How to make DC-DC Boost & Buzzer Driver
This project explains how to create a Piezo Driver and Boost DC-DC Converter using one HVPAK SLG47105.
Introduction
The HVPAK SLG47105 is a flexible configurable mixed-signal IC able to combine a Boost DC-DC Converter and a Piezo Driver in a single package with a small number of external components. The main goal of this project is to show how to configure HVPAK to drive a 2.5 kHz Piezo and how to create a Boost DC-DC Converter from 3 V to 13 V. The whole circuit is powered with a 3V CR2032 battery. Such a schematic can be used in devices that require short-term notifications (keychains for finding things, and others). When the push button is pressed, the DC-DC Converter boosts the voltage to 13 V which powers the Piezo Driver. Then the short pattern is played, and the circuit goes to sleep mode until the button is pressed again. When the circuit is ON — it consumes nearly 15 mA, and in sleep mode less than 50 nA. This ensures up to 800 activations on one battery.
Below we described steps of our project needed to understand how the solution has been programmed to design a Piezo Driver and Boost DC-DC Converter using one SLG47105. However, if you just want to get the result of programming, download Go Configure™ Software Hub, to view the already completed GreenPAK Design File.
Operating Principle and HVPAK Design
The DC-DC Boost & Buzzer Driver Circuit Diagram is shown in Figure 1.
The design consists of a DC-DC Boost Converter and Buzzer Driver parts.
For the DC-DC Boost Converter, the PWM0 forms the ~197 kHz signal. The DFF1, DFF5, and DFF6 form the clock for a soft start to reduce inrush current, which can occur when the device is first turned on. Minimum and maximum duty cycles are set by Pipe Delay and CNT4/DLY4.
The VDD and VDD2_B are connected to a 3 V battery. VDD2_A is connected to Boost output. To monitor this voltage, the resistors R2 and R4 form the resistive divider with a feedback signal, which goes to PIN20 (Analog Input). This feedback voltage is compared with 1024 mV Vref by ACMP1H forming the ACMP signal which goes to the CHOP input of the PWM Chopper 0. If the VDD2 exceeds 9.5 V, the ACMP signal is HIGH and chop the formed PWM signal. The PWM Chopper 0 output goes to HV OUT CTRL1 (Half Bridge) input IN0. Then PIN 9 drives an NFET of Boost Converter.
To reduce the current consumption, a resistive divider is connected to PIN 10 (Low Side ON) with a GND input.
Note: it’s possible to change the ACMP1H Vref and boost the voltage up to 13 V.
The HVPAK Design is shown in Figure 2.
The HV OUT CTRL0 (Full Bridge) drives a Piezo. PWM1 is used as a frequency divider and forms a 2.5 kHz signal (resonant frequency of a piezo), this signal comes to PH input of HV OUT CTRL0.
The 3-bit LUT4 forms the EN signal for the HV OUT CTRL0. It consists of the sound pattern signal and the general EN signal. The PGEN generates the sound pattern (01010101101011). The EN signal — the general ENABLE signal for the whole design is HIGH for 875 ms (CNT3/DLY3 One Shot) if the button is pressed (MF1) and the VDD is higher than ~2.6 V (ACMP0H + MF0).
The 3-bit LUT9 inverts the EN signal forming the SLEEP signal to shut down the blocks when they are not used to reduce the power consumption.
The 3-bit LUT0 forms the BOOST_SLEEP signal. The Boost will power down if there is no POR signal, the SLEEP signal is HIGH, or the OCP signal is HIGH. The CCMP0 monitors the piezo current and if it exceeds 200 mA, the OCP signal is HIGH (MF2).
Design Testing
Channel 1 (blue / 1st line) — PIN 7 (Piezo).
Channel 2 (yellow / 2nd line) — GND (current).
As can be seen in Figure 3, the VDD2 level is 9.5 V as expected, and the Piezo frequency is 2.5 kHz. The average current consumption is 15 mA. The current in sleep mode is below 50 nA, which means up to 800 activations without replacing the battery!
PCB Design
The proposed Demo PCB Design is shown in Figure 4 (top) and Figure 5 (bottom). As can be seen in Figure 4, the design is so compact that it can be placed under the buzzer.
BOM
Conclusion
This article describes how to configure the HVPAK SLG47105 to create a Boost & Buzzer Driver device that can work with a single 3 V CR2032 battery. With its extremely low current consumption, up to 800 activations without battery replacement are possible!
The flexibility of the internal resources allows adapting it to the needs of the customer without effort.
