CN104143913A - Frequency detection device - Google Patents

Abstract

A frequency detection device comprises a constant current generation unit, a first capacitor, a first transistor, a second capacitor and a second transistor. The constant current generation unit is used for providing a constant current for a voltage output end. The first capacitor is coupled between the voltage output end and a first reference voltage. The first transistor is provided with a first connecting end coupled to the voltage output end and a control end coupled to an input signal. The second capacitor is coupled between a second connecting end of the first transistor and the first reference voltage. The second transistor is provided with a first connecting end coupled to the second connecting end of the first transistor, a second connecting end coupled to the first reference voltage and a control end coupled to an inverted input signal, and the inverted input signal is opposite to the input signal in phase. The voltage output of the voltage output end will change with the input signal frequency of the input signal.

Description

Frequency detecting device

Technical field

The disclosed embodiment of the present invention relates to a kind of frequency detecting, the frequency detecting device that espespecially a kind of builtin voltage output meeting changes along with the frequency input signal of input signal.

Background technology

Along with the fast development of communication system and the requirement of power saving, many electronic equipments all must consider that in operator scheme and standby mode the power management design of power consumption, especially portable equipment more faces the new challenge of the aspect such as core and I/O (I/O) voltage, power management and service time of battery.The synchronous buck converter of portable applications provides a power saving operating mode now, to maintain the high efficiency of whole loading range.It is the in the situation that of slight load, transducer is with pulse frequency modulated (Pulse Frequency Modulation, PFM) mode operating, and in the time of intermediate part load or severe load, automatically switch to pulse width modulation (Pulse Width Modulation, PWM) pattern.Known framework may need to detect the voltage loads of the element (for example I/O element) outside core parts (core device), therefore comparatively power consumption and need larger chip area.Therefore,, in communication system, how more efficiently switch pulse frequency modulation(FM) and pulse width modulation, obviously become for this reason a considerable subject under discussion in field.

Summary of the invention

The frequency detecting device that provides a kind of builtin voltage output meeting to change along with the frequency input signal of input signal is provided one of object of the present invention, to switch between pulse frequency modulated and pulse width modulation more efficiently.

According to one first embodiment of the present invention, it provides a kind of frequency detecting device.This frequency detecting device includes certain current generating unit, one first capacitor, a first transistor, one second capacitor and a transistor seconds.Wherein, this is determined current generating unit and is used to provide certain electric current and gives a voltage output end; This first capacitor is coupled between this voltage output end and one first reference voltage; This first transistor has one first link, a control end and one second link, and wherein, this first link is coupled to this voltage output end, and this control end is coupled to an input signal; This second capacitor system is coupled between this second link and this first reference voltage of this first transistor; And this transistor seconds has one first link, a control end and one second link, wherein, this of this transistor seconds the first link is coupled to this second link of this first transistor, this of this transistor seconds the second link is coupled to this first reference voltage, and this control end of this transistor seconds is coupled to a rp input signal, wherein, this rp input signal and this input signal are inverting each other; Wherein, a Voltage-output of this voltage output end can change along with a frequency input signal of this input signal.

According to one second embodiment of the present invention, it provides a kind of frequency detecting device.This frequency detecting device includes certain current generating unit and one frequency-voltage conversion unit.Wherein, this is determined current generating unit and is used to provide certain electric current and gives a voltage output end; This frequency-voltage conversion unit is used for receiving an input signal, a rp input signal and this determines electric current, and determines electric current and produce a Voltage-output in a voltage output end according to this input signal, this rp input signal and this; Wherein, this Voltage-output of this voltage output end and this frequency input signal of this input signal have a predetermined ratio relation.

Frequency detecting device proposed by the invention can not need to detect the voltage loads of the element outside core parts, and can automatically judge when pulse frequency modulated should be converted to pulse width modulation, to bring into play the waste of higher efficiency and the minimizing energy.In other words, frequency detecting device proposed by the invention can extend the service time of battery of multifunctional portable application, and consumes energy and dispel the heat still less.

Brief description of the drawings

Fig. 1 is the schematic diagram according to an embodiment of a frequency detecting device of the present invention.

Fig. 2 is the schematic diagram according to another embodiment of a frequency detecting device of the present invention.

