TW201101690A - Ramp generator capable of stabilizing modulator gain, power converting system, and method thereof - Google Patents

Abstract

A ramp generator capable of stabilizing modulator gain for generating a ramp signal is disclosed. The ramp generator includes a ramp capacitor, a current charging module, and a discharging module. The ramp capacitor outputs the ramp signal. The current charging module generates a charging current for charging the ramp capacitor according to an input voltage. The discharging module compares the ramp signal and a threshold voltage and discharges the ramp capacitor according to the comparing result. The threshold voltage varies according to the charging current. In this way, the ratio of the input voltage and the peak-to-peak voltage of the ramp signal can be approximately fixed, which stabilizes the modulator gain.

Description

201101690 VI. Description of the Invention: [Technical Field] The present invention relates to a ramp generator, and more particularly to a ramp generator that stabilizes a variable gain. Q [Prior Art] Please refer to Figure 1. Figure 1 is a schematic diagram illustrating a prior art buck power converter 100. The buck power converter 1 is used to reduce the voltage of an input voltage source Vnsj to generate an output voltage ν 〇υ τ. The buck power converter 1A includes a power switch Q!, an inductor L, a diode D!, a capacitor COUT, two resistors Ri and R2, and a duty cycle adjuster 11A. The duty cycle adjuster includes a comparator CMP!, an error amplifier in, and a ramp generator 112. The connection relationship of the components in the figure j is clearly disclosed, and will not be described here. Where Vss is a voltage source, such as the ground. In Fig. 1, the resistance and the heart generate a feedback voltage VFB according to the output voltage ν 〇υ τ and are transmitted to the negative input terminal of the error amplifier ill. The error amplifier 111 generates a duty voltage VDUTY based on the feedback voltage VFB and the reference voltage Vref, and transmits it to the comparator input. The comparator cmp! compares a ramp signal VRAMP from the ramp generator 112 with a duty voltage VDUTY to generate a switch control signal Ssw. The switch control signal Ssw is a Pulse Width Modulation (PWM). When the switch control signal Ssw is low voltage reference 201101690 bit, the power switch Q1 is turned on; when the switch control signal ssw is at the high voltage level, the power switch Q1 is turned off. Therefore, the duty cycle adjuster 110 can switch the control signal Ssw' according to the feedback voltage Vfb to determine that the power off Qi is the material pass, and maintain the voltage level of the output voltage 8 V〇ut at a predetermined voltage level. 3 > Test 2 2 4 2 is a schematic diagram of the relationship between the switch control signal and the output voltage vOUT in Figure 1. The relationship between the duty cycle 〇D of the switch control signal Ssw, the output voltage ν〇υτ and the input voltage can be expressed by the following formula: D - T0N/TS = Vduty/VramP PTP ... (1); V〇UT/Vin = D = 乂瞻~Read,...(2); ' where T〇N indicates the time when the power switch Qi is turned on, ts indicates the switch control signal Ssw - one (4), D wire X, V_p pTp indicates the ramp signal v_ Peak-to-peak voltage. The buck power converter can also be used to adjust the gain (Modulator Gain) GModuiator and loop gain (Loop Gain) Gloop can be expressed by the following formula:

U GModulator Δνουτ/ΔνουΤΥ—△[V'lN X CVdUTy/Vramp-ptp^JMVduty = ^WVramp-PTP ...(3);

