TW200924362A - DC/DC converters and related methods - Google Patents

Abstract

A DC/DC converter configured to receive an input voltage to generate an output voltage, comprising a PWM generator, a PFM generator, a first switch device, and a buck circuit. The PWM and PFM generators respectively generate a PWM signal and a PFM signal according to the input voltage and the output voltage. The first switch circuit generates a driving signal according to one of the PWM and PFM signals. The buck circuit receives the driving signal to generate the output voltage.

Description

200924362 IX. Description of the Invention: [Technical Field] The present invention relates to a DC/DC converter, and more particularly to a discontinuous current mode (DCM) and a continuous current mode. (continuous current mode, CCM) System and method for smooth switching [Prior Art] The DC conversion controller converts the input DC voltage to a higher or lower output DC voltage. The traditional DC conversion controller can be divided into two types: pulse width modulation and pulse frequency modulation. If the DC conversion controller outputs a voltage to a light load, the DC conversion controller may be in a discontinuous current mode, or a pulse frequency modulation (PFM) mode, to cause an inductor current in the DC conversion circuit. Keep continuous and not zero to reduce its power consumption. Conversely, if the DC converter controller outputs a voltage to a heavy load, the DC converter controller can be in a continuous current mode, or pulse width modulation (PWM) mode. Traditionally, the pulse design of pulse frequency modulation signals can be classified into two categories. The first type is that the pulse width of the pulse frequency modulation signal is fixed wider than the pulse width modulation signal (for example, the pulse width of the pulse frequency modulation signal is 130% of the pulse width of the pulse width modulation signal). The second type uses the peak value of the inductor current to determine the pulse width of the pulse frequency modulation signal. For example, when the inductor current rises to a predetermined value, the pulse is turned off. However, these two methods are not continuous

Client’s Docket No.: IT’s Docket No:0975-A41243-TW/Final/LukeLee 5 200924362 The output voltage in streaming mode and continuous current mode can vary greatly. For example, if the inductance value of the DC conversion circuit is small or the input voltage varies greatly, in the conventional method, the switching of the two modes will greatly change the ripple of the output voltage. Or it is because of mode misjudgment and constantly switching between the two modes. Therefore, there is a need in the art for a technique that allows the DC conversion controller to switch between a discontinuous current mode and a continuous current mode to be extremely smooth. SUMMARY OF THE INVENTION The present invention provides a DC conversion control system for receiving an input voltage to generate an output voltage, wherein the input voltage and the output voltage are both direct current. The DC conversion control system includes a pulse width modulator, a pulse frequency modulator, a first switching device, and a DC conversion circuit. The pulse width modulator generates a pulse width modulation signal having a variable duty cycle based on the input voltage and the output voltage. The pulse frequency modulator generates a pulse frequency modulation signal having a variable clock frequency according to the input voltage and the output voltage. The first switching device is coupled between an input voltage and a ground voltage, and switches the input voltage and the ground voltage to generate a driving according to one of the pulse width modulation signal and the pulse frequency modulation signal. Signal. The DC conversion circuit is coupled to the first switching device for receiving the driving signal to generate the output voltage. The present invention also provides a DC conversion control method for a DC conversion control circuit that converts an input voltage into an output voltage, wherein the input voltage and the output voltage are both DC. This method includes detecting the above

