TWI879322B - Power supply with reverse curremt compensation mechanism - Google Patents

Abstract

A power supply includes an active power factor correction circuit, a resonation conversion circuit, a zero-current detection and reverse current compensation circuit, and a control circuit. When determining that the status of the output voltage provided by the resonation conversion circuit is normal and that the boost inductor current in the active power factor correction circuit is in zero-current state, the zero-current detection and reverse current compensation circuit is configured to conduct the signal transmission path from a resonation capacitor in the resonation conversion circuit to a boost inductor in the active power factor correction circuit. This way, the energy stored in the resonation capacitor may be transmitted to the input end of the power supply for compensating the reverse current.

Description

Power supply with reverse current compensation structure

The present invention relates to a power supply with a reverse current compensation structure, and in particular to a power supply capable of providing a reverse current compensation structure under a zero boost inductor current state.

Different components in a computer system require different operating voltages, so power supplies are commonly used to convert AC indoor power into DC power to drive different components through transformation, rectification and filtering. With the rise of environmental awareness, countries have set energy-saving specifications for consumer electronic products, office equipment, home appliances and external power supplies. For example, the US Energy Star is a certification program jointly sponsored by the US Department of Energy and the Environmental Protection Agency, which specifies relevant energy-saving specifications for power supplies with different rated output power.

For example, for power supplies with an output power greater than 70W and their overall system configuration, the US Energy Star standard requires that the rated power factor must be greater than 0.9. Therefore, the design architecture of a high-power power supply is usually divided into a front-stage boost active power factor correction (PFC) circuit and a rear-stage buck resonant conversion circuit. The front-stage circuit uses a power switch to switch the energy storage charging operation and energy release discharge operation of the boost inductor, thereby optimizing the power factor of the power supply. The rear-stage circuit can control the mutual resonance between components such as inductors and capacitors through a resonant switch to convert the high-voltage output of the front-stage circuit into a low-voltage output to drive the load device.

The control methods of active power factor correction operation can be divided into continuous conduction mode (CCM), boundary conduction mode (BCM) and discontinuous conduction mode (DCM). Boundary conduction mode uses variable frequency operation. When the boost inductor current drops to zero, the power switch element will be turned on again. Its control circuit is simpler and can achieve high-efficiency power switch zero-current conduction switching. Therefore, for low-wattage application ranges of 130W to 230W, the boost inductor current is usually designed in boundary current mode to achieve high-efficiency power switch zero-current conduction switching. However, when the boost inductor current is zero, the parasitic capacitance on the power switch will resonate with the boost inductor, thereby generating a reverse current that is returned to the AC power supply. The reverse current will generate heat loss and affect the boost conversion efficiency of the active power factor corrector, and will also cause a higher total harmonic distortion problem.

Therefore, a power supply is needed that can compensate for reverse current in the state of zero boost inductor current.

The present invention provides a power supply with a reverse current compensation structure, which includes a boost type active power factor correction circuit, a resonant conversion circuit, a zero current detection and reverse current compensation circuit, and a control circuit. The boost type active power factor correction circuit is used to convert an AC voltage supplied by a mains power supply into a DC voltage, and then convert the DC voltage into a pulsed DC voltage, and includes a boost inductor and a power switch. The boost inductor is used to store or release the energy of the DC voltage, and includes a first end coupled to the DC voltage, and a second end. The power switch is used to control the boost inductor to store and release energy according to a first control signal, and includes a first terminal coupled to the second terminal of the boost inductor, a second terminal coupled to the first ground potential, and a control terminal for receiving the first control signal that periodically switches between a first enabling potential and a first disabling potential. The resonant conversion circuit is used to convert the pulsed DC voltage into an output voltage, and includes a transformer, a magnetizing inductor, a resonant inductor, a resonant capacitor, a first resonant switch, and a second resonant switch. The transformer is used to induce the energy of the first pulsed DC voltage from a first primary side to a first secondary side to supply the output voltage, and includes a primary side winding, which is arranged on the first primary side, and includes a first hit end and a first non-hit end; a first secondary side winding, which is arranged on the first secondary side, and includes a second hit end and a second non-hit end; and a second secondary side winding, which is arranged on the first secondary side, and includes a third hit end and a third non-hit end, wherein the second non-hit end is coupled to the third hit end. The excitation inductor includes a first end coupled to the first hit end, and a second end coupled to the first non-hit end. The resonant inductor includes a first end coupled to the first hit end, and a second end. The resonant capacitor includes a first terminal coupled to the first non-striking terminal and a second terminal coupled to the first ground potential. The first resonant switch is used to control the operation of the resonant conversion circuit according to a second control signal, and includes a first terminal coupled to the pulsed DC voltage, a second terminal coupled to the second terminal of the resonant inductor, and a control terminal for receiving the second control signal that is periodically switched between a second enabling potential and a second disabling potential. The second resonant switch is used to control the operation of the resonant conversion circuit according to a third control signal, and includes a first terminal coupled to the second terminal of the resonant inductor, a second terminal coupled to the first ground potential, and a control terminal for receiving the third control signal that is periodically switched between a third enabling potential and a third disabling potential. The zero current detection and reverse current compensation circuit is used to detect a boost inductor current flowing through the boost inductor; when it is determined that the boost inductor current is in a zero current state, the signal transmission path from the first end of the resonant capacitor to the first end of the magnetizing inductor is turned on; and when it is determined that the boost inductor current is not in a zero current state, the signal transmission path from the first end of the resonant capacitor to the first end of the magnetizing inductor is turned off. The control circuit is used to provide the first control signal, the second control signal and the third control signal; and to provide a fourth control signal having a fourth enabling potential or a fourth disabling potential according to a logic voltage to selectively turn on or off the signal transmission path from the first end of the resonant capacitor to the first end of the magnetizing inductor.