Gl〇〇p = (Vin/VRamp_ptp) x (Vref/V0Ut) = GModulator x (Vref/Vout)...(4); As shown in Figure 2, when the input voltage VlN drops, the output voltage ν〇υτ will follow The drop is made, and the feedback voltage VFB is lowered, so the duty voltage vDUTY rises. At this time, the comparator CMP! compares the ramp signal VramP with the rising duty voltage VDUTY, and generates a switch control signal ssw having a longer duty cycle D (as indicated by the period Tx in FIG. 2), thereby making the output voltage V0UT rises back to the preset voltage level, but when the input voltage Vjn is unstable 201101690 timing (regardless of sudden rise or sudden drop), it can be known from equations (7) and (4) that it can adjust the gain of the shadow converter 100, h The up to power supply is unstable. The voltage is turned on and the voltage is turned on. When the input voltage is unstable, the voltage becomes unstable, causing the use. Therefore, the power converter of the prior art affects the adjustable gain of the power converter. And the output is greatly inconvenient. Ο [Summary] The real-world relationship of the present invention provides a scale generation _, which can generate and adjust the ship signal according to the change of the input signal to stabilize the adjustable gain. The ramp generator includes a ramp wave valley, a charging current module, and a discharge module. The ramp capacitor is used to output the ramp signal. The charging current module is configured to generate a corresponding charging current according to a voltage of an input voltage source and an input reference voltage to charge the ramp generating capacitor. The discharge module is configured to compare the ramp signal with a threshold voltage to cause the ramp to generate a capacitor discharge, wherein the threshold voltage varies according to the charge current. One embodiment of the present invention provides a method of stabilizing a variable gain of a power conversion system. The method includes: adjusting a charging current according to a voltage of an input voltage source, charging a ramp generating capacitor with the charging current, generating a ramp signal, adjusting a threshold voltage according to a voltage of the input voltage source, and when The ramp signal is approximately higher than or 201101690; when the voltage is ▲, the capacitor of the ramp is discharged, so that the adjustable gain is about a certain value. [Embodiment]

See Figure 3 for the next month. Figure 3 is a block diagram of a ramp generator 3 (8) 2 in accordance with a preferred embodiment of the present invention. As shown in FIG. 3, the ramp generator 3A includes a ramp capacitor c_, a charge current module 310, and a discharge module 320. The peak-to-peak value Vrampj>tp of the ramp signal can be generated and adjusted by detecting the change of the input voltage VrN, so that the adjustable gain is maintained at a certain value. When the ramp signal VraMP is lowered to the low threshold voltage V1 (set value), the charging current module 310 starts to charge the ramp capacitor 0_ to increase the voltage of the ramp signal 乂_, when the ramp signal Vramp rises to a high level. When the voltage level of the threshold voltage Vh is (approximately) equal to or higher than), the discharge module 320 discharges the ramp capacitor c_ to reduce the ramp frequency Vramp. Therefore, the high peak value of the ramp signal is the high threshold voltage Vh; the low peak value of the ramp signal v_ is the low threshold voltage V1. In other words, the peak-to-peak value ν_ρ ρτρ of the ramp signal VramP is (Vh_Vl). The ramp generator 3 generates a periodic ramp signal VraMP by the charging and discharging process of the charging current module 310 and the discharging module 320. One circuit embodiment of the charging current module 310 is as shown in FIG. 4, and the charging current module 310 includes a constant current source 511 and a supplementary current source 512. The constant current source 201101690 511 is used to generate the input reference current 111£1; the supplementary current source 512 is used to generate the supplemental current ΔI, and the sum of the input reference current and the supplemental current ΔΙ is the charging current k. The constant current source 511 includes a transistor q4, an operational amplifier 〇p3, and an input reference resistor Rref. The input terminal of the operational amplifier 〇p3 receives the input reference voltage Vin_ref; the operational amplifier 5b is controlled by the operational amplifier 〇p3, and the current of the current source 5U is generated to generate a current of (VrN REF/RREF) and set it as an input. Reference current Iin ref.补 Supplementary current source 512 includes two transistors q2 and q3, two operational amplifiers OP1 and 01>2, and an adjustment resistor RX1. The input terminal of the operational amplifier 〇Ρι receives the input reference voltage ViN REF, and the input terminal of the operational amplifier OP2 receives the input voltage ViN; the operational amplifiers 0Ρ#0Ρ2 respectively control the transistors Q2 and Q3, and the current source 512 is supplemented to generate the size. The current of [(Vnsj - V^ ref) / ^] is set to the supplementary current ΔI. The charging current Ic can charge the ramp capacitor Cramp, which can be expressed by:

