JP2010521954A - Primary control switching regulator - Google Patents

Abstract

The switching regulator includes a switching device (20) for switching the transformer (10) from the primary side to the secondary side. The control circuit (70) generates a switching signal for adjusting the output of the switching regulator. The control circuit measures a reflected signal of the transformer to thereby generate a first circuit (100) that generates a first signal and a timing signal, and a current signal that represents a switching signal on the primary side of the transformer. 2, a third circuit that generates the second signal by integrating the current signal with the timing signal, and a first that generates the first feedback signal in response to the first signal and the reference signal A feedback circuit, a second feedback circuit that generates a second feedback signal in response to the second signal, and a switching control circuit that generates a switching signal in response to the feedback signal. The timing signal represents the discharge time of the transformer, and the reference signal changes in response to changes in the second signal.

Description

  The present invention relates to a switching regulator, and more particularly to a separation type switching regulator.

  Various switching regulators are widely used to provide regulated voltages and currents. For safety reasons, an off-line switching regulator must separate between the primary side and the secondary side. Therefore, a control circuit is provided on the primary side of the switching regulator, and an optical coupler and a secondary side circuit are required to adjust the output voltage and output current of the switching regulator. The trend is to eliminate the need for optical couplers and secondary circuits to reduce the size and cost of switching regulators.

In recent developments, many primary side control schemes have been disclosed as follows.
Patent Document 1 (US Pat. No. 6,721,192, title of invention “PWM controller regulating output voltage and output current in primary side”), inventor Yang et al. (Yang et al.))
Patent Document 2 (US Pat. No. 6,836,415, entitled “Primary-side regulated pulse width modulation controller with improved load regulation”, inventor) Yang et al.)
Patent Document 3 (US Pat. No. 6,862,194, title of invention “Flyback power converter having a constant voltage and a constant current output under a primary side PWM control” under primary-side PWM control) ”, inventor Yang et al.)
However, the disadvantage of the conventional primary side control scheme is that the output voltage and output current are not accurately controlled.

US Pat. No. 6,721,192 US Pat. No. 6,836,415 US Pat. No. 6,862,194

  An object of the present invention is to provide a switching regulator capable of accurately controlling the output voltage and output current on the primary side of the switching regulator. This reduces the size and cost of the switching regulator.

  A primary-side-controlled switching regulator (switching regulator) includes a switching device for switching a transformer of the switching regulator that sends energy from the primary side to the secondary side. The control circuit is coupled to the transformer, generates a switching signal for switching the switching device, and adjusts the output of the switching regulator. A first circuit coupled to the transformer is included in the control circuit and generates a first signal and a timing signal by measuring the reflected signal of the transformer. The timing signal represents the transformer discharge time. A second signal is generated by integrating the current signal representing the primary switching current of the transformer with the timing signal by the second circuit and the third circuit. The time constant of the third circuit is correlated with the switching cycle of the switching signal. A first error amplifier having a first reference signal is used to generate a first feedback signal in response to the first signal. To improve load regulation, the first reference signal is increased in response to an increase in the second signal. A second error amplifier having a second reference signal generates a second feedback signal in response to the second signal. Accordingly, the switching signal is generated by the switching control circuit in response to the first feedback signal and the second feedback signal. When the switching signal is enabled, the switching signal has a minimum on-time, which further ensures a minimum discharge time for multi-sampling of the reflected signal.

  It should be understood that the foregoing general description and the following detailed description are exemplary and are intended to further illustrate the invention as claimed. Further objects and advantages will become apparent from consideration of the following description and drawings.

  The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of the specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 is a circuit diagram of a conventional primary-side control switching regulator. FIG. 2 is a plurality of main waveform diagrams of the conventional switching regulator. FIG. 3 is a circuit diagram of a control circuit according to an embodiment of the present invention. FIG. 4 is a circuit diagram of a first circuit according to an embodiment of the present invention. FIG. 5 is a circuit diagram of an oscillator according to an embodiment of the present invention. FIG. 6 is a circuit diagram of a second circuit according to one embodiment of the present invention. FIG. 7 is a circuit diagram of a third circuit according to one embodiment of the present invention. FIG. 8 is a circuit diagram of a PWM circuit according to an embodiment of the present invention. FIG. 9 is a circuit diagram of an adder according to an embodiment of the present invention. FIG. 10 is a circuit diagram of an adjustment circuit for programming a reference signal according to an embodiment of the present invention.

FIG. 1 shows a conventional primary side control switching regulator. The switching regulator includes an auxiliary winding N _A, a primary winding N _P, a transformer 10 having a secondary winding N _S. In order to adjust the output voltage V _O and the output current I _O of the switching regulator, the control circuit 70 generates a switching signal V _PWM in the transistor 20 for switching the transformer 10.

