Isolation power supply circuit

Abstract

The invention provides an isolation power supply circuit, the isolation power supply circuit comprises a power transmission circuit, an isolation transmission circuit, a rectification filter circuit, an anti-overshoot circuit and a feedback circuit, and the power transmission circuit comprises a bias supply circuit, a frequency dividing circuit and an oscillator. By adding the bias supply circuit, it can be ensured that the oscillator can be started in a low-voltage domain, so that the compatibility of a wide power domain can be improved, and the range of input voltage is widened; the frequency dividing circuit can provide a frequency dispersion function so as to improve the overall anti-interference performance of the isolation power supply circuit; the anti-overshoot circuit is used, so that surge current and output voltage overshoot generated in the starting process of the isolation power supply can be suppressed, and the stability and reliability of the whole circuit are improved; and stable and reliable direct-current voltage can be output after being processed by the isolation transmission circuit and the rectification filter circuit.

Description

Technical Field

[0001] The present application relates to the field of circuit technology, and in particular to an isolated power supply circuit. Background Art

[0002] With the rapid development of efficient power management and integration technology, integrated isolated power supplies can now meet the needs of high integration. The basic structure of the isolated power supply circuit is as follows: Figure 1 As shown, the DC input source on the primary side is converted into an AC signal through the power transmission circuit, and then drives the devices in the power isolation channel. The energy is coupled to the secondary side, and the AC signal is converted into a DC output voltage after the rectification and filtering circuit.

[0003] In the related art, the isolation device of the isolated power supply generally selects an isolation transformer, which is limited by the small Q value (i.e., quality factor) of the transformer on the isolation chip and the demand for high efficiency and heavy load performance of the isolated power supply, and the power transmission circuit in the isolated power supply generally needs to output a high-frequency AC high-voltage signal. Therefore, the driving tube of the power transmission circuit needs to be a high-voltage metal oxide transistor (HV-MOS), which has the disadvantages of high process manufacturing cost, large area, and narrow input power domain. In addition, due to the transmission of high-frequency AC high-voltage signals, a high-frequency common-mode voltage exists on the primary side, which in turn affects the EMI performance of the isolated power supply circuit. In addition, in order to ensure the stability and accuracy of the output voltage, the isolated power supply generally also applies a loop feedback circuit, but the feedback signal on the secondary side of the isolated power supply will be delayed, especially in the initial state of the output of the entire power supply circuit, the input current will have a large surge, thereby affecting the front-stage power supply and interfering with the power supply equipment; and the DC output voltage will overshoot and cause overvoltage problems at the output port of the power supply circuit, thereby affecting the overall reliability and life of the isolated power supply, and when the overshoot voltage exceeds the limit voltage required by the subsequent load, it will also cause equipment damage. Summary of the invention

[0004] The main purpose of the present application is to provide an isolated power supply circuit, which can at least solve the problems in the related art that the DC output voltage overshoot of the isolated power supply circuit affects the stability and reliability of the power supply circuit and the input voltage range of the power transmission circuit is narrow.

[0005] To achieve the above-mentioned purpose, the present application provides an isolated power supply circuit, including: a power transmission circuit, an isolated transmission circuit, a rectifier and filter circuit, an anti-overshoot circuit and a feedback circuit, wherein the power transmission circuit includes a bias supply circuit, a frequency division circuit and an oscillator; the oscillator is electrically connected to the bias supply circuit, the frequency division circuit, the anti-overshoot circuit and the isolated transmission circuit, respectively; the rectifier and filter circuit is electrically connected to the isolated transmission circuit; and the feedback circuit is electrically connected to the rectifier and filter circuit, the frequency division circuit, the anti-overshoot circuit, the bias supply circuit and the oscillator, respectively.

[0006] Further, the oscillator includes a first power transmission tube, a second power transmission tube, a first inductor, a second inductor and an oscillation start control circuit; the first end of the first power transmission tube is electrically connected to one end of the first inductor and the isolation transmission circuit respectively, the first end of the second power transmission tube is electrically connected to one end of the second inductor and the isolation transmission circuit respectively, the second end of the first power transmission tube is electrically connected to the first end of the second power transmission tube, the second end of the second power transmission tube is electrically connected to the first end of the first power transmission tube, the third ends of the first power transmission tube and the second power transmission tube are both grounded, the other ends of the first inductor and the second inductor are both electrically connected to a power supply, and the oscillation start control circuit is electrically connected to the second ends of the first power transmission tube and the second power transmission tube, the feedback circuit and the anti-overshoot circuit respectively.

[0007] Further, the power transmission circuit also includes a stability compensation circuit, which includes a third power transmission tube and a fourth power transmission tube; the first end of the third power transmission tube is electrically connected to the second end of the first power transmission tube, the first end of the fourth power transmission tube is electrically connected to the second end of the second power transmission tube, the second end of the third power transmission tube is electrically connected to the first end of the fourth power transmission tube, the second end of the fourth power transmission tube is electrically connected to the first end of the third power transmission tube, and the third ends of the third power transmission tube and the fourth power transmission tube are both grounded.

