Patent Publication Number: US-2023155510-A1

Title: Switching power supply circuit

Description:
RELATED APPLICATIONS 
     This application claims the benefit of Chinese Patent Application No. 202111349904.1, filed on Nov. 15, 2021, which is incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present invention generally relates to the field of power electronics, and more particularly to switching power supply circuitry. 
     BACKGROUND 
     A switched-mode power supply (SMPS), or a “switching” power supply, can include a power stage circuit and a control circuit. When there is an input voltage, the control circuit can consider internal parameters and external load changes, and may regulate the on/off times of the switch system in the power stage circuit. Switching power supplies have a wide variety of applications in modern electronics. For example, switching power supplies can be used to drive light-emitting diode (LED) loads. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic block diagram of a switching power supply circuit, in accordance with embodiments of the present invention. 
         FIG.  2    is a schematic block diagram of the first example of the switching power supply circuit, in accordance with embodiments of the present invention. 
         FIG.  3    is a schematic diagram of an example of the first switch unit, in accordance with embodiments of the present invention. 
         FIG.  4    is a schematic diagram of another example of the first switch unit, in accordance with embodiments of the present invention. 
         FIG.  5    is a schematic diagram of yet another example of the first switch unit, in accordance with embodiments of the present invention. 
         FIG.  6    is a schematic diagram of the waveforms on each node of the first example of the switching power supply circuit, in accordance with embodiments of the present invention. 
         FIG.  7    is a schematic block diagram of the first example of the switching power supply circuit operated in the AHB mode, in accordance with embodiments of the present invention. 
         FIG.  8    is a schematic block diagram of the first example of the switching power supply circuit operated in the LLC mode, in accordance with embodiments of the present invention. 
         FIG.  9    is a schematic block diagram of the second example of the switching power supply circuit, in accordance with embodiments of the present invention. 
         FIG.  10    is a schematic block diagram of the second example of the switching power supply circuit operated in the AHB mode, in accordance with embodiments of the present invention. 
         FIG.  11    is a schematic block diagram of the second example of the switching power supply circuit operated in the LLC mode, in accordance with embodiments of the present invention. 
         FIG.  12    is a schematic block diagram of the third example of the switching power supply circuit, in accordance with embodiments of the present invention. 
         FIG.  13    is a schematic block diagram of the third example of the switching power supply circuit operated in the AHB mode, in accordance with embodiments of the present invention. 
         FIG.  14    is a schematic block diagram of the third example of the switching power supply circuit operated in the LLC mode, in accordance with embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference may now be made in detail to particular embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention may be described in conjunction with the preferred embodiments, it may be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents that may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it may be readily apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, processes, components, structures, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present invention. 
     A switching power supply uses modern power electronics technology to control the time ratio of turning on and off the switch to maintain a stable output voltage. Switching power supplies generally include pulse-width modulation (PWM) control ICs and MOSFETs. With the development and innovation of the power electronics technology, switching power supply technology continues to be innovated. Switching power supplies are widely used in many electronic devices due to its characteristics of small size, light weight, and high efficiency, and is an indispensable power supply for the rapid development of the electronic information industry. 
     Inductor-inductor-capacitor (LLC) topology and asymmetrical half-bridge (AHB) topology are two common topologies for switching power supplies. Among them, LLC topology uses the structure of the resonant inductance, the excitation inductance, and the resonant capacitor in series, which has high efficiency. However, the frequency can change too much when applied in a wide range, and the efficiency can be sacrificed if the control of LLC topology is not suitable. The input and output of the AHB topology may achieve a relatively wide range. Nevertheless, when AHB topology is fully loaded, the transformer may only transfer the load energy during a portion of the time, and the efficiency may be slightly lower than that of the LLC. Accordingly, AHB topology is not suitable for the conditions that require relatively high power density and efficiency. In particular embodiments, a wide input and output voltage range can be satisfied, along with high system efficiency of the switching power supply. 