ここで、V_INは変圧器１０に印加される入力電圧であり、L_Pは変圧器１０の一次巻線N_Pのインダクタンスであり、T_ONはスイッチング信号V_PWMのオン時間である。 FIG. 2 shows a plurality of signal waveforms of the conventional switching regulator shown in FIG. When the switching signal V _PWM goes to a logic high level, a primary side switching current I _P is generated accordingly. The peak value of the primary side switching current I _P is expressed by the following equation:

Here, V _IN is an input voltage applied to the transformer 10, L _P is an inductance of the primary winding N _P of the transformer 10, and T _ON is an ON time of the switching signal V _PWM .

ここで、V_Oはスイッチングレギュレータの出力電圧であり、V_Fは整流器４０の順方向電圧降下であり、L_Sは変圧器１０の二次巻線N_Sのインダクタンスであり、T_DSは二次側のスイッチング電流I_Sの放電時間である。 Once the switching signal V _PWM drops to a logic low level, the energy stored in the transformer 10 is transferred to the secondary side of the transformer 10 and the output of the switching regulator via the rectifier 40. Accordingly, a secondary side switching current _IS is generated. The peak value I _S1 of the secondary side switching current I _S is expressed by the following equation:

Here, V _O is the output voltage of the switching regulator, V _F is the forward voltage drop of the rectifier 40, L _S is the inductance of the secondary winding N _S of the transformer 10, T _DS secondary is the discharge time of the side of the switching current I _S.

ここで、T_NAとT_NSは、それぞれ、変圧器１０の補助巻線N_A及び二次巻線N_Sの複数の巻線数である。 In the meantime, the reflected signal V _AUX is generated in the auxiliary winding N _A of the transformer 10. This reflected signal V _AUX is expressed by the following equation:

Here, T _NA and T _NS, respectively, of a plurality of winding turns of the auxiliary winding N _A and the secondary winding N _S of the transformer 10.

ここで、T_NPは、変圧器１０の一次巻線N_Pの複数の巻線数である。 When the secondary-side switching current I _S decreases to zero, reflected signal V _AUX starts to drop. This also indicates that at that instant, the energy of the transformer 10 has been completely released. Therefore, as shown in FIG. 2, the discharge time T _DS in the equation (2) is measured from the falling edge of the switching signal V _PWM to the time when the reflected signal V _AUX starts to drop. The secondary-side switching current I _S is determined by the primary-side switching current I _P and the number of windings of the transformer 10. The switching current I _S on the secondary side is expressed by the following equation:

Here, T _NP is a plurality of winding turns of the primary winding N _P of the transformer 10.

ここで、R₅₀とR₅₁は、それぞれ抵抗５０と抵抗５１の抵抗値である。 As shown in FIG. 1, the control circuit 70 includes a supply terminal VCC for receiving power and a ground terminal GND. _A voltage divider formed by a resistor 50 and a resistor 51 is connected between the auxiliary winding N _A of the transformer 10 and the ground reference plane. The detection terminal DET of the control circuit 70 is connected to a coupling portion between the resistor 50 and the resistor 51. The voltage V _DET generated at the detection terminal DET is expressed by the following equation:

Here, R ₅₀ and R ₅₁ are resistance values of the resistors 50 and 51, respectively.

Capacitor 65 is further charged by reflected signal V _AUX through rectifier 60 to energize control circuit 70. The current detection resistor 30 functions as a current detection device. The current detection resistor 30 is connected from the source of the transistor 20 to the ground reference plane in order to convert the primary side switching current I _P into a current detection signal V _CS . Sense terminal CS of the control circuit 70 is connected to the current sensing resistor 30 for detecting the current sense signal V _CS.

The switching signal V _PWM is generated at the output terminal OUT of the control circuit 70 and switches the transformer 10. The voltage compensation terminal COMV is connected to a first compensation network for frequency compensation for the first error amplifier. This first compensation network may be a capacitor connected to the ground reference plane, such as capacitor 31. The current compensation terminal COMI is connected to a second compensation network for frequency compensation for the second error amplifier. This second compensation network may also be a capacitor connected to the ground reference plane, such as capacitor 32. The programmable terminal COMR has a grounded resistor 33 and adjusts the reference signal V _REF for the voltage feedback loop of the control circuit 70 according to the output current I _O. The adjustment of the reference signal V _REF is to compensate for the voltage drop in the output cable 46 in order to achieve better load regulation.

FIG. 3 shows a control circuit 70 according to one embodiment of the present invention. The first circuit 100 multi-samples the voltage V _DET to generate the first signal V _V and the timing signal S _DS . The charging time T _DS of the secondary side switching current I _S is represented by the timing signal S _DS . By measuring the current detection signal V _CS by the second circuit 300, the current signal V _W is generated. The oscillator 200 generates an oscillation signal PLS for determining the switching frequency of the switching signal V _PWM . The second signal V _I is generated by integrating the current signal V _W with the timing signal S _DS by the third circuit 400. The operational amplifier 71 and the reference signal V _REF are used to amplify the first signal V _V and create a first error amplifier that forms a first feedback loop circuit for output voltage control. The operational amplifier 72 and the reference signal V _REF2 amplify the second signal V _I and create a second error amplifier that forms a second feedback loop circuit for output current control. The adjustment circuit 700 is coupled to the programmable terminal COMR to adjust the reference signal V _REF according to the reference signal V _REF1 and the second signal V _I. PWM circuit 500 and a plurality of comparators 73, 75 form a switching control circuit, the switching signal V generates a _PWM, the first error amplifier and responsive to the switching signal V _PWM pulse width to the output of the second error amplifier To control. Both operational amplifier 71 and operational amplifier 72 have transconductance outputs. The output of the operational amplifier 71 is connected to the voltage compensation terminal COMV and the positive input of the comparator 73. The output of the operational amplifier 72 is connected to the current compensation terminal COMI and the positive input of the comparator 75. The negative input of the comparator 73 is connected to the output of the adder 600. A ramp signal RMP generated from the oscillator 200 is supplied to the negative input of the comparator 75.