Client’s Docket No.: TT^ Docket No:0975-A41243-TW/Final/LukeLee t 200924362 Input voltage and the above output electric grinder. A pulse width modulation signal having a variable duty cycle is generated based on the input voltage and the above-described power-off ’. Based on the input voltage and the output voltage, a pulse-disappearing signal having a variable clock frequency is generated. Receiving one of the pulse width modulation signal and the pulse frequency modulation signal to a switching device to generate a driving signal. The above driving signal is input to the DC conversion circuit to output the above output voltage. [Embodiment] FIG. 1 is a schematic diagram of a DC conversion controller according to the present invention, which is configured to receive a direct input voltage VIN and output a DC output voltage ν 〇υ τ, and can be in a discontinuous current mode and a continuous electric dragon type. Smooth switching between. The DC conversion controller 100 includes a pulse frequency modulator '1', a pulse width modulator 104, voltage detectors 106 and 1B, a multiplexer 11A, a switching device 112, a DC conversion circuit 114, and a control Unit 116. The voltage detectors 106 and 108 are respectively configured to detect the input voltage Vin and the output voltage ν〇υτ, and respectively output the first detection signal and the second detection signal to the pulse frequency modulation i 102 and the pulse width adjustment according to the side wire respectively. The transformer is 1〇4. The pulse frequency modulator 102 can output a pulse signal (pulse frequency modulation signal PFM) of a variable pulse frequency according to the first detection signal and the second detection signal, that is, according to the input voltage VIN and the output voltage νουτ. Similarly, the pulse width modulator 1〇4 can output a pulse signal of a variable pulse width (pulse I degree modulation signal PWM) according to the input electric dust vIN and the output voltage ν〇υτ. The switching device 1 can be a multiplexer coupled to the pulse frequency modulator 1〇2 and the pulse width modulator 104 for selecting an output pulse according to a control signal for controlling the single magic 16 output.

Client's Docket No.: TT's Docket No:0975-A41243-TW/FinayLukeLee 200924362 The pulse frequency modulation signal PFM or the pulse width modulation signal pWM. The switching device 112 is coupled between the input voltage Vin and the ground voltage for receiving the output of the switching device 11 to switch the input voltage Vin and the ground voltage to output a driving signal. Switching device 112 includes a buffer 12A, an inverter 124, and transistors 126 and 128. Both transistors 126 and 128 are N-type gold oxide half field effect transistors. For example, when the signal received by the switching device 112 is high, the transistor 126 is turned on and the transistor 128 is turned off. The output of the switching device 112 is the input voltage vIN. On the contrary, when the signal received by the switching device 112 is low, the transistor 126 is non-conducting and the transistor 128 is turned on. At this time, the output of the switching device 112 is a ground voltage. The DC conversion circuit 114 is entangled to the switch device 112' to receive the drive signal output from the switch device 112 to generate an output voltage vOUT. The DC conversion circuit 114 includes an inductor 13A, a resistor 132, and a capacitor 134, and is a buck circuit that converts the input voltage VlN into a lower potential output voltage V0UT according to the received driving signal. The output power M VOUT can be supplied to a load as a supply voltage, such as an integrated circuit chip. The control unit 116 can sense the inductor current l flowing through the inductor 13 ,, and the waveform of the inductor current IL during the voltage conversion exhibits a triangular wave. In the continuous current mode, when the valley of the inductor current iL continuously generates a zer〇crossing point (that is, the value of the valley is lower than zero) exceeds a predetermined number of times or is less than zero for more than a predetermined time. At this time, the control unit 116 determines that the system enters the discontinuous current mode, and outputs a control signal to the switching device 110 to output the pulse frequency modulation signal PFM to the switching device 112. phase

