor corrector of the SEPIC architecture with high overall efficiency and high power factor.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are designated by the same reference numerals.

Referring to FIG. 1 , an embodiment of the power factor corrector of the present invention is suitable for an AC voltage source 9 and a load R _PFC , and includes a rectifier unit 1 , a single-ended primary inductance converter 2 , and a current sensor 3 , a resonance unit 4, and a control unit.

The rectifier unit 1 is electrically connected to the AC voltage source 9 to receive an AC input voltage V _AC , and convert it to output a DC input voltage V _in . In this embodiment, the rectifier unit 1 includes a first rectifier diode D1, a second rectifier diode D2, a third rectifier diode D3, and a fourth rectifier diode D4, namely A total of four diode diode bridges (Diode bridge). The rectifier unit 1 further includes a positive output terminal and a negative output terminal for outputting the DC input voltage _Vin , that is, the voltage across the positive output terminal and the negative output terminal is equal to the DC input voltage _Vin .

The single ended primary inductor converter (SEPIC) 2 is electrically connected to the rectifier unit 1 and the load R _PFC to receive the DC input voltage V _in and convert it to output a DC output voltage V _Cbus to the load R _PFC .

More specifically, the single-ended primary inductance converter 2 includes a first inductor L _1,PFC , a main switch Q _main , a first capacitor C _1,PFC , a second inductor L _2,PFC , a first The diode D _PFC , and an output capacitor C _bus . The first inductor L _{1 , PFC} includes a first end and a second end electrically connected to the positive output end of the rectifier unit 1 . The main switch Q _main includes a back-connected diode D _b,main , a parasitic capacitance C _oss,main , a first terminal electrically connected to the second terminal of the first inductor L _{1 , the PFC} , and receives a main control signal A control terminal of S1 and a second terminal electrically connected to the negative output terminal of the rectifier unit 1 are controlled by the main control signal S1 to determine whether the first terminal and the second terminal are conductive or non-conductive . The first capacitor C1 _,PFC includes a first end and a second end electrically connected to the second end of the first inductor L1 _,PFC . The second inductor L _{2 , PFC} includes a first terminal electrically connected to the second terminal of the first capacitor C _{1 , PFC} , and a second terminal electrically connected to the negative output terminal of the rectifier unit 1 . The first diode D _PFC includes an anode terminal and a cathode terminal electrically connected to the first terminal of the second inductor L _{2 , the PFC} . The output capacitor C _bus includes a first terminal electrically connected to the cathode terminal of the first diode D _PFC , and a second terminal electrically connected to the negative output terminal of the rectifier unit 1 . The load R _PFC is connected in parallel with the output capacitor C _bus .

The current sensor 3 is used to detect the magnitude of a first inductor current i _{L1, PFC} flowing through the first inductor L1, _PFC of the single-ended primary inductance converter 2, and is, for example, disposed in the rectifier unit Between the positive output terminal of 1 and the first inductor L _{1 , the first terminal of the PFC} .

The resonant unit 4 is electrically connected to the single-ended primary inductance converter 2 and includes an auxiliary switch Q _aux , a resonant inductor L _r,PFC , and a clamping capacitor C _c,PFC to form a resonant path. In more detail, the clamping capacitor C _c,PFC is connected in series with the auxiliary switch Q _aux , and is then connected in parallel with the main switch Q _main of the single-ended primary inductance converter 2 . The resonant inductor L _{r , PFC} is electrically connected between the second end of the first capacitor C _{1 , PFC} of the single-ended primary inductance converter 2 and the first end of the second inductor L _{2 , PFC} . The auxiliary switch Q _aux includes a parallel diode D _b,aux and a parasitic capacitance C _oss,aux , and is controlled by an auxiliary control signal S2 to decide whether to conduct or not.