10: Boost type active power factor correction circuit

12: Rectifier circuit

20: Resonance conversion circuit

30: Zero current detection and reverse current compensation circuit

32: Zero current detection unit

34: Comparator

36:Logic circuit

38: Amplifier

40: Control circuit

100: Power supply

TR: Transformer

N1: Primary side winding and number of turns

N2, N3: Secondary winding and number of turns

N4: Excitation winding and number of turns

N5: Detect windings and turns

GND1, GND2: ground potential

Q1: Power switch

Q2, Q3: Resonance switch

Q4: Auxiliary switch

DO1: boost diode

DO2, DO3: output diodes

D1-D4: diodes

CO1, CO2: Energy storage capacitor

LM1: boost inductor

LM2: Magnetizing inductance

LR: Resonance inductor

RS: Detection resistance

RZ: Conductive resistance

V _IN : DC voltage

V _OUT : Output voltage

V _AC : Alternating current voltage

V _LM1 : Boost inductor voltage

V _LM2 : Inductive voltage

VS: Detection voltage

VF: reference voltage

VF’: Adjusted reference voltage

VCP: Comparative voltage

VAA: logic voltage

VO1: Pulsating DC voltage

I _LM : Boost inductor current

I _OUT : Output current

IN1-IN3: Input terminal of logic circuit

OUT: Output terminal of logic circuit

GD1-GD4: control signal

P1-P7: Foot position

Figure 1 is a functional block diagram of a power supply with a reverse current compensation structure in an embodiment of the present invention.

Figure 2 is a schematic diagram of an implementation of a power supply with a reverse current compensation structure in an embodiment of the present invention.

Figure 3 is a waveform diagram of related signals when a power supply with a reverse current compensation structure is in operation in an embodiment of the present invention.

FIG. 1 is a functional block diagram of a power supply 100 with a reverse current compensation structure in an embodiment of the present invention. The power supply 100 includes a boost type active power factor correction circuit 10, a resonant conversion circuit 20, a zero current detection and reverse current compensation circuit 30, and a control circuit 40. The power supply 100 can convert the alternating current voltage V _AC supplied by the mains into an output voltage V _OUT to drive a load device (not shown in FIG. 1 ).

FIG. 2 is a schematic diagram of the implementation of the power supply 100 in the embodiment of the present invention. In the embodiment of the present invention, the boost type active power factor correction circuit 10 of the power supply 100 includes a rectifier 12, a power switch Q1, a boost diode DO1, an energy storage capacitor CO1, and a boost inductor LM1, which can provide a pulsed DC voltage VO1 according to the AC voltage V _AC supplied by the mains. In the embodiment of the present invention, the rectifier 12 can be a bridge rectifier, which includes rectifier diodes D1-D4, and is used to convert the AC voltage V _AC supplied by the mains into a DC voltage V _IN . However, the implementation of the rectifier 12 does not limit the scope of the present invention.