The ramp signal R _SLP is generated by adding the ramp signal RMP to the current detection signal V _CS by the adder 600. A reference signal V _REF3 is supplied to the positive input of the comparator 74. The negative input of the comparator 74 is connected to the detection terminal CS for current limiting every cycle. Three inputs of the NAND gate 79 are connected to outputs of the comparators 73, 74, and 75, respectively. A reset signal RST is generated by the output of the NAND gate 79. This reset signal RST is supplied to the PWM circuit 500 in order to control the duty cycle of the switching signal V _PWM .

従って、スイッチングレギュレータの出力電流I_Oは調整される。 A current control loop is formed between detection of the switching current I _P on the primary side and pulse width modulation of the switching signal V _PWM , and controls the magnitude of the primary side switching current I _P in response to the reference signal V _REF2. . As shown in Equation (4), the secondary side switching current I _S is the ratio of the primary side switching current I _P. According to the signal waveform of FIG. 2, the output current I _O of the switching regulator is the average of the switching current I _S on the secondary side. The output current I _O of the switching regulator is expressed by the following equation.

Therefore, the output current _IO of the switching regulator is adjusted.

ここで、電流信号V_Wは、次式によって表わされ、

ここで、T_Iは第３の回路４００の時定数である。
式（６）〜（８）から分かるように、第２の信号V_Iは、次式のように、書き換えることができる。

The current detection signal V _CS is detected by the second circuit 300, and the current signal V _W is generated. By integrating the current signal V _W by the discharge time T _DS by the third circuit 400, the second signal V _I is further generated. Therefore, the second signal V _I is represented by the following equation:

Here, the current signal V _W is expressed by the following equation:

Here, T _I is the time constant of the third circuit 400.
As can be seen from the equations (6) to (8), the second signal V _I can be rewritten as the following equation.

ここで、KはT_I/Tに等しい定数、G_Aは第２のエラーアンプのゲイン、G_SWはスイッチング回路のゲインである。 It can be seen that the second signal V _I is proportional to the output current I _O of the switching regulator. This second signal V _I increases as the output current I _O increases. However, the maximum value of the second signal V _I is limited to the value of the reference signal V _REF2 by adjusting the current control loop. Under feedback control of the current control loop, the maximum output current I _{O (max)} is expressed by

Here, K is a constant equal to T _I / T, G _A is the gain of the second error amplifier, and G _SW is the gain of the switching circuit.

Since the gain of the loop of the current control loop is large _{(G A × G SW >> 1} ), the maximum output current I _{O (max),} as follows, can be simplified.

Therefore, the maximum output current _{IO (max)} of the switching regulator is adjusted as a constant current in response to the reference signal _VREF2 .

Furthermore, a voltage control loop is formed between the sampling of the reflected signal V _AUX and the pulse width modulation of the switching signal V _PWM , and the magnitude of the reflected signal V _AUX is controlled in response to the reference signal V _REF . It reflected signal V _AUX, as shown in equation (3), which is the ratio of the output voltage V _O. The reflected signal V _AUX is further attenuated to the voltage V _DET as shown in Equation (5). The first signal V _V is generated by multi-sampling the voltage V _DET by the first circuit 100. The value of the first signal V _V is controlled by adjustment of the voltage control loop in response to the value of the reference signal V _REF . The loop gain of the voltage control loop is provided by the first error amplifier and the switching circuit. Therefore, the output voltage V _O can be easily determined as in the following equation.

The reflected signal V _AUX is multisampled by the first circuit 100. Before switching current I _S of the secondary side drops to 0, the voltage is measured is sampled instantaneously. Thus, variations of the switching current I _S of the secondary side has no effect on the forward voltage drop V _F of the rectifier 40. However, when the output current _IO changes, the voltage drop of the output cable changes. The regulation circuit 700 was developed to compensate for the voltage drop in the output cable. Resistor 33 is used to program a slope for determining a change in reference signal V _REF in response to a change in second signal V _I. Thus, the voltage drop is compensated in proportion to the output current _IO . By using different values of resistor 33, compensation for various output cables 46 can be programmed.

