DC-DC CONVERTER AND CONTROL METHOD THEREOF

Abstract

A DC-DC converter includes: a power stage having an inductor and a plurality of switches, for generating a plurality of output voltages from an input voltage; a control circuit, for performing time multiplexing constant charge transfer control having valley current control by transferring electrical energy from the input voltage to the plurality of output voltages sequentially one-by-one, further generating a control voltage to control respective output charges of the plurality of output voltages as respective constant predetermined values, and response to all load currents for making input power and output power balance by automatically generating a valley current so that the DC-DC converter switches between DCM and CCM; and a logic control and gate driver for generating a plurality of switch control signals, the plurality of switch control signals for controlling the plurality of switches of the power stage.

Claims

1. A DC-DC converter including: a power stage having an inductor and a plurality of switches coupled to the inductor, the power stage generating a plurality of output voltages from an input voltage; a control circuit coupled to the power stage, the control circuit performing time multiplexing constant charge transfer control having valley current control by transferring electrical energy from the input voltage to the plurality of output voltages sequentially one-by-one, the control circuit further generating a control voltage to control respective output charges of the plurality of output voltages as respective constant predetermined values, and the control circuit response to all load currents for making input power and output power balance by automatically generating a valley current so that the DC-DC converter switches between a discontinuous conduction mode (DCM) and a continuous conduction mode (CCM) depending on different valley current levels; and a logic control and gate driver, coupled to the control circuit and the power stage, the logic control and gate driver generating a plurality of switch control signals based on a plurality of control signals from the control circuit, the plurality of switch control signals for controlling the plurality of switches of the power stage.

2. The DC-DC converter according to claim 1, wherein the DC-DC converter is either a single-inductor multiple-output (SIMO) or a single inductor multiple bipolar output (SIMBO) DC-DC converter.

3. The DC-DC converter according to claim 1, wherein each conversion for each positive output voltage among the plurality of output voltages is operated at a buck mode, a boost mode or a buck-boost mode in response to conditions of the input voltage and the output voltage.

4. The DC-DC converter according to claim 1, wherein one of the output voltages is operated at an inverting mode.

5. The DC-DC converter according to claim 1, wherein a conversion mode of a selected channel is decided by a mode decision circuit of the control circuit.

6. The DC-DC converter according to claim 1, wherein the control circuit includes a first-in-first-out (FIFO) and priority logic for performing FIFO and priority determination on a plurality of voltage comparator outputs from a voltage comparator circuit of the control circuit when triggered by a valley current detection result; the FIFO and priority logic loads the voltage comparator outputs at positive edges of a valley current signal according to a pre-set priority; while more than one of the voltage comparator outputs concurrently go high at the positive edge of the valley current signal, the high voltage comparator outputs are sequentially loaded into the FIFO and priority logic according to the pre-set priority; the voltage comparator output loaded first into the FIFO and priority logic is first dumped out at the positive edge of the valley current signal; only one output is selected in each time slot between two of the valley current signals; and the control circuit is in response to each output, and the FIFO and Priority circuit decides the selected output channel for a time instance.

7. The DC-DC converter according to claim 6, wherein the control circuit includes a time multiplexing constant charge transferred (TMCCT) control logic coupled to the FIFO and priority logic, while a channel is selected, a corresponding output signal from the FIFO and priority logic is high for a whole time slot between two of the valley current signals; for a DC-DC conversion, a first peak current signal generated from a peak current detector terminates an inductor current charging phase and an inductor current discharging phase is following; the Inductor current charging phases for all conversion modes are terminated by the first peak current signal; the first peak current signal and a second peak current signal are response to the control voltage to transfer a constant charge to the selected channel at the discontinuous conduction mode; the inductor discharging phases for all conversion modes are terminated by the inductor current discharged to a valley current level among the different valley current levels; the valley current level is response to a valley current detection result of the control circuit; a channel selection signal is used to indicate the selected channel under processed; and an enable signal generated by the TMCCT control logic is to reset and enable the peak current detector.

8. The DC-DC converter according to claim 7, wherein the control circuit further includes a control voltage generator generating the control voltage based on the channel select signal, a mode signal, the input voltage and the output voltages; the control voltage is generated with response to the required conversion mode, the predetermined constant output charge, the input voltage and the output voltage of the selected channel.

9. The DC-DC converter according to claim 8, wherein the valley current level is in response to the freewheel duty cycles; if the freewheel duty cycle is larger than a first time interval, the valley current level is decreased; if the freewheel duty cycle is smaller a second time interval, the valley current level is increased, wherein the first time interval is equal to or larger than the second time interval; if the freewheel duty cycle is equal to the first and second time intervals, the valley current level is not changed; if the freewheel duty cycle is smaller than the first time interval and larger than the second time interval, the valley current level is not changed; and the valley current level is equal to or larger than zero value.

10. The DC-DC converter according to claim 9, wherein the TMCCT control logic decides a switching sequence for the selected channel in response to the valley current detection result, a peak current detection result and a mode decision result.

11. A control method for a DC-DC converter, the control method including: generating a plurality of output voltages from an input voltage by a power stage having an inductor and a plurality of switches coupled to the inductor; performing time multiplexing constant charge transfer control having valley current control by transferring electrical energy from the input voltage to the plurality of output voltages sequentially one-by-one; generating a control voltage to control respective output charges of the plurality of output voltages as respective constant predetermined values; response to all load currents, making input power and output power balance by automatically generating a valley current so that the DC-DC converter switches between a discontinuous conduction mode (DCM) and a continuous conduction mode (CCM) depending on different valley current levels; and generating a plurality of switch control signals based on a plurality of control signals, the plurality of switch control signals for controlling the plurality of switches of the power stage.

12. The control method for the DC-DC converter according to claim 11, wherein the DC-DC converter is either a single-inductor multiple-output (SIMO) or a single inductor multiple bipolar output (SIMBO) DC-DC converter.

13. The control method for the DC-DC converter according to claim 11, wherein each conversion for each positive output voltage among the plurality of output voltages is operated at a buck mode, a boost mode or a buck-boost mode in response to conditions of the input voltage and the output voltage.

14. The control method for the DC-DC converter according to claim 11, wherein one of the output voltages is operated at an inverting mode.

15. The control method for the DC-DC converter according to claim 11, wherein a conversion mode of a selected channel is decided by a mode decision result.

