CN109962871B - ASK amplitude modulation signal envelope detection system - Google Patents
ASK amplitude modulation signal envelope detection system Download PDFInfo
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- CN109962871B CN109962871B CN201910246455.4A CN201910246455A CN109962871B CN 109962871 B CN109962871 B CN 109962871B CN 201910246455 A CN201910246455 A CN 201910246455A CN 109962871 B CN109962871 B CN 109962871B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/02—Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation
- H04L27/06—Demodulator circuits; Receiver circuits
Abstract
The invention particularly relates to an ASK amplitude modulation signal envelope detection system which comprises a high-voltage signal acquisition circuit, an envelope detection circuit and a band-pass amplification circuit which are sequentially connected in series, wherein the input end of the high-voltage signal acquisition circuit is connected with one end of a coil and used for acquiring a high-voltage signal of the coil, attenuating the high-voltage signal and outputting the high-voltage signal to the envelope detection circuit, the envelope detection circuit demodulates a low-frequency signal from the amplitude modulation signal and outputs the low-frequency signal to the band-pass amplification circuit, and the band-pass amplification circuit is used for filtering a carrier signal and a common-mode signal and outputting a baseband signal to a post-stage demodulation circuit for further demodulation. By the scheme, an off-chip diode, a high-voltage capacitor and a part of resistor are removed, so that the cost of the wireless charging system is greatly reduced; meanwhile, a highly integrated detection scheme is realized, the circuit size is reduced, and in practical use, the off-chip resistor R is removed1Besides, other circuit parts can be integrated into the chip, so that the use is very convenient.
Description
Technical Field
The invention relates to the technical field of electronics, in particular to an ASK amplitude modulation signal envelope detection system.
Background
The market demand of wireless charging technology is increasing, wherein a scheme based on wireless charging alliance (WPC) QI standard becomes a mainstream scheme. The QI standard specifies that the wireless charging system performs data communication from the receiving end to the transmitting end in an ASK manner, the frequency of the amplitude-modulated signal is as low as about 2kHz, and the amplitude-modulated carrier frequency is 87kHz to 250 kHz. The scheme of the mainstream wireless charging system in the market, such as P9242R from IDT company, BQ50002 from TI company, and the like, adopts a conventional envelope detection method, which is shown in fig. 1, and a high-voltage ASK signal is collected from one end of a charging coil, and the signal is transmitted to an SOC chip for signal processing through a half-wave rectification envelope detection circuit composed of a discrete diode, a capacitor and a resistor, and a high-pass filter capacitor. The main disadvantages of this solution are the need for off-chip diodes, high voltage tolerant capacitors, and several resistors, which increase the overall cost of the system solution.
Disclosure of Invention
The invention aims to provide an ASK amplitude modulation signal envelope detection system with low cost and high integration level.
In order to realize the purpose, the invention adopts the technical scheme that: the utility model provides an ASK amplitude modulation signal envelope detection system, is including high-voltage signal acquisition circuit, envelope detection circuit and the band-pass amplifier circuit that establishes ties in proper order, high-voltage signal acquisition circuit's one end of input connection coil be used for gathering the high-voltage signal of coil and carry out output to envelope detection circuit after the decay, envelope detection circuit exports to band-pass amplifier circuit after demodulating low frequency signal from amplitude modulation signal, band-pass amplifier circuit is used for filtering carrier signal, common mode signal back output baseband signal to back level demodulation circuit and carries out further demodulation.
Compared with the prior art, the invention has the following technical effects: by the scheme, an off-chip diode, a high-voltage capacitor and a part of resistor are removed, so that the cost of the wireless charging system is greatly reduced; meanwhile, a high-voltage signal acquisition circuit with very high integration level, an envelope detection circuit and a band-pass amplification circuit are adopted, a highly integrated detection scheme is realized, the circuit size is reduced, and in practical use, the off-chip resistor R is removed1Besides, other circuit parts can be integrated into the chip, so that the use is very convenient.
