Active clamping control circuit and switching power supply
By adjusting the clamping logic timing through the active clamping control circuit, the problem of unbalanced clamping timing of the forward topology switching power supply under a wide voltage input is solved, stable operation and stress spike absorption under high and low voltage inputs are achieved, and the reliability of the switching power supply is improved.
Patent Information
- Application Number
- CN202422726508.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-08
- Publication Date
- 2025-09-19
- Estimated Expiration
- 2034-11-08
AI Technical Summary
In a forward-type topology switching power supply, when the input voltage is wide, it is difficult to set the clamping timing evenly under high and low voltage inputs, resulting in stress spikes on the secondary side that affect the operation of the entire device.
An active clamp control circuit is used to adjust the active clamp logic timing according to the input voltage through the isolation transmission circuit, logic control circuit and logic switch circuit. The clamp is closed at low voltage and opened at high voltage to control the conduction and shutdown of the clamp tube.
The stability of the active clamping logic timing is achieved under a wide voltage input, avoiding the influence of the timing advance in the low voltage section on the operation of the whole machine, and normally absorbing the stress spike at high voltage, thereby improving the reliability of the switching power supply.
Smart Images
Figure CN223364036U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of power supplies, and in particular relates to an active clamping control circuit and a switching power supply. Background Art
[0002] Among the topologies of switching power conversion, the forward topology is widely used in switching power modules due to its advantages of high efficiency and high output power. When the forward topology outputs high power, the output current is large. Due to the resonance of leakage inductance, capacitance and parasitic parameters, a high stress spike is generated on the secondary side switch tube. Therefore, a clamping circuit is often added to the secondary side to absorb the stress spike and improve the reliability of the switching power module. Figure 1 This is the industry-wide active clamp secondary power stage schematic diagram, in which the circuit composed of MOS tube TR20 and capacitor C20 is the clamping circuit.
[0003] After research, the inventors of this application found that when the input voltage of the forward topology is expanded to 4:1 or greater, since the stress of the clamped tube D21 is very different at high and low voltage inputs, the clamping timing will move forward as the stress platform decreases. Under the conditions of meeting the minimum duty cycle of the control chip and not exceeding the stress, the advance or lag time of the clamping timing is difficult to set. In the case of severe low-voltage timing advance, it may even affect the operation of the entire machine. Utility Model Content
[0004] In view of this, the technical problem to be solved by the present invention is to overcome the conventional active clamping logic control problem of wide voltage input in the above-mentioned prior art, and to provide an active clamping control circuit and a switching power supply to solve the timing problem of high and low voltage input clamping tubes.
[0005] The inventive concept of the present application is as follows: in the low-voltage input section, when the stress spike on the secondary side is not high, the active clamping can be turned off; in the high-voltage input section, when the stress on the secondary side is high, the active clamping can be turned on; in this way, the active clamping logic timing offset can be controlled within a small range, which can ensure that the active clamping timing does not affect the operation of the product, and at the same time the high-voltage input clamping circuit can work normally and the stress meets the derating requirement.
[0006] As a first aspect of the present invention, the technical solution of the active clamping control circuit embodiment provided is as follows:
[0007] An active clamping control circuit is applied to a switching power supply, the switching power supply being a forward type switching power supply, comprising a primary circuit, a secondary circuit, and a main control chip. The primary circuit comprises a main power switch tube, and the main control chip outputs a first drive signal to control the on and off of the main power switch tube. The secondary circuit comprises a rectifier tube and an active clamping circuit, and the active clamping circuit is used to absorb stress spikes of the rectifier tube. The active clamping control circuit comprises:
[0008] An isolated transmission circuit, wherein the primary side inputs a first driving signal and the secondary side outputs a second driving signal after isolation processing;
[0009] a logic control circuit, connected to the isolation transmission circuit, configured to chop, invert, and enhance the driving capability of the second drive signal to output a third drive signal, wherein the third drive signal is used to control the on and off of the clamping tube in the clamping circuit;
[0010] a logic switch circuit, connected to the switching power supply and the isolated transmission circuit, for sampling the input voltage of the switching power supply and generating an enable signal to enable the isolated transmission circuit to operate: when the input voltage of the switching power supply is less than or equal to a set value, the enable signal disables the isolated transmission circuit; when the input voltage of the switching power supply is greater than the set value, the enable signal enables the isolated transmission circuit to operate.