[0008] From the above description, it can be seen that the power transmission circuit of the present application adds a bias supply circuit, changes the traditional B / D type oscillator architecture, and can ensure that the oscillator can be started in the low-voltage domain, thereby improving the compatibility of the wide power domain and realizing an increase in the input voltage range; the use of a frequency division circuit can provide a frequency discrete function, which is applied to the power transmission circuit on the primary side, and can increase the overall anti-interference ability of the isolated power supply circuit; in order to suppress the surge current and output voltage overshoot generated during the startup of the isolated power supply, an anti-overshoot circuit is used to improve the overall stability and reliability of the circuit; and after processing by the isolation transmission circuit and the rectifier and filter circuit, a stable and reliable DC voltage can be output. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0010] Figure 1 It is a basic structural schematic diagram of an isolated power supply circuit in the related technology; Figure 2 is a structural schematic diagram of a first isolated power supply circuit according to an embodiment of the present application; Figure 3 is a circuit schematic diagram of a power transmission circuit according to an embodiment of the present application; Figure 4 is a circuit schematic diagram of a frequency division circuit according to an embodiment of the present application; Figure 5 is a schematic diagram of a spectrum corresponding to a frequency division technology in an embodiment of the present application; Figure 6 is a circuit schematic diagram of an anti-overshoot circuit according to an embodiment of the present application; Figure 7 is a structural schematic diagram of a second isolated power supply circuit in an embodiment of the present application; Figure 8 is a circuit schematic diagram of a first soft start integrator circuit according to an embodiment of the present application; Fig. 9 is a circuit schematic diagram of a second soft start integrator circuit according to an embodiment of the present application; Fig.10 is a functional schematic diagram of a PWM signal generating circuit according to an embodiment of the present application; Fig.11 is a structural schematic diagram of an isolated transmission circuit according to an embodiment of the present application; Fig.12 It is a schematic diagram of a typical signal waveform of an isolated power supply circuit in an embodiment of the present application. DETAILED DESCRIPTION

[0011] In order to make the purpose, features, and advantages of the invention of this application more obvious and easy to understand, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0012] In the related art, since the isolated power supply circuit has a DC output voltage overshoot that affects the stability and reliability of the power supply circuit and the input voltage range of the power transmission circuit is narrow, an embodiment of the present application provides an isolated power supply circuit.

[0013] like Figure 2 FIG. 1 is a schematic diagram of the structure of the first isolated power supply circuit provided in the embodiment of the present application, see Figure 2 The isolated power supply circuit includes: a power transmission circuit 100, an isolated transmission circuit 200, a rectifier and filter circuit 300, an anti-overshoot circuit 400 and a feedback circuit 500. The power transmission circuit 100 includes a bias supply circuit 110, a frequency division circuit 120 and an oscillator 130; the oscillator 130 is electrically connected to the bias supply circuit 110, the frequency division circuit 120, the anti-overshoot circuit 400 and the isolated transmission circuit 200 respectively, the rectifier and filter circuit 300 is electrically connected to the isolated transmission circuit 200, and the feedback circuit 500 is electrically connected to the rectifier and filter circuit 300, the frequency division circuit 120, the anti-overshoot circuit 400, the bias supply circuit 110 and the oscillator 130 respectively.

[0014] Specifically, in this embodiment, the oscillator 130 is used to generate two high-frequency and high-voltage signals and input them into the isolation transmission circuit 200 to complete the DC-AC conversion process. The isolation transmission circuit 200 is used to realize AC-AC signal isolation transmission. The rectifier filter circuit 300 includes a rectifier circuit and a filter circuit. The input end of the rectifier circuit is the output end of the isolation transmission circuit 200. After passing through the filter circuit, the output end of the rectifier circuit is the output end of the isolation power supply circuit, which is used to output a DC voltage signal. The bias supply circuit 110 can be selectively connected to the oscillator 130 according to the control of the feedback signal transmitted by the feedback circuit 500 to provide a bias for the oscillator 130. Compared with the traditional B / D class oscillator, after the bias supply circuit 110 is set, the oscillator 130 can be started in a low-voltage power domain, thereby improving the compatibility of the wide input power domain and ensuring the improvement of the input voltage range. The frequency division circuit 120 can be used to change the frequency of the oscillator 130, provide a frequency discrete function, and achieve the effect of reducing the common mode voltage or common mode current amplitude caused by electromagnetic radiation, thereby improving the ability to resist electromagnetic radiation interference and achieving high reliability characteristics of low EMI. The overshoot circuit can suppress the surge current and output voltage overshoot generated during the startup of the isolated power supply circuit, so that the overall reliability of the circuit is improved.

