Bias Power Supply Apparatus and Control Method

An apparatus includes a first switch connected between an input voltage bus of a hybrid switched capacitor converter and an input of a bias power regulator, a second switch connected between a first switching node of the hybrid switched capacitor converter and the input of the bias power regulator, wherein the second switch is configured such that when the second switch is turned on, a voltage on the first switching node is equal to (N/M) of a voltage on the input voltage bus, a third switch connected between a second switching node of the hybrid switched capacitor converter and the input of the bias power regulator, wherein the third switch is configured such that when the third switch is turned on, a voltage on the second switching node is equal to (L/M) of the voltage on the input voltage bus.

TECHNICAL FIELD

The present invention relates to a bias power supply apparatus and control method, and, in particular embodiments, to a bias power supply apparatus and control method for efficiently operating a hybrid switched capacitor power converter.

BACKGROUND

Data centers often employ a power conversion system having a 12-V voltage bus. The 12-V bus voltage is generated from an ac/dc power supply. Alternatively, the 12-V bus voltage is converted from a 48-V voltage bus. The 12-V bus is further converted into low voltages, such as 0.7V, 1.0V, 1.2V, 1.5V, 1.8V and the like to power up different system loads including central processing units (CPUs), graphics processing units (GPUs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), communication input/output (I/O) bus voltages and the like.

As the power level has been increasing dramatically in recent developments of fast/large scale processors, the power losses in the power supplies that power up these system loads also increase dramatically. Additional heat management devices are required to remove the heat generated by the additional power losses from these power supplies, resulting in product cost increases.

Hybrid power converters have drawn much attention recently to replace the commonly used buck converters in the applications where a sub 1V output voltage is generated from a 12-V bus voltage.FIG.1shows a hybrid converter with a single flying capacitor. The power conversion system100shown inFIG.1comprises one input filtering capacitor101, four switches S101, S102, S103, S104, one flying capacitor106, two output inductors107,108, and one output filtering capacitor109. The power conversion system100further comprises one low-dropout (LDO) regulator113and one LDO output capacitor114.

FIG.2illustrates various waveforms associated with the hybrid converter shown inFIG.1. In one switching period (Ts), there are four time intervals. A first time interval T1is from t0to t1. A second time interval T2is from t1to Ts/2. A third time interval T3is from Ts/2 to t3. A fourth time interval T4is from t3to Ts. In steady state operation, T1is equal to T3. T2is equal to T4. The duty cycle of the hybrid converter is denoted as D. D is equal to T1/Ts or T3/Ts.

In the T1interval, switches S101and S104are turned on. Power is delivered from the input Vin to the output capacitor109through the power switch S101, the flying capacitor106and the inductor108. The flying capacitor106and the output inductor108are charged. In the T1interval, energy stored in the inductor107is discharged to the output capacitor109through the switch S104. The voltage on the switching node110is equal to Vin minus the voltage V106across the flying capacitor106. The voltage on the switching node111is equal to zero.

In the T2interval, switches S103and S104are turned on, and switches S101and S102are turned off. Energy stored in the output inductors107and108are discharged to the output capacitor109. No power is transferred from the input Vin to the output capacitor109in this interval.

In the T3interval, switches S102and S103are turned on, and switches S101and S104are turned off. Energy stored in the flying capacitor106is discharged to the output capacitor109through the switch S103, the switch S102and the output inductor107. The output inductor107is charged. The energy stored in the output inductor108is discharged to the output capacitor109through the switch S103. Voltages on switching nodes112and111are equal to V106. The voltage on the switching node110is equal to zero. No power is transferred from the input Vin to the output.

In the T4interval, switches S103and S104are turned on, and switches S101and S102are turned off. Energy stored in the output inductors107and108are discharged to the output capacitor109. No power is transferred from the input Vin to the output capacitor109in this interval.

According to the description above, the average voltages on switching nodes110and111over one switching cycle are given in the following equations:

In Equation (1), V110_AVG is the average voltage on the switching node110. In Equation (2), V111_AVG is the average voltage on the switching node111. In steady state operation, the average voltages of switching nodes110and111must be equal, otherwise, the voltage difference between V110_AVG and V111_AVG generates a de current flowing through the output inductors107and108. This dc current discharges or charges the flying capacitor106until V110_AVG is equal to V111_AVG. Once V110_AVG is equal to V111_AVG, the following equation holds:

Since T1is equal to T3, the following equation can be obtained:

When the power conversion system100is integrated into a monolithic IC, a bias supply (e.g., a 5-V bias power supply) is needed to power up the internal control and driver circuitry to operate the power conversion system100properly. A simple way is to use a LDO to generate the 5-V bias supply from the input Vin as shown inFIG.1. This bias power supply may cause a significant power loss. For example, Vin is equal to 12 V. The output voltage of the bias LDO is 5 V. The current flowing through the LDO is about 50 mA. If Vin is directly applied to the input of the LDO, the power loss is about 350 milliwatts. This power loss prevents the power conversion system100from achieving high efficiency. It would be desirable to have an efficient bias power supply apparatus to reduce the losses in the LDO. The present disclosure addresses this need.

SUMMARY

These and other problems are generally solved or circumvented, and technical advantages are generally achieved, by preferred embodiments of the present disclosure which provide a bias power supply apparatus and control method for efficiently operating a hybrid switched capacitor power converter.

In accordance with an embodiment, an apparatus comprises a first switch connected between an input voltage bus of a hybrid switched capacitor converter and an input of a bias power regulator, a second switch connected between a first switching node of the hybrid switched capacitor converter and the input of the bias power regulator, wherein the second switch is configured such that when the second switch is turned on, a voltage on the first switching node is equal to (N/M) of a voltage on the input voltage bus, and a third switch connected between a second switching node of the hybrid switched capacitor converter and the input of the bias power regulator, wherein the third switch is configured such that when the third switch is turned on, a voltage on the second switching node is equal to (L/M) of the voltage on the input voltage bus, and wherein L, M and N are positive integers, N is less than M, and L is less than M.

In accordance with another embodiment, a method comprises in a startup process of a hybrid switched capacitor converter, configuring an input of a bias power regulator to be connected to an input voltage bus of the hybrid switched capacitor converter through a first switch, and after the startup process of the hybrid switched capacitor converter finishes, configuring the input of the bias power regulator to be connected to a first switching node and/or a second switching node of the hybrid switched capacitor converter through a second switch and/or a third switch, respectively, wherein the second switch and the third switch are configured such that a voltage on the input of the bias power regulator is equal to (L/M) of a voltage on the input voltage bus, and wherein L and M are positive integers, and M is greater than L.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present disclosure will be described with respect to preferred embodiments in a specific context, namely a bias power supply apparatus and control method for efficiently operating a hybrid switched capacitor power converter. The disclosure may also be applied, however, to a variety of power converters. Hereinafter, various embodiments will be explained in detail with reference to the accompanying drawings.