Client's Docket No.: TT's Docket No:0975-A41243-TW/Final/LukeLee 200924362 In the discontinuous current mode, if the valley of the inductor current L is far from the crossover, or higher than zero When the time is exceeded, the control system determines that the system enters the continuous current mode, and outputs a control signal to the switching device 110 to output the pulse width modulation signal pwM to the switching device 112. Pulse width modulator 1〇4 7 4^_ & J Wenchuan 4 includes the two-wave generator M〇, error amplifier! 42. A compensation circuit 144 and a comparator 146. The error amplifier 142 receives the voltage from the output voltage ¥(10) and outputs a differential signal v_p after the yoke is compared with the reference voltage Vref. The feedback voltage can be obtained from the output voltage, '歪' by the power P and 148 and 15 作为 as the feedback voltage. The error signal, vcomp can be adjusted by the compensation circuit 144 and output to the ratio 146. The angle generator 14 outputs the triangular wave signal according to the wheeling voltage Vin and the output voltage v0UT. The comparator 146 compares the triangular wave signal νι with the sickness signal Ve〇mp and outputs a pulse width modulation signal pWM. For example, when the potential of the triangular wave signal VI is lower than the error signal \, the comparison benefit 146 outputs a high potential, and vice versa, the output low potential. During the period in which the comparator 146 outputs two potentials, the pulse width modulation signal PWM is used. Pulse width. The principle of generating the binary wave generator 140 is as shown in Fig. 2. The triangular wave generator 140 includes current sources 2〇2 and 206, switching devices 2〇4, and a capacitor 208. Current source 206 is a control current source that produces current l based on the input voltage vIN multiplied by a gain value G1. Switching device 2〇4 is coupled to current sources 2〇2 and 206 for switching current sources 202 and 206 to capacitor 208. The triangular wave signal VI generated by the triangular wave generator 140 is as shown in Fig. 4. During the rising period of the triangular wave signal VI, the switching device 204 switches to the current source.

Client's Docket No.: TT's Docket No: 〇975-A41243-TW/Final/LukeLee 9 200924362 202, capacitor 208 is charged by current source 202; conversely, during the falling period of triangle wave signal VI, switching device 204 switches to current source 206 The capacitor 208 is discharged by the current 1 电流 of the current source 206. Therefore, the falling slope of the triangular wave signal VI is the current Ι divided by the capacitance of the capacitor 208. In this embodiment, the amplitude VR3 of the triangular wave signal VI is the input voltage VIN divided by an integral multiple (VR3=VIN/A), and the triangular wave signal VI is smaller than the amplitude Vx of the compensation voltage Vcomp by dividing the output voltage VOUT by the above integer multiple ( Vx=V0UT/A). When the triangular wave signal VI is smaller than the error signal Vcomp, the comparator 146 outputs a high potential, so in Fig. 4, the pulse width of the pulse width modulation signal PWM is equal to the time when the triangular wave signal VI is smaller than the error signal Vc_p. The operation of the pulse frequency modulator 102 is as shown in FIG. The pulse frequency modulator 102 includes a current source 302, a switching device 304, a capacitor 306, and a comparator 308. Current source 302 is a control current source that produces current 12 based on the input voltage VIN multiplied by a gain value G2. The switching device 304 is coupled between the current source 302 and the ground power source for switching the current source 202 and the ground power source to the capacitor 306. The comparator 308 compares the triangular wave signal V2 with the voltage Vx and outputs a pulse frequency modulation signal PFM. The voltage Vx is the output voltage VOUT divided by an integral multiple (Vx = VOUT/A) which is equal to the amplitude of the triangular wave signal VI being less than the compensation voltage Vcomp. The triangular wave signal V2 generated by the capacitor 306 is as shown in Fig. 4. During the rising period of the triangular wave signal V2, the switching device 304 is connected to the current source 302 and the capacitor 208, and the capacitor 208 is charged by the current 12. Therefore, the rising slope of the triangular wave signal V2 is the current 12 divided by the capacitance of the capacitor 306. In addition, since the triangular wave signal V2 is small at this time

