Current expanding circuit of DCDC chip
By designing the current expansion circuit of the DCDC chip and using the SW pin to achieve output current expansion, the problem of high manufacturing costs in existing DCDC chips under high current loads is solved, and the effect of reducing manufacturing costs and power consumption is achieved.
Patent Information
- Application Number
- CN202421096468.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-20
- Publication Date
- 2025-02-18
- Estimated Expiration
- 2034-05-20
AI Technical Summary
When the load current is greater than its maximum output current capability, it is difficult to effectively drive a large current load, resulting in the need to select chips with higher output current capabilities, which increases manufacturing costs.
A current expansion circuit of DCDC chip is designed. By using the SW pin of DCDC chip to achieve output current expansion, the load current is pulled from both the DCDC chip and its power input, so that the chip with a larger current specification is not selected. In the case of high current load requirements.
When the load current is greater than the maximum output current capability of the DCDC chip, it is not necessary to choose a chip with higher output current capability, which reduces the manufacturing cost of the circuit, and reduces the working current and power consumption of the DCDC chip, avoiding the problem of self-heating.
Smart Images
Figure CN222509118U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a power supply circuit, in particular to a current expansion circuit of a DCDC chip. Background Art
[0002] As a voltage conversion chip, the DCDC chip supplies power to the next stage through the output end. When designing a circuit, a DCDC chip that meets the current requirements will be selected according to the load current. If the load current is higher than the output current capability of the DCDC chip, a DCDC chip with a higher output current capability is usually selected to meet product design requirements. Since the output current of the DCDC chip increases in a gradient, and the greater the output current capability, the higher the price, therefore, choosing a DCDC chip with a higher output current capability means an increase in manufacturing costs. Summary of the invention
[0003] The technical problem to be solved by the utility model is to provide a current expansion circuit of a DCDC chip, which can enable a DCDC chip with a small output current to drive a load with a large current.
[0004] A current expansion circuit of a DCDC chip according to an embodiment of the utility model comprises a power input terminal VIN, a power output terminal VOUT, a DCDC chip U1, a PNP transistor Q1, a switch element Q2, a voltage divider circuit, a resistor R1 and a capacitor C2; the power input terminal VIN is respectively connected to a Vin pin of the DCDC chip U1 and an emitter of the PNP transistor Q1, the collector of the PNP transistor Q1 is connected to a power output terminal VOUT, the base of the PNP transistor Q1 is connected to a first end of the resistor R1, the second end of the resistor R1 is connected to a first conduction end of the switch element Q2, and the second conduction end of the switch element Q2 is grounded; the SW pin of the DCDC chip U1 is respectively connected to an input end of the voltage divider circuit and a first end of the capacitor C2, the output end of the voltage divider circuit is connected to a controlled end of the switch element Q2; the first end of the capacitor C2 is connected to the power output terminal VOUT, and the second end of the capacitor C2 is grounded.
[0005] The utility model has at least the following technical effects:
[0006] 1. According to the current expansion circuit of the embodiment of the utility model, based on the working characteristics of the DCDC chip, the SW pin of the DCDC chip is used to realize output current expansion, so that the load current is pulled from the DCDC chip and the power input end of the DCDC chip. Therefore, when the load current is greater than the maximum output current capacity of the DCDC chip, there is no need to select a DCDC chip with a larger current specification, thereby reducing the manufacturing cost of the circuit;
[0007] 2. According to the current expansion circuit of the embodiment of the utility model, under the same working conditions, the working current of the DCDC chip can be reduced, thereby reducing the power consumption of the DCDC chip and solving the problem of serious self-heating of the DCDC chip under high current working conditions. BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Figure 1 The circuit schematic diagram of the current expansion circuit of the DCDC chip according to the embodiment of the utility model is shown. DETAILED DESCRIPTION
[0009] The utility model is described in detail below with reference to the accompanying drawings and specific embodiments.
[0010] Please refer to Figure 1 The current expansion circuit of the DCDC chip according to an embodiment of the present invention includes a power input terminal VIN, a power output terminal VOUT, a DCDC chip U1, a PNP transistor Q1, a switch element Q2, a voltage divider circuit 1, a resistor R1 and a capacitor C2.