[symbol description]

100,200 frequency detecting devices

102,202 determine current generating unit

104,204 frequencies-voltage conversion unit

106,206 comparators

1022,1032 resistance

1024,1026,1028,1044,1048 transistors

1030 amplifiers

1042,1046 electric capacity

Embodiment

Please refer to Fig. 1, Fig. 1 is that wherein, frequency detecting device 100 includes certain current generating unit 102, one frequency-voltage conversion unit 104 and a comparator 106 according to the schematic diagram of an embodiment of a frequency detecting device 100 of the present invention.Determine current generating unit 102 and be used to provide certain electric current I _totalgive a voltage output end N of frequency-voltage conversion unit 104 _out; And frequency-voltage conversion unit 104 is used for receiving an input signal S _pFM, a rp input signal with determine electric current I _total, wherein, input signal S _pFMwith rp input signal inverting each other; And frequency-voltage conversion unit 104 is according to input signal S _pFM, rp input signal with determine electric current I _totaland in voltage output end N _outproduce a Voltage-output V _out, and Voltage-output V _outcan be along with input signal S _pFMa frequency input signal f and change; Comparator 106 has a first input end (+) and one second input (-), and wherein, first input end (+) is coupled to voltage output end N _out, and the second input (-) is coupled to a corresponding preset frequency f _pda predetermined voltage V _pd, wherein, comparator 106 is used for judging input signal S _pFMfrequency input signal f whether exceed preset frequency f _pd.

Furthermore, determine current generating unit 102 and include one first resistance 1022, a first transistor 1024, a transistor seconds 1026, one the 3rd transistor 1028, an amplifier 1030 and one second resistance 1032.The first resistance 1022 has and is coupled to one second reference voltage V ₂an and resistance value R between this voltage output end; The first transistor 1024 has one first link, a control end and one second link, and wherein, this first link is coupled to voltage output end N _out, this second link is coupled to the second reference voltage V ₂; Transistor seconds 1026 has one first link, a control end and one second link, wherein, the first link of transistor seconds 1026 is coupled to the control end of the first transistor 1024 and the control end of transistor seconds 1026, and the second link of transistor seconds 1026 is coupled to the second reference voltage V ₂; The 3rd transistor 1028 has one first link, a control end and one second link, and wherein, the first link of the 3rd transistor 1028 is coupled to the first link of transistor seconds 1026.Amplifier 1030 has a normal phase input end (+), an inverting input (-) and an output, and wherein, normal phase input end (+) is coupled to voltage output end N _out, inverting input (-) is coupled to this second link of the 3rd transistor 1028, and this output is coupled to the control end of the 3rd transistor 1028.In addition, the second resistance 1032 can have the resistance value identical with the resistance value R of the first resistance 1022, and is coupled to this second link and the first reference voltage V of the 3rd transistor 1028 ₁between (the first reference voltage is ground connection in the present embodiment).It should be noted, in practice, transistor in the present embodiment can use and anyly can reach the design that is similar to switch effect, and the variation in these designs all belongs to scope of the present invention, for instance, transistor in the present embodiment can be mos field effect transistor (Metal – Oxide – Semiconductor Field-Effect Transistor, MOSFET), and transistorized the first link, control end and the second link can be respectively drain electrode end (drain terminal), gate terminal (gate terminal) and source terminal (source terminal).

The output of amplifier 1030 is coupled to the control end of the 3rd transistor 1028, and the normal phase input end (+) of amplifier 1030 receives by voltage output end N _outthe Voltage-output V producing _out, and the inverting input (-) of amplifier 1030 output one output voltage V _outand be coupled to resistance 1032, make output voltage V _outproducing a control electric current I through resistance 1032 (is also ).In addition, transistor 1024 in the present embodiment and transistor 1026 can have same breadth length ratio (aspect ratio) design, therefore can obtain transistor 1024 by the framework of current mirroring circuit can produce and the same control electric current I of transistor 1026, and determining current generating unit 1022 can provide and determine electric current I _totalgive this voltage output end of frequency-voltage conversion unit 104, therefore, entirety determine electric current I _totalcan be expressed as follows:

$I_{\mathrm{total}}=\frac{V_{\mathrm{out}}}{R}+\frac{V_2-V_{\mathrm{out}}}{R}=\frac{V_2}{R}---\left(1\right)$

That is to say, determine electric current I _totalvalue be a fixed value, and can not be subject to the voltage output end N of frequency-voltage conversion unit 104 _outvoltage-output V _outimpact.It should be noted, the detailed operation of determining current generating unit 102 is not emphasis of the present invention, those of ordinary skill in the art should be able to illustrate more than reference and equation (1) is understood the principle of determining current generating unit 102 afterwards easily, therefore do not do more and repeat determining the implementation detail of current generating unit 102 at this, in addition the design (for example breadth length ratio of transistor 1024 and 1026) of determining current generating unit 102 is only illustrative purposes at this, in practice, any other can reach design or the variation of identical object, all belongs to scope of the present invention.

