DC-DC Converter Frequency Synchronization via Capacitor Impedance Control
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Solution Overview
Problem
Existing power supply devices with multiple DC-DC converters face difficulties in synchronizing switching frequencies, which affects noise control and efficiency, especially when using different types of switching control ICs and voltage outputs ranging from high to low voltages.
Innovation Solution
A DC-DC converter configuration that includes a triangular wave generation circuit and a PWM control circuit, allowing synchronization of switching frequencies through a synchronizing signal applied to a capacitor, with a switch to change impedance and prevent overvoltage, enabling a single master converter to synchronize multiple slave converters across a wide voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple DC-DC converters are used to provide different power supply voltages, then the power supply capability is improved, but the switching frequency synchronization becomes difficult and noise control deteriorates
Solution Approach 1:
The patent merges the oscillation circuits of multiple DC-DC converters by connecting their capacitor connection terminals through balancing capacitors. This allows the converters to share a common oscillation frequency determined by the total capacitance at the connected terminals, thereby achieving frequency synchronization without requiring separate synchronization circuits for each converter.
Solution Approach 2:
The patent introduces balancing capacitors as intermediary elements connected between the capacitor connection terminals of different DC-DC converters. These balancing capacitors act as mediators that enable frequency synchronization by forming part of the total capacitance that determines the oscillation frequency, allowing independent converters to operate at a unified frequency.
2Loss of energy
If a synchronous rectifier circuit with low on-resistance switching element is used for low output voltage DC-DC converter, then the loss due to voltage drop is reduced, but the control IC complexity increases due to VCO requirement
Solution Approach 1:
The patent makes the control IC universal by enabling it to operate in multiple modes: it can function as a master converter with VCO-based frequency generation, as a slave converter with externally determined frequency, or as a frequency reference for other converters. This multi-functionality allows the same control IC architecture to support both high-voltage flywheel diode configurations and low-voltage synchronous rectifier configurations without requiring different IC designs.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration ensures synchronized switching frequencies across multiple DC-DC converters, improving noise control and efficiency by allowing a single master converter to synchronize multiple slave converters, effectively managing voltage outputs from high to low voltages.
Implementation Method 1
a triangular wave generation circuit for charging and discharging a capacitor and for generating a triangular wave by switching between charging and discharging
Implementation Method 2
a PWM control circuit for controlling an output of the DC-DC converter by controlling an on duty ratio of a switching element
Implementation Method 3
by applying a voltage of a synchronizing signal that is a pulse voltage signal to the capacitor to control an electric charge of the capacitor
Data Source
AI summary
A switching control IC is provided with a circuit for generating a triangular wave using a frequency that is dependent on a capacitor connected to a CT terminal of the switching control IC, and a resistor connected to an RT terminal thereof. A synchronizing signal input circuit for externally receiving a synchronizing signal that is a pulse voltage signal is connected to the CT terminal. A charging voltage for the capacitor connected to the CT terminal is changed by the synchronizing signal, which synchronizes the frequency of the triangular wave with the synchronizing signal, whereby the frequencies of a plurality of DC-DC converters are synchronized.