Buck or buck / boost derived dc / dc converter with two separate outputs and quasi-decoupled control
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- SIGNIFY HOLDING BV
- Filing Date
- 2024-07-30
- Publication Date
- 2026-06-10
AI Technical Summary
Existing DC/DC converters with multiple outputs suffer from high cost and poor load regulation, as they require multiple auxiliary power supplies or a single supply with cascaded outputs, leading to inflexible power adjustment between outputs.
A driving circuit with a main output and an auxiliary output, incorporating a resonance mechanism that allows for independent control of the auxiliary output power by adjusting the time duration of resonance during the freewheeling duration of the main switched mode power converter.
This solution enables more flexible and independent regulation of the auxiliary output power, improving load regulation and reducing costs by eliminating the need for multiple power supplies.
Smart Images
Figure EP2024071548_06022025_PF_FP_ABST
Abstract
Description
[0001] BUCK OR BUCK / BOOST DERIVED DC / DC CONVERTER WITH TWO SEPARATE OUTPUTS AND QUASI-DECOUPLED CONTROL
[0002] FIELD OF THE INVENTION
[0003] The present invention relates to the field of electronics, and in particular to a driving circuit.
[0004] BACKGROUND OF THE INVENTION
[0005] In a modern electronic appliance, there is generally more than one load. Taking an intelligent lighting device for example, besides a LED arrangement to emitting light, there is usually other intelligent modules such as MCU, RF module and / or sensor module. All loads need power and most often the voltage required by the different loads are different, such as 12V, 5V, 3.3V. Multiple auxiliary power supplies or an auxiliary power supply with multiple outputs are needs to supply the modules.
[0006] Figures 1 and 2 show different implementations comprising multiple auxiliary power supplies to provide different output power OUT1 and OUT2. In figure 1 the multiple auxiliary power supplies are connected in parallel, and in figure 2 the multiple auxiliary power supplies are cascaded. A drawback of such implementations is high cost since two power supplies are used.
[0007] Figure 3 shows an auxiliary power supply with multiple outputs, wherein LI is formed by two coupled windings, and each winding provides one output. One winding is connected with the input electrically to form a buck converter, the other winding equivalently forms a flyback converter. When the buck converter is in freewheeling state, the other winding also release energy. The drawback of this topology is the bad load regulation performance - the output of the other winding is influenced a lot by the load condition at the output of the buck winding. In other words, the power at the other winding is strongly determined by the output of the buck winding and does not have much freedom to be adjusted. For example, if the load at the buck converter is light weighted, it is not easy to provide a heavy weighted power at the other winding.
[0008] US3671853A1 discloses a buck converter with a frequency-to-voltage converter and the frequency of the buck converter can be controlled to control an output of the frequency-to-voltage converter. SUMMARY OF THE INVENTION
[0009] The present invention provides a new topology of a driving circuit with a main output and an auxiliary output wherein the power at the auxiliary output can be adjusted with more freedom. The underlying idea of the present invention is using adding a resonance mechanism related to the auxiliary output on top of the original switching mode power conversion related to the main output, and controlling the resonance so as to regulate the auxiliary output power. More specifically, the resonance is made happen at the freewheeling duration of the main switched mode power converter. The resonance can be controlled in several aspect so as to influence the auxiliary power output.
[0010] A first aspect of the invention provides a driving circuit comprising an input to receive an input power, a switched mode power converter coupled with the input and having a switched mode power, synchronous rectifying buck, converter output, and adapted to convert the input power into a switched mode power converter output power at the switched mode power converter output, the switched mode power converter including a power inductor and a set of synchronous rectifying switches operating in synchronous rectifying manner, wherein the synchronous rectifying switches are adapted to be switched into a first state to couple the input power to charge the power inductor, and a second state to couple the power inductor to the switched mode power converter output so as to discharge the power inductor for providing the switched mode power converter output power; and an auxiliary converter having a resonance capacitor, the power inductor and an auxiliary output, different from the switched mode power converter output, coupled with the resonance capacitor and the power inductor, wherein when the synchronous rectifying switches are in the second state, the power inductor and the resonance capacitor are adapted to resonate with each other in which in the first state the synchronous rectifying switches are adapted to connect the input power in series with the power inductor, the resonance capacitor and the auxiliary output to provide power at the auxiliary output, in a positive resonance duration in the second state, the power inductor is adapted to release power to the series connection of the resonance capacitor and the auxiliary output, and in a negative resonance duration in the second state, the resonance capacitor is adapted to charge in a reverse direction the power inductor without through the auxiliary output; and a controller adapted to control a time duration of the resonance so as to regulate the auxiliary output power.
[0011] By controlling the time duration of the resonance, certain electrical values in the auxiliary converter can be adapted so as to regulate the auxiliary output power. This aspect of the invention has more freedom in regulating the auxiliary output power. In a more specific embodiment, the durations of the first state and the second state are constant, or the frequency of the synchronous rectifying buck converter is constant. Makin the time durations or frequency of switching constant simplfies the control of the buck converter.