FIG. 4 shows a first circuit 100 according to one embodiment of the invention. A sample pulse signal is generated by a sample pulse generator 190 for multi-sampling. The threshold voltage 156 is added to the reflected signal V _AUX to generate a level shift reflected signal. The first signal generator includes a counter 171 and AND gate 165 ... 166, to generate a sample signal V _SP1 ... V _SPN. The second signal generator includes a D flip-flop 170, a NAND gate 163, an AND gate 164, and a comparator 155, and generates a timing signal S _DS. The time delay circuit includes an inverter 162, a current source 180, a transistor 181, and a capacitor 182, and generates a delay time _Td when the switching signal _VPWM is disabled. A switching signal V _PWM is supplied to the input of the inverter 161. The output of the inverter 161 is connected to the input of the inverter 162, the first input of the AND gate 164, and the clock input of the D flip-flop 170. The transistor 181 is turned on / off by the output of the inverter 162. The capacitor 182 is connected to the transistor 181 in parallel. Current source 180 is used to charge capacitor 182. Therefore, the delay time T _d of the time delay circuit is determined by the current of the current source 180 and the capacitance of the capacitor 182. The output of the delay circuit is obtained across the capacitor 182. The D input of the D flip-flop 170 is pulled up to a high level by the supply voltage V _CC . The output of D flip-flop 170 is connected to the second input of AND gate 164. The timing signal _SDS is output from the AND gate 164. Therefore, the timing signal _SDS is enabled when the switching signal V _PWM is disabled. The output of the NAND gate 163 is connected to the reset input of the D flip-flop 170. Two inputs of the NAND gate 163 are connected to the output of the time delay circuit and the output of the comparator 155, respectively. A level shift reflection signal is supplied to the negative input of the comparator 155. The holding voltage V _HD is supplied to the positive input of the comparator 155. Therefore, after the delay time T _d, the level shift reflected signal is temporarily lower than the holding voltage V _HD, the timing signal S _DS is disabled. Further, as long as the switching signal V _PWM is enabled, the timing signal S _DS also becomes disabled.

The sample pulse signal is supplied to the third input of the counter 171 and the AND gates 165. The outputs of the counter 171 are connected to the second inputs of the AND gates 165. A timing signal _SDS is supplied to the first input of the AND gates 165. The fourth input of the AND gates 165... 166 is connected to the output of the time delay circuit. Therefore, the sample signals V _SP1 ... V _SPN are generated in response to the sample pulse signal. Further, the sample signal V _SP1 · · V _SPN, during the enable period of the timing signal S _DS, are generated alternately. However, in order to suppress the sample signals V _SP1 · · V _SPN at the beginning of the timing signal S _DS, the delay time T _d is inserted. Therefore, the sample signals V _SP1 ... V _SPN are disabled during the delay time _Td .

The sample signals V _SP1 ... V _SPN are used to sequentially sample the reflected signal V _AUX via the detection terminal DET and the voltage divider. The switches 121 and 122 are controlled by the sample signals V _{SP1 and} V _{SPN in} order to obtain a holding voltage between the capacitors 110 and 111, respectively. The switches 123... 124 are connected in parallel to the capacitors 110... 111 in order to discharge the capacitors 110. The buffer circuit includes operational amplifiers 150... 151, diodes 130... 131, and a current source 135, and generates a holding voltage V _HD . The positive inputs of the operational amplifiers 150... 151 are connected to the capacitors 110. The negative inputs of the operational amplifiers 150... 151 are connected to the output of the buffer circuit. The diodes 130 and 131 are provided between the output of the operational amplifiers 150 and 151 and the output of the buffer circuit. The holding voltage V _HD is thus obtained from a higher holding voltage. The current source 135 is used for termination. The holding voltage V _HD is periodically conducted to the capacitor 115 by the switch 125 in order to generate the first signal V _V. The switch 125 is turned on / off by the oscillation signal PLS. After the delay time _Td , the sample signal V _SP1 ... V _SPN starts to generate a holding voltage. Spike interference of the reflected signal V _AUX is removed. The spike disturbance of the reflected signal V _AUX occurs when the switching signal V _PWM is disabled and the transistor 20 is turned off.

As the secondary side switching current I _S drops to zero, the reflected signal V _AUX begins to decrease, which is detected by the comparator 155 and disables the timing signal S _DS . Therefore, the pulse width of the timing signal S _DS correlates with the discharge time T _{DS of the} secondary side switching current I _S. Meanwhile, the sample signals V _SP1 ... V _SPN are disabled, and the multi-sampling operation stops when the timing signal S _DS is disabled. Thus, the instantaneous voltage held V _HD is produced at the output of the buffer circuit is correlated with the reflected signal V _AUX of switching current I _S of the secondary side is sampled at the time the once drops to zero. The holding voltage V _HD is obtained from the higher one of the holding voltages, so that the voltage sampled when the reflected signal V _AUX starts to decrease is ignored.

