TW201433064A - Single-stage high power factor zero-current detecting variable-frequency asymmetric half-bridge converter - Google Patents

Abstract

The present invention relates to a single-stage high power factor zero-current detecting variable-frequency asymmetric half-bridge converter, which comprising a switching unit, a power conversion unit, a drive circuit, a feedback circuit, a zero-current detection circuit, a duty cycle limiting circuit and an AND gate. The drive circuit is a current-mode controlled pulse width modulation (PWM) control loop, which is a current-mode controlled PWM integrated circuit. The feedback circuit is a feedback integrated circuit, and the AND gate is integrated into the feedback unit. The power conversion unit comprises a transformer and a rectifier/filter circuit. The zero-current detection unit can detect whether the input inductor current is zero, if the input inductor current is zero, a first logic signal is generated, then the asymmetric half-bridge switch is allowed to perform switching. The duty cycle limiting circuit extracts a conduction cycle signal, determines whether the conduction cycle signal is less than 0.5, and generates a second logic signal, so as to ensure that the asymmetric half-bridge has a duty cycle ratio less than 0.5. When the first logic signal and the second logic signal are both true, a switch conduction signal is generated through the AND gate to ensure the zero-current switching and that the duty cycle ratio is less than 0.5. The present invention mainly addresses the problem of conventional single-stage high power factor asymmetric half-bridge converters, in which the circuit component specifications must be subjected to special calculations in order to achieve the zero-voltage switching. With the circuit configuration disclosed in this invention, not only the zero-voltage switching function can be achieved without requiring special design of the input inductor, but also the duty cycle ratio of the switching device in a half-bridge converter can be guaranteed to be less than 0.5, thereby ensuring the normal operation of a single-stage high power factor half-bridge switching unit.

Description

Single-stage high-power zero-current detection variable frequency asymmetric half-bridge converter

[1] The present invention relates to a single-stage high-power-dependent zero-current detecting variable-frequency asymmetric half-bridge converter, in particular to a zero-input inductor current in a detectable power conversion unit, ensuring zero voltage of the switching device Zero Voltage Switching (ZVS) reduces switching switching efficiency loss by up to 91% and ensures that the switching device duty cycle ratio is less than 0.5 for the asymmetric half-bridge converter to work properly.

[2] With the advancement of modern technology and the booming of portable electronic products, converter performance and various applications are receiving more and more attention, and Power Factor Correction (PFC) is the inspection converter. One of the important indicators of effectiveness. [3] Today's converter technology has been able to integrate the power factor correction function into an asymmetric half-bridge converter to make it a single-stage circuit, so that the power of the converter can be avoided due to the transmission between the two-stage circuits. The conversion efficiency is reduced; and the technology for achieving this purpose is usually to add an input inductor in front of the switching device, and use the filtering characteristic of the input inductor to correct the current waveform, thereby achieving the function of the circuit self-power factor correction. However, the specification of the input inductor needs to be complicated with the circuit to make the switch reach Zero Voltage Switching (ZVS) to avoid the switching loss caused by operating the asymmetric half-bridge switching unit at non-zero voltage. . [4] As shown in the first figure, the figure is a conventional asymmetric half bridge converter 2, which is a first DC power to be output by the DC power source 1. Converting to a second DC power, the current and voltage of the second DC power will have a fixed level to form a smooth output, and the second DC power can be changed by the setting of the converter circuit The voltage level; the converter structure used today is as shown in the first figure, the converter comprises an asymmetric half-bridge switching unit 21, a power conversion unit 22, and a driving circuit for generating a conduction period signal. And a feedback circuit 24 for generating a feedback signal, wherein the asymmetric half-bridge switch unit 21 has at least two switching devices 211 for connecting the DC power source 1 to obtain a first DC power, and the ON period signal Controlling the switching device 211 to turn on a duty cycle of the first DC power flowing through the power conversion unit 22, and the power conversion unit 22 converts the first DC power into a second DC power And outputting the feedback circuit 24 from the second DC power to the drive circuit 23, thereby adjusting the conduction period signal to change the duty cycle of the half bridge switch unit 21, to achieve the The output of the converter has a feedback regulation that is adjusted with the load. [5] When the switching device 211 is to achieve normal and stable operation of the converter, the duty cycle ratio of the asymmetric half-bridge switching circuit 21 must be less than 0.5, and when the duty cycle ratio is greater than 0.5, The converter does not operate normally; in order to prevent the output of the converter from changing with the load, the output feedback function will adjust the duty cycle ratio of the switching device 211 to change, if the converter cannot maintain the duty cycle ratio at all times Less than 0.5 will cause the asymmetric half-bridge converter to malfunction, and an improvement should be provided.

