Electric leakage compensation circuit and method of charge pump and phase-locked loop

Abstract

The invention belongs to the technical field of electronic circuits, and particularly discloses a charge pump electric leakage compensation circuit and method and a phase-locked loop, the circuit comprises a current source, a comparator and two pulse width detectors, two input ends of the comparator are respectively connected with the two pulse width detectors, and an output end of the comparator is connected with a control end of the current source. The output end of the current source is connected to the common connection end of the low-pass filter and the voltage-controlled oscillator in the phase-locked loop, and the input ends of the two pulse width detectors are connected with the two control signal input ends of the charge pump in the phase-locked loop respectively. The optimal electric leakage compensation current can be effectively determined, the electric leakage problem of the charge pump is solved, the jitter effect of the VC voltage received by the voltage-controlled oscillator can be effectively reduced, the problem that the output clock frequency of the voltage-controlled oscillator is unstable due to the jitter of the VC voltage is solved, and the voltage-controlled oscillator outputs an ideal clock.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic circuits, and in particular relates to a charge pump leakage compensation circuit, method and phase-locked loop. Background Art

[0002] Existing phase-locked loops such as Figure 1 As shown, the phase difference between the reference clock and the feedback clock is identified by the phase frequency detector (PFD), and then the corresponding up pulse signal (UP) and down pulse signal (DN) are generated according to the phase difference to control the current output of the charge pump (CP). The charge pump outputs the current iout to the low-pass filter (LPF), and the low-pass filter generates the corresponding voltage VC to adjust the output clock frequency of the voltage-controlled oscillator (VCO). The output of the voltage-controlled oscillator is then divided by the divider to obtain the feedback clock. Ideally, the current signal width of the charge pump is the same as the signal width of UP / DN, and the voltage VC remains unchanged. However, when the charge pump leaks, such as Figure 2 As shown, the voltage VC will change, but in order to maintain the stability of the entire loop, the average value of the voltage VC remains unchanged, so the charge pump will output additional current to the low-pass filter, which will eventually cause the voltage VC to fluctuate. The fluctuation of VC will eventually cause the output frequency of the voltage-controlled oscillator to fluctuate, thereby generating a non-ideal clock signal.

[0003] The traditional method to solve the charge pump leakage problem is to change the transistor type or reduce the size of the tube. Although this method can reduce leakage to a certain extent and reduce the jitter of VC, it will introduce other undesirable factors, such as the limitation of tube size, too small tube will increase tube noise, VC cannot have a wider range, etc., and transistors are difficult to avoid leakage, and the problem caused by leakage cannot be fundamentally solved. Therefore, an effective method that can better solve the corresponding problems caused by charge pump leakage is urgently needed. Summary of the invention

[0004] The purpose of the present invention is to provide a charge pump leakage compensation circuit, method and phase-locked loop to solve the above problems existing in the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a charge pump leakage compensation circuit, comprising a current source, a comparator and two pulse width detectors, wherein two input ends of the comparator are respectively connected to the two pulse width detectors, and the output end is connected to the control end of the current source, and the output end of the current source is connected to the common connection end of a low-pass filter and a voltage-controlled oscillator in a phase-locked loop, and the input ends of the two pulse width detectors are respectively connected to two control signal input ends of the charge pump in the phase-locked loop, wherein one pulse width detector is used to collect an upper pulse signal output from a phase detector in the phase-locked loop to the charge pump, detect the pulse width of the upper pulse signal, and output a first pulse width detection signal to the comparator, and the other pulse width detector is used to collect a lower pulse signal output from the phase detector in the phase-locked loop to the charge pump, detect the pulse width of the lower pulse signal, and output a second pulse width detection signal to the comparator, wherein the comparator is used to compare the first pulse width detection signal and the second pulse width detection signal, and output a corresponding current compensation signal to the current source according to the comparison result, and the current source is used to output a corresponding compensation current to the common connection end of the low-pass filter and the voltage-controlled oscillator according to the current compensation signal.

[0006] When it is used, the upper pulse signal and the lower pulse signal transmitted to the charge pump by the phase detector in the phase-locked loop can be respectively collected through two pulse width detectors to perform corresponding pulse width detection, so as to output the first pulse width detection signal and the second pulse width detection signal to the comparator respectively. The comparator can compare the sizes of the two pulse width detection results, and then output the corresponding current compensation signal to the current source according to the comparison result, so that the current source adjusts the output compensation current to the common connection end of the low-pass filter and the voltage-controlled oscillator according to the current compensation signal, thereby realizing leakage compensation for the charge pump in the phase-locked loop.