[0011] Preferably, the isolated transmission circuit includes a resistor R1, a diode D1, a diode D2 and a chip U1, and the chip U1 is a signal transmission chip; a logic input end of the primary side of the chip U1, the cathode of the diode D2, the anode of the diode D1 and one end of the resistor R1 are connected together for inputting the enable signal, the anode of the diode D2 is connected to the primary ground of the chip U1 and the primary ground of the switching power supply, and the cathode of the diode D1 and the other end of the resistor R1 are used to input the first drive signal.
[0012] Preferably, the chip U1 is any one of Nanochip's gate signal isolation transmission chips NSi6601, NSi6602 and NSI8220.
[0013] Preferably, the logic control circuit includes a capacitor C1, a capacitor C2, a resistor R2, a resistor R3, a diode D3, a diode D4 and a chip U2, and the chip U2 is an inverting drive chip; one end of the capacitor C1 inputs the second drive signal, the other end of the capacitor C1 is connected to the logic input end of the chip U2, one end of the resistor R2 and the cathode of the diode D3, the other end of the resistor R2 and the anode of the diode D3 are connected to the ground of the chip U2, one end of the capacitor C2 is connected to the output end of the chip U2, the other end of the capacitor C2 is connected to the anode of the diode D4 and one end of the resistor R3, the cathode of the diode D4 is used to connect to the secondary ground of the switching power supply, and the other end of the resistor R3 outputs the third drive signal.
[0014] Preferably, the chip U2 is SGM48002 produced by Shengbang Microelectronics.
[0015] Preferably, the logic switch circuit includes a resistor R10, a resistor R11, a resistor R12, a resistor R13, a switch tube Q1, and a switch tube Q2; one end of the resistor R10 is used to input a voltage signal Vin representing the magnitude of the input voltage of the switching power supply, the other end of the resistor R10 is connected to one end of the resistor R11 and the first electrode of the switch tube Q1, the second electrode of the switch tube Q1 is connected to one end of the resistor R12 and the first electrode of the switch tube Q2, the other end of the resistor R12 is used to connect to the power supply VDD1, the second electrode of the switch tube Q2 is connected to one end of the resistor R13, the other end of the resistor R13 outputs the enable signal, and the other end of the resistor R11, the third electrode of the switch tube Q1, and the third electrode of the switch tube Q2 are used to connect to the primary ground of the switching power supply.
[0016] Preferably, the switch tube Q1 and the switch tube Q2 are both enhancement-mode MOS tubes, the first electrodes of the switch tube Q1 and the switch tube Q2 are both drain electrodes, the second electrodes are both sources, and the control electrodes are both gate electrodes.
[0017] Preferably, the switch tube Q1 and the switch tube Q2 are both NPN triodes, the first electrodes of the switch tube Q1 and the switch tube Q2 are both base electrodes, the second electrodes are both collector electrodes, and the third electrodes are both emitters.
[0018] Preferably, the switch tube Q1 and the switch tube Q2 are both enhancement-mode MOS tubes, and the first electrodes of the switch tube Q1 and the switch tube Q2 are both gate electrodes, the second electrodes are both drain electrodes, and the third electrodes are both sources electrodes.
[0019] Preferably, the switch tube Q1 is an enhancement mode MOS tube, the first electrode of the switch tube Q1 is the gate, the second electrode is the drain, and the third electrode is the source; the switch tube Q2 is a 431 controller, the first electrode of the switch tube Q2 is the reference electrode, the second electrode is the cathode drain, and the third electrode is the anode.
[0020] As a second aspect of the present invention, the technical solution of the switching power supply embodiment provided is as follows:
[0021] A switching power supply, wherein the switching power supply is a forward-type switching power supply, comprising a primary circuit, a secondary circuit, and a main control chip; the primary circuit comprises a main power switch tube; the main control chip outputs a first drive signal to control the on and off of the main power switch tube; the secondary circuit comprises a rectifier tube and an active clamping circuit; the active clamping circuit is used to absorb stress spikes of the rectifier tube; wherein: the switching power supply further comprises the source clamping control circuit described in any one of the first aspects above.