[6] Therefore, in order to solve the problem of the conventional method, the inventor has carefully studied and experimented and developed the single-stage high-power zero-current detection variable-frequency asymmetric half-bridge converter proposed in this case, which will be a single stage. In the high-power asymmetric half-bridge converter, the input inductance in the single-stage high-power half-bridge switching unit is coupled to a zero current detecting circuit, thereby detecting whether the current in the input inductor is zero or not. In order to prevent the current from affecting the switching device and failing to achieve zero voltage switching; in addition, in order to prevent the operation of the zero current detecting circuit from affecting the switching device, the duty cycle ratio of the switching device cannot be less than 0.5 and cannot operate normally, so an additional one is added. A duty cycle control circuit to ensure proper operation of the asymmetric half bridge converter. [7] For the purpose of the foregoing, the present invention provides a single-stage high-power zero-current detection variable frequency asymmetric half-bridge converter, which comprises: a single-stage high-power-dependent asymmetric half-bridge switching unit, and a power conversion a unit, a driving circuit, a feedback circuit, a zero current detecting circuit, a duty cycle limiting circuit, and an AND gate; the single-stage high-power asymmetric half-bridge switching unit includes an input inductor And at least two switching devices; the single-stage high-power switch receives a first DC power due to the asymmetric half-bridge switching unit, and drives the switching device through a driving period signal generated by the driving circuit to switch the first DC power to the a power conversion unit, wherein the power conversion unit converts the first DC power into a second DC power; the feedback circuit draws an output voltage from the second DC power, and performs the output voltage and the predetermined voltage Comparing to generate an error voltage, when the voltage on the switch current sensing resistor exceeds the error voltage, generating a turn-off signal; the zero current detecting circuit is coupled to the input inductor to Determining whether the current on the input inductor is zero, and generating a first logic signal to ensure that the lower switch can complete the zero current Turn-on; the duty cycle limiting circuit takes the conduction period signal to determine whether the conduction period signal is The feedback is less than 0.5 and generates a second logic signal; the gate receives the first logic signal and the second logic signal to generate a determination signal to the feedback circuit, so that the feedback circuit generates an enable signal; The driving circuit generates the conduction period signal by receiving the closing signal and the opening signal of the feedback circuit. [8] The single-stage high-power zero-current detection variable-frequency asymmetric half-bridge converter proposed in this case has the following beneficial effects: [9] 1. Connected to a single-stage high-power-dependent asymmetry through a zero-current detection circuit The input inductor in the half-bridge power control unit is used to detect zero current in the input inductor to ensure that the single-stage high-power function can achieve zero voltage switching due to the asymmetric half-bridge switching unit. [10] 2. A duty cycle limiting circuit is coupled to a driving circuit, receives the conduction period signal generated by the driving circuit, and determines and adjusts the output of the PWM signal to avoid that the duty cycle ratio of the switching device is greater than 0.5. The problem caused by the asymmetric half-bridge converter is not working properly.

