JP7747458B2 - Resonant switched capacitor converter, its controller circuit, and electronic device using the same - Google Patents

Description

This disclosure relates to a resonant switched-capacitor converter.

DC/DC converters and charge pumps are used to generate voltages higher or lower than the power supply voltage. DC/DC converters that use inductors as energy storage elements can control the output voltage, but they have the problem of reduced efficiency due to switching operations.

In applications that require high efficiency, switched capacitor converters (charge pumps) are used, as they do not require an inductor as an energy storage element. One type of switched capacitor converter is known to operate in resonance by adding a resonant inductor in series with the flying capacitor (called a resonant switched capacitor converter). Resonant switched capacitor converters enable zero-current switching (soft switching), enabling highly efficient operation.

One known form of resonant switched capacitor converter is a configuration in which an inductor is added to a Dickson-type charge pump (switched tank converter).

U.S. Patent No. 9,917,517

It is in this context that the present disclosure has been made, and one of its exemplary purposes is to provide a resonant switched-capacitor converter with overcurrent protection.

One aspect of the present disclosure relates to a controller circuit for a resonant switched capacitor converter. The controller circuit includes an oscillator that generates a clock signal, a drive circuit that drives multiple switches that constitute a switch circuit of the resonant switched capacitor converter in response to the clock signal, and an overcurrent protection circuit that, upon detecting an overcurrent state in the resonant switched capacitor converter, changes the frequency of the clock signal in a direction away from the resonant frequency.

Another aspect of the present disclosure is a method for controlling a resonant switched capacitor converter, comprising the steps of detecting an output current of the resonant switched capacitor converter, and, when the output current exceeds a predetermined threshold, changing the switching frequency of the resonant switched capacitor converter in a direction away from the resonant frequency.

In addition, any combination of the above components, or mutual substitution of components or expressions between methods, devices, systems, etc., are also valid aspects of the present invention.

According to certain aspects of the present disclosure, overcurrent protection can be achieved.

FIG. 1 is a circuit diagram of a resonant switched capacitor converter according to an embodiment. FIG. 2 is a diagram showing the relationship between the gain and the switching frequency ω of the resonant switched capacitor converter. FIG. 3 is a circuit diagram of a resonant switched capacitor converter according to the first embodiment. FIG. 4 is a time chart illustrating the operation of the resonant switched capacitor converter. FIG. 5 is a circuit diagram of the controller IC according to the first embodiment. FIG. 6 is a circuit diagram of a controller IC according to the second embodiment. FIG. 7 is a diagram for explaining the operation of the frequency controller of FIG. FIG. 8 is a circuit diagram of a resonant switched capacitor converter according to a third embodiment. FIG. 9 is a diagram illustrating the operation of the resonant switched capacitor converter of FIG. FIG. 10 is an operational waveform diagram of the resonant switched capacitor converter of FIG. FIG. 11 is a circuit diagram of a resonant switched capacitor converter according to a fourth embodiment. FIG. 12 is a circuit diagram of a resonant switched capacitor converter according to a fifth embodiment. FIG. 13 is a diagram illustrating an example of an electronic device including a resonant switched capacitor converter.

(Outline of the embodiment)
A summary of some exemplary embodiments of the present disclosure is provided. This summary is intended to provide a simplified overview of some concepts of one or more embodiments in order to provide a basic understanding of the embodiments as a prelude to the more detailed description that follows. It is not intended to limit the scope of the invention or disclosure. This summary is not an exhaustive overview of all possible embodiments, and is not intended to identify key elements of all embodiments or to delineate the scope of some or all aspects. For convenience, the term "one embodiment" may refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed herein.

In one embodiment, a controller circuit for a resonant switched capacitor converter includes an oscillator that generates a clock signal, a drive circuit that drives multiple switches that make up the switch circuit of the resonant switched capacitor converter in response to the clock signal, and an overcurrent protection circuit that changes the frequency of the clock signal away from the resonant frequency when an overcurrent state in the resonant switched capacitor converter is detected.

With this configuration, by moving the switching frequency away from the resonant frequency, the gain of the resonant switched capacitor converter can be reduced, the output voltage can be lowered, and the output current can be reduced.

In one embodiment, the controller circuit may further include a frequency controller that controls the oscillation frequency of the oscillator in response to the output voltage of the resonant switched capacitor converter under normal conditions.