[0022] The beneficial effects of the present invention are as follows: when the input voltage of the full-bridge, half-bridge, forward and other forward-type topologies is relatively wide, the logic switch can pull down the input signal of the isolation transmission circuit in the low voltage segment, so that the secondary-side active clamping logic control circuit in the low voltage segment does not work, thereby avoiding serious advance of the secondary-side active clamping logic timing in the low voltage segment, and even affecting the operation of the entire machine; when the high voltage stress spike is large, the enable signal of the logic switch is canceled, so that the primary-side drive signal can be normally transmitted to the secondary side, and the secondary-side active clamping logic control circuit works normally, thereby achieving the stress absorption effect. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 This is the industry-standard active clamp secondary power stage schematic;
[0024] Figure 2 This is a principle block diagram of the first embodiment of the utility model;
[0025] Figure 3 This is a first active clamping control circuit diagram of the first embodiment of the utility model;
[0026] Figure 4 This is a second active clamping control circuit diagram of the first embodiment of the utility model;
[0027] Figure 5 This is a third active clamping control circuit diagram of the first embodiment of the utility model. DETAILED DESCRIPTION
[0028] To make the above-mentioned purposes, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.
[0029] It should be noted that the terms "including" and "having" and any variations thereof described in the specification and claims of this application are intended to cover non-exclusive inclusions. For example, the inclusion of a series of components, unit circuits or control timings is not necessarily limited to those components, unit circuits or control timings clearly listed, but may include components, unit circuits or control timings that are not clearly listed or are inherent to these circuits.
[0030] In addition, the embodiments and features in the embodiments of the present application may be combined with each other unless there is any conflict.
[0031] It should be understood that, in the specification and the claims, when an element is described as being “connected” to another element, the element may be “directly connected” to the other element, or be “connected” to the other element through a third element; when a step is described as being continued to another step, the step may be directly continued to the other step, or be continued to the other step through a third step.
[0032] First embodiment
[0033] This embodiment provides an active clamping control circuit, which is applied to a switching power supply. The switching power supply is a forward-type switching power supply, including a primary circuit, a secondary circuit, and a main control chip. The primary circuit includes a main power switch tube. The main control chip outputs a first drive signal to control the on and off of the main power switch tube. The secondary circuit includes a rectifier tube and an active clamping circuit. The active clamping circuit is used to absorb stress spikes of the rectifier tube. Figure 2 This is a principle block diagram of the first embodiment of the present utility model, see Figure 2 , wherein the source clamp control circuit includes:
[0034] An isolated transmission circuit, wherein the primary side inputs a first driving signal and the secondary side outputs a second driving signal after isolation processing;
[0035] a logic control circuit connected to the isolation transmission circuit, configured to chop, invert, and enhance the driving capability of the second drive signal to output a third drive signal, wherein the third drive signal is used to control the on and off of the clamping tube in the clamping circuit;
[0036] The logic switch circuit is connected to the switching power supply and the isolation transmission circuit, and is used to sample the input voltage of the switching power supply and generate an enable signal to enable the isolation transmission circuit to work: when the input voltage of the switching power supply is less than or equal to the set value, the enable signal enables the isolation transmission circuit to not work; when the input voltage of the switching power supply is greater than the set value, the enable signal enables the isolation transmission circuit to work.
[0037] The active clamping control circuit of this embodiment, when the input voltage is wide in the full-bridge, half-bridge, forward and other forward-type topologies, the logic switch can pull down the input signal of the isolation transmission circuit in the low voltage segment, so that the secondary active clamping logic control circuit of the low voltage segment does not work, thereby avoiding serious advance of the active clamping logic timing of the secondary side in the low voltage segment, and even affecting the operation of the entire machine; when the high voltage stress spike is large, the enable signal of the logic switch is canceled, so that the primary side drive signal can be normally transmitted to the secondary side, and the secondary side active clamping logic control circuit works normally, achieving the stress absorption effect.