     Referring now to  FIG.  1   , shown is a schematic block diagram of a switching power supply circuit, in accordance with embodiments of the present invention. In this particular example, switching power supply circuit  1  can include transformer  11 , resonant capacitor Cr, resonant inductor Lr, power switch module  12 , output rectification module  13 , and operating mode control module  14 . Transformer  11  can include a primary winding and a secondary winding. For example, the structure and the number of the primary windings in transformer  11  can be determined by the structure of power switch module  12  (e.g., including a full bridge or a half bridge). The structure and the number of the secondary windings in transformer  11  may be determined by the structure of output rectification module  13  (e.g., including a full bridge or a half bridge). 
     Resonant capacitor Cr and resonant inductor Lr can connect in series with the primary winding to form a series structure. For example, resonant inductor Lr and resonant capacitor Cr can be located on two sides of the primary winding respectively. Resonant inductor Lr may be located on the high-voltage side, and resonant capacitor Cr on the low-voltage side. In some cases, resonant capacitor Cr, resonant inductance Lr, and the primary winding can connect in series to form a resonant circuit with power switch module  12 . Power switch module  12  may receive input voltage Vin and couple two terminals of the series structure to form the resonant circuit. For example, power switch module  12  can include a plurality of power switches to form a half-bridge structure or full-bridge structure. 
     Output rectification module  13  can connect to the secondary winding and can generate an output voltage. For example, output rectification module  13  can include a half-bridge rectification structure or a full-bridge rectification structure, which may be set according to actual needs. Operating mode control module  14  may receive input voltage Vin and output voltage Vout, and can control output rectification module  13  to switch the operating mode based on the ratio of input voltage Vin to output voltage Vout. For example, when the ratio of the input voltage Vin to the output voltage Vout is less than or equal to a predetermined value, output rectification module  13  can be controlled such that the switching power supply circuit operates in the LLC mode. When the ratio of input voltage Vin to output voltage Vout is greater than the predetermined value, output rectification module  13  can be controlled such that the switching power supply circuit operates in the AHB mode. 
     It should be noted that the predetermined value may be set according to particular requirements. In this example, the predetermined value is k*N, where N is the turns ratio of the primary winding to the secondary winding in the transformer. As an example, when the ratio of the input voltage Vin to the output voltage Vout is close to 2N, the switching power supply circuit may operate in the LLC mode. When the ratio of the input voltage Vin to the output voltage Vout is much larger than 2N, the switching power supply circuit may operate in the AHB mode, and k can optionally be set to be a real number less than or equal to 5, 6, 7, 8, 9 or 10. The ratio of input voltage Vin to output voltage Vout for operating in LLC mode and AHB mode may be determined according to particular applications, and then the value of k can be set. 
     Referring now to  FIG.  2   , shown is a schematic block diagram of the first example of the switching power supply circuit, in accordance with embodiments of the present invention. In this particular example, switching power supply circuit  1  can include transformer  11 , resonant capacitor Cr, resonant inductor Lr, power switch module  12 , output rectification module  13 , and operating mode control module  14  (e.g., a controller). 
     For example, power switch module  12  is a half-bridge structure, which can include power switches Q 1  and Q 2  connected in series between input voltage Vin and the reference ground. The first terminal of power switch Q 1  may receive the input voltage Vin, and the second terminal of power switch Q 1  can connect to the first terminal of power switch Q 2 . The second terminal of power switch Q 2  is grounded. The second terminal of power switch Q 1  and the first terminal of power switch Q 2  may be grounded through resonant inductor Lr, the primary winding of the transformer  11 , and resonant capacitor Cr in sequence (both terminals of the primary winding can also connect in parallel with a magnetizing inductor Lm) to form a resonant circuit. In this example, power switch module  12  can also include resonance control module  121  and drive module  122 . Resonance control module  121  can generate the switch control signals (e.g., PWMH and PWML). Drive module  122  can drive the control terminals of power switches Q 1  and Q 2  according to the switch control signals. Power switches Q 1  and Q 2  can be complementarily turned on. In this example, power switches Q 1  and Q 2  can be NMOS transistors. 