The first end of the boost inductor LM1 is coupled to the rectifier 10 to receive the DC voltage V _IN , and the second end is coupled to the ground potential GND1 through the power switch Q1, which can store the energy of the DC voltage V _IN , wherein the boost inductor current I _LM flowing through the boost inductor LM1 is the input current of the power supply 100. The anode of the boost diode DO1 is coupled to the second end of the boost inductor LM1 , and the cathode is coupled to the resonant conversion circuit 20 and the energy storage capacitor CO1. The first end of the energy storage capacitor CO1 is coupled to the cathode of the boost diode DO1 , and the second end is coupled to the ground potential GND1 , which can store the energy of the pulsed DC voltage VO1 . The first end of the power switch Q1 is coupled between the second end of the boost inductor LM1 and the anode of the boost diode DO1, the second end is coupled to the ground potential GND1, and the control end is coupled to the control circuit 40 to receive a control signal GD1. According to the control signal GD1, high-frequency switching can be performed to allow the boost inductor LM1 to store and release energy, so that the input current tracks the input voltage, thereby improving the power factor and reducing current harmonics.

The boost inductor LM1, boost diode DO1, energy storage capacitor CO1 and power switch Q1 can achieve the purpose of boosting. When the power switch Q1 is turned on during the period when the AC voltage V _AC is supplied by the mains, the second end of the boost inductor LM1 will be coupled to the ground potential GND1. At this time, the boost inductor LM1 will generate an induced voltage in response to the change of the DC voltage V _IN , and then convert the electrical energy into magnetic energy for storage. When the power switch Q1 is turned off, the ground loop of the boost inductor LM1 is disconnected, and the magnetic energy stored in it will be converted into electrical energy, allowing a large current to pass through the boost diode DO1 to charge the energy storage capacitor CO1. After multiple rapid switching of the power switch Q1, the DC voltage V _IN can be increased to provide the pulse DC voltage VO1.

In the embodiment of the present invention, the resonant conversion circuit 20 of the power supply 100 includes a transformer TR, resonant switches Q2-Q3, a magnetizing inductor LM2, a resonant inductor LR, a resonant capacitor CR, an energy storage capacitor CO2, a detection resistor RS, and two output diodes DO2-DO3. The resonant conversion circuit 20 can receive a pulsed DC voltage VO1 at its input terminal, convert the pulsed DC voltage VO1 into an output voltage V _OUT , and then drive a load device (not shown in FIG. 2 ).

In the resonant converter circuit 20 of the embodiment of the present invention, the transformer TR includes a primary winding (represented by the number of turns N1) and two secondary windings (represented by the number of turns N2 and N3), wherein the primary winding N1 is arranged on the primary side of the transformer TR, and the secondary windings N2 and N3 are arranged on the secondary side of the transformer TR. The first end of the resonant switch Q2 is coupled to the cathode of the boost diode DO1 in the boost active power factor correction circuit 10 to receive the pulsed DC voltage VO1, the second end is coupled to the resonant switch Q3, and the control end is coupled to the control circuit 40 to receive a control signal GD2. The first end of the resonant switch Q3 is coupled to the second end of the resonant switch Q2, the second end is coupled to the ground potential GND1, and the control end is coupled to the control circuit 40 to receive a control signal GD3. The first end of the resonant inductor LR is coupled between the second end of the resonant switch Q2 and the first end of the resonant switch Q3, and the second end is coupled to the tapping end of the primary winding N1 in the transformer TR. The first end of the magnetizing inductor LM2 is coupled to the tapping end of the primary winding N1 in the transformer TR, and the second end is coupled to the non-tapping end of the primary winding N1 in the transformer TR. The first end of the resonant capacitor CR is coupled to the non-pointing end of the primary winding N1 in the transformer TR, and the second end is coupled to the ground potential GND1. In one embodiment, the resonant inductor LR, the magnetizing inductor LM2 and the resonant capacitor CR form an inductor-inductor-capacitor (LLC) resonant circuit, but the implementation of the resonant structure in the resonant converter circuit 20 does not limit the scope of the present invention.

In the resonant converter circuit 20 of the present embodiment, the anode of the output diode DO2 is coupled to the tapped end of the secondary winding N2 in the transformer TR, and the cathode is coupled to the output end (output voltage V _OUT ) of the power supply 100. The anode of the output diode DO3 is coupled to the non-tapped end of the secondary winding N3 in the transformer TR, and the cathode is coupled to the output end (output voltage V _OUT ) of the power supply 100. The first end of the energy storage capacitor CO2 is coupled to the cathode of the output diode DO2, and the second end is coupled to the non-striking end of the secondary winding N2 and the tapping end of the secondary winding N3 in the transformer TR, for storing the energy of the output voltage V _OUT , wherein the current flowing through the energy storage capacitor CO2 is the output current I _OUT of the power supply 100. The first end of the detection resistor RS is coupled to the second end of the energy storage capacitor CO2, and the second end is coupled to the ground potential GND2, for detecting the output current I _OUT , and further providing a detection voltage VS related to the output voltage V _OUT.