[0007] In one possible design, the pulse width detector employs a time-to-digital converter.

[0008] In a possible design, the comparator is a digital comparator.

[0009] In a possible design, the current source is an adjustable current source.

[0010] In a second aspect, the present invention provides a charge pump leakage compensation method, which is applied to the charge pump leakage compensation circuit in the first aspect, comprising: S1. Collect the upper pulse signal output from the phase detector in the phase-locked loop to the charge pump through a pulse width detector, detect the pulse width of the upper pulse signal, output a first pulse width detection signal to the comparator, collect the lower pulse signal output from the phase detector in the phase-locked loop to the charge pump through another pulse width detector, detect the pulse width of the lower pulse signal, and output a second pulse width detection signal to the comparator; S2a. The comparator receives the first pulse width detection signal and compares it with the second pulse width detection signal, and outputs a first current compensation signal to the current source when the comparison determines that the first pulse width detection signal is greater than the second pulse width detection signal; S3a. The current source increases the compensation current according to the first current compensation signal, and outputs the increased compensation current to the common terminal of the low-pass filter and the voltage-controlled oscillator; S4a repeats the above steps S2a- S3a until the first pulse width detection signal is equal to the second pulse width detection signal, and the compensation current output by the current source is finally used as the optimal compensation current; S5. The current source maintains outputting the optimal compensation current to perform leakage compensation on the charge pump.

[0011] In one possible design, the method further includes: S2b. The comparator receives the first pulse width detection signal and compares it with the second pulse width detection signal, and outputs a second current compensation signal to the current source when the comparison determines that the first pulse width detection signal is less than the second pulse width detection signal; S3b the current source reduces the compensation current according to the second current compensation signal, and outputs the reduced compensation current to the common terminal of the low-pass filter and the voltage-controlled oscillator; S4b. Repeat the above steps S2b to S3b until the first pulse width detection signal is equal to the second pulse width detection signal, and take the compensation current finally output by the current source as the optimal compensation current.

[0012] In a third aspect, the present invention provides a charge pump leakage compensation phase-locked loop, comprising a phase detector, a charge pump, a low-pass filter, a voltage-controlled oscillator, a frequency divider and the charge pump leakage compensation circuit in the first aspect, wherein two clock signal input ends of the phase detector are respectively connected to a reference clock signal and a feedback clock signal output by the frequency divider, an upper pulse signal output end and a lower pulse signal output end of the phase detector are respectively connected to two control signal input ends of the charge pump, an output end of the charge pump is connected to a low-pass filter for outputting an iout current to the low-pass filter, an output end of the low-pass filter is connected to a voltage-controlled oscillator for outputting a VC voltage to the voltage-controlled oscillator, an output end of the voltage-controlled oscillator is connected to a frequency divider for outputting a corresponding frequency clock signal to the frequency divider, the frequency divider is used to perform frequency division processing on the frequency clock signal output by the voltage-controlled oscillator, and output a feedback clock signal to the phase detector, input ends of two pulse width detectors are respectively connected to two control signal input ends of the charge pump, and an output end of the current source is connected to a common connection end of the low-pass filter and the voltage-controlled oscillator.

[0013] In one possible design, the phase detector is a phase frequency detector.

[0014] Beneficial effect: The present invention detects the pulse width of the upper pulse signal and the lower pulse signal received by the charge pump to compare and determine the leakage situation of the charge pump, and offsets the leakage current by adjusting the size of the compensation current. It can not only effectively determine the optimal leakage compensation current and solve the leakage problem of the charge pump, but also effectively reduce the jitter effect of the VC voltage received by the voltage-controlled oscillator, solve the problem of unstable output clock frequency of the voltage-controlled oscillator caused by VC voltage jitter, and make the voltage-controlled oscillator output a more ideal clock. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 It is a structural schematic diagram of an existing phase-locked loop; Figure 2 A schematic diagram of a signal showing a charge pump leakage in an existing phase-locked loop; Figure 3 A schematic diagram of a phase-locked loop including a charge pump leakage compensation circuit provided by the present invention; Figure 4 It is a schematic diagram of signals of the phase-locked loop of the present invention after charge pump leakage compensation. DETAILED DESCRIPTION

[0017] It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. The specific structures and functional details disclosed herein are only used to describe the exemplary embodiments of the present invention. However, the present invention can be embodied in many alternative forms, and it should not be understood that the present invention is limited to the embodiments set forth herein.

