TWI670919B - Power supply with resonant converter and control method thereof - Google Patents

Abstract

The present invention relates to a power supply having a resonant converter including an alternating current to direct current converter and a direct current to direct current resonant converter, and the alternating current to direct current converter converting an input alternating current power source into a direct current power source, And sent to a DC-to-DC resonant converter to convert the output voltage into a DC power supply; the DC-to-DC resonant converter includes a resonant converter that detects the resonant current and utilizes a zero-crossing point detection and a peak detection. Obtaining the resonant frequency of the resonant converter, and adjusting the switching output frequency of the resonant converter to adjust the switching frequency of the resonant converter to be close to or equal to the resonant frequency to improve efficiency by adjusting the DC output voltage of the AC-DC converter. Resonant frequency tracking; thereby solving the problem that the previous resonant frequency cannot be calculated due to the specification error of the resonant component, so that the switching frequency cannot be operated at the resonant frequency; the control method includes the steady state control mode and the transient control mode. In the steady-state control mode, the above-mentioned resonant frequency tracking is performed to improve efficiency; in the transient control mode, the DC link voltage is fixed, the resonant converter adjusts the switching frequency according to the load, and the output voltage is quickly adjusted to improve the transient response.

Description

Power supply with resonant converter and control method thereof

The present invention relates to a power supply having a resonant converter and a control method thereof, and more particularly to a related art that can detect the actual resonant frequency of the resonant converter and accelerate its response speed.

A known power supply having a resonant converter is shown in FIG. 1, which includes an AC-to-DC converter 10 and a DC-DC resonant converter, and the DC-DC resonant converter is a resonant converter 21 The AC-to-DC converter 10 inputs an AC power source into a high-voltage DC power source, and converts the high-voltage DC power source into a low-voltage DC power source via the DC converter of the DC-DC converter.

The DC-DC converter of the power source is composed of a resonant converter 21, as shown in FIG. 1 is a resonant converter 21 architecture, which mainly has a full-bridge circuit 11, a resonant tank 12, a transformer 27, and an output circuit 13. . The input end of the full-bridge circuit 11 is a high-voltage power supply connected to the resonant tank 12, and the resonant tank includes a resonant capacitor C _r , a resonant inductor L _r and a magnetizing inductance L _{m of} a transformer; the resonant frequency is further divided into two resonant frequencies The first resonant frequency f _r is determined by a resonant capacitor C _r and a resonant inductor L _r ; the second resonant frequency f _m is determined by a resonant capacitor C _r , a resonant inductor L _{r ,} and a magnetizing inductance L _m of a transformer. .

The resonant converter of the power supply uses voltage modulation to achieve voltage regulation; when the load becomes heavy, the frequency moves from high frequency to low frequency to adjust the voltage to achieve a voltage stabilization mechanism.

The resonant converter of the power supply can be divided into three regions according to different characteristics, wherein the operation of Region 3 is characterized by capacitive zero current switching, and is less operated in this interval. Operating in Region 1 (the switching frequency is greater than the first resonant frequency f _r ) is characterized by inductive zero voltage switching. The advantage is that when there is zero voltage switching when the power switch is turned on, the switching loss when turning on is reduced, but when the power switch is turned off The switching loss is large because the current at the time of shutdown is large; when the operation is in Region 2 (the switching frequency is between the first resonance frequency f _r and the second resonance frequency f _m ), the voltage gain is greater than 1, and the advantage is the same as having zero. The voltage is switched to the power switch to be turned on, and the disadvantage is that a large circulating current loss increases the conduction loss in the resonant tank.

The switching frequency of the resonant converter of the power supply operates at the first resonant frequency, reducing the above-mentioned operation of the converter with a large switching loss of Region 1 and operating with a large conduction loss of Region 2, when the switching frequency is close to the first At the resonant frequency, the characteristic of zero voltage switching reduces the loss of additional circulating current in the resonant tank when the power switch is turned off, and also reduces the switching loss at this time to improve the efficiency of the resonant converter.

A technique for operating a resonant converter of a power source to operate at a resonant frequency is described in a prior art (refer to Patent Document 1) for a first resonance The frequency detection method needs to send a switching frequency to make the resonant current appear a sine wave. The switching frequency is the first resonant frequency. After learning the first resonant frequency, the reference frequency is set to adjust the output of the AC to DC converter. The voltage maintains the switching frequency of the resonant converter at the resonant frequency and reaches regulation, improving the efficiency of the overall power converter.