[0015] like Figure 3 FIG. 1 is a schematic diagram of a power transmission circuit provided in this embodiment. Figure 2 and Figure 3The oscillator 130 includes a first power transmission tube M1, a second power transmission tube M2, a first inductor L1, a second inductor L2 and an oscillation start control circuit; the first end of the first power transmission tube M1 is electrically connected to one end of the first inductor L1 and the isolation transmission circuit 200, the first end of the second power transmission tube M2 is electrically connected to one end of the second inductor L2 and the isolation transmission circuit 200, the second end of the first power transmission tube M1 is electrically connected to the first end of the second power transmission tube M2, the second end of the second power transmission tube M2 is electrically connected to the first end of the first power transmission tube M1, the third ends of the first power transmission tube M1 and the second power transmission tube M2 are both grounded, the other ends of the first inductor L1 and the second inductor L2 are both electrically connected to the power supply, and the oscillation start control circuit is electrically connected to the second ends of the first power transmission tube M1 and the second power transmission tube M2, the feedback circuit 500 and the anti-overshoot circuit 400.

[0016] Specifically, in this embodiment, the oscillator 130 is an LC oscillator, the gate-drain interconnection of the two power transmission tubes forms a positive feedback negative resistance, and the inductor and the positive feedback negative resistance are cross-coupled to realize self-resonant oscillation, which serves as the primary side of the isolated power supply. The input voltage of the oscillator 130 comes from the DC power supply VDD, and the power transmission tube can be a MOS tube. The MOS tubes M1 and M2 are the main power transmission tubes, and the MOS tubes M1 and M2 are alternately turned on in one cycle. The oscillation start control circuit is used to control the opening and closing of the oscillator 130, which is controlled by the feedback signal on the secondary side or the output signal of the anti-overshoot circuit 400. In the initial state where the entire power supply circuit has no DC output, the circuit has no feedback signal. In order to ensure that the oscillator 130 can be started, the oscillation start circuit is controlled by the output signal of the anti-overshoot circuit 400 to start the oscillator 130. When the feedback signal is generated, the feedback signal is used as the control signal of the oscillation start control circuit. The selection can be made through a digital logic circuit, such as using an OR gate circuit or other gate circuit combinations. The output of the anti-overshoot circuit 400 needs to pass through an inverter and then be logically selected with the output of the feedback circuit to start the oscillator.

[0017] For further information, see Figure 3 The oscillator 130 also includes a first capacitor Cshift1 and a second capacitor Cshift2. The first capacitor Cshift1 is electrically connected to the first end of the first power transmission tube M1 and the second end of the second power transmission tube M2, respectively. The second capacitor Cshift2 is electrically connected to the second end of the first power transmission tube M1 and the first end of the second power transmission tube M2, respectively.

[0018] Specifically, in the present embodiment, the oscillator 130 further includes an AC coupling capacitor voltage divider, which includes two voltage dividing capacitors, and the voltage dividing capacitors are high voltage capacitors; in view of the fact that the output amplitude of the oscillator 130 is high voltage, in order to save cost and wafer area, and the gate voltage of the cross-coupled tube will affect the overall efficiency, the signal generated by the oscillator 130 can be divided by the two voltage dividing capacitors and the parasitic capacitance of the power transmission tube, and by reasonably setting the fixed ratio, the voltage divided to the input pair of tubes of the oscillator 130 (that is, the two main power transmission tubes M1 and M2) can be a normal voltage, thereby avoiding losses caused by low gate voltage.

[0019] For further information, see Figure 3 The oscillation start control circuit includes a first MOS tube M3 and a second MOS tube M4. The first end of the first MOS tube M3 is electrically connected to the second end of the first power transmission tube M1, and the first end of the second MOS tube M4 is electrically connected to the second end of the second power transmission tube M2. The second ends of the first MOS tube M3 and the second MOS tube M4 are electrically connected to the feedback circuit 500 and the anti-overshoot circuit 400 respectively, and the third ends of the first MOS tube M3 and the second MOS tube M4 are grounded.

[0020] Specifically, in this embodiment, the oscillation start control circuit includes two MOS tubes such as Figure 3 The gates of the NMOS tubes, MOS tubes M3 and M4 receive the feedback signal transmitted from the secondary side or the output signal of the anti-overshoot signal to control the oscillator 130 to be turned on or off.

[0021] For further information, see Figure 3 The bias supply circuit 110 includes a first resistor R1, a second resistor R2, a first switch device SW1 and a second switch device SW2; one end of the first resistor R1 is electrically connected to the second end of the first power transmission tube M1, one end of the second resistor R2 is electrically connected to the second end of the second power transmission tube M2, the first switch device SW1 is electrically connected to the power supply, the other end of the first resistor R1 and the feedback circuit 500 respectively, and the second switch device SW2 is electrically connected to the power supply, the other end of the second resistor R2 and the feedback circuit 500 respectively.