Drawings
FIG. 1 is a block diagram of a conventional off-chip envelope detection scheme;
FIG. 2 is a block diagram of the architecture of the present invention;
FIG. 3 is a circuit diagram of a first embodiment of a high voltage signal acquisition circuit according to the present invention;
FIG. 4 is a circuit diagram of a second embodiment of the high voltage signal acquisition circuit of the present invention;
FIG. 5 is a circuit diagram of a third embodiment of the high voltage signal acquisition circuit of the present invention;
FIG. 6 is a circuit diagram of the envelope detection circuit of the present invention;
FIG. 7 is a waveform diagram of the important nodes of the present invention;
fig. 8 is an enlarged view of the waveform of fig. 7 around 9.3 ms.
Detailed Description
The present invention will be described in further detail with reference to fig. 2 to 8.
Referring to fig. 2, an ASK amplitude modulation signal envelope detection system includes a high-voltage signal acquisition circuit, an envelope detection circuit and a band-pass amplification circuit which are connected in series in sequence, wherein an input end of the high-voltage signal acquisition circuit is connected with one end of a coil and used for acquiring a high-voltage signal of the coil and outputting the high-voltage signal to the envelope detection circuit after attenuation, the envelope detection circuit demodulates a low-frequency signal from the amplitude modulation signal and outputs the low-frequency signal to the band-pass amplification circuit, and the band-pass amplification circuit is used for filtering a carrier signal and a common-mode signal and then outputting a baseband signal to a post-stage demodulation circuit for further demodulation. By the scheme, an off-chip diode, a high-voltage capacitor and a part of resistor are removed, so that the cost of the wireless charging system is greatly reduced; meanwhile, a high-voltage signal acquisition circuit with very high integration level, an envelope detection circuit and a band-pass amplification circuit are adopted, a highly integrated detection scheme is realized, the circuit size is reduced, and in practical use, the off-chip resistor R is removed1Besides, other circuit parts can be integrated into the chip, so that the use is very convenient.
The system removes off-chip discrete devices to achieve a highly integrated detection scheme, where the following three problems are solved by providing three circuits. Firstly, as the high-voltage signal of the coil can reach 40V, in order to ensure that the sampling voltage range does not exceed the withstand voltage range of the SOC chip, the functions of attenuating the signal, increasing clamp protection or overvoltage protection and the like are required; secondly, in order to ensure that the detection precision of the on-chip detection scheme is large enough, the envelope signal needs to be amplified and conditioned, and a baseband signal is extracted; thirdly, in order to ensure that the low-frequency common-mode voltage fluctuation of the ASK signal does not influence the post-stage signal processing, high-pass filtering is required.
As preferred in the present inventionIn one embodiment, the high voltage signal acquisition circuit comprises an off-chip resistor R1On-chip clamping protection circuit, on-chip trans-impedance amplifier and high-voltage signal V on coilcoilOff-chip resistor R1Conversion to current IsnsCurrent I ofsnsConverted into an output voltage V by an on-chip trans-impedance amplifiersnsThen output to an envelope detection circuit, and an on-chip clamping protection circuit is used for ensuring an off-chip resistor R1Port voltage V of output terminalpadIs in the full range. There are many configurations of on-chip transimpedance amplifiers that can be implemented, and three preferred embodiments are provided herein for reference.
Referring to fig. 3, in the first embodiment, the on-chip clamp protection circuit is composed of an on-chip resistor R2The on-chip trans-impedance amplifier comprises an amplifier A and a resistor RZ(ii) a One end of coil is connected with external resistance R of sheet1One terminal of (1), an off-chip resistance R1The other end of the first resistor is connected with the inverting input end of the amplifier A and the off-chip resistor R1A branch is led out between the inverting input end of the amplifier A and passes through an on-chip resistor R2The non-inverting input end of the amplifier A is grounded, and a resistor R is connected in series between the output end and the inverting input end of the amplifier AZThe output end of the amplifier A is connected with the envelope detection circuit.