A technique for operating a resonant converter of a power source to operate at a first resonant frequency is described in another prior art (refer to Patent Document 2) for detecting a change in current on a line to adjust a switching frequency for a first resonant frequency detecting method, The switching frequency is operated at the first resonant frequency to increase the efficiency of the resonant converter.

【references】

Zih-Jie Su and Yen-Shin Lai, "On-line DC-link voltage control of LLC resonant converter for server power applications," IEEE Conference Publications, Publication Year: 2014, pp. 5422-5428.

TW 1617126

The main object of the present invention is to provide a power supply including a resonant converter and a control method thereof, which are configured to detect an actual first resonant frequency according to an operating state of the power source, and then make the switching frequency of the resonant converter approach or equal to the actual first Resonant frequency, thereby achieving an increase in efficiency.

In order to achieve the technology of the present invention, the above needs to have a resonant converter The power supply comprises: an AC-to-DC converter having an AC power input terminal, a DC power output terminal and a control terminal; a DC-to-DC resonant converter having a resonant converter, a DC power input terminal, and a DC current Power output, a resonant converter controller, a resonant current zero-crossing point detection, and a resonant current peak detection. The resonant current zero-crossing point detection and peak detection of the power supply are respectively connected with the resonant converter and the resonant converter controller to respectively obtain a zero-crossing point detection and peak detection square wave voltage signal, and detect two The rising edge of the square wave voltage is used to calculate the period of time, and it is known that this period is one quarter of the actual first resonance period, and then converted by the resonant converter controller into the actual first resonant frequency and the current switching frequency. The operation is performed, and the compensation amount is transmitted to the control end of the AC to DC converter to change the output voltage of the AC to DC converter of the power supply, thereby controlling the switching frequency of the resonant converter of the power supply.

The square wave voltage signal detected by the resonant converter controller is a resonant current of the resonant converter, and the two square wave voltage signals generated by the zero crossing point detection and the peak detection generate the two square wave voltage signals. The time between the rising edges, the actual first resonance period is known in an online calculation manner, and the actual first resonance period is calculated with the current switching period and an adjustable voltage is applied to the control unit to generate an adjusted AC to DC. The converter outputs a reference value of the voltage, and the switching frequency of the resonant converter is controlled to be close to the first resonant frequency by adjusting the output voltage of the alternating current to the direct current converter to improve efficiency.

Another object of the present invention is to provide a response speed that accelerates the switching frequency of a resonant converter at a first resonant frequency to overcome The problem of resonant frequency tracking, when the resonant converter controller fixes the switching frequency of the resonant converter to the first resonant frequency, at this time, the conventional resonant converter is not regulated by frequency modulation, but is adjusted by using AC to DC. The output voltage of the converter is such that it is stable to the DC-to-DC converter output.

The foregoing invention mainly performs mode control according to the error value which the voltage of the resonant converter output terminal of the power supply is fed back to the controller, and the error value is low at steady state, and the mode control module makes the resonant converter switching frequency approach or equal to The first resonant frequency is an online resonant frequency tracking module; when the load changes, the error value is large, and the mode determining module determines that it is necessary to use the resonant converter controller to achieve rapid voltage regulation, thereby improving the response speed of the output end.

In order to further understand the technology and efficacy of the present invention in order to achieve the intended purpose, reference should be made to the following detailed description of the invention and the accompanying drawings. The drawings are to be considered in all respects as illustrative and not restrictive