     As another example, power switch module  12  is a full-bridge structure, including third, fourth, fifth, and sixth power switches. The third and fourth power switches can connect in series between the input voltage and the reference ground. The fifth and sixth power switches can connect in series between the input voltage and the reference ground. The control terminals of the third, fourth, fifth, and sixth power switches may receive the switch control signals. The first terminal of the series structure can connect to the connection node of the third and fourth power switches, and may pass through resonant inductor Lr, the primary winding of transformer  11 , and the resonant capacitor Cr in sequence for connecting to the connection node of the fifth and sixth power switches. 
     As shown in  FIG.  2   , transformer  11  can include a primary winding, a first secondary winding, and a second secondary winding. A half-bridge rectification structure can be used by output rectification module  13 . In this particular example, output rectification module  13  can include switch units S 1  and S 2 . The current input terminal of switch unit S 1  can connect to the dotted terminal of the first secondary winding and the primary winding, and the current output terminal of switch unit S 1  can connect to the upper plate of output capacitor Cout. When the switching power supply circuit  1  is in the LLC mode, switch unit S 1  can be turned on and may rectify the signal input to switch unit S 1 . When the switching power supply circuit  1  is in the AHB mode, switch unit S 1  can be turned off. The current input terminal of switch unit S 2  can connect to the non-dotted terminal of the second secondary winding and the primary winding, and the current output terminal of switch unit S 2  can connect to the upper plate of output capacitor Cout. When the switching power supply circuit  1  is in the LLC mode, and when the switching power supply circuit  1  is in the AHB mode, the signal input to switch unit S 2  may be rectified. The lower plate of output capacitor Cout, the non-dotted terminal of the first secondary winding and the primary winding, and the dotted terminal of the second secondary winding and the primary winding can be grounded. 
     For example, switch unit S 1  can include switches S 11  and S 12  connected in series. Switch S 11  is a switch in a high-speed control mode, and switch S 12  is a switch in the low-speed control mode. In other words, the operating frequency of switch S 12  is lower than the operating frequency of switch S 11 . Switch S 11  can include a synchronous rectification switch and a rectification diode, whereby a diode may be regarded as an uncontrolled switch. Switch S 12  can include a relay and a semiconductor switch. For example, switch S 11  is a rectification diode, and switch S 12  is a semiconductor switch. The anode of the rectification diode may serve as the current input terminal of switch unit S 1 . The cathode of the rectification diode can connect to one terminal of the semiconductor switch, and the other terminal of the semiconductor switch may serve as the current output terminal of switch unit S 1 . In this example, the rectification diode is used for rectification, and the semiconductor switch is controlled by operating mode control module  14  to switch the operating mode. 
     Referring now to  FIG.  3   , shown is a schematic diagram of an example of the first switch unit, in accordance with embodiments of the present invention. In this particular example, switch S 11  is a synchronous rectification switch, and switch S 12  is a semiconductor switch. The drain of the synchronous rectification switch may serve as the current input terminal of switch unit S 1 . The source of the synchronous rectification switch can connect to one terminal of the semiconductor switch, and the other terminal of the semiconductor switch may serve as the current output terminal of switch unit S 1 . In this example, the synchronous rectification switch is used for rectification, and switch is controlled by operating mode control module  14  to switch the operating mode. The positions of the semiconductor switch and the synchronous rectification switch may be interchanged in some cases. In particular embodiments, switch unit S 1  can be a bidirectional switch including two synchronous rectification switches connected in series with opposite direction. 
