Comparator offset voltage compensation circuit, compensation method and zero-crossing detection circuit

Abstract

The present invention proposes a comparator offset voltage compensation circuit, a compensation method and a zero-crossing detection circuit, wherein the compensation circuit is a digital circuit for compensating the offset voltage of a main comparator, wherein the main comparator compares a first signal with a second signal, and the compensation circuit comprises an auxiliary comparator, wherein the auxiliary comparator compares a third signal with the second signal and outputs a discrimination signal; wherein the third signal is equal to the first signal, or the third signal is positively correlated with the first signal; and wherein the discrimination signal controls the compensation amount for the offset voltage of the main comparator. The offset voltage calibration accuracy of the comparator of the present invention is high and the calibration time is low.

Description

Technical Field

[0001] The present invention relates to the field of power electronics, and in particular to a comparator offset voltage compensation circuit, a compensation method and a zero-crossing detection circuit. Background Art

[0002] Comparator is a common module in analog integrated circuits and is widely used in switching power supply control circuits. The performance of the comparator greatly affects the performance of the system, but the performance of the comparator is severely restricted by its offset voltage. In particular, as the feature size of the CMOS process gradually decreases, the offset caused by the mismatch of threshold voltage, area factor and parasitic capacitance gradually increases.

[0003] Traditional offset voltage elimination technologies, such as input offset storage (IOS) and output offset storage (OOS), use two-phase non-overlapping clocks and storage capacitors to eliminate offsets, which will introduce additional capacitors at the input or output of the comparator, greatly reducing the speed of the comparator; at the same time, the leakage of the capacitor will affect the accuracy of the comparator offset voltage calibration. Summary of the invention

[0004] The purpose of the present invention is to provide a comparator offset voltage compensation circuit, a compensation method and a zero-crossing detection circuit, which are used to solve the problems of inaccurate offset voltage correction and long calibration time in the prior art.

[0005] To achieve the above object, the present invention provides a comparator offset voltage compensation circuit, which is used to compensate the offset voltage of a main comparator, wherein the main comparator compares a first signal with a second signal, and the compensation circuit is a digital circuit, comprising an auxiliary comparator, wherein the auxiliary comparator compares a third signal with the second signal and outputs a discrimination signal, wherein the discrimination signal controls the compensation amount of the offset voltage of the main comparator;

[0006] The third signal is equal to the first signal, or the third signal is positively correlated with the first signal.

[0007] Optionally, the compensation circuit also includes an adaptive adjustment circuit, which receives the discrimination signal and outputs a compensation voltage, wherein the compensation voltage is used to compensate for the offset voltage of the main comparator; according to the discrimination signal, the compensation voltage is controlled to increase or decrease; the compensation voltage is adjusted one step at a time; or, the compensation voltage is adjusted using a binary method.

[0008] Optionally, the adaptive regulation circuit includes a counter, which sets an initial value and adjusts the output value according to the discrimination signal; the output value of the counter represents the compensation amount of the offset voltage of the main comparator; when the discrimination signal is high, the output value of the counter increases; when the discrimination signal is low, the output value of the counter decreases.

[0009] Optionally, the compensation circuit also includes a plurality of series circuits connected in parallel, and the output value of the counter controls the conduction of the corresponding series circuit to output a corresponding current signal; after all the series circuits are connected in parallel, they are connected in series with a first resistor, and the voltage on the first resistor represents the compensation voltage.

[0010] The present invention also provides a zero-crossing detection circuit, which detects the zero-crossing point of the inductor current in the switching power supply, and includes any one of the comparator offset voltage compensation circuits described above, wherein the first signal is the voltage at the common connection end of the main switch tube and the synchronous rectifier tube of the switching power supply, and the second signal is zero; when the synchronous rectifier tube is turned off, the auxiliary comparator outputs a judgment signal, and when the synchronous rectifier tube is turned on in the next switching cycle, the offset voltage of the main comparator is adjusted according to the judgment signal, and the main comparator outputs a zero-crossing detection signal.

[0011] The present invention also provides a comparator offset voltage compensation method for compensating the offset voltage of a main comparator, wherein the main comparator compares a first signal with a second signal, and the compensation method is based on a digital circuit, including an auxiliary comparator, wherein the auxiliary comparator compares a third signal with the second signal and outputs a judgment signal, and the judgment signal controls the compensation amount for the offset voltage of the main comparator; the third signal is equal to the first signal, or the third signal is positively correlated with the first signal.

[0012] Compared with the prior art, the present invention has the following advantages: the compensation circuit of the present invention is a digital circuit, which is used to compensate for the offset voltage of the main comparator. The main comparator compares the first signal with the second signal. The compensation circuit includes an auxiliary comparator, which compares the third signal with the second signal and outputs a discrimination signal; the third signal is equal to the first signal, or the third signal is positively correlated with the first signal; the discrimination signal controls the compensation amount of the offset voltage of the main comparator. The offset voltage calibration accuracy of the main comparator of the present invention is high and the calibration time is short. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of an embodiment of a comparator offset voltage compensation circuit of the present invention;

[0014] Figure 2 This is a schematic diagram of the adaptive regulation circuit of the present invention; DETAILED DESCRIPTION

[0015] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitution, modification, equivalent method and scheme made within the spirit and scope of the present invention.