V _ac ‧‧‧AC input voltage

V _bus ‧‧‧AC to DC output voltage

S1‧‧‧first power switch

S2‧‧‧second power switch

S3‧‧‧ third power switch

S4‧‧‧fourth power switch

S5‧‧‧ fifth power switch

S6‧‧‧ sixth power switch

C _r ‧‧‧Resonance capacitor

L _r ‧‧‧Resonant inductance

L _m ‧‧‧Magnetic inductance

T‧‧‧Transformer

CT‧‧‧ current detector

V _out ‧‧‧Resonant converter output voltage

N _P ‧‧‧ Transformer primary winding

N _s1 ‧‧‧ transformer secondary side first winding

N _s2 ‧‧‧second secondary winding of transformer

C _o ‧‧‧output capacitor

V _{out_FB ‧‧‧Output} voltage feedback

V _{out_ref ‧‧‧Output} voltage feedback reference

V _gs1 ~V _gs6 ‧‧‧S1~S6 gate signal

T1‧‧‧ zero crossing point detection square wave voltage signal rising edge time

T2‧‧‧ peak detection square wave voltage signal rising edge time

T _r ‧‧‧resonance cycle

T _s ‧‧‧ switching cycle

10‧‧‧AC to DC converter

11‧‧‧Full bridge circuit

12‧‧‧Resonance tank

13‧‧‧Output circuit

14‧‧‧ Zero crossing detection

15‧‧‧ Peak detection

16‧‧‧On-line resonant frequency calculation unit

17‧‧‧Gate signal generator

18‧‧‧Resonant Converter Controller

19‧‧‧ Controller

20‧‧‧AC to DC converter controller

21‧‧‧Resonance Converter

22‧‧‧ Half-bridge circuit

23‧‧‧Adjustable voltage control unit

24‧‧‧Online Resonant Frequency Tracking Module

26‧‧‧Mode Control Module

27‧‧‧Transformers

1 is a circuit diagram of a preferred embodiment of a power supply having a resonant converter of the present invention; and FIG. 2 is a circuit diagram of another preferred embodiment of a power supply having a resonant converter of the present invention; FIG. 3 is a view of the present invention Adjustable voltage control unit block diagram; Figure 4 is an operational block diagram of another invention;

The technical content and detailed description of the present invention are as follows with reference to the drawings: Please refer to FIG. 1 for a circuit diagram of a first preferred embodiment of a power supply having a resonant converter of the present invention. The utility model comprises an AC-to-DC converter 10 and a DC-to-DC resonant converter. The AC-DC converter has an AC input power source V _ac , a DC output power source V _bus and an AC-DC controller 20 . The structure is mainly converted into a high-voltage DC voltage by inputting the commercial AC voltage from the AC input power terminal, and then outputted to the V _bus via the DC power output.

In this embodiment, the DC-to-DC resonant converter of the power supply is a resonant converter 21, and the resonant converter is composed of a resonant converter having a full bridge circuit 11, a resonant tank 12, a transformer 27, An output circuit 13, a resonant converter controller 18, a zero crossing point detection 14, a peak detection 15, a line resonance frequency calculation unit 16 and a gate signal generator 17. The switching signal of the power switch of S1~S4 in the full bridge circuit is generated and controlled by the gate signal generator 17, and the full bridge circuit is connected to the resonant tank 12, and the resonant tank includes a resonant inductor _Lr and a resonance. The capacitor C _r and a magnetizing inductance L _m , the magnetizing inductance, use the magnetizing inductance L _{m of the} transformer 27; and the resonant tank 12 is connected to the output circuit 13 of the DC-to-DC converter.

In this embodiment, the current detector CT is used to capture the resonant current in the resonant tank and connect the zero-crossing point detection 14 with the peak detection 15; The measurement will generate two square wave voltage signals. At this time, the rising edge of the square wave voltage signal generated by the zero crossing point detection 14 is t1, and the rising edge of the square wave voltage signal generated by the peak detection 15 is t2, and then via the line resonance. The frequency calculation unit 16 takes time t1 and t2 and performs calculations, and this period of time is one quarter of the actual first resonance period.

The control block diagram of Fig. 3 shows that after the actual resonance period T _r is known by the on-line resonance frequency calculation unit 16, and is calculated with the switching period at that time, the obtained error value enters an adjustable voltage control unit 23, and the compensation is obtained. The amount will be calculated with the original AC to DC converter output voltage reference value, and passed to the AC to DC converter controller 20 to change the output voltage of the AC to DC converter, and adjust the output voltage to make the switching frequency of the resonant converter Modulate to the first resonant frequency to achieve the effect of efficiency improvement.

2 is a circuit diagram of a second preferred embodiment of a power supply having a resonant converter of the present invention. In the present embodiment, the DC-DC converter 21 has a resonant converter composed of a resonant converter having a half bridge circuit 22, a resonant tank 12, a transformer 27, and an output circuit 13. A resonant converter controller 18, a zero crossing point detection 14, a peak detection 15, a line resonance frequency calculation unit 16 and a gate signal generator 17. The switching signals of the power switches of S1 and S2 in the half-bridge circuit are generated and controlled by the gate signal generator 17, and the half-bridge circuit is connected to the resonant tank 12, and the resonant tank includes a resonant inductor L _r and a resonance. The capacitor C _r and a magnetizing inductance L _m , the magnetizing inductance, use the magnetizing inductance L _{m of the} transformer 27; and the resonant tank 12 is connected to the output circuit 13 of the DC-to-DC resonant converter. The rest of the action states are the same as in the first embodiment.

