TWI477065B - Switched capacitor circuit capable of reducing external capacitance - Google Patents

Description

Switched capacitor circuit capable of reducing external capacitance

The invention is a switching capacitor circuit capable of reducing the value of the external capacitor, in particular, a switching capacitor circuit capable of integrating the external capacitor inside the chip.

Nowadays, the use of capacitors in analog electronic circuits or digital electronic circuits is becoming more and more common. From the traditional circuits of various voltage and current amplifiers, filters, operational amplifiers or waveform generators, etc., they are used simply. Filtering impurity waveforms, such as operational amplifiers, utilizes the characteristics of the capacitor in the Laplace transform domain; in short, capacitors are now used in different places, depending on the desired function.

However, if it is used as an external capacitor, the value of the external capacitor is often large. Separate external capacitors must be provided on the circuit board. In addition to the additional cost of the external external capacitor, the circuit design on the circuit board is also caused. Increased considerations; in general switched capacitor circuits, because the external capacitors need to be extremely large, they are not suitable for integration inside the chip.

Please refer to the first figure, which is a schematic diagram of a general switched capacitor circuit, comprising: an external capacitor 14, one end of the external capacitor 14 is grounded; an input switch 11 is used to open the input One end of the switch 11 is coupled to the external input voltage; an output switch 12, one end of the output switch 12 is coupled to the other end of the input switch 11, and the other end of the output switch 12 is coupled to the external capacitor 14; 13. One end of the capacitor 13 is coupled between the input switch 11 and the output switch 12, and the other end is grounded. In the absence of an external voltage, both the output switch 11 and the input switch 12 are open and open.

In the case of external voltage, during the one-year period of the external AC voltage, the input switch 11 is closed and the output switch 12 is opened to open the circuit, so that the capacitor 13 is charged; the input switch 11 is opened and the output switch 12 is closed, and the capacitor 13 is turned on. The current flows through the output switch to charge the external capacitor 14, and discharges the capacitor 13.

Since the operating current and voltage must be maintained, the value of the external capacitor is maintained at a large value and is independent of the wafer; in addition to the additional cost of the external external capacitor, the circuit design on the circuit board is increased.

In view of this, it is urgent to propose a novel switched capacitor circuit architecture, which enables a switched capacitor circuit to be implemented in a simpler and cheaper manner.

The main purpose of the invention is to reduce the external capacitor, and the external capacitor can be integrated into a chip to save the external capacitor and reduce the cost.

Another object of the present invention is to provide a method of extending the time of charging the external capacitor so as to avoid wasting waiting time.

The invention relates to a switched capacitor circuit capable of reducing an external capacitor, comprising: An external capacitor, the one end of the external capacitor is grounded; at least two switching modules, each of the at least two switching modules includes: an input switch, one end of the input switch is coupled to an external input voltage; An output switch, one end of the output switch is coupled to the other end of the input switch, and the other end of the output switch is coupled to the other end of the external capacitor; a module capacitor, one end of the module capacitor is coupled to the input Between the switch and the output switch, the other end is grounded, and the module capacitance values of each switching module are the same.

Wherein, the input switch of any one of the switching modules must be linked with the output switch of any other switching module, and the output switch of any one of the switching modules must be linked with the input switch of any other switching module, and each linkage relationship is Strict one-to-one relationship, meaning that the input switch of one switching module does not interlock with the output switch of the other two switching modules, or the output switch of one switching module is linked with the input switch of the other two switching modules. Only one input switch of the switch module corresponds to the output switch of another switch module, and the output switch of one switch module corresponds to the input switch of another switch module, and does not overlap; in the case of no external voltage, all switch modes Both the output switch and the input switch in the group open the open circuit.

In the case of external voltage, in the one-week period of external AC voltage, the input and output switches with different linkage relationship can be switched on and off, so that the external capacitor and the module capacitor are charged, and only one group has a linkage relationship in each conduction time. The input switch and the output switch are closed and turned on, so that the charging time can be increased within one week of the external AC voltage.