[0016] In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without these detailed descriptions.

[0017] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the accompanying drawings are all simplified and not in exact proportions, in order to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0018] like Figure 1 As shown, a schematic diagram of an embodiment of a comparator offset voltage compensation circuit of the present invention is illustrated. The compensation circuit is a digital circuit, which is used to compensate for the offset voltage of the main comparator U00. The main comparator U00 can be used in a zero-crossing detection circuit of a switching power supply to detect the zero-crossing point of the inductor current. In this embodiment, the switching power supply takes a step-down circuit as an example, detects the common terminal voltage Vsw of the main switch tube and the synchronous rectifier tube, and uses the main comparator U00 to compare the voltage Vsw with zero. When the output signal of the main comparator is converted from a high level to a low level, it indicates that the inductor current crosses zero. The compensation circuit includes an auxiliary comparator U01 and an adaptive adjustment circuit U02. At the moment when the main switch tube is turned on, the auxiliary comparator U01 compares Vsw with zero and outputs a judgment signal VC1; the adaptive adjustment circuit receives the judgment signal VC1 and outputs a compensation voltage VOS. One method of adjusting the compensation voltage is to adjust the compensation voltage by one step each time according to the judgment signal. When VC1 is at a high level, the compensation voltage VOS increases by one step, and when VC1 is at a low level, the compensation voltage VOS decreases by one step. Another method of adjusting the compensation voltage is to adjust the compensation voltage by binary division according to the discrimination signal: first adjust one step size, then adjust 1 / 2 of the previous step size the next time, and so on.

[0019] like Figure 2As shown, the principle diagram of the adaptive regulation circuit of the present invention is illustrated, including a counter U201, a control circuit U202, a plurality of parallel series circuits and an operation circuit U203; each series circuit is connected in parallel and connected to a first resistor R1. The counter U201 sets an initial value, and according to the discrimination signal VC1, the counter U201 outputs a count value N based on the initial value N0; the difference N-N0 between the count value and the initial value represents the compensation amount of the offset voltage of the main comparator U00; when the discrimination signal VC1 is greater than zero, the count value is added by one to the count value obtained in the previous cycle; when the discrimination signal is less than zero, the count value is subtracted by one from the count value obtained in the previous cycle, and the count value plus or minus one represents that the compensation voltage increases or decreases once. The control circuit U202 receives the count value N and outputs a switch control signal according to the count value. The switch control signal controls the conduction of the corresponding series circuit to output a corresponding current signal, and the current signal obtains a voltage VN through the first resistor R1. When the count value is the initial value, the corresponding voltage of the first resistor R1 is the initial voltage V0; the voltage VN-V0 obtains the compensation voltage VOS, and the compensation voltage VOS is used to compensate for the offset voltage of the main comparator U00.

[0020] Although the embodiments are described and illustrated separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that the embodiments can be replaced and integrated. If the content is not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0021] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. A comparator offset voltage compensation circuit, for compensating an offset voltage of a main comparator, wherein the main comparator compares a first signal with a second signal, wherein: The compensation circuit is a digital circuit, comprising an auxiliary comparator, the auxiliary comparator compares the third signal with the second signal, and outputs a determination signal, the determination signal controls the compensation amount for the offset voltage of the main comparator; The third signal is equal to the first signal, or the third signal is positively correlated with the first signal; The compensation circuit further comprises an adaptive adjustment circuit, wherein the adaptive adjustment circuit receives the discrimination signal and outputs a compensation voltage, wherein the compensation voltage is used to compensate for the offset voltage of the main comparator; According to the discrimination signal, the compensation voltage is controlled to increase or decrease; the compensation voltage is adjusted by one step each time; or the compensation voltage is adjusted by a binary method; The main comparator and the compensation circuit are integrated in a controller of a switching power supply.

2. The comparator offset voltage compensation circuit according to claim 1, characterized in that: The adaptive regulation circuit includes a counter, the counter sets an initial value, and the counter adjusts the output value according to the discrimination signal; The output value of the counter represents the compensation amount of the offset voltage of the main comparator; when the discrimination signal is high, the output value of the counter increases; when the discrimination signal is low, the output value of the counter decreases.

3. The comparator offset voltage compensation circuit according to claim 2, characterized in that: The adaptive regulation circuit also includes a plurality of series circuits connected in parallel, and the output value of the counter controls the corresponding series circuit to be turned on to output a corresponding current signal; all the series circuits are connected in parallel and in series with a first resistor, and the voltage on the first resistor represents the compensation voltage.

4. A zero-crossing detection circuit, the zero-crossing detection circuit detecting the zero-crossing point of the inductor current in a switching power supply, characterized in that: It comprises any one of the comparator offset voltage compensation circuits described in claims 1-3, wherein the first signal is the voltage at the common connection terminal of the main switch tube and the synchronous rectifier tube of the switching power supply, and the second signal is zero; when the synchronous rectifier tube is turned off, the auxiliary comparator outputs a judgment signal, and when the synchronous rectifier tube is turned on in the next switching cycle, the offset voltage of the main comparator is adjusted according to the judgment signal, and the main comparator outputs a zero-crossing detection signal.

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