The control unit is, for example, a microcontroller (MCU), and is electrically connected to the rectifier unit 1 to detect the DC input voltage V _in , and is electrically connected to the current sensor 3 to obtain the first inductor current i _{L1 , PFC} It is also electrically connected to the load R _PFC to detect the DC output voltage V _Cbus , and is also electrically connected to the single-ended primary inductance converter 2 and the resonance unit 4 . The control unit generates the main control signal S1 and the auxiliary control signal S2 according to the DC input voltage V _in , the first inductor current i _L1,PFC , and the DC output voltage V _Cbus to control the main switches Q _main and The auxiliary switch Q _aux is turned on or off, thereby achieving zero-voltage switching.

More specifically, the control unit makes the single-ended primary inductance converter 2 operate in a continuous conduction mode (CCM) by generating the main control signal S1 and the auxiliary control signal S2, and in a complete switching The period can be divided into six intervals, namely a first interval to a sixth interval. Therefore, FIG. 2 exemplarily illustrates the main control signal S1, the auxiliary control signal S2, the cross voltage v _DS,main of the first terminal and the second terminal of the main switch Q _main , the voltage across the two terminals of the auxiliary switch Q _aux Across voltage v _DS,aux , a main switch current i _DS,main flowing through the main switch Q _main , an auxiliary switch current i _DS,aux flowing through the auxiliary switch Q _aux , flowing through the first inductor L _{1 ,} The first inductor current i _{L1,PFC of} the PFC, a second inductor current i _L2,PFC flowing through the second inductor L _2,PFC , a resonant inductor current i _Lr flowing through the resonant inductor L _r,PFC , _PFC , and a diode current i D flowing through the first diode D _PFC , the state _{of PFC} in the first interval to the sixth interval.

In addition, it should be added that: in order to simplify the analysis, the following three conditions are assumed: the on-resistance of the main switch Q _main and the auxiliary switch Q _aux can be ignored; the first diode D _PFC is regarded as ideal, and no Forward conduction voltage and losses; the output capacitor C _bus is large enough to be regarded as a constant voltage source.

Referring to FIG. 1, FIG. 2 and FIG. 3, in the first interval (ie t0≤t≤t1), the main switch Q _main is turned on, the auxiliary switch Q _aux and the first diode D _PFC are turned off (ie not turned on ), the first inductor current i _{L1, PFC} rises linearly, the first inductor L _{1, PFC stores} energy, and at the same time because the first capacitor C _{1, PFC} cross voltage V _{C1, PFC} is equal to the DC input voltage V _in , the first capacitor C1 _{, PFC} releases energy, the second inductor current i _{L2, PFC} also rises linearly, the second inductor L2 _{, PFC stores} energy, the energy required by the load R _PFC by the output capacitor C _bus provided. When t=t1, the main switch Q _main is turned off, and this time interval ends. The first inductor current i _{L1 , PFC} and the second inductor current i _{L2 , PFC} in this time interval can be expressed as formulas (1) and (2).

Referring to FIG. 1 , FIG. 2 and FIG. 4 , in the second interval (ie, t1≤t≤t2), the main switch Q _main , the auxiliary switch Q _aux , and the first diode D _PFC are all turned off, due to the inductance The characteristic of continuous current, the energy passes through the parasitic capacitance C _oss,main of the main switch Q _main and charges, this time interval is quite short, the first inductor current i _L1,PFC and the second inductor current i _L2,PFC can be regarded as Value. When t=t2, the cross-voltage of the parasitic capacitance C _oss,main of the main switch Q _main gradually rises so that the first diode D _PFC is turned on, and the time interval ends. The cross voltage v _DS,main of the main switch Q _main in this time interval can be expressed as formula (3).