を決定し、ここでV_OSC = V_H-V_Lである。 FIG. 5 illustrates an oscillator 200 according to one embodiment of the present invention. The operational amplifier 201, the resistor 210, and the transistor 250 form a first VI converter. The first VI converter generates a reference current I ₂₅₀ in response to the reference signal V _R. For example, a plurality of transistors, such as transistors 251, 252, 253, 254, 255, form a current mirror and generate an oscillator charge current I ₂₅₃ and an oscillator discharge current I ₂₅₅ in response to a reference current I ₂₅₀ . Oscillator charging current I ₂₅₃ is generated by the drain of transistor 253. Oscillator discharge current I ₂₅₅ is generated by the drain of transistor 255. A switch 230 is connected between the drain of the transistor 253 and the capacitor 215. A switch 231 is connected between the drain of the transistor 255 and the capacitor 215. A ramp signal RMP is obtained between both ends of the capacitor 215. Comparator 205 has a positive input connected to capacitor 215. The comparator 205 outputs an oscillation signal PLS. The oscillation signal PLS determines the switching frequency of the switching signal V _PWM . The high threshold voltage V _H is supplied to the first terminal of the switch 232. The low threshold voltage V _L is supplied to the first terminal of the switch 233. Both the second terminal of the switch 232 and the second terminal of the switch 233 are connected to the negative input of the comparator 205. The input of the inverter 260 is connected to the output of the comparator 205 to generate the inverted oscillation signal / PLS. The switches 231 and 233 are turned on / off by the oscillation signal PLS. The switches 230 and 232 are turned on / off by the inverted oscillation signal / PLS. The resistance value R 210 of the resistor ₂₁₀ and the capacitance of the capacitor 215 are the switching period T of the switching frequency

Where V _OSC = V _H -V _L.

FIG. 6 shows a second circuit 300 according to one embodiment of the invention. The comparator 310, the current source 320, the plurality of switches 330 and 340, and the capacitor 361 form a fourth circuit. A peak value of the current detection signal V _CS is sampled to generate a fourth signal. The current detection signal V _CS is supplied to the positive input of the comparator 310. The negative input of the comparator 310 is connected to the capacitor 361. The switch 330 is connected between the current source 320 and the capacitor 361. The switch 330 is turned on / off by the output of the comparator 310. Switch 340 is connected in parallel with capacitor 361 to discharge capacitor 361. The fourth signal is periodically conducted to the capacitor 362 by the switch 350 and generates a current signal V _W. The switch 350 is turned on / off by the oscillation signal PLS.

ここで、R₄₅₀は抵抗４５０の抵抗値である。 FIG. 7 shows a third circuit 400 according to one embodiment of the invention. The operational amplifier 410, the resistor 450, and the transistors 420, 421, and 422 form a second VI converter. The current signal V _W is supplied to the positive input of the operational amplifier 410. The negative input of the operational amplifier 410 is connected to the resistor 450. The gate of the transistor 420 is driven by the output of the operational amplifier 410. The source of transistor 420 is coupled to resistor 450. In response to the current signal V _W , a current I ₄₂₀ is generated via the drain of the transistor 420 by the second VI converter. Transistors 421 and 422 form a current mirror having a 2: 1 ratio. Current I ₄₂₀ drives the current mirror and generates a programmable charge current I _PRG via the drain of transistor 420. This programmable charge flow I _PRG is represented by the following equation:

Here, R ₄₅₀ is the resistance value of the resistor 450.

The capacitor 471 is used to generate an integration signal. A switch 460 is connected between the drain of the transistor 422 and the capacitor 471. Switch 460 is turned on / off by the timing signal S _DS. The switch 462 is connected in parallel with the capacitor 471 in order to discharge the capacitor 471. The integration signal is periodically conducted by the switch 461 to the capacitor 472 to generate the second signal V _I. The switch 461 is turned on / off by the oscillation signal PLS. Therefore, the second signal V _I as expressed by the following equation is obtained between both ends of the capacitor 472.

ここで、mは以下の式で定められる定数である。

According to the embodiment of the present invention shown in FIGS. 4 to 7, the second signal V _I correlates with the secondary-side switching current I _S and the output current I _{O of the} switching regulator. Therefore, equation (9) can be rewritten as

Here, m is a constant determined by the following equation.

The resistance value R ₄₅₀ of the resistor ₄₅₀ correlates with the resistance value R ₂₁₀ of the resistor 210. Capacitance C ₄₇₁ of capacitor ₄₇₁ correlates with capacitance C _{215 of} capacitor 215. Therefore, the second signal V _I is proportional to the output current I _O of the switching regulator.

ここで、T_ONはスイッチング信号V_PWMのオン時間である。 FIG. 8 shows a circuit diagram of a PWM circuit 500 according to an embodiment of the present invention. The PWM circuit 500 includes a NAND gate 511, a D flip-flop 515, an AND gate 519, a blanking circuit 520, and inverters 512 and 518. The D input of the D flip-flop 515 is pulled up by the supply voltage V _CC . The input of the inverter 512 is driven by the oscillation signal PLS. The output of inverter 512 is connected to the clock input of D flip-flop 515 to enable switching signal V _PWM . The output of the D flip-flop 515 is connected to the first input of the AND gate 519. A second input of AND gate 519 is coupled to the output of inverter 512. The AND gate 519 outputs the switching signal V _PWM to switch the transformer 10. The reset input of the D flip-flop 515 is connected to the output of the NAND gate 511. A first input of the NAND gate 511 is supplied with a reset signal RST, which disables the switching signal V _PWM every cycle. The second input of the NAND gate 511 is connected to the output of the blanking circuit 520 to ensure a minimum on-time of the switching signal V _PWM when the switching signal V _PWM is enabled. The minimum on-time of the switching signal V _PWM ensures a minimum value of the discharge time T _DS , which ensures proper multi-sampling of the reflected signal V _AUX in the first circuit 100. Discharge time T _DS correlates with the ON time of the switching signal V _PWM. With reference to the equations (1), (2) and (4) and the secondary-side inductance L _S shown in the equation (18), the discharge time T _DS can be expressed as the following equation (19). it can.