[0011] The power input terminal VIN is connected to the Vin pin of the DCDC chip U1 and the emitter of the PNP transistor Q1 respectively, the collector of the PNP transistor Q1 is connected to the power output terminal VOUT, the base of the PNP transistor Q1 is connected to the first end of the resistor R1, the second end of the resistor R1 is connected to the first conduction end of the switch element Q2, and the second conduction end of the switch element Q2 is grounded.
[0012] The SW pin of the DCDC chip U1 is connected to the input end of the voltage divider circuit 1 and the first end of the capacitor C2 respectively, and the output end of the voltage divider circuit 1 is connected to the controlled end of the switch element Q2.
[0013] The Vin pin of the DCDC chip U1 is a power input pin, and the SW pin is a switch control pin.
[0014] In this embodiment, the model of the DCDC chip U1 used is LM61460-Q1, but not limited thereto. The switch element Q2 is an NPN transistor, which acts as a switch tube, the base of the NPN transistor Q2 is a controlled end, the collector of the NPN transistor Q2 is a first conduction end, and the emitter of the NPN transistor Q2 is a second conduction end.
[0015] In the present embodiment, the voltage divider circuit 1 includes a resistor R2 and a resistor R3, and the resistor R2 is connected in series with the resistor R3. The first end of the resistor R2 constitutes the input end of the voltage divider circuit 1, and the common point of the second end of the resistor R2 and the first end of the resistor R3 constitutes the output end of the voltage divider circuit 1, and the second end of the resistor R3 is grounded. Preferably, the current expansion circuit of the DCDC chip of the present embodiment also includes a filter capacitor C1, and the filter capacitor C1 is connected in parallel with the resistor R3. The resistors R2 and R3 act as voltage divider resistors, and the selection of the resistors R2 and R3 needs to meet the requirement that when the C point is at a high level, the voltage divider value of the resistor R3 (i.e., the voltage value of the B point) is greater than the turn-on voltage value of the NPN transistor Q2. The filter capacitor C1 can prevent the NPN transistor Q2 from being mis-conducted due to sudden voltage fluctuations.
[0016] The first end of the capacitor C2 is connected to the power output terminal VOUT, and the second end of the capacitor C2 is grounded. Preferably, the current expansion circuit of the DCDC chip of this embodiment also includes a filter inductor L1, the first end of the filter inductor L1 is connected to the SW pin of the DCDC chip U1, and the second end of the filter inductor L1 is connected to the first end of the capacitor C2.
[0017] The SW pin of the DCDC chip U1 outputs a periodic square wave signal. The voltage divider circuit 1 turns on the switch element Q2 when the SW pin outputs a high level, and turns off the switch element Q2 when the SW pin outputs a low level.
[0018] Specifically, when the output signal of the SW pin is high (i.e., point C is high), the voltage divider value of resistor R3 (i.e., the voltage value of point B) is greater than the turn-on voltage value of NPN transistor Q2, and NPN transistor Q2 is turned on. The voltage at point A is the input power supply voltage of DCDC chip U1. At this time, the voltage drop between point A and point D is greater than the voltage drop between the emitter and base of PNP transistor Q1 (i.e., the body diode voltage drop of PNP transistor Q1), so PNP transistor Q1 is turned on. At this time, the load connected to the power output terminal VOUT can draw current from the power input terminal VIN of DCDC chip U1 through PNP transistor Q1. Resistor R1 is a current limiting resistor that controls the base current value of PNP transistor Q1, so that PNP transistor Q1 is in an amplified state when turned on. When the output signal of the SW pin is high, the load current consists of two parts. One part is the load pulling current from the power input terminal VIN of the DCDC chip U1 through the PNP transistor Q1, and the other part is provided by the DCDC chip U1 (referring to the path from the SW pin to the inductor L1 and then to the power output terminal VOUT). Therefore, when the load current is greater than the maximum output current capacity of the DCDC chip U1, the current exceeding the current output capacity of the DCDC chip is pulled from the power input terminal VIN to achieve the effect of expanding the output current capacity. Due to the working characteristics of the DCDC chip, when the SW pin is high, in addition to supplying power to the load, it will also charge the capacitor C2 of the output part.