In the embodiment of the present invention, the zero current detection and reverse current compensation circuit 30 of the power supply 100 includes a zero current detection unit 32, a comparator 34, a logic circuit 36, an amplifier 38, a conduction resistor RZ, and an auxiliary switch Q4. The zero current detection unit 32 can be implemented by a transformer, which includes an excitation winding (represented by the number of turns N4) and a detection winding (represented by the number of turns N5). The excitation winding N4 is arranged on the primary side of the zero current detection unit 32 and is connected in parallel to the boost inductor LM1. The secondary winding N5 is disposed on the secondary side of the zero current detection unit 32, with a first end coupled to the first end of the conduction resistor RZ, and a second end coupled to the ground potential GND1. The zero current detection unit 32 can sense the boost inductor voltage V _LM1 (the voltage across the boost inductor LM1) from the excitation winding N4 to the detection winding N5, so as to provide an induced voltage V _LM2 on the secondary side. The first input terminal (e.g., the positive input terminal) of the comparator 34 is coupled to the control circuit 40 to receive a reference voltage VF (VF>0), the second input terminal (e.g., the negative input terminal) is coupled to the second end of the conductive resistor RZ to receive the sense voltage V _LM2 , and the output terminal is coupled to the logic circuit 36. According to the potential relationship between the reference voltage VF and the sense voltage V _LM2 , the comparator 34 can output a corresponding comparison voltage VCP. For example, when the boost inductor current I _LM flowing through the boost inductor LM1 is zero current, the induced voltage V _LM2 is zero voltage. At this time, the potential of the first input terminal in the comparator 34 will be higher than the potential of the second input terminal, so a comparison voltage VCP with a first potential (for example, a positive potential) will be output at the output terminal; when the boost inductor current I _LM flowing through the boost inductor LM1 is not zero current, the induced voltage V _LM2 is not zero voltage. At this time, the potential of the first input terminal in the comparator 34 will not be higher than the potential of the second input terminal, so a comparison voltage VCP with a second potential (for example, zero potential) will be output at the output terminal.

In the zero current detection and reverse current compensation circuit 30 of the present embodiment, the first end of the auxiliary switch Q4 is coupled to the first end of the resonant capacitor CR in the resonant conversion circuit 20, the second end thereof is coupled to the first end of the boost inductor LM1 in the boost type active power factor correction circuit 10, and the control end thereof is coupled to the control circuit 40 to receive a control signal GD4. The amplifier 38 is coupled between the control circuit 40 and the logic circuit 36, and can receive the reference voltage VF and adjust the potential of the reference voltage VF to provide an adjusted reference voltage VF' that meets the voltage operating range of the logic circuit 36. The first input terminal IN1 of the logic circuit 36 is coupled to the first terminal of the energy storage capacitor CO2 to receive the output voltage V _OUT , the second input terminal IN2 thereof is coupled to the amplifier 38 to receive the adjusted reference voltage VF′, and the third input terminal IN3 thereof is coupled to the output terminal of the comparator 34 to receive the comparison voltage VCP. A logic voltage VAA can be provided at its output terminal OUT according to the values of the output voltage V _OUT , the adjusted reference voltage VF′ and the comparison voltage VCP.

In one embodiment, the logic circuit 36 is an AND gate. When the first input terminal IN1, the second input terminal IN2 and the third input terminal IN3 of the logic circuit 36 all receive a high-level signal, the output logic voltage VAA will be a high level; when at least one of the first input terminal IN1, the second input terminal IN2 and the third input terminal IN3 of the logic circuit 36 does not receive a high-level signal, the output logic voltage VAA will be a low level. However, the implementation of the logic circuit 36 does not limit the scope of the present invention.