Here, T _ON is the ON time of the switching signal V _PWM .

The switching signal V _PWM is supplied to the input of the blanking circuit 520. When the switching signal V _PWM is enabled, the blanking circuit 520 generates a blanking signal V _BLK to prevent the D flip-flop 515 from being reset. The blanking circuit 520 further includes a NAND gate 523, a current source 525, a capacitor 527, a transistor 526, and a plurality of inverters 521 and 522. The switching signal V _PWM is supplied to the input of the inverter 521 and the first input of the NAND gate 523. Current source 525 charges capacitor 527. The capacitor 527 is connected to the transistor 526 in parallel. The transistor 526 is turned on / off by the output of the inverter 521. The input of inverter 522 is coupled to capacitor 527. The output of the inverter 522 is connected to the second input of the NAND gate 523. The blanking signal V _BLK is output by the output of the NAND gate 523. The pulse width of the blanking signal V _BLK, due the capacitance of the current and the capacitor 527 of the current source 525, is determined. The input of the inverter 518 is connected to the output of the NAND gate 523. A clear signal (CLR) is generated by the output of the inverter 518, and the switches 123, 124, 340, and 462 are turned on and off.

FIG. 9 shows a circuit diagram of an adder according to an embodiment of the present invention. The operational amplifier 610, the plurality of transistors 620, 621, 622, and the resistor 650 form a third VI converter and generate a current I ₆₂₂ in response to the ramp signal RMP. A current detection signal V _CS is supplied to the positive input of the operational amplifier 611. The negative input and output of the operational amplifier 611 are connected together, and this operational amplifier 611 is constructed as a buffer. The drain of the transistor 622 is connected to the output of the operational amplifier 611 via a resistor 651. A slope signal V _SLP is generated at the drain of the transistor 622. Therefore, the slope signal V _SLP correlates with the ramp signal RMP and the current detection signal V _CS .

FIG. 10 shows a circuit diagram of an adjustment circuit 700 according to an embodiment of the present invention. Op 710, the VI converter is formed by a plurality of transistors 711,714,715, and resistor 712, it generates a current I ₇₁₅ in response to the second signal V _I. The second signal V _I is supplied to the positive input of the operational amplifier 710. The current I ₇₁₅ is output to the programmable terminal COMR. The current I ₇₁₅ is associated with a resistor 33 that generates a voltage V _COMR that is supplied to the operational amplifier 720. The operational amplifier 720, the plurality of transistors 721, 724, 725, and the resistor 722 form another VI converter and generates a current I ₇₂₅ at the drain of the transistor 725 in response to the voltage V _COMR . The negative input and output of the operational amplifier 750 are connected together to construct the operational amplifier 750 as a buffer. The positive input of the operational amplifier 750 is connected to the reference signal V _REF1 . The drain of the transistor 725 is connected to the output of the operational amplifier 750 via a resistor 760. A reference signal V _REF is generated at the drain of transistor 725. Based on the reference signal V _REF1, the reference signal V _REF is adjusted by a second signal V _I, it is programmed by the resistor 33.

  It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. From the above viewpoint, if the modifications or changes of the present invention fall within the scope of the following claims and equivalents thereof, the present invention shall cover these modifications or changes.

Claims (27)