[0012] In a first embodiment, said resonance capacitor and the auxiliary output are in series connection, and said controller is adapted to control the time duration of the resonance to regulate a voltage on the resonance capacitor so as to regulate a voltage on the auxiliary output.
[0013] Since the resonance capacitor is in series with the auxiliary output, the voltage on the resonance capacitor can effectively influence the voltage on the auxiliary output. Thus by regulating the voltage on the resonance capacitor, the auxiliary output voltage can be regulated.
[0014] More specifically, the resonance capacitor is adapted to counteract the voltage applied across the series connection of the resonance capacitor and the auxiliary output, thereby regulating the voltage on the auxiliary output. In this embodiment, the voltage on the resonance capacitor can be regulated low so as to provide a high auxiliary output voltage; vice versa.
[0015] In one embodiment, the synchronous rectifying switches are adapted to be switched into a synchronous rectifying state in the second state wherein said resonance capacitor is adapted to be charged by said power inductor first and discharge so as to vary a voltage on the resonance capacitor, and said synchronous rectifying switches are adapted to be switched into off state after the synchronous rectifying state.
[0016] In the first cycle of resonance, the voltage on the resonance capacitor would vary by a large extend thus it can be regulated at a wide range, therefore the auxiliary output voltage can also be regulated at a wide range.
[0017] In one embodiment, the controller is adapted to control a time duration of the synchronous rectifying state so as to regulate the voltage on the resonance capacitor. The voltage on the resonance capacitor is time-variable thus by controlling a time duration of the synchronous rectifying state the volage on the resonance capacitor can be set at a desired value for providing a desired auxiliary output voltage.
[0018] Alternative or additional to the above first embodiment, the auxiliary output power is provided to the auxiliary output by the resonance capacitor in each cycle of resonance, thus by controlling how much times / cycles the resonance happens, the auxiliary output power can be adjusted. Thus a light-weighted load at the auxiliary output requires a shorter time duration for less times / cycles of resonance, and a heavy-weighted load at the auxiliary output requires a longer time duration for less times / cycles of resonance.
[0019] In a further embodiment, the controller is adapted to control a time duration of the second state so as to control the times of discharging thereby regulating the auxiliary output power. If more cycles of resonance are allowed, the resonance capacitor would discharge more energy at the auxiliary output and vice versa.
[0020] In a further embodiment, the controller is further adapted to control a time duration of the first state thereby regulating the switched mode power converter output power. This embodiment can independently adjust the switched mode power converter output power and the auxiliary output power.
[0021] In one embodiment, the power inductor comprises a first inductor segment and a second inductor segment connected in series, and the resonance capacitor is connected in series with the first inductor segment and decoupled from the second inductor segment thereby adapted to resonate with the first inductor without resonating with the second inductor segment.
[0022] In one embodiment, said auxiliary converter further comprises: a first unidirectional component adapted to series connect said auxiliary output, said resonance capacitor and said power inductor, said first unidirectional component is adapted to allow resonance electricity of one direction in each resonance cycle to the auxiliary output and block the resonance electricity of the other direction; and a second, reverse, unidirectional component connected anti-parallel with the said auxiliary output and the first unidirectional component, said second unidirectional component is adapted to allow the resonance electricity of the other direction but without passing through the auxiliary output.
[0023] This embodiment uses two unidirectional components to control the power conversion in the resonance. The unidirectional components could be implemented by diodes and the cost is low.
[0024] In one further embodiment, the driving circuit further comprises a first sensing element coupled with the switched mode power converter output adapted to provide feedback of the switched mode power converter output power to the controller for regulating switched mode power converter output power.
[0025] In another embodiment, the driving circuit further comprises a second sensing element coupled with the auxiliary output adapted to provide feedback of the auxiliary output power to the controller for regulating auxiliary output power. Those embodiments provide close-loop feedback for the switched mode power converter and the auxiliary converter. Notably, feedforward control can be used as an alternative.
[0026] In one specific implementation, in the first state the synchronous rectifying switches are adapted to connect the input power in series with the power inductor and the switched mode power converter output to provide power at the switched mode power converter output, and charge the power inductor. And in the second state, the synchronous rectifying switches are adapted to disconnect the input power and allow the power inductor to freewheel to discharge at the switched mode power converter output.
[0027] This embodiment describes how to implement the synchronous rectifying buck converter.
[0028] In one embodiment, the synchronous rectifying switches comprise a power switch and a freewheeling switch which is a bidirectional component, and the power inductor is adapted to charge the resonance capacitor and the resonance capacitor is adapted to charge in a reverse direction the power inductor both through the freewheeling switch. In this embodiment, the bidirectional component is used for facilitating the resonance, and both cost and power loss are low. Preferably, the bidirectional component is a MOSFET.