     Referring now to  FIG.  4   , shown is a schematic diagram of another example of the first switch unit, in accordance with embodiments of the present invention. In this particular example, the source of synchronous rectification switch S 12  may serve as the current input terminal of switch unit S 1 . The drain of synchronous rectification switch S 12  can connect to the drain of synchronous rectification switch S 11 . The source of synchronous rectification switch S 11  may serve as the current output terminal of switch unit S 1 . In this example, synchronous rectification switch S 11  (e.g., the parasitic diode) can be used for rectification. Synchronous rectification switch S 12  can be controlled by operating mode control module  14  to switch operating modes (e.g., both S 11  and S 12  are turned off when operated in the AHB mode). 
     Referring now to  FIG.  5   , shown is a schematic diagram of yet another example of the first switch unit, in accordance with embodiments of the present invention. In this particular example, the positions of the first synchronous rectification switch S 11  the synchronous rectification switch S 12  may be interchanged. For example, switch unit S 2  is a rectification diode. As another example, switch unit S 2  is a synchronous rectification switch. Here, the N-type synchronous rectification switch is taken as an example. In other cases, the corresponding device type of switch unit S 2  may be selected based on particular requirements, and the connection relationship may suitably be adjusted. Any switch capable of realizing the above-mentioned rectification function and the mode switching function can be utilized in certain embodiments. 
     As shown in  FIG.  2   , operating mode control module  14  can generate a mode switching signal based on Vin/(Vout*N) to control switching power supply circuit  1  to operate in different modes. For example, power switch module  12  is a half-bridge structure, the rectification diode and a semiconductor switch are used as switch unit S 1 , and the rectification diode is used as switch unit S 2 . 
     Referring now to  FIG.  6   , shown is a schematic diagram of the waveforms on each node of the first example of the switching power supply circuit, in accordance with embodiments of the present invention. In this particular example, with the switching of switch control signals PWMH and PWML, voltage VHB of a middle node between the second terminal of power switch Q 1  and at the first terminal of power switch Q 2 , voltage VCr on the resonance capacitor Cr, current iLr on resonant inductor Lr, and current iLm on magnetizing inductor Lm can increase or decrease correspondingly. 
     Referring now to  FIG.  7   , shown is a schematic block diagram of the first example of the switching power supply circuit operated in the AHB mode, in accordance with embodiments of the present invention. As shown in  FIGS.  6  and  7   , e.g., when Vin/(Vout*N) is more than 2, the mode switching signal mode=0, switch S 12  is turned off, and the switching power supply circuit  1  is operated in AHB mode. At this moment, the first secondary winding and the branch where the first switch is located can be disconnected and not operate. Only the second secondary winding and switch unit S 2  may perform the rectification operation, and when power switch Q 1  is turned off and power switch Q 2  is turned on, current iD 2  may flow through power switch Q 2 . In this way, advantages of a wide input and output range may be achieved. 
     Referring now to  FIG.  8   , shown is a schematic block diagram of the first example of the switching power supply circuit operated in the LLC mode, in accordance with embodiments of the present invention. As shown in  FIGS.  6  and  8   , e.g., when Vin/(Vout*N) is close to 2, the mode switching signal mode=1, switch S 12  is turned on, and switching power supply circuit  1  may operate in the LLC mode. At this moment, the branch where the first secondary winding and the first switch are located, and the branch where the second secondary winding and switch unit S 2  are located, may all perform the rectification operation. Also, when the current in the primary winding flows into the dotted terminal, current iD 1  may flow through switch unit S 1 . When the current in the primary winding flows out of the dotted terminal, current iD 2  may flow through switch unit S 2 , in order to provide relatively high efficiency. 
     Referring now to  FIG.  9   , shown is a schematic block diagram of the second example of the switching power supply circuit, in accordance with embodiments of the present invention. In this particular example, the structure of output rectification module  13  is different. As shown, the secondary winding can include a third and fourth secondary windings. Output rectification module  13  can include switch units S 3 , S 4 , S 5 , capacitor C 1 , and capacitor C 2 . The current input terminal of switch unit S 3  can connect to the dotted terminal of the third secondary winding. The current output terminal of switch unit S 3  can connect to output capacitor Cout and the upper plate of capacitor C 1 . In the LLC mode, switch unit S 3  can be turned on and may rectify the signal input to switch unit S 3 . In the AHB mode, switch unit S 3  can be turned off. The lower plate of capacitor C 1  can connect to the non-dotted terminal of the third secondary winding. Switch unit S 4  can connect in parallel with both terminals of capacitor C 1 . 
