Regulation circuit, ramp signal generating circuit and control method thereof

Abstract

A regulation circuit includes: an operational amplifier, a first regulation unit, a second regulation unit, a first resistor, and a second resistor. The input of the first regulation unit is adapted to receive a ramp signal, and the output of the first regulation unit is connected to the input of the second regulation unit and the negative input of the operational amplifier. The output of the second regulation unit is connected to the output of the operational amplifier and the first end of the first resistor. The second end of the first resistor is connected to the first end of the second resistor and the output of the regulation circuit. The second end of the second resistor is adapted to be grounded. The first regulation unit includes a sampling capacitor, and the second regulation unit includes a feedback capacitor and a first switch; alternatively, the first regulation unit includes a sampling resistor, and the second regulation unit includes a feedback resistor.

Description

Technical Field

[0001] The present invention relates to the field of circuits, and in particular to a regulating circuit, a ramp signal generating circuit and a control method thereof. Background Art

[0002] CMOS image sensors are widely used in image acquisition due to their high integration, low power consumption, and low cost. CMOS image sensors typically use a column-level ADC architecture, which offers a good compromise between readout speed, chip area, and power consumption.

[0003] The mainstream structure of column-level ADC is single-slope ADC, such as Figure 1 The single-slope ADC comprises a counter 1 and a digital-to-analog converter 2. Counter 1 generates an increasing number, which, after passing through digital-to-analog converter 2, forms a ramp signal Vramp0. Adjusting the slope of ramp signal Vramp0 is typically accomplished by changing the input reference voltage or current of digital-to-analog converter 2. Summary of the Invention

[0004] The problem solved by the present invention is that the existing slope adjustment method of the ramp signal is not flexible enough.

[0005] To solve the above problem, the present invention provides a regulating circuit, comprising: an operational amplifier, a first regulating unit, a second regulating unit, a first resistor, and a second resistor.

[0006] The input of the first regulating unit is adapted to receive a ramp signal, and the output of the first regulating unit is connected to the input of the second regulating unit and the negative input of the operational amplifier. The output of the second regulating unit is connected to the output of the operational amplifier and the first end of the first resistor. The second end of the first resistor is connected to the first end of the second resistor and the output of the regulating circuit. The second end of the second resistor is adapted to be grounded. The first regulating unit includes a sampling capacitor, and the second regulating unit includes a feedback capacitor and a first switch; alternatively, the first regulating unit includes a sampling resistor, and the second regulating unit includes a feedback resistor.

[0007] When the first regulating unit includes the sampling capacitor and the second regulating unit includes the feedback capacitor and the first switch, the first end of the sampling capacitor is connected to the input end of the first regulating unit, the second end of the sampling capacitor is connected to the output end of the first regulating unit, the first end of the feedback capacitor is connected to the first end of the first switch and the input end of the second regulating unit, and the second end of the feedback capacitor is connected to the second end of the first switch and the output end of the second regulating unit.

[0008] When the first regulating unit includes the sampling resistor and the second regulating unit includes the feedback resistor, the first end of the sampling resistor is connected to the input end of the first regulating unit, the second end of the sampling resistor is connected to the output end of the first regulating unit, the first end of the feedback resistor is connected to the input end of the first regulating unit, and the second end of the feedback resistor is connected to the output end of the first regulating unit.

[0009] Optionally, the first resistor, the second resistor, the sampling resistor and the feedback resistor are all adjustable resistors; and the sampling capacitor and the feedback capacitor are both adjustable capacitors.

[0010] Optionally, the regulation circuit further includes: a second switch and a first capacitor. The first end of the second switch is adapted to input a reference voltage, and the second end of the second switch is connected to the first end of the first capacitor and the non-inverting input terminal of the operational amplifier. The second end of the first capacitor is adapted to be grounded.

[0011] An embodiment of the present invention further provides a ramp signal generating circuit, comprising: a ramp signal generator and the aforementioned regulating circuit; the ramp signal generator is adapted to generate a ramp signal to the input end of the first regulating unit.

[0012] An embodiment of the present invention further provides a control method for the ramp signal generating circuit, comprising:

[0013] Before the ramp signal generator generates the ramp signal, closing the second switch;

[0014] When the ramp signal generator generates the ramp signal, the second switch is turned off.

[0015] Optionally, the control method of the ramp signal generating circuit further includes: adjusting the resistance value of the first resistor, the second resistor, the sampling resistor or the feedback resistor, or the capacitance value of the sampling capacitor and the feedback capacitor to change the slope of the ramp signal.

[0016] Optionally, the control method of the ramp signal generating circuit also includes: when the first adjustment unit includes the sampling capacitor and the second adjustment unit includes the feedback capacitor and the first switch, closing the first switch before the ramp signal generator generates the ramp signal; and opening the first switch when the ramp signal generator generates the ramp signal.