[0029] In a second aspect of the invention, it is provided an electronic appliance comprising the driving circuit of the first aspect. Preferably, the electronic appliance is a lighting device.
[0030] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment s) described hereinafter.
[0031] BRIEF DESCRIPTION OF THE DRAWINGS
[0032] For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:
[0033] Figs 1 and 2 illustrates known circuits comprising two power supplies for providing two outputs;
[0034] Fig. 3 is also a known circuits of one power supply for providing two outputs;
[0035] Fig. 4 illustrates a driving circuit according to one embodiment of the invention;
[0036] Figs 5 a, 5b and 5 c illustrate voltage and current waveform in the driving circuit of fig. 4 under different outputs. Fig. 6 illustrates a driving circuit according to another embodiment of the invention; and
[0037] Figs 7a and 7b illustrate resonance current in the driving circuit of fig. 6.
[0038] DETAILED DESCRIPTION OF THE EMBODIMENTS
[0039] The invention will be described with reference to the Figures.
[0040] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.
[0041] Figure 4 shows an embodiment of implementing the invention in a buck converter. It is a driving circuit comprising an input IN to receive an input power V 1 , a switched mode power converter coupled with the input and having a switched mode power converter output Cl, and adapted to convert the input power VI into a switched mode power converter output power OUT1 at the switched mode power converter output Cl, the switched mode power converter including a power inductor L3, LI and a set of synchronous rectifying switches QI, Q2 operating in synchronous rectifying manner, wherein the synchronous rectifying switches is adapted to be switched into a first state to couple the input power to charge the power inductor L3, LI, and a second state to couple the power inductor L3, LI to the switched mode power converter output Cl so as to discharge the power inductor L3, LI for providing the switched mode power converter output power; and an auxiliary converter having a resonance capacitor C6, the power inductor L3, LI and an auxiliary output C7, different from the switched mode power converter output Cl, coupled with the resonance capacitor C6 and the power inductor L3, LI, wherein when the synchronous rectifying switches QI, Q2 are in the second state, the power inductor LI, L3 and the resonance capacitor C6 are adapted to resonate with each other; and a controller adapted to control a time duration of the resonance so as to regulate the auxiliary output power.
[0042] More specifically, in the circuit in figure 4, the capacitor C3 is an optional input buffer capacitor. The Buck controller is an IC or MCU that controls the synchronous MOSFET switches QI, Q2. MOSFET QI is the power switch of the buck converter and MOSFET Q2 is the freewheel switch of the buck converter. Voltage detector Rl, R2 is used for detecting the voltage on the buck output capacitor Cl and feedback it to the Buck controller. Voltage detector R3, R4 is used for detecting the voltage on the auxiliary output capacitor C7 and feedback it to the Buck controller.
[0043] Figure 5a shows the current and voltage waveform.
[0044] In a synchronous rectifying buck converter, MOSFET Q2 is used for replacing the freewheeling diode in an ordinary buck converter because the voltage drop and power loss on the MOSFET is substantially lower than the diode. More specifically, in the first state of buck charging starting from time tO to time tl, the synchronous rectifying switch QI is closed and the switch Q2 is open to connect the input power in series with the power inductor L3, LI, and charge the power inductor L3, LI. The input power also charges the switched mode power converter output CL Even more, the input power is also applied on a series connection of the resonance capacitor C6 and the auxiliary power output C7, wherein the residual voltage on the resonance capacitor C6 would influence how much voltage can be provided to the auxiliary power output C7. In one embodiment, by controlling the residual voltage on the resonance capacitor C6 as below, the auxiliary power output voltage can be regulated.
[0045] In a positive resonance duration tl to t2 in the second state from tl to t4 after the first state tO to tl, the MOSFET QI is turned off and the MOSFET Q2 is turned on. The power inductor L3 is adapted to charge the resonance capacitor C6 and also release power to the auxiliary output C7. The resonance in the positive resonance duration is clockwise. A first inductor segment L3 of the power inductor freewheels the current from left to right, and this current goes to charge the capacitor C6, and flows to the auxiliary output C7 via a diode D3, to the ground and back to the first inductor segment L3 via the freewheeling switch Q2 in close state. This current also contributes to the auxiliary output power OUT2. The voltage on the inductor L3 is applied on a series connection of the resonance capacitor C6 and the auxiliary power output C7, wherein the residual voltage on the resonance capacitor C6 would influence how much voltage can be provided to the auxiliary power output C7. In this duration, the power inductor LI, L3 also freewheels power to the switched mode power converter output Cl via the conducted MOSFETQ2.