[0018] It should be understood that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments can be understood according to specific circumstances.

[0019] In the following description, certain details are provided to facilitate a complete understanding of the example embodiments. However, it will be appreciated by those of ordinary skill in the art that the example embodiments may be implemented without these certain details. For example, the system may be shown in a block diagram to avoid obscuring the example with unnecessary details. In other embodiments, well-known processes, structures, and techniques may not be shown in unnecessary detail to avoid obscuring the embodiments.

[0020] Embodiment 1: The present embodiment provides a charge pump leakage compensation circuit, including a current source, a comparator and two pulse width detectors, wherein two input ends of the comparator are respectively connected to the two pulse width detectors, and the output end is connected to the control end of the current source, and the output end of the current source is connected to the common connection end of the low-pass filter and the voltage-controlled oscillator in the phase-locked loop, and the input ends of the two pulse width detectors are respectively connected to the two control signal input ends of the charge pump in the phase-locked loop, wherein one pulse width detector is used to collect an upper pulse signal output from a phase detector in the phase-locked loop to the charge pump, detect the pulse width of the upper pulse signal, and output a first pulse width detection signal to the comparator, and the other pulse width detector is used to collect a lower pulse signal output from the phase detector in the phase-locked loop to the charge pump, detect the pulse width of the lower pulse signal, and output a second pulse width detection signal to the comparator, wherein the comparator is used to compare the first pulse width detection signal and the second pulse width detection signal, and output a corresponding current compensation signal to the current source according to the comparison result, and the current source is used to output a corresponding compensation current to the common connection end of the low-pass filter and the voltage-controlled oscillator according to the current compensation signal.

[0021] In specific implementation, two pulse width detectors can respectively collect the upper pulse signal and the lower pulse signal transmitted to the charge pump by the phase detector in the phase-locked loop for corresponding pulse width detection, so as to output the first pulse width detection signal and the second pulse width detection signal to the comparator respectively. The comparator can compare the magnitudes of the two pulse width detection results, and then output the corresponding current compensation signal to the current source according to the comparison result, so that the current source adjusts the output compensation current to the common connection end of the low-pass filter and the voltage-controlled oscillator according to the current compensation signal, so as to realize the leakage compensation of the charge pump in the phase-locked loop. The comparator can be a digital comparator; the current source can be an adjustable current source; and the pulse width detector can be a time-to-digital converter TDC.

[0022] Furthermore, the charge pump leakage compensation circuit of this embodiment can be applied to Figure 3The charge pump leakage compensation phase-locked loop shown in the figure comprises a phase detector, a charge pump, a low-pass filter, a voltage-controlled oscillator, a frequency divider and a charge pump leakage compensation circuit, wherein two clock signal input ends of the phase detector are respectively connected to a reference clock signal and a feedback clock signal output by the frequency divider, an upper pulse signal output end and a lower pulse signal output end of the phase detector are respectively connected to two control signal input ends of the charge pump, an output end of the charge pump is connected to a low-pass filter for outputting an iout current to the low-pass filter, an output end of the low-pass filter is connected to a voltage-controlled oscillator for outputting a VC voltage to the voltage-controlled oscillator, an output end of the voltage-controlled oscillator is connected to a frequency divider for outputting a corresponding frequency clock signal to the frequency divider, the frequency divider is used to perform frequency division processing on the frequency clock signal output by the voltage-controlled oscillator, and output a feedback clock signal to the phase detector, input ends of two pulse width detectors are respectively connected to two control signal input ends of the charge pump, and an output end of the current source is connected to a common connection end of the low-pass filter and the voltage-controlled oscillator.