[0022] Specifically, in this embodiment, in order to be compatible with a wide input power domain, under the premise of ensuring a fixed voltage division, when the threshold voltage of the oscillator 130 input to the tube is too high, the low voltage power domain may not be able to start it; at this time, a dynamic bias supply circuit 110 with a switching device can be used for assistance, so that the oscillator 130 can be started in the low voltage power domain to increase the input voltage range. The bias supply circuit 110 includes an input power supply, a switching device, and a voltage dividing resistor, wherein the switching device can be switched on and off by a feedback signal transmitted by the feedback circuit 500 to dynamically control the access of the voltage dividing resistor to provide a bias for the power transmission tube.

[0023] For further information, see Figure 3 The power transmission circuit 100 also includes a stability compensation circuit 140, which includes a third power transmission tube M7 and a fourth power transmission tube M8; a first end of the third power transmission tube M7 is electrically connected to the second end of the first power transmission tube M1, a first end of the fourth power transmission tube M8 is electrically connected to the second end of the second power transmission tube M2, a second end of the third power transmission tube M7 is electrically connected to the first end of the fourth power transmission tube M8, a second end of the fourth power transmission tube M8 is electrically connected to the first end of the third power transmission tube M7, and third ends of the third power transmission tube M7 and the fourth power transmission tube M8 are both grounded.

[0024] Specifically, the power transmission circuit 100 in this embodiment also includes a stability compensation circuit 140, which includes devices with negative resistance characteristics, namely auxiliary power transmission tubes M7 and M8. This functional circuit can not only enable the oscillator 130 to start quickly, but also assist it to stabilize quickly after startup.

[0025] For further information, see Figure 3 The frequency division circuit 120 includes a random code generation circuit 121 and a plurality of sub-oscillators (i.e. Figure 3 In the sub-oscillator array 122, each sub-oscillator includes a fifth power transmission tube, a sixth power transmission tube, a third capacitor and a fourth capacitor; the first end of the fifth power transmission tube is electrically connected to the oscillator 130 through the third capacitor, the first end of the sixth power transmission tube is electrically connected to the oscillator 130 through the fourth capacitor, the second ends of the fifth power transmission tube and the sixth power transmission tube are both electrically connected to the random code generation circuit 121, the third ends of the fifth power transmission tube and the sixth power transmission tube are both grounded, and the random code generation circuit 121 is also electrically connected to the feedback circuit 500; wherein the random code generation circuit 121 is used to generate a corresponding number of pseudo-random codes according to the length of the feedback signal, and convert the pseudo-random codes into switch control signals, and the switch control signals are used to control the corresponding sub-oscillators to connect to the oscillator 130.

[0026] Specifically, in this embodiment, in order to reduce the power spectrum peak of the interference signal through circuit design and improve the electromagnetic compatibility characteristics of the overall circuit, the power transmission circuit 100 is further added with a frequency division circuit 120, which includes a random code generation circuit 121 and a sub-oscillator array 122. The random code generated by the random code generation circuit 121 is applied to the power transmission tube of the sub-oscillator. By connecting different numbers of sub-oscillators to the main oscillator 130, the frequency of the oscillator 130 can be changed. The circuit principle of the frequency division circuit 120 is as follows: Figure 4As shown, the random code generation circuit 121 is mainly composed of a pseudo-random code source generator and a random code combination control circuit. For example, the pseudo-random code source generator can be composed of 25 shift registers, and the feedback line is sent from the 22nd and 25th stages to the first stage input terminal through a modulo-2 addition operation. The generated characteristic polynomial is f(x)=1+x 22 +x 25 At each moment, the contents of each shift register constitute a state of the shift register, so there are at most 2 n If the initial states of these shift registers are all 0, then their states will continue to be all 0. Therefore, the output state cycle of the n-stage shift register is no more than 2 n -1. The random code combination control circuit mainly performs combinational logic operations on the multi-bit random code generated by the pseudo-random code source generator, and then connects a D flip-flop to complete the clock edge alignment function, thereby generating a hot code for the switch signal. The function of the entire random code generation circuit 121 is to convert the generated pseudo-random code into a switch signal for controlling the sub-oscillator. The capacitor and input pair in the sub-oscillator are controlled by the pseudo-random code, and then the negative resistance and capacitor of the sub-oscillator are connected to the main oscillator 130 through switch control to achieve spectrum dispersion of the oscillator 130. Figure 5 The schematic diagram of the spectrum corresponding to the frequency division technology is shown, where f is the frequency of the primary side oscillator or the secondary side oscillator for generating the PWM signal without the frequency division circuit. After being processed by the frequency division circuit 120, different frequency division spectra can be obtained according to the number of random code bits used. For example, if the number of random code bits used is n, the generated spectrum is f(2 n ) , the theoretical spurious amount can be reduced by 20log(2 N ) dB. If there are power consumption restrictions and ripple-free accuracy requirements, the frequency division circuit on the secondary side may not be synchronized with the primary side or may not be configured.