FIG.3illustrates a block diagram of a bias power supply apparatus and the associated hybrid switched capacitor converter in accordance with various embodiments of the present disclosure. The hybrid switched capacitor converter150is connected between an input voltage bus Vin and ground. Two switching nodes SW1and SW2of the hybrid switched capacitor converter150are connected to the bias power supply apparatus155. The hybrid switched capacitor converter150has an output Vout configured to generate a steady voltage providing power for various loads coupled to the output of the hybrid switched capacitor converter150.

In some embodiments, the hybrid switched capacitor converter150is implemented as a single-phase hybrid switched capacitor converter. The detailed structure and operating principle of this implementation will be described below with respect toFIGS.4-6. In alternative embodiments, the hybrid switched capacitor converter150is implemented as a dual-phase hybrid switched capacitor converter. The detailed structure and operating principle of this implementation will be described below with respect toFIGS.7-11.

The bias power supply apparatus155comprises a first switch S1, a second switch S2, a third switch S3, a bias power regulator152and a bias output capacitor Co. In some embodiments, the bias power regulator152is implemented as a bias LDO. The bias LDO is configured to convert an input voltage fed into the bias LDO into a suitable bias voltage VCC (e.g., 5 V). Throughout the description, the bias power regulator152may be alternatively referred to as a bias LDO152.

As shown inFIG.3, the first switch S1is connected between the input voltage bus Vin and the input of the bias power regulator152. The second switch S2is connected between a first switching node SW1of the hybrid switched capacitor converter150and the input of the bias power regulator152. The third switch S3is connected between a second switching node SW2of the hybrid switched capacitor converter150and the input of the bias power regulator152.

In operation, in a startup process, the first switch S1is turned on, and the second switch S2and the third switch S3are turned off. The voltage on the input voltage bus Vin is configured to provide power for the bias power regulator152. Once the voltages on the switching nodes have been fully established, the voltage on SW1and/or the voltage on SW2are configured to provide power for the bias power regulator152.

In operation, when the hybrid switched capacitor converter150is implemented as a single-phase hybrid switched capacitor converter, the second switch S2and the third switch S3are configured to operate in two different operating modes (e.g., the first two operating modes described below). When the hybrid switched capacitor converter150is implemented as a dual-phase hybrid switched capacitor converter, the second switch S2and the third switch S3are configured to operate in three different operating modes (e.g., three operating modes described below).

In a first operating mode, a voltage on the first switching node SW1is equal to a fraction (e.g., one half) of a voltage on the input voltage bus, and a voltage on the second switching node SW2is not equal to the fraction (e.g., one half) of the voltage on the input voltage bus. The third switch S3is configured to be turned off. The second switch S2is configured to be turned on so that the voltage on the first switching node SW1is configured to provide power for the bias power regulator152. The first operating mode is applicable to both the single-phase hybrid switched capacitor converter and the dual-phase hybrid switched capacitor converter.

In a second operating mode, a voltage on the first switching node SW1is not equal to a fraction (e.g., one half) of a voltage on the input voltage bus, and a voltage on the second switching node SW2is equal to the fraction (e.g., one half) of the voltage on the input voltage bus. The second switch S2is configured to be turned off. The third switch S3is configured to be turned on so that the voltage on the second switching node SW2is configured to provide power for the bias power regulator152. The second operating mode is applicable to both the single-phase hybrid switched capacitor converter and the dual-phase hybrid switched capacitor converter.

In a third operating mode, a voltage on the first switching node SW1is equal to a fraction (e.g., one half) of a voltage on the input voltage bus, and a voltage on the second switching node SW2is equal to the fraction (e.g., one half) of the voltage on the input voltage bus. Either one of the third switch S3and the second switch S2can be configured to be turned on, or both the third switch S3and the second switch S2are configured to be turned on so that the voltage on the first switching node SW1and/or the voltage on the second switching node SW2are configured to provide power for the bias power regulator152separately or concurrently. The third operating mode is applicable to the dual-phase hybrid switched capacitor converter.

The hybrid switched capacitor converter150may be implemented as different hybrid switched capacitor converters. Depending on the power topology difference, the voltages on the first switching node and the second switching node may vary accordingly. In operation, the second switch S2is configured such that when the second switch S2is turned on, a voltage on the first switching node SW1is equal to (L/M) of the voltage on the input voltage bus. The third switch S3is configured such that when the third switch S3is turned on, a voltage on the second switching node SW2is equal to (L/M) of the voltage on the input voltage bus. L and M are positive integers. L is less than M. In some embodiments (e.g., the hybrid switched capacitor converter shown inFIG.4), L is equal to 1. M is equal to 2. In some embodiments (e.g., the hybrid switched capacitor converter shown inFIG.6), L is equal to 1. M is equal to 3. In some embodiments (e.g., the hybrid switched capacitor converter shown inFIG.11), L is equal to 2. M is equal to 3.

FIG.4illustrates a schematic diagram of a first implementation of the hybrid switched capacitor converter shown inFIG.3in accordance with various embodiments of the present disclosure. The power conversion system200shown inFIG.4comprises a hybrid switched capacitor converter and a bias power supply apparatus220. The hybrid switched capacitor converter is a single-phase hybrid switched capacitor converter. The hybrid switched capacitor converter comprises an input capacitor201, a first power switch S201, a second power switch S202, a third power switch S203, a fourth power switch S204, a flying capacitor206, a first inductor208, a second inductor207and an output capacitor209. The bias power supply apparatus220comprises a first switch S1, a second switch S2, a third switch S3, a bias LDO224, a bias capacitor226and a bias output capacitor225.

As shown inFIG.4, the first power switch S201, the flying capacitor206and the third power switch S203are connected in series between the input voltage bus Vin and ground. The second power switch S202and the fourth power switch S204are connected in series between a common node of the first power switch S201and the flying capacitor206, and ground. The first inductor208is connected between a common node of the flying capacitor206and the third power switch S203, and an output voltage bus of the hybrid switched capacitor converter. The second inductor207is connected between a common node of the second power switch S202and the fourth power switch S204, and the output voltage bus of the hybrid switched capacitor converter.

Referring back toFIG.3, the common node212of the first power switch S201and the flying capacitor206is the first switching node SW1of the hybrid switched capacitor converter. The common node210of the flying capacitor206and the third power switch S203is the second switching node SW2of the hybrid switched capacitor converter.

The bias power supply apparatus220has three inputs. A first input is the input voltage bus Vin. A second input is the first switching node212. A third input is the second switching node210. The bias power regulator224is coupled to the input voltage bus Vin through the first switch S1. The bias power regulator224is coupled to the first switching node212through the second switch S2. The bias power regulator224is coupled to second switching node210through the third switch S3. The bias capacitor226is connected between the input of the bias power regulator224and ground.