[14] To enable a further understanding of the features and technical aspects of the present invention, reference is made to the following detailed description of the invention and the accompanying drawings, so that those skilled in the art can do so. It is used to achieve the effect of voltage conversion and stable output voltage, and the switching device can achieve the effect of zero current switching, and the converter has the function of adjusting the power factor. [15] In order to help the implementer to clarify the essence of the present invention, please refer to the second figure, which is a single-stage high-power zero-current detecting variable frequency asymmetric half-bridge converter 3 of the present invention, which is high in single stage. The power factor zero current detection variable frequency asymmetric half bridge converter 3 comprises a single stage high power factor asymmetric half bridge type switching unit 31, a power conversion unit 32, a driving circuit 33, a feedback circuit 34, and a zero a current detecting circuit 35, a duty cycle limiting circuit 36, and an AND gate 37; the single-stage high-power asymmetrical half-bridge switching unit 31 includes an input inductor 311 and at least two switching devices 312; The single-stage high-power asymmetrical half-bridge switch unit 31 receives a first DC power, and drives the switch device 312 through a turn-on period signal generated by the drive circuit 33 to switch the first DC power to the power conversion unit 32. The power conversion unit 32 converts the first DC power into a second DC power; wherein the input inductor 311 itself has a filtering characteristic of the passive component, and the switch ON time is fixed, thereby achieving the power factor correction function. [16] The driving period 312 of the switching device 312 is determined by the driving circuit 312 receiving an opening signal or a closing signal generated by the feedback circuit 34; the feedback circuit 34 is from the second The DC power draws an output voltage and performs a comparison of the output voltage with the predetermined voltage to generate a turn-off signal. The zero current detecting circuit 35 is coupled to the input inductor 311 to determine whether the current on the input inductor 311 is zero, and generates a first logic signal, and the zero current detecting circuit 35 ensures the The switching device 312 does not have the effect of zero voltage switching (ZVS) due to the influence of the current generated on the input inductor 311. [18] Since the input voltage of the first DC voltage is in the form of an M-type wave, the current on the input inductor 311 changes due to the change of the input voltage, and the time for returning the current to the zero is not necessarily, so If the zero current detection is simply to avoid interference with the zero voltage switching of the asymmetric half bridge, the switch of the asymmetric half bridge can be switched when the input inductor current is zero. When the inductor current is zero, The zero current detecting circuit 35 outputs the first logic signal. [19] If the opening time of the switching device 312 is greater than the closing time, that is, the duty cycle ratio cannot be less than 0.5, the single-stage high power due to the asymmetric half-bridge switching unit cannot operate normally, causing the output power to drop or even fail to output. Therefore, the duty cycle limiting circuit 36 needs to be added to the above circuit. [20] The duty cycle limiting circuit 36 captures the conduction period signal, determines whether the conduction period signal meets less than 0.5, and generates a second logic signal; and receives the first logic signal and the first through the gate 37 The two logic signals determine that both the "input inductor 311 zero current" and the "responsibility period is less than 0.5" are satisfied, and the gate 37 generates a judgment signal to the feedback circuit 24, so that the feedback circuit 24 generates a When the signal is turned on, the driving circuit 33 receives the turn-off signal and the turn-on signal, thereby generating a switch-on period signal. [21] As shown in the third figure, the figure is a circuit diagram of the first embodiment of the present invention. As shown in the figure, the gate 37 is not limited to the type of the independent circuit, but the gate is The circuit function is integrated into the feedback circuit 24, and is not limited to only presenting the NAND gate in a separate circuit. [22] The above description is only for the purpose of explaining the preferred embodiments of the present invention, and is not intended to limit the invention in any way. Any modification or alteration of the present invention in the spirit of the same invention. All should still be included in the scope of the intention of the present invention.