[0023] The phase detector adopts a frequency detector. The phase detector is a key module in the phase-locked loop PLL, which can be used to compare the phase difference between the input reference clock and the feedback clock. When the frequency of the feedback clock signal output by the frequency divider is lower than the reference clock signal, the upper pulse signal UP of the phase detector is activated, indicating that the output frequency of the voltage-controlled oscillator VCO needs to be increased to reduce the frequency difference. On the contrary, when the frequency of the feedback clock signal output by the frequency divider is higher than the reference clock signal, the lower pulse signal DN signal of the phase detector is activated, indicating that the output frequency of the voltage-controlled oscillator VCO needs to be reduced. These two signals are transmitted to the charge pump, and the frequency of the voltage-controlled oscillator VCO is adjusted by controlling the charging and discharging of the charge pump to achieve the locked state of the phase-locked loop, that is, the frequency and phase of the output signal are consistent with or very close to the reference signal. Specifically, when the phase of the reference clock signal is ahead of the feedback clock signal, the upper pulse signal UP output by the phase detector is a high-level rectangular pulse, which indicates that the feedback clock of the frequency divider is slower than the reference clock, and the frequency of the voltage-controlled oscillator VCO needs to be increased. On the contrary, when the phase of the feedback clock signal is ahead of the reference clock signal, the output down pulse signal DN of the phase detector is a high-level rectangular pulse, which means that the feedback clock of the frequency divider is faster than the reference clock, and the frequency of the voltage-controlled oscillator VCO needs to be reduced. When the two are in the same phase, both the up pulse signal UP and the down pulse signal DN remain at a low level. This working mechanism ensures that the phase-locked loop can quickly and accurately lock to the input reference frequency, thereby achieving synchronization of the output signal with the input signal.

[0024] The time-to-digital converter is an electronic device used to measure time intervals. It can accurately measure the time interval between two pulses and can also be used to detect pulse widths. The time-to-digital converter TDC can detect the pulse widths of the up pulse signal UP and the down pulse signal DN. Figure 2 As shown in the figure, UP has a wider pulse width than DN. The width difference between UP and DN can be detected by using two time-to-digital converters TDC and comparators. If the pulse width of UP is wider than that of DN, or the pulse width of UP is narrower than that of DN, it indicates that the charge pump CP has leakage. This leakage current can be offset by adjusting the magnitude of the current source compensation current. The final effect after using the compensation circuit for leakage compensation is as follows: Figure 4 As shown, this method can not only compensate for the leakage of the charge pump CP, but also optimize the jitter performance of the VC voltage, so that the voltage-controlled oscillator VCO outputs a more ideal clock and eliminates the phase difference between the reference clock and the feedback clock.

[0025] Embodiment 2: This embodiment provides a charge pump leakage compensation method, which is applied to the charge pump leakage compensation circuit in Embodiment 1. The method includes the following steps: S1. Collect the upper pulse signal output from the phase detector in the phase-locked loop to the charge pump through a pulse width detector, detect the pulse width of the upper pulse signal, output a first pulse width detection signal to the comparator, collect the lower pulse signal output from the phase detector in the phase-locked loop to the charge pump through another pulse width detector, detect the pulse width of the lower pulse signal, and output a second pulse width detection signal to the comparator; S2a. The comparator receives the first pulse width detection signal and compares it with the second pulse width detection signal, and outputs a first current compensation signal to the current source when the comparison determines that the first pulse width detection signal is greater than the second pulse width detection signal; S3a. The current source increases the compensation current according to the first current compensation signal, and outputs the increased compensation current to the common terminal of the low-pass filter and the voltage-controlled oscillator; S4a repeats the above steps S2a- S3a until the first pulse width detection signal is equal to the second pulse width detection signal, and the compensation current output by the current source is finally used as the optimal compensation current; S5. The current source maintains outputting the optimal compensation current to perform leakage compensation on the charge pump.

[0026] Furthermore, the method further comprises: S2b. The comparator receives the first pulse width detection signal and compares it with the second pulse width detection signal, and outputs a second current compensation signal to the current source when the comparison determines that the first pulse width detection signal is less than the second pulse width detection signal; S3b the current source reduces the compensation current according to the second current compensation signal, and outputs the reduced compensation current to the common terminal of the low-pass filter and the voltage-controlled oscillator; S4b. Repeat the above steps S2b to S3b until the first pulse width detection signal is equal to the second pulse width detection signal, and take the compensation current finally output by the current source as the optimal compensation current.

[0027] like Figure 4 As shown, this method can compensate for the leakage of the charge pump CP, solve the problem caused by the leakage of the charge pump CP, maintain the stability of the VC voltage, make the voltage-controlled oscillator VCO output a more ideal clock, and eliminate the phase difference between the reference clock and the feedback clock.