16. The control method for the DC-DC converter according to claim 11, further including: performing FIFO and priority determination on a plurality of voltage comparator outputs when triggered by a valley current detection result; loading the voltage comparator outputs at positive edges of a valley current signal according to a pre-set priority; while more than one of the voltage comparator outputs concurrently go high at the positive edge of the valley current signal, the high voltage comparator outputs are sequentially loaded according to the pre-set priority; the voltage comparator output loaded first is first dumped out at the positive edge of the valley current signal; only one output is selected in each time slot between two of the valley current signals; and deciding the selected output channel for a time instance.

17. The control method for the DC-DC converter according to claim 16, further including: performing time multiplexing constant charge transferred (TMCCT) control, while a channel is selected, a corresponding output signal from the FIFO and priority determination is high for a whole time slot between two of the valley current signals; for a conversion, a first peak current signal terminates an inductor current charging phase and an inductor current discharging phase is following; the Inductor current charging phases for all conversion modes are terminated by the first peak current signal; the first peak current signal and a second peak current signal are response to the control voltage to transfer a constant charge to the selected channel at the discontinuous conduction mode; the inductor discharging phases for all conversion modes are terminated by the inductor current discharged to a valley current level among the different valley current levels; the valley current level is response to a valley current detection result; a channel selection signal is used to indicate the selected channel under processed; and an enable signal generated by the TMCCT control is to reset and enable the peak current detection.

18. The control method for the DC-DC converter according to claim 17, wherein the control voltage is generated based on the channel select signal, a mode signal, the input voltage and the output voltages; the control voltage is generated with response to the required conversion mode, the predetermined constant output charge, the input voltage and the output voltage of the selected channel.

19. The control method for the DC-DC converter according to claim 18, wherein the valley current level is in response to the freewheel duty cycles; if the freewheel duty cycle is larger than a first time interval, the valley current level is decreased; if the freewheel duty cycle is smaller a second time interval, the valley current level is increased; the first time interval is equal to or larger than the second time interval; if the freewheel duty cycle is equal to the first and second time intervals, the valley current level is not changed; if the freewheel duty cycle is smaller than the first time interval and larger than the second time interval, the valley current level is not changed; and the valley current level is equal to or larger than zero value.

20. The control method for the DC-DC converter according to claim 19, wherein the TMCCT control decides a switching sequence for the selected channel in response to the valley current detection result, a peak current detection result and a mode decision result.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 shows a circuit diagram of a SIMO (Single Inductor Multiple Output) DC-DC converter according to one embodiment of the application.

[0012] FIG. 2 shows a circuit diagram of a SIMBO (Single Inductor Multiple Bipolar Output) DC-DC converter according to one embodiment of the application.

[0013] FIG. 3 shows inductor current waveforms and switching sequence for various conversion modes of the SIMBO DC-DC converter according to one embodiment of the application.

[0014] FIG. 4 shows TMCCT according to one embodiment of the application.

[0015] FIG. 5A and FIG. 5B show two possible of the peak current detector in one embodiment of the application.

[0016] FIG. 6A to FIG. 6D show various conversion modes of TMCCT according to one embodiment of the application.

[0017] FIG. 7 shows operations of the mode decision circuit according to one embodiment of the application.

[0018] FIG. 8 shows the waveforms of the FIFO and priority logic 123 according to one embodiment of the application.

[0019] FIG. 9A shows a circuit diagram of the valley voltage generator and the valley current detector according to one embodiment of the application.

[0020] FIG. 9B shows the waveforms of the valley voltage generator and the valley current detector according to one embodiment of the application.

[0021] FIG. 10 shows an example of switch logic waveforms according to one embodiment of the application.

[0022] In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.

DESCRIPTION OF THE EMBODIMENT

[0023] Technical terms of the disclosure are based on general definition in the technical field of the disclosure. If the disclosure describes or explains one or some terms, definitions of the terms are based on the description or explanation of the disclosure. Each of the disclosed embodiments has one or more technical features. In possible implementation, one skilled person in the field could selectively implement part or all technical features of any embodiment of the disclosure or selectively combine part or all technical features of the embodiments of the disclosure.

[0024] FIG. 1 shows a circuit diagram of a SIMO (Single Inductor Multiple Output) DC-DC converter according to one embodiment of the application. As shown in FIG. 1, the SIMO DC-DC converter 100 according to one embodiment of the application includes a power stage 110, a control circuit 120 and a logic control and gate driver 150. The power stage 110 of the SIMO DC-DC converter 100 generates a plurality of output voltages V.sub.O1, V.sub.O2, ..., V.sub.Om (m being a positive integer) from an input voltage V.sub.IN. In the following, the SIMO DC-DC converter 100 has a plurality of channels; and a channel is defined as a signal path for generating an output voltage among the plurality of output voltages V.sub.O1, V.sub.O2, ..., V.sub.Om. The plurality of output voltages V.sub.O1, V.sub.O2, ..., Vom may be also referred as channel output voltages. Also, the plurality of output voltages V.sub.O1, V.sub.O2, ..., Vom are positive output voltages.

[0025] The power stage 110 includes an inductor L.sub.1, a plurality of switches SW1, SW2, SW3, SWO.sub.1, SWO.sub.2, ..., SWO.sub.m, a plurality of capacitors C.sub.0, C.sub.1, C.sub.2, ... C.sub.m, and a plurality of loads (for example but not limited by resistors R.sub.L1, R.sub.L2..., R.sub.Lm). The switches SW1, SW2, SW3 are also referred as input switches while the switches SWO.sub.1, SWO.sub.2, ..., SWO.sub.m are also referred as output switches.

[0026] The inductor L.sub.1 is coupled between a first node LX1 and a second node LX2. An inductor current I.sub.L flows through the inductor L.sub.1. The inductor L.sub.1 is coupled to the switches SW1, SW2, SW3, SWO.sub.1, SWO.sub.2, ..., SWO.sub.m.

[0027] The switch SW1 is coupled between the input voltage V.sub.IN and the first node LX1. The switch SW2 is coupled between a ground terminal GND and the first node LX1. The switch SW3 is coupled between the input voltage V.sub.IN and the second node LX2. The switch SWO.sub.1 is coupled between the second node LX2 and the first output voltage V.sub.O1. The switch SWO.sub.2 is coupled between the second node LX2 and the second output voltage V.sub.O2. The switch SWO.sub.m is coupled between the second node LX2 and the m-th output voltage Vom.

[0028] The capacitor C.sub.0 is coupled between the input voltage V.sub.IN and the ground terminal GND. The plurality of capacitors C.sub.1, C.sub.2, ... C.sub.m, and the plurality of loads R.sub.L1, R.sub.L2..., R.sub.Lm are coupled in parallel between the output voltages V.sub.O1, V.sub.O2, ... V.sub.Om and the ground terminal GND, respectively. Still further, the power stage 110 has a current sense circuit which senses a current I.sub.SNS=I.sub.L/k (k being a positive number) to the control circuit 120. The current I.sub.L/k is 1/k of the inductor current I.sub.L.

