Oscillator

Abstract

An oscillator comprises a reference current generating circuit, a voltage modulator circuit and an oscillating circuit. The reference current generating circuit is used for generating a reference current. The voltage modulator circuit is configured to receive a feedback voltage and perform a voltage modulation operation according to a first reference voltage and the feedback voltage to generate a modulated voltage. The oscillation circuit is coupled to the reference current generating circuit and the voltage modulator circuit and is used for generating an oscillation signal with an oscillation frequency according to the reference current and the modulated voltage.

Description

Technical Field

[0001] This invention relates to frequency modulation, and more particularly to an oscillator capable of linearly frequency modulating an oscillating signal output to a DC-to-DC converter in voltage mode. Background Technology

[0002] During the initial startup phase, DC-DC converters may experience severe ringing at the output voltage, which can be relatively low. This can lead to a steep inductor current slope, making it difficult to control the inductor current at high frequencies. Furthermore, when the output of the DC-DC converter is short-circuited to ground, the voltage difference between the input and output voltages can be substantial, potentially causing a steep inductor current slope and damaging the converter.

[0003] To address the aforementioned issues, the oscillation signal generated by the oscillator of the DC-DC converter can be frequency-modulated to ensure that the current sensing operation of the inductor current effectively reflects changes in the inductor current. Existing methods may employ frequency hopping modulation; however, this operation can cause drastic changes in both the output voltage and the inductor current. Summary of the Invention

[0004] Therefore, one of the objectives of this invention is to provide an oscillator capable of linearly frequency modulating the oscillation signal output to a DC-DC converter in voltage mode, in order to solve the above-mentioned problems.

[0005] According to one embodiment of the present invention, an oscillator is provided. The oscillator includes a reference current generating circuit, a voltage modulator circuit, and an oscillation circuit. The reference current generating circuit is used to generate a reference current. The voltage modulator circuit is used to receive a feedback voltage and perform a voltage modulation operation based on a first reference voltage and the feedback voltage to generate a modulated voltage. The oscillation circuit is coupled to the reference current generating circuit and the voltage modulator circuit, and is used to generate an oscillation signal having an oscillation frequency based on the reference current and the modulated voltage.

[0006] One advantage of this invention is that, by applying this invention to the oscillator of a DC-DC converter, overshoot / undershoot of the inductor current of the DC-DC converter can be effectively suppressed by performing linear frequency modulation operation. Furthermore, during the startup cycle of the pre-biased output of the DC-DC converter, the output voltage variation of the DC-DC converter for linear frequency modulation operation can be smoother than that of the DC-DC converter for frequency hopping modulation operation. Attached Figure Description

[0007] Figure 1 This is a block diagram illustrating the relationship between a DC-to-DC converter and an oscillator according to an embodiment of the present invention.

[0008] Figure 2 This is a schematic diagram of an oscillator according to an embodiment of the present invention.

[0009] Figure 3 This is a schematic diagram of a voltage modulator circuit according to an embodiment of the present invention. Detailed Implementation

[0010] Figure 1 This is a block diagram illustrating the relationship between a DC-to-DC converter 100 and an oscillator 102 according to an embodiment of the present invention. Examples of the DC-to-DC converter 100 may include, but are not limited to, a buck converter or a boost converter. The DC-to-DC converter 100 converts an input DC voltage into a stable output DC voltage and provides the output voltage to a connected load (not shown). Figure 1 (in the middle). Oscillator 102 can output an oscillation signal SOSC with an oscillation frequency FOSC to DC-DC converter 100. In this embodiment, the feedback voltage VFB can be obtained from the output voltage of DC-DC converter 100 (for example, the output voltage can be divided to obtain the feedback voltage VFB), and the feedback voltage VFB can be provided to oscillator 102 for linear frequency modulation of the oscillation frequency FOSC in voltage mode.