[0027] like Figure 6 , Figure 7 The figures are respectively a circuit schematic diagram of an anti-overshoot circuit provided in this embodiment and a structural schematic diagram of a second isolated power supply circuit, see Figure 6 and Figure 7 The anti-overshoot circuit 400 includes a soft start integrator circuit 410 and a PWM signal generating circuit 420. The PWM signal generating circuit 420 is electrically connected to the soft start integrator circuit 410 and the oscillator 130 respectively. The soft start integrator circuit 410 is used to generate a step-up voltage signal. The PWM signal generating circuit 420 is used to compare the step-up voltage with a preset triangular wave voltage signal and output a PWM signal with a decreasing duty cycle.

[0028] Specifically, the soft start integrator circuit 410 includes an operational amplifier U1, a third switch device SW7, a fourth switch device SW8, a first energy storage device C1, a second energy storage device C3, a first transmission gate SW4, a second transmission gate SW5, a third transmission gate SW6 and a third MOS transistor NM1. The first input terminal of the operational amplifier U1 is used to be electrically connected to an external first reference signal generator, the second input terminal of the operational amplifier U1 is electrically connected to one end of the first energy storage device C1, the output terminal of the operational amplifier U1 is electrically connected to the first end of the third MOS transistor NM1 through the second transmission gate SW5, and the other end of the first energy storage device C1 is electrically connected to the third MOS transistor NM1. The first ends of the third switch device SW7 and the fourth switch device SW8 are electrically connected, the second end of the third switch device SW7 is used to be electrically connected to the external second reference signal generator, the second end of the fourth switch device SW8 is used to be electrically connected to the first reference signal generator, the first transmission gate SW4 is electrically connected to the output end and the second input end of the operational amplifier U1, the second energy storage device C3 is electrically connected to the second input end of the operational amplifier U1 and the third transmission gate SW6, the second end of the third MOS transistor NM1 is electrically connected to the third transmission gate SW6 and the PWM signal generating circuit 420, and the third end of the third MOS transistor NM1 is electrically connected to the power supply. The energy storage device can be a capacitor.

[0029] It should be noted that since the output end of the entire power supply circuit also has an undervoltage protection function, the output voltage V ISO Before the undervoltage protection is released, the output signal A of the undervoltage protection circuit UVLO is always maintained at a high level, and the signal B is maintained at a low level, shielding the coded signal so that the PWM signal is always maintained at a low level. If the power supply circuit does not have an anti-overshoot circuit 400, the oscillator 130 of the power transmission circuit 100 will not start oscillating, the rectifier filter circuit 300 has no output, and the circuit is always in a locked state. Therefore, in order to enable the oscillator 130 of the power supply circuit to start oscillating before the undervoltage protection is released, an anti-overshoot circuit 400 is added to ensure that the output voltage V ISO Before the undervoltage protection is released, it rises steadily to the undervoltage protection release voltage point to avoid voltage overshoot. After the undervoltage protection is released, the feedback circuit 500 is stably established, and the anti-overshoot circuit 400 can be turned off to stabilize the output isolation voltage V ISO .

[0030] The anti-overshoot circuit 400 in this embodiment includes a bias circuit, a reference voltage generating circuit, a switched capacitor amplifier, and a digital timing control circuit. The function of the anti-overshoot circuit 400 is to achieve a fast and stable soft start of the output voltage, thereby suppressing the surge current and output voltage overshoot generated during the startup of the isolated power supply, and achieving an output voltage V ISO A steady rise from zero to the set value. Among them, the switched capacitor amplifier is the main part, such as Figure 6As shown, the switched capacitor amplifier includes a soft start integrator circuit 410 and a PWM signal generating circuit 420. The no-overshoot, soft start operation process in this embodiment can be divided into the following processes: REF <V th_down When the comparator output of the PWM signal generating circuit 420 is always high level; when the output V REF >V th_down When Vth_down <V REF <V th_up , the comparator outputs a PWM signal with a gradually decreasing duty cycle; when the PWM decoding circuit 530 decodes successfully and the first rising edge is output, the soft-start integrator circuit 410 is turned off, and its output is pulled to 0 by the switch tube NM1.

[0031] The soft start integrator circuit 410 actually works in two phases, respectively realizing the sampling mode and the integration mode. The principle of the soft start integrator circuit 410 in the sampling mode is as follows: Figure 8 As shown, when the circuit operates in the PH1 phase, the operational amplifier U1 operates in the unity gain feedback mode and V x Potential clamped to V REF1 , at this time V REF1 This is to provide a suitable input common-mode level for the operational amplifier U1. When the switch SW4 is turned off, the node V x Keep this voltage (V REF1 ), the op amp can work normally. The circuit works in phase 1 (PH1), such as Figure 8 As shown, switches SW7 and SW4 are closed respectively, and operational amplifier U1 works in unity gain feedback mode. x1 Voltage bias at V REF2 , V x2 Voltage clamped to V REF1 (The concept of "virtual short" in operational amplifiers) is analyzed through charge transfer, that is, the charge stored on capacitor C1 is: The circuit principle of the soft start integrator in the integration (amplification) mode is as follows: Fig. 9 As shown, the circuit works in phase 2 (PH2), switches SW8, SW5, and SW6 are closed respectively, and the circuit forms a switched capacitor integrator, that is, the input differential voltage of the operational amplifier U1 is driven by the negative feedback of capacitor C3, so that the voltage across the capacitor C1 becomes V REF1 Due to the law of conservation of charge, the charge stored in capacitor C1 at phase PH1 cannot disappear, and since the input impedance of CMOS operational amplifier U1 is large, the charge can only be transferred to the plate of capacitor C3. Therefore, ; Wherein, C3 = A*C1. Thus, the sampling mode and the integration mode work together to amplify the voltage by A times, which is the height of a step. Finally, after the above sampling and integration processing, the output voltage can be increased in steps.