Client's Docket No.: TT^s Docket No:0975-A41243-TW/Final/LukeLee 10 200924362 At voltage Vx, comparator 308 outputs a high potential. If it rises to the voltage Vx day temple, the comparator 3〇8 changes round out = tiger $ continuation - segment minimum cut-off time (a... minimum cut = the first wide crystal 128 ' and detects the electric current through the electro-crystal ^:疋 No is too large and needs overcurrent protection. In the second and third figures, the current 1! can be the current I k k times, the capacitance of the capacitor 2 〇 8 can be the capacitance ^ k times, so the triangular wave signal V2 The rising slope is equal to the falling slope of the triangular wave signal π 1 . It is worth noting that, as can be seen from Fig. 4, the pulse width modulation signal PFM is equal to the pulse width modulation signal pWM by almost 1〇〇%. The pulse width of the signal PFM can also be precisely controlled by the above embodiment to precisely control the pulse width of the pulse frequency modulation signal pFM to be a multiple of the pulse width of the pulse width modulation signal PWM. For example, using the charge and discharge time of the control valley The current value is changed, or the capacitance value of the capacitor is changed, and the pulse width of the control pulse frequency modulation signal PFM is 90%, 11 〇%, or other multiples of the pulse width of the pulse width modulation signal PWM. An embodiment of a DC conversion control method of the present invention is used for The flow conversion control circuit converts an input voltage (VIN) into an output voltage (V0UT) 'where the input voltage and the output voltage are both DC voltages. The method first detects the input voltage and the output voltage (step S502), Then, according to the input voltage and the output voltage, a pulse width modulation signal and a pulse frequency modulation signal are respectively generated (steps S504 and S506), wherein the pulse width modulation signal and the pulse frequency modulation signal have the same pulse width. Receiving one of the pulse width modulation signal and the pulse frequency modulation signal to

Client's Docket No.: TT's Docket No: 0975-A41243-TW/Final/LukeLee 200924362 A switching device generates a driving signal (step S508), and finally inputs a driving signal to the DC conversion circuit to generate an output voltage (step S510). . In step S504, the pulse width modulation signal is generated by first generating a triangular wave signal according to the input voltage and the output voltage. The triangular wave signal can be generated by charging and discharging a capacitor whose amplitude VR3 is an input voltage divided by an integral multiple (VIN/A). The capacitor discharges with one current generated according to the input voltage and is charged by another current source, so the falling slope of the triangular wave signal is equal to the current divided by the capacitance of one of the above capacitors. The triangular wave signal is further compared with an error signal to generate a pulse width modulation signal, wherein the error signal is generated by comparing the output voltage with a reference voltage after being subjected to resistance voltage feedback. In step S506, the pulse frequency modulation signal is generated by first generating a triangular wave signal according to the input voltage and the output voltage, and comparing the triangular wave signal with a voltage Vx to generate a pulse frequency modulation signal. The voltage Vx is the output voltage divided by the above integral multiple (VOUT/A). The triangular wave signal can be generated by charging and discharging a capacitor, and its amplitude is also a voltage Vx. The capacitor is charged by one current generated according to the input voltage, and is discharged by the ground power supply. Therefore, the rising slope of the triangular wave signal is equal to the current divided by the capacitance of one of the above capacitors. In step S508, when one of the output currents of one of the step-down circuits generates one of the output currents, the trough is less than zero (or the crossover point) continuously exceeds a predetermined number of times, the pulse frequency modulation signal is received to the switching device; Then, the pulse width modulation signal is received to the switching device. 6 and 7 are simulation diagrams of the DC conversion controller 100

Client's Docket No.: TT's Docket No: 0975-A41243-TW/Final/LukeLee 12 200924362 Form 'where the input voltage Vin is 12 volts' and the output voltage V〇ut is 5 volts. Fig. 6 is a waveform diagram of the triangular wave signal VI and the compensation signal Vcomp, and Fig. 7 is a waveform diagram of the inductor current IL and the output voltage V〇ut. The system is initially set to continuous current mode (CCM). As time advances, the valley of inductor current II continuously passes through the crossover point for more than a predetermined number of times, so the system switches to discontinuous current mode (DCM), inductor current IL The waveform is thus increased. After the inductor current has not crossed the crossover point for more than a predetermined number of times, the system switches to the continuous current mode again. As can be seen from the figure, the DC conversion controller 100 has experienced two consecutive current modes and two discontinuous current modes. It is worth noting that the output voltage νουτ is extremely smooth during the switching between the continuous current mode and the discontinuous current mode, that is, the continuous wave of the output voltage V〇ut does not change due to the mode change. While the present invention has been described above in terms of several embodiments, it is not intended to limit the invention, and the invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is subject to the definition of the scope of the patent application. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an embodiment of a DC conversion controller of the present invention, which can smoothly switch between a continuous current mode and a continuous current mode, and FIG. 2 shows a triangular wave generator 140 generating a triangular wave signal VI. The principle of generating the pulse frequency modulation device 102 generates the principle of generating the pulse frequency modulation signal PFM; FIG. 4 is a schematic diagram of the signal waveform of the embodiment of the first embodiment;