In the embodiment shown in FIG. 2, the control circuit 40 may be a microprocessor controller (MCU), which includes pins P1-P7, wherein the pin P1 is used to output a control signal GD1 for high-frequency switching between a first enable potential and a first disable potential to the control end of the power switch Q1, the pin P2 is used to output a control signal GD2 for high-frequency switching between a second enable potential and a second disable potential to the control end of the resonant switch Q2, and the pin P3 is used to output a control signal GD1 for high-frequency switching between a third enable potential and a third disable potential to the control end of the resonant switch Q2. The high-frequency switching control signal GD3 is sent to the control end of the resonant switch Q3, the pin P4 is used to send a control signal GD4 with a fourth enable potential or a fourth disable potential to the control end of the auxiliary switch Q4, the pin P5 is coupled to the output end of the logic circuit 36 in the zero current detection and reverse current compensation circuit 30 to receive the logic voltage VAA, the pin P6 is coupled to the resonant conversion circuit 20 to receive the detection voltage VS, and the pin P7 is used to output a reference voltage VF with a fixed positive value to the zero current detection and reverse current compensation circuit 30.

As shown in FIG. 2 , when the power supply 100 is not connected to the mains, all control signals are 0, and the power supply 100 has no output (V _OUT =0). When the power supply 100 is connected to the mains, the boost active power factor correction circuit 10 starts to operate first. The rectifier 10 can convert the AC voltage V _AC supplied by the mains into a DC input voltage V _IN , and the control circuit 40 outputs a control signal GD1 that switches between a first enable potential and a first disable potential at a high frequency to the control end of the power switch Q1 through the pin P1, so that the power switch Q1 can switch between the on and off states at a high frequency accordingly, thereby allowing the boost inductor LM1 to periodically store and release energy, so as to provide a boosted pulsating DC voltage VO1 on the primary side of the transformer TR.

Next, the pulsed DC voltage VO1 outputted after the boost active power factor correction circuit 10 operates stably is the input voltage of the resonant converter circuit 20, and the control circuit 40 outputs a control signal GD2 for high-frequency switching between the second enable potential and the second disable potential to the control end of the resonant switch Q2 through the pin P2, and outputs a control signal GD3 for high-frequency switching between the third enable potential and the third disable potential to the control end of the resonant switch Q3 through the pin P3. The control signals GD2 and GD3 are complementary signals, that is, when the control signal GD2 has the second enable potential, the control signal GD3 will have the third disable potential, and when the control signal GD2 has the second disable potential, the control signal GD3 will have the third enable potential, so that the resonant switches Q2 and Q3 can perform high-frequency complementary switching according to the control signals GD2 and GD3 respectively, thereby making the resonant inductor LR, the excitation inductor LM2 and the resonant capacitor CR resonate with each other to achieve flexible switching of zero voltage or zero current to reduce switching loss. In this case, the transformer TR can induce the energy of the corresponding pulse DC voltage VO1 stored in the primary winding NP to the secondary windings N2 and N3 to provide the output voltage V _OUT . At the same time, the output current I _OUT of the output voltage V _OUT will flow to the ground potential GND2 through the energy storage capacitor CO2 and the detection resistor RS, and establish the detection voltage VS on the detection resistor RS. The control circuit 40 receives the detection voltage VS through the pin P6, thereby knowing the instantaneous state of the output current I _OUT , and adjusting the duty cycle of the control signals GD1 - GD3 according to the value of the detection voltage VS to achieve the purpose of stabilizing the output voltage V _OUT .

FIG. 3 is a waveform diagram of related signals when the power supply 100 is operating in the embodiment of the present invention. The upper portion of FIG. 3 shows a waveform of the boost inductor current I _LM ' when the power supply of the prior art operates without a reverse current compensation structure. The center of FIG. 3 shows a waveform of the boost inductor current I _LM when the power supply 100 with a reverse current compensation structure in the embodiment of the present invention operates. The lower portion of FIG. 3 shows a waveform of the control signal GD4 when the power supply 100 with a reverse current compensation structure in the embodiment of the present invention operates. According to Lenz's law of the inductor element, the cross-voltage V _LM1 of the boost inductor LM1 changes with the boost inductor current I _LM flowing through the boost inductor LM1. During the period when the AC voltage V _AC is supplied by the mains, when the control signal GD1 has the first enabling level, the boost inductor LM1 will be coupled to the ground potential GND1 by the turned-on power switch Q1 to perform energy storage charging operation, and during the energy storage charging operation, the boost inductor current I _LM will increase, and at this time, the boost inductor voltage V _LM1 is a positive voltage with increasing potential; during the period when the AC voltage V _AC is supplied by the mains, when the control signal GD1 has the first disabling level, the charging path of the boost inductor LM1 will be cut off by the turned-off power switch Q1, so that an energy release discharge operation will be performed, and during the energy release discharge operation, the boost inductor current I _LM will decrease downward, and at this time, the boost inductor voltage V _LM1 is a positive voltage with decreasing potential.