In operation, before a steady voltage has been established across the flying capacitor206, the first switch S1is turned on to power up the bias power regulator224to generate a bias voltage VCC. During this time period, the second switch S2and the third switch S3are turned off. Once the hybrid switched capacitor converter is in normal operation and the voltage across the flying capacitor206is equal to one half of the voltage on the input voltage bus, the first switch S1is turned off, and the second switch S2and the third switch S3are turned on/off alternately based on the switching status of switches S203and S201. More specifically, the second switch S2is turned on/off in sync with the third power switch S203. The third switch S3is turned on/off in sync with an inverted signal of the gate drive signal of the third power switch S203. The second switch S2and the third switch S3are configured such that the input voltage of the bias power regulator224is maintained at a level equal to one half of Vin. By lowering the input voltage to one half of Vin, the power dissipation can be reduced accordingly. For example, the bias power regulator is an LDO. Vin is equal to 12 V. The output voltage of the bias power regulator224is 5 V. The current flowing through the LDO is about 50 mA. If Vin is directly applied to the input of the LDO, the power loss is about 350 milliwatts. In contrast, the control scheme described above can reduce the input voltage of the LDO from 12 V to 6 V. Accordingly, the power loss can be reduced from 350 milliwatts to 50 milliwatts. In some embodiments, the output voltage of the hybrid switched capacitor converter is 0.7 V. The load current of the hybrid switched capacitor converter is about 50 A. The reduced power loss (300 milliwatts) may improve the efficiency of the hybrid switched capacitor converter by about 1%.

FIG.5illustrates various waveforms associated with the circuit shown inFIG.4in accordance with various embodiments of the present disclosure. The horizontal axis ofFIG.5represents intervals of time. There may be eight rows inFIG.5. The first row represents the gate drive signals of the first power switch S201and the third switch S3. The second row represents the gate drive signals of the third power switch S203and the second switch S2. The third row represents the gate drive signal of the second power switch S202. The fourth row represents the gate drive signal of the fourth power switch S204. The fifth row represents the voltage on the input node227of the bias LDO224. The sixth row represents the voltage on the node211. The seventh row represents the voltage on the node212(SW1). The eighth row represents the voltage on the node210(SW2).

A switching period Ts of the hybrid switched capacitor converter includes four consecutive time intervals. A first time interval T1is from t0to t1. A second time interval T2is from t1to Ts/2. A third time interval T3is from Ts/2 to t3. A fourth time interval T4is from t3to Ts.

According to the operating principle of the single-phase hybrid switched capacitor converter, in normal operation, the voltage V206across the flying capacitor206is equal to one half of the input voltage Vin.

In operation, before a steady voltage has been established across the flying capacitor206, the first switch S1is turned on to power up the bias power regulator224to generate a bias voltage VCC. During this time period, the second switch S2and the third switch S3are turned off. Once the hybrid switched capacitor converter is in normal operation and the voltage across the flying capacitor206is equal to one half of the voltage on the input voltage bus, the first switch S1is turned off, and the second switch S2and the third switch S3are turned on/off alternately.

In the first time interval T1, the gate drive signals indicate that the first power switch S201, the fourth power switch S204and the third switch S3are turned on. The second power switch S202, the third power switch S203and the second switch S2are turned off. Since S204is turned on, the voltage on the node211is equal to zero. Since S201is turned on, the voltage on the first switching node212is equal to Vin. The voltage across the flying capacitor206tis equal to Vin/2. As such, the voltage on the second switch node210is equal to Vin/2. In the first time interval T1, the third switch S3is turned on. The voltage on the second switching node210is configured to provide power for the bias power regulator224. In other words, the bias power regulator224draws power from the input voltage bus through S201and the flying capacitor206. The voltage on the node227is equal to Vin/2. The voltage difference between the input voltage Vin and the voltage on the node227is dropped across the flying capacitor206. Instead of dissipating the power in the bias power regulator224, the current I224flowing through the bias power regulator224charges the flying capacitor206to store the energy in the flying capacitor206.

In a second time interval T2, the gate drive signals indicate that the third power switch S203, the fourth power switch S204and the second switch S2are turned on. The first power switch S201, the second power switch S202and the third switch S3are turned off. Since S203is turned on, the voltage on the second switching node210is equal to zero. Since S204is turned on, the voltage on the node211is equal to zero. The voltage on the first switching node212is equal to Vin/2. In the second time interval T2, the second switch S2is turned on. The flying capacitor206coupled to the first switching node212is configured to provide power for the bias power regulator224. In the second time interval T2, the flying capacitor206is discharged by the current I224flowing through the bias power regulator224.

In the second time interval T2, the third switch S3is turned off to prevent the voltage on the node227from being pulled down to ground by the third power switch S203. The second switch S2is turned on to maintain the voltage on the node227equal to Vin/2.

In the third time interval T3, the gate drive signals indicate that the second power switch S202, the third power switch S203and the second switch S2are turned on. The first power switch S201, the fourth power switch S204and the third switch S3are turned off. Since S203is turned on, the voltage on the second switching node210is equal to zero. The voltage across the flying capacitor206tis equal to Vin/2. The voltage on the first switching node212is equal to Vin/2. Since S202is turned on, the voltage on the node211is equal to Vin/2. The flying capacitor206coupled to the first switching node212is configured to provide power for the bias power regulator224. In the third time interval T3, the flying capacitor206is discharged by both the current I224flowing through the bias power regulator224and the current I207flowing through the inductor207.

In the fourth time interval T4, the gate drive signals indicate that the third power switch S203, the fourth power switch S204and the second switch S2are turned on. The first power switch S201, the second power switch S202and the third switch S3are turned off. Since S203is turned on, the voltage on the second switching node210is equal to zero. Since S204is turned on, the voltage on the node211is equal to zero. The voltage on the first switching node212is equal to Vin/2. In the fourth time interval T2, the second switch S2is turned on. The flying capacitor206coupled to the first switching node212is configured to provide power for the bias power regulator224. In the fourth time interval T2, the flying capacitor206is discharged by the current I224flowing through the bias power regulator224.

As shown inFIG.5, the gate drive signal of the second switch S2is the same as the gate drive signal for the third power switch S203. The gate drive signal for the third switch S3is the same as the gate drive signal for the first power switch S201and complementary to the gate drive signal for the third power switch S203.

The current flowing through the bias LDO224charges the flying capacitor206in the first time interval T1and discharges the flying capacitor206during the rest of the switching period. This means that due to the bias LDO current I224, the net charge on the flying capacitor206is not equal to zero, resulting in the decrease of the average voltage across the flying capacitor206. The speed of the decrease of the voltage V206across the flying capacitor206can be very slow since the bias LDO current is much smaller than the output current of the hybrid switched capacitor converter.

The decrease in the flying capacitor voltage V206can be corrected by the output inductor current. Due to the decrease of the flying capacitor voltage V206by the bias LDO current I224, the voltage V206is less than Vin/2. The variation in V206causes the inductor current I208increasing and the inductor current I207decreasing. Such a difference between two inductor currents I208and I207creates an equivalent net current. In the T1interval, the equivalent net current flows from the input Vin, the first power switch S201, the flying capacitor206, the inductors208,207, the fourth power switch S204, and returns to the input from ground. In the T3interval, the equivalent net current flows in a loop formed by the second power switch S202, the flying capacitor206, the inductors207and208. The net equivalent current charges the flying capacitor206. As a result, the voltage V206can be maintained at Vin/2 during the normal operation at the cost of having a slight difference between the two inductor currents I208and I207. The difference between the two inductor currents I208and I207depends on the bias LDO current I224. This difference can be expressed by following equation:

In Equation (5), D is equal to T1/Ts or T3/Ts. D is in a range from 0 to 0.5. From Equation (5), the worst case happens at a small duty cycle. For example, when D is equal to 0.1 and the bias LDO current is equal to 50 mA, the current difference is equal to 400 mA. On the other hand, when D is equal to 0.3, the current difference is reduced to 67 mA, which is significantly less than the full load inductor current (e.g., full load inductor current in a range from 20 A to 30 A). Therefore, at a relatively large duty cycle, for example, D is equal to 0.23 and the power conversion is from 12 V to 0.7 V. The difference between inductor current I208and I207is acceptable. In some applications, this current difference may not be acceptable. One additional capacitor226can be added to the input node227. In this case, the current charging the flying capacitor206is the sum of the inductor current I208, the bias LDO current I224, and the current I226of the capacitor226. The capacitor226is charged during the T1interval. During the T3interval, the discharging current of the flying capacitor206is equal to the sum of the inductor current I207, the bias LDO current I224, and the current I226of the capacitor226. During the T2and T4intervals, the flying capacitor206supplies the bias LDO current I224only. The amplitude of the capacitor current I226is equal to ΔIL/2. Due to the addition of the capacitor226, the charging current seen by the flying capacitor206is increased by ΔIL/2 during the T1interval and is decreased by ΔIL/2 during T3interval, resulting in a zero average current over one switching cycle. Thus, the voltage across the flying capacitor206can be maintained at a constant voltage level equal to Vin/2.

It should be noted that the addition of the capacitor226also introduces an additional function of maintaining the voltage across the flying capacitor206equal to Vin/2 under various operating conditions (e.g., temporary unbalance of the output inductor currents I208and I224caused by various unknown reasons). The capacitor226can also eliminate the voltage glitch occurred during on/off transitions of switches S2and S3.

In some applications where a higher input voltage is used (e.g., 18 V), the hybrid switched capacitor converter shown inFIG.4can be expanded to achieve a higher voltage conversion ratio by adding a plurality of expansion units.

FIG.6illustrates a schematic diagram of a second implementation of the hybrid switched capacitor converter shown inFIG.3in accordance with various embodiments of the present disclosure. The power conversion system280shown inFIG.6comprises a hybrid switched capacitor converter and a bias power supply apparatus220. The hybrid switched capacitor converter shown inFIG.6is similar to the hybrid switched capacitor converter shown inFIG.4except that an expansion unit230is added.

As shown inFIG.6, the expansion unit230comprises a first expansion power switch S231and a first expansion flying capacitor236. As shown inFIG.6, the first power switch S201, the first expansion power switch S231, the second power switch S202and the third power switch S203are connected in series between the input voltage bus Vin and ground. The first expansion flying capacitor236is connected between a common node of the second power switch S202and the fourth power switch S204, and a common node of the first power switch S201and the first expansion power switch S231.

In steady state operation, the first power switch S201and the second power switch S202are configured to turned on and off at the same time. The first expansion power switch S231and the third switch S3are configured to turn on and off at the same time. The second switch S2and the third power switch S203are configured to turned on and off together, complementary to the first expansion power switch S231. The fourth power switch S204and the second power switch S202operate in a complementary fashion. The first power switch S201and the first expansion power switch S231operate out of phase.

According to the operating principle of the single-phase hybrid switched capacitor converter, in normal operation, the voltage V206across the flying capacitor206is equal to one third of the input voltage Vin, and the voltage V236across the flying capacitor236is equal to two thirds of the input voltage Vin.

In operation, before a steady voltage has been established across the flying capacitor206, the first switch S1is turned on to power up the bias power regulator224to generate a bias voltage VCC. During this time period, the second switch S2and the third switch S3are turned off. Once the hybrid switched capacitor converter is in normal operation and the voltage across the flying capacitor206is equal to one third of the voltage on the input voltage bus, the first switch S1is turned off, and the second switch S2and the third switch S3are turned on/off alternately based on the switching status of power switch S203. More specifically, the second switch S2is turned on/off the same time as the third power switch S203, and the third switch S3is turned on/off the same time as the first expansion power switch S231, which is complementary to the third power switch S203. The second switch S2and the third switch S3are configured such that the input voltage of the bias power regulator224is maintained at a level equal to one third of Vin. In some high voltage applications (e.g., 18 V), by lowering the input voltage to one third of Vin (6 V), the power dissipation can be reduced accordingly.

Similarly, the single-phase hybrid switched capacitor converter shown inFIG.6may include N cascading expansion units230to offer a voltage conversion ratio (between VIN and the peak voltage at node SW2) of (N+2):1. Regardless of the voltage conversion ratio, the second switch S2can always be connected to the common node of the second power switch S202and the flying capacitor206(e.g., first switching node SW1shown inFIG.6). The third switch S3can always be connected to the common node of the third power switch S203an and the flying capacitor206(e.g., second switching node SW2shown inFIG.6).

During steady state operation, the second switch S2is turned on/off the same time as the third power switch S203. In other words, the second switch S2is turned on and off in sync with the third power switch S203. The third switch S3is turned on/off complementary to the third power switch S203. S2and S3are configured such that input voltage of the bias power regulator224is maintained at a level equal to 1/(N+2) of Vin. By lowering the input voltage to 1/(N+2) of Vin, the power dissipation can be reduced accordingly.

As described above, through cascading different number of expansion units230to the single-phase hybrid switched capacitor converter and connecting the second and third switches to the two terminals of the flying capacitor (e.g., flying capacitor206) connected to the third power switch S203, all unit fractions (½, ⅓, ¼, etc.) of the input voltage Vin can be supplied to the bias power regulator224during steady state operation. The various input voltage options of the bias power regulator224offer flexibility to designers in achieving a higher efficiency power conversion for power converters having a very wide input voltage range.

FIG.7illustrates a schematic diagram of a third implementation of the hybrid switched capacitor converter shown inFIG.3in accordance with various embodiments of the present disclosure. The power conversion system300shown inFIG.7comprises a hybrid switched capacitor converter and a bias power supply apparatus320. The hybrid switched capacitor converter is a dual-phase hybrid switched capacitor converter. The hybrid switched capacitor converter comprises an input capacitor301, a first power switch S301, a second power switch S302, a third power switch S303, a fourth power switch S304, a fifth power switch S305, a sixth power switch S306, a first flying capacitor305, a second flying capacitor315, a first inductor306, a second inductor316and an output capacitor310. The bias power supply apparatus320comprises a first switch S1, a second switch S2, a third switch S3, a bias LDO324and a bias output capacitor325.

As shown inFIG.7, the first power switch S301, the second power switch S302and the third power switch S303are connected in series between the input voltage bus Vin and ground. The fourth power switch S304, the fifth power switch S305and the sixth power switch S306are connected in series between the input voltage bus Vin and ground. The first flying capacitor305is connected between a common node307of the first power switch S301and the second power switch S302, and a common node318of the fifth power switch S305and the sixth power switch S306. The second flying capacitor315is connected between a common node317of the fourth power switch S304and the fifth power switch S305, and a common node308of the second power switch S302and the third power switch S303. The first inductor306is connected between the common node308of the second power switch S302and the third power switch S303, and an output voltage bus Vout of the hybrid switched capacitor converter. The second inductor316is connected between the common node318of the fifth power switch S305and the sixth power switch S306, and the output voltage bus Vout of the hybrid switched capacitor converter.

Referring back toFIG.3, the common node317of the fourth power switch S304and the fifth power switch S305is the first switching node SW1of the hybrid switched capacitor converter. The common node307of the first power switch S301and the second power switch S302is the second switching node SW2of the hybrid switched capacitor converter.

In operation, before a steady voltage has been established across the flying capacitors305and315, the first switch S1is turned on to power up the bias power regulator324to generate a bias voltage VCC. During this time period, the second switch S2and the third switch S3are turned off. Once the hybrid switched capacitor converter is in normal operation and the voltages across the flying capacitors305and315are equal to one half of the voltage on the input voltage bus, the first switch S1is turned off, and the second switch S2and the third switch S3are turned on/off based on the switching status of switches S303and S306, respectively. The second switch S2and the third switch S3are configured such that the input voltage of the bias power regulator324is maintained at a level equal to one half of Vin.

FIG.8illustrates various waveforms associated with the circuit shown inFIG.7in accordance with various embodiments of the present disclosure. The horizontal axis ofFIG.8represents intervals of time. There may be seven rows inFIG.8. The first row represents the gate drive signals of the first power switch S301and the fifth power switch S305. The second row represents the gate drive signals of the sixth power switch S306and the third switch S3. The third row represents the gate drive signals of the second power switch S302and the fourth power switch S304. The fourth row represents the gate drive signals of the third power switch S303and the second switch S2. The fifth row represents the voltage on the node317(the first switching node SW1). The sixth row represents the voltage on the node307(the second switching node SW2). The seventh row represents the voltage on the input326of the bias LDO324.

A switching period of the hybrid switched capacitor converter includes four consecutive time intervals. A first time interval T1is from t0to t1. A second time interval T2is from t1to Ts/2. A third time interval T3is from Ts/2 to t3. A fourth time interval T4is from t3to Ts.

According to the operating principle of the dual-phase hybrid switched capacitor converter, the voltage across the first flying capacitor305is equal to one half of the input voltage Vin as shown inFIG.7. Likewise, the voltage across the second flying capacitor315is equal to one half of the input voltage Vin as shown inFIG.7.

In the first time interval T1, the gate drive signals indicate that the first power switch S301, the third power switch S303, the fifth power switch S305and the second switch S2are turned on. The second power switch S302, the fourth power switch S304, the sixth switch S306and the third switch S3are turned off. Since S301is turned on, the voltage on the node307is equal to Vin. Since S303is turned on, the voltage on the node317is equal to Vin/2. S2is turned on. The voltage on the node317is fed into the bias power regulator324. As such, the voltage on the node326is equal to Vin/2. In the first time interval T1, the second flying capacitor315coupled to the first switching node317is configured to provide power for the bias power regulator324.

In the second time interval T2, the gate drive signals indicate that third power switch S303, the sixth power switch S306, the second switch S2and the third switch S3are turned on. The first power switch S301, the second power switch S302, the fourth power switch S304and the fifth switch S305are turned off. Since S303and S306are turned on, the voltages on the first switching node317and the second switching node307are equal to one half of the voltage on the input voltage bus. Both the first flying capacitor305and the second flying capacitor315are configured to provide power for the bias power regulator324.

In the third time interval T3, the gate drive signals indicate that the second power switch S302, the fourth power switch S304, the sixth switch S306and the third switch S3are turned on. The first power switch S301, the third power switch S303, the fifth power switch S305and the second switch S2are turned off. Since S304is turned on, the voltage on the node317is equal to Vin. Since S306is turned on, the voltage on the node307is equal to Vin/2. S3is turned on. The voltage on the node307is fed into the bias power regulator324. As such, the voltage on the node326is equal to Vin/2. In the third time interval T3, the first flying capacitor305coupled to the second switching node307is configured to provide power for the bias power regulator324.

In the fourth time interval T4, the gate drive signals indicate that third power switch S303, the sixth power switch S306, the second switch S2and the third switch S3are turned on. The first power switch S301, the second power switch S302, the fourth power switch S304and the fifth switch S305are turned off. Since S303and S306are turned on, the voltages on the first switching node317and the second switching node307are equal to one half of the voltage on the input voltage bus. Both the first flying capacitor305and the second flying capacitor315are configured to provide power for the bias power regulator324.

In operation, the flying capacitor305is charged by the inductor current I316during the T1interval, and is discharged by partial of the bias LDO current I324during the rest of the switching period. On the other hand, the flying capacitor315is charged by the inductor current I306during the T3interval, and is discharged by partial of the bias LDO current I324during the rest of the switching period. The operation of the dual-phase hybrid switched capacitor converter is not disturbed by powering the bias LDO324from the flying capacitors305and315. Since both switches S2and S3are turned on during the intervals T2and T4, there is not glitch at the input node326during the switching transitions of the switches S2and S3. Thus, there is no need to add an additional capacitor at the input node326.

FIG.9shows three different operating modes of the circuit shown inFIG.7in accordance with various embodiments of the present disclosure. Referring back toFIGS.7-8, during T1, S301, S303and S305are turned on. The first flying capacitor305and the second flying capacitor315are connected in series between Vin and ground. The voltage across the second flying capacitor315is fed into the bias LDO324. The equivalent circuit of this flying capacitor configuration is shown in the dashed rectangle902.

Referring back toFIGS.7-8, during T3, S302, S304and S306are turned on. The second flying capacitor315and the first flying capacitor305are connected in series between Vin and ground. The voltage across the first flying capacitor305is fed into the bias LDO324. The equivalent circuit of this flying capacitor configuration is shown in the dashed rectangle904.

Referring back toFIGS.7-8, during T2and T4, S303and S306are turned on. The first flying capacitor305and the second flying capacitor315are connected in parallel. Both S2and S3are turned on. Both the voltage across the first flying capacitor305and the voltage across the second flying capacitor315are fed into the bias LDO324concurrently. The equivalent circuit of this flying capacitor configuration is shown in the dashed rectangle906.

As shown in the dashed rectangles902and904, the two flying capacitors are connected in series. This means that if the sum of the voltages across the two flying capacitors is less than Vin, a charging current from the input Vin to ground charges the flying capacitors to make the sum of their voltages equal to Vin. The bias LDO input drawing power from the flying capacitors does not disturb the normal operation of the dual-phase hybrid switched capacitor converter.

In operation, if the voltages across the flying capacitors305and315are close to the regulation voltage of the bias power supply apparatus320due to the variations of the input voltage, the bias LDO324operates in a dropout state. The output capacitor325and the two flying capacitors305and315are configured to function as a dual-phase charge pump having very high operation efficiency. If the voltages across the flying capacitors305and315are much lower than the regulation voltage of the bias power supply apparatus320, the switches S2and S3are turned off, and the switch S1is turned on to keep the output voltage of the bias power supply apparatus320in regulation.

In some implementations of the dual phase hybrid switched capacitor converter shown inFIG.7, the second switch S2and third switch S3are configured to be turned on and off alternately, to provide one half of the voltage of the input voltage bus to the bias LDO324separately. In this scenario, the second switch S2is no longer turning on and off completely in sync with the power switch S303. Instead, the second switch S2only turns off in sync with the power switch S303and turns on in sync with the power switches S301and S305. Similarly, the third switch S3is no longer turning on and off completely in sync with the power switch S306. Instead, the third switch only turns off in sync with the power switch S306, and turns on in sync with the power switches S302and S304. In this way, for switches S2and S3, each switch conducts during one half of the switching period Ts, and switches S2and S3alternately provide one half of the power fed into the bias LDO324. The benefit of having this configuration is to avoid the charge sharing loss associated with connecting the flying capacitors305and315in parallel (as shown in state906ofFIG.9). When switches S2and S3are turned on alternately, the circuit connection alternates between the state902and the state904as shown inFIG.9, avoiding parallel connections of flying capacitors305and315, thereby preventing in-rush current and charge sharing losses associated with connecting two capacitors with slightly different voltages in parallel.

In a more general case, as long as the second switch S2is configured such that when it is turned on, a voltage on the first switching node SW1is equal to one half of a voltage on the input voltage bus. The third switch S3is configured such that when it is turned on, a voltage on the second switching node SW2is equal to one half of a voltage on the input voltage bus. At least one of the second switch S2and the third switch S3is turned on during the entire switching period Ts. A consistent one half of a voltage on the input voltage bus can be provided to the bias LDO324to achieve higher efficiency during steady state operation.

The hybrid switched capacitor converter shown inFIG.7can be expanded to higher voltage conversion ratios by adding dual-phase expansion units as shown inFIGS.10-11. By adding the expansion unit330, the peak voltage at nodes308and318changes from one half of the voltage on the input voltage bus (Vin) to one third of Vin.

FIG.10illustrates a schematic diagram of a fourth implementation of the hybrid switched capacitor converter shown inFIG.3in accordance with various embodiments of the present disclosure. The power conversion system380shown inFIG.10comprises a hybrid switched capacitor converter and a bias power supply apparatus320. The hybrid switched capacitor converter shown inFIG.10is similar to the hybrid switched capacitor converter shown inFIG.7except that a dual-phase expansion unit330is added to adjust the power conversion ratio from 2:1 to 3:1.

As shown inFIG.10, the dual-phase expansion unit330comprises a first expansion power switch S332, a second expansion power switch S335a first expansion flying capacitor335and a second expansion flying capacitor345.

As shown inFIG.10, the first power switch S301, the first expansion power switch S332, the second power switch S302and the third power switch S303are connected in series between the input voltage bus Vin and ground. The first expansion flying capacitor335is connected between a common node of the second power switch S302and the third power switch S303, and a common node of the first power switch S301and the first expansion power switch S332.

As shown inFIG.10, the fourth power switch S304, the second expansion power switch S335, the fifth power switch S335and the sixth power switch S306are connected in series between the input voltage bus Vin and ground. The second expansion flying capacitor345is connected between a common node of the fifth power switch S305and the sixth power switch S306, and a common node of the fourth power switch S304and the second expansion power switch S335.

In steady state operation, the first power switch S301, the second power switch S302and the second expansion power switch S335are configured to turned on and off at the same time with a duty cycle D. The fourth power switch S304, the first expansion power switch S332and the fifth power switch S305are configured to turned on and off at the same time, out of phase with the first power switch S301with the same duty cycle D. The third power switch S303and the second switch S2turn on and off at the same time and operate in a complementary fashion with respect to the second power switch S302. The sixth power switch S306and the third switch S3turn on and off at the same time and operate in a complementary fashion with respect to the fifth power switch S305.

According to the operating principle of the dual-phase hybrid switched capacitor converter, in steady state operation, the voltages across the flying capacitors305and315are both equal to one third of the input voltage Vin. The voltages across the first expansion flying capacitor335and second expansion flying capacitor345are both equal to two thirds of the input voltage Vin.

In operation, before a steady voltage has been established across the flying capacitors305and315, the first switch S1is turned on to power up the bias power regulator324to generate a bias voltage VCC. During this time period, the second switch S2and the third switch S3are turned off. Once the dual-phase hybrid switched capacitor converter380is in normal operation and the voltages across the flying capacitors305and315are equal to one third of the voltage on the input voltage bus, the first switch S1is turned off, and the second switch S2and the third switch S3are turned on/off alternately based on the switching status of power switches S303and S306. More specifically, the second switch S2is turned on/off together with the third power switch S303, and the third switch S3is turned on/off the together with the sixth power switch S306. The second switch S2and the third switch S3are configured such that the input voltage of the bias power regulator324is maintained at a level equal to one third (⅓) of Vin. By lowering the input voltage to one third of Vin, the power dissipation can be reduced accordingly.

Similarly, the dual-phase hybrid switched capacitor converter shown inFIG.10can include N cascading expansion units330to offer a voltage conversion ratio (VIN/the peak voltage at node308and/or VIN/the peak voltage at node318) of (N+2):1. Regardless of the voltage conversion ratio, the second switch S2can always be connected to the common node of the fifth power switch S305and the flying capacitor315(e.g., first switching node SW1shown inFIG.10). The third switch S3can always be connected to the common node of the second power switch S302an and the flying capacitor305(e.g., second switching node SW2shown inFIG.10).

During steady state operation, the second switch S2is turned on/off at the same time as the third power switch S303. The third switch S3is turned on/off at the same time as the sixth power switch S306. The second switch S2and the third switch S3are configured such that input voltage of the bias power regulator324is maintained at a level equal to 1/(N+2) of Vin. By lowering the input voltage to 1/(N+2) of Vin, the power dissipation can be reduced accordingly.

As described above, through cascading different number of expansion units330to the dual-phase hybrid switched capacitor converter300inFIG.7, connecting the second switch S2to the terminal of flying capacitor315that is not connected to an output inductor, and connecting the third switch S3to the terminal of flying capacitor305that is not connected to an output inductor, all unit fractions (½, ⅓, ¼, etc.) of the input voltage Vin can be supplied to the bias power regulator324during steady state operation. The various input voltage options of the bias power regulator324offer flexibility to designers in achieving a higher efficiency power conversion for power converters having a very wide input voltage range.

FIG.11illustrates a schematic diagram of a fifth implementation of the hybrid switched capacitor converter shown inFIG.3in accordance with various embodiments of the present disclosure. The power conversion system390shown inFIG.11comprises a hybrid switched capacitor converter and a bias power supply apparatus320. The hybrid switched capacitor converter shown inFIG.11is similar to the hybrid switched capacitor converter shown inFIG.10except that S2and S3are connected to expansion flying capacitors345and335, respectively. Since the voltages across the expansion flying capacitors335and345are equal to the unit fraction of Vin multiplied by an integer, the configuration shown inFIG.11allows non-unit fractions (e.g., ⅔) of Vin to be supplied to the bias power regulator324.

As shown inFIG.11, the second switch S2is connected to the terminal of second expansion flying capacitor345that is not connected to an output inductor. The third switch S3is connected to the terminal of first expansion flying capacitor335that is not connected to an output inductor. During steady state operation, the second switch S2is turned on/off in sync with the sixth power switch S306. The third switch S3is turned on/off in sync with the third power switch S303.

In operation, since the voltages across the expansion flying capacitors345and335are equal to two thirds (⅔) of the input voltage Vin, two thirds (⅔) of Vin can be continuously supplied to the bias power regulator324during steady state operation. This is uniquely useful for hybrid converters with a 12-V input voltage and a bias voltage of 5 V. In this application, the input to the bias LDO can be reduced to 8V instead of 12V during steady state in order to achieve higher efficiency.

When a plurality of (e.g., N) dual-phase expansion units are added to the dual-phase hybrid switched capacitor converter in a cascading fashion, a pair of the expansion flying capacitors carrying 1/(N+2) of Vin multiplied by an integer can be selected, where the terminals of the expansion flying capacitors that are not connected to an output inductor can be assigned as the two switching node SW1and SW2respectively to supply fractions of Vin through the second switch S2and third switch S3to the bias LDO324during steady state operation.

In some implementations of the dual phase hybrid switched capacitor converter shown inFIG.11andFIG.12, the second switch S2and third switch S3can be configured to be turned on and off alternately, to connect a fraction of the input voltage bus carried by a pair of flying capacitors to the bias LDO324separately. In this way, each of the switches S2and S3conducts during one half of the switching period Ts. The benefit of having this configuration is to avoid the charge sharing loss associated with connecting the flying two capacitors in parallel, thereby eliminating the associated in-rush current and charge sharing losses.

In a more general case, as long as the second switch S2is configured such that when it is turned on, a voltage on the first switching node SW1is equal to a fraction of a voltage on the input voltage bus. The third switch S3is configured such that when it is turned on, a voltage on the second switching node SW2is equal to the same fraction of voltage on the input voltage bus. At least one of the second switch S2and the third switch S3is turned on during the entire switching period Ts. A stable voltage, representing a fraction of the voltage on the input voltage bus, can be provided to the bias LDO324to achieve higher efficiency during steady state operation.

FIG.12shows one example of implementing the switches in the bias power supply apparatus in accordance with various embodiments of the present disclosure. The power conversion system400shown inFIG.12comprises a hybrid switched capacitor converter and a bias power supply apparatus420. The hybrid switched capacitor converter is a dual-phase hybrid switched capacitor converter. The hybrid switched capacitor converter comprises an input capacitor401, a first power switch S401, a second power switch S402, a third power switch S403, a fourth power switch S404, a fifth power switch S405, a sixth power switch S406, a first flying capacitor405, a second flying capacitor415, a first inductor406, a second inductor416and an output capacitor410. The bias power supply apparatus420comprises a first switch421, a second switch422, a third switch423, a fourth switch427, a bias LDO424and a bias output capacitor425. The operating principle of the hybrid switched capacitor converter shown inFIG.12is similar to that of the hybrid switched capacitor converter shown inFIG.7, and hence is not discussed again to avoid repetition.

As shown inFIG.12, the first switch421is a first MOSFET. The second switch422, the third switch423and the fourth switch427form two isolation switches. As shown inFIG.12, the second switch422is a second MOSFET connected between the first switching node SW1and an internal node450. The third switch423is a third MOSFET connected between the second switching node SW2and the internal node450. The fourth switch427is a fourth MOSFET connected between the internal node450and the input of the bias power regulator. As shown inFIG.12, the second MOSFET and the fourth MOSFET are back-to-back connected to each other to form a first isolation switch. The third MOSFET and the fourth MOSFET are back-to-back connected to each other to form a second isolation switch.

In operation, due to the body diodes the switches422and423, the switch427is added to prevent the input voltage Vin from being applied to the flying capacitors405and415through the body diodes of the switches422and423. More particularly, when the switch421is turned on to power up the bias LDO424initially, without having the switch427, the input voltage Vin is applied to the flying capacitors405and415through the body diodes of the switches423and422, respectively. In normal operation, the voltage across the flying capacitor is one half of the input voltage. If the switch427is not added, the flying capacitors are charged to the input voltage Vin once the switch421is turned on. The high voltage across the flying capacitors can cause damage to the hybrid switched capacitor converter.

In normal operation, the voltage across the flying capacitors reaches Vin/2. The switch421can be turned off and the switch427can be turned on. The voltage at the input node426starts to decrease and is then clamped by the flying capacitors at Vin/2 through the switches422and423. The switches422and423are turned on and off by the same control signals for the switches S403and S406, respectively.

FIG.13illustrates various waveforms associated with the circuit shown inFIG.12in accordance with various embodiments of the present disclosure. The horizontal axis ofFIG.13represents intervals of time. There may be nine rows inFIG.13. The first row represents the gate drive signal of switch421. The second row represents the gate drive signal of switch427. The third row represents the gate drive signal of switch S403. The fourth row represents the gate drive signal of switch422. The fifth row represents the gate drive signal of switch S406. The sixth row represents the gate drive signal of switch423. The seventh row represents an enable (EN) signal. The enable signal is employed to turn on the hybrid switched capacitor converter. The eighth row represents an output voltage Vout of the hybrid switched capacitor converter. The ninth row is a power good (PG) signal. The PG signal is configured to be high when the output voltage is in regulation and to be low when the output voltage is not in regulation.

There are three significant intervals shown inFIG.13. T1represents the soft start interval of the hybrid switched capacitor converter. T2represents the normal operation interval. T3represents the power off interval. During the T1interval, initially the switch421is turned on to generate the VCC voltage from the input Vin. During the T1interval, the rest of the switches are kept off before the enable signal changes from a logic low state to a logic high state. Once the enable signal has a logic high state, the switches S401, S402, S403, S404, S405and S406start switching. The output voltage Vout starts to rise. Before the PG signal changes from a logic low state to a logic high state, the switches422,423and427are kept off by the PG signal. Once the output voltage Vout reaches regulation, the PG signal goes high. In response to the logic state change of the PG signal, the switch421is turned off and the switch427is turned on. At the same time, the switches422and423are turned on and off in sync with the on and off of the switches S403and S406, respectively, to supply Vin/2 voltage to the input node426, from the flying capacitors415and405. The hybrid switched capacitor converter enters the T2interval. When the EN signal is pulled low, the hybrid switched capacitor converter starts powering off its output. Once the output voltage is below the PG low threshold, the PG signal goes low. As shown inFIG.13, at this time instant, the switch427is turned off, and the switch421is turned on. Thus, the bias LDO424is powered from the input Vin again. Meanwhile, the switches422and423are kept off by the PG signal. The hybrid switched capacitor converter enters the third interval T3.

FIG.14illustrates a flow chart of controlling the bias power supply apparatus shown inFIG.3in accordance with various embodiments of the present disclosure. This flowchart shown inFIG.14is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. For example, various steps illustrated inFIG.14may be added, removed, replaced, rearranged and repeated.

At step1402, in a startup process of a hybrid switched capacitor converter, an input of a bias power regulator is configured to be connected to an input voltage bus of the hybrid switched capacitor converter through a first switch.

At step1404, after the startup process of the hybrid switched capacitor converter finishes, the input of the bias power regulator is configured to be connected to a first switching node and/or a second switching node of the hybrid switched capacitor converter through a second switch and/or a third switch, respectively. The second switch and the third switch are configured such that a voltage on the input of the bias power regulator is equal to (L/M) of a voltage on the input voltage bus. L and M are positive integers, and M is greater than L.

Referring back toFIG.4, the hybrid switched capacitor converter comprises a flying capacitor and a third power switch connected in series between the first switching node and ground, and a first power switch having a first drain/source terminal connected to the input voltage bus and a second drain/source terminal coupled to the first switching node, a second power switch and a fourth power switch connected in series between the first switching node and ground, a first inductor connected between a common node of the flying capacitor and the third power switch, and an output voltage bus of the hybrid switched capacitor converter, and wherein the common node of the flying capacitor and the third power switch is the second switching node, and a second inductor connected between a common node of the second power switch and the fourth power switch, and the output voltage bus of the hybrid switched capacitor converter.

Referring back toFIG.5, the method further comprises after the startup process of the hybrid switched capacitor converter finishes, configuring the second switch to turn on and off in sync with the third power switch, and configuring the third switch to turn on and off complementary to the second switch, wherein the second switch and the third switch are configured such that the voltage on the input of the bias power regulator is equal to one half of the voltage on the input voltage bus.

Referring back toFIG.6, the hybrid switched capacitor converter further comprises an expansion unit connected between the first power switch and the first switching node, and wherein the expansion unit comprises an expansion power switch connected between the first power switch and the first switching node, and an expansion flying capacitor connected between a common node of the first power switch and the expansion power switch, and the common node of the second power switch and the fourth power switch.

Referring back toFIG.6, the method further comprises after the startup process of the hybrid switched capacitor converter finishes, configuring the second switch to turn on and off in sync with the third power switch, and configuring the third switch to turn on and off complementary to the second switch, wherein the second switch and the third switch are configured such that the voltage on the input of the bias power regulator is equal to one third of the voltage on the input voltage bus.

Referring back toFIG.7, the hybrid switched capacitor converter comprises a second power switch and a third power switch connected in series between the second switching node and ground, and a first power switch having a first drain/source terminal connected to the input voltage bus and a second drain/source terminal coupled to the second switching node, a fifth power switch and a sixth power switch connected in series between the first switching node and ground, and a fourth power switch having a first drain/source terminal connected to the input voltage bus and a second drain/source terminal coupled to the first switching node, a first flying capacitor connected between the second switching node, and a common node of the fifth power switch and the sixth power switch, a second flying capacitor connected between the first switching node, and a common node of the second power switch and the third power switch, a first inductor connected between the common node of the second power switch and the third power switch, and an output voltage bus of the hybrid switched capacitor converter and a second inductor connected between the common node of the fifth power switch and the sixth power switch, and the output voltage bus of the hybrid switched capacitor converter.

Referring back toFIG.7, the method further comprises after the startup process of the hybrid switched capacitor converter finishes, configuring the second switch and the third switch to turn on and off alternately such that the voltage on the input of the bias power regulator is equal to one half of the voltage on the input voltage bus.

Referring back toFIG.8, the method further comprises after the startup process of the hybrid switched capacitor converter finishes, configuring the second switch to turn on and off in sync with the third power switch, and configuring the third switch to turn on and off in sync with the sixth power switch, wherein the second switch and the third switch are configured such that the voltage on the input of the bias power regulator is equal to one half of the voltage on the input voltage bus.

Referring back toFIG.10, the hybrid switched capacitor converter further comprises an expansion unit connected to the first switching node and the second switching node, wherein the expansion unit comprises a first expansion power switch connected between the first power switch and the second switching node, a second expansion power switch connected between the fourth power switch and the first switching node, a first expansion flying capacitor connected between a common node of the first power switch and the first expansion power switch, and the common node of the second power switch and the third power switch, and a second expansion flying capacitor connected between a common node of the fourth power switch and the second expansion power switch, and the common node of the fifth power switch and the sixth power switch.

Referring back toFIG.10, the method further comprises after the startup process of the hybrid switched capacitor converter finishes, configuring the second switch to turn on and off in sync with the third power switch, and configuring the third switch to turn on and off in sync with the sixth power switch, wherein the second switch and the third switch are configured such that the voltage on the input of the bias power regulator is equal to one third of the voltage on the input voltage bus.

Referring back toFIG.11, the hybrid switched capacitor converter comprises a second power switch and a third power switch connected in series between a first internal node and ground, and a first power switch having a first drain/source terminal connected to the input voltage bus and a second drain/source terminal coupled to the first internal node, a fifth power switch and a sixth power switch connected in series between a second internal node and ground, and a fourth power switch having a first drain/source terminal connected to the input voltage bus and a second drain/source terminal coupled to the second internal node, a first flying capacitor connected between the first internal node, and a common node of the fifth power switch and the sixth power switch, a second flying capacitor connected between the second internal node, and a common node of the second power switch and the third power switch, a first inductor connected between the common node of the second power switch and the third power switch, and an output voltage bus of the hybrid switched capacitor converter, a second inductor connected between the common node of the fifth power switch and the sixth power switch, and the output voltage bus of the hybrid switched capacitor converter, and an expansion unit comprising a first expansion power switch connected between the first power switch and the first internal node, wherein a common node of the first power switch and the first expansion power switch is the second switching node, a second expansion power switch connected between the fourth power switch and the second internal node, wherein a common node of the second expansion power switch and the fourth power switch is the first switching node, a first expansion flying capacitor connected between a common node of the first power switch and the first expansion power switch, and the common node of the second power switch and the third power switch, and a second expansion flying capacitor connected between a common node of the fourth power switch and the second expansion power switch, and the common node of the fifth power switch and the sixth power switch.

Referring back toFIG.11, the method further comprises after the startup process of the hybrid switched capacitor converter finishes, configuring the second switch to turn on and off in sync with the sixth power switch, and configuring the third switch to turn on and off in sync with the third power switch, wherein the second switch and the third switch are configured such that the voltage on the input of the bias power regulator is equal to two thirds of the voltage on the input voltage bus.