With this configuration, by optimizing the switching frequency according to the output voltage of the resonant switched capacitor converter, the resonant switched capacitor converter can be operated in soft switching mode, even when the resonant frequency varies, thereby improving efficiency. Furthermore, in an overcurrent state, frequency control by the frequency controller can be disabled, allowing the switching frequency to be moved away from the resonant frequency.

In one embodiment, the frequency controller may control the oscillation frequency of the oscillator so that the output voltage of the resonant switched capacitor converter approaches its maximum value under normal conditions, thereby achieving zero current switching (ZCS).

In one embodiment, when the output voltage of the resonant switched capacitor converter increases as a result of changing the oscillation frequency of the oscillator in a first direction, the frequency controller may change the oscillation frequency of the oscillator in the first direction in the next frequency control cycle, and when the output voltage of the resonant switched capacitor converter decreases, the frequency controller may change the oscillation frequency of the oscillator in a second direction opposite to the first direction in the next frequency control cycle.

In one embodiment, the frequency controller may vary the oscillator's oscillation frequency in a region where, under normal conditions, the oscillator's oscillation frequency is higher than the resonant frequency of the resonant switched capacitor converter. In this case, efficiency can be improved by zero voltage switching (ZVS).

In one embodiment, the frequency controller may vary the oscillation frequency of the oscillator so that the output voltage of the resonant switched capacitor converter approaches a target voltage under normal conditions, thereby allowing the output voltage to be set to any desired voltage level.

In one embodiment, the controller circuit may be monolithically integrated on a single semiconductor substrate. "Monolithic integration" includes cases where all of the circuit's components are formed on a semiconductor substrate, or where the main circuit components are monolithically integrated, and some resistors, capacitors, etc. may be provided outside the semiconductor substrate to adjust circuit constants. By integrating the circuit on a single chip, the circuit area can be reduced and the characteristics of the circuit elements can be maintained uniformly.

(Embodiment)
The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing are designated by the same reference numerals, and redundant descriptions will be omitted where appropriate. Furthermore, the embodiments are illustrative and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In this specification, "a state in which component A is connected to component B" refers not only to cases in which component A and component B are directly physically connected, but also to cases in which component A and component B are indirectly connected via other components that do not substantially affect their electrical connection state or impair the function or effect achieved by their connection.

Similarly, "a state in which component C is provided between components A and B" includes not only cases in which components A and C, or components B and C, are directly connected, but also cases in which they are indirectly connected via other components that do not substantially affect their electrical connection state or impair the function or effect achieved by their combination.

Furthermore, "signal A (voltage, current) corresponds to signal B (voltage, current)" means that signal A has a correlation with signal B, and specifically means (i) when signal A is signal B, (ii) when signal A is proportional to signal B, (iii) when signal A is obtained by level-shifting signal B, (iv) when signal A is obtained by amplifying signal B, (v) when signal A is obtained by inverting signal B, (vi) or any combination thereof. Those skilled in the art will understand that the scope of "corresponding" is determined depending on the type and application of signals A and B.

The vertical and horizontal axes of the waveform diagrams and time charts referenced in this specification have been enlarged or reduced as appropriate to facilitate understanding, and the waveforms shown have been simplified, exaggerated, or emphasized to facilitate understanding.

(Embodiment)
1 is a circuit diagram of a resonant switched capacitor converter 100 according to an embodiment. The resonant switched capacitor converter 100 includes at least one capacitor C1 to Cn, an inductor L, a switch circuit 110, a drive circuit 120, an oscillator 150, and an overcurrent protection circuit 160. Of these, at least the drive circuit 120, the oscillator 150, and the overcurrent protection circuit 160 are integrated into a single semiconductor chip (hereinafter referred to as a controller IC (Integrated Circuit)) 200. The switch circuit 110 may also be integrated into the controller IC 200.

The topology of the resonant switched capacitor converter 100 is not particularly limited, and the gain of the resonant switched capacitor converter 100, i.e., the voltage division ratio or voltage step-up ratio, is also not particularly limited.

Inductor L1 is connected in series with one of capacitors C1 to Cn (a flying capacitor) to form an LC resonant circuit. Note that multiple inductors may be provided to correspond to multiple flying capacitors.