[0038] Figure 3 This is the first active clamping control circuit diagram of the first embodiment of the utility model, Figure 4 This is the second active clamping control circuit diagram of the first embodiment of the utility model, Figure 5This is the third active clamping control circuit diagram of the first embodiment of the utility model; please refer to Figures 3 to 5 ,in:
[0039] The isolated transmission circuit includes a resistor R1, a diode D1, a diode D2, and a chip U1. Chip U1 is a signal transmission chip. A logic input terminal on the primary side of chip U1, the cathode of diode D2, the anode of diode D1, and one end of resistor R1 are connected together for inputting an enable signal. The anode of diode D2 is connected to the primary ground of chip U1 and the primary ground of the switching power supply. The cathode of diode D1 and the other end of resistor R1 are used to input a first drive signal. Preferably, chip U1 is any one of Nanochip's gate signal isolation transmission chips: NSi6601, NSi6602, and NSI8220.
[0040] The logic control circuit includes capacitor C1, capacitor C2, resistor R2, resistor R3, diode D3, diode D4, and chip U2. Chip U2 is an inverting drive chip. One end of capacitor C1 inputs the second drive signal. The other end of capacitor C1 is connected to the logic input of chip U2, one end of resistor R2, and the cathode of diode D3. The other end of resistor R2 and the anode of diode D3 are connected to the ground of chip U2. One end of capacitor C2 is connected to the output of chip U2. The other end of capacitor C2 is connected to the anode of diode D4 and one end of resistor R3. The cathode of diode D4 is used to connect to the secondary ground of the switching power supply. The other end of resistor R3 outputs the third drive signal. Preferably, chip U2 is Shengbang Micro's SGM48002.
[0041] The logic switch circuit includes resistors R10, R11, R12, R13, switches Q1, and Q2. One end of resistor R10 is used to input a voltage signal Vin representing the magnitude of the input voltage of the switching power supply. The other end of resistor R10 is connected to one end of resistor R11 and the first electrode of switch Q1. The second electrode of switch Q1 is connected to one end of resistor R12 and the first electrode of switch Q2. The other end of resistor R12 is used to connect to power supply VDD1. The second electrode of switch Q2 is connected to one end of resistor R13. The other end of resistor R13 outputs an enable signal. The other end of resistor R11, the third electrode of switch Q1, and the third electrode of switch Q2 are used to connect to the primary ground of the switching power supply.
[0042] The switch tube Q1 and the switch tube Q2 are both enhancement-type MOS tubes. The first electrodes of the switch tube Q1 and the switch tube Q2 are both drain electrodes, the second electrodes are both sources, and the control electrodes are both gate electrodes.
[0043] See Figure 3 , wherein the switch tube Q1 and the switch tube Q2 are both NPN transistors, the first electrodes of the switch tube Q1 and the switch tube Q2 are both base electrodes, the second electrodes are both collector electrodes, and the third electrodes are both emitters.
[0044] See Figure 4 , wherein the switch tube Q1 and the switch tube Q2 are both enhancement-mode MOS tubes, the first electrodes of the switch tube Q1 and the switch tube Q2 are both gate electrodes, the second electrodes are both drain electrodes, and the third electrodes are both sources.
[0045] See Figure 5 The switch tube Q1 is an enhancement MOS tube, the first electrode of the switch tube Q1 is the gate, the second electrode is the drain, and the third electrode is the source; the switch tube Q2 is a 431 controller, the first electrode of the switch tube Q2 is the reference electrode, the second electrode is the drain cathode, and the third electrode is the anode.
[0046] by Figure 3 Taking a specific circuit as an example, the working principle of this embodiment is further analyzed as follows:
[0047] Chip U1 is an isolated signal transmission IC; chip U2 is a driver IC, which is an integrated chip (inverter + driver) with two functions: (1) inverting the signal, and (2) improving the signal driving capability. When the driving signal GATE is positive, it is isolated and output to pin 7 of the secondary side through chip U1, and then chopped by capacitor C1 and resistor R2 and input to pin 2 of chip U2. When the input signal of pin 2 of chip U2 is high, pin 7 of chip U2 outputs a low level. Since capacitor C2 is fully charged in the previous cycle, the output terminal V_PMOS of the logic control circuit obtains a negative voltage to drive PMOS. When the driving signal GATE is zero, it is isolated and output to the secondary side through chip U1, and then capacitor C1 is quickly discharged through diode D3. Pin 7 of chip U2 outputs a high level. Capacitor C2 is charged in this cycle, and the output terminal V_PMOS of the control circuit obtains a positive voltage of 0.7V, turning off PMOS.