[0032] The functions implemented by the PWM signal generating circuit 420 are as follows: Fig.10 As shown, the step-type rising voltage output by the soft start integrator circuit 410 is connected to the pulse signal generating circuit (eg Fig.10 The triangular wave voltage signal generated by the oscillator OSC in the middle is compared to generate an SS_PWM signal with a decreasing output duty cycle. The feedback control signal of the subsequent oscillator 130 is high level effective. Therefore, after the SS_PWM signal is processed by the inverter, the LC oscillator 130 can be gradually started, and then a steadily rising voltage V is output through rectification and filtering. ISO , and finally realize the circuit's step-type soft start without overshoot. After the startup is completed, the soft start circuit is turned off to achieve low power consumption design. In addition, the anti-overshoot circuit 400 is integrated inside the isolated power supply, without the need for a soft start pin and an external soft start capacitor, which is conducive to reducing the chip area and achieving high integration.

[0033] For further information, see Figure 7 The feedback circuit 500 includes an error amplifier, a PWM encoding circuit, a first isolation transformer 210 in the isolation transmission circuit 200 and a PWM decoding circuit. The error amplifier is electrically connected to the rectifier filter circuit 300 and the PWM encoding circuit respectively. The first isolation transformer 210 is electrically connected to the PWM encoding circuit and the PWM decoding circuit respectively. The PWM decoding circuit is also electrically connected to the oscillator 130, the frequency division circuit 120 and the bias supply circuit 110.

[0034] Specifically, in this embodiment, the feedback circuit 500 includes an error amplifier, a PWM encoding circuit, a signal isolation transformer 210, and a PWM decoding circuit. The input end of the feedback circuit 500 is the output end of the isolated power supply circuit, and after encoding and decoding, it is restored to a PWM control signal that can control the oscillator 130. A frequency division circuit can also be set on the secondary side, which is similar to the frequency division circuit 120 on the primary side. The frequency division circuit on the secondary side can output the required effective bits fixedly or dynamically according to the application requirements, thereby improving the ripple accuracy of the output voltage of the isolated power supply. The secondary side can also include a protection circuit, which can include a reference establishment circuit, an undervoltage protection circuit and a power reset circuit, and a combinational logic control circuit.

[0035] like Fig.11 FIG. 1 is a schematic diagram of a structure of an isolated transmission circuit provided in this embodiment. Fig.11The isolation transmission circuit 200 further includes a second isolation transformer 220, and the second isolation transformer 220 is electrically connected to the power transmission circuit 100 and the rectifier and filter circuit 300 respectively.

[0036] Specifically, the isolation transmission circuit 200 includes a power isolation transformer (i.e., the second isolation transformer 220) and a signal isolation transformer (i.e., the first isolation transformer 210). The power isolation transformer 220 is used for power transmission from AC signal to AC signal; the signal isolation transformer 210 is used to transmit the secondary side coded signal to the primary side decoding circuit. The power isolation transformer 220 includes a primary coil and a secondary coil, and both are S-shaped structures; the primary coil is applied to the power transmission circuit 100 and is located at the bottom layer; the secondary coil is applied to the rectifier filter circuit 300 and is located at the top layer. A high-voltage resistant insulating material is applied between the primary coil and the secondary coil to ensure that the high-voltage breakdown index requirements can be met between the two. The primary coil is in the lower layer and is applied to the power transmission circuit 100. Due to the eddy current loss effect of the substrate, the inductance value of the primary coil applied to the power transmission circuit 100 is small, which makes it easy to increase the frequency of the oscillator 130, and is beneficial to the design and optimization of the frequency division circuit 120, thereby reducing EMI; the secondary coil applied to the rectifier filter circuit 300 is far away from the substrate, so it is less affected by the eddy current loss effect of the substrate, and thus its inductance value is large, which increases the coupling voltage ratio of the power isolation transformer, which is beneficial to the improvement of efficiency. At the same time, the bottom layer coil and the upper layer coil are surrounded by a metal shielding wall ring, which not only shields the electromagnetic interference of the peripheral circuit or system, but also effectively suppresses the external radiation and internal loss of the isolated transmission circuit 200, which is convenient for the realization of the function of the codec circuit (in view of the characteristics of the planar inductor of the on-chip isolation transformer, as the radius increases, the voltage loss caused by its magnetic flux rate increases, which will cause the code error state of the codec circuit), thereby improving the overall efficiency conversion performance and reliability of the isolated power supply.