The switch circuit 110 includes an input node IN, an output node OUT, a ground node GND, and a plurality of switches SW. The input node IN is supplied with an input voltage _VIN of the resonant switched capacitor converter 100, and the output node _OUT generates an output voltage VOUT of the resonant switched capacitor converter 100. The ground node GND is grounded.

The oscillator 150 generates a clock signal CLK. The resonant switched capacitor converter 100 switches in synchronization with this clock signal CLK. That is, the switching frequency of the resonant switched capacitor converter 100 is based on the frequency of the clock signal CLK (the oscillation frequency of the oscillator 150). For example, the oscillation frequency of the oscillator 150 may be fixed at or near the resonant frequency _ω0 of the resonant switched capacitor converter 100. Alternatively, as will be described later, the oscillation frequency of the oscillator 150 may be feedback-controlled in accordance with the output voltage _VOUT .

Driver circuit 120 drives multiple switches SW1-SWm that make up switch circuit 110 in synchronization with clock signal CLK. Drive circuit 120 includes drivers Dr1-Drm that correspond to the multiple switches SW1-SWm.

A current detection signal IS indicating the output current _IOUT of the resonant switched capacitor converter 100 is input to a current detection pin CS of the controller IC 200. For example, a sense resistor _RCS may be inserted in the path of the output current _IOUT , and the voltage across the resistor (voltage drop) may be input to the current detection pin CS as the current detection signal IS.

The overcurrent protection circuit 160 detects an overcurrent state of the resonant switched capacitor converter 100 based on the current detection signal IS. For example, the overcurrent protection circuit 160 may determine that an overcurrent state has occurred when the current detection signal IS exceeds a predetermined threshold. When the overcurrent protection circuit 160 detects an overcurrent state, it changes the frequency of the clock signal CLK generated by the oscillator 150 in a direction away from the resonant frequency.

The above is the configuration of the resonant switched capacitor converter 100. Next, we will explain its operation.

2 is a diagram showing the relationship between the gain and switching frequency ω of the resonant switched capacitor converter 100. Here, a ½-times switched capacitor converter will be described as an example. The characteristics of the switched capacitor converter are expressed by the following equation:

ω ₀ is the resonant frequency, and when the switching frequency ω coincides with the resonant frequency ω ₀ , the gain G reaches a maximum value of ½, and decreases as the switching frequency ω deviates from this value.

R represents the impedance of the load of the resonant switched capacitor converter 100. _QL is the Q factor of the circuit, and _Z0 is the characteristic impedance.

When the load is heavy (when R is small), the Q value becomes large, and the decrease in gain becomes large when the switching frequency ω deviates from the resonant frequency ω ₀ .

For example, in a normal state (non-overcurrent state), the oscillation frequency of oscillator 150 is set within the hatched region (NORMAL) near the resonant frequency _ω0 , and the gain of resonant switched capacitor converter 100 is close to 1/2. At this time, resonant switched capacitor converter 100 generates output voltage _VOUT that is 1/2 times the input voltage _VIN .

When the overcurrent protection circuit 160 detects an overcurrent state, the oscillation frequency of the oscillator 150 is changed in a direction away from the resonant frequency _ω0 . In the example of FIG. 2, the resonant frequency _ω0 is increased to the region marked OCP. This allows the gain of the oscillator 150 to be reduced from ½. This reduces the output voltage _VOUT of the resonant switched capacitor converter 100 and also reduces the output current _IOUT . Note that in an overcurrent state, the switching frequency may be changed in a direction lower than the resonant frequency _ω0 .

This disclosure extends to various devices and methods that can be understood as the block diagram or circuit diagram in Figure 1 or derived from the above description, and is not limited to any particular configuration. Below, more specific configuration examples and examples will be described, not to narrow the scope of this disclosure, but to aid in understanding and clarify the essence and operation of this disclosure and the present invention.

Example 1
3 is a circuit diagram of a resonant switched capacitor converter 100A according to a first embodiment. The resonant switched capacitor converter 100A has a gain of 1/2, reduces the input voltage V _IN of an input line 102 to 1/2, and generates an output voltage V _OUT =V _IN /2 on an output line 104. The resonant switched capacitor converter 100A includes two capacitors C1 and C2, one inductor L1, and a controller IC 200A. The switch circuit 110A also includes switches SW1 to SW4. This resonant switched capacitor converter 100A has a configuration in which an inductor is added in series with the flying capacitor of a 1/2 charge pump.