[0048] When the input signal VIN is a low voltage, the switch tube Q1 is turned off, the first pole of the switch tube Q2 is a high level, the switch tube Q2 is turned on, and the A2 signal is forcibly pulled to the ground, so that the A2 signal is pulled down to the high-level logic voltage of the chip U1, thereby realizing the function of closing the A2 transmission channel.
[0049] When the input signal VIN is a high voltage, the switch tube Q1 is turned on, the first pole of the switch tube Q2 is pulled low by the switch tube Q1, the switch tube Q2 is turned off, the A2 signal is not pulled to the ground, the GATE drive signal can be normally input into the detection end of the chip U1, and the chip U1 normally outputs the signal to the logic control circuit.
[0050] Second embodiment
[0051] This embodiment provides a switching power supply, which is a forward-type switching power supply and includes a primary circuit, a secondary circuit, and a main control chip. The primary circuit includes a main power switch tube. The main control chip outputs a first drive signal to control the on and off of the main power switch tube. The secondary circuit includes a rectifier tube and an active clamping circuit. The active clamping circuit is used to absorb stress spikes of the rectifier tube. The switching power supply also includes any source clamping control circuit in the first embodiment.
[0052] It should be noted that the forward switching power supply refers to a power supply in which, when the switch tube is turned on, the output transformer acts as a medium to directly couple the magnetic field energy, converting electrical energy into magnetic energy, and magnetic energy into electrical energy, thereby achieving simultaneous input and output. In addition to the forward switching power supply, the forward switching power supply also includes full-bridge, half-bridge and other switching power supplies.
[0053] Since the switching power supply of this embodiment includes any one of the source clamp control circuits of the first embodiment, the input voltage can be expanded to 4:1 or even greater, and the reliability is high. There will be no problem of serious advance of the active clamp logic timing on the secondary side of the low voltage segment, which may even affect the operation of the entire device.
[0054] The above examples are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be construed as limiting the present invention. It will be apparent to those skilled in the art that various improvements and modifications may be made without departing from the spirit and scope of the present invention. These improvements and modifications are readily apparent from prior art and should be considered within the scope of the present invention. These examples will not be further detailed herein.
Claims
1. An active clamping control circuit, applied to a switching power supply, wherein the switching power supply is a forward-type switching power supply, comprising a primary circuit, a secondary circuit, and a main control chip. The primary circuit comprises a main power switch tube, and the main control chip outputs a first drive signal to control the on and off of the main power switch tube. The secondary circuit comprises a rectifier tube and an active clamping circuit, wherein the active clamping circuit is used to absorb stress spikes of the rectifier tube. The invention is characterized in that: The source clamp control circuit comprises: An isolated transmission circuit, wherein the primary side inputs a first driving signal and the secondary side outputs a second driving signal after isolation processing; a logic control circuit, connected to the isolation transmission circuit, configured to chop, invert, and enhance the driving capability of the second drive signal to output a third drive signal, wherein the third drive signal is used to control the on and off of the clamping tube in the clamping circuit; a logic switch circuit, connected to the switching power supply and the isolated transmission circuit, for sampling the input voltage of the switching power supply and generating an enable signal to enable the isolated transmission circuit to operate: when the input voltage of the switching power supply is less than or equal to a set value, the enable signal disables the isolated transmission circuit; when the input voltage of the switching power supply is greater than the set value, the enable signal enables the isolated transmission circuit to operate.