[0011] In detail, refer to Figure 2 . Figure 2 This is a schematic diagram of an oscillator 200 according to an embodiment of the present invention, wherein... Figure 1 The oscillator 102 shown can be implemented using oscillator 200. For example... Figure 2 As shown, the oscillator 200 may include a reference current generation circuit 202, a voltage modulator circuit 204, and an oscillation circuit 206. The reference current generation circuit 202 may include an amplifier 208, multiple p-type transistors M1 and M2, an n-type transistor M3, and a resistor R.T In this configuration, p-type transistors M1 and M2 form a current mirror. Amplifier 208 has a current mirror coupled to a reference voltage V. ref1 One of the non-inverting input terminals (in) Figure 2 (marked with "+"), an inverting input terminal coupled to the source of n-type transistor M3 (in) Figure 2 The resistor R is marked with a "-" and has an output terminal coupled to the gate of the n-type transistor M3. T The n-type transistor M3 has a first terminal coupled to the source of the transistor and a second terminal coupled to the ground voltage GND. The p-type transistor M1 has a second terminal coupled to the supply voltage V. DD The source of the transistor M2 is coupled to the drain of the n-type transistor M3, and the gate is coupled to the drain of the p-type transistor M1. The p-type transistor M2 has a source coupled to the drain of the p-type transistor M1. DD The source of the p-type transistor M1 and the gate of the p-type transistor M2 are connected to the gate of the p-type transistor M1. The current mirror formed by the p-type transistors M1 and M2 can be determined based on the current flowing through the resistor R. T The current is used to generate the mirror current I. ref .

[0012] Voltage modulator circuit 204 can be used to receive feedback voltage V from DC to DC converter 100. FB And according to the reference voltage V ref3 With feedback voltage V FB To perform voltage modulation operation to generate modulated voltage V M Specifically, refer to Figure 3 . Figure 3 This is a schematic diagram of a voltage modulator circuit 300 according to an embodiment of the present invention, wherein... Figure 2 The voltage modulator circuit 204 shown can be implemented using the voltage modulator circuit 300. For example... Figure 3 As shown, the voltage modulator circuit 300 may include an amplifier 302, multiple current mirrors 304 and 306, a current source 308, and multiple resistors R. A With R B Multiple n-type transistors M7, M8, M 10 M 11 With M 12 And multiple p-type transistors M5, M6, and M9. Amplifier 302 has a feedback voltage V received from DC-to-DC converter 100. FB One of the non-inverting input terminals (in) Figure 3 (marked with "+"), coupled to n-type transistor M 10 The source of the inverting input terminal (in) Figure 3 (marked as "-"), and coupled to n-type transistor M 10 One output terminal of the gate. Resistor RA It has a connection to an n-type transistor M 10 The first terminal of the source electrode and the second terminal coupled to the ground voltage GND.

[0013] The current mirror 304 can be coupled to the n-type transistor M. 10 The drain and the supply voltage V DD Between, and can be used according to the flow through resistor R A The current I1 is used to generate the mirror current I2, where the feedback voltage V at the non-inverting input terminal of amplifier 302 is... FB The voltage value is approximately equal to that at the resistor R. A The voltage V at the first terminal A Given the voltage value, the formula can be used: To obtain the current value of current I1. Specifically, the current mirror 304 can be composed of p-type transistors M5 and M6. The p-type transistor M5 is coupled to the supply voltage V. DD The source is coupled to the n-type transistor M. 10 The drain of the p-type transistor M5 and the gate of the p-type transistor M6 are coupled to the drain of the p-type transistor M5. The p-type transistor M6 has a gate coupled to the supply voltage V. DD The source of the p-type transistor M5 and the gate of the p-type transistor M6 coupled to the gate of the p-type transistor M5. Assuming that the ratio of the width of the p-type transistor M5 to the length of the p-type transistor M6 is from 1 to k, in this case, the current value of the mirror current I2 can be k times the current value of the current I1 (that is, I2 = k * I1).