Frequency-voltage conversion unit 104 includes one first capacitor 1042, a first transistor 1044, one second capacitor 1046 and a transistor seconds 1048.The first capacitor 1042 has a capacitance C ₁, and be coupled to voltage output end N _outwith the first reference voltage V ₁between; The first transistor 1044 has one first link, a control end and one second link, and wherein, this first link is coupled to voltage output end N _out, and this control end is coupled to input signal S _pFM; The second capacitor 1046 has a capacitance C ₂, and be coupled to this second link and the first reference voltage V of this first transistor ₁between; Transistor seconds 1048 has one first link, a control end and one second link, wherein, this first link of transistor seconds 1048 is coupled to this second link of the first transistor 1044, and this second link of transistor seconds 1048 is coupled to the first reference voltage V ₁, and this control end of transistor seconds 1048 is coupled to rp input signal in this embodiment, input signal S _pFMbe an output signal of pulse frequency modulated, its frequency is frequency input signal f.

The operating principle of frequency detecting device 100 of the present invention will be described in detail below.Refer to Fig. 1, the first transistor 1044 in frequency-voltage conversion unit 104 is according to input signal S _pFMdecide whether conducting of the first transistor 1044; And transistor seconds 1048 is according to rp input signal decide whether conducting of transistor seconds 1048, therefore, the operation of frequency-voltage conversion unit 104 can be divided into two stages, in the time of the first stage, and input signal S _pFMfor logical zero, rp input signal for logical one, the first transistor 1044 is closed condition, and transistor seconds 1048 is conducting state.Now, determine electric current I _totalcharged state to electric capacity 1042 is as follows:

$I_{\mathrm{total}}=C_1\frac{\mathrm{dv}}{\mathrm{dt}}\⇒{\∫}_0^{V_1}\mathrm{dv}=\frac{I_{\mathrm{total}}}{C_1}{\∫}_0^{\frac{1}{2f}}\mathrm{dt}\⇒V_1=\frac{I_{\mathrm{total}}}{C_1}\frac{1}{2f}---\left(2\right)$

Wherein, V ₁for the voltage increasing on electric capacity 1042, and f is input signal S _pFMwith rp input signal signal frequency.

In the time of second stage, input signal S _pFMfor logical one, rp input signal for logical zero, the first transistor 1044 is conducting state, and transistor seconds 1048 is closed condition.Because the first transistor 10442 is switched on, will there is electric charge and share (charge sharing) effect in the second electric capacity 1046 and the first electric capacity 1042, and relevant derivation formula is as follows:

$V_1{C}_1=V_x(C_1+C_2)\⇒V_X=\frac{C_1}{C_1+C_2}{V}_1---\left(3\right)$

Wherein, V _xshare for being subject to electric charge on electric capacity 1046 voltage reducing under effects.

Therefore,, in the time of second stage, determine electric current I _totalcan be expressed as the charged state of the first electric capacity 1042:

$I_{\mathrm{total}}=(C_1+C_2)\frac{\mathrm{dv}}{\mathrm{dt}}\⇒{\∫}_{v_x}^{v_2}\mathrm{dv}=\frac{I_{\mathrm{total}}}{C_1+C_2}{\∫}_{\frac{1}{2f}}^{\frac{1}{f}}\mathrm{dt}\⇒V_2-V_x=\frac{I_{\mathrm{total}}}{C_1+C_2}\frac{1}{2f}---\left(4\right)$

$V_2=V_x+\frac{I_{\mathrm{total}}}{C_1+C_2}\frac{1}{2f}=\frac{C_1}{C_1+C_2}{V}_1+\frac{I_{\mathrm{total}}}{C_1+C_2}\frac{1}{2f}---\left(5\right)$

Wherein, V ₂for when the second stage, the voltage increasing on the second electric capacity 1046.