As shown in the upper part of Figure 3, because the power supply of the prior art does not provide a reverse current compensation structure, in the boundary conduction mode, when the boost inductor current I _LM ' drops to zero, the parasitic capacitance of the power switch Q1 will resonate with the boost inductor LM1 to generate a reverse current returned to the AC power supply end (the value of the boost inductor current I _ILM ' is a negative interval). The above reverse current will generate heat loss and affect the boost conversion efficiency of the active power factor corrector, and will also cause a higher total harmonic distortion problem.

As shown in FIG. 2 and FIG. 3 , the power supply 100 of the embodiment of the present invention can use the zero current detection unit 32 to detect the state where the boost inductor current I _LM is zero between the energy storage charging operation and the energy release discharging operation. The exciting winding N4 will transfer the instantaneous inductor energy to the detection winding N5. When the energy of the detection winding N5 is zero, it means that the boost inductor current I _LM is zero current. At this time, the inductive voltage V _LM2 provided by the zero current detection unit 32 on its secondary side is also zero voltage. When the sense voltage V _LM2 is zero voltage, the potential of the first input terminal of the comparator 34 will be higher than the potential of the second input terminal. At this time, a comparison voltage VCP having a first potential (eg, a positive potential) will be output at its output terminal.

When the power supply 100 operates normally during the period of the AC voltage V _AC supplied by the mains, the output voltage V _OUT provided by the resonant converter circuit 20 will be maintained at a high level, and the control circuit 40 will provide a reference voltage VF with a high level. Therefore, during the period of the AC voltage V _AC supplied by the mains, when the power supply 100 operates normally and detects that the boost inductor current I _LM is zero, the voltages of the first to third input terminals of the logic circuit 36 are all high, so a logic voltage VAA with a third level (e.g., high level) is provided at its output terminal. On the other hand, during the period when the AC voltage V _AC is supplied by the mains, when the power supply 100 does not detect that the boost inductor current I _LM is zero, the voltages at the first to third input terminals of the logic circuit 36 are not all high voltages, and therefore a logic voltage VAA having a fourth voltage (e.g., a low voltage) is provided at its output terminal.

When the control circuit 40 receives the logic voltage VAA having a fourth potential (e.g., a low potential) through the pin P5, it indicates that the current value of the boost inductor current I _LM is not zero. At this time, the control circuit 40 outputs a control signal GD4 having a fourth disable potential through the pin P4 to turn off the auxiliary switch Q4, thereby cutting off the signal transmission path from the first end of the resonant capacitor CR to the first end of the boost inductor LM1. When the control circuit 40 receives the logic voltage VAA having a third potential (e.g., a high potential) through the pin P5, it indicates that the current value of the boost inductor current I _LM is zero. At this time, the control signal GD4 having a fourth enable potential is output through the pin P4 to turn on the auxiliary switch Q4, thereby turning on the signal transmission path from the first end of the resonant capacitor CR to the first end of the boost inductor LM1. In this way, the energy stored in the resonant capacitor CR can be transmitted to the first end of the boost inductor LM1 to offset the reverse current.

In the embodiment of the present invention, when the output power of the power supply 100 is larger, the output load IO is also larger, and the average energy of the boost inductor LM1 is also larger, so when the value of the boost inductor current I _LM is zero, a larger resonant reverse current will be generated. Therefore, the present invention can determine the total on-time TT of the auxiliary switch Q4 (i.e., the time when the control signal GD4 has the fourth enabling potential) according to the output current I _OUT .

In one embodiment, the control circuit 40 can determine the size of the output load IO according to the detection voltage VS established on the detection resistor RS, and then determine the duty cycle of the auxiliary switch Q4 accordingly, so that the total conduction time TT of the auxiliary switch Q4 is sufficient to provide corresponding energy to offset the reverse current. The following table 1 shows the corresponding relationship between the output load IO, the detection voltage VS and the total conduction time TT, where IO _MAX represents the maximum output load of the power supply 100, and TX represents the unit time. It is worth noting that the values shown in Table 1 are for illustrative purposes only and do not limit the scope of the present invention.