[0029] The switches SW1, SW2, SW3, SWO.sub.1, SWO.sub.2, ..., SWO.sub.m are controlled by a plurality of switch control signals S.sub.1, S.sub.2, S.sub.3, S.sub.O1, S.sub.O2, ..., S.sub.Om, respectively. The switch control signals S.sub.1, S.sub.2, S.sub.3, S.sub.O1, S.sub.O2, ..., S.sub.Om are generated by the control circuit 120 and the logic control and gate driver 150.

[0030] The control circuit 120 is coupled to the power stage 110. The control circuit 120 includes a voltage comparator (CMP) circuit 121 having a plurality of voltage comparators (CMPs) 121_1~121_m, a FIFO (first-in-first-out) and priority logic 123, a Time Multiplexing Constant Charge Transferred (TMCCT) control logic 125, a mode decision circuit 127, a control voltage generator 129, a peak current detector 131, a valley voltage generator 133, a valley current detector 135, an overcurrent protection circuit 137, and a logic gate 139.

[0031] The sense current I.sub.SNS=I.sub.L/k from the power stage 110 is fed into the control circuit 120 (k being a constant number). Also, the sense current I.sub.SNS from the power stage 110 is fed into the peak current detector 131 for peak current control. Also, the sense current I.sub.SNS from the power stage 110 is fed into the valley voltage generator 133 for generating the valley voltage. Also, the sense current I.sub.SNS from the power stage 110 is fed into the overcurrent protection circuit 137 for overcurrent protection.

[0032] The plurality of voltage comparators 121_1~121_m generate a plurality of voltage comparator output signals CP.sub.1~CP.sub.m based on the output voltages V.sub.O1, V.sub.O2, ... Vom and a plurality of reference voltages VR.sub.1, VR.sub.2, ..., VR.sub.m, respectively. For example but not limited by, the plurality of voltage comparators 121_1~121_m generate the plurality of voltage comparator output signals CP.sub.1~CP.sub.m as high when the output voltages V.sub.O1, V.sub.O2, ... Vom are lower than the plurality of reference voltages VR.sub.1, VR.sub.2, ..., VR.sub.m, respectively. The voltage comparator output signals CP.sub.1~CP.sub.m are input into the FIFO and priority logic 123. When the output voltages V.sub.O1, V.sub.O2, ... Vom are lower than the reference voltages VR.sub.1, VR.sub.2, ..., VR.sub.m, it means the corresponding channel need to receive more power from the input voltage V.sub.IN. When the voltage comparator output signals CP.sub.1~CP.sub.m are logic high, the control circuit 120 will control to supply power to the corresponding channel whose output voltage is lower than the reference voltage.

[0033] The FIFO and priority logic 123 is coupled to the plurality of voltage comparators 121_1~121_m for performing FIFO and priority determination on outputs CP.sub.1~CP.sub.m from the plurality of voltage comparators 121_1~121_m to generate a plurality of signals CT.sub.1~CT.sub.m based on the valley current VC.

[0034] The TMCCT control logic 125 decides the switching sequence for the selected channel in response to outputs from the valley current detector 135, the peak current detector 131, and the mode decision circuit 127 based on the a plurality of signals CT.sub.1~CT.sub.m, the valley current VC, the mode signal MD (from the mode decision circuit 127) and the peak current signals PKC and PK13.

[0035] The mode decision circuit 127 decides the conversion mode for the selected channel based on the channel select signal CHS and the input voltage V.sub.IN and the output voltages V.sub.O1, V.sub.O2, ... V.sub.Om.

[0036] The control voltage generator 129 generates a control voltage V.sub.CX to the peak current detector for controlling the output charge as a constant predetermined value based on the channel select signal CHS, the mode signal MD and the input voltage V.sub.IN and the output voltages V.sub.O1, V.sub.O2, ... V.sub.Om.

[0037] The peak current detector 131 detects the sense current I.sub.SNS to determine whether the sense current I.sub.SNS exceeds a threshold which is corresponding to the control voltage V.sub.CX. If yes, the output signal PKC from the peak current detector 131 will terminate the inductor current charging phases for all conversion modes.

[0038] The peak current detector 131 includes a multiplexer 131_1, two voltage comparators 131_2 and 131_3, a capacitor C.sub.T and a voltage divider 131_4.

[0039] The multiplexer 131_1 selects one among the two input (the sense current I.sub.SNS and GND) as the voltage V.sub.CT (which is the cross voltage on the capacitor C.sub.T) under control of the enable signal CG from the TMCCT control logic 125. For example but not limited by, when the enable signal CG is logic 1, the multiplexer 131_1 selects the sense current I.sub.SNS and vice versa.

[0040] The voltage comparator 131_2 compares the voltage V.sub.CT with the control voltage V.sub.CX to generate the peak current PKC. For example but not limited by, when the voltage V.sub.CT is higher than the control voltage V.sub.CX, the voltage comparator 131_2 generates the high peak current PKC and vice versa.

[0041] The voltage comparator 131_3 compares the voltage V.sub.CT with the control voltage Vcx/m (m>1) to generate the peak current PK13. For example but not limited by, when the voltage V.sub.CT is higher than the control voltage Vcx/m, the voltage comparator 131_3 generates the high peak current PK13 and vice versa.

[0042] The capacitor C.sub.T is coupled to the output of the multiplexer 131_1.

[0043] The voltage divider 131_4 receives the control voltage V.sub.CX to output the control voltage V.sub.CX/m (m>1).

[0044] The valley voltage generator 133 generates the valley voltage V.sub.VLLY to the valley current detector 135 based on the signal MOT and the free-wheel cycle FW. Details of the valley voltage generator 133 are described as follows.

[0045] The valley current detector 135 generates the valley current signal VC based on the sense current I.sub.SNS and the valley voltage V.sub.VLLY from the valley voltage generator 133.

[0046] The valley current detector 135 includes a voltage comparator 135_1 and a resistor Rx. The voltage comparator 135_1 compares the valley voltage V.sub.VLLY with the voltage Rx*I.sub.SNS. The resistor Rx is coupled to the voltage comparator 135_1.

[0047] For example but not limited by, when the valley voltage V.sub.VLLY is higher than the voltage Rx*I.sub.SNS, the voltage comparator 135_1 generates the valley current signal VC as logic high and vice versa.