Here, amplifier A and resistor RZThe trans-impedance amplifier is formed. When the input voltage of the coil is negative, the trans-impedance amplifier converts the coil voltage into a current flowing through an off-chip resistor R1The generated current flows through a resistor RZIs converted into an output voltage VsnsThereby realizing the function of signal attenuation, and the on-chip resistor R due to the high gain characteristic of the amplifier A2Only weak current, no influence on conversion accuracy, VsnsThe calculation formula is as follows:
in the formula: a is the gain of the amplifier, and when A is large enough, for example, A >60dB, the above equation can be simplified to
When the input voltage of the coil is positive, the trans-impedance amplifier is saturated, the gain is reduced, the output is 0, and the on-chip resistor R is at the moment2And an off-chip resistor R1The attenuation circuit is configured to provide a clamp protection function, clamp voltage VclampThe calculation formula is as follows:
referring to fig. 4, in the second embodiment, the on-chip clamp protection circuit is composed of an on-chip resistor R2The on-chip trans-impedance amplifier comprises an amplifier A, MOS tube M1And a resistance RZ(ii) a One end of coil is connected with external resistance R of sheet1One terminal of (1), an off-chip resistance R1The other end of the first resistor is connected with the inverting input end of the amplifier A and the off-chip resistor R1A branch is led out between the inverting input end of the amplifier A and passes through an on-chip resistor R2The non-inverting input end of the amplifier A is grounded, and the output end of the amplifier A is connected with the MOS tube M1Grid of (3), MOS transistor M1Is connected with the inverting input end of the amplifier A, and the MOS tube M1Drain through resistance RZConnected to power supply VDD and MOS transistor M1The drain of the circuit is also connected as an output terminal to the envelope detection circuit.
The second embodiment is an implementation way using the power voltage as the output reference voltage, and V issnsThe calculation formula is as follows:
clamping voltage V of input pinclampThe calculation formula is as follows:
referring to fig. 5, in the third embodiment, the on-chip clamp protection circuit is composed of an on-chip resistor R2The on-chip transimpedance amplifier comprises an amplifier A1, an amplifier A2 and a MOS transistor M1And a resistance RZ(ii) a One end of coil is connected with external resistance R of sheet1One terminal of (1), an off-chip resistance R1The other end of the first resistor is connected with the inverting input end of the amplifier A1 and the off-chip resistor R1And a branch is led out between the inverting input end of the amplifier A1 and passes through the on-chip resistor R2The non-inverting input end of the amplifier A1 is grounded, and the output end of the amplifier A1 is connected with the MOS transistor M1Grid of (3), MOS transistor M1Is connected with the inverting input end of the amplifier A1, and the MOS transistor M1Is connected to the inverting input of amplifier a2, and the non-inverting input of amplifier a2 is connected to the common-mode voltage VBA resistor R is connected in series between the output end and the inverting input end of the amplifier A2ZThe output end of the amplifier A2 is connected with an envelope detection circuit.
The third embodiment is an implementation manner with a function of setting an output common-mode voltage, and the first-stage amplifier a1 and the MOS transistor M1Will flow through R1Is transmitted to the second stage amplifier A2 and the resistor RZThe final output common-mode voltage of the formed trans-impedance amplifier is VBThe output signal of (1). It VsnsThe calculation formula is as follows:
clamping voltage V of input pinclampThe calculation formula is the same as that in the second embodiment, and is not described here again.
Referring to fig. 6, there are many possible implementations of the envelope detection circuit, and preferably, the envelope detection circuit includes an amplifier A3, an amplifier a4, and a MOS transistor M2(ii) a The output end of the high-voltage signal acquisition circuit is connected with the non-inverting input end of an amplifier A3, and the output end of an amplifier A3 is connected with a MOS (metal oxide semiconductor) transistor M2Grid of (3), MOS transistor M2Is connected with a power supply VDD, an inverting input end of an amplifier A3 and a capacitor CrecOne end of (1), MOS tube M2Source of amplifier a4, non-inverting input of amplifier a4, resistor RrecAre connected together, a capacitor CrecThe other end of (3) is grounded, and a resistor RrecThe other end of the resistor is divided into two paths, wherein one path passes through a resistor Rrec1The output end of the amplifier A4 is connected, and the other path is connected with the output end of the amplifier A4 through a resistor Rrec2The output end of the amplifier A4 is used as the output end of the envelope detection circuit and is connected with the band-pass amplification circuit. The envelope detection circuit comprises a peak detection circuit amplifier A3 and a MOS transistor M2Form a pair of capacitors CrecThe charging path of (a); amplifier A4, resistor Rrec1、Rrec2And RrecForm a pair of capacitors CrecThe discharge path of (a). When the charging path speed is enough to track the peak value of the input signal, and the discharging path time constant is far larger than the carrier period of the envelope and is close to the baseband period, the peak value circuit has the envelope detection function.