Ic = Iref + ΔΙ = IREF + Δ Vn^ / Rx = Vin_ref / Rref + (V^-V^ref) / Rx (5); Therefore, it can be seen from the above equation that the charging current Ic changes with the input voltage ViN And change. Figure 5 is a schematic diagram of another circuit embodiment of the charging current module 31A of the ramp generator of the preferred embodiment of the present invention. As shown in FIG. 5, the charging current module 31 includes a current source 611 and a supplemental current source 612. The operating principle of the constant current source 611 201101690 is the same as the constant current source 511 described above, and will not be described here. Supplemental current source 612 includes a primary supplemental current source 6121 and a multiplier 6122. The secondary supplemental current source 6121 operates in the same manner as the supplemental current source 512 in Figure 4. Therefore, the voltage across the voltage difference (ViN - Vi^REF) across the resistor RX2 causes the current drawn by the transistor Q6 to be [(ViN - ViN). R^/RxJ is set to the difference current Im. The multiplier 6122 includes a comparator CMP2, a low pass filter LPF, a switch S% 〇, and a resistor RM. The multiplier 6122 is used to supplement the current. The difference current Im generated by the source 6121 is multiplied by 11N_REF times to generate a supplemental current ΔΙ. In other words, the resistance of the adjustment resistor RX2 in FIG. 5 should be the IiN_REF of the resistance of the adjustment resistor RX1 in FIG. In addition, the complementary current generated by the current sources 612 and 512 is the same. In the multiplier 6122, the comparator CMP2 receives an external ramp signal Vramp Εχτ ^ and the input reference voltage Vin ref; the comparator CMP2 compares the external slope Wave signal

VraMP_EXT and the input reference voltage Vn^REF are used to generate a switch control signal Sm to control the switch SW to be turned on or _. When the switch SW1 is turned on (its control terminal i is to the control terminal 2), the differential current IM flows directly to the voltage source Vcc without flowing into the low-pass chopper LPF. On the contrary, when the switch SW1 is turned off (its control terminal) When the light is connected to the control terminal, the difference current ιΜ will be the secret bribe 妓 LPF, the low-pass enemy lpf will be the low-pass filter LPF differential current lM average, so to complete the multiplier: 201101690 In addition, one circuit embodiment of the discharge module 320 is as shown in FIG. 6. The discharge module 320 includes a comparator cMp", a switch SW2, a threshold voltage circuit 321, and a discharge power source 322. The threshold voltage circuit 321 According to the charging current Ic from the charging current module 31, a high threshold voltage VH is generated and input to the negative input terminal of the comparator CMPi. In FIG. 6, the threshold voltage circuit 321 can be realized by a critical resistance. The comparator CMP3 is configured to receive the ramp signal Vramp and the high threshold voltage Vh, and compare the ramp signal VraMP with the high threshold voltage Vh to generate a discharge trigger signal center. When the ramp signal is raised to a voltage of a high threshold voltage Vh Level (about equal to or high) The comparator CMP3 outputs a discharge trigger signal signal representing "on" to the control terminal C of the switch SW2, so that the control terminal 1 of the switch SW2 is coupled to the control terminal 2 of the switch SW2. Therefore, the discharge power source 322 is coupled through the switch SW2. Connected to the ramp capacitor C_P, and the discharge current ID is extracted from the ramp capacitor Cramp to discharge the ramp capacitor Cramp to reduce the ramp signal Vramp. In addition, the discharge source 322 can be implemented by a voltage source Vd. In the palladium case, the high-critical current VH of the discharge module 320 is dynamically changed. More specifically, the discharge module 32 determines the size of the high threshold voltage VH according to the magnitude of the charging current ^. The high threshold voltage γΗ can The following equation is expressed as: VH = Vh_reF + ΔνΗ = VH - REF + δι X Rh... (6); where ν Η, the wire high critical reference lag (grain), the AVh Hz threshold voltage, RH represents the critical resistance; AVh is equal to ΔΙ χ & (_ The person changes depending on the change), so it can be seen from the above equation that the high threshold voltage % will change as the charging current changes. And because the peak-to-peak value of the ramp signal v_ is v_-pt4 (Vh-Vl), and Low threshold voltage vL is fixed value 'so oblique The peak-to-peak difference of the signal 乂_ will change with the high threshold voltage vH of 201101690. Further, since the input voltage will affect the magnitude of the charging current ic, and the charging current Ic will also affect the high threshold voltage^ The size of ^, so it can be inferred that the peak-to-peak value of the ramp signal Vramp Vrampptp will follow the input voltage

The size of Vjn changes. That is, when the input voltage ViN changes, the ramp signal

The peak-to-peak value of Vramp Vramp-ptp will change accordingly' thus enabling the adjustable gain to be approximately stable to a certain value. FIG. 7 is a schematic diagram of related signals in a ramp generator according to a preferred embodiment of the present invention. As can be seen from FIG. 7, the spirit of the present invention is the magnitude of the charging current Ic and the high threshold voltage when the input voltage is changed. The size of ¥}{ changes, and the peak of the ramp signal Vramp changes with the peak value ρΤρ, so that the adjustable gain will be approximately steady-set. As shown in Fig. 7, when the input impurity I rises (increases △ &), the charging current Ic rises (increases Δ!), the high threshold voltage % also rises (increases Δ%), and the peak of the ramp signal Vmmp The peak value of Vramp_ptp also changes, so that the adjustable gain is maintained at a constant value.