[0048] The overcurrent protection circuit 137 includes a voltage comparator 137_1 for comparing a sense voltage (equal to I.sub.SNS*R.sub.OCP) with a reference current V.sub.OCP. When the sense voltage exceeds the reference current V.sub.OCP, the overcurrent protection circuit 137 outputs a high overcurrent indication signal OC to the logic control and gate driver 150. In response to the overcurrent indication signal OC, the logic control and gate driver 150 resets the switch control signal S.sub.1 to logic low to turn off the switch SW1 and thus stops energy transfer from the input voltage V.sub.IN to the inductor L.sub.1. By so, the overcurrent protection is achieved.

[0049] The logic gate 139 generates the free-wheel (FW) duty cycle based on the switch control signals S.sub.2 and S.sub.3. For example but not limited by, the logic gate 139 is an AND logic gate; and thus the logic gate 139 generates the high free-wheel (FW) duty cycle when both the switch control signals S.sub.2 and S.sub.3 are logic high.

[0050] The logic control and gate driver 150 is coupled to the power stage 110 and the control circuit 120. The logic control and gate driver 150 generates the plurality of switch control signals S.sub.1, S.sub.2, S.sub.3, S.sub.O1, S.sub.O2, ..., S.sub.Om, and the signal MOT.

[0051] The logic control and gate driver 150 includes a logic control 151 and a gate driver 155.

[0052] The logic control 151 includes a first logic 151_1, a second logic 151_3 and a plurality of SR flip-flops SR_1~SR_(m+2).

[0053] The first logic 151_1 generates an output based on the switch control signal S.sub.1. The output of the first logic 151_1 is fed into the gate driver 155 for generating the switch control signal S.sub.2.

[0054] The second logic 151_3 generates an output based on the signal RS.sub.1 and the over current OC. The output of the second logic 151_2 is input into the SR flip-flop SR_(m+2).

[0055] The SR flip-flop SR_(m+1) generates an output based on the signals RS.sub.3 and ST.sub.3.

[0056] The SR flip-flops SR_1~SR_m generate outputs based on the signals ST.sub.O1~ST.sub.Om and the valley current VC.

[0057] The gate driver 155 generates the signals S.sub.1, S.sub.2, S.sub.3, S.sub.O1, S.sub.O2, ..., S.sub.Om, and MOT based on the outputs from the first logic 151_1, the second logic 151_3 and the plurality of SR flip-flops SR_1~SR_(m+2).

[0058] FIG. 2 shows a circuit diagram of a SIMBO (Single Inductor Multiple Bipolar Output) DC-DC converter 200 according to one embodiment of the application. As shown in FIG. 2, the SIMBO DC-DC converter 200 according to one embodiment of the application includes a power stage 210, a control circuit 220 and a logic control and gate driver 250. The power stage 210 of the SIMBO DC-DC converter 200 generates a plurality of positive output voltages V.sub.O1, V.sub.O2, ..., Vom and a negative output voltage V.sub.N from the input voltage V.sub.IN. In the following, the SIMBO DC-DC converter 200 has a plurality of channels; and a channel is defined as a signal path for generating an output voltage among the plurality of output voltages V.sub.O1, V.sub.O2, ..., V.sub.Om, V.sub.N. The plurality of output voltages V.sub.O1, V.sub.O2, ..., V.sub.Om, V.sub.N may be also referred as channel output voltages.

[0059] The power stage 210 includes an inductor L.sub.1, a plurality of switches SW1, SW2, SW3, SWO.sub.1, SWO.sub.2, ..., SWO.sub.m, SWN, a plurality of capacitors C.sub.0, C.sub.1, C.sub.2, ... C.sub.m, C.sub.N, and a plurality of loads (for example but not limited by resistors R.sub.L1, R.sub.L2..., R.sub.Lm, R.sub.LN).

[0060] The power stage 210 of the SIMBO DC-DC converter 200 is similar to the power stage 110 of the SIMO DC-DC converter 100 and thus the details are omitted here.

[0061] The control circuit 220 is coupled to the power stage 210. The control circuit 220 includes a voltage comparator (CMP) circuit 221 having a plurality of voltage comparator 221_1~221_m and 221_N, a FIFO and priority logic 223, a Time Multiplexing Constant Charge Transferred (TMCCT) control logic 225, a mode decision circuit 227, a control voltage generator 229, a peak current detector 231 (including a multiplexer 231_1, two voltage comparators 231_2 and 231_3, a capacitor C.sub.T and a voltage divider 231_4), a valley voltage generator 233, a valley current detector 235 (including a voltage comparator 235_1 and a resistor Rx), an overcurrent protection circuit 237 (including a voltage comparator 237_1 and a resistor R.sub.OCP), and a logic gate 239.

[0062] The control circuit 220 of the SIMBO DC-DC converter 200 is similar to the control circuit 120 of the SIMO DC-DC converter 100 and thus the details are omitted here.

[0063] The logic control and gate driver 250 is coupled to the power stage 210 and the control circuit 220. The logic control and gate driver 250 generates the plurality of switch control signals S.sub.1, S.sub.2, S.sub.3, S.sub.O1, S.sub.O2, ..., S.sub.Om, S.sub.N, and the signal MOT.

[0064] The logic control and gate driver 250 includes a logic control 251 (including a first logic 251_1, a second logic 251_3 and a plurality of SR flip-flops SR_1~SR_(m+2) and SR_N) and a gate driver 255.

[0065] The logic control and gate driver 250 of the SIMBO DC-DC converter 200 is similar to the logic control and gate driver 150 of the SIMO DC-DC converter 100 and thus the details are omitted here.

[0066] FIG. 3 shows inductor current waveforms and switching sequence for various conversion modes of the SIMBO DC-DC converter 200 according to one embodiment of the application. However, FIG. 3 is also applicable to the SIMO DC-DC converter 100 according to one embodiment of the application.

[0067] In the cycle (A), the SIMBO DC-DC converter 200 sequentially operates in the buck-boost mode, the Free-Wheel (FW) mode, the buck mode, the FW mode and the boost mode. During the buck-boost mode, the symbol “13” refers to that the switches SW1 and the SW3 are turned on. During the buck-boost mode, the switches SW1 and SW3 are turned on and thus power is supplied from the input voltage V.sub.IN to the inductor L.sub.1 to increase the inductor current I.sub.L. Then, the switches SW1 and SWO.sub.1 are turned on to transfer the power stored in the inductor L.sub.1 into the output voltage V.sub.O1. Then, the switches SW2 and SWO.sub.1 are turned on to release the redundant power from the output voltage V.sub.O1 to GND to decrease the inductor current I.sub.L till zero.