[0046] And in a negative resonance duration t2 to t3 in the second state, the MOSFET QI is turned off and the MOSFET Q2 is turned on still. The resonance capacitor C6 is adapted to discharge in a reverse direction to the power inductor L3 without through the auxiliary output C7. The resonance in the negative resonance duration is counterclockwise. The resonance capacitor C6 discharges from downside electrode, the discharging current flows into the first inductor segment L3 from right to left, and flow to the ground via the freewheel switch Q2, and from ground to the diode D2 and finally to the upside electrode of the resonance capacitor C6. The diode D2 is anti-parallel with the diode D3 and the auxiliary output C7 thus the resonance power in the negative resonance duration does not flow to the auxiliary output C7 as auxiliary output power OUT2. In this duration, the power inductor LI, L3 still freewheels power to the switched mode power converter output Cl via the conducted MOSFETQ2.
[0047] At a certain time t3, the synchronous rectifying switch Q2 is also turned off and a voltage V(C6) on the resonance capacitor C6 is obtained. Moreover, after the time t3, the resonance capacitor voltage V(C6) still oscillates with the power inductor L3 and the parasitic capacitor of the synchronous rectifying switch Q2, so the resonance capacitor voltage V(C6) still rise a little from time t3 to t4. The power inductor LI, L3 also freewheels power to the switched mode power converter output Cl via the body diode of the MOSFETQ2.
[0048] At time t4 the next buck charging phase starts. The final residual resonance capacitor voltage V(C6) counteracts with the input voltage (and the induced voltage on the power inductor L3) again so as to regulate the auxiliary output voltage to the desired value, as explained above.
[0049] It can be understood that the resonance capacitor voltage V(C6) is relevant with the inductance of the first inductor segment and the capacitance of the resonance capacitor as well as how long the resonance happens. The Buck controller can control the kicking in of time t3 (turning off time of the synchronous rectifying switch Q2), namely the time t2 to t3 of the resonance so as to control the resonance capacitor voltage V(C6).
[0050] In a close-loop feedback control, the voltage divider R3, R4 connected at the auxiliary output C7 to detect the voltage of the auxiliary output power OUT2 and feeds back to the Buck controller. The Buck controller could control the kicking in of time t3 such that the OUT2 reaches a desired reference value. Alternatively, feedforward control can also be used.
[0051] On top of the time length (duty cycle) of the resonance being adjusted to regulate the auxiliary output power OUT2, the duty cycle of the first state, with respect to the overall first state and the second state, is adjusted to regulate the switched mode power converter output voltage OUT1. This is a well-known technique in buck converter control. In a close-loop feedback control, there is a voltage divider Rl, R2 connected at the switched mode power converter output Cl to detect the voltage of the switched mode power converter output power OUT1 and feeds back to the Buck controller. The Buck controller could control the time duration such that the OUT1 reaches a desired reference value. Alternatively, feedforward control can also be used.
[0052] In the waveform in figure 5a, assumed the duty cycle of QI and Q2 on time are respectively 28% and 35%, and assumed the Voutl is 6.6V and Vout2 is 8.4V.
[0053] In the waveform in figure 5b, assumed the duty cycle of QI on time is kept as 28% and Q2 on time is reduced to 12.5%, and the obtained the Voutl is 6.6V and Vout2 is 6.5V. Because the resonance happens for a less time, the residual voltage on the resonance capacitor C6 is higher than that in figure 5a thus less voltage is provided at the auxiliary output.
[0054] In the waveform in figure 5c, assumed the duty cycle of QI on time is reduced to 13.75% and Q2 on time is kept to 35%, and the obtained the Voutl is 3.7V and Vout2 is 8.4V. In this case, although the input power is reduced compared with figure 5a, in the operation, the same duty cycle of Q2 obtains a reduced resonance capacitor voltage and the final auxiliary output voltage can be kept.
[0055] In the above embodiment, it is to control the residual voltage on the resonance capacitor C6 so as to counteract the total voltage across the series connection of the resonance capacitor C6 and the auxiliary output thereby regulating the voltage on the auxiliary output. Another embodiment is to control the times of resonance so as to regulate the auxiliary output, wherein the resonance capacitor is able to release power to the auxiliary output in each resonance.
[0056] More specifically, in a synchronous rectifying buck converter, MOSFET Q2 is used for replacing the freewheeling diode in an ordinary buck converter because the voltage drop and power loss on the MOSFET is substantially lower than the diode. More specifically, in the first state of buck charging, the synchronous rectifying switch QI is closed and the switch Q2 is open to connect the input power in series with the power inductor L3, LI and the switched mode power converter output Cl to provide power at the switched mode power converter output Cl, and charge the power inductor L3, LI. In the second state of buck freewheeling, the synchronous rectifying switch QI is open to disconnect the input power and the synchronous rectifying switch Q2 is close to allow the power inductor L3, LI to freewheel to discharge at the switched mode power converter output CL The power to the output Cl in both of the buck charging duration and the buck freewheeling duration contributes to produce the switched mode power converter output power OUT1. Synchronous rectifying buck converter is a well-known technique for those skilled in the art thus the present application will not describe in more details.