Referring to FIG. 1 , FIG. 2 and FIG. 5 , in the third interval (ie t2≤t≤t3), the first diode D _PFC is turned on, the main switch Q _main and the auxiliary switch Q _aux are turned off, and the second diode D PFC is turned off. The cross-voltage v _{L2, PFC} of the inductor L _2, the PFC is clamped at the DC output voltage V _Cbus , the resonant inductor L _{r, the PFC} and the parasitic capacitance C _{oss, main} of the main switch Q _main resonate, and the energy passes through the first The diode D _PFC is delivered to the load R _PFC and charges the output capacitor C _bus . When t=t3, the parasitic capacitance C _oss,main of the main switch Q _main is charged to the cross voltage v _Cc,PFC and the back diode D _b,aux of the auxiliary switch Q _aux is turned on, the main switch The cross voltage v _DS,main of Q _main is clamped at the cross voltage v _Cc,PFC of the clamping capacitor C _c, PFC, the first inductor current i _L1,PFC and the second inductor current i _L2,PFC decrease linearly and Through the back-connected diode D _b,aux of the auxiliary switch Q _aux , the clamping capacitor C _{c, PFC} is charged at the same time. Since this time interval is quite short, the first inductor current i _{L1, PFC} and the second The inductor current i _{L2, PFC} can still be regarded as a fixed value.

其中，

，

Referring to FIG. 1 , FIG. 2 and FIG. 6 , in the fourth interval (ie t3≤t≤t4), the first diode D _PFC and the back-connected diode D _b,aux of the auxiliary switch Q _aux are turned on , the main switch Q _main and the auxiliary switch Q _aux are turned off, the resonant inductor L _r,PFC , the first capacitor C _1,PFC , and the clamping capacitor C _c,PFC resonate, and the resonant inductor current i _Lr, The _PFC is commutated, so that the auxiliary switch Q _aux is turned on at zero voltage, the first inductor current i _{L1 , PFC} and the second inductor current i _{L2 , PFC} still decrease linearly, and transfer energy to the load R _PFC and The output capacitor C _bus is charged. When t=t4, the auxiliary switch Q _aux is turned off, and this time interval ends. The cross-voltage v _{Cc, PFC} of the clamping capacitor C _c, PFC and the resonant inductor current i _{Lr, PFC} in this time interval can be expressed as formulas (4) and (5).

in,

,

Referring to FIG. 1, FIG. 2 and FIG. 7, in the fifth interval (ie t4≤t≤t5), the first diode D _PFC is turned on, the main switch Q _main and the auxiliary switch Q _aux are turned off, and the resonant inductor The parasitic capacitance C _{oss,main of} L _r,PFC and the main switch Qmain resonates again and starts to discharge, the first inductor current i _L1,PFC and the second inductor current i _L2,PFC still show a linear decline, and the Energy is delivered to the load R _PFC and charges the output capacitor C _bus . When t=t5, the parasitic capacitance C _oss,main of the main switch Q _main is discharged to zero, the back-connected diode D _{b, main} of the main switch Q _main is turned on, and the time interval ends.

Referring to FIG. 1, FIG. 2 and FIG. 8, in the sixth interval (ie t5≤t≤t6), the first diode D _PFC and the back-connected diode D _b,main of the main switch Q _main are turned on , the main switch Q _main and the auxiliary switch Q _aux are turned off, the main switch current i _DS,main through the back-connected diode D _b,main gradually becomes zero from a negative value, the first inductor current i _L1,PFC And the second inductor current i _L2,PFC still decreases linearly, while the first diode current i _D,PFC also decreases linearly. When t=t6, before the main switch current i _DS,main becomes a positive value, the main switch Q _main can reach zero voltage turn-on, when the resonant inductor current i _Lr,PFC is equal to the second inductor current i _L2,PFC , the first diode current i _{D, PFC} is zero, the first diode D _PFC is turned off, and this time interval ends. The timing returns to the equivalent circuit state of the first interval, and cycles periodically.