Since the total charge change is equal to the voltage subtraction between the input and output terminals multiplied by the sum of the module capacitance values of all the switching modules, please refer to the following formula; △Q=Σ C _n ×(V _i -V _o ) (1)

△Q: total charge change

C _n : module capacitance value of any switching module

V _i : input voltage value

V _o : output voltage value

I _n : the on current of any switching module

t _n : on time

The output voltage variation is equal to the charge change of any switching module except the value of the external capacitor. It is also equal to the voltage subtraction between the input terminal and the output terminal. Multiply the module capacitance value of any switching module and divide the external capacitor value. Refer to the following formula: △V _o =△Q _n /C _o =C _n ×(V _i -V _o )/C _o (2)

△V _o : output voltage change

△Q _n : the amount of charge change of any switching module

C _o : external capacitor value

C _n : module capacitance value of any switching module

V _i : input voltage value

V _o : output voltage value

According to the formula (2), if the output voltage variation ΔV _o and the voltage reduction (V _i -V _o ) between the input terminal and the output terminal are fixed, the module capacitance value C _{n of} any switching module is proportional to the plug-in. The capacitance value C _o means that if the external capacitance value C _{o is} halved, the module capacitance value C _{n of} any switching module is also halved, but this action will affect the total charge change amount ΔQ in (1) The total charge change ΔQ is also halved (since the module capacitance C _n of each switching module is halved, the sum of the module capacitance values of all switching modules Σ C _{n is} also halved); please refer to (1) In order to make the total charge change amount ΔQ also fixed (if the voltage reduction (V _i -V _o ) between the input terminal and the output terminal is fixed), the number of switching modules must be doubled, and switched by different modules. The action increases the on-time, so that the sum of the module capacitance values of all the switching modules multiplied by the voltage drop of the input end and the output end is still equal to the original total charge change amount ΔQ; therefore, as can be seen from the foregoing, the external capacitor value can be The module capacitance value in any switching module is proportionally reduced. If it is reduced to a certain value, it can be integrated into the chip; but the mode of all switching modules Capacitance value of the number is inversely proportional to the switching module.

11‧‧‧Input switch of the general embodiment

12‧‧‧Output switch of the general embodiment

13‧‧‧General Example Capacitance

14‧‧‧General examples of external capacitors

2‧‧‧ external capacitor

21‧‧‧First switching module

211‧‧‧First input switch

212‧‧‧First output switch

213‧‧‧First module capacitor

22‧‧‧Second switching module

221‧‧‧Second input switch

222‧‧‧Second output switch

223‧‧‧Second module capacitor

23‧‧‧The third switching module

231‧‧‧ third input switch

232‧‧‧ third output switch

233‧‧‧The third switching module

24‧‧‧fourth switching module

241‧‧‧fourth input switch

242‧‧‧fourth output switch

243‧‧‧Fourth Module Capacitor

The first figure is a schematic diagram of a general switched capacitor circuit of the prior art of the present invention; the second figure is a schematic diagram of a first embodiment of the present invention; the third (A) is a first operation diagram of the first embodiment of the present invention; 1 is a second operation diagram of a first embodiment of the present invention; a fourth diagram is a schematic diagram of a second embodiment of the present invention; and a fifth (A) diagram is a first operation diagram of the second embodiment of the present invention; The second operation diagram is a second embodiment of the present invention; the fifth (C) diagram is a fourth operation diagram of the second embodiment of the present invention; and the fifth (D) diagram is a fourth operation diagram of the second embodiment of the present invention.

The various possible embodiments of the present invention are illustrated by the following description of exemplary embodiments. It is to be understood that other embodiments are possible, and that structural or operational modifications may be made without departing from the scope of the invention.

Please refer to the second figure, which is a schematic diagram of a first embodiment of a switched capacitor circuit capable of reducing an external capacitor, comprising: an external capacitor 2, one end of the external capacitor 2 is grounded; and a first switching module 21, The first switching module 211 includes: a first input switch 211, one end of the first input switch 211 is coupled to an external input voltage; a first output switch 212, one end of the first output switch 212 and the first input The other end of the first output switch 212 is coupled to the other end of the external capacitor 2; a first module capacitor 213, one end of the first module capacitor 213 is coupled to the first An input switch 211 and the first output switch 212 are connected to each other; a second switching module 22 includes: a second input switch 221, and one end of the second input switch 221 The second output switch 222 is coupled to the other end of the second input switch 221, and the other end of the second output switch 221 is connected to the external capacitor 2 The other end is coupled; a second mode a capacitor 223, one end of the second module capacitor 223 is coupled between the second input switch 221 and the second output switch 222, and the other end is grounded; and the first module capacitor 213 and the second module Capacitor 223 has the same value.

The first input switch 211 of the first switching module 21 and the second output switch 222 of the second switching module 22 are linked, and the first output switch 212 and the second switching module 22 of the first switching module 21 are The two input switches 221 are connected to each other; in the case of no external voltage, the first input switch 211, the first output switch 212 and the second input switch 221 and the second output in the second switching module 22 in the first switching module 21 Switch 222 is open and open.