[0068] During the cycle (A), all output current I.sub.O1, I.sub.O2, I.sub.O3 and I.sub.ON are constant; and the total FW period in each switching cycle is longer than a predetermined value t.sub.A. Thus, the valley voltage V.sub.VLLY is reduced till zero and also the DC current I.sub.DC is reduced till zero. During the cycle (A), the charging current is decided by the peak current control voltage V.sub.CX generated by the control voltage generator 129.

[0069] In the cycle (B), the SIMBO DC-DC converter 200 sequentially operates in the inverting mode, the boost mode, the buck-boost mode and the boost mode.

[0070] During the cycle (B), one or more of the output current I.sub.O1, I.sub.O2, I.sub.O3 and I.sub.ON goes to a larger level; and the total FW period in a predetermined number of switching cycles is shorter than another predetermined value t.sub.B (t.sub.B<t.sub.A). Thus, the valley voltage V.sub.VLLY is increased and also the DC current I.sub.DC is increased. During the cycle (B), the end current level for discharging to the output channel is decided by the valley voltage V.sub.VLLY.

[0071] In the cycle (C), the SIMBO DC-DC converter 200 sequentially operates in the FW mode, the buck mode, the buck-boost mode, the boost mode, the FW mode and the inverting mode.

[0072] During the cycle (C), the output current I.sub.O1, I.sub.O2, 1.sub.O3 and I.sub.ON keep constant; and the total FW period in a predetermined number of switching cycle is shorter than t.sub.A and longer than t.sub.B (tB<tA). Thus, the valley voltage V.sub.VLLY keeps and also the DC current I.sub.DC keeps.

[0073] In the cycle (D), the SIMBO DC-DC converter 200 sequentially operates in the boost mode, the buck-boost mode, the boost mode and the inverting mode.

[0074] During the cycle (D), one or more of the output current I.sub.O1, I.sub.O2, 1.sub.O3 and I.sub.ON goes to a lower level; and the total FW period in a predetermined number of switching cycle is longer than t.sub.A. Thus, the valley voltage V.sub.VLLY is reduced to zero and also the DC current I.sub.DC is reduced to zero. During the cycle (D), the end current level for discharging to the output channel is decided by the valley voltage V.sub.VLLY.

[0075] In the cycle (E), the SIMBO DC-DC converter 200 sequentially operates in the boost mode, the FW mode, the buck mode, the FW mode and the buck-boost mode.

[0076] During the cycle (E), all output current I.sub.O1, I.sub.O2, 1.sub.O3 and I.sub.ON are constant; and the total FW period in a predetermined number of switching cycle is longer than t.sub.A. The DC current IDC is reduced gradually till zero. Longer FW period means lower output current loading.

[0077] FIG. 4 shows TMCCT according to one embodiment of the application. In FIG. 4, the boost conversion mode is taken an example but the application is not limited by.

[0078] The peak current I.sub.PK1Ox is the increased inductor current level at the inductor charging phase t.sub.1 and the decreased inductor current level at the inductor discharging phase t.sub.2. That is, during the inductor charging phase t.sub.1, the inductor current I.sub.L is increased from the DC current I.sub.DC (equal to the valley current I.sub.VLLY) to “I.sub.DC+I.sub.PK1Ox”, and in the inductor discharging phase t.sub.2, the inductor current I.sub.L is decreased from “I.sub.DC+I.sub.PK1Ox”to the valley current I.sub.VLLY.

[0079] The inductor charging phase t.sub.1 and the inductor discharging phase t.sub.2 are expressed as the formula (1).

[00001]$\begin{array}{l}{\text{t}}_1{\text{= I}}_{\text{PK10x}}{\text{*L/V}}_{\text{IN}}\\ \\ {\text{t}}_2{\text{= I}}_{\text{PK10x}}\text{*L/}\left({\text{V}}_{\text{Ox}}{\text{-V}}_{\text{IN}}\right)\end{array}$

[0080] The total output charge Qox is expressed as the formula (2).

[00002]$\begin{array}{l}\text{Total output charge:}{Q}_{Ox}\\ ={\displaystyle {\int }_0^{t_2}\left(I_{DC}+I_{PK1Ox}-\frac{V_{Ox}-V_{IN}}{L}\cdot t\right)\text{d}t}\\ =\frac{L\cdot I_{PK1Ox}}{\left(V_{Ox}-V_{IN}\right)}\cdot \left(\frac{I_{PK1Ox}}{2}+I_{DC}\right)\end{array}$

[0081] The output current lox is expressed as the formula (3).

[00003]$\text{Output current:}{I}_{Ox}=\frac{Q_{Ox}}{T_x}=\frac{1}{T_x}\cdot \frac{L\cdot I_{PK1Ox}}{\left(V_{Ox}-V_{IN}\right)}\cdot \left(\frac{I_{PK1Ox}}{2}+I_{DC}\right)$

[0082] Output voltage ripple V.sub.PPOx of the output voltage V.sub.Ox is expressed approximately as the formula (4).

[00004]$\begin{array}{l}\text{Output voltage ripple of}{V}_{Ox}:V_{PPOx}\cong \\ \frac{1}{C_x}\cdot \frac{L\cdot I_{PK1Ox}}{\left(V_{Ox}-V_{IN}\right)}\cdot \left(\frac{I_{PK1Ox}}{2}+I_{DC}\right)\end{array}$

[0083] The precise output voltage ripple should also consider the charge reduced on the output cap sunk by the load current during the switching period, which is ignored in this formula.

[0084] While the DC current is zero (I.sub.DC=0), the total output charge Q.sub.OX0, the output current I.sub.OX0 and the output voltage ripple V.sub.PPOx of the output voltage V.sub.Ox are expressed as the formula (5).

[00005]$\begin{array}{c}\text{Total output charge:}{Q}_{Ox0}\left(@I_{DC}=0\right)\frac{L\cdot I_{PK1Ox}^2}{2\left(V_{Ox}-V_{IN}\right)}\\ \text{Output current:}{I}_{Ox0}\left(@I_{DC}=0\right)=\frac{Q_{Ox}}{T_x}=\frac{L\cdot I_{PK1Ox}^2}{2T_x\left(V_{Ox}-V_{IN}\right)}\end{array}$

[00006]$\begin{array}{l}\text{Output voltage ripple of}{V}_{Ox0}:V_{PPOx}\left(@I_{DC}=0\right)\\ \cong \frac{L\cdot I_{PK1Ox}^2}{2C_x\left(V_{Ox}-V_{IN}\right)}\end{array}$

[0085] In one embodiment, the switching cycle (t.sub.1 + t.sub.2) depends on the inductance of the inductor L.sub.1, the input voltage V.sub.IN, the output voltage Vox and the peak current I.sub.PK1Ox.