J and FIG. 8 are circuit diagrams of a ramp generator 3〇〇 according to a preferred embodiment of the present invention. In the figure of Fig. 8, the charging current module 31() is exemplified by the circuit embodiment of Fig. $ to make the two fully understood; however, it can also be implemented by the embodiment of Fig. 4 or other means. In Figure 8, the transistors Q7, Q8 and Q9 are additionally added. The transistor (^ and 仏 form a motor mirror to reproduce the charging current Ic to charge the ramp wave. The transistor Q7 is recorded with n to reproduce the charge, so that the critical resistance is known to produce a critical turn Vh. The principle and structure of the module X is the same as that of the 5th 11 201101690. The charging current module 31 产生 generates a charging current ic according to the input reference voltage ViNjtEF and the input voltage - the voltage of the source VlN (set to the input voltage Vin). The operation principle of the circuit of Fig. 8 is the same as the above, and will not be described here. Further, although in the embodiment of the present invention, only the input voltage Vin is increased as an example, the case where the input voltage Vm is decreased is also included in In the present invention, more specifically, when the input voltage Vtn drops, the charging current Ic and the high threshold voltage % also drop down to lower the peak-to-peak value of the ramp signal v_>___TPP. Therefore, the adjustable gain can still be stabilized at a certain value. Please refer to Fig. 9. Fig. 9 is a schematic diagram of a buck power converter 900 to which the ramp generator of the present invention is applied, except for the ramp generator 3〇. In addition to 〇, buck-type electricity The structure and working principle of the converter 900 are similar to those of the buck converter in FIG. i, and therefore will not be described again. Since the buck power converter 9(10) uses the ramp generator 300 of the present invention, it can The modulation gain does not change with the input voltage and change, but is maintained at a constant value. Thus, the buck power converter can provide a stable input, although in the present invention, only the oblique application of the present invention is applied. Wave generator generation power conversion (four), "other types of power transfer difficulties, such as boost power supply turn" / buck power conversion H, can be _ the invention of the oblique wave production ^, simple _ know, so I will not repeat the input voltage change _ 峨 gain. Other _ electric conversion materials industry habits 12 201101690 & described above 'the ramp generator of the present invention can adjust the ramp signal according to the input voltage. Therefore, the use In the ramp generator of the present invention, when the input voltage of the power converter is unstable, the adjustable gain of the power converter can be maintained, thereby generating a more stable turn-off voltage, which provides greater convenience to the user. Sex. The above is only for this. The preferred embodiments of the present invention, all of which vary within the scope of the present invention, are intended to be within the scope of the present invention. [FIG. 1 is a description of a prior art buck. Schematic diagram of the power converter. Fig. 2 is a schematic diagram showing the relationship between the switching control signal and the output voltage in the Fig. 帛3 diagram is the ramp generator capable of maintaining the variable gain constant in the present invention. Figure 4 is a schematic view of the first embodiment of the charging current module of the ramp wave generating device of the present invention. Fig. 5 is the second embodiment of the charging electric panel of the ramp generator of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 6 is a schematic view showing an embodiment of a discharge module of the present invention. The =7 picture is a schematic diagram of the ramp wave generated by the ramp wave of the present invention which maintains the adjustable gain according to the input voltage change. 13 201101690 Figure 8 is a schematic diagram of the circuit of the ramp generator of the present invention. Figure 9 is a schematic diagram of a buck power converter to which the ramp generator of the present invention is applied. [Main component symbol description] 100, 900 buck power converter Ο 110 duty cycle regulator 111 error amplifier 112, 300 ramp generator 310 charging current module 320 discharge module 321 critical voltage circuit 322 discharge power supply 511 > 611 constant current source 〇 512, 612 supplementary current source 6121 times secondary current source 6122 multiplier CMPi ' CMP2 ' CMP3 comparator Di diode Ic charging current Id discharge current Im differential current 201101690