[0037] like Fig.12 The figure shows a typical signal waveform diagram of an isolated power supply circuit provided by the present embodiment. Among them, the wide voltage domain is realized by the power transmission circuit 100, which can generate a voltage waveform with an amplitude several times that of the input voltage, and in view of the introduction of the frequency division circuit 120, the oscillator 130 and the PWM signal are both discrete frequency spectra, and after passing through the isolation transmission circuit 200, they enter the rectifier circuit and are converted into a signal waveform with amplitude loss, and then the DC signal output is completed after passing through the low-pass filter circuit. The feedback circuit 500 is fed back to the primary side in the form of a PWM signal, and completes the functional conversion of encoding and decoding under the premise of ensuring the isolation withstand voltage.

[0038] Therefore, in the isolated power supply circuit provided in the embodiment of the present application, the AC coupling voltage-dividing capacitor meets the requirements of low chip manufacturing cost and conventional process design; the bias supply circuit 110 and the stability compensation circuit 140 solve the problems of wide input power domain and stability after startup; the introduction of the frequency division circuit 120 enables the function of weakening the common-mode voltage or common-mode current amplitude caused by electromagnetic radiation to be completed by means of a discrete working frequency spectrum, thereby improving the ability to resist electromagnetic radiation interference and achieving high reliability characteristics of low EMI; in addition, the frequency division circuit 120 is also applicable to the PWM signal on the secondary side, which can improve the output voltage ripple accuracy characteristics while improving electromagnetic radiation interference; the circular design of the isolation transformer is used to facilitate power transmission and avoid chamfering losses; The S-shaped design satisfies the symmetry and exhibits the effect of opposite cancellation of the magnetic flux directions of two adjacent coils on the same layer, which can effectively increase the transmission efficiency and reduce electromagnetic interference; the directional research and design of the input and output ends of the isolation transformer in the isolation transmission circuit 200 fully utilizes the circuit properties of the primary side circuit and the secondary side circuit and the eddy current loss effect of the substrate, which can effectively improve the oscillation frequency of the primary side and the receiving voltage ratio of the secondary side, thereby maximizing the overall conversion efficiency; the metal wall ring surrounding the outer ring of the isolation transformer can effectively shield the electromagnetic interference of the peripheral circuit or system to the isolation transformer, and to a certain extent suppress the external radiation and internal loss of the isolation transmission circuit 200, reduce the impact on the encoding and decoding circuit, and improve the EMI performance of the entire isolated power supply.

[0039] It should be noted that the various embodiments in the present application are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0040] It should also be noted that, in the content of the present application, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first" and "second" can expressly or implicitly include one or more of the features. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements that are not clearly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "include one..." do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

[0041] The above description of the disclosed embodiments enables professionals and technicians in the field to implement or use the present application. Various modifications to these embodiments will be apparent to professionals and technicians in the field, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown in the present application, but will conform to the widest range consistent with the principles and novel features disclosed in the present application.

Claims

1. An isolated power supply circuit, characterized in that: include: A power transmission circuit, an isolation transmission circuit, a rectification and filtering circuit, an anti-overshoot circuit and a feedback circuit, wherein the power transmission circuit includes a bias supply circuit, a frequency division circuit and an oscillator; The oscillator is electrically connected to the bias supply circuit, the frequency division circuit, the anti-overshoot circuit and the isolation transmission circuit, respectively; the rectification and filtering circuit is electrically connected to the isolation transmission circuit; and the feedback circuit is electrically connected to the rectification and filtering circuit, the frequency division circuit, the anti-overshoot circuit, the bias supply circuit and the oscillator, respectively.

2. The isolated power supply circuit according to claim 1, characterized in that: The oscillator includes a first power transmission tube, a second power transmission tube, a first inductor, a second inductor and an oscillation start control circuit; The first end of the first power transmission tube is electrically connected to one end of the first inductor and the isolation transmission circuit respectively, the first end of the second power transmission tube is electrically connected to one end of the second inductor and the isolation transmission circuit respectively, the second end of the first power transmission tube is electrically connected to the first end of the second power transmission tube, the second end of the second power transmission tube is electrically connected to the first end of the first power transmission tube, the third ends of the first power transmission tube and the second power transmission tube are both grounded, the other ends of the first inductor and the second inductor are both electrically connected to a power supply, and the oscillation start control circuit is electrically connected to the second ends of the first power transmission tube and the second power transmission tube, the feedback circuit and the anti-overshoot circuit respectively.

3. The isolated power supply circuit according to claim 2, characterized in that: The oscillator also includes a first capacitor and a second capacitor, the first capacitor is electrically connected to the first end of the first power transmission tube and the second end of the second power transmission tube respectively, and the second capacitor is electrically connected to the second end of the first power transmission tube and the first end of the second power transmission tube respectively.