It can be seen from FIG. 2 that when the main control signal S1 controls the main switch Q _main to be turned on, the auxiliary control signal S2 controls the auxiliary switch Q _aux to be turned off. When the main control signal S1 controls the main switch Q _main to be turned off, the auxiliary control signal S2 controls the auxiliary switch Q _aux to be turned on. And the main control signal S1 and the auxiliary control signal S2 include two dead zone times (also known as blank times) in each switching cycle, namely t3-t1 and t4 and the main control signal S1 by The moment when a logic 0 becomes a logic 1. Each of the dead time is typically less than 1% of the switching period. Furthermore, since the single-ended primary inductance converter 2 has the same characteristics as the output voltage (ie the DC output voltage V _Cbus ) and the input voltage (ie the DC input voltage V _in ), and uses the auxiliary switch Q _aux and the resonance The inductors L _{r , PFC} and the resonant capacitor are combined to form the resonant path, so that the main switch Q _main and the auxiliary switch Q _aux can achieve zero-voltage switching at the moment of turn-on, so that the overall efficiency and power factor can be considered. For example, the AC input voltage V _AC is 110V~220V/60Hz, the DC output voltage V _Cbus is 24V and the maximum output power is 300W, then the maximum efficiency of the power factor corrector is 95.4%, and the highest power factor above 0.99.

In summary, the control unit controls the main switch Q _main and the auxiliary switch Q _aux to achieve zero according to the first inductor current i _L1,PFC , the DC input voltage V _in , and the DC output voltage V _Cbus . voltage switching, thereby realizing a power factor corrector with a SEPIC architecture with high overall efficiency and high power factor, so the object of the present invention can be achieved indeed.

However, the above are only examples of the present invention, and should not limit the scope of implementation of the present invention. Any simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the contents of the patent specification are still included in the scope of the present invention. within the scope of the invention patent.

1: rectifier unit D1~D4: first rectifier diode~4th rectifier diode 2: single-ended primary inductance converter L1, _PFC : first inductor i _{L1, PFC} : first inductor current v _{L1, PFC} : cross voltage L _{2, PFC} : second inductor i _{L2, PFC} : second inductor current v _{L2, PFC} : cross voltage C _{1, PFC} : first capacitor v _{C1, PFC} : cross voltage Q _main : main switch S1: main switch Control signal v _DS,main : across voltage i _DS,main : main switch current D _b,main : back-connected diode C _oss,main : parasitic capacitance D _PFC : first diode i _{D, PFC} : diode Current C _bus : output capacitor 3 : current sensor 4 : resonance unit Q _aux : auxiliary switch S2 : auxiliary control signal v _DS,aux : across voltage i _DS,aux : auxiliary switch current D _b,aux : back-connected diode Body C _oss,aux : parasitic capacitance L _{r, PFC} : resonant inductance i _{Lr, PFC} : resonant inductor current C _{c, PFC} : clamping capacitance v _{Cc, PFC} : cross voltage 9: AC voltage source R _PFC : load V _AC : AC input voltage V _in : DC input voltage V _Cbus : DC output voltage

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein: 1 is a block diagram illustrating an embodiment of a power factor corrector of the present invention; 2 is a timing diagram illustrating the relationship between a plurality of signals in this embodiment of the present invention; 3 is a circuit diagram illustrating an equivalent circuit of the embodiment operating in a first interval; 4 is a circuit diagram illustrating an equivalent circuit of the embodiment operating in a second interval; 5 is a circuit diagram illustrating an equivalent circuit of the embodiment operating in a third interval; 6 is a circuit diagram illustrating an equivalent circuit of the embodiment operating in a fourth interval; 7 is a circuit diagram illustrating an equivalent circuit of the embodiment operating in a fifth interval; FIG. 8 is a circuit diagram illustrating the equivalent circuit of the embodiment operating in a sixth interval.