A switching regulator for primary control,
The primary side control switching regulator is:
A transformer that sends energy from the primary side to the secondary side of the transformer;
A switching device for switching the transformer;
A control circuit coupled to the transformer for generating a switching signal for switching the switching device and adjusting an output of the switching regulator;
The control circuit includes:
A first circuit coupled to the transformer and generating a first signal and a timing signal by measuring a reflected signal of the transformer, wherein the timing signal represents a discharge time of the transformer;
Integrating a current signal with the timing signal to generate a second signal, the current signal representing a switching current on a primary side of the transformer; a second circuit and a third circuit;
Having a first reference signal, generating a first feedback signal in response to the first signal, the first reference signal increasing in response to an increase in the second signal, Error amplifier,
A second error amplifier having a second reference signal and generating a second feedback signal in response to the second signal;
A switching control circuit for generating the switching signal in response to the first feedback signal and the second feedback signal;
Including a primary-side controlled switching regulator. A switching regulator for primary side control according to claim 1,
The control circuit further includes:
A supply terminal and a ground terminal for receiving power;
A detection terminal for connecting the first circuit to the transformer via a resistor of a voltage divider;
Connecting the second circuit to a current sensing device used to convert the primary-side switching current into the current signal; and a sensing terminal for receiving the current signal;
An output terminal for generating the switching signal for switching the transformer by the switching device;
A voltage compensation terminal connected to a first compensation network for frequency compensation for the first error amplifier;
A current compensation terminal connected to a second compensation network for frequency compensation for the second error amplifier;
A programmable terminal connected to a ground resistor for determining a slope representative of a change in the first reference signal relative to a change in the second signal;
A primary-side control switching regulator. A switching regulator for primary side control according to claim 1,
The time constant of the third circuit is a primary-side controlled switching regulator that correlates with a switching period of the switching signal. A switching regulator for primary side control according to claim 1,
The first circuit includes:
A threshold voltage that is added to the reflected signal to generate a level shift signal;
Multiple capacitors,
A first signal generator for generating a sample signal, wherein the sample signal is used to sample the reflected signal, and a holding voltage is generated between both ends of the capacitor; A first signal generator sequentially generated during the enable period;
A buffer circuit for generating a holding signal from a high voltage of the holding voltages;
A first output capacitor for generating the first signal in response to the holding signal;
A second signal generator for generating the timing signal; enabling the timing signal when the switching signal is disabled; and disabling the timing signal when the level shift signal is lower than the holding signal. A second signal generator;
A primary-side control switching regulator. A switching regulator for primary side control according to claim 1,
The first circuit generates the first signal by multi-sampling the reflected signal, and the first signal is obtained when the discharge current of the transformer once drops to zero. Control switching regulator. A switching regulator for primary side control according to claim 1,
The second circuit includes:
A fourth circuit for generating a fourth signal by sampling the current signal;
A third capacitor for holding the fourth signal;
A second output capacitor for generating a current waveform signal;
A switch for directing the fourth signal to the second output capacitor;
A primary-side control switching regulator. A switching regulator for primary side control according to claim 1,
The third circuit includes:
A VI converter that generates a charging current in response to a current waveform signal;
A timing capacitor coupled to the charging current via a first switch and generating an integral signal in response to the timing signal;
A second switch connected in parallel to the timing capacitor and discharging the timing capacitor;
A third output capacitor for generating the second signal;
A third switch for directing the integral signal to the third output capacitor;
A primary-side control switching regulator. A switching regulator for primary side control according to claim 1,
The switching signal has a minimum on-time when the switching signal is enabled, which further guarantees a minimum value of the discharge time for multi-sampling the reflected signal;
Primary side switching regulator. A switching regulator,
The switching regulator is
A transformer that sends energy from the primary side to the secondary side of the transformer;
A switching device for switching the transformer;
A control circuit coupled to the transformer for generating a switching signal for switching the switching device and adjusting an output of the switching regulator;
The control circuit includes:
A first circuit coupled to the transformer and generating a first signal and a timing signal by measuring a reflected signal of the transformer, wherein the timing signal represents a discharge time of the transformer;
Integrating a current signal with the timing signal to generate a second signal, the current signal representing a switching current on a primary side of the transformer;
A first feedback circuit for generating a first feedback signal in response to the first signal;
A second feedback circuit for generating a second feedback signal in response to the second signal;
A switching control circuit for generating the switching signal in response to the first feedback signal and the second feedback signal;
Including a switching regulator. The switching regulator according to claim 9, wherein
The first feedback circuit further includes:
Having a first reference signal, generating the first feedback signal in response to the first signal and the first reference signal, and responding to a change in the second signal A switching regulator that changes the reference signal. The switching regulator according to claim 9, wherein
The control circuit further includes:
A supply terminal and a ground terminal for receiving power;
A sensing terminal for coupling the first circuit to the transformer;
Coupling the second circuit to a current sensing device used to convert a primary side switching current into a current signal; and a sensing terminal for receiving the current signal;
An output terminal for generating the switching signal for switching the transformer by the switching device;
A voltage compensation terminal for frequency compensation of the first feedback circuit;
A current compensation terminal for frequency compensation of the second feedback circuit;
A switching regulator comprising: The switching regulator according to claim 9, wherein
The first circuit includes:
A threshold voltage that is added to the reflected signal to generate a level shift signal;
Multiple capacitors,
A first signal generator for generating a sample signal, sampling the reflected signal and holding the reflected signal in the capacitor, wherein holding voltages are respectively generated across the capacitor, and the timing signal is enabled by the timing signal; A first signal generator generated in response to
A buffer circuit for generating the first signal according to the holding voltage;