The foregoing inventive technology resonant frequency tracking is mainly used to control the switching frequency of the resonant type converter to be close to or equal to the resonant frequency when the converter operates at a steady state to improve efficiency; when the output load changes, the resonant converter The switching frequency is fixed and cannot be adjusted by frequency to achieve the voltage regulation action, so that the output voltage of the AC to DC converter needs to be adjusted to achieve the voltage regulation, and the response speed is relatively slow. This patent proposes another invention to solve the above problems, the main purpose of which is to accelerate the transient response that changes rapidly in the load.

Please refer to FIG. 4 for a block diagram of combining resonant frequency tracking and accelerating transient response speed, comprising an on-line resonant frequency tracking module 24, a resonant converter controller 18 and a mode control module 26, and on-line resonance The frequency tracking module 24 tracks the inventive techniques for the resonant frequency described above.

The decision to switch between different modules is primarily determined by the mode control module 26. The mode control module is subtracted from the output voltage feedback of the feedback resonant converter 21 and the output voltage reference value, and the output voltage error value is obtained. In the normal steady state, the S switching variable in the mode control module is 0, indicating that the resonant frequency tracking module is executed at this time. When the output voltage error value is greater than the upper limit of the error value, the load is undergoing a large change, S The switching variable will be 1 and the mode is switched to the resonant converter controller, with the resonant converter controller 18 of the resonant converter 21 utilizing the variation of the switching frequency to achieve the output voltage regulation action; and when the load stops changing, the output The error value of the voltage gradually becomes smaller and the original The lower limit of the error value is compared. If the S switch variable is less than 0, it will return to the execution of the on-line resonant frequency tracking module.

According to the above two inventions, when the resonance frequency is tracked to the steady state of the power converter, the error of the components of the resonant converter and the parasitic effects generated on the circuit affect the actual resonant frequency and operate at the actual resonant frequency. In order to improve efficiency; in the load change transient response mode control module to mode switching, speed up the slow response speed caused by the resonance frequency tracking.

Claims (8)

A power supply having a resonant converter, comprising: an AC to DC converter, having an AC power input terminal, a DC power output terminal, and a control terminal; a DC-to-DC resonant converter, a resonant converter controller, and a control unit Zero-crossing point detection, one-peak detection, one-line resonance frequency calculation unit, and adjustable voltage control unit; the zero-crossing point detection and peak detection are respectively connected with a DC-to-DC resonant converter to obtain square wave voltage signals respectively Entering the online resonant frequency calculation unit to calculate the actual first resonance period; obtaining the actual first resonance period and the actual switching period after the calculated error enters the adjustable voltage control unit, wherein the output compensation of the controller of the adjustable voltage control unit The AC-to-DC converter output voltage reference value is sent to the control terminal of the AC-to-DC converter to adjust the output voltage of the AC-DC converter, thereby controlling the switching frequency of the resonant converter to approach the first resonance of the resonant converter. frequency. A power supply having a resonant converter as claimed in claim 1, wherein the resonant converter of the power supply comprises a resonant tank, and the resonant tank comprises a resonant capacitor, a resonant inductor and a magnetizing inductance; and a current detector is connected in series in the resonant tank , draw resonant current to zero crossover detection and peak detection. If the power supply with the resonant converter described in Item 2 is requested, the on-line resonant frequency calculation unit of the power supply detects the rise time of the square wave voltage signal and the rising edge time of the peak detection square wave voltage signal. After the two time points are calculated, the period of time is one quarter of the first resonance period, and then the first resonance period is obtained by pushing back. A power supply having a resonant converter as claimed in claim 3, the resonant converter of the power supply having a voltage feedback coupled between the output of the resonant converter and the resonant converter controller. If the power supply with the resonant converter described in claim 4 is requested, the resonant converter controller of the power supply mainly receives the output voltage feedback and calculates the current switching frequency to be sent to the adjustable voltage controller. If the power supply with the resonant converter according to Item 5 is requested, the switching period sent by the power resonant converter controller and the first resonant period sent by the online resonant frequency calculating unit are calculated, and the calculated error value is adjusted. The voltage control unit, the output compensation amount can be used to adjust the output voltage of the AC to DC converter. As claimed in claim 6, the power supply having the resonant converter, the switching frequency of the resonant converter of the power supply, in the transient state, will switch to the output of the resonant converter controller and stop the voltage change of the alternating current to the direct current converter; At steady state, it switches to the online resonant frequency calculation output and changes the voltage reference of the AC to DC converter. If the power supply with the resonant converter described in claim 7 is requested, the transient or steady-state control judgment of the resonant converter of the power supply is based on the output voltage error, the output current error, or the input/output current variation, and the error amount or variation The large amount is transient, and vice versa.