Iref input reference current L inductor LPF low pass chopper OP! ' OP2 ' OP3 ' 〇 P4 ' OP5 operational amplifier Qi Q2, Q3, Q4, Q5, Q6, Q7, Q8, Q9 power switch transistor Ri, R2, Rm Resistor Rh Critical resistance Rx Adjustment resistance sc Discharge trigger signal Ssw, Sm Switch control signal sw!, SW2 Switch T〇N ' Τχ On time Ts Period Vduty Responsible voltage Vfb Feedback voltage Vh Threshold voltage VhreF Critical reference voltage ViN Input voltage ViNREF Input Reference voltage V〇UT Output voltage 15 201101690

VramP ramp signal VraMP—EXT external ramp signal Vref reference voltage Vcc, Vss, Vd voltage source ΔΙ supplementary current △vH threshold voltage difference ΔΥιν input voltage difference 16

Claims (1)

201101690 •1 VII. Patent application scope: 1. A ramp generator with stable adjustable gain, which is used to generate a ramp signal, the ramp generator includes: a ramp capacitor, The charging current module is configured to generate a corresponding charging current according to a voltage of an input voltage source and an input reference voltage to charge the ramp capacitor; and The discharge module ' is configured to compare the ramp signal and a threshold voltage to discharge the ramp capacitor, wherein the threshold voltage varies according to the charging current. 2. The ramp generator of claim 1, wherein the discharge module comprises: a threshold voltage circuit for generating the threshold voltage according to the charging current; a comparator 'for using the threshold voltage according to the threshold voltage The ramp signal outputs a discharge touch signal, and a discharge circuit for discharging the ramp capacitor according to the discharge trigger signal. 3. The ramp generator of claim 2, wherein the threshold voltage circuit comprises a threshold resistor for converting the charging current to the threshold voltage. 4. The ramp generator of claim 2, wherein the discharge circuit comprises: a discharge power source; and a switch 'for coupling the ramp capacitor to the discharge according to the discharge trigger signal. 17.201101690 * ; An electric voltage source to discharge. 5. The ramp generator of claim 1, wherein the charging current module comprises: a constant current source for generating an input reference current of a corresponding magnitude according to the input reference voltage; and a supplemental current source for And generating a supplemental current according to the difference between the voltage of the input voltage source and the input reference voltage; wherein the sum of the input reference current and the supplemental current is the charging current. 6. The ramp generator of claim 1, wherein the charging current module comprises: a constant current source for generating an input reference current of a corresponding magnitude according to the input reference voltage; and a supplemental current source 'used Generating a supplemental current according to the difference between the voltage of the input voltage source and the input reference voltage, the supplemental current source comprising: a supplemental current source for determining a difference between the voltage of the input voltage source and the input parameter D μ test voltage And generating a difference current; and a multiplier comprising: a comparator for generating a switch control signal according to the input reference voltage and an external ramp signal; and a low pass filter for outputting the supplemental current; And a switch coupled between the supplemental current source and a certain voltage source to be used to conduct the differential current to the constant voltage source or the low pass filter according to the switch control signal; 18 .201101690 wherein the input The sum of the reference current and the supplemental current is the charging current. 7. A power conversion system with stable adjustable gain, comprising: a power switch coupled to an input power source; a duty cycle adjuster for generating a switch having an adjustable duty cycle duty ratio Controlling the signal ' to control the power switch, the duty cycle adjuster comprising: the ramp generator as described in claim 1; and ❹ - comparing 11 ' for comparing a responsible voltage with the ramp produced by the ramp generator Wave signal to generate the switch control signal. 8. A method for stabilizing a variable gain of a power conversion system, comprising: adjusting a charging current according to a voltage of an input voltage source; charging the ramp capacitor with the charging current to generate a ramp signal; The voltage of the input voltage source is adjusted by a threshold voltage; and when the ramp wave is about S or equal to the threshold, the hash capacitor is discharged so that the adjustable gain is about a certain value. 9. The method of claim 8 wherein the charging current is adjusted according to the voltage of the input electrical source includes: providing an input reference voltage; according to the power source of the input source Turning, generating a supplemental current; and merging the input reference voltage corresponding to -, T, the I input reference current and the supplemental current, making 19 201101690 as the charging current. 10. The method of claim 9, wherein adjusting the threshold voltage according to a voltage of the input voltage source comprises: generating the threshold voltage according to the charging current. Eight, the pattern: 20