In the invention, the charging path part of the envelope detection circuit belongs to a part of the traditional peak value detection circuit, and the discharging path part optimizes the area, the temperature drift and the process consistency of the traditional discharging circuit. Conventional discharge circuits are often implemented with a single discharge resistor or a controllable discharge current source. The frequency of a baseband signal of wireless charging under the QI standard is 2kHz, the lowest frequency of a carrier signal is 87kHz, and in order to meet the performance requirement of envelope detection, a discharge time constant needs to exceed millisecond magnitude. Taking a capacitor with 20pF, if a traditional single discharge resistor is adopted, a resistor with the resistance of more than 50Mohm is needed, and a large amount of chip area is occupied; if a discharge current source is adopted, the current less than 20nA needs to be provided, and the weak current has large deviation with temperature and process and very poor consistency. The discharge circuit of the invention adopts smaller resistance, realizes great equivalent discharge resistance and avoids the consistency problem of weak current source. The equivalent discharge resistance is as follows:
for example, take RrecIs 2.5Mohm, Rrec1Is 10k, Rrec2At 200k, an equivalent discharge resistance of 50Mohm is achieved.
The band-pass amplifying circuit of the invention can adopt any band-pass amplifying circuit meeting the index, and the band-pass amplifying circuit is not expanded in detail, and the output signal of the envelope detection circuit outputs a baseband signal V after further filtering carrier signals and common-mode signals by the band-pass amplifying circuitenvThe back stage is given further demodulation.
Fig. 7 is a waveform diagram of an important node of the scheme of the present invention, and fig. 8 is an enlarged waveform diagram of fig. 7 in the vicinity of 9.3 ms. The waveform diagram is acquired based on the three high-voltage signal acquisition circuits of the embodiment, wherein the common-mode voltage VBSet to 1.25V. It can be seen that although VcoilHigh pressure of approximately 12V to-6V, VpadThe voltage is still kept near 0V, so that the chip is ensured to be in a safe voltage range; the coil high-voltage signal acquisition circuit will obtain a V of-6VcoilThe voltage is reduced by 20 times to V with the amplitude of about 300mVsnsAnd keep VcoilEnvelope information of (a); peak detection output voltage VrecTrack VsnsA peak value of the voltage; vrecAfter carrier and common mode voltage are filtered by a rear-stage band-pass amplifier, V is outputenvThe 2kHz baseband signal is recovered.
Claims (4)
- An ASK amplitude modulation signal envelope detection system, characterized by: the high-voltage signal acquisition circuit is connected with one end of a coil, is used for acquiring a high-voltage signal of the coil, attenuates the high-voltage signal and outputs the high-voltage signal to the envelope detection circuit, the envelope detection circuit demodulates a low-frequency signal from an amplitude modulation signal and outputs the low-frequency signal to the band-pass amplification circuit, and the band-pass amplification circuit is used for filtering a carrier signal and a common-mode signal and then outputs a baseband signal to a post-stage demodulation circuit for further demodulation;the high-voltage signal acquisition circuit comprises an off-chip resistor R1On-chip clamping protection circuit, on-chip trans-impedance amplifier and high-voltage signal V on coilcoilQuilt sheetExternal resistance R1Conversion to current IsnsCurrent I ofsnsConverted into an output voltage V by an on-chip trans-impedance amplifiersnsThen output to an envelope detection circuit, and an on-chip clamping protection circuit is used for ensuring an off-chip resistor R1Port voltage V of output terminalpadIs in the full range;the envelope detection circuit comprises an amplifier A3, an amplifier A4 and a MOS transistor M2(ii) a The output end of the high-voltage signal acquisition circuit is connected with the non-inverting input end of an amplifier A3, and the output end of an amplifier A3 is connected with a MOS (metal oxide semiconductor) transistor M2Grid of (3), MOS transistor M2Is connected with a power supply VDD, an inverting input end of an amplifier A3 and a capacitor CrecOne end of (1), MOS tube M2Source of amplifier a4, non-inverting input of amplifier a4, resistor RrecAre connected together, a capacitor CrecThe other end of (3) is grounded, and a resistor RrecThe other end of the resistor is divided into two paths, wherein one path passes through a resistor Rrec1The output end of the amplifier A4 is connected, and the other path is connected with the output end of the amplifier A4 through a resistor Rrec2The output end of the amplifier A4 serving as the output end of the envelope detection circuit is connected with the band-pass amplification circuit; the envelope detection circuit removes an off-chip diode and a high-voltage capacitor, and reduces the cost of the ASK amplitude modulation signal envelope detection system.
