Patent Publication Number: US-2022224340-A1

Title: Counting circuit and chip

Description:
TECHNICAL FIELD 
     The present invention relates to the field of power chips and, in particular, to a counting circuit and a chip. 
     BACKGROUND 
     Most conventional counting circuits in power chips are fabricated using a metal-oxide-semiconductor (MOS) field effect transistor (FET) digital integrated circuit (IC) process, and in order to achieve desired counting accuracy, pulse signals suitable to be input to such circuits are limited to, for example, digital pulse signals, signals at specified frequencies or with specified duty cycles, or continuous clock signals. Counting a random, discontinuous, linear or analog pulse signal using a conventional counting circuit requires pretreatment of the signal by filtering, processing and computation or the addition of a micro processing unit with determining, analyzing and processing capabilities. Otherwise, the counting circuit may not be able to operate normally. This increases the circuit&#39;s complexity and cost to a certain extent. 
     All in all, the conventional counting circuits are associated with the problem that they may not be able to cope with irregular (e.g., random, discontinuous, linear or analog) pulse signals and may even not be able to operate normally when such a signal is input. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to solve the problem associated with the conventional counting circuits that they may not be able to cope with irregular pulse signals and may even not be able to operate normally when such a signal is input by presenting a novel counting circuit and a chip. 
     To this end, the provided counting circuit includes a charge counter module including a pulse processing module, a first capacitor, a voltage comparison module and a signal processing module. 
     The pulse processing module includes a first circuit, a second circuit and a current mirror. The first circuit includes a first transistor and a resistor. The second circuit includes a second transistor. The first circuit is connected to the second circuit via the current mirror, and the first transistor is configured to convert a received pulse signal into a first current. The current mirror is configured to mirror the first current to a second current, and the second transistor is configured to convert the second current into a counting current and transfer it to the first capacitor. A ratio of an effective value of the second current to an effective value of the counting current is equal to 100 or greater. 
     The first capacitor is configured to receive the counting current and store charge carried by the counting current. 
     A voltage of the first capacitor is taken by the counting circuit as a basis for counting. 
     The voltage comparison module includes a first input terminal and a second input terminal. The first input terminal is configured to receive the voltage of the first capacitor, and the second input terminal is configured to receive a preset reference voltage. The voltage comparison module is configured to output a trigger signal in the event of the voltage of the first capacitor rising beyond the reference voltage. 
     The signal processing module is configured to convert the trigger signal into a stop signal, marking the end of a counting cycle. 
     Optionally, the first transistor may be an NPN transistor and have a base for receiving the pulse signal, a collector connected to an input terminal of the current mirror, and an emitter connected to one end of the resistor. The other end of the resistor may be grounded. 
     The second transistor may be a PNP transistor and have an emitter connected to an output terminal of the current mirror, a collector that is grounded, and a base for outputting the counting current. 
     Optionally, the first input terminal may include a p-channel junction field effect transistor (JFET) having a gate connected to the first capacitor. 
     Optionally, the second input terminal may include a p-channel JFET having a gate connected to an adjustable constant voltage supply. 
     Optionally, the signal processing module may include a second capacitor and a stop signal output terminal. The second capacitor may have a first terminal connected to the voltage comparison module, and the second capacitor may have a second terminal connected to the stop signal output terminal. In the event of the trigger signal being at a high level, the second capacitor may be configured to be charged or held, with the first terminal being positive, resulting in a low level being output from the signal processing module. In the event of the trigger signal being at a low level, the second capacitor may be configured to charged, with the second terminal being positive, resulting in a high level being output from the signal processing module during the charging process. 
     Optionally, the counting circuit may further include a discharge module connected to the first capacitor. The discharge module may have a trigger terminal connected to the stop signal output terminal of the signal processing module, and the discharge module may be configured to discharge the first capacitor in response to the stop signal being output from the signal processing module. 
     Optionally, the counting circuit may further include a reset module connected to the first capacitor. The reset module may have a reset trigger terminal, and the reset module may be configured to discharge the first capacitor in response to a reset signal being received at the reset trigger terminal. 
     The above object is also attained by a chip provided in the present invention, which includes the counting circuit as defined above. The chip is fabricated using a transistor IC fabrication process or a metal-oxide-semiconductor field effect transistor (MOSFET) IC fabrication process. 