[0014] The current mirror 306 can be coupled between the drain of the p-type transistor M6 and the ground voltage GND, and can be used to generate the mirror current I based on the mirror current I2. M Specifically, the current mirror 306 can be composed of n-type transistors M7 and M8. The n-type transistor M7 has a drain coupled to the drain of the p-type transistor M6, a source coupled to ground voltage GND, and a gate coupled to the drain of the n-type transistor M7. The n-type transistor M8 has a drain coupled to the current source 308, a source coupled to ground voltage GND, and a gate coupled to the gate of the n-type transistor M7, wherein the modulated voltage V... M This is generated at the drain of n-type transistor M8. Assuming the ratio of the width of n-type transistor M7 to its length to the ratio of the width of n-type transistor M8 to its length is between 1 and n, in this case, the mirror current I... M The current value can be n times the current value of the mirror current I2 (that is...)

[0015] Current source 308 can be used to provide supply current I BResistance R B It has a first terminal coupled between the current source 308 and the current mirror 306, and a second terminal coupled to the ground voltage GND, wherein the modulated voltage V M Relevant to resistor R B The first terminal generates it. In this embodiment, the reference voltage V ref3 The voltage value can be defaulted to the supply current I. B The current value and resistance R B The product of the resistance values ​​is equal (i.e., V). ref3 =I B *R B ), where the reference voltage V ref3 The voltage value is greater than or equal to the modulated voltage V. M The voltage value (i.e., V) ref3 ≥V M ), and supply voltage V DD The voltage value is greater than or equal to the reference voltage V. ref3 The voltage value (i.e., V) DD ≥V ref3 Modulated voltage V M The voltage value can be compared with the supply current I. B With mirror current I M The difference in current and resistance R between them B The product of the resistance values ​​is equal (i.e., V). M =(I B -I M )*R B Due to V ref3 =I B *R B and Therefore, the modulated voltage V M The voltage value can be obtained from the formula: What was obtained.

[0016] In addition, p-type transistor M9 and n-type transistor M 11 With n-type transistor M 12 Each transistor in the circuit can be considered a switching circuit. The p-type transistor M9 is coupled to the supply voltage V. DD The source, the drain coupled to the drain of the p-type transistor M5, and the terminal used to receive the first switching voltage V EN The gate of the n-type transistor M. 11 It has a source coupled to ground voltage GND, a drain coupled to the drain of p-type transistor M6, and a terminal for receiving the second switching voltage V. ENB The gate, wherein the second switching voltage V ENB The first switching voltage V EN The inverting voltage. n-type transistor M12 It has a source coupled to ground voltage GND and a resistor R. B The drain of the first terminal, and the terminal used to receive the second switching voltage V. ENB The gate. Responding to the first switching voltage V EN It is located at a high level (i.e., the second switching voltage V). ENB (The circuit is at a low level), p-type transistor M9, n-type transistor M 11 With n-type transistor M 12 All transistors in it are turned off, and the modulated voltage V M The voltage value can be obtained by the above formula (i.e.) To obtain. Responding to the first switching voltage V EN It is located at a low level (i.e., the second switching voltage V). ENB (The circuit is at a high level), p-type transistor M9, n-type transistor M 11 With n-type transistor M 12 All the transistors in it are turned on, and the modulated voltage V M The voltage value is 0.

[0017] Refer to the return Figure 2 The oscillation circuit 206 can be coupled to the reference current generation circuit 202 and the voltage modulator circuit 204, and can be used to adjust the voltage based on the mirror current I. ref With modulated voltage V M To generate an oscillation frequency F OSC The oscillation signal S OSC In detail, the oscillation circuit 206 may include a comparator 210, an inverter 212, a pulse generator 214, an n-type transistor M4, and a capacitor C. OSC Capacitor C OSC It may have a first terminal and a second terminal, wherein the first terminal is coupled to the reference current generating circuit 202 to receive the mirror current I. ref The second terminal is coupled to the ground voltage GND and the voltage V. SAW Based on the mirror current I at the first end ref With capacitor C OSC The capacitance value is generated. Comparator 210 has a capacitance value coupled to the reference voltage V. ref2 The first non-inverting input terminal (in) Figure 2 (marked with "+"), coupled to the modulated voltage V M The second non-inverting input terminal (in) Figure 2 The symbol marked "+" in the middle, and coupled to capacitor C OSC The first terminal receives voltage V SAW One of the inverting input terminals (in) Figure 2 The modulated voltage V is marked with "-". MThe voltage value is greater than or equal to the reference voltage V. ref2 The voltage value (i.e., V) M ≥V ref2 The N-type transistor M4 has a source coupled to ground voltage GND, a drain coupled to the inverting input of comparator 210, and a gate coupled to one of the outputs of pulse generator 214.