1: rectifier unit D1~D4: first rectifier diode~4th rectifier diode 2: single-ended primary inductance converter L1, _PFC : first inductor i _{L1, PFC} : first inductor current v _{L1, PFC} : cross voltage L _{2, PFC} : second inductor i _{L2, PFC} : second inductor current v _{L2, PFC} : cross voltage C _{1, PFC} : first capacitor v _{C1, PFC} : cross voltage Q _main : main switch S1: main switch Control signal v _DS,main : across voltage i _DS,main : main switch current D _b,main : back-connected diode C _oss,main : parasitic capacitance D _PFC : first diode i _{D, PFC} : diode Current C _bus : output capacitor 3 : current sensor 4 : resonance unit Q _aux : auxiliary switch S2 : auxiliary control signal v _DS,aux : across voltage i _DS,aux : auxiliary switch current D _b,aux : back-connected diode Body C _oss,aux : parasitic capacitance L _{r, PFC} : resonant inductance i _{Lr, PFC} : resonant inductor current C _{c, PFC} : clamping capacitance v _{Cc, PFC} : cross voltage 9: AC voltage source R _PFC : load V _AC : AC input voltage V _in : DC input voltage V _Cbus : DC output voltage

Claims (6)

A power factor corrector, suitable for receiving an AC input voltage and a load, and comprising: a rectifier unit, receiving the AC input voltage, and converting and outputting a DC input voltage; a single-ended primary inductance converter (Single ended primary inductance converter) inductor converter (SEPIC), electrically connected to the rectifier unit and the load, to receive the DC input voltage and convert it to output a DC output voltage to the load, and includes a first inductor and a main switch; a current sensor that detects measuring the magnitude of a first inductor current flowing through the first inductor of the single-ended primary inductor converter; a resonant unit electrically connected to the single-ended primary inductor converter and comprising an auxiliary switch, a resonant inductor, and a a clamping capacitor to form a resonant path; and a control unit, electrically connected to the rectifier unit to detect the DC input voltage, electrically connected to the current sensor to obtain the magnitude of the first inductor current, and also electrically connected The load detects the DC output voltage, and is also electrically connected to the single-ended primary inductance converter and the resonance unit to control the main switch and the auxiliary switch to achieve zero-voltage switching. The power factor corrector of claim 1, wherein the control unit generates a main control signal and an auxiliary control signal according to the DC input voltage, the first inductor current, and the DC output voltage to control the main control signal respectively. The switch and the auxiliary switch operate in conduction or non-conduction. The power factor corrector of claim 2, wherein the rectifier unit is A Diode bridge consisting of four diodes. The power factor corrector of claim 2, wherein the main switch of the single-ended primary inductance converter and the auxiliary switch of the resonant unit both comprise a back-connected diode and a parasitic capacitor connected in parallel. The power factor corrector according to claim 2, wherein the rectifier unit includes a positive output terminal and a negative output terminal for outputting the DC input voltage, and the single-ended primary inductance converter further includes a first capacitor, a first Two inductors, a first diode, and an output capacitor, the first inductor includes a first end and a second end that are electrically connected to the positive output end of the rectifier unit, and the main switch includes an electrical connection to the first inductor a first end of the second end, a control end that receives the main control signal, and a second end that is electrically connected to the negative output end of the rectifier unit, the first capacitor includes the first capacitor that is electrically connected to the first inductor A first end and a second end of two ends, the second inductor includes a first end that is directly or indirectly electrically connected to the second end of the first capacitor, and a second end that is electrically connected to the negative output end of the rectifier unit terminal, the first diode includes an anode terminal and a cathode terminal electrically connected to the first terminal of the second inductor, the output capacitor includes a first terminal electrically connected to the cathode terminal of the first diode, and A second end of the negative output end of the rectifier unit is electrically connected, and the load is connected in parallel with the output capacitor. The power factor corrector according to claim 5, wherein the clamping capacitor of the resonant unit is connected in series with the auxiliary switch, and is then connected in parallel with the main switch of the single-ended primary inductance converter, and the resonant inductor is electrically connected to Between the second end of the first capacitor and the first end of the second inductor of the single-ended primary inductance converter.

Images