     Compared with the prior art, in the counting circuit and chip provided in the present invention, the charge counter module includes the pulse processing module and the first capacitor. The pulse processing module is configured to covert a received pulse signal into a counting current and to transfer the converted counting current to the first capacitor, and the first capacitor is configured to receive the counting current and store charge carried in the counting current. The counting circuit takes the voltage of the first capacitor as a basis for counting. With this arrangement, the input voltage pulse signal is converted to a current signal in the form of micro pulses for charging the first capacitor, and a counting result is obtained by detecting the voltage of the first capacitor, achieving the following advantages: no need to take care of whether the input pulse signal is continuous or discrete; high resistance to interference; adaptiveness to various input pulse signals of different waveforms and/or with different frequencies; and the ability to solve the problem with the conventional counting circuits that they may not be able to cope with irregular pulse signals and may even not be able to operate normally when such an irregular pulse signal is input. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Those of ordinary skill in the art would appreciate that the following drawings are presented merely to enable a better understanding of the present invention rather than limit the scope thereof in any sense. In the drawings: 
         FIG. 1  is a schematic diagram illustrating the structure of a counting circuit according to an embodiment of the present invention; 
         FIG. 2  is a schematic circuit diagram of the counting circuit according to an embodiment of the present invention; 
         FIG. 3  is a schematic waveform diagram of the counting circuit for a continuous pulse signal according to an embodiment of the present invention; and 
         FIG. 4  is a schematic waveform diagram of the counting circuit for a series of discrete pulse signals according to an embodiment of the present invention. 
     
    
    
     In these figures,
           100 —charge counter module;  200 —voltage comparison module;  300 —signal processing module;  400 —discharge module;  500 —reset module;     110 —pulse processing module;  111 —first transistor;  112 —current mirror;  113 —second transistor;  114 —resistor;  120 —first capacitor;  210 —first input terminal;  220 —second input terminal;  230 —constant voltage supply;  310 —second capacitor;  320 —stop signal output terminal;  410 —trigger terminal;  510 —reset trigger terminal.       

     DETAILED DESCRIPTION 
     Objectives, advantages and features of the present invention will become more apparent from the following detailed description of specific embodiments thereof, which is to be read in connection with the accompanying drawings. Note that the figures are provided in a very simplified form not necessarily drawn to exact scale for the only purpose of helping to explain the disclosed embodiments in a more convenient and clearer way. In addition, structures shown in the figures are usually part of actual structures. In particular, as the figures tend to have distinct emphases, they are often drawn to different scales. 
     As used herein, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. The term “or” is employed in the sense including “and/or” unless the context clearly dictates otherwise. The term “several” is used in the sense of “at least one”, and the phrase “at least two” is used in the sense of “two or more”. Moreover, the use of the terms “first”, “second” and “third” herein is intended for illustration only and is not to be construed as denoting or implying relative importance or as implicitly indicating the numerical number of the referenced item. Accordingly, defining an item with “first”, “second” or “third” is an explicit or implicit indication of the presence of one or at least two of the item. The terms “one end” and “the other end”, or “proximal end” and “distal end”, are generally used to refer to opposing end portions including the opposing endpoints, rather than only to the endpoints. Further, the terms “installation”, “connection” and “coupling” should be interpreted in a broad sense. For example, a connection may be a permanent, detachable or integral connection, or a mechanical or connection, or a direct or indirect connection with one or more intervening elements, or an internal communication or interaction between two components, unless the context clearly dictates otherwise. Those of ordinary skill in the art can understand the specific meanings of the above-mentioned terms herein according to the specific circumstances. 
     The core concept of the present invention is to solve the problem associated with the conventional counting circuits that they may not be able to cope with irregular pulse signals and may even not be able to operate normally when such a signal is input by presenting a novel counting circuit and a chip. 
     In the following description, reference is made to the accompanying drawings. 
     EMBODIMENTS 
     Reference is now made to  FIGS. 1 to 4 .  FIG. 1  is a schematic diagram illustrating the structure of a counting circuit according to an embodiment of the present invention.  FIG. 2  is a schematic circuit diagram of the counting circuit according to an embodiment of the present invention.  FIG. 3  is a schematic waveform diagram of the counting circuit for a continuous pulse signal according to an embodiment of the present invention.  FIG. 4  is a schematic waveform diagram of the counting circuit for a series of discrete pulse signals according to an embodiment of the present invention. 