[0017] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0018] The present invention provides a regulation circuit with a novel structure. Based on the regulation circuit, the gain of the regulation circuit can be adjusted by changing the capacitance values of a sampling capacitor and a feedback capacitor, or changing the resistance values of a sampling resistor, a feedback resistor, a first resistor, or a second resistor, thereby changing the slope of a ramp signal and generating ramp signals with different slopes at the output end. This slope adjustment method is more flexible. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the existing single slope ADC structure;

[0020] Figure 2 is a schematic diagram of a regulating circuit according to an embodiment of the present invention;

[0021] Figure 3 This is another schematic diagram of a regulating circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0023] like Figure 2 As shown, an embodiment of the present invention provides a regulating circuit, including: an operational amplifier OP, a first regulating unit, a second regulating unit, a first resistor R1 and a second resistor R2.

[0024] The input of the first regulating unit is adapted to receive a ramp signal Vramp, and the output of the first regulating unit is connected to the input of the second regulating unit and the negative input of the operational amplifier OP. The output of the second regulating unit is connected to the output of the operational amplifier OP and the first end of the first resistor R1. The second end of the first resistor R1 is connected to the first end of the second resistor R2 and the output Vout of the regulating circuit. The second end of the second resistor R2 is adapted to be grounded.

[0025] exist Figure 2 In the embodiment, the first regulating unit may include: a sampling capacitor Cs, and the second regulating unit may include: a feedback capacitor Cf and a first switch S1.

[0026] The first end of the sampling capacitor Cs is connected to the input end of the first regulating unit, which is used to input the ramp signal Vramp. The second end of the sampling capacitor Cs is connected to the output end of the first regulating unit, which is used to connect to the negative input end of the operational amplifier OP.

[0027] A first end of the feedback capacitor Cf is connected to the first end of the first switch S1 and the input end of the second regulating unit, and is used to connect the negative input end of the operational amplifier OP and the second end of the sampling capacitor Cs. A second end of the feedback capacitor Cf is connected to the second end of the first switch S1 and the output end of the second regulating unit, and is used to connect the output end of the operational amplifier OP and the first end of the first resistor R1.

[0028] The regulating circuit may further include: a second switch S2 and a first capacitor Ccm.

[0029] The first end of the second switch S2 is adapted to input a reference voltage Vcm, the second end of the second switch S2 is connected to the first end of the first capacitor Ccm and the non-inverting input end of the operational amplifier OP, and the second end of the first capacitor Ccm is adapted to be grounded.

[0030] During operation, before the ramp signal generator 10 generates the ramp signal Vramp to the first terminal of the sampling capacitor Cs, the first switch S1 and the second switch S2 can be controlled to be closed, thereby resetting the voltages at the positive and negative input terminals of the operational amplifier OP to approximately the reference voltage Vcm. After the reset is complete, the ramp signal generator 10 generates the ramp signal Vramp to the first terminal of the sampling capacitor Cs, and the first and second switches S1 and S2 are controlled to be open.

[0031] Figure 2 The gain formula for the regulation circuit shown is:

[0032] A=Cs / Cf*R2 / (R1+R2) Formula 1

[0033] In Formula 1, A represents the gain of the regulating circuit, Cs represents the capacitance value of the sampling capacitor, Cf represents the capacitance value of the feedback capacitor, R1 represents the resistance value of the first resistor, and R2 represents the resistance value of the second resistor.

[0034] In this embodiment, both the first resistor R1 and the second resistor R2 can be adjustable resistors, and both the sampling capacitor Cs and the feedback capacitor Cf can be adjustable capacitors. As can be seen from Formula 1, changing the capacitance of the sampling capacitor Cs and the feedback capacitor Cf, or changing the resistance of the first resistor R1 and the second resistor R2, can change the gain of the regulation circuit, thereby changing the slope of the ramp signal Vramp and generating ramp signals of different slopes at the output terminal Vout. This method achieves higher slope accuracy and more flexible regulation.

[0035] like Figure 3 As shown, optionally, the first regulating unit may include: a sampling resistor Rs, and the second regulating unit may include: a feedback resistor Rf.

[0036] The first end of the sampling resistor Rs is connected to the input end of the first regulating unit, which is used to input the ramp signal Vramp. The second end of the sampling resistor is connected to the output end of the first regulating unit, which is used to connect to the negative phase input end of the operational amplifier OP.

[0037] The first end of the feedback resistor Rf is connected to the input end of the first regulating unit, and is used to connect the negative phase input end of the operational amplifier OP and the second end of the sampling resistor Rs. The second end of the feedback resistor Rf is connected to the output end of the first regulating unit, and is used to connect the output end of the operational amplifier OP and the first end of the first resistor R1.