[0086] In one embodiment, a control scheme is designed to transfer the output charge Q.sub.Ox0 as a constant at the zero DC current (I.sub.DC=0) for the corresponding output channel. Thus, in one embodiment, the output current capability can be increased by rising the valley current (I.sub.VLLY=I.sub.DC) value. However, in possible example, the output voltage ripple V.sub.PPOx of the output voltage Vox becomes larger while the DC current I.sub.DC goes larger.

[0087] Still, in one embodiment, While the DC current is higher than zero (I.sub.DC>0), the total output charge Q.sub.OX0, the output current I.sub.OX0 and the output voltage ripple V.sub.PPOx of the output voltage V.sub.Ox are expressed as the formula (6).

[00007]$\begin{array}{l}\text{Total output charge:}{Q}_{Ox}\\ =\frac{L\cdot I_{PK1Ox}}{\left(V_{Ox}-V_{IN}\right)}\cdot \left(\frac{I_{PK1Ox}}{2}+I_{DC}\right)\\ =Q_{Ox0}+\frac{L\cdot I_{PK1Ox}}{\left(V_{Ox}-V_{IN}\right)}\cdot I_{DC}\end{array}$

[00008]$\begin{array}{l}\text{Output current:}{I}_{Ox}=\frac{Q_{Ox}}{T_x}=\frac{1}{T_x}\cdot \frac{L\cdot I_{PK1Ox}}{\left(V_{Ox}-V_{IN}\right)}\cdot \left(\frac{I_{PK1Ox}}{2}+I_{DC}\right)\\ =\frac{Q_{Ox0}}{T_x}+\frac{1}{T_x}\cdot \frac{L\cdot I_{PK1Ox}}{\left(V_{Ox}-V_{IN}\right)}\cdot I_{DC}\\ {\text{Output voltage ripple of V}}_{Ox}:V_{PPOx}\\ \cong \frac{1}{C_{Ox}}\cdot \frac{L\cdot I_{PK1Ox}}{\left(V_{Ox}-V_{IN}\right)}\cdot \left(\frac{I_{PK1Ox}}{2}+I_{DC}\right)\\ =\frac{Q_{Ox0}}{C_{Ox}}+\frac{L\cdot I_{PK1Ox}}{C_{Ox}\cdot \left(V_{Ox}-V_{IN}\right)}\cdot I_{DC}\end{array}$

[0088] Now, TMCCT switch control scheme in one embodiment of the application is described. FIG. 5A and FIG. 5B show two possible of the peak current detector 131 in one embodiment of the application.

[0089] FIG. 5A shows peak current controlled integrating (I.sub.SNS-I.sub.DC)/k with the capacitor C.sub.T. FIG. 5B shows peak current controlled by peak current detection.

[0090] In one embodiment, the inductor charging phase (i.e. t.sub.1 in FIG. 4) stops at the inductor peak current achieving I.sub.DC+I.sub.PK1OX; and the inductor discharging phase (i.e. t.sub.2 in FIG. 4) stops as the inductor current achieving the valley current I.sub.VLLY (I.sub.VLLY=I.sub.DC). The valley current is decided by the valley current detector 135 and the valley voltage generator 133.

[0091] In one embodiment, the total integrated charge Q.sub.CT at the capacitor C.sub.T at the inductor charging phase is expressed as the formula (7).

[00009]$\begin{array}{c}{Q}_{CT}={\displaystyle {\int }_0^{t_1}\left(I_{SNS}\left(t\right)-\frac{I_{DC}}{k}\right)}\cdot \text{d}t={\displaystyle {\int }_0^{t_1}\frac{I_L\left(t\right)-I_{DC}}{k}\cdot \text{d}t=}\\ {\displaystyle {\int }_0^{t_1}\frac{V_{IN}}{kL}\cdot t\cdot \text{d}t=\frac{L\cdot I_{PK1Ox}^2}{2k{V}_{IN}}=C_T\times V_{Cx}}\end{array}$

[0092] In one embodiment, in FIG. 5A, the peak current control voltage V.sub.CX is expressed as the formula (8).

[00010]$\begin{array}{l}\text{Peak current control voltage:}{V}_{Cx}=\frac{L\cdot I_{PK1\text{O}x}^2}{2k{V}_{IN}{C}_T}=\\ \frac{Q_{Ox0}}{k{C}_T}\times \frac{V_{Ox}-V_{IN}}{{\text{V}}_{\text{IN}}}\end{array}$

[0093] In one embodiment, in FIG. 5B, the peak current control voltage V.sub.CX is expressed as the formula (9).

[00011]$\begin{array}{l}{\text{V}}_{\text{C}x}=\left(\frac{I_{PK1Ox}+I_{DC}}{k}-\frac{I_{DC}}{k}\right)\times R_T=\frac{I_{PK1Ox}}{k}\times R_T=\\ \frac{R_T}{k}\sqrt{\frac{2\left(V_{Ox}-V_{IN}\right)Q_{Ox0}}{L}}\end{array}$

[0094] Q.sub.Ox0 is a parameter to determine the output charge of the selected output channel for each conversion so that the control scheme is referred as the time-multiplexing constant charge transferred control scheme.

[0095] FIG. 6A to FIG. 6D show various conversion modes of TMCCT according to one embodiment of the application. In FIG. 6A to FIG. 6D, m>1.

[0096] FIG. 6A shows the boost mode. In FIG. 6A, the relationship between the input voltage V.sub.IN and the output voltage Vox is as: Vox*(m-1)/m > V.sub.IN; the inductor charging phase t.sub.1 is expressed as t.sub.1=I.sub.PK1Ox*L/V.sub.IN; the inductor discharging phase t.sub.2 is expressed as: t.sub.2= (I.sub.PK1Ox*L)/(V.sub.OX -V.sub.IN); and the peak current control voltage V.sub.CX is expressed as: V.sub.CX =Q.sub.Ox0*(V.sub.OX -V.sub.IN)/(kC.sub.T*V.sub.IN).

[0097] FIG. 6B shows the buck-boost mode. In FIG. 6B, the relationship between the input voltage V.sub.IN and the output voltage Vox is as: V.sub.OX*(m-1)/m<V.sub.IN< V.sub.OX+V.sub.T; the inductor charging phase t.sub.1 is expressed as t.sub.1=I.sub.PK1Ox*L/V.sub.IN; the inductor charging phase t.sub.2 is expressed as: t.sub.2= (I.sub.PK2Ox-I.sub.PK1Ox)*L/(V.sub.IN-V.sub.OX); the inductor discharging phase t.sub.3 is expressed as: t.sub.3=I.sub.PK2Ox*L/V.sub.OX; and the peak current control voltage V.sub.CX is expressed as: V.sub.CX =Q.sub.Ox0*(V.sub.OX)/(kC.sub.T*V.sub.IN).