[0018] Comparator 210 can be used to determine the reference voltage V ref2 Modulated voltage V M With voltage V SAW A comparison operation is performed to produce a comparison result. Inverter 212 can be coupled to an output of comparator 210 and used to invert an output of comparator 210 (e.g., the comparison result) to produce an inverted result. Pulse generator 214 can be used to generate an oscillation frequency F based on the inverted result. OSC The oscillation signal S OSC Oscillation frequency F OSC It can be linearly modulated using the following formula:

[0019] F OSC_ORI =D*F OSC_MOD

[0020] Where F OSC_ORI The original oscillation frequency, F OSC_MOD The oscillation frequency after modulation is D-type, and the voltage V after modulation is D-type. M To reference voltage V ref2 The proportion (i.e.) ), and D is greater than or equal to 1 (i.e., D≥1). Since the architecture of the oscillator circuit 206 is well known to those skilled in the art, and the focus of this invention is on linear frequency modulation, the detailed operation of the oscillator circuit 206 will not be described here.

[0021] In summary, by applying this invention to the oscillator of a DC-DC converter, overshoot / undershoot of the inductor current of the DC-DC converter can be effectively suppressed by performing linear frequency modulation operation. Furthermore, during the startup cycle of the pre-biased output of the DC-DC converter, the output voltage variation of the DC-DC converter with linear frequency modulation operation can be smoother than that of the DC-DC converter with frequency hopping modulation operation.

[0022] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made in accordance with the claims of the present invention shall be covered by the present invention.

[0023] [Symbol Explanation]

[0024] 100: DC to DC converter

[0025] 102, 200: Oscillators

[0026] V FB Feedback voltage

[0027] S OSC Oscillation signal

[0028] 202: Reference Current Generation Circuit

[0029] 204, 300: Voltage modulator circuit

[0030] 206: Oscillator Circuit

[0031] 208, 302: Amplifiers

[0032] 210: Comparator

[0033] 212: Inverter

[0034] 214: Pulse Generator

[0035] M1, M2, M5, M6, M9: p-type transistors

[0036] M3, M4, M7, M8, M 10 M 11 M 12 n-type transistor

[0037] V ref1 V ref2 V ref3 Reference voltage

[0038] GND: Grounding voltage

[0039] R T R A R B :resistance

[0040] V DD Supply voltage

[0041] I ref I2, I M Mirror current

[0042] V SAW V A :Voltage

[0043] C OSC :capacitance

[0044] V M Modulated voltage

[0045] F OSC : Oscillation frequency

[0046] 304, 306: Current mirror

[0047] 308: Current Source

[0048] V EN First switching voltage

[0049] V ENB Second switching voltage

[0050] I1: Current

[0051] I B Supply current

[0052] [Simplified Explanation of Symbols in the Representative Diagram]

[0053] 200: Oscillator

[0054] 202: Reference Current Generation Circuit

[0055] 204: Voltage Modulator Circuit

[0056] 206: Oscillator Circuit

[0057] 208: Amplifier

[0058] 210: Comparator

[0059] 212: Inverter

[0060] 214: Pulse Generator

[0061] M1, M2: p-type transistors

[0062] M3, M4: n-type transistors

[0063] V ref1 V ref2 V ref3 Reference voltage

[0064] GND: Grounding voltage

[0065] R T :resistance

[0066] V DD Supply voltage

[0067] I ref Mirror current

[0068] V SAW :Voltage

[0069] C OSC :capacitance

[0070] V FB Feedback voltage

[0071] V M Modulated voltage

[0072] F OSC : Oscillation frequency

[0073]