A second signal generator for generating the timing signal in response to the holding voltage and the level shift signal; when the switching signal is disabled, the timing signal is enabled, and the level shift signal is A second signal generator that disables the timing signal when lower than the holding voltage;
A switching regulator comprising: The switching regulator according to claim 9, wherein
A switching regulator, wherein the first circuit multisamples the reflected signal to generate the first signal, and the first signal is obtained after the discharge current of the transformer once drops to zero. A switching regulator for primary side control according to claim 9,
The second circuit includes:
A current generator that generates a charging current by sampling the current signal;
A capacitor coupled to the charging current to generate the second signal in response to the timing signal;
A primary-side control switching regulator. The switching regulator according to claim 9, wherein
The switching signal has a minimum on-time when the switching signal is enabled, which further guarantees a minimum value of the discharge time for multi-sampling the reflected signal. A switching power converter,
The switching regulator is
A transformer that sends energy from the primary side to the secondary side of the transformer;
A switching device for switching the transformer;
A control circuit coupled to the transformer for switching the switching device to generate a switching signal that regulates the output of the switching regulator;
The control circuit includes:
A first circuit coupled to the transformer and generating a first signal by measuring a reflected signal of the transformer;
A second circuit in response to a current signal, wherein the current signal represents a primary side switching current of the transformer;
A first feedback circuit for generating a first feedback signal in response to the first signal;
A second feedback circuit for generating a second feedback signal in response to the second signal;
A switching control circuit for generating the switching signal in response to the first feedback signal and the second feedback signal;
Including a switching power converter. A switching power converter according to claim 16, comprising:
The first feedback circuit further includes:
Switching having a first reference signal, generating the first feedback signal in response to the first signal, and changing the first reference signal in response to a change in the second signal Power converter. A switching power converter according to claim 16, comprising:
The control circuit further includes:
A supply terminal and a ground terminal for receiving power;
A detection terminal for connecting the first circuit to the transformer via a resistor of a voltage divider;
Connecting the second circuit to a current sensing device used to convert the primary side switching current into the current signal, and a sensing terminal for receiving the current signal;
An output terminal for generating the switching signal for switching the transformer by the switching device;
A first compensation terminal for frequency compensation of the first feedback circuit;
A second compensation terminal for frequency compensation of the second feedback circuit;
A switching power converter. A switching power converter according to claim 16, comprising:
The first circuit includes:
Multiple capacitors,
A first signal generator that generates a sample signal, samples the reflected signal, and holds the sampled signal in the capacitor; a holding voltage is generated between both ends of the capacitor; and the sample signal enables the timing signal. A first signal generator generated in response;
A buffer circuit for generating the first signal according to the holding voltage;
A second signal generator for generating the timing signal in response to a holding voltage, when the switching signal is disabled, the timing signal is enabled and the reflected signal is significantly lower than the holding signal; A second signal generator for disabling the timing signal;
A switching power converter. A switching power converter according to claim 16, comprising:
The first circuit generates the first signal by multi-sampling the reflected signal, and the first signal is obtained when the discharge current of the transformer once drops to zero. Switching power converter. A switching power converter according to claim 16, comprising:
The switching signal has a minimum on-time when the switching signal is enabled, which further ensures a minimum value of the discharge time for multi-sampling the reflected signal. . A switching regulator,
The switching regulator is
A transformer that sends energy from the primary side to the secondary side of the transformer;
A switching device for switching the transformer;
A control circuit coupled to the transformer for switching the switching device to generate a switching signal that regulates the output of the switching regulator;
The control circuit includes:
A first circuit coupled to the transformer and generating a first signal by measuring a reflected signal of the transformer;
A second circuit that generates a second signal by measuring a current signal, the current signal correlating with an output current of the switching regulator;
A feedback circuit having a reference signal, generating a feedback signal in response to the first signal and the reference signal, and changing the reference signal in response to the second signal;
And a switching control circuit that generates the switching signal in response to the feedback signal. A switching regulator according to claim 22,
The first circuit includes:
Multiple capacitors,
A first signal generator for generating a sample signal, sampling the reflected signal and holding it in the capacitor, wherein holding voltages are respectively generated across the capacitor, the sample signal responding to the enable of the timing signal; A first signal generator generated by:
A buffer circuit for generating the first signal according to the holding voltage;
A second signal generator for generating the timing signal in response to a holding voltage, when the switching signal is disabled, the timing signal is enabled and the reflected signal is significantly lower than the holding signal; A second signal generator for disabling the timing signal;
A switching regulator comprising: A switching regulator according to claim 22,
The first circuit generates the first signal by multi-sampling the reflected signal, and the first signal is obtained when the discharge current of the transformer once drops to zero. . A switching regulator according to claim 22,
The second circuit includes:
A current generator for generating a charging current in response to the current signal;
And a capacitor coupled to the charging current and generating the second signal in response to the timing signal. A switching regulator according to claim 22,
When the switching signal is enabled, the switching signal has a minimum on-time, which further guarantees a minimum value of the discharge time for multi-sampling the reflected signal. A switching regulator,
The switching regulator is
A transformer that sends energy from the primary side to the secondary side of the transformer;
A switching device for switching the transformer;
A control circuit coupled to the transformer for switching the switching device to generate a switching signal that regulates the output of the switching regulator;
The control circuit includes:
A first circuit coupled to the transformer and generating a first signal by measuring a reflected signal of the transformer;
Generating a second signal by measuring a current signal correlated with an output current of the switching regulator, the current signal comprising: a second circuit;
A feedback circuit that generates a feedback signal in response to the first signal, the first signal changing in response to the second signal;
A switching control circuit for generating the switching signal in response to the feedback signal;
Including a switching regulator.

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