Client's Docket No.: TT's Docket No:0975-A41243-TW/Final/LukeLee 13 200924362 FIG. 5 is an embodiment of a DC conversion control method according to the present invention; FIG. 6 and FIG. 7 are implementations of the DC conversion controller 100. Analog graphics. [Description of main component symbols] 100 to DC conversion controller 102 to pulse frequency modulator 104 to pulse width modulator 106, 108 to voltage detector 110 to switching device 112 to switch device 114 to DC converter circuit 116 to Control unit 120 to buffer 124 to • inverter 126, 128 to transistor 130 to • inductor 132 to resistor 134 to • capacitor 140 to triangle wave generator 142 to error amplifier 144 to compensation circuit 146, 308 to comparator 202, 206, 302~ current source 204, 304~ switching device 208, 306~ capacitor

Client’s Docket No.: TT5s Docket No:0975-A41243-TW/Final/LukeLee

Claims (1)

200924362 X. Patent application scope: 1. A DC conversion control system for receiving an input electric generator and an output voltage 'where the input voltage and the output voltage are both DC, including: β-pulse width modulator, according to The input voltage and the output voltage 'generate a pulse-width modulation signal with a variable period of one cycle; a pulse frequency, and generate a pulse frequency with a variable clock frequency according to the wheel voltage and the output voltage Modulating signal; a first-switching device 'supplied to - between the input voltage and the ground voltage', according to the pulse width modulation signal and the pulse frequency modulation signal, switching the voltage of the wheel and the above The ground voltage is used to generate a driving signal; and the DC conversion circuit is coupled to the first switching device for receiving the driving signal to generate the wheeling voltage. 2. The DC switching control system of claim 1, further comprising a switching device for outputting one of the pulse width modulation signal and the pulse frequency modulation signal to the first switching device. 3. The DC conversion control system of claim 1, further comprising: a first voltage detector for detecting the input voltage, and generating a first detection signal according to the detection result, And outputting to the pulse width modulator and the pulse frequency modulator; and a second voltage detector for detecting the output voltage, and generating a second detection signal according to the detection result, and outputting to The above pulse width adjustment Client's Docket No.: IT'S Docket No: 0975-A41243-TW/Final/LukeLee 15 200924362 transformer and the above pulse frequency modulator. 4. The DC conversion control system of claim 1, wherein the pulse width modulator further comprises: a triangular wave generator for generating a triangular wave signal according to the input voltage and the output voltage, wherein the triangular wave One of the amplitudes of the signal is the input voltage divided by an integer multiple; an error amplifier for comparing the output voltage feedback feedback voltage and a reference voltage to generate an error signal; and a comparator for comparing the above The error signal and the triangular wave signal are used to generate the pulse width modulation signal. 5. The DC conversion control system of claim 4, wherein the triangular wave generator further comprises: a capacitor; a first current source for charging the capacitor; and a second current source for The input voltage is used to generate a current to discharge the capacitor at the current; and a second switching device is coupled to the first current source and a second current source for switching the first and second current source connections To the above capacitors. 6. The DC conversion control system of claim 5, wherein one of the triangular wave signals has a falling slope of the current divided by a capacitance of the capacitor. 7. The DC conversion control system of claim 1, wherein the pulse frequency modulator further comprises: a capacitor; Client's Docket No.: TT^s Docket No: 0975-A41243-TW/Final/LukeLee 16 200924362 a current source for generating a current according to the input voltage to charge the capacitor with the current; a second switching device coupled to the current source and a ground power source for switching the current source and the The grounding voltage is connected to the capacitor, and the capacitor is charged by the current or discharged to generate a triangular wave signal, wherein an amplitude of one of the triangular wave signals is equal to the output voltage divided by an integer multiple; and a comparator is used The pulse frequency modulation signal is output by comparing the triangular wave signal and the output voltage by the integer multiple. 