     As shown in  FIG. 1 , the counting circuit of the present invention includes a charge counter module  100 . The charge counter module  100  includes a pulse processing module  110  and a first capacitor  120 . 
     The pulse processing module  110  is configured to convert a received pulse signal into a counting current I 3  and transfer it to the first capacitor  120 . 
     The first capacitor  120  is configured to receive the counting current I 3  and store the charge carried by the counting current I 3 . 
     The counting circuit takes a voltage VC of the first capacitor  120  as a basis for counting. 
     Conventional counters typically require input signals to be digital pulse signals or clock signals, which are continuous, at specified frequencies and with specified duty cycles and voltage amplitudes, and typically count the signals by timekeeping or multi-step frequency division. Therefore, they present limitations and restrictions to input pulse signals. 
     The counting circuit according to the embodiment counts an input voltage pulse signal by converting it into a current signal in the form of micro pulses, charging the first capacitor  120  with the micro pulses, and detecting the voltage of the first capacitor  120 . It has the following advantages: 
     1. Counting by storage of charge is independent of the time domain, making it irrelevant whether the input pulse signal is continuous or not. 
     2. It relies on the accumulation of charge and is highly resistant to interference. The counting performance will not be affected if small voltage spikes or other interfering signals (absence of energy or presence of extremely weak energy). 
     3. As the counting circuit according to the embodiment operates only in a linear analog region and relies on storage of charge for counting, the input pulse signal is allowed to be either analog or digital. Therefore it is adaptive and applicable to multiple types of input pulse signal. 
     Referring to  FIG. 2 , in one embodiment, the pulse processing module  110  includes a first transistor  111 , a current mirror  112  and a second transistor  113 . 
     The first transistor  111  is configured to convert the pulse signal into a first current I 1 . 
     The current mirror  112  is configured to mirror the first current I 1  to a second current I 2  and stabilize the current. 
     The second transistor  113  is configured to convert the second current I 2  into the counting current I 3 . A ratio of an effective value of the second current to an effective value of the counting current is equal to 100 or greater. 
     With this arrangement, the input voltage pulse signal can be effectively converted to the current signal in the form of micro pulses. During fabrication of chip, due to limitations in terms of area and cost, it is challenging to integrate a high-capacitance capacitor in the chip. Built-in capacitors typically have a capacitance of tens of pF. For this reason, it is sensible to assume that the first capacitor  120  has a capacitance of pF order. In order to achieve an extended charge period and more pulse cycles available for counting, it is necessary to limit the effective value of the counting current I 3  through providing it as micro pulses. Through repeated experiments, the inventors have found that the ratio of the effective value of the second current to that of the counting current that is equal to 100 or greater allows good use to be made of the capacitance of the first capacitor  120 , resulting in an expanded counting range. 
     The pulse processing module  110  further includes a first circuit (i.e., the circuit in which I 1  flows, as shown in  FIG. 2 ), a second circuit (i.e., the circuit in which I 2  flows, as shown in  FIG. 2 ) and a resistor  114 . The first transistor  111  may be an NPN transistor, while the second transistor  113  may be a PNP transistor. 
     The first transistor  111  has a base for receiving the pulse signal, as well as a collector and an emitter, which are both connected, together with the resistor  114  and an input terminal of the current mirror  112 , in the first circuit. 
     An output part of the current mirror  112  is connected in the second circuit, together with an emitter and a collector of the second transistor  113 . 
     The first circuit is connected to the second circuit via the current mirror  112 . 
     The second transistor  113  is configured to output from a base thereof the counting current I 3 . 