Please refer to the third (A) diagram and the third (B) diagram for the operation diagram of the first embodiment of the present invention; in the third (A) diagram, the first switching module having the linkage relationship during the on time The first input switch 211 of 21 and the second output switch 222 of the second switching module 22 are closed, and the first output switch 212 of the first switching module 21 and the second of the second switching module 22 have a linked relationship. The input switch 221 is an open circuit, so that the current flowing through the first input switch 211 of the first switching module 21 flows into the first module capacitor 213 for charging, and the current in the second module capacitor 223 flows through the second switching mode. The second output switch 222 of the group 22 charges the external capacitor 2 and discharges the second module capacitor 223.

Conversely, in the third (B) diagram, the first input switch 211 of the first switching module 21 having the interlocking relationship and the second output switch 222 of the second switching module 22 are open and open during the on-time. The first output switch 212 of the first switching module 21 and the second input switch 221 of the second switching module 22 are closed and the input current flows through the second input switch of the second switching module 22 221 flows into the second module capacitor 223 for charging, and the current in the first module capacitor 213 flows through the first output switch 212 of the first switching module 21 to charge the external capacitor 2, and discharges the first module capacitor 213.

According to the foregoing disclosure, the value of the first module capacitor 213 is the same as the value of the second module capacitor 223 and is half of the capacitance of the general switched capacitor circuit. The external capacitor value 2 is a general switched capacitor circuit. The capacitance value is half of 14.

The embodiment is not limited to the two switching modules, but at least two switching modules are required. Please refer to the fourth figure, which is another embodiment of the switching capacitor circuit capable of reducing the external capacitor, and the display has four switching modules. The second embodiment includes: an external capacitor 2, one end of the external capacitor 2 is grounded; a first switching module 21, the first switching module 21 includes: a first input switch 211, one end of the first input switch 211 is coupled to an external input voltage; a first output switch 212, the first output One end of the switch 212 is coupled to the other end of the first input switch 211, and the other end of the first output switch 212 is coupled to the other end of the external capacitor 2; a first module capacitor 213, the first module One end of the capacitor 213 is coupled between the first input switch 211 and the first output switch 212, and the other end is grounded; a second switching module 22, the second switching module 22 includes: a second input switch 221 The second input switch 221 is coupled to the external input voltage. The second output switch 222 is coupled to the other end of the second input switch 221. The second output switch 222 is coupled to the other end of the second input switch 221. The other end is coupled to the other end of the external capacitor 2; a second module capacitor 223, one end of the second module capacitor 223 is coupled between the second input switch 221 and the second output switch 222, The other end is grounded; a third switching module 23, the third switching The group 23 includes: a third input switch 231, one end of the third input switch 231 is coupled to an external input voltage; a third output switch 232, one of the third output switch 232 and the third input switch 231 The other end of the third output switch 232 is coupled to the other end of the external capacitor 2; a third module capacitor 233, one end of the third module capacitor 233 is coupled to the third input switch 231 And the third output switch 232, the other end is grounded; a fourth switching module 24, the fourth switching module 24 includes: a fourth input switch 241, the fourth input switch 242 and the external input voltage The fourth output switch 242 is coupled to the other end of the fourth input switch 241, and the other end of the fourth output switch 242 is coupled to the other end of the external capacitor 2 One a module capacitor 243, one end of the fourth module capacitor 243 is coupled between the fourth input switch 241 and the fourth output switch 242, and the other end is grounded; and the module capacitance values of the four switch modules are the same.

The first input switch 211 of the first switching module 21 is interlocked with the second output switch 222 of the second switching module 22, and the second input switch 221 and the third switching module 23 of the second switching module 22 are The three output switches 232 are interlocked, the first input switch 231 of the third switching module 23 is interlocked with the fourth output switch 242 of the fourth switching module 24, and the fourth input switch 241 of the fourth switching module 24 is coupled to the first switching mode. The first output switch 212 of the group 21 is interlocked, and the foregoing linkage relationship is not fixed, as long as the corresponding correspondence is not repeated; in the case of no external voltage, the input switch and the output switch in all modules are opened and open.