[0057] In a positive resonance duration in the second state, the power inductor L3 is adapted to charge the resonance capacitor C6 and release power to the auxiliary output C7. The resonance in the positive resonance duration is clockwise. A first inductor segment L3 of the power inductor freewheels the current from left to right, and this current goes to charge the capacitor C6, and flows to the auxiliary output C7 via a diode D3, to the ground and back to the first inductor segment L3 via the freewheeling switch Q2 in close state, this current produces the auxiliary output power OUT2.
[0058] And in a negative resonance in the second state, the resonance capacitor C6 is adapted to charge in a reverse direction the power inductor L3 without through the auxiliary output C7. The resonance in the negative resonance duration is counterclockwise. The resonance capacitor C6 discharges from downside electrode, the discharging current flows into the first inductor segment L3 from right to left, and flow to the ground via the freewheel switch Q2, and from ground to the diode D2 and finally to the upside electrode of the resonance capacitor C6. The diode D2 is anti-parallel with the diode D3 and the auxiliary output C7 thus the resonance power in the negative resonance duration does not flow to the auxiliary output C7 as auxiliary output power OUT2. At last the resonance current goes to zero, and the resonance capacitor C6 become upper positive.
[0059] And then the positive resonance happens again, the resonance capacitor C6 starts to discharge via the diode D3, the auxiliary output C7, the MOSFET Q2 and the inductor L3. When the resonance capacitor C6 voltage reaches zero, the resonance current through the inductor L3 is at the peak value, then the inductor L3 still freewheels the resonance current to charge the resonance capacitor C6 into opposite polarity, meanwhile the resonance current also goes to the auxiliary output C7. At last, the resonance current goes to zero and the voltage at the resonance capacitor C6 is at an opposite peak value. And the negative resonance happens again, the resonance capacitor C6 is adapted to charge in a reverse direction the power inductor L3 without through the auxiliary output C7. The resonance in the negative resonance duration is counterclockwise. The resonance capacitor C6 discharges from downside electrode, the discharging current flows into the first inductor segment L3 from right to left, and flow to the ground via the freewheel switch Q2, and from ground to the diode D2 and finally to the upside electrode of the resonance capacitor C6. The diode D2 is anti-parallel with the diode D3 and the auxiliary output C7 thus the resonance power in the negative resonance duration does not flow to the auxiliary output C7 as auxiliary output power OUT2. At last the resonance current goes to zero, and the resonance capacitor C6 become upper positive again and ready to start a new positive resonance similar as above.
[0060] The positive and negative resonance durations alternate.
[0061] The time lengths of the positive resonance duration and the negative resonance duration are relevant with the inductance of the first inductor segment and the capacitance of the resonance capacitor. The Buck controller can control the time duration of the second state so as to control the total time duration of the resonance, thereby controlling how much times / cycles the resonance happens. The more cycles of resonance, the higher the auxiliary output power OUT2 and vice versa.
[0062] In a close-loop feedback control, there is a voltage divider R3, R4 connected at the auxiliary output C7 to detect the voltage of the auxiliary output power OUT2 and feeds back to the Buck controller. The Buck controller could control the time duration such that the OUT2 reaches a desired reference value. Alternatively, feedforward control can also be used.
[0063] On top of the duty cycle of the second state being adjusted to regulate the auxiliary output power OUT2, the duty cycle of the first state, with respect to the overall first state and the second state, is adjusted regulate the switch mode power supply output OUT1. This is a well-known technique in buck converter control. In a close-loop feedback control, there is a voltage divider Rl, R2 connected at the switched mode power converter output Cl to detect the voltage of the switched mode power converter output power OUT1 and feeds back to the Buck controller. The Buck controller could control the time duration such that the OUT1 reaches a desired reference value. Alternatively, feedforward control can also be used.
[0064] The invention could also be applied with other type of converter as the switched mode power converter. An implementation of using buck-boost converter is also proposed with reference to figures 6, 7a and 7b. The buck-boost block shows a controller, either IC, MCU, or even discrete circuit that controls the synchronous MOSFET switches QI, Q2. MOSFET QI is the power switch of the buck-boost converter and MOSFET Q2 is the synchronous rectifying switch of the buck-boost converter. Voltage detector Rl, R2 is used for detecting the voltage on the buck-boost output capacitor Cl and feedback it to the Buck-boost controller. Voltage detector R3, R4 is used for detecting the voltage on the auxiliary output capacitor C7 and feedback it to the Buck-boost controller. Similar as the above embodiment in figure 4, there are also two ways of controlling the resonant converter in figure 6 to regulate the auxiliary output power.
[0065] In a first way, it is to control the residual voltage on the resonance capacitor C6 so as to counteract the total voltage across the series connection of the resonance capacitor C6 and the auxiliary output and to regulate the voltage on the auxiliary output.