[0098] FIG. 6C shows the buck mode. In FIG. 6C, the relationship between the input voltage V.sub.IN and the output voltage Vox is as: V.sub.IN>V.sub.OX+V.sub.T; the inductor charging phase t.sub.2 is expressed as: t.sub.2=I.sub.PK2Ox*L/(V.sub.IN-V.sub.OX); the inductor discharging phase t.sub.3 is expressed as: t.sub.3=I.sub.PK2Ox*L/V.sub.OX; and the peak current control voltage V.sub.CX is expressed as: V.sub.CX =Q.sub.Ox0*V.sub.OX/(kC.sub.T*V.sub.IN).

[0099] FIG. 6D shows the inverting mode. In FIG. 6D, the inductor charging phase t.sub.1 is expressed as: t.sub.1=I.sub.PKN*L/V.sub.IN); the inductor discharging phase t.sub.2 is expressed as: t.sub.3=I.sub.PKN*L/V.sub.OX; and the peak current control voltage V.sub.CX is expressed as: V.sub.CX =Q.sub.Ox0*V.sub.OX/(kC.sub.T*V.sub.IN).

[0100] FIG. 7 shows operations of the mode decision circuit according to one embodiment of the application. The mode decision circuit 127 according to one embodiment of the application generates the mode signal MD based on the input voltage VIN, the channel select signal CHS and the output voltages V.sub.O1, V.sub.O2, ..., V.sub.Om, V.sub.N.

[0101] When the relationship between the input voltage V.sub.IN and the output voltage Vox is as: Vox*(m-1)/m > V.sub.IN, the mode decision circuit 127 generates the mode signal MD which indicates the boost mode (for example but not limited by, MD=10).

[0102] When the relationship between the input voltage V.sub.IN and the output voltage Vox is as: V.sub.IN >V.sub.OX*(m-1)/m+V.sub.hys, the mode decision circuit 127 generates the mode signal MD which indicates the buck-boost mode (for example but not limited by, MD=01).

[0103] When the relationship between the input voltage V.sub.IN and the output voltage Vox is as: V.sub.IN <V.sub.OX+V.sub.T, the mode decision circuit 127 generates the mode signal MD which indicates the buck-boost mode (for example but not limited by, MD=01).

[0104] When the relationship between the input voltage V.sub.IN and the output voltage Vox is as: V.sub.IN>V.sub.OX+V.sub.T+V.sub.hys, the mode decision circuit 127 generates the mode signal MD which indicates the buck mode (for example but not limited by, MD=00).

[0105] FIG. 8 shows the waveforms of the FIFO and priority logic 123 according to one embodiment of the application.

[0106] The FIFO and priority logic 123 loads the input signals (i.e. the voltage comparator output signals CP.sub.1~CP.sub.m and/or CP.sub.N) at the positive edge of the valley current VC with pre-set priority.

[0107] While more than one of the input signals concurrently go high at the positive edge of the valley current VC, all the high signals will be loaded into the FIFO and priority logic 123 with higher priority signals being placed first into the FIFO and priority logic 123.

[0108] The signal loaded first into the FIFO and priority logic 123 will be also first dumped out at the positive edge of the valley current VC signal. Only one output is selected in each time slot between two VC signals.

[0109] As shown in FIG. 8, at the first positive edge of the valley current VC, only the input signal CP.sub.1 goes high. The high signal CP.sub.1 is loaded into the FIFO and priority logic 123; and the signal CP.sub.1 loaded first into the FIFO and priority logic 123 is also first dumped out as the signal CT.sub.1 at the first positive edge of the valley current VC.

[0110] As shown in FIG. 8, at the second positive edge of the valley current VC, the input signals CP.sub.2 and CP.sub.3 go high at the same time. It is assumed that the priority is CP.sub.1>CP.sub.2>CP.sub.3... > CP.sub.N. The high signals CP.sub.2 and CP.sub.3 will be loaded into the FIFO and priority logic 123. In details, the high signal CP.sub.2 having priority higher than the high signal CP.sub.3 is first placed into the FIFO and priority logic 123, and the first-loaded high signal CP.sub.2 is first dumped out as the signal CT.sub.2 at the second positive edge of the valley current VC. Then, the high signal CP.sub.3 having lower priority is placed into the FIFO and priority logic 123, and the second-loaded high signal CP.sub.3 is second dumped out as the signal CT.sub.3 at the third positive edge of the valley current VC.

[0111] By so, the FIFO and priority logic 123 loads the input signals (i.e. the voltage comparator output signals CP.sub.1~CP.sub.m and/or CP.sub.N) at the positive edges of the valley current VC with pre-set priority and dumped out at the positive edge of the valley current VC. The priority is assumed as CP.sub.1>CP.sub.2>CP.sub.3... > CP.sub.N in this example. However, the proposed method is not limited by this priority assumption and different priority assumption can be also achieved by modifying the priority logic apparently.

[0112] Operations of the TMCCT control logic 125 are described.

[0113] The mode signal MD means the power conversion mode for the selected channel, which can be buck, buck-boost, boost or inverting modes. The mode signal is generated from the mode decision circuit 127.

[0114] While a channel x is selected, the signal CTx will be high for the whole time slot between two valley current VC signals. The signal CTx is output from the FIFO and priority logic 123 as shown in FIG. 8.

[0115] For buck-boost conversion, the peak current signal PK13 terminates the 13 phase (i.e. the switches SW1 and SW3 are conducted) and the 1O.sub.x phase (i.e. the switches SW1 and SWO.sub.x are conducted) is following. The peak current signal PK13 is generated from the peak current detector 131.

[0116] The Inductor current charging phases for all conversion modes are terminated by the peak current signal PKC which is generated from the peak current detector 131.

[0117] The peak current signals PKC and PK13 are response to the control voltage V.sub.CX to transfer a constant charge Q.sub.Ox0 to the selected channel at the discontinuous conduction mode (DCM).

[0118] The inductor discharging phases for all conversion modes are terminated by the inductor current I.sub.L discharged to the valley current level.

[0119] The valley current level is response to the valley current detector 135.

[0120] The channel selection signal CHS is used to inform the mode decision circuit 127 and the control voltage generator 129 to indicate the selected channel under processed.

[0121] The signal CG generated by the TMCCT control logic 125 is to reset and enable the peak current detector 131 that generates the peak current signals PKC and PK13.