Because first stage and second stage can constantly repeat, therefore can suppose:

$\mathrm{\β}=\frac{C_1}{C_1+C_2}$

$V_C=\frac{I_{\mathrm{total}}}{C_1+C_2}\frac{1}{2f}$

So, the voltage output end N of frequency-voltage conversion unit 104 _outvoltage-output V _outcan be derived from as follows:

$V_{2n}=({\mathrm{\βV}}_1+V_{\mathrm{out}})({\mathrm{\β}}^{n-1}+{\mathrm{\β}}^{n-2}+...+1)=>V_{\mathrm{out}}=\frac{I_{\mathrm{total}}}{{\mathrm{fC}}_2}---\left(6\right)$

Control electric current I and Voltage-output V again, _outbetween relation show as follows:

$I=\frac{V_{\mathrm{out}}}{R}---\left(7\right)$

In conjunction with equation (6) and equation (7), can be derived from input signal S _pFMwith rp input signal signal frequency f be:

$f=\frac{V_2}{{\mathrm{RC}}_2{V}_{\mathrm{out}}}---\left(8\right)$

Also can be expressed as:

$V_{\mathrm{out}}=\frac{V_2}{{\mathrm{fRC}}_2}---\left(9\right)$

In other words, the voltage output end N of frequency-voltage conversion unit 104 _outvoltage-output V _outwith input signal S _pFMfrequency input signal f be inversely proportional to, namely input signal S _pFMfrequency input signal f higher, voltage output end N _outvoltage-output V _outcan be less.

As the input signal S producing via pulse frequency modulated _pFMfrequency input signal f when more and more higher, for overall modulation efficiency, it is a way of relatively saving overall power consumption that pulse frequency modulated is switched to pulse width modulation meeting, and in this embodiment, we can utilize the voltage output end N of frequency-voltage conversion unit 104 _outvoltage-output V _outjudge the size of frequency input signal f, for example, preset a preset frequency f _pd, as input signal S _pFMfrequency input signal f exceed preset frequency f _pdtime, just pulse frequency modulated is switched to pulse width modulation, therefore can utilize equation (9) to obtain corresponding to preset frequency f _pda predetermined voltage V _pd, and with comparator 106 by Voltage-output V _outwith predetermined voltage V _pdcompare, as Voltage-output V _outmore and more lower, and lower than predetermined voltage V _pdtime, comparator 106 can produce the variation of logical one to logical zero, carrys out by this control impuls frequency modulation(FM) and switches to pulse width modulation.

It should be noted, the foregoing is only an embodiment details of frequency detecting device of the present invention, in practice, any other can reach design or the variation of identical object, all belongs to scope of the present invention.Please refer to Fig. 2, Fig. 2 is that wherein, frequency detecting device 200 includes certain current generating unit 202, one frequency-voltage conversion unit 204 and a comparator 106 according to the schematic diagram of an embodiment of a frequency detecting device 200 of the present invention.Determine current generating unit 102 and be used to provide certain electric current I _totalgive a voltage output end of frequency-voltage conversion unit 204; And frequency-voltage conversion unit 204 is used for receiving an input signal, a rp input signal and determines electric current I _total, wherein, input signal and rp input signal are inverting each other; And frequency-voltage conversion unit 104 can and be determined electric current I according to input signal, rp input signal _totaland produce a Voltage-output V in this voltage output end _out, and Voltage-output V _outcan change along with a frequency input signal f of this input signal; Comparator 106 has a first input end (+) and one second input (-), and wherein, first input end (+) is coupled to this voltage output end, and the second input (-) is coupled to a corresponding preset frequency f _pda predetermined voltage V _pd, wherein, comparator 106 is used for judging whether the frequency input signal f of input signal exceedes preset frequency f _pd.In this embodiment, the circuit framework of the frequency-voltage conversion unit 204 in frequency detecting device 200 can be different from frequency-voltage conversion unit 104, as long as the voltage of output of frequency-voltage conversion unit 204 and the frequency of the input signal of frequency-voltage conversion unit 204 have a predetermined ratio relation, i.e. spirit according to the invention.

In sum, frequency detecting device proposed by the invention can utilize the mode that detects frequency change to control the module of executive signal processing, for instance, frequency detecting device 100/200 can not need to detect the voltage loads of the element outside core parts, and can automatically judge when pulse frequency modulated should be converted to pulse width modulation by the frequency that detects input signal, make the waste of the higher efficiency of its performance and the minimizing energy.In other words, frequency detecting device proposed by the invention can extend the service time of battery of multifunctional portable application, and consumes energy and dispel the heat still less.

The foregoing is only the preferred embodiments of the present invention, all equalizations of doing according to the claims in the present invention scope change and modify, and all should belong to covering scope of the present invention.