[0066] In a synchronous rectifying buck-boost converter, MOSFET Q2 is used for replacing the freewheeling diode in an ordinary buck converter because the voltage drop and power loss on the MOSFET is substantially lower than the diode. More specifically, in the first state of buck charging starting, the synchronous rectifying switch QI is closed and the switch Q2 is open to connect the input power in series with the power inductor L3, LI, and charge the power inductor L3, LI.
[0067] In a positive resonance duration in the second state, the MOSFET QI is turned off and the MOSFET Q2 is turned on. The power inductor L3 is adapted to charge the resonance capacitor C6 and also release power to the auxiliary output C7. The resonance in the positive resonance duration is counterclockwise as shown in figure 7a. The first inductor segment L3 of the power inductor freewheels the current from up to down, and this current goes to charge the capacitor C6, and flows to the auxiliary output C7 via a diode D3, and back to the first inductor segment L3 via the freewheeling switch Q2 in close state. This current also contributes to the auxiliary output power OUT2. The voltage on the inductor L3 is applied on a series connection of the resonance capacitor C6 and the auxiliary power output C7, wherein the residual voltage on the resonance capacitor C6 would influence how much voltage can be provided to the auxiliary power output C7. In this duration, the power inductor LI, L3 also freewheels power to the switched mode power converter output Cl via the conducted MOSFETQ2.
[0068] And in a negative resonance duration in the second state, the MOSFET Q2 is turned on still. The resonance capacitor C6 is adapted to discharge in a reverse direction to the power inductor L3 without through the auxiliary output C7. The resonance in the negative resonance duration is clockwise as shown in figure 7b. The resonance capacitor C6 discharges from downside electrode, the discharging current flows into the first inductor segment L3 from down to up, and flow via the freewheel switch Q2, and to the diode D2 and finally to the upside electrode of the resonance capacitor C6. The diode D2 is anti-parallel with the diode D3 and the auxiliary output C7 thus the resonance power in the negative resonance duration does not flow to the auxiliary output C7 as auxiliary output power OUT2. In this duration, the power inductor LI, L3 also freewheels power to the switched mode power converter output Cl via the conducted MOSFETQ2.
[0069] At a certain time, a voltage V(C6) on the resonance capacitor C6 is obtained. And this final residual resonance capacitor voltage V(C6) counteracts with the induced voltage on the power inductor L3 again in the next cycle so as to regulate the auxiliary output voltage to the desired value, as explained above.
[0070] It can be understood that the resonance capacitor voltage V(C6) is relevant with the inductance of the first inductor segment and the capacitance of the resonance capacitor as well as how long the resonance happens. The Buck-boost controller can control the kicking in of turning off time of the synchronous rectifying switch Q2, so as to control the resonance capacitor voltage V(C6).
[0071] In a close-loop feedback control, the voltage divider R3, R4 connected at the auxiliary output C7 to detect the voltage of the auxiliary output power OUT2 and feeds back to the Buck-boost controller. The Buck-boost controller could control the Q2 turning off time such that the OUT2 reaches a desired reference value. Alternatively, feedforward control can also be used.
[0072] On top of the time length of the resonance being adjusted to regulate the auxiliary output power OUT2, the duty cycle of the first state, with respect to the overall first state and the second state, is adjusted to regulate the switched mode power converter output voltage OUT1. This is a well-known technique in buck-boost converter control. In a closeloop feedback control, there is a voltage divider Rl, R2 connected at the switched mode power converter output Cl to detect the voltage of the switched mode power converter output power OUT1 and feeds back to the Buck controller. The Buck controller could control the time duration such that the OUT1 reaches a desired reference value. Alternatively, feedforward control can also be used.
[0073] In a second way, it can control the times of resonance so as to regulate the auxiliary output, wherein the resonance capacitor is able to release power to the auxiliary output in each resonance. In a synchronous rectifying buck-boost converter, MOSFET Q2 is used for replacing the freewheeling diode in an ordinary buck-boost converter because the voltage drop and power loss on the MOSFET is substantially lower than the diode. More specifically, in the first state of buck-boost charging, the synchronous rectifying switch QI is closed and the switch Q2 is open to connect the input power in series with the power inductor L3, LI, and charge the power inductor L3, LI. In the second state of buck-boost freewheeling, the synchronous rectifying switch QI is open to disconnect the input power and the synchronous rectifying switch Q2 is close to allow the power inductor L3, LI to freewheel to discharge at the switched mode power converter output C 1 to produce the switched mode power converter output power OUT1 in a counterclockwise direction shown by the arrow in figure 7a. Synchronous rectifying buck-boost converter is a well-known technique for those skilled in the art thus the present application will not describe in more details.
[0074] And most notably, the resonance happens in the second state of buck-boost freewheeling.