[0019] When the SW pin signal is low (i.e., point C is low), point B is low, and the voltage at point B is less than the turn-on voltage of the NPN transistor Q2, so the PNP transistor Q2 is cut off, point D is in a high impedance state, and the voltage drop between points A and D is less than the voltage drop between the emitter and base of the transistor Q1, so that the PNP transistor Q1 is cut off (not conducting), and the load cannot draw current from the power input terminal VIN of the DCDC chip through the PNP transistor Q1. At this time, the DCDC chip is also in the off state, so the load can only work normally with capacitor C2. When the charge of capacitor C2 decreases, due to the working characteristics of the DCDC chip, the SW pin level becomes high again, and the load and capacitor C2 can continue to be charged in the above manner, and so on.
[0020] The current expansion circuit of this embodiment uses the working characteristics of the SW pin of the DCDC chip to expand the circuit current. The output signal of the SW pin is a periodic square wave, that is, a periodic high level and a low level. The high level voltage value is related to the voltage of the input Vin pin, and the low level voltage can be understood to be equal to the ground GND. Since the load current is pulled from the DCDC chip and the power input end of the DCDC chip, it is achieved that when the load current is greater than the maximum output current capacity of the DCDC chip, there is no need to select a DCDC chip with a larger current specification, thereby reducing the manufacturing cost of the circuit.
Claims
1. A current expansion circuit of a DCDC chip, characterized in that: It includes a power input terminal VIN, a power output terminal VOUT, a DCDC chip U1, a PNP transistor Q1, a switch element Q2, a voltage divider circuit, a resistor R1 and a capacitor C2; The power input terminal VIN is connected to the Vin pin of the DCDC chip U1 and the emitter of the PNP transistor Q1 respectively, the collector of the PNP transistor Q1 is connected to the power output terminal VOUT, the base of the PNP transistor Q1 is connected to the first end of the resistor R1, the second end of the resistor R1 is connected to the first conduction end of the switch element Q2, and the second conduction end of the switch element Q2 is grounded; The SW pin of the DCDC chip U1 is connected to the input end of the voltage divider circuit and the first end of the capacitor C2 respectively, and the output end of the voltage divider circuit is connected to the controlled end of the switch element Q2; A first end of the capacitor C2 is connected to the power output terminal VOUT, and a second end of the capacitor C2 is grounded.
2. The current expansion circuit of the DCDC chip according to claim 1, characterized in that: The voltage divider circuit includes a resistor R2 and a resistor R3, and the resistor R2 and the resistor R3 are connected in series; The first end of the resistor R2 constitutes the input end of the voltage divider circuit, the common point of the second end of the resistor R2 and the first end of the resistor R3 constitutes the output end of the voltage divider circuit, and the second end of the resistor R3 is grounded.
3. The current expansion circuit of the DCDC chip according to claim 2, characterized in that: The current expansion circuit of the DCDC chip includes a filter capacitor C1, and the filter capacitor C1 is connected in parallel with a resistor R3.
4. The current expansion circuit of the DCDC chip according to claim 1, characterized in that: The current expansion circuit of the DCDC chip includes a filter inductor L1, a first end of the filter inductor L1 is connected to the SW pin of the DCDC chip U1, and a second end of the filter inductor L1 is connected to the first end of the capacitor C2.
5. The current expansion circuit of the DCDC chip according to claim 1, characterized in that: The switch element Q2 is an NPN transistor, the base of the NPN transistor Q2 is a controlled terminal, the collector of the NPN transistor Q2 is a first conduction terminal, and the emitter of the NPN transistor Q2 is a second conduction terminal.
6. The current expansion circuit of the DCDC chip according to any one of claims 1 to 5, characterized in that: The model of the DCDC chip U1 is LM61460-Q1.