[0122] The control voltage generator 129 generates the control voltage V.sub.CX based on the channel select signal CHS, the mode signal MD, the input voltage VIN and the output voltages V.sub.O1, V.sub.O2, ..., V.sub.Om, V.sub.N. The channel select signal CHS indicates the selected channel to be processed of this time slot. The mode signal MD means power conversion mode for the selected channel, which can be buck, buck-boost, boost or inverting modes.

[0123] The control voltage VCX will be generated with response to the required conversion mode, the predetermined constant output charge Q.sub.Ox0, the input voltage and the output voltage levels of the selected channel, as shown by equations above and in FIG. 6A to FIG. 6D.

[0124] FIG. 9A shows a circuit diagram of the valley voltage generator 133 and the valley current detector 135 according to one embodiment of the application. FIG. 9B shows the waveforms of the valley voltage generator 133 and the valley current detector 135 according to one embodiment of the application.

[0125] The valley voltage generator 133 according to one embodiment of the application includes an inverter 133_1, a MOS transistor 133_2, a first current source 133_3, a second current source 133_4, a MOS transistor 133_5, a resistor Rv and a capacitor Cv.

[0126] The inverter 133_1 receives the minimum-on-time pulse signal MOT and outputs the inverted MOT to the gate of the MOS transistor 133_2. The minimum-on-time pulse signal MOT has a predetermined on-time and is triggered by the positive edge of the switch control signal S.sub.1.

[0127] The MOS transistor 133_2 has a first terminal (for example but not limited by a source terminal) coupled to the input voltage V.sub.IN, a second terminal (for example but not limited by a drain terminal) coupled to the first current source 133_3 and a control terminal (for example but not limited by a gate terminal) receiving the inverted MOT.

[0128] The first current source 133_3 is coupled to the MOS transistor 133_2 for generating a first constant current I1.

[0129] The second current source 133_4 is coupled to the MOS transistor 133_5 for generating a second constant current I2.

[0130] The MOS transistor 133_5 has a first terminal (for example but not limited by a source terminal) coupled to the second current source 133_4, a second terminal (for example but not limited by a drain terminal) coupled to ground and a control terminal (for example but not limited by a gate terminal) receiving the FW time period (the FW time period is generated by the AND logic 139 based on the switch control signals S.sub.2 and S.sub.3).

[0131] The resistor Rv is coupled to the first current source 133_3 and the second current source 133_4.

[0132] The capacitor Cv is coupled to the resistor Rv.

[0133] While the valley voltage V.sub.VLLY is equal to zero, the valley current I.sub.VLLY is also zero. While the valley voltage V.sub.VLLY goes higher, the valley current I.sub.VLLY also goes higher. Longer FW time period makes the valley voltage V.sub.VLLY lower gradually even till zero. While FW time period is short enough, the valley voltage V.sub.VLLY goes higher till FW time period becomes shorter than a predetermined value (t.sub.A) and longer than another predetermined value (t.sub.B).

[0134] FIG. 10 shows an example of switch logic waveforms according to one embodiment of the application.

[0135] In the first positive edge of the valley current VC, the FIFO and priority logic 123 generates the high signal CT.sub.1. Based on the high signal CT.sub.1, the TMCCT control logic 125 generates the high signals ST.sub.1 and ST.sub.3. In response to the high signals ST.sub.1 and ST.sub.3, the logic control and gate driver 150 generates the high switch control signals S.sub.1 and S.sub.3 to conduct the switches SW1 and SW3. Because the switches SW1 and SW3 are turned on, energy is transferred from the input voltage V.sub.IN to the inductor L.sub.1. Thus, the inductor current I.sub.L is increased. During the inductor charging phase, when the inductor current I.sub.L is increased from the DC current I.sub.DC (equal to the valley current I.sub.VLLY) to “I.sub.DC+I.sub.PK1Ox”, the peak current signal PKC is triggered by the peak current detector 131. In response to the peak current signal PKC, the TMCCT control logic 125 generates the signal ST.sub.O1 and RS.sub.3; and in response the signal RS.sub.3, the logic control and gate driver 150 generates a low signal S.sub.3 to turn-off the SW3 and the high signal S.sub.1 and S.sub.O1 to turn-on the switches SW1 and SWO.sub.1 for discharging the inductor current I.sub.L to the output node, till the inductor current I.sub.L to zero.

[0136] Other switching cycles are similar and thus the details are omitted.

[0137] As described above, one embodiment of the application provides a single inductor multiple-output (or SIMBO) DC-DC converter comprising: a time multiplexing constant charge transferred (TMCCT) control logic having valley current control by transferring electrical energy to output sequentially (1-by-1), a control voltage generator generating a control voltage V.sub.CX to the peak current detector to control the respective output charges of the output channels as respective constant predetermined values. Also, the valley current is response to the load current (i.e. the current sense I.sub.SNS) to a value that can make input and output power be balance so that the SIMO or SIMBO DC-DC converter can operate at both DCM and CCM.

[0138] Still further, in one embodiment of the application, each conversion for each positive output V.sub.O1~V.sub.Om can be operated at the buck, the boost or the buck-boost mode in response to the input voltage V.sub.IN and the output voltage conditions.

[0139] Still further, in one embodiment of the application, one of the outputs can be operated at inverting mode (i.e. one of the outputs can have negative output voltage).

[0140] Still further, in one embodiment of the application, the conversion mode of the selected channel is decided by the mode decision circuit.

[0141] Still further, in one embodiment of the application, the valley current level is in response to freewheel (FW) duty cycles. If the freewheel (FW) duty cycle is larger than a first time interval t.sub.A, the valley current level is decreased; and if the freewheel (FW) duty cycle is smaller a second time interval t.sub.B the valley current level is increased. The first time interval is equal to or larger than the second time interval. The valley current level is equal to or larger than zero value.

[0142] Still further, in one embodiment of the application, the control circuit 120 is in response to each output and the FIFO and Priority circuit decides the selected output channel for the time instance.

[0143] Still further, in one embodiment of the application, the TMCCT control logic decides the switching sequence for the selected channel in response to outputs from the valley current detector, the peak current detector, and the mode decision circuit.

[0144] Still further, in one embodiment of the application, for loading that DCM cannot support, the valley voltage generator and the valley current detector will raise the valley current to increase the output current capability as a CCM.

[0145] Still further, in one embodiment of the application, the power stage (110) can be multiple positive output rails and multiple negative output rails.

[0146] The application gains some of the limited space in the space-constrained electronic products back by using the single-inductor multiple-output (SIMO) or SIMBO DC-DC converter architecture. The SIMO or SIMBO architecture enables to extend battery life for space-constrained electronic products.

[0147] It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.