Introduction
Designing a MOSFET driver supply for a 12-V car supply is quite challenging. The 12-V battery supply voltage is normally in the range of 9 V to 16 V under normal operating conditions depending on charge and load variation. The TPS61041-Q1 is a high-frequency, low-cost boost converter dedicated for a small to medium supply. The device allows the use of small external components, which gives a very small overall solution size. However, its input voltage range is from 1.8 V and 6 V. This application brief proposes an external circuit that can generate an output voltage following the input voltage adjustment and change.
For automotive applications that require a high-side MOSFET driver, the MOSFET gate needs a stable stepped-up voltage to ensure the MOSFET is fully turned on. The 12-V battery supply voltage is normally in the range of 9 V to 16 V under normal operating conditions depending on charge and load variation. Therefore, the driver voltage should follow the input voltage adjustment and change. Figure 1-1 shows the block diagram.
VDD/V | VOUT/V | IOUT/mA |
---|---|---|
9 V to 16 V | VDD + 10 V | 5 V |
The TPS61041-Q1 is a high-frequency boost converter dedicated for low-power applications. The device is ideal to generate output voltages up to 28 V from 1.8-V to 6-V input voltage range. The TPS61041-Q1 operates with a switching frequency up to 1 MHz.
This document introduces a circuit to generate the high-side MOSFET driver voltage using the TPS61041-Q1. Theoretical analysis and bench test results are presented to verify the proposed circuit. Table 1-1 shows the circuit specification.
Proposed Circuit Principle
Figure 2-1 shows the schematic of a boost converter using the TPS61041-Q1. Because the TPS61041-Q1 recommended input voltage maximum value is 6 V, the device VIN and GND pin cannot be connected to 12-V car battery directly. A level-shift circuit composed of D3, D2, and Q1 pulls up the IC GND pin voltage potential.
D3 is a Zener diode that clamps the PNP transistor Q1 base voltage VA to:
The PNP transistor Q1 turns on, IC_GND voltage follows the calculation in Equation 2:
In this application, a 6-V Zener diode
is selected for D3. So, the TPS61041 VIN pin to GND pin voltage is clamped to below
6 V to protect the IC. Set the TPS61041 output voltage to 10 V higher than
Vin as in
Equation 3:
Where Vref is 1.233 V.
Set R1 at 1.87 MΩ and
R2 at 167 kΩ. Assume the PNP transistor VBE is 0.3 V, the
VOUT – Vin equals
9.63 V.
Bench Test Result
Using the setup shown in Figure 2-1, the Vin line transient waveform is shown in Figure 3-1. When Vin is 9 V, the TPS61041-Q1 device output voltage is 19 V. When Vin is 16 V, the TPS61041-Q1 device output voltage is 26 V. The device VOUT is always 10 V higher than input voltage.
Summary
This document proposes an external circuit that can generate an output voltage following the input voltage adjustment and change by using the high-efficiency low-cost boost converter, TPS61041-Q1.
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