     With this arrangement, if the pulse signal received at the base of the first transistor  111  is at a high level, the first circuit is conducted to produce the first current I 1 , achieving the aforementioned conversion. Specifically, an instantaneous value of the first current I 1  is equal to (Vpulse−Ube)/R 1 , where Vpulse is an instantaneous amplitude of the pulse signal, Ube is a base-to-emitter voltage drop of the first transistor  111 , and R 1  is the resistance of the resistor  114 . The first current I 1  is then mirrored by the current mirror  112  to the second current I 2 , the second current I 2  has the same instantaneous value as the first current I 1 . In this way, stabilization of the second current I 2  is achieved. Finally, taking advantage of the characteristic of a transistor that an emitter current thereof is approximately equal to its base current times the transistor&#39;s DC amplification coefficient Beta, the second transistor  113  provides the counting current I 3 , the counting current I 3  has an instantaneous value equal to (Vpulse−Ube)/R 1 /Beta, where Beta denotes the amplification coefficient of the second transistor  113 . As apparent from the expression, the instantaneous value of I 3  is relatively low, demonstrating the effectiveness of this design. In an exemplary embodiment, Beta is equal to 100. 
     It is to be understood that the foregoing embodiment presents merely one example circuit implementation that can produce the micro-pulse current. Indeed, there are many other alternative implementations capable of performing the same function. 1) In some of such implementations, a different wiring design is employed. For example, differing from the design shown in  FIG. 2  in which a common node for the current mirror  112  is a positive terminal of a power supply, the ground may be instead designed as the common node for the current mirror  112 . In this case, in the first circuit, the positive terminal of the power supply is connected to the collector of the first transistor  111 , and the emitter of the first transistor  111  is connected to one end of the resistor  114 . The other end of the resistor  114  is connected to a collector of a transistor at the input terminal of the current mirror  112 , and an emitter of this transistor at the input terminal of the current mirror  112  is grounded. In the second circuit, the positive terminal of the power supply is connected to the emitter of the second transistor  113 , and the collector of the second transistor  113  is connected to a collector of a transistor at the output terminal of the current mirror  112 . An emitter of the transistor at the output terminal of the current mirror  112  is grounded. 2) Some other implementations replace one or more of the above components with more sophisticated but functionally equivalent circuits. For example, the second transistor  113  may be replaced with a current amplification circuit. 3) In still some other implementations, some part, e.g., the current mirror  112  may be omitted, and a circuit that can counteract the adverse effects arising from the omission of the current mirror  112  with the current stabilization capabilities may be added downstream. All in all, the pulse processing module  110  functions to properly convert the received pulse signal into the counting current I 3 , and any particular circuit implementation based on this idea is considered to be within the scope as defined in the appended claims. 
     Referring to  FIG. 1 or 2 , in a particular embodiment, the counting circuit further includes a voltage comparison module  200 , the voltage comparison module  200  has a first input terminal  210  and a second input terminal  220 . 
     The first input terminal  210  is configured to receive the voltage of the first capacitor  120 . 
     The second input terminal  220  is configured to receive a preset reference voltage VT. 
     When the voltage VC of the first capacitor  120  rises beyond the reference voltage VT, the voltage comparison module is configured to output a trigger signal VOUT, concurrently with the counting circuit outputting a predetermined stop signal STOP. 
     The reference voltage VT is provided by an adjustable constant voltage supply  230 . 
     As discussed above, the voltage VC of the first capacitor  120  is taken as a basis for subsequently obtaining a count using one of several methods. For example, an analog-to-digital conversion module may be used to convert the voltage VC of the first capacitor  120  into a digital signal, from which the count may be determined using an empirical formula derived from many experiments. Compared with such approaches, directly obtaining the trigger signal VOUT using the voltage comparison module  200  in accordance with this embodiment allows higher operability and improved accuracy while not compromising the counting performance. It is to be understood that, after being output from the counting circuit, the predetermined trigger signal VOUT may be either directly taken as the stop signal STOP, or further processed by another module to derive the stop signal STOP. It is to be understood that, in this embodiment, the trigger signal VOUT is a low-level pulse. However, in alternative embodiments, it may assume another form such as a high-level pulse, a rising edge, a falling edge, etc. The stop signal STOP should be construed in the same way. 
     Based on the above description, the quantity of charge carried in each pulse in the counting current I 3  may be given by: Q 1 =MI 3 ×Dutycycle×T=Delta_I 3 ×T, where MI 3  represents amplitude of the counting current I 3 ; Dutycycle, a duty cycle of the pulse; Delta_I 3 , an equivalent current; and T, a time duration of the pulse. 