The switches SW1 to SW4 are driven by a controller IC 200A. In this embodiment, the switches SW1 to SW4 are N-channel metal oxide semiconductor field effect transistors (MOSFETs). The drive signal for the i-th switch SWi is denoted as _Si , and when _Si is H (high), the switch SWi is on, and when _Si is L (low), the switch SWi is off.

The resonant switched capacitor converter 100A can be switched between a first state φ1 and a second state φ2. In the first state φ1, the first switch SW1 and the third switch SW3 are on, and the second switch SW2 and the fourth switch SW4 are off. At this time, an LC resonant circuit 106 including a capacitor C1 and an inductor L1 is connected in series with a capacitor C2, and an input voltage V _IN is applied across the two terminals. When C1 = C2, the voltage across each of the capacitors C1 and C2 is charged to V _IN /2.

In the second state φ2, the first switch SW1 and the third switch SW3 are off, and the second switch SW2 and the fourth switch SW4 are on. At this time, the LC resonant circuit 106 including the capacitor C1 and the inductor L1 is connected in parallel with the capacitor C2, and V _OUT =V _IN /2 is generated on the output line 104.

4 is a time chart illustrating the operation of the resonant switched capacitor converter 100 A. FIG. 4 shows the drive signals S ₁ to S ₄ , the resonant current I _RES flowing through the LC resonant circuit 106, the input current I _in , and the output current I _OUT .

When the frequency of the resonant current _IRES (resonant frequency) matches the switching frequency, zero current switching (soft switching) occurs, enabling highly efficient operation. _TSW is the switching period, which is the period of the clock CLK generated in the controller IC 200A and represents the reciprocal of the switching frequency.

Next, we will explain the configuration of the controller IC 200A.

Figure 5 is a circuit diagram of a controller IC 200A according to the first embodiment. The controller IC 200A includes a drive circuit 120A, a frequency controller 130A, and an overcurrent protection circuit 160. The drive circuit 120A includes four drivers Dr1 to Dr4 corresponding to four switches SW1 to SW4. Drivers Dr1 and Dr3 operate in phase with the clock CLK, while drivers Dr2 and Dr4 operate out of phase with the clock CLK.

The frequency controller 130A includes a variable frequency oscillator 132 and a frequency adjustment unit 134. The variable frequency oscillator 132 corresponds to the oscillator 150 in Fig. 1. In a normal state, the frequency adjustment unit 134 adaptively controls the frequency of the variable frequency oscillator 132 based on the feedback voltage _VFB (output voltage _VOUT ) input to the feedback pin FB.

Specifically, the frequency adjusting unit 134 controls the frequency of the variable frequency oscillator 132 for each frequency control cycle j so that the output voltage V _OUT approaches its maximum value. The frequency adjusting unit 134 is configured to be able to compare a current value V _FBj of the feedback voltage V _FB with a previous value V _{FB (j-1)} of the feedback voltage V FB. The frequency adjusting unit 134 includes a storage unit 136 such as a sample-and-hold circuit or memory that holds the previous value V _FBj-1 of the feedback voltage V _FB , and a comparison circuit 138.

In a certain frequency control cycle j, the frequency adjustment unit 134 changes the switching frequency, i.e., the frequency of the frequency variable oscillator 132, in a first direction (e.g., an upward direction). The resulting feedback voltage V _FBj is compared with a past feedback voltage V _FBj-1 by a comparison circuit 138. If the comparison shows that the output voltage V _OUT (feedback voltage V _FB ) has increased, the frequency of the frequency variable oscillator 132 is also changed in the first direction (upward direction) in the next frequency control cycle j+1. Conversely, if the output voltage V _OUT (feedback voltage V _FB ) has decreased, the frequency of the frequency variable oscillator 132 is changed in a second direction (downward direction) opposite to the first direction in the next frequency control cycle j+1. The current value V _FBj in frequency control cycle j becomes the past value V _FBj in the next frequency control cycle j+1.

The frequency adjuster 134 repeats this frequency control cycle to maximize the output voltage _VOUT . As can be seen from Fig. 2, when the output voltage _VOUT reaches its maximum value, the switching frequency ω and the resonant frequency _ω0 coincide, enabling zero-current switching and improving efficiency.