[0075] In a positive resonance duration in the second state as shown in figure 7a, the power inductor L3 is adapted to charge the resonance capacitor C6 and release power to the auxiliary output C7. The resonance in the positive resonance duration is counterclockwise as shown by the arrow in figure 7a. A first inductor segment L3 of the power inductor freewheels the current from up side to down side, and this current goes to charge the capacitor C6, and flows to the auxiliary output C7 via a diode D3, and back to the first inductor segment L3 via the freewheeling switch Q2 in close state. This current produces the auxiliary output power OUT2. At last, the resonance capacitor C6 becomes down side positive and upper side negative.
[0076] And in a negative resonance duration in the second state, the resonance capacitor C6 is adapted to charge in a reverse direction the power inductor L3 without through the auxiliary output C7. The resonance in the negative resonance duration is clockwise shown by the arrow in figure 7b. The resonance capacitor C6 discharges from downside electrode, the discharging current flows into the first inductor segment L3 from downside to upside, and flow via the freewheel switch Q2, and finally to the upside electrode of the resonance capacitor C6. The diode D2 is anti-parallel with the diode D3 and the auxiliary output C7 thus the resonance power in the negative resonance duration does not flow to the auxiliary output C7 as auxiliary output power OUT2. At last the resonance capacitor C6 becomes upper side positive and lower side negative. Then a positive resonance duration happens again wherein the resonance capacitor discharge to the auxiliary output C7 and charges the power inductor L3 again, similar as explained above. Following this positive resonance duration, a negative resonance duration happens too. So the positive and negative resonance durations alternate.
[0077] The time lengths of the positive resonance duration and the negative resonance duration are relevant with the inductance of the first inductor segment L3, the capacitance of the resonance capacitor C6 and the impedance at the auxiliary output C7 / Rloadl. The Buckboost controller can control the time duration of the second state so as to control the time duration of the resonance, thereby controlling how much times / cycles the resonance happens. The more cycles of resonance, the higher the auxiliary output power OUT2 and vice versa.
[0078] In a close-loop feedback control, there is a voltage divider R3, R4 connected at the auxiliary output C7 to detect the voltage of the auxiliary output power OUT2 and feeds back to the Buck-boost controller. The Buck-boost controller could control the time duration such that the OUT2 reaches a desired reference value. Alternatively, feedforward control can also be used.
[0079] Once sufficient energy has been delivered to the auxiliary output power OUT2, the buck-boost converter can switch back to the first state of buck-boost charging.
[0080] On top of the duty cycle of the second state being adjusted to regulate the auxiliary output power OUT2, the duty cycle of the first state, with respect to the overall first state and the second state, is adjusted to regulate the switched mode power converter output power OUT1. This is a well-known technique in buck-boost converter control. In a closeloop feedback control, there is a voltage divider Rl, R2 connected at the switched mode power converter output Cl to detect the voltage of the switched mode power converter output power OUT1 and feeds back to the Buck-boost controller. The Buck-boost controller could control the time duration such that the OUT1 reaches a desired reference value. Alternatively, feedforward control can also be used.
[0081] In the above two embodiments, it is the voltage of the switched mode power converter output power OUT1 and the auxiliary output power OUT2 is detected and regulated. Alternatively, the current of one or the switched mode power converter output power OUT1 and the auxiliary output power OUT2 can be detected and regulated, and the voltage of the other one output power is detected and regulated. Further alternatively, the current of both of the switched mode power converter output power OUT1 and the auxiliary output power OUT2 is detected and regulated. The embodiments in the invention are suitable for powering different loads with respective input voltage requirements, such as 12V, 5V and 3.3V. Thus there is no need to use different driving circuits to provide the different voltages.
[0082] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.
[0083] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. If the term "adapted to" is used in the claims or description, it is noted the term
[0084] "adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa.
[0085] Any reference signs in the claims should not be construed as limiting the scope.
Claims
CLAIMS:
1. A driving circuit comprising an input to receive an input power, a switched mode power, synchronous rectifying buck, converter coupled with the input and having a switched mode power converter output (Cl), and adapted to convert the input power into a switched mode power converter output power (0UT1) at the switched mode power converter output (Cl), the switched mode power converter including a power inductor (L3, LI) and a set of synchronous rectifying switches (QI, Q2), wherein the synchronous rectifying switches are adapted to be switched into a first state to couple the input power to charge the power inductor (L3, LI), and a second state to couple the power inductor (L3, LI) to the switched mode power converter output (Cl) so as to discharge the power inductor (L3, LI) for providing the switched mode power converter output power (0UT1); an auxiliary converter having a resonance capacitor (C6), the power inductor (L3, LI), and an auxiliary output (C7), different from the switched mode power converter output (Cl), coupled with the resonance capacitor (C6) and the power inductor (L3, LI), wherein when the synchronous rectifying switches (QI, Q2) are in the second state, the power inductor (LI, L3) and the resonance capacitor (C6) are adapted to resonate with each other in which in the first state the synchronous rectifying switches (QI, Q2) are adapted to connect the input power in series with the power inductor (L3, LI), the resonance capacitor (C6) and the auxiliary output (C7) to provide power at the auxiliary output (C7), in a positive resonance duration in the second state, the power inductor (L3, LI) is adapted to release power to the series connection of the resonance capacitor (C6) and the auxiliary output (C7), and in a negative resonance duration in the second state, the resonance capacitor (C6) is adapted to charge in a reverse direction the power inductor (L3, LI) without through the auxiliary output (C7); and- a controller adapted to control the time duration of the resonance so as to regulate the auxiliary output power (0UT2).