     Accordingly, the reference voltage VT may be mapped to a countdown value SUM according to: 
     SUM=C×VT/Q 1 , where C is the capacitance of the first capacitor  120 . 
     In practical applications, SUM may be determined by design, and VT may be derived based on the characteristics of the pulse signal concerned. Alternatively, VT may be roughly determined, and other parameters of the circuit, such as the capacitance C of the first capacitor  120  and the amplification coefficient Beta of the second transistor, may be then finely tuned based on SUM until the design meets the desired design specification. 
     It is to be understood that the adjustable constant voltage supply  230  is not part of the counting circuit and is used herein for the only purpose of providing the reference voltage VT. It may be of any conventional structure and may employ any conventional method, without limiting the scope of present invention in any sense. 
     Additionally, referring to  FIG. 2 , a biasing circuit for a key voltage comparison circuit in the voltage comparison module  200  may be provided by a constant current source S  1 . The use of this constant current source Si enables the voltage comparison module  200  to have improved accuracy and enhanced resistance to interfering signals. 
     Referring to  FIG. 2 , the first input terminal  210  includes a p-channel junction field effect transistor (JFET) PJ 1 , the p-channel JFET has a gate connected to the first capacitor  120 . As can be seen from the above description, any leakage of charge from the first capacitor  120  may degrade the accuracy of the counting circuit. In order to overcome this, it is necessary for input impedance of the first input terminal  210  to be infinite. The p-channel JFET is chosen for this reason while taking into account that it facilitates the fabrication of the circuit with lower cost. Conventional integrated circuit (IC) fabrication processes do not involve the formation of p-channel JFET devices. However, the IC fabrication process in which the inventors are engaged has been developed to allow the formation of p-channel JFET devices. More preferably, the second input terminal also includes a p-channel JFET PJ 2  to reduce the requirements on the reliability of the adjustable constant voltage supply  230  and additionally increase the counting circuit&#39;s accuracy. 
     Preferably, the counting circuit further includes a signal processing module  300 , the signal processing module  300  is configured for converting the trigger signal VOUT into the stop signal STOP, marking the end of a counting cycle. The signal processing module  300  is able to decouple the trigger signal VOUT from the stop signal STOP that is required by the other subsequent circuit, making it unnecessary to take into account output waveform considerations in the design of the voltage comparison module  200 . This simplifies the design as only performance of the circuit such as accuracy and reliability needs to be considered. 
     In one embodiment, the trigger signal VOUT is a low-level pulse, while the stop signal STOP is required to be a high-level pulse. To this end, in this embodiment, the signal processing module  300  includes a second capacitor  310  and a terminal  320  for outputting the stop signal. A first terminal of the second capacitor  310  is connected to the voltage comparison module  200 , and a second terminal of the second capacitor  310  is connected to the terminal  320 . When the trigger signal VOUT is high, with the first terminal being positive, the second capacitor  310  is charged or held, and the signal processing module  300  outputs a low level. When the trigger signal VOUT is low, with the second terminal being positive, the second capacitor  310  is charged, and the signal processing module  300  outputs a high level during the charging process. The signal processing module  300  may further include other components wired as shown in  FIG. 2 . This embodiment operates as follows: 
     (1) When VOUT is kept high, with the first terminal being positive, the second capacitor  310  is charged and held. Since VOUT is high for the most part, the second capacitor  310  is almost always in a fully charged state. As a result, the power supply voltage, i.e., vdd, is present at the first terminal of the second capacitor  310 , and a voltage of 0.7 V (i.e., Ube, this value may vary with the size of the transistor) is present at the second terminal of the second capacitor  310 . Therefore, there is a voltage difference that is equal to vdd minus 0.7 V between the terminals of the second capacitor  310 . 
     (2) When VOUT drops low, a transistor Q 16  is turned on, abruptly bringing the voltage at the first terminal of the second capacitor  310  to 0.7 V. However, due to the voltage difference between the terminals of the second capacitor  310  does not change therewith, the voltage at the second terminal of the second capacitor  310  shifts to 0.7 V−(vdd−0.7 V)=1.4 V−vdd, the voltage at the second terminal of the second capacitor  310  is negative because vdd is higher than 1.4 V. As a result, a transistor Q 17  is turned off, and the stop signal STOP output from the signal processing module  300  is pulled high. 