When the overcurrent protection circuit 160 asserts the overcurrent detection signal OCP, the operation of the frequency adjuster 134 stops, and the frequency of the variable frequency oscillator 132 is set to a predetermined frequency ω _OCP that is separated from the resonant frequency ω _0. This enables overcurrent protection.

Example 2
6 is a circuit diagram of a controller IC 200B according to Example 2. The controller IC 200B can be used in the resonant switched capacitor converter 100A of FIG. 3 as a substitute for the controller IC 200A.

The controller IC 200B includes a drive circuit 120B, a frequency controller 130B, and an overcurrent protection circuit 160. The configuration of the drive circuit 120B is similar to that of the drive circuit 120A in Figure 5.

The frequency controller 130B includes a variable frequency oscillator 132 and a feedback circuit 140.

The variable frequency oscillator 132 is a voltage controlled oscillator (VCO) or a digital controlled oscillator (DCO), and oscillates at a frequency that corresponds to the signal level of the control signal S _CTRL . The variable frequency oscillator 132 corresponds to the oscillator 150 in FIG.

A reference voltage _VREF that defines a target level VOUT _(REF) of the output voltage _VOUT is input to the feedback circuit 140. If the output voltage _VOUT is used as the feedback voltage _VFB as is, the target level _VOUT(REF) of the output voltage _VOUT becomes the reference voltage _VREF .

In a normal state, the feedback circuit 140 controls the frequency of the variable frequency oscillator 132 within the range where ω > ω _0. Since the resonant switched capacitor converter 100A operates within the range where ω > ω ₀ , its gain operates within a range smaller than ½, and the target level V _{OUT (REF)} of the output voltage V _OUT is set lower than V _IN /2.

Feedback circuit 140 controls the frequency of variable frequency oscillator 132 so that the error between feedback voltage _VFB and reference voltage _VREF approaches zero. Feedback circuit 140 can be configured with an analog circuit or a digital circuit. For example, feedback circuit 140 includes an error amplifier that amplifies the error between feedback voltage _VFB and reference voltage _VREF , and supplies a control signal _SCTRL based on the output of the error amplifier to variable frequency oscillator 132. Alternatively, feedback circuit 140 may be configured with a digital circuit including a PI (proportional integral) controller or a PID (proportional integral derivative) controller.

Fig. 7 is a diagram illustrating the operation of the frequency controller 130B of Fig. 6. The operating range of the resonant switched capacitor converter 100A is limited to the range ω > ω ₀ , and the target level V _{OUT (REF)} of the output voltage V _OUT is determined within this range.

As a result of the feedback control of frequency controller 130B, the frequency of variable frequency oscillator 132, ie, the switching frequency ω of resonant switched capacitor converter 100A, is stabilized to the optimum frequency ω _OPT at which V _OUT =V _OUT(REF) .

When the overcurrent protection circuit 160 detects an overcurrent state, the feedback control by the feedback circuit 140 is stopped, and the frequency of the variable frequency oscillator 132 is set to a predetermined frequency ω _OCP that is set higher than the operating range, thereby providing overcurrent protection.

The above is the operation of the controller IC 200B. In the first embodiment, zero current switching is realized by operating at ω= _ω0 , whereas in the second embodiment, zero voltage switching is possible by operating at ω> _ω0 , thereby realizing highly efficient operation.

In the first embodiment, the output voltage _VOUT is stabilized at a voltage level that is half the input voltage _VIN , so that if the input voltage _VIN fluctuates, the output voltage _VOUT also fluctuates. In contrast, according to the second embodiment, even if the input voltage _VIN fluctuates, the output voltage _VOUT can be stabilized at a target level determined according to the reference voltage _VREF .

Example 3
8 is a circuit diagram of a resonant switched capacitor converter 100C according to Example 3. This resonant switched capacitor converter 100C is a switched tank converter having a gain of 1/4, and reduces the input voltage V _IN on the input line 102 to 1/4, generating an output voltage V _OUT =V _IN /4 on the output line 104.

The resonant switched capacitor converter 100C includes three capacitors C1 to C3, two inductors L1 and L3, and a controller IC 200C. The switch circuit 110C also includes switches SW1 to SW10. This resonant switched capacitor converter 100C is a Dickson-type charge pump with inductors L1 and L3 added (a switched tank converter).