8. The DC conversion control system of claim 7, wherein a rising slope of one of the triangular wave signals is equal to the current divided by a capacitance value of the capacitor. 9. The DC switching control system of claim 1, wherein the switching device outputs the pulse frequency modulation signal when one of the inductive circuits of the one of the step-down circuits generates an output current that is less than zero for more than a predetermined number of times. Otherwise, the switching device outputs the pulse width modulation signal. 10. The DC conversion control system of claim 1, wherein the pulse frequency modulation signal has the same pulse width as the pulse width modulation signal. A DC conversion control method for a DC conversion control circuit for converting an input voltage into an output voltage, wherein the input voltage and the output voltage are both DC, comprising: detecting the input voltage and the output voltage; Client's Docket No.: TT's Docket No:0975-A41243-TW/Final/LukeLee 17 200924362 According to the above input voltage and the above output voltage, a pulse width modulation signal having a variable duty cycle is generated; according to the above input voltage and the above output a voltage, generating a pulse frequency modulation signal having a variable daily pulse frequency; receiving the pulse width modulation signal and the pulse frequency modulation signal #u to the switching device to generate a driving signal, And driving the above driving signal to the DC conversion circuit to output the output voltage. 12. The DC conversion control method of claim 11, wherein the generating the pulse width modulation signal further comprises: generating an amplitude of the one of the triangular wave signals in the triangular wave signal according to the input voltage and the output voltage. The input voltage is divided by an integer multiple; μ compares one of the output voltages and a reference voltage to generate an error signal; and compares the error signal and the triangular signal to generate the pulse width modulation signal. 13. The DC conversion control method of claim 12, wherein the generating the triangular wave signal further comprises: generating a current according to the input voltage; discharging a capacitor by using the current, and using a current source pair The capacitor is charged to generate the triangular wave signal. 14. The DC conversion control method according to claim 13, wherein a falling slope of one of the above-mentioned two-wave signals is equal to the current divided by Client's Docket No.: TT5s Docket No: 0975-A41243-TW/Final/LukeLee 18 200924362 One of the above capacitance values. 15. The DC conversion control method of claim π, wherein the generating the pulse frequency modulation signal further comprises: generating a triangular wave signal according to the input voltage and the output voltage, wherein an amplitude of one of the triangular wave signals is the above The output voltage is divided by an integer multiple; and the triangular wave signal is compared and the output voltage is divided by the integer multiple to generate the pulse frequency modulation signal. 16. The DC conversion control method of claim 15, wherein the generating the triangular wave signal further comprises: receiving the input voltage to generate a current; and charging a capacitor by using the current, and using a ground power source The capacitor is discharged to generate the triangular wave signal. 17. The DC conversion control method of claim 16, wherein a rising slope of one of the two-wave signals is equal to the current divided by a capacitance of the capacitor. 18. The DC conversion control method according to claim 5, wherein when one of the inductive circuits of the one of the step-down circuits generates an output current that is less than zero for more than a predetermined number of times, receiving the pulse frequency modulation signal to generate the above Driving the signal; otherwise, receiving the pulse width modulation signal to generate the driving signal. I. The DC conversion control method of claim U, wherein the pulse frequency modulation signal has the same pulse width as the pulse width modulation signal. Client’s Docket No.: TT's Docket N〇: 0975-A41243-TW/Final/LukeLee