4. The isolated power supply circuit according to claim 2, characterized in that: The power transmission circuit further includes a stability compensation circuit, and the stability compensation circuit includes a third power transmission tube and a fourth power transmission tube; The first end of the third power transmission tube is electrically connected to the second end of the first power transmission tube, the first end of the fourth power transmission tube is electrically connected to the second end of the second power transmission tube, the second end of the third power transmission tube is electrically connected to the first end of the fourth power transmission tube, the second end of the fourth power transmission tube is electrically connected to the first end of the third power transmission tube, and the third ends of the third power transmission tube and the fourth power transmission tube are both grounded.

5. The isolated power supply circuit according to claim 2, characterized in that: The oscillation start control circuit includes a first MOS tube and a second MOS tube, wherein the first end of the first MOS tube is electrically connected to the second end of the first power transmission tube, the first end of the second MOS tube is electrically connected to the second end of the second power transmission tube, the second ends of the first MOS tube and the second MOS tube are both electrically connected to the feedback circuit and the anti-overshoot circuit, and the third ends of the first MOS tube and the second MOS tube are both grounded.

6. The isolated power supply circuit according to claim 2, characterized in that: The bias supply circuit includes a first resistor, a second resistor, a first switch device and a second switch device; One end of the first resistor is electrically connected to the second end of the first power transmission tube, one end of the second resistor is electrically connected to the second end of the second power transmission tube, the first switching device is electrically connected to the power supply, the other end of the first resistor and the feedback circuit respectively, and the second switching device is electrically connected to the power supply, the other end of the second resistor and the feedback circuit respectively.

7. The isolated power supply circuit according to claim 1, characterized in that: The frequency division circuit includes a random code generation circuit and a plurality of sub-oscillators, wherein the sub-oscillators include a fifth power transmission tube, a sixth power transmission tube, a third capacitor and a fourth capacitor; The first end of the fifth power transmission tube is electrically connected to the oscillator through the third capacitor, the first end of the sixth power transmission tube is electrically connected to the oscillator through the fourth capacitor, the second ends of the fifth power transmission tube and the sixth power transmission tube are both electrically connected to the random code generation circuit, the third ends of the fifth power transmission tube and the sixth power transmission tube are both grounded, and the random code generation circuit is also electrically connected to the feedback circuit; The random code generation circuit is used to generate a corresponding number of pseudo-random codes according to the feedback signal, and convert the pseudo-random codes into switch control signals, and the switch control signals are used to control the corresponding sub-oscillators to be connected to the oscillator.

8. The isolated power supply circuit according to claim 1, characterized in that: The anti-overshoot circuit comprises a soft start integrator circuit and a PWM signal generating circuit, and the PWM signal generating circuit is electrically connected to the soft start integrator circuit and the oscillator respectively; The soft start integrator circuit is used to generate a step-up voltage signal, and the PWM signal generating circuit is used to compare the step-up voltage with a preset triangle wave voltage signal and output a PWM signal with a decreasing duty cycle.

9. The isolated power supply circuit according to claim 8, characterized in that: The soft start integrator circuit includes an operational amplifier, a third switch device, a fourth switch device, a first energy storage device, a second energy storage device, a first transmission gate, a second transmission gate, a third transmission gate and a third MOS tube. The first input end of the operational amplifier is used to be electrically connected to an external first reference signal generator, the second input end of the operational amplifier is electrically connected to one end of the first energy storage device, the output end of the operational amplifier is electrically connected to the first end of the third MOS tube through the second transmission gate, the other end of the first energy storage device is electrically connected to the first ends of the third switch device and the fourth switch device respectively, the second end of the third switch device is used to be electrically connected to an external second reference signal generator, the second end of the fourth switch device is used to be electrically connected to the first reference signal generator, the first transmission gate is electrically connected to the output end and the second input end of the operational amplifier respectively, the second energy storage device is electrically connected to the second input end of the operational amplifier and the third transmission gate respectively, the second end of the third MOS tube is electrically connected to the third transmission gate and the PWM signal generating circuit respectively, and the third end of the third MOS tube is electrically connected to a power supply.

10. The isolated power supply circuit according to claim 1, characterized in that: The feedback circuit includes an error amplifier, a PWM encoding circuit, a first isolation transformer in the isolation transmission circuit and a PWM decoding circuit. The error amplifier is electrically connected to the rectification and filtering circuit and the PWM encoding circuit respectively. The first isolation transformer is electrically connected to the PWM encoding circuit and the PWM decoding circuit respectively. The PWM decoding circuit is also electrically connected to the oscillator, the frequency division circuit and the bias supply circuit.

11. The isolated power supply circuit according to claim 10, characterized in that: The isolation transmission circuit also includes a second isolation transformer, which is electrically connected to the power transmission circuit and the rectification and filtering circuit respectively.

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