     (3) Subsequently, as shown in  FIG. 2 , the second capacitor  310  is charged with a current I 4 , and Q 17  remains off before the voltage at the second terminal of the second capacitor  310  reaches 0.7 V. As a result, the stop signal STOP remains high. 
     (4) Upon the voltage at the second terminal of the second capacitor  310  reaching 0.7 V, Q 17  is turned on, pulling the stop signal STOP low. 
     In summary, the stop signal STOP is high in the period Tc in which the voltage at the second terminal of the second capacitor  310  is charged with the current I 4  from 1.4 V-vdd to 0.7 V, i.e., experience a change of 0.7 V−(1.4 V−vdd)=vdd−0.7 V. The charge period Tc (i.e., the period in which the stop signal STOP is high) can be according to Tc=C 2 *(vdd-0.7 V)/I 4 , where C 2  denotes the capacitance of the second capacitor  310 . 
     Referring to  FIG. 2 , in the signal processing module  300 , a biasing current for I 4  for charging the second capacitor  310  may be provided by a constant current source  51 . This ensures stability of I 4  and pulse width accuracy of the stop signal STOP. 
     It is to be understood that the foregoing embodiment presents merely one possible implementation of the signal processing module  300 . Any and all circuit variants capable of taking advantage of the charge and discharge properties of the second capacitor  310 , utilizing transitions of the trigger signal VOUT to reverse the signs of the terminals during charging of the second capacitor  310  and working with another circuit to accomplish at least one of signal conversion, stabilization, rectification and amplification of the output current from the second capacitor  310  are considered to be within the scope of the appended claims. 
     It is to be understood that this embodiment aims to address the situation where the trigger signal VOUT is a low-level pulse while the stop signal STOP is required to be a high-level pulse, and for different requirements placed on the trigger signal VOUT and the stop signal STOP, the signal processing module  300  should be modified accordingly. Any and all variants of the signal processing module  300  based on the design concept as disclosed above as well as common general knowledge in the art are intended to fall within the scope of the appended claims. 
     Referring to  FIG. 1 , in one embodiment, the counting circuit further includes a discharge module  400 , the discharge module  400  is connected to the first capacitor  120 , and a trigger terminal  410  of the discharge module  400  is connected to the terminal  320  of the signal processing module  300 . In response of the signal processing module  300  outputting the stop signal STOP, the discharge module  400  is configured to discharge the first capacitor. This arrangement enables the counting circuit to be automatically reset so that immediately after outputting the stop signal STOP, the counting circuit can start another counting cycle. It is to be understood that the trigger terminal  410  of the discharge module  400  may be connected to an output terminal of the signal processing module  300  either directly or via one or more other components. For example, the output terminal of the signal processing module  300  may be connected to a microprocessor, which has an output terminal that is in turn connected to the trigger terminal  410  of the discharge module  400 . The microprocessor may have an internal logic configured to, upon receiving the stop signal STOP, output, from the aforesaid output terminal, another signal that triggers a discharge process. 
     Referring to  FIG. 1 , the counting circuit may further include a reset module  500 , the reset module  500  is connected to the first capacitor  120 . The reset module  500  may have a reset trigger terminal  510 , and the reset module  500  may be configured to discharge the first capacitor  120  when a reset signal RESET is received at the reset trigger terminal  510 . 
     It is to be understood that the discharge module  400  and the reset module  500  may be configured either as described above and shown in  FIG. 2 , or otherwise based on the same design principles as have been described hereinabove. 
     In a representative embodiment, major components of a particular implementation of the counting circuit and wiring thereof are as shown in  FIG. 2 , and a waveform of this embodiment in response to a continuous pulse signal is shown in  FIG. 3 . 