The first switch SW1 to the fourth switch SW4 are N-channel MOSFETs connected in series between the input terminal IN and the output terminal OUT.

The pair of the fifth switch SW5 and the sixth switch SW6, the pair of the seventh switch SW7 and the eighth switch SW8, and the pair of the ninth switch SW9 and the tenth switch SW10 constitute inverters INV1 to INV3, respectively.

Switches SW1 to SW10 are driven by controller IC 200C. Controller IC 200C can be configured similarly to controller IC 200A and controller IC 200B.

Figure 9 is a diagram explaining the operation of the resonant switched capacitor converter 100C in Figure 8. The resonant switched capacitor converter 100C can switch between a first state φ1 and a second state φ2. In the first state φ1, switches SW1, SW3, SW5, SW7, and SW9 are on, and the remaining switches SW2, SW4, SW6, SW8, and SW10 are off.

In the second state φ2, switches SW1, SW3, SW5, SW7, and SW9 are off, and the remaining switches SW2, SW4, SW6, SW8, and SW10 are on.

By alternately repeating the first state φ1 and the second state φ2, the voltage across the LC resonant circuit 106_1 of the capacitor C1 and the inductor L1 becomes 36 V, the voltage across the capacitor C2 becomes 24 V, and the voltage across the LC resonant circuit 106_2 of the capacitor C3 and the inductor L3 becomes 12 V, and an output voltage _VOUT of 12 V can be obtained.

Fig. 10 is an operational waveform diagram of the resonant switched capacitor converter 100C of Fig. 8. Fig. 10 shows the states of the switches SW1 to SW10, the current _iφ1 that flows in the first state φ1, and the current _iφ2 that flows in the second state φ2.

By operating in a resonant state where ω= _ω0 , zero current switching (ZCS), that is, ZCS turn-on and ZCS turn-off, becomes possible, and high efficiency can be obtained.

The controller IC 200C of the resonant switched capacitor converter 100C according to the third embodiment can be configured based on the controller IC 200A described in the first embodiment, by simply increasing the number of drivers in the drive circuit 120A of the controller IC 200A to 10. With this configuration, zero current switching becomes possible, similar to the first embodiment, and high efficiency can be achieved.

Alternatively, the controller IC 200C of the resonant switched capacitor converter 100C according to the third embodiment may be configured based on the controller IC 200B described in the second embodiment, by simply increasing the number of drivers in the drive circuit 120B of the controller IC 200B to 10. This configuration enables zero voltage switching and high efficiency, as in the second embodiment. Furthermore, the output voltage _VOUT can be stabilized at an arbitrary target level VOUT _(REF) in the range of _VOUT < _VIN /4.

Example 4
11 is a circuit diagram of a resonant switched capacitor converter 100D according to Example 4. Similar to Example 3, this resonant switched capacitor converter 100D has a gain of 1/4, reduces the input voltage V _IN on the input line 102 to 1/4, and generates an output voltage V _OUT =V _IN /4 on the output line 104.

The resonant switched capacitor converter 100D has a configuration in which two 1/2-multiplication resonant switched capacitor converters 100A described in the first embodiment are connected in series. The front-stage resonant switched capacitor converter 100A multiplies the input voltage V _IN by 2 to generate an intermediate voltage V _MID . The rear-stage resonant switched capacitor converter 100B multiplies the intermediate voltage V _MID by 2 to generate an output voltage V _OUT .

In the fourth embodiment, a controller IC 200A (or 200B) is provided for each resonant switched capacitor converter 100A. The controller IC 200A (200B) of the upstream resonant switched capacitor converter 100A controls the switching frequency of the upstream resonant switched capacitor converter 100A based on the intermediate voltage V _MID . The controller IC 200A (200B) of the downstream resonant switched capacitor converter 100A controls the switching frequency of the downstream resonant switched capacitor converter 100A based on the output voltage V _OUT .

This configuration allows a 1/4 resonant switched capacitor converter to operate with high efficiency.

Example 5
12 is a circuit diagram of a resonant switched capacitor converter 100E according to Example 5. Like Examples 3 and 4, this resonant switched capacitor converter 100E has a gain of 1/4, reduces the input voltage V _IN on the input line 102 to 1/4, and generates an output voltage V _OUT =V _IN /4 on the output line 104.