[0038] During operation, before the ramp signal generator 10 generates the ramp signal Vramp to the first end of the sampling resistor Rs, the second switch S2 can be controlled to be closed, resetting the voltages at the positive and negative input terminals of the operational amplifier OP to approximately the reference voltage Vcm. After the reset is complete, the ramp signal generator 10 generates the ramp signal Vramp to the first end of the sampling resistor Rs, and the second switch S2 is controlled to be open.

[0039] Figure 3 The gain formula for the regulation circuit shown is:

[0040] A=Rf / Rs*R2 / (R1+R2) Formula 2

[0041] In Formula 2, A represents the gain of the regulating circuit, Rs represents the resistance value of the sampling resistor, Rf represents the resistance value of the feedback resistor, R1 represents the resistance value of the first resistor, and R2 represents the resistance value of the second resistor.

[0042] As can be seen from Equation 2, changing the resistance values of the sampling resistor Rs, the feedback resistor Rf, the first resistor R1, or the second resistor R2 can change the gain of the regulation circuit, thereby generating ramp signals of varying slopes at the output terminal Vout. Therefore, in this embodiment, the sampling resistor Rs, the feedback resistor Rf, the first resistor R1, and the second resistor R2 can all be adjustable resistors.

[0043] The regulating circuit of this embodiment is also implemented using a fully differential operational amplifier, which will not be described in detail here.

[0044] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A regulating circuit, characterized in that: include: An operational amplifier, a first regulating unit, a second regulating unit, a first resistor and a second resistor; The input terminal of the first regulating unit is suitable for inputting a ramp signal, and the output terminal of the first regulating unit is connected to the input terminal of the second regulating unit and the negative phase input terminal of the operational amplifier; The output end of the second regulating unit is connected to the output end of the operational amplifier and the first end of the first resistor; The second end of the first resistor is connected to the first end of the second resistor and the output end of the regulating circuit; The second end of the second resistor is suitable for being grounded; The first regulating unit includes a sampling capacitor, and the second regulating unit includes a feedback capacitor and a first switch; or the first regulating unit includes a sampling resistor, and the second regulating unit includes a feedback resistor; When the first regulating unit includes the sampling capacitor, and the second regulating unit includes the feedback capacitor and the first switch, the first end of the sampling capacitor is connected to the input end of the first regulating unit, the second end of the sampling capacitor is connected to the output end of the first regulating unit, the first end of the feedback capacitor is connected to the first end of the first switch and the input end of the second regulating unit, and the second end of the feedback capacitor is connected to the second end of the first switch and the output end of the second regulating unit; When the first regulating unit includes the sampling resistor and the second regulating unit includes the feedback resistor, the first end of the sampling resistor is connected to the input end of the first regulating unit, the second end of the sampling resistor is connected to the output end of the first regulating unit, the first end of the feedback resistor is connected to the input end of the first regulating unit, and the second end of the feedback resistor is connected to the output end of the first regulating unit.

2. The regulating circuit according to claim 1, wherein: The first resistor, the second resistor, the sampling resistor and the feedback resistor are all adjustable resistors; the sampling capacitor and the feedback capacitor are all adjustable capacitors.

3. The regulating circuit according to claim 1, wherein: Also includes: a second switch and a first capacitor; The first end of the second switch is suitable for inputting a reference voltage, and the second end of the second switch is connected to the first end of the first capacitor and the non-inverting input terminal of the operational amplifier; The second terminal of the first capacitor is suitable for being grounded.

4. A ramp signal generating circuit, characterized in that: It comprises a ramp signal generator and the regulating circuit according to claim 1 or 2; the ramp signal generator is suitable for generating a ramp signal to the input end of the first regulating unit.

5. A ramp signal generating circuit, characterized in that: It comprises a ramp signal generator and the regulating circuit according to claim 3; the ramp signal generator is suitable for generating a ramp signal to the input end of the first regulating unit.

6. A control method for the ramp signal generating circuit according to claim 5, characterized in that: include: Before the ramp signal generator generates the ramp signal, closing the second switch; When the ramp signal generator generates the ramp signal, the second switch is turned off.

7. The control method of the ramp signal generating circuit according to claim 6, wherein: Also includes: The resistance values of the first resistor, the second resistor, the sampling resistor or the feedback resistor, or the capacitance values of the sampling capacitor and the feedback capacitor are adjusted to change the slope of the ramp signal.

8. The control method of the ramp signal generating circuit according to claim 6, wherein: Also includes: When the first regulating unit includes the sampling capacitor and the second regulating unit includes the feedback capacitor and a first switch, the first switch is closed before the ramp signal generator generates the ramp signal; and the first switch is opened when the ramp signal generator generates the ramp signal.

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