In the embodiment of the present invention, the power switch Q1, the resonant switches Q2-Q3 and the auxiliary switch Q4 can be metal-oxide-semiconductor field-effect transistors (MOSFET), bipolar junction transistors (BJT), or other components with similar functions. For N-type transistors, the enable potential is high and the disable potential is low; for P-type transistors, the enable potential is low and the disable potential is high. However, the types of the above switches do not limit the scope of the present invention.

In summary, the power supply 100 of the present invention can detect the state of the boost inductor current I _LM , and when it is determined that the output voltage V _OUT is normal and the boost inductor current I _LM is detected to be zero, the auxiliary switch Q4 is used to turn on the signal transmission path from the resonant capacitor CR to the boost inductor LM1, thereby allowing the energy stored in the resonant capacitor CR to be transmitted to the input end to offset the reverse current. In addition, the power supply 100 of the present invention can also detect the state of the output voltage V _OUT to provide a corresponding detection voltage VS, and judge the size of the output load according to the detection voltage VS, and then determine the total conduction time TT of the auxiliary switch Q4 to provide corresponding energy to offset the reverse current. Therefore, the power supply of the present invention can reduce heat loss, improve the boost conversion efficiency of the active power factor corrector, and reduce the probability of total harmonic distortion.

The above is only the preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the patent application of the present invention shall fall within the scope of the present invention.

10: Boost type active power factor correction circuit

20: Resonance conversion circuit

30: Zero current detection and reverse current compensation circuit

40: Control circuit

100: Power supply

V _OUT : Output voltage

V _AC : Alternating current voltage

VO1: Pulsating DC voltage

Claims (10)