     In  FIG. 3 , the pulse signal is indicated at PULSE, the counting current at I 3 , the reset signal at RESET, the reference voltage at VT, the voltage of the first capacitor  120  at VC, the trigger signal at VOUT, and the stop signal at STOP, and the abscissa represents time. In the period from 0 to 200 μs, RESET is kept high. Therefore, despite the presence of the counting current I 3 , the voltage VC of the first capacitor  120  does not experience any change. RESET is pulled low at the time point 200 μs, leading to a stepwise ramp of the voltage VC of the first capacitor  120  under the action of the incoming counting current I 3  until VC exceeds the reference voltage VT. At this point, the trigger signal VOUT is output as a low-level pulse, and the stop signal STOP is simultaneously output as a high-level pulse having a pulse width corresponding to the length of the charge time period Tc of the second capacitor  310  as detailed above. Under the action of the stop signal STOP, the voltage VC of the first capacitor  120  is reset to 0, starting the next counting cycle. 
     A waveform of this embodiment in response to a series of discrete pulse signals is shown in  FIG. 4 , in which the series of pulse signals is indicated at PULSE, the counting current at I 3 , the reset signal at RESET, the reference voltage at VT, the voltage of the first capacitor  120  at VC, the trigger signal at VOUT, and the stop signal at STOP, and the abscissa represents time. In the period from 0 to 200 μs, RESET is kept high. Therefore, despite the presence of the counting current I 3 , the voltage VC of the first capacitor  120  does not show any change. RESET is pulled low at the time point 200 μs, leading to a stepwise ramp of the voltage VC of the first capacitor  120  under the action of the incoming counting current I 3 . In this process, if there is an interruption in PULSE, the voltage VC of the first capacitor  120  will stop ramping and be held without changing, until the next pulse signal appears. When this happens, the voltage VC of the first capacitor  120  continues to ramp until VC exceeds the reference voltage VT. At this point, the trigger signal VOUT is output as a low-level pulse, and the stop signal STOP is simultaneously output as a high-level pulse. Under the action of the stop signal STOP, the voltage VC of the first capacitor  120  is reset to 0, starting the next counting cycle. 
     As additionally demonstrated by  FIGS. 3 and 4 , irrespective of whether the pulse signal PULSE is continuous or not, the number of pulses SUM recorded in the countdown counter remains the same. Moreover, when the pulse signal PULSE has non-variable amplitude and duty cycle, according to the above formula, the initial value SUM of the countdown counter may be modified simply by adjusting the capacitance C of the first capacitor  120  and the reference voltage VT. Thus, as a major advantage, this counting circuit can be used as a countdown counter that is adaptive to multiple types of input pulse signals (continuous or discrete signals with different amplitudes, duty cycles and frequencies) simply by adjusting external parameters without needing to modify the internal structure of the counting circuit. 
     In this embodiment, there is also provided a chip including the counting circuit as defined above. The chip is fabricated using a transistor IC fabrication process or a metal-oxide-semiconductor field effect transistor (MOSFET) IC fabrication process, and has the same advantages as the above-described counting circuit. In particular, when it is fabricated using a transistor IC fabrication process, it can be produced at reduced cost, which is conducive to massive production. The chip may also be fabricated using an MOSFET IC fabrication process. Those skilled in the art can understand and appreciate how to configure and form other components of the chip based on common general knowledge in the art, and a detailed description thereof is deemed unnecessary and omitted. 
     In summary, compared with the prior art, in the counting circuit and chip provided in the present invention, the charge counter module  100  includes the pulse processing module  110  and the first capacitor  120 . The pulse processing module  110  is configured to covert a received pulse signal into a counting current I 3  and to transfer the converted counting current I 3  to the first capacitor  120 , and the first capacitor  120  is configured to receive the counting current I 3  and store charge carried in the counting current I 3 . The counting circuit takes the voltage of the first capacitor  120  as a basis for counting. With this arrangement, the input voltage pulse signal is converted to a current signal in the form of micro pulses for charging the first capacitor  120 , and a counting result is obtained by detecting the voltage of the first capacitor  120 , achieving the following advantages: no need to take care of whether the input pulse signal is continuous or discrete; high resistance to interference; adaptiveness to various input pulse signals of different waveforms and/or with different frequencies; and the ability to solve the problem with the conventional counting circuits that they may not be able to cope with irregular pulse signals and may even not be able to operate normally when such an irregular pulse signal is input. 
     The description presented above is merely that of a few preferred embodiments of the present invention and is not intended to limit the scope thereof in any sense. Any and all changes and modifications made by those of ordinary skill in the art based on the above teachings fall within the scope as defined in the appended claims.