2. The active clamping control circuit according to claim 1, wherein: The isolated transmission circuit includes a resistor R1, a diode D1, a diode D2 and a chip U1, wherein the chip U1 is a signal transmission chip; a logic input end of the primary side of the chip U1, the cathode of the diode D2, the anode of the diode D1 and one end of the resistor R1 are connected together for inputting the enable signal, the anode of the diode D2 is connected to the primary ground of the chip U1 and the primary ground of the switching power supply, and the cathode of the diode D1 and the other end of the resistor R1 are used to input the first drive signal.
3. The active clamping control circuit according to claim 2, wherein: The chip U1 is any one of Nanochip's gate signal isolation transmission chips NSi6601, NSi6602 and NSI8220.
4. The active clamping control circuit according to claim 1, wherein: The logic control circuit includes a capacitor C1, a capacitor C2, a resistor R2, a resistor R3, a diode D3, a diode D4 and a chip U2, wherein the chip U2 is an inverting drive chip; one end of the capacitor C1 inputs the second drive signal, the other end of the capacitor C1 is connected to the logic input end of the chip U2, one end of the resistor R2 and the cathode of the diode D3, the other end of the resistor R2 and the anode of the diode D3 are connected to the ground of the chip U2, one end of the capacitor C2 is connected to the output end of the chip U2, the other end of the capacitor C2 is connected to the anode of the diode D4 and one end of the resistor R3, the cathode of the diode D4 is used to connect to the secondary ground of the switching power supply, and the other end of the resistor R3 outputs the third drive signal.
5. The active clamping control circuit according to claim 4, wherein: The chip U2 is SGM48002 from Shengbang Microelectronics.
6. The active clamping control circuit according to claim 5, wherein: The logic switch circuit includes a resistor R10, a resistor R11, a resistor R12, a resistor R13, a switch tube Q1, and a switch tube Q2; one end of the resistor R10 is used to input a voltage signal Vin representing the magnitude of the input voltage of the switching power supply, the other end of the resistor R10 is connected to one end of the resistor R11 and the first electrode of the switch tube Q1, the second electrode of the switch tube Q1 is connected to one end of the resistor R12 and the first electrode of the switch tube Q2, the other end of the resistor R12 is used to connect to the power supply VDD1, the second electrode of the switch tube Q2 is connected to one end of the resistor R13, the other end of the resistor R13 outputs the enable signal, the other end of the resistor R11, the third electrode of the switch tube Q1, and the third electrode of the switch tube Q2 are used to connect to the primary ground of the switching power supply. The switch tube Q1 and the switch tube Q2 are both enhancement-type MOS tubes. The first electrodes of the switch tube Q1 and the switch tube Q2 are both drain electrodes, the second electrodes are both sources, and the control electrodes are both gate electrodes.
7. The active clamping control circuit according to claim 6, wherein: The switch tube Q1 and the switch tube Q2 are both NPN triodes, and the first electrodes of the switch tube Q1 and the switch tube Q2 are both base electrodes, the second electrodes are both collector electrodes, and the third electrodes are both emitters.
8. The active clamping control circuit according to claim 6, wherein: The switch tube Q1 and the switch tube Q2 are both enhancement-mode MOS tubes. The first electrodes of the switch tube Q1 and the switch tube Q2 are both gate electrodes, the second electrodes are both drain electrodes, and the third electrodes are both sources electrodes.
9. The active clamping control circuit according to claim 6, wherein: The switch tube Q1 is an enhancement mode MOS tube, wherein the first electrode of the switch tube Q1 is a gate electrode, the second electrode is a drain electrode, and the third electrode is a source electrode; the switch tube Q2 is a 431 controller, wherein the first electrode of the switch tube Q2 is a reference electrode, the second electrode is a cathode drain electrode, and the third electrode is an anode electrode.
10. A switching power supply, wherein the switching power supply is a forward switching power supply, comprising a primary circuit, a secondary circuit, and a main control chip, wherein the primary circuit comprises a main power switch tube, and the main control chip outputs a first drive signal to control the on and off of the main power switch tube, and the secondary circuit comprises a rectifier tube and an active clamping circuit, wherein the active clamping circuit is used to absorb stress spikes of the rectifier tube, characterized in that: The switching power supply further comprises the source clamp control circuit according to any one of claims 1 to 9.