     In the LLC mode, switch unit S 4  can be turned off. In the AHB mode, switch unit S 4  can be turned on. The current input terminal of switch unit S 5  may be grounded. The current output terminal of switch unit S 5  can connect to the dotted terminal of the fourth secondary winding. In both the LLC mode and the AHB mode, the signal input to switch unit S 5  can be rectified. The upper plate of capacitor C 2  can connect to the non-dotted terminal of the fourth secondary winding. The lower plate of capacitor C 2  may be grounded, and the lower plate of output capacitor Cout is grounded. The non-dotted terminal of the third secondary winding can connect to the non-dotted terminal of the fourth secondary winding. 
     For example, switch unit S 3  is a bidirectional switch having two synchronous rectification switches connected in series in opposite phases. In another example, switch unit S 3  is a series structure of a high-speed control mode switch and a low-speed control mode switch, and the operating frequency of the low-speed control mode switch is less than the operating frequency of the high-speed control mode switch. For example, the high-speed control mode switch may be a synchronous rectification switch or a rectification diode, and the low-speed control mode switch can be a relay or a semiconductor switch. For example, switch unit S 4  can include a relay and a semiconductor switch. Any device capable of switching the mode may be suitable in certain embodiments. For example, switch unit S 5  can include a synchronous rectification switch and a rectification diode. Any device capable of realizing a rectification function may be utilized in certain embodiments. 
     Referring now to  FIG.  10   , shown is a schematic block diagram of the second example of the switching power supply circuit operated in the AHB mode, in accordance with embodiments of the present invention. In this particular example, taking switch unit S 3  as an example of a series structure of a rectification diode and a semiconductor switch, when Vin/(Vout*N) is more than 2, the mode switching signal mode=0. The slow control mode switch in switch unit S 3  can be turned off, and switch unit S 4  turned on. Switching power supply circuit  1  can be operated in the AHB mode. At this moment, the branch where the third secondary winding and switch unit S 3  are located can be disconnected and not operate. Only the fourth secondary winding and switch unit S 5  may perform the rectification operation. 
     Referring now to  FIG.  11   , shown is a schematic block diagram of the second example of the switching power supply circuit operated in the LLC mode, in accordance with embodiments of the present invention. In this particular example, when Vin/(Vout*N) is close to 2, the mode switching signal mode=1. The slow control mode switching switch in switch unit S 3  can be turned on, and switch unit S 4  disconnected. Switching power supply circuit  1  can be operated in the LLC mode. At this moment, the third secondary winding, switch unit S 3 , the fourth secondary winding, and switch unit S 5  may operate. Output voltage Vout can be the sum of the voltages on capacitors C 1  and C 2 . Also, the circuit on the output side of switching power supply circuit  1  is a double-voltage rectification circuit. 
     Referring now to  FIG.  12   , shown is a schematic block diagram of the third example of the switching power supply circuit, in accordance with embodiments of the present invention. In this particular example, rectification module  13  can include switch units S 6 , S 7 , S 8 , and S 9 . The current input terminal of switch unit S 6  can connect to the dotted terminal of the fifth secondary winding. The current output terminal of switch unit S 6  can connect to the upper plate of output capacitor Cout. In both the LLC mode and the AHB mode, the signal input to switch unit S 6  can be rectified. The current input terminal of switch unit S 7  may be grounded, and the current output terminal of switch unit S 7  can connect to the current input terminal of switch unit S 6 . 