- 2. An ASK amplitude modulated signal envelope detection system as defined in claim 1, wherein: the on-chip clamping protection circuit is composed of an on-chip resistor R2The on-chip trans-impedance amplifier comprises an amplifier A and a resistor RZ(ii) a One end of coil is connected with external resistance R of sheet1One terminal of (1), an off-chip resistance R1The other end of the first resistor is connected with the inverting input end of the amplifier A and the off-chip resistor R1A branch is led out between the inverting input end of the amplifier A and passes through an on-chip resistor R2The non-inverting input end of the amplifier A is grounded, and a resistor R is connected in series between the output end and the inverting input end of the amplifier AZThe output end of the amplifier A is connected with the envelope detection circuit.
- 3. As claimed inASK the ASK amplitude modulation signal envelope detection system of 1, its characterized in that: the on-chip clamping protection circuit is composed of an on-chip resistor R2The on-chip trans-impedance amplifier comprises an amplifier A, MOS tube M1And a resistance RZ(ii) a One end of coil is connected with external resistance R of sheet1One terminal of (1), an off-chip resistance R1The other end of the first resistor is connected with the inverting input end of the amplifier A and the off-chip resistor R1A branch is led out between the inverting input end of the amplifier A and passes through an on-chip resistor R2The non-inverting input end of the amplifier A is grounded, and the output end of the amplifier A is connected with the MOS tube M1Grid of (3), MOS transistor M1Is connected with the inverting input end of the amplifier A, and the MOS tube M1Drain through resistance RZConnected to power supply VDD and MOS transistor M1The drain of the circuit is also connected as an output terminal to the envelope detection circuit.
- 4. An ASK amplitude modulated signal envelope detection system as defined in claim 1, wherein: the on-chip clamping protection circuit is composed of an on-chip resistor R2The on-chip transimpedance amplifier comprises an amplifier A1, an amplifier A2 and a MOS transistor M1And a resistance RZ(ii) a One end of coil is connected with external resistance R of sheet1One terminal of (1), an off-chip resistance R1The other end of the first resistor is connected with the inverting input end of the amplifier A1 and the off-chip resistor R1And a branch is led out between the inverting input end of the amplifier A1 and passes through the on-chip resistor R2The non-inverting input end of the amplifier A1 is grounded, and the output end of the amplifier A1 is connected with the MOS transistor M1Grid of (3), MOS transistor M1Is connected with the inverting input end of the amplifier A1, and the MOS transistor M1Is connected to the inverting input of amplifier a2, and the non-inverting input of amplifier a2 is connected to the common-mode voltage VBA resistor R is connected in series between the output end and the inverting input end of the amplifier A2ZThe output end of the amplifier A2 is connected with an envelope detection circuit.
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| CN110338776B (en) * | 2019-07-11 | 2022-04-01 | 无锡金童科技有限公司 | PPG signal acquisition chip and device based on CMOS integrated circuit technology |
| CN112532197A (en) * | 2020-11-17 | 2021-03-19 | 北京中电华大电子设计有限责任公司 | Envelope restoration circuit |
| CN113055326B (en) * | 2021-03-10 | 2022-06-17 | 四川省博瑞恩科技有限公司 | Amplitude shift keying demodulation circuit based on sampling subtraction method |
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