Characteristic Chemical Formula

[0074] none

Claims

1. An oscillator comprising: A reference current generating circuit is used to generate a reference current; A voltage modulator circuit is configured to receive a feedback voltage and perform a voltage modulation operation based on a first reference voltage and the feedback voltage to generate a modulated voltage; and An oscillation circuit is coupled to the reference current generation circuit and the voltage modulator circuit, and is used to generate an oscillation signal with an oscillation frequency based on the reference current and the modulated voltage.

2. The oscillator of claim 1, wherein the oscillator is applied to a DC-to-DC converter, the oscillation signal is output to the DC-to-DC converter, and the feedback voltage is derived from the DC-to-DC converter.

3. The oscillator of claim 1, wherein the voltage modulator circuit comprises: An n-type transistor; An amplifier has a non-inverting input terminal for receiving the feedback voltage, an inverting input terminal coupled to one source terminal of the n-type transistor, and an output terminal coupled to one gate terminal of the n-type transistor; A first resistor having a first terminal coupled to the source terminal of the n-type transistor and a second terminal coupled to a second reference voltage; A first current mirror is coupled between one drain terminal of the n-type transistor and a third reference voltage, and is used to generate a first mirror current based on a current flowing through the first resistor, wherein a voltage value of the second reference voltage is less than a voltage value of the third reference voltage. A second current mirror is coupled between the first current mirror and the second reference voltage, and is used to generate a second current mirror based on the first current mirror current. A current source is used to provide a supply current; as well as A second resistor has a first terminal coupled between the current source and the second current mirror, and a second terminal coupled to the second reference voltage.

4. The oscillator of claim 3, wherein the modulated voltage is generated from the first terminal of the second resistor.

5. The oscillator of claim 3, wherein a voltage value of the first reference voltage is equal to the product of a current value of the supply current and a resistance value of the second resistor.

6. The oscillator of claim 3, wherein the first current mirror comprises: A first p-type transistor has a source terminal coupled to the third reference voltage, a drain terminal coupled to the drain terminal of the n-type transistor, and a gate terminal coupled to the drain terminal of the first p-type transistor; and A second p-type transistor has a source terminal coupled to the third reference voltage and a gate terminal coupled to the gate terminal of the first p-type transistor.

7. The oscillator of claim 6, wherein the second current mirror comprises: A first n-type transistor has a drain terminal coupled to a drain terminal of a second p-type transistor, a source terminal coupled to a second reference voltage, and a gate terminal coupled to the drain terminal of the first n-type transistor; and A second n-type transistor has a drain terminal coupled to the current source, a source terminal coupled to the second reference voltage, and a gate terminal coupled to the gate terminal of the first n-type transistor, wherein the modulated voltage is generated from the drain terminal of the second n-type transistor.

8. The oscillator of claim 1, wherein a voltage value of the first reference voltage is greater than or equal to a voltage value of the modulated voltage.

9. The oscillator of claim 1, wherein the oscillation circuit comprises: A capacitor having a first terminal coupled to the reference current generating circuit and a second terminal coupled to a second reference voltage; A comparator has a first non-inverting input coupled to a fourth reference voltage, a second non-inverting input coupled to the modulated voltage, and an inverting input coupled to the first terminal of the capacitor. An inverter is coupled to an output of the comparator and is used to invert an output of the comparator to produce an inverted result. A pulse generator is used to generate the oscillation signal based on the inverted result; as well as An n-type transistor has a drain terminal coupled to the inverting input of the comparator, a source terminal coupled to the second reference voltage, and a gate terminal coupled to one of the outputs of the pulse generator.

10. The oscillator of claim 9, wherein a voltage value of the modulated voltage is greater than or equal to a voltage value of the fourth reference voltage.

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