2. The driving circuit of claim 1, wherein the durations of the first state and the second state are constant, or the frequency of the synchronous rectifying buck converter is constant.
3. The driving circuit of claim 1, wherein said resonance capacitor (C6) and the auxiliary output (C7) are in series connection, and said controller is adapted to control the time duration of the resonance to regulate a voltage on the resonance capacitor (C6) so as to regulate a voltage on the auxiliary output (C7).
4. The driving circuit of claim 3, wherein said resonance capacitor (C6) is adapted to counteract a voltage applied across the series connection of the resonance capacitor (C6) and the auxiliary output (C7), thereby regulating the voltage on the auxiliary output (C7).
5. The driving circuit of claim 3 or 4, wherein said synchronous rectifying switches are adapted to be switched into a synchronous rectifying state in the second state wherein said resonance capacitor (C6) is adapted to be charged by said power inductor (LI, L3) first and discharge so as to vary a voltage on the resonance capacitor (C6), and said synchronous rectifying switches are adapted to be switched into off state after the synchronous rectifying state.
6. The driving circuit of claim 5, wherein the controller is adapted to control a time duration of the synchronous rectifying state so as to regulate the voltage on the resonance capacitor (C6).
7. The driving circuit of claim 1, wherein said resonance capacitor (C6) is adapted to discharge an auxiliary output power (OUT2) on the auxiliary output (C7) in one or more resonance cycles.
8. The driving circuit of claim 7, wherein the controller is adapted to control a time duration of the second state so as to control the times of discharging thereby regulating the auxiliary output power (OUT2).
9. The driving circuit of claim 1 or 2, wherein the controller is further adapted to control a time duty cycle of the first state thereby regulating the switched mode power converter output power (OUT1).
10. The driving circuit of claim 1, wherein the power inductor (L3, LI) comprises a first inductor segment (L3) and a second inductor segment (LI) connected in series, and the resonance capacitor (C6) is connected in series with the first inductor segment (L3) and decoupled from the second inductor segment (LI) thereby adapted to resonate with the first inductor (L3) without resonating with the second inductor segment (LI).
11. The driving circuit of claim 10, wherein said auxiliary converter further comprises: a first unidirectional component (D3) adapted to series connect said auxiliary output (C7), said resonance capacitor (C6) and said power inductor (L3), said first unidirectional component (D3) is adapted to allow resonance electricity of one direction in each resonance cycle to the auxiliary output (C7) and block the resonance electricity of the other direction; and a second, reverse, unidirectional component (D2) connected anti-parallel with the said auxiliary output (C7) and the first unidirectional component (D3), said second unidirectional component (D2) is adapted to allow the resonance electricity of the other direction but without passing through the auxiliary output (C7).
12. The driving circuit of claim 1, further comprising a first sensing element (Rl, R2) coupled with the switched mode power converter output (Cl) adapted to provide feedback of the switched mode power converter output power (OUT1) to the controller for regulating switched mode power converter output power, and a second sensing element (R3, R4) coupled with the auxiliary output (C7) adapted to provide feedback of the auxiliary output power (OUT2) to the controller for regulating auxiliary output power (OUT2).
13. The driving circuit of claim 1, wherein in the first state the synchronous rectifying switches (QI, Q2) are adapted to connect the input power in series with the powerinductor (L3, LI) and the switched mode power converter output (Cl) to provide power at the switched mode power converter output (Cl), and charge the power inductor (L3, LI); in the second state, the synchronous rectifying switches (QI, Q2) are adapted to disconnect the input power and allow the power inductor (L3, LI) to freewheel to discharge at the switched mode power converter output (Cl).
14. The driving circuit of claim 1, wherein the synchronous rectifying switches (QI, Q2) comprises a power switch (QI) and a freewheeling switch (Q2) which is a bidirectional component, and the power inductor (L3, LI) is adapted to charge the resonance capacitor (C6) and the resonance capacitor (C6) is adapted to charge in a reverse direction the power inductor (L3, LI) both through the freewheeling switch (Q2).
15. An electronic appliance, optionally a lighting device, comprising the driving circuit of any one of claims 1 to 14, a first load (Rload), optionally a first non-lighting load, connected at the switched mode power converter output (Cl), and a second load (Rload 1), optionally a second non-lighting load, connected at the auxiliary output (C7).