Please refer to the fifth (A) diagram, the fifth (B) diagram, the fifth (C) diagram, and the fifth (D) diagram, which are operation diagrams of the second embodiment of the present invention; in the fifth (A) diagram, During the on-time, the first input switch 211 of the first switching module 21 having the linked relationship and the second output switch 222 of the second switching module 22 are closed, and the other input and output switches having the interlocking relationship are open and open. The input current flows through the first input switch 211 of the first switching module 21 to the first module capacitor 213 for charging, and the current in the second module capacitor 223 flows through the second output switch of the second switching module 22 The 222 external capacitor 2 is charged, and the second module capacitor 223 is discharged.

Similarly, in the fifth (B) diagram, in the on-time, the second input switch 221 of the second switching module 22 having the interlocking relationship and the third output switch 232 of the third switching module 23 are closed. The other input/output switch having the interlocking relationship is to open the open circuit, so that the input terminal current flows through the second input switch 221 of the second switching module 22 The second module capacitor 223 is charged, and the current in the third module capacitor 233 flows through the third output switch 232 of the third switching module 23 to charge the external capacitor 2, and discharges the third module capacitor 233.

The fifth (C) diagram and the fifth (D) diagram have the same operation mode, so it can be analogized.

According to the foregoing disclosure, the first module capacitor 213 has the same value as the second module capacitor 223, the third module capacitor 233, and the fourth module capacitor 243, and is a general switched capacitor circuit. The capacitor 13 has a value of one quarter, and the external capacitor value 2 is one quarter of the value of the external capacitor of the switched capacitor circuit. By analogy, if the number of switching modules is increased to a certain extent, the value of the external capacitor can be reduced to a certain extent, and then integrated into the chip, which has certain advantages for industrial utilization and cost consideration; for the semiconductor process, Small improvements in turn have great advantages and are also an advancement of the invention.

The above embodiments are intended to be illustrative and exemplary only, and are not intended to limit the invention. Based on the above teachings, many modifications and variations can be derived. The scope of the present invention is not limited to the description of the embodiments, but the scope of the appended claims will be limited.

2‧‧‧ external capacitor

21‧‧‧First switching module

211‧‧‧First input switch

212‧‧‧First output switch

213‧‧‧First module capacitor

22‧‧‧Second switching module

221‧‧‧Second input switch

222‧‧‧Second output switch

223‧‧‧Second module capacitor

Claims (8)

A switching capacitor circuit capable of reducing an external capacitor includes: an external capacitor, one end of the external capacitor is grounded; at least two switching modules, each of the at least two switching modules includes: an input switch One end of the input switch is coupled to an external input voltage; an output switch, one end of the output switch is coupled to the other end of the input switch, and the other end of the output switch is coupled to the other end of the external capacitor; Capacitor, one end of the module capacitor is coupled between the input switch and the output switch, and the other end is grounded, and the module capacitance values of each switching module are the same. For example, the switched capacitor circuit capable of reducing the external capacitor according to the first aspect of the patent application, wherein the input switch of any one of the switching modules must be linked with the output switch of the other switching module, and the output of any one of the switching modules The switch must be linked with the input switch of another switching module, and each linkage relationship is strictly one-to-one relationship and cannot overlap. For example, the switched capacitor circuit capable of reducing the external capacitor according to the second aspect of the patent application, wherein the module capacitance value of all the switching modules is inversely proportional to the number of switching modules. For example, the switched capacitor circuit capable of reducing the external capacitor according to the second aspect of the patent application, wherein the external capacitor value can be reduced in proportion to the module capacitance value in the switching module. Such as the switching capacitor circuit which can reduce the external capacitor as described in the third paragraph of the patent application, in the case of external voltage, one cycle of the external alternating current, all cut The input switch and the output switch with interlocking relationship in the replacement module all perform a switching action: the original open circuit state, the rear closed conduction period and then the open circuit, and the open circuit state is maintained. A switching capacitor circuit capable of reducing an external capacitor according to the fifth aspect of the patent application, wherein, in each of the on-times, only one set of input switches having a linked relationship and the output switch are turned on, and the input switch is turned on by using The input switch of the conduction switch is charged by the module capacitor of the switching module, and the output switch of the conduction switch discharges the module capacitor of the switching module of the conduction output switch, and charges the external capacitor. For example, a switched capacitor circuit capable of reducing an external capacitor as described in claim 6 can be controlled to have different lengths of each conduction time, but there must be an interval between each conduction time, so as not to affect the charging process. . A switching capacitor circuit capable of reducing an external capacitor as described in claim 5, wherein the external capacitor value is reduced to a certain value and integrated into the wafer.