     In both the LLC mode and the AHB mode, the signal input to switch unit S 7  can be rectified. The current input terminal of switch unit S 8  can connect to the non-dotted terminal of the fifth secondary winding. The current output terminal of switch unit S 8  can connect to the upper plate of output capacitor Cout. In both the LLC mode and the AHB mode, the signal input to switch unit S 8  can be rectified, and the current input terminal of switch unit S 9  may be grounded. The current output terminal of switch unit S 9  can connect to the current input terminal of switch unit S 8 . When switching power supply circuit  1  is in the LLC mode, switch unit S 9  can be turned on and may rectify the signal input to switch unit S 9 . When switching power supply circuit  1  is in the AHB mode, switch unit S 9  can be turned off, and the lower plate of output capacitor Cout may be grounded. 
     For example, switch units S 6 , S 7 , and S 8  can each include a synchronous rectification switch and a rectification diode. Any device capable of realizing a rectification function can be utilized in certain embodiments. It should be noted that the device types of switch units S 6 , S 7 , and S 8  may be the same or different. For example, switch unit S 9  is a bidirectional switch having two synchronous rectification switches connected in series in opposite direction. In another example, switch unit S 9  is a series structure of a high-speed control mode switch and a low-speed control mode switch, and the operating frequency of the low-speed control mode switch is less than the operating frequency of the high-speed control mode switch. For example, the high-speed control mode switch may be a synchronous rectification switch or a rectification diode, and the low-speed control mode switch can be a relay or a semiconductor switch. 
     Referring now to  FIG.  13   , shown is a schematic block diagram of the third example of the switching power supply circuit operated in the AHB mode, in accordance with embodiments of the present invention. In this particular example, switch units S 6 , S 7 , and S 8  are the rectification diodes, and switch unit S 9  is a series structure of a rectification diode and a semiconductor switch, whereby when Vin/(Vout*N) is more than 2, the mode switching signal mode=0. The slow control mode switch in switch unit S 9  can be turned off. Switching power supply circuit  1  may be operated in AHB mode. When the current of the primary winding flows out from the dotted terminal, the current can pass from the non-dotted terminal of the fifth secondary winding through switch unit S 8 , output capacitor Cout, switch unit S 7  in sequence, and may return to the dotted terminal of the fifth secondary winding, thereby realizing rectification output. 
     Referring now to  FIG.  14   , shown is a schematic block diagram of the third example of the switching power supply circuit operated in the LLC mode, in accordance with embodiments of the present invention. In this particular example, when Vin/(Vout*N) is close to 2, the mode switching signal mode=1. The slow control mode switching switch in switch unit S 9  can be turned on, and switching power supply circuit  1  may be operated in LLC mode. When the current of the primary winding flows out from the dotted terminal, the current can pass from the non-dotted terminal of the fifth secondary winding through switch unit S 8 , output capacitor Cout, switch unit S 7  in sequential, and return to the dotted terminal of the fifth secondary winding. When the current of the primary winding flows into the dotted terminal, the current may pass from the dotted terminal of the fifth secondary winding through switch unit S 6 , output capacitor Cout, and switch unit S 9  in sequence, and return to the non-dotted terminal of the fifth secondary winding, thereby realizing rectification output. 
     In particular embodiments, a switching power supply circuit can include: a transformer having a primary winding and a secondary winding; a resonant capacitor and a resonant inductor coupled in series with the primary winding to form a series structure; a power switch module configured to receive an input voltage and connecting two terminals of the series structure to form a resonance circuit; an output rectification module coupled to the secondary winding and configured to generate an output voltage; an operating mode control module configured to receive the input voltage and the output voltage, to control the output rectification module such that the switching power supply circuit is operated in the LLC mode when a ratio of the input voltage and the output voltage is less than or equal to a predetermined value, and to control the output rectification module such that the switching power supply circuit is operated in the AHB mode when the ratio of the input voltage and the output voltage is greater than the predetermined value. In this way, the topologies of AHB and LLC can effectively be unified, and allow the switching power supply circuit to have advantages of relatively high efficiency and wide input and output range as well by switching the topology operating modes. 
     The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with modifications as are suited to particular use(s) contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.