Claims (10)

1. a frequency detecting device, includes:

Certain current generating unit, is used to provide certain electric current and gives a voltage output end;

One first capacitor, is coupled between described voltage output end and one first reference voltage;

One the first transistor, has one first link, a control end and one second link, and the first link of wherein said the first transistor is coupled to described voltage output end, and the control end of described the first transistor is coupled to an input signal;

One second capacitor, is coupled between second link and described the first reference voltage of described the first transistor; And

One transistor seconds, there is one first link, a control end and one second link, wherein, the first link of described transistor seconds is coupled to the second link of described the first transistor, the second link of described transistor seconds is coupled to described the first reference voltage, and the control end of described transistor seconds is coupled to a rp input signal;

Wherein, a Voltage-output of described voltage output end can change along with a frequency input signal of described input signal.

2. frequency detecting device according to claim 1, wherein, the described Voltage-output of described voltage output end and the described frequency input signal of described input signal are inversely proportional to.

3. frequency detecting device according to claim 1, also includes:

One comparator, has a first input end and one second input, and wherein, described first input end is coupled to described voltage output end, and described the second input is coupled to the predetermined voltage corresponding to a preset frequency;

Wherein, described comparator is used for judging whether the described frequency input signal of described input signal exceedes described preset frequency.

4. frequency detecting device according to claim 1, wherein, describedly determine current generating unit and include:

One first resistance, is coupled between one second reference voltage and described voltage output end;

One the first transistor, has one first link, a control end and one second link, and wherein, the first link of described the first transistor is coupled to described voltage output end, and the second link of described the first transistor is coupled to described the second reference voltage;

One transistor seconds, there is one first link, a control end and one second link, wherein, the first link of described transistor seconds is coupled to the control end of described the first transistor and the control end of described transistor seconds, and the second link of described transistor seconds is coupled to described the second reference voltage;

One the 3rd transistor, has one first link, a control end and one second link, and wherein, described the 3rd transistorized the first link is coupled to the first link of described transistor seconds;

One amplifier, there is a normal phase input end, an inverting input and an output, wherein, described normal phase input end is coupled to described voltage output end, described inverting input is coupled to described the 3rd transistorized the second link, and described output is coupled to described the 3rd transistorized control end; And

One second resistance, is coupled between described the 3rd transistorized the second link and described the first reference voltage.

5. frequency detecting device according to claim 1, wherein, the pulse frequency modulated signal that described input signal is exported for a modulating unit of execution one pulse frequency modulated program.

6. a frequency detecting device, includes:

Certain current generating unit, is used to provide certain electric current and gives a voltage output end; And

One frequency-voltage conversion unit, is used for receiving an input signal, a rp input signal and describedly determines electric current, and according to described input signal, described rp input signal and describedly determine electric current and produce a Voltage-output at a voltage output end;

Wherein, a frequency input signal of described Voltage-output and described input signal has a predetermined ratio relation.

7. frequency detecting device according to claim 6, wherein, it is an inverse relation that described predetermined ratio is closed.

8. frequency detecting device according to claim 6, also includes:

One comparator, has a first input end and one second input, and wherein, described first input end is coupled to described voltage output end, and described the second input is coupled to the predetermined voltage corresponding to a preset frequency;

Wherein, described comparator is used for judging whether the described frequency input signal of described input signal exceedes described preset frequency.

9. frequency detecting device according to claim 6, wherein, describedly determine current generating unit and include:

One first resistance, couples between a reference voltage and described voltage output end;

One the first transistor, has one first link, a control end and one second link, and wherein, the first link of described the first transistor is coupled to described voltage output end, and the second link of described the first transistor is coupled to described reference voltage;

One transistor seconds, there is one first link, a control end and one second link, wherein, the first link of described transistor seconds is coupled to the control end of described the first transistor and the control end of described transistor seconds, and the second link of described transistor seconds is coupled to described reference voltage;

One the 3rd transistor, has one first link, a control end and one second link, and wherein, described the 3rd transistorized the first link is coupled to the first link of described transistor seconds;

One amplifier, have a normal phase input end, an inverting input and an output, wherein, described normal phase input end is coupled to described voltage output end, described anti-phase input is coupled to described the 3rd transistorized the second link, and described output is coupled to described the 3rd transistorized control end; And

One second resistance, is coupled between described the 3rd transistorized the second link and another reference voltage.

10. frequency detecting device according to claim 6, wherein, the pulse frequency modulated signal that described input signal is exported for a modulating unit of execution one pulse frequency modulated program.