A power supply with a reverse current compensation structure includes: a boost type active power factor correction circuit for converting an AC voltage of a mains supply into a DC voltage, and then converting the DC voltage into a pulsed DC voltage, including: a boost inductor for storing or releasing the energy of the DC voltage, including: a first end coupled to the DC voltage; and a second end; and a power The switch is used to control the boost inductor to store and release energy according to a first control signal, and includes: a first end coupled to the second end of the boost inductor; a second end coupled to a first ground potential; and a control end for receiving the first control signal that periodically switches between a first enabling potential and a first disabling potential; a resonant conversion circuit for converting the pulsed DC The voltage is converted into an output voltage, which includes: a transformer for inducing the energy of the pulsed DC voltage from a first primary side to a first secondary side to supply the output voltage, which includes: a primary side winding, arranged on the first primary side, including a first dotted end and a first non-dotted end; a first secondary side winding, arranged on the first secondary side, including a second dotted end and a second non-dotted end; end; and a second secondary side winding, arranged on the first secondary side, comprising a third dotted end and a third non-dotted end, wherein the second non-dotted end is coupled to the third dotted end; an excitation inductor, comprising: a first end, coupled to the first dotted end; and a second end, coupled to the first non-dotted end; a resonant inductor, comprising: a first end, coupled to the first dotted end; and a a second end; a resonant capacitor, comprising: a first end coupled to the first non-striking end; and a second end coupled to the first ground potential; a first resonant switch, used to control the operation of the resonant conversion circuit according to a second control signal, comprising: a first end coupled to the pulsating DC voltage; a second end coupled to the second end of the resonant inductor; and a control end for receiving the second control signal that periodically switches between a second enabling potential and a second disabling potential; and a second resonant switch, used to control the operation of the resonant conversion circuit according to a third control signal, comprising: a first end coupled to the second end of the resonant inductor; a second end coupled to the first ground potential; and a control end for receiving a third enabling potential and a third disabling potential. a third control signal periodically switched between the first and second control signals; a zero current detection and reverse current compensation circuit, used to: detect a boost inductor current flowing through the boost inductor; when the boost inductor current is determined to be in a zero current state, conduct the signal transmission path from the first end of the resonant capacitor to the first end of the boost inductor; and when the boost inductor current is determined not to be in a zero current state, disconnect the first end of the resonant capacitor from the first end of the boost inductor. A signal transmission path from one end of the resonant capacitor to the first end of the boost inductor; and a control circuit for: providing the first control signal, the second control signal and the third control signal; and providing a fourth control signal with a fourth enable potential or a fourth disable potential according to a logic voltage to selectively turn on or off the signal transmission path from the first end of the resonant capacitor to the first end of the boost inductor. The power supply as described in claim 1, wherein the zero current detection and reverse current compensation circuit is further used to: receive the output voltage; and when it is determined that the power supply can operate normally based on the output voltage and the boost inductor current is determined to be in a zero current state, conduct the signal transmission path from the first end of the resonant capacitor to the first end of the boost inductor. A power supply as claimed in claim 2, wherein the control circuit is further used to provide a first reference voltage having a fixed potential, and the zero current detection and reverse current compensation circuit comprises: a zero current detection unit, used to induce the energy of the boost inductor current from a second primary side to a second secondary side to provide an induced voltage, which comprises: an excitation winding, arranged on the second primary side, wherein a first end of the excitation winding is coupled to the first terminal of the boost inductor; The invention relates to a first input winding, wherein the first end of the detection winding is used to provide the induced voltage, and the second end of the detection winding is coupled to the first ground potential; a comparator, which is used to selectively provide a comparison voltage with a first potential or a second potential according to the potential relationship between the induced voltage and the reference voltage, and comprises: a first input A first input terminal coupled to the control circuit to receive the first reference voltage; a second input terminal coupled to the zero current detection unit to receive the induced voltage; and an output terminal for outputting the comparison voltage; a logic circuit for selectively providing the logic voltage with a third potential or a fourth potential according to the potential of the comparison voltage and a second reference voltage related to the first reference voltage, comprising: a first input terminal for receiving the output voltage; a second input terminal coupled to the zero current detection unit to receive the induced voltage; and an output terminal for outputting the comparison voltage. An input terminal for receiving the second reference voltage; a third input terminal coupled to the output terminal of the comparator to receive the comparison voltage; and an output terminal for outputting the logic voltage; and an auxiliary switch, which operates according to the fourth control signal and includes: a first terminal coupled to the first terminal of the resonant capacitor; a second terminal coupled to the first terminal of the boost inductor; and a control terminal coupled to the control circuit to receive the fourth control signal. A power supply as described in claim 3, wherein the zero current detection and reverse current compensation circuit further comprises an amplifier coupled between the control circuit and the second input terminal of the logic circuit, for adjusting the potential of the first reference voltage to provide the second reference voltage that meets the voltage operating range of the logic circuit. A power supply as described in claim 3, wherein the zero current detection and reverse current compensation circuit further comprises a conductive resistor coupled between the first end of the detection winding and the second input end of the comparator. The power supply as described in claim 3, wherein: the comparator is further used to: when the potential of the first reference voltage is higher than the potential of the induced voltage, output the comparison voltage having the first potential; and when the potential of the first reference voltage is not higher than the potential of the induced voltage, output the comparison voltage having the second potential; the logic circuit is further used to: when the output voltage has a first high potential, the comparison voltage has the first potential, and the second reference voltage has a second high potential, output the logic voltage having the third potential; and when the comparison voltage has the second high potential When the logic voltage with the third potential is received, the fourth control signal with the fourth enabling potential is output to turn on the auxiliary switch, thereby turning on the signal transmission path from the first end of the resonant capacitor to the first end of the boost inductor; and when the logic voltage with the fourth potential is received, the fourth control signal with the fourth disabling potential is output to turn off the auxiliary switch, thereby cutting off the signal transmission path from the first end of the resonant capacitor to the first end of the boost inductor. A power supply as described in claim 1, wherein the control circuit is further used to: receive a detection voltage related to the output voltage; and determine the duty cycle of the fourth control signal based on the detection voltage. The power supply as described in claim 1, wherein the boost type active power factor correction circuit further comprises: a first energy storage capacitor, a first end of which is coupled to the pulsed DC voltage, and a second end of which is coupled to the first ground potential, for storing the energy of the pulsed DC voltage; and a first diode, an anode of which is coupled to the second end of the boost inductor, and a cathode of which is coupled to the first end of the first energy storage capacitor. The power supply as described in claim 1, wherein the resonant conversion circuit further comprises: a second energy storage capacitor, whose first end is coupled to the output voltage, and whose second end is coupled to the second non-dot terminal and the third dot terminal, for storing the energy of the output voltage; a second diode, whose anode is coupled to the second dot terminal, and whose cathode is coupled to the first end of the second energy storage capacitor; and a third diode, whose anode is coupled to the third non-dot terminal, and whose cathode is coupled to the first end of the second energy storage capacitor. The power supply as described in claim 9, wherein the resonant conversion circuit further comprises: a detection resistor, a first end of which is coupled to the second end of the second energy storage capacitor, and a second end of which is coupled to a second ground potential, for detecting an output current flowing through the second energy storage capacitor, thereby providing a detection voltage related to the output voltage.

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