1. . . DC power supply

2. . . Asymmetric half bridge converter

twenty one. . . Asymmetric half bridge switch unit

211. . . Switching device

twenty two. . . Power conversion unit

twenty three. . . Drive circuit

twenty four. . . Feedback circuit

3. . . Single-stage high-power zero-current detection variable frequency asymmetric half-bridge converter

31. . . Single-stage high-power-dependent asymmetric half-bridge switching unit

311. . . Input inductance

312. . . Switching device

32. . . Power conversion unit

33. . . Drive circuit

34. . . Feedback circuit

35. . . Zero current detection circuit

36. . . Accountability cycle limiting circuit

37. . . Gate

4. . . Full-wave rectified to M-wave DC power supply

[11] First: Circuit diagram of a conventional asymmetric half-bridge converter. [12] The second figure: The circuit diagram of the single-stage high-power zero-current detecting variable frequency asymmetric half-bridge converter of the present invention. [13] Third drawing: A circuit diagram of the first embodiment of the present invention.

3. . . Single-stage high-power zero-current detection variable frequency asymmetric half-bridge converter

31. . . Single-stage high-power-dependent asymmetric half-bridge switching unit

311. . . Input inductance

312. . . Switching device

32. . . Power conversion unit

33. . . Drive circuit

34. . . Feedback circuit

35. . . Zero current detection circuit

36. . . Accountability cycle limiting circuit

37. . . Gate

4. . . Full-wave rectified to M-wave DC power supply

Claims (9)

A single-stage high-power zero-current detecting variable frequency asymmetric half-bridge converter comprises: a single-stage high-power-dependent asymmetric half-bridge switching unit, a power conversion unit, a driving circuit, a feedback circuit, and a a zero current detecting circuit, a duty cycle limiting circuit and an AND gate; the single stage high power asymmetrical half bridge switching unit comprises an input inductor and at least two switching devices; the single stage high power factor The asymmetric half-bridge power control unit receives a first DC power, drives the switching device through a driving period signal generated by the driving circuit, and switches the first DC power to the power conversion unit to convert the power conversion unit The first DC power is a second DC power; the feedback circuit draws an output voltage from the second DC power, and performs comparison of the output voltage with the predetermined voltage to generate an error signal for determining a lower switch detection time; the zero current detection circuit is coupled to the input inductor to determine whether the current on the input inductor is zero, and generate a first logic signal; The period limiting circuit captures the conduction period signal, determines whether the conduction period signal meets less than 0.5, and generates a second logic signal; the gate receives the first logic signal and the second logic signal to generate a determination signal The feedback circuit is configured to generate an enable signal by the feedback circuit; the drive circuit generates the turn-on period signal by receiving the turn-off signal and the turn-on signal. The single-stage high-power zero-current detecting variable frequency asymmetric half-bridge converter according to the first application of the patent application scope, wherein the driving circuit is a pulse mode width modulation (PWM) of current mode control. Control loop. The single-stage high-power zero-current detecting variable frequency asymmetric half-bridge converter according to the second application of the patent application scope, wherein the current mode control pulse width modulation control loop is a current mode controlled pulse width Modulate the integrated circuit. The single-stage high-power zero-current detecting variable frequency asymmetric half-bridge converter according to the first application of the patent application scope, wherein the feedback circuit is a back-embedded circuit. The single-stage high-power zero-current detecting variable frequency asymmetric half-bridge converter according to the first aspect of the patent application, wherein the gate is integrated in the feedback unit. The single-stage high-power zero-current detecting variable frequency asymmetric half-bridge converter according to the first aspect of the patent application, wherein the power conversion unit comprises a transformer and a rectifying and filtering circuit. The single-stage high-power zero-current detecting variable frequency asymmetric half-bridge converter according to the first application of the patent application scope, wherein the zero current detecting unit can detect that the input inductor current is zero, if the input inductor current is zero When the first logic signal is generated, the asymmetric half bridge switch can perform the switching action. The single-stage high-power zero-current detecting variable frequency asymmetric half-bridge converter according to the first aspect of the patent application, wherein the duty cycle limiting circuit captures the conduction period signal to determine whether the conduction period signal is less than 0.5, and generate a second logic signal to ensure that the asymmetric half-bridge duty cycle is less than 0.5, so that the circuit can operate normally. When both the first logic signal and the second logic signal are established, a switch communication number is generated via the AND gate to ensure zero current switching, and the duty cycle is less than 0.5.