[0028] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A charge pump leakage compensation circuit, characterized in that: The invention comprises a current source, a comparator and two pulse width detectors, wherein two input ends of the comparator are respectively connected to two pulse width detectors, and the output end is connected to the control end of the current source, and the output end of the current source is connected to the common connection end of a low-pass filter and a voltage-controlled oscillator in a phase-locked loop, and the input ends of the two pulse width detectors are respectively connected to two control signal input ends of a charge pump in the phase-locked loop, wherein one pulse width detector is used to collect an upper pulse signal output from a phase detector in the phase-locked loop to the charge pump, detect the pulse width of the upper pulse signal, and output a first pulse width detection signal to the comparator, and the other pulse width detector is used to collect a lower pulse signal output from a phase detector in the phase-locked loop to the charge pump, detect the pulse width of the lower pulse signal, and output a second pulse width detection signal to the comparator, wherein the comparator is used to compare the first pulse width detection signal and the second pulse width detection signal, and output a corresponding current compensation signal to the current source according to the comparison result, and wherein the current source is used to output a corresponding compensation current to the common connection end of the low-pass filter and the voltage-controlled oscillator according to the current compensation signal.

2. A charge pump leakage compensation circuit according to claim 1, characterized in that: The pulse width detector employs a time-to-digital converter.

3. The charge pump leakage compensation circuit according to claim 1, characterized in that: The comparator is a digital comparator.

4. The charge pump leakage compensation circuit according to claim 1, characterized in that: The current source is an adjustable current source.

5. A charge pump leakage compensation method, applied to the charge pump leakage compensation circuit according to any one of claims 1 to 4, characterized in that: include: S1. Collect the upper pulse signal output from the phase detector in the phase-locked loop to the charge pump through a pulse width detector, detect the pulse width of the upper pulse signal, output a first pulse width detection signal to the comparator, collect the lower pulse signal output from the phase detector in the phase-locked loop to the charge pump through another pulse width detector, detect the pulse width of the lower pulse signal, and output a second pulse width detection signal to the comparator; S2a. The comparator receives the first pulse width detection signal and compares it with the second pulse width detection signal, and outputs a first current compensation signal to the current source when the comparison determines that the first pulse width detection signal is greater than the second pulse width detection signal; S3a. The current source increases the compensation current according to the first current compensation signal, and outputs the increased compensation current to the common terminal of the low-pass filter and the voltage-controlled oscillator; S4a repeats the above steps S2a- S3a until the first pulse width detection signal is equal to the second pulse width detection signal, and the compensation current output by the current source is finally used as the optimal compensation current; S5. The current source maintains outputting the optimal compensation current to perform leakage compensation on the charge pump.

6. A charge pump leakage compensation method according to claim 5, characterized in that: The method further comprises: S2b. The comparator receives the first pulse width detection signal and compares it with the second pulse width detection signal, and outputs a second current compensation signal to the current source when the comparison determines that the first pulse width detection signal is less than the second pulse width detection signal; S3b the current source reduces the compensation current according to the second current compensation signal, and outputs the reduced compensation current to the common terminal of the low-pass filter and the voltage-controlled oscillator; S4b. Repeat the above steps S2b to S3b until the first pulse width detection signal is equal to the second pulse width detection signal, and take the compensation current finally output by the current source as the optimal compensation current.

7. A charge pump leakage compensation phase-locked loop, characterized in that: The invention comprises a phase detector, a charge pump, a low-pass filter, a voltage-controlled oscillator, a frequency divider and the charge pump leakage compensation circuit according to any one of claims 1 to 4, wherein the two clock signal input terminals of the phase detector are respectively connected to the reference clock signal and the feedback clock signal output by the frequency divider, the upper pulse signal output terminal and the lower pulse signal output terminal of the phase detector are respectively connected to the two control signal input terminals of the charge pump, the output terminal of the charge pump is connected to the low-pass filter for outputting the iout current to the low-pass filter, the output terminal of the low-pass filter is connected to the voltage-controlled oscillator for outputting the VC voltage to the voltage-controlled oscillator, the output terminal of the voltage-controlled oscillator is connected to the frequency divider for outputting the corresponding frequency clock signal to the frequency divider, the frequency divider is used to divide the frequency clock signal output by the voltage-controlled oscillator, and output the feedback clock signal to the phase detector, the input terminals of the two pulse width detectors are respectively connected to the two control signal input terminals of the charge pump, and the output terminal of the current source is connected to the common connection terminal of the low-pass filter and the voltage-controlled oscillator.

8. A charge pump leakage compensation phase-locked loop according to claim 7, characterized in that: The phase detector is a frequency detector.

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