The resonant switched capacitor converter 100E has a configuration in which ½-times resonant switched capacitor converters 100A are connected in series in two stages, as in the fourth embodiment, but in the fifth embodiment, the controller IC 200E for the two resonant switched capacitor converters 100A is integrated onto a single chip. Only the output voltage _VOUT of the resonant switched capacitor converter 100A in the latter stage is fed back to the controller IC 200E, and the switching frequencies of both the former stage and the latter stage are controlled in the same way based on the output voltage _VOUT .

This configuration allows a 1/4 resonant switched capacitor converter to operate with high efficiency.

(Modification)
The above-described embodiment is merely an example, and it will be understood by those skilled in the art that various modifications are possible in the combination of the components and the processing steps. Such modifications will be described below.

In the embodiments, a 1/2 or 1/4 converter was described, but the application of this disclosure is not limited to this and can be applied to converters with other gains. It can also be applied to switched capacitor converters with a gain greater than 1.

(Application)
13 is a diagram showing an example of an electronic device 700 including a resonant switched capacitor converter 100. A suitable example of the electronic device 700 is a server. Originally, a 12V power line was connected to the server, and therefore the internal circuit 710 is designed to operate at 12V. The internal circuit 710 may include a CPU (Central Processing Unit), memory, a LAN (Local Area Network) interface circuit, a DC/DC converter that steps down the 12V voltage, and the like.

In recent years, there has been a trend to replace bus voltages from 12V with 48V in order to reduce the current flowing through power lines. In this case, a power supply circuit 720 is required to step down the 48V power supply voltage to 12V. The resonant switched capacitor converter 100 with a gain of 1/4 described above is suitable for use in such a power supply circuit 720.

The electronic device 700 is not limited to a server, but may also be an in-vehicle device. While conventional automobile batteries are mainly 12V or 24V, hybrid vehicles may use 48V systems, which also require a power supply circuit to convert the 48V battery voltage to 12V or 24V. In such cases, a 1/2 or 1/4 resonant switched capacitor converter 100 can be suitably used.

In addition, the electronic device 700 may be industrial equipment, office automation equipment, or consumer equipment such as audio equipment.

The embodiments are illustrative, and those skilled in the art will understand that there are various variations in the combination of each component and each treatment process, and that such variations are also included in this disclosure and may constitute the scope of the present invention.

100 Resonant switched capacitor converter 102 Input line 104 Output line 106 LC resonant circuit 110 Switch circuit 120 Drive circuit 130 Frequency controller 132 Variable frequency oscillator 134 Frequency adjustment unit 136 Memory unit 138 Comparison circuit 140 Feedback circuit 150 Oscillator 160 Overcurrent protection circuit 200 Controller IC
SW Switch C Capacitor L Inductor

Claims (5)

1. A controller circuit for a resonant switched capacitor converter, comprising:
an oscillator for generating a clock signal;
a drive circuit that drives a plurality of switches that constitute a switch circuit of the resonant switched capacitor converter in response to the clock signal;
a frequency controller that controls the oscillation frequency of the oscillator so that a feedback voltage indicating the output voltage of the resonant switched capacitor converter approaches a maximum value under normal conditions;
an overcurrent protection circuit that, when detecting an overcurrent state of the resonant switched capacitor converter , disables the control of the oscillation frequency by the frequency controller and changes the oscillation frequency of the oscillator to a predetermined frequency that is away from the resonant frequency;
A controller circuit comprising: The frequency controller, for each control cycle,
(i) changing the oscillation frequency of the oscillator in one of an upward direction and a downward direction;
(ii) when a present value of the feedback voltage in a current control cycle is greater than a past value of the feedback voltage in a control cycle immediately preceding the current control cycle, changing the oscillation frequency of the oscillator in the same direction in the next control cycle;
(iii) when the present value of the feedback voltage is decreased from the past value of the feedback voltage, changing the oscillation frequency of the oscillator in the opposite direction in the next control cycle;
The controller circuit of claim 1 that performs the process. 3. The controller circuit according to claim 1, wherein the controller circuit is monolithically integrated on a single semiconductor substrate. A resonant switched capacitor converter comprising a controller circuit according to any one of claims 1 to 3 . An electronic device